2-Step-Scores with optional nephropathology for the prediction of adverse outcomes for brain-dead donor kidneys in Eurotransplant

BACKGROUND AND HYPOTHESIS

The decision for acceptance or discard of the increasingly rare and marginal brain-dead donor kidneys in Eurotransplant (ET) countries has to be made without solid evidence. Thus, we developed and validated flexible clinicopathological scores called 2-Step Scores for the prognosis of delayed graft function (DGF) and one-year death-censored transplant loss (1y-tl) reflecting the current practice of six ET countries including Croatia and Belgium.

METHODS

The training set was n=620 for DGF and n=711 for 1y-tl, with validation sets n=158 and n=162. In step 1, stepwise logistic regression models including only clinical predictors were used to estimate the risks. In step 2, risk estimates were updated for statistically relevant intermediate risk percentiles with nephropathology.

RESULTS

Step 1 revealed an increased risk of DGF with increased cold ischaemia time, donor and recipient BMI, dialysis vintage, number of HLA-DR mismatches or recipient CMV IgG positivity. On the training and validation set, c-statistics were 0.672 and 0.704, respectively. At a range between 18% and 36%, accuracy of DGF-prognostication improved with nephropathology including number of glomeruli and Banff cv (updated overall c statistics of 0.696 and 0.701, respectively).Risk of 1y-tl increased in recipients with cold ischaemia time, sum of HLA-A. -B, -DR mismatches and donor age. On training and validation sets, c-statistics were 0.700 and 0.769, respectively. Accuracy of 1y-tl prediction improved (c-statistics = 0.706 and 0.765) with Banff ct. Overall, calibration was good on the training, but moderate on the validation set; discrimination was at least as good as established scores when applied to the validation set.

CONCLUSION

Our flexible 2-Step Scores with optional inclusion of time-consuming and often unavailable nephropathology should yield good results for clinical practice in ET, and may be superior to established scores. Our scores are adaptable to donation after cardiac death and perfusion pump use.

Histologic and Clinical Factors Associated with Kidney Outcomes in IgA Vasculitis Nephritis

BACKGROUND

Nephritis is a common manifestation of IgA vasculitis and is morphologically indistinguishable from IgA nephropathy. While MEST-C scores are predictive of kidney outcomes in IgA nephropathy, their value in IgA vasculitis nephritis has not been investigated in large multiethnic cohorts.

METHODS

Biopsies from 262 children and 99 adults with IgA vasculitis nephritis ( N =361) from 23 centers in North America, Europe, and Asia were independently scored by three pathologists. MEST-C scores were assessed for correlation with eGFR/proteinuria at biopsy. Because most patients ( N =309, 86%) received immunosuppression, risk factors for outcomes were evaluated in this group using latent class mixed models to identify classes of eGFR trajectories over a median follow-up of 2.7 years (interquartile range, 1.2-5.1). Clinical and histologic parameters associated with each class were determined using logistic regression.

RESULTS

M, E, T, and C scores were correlated with either eGFR or proteinuria at biopsy. Two classes were identified by latent class mixed model, one with initial improvement in eGFR followed by a late decline (class 1, N =91) and another with stable eGFR (class 2, N =218). Class 1 was associated with a higher risk of an established kidney outcome (time to ≥30% decline in eGFR or kidney failure; hazard ratio, 5.84; 95% confidence interval, 2.37 to 14.4). Among MEST-C scores, only E1 was associated with class 1 by multivariable analysis. Other factors associated with class 1 were age 18 years and younger, male sex, lower eGFR at biopsy, and extrarenal noncutaneous disease. Fibrous crescents without active changes were associated with class 2.

CONCLUSIONS

Kidney outcome in patients with biopsied IgA vasculitis nephritis treated with immunosuppression was determined by clinical risk factors and endocapillary hypercellularity (E1) and fibrous crescents, which are features that are not part of the International Study of Diseases of Children classification.

Histological and clinical evaluation of discarded kidneys in a European cohort of deceased brain death donor kidneys of marginal quality

BACKGROUND

Despite organ shortages, the discard rate of deceased donor kidneys is high. Risk factors for this trend warrant further study.

METHODS

We investigated reasons for discard in a cohort of brain death donors with marginal kidneys and procurement biopsies. Paraffin embedded procurement biopsies were systematically reevaluated and graded for the purpose of the study. Assessment included percentage of global glomerulosclerosis, Banff Lesion scores and tubular epithelial damage. Donor-, transplant process-, perfusion quality-, histopathology-, and recipient-related parameters were compared between discarded and transplanted organs.

RESULTS

Although most clinical characteristics were similar between donors whose kidneys were transplanted and those whose kidneys were procured but discarded, discarded kidneys were more likely to be from donors with hepatitis C, to have undergone wedge biopsies, to show changes of acute and chronic injury and to be deemed poor quality. Except for obvious anatomic abnormalities, kidneys were often discarded due to the findings of procurement biopsies. Donors of kidneys discarded for histologic reasons more often had hypertension, coronary artery disease, stroke, and increased serum creatinine. The reason for discard was unknown in 20% of cases. Discarded kidneys came from donors who appeared to be clinically similar to donors whose kidneys were utilized for transplant.

CONCLUSION

A considerable proportion of discarded kidneys were of acceptable quality. The analysis of the outcome of every recovered organ could help to overcome this problem. Procurement biopsies more often lead to discard than to transplantation of recovered organs. Proper handling during allocation has to be determined.

Early progression of chronic histologic lesions in kidney transplant biopsies is not associated with HLA histocompatibility

BACKGROUND

Early progression of chronic histologic lesions in kidney allografts represents the main finding in graft attrition. The objective of this retrospective cohort study was to elucidate whether HLA histocompatibility is associated with progression of chronic histologic lesions in the first year post-transplant. Established associations of de novo donor-specific antibody (dnDSA) formation with HLA mismatch and microvascular inflammation (MVI) were calculated to allow for comparability with other study cohorts.

METHODS

We included 117 adult kidney transplant recipients, transplanted between 2016 and 2020 from predominantly deceased donors, who had surveillance biopsies at three and twelve months. Histologic lesion scores were assessed according to the Banff classification. HLA mismatch scores (i.e. eplet, predicted indirectly recognizable HLA-epitopes algorithm (PIRCHE-II), HLA epitope mismatch algorithm (HLA-EMMA), HLA whole antigen A/B/DR) were calculated for all transplant pairs. Formation of dnDSAs was quantified by single antigen beads.

RESULTS

More than one third of patients exhibited a progression of chronic lesion scores by at least one Banff grade in tubular atrophy (ct), interstitial fibrosis (ci), arteriolar hyalinosis (ah) and inflammation in the area of interstitial fibrosis and tubular atrophy (i-IFTA) from the three to the twelve-month biopsy. Multivariable proportional odds logistic regression models revealed no association of HLA mismatch scores with progression of histologic lesions, except for ah and especially HLA-EMMA DRB1 (OR = 1.10, 95%-CI: 1.03-1.18). Furthermore, the established associations of dnDSA formation with HLA mismatch and MVI (OR = 5.31, 95-% CI: 1.19-22.57) could be confirmed in our cohort.

CONCLUSIONS

These data support the association of HLA mismatch and alloimmune response, while suggesting that other factors contribute to early progression of chronic histologic lesions.

Performance of Scores Predicting Adverse Outcomes in Procurement Kidney Biopsies From Deceased Donors With Organs of Lower-Than-Average Quality

Several scores have been devised for providing a prognosis of outcomes after kidney transplantation. This study is a comprehensive test of these scores in a cohort of deceased donors with kidneys of lower-than-average quality and procurement biopsies. In total, 15 scores were tested on a retrospective cohort consisting of 221 donors, 223 procurement biopsies, and 223 recipient records for performance on delayed graft function, graft function, or death-censored graft loss. The best-performing score for DGF was the purely clinical Chapal score (AUC 0.709), followed by the Irish score (AUC 0.684); for graft function, the Nyberg score; and for transplant loss, the Snoeijs score (AUC 0.630) and the Leuven scores (AUCs 0.637 and 0.620). The only score with an acceptable performance was the Chapal score. Its disadvantage is that knowledge of the cold ischemia time is required, which is not known at allocation. None of the other scores performed acceptably. The scores fared better in discarded kidneys than in transplanted kidneys. Our study shows an unmet need for practical prognostic scores useful at the time of a decision about discarding or accepting deceased donor kidneys of lower-than-average quality in the Eurotransplant consortium.

