Noncollagenous bone matrix proteins, calcification, and thrombosis in carotid artery atherosclerosis

Advanced atherosclerosis is often associated with dystrophic calcification, which may contribute to plaque rupture and thrombosis. In this work, the l ocalization and association of the noncollagenous bone matrix proteins oste onectin, osteopontin, and osteocalcin with calcification, lipoproteins, thr ombus/hemorrhage (T/H), and matrix metalloproteinases (MMPs) in human carot id arteries from endarterectomy samples have been determined. According to the recent American Heart Association classification, 6 of the advanced les ions studied were type V (fibroatheroma) and 16 type VI (complicated). Oste onectin, osteocalcin, and osteopontin were identified by monoclonal antibod ies IIIA(3)A(8), G12, and MPIIIB10(1), and antiserum LF-123. Apolipoprotein (apo) AI, B, and E; lipoprotein(a); fibrinogen; fibrin; fragment D/D-dimer ; MMP-2 (gelatinase A); and MMP-3 (stromelysin-1) were identified with prev iously characterized antibodies. Calcium phosphate deposits (von Kossa's st ain) were present in 82% of samples (3 type; V and 15 type VT). Osteonectin was localized in endothelial cells, SMCs, and macrophages and was associat ed with calcium deposits in 33% of type V and &8% of type VI lesions. Osteo pontin was distributed similarly to osteonectin and was associated with cal cium deposits in 50% of type V and 94% of type VI lesions. Osteocalcin was localized in large; calcified areas only tin 17% of type V and 38% of type VI lesions. ApoB colocalized with cholesterol crystals and calcium deposits . Lipoprotein(a) was localized in the intima, subintima, and plaque shoulde r. Fibrin (T/H) colocalized with bone matrix proteins in 33% of type V and 69% of type VT lesions. MMP-3 was cytoplasmic in most cells and colocalized with calcium and fibrin deposits. MMP-2 was less often associated with cal cification. The results of this study show that osteonectin, osteopontin, a nd osteocalcin colocalized with calcium deposits with apoB, fibrin, and MMP -3 in advanced, symptomatic carotid lesions. These data suggest that the oc currence of T/H might contribute to dystrophic arterial calcification in th e progression and complications of atherosclerosis.