How they begin and how they end: classic and new theories for the development and deterioration of congenital anomalies of the kidney and urinary tract, CAKUT

Expression of Autophagy Markers LC3B, LAMP2A, and GRP78 in the Human Kidney during Embryonic, Early Fetal, and Postnatal Development and Their Significance in Diabetic Kidney Disease

Autophagy is the primary intracellular degradation system, and it plays an important role in many biological and pathological processes. Studies of autophagy involvement in developmental processes are important for understanding various processes. Among them are fibrosis, degenerative diseases, cancer development, and metastasis formation. Diabetic kidney disease is one of the main causes of chronic kidney disease and end-stage renal failure. The aim of this study was to investigate the immunohistochemical expression patterns of LC3B, LAMP2A, and GRP78 during different developmental stages of early-developing human kidneys and in samples from patients with type II diabetes mellitus. During the 7/8th DW, moderate expression of LC3B and LAMP2A and strong expression of GRP78 were found in the mesonephric glomeruli and tubules. In the 9/10th DW, the expression of LC3B and LAMP2A was even more pronounced in the mesonephric tubules. LC3B, LAMP2A, and GRP78 immunoreactivity was also found in the paramesonephric and mesonephric ducts and was stronger in the 9/10th DW compared with the 7/8th DW. In addition, the expression of LC3B, LAMP2A, and GRP78 also appeared in the mesenchyme surrounding the paramesonephric duct in the 9/10th DW. In the 15/16th DW, the expression of LC3B in the glomeruli was weak, that of LAMP2A was moderate, and that of GRP78 was strong. In the tubuli, the expression of LC3B was moderate, while the expression of LAMP2A and GRP78 was strong. The strongest expression of LC3B, LAMP2A, and GRP78 was observed in the renal medullary structures, including developing blood vessels. In postnatal human kidneys, the most extensive LC3B, LAMP2A, and GRP78 expression in the cortex was found in the epithelium of the proximal convoluted tubules, with weak to moderate expression in the glomeruli. The medullary expression of LC3B was weak, but the expression of LAMP2A and GRP78 was the strongest in the medullary tubular structures. Significantly lower expression of LC3B was found in the glomeruli of the diabetic patients in comparison with the nondiabetic patients, but there was no difference in the expression of LC3B in the tubule-interstitial compartment. The expression of LAMP2A was significantly higher in the tubule-interstitial compartments of the diabetic patients in comparison with the nondiabetic patients, while its expression did not differ in the glomeruli. Extensive expression of GRP78 was found in the glomeruli and the tubule-interstitial compartments, but there was no difference in the expression between the two groups of patients. These data give us new information about the expression of LC3B, LAMP2A, and GRP78 during embryonic, fetal, and early postnatal development. The spatiotemporal expression of LC3B, LAMP2A, and GRP78 indicates the important role of autophagy during the early stages of renal development. In addition, our data suggest a disturbance in autophagy processes in the glomeruli and tubuli of diabetic kidneys as an important factor in the pathogenesis of diabetic kidney disease.

Brain and spine malformations and neurodevelopmental disorders in a cohort of children with CAKUT

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) represent 20-30% of all birth defects and are often associated with extra-renal malformations. We investigated the frequency of brain/spine malformations and neurological features in children with CAKUT.

METHODS

We reviewed the clinico-radiological and genetic data of 199 out of 1,165 children with CAKUT evaluated from 2006 to 2023 (99 males, mean age at MRI 6.4 years) who underwent brain and/or spine MRI. Patients were grouped according to the type of CAKUT (CAKUT-K involving the kidney and CAKUT-H involving the inferior urinary tract). Group comparisons were performed using χ2 and Fisher exact tests.

RESULTS

Brain/spine malformations were observed in 101/199 subjects (50.7%), 8.6% (101/1165) of our CAKUT population, including midbrain-hindbrain anomalies (40/158, 25.3%), commissural malformations (36/158, 22.7%), malformation of cortical development (23/158, 14.5%), Chiari I anomaly (12/199, 6%), cranio-cervical junction malformations (12/199, 6%), vertebral defects (46/94, 48.9%), caudal regression syndrome (29/94, 30.8%), and other spinal dysraphisms (13/94, 13.8%). Brain/spine malformations were more frequent in the CAKUT-K group (62.4%, p < 0.001). Sixty-two subjects (62/199, 31.2%) had developmental delay/intellectual disability. Neurological examination was abnormal in 40/199 (20.1%). Seizures and/or electroencephalographic anomalies were reported in 28/199 (14%) and behavior problems in 19/199 subjects (9%). Developmental delay/intellectual disability was more frequent in kidney dysplasia (65.2%) and agenesis (40.7%) (p = 0.001).

CONCLUSIONS

We report a relative high frequency of brain/spine malformations and neurodevelopmental disorders in children with CAKUT who underwent MRI examinations in a tertiary referral center, widening the spectrum of anomalies associated with this condition.

Risks of obstructive genitourinary birth defects in relation to trihalomethane and haloacetic acid exposures: expanding disinfection byproduct mixtures analyses using relative potency factors

BACKGROUND

Some disinfection byproducts (DBPs) are teratogens based on toxicological evidence. Conventional use of predominant DBPs as proxies for complex mixtures may result in decreased ability to detect associations in epidemiological studies.

OBJECTIVE

We assessed risks of obstructive genitourinary birth defects (OGDs) in relation to 12 DBP mixtures and 13 individual component DBPs.

METHODS

We designed a nested registry-based case-control study (210 OGD cases; 2100 controls) in Massachusetts towns with complete quarterly 1999-2004 data on four trihalomethanes (THMs) and five haloacetic acids (HAAs). We estimated temporally-weighted average DBP exposures for the first trimester of pregnancy. We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for OGD in relation to individual DBPs, unweighted mixtures, and weighted mixtures based on THM/HAA relative potency factors (RPF) from animal toxicology data for full-litter resorption, eye defects, and neural tube defects.

