Catagen in the Hairless House Mouse

The study focused on the catagen phase of the first hair cycle in hairless (hr) mice, examining morphological and histochemical aspects. Key findings included that the mutant epithelial column shortened at a slower rate, resulting in a greater total follicle length at catagen VII, while the hair shaft's position remained 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.