ABSTRACT
The development of sweat glands is a very complex biological process, which involves many factors. In this study, the correlation between epidermal growth factor (EGF), matrix metalloproteinases (MMP 2,MMP 7) and development of sweat glands in human embryos was explored. Furthermore, the mechanism(s) underlying the induction of epidermal stem cells into sweat gland cells was elucidated. Skin biospies of human embryos obtained from spontaneous abortions at different gestational ages from 11 to 31 weeks were used. The dynamical expression of EGF, MMP 2, MMP 7 and keratin 7(K7) in developing sweat gland cells or extracellular stroma surrounding the sweat gland cells were examined with S P immunohistochemical methods. The localization of the cellular sources of MMP 2 and MMP 7 was examined with in situ hybridization. The results showed that at 14 20 wk of gestation, a gradual increase of EGF immunoreactivity was observed not only in developing sweat gland buds but also in extracellular stroma surrounding the buds,and the expression intensity peaked at 20～22 wk of gestational age. All mRNA positive buds or cells in developing sweat glands contained corresponding immunoreactive proteins. The immunostaining for K7 appeared in early sweat gland buds at 14～16wk of gestation, and from then on, K7 was concentrated in developing sweat gland cords or cells. It is suggested that the morphogenesis of sweat gland in human fetal skin begins at 14～16wk of gestational age, and essentially completes by 24wk. There is a close relationship among EGF ,extracellular matrix remodeling and morphogenesis of sweat glands, and EGF is one of the inducers in the development and maturity of sweat gland buds or cells.