Small extracellular vesicles from epicardial fat of patients with atrial fibrillation induce inflammation, fibrosis and re-entrant arrhythmias

Abstract

Background and aim Epicardial fat (eFat) has been linked to atrial remodeling and fibrillation (AF). Small extracellular vesicles (sEVs) are heterogeneous membrane vesicles released by all cell types. They can both protect and damage tissues by the delivery of multiple different messengers. Surprisingly, the role of sEVs in the pathogenesis of AF has not been studied. Thus, we aimed to determine whether sEVs derived from eFat play a role in the pathogenesis of AF. Methods and results We collected eFat specimens from patients with and without chronic or paroxysmal AF undergoing open-heart surgery. Isolated eFat specimens were cut into small pieces and incubated as organ cultures. We isolated sEVs from the medium of the explant by differential ultra-centrifugation, high-density gradient or size exclusion chromatography (SEC), and characterized vesicle size distribution, morphology, specific markers, histology and molecular cargo. Immunostaining for macrophage accumulation, fibrosis and apoptosis confirmed the pro-inflammatory and pro-fibrotic properties of eFat sEVs from patients with AF (Fig. 1). eFat sEVs labeled with PKH26 were massively up taken by endothelial cells (Fig. 2). Real-time PCR showed an increased level of oxidative stress genes in endothelial cells. eFat sEVs from patients with AF caused more fibrosis after injection into rat hearts than those without AF. (Fig. 3). Finally, while eFat sEVs from patients with and without AF induced shorter action potential duration, only eFat sEVs from patients with AF induced sustained re-entry (rotor) in human induced pluripotent stem cell (iPS)-derived cardiomyocytes (Fig. 4) Conclusion We show, for the first time, that sEVs from eFat of patients with AF demonstrate unique pro-inflammatory, pro-fibrotic and pro-arrhythmic properties. Our findings suggest that eFat sEVs can induce cellular, molecular and electrophysiological remodeling that can subsequently lead to the development of AF. Funding Acknowledgement Type of funding source: None