Resident and newly formed αSMA+ cells in bleomycin-induced fibrosis were genetically labeled using the Acta2-CreERT2; tdTomatoflox mouse line (Acta2-tdT) as previously described (10), and cellular changes were investigated in the lung 2 wk after bleomycin application (Supplemental Fig. S1; https://doi.org/10.5281/zenodo.3532795). The gene discussed is ACTA2; the disease is fibrosis.