RESULTS

We detected elevated aORs for OGDs for the highest of bromodichloromethane (aOR = 1.75; 95% CI: 1.15-2.65), dibromochloromethane (aOR = 1.71; 95% CI: 1.15-2.54), bromodichloroacetic acid (aOR = 1.56; 95%CI: 0.97-2.51), chlorodibromoacetic acid (aOR = 1.97, 95% CI: 1.23-3.15), and tribromoacetic acid (aOR = 1.90; 95%CI: 1.20-3.03). Across unweighted mixture sums, the highest aORs were for the sum of three brominated THMs (aOR = 1.74; 95% CI: 1.15-2.64), the sum of six brominated HAAs (aOR = 1.43; 95% CI: 0.89-2.31), and the sum of nine brominated DBPs (aOR = 1.80; 95% CI: 1.05-3.10). Comparing eight RPF-weighted to unweighted mixtures, the largest aOR differences were for two HAA metrics, which both were higher with RPF weighting; other metrics had reduced or minimally changed ORs in RPF-weighted models.

The Burden of Congenital Heart Disease and Urogenital Lesions in a National Cohort of Hirschsprung Patients

BACKGROUND

Hirschsprung's disease (HSCR) is often associated with other congenital and chromosomal defects. This study aimed to describe the prevalence of congenital heart disease (CHD) and congenital urogenital lesions in children with HSCR, with and without Trisomy 21 and other associated anomalies, to guide appropriate screening.

METHODS

The Pediatric Health Information System was queried for patients with HSCR who underwent surgical treatment between 2016 and 2021. The prevalence of CHD, congenital urogenital lesions, Trisomy 21 and other congenital syndromes were calculated. Multivariable regression modeling was used to identify predictors of postoperative intensive care unit (ICU) admission and postoperative length of stay (LOS).

RESULTS

Of 2021 HSCR patients at 47 children's hospitals, 264 (13.1%) had CHD, 244 (12.1%) had Trisomy 21, and 103 (5.1%) had a congenital urogenital lesion. The prevalence of CHD (49.6 vs. 8.1%, P < 0.001) and of undergoing a cardiac intervention with associated CHD (40.5 vs. 23.1%, P = 0.002) were higher in patients with Trisomy 21 compared to those without. CHD was associated with an increased likelihood of postoperative ICU admission (OR: 1.6, 95% CI: 1.1, 2.2) and greater postoperative LOS (IRR: 2.6, 95% CI: 2.6, 2.7), irrespective of Trisomy 21 diagnosis.

CONCLUSIONS

The prevalence of CHD among HSCR patients (13.1%) was higher than previously reported, and CHD patients required more resource-intensive care after pull-through. While Trisomy 21 was associated with higher rates of CHD and cardiac intervention, 8.1% of HSCR patients without Trisomy 21 had CHD. Screening echocardiogram should be considered in all children diagnosed with HSCR, as CHD may influence perioperative risk stratification. However, screening renal ultrasound may have limited utility given the low prevalence of urogenital lesions in this population.

LEVEL OF EVIDENCE

Level III.

Immunoexpression Pattern of Autophagy Markers in Developing and Postnatal Kidneys of Dab1−/−(yotari) Mice

The purpose of this study was to compare the immunofluorescence patterns of autophagic markers: Light chain 3 beta (LC3B), Glucose regulating protein 78 (GRP78), Heat shock cognate 71 (HSC70) and Lysosomal-associated membrane protein 2A (LAMP2A) in the developing and postnatal kidneys of Dab1−/− (yotari) mice to those of wild-type samples. Embryos were obtained on gestation days 13.5 and 15.5 (E13.5 and E15.5), and adult animals were sacrificed at postnatal days 4, 11 and 14 (P4, P11, and P14). After fixation and dehydration, paraffin-embedded kidney tissues were sectioned and incubated with specific antibodies. Using an immunofluorescence microscope, sections were analyzed. For statistical analysis, a two-way ANOVA test and a Tukey’s multiple comparison test were performed with a probability level of p < 0.05. A significant increase in GRP78 and LAMP2A expression was observed in the renal vesicles and convoluted tubules of yotari in embryonic stages. In postnatal kidneys, all observed proteins showed higher signal intensities in proximal and distal convoluted tubules of yotari, while a higher percentage of LC3B-positive cells was also observed in glomeruli. Our findings suggest that all of the examined autophagic markers play an important role in normal kidney development, as well as the potential importance of these proteins in renal pathology, where they primarily serve a protective function and thus may be used as diagnostic and therapeutic targets.

Robotic ureteral reimplantation and uretero-ureterostomy treating the ureterovesical junction pathologies in children: technical considerations and preliminary results

Robot-assisted laparoscopic extravesical ureteral reimplantation (RALUR) and robotic ureteroureterostomy (RUU) are two mini-invasive surgical techniques that have begun to be performed in pediatric urology in recent years. RALUR has been employed especially for VUR treatment, while RUU is considered principally in case of complex doubled ureteral systems. Our aim is to discuss the safety and feasibility of these approaches in children, focusing on technical considerations and supporting their use in different anomalies and pathologies of the ureterovesical junction. We retrospectively collected data about 58 patients who underwent 44 dismembered RALUR (D-RALUR), 28 non-dismembered RALUR (ND-RALUR) and 5 RUU between May 2020 and December 2021. Indications for surgery were primary or secondary vesicoureteral reflux, megaureter, secondary UVJ obstructions, complicated doubled ureteral systems. Mean age was 3.5 years (range 0.6-12.9) and mean weight 17.1 (range 7.2-80). No intraoperative complications occurred nor conversion to open approach were reported. Major postoperative complications were reported in 11.7% of cases with a higher incidence for ND-RALUR. Mean hospital stay was 2.14 days (range 1-8). Success rate at the short-term follow-up was 91.9% for D-RALUR, 96.3% for ND-RALUR and 100% for RUU. RALUR and RUU are two feasible and safe procedures to perform in children. RALUR represents the most required and adequate technique in the treatment of UVJ pathologies, however, in selected cases RUU could represent an effective alternative that has to be considered.

