Among them, the use of a fibrotic cocktail induces structural and cellular changes in hPCLS recapitulating early stages of lung fibrosis characterized by upregulation of alpha smooth muscle actin (ACTA2, aSMA) a marker for activated myofibroblasts, as well as extracellular matrix proteins like Fibronectin (FN1) and Collagen 1A1 (COL1A1) after 5 days of treatment [2]. Here, COL1A1 is linked to pulmonary fibrosis.