Microfluidic organoid model of cardio-hepatic physiology and disease - SUMMARY As clinical trials have high failure rates, in part due to reliance on animal testing that can produce inaccurate results, accurate in vitro models of human physiology and disease are needed to bridge this gap. Recent progress in organoid and organ-on-chip systems demonstrates promising potential to do this; however, in vitro models have their own limitations. Stem cell derived models tend to have immature phenotypes, primary cell derived models may be difficult to keep functioning for long periods of time, and in vitro models in general do not recapitulate the full functionality of human organs. In an effort to increase the physiological relevance of these systems, we have developed a cardiovascular microfluidic organoid chip, the µCV chip, which develops according to biomimetic morphogen gradients, and can self-assemble into elongated tube-like structures when the cells are seeded in specific starting geometries with a robotic seeding machine. These pumping tube-like structures can generate flow autonomously in our microfluidic chips. Although this preliminary data is compelling, it remains to be tested whether these tube-like structures have cellular spatial organization or heart-like functionality that is more physiologically accurate than simpler cardiac spheroids. In this proposal, we aim to systematically compare cardiovascular spheroids and cardiovascular tube-shaped microfluidic organoids in depth, in order to further understand how the organization and functionality of organoids change when seeded with different starting geometries and exposed to different flow conditions, and test the hypothesis that tube-shaped flow-generating cardiovascular organoids have microphysiology more similar to a simplified human heart. We will further expand the repertoire of our microfluidic organoid chip by teaming up with colleagues in the Division of Liver Diseases to create hepatic organoids, both iPSC derived and primary cell derived, in order to similarly evaluate differences in hepatic function when the organoids are created with spheroid versus tubular geometries and exposed to different flow conditions. Finally, we will combine these two microfluidic organoid systems into a single microfluidic heart-liver microphysiologic system, the µCV-MPS, and characterize the two organoids as they co-develop and function within a single circulatory system. As the liver is responds to flow and beat rate, and the heart responds to factors secreted by the liver, we hypothesize that we will observe improvements in functionality, viability, and microphysiology by studying heart and liver organoids while they are connected via paracrine signaling and homeostatic regulatory mechanisms. We will additionally use the µCV-MPS as a model of Nonalcoholic Fatty Liver Disease, which is known to lead to cardiovascular disease including left ventricular hypertrophy and diastolic disfunction, pathologies which we hypothesize to be observable inthe µCV-MPS. Validation of this model system would represent a significant step forward in the sophistication and capabilities of human MPS models, helping to provide more predictive alternatives to animal models for next-generation therapeutic development and regulatory approval.
