For example, it was found that the injection of miR-326 into mice with bleomycin-induced pulmonary fibrosis caused significant downregulation of TGF-β1, Smad3, matrix metalloproteinase-9 (MMP-9), and upregulation of Smad7, which in turn have good anti-fibrosis effects [39]. This evidence concerns the gene MMP9 and pulmonary fibrosis.