Histological and biochemical analysis of lung fibrosis in vivo . Histological analysis of injured lungs treated with different types of conditioned media. Marked fibrosis was seen in the control groups treated with (a) media only (b) or fibroblast conditioned medium (CCD1-cm), whereas a significant decrease of fibrosis was observed in (c) the induced pluripotent stem cell conditioned medium ( iPSC-cm)-treated group. Hematoxylin and eosin staining, scale bar =200 μm. (d) Semiquantitative histological analysis of lung fibrosis using the Ashcroft score showed significant reduction of fibrosis after treatment with iPSC-cm compared with media control or CCD-1-cm. Data indicated as mean ± standard error of the mean (SEM), **P <0.001. (e) In accordance with histological data, the collagen content was reduced after treatment with iPSC-cm compared with media control or CCD-1-cm. Data indicated as mean ± SEM, *P <0.01, **P <0.001.