The Angiotensin AT2 Receptor: From a Binding Site to a Novel Therapeutic Target

Discovered more than 30 years ago, the angiotensin AT2 receptor (AT2R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT2R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT2R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT2R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT2R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT2R and its abundant protective effects in multiple experimental disease models and expound on AT2R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT2R research. SIGNIFICANCE STATEMENT: The angiotensin AT2 receptor (AT2R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT2R, which has progressed from being an enigma to becoming a therapeutic target.

Posterior urethral valves: Role of prenatal diagnosis and long-term management of bladder function; a single center point of view and review of literature

Posterior Urethral Valves (PUV) are the most common cause of lower urinary tract obstruction. More severe forms are detected early in pregnancy (mainly type I), while other forms are usually discovered later in childhood when investigating lower urinary tract symptoms. Bladder dysfunction is common and is associated with urinary incontinence in about 55% (0%-72%). Despite the removal of the obstruction by urethral valve ablation, pathological changes of the urinary tract can occur with progressive bladder dysfunction, which can cause deterioration of the upper urinary tract as well. For this reason, all children with PUV require long-term follow-up, always until puberty, and in many cases life-long. Therefore, management of PUV is not only limited to obstruction relief, but prevention and treatment of bladder dysfunction, based on urodynamic observations, is paramount. During time, urodynamic patterns may change from detrusor overactivity to decreased compliance/small capacity bladder, to myogenic failure (valve bladder). In the past, an aggressive surgical approach was performed in all patients, and valve resection was considered an emergency procedure. With the development of fetal surgery, vesico-amniotic shunting has been performed as well. Due to improvements of prenatal ultrasound, the presence of PUV is usually already suspected during pregnancy, and subsequent treatment should be performed in high-volume centers, with a multidisciplinary, more conservative approach. This is considered to be more effective and safer. Primary valve ablation is performed after clinical stability and is no longer considered an emergency procedure after birth. During childhood, a multidisciplinary approach (pediatric urologist, nephrologist, urotherapist) is recommended as well in all patients, to improve toilet training, using an advanced urotherapy program with medical treatments and urodynamic evaluations. The aim of this paper is to present our single center experience over 30 years.

Congenital anomalies of the kidney and urinary tract in a cohort of 280 consecutive patients with Hirschsprung disease

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) have been underestimated in Hirschsprung disease (HSCR). This paper aims at reporting results of patients with HSCR who underwent kidney and urinary tract assessment.

METHODS

Patients seen between December 2005 and November 2020 underwent a complete kidney and urinary tract diagnostic workup. Data regarding CAKUT, gender, length of aganglionosis, familial history, HSCR-associated enterocolitis (HAEC), RET genotype, and outcome were collected.

RESULTS

Out of 472 patients, 280 completed the workup and represented the focus. Male to female ratio was 3.24:1. Familial cases accounted for 9.8% of patients. RET mutations were detected in 19.8%. We encountered a total of 61 patients with 70 nephrological issues (21.8%), including 28 hypoplasia/dysplasia, 12 hydronephrosis, 11 vesicoureteric reflux, 7 duplex collecting system, 2 kidney agenesis, 2 horseshoe kidney, and 8 miscellanea, involving 91 kidneys without side preponderance (50 right, 41 left). Of these 61 patients, 20 (7.1% of the whole series) required medical or surgical treatment. When comparing patients with and without CAKUT, familial history proved to occur with a significantly lower frequency in the former as did better patient perspectives of outcome.

CONCLUSIONS

We confirmed that all diagnostic workups in HSCR should include a complete kidney and urinary tract diagnostic workup. Our study suggests that genes other than RET could play a role in determining CAKUT. Given worse patient perspectives of outcome, CAKUT seems to significantly interfere with quality of life thus confirming the need for early diagnosis and tailored prevention strategies.

