Dagmar Csaicsich

Risk factors for peritonitis in pediatric peritoneal dialysis: a single-center study.

Recent US registry data and a European multicenter study described increased risk of peritonitis in young children on peritoneal dialysis (PD). No underlying age-specific risk factors could be defined in these reports. Therefore, we analyzed risk factors for peritonitis in children treated by PD as primary renal replacement therapy at the Kinderdialyse, Vienna, and particularly searched for age-specific aspects. Thirty children (15 boys, mean age 4.6 years) received PD [21 automated peritoneal dialysis (APD), nine continuous ambulatory peritoneal dialysis (CAPD)] for 13 months (3–49 months). During the total observation period of 395 dialysis months, 27 peritonitis episodes were diagnosed (1:14.6 months or 0.82/patient per year). Of our population, 43% remained peritonitis free; seven patients suffered from more than one peritonitis episode. Ten potential risk factors [age, gender, PD modality, duration of PD, exit-site status, urine volume, residual glomerular filtration rate (GFR), Kt/V, normalized protein catabolic rate (nPCR), albumin] and four indices of peritonitis outcome (peritonitis incidence, peritonitis burden, risk of suffering more than one episode of peritonitis and chance of staying free from peritonitis) were analyzed. Our study identified six risk factors in univariate analysis, namely age, APD treatment, exit-site infections, low urinary volume, low residual GFR and low nPCR, which were significantly correlated with two or more of the outcome indices. Multivariate analysis identified exit-site infection and residual urine volume as strong independent predictors. In summary, our study identified several age-dependent and age-independent risk factors for peritonitis in pediatric PD. These data demonstrate that the risk for peritonitis in small children is not pre-determined but might be open to therapeutic interventions, such as optimizing exit-site care, dialysis prescription and nutrition management.

Upper urinary tract: when is obstruction obstruction?

Purpose of review Obstruction can either be defined as a condition that hampers optimal renal development, or, more conservatively, as a restriction to urinary outflow that, when left untreated, will cause progressive renal deterioration. Currently, management is mostly based on the latter definition, but still remains controversial. Relevant work published before 2002 is considered because of a lack of recent literature. Recent findings Almost all reports comparing the primary conservative treatment of suspected obstruction versus early surgical intervention show comparable results, but there are different interpretations. The approach of ‘watch and wait’ for a unilateral hydronephrotic kidney with normal function is usually quite safe, with a very low risk of the permanent loss of renal function when accompanied by close monitoring, but it is certainly not without risk. At this time, the main underlying problems are that all currently applied diagnostic methods only detect effects secondary to obstruction, and the currently used definition of obstruction is based on a longitudinal observation period. The most relevant publication in the observation period was an in-depth report on a workshop in which the need for valid prospective markers for renal maldevelopment and ‘significant’ obstruction was expressed. Summary The optimal management of infants with congenital hydronephrosis and suspected obstruction will remain controversial until new diagnostic methods are able to discriminate between ‘harmful’ and ‘harmless’ obstruction. Most experts currently advocate primary conservative management, with close follow-up and surgical intervention only if there are signs of reduced function of the obstructed kidney.

WDR73 Mutations Cause Infantile Neurodegeneration and Variable Glomerular Kidney Disease

Infantile‐onset cerebellar atrophy (CA) is a clinically and genetically heterogeneous trait. Galloway–Mowat syndrome (GMS) is a rare autosomal recessive disease, characterized by microcephaly with brain anomalies including CA in some cases, intellectual disability, and early‐infantile‐onset nephrotic syndrome. Very recently, WDR73 deficiency was identified as the cause of GMS in five individuals. To evaluate the role of WDR73 mutations as a cause of GMS and other forms of syndromic CA, we performed Sanger or exome sequencing in 51 unrelated patients with CA and variable brain anomalies and in 40 unrelated patients with a diagnosis of GMS. We identified 10 patients from three CA and from two GMS families with WDR73 mutations including the original family described with CA, mental retardation, optic atrophy, and skin abnormalities (CAMOS). There were five novel mutations, of which two were truncating and three were missense mutations affecting highly conserved residues. Individuals carrying homozygous WDR73 mutations mainly presented with a pattern of neurological and neuroimaging findings as well as intellectual disability, while kidney involvement was variable. We document postnatal onset of CA, a retinopathy, basal ganglia degeneration, and short stature as novel features of WDR73‐related disease, and define WDR73‐related disease as a new entity of infantile neurodegeneration.

