Rapid thawing increases the fragility of the cryopreserved arterial wall

Objective: to extend present knowledge of the biomechanical and structural changes which occur in the cryopreserved, rapidly thawed arterial wall. Materials and methods: minipig iliac arterial segments were cryopreserved a t -196 degrees C in either minimum essential medium or Wisconsin solution. Fresh segments served as the control group. After 1 month, the specimens we re rapidly thawed (37 degrees C) and processed for biomechanical, ultrastru ctural, morphological and immunohistochemical (MMP-1, MMP-2, MMP-3 ;and MMP -9) for analysis. Visualisation of apoptotic cells was performed by TUNEL m ethod. For the mechanical distension analysis, an in vitro circuit was desi gned. Results: the cryopreserved segments showed a 42% incidence of spontaneous f racture and the appearance of microfractures which affected the endoluminal third of the vessel. An accumulation of liquid in the subelastica was obse rved. An increased expression of wall-degradative enzymes (mainly MMP-2) wa s also observed following cryopreservation. No significant differences were detected in the proportional elasticity module or tensile strength of the specimen groups. No differences in mechanical distension were observed betw een groups after the vessel segments were subjected to the pulsatile circui t flow for 72 h. Cell damage was most intense in the specimens cryopreserve d in the Wisconsin solution. Conclusions: cryopreservation in both the solutions employed, followed by r apid thawing, induce changes in the permeability which increase the fragili ty of the cryopreserved arterial wall. Both increased expression of wall-de gradative enzymes and accumulation of liquid may contribute to graft failur e after implantation.