Rainer Büscher

Immunosuppression and Renal Outcome in Congenital and Pediatric Steroid-Resistant Nephrotic Syndrome

BACKGROUND AND OBJECTIVESnMutations in podocyte genes are associated with steroid-resistant nephrotic syndrome (SRNS), mostly affecting younger age groups. To date, it is unclear whether these patients benefit from intensified immunosuppression with cyclosporine A (CsA). The aim of this study was to evaluate the influence of podocyte gene defects in congenital nephrotic syndrome (CNS) and pediatric SRNS on the efficacy of CsA therapy and preservation of renal function.nnnDESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTSnGenotyping was performed in 91 CNS/SRNS patients, irrespective of age at manifestation or response to CsA.nnnRESULTSnMutations were identified in 52% of families (11 NPHS1, 17 NPHS2, 11 WT1, 1 LAMB2, 3 TRPC6). Sixty-eight percent of patients with nongenetic SRNS responded to CsA, most of them achieved complete remission. In contrast, none of the patients with genetic CNS/SRNS experienced a complete remission and only two (17%) achieved a partial response, both affected by a WT1 mutation. Preservation of renal function was significantly better in children with nongenetic disease after a mean follow-up time of 8.6 years (ESRD in 29% versus 71%).nnnCONCLUSIONSnThe mutation detection rate in our population was high (52%). Most patients with genetic CNS/SRNS did not benefit from CsA with significantly lower response rates compared with nongenetic patients and showed rapid progression to end-stage renal failure. These data strongly support the idea not to expose CNS/SRNS patients with inherited defects related to podocyte function to intensified immunosuppression with CsA.

Continuous venovenous haemodialysis (CVVHD) and continuous peritoneal dialysis (CPD) in the acute management of 21 children with inborn errors of metabolism

BACKGROUNDnNewborns with inborn errors of metabolism often present with hyperammonaemic coma, requiring prompt diagnosis and specific medical therapy, nutritional support and efficient toxin removal. Little information regarding the efficacy and safety of continuous venovenous haemodialysis (CVVHD) as an option for extracorporal ammonia detoxification in children is available.nnnMETHODSnTwenty-one patients with hyperammonaemia [19 neonates (mean age 4.1 +/- 2.4 days) and two children 1 and 7 years of age, respectively] were admitted to our hospital for dialysis between 1996 and 2008. Seventeen children (15 neonates), received CVVHD. Four neonates received continuous peritoneal dialysis (CPD). All started medical treatment with sodium benzoate, l-arginine hydrochloride and carnitine as well as protein-restricted parenteral diets with high caloric intake before dialysis.nnnRESULTSnPlasma ammonia levels (range 464-7267 microg/dl before dialysis and 27-3317 microg/dl after dialysis) were significantly reduced by 50% within 4.7 +/- 2.5 h with CVVHD compared with 13.5 +/- 6.2 h with CPD (P < 0.0001). Plasma ammonia levels <200 microg/dl critical range were achieved within 22.4 +/- 18.1 h in CVVHD patients compared with 35.0 +/- 24.1 h with CPD. Depending on the weight and blood pressure stability of the patients, mean blood flow velocities of 9.8 +/- 3.4 ml/kg/min and mean dialysate flow rates of 3925 +/- 2398 ml/min/1.73 m(2) were employed. Blood and dialysate flows significantly correlated with ammonia clearance and decay of ammonia in vivo. Because of the severe underlying disease, 18% of CVVHD patients died compared with 50% undergoing CPD. In total, 82% of CVVHD patients survived the first 6 months after dialysis. Among these, 43% were without sequelae, 43% developed moderate mental retardation, and two (14%) developed severe mental retardation.nnnCONCLUSIONnCVVHD effectively and quickly eliminates plasma ammonia. To optimize long-term mental outcome, rapid identification and appropriate treatment of the underlying disease as well as starting dialysis early are of enormous therapeutic value.

Cardiac geometry in children receiving chronic peritoneal dialysis: findings from the International Pediatric Peritoneal Dialysis Network (IPPN) registry.

