Background and aim: SARS-CoV-2 infection is associated with increased cardiovascular morbidity and mortality, including myocarditis. However, the mechanisms how SARS-CoV-2 enters and infects cardiomyocytes and endothelial cells remains unclear. Here, we explore the role of extracellular vesicles (EV) as mediators of communication between cardiomyocytes and endothelial cells during infection. EVs are lipid-bound vesicles released from a variety of cell types and can be found in all biological fluids. They are known for their pivotal role in transporting proteins, RNA, DNA, lipids, and metabolites between cells and organs.
Methods: We performed imaging of cardiac tissue, EVs, and serum derived from SARS-CoV-2 patients via confocal microscopy and transmission electron microscopy (TEM). Furthermore, cardiac tissue was used for a mass spectrometry protocol, specifically developed to detect oxidized cysteines in proteins (OxICAT labeling). The Gene Ontology (GO) analysis was performed to assess oxidative stress-affected pathways and cellular components. To elucidate the effects of SARS-CoV-2 patient-derived EVs on mitochondrial function, inflammatory, apoptotic, and glycolytic events, we conducted endothelial cell culture experiments. For this purpose, serum-derived EVs were isolated via polyethylene glycol precipitation and subsequent size exclusion chromatography (SEC).
Results: Our results verify the close proximity/interaction of EVs and SARS-CoV-2 components in cardiac tissue, as well as serum of infected patients. Mass spectrometry revealed a high burden of oxidative stress inside cardiac tissue, reflected by highly oxidized cysteines in various proteins involved in exosomal traffic and mitochondrial function. In addition, patient-derived EVs were able to trigger inflammatory events and reduce energy metabolism in endothelial cells.
Conclusion: Taken together, our data suggest that SARS-CoV-2 infects cardiomyocytes and endothelial cells. Extracellular vesicles (EVs) are a prominent alternative route of virus dissemination. Our results further hint at the potential of EVs to affect macroenvironment causing alterations of protein functionality and expression, enzyme activity, inflammation, and oxidative stress, ultimately causing an impairment of mitochondrial function. We propose that EVs are an important mediator of cellular stress signals and viral particles during infection, suggesting their potential to trigger severe cardiomyocyte damage and subsequent cell death.
