EZH2-mediated Inhibition of MicroRNA-22 Promotes Differentiation of Hair Follicle Stem Cells by Elevating STK40 Expression

Hair follicle stem cells (HFSCs) contribute to the regeneration of hair follicles (HFs), thus accelerating hair growth. microRNAs (miRs) are potential regulators in various cellular processes, including HFSC proliferation and differentiation. This study proposed a potential target, enhancer of zeste homolog 2 (EZH2) for facilitating hair growth, due to its function over HFSC activities by mediating the miR-22/serine/threonine kinase 40 (STK40)/myocyte enhancer factor 2 (MEF2)/alkaline phosphatase (ALP) axis. Gain- and loss-of-function approaches were adopted to explore the roles of EZH2, miR-22, and STK40 in the proliferation and apoptosis of HFSCs, along with the functional relevance of MEF2-ALP activity. STK40 was elevated during HFSC differentiation, which was found to facilitate HFSC proliferation, but impede their apoptosis by activating MEF2-ALP. Mechanically, miR-22 targeted and inversely regulated STK40, which inhibited MEF2-ALP activity to impede HFSC proliferation and differentiation. Moreover, EZH2 elevated the STK40 expression by repressing miR-22 to promote the proliferation and differentiation of HFSCs. Furthermore, experiments further validated the roles of EZH2 and STK40 on hair follicle neogenesis and hair growth. Collectively, EZH2 elevated the STK40 expression by downregulating miR-22, consequently accelerating differentiation of HFSCs and hair growth, which sheds light on the underlying molecular mechanism responsible for hair growth.