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

Background: Vascular calcification (VC) is prevalent among patients with end stage kidney disease (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 and their potential role in accelerating VC.

Methods: Twenty hemodialysis patients with VC and 10 healthy volunteers were recruited. Cardiac and brain VC were assessed among patients with ESKD treated with dialysis. Serum samples were taken at dialysis initiation for exosome isolation. Human umbilical vein endothelial cells (HUVEC) 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 HUVECs. After 24h, endothelial markers CD31 and VE-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 to healthy exosomes. After 96h 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, EC and VC, emphasizing the critical necessity for therapeutic strategies to disrupt this pathway and mitigate calcification advancement.