Markus Storr

Efficient Removal of Immunoglobulin Free Light Chains by Hemodialysis for Multiple Myeloma: In Vitro and In Vivo Studies

Of patients with newly diagnosed multiple myeloma, approximately 10% have dialysis-dependent acute renal failure, with cast nephropathy, caused by monoclonal free light chains (FLC). Of these, 80 to 90% require long-term renal replacement therapy. Early treatment by plasma exchange reduces serum FLC concentrations, but randomized, controlled trials have shown no evidence of renal recovery. This outcome can be explained by the low efficiency of the procedure. A model of FLC production, distribution, and metabolism in patients with myeloma indicated that plasma exchange might remove only 25% of the total amount during a 3-wk period. For increasing FLC removal, extended hemodialysis with a protein-leaking dialyzer was used. In vitro studies indicated that the Gambro HCO 1100 dialyzer was the most efficient of seven tested. Model calculations suggested that it might remove 90% of FLC during 3 wk. This dialyzer then was evaluated in eight patients with myeloma and renal failure. Serum FLC reduced by 35 to 70% within 2 hr, but reduction rates slowed as extravascular re-equilibration occurred. FLC concentrations rebounded on successive days unless chemotherapy was effective. Five additional patients with acute renal failure that was caused by cast nephropathy then were treated aggressively, and three became dialysis independent. A total of 1.7 kg of FLC was removed from one patient during 6 wk. Extended hemodialysis with the Gambro HCO 1100 dialyzer allowed continuous, safe removal of FLC in large amounts. Proof of clinical value now will require larger studies.

Serum Free‐Light Chain Removal by High Cutoff Hemodialysis: Optimizing Removal and Supportive Care

In multiple myeloma the predominant cause of irreversible renal failure is cast nephropathy, secondary to excess kappa or lambda serum free light chains (FLCs). These molecules are efficiently cleared by hemodialysis (HD) using the Gambro HCO 1100 dialyzer. To optimize the removal of FLCs by this dialyzer we have studied the effect of dialyzers in series, dialyzer change, and hemodiafiltration in 14 patients with multiple myeloma and renal failure. The clearance rates of both kappa FLCs and lambda FLCs were significantly increased on two dialyzers from 19 (7.3-34)-15.3 (9-28) mL/min to 47 (17-79)-35.5 (20-57) mL/min, respectively. Clearance rates of both FLCs decreased over the course of the dialysis sessions (both P < 0.001). Changing the dialyzer during a HD session increased lambda FLC clearance rates (22.5 [6-41] to 37.6 [9-52] mL/min; P < 0.001) and decreased kappa FLC clearance rates (39.6 [9-72] to 19 [8-59] mL/min; P < 0.003). Ultrafiltration during HD increased the clearance rates of kappa FLCs (R 0.52, P < 0.01) but not lambda FLCs (R -0.25; P < 0.076). Hemodiafiltration increased the clearance rates of both kappa (19 [SD 6.8] to 32 [SD 9.8] mL/min) and lambda FLCs (15 [SD 7.8] to 20 [SD 7.7] mL/min). Albumin replacement requirements for 8 h of HD increased from 12 g for a single dialyzer to 45 g for two dialyzers in series (P < 0.001). Different protocols are required to optimize the removal of kappa and lambda FLCs in patients with myeloma and renal failure.

Extended characterization of a new class of membranes for blood purification: The high cut-off membranes

High cut-off membranes are a new class of blood purification membranes whose particular characteristics present challenges for commonly-used characterization methods. Dextran sieving curves for representative blood purification membranes of the high-flux and high cut-off types were measured and compared to curves for the glomerular filtration barrier (GFB). The performance was also determined after blood exposure for the most permeable synthetic membranes. High cut-off membranes were observed to be more open than the GFB before blood exposure, but become tighter and more selective after the exposure, keeping the permeation for low and middle molecules while restraining the filtration of large species. Based on dextran sieving experiments for a variety of commercially available blood purification membranes, we present a novel method for classifying blood purification membranes. By using a well-established technique and introducing a new characteristic parameter for the sieving curve – the molecular weight retention onset (MWRO) – a graph of molecular weight cut-off versus molecular weight retention onset provides the landscape of dialysis membrane types. This meaningful representation is based on only one in vitro method, and allows the membrane classification by indirectly considering two structural parameters: pore size and pore size distribution. In this way, the families of low-flux, high-flux, protein leaking, and high cut-off membranes are clearly differentiated. The differentiation allows for the definition of MWCO/MWRO regions for the different types, so that further classification of newly developed membranes can be easily achieved.

