Downregulated miR-129-5p expression inhibits rat pulmonary fibrosis by upregulating STAT1 gene expression in macrophages

•We explored effect of miR-129-5p targeting STAT1 on rat pulmonary fibrosis.•miR-129-5p expression was increased in rats with pulmonary fibrosis.•Exosomes secreted by M2 macrophages affected pulmonary fibrosis.•M2 macrophage secreted exosomes can carry miR-129-5p into fibroblasts.•It provides a new idea for treating pulmonary fibrosis. This study investigated the mechanism by which microRNA-129-5p (miR-129-5p) in macrophages affects pulmonary fibrosis in rats by regulating the expression of the signal transducer and activator of transcription 1 (STAT1) gene. After the establishment of a pulmonary fibrosis rat model, quantitative real-time polymerase chain reaction (qRT-PCR) was employed to detect the expression of miR-129-5p in the sham group and model group. The binding sites between miR-129-5p and STAT1 were predicted online and verified by using a dual luciferase reporter system. qRT-PCR and Western blot analyses were used to test the effect of miR-129-5p on STAT1 gene expression. M2 macrophages were isolated and induced, and exosomes were extracted. Cell proliferation was detected by EdU. Furthermore, qRT-PCR was performed to detect the expression of STAT1, collagen type I A2 (COL1A2), collagen type III A1 (COL3A1), fibronectin, and α-SMA in cells and tissues followed by the detection of CD9, CD63, CD81, CD31 and STAT1 protein expression using a Western blot analysis. The pulmonary fibrosis area was detected by Masson staining followed by the immunohistochemical detection of α-smooth muscle actin (α-SMA) and type I collagen (COL-I) expression in pulmonary fibroblasts. Compared with the sham group, the expression level of miR-129-5p in the model group was significantly increased (P