Accentuated pulmonary fibrosis and increased TGFβ1 in PN-1^−/−mice. Lungs from PN-1^−/− mice and their PN-1^+/+ littermates were harvested at the indicated time points after bleomycin-induced lung injury (BLM) instillation for the following analyses. (A) Masson’s trichrome (i-iv, ix-xii) and Sirius red (v-viii, xiii-xvi) staining of lung sections from PN-1^+/+ and PN-1^−/− mice 3 and 9 days after saline (sham) or BLM treatment. Representative images are shown. Scale bars, 1 mm (main images) and 100 μm (enlargements). (B) Hydroxyproline contents in lung tissues from PN-1^−/− and PN-1^+/+ mice were measured 3, 6, and 9 days after bleomycin treatment vs saline treatment (sham). Data (mean ± SEM; n = 4-5 per group) were analyzed by 2-tailed Mann-Whitney U test. (C) Total TGFβ levels were measured by enzyme-linked immunosorbent assay in BALFs collected 9 days after saline (sham) or BLM treatment. Data (mean ± SEM; n = 10-13 per group) were analyzed by Kruskall-Wallis test with Dunn’s multiple comparison test. *P < .05, **P < .01 vs sham.