Effect Of Bone Morphogenetic Protein 7 On Calcified Vascular Smooth Muscle Cell Induced By High Phosphate

Objective:To investigate the effect of bone morphogenetic protein 7 (BMP7) on calcified vascular smooth muscle cell (VSMC) induced by high phosphate.Methods:Rat aortic VSMC were cultured for 3,6 or 9days. Cells were divided into three groups:normal phosphate group (culture medium containing 1.4mmol/L phosphate), high phosphate group (culture medium containing 2.4mmol/L phosphate), treated with high phosphate and BMP7(200ng/ml) group. The first day of cells cultured in a specific medium was defined as day 0. Calcium deposition in cells was measured by BCA. Osteocalcin levels were detected by radioimmunity assay. The expression of Core Binding Factor a 1 (Cbf a 1) was detected by ELISA. The expression ofα-smooth muscle actin(α-SMA) were detected by immunohistochemistry.Results:No significant change was found for 9 days in normal phosphate group. The calcium deposition in D3,D6 and D9 was significantly more than that in DO in high phosphate group (P<0.01). The calcium deposition in D6 and D9 in treated with high phosphate and BMP7 group was significantly less than that in high phosphate group in each time (P<0.05). After culture for 72h, osteocalcin level of supernatant in high phosphate group was significantly more than that in normal phosphate group(P<0.01), while osteocalcin level of supernatant in treated with high phosphate and BMP7 group was significantly less than that in high phosphate group(P<0.05). In high phosphate group, VSMC lost the expression ofα-SMA partly. Along with time prolonged, the positive cell percentage fall-off. While in treated with high phosphate and BMP7 group, VSMC restored the expression ofα-SMA partly. The Cbfα1 activity in D6 and D9 was significantly stronger than that in DO in high phosphate group (P<0.05). The Cbf a 1 activity in D6 and D9 in treated with high phosphate and BMP7 group was significantly weaker than that in high phosphate group in each time(P <0.05).Conclusion:High phosphate may directly increase calcium deposition and osteocalcin level in rat VSMC. BMP7 may inhibit calcium deposition and osteocalcin level in rat VSMC. These changes is possibly related with Cbfα1 up-regulation or down-regulation in VSMC.