Many researchers believe that multiple sclerosis (MS) is caused by immune system attack on the nervous system. In particular, the immune system is thought to damage the myelin sheath that serves as insulation covering nerve cells. This myelin sheath speeds the transmission of nerve signals. Some Caltech researchers have found that remyelination (rebuilding of the lost insulation) can be done by with a gene therapy that delivers a gene for a protein that promotes growth of neural stem cells.
But myelin, and the specialized cells called oligodendrocytes that make it, become damaged in demyelinating diseases like multiple sclerosis (MS), leaving neurons without their myelin sheaths. As a consequence, the affected neurons can no longer communicate correctly and are prone to damage. Researchers from the California Institute of Technology (Caltech) now believe they have found a way to help the brain replace damaged oligodendrocytes and myelin.
The therapy, which has been successful in promoting remyelination in a mouse model of MS, is outlined in a paper published February 8 in The Journal of Neuroscience.
"We've developed a gene therapy to stimulate production of new oligodendrocytes from stem and progenitor cells—both of which can become more specialized cell types—that are resident in the adult central nervous system," says Benjamin Deverman, a postdoctoral fellow in biology at Caltech and lead author of the paper. "In other words, we're using the brain's own progenitor cells as a way to boost repair."
The therapy uses leukemia inhibitory factor (LIF), a naturally occurring protein that was known to promote the self-renewal of neural stem cells and to reduce immune-cell attacks to myelin in other MS mouse models.
The report mentions this treatment might also be useful for repair of spinal cord nerve damage. It also potentially could benefit all of us as we grow old since myelin sheath deteriorates with age. This fits with a larger pattern: Many gene therapies and stem cell therapies aimed at specific diseases will likely turn out useful for rejuvenation. Any advance in tissue repair is likely to have benefit as a rejuvenation therapy.
One of their challenges is to develop better gene deliver mechanisms. That's one of the big challenges of gene therapy. How to get the genes into cells without getting stopped by the immune system and various natural barriers in the body? Also, how to prevent the genes from damaging chromosomes once they enter cells? Also, how to control dosage? Some cells will get many copies of genes and other cells will get none.
To move the research closer to human clinical trials, the team will work to build better viral vectors for the delivery of LIF. "The way this gene therapy works is to use a virus that can deliver the genetic material—LIF—into cells," explains Patterson. "This kind of delivery has been used before in humans, but the worry is that you can't control the virus. You can't necessarily target the right place, and you can't control how much of the protein is being made."
Gene therapy might find greater usage in the short to medium term to modify cells removed from the body before the cells are introduced back into the body. Basically gene therapy will get used to train cells to work better as cell therapy.
Rabbits the world over are celebrating the good news that a gene therapy for rabbits prevents clogging up of arteries. Rats and mice seethe in jealousy and resentment.
A one-dose method for delivering gene therapy into an arterial wall effectively protects the artery from developing atherosclerosis despite ongoing high blood cholesterol. The promising results, published July 19 in the journal Molecular Therapy, came from research in rabbits.
The gene therapy turns on a protein thought to be involved in delivering the benefits of high HDL blood cholesterol.
The deployed gene produces a protein that is likely responsible for the beneficial effects of high-density lipoprotein, or HDL, commonly known as good cholesterol.
This substance is apolipoprotein A-1, or apoA-1. It pumps out harmful cholesterol from the scavenger-type cells that ingest fats and congregate in early atherosclerotic lesions.
ApoA-1 appears to remove cholesterol from the lesions and is capable of transporting it to the liver, where it can be excreted from the body.
Why take daily drugs for decades when you can reprogram the body to do something better?
"Localized one-time gene therapy might someday be an alternative or an important adjunct to systemic drugs such as statins that patients take for decades," Dichek said. "In gene-therapy trials for other diseases, one-time treatments have shown efficacy for at least nine years and will likely continue to be effective indefinitely. Because atherosclerosis is a life-long threat, gene therapy that protects blood vessels for a lifetime makes a lot of sense."
What I'd like to see: a gene therapy that is tied to activator and deactivator drugs. If this gene therapy is done and lasts for decades you could find yourself with a serious problem if a dangerous side effect turned up 5 or 10 years later. Better to have some way to limit the duration of the therapy.
About 1 in 6000 babies is born with a genetic disorder of the nervous system called Spinal muscular atrophy (SMA). The mouse equivalent of SMA has now been treated with gene therapy with substantial improvement.
COLUMBUS, Ohio – Reversing a protein deficiency through gene therapy can correct motor function, restore nerve signals and improve survival in mice that serve as a model for the lethal childhood disorder spinal muscular atrophy, new research shows.
This muscle-wasting disease results when a child’s motor neurons – nerve cells that send signals from the spinal cord to muscles – produce insufficient amounts of what is called survival motor neuron protein, or SMN. This reduced protein in motor neurons specifically – rather than in other cells throughout the body that contain the protein – is caused by the absence of a single gene.
Better ways to deliver gene therapy will eventually enable many types of human body repair. Gene therapy amounts to installing a software update.
The gene therapy delivered inside a virus reached almost half of mouse neurons. That's an impressive delivery rate. The result was better functioning nervous systems and better muscle control.
The researchers used an altered virus to deliver a portion of DNA that makes the SMN protein into the veins of newborn mice ranging in age from 1 to 10 days old. The SMN-laced viral vector injected into the youngest mice reached almost half of their motor neurons, resulting in improved muscle coordination, properly working electrical signals to the muscles and longer survival than in untreated mice, scientists said.
The gene therapy works better than drugs under study for use in humans. That superiority of gene therapy should not be surprising because the gene therapy fixes the root cause. Fix the gene that causes the disease and the disease gets better.
