Storage of porcine articular cartilage at high subzero temperatures

Transplantation of osteochondral allograft tissue can treat large joint defects but is limited by tissue availability, surgical timing, and infectious disease transmission. Fresh allografts perform the best but requirements for infectious disease testing delay the procedure with subsequent decrease in cell viability and function. Hypothermic storage at lower temperatures can extend tissue banking time without loss of cell viability and, therefore, increase the supply of allograft tissue. This study investigated the effects of different cryoprotectant solutions on intact AC at various subzero temperatures.

10 mm porcine osteochondral dowels were immersed for 30 minutes in various combinations of solutions [(XVIVO, propylene glycol (51% w/w), sucrose (46% w/w)] cooled to various subzero temperatures (-10, -15, and -20 degrees C), and held for 30 min. After warming, 70 mum slices were stained with membrane integrity dyes, viewed under fluorescence microscopy and cell recovery calculated relative to fresh controls.

Results demonstrated excellent cell recovery (>75%) at -10 degrees C provided ice did not form. Excellent cell recovery (>70%) occurred at -15 degrees C in solutions containing 51% propylene glycol but formation of extra-matrix ice in other solutions resulted in significant cell loss. All groups had <6% cell recovery at -20 degrees C and propylene glycol did not provide a protective effect even though extra-matrix ice did not form

These results suggest that extra-matrix ice plays an important role in cell damage during cryopreservation. Excellent cell recovery can be obtained after storage at subzero temperatures if ice does not form. Hypothermic preservation at high subzero temperatures may extend AC storage time in tissue banks compared to current techniques.