Exosomes Derived from Dialysis Patients' Serum Enhance Endothelial-Mesenchymal Transition and Calcification in Endothelial Cells.

KEY POINTS: Vascular calcification (VC) is an independent risk factor of cardiovascular disease in patients with ESKD. We found that exosomes derived from serum of dialysis patients with VC induced endothelial–mesenchymal transition and thus contribute to calcification. The complex interplay between exosomes from dialysis patients with VC and endothelial cells highlights the critical need for therapeutic strategies. BACKGROUND: Vascular calcification (VC) is prevalent among patients with ESKD. Exosomes, small extracellular vesicles actively secreted by cells, contain proteins, nucleic acids, lipids, and other bioactive substances and are considered major mediators of cell–cell interactions. Endothelial–mesenchymal transition (EndMT) has been observed in a variety of pathological conditions, such as abnormal shear stress, vascular damage, and chronic inflammation. The aim of this research was to assess the effects of serum-derived exosomes from ESKD patients with VC on the induction of EndMT in endothelial cells (ECs) and their potential role in accelerating VC. METHODS: Twenty patients on hemodialysis with VC and ten healthy volunteers were recruited. Cardiac and brain VCs were assessed among patients with ESKD treated with dialysis. Serum samples were obtained at dialysis initiation for exosome isolation. Human umbilical vein ECs were treated with 100 µg/ml exosomes for 24–96 hours. At the end of incubation, cells were collected for mRNA and protein analysis. RESULTS: Exosomes isolated from dialysis patients with VC induced EndMT in human umbilical vein ECs. After 24 hours, endothelial markers CD31 and vascular endothelial-cadherin were decreased (31% and 51%, respectively; P < 0.001) and the mesenchymal proteins Vimentin and N-cadherin were increased (283% and 156%, respectively; P < 0.001), compared with healthy exosomes. After 96 hours of incubation, expression of genes essential for osteoblast differentiation, including the bone morphogenetic genes (BMP2, BMPR2, BMP4, and BMP9), and the transcription factor RUNX2 were significantly elevated. CONCLUSIONS: Exosomes derived from the serum of dialysis patients with VC induced EndMT and contributed to calcification. The vicious cycle highlighted the intricate interplay between exosomes, ECs, and VC, emphasizing the critical necessity for therapeutic strategies to disrupt this pathway and mitigate calcification advancement.