Fig. 4.

Bleomycin (BLM) induces lung epithelial cell senescence in aged mice, and this senescent phenotype is attenuated in the fibrotic lungs of aged miR-34a−/− mice. A and B: aged WT mice (20 mo old) were intratracheally instilled with BLM. Three weeks after treatment, mice were killed, and lung epithelial cells isolated. mRNA and protein levels of p21 and PAI-1 were determined by real-time PCR (A) and Western blotting (B). A: values are means ± SE; n = 3. *P < 0.05 and **P < 0.01 compared with saline group. C: aged WT and miR-34a−/− mice were intratracheally instilled with BLM. Three weeks after treatment, mice were killed, and lung epithelial cells isolated. Levels of p21 and PAI-1 were determined by Western blotting and densitometric analyses performed using ImageJ (National Institutes of Health). *P < 0.05 compared with BLM WT group.