“We’re replacing what we know is lost. And we have shown that when you put the protein in postnatally, it will rescue the genetic defect,” said Arthur Burghes, professor of molecular and cellular biochemistry at Ohio State University and a senior co-author of the study. “This technique corrects the mice considerably more than any drug cocktails being studied as a potential treatment in humans.”
We need better carriers of gene therapy into cells. Viruses elicit an immune response and they do not reach all the cells that need the gene therapy payload they carry. Plus, once genes reach inside cells they are at risk of integrating into the genome in locations that can cause cancer. But solve all those problems and then we can do some serious updating of our genetic software.
An MIT press release about the use of nanoparticles to deliver gene therapy contains an interesting statistic about the size of the overall effort to develop clinically useful gene therapies: In the United States alone almost 1000 gene therapy clinical trials are underway. That's a surprisingly large number. Is it true? Seems too high to be possible.
There are nearly 1,000 clinical trials under way in the United States involving gene therapy, for diseases including cancer, cardiovascular disease and neurological disorders. However, no gene therapy treatments have been approved in the United States.
This is an example of why it is hard to predict the future. It is hard to predict the success rate of those many attempts. Once some succeed we also do not know how much of the successful techniques for a particular disease target will be reusable against other diseases. Gene therapy researchers in the early 1990s sounded pretty optimistic. But their high hopes were repeatedly dashed in failed experiments. Is success just around the corner or another 15 years away? For some of us (though we mostly do not know it yet personally) the answer is a matter of life and death.
Gene therapy has huge potential because it delivers instructions. Most diseased cells could be restored to a non-diseased state if they could only be sent enough instructions on how to repair themselves. Cell therapies get more press in part because of the ethical debate about embryonic stem cells. But gene therapies are crucial for rejuvenation because of the need to repair damaged brain cells. Lots of organs will some day just be replaced by organs grown in special vats. But the brain replacement is effectively person replacement. You have get your brain repaired in order to save your identity from death by aging.
The MIT press release on nanoparticles for gene therapy delivery sounds promising because these researchers at MIT and U Wisc have automated the process of searching the potential solution space by making large numbers of nanoparticle variations,
Anderson and chemist David Lynn, then a postdoctoral fellow in Langer’s lab and now a professor at the University of Wisconsin, developed a large collection of different biodegradable polymers (large molecules composed of repeating subunits) known as poly(beta-amino esters).
When these synthetic polymers are mixed with DNA, they spontaneously assemble to form nanoparticles. These nanoparticles can travel through the body to the target cells, where they are taken up by a process known as endocytosis, the equivalent of cellular eating. Once “eaten” by the cells, the nanoparticles release their DNA payload inside of the cell, where it can then be activated by the cellular machinery. In some ways, these polymer-DNA nanoparticles can act like an artificial virus, delivering functional DNA when injected into or near the targeted tissue.
There are infinite possible sequences for such polymers, and small variations can make a polymer more or less efficient at delivering DNA. Anderson and Langer's group have developed a way to automate both the production of vast numbers of particles with slight variations and the screening techniques used to determine the particles’ effectiveness.
“Instead of trying to make one perfect polymer, we make thousands,” says Anderson. That increases the odds that the researchers will hit on a nanoparticle that does what they want.
Will they succeed in developing useful gene therapy delivery vehicles? I hope so.
All male squirrel monkeys are naturally red-green color blind. Gene therapy has successfully restored vision of 2 male squirrel monkeys.
Researchers have used gene therapy to restore colour vision in two adult monkeys that have been unable to distinguish between red and green hues since birth — raising the hope of curing colour blindness and other visual disorders in humans.
The problem with gene therapy is cancer risk. Whenever scientists figure out how to delivery gene therapy safely lots of diseases will become treatable. But when will that happen? Seems like a real hard problem. The Nature article above reports on 3 gene therapy phase 1 trials for underway in humans for retinal regeneration. I'd be curious to know what the scientists involved in these trials see as risks.
Most striking, says Ali, is the discovery that the brains and retinas of the adult monkeys weren't too "hard-wired" or fixed to respond to the treatment. "What's so exciting about this study is that is demonstrates there's more plasticity in the brain and cone cells than we thought," says Ali. "It forces us to reconsider our assumptions, and opens up more possibilities than we thought for treating blindness."
What I want to know: If gene therapy was used to add a 4th and 5th pigment could humans gain the ability to see a wider range of colors? Just what would the additional colors look like?
Researchers, led by principal investigator Zhongjie Sun, tested the effect of an anti-aging gene called klotho on reducing hypertension. They found that by increasing the expression of the gene in laboratory models, they not only stopped blood pressure from continuing to rise, but succeeded in lowering it. Perhaps most impressive was the complete reversal of kidney damage, which is associated with prolonged high blood pressure and often leads to kidney failure.
“One single injection of the klotho gene can reduce hypertension for at least 12 weeks and possibly longer. Klotho is also available as a protein and, conceivably, we could ingest it as a powder much like we do with protein drinks,” said Sun, M.D., Ph.D., a cardiovascular expert at the OU College of Medicine.
Would this work for humans?
The decline in klotho protein seen with age might play a contributing role with rising hypertension and kidney damage.
Scientists have been working with the klotho gene and its link to aging since 1997 when it was discovered by Japanese scientists. This is the first study showing that a decline in klotho protein level may be involved in the progression of hypertension and kidney damage, Sun said. With age, the klotho level decreases while the prevalence of hypertension increases.
