In this study, the results showed that miR-21promotes lung fibrosis, as well as TGFβ1-induced ECM over-synthesis, after binding of TGFβ1 to TGFβ1R1, which activates the SMAD2/3 complex and the nuclear entry of SMAD4, facts that regulate both miR-21 expression and ECM protein expression [126]. Here, TGFB1 is linked to pulmonary fibrosis.