Investigations of low-temperature storage of articular cartilage for transplantation

Isolated bovine articular cartilage chondrocytes and intact slices of cartilage were investigated to determine the effects of low-temperature cryopreservation on articular cartilage. Studies have focused on prefreezing conditions of cartilage, including the incubation medium and temperature of incubation, type and toxicity of the cryopreservative used, and the penetration of cryopreservative agents into cartilage cells. Cartilage freezing conditions were examined with respect to rate of freezing, controlled differential freezing rates, the ultimate storage temperature, and the time of storage. Cartilage thawing conditions were observed to ascertain the role of membrane osmotic stress during thawing and the effect of variable thawing rates on the viability of chondrocytes. Careful control of these variables can yield cartilage with cellular viability of over 50%. Optimum cryopreservation of viable cartilage should include prefreezing treatment with 7.5%-10% DMSO in nutrient medium, controlled slow freezing to -70 degrees, and rapid thawing in DMSO containing medium. A significant number of chondrocytes in deep-frozen cryopreserved articular cartilage can survive. The work recommends continued clinical use of deep-frozen cartilage.