Johannes Donauer

Implementation of a Protocol for ABO-incompatible kidney transplantation--a three-center experience with 60 consecutive transplantations

Background. A new protocol for ABO-incompatible kidney transplantation has recently been introduced. We report here on the joint experience of the implementation in Stockholm and Uppsala, Sweden and Freiburg, Germany. Methods. The new protocol utilizes antigen-specific immunoadsorption to remove existing ABO-antibodies, rituximab, and intravenous immunoglobulin to prevent the rebound of antibodies, and conventional tacrolimus, mycophenolate-mofetil, and prednisolone immunosuppression. Sixty consecutive ABO-incompatible kidney transplantations were included in the study. The outcome is compared with the results of 274 ABO-compatible live donor transplantations performed during the same period. Results. Two of the ABO-incompatible grafts have been lost (non-compliance and death with functioning graft). All the remaining 58 grafts had good renal function at a follow-up of up to 61 months. We did not observe any late rebound of antibodies and there were no humoral rejections. Graft survival was 97% for the ABO-incompatible compared with 95% for the ABO-compatible. Patient survival was 98% in both groups. There was a significant variation in preoperative A/B-antibody titer between the centers, with a median 1:8 in Uppsala, median 1:32 in Stockholm and median 1:128 in Freiburg. More preoperative antibody adsorptions were therefore needed in Freiburg than in Stockholm and Uppsala. Conclusions. The new protocol was easily implemented and there were no graft losses that could be related to ABO-incompatibility. A significant inter-institutional variation in the measurement of anti-AB-antibodies was found, having a substantial impact on the number of immunoadsorptions and consequently on the total cost for the procedure. A standardized fluorescence-activated cell sorting technique for antibody quantification is much needed.

Gene expression profiling in polycythaemia vera: overexpression of transcription factor NF-E2

The molecular aetiology of polycythaemia vera (PV) remains unknown and the differential diagnosis between PV and secondary erythrocytosis (SE) can be challenging. Gene expression profiling can identify candidates involved in the pathophysiology of PV and generate a molecular signature to aid in diagnosis. We thus performed cDNA microarray analysis on 40 PV and 12 SE patients. Two independent data sets were obtained: using a two‐step training/validation design, a set of 64 genes (class predictors) was determined, which correctly discriminated PV from SE patients. Separately 253 genes were identified to be upregulated and 391 downregulated more than 1·5‐fold in PV compared with healthy controls (P < 0·01). Of the genes overexpressed in PV, 27 contained Sp1 sites: we therefore propose that altered activity of Sp1‐like transcription factors may contribute to the molecular aetiology of PV. One Sp1 target, the transcription factor NF‐E2 [nuclear factor (erythroid‐derived 2)], is overexpressed 2‐ to 40‐fold in PV patients. In PV bone marrow, NF‐E2 is overexpressed in megakaryocytes, erythroid and granulocytic precursors. It has been shown that overexpression of NF‐E2 leads to the development of erythropoietin‐independent erythroid colonies and that ectopic NF‐E2 expression can reprogram monocytic cells towards erythroid and megakaryocytic differentiation. Transcription factor concentration may thus control lineage commitment. We therefore propose that elevated concentrations of NF‐E2 in PV patients lead to an overproduction of erythroid and, in some patients, megakaryocytic cells/platelets. In this model, the level of NF‐E2 overexpression determines both the severity of erythrocytosis and the concurrent presence or absence of thrombocytosis.

ABO‐incompatible kidney transplantation using antigen‐specific immunoadsorption and rituximab: a single center experience

Abstract: Background: For years ABO‐incompatible kidney transplantations were preferentially performed in Japanese centers. In order to overcome the increased risk of humoral rejections, patients were treated with multiple sessions of plasmapheresis, intensified immunosuppressive therapy and splenectomy before transplantation. Despite good long‐term results regarding patient and organ survival rates, increased morbidity during the early post‐transplant period prevented a broad application of this method. Recently, a new protocol including the anti‐CD20‐antibody (Ab) rituximab and blood group‐specific immunoadsorption instead of splenectomy and plasmapheresis was published with excellent short‐term results.

Expression profiling on chronically rejected transplant kidneys.

Background. Chronic transplant nephropathy remains a poorly defined inflammatory process that limits the survival rate of most renal transplants. We analyzed the gene profile of chronically rejected kidney transplants to identify candidate genes that characterize chronic transplant nephropathy. Methods. To distinguish genes present in normal renal tissue or specific for end-stage renal failure, we compared the gene profiles of 13 chronically rejected kidney transplants with 16 normal kidneys and 12 end-stage polycystic kidneys using a 7K human cDNA microarray. After elimination of genes with signals close to background, 2,190 genes were available for statistical analysis. Results. More than 20% of the examined genes were significantly regulated when compared with the expression level of normal renal tissue (P <0.0003). Hierarchic clustering based on 571 genes differentiated normal and transplant tissue, and transplant and polycystic kidney tissue. Most of these genes encoded proteins involved in cellular metabolism, transport, signaling, transcriptional activation, adhesion, and the immune response. Notably, comprehensive gene profiling of chronically rejected kidneys revealed two distinct subsets of chronically rejected transplants. Neither clinical data nor histology could explain this genetic heterogeneity. Conclusions. Microarray analysis of rejected kidneys may help to define different entities of transplant nephropathy, reflecting the multifactorial cause of chronic rejection.

