Spontaneous atrial fibrilation-like re-entrant activity and associated transcriptomic changes in hiPSC-derived atrial cardiomyocytes

AF is a prevalent cardiac arrhythmia marked by rapid and irregular atrial activity. Its complex nature complicates both mechanistic understanding and therapeutic development. Atrial cardiomyocytes were differentiated from two independent hiPSC lines with retinoic acid and their phenotype was assessed using molecular, electrophysiological and mechanical approaches. hiPSC­derived atrial cardiomyocytes (hiPSC-aCM) were then plated at a uniform density into large or small surface plates to study their fibrillatory activity. Optical mapping experiments and RNAseq analysis were performed to characterize electrophysiological activity and transcriptomic differences associated with the fibrillatory condition. We established an in vitro hiPSC-aCM model exhibiting spontaneous AF-like re-entrant activity. Large surfaces offered sufficient space to sustain re-entrant activity, whereas small surfaces did not permit the formation of re-entrant circuits. The activation period in large confluent cultures was 0.8 ± 0.2 sec, which was significantly faster and more irregular than that observed in small confluent cultures, which had an activation period of 1.3 ± 0.3 sec. Gene expression analysis revealed an upregulation of pathways related to fibrosis and immune response in fibrillating cells. This study establishes a human hiPSC-aCM model for investigating electrophysiological and molecular features associated with sustained AF-like re-entrant activity and supports its potential use for pharmacological studies in AF.