EFFECT OF CRYOPRESERVATION ON SURVIVAL OF COMPOSITE TISSUE GRAFTS

The problems in cryopreserving complex tissues remain poorly understoo d. In the present study, the viability of cryopreserved complex tissue , including skin and muscle flaps, and tail, was compared to simple ar tery and vein grafts in a rat model. Forty-four grafts, including the femoral artery (n = 15), femoral vein (n = 9), gracilis muscle flap (n = 8), groin cutaneous flap (n = 9), and tail (n = 3) were cryopreserv ed at -196 degrees C for 1 to 2 weeks, and then microvascularly transf erred to analogous sites in inbred recipient animals. Three to 60 days post-transplant, all cryopreserved femoral arteries and veins were pa tent. Host groin cutaneous flaps with cryopreserved vessels grafted in to the arterial pedicle survived with no complications. However, sever e endothelial-cell damage with extensive sloughing in the grafts was d emonstrated at 30 min and 1 week following reperfusion, using factor V III immunologic stain. Reendothelialization was evident at 2 months po stoperatively. All cryopreserved composite tissue underwent early pedi cle thrombosis. The muscle and cutaneous tissue also showed gross and microscopic edema, with extensive red-cell extravasation within 30 min of reperfusion. Cryopreservation thus can maintain the functional int egrity of simple vessel grafts, but these grafts survive only as a con duit, given the severe endothelial-cell damage. The failure of transfe rred complex cryopreserved tissue may reflect a combination of cellula r or architectural damage to the capillary bed from ice Formation duri ng the freezing process and from reperfusion injury.