Role of Macrophages in Collagen Resorption During Hair Growth Cycle

The study from 1969 investigated the role of macrophages in collagen resorption during the hair growth cycle, specifically during the catagen phase. During this phase, macrophages formed a tightly packed layer around the hair follicle and actively degraded the collagen fibers surrounding it. The macrophages' cytoplasm contained collagen in various stages of degradation. In mice, where hair growth is synchronous, a significant amount of collagen was degraded during the brief 2-3 day catagen phase of each hair cycle.