(a) PiT-2 mRNA level. (b) PiT-1 mRNA level. (c) OPG mRNA level. (d) OPG protein expression levels in the conditioned media of wild-type-derived VSMCs treated with either scrambled siRNA or PiT-2 siRNA and cultured under normal (1.0 mM) P medium for three days. (e) Quantification of calcium deposit in the matrix in WT-derived VSMCs treated with either scrambled siRNA or PiT-2 siRNA under OPG supplementation (0, 1, 10, or 100 ng/mL). Data are expressed as mean ± SEM (n=3) and compared by un-paired t-test or one-way ANOVA followed by Tukey–Kramer test. A two-tailed P<0.05 was considered statistically significant. *P<0.05 versus scrambled siRNA- VSMCs treated with 1% P medium aP<0.05 versus scrambled siRNA- VSMCs treated with 1 mM P medium without OPG supplementation. bP<0.05 versus scrambled siRNA- VSMCs treated with 2.8 mM P medium without OPG supplementation. cP<0.05 versus PiT-2 siRNA-VSMCs treated with 1 mM P medium without OPG supplementation. dP<0.05 versus PiT-2 siRNA-VSMCs treated with 2.8 mM P medium without OPG supplementation. AU, arbitrary unit; OPG, osteoprotegerin; P, phosphate; siRNA, small interfering RNA; VSMCs, vascular smooth muscle cells; WT, wild-type.