WASHINGTON (Dispatches) -- University of Connecticut bioengineers have been able to regrow cartilage in a rabbit’s knee.
The best treatments available try to replace the damaged cartilage with a healthy piece taken from elsewhere in the body or a donor. But healthy cartilage is in limited supply. If it’s your own, transplanting it could injure the place it was taken from; if it’s from someone else, your immune system is likely to reject it.
The best possible treatment would be to regrow healthy cartilage in the damaged joint itself. Some researchers have tried amplifying chemical growth factors to induce the body to grow cartilage on its own; other attempts rely on a bioengineered scaffold to give the body a template for the fresh tissue. But neither of these approaches works, even in combination.
University of Connecticut bioengineer Thanh Nguyen says that the regrown cartilage doesn’t behave like native cartilage and that it breaks, under the normal stresses of the joint.
Nguyen’s lab has also been working on cartilage regeneration, and they’ve discovered that electrical signals are key to normal growth. They designed a tissue scaffold made out of nanofibers of poly-L lactic acid (PLLA), a biodegradable polymer often used to stitch up surgical wounds. The nanomaterial has a neat property called piezo-electricity. When it is squeezed, it produces a little burst of electrical current. The regular movement of a joint, such as a person walking, can cause the PLLA scaffold to generate a weak but steady electrical field that encourages cells to colonize it and grow into cartilage. No outside growth factors or stem cells (which are potentially toxic or risk undesired adverse events) are necessary, and crucially, the cartilage that grows is mechanically robust.