Fig. 5.

Overexpression of Smad3 reverses the inhibitory effect of transforming growth factor-β (TGF-β) on smooth muscle cell (SMC) proliferation (tritiated thymidine incorporation assays). A: the effect of TGF-β dose on rat aortic SMC (RSMC) proliferation. *P < 0.05 compared with control (solvent). B: a representative result from 3 separate experiments is shown. RSMCs were infected with AdNull or AdSmad3 followed by stimulation with TGF-β₁ in either low serum or in the presence of PDGF-BB. The inhibitory effect of TGF-β on SMC proliferation is reversed in cells infected with AdSmad3, both in low serum and in the presence of a growth stimulant. *P < 0.05 comparing treatment with TGF-β to treatment with solvent, n = 3 wells treated for each condition for each group in each experiment. C: a representative result from 3 separate experiments showing the effect of Smad3 small-interfering (si)RNA on RSMC proliferation. *P < 0.05 compared with cells treated with scrambled siRNA and 0.5% FBS. cpm, Counts/minute.