Distinctive Inflammatory and Fibrotic Signature of Extracellular Vesicles from Epicardial Fat of Patients with Atrial Fibrillation

Olga Shaihov - Teper ^1,2 Eilon Ram ³ La-Paz Levin-Kotler ^1,2 Nili Naftali-Shani ^1,2 Nimer Ballan ⁴ Lior Gepstein ⁴ Ehud Raanani ³ Jonathan Leor ^1,2

¹Neufeld and Tamman Cardiovascular Research Institute, Sheba Medical Center, Sackler School of Medicine, Tel Aviv University, Israel
²Sheba Regenerative Medicine, Stem Cell and Engineering Center, Tel-Hashomer, Israel
³Heart Institute, Sheba Medical Center, Tel Hashomer, Israel
⁴The Sohnis, Family Laboratory for Cardiac Electrophysiology and Regenerative Medicine, Rappaport Faculty of Medicine, Technion Institute of Technology, Israel

Background and Aim: Epicardial fat (eFat) has been linked to atrial remodeling and fibrillation (AF). We aimed to determine whether extracellular vesicles (EVs) derived from eFat play a role in the pathogenesis of AF.

Methods and Results: We collected small specimens of eFat from patients (pts) with and without (w/o) AF undergoing heart surgery. eFat specimens were incubated as organ cultures and EVs were isolated from the culture medium by ultra-centrifugation. We used immunoblotting, electron microscopy, and nanoparticle tracking analysis to characterize the EVs. Significantly, eFat specimens from AF pts secreted greater amounts of EVs compared with patients w/o AF. Moreover, eFat EVs from AF pts secreted a higher concentration of inflammatory and fibrotic cytokines but less anti-inflammatory cytokines, compared with patients w/o AF. Notably, EV cytokines reflected the inflammatory and fibrotic status of eFat in AF pts better than free cytokines. Next, we tested several miRNA that could influence cardiac fibrosis. For example, miR-133 inhibits TGF-β, decreases collagen content and inhibits atrial remodeling. Expression of EV miR-133 was lower in eFat of AF pts than in patients w/o AF. Eventually, “wound healing” scratch assay show that fibroblast migration was greater after incubation with eFat EVs from AF patients, compared with pts w/o AF.

Conclusions: eFat from AF patients secretes a higher number of EVs with an inflammatory and fibrotic profile. Our findings suggest that eFat EVs contribute to inflammation and fibrosis, both of which contribute to the pathogenesis of atrial remodeling and fibrillation.