Integrated Extracellular Matrix Mimetic Biomaterials and Microfabricated Platforms for Studying Mechanobiology in Cardiomyocyte Maturation and Cardiac Disease
DePalma, Samuel
2024
Abstract
The mechanical function of the myocardium is dictated by contractile cardiomyocytes (CMs) and the fibrous extracellular matrix (ECM) that surrounds, organizes, and supports bundles of CMs. Previous studies have implicated ECM mechanics in driving cardiac tissue assembly and overall contractile function through mechanosensitive CM-ECM adhesion complexes called costameres. However, due to limitations in existing engineered models of myocardium which require the inclusion of stromal cells or lack orthogonal mechanical control over matrix properties, how CMs sense and respond to specific mechanical microenvironmental cues has not been established. Therefore, the focus of this dissertation is to develop improved in vitro models of the cardiac ECM to advance our understanding of how microenvironmental mechanics impact cardiac tissue assembly and function in both healthy and diseased contexts. First, this thesis reviews the vast array of engineered heart tissue platforms that have been previously developed to study the maturation of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and the utility of these platforms for studying CM maturation, modeling disease processes, or screening drugs for cardiotoxicity. Through an in-depth meta-analysis of >300 manuscripts, we highlight the vast array of iPSC-CM differentiation protocols, iPSC-CM maturation techniques, and analysis methods used to generate and assess previously established in vitro cardiac model systems and note significant progress in the field over time. Additionally, we discuss opportunities to unify and compare these various techniques by using common controls and tunable engineered heart tissue platforms, enabling continued comprehensive benchmarking of progress in developing physiological relevant models of the adult myocardium. Next, we describe the development and characterization of two biomaterial platforms composed of electrospun dextran vinyl sulfone (DVS) fiber matrices that recapitulate the architecture and mechanics of collagen fiber networks that scaffold CMs. Taking inspiration from previously established engineered heart tissue models, these cardiac microtissues systems enable orthogonal tuning of various biophysical and biochemical properties of the cardiac microenvironment. Using these platforms, we define a set of scaffold parameters that drive the efficient assembly of functional myocardial syncytia and promote both structural and functional maturation of iPSC-CMs. In particular, we demonstrate that iPSC-CM mechanosensing of changes in matrix stiffness underlies the formation of costameres which corresponds to greater structural, electrical, and contractile maturity of engineered cardiac tissues. Finally, this thesis describes a platform using the same fibrous DVS matrices that enables co-culture of cardiac fibroblasts and iPSC-CMs to explore how biophysical and biochemical microenvironmental cues impact heterocellular signaling in the heart. As fibroblasts sit within the collagen networks between CMs in the native myocardium, bilayer tissues composed of CMs and cardiac fibroblasts separated by synthetic ECM-mimetic matrices were utilized for two major objectives: 1) examining how cardiac fibroblasts sense and respond to mechanical changes of fibrous matrices, and 2) dissecting how physical and paracrine signaling between CMs and fibroblasts regulates fibroblast quiescence versus fibrogenic activation. Overall, the work presented in this dissertation integrates stem cells, biomaterials, tissue engineering, and microfabrication approaches to develop highly tunable cardiac microtissue platforms to study how microenvironmental cues influence fundamental biological processes involved in cardiac tissue assembly, healthy function, or disease. The results presented here help inform the design of biomaterial scaffolds for use in engineered tissue replacement therapies and provide new insights into how cellular mechanosensing in the heart regulates tissue development and disease processes.Deep Blue DOI
Subjects
Cardiac tissue engineering Extracellular matrix Induced pluripotent stem cell Cardiomycoytes Mechanobiology Electrospinning
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