Effect of creatinine metrics on outcome after transplantation of marginal donor kidneys

INTRODUCTION

Predicting outcome after transplantation of marginal kidneys is a challenging task. Donor creatinine or estimated glomerular filtration rate (eGFR) are integral components of the respective risk scores. However, there is uncertainty on which of their values obtained successively during procurement is the most suitable.

MATERIAL AND METHODS

This is a retrospective study of 221 adult brain death donors with marginal kidneys, transplanted in 223 recipients. We applied logistic regression analysis to investigate the association between initial (at hospital admission), nadir (lowest), zenith (highest) and terminal (at recovery) donor eGFR with primary non-function (PNF), delayed graft function (DGF), 3- and 12-month graft function and 1- and 3-year patient- and death-censored graft survival.

RESULTS

In the multivariate analysis, admission, terminal, and the lowest donor eGFR could most accurately predict DGF. The respective ORs [95% CI] were: 0.875 [0.771-0.993], 0.818 [95% CI: 0.726-0.922] and 0.793 [0.689-0.900]. Although not being significant for DGF (OR 0.931 [95% CI: 0.817-1.106]), the highest eGFR was the best predictor of 3-month graft function (adjusted b coefficient 1.161 [95% CI: 0.355-1.968]). Analysis of primary nonfunction showed that determination of initial and the highest eGFR proved to be the best predictors. The respective ORs [95% CI] were: 0.804 [0.667-0.968] and 0.750 [0.611-0.919]. There were no differences in the risk associations of each of the four eGFR recordings with patient- and graft survival.

CONCLUSION

The various eGFR recordings determined during the procurement process of marginal donors can predict PNF, DGF and 3- and 12-month graft function. Regarding short-term patient- and graft survival, there appears to be impacted by recipient factors rather than donor kidney function.

Feasibility and Potential of Transcriptomic Analysis Using the NanoString nCounter Technology to Aid the Classification of Rejection in Kidney Transplant Biopsies

BACKGROUND

Transcriptome analysis could be an additional diagnostic parameter in diagnosing kidney transplant (KTx) rejection. Here, we assessed feasibility and potential of NanoString nCounter analysis of KTx biopsies to aid the classification of rejection in clinical practice using both the Banff-Human Organ Transplant (B-HOT) panel and a customized antibody-mediated rejection (AMR)-specific NanoString nCounter Elements (Elements) panel. Additionally, we explored the potential for the classification of KTx rejection building and testing a classifier within our dataset.

METHODS

Ninety-six formalin-fixed paraffin-embedded KTx biopsies were retrieved from the archives of the ErasmusMC Rotterdam and the University Hospital Cologne. Biopsies with AMR, borderline or T cell-mediated rejections (BLorTCMR), and no rejection were compared using the B-HOT and Elements panels.

RESULTS

High correlation between gene expression levels was found when comparing the 2 chemistries pairwise (r = 0.76-0.88). Differential gene expression (false discovery rate; P  < 0.05) was identified in biopsies diagnosed with AMR (B-HOT: 294; Elements: 76) and BLorTCMR (B-HOT: 353; Elements: 57) compared with no rejection. Using the most predictive genes from the B-HOT analysis and the Element analysis, 2 least absolute shrinkage and selection operators-based regression models to classify biopsies as AMR versus no AMR (BLorTCMR or no rejection) were developed achieving an receiver-operating-characteristic curve of 0.994 and 0.894, sensitivity of 0.821 and 0.480, and specificity of 1.00 and 0.979, respectively, during cross-validation.

CONCLUSIONS

Transcriptomic analysis is feasible on KTx biopsies previously used for diagnostic purposes. The B-HOT panel has the potential to differentiate AMR from BLorTCMR or no rejection and could prove valuable in aiding kidney transplant rejection classification.

Gasdermin D-deficient mice are hypersensitive to acute kidney injury

Signaling pathways of regulated necrosis, such as necroptosis and ferroptosis, contribute to acute kidney injury (AKI), but the role of pyroptosis is unclear. Pyroptosis is mediated by the pore-forming protein gasdermin D (GSDMD). Here, we report a specific pattern of GSDMD-protein expression in the peritubular compartment of mice that underwent bilateral ischemia and reperfusion injury (IRI). Along similar lines, the GSDMD-protein expression in whole kidney lysates increased during the first 84 h following cisplatin-induced AKI. Importantly, unlike whole kidney lysates, no GSDMD-protein expression was detectable in isolated kidney tubules. In IRI and cisplatin-induced AKI, GSDMD-deficient mice exhibited hypersensitivity to injury as assessed by tubular damage, elevated markers of serum urea, and serum creatinine. This hypersensitivity was reversed by a combined deficiency of GSDMD and the necroptosis mediator mixed lineage kinase domain-like (MLKL). In conclusion, we demonstrate a non-cell autonomous role for GSDMD in protecting the tubular compartment from necroptosis-mediated damage in IRI.

A cloud-based tool for federated segmentation of whole slide images

It is commonly known that diverse datasets of WSIs are beneficial when training convolutional neural networks, however sharing medical data between institutions is often hindered by regulatory concerns. We have developed a cloud-based tool for federated WSI segmentation, allowing collaboration between institutions without the need to directly share data. To show the feasibility of federated learning on pathology data in the real world, We demonstrate this tool by segmenting IFTA from three institutions and show that keeping the three datasets separate does not hinder segmentation performance. This pipeline is deployed in the cloud for easy access for data viewing and annotation by each site's respective constituents.

PodoSighter: A Cloud-Based Tool for Label-Free Podocyte Detection in Kidney Whole-Slide Images

BACKGROUND

Podocyte depletion precedes progressive glomerular damage in several kidney diseases. However, the current standard of visual detection and quantification of podocyte nuclei from brightfield microscopy images is laborious and imprecise.

METHODS

We have developed PodoSighter, an online cloud-based tool, to automatically identify and quantify podocyte nuclei from giga-pixel brightfield whole-slide images (WSIs) using deep learning. Ground-truth to train the tool used immunohistochemically or immunofluorescence-labeled images from a multi-institutional cohort of 122 histologic sections from mouse, rat, and human kidneys. To demonstrate the generalizability of our tool in investigating podocyte loss in clinically relevant samples, we tested it in rodent models of glomerular diseases, including diabetic kidney disease, crescentic GN, and dose-dependent direct podocyte toxicity and depletion, and in human biopsies from steroid-resistant nephrotic syndrome and from human autopsy tissues.

RESULTS

The optimal model yielded high sensitivity/specificity of 0.80/0.80, 0.81/0.86, and 0.80/0.91, in mouse, rat, and human images, respectively, from periodic acid-Schiff-stained WSIs. Furthermore, the podocyte nuclear morphometrics extracted using PodoSighter were informative in identifying diseased glomeruli. We have made PodoSighter freely available to the general public as turnkey plugins in a cloud-based web application for end users.

CONCLUSIONS

Our study demonstrates an automated computational approach to detect and quantify podocyte nuclei in standard histologically stained WSIs, facilitating podocyte research, and enabling possible future clinical applications.

