Abstract 253: Modeling of Pathologic Hypertophy with Cardiac Microtissues

Abstract

Introduction: Pathological myocyte hypertrophy and fibroblast activation are key features of myocardial remodeling in hypertension and heart failure. Crosstalk between myocytes and fibroblasts contributes to the structural, mechanical, and electrical remodeling involved in various forms of heart failure. Replicating these responses in traditional 2D cell culture conditions has proven difficult. In this study, we utilized a novel platform to examine the cellular crosstalk and biological processes that underlie functional and structural changes in the 3D engineered tissues when exposed to pathological factors. We hypothesized that engineered cardiac tissues can report structural and functional responses to pathologic biochemical stimuli. Methods: These studies employ microfabricated polydimethylsiloxane (PDMS) templates to engineer arrays of 3D cardiac microtissues (CMT). Cantilevers within templates provide physiologically-relevant biomechanical loading to the CMTs, promote the appropriate organization of neonatal rat cardiac myocytes and fibroblasts, and report active and passive force generation in real time. Data was collected using fluorescent and confocal microscopy. Results: CMTs in a controlled mechanical environment demonstrate mechanical and structural changes within 24 hours of exposure to a cocktail of factors involved in maladaptive remodeling, including Transforming Growth Factor-β, Endothelin-1, and Angiotensin II. Analysis of 40 microtissues revealed that the percent change in passive tension was 45% higher (16.4 ± 10.3% vs. 61.1 ± 11.8%, p<0.01) and in active tension 170% higher (24.9 ± 9.5% vs.196.1 ± 76.0%, p<0.001) in treated CMTs compared to untreated CMTs. The percentage change in cross-sectional area of CMTs treated with pathological factors was 35% higher (-24.5 ± 15.6% vs.11.6 ± 7.9%, p<0.001) than untreated samples. Conclusions: These findings demonstrate that the CMT model can be used to study and dissect the dynamics of pathological hypertrophy. Ongoing experiments are examining the distinct contributions of the pathologic growth factors, the relative contributions of fibroblasts and cardiomyocytes to the pathologic growth response, and the interactions between biomechanical and humoral inputs.