Epidermal growth factor and keratinocyte growth factor differentially regulate epidermal migration, growth, and differentiation.

Abstract

Various growth factors such as epidermal growth factor and keratinocyte growth factor have been reported to promote wound closure and epidermal regeneration. In the present study epidermis reconstructed on de-epidermized dermis was used to investigate the effects of epidermal growth factor and keratinocyte growth factor on keratinocyte proliferation, migration and differentiation. Our results show that epidermal growth factor supplemented cultures share many of the features which are observed during regeneration of wounded epidermis: a thickening of the entire epidermis, an enhanced rate of proliferation and migration, and an increase in keratin 6, keratin 16, skin-derived antileukoproteinase, involucrin and transglutaminase 1 expression. The increase in transglutaminase 1 protein is accompanied by an increase in the amount of active transglutaminase 1 enzyme. Surprisingly no increase in keratin 17 is observed. Prolonging the culture period for more than two weeks results in rapid senescence and aging of the cultures. In contrast, keratinocyte growth factor supplemented cultures have a tissue architecture that is similar to healthy native epidermis and remains unchanged for at least 4 weeks of air-exposure. The rate of proliferation and the expression of keratins 6, 16 and 17, skin-derived antileukoproteinase, involucrin and transglutaminase 1 is similar to that found in healthy epidermis and furthermore keratinocyte migration does not occur. When the culture medium is supplemented with a combination of keratinocyte growth factor and a low concentration of epidermal growth factor, skin-derived antileukoproteinase, involucrin and keratins 6, 16 and 17 expression is similar to that found in cultures supplemented with keratinocyte growth factor alone and in healthy epidermis. Only high transglutaminase 1 expression remains similar to that observed in cultures supplemented with epidermal growth factor alone. Our results show that the regulation of keratinocyte growth, migration and differentiation depends on the availability of these growth factors. Epidermal growth factor may play a dominant early role in wound healing by stimulating keratinocyte proliferation and migration while keratinocyte growth factor may play a role later in the repair process by stabilizing epidermal turnover and barrier function.