Dynamic Quantitative Imaging of Live Embryogenesis via Micro-CT

The vast majority of our understanding of multi-scale ventricular remodeling has been inferred via fixed specimens, precluding elucidation of how evolving compact and trabeculated myocardial architecture controls dynamic cardiac output and downstream morphogenesis and defect propagation. Quantitative live imaging technology is essential to unlock these secrets, but most embryonic imaging studies have focused on the earliest heart formation events using optical imaging techniques. Recent studies using optically advantageous zebrafish have highlighted mechanistic connections between forces and ventricular remodeling, but this model cannot answer clinically relevant questions involving septation, left and right sided ventricular myocardial remodeling, and its relationship to valve and outflow vessel morphogenesis and alignment. The avian embryo is a well-established experimentally and genetically accessible model system to answer these questions. Other technologies like high frequency ultrasound or magnetic resonance lack the spatial resolution, contrast, and/or 4D capacity for analyses of live embryonic ventricular architecture analysis. Micro-computed tomography (microCT) is an attractive modality to noninvasively image the avian embryo in 3D with the high spatial and temporal resolution needed to capture the dense and tortuous anatomical changes longitudinally throughout the full range of cardiac morphogenesis. We are establishing and validating the requisite but currently unavailable technology to enable dynamic volumetric imaging of intra-beat and longitudinal ventricular morphogenesis and function. These include: novel exogenous contrast media, prospective gating technology, and quantitative algorithms. We are developing size specific nanoparticles that exhibit unique CT contrast persistence and volumetric biodistribution characteristics during avian embryonic cardiogenesis. We have further developed novel strategies to quantitatively map molecular and cellular expression in 3D using CT contrast. We also develop and utilize novel gating and reconstruction algorithms to quantify the dynamic and multi-scale 5D (3D in space + 2D in time) ventricular, valve, and vascular wall architecture changes across the cardiac cycle and at different stages. We use these technologies to test how targeted alteration of cardiac formation and/or function via genetic or mechanical alterations controls downstream remodeling events in the same embryo over time, integrating hemodynamic, morphological, structural, and molecular datasets.