Figure 5. Aging protects Zmpste24 deficient mice from bleomycin-induced pulmonary fibrosis. (A) Representative Masson Trichrome staining of lung sections from old saline control WT (panel a), and 21 days after bleomycin (panels b, c), and Zmpste24 deficient mice saline control (panel d) and at 21 d after bleomycin (panels e, f). Scale bar, 100 μm. (B) Fibrosis score for grading lung histopathological changes. Graphs represent means ± SD. *p< 0.05. (C) OH-Proline content in lungs after saline or 21 days of bleomycin injury. *p< 0.05; Old WT (n=3); Zmpste24 deficient mice (n=6).