Pulsing heart at the microscale: : Generation and characterization of human organotypic cardiac microtissues for translational medicine

Abstract

As cardiovascular diseases (CVD) remain the leading cause of mortality worldwide; there is an increasing demand for developing physiologically relevant in vitro cardiovascular tissue models suitable for studying personalized medicine and pre-clinical tests. Although recent technologies provide some insight into how human CVDs can be modelled in vitro, they may not always give a comprehensive overview of the complexity of the human heart due to their limits in cellular heterogeneity, physiological complexity and maturity. The aim of this dissertation is to provide a deeper understanding of microphysiological technologies in cardiovascular biology, and to establish a miniaturized cardiac tissue model in vitro that could better reflect the physiological complexity, cellular heterogeneity and maturity of a human heart, and demonstrate its functional applications for translational research. We have developed a simple and effective protocol to generate scaffold-free multicellular beating human cardiac microtissues in vitro from human induced pluripotent stem cells (hiPSCs) – namely human organotypic cardiac microtissues (hOCMTs) – that show a degree of proto-self-organization and can be cultured for long term. The 3D hOCMTs contain multiple cell types of the heart, and show functional beating activity without external stimuli for more than 100 days. The 3D hOCMTs show improved cardiac specification, survival and metabolic maturation compared to standard 2D monolayer cardiac differentiation. Furthermore, we show that the 3D hOCMTs could respond to cardioactive and cardiotoxic drugs in a dose dependent manner. Due to their tendency for self-organization, cellular heterogeneity, and functionality in our 3D microtissues over extended culture time, we could confirm these constructs as human cardiac organoids (hCOs). Finally, we reviewed in vitro technologies already described in the literature and proposed to enable in-vivo-like biomechanical cues in microphysiological tissue models, and further overviewed nanomedical applications for cardiac therapies. This work shows the potential of 3D hCOs to enable the development of more physiologically-relevant cardiac tissue models, and represent a powerful platform that could lead to future translational research in cardiovascular biology.