Pathophysiological mechanisms of hair follicle regeneration and potential therapeutic strategies.

Abstract

Androgenetic alopecia (AGA) is a chronic and progressive hair loss disorder marked by follicular miniaturization and a shortened anagen phase. While androgenic and genetic factors contribute to its pathogenesis, increasing evidence highlights the importance of dysregulated molecular signaling in impaired hair follicle (HF) regeneration.This review explores the interconnected signaling pathways that govern HF cycling and regeneration-Wnt/β-catenin, Sonic Hedgehog (Shh), Bone Morphogenetic Protein (BMP), and Notch. Wnt/β-catenin activation initiates anagen by stimulating stem cell proliferation and follicle formation, while Shh supports follicular proliferation and morphogenesis. Notch regulates HF stem cell (HFSC) fate, and BMP enforces quiescence and catagen onset. Crucially, crosstalk between Wnt-BMP and Shh-Notch pathways ensures follicular homeostasis, highlighting the need to view these pathways as an integrated regulatory network.Recent therapeutic innovations focus on modulating these signaling cascades. Small molecules such as valproic acid and CHIR99021 activate Wnt signaling; smoothened agonists target Shh; and Noggin mimetics or BMP-neutralizing antibodies inhibit BMP activity. These approaches have shown promising outcomes in preclinical models, including mouse studies, in vitro HFSC systems, etc. Additionally, emerging gene editing technologies (e.g., CRISPR-Cas9) and stem cell-biomaterial integration offer regenerative strategies that move beyond symptomatic treatments like minoxidil or hair transplantation.Given that AGA is associated with androgen-mediated Wnt suppression and TGF-β activation, targeting these dysregulated networks presents a promising route for long-term management. A deeper understanding of pathway interactions lays the groundwork for precise, durable, and disease-modifying therapies in the evolving landscape of alopecia treatment.