BACKGROUND:Identification of prognostic gene expression markers from clinical cohorts might help to better understand disease etiology. A set of potentially important markers can be automatically selected when linking gene expression covariates to a clinical endpoint by multivariable regression models and regularized parameter estimation. However, this is hampered by instability due to selection from many measurements. Stability can be assessed by resampling techniques, which might guide modeling decisions, such as choice of the model class or the specific endpoint definition.METHODS:We specifically propose a strategy for judging the impact of different endpoint definitions, endpoint updates, different approaches for marker selection, and exclusion of outliers. This strategy is illustrated for a study with end-stage renal disease patients, who experience a yearly mortality of more than 20 %, with almost 50 % sudden cardiac death or myocardial infarction. The underlying etiology is poorly understood, and we specifically point out how our strategy can help to identify novel prognostic markers and targets for therapeutic interventions.RESULTS:For markers such as the potentially prognostic platelet glycoprotein IIb, the endpoint definition, in combination with the signature building approach is seen to have the largest impact. Removal of outliers, as identified by the proposed strategy, is also seen to considerably improve stability.CONCLUSIONS:As the proposed strategy allowed us to precisely quantify the impact of modeling choices on the stability of marker identification, we suggest routine use also in other applications to prevent analysis-specific results, which are unstable, i.e. not reproducible.

BACKGROUND ABO-incompatible kidney transplantation (ABOi KTx) expands the living donor transplantation options. However, long-term outcome data, especially in comparison with ABO-compatible kidney transplantation (ABOc KTx), remain limited. Since the first ABOi KTx in Germany on 1 April 2004 at our centre, we have followed 100 ABOi KTx over up to 10 years. METHODS One hundred ABOi KTx and 248 ABOc KTx from 1 April 2004 until 28 October 2014 were analysed in this observational, single-centre study. Three ABOi KTx and 141 ABOc KTx were excluded because of cyclosporine A-based immunosuppression, and 1 ABOc KTx was lost to follow-up. RESULTS Median estimated 10-year patient and graft survival in ABOi KTx was 99 and 94%, respectively, and surpassed ABOc-KTx patient and graft survival of 80 and 88%, respectively. The incidence rate of antibody-mediated rejections was 10 and 8%, and that of T-cell-mediated rejections was 17 and 20% in ABOi KTx and ABOc KTx, respectively. Infectious and malignant complications in ABOi KTx were not more common than in ABOc KTx. However, postoperative lymphoceles occurred more frequently in ABOi KTx. Subgroup analysis of ABOi-KTx patients revealed that patients with high-titre isohaemagglutinins before transplantation had equal long-term results compared with low-titre isohaemagglutinin patients. CONCLUSION Taken together, long-term outcome of ABOi KTx is not inferior to ABOc KTx. Incidences of rejection episodes, infectious complications and malignancies are not increased, despite the more vigorous immunosuppression in ABOi KTx. Our data provide further evidence that ABOi KTx with living donation is a safe, successful and reasonable option to reduce the organ shortage.

Pulmonary hypertension (PH) occurs in end-stage renal disease (ESRD) patients on long-term haemodialysis (HD) using an arterio-venous (A-V) access and can be attenuated by either kidney transplantation per se or surgical fistula ligation/revision. We report an exceptional case with severe PH after kidney transplantation due to ESRD and prior chronic intermittent HD via a patent A-V fistula. Gold-standard right heart catheterization findings have-for the first time-proven that following surgical shunt ligation of the A-V fistula, haemodynamics normalized completely in this patient.

We report on the case of an ABO-incompatible renal re-transplant recipient maintained on an intensified immunosuppressive regimen for recurrent cellular rejection episodes and transplant glomerulopathy who presented with rapidly growing hepatic tumors, radiologically suggestive of hemangiosarcoma. Upon resection and pathological work-up, the lesions revealed alveolar echinococcosis, a rare but potentially life-threatening parasitosis. Usually infection with Echinococcus multilocularis remains asymptomatic for extended periods of time and can go unrecognized for years. In the case presented, we observed an atypically rapid growth pattern of E. multilocularis that might have been due to the extent of the immunosuppressive regimen, which included repetitive anti-CD20 treatments. Retrospectively performed serological studies with enzyme-linked immunosorbent assays known to provide high sensitivity and specificity for the detection of echinococcosis in the general population, yielded ambiguous results in our immunocompromised host, which could be, in part, explained by B-cell depletion and its effects on antibody production and indirect actions on cellular immunity. In conclusion, this is the first report to our knowledge of hepatic alveolar echinococcosis in a renal transplant recipient. This case documents an altered clinical course of the parasitosis and the challenge of serological diagnostic tools under an intensified regimen of immunosuppressive agents, including rituximab.

