Cartilage oligomeric matrix protein (thrombospondin-5) is expressed by human vascular smooth muscle cells

Cartilage oligomeric matrix protein (COMP/thrombospondin [TSP]-5) belongs t o the thrombospondin gene family and is an extracellular glycoprotein found predominantly in cartilage and tendon. To date, there is limited evidence of COMP/TSP-5 expression outside of the skeletal system. The aim of the pre sent study was to investigate the expression of COMP/TSP-5 in cultured huma n vascular smooth muscle cells and human arteries. COMP/TSP5 mRNA and prote in expression was detected in cultured human vascular smooth muscle cells w ith both Northern blotting and immunoprecipitation. Serum, as well as trans forming growth factor (TGF)-beta1 and TGF-beta3, stimulated COMP/TSP-5 mRNA expression. COMP/TSP-5 was detected in normal as well as atherosclerotic a nd restenotic human arteries with immunohistochemistry. The majority of COM P/TSP5 was expressed in close proximity to vascular smooth muscle cells, in vitro attachment assays demonstrated strong adhesion of smooch muscle cell s to COMP/TSP-5-coated surfaces, with the majority of cells spreading and f orming stress fibers. Tn addition, COMP/TSP-5 supported the migration of sm ooth muscle cells in vitro. The present study shows that COMP/TSP-5 is pres ent in human arteries and may play a role in the adhesion and migration of vascular smooth muscle cells during vasculogenesis and in vascular disease settings such as atherosclerosis.