Mechanical barrier as a protection against rejection of allogeneic cartilage formed in joint surface defects in rats

Cartilage formed in transplants of allogeneic chondrocytes into joint carti lage defects in rats was infiltrated by immune cells migrating from the bon e marrow while the surface on the side of the joint cavity remained free of infiltrations. This suggested that immunization occurred via bone marrow a nd not via joint cavity. Because articular cartilage is nourished exclusive ly by the synovial fluid, we have attempted to prevent cartilage rejection by protecting transplants from the contact with bone marrow. Defects in art icular surface were filled with bone cement and chondrocytes were transplan ted into a cavity prepared within the bone cement plug. Cartilage formed wi thin the cement shell remained free of infiltrations and did not evoke syst emic immunological response. However, distribution of glycosaminoglycans in the matrix of protected transplants was irregular. Cultures of chondrocyte s growing in vitro on cement contained less glycosaminoglycans than the con trols. This suggests that some factor(s) released from the cement unfavorab ly influenced chondrocytes and matrix production in protected transplants.