Abstract
Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have the potential to remuscularize infarcted hearts but their arrhythmogenicity remains an obstacle to safe transplantation. Myofbroblasts are the predominant cell-type in the infarcted myocardium but their impact on transplanted hiPSC-CMs remains poorly defned. Here, we investigate the efect of myofbroblasts on hiPSC-CMs electrophysiology and Ca2+ handling using optical mapping of advanced human cell coculture systems mimicking cell–cell interaction modalities. Human myofbroblasts altered the electrophysiology and Ca2+ handling of hiPSC-CMs and downregulated mRNAs encoding voltage channels (KV4.3, KV11.1 and Kir6.2) and SERCA2a calcium pump. Interleukin-6 was elevated in the presence of myofbroblasts and direct stimulation of hiPSC-CMs with exogenous interleukin-6 recapitulated the paracrine efects of myofbroblasts. Blocking interleukin-6 reduced the efects of myofbroblasts only in the absence of physical contact between cell-types. Myofbroblast-specifc connexin43 knockdown reduced functional changes in contact cocultures only when combined with interleukin-6 blockade. This provides the frst in-depth investigation into how human myofbroblasts modulate hiPSC-CMs function, identifying interleukin-6 and connexin43 as paracrine- and contact-mediators respectively, and highlighting their potential as targets for reducing arrhythmic risk in cardiac cell therapy