Recent research efforts from both Northwestern University in Chicago and the University of Pittsburgh Medical Center have described work on the use of a new nanofiber gel that promotes cartilage growth in joints.
The material is injected into the damaged joint and stimulates bone marrow stem cells to produce natural cartilage.
The nanofibers allow stem cells from bone marrow to produce cartilage containing type II collagen and repair a damaged joint.
Type II collagen is the major protein component in articular cartilage, the gristle that caps the ends of long bones within a joint.
This is distinctly different from the Type I collagen produced as a result of another procedure used to heal cartilage damage called microfracture. Microfracture is a surgical procedure where small holes are drilled into the bone beneath the area of cartilage damage. This leads to bleeding from the bone marrow.
Ostensibly, stem cells from the marrow create new cartilage.
Microfracture causes the production of cartilage having predominately type I collagen. Type I collagen is the type found most commonly in scar tissue.
Type II collagen is weaker than Type I collagen and probably does not hold up as well. This may be one explanation why microfracture surgery has not been as successful as first thought.
Another type of procedure called autologous chondrocyte transplantation has also been used. In this procedure, cartilage is harvested from a non-weight-bearing part of the joint. The cartilage is then specially treated in a laboratory so that individual cartilage cells multiply. The cartilage cells are then put back into the joint under a small flap of tissue that is sewn into place. Recovery is long and the cartilage produced also appears to contain mostly Type I collagen.
Mosaicplasty where multiple cartilage plugs are fitted into the cartilage defect has also been used. Results are mixed.
Stem cell treatment has the appeal of being less invasive and requiring less recovery time. However, controlled data is nonexistent. Supportive evidence consists of case studies and small numbers.
One issue that has plagued researchers and clinicians alike is the mechanical forces present within weight-bearing joints such as the hip and knee.
When asked his opinion regarding the nanofiber issue, Dr. William Arnold, a Chicago-based rheumatologist stated, "This isn't the first 'cartilage growth stimulator'...and it won't be the last. There's no way that cartilage regrows on the surface of the medial femoral condyle (of the knee) without a mechanical correction accompanying the "regrowth". The shear compression forces in the medial compartment are formidable... and would quickly chew up any flimsy cartilage surface beginning to grow on the surface of the condyle."
Dr. Nathan Wei, a rheumatologist specializing in stem cell treatment for osteoarthritis, concurs with Dr. Arnold to a point. He states, "The impact loading forces on weight-bearing joints such as the knee and hip are one thing to contend with but with the hip there is the added stress of rotational movement and in the knee there are gliding and rotational forces to deal with as well."
He argues though, "Animal models have demonstrated that stem cell procedures are effective. And while human data is sparse, early evidence supports further investigation... I do agree that mechanical forces need to be dealt with through various means in order to allow stem cells to 'take'. We are currently attempting to address this issue. Our results so far are very encouraging."
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