Skin regeneration and repaircédric BlanpainDifferent types of stem cell maintain the skin’s epidermis and contribute to its healing after damage. The identity of a stem-cell type that gives rise to different epidermal-cell lineages has just been revealed.Skin acts as an essential barrier, protecting organisms from their environment. It is composed of two parts: the epidermis, the cells of which form the barrier; and the dermis, which provides support and nutrition to the epidermis. The epidermis also produces appendages, including sweat glands, and hair follicles and their associated sebaceous glands. The different epidermal compartments undergo constant cellular turn over to replace the dead or damaged cells. This homeostatic process is thought to involve several types of stem cell, each located in a specific epidermal region and contributing to the maintenance of a discrete compartment of the skin1 (Fig. 1a). In a paper published in Science, Snippert et al. identify the “Lgr6” protein as the marker of progenitors that can differentiate into different cell lineages of the skin epidermis.The first evidence that skin stem cells can differentiate into interfollicular epidermis,sebaceous gland and hair follicle lineages came from transplantation of bulge stem cells(3,4) — a cell population located at the base of hair follicles. Further experiments revealed that, during both embryonic development and normal adult skin homeostasis, bulge stem cells and their progeny contribute to hair-follicle regeneration but not to the maintenance of the interfollicular epidermis(4–6). In conditions such as wounding, however, bulge stem cells rapidly migrate towards the interfollicular epidermis to help with the rapid regenerati...