MCO Membranes: Enhanced Selectivity in High-Flux Class

Novel MCO high-flux membranes for hemodialysis have been developed with optimized permeability, allowing for filtration close to that of the natural kidney. A comprehensive in vitro characterization of the membrane properties by dextran filtration is presented. The sieving profile of pristine membranes, as well as that of membranes exposed to blood for 40 minutes, are described. The effective pore size (Stokes-Einstein radius) was estimated from filtration experiments before and after blood exposure, and results were compared to hydrodynamic radii of middle and large uremic toxins and essential proteins. The results indicate that the tailored pore sizes of the MCO membranes promote removal of large toxins while ensuring the retention of albumin.

High cut-off dialysis in chronic haemodialysis patients

Haemodialysis patients suffer from chronic systemic inflammation and high incidence of cardiovascular disease. One cause for this may be the failure of diseased kidneys to eliminate immune mediators. Current haemodialysis treatment achieves insufficient elimination of proteins in the molecular weight range 15–45 kD. Thus, high cut‐off dialysis might improve the inflammatory state.

Medium Cut-Off (MCO) Membranes Reduce Inflammation in Chronic Dialysis Patients—A Randomized Controlled Clinical Trial

Background To increase the removal of middle-sized uremic toxins a new membrane with enhanced permeability and selectivity, called Medium Cut-Off membrane (MCO-Ci) has been developed that at the same time ensures the retention of albumin. Because many middle-sized substances may contribute to micro-inflammation we hypothesized that the use of MCO-Ci influences the inflammatory state in hemodialysis patients. Methods The randomized crossover trial in 48 patients compared MCO-Ci dialysis to High-flux dialysis of 4 weeks duration each plus 8 weeks extension phase. Primary endpoint was the gene expression of TNF-α and IL-6 in peripheral blood mononuclear cells (PBMCs), secondary endpoints were plasma levels of specified inflammatory mediators and cytokines. Results After four weeks of MCO-Ci the expression of TNF-α mRNA (Relative quantification (RQ) from 0.92 ± 0.34 to 0.75 ± 0.31, -18.5%, p<0.001)-α and IL-6 mRNA (RQ from 0.78 ± 0.80 to 0.60 ± 0.43, -23.1%, p<0.01) was reduced to a significantly greater extent than with High-flux dialyzers (TNF mRNA-RQ: -14.3%; IL-6 mRNA-RQ: -3.5%). After retransformation of logarithmically transformed data, measurements after MCO were reduced to 82% of those after HF (95% CI 74%–91%). 4 weeks use of MCO-Ci resulted in long-lasting change in plasma levels of several cytokines and other substances with a significant decrease for sTNFR1, kappa and lambda free light chains, urea and an increase for Lp-PLA2 (PLA2G7) compared to High-flux. Albumin levels dropped significantly after 4 weeks of MCO dialysis but increased after additional 8 weeks of MCO dialysis. Twelve weeks treatment with MCO-Ci was well tolerated regarding the number of (S)AEs. In the extension period levels of CRP, TNF-α-mRNA and IL-6 mRNA remained stable in High-flux as well as in MCO-Ci. Conclusions MCO-Ci dialyzers modulate inflammation in chronic HD patients to a greater extent compared to High-flux dialyzers. Transcription of pro-inflammatory cytokines in peripheral leukocytes is markedly reduced and removal of soluble mediators is enhanced with MCO dialysis. Serum albumin concentrations stabilize after an initial drop. These results encourage further trials with longer treatment periods and clinical endpoints.

Randomized controlled pilot study of 2 weeks' treatment with high cutoff membrane for hemodialysis patients with elevated C-reactive protein.

Chronic inflammation in hemodialysis (HD) patients is associated with cardiovascular complications and mortality. Circulating immune active proteins in the molecular range 15-45 kD that cannot be efficiently cleared by high-flux (HF) dialysis may be causally involved. We intended to test the feasibility of using a high cutoff (HCO) dialyzer in chronic HD patients and its influence on inflammation and monocyte activation. The Gambro HCO1100 dialyzer was compared to a conventional HF membrane in a randomized double-blind crossover trial in 19 chronic HD patients selected for the presence of elevated serum C-reactive protein levels. Patients were treated for six consecutive dialysis sessions (2 weeks) with each membrane. Safety analysis recorded adverse events and albumin losses through the protein-leaking membranes. Efficacy analysis observed reductions in the number of proinflammatory (CD14+CD16+) monocyte subpopulations in circulating blood. Treatment with the HCO membrane was well tolerated, although the number of adverse events was slightly higher. Despite significant serum albumin loss (from 34.1 ± 2.7 to 29.6 ± 3.0 g/L; P < 0.01), there was no need to supplement albumin, and rising activity of cholinesterase during HCO treatment indicated compensation by enhanced hepatic synthesis. The HCO membrane cleared high amounts of proinflammatory cytokines, but did not reduce predialysis inflammatory monocytes and markers. Although the time of HD session was extended, the study was hampered by a lower Kt/V in the HCO compared to the HF period. Treatment of chronic HD patients with this HCO dialyzer for 2 weeks is tolerable in terms of albumin loss and able to clear proinflammatory cytokines; however, this was not sufficient to decrease monocyte activation. Therefore, a more selective, less albumin-leaking membrane is desirable to allow prolonged high-efficient dialysis with more effective cytokine clearance.

