Pretreatment of human keratinocyte sheets with laminin 5 improves their grafting efficiency

Laminin 5 is essential in epithelial attachment to stromal tissues, suggesting that it might improve keratinocyte attachment in a variety of clinical situations. In this study, we examined the effect of exogenous laminin 5 upon the efficiency of transplantation of keratinocyte sheets in animal models. Keratinocyte sheets were prepared according to the method of Rheinwald & Green (1975). Purified laminin 5 was added to the sheets of group 1 (1.0 microg per cm2), Dulbecco's modified Eagle's medium alone was added to group 2. The sheets were grafted to the panniculus carnosus of nude mice (BALB/C nu/nu) (n = 12) and nude rats (Fisher 344) (n = 15). The take rate was assessed by measurement of the area of surviving epithelium at 7 d postgrafting. Laminin 5 bound the keratinocyte sheets of group 1. At 7 d postgrafting, the area of epithelialization of group 1 was significantly larger than that of group 2. Immunohistochemistry staining showed that collagen IV, laminin 5, and collagen VII stained more strongly at the dermal-epidermal junction in group 1 than in group 2. Integrin chains alpha6 and beta4 were similar in both groups. Electron microscopy at day 3 after grafting, showed the lamina densa of group 1 to be more continuous than in group 2. Pretreatment of cultured human keratinocyte sheets with laminin 5 improved the extent of epithelial coverage and increased the rate of neobasement membrane formation. The results suggest that laminin 5 promotes epithelial attachment by increasing the rate of basement membrane assembly.