We are all wearing out. So it is good news that more progress is being made in developing our future needed replacement parts.
WINSTON-SALEM, N.C. – Saturday, Oct. 30, 2010 – Researchers at the Institute for Regenerative Medicine at Wake Forest University Baptist Medical Center have reached an early, but important, milestone in the quest to grow replacement livers in the lab. They are the first to use human liver cells to successfully engineer miniature livers that function – at least in a laboratory setting – like human livers. The next step is to see if the livers will continue to function after transplantation in an animal model.
The ultimate goal of the research, which will be presented Sunday at the annual meeting of the American Association for the Study of Liver Diseases in Boston, is to provide a solution to the shortage of donor livers available for patients who need transplants. Laboratory-engineered livers could also be used to test the safety of new drugs.
"We are excited about the possibilities this research represents, but must stress that we're at an early stage and many technical hurdles must be overcome before it could benefit patients," said Shay Soker, Ph.D., professor of regenerative medicine and project director. "Not only must we learn how to grow billions of liver cells at one time in order to engineer livers large enough for patients, but we must determine whether these organs are safe to use in patients."
Organ replacement is not just about replacing aged organs. Another important purpose for new organ transplants: they will become a great way to get rid of cancer. Genetic testing can identify very early stage cancers. Those genetic tests will let us know with lots of warning when we will need a replacement part. But we will need home genetic testing for cancer to enable sufficiently cheap and convenient testing to enable early stage identification of cancers. Home genetic testing is an essential technology for extending our lives.
Once we know that we need replacement organs then genetic testing in tissue engineering labs will help to identify genetically undamaged cell lines suitable for growing replacement parts. Genetic testing has many uses in maintaining our health because the biological software that is our DNA has to be maintained in an uncorrupted state in order to assure our continued good health.
MINNEAPOLIS / ST. PAUL (January, 13 2008) – University of Minnesota researchers have created a beating heart in the laboratory.
By using a process called whole organ decellularization, scientists from the University of Minnesota Center for Cardiovascular Repair grew functioning heart tissue by taking dead rat and pig hearts and reseeding them with a mixture of live cells. The research will be published online in the January 13 issue of Nature Medicine.
“The idea would be to develop transplantable blood vessels or whole organs that are made from your own cells,” said Doris Taylor, Ph.D., director of the Center for Cardiovascular Repair, Medtronic Bakken professor of medicine and physiology, and principal investigator of the research.
Lots of people have dodgy hearts that need replacement.
Nearly 5 million people live with heart failure, and about 550,000 new cases are diagnosed each year in the United States. Approximately 50,000 United States patients die annually waiting for a donor heart.
While there have been advances in generating heart tissue in the lab, creating an entire 3-dimensional scaffold that mimics the complex cardiac architecture and intricacies, has always been a mystery, Taylor said.
It seems decellularization may be a solution – essentially using nature’s platform to create a bioartifical heart, she said.
The problem with decellularization is that you need a dead heart to start with. But perhaps studies on the extracellular matrix will lead to ways to make a purely synthetic extracellular matrix.
Decellularization is the process of removing all of the cells from an organ – in this case an animal cadaver heart – leaving only the extracellular matrix, the framework between the cells, intact.
After successfully removing all of the cells from both rat and pig hearts, researchers injected them with a mixture of progenitor cells that came from neonatal or newborn rat hearts and placed the structure in a sterile setting in the lab to grow.
The results were very promising, Taylor said. Four days after seeding the decellularized heart scaffolds with the heart cells, contractions were observed. Eight days later, the hearts were pumping.
Growth of replacement hearts, as great as it would be, is not the ideal way to solve heart disease. Better to be able to send in gene therapy and/or cell therapy to repair the existing heart while it still beats. But even once such treatments become available some will still need replacement hearts due to sudden trauma.
A British research team led by the world's leading heart surgeon has grown part of a human heart from stem cells for the first time. If animal trials scheduled for later this year prove successful, replacement tissue could be used in transplants for the hundreds of thousands of people suffering from heart disease within three years.
Sir Magdi Yacoub, a professor of cardiac surgery at Imperial College London, has worked on ways to tackle the shortage of donated hearts for transplant for more than a decade. His team at the heart science centre at Harefield hospital have grown tissue that works in the same way as the valves in human hearts, a significant step towards the goal of growing whole replacement hearts from stem cells.
Yacoub thinks his team might be able to grow a complete heart within 10 years. That's 2017. So if you need a new heart in 2025, no problem - at least if you can afford it. But if full replacement hearts become possible by, say, 2020 (add a few years for complications along the way) then why won't all the other organs follow shortly thereafter? By the year 2030 should anyone in an industrialized country die from internal organ failure? It seems totally avoidable.
Next throw in some stem cell therapies that repair blood vessels and muscles. We''ll also need therapies to repair immune cells. That will leave the last great rejuvenation frontier: the brain. Can't replace that. Need to repair the existing cells. Brain rejuvenation is the hardest challenge of all. For that we'll need excellent gene therapy and nano repair devices. I hope many of us do not become too brain aged and dumb before such therapies become available.
CHARLOTTESVILLE, Va., Feb. 19, 2007 - A research team led by Cato T. Laurencin, M.D., Ph.D., at the University of Virginia Health System has created a synthetic matrix on which the ACL (anterior cruciate ligament) can be regenerated effectively for treatment of ACL tears.
This is an important discovery, because the ACL, the stabilizing ligament that connects the thighbone to the legbone, usually does not heal after it is torn during sports or other injuries. The ACL unravels like an unbraided rope when torn, making healing difficult. More than 200,000 people in the United States suffer this rupture each year.
"This is the first tissue-engineered matrix for ACL to demonstrate such substantial neo-ligament formation, in terms of both vascularity and collagen formation," said Dr. Laurencin, Chairman of the UVa Department of Orthopaedic Surgery and leader of the team. "We tested one synthetic matrix with actual ACL cells from our animal model and one without these cells. While both systems encouraged the ingrowth of neo-ligament tissue, matrices with seeded cells performed particularly well in this study."
Dr. Laurencin concluded that the ACL replacement with ACL cells had a robust functional tissue outcome in the rabbits that received this matrix.
Tissue engineering doesn't get as much attention as stem cell research. But we need tissue engineering advances as much as we need stem cell research advances.
The team grew ligament tissue after first weaving together strands of biodegradable polyester using a machine originally designed for textile production. This material, called polylactide, naturally dissolves in the body over time.
Every industry that develops technology for manipulating small pieces of matter potentially could produce technology also useful for biological manipulations. We see this with gene chips and microfluidic devices developed as spin-offs of the computer semiconductor industry. But we also see scientists using ink jet printers to deposit cells for tissue engineering.
Laurencin's team seeded the woven polylactide structure with cells taken from rabbits' anterior cruciate ligaments and cultured them in a dish for two days. Finally, they surgically replaced whole anterior cruciate ligaments in another group of rabbits with the polylactide scaffold material, attaching it to the joint in the same way as a normal ligament.
Twenty-four hours later, the rabbits could already bear their own weight on their knees, and showed fairly normal mobility.
We need the ability to build and grow replacement parts for our bodies. With these parts most chronic, painful, and debilitating diseases will become curabel. Eventually full body rejuvenation will become possible.
Scientists have grown an artificial liver that is set to revolutionise the medical world, it was revealed today.
A team based at Newcastle University have grown a tiny liver, believed to be the first of its kind in the world.
Using stem cells taken from umbilical cords, Dr Nico Forraz and Professor Colin McGuckin made the breakthrough.
The two scientists also took a trip to Houston, Texas, to work with scientists at Nasa.
And using some skills they learned at Nasa they were able to make the miniature livers, which can now be used for drug and pharmaceutical testing, eradicating the need to test on animals and humans.
Dr Forraz said: "We have taken a little bit of umbilical cord blood, and then it is all about enhancing things that already exist.
"We cannot build a fullsized liver yet. That will take about 10 years. But this is the first important step.
"We expect this to really take off in the next 18 months or so.
Livers are relatively simpler things to grow than 3 dimensionally more complex structures such as hearts and kidneys. So I'm expecting we'll see replacement livers before replacement hearts or kidneys.
As it stands, the mini organ can be used to test new drugs, preventing disasters such as the recent 'Elephant Man' drug trial. Using lab-grown liver tissue would also reduce the number of animal experiments.
Within five years, pieces of artificial tissue could be used to repair livers damaged by injury, disease, alcohol abuse and paracetamol overdose.
And then, in just 15 years' time, entire liver transplants could take place using organs grown in a lab.
These scientists intend to commercialize their work with their company ConoStem.
Liver replacement has applications beyond liver cirrhosis. First off, some people die from liver failure brought on by the trauma of accidents. Also, liver cancer is another kind of liver failure which kills people. Liver cancer cases that are now inoperable will become operable when it becomes possible to remove an entire liver and replace it with a new one.
For a number of types of organs replacement to treat cancer might end up saving more lives than replacement due to accidents and other diseases. Got pancreatic cancer? Replace it. Got kidney cancer? Replace it. Advances in testing will allow identification of a growing portion of all cancers before metastasis. If a cancer is still contained within a single organ then an excellent solution might some day be to just replace that whole organ. Though other ways to cure cancer might eventually avoid the need for this approach.
We can develop the technology to grow replacement parts for just about every part of the body and this can be accomplished within the lifetimes of most of the people reading this. So why aren't we trying much harder? Government research funding for stem cells and tissue engineering should be at least an order of magnitude larger.
The University of Pittsburgh Medical Center and biotech company Revivicor are attempting to revive efforts to genetically engineer pigs to make organs for xenotransplantation into humans. Writing for the Pittsburgh Tribune-Review Luis Fabregas covers a lot of territory in a survey of the UPMC-Revivicor efforts. Human trials for some types of transplants might be just a few years off.
Momentum is building for two promising projects.
One is using insulin-making pig islets to bolster the insulin levels of people with type 1 diabetes, something routinely done in at least one hospital in Mexico City. In the last five years, about 40 patients at Children's Hospital of Mexico have received the pig islet transplants. Some of them have significantly reduced their insulin intake, said spokeswoman Isis Casanova.
Researchers at Children's Hospital of Pittsburgh, led by Dr. Massimo Trucco, have been testing pig islets in small monkeys since 2004.
Another project would use pig hearts in people with severe heart failure instead of mechanical pumps.
By Revivicor's own estimates, the market for pig organs could be worth at least $6 billion.
The intensity of UPMC's efforts, including discussions between Revivicor and the U.S. Food and Drug Administration, suggest UPMC is poised to begin human clinical trials within two or three years.
Revivicor's pigs have been genetically modified to not produce alpha-1-galactose sugar which causes human immune rejection. Much more could be done along those lines to make pig organs more like human organs in order to enhance compatibility. This strikes me as a direction that ought to get huge amounts of funding.
Pigs have a virus incorporated into their genomes called porcine endogenous virus (PERV) which could potentially infect humans. But such viruses could be knocked out of pigs genetically engineered for organ production. At the same time, a variety of human genes could get transplanted into pigs to make them have immune systems, livers, and other organs more like humans. It is a lot of work. All the more reason to start doing in sooner and on a greater scale.
Every day that goes by your organs all get one day older and closer to failure. If we start trying a lot harder now many of us could get youthful organs transplanted from pigs when our own organs get old and start to fail. Time's a wasting. Time is wasting our body parts and making them slowly break down. We ought to develop the means to repair and replace old human body parts.
ATLANTA -- Islet cell xenotransplantation presents a promising near-term solution to the critically low islet cell supply for humans suffering from type 1 diabetes, according to researchers from the Emory Transplant Center, the Yerkes National Primate Research Center of Emory University and the University of Alberta, Canada. The Emory/Yerkes researchers successfully transplanted and engrafted insulin-producing neonatal porcine islet cells harvested by the University of Alberta researchers into diabetic rhesus macaque monkeys, restoring the monkeys' glucose control and resulting in sustained insulin independence. This research, published in the February 26 advanced online edition of Nature Medicine, also examines the effectiveness of a costimulation blockade-based regimen developed at Emory proven to have fewer toxic side effects than currently used immunosuppressive regimens, and provides essential answers to the possibility of cross-species viral transmission, a common concern of xenotransplantation use in humans.
If we had a much larger effort aimed at implementing all the Strategies for Engineered Negligible Senescence (SENS) there'd be a lot more money available for genetically engineering pigs to become more immuno-compatible with humans. That would make xenotransplantation a lot easier.
We need replacement parts. We should be trying much harder to develop them.
In a major step towards understanding prostate disease, Melbourne scientists have grown a human prostate from embryonic stem cells.
A study published in the March edition of Nature Methods describes how human embryonic stem cells were developed into human prostate tissue equivalent to that found in a young man, in just 12 weeks.
Hey, I want to grow a new prostate and replace mine before mine gets old enough to cause really serious problems. The idea of getting youthful replacement parts becomes more appealing with every passing year.
We should be able to get replacement parts that last longer than the originals. Not every man gets BPH or prostate cancer. Once DNA sequencing is cheap and large numbers of people get their medical histories and DNA sequences compared scientists will identify large numbers of genetic variations that contribute to disease risk. My guess is DNA sequencing will get cheap before replacement organs become feasible. So we'll know what to change. One's own DNA might still be used for making replacement parts (reduces immuno-rejection problems). But gene therapy to patch our DNA (rather like software patches) with the best sequences for reducing specific disease risk will fix it to make it last longer.
For making organs last longer there's a step beyond using best existing genetic variations: Develop genetic sequences that are better than any that have evolved naturally. For example, move all the genes now found in the mitochondria (which have about 15,000 genetic letters of code) into the nucleus where they will be better protected from free radical damage.
The researchers expect a more immediate benefit from their work in the form of prostate cells that can be studied for showing how prostates deteriorate and become diseased.
The study was co-authored by Dr Renea Taylor from Monash University's Immunology and Stem Cell Laboratories, PhD researcher Ms Prue Cowin from the Monash Institute of Medical Research and other Australian and US researchers.
Dr Taylor said the discovery would allow scientists to monitor the progression of the prostate from a normal to a diseased state.
"We need to study healthy prostate tissue from 15-25 year old men to track this process," she said. "Understandably, there is a lack of access to samples from men in this age group, so to have found a way we can have an ongoing supply of prostate tissue is a significant milestone.
"As nearly every man will experience a problem with their prostate, we're very excited about the impact our research will have."
Although prostate cancer is the most common cancer in men, the impact of benign prostate disease (BPH) is equally significant - up to 90 percent of men will have BPH by the time they're 80. BPH is not usually life-threatening, but has a dramatic impact on quality of life.
My guess is that a lot of men with ambivalent feelings about embryonic stem cells who have benign prostate hyperplasia (i.e. difficulty urinating - which also increases the odds of kidney failure btw) are going to resolve those ambivalent feelings in favor of embryonic stem cells if they can get offered replacement prostates that solve their problem.
The cells were planted into mice after being treated in ways that instructed the cells to become prostate tissue.
"We grew the prostate tissue by 'telling' the embryonic stem cells how to become a human prostate gland. We then implanted the cells into mice, where they developed into a human prostate, secreting hormones and PSA; the substance in the blood used to diagnose prostate disease,'' Ms Cowin said.
We really need the ability to grow whole replacement organs. These ladies have taken a big step in that direction. But additional problems must also be solved to grow organs in the right three dimensional shape and ideally to do that in a human body. Mice are obviously too small to grow replacement organs for humans and present problems with disease transfer as well.
An international team of biomedical engineers has demonstrated for the first time that it is possible to grow healthy new bone reliably in one part of the body and use it to repair damaged bone at a different location.
The research is described in a paper titled 'In Vivo Engineering of Organs: The Bone Bioreactor' published online by the Proceedings of the National Academy of Sciences.
Researchers from Imperial College London, the Massachusetts Institute of Technology and Vanderbilt University hope their discovery, which takes advantage of the body's natural wound-healing response, will transform treatments for serious bone breaks and diseases.
New Zealand White rabbits were used to test this procedure. The researchers successfully transferred the bone to another location in the rabbits to repair a bone injury at the other location.
The periosteum layer on the outside of bones has stem cells which can be coaxed into growing replacement bone.
This new research, however, takes a new approach that has proven to be surprisingly simple. Long bones in the body are covered by a thin outer layer called the periosteum. The layer is a little like scotch tape: the outside is tough and fibrous but the inside is covered with a layer of special pluripotent cells which, like marrow cells, are capable of transforming into the different types of skeletal tissue. Because of this, Dr Stevens and her colleagues decided to create the bioreactor space just under this outer layer.
They created the space by making a tiny hole in the periosteum and injecting saline water underneath. This loosened the layer from the underlying bone and inflated it slightly. When they had created a cavity the size and shape that they wanted, next the researchers removed the water and replaced it with a gel that is commercially available and approved by the FDA for delivery of cells within the human body. They chose the material because it contained calcium, a known trigger for bone growth. Their major concern was that the bioreactor would fill with scar tissue instead of bone, but that didn't happen. Instead, it filled with bone that is indistinguishable from the original bone.
Here is the really cool part: This approach might work for growing replacement tissue for organs such as the liver and pancreas.
"This research has important implications not only for engineering bone, but for engineering tissues of any kind," said researcher Robert S. Langer, Institute Professor at the Massachusetts Institute of Technology and a pioneer in the field of tissue engineering. "It has the potential for changing the way that tissue engineering is done in the future."
The scientists intend to proceed with the large animal studies and clinical trials necessary to determine if the procedure will work in humans and, if it does, to get it approved for human treatment. At the same time, they hope to test the approach with the liver and pancreas, which have outer layers similar to the periosteum.
While some organ fail too quickly to allow patients to grow new organs to replace them for some types of organ failure the decline of organ function takes months or years and the problem is diagnosed long before the organ reaches an advanced stage of failure. Plus, advances in embedded nanosensors will lead to much earlier identification of failing organs to provide even more time to grow replacements. Therefore the ability to grow replacement organs within one's own body using one's own cells (which will not suffer from immune rejection) would have great value.
An essential component in Strategies for Engineered Negligible Senescence (SENS) is the replenishment of adult stem cell reservoirs in the body with youthful adult stem cells. Imagine then a two stage process for rejuvenation of organs. First, add youthful stem cells to an existing old organ. Then induce the growth of a new replacement organ in a layer created on the surface of the existing organ. Then once the replacement organ develops to full size remove the old organ.
We still need the ability to grow organs outside of a human body. However, for those cases where replacement organs can grow inside one's body we might gain the ability to grow organs much sooner by use of this "in vivo bioreactor" approach.
Using human embryonic stem cells and a mixture of tissue types a group of researchers has found a way to grow replacement muscle tissue which has blood vessels.
CAMBRIDGE, Mass.--For years, a major obstacle has dashed the hopes of creating "replacement parts" for the human body: the lack of an internal, nourishing blood system in engineered tissues. Without it, thicker tissues can't thrive, which has confined tissue engineering's practical application to thin skin, which can recruit blood vessels from underlying tissue.
Now, researchers in Institute Professor Robert Langer's lab at MIT have used a novel cocktail of cells to coax muscle tissue to develop its own vascular network, a process called pre-vascularization. When implanted in living mice and rats, these tissues integrated more robustly with the body's own tissues than similar implants without blood vessels.
This approach should work with other tissue types.
"What's even more exciting than being able to make skeletal muscles for reconstructive surgery or to repair congenitally defective muscles, for instance, is that this a generic approach that can be applied towards making other complex tissues. It could allow us to do really wonderful things," says collaborator Daniel Kohane, an affiliate at MIT and assistant professor of pediatrics at Harvard Medical School.
The researchers published their work in Nature Biotechnology, available online in advance on June 19, 2005. An accompanying News and Views commentary says this "landmark paper" provides "a compelling demonstration of the benefits of pre-vascularization for engineering larger pieces of tissue."
"When I came to work with Bob Langer for my postdoc, it was my dream to vascularize a tissue," recalls first author Shulamit Levenberg, who is now on the faculty of the biomedical engineering department at Technion in Haifa, Israel where she completed these studies. She chose to tackle muscles, since they depend on blood vessels interspersed with muscle fibers and also serve as a model for highly vascularized organs such as the liver, heart, and lung.
The researchers used three cell types: myoblasts, endothelial cells, and fibroblasts. Some of the endothelial cells formed the needed blood vessels.
Levenberg theorized she needed to combine three cell types: myoblasts that form muscle fibers; endothelial cells that independently self-organize into vessel tubes; and fibroblasts that are the precursors for the smooth muscle cells that stabilize the vessel amidst the tissue's gooey extracellular matrix. "No one had tried a 3-D tri-culture scaffold before. It's hard enough to work with one cell type, let alone three!" explains senior author Langer, who is a pioneer in tissue engineering.
The VEGF mentioned here is a Vascular Endothelial Growth Factor, a hormone that causes blood vessels to form. The process of blood vessel formation is called angiogenesis. Angiogenesis has come to be well understood as a result of Harvard cancer researcher Judah Folkman's decades of pursuit of anti-angiogenesis compounds as an approach to stopping cancer tumor growth. The field of tissue engineering therefore benefits from insights developed by cancer researchers.
In vitro experiments validated Levenberg's hypothesis: "The endothelial cells formed vessels, recruited the fibroblasts, and differentiated them into smooth muscle cells," she says. "The differentiated fibroblasts expressed the angiogenic growth factor, VEGF, which further stimulated vessel growth." The constructs measured 5mm by 5mm by 1mm.
Note the use of human embryonic stem cells to make endothelial cells. My guess is that work was done in Israel.
For implantation in living animals, the lab used immunodeficient mice and rats that would not reject the human-derived endothelial cells. At the beginning of the project, Levenberg had isolated endothelial cells from human embryonic stem cells – a first. Human derivation is key for clinical use to avoid an immune rejection.
The animal studies progressed in stages. First, the researchers implanted a muscle construct under the skin, then inserted one within a leg muscle, and finally replaced a piece of a rat's abdominal muscle with a construct, simulating a situation applicable to trauma victims, for instance. Later tissue staining showed that the implants' vessels grew into the host tissue and the host's vessels grew into the constructs.
But what good are blood vessels if they don't deliver the goods – blood? Using two non-invasive live imaging techniques (labeled lectin injected into the tail vein and a luminescent luciferase-based system), the researchers could watch the host's blood flow into the engineered vessels. About 41% of the constructed vessels became perfused with the hosts' blood, meaning they functioned in the living body. "That's pretty good for a first try," Levenberg asserts.
Importantly, twice as many of the cells survived in the tri-culture implants compared to implants without endothelial cells. "The myoblasts also became even longer tubes when implanted, and they began to align themselves with the host's muscle fibers," Levenberg recounts.
"This tri-culture system shows a whole new way of creating a vascular network in the tissue," summarizes Langer. "We've also demonstrated another powerful use of human embryonic stem cells."
In addition to Kohane, Levenberg and Langer collaborated with Patricia D'Amore and Diane Darland at The Schepens Eye Research Institute, Evan Garfein at Brigham and Women's Hospital, Robert Martin of MIT's Division of Comparative Medicine, Richard Mulligan of Children's Hospital and Harvard Medical School, Clemens van Blitterswijk at Twente University in the Netherlands, and present and former MIT graduate students Mara Macdonald Jeroen Rouwkema.
The discovery of an approach which causes the growth of blood vessels in bioengineered organs lifts a major obstacle in the way of tissue engineering. If tissue engineers can cause cells to build vascular networks then the construction of larger three dimensional pieces of tissue becomes possible.
One of the 7 Strategies for Engineered Negligible Senescence (SENS) is the introduction of replacement cells. I think the category should be worded a bit more broadly since we have parts that are not even cells (e.g. heart valves). Also, while some of those replacement parts will be delivered as cell types injected into the body for many organ failure problems we will need to grow replacement organs. That requires the development of an additional set of capabilities for doing tissue engineering to create three dimensional structures. This latest result is a very helpful step in that direction.
Muscle cells are one of the types of cells that have lost the ability to divide. Biologists call such cells post-mitotic because normal cell division is called mitosis. Knock out of the p38 gene in rats and mice allows muscle cells to divide.
It has long been believed that after initial development, the heart muscle cells can no longer proliferate. The new findings demonstrate that by eliminating a brake that halts the division of the muscle cells, researchers can then trigger the proliferation of the cells by adding specific cardiac growth factors.
The researchers will publish their findings in the May 15, 2005, issue of the journal Genes & Development. The paper was published online on May 3.
The research team was led by Howard Hughes Medical Institute investigator Mark T. Keating at Children's Hospital Boston and Harvard Medical School. Keating and his colleagues collaborated with researchers from the University of California, Los Angeles and Boehringer Ingelheim Pharmaceuticals in Ridgefield, Conn.
“There has been a longstanding controversy going back more than a hundred years about whether cardiomyocytes (cardiac muscle cells) in adult mammals have the capacity to proliferate,” said Keating. “While there have been occasional studies indicating this possibility, the dogma has been that they can't.” According to Keating, researchers thought that once an animal's heart has fully developed, cardiomyocytes lose the molecular plasticity that allows them to divide.
Whenever you read a scientist claim that some cell type X can't be made to do something that another cell type Y can do translate that statement into "We do not yet know how to make cell type X act like cell type Y". Cells in your body are like different computers running the same computer program. The different copies of the computer program may be in different states. But it is inevitable that ways will be found to get cells in one state to change into the state that another cell type uses. This wil be achieved for just about any pairs of cell types that exist in the body (exceptions being red blood cells that have lost their DNA and egg and sperm cells that no longer have full copies of their DNA).
The researchers accomplished their feat by knocking out a gene in rat cells for a protein called p38.
In their studies, Keating and his colleagues explored whether an enzyme called p38 acted as a brake on proliferation of adult cardiomyocytes. Although p38 is known to be involved in regulating cell division, very little is understood about its possible role in cardiomyocytes, said Keating.
In their experiments, the researchers explored whether knocking out p38 activity in cultures of rat cardiomyocytes could induce proliferation. The researchers found that knocking out p38 in the cell cultures of both infant and adult rats — in the presence of a cardiomyocyte growth factor protein called FGF1 — induced DNA synthesis, an important component in cell proliferation.
They also found other indications that the p38-knockout cells were undergoing mitotic proliferation. For example, they found that the proliferating cells dedifferentiated, meaning they temporarily lost the characteristics of mature heart muscle cells and reverted to a more fetal type of proliferating cell. Additional genetic studies of p38 inhibition showed that it regulates genes thought to be critical for cardiomyocyte proliferation.
Importantly, they found that the cardiomyocytes lacking p38 activity could continue to proliferate through many rounds of cell division in the presence of FGF1. “The fact that we could show that were multiple rounds of division is important, because clinical regeneration of cardiac muscle would require the cells to divide again and again,” said Keating.
