Defining microRNA signatures of hair follicular stem and progenitor cells in healthy and androgenic alopecia patients

•Introducing a platform for understanding miRNA dynamic regulation in hair follicular cells in baldness.•This study represents that miR-324-3p is depleted in bald stem cells compared to normal hair stem and progenitor cells.•MiR-324-3p overexpression impact significantly keratinocytes differentiation program, promotes cell migration and reduces proliferation. The exact pathogenic mechanism causes hair miniaturization during androgenic alopecia (AGA) has not been delineated. Recent evidence has shown a role for non-coding regulatory RNAs, such as microRNAs (miRNAs), in skin and hair disease. There is no reported information about the role of miRNAs in hair epithelial cells of AGA. To investigate the roles of miRNAs affecting AGA in normal and patient’s epithelial hair cells. Normal follicular stem and progenitor cells, as well as follicular patient’s stem cells, were sorted from hair follicles, and a miRNA q-PCR profiling to compare the expression of 748 miRNA (miRs) in sorted cells were performed. Further, we examined the putative functional implication of the most differentially regulated miRNA (miR-324-3p) in differentiation, proliferation and migration of cultured keratinocytes by qRT-PCR, immunofluorescence, and scratch assay. To explore the mechanisms underlying the effects of miR-324-3p, we used specific chemical inhibitors targeting pathways influenced by miR-324-3p. We provide a comprehensive assessment of the "miRNome" of normal and AGA follicular stem and progenitor cells. Differentially regulated miRNA signatures highlight several miRNA candidates including miRNA-324-3p as mis regulated in patient’s stem cells. We find that miR-324-3p promotes differentiation and migration of cultured keratinocytes likely through the regulation of mitogen-activated protein kinase (MAPK) and transforming growth factor (TGF)-β signaling. Importantly, pharmacological inhibition of the TGF-β signaling pathway using Alk5i promotes hair shaft elongation in an organ-culture system. Together, we offer a platform for understanding miRNA dynamic regulation in follicular stem and progenitor cells in baldness and highlight miR-324-3p as a promising target for its treatment.