Role of dermal stem cells in hair follicle cycling

The hair follicle is composed of the epidermal (epithelial) and dermal (mesenchymal) compartments, whose interaction plays an important role in the morphogenesis and growth of hair follicles, and is also a key factor for successful reconstruction of hair follicles. Generally, dermal cells are considered as inducers, and epithelial cells as responders during the process of hair formation. There are hair follicle dermal stem cells (HFDSCs) in the dermal sheath and hair papilla, which belong to adult stem cells, and are characterized by slow periodicity, undifferentiation, self-renewal and strong proliferative ability in vitro. HFDSCs in the dermal sheath show a relatively long life, and can survive several hair follicle cycles to reconstitute the dermal sheath. In the anagen phase of hair follicle cycles, stem cells in the dermal sheath generate new cells for the hair papilla. In the catagen phase, dermal stem cell progenies move out of the hair papilla or die. HFDSCs are of great significance for reconstruction and repair of hair follicles after occurrence of injuries and diseases. Key words: Hair follicle; Dermis; Stem cells; Biological processes; Hair diseases