P1052EXPANDED HEMODIALYSIS (HDX) DOES NOT AFFECT EPIGENETIC INTERCELLULAR SIGNALS INVOLVED IN INFLAMMATION AND CARDIOVASCULAR DISEASE
Authors: Vida Carmen , Alique Matilde , De Sequera Ortiz Patricia , Bodega Guillermo , Oliva Carlos , Carracedo Julia , Ramírez Chamond Manuel 
Published: June 2020

Abstract

Background and Aims
Epigenetic signals play a principal role in homeostasis, but also may promote diseases including cardiovascular diseases (CVDs) when are altered. Extracellular vesicles (EVs) or plasma circulating DNA and RNA may have relevant functions in both physiological and pathophysiological contexts related to the epigenetic intercellular communication. Thus, changes in the endothelial or platelet EVs, or the plasma circulating methylated DNA may contribute to the chronic inflammation and the subsequent CVDs in chronic kidney disease patients, particularly when are in hemodialysis (HD). Dialysis membranes do not usually allow the passage of molecules larger than 30-40 kDa. However, the new system of expanded hemodialysis (HDx) with a medium-cut-off membrane (MCO), due to its characteristics, could alter the plasma content of these EVs and DNA methylation, and thereby, promote the development of CVDs. Therefore, our study evaluates whether global plasma DNA methylation and EVs content are modified during an HDx session.

Method
For this study, we selected 12 dialysis patients: HDx patients (n=6; dialyzed with MCO) and control group (n=6; dialyzed with other HD membranes). Before and after a dialysis session, plasma samples were obtained. EVs were isolated by ultracentrifugation, and the total number of EVs and platelet and endothelial-derived EVs were characterized and quantified by flow cytometry. RNA and DNA extraction and quantification were carried out using different kits and NanoDrop spectrophotometer. DNA methylation was assessed with a 5-methyl cytosine (5-mC) DNA assay kit.

Results
As shown in the figure, after a dialysis session with the HDx, no significant differences were observed in the total number of EVs, as well in the number of platelet- and endothelial-derived EVs, in comparison to those observed in HDx patients before the dialysis session. By contrast, patients dialyzed with other HD membranes presented differences in the number of total EVs and platelet and endothelial EVs, which decreased significantly (p&lt;0.05) after the dialysis session. Concerning DNA methylation, no statistically significant changes in total DNA 5-mC (%) were observed in both HDx and control patients after the dialysis session. However, a slight tendency to decrease methylated DNA was observed with the HDx compared to other HD membranes (control). Moreover, no significant changes in DNA and RNA % were observed after dialysis session in both HDx and control group.

Conclusion
To our knowledge, this is the first study to investigate the influence of the HDx technique on the content of plasma cellular EVs and DNA methylation status. HDx does not affect EVs levels, although it shows a tendency to purify plasma methylated DNA. Although this study was not designed to analyze the comparative effectiveness between different membranes, interestingly this effect in epigenetic signals was not observed with other HD membranes, where patients showed a marked reduction of EVs content. The differential activity of HDx about other HD membranes deserves further investigation.

Funding
(PI17/01029; PI19/00240; ISCIII-FEDER). Santander/UCM PR41/17-20964. Spanish Society of Nephrology 2018. UAH-GP2018-4