Effects of Human Hair Outer Root Sheath Cell- and Human Bone Marrow Mesenchymal Stem Cell-Derived Exosomes on Human Hair Follicle Stem Cells.

INTRODUCTION: The cyclical growth of hair follicles depends on the periodic proliferation and differentiation of hair follicle stem cells (HFSCs). Previous studies have shown that extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) and human hair outer root sheath cells (HHORSCs) can enhance hair follicle development, ameliorate androgenetic alopecia, and support the inductive capacity of dermal papilla cells. However, the regulatory effects of HHORSC-derived EVs (HHORSC-EVs) and human bone marrow mesenchymal stem cell-derived EVs (HBMMSCEVs) on HFSCs remain unclear. METHODS: HFSCs were treated with HHORSC-EVs or HBMMSC-EVs for 10 days. The effects of EVs on HFSC proliferation, apoptosis, and differentiation were evaluated using a Cell Counting Kit8 assay, flow cytometry, and immunofluorescence staining, respectively. RESULTS: EVs from both HHORSCs and HBMMSCs did not enhance hair follicle growth by improving the proliferation of HFSCs, but rather by inhibiting apoptosis. In addition, HBMMSC-EVs further promoted HFSC stemness maintenance by upregulating K15 and CD34 expression. DISCUSSION: HFSCs may serve as a novel target for both HHORSC-EVs and HBMMSC-EVs, highlighting their therapeutic potential for hair loss disorders. CONCLUSION: This study offers new insights into developing EV-based therapies for hair loss disorders.