Modeling the atrioventricular conduction axis using human pluripotent stem cell-derived cardiac assembloids

The atrioventricular (AV) conduction axis provides electrical continuity between the atrial and ventricular chambers. The “nodal” cardiomyocytes populating this region (AV canal in the embryo, AV node from fetal stages onward) propagate impulses slowly, ensuring sequential contraction of the chambers. Dysfunction of AV nodal tissue causes severe disturbances in rhythm and contraction, and human models that capture its salient features are limited. Here, we report an approach for the reproducible generation of AV canal cardiomyocytes (AVCMs) with in vivo-like gene expression and electrophysiological profiles. We created the so-called “assembloids” composed of atrial, AVCM, and ventricular spheroids, which effectively recapitulated unidirectional conduction and the “fast-slow-fast” activation pattern typical for the vertebrate heart. We utilized these systems to reveal intracellular calcium mishandling as the basis of LMNA-associated AV conduction block. In sum, our study introduces novel cell differentiation and tissue construction strategies to facilitate the study of complex disorders affecting heart rhythm. [Display omitted] •WNT2 and retinoic acid drive mesoderm from hiPSCs toward AV canal cardiomyocytes•Assembloids containing AV canal cardiomyocytes simulate atrium-ventricle interface•Assembloids facilitate the study of complex conduction disorders such as AV block•Intracellular calcium handling is aberrant in LMNAc.1477C>T AV canal cardiomyocytes The atrioventricular (AV) canal maintains the electrical conduction between atria and ventricles. Devalla and colleagues generate AV canal cardiomyocytes from hiPSCs using WNT2 and retinoic acid. They incorporate these cells in cardiac assembloids, which effectively simulate the AV conduction axis, facilitating the modeling of complex disorders such as AV block.