Engineering Cardiac Tissues with Three-Dimensional Bioprinting for Biomedical Applications
The role of a biomedical engineer is to solve unmet health-related needs that face society. For the past couple of decades, heart disease (HD) has remained the leading cause of mortality and morbidity worldwide. The disease is characterized by various pathologies that affect the heart. Indeed, malfunction of one of the body’s most vital organs is bound to manifest poor health and even death in patients. Despite advances in medicine and technology, heart disease continues to be prevalent and diminishes the quality of life for many around the world. Certainly, there exists a need for developing new tools to better understand and treat HD. Tissue engineering cardiac tissues in-vitro offers an alternative, useful platform to study diseases and navigate towards generating biologically relevant artificial tissues for clinical translation. Tissue engineering combines biomaterial scaffolds, cells, and construction methods to grow viable tissues in-vitro and in-vivo. Advent of three-dimensional bioprinting has allowed for creation of living tissues that mimic the geometries and physiologies of native tissues. In accordance to the principles of this field, this work aims to exploit the benefits afforded by extrusion-based 3D-bioprinting to engineer viable cardiac tissues in-vitro for biomedical applications. Studies include development of a furfuryl-gelatin-fibrinogen bioink that was crosslinked enzymatically by the conversion of fibrinogen into fibrin and with photo-oxidation with visible light. Cardiomyogenesis was observed in bioprinted constructs, characterized by the coupling of human cardiomyocytes and fibroblasts. Furthermore, cells within bioprinted constructs showed characteristic cardiac biomarkers and preferred cellular organization in the direction of bioprinted filaments. In another investigation, a murine animal model was adopted to develop a method of cryo-inducing myocardial infarction in-vivo. A reproducible zone of necrotic myocardium that resembled many of the histopathological characteristics of the naturally-occurring MI was produced using a cryo-probe. Developing protocols for generating controlled infarcts on demand provide a beneficial in-vivo model for future implantation of 3D-bioprinted cardiac grafts. Development of 3D-bioprinted constructs was further explored through the development of a scaffold able to culture endothelial cells, a third major cell type found in the heart. The scaffold was tailored to house all three heterogenous cardiac cell types for future study of microgravity-induced cardiac atrophy during spaceflight. Finally, modulation of cardiomyocyte physiology was probed in response to variation in hydrogel mechanical composition. A hydrogel system was adopted to mimic various developmental stages of the heart. Mechanical properties of gels were optimized to mimic stiffness of embryonic, physiologic, and fibrotic cardiac tissue. CMs cultured in softer gels showed enhanced cellular networking and alignment within hydrogel scaffolds as compared to those cultured to stiffer ones. Results from this work give insight into biomaterial selection for three-dimensional culture and their effect on the construction of cardiac tissues in-vitro. Generating viable cardiac tissues on-demand with three-dimensional bioprinting has the potential to greatly benefit society and provide an extra tool to understand and battle heart disease. Bioprinting creates architecturally similar tissues to those of the native heart, as well as provide physiologically responsive platforms for disease modeling and pharmaceutical testing. They further hold potential to be used for as grafts to replace necrotic or fibrotic myocardium. Work from this dissertation sets a foundation for further development of 3D-bioprinted cardiac tissues in-vitro.
Alonzo, Matthew, "Engineering Cardiac Tissues with Three-Dimensional Bioprinting for Biomedical Applications" (2021). ETD Collection for University of Texas, El Paso. AAI28497496.