Removal of Cell-Activating Substances Using Dialyzers With Various Permeability Profiles.

Despite multiple efforts to target an improvement in clinical outcomes of patients with end-stage renal disease, several challenges must still be addressed. Dialysis patients are at a high risk for complications, as reflected by increasing mortality rates. The objective of this study is to assess the impact of the application of dialyzers with varying permeability profiles on the removal of cell-activating substances from the blood of hemodialysis (HD) patients. Dialysate samples were collected using Revaclear 400 (RC) and MCO-Ci400 (MCO-CI). Total protein and solute marker concentrations were determined for the concentrated sample. The response of tubular epithelial cells (TECs) to the dialysate samples was assessed via measurement of interleukin 6, cell viability, and morphology. Proteomic analysis of the dialysate samples was performed using liquid chromatography coupled to tandem mass spectrometry. Treatment of TECs with the MCO-CI dialysate resulted in significantly decreased cell viability compared with the RC dialysate. TECs incubated with samples from MCO-CI lost their typical brick-like shape and cell-cell connections. Proteomic analysis of dialysate samples indicated multiple pro-apoptotic and pro-inflammatory proteins, supporting the observed phenotype. Additionally, application of the MCO-CI dialyzer allowed for more efficient removal of proteins associated with advanced chronic kidney disease stages. Collectively, the use of dialyzer with a higher permeability profile enabled more efficient removal of cell-activating and toxic substances from the blood of HD patients. However, a further large-scale study is needed to address benefits and associated risks for patients.

In Vitro Dialysis of Cytokine-Rich Plasma With High and Medium Cut-Off Membranes Reduces Its Procalcific Activity.

Recently developed high-flux (HF) dialysis membranes with extended permeability provide better clearance of middle-sized molecules such as interleukins (ILs). Whether this modulation of inflammation influences the procalcific effects of septic plasma on vascular smooth muscle cells (VSMCs) is not known. To assess the effects of high cut-off (HCO) and medium cut-off (MCO) membranes on microinflammation and in vitro vascular calcification we developed a miniature dialysis model. Plasma samples from lipopolysaccharide-spiked blood were dialyzed with HF, HCO, and MCO membranes in an in vitro miniature dialysis model. Afterwards, IL-6 concentrations were determined in dialysate and plasma. Calcifying VSMCs were incubated with dialyzed plasma samples and vascular calcification was assessed. Osteopontin (OPN) and matrix Gla protein (MGP) were measured in VSMC supernatants. IL-6 plasma concentrations were markedly lower with HCO and MCO dialysis. VSMC calcification was significantly lower after incubation with MCO- and HCO-serum compared to HF plasma. MGP and OPN levels in supernatants were significantly lower in the MCO but not in the HCO group compared to HF. In vitro dialysis of cytokine-enriched plasma samples with MCO and HCO membranes reduces IL-6 levels. The induction of vascular calcification by cytokine-enriched plasma is reduced after HCO and MCO dialysis.

In vitro benchmark of cytokine removal by dialyzers with various permeability profiles.

PURPOSE: Removal of cytokines is relevant for dialysis patients as they are suspected to promote cardiovascular complications. The objective of this study was to benchmark membranes with different permeability profiles under standardized in vitro test conditions using miniaturized devices with respect to their ability to remove cytokines from human serum and to lower cell activating potential. METHODS: In vitro dialysis was used to dialyze cytokine enriched serum in 3 independent experiments per tested membrane. IL-6 in the serum and dialysate was measured at defined times by enzyme-linked immunosorbent assay. IL-8, IL-1ß, IL-6 and TNF-α in dialysate were measured by immunoassay. Dialysate samples were subjected to cultured tubular epithelial cells or human fibroblasts to study cell activation via IL-6 generation. Dialysate samples were added to human whole blood with subsequent analysis of granulocyte and monocyte activation by detection of CD11b. RESULTS: IL-6 decreased in serum and increased in dialysate during in vitro dialysis. IL-8, IL-1ß, and TNF-α were identified in dialysate. Dialysate added to cell cultures increased IL-6 concentration in culture medium or increased expression of CD11b. High cut-off membranes showed the strongest transfer of cytokines, albumin and total proteins from serum to dialysate and led to strongest cell activation. This effect was lower for medium cut-off membranes and lowest for conventional high-flux membranes. CONCLUSIONS: This study demonstrated an in vitro test by which membranes were benchmarked with respect to cytokine and cell activation removal capacity. Cell activation levels could be influenced by the choice of membrane by altering cytokine concentration levels.

Looking beyond endotoxin: a comparative study of pyrogen retention by ultrafilters used for the preparation of sterile dialyis fluid.

Sterile single-use ultrafilters are used in dialysis for the preparation of the substitution fluid given to patients undergoing dialysis treatments with high convective fluid removal. The retention of pyrogenic agents by the ultrafilters is crucial to avoiding inflammatory responses. The performance of a new single-use ultrafilter (NUF) with a positively charged flat sheet membrane of relatively small membrane area and large pore size was compared to a reference ultrafilter (RUF) with a hollow fiber membrane. Filter performance was tested with various pyrogen-contaminated dialysis fluids by direct pyrogen quantification and by measuring inflammatory responses in cell-based bioassays. The NUF completely retained oligodeoxynucleotides (ODN), whereas the RUF was fully permeable. Both filters tended to decrease biological activity of DNA in filtered bacterial lysates. The NUF reduced lipopolysaccharides (LPS) and LPS-induced biological activity by 100%, whereas the RUF produced filtrates with low but detectable levels of LPS in most cases. Peptidoglycans (PGN) were fully retained both by the NUF and the RUF. The new ultrafilter retained biologically active ODN, which has not yet been described for any other device used in dialysis, and it showed better or equal retention of LPS and PGN even with a smaller membrane surface and larger pore size.