Keratinocyte Stem Cells: Role in Aging

The document discusses the role of keratinocyte stem cells in skin and hair aging. These cells, found in the skin's epidermis, dermis, and hair follicles, are responsible for skin regeneration, wound healing, and hair growth. However, their functionality declines with age, leading to skin aging symptoms such as alopecia, reduced hair density, and gray or thin hair. The document also highlights the role of interfollicular stem cells in epidermis regeneration and hair follicle stem cells in hair regeneration. Techniques used to study these cells include label retention, clonogenic assays, skin reconstitution, and genetic lineage tracing. Aging increases DNA damage and senescence in these cells, affecting their self-renewal capacity and leading to skin aging phenotypes. Chronic UV exposure can cause DNA damage, telomere shortening, and reduced stem cell renewal capacity. The aging of hair follicles is driven by the elimination of stem cells via COL17A1 proteolysis.