Objectives:

The progression of vascular calcification, an active process promoted by osteo/chondrogenic transformation of vascular smooth muscle cells (VSMCs) is attenuated by activation of the calcium-sensing receptor (CASR). Recent in-vitro studies revealed that vascular calcification could be blunted by Mg 2+, but the underlying mechanisms remained elusive. The present study explored whether the effects of MgCl 2 on vascular calcification involve the CASR.

Methods:

Experiments were performed in primary human aortic smooth muscle cells (HAoSMCs) and in the mouse vascular calcification model of vitamin D 3 overload.

Results:

Phosphate-induced calcium deposition and mRNA expression of the osteogenic markers msh homeobox 2 (MSX2), CBFA1 (core-binding factor α 1), and ALPL (tissue-nonspecific alkaline phosphatase) in HAoSMCs were blunted by additional treatment with MgCl 2. MgCl 2 upregulated CASR mRNA expression in HAoSMCs in a dose-dependent manner. Furthermore, the inhibitory effects of MgCl 2 on phosphate-induced calcium deposition and osteogenic markers mRNA expression were mimicked by the CASR agonist GdCl 3 and reversed by additional treatment with the CASR antagonist NPS-2143 or by silencing of the CASR gene in HAoSMCs. MgCl 2 also blunted the osteogenic transformation of VSMCs induced by hydroxyapatite particles. High-dosed cholecalciferol treatment induced vascular calcification and upregulated aortic osteogenic markers Msx2, Cbfa1 and Alpl and collagen type I (Col1a1), collagen type III (Col3a1) and fibronectin (Fbn) mRNA expression in mice, effects reduced by additional treatment with MgCl 2. These effects were paralleled by increased aortic Casr mRNA expression in cholecalciferol-treated mice, which was further augmented by MgCl 2.

Conclusion:

The protective effects of MgCl 2 on osteo/chondrogenic transformation of VSMCs and vascular calcification involve regulation of CASR and CASR-dependent signaling.