Figure 3.

Impaired capacity for dedifferentiation in senescent myofibroblasts is associated with apoptosis resistance. Nonsenescent and senescent lung fibroblasts were serum starved for 16 hours, treated with TGF-β (2 ng/ml) for 48 hours (Day 0), and then treated with 0% or 20% FBS for 5 days. Cells were treated with vehicle or staurosporine (300 nM), an apoptosis-inducing agent, for 8 hours. (A) Schematic diagram illustrating the treatment protocol and endpoints assessed. (B) Caspase 3 activity was assessed. (C–E) Expression of cPARP, cCaspase 3, α-SMA, and GAPDH was assessed by Western blotting (C and D) and by densitometric analyses (E). All values represent means ± SEM; n = 3 biological replicates from 2 independent experiments; **P < 0.01 and ***P < 0.001 as compared with nonsenescent, using Student’s two-tailed t-test. cPARP = cleaved poly-ADP-ribose polymerases.