A lot of problems with age seem to come in cascades. In this case the level of a protein goes down causing hypertension which in turn damages the kidneys. Lots of other cascades of failure are building up in all of use. We need the biotechnologies which can stop and reverse these cascades of failure.
Long-term gene therapy resulted in improved cardiac function and reversed deterioration of the heart in rats with heart failure, according to a recent study conducted by researchers at Thomas Jefferson University’s Center for Translational Medicine. The study was published online in Circulation.
The delivered gene inhibits another gene that has higher activity in diseased hearts.
The rats were treated with a gene that generates a peptide called βARKct, which was administered to hearts in combination with recombinant-adeno-associated virus serotype 6 (rAAV6). βARKct works by inhibiting the activation of G protein-coupled receptor kinase 2 (GRK2).
In order to do this experiment the scientists first needed to know that the kinase enzyme GRK2 is expressed more in failing hearts and that it contributes to the failure. Then they needed to know which gene to use to inhibit this kinase. Then they needed a delivery vehicle for getting this gene into the heart. A lot of work went into each of these pieces of the puzzle.
GRK2 is a kinase that is increased in heart failure myocardium. Enhanced GRK enzymatic activity contributes to the deterioration of the heart in heart failure, according to Walter J. Koch, Ph.D., the W.W. Smith Professor of Medicine and the director of the Center for Translational Medicine at Jefferson Medical College of Thomas Jefferson University. Dr. Koch’s research team carried out the study, which was led by Giuseppe Rengo, M.D., a post-doctoral fellow.
“The theory is that by inhibiting this kinase, the heart will recover partially due to reversal of the desensitization of the β-adrenergic receptors,” Dr. Koch said. “The expression of βARKct leads to a negative neurohormonal feedback that prevents the heart from continuing on the downward slope during heart failure. This was one novel finding of the study.”
Dr. Koch and his colleagues used five groups of rats in their study. Two groups received rAAV6 with the βARKct peptide, two groups received rAAV6 with green fluorescent protein (GFP), and the last group received a saline treatment. One of the βARKct groups and one of the GFP groups also received the beta blocker metoprolol concurrently.
Twelve weeks after receiving the treatment, the rats who received the βARKct had a significantly increased left ventricular ejection fraction. The treatment also reversed the left ventricular deterioration and normalized the neurohormonal status. Dr. Koch said that targeting the GRK2 enzyme with βARKct was sufficient to reverse heart failure even without concomitant metoprolol.
One of the ways that cheap DNA sequencing helps is that it leads to the identification of genes that contribute to heart disease risk. Those genes then become candidates to use in gene therapy to either turn them up or turn them down or modify how they work. The expanding knowledge about which genes get more or less expressed in disease tissue will help in the identification of potential targets for gene therapy. Though there's a lot more work involved beyond just identifying which genes are turned up or down in diseased tissue.
Gene therapy has been pretty slow in coming. The problem isn't just in identifying which gene(s) to deliver but also how to package them, how to get them into only the cell types you want to treat (turning on heart genes in the liver is not a good idea), and how to do all this without damaging the genome of the targeted cells. Cancer is a real threat and some gene therapy development efforts have failed due to cancer.
The experiment above suggests some good news. If we can find a way to deliver gene therapy safely into heart cells then at least some types of heart disease can be stopped and reversed.
The brain, not space, is the final frontier. Our brains are all growing old and are the hardest part of the body to repair and rejuvenate. We need gene therapy to do brain rejuvenation. So I'm always happy to come across reports on advances in brain gene therapy. Some researchers have found a way to get really good coverage of gene therapy delivered in to the brains of mice.
By targeting a site in a mouse brain well connected to other areas, researchers successfully delivered a beneficial gene to the entire brain—after one injection of gene therapy. If these results in animals can be realized in people, researchers may have a potential method for gene therapy to treat a host of rare but devastating congenital human neurological disorders, such as Tay-Sachs disease.
Researchers from The Children’s Hospital of Philadelphia and the University of Pennsylvania reported their findings in the September 12 issue of the Journal of Neuroscience.
“After a single injection, this technique succeeded in correcting diseased areas throughout the brain,” said study leader John H. Wolfe, V.M.D., Ph.D., a neurology researcher at The Children’s Hospital of Philadelphia and a professor of pathology and medical genetics at the Penn School of Veterinary Medicine. “This may represent a new strategy for treating genetic diseases of the central nervous system.”
Wolfe and Penn graduate student Cassia N. Cearley performed the study in mice specially bred to have the neurogenetic disease mucopolysaccharidosis type VII (MPS VII). In people, MPS VII, also called Sly syndrome, is a rare, multisystem disease causing mental retardation and death in childhood or early adulthood.
The fact that this gene therapy worked against a lysosomal storage disorder is reason for optimism for brain rejuvenation gene therapies.
Sly syndrome is one of a class of some 60 disorders called lysosomal storage diseases that collectively cause disabilities in about one in 5,000 births. Those diseases account for a significant share of childhood mental retardation and severe, often fatal, disabilities. In each of the lysosomal storage diseases, a defect in a specific gene disrupts the production of an enzyme that cleans up waste products from cells. Cellular debris builds up within cell storage sites called lysosomes, and the waste deposits interfere with basic cell functions. Other examples of lysosomal storage diseases are Tay-Sachs disease, Hunter disease and Pompe disease.
One of Aubrey de Grey's proposed SENS (Strategies for Engineered Negligible Senescence) therapies involves sending genes into cells to enhance lysosomal breakdown of accumulated trash. Basically, use genes from other species to help take out the cellular trash. A successful gene therapy that moves into large numbers of brain cells to enhance lysosomal function would be a step in the right direction for future development of SENS therapies.