We wouldn't want to have p38 permanently knocked out in our heart muscle cells. The heart muscle cells might grow too much and possibly even become cancerous. Also, p38 might serve some other as yet undiscovered purposes. But this result demonstrates that the process by which cells become unable to divide (post-mitotic) is reversible.
The scientists also raised mice with the p38 gene knock-out.
“As a result of these experiments, we felt quite confident that we could induce cardiomyocytes to proliferate, at least in vitro,” said Keating. “However, an in vitro system is quite artificial, and there could be many reasons why it would not be relevant in vivo.” So, in further experiments in collaboration with co-author Yibin Wang and his colleagues at UCLA, the researchers tested whether a genetic knockout mouse lacking p38 would show evidence of cardiomyocyte proliferation. Those experiments did yield significant evidence for such proliferation, said Keating.
Keating says a drug that would temporarily knock out p38 activity might enable heart repair after a heart attack. If heart cells could temporarily be given the ability to divide they could grow replacements for lost cells.
“These findings represent the first step toward showing that drugs that eliminate p38 activity could reduce scar tissue formation and enhance cardiac regeneration after cardiac injury,” said Keating. The formation of scar tissue in damaged hearts is the major reason myocardial infarctions lead to subsequent abnormalities and compromised heart function, he said.
A drug aimed at knocking out p38 might also induce regular muscles to grow. But for an old person who has lost a lot of muscle cells throughout the body due to aging such a side effect might even be a benefit. But does p38 also prevent other types of cells from dividing? If a drug that suppresses p38 activity also caused, for example, nerve cells to divide then that would be a very problematic side effect.
Adult and embryonic stem cells are the other major alternatives being investigated for replacing lost heart muscle cells. But if existing muscle cells can be induced to divide they'd offer a few advantages. Most notably, they are already located where the replacement cells are needed. Also, as compared to adult stem cells their DNA might be in better shape because they haven't been dividing for decades collecting errors on each cell division. Though muscle cell DNA does accumulate damage.
We need complete understanding and mastery of the mechanisms which govern cell division both to replenish lost cells and also to cure cancer and other diseases which are caused by excessive cell division. This latest report provides yet another piece of the puzzle.
The Norwegian team used a micro-surgery technique to cut out a small section of the developing spinal cord within the chicken egg.
Human haematopoietic stem cells (hHSCs) from bone marrow were then implanted into the damaged area.
The eggs were incubated before the embryos were removed, and spinal cord slices containing human cells dissected out and analysed.
These neurons were found to be very functional and even have the ability to send signals to other neurons.
Senior researcher Joel C. Glover, of the Institute of Basic Medical Science at the University of Oslo, in Norway said, "We found that bone marrow stem cells did make neurons in the environment of the regenerating embryonic [chick] spinal cord."
There are a number of types of neurons. While the news reports on this study do not say what types of neurons were produced I'm going to guess that they were cholinergic. Parkinson's Disease sufferers need dopaminergic neurons. However, getting the bone marrow stem cells to turn into any kind of neuron is probably the bigger obstacle to get past than getting them to turn into a particular type of neuron. So this result is good news for Parkinson's sufferers.
The key to the success of this model lies in as-yet-unidentified compounds within the quickly developing "microenvironment" of the embryonic spinal cord, said Paul Sanberg, a professor of neurosurgery and director of the University of South Florida's Center for Aging and Brain Repair.
Sanberg, an expert in this kind of research, believes that if scientists can identify those compounds, they might then be able to use them as a kind of cellular fertilizer -- encouraging adult stem cells to generate into human neurons.
Sanberg also commented that since chicken eggs are used on a massive scale to make vaccines (notably influenza vaccine - and that method is too slow to handle deadly pandemics btw) that the infrastructure and considerable experience already exists for using chicken embryos to make suitable cell types for therapeutic purposes.
The ability to take an adult stem cell type and turn it into a differentiated cell type which it does not normally become is strongly suggestive that adult stem cells can be made quite pliable if only scientists can discover the right combinations and concentrations of growth factors to change them. I've always expected this to be the case. But the question has always been just how hard will the search turn out to be to discover the compounds and techniques for converting adult stem cells into a larger range of cell types? Perhaps experiments with chick embryos will provide the means to more rapidly discover how to change the differentiation state of adult stem cells.
While the use of human embryonic stem cells (hESCs) remains morally objectionable in some quarters it is important to note that the use of hESCs may still be a faster approach for the development of some forms of cell therapies. However, even if hESC research is slowed by political opposition it is my very strong expectation that for any therapy that can be developed using hESCs eventually a way will be found to provide an equivalent therapy using adult stem cells instead.
One other point is too often missed in the adult versus embryonic stem cell debate: A larger research effort (meaning more money) would accelerate either of these approaches. I wish as much effort would go into pushing for increased stem cell research funding (even if that funding would come with strings attached with regard to use of hESCs) as currently goes into arguing about hESC research. Lots of questions about stem cells can be answered with research into animal models and lots of progress can be made with adult stem cell research.
An Israeli research team at the Weizmann Institute of Science in Rehovot, Israel has discovered that tissues can be transplanted from organs in developing pig embryos to produce functioning organs in mice if the tissues are extracted from pig embryo organs during an optimal time window that is specific to each organ. (same article here)
Scientists at the Weizmann Institute of Science have determined distinct gestational time windows for the growth of transplanted pig embryonic liver, pancreas and lung precursor tissue into functioning organs in mice. These findings -- appearing this week in PNAS online Early Edition -- could help enhance the chances for successful implementation of embryonic pig tissue in the treatment of a wide spectrum of human diseases.
The study, led by Prof. Yair Reisner of the Institute's Immunology Department, involved the extraction of embryos from sows at various stages of pregnancy and implantation of organ-committed cell tissue into immunodeficient mice. His novel approach did not involve the growth of any tissue in culture. The analysis of embryonic-tissue at various gestational ages revealed a unique pattern of growth and differentiation for each organ.
The potential of embryonic pig tissues as a new source for organ transplantation in humans has been advocated for more than two decades. Transplant too early, however, and the risk is undifferentiated embryonic tissue that can develop into undesirable and possibly malignant tissue, a type of tumor known as "teratoma." Transplant too late and the risk is that the tissues will have reached the stage where they have been marked with certain identifiers that trigger rejection by the new host.
The study demonstrated that maximal liver growth and function were achieved at the earliest teratoma-free gestational age (four weeks). The growth and functional potential of the pancreas occurred later (six weeks) and its optimal transplant age limit was defined by a decline in the insulin- secreting capacity beyond 10 weeks gestational age. Development of mature lung tissue containing essential respiratory system elements was observed at a relatively late gestational age. The sequence of transplanted organ development paralleled that of normal embryonic development in which the liver and pancreas precede the lungs.
"Disappointing results in past transplantation trials may be explained, at least in part, by these results," explains Reisner. Early studies that attempted to cure diabetic patients by implantation of pig embryonic pancreas, made use of late gestation tissue which is now shown to be inferior compared to the optimal six weeks gestational time.
In previous studies, Reisner's group demonstrated that transplanted human and pig kidney embryonic tissue could grow into miniature, functioning human or pig kidneys inside a mouse. His novel approach was a matter of timing: gestational age proved to be the key to successful kidney growth from transplanted embryonic tissue.
Some pretty simple knowledge (the optimal time to take the cells from each organ) may make possible trans-species organ cell transplants (a.k.a. xenotransplantation).
Growing new organs in humans from embryonic pig tissues may be feasible, researchers report, but the cells need to come from specific stages of an embryo's development. Using pig tissue to replace human organs could help patients with diseases such as diabetes, Parkinson's disease, and liver failure, but researchers have so far faced a challenge of balance. On the one hand, stem cells taken from very early in an embryo's development tend to develop tumors after transplantation, whereas tissue from adult organs face rejection by the recipient's immune system. Taking cells from an embryonic organ soon after it has begun to form may strike the ideal balance. To investigate the best time to harvest embryonic cells, Yair Reisner and colleagues took embryonic pig tissue that had begun to form particular organs at various developmental stages and transplanted them into mice. The researchers studied three types of organs--liver, pancreas, and lung--and found unique growth patterns. Optimal time windows were clearly seen for each organ. The authors say these findings may help in part to explain the failure of previous transplantation trials of pancreatic islets in diabetic patients.
This research was sponsored by a American-Israeli tissue transplantation biotech company called Tissera.
Other labs are working on making pigs genetically more compatible with humans by transferring human genes into pigs in order to grow up organs that are highly compatible with humans. See my previous posts "Human Genes Put Into Pig Sperm"and "Genetically Engineering Pigs for Xenotransplantation" for some details. The promise of the genetic engineering approaches is that potentially fully grown organs could be transferred from pigs to humans. Such transfers of fully formed organs might require immunosuppressive drugs to make them compatible. Whereas the transfer of starter cells from early embryo proto-organs may provide greater immunocompatibility.
The obvious advantage of transferring fully formed organs is that they can be used to save people's lives in cases of acute organ failure. When the liver or another vital organ has stopped working entirely there is not enough time to transfer some cells and wait for those cells to grow up into a complete organ. Full sized organs are needed to deal with emergencies. However, in cases where an organ is failing slowly the ability to gradually grow a replacement alongside of it offers the potential for a more immunocompatible replacement.
My guess is that in the future both the use of starter cells to grow replacement organs in a human body and the transfer of fully grown xenotransplants will become commonly used treatments for organ failures. These treatments might even be used in a complementary fashion. Get an emergency full sized xenotransplant organ with immunosuppressive drugs to meet an immediate emergency need and then once the patient is stabilized and healthy transfer in some more immunologically compatible cells to grow yet another organ that will serve as the permanent replacement.
In the longer run it seems reasonable to expect the development of techniques that allow the growth of full sized immunologically compatible organs. Alternatively, full sized organs will be grown up and then immune system modification therapies will be developed that will be able to adjust an immune system to teach it that a transplant organ should be treated as native tissue.
Human embryonic stem cells (hESCs) have previously been converted into many different cell types including a number of nerve cell types. But until now no lab has been successful in converting hESCs into motor neurons. Motor neurons are the nerve cells that run down the spinal cord to send messages to muscle cells to cause muscles to contract. Your body won't motor around without motor neurons to order your muscles to push you along. Suffer from an injury that cuts your motor neurons in your spine and you'll find yourself desiring some replacement motor neurons about as soon as you regain consciousness and are apprised of you tragic predicament. Well, University of Wisconsin-Madison scientists Su-Chun Zhang and Xue-Jun Li have found a sequence of growth factors and other chemicals that can be allied to hESCs to turn them into motor neurons. (also found here)
MADISON - After years of trial and error, scientists have coaxed human embryonic stem cells to become spinal motor neurons, critical nervous system pathways that relay messages from the brain to the rest of the body.
The new findings, reported online today (Jan. 30, 2005) in the journal Nature Biotechnology by scientists from the University of Wisconsin-Madison, are important because they provide critical guideposts for scientists trying to repair damaged or diseased nervous systems.
Motor neurons transmit messages from the brain and spinal cord, dictating almost every movement in the body from the wiggling of a toe to the rolling of an eyeball. The new development could one day help victims of spinal-cord injuries, or pave the way for novel treatments of degenerative diseases such as amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. With healthy cells grown in the lab, scientists could, in theory, replace dying motor neurons to restore function and alleviate the symptoms of disease or injury.
Much sooner in the future, the advance will allow researchers to create motor neuron modeling systems to screen new drugs, says study leader Su-Chun Zhang, an assistant professor of anatomy and neurology in the Stem Cell Research Program at the Waisman Center at UW-Madison.
Scientists have long believed in the therapeutic promise of embryonic stem cells with their ability to replicate indefinitely and develop into any of the 220 different types of cells and tissues in the body.
But researchers have struggled to convert blank-slate embryonic stem cells into motor neurons, says Zhang. The goal proved elusive even in simpler vertebrates such as mice, whose embryonic stem cells have been available to scientists for decades.
There is a fairly small window in time during which developing embryo cells possess the capacity to turn into motor neurons.
One reason scientists have had difficulty making motor neurons, Zhang believes, may be that they are one of the earliest neural structures to emerge in a developing embryo. With the ticking clock of development in mind, Zhang and his team deduced that there is only a thin sliver of time - roughly the third and fourth week of human development - in which stem cells could be successfully prodded to transform themselves into spinal motor neurons.
I think it is inevitable that methods will be found to dedifferentiate (i.e. make less specialized or less committed to a single purpose) both adult stem cell types and fully specialized cell types (e.g. liver cells or skin fibroblast cells) to turn these cells back into less differentiated stem cells and even all the way back into embryonic stem cells. So for the production of motor neurons we will not always be limited to starting with embryonic stem cells to pass them through that 2 week window in early embryonic development during which embryonic stem cells can be converted into motor neurons. In fact, compounds that cause cellular dedifferentiation have already been found. I expect many more techniques for dediffentiating cells will be found.
Think of cells as enormously complex state machines. Currently it is much easier (though not easy in an absolute sense) to coax cells to switch from the embryonic state into other states. The reason for this is pretty obvious: Cells in the embryonic state must be capable of transitioning through a series of steps into all the other states (e.g. to the state that heart muscle cells are in or the state that liver cells are in or the state that insulin-secreting Pancreatic Isles of Langerham cells are in) because embryos develop to produce cells in all those states. They must have that capacity or else a full organism couldn't develop starting from an embryo. However, just because there are some cell state transitions that do not happen under normal conditions of development that doesn't mean that those transitions can't be made to happen with the right (and waiting to be discovered) sequences of hormones, growth factors, gene therapies, and other stimuli.
Just because some day we will have methods to turn non-embryonic cell types into all other cell types that does not mean that avoidance of the use of hESCs in developing therapies has no future cost in terms of the health of some fraction of the human population. There is a very real possibility that hESCs can be developed for some therapeutic uses faster than other cell types can be developed for all uses. My guess is that at least for some purposes hESCs will be ready to provide treatments faster than adult stem cell types can be coaxed to do the same. We will see more research results such as this paper offering the possibilty of a cell therapy treatment for which the development of alternative non-hESC based cell therapy treatments are a more distant prospect.
Zhang's group had to use precise timings of changes in the biochemical cocktails fed to the cells to produce the desired outcome.
In addition to the narrow time frame, it was also critical to expose the growing stem cells to an array of complex chemical cocktails. The cocktails constitute naturally secreted chemicals - a mix of growth factors and hormones - that provide the exact growing conditions needed to steer the cells down the correct developmental pathway. "You need to teach the [embryonic stem cells] to change step by step, where each step has different conditions and a strict window of time," says Zhang. "Otherwise, it just won't work."
To differentiate into a functional spinal motor neuron, the stem cells advanced through a series of mini-stages, each requiring a unique growing medium and precise timing. To start, the Wisconsin team generated neural stem cells from the embryonic stem cells. They then transformed the neural cells into progenitor cells of motor neurons, which in turn developed in a lab dish into spinal motor neuron cells.
Note that this group had to try many different compounds and timings to find a recipe that worked. Greater automation of lab equipment is accelerating and will continue to accelerate this kind of work by increasing the rate at which different chemical cocktails can be tried in searches for techniques to turn various cell types into other cell types. So I expect the rate of advance of stem cell research of all kinds to accelerate regardless of the likely outcomes of political debates about human embryonic stem cell research.
Bioengineering researchers at the University of California, San Diego have invented a process to help turn embryonic stem cells into the types of specialized cells being sought as possible treatments for dozens of human diseases and health conditions. Sangeeta Bhatia and Shu Chien, UCSD bioengineering professors, and Christopher J. Flaim, a bioengineering graduate student, described the cell-culture technique in a paper published in the February issue of Nature Methods, which became available online on Jan. 21.
It is very likely this technique would be useful in testing proteins for their ability to turn non-embryonic stem cells into other cell types as well.
To find out what would work they had to develop the means to automatically test many different combinations and concentrations of proteins.
“We kept the other factors constant and developed a miniaturized technique to precisely vary extracellular matrix proteins as a way to identify which combinations were optimal in producing differentiated cells from stem cells,” said Bhatia. She, Chien, and Flaim described in their paper a technique that enabled them to identify the precise mix of proteins that optimally prompted mouse embryonic stem cells to begin the differentiation process into liver cells. Bhatia, Chien, and Flaim designed the technique with other cell biologists in mind so that any of them could duplicate it with off-the-shelf chemicals and standardized laboratory machinery. “We think other researchers could easily use this technique with any other tissue in mouse, or human, or any other species,” said Bhatia.
They adopted an existing machine that delivers tiny volumes of DNA and made it deliver protein instead.
In their experiments, the UCSD researchers took advantage of the knowledge that the extracellular matrix in liver is comprised primarily of just five proteins. They applied spots of all 32 possible combinations of the five proteins as engineered niches onto the surface of gel-coated slides, and then added mouse embryonic stem cells to the niches. After the cells were allowed to grow, the researchers assayed their progression into liver cells. “We looked at all the combinations at once,” said Bhatia. “Nobody has done this combinatorial approach before.”
Bhatia, Chien, and Flaim reported that either collagen-1 or fibronectin had strongly positive effects on the differentiation of the stem cells they tested. Unexpectedly however, when both collagen-1 and fibronectin were combined in one niche, the liver cell differentiation process was subtly inhibited. “You would not predict that from the customary cell biology experiments,” said Bhatia. “By using this combinatorial technique we were surprised to find many interesting interactions, and we were able to tease out the effects of each protein, alone and in combination with others.”
Cell biologists have not performed such combinatorial assays for other desired cell types because they had no practical way to do so. Bhatia, Chien, and Flaim seized on the unique ability of so-called DNA spotting machines to deliver tiny volumes of liquid, about one trillionth of a liter per spot. The spotting machines, which cost about $20,000, have become common fixtures at most research universities, but the innovation reported today in Nature Methods involved using such a machine to spot solutions of proteins rather than DNA. The UCSD researchers also refined other parameters so that the technique would be reproducible in other research laboratories.
The more important story here is not the discovery of particular protein combinations that make stem cells differentiate into liver cells. What will be more valuable in the longer run is the ability to apply their technique to more combinations of proteins to convert embryonic and other cell types into various desired cell types. With better tools the rate of progress can accelerate by orders of magnitude. This is yet another example of the general trend toward the development of techniques that are accelerating the rate of advance of biomedical research.
Here is a stem cell therapy, just now entering practical clinical use, that is great because illustrates the future of medicine: it fixes the underlying problem. Make the problem stop happening. A person's own cells extracted from muscle can strengthen bladder muscles and cure incontinence.
CHICAGO - Austrian researchers are successfully treating incontinent women with the patient's own muscle-derived stem cells. The findings of the first clinical study of its kind were presented today at the annual meeting of the Radiological Society of North America (RSNA).
"Urinary incontinence is a major problem for women, and for an increasing number of men," said Ferdinand Frauscher, M.D., associate professor of radiology at the Medical University of Innsbruck and the head of uroradiology at University Hospital. "We believe we have developed a long-lasting and effective treatment that is especially promising because it is generated from the patient's own body."
The stem cells are removed from a patient's arm, cultured in a lab for six weeks, and then injected into the wall of the urethra and into the sphincter muscle. The result is increased muscle mass and contractility of the sphincter and a thicker urethra. Many patients have no urinary leakage within 24 hours after the 15- to 20-minute outpatient procedure.
Stress incontinence affects nearly 15 million people — primarily women — around the world. It occurs when the urethra narrows or becomes otherwise abnormal, or when the sphincter muscles that help open and close the urethra become weak or diminished, causing urine leakage when an individual exercises, coughs, sneezes, laughs or lifts heavy objects.
Twenty females, ages 36 to 84, who were experiencing minor to severe stress incontinence participated in the research. Muscle-derived stem cells were removed from each patient's arm and cultured, or grown, using a patented technique that yielded 50 million new muscle cells (myoblasts) and 50 million connective tissue cells (fibroblasts) after six weeks. When implanted into the patient under general or local anesthetia, the new stem cells began to replicate the existing cells nearby. One year after the procedure, 18 of the study's 20 patients remain continent.
"These are very intelligent cells," Dr. Frauscher said. "Not only do they stay where they are injected, but also they quickly form new muscle tissue and when the muscle mass reaches the appropriate size, the cell growth ceases automatically."
Since the stem cells must be in contact with urethra and sphincter tissue for the procedure to work, a major factor in the success of this treatment was the development of transurethral three-dimensional ultrasound. "With real-time ultrasound, we are able to see exactly where the new cells must be placed," Dr. Frauscher said.
This treatment is a far greater economic value because it is of similar cost to existing treatments but works better because it actually fixes the cause of the problem.
Dr. Frauscher said the cost of the stem cell procedure was comparable to two popular treatments for incontinence: the long-term purchase and use of absorbents, such as adult diapers, and collagen injections, which show improvement during the first six months but often result in symptoms returning after a year. Dr. Frauscher also said the stem cell treatment appears to be more successful with women at this time. For men, incontinence is often caused by prostate surgery, which may result in scar tissue formation, where the stem cells do not grow very well. In men without scar tissue stem cell therapy seems to work as well as in women, Dr. Frauscher said.
Think about the economic value of stem cell treatments. Our problem in the United States isn't that we spend $1.6 trillion (as of 2002 - surely higher now) per year on medical care. Our problem is that so much of that care does not really fix the underlying causes of various medical conditions. Imagine medical treatments were capable of fixing everything that breaks just as auto mechanics can fix cars. Imagine you could therefore live in perfect health. Then I for one would not complain if that takes 15+% of the GDP.
Curiously, the one woman who gained no benefit from the procedure was 84 years old. One plausible explanation for the failure in her case is that her muscle stem cells are too old to form vigorous muscle cells.
The team is currently treating eight to 10 women per week and long waiting lists are building up.
Frauscher, head of uroradiology at University Hospital in Innsbruck, Austria, said his team has plans to start using this technique at other centers. "Next year we will start in three centers in Austria, two in Germany, one in Switzerland and one in the Netherlands," he said. "We are also planning to perform this in the USA."
The needed cells were extracted from the muscle cells and grown up by a company called InnovaCell. They claim to use some patented processes to accomplish this.
What I find great about this report is that it shows that stem cell therapies that really fix what is wrong are moving into regular clinical practice. Stem cell therapies are not some distant prospect. They are happening now and every year that goes by from here on out we will have more stem cell therapies that successfully treat more diseases and disorders.
The tricked eggs divide for four or five days until they reach 50 to 100 cells – the blastocyst stage. These blastocysts should in theory yield stem cells, but because they are parthenogenetic – produced from the egg only – they cannot be viewed as a potential human life, says Karl Swann of the University of Wales College of Medicine in Cardiff, UK.
An enzyme which is normally present in sperm and involved in fertilization was isolated and applied to eggs with no sperm in sight.
Swann’s team tricked the eggs into dividing by injecting phospholipase C-zeta (PLC-zeta), an enzyme produced by sperm that Swann discovered two years ago with Cardiff colleague Tony Lai.
It sounds like Swann's group is repeating with human eggs a process he already demonstrated with mouse eggs a couple of years ago.
This brings up a question I raised in the context of possibly being able to some day isolate pluripotent stem cells from the blood of pregnant women: Will religiously motivated opponents of human embryonic stem cell research (hESC) find this latest technique to be an objectionable way to get cells to use to study embryo development or to induce cells to become organs? After all, there is no fertilization by a sperm (and, as we all know, Every Sperm is Sacred) to trigger the hypothesized moment of ensoulment. So are these cells ethically acceptable for stem cell research?
Biological scientists are going to continue to come up with new ways of manipulating cells that make them hard to place into traditional categories based on their origins. Either the religious folks are going to adopt a definition of human life as beginning at conception or they are going to have to define a cell as the beginning point of life by use of a still-to-be-elucidated statement of epigenetic state of an embryonic cell. If they go the latter route they are going to have to wait till science advances far enough that it can describe the epigenetic state (which will likely be a range of states) that can come into existence right after fertilization and then apply that definition to all other cells that have one of those states regardless of how it got there.
A new study finds surgery to transplant an ovary to the upper arm is feasible and preserves hormonal function in women undergoing treatment for cervical cancer. The report details the technical procedure and outcome of only the second successful human ovarian autotransplantation in the world. The study will be published in the December 15, 2004 issue of CANCER, a peer-reviewed journal of the American Cancer Society. A free abstract of this study will be available via the CANCER News Room upon online publication.
While treatment for cervical cancer, including systemic chemotherapy and regional administration of ionizing radiation, improves survival and cure rates, it can also cause permanent ovarian failure. Since cervical cancer is diagnosed during reproductive years, ovarian failure can be a severe blow to a patient's quality of life. While protecting a patient's fertility has often been studied, there have been no effective options.
Hormonal regulators, such as gonadotropin-releasing hormone, have demonstrated ovarian protection in rats but conflicting data in nonhuman primates. Cryopreservation of embryos has been successful, but there have been no reported successful cryopreservation and transplantation of oocytes or primordial follicles, which are necessary for future fertility. Attempts at ovarian tissue autograft or xenograft without blood vessel anastamoses in animal models and human cases have been promising but hampered by large follicle loss due to ischemia. However, animal models with anastamoses have demonstrated success, but there has been only one prior successful human autotransplant.
In this second successful human trial, C. Hilders, M.D., Ph.D., and a gynecologic surgical team of the Leiden University Hospital, The Netherlands developed a new method of ovarian autotransplantation to preserve ovarian function in a woman treated for cervical cancer. This method does not require developing a donor site with an implant over several months and utilizes a donor site that is easily accessible to noninvasive monitoring and has suitable vasculature.
Autotransplantation of a healthy ovary into the upper arm using brachial vessels to establish blood supply resulted in a functional ovary. Blood flow to and from the ovary was adequate to maintain cyclical follicular growth as verified by ultrasound and clinical examination. Moreover, the surgery did not result in additional operating time.
The authors conclude, "it seems likely that ovarian autotransplantation will be a realistic goal to achieve for women facing cancer, treated by high dose pelvic radiation, to preserve reproductive and hormonal function, thereby substantially improving the quality of life post-treatment."
Note that this is a case of autotransplantation, meaning transplantation between locations in the same body. However, the approach taken here opens up the possibility of temporary transplantation of ovaries between people as well. One can imagine a woman with cervical cancer asking all her friends to volunteer for tissue type compatibility testing so that one of them can keep an ovary alive for her during some more severe form of cancer treatment where the use of chemotherapy would pose a hazard to the ovary even if the organ was placed on the woman's own arm.
But ovary transplants onto arms is still mighty inconvenient and obviously a temporary measure. Another future possibility is that cryopreservation techniques might be improved enough to make cryopreservation a viable option. Cryopreservation would be useful as a way to allow a woman to more reliably reproduce in her late 30s, 40s, and even later ages. Take just one ovary out of a woman when she is, say, 20 years old, cryopreseve it for 20 years, and then transplant it back into the woman to serve as a much younger ovary. This might not only raise the fertility of middle aged women but might also reduce the rate of birth defects for women who reproduce later in life since a cryopreserved ovary would presumably produce a younger egg that would be less likely to contain genetic mutational damage.
