Changing Patterns of Localization of Putative Stem Cells in Developing Human Hair Follicles

The study examined the localization of putative stem cells in developing human hair follicles by analyzing the expression of β1 integrin, E-cadherin, and β- and γ-catenins in skin samples from 12 human fetuses at various gestational ages. It was found that β1 integrin-rich, E-cadherin-, and β- and γ-catenin-poor cells, considered potential stem cells, initially appeared throughout the hair germ and later localized to the outermost cells of the hair peg, eventually residing in the bulge and outermost layer of the outer root sheath in more developed follicles. This pattern mirrored that of cells rich in epidermal growth factor receptor and positive for keratin 19, supporting the hypothesis that the human fetal hair follicle bulge is a site of stem cells for follicular epithelium, thus contributing to the understanding of hair follicle morphogenesis.