RESUMEN
Microvascular pericytes have been demonstrated as an origin for myofibroblasts that produce excessive extracellular matrix (ECM) proteins such as α-smooth muscle actin (α-SMA) and type I collagen (ColIA1) and contribute to pulmonary fibrosis (PF). However, the signaling mechanism responsible for ECM production within pericytes is poorly understood. In this study, we examined exosomal miR-107 in the fibrotic phenotypes of pericytes and the pathogenesis of PF. Using RT-qPCR, MiR-107 level was compared between clinical or bleomycin-induced PF and normal pulmonary tissues. Exosomes were isolated from cultured microvascular endothelial cells (ECs) derived from either normal or PF tissues, characterized using dynamic light scattering, transmission electron microscopy, flow cytometry, Western blot, and immunofluorescence, and then applied to pericytes. The effects of exosomes or different fibrosis-related signaling molecules were examined by Western blot, and the potential regulations between the signaling molecules were identified using bioinformatic analysis and assessed by electrophoretic mobility shift assay, chromatin immunoprecipitation, luciferase assay, and RNA binding protein immunoprecipitation. MiR-107 was downregulated in clinical or experimental PF tissues and also in exosomes from PF-derived ECs. EC-derived exosomal miR-107 essentially controlled the miR-107 level and inhibited α-SMA and ColIA1 expression in pericytes. The antifibrosis effect of miR-107 was mediated through the suppression of a pathway involving HIF-1α/Notch1/PDGFRß/YAP1/Twist1, where miR-107 directly targeted HIF-1α mRNA, whereas the latter directly activated the transcriptions of both Notch1 and PDGFRß. Functionally, targeting miR-107 promoted and targeting HIF-1α abolished the fibrotic phenotypes of pericytes. Exosomal miR-107 produced by pulmonary vascular ECs may alleviate pericyte-induced fibrosis by inhibiting a signaling pathway involving HIF-1α/Notch1/PDGFRß/YAP1/Twist1.NEW & NOTEWORTHY This work reveals a novel mechanism by which pulmonary vascular endothelial cells, via regulating the transdifferentiation of microvascular pericytes into myofibroblasts, contribute to the pathogenesis of pulmonary fibrosis. Since targeting the formation of myofibroblasts may prevent the development and benefit the treatment of pulmonary fibrosis, this study provides not only mechanistic understanding but also promising therapeutic targets for pulmonary fibrosis.