Asian guidelines for urinary tract infection in children

The followings are the level of evidence (LE) and grade of recommendation (GR) on pediatric UTI in Asia. Classification according to the sites of infection (lower versus upper tract), the number of episode (first versus recurrent), the severity (simple versus severe), or the existence of complicating factor (uncomplicated versus complicated) is useful to differentiate children with UTI whether they are at risk of renal damage or not (LE: 2, GR: B). Diagnosis of UTI requires both urinalysis that suggests infection and positive urine culture (LE:3, GR B). For pre-toilet trained children, urine specimen for culture should be collected by urethral catheterization or suprapubic aspiration. For toilet trained children, midstream clean catch urine is reliable (LE: 3, GR: A). Urine culture is considered positive if it demonstrates growth of a single bacterium with the following colony counts: (1) any growth by suprapubic aspiration, (2) >5 × 104 CFU/ml by urethral catheterization, or (3) >105 CFU/ml by midstream clean catch (LE:3, GR: B). For children with febrile UTI, renal and bladder ultrasonography (RBUS) should be routinely performed as soon as possible (LE: 3, GR: C). RBUS should be followed up 6 months later in children with acute pyelonephritis and/or VUR (LE: 3, GR: C). Acute DMSA scan can be performed when severe acute pyelonephritis or congenital hypodysplasia is noted on RBUS or when the diagnosis of UTI is in doubt by the clinical presentation (LE: 3, GR: C). Late DMSA scan (>6 months after the febrile UTI) can be performed in children with severe acute pyelonephritis, high-grade VUR, recurrent febrile UTIs, or abnormal renal parenchyma on the follow-up RBUS (LE: 3, GR: C). Top-down or bottom-up approach for febrile UTI is suggested for the diagnosis of VUR. For top-down approach, VCUG should not be performed routinely for children after the first febrile UTI. VCUG is indicated when abnormalities are apparent on either RBUS or DMSA scan or both (LE: 2, GR: B). VCUG is also suggested after a repeat febrile UTI (LE:2, GR: B). Appropriate antibiotic should be given immediately after urine specimen for culture has been obtained (LE:2, GR: A). Initiating therapy with oral or parenteral antibiotics is equally efficacious for children (>3 months) with uncomplicated UTI (LE: 2: GR: A). The choice of empirical antibiotic agents is guided by the expected pathogen and the local resistance patterns (LE: 2, GR: A). For children with febrile UTI, the total course of antibiotic therapy should be 7-14 days (LE: 2, GR: B). Circumcision may, but not definitively, reduce the risk of febrile UTI in males and breakthrough febrile UTI in males with VUR. Circumcision should be offered to uncircumcised boys with febrile UTI and VUR in countries where circumcision is accepted by the general population (LE: 3, GR: B), while in countries where childhood circumcision is rarely performed, other measures for febrile UTI/VUR should be the preferred choice (LE: 4, GR: C). Bladder bowel dysfunction (BBD) is one of the key factors of progression of renal scarring (LE: 2). Early recognition and management of BBD are important in prevention of UTI recurrence (LE:2, GR: A). Antibiotic prophylaxis to prevent recurrent febrile UTI is indicated in children with moderate to high grade (III-V) VUR (LE: 1b, GR: A). Surgical intervention may be used to treat VUR in the setting of recurrent febrile UTI because it has been shown to decrease the incidence of recurrent pyelonephritis (LE: 2, GR: B).

Exploring AT2R and its polymorphism in different diseases: An approach to develop AT2R as a drug target beyond hypertension

The Angiotensin II type 2 receptor (AT2R) is one of the critical components of the renin-angiotensin system (RAS), which performs diverse functions like inhibiting cell differentiation, cell proliferation, vasodilatation, reduces oxidative stress and inflammation. AT2R is relatively less studied in comparison to other components of RAS despite its uniqueness (sex-linked) and diverse functions. The AT2R is differentially expressed in different tissues, and its gene polymorphisms are associated with several diseases. The molecular mechanism behind the association of AT2R and its gene polymorphisms with the diseases remains to be fully understood, which hinders the development of AT2R as a drug target. Single nucleotide polymorphisms (SNPs) in AT2R are found at different locations (exons, introns, promoter, and UTR regions) and were studied for association with different diseases. There may be different mechanisms behind these associations as some AT2R SNP variants were associated with differential expression, the SNPs (A1675G/A1332G) affect the alternate splicing of AT2R mRNA, A1332G genotype results in shortening of the AT2R mRNA and subsequently defective protein. Few SNPs were found to be associated with the diseases in either females (C4599A) or males (T1334C). Several other SNPs were expected to be associated with other similar/related diseases, but studies have not been done yet. The present review emphasizes on the significance of AT2R and its polymorphisms associated with the diseases to explore the precise role of AT2R in different diseases and the possibility to develop AT2R as a potential drug target.

Renal outcomes in adult patients with horseshoe kidney

BACKGROUND

Horseshoe kidney (HSK) is a congenital disorder that is usually asymptomatic, but that increases the risks of kidney stones and infectious disease. However, renal outcomes such as end-stage renal disease (ESRD) in patients with HSK remain unclear.

METHODS

In total, 146 patients with HSK (age of ≥20 years) from two tertiary hospitals were included in this study. Control individuals who underwent medical check-ups were selected by matching for age, sex, serum creatinine level, hypertension and diabetes. The hazard ratios (HRs) for the risks of ESRD and all-cause mortality were calculated after adjustment for multiple variables.

RESULTS

The proportions of HSK-related complications for obstruction, kidney stones, urinary tract infection and urogenital cancer were 26, 25, 19 and 4%, respectively. During the median follow-up period of 9 years (maximum 32 years), the incidence of ESRD was 2.6/10 000 person-years. The risk of ESRD in patients with HSK was higher than in control individuals [adjusted HR = 7.6; 95% confidence interval (CI) 1.14-50.47]. All-cause mortality did not differ between the two groups (adjusted HR = 0.6; 95% CI 0.08-4.29).

CONCLUSIONS

Patients with HSK are at risk of ESRD, which may be attributable to the high prevalence of complications. Accordingly, these patients should be regarded as having chronic kidney disease and require regular monitoring of both kidney function and potential complications.

Clinical Integration of Genome Diagnostics for Congenital Anomalies of the Kidney and Urinary Tract

Revolutions in genetics, epigenetics, and bioinformatics are currently changing the outline of diagnostics and clinical medicine. From a nephrologist's perspective, individuals with congenital anomalies of the kidney and urinary tract (CAKUT) are an important patient category: not only is CAKUT the predominant cause of kidney failure in children and young adults, but the strong phenotypic and genotypic heterogeneity of kidney and urinary tract malformations has hampered standardization of clinical decision making until now. However, patients with CAKUT may benefit from precision medicine, including an integrated diagnostics trajectory, genetic counseling, and personalized management to improve clinical outcomes of developmental kidney and urinary tract defects. In this review, we discuss the present understanding of the molecular etiology of CAKUT and the currently available genome diagnostic modalities in the clinical care of patients with CAKUT. Finally, we discuss how clinical integration of findings from large-scale genetic, epigenetic, and gene-environment interaction studies may improve the prognosis of all individuals with CAKUT.

