CD44 - a new cardiovascular drug target or merely an innocent bystander?

CD44, short for cluster of differentiation 44, is an adhesion molecule of the hyaluronate receptor family. Expressed on the surface of most vertebrate cells, it functions as a receptor for several extracellular matrix components, e.g., hyaluronan, collagen, laminin, fibronectin, and osteopontin. CD44 has in recent years been intensively studied in connection with different forms of cancer, where CD44 may regulate invasiveness and tumor progression. Although major functions involve adhesion and migration, CD44 also affects leukocyte homing and recruitment, phagocytosis, matrix remodeling, proliferation, and apoptosis. As such, CD44 is an interesting putative molecule in cardiovascular drug therapy. Accumulating evidence from human studies point to CD44 as involved in inflammatory diseases such as atherosclerosis and human abdominal aneurysms. To date, several animal studies have shown that the role of CD44 in atherogenesis may vary depending on experimental model. In this Review, we trace CD44 and its potential role in the context of cardiovascular diseases by highlighting both human and animal studies that may help us understand; is CD44 a new cardiovascular drug target or merely an innocent bystander?