Increased Expression of Secreted Frizzled-Related Protein 4 in Polycystic Kidneys

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.

Hemodialysis‐Induced Hypotension: Impact of Technologic Advances

Hemodialysis‐induced hypotension is one of the most serious complications in renal replacement therapy. The main cause of intradialytic hypotension is hypovolemia due to an imbalance between the amount of fluid removed and the refilling capacity of the intravascular compartment. Hypotension occurs when compensatory mechanisms for hypovolemia are overwhelmed by excessive fluid removal. As long as renal replacement therapy is limited to only a few hours per week, intradialytic hypotension will continue to be a relevant problem. Research has mainly focused on enlarging the compensatory capacity for ultrafiltration‐induced hypovolemia. This article critically discusses the technical approaches that have been introduced into therapy in recent years with the promise of reducing dialysis‐induced hypotensive episodes.

Host cell responses induced by hepatitis C virus binding

Initiation of hepatitis C virus (HCV) infection is mediated by docking of the viral envelope to the hepatocyte cell surface membrane followed by entry of the virus into the host cell. Aiming to elucidate the impact of this interaction on host cell biology, we performed a genomic analysis of the host cell response following binding of HCV to cell surface proteins. As ligands for HCV–host cell surface interaction, we used recombinant envelope glycoproteins and HCV‐like particles (HCV‐LPs) recently shown to bind or enter hepatocytes and human hepatoma cells. Gene expression profiling of HepG2 hepatoma cells following binding of E1/E2, HCV‐LPs, and liver tissue samples from HCV‐infected individuals was performed using a 7.5‐kd human cDNA microarray. Cellular binding of HCV‐LPs to hepatoma cells resulted in differential expression of 565 out of 7,419 host cell genes. Examination of transcriptional changes revealed a broad and complex transcriptional program induced by ligand binding to target cells. Expression of several genes important for innate immune responses and lipid metabolism was significantly modulated by ligand–cell surface interaction. To assess the functional relevance and biological significance of these findings for viral infection in vivo, transcriptional changes were compared with gene expression profiles in liver tissue samples from HCV‐infected patients or controls. Side‐by‐side analysis revealed that the expression of 27 genes was similarly altered following HCV‐LP binding in hepatoma cells and viral infection in vivo. In conclusion, HCV binding results in a cascade of intracellular signals modulating target gene expression and contributing to host cell responses in vivo. Reprogramming of cellular gene expression induced by HCV–cell surface interaction may be part of the viral strategy to condition viral entry and replication and escape from innate host cell responses. (HEPATOLOGY 2006;43:1326–1336.)

Preemptive Postoperative Antigen-Specific Immunoadsorption in ABO-Incompatible Kidney Transplantation: Necessary or Not?:

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.

cDNA Microarray Analysis of Adaptive Changes after Renal Ablation in a Sclerosis-Resistant Mouse Strain

Background:5/6 nephrectomy (Nx) in susceptible animals causes glomerular sclerosis and interstitial fibrosis in the remnant kidney. Oxidative stress, transforming growth factor-β (TGF-β), and the de novo synthesis of collagen seem to contribute to this process. However, these factors might also be required for tissue repair without fibrosis. Methods:We examined dynamic changes after nephron loss in a mouse strain capable of complete recovery. C57BL/6 mice underwent single-session Nx and were followed for 40 weeks. Gene expression was monitored over 20 days using 22,000 cDNA microarrays. Results:The mice developed transient hypertension and glomerular hypertrophy after Nx but failed to progress to glomerular sclerosis or renal failure. Gene expression profiles revealed three stages of recovery, an early phase of injury response, an intermediate phase of extracellular matrix (ECM) production and a later phase of reconstitution. Surprisingly, oxidative stress responses and collagen production were strongly upregulated soon after Nx. Furthermore, TGF-β1 and connective tissue growth factor were rapidly upregulated and remained elevated. Conclusion:We suggest that oxidative stress, collagen production, profibrotic growth factors and ECM turnover are part of the comprehensive adaptation to nephron loss and not necessarily associated with progressive loss of renal function.

Rationale for the Use of Blood Volume and Temperature Control Devices during Hemodialysis

Despite substantial progress in blood purification techniques over the last three decades, treatment-related hypotensive episodes remain one of the major problems in hemodialysis therapy. There are two main reasons for hypotension occurring during dialysis treatments. First, hypovolemia is frequently induced by rapid fluid removal from the blood compartment which is in excess of refilling of fluids from the interstitial space. Second, many patients fail to support blood pressure by adequate vasoconstriction or increased heart rate as a response to hypovolemia. The capacity to respond adequately to volume contraction may be reduced due to patient- or treatment-related factors, among which heat accumulation within the body plays a major role. Recently, two newer technical developments became commercially available for use in hemodialysis therapy: devices for blood volume and blood temperature control were designed to reduce the incidence of intradialytic hypotension. Although blood volume and temperature measurements are easy to perform today, there is some uncertainty in the dialysis community how and when their use may be helpful and in which patients it is indicated. This review critically discusses the application of blood volume- and temperature-measuring devices with regard to their usefulness in the clinical setting.