Since growth of replacement ovaries will most likely become feasible in two or three decades the long term cryopreservation of ovaries is likely at most to be a transitional technique. Better to just grow a new pair of ovaries for a woman in her late 30s and throw in some genetic engineering to remove a few harmful genetic variations that she doesn't want to pass on to her kids along with adding a few genetic variations that she does want to pass along (e.g. I predict natural blondness will be incredibly popular).
However, there is another potential use of organ cryopreservation: provide a supply of key organs in event of traumatic injury. Combine the ability to grow replacement organs with the ability to freeze them. Anyone with enough money and fear of death from injury could have organs grown from their own starter cells to ensure immunocompatibility Then in event of an injury an organ could be thawed and transplanted to supply a heart, liver, or other needed replacement part.
Even cryopreservation for emergency replacement organs is likely to be a transitional technology at most. If immuno-suppressive techniques improve enough then it will not be necessary to store emergency replacement organs for each individual. If each replacement organ can be made compatible with a large range of people then a much smaller stock of recently grown organs could be constantly replenished to provide replacements to the small subset of the population that needs them. In that scenario organs there would still be a place for organs that are grown for individuals since people will want to replace organs as they age as part of a regular maintenance regime of rejuvenation therapies.
My guess is that by the time tissue engineering techniques have advanced far enough to make routine growth of replacement organs possible immunosuppression techniques will allow a fairly small stocks of organs to serve as the sources of emergency replacement organs. If there is a cost in terms of general suppressed immune response for such an approach then the emergency organs will be used to keep a patient alive until a custom and fully immune compatible organ can be grown up to provide a more compatible replacement for the temporary and less compatible organ.
There is of course one other option worth mentioning: artificial organs. Artificial heart technology is maturing with a number of promising products under development. The CardioWest Temporary Total Artificial Heart won US FDA approval in October 2004.
The CardioWest Temporary Total Artificial Heart (TAH) on Monday became the only device of its kind to be approved by the U.S. Food and Drug Administration.
"This takes the CardioWest TAH off of the Medicare 'experimental list,'" said University of Arizona cardiothoracic surgeon Dr. Jack G. Copeland, who led the study of the device. "It's a huge relief to know that 19 years of work with the device has been officially recognized and that a technology that we believed in has now been released for use by others."
The CardioWest TAH is not being pitched as a permanent solution but rather a tool to use to strengthen a body so that eventual donor heart transplantation has better odds of success.
Then there are cyborg-like bioartificial organs that blend artificial parts with human cells. A bioartificial kidney has recently been tested successfully at the University of Michigan.
ANN ARBOR, Mich. -- The first test in humans of a bioartificial kidney offers hope of the device's potential to save the lives of people with acute renal failure, researchers at the University of Michigan Health System report.
While the phase I/II study was designed primarily to look at the safety of using this device on humans, the results also suggest improvement in kidney function. The patients enrolled in the trial faced an average 86 percent likelihood of dying at the hospital. Six of those 10 patients survived more than 30 days after treatment with the bioartificial kidney. The study appears in the October issue of the journal Kidney International.
"These results showed this type of human adult progenitor/stem cell is well-tolerated by patients with acute renal failure, and resulted in some improvement of the patients' clinical conditions. It's a small study but it was compelling enough for us and the FDA to go forward with a full phase II study," says lead study author H. David Humes, M.D., professor of Internal Medicine at the U-M Medical School. Humes developed the renal tubule assist device, or RAD, the cell cartridge that is key to the bioartificial kidney.
The RAD is being developed for future commercial applications under license to Nephros Therapeutics Inc.
The bioartificial kidney includes a cartridge that filters the blood as in traditional kidney dialysis. That cartridge is connected to a renal tubule assist device, which is made of hollow fibers lined with a type of kidney cell called renal proximal tubule cells. These cells are intended to reclaim vital electrolytes, salt, glucose and water, as well as control production of immune system molecules called cytokines, which the body needs to fight infection.
Conventional kidney dialysis machines remove these important components of blood plasma, along with toxic waste products, and cannot provide the cytokine regulation function of living cells. Traditional therapy for patients with acute or chronic renal failure involves dialysis or kidney transplant, both of which have limitations.
While this device operates outside of the body its developers hope to eventually miniaturize it to allow implantation in the body for long term use.
There is a general thread running through all these reports and speculations: organs are going to become as manipulable and replaceable as auto car parts. The sooner this happens the better.
Master cells nestled within hair follicles of the skin retain the ability to form new hairs as well as skin, new research reported in the September 3 issue of Cell confirms. While earlier work had suggested the presence of stem cells in skin, the new study by Howard Hughes Medical Institute investigators at Rockefeller University in New York provides the first direct evidence that cells extracted from the hair follicles of mice exhibit all of the defining features of true stem cells. The skin stem cells offer potential new methods to reverse baldness and boost wound healing in burn victims and those suffering from other skin injuries, the researchers said.
The putative skin stem cells reproduce themselves seemingly indefinitely in the laboratory, the study found. When engrafted onto the backs of hairless mice, the cells also formed stretches of skin, tufts of hair, and sebaceous glands, which secrete an oily substance known as sebum that lubricates skin and hair.
"We've identified cells within skin that bear all the characteristics of true stem cells--the ability for self renewal and the multipotency required to differentiate into all lineages of epidermis and hair," said Elaine Fuchs, cell biologist at Rockefeller University and senior author of the study. "The results demonstrate for the first time that individual cells isolated from hair follicles can be cultured in the laboratory and retain a capacity to make multiple cell types when grafted."
“An important aspect of this paper was that we found we could isolate and characterize these cells by taking advantage of the cell-surface markers that we had previously identified from molecular profiling experiments,” said Fuchs. “We can now utilize similar methods to begin to compare mouse and human skin stem cells.”
The scientists' analyses of the biochemical characteristics of the isolated mouse stem cells revealed that the bulge contained two distinct populations of stem cells. One type, called “basal” cells, is active during early development. In contrast the “suprabasal” cells appear only after the first hair generation cycle. This distinction offers biologists an opportunity to compare the two groups of cells, in terms of the control that the bulge exerts over their proliferation and differentiation.
The two stem cell types appear at different stages of development.
According to Fuchs, previous studies in her laboratory and others suggested that a structure called the bulge, which is located within each hair follicle, might contain stem cells. Those studies hinted that the stem cells might provide the source of both new skin and hair follicles.
The scientists' analyses of the biochemical characteristics of the isolated mouse stem cells revealed that the bulge contained two distinct populations of stem cells. One type, called “basal” cells, is active during early development. In contrast the “suprabasal” cells appear only after the first hair generation cycle. This distinction offers biologists an opportunity to compare the two groups of cells, in terms of the control that the bulge exerts over their proliferation and differentiation.
Both isolated stem cell types can be used to grow hair.
Despite the fact that the stem cells expressed many different genes, both populations were capable of self-renewal when grown in culture, said Fuchs. The researchers also found that both types of cells — even after being cultured — produced hair follicles when grafted onto the skin of a strain of hairless mice.
“I think clinicians will be interested in the fact that both of these populations can produce hair follicles after culture,” said Fuchs. “Previously, researchers have done similar transplant experiments with dissected parts of the hair follicle. And, while they've had evidence that hair follicle structures were forming, they didn't see generation of hair.
“In contrast, in our experiments, we saw quite a density of hairs, in some cases at a density that's very similar to that of normal mouse fur,” said Fuchs. “While we are not yet able to achieve such density a hundred percent of the time, the fact that we do get such density in some cases tells us that the system is working well. We just need to tweak it to the point where we can get such results consistently,” she said.
Imagine this process repeated using human hair follicles to isolate human follicle stem cells. Those stem cells could be grown up and used to get hair growing again on bald scalps. One can also imagine a modified variation of this approach being used to develop cells that can restore hair color in aged hair follicles.
This is not the first result along these lines. See: Transplanted Stem Cells Grow Hair In Mice. However, the latest result goes further in locating, categorizing, and characterizing the stem cells found in hair follicles.
Diana W. Bianchi, M.D. of the Tufts University Sackle School of Graduate Biomedical Research has found that cells from fetuses during pregnancy cross over into mothers and become a large assortment of types of specialized cells in the mothers and persist for years.
Bianchi and her colleagues retrieved cells from the tissue samples of 10 women who had male sons and compared them to tissue samples from 11 women who had never had male offspring. The reason the researchers chose women with male offspring is that it would be easy to detect cells from male offspring because male cells carry the Y chromosome, while female cells do not.
The tissue samples were from the thyroid, cervix, liver, lymph node, intestine, spleen and gallbladder. Skin samples were also collected from 11 women in a control group.
Bianchi said that not only did they find fetal cells present in the mothers' tissue samples, but that the fetal cells had taken on the characteristics of the mother's cells.
This result is very important for the stem cell debate. (same article here)
The findings could also affect the national debate over stem cells, she said, in that they raise the possibility of obtaining stem cells, which can change into many tissues of the body, without the ethical issues involved in creating or destroying human embryos. President Bush has sharply restricted federal funding for research on human embryonic stem cells to keep the government from supporting research that he believes destroys human life.
Likewise, the author of the Tufts study, Dr. Diana Bianchi, said another potential source of stem cells is women who have been pregnant.
"Studies have virtually ignored the role of pregnancy, but women who have been pregnant potentially have cells with therapeutic potential from their fetus," she said.
It is possible that many years after a pregnancy there are no longer cells in the mother's body that are fetal and capable of becoming all cell types. But a better point at which to try to catch fetal cells from the blood stream of women would be while they are still pregnant or perhaps shortly after giving birth. If fully pluripotent stem cells can be isolated from the blood of pregnant women then this may well provide a source for such cells that will not raise religious hackles.
Back in 1996 Bianchi first found fetal cells in mothers. But those cells were blood cells only. Her finding that fetal cells are becoming other cell types strongly suggests that fetal cells that are fairly undifferentiated are crossing over into women from fetuses and then differentiating (specializing) into various adult cell types. If those fetal cells that are crossing over are capable of converting into a large variety of specialized cell types then they are quite possibly the equivalent of pluripotent embryonic stem cells.
A confirmation of this result poses what seems to me an ethical problem for the religious opponents of embryonic stem cell research. If developing embryos effectively are donating human embryonic stem cells (hESC) to mothers and literally doing cell therapy to mothers then this natural process is doing something that at least some hESC therapy opponents consider to be morally repugnant.
It will be interesting to see where the various hESC research opponents come down on this result. Will they oppose the extraction of embryonic stem cells from a mother's blood while she is pregnant. If so, on what moral basis?
My guess is that a large fraction of the hESC research opponents will decide that extraction of hESC from a mother's blood is morally acceptable. No fetus will be killed by the extraction. The cells so extracted are not cells that would go on to become a complete new human life. If a sizable portion of the religious hESC opponents can be satisfied by this approach for acquiring hESC then Bianchi's research may well lead to a method to get hESC that will open the gates to a much larger effort to develop therapies based on hESC.
Working with freshly extracted human third molars (wisdom teeth) scientists have been able to isolate stem cells that can turn into the ligament that hold teeth into place.
Scientists at the National Institute of Dental and Craniofacial Research (NIDCR), one of the National Institutes of Health, and their colleagues have isolated human postnatal stem cells for the first time directly from the periodontal ligament, the fibrous, net-like tendon that holds our teeth in their sockets.
The scientists also say these cells have "tremendous potential" to regenerate the periodontal ligament, a common target of advanced gum (periodontal) disease. This enthusiasm is based on follow up experiments, in which the researchers implanted the human adult stem cells into rodents, and most of the cells differentiated into a mixture of periodontal ligament — including the specific fiber bundles that attach tooth to bone — and the mineralized tissue called cementum that covers the roots of our teeth.
"The stem cells produced beautifully dense, regenerated tissue in the animals," said Dr. Songtao Shi, a senior author on the paper and an NIDCR scientist. "That was when we knew they had great potential one day as a treatment for periodontal disease, and we're continuing to follow up on this promise with additional animal work." The results are published in the current issue of The Lancet.
The isolated cells were able to form periodontal ligament.
After further validation of their findings, Shi said he and his colleagues decided to pursue the next big question: Could these stem cells actually form periodontal ligament and cementum when transplanted into mice?
Of the 13 transplants — each of which was derived from a distinct colony of stem cells cultured in the laboratory and loaded into a hydroxyapetite carrier — eight produced a dense mixture of cementum and periodontal ligament. Interestingly, the cells even produced fibrous structures similar to the so-called Sharpey's fibers, which insert into both cementum and bone to hold teeth in place. The other five transplants showed no signs of differentiation.
Shi said his group is now following up on this finding in larger animals. If successful, Shi said he would be eager to evaluate their regenerative ability in people with advanced periodontal disease, which can be extremely difficult to control with current treatments.
My guess is they want to extract similar cells from large non-human animals because for ethical and practical reasons it is easier to do most of the work toward developing therapies using animals before attempting trials in humans.
While the press release has just been released to announce the publishing of the results in Lancet it appears this work was done last year, a patent has already been filed on it, and the final confirming step involved putting the human cells into immunicompromised mice to form the specialized ligament cells.
The NIH announces a new technology wherein stem cells from the PDL have been isolated from adult human PDL. These cells are capable of forming cementum and PDL in immunocompromised mice. In cell culture, PDL stem cells differentiate into collagen fiber forming cells (fibroblasts), cementoblasts, and adipocytes. It is anticipated that these PDL stem cells will be useful for periodontal tissue regeneration to treat periodontal disease.
It is hard to guess when this work will translate into wide availability of human treatments. But the consensus of German stem cell researchers is that some stem cell therapies will be available within 10 years.
My guess is that there are many more sources of adult stem cells hiding in various locations of the human body waiting to be found. Expect to read many more reports of discoveries of types of adult stem cells. Each such discovery is helpful not just as a potential starting source of cells for cell thearpies but also to compare to other cell types to develop a better understanding of how cells differentiate. The more cell types scientists have to compare the better they will be able to figure out how cells control their cell types and how to intervene to alter cell types for therapeutic purposes.
Helmut Drexler of University of Freiburg, Germany and his colleagues treated sufferers of acute myocardial infarctions (i.e. heart attacks) with bone marrow stem cells and found that the bone marrow stem cells boosted the volume of blood pumped by the left ventricle of the heart.
60 patients who had undergone successful percutaneous coronary intervention (PCI; balloon angioplasty and coronary stenting) to restore coronary artery bloodflow took part in the study. Half were given bone marrow stem-cell transfer 5 days after PCI, the other half were given optimum medical therapy. Patients who had been given stem-cell transfer had around a 7% improvement in left-ventricular function compared with only a 0.7% increase for patients given medical therapy.
But he added: "Larger trials are needed to address the effect of bone marrow cell transfer on clinical endpoints, such as the incidence of heart failure and survival."
While other studies have used adult stem cells to attempt to repair damaged hearts this is the first study done using adult stem cells and a proper control group of patients. (same article here)
"What makes this notable is it's the first controlled study where they actually have a control group," said Dr. Robert Bonow, chief of cardiology and professor of medicine at Northwestern University in Chicago and past president of the American Heart Association. "In previous studies, you didn't know whether the stem cells were responsible or if it was going to happen anyway."
Note that this research is being done in Germany. In the United States the US Food and Drug Administration (FDA) is throwing up roadblocks even for adult stem cell therapy. The FDA's stance has nothing to do with the debate about embryonic stem cells. Rather, it is part of the FDA's never-ending quest to protect people with fatal diseases from the risk that experimental therapies might harm them. In my view people with fatal diseases ought to be allowed to try experimental therapies and the FDA's position both slows the rate at which treatments are developed and unjustifiably takes away the individual's right to choose which treatment risks are worth taking.
Better Humans reports on research by Siddharthan Chandran of the University of Cambridge, UK Cambridge Centre for Brain Repair on the use of a mix of growth factors to successfully turn skin cells into neural stem cells.
This resulted in large numbers of nestin-positive neural precursors.
"The generation of almost limitless numbers of neural precursors from a readily accessible, autologous adult human source provides a platform for further experimental studies and has potential therapeutic implications," say the researchers.
The presence of nestin protein is generally seen as an indicator that a cell type has become a neural stem cell. But that indicator alone is not a certain measure of success. Other cases of seeming success with stem cell transformation have been thrown into question with the use of more sensitive means of measuring cell state (though if you click thru on that you will see even in that case the more sensitive means did not absolutely disprove the original result because cell culture media vary too much in composition in unknown and uncontrollable ways between lots). However, Chandran's team may really have succeeded in doing what they have reported.
My take on all this is that what Chandran is trying to do is at least theoretically possible. One does not always have to start with embryonic stem cells to get cells to differentiate (specialize) into any desired type. Systematic searches for compounds that turn more specialized cells into less specialized cells have turned up promising compounds for making stem cells from fully differentiated adult cells. Expect to see many more such reports.
Diane Krause and colleagues at Yale report that bone marrow stem cells can differentiate into epithelial cells. (which are found in skin and on the surface of inner body cavities)
New Haven, Conn. -- Epithelial cells derived from bone marrow cells can be a result of differentiation, not fusion, according to a study published in Science by Yale researchers who arrived at some of the earliest findings on non-blood cells derived from bone marrow.
Led by Diane Krause, associate professor of Laboratory Medicine and Pathology at Yale School of Medicine, the investigators transplanted marrow-derived cells from male mice into female mice. They followed the fate of the marrow-derived cells (male) by detecting the Y chromosome. If resulting epithelial cells were formed by cell-to-cell fusion, they should express green fluorescent protein (GFP) and not beta-galactosidase.
"Our results show that under normal circumstances, the green fluorescent protein was not expressed, which means that no fusion has occurred and that the marrow derived cells can become non-blood cells without fusing," said Krause, attending physician in Laboratory Medicine at Yale-New Haven Hospital.
Krause said they did find that when the tissues were damaged, there were some cells that expressed GFP and therefore were derived from donor cells fusing with recipient cells.
Several years ago Krause's laboratory published a study showing that bone marrow stem cells can differentiate into liver, lung, kidney, skin, muscle and other cells. Later studies published by other researchers postulated that the bone marrow derived cells had actually fused with epithelial cells.
Krause said the ramifications of these latest findings are still unclear. "The absence of fusion in this model does not necessarily imply that trans-differentiation, a change in phenotype of one mature cell type to that of another mature cell type, has occurred," she said. "In fact, we carefully refrain from using that terminology in this report to avoid making assumptions about the mechanism of the phenotypic change."
She said it may be that an as-yet-unidentified, multipotent epithelial precursor exists in the bone marrow or that a separate population of marrow precursors exhibit a gene expression pattern that can be reprogrammed to express markers of other cell types.
This result is important because it restores some of the luster of adult stem cells that was lost when it was found that in at least some cases adult stem cells were providing benefits by fusing with existing cells. In 2003 some researchers reported that bone marrow hematopoietic stem cells were repairing livers by fusing with existing liver cells rather than by differentiation into liver cells.
The phenomenon of cell fusion between adult stem cells and other cell types has been demonstrated with heart, brain, and liver cells.
In a study that calls into question the plasticity of adult stem cells, Howard Hughes Medical Institute (HHMI) researchers and colleagues at the University of California, San Francisco, have demonstrated that adult bone marrow cells can fuse with brain, heart and liver cells in the body.
The phenomenon of fusion would give the appearance that bone marrow stem cells are altering themselves to become mature cells in other tissues, when in fact they are not, according to one of the study's senior authors, HHMI investigator Sean J. Morrison at the University of Michigan.
Note that the fusion does appear to provide benefits. If, say, you have a fatal liver disease and you can get better by having adult stem cells fuse instead of having the stem cells convert into liver cells are you going to turn down the treatment? Of course not. But the ability of adult stem cells to convert into various fully differentiated (specialized for particular functions) cells opens up the door for many more potential medical uses such as growth of replacement organs and replacement of lost cells such as happens with Parkinson's Disease and heart disease.
Krause's group is not the only team to recently report success at getting bone marrow stem cells to take on specialized liver cell functions without fusing with existing liver cells. A month ago a team at Johns Hopkins also reported success in using bone marrow stem cells to convert into liver cells without fusing with existing liver cells.
Bone marrow stem cells, when exposed to damaged liver tissue, can quickly convert into healthy liver cells and help repair the damaged organ, according to new research from the Johns Hopkins Kimmel Cancer Center.
There has been debate among the scientific community over whether these cells also can differentiate into other tissue types such as the liver, says Saul J. Sharkis, Ph.D., senior author of the study and a professor of oncology at the Johns Hopkins Kimmel Cancer Center. Some studies suggest that the bone marrow cells fuse with other types of cells, taking on those cells' properties. But in this study, the researchers found, through highly thorough analysis with a microscope and other tests, that the cells did not fuse, suggesting that "microenvironmental" cues from existing liver cells caused them to convert.
I've never viewed the obstacles to making adult stem cells more plastic (i.e. capable of changing into more cell types) as insurmountable. It is possible that it will be quicker to use embryonic stem cells for some purposes. But eventually techniques will be developed to allow adult stem cells to be converted into all cell types. As more adult stem cell sources are found in the body and as better techniques for growing them are discovered the range of potential target cell types that adult stem cells will be able to make will steadily increase.
My point here is not to argue for or against embryonic stem cell research. My point is that even a complete ban on human embryonic stem cell research will only delay the developmetn of cell therapies and organ growth methods. Granted, such a delay would result in human deaths that would otherwise would be avoided. But legal obstacles can be literally programmed around once our knowledge of genetic programming advances far enough and we have the ability to change the epigenetic programming of cells to whatever state we desire.
These kidneys grown inside the rats from transplanted were not perfect and only externded life for several days. However, one of the scientists likens this first successful attempt to grow kidneys in a mammal to the short first flight of the Wright brothers at Kitty Hawk.
St. Louis, June 21, 2004 -- Growing new organs to take the place of damaged or diseased ones is moving from science fiction to reality, according to researchers at Washington University School of Medicine in St. Louis.
Scientists have previously shown that embryonic tissue transplants can be used to grow new kidneys inside rats. In their latest study, though, they put the new kidneys to an unprecedented and critical test, removing the rat's original kidneys and placing the new kidneys in position to take over for them. The new kidneys were able to successfully sustain the rats for a short time.
"We want to figure out how to grow new kidneys in humans, and this is a very important first step," says Marc R. Hammerman, M.D., the Chromalloy Professor of Renal Diseases and leader of the study. "These rats lived seven to eight days after their original kidneys were removed, long enough for us to know that their new kidneys worked."
The study will appear in the July/August issue of Organogenesis, a new scientific journal. It is also available online.
Hammerman is a leader in the burgeoning field of organogenesis, which focuses on growing organs from stem cells and other embryonic cell clusters known as organ primordia. Unlike stem cells, organ primordia cannot develop into any cell type--they are locked into becoming a particular cell type or one of a set of cell types that make up an organ.
My guess is they are getting these organ primordia cells by letting an embryo develop further than the initial stem cell stage. Using human organ primorida cells would likely elicit much stronger ethical objections than using embryonic stem cells since the fetus would need to develop to a later stage before being aborted to use its tissue for this purpose. Still, even if this approach was not allowed in practice this research is still going to yield important information for other approaches.
"Growing a kidney is like trying to construct an airplane--you can't just make a single part like a propeller, you have to build several different parts and systems and get them all working together properly," Hammerman explains. "Fortunately, kidney primordia already know how to grow different parts and self-assemble into a kidney--we just have to give them the right cues and a little assistance at various points."
For the study, Hammerman and coauthor Sharon Rogers, research instructor in medicine, gave renal primordia transplants to 5- and 6-week-old rats. Prior to insertion, scientists soaked the transplant tissue in a solution that included several human growth factors, proteins and hormones. One of the rats' original kidneys was removed at the same time.
Three weeks after the transplant, researchers connected the new kidneys to the bladder and administered a second dose of growth factors.
Approximately five months after the transplants, scientists removed the remaining original kidney in control and experimental rats. To help resolve uncertainty about which kidney functions are critical to sustaining life, scientists cut the connections between the bladder and the new kidneys in a subset of the experimental rats.
Rats with no new kidneys lived for two to three days, and rats whose new kidneys were disconnected from their bladders lived no longer. However, the rats with new kidneys connected to their bladders lived seven to eight days.
"This tells us that the urine-producing functions of the kidney are key to preservation of life," says Rogers.
"Seven to eight days may not seem like a long time," adds Hammerman. "However, what we have done is akin to building the first airplane and showing that it can fly, if only for a few minutes. It's just as revolutionary."
Hammerman's goal of using pig cells to grow kidneys in humans would sidestep ethical opposition to the use of human stem cells and human embryos.
Hammerman, who is director of the Renal Division at the school's affiliate Barnes-Jewish Hospital, hopes to use animal-to-human transplants, known as xenotransplants, as a solution for chronic organ donation shortages.
"Every year, approximately 10,000 kidneys become available for transplant into patients with end-stage kidney disease," Hammerman says. "But the waiting lists for kidney transplants can run as high as 100,000 individuals, and most patients die of the disease before an organ becomes available."
Kidney function in pigs is similar to that in humans, and Hammerman's eventual goal is to use embryonic pig tissue transplants to help renal failure patients live longer.
Would Jews or Muslims who will not eat pork also object to having a pig kidney grown inside them?
The vascular system that grows for these embryonic kidneys appears to be partially or fully made from host cellls that serve as precursors for formation of blood vessels that then grow into the shape needed for the kidneys. That explains why the use of early stage transplants would avoid immune rejection via an attack on the vascular system. The vascular system is not foreign tissue even though the actual kidney cells are foreign.
Working with embryonic tissues that grow into organs inside the patient lets Hammerman avoid hyperacute and acute vascular rejection, two immune system responses that can destroy xenotransplants. In both of these responses, the body's immune system recognizes the blood vessels of transplanted tissue as foreign and attacks them.
"Those two types of rejection have so far made it impossible to xenotransplant fully grown kidneys," Hammerman explains. "However, we can avoid this by transplanting embryonic kidneys before blood vessels develop."
The primordia are small enough that survival can be maintained after transplantation through diffusion of oxygen and nutrients. The transplanted cells attract the growth of new blood vessels from the host as they grow into a mature organ.
This approach of using organ primordia cells may avoid the immune system rejection of the vascular system in the kidneys but will it avoid the immune system's eventual rejection of the pig kidney cells? If one could grow kidneys from one's own adult stem cells then the immune rejection problem could be avoided.
We really need a number of different organ growth capabilities. The ability to grow an organ ahead of time outside of the human that can be put into any body would allow replacement organs to be used in acute emergencies (e.g. after a bullet has shredded a heart). Such an organ would not necessarily have to be perfectly immune compatible. In an emergency immune suppression drugs could suppress the immune response while a more immuno-compatible replacement organ was grown.
