Myofibroblasts expressed type 1 collagen in bleomycin-injured lungs. Saline-treated lungs were fixed in formalin and examined by H & E stain (A) and using anti-α-SMA antibody (B) and anti-Col1A1 antibody (C). 12 days after bleomycin had been administered, bleomycin-injured lungs fixed in formalin were examined by H & E stain (D) and using anti-α-SMA antibody (E) and anti-Col1A1 antibody (F). Snap-frozen bleomycin-injured lungs at day 12 were fixed in cold acetone and examined by immunofluorescence using anti-α-SMA antibody (G) and anti-Col1A1 antibody (H), and these latter two images were merged with nuclear stain using DAPI (I). Asterisk and arrow indicate pulmonary and bronchial epithelium, respectively. In (G), (H), and (I), arrows indicate cells that were α-SMA- and Col1A1 double-positive. The asterisk indicates Col1A1 in the interstitial space. Figures show representative results. Scale bars in (A to F) indicate 200 μm. Scale bars in (G to I) indicate 100 μm. α-SMA, α-smooth muscle actin; Col1A1, collagen 1A1, DAPI, 4´,6-diamidino-2-phenylindole.