Background: The role of epicardial fat (eFat)-derived extracellular vesicles (EVs) in the pathogenesis of atrial fibrillation (AF) has never been studied. We tested the hypothesis that eFat-EVs transmit proinflammatory, profibrotic, and proarrhythmic molecules that induce atrial myopathy and fibrillation. Methods: We collected eFat specimens from patients with (n=32) and without AF (n=30) during elective heart surgery. eFat samples were grown as organ cultures, and the culture medium was collected every two days. We then isolated and purified eFat-EVs from the culture medium, and analyzed the EV number, size, morphology, specific markers, encapsulated cytokines, proteome, and miRNAs. Next, we evaluated the biological effects of unpurified and purified EVs on atrial mesenchymal stromal cells (MSCs) and endothelial cells (ECs) in vitro. To establish a causal association between eFat-EVs and vulnerability to AF, we modeled AF in vitro using induced pluripotent stem cell-derived cardiomyocytes (iCMs). Results: Microscopic examination revealed excessive inflammation, fibrosis, and apoptosis in fresh and cultured eFat tissues. Cultured explants from patients with AF secreted more EVs and harbored greater amounts of proinflammatory and profibrotic cytokines, as well as profibrotic miRNA, than those without AF. The proteomic analysis confirmed the distinctive profile of purified eFat-EVs from patients with AF. In vitro, purified and unpurified eFat-EVs from patients with AF had a greater effect on proliferation and migration of human MSCs and ECs, compared to eFat-EVs from patients without AF. Finally, while eFat-EVs from patients with and without AF shortened the action potential duration of iCMs, only eFat-EVs from patients with AF induced sustained reentry (rotor) in iCMs. Conclusions: We show, for the first time, a distinctive proinflammatory, profibrotic, and proarrhythmic signature of eFat-EVs from patients with AF. Our findings uncover another pathway by which eFat promotes the development of atrial myopathy and fibrillation.

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Background: Inflammation and fibrosis limit the reparative properties of human mesenchymal stromal cells (hMSCs). We hypothesized that disrupting the toll-like receptor 4 (TLR4) gene would switch hMSCs toward a reparative phenotype and improve the outcome of cell therapy for infarct repair. Methods and results: We developed and optimized a new electroporation protocol for CRISPR-Cas9 gene editing. This protocol achieved a 68% success rate when applied to isolated hMSCs from the heart and epicardial fat of patients with ischemic heart disease. While cell editing lowered TLR4 expression in hMSCs, it did not affect classical markers of hMSCs, proliferation, and migration rate. Protein mass spectrometry analysis revealed that edited cells secreted fewer proteins involved in inflammation. Analysis of biological processes revealed that TLR4 editing reduced processes linked to inflammation and extracellular organization. Furthermore, edited cells expressed less NF-ƙB and secreted lower amounts of extracellular vesicles, pro-inflammatory and pro-fibrotic cytokines than unedited hMSCs. Cell therapy with both edited and unedited hMSCs improved survival, left ventricular (LV) remodeling, and cardiac function after myocardial infarction (MI) in mice. Postmortem histologic analysis revealed clusters of edited cells that survived in the scar tissue 28 days after MI. Morphometric analysis showed that implantation of edited cells increased the area of myocardial islands in the scar tissue, reduced the occurrence of transmural scar, increased scar thickness, and decreased expansion index. Conclusions: We show, for the first time, that CRISPR-Cas9-based disruption of the TLR4-gene reduces pro-inflammatory polarization of hMSCs, and improves infarct healing and remodeling in mice. Our results provide a new approach to improve the outcomes of cell therapy for cardiovascular diseases.

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Background and Aim: Heart disease might be an independent risk factor for cancer (reverse cardio-oncology). The cellular and molecular mechanisms that link heart disease to cancer remain elusive, and specific therapies are limited. We hypothesized that cardiac extracellular vesicles (cEVs) secreted by diseased hearts carry and disseminate factors that promote tumor growth. Methods & Results: We subjected female mice to myocardial infarction (MI) or sham-MI and 28 days of follow-up. Left ventricular remodeling was confirmed by echocardiography. To determine the role of cEVs in tumor growth, we focused on cardiac mesenchymal stromal cells (cMSCs), which play a central role in cardiac repair, remodeling, and fibrosis. Thus, we isolated cMSCs from mice hearts 10 or 28 days after MI or sham MI. cMSCs after MI secreted more small EVs than cMSCs from sham-MI. Proteomic analysis revealed a distinctive profile of cEVs after MI ( Fig A ). Purified cMSC-EVs targeted both breast and lung cancer cells in vitro. A scratch assay showed that MI-cEVs facilitated cancer cell proliferation and migration two times faster than sham-MI cEVs ( Fig B , p=0.0002). Finally, lung or breast cancer cells were inoculated into the hind limb or mammary pad 10 days before or after MI. Tumor growth was monitored by serial ultrasound examinations. While MI stimulated tumor growth, EV inhibition by GW4869 markedly attenuated this effect ( Fig C ). Conclusions: We show, for the first time, that cMSCs from the infarcted and remodeling heart secret EVs that target tumor cells and facilitate tumor growth. We propose cEVs as potential mediators and therapeutic targets in patients with concomitant heart disease and cancer.

Inflammation and fibrosis limit the reparative properties of human mesenchymal stromal cells (hMSCs). We hypothesized that disrupting the toll-like receptor 4 (TLR4) gene would switch hMSCs toward a reparative phenotype and improve the outcome of cell therapy for infarct repair. We developed and optimized an improved electroporation protocol for CRISPR-Cas9 gene editing. This protocol achieved a 68% success rate when applied to isolated hMSCs from the heart and epicardial fat of patients with ischemic heart disease. While cell editing lowered TLR4 expression in hMSCs, it did not affect classical markers of hMSCs, proliferation, and migration rate. Protein mass spectrometry analysis revealed that edited cells secreted fewer proteins involved in inflammation. Analysis of biological processes revealed that TLR4 editing reduced processes linked to inflammation and extracellular organization. Furthermore, edited cells expressed less NF-ƙB and secreted lower amounts of extracellular vesicles and pro-inflammatory and pro-fibrotic cytokines than unedited hMSCs. Cell therapy with both edited and unedited hMSCs improved survival, left ventricular remodeling, and cardiac function after myocardial infarction (MI) in mice. Postmortem histologic analysis revealed clusters of edited cells that survived in the scar tissue 28 days after MI. Morphometric analysis showed that implantation of edited cells increased the area of myocardial islands in the scar tissue, reduced the occurrence of transmural scar, increased scar thickness, and decreased expansion index. We show, for the first time, that CRISPR-Cas9-based disruption of the TLR4-gene reduces pro-inflammatory polarization of hMSCs and improves infarct healing and remodeling in mice. Our results provide a new approach to improving the outcomes of cell therapy for cardiovascular diseases.

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 ( Fig. A-C ). Significantly, eFat specimens from AF pts secreted greater amounts of EVs compared with patients w/o AF ( Fig. D ). 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 ( Fig. E-H ). Notably, EV cytokines reflected the inflammatory and fibrotic status of eFat in AF pts better than free cytokines ( Fig. I-L ). 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 ( Fig. M ). 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. ( Fig. N ). 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.

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