Influences of keratinocyte–fibroblast interaction on the expression of epimorphin by fibroblasts in vitro

Epimorphin was demonstrated to be a mesenchymal signal factor modulating epithelial morphogenesis of skin, lung and liver in vitro. Most of the previous studies were performed biochemically and functionally. In the present study, expression of epimorphin was immunohistochemically compared between cultured fibroblasts and cocultured fibroblasts with keratinocytes obtained from normal skin. Cultured fibroblasts revealed a low level of epimorphin expression. In contrast, the expression by fibroblasts was greatly enhanced in skin explant culture where both fibroblasts and keratinocytes were present. In three-dimensional coculture of fibroblasts and keratinocytes, the expression of epimorphin was enhanced. The staining pattern of epimorphin in three-dimensional coculture was similar to that in human skin. These results suggest that dermal fibroblasts are manufacturers of epimorphin, and keratinocyte–fibroblast interaction may play important roles in the expression of epimorphin in vitro.