Oral, H. | Search bioRxiv

bioRxiv2025

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

BackgroundHuman 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. ObjectivesTo 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 ResultshiPSC-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 TGF{beta}1). ITPP led to increased spontaneous AP frequency ({Delta}=+31{+/-}7%, P<0.0001) and reduced AP duration at 80% repolarization (APD80%; {Delta}=-15{+/-}4%, P=0.001). Additionally, the upstroke slope ({Delta}=-41{+/-}11%, P=0.001) and amplitude (dF/F0; {Delta}=-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 ({Delta}Hz=-61{+/-}6%, P<0.0001), prolonged {Delta}APD80% ({Delta}=+130{+/-}10%, P<0.0001), prolonged AP triangulation ({Delta}APDTri=+143{+/-}13%, P<0.0001), reduced upstroke slope ({Delta}=-66{+/-}6%, P<0.0001), conduction block ({Delta}=-52{+/-}18%, P=0.0260), and diminished intracellular calcium handling (upstroke slope {Delta}=-50{+/-}8%, P<0.0001; {Delta}dF/F0=-34{+/-}9%, P=0.0003). Finally, the application of ITPP to the 70/30 co-culture model recapitulated an AF-mediated phenotype ({Delta}Hz=+25{+/-}8%, P=0.02; {Delta}APD80%=-16{+/-}6%, P=0.01) while introducing conduction block ({Delta}CV100/0 vs 70/30= -27{+/-}15%; P=0.0005). ConclusionsCo-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. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=177 SRC="FIGDIR/small/655123v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@1c56760org.highwire.dtl.DTLVardef@105d4a2org.highwire.dtl.DTLVardef@1cb18d4org.highwire.dtl.DTLVardef@cb3353_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO Human iPSC-Model for Atrial Fibrillation C_FIG

bioengineering↗

bioRxiv2025

Mineralocorticoid Receptor Antagonism Reduces Atrial Arrhythmias Post-Cardiac Surgery and Attenuates Atrial Stress Responses to Cardioplegic Arrest

BackgroundNew postoperative atrial fibrillation (POAF) occurs in about 40% after cardiac surgery. Mineralocorticoid receptor antagonists (MRA) are known to reduce chronic atrial fibrillation (AF) development and burden. We examined the impact of preoperative MRA use on POAF and also examine the atrial cell type impacted by MRA treatment during cold cardiac preservation. MethodsRetrospective study of 19,042 patients who underwent cardiac surgery at Mayo Clinic in Minnesota, and performed 1:3 propensity matching to obtain 298 patients on preoperative MRA matched to 894 who were not. We also separately matched patients using preoperative diuretics. Single-nuclei RNA sequencing (snRNA-seq) examined MRAs effects on different atrial cell types in canrenone (water soluble MRA) treated human donor hearts undergoing cold preservation followed by ex-vivo reperfusion and compared gene expression to the atria of patients with AF. ResultsPropensity matched preoperative MRA group had less new onset POAF (19.8% vs 31.5%, P<0.001). To account for the possibility that preoperative diuretic use and volume reduction may impact POAF, we propensity matched 298 preop diuretic users that included MRA use to another 894 patients who used a non-MRA diuretic preoperatively. Those who used preoperative MRA similarly had a lower incidence of POAF (19.8% vs 33.2%, P<0.001). No survival difference was present between the propensity matched groups that used preoperative diuretics (P=0.079). Preoperative MRA use also reduced the development of paroxysmal and chronic AF at 6 years of follow up. From our snRNA-seq data, we identified a subpopulation of atrial cardiomyocytes (CM2) that had high MR expression where canrenone suppressed the increase in MR target gene expression associated with cold preservation-reperfusion. These MR targets were conversely elevated in patients with chronic AF. Canrenone also suppressed other cardiac preservation associated genes that show elevated expression in atrial macrophages and pericytes from chronic AF atria. ConclusionsOur studies show that preoperative MRA use is associated with 40% reduction in POAF as well as lowering long standing AF development by about 41%. Our cold cadiac preservation-reperfusion model showed that canrenone reduced expression of MR target genes associated with chronic AF, particular in cardiomyocytes with important roles in electrical conduction. Clinical PerspectiveO_ST_ABSWhat is New?C_ST_ABSO_LIThis study shows that preoperative use of mineralocorticoid receptors antagonists (MRA) is associated with a reduced incidence of new onset perioperative atrial fibrillation after cardiac surgery utilizing cardiopulmonary bypass. C_LIO_LIWe show that preoperative MRA use is associated with a lower incidence of developing more chronic paroxymal or sustained atrial fibrillation. C_LIO_LIAddition of canrenone, a clinically utilized water soluble MRA, to cardioplegia solution used during cardiac preservation can attenuate atrial inflammatory reponses and reduce signaling through molecular pathways that promote atrial fibrillation. C_LI What are the clinical implications?O_LIPerioperative use of MRAs may be considered to reduce early postoperative atrial fibrillation as well as lowering the risk of developing more chronic atrial arrhythmias. C_LIO_LIThese findings support pursuing a clinical trial to determine the impact of MRA use on atrial arrhythmias following cardiac surgery in the setting of cardiopulmonary bypass with cold cardiac preservation. C_LI

molecular biology↗