TGFB1 and pulmonary fibrosis: In addition, TGF-β1 stimulates fibroblast chemotaxis toward fibronectin [7, 8] and augments fibroblast-mediated contraction of ECM by stimulating contractile stress fibers (α-smooth muscle actin [α-SMA]) [9], generating lung fibroblasts that can be used as in vitro model of lung fibrosis.