Interaction between Wall Shear Stress and Circumferential Strain Affects Endothelial Cell Biochemical Production

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Abstract
The wall shear stress (WSS) of flowing blood and the circumferential strain (CS) driven by the pressure pulse interact to impose a dynamic force pattern on endothelial cells (ECs) which can be characterized by the temporal phase angle between WSS and CS, a quantity which varies significantly throughout the circulation. To study the interaction of WSS and CS on endothelial production of vasodilators (prostacyclin and nitric oxide) and a vasoconstrictor (endothelin-1), bovine aortic ECs were cultured on the inner surface of compliant tubes and subjected to various flow conditions: steady shear (10 dyn/cm2), oscillatory shear (10 ± 10 dyn/cm2, rigid tube), and oscillatory shear (10 ± 10 dyn/cm2) with CS (8%) either in or out of phase with shear. The 4-hour production rates of vasoactive agents show that steady shear stimulates the highest production of vasodilators whereas oscillatory shear stimulates the highest vasoconstrictor production. The addition of CS in concert with oscillatory shear enhances the production of vasodilators and inhibits the production of vasoconstrictors, and this effect is modulated by the phase angle between WSS and CS. These data suggest that the interactions of WSS and CS are important in vascular regulation and remodeling.