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.
Asunto(s)
Exosomas/metabolismo , MicroARNs/metabolismo , Pericitos/metabolismo , Fibrosis Pulmonar/metabolismo , Actinas/genética , Actinas/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Animales , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Células Cultivadas , Colágeno Tipo I/genética , Colágeno Tipo I/metabolismo , Endotelio Vascular/metabolismo , Endotelio Vascular/patología , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , MicroARNs/genética , Pericitos/patología , Fenotipo , Fibrosis Pulmonar/genética , Receptor Notch1/genética , Receptor Notch1/metabolismo , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/genética , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/metabolismo , Proteína 1 Relacionada con Twist/genética , Proteína 1 Relacionada con Twist/metabolismo , Proteínas Señalizadoras YAPRESUMEN
The pathogenesis of pulmonary fibrosis (PF) was mediated by the progressive deposition of excessive extracellular matrix, but little is known about the regulatory mechanisms of fibrogenesis by lung pericytes. The mouse PF model was established by treatment with bleomycin, followed by isolation of exosomes from mouse broncho-alveolar lavage fluids by the centrifuge method. Relative mRNA/microRNA levels and protein expression were assessed by qRT-PCR and Western blotting, respectively. The binding of let-7d with gene promoter was validated by dual-luciferase reporter assay. Protein interactions were verified via GST pull-down and co-immunoprecipitation. Nuclear retention of Smad3 was analysed by extraction of cytoplasmic and nuclear fraction of pericytes followed by Western blotting. Association of FoxM1 with gene promoter was detected by EMSA and ChIP-PCR methods. FoxM1 expression is significantly elevated in human lung fibroblasts of PF patients and mouse PF model. The expression of let-7d is repressed in exosomes derived from broncho-alveolar lavage fluids of PF mice. Let-7d or FoxM1 knockdown suppressed the expression of FoxM1, Smad3, ß-catenin, Col1A and α-SMA expression in mouse lung pericytes under TGF-ß1 treatment. FoxM1 overexpression elevated above gene expression in mouse lung pericytes under TGF-ß1 treatment. Let-7d directly targets TGFßRI to regulate FoxM1 and downstream gene expression in mouse lung pericytes. FoxM1 directly interacts with Smad3 proteins to promote Smad3 nuclear retention and binds with ß-catenin promoter sequence to promote fibrogenesis. Exosomes with low let-7d from pulmonary vascular endothelial cells drive lung pericyte fibrosis through activating the TGFßRI/FoxM1/Smad/ß-catenin signalling pathway.