BACKGROUND AND OBJECTIVESnLeft ventricular hypertrophy (LVH) is an independent risk factor and an intermediate end point of dialysis-associated cardiovascular comorbidity. We utilized a global pediatric registry to assess the prevalence, incidence, and predictors of LVH as well as its evolution in the longitudinal follow-up in dialyzed children.nnnDESIGN, SETTING, PARTICIPANTS, & MEASUREMENTSnCross-sectional echocardiographic, clinical, and biochemical data were evaluated in 507 children on peritoneal dialysis (PD), and longitudinal data were evaluated in 128 patients. The 95(th) percentile of LV mass index relative to height age was used to define LVH.nnnRESULTSnThe overall LVH prevalence was 48.1%. In the prospective analysis, the incidence of LVH developing de novo in patients with normal baseline LV mass was 29%, and the incidence of regression from LVH to normal LV mass 40% per year on PD. Transformation to and regression from concentric LV geometry occurred in 36% and 28% of the patients, respectively. Hypertension, high body mass index, use of continuous ambulatory peritoneal dialysis, renal disease other than hypo/dysplasia, and hyperparathyroidism were identified as independent predictors of LVH. The use of renin-angiotensin system (RAS) antagonists and high total fluid output (sum of urine and ultrafiltration) were protective from concentric geometry. The risk of LVH at 1 year was increased by higher systolic BP standard deviation score and reduced in children with renal hypo/dysplasia.nnnCONCLUSIONSnUsing height-adjusted left ventricular mass index reference data, LVH is highly prevalent but less common than previously diagnosed in children on PD. Renal hypo/dysplasia is protective from LVH, likely because of lower BP and polyuria. Hypertension, fluid overload, and hyperparathyroidism are modifiable determinants of LVH.

α1-adrenoceptor subtype affinities of drugs for the treatment of prostatic hypertrophy

SummaryWe have used radioligand binding and inositol phosphate accumulation studies to determine the affinity at mixed α1A- and α1B-adrenoceptors (rat cerebral cortex and kidney), α1A-adrenoceptors (rat cerebral cortex and kidney following inactivation of α1B-adrenoceptors by chloroethylclonidine treatment) and α1B-adrenoceptors (rat spleen) for drugs currently under investigation for the treatment of benign prostatic hypertrophy, alfuzosin, naftopidil and (−)- and (+)-tamsulosin. Alfuzosin and naftopidil had similar affinities in all model systems (approximately 10 nM and 130 nM, respectively) and lacked relevant selectivity for α1-adrenoceptor subtypes. Their potency to inhibit noradrenaline-stimulated inositol phosphate formation in cerebral cortex matched their affinities as determined in the binding studies. Tamsulosin had higher affinity at α1A- than at α1B-adrenoceptors, and was slightly more potent than alfuzosin and naftopidil at α1B- and considerably more potent at α1A-adrenoceptors. However, the interaction of the tamsulosin isomers with chloroethylclonidine-insensitive (α1A-like) adrenoceptors was complex. A detailed analysis of the tamsulosin data and those obtained with other drugs, most notably noradrenaline and oxymetazoline, suggested that chloroethylclonidine-insensitive α1-adrenoceptors may be heterogenous and that this heterogeneity may differ between cerebral cortex and kidney of the rat.We have used radioligand binding and inositol phosphate accumulation studies to determine the affinity at mixed alpha 1A- and alpha 1B-adrenoceptors (rat cerebral cortex and kidney), alpha 1A-adrenoceptors (rat cerebral cortex and kidney following inactivation of alpha 1B-adrenoceptors by chloroethylclonidine treatment) and alpha 1B-adrenoceptors (rat spleen) for drugs currently under investigation for the treatment of benign prostatic hypertrophy, alfuzosin, naftopidil and (-)- and (+)-tamsulosin. Alfuzosin and naftopidil had similar affinities in all model systems (approximately 10 nM and 130 nM, respectively) and lacked relevant selectivity for alpha 1-adrenoceptor subtypes. Their potency to inhibit noradrenaline-stimulated inositol phosphate formation in cerebral cortex matched their affinities as determined in the binding studies. Tamsulosin had higher affinity at alpha 1A- than at alpha 1B-adrenoceptors, and was slightly more potent than alfuzosin and naftopidil at alpha 1B- and considerably more potent at alpha 1A-adrenoceptors. However, the interaction of the tamsulosin isomers with chloroethylclonidine-insensitive (alpha 1A-like) adrenoceptors was complex. A detailed analysis of the tamsulosin data and those obtained with other drugs, most notably noradrenaline and oxymetazoline, suggested that chloroethylclonidine-insensitive alpha 1-adrenoceptors may be heterogeneous and that this heterogeneity may differ between cerebral cortex and kidney of the rat.

