Modeling Atrial Fibrillation through Intermittent Tachypacing-Induced Remodeling in hiPSC-Derived Atrial Cardiomyocytes and Atrial Fibroblast

Background Human in vitro models for atrial fibrillation (AF) are limited. Human-induced pluripotent stem cell-derived atrial cardiomyocytes (hiPSC-aCMs) provide a valuable tool to study AF pathophysiology by facilitating in vitro modeling. Objectives To investigate the effects of an intermittent tachypacing protocol (ITPP) in matured hiPSC-aCMs co-cultured with human atrial cardiac fibroblast (haCF) to mimic AF-associated electroanatomical phenotypes. Methods and Results hiPSC-aCMs were cultured alone or co-cultured with haCFs at 90/10 and 70/30 ratios. ITPP was applied through field stimulation, and optical mapping assessed action potentials (APs) and calcium transients (CaTs). Immunostaining was performed to quantify pro-fibrotic biomarkers (Collagen III and TGFβ1). ITPP led to increased spontaneous AP frequency (Δ=+31±7%, P<0.0001) and reduced AP duration at 80% repolarization (APD 80% ; Δ=-15±4%, P=0.001). Additionally, the upstroke slope (Δ=-41±11%, P=0.001) and amplitude (dF/F 0 ; Δ=-51±13%, P<0.001) of intracellular CaT were significantly reduced. Co-culture at the 70/30 hiPSC-aCM/haCF ratio, showed a >100-fold increase in Collagen III expression (P<0.0001), diminished excitability (ΔHz=-61±6%, P<0.0001), prolonged ΔAPD 80% (Δ=+130±10%, P<0.0001), prolonged AP triangulation (ΔAPD Tri =+143±13%, P<0.0001), reduced upstroke slope (Δ=-66±6%, P<0.0001), conduction block (Δ=-52±18%, P=0.0260), and diminished intracellular calcium handling (upstroke slope Δ=-50±8%, P<0.0001; ΔdF/F0=-34±9%, P=0.0003). Finally, the application of ITPP to the 70/30 co-culture model recapitulated an AF-mediated phenotype (ΔHz=+25±8%, P=0.02; ΔAPD 80% =-16±6%, P=0.01) while introducing conduction block (ΔCV 100/0 vs 70/30 = −27±15%; P=0.0005). Conclusions Co-cultures of matured hiPSC-aCMs and haCFs exhibited structural and electrophysiological remodeling, including conduction abnormalities, mirroring key AF mechanisms. This model holds potential for patient-specific therapies and drug discovery. Abstract Figure Graphical Abstract Human iPSC-Model for Atrial Fibrillation