Heart spheroids from primary cells for studying cardiac development

Organoids can be broadly classified based on their source: either from primary cells or from in vitro stem cell differentiation. Organoids derived from primary cells have been developed for various organs such as the liver, intestine, and colon, demonstrating significant value in disease modeling and drug screening. However, primary cell-derived heart organoids have not yet been reported. In this study, we developed heart organoid-like spheroids using murine atrial and ventricular cells. We demonstrated that these spheroids largely preserved the cell lineages present in vivo. We further evaluated their responses to treatment with growth factors. Subsequently, we fused atrial and ventricular spheroids to observe the migration patterns of different cell types. Then, we generated mixed spheroids composed of cells from different heart regions or organs and found that region- or organ-specific cells tended to cluster together. Notably, liver- and intestine-derived cells promoted cardiomyocyte maturation within these mixed organoids. Finally, we performed a fibroblast ablation assay in heart spheroids derived from transgenic mice and observed the effects on other cell lineages. Overall, we successfully generated heart spheroids from murine primary cells and demonstrated their in vivo-like characteristics. Compared to stem cell-derived organoid systems, this primary cell-derived approach holds great promise for translational research due to its potential to better preserve native cellular features.