C4d in pediatric renal allograft biopsies: A marker for negative outcome in steroid‐resistant rejection

Abstract:  Recently, deposition of C4d, reflecting complement activation via the classical pathway, has been established as marker of antibody‐mediated rejection. As C4d can be detected in paraffin sections, it allows for retrospective analysis in populations with low case loads, such as in pediatric transplantation. In this study we re‐evaluated consecutive renal transplant biopsies obtained since 1990 in 36 children (18 boys, 18 girls) who had received their allograft (nine living, 27 cadaveric) at an age of 10.12±4.4 yr. Clinical indications for biopsy were 16 acute steroid resistant rejections (ASRs), 11 chronic rejections and nine other diagnoses. Overall, C4d deposition was found in nine cases (25%), eight of them with diagnosed ASR. Six out of these eight allografts were lost during 36 months of clinical follow‐up, a significantly higher rate than in C4d‐negative biopsies (p<0.05). C4d status therefore turned out to be an excellent predictor for inferior graft survival following ASR. None of the other histopathologic markers were sensitive for humoral rejections. In conclusion, the high prevalence of C4d‐positive staining in ASR demonstrates the importance of the humoral part of the immune system in pediatric transplantation. The worse outcome of C4d‐positive rejections despite massive immunosuppressive therapy clearly indicates the need for innovative therapies in this high‐risk population.

Addition of Alanyl-Glutamine to Dialysis Fluid Restores Peritoneal Cellular Stress Responses – A First-In-Man Trial

Background Peritonitis and ultrafiltration failure remain serious complications of chronic peritoneal dialysis (PD). Dysfunctional cellular stress responses aggravate peritoneal injury associated with PD fluid exposure, potentially due to peritoneal glutamine depletion. In this randomized cross-over phase I/II trial we investigated cytoprotective effects of alanyl-glutamine (AlaGln) addition to glucose-based PDF. Methods In a prospective randomized cross-over design, 20 stable PD outpatients underwent paired peritoneal equilibration tests 4 weeks apart, using conventional acidic, single chamber 3.86% glucose PD fluid, with and without 8 mM supplemental AlaGln. Heat-shock protein 72 expression was assessed in peritoneal effluent cells as surrogate parameter of cellular stress responses, complemented by metabolomics and functional immunocompetence assays. Results AlaGln restored peritoneal glutamine levels and increased the primary outcome heat-shock protein expression (effect 1.51-fold, CI 1.07–2.14; p = 0.022), without changes in peritoneal ultrafiltration, small solute transport, or biomarkers reflecting cell mass and inflammation. Further effects were glutamine-like metabolomic changes and increased ex-vivo LPS-stimulated cytokine release from healthy donor peripheral blood monocytes. In patients with a history of peritonitis (5 of 20), AlaGln supplementation decreased dialysate interleukin-8 levels. Supplemented PD fluid also attenuated inflammation and enhanced stimulated cytokine release in a mouse model of PD-associated peritonitis. Conclusion We conclude that AlaGln-supplemented, glucose-based PD fluid can restore peritoneal cellular stress responses with attenuation of sterile inflammation, and may improve peritoneal host-defense in the setting of PD.

Overexpression of Hsp70 confers cytoprotection during gliadin exposure in Caco-2 cells

Background:In Celiac disease (CD), cytoskeletal integrity of intestinal cells is disrupted by gliadin exposure. This study investigates the role of heat shock protein (Hsp)70 during cytoskeletal recovery in CD by assessing its induction and effects on junctional proteins.Methods:Using an in-vitro model of CD, cytoskeletal injury and recovery was assessed in gliadin-exposed Caco-2 cells by measuring cellular distribution of ezrin, E-cadherin, and Hsp70 by differential centrifugation. Effects of Hsp70 were tested by an in-vitro repair assay, based on the incubation of injured or recovered cytoskeletal cellular fractions in noncytoskeletal supernatants containing low or high levels of Hsp70, or by transient transfection of Caco-2 cells with Hsp70.Results:Cytoskeletal disruption of ezrin and E-cadherin was demonstrated in gliadin-exposed Caco-2 cells by their significant shift from the cytoskeletal pellet into the noncytoskeletal supernatant fraction. Recovery from gliadin exposure was associated with induction and cytoskeletal redistribution of Hsp70. The in-vitro repair assay delineated direct evidence for HSP-mediated repair by stabilization of junctional proteins by Hsp70. Overexpression of Hsp70 resulted in significantly increased cytoskeletal integrity.Conclusion:Our results establish an essential role of HSP-mediated cytoskeletal repair in Caco-2 cells during recovery from in-vitro gliadin exposure.

Donor-specific HLA antibodies and graft function in kidney-transplanted children - the Vienna cohort.

In the pediatric population, little is known on de novo DSA development, its impact on graft function, and association with suboptimal IS. We assessed the prevalence of de novo DSA in the Vienna cohort of 40 renal transplanted children and adolescents and prospectively followed its association with clinical parameters, graft function, and proteinuria for one yr. At the cross‐sectional analysis (median post‐transplant time of five yr), 17% of the patients had developed de novo DSA. All HLA‐Ab were anti‐HLA class II antibodies and persisted in 85% of the cases until the follow‐up screening performed within one yr. Basic clinical and laboratory parameters did not differ between DSA‐negative and DSA‐positive patients at the time of HLA‐Ab screening. Suboptimal IS due to reduced medication or non‐adherence could not be proven in DSA‐positive patients. The changes in eGFR did not differ during the prospective study period, but there was a significantly higher proteinuria in the DSA‐positive patients during the follow‐up. Our data demonstrate an overall prevalence of 17% of de novo DSA in a pediatric renal transplant cohort. During 12 months of prospective follow‐up time, we could demonstrate a significant impact of de novo DSA presence on proteinuria.