After decades of experimentation scientists still do not have good ways to deliver gene therapy into cells in humans or other animals. Gene therapy is a crucial piece of the puzzle needed to cure many diseases (notably cancer) and to rejuvenate old bodies. Gene therapy is especially needed for brain rejuvenation. For the rest of the body cell therapies and replacement organs will provide easier ways to make worn out parts young again. But most neurons need to be repaired rather than replaced. So we need brain gene therapy to prevent our minds from growing old. With this thought in mind, recent MIT research looks promising for a better way to deliver gene therapy.
The new MIT work, published this week in Advanced Materials, focuses on creating gene carriers from synthetic, non-viral materials. The team is led by Daniel Anderson, research associate in MIT's Center for Cancer Research.
"What we wanted to do is start with something that's very safe--a biocompatible, degradable polymer--and try to make it more effective, instead of starting with a virus and trying to make it safer," said Jordan Green, a graduate student in biological engineering and co-first author of the paper.
The polymers self-assemble with DNA and package the DNA inside them.
Over 1,000 gene therapy clinical trials have failed so far.
Gene therapy has been a field of intense research for nearly 20 years. More than 1,000 gene-therapy clinical trials have been conducted, but to date there are no FDA-approved gene therapies.
A string of successful gene therapy clinical trials will some day mark a really big turn in the road toward the development of much more powerful medical treatments.
Key to this advance was the development of techniques to rapidly create and test large numbers of variations in polymers.
The researchers developed methods to rapidly optimize and test new polymers for their ability to form DNA nanoparticles and deliver DNA. They then chemically modified the very ends of the degradable polymer chains, using a library of different small molecules.
"Just by changing a couple of atoms at the end of a long polymer, one can dramatically change its performance," said Anderson. "These minor alterations in polymer composition significantly increase the polymers' ability to deliver DNA, and these new materials are now the best non-viral DNA delivery systems we've tested."
The polymers have already been shown to be safe in mice, and the researchers hope to ultimately run clinical trials with their modified polymers, said Anderson.
Even if this delivery vehicle turns out to work well to get DNA into cells that does not mean that a gene therapy which uses this delivery vehicle will be safe. Once the DNA gets into a cell it can integrate into a chromosome at a location that causes eventual cancer. So there's a second problem of how to get the newly introduced DNA to play nice with the cell it gets inserted into. Gene therapy is hard.
Viruses as gene therapy carriers are problematic because they usually cause an immune response. Plus, the amount of DNA which these polymers can carry looks to be larger than the amount that virus coatings can carry into cells.
Non-viral vectors could prove not only safer than viruses but also more effective in some cases. The polymers can carry a larger DNA payload than viruses, and they may avoid the immune system, which could allow multiple therapeutic applications if needed, said Green.
The researchers report success in getting their polymers to carry DNA into ovarian tumors. Gene therapy for cancer cells holds the promise of either reprogramming the cells to stop dividing or to even tell the cells to commit suicide.
Early-stage research has found that a new gene therapy can nearly eliminate arthritis pain, and significantly reduce long-term damage to the affected joints, according to a study published today in the journal Arthritis and Rheumatism. While the study was done in mice, they are the first genetically engineered to develop osteoarthritis like humans, with the same genetic predisposition that makes some more likely to develop the disease, the authors said.
In the current study, researchers found that one injection of a newly designed gene therapy relieved 100 percent of osteoarthritic pain in the study model. In addition, researchers were surprised to find that the therapy also brought about a nearly 35 percent reduction in permanent structural to joints caused by round and after round of osteoarthritic inflammation.
Yet more evidence for the damage caused by chronic inflammation. Anti-inflammatory effects of foods should be considered when trying to choose an optimal diet. Also, the results illustrate how the deterioration of an aging body feeds on itself in a vicious cycle. Damage initiates processes which cause yet more damage which initiates still more damage-producing reactions.
All they did was to increase the number of opioid receptors on nerve cells. This was done so that arthritic joints wouldn't cause pain signals to get sent to the brain.
On nerve cells for instance, certain receptors are shaped to accept naturally occurring painkillers called opioids, which when they dock, prevent the sending of pain messages along nerve pathways.
In the current study, researchers used gene therapy to increase by about one thousand times the number of opioid receptors expressed on the surfaces of nerve cells that carry pain messages back and forth between an osteoarthritic jaw joint and the spinal cord. Thus, nerve cells involved in pain transmission, with so many more receptors on their surfaces, became drastically more responsive to the naturally occurring painkiller, researchers found.
The researchers hypothesize that the chronic pain signals from a bad joint trigger an inflammation response in other parts of the body causing more joints to become arthritic. They also suspect the chronic pain might contribute to the development of brain diseases such as Alzheimer's and Multiple Sclerosis.
This result strongly suggests that better methods to control pain will slow aging. It also draws attention to the importance of inflammation in disease development (and probably argues for eating more fish more omega 3 fatty acids in order to reduce inflammation). This result also demonstrates how scientific experimentation will sometimes turn up useful results that are unexpected. Direction of scientific research does not work well with too much central planning since results are so often unforeseeable. Individual scientists deserve considerable latitude in choice of experiments.
David M. Lynn and his colleagues have created ultrathin, nanoscale films composed of DNA and water-soluble polymers that allow controlled release of DNA from surfaces. When used to coat implantable medical devices, the films offer a novel way to route useful genes to exactly where they could do the most good.
