SMAD2 and idiopathic pulmonary fibrosis: TGF-β1-stimulated phosphorylated Smad2/3 translocates into the nucleus, regulates target gene expressions, and further participates in EMT, fibroblast proliferation, and myofibroblast differentiation, which promotes the pathogenesis of IPF (Lee et al., 2014; Shen et al., 2021).