TGFB1 and pulmonary fibrosis: We found that Acta2-reporter activity was comparable between BLM-treated and non-treated organoids of Tgfbr2-null AT2 cells (Fig. 7e), demonstrating that autocrine TGF-β signaling in AT2 cells plays a crucial role in fibroblast-to-myofibroblast differentiation in BLM-induced lung fibrosis.