Effect of storage and preservation methods on viability in transplantable human skin allografts

This study compared the metabolic activity of fresh skin samples to that of cadaver human skin allografts processed and stored by current tissue banking methods. We chose to use two metabolic assays as surrogate measures for viability in these grafts. Skin allografts stored either in liquid media at 4 degrees C for varying periods of time or stored by cryopreservation were quantitatively assessed for viability by tetrazolium reduction and oxygen consumption assays. These measurements were compared to viability assessments of fresh autograft skin. Human cadaver skin grafts, after procurement and just prior to further tissue bank processing, exhibited approximately 60% of the metabolic activity found in fresh skin samples obtained from living surgical donors. If allowed an overnight (18-24 h) incubation period at 37 degrees C, cadaver samples showed a recovery of their metabolic activity to 95% of that found in the autograft skin samples. When stored in liquid media at 4 degrees C, the cadaver skin declined steadily in cellular metabolic activity, arriving in less than 5 days storage at a measurement below that of cryopreserved skin. The cryopreserved skin was measured both immediately after thawing and dilution of cryoprotectant, as well as after equilibration and overnight incubation. Skin cryopreserved with dimethylsulfoxide Me(2)SO retained higher viability than glycerol cryopreserved skin. Residual concentrations of cryoprotectants were determined following typical recommendations for thawing and diluting skin allografts. The implications of these findings for transplantation and tissue banking are discussed.