Differential expression of microRNA miR-150-5p in IgA nephropathy as a potential mediator and marker of disease progression

Understanding why certain patients with IgA nephropathy progress to kidney failure while others maintain normal kidney function remains a major unanswered question. To help answer this, we performed miRNome profiling by next generation sequencing of kidney biopsies in order to identify microRNAs specifically associated with the risk of IgA nephropathy progression. Following sequencing and validation in independent cohorts, four microRNAs (-150-5p, -155-5p, -146b-5p, -135a-5p) were found to be differentially expressed in IgA nephropathy progressors compared to non-progressors, and patients with thin membrane nephropathy, lupus nephritis and membranous nephropathy, and correlated with estimated glomerular filtration rate, proteinuria, and the Oxford MEST-C scores (five histological features that are independent predictors of clinical outcome). Each individual microRNA increased the discrimination score of the International IgAN Prediction Tool, although due to the small number of samples the results did not reach statistical significance. miR-150-5p exhibited the largest amplitude of expression between cohorts and displayed the best discrimination between IgA nephropathy progressors and non-progressors by receiver operating curve analysis (AUC: 0.8). However, expression was similarly upregulated in kidneys with established fibrosis and low estimated glomerular filtration rates at the time of biopsy. Consistent with a more generic role in kidney fibrosis, in situ hybridization revealed that miR-150-5p was found in lymphoid infiltrates, and areas of proliferation and fibrosis consistent with the known drivers of progression. Thus, miR-150-5p may be a potential functional mediator of kidney fibrosis that may add value in predicting risk of progression in IgA nephropathy and other kidney diseases.

The Banff 2019 Kidney Meeting Report (I): Updates on and clarification of criteria for T cell- and antibody-mediated rejection

The XV. Banff conference for allograft pathology was held in conjunction with the annual meeting of the American Society for Histocompatibility and Immunogenetics in Pittsburgh, PA (USA) and focused on refining recent updates to the classification, advances from the Banff working groups, and standardization of molecular diagnostics. This report on kidney transplant pathology details clarifications and refinements to the criteria for chronic active (CA) T cell-mediated rejection (TCMR), borderline, and antibody-mediated rejection (ABMR). The main focus of kidney sessions was on how to address biopsies meeting criteria for CA TCMR plus borderline or acute TCMR. Recent studies on the clinical impact of borderline infiltrates were also presented to clarify whether the threshold for interstitial inflammation in diagnosis of borderline should be i0 or i1. Sessions on ABMR focused on biopsies showing microvascular inflammation in the absence of C4d staining or detectable donor-specific antibodies; the potential value of molecular diagnostics in such cases and recommendations for use of the latter in the setting of solid organ transplantation are presented in the accompanying meeting report. Finally, several speakers discussed the capabilities of artificial intelligence and the potential for use of machine learning algorithms in diagnosis and personalized therapeutics in solid organ transplantation.

Utility of immunohistochemistry with C3d in C3 glomerulopathy

C3-dominance by immunofluorescence is a defining feature in the diagnosis of C3 glomerulopathy. Most pathologists stain for C3c, which has been reported as a trace/negative even in otherwise clear-cut cases of dense deposit disease. We investigated the usefulness of C3d immunohistochemistry in biopsies with C3 glomerulopathy as an ancillary diagnostic tool. All biopsies from patients diagnosed with C3 glomerulopathy in the period January 2005 to June 2017 in the Erasmus MC, Rotterdam were included (n = 14; 10 C3 glomerulonephritis, 4 dense deposit disease). The staining pattern of C3d and C4d by immunohistochemistry was analyzed. As controls, biopsies from patients with immune complex membranoproliferative glomerulonephritis (n = 2), infection-associated glomerulonephritis (n = 6), pauci-immune crescentic glomerulonephritis (n = 7), tubulointerstitial nephritis (n = 7) and chronic-active antibody-mediated rejection (n = 9) were included. All 14 biopsies with C3 glomerulopathy showed a C3d score of ≥2, including two clear-cut biopsies with C3 glomerulopathy originally showing a trace/negative staining for C3c. In the control group, a C3d score ≥2 was observed in 11 biopsies (35%; 2 with immune complex membranoproliferative glomerulonephritis (100%), 6 with infection-associated glomerulonephritis (100%), 1 with pauci-immune crescentic glomerulonephritis (14%), 1 with tubulointerstitial nephritis (14%) and 1 with chronic-active antibody-mediated rejection (11%)). C4d was positive in 71% of the biopsies with C3 glomerulopathy (10/14). In conclusion, C3d immunohistochemistry is a valuable tool in the diagnosis of C3 glomerulopathy, especially in cases in which C3c immunofluorescence shows a trace/negative. We recommend the use of C3d in addition to C3c in cases suspicious for C3 glomerulopathy.

Case report: a peculiar glomerulopathy in a patient suffering from nephrotic syndrome

Background

Podocyte infolding glomerulopathy (PIG) is a rare histopathologic finding with global infolding of the podocytes into the glomerular basement membrane (GBM), accompanied by microstructures underneath. Described in 2002 for the first time, PIG was proposed as a new pathological entity in 2008 based on the largest case series so far. Yet all of the described cases derive from Asian countries. We report a case from Germany fulfilling the diagnostic criteria of PIG. Considering the scarcity of data on this entity especially in Western countries, collecting cases like ours and multicentric meta-analyses will be crucial to obtain a better understanding of PIG, its causes, clinical course and potential treatment options.

Case presentation

A 56-year-old Caucasian woman with a history of rheumatoid arthritis (RA), no other comorbidities and no known renal disease was admitted to the hospital with acute kidney injury (AKI) and nephrotic syndrome. Physical examination was unremarkable except for anasarca. Renal ultrasound revealed no abnormalities. Laboratory and urine analyses were consistent with the nephrotic syndrome and renal failure. Serological studies regarding ANA, ANCA, anti-PLA2R autoantibodies, complement, virus infections, immunofixation and quantitative light chain analysis were unremarkable. A renal biopsy was performed. Light microscopic examination showed flattened tubular epithelium consistent with acute tubular damage, no infiltrates and unremarkable glomeruli except diffuse and global holes in the GBM (Fig. 1a) and negative staining for immunoglobulin heavy-chains, light-chains and complement split products. Electron microscopy revealed a rare correlate for these holes: global peculiar infolding of podocyte cytoplasm into the GBM. Most of these infoldings were accompanied by condensation of the GBM underneath. No such condensation or electron dense deposits were found without these infoldings or outside the GBM.

Conclusion

Here we report the first case of PIG outside of Asia. Since there are only few reports about this specific finding, we feel there is a need to share information in an attempt to accumulate knowledge about this possible new entity and potential treatment options.

Mitochondria Permeability Transition versus Necroptosis in Oxalate-Induced AKI

BACKGROUND

Serum oxalate levels suddenly increase with certain dietary exposures or ethylene glycol poisoning and are a well known cause of AKI. Established contributors to oxalate crystal-induced renal necroinflammation include the NACHT, LRR and PYD domains-containing protein-3 (NLRP3) inflammasome and mixed lineage kinase domain-like (MLKL) protein-dependent tubule necroptosis. These studies examined the role of a novel form of necrosis triggered by altered mitochondrial function.

METHODS

To better understand the molecular pathophysiology of oxalate-induced AIK, we conducted in vitro studies in mouse and human kidney cells and in vivo studies in mice, including wild-type mice and knockout mice deficient in peptidylprolyl isomerase F (Ppif) or deficient in both Ppif and Mlkl.

RESULTS

Crystals of calcium oxalate, monosodium urate, or calcium pyrophosphate dihydrate, as well as silica microparticles, triggered cell necrosis involving PPIF-dependent mitochondrial permeability transition. This process involves crystal phagocytosis, lysosomal cathepsin leakage, and increased release of reactive oxygen species. Mice with acute oxalosis displayed calcium oxalate crystals inside distal tubular epithelial cells associated with mitochondrial changes characteristic of mitochondrial permeability transition. Mice lacking Ppif or Mlkl or given an inhibitor of mitochondrial permeability transition displayed attenuated oxalate-induced AKI. Dual genetic deletion of Ppif and Mlkl or pharmaceutical inhibition of necroptosis was partially redundant, implying interlinked roles of these two pathways of regulated necrosis in acute oxalosis. Similarly, inhibition of mitochondrial permeability transition suppressed crystal-induced cell death in primary human tubular epithelial cells. PPIF and phosphorylated MLKL localized to injured tubules in diagnostic human kidney biopsies of oxalosis-related AKI.

