Cellular biology of cryopreserved allograft valves

Although analyzing the precise mechanisms of cryopreserved allograft valve failure may be difficult due to a number of crucial reasons and the interrelationships between the overlapping mechanisms, there is some evidence that cryopreservation is currently the best method of storing allograft valves. The present review shows the basic cellular biology of cryopreserved allograft valves for long-term durability, particularly relevant to allograft valve cellular viability, the immune response mainly caused by viable donor cells, and the preservation and regeneration of the intrinsic extracellular matrix. The present findings are as follows. First, cryopreservation produces serious damage to cytosolic and mitochondrial functions of both endothelial cells and fibroblasts, which may cause valve failure after implantation. Second, although the collagen synthesis of cryopreserved valves was relatively maintained, total protein synthesis was highly diminished and the collagenolytic ability was activated immediately after the thawing process. These findings imply that the cryopreservation itself may cause the collagen metabolism to become degradable, which will lead to valve failure. Further examination of collagen metabolism and modulation of the collagenolytic activity will be necessary to improve the tissue preservation for improved clinical use.