Mutations in nuclear pore genes NUP93, NUP205 and XPO5 cause steroid-resistant nephrotic syndrome

Nucleoporins are essential components of the nuclear pore complex (NPC). Only a few diseases have been attributed to NPC dysfunction. Steroid-resistant nephrotic syndrome (SRNS), a frequent cause of chronic kidney disease, is caused by dysfunction of glomerular podocytes. Here we identify in eight families with SRNS mutations in NUP93, its interaction partner NUP205 or XPO5 (encoding exportin 5) as hitherto unrecognized monogenic causes of SRNS. NUP93 mutations caused disrupted NPC assembly. NUP93 knockdown reduced the presence of NUP205 in the NPC, and, reciprocally, a NUP205 alteration abrogated NUP93 interaction. We demonstrate that NUP93 and exportin 5 interact with the signaling protein SMAD4 and that NUP93 mutations abrogated interaction with SMAD4. Notably, NUP93 mutations interfered with BMP7-induced SMAD transcriptional reporter activity. We hereby demonstrate that mutations of NUP genes cause a distinct renal disease and identify aberrant SMAD signaling as a new disease mechanism of SRNS, opening a potential new avenue for treatment.

Alterations in appetite-regulating hormones influence protein–energy wasting in pediatric patients with chronic kidney disease

Protein–energy wasting is a common problem in pediatric patients with chronic kidney disease (CKD). Disturbances in appetite-regulating hormones have been suggested as causative factors. Acyl ghrelin is a potent orexigenic hormone, whereas desacyl ghrelin and obestatin have the opposite effect. The regulation of acyl ghrelin and its anorexigenic opponents and its role in the development of CKD-associated protein–energy wasting is poorly understood. We measured total and acylated ghrelin, obestatin, leptin, and adiponectin in children with CKD (nu2009=u200929), children undergoing hemodialysis (HD) or peritoneal dialysis (PD; nu2009=u200929), renal transplant recipients (RTx; nu2009=u200991), and healthy controls (nu2009=u200927), and analyzed the data in relation to body mass index (BMI) and height. Patients with renal insufficiency showed lower BMI standard deviation score (SDS) values and height SDS compared with controls and RTx patients. Total ghrelin was elevated in CKD and dialyzed patients compared with controls or transplant recipients (Pu2009<u20090.001). Acyl ghrelin did not differ between groups, and the acyl ghrelin/total ghrelin ratio was reduced in uremic patients (Pu2009<u20090.05). Obestatin plasma levels were increased in patients with renal insufficiency compared with controls and RTx patients (Pu2009<u20090.01). Uremia leads to an accumulation of the anorexigenic hormones desacyl ghrelin and obestatin. Orexigens like acyl ghrelin are not elevated. A disturbed balance between anorexigenic and orexigenic hormones may influence development of CKD-associated protein–energy wasting in pediatric patients.

Clinical manifestations of autosomal recessive polycystic kidney disease (ARPKD): kidney-related and non-kidney-related phenotypes

Autosomal recessive polycystic kidney disease (ARPKD), although less frequent than the dominant form, is a common, inherited ciliopathy of childhood that is caused by mutations in the PKHD1-gene on chromosome 6. The characteristic dilatation of the renal collecting ducts starts in utero and can present at any stage from infancy to adulthood. Renal insufficiency may already begin in utero and may lead to early abortion or oligohydramnios and lung hypoplasia in the newborn. However, there are also affected children who have no evidence of renal dysfunction in utero and who are born with normal renal function. Up to 30xa0% of patients die in the perinatal period, and those surviving the neonatal period reach end stage renal disease (ESRD) in infancy, early childhood or adolescence. In contrast, some affected patients have been diagnosed as adults with renal function ranging from normal to moderate renal insufficiency to ESRD. The clinical spectrum of ARPKD is broader than previously recognized. While bilateral renal enlargement with microcystic dilatation is the predominant clinical feature, arterial hypertension, intrahepatic biliary dysgenesis remain important manifestations that affect approximately 45xa0% of infants. All patients with ARPKD develop clinical findings of congenital hepatic fibrosis (CHF); however, non-obstructive dilation of the intrahepatic bile ducts in the liver (Caroli’s disease) is seen at the histological level in only a subset of patients. Cholangitis and variceal bleeding, sequelae of portal hypertension, are life-threatening complications that may occur more often in advanced cases of liver disease. In this review we focus on common and uncommon kidney-related and non-kidney-related phenotypes. Clinical management of ARPKD patients should include consideration of potential problems related to these manifestations.

