Multiple action potentials and complex calcium dynamics following electroporation of S-HEK cells depend on gap junction coupling

Abstract In recent years, irreversible electroporation has been increasingly used to treat cardiac arrhythmias, an approach termed pulsed field ablation. The mechanisms of how electroporation affects the generation and propagation of action potentials (AP) in the myocardium (and other excitable tissues) remain to be elucidated. In our previous in vitro studies using genetically engineered S-HEK cells as a simple model of excitable cells we identified two unexpected phenomena that remain unexplained: (1) multiple APs triggered by a single electric pulse, and (2) a pulse-induced complex (bi- or multiphasic) calcium response not observed in their non-excitable counterparts NS-HEK cells. In this study, we employed fluorescence microscopy for optical monitoring of APs and intracellular calcium, pharmacological interventions targeting specific ion channels, and molecular biology techniques to characterize the expression of selected ion channels in S-HEK and NS-HEK cells. Our findings show that (1) multiple APs result primarily from sustained AP propagation along the cell monolayer through gap junctions, and (2) the complex calcium response in S-HEK cells reflects synchronized calcium influx during these propagating APs, with extracellular calcium being primary source rather than internal store release.