Keratinocytes can differentiate into eccrine sweat ducts in vitro: involvement of epidermal growth factor and fetal bovine serum

BACKGROUND: in addition to formation of an epidermal sheet and dermal substitution, reconstruction of skin that possesses functionality is an important goal for dermatologists. OBJECTIVE: we attempted to regenerate eccrine sweat glands in vitro. METHODS: we constructed skin equivalent models with various combination of normal human keratinocytes and fibroblasts and also examined the effect of various growth factors. RESULTS: we found that keratinocytes invaded the collagen gels and formed eccrine duct-like structures, only when (i) the culture media contained at least 15 ng/ml of epidermal growth factor (EGF) and fetal bovine serum (FBS), (ii) the keratinocytes were derived from young donors, and (iii) fibroblasts were present in the gel. Interestingly, when cultured under the same conditions eccrine gland duct cells were unable to invade the gel. Immunohistochemical analyses revealed induction of carcinoembryonic antigen by EGF at the inner part of the eccrine duct-like structures. Proliferating cell nuclear antigen was expressed mainly in basal layers of the epithelia but was not observed in the deeply invaded part. Cytokeratin profiles of the reconstructed epithelia were consistent with those of the regenerating epidermis and partly with the eccrine sweat duct. CONCLUSIONS: although not perfect model, these results indicate that 'young' keratinocytes could differentiate into/toward eccrine sweat ducts in vitro in the presence of EGF and FBS in cooperation with dermal fibroblasts.