CASK Soluble a New Factor Implicated in Pathogenesis of Recurrence of Segmental and Focal Glomerulosclerosis after Renal Transplantation

La hyalinose segmentaire et focale (HSF) est une maladie rénale sévère dont la physiopathologie est complexe. La récidive de la maladie après transplantation rénale et l’obtention de sa rémission après un traitement par immunoadsorption (IA) illustre l’implication d’un facteur circulant dans sa physiopathologie, capable de se fixer à la protéine A. Récemment, suPAR a été rapporté comme agent causal et marqueur de la HSF. Le premier objectif de notre travail a été de vérifier si suPAR se fixe à la protéine A. Le deuxième objectif a été d’identifier le facteur circulant responsable de la récidive de la HSF après transplantation rénale, à partir de l’analyse par spectrométrie de masse des protéines liées à la colonne de protéine A après (IA). Premièrement, nous avons mesuré la concentration de suPAR par un test ELISA parmi les protéines fixées à la colonne de protéine A après IA chez 7 patients atteints de HSF récidivantes et dans le sérum de 13 patients atteints de HSF récidivantes et de 11 contrôles sains. Le sérum des patients a été immunoadsorbé in vitro sur bille de protéine A sépharose. Nous avons quantifié suPAR avant et après la procédure et dans l’éluat des protéines fixées à la protéine A. La concentration de suPAR est plus élevée chez les patients atteints de HSF récidivantes par rapport aux groupes contrôles. La concentration de suPAR est très faible dans les proteines éluées à partir de la colonne de protéine A, indiquant que suPAR ne se lie pas à la protéine A et n’est pas le facteur circulant élué par les colonnes de protéines A. Deuxièmement, nous avons identifié le FC à partir des protéines fixées à la colonne de protéine A par une caractérisation des protéines par spectrométrie de masse chez des patients traités pour récidive de HSF et chez un patient contrôle. Nous avons recherché le FC dans le sérum de patient atteint de HSF, de patient ayant une néphropathie diabétique et chez des contrôles sains. L’effet de la protéine recombinante du FC a été testé in vitro sur une culture de podocytes et in vivo chez la souris. Nous avons identifié une forme sérique de CASK (calcium calmoduline sérine thréonine kinase), à partir des protéines fixées à la colonne de protéine A après IA. CASK est présente uniquement dans le sérum de patients atteints de HSF et non dans les groupes contrôles. In vitro, la protéine recombinante de CASK (CASKr) induit une redistribution de l’actine du cytosquelette des podocytes en culture par une interaction avec CD98. CASKr altére la perméabilité des podocytes à l’abumine et induit in vivo une protéinurie chez la souris associé à un effacement des pédicelles.En conclusion, suPAR ne se fixe pas à la protéine A ni in vivo ni in vitro. Une forme sérique de CASK est impliqué dans la récidive de la HSF avec comme cible potentiel CD98 sur le podocyte.Focal and segmental glomerulosclerosis (FSGS) is a serious disease, the pathogenesis of which is unknown. Its recurrence after transplantation (Tx) and its partial remission after treatment with immunoadsorption (IA) on a protein A column indicate the existence of a circulating factor (CF) responsible for the disease that is able to bind to a protein A column. Recently, the soluble receptor of urokinase (suPAR) was described as the factor responsible for FSGS. The first aim of my work was to test the capacity of suPAR to bind to protein A and to be eliminated by IA. The second aim was to identify the CF responsible of the recurrence of the disease after renal transplantation from the analysis of proteins eluted from protein-A columns from patients with rFSGS who had undergone therapeutic (IA). First, we measured suPAR in eluates of protein A columns from 7 patients with recurrent FSGS after Tx (rFSGS) treated with IA, and in the serum of 13 patients with rFSGS and 11 healthy donors (HD). Additionally, the plasma of these patients was immunoadsorbed in vitro on a protein A Sepharose column and we quantified suPAR in the eluates and in pre- and post-column samples. The concentration of suPAR was higher in the plasma of patients with rFSGS than in the plasma of HD patients. However, the concentration of suPAR was similar before and after IA on protein A for the rFSGS and HD samples. The suPAR concentration was very low in the eluates from protein A columns incubated with plasma from HD or rFSGS patients. However, 85% of rFSGS patients showed a decrease in immunoglobulin G and proteinuria. Secondly, we analyzed proteins eluted from protein-A columns from patients with rFSGS who had undergone therapeutic immunoadsorption. Compared to control a differential band was identified by mass spectrometry. The expression of this protein was tested by immunochemical methods in sera from healthy controls, from patients with proteinuria caused by diabetic nephropathy, and from rFSGS patients. The effect of the recombinant protein was evaluated in vitro (podocytes) and in vivo experiments (mice). A soluble form of calcium/calmodulin-dependent serine/threonine kinase (CASK) eluted from protein-A columns was identified by mass spectrometry. CASK was immunoprecipitated only in the sera from patients with rFSGS. Recombinant CASK induced reorganization of the actin cytoskeleton of cultured podocytes through an interaction with CD98 at the cell surface. In vitro, CASK increased the permeability of podocyte monolayers, and induced proteinuria and foot-process effacement in miceIn conclusion, suPAR does not significantly bind to protein A in vitro or in vivo. Soluble CASK acts as a permeability factor in patients with rFSGS bindinding CD98 on podocytes

