Effect of Cryopreservation on Survival of Composite Tissue Grafts

ABSTRACT

The problems in cryopreserving complex tissues remain poorly understood. In the present study, the viability of cryopreserved complex tissue, including skin and muscle flaps, and tail, was compared to simple artery 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 cryopreserved at -196°C for 1 to 2 weeks, and then microvascularly transferred to analogous sites in inbred recipient animals. Three to 60 days post-transplant, all cryopreserved femoral arteries and veins were patent. Host groin cutaneous flaps with cryopreserved vessels grafted into the arterial pedicle survived with no complications. However, severe endothelial-cell damage with extensive sloughing in the grafts was demonstrated at 30 min and 1 week following reperfusion, using factor VIII immunologic stain. Reendothelialization was evident at 2 months postoperatively. All cryopreserved composite tissue underwent early pedicle 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 integrity of simple vessel grafts, but these grafts survive only as a conduit, given the severe endothelial-cell damage. The failure of transferred complex cryopreserved tissue may reflect a combination of cellular or architectural damage to the capillary bed from ice formation during the freezing process and from reperfusion injury.