From a Stem-Cell-Centered to a Niche-Centered View: The Core Role of Collagen Networks in Hair Loss and Hair Follicle Miniaturization

This paper challenges the traditional "stem cell–centric" view of hair follicle miniaturization in alopecia, suggesting instead a "niche-centered" perspective that emphasizes the role of collagen networks. While hair follicle stem cells (HFSCs) may remain present, their conversion into progenitor cells is impaired, contributing to miniaturization. The authors propose "niche identity," focusing on structural and mechanical constraints within the follicular niche, defined by five state variables: basement membrane integrity, adhesion apparatuses, fibrillar organization, mechanical set-points, and dynamic remodeling windows. These elements may be affected by androgen-biased remodeling, inflammation, and aging, leading to a low-output state. The paper also introduces the concept of "signal–structure mismatch" as a reason for unstable therapeutic outcomes and suggests a niche identity–oriented framework for future research.