Cardiac assembloids from human pluripotent stem cells model the atrioventricular conduction axis.
In this study, we aimed to differentiate atrioventricular (AV) canal-like cardiomyocytes (AVCM) from hiPSCs to facilitate the study of disorders that affect the AV conduction axis. hiPSC-derived AVCM preferentially expressed AV canal-associated genes MSX2, TBX2 and TBX3. Single cell RNA sequencing and comparative analysis with mouse heart further validated their AV canal-like identity. In addition, hiPSC-AVCM demonstrated sensitivity to ivabradine and carbachol, indicating the presence of key nodal currents If and IKACh. To model the AV conduction axis, we created an organoid-based tissue model. These so-called “assembloids” consisted of atrial, AVC, and ventricular organoids, which exhibited spontaneous contractions and unidirectional conduction with impulses initiated predominantly at the atrial end. Remarkably, we observed slower conduction in the AVC region of the assembloid, effectively recapitulating the “fast-slow-fast” conduction pattern found in the early heart tube. Our results demonstrate that hiPSC-derived AVCM recapitulate molecular and electrophysiological properties of in vivo AV canal cardiomyocytes and tissue models incorporating this cell type enhance our ability to evaluate complex cardiac conduction disorders. Overall design: single cell RNA sequencing of human induced pluripotent stem cell-derived atrioventricular canal-like cells. Single cell collection was performed at day 19 of differentiationand and 768 cells were collected in total.