TGFB1 and chronic obstructive pulmonary disease: Among its downstream pathways, TGF-β1/Smad2.3 signaling pathways facilitate epithelial mesenchymal transition (EMT) and endothelial mesenchymal transition (EndMT), key participants in airway-vessel remodeling in COPD (Soltani et al., 2012; Mahmood et al., 2017; Sohal, 2017).