Transplantation performance of human skin cryopreserved by programmed or stepwise freezing and stored at -80 degrees C or -180 degrees C.

Abstract

We developed a mouse recipient model that was used to evaluate and compare four cryopreservation procedures for human cadaveric skin stored for two time periods. Skin specimens were identically processed and preserved by programmed (1 degree C/min), or stepwise freezing, and stored at -180 degrees C or -80 degrees C for periods of 1 month and 6 to 10 months. Samples were grafted on Balb/c mice, and primary take was evaluated after 7 days. The results indicate that although all grafted specimens were initially accepted, as indicated by gross observations, histologic differences were evident and significant. The study groups were analyzed for the effect of method and skin sample variety; the effect of freezing procedure and temperature level; time effect (storage period); and advantage of method 1 (programmed freezing at -180 degrees C) over the other methods. The significance (p value) was determined for separate histologic criteria and average skin score or quality. The overall results indicate that average score of skin preserved by method 1 is highest for both storage periods. This method has an almost significant advantage (p = 0.057) over the others on quality of skin stored for 1 month, and a highly significant advantage (p = 0.007) on graft adherence of skin stored for 6 to 10 months. The effect of method and samples variety on the separate histologic criteria and average score of skin is not always significant. However, an interaction factor (between method and samples) has a highly significant effect (p < 0.001) on almost all of the histologic criteria and average skin score. The effects of freezing method is significant only on average skin score, for 1 month of storage; whereas temperature effect is seldom significant. Evaluating the effects of time, samples, and the interaction factor (between time and samples) indicated that the interaction factor is highly significant (p < 0.001). Time and samples effects are rarely significant. Thus the quality of the final product-the cryopreserved skin-is determined by many factors, and quite often they interact. Highly significant is the combined effect, or interaction factor, of sample variability with method of cryopreservation or with storage period.