Cryopreservation of composite tissue flaps: experimental studies in the rat

Cryopreservation has the potential to improve availability of donor parts for composite tissue allotransplantation and may reduce their antigenicity. This study investigates whether the component tissues of composite flaps remain viable after cryopreservation. Forty-one epigastric flaps were harvested from Lewis rats. Twenty-one flaps were perfused with DMSO/trehalose, frozen by controlled cooling to -140 degrees C, and stored in liquid nitrogen for 2 weeks. Ten fresh and 10 cryopreserved/thawed flaps were examined histologically with hematoxylin & eosin and factor VIII staining. An epithelial viability index was calculated for 10 fresh and 11 cryopreserved flaps using the MTT assay. In all cryopreserved samples, hematoxylin & eosin, and factor VIII staining revealed a well-preserved cellular architecture, which was indistinguishable from fresh specimens. The viability index for the cryopreserved samples was 10.90 +/- 2.09 compared with 12.15 +/- 1.32 for fresh flaps (P = 0.123). Results suggest that the skin, adipose, and vascular endothelial cells of composite tissue flaps retain their viability after cryopreservation and thawing.