Histological characteristics of the healing process of frozen skin allograft used in the treatment of burns.

Combined transplantation of skin autograft and allograft was used for the treatment of severe burns. The allografts were obtained from cadavers and were pretreated with 15 per cent glycerol for 2 h at 4 degrees C then frozen at -80 degrees C until used. Patches of autografts were placed over the burns and were covered by a stretched mesh of allografts. Biopsy samples of transplanted skin were obtained from 5 days to 4 weeks after grafting. Sections were examined by histological and immunohistochemical strainings. At 4 days, the epidermal-dermal junction of allografted skin was separated due to migration of epithelial cells derived from autograft epidermis or from skin appendages of recipient dermis. At 2 weeks, dermal fibroblasts and capillaries proliferated in autografts. At 3 weeks, the dermal components of the allograft were covered by epithelial cells from recipient tissue and were invaded by fibroblasts and capillaries. At 4 weeks, allografted skin was replaced by granulation tissue, which mediated the adhesion of the grafts to the underlying tissue. Skin allografts with a freeze-thawing pretreatment provide an appropriate matrix for the epithelial relining and for the growth of granulation tissue in burned skin.