Wall Shear Stress Measurements in an Arterial Flow Bioreactor

Physiological flow parameters such as pressure and stress inside the vascular system strongly influence the physiology and function of vascular endothelial cells [1]. Variations in the shear stress experienced by endothelial cells affect morphology, alignment with the flow, mechanical strength, rate of proliferation, and gene expression [2]. Although it is known that these factors are dependent on the hemodynamics of the flow, the relationship has not been accurately quantified. In vitro bioreactor flow loops have been developed to simulate vascular flow for tissue conditioning and measurement of the endothelial cell response to varying shear [3–5]; however, wall shear stresses (WSS) have been estimated from the bulk flow rate by assuming Poiseuille flow [2, 6]. Due to the pulsatility of the flow, biochemical interactions, and the typically short vessel length, this assumption is fundamentally incorrect; however, the level of inaccuracy has not been quantified.