Matrix Gla protein (MGP) is a vitamin K-dependent protein, which is synthesized
in bone and many other mesenchymal cells, which is also highly expressed by vascular
smooth muscle cells (VSMCs) and chondrocytes. Numerous studies have confirmed that
MGP acts as a calcification-inhibitor although the mechanism of action is still not fully understood.
The modulation of tissue calcification by MGP is potentially regulated in several ways
including direct inhibition of calcium-phosphate precipitation, the formation of matrix vesicles
(MVs), the formation of apoptotic bodies (ABs), and trans-differentiation of VSMCs.
MGP occurs as four species, i.e. fully carboxylated (cMGP), under-carboxylated, i.e. poorly
carboxylated (ucMGP), phosphorylated (pMGP), and non-phosphorylated (desphospho,
dpMGP). ELISA methods are currently available that can detect the different species of MGP.
The expression of the MGP gene can be regulated via various mechanisms that have the potential
to become genomic biomarkers for the prediction of vascular calcification (VC) progression.
VC is an established risk factor for cardiovascular disease and is particularly prevalent
in those with chronic kidney disease (CKD). The specific action of MGP is not yet clearly
understood but could be involved with the functional inhibition of BMP-2 and BMP-4, by
blocking calcium crystal deposition and shielding the nidus from calcification.