This approach reported above both requires the host to grow the organ and may not yield a perfectly immune compatible organ. Still, artifiical kidneys have deficiencies that eventually result in death and with time we will have better techniques for coaxing a body's immune system to treat an organ as compatible. This approach might end up working for many puposes until a more ideal approach is developed.
Duke University researchers have demonstrated the ability to extract stromal cells from mouse fat tissue and convert it into nerve cells.
DURHAM, N.C. -- Two years after transforming human fat cells into what appeared to be nerve cells, a group led by Duke University Medical Center researchers has gone one step further by demonstrating that these new cells also appear to act like nerve cells.
The team said that the results of its latest experiments provide the most compelling scientific evidence to date that researchers will in the future be able to take cells from a practically limitless source -- fat -- and retrain them to differentiate along new developmental paths. These cells, they said, could then be used to possibly treat a number of human ailments of the central and peripheral nervous systems.
The results of the team's latest experiments were published June 1, 2004, in the journal Experimental Neurology.
Using a cocktail of growth factors and induction agents, the researchers transformed cells isolated from mouse fat, also known as adipose tissue, into two important nerve cell types: neurons and glial cells. Neurons carry electrical signals from cell to cell, while glial cells surround neurons like a sheath.
"We have demonstrated that within fat tissue there is a population of stromal cells that can differentiate into different types of cells with many of the characteristics of neuronal and glial cells," said Duke's Kristine Safford, first author of the paper. "These findings support more research into developing adipose tissue as a viable source for cellular-based therapies."
Over the past several years, Duke scientists have demonstrated the ability to reprogram these adipose-derived adult stromal cells into fat, cartilage and bone cells. All of these cells arise from mesenchymal, or connective tissue, parentage. However, the latest experiments have demonstrated that researchers can transform these cells from fat into a totally different lineage.
Earlier this year, Duke researchers demonstrated that these adipose-derived cells are truly adult stem cells. As a source of cells for treatment, adipose tissue is not only limitless, it does not carry the potentially charged ethical or political concerns as other stem cell sources, the researchers said.
"This is a big step to take undifferentiated cells that haven't committed to a particular future and redirect them to develop down a different path," said Duke surgeon Henry Rice, M.D., senior member of the research team. "Results such as these challenge the traditional dogma that once cells become a certain type of tissue they are locked into that destiny. While it appears that we have awakened a new pathway of development, the exact trigger for this change is still not known."
For their latest experiments, the researchers demonstrated that the newly transformed adipose cells expressed many similar cellular proteins as normal nerve and glial cells. Furthermore, they showed that the function of these cells is similar to nerves.
The problem of how to change differentiated cells (cells specialized to perform particular functions) into less differentiated cells is obviously very solvable. Differentiation of cells into specialized types is not a one way street. This should not be too surprising. Cells are made up of matter and matter is malleable. The arrangement of the cellular matter that determines cellular type (known as epigenetic information) is becoming steadily more malleable with each discovery of how to manipulate cells. Recently Scripps researchers found a compound they labelled reversine that converts differentiated cells into stem cells. They had to search through only 50,000 compounds to find one that would do that. Surely there are huge numbers of other compound waiting to be discovered that will dedifferentiate (i.e. despecialize) cells to turn them back into stem cells and even turn them all the way back into the equivalent of embryonic stem cells.
Embryonic stem cells may turn out to provide a starting point for therapy development that allows the more rapid development of some types cell therapies. But there is no treatment that can be developed from embryonic stem cells that won't also eventually be solvable using adult stem cells or fully adult differentiated cells as starting points. Of course, in the short term one can understand why those who have no moral qualms about using embryonic stem cells want to see them used to develop therapies. Embryonic stem cells may save some lives. But for those who will need cell therapy-based treatments in the medium to long term the debate about embryonic stem cell therapy will probably have no impact on the availability of treatments.
A combination therapy using transplanted cells plus two experimental drugs significantly improves function in paralyzed rats, a new study shows. The results suggest that a similar therapy may be useful in humans with spinal cord injury. The study was funded in part by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health, and appears in the June 2004 issue of Nature Medicine.*
About 10,000 people in the United States suffer spinal cord injuries each year. Studies in animals during the past decade have shown that supporting cells from nerves outside the brain and spinal cord, called Schwann cells, can be used to make a "bridge" across the damaged spinal cord that encourages nerve fibers to regrow. Other research has suggested that a substance called cyclic AMP (cyclic adenosine monophosphate) can turn on growth factor genes in nerve cells, stimulating growth and helping to overcome signals that normally inhibit regeneration. This study is the first to try a combination of the two approaches in an animal model of spinal cord injury.
In the new study, Mary Bartlett Bunge, Ph.D., Damien Pearse, Ph.D., and colleagues at the Miami Project to Cure Paralysis at the University of Miami School of Medicine, found that spinal cord injury triggers a loss of cAMP in the spinal cord and in some parts of the brain. They then transplanted Schwann cells into the spinal cords of rats in a way that bridged the damaged area. The researchers also gave the rats a form of cAMP and a drug called rolipram, which prevents cAMP from being broken down.
Treatment with the triple-combination therapy preserved and even elevated cAMP levels in nerve cells after injury. It also preserved many of the myelinated nerve fibers in treated animals, compared to untreated rats and those that did not receive the triple combination, the researchers found. Myelin is a fatty substance that insulates the nerve fibers and improves transmission of signals. The treated rats also grew back many more nerve fibers than untreated rats or rats that received only one or two of the therapies. The regenerated nerve fibers included many that carry the nerve-signaling chemical serotonin, which is important for locomotion.
Rats that received the triple therapy had much better locomotion and coordination 8 weeks after treatment than control rats.
"The behavioral improvements in the rats receiving the triple therapy are dramatically better than those reported previously using Schwann cell bridges or cAMP strategies in spinal cord-injured animals," says Naomi Kleitman, Ph.D., the NINDS program director for spinal cord injury research. Previous studies using Schwann cells found that nerve fibers from cells above the injury could travel onto the Schwann cell bridge, but they did not leave the bridge, she explains. The triple therapy "punches the cells into overdrive and helps them get off the bridge."
The therapies tested in this study were selected for their likely feasibility in humans, Dr. Kleitman adds. Rolipram has already been tested in clinical trials for other disorders, and Schwann cells can be grown from patients' own peripheral nerves.
The researchers are now planning follow-up studies to confirm their results and to try to learn more about how the triple therapy works, Dr. Bunge says. Their studies might also lead to the development of better drugs to prevent the breakdown of cAMP, she adds.
Humans are going to become so much more repairable in the future that we live at the tail end of what will be seen as the medical dark ages. You'll be able to tell your grandchildren "well, back when I was your age when people suffered peripheral nerve damage they just had to stay broken". The kids will think "how backward" and wonder how ever did people accept that nothing could be done to replace missing limbs or fix spinal cords. Of course humans should be as repairable as cars. It should be possible to grow replacement parts and to rebuild worn out components. Well, my guess is that most of us are going to live to see all that happen. Here above is another report of how more pieces of the puzzle are coming together and successes are happening in animal models. Human successes can't be too many years behind.
The Scientist has a report on a Delphi Study of German stem cell researchers about the prospects for stem cell treatments in the next 20 years. (requires free registration)
The survey contained a list of potential stem cell–based medical applications, and asked participants when they felt these might be successfully done. Within the next 6 to 10 years, a majority of participants believe stem cell-based applications will be used for treatment of diabetes mellitus, heart disease, and Parkinson disease.
In the next 11 to 15 years, they see treatments for multiple sclerosis and the damaged nerves of paraplegics. Slightly more half expect stem cell treatments for Alzheimer disease in the next 11 to 20 years, while 36% say more than 20 years and 10% say such treatments will never come.
Alzheimer's strikes me as more likely to be solved by vaccines aimed at beta amyloid proteins than by stem cell treatments. For the average person who doesn't have type I diabetes the estimates for heart disease and Parkinson's are more exciting. While most people realize they are at risk of heart disease what is perhaps less widely appreciated is that above the age of 75 more than 1 in 10 persons get Parkinson's Disease. Also, people generally become less coordinated with age due to nerve cell loss. A stem cell treatment for Parkinson's might also help improve coordination and perhaps even cognitive function among the aged.
Curiously, more researchers were optimistic about the future of treatments based on adult stem cells than on embryonic stem cells. The reason for this is not clear from the report. Do the researchers see more difficult scientific problems or political obstacles for embryonic stem cells?
Also, the article makes no mention of organ replacement. Some form of stem cells will be the starting point for growing most types of replacement organs. It would be very interesting to know what these stem cell researchers see as the time line for solving stem cell and tissue engineering problems associated with growing replacement organs.
Once stem cells can be coaxed to go in and replace lost cells and to grow into replacement organs human life extension will become a reality. The replacement of worn out parts in cars allows cars to run far longer than their original design lifes. Building and installing replacement parts in humans is much more difficult. But all of the problems involved in human parts replacement are solvable. Some German stem cell researchers expect many of those problems to be solved in the next 20 years. Hurrah!
Instead of false teeth, a small ball of cells capable of growing into a new tooth will be implanted where the missing one used to be.
The procedure needs only a local anaesthetic and the new tooth should be fully formed within a few months of the cells being implanted.
Professor Paul Sharpe, Head of the Department of Craniofacial Development, King’s College London, is leading the effort to grow replacement teeth inside human gums.
He tells the AAAS Annual Meeting in Seattle* that by understanding the genetic control of the key processes that form teeth in the embryo, the development of a tooth could be recreated in the mouth of an adult patient.
Results obtained from mice populations show that tooth rudiments can be formed from in vitro cultures of non-dental stem cell populations and complete teeth and associated bone can be obtained when these rudiments are transferred to adults.
The goal is to take adult stem cells, treat them in cell culture, and then transfer the treated stem cells into the gum where they will grow a replacement tooth just as happens when humans grow their original adult teeth.
Stem cells, the so-called master cells, would be programmed to develop into teeth and then transplanted into the patient's jaw where the gap is.
It is thought it would then take two months for the tooth to fully develop.
A commercial company, Odontis, has been set up to develop this new approach, which has been studied by Prof Sharpe for the past two years. The next step will take the team to the point where they can form a tooth rudiment consisting of both types of basic cells from stem cells. The method could be ready to test on patients by 2007, he said.
The project is receiving a total investment of £500,000: £100,000 from NESTA, £300,000 University Translation Award from the Wellcome Trust and £100,000 from a business angel. Kinetique Biomedical Seed Fund has already invested £250,000 in the proof of concept phase.
Professor Sharpe, adds: “A key medical advantage of our technology is that a living tooth can preserve the health of the surrounding tissues much better than artificial prosthesis. Teeth are living, and they are able to respond to a person’s bite. They move, and in doing so they maintain the health of the surrounding gums and teeth.”
It is hard to judge the prospects of this effort for a couple of reeasons. First of all, the original mouse work relied on both adult stem cells and cells extracted from embryos. For humans it sounds like Sharpe's team is trying to use adult stem cells for both of the cell types they think they need. Also, since the research has taken a more commercial turn Sharpe is not revealing which adult stem cell type(s) will be used or all the manipulations that his group will do on those cells in culture before implanting them.
If Sharpe's team succeeds this may well become the effort to coax stem cells into growing replacement body parts which will pass into widespread use. I consider that to be an important turning point from a psychological standpoint because it will show the public at large that the growth of aged and lost body parts is going to become routine. This should lead to much greater government and commercial support for development of techniques to grow replacements for still more types of body parts.
Ultimately we will reach a point where it is possible to grow replacements for all body parts aside from the brain. In situ repair of the brain will become the other major obstacle to the achievement of engineered negligible senescence which is a scientific term for what will be, for all intents and purposes, eternal youthfulness.
George Cotsarelis, M.D. of the University of Pennsylvania Medical School has shown in mice stem cells in hair follicles can be labelled, extracted, and reimplanted to cause hair growth in the target implant area.
Stem cells plucked from the follicles of mice can grow new hair when implanted into another animal. The work represents a dramatic step forward that is sure to stimulate new research into treatments for human baldness.
Cotarelis' group and a different group at Rockefeller University headed by Elaine Fuchs each separaately developed means to label the stem cells around follicles so that they could be isolated from other cells around them. Then gene arrays were used to study which genes were on and off. That pattern of gene state ought to be useful for discovering the same cell type in humans.
After purifying a sufficient amount of these cells, both groups used gene chips to find which genes were switched on in the stem cells. For the first time, this provides a signature that researchers can use to identify the same cells in humans.
"We've shown for the first time these cells have the ability to generate hair when taken from one animal and put into another," Cotsarelis said in a telephone interview. "You can envision a process of isolating existing stem cells and re-implanting them in the areas where guys are bald."
One advantage of using your own adult stem cells for this purpose is that immune rejection problems are avoided.
"I think this or something like it will be available in the next five to 10 years," said George Cotsarelis
Many adult regenerative cells divide infrequently but have high proliferative capacity. We developed a strategy to fluorescently label slow-cycling cells in a cell type-specific fashion. We used this method to purify the label-retaining cells (LRCs) that mark the skin stem cell (SC) niche. We found that these cells rarely divide within their niche but change properties abruptly when stimulated to exit. We determined their transcriptional profile, which, when compared to progeny and other SCs, defines the niche. Many of the >100 messenger RNAs preferentially expressed in the niche encode surface receptors and secreted proteins, enabling LRCs to signal and respond to their environment.
The Boston Globe has reported that Harvard University is going to create a stem cell research institute using private funding that will work with human embryonic stem cells.
Set to be announced in April, the stem cell plan will bring together researchers from Harvard and all of the Harvard-affiliated hospitals to unlock the mysteries of a type of cell that has the potential to develop into any healthy tissue in the body, but has triggered ethical controversy over the way it is created. Though not housed in a central building, the initiative will be large, even by Harvard standards, with a fund-raising goal of about $100 million, according to the scientists involved.
Harvard issued a statement Sunday confirming its plans, saying the school is "proceeding in the direction of establishing a stem cell institute." Final details are not complete, it said.
Provost Steven E. Hyman confirmed plans were in progress for the Harvard Stem Cell Center, which would bring together researchers from the University and affiliated hospitals who are already exploring the promising cells’ potential to help cure diseases like AIDS and diabetes. “We are moving forward on a stem cell center,” Hyman said. “It’s something Harvard ought to be doing. It is something we can be preeminent in.”
The revelation, first reported yesterday in The Boston Globe, comes two weeks after a South Korean laboratory became the first to extract a line of stem cells from a cloned human embryo, disappointing Harvard researchers who had been pursuing the achievement.
A report circulated by Dean of the Faculty of Arts and Sciences (FAS) William C. Kirby in January included a proposal to establish a stem cell research program on the University’s lands in Allston.
“Not only does the Institute propose to bridge the gap from basic to applied life science, it also proposes to address the complex social, ethical and religious questions that have arisen as stem cell research has advanced,” read the report obtained by The Crimson.
Human embryonic stem cells, which can harness the potency of fertilized eggs to form any variety of human tissue, have emerged as a pivotal—and controversial—field of study.
Bush administration restrictions limit government-financed research to pre-existing stem cells, but Hyman said the University would seek funding for the center from private donors and foundations.
One way or another human embryonic stem cell research is going to be done. It will be done by private money in the United States. It will be done in some other countries, particularly in East Asia where there is enough scientific talent and money and little in the way of government restrictions.
I think some proponents of human embryonic stem cell research have promoted unrealistic expectations about how quickly human embryonic stem cell research would produce useful treatments if only there were fewer political obstacles to this area of research.. Much of the work that needs to be done to understand how to manipulate stem cells can be and is being done in various animal models. This is similar to how many other kinds of research are done in other species for reasons of cost, ethics, ease of the work, and other factors. Plus, a lot of work on stem cells can be done on non-embryonic stem cells.
I'm not saying all this to make an argument against human embryonic stem cell (hESC) research. Decide for yourself whether you think that kind of research is ethically acceptable. My point is that in order to fight for the legality of this research the proponents have overstated how urgent the need is for doing human embryonic stem cell research at this point in time and at least one prominent stem cell researcher has put forth a similar view on this controversy.
Update: On a related note a group at Harvard led by researcher Douglas Melton has used private funding from the Howard Hughes Medical Institute (HHMI) to develop 17 new human embryonic stem cell (hESC) lines.
March 3, 2004— Howard Hughes Medical Institute researchers at Harvard University announced today that they have derived 17 new human embryonic stem-cell lines. The new cell lines will be made available to researchers, although at this time United States policies prohibit the use of federal funds to investigate these cells.
The cell lines were derived using private funds by researchers in the laboratory of Douglas A. Melton, a Howard Hughes Medical Institute (HHMI) investigator at Harvard University. The researchers described the stem-cell lines in an article published online on March 3, 2004, in the New England Journal of Medicine (NEJM). The article will also be in the March 25, 2004, print edition of NEJM.
HHMI funds a lot of excellent quality biomedical research and has an endowment which is currently about $11 billion dollars and which currently provides $450 million per year in biomedical research funding to hundreds of investigators. So HHMI has pockets deep enough to make hESC research happen in the United States without federal government money.
Scripps Research Institute researchers have discovered a molecule called cardiogenol C that will turn mouse embryonic stem cells into heart muscle cardiomyocyte cells. (same article here)
A group of researchers from The Skaggs Institute for Chemical Biology at The Scripps Research Institute and from the Genomics Institute of the Novartis Research Foundation (GNF) has identified a small synthetic molecule that can control the fate of embryonic stem cells.
This compound, called cardiogenol C, causes mouse embryonic stem cells to selectively differentiate into "cardiomyocytes," or heart muscle cells, an important step on the road to developing new therapies for repairing damaged heart tissue.
Normally, cells develop along a pathway of increasing specialization. In humans and other mammals, these developmental events are controlled by mechanisms and signaling pathways we are only beginning to understand. One of scientists' great challenges is to find ways to selectively differentiate stem cells into specific cell types.
"It's hard to control which specific lineage the stem cells differentiate into," says Xu Wu, who is a doctoral candidate in the Kellogg School of Science and Technology at Scripps Research. "We have discovered small molecules that can [turn] embryonic stem cells into heart muscle cells."
Wu is the first author of the study to be published in an upcoming issue of the Journal of the American Chemical Society and which was conducted under the direction of Peter G. Schultz, Ph.D., who is a professor of chemistry and Scripps Family Chair of the Skaggs Institute for Chemical Biology at The Scripps Research Institute, and Sheng Ding, Ph.D, who is an assistant professor in the Department of Chemistry at Scripps Research.
The researchers developed a means to test 100,000 molecules in a fairly automated fashion to find a few compounds that appeared to have the ability to cause stem cells to convert into heart muscle cells.
Scripps Research scientists reasoned that if stem cells were exposed to certain synthetic chemicals, they might selectively differentiate into particular types of cells. In order to test this hypothesis, the scientists screened some 100,000 small molecules from a combinatorial small molecule library that they synthesized. Just as a common library is filled with different books, this combinatorial library is filled with different small organic compounds.
From this assortment, Wu, Ding, and Schultz designed a method to identify molecules able to differentiate the mouse embryonic stem cells into heart muscle cells. They engineered embryonal carcinoma (EC) cells with a reporter gene encoding a protein called luciferase, and they inserted this luciferase gene downstream of the promoter sequence of a gene that is only expressed in cardiomyocytes. Then they placed these EC cells into separate wells and added different chemicals from the library to each. Any engineered EC cells induced to become heart muscle cells expressed luciferase. This made the well glow, distinguishing it from tens of thousands of other wells when examined with state-of-the-art high-throughput screening equipment. These candidates were confirmed using more rigorous assays.
In the end, Wu, Ding, Schultz, and their colleagues found a number of molecules that were able to induce the differentiation of EC cells into cardiomyocytes, and they chose one, called Cardiogenol C, for further studies. Cardiogenol C proved to be effective at directing embryonic stem cells into cardiomyocytes. Using Cardiogenol C, the scientists report that they could selectively induce more than half of the stem cells in their tests to differentiate into cardiac muscle cells. Existing methods for making heart muscle cells from embryonic stem cells are reported to result in merely five percent of the stem cells becoming the desired cell type.
Now Wu, Ding, Schultz, and their colleagues are working on understanding the exact biochemical mechanism whereby Cardiogenol C causes the stem cells to differentiate into cardiomyocytes, as well as attempting to improve the efficiency of the process.
The article, "Small Molecules that Induce Cardiomyogenesis in Embryonic Stem Cells" was authored by Xu Wu, Sheng Ding, Qiang Ding, Nathanael S. Gray, and Peter G. Schultz and is available to online subscribers of the Journal of the American Chemical Society at: http://pubs.acs.org/cgi-bin/asap.cgi/jacsat/asap/abs/ja038950i.html. The article will also be published in an upcoming issue of the Journal of the American Chemical Society.
This is not the first use by Scripps researchers of an automated method to screen tens of thousands of compounds for activity that changes the diferentiation state of cells. Fairly recently some of the same Scripps researchers (Sheng Ding and Peter Schultz mentioned above) have also recently also discovered a molecule called reversine that will dedifferentiate (convert into a less specialized form) muscle cells into stem cells.
A group of researchers from The Scripps Research Institute has identified a small synthetic molecule that can induce a cell to undergo dedifferentiation--to move backwards developmentally from its current state to form its own precursor cell.
This compound, named reversine, causes cells which are normally programmed to form muscles to undergo reverse differentiation--retreat along their differentiation pathway and turn into precursor cells.
The team hit upon reversine by systematically treating mouse muscle cells with some 50,000 different candidate molecules that they hoped might stick to and switch on enzymes capable of producing dedifferentiation
To do stem cell therapies we need the ability to put cells into various states of differentiation. Adult stem cells and progenitor cells can be thought of as being in partially differentiated states. We need the ability to put cells into those partially differentiated states in order to be able to replenish adult stem cell reservoirs. We also need the ability to shift cells into fully differentiated states. There are likely hundreds and perhaps even thousands of different states that cells can be in and we need the ability to put cells into many of those states. The Scripps researchers are making progress developing tools and techniques that automate the testing of compounds for the ability to change the differentiation state of cells into different cell types.
Automation is speeding up the rate of advance of biological science and biotechnology.
See this previous post for more on reversine.
February 18, 2004— Researchers have found an unexpected source of stem cells in the adult human brain. They have demonstrated for the first time that human astrocytes — brain cells thought to play more of a secondary role by providing a supportive, nurturing environment for the neuron — can actually function as stem cells. The astrocytes can form new stem cells and are able to generate all three types of mature brain cells.
But these astrocytes are different: They form a novel ribbon-like structure in the brain's lateral ventricle. Stem cells from comparable areas in the rodent brain follow a distinct path from their place of origin to the olfactory bulb (a brain region that processes smells), where they create new neurons.
The work, led by former HHMI medical student fellow Nader Sanai and Arturo Alvarez-Buylla, Heather and Melanie Muss Professor of Neurological Surgery at the University of California, San Francisco, opens the possibility that such stem cells could be harnessed and one day used to regenerate damaged areas in the central nervous system. The scientists reported their findings February 19, 2004, in the journal Nature.
“We've found a structure in the human brain that represents a significant departure from other species,” Sanai said. “The differences we see imply that this region in the human brain doesn't necessarily do the same things as its primate and rodent counterparts. This is a cell population that has the potential to regenerate parts of the brain, though it's not clear what regions those may be. Neurons generated in this area may migrate to other areas of the brain and potentially regenerate those areas.”
What is not clear to me is whether this exact same experiment has been tried in the primate species (chimpanzees and bonobos) that are closest to humans in evolution. Would a repeat of this experiment on chimp astrocytes from the same part of the brain yield the same result? Does anyone know whether this has been tried? I'm not quite ready yet to accept this a feature of neurobiology that is totally unique to humans. Does any reader have enough expertise in the relevant areas of research to answer this question?
What seems surprising about this result is that only now in the year 2004 has anyone even checked to see if astrocytes can become nerve cells.
They studied brain tissue from the lateral ventricles - two cerebrospinal fluid-filled cavities in the center of the brain - available from either surgery patients or from pathology samples after autopsy. The researchers first stained the tissue to locate astrocytes, and immediately saw the ribbon of astrocytes lining the ventricle walls. They subsequently determined that cells within the ribbon were dividing, implying that they were part of a region of proliferative stem cells.
Next, the scientists decided to look for the stem cells. They took representative sections of tissue from the lining of the lateral ventricles, and found that these specimens could generate neurospheres in a dish. Neurospheres contain all of the precursors for the major central nervous system cell types the stem cell produces: neurons, astrocytes, and oligodendrocytes. They result from a stem cell being put in a culture dish with various growth factors.
To make sure, they subsequently isolated individual human astrocytes and put each in a dish with growth factors, showing they could form neurospheres as well.
This was the first time anyone had shown that a single human astrocyte could function as a stem cell. Alvarez-Buylla, Sanai, and their co-workers then found that single astrocytes from the lateral ventricle could generate neurons without added growth factors — direct evidence that a single astrocyte could generate a neuron.
The findings are provocative because astrocytes have traditionally been considered simple helper cells, Sanai said.
“This speaks to the plasticity of the human brain,” he said. “Certain cell types may have hidden potential.” These subtypes of astrocytes appear no different from any other astrocytes, implying that “it's possible that other astrocytes in other regions of the body have the same potential.”
The hippocampus has been previously known as a site in the brain for adult neural stem cells. The existence of stem cells in the brain was first discovered in canaries and this discovery upset the received wisdom for many decades that the adult brain never gained new nerve cells. In fact, it has been previously reported that astrocytes provide growth factors that help hippocampal stem cells convert more rapidly into neurons. Now that it is known that astrocytes can convert into neurons this opens up the potential to stimulate astrocytes to divide and create neurons to do repair for various neurological disorders and even to replace nerve cells lost to aging. This result also means that future development of the ability to replenish astrocytes with rejuvenated replacement cells could turn out to be a useful rejuvenation therapy for the brain.
This particular discovery is also part of a larger pattern of discovery in which new sources of adult stem cells are being found in different parts of the body. It seems likely that many more sources of adult stem cells are still waiting to be discovered.
A team led by Steven Goldman, M.D., Ph.D., of the University of Rochester Medical Center has injected both embryonic and adult stem cells into mice that were previously genetically engineered to be deficient in the insulation covering nerve cells that is called myelin sheath. The injected stem cells restored some of the missing myelin sheath.
The team remyelinated the mice – restored the “insulation” to the brain cells– by injecting into the mice highly purified human “progenitor” cells, which ultimately evolve into the cells that make myelin. These cells are known as oligodendrocytes: While these and other types of glial cells aren’t as well known as information-processing brain cells called neurons, they are vital to the brain’s health.
“Neurons get all the press, but glial cells are crucial to our health,” says Goldman.
