Exosome-derived microRNA-22 ameliorates pulmonary fibrosis by regulating fibroblast-to-myofibroblast differentiation in vitro and in vivo

Abstract

Background: Although aberrant proliferation and activation of lung fibroblasts are implicated in the in-itiation and progression of idiopathic pulmonary fibrosis (IPF), the underlying mechanisms are not well characterized. Numerous microRNAs (miRNAs) have been implicated in this process; however, miRNAs derived from exosomes and the relevance of such miRNAs to fibroblast-to-myofibroblast differentiation are not well understood. In this study, we attempted to identify exosome-derived miRNAs relevant to fibrosis development. Methods: Using miRNA array analysis, we profiled exosome-derived miRNA expression in sera of C57BL/6 mice exhibiting bleomycin-induced pulmonary fibrosis. After validating a selected miRNA by quantitative reverse-transcription polymerase chain reaction, its effect on fibroblast-to-myofibroblast differentiation was investigated in human lung fibroblasts. Furthermore, we determined the role of the selected miRNA in an in vivo model of pulmonary fibrosis. Results: MiRNA array analysis revealed that miR-22 expression was increased by up to 2 fold on day 7 after bleomycin treatment compared with that in vehicle-treated mice. In vitro, miR-22 transfection sup-pressed TGF-β1-induced α-SMA expression. This was mediated via inhibition of the ERK1/2 pathway. Baseline α-SMA expression was increased upon miR-22 inhibitor transfection. Furthermore, miR-22 negatively regulated connective tissue growth factor expression in the presence of TGF-β1. In vivo, administration of a miR-22 mimic on day 10 after bleomycin challenge ameliorated pulmonary fibrosis lesions accompanied by decreased α-SMA expression in the model mice. Conclusions: Exosomal miR-22 modulates fibroblast-to-myofibroblast differentiation. The present findings warrant further study, which could shed light on miR-22 as a novel therapeutic target in IPF. (J Nippon Med Sch 2020; 87: 118―128).