In Vitro Methods to Investigate Embryonic Cardiac Development Modulated by Fluid Flow
Watson, Matthew.
2021
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Thesis
(Ph.D.)--Tufts University, 2021.
Submitted to the Dept. of Mechanical Engineering.
Advisors: Erica Kemmerling, and Lauren Black III.
Committee: Glenn Gaudette, and Jeffrey Guasto.
Keywords: Biomechanics, Fluid mechanics, and Biomedical engineering.
Congenital heart defects (CHDs) are the leading cause of morbidity and death in children with ... read morebirth defects and are caused by both genetic and epigenetic factors during embryonic development. Cardiac cells sense and respond to stresses induced by the onset of blood flow during embryonic development, and a better understanding of hemodynamics and the cellular response to flow during embryonic cardiac development may offer opportunities to improve therapies and treatments for patients living with CHDs. In vitro models provide non-invasive ways to investigate cellular responses to various biophysical cues, and these models must accurately mimic behaviors present in vivo. We present various improvements to in vitro models that better mimic biomechanical conditions present during embryonic cardiac development. Tools that characterize and quantify cellular behavior are necessary to understand cellular responses to different environmental cues. To this end, we first developed a MATLAB package to quantify subcellular protein localization in two-dimensional images of fluorescently labeled cells. Next, to study the effects of blood flow-induced shear stresses on endothelial cells (luminal cardiac cells), we developed a custom bioreactor system capable of culturing cells under biomimetic steady or pulsatile shear stress conditions. In another set of experiments, we examined cardiomyocyte (heart muscle cell) phenotype when cultured with endothelial cells exposed to shear stresses or cultured with a protein released by cells under shear stress to elucidate potential developmental behaviors. Next, we characterized stresses induced by blood flow during embryonic heart formation. Computational fluid dynamics (CFD) evaluated pulsatile non-Newtonian blood flow through stages of embryonic heart formation and revealed discrepancies in wall shear stresses and pressures between Newtonian models. Finally, blood flow-induced stresses are not the only epigenetic factors that affect cardiac function and formation during embryonic development. We present work demonstrating that both mechanical stretch and developmental age of cardiac extracellular matrix promote cardiac function by improving contraction force dynamics in engineered cardiac tissues. Combined, our work presents data and platforms which elucidate flow mechanics and developmental mechanics throughout physiological and pathological cardiac development.read less - ID:
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