Urokinase plasminogen activator (uPA) is a positive regulator of outer root sheath keratinocyte proliferation

The study investigated the role of urokinase plasminogen activator (uPA) in the proliferation of outer root sheath keratinocytes (ORS KC) in mouse vibrissa follicles. It was found that uPA expression was detectable in ORS KC during the early anagen phase but not in later phases. Inhibitors of uPA, such as amiloride and uPA antibody, significantly reduced ORS KC proliferation. This suggested that uPA was a crucial mediator of the hair follicle cycle, as its activity was associated with the proliferation of hair follicle keratinocytes.