Valve Endothelial Cells - Not Just Any Old Endothelial Cells.

Heart valves are sophisticated cellularised structures that perform a complex series of dynamic functions during each cardiac cycle. The endothelial cells (ECs) that cover both surfaces of the valve, play an important role in ensuring that the valve functions are in an optimal manner. They are also postulated to protect the valve against calcific disease. These functions include a role in embryonic development, regulation of cellular attachment, modulation of the mechanical properties of the valve, prevention of valve interstitial cell differentiation into pathological cell phenotypes and regulation of the valve extracellular matrix. It is believed that valve endothelial cells (VECs) are a specialised population of ECs which have a distinctive range of properties not seen elsewhere in the vasculature. This allows them to function in a unique haemodynamic environment. Each surface of the valve is exposed to vastly different patterns of blood flow and levels of shear stress, resulting in further specialisation of the VECs on the aortic and ventricular surfaces of the valve. This review will examine the role of VECs on either surface of the valve and demonstrate how they contribute to the function and durability of heart valves.