Alopecia

The document from 2018 provides a comprehensive overview of hair growth, hair follicle anatomy, and the role of stem cells in hair cycling, with a focus on various forms of alopecia, particularly androgenic alopecia (AGA) and alopecia areata (AA). It explains the complex signaling involved in hair growth, the impact of sex hormones and growth factors, and the importance of mitochondrial-generated reactive oxygen species in hair follicle morphogenesis. AGA, the most common form of hair loss, is characterized by its patterns, genetic factors, and the role of androgens. The document contrasts AGA with chemotherapy-induced alopecia (CIA), noting that CIA spares stem cells, allowing for hair regrowth post-treatment. It also discusses the discovery of microRNAs and their role in hair loss, the reduced blood flow in balding areas, and the differences between mouse and human skin for research models. The document highlights the genetic associations of AA, the role of T cells and autoantibodies, and the identification of AA-reactive HF-specific antigens. It concludes by discussing the social and psychological impacts of alopecia and the resulting industry for hair loss treatments.