Poster V11 - Identifying the role of macrophages during human heart development in a stem cell-derived heart organoid

Introduction: Congenital heart defects (CHDs) are the most common birth defect in humans, accounting for 1% of all births per year in the United States. The exact pathogenesis of CHDs remain largely unknown due to several reasons: complex interaction of genetic and environmental factors, lack of appropriate animal models, and the inability to directly study human heart development. Our group recently developed an advanced, three-dimensional (3D) human heart organoid (hHO) system derived from human pluripotent stem cells (hPSCs) (Lewis-Israeli et al., Nat Comm, 2021). hHOs recapitulated human heart development to a significant extent and could be used for disease modeling maternal diabetes-induced CHDs. Although our current hHO system mimics many aspects of the developing human heart, it still lacks some key features, such as embryonic tissue-resident macrophages (MPs). In mice, resident MPs contribute to electrical conductance, lymphatic channel development, and endothelial network patterning, however their role in human heart development remains poorly understood.

Materials and

Methods: We created a stepwise protocol to generate hHOs with integrated MPs from human pluripotent stem cells. We used immunofluorescence confocal microscopy (IF) to visualize MPs within the hHOs and flow cytometry to confirm their presence in the hHOs over 60 days. We also utilized single cell RNA sequencing (scRNAseq) data of hHMOs to identify cell population and gene expression changes over time.

Results, Conclusions, and Discussions: We observed MPs persisted in the hHOs for up to 60 days in culture. scRNAseq demonstrated expansion of cardiomyocyte populations and notable decreases in other cell populations in the hHMOs, such as conductance cells, stromal cells, and epicardial cells. Future work will aim identify structural changes in the hHOs using IF and functional changes in heart conductance using live cell imaging with calcium and ion signaling dyes. We have created an in vitro model of the human heart that recapitulates early aspects of immune cell integration in the developing heart that can be used to identify developmental changes induced by resident MPs.

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