A liquidus tracking approach to the cryopreservation of human cartilage allografts

Human articular cartilage was obtained from deceased donors and dimethyl sulphoxide (DMSO) was used as the CPA, cooling was at 0.14 °C/min and warming at 0.42 °C/min. The vehicle solution was CPTes2. A program of increasing DMSO concentration was developed for cooling and this gave satisfactory tissue concentrations but reduction of DMSO concentration during warming was inadequate, resulting in higher tissue concentrations than required. Biomechanical testing indicated a compressive modulus of 9.5 ± 1.3 MPa in LT-processed cartilage, with control values of 11.6 ± 0.8 MPa (p > 0.05, Student's t-test). Measurement of GAG synthesis sometimes approached 65% or 85% of control, but the variability of replicate data prevented firm conclusions. Ideally allograft tissue should score 1A or above on the Noyes scale and the donor age should be less than 46 years but the cartilage used in this study did not meet these standards.