The skin carries out specialist functions such as barrier formation and thermoregulation. The mode of cellular replenishment of the surface epithelium that forms the outermost layer during steady‐state homeostasis is a subject of intensive investigations. A detailed analysis of the interfollicular epidermis reported in this issue of The EMBO Journal (Roy et al, 2016) reveals that hair follicles in their growth phase influence cellular behaviour of epithelial cells in their immediate proximity.
See also: E Roy et al
The interfollicular epidermis (IFE) constitutes the outer layer of the skin, which forms the water‐impermeable barrier that protects from excessive loss of moisture and exposure to infections and other environmental factors. Associated structures, such as the hair follicle (HF), provide adnexal functions such as a coat of hair and sebum production. The epidermis is a multi‐layered stratified epithelium with proliferating cells confined to the basal layer, where they attach to the basement membrane. As cells detach from the basement membrane, they lose their proliferative potential and initiate a terminal differentiation programme as they move through the upper layers of the skin and eventually end up as squames in the heavily cross‐linked epithelium that forms the water‐impermeable barrier. Due to the constant and lifelong physical demands on the surface of the epithelium and the incessant loss of dead squames, the IFE is continuously replenished by proliferating cells in the basal layer (Schepeler et al, 2014). In order to maintain steady‐state tissue homeostasis, the production of new cells and the loss of differentiated progeny must be carefully balanced. The mode of cellular replenishment has therefore been the subject of intensive research in order to understand how it is possible to balance cell fate on a population basis. To date, numerous studies have provided various models of tissue replenishment in the mouse IFE converging on a model …
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