Lynn, a UW-Madison professor of chemical and biological engineering, has used his nanoscale films to coat intravascular stents, small metal-mesh cylinders inserted during medical procedures to open blocked arteries. While similar in concept to currently available drug-coated stents, Lynn's devices could offer additional advantages. For example, Lynn hopes to deliver genes that could prevent the growth of smooth muscle tissue into the stents, a process which can re-clog arteries, or that could treat the underlying causes of cardiovascular disease.
What is our biggest need for gene therapy? Brain rejuvenation. That's right. Brain rejuvenation. For most of the rest of the body the development of cell therapies and means to grow replacement organs will do most rejuvenation. But in the brain we need to repair each neuron. Stem cell therapies will still deliver benefits for the brain, for instance by repairing blood vessels. But we need to turn back the biological clock on our about 100 billion neurons per brain.
The polymers gradually dissolve once placed in the body. Then the DNA they contain seeps out and some of it presumably enters cells.
As it turns out, making the DNA-containing films is relatively straightforward, Lynn says, but "getting [the DNA] back out of the films is the hard part."
The secret to films that release DNA is in the choice of the polymer and the layer-cake design. The researchers alternate layers of DNA with layers of a polymer that is stable when dry but that degrades when exposed to water. Because the polymers carry a positive electric charge that is attractive to DNA, each polymer layer also "primes" the surface to accept the next layer of DNA. While electrostatic forces between the layers keep the film stable in dry, room-temperature conditions, the polymers break down easily in a wet biological environment - like the inside of a patient's body.
Here's the really cool part. Lynn's group is designing different variations on thin films that will deliver gene therapies at different speeds and even deliver different genes in sequential order.
Lynn's laboratory has engineered a whole toolbox of different polymers to fine-tune the DNA delivery properties of their films. Using the layering method, they can control the amount of DNA by adding more layers, or can even layer multiple ingredients in a specific order. Tweaking the polymer structure slightly can change how quickly the films erode and thus how long cells are exposed to the gene therapy. "We ultimately need an effect prolonged enough to be therapeutically relevant - whatever time scale that might turn out to be, " explains Lynn.
The value of accelerating gene therapy development is enormous. Gene therapy used to make brains young again will some day boost economic productivity by trillions of dollars per year. Making that day come years sooner would gain us a total of tens of trillions of dollars or more. We underspend on body and brain rejuvenation research.
MIT's Technology Review has an interview with gene therapy researcher James Wilson MD Ph.D. who is a professor at University of Pennsylvania's School of Medicine. Wilson has been searching for better and safer gene therapy delivery vehicles (vectors) and he thinks he's found some very promising ways to deliver gene therapy.
Fortunately, evolution has generated a diversity of viruses. We screened monkeys and humans for lingering adenovirus-associated viral infection. Adenovirus-associated viruses infect humans and primates. No one knows what the virus does, what the infection looks like or whether it hurts or helps you. We discovered that 40 percent of human livers have persistent infections, and we identified over 100 new subtypes.
Parenthetically, Paul Ewald is looking more and more correct with his argument that we've underestimated the degree to which pathogens play a role in development of human diseases. Think about all those viruses these researchers found while looking for better viruses to use for gene therapy.
Now we are looking at the properties of the vectors and how well they can be transferred to different organs. We found that a variation of a vector called AAV9 can efficiently transfer genes to the heart.
TR: Have AAV vectors been tested in human trials? How safe are they?
JW: Yes. AAV2 has been tested for cystic fibrosis, muscular dystrophy, neurological disease, and hemophilia. Two patients in the hemophilia trial developed liver inflammation, although they did recover. Other than that, there have been no safety issues.
Since then, we've tried to determine if the new AAV vectors will have the same response. We don't think they will -- we think we've figured out what happened in those patients and how to get around it.
The identification of the genetic causes of disease has been done for a long list of disorders such as sickle cell anemia, cystic fibrosis, Huntington's disease, Marfan syndrome, Gaucher disease, and Werner syndrome. For the vast bulk of such diseases no effective treatments followed from identification of their genetic causes. Why? We still need really good ways to deliver gene therapy. Once we develop excellent methods to deliver gene therapy into cells and into chromosomes many diseases will become treatable.
Gene therapy has uses for diseases beyond the classic single mutation diseases. For example, cancers could be stopped if heavily mutated cancer cells could be reprogrammed by gene therapy to restore genes that normally control cell growth. Also, many mutations that accumulate with age that cause cells to work less well could be repaired with appropriate gene therapies. So the stakes are high for the development of excellent gene therapy delivery vehicles and techniques. I cheer every success of Dr. Wilson and other scientists working on gene therapy methods.
University of Rochester Medical Center researchers have show that UV light can turn on gene therapy just in the cells that need it.
An early study has demonstrated for the first time that laser light can target gene therapy right up to the edge of damaged cartilage, while leaving nearby healthy tissue untouched, according to an article published in the April edition of the Journal of Bone and Joint Surgery. True repair of injuries to articular cartilage would enable millions of patients, currently consigned to worsening arthritis and joint replacement, to return to athletic exercise.
Study authors say that dramatic progress is being made toward a new form of light-activated gene therapy for cartilage repair that will be safe, fast, easy on patients and compatible with techniques used by most surgeons (e.g. arthroscopy). Beyond knee injuries, researchers believe the technology could one day guide precision gene therapy for cancer or heart disease, restore vision by repairing eye tissue and rebuild skin destroyed by burns.
UV light turns on stress kinase enzymes that turn on DNA polymerase that causes the single stranded DNA in the gene therapy delivery package to get converted into an active form.
