miR-207 mitigates silica-induced pulmonary fibrosis by suppressing fibroblast-to-Myofibroblast transition via multi-target modulation of the TGF-β1/SMADs signaling pathways in mice.

Abstract

TGF-β1/SMADs signaling pathway plays a vital role in development of silicosis, with SMADs serving as the core transducers. Accordingly, any fluctuation in SMAD abundance can decisively steer the disease trajectory. Our previous research revealed miR-207 suppresses the progression of silicosis fibrosis by targeting Smad3. Further bioinformatic analysis suggested that miR-207 could also bind to the sequences of genes of Smad2 and Smad7, raising the possibility that miR-207 functions as a coordinated rheostat of multiple SMADs. However, the specific regulatory mechanisms of miR-207 in silicosis remains unexplored. In this study, a mouse model of silicosis was established by administering a silica suspension (20 μg/μL, 80 μL) via nasal drip daily for 16 days. On day 17, the silica-dusted mice were transfected with either miR-207 mimics or inhibitors. Lungs samples were harvested on day 45 for histological assessment of injury. Then, the expression levels of miR-207, Smad2, and Smad7 were determined using RT-qPCR, and the levels of SMAD2 and 7, Collagen I and III, and indicators of fibroblast-to-myofibroblast transdifferentiation (FMT) (α-SMA, FAP-1, and Vimentin) were determined using Western blot. The results showed that miR-207 coordinately downregulated SMAD2 and upregulated SMAD7 at both the mRNA and protein levels in silica-exposed mice, with concomitant reductions in FMT indicators (α-SMA, FAP-1 and Vimentin) and collagen levels. Therefore, we concluded that miR-207 suppresses silicosis progression in mice by inhibiting FMT via modulation of the TGF-β1/SMADs signaling pathway by targeting SMADs.