P2581Unique molecular profile of exosomes from epicardial fat of patients with atrial fibrillation

Abstract

Abstract Background and aim Exosome, the smallest vesicles that originate from intracellular compartments, contains and delivers specific bioactive proteins, lipids, mRNA, and miRNA to facilitate intercellular signaling. However, the role and mechanism of exosomes in atrial remodeling and fibrillation (AF) has not been determined. While epicardial fat (eFat) and inflammation have been linked to atrial remodeling and fibrillation (AF), the role of eFat exosomes in the pathogenesis of AF remains unknown. Thus, we aimed to determine whether eFat exosomes play a role in the initiation and progression of AF. Methods and results We collected eFat specimens from patients with and without chronic or paroxysmal AF undergoing heart surgery. Isolated fat specimens were cut into small pieces and incubated as organ cultures. We isolated exosomes from the medium of the explant by differential ultra-centrifugation and characterized the vesicle size distributions, morphology, specific markers, and molecular cargo. Immunoblotting of CD63, CD81 and TSG101 confirmed the presence of exosomes (Fig.1 B). Significantly, eFat from patients with AF secreted higher amounts of exosomes compared with controls (p<0.001), which confirmed by Nanoparticle Tracking Analysis (NTA) (Fig.1 A). The levels of exosomal pro-inflammatory and pro-fibrotic cytokines were higher in exosomes from patients with, compared with those without, AF (Fig.1 C, D). Measurements of micro RNA (miRNA) by real-time PCR showed lower levels of anti-fibrotic miRNA-133a (p=0.2), and higher levels of pro-fibrotic miRNA-146b (p=0.2) in exosomes from patients with, compared with those without, AF (Fig.1 E, F) Conclusion We show, for the first time, that exosomes from eFat of patients with AF have a unique pro-inflammatory and pro-fibrotic profile. We suggest a novel mechanism that links eFat to AF and eFat exosomes as novel biomarkers and potential therapeutic targets for AF.