Effect of the thawing process on cryopreserved arteries

This study was designed to explore the changes that occur in cryopreserved pig arteries following different thawing procedures, before and after being placed in an in vitro flow circuit. Segments of minipig iliac artery were cryopreserved in complete minimal essential medium plus 10% dimethylsulphox ide and stored in liquid nitrogen at -196 degreesC for 30 days. Three study groups were established according to whether the arterial specimens were f resh (control, n = 20), cryopreserved and rapidly thawed (RT) at 37 degrees C (n = 22) or cryopreserved and subjected to controlled, automated slow tha wing (ST) (n = 22). Half of the specimens of each group were subsequently p laced in the flow circuit for 72 hr. Evaluation was made of morphological a nd ultrastructural changes. Cell damage was established using the TUNEL met hod. All cryopreserved specimens showed endothelial denudation that was mos t extensive in those subjected to rapid thawing. Slowly thawed specimens sh owed improved cell viability and organization of the vessel wall, compared to those thawed rapidly. Under conditions of flow, the damage induced by th e freezing/thawing process was enhanced. These findings suggest that (a) sl ow thawing of cryopreserved arteries results in improved preservation of th e structure and viability of vessels, and (b) the damage induced by freezin g/thawing is enhanced when vessels are subjected to flow in an in vitro cir cuit.