Inflammatory mediators in human renal dysplasia

Definition, diagnosis and clinical management of non-obstructive kidney dysplasia: a consensus statement by the ERKNet Working Group on Kidney Malformations

Kidney dysplasia is one of the most frequent causes of chronic kidney failure in children. While dysplasia is a histological diagnosis, the term 'kidney dysplasia' is frequently used in daily clinical life without histopathological confirmation. Clinical parameters of kidney dysplasia have not been clearly defined, leading to imprecise communication amongst healthcare professionals and patients. This lack of consensus hampers precise disease understanding and the development of specific therapies. Based on a structured literature search, we here suggest a common basis for clinical, imaging, genetic, pathological and basic science aspects of non-obstructive kidney dysplasia associated with functional kidney impairment. We propose to accept hallmark sonographic findings as surrogate parameters defining a clinical diagnosis of dysplastic kidneys. We suggest differentiated clinical follow-up plans for children with kidney dysplasia and summarize established monogenic causes for non-obstructive kidney dysplasia. Finally, we point out and discuss research gaps in the field.

Constitutive metanephric mesenchyme-specific expression of interferon-gamma causes renal dysplasia by regulating Sall1 expression

Transplacental viral and parasitic infections have been shown to initiate an innate response in the mammalian embryo by increasing the expression of pro-inflammatory cytokines such as interferon-gamma (Ifng). However, the developmental consequences of an activated innate immunity and, in particular, the effects of induction of Ifng expression independent of infection have been largely overlooked. Here, we demonstrate in vivo that the conditional overexpression of Ifng in metanephric mesenchymal (MM) progenitors results in renal agenesis or hypoplasia. Cell death was observed in and around the MM region of E10.5-11.5 mutants where Ifng was constitutively expressed during early kidney development and resulted in a retardation of branching morphogenesis. Furthermore, isolated mutant or normal Ifng-treated metanephroi replicated this phenotype in culture, demonstrating the inherent nature of the aberrant morphogenesis. The expression of renal progenitor marker Sall1 was significantly decreased in the MM of mutant kidneys, suggesting that a reduction in Sall1 may be the cause of cell death in the MM during early kidney development and that, in turn, retards UB branching in the mutants. Therefore, the aberrant induction of Ifng expression, as part of an innate immune response, may contribute to renal agenesis or hypoplasia during early metanephric development by regulating the MM progenitor population.

Analysis of the IL-10, IL-12, and TNF-α Gene Polymorphisms in Patients With Vesicoureteral Reflux Among the Southeast Iranian Population

Background

Vesicoureteral reflux (VUR) is a common childhood disorder that is characterized by the abnormal movement of urine from the bladder into the ureters or kidneys.

Objectives

The aim of this study was to determine whether the genetic polymorphisms of the IL-10, IL-12, and TNF-α genes are involved in the development of VUR.

Patients and Methods

The tetra amplification mutation refractory system-polymerase chain reaction (Tetra-ARMS PCR) was applied to analyze the four polymorphic sites of the IL-10AG-1082, IL-10CA597, IL-12CA1188, and TNF308GA genes in 124 VUR children and 110 healthy controls.

Results

A significant, highly increased risk of VUR disease was found for the CA, AA, and combined genotypes of IL-10CA597 (OR = 5.2, 95% CL: 1.80 - 18.25; P = 0.0006, OR = 9.1, 95% CL: 1.11 - 122.75; P = 0.02, OR = 5.3, 95% CL: 1.82 - 18.61; P = 0.00052, respectively); the AG, GG, and AG + GG genotypes of IL-10AG-1082 (OR = 12.8, 95% CL; 2.9 - 113.9; P = 0.00003, OR = 12.62, 95% CL: 2.93 - 114.53; P = 0.00003, respectively); and the AA genotype of IL-12 (AA, OR = 0.19, 95% CL: 0.5 - 0.55; P = 0.0006). The frequency of the C allele in both IL-10CA and IL-12CA was greater in patients with VUR than in the healthy controls. No association was found between TNF308GA and the risk of VUR.

Conclusions

The results demonstrated significant associations between the IL-10 (AG-1089, IL-10CA) and IL-12 (AA) gene polymorphisms and a highly increased risk of VUR.

Vesicoureteric reflux and tumor necrosis factor-alpha gene polymorphism

AIM

To determine the role of tumor necrosis factor-alpha (TNF-alpha) gene polymorphism in promoting renal scarring among patients with vesicoureteric reflux (VUR). This genetic variant involves a guanosine to adenine transition at position -308, and this single-base polymorphism is associated with increased transcription of the TNF-alpha gene. Recent studies suggest that the TNF-alpha gene may be associated with predisposition to renal scarring.

