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A hair follicle is the primary unit that produces a single outgrowing visible hair shaft. All hair follicles have a regeneration cycle consisting growth, destruction and resting phase, all of which are controlled by several intrinsic and extrinsic mechanisms. All hair forming cell populations arise from hair follicle stem cells that are located in bulge and hair germ. Epithelial progenitors themselves surround a core cluster of mesenchymal cells, the dermal papilla, which is thought to provide signals to coordinate hair growth. The exchange of molecular cues between epithelial and mesenchymal compartments begins during embryogenesis, when hair follicles are first formed. After initial hair follicle formation and a prolonged period of growth, follicles undergo cycles of destruction and regeneration throughout life. For new hair re-growth, signal exchange between dermal papilla cells and stem/progenitor cells is thought to occur in a process that is reminiscent of embryonic hair follicle formation. Many diverse developmental programs require coordinated mesenchymal-epithelial interactions for completion, and studies of hair growth provide an exquisite system in which to study the complexities of this universally important process. The purpose of this mini review is to provide a short glance at the growth cycle of the hair and to present the conceptual data regarding the hair homeostasis. [ABSTRACT FROM AUTHOR]

A hair follicle is the primary unit that produces a single outgrowing visible hair shaft. All hair follicles have a regeneration cycle consisting growth, destruction and resting phase, all of which are controlled by several intrinsic and extrinsic mechanisms. All hair forming cell populations arise from hair follicle stem cells that are located in bulge and hair germ. Epithelial progenitors themselves surround a core cluster of mesenchymal cells, the dermal papilla, which is thought to provide signals to coordinate hair growth. The exchange of molecular cues between epithelial and mesenchymal compartments begins during embryogenesis, when hair follicles are first formed. After initial hair follicle formation and a prolonged period of growth, follicles undergo cycles of destruction and regeneration throughout life. For new hair re-growth, signal exchange between dermal papilla cells and stem/progenitor cells is thought to occur in a process that is reminiscent of embryonic hair follicle formation. Many diverse developmental programs require coordinated mesenchymal-epithelial interactions for completion, and studies of hair growth provide an exquisite system in which to study the complexities of this universally important process. The purpose of this mini review is to provide a short glance at the growth cycle of the hair and to present the conceptual data regarding the hair homeostasis. [ABSTRACT FROM AUTHOR]