End-stage Renal Failure In Children Research Articles

ICAM-1 expression is upregulated in reflux nephropathy.

Reflux nephropathy (RN) is a major cause of end-stage renal failure in children and young adults. Intercellular adhesion molecule-1 (ICAM-1), a cell surface glycoprotein, has a role in the regulation of interaction among immune cells. It has been demonstrated that increased levels of tubular ICAM-1 correlate with an extent of tubular damage in diabetic nephropathy. We hypothesized that ICAM-1 local synthesis is altered in reflux nephropathy and therefore designated this study to investigate ICAM-1 expression in RN. The kidney specimens from six patients with severe reflux nephropathy secondary to primary vesicoureteral reflux were obtained at the time of nephrectomy. Control materials included normal kidney specimens obtained from three adult patients during partial nephrectomy for an incidentaloma. Fluorescent immunohistochemistry was carried out using monoclonal antibodies to ICAM-1 utilizing confocal laser scanning microscopy. Reverse transcriptase polymerase chain reaction (RT-PCR) was performed to evaluate the relative amount of ICAM-1. In the control kidneys, there was lack of ICAM-1 immunoreactivity in the interstitium and proximal tubules and moderate immunoreactivity in the glomerulus. In the refluxing kidney there was strong ICAM-1 immunoreactivity in the glomerulus, interstitium and proximal tubules. The RT-PCR showed strong ICAM-1 mRNA expression in the refluxing kidneys and absent or weak ICAM-1 expression in the controls. Our findings of increased expression of ICAM-1 in the severe reflux nephropathy kidney suggests that ICAM-1 may play a role in the pathogenesis of renal parenchymal damage associated with RN.

Urinary Outflow Obstruction Increases Apoptosis and Deregulates Bcl-2 and Bax Expression in the Fetal Ovine Bladder

During organogenesis, net growth of tissues is determined by a balance between proliferation, hypertrophy, and apoptotic death. Human fetal bladder outflow obstruction is a major cause of end-stage renal failure in children and is associated with complex pathology in the kidney and lower urinary tract. Experimental manipulation of the fetal sheep urinary tract has proved informative in understanding the pathobiology of congenital obstructive uropathy. In this study we used an ovine model of fetal bladder outflow obstruction to examine effects on apoptotic cell death in the developing urinary bladder. While 30 days of obstruction in utero between 75 and 105 days gestation resulted in overall growth of the fetal bladder as assessed by weight, protein, and DNA measurements, we found that apoptosis, as assessed by in situ end-labeling, was up-regulated in fetal bladder detrusor muscle and lamina propria cells and that this was accompanied by a down-regulation of the anti-death protein Bcl-2 and an up-regulation of the pro-death protein Bax. Moreover, activated caspase-3, an effector of apoptotic death, was increased in obstructed bladders. This is the first study to define altered death in an experimental fetal model of bladder dysmorphogenesis. We speculate that enhanced apoptosis in detrusor smooth muscle cells is part of a remodeling response during compensatory hyperplasia and hypertrophy. Conversely, in the lamina propria, an imbalance between death and proliferation leads to a relative depletion of cells.

Neurotransmission and viscoelasticity in the ovine fetal bladder after in utero bladder outflow obstruction.

Fetal bladder outflow obstruction, predominantly caused by posterior urethral valves, results in significant urinary tract pathology; these lesions are the commonest cause of end-stage renal failure in children, and up to 50% continue to suffer from persistent postnatal bladder dysfunction. To investigate the physiological development of the fetal bladder and the response to urinary flow impairment, we performed partial urethral obstruction and complete urachal ligation in the midgestation fetal sheep for 30 days. By electrical and pharmacological stimulation of bladder strips, we found that muscarinic, purinergic, and nitrergic mechanisms exist in the developing fetal bladder at this gestation. After bladder outflow obstruction, the fetal bladder became hypocontractile, producing less force after nerve-mediated and muscarinic stimulation with suggested denervation, and also exhibited greater atropine resistance. Furthermore, fetal bladder urothelium exerted a negative inotropic effect, partly nitric oxide mediated, that was not present after obstruction. Increased compliance, reduced elasticity, and viscoelasticity were observed in the obstructed fetal bladder, but the proportion of work performed by the elastic component (a physical parameter of extracellular matrix) remained the same. In addition to denervation, hypocontractility may result from a reduction in the elastic modulus that may prevent any extramuscular components from sustaining force produced by detrusor smooth muscle.

