SMAD3 and pulmonary fibrosis: H19 is upregulated via diminishing miR‐140 expression in fibrotic tissues from IPF patients and bleomycin‐induced pulmonary fibrosis in mice and TGFβ1‐induced HBE and A549 cells, in which the TGFβ/Smad3 signal pathway is involved in myofibroblast generation and extracellular matrix deposition.