"Designer” Gel May Improve Cartilage Repair

A new technique to improve cartilage repair with an implant of new cells grown outside the body has been developed by engineers at the Massachusetts Institute of Technology (MIT, Cambridge, USA). Their work was reported in the issue of the Proceedings of the National Academy of Sciences published online the week of July 15-19, 2002.

According to the new technique, cartilage cells are grown outside the body within a novel "designer” gel. The cell-seeded gel is then delivered into a damaged joint, where the tissue grows and integrates with the normal cartilage while the gel slowly degrades. The researchers hope the cartilage gel could be implanted arthroscopically, through a small external incision. This minimally invasive surgery would be less expensive and reduce recovery time. Currently, a procedure approved by the US Food and Drug Administration (FDA) consists of extracting a small amount of cartilage cells from a patient, coaxing them to multiply outside the body, and then implanting the new cells into the damaged area. However, the procedure is very expensive (around $US30,000) and does not result in the generation of a true articular cartilage, according to the MIT team.

The team is using a peptide scaffold hydrogel that has been proven useful for growing a range of cell and tissue types for regenerative medicine. The hydrogel is also biocompatible and can be tailored to have different properties. For example, the gel could be designed to degrade over a specific time frame. Since the peptide is not extracted from animal tissues, there is less risk of passing along viruses to the engineered tissue.

The peptide hydrogel is made of interwoven fibers only 10-20 nm in diameter. "This is in sharp contrast to other biopolymer microfibers, which are some 1,000 times larger in diameter,” said Shuguang Zhang, associate director of MIT's Center for Biomedical Engineering. "That smaller size scale makes all the difference in the world,” he noted. For example, growth factors could be tethered to the peptide structure of the gel to directly stimulate the cartilage cells.




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