Effect of vitamin K2 on β-glycerophosphate-induced calcification in rat vascular smooth muscle cells and the mechanism

Objective To explore the effect of vitamin K2 on β-glycerophosphate(β-GP)-induced rat vascular smooth muscle cells (VSMCs) calcification and and the mechanism. Methods VSMCs were obtained from rat aortic, and identified by immunocytochemistry, then randomly divided into control group, high phosphorus group, vitamin K2 group (the group was settled three subgroups according to the concentration of vitamin K2 based on the high phosphorus medium, namely 10 μmol/L, 25 μmol/L, 50 μmol/L) and noggin (bone morphogenetic protein pathway inhibitor) group. Calcification was visualized by Alizarin red staining, calcium load in cells was quantified by o-cresolphthalein complexone method and alkaline phosphatase (ALP) activity was measured after stimulating 14 days, gene expressions of bone morphogenetic protein - 2 (BMP-2), SMAD1, SMAD7 and Runx2 mRNA were detected by RT-PCR, Runx2 protein levels was detected by Western blotting after stimulating 3 days. Results Compared with the cells in control group, high phosphorus induced cell calcification, increased ALP activity, up-regulated the expression of BMP-2, SMAD1, Runx2 mRNA (P＜0.05) and down-regulated the expression of SMAD7 (P＜0.01)，while compared with high phosphorus group, the calcium deposition, ALP activity and the expression of BMP-2, SMAD1, Runx2 mRNA were remarkably reduced in a dose-dependent manner by treatment with vitamin K2 (P＜0.05) and the expression of SMAD7 was increased (P＜0.01). Compared with high phosphorus group, SMAD1 and Runx2 expression in noggin group were remarkably reduced(P＜0.01). Conclusion Vitamin K2 inhibits β-glycerophosphate-induced VSMCs calcification which correlates with the suppression of the expression of osteoblast markers through the down-regulation of bone morphogenetic protein pathway.