Matrix Gla protein accumulates at the border of regions of calcification and normal tissue in the media of the arterial vessel wall

Vitamin K-dependent matrix Gla protein (MGP) has been suggested to play a r ole in the inhibition of soft-tissue calcification. Here we report the expr ession of recombinant prokaryotic MGP as part of a fusion protein and the p reparation of two antibodies that specifically recognize MGP. Monoclonal an tibodies were raised against synthetic peptides homologous to the sequences 3-15 and 63-75 of human MGP. Both antibodies recognize recombinant and syn thetic human MGP. Immunohistochemical analysis showed that MGP was associat ed with the extracellular matrix of noncalcified bone and with chondrocytes in cartilage. In the healthy human arterial vessel wall, MGP antigen was d emonstrated in association with smooth muscle cells and elastic laminae of the tunica media and with the extracellular matrix of the adventitia. Coloc alization with the elastic laminae was lost at sites of medial calcificatio n; in both human and rat arteries, high amounts of MGP were found in the ex tracellular matrix at borders of intimal and medial calcification. Our data demonstrate the close association between MGP and calcification. It is sug gested that undercarboxylated MGP is biologically inactive and that poor va scular vitamin K status may form a risk factor for vascular calcification. (C) 2001 Elsevier science.