Complications osseuses chez les patients en hémodialyse (mise au point d'un score radiologique, étude comparative de deux membranes synthétiques de dialyse sur l'évolution de ce score au long cours)

TOURS-BU Médecine (372612103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Le contenu hépatique en fer diffère de façon significative entre les patients en dialyse péritonéale et les patients en hémodialyse

Introduction Iron overload is one of the most controversial topics in the management of anemic dialysis patients. Parenteral iron supplementation is commonly prescribed to hemodialysis (HD) patients but less frequently to peritoneal dialysis (PD) patients. Moreover, ferritin targets are far lower and more physiological in PD than in HD.  Methods We compared the liver iron concentration (LIC) measured by means of Signal-Intensity ratio (SIR) magnetic resonance imaging (MRI) according to Rennes University method in a cohort of 32 PD patients living in the Paris region published in 2017, with two cohorts of French HD patients studied in the same way (119 patients reported in 2012 and 80 further patients reported in 2014). Results Normal hepatic iron load (LIC ≤ 50 µmol/g of dry weight) was observed in 81.3% of the 32 PD patients (CI: 64.3-91.5%), as compared to only 16% (CI: 10.4-23.7%) in the first HD cohort and 35% (CI: 25.4-45.9%) in the second HD cohort (p<0.0001 for both comparisons; X2 test). Mild iron overload (50 < LIC ≤ 100 µmol/g) was found in 5 PD patients and severe overload (LIC > 200 µmol/g) in only one PD patient (who had received IV iron) (3.1%; CI: 0-17.1%). Conversely, severe iron overload was found in 30.3% of patients in the first HD cohort (CI: 22.7-39%) and 11.3% of those in the second HD cohort (CI: 5.8-20.2%) (p= 0.0033 versus the first HD cohort, X2 test). Conclusion Contrary to hemodialysis patients, iron overload is rare and mostly mild in peritoneal dialysis patients.Introduction La surcharge martiale est l’un des sujets les plus controversés dans la prise en charge de l’anémie des patients dialysés. La supplémentation parentérale (IV) en fer est couramment prescrite aux patients en hémodialyse (HD), mais moins fréquemment aux patients traités par dialyse péritonéale (DP). De plus les cibles de ferritine sérique sont beaucoup plus faibles et physiologiques en DP qu’en HD. Méthodes Nous avons comparé la concentration hépatique en fer (CHF), mesurée par imagerie par résonance magnétique (IRM), à l’aide de la méthode du rapport signal-intensité (SIR) selon l'Université de Rennes, dans une cohorte de 32 patients en DP résidant en région parisienne (publiée en 2017), avec deux cohortes de patients hémodialysés français, étudiés de la même manière (119 patients publiés en 2012 et 80 patients supplémentaires publiés en 2014). Résultats Une charge hépatique normale en fer (CHF ≤ 50 µmol/g de poids sec) a été observée chez 81,3% des 32 patients de DP (IC: 64,3-91,5%), comparativement à seulement 16% (IC: 10,4­-23,7%) dans la première cohorte HD et 35% (IC: 25,4-45,9%) dans la deuxième cohorte HD (p<0,0001 dans les deux cas ; test X2). Une surcharge légère en fer (50 < CHF ≤ 100 µmol/g) a été observée chez 5 patients de DP et une surcharge importante (CHF> 200 µmol/g) chez un seul patient de DP (qui avait reçu du fer intraveineux (IV)) (3,1% ; IC: 0-17,1%). Inversement, une surcharge en fer importante a été observée chez 30,3% des patients de la première cohorte HD (IC: 22,7-39%) et 11,3% de ceux de la deuxième cohorte HD (IC: 5,8-20,2%) (p = 0,0033 par rapport à la première cohorte ; test X2). Conclusion Contrairement à l'hémodialyse, la surcharge en fer est rare et généralement légère chez les patients en dialyse péritonéale

