Effect of cryopreservation on human articular chondrocyte viability, proliferation, and collagen expression

Autotransplantation of human chondrocytes is an alternative therapeutic treatment for focal lesions of cartilage. During the process of isolation and culture of chondrocytes some problems that render the implantation of the cells unsuitable can occur. For security, some cells must be stored using cryopreservation. The objective of this study was to analyze the effect of cryopreservation on cellular viability, proliferation, and collagen expression of human chondrocytes. Human osteoarthritic cartilage (n = 23) was obtained and transferred to a sterile flask containing Dulbecco's modified Eagle's medium (DMEM) and antibiotics. Chondrocytes were isolated, cultured for 3-4 weeks, and frozen in DMEM containing 10% human serum and 10% dimethyl sulfoxide by use of three different protocols. A cellular fraction was frozen directly to -80 degrees C (Protocol I). Another fraction was directly frozen to -80 degrees C and 24 h later introduced into liquid nitrogen (Protocol II). The last aliquot was frozen with controlled freezing using a freezing rate of -1 degrees C/min to a temperature of -40 degrees C, 2 degrees C/min to -60 degrees C, and 5 degrees C/min to -150 degrees C (Protocol III). Cells were cryopreserved for 2 weeks. Cells from each cryopreservation method were then cultured for 7 days and cellular proliferation was evaluated by the counting of the total cells in each flask. Cryopreservation had a negative effect on chondrocyte survival and proliferation. The survival after cryopreservation with the three protocols was 70-75%. There was no significative difference between the methods used to cryopreserve (P = 0.4117). However, there was a significant difference among the donors (P = 0.0111). Cellular proliferation of chondrocytes was reduced by cryopreservation (P = 0.024). The rate of proliferation of different groups was control samples 6.56, Protocol I 4.66, Protocol II 4.69, and Protocol III 5.58. Statistical analysis showed that the programmed protocol was the best method to preserve cellular functions. Chondrocytes were able to express collagen type II 1 week after cryopreservation. Cryopreservation modifies the survival and proliferation of chondrocytes. Of all protocols used to cryopreserve, the programmed protocol seems to be the best technique. Cryopreservation does not alter the collagen type II expression.