Flow Patterns in a Flow-Stretch-Flexure Bioreactor System: Implications for the Conditioning of Engineered Heart Valve Tissue

In heart valve tissue engineering, there is general agreement that appropriate mechanical conditioning may provide the necessary stimuli to promote proper tissue formation [1–3]. For example, in combined flow-flexure-stretch (FSF) studies conducted in our laboratory [4], we demonstrated that flow or flexure bio-mechanical conditioning alone only produced marginally enhanced mass and quality of the engineered tissue. However, combined fluid and flexural stresses resulted in substantially larger de-novo synthesized tissue mass accumulations rates. Interestingly, surface fluid induced stresses acting on the forming tissue/scaffold were the sole difference in the mechanical environment under combined stimulation regimes. However, combined flow and flexural modes of biomechanical conditioning produce highly complex local flow patterns. Understanding these patterns can help identify specific fluid-induced shear characteristics that can potentially be responsible for improving tissue formation in tissue engineered heart valves (TEHVs). In the present study, we developed a computational fluid dynamic (CFD) model to simulate the motion of rectangular scaffold strips housed in the bioreactor. In order to maximize the benefits of flow-based conditioning at physiological scales that emulates the native valve environment, we also present our efforts in designing a new FSF bioreactor system.