[Epidermal stem cells--biology and potential applications in regenerative medicine]

Stem cells are involved in the renewal and regeneration of the epithelium of various organs. The largest reservoir of epithelial stem cells in the human body is the skin. This organ is a specialized interior barrier protecting the body from the influence of physical, chemical and biological factors, ensuring at the same time the reception of signals from the external environment. Skin is also involved in numerous physiological processes which determine the homeostasis of the body. Renewal and regeneration of the epidermis which is the outer layer of the skin, is possible by the presence of different populations of stem cells that reside in microenvironments (niches), that creates specific conditions to preserve the biological properties of these cells. Because divisions of cells in niches are quite rare, it became possible to distinguish them from other rapidly proliferating cells of the skin. On this basis, the stem cells in the interfollicular epidermis, bulge region of the hair follicles, and within the sebaceous glands were located. Moreover hair follicles are suggested to be a niche for melanocyte progenitor cells and other multipotent stem cells derived from the neural crest, as well as mesenchymal stem cells. The presence of stem cells that are characterized by high proliferative potential and the ability to self-renew allow maintaing homeostasis and regeneration of epidermis. Identification, isolation and characterization of epithelial stem cells is necessary to understand skin diseases background, develop effective methods for their treatment and for wider use of stem cells in regenerative medicine, gene therapy or cosmetology.