Microbiology and outcomes of polymicrobial peritonitis associated with peritoneal dialysis: a register-based cohort study from the French Language Peritoneal Dialysis Registry

International audienceBACKGROUND: Previous studies have reported that polymicrobial peritonitis in peritoneal dialysis (PD) is associated with poor outcomes, but recent data from European cohorts are scarce. METHODS: We included from the French Language Peritoneal Dialysis Registry all patients ≥18 years of age who started PD between January 2014 and November 2020. We compared microbiology and patient characteristics associated with mono- and polymicrobial peritonitis. We assessed patient outcomes after a first polymicrobial peritonitis using survival analysis with competing events. We differentiated microorganisms isolated from dialysis effluent as enteric or non-enteric pathogens. RESULTS: A total of 8848 patients contributed 13 023 patient-years of follow-up and 3348 culture-positive peritonitis episodes, including 251 polymicrobial ones. This corresponded to rates of 0.32 and 0.02 episodes/patient-year, respectively. For most patients (72%) who experienced polymicrobial peritonitis, this was their first peritonitis episode. Enteric pathogens were more frequently isolated in polymicrobial than in monomicrobial peritonitis (57 versus 44%; P < .001). In both cases of peritonitis with and without enteric pathogens, the polymicrobial versus monomicrobial character of the peritonitis was not associated with mortality in patients who did not switch to haemodialysis {adjusted cause-specific hazard ratio [acsHR] 1.2 [95% confidence interval (CI) 0.3-5.0], P = .78 and 1.1 [95% CI 0.7-1.8], P = .73, respectively}. However, the risks of death and switch to haemodialysis were higher for monomicrobial peritonitis with enteric pathogens compared with those without [acsHR 1.3 (95% CI 1.1-1.7), P = .02 and 1.9 (95% CI 1.5-2.4), P < .0001, respectively]. CONCLUSION: Isolation of enteric pathogens, rather than the polymicrobial character of the peritonitis, is associated with poorer outcomes

Arteriovenous fistulas thrombosis in hemodialysis patients with COVID-19

International audienceBackground: The current Coronavirus disease 2019 (COVID-19) outbreak is associated with significant mortality, especially in patients suffering from end stage renal disease (ESRD) and hemodialysis patients. Several previous studies reported an over-risk of arterial and venous thrombosis, in particular pulmonary embolism and venous thrombosis of catheter in COVID19 patients in intensive care unit. However, arteriovenous fistula (AVF) thrombosis has rarely been reported yet in these patients. AVF thrombosis is a serious complication that impacts significantly patients outcome. Here, we aim to describe characteristics and prognosis of a cohort of COVID-19 hemodialysis (HD) patients presenting with AVF thrombosis. Methods: In the Ile de France region (Paris area) during the March 11th–April 30th 2020 period, fistula thrombosis cases were collected among COVID-19 hemodialysis patients in seven dialysis units and in interventional vascular departments. These patients’ characteristics were analyzed through a review of the patient’s medical records. Results: Seventeen patients were included in our study (median age 69 years). Ten patients (59%) were men. Ten patients (59%) were diabetic and 88% had a high blood pressure. The mortality rate in these patients was 47%. All thrombosis treated with a declotting procedures (64%) were successfully cleared, but with early relapse in 36%. Conclusion: Our study highlights AVF thrombosis as a severe complication in COVID-19 hemodialysis patients that contributed to the severity and accelerated death