A Gene Mutated in Nephronophthisis and Retinitis Pigmentosa Encodes a Novel Protein, Nephroretinin, Conserved in Evolution

Nephronophthisis (NPHP) comprises a group of autosomal recessive cystic kidney diseases, which constitute the most frequent genetic cause for end-stage renal failure in children and young adults. The most prominent histologic feature of NPHP consists of development of renal fibrosis, which, in chronic renal failure of any origin, represents the pathogenic event correlated most strongly to loss of renal function. Four gene loci for NPHP have been mapped to chromosomes 2q13 (NPHP1), 9q22 (NPHP2), 3q22 (NPHP3), and 1p36 (NPHP4). At all four loci, linkage has also been demonstrated in families with the association of NPHP and retinitis pigmentosa, known as "Senior-Løken syndrome" (SLS). Identification of the gene for NPHP type 1 had revealed nephrocystin as a novel docking protein, providing new insights into mechanisms of cell-cell and cell-matrix signaling. We here report identification of the gene (NPHP4) causing NPHP type 4, by use of high-resolution haplotype analysis and by demonstration of nine likely loss-of-function mutations in six affected families. NPHP4 encodes a novel protein, nephroretinin, that is conserved in evolution--for example, in the nematode Caenorhabditis elegans. In addition, we demonstrate two loss-of-function mutations of NPHP4 in patients from two families with SLS. Thus, we have identified a novel gene with critical roles in renal tissue architecture and ophthalmic function.

The role of nitric oxide in reflux nephropathy.

Reflux nephropathy (RN) is recognized as a major cause of end-stage renal failure in children and young adults. Inhibition of nitric oxide (NO) exacerbates and enhanced production ameliorates tubulointerstitial fibrosis (TIF) in experimental obstructive uropathy. NO is synthesised by NO synthase (NOS), three distinct isoforms of which have been identified: inducible (iNOS), endothelial (eNOS), and neuronal (nNOS). It has been reported that iNOS induces immunologic injury to glomerular cells and enhances accumulation of extracellular matrix in the glomerulus and tubulointerstitial space. Furthermore, it has been suggested that nNOS and eNOS have beneficial effects in ameliorating TIF. We investigated the expression of different isoforms of NOS in severe refluxing kidneys in order to further understand the pathogenesis of RN in kidney specimens from nine children with severe RN obtained at nephrectomy. Control material included normal kidney specimens from three adult patients undergoing partial nephrectomy for small kidney tumours. Histochemistry for NO was performed using nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase. Single-label immunofluorescence histochemistry was carried out using polyclonal antibodies to nNOS, iNOS, eNOS, and transforming growth factor (TGF)-beta 1 employing laser-scanning confocal microscopy. The TUNEL method was used to assess tubular apoptosis. Strong NADPH staining was observed in the proximal tubules of RN kidneys compared to controls, where there was weak staining. Control kidneys demonstrated weak immunoreactivity for iNOS in the proximal tubules and a lack of immunoreactivity for nNOS and eNOS. RN kidneys demonstrated strong immunoreactivity for nNOS in the tubulointerstitial space, for eNOS in the glomerulus, and for iNOS in the glomerulus and proximal tubules. Strong immunoreactivity for TGF beta 1 was seen in the glomerulus and proximal tubules identical to iNOS. Increased immunoreactivity for iNOS and TGF-beta 1 strongly correlated with the severity of apoptosis in RN. Our data demonstrate that NO derived from nNOS, iNOS, and eNOS is strongly expressed in RN. The selective shunting of NO via iNOS may induce renal fibrosis in RN. The upregulation of nNOS and eNOS in RN appears to be a compensatory mechanism of ameliorating TIF.

Nitric oxide, enhanced by macrophage-colony stimulating factor, mediates renal damage in reflux nephropathy

Reflux nephropathy (RN) is a major cause of end-stage renal failure in children and young adults. Nitric oxide (NO) is an important mediator of tissue injury and inflammation. NO production is enhanced by hematopoietic growth factor including macrophage colony stimulating factor (M-CSF). M-CSF plays a pivotal role in the development of nephritis via macrophage activation. The aim of this study was to investigate the expression of inducible NO synthase (iNOS) and M-CSF in the refluxing kidney, in order to further understand the pathogenesis of RN. The kidney specimens from 6 patients with severe RN and 6 controls were examined by NADPH-diaphorase histochemistry and immunohistochemistry using ABC method with anti-M-CSF antibody. Double staining using NADPH-diaphorase histochemistry/M-CSF immunohistochemistry and M-CSF/iNOS fluorescence immunohistochemistry also was performed. In situ hybridization was performed using digoxigenin labeled M-CSF specific probe. RT-PCR was performed to evaluate the relative amount of iNOS mRNA expression. Apoptosis was determined using the in situ end-labeling technique. The most striking difference between tissues from RN patients and controls was the marked increase in NADPH-d activity, iNOS immunoreactivity and mRNA and M-CSF immunoreactivity and mRNA expression in the kidneys of RN patients, particularly in the distal tubules, collecting system. Apoptotic cells were markedly increased in RN compared to controls. Our findings suggest that the increase in M-CSF-stimulated local production of nitric oxide may be a major mediator in the development of reflux nephropathy.