The team studied 44 mice that were born without any myelin wrapped around their brain cells. Within 24 hours of their birth, scientists injected cells that become oligodendrocytes –myelin-producing cells – into one precisely selected site in the mice.
Scientists found that the cells quickly migrated extensively throughout the brain, then developed into oligodendrocytes that produced myelin which coated or “ensheathed” the axons of cells in the brain.
“These cells infiltrate exactly those regions of the brain where one would normally expect oligodendrocytes to be present,” says Goldman. “As they spread, they begin creating myelin which wraps around and ensheaths the axons.”
Goldman says that while scientists have used other methods during the past two decades to remyelinate neurons in small portions of the brains of mice, the remyelination seen in the Nature Medicine paper is much more extensive. He estimates that about 10 percent of the axons in the mouse brains were remyelinated, compared to a tiny fraction of 1 percent in previous studies.
If the auto-immune attack on the myelin could be stopped in Multiple Sclerosis (MS) suffers then even a repair of 10% of the damage would improve functionality. That might be enough of a difference to allow someone in a wheelchair to walk with the assistance of a walker or it might be enough to allow a person to feed himself.
Currently, demyelinating diseases are permanent, and problems worsen as time goes on because there is no way to fix the underlying problem – restoring the myelin around the axons of brain cells. Goldman is hopeful that infusion of cells like oligodendrocyte progenitors might be used to offer relief to patients.
“The implantation of oligodendrocyte progenitors could someday be a treatment strategy for these diseases,” says Goldman, a neurologist whose research was supported by the National Multiple Sclerosis Society and the National Institute of Neurological Disorders and Stroke. While the experiment provides hope for patients, Goldman says that further studies are necessary before considering a test in humans. Currently he’s conducting experiments in an attempt to remyelinate not just the brains but the entire nervous system of mice.
While it is widely known that Multiple Sclerosis (MS) is caused by an auto-immune attack that eats away at the myelin sheath Goldman points out that many other diseaes involve myelin damage. Therefore myelin restoration would help repair damage associated with many disease which become more common as we age.
In addition to MS, many diseases affecting tens of millions of people in the United States involve myelin problems, Goldman says. These include widespread diseases like diabetes, heart disease and high blood pressure, where decreased blood flow can damage myelin and hurt brain cells, as well as strokes, which often destroy brain cells in part by knocking out the cells that pump out myelin. In addition, cerebral palsy is largely caused by a myelin problem in infants born prematurely.
Given that myelin, like everything else, deteriorates with age the ability to even partially repair it with a stem cell therapy would even offer some prospects for improving cognitive function in the aged.
Nervous system repair is an especially important and especially difficult rejuvenation challenge. Eventually it will be possible to grow replacements for most organs. But the brain must be repaired in place and in ways that do not cause any damage to existing networks of nerves. Therapies that hold the prospect of repairing even a limited subset of all nervous system age-related damage are cause for excitement.
The team found that adult human cells were much more adept at settling into the brain, becoming oligodendrocytes and producing myelin than the fetal cells. After just four weeks, adult cells but not fetal cells were producing myelin. After 12 weeks, four times as many oligodendrocytes derived from adult cells were producing myelin – 40 percent, compared to 10 percent of the cells from fetal cells. In addition, adult cells were likely to take root and form oligodendrocytes, not other brain cells such as neurons or astrocytes, which are not necessary for myelin production. On average, each oligodendrocyte from an adult cell successfully remyelinated five axons, compared to just one axon for fetal cells.
“The adult-acquired cells not only myelinate much more quickly, but more extensively – they myelinate many more axons per cell, and they do so with much higher efficiency. The adult cells were far more efficient than fetal cells at getting the job done,” Goldman says.
The adult-acquired cells (a.k.a. adult stem cells) have a big advantage: they are already more specialized for the desired task. The biggest advantage of embryonic stem cells is also their biggest disadvantage: they can become any kind of cell. Well, to develop a stem cell therapy for a particular disease one usually has to make stem cells become more specialized to produce only one or a few final functional cell types (what biologists call differentiated cells). Embryonic stem cells delivered into a diseased organ that needs a particular cell type may turn themselves into a number of different cell types and many of the cell types the embryonic cells will become are cell types that are not going to help in treating the disease that is being targetted for therapy.
This is not to say that adult stem cells are ideal in all respects. First of all, one needs to find a type of adult stem cell that is capable of becoming the target differentiated cell type that is needed. We do not know adult stem cell types for each final differentiated type and some adult stem cell types are hard to isolate. Plus, adult stem cells from adults frequently act like they are older. They grow more slowly. In fact, the aging of stem cells in adult stem cell reservoirs is a major contriibutor to general aging and we need the ability to replenish adult stem cell reservoirs with younger adult stem cells. For instance, it may be possible to avoid or delay atherosclerosis and heart disease by rejuvenating adult stem cell reservoirs. Whether this is best done by taking adult stem cells and rejuvenating them or by taking embryonic stem cells and turning them into adult stem cells remains to be seen. But one advantage of rejuvenation of one's own adult stem cells is that this would avoid auto-immune problems from use of embryonic stem cells that are not from one's own tissue.
The classic leukodystrophies include adrenoleukodystrophy, Krabbe's globoid cell, and metachromatic leukodystrophy, and a few other less well known entities. They have in common a genetic origin and involve the peripheral nerves as well as the central nervous system. Each is caused by a specific inherited biochemical defect in the metabolism of myelin proteolipids that results in abnormal accumulation of a metabolite in brain tissue. Progressive visual failure, mental deterioration, and spastic paralysis develop early in life, however, variants of these diseases have a more delayed onset and a less progressive course. The other primary white matter disorders include Alexander's disease, Canavan disease, Cockayne's syndrome, and Pelizaeus-Merzbacher's disease
When babies are born, many of their nerves lack mature myelin sheaths, so their movements are gross, jerky, and uncoordinated. The normal development of myelin sheaths is impaired in children born with certain inherited diseases, such as Tay-Sachs disease, Niemann-Pick disease, Gaucher's disease, and Hurler's syndrome. Such abnormal development can result in permanent, often extensive, neurologic defects.
A pair of press releases from the National Institute of Standards and Technology (NIST) draw attention to efforts of NIST researchers to come up with assays and instrumentation to enable the acceleration of research on tissue engineering. Tissue engineering is a very important discipline for the development of the means to grow replacement organs and to fix existing organs and other tissues. I especially love research and engineering into tools and techniques that essentially enable other researchers to solve problems that provide direct benefit. The development of enabling tools and techniques can shrink the amount of time needed to do biomoedical research by years and even decades and, in my view, the development of enabling tools does not get the attention it deserves.
The first report is for a new technique for testing the biocompatibility of synthetic materials.
A new method for quantitatively measuring the compatibility of materials with living tissues has been developed by researchers at the National Institute of Standards and Technology (NIST). Described in a Dec. 11 presentation at the Tissue Engineering Society International's conference in Orlando, Fla., the technique should provide a more sensitive and reliable means to evaluate the biocompatibility of new materials for a wide range of applications from contact lenses to dental coatings to bone implants.
A paper outlining the new method has been accepted for publication in the Journal of Biomedical Materials Research.
The new method, which represents a novel application of existing bench-top scientific instruments, is a two-step process. The first step involves using a device called a polymerase chain reaction instrument to measure the levels of an organism's cytokines when exposed to a given material. Cytokines are signaling molecules released by white blood cells to protect the body from foreign materials. Higher levels of cytokine production generally indicate non-biocompatible materials have caused inflammation. The second step involves testing exposed cells for a specific protein in the cell membrane, the presence of which indicates cells are dying. This is a complementary test for more serious responses to materials because dying cells are often not capable of producing cytokines. The NIST tests were conducted on cultured mouse cells, which produce similar responses as whole tissues.
NIST post-doctoral researcher LeeAnn Bailey called the new method a "barometer" of biocompatibility.
Whereas current means to test biocompatibility produce a yes/no result that a material is minimally biocompatible or not, the new analysis can tell which materials are more biocompatible than others. Industry and researchers should be able to use this method to produce new materials for dentistry and other medical applications that are even more well matched to the human body.
In the November issue of Optics Express*, National Institute of Standards and Technology (NIST) scientists describe a novel combination of microscopes that can peer deep into tissue-engineering scaffolds and monitor the growth and differentiation of cells ultimately intended to develop into implantable organs or other body-part replacements.
The new dual-imaging tool provides a much needed capability for the emerging tissue engineering field, which aims to regenerate form and function in damaged or diseased tissues and organs. Until now, scrutiny of this complicated, three-dimensional process has been limited to the top-most layers of the scaffolds used to coax and sustain cell development.
Composed of biodegradable polymers or other building materials, scaffolds are seeded with cells that grow, multiply, and assemble into three-dimensional tissues. Whether the cells respond and organize as intended in this synthetic environment depends greatly on the composition, properties, and architecture of the scaffolds' porous interiors. Tools for simultaneously monitoring microstructure and cellular activity can help scientists to tease apart the essentials of this interactive relationship. In turn, such knowledge can speed development of tissue-engineered products ranging from skin replacements to substitute livers to inside-the-body treatments of osteoporosis.
NIST scientist Joy Dunkers and her colleagues paired an optical coherence microscope---a high-resolution probe of the scaffold interior---with a confocal fluorescence microscope---used to track cells stained with a fluorescent dye. The instruments provide simultaneous images that can be merged to create a comprehensive rendering of microstructure and cellular activity. By stacking the sectional images, they can create a top-to-bottom movie showing structural and cellular details throughout the scaffold's volume.
*J. P. Dunkers, M. T. Cicerone, and N. R. Washburn, "Collinear optical coherence and confocal fluorescence microscopies for tissue engineering," Optics Express, Vol. 11, No. 23, pp. 3074-3079. [http://www.opticsexpress.org].
If I could make one change in US government research funding policy I'd rechannel funding in biomedical sciences away from clinical trials and away from people who are trying to use existing tools and techniques and toward researchers who are developing new tools. So, for instance, some of the money spent sequencing genomes would be reallocated toward research in microfluidics and nanopore technology to develop new means of DNA sequencing that will eventually be orders of magnitude faster and cheaper. Also, I'd channel more money in the direction of people like the NIST researchers above who are working on enabling technologies for tissue engineering.
With the right set of tools any question can be answered very quickly. The fact that we are spending decades trying to develop cures for cancer, heart disease, degenerative neurological diseases and the like is a sign that our tools are inadequate for the problems which researchers are attempting to solve. We need better tools.
Scientists have identified a gene in the cerebral cortex that apparently controls the developmental clock of embryonic nerve cells, a finding that could open another door to tissue replacement therapy in the central nervous system. In a new study, the researchers found that they could rewind the clock in young cortical cells in mice by eliminating a gene called Foxg1. The finding could potentially form the basis of a new method to push progenitor cells in the brain to generate a far wider array of tissue than is now possible.
The study, led by researchers at NYU School of Medicine, is published in the January 2, 2004 issue of Science magazine.
"What we found was a complete surprise," says Gordon Fishell, Ph.D., Associate Professor in the Department of Cell Biology at New York University School of Medicine. "No one had believed that it was possible to push back the birth date of a cortical neuron. There is this central tenet governing the process of brain development, which says that late progenitor cells [forerunners of mature cell types] cannot give rise to cell types produced earlier in development," he explains.
"Consequently, while some populations of stem cells exist in the adult brain, these cells are restricted to producing only a subset of cell types," notes Dr. Fishell. "If one's goal is to produce cells for replacement therapy, some method must be found to turn back the clock and allow adult stem cells to give rise to the wide variety of cells made during normal brain development."
Eseng Lai, Ph.D., of Merck & Co. and one of the study's co-authors, cloned the Foxg1 gene while he was working at Memorial Sloan-Kettering Cancer Center in New York. He also did seminal work in the late 1990s showing that when the gene is eliminated in embryonic mice, the brain's cerebral hemispheres barely develop. Subsequent work demonstrated that the gene played a role in the early phases of cortical development.
While the press release makes it sound like the researchers have converted more differentiated cells into less differentiated cells my take on this is that what they have really done is found that by knocking out a gene they can prevent nerve stem cells from becoming more differentiated in the first place. They are not converting cells into a less differentiated state. (someone correct me if I'm wrong). They are instead blocking the process of differentiation. That is not nearly as exciting and yet it is a very useful piece of information. But would suppression of the Foxg1 gene in cells that are already more differentiated (more specialized toward becoming neurons of some specific later stage type) cause those cells to revert to a less differentiated state? I don't think these researchers have demonstrated that yet. I also don't think Foxg1 gene suppression in differentiated nerve cells will necessarily cause those cells to revert back into partially differentiated stem cells. The Foxg1 gene might cause methyl groups to be placed in spots on the genome that cause the cells to stay differentiated even once Foxg1 is turned off (just speculating but this is not an unreasonable speculation).
Still, this is useful information. Every discovery of a gene that plays a role in cellular differentiation (the process by which cells become changed to become specialized for specific tasks) provides researchers with useful information that will help point the way toward experiments to attempt that may cause cells to change differentiation state and to revert to some type of stem cells or to convert into a more specialized cell.
There have been a number of recent reports on promising techniques for producing adult stem cells for a variety of purposes. These other reports strike me as more advanced than this latest report excerpted above. See my previous posts Scripps Researchers Find Molecule That Turns Adult Cells Into Stem Cells, TriStem Claims Converts Blood Cells To Stem Cells, and MIT Technique To Produce Large Numbers Of Adult Stem Cells.
There is another angle to this latest report: it may turn out to be useful information for future techniques in intelligence enhancement. If Foxg1 and other related genes can be manipulated to cause more cerebral cortex cells to be made then it may be possible to improve reasoning ability or memory capacity. More generally, research on cellular differentiation and growth regulation of nerve cells will eventually yield information that will be useful for doing intelligence enhancement.
Scripps Research Institute researchers have found a molecule that will convert adult differentiated adult muscle cells into undifferentiated stem cells.
La Jolla, CA. December 22, 2003—A group of researchers from The Scripps Research Institute has identified a small synthetic molecule that can induce a cell to undergo dedifferentiation—to move backwards developmentally from its current state to form its own precursor cell.
This compound, named reversine, causes cells which are normally programmed to form muscles to undergo reverse differentiation—retreat along their differentiation pathway and turn into precursor cells. These precursor cells are multipotent; that is, they have the potential to become different cell types. Thus, reversine represents a potentially useful tool for generating unlimited supply of such precursors, which subsequently can be converted to other cell types, such as bone or cartilage.
"This [type of approach] has the potential to make stem cell research more practical," says Sheng Ding, Ph.D. "This will allow you to derive stem-like cells from your own mature cells, avoiding the technical and ethical issues associated with embryonic stem cells."
Ding, who is an assistant professor in the chemistry department at Scripps Research conducted the study—to be published in an upcoming issue of the Journal of the American Chemical Society—with Peter G. Schultz, Ph.D., who is a professor of chemistry and Scripps Family Chair of Scripps Research's Skaggs Institute of Chemical Biology, and their colleagues.
Stem cell therapy would be most effective if you could use your own stem cells, since using one's own cells would avoid potential complications from immune rejection of foreign cells. However, in general it has proven very difficult to isolate and propagate stem cells from adults. Embryonic stem cells (ESCs) offer an alternative, but face both practical and ethical hurdles associated with the source of cells as well as methods for controlling the differentiation of ESCs. A third approach is to use one's own specialized cells and dedifferentiate them.
This is excellent news. The ability to use one's own cells as a starting point for making stem cells to treat one's own illnesses would avoid the immune rejection problems that make stem cells from non-self sources so problematic.
This molecule reversine is not the only molecule discovered recently that is useful for controlling the differentiation state of cells. Currently human embryonic stem cells have to be grown on top of mouse cells in order to prevent the stem cells from differentiating. The mouse cells release compounds that prevent the cells from differentiating. The problem with doing this is that the human cells may get contaminated in some way that could make them risky to be used in human therapy. Well, Ali Brivanlou of Rockefeller University has identified a compound extracted from sea snails that prevents stem cell differentiation.
Ali Brivanlou of Rockefeller University in New York says that he and his colleagues may have found a partial solution to these problems. Brivanlou treated ES cells with a chemical, nicknamed BIO, from a sea snail.
BIO stopped ES cells turning into specialized adult cells, Brivanlou and his colleagues found. BIO works by activating a set of protein signals - called the Wnt pathway - in the ES cells1.
Slowly but surely more tools and techniques are being developed to make stem cell growth and differentiation and dedifferentiation controllable.
New Scientist magazine has a report about the claims of London UK biotech company TriStem that it has developed a very rapid way to convert blood cells to less differentiated stem cells.
TriStem has been claiming for years that it can take a half a litre of anyone's blood, extract the white blood cells and make them revert to a "stem-cell-like" state within hours. The cells can be turned into beating heart cells for mending hearts, nerve cells for restoring brains and so on.
The company has now finally provided proof that at least some of its claims might be true. In collaboration with independent researchers in the US, the company has used its technique to turn white blood cells into the blood-generating stem cells found in bone marrow.
The ability to dedifferentiate stem cells (the article uses the term retrodifferentiation) would be incredibly valuable just for leukemia treatment. Though if all their claims are correct the number of applications would be enormous. TriStem hasn't yet proven all their claims and if you read the full article you will find different scientists voicing varying degrees of skepticism about those claims. But TriStem has begun to demonstrate some of their claims to outside scientists including Tim McCaffrey of George Washington University and a clinical trial in Britain will attempt to use TriStem's technique to treat aplastic anemia with results due by March 2004. So we will soon know a lot more about their claims.
The ability to use a person's own blood cells, dedifferentiate them and to grow them in large number for conversion into a wide variety of cell types would provide the advantages of hESC while avoiding political opposition in the form of the types of ethical objections which have been raised about the use of human embryonic stem cells (hESCs). Such cells would have a big advantage over hESCs because the use of hESCs from another person poses potential immune incompatibility problems whereas one's own cells are unlikely to cause an auto-immune response.
There have been a lot of reports lately of success using and manipulating adult stem cells. See recent posts MIT Technique To Produce Large Numbers Of Adult Stem Cells, Stem Cells On Spinal Cord Injury Opened Connection To Brain, and Adult Stem Cell Research Promising For Heart, Lung Disease.
Many researchers have been pursuing what they have believed two separate parts of the solution to type I diabetes: A) stop the auto-immune response that kills pancreatic isle of Langerhan cells and B) either replace the lost cells or deliver gene therapy to instruct other cells to take their place as insulin releasers. Well, the good news is that while pursuing these problems researchers may have discovered that there are adult precursor stem cells in the spleen that have the ability to take over the function of the lost pancreatic insulin-making islet cells.
Cells from an unexpected source, the spleen, appear to develop into insulin-producing pancreatic islet cells in adult animals. This surprising finding from Massachusetts General Hospital (MGH) researchers, published in the Nov. 14 issue of Science, is a followup to the same team's 2001 report of a treatment that cures advanced type 1 diabetes in mice. In discovering the biological mechanism behind that accomplishment, the researchers also have opened a potential new approach to replacing diseased organs and tissues using adult precursor cells.
"We have found that it is possible to rapidly regrow islets from adult precursor cells, something that many thought could not be done," says Denise Faustman, MD, PhD, director of the MGH Immunobiology Laboratory and principal investigator of the study. "By accomplishing effective, robust and durable islet regeneration, this discovery opens up an entirely new approach to diabetes treatment."
David M. Nathan, MD, director of the MGH Diabetes Center, notes, "These exciting findings in a mouse model of Type 1 diabetes suggest that patients who are developing this disease could be rescued from further destruction of their insulin-producing cells. In addition, patients with fully established diabetes possibly could have their diabetes reversed." Nathan has developed a protocol to test this approach in patients, but additional grant support is needed before a clinical trial can begin. Type 1 diabetes develops when the body's immune cells mistakenly attack the insulin-producing islet cells of the pancreas. As islet cells die, insulin production ceases, and blood sugar levels rise, damaging organs throughout the body. In their earlier study, Faustman's team directly attacked this process by retraining the immune system not to attack islet cells. They first used a naturally occurring protein, TNF-alpha, to destroy the mistargeted cells. Then they injected the mice with donor spleen cells from nondiabetic mice. A protein complex on these cells plays a key role in teaching new immune cells to recognize the body's own tissues, a process that goes awry in diabetes and other autoimmune disorders.
The earlier study's results are also quite important because it is essential to develop the ability to selectively knock out immune cells that are causing an auto-immune response in order to cure diabetes, rheumatoid arthritis, lupus, multiple sclerosis, and other auto-immune disorders.
The researchers expected to follow that process, which eliminated the autoimmune basis of the animals' diabetes, with transplants of donor islet cells. However, they were surprised to find that most of the mice did not subsequently need the transplant: Their bodies were producing normal islet cells that were secreting insulin.
"The unanswered question from that study was whether this was an example of rescuing a few remaining islet cells in the diabetic mice or of regeneration of the insulin-secreting islets from another source," says Faustman. "We've found that islet regeneration was occurring and that cells were growing from both the recipient's own cells and from the donor cells." An associate professor of Medicine at Harvard Medical School, Faustman notes that it has been generally believed that most adult organs cannot regenerate and that adult stem cells or cellular precursors would not be powerful enough to reconstitute functioning insulin-secreting islets.
In order to determine whether or not the new islets had developed from the donated spleen cells, the researchers carried out the same treatment using spleen cells from healthy male donors to re-educate the immune cells of female diabetic mice. In those diabetic mice that achieved long-term normal glucose metabolism, the researchers found that all of the new functioning islets had significant numbers of cells with Y chromosomes, indicating they had come from the male donors. In another experiment, donor spleen cells were marked with a fluorescent green protein, and again donor cells were found throughout the newly developed islets.
Here comes the especially interesting part: if the auto-immune response can be halted in human diabetes sufferers then it is likely that over a period of months the body will slowly develop the ability to secrete enough insulin to control blood sugar without insulin shots.
A separate experiment, however, indicated that islets also could grow from remaining precursor cells in the diabetic mice and resume insulin secretion once the autoimmune process had been halted. Such regrowth from the animal's own cells was slightly slower than regeneration from donor cells – taking about 120 days – but the eventual regeneration of islets was just as complete. The result suggests that, given time, regrowth of islets can occur in animals who have immune system re-education to eradicate their diabetes but do not receive the donor islet cell precursors.
The researchers then separated spleen cells into those with a surface molecule called CD45, which indicates the cell is destined to become an immune cell, and those without CD45. They injected labeled spleen cells with or without CD45 – or unseparated cells – into young mice in which autoimmunity had begun but full-blown diabetes had not yet developed. After the immune system re-education therapy, all of the mice maintained normal glucose control, while their untreated littermates soon became diabetic. However, close examination of pancreatic tissue from the treated mice revealed markers from the donor cells only in the islets of those who had received spleen cells without CD45.
"It's the cells without CD45 that are the precursors for pancreatic islets. They have a distinct function that has not previously been identified for the spleen," Faustman says.
Any time a new source of cells are found in the body that are capable of turning into other cell types that alone is a small reason to celebrate. Each type of stem cell that is identified is another useful piece in the puzzle and helps with the development of future stem cell treatments. But this report is also great news because it indicates that cell therapy to replace islet cells may not even be necessary in order to cure type I diabetes.
The buttheads at the US Food and Drug Administration are standing in the way of rapid trials to test the efficacy of the use of blood stem cells to treat heart disease.
“After we went public, FDA told us not to conduct any similar procedures,” says Steven Timmis, the cardiologist at Beaumont who performed the bone marrow transplant. “We had also proposed a 100-patient randomized clinical trial, but FDA has denied this.”
The doctors did not seek FDA approval prior to the transplant because it was an emergency operation and they believed the procedure was allowed because the teen received injections of stem cells from his own blood. Transplants of bone marrow, the primary source of stem cells, have been performed routinely in the United States for more than 30 years.
The teenager first received a drug that increases the production of stem cells in the bone marrow. The stem cells are released into the bloodstream. The doctors then collected the cells from his circulating blood.
In 1999, researchers showed that bone marrow stem cells injected into mice with damaged heart muscle homed in to the damaged tissue and restored function. Since then, clinical trials in Britain, Germany, Hong Kong, China, and Brazil have shown that heart patients with heart disease who are injected with their own bone marrow stem cells improve significantly.
When people have heart disease that is going to kill them in a few months or a few years it is time for the government to butt out and let people choose what risks they want to take with their lives. This sort of report infuriates me. The FDA is insisting that the researchers spend a couple of years on animal trials when groups in other countries are charging ahead of US researchers and getting promising results.
The doctors working on this method at Beaumont Hospital in Royal Oak Michigan tried it out as an emergency treatment on a 16 year old kid named Dmitiri Bonneville who had nail gun nails puncture his heart in an accident. The kid would probably be dead by now and instead the emergency treatment worked and he's running around being a kid again. But the FDA doesn't like surprise trials of treatments with press conferences to announce the unexpected results. That sort of thing is not controlled by expert bureaucrats sitting in committees passing expert judgement and so we can't have that.
The FDA's jurisdiction is questionable since use of one's own tissues (homologous use) is supposed to be allowed without approval. So the FDA is claiming the pressure at which the catheter is injecting the cells is experimental.
In my very strongly held view anyone with a terminal illness should be free to try any experimental therapy that they can find a medical doctor to deliver. Will there be abuse? Sure. But do we own our own lives or not? Also, greater freedom to experiment will accelerate the rate of medical advance and more lives will be saved than will be lost by failed experimental therapies. Keep in mind that if the people allowed this exception are ones who have only a few years or months or weeks or days to live they may feel the gamble is worth it. Who are government bureaucrats to make a value judgement about such a decision?
Update: Some other blogs are linking to this item and the comments made on those blogs indicate that there seems to be some misunderstanding about why the FDA is taking the position they are taking toward the Michigan researchers. The FDA's position has nothing to do with the controversy over human embryonic stem cells. The stem cells used by the Michigan researchers are not embryonic and there is no substantial religious opposition to the use of non-embryonic stem cells. To those misinterpreters: Back off on the intense reflexive unthinking irrational partisanship. This is not a story about ethical objections to a promising medical treatment. The FDA is not following the instructions of the Bush White House on this question. This is just the FDA acting the way it normally acts under both Democratic and Republican administrations. If you don't like it then you ought to tell your Congressional representative that the FDA has too much power to prevent terminally ill people from trying experimental therapies..
The biotech company Geron Corporation is working with human embryonic stem cells (hESC) converted into oligodendroglial progenitor cells for use in treating spinal cord injuries in rats and mice.
Menlo Park, CA – November 13, 2003 – Geron Corporation (Nasdaq: GERN) today announced the presentation of results demonstrating that the transplant of cells differentiated from human embryonic stem cells (hESCs) can result in functional improvement in animals with spinal cord injuries. This work provides proof of concept of the efficacy of hESC-based therapies in spinal cord injury.