BACKGROUND:ABO-incompatible living donor kidney transplantation based on specific conditioning has been successfully adopted by transplant centres worldwide. Excellent short-term results have been reported in small cohorts. However, long-term data and comparative analyses are still sparse. We report on the outcome of 40 consecutive ABO-incompatible living donor kidney transplant recipients and compare their clinical course to a control group of 43 ABO-compatible living donor transplant patients transplanted during the same time period.METHODS:This is an observational single-centre analysis of 40 consecutive patients undergoing ABO-incompatible kidney grafting between April 2004 and April 2009, using a protocol of rituximab, antigen-specific immunoadsorption, intravenous immunoglobulin, basiliximab induction and oral triple immunosuppression with tacrolimus, mycophenolic acid and prednisone. Forty-three ABO-compatible kidney transplant recipients served as controls. The control group had also received basiliximab induction and an identical initial maintenance immunosuppression. The two groups were observed for an average of 39 and 19 months, respectively.RESULTS:There was a significantly higher incidence of lymphoceles requiring surgical revisions in the ABO-incompatible group. However, this surgical complication did not affect patient or graft survival. Mean serum creatinine, estimated glomerular filtration rate and proteinuria did not differ between the two groups. Furthermore, ABO-incompatible and ABO-compatible patients had the same incidence of humoral and cellular rejections. Despite a more aggressive induction therapy, no differences in infectious or malignant complications were observed.CONCLUSIONS:ABO-incompatible living donor kidney transplantation utilizing a combination of rituximab and antigen-specific immunoadsorption yielded results identical to ABO-compatible transplantation despite a significantly higher number of human leukocyte antigen mismatches.

Pisarski, P.; Drognitz, O.; Neef, H.; Geyer, M.; Fischer, K.; Hopt, U. T. Author Information

Potassium and angiotensin II are the main stimulators of aldosterone secretion from the adrenal cortex. As potassium-induced in vivo gene regulation in the adrenal cortex has not been studied in detail, we applied a stepwise screening approach: first, we investigated the effects of chronic potassium substitution in mice. Microarray analysis of adrenal glands revealed a set of genes (set A) that were counter-regulated in a high potassium (HP) and low potassium substitution group, while others (set B) were highly upregulated in the HP intake group. In a second step, time dependency of expression changes of these pre-defined genes was studied following short-term potassium stimulation experiments in vivo. Thirdly, dose dependency of potassium-induced gene regulation was investigated in vitro. Finally, to provide indirect evidence for the potential relevance of the detected changes for autonomous aldosterone secretion, expression analysis of aldosterone-producing adenomas was compared with normal adrenal glands. While most investigated genes were similarly regulated following long- and short-term potassium stimulation in vivo, observed changes were reproducible in NCI h295R adrenocortical cells mostly for the set of genes identified in the HP group (set B). Similarly, in Conn's adenomas, mostly genes from set B displayed changes in expression pattern in comparison to normal adrenal glands, while genes from set A were mostly unchanged. Thus, while in vivo models can help in identifying genes potentially involved in potassium-dependent aldosterone secretion, these findings also underline the necessity to interpret potassium-induced gene regulation on the basis of the experimental setting.

Autosomal dominant polycystic kidney disease (ADPKD) is a common hereditary disease associated with progressive renal failure. Although cyst growth and compression of surrounding tissue may account for some loss of renal tissue, the other factors contributing to the progressive renal failure in patients with ADPKD are incompletely understood. Here, we report that secreted frizzled-related protein 4 (sFRP4) is upregulated in human ADPKD and in four different animal models of PKD, suggesting that sFRP4 expression is triggered by a common mechanism that underlies cyst formation. Cyst fluid from ADPKD kidneys activated the sFRP4 promoter and induced production of sFRP4 protein in renal tubular epithelial cell lines. Antagonism of the vasopressin 2 receptor blocked both promoter activity and tubular sFRP4 expression. In addition, sFRP4 selectively influenced members of the canonical Wnt signaling cascade and promoted cystogenesis of the zebrafish pronephros. sFRP4 was detected in the urine of both patients and animals with PKD, suggesting that sFRP4 may be a potential biomarker for monitoring the progression of ADPKD. Taken together, these observations suggest a potential role for SFRP4 in the pathogenesis of ADPKD.

Background. Optimal treatment of polyomavirus-induced allograft nephropathy (PVAN) with immunosuppressive and antiviral therapy is uncertain at present. Reduced immunosuppression is accompanied by increased risk of rejection, and antiviral agents are nephrotoxic. Leflunomide has immunosuppressive and antiviral properties and may be an alternative treatment agent. We report a two-center experience with use of leflunomide for treatment of PVAN.Patients and Methods. Thirteen renal allograft recipients were diagnosed with biopsy-proven PVAN. Treatment consisted of lowering the calcineurin-inhibitor trough level, discontinuing mycophenolate mofetil therapy, and initiating leflunomide therapy. In 8 of the 13 patients, the serum concentration of the leflunomide active metabolite A771726 was monitored.Results. Exchange of mycophenolate mofetil with leflunomide in patients with PVAN was well tolerated and safe, with no serious adverse effects or episodes of graft rejection. Mean follow-up after transplantation was 717 days, and after initiation of leflunomide therapy was 465 days. With the modified therapy, 12 patients cleared the virus at a mean of 109 days. One graft was lost due to refractory rejection accompanied by a decreasing viral load. In the other 12 patients, graft function stabilized or improved (mean [median] creatinine concentration at diagnosis, 2.39 [2.5] mg/mL, vs 2.27 [2.0] mg/dL at follow-up). Leflunomide concentration did not correlate with treatment efficiency.Conclusions. Treatment of PVAN with leflunomide, a low-dose calcineurin inhibitor, and prednisone seems to reduce viral load and stabilize renal graft function without increasing the risk of rejection. Even low serum concentrations of leflunomide support viral elimination and prevention of graft rejection.

