Osteopontin expression in cardiovascular diseases.

Adhesive interactions are recognized requirements for cellular proliferation, migration and differentiation during normal morphogenesis as well as disease. By differential cloning, osteopontin was identified as an adhesive protein upregulated during vascular remodeling and neointima formation in both rat models and human vascular diseases including atherosclerosis and restenosis. In functional studies, purified osteopontin promoted adhesion, focal contact formation, and migration of vascular smooth muscle and endothelial cells. Utilizing neutralizing antibodies, three integrin-type receptors, alpha v beta 3, alpha v beta 1, and alpha v beta 5 were found to support cellular adhesion to osteopontin. In contrast, only cells containing the alpha v beta 3 integrin could migrate towards an osteopontin gradient, demonstrating for the first time that different functions of osteopontin are mediated via distinct receptors. These results suggest a model whereby osteopontin, via its integrin-type receptors, contributes to vascular remodeling during development and disease by facilitating smooth muscle migration and simultaneously promoting endothelial coverage of the affected area.