Studies on cryopreservation of articular cartilage chondrocytes

We used cartilage cells isolated from bovine articular cartilage in experiments to: (1) determine the toxicity of cryopreservatives (glycerol and dimethyl sulphoxide) on chondrocytes, (2) evaluate methods of freezing chondrocytes to maximize viability after freezing, and (3) examine the biosynthetic activity of frozen and thawed chondrocytes in culture. Results showed that the toxicity of cryopreservatives to chondrocytes is dependent on the time and temperature of exposure as well as on the concentration of the cryopreservative. Maximum viability was obtained by a two-stage freezing procedure using a slow cooling period initially, with equilibration of the cells at -40 degrees Celsius before further rapid freezing to -80 degrees Celsius. After seventy-two hours in culture, chondrocytes that had been frozen using this protocol synthesized products that appeared by column chromatography to form proteoglycan aggregates.

One of the reasons for failure of frozen osteochondral allografts is the deterioration of joint function after transplantation due to degeneration of the articular cartilage. An important factor in the survival of these cartilage grafts may be preservation of the viability of the chondrocytes during storage and maintenance of the cell's ability to function following storage. In this study we evaluated the ability to store chondrocytes in a frozen state with the aid of cryopreservatives. The results confirmed that chondrocytes will survive freezing and remain capable of functioning in the same manner as fresh chondrocytes. This suggests that chondrocytes in articular cartilage should be able to survive freezing. The pursuit of methods of preserving articular cartilage by freezing appears to be warranted.