Myofibroblast accumulation in vivo is reduced after treatment with induced pluripotent stem cell conditioned medium, in part by a hepatocyte growth factor-dependent mechanism. Immunohistochemistry was performed to detect myofibroblasts using alpha smooth muscle actin (αSMA) antibody. In (c) media control and (b) fibroblast (CCD1) conditioned medium-treated animals, strong αSMA staining was detected; whereas in (a) induced pluripotent stem cell conditioned medium (iPSC-cm)-treated animals, the number of αSMA-positive signals was reduced. (d) When iPSC-cm was pretreated with neutralizing anti-hepatocyte growth factor (HGF) antibody before intratracheal instillation to bleomycin-injured lungs, αSMA positivity increased compared with treatment with iPSC-cm alone. (e) Treatment with HGF neutralizing anti-HGF alone did not show any effect compared with control animals. Scale bar =500 μm.