CONCLUSIONS

Mitochondrial permeability transition-related regulated necrosis and necroptosis both contribute to oxalate-induced AKI, identifying PPIF as a potential molecular target for renoprotective intervention.

Pathological manifestations of Farber disease in a new mouse model

Farber disease (FD) is a rare lysosomal storage disorder resulting from acid ceramidase deficiency and subsequent ceramide accumulation. No treatments are clinically available and affected patients have a severely shortened lifespan. Due to the low incidence, the pathogenesis of FD is still poorly understood. Here, we report a novel acid ceramidase mutant mouse model that enables the study of pathogenic mechanisms of FD and ceramide accumulation. Asah1tmEx1 mice were generated by deletion of the acid ceramidase signal peptide sequence. The effects on lysosomal targeting and activity of the enzyme were assessed. Ceramide and sphingomyelin levels were quantified by liquid chromatography tandem-mass spectrometry (LC-MS/MS) and disease manifestations in several organ systems were analyzed by histology and biochemistry. We show that deletion of the signal peptide sequence disrupts lysosomal targeting and enzyme activity, resulting in ceramide and sphingomyelin accumulation. The affected mice fail to thrive and die early. Histiocytic infiltrations were observed in many tissues, as well as lung inflammation, liver fibrosis, muscular disease manifestations and mild kidney injury. Our new mouse model mirrors human FD and thus offers further insights into the pathogenesis of this disease. In the future, it may also facilitate the development of urgently needed therapies.

The proteome microenvironment determines the protective effect of preconditioning in cisplatin-induced acute kidney injury

Acute kidney injury (AKI) leads to significant morbidity and mortality; unfortunately, strategies to prevent or treat AKI are lacking. In recent years, several preconditioning protocols have been shown to be effective in inducing organ protection in rodent models. Here, we characterized two of these interventions-caloric restriction and hypoxic preconditioning-in a mouse model of cisplatin-induced AKI and investigated the underlying mechanisms by acquisition of multi-layered omic data (transcriptome, proteome, N-degradome) and functional parameters in the same animals. Both preconditioning protocols markedly ameliorated cisplatin-induced loss of kidney function, and caloric restriction also induced lipid synthesis. Bioinformatic analysis revealed mRNA-independent proteome alterations affecting the extracellular space, mitochondria, and transporters. Interestingly, our analyses revealed a strong dissociation of protein and RNA expression after cisplatin treatment that showed a strong correlation with the degree of damage. N-degradomic analysis revealed that most posttranscriptional changes were determined by arginine-specific proteolytic processing. This included a characteristic cisplatin-activated complement signature that was prevented by preconditioning. Amyloid and acute-phase proteins within the cortical parenchyma showed a similar response. Extensive analysis of disease-associated molecular patterns suggested that transcription-independent deposition of amyloid P-component serum protein may be a key component in the microenvironmental contribution to kidney damage. This proof-of-principle study provides new insights into the pathogenesis of cisplatin-induced AKI and the molecular mechanisms underlying organ protection by correlating phenotypic and multi-layered omics data.

Mycophenolate mofetil following glucocorticoid treatment in Henoch-Schönlein purpura nephritis: the role of early initiation and therapeutic drug monitoring

BACKGROUND

Henoch-Schönlein purpura (HSP) is the most common vasculitis in childhood and traditionally considered as a self-limiting disease. However, renal involvement can unfavorably determine long-term prognosis. The reported regimens to treat HSP nephritis (HSPN) are diverse, indicating that the most effective treatment remains controversial.

METHODS

This retrospective, single-center study involved 18 patients presenting with HSPN and nephrotic-range proteinuria. We aimed to investigate the efficacy and safety of mycophenolate mofetil (MMF) and identify a cut-off level for estimated mycophenolic acid area under the curve (eMPA-AUC_0-12h) values, which can predict complete remission with high sensitivity.

RESULTS

Despite prior insufficient therapeutic response to corticosteroids, 89% of patients showed a significant decrease in proteinuria after 1 month of MMF treatment. None of them relapsed during treatment; however, two children relapsed after discontinuation. Based on results of a receiver operating characteristic (ROC) analysis, an eMPA-AUC_0-12h >56.4 mg*h/l was a predictor for complete remission within 3 months (80% sensitivity, 83.3% specificity, p = 0.035). During MMF administration, we encountered no adverse event requiring discontinuation of treatment.

CONCLUSION

Our study demonstrates that MMF is a safe and potentially effective secondary treatment option for children with HSPN to achieve and maintain long-term remission without serious side effects. To achieve complete remission within 3 months, resolve severe inflammatory glomerular lesions, and avoid progression to chronic kidney disease, we propose timely diagnosis and early initiation of MMF with an eMPA-AUC_0-12h value of 56.4 mg*h/l.

Live or Let Die: Is There any Cell Death in Podocytes?

Ultimately, the common final pathway of any glomerular disease is podocyte effacement, podocyte loss, and, eventually, glomerular scarring. There has been a long-standing debate on the underlying mechanisms for podocyte depletion, ranging from necrosis and apoptosis to detachment of viable cells from the glomerular basement membrane. However, this debate still continues because additional pathways of programmed cell death have been reported in recent years. Interestingly, viable podocytes can be isolated out of the urine of proteinuric patients easily, emphasizing the importance of podocyte detachment in glomerular diseases. In contrast, detection of apoptosis and other pathways of programmed cell death in podocytes is technically challenging. In fact, we still are lacking direct evidence showing, for example, the presence of apoptotic bodies in podocytes, leaving the question unanswered as to whether podocytes undergo mechanisms of programmed cell death. However, understanding the mechanisms leading to podocyte depletion is of particular interest because future therapeutic strategies might interfere with these to prevent glomerular scarring. In this review, we summarize our current knowledge on podocyte cell death, the different molecular pathways and experimental approaches to study these, and, finally, focus on the mechanisms that prevent the onset of programmed cell death.

Glomerulocapillary miRNA response to HLA-class I antibody in vitro and in vivo

Changes in miRNA expression glomerular of capillaries during antibody-mediated rejection (ABMR) are poorly understood and could contribute to the deleterious inflammation and fibrosis of ABMR via suppression of target genes. A better understanding could lead to novel diagnostic tools and reveal novel therapeutic targets. We explored deregulated miRNAs in an glomeruloendothelial in vitro model of ABMR due to class I human leukocyte antigen (HLA) with and without complement activation. We studied a set of 16 promising candidate miRNAs in microdissected glomeruli a confirmation set of 20 human transplant biopsies (DSA+) compared to 10 matched controls without evidence for ABMR. Twelve out of these 16 glomerulocapillary miRNAs could successfully be confirmed as dysregulated in vivo with 10 upregulated (let-7c-5p, miR-28-3p, miR-30d-5p, miR-99b-5p, miR-125a-5p, miR-195-5p, miR-374b-3p, miR-484, miR-501-3p, miR-520e) and 2 downregulated (miR29b-3p, miR-885-5p) in DSA+ vs.

CONTROLS

A random forest analysis based on glomerular miRNAs identified 18/20 DSA+ and 8/10 controls correctly. This glomerulocapillary miRNA signature associated with HLA class I-DSA could improve our understanding of ABMR and be useful for diagnostic or therapeutic purposes.

