Engineering a Microphysiological System to Model the Infarct Border Zone and Interrogate Oxygen-Dependent Cell-Cell Communication in the Myocardium

PROJECT SUMMARY/ABSTRACT Myocardial infarctions are caused by coronary artery occlusions that acutely deprive a localized region of myocardium of oxygenated blood, resulting in a steep oxygen gradient at the infarct border zone. Infarcted tissue then progresses through a pro-inflammatory phase of wound healing, followed by an anti-inflammatory, pro-fibrotic phase. However, for reasons that are poorly understood, the infarct border zone often undergoes adverse remodeling that does not resolve, leading to pathologies such as prolonged inflammation, fibrosis, arrhythmias, pathological hypertrophy, and heart failure. Cardiomyocytes, macrophages, and fibroblasts are each key components of the myocardium and are known to regulate each other. However, how an oxygen gradient (a defining feature of the infarct border zone) impacts crosstalk between these three cell types and downstream remodeling is poorly understood, largely due to limitations of existing model systems. During the first funding period of this R01, we engineered innovative “Myocardial Infarct on a Chip” devices that enabled us to co-culture hypoxic and normoxic cardiomyocytes and/or fibroblasts, which led to the new discovery that hypoxic-normoxic crosstalk had a detrimental effect on cardiomyocyte physiology and heightened pro- inflammatory signaling in both cell types compared to uniform normoxia and uniform hypoxia. Building on these results, our new goal is to test the hypothesis that oxygen-dependent crosstalk between cardiomyocytes, fibroblasts, and macrophages is a driving factor of pathological remodeling after myocardial infarction. To test this hypothesis, we will use devices that we developed during the first funding period to map intercellular circuits between cardiomyocytes, fibroblasts, and macrophages in non-uniform oxygen environments and quantify the molecular and functional phenotypes of each cell type. In Aim 1, we will determine the impact of hypoxic-normoxic crosstalk between cardiac fibroblasts and macrophages on functional and transcriptional phenotypes, including proliferation, phagocytosis, and migration. In Aim 2, we will determine the impact of cardiomyocyte-fibroblast-macrophage hypoxic-normoxic crosstalk on cardiac tissue functional and transcriptional phenotypes. We will measure cardiomyocyte tissue physiology (electrophysiology and contractility) and use single-cell proteomic technologies to deconvolve cell type-specific secretions and changes to the proteome. In Aim 3, we will determine the independent and combined impact of an oxygen gradient and direct contact with fibroblasts and/or macrophages on cardiomyocyte tissue phenotypes. We will establish technologies to perform spatial RNA sequencing in engineered cardiac tissues comprising cardiomyocytes, fibroblasts, and macrophages on our oxygen gradient device, which will also enable us to benchmark our transcriptomic data to published datasets of infarcted myocardium. Our project combines cutting-edge technologies in tissue engineering and molecular analyses and will lead to new discoveries that will inform novel therapeutic strategies to mitigate pathological remodeling after myocardial infarction.