Circulating Exosomal miR-493-3p Affects Melanocyte Survival and Function by Regulating Epidermal Dopamine Concentration in Segmental Vitiligo.

Circulating exosomal microRNAs have been used as potential biomarkers for various disorders. However, to date, the microRNA expression profile of circulating exosomes in patients with segmental vitiligo (SV) has not been identified. Thus, we aimed to identify the expression profile of circulating exosomal microRNAs and investigate their role in the pathogenesis of SV. Our study identified the expression profile of circulating exosomal microRNAs in SV and selected miR-493-3p as a candidate biomarker whose expression is significantly increased in circulating exosomes and perilesions in patients with SV. Circulating exosomes were internalized by human primary keratinocytes and increased dopamine secretion in vitro. Furthermore, miR-493-3p overexpression in keratinocytes increased dopamine concentration in the culture supernatant, which led to a significant increase in ROS and melanocyte apoptosis as well as a decrease in melanocyte proliferation and melanin synthesis in the coculture system by targeting HNRNPU. We also confirmed that HNRNPU could bind to and regulate COMT, a major degradative enzyme of dopamine. Hence, circulating exosomal miR-493-3p is a biomarker for SV, and the miR-493-3p/HNRNPU/COMT/dopamine axis may contribute to melanocyte dysregulation in the pathogenesis of SV.