Role of the Wnt/β-Catenin Signaling Pathway in Mediating Outer Root Sheath Stem Cells to Promote Hair Follicle Regeneration and Skin Wound Healing in Mice

Hair follicle (HF) stem cells are multipotent adult stem cells that play a key role in the hair follicle cycle. However, it remains poorly understood how the outer root sheath (ORS)-specifically, the stem cells in the bulge region of the hair follicle-promotes skin repair. This study aims to investigate the role of bulge stem cells in tissue growth and repair and to determine whether the ORS of transplanted hair follicles can facilitate skin repair. We further seek to elucidate the mechanisms by which bulge stem cells contribute to hair follicle development, regeneration, and skin wound healing. In this study, hair follicle samples were obtained from neonatal mice using microdissection. Hair follicle morphology was assessed by Sirius red staining, H&E staining, and transmission electron microscopy. Immunofluorescence staining was used to detect changes in CD34 and SOX9 protein expression. Additionally, microdissection-based hair follicle transplantation and Western blotting were employed to investigate protein activation and inhibition in the Wnt/β-catenin signaling pathway. The results show that the hair follicle bulge, inner root sheath, and dermal papilla all increase in size as hair follicles grow, with each structure growing relatively rapidly on day 7. Treatment with Teplinovivint effectively inhibits the expression of Wnt/β-catenin signaling pathway-related proteins and hair follicle stem cell markers. Damaged hair follicle tissues cultured in vitro are capable of self-repair. At the transplantation site, the skin gradually closes as the outer root sheath wound heals. In contrast, the central region of the outer root sheath becomes progressively filled with numerous dividing cells and extracellular matrix. The inner portion of the outer root sheath is densely populated with cells, and the markers CD34 and SOX9 are also widely distributed. This indicates that activation of the Wnt/β-catenin signaling pathway enhances the proliferation and differentiation of hair follicle stem cells, thereby promoting hair follicle growth, repair of damaged follicles, and healing of skin wounds. Furthermore, this study demonstrates the feasibility of using transplanted outer root sheath (ORS) to repair skin wounds-specifically, the potential to achieve large-scale hair regeneration from a limited number of hair follicle stem cells-providing a new approach for the clinical treatment of skin injury disorders. Nevertheless, achieving long-term, stable, and scalable clinical translation of ORS stem cells for hair follicle regeneration remains a major challenge.