Cellular Mechanisms of Aortic Valve Calcification

Acquired aortic valve disease and valvular calcification is highly prevalent in adult populations worldwide and is associated with significant cardiovascular morbidity and mortality. At present, there are no medical therapies that will prevent or regress aortic valve calcification or stenosis and surgical or transcatheter aortic valve replacement remain the only effective therapies for treating this disease. In the setting of valve injury as a result of exposure to biochemical mediators or hemodynamic forces, normal homeostatic processes are disrupted resulting in extracellular matrix degradation, aberrant matrix deposition and fibrosis, inflammatory cell infiltration, lipid accumulation, and neoangiogenesis of the valve tissue and, ultimately, calcification of the valve. Calcification of the aortic valve is now understood to be an active process that involves the coordinated actions of resident valve endothelial and interstitial cells, circulating inflammatory and immune cells, and bone marrow-derived cells. These cells may undergo a phenotype transition to become osteoblast-like cells and elaborate bone matrix, endothelial-to-mesenchymal transition, and form matrix vesicles that serve as a nidus for microcalcifications. Each of these mechanisms has been shown to contribute to aortic valve calcification suggesting that strategies that target these cellular events may lead to novel therapeutic interventions to halt the progression or reverse aortic valve calcification.