Injectable Gel Repairs Torn Cartilage

An injectable gel is being developed that could speed the repair of torn cartilage and help injured athletes return to competition sooner, according to researchers at the Massachusetts Institute of Technology (MIT) and Harvard Medical School (both in Boston, MA, USA).

The new technique uses the patient's own cartilage-producing cells and is less invasive than conventional cartilage repair techniques, which may include surgery and a slow, painful recovery. When the liquid mixture is injected into areas where cartilage is torn, such as a knee joint, the material hardens into a gel upon exposure to ultraviolet light, leaving the transplanted cells in place so they can grow new cartilage where it is needed. The gel material is composed of a natural polysaccharide called hyaluronic acid, which is modified with photoreactive groups (methacrylates) and a photosensitive molecule.

In a proof-of-concept experiment, the researchers implanted cartilage-producing cells obtained from the ears of pigs under the skin of a small group of mice. The material produced progressively higher amounts of healthy new cartilage over the three-month study period. Although ultraviolet light is used in the current gelling process, the scientists say the process can eventually be performed using visible light.

"The gel itself won't initially replace damaged cartilage, but will provide an optimum growth environment for implanted cartilage-producing cells so that new cartilage can be formed and help restore function,” explained lead author Jason A. Burdick, Ph.D., a postdoctoral fellow at the department of chemical engineering at MIT (www.mit.edu). The new technique is described in the January 10, 2005, issue of Biomacromolecules.

Dr. Burdick predicts that one day it may be possible to use the technique to repair worn cartilage covering large surface areas, such as arthritic joints, or used to "clay” custom-mold new cartilages outside the body for eventual use in plastic surgery reconstruction, such as building new ears and noses.




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