Feasibility of Metabolomics Analysis of Dialysate Effluents from Patients Undergoing Peritoneal Equilibration Testing

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A Combined Transcriptome and Bioinformatics Approach to Unilateral Ureteral Obstructive Uropathy in the Fetal Sheep Model

PURPOSE Fetal obstructive uropathy is a leading cause of loss of renal function. Characterizing the molecular fingerprint of cellular responses to obstruction in a fetal model of complete unilateral ureteral obstruction may help elucidate the activated mechanisms and suggest new therapeutic interventions. MATERIAL AND METHODS Unilateral ureteral obstruction was created in 3 sheep fetuses at day 60 of gestation. For transcriptome analysis total RNA was extracted from vital renal biopsies 2 weeks after intervention from obstructed kidneys and from control kidneys of untreated twins. cDNA preparation, hybridization to the GeneChip® Bovine Genome Array and array scanning were done according to manufacturer protocols. Bioinformatics analysis was used to derive functional biological processes linked to obstructive uropathy. Quantitative reverse-transcriptase-polymerase chain reaction and immunohistochemistry were used to validate microarray results. RESULTS Seven biological processes were identified as significantly affected by differentially regulated features that characterize unilateral ureteral obstruction, namely protein metabolism and modification, other metabolism, neuronal activity, ligand mediated signaling, amino acid metabolism, coenzyme/prosthetic group metabolism and rRNA metabolism. Literature mining identified 17 candidate genes previously reported as key in the context of unilateral ureteral obstruction, related pathological mechanisms or other kidney diseases. CONCLUSIONS Combined transcriptome and bioinformatics analysis allowed the identification of enriched processes in the fetal sheep model of unilateral ureteral obstruction that are likely associated with renal damage but to our knowledge have not been previously identified. Future clarification of these molecular fingerprints may eventually provide therapeutic targets and early predictive markers involved in the pathogenesis of fetal uropathy.

A fetal sheep model for studying compensatory mechanisms in the healthy contralateral kidney after unilateral ureteral obstruction.

INTRODUCTION Fetal unilateral ureteral obstruction (UUO) triggers complex pathophysiology involving not only the affected organ but also the contralateral kidney, which undergoes evident compensatory changes. OBJECTIVE We hypothesized that it would be possible to characterize a transcriptomic fingerprint and selected molecular mechanisms for compensatory growth of contralateral kidneys in UUO, specifically focusing on mediators, carriers, membrane transport, and organ crosstalk in an ovine fetal UUO model. STUDY DESIGN A fetal ovine model of complete UUO was created on the 60th day of gestation. For transcriptomics profiling, total RNA was extracted from vital renal biopsies of contralateral (non-obstructed) kidneys harvested on the 80th day of gestation, and kidneys of untreated fetuses served as controls. Statistical analysis provided the set of differentially regulated genes further forwarded to bioinformatics analysis for identification of eventual compensatory molecular mechanisms. Histological analysis was performed with hematoxylin and eosin and periodic acid-Schiff stains. RESULTS Contralateral kidneys showed compensatory hypertrophic renal growth, represented on the molecular side by 324 protein coding genes differentially regulated compared with the control kidney samples. Bioinformatics analysis identified an interactome (Figure) consisting of 102 genes with 108 interactions mainly involving transporters (protein transport and protein localization as well as in protein degradation), signaling molecules, DNA/nucleotide/RNA processing, and components of catabolism and cell cycle regulation. Within the interactome, nine receptors were identified as differentially regulated on the contralateral kidney, involving potential renoprotective ligands of the prostaglandin and the bradykinin receptor, arginine vasopressin receptor 1B, and integrin beta 4. Interestingly, a broad range of molecules found differentially expressed, has been previously described in stress response, renoprotection and repair (e.g., MAPK3, MCP1, DICER1, and others). DISCUSSION The compensatory renal growth interactome provides a network of transcripts significantly altered in the contralateral kidney, potentially allowing novel insights into mechanisms, interactions, and signaling pathways associated with compensatory growth, and renal protection and repair. Interestingly, the finding of an embedded gene signature reflecting signaling and communication suggests a key role of these processes in CRG either by crosstalk, soluble substances, carriers, or membrane signaling. CONCLUSIONS Using a transcriptomics approach, it was possible to identify a gene expression fingerprint of contralateral renal growth in a fetal UUO model. Further studies are warranted to validate those processes and to allow incorporation of this knowledge in new fetal diagnostic or even therapeutic strategies.