Design of a Novel Multidirectional Fluid Shear Stress Bioreactor to Replicate Bicuspid Aortic Valve Aorta Hemodynamics In Vitro
Janet Liu, Kurtis Cornelius, Mathew Graham, Tremayne Leonard, Austin Tipton, Abram Yorde, Philippe Sucosky.
Wright State University, Dayton, OH, USA.
OBJECTIVE: The bicuspid aortic valve (BAV) is a major risk factor for aortic dilation and subjects the aortic wall to increased wall shear stress (WSS) level and multidirectionality, marked by the existence of a substantial transverse component. While studies have evidenced the adverse impact of WSS overloads on aortic medial degeneration, the effects of WSS multidirectionality remain largely unknown due to the challenge to replicate this characteristic in vitro. This study aimed at designing a bioreactor capable of replicating the time-varying magnitude and directionality of BAV aorta WSS in vitro.
METHODS: The device was based on a cone-and-plate bioreactor accommodating four circular aortic tissue samples fixed on rotating mounts. The cone rotation generates a fluid flow subjecting the samples to desired WSS magnitude, while the rotation of the mounts achieves desired sample alignment relative to the flow at each instant of time (Fig. 1A). The ability of the device to replicate native aortic WSS was verified computationally by comparing the WSS magnitude and direction predicted on the tissue surface to the native WSS of the aorta convexity. The determination of appropriate operating conditions was performed using an iterative optimization procedure.
RESULTS: With the tissue mount rotation replicating the target instantaneous change in WSS directionality, the initial cone angular velocity determined from fluid mechanics theory generated a 32% error in WSS magnitude and a correlation coefficient R2=0.59 relative to the target waveform. The optimization procedure reduced this error to 10.4%, yielding a correlation coefficient R2=0.84 (Fig. 1B and C).
CONCLUSIONS: The new device provides the ability to subject aortic tissue to in vivo-like WSS magnitude and multidirectionality. Implementation of this tool will provide new insights into the potential impact of the native BAV WSS abnormalities on aortopathy.
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