Screening of renal anomalies in first-degree relatives of children diagnosed with non-syndromic congenital anomalies of kidney and urinary tract

BACKGROUND

Non-syndromic congenital anomalies of kidney and urinary tract (CAKUT) are usually sporadic in nature but familial clustering of cases have been observed suggesting a genetic predisposition to this condition. We aimed to determine the frequency and pattern of renal anomalies in first-degree relatives of children with non-syndromic CAKUT.

METHODS

We screened all the first-degree relatives of children with CAKUT. A total of 149 first-degree relatives, belonging to 62 families were screened with ultrasonography.

RESULTS

A renal anomaly was detected in 9 out of the 62 families. Two of these nine families had identical anomalies (child and a parent) indicating single-gene disorders with possible autosomal dominant inheritance, while the rest of families had a non-identical anomaly. The anomalies detected in the first-degree relatives were renal hypodysplasia (n = 2), multicystic dysplastic kidney (n = 3), pelviureteric junction obstruction (n = 2) and mild hydronephrosis (n = 2). The incidence of a sonographically detected anatomic renal anomaly in first-degree relatives of children with CAKUT was found to be 6.0%. Familial cystic kidney disease was found in two out of the 4 families with cystic kidney disease.

CONCLUSION

Significant renal anomalies were identified in first-degree relatives of children with non-syndromic CAKUT and hence, attempts must be made to screen the family members of children with non-syndromic CAKUT.

Male infertility and genitourinary birth defects: there is more than meets the eye

Male factor infertility is a significant problem present in up to 50% of infertile couples. The relationship between male infertility and systemic disease is of significant interest, and emerging evidence suggests a relationship between male infertility and male genitourinary (GU) birth defects (cryptorchidism, hypospadias, ambiguous genitalia, and congenital anomalies of the kidney and urinary tract). Many of these birth defects are treated in isolation by busy urologists without acknowledgment that these may be related to more global syndromic conditions. Conversely, geneticists and nonurologists who treat variable systemic phenotypes may overlook GU defects, which are indeed related conditions. Many of these defects are attributed to copy number variants dosage-sensitive genes due to chromosome microdeletions or microduplications. These variants are responsible for disease phenotypes seen in the general population. The copy number variants described in this review are syndromic in some cases and responsible for both GU birth defects as well as other systemic phenotypes. This review highlights the emerging evidence between these birth defects, male infertility, and other systemic conditions.

Urinary tract anomalies and urinary tract dysfunction in children with Hirschsprung disease-Is follow-up indicated?

BACKGROUND/PURPOSE

Urinary tract function in children with Hirschsprung disease (HD) is rarely considered.

AIM

to evaluate the prevalence of urinary tract anomalies and dysfunction in children with HD compared to controls.

METHODS

This was an observational cross sectional case-control study. Children with HD who underwent transanal endorectal pull-through technique (TERPT) from 2005 to 2017 were invited to participate. Ultrasound of the urinary tract was performed postoperatively. Children >4 years were asked to answer a urinary tract function questionnaire. Controls were age-matched healthy children. Ethical approval was obtained.

RESULTS

Seventy two children with HD and TERPT were included. Ultrasound was performed in 58 children (83%) post-TERPT. Ten anomalies were diagnosed in six children (10%). Structural anomalies included abnormal kidney size (7%), renal agenesis (2%), prominent calyces (2%) and renal pelvis anomaly (25). Probable acquired anomalies included hydronephrosis (2%), hydroureter (2%) and parenchymal damage (2%). One child had a prior nephrectomy owing to a Wilms' tumor. All 37 children >4 years (27 boys and 10 girls), median aged 8 years (range 4-12), answered the questionnaire as did 284 healthy controls (144 boys and 140 girls). Boys with HD reported a higher frequency of enuresis: 65% versus 9% (p = 0.001) and urinary tract infections: 18% versus 3% (p = 0.012). Girls with HD reported enuresis more frequently (60%) than healthy girls (7%) (p = 0.001). Children with HD with constipation reported enuresis more frequently (p = 0.038).

CONCLUSIONS

Urinary tract anomalies and dysfunction deserve attention in the follow-up of children with HD. We suggest screening for urinary tract anomalies and urinary tract symptoms in follow-up of children with HD.

TYPE OF STUDY

Treatment study.

LEVEL

III.

Three Optimized Methods for In Situ Quantification of Progenitor Cell Proliferation in Embryonic Kidneys Using BrdU, EdU, and PCNA

Background:

Nephron progenitor cells derived from the metanephric mesenchyme undergo a complex balance of self-renewal and differentiation throughout kidney development to give rise to the mature nephron. Cell proliferation is an important index of progenitor population dynamics. However, accurate and reproducible in situ quantification of cell proliferation within progenitor populations can be technically difficult to achieve due to the complexity and harsh tissue treatment required of certain protocols.

Objective:

To optimize and compare the performance of the 3 most accurate S phase–specific labeling methods used for in situ detection and quantification of nephron progenitor and ureteric bud cell proliferation in the developing kidney, namely, 5-bromo-2’-deoxyuridine (BrdU), 5-ethynyl-2’-deoxyuridine (EdU), and proliferating cell nuclear antigen (PCNA).

Methods:

Protocols for BrdU, EdU, and PCNA were optimized for fluorescence labeling on paraformaldehyde-fixed, paraffin-embedded mouse kidney tissue sections, with co-labeling of nephron progenitor cells and ureteric bud with Six2 and E-cadherin antibodies, respectively. Image processing and analysis, including quantification of proliferating cells, were carried out using free ImageJ software.

Results:

All 3 methods detect similar ratios of nephron progenitor and ureteric bud proliferating cells. The BrdU staining protocol is the lengthiest and most complex protocol to perform, requires tissue denaturation, and is most subject to interexperimental signal variability. In contrast, bound PCNA and EdU protocols are relatively more straightforward, consistently yield clear results, and far more easily lend themselves to co-staining; however, the bound PCNA protocol requires substantive additional postexperimental analysis to distinguish the punctate nuclear PCNA staining pattern characteristic of proliferating cells.

