New Knees
A gel could mend cartilage
By Sally Atwood

MIT and Harvard Medical School researchers have developed a less invasive method for repairing damaged cartilage. The technique involves injecting the injury with a liquid that comprises cartilage-producing cells taken from elsewhere in the patient’s body and hyaluronic acid—a natural polysaccharide—that has been modified to be light-sensitive. After minutes of exposure to ultraviolet light, the liquid gels to hold the cells in place as they start to produce new tissue. Enzymes made by the cells eventually break up the gel into water-soluble components that the body can absorb. Viewed under a microscope, the new cartilage is virtually indistinguishable from natural cartilage.

The method, which is being tested in the knees of pigs, could not only offer a way to fix cartilage but also be used for plastic surgery. Jason Burdick, the MIT chemical engineering postdoctoral fellow who is the project’s lead researcher, says the gel might one day be injected into molds to make ears and noses that plastic surgeons could use as implants. Burdick says the long-term goal is to use the patient’s stem cells, which are easily obtained through routine biopsy, rather than cartilage cells, which must be harvested in a process that does further damage to the patient.

Beyond knees, Burdick says the process could one day be used to surface entire joints, helping millions who suffer from arthritis.