Regardless of etiology, progressive renal disease causes ultrastructural and functional alterations of peritubular capillaries

Progressive renal diseases are associated with rarefaction of peritubular capillaries, but the ultrastructural and functional alterations of the microvasculature are not well described. To study this, we analyzed different time points during progressive kidney damage and fibrosis in 3 murine models of different disease etiologies. These models were unilateral ureteral obstruction, unilateral ischemia-reperfusion injury, and Col4a3-deficient mice, we analyzed ultrastructural alterations in patient biopsy specimens. Compared with kidneys of healthy mice, we found a significant and progressive reduction of peritubular capillaries in all models analyzed. Ultrastructurally, compared with the kidneys of control mice, focal widening of the subendothelial space and higher numbers of endothelial vacuoles and caveolae were found in fibrotic kidneys. Quantitative analysis showed that peritubular capillary endothelial cells in fibrotic kidneys had significantly and progressively reduced numbers of fenestrations and increased thickness of the cell soma and lamina densa of the capillary basement membrane. Similar ultrastructural changes were also observed in patient's kidney biopsy specimens. Compared with healthy murine kidneys, fibrotic kidneys had significantly increased extravasation of Evans blue dye in all 3 models. The extravasation could be visualized using 2-photon microscopy in real time in living animals and was mainly localized to capillary branching points. Finally, fibrotic kidneys in all models exhibited a significantly greater degree of interstitial deposition of fibrinogen. Thus, peritubular capillaries undergo significant ultrastructural and functional alterations during experimental progressive renal diseases, independent of the underlying injury. Analyses of these alterations could provide read-outs for the evaluation of therapeutic approaches targeting the renal microvasculature.

A Multicenter Study of the Predictive Value of Crescents in IgA Nephropathy

The Oxford Classification of IgA nephropathy does not account for glomerular crescents. However, studies that reported no independent predictive role of crescents on renal outcomes excluded individuals with severe renal insufficiency. In a large IgA nephropathy cohort pooled from four retrospective studies, we addressed crescents as a predictor of renal outcomes and determined whether the fraction of crescent-containing glomeruli associates with survival from either a ≥50% decline in eGFR or ESRD (combined event) adjusting for covariates used in the original Oxford study. The 3096 subjects studied had an initial mean±SD eGFR of 78±29 ml/min per 1.73 m² and median (interquartile range) proteinuria of 1.2 (0.7-2.3) g/d, and 36% of subjects had cellular or fibrocellular crescents. Overall, crescents predicted a higher risk of a combined event, although this remained significant only in patients not receiving immunosuppression. Having crescents in at least one sixth or one fourth of glomeruli associated with a hazard ratio (95% confidence interval) for a combined event of 1.63 (1.10 to 2.43) or 2.29 (1.35 to 3.91), respectively, in all individuals. Furthermore, having crescents in at least one fourth of glomeruli independently associated with a combined event in patients receiving and not receiving immunosuppression. We propose adding the following crescent scores to the Oxford Classification: C0 (no crescents); C1 (crescents in less than one fourth of glomeruli), identifying patients at increased risk of poor outcome without immunosuppression; and C2 (crescents in one fourth or more of glomeruli), identifying patients at even greater risk of progression, even with immunosuppression.

Banff Borderline Changes Suspicious for Acute T Cell-Mediated Rejection: Where Do We Stand?

The definition of Banff Borderline became ambiguous when the Banff 2005 consensus modified the lower threshold from i1t1 (10-25% interstitial inflammation with mild tubulitis) to i0t1 (0-10% interstitial inflammation with mild tubulitis). We conducted a worldwide survey among members of the Renal Pathology Society about their approach to this diagnostic category. A web-based survey was sent out to all 503 current members (153 respondents). A database search yielded which threshold for Banff i was applied in the most influential manuscripts about Borderline. Among the 139 nephropathologists using the Borderline category, 67% use the Banff 1997 definition, requiring Banff i1. Thirty-seven percent admitted to sometimes exaggerating Banff i in the presence of tubulitis, to reach a diagnosis of Borderline. Forty-eight percent were dissatisfied with the definition of Borderline. The majority of the most influential manuscripts used the 1997 definition, contrary to the current one. There is considerable dissatisfaction with Borderline, and practice in Banff i thresholds is variable. Until additional studies inform a revision, we suggest leaving it to each pathologist's discretion whether to use i0 or i1 as the minimal threshold. In order to avoid future ambiguity, a web-based synopsis of all scattered current Banff definitions and rules should be created.

Comparison of different normalization strategies for the analysis of glomerular microRNAs in IgA nephropathy

Small nucleolar RNAs (snoRNAs) have been used for normalization in glomerular microRNA (miRNA) quantification without confirmation of validity. Our aim was to identify glomerular reference miRNAs in IgA nephropathy. We compared miRNAs in human paraffin-embedded renal biopsies from patients with cellular-crescentic IgA-GN (n = 5; crescentic IgA-GN) and non-crescentic IgA-GN (n = 5; IgA-GN) to mild interstitial nephritis without glomerular abnormalities (controls, n = 5). Laser-microdissected glomeruli were used for expression profiling of 762 miRNAs by low-density TaqMan arrays (cards A and B). The comparison of different normalization methods (GeNormPlus, NormFinder, global mean and snoRNAs) in crescentic IgA-GN, IgA-GN and controls yielded similar results. However, levels of significance and the range of relative expression differed. In median, two normalization methods demonstrated similar results. GeNormPlus and NormFinder gave different top ranked reference miRNAs. Stability ranking for snoRNAs varied between cards A and B. In conclusion, we suggest the geometric mean of the most stable reference miRNAs found in GeNormPlus (miR-26b-5p), NormFinder (miR-28-5p) and snoRNAs (RNU44) as reference. It should be considered that significant differences could be missed using one particular normalization method. As a starting point for glomerular miRNA studies in IgA nephropathy we provide a library of miRNAs.

Intratumoral expression of programmed death ligand 1 (PD-L1) in patients with clear cell renal cell carcinoma (ccRCC)

The immunological checkpoints of programmed death 1 and its ligand (PD-L1) are currently in focus as novel therapeutic targets in renal cell carcinoma (RCC). The aim of this study was to evaluate the prognostic association of PD-L1 expression in clear cell (cc) RCC with clinical parameters, tumor aggressiveness and overall survival (OS). Patients who underwent renal surgery due to RCC between 1994 and 2003 were retrospectively evaluated. Tumor specimens were analyzed for PD-L1 expression by immunohistochemistry. One hundred and seventy-seven ccRCC patients were eligible for analysis, in which 140 (79.1 %) were negative and 37 (20.9 %) were positive for PD-L1 expression. PD-L1 positivity was associated with female gender (p = 0.001), lymph node metastasis (p = 0.004), distant metastasis (p = 0.002), higher AJCC stage (p = 0.004), as well as advanced disease (pT3/4 and/or N+ and/or M1) (p < 0.001). Kaplan-Meier analysis revealed a significantly diminished 5- and 10-year overall survival of 46.7 and 28.3 % for PD-L1(+) compared to PD-L1(-) tumors with 66 and 53.4 % (p = 0.005), respectively. Univariate analysis showed a significant negative association of OS with PD-L1 positivity [p = 0.005; HR: 2 (95 % CI 1.2-3.3)], even though PD-L1 positivity only tends to predict independently the OS using multivariate analyses [p = 0.066; HR: 1.6 (95 % CI 0.98-2.7)]. PD-L1 expression in ccRCC is associated with parameters of aggressiveness, as well as with poor OS, even though PD-L1 status was not identified as a significant independent prognostic parameter. However, further studies in larger cohorts are warranted.

Do programmed death 1 (PD-1) and its ligand (PD-L1) play a role in patients with non-clear cell renal cell carcinoma?

