Effects of rapid cooling on articular cartilage.

In order to improve the technique and protocols of cryopreservation of articular cartilage, a study was carried out to assess the effects of rapid cooling on the intact articular cartilage. Cartilage slices with a thickness ranging from 0.2 to 0.5 mm taken from bovine metacarpal-phalangeal joints were subjected to rapid cooling by immersing them in liquid nitrogen with and without treatment of the VS55 cryoprotective agent (CPA). The ultrastructure, chondrocyte viability, swelling property, and glycosaminoglycan (GAG) content were then examined before and after cryopreservation to give qualitative and quantitative evaluation on the functional state of both chondrocytes and extracellular matrix. The transmission electron microscopy study demonstrated that damage to chondrocytes without CPA was far more pronounced than those with VS55 protection while the structure of the extracellular matrix altered little in either group. The cell viability assay showed that although the exposure to VS55 led to about 36% chondrocytes losing membrane integrity, the VS55 could provide protection to chondrocytes during rapid cooling and thawing, with approximately 51% of the cells having survived rapid cooling compared to fewer than 5% in the absence of CPA. There were no significant differences in degrees of swelling or the GAG contents of cartilage slices after cryopreservation indicating rapid freezing caused little damage to the matrix. Future research activities include searching improved CPA formulation, optimising the treatment protocol and investigating the long-term effects of rapid cooling on articular cartilage.