FAT1 mutations cause a glomerulotubular nephropathy

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we show that recessive mutations in FAT1 cause a distinct renal disease entity in four families with a combination of SRNS, tubular ectasia, haematuria and facultative neurological involvement. Loss of FAT1 results in decreased cell adhesion and migration in fibroblasts and podocytes and the decreased migration is partially reversed by a RAC1/CDC42 activator. Podocyte-specific deletion of Fat1 in mice induces abnormal glomerular filtration barrier development, leading to podocyte foot process effacement. Knockdown of Fat1 in renal tubular cells reduces migration, decreases active RAC1 and CDC42, and induces defects in lumen formation. Knockdown of fat1 in zebrafish causes pronephric cysts, which is partially rescued by RAC1/CDC42 activators, confirming a role of the two small GTPases in the pathogenesis. These findings provide new insights into the pathogenesis of SRNS and tubulopathy, linking FAT1 and RAC1/CDC42 to podocyte and tubular cell function.

The response to cyclophosphamide in steroid-sensitive nephrotic syndrome is influenced by polymorphic expression of glutathion-S-transferases-M1 and -P1

Glutathione-S-transferases (GST) play a central role in the inactivation of toxic drugs like cyclophosphamide (CP). These enzymes depict several polymorphisms with altered activity, and it has been shown that different polymorphisms influence the risk of malignancies and the outcome after chemotherapy. To prove the hypothesis that CP efficacy in children with nephrotic syndrome is influenced by polymorphic expression of GSTs, the genotype of 26 patients was analyzed and correlated with the outcome after CP treatment. All 26 children with steroid-sensitive nephrotic syndrome and frequent relapses or steroid dependency were treated with CP at a mean age of 6.7±4.0xa0years. CP was given in a dose of 2xa0mg/kg/day for 12±1xa0week. GST-M1, GST-P1 and GST-T1 polymorphisms were detected by PCR. In patients with GST-M1 null polymorphism, a significantly better rate of sustained remission was seen than in patients with the heterozygous or homozygous GST-M1 wildtype (0 versus 29%, P <0.01). In contrast, children with GST-P heterozygous or homozygous polymorphism had a significantly lower rate of sustained remission compared to homozygous wildtype (7 versus 38%, P <0.02). The GST-T1 genotype did not influence the outcome after CP treatment (P =0.32). Patients with the combination of GST-M1 null and GST-P1 wildtype did not relapse in 50%, compared to 6% in other children (P <0.01). We conclude that the polymorphic expression of GST-M1 and -P1 did significantly influence the long-term remission rate after CP treatment of steroid-sensitive nephrotic syndrome in children. Whereas GST-M1 null will increase cyclophosphamide efficacy, GST-P1 polymorphism seems to be related to enhanced susceptibility to further relapses.

Regional citrate anticoagulation is safe in intermittent high-flux haemodialysis treatment of children and adolescents with an increased risk of bleeding

BACKGROUNDnRegional citrate anticoagulation (RCA) is strongly recommended for adults with an increased risk of bleeding complications. The objective of this retrospective analysis was to evaluate an RCA protocol concerning feasibility and safety in intermittent high-flux haemodialysis (iHD) treatment in children and adolescents.nnnMETHODSnEighteen children and adolescents aged 5-17 years (median 15 years) underwent 74 iHD treatment sessions with RCA. Twelve of 18 patients presented with overt local or diffuse haemorrhage before beginning the HD sessions, and six had an increased risk of haemorrhagic complications. Forty children on acute haemodialysis with general heparin anticoagulation, matched for bleeding risk, age and body surface area, served as a control group. Citrate 3% solution was begun with 3.3% blood flow rate, and calcium gluconate 10% substitution was started with 0.4% of blood flow rate. Citrate flow was adapted to achieve a post-filter ionized calcium of ≤0.30 mmol/L; calcium substitution was adapted to maintain the patients serum calcium levels within the physiological range. Calcium-free dialysis fluid was used. The blood flow rate ranged from 3 to 5 mL per minute and kilogram body weight.nnnRESULTSnRegional anticoagulation was successfully achieved within the extracorporeal blood circuit, while the coagulation of all 18 patients remained within physiological parameters. No adverse effects of RCA were observed. In all 18 children, neither new haemorrhage nor worsening of the bleeding situation occurred, and in 10/12 patients, bleeding stopped during dialysis with RCA. In contrast, one-third of the control group developed new haemorrhagic complications or presented with worsening of pre-existing bleeding during haemodialysis (P = 0.006).nnnCONCLUSIONnRCA is feasible, safe and effective in paediatric intermittent haemodialysis treatment.