The solution to the problem of how to target some cells for gene therapy, while missing their neighbors, came from a strange source: our cellular defenses against sunlight. The sun gives off ultraviolet (UV) light, which can cause destructive changes (genetic mutations) when exposed to sensitive molecules like DNA. If not defended against, the changes in DNA caused by UV light would cause humans to constantly develop cancer, for instance, in exposed tissue. Thus, an SOS system evolved that calls for genetic repairs when UV light causes too many mutations. Specifically, UV light turns on signaling proteins called stress kinases, which activate DNA polymerase, the enzyme that re-builds DNA chains when damaged.
Current technologies can direct UV light with great precision. That, combined with the ability of UV light to turn on DNA polymerase, has granted researchers the ability to turn on gene therapy in one cell, but not its neighbors. In recent years, researchers have been working to develop a system where UV light pre-treats target tissue, so that only the cells exposed to light gain the ability to copy themselves and grow. What remained was to find the right combination of vector and light to make the therapy safe as well as effective.
Recombinant adeno-associated virus (rAAV) turned out to be the right vector because it has evolved to deliver into the cell only a single strand of deoxyribonucleic acids (DNA), not the usual two strands of molecules. A second strand of DNA must be built by DNA polymerase to form active, double-stranded DNA before genes, or a gene therapy, can take effect. Single-stranded delivery is the key rAAV's usefulness as part of light-activated gene therapy because, of the all the cells infected with a gene therapy, only those struck by UV light will turn on DNA polymerase. Only those cells will activate the therapeutic gene, divide and re-grow tissue.
Cell damage from UV light is a concern.
The current study evaluated the ability of long-wavelength ultraviolet light to stimulate gene expression following infection by rAAV. Researchers evaluated the safety and efficacy of long-wavelength ultraviolet laser light to induce light-activated gene therapy in articular cartilage cells (chondrocytes). The study authors believe this is the first demonstration that site-directed gene delivery can safely and effectively treat articular defects in higher animal cartilage cells.
Given the safety concerns found with short wavelength, researchers were excited to find that the new long wavelength system is an order of magnitude more likely to turn on gene therapy as designed than to cause death by mutation (cytotoxity). Along with previous studies, the current research found rAAV to be highly efficient at turning on gene therapy in articular chondrocytes. Pretreatment with 6000 Joules per meter squared, a standard dose of UV light, led to a tenfold increase in the effect of gene therapy in target cells after one week. In addition, nearly half of cells exposed to the light expressed the inserted, therapeutic gene.
If the UV light was an order of magnitude more likely to turn on the gene therapy than to kill the target cells then was the gene therapy activated in every 10 cells per 1 cell that died from the UV? That doesn't sound so exciting. If the 1 cell died then the other 10 cells might have suffered some permanent DNA damage from the UV. But maybe the press release isn't explaining the actual results well.
This approach could be refined to allow the use of smaller doses of UV. Imagine a molecule activated by UV light and delivered along with the gene therapy. Such a molecule, properly chosen, could activate DNA polymerase. Finding such a molecule would be hard. Though development of a better understandnig of how UV light activates DNA polymerase might lead to identification of such a molecule. Mechanisms for amplifying the selective effects of UV light would allow smaller amounts of UV light to be used.
Lipid DNA complexes are attracting increasing attention as non-viral DNA delivery vehicles. They have been described as one of the "hottest new technologies" for gene therapy, accounting for nearly 10 percent of ongoing clinical trials.
Lipids are molecules with two parts, a water-liking "headgroup" and oily tails that assemble together to avoid water. Lipids, along with carbohydrates and proteins, constitute the main structural material of living cells.
The novel lipid molecule created at UC Santa Barbara has a tree-shaped, nanoscale headgroup and displays unexpectedly superior DNA-delivery properties. "It generates a honeycomb phase of lipid DNA complexes," said Cyrus R. Safinya, a professor of materials; of molecular, cellular and developmental biology; and of physics at UCSB. The new molecule was synthesized in Safinya's laboratory by first author Kai K. Ewert, a synthetic chemist who is a project scientist in the research group.
"We've been trying to get a lipid-based honeycomb lattice for a long time," said Ewert. The structure of lipid DNA complexes strongly affects their ability to deliver DNA.
"Complexes containing sheets or tubes of lipids have been known since Safinya's group found these structures in 1997 and 1998, but no one had ever seen nanoscale cylinders such as the ones in our honeycomb lattice," Ewart said. The scientists proved the formation of this novel structure with X-ray scattering experiments. Ewert designed and synthesized the new lipid by manipulating the size, shape and charge of a series of molecules. He explained that the new lipid molecule has 16 positive charges in its tree-shaped headgroup, the largest number by far in the field of gene delivery.
The process of delivering a gene of interest into the cell is known as "transfection." In the paper, the authors describe transfection efficiency studies carried out in four cancer cell lines using the new molecule. Two of these are mouse cell lines and two are human cell lines. The honeycomb structure turned out to be highly effective.
The use of cancer cells as targets for gene therapy experiments makes sense for two reasons. First off, if the right genes could be delivered into cancer cells then the cells could be instructed to stop dividing and even to kill themselves. Second, since gene therapy still has considerable risks it makes sense to test gene therapies against diseases that are fatal. Lots of people are dying of terminal cancer every day. The risk that a gene therapy might itself some day cause cancer matters less to people who are already dying of cancer. Better to trade a fatal cancer of today for a (probaly less likely to be fatal) potential cancer 10 or 20 years hence.
Their approach is an improvement on efficiency as compared to existing approaches.
"Our new gene carrier shows superior transfection efficiency compared to commercially available carriers," said Ewert. "However, the most surprising result was obtained with the mouse embryonic fibroblast cells known as MEFs. These are empirically known to be extremely hard to transfect."
Safinya added: "Our data confirm that MEFs are generally hard to transfect. And the new molecule is far superior for transfection of these cells as compared to commercial lipids."
Gene therapy doesn't get the attention it deserves because it does not create ideological divisions and disagreement even beginning to approach those that have sprung up around human embryonic stem cell research. But gene therapy is probably at least of equal importance to cell therapy. The ability to upload patches to our genetic programs would be a boon. Cancer, heart disease, and general aging could be attacked with gene therapies. Ditto for many other diseases. Many genetic diseases could be cured with gene therapies.
In theory gene therapy ought to be the ideal way to cure cancer. Cancer develops as a result of a series of mutations that make cells divide and spread out of control. Gene therapies that correct the mutations ought to stop cancer. But delivery mechanisms that can reach the vast bulk of cancer cells are hard to find. Also, adding back in correct p53 and other mutated genes might mess up normal cells by causing them to have too many copies of those genes. University of Texas M.D. Anderson Cancer Center researchers haven't solved all those problems but they are testing nanoparticles as a delivery mechanism for gene therapy against cancer.
Nanoparticles may offer an answer. The newest strategy to emerge out of Roth's lab is a blob of lipid smaller than a cell or nanoscale, a type of fat that holds therapeutic genes. Developed by Nancy Templeton, Ph.D., of Baylor College of Medicine, the special nanoparticle is of a size that is easily absorbed into cells. "Dr. Templeton hit upon a nanoparticle that had a very efficient transfer into cells," says Charles Lu, M.D., an assistant professor in the Department of Thoracic/Head and Neck Medical Oncology and co-investigator.
The nanoparticles carry a new payload as well. They encase, like shrink wrap, a normal p53 gene as well as a second gene, FUS1, which is frequently altered or missing early in the development of many solid tumors.
So far, nine patients with metastatic lung cancer have been tested with the therapy in a phase I trial headed by Lu. In all, 30 patients are expected to be enrolled. The trial is a "dose escalation" study, which looks for side effects as doses of the drug are increased. "So far, there have been no significant safety issues," says Lu.
The study is the first to test nanoparticle therapy in treating human cancer, according to Lu. "No one before has tried intravenous injections using nanoparticles to replace genes that are lost or defective. This non-viral aspect is very different in gene therapy. It may offer major benefits because nanoparticles are non-infectious. They are inert; there are no infection risks to use bubbles of fat.
"If successful - and that is a very big if - nanoparticles may prove to be a way to deliver gene therapy systemically, potentially treating metastatic disease in multiple cancer sites," says Lu.
What isn't known yet, however, is how often normal cells will absorb the drug and what effect that will cause. Preclinical study seems to show that tumor cells preferentially take up the bubbles - and researchers are pleased with that finding, although they don't know why it happens - but healthy cells can also sop up the new genes. "It may not have too much of an effect on normal cells because they already have these beneficial genes, but we just don't know yet," says Lu.
An excess of p53 activity in normal cells would accelerate aging by causing too many cells to kill themselves through a process called apoptosis. But if you are faced with terminal cancer the risk of accelerated aging seems like the smaller immediate threat.
The full article outlines other gene therapy approaches M.D. Anderson reseachers are pursuing against cancer.
Successful development of gene therapy delivery mechanisms against cancer would open up many other diseases for gene therapy treatments. Gene therapy has failed to deliver on its early promise. We know the genetic causes of hundreds of diseases. So we know what needs reprogramming to cure many diseases. But we lack the ability to easily upload new genetic programs into cells. Once we have much better ways to do that the continued accumulation of knowledge about harmful genetic mutations will finally find ways to be used in therapies.
PITTSBURGH, Aug. 15 – Researchers from the University of Pittsburgh report the first study to achieve success with gene therapy for the treatment of congenital muscular dystrophy (CMD) in mice, demonstrating that the formidable scientific challenges that have cast doubt on gene therapy ever being feasible for children with muscular dystrophy can be overcome. Moreover, their results, published in this week's online edition of the Proceedings of the National Academy of Sciences (PNAS), indicate that a single treatment can have expansive reach to muscles throughout the body and significantly increase survival.
CMD is a group of some 20 inherited muscular dystrophies characterized by progressive and severe muscle wasting and weakness first noticed soon after birth. No effective treatments exist and children usually die quite young.
Despite gene therapy being among the most vigorously studied approaches for muscular dystrophy, it has been beset with uniquely difficult hurdles. The genes to replace those that are defective in CMD are larger than most, so it has not been possible to apply the same methods successfully used for delivering other types of genes. And because CMD affects all muscles, an organ that accounts for 40 percent of body weight, gene therapy can only have real therapeutic benefit if it is able to reverse genetic defects in every cell of the body's 600 muscle groups.
Aside: If a virus can get into all the muscle groups of the body it is no wonder that some kinds of viral infections make your muscles ache all over.
Think about what the passage above says about the state of gene therapy in the year 2005. Delivering a single large gene is too difficult. Well, gene therapies for rejuvenation will need to fix dozens and perhaps hundreds of genes. Some of those genes are large. We need much better gene therapy delivery vehicles.
The researchers use a couple of approaches to make the gene therapy work for CMD.
By using a miniature gene, similar in function to the one defective in CMD, and applying a newly developed method for "systemic" gene delivery, the Pitt researchers have shown that gene therapy for muscular dystrophy is both feasible and effective in a mouse model of especially profound disease. Using this approach, the team, led by Xiao Xiao, Ph.D., associate professor of orthopaedic surgery and molecular genetics and biochemistry at the University of Pittsburgh School of Medicine, report that treated mice had physiological improvements in the muscles of the heart, diaphragm, abdomen and legs; and they grew faster, were physically more active and lived four times as long as untreated animals.
The miniature gene they speak of here might be just the portion of the gene that gets translated into a protein. Many mammalian genes have what are called "introns" and "exons". The introns do not get translated into proteins but rather are spliced out in the process of going from gene to protein. The "exons" therefore can be combined into a gene that is smaller than the naturally occurring gene but which probably (barring some regulatory role for the "introns") can be made to work just as well.
"While we have much farther to go until we can say gene therapy will work in children, we have shown here a glimmer of hope by presenting the first evidence of a successful gene therapy approach that improved both the general health and longevity in mice with congenital muscular dystrophy," said Dr. Xiao.
The most common form of CMD, and also one of the most severe, is due to a genetic mutation of laminin alpha-2, a protein that is essential for maintaining the structures that surround muscle cells and is an integral link in the chain of proteins that regulate the cell's normal contraction and relaxation. If the protein is defective, or is lacking, this outside scaffold, called the extra-cellular matrix, disintegrates, and the muscle cells become vulnerable to damage.
One limit to their approach is the use of a virus to deliver genes. The adeno-associated virus (AAV) which they mention below is only 4675 DNA letters long. While the virus gets transported well into muscle cells (and muscle cells age and need gene therapy for rejuvenation) the Adeno-Associated Virus (AAV) just can not carry much DNA into a cell.
Simply replacing the defective gene with a good laminin alpha-2 gene is not possible because its size makes it impossible for researchers to get it to squeeze inside viral vectors – disarmed viruses that are used to shuttle genes into cells. But the team found a good stand-in in a similar protein called agrin that when miniaturized could be inserted inside an adeno-associated virus (AAV) vector. Dr. Xiao's laboratory is known for its work developing this vector, which they have previously shown is the most efficient means for delivering genes to muscle cells.
In the current study, the authors show that two strains of AAV, AAV-1 and AAV-2, were effective in transferring the mini-agrin gene to cells in two mouse models. The AAV-1 vector was given by systemic delivery – a single infusion into the abdominal cavity – a method the authors only recently described and which they used for the first time in this study to transfer a therapeutic gene. The AAV-2 vector was delivered locally, given by intramuscular injection to different muscles of the leg. With both approaches, muscle cells were able to assimilate and copy the genetic instructions for making mini-agrin. Once produced, the mini-agrin protein functionally took the place of the laminin alpha-2 protein by binding to the key proteins on either end, thus restoring the cell's outside scaffolding and reestablishing the missing link to key structures inside the cell.
I'm less excited than the authors because I want vectors (delivery vehicles or carriers) for gene therapy that can delivery much more DNA into each cell for more extensive reprogramming.
Clearly, the authors are most excited about the impressive results achieved in their experiments using systemic gene delivery, which proved there could be significant therapeutic improvements and even be life-saving. Yet they say their results are far from ideal and more work lies ahead.
"It's probably not realistic to expect that we can achieve complete success using the mini-agrin gene, which while somewhat similar, is structurally unrelated to laminin alpha-2. Unless we address the underlying cause of congenital muscular dystrophy we're not likely to be able to completely arrest or cure CMD," added Chungping Qiao, M.D., Ph.D., the study's first author and a research associate fellow in Dr. Xiao's lab.
Future directions for research include finding a way to engineer the laminin alpha-2 gene. For this study, the authors chose to use the mini-agrin gene because researchers from the University of Basel, Switzerland, had already demonstrated it could improve the symptoms of muscular dystrophy in a transgenic mouse model, which has little clinical relevance. The Pitt researchers might also explore approaches that combine genes that promote both muscle and nerve growth, as well as focus on improving the AAV vectors.
In addition to Drs. Xiao and Qiao, other authors are Jianbin Li; Tong Zhu, M.D., Ph.D.; Xiaojung Ye, M.D., Ph.D.; Chunlian Chen; and Juan Li, M.D., all from the department of orthopaedic surgery; and from the department of cell biology and physiology, Romesh Draviam and Simon Watkins, Ph.D.
Gene therapy does not get as much press as cell therapy. Yet gene therapy is crucial for rejuvenation. We will be able to replace many cells and organs using stem cell therapies and also tissue engineering techniques combined with stem cells to grow replacement organs. But the toughest problem for rejuvenation is the brain. We need to rejuvenate all the cells which are already in the brain. We will do part of that job by sending in immunotherapies that attack extracellular junk. Also, stem cells will help some. But to fix aged neurons, glial cells, and blood vessels in the brain we are going to need gene therapies that can deliver lots of genetic instructions to carry out repair and to replace damaged genes.
Another problem with viral gene therapy delivery mechanisms is the immune system's tendency to quite correctly recognize viruses as invaders. One way around that problem might to be to develop methods to very briefly suppress the immune system. If the viruses move out of the bloodstream pretty quickly then immune system suppression drugs might not need to suppress the immune system so long as to put one at risk of a major infection. Or perhaps the immune system could be trained to recognize a particular and not naturally occurring variation of AAV as self.
AAV still can play a role in rejuvenation therapies. One way to get around its size limitation might be to send in lots of small genes in successive AAV packages. Other way might be to genetically engineer AAV packaging proteins to form larger cases to carry larger genes into cells. Therefore the report above is a good step in the right direction and the researchers should be applauded. We just need many more such steps to produce successively better gene therapy techniques.
Thanks to Andy Price for pointing out this report. Says Andy "The cool thing for everyone (SENS) here that this treatment gets to ALL muscle groups.". His reference is to Strategies for Engineered Negligible Senescence or SENS.