Circulating Extracellular Vesicles as Mediators of Impaired Angiogenesis in Pediatric CKD

Background: Patients with chronic kidney disease (CKD) suffer from high morbidity and mortality due to cardiovascular disease (CVD). Nonetheless, underlying mechanisms of CVD in CKD remain elusive. Extracellular vesicles (EVs) have lately been identified as facilitators of inter-organ communication and EVs of endothelial origin (EC-EVs) have been linked to CVD development. We hypothesized that altered EV release and cargo mediate CVD development in CKD. Methods: 94 children with different CKD stages (before or on dialysis, after kidney transplantation and age-matched healthy donors), were enrolled in this study, yielding analyses on plasma EV phenotype in the absence of age-related comorbidities. The impact of CKD EVs on CVD processes was analyzed in vitro on transcriptomic and functional level. Results: Concentrations of EC-EVs were increased in hemodialysis patients and decreased after kidney transplantation. According to small RNA sequencing, CKD EVs had lower abundance of 30 specific microRNAs, which were predicted to affect angiogenesis and smooth muscle cell proliferation. In vitro, CKD EVs altered the transcriptome of aortic endothelial cells, with most differentially enriched genes implicated in angiogenesis pathways. CKD EVs functionally impaired angiogenic properties of umbilical vein endothelial cells, as illustrated by reduced vascular tube formation with reduced vascular density, impaired migration and lowered proliferation. The combination of high shear stress, as present in arterio-venous fistulas, and the uremic toxin indoxyl sulfate was identified as trigger of increased EV formation from venous endothelial cells, which also recapitulated EV microRNA changes observed in CKD in vivo. Conclusion: CKD leads to quantitative and compositional dysregulation in EV release. Altered EV microRNA cargo associates with detrimental effects of CKD EVs on angiogenesis, going in line with the cardiovascular phenotype of CKD patients. EVs and in particular their microRNA cargo could form promising targets for novel therapeutic strategies to fight CVD in CKD.