Developing a Structurally-Motivated Model of Coronary Microcirculation Mechanics and Hemodynamics

Project Summary The myocardium relies on a continuous supply of oxygen from a complex system of blood vessels that make up the coronary circulation. Despite its importance, the coronary circulation and how its flow is regulated are not fully understood. To facilitate insights into the functioning of this complex physiological system, various

computational models have been developed to study a variety of characteristics of coronary flow, providing a unique framework to integrate physiological and mechanical processes across different scales. The study of coronary flow requires detailed knowledge of its network structure, from the large epicardial vessels, down to

the capillaries, and across the myocardium (from the epicardium to the endocardium). Most studies thus far have relied on direct morphometric characterization of the larger coronary arteries (e.g., Kassab’s studies on swine heart’s from nearly two decades ago), and on physics-based assumptions to generate volume-filling

microvascular networks. However, the structural design of the coronary microvasculature is non-trivial with numerous elements influencing its form. Imaging the three-dimensional (3D) organization of the coronary microvasculature with modern imaging techniques can facilitate insights into its function, structure, and

pathophysiology. In this proposal, I aim to conduct high-resolution imaging of a swine heart to perform quantitative analysis of its coronary vascular morphometry across spatial scales. In Aim 1, I will define a tissue clearing and vascular imaging protocol. To achieve this, I will optimize optical tissue clearing techniques to

render myocardial tissue homogeneously transparent using tailored treatments with hydrophilic chemical cocktails (i.e. CUBIC reagents) for tissue delipidation, decoloring, and refractive index matching in combination with fluorescent labeling of endothelial cells with tomato lectin and casting of the vasculature with dextrin-

rhodamine. Optimization of our approach will be accomplished in mice hearts, facilitating iterations, guiding its application to larger swine hearts. Sub-micron vascular details will be captured over large tissue volumes using episcopic techniques with a laser scanning confocal microscopy. In Aim 2, I will characterize the network

structure of the coronary microvasculature and identify adaptations in the setting of obesity. In order to study the network structure, I will develop methods to segment the vasculature by creating toolkits that correct for image artifacts, filter to enhance vessel-like structures, binarize and segment vessels, perform skeletonization

to preserve network topology, and merge vessel graphs. Custom analyses will be performed on merged vessel graphs to quantify its morphology and topology. Using a clinically relevant metabolic syndrome model in Ossabaw swine, I will then compare the microvasculature among lean and obese swine for quantitative

differences in morphology and topology. Successful completion of the proposed aims will provide critical insight into the role of structural adaptations of the coronary microcirculation in disease states such as obesity and will propel further coronary flow modeling by providing detailed anatomic data of the coronary microvasculature.