Knockdown of HIF-1α mRNA and protein expression by RNA interference in HUASMCs. Growth-arrested HUASMCs were transfected with wild type HIF-1α, HIF-1α-siRNA or scrambled siRNA expressing plasmids for 24 h and then exposed to normoxia or hypoxia (3% O2) for 24 h. (A) Inhibition HIF-1α mRNA expression in HUASMCs by siRNA. HIF-1α mRNA expression were assayed by Q-PCR (n = 3 in each group). *P < 0.05 vs control or scrambled siRNA transfection under hypoxia. # P < 0.05 vs control cells under normoxia or hypoxia conditions. (B)Suppression and over-expression of HIF-1α: western blot analysis. Representative Western blot (top) and values of HIF-1α production (mean ± SEM of 3 experiments, bottom). Results of HIF-1α protein production were obtained from densitometric analysis and expressed as ratio of HIF-1α/β-actin. *P < 0.05 vs control or scrambled siRNA transfection under hypoxia. # P < 0.05 vs control cells under normoxia or hypoxia conditions. HIF-1: wild type HIF-1α plasmid transfection; Scrambled-siRNA: scrambled-siRNA plasmid transfection; HIF-1α-siRNA: HIF-1α-siRNA plasmid transfection.