In two presentations at the Society for Neurosciences Annual Meeting in New Orleans, Dr. Hans Keirstead and his colleagues from the University of California at Irvine detailed studies demonstrating that when hESC-derived oligodendroglial progenitors were transplanted into rats that had received a thoracic spinal cord contusion injury, statistically significant improvements in the ambulatory activity of the rats could be observed approximately one month later. In these blinded studies, animals showed evidence of improved weight-bearing capacity, paw placement, tail elevation and toe clearance activity compared to injured untreated animals. Control animals that received transplants of human fibroblasts instead of oligodendroglial progenitors showed little, if any improvement.
“These results are exciting. They show that cells derived from hESCs can have therapeutic efficacy in a model of human disease,” stated Jane S. Lebkowski, Ph.D., Geron’s vice president of regenerative medicine.
In these studies, the cells were transplanted directly into the spinal cord lesions seven days after injury. Dr. Keirstead found evidence of both increased oligodendrocyte-mediated myelination and some neural sprouting upstream of the lesion in the test animals. These observations were further supported by additional transplant studies from Dr. Keirstead’s lab in which the oligodendroglial progenitors were implanted into the spinal cord of Shiverer mice, a mutant mouse that is deficient in myelin basic protein and hence lacks normal neuronal myelination. In those mice the researchers observed evidence of oligodendrocyte-mediated remyelination of nerve cell axons. No evidence of tumor formation from the transplanted cells or other adverse events was observed in any of these studies.
In a third presentation at the meeting, Dr. Keirstead and his colleagues presented data showing how hESCs can be differentiated in tissue culture to oligodendroglial progenitors, the precursors of oligodendrocytes. Oligodendrocytes are specialized neural cells that produce myelin, the protective sheath that insulates the axons of nerve cells allowing normal nerve impulse conduction. Oligodendrocytes also produce a variety of neurotropic factors which can induce the sprouting of nerve cells. In a spinal cord contusion injury, neurons that are spared during the initial injury can be demyelinated during the subsequent inflammatory response. Such demyelination can lead to decreased nerve conduction velocity and eventual death of the “denuded” axons, producing impaired sensory and motor function.
“This work demonstrates the versatility of hESCs and their potential utility for broad-based cellular therapeutics,” added Thomas B. Okarma, Ph.D., M.D., Geron’s president and chief executive officer. “In these studies, oligodendroglial progenitors were produced multiple times from the same human embryonic stem cell line over a period of months. The success of these studies and potential economies from large batch production of oligodendroglial progenitors from hESCs supports development of this potential product for the treatment of patients with acute spinal cord injury.”Geron is now initiating formal preclinical safety and efficacy studies and is planning for scaled-up production of the cells for potential use in human clinical trials.
Suppose that within 5 or 10 years a Geron has a therapy derived from hESC ready for market for those suffering from spinal cord injuries. Suppose that therapy will help restore some spinal cord function with some degree of restoration of control and feeling in the lower body. The opponents of the use of hESC for therapeutic purposes are going to be faced with a much more difficult political position as the larger public has to weigh ethical concerns voiced by hESC therapy opponents against the very concrete ability to allow children and adults to arise from wheelchairs. My guess is that the hESC opponents will fail to keep hESC therapies off the market since they have failed to get a complete ban on the development of hESC therapies. Once a single therapy that provides a benefit as dramatic as helping crippled people walk again reaches the market the political opposition to hESC-based therapies will wither.
Geron is working on the basic nuts and bolts of being able to deliver therapies based on hESC as demonstrated by a report of their progress on developing better techniques for growing hESC in culture.
Menlo Park, CA – November 19, 2003 – Geron Corporation (Nasdaq: GERN) today announced the development of a defined, serum-free culture system for the propagation of human embryonic stem cells (hESCs). This new culture system relies solely on completely defined components for hESC growth, facilitating safe and scalable expansion of these cells for cell-based therapeutics.
In a presentation at the 2003 annual meeting of the American Institute of Chemical Engineers in San Francisco, Geron presented studies demonstrating that hESCs could be expanded in a culture medium that contains only human-sourced proteins and defined recombinant growth factors. Using these defined conditions, hESCs could be propagated for at least 120 days in culture while maintaining normal morphology, doubling time, and expression of a panel of markers characteristic of hESCs. Moreover, hESCs propagated under these conditions continued to be pluripotent, differentiating into cells representative of endoderm, mesoderm, and ectoderm, the three cell lineages of the human body.
This work extends Geron’s previous development of feeder-free growth conditions for hESCs. Geron had earlier developed protocols to culture hESCs in the absence of direct contact with feeder cells by using extracellular matrix proteins and cell-free media that had been previously conditioned by feeder cells. “This new development allows the replacement of conditioned medium with a fully defined medium that contains only human-sourced proteins and purified growth factors,” stated Jane S. Lebkowski, Ph.D., Geron’s vice president of regenerative medicine. “This advance greatly facilitates the scalable production of the cells while essentially eliminating the risk of contamination by non-human infectious agents in the culture process for undifferentiated cells.”
An MIT researcher has discovered a way to produce large numbers of adult stem cells.
CAMBRIDGE, Mass. -- In a finding that may help create unlimited quantities of therapeutically valuable adult stem cells, an MIT researcher fortified adult rat liver stem cells with a metabolite that allows them to multiply like embryonic stem cells.
In the absence of the metabolite, the cells revert to acting like normal adult stem cells, which produce differentiating cells without increasing their own numbers. Stem cells proliferating unchecked can cause cancer.
The idea here is that when an adult stem cell divides normally the result is one adult stem cell as well as one differentiated cell to supply to the target tissue that needs a new cell. The problem is that for therapeutic purposes what is needed is a way to tell an adult stem cell to divide to create two adult stem cells and then to divide to each create two more adult stem cells and so on until many times more adult stem cells are available. Only then in most therapies would there be enough stem cells to do cell division to produce the needed amount of differentiated cells for target tissues.
“If we want to do cell replacement therapy with stem cells, we have to be able to monitor them and avoid mutations that cause tumors in people,” said James L. Sherley, associate professor of biological engineering in MIT’s Biotechnology Process Engineering Center, Center for Environmental Health Science and Center for Cancer Research.
Embryonic stem cells can become virtually any human tissue or organ, offering potentially powerful treatments for damaged or diseased organs, spinal injuries, neurological diseases and more. Unlike embryonic stem cells, which exist only during early prenatal development, adult stem cells create new tissues throughout our lifetimes. Their potential to produce mature tissue cells may be limited to cells of the tissues in which they reside.
Actually, some adult stem cell types can become several different differentiated (i.e. fully specialized) cell types. But any one kind of adult stem cell can not become all cell types. Though at some point in the future expect to see techniques developed that will make it possible to instruct adult stem cells to become more kinds of differentiated cell types. A simple rule to remember that FuturePundit thinks by: Matter becomes steadily more manipulable and transformable to achieve more kinds of outcomes as technology advances.
One of the problems of working with adult stem cells is that they are very rare and difficult to isolate. Researchers who attempt to grow adult stem cells in the laboratory find that they cannot increase the number of stem cells in culture, because when adult stem cells divide, they produce both new replacement stem cells and regular cells, which quickly proliferate and vastly outnumber the stem cells. Adult stem cells divide to replace themselves and create daughter cells, which either differentiate immediately or divide exponentially to produce expanded lineages of differentiating cells.
In previous work, Sherley created cells that divide the way adult stem cells do -- by hanging onto their original DNA and passing copies on to the next generation of daughter cells. The theory goes that through this unique pattern of chromosome segregation, adult stem cells avoid mutations that may arise from DNA replication errors.
DIVIDING IN TWO
Sherley has dubbed this pattern asymmetrical cell kinetics because the cells don’t divide symmetrically into two identical cells. His new approach to growing adult stem cells suppresses this asymmetrical mechanism. He calls it SACK (suppression of asymmetrical cell kinetics).
Through SACK, Sherley created a way to make cells that were dividing asymmetrically like stem cells revert to dividing symmetrically. This involves manipulating biochemical pathways regulated by the expression of the p53 gene (tied to many human cancers) by exposing cells to certain nucleotide metabolites that activate growth regulatory proteins. In the absence of the metabolites, cells are converted from asymmetric cell kinetics to symmetric cell kinetics.
When p53 is switched on, cells grow like adult stem cells. While others have attempted to alter adult stem cells genetically to force them to duplicate themselves, “what’s neat about this approach is that we are regulating the biochemistry of the cell, not changing its genetics,” Sherley said.
It sounds like he has a technique that suppresses p53 and that as a result the cells start dividing in a way that each division produces two adult stem cells.
What is needed for use in conjunction with this technique are better ways to test DNA quality noninvasively. There are many genes which, if they mutate, put a cell one step closer to becoming a cancer. To develop safe rejuvenation therapies what we need is a way to test stem cells and weed out cells that have accumulated mutations in genes that are crucial for cell division control. Then aged adult stem cell reservoirs could safely be replenished with cells that are at very low risk of going on a rampage of cancerous growth.
One other point: It would be interesting to know whether this research team tested the stem cells induced to divide in this manner to discover whether the cells became any less differentiated as a result of being induced to make two cells that are still stem cells. Would continued division of this sort result in daughter cells that do not replicate the methylation patterns and other epigenetic state that the adult stem cells started out with?
Update: The ability to replicate adult stem cells would be useful for use in leukemia treatments and other treatments that are already being practiced today. Keith Sullivan M.D. of Duke University explains the difficulties involved in collecting stem cells today.
Sullivan explains that there are two ways to donate stem cells. "The first is from one's own bone marrow," he says. "This typically requires an hour or two in the operating room under anesthesia to have stem cells collected by a mini-surgical procedure in the area of the hip bone.
"The other option is to collect blood for stem cells, which is not the same as simply giving blood. Stem cells are quite rare in circulating blood, so what's needed is three or four days' worth of growth factors and shots to increase the percentage of stem cells. These stem cells are then collected on a pheresis machine, which collects the stem cells and gives the red and white platelets back."
Sullivan also notes one other important source of stem cells: "If a woman is pregnant and wishes to donate some of the blood in the umbilical cord at the time of birth, these cells have the advantage of being early, undifferentiated cells. Therefore they have less potential for reactivity and adverse complications."
If stem cells could be easily replicated then just a few could be removed from the blood and grown up to large quantities. This might eliminate the need for surgery or the administration of a few days worth of growth factors.
A Brazilian team took blood stem cells from patients suffering from paralysis and delivered the stem cells to an artery running to the site of injury.
The researchers harvested stem cells from the patients' blood, and reintroduced them into the artery supplying the area which was damaged.
Electrical nerve signals evoked in the part of the body below the injury site could be found showing up as brain activity.
"Two to six months after treatment, we found that some patients were showing signs of responding to somatosensory evoked potential tests," says Barros.
A team from the University of San Paulo in Brazil, led by Tarciscio Barros, said after treatment 12 out of 30 patients responded to electrical stimulation of their paralysed limbs.
Keep in mind that these patients did not get a large amount of function restored. They had to be tested to see a measurable difference.
The published accounts of this work do not provide enough details to be able to make any guess as to the quality of the work. Two obvious questions come to mind: Were the somatosensory evoked potential tests also performed on all the patients before they had the stem cell treatment? Also, were any controls used to compare the difference between getting and not getting the treatment?
If there really was a benefit then the question is why? The mechanism of the effect is unknown at this time. The stem cells might be delivering growth factors to the existing nerve cells to cause them to recover and grow. Or the stem cells might be merging with the nerve cells and, as a result, enhancing their functionality. Or the stem cells might be differentiating into nerve cells that bridge the gap of the injury site.
A medical conference of the American Heart Association, Scientific Sessions 2003, has produced a number of encouraging reports on the use of bone marrow stem cells to regenerate hearts, blood vessels, and even lungs. A German group used bone marrow stem cells in humans to restore heart muscle function in failing hearts.
ORLANDO, Fla., Nov. 10 – Bone marrow stem cells restored heart muscle that was damaged from a heart attack, providing a new treatment for failing hearts, researchers reported today at the American Heart Association’s Scientific Sessions 2003.
The bone marrow cells came from patients’ own blood and were injected into their ailing hearts. The cells fueled new cell growth, which strengthened the heart’s pumping capacity.
“These results demonstrate for the first time that transplantation of a person’s own stem cells through direct intracoronary injection increased cardiac function, blood flow and metabolism in the damaged zone,” said senior author Bodo E. Strauer, M.D., professor of medicine at Heinrich Heine University in Düsseldorf, Germany.
“If a prospective, randomized, multicenter study confirms these encouraging results, a new therapy for heart attacks could be in reach,” he said.
“This is a novel and exciting approach,” said Duncan Stewart, M.D., professor and director of cardiology at the University of Toronto and head of cardiology at St. Michael’s Hospital.
Pulmonary arterial hypertension (PAH) is abnormally high blood pressure in the arteries between the heart and lungs. It is a progressive disease that can affect the arterioles and capillaries that supply blood to the lungs.
“PAH reduces the heart’s ability to pump blood through the lungs and gradually leads to heart failure. Today, we can achieve some improvement with drugs, but the treatment is palliative and can only delay death,” Stewart said.
Restoring blood flow to the lungs with a stem cell transplant in the pulmonary vessels may hold promise as a new treatment for PAH, Stewart said.
His team used endothelial progenitor cells. Endothelial cells form a thin lining in blood vessels, providing an interface between the vessel and blood. This lining, called the endothelium, regulates a host of basic processes, such as blood clotting and blood pressure.
“Our results show that endothelial progenitor cells from the bone marrow circulate in the bloodstream. We can use them to form new blood vessels or repair damaged ones,” Stewart said.
Stewart and co-investigator Yidan Zhao, M.D., a research associate at the University of Toronto and St. Michael’s Hospital, removed vascular progenitor cells from rats’ bone marrow. The cells were cultured for five days, then injected into the pulmonary circulation of rats with PAH. A second group of rats with PAH received skin fibroblasts (cells), while a third group, which did not have PAH, were used as controls.
Right ventricular systolic blood pressure (the pressure when the heart contracts) was measured 21 days later. The systolic pressure of the untreated, normal rats was 26 millimeters of mercury (mm Hg). Rats with PAH had a systolic pressure of 47 mm Hg. Systolic pressure fell to 32 mm Hg in those treated with endothelial progenitor cells, and it was relatively unchanged (45 mm Hg) in control animals treated with skin fibroblasts.
Researchers at the Texas Heart Institute in Houston tested mononuclear bone marrow cell transplant injections in patients with severe ischemic heart failure — the first such study in a severely ill population. There are few treatment options for patients with end-stage ischemic heart failure, according to the study’s lead author Emerson C. Perin, M.D., Ph.D., a clinical assistant professor of medicine at Baylor College of Medicine at the University of Texas Health Science Center in Houston.
Previous laboratory research has shown that mononuclear cells taken from bone marrow then injected into human tissue can promote growth in oxygen-deprived tissue. Mononuclear cells can differentiate into tissue and new blood vessels, and secrete a wide variety of proteins and growth factors, said Perin, who is also director of new cardiovascular interventional technology at the Texas Heart Institute.
Treated patients had better blood flow and could walk longer on treadmill tests than controls. They also reported less chest pain and were able to breathe better.
“To have the sustained ability to exercise at six months is significantly different than the controls. They’re functional and they have their lives back,” Perin said.
In what could turn out to be a useful discovery for purposes extending beyond heart disease treatment a Tufts University group discovered a new kind of stem cell in bone marrow that may be able to differentiate into a wide range of cell types.
ORLANDO, Fla., Nov. 10 – A “universal stem cell clone” found in adult bone marrow regenerated blood vessels and heart muscle, according to research reported at the American Heart Association’s Scientific Sessions 2003.
The cells, called human bone marrow-derived multipotent stem cells (hBMSC), were implanted into animal hearts where they formed multiple cell types.
The hBMSC improved animals’ heart function, said the study’s lead author, Young Sup Yoon, M.D., Ph.D., assistant professor of medicine at Tufts University School of Medicine in Boston.
“This study is exciting because it is the first to show that human bone marrow includes a clonal stem cell population that can differentiate into both vessels and heart muscle. These cells can regenerate the essential tissues of the heart,” Yoon said. This finding comes from animal and laboratory research.
Such stem cells might be used to regenerate damaged hearts for people who have acute and chronic heart failure. They also might help people with hypertension, diabetes or other blood vessel diseases.
The researchers found that these stem cells didn’t belong to any previously known bone marrow-derived stem cell population (such as hematopoietic cells, the source for all types of blood cells or mesenchymal cells that give rise to cell types like bone and cartilage).These adult bone marrow stem cells have been shown to differentiate into all three so-called “germ layers.” The three germ layers of cells in early human development are the beginnings of the body’s tissues and organs. Differentiation is the term that describes the process in which stem cells change into these specialized cells.
A University of Ottawa group has found that a bone marrow stem cell growth factor helped five heart attack patients.
ORLANDO, Fla., Nov. 11 – A drug that stimulates bone marrow to produce stem cells helped regenerate damaged heart muscle in one of the first studies of its kind, according to a report presented at the American Heart Association’s Scientific Sessions 2003.The drug, granulocyte colony stimulating factor (G-CSF), treats some forms of cancer. It stimulates bone marrow to produce the different types of blood cells, including white blood cells that can become depleted after disease or chemotherapy. G-CSF might help repopulate the heart’s muscle cells, which in turn could help repair the damaged heart, said lead author Chris A. Glover, M.D. “Research has shown that there are cells in the heart that come from bone marrow stem cells. We hypothesized increasing these cells after a heart attack may help the heart regenerate heart muscle cells, and this is supported by our results,” said Glover, assistant professor of medicine at the University of Ottawa and the Ottawa Heart Institute in Ontario.
The drug -- granulocyte colony stimulating factor, or G-CSF -- was tested in only five heart-attack patients, says Chris Glover, a researcher at the University of Ottawa and the Ottawa Heart Institute. A clinical trial will begin this spring involving up to 85 to 100 patients.
ORLANDO, Fla., Nov. 12 – Heart valves engineered from patients’ own tissue may offer a new treatment for valvular heart disease, researchers reported today at the American Heart Association’s Scientific Sessions 2003.
“Using this tissue-engineered valve overcomes many of the problems with mechanical or donor valves because it is a living structure from the patient’s own tissue, and so it does not cause an immunological reaction,” said Pascal M. Dohmen, M.D., head of tissue engineering research and staff surgeon of the department of cardiovascular surgery at Charité Hospital in Berlin, Germany.
The action in heart disease research aimed at developing therapies has obviously shifted toward repair using cell therapies and the use of growth factors to stimulate and guide cells as part of cell therapies. The sheer number of research groups reporting encouraging results at a single conference suggests an even larger number of groups must be working on therapies. It is also worth noting that many of the results mentioned above were done on humans. Heart disease is a major killer. These reports in total suggest that cell therapies to repair hearts are no longer a distant uncertain prospect and successful therapies will not have to wait on advances in poorly funded embryonic stem cell research. The ability to use a patient's own cells to do repair also avoids immune incompatibility problems.
These reports are not a reason for complacency about your diet. If you think that heart disease will be curable by the time you become old enough to have a heart attack then that is not a reason for complacency about diet or exercise. The risk factors for heart disease also cause general aging to happen more quickly. A high level of cholesterol in the blood probably increases total free radical oxidative stress on the body. There is considerable overlap between a diet that is ideal for reducing heart disease risk and cancer risk. General brain aging is going to be accelerated by a high level of oxidative stress. Plaque build-up puts you at risk for a stroke and brain damage. Eat a great diet. Get plenty of exercise. We are decades away from the day when medicine can fully protect us from our vices.
"This is the first study to show that cells in the artery wall have the potential to develop into a number of other cell types," said Dr. Linda Demer, principal investigator, Guthman Professor of Medicine and Physiology, and vice chair for cardiovascular and vascular medicine at the David Geffen School of Medicine at UCLA.
UCLA researchers also report that the artery wall cells, called calcifying vascular cells (CVC), are the only cells other than actual bone marrow stromal cells that support survival of immature (developing) blood cells. This finding may have future applications in reconstitution of bone marrow after cancer treatment.
UCLA researchers cultured bovine CVC artery wall cells in the lab to see if the cells would turn into bone, fat, cartilage, marrow and muscle cells. They checked for expression of proteins and tissue matrix characteristic of each cell type.
"We wanted to see if CVC cells would become specific cell types that actually produce their own characteristic matrix (mortar-like) substance. For example, if the cell actually produced bone mineral, it would indicate that the cell had taken on a bone identity," said first author Yin Tintut, Division of Cardiology at the David Geffen School of Medicine at UCLA.
Researchers found that CVC cells had the potential to become several cell types, including bone, cartilage, marrow stromal and muscle cells, but not adipogenic, or fat, cells. Demer suggests this indicates that the CVC cells may not have the entire range of conventional stem cells. However, this may be especially useful in cases where one would not want the stem cell turning into a fat cell — such as in trying to regenerate cartilage.
The next step involves "assessing CVC cells' potential to follow other lineages and also testing human cells," Demer said.
The ability to convert into muscle cells is notable because of the need for therapies to repair damaged heart muscle. It would be interesting to know whether these scientists tried to convert the cells to any internal organ cell types.
DALLAS, Oct. 14 – Infusing a patient’s own cells into a heart artery several days after a heart attack speeds the healing process and strengthens the heart’s pumping power, researchers report in today’s rapid access issue of Circulation: Journal of the American Heart Association.
In a small study of heart attack patients, German researchers extracted progenitor cells from patient’s blood or bone marrow and infused them into an artery. Progenitor cells are derived from stem cells, which have the potential to develop into any cell in the body. Progenitor cells are already on their way to becoming a specific type of cell.
“The infusion of progenitor cells was associated with a reduction in the size of muscle damage, a significant improvement in pumping function, and less enlargement of the heart within four months after a heart attack,” said co-author Andreas M. Zeiher, M.D., chairman of the department of internal medicine at the University of Frankfurt in Germany.
This latest report comes after a recent report about bone marrow stem cells merging with brain Purkinje neurons rather than forming new cells. The authors of that report voiced skepticism that bone marrow stem cells will ultimately prove to be useful in treating conditions in a large number of different types of tissue. This latest report from the University of Frankfurt did not use enough patients or double-blinded controls and will need to be followed up by a larger study with better controls. But it is promising.
Sufferers of cataracts and just about anyone over the age of 40 and suffering from presbyopia (aka farsightedness - inability to focus on close-up objects) may be helped by a new replacement gel material for eye lenses to restore the lens flexibility that is lost with age.
"The gel material is soft to the touch, and it has elastic properties similar to those found in the natural human lens," Fetsch says. "It also looks as if it has the potential to be injectable, which would mean it could be deliverd with less invasive surgery."
Ravi and Fetsch say that using molecular techniques, it's possible to change the artificial lens material from a gel to a liquid. That liquid then can become a gel again in the presence of oxygen in the body after it is injected into the capsular bag. The hope would be that only a very small injection hole would be required during cataract or other lens replacement surgery so that patients undergoing the operation would not require stitches.
The researchers expect to begin animal testing early next year. What they reported to the American Chemical Society was work that involved mechanical and physical testing of the hydrogel that was done in the laboratory. Before testing the hydrogel in animals, the researchers also hope to improve the material's refractive index — the degree at which it refracts light — a key to how well the eye can focus once the material is implanted.
"Currently, in this particular system, the refractive index has been a little low," Fetsch says. "It's not good enough to be able to provide much more than blurry vision."
But other researchers in Ravi's group, particularly research associates Hyder Ali Aliyar, Ph.D., and Paul Hamilton, Ph.D., have successfully formed several soft gels with the appropriate refractive index. "It's a very significant breakthrough," Ravi says.
The researchers admit there is still much work ahead before an injectable lens could be used in human patients, but Fetsch and Ravi expect it would be introduced into cataract patients first.
This latest report from a Washington University of St. Louis research led by Nathan Ravi MD PhD follows on the heels of an Australian group's report of the development of a competing material that holds promise for the same purpose. It seems very likely that within 10 years effective treatments for reversing age-related presbyopia will be available.
Dr. Arthur Ho of the University of New South Wales and a member of Australia's Vision Co-operative Research Centre (Vision CRC) believe his team has developed a gel which can be placed inside aged eye lenses to correct eyesight.
A CURE FOR AGING EYESIGHT is on the way, with the development by an Australian team of a permanent lens and gel that can replace the normal lens of the eye.
Scientists at the Vision CRC are well advanced in their quest to develop an implant that overcomes both loss of focus in aging eyes - or presbyopia - and other vision problems such as short sightedness.
Its developers believe that if successful in human trials - due to begin in 2004/05 - the technique will also overcome cataracts as a cause of loss of sight.
Tests found that the implantable gel lens has around four times the focal power of a pair of reading glasses - significantly better than the researchers' had aimed for, says team leader Dr Arthur Ho. "However we have yet to test it in human patients, so we won't know for sure till then," he adds.
Work on the implantable gel lens began in the CRC for Eye Research and Technology and is being carried on in the new Vision CRC. "Our initial aim was to overcome the inability of the aging eye to focus close-up, caused by the gradual hardening of the lens," Dr Ho explains. "This affects almost everyone aged 45 or more. In Australia, that's about 6.7 million people now - and around 9.9 million by the end of this decade, or 44 per cent of the population."
However the team also wanted to combine the ability to focus close-up with other forms of vision correction, such as distance refractive error - to provide total correct vision, short and long, for the ageing eye.
Besides inserting the soft gel lens, they also propose to insert a novel 'mini-lens' to correct other aspects of vision. This 'mini-lens' will be embedded in the gel within the human lens itself, giving both distance and close-up vision and, potentially, good vision at all distances that will last many years - maybe even a lifetime.
The theoretical potential of this approach has been known for some time due to research at other universities. But a suitable material has not been found up till now. The scientists will not reveal many details about the material until it is patented.
After evaluating more than 30 different polymer formulations created at collaborating Australian research institute, CSIRO Molecular Science in Melbourne, Ho thinks the group has cracked it. Vision CRC is staying tight-lipped about the new formulation while it is being patented. All the team will say is that it is a siloxane-based material, which is cured with UV or visible light after injection to turn it from a liquid to a gel.
The gel, which has the consistency of thick oil, is pumped in and a burst of UV or visible light transforms it into jelly. "This could be a quick 15-minute procedure," said Mr Ho.
Anyone in their mid 40s or older could benefit from this technique once it becomes available. Five years from now the market for reading glasses may be shrinking rapidly.
Cambridge University researcher John Gurdon and colleagues have transplanted adult mouse and human nuclei into frogs eggs and found that frog egg cytoplasm has compounds in it that induce the production of Oct4 RNA which is normally expressed only in pluripotent embyonic stem cells.
