Xu et al. (2019) discovered a significant increase in miR-145 expression in MRC-5 cells following stimulation. Subsequently, miR-145 suppressed the TGF-β1/Smad pathway, which promotes fibrosis, by targeting a key factor, Smad3. These findings suggest that the presence of one or more positive feedback loops in the fibrosis pathway, and miRNAs may serve as negative feedback regulators of the TGF-β1-induced fibrosis pathway. Modulating their expression could offer a novel therapeutic approach for preventing or partially reversing the progression of IPF (Table 2). This evidence concerns the gene SMAD3 and idiopathic pulmonary fibrosis.