From Telogen to Exogen: Mechanisms Underlying Formation and Subsequent Loss of the Hair Club Fiber

The document reviewed the hair follicle cycle, particularly focusing on the shedding phase known as exogen. It proposed that exogen is an active phase where the club fiber is released from the follicle, distinct from anagen, catagen, and telogen phases. The review discussed the formation, retention, and release of the club fiber, suggesting that exogen can be subdivided into early and late phases. It also considered the clinical relevance of exogen in hair loss conditions and the potential for therapeutic strategies to stabilize shedding. The document highlighted that exogen is an active process, potentially influenced by factors affecting epidermal differentiation, and that understanding the molecular mechanisms of exogen could lead to interventions for hair loss conditions. The need for further research to fully understand the signals and structures involved in club fiber release was emphasized. The work was supported by a Biotechnology and Biological Sciences Research Council CASE Studentship award, with no conflict of interest declared by the authors.