When the researchers injected the adult nuclei into frog egg nucleii, rather than into the surrounding cytoplasm, Oct4 levels shot up by a factor of ten. "The reprogramming activity is particularly concentrated here," says Gurdon. Molecules in the frog nucleus may be responsible for the eggs' revitalizing abilities, he speculates
"We believe that the ability of amphibian oocyte components to induce stem cell gene expression in normal mouse and human adult somatic cells, and the abundant availability of amphibian oocytes, encourages the long-term hope that it may eventually be possible to directly reprogram cells, easily obtained from adult human patients, to a stem cell condition,"
Frog eggs are larger and much easier to work with. Also, since they are larger and have now been demonstrated to contain compounds that can cause mouse and human genomes to revert to a state more like the embryonic state it will be much easier for the scientists to isolate the compounds in the eggs that can do this. Trying to get enough human or mouse egg contents to fractionate and look for active compounds for this purpose would be much harder.
The obvious larger goal behind this research is to be able to take a sample of a person's cells, make those cells revert to an embryonic state. Those cells then would hold the potential to be coaxed into growing replacement organs or to supply various adult stem cell lines to replenish depleted aged stem cell reservoirs in the body.
Keep in mind that while a great deal of debate centers around whether human embryonic stem cell research should be allowed and in what ways it is ethical to acquire embryonic stem cells there is a great deal of research work on the state of other cell types that needs to be done to make useful therapies as well. Just as we need to understand better what exactly defines an embryonic stem cell or how to make a cell become an embryonic stem cell we also need to understand how cells become and maintain their state as other cell types.
Imagine you wanted to take some embryonic stem cells and convert them into liver cells in order to grow a new liver. Cells converted from one cell type to another cell type using some manipulation may be converted to a state that makes them seem like liver cells. But since they would not have experienced the exact sequence of signals and timings of signals that cells would experience in a developing embryo they may in some subtle way be different than liver cells in the regulatory state of their genes. Then the one potential danger is that they might revert to an embryonic state or convert into cancer cells or become some other undesired cell type.
See also the Better Humans report on this for other relevant links.
This report comes on the heels of the discovery of the gene Nanog which can turn adult cells into embryonic stem cells.
Technology Review has a good review article on various efforts to use cells grown in mechanical devices to create temporary organ replacements for kidneys, livers,
“Patients who are undergoing chronic dialysis become malnourished, and they sort of wither,” says Harmon. The solution, believes Humes, lies in harnessing kidney cells themselves—cells that can rapidly react to changes in the body’s environment in a way that machines simply can’t.
The kidney-in-a-cartridge, which is being developed by Lincoln, RI-based University of Michigan spinoff Nephros Therapeutics, could be ready for widespread use in as little as three years. And it’s only one example of the increasingly popular strategy of using living cells to do the heavy lifting in artificial organs. Several academic labs are developing similar devices packed with liver cells to chew up the toxins that accumulate in the blood when the liver suddenly fails. Already in human trials, these bioartificial livers could help patients in acute liver failure, whose only chance today is a rare organ transplant.
Nephros Therapeutics, Inc. announced today the successful completion of a Series C financing totaling $17 million to accelerate the clinical development of its lead product, the Renal Assist Device (RAD). Based on patented renal stem cell technology licensed from the University of Michigan and invented by Dr. H. David Humes, Nephros is developing the RAD for the potential treatment of Acute Renal Failure (ARF). Lurie Investments of Chicago, IL led the financing round. New investors participating in this round include CDP Capital of Montreal, QC, as well as Foster & Foster of Greenwich, CT. All of Nephros’ existing investors, including BD Ventures, Portage Venture Partners, North Coast Technology Investors, Palermo Group (an affiliate of the Apjohn Group), and the founding investor, Seaflower Ventures, also participated in this round.
Nephros’ Renal Assist Device (RAD) is a cellular replacement therapy system that leverages the Company’s proprietary Renal Proximal Tubule (RPT) cell technology for the potential treatment of ARF patients. RPT cells play a key role in the regulation of response to inflammation and stress and are critical to normal kidney function and the patient’s ability to fight infection. Nephros has established pioneering technologies to isolate and expand (ex vivo) kidney-derived stem cells and to then create delivery systems. In contrast to the limitations associated with current replacement therapy (e.g. hemodialysis), the RAD’s RPT therapy is being investigated for the potential to replace and maintain a full range of key functions of the kidney, including endocrine equilibrium, metabolic activity and immune surveillance. Nephros is currently supporting two Phase I/II physician-sponsored clinical trials for RAD, at the University of Michigan and the Cleveland Clinic, for the potential treatment of ARF.
David Humes, M.D., Professor of Internal Medicine at the University of Michigan has worked for a decade to develop the bioartificial kidney that is going thru clinical trials.
A bioartificial kidney device invented by Dr. Humes is being clinically evaluated for treatment of patients in acute renal failure. Phase II human trial of the device has been approved by FDA and is expected to commence in the Fall of 2003.
The same core technology using adult kidney stem cells will be soon be tested in a device designed to ameliorate hyperinflammation associated with End Stage Renal Disease. Hyperinflammation may lead to infections and cardiovascular problems, leading causes of early death in chronic renal failure patients.
No volunteers are needed for either of these studies.
Phase I trial recently concluded on the device for treating acute renal failure was led by principal investigator Robert Bartlett and co-investigators William (Rick) Weitzel and Fresca Swaniker in Ann Arbor and by Emil Paganini in Cleveland. The initial study demonstrated that the device is safe for further testing. The next investigations will measure the treatment's effectiveness. Published results, as they become available, will be added to the link at the bottom of this page.
Acute renal failure is a sudden onset of kidney failure brought on by accident or poisoning. Unlike chronic renal failure, acute renal failure is potentially reversible, if the patient can be sustained through the episode. Most cannot. The mortality rate of ARF is greater than 50%.
The poor survivability of ARF appears to be linked to the loss of certain functions of the kidney that reside in cells called renal proximal tubule (RPT) cells. The RAD conceived by Dr. Humes contains living human renal proximal tubule cells. In large animal studies [reported in the journal Nature Biotechnology (April 30 1999)], the Humes lab demonstrated that the cells in the RAD perform the metabolic and hormonal functions lost in ARF. Restoring these critical functions by use of the RAD may be key to helping patients survive acute renal failure.
Because the RAD contains living human tissue it is termed a bioartificial kidney.
Initial trials with patients suffering from acute kidney failure were more successful than expected probably because the bioartifiical kidney cells released chemical messengers that suppressed an immune response that was damaging the kidneys of the patients experiencing kidney failure.
In early clinical trials at the University of Michigan, a bioartificial kidney has been used in a handful of intensive-care patients who were deemed very likely to die because kidneys and other organs were failing. All but one recovered with normal kidney function.
Also see this previous post entitled Device Maintains External Liver Cells For Blood Filtration.
Current purely artificial kidney dialysis machines do only a subset of what a real kidney does and there is a clear need for functionally richer replacement devices. Bioartificial livers and kidneys which use living cells are going to reach the market well before fully functional purely artificial versions of those same organs are ready. In large part this is because we do not know all the functions that livers and kidneys carry out. Best to use cells that know how to do all the functions while scientists try to figure out how those organs work in greater detail.
Complete organs grown to replace diseased organs are also further into the future than bioartificial devices. The tissue engineering problems involved in growing complete organs are also a lot tougher to solve than problems involved in growing cells in artificial apparatuses. My guess is that for more complex organs such as the liver and the kidney the ability to grow replacement organs will be achieved many years before the ability is developed to build a totally artificial organ that carries out all the functions that the real organs do.
Whitaker Foundation and University of Toronto researcher Molly Shoichet has developed a polymer scaffolding that looks like bone which bone marrow cells can infuse into and then grow bone that replaces the slowing dissolving scaffolding.
The new bone grows naturally without the addition of chemical growth stimulants, said Whitaker investigator Molly Shoichet, Ph.D., of the University of Toronto. The innovation is in the design of the synthetic scaffold that provides a framework for the growing tissue.
The design mimics the structure of natural bone so faithfully that some experts in the field cannot distinguish between the two when shown micrographs of each side-by-side, Shoichet said. The research was published in the June 15 issue of the Journal of Biomedical Materials Research Part A.
"The structure is very open and porous," she said. "There are large interconnections between the pores separated by struts, rather than solid walls."
Into this spongy matrix, the researchers drizzle bone marrow cells, which can differentiate into osteoblasts, the strong, mineral-like cells of mature bone. The marrow cells take up residence in the scaffold and begin growing and multiplying. As they mature, the scaffold itself dissolves.
"You don't need growth factors to get the cells into the scaffold," Shoichet said. "The cells almost fall through it and get stuck along the way."
The scaffold, developed with coinvestigator John Davies of the University of Toronto, is made of poly(lactide-co-glycolide), a polymer used in sutures. The polymer is processed in a unique way to yield the open, sponge-like structure with pores more than 10 times larger than those that result from conventional processing.
Animal studies show that the scaffold provides an intricate framework for dense new bone growth while it slowly dissolves. In rabbits, strong new bone completely replaced the scaffold in about eight weeks.
Researchers from the University of Pittsburgh McGowan Institute for Regenerative Medicine have developed a device for growing liver tissue outside of the body to use as a blood filtering device that is analogous to a kidney dialysis device. This device has been used on 8 people so far.
Growing functioning liver tissue in a fist-sized device that works in a way similar to kidney dialysis has kept patients in liver failure alive until donor organs have become available, according to Jörg Gerlach, M.D., Ph.D., professor of surgery at the University of Pittsburgh School of Medicine. "We have treated eight patients in acute liver failure - some of whom were in a coma - who were able to be bridged to transplant," said Dr. Gerlach, who also is a faculty member of the university's McGowan Institute.
Dr. Gerlach and his colleagues have been able to grow functioning liver tissue from human liver stem cells derived from organs that had been deemed unsuitable for transplant because of damage or underlying disease. Such cells have been shown to proliferate and form liver-like tissues in bioreactors, and persist in culture for many weeks.
About 25 million Americans - one in 10 - have liver disease, according to the American Liver Foundation. More than 43,000 people die of liver disease yearly. Annual hospitalization costs exceed $8 billion. Dr. Gerlach's bioreactor could have an impact for the sickest of these patients, who often do not survive the wait for transplantation or become too sick to qualify for a transplant.
Once the ability to grow replacement livers is developed then one future application for this type of device would be to give a person time to live while a replacement liver was grown from his own cells in an artificial vat.
Teams led by Austin Smith of the University of Edinburgh in Scotland and by Shinya Yamanaka of the Nara Institute of Science and Technology in Japan have discovered a gene they named nanog which may be capable of turning any cell into an embryonic stem cell.
In one crucial experiment, Smith's team inserted copies of the human nanog gene into mouse embryonic stem cells, and subjected those cells to laboratory conditions that normally force such cells to mature and become one kind of tissue. The human nanog gene prevented that process.
The experiments suggest that as long as the nanog gene is turned on a cell will not differentiate into a specialized adult cell type. What would be interesting to know is whether non-embryonic stem cells also have nanog turned on.
The development of the means to control the expression of genes such as nanog which regulate the type of tissue that cells become will eventually open the door to the ability to grow replacement organs and stem cell therapies to rejuvenate aged stem cell reservoirs. In other words, this latest result is an important step toward the development of the means to reverse the aging process.
So why did they call the gene Nanog? Tir Nan Og is the land of the forever young in Celtic mythology. Tir means Land. Na Nog or Nan Og stands for "Of Youth" or "Of The Young". We in this age are living so close to the time when the breakthroughs that will make Engineered Negligible Senescence possible that we could fairly be said to be living in Tir Tairngire or "Land of Promise". Tir Na Nog is pronounced teer na no-'gue and many of us may live in it some day.
Tir Na Nog is also known as Mag Mell or "plain of joy". It bears some resemblance to Philip Jose Farmer's Riverworld since anyone who dies there reawakes the next day fully restored.
Tir Nan Og is the land to which the Irish faeries know as Tuatha de Danann (Too-ah day Thay-nan, or Tootha day danan) flead when their lands were taken by the Milesians. In Tir Nan Og they spend their days feasting, gaming, love-making and partaking of beautiful music. The faeries can even enjoy the thril of battle, for anyone slain is resurected the following day. It is the paradise that mortals can only dream of.
No ploughing, no work is needed to make a living in Tir Nan Og: the faerie make love, have feasts, hunt and even play at war with one another--those that die one day are resurrected the next morning to join in the fun again. Occasionally, they grow curious about the humans who live on the other side of the Great Mist, or need to strengthen themselves with a fresh and vigorous human bloodline--and that is when they step out of their dark forests, through the silvery mist to be called into Legend...
Update: New Scientist coverage:
"Nanog seems to be a master gene that makes ESCs grow in the laboratory," says Ian Chambers, one of the team at the Institute for Stem Cell Research (ISCR), Edinburgh, Scotland. "In effect this makes stem cells immortal."
Their finding could ultimately enable scientists to transform stem cells from adults into cells that have all the characteristics of those taken from embryos.
Researchers at Genzyme published some results last fall that suggesd that two different types of adult stem cells extracted from different parts of the body may not be different from each other.
Date: October 28, 2002
Genzyme Biosurgery (Nasdaq: GZBX), a division of Genzyme Corporation, today announced the publication of a research paper that casts new light on the nature of adult stem cells. In a paper published in the Oct. 28 issue of Tissue Engineering, scientists in Genzyme's Stem Cell Biology Research Laboratory demonstrate that many adult stem cells that have been claimed to be unique are actually "virtually indistinguishable" from one another in the laboratory, sharing many of the same physical and functional properties. The finding helps to clarify the many competing claims about the potential use of adult stem cells in a range of therapeutic applications.
In recent years, a growing number of researchers have reported that through a variety of proprietary methods they could generate cells with the potential to differentiate into a variety of specialized cell types, including nerve, cartilage, muscle, and endothelial cells. What has not been clear in these individual studies is whether the adult stem cells themselves are actually distinct, or whether they gained their distinction in the laboratory.
To help answer this question, Genzyme's study team systematically tested the approaches taken by various companies and laboratories. The Genzyme team isolated mesenchymal stem cells derived from the bone marrow of adults, and subjected them to a variety of the laboratories' research protocols used to develop cells capable of differentiating into nerve, cartilage, muscle, and endothelial cells. They found that regardless of the protocols used to isolate and propogate these cells, they were "virtually indistinguishable" from one another in several important ways. Each cell, for example, expressed the same or similar cell surface markers, or antigens. They also showed a common ability to undergo differentiation into nerve, cartilage, muscle, and endothelial cells based on culture conditions. The researchers concluded that although these stem cell populations were previously reported to be distinct from one another, on closer analysis they are not.
"We have shown that we can reproducibly isolate and propogate adult stem cells and demonstrate their potential to differentiate using a variety of methods," said Ross Tubo, PhD, director of Genzyme's Stem Cell Biology Research Laboratory. "These results give a strong indication that adult stem cells are robust and have great therapeutic potential for use in tissue regeneration. These findings help to clarify the complex and many times confusing literature surrounding adult stem cells."
Commenting on the findings of the Genzyme study, Dr. Diane Krause, associate professor of laboratory medicine at Yale University said: "The finding that these cells are very similar in their surface phenotype and their ability to differentiate into chondrocytes and neural-type cells helps us to make sense of the diverse literature in this field, paving the way for uniform isolation and propagation of mesenchymal stem cells for tissue engineering."
If adult cells from different reservoirs in the body that get used for different purposes are (at least in some cases) essentially the same as stem cells in other parts of the body then that would make it easier to get stem cells to use to develop various types of therapeutic treatments. It might turn out to be easier to, for instance, get some stem cells that would make good starters for growing replacement organs. This would be good.
The New Scientist has just picked up on this report and their story includes quotes from scientists who voice doubts about the conclusions which Genzyme researchers are drawing from their work. Some other stem cell researchers do not view the 12 chosen surface protein markers as definitive indicators of the type of a stem cell.
But not everyone agrees. Looking at 12 markers and two cell fates does not justify conclusions of such magnitude, says stem cell biologist Leonard Zon of Harvard University. "It's far from settled," he says. "I'd love for it to be simple, but it's not."
The other major point of contention has to do with how the cells were grown:
There is also debate over a seemingly small, but potentially important change in the method that Genzyme used to obtain MAPCs. A key step in obtaining MAPCs, according to Ohio-based Athersys, the company that has licensed the technology, is to grow bone marrow cells at a very low density. Yet Tubo's team obtained nothing this way and instead grew cells at a high concentration.
My guess is that it will be necessary to check a lot more markers (especially by measuring the expression of a large number of genes) to find out whether these stem cell types are really the same. If, for instance, growing stem cells at different densities changes what kinds of stem cells they are then what is really being demonstrated by these results might be just another way to change adult stem cell types into other adult stem cell types.
The bigger mystery continues to be just how difficult will it be to make stem cells into useful medical therapies? The potential payoffs include replacement organs, treatments for degenerative neurological disorders, and revitalization of aged stem cell reservoirs with youthful replacements. All of these uses of stem cells will eventualy help to reverse the aging process.
Human adult bone marrow stem cells transplanted into immune-deficient mice migrated to the livers of the mice and showed signs of differentiating into functional liver cells.
"There is a huge demand for liver transplants but there are never enough organs, and the procedure is not always successful," says study leader Jan A. Nolta, Ph.D., associate professor of medicine. "We're hoping that in the future we can use bone marrow or umbilical cord blood stem cells from matched donors to help treat liver disease and reduce the need for liver transplants."
Nolta and her colleagues isolated highly purified human stem cells from bone marrow and umbilical cord blood and transplanted them into immune-deficient mice. The purified stem cells normally give rise to cells that mature into red blood cells and white blood cells.
A month later, after the human stem cells had established themselves in the animal's bone marrow, the investigators induced liver damage. Some mice also were given human hepatocyte growth factor to increase the number of stem cells that developed, or differentiated, into liver cells (also known as hepatocytes).
A month after inducing the liver damage, the investigators compared the damaged organs to healthy ones from control mice that also had been transplanted with human stem cells. They tested the livers for the presence of human albumin, a protein produced only by liver cells. Any human albumin found in these mice would have to have come from transplanted human stem cells that had developed into liver-like cells.
Nolta and her colleagues found the greatest number of human-albumin-producing cells in the damaged livers of mice that had been treated with human hepatocyte growth factor. In some cases, albumin began showing up as early as five days after treatment. The number of stem cells that had differentiated into liver-like cells was low, however, making up less than 1 percent of all liver cells. Human albumin was not detected in mice with healthy livers.
The investigators believe that the stem cells moved from the bone marrow into the circulating blood, then left the blood to reside in the damaged liver, where they became liver-like cells that produced human albumin.
"These results show that human stem cells from bone marrow and umbilical cord blood are a potential source of liver cells," says Nolta, who also is a member of the Hematopoietic Development and Malignancy Research Program at the Alvin J. Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine.
The study also represents the first successful animal model for studying how stem cells from human bone marrow and umbilical cord blood might be used to treat liver disease.
Nolta and her colleagues now are working to increase the number of human stem cells that differentiate into liver cells in this model by studying the signals that draw the cells into the liver and control their transformation, a feature known as stem-cell plasticity. In addition, they are investigating the use of blood-forming stem cells for the repair of heart and skeletal muscle.
Cell therapies will become incredibly useful very quickly once scientists develop better ways to control how stem cells migrate and turn into target tissue cell types (the process of cellular differentiation). Gene therapies will be developed that have the effect of ordering stem cells to become particular types or go to particular organs. Also, additional growth factors will be identified and worked into therapeutic regimes performed on stem cells to instruct them to multiply and become desired cell types.
We are coming ever closer to the era when repair and replacement of the most diseased and damaged tissue will become routine and easy to do. It is difficult to say when that era will arrive in full force. However, there are enough early stage successes being reported that it seems unlikely that we will have to wait longer than 20 years before it becomes common to basically order large numbers of stem cells to go hither or thither to meet some urgent need.
Fifty years from now youth will find it hard to believe that people used to die because of organ failure. The techniques used for the production of human replacement parts will become so well understood and cheap to employ that the idea of dying for lack of a healthy liver or kidney will seem as absurd as dying of scarlet fever seems today in industrialized countries (where most people no longer even know what scarlet fever is).
The future will be marked by the end of long-believed inevitabilities. The biggest shock to come will happen when people realize that aging is going to cease to be inevitable. There are already hundreds of millions of people alive who will live to see that day.
Tissue engineers who recently demonstrated penis replacement in animals have now added a vital missing component - nerve cells.
"The nerve cells are very important - they are responsible for all the sensory function," says Anthony Atala, at Boston Children's Hospital. "In order to do complete [penile] replacements we need to make sure all of the parts are there, including the nerves."
Keep in mind FuturePundit's rule for biotechnology: any biotechnology developed for repair will eventually be used for enhancement. There will be a big demand for this.
Biotechnology offers other promising future improvements. A couple of years ago a report was made on growth of breast tissue. The days of silicone implants are numbered.
One of the problems holding back the use of other species to grow organs for transplant into humans is the presence of retroviruses in their genomes that could activate in humans and cause a devastating infection. There is even a risk that such an infection could turn out to be transmissable to other humans. This problem has so far ruled out the use of other primate species as a source of organ transplants in spite of their greater genetic similarity to humans than is the case with other types of species. However, a type of miniature pig (mini for a pig still means 250 pounds when fully grown) that has been found to not have viable retroviruses. In particular it doesn't have viable Porcine Endogenous Retrovirus or PERV. For this reason this pig breed has attracted the attention of researchers who want to develop pigs as a source of replacement organs.
One obstacle to the use of pigs is an enzyme that pigs have called a-1,3-galactosyltransferase or GGTA1. GGTA1 puts a sugar of surface of cell membrane proteins that causes human immune systems to recognize those proteins as foreign and to vigorously and rapidly attack them. Some scientists have recently created a pig that lacks this problematic enzyme.
AUCKLAND, NZ, January 13, 2003 -- In a session today at the annual meeting of the International Embryo Transfer Society (IETS), Randall Prather, Ph.D., Distinguished Professor of Reproductive Biotechnology at the University of Missouri-Columbia, announced the successful cloning of the first miniature swine with both copies of a specific gene "knocked out" of its DNA. The ultimate goal of this research, which is being conducted in partnership with Immerge BioTherapeutics, Inc (a BioTransplant Incorporated (Nasdaq:BTRN)/Novartis Pharma AG (NYSE:NYS) joint venture company), is to develop a herd of miniature swine that can be used as a safe source for human transplantation, a process known as xenotransplantation.
"The fact that we have been able to clone this particular strain of miniature swine with both copies of the gene that produces GGTA1 knocked out is a very exciting step for the field of xenotransplantation," said Dr. Prather, a researcher in MU's College of Agriculture, Food and Natural Resources. "Organs from regular swine are too large for human transplant, and this particular strain of miniature swine has been refined for years solely for its potential use in humans."
New options for organ sources are desperately needed to treat the rapidly increasing number of critically ill people on the transplant waiting list (more than 80,000 in the U.S. alone). Researchers have targeted the pig as the best potential candidate for an alternative organ source because of the similarity between human and pig organs and the relative ease of breeding. However, the massive rejection response mounted by the human immune system has been a major hurdle in this research.
A key player in this rejection process is the gene called a-1,3-galactosyltransferase or GGTA1 that produces a sugar molecule. When a foreign organ is introduced, human antibodies attach to the sugar molecule on the surface of pig cells produced from the action of the GGTA1 molecule, thus killing the organ. With both copies of this gene eliminated, the antibodies cannot attach, halting the early rejection process.
Dr. Robert Hawley and scientists at Immerge, in collaboration with Dr. Kenth Gustafsson, first identified the gene that produces GGTA1 and eliminated, or knocked it out, of the DNA of the cells from the miniature swine. This genetic material was then sent to Dr. Prather's lab, where Dr. Liangxue Lai and colleagues implanted it into an egg that had its DNA eliminated. The egg was stimulated to begin dividing and was later implanted into a sow. Prather and Immerge announced in January 2002 in the journal Science that they had successfully cloned the world's first single knock-out miniature swine. The genetic material from these swine was then re-engineered with the aim of knocking out the second copy of this critical gene. These cells were then subjected to another round of nuclear transfer cloning, leading to the birth of the double knock-out piglet on November 18, 2002.
The presence of the sugar on pig organs has provoked such a strong immune reaction in primates that it has not been possible keep pig organs alive in primates for more than a few hours. However, with the removal of this sugar it will likely be possible to test organs for other immune incompatibilities. It may well turn out that there are many other causes of immune incompatibility and it may require a series of cycles of testing, genetic modification of pig genomes, and then recloning to create pigs that are more immunologically compatible. It is difficult to say at this point how many iterations of genetic engineering modiifications, cloning, and testing will be required to make pigs that are immunologically compatible with humans. The process could take several years or even as long as a couple of decades.
Researchers said many issues must be resolved before the promise of transplanting pig organs becomes a reality. They predict it will be at least two or three years before the transplants can be tested in humans, and then only if they can show that the transplanted organs survive in primates for more than six months without requiring such severe suppression of the immune system as to pose a danger to patients.
Another approach would be to use human stem cells to develop into organs in pigs or another species. That way the resulting organ would be more likely to be immunologically compatible with a human recipient. However, then one runs into ethical problems (see the previous post on mini human kidneys grown in mice) because of the methods used to get stem cells that are in the proper genetic regulatory state to be able to become the desired type of organ. Some scientists still think the use of human stem cells will be what wins the race in the long run but others say that the use of pigs will produce useful transplantable organs before a technique utilising human stem cells does.
On the bright side the competition between different technological approaches increases the odds that at least one approach will succeed in producing transplantable organs in 10 or 15 years.
Update: A friend raises an excellent point that I've not seen raised before in discussions about xenotransplantation: xenotransplant organs from a species which has a shorter lifespan than humans (which pretty much describes all species that are candidates for use as xenotransplant organ sources) will probably not last as long as organs grown from human stem cells. Pigs in the wild have a life expectancy of about 25 years and some of their organs will be fairly aged by the time they die. This doesn't seem like a major obstacle to the use of pig organs though. Suppose pig organ transplanted into a human will last 20 years. Someone getting a pig organ transplant in 2010 would have until 2030 to come up with a replacement. By that time it seems very likely that the growth of replacement organs from human stem cells will be possible.
In the longer run the genetic variations that make organs wear out more or less quickly will become identified. DNA sequence comparisons of shorter and longer lived humans will be done once the cost of DNA sequencing drops by orders of magnitude. This will lead to the identification of all genetic variations that affect longevity. This information will be used to do gene therapy treatments to human stem cells to make organs grown from them last for much longer periods of time. Also, entirely new genetic changes will be developed to make organs last far longer than any human's organs can last naturally.
Cynthia Cohen, senior research fellow at the Kennedy Institute of Ethics at Georgetown University and member of a national Episcopal task force on ethics and genetics, said the moral status of the embryo "arouses the most vehement discussion" when she addresses church and civic groups.