Clinical trials targeting programmed death 1 (PD-1) and its ligand PD-L1 (PD-L1) for metastatic renal cell cancer (RCC) are ongoing. The aim of this study is to validate their roles as prognostic markers in non-clear cell (non-cc) RCC. Sixty-four non-cc RCC tissue specimens were collected from patients undergoing renal tumor surgery. Expressions of biomarkers were assessed using immunohistochemistry and compared with clinical characteristics. Survival analyses were performed with a median follow-up of 77.5 (range: 0-176) months. No significant correlations were found for PD-1(+) tumor-infiltrating mononuclear cells (TIMC) or PD-L1(+) expression and clinical attributes in patients with non-cc RCC. Kaplan-Meier analysis revealed no differences in 5- and 10-year cancer-specific survival (CSS) for PD-1(-) TIMC compared to PD-1(+) TIMC (71.4 and 63 % versus 72.2 and 61.9 %; p = 0.88). Intratumoral expression of PD-L1 did not appear to influence the 5- and 10-year CSS significantly, even though a trend was identified (68 and 53.6 % versus 80.1 and 75.7 %; p = 0.08). In multivariate analysis, neither PD-1(+) TIMC nor intratumoral PD-L1(+) expression proved to be independent predictors of CSS (p = 0.99 and p = 0.68, respectively). Our study demonstrates that PD-1(+) TIMC and intratumoral PD-L1(+) expression did not significantly impact tumor aggressiveness or clinical outcome in non-ccRCC specimens. Due to rare incidence of non-cc RCC in particular according to PD-L1 expression, further analyzes are warranted.

German recommendations for pretransplantation donor kidney biopsies

PURPOSE

This manuscript reviews the data about the histopathologic and develops recommendations to standardise and improve the biopsy procedure, the biopsy handling, the histopathological evaluation, the communication of results and the collection of data from pretransplantation kidney biopsies of deceased donors in Germany.

METHODS

The recommendations are based on this literature review, on discussions at two workshops held by the German Society of Pathology and the German Organ Transplantation Foundation and on personal experiences of the authors.

RESULTS

These German recommendations advocate the use of punch biopsies, paraffin embedding and detailed descriptive reporting of histopathological findings.

CONCLUSIONS

These recommendations constitute only a starting point. Periodical revisions will help to simplify and optimise the recommendations with the ultimate goal to prospectively gather data for the elaboration of a computer-based algorithm that allows the exact prediction of transplantation outcome for a given match of donor and recipient.

TRPC6 G757D Loss-of-Function Mutation Associates with FSGS

FSGS is a CKD with heavy proteinuria that eventually progresses to ESRD. Hereditary forms of FSGS have been linked to mutations in the transient receptor potential cation channel, subfamily C, member 6 (TRPC6) gene encoding a nonselective cation channel. Most of these TRPC6 mutations cause a gain-of-function phenotype, leading to calcium-triggered podocyte cell death, but the underlying molecular mechanisms are unclear. We studied the molecular effect of disease-related mutations using tridimensional in silico modeling of tetrameric TRPC6. Our results indicated that G757 is localized in a domain forming a TRPC6-TRPC6 interface and predicted that the amino acid exchange G757D causes local steric hindrance and disruption of the channel complex. Notably, functional characterization of model interface domain mutants suggested a loss-of-function phenotype. We then characterized 19 human FSGS-related TRPC6 mutations, the majority of which caused gain-of-function mutations. However, five mutations (N125S, L395A, G757D, L780P, and R895L) caused a loss-of-function phenotype. Coexpression of wild-type TRPC6 and TRPC6 G757D, mimicking heterozygosity observed in patients, revealed a dominant negative effect of TRPC6 G757D. Our comprehensive analysis of human disease-causing TRPC6 mutations reveals loss of TRPC6 function as an additional concept of hereditary FSGS and provides molecular insights into the mechanism responsible for the loss-of-function phenotype of TRPC6 G757D in humans.

Induction of cardiac FGF23/FGFR4 expression is associated with left ventricular hypertrophy in patients with chronic kidney disease

BACKGROUND

In chronic kidney disease (CKD), serum concentrations of fibroblast growth factor 23 (FGF23) increase progressively as glomerular filtration rate declines, while renal expression of the FGF23 coreceptor Klotho decreases. Elevated circulating FGF23 levels are strongly associated with mortality and with left ventricular hypertrophy (LVH), which is a major cause of cardiovascular death in CKD patients. The cardiac FGF23/FGF receptor (FGFR) system and its role in the development of LVH in humans have not been addressed previously.

METHODS

We conducted a retrospective case-control study in 24 deceased patients with childhood-onset end-stage renal disease (dialysis: n = 17; transplanted: n = 7), and 24 age- and sex-matched control subjects. Myocardial autopsy samples of the left ventricle were evaluated for expression of endogenous FGF23, FGFR isoforms, Klotho, calcineurin and nuclear factor of activated T-cells (NFAT) by immunohistochemistry, immunofluorescence microscopy, qRT-PCR and western blotting.

RESULTS

The majority of patients presented with LVH (67%). Human cardiomyocytes express full-length FGF23, and cardiac FGF23 is excessively high in patients with CKD. Enhanced myocardial expression of FGF23 in concert with Klotho deficiency strongly correlates with the presence of LVH. Cardiac FGF23 levels associate with time-averaged serum phosphate levels, up-regulation of FGFR4 and activation of the calcineurin-NFAT signaling pathway, an established mediator of cardiac remodelling and LVH. These changes are detected in patients on dialysis but not in those with a functioning kidney transplant.

CONCLUSIONS

Our results indicate a strong association between LVH and enhanced expression levels of FGF23, FGFR4 and calcineurin, activation of NFAT and reduced levels of soluble Klotho in the myocardium of patients with CKD. These alterations are not observed in kidney transplant patients.

Circulating ADAM17 Level Reflects Disease Activity in Proteinase-3 ANCA-Associated Vasculitis

ANCA-associated vasculitides are characterized by inflammatory destruction of small vessels accompanied by enhanced cleavage of membrane-bound proteins. One of the main proteases responsible for ectodomain shedding is disintegrin and metalloproteinase domain-containing protein 17 (ADAM17). Given its potential role in aggravating vascular dysfunction, we examined the role of ADAM17 in active proteinase-3 (PR3)-positive ANCA-associated vasculitis (AAV). ADAM17 concentration was significantly increased in plasma samples from patients with active PR3-AAV compared with samples from patients in remission or from other controls with renal nonvascular diseases. Comparably, plasma levels of the ADAM17 substrate syndecan-1 were significantly enhanced in active AAV. We also observed that plasma-derived ADAM17 retained its specific proteolytic activity and was partly located on extracellular microparticles. Transcript levels of ADAM17 were increased in blood samples of patients with active AAV, but those of ADAM10 or tissue inhibitor of metalloproteinases 3, which inhibits ADAMs, were not. We also performed a microRNA (miR) screen and identified miR-634 as significantly upregulated in blood samples from patients with active AAV. In vitro, miR-634 mimics induced a proinflammatory phenotype in monocyte-derived macrophages, with enhanced expression and release of ADAM17 and IL-6. These data suggest that ADAM17 has a prominent role in AAV and might account for the vascular complications associated with this disease.

A rolling circle amplification screen for polyomaviruses other than BKPyV in renal transplant recipients confirms high prevalence of urinary JCPyV shedding

OBJECTIVES

Multiple novel human polyomaviruses (HPyVs) have been discovered in the last few years. These or other, unknown, nephrotropic HPyVs may potentially be shed in urine.

METHODS

To search for known and unknown HPyVs we investigated BKPyV-negative urine samples from 105 renal transplant recipients (RTR) by rolling circle amplification (RCA) analysis and quantitative JCPyV PCR. Clinical data was analysed to identify risk factors for urinary polyomavirus shedding.

RESULTS

In 10% (11/105) of the urine samples RCA with subsequent sequencing revealed JCPyV, but no other HPyV sequences. Using quantitative JCPyV PCR, 24% (25/105) of the samples tested positive. Overall sensitivities of RCA of 44% (11/25) in detecting JCPyV in JCPyV DNA-positive urine and 67% (10/15) for samples with JCPyV loads >10,000 copies/ml can be assumed. Despite frequent detectable urinary shedding of JCPyV in our cohort, this could not be correlated with clinical risk factors.

CONCLUSION

Routine urinary JCPyV monitoring in BKPyV-negative RTR without suspected polyomavirus-associated nephropathy might be of limited diagnostic value. As RCA works in a sequence-independent manner, detection of novel and known polyomaviruses shed in sufficient quantities is feasible. High-level shedding of HPyVs other than BKPyV or JCPyV in the urine of RTR is unlikely to occur.

