ACTA2 and pulmonary fibrosis: To elucidate the temporal sequence of lung fibrosis, we generated a BLM-induced lung fibrosis model using an Acta2-DsRed mouse line, which exhibits fibroblast-to-myofibroblast differentiation by expressing DsRed fluorescent protein, and examined the fibrosis phenotype on days 0 to 21 (Fig. 1a).