PATIENTS AND METHODS

A total of 195 (51.8% females) patients with VUR demonstrated by voiding cystourethrogram were recruited, 126 of them with reflux nephropathy diagnosed by dimercaptosuccinic scan. The control group included 266 healthy individuals. Genotyping was performed by polymerase chain reaction and digestion with a restriction enzyme.

RESULTS

Allele frequencies of -308G and -308A were 83.8% and 16.2%, respectively in patients with VUR and 88.9% and 11.1%, respectively in controls (P<0.05). No differences were found in genotype distribution related to presence/absence of renal scars. There was no relationship between TNF-alpha genotype and grade of VUR or the presence of proteinuria.

CONCLUSIONS

Our data suggest that the TNF-alpha AA genotype is not associated with reflux nephropathy. The TNF-alpha-308A allele could be related to a higher susceptibility to VUR.

Persistent metanephric ducts in a geriatric white tiger

An 18-year-old male intact white Tiger (Panthera tigris) was euthanized after a clinical diagnosis of severe renal failure. Postmortem macroscopic examination of the kidneys revealed unilateral hydronephrosis with renal calculi and bilateral cortical and medullary fibrosis and papillary coagulation necrosis. Interestingly, multiple large persistent metanephric ducts were found at the corticomedullary junctions accompanied by marked interstitial fibrosis, tubular atrophy, and lymphoplasmacytic interstitial nephritis. To our knowledge, this is the first reported case of persistent metanephric ducts in cats.

Dysplastic and polycystic kidneys: diagnosis, associations and management

Cystic and bright kidneys can pose a significant diagnostic dilemma when discovered as an incidental finding at the time of a routine fetal ultrasound scan. There are diverse aetiologies with equally variable implications for the prognosis in the affected fetus, and for future pregnancies. Accurate antenatal diagnosis in the absence of any positive family history is often not possible and a team approach to management (to include the fetal medicine specialist, paediatric nephrologist or urologist, geneticists and in some cases, pathologist) is essential. In this review we will attempt to describe the embryology and aetiology of these conditions and suggest an approach to management.

Congenital obstructive uropathy: its origin and contribution to end-stage renal disease in children

Most children with end-stage renal failure are born with abnormal kidneys, with fetal obstructive uropathy accounting for about half these cases. Posterior urethral valves (PUV) is overwhelmingly the most common, specific diagnosis, and is confined to boys. In general, the condition is sporadic, although familial cases have been reported, perhaps suggesting that genetic factors play a role in pathogenesis. PUV can present antenatally, detected on routine fetal ultrasonography, or postnatally, when it is associated with renal failure and bladder dysfunction. Advances in postnatal surgery and medical management have reduced the mortality in PUV, but it is uncertain whether antenatal diagnosis or treatment (eg, with vesicoamniotic shunts) improves long-term renal outcome. Other disorders associated with human fetal obstructive uropathy are urethral atresia, the prune belly syndrome, and multicystic dysplastic kidney. The nephropathy associated with fetal obstructive uropathy is renal dysplasia and comprises undifferentiated and metaplastic tissues. Several studies in animals and in humans suggest that fetal urine flow impairment causes deregulation of renal precursor cell turnover and expression of growth factor/survival and transcription factor genes. Furthermore, some of these morphologic and molecular changes can be ameliorated experimentally by fetal surgical decompression or administration of specific growth factors.

Potential biological role of transforming growth factor-beta1 in human congenital kidney malformations

Transformations between epithelial and mesenchymal cells are widespread during normal development and adult disease, and transforming growth factor-beta1 (TGF-beta1) has been implicated in some of these phenotypic switches. Dysplastic kidneys are a common cause of chronic kidney failure in young children and result from perturbed epithelial-mesenchymal interactions. In this study, we found that components of the TGF-beta1 axis were expressed in these malformations: TGF-beta1 mRNA and protein were up-regulated in dysplastic epithelia and surrounding mesenchymal cells, whereas TGF-beta receptors I and II were expressed in aberrant epithelia. We generated a dysplastic kidney epithelial-like cell line that expressed cytokeratin, ZO1, and MET, and found that exogenous TGF-beta1 inhibited proliferation and decreased expression of PAX2 and BCL2, molecules characterizing dysplastic tubules in vivo. Furthermore, addition of TGF-beta1 specifically induced morphological changes compatible with a shift to a mesenchymal phenotype, accompanied by loss of ZO1 at cell borders and up-regulation of the mesenchymal markers alpha-smooth muscle actin and fibronectin. The descriptive and functional data presented in this report potentially implicate TGF-beta1 in the pathobiology of dysplastic kidneys and our results provide preliminary evidence that an epithelial-to-mesenchymal phenotypic switch may be implicated in a clinically important developmental aberration.