Advances in Bulge region stem cells of the human, mouse and rat

stem cells have the unique capacity to self-newal and to differentiate into the cell lineages that constitute their . tissue of origin. within the tissue, they often reside in niches that provide a specialized environment thought to regulate their proliferation and differentiation. Hair follicle is composed of concentric rings of an external outer root sheath attached to the basal lamina and contiguous with epidermis, channel and finally the hair shaft. the hair is growth from the bulb of the follicle. In catagen period, hair growth cease and lower half of each follicle degenerate. After arrest period(telogen) the lower follicle grew and produce a new hair. Studies in human, rat and mouse suggested that, stem cells reside in the bulge region when cultured in vitro. Bulge keratinocytes yield larger colonies than those from other skin regions. Finally they can change to epidermis, hair follicle and sebaceous glands. Bulge stem cells can express keratin 15, keratin 1, integrin and nestin. hair follicle stem cells have slow cycling and label retaining properties, so they grown in culture media that have epidermal growth factor and collagen coated flasks or in feeder cell layer. They are multipotent, able to differentiate into Schwann cells, astrocytes, oligodendrocytes and neurons