Fig. 3

Myofibroblasts during lung fibrosis and fibrosis resolution. A Schematic illustration of the experimental setup for the induction of lung fibrosis. PDGFRβ-tdTomato reporter mice were injected with tamoxifen (tam) on 5 consecutive days to induce the expression of the fluorescent dye tdTomato under control of the PDGFRβ promotor (PDGFRβ-tom). 50 days later, mice were either sacrificed (= d0; B) or treated with bleomycin (bleo) and sacrificed after 21 (= d21; C) or 56 (= d56; D) days. Tissues show αSMA immunostaining (green) and PDGFRβ-tdTomato fluorescence (red). Arrows in (C) indicate myofibroblasts co-expressing αSMA and PDGFRβ-tdTomato. In (B and D), arrowheads indicate bronchial or vascular smooth muscle cells. DIC/pol illustrates tissue structure. DAPI was used to stain nuclei (blue). E–J Quantitative analyses of αSMA expression (20 × images), total myofibroblast proportion as well as proportions of intra-alveolar and interstitial myofibroblasts (63 × images, see Additional file 1: Fig. S5) for the respective time-points (n = 9 images from N = 3 animals; ns, not significant; *** = p < 0.001; one-way ANOVA followed by Tukey post-hoc test). Single channels are shown in b2–d2, b3–d3, b4–d4 and b5–d5