MO555: Exosomes From Endothelial Cells to Smooth Muscle Cells Induce Vascular Calcification in Early Chronic Kidney Disease

BACKGROUND AND AIMS Vascular calcification can occur in the early stages of chronic kidney disease (CKD) and result in a poor prognosis. How the calcification signal in the blood is transduced from endothelial cells in the tunica intima to vascular smooth muscle cells in the tunica media in the early stages of CKD is still unknown. The aim of this study was to explore the role of exosomes in signal transduction in vascular calcification. METHOD Exosomes were isolated from normal phosphate- and high phosphate-stimulated human umbilical vein endothelial cells (HUVECs) by superspeed centrifugation. We used transmission electron microscopy, molecular size analysis and Western blot analysis of exosome markers to identify exosomes (Figure 1). VSMC calcification was assessed by Alizarin Red Staining and Western blot. Proteomics analysis and miRNA microarray analysis were carried out to detect the differences in exosomal proteins and miRNAs. The results were analysed via Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. RESULTS Fluorescence microscopy verified that VSMCs took up exosomes from HUVECs. Exosomes isolated from high phosphate-stimulated HUVECs (HP-HUVEC-exos) induced VSMC calcification (assessed by Alizarin Red Staining), increased osteopontin expression and increased alkaline phosphatase activity (Figure 2). Proteomics analysis showed different protein expressions including STAT1, STAT3, HDAC1, PARP1, WDR5 et al. MiRNA microarray analysis showed different miRNA levels including miR-223–3p, miR-6776–5p, miR-6851–5p, miR-2116–3p, miR-6849–5p et al. (Figure 3). Target GO analysis showed that both miRNA and protein difference focused on some biological processes (RNA splicing, mRNA processing, RNA targeting), molecular function (cadherin binding, cell adhesion molecule binding, ubiquitin-like protein ligase binding) and cellular component (focal adhesion, cell-substrate junction, spliceosomal complex). KEGG analysis revealed that both miRNA and protein differences were focused on pathways associated with the cell cycle, virus infection and protein processing in the endoplasmic reticulum. CONCLUSION Exosome-mediated miRNA and protein transfer from endothelial cells to VSMCs may induce vascular calcification via RNA processing, protein processing and cell adhesion.