Figure 1.

A. Kaplan-Meier curve shows the survival condition of mice during the course of 21 days. 50% of the metformin treated mice still survived at day 21, but only 10% of the bleomycin treated mice survived for the same period. *P<0.05. B. Photomicrographs (original magnification 200×) of H&E staining (upper panel) and Masson’s trichrome staining (lower panel) of mouse lungs at day 21. The first column is normal control group which shows normal alveoli with intact lung tissue architecture and small amount of collagen fibers (stained blue) in the bronchiolar wall. The second column is bleomycin-treated group which shows alveolar damage with thickened alveolar septum, fibroblast proliferation and replacement by fibrosis tissue, like severe collagen deposition. The third column is metformin-treated group which shows marked reduction in alveolar damage, fibrosis and the content of collagen fiber.