Conclusions:

All 3 markers exhibit distinct advantages and disadvantages in quantifying cell proliferation in kidney progenitor populations, with EdU and PCNA protocols being favored due to greater technical ease and reproducibility of results associated with these methods.

Why Does Prevention of Recurrent Urinary Tract Infection not Result in Less Renal Scarring? A Deeper Dive into the RIVUR Trial

PURPOSE

The RIVUR (Randomized Intervention for Children with Vesicoureteral Reflux) trial reported that antibiotic prophylaxis reduced recurrent urinary tract infection but antibiotic prophylaxis was not associated with decreased new renal scarring. However, the original reports did not assess the relationship among recurrent urinary tract infection, new renal scarring and antibiotic prophylaxis in detail. Therefore, we investigated the relationship among these issues.

MATERIALS AND METHODS

We included subjects with dimercaptosuccinic acid scan within 6 months of enrollment and at least 1 followup dimercaptosuccinic acid scan from the RIVUR trial. The primary outcome was recurrent urinary tract infection associated new renal scarring, defined as recurrent urinary tract infection and new changes on dimercaptosuccinic acid scan. Due to a low number of events, propensity score was used to adjust for confounders. Multivariate logistic regression was fitted to investigate the associations between the covariates and the outcome.

RESULTS

A total of 489 patients (91% female, mean age 20.3 months) were included in the study. Any new renal scarring was more common among those with recurrent urinary tract infection (OR 4.1, 95% CI 2.0-8.5, p <0.01) after adjusting for age, sex, index urinary tract infection, duplication, bowel bladder dysfunction and antibiotic prophylaxis. Recurrent urinary tract infection associated new renal scarring occurred in 5 of 244 (2%) patients on antibiotic prophylaxis and 13 of 245 (5%) on placebo. Compared to antibiotic prophylaxis, placebo was associated with a higher risk of recurrent urinary tract infection associated new renal scarring (OR 3.1, 95% CI 1.0-8.8, p=0.04) after adjusting for age, sex, race, index urinary tract infection, bowel bladder dysfunction, duplication, hydronephrosis, vesicoureteral reflux grade and baseline renal scarring. There were no differences in scar severity at final dimercaptosuccinic acid scan (p=0.88) or change from baseline (p=0.53) between antibiotic prophylaxis and placebo.

CONCLUSIONS

Recurrent urinary tract infection was associated with new renal scarring in the RIVUR trial. When limited to recurrent urinary tract infection associated new renal scarring, antibiotic prophylaxis was associated with a decreased risk of this outcome. It remains unclear why new renal scarring developed in a proportion of subjects without recurrent urinary tract infection. The results should be carefully interpreted due to the inherent limitations.

Developmental pathology of congenital kidney and urinary tract anomalies

Congenital anomalies of the kidneys or lower urinary tract (CAKUT) are the most common causes of renal failure in children and account for 25% of end-stage renal disease in adults. The spectrum of anomalies includes renal agenesis; hypoplasia; dysplasia; supernumerary, ectopic or fused kidneys; duplication; ureteropelvic junction obstruction; primary megaureter or ureterovesical junction obstruction; vesicoureteral reflux; ureterocele; and posterior urethral valves. CAKUT originates from developmental defects and can occur in isolation or as part of other syndromes. In recent decades, along with better understanding of the pathological features of the human congenital urinary tract defects, researchers using animal models have provided valuable insights into the pathogenesis of these diseases. However, the genetic causes and etiology of many CAKUT cases remain unknown, presenting challenges in finding effective treatment. Here we provide an overview of the critical steps of normal development of the urinary system, followed by a description of the pathological features of major types of CAKUT with respect to developmental mechanisms of their etiology.

Gene-targeted deletion in mice of the Ets-1 transcription factor, a candidate gene in the Jacobsen syndrome kidney "critical region," causes abnormal kidney development

Ets-1 is a member of the Ets family of transcription factors and has critical roles in multiple biological functions. Structural kidney defects occur at an increased frequency in Jacobsen syndrome (OMIM #147791), a rare chromosomal disorder caused by deletions in distal 11q, implicating at least one causal gene in distal 11q. In this study, we define an 8.1 Mb "critical region" for kidney defects in Jacobsen syndrome, which spans ~50 genes. We demonstrate that gene-targeted deletion of Ets-1 in mice results in some of the most common congenital kidney defects occurring in Jacobsen syndrome, including: duplicated kidney, hypoplastic kidney, and dilated renal pelvis and calyces. Taken together, our results implicate Ets-1 in normal mammalian kidney development and, potentially, in the pathogenesis of some of the most common types of human structural kidney defects.

Transcription Factor 21 Is Required for Branching Morphogenesis and Regulates the Gdnf-Axis in Kidney Development

BACKGROUND

The mammalian kidney develops through reciprocal inductive signals between the metanephric mesenchyme and ureteric bud. Transcription factor 21 (Tcf21) is highly expressed in the metanephric mesenchyme, including Six2-expressing cap mesenchyme and Foxd1-expressing stromal mesenchyme. Tcf21 knockout mice die in the perinatal period from severe renal hypodysplasia. In humans, Tcf21 mRNA levels are reduced in renal tissue from human fetuses with renal dysplasia. The molecular mechanisms underlying these renal defects are not yet known.

METHODS

Using a variety of techniques to assess kidney development and gene expression, we compared the phenotypes of wild-type mice, mice with germline deletion of the Tcf21 gene, mice with stromal mesenchyme-specific Tcf21 deletion, and mice with cap mesenchyme-specific Tcf21 deletion.