Cohen said she believes, as do many scientists and religious leaders, that "very early embryos" -- those younger than 14 days -- cannot be considered human because cells have not formed a single, individualized entity.
The argument of ethicists who make the 14 day distinction is that cells that are not yet organized 3 dimensionally into shapes haven't really started to create a life. They argue therefore that it is ethical to take cells from an embryo that is less than 2 weeks old and starting doing things to those cells to induce them to change into a more differentiated (i.e. specialized, less general purpose) state in order to grow organs or to make non-embyronic stem cells for stem cell therapeutic uses.
If the 14 day dividing point was legally adopted this would not move us that much closer to being able to grow replacement organs. Cells from the first two weeks of embryo development would not immediately be usable for, say, growing organs. As was demonstrated recently with mini human kidneys grown in mice it is not until the later stages of embryo development (7-8 weks in the case of kidney progenitor cells) that cells change into progenitor cells that are suitable for growing organs. Without the larger developing embryo to use as a context that interacts with organ progenitor cells to bring them to the point where they are readly to become organs scientists would have to figure out how to make early embryo cells turn into cells that are for growing particular organ types. That may turn out to be a fairly difficult problem to solve.
The strong opponents of therapeutic cloning in the United States are not going to find the 14 day development point an acceptable boundary for the last point to which human embryos can be grown to for the purpose of extracting cells for therapeutic cloning. In cloning an adult cell nucleus is placed in an unfertilized egg in place of the egg's nucleus. This is done to make the regulatory state of the adult nucleus (which has a full genetic complement whereas the egg has only half a genetic complement and normally gets the other half by fertilization by a sperm) revert back into the state close to that of a freshly fertilised egg.
Any technique is going to elicit religiously motivated ethical objections as long as the technique causes a nucleus to revert to the state that is the same as that of a freshly fertilized egg's nucleus. If one could get an adult nucleus to convert directly into the genetic state of an organi progenitor cell (e.g. the genetic state of a kidney progenitor cell between the 7th and 8th week of embryonic development) then one would effectively avoid the main ethical objection raised against the technique of therapeutic cloning.
Tissue engineering is a hot field. Electrospinning is a promising technique for making a three dimensional scaffold for growing replacement tissue.
RICHMOND, Va. – Traditional heart bypass surgeries require using veins from the leg to replace damaged blood vessels. Using a nanotechnology developed by Virginia Commonwealth University researchers, doctors soon could be using artificial blood vessels grown in a laboratory to help save half a million lives every year.
The new technology produces a natural human blood vessel grown around a scaffold, or tube, made of collagen. Using a process called electrospinning, VCU scientists are making tubes as small as one millimeter in diameter. That’s more than four times smaller than the width of a drinking straw and six times smaller than the smallest commercially available vascular graft.
VCU Biomedical Engineer Gary L. Bowlin, Ph.D., said patients don’t always have enough spare veins for a heart bypass, and even when they do, complications and failures often result because they are not compatible. “So what’s really needed is a blood vessel you can pull off the shelf,” said Bowlin.
After the scaffold is spun, smooth muscle cells are “seeded” or placed on its surface in a laboratory. The cells grow and within three-to-six weeks the tissue-engineered blood vessel is ready to implant.
Unlike current synthetic plastic blood vessels, collagen is a natural component of the body, allowing cells to grow on its surface and avoid rejection. “The cells are in a happy environment and they’re just going to stay and think ‘I’m a blood vessel, I’m going to act like a blood vessel,’” said Bowlin.
The collagen scaffold is biodegradable and eventually is replaced by the body. Pre-made blood vessels could be made available to emergency rooms where every second counts. Other applications include pediatric surgery where implanted blood vessels must grow with the patient and diabetic patients who often lose blood vessels to vascular disease.
The same collagen electrospinning technology can also be used to regenerate or replace skin, bone, nerves, muscles and even repair spinal cord injuries, according to co-inventor Gary E. Wnek, Ph.D., a VCU chemical engineer. “Anything you want to repair can start from a scaffold. We’re very excited about the potential,” said Wnek.
Practical applications of the new technology could be commercially available within three years.
Through VCU, the researchers formed a company called NanoMatrix to produce and test their products. Within two to three years, NanoMatrix expects to have products on the market, Bowlin said.
His co-inventors are Gary E. Wnek, a chemical engineer interested in nerve repair, and David Simpson, an associate professor of anatomy and neurobiology, who is looking at hearts and skeletal muscles.
``We're trying to make corneas, cartilage, skin, bones, tendons,'' Bowlin said. ``The Holy Grail is to make a whole liver, a whole heart, but we have to take baby steps.''
NanoMatrix and VCU are pursuing US government funding thru the National Institute of Standards and Techology Advanced Technology Program. The NanoMatrix grant application summary provides an idea of their direction of development.
More than 1.4 million surgical procedures that require arterial prostheses are performed each year in the United States, approximately 500,000 of these are coronary artery bypass operations. Because there are no acceptable synthetic prostheses for small-diameter blood vessels, surgeons must harvest the patient's own blood vessels for the transplant. This procedure is time-consuming, prone to complications, and greatly increases the recovery time for the patient. It also limits the number of patients who are good candidates for the surgery, because there are only a few vessels in the body potentially available for transplantation. Attempts have been made for years to develop a viable synthetic or tissue-engineered prostheses for small blood vessels, but all have had high failure rates for one reason or another. To answer this need, NanoMatrix proposes a three-year project to design and fabricate three-dimensional (3D) "scaffolds" out of collagen, the body's natural structural material, that can be seeded with various types of cells to mimic natural, small-diameter blood vessels. Studies suggest that muscle cells, once implanted in the scaffold, will develop the function, shape, morphology, and cellular architecture of the "normal" vessel. In practice, natural blood vessels are difficult to mimic -- they are composed of three distinct layers of different types of cells and attempts to artificially create the blood-vessel tube have been frustrating. NanoMatrix's innovation is a novel "electrospinning" technology to produce nanofibers from collagen and other biological proteins, together with a special bioreactor to culture the implanted cells on this scaffold of collagen. Electrospinning has been used in the past to produce very fine fibers of polymers -- and even collagen -- but lacking precise, controlled orientation of the fibers. NanoMatrix will design and build an electrospinning device that incorporates computerized, multi-axis controls to build collagen scaffolds with the proper layering and orientation to mimic blood vessels. A novel cell culture bioreactor will maintain the constructs and prevent necrosis as the cells grow. Human endothelial cells, smooth muscle cells, and fibroblasts will be used in the inner, middle, and outer layers, respectively, of the vascular constructs. A key challenge will be to achieve the proper alignment, architecture, abundance of cell types, and behavior in each cell layer. The company will optimize the structure, mechanical properties, and biological efficacy of the vascular grafts and then conduct implantation studies. Virginia Commonwealth University (Richmond, Va.) will be subcontracted to conduct the tests. ATP support is necessary because the long history of previous failures to develop small artificial blood vessels discourages venture capital. If successfully developed and approved for clinical use, the new technology could replace all other vascular grafts, reduce coronary bypass surgical costs by 10 percent and other hospital costs as well, and improve productivity and quality of life for people who undergo vascular graft procedures. The technology platform also would be applicable to the engineering of skin, cartilage, bone, muscle, heart muscle, neural tissue, and other tissues.
In 1934, a process was patented by Formhals [1-3], wherein an experimental setup was outlined for the production of polymer filaments using electrostatic force. When used to spin fibers this way, the process is termed as electrospinning.
In the electrospinning process a high voltage is used to create an electrically charged jet of polymer solution or melt, which dries or solidifies to leave a polymer fiber [4, 5]. One electrode is placed into the spinning solution/melt and the other attached to a collector. Electric field is subjected to the end of a capillary tube that contains the polymer fluid held by its surface tension. This induces a charge on the surface of the liquid. Mutual charge repulsion causes a force directly opposite to the surface tension . As the intensity of the electric field is increased, the hemispherical surface of the fluid at the tip of the capillary tube elongates to form a conical shape known as the Taylor cone . With increasing field, a critical value is attained when the repulsive electrostatic force overcomes the surface tension and a charged jet of fluid is ejected from the tip of the Taylor cone. The discharged polymer solution jet undergoes a whipping process  wherein the solvent evaporates, leaving behind a charged polymer fiber, which lays itself randomly on a grounded collecting metal screen. In the case of the melt the discharged jet solidifies when it travels in the air and is collected on the grounded metal screen.
The collage scaffolding is biodegradable. Now, you might be asking "Sounds great, but where will we get the natural immunocompatible human collagen from?" Silk worms! Japanese researchers have genetically engineered silk worms to make human collagen.
The team, from Hiroshima University and other institutions, constructed a DNA sequence that encodes for the production of human Type III procollagen, a mini-chain that is a kind of precursor to the full collagen molecule, which is a long-chained polymer. This DNA was combined with other genetic material and then injected into silkworm embryos.
The resulting silkworms secreted procollagen along with silk proteins in forming their cocoons. The researchers reported in Nature Biotechnology that they had found it relatively simple to separate the procollagen from the silk.
Los Angeles, Dec. 23 –– Researchers at the Keck School of Medicine of the University of Southern California, along with colleagues from across the country, have for the first time genetically engineered mouse cells to produce a type of human collagen--type VII--that is missing in a family of inherited skin diseases called dystrophic epidermolysis bullosa. They also prompted the mouse cells to create the structural fibers that normally arise from type VII collagen. Their work was published in the December issue of Nature Genetics.
"This is the first demonstration of in vivo gene therapy where the genes have made a large extracellular molecular structure that you can actually see with a microscope," says David Woodley, M.D., professor and chief of dermatology at the Keck School and the principal investigator on this study. Scientists from Shriners Hospital for Children in Portland, Oregon, Northwestern University in Chicago, and Xgene Corporation in San Carlos, California, also participated in the study.
Woodley was helped by his previous efforts in the field: In 1992, he and some of his colleagues became the first team to clone the human gene for type VII collagen, which is one of the key components of the skin's extracellular matrix. Collagen makes up the tendrils and fibrils that provide a cushion for the skin's cells to rest upon; type VII collagen, in particular, is critical to the creation of the skin's so-called anchoring fibrils.
The goal of the USC researchers is to treat some human inherited skin diseases. They are studying the human type VII collagen gene in the mouse in preparation for the development of a gene therapy to treat the sufferers of these diseases. The mouse may not turn out to be a useful organism for the production of human collagen. Still, its an important result.
Vladimir Mironov, head of the Medical University of South Carolina’s (MUSC) Shared Tissue Engineering Laboratory, has proposed the development of a method to grow steak from cell culture for space missions. NASA turned down his grant. The reason given for rejecting the grant application is that astronauts can do fine on protein pills. How unimaginative. Space exploration should be conducted in ways that maximize the fun and innovation. Mironov could still turn to the big fast food companies for funding. Imagine Burger King, McDonalds, or Wendy's patties grown to the exact needed shape.
One problem that meat cell growth faces is the need to exercise the growing muscle cells to develop the ideal texture.
He suggests using a bioreactor with a branching network of hundreds of tiny edible tubes that act like artificial capillaries to convey nutrients to the growing meat. But to satisfy those who crave the texture and mouthfeel of a good steak, you need to develop something that mimics the texture of real meat.
That means generating a complex structure of muscle and connective tissue, and to do that, the muscle myoblasts need to stretch and contract regularly. In other words, not only must you feed your steak well, you have to give it plenty of exercise too.
The article mentions a vegan student who wanted to take a biopsy of her own tissue and then culture it to make self-steaks that would allow her to eat meat without feeling that she killed an animal. Of course, if one took a biopsy from a cow and grew a steak its not like one would have to kill the cow in order to get meat either. Still, perhaps you taste good. Since it will probably be no harder to grow human muscle tissue than to grow cow muscle tissue this could become quite a popular thing to do for anyone who doesn't find the idea of eating their own tissue to be nauseating (makes me queasy just thinking about it).
Mironov's main interests appear to be the growth of cardiovascular replacement tissues
Perfusion Bioreactor with Circumferential and Longitudinal Strain of a Tubular Construct for Accelerated Tissue Engineered Vascular Wall Histogenesis
Department of Cell Biology and Anatomy
Medical University of South Carolina, Charleston
A bioreactor is a key element of cardiovascular tissue engineering technologies. Increased use of stem cells as a cell source in cardiovascular tissue engineering is transforming this field into an in vitro approach that seeks to accelerate recapitulation of in vivo embryonic vascular development. The purpose and goal of existing bioreactors are to provide the pulsatile flow through an engineered construct and thus to generate periodic radial distension (circumferential strain) of the vessel wall. The important mechanical element of embryonic vascular development is longitudinal strain associated with arterial longitudinal growth. Thus, in order to "biomimic" the embryonic mechanical vascular environment (EMVE), perfusion bioreactor must also include the functional capacity for longitudinal strain. To accomplish this, we have developed a novel perfusion bioreactor. This bioreactor was designed and fabricated to provide the simulation of the EMVE including capacities for both circumferential and longitudinal strain of cardiovascular engineered tubular constructs. Results indicate this new bioreactor can provide the new critical component of biomechanical conditioning which is essential to mimic EMVE and accelerate vascular wall histogenesis.
Mironov points out that the discovery of stem cells (and by this he means non-embryonic stem cells that are found in adult organisms) has greatly increased the prospects for tissue engineering.
“Anatomy is no longer a static science,” Mironov said. “The discovery of stem cells has reinvented a classical microscopical anatomy—a tissue biology science, which is now again a vibrant, booming discipline. It no longer considers tissue a static, solid structure, but rather as elastoviscous, constantly renewing its dynamic community of cells and extracellular matrix.”
In the labs and on the near horizon are perfusion and bioengineering techniques to keep transplant organs alive and fresh longer, procedures to shrink a malignant tumor by blocking its blood supply, and plans to grow human organs with the careful manipulation of stem cells.
The growth of muscle tissue for human consumption is relatively easy as compared to its growth for medical applications. Quite a few scientists working on that harder problem. Here's a discussion by UCLA graduate student Carrie Caulkins on the problems that need to be solved to grow muscle tissue to replace damaged, diseased, or aged muscle.
One of the main focuses of the Tissue Engineering Department at UCLA is the design and fabrication of highly porous tissue engineering scaffolds with novel material formulations to control cell-substrate, cell-cell, and cell-signal interactions.
Future challenges in polymer scaffold processing include the development of fabrication techniques that will allow manufacturing of high-strength scaffolds for hard tissue replacement at load-bearing sites, and the ability to incorporate and deliver growth factors into scaffold construction, without loss of growth factor activity. This challenge likewise affects the cellular and signaling aspects of tissue engineering, and prompts the need for more research on cell-cell interactions and the chemical and protein signaling involved.
Once the harder case of muscle or organ growth outside of a living organism has been solved for medical purposes the ability to do it for food production will be trivial by comparison. Therefore it seems reasonable to expect the easier problem of growing cells for meat consumption will be solved as well. When that technology becomes really mature we'll be able to buy home meat growing devices just as we can today buy home bread makers.Herman Vandenburgh of Brown University is working on modelling the effects of gravity on muscle development.
For Vandenburgh, the primary goal of his space research is developing pharmaceutical countermeasures to prevent the muscle wasting that occurs in space, "helping man explore a new environment, and a very hostile environment at that." His research group has developed a tissue culture system for preliminary tests of these countermeasures. "It's really the classical way of doing these types of experiments," he said, "You first test out new drugs in tissue culture, on cells outside the body, and then the next set of experiments are in animals. You hope you see a similar type of effect as you saw in cell culture. Then you go from animal to human. At each stage you have to hope that what happens early on is going to follow through. It's much more difficult to predict what's going to happen if you go right into doing animal studies."
While Vandenburgh is interested in solving this problem for astronauts this work might also be useful for growing meat in a cell culture. Recall that the first article above mentioned the problem of exercising the growing muscle tissue. Exercise and gravity both affect how muscle cells grow and organize themselves. so any attempt to solve those problems for human health will provide useful information for how to grow more realistic steaks.
Robert G. Dennis, Ph.D., University of Michigan Biomedical Engineering Assistant Professor, and member of the U Mich and MIT Biomechatronics (cool word, no?) Groups, lays out his tissue engineering Vision for the Future
Imagine the technology to seamlessly integrate hybrid prosthetic devices with their human users. Instead of bulky and ineffective synthetic mechanisms, prosthetic devices could have tissues integrated directly into them. One of our primary objectives is to integrate living muscle actuators into prosthetic devices. As the art and science of tissue engineering evolves, so too will the hybrid prosthetic devices, incorporating a greater percentage of more sophisticated engineered tissues, until the device eventually becomes fully biologic. We are working on the technology to grow the engineered tissues from small samples of the native tissue of the user, so that when complete the engineered prosthetic device will be fully compatible with the user, employing no foreign biological elements.
Imagine engineered tissues that can fully replace injured tissue, or be used for the surgical correction of congenital deformity.
Imagine the end of animal testing. New drugs and surgical procedures will be tested directly on engineered tissues. Tissues will be grown from small samples of cells without requiring animals to be killed. New drugs and procedures can be tested on human tissues that are engineered in culture, eliminating the cost and clinical uncertainty of animal testing.
Imagine engineered meat as a food source, eliminating the need for raising and slaughtering livestock.
Imagine a world with living computers, robots, and other devices, that operate silently and efficiently, are fault tolerant and can heal themselves, can adapt to their environment, are energy efficient, produce no harmful byproducts, and are 100% biodegradable. Humans will be able to interact with their creations in ways never dreamed possible.
Imagine the day when clattering, inefficient, synthetic electro-mechanical contrivances seem quaint and frivolous. From the first time that a proto-human grasped the first stone tool and used it to shape the environment, the use of living tissues as tools has been set in our destiny.
This is a future that most of us will live long to see. Tissue engineering will allow the reversal of aging of many parts of our bodies by replacement with newer and even better and longer lasting parts.
Robert G. Dennis say there are only three groups in the world working on engineering functional skeletal muscle.
The State of the Art in Functional Skeletal Muscle Tissue Engineering can be easily summarized by first defining the function of skeletal muscle. Though muscle tissue performs many functions for the body, some arising from the emergent properties of muscle cells organized into whole muscle organs, such as heat generation and protein synthesis, the most basic definition of muscle tissue function is the generation of controlled force, work, and power. It is necessary to quantify the contractility of the muscle tissue, to organize the tissue in such a way as to promote the generation of directed force, and exert control over the contractions for research in this area to be considered engineering, rather than cell biology. After all, spontaneous contractions in cultured skeletal muscle cells were first reported in 1915 (Lewis), and this was not construed as 'engineering'. Defining Functional Skeletal Muscle Tissue Engineering in this way, it is possible to assert that at this time there are only three research groups in the world engineering functional skeletal muscle in vitro: Herman Vandenburgh and Paul Kosnik in Providence, RI; myself and Hugh Herr at MIT, and the Muscle Mechanics Laboratory at the University of Michigan.
Update: Some Chinese eat aborted and stillborn babies. I'd excerpt from it but its too disgusting.
Update II: More on cannibalism in China. Not for the faint of heart.
Prof. Yair Reisner of the Weizmann Institute of Science in Rehovot Israel is the leader of a team that has successfully grown functional kidneys in mice from pig and human stem cells taken from embryos.
Reisner and Ph.D. student Benny Dekel of the Weizmann Institute's Immunology Department, with Prof. Justen Passwell, the head of the pediatric department at the Sheba Medical Center, transplanted human and porcine "kidney precursor cells" (stem cells that are destined to become kidney cells) into mice. Both human and porcine tissues grew into perfect kidneys, the size of the mice's kidneys. The miniature human and pig kidneys were functional, producing urine. In addition, blood supply within the kidney was provided by host blood vessels as opposed to donor blood vessels, greatly lowering the risk of rejection.
The scientists pinpointed the ideal time during embryonic development in which the stem cells have the best chance to form well-functioning kidneys with minimal risk for immune rejection. Their findings suggest that 7-8 week (human) and 4 week (porcine) tissue offers an optimal window of opportunity for transplantation. If taken at earlier time points the tissues will develop disorganized tissue that would include non-kidney structures such as bone, cartilage, and muscle. If taken at later time points the risk for immune rejection is substantial.
Within this optimal time range the tissue doesn't contain certain cells that the body recognizes as foreign (antigen-presenting cells), the scientists found. These cells, which originate in the blood system, reach a developing kidney only after ten weeks.
After growing the human and porcine kidney tissue in mice, the scientists checked how human lymphocytes (fighter cells in the immune system) might react to it. They injected human lymphocytes into immunodeficient mice (that have no immune system and thus do not interfere with the immune response). The findings were encouraging: as long as the kidney precursors were transplanted within the right time range, the lymphocytes did not attack the new pig or human kidneys – despite the fact that lymphocytes and kidney precursors originated from different donors. Immune rejection was also tested in normal mice and was shown to be reduced compared to that induced by precursors from later time points.
There is an obvious problem for the use of this approach in the United States: The precursor stem cell tissue has to be harvested from 7-8 week old human embryos (which were aborted embryos). The idea of allowing an embryo to develop for 2 whole months before harvesting will elicit strong opposition from the opponents of embryonic stem cell use. An attempt to make organs available which are grown by this method (whether from abortions or from embryos grown in a lab) may well lead the US Congress to outlaw the technique.
As an alternative approach there is a chance that pig embryonic stem cells could be coaxed into forming kidneys that would be immunologically compatible with humans and compatible with human metabolic needs for kidney function. That is likely the reason why the Israeli group also used porcine stem cells in this set of experiments. But the use of porcine stem cells to create human-compatible kidneys may be technically harder than the use of human stem cells for the same purpose. In order to make the porcine stem cell approach work it may be necessary to put human versions of some genes into pigs.
Another alternative approach would be to figure out how to instruct cells that are more differentiated to become less differentiated cell types. Then it might be possible to, for instance, tell an adult kidney cell to revert back to the state that its progenitors were in at the 7th or 8th week of embryonic development. It is difficult to say how long it would take to develop a way to do that. By contrast, the ethically and legally more problematic approach of allowing a human embryo to develop thru the series of steps it normally goes thru is technically well understood and doesn't require as much knowledge of how cells differentiate. Therefore what is today the easiest technical approach also happens to be the approach that elicits the greatest political opposition.
Update: Charles Murtaugh corrects my sloppy use of the term "embryonic stem cells" (which you will no longer see above since I fixed it). In these experiments the embryos were sufficiently far along in their development that the cells taken from the embryos had undergone enough differentiation that they were no longer capable of becoming all cell types (i.e. no longer pluripotent). Therefore they were not embryonic stem cells (which are pluripotent and undifferentiated) even though they were stem cells extracted from embryos. So what to call these cells? The widely used term "adult stem cells" hardly seems adequate to describe stem cells that are not pluripotent but which come from an embryo. The word "adult" implies cells rather older than those used in this experiment and stem cells taken from an adult wouldn't have the same qualities. Though some writers use the term "non-embryonic stem cells" it seems to my ear that "non-pluripotent stem cells" would be an even more precise term.
A new method for putting genes into an animal species by gene therapy on sperm has been tested in pigs:
Genetically-modified animals can be created simply by washing sperm, swishing it in a centrifuge with an additional gene, and using the altered sperm for artificial insemination, say Italian researchers.
Marialuisa Lavitrano's team at the University of Milan-Bicocca in Milan have demonstrated how well the simple method works by creating pigs that could one day provide rejection-free organs for transplantation into people. The technique worked 25 times more efficiently than the standard way of engineering animals.
Pigs are being used because genetically modified pigs are excellent candidates as methods to grow replacement human organs:
"In the U.S., every 18 minutes a person dies on the waiting list for organ transplants without receiving one. Every 18 minutes is a lot. Xenotransplation could really be a solution," lead researcher Marialuisa Lavitrano, an immunologist and pathologist at the University of Milan-Bicocca, told United Press International.
This sperm-based technique also is relatively cheap and about 14 to 114 times more effective at implanting genes in pigs than the direct injection of DNA, the most common way of making genetically engineered animals.
This method is cheaper and has a higher success rate than gene injection:
Ninety-three piglets were born after the researchers tinkered with the pig sperm, and 57 percent of them contained the human gene, suggesting the sperm soaked it up from the solution. When researchers injected sperm with the gene, only 4 percent of the piglets born had the gene inside them.
These researchers are pursuing the development of this technique in order to be able to transplant a large number of human genes into pigs. Their goal is to create pigs which would contain internal organs that would be sufficiently compatible both physiologically and immunologically to allow transplantation into humans. My guess is that this technique alone will not be sufficient to do the amount of genetic engineering that will be required to achieve this ambitious goal. It may be necessary to both remove and add genes in order to create pigs with all the desired biological qualities. Also, the process of adding the sheer number of required genes may end up causing harmful mutations in the sperm chromosomes. Still, its a great piece of research.
There is another obvious purpose that this technique might eventually be used for: human progeny genetic engineering. Human sperm could be treated using the same technique in order to put desired genes into human progeny. Of course, the technique might require a much greater degree of refinement in order to prevent harmful mutations. One potential risk is the possibility that any gene transplanted into sperm chromosomes could get incorporated into the middle of an existing gene. That could cause harmful genetic defects in progeny that would manifest at birth or at a later time in life.
Update: This story from CNN confirms that deletion and modification of existing genes are also necessary to make pigs suitable for xenotransplantation:
"You can add a gene, but you cannot alter or remove a gene using this technique," said Prather. It is known that some other genes will have to be altered or removed in order to create animals for the xenotransplantation of organs, he said.
A scientist at Oklahoma State is working on growing blood vessels from umbilical cord stem cells:
Sundar Madihally has already found a way to turn stem cells from umbilical cords into endothelial cells, which line the inside of blood vessels.
Within five years, he hopes to create a process that will make blood vessels in large quantities. He plans to patent the idea.
His next project will be to turn the CD34 positive stem cells into tissue for livers and heart valves.
People who are about to have a baby who want to plan way ahead for their baby's future could take the umbilical cord and store cells from it as a future stem cell source. My guess is that the cells would be frozen for long term storage and, while most cells would die, enough would survive being frozen for decades to eventually be usable as stem cells.
Ideally, Madihally said, stem cells would come from umbilical cord blood stored by families, so the blood has the same genetic makeup as the patient.
However, it may well turn out that this technique will never be practically useful. By the time someone born now would be old enough to need umbilical stem cells it is likely other techniques will be available for growing compatible organs from one's own regular cells.Lots of other tissue growing research is actively being pursued:
One of Madihally's undergraduate students is trying to grow teeth. Other researchers in Cleveland are creating bone and cartilage. A doctor in Philadelphia was able insert stem cells into a baby in the womb and cure the baby's immune deficiency disease, commonly known as the "bubble boy syndrome," before birth.