Exogen Involves Gradual Release of the Hair Club Fiber in the Vibrissa Follicle Model

The study investigated the exogen phase of the hair cycle, which is the shedding of the hair club fiber, using the vibrissa follicle model from rodents. The researchers discovered that the amount of outer root sheath (ORS) material on the club fiber after plucking was indicative of the time until natural release. They observed that 66% of club fibers from early anagen follicles had a significant amount of cellular material, suggesting immaturity for release, while 81% of club fibers from late anagen follicles had little to no cellular material, indicating readiness for release. This led to the suggestion of dividing exogen into 'early exogen' and 'late exogen' based on club fiber adhesion states. The study concluded that the vibrissa follicle model is effective for studying exogen and that club fiber release involves a gradual loosening from the epithelial sac.