RESULTS

Germline deletion of Tcf21 leads to impaired ureteric bud branching and is accompanied by downregulated expression of Gdnf-Ret-Wnt11, a key pathway required for branching morphogenesis. Selective removal of Tcf21 from the renal stroma is also associated with attenuation of the Gdnf signaling axis and leads to a defect in ureteric bud branching, a paucity of collecting ducts, and a defect in urine concentration capacity. In contrast, deletion of Tcf21 from the cap mesenchyme leads to abnormal glomerulogenesis and massive proteinuria, but no downregulation of Gdnf-Ret-Wnt11 or obvious defect in branching.

CONCLUSIONS

Our findings indicate that Tcf21 has distinct roles in the cap mesenchyme and stromal mesenchyme compartments during kidney development and suggest that Tcf21 regulates key molecular pathways required for branching morphogenesis.

Impact of next generation sequencing on our understanding of CAKUT

Congenital abnormalities of the kidney and urinary tract (CAKUT) form the leading cause of pediatric end-stage renal disease. Knowledge on the molecular mechanisms that underlie CAKUT leads to the improvement of DNA diagnostics and counseling regarding prognosis and recurrence risk estimation for CAKUT patients and their relatives. Implementation of next generation sequencing in research and diagnostic settings has led to the identification of the molecular basis of many developmental diseases. In this review, we summarize the efforts on next generation sequencing in CAKUT research and we discuss how next generation sequencing added to our understanding of CAKUT genetics. Although next generation sequencing has certainly proven to be a game changer in the field of disease gene identification and novel CAKUT-causing gene variants have been identified, most CAKUT cases still remain unsolved. Occurring with genetic and phenotypic heterogeneity along with incomplete penetrance, the identification of CAKUT etiology poses many challenges. We see great potential for combined -omics approaches that include next generation sequencing in the identification of CAKUT-specific biomarkers, which is necessary to optimize the care for CAKUT patients.

Decreasing deceased donor transplant rates among children (≤6 years) under the new kidney allocation system

The Kidney Allocation System (KAS) was implemented in December 2014 with unknown impact on the pediatric waitlist. To understand the effect of KAS on pediatric registrants, deceased donor kidney transplant (DDKT) rate was assessed using interrupted time series analysis and time-to-event analysis. Two allocation eras were defined with an intermediary washout period: Era 1 (01/01/2013-09/01/2014), Era 2 (09/01/2014-03/01/2015), and Era 3(03/01/2015-03/01/2017). When using Cox proportional hazards, there was no significant association between allocation era and DDKT likelihood as compared to Era 1 (Era 3: aHR: 1.07, 95% CI: 0.97-1.18, P = .17). However, this was not consistent across all subgroups. Specifically, while highly sensitized pediatric registrants were consistently less likely to be transplanted than their less sensitized counterparts, this disparity was attenuated in Era 3 (Era 1 aHR: 0.04, 95%CI: 0.01-0.14, P < .001; Era 3 aHR: 0.33, 95% CI: 0.21-0.53, P < .001) whereas the youngest registrants aged 0-6 experienced a 21% decrease in DDKT likelihood in Era 3 as compared to Era 1 (aHR: 0.79, 95% CI: 0.64-0.98, P = .03). Thus, while overall DDKT likelihood remained stable with the introduction of KAS, registrants ≤ 6 years of age were disadvantaged, warranting further study to ensure equitable access to transplantation.

Reciprocal Spatiotemporally Controlled Apoptosis Regulates Wolffian Duct Cloaca Fusion

The epithelial Wolffian duct (WD) inserts into the cloaca (primitive bladder) before metanephric kidney development, thereby establishing the initial plumbing for eventual joining of the ureters and bladder. Defects in this process cause common anomalies in the spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). However, developmental, cellular, and molecular mechanisms of WD-cloaca fusion are poorly understood. Through systematic analysis of early WD tip development in mice, we discovered that a novel process of spatiotemporally regulated apoptosis in WD and cloaca was necessary for WD-cloaca fusion. Aberrant RET tyrosine kinase signaling through tyrosine (Y) 1062, to which PI3K- or ERK-activating proteins dock, or Y1015, to which PLCγ docks, has been shown to cause CAKUT-like defects. Cloacal apoptosis did not occur in RetY1062F mutants, in which WDs did not reach the cloaca, or in RetY1015F mutants, in which WD tips reached the cloaca but did not fuse. Moreover, inhibition of ERK or apoptosis prevented WD-cloaca fusion in cultures, and WD-specific genetic deletion of YAP attenuated cloacal apoptosis and WD-cloacal fusion in vivo Thus, cloacal apoptosis requires direct contact and signals from the WD tip and is necessary for WD-cloacal fusion. These findings may explain the mechanisms of many CAKUT.

Genetic basis of human congenital anomalies of the kidney and urinary tract

The clinical spectrum of congenital anomalies of the kidney and urinary tract (CAKUT) encompasses a common birth defect in humans that has significant impact on long-term patient survival. Overall, data indicate that approximately 20% of patients may have a genetic disorder that is usually not detected based on standard clinical evaluation, implicating many different mutational mechanisms and pathogenic pathways. In particular, 10% to 15% of CAKUT patients harbor an unsuspected genomic disorder that increases risk of neurocognitive impairment and whose early recognition can impact clinical care. The emergence of high-throughput genomic technologies is expected to provide insight into the common and rare genetic determinants of diseases and offer opportunities for early diagnosis with genetic testing.