Beta2-microglobulin removal and plasma albumin levels with high cut-off hemodialysis.

Purpose. β2-microglobulin (β2MG) is pivotal to the pathogenesis of dialysis-related amyloidosis. We compared the effects of high cut-off hemodialysis (HCO-HD) with those of standard high-flux hemodialysis (HF-HD) regarding the concentration and clearance of β2MG and albumin. Design. We enrolled ten patients with acute renal failure in a double-blind, cross-over, randomized controlled trial. Procedures Each patient received four hours of HCO-HD (estimated in vivo cutoff 50–60 kDa) and four hours of HF-HD (estimated in vivo cutoff 15–20 kDa) in random order. Statistical methods and outcome measures: As data lacked normal distribution, we used non-parametric statistical analysis. Plasma and dialysate concentrations of β2MG and albumin were measured at baseline and after four hours of each study treatment. Main findings. We found significantly greater diffusive β2MG clearances for HCO-HD compared to HF-HD (at the start: 71.8 ml/min vs. 5.1 ml/min; P=0.008 and at the end: 68.8 ml/min vs. 5.7 ml/min; P=0.008). We found a reduction in plasma β2MG concentrations of -31.6% during HCO-HD compared to an increase by 25.7% during HF-HD; P=0.008. At baseline (HCO-HD: 26.0 g/L vs. HF-HD: 26.5 g/L), and at the end of both treatments, plasma albumin concentrations were comparable (HCO-HD: 25.5 g/L vs. HF-HD: 26.5 g/L; P=0.25). During HCO-HD, albumin clearance was 1.9 ml/min at the start and decreased significantly to 0.8 ml/min at the end; P=0.008. HF-HD had an albumin clearance of 0.01 ml/min. Conclusions. HCO-HD was more effective in decreasing plasma β2MG concentrations than standard HF-HD and did not reduce plasma albumin levels. Further studies of HCO-HD in the treatment of dialysis-related β2MG accumulation appear warranted. (ClinicalTrials.gov number, NCT00333593 [ClinicalTrials.gov]) (Int J Artif Organs 2007; 30: 385–92)

Combination of bortezomib-based chemotherapy and extracorporeal free light chain removal for treating cast nephropathy in multiple myeloma

Besides amyloidosis and light chain deposition disease, the most common histological type of renal lesion is cast nephropathy in 30% of patients with multiple myeloma [2]. In contrast to amyloidosis, cast nephropathy is believed to be potentially reversible when circulating light chains are rapidly reduced. We report on three patients with multiple myeloma and cast nephropathy treated with a bortezomib-based chemotherapy in addition to a newly developed high-cutoff polyflux® haemofilter. Reduction in serum free light chain levels was achieved within 10–12 days, with all three patients improving their renal function.

High cut-off dialysis in chronic haemodialysis patients reduces serum procalcific activity

BACKGROUND Vascular calcification is enhanced in chronic dialysis patients, possibly due to the insufficient removal of various intermediate molecular weight uraemic toxins such as interleukins with conventional membranes. In this study, we assessed the modulation of in vitro vascular calcification with the use of high cut-off (HCO) membranes in chronic dialysis patients. METHODS In a PERCI trial, 43 chronic dialysis patients were treated with conventional high-flux and HCO filters for 3 weeks in a randomized order following a 2-period crossover design. After each phase, serum predialysis samples were drawn. Calcifying human coronary vascular smooth muscle cells (VSMCs) were incubated with the patients serum samples. Calcification was assessed with alkaline phosphatase (ALP) and alizarin red staining. In the clinical trial, HCO dialysis reduced the serum levels of the soluble tumour necrosis factor receptor (sTNFR) 1 and 2, vascular cell adhesion molecule 1 (VCAM-1) and soluble interleukin-2 receptor (sIL2R). We therefore investigated the in vitro effects of these mediators on vascular calcification. RESULTS VSMCs incubated with HCO dialysis serum showed a 26% reduction of ALP with HCO serum compared with high-flux serum. Alizarin was 43% lower after incubation with the HCO serum compared with the high-flux serum. While sIL2R and sTNFR 1 and 2 showed no effects on VSMC calcification, VCAM-1 caused a dose-dependent enhancement of calcification. CONCLUSIONS The use of HCO dialysis membranes in chronic dialysis patients reduces the procalcific effects of serum on VSMC in vitro. The mechanisms of the strong effect of HCO on in vitro calcification are not completely understood. One factor may be lower levels of VCAM-1 in HCO serum samples, since VCAM-1 was able to induce vascular calcification in our experiments. Neither sTNFR 1, sTNFR 2 nor sIL2R enhance vascular calcification in vitro. Regardless of the mechanisms, our results encourage further studies of highly permeable filters in chronic dialysis patients.