The heart wall tissue, or the myocardium, is one of the main targets in cardiovascular disease prevention and treatment. Animal models have not been sufficient in mimicking the human myocardium as evident by the very low clinical translation rates of cardiovascular drugs. Additionally, current models of the human myocardium possess several shortcomings such as lack of physiologically relevant co-culture of myocardial cells, lack of a 3D biomimetic environment, and the use of non-human cells. In this study, we address these shortcomings through the design and manufacture of a myocardium-on-chip (MOC) using 3D cell-laden hydrogel constructs and human induced pluripotent stem cell (hiPSC) derived myocardial cells. The MOC utilizes 3D spatially controlled co-culture of hiPSC derived cardiomyocytes (iCMs) and hiPSC derived endothelial cells (iECs) integrated among iCMs as well as in capillary-like side channels, to better mimic the microvasculature seen in native myocardium. We first fully characterized iCMs using immunostaining, genetic, and electrochemical analysis and iECs through immunostaining and alignment analysis to ensure their functionality, and then seeded these cells sequentially into the MOC device. We showed that iECs could be cultured within the microfluidic device without losing their phenotypic lineage commitment, and align with the flow upon physiological level shear stresses. We were able to incorporate iCMs within the device in a spatially controlled manner with the help of photocrosslinkable polymers. The iCMs were shown to be viable and functional within the device up to 7 days, and were integrated with the iECs. The iCMs and iECs in this study were derived from the same hiPSC cell line, essentially mimicking the myocardium of an individual human patient. Such devices are essential for personalized medicine studies where the individual drug response of patients with different genetic backgrounds can be tested in a physiologically relevant manner.

The tumor microenvironment (TME) is distinctly heterogeneous and is involved in tumor growth, metastasis, and drug resistance. Mimicking this diverse microenvironment is essential for understanding tumor growth and metastasis. Despite the substantial scientific progress made with traditional cell culture methods, microfabricated three-dimensional (3D) cell cultures that can be precisely controlled to mimic the changes occur in the TME over tumor progression are necessary for simulating organ-specific TME in vitro. In this research, to simulate the breast cancer TME, microwell arrays of defined geometry and dimensions were fabricated using photo-reactive hydrogels for a cancer cell line and primary explant tissue culture. Microwell arrays fabricated from 4-arm polyethylene glycol acrylate and methacrylated gelatin with different degrees of methacrylation for controlled cell-matrix interactions and tunable stiffness were used to create a platform for studying the effects of distinct hydrogel compositions and stiffness on tumor formation. Using these microwell arrays, size-controlled spheroids of human breast cancer cell line HCC1806 were formed and the cell attachment properties, viability, metabolic activity, and migration levels of these spheroids were examined. In addition, primary mammary organoid tissues explanted from mice were successfully cultured in these hydrogel-based microwell arrays and the organoid morphology and viability, as well as organoid branching were studied. The microwell array platform developed and characterized in this study could be useful for generating a tissue-specific TME for in vitro high throughput studies of breast cancer development and progression as well as in drug screening studies for breast cancer treatment.

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Aging remains a fundamental open problem in modern biology. Although there exist a number of theories on aging on the cellular scale, nearly nothing is known about how microscopic failures cascade to macroscopic failures of tissues, organs and ultimately the organism. The goal of this work is to bridge microscopic cell failure to macroscopic manifestations of aging. We use tissue engineered constructs to control the cellular-level damage and cell-cell distance in individual tissues to establish the role of complex interdependence and interactions between cells in aging tissues. We found that while microscopic mechanisms drive aging, the interdependency between cells plays a major role in tissue death, providing evidence on how cellular aging is connected to its higher systemic consequences.

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