Holding Water: Congenital Anomalies of the Kidney and Urinary Tract, CKD, and the Ongoing Role of Excellence in Plumbing

Congenital anomalies of the kidneys and urinary tracts can result in diminished natal kidney function, possibly through common embryologic pathway disruption or as a result of development taking place in the face of disordered 'post-renal' drainage. Impaired conduit and reservoir function present potential for an ongoing assault leading to further deterioration and progression of chronic kidney disease, a risk that extends to adults with these conditions, even after "correction". The drainage and storage aspects of the urinary system that can impact kidney function are reviewed with attention to correctable or manageable problems including: Bladder dysfunction wherein the low pressure storage of urine is compromised requiring the kidney to work against a pressure gradient, the classic post renal failure problem. The kidney in the aftermath of obstruction which may have lost concentrating capacity leading to a tendency to dehydration ('pre-renal' failure) and through polyuria which exacerbates bladder pressure problems. Further there is an added challenge in evaluation for ongoing or reemergent obstruction in a significantly dilated system where the capacious system leads to slow turnover of urine often requiring a ureteral stent or nephrostomy to clearly establish clinical significance of delayed drainage. Stasis where slow urine flow leads to buildup of debris (stone) or potentiates infection. Vessicoureteral reflux which allows for introduction of lower urinary tract bacteria to the kidney and can lead to pyelonephritis. Conditions which combine problems such as posterior urethral valves where the bladder outlet obstruction compromises kidney function potentially impairing concentrating ability, creates bladder compromise often reducing emptying efficiency or elevating bladder storage pressures, as well as dilating the system potentially promoting stasis. Cognizance of the potential for plumbing problems to further kidney deterioration as patients with congenital urinary tract anomalies, even after they have been repaired is incumbent on those caring for these patients as they age. Thoughtful evaluation of those patients in whom kidney compromise maybe aggravated by drainage and storage disorder will optimize native renal function.

Genetics of Congenital Anomalies of the Kidney and Urinary Tract: The Current State of Play

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most frequent form of malformation at birth and represent the cause of 40–50% of pediatric and 7% of adult end-stage renal disease worldwide. The pathogenesis of CAKUT is based on the disturbance of normal nephrogenesis, secondary to environmental and genetic causes. Often CAKUT is the first clinical manifestation of a complex systemic disease, so an early molecular diagnosis can help the physician identify other subtle clinical manifestations, significantly affecting the management and prognosis of patients. The number of sporadic CAKUT cases explained by highly penetrant mutations in a single gene may have been overestimated over the years and a genetic diagnosis is missed in most cases, hence the importance of identifying new genetic approaches which can help unraveling the vast majority of unexplained CAKUT cases. The aim of our review is to clarify the current state of play and the future perspectives of the genetic bases of CAKUT.

Maternal obesity is associated with congenital anomalies of the kidney and urinary tract in offspring

BACKGROUND

Congenital abnormalities of the kidney and urinary tract (CAKUT) are diagnosed in up to 1 % of pregnancies and account for 20-30 % of the abnormalities identified in the prenatal period. In previous studies, maternal obesity has been associated with congenital malformations in offspring. Our aim was to evaluate the association between maternal obesity [body mass index (BMI) ≥ 30 kg/m²] and CAKUT in offspring.

METHODS

We conducted a population-based, case-control study using linked birth-hospital discharge records from Washington State, 2003-2012. We identified 3093 CAKUT cases using International Classification of Diseases, Ninth Revision (ICD-9) codes. Controls were defined as births without any ICD-9 codes denoting congenital malformations, matched to cases by year of birth in an approximate 4:1 ratio.

RESULTS

Compared to controls, mothers giving birth to infants with CAKUT were more likely to be obese [odds ratio (OR) 1.24, 95 % confidence interval (CI) 1.11-1.38]. We found a significant positive trend between odds of CAKUT in offspring and increasing severity of obesity (score test for trend of odds p < 0.001). This association remained significant in offspring with isolated CAKUT (OR 1.19, 95 % CI 1.06-1.35) and upper urinary tract anomalies (OR 1.26, 95 % CI 1.13-1.41). Maternal overweight (BMI 25-29.9 kg/m²) was not associated with CAKUT in offspring.

CONCLUSIONS

Our results demonstrate a positive association between maternal obesity and CAKUT in offspring, as well as between obesity severity and the odds of CAKUT in offspring. These findings provide additional evidence for the public health importance of obesity, particularly as a potentially modifiable risk factor.

Zeb1 Is a Potential Regulator of Six2 in the Proliferation, Apoptosis and Migration of Metanephric Mesenchyme Cells

Nephron progenitor cells surround around the ureteric bud tips (UB) and inductively interact with the UB to originate nephrons, the basic units of renal function. This process is determined by the internal balance between self-renewal and consumption of the nephron progenitor cells, which is depending on the complicated regulation networks. It has been reported that Zeb1 regulates the proliferation of mesenchymal cells in mouse embryos. However, the role of Zeb1 in nephrons generation is not clear, especially in metanephric mesenchyme (MM). Here, we detected cell proliferation, apoptosis and migration in MM cells by EdU assay, flow cytometry assay and wound healing assay, respectively. Meanwhile, Western and RT-PCR were used to measure the expression level of Zeb1 and Six2 in MM cells and developing kidney. Besides, the dual-luciferase assay was conducted to study the molecular relationship between Zeb1 and Six2. We found that knock-down of Zeb1 decreased cell proliferation, migration and promoted cell apoptosis in MM cells and Zeb1 overexpression leaded to the opposite data. Western-blot and RT-PCR results showed that knock-down of Zeb1 decreased the expression of Six2 in MM cells and Zeb1 overexpression contributed to the opposite results. Similarly, Zeb1 promoted Six2 promoter reporter activity in luciferase assays. However, double knock-down of Zeb1 and Six2 did not enhance the apoptosis of MM cells compared with control cells. Nevertheless, double silence of Zeb1 and Six2 repressed cell proliferation. In addition, we also found that Zeb1 and Six2 had an identical pattern in distinct developing phases of embryonic kidney. These results indicated that there may exist a complicated regulation network between Six2 and Zeb1. Together, we demonstrate Zeb1 promotes proliferation and apoptosis and inhibits the migration of MM cells, in association with Six2.

Understanding normal and abnormal development of the Wolffian/epididymal duct by using transgenic mice

The development of the Wolffian/epