It is important to remember why old cars can outlast old humans: Failed car parts can be replaced. With rare exception failed human parts can't be replaced. But a team of researchers has recently developed a way to grow replacement joints in rabbits.
A pioneering study published Online First in the Lancet has shown that failing joints can be replaced with a joint grown naturally using the host's own stem cells. The work paves the way for a future of naturally grown joints that would last longer than currently used artificial joints. The work was carried out by Professor Jeremy J Mao, and his team at Columbia University Medical Center, New York, USA, and colleagues from University of Missouri and Clemson University.
Rather than try to grow replacement parts outside the body the trend in tissue engineering is to try to create the right local conditions within the body. This would probably be harder to do when growing replacement organs since existing organs often can't be removed to make room for new organs. The existing heart or liver needs to keep functioning while the replacement is grown. Though I wonder whether a big cavity could be created in the body where replacement organs could grow. Imagine walking around with an extended gut similar to pregnant women. But rather than growing a new baby you'd be growing a new full-sized heart or kidney or pancreas.
Growth factor was used to attract the rabbits' own stem cells to very rapidly build up a new joint on implanted scaffolds.
In this proof-of-concept study, Professor Mao and colleagues removed the forelimb thigh joint of 10 rabbits, and then implanted three dimensional biomaterial scaffolds infused with growth factor. The rabbits' own stem cells were 'homed' by the growth factor to go to the location of the missing joint, and regenerated cartilage and bone in two separate layers. Just four weeks later, the rabbits were able to resume normal movements, similar to rabbits with normal functional joints. These rabbits had grown their own joint using their own stem cells, instead of stem cells harvested apart or outside of the host.
This is an amazing result. His team is going to try goats next. How many years will we have to wait before this technique is tried in humans?
Check out the pictures for how this is done.
EVANSTON, Ill. --- Northwestern University researchers are the first to design a bioactive nanomaterial that promotes the growth of new cartilage in vivo and without the use of expensive growth factors. Minimally invasive, the therapy activates the bone marrow stem cells and produces natural cartilage. No conventional therapy can do this.
The results will be published online the week of Feb. 1 by the Proceedings of the National Academy of Sciences (PNAS).
"Unlike bone, cartilage does not grow back, and therefore clinical strategies to regenerate this tissue are of great interest," said Samuel I. Stupp, senior author, Board of Trustees Professor of Chemistry, Materials Science and Engineering, and Medicine, and director of the Institute for BioNanotechnology in Medicine. Countless people -- amateur athletes, professional athletes and people whose joints have just worn out -- learn this all too well when they bring their bad knees, shoulders and elbows to an orthopaedic surgeon.
I know people who experience daily pain from worn knee joints. Some started feeling this pain in their 30s. That's a long time to go thru life with a disability that, absent a treatment such as this one, will mean only worsening pain to look forward to.
In an animal model the nanofiber gel with growth factor injected into the injured joint stimulates stem cells to produce the desired type II collagen.
"Our material of nanoscopic fibers stimulates stem cells present in bone marrow to produce cartilage containing type II collagen and repair the damaged joint," Shah said. "A procedure called microfracture is the most common technique currently used by doctors, but it tends to produce a cartilage having predominantly type I collagen which is more like scar tissue."
The Northwestern gel is injected as a liquid to the area of the damaged joint, where it then self-assembles and forms a solid. This extracellular matrix, which mimics what cells usually see, binds by molecular design one of the most important growth factors for the repair and regeneration of cartilage. By keeping the growth factor concentrated and localized, the cartilage cells have the opportunity to regenerate.
Anyone know what the obstacles are to trying this in humans? In the United States is FDA approval needed?
Osteoarthritis (OA) is one of the ten most disabling diseases in the developed world and is set to become more of a financial burden on health services as average life expectancy increases.
OA is the most common form of arthritis, affecting nearly 27 million Americans or 12.1% of the adult population of the United States, according to Laurence et al.Ļ A 2001 study showed that the disease costs US health services about $89.1 billion,2 and indirect costs relating to wages and productivity losses and unplanned home care averaged $4603 per person.3
Aging and accumulated damage are expensive. If they didn't happen the total cost of health care would be a small fraction of what it is today.
Rejuvenation of the body's own repair systems is the best way to solve most aging problems. The most promising technique for joint repair involves extracting cells from cartilage, growing up the cells, and then reinjecting these cells so that they'll repair the joint.
In a review for F1000 Medicine Reports, Yves Henrotin and Jean-Emile Dubuc examine the range of therapies currently on offer for repairing cartilaginous tissue. They also consider how recent technological developments could affect the treatment of OA in elderly populations.
The most promising therapeutic technique is Autologous Chondrocyte Implantation (ACI), which involves non-invasively removing a small sample of cartilage from a healthy site, isolating and culturing cells, then re-implanting them into the damaged area.
A recent enhancement to this method is matrix-assisted ACI (MACI) - where the cultured cells are fixed within a biomaterial before being implanted to promote a smooth integration with the existing tissues. ACI and MACI have previously been reserved for younger patients who are not severely obese (i.e. with a BMI below 35), whose cartilage defect is relatively small and where other therapies have already been tried.
Reserved for younger patients: Of course. Cells in older people do not divide and do repairs as vigorously as cells in younger people. To make ACI and MACI useful for older people will probably require development of ways to either rejuvenate stem cells or to create local environments that stimulate the cells to grow. Irina Conboy is working that problem.
My worry: can the problem of tired stem cells be solved without raising the risk of cancer? Will we have to wait for non-toxic and effective ways to knock out cancer cells before we can safely turn up the activity of stem cells in aged bodies?
Does your knee hurt? We need better methods for the repair of worn and aging body parts. With better ways to repair we could keep bodies running far beyond their original design life just like antique cars. The best knee cartilage repair surgery helps some but far from enough.
ďA small hole is going turn into a big hole eventually, given enough time," says Riley Williams, M.D., orthopedic surgeon, Sports Medicine and Shoulder Service, Hospital for Special Surgery in New York, and director of the Institute for Cartilage Repair at HSS.
After an initial injury that has caused damage to a specific area of the cartilage, there are few options that can repair the damage which is likely to lead to severe osteoarthritis. The most popular current treatment for such lesions is called the microfracture procedure. In this surgery, a tiny 'pick' spikes holes into the base of the damaged cartilage area to promote bleeding. This allows the patientís bone marrow cells to come to the surface of the damaged tissue. As a result, the cells then change into fibrocartilage cells and heal the defect.
While microfracture is minimally invasive and very quick, research has found that the defect may not always be fully repaired. The fibrocartilage does not hold up as well under everyday wear and tear as normal cartilage and has a much higher risk of breaking down again. As a result, surgeons in this area continue to pursue new methods of repairing cartilage injuries.
Some improvements in tissue engineering using a patient's own cells might produce a far more lasting layer of replacement cartilage.
A new multi-center clinical trial led by Dr. Williams at Hospital for Special Surgery uses a patientís own cells to heal damaged cartilage, but in a much different way. First, a small piece of the patientís healthy cartilage is taken and then the cells are grown in a laboratory. These cells are put into a piece of protein matrix, called NeoCartģ, which has an internal structure shaped like a honeycomb. The cells use the NeoCartģ as a scaffold and begin to grow over and around the structure. This creates a piece of new cartilage which is then, through a tiny incision, implanted into the patientís joint over the damaged area, much like a living patch. The hope is that the new cartilage will repair the damage and integrate seamlessly with the surrounding cartilage.
Cell manipulation and tissue engineering technologies will produce much better results in the coming years. Some of the more mechanical parts of the body such as joints are lower lying fruit for repair and rejuvenation.
My biggest concern with the clinical trial above has to do with the age of the patients. Will the cells of older patients grow vigorously enough to create enough replacement cartilage? Will we need to wait for rejuvenating therapies for cells before an elderly patient's own cells can build replacement parts? The odds of success might be higher the younger you are.