Several protocols have been developed to effectively overcome the blood group barrier in renal transplantation. In the evolution of these protocols, one of the latest steps was the combination of anti-CD20 treatment with antigen-specific immunoadsorptions. Over the last years we have learned that these relatively new protocols carry very promising short-term and intermediate-term results which compare favorably to the outcome of ABO-compatible living donor transplantations. Latest reports suggest that combining immunoadsorptions with rituximab does not result in an increased risk of infectious complications or tumors in the first years after transplantation compared to ABO-compatible living donor transplanta-tions. We recently demonstrated that a majority of patients with isoagglutinin titers >1:128 can be safely transplanted using rituximab and immunoadsorptions without an added risk of early antibody-mediated rejections. We have also shown that a cost saving ‘on-demand strat-egy’ of postoperative immunoadsorptions based on careful titer monitoring can be used as an alternative to preemptively scheduled immunoadsorptions. Although rituximab and antigen-specific immunoadsorptions are significantly less invasive than splenectomy and plasma-pheresis, long-term follow-up of patients treated with a combination of anti-CD20 antibody and antigen-specific immunoadsorption will be needed to benchmark this therapeutic option in relation to more established protocols.

increased by 1.9% ± 0.6% (INR catheter: 2.20 ± 0.16; INR peripheral vein: 2.19 ± 0.16). These results clearly demonstrate that sodium citrate catheter locking minimally interferes with INR measurements when blood is drawn directly from the catheter prior to dialysis treatment. They also demonstrate that the overestimation of INR with heparin locking is more frequent than reported by Grudzinski et al. [1]. Hence, the use of citrate catheter locking improves INR measurement reliability and thus facilitates the management of anticoagulation in HD patients.

Renal dopamine receptors have been shown to play a critical role in ROS-dependent hypertension. D5 dopamine receptor deficient (D5-/-) mice are hypertensive and have increased systemic oxidative stress which is manifested in the kidney and the brain. To further investigate the underlying mechanisms of hypertension in D5-/- mice, we used RNA arrays to compare mRNA levels of kidneys from wildtype and D5-/- mice. Our data show, that the mRNA level of alpha/beta hydrolase 1 (ABHD1) is significantly upregulated in D5-/- mice. Additionally, overexpression of ABHD1 in a new established renal proximal tubule cell line reduced the amount of O(2)(-) produced by the NADPH oxidase. Therefore the upregulation of ABHD1 in D5-/- mice could be an answer to the increased oxidative stress. While oxidative stress is an important factor for the development of hypertension, ABHD1 could play a protective role in the pathogenesis of hypertension.

Several standard protocols for ABO-incompatible kidney transplantation use scheduled preemptive antigen-specific immunoadsorption during the postoperative period. Our center has developed a different approach. Our patients undergo antigen-specific immunoadsorption postoperatively only if their isoagglutinine titers (immunoglobulin G anti-A/B) exceed 1:8 in the first postoperative week and 1:16 in the second postoperative week. Using this strategy, 22 ABO-incompatible kidney transplantations have been performed at our center since 2004. Only 32% of these patients (7 of 22) needed to undergo postoperative immunoadsorption (mean 4.1 immunoadsorption sessions per patient). The renal outcome in patients receiving postoperative immunoadsorption treatment versus the outcome in patients without postoperative immunoadsorption remained equal at a mean follow-up of 17 months. We identified a shorter pretransplant time on dialysis, a blood type constellation of donor A1/recipient O, and high initial starting titers as predictors for the need for postoperative immunoadsorption treatment. A more detailed version of this study, with modified tables and figures, has been accepted for publication in Nephrology Dialysis Transplantation.

Background. Since 2001, approximately 100 ABO-incompatible kidney transplantations have been performed in Europe. The standard protocol, employed by most transplant centres, uses rituximab and scheduled pre-emptive antigen-specific immunoadsorption on post-operative days 3, 6 and 9.Methods. Our centre has performed 22 ABO-incompatible kidney transplantations since 2004, using a different approach; like in Sweden, all patients received immunoadsorptions preoperatively, but instead of scheduling pre-emptive post-transplant immunoadsorptions, we submitted patients to immunoadsorptions post-operatively only, if their isoagglutinine titers ( IgG-Anti-A or -B) exceeded certain thresholds. These thresholds were greater than 1 : 8 in the first post-operative week and greater than 1 : 16 in the second post-operative week, respectively.Results. A shorter pre-operative length on dialysis, a blood-type constellation of donor A1/recipient 0 and 9a high initial starting-titer were identified as predictors for post-operative immunoadsorptions.Conclusion. Using this on-demand strategy, our data reveal that a titer-dependent protocol reduces costs at no additional risk for the patient.