Remodeling of desmosomal and hemidesmosomal adhesion systems during early morphogenesis of mouse pelage hair follicles.

Early hair follicle morphogenesis proceeds with the formation of a hair placode, the downgrowth of the hair plug into the mesenchyme, and the development of an elongated hair follicle - processes that involve a series of exchange of messages between epithelium and mesenchyme. Regulation of epithelial cell adhesion during hair morphogenesis has been demonstrated in terms of the changing expression patterns of E- and P-cadherins. In this study, distribution patterns of several major components of desmosomes and hemidesmosomes, which are the most prominent cell adhesion systems in epidermal tissues, were examined during early morphogenesis of mouse pelage hair follicles. We found that both desmosomal and hemidesmosomal adhesion systems became downregulated in hair placodes and were much reduced or almost lost in hair plugs, which persisted in the region containing hair matrix. Downregulation of the adhesion systems in hair plugs was confirmed by electron microscopy. Similar distribution patterns of these molecules were obtained in the developing follicles in cultured skin. It may be that epidermal cells at the initial stages of hair development respond to the first mesenchymal message by grossly changing their cell adhesion systems and that the resultant changes in cell adhesivity underlie early hair follicle morphogenesis.