Primary mucinous adenocarcinoma of the renal pelvis with carcinoma in situ in the ureter

Primary epithelial tumor of the renal pelvis is rare and only 100 cases are reported in the literature [1]. Histological examination of the tumor showed glands, cysts, and papillae lined by pseudostratified columnar epithelium with hyperchromatic nuclei. Scattered signet ring-type cells were also seen floating in large pools of extracellular mucin. Sections from the ureter showed a component of adenocarcinoma in situ. No invasive tumor was identified in ureteric tissue. One case was reported with carcinoma in situ of the ureter (2). Immunohistochemically: The tumor showed positivity for CK7, CK20, CK8/18, GATA-3, MSH-2, MSH-6, MLH-1, Ber-EP4, and S-100-P with focal positivity for CDX-2, weak positivity for PMS-2 and negativity in TTF-1 and Her-2. Molecular pathological analysis revealed microsatellite stability and without mutation in K-ras-gene. Thus, a diagnosis of mucinous adenocarcinoma of the renal pelvis with in situ adenocarcinoma of the ureter was made.

Renal phospholipidosis possibly induced by ranolazine

A 76-year-old male Caucasian patient was treated in our hospital for acutely decompensated heart failure due to restrictive cardiomyopathy. Acute-on-chronic kidney failure developed with serum creatinine rising from 160 to 345 μmol/L (1.8-3.9 mg/dL); therefore, a kidney biopsy was performed. Besides secondary focal-segmental glomerulosclerosis and minimal amyloidosis, histological analysis showed zebra bodies in the cytoplasm of some podocytes, suggesting renal phospholipidosis (PL). Possible causes for this storage disorder encompass Fabry's disease, in rare cases silicosis, and an iatrogenic drug-induced aetiology. The main suspects are cationic amphiphilic drugs, such as amiodarone and chloroquine. The only cationic amphiphilic drug our patient had taken was the anti-anginal ranolazine, a compound not yet associated with PL. The patient had taken ranolazine for diastolic dysfunction over a period of 9 months until 6 weeks before renal biopsy. In the absence of a hereditary disorder, silicosis and well-known pharmaceutical triggers, a causative role of ranolazine seems likely, and this drug should be considered in the differential diagnosis of drug-induced PL.

Effects of everolimus on oxidative stress in kidney model of ischemia/reperfusion injury

BACKGROUND/AIMS

Reactive oxygen species play an important role in the pathogenesis of kidney ischemia/reperfusion injury (IRI) which may be influenced by immunosuppressive therapy. Pertinent to this, we investigated the effects of the mTOR inhibitor everolimus on redox settings and the activity of the anti-oxidative system in kidneys exposed to IRI.

METHODS

C57BL/6 mice were subjected to IRI by clamping both renal pedicles for 45 min. Everolimus was applied in daily, subcutaneous doses (0.25 mg/kg body weight), starting 1 day before IRI induction. Both everolimus-treated and non-treated mice were sacrificed at several time points, starting 30 min and finishing 7 days after IRI induction. Markers of oxidation such as glutathione and NADPH levels and anti-oxidative enzyme activities were determined in the kidneys.

RESULTS

In comparison to both sham and non-treated animals, the treatment with everolimus resulted in an increased level of markers of oxidation, including a lower level of glutathione, increased level of oxidized glutathione and reduced level of NADPH. The activity of superoxide dismutase was reduced in both experimental groups, but the effects were less pronounced in everolimus-treated animals. In the early phase of reperfusion, everolimus-treated animals showed higher activity of glutathione reductase in comparison to non-treated animals, whereas the activities of glutathione peroxidase and catalase were generally similar. The treatment with everolimus significantly reduced heme oxygenase-1 expression and increased iNOS mRNA expression when compared to non-treated animals.

CONCLUSION

Our data imply that everolimus treatment may decrease cytoprotective capacity in kidneys exposed to IRI due to promoted oxidative/nitrosative stress.

Hypoxia Induces Mesenchymal Gene Expression in Renal Tubular Epithelial Cells: An in vitro Model of Kidney Transplant Fibrosis

BACKGROUND

The development of interstitial fibrosis and tubular atrophy is a common complication after kidney transplantation and is associated with reduced long-term outcome. The hallmark of tubulointerstitial fibrosis is an increase in extracellular matrix resulting from exaggerated activation of fibroblasts/myofibroblasts, and tubular atrophy is characterized by a decrease in tubular diameter and loss of function. Atrophic epithelial cells may undergo epithelial-to-mesenchymal transition (EMT) with potential differentiation into interstitial fibroblasts. One potential driver of EMT in developing interstitial fibrosis and tubular atrophy is chronic hypoxia.

METHODS

The expression of 46 EMT-related genes was analyzed in an in vitro hypoxia model in renal proximal tubular epithelial cells (RPTEC). Furthermore, the expression of 342 microRNAs (miR) was evaluated in hypoxic culture conditions.

RESULTS

Hypoxic RPTEC expressed markers of a more mesenchymal phenotype and showed an increased expression of matrix metalloproteinase-2 (MMP2). MMP2 expression in RPTEC correlated inversely with a decreased expression of miR-124, which was found to have a putative binding site for the MMP2 transcript. Overexpression of miR-124 inhibited MMP2 protein translation. Hypoxia was associated with increased migration/proliferation of RPTEC which was reversed by miR-124.

CONCLUSIONS

These results indicate that hypoxia promotes a mesenchymal and migratory phenotype in renal epithelial cells, which is associated with increased MMP2 expression. Hypoxia-dependent MMP2 expression is regulated via a reduced transcription of miR-124. Overexpression of miR-124 antagonizes hypoxia-induced cell migration. Further research is needed to elucidate the functional role of miR-124 and MMP2 in the development of fibrosis in renal transplant degeneration.

Reduced mRNA expression level of corticotropin-releasing hormone-binding protein is associated with aggressive human kidney cancer

Background

Significance of Urocortin (Ucn or UcnI), Ucn2, Ucn3 and their receptors, Corticotropin Releasing Factor Receptor 1 and 2 (CRFR1 and CRFR2), and the binding protein, Corticotropin-Releasing Hormone-Binding Protein (CRHBP) in oncology is growing rapidly. The objective of our study was to assess the expression of the CRHBP mRNA and protein in renal cancer.

Methods

Tumoral tissues of 78 patients with clear cell renal cell cancer and their corresponding normal tissues were analyzed using quantitative mRNA expression analysis for detection of mRNA expression level. Protein expression and tissue localization of CRHBP protein in renal specimens was evaluated using western blotting, immunohistochemistry and double immunofluorescence, respectively.

Results

We found an approx. 33 fold decrease of average CRHBP mRNA level in tumoral tissues compared to paired normal tissues (p<0.001). Diminished CRHBP mRNA expression was positively correlated with advanced, metastasized and higher stage of disease (p<0.001, p=0.026, p=0.028 respectively). CRHBP protein was detected in glomeruli and proximal tubules of normal kidney while none or weak immunopositivity was found in cc-RCC (p<0.001).

Conclusions

The expression analysis of CRHBP shows that cc-RCC is characterized by a significant loss of CRHBP mRNA expression that furthermore is associated with a more aggressive state of tumors. Depletion of CRHBP proteins also indicate that the protein as part of the UCN system may be involved in renal carcinogenesis.

Adenocarcinoma of the urinary bladder, mesonephroid type: a rare case

Primary adenocarcinoma of the urinary bladder is a rare disease. It occurs in 0.5–2% of all bladder cancers and is discussed as the malignant counterpart of nephrogenic adenomas. We report a 46-year-old white female presented with gross hematuria for clinical examination. Histopathology revealed pT2, Pn1, L1, G2 adenocarcinoma of the bladder and carcinoma in situ according to the TNM classification. Computed tomography scan diagnostic was unremarkable. Patients with adenocarcinoma of the urinary bladder should be treated vigorously and without time delay. Only 7 cases of adenocarcinoma in the urinary bladder (mesonephroid) have been described until now. We present a case of clear cell adenocarcinoma of the urinary bladder, mesonephroid type that early diagnosed and till now 3 months after the cystectomy without symptoms and without complications.