Renal function in congenital anomalies of the kidney and urinary tract.

Congenital anomalies of the kidneys and urinary tract are a major cause of chronic and end-stage renal failure in children. The molecular mechanisms having been elaborated, there is now growing evidence that kidney function is to a large extent determined genetically at an early stage. Assessment of kidney function is an important tool in clinical medicine and is feasible in utero. Postnatally, determination of absolute glomerular filtration rate and also of split and excretory renal function play an important role in the determination of treatment and prognosis. This is supplemented by other biochemical, molecular and interventional prognostic factors, which are of help in preservation of kidney survival by minimizing modulating factors. If chronic or terminal renal failure ensues in childhood or even in early infancy, however, improved medical care has led to encouraging results, ultimately influencing the motivation in the care of children with congenital anomalies of the kidney and urinary tract.

Rapid detection of an Angiotensin Type 2 Receptor Gene variant: no evidence for linkage and association with primary vesicoureteral reflux

Primary vesicoureteral reflux (VUR) affects approximately 1−2% of the general population and is a common cause of end-stage renal failure in children. VUR appears to have a genetic basis and several loci including the Angiotensin Type 2 Receptor Gene (AGTR2) on the X chromosome have been suggested. Using single-strand conformation analysis (SSCA) we typed 103 DNA samples from 17 families with two or more affected individuals for the presence of a splice site mutation in the AGTR2 gene. Linkage analysis revealed a parametric LOD score of −3.977 and a NPL-score of −6,522 by affected-only analysis. Our family-data do not support linkage of VUR to the AGTR2.

Primary, Nonsyndromic Vesicoureteric Reflux and Its Nephropathy Is Genetically Heterogeneous, with a Locus on Chromosome 1

Primary vesicoureteric reflux (VUR) affects 1%-2% of whites, and reflux nephropathy (RN) causes up to 15% of end-stage renal failure in children and adults. There is a 30-50-fold increased incidence of VUR in first-degree relatives of probands, compared with the general population. We report the results of the first genomewide search of VUR and RN; we studied seven European families whose members exhibit apparently dominant inheritance. We initially typed 387 polymorphic markers spaced, on average, at 10 cM throughout the genome; we used the GENEHUNTER program to provide parametric and nonparametric linkage analyses of affected individuals. The most positive locus spanned 20 cM on 1p13 between GATA176C01 and D1S1653 and had a nonparametric LOD score (NPL) of 5.76 (P=.0002) and a parametric LOD score of 3.16. Saturation with markers at 1-cM intervals increased the NPL to 5.94 (P=.00009). Hence, VUR maps to a locus on chromosome 1. There was evidence of genetic heterogeneity at the chromosome 1 locus, and 12 additional loci were identified genomewide, with P<.05. No significant linkage was found to 6p, where a renal and ureteric malformation locus has been reported, or to PAX2, mutations of which cause VUR in renal-coloboma syndrome. Our results support the hypothesis that VUR is a genetic disorder.

Unravelling the genetics of vesicoureteric reflux: a common familial disorder.

Primary vesicoureteric reflux (VUR) is one of the more common genetic disorders. Little is yet known about the genetics of this potentially manageable childhood condition, which is characterised by regurgitation of urine from the bladder to the kidney. The VUR phenotype is associated with shortness of the submucosal segment of the ureter due to congenital lateral ectopia of the ureteric orifice. VUR is found in 30-50% of infants and young children with a urinary tract infection. A serious concern in families with an affected patient is that approximately one half of siblings or offspring will be affected, but up to a half of these affected siblings and offspring may be asymptomatic in childhood. If left untreated, these patients may present later in life with proteinuria, hypertension or renal failure. VUR is the commonest cause of end-stage renal failure in children, and an important cause in adults. As the kidney damage resulting from severe VUR is preventable, early detection is desirable. The techniques for clinical diagnosis are invasive and costly, reinforcing the importance of identification of a gene for VUR to facilitate genetic screening. Although family studies suggest a major dominant gene, the inheritance pattern is still a matter of debate. In rare instances, VUR occurs in association with other diseases, such as the coloboma-ureteric-renal syndrome, which is caused by a PAX2 gene mutation. In this review, we present evidence that this common disorder may be caused by mutations in the developmental pathway of which the PAX2 gene forms a part.

