Epidermal Homeostasis: A Balancing Act of Stem Cells in the Skin

The document from 2009 explores the critical role of stem cells (SCs) in maintaining the homeostasis of the skin's epidermis, hair follicles, and sebaceous glands. It details how skin stem cells are essential for cell replacement during normal tissue turnover and injury repair. The paper describes the different pools of skin stem cells and their contributions to epidermal maintenance and repair, including the importance of bulge SCs in hair follicles for hair cycling and development. It also discusses the molecular mechanisms, such as the role of transcription factors and signaling pathways like Wnt/ß-catenin and BMP, that regulate these processes. The document emphasizes the multipotency of bulge stem cells, their role in wound repair, and the importance of the niche in determining hair follicle fate. It concludes that skin stem cells use intrinsic and extrinsic resources to restore and maintain homeostasis, with a complex interplay of signaling pathways being critical for the maintenance of skin and hair follicle homeostasis.