Catagen in the Hairless House Mouse

The study examined the catagen phase of the first hair cycle in hairless (hr) mice, focusing on morphological and histochemical aspects. It found that the mutant epithelial column shortened more slowly than normal, resulting in a longer total follicle length at catagen VII, although the hair shaft's position was normal. The keratinization sequence of the mutant club appeared normal, but there was a failure to form an anchoring brush due to variations in cell shapes and fibrils. The inner root sheath extended further than normal, enclosing the club. Additionally, the glassy membrane and connective tissue sheath were abnormally narrow, primarily due to reduced collagen and a narrower band of PAS-positive material.