Host defences in continuous ambulatory peritoneal dialysis and the genesis of peritonitis

Continuous ambulatory peritoneal dialysis (CAPD) has come to be extensively used for the treatment of end-stage renal failure in children, and especially infants, such that now more than half of children on dialysis worldwide receive treatment by this means. Peritonitis, however, is commoner in children than in adults receiving treatment, and is a major source of morbidity and treatment failure in children started on CAPD. Only recently has the immunology of the normal peritoneum been studied extensively, with the need to assess the impact of the installation of large volumes of fluid into the peritoneal sac during dialysis. The main phagocytic defences of the peritoneum depend upon a unique set of macrophages which are present free in the peritoneal fluid but also in the submesothelium and in perivascular collections together with B lymphocytes in the submesothelial area. Both the number of macrophages per unit volume and the concentration of opsonic proteins, such as IgG, complement and fibronectin, are reduced to between only 1% and 5% when dialysis fluid is continuously present in the peritoneal sac. In addition, the fluids used for CAPD are toxic to both macrophages and to mesothelial cells. Thus minor degrees of contamination frequently lead to peritonitis and in addition the majority of patients have catheters inserted in their peritoneum which become colonised with organisms capable of producing exopolysaccharide (slime), which promotes adhesion of the organism to the plastic and protects them against phagocytic attack and the penetration of antibiotics. Thus the peritoneum is in a state of continual inflammation, as well as being a markedly more vulnerable site than the normal peritoneum to the entry of organisms. Whether clinical peritonitis appears in this state of chronic contamination probably depends on perturbation in the balance between host defences and the organism. Whilst Staphylococcus epidermidis is the commonest cause of peritonitis, Staphylococcus aureus and Gram-negative organisms are much more serious and more frequently lead either to temporary catheter removal or discontinuation of dialysis altogether. This review describes the peritoneal defences in relation to the genesis of peritonitis.

Chronic renal failure — is modern management of urinary tract infection and antenatal hydronephrosis affecting the outcome?

End stage renal failure (ESRF) due to urinary tract infection (UTI) is the commonest potentially preventable cause of ESRF in children and adults. Despite this the simple answer to the question posed in the title is that there is no good evidence to support the proposition that modem management of UTI has affected the incidence of ESRF either in children or in adults. There is, however, overwhelming evidence that modem approaches to UTI should reduce the incidence of ESRF. This paradox is worth exploring because in many respects UTI could be considered a paradigm of present day paediatrics. It is difficult to demonstrate a direct link between UTI and the remote outcome of ESRF which may be delayed for decades after the initial insult and even more difficult, if not impossible, to demonstrate that any intervention has affected this outcome. There is a danger if health provision is increasingly dependent on demonstration of measurable, often short-term, improvements in outcome that problems such as UTI that cannot be encapsulated in such a simple way will not receive the attention they deserve. There are many other problems in paediatrics which are similarly threatened. A further difficulty is that almost all reports of management of UTI have identified deficiencies in clinical practice which reduce the impact of rational management based on research findings and this further hinders the demonstration of an improving outcome. For a variety of reasons the evidence with regards to the impact of the management of antenatal hydronephrosis is even more debatable.

Refined mapping of a gene (NPH1) causing familial juvenile nephronophthisis and evidence for genetic heterogeneity.

Familial juvenile nephronophthisis (NPH) is an autosomal recessive progressive tubulo-interstitial kidney disorder, responsible for 6-10% of end-stage renal failure in children, and is frequently associated with Leber amaurosis (termed Senior-Løken syndrome). The biochemical basis of NPH is unknown. We recently reported linkage of the purely renal form of NPH to three markers on chromosome 2. Our results also suggested the existence of genetic heterogeneity between NPH and SLS. To map this NPH gene more precisely, we have now tested the segregation of six new microsatellite markers and five additional families. Haplotype analyses show unequivocally that four NPH families are not linked to the chromosome 2 markers, although there are no clinical or pathological features discernible in these families that could separate them from the families linked to the chromosome 2 NPH locus (NPH1). This reveals genetic heterogeneity in the purely renal form of NPH. In situ hybridization of YAC clones isolated with two closely linked markers assigned the NPH1 region to 2q13. Furthermore, based on haplotype analysis and specific recombination events, the NPH1 gene has been placed between D2S293/D2S340 and D2S121, a genetic interval of about 5-7 cM.

Continuous-Cycling Peritoneal Dialysis for Children: An Alternative to Hemodialysis Treatment

Treatment of end-stage renal failure in children is invasive and prolonged. Although kidney transplantation is often the desired therapy, children usually require some form of life-sustaining dialysis until a suitable donor is found. Home continuous-cycling peritoneal dialysis (CCPD) is a useful alternative to in-center hemodialysis for these children. Adequate biochemical control of the uremic state can be achieved with continuous-cycling peritoneal dialysis. Peritonitis remains the major complication of this form of dialysis, averaging approximately one episode per 12 patient-months. Growth rates of children maintained on continuous-cycling peritoneal dialysis appear to be equivalent to growth rates of children treated with hemodialysis. The advantage of continuous-cycling peritoneal dialysis lies in the fact that exchanges occur during the evening hours and parental intervention is minimized.