Rationale and design of the RIACT-study: a multi-center placebo controlled double blind study to test the efficacy of RItuximab in Acute Cellular tubulointerstitial rejection with B-cell infiltrates in renal Transplant patients: study protocol for a randomized controlled trial

BACKGROUND

Acute kidney allograft rejection is a major cause for declining graft function and has a negative impact on the long-term graft survival. The majority (90%) of acute rejections are T-cell mediated and, therefore, the anti-rejection therapy targets T-cell-mediated mechanisms of the rejection process. However, there is increasing evidence that intragraft B-cells are also important in the T-cell-mediated rejections. First, a significant proportion of patients with acute T-cell-mediated rejection have B-cells present in the infiltrates. Second, the outcome of these patients is inferior, which has been related to an inferior response to the conventional anti-rejection therapy. Third, treatment of these patients with an anti-CD20 antibody (rituximab) improves the allograft outcome as reported in single case observations and in one small study. Despite the promise of these observations, solid evidence is required before incorporating this treatment option into a general treatment recommendation.

METHODS/DESIGN

The RIACT study is designed as a randomized, double-blind, placebo-controlled, parallel group multicenter Phase III study. The study examines whether rituximab, in addition to the standard treatment with steroid-boli, leads to an improved one-year kidney allograft function, compared to the standard treatment alone in patients with acute T-cell mediated tubulointerstitial rejection and significant B-cell infiltrates in their biopsies. A total of 180 patients will be recruited.

DISCUSSION

It is important to clarify the relevance of anti-B cell targeting in T-cell mediated rejection and answer the question whether this novel concept should be incorporated in the conventional anti-rejection therapy.

TRIAL REGISTRATION

Clinical trials gov. number: NCT01117662.

[Acute tubulointerstitial nephritis as hyperergic reaction of the kidneys]

Acute tubulointerstitial nephritis was formerly only observed during the early phase of infections. With the emergence of antibiotics this disease became a rarity. In contrast the importance of drug-associated acute tubulointerstitial nephritis grew in importance and is now the most common form and expression of a hyperergic reaction of the kidneys. Acute tubulointerstitial nephritis occurs as a third form in cases of systemic autoimmune diseases, e.g., in idiopathic tubulointerstitial nephritis or within the scope of Sjögrens syndrome with distal tubular acidosis. The common symptoms of the drug-induced form are fever, side pain, microhematuria or macrohematuria and a mostly sharp increase in creatinine levels but to a greatly differing extent. Histologically, there is interstitial edema and interstitial lymphocyte-rich infiltration with tubulitis. The symptoms can be subclinical or even non-existent. In most case remission occurs, sometimes only partial remission or transformation to chronic interstitial nephritis. Risk factors are for example delayed diagnosis, recurrent episodes and the accompanying use of analgesics. The more acute and intense the clinical symptoms are, the earlier the diagnosis and therefore the better the prognosis. A temporary steroid treatment can promote regression.

Rho-kinase inhibition prevents proteinuria in immune-complex-mediated antipodocyte nephritis

Podocyte foot process retraction is a hallmark of proteinuric glomerulonephritis. Cytoskeletal rearrangement causes a redistribution of slit membrane proteins from the glomerular filtration barrier towards the cell body. However, the underlying signaling mechanisms are presently unknown. Recently, we have developed a new experimental model of immune-mediated podocyte injury in mice, the antipodocyte nephritis (APN). Podocytes were targeted with a polyclonal antipodocyte antibody causing massive proteinuria around day 10. Rho-kinases play a central role in the organization of the actin cytoskeleton of podocytes. We therefore investigated whether inhibition of Rho-kinases would prevent podocyte disruption. C57/BL6 mice received antipodocyte serum with or without daily treatment with the specific Rho-kinase inhibitor HA-1077 (5 mg/kg). Immunoblot analysis demonstrated activation of Rho-kinase in glomeruli of antipodocyte serum-treated mice, which was prevented by HA-1077. Increased Rho-kinase activity was localized to podocytes in APN mice by immunostainings against the phosphorylated forms of Rho-kinase substrates. Rho-kinase inhibition significantly reduced podocyte loss from the glomerular tuft. Periodic acid staining demonstrated less podocyte hypertrophy in Rho-kinase-inhibited APN mice, despite similar amounts of immune complex deposition. Electron microscopy revealed reduced foot process effacement compared with untreated APN mice. Internalization of the podocyte slit membrane proteins nephrin and synaptopodin was prevented by Rho-kinase inhibition. Functionally, Rho-kinase inhibition significantly reduced proteinuria without influencing blood pressure. In rats with passive Heymann nephritis and human kidney biopsies from patients with membranous nephropathy, Rho-kinase was activated in podocytes. Together, these data suggest that increased Rho-kinase activity in the podocyte may be a mechanism for in vivo podocyte foot process retraction.

The hormone melatonin stimulates renoprotective effects of "early outgrowth" endothelial progenitor cells in acute ischemic kidney injury

Endothelial progenitor cells (EPCs) protect the kidney from acute ischemic injury. The aim of this study was to analyze whether pretreatment of murine "early outgrowth" EPCs (eEPCs) with the hormone melatonin increases the cells' renoprotective effects in the setting of murine acute ischemic renal failure. Male (8-12 wk old) C57Bl/6N mice were subjected to unilateral ischemia-reperfusion injury postuninephrectomy (40 min). Postischemic animals were injected with either 0.5×10(6) untreated syngeneic murine eEPCs or with cells, pretreated with melatonin for 1 h. Injections were performed shortly after reperfusion of the kidney. While animals injected with untreated cells developed acute renal failure, eEPC pretreatment with melatonin dramatically improved renoprotective actions of the cells. These effects were completely reversed after cell pretreatment with melatonin and the MT-1/-2 antagonist luzindole. In vitro analysis revealed that melatonin reduced the amount of tumor growth factor-β-induced eEPC apoptosis/necrosis. Secretion of vascular endothelial growth factor by the cells was markedly stimulated by the hormone. In addition, migratory activity of eEPCs was enhanced by melatonin and supernatant from melatonin-treated eEPCs stimulated migration of cultured mature endothelial cells. In summary, melatonin was identified as a new agonist of eEPCs in acute ischemic kidney injury.

Prognostic and diagnostic relevance of hypermethylated in cancer 1 (HIC1) CpG island methylation in renal cell carcinoma

The tumour suppressor gene hypermethylated in cancer 1 (HIC1) is a transcriptional repressor, which functionally cooperates with p53. Loss of HIC1 function is associated with the development of various tumor entities. The aim of this study was to elucidate the relevance of CpG island (CGI) methylation of HIC1 in renal cell carcinoma (RCC). DNA methylation of HIC1 was analysed in a total of 98 tumor and 70 tumor adjacent normal specimens. After conducting bisulfite conversion, relative methylation levels were quantitated using pyrosequencing. Relative methylation values were compared for paired tumor and normal specimen and for correlation with clinico-pathologic and follow-up data of patients. Tumor-specific hypermethylation could not be detected for the subregion of the HIC1 - CGI analyzed in this study. Comparing the level of methylation in tumors to clinicopathological data solely, patients without lymph node metastases demonstrated a higher level of methylation compared to patients with lymph node metastases (p=0.030). Patients recurrence-free survival (p=0.0074) both in univariate as well as bivariate cox regression analysis. This study identifies HIC1 hypermethylation in tumors as an independent predictor of reduced recurrence-free survival, which fits into our current understanding of hypermethylated HIC1 being a marker for poor prognosis. Therefore, HIC1 - CGI methylation could be a candidate marker to improve individualized therapy and risk stratification.