Hair Follicle Stem Cells: Their Function, Location, and Importance

Hair follicle stem cells (HFSCs) are a unique population of cells found in the hair follicle, playing a crucial role in hair growth, regeneration, wound healing, and maintaining skin homeostasis. These fascinating cells are garnering increasing attention from researchers seeking a better understanding of their potential applications in regenerative medicine. HFSCs reside primarily in the bulge region of the hair follicle, a niche specifically created to protect and maintain the stem cell population (Cotsarelis, 2006). These stem cells are in a quiescent state, meaning they are not actively dividing until they receive the necessary signals from the surrounding environment. Once activated, HFSCs give rise to transient amplifying cells, which in turn participate in the formation of new hair follicles or aid in skin repair (Blanpain et al., 2004). One of the key functions of hair follicle stem cells is hair growth. The growth of hair occurs through cyclical phases, namely the anagen (growth), catagen (regression), and telogen (rest) phases, controlled by a complex interaction between various signaling pathways (Stenn & Paus, 2001). HFSCs proliferate during the anagen phase, contributing to the growth and differentiation of new hair follicles. A disruption in the signals governing HFSC activation or an imbalance in abundance can lead to hair loss or alopecia (Plikus et al., 2008). Another vital function of HFSCs is their contribution to wound healing and skin regeneration. Upon injury, they activate and migrate to the wounded area, playing a central role in re-epithelialization, an essential part of wound closure (Ito et al., 2005). Activated HFSCs provide a source of keratinocytes, the predominant cell type in the epidermis, accelerating the wound healing process (Gurtner et al., 2008). In conclusion, hair follicle stem cells are key players in maintaining the normal functions and homeostasis of our skin and hair. Their abilities to participate in hair growth and wound healing hold promising potential for future developments in regenerative medicine, highlighting the importance of ongoing research in this field. References: Blanpain, C., Lowry, W. E., Geoghegan, A., Polak, L., & Fuchs, E. (2004). Self-renewal, multipotency, and the existence of two cell populations within an epithelial stem cell niche. Cell, 118(5), 635-648. Cotsarelis, G. (2006). Epithelial stem cells: a folliculocentric view. The Journal of investigative dermatology, 126(7), 1459-1468. Gurtner, G. C., Werner, S., Barrandon, Y., & Longaker, M. T. (2008). Wound repair and regeneration. Nature, 453(7193), 314-321. Ito, M., Liu, Y., Yang, Z., Nguyen, J., Liang, F., Morris, R. J., & Cotsarelis, G. (2005). Stem cells in the hair follicle bulge contribute to wound repair but not to homeostasis of the epidermis. Nature medicine, 11(12), 1351-1354. Plikus, M. V., Mayer, J. A., De La Cruz, D., Baker, R. E., Maini, P. K., Maxson, R., & Chuong, C. M. (2008). Cyclic dermal BMP signalling regulates stem cell activation during hair regeneration. Nature, 451(7176), 340-344. Stenn, K. S., & Paus, R. (2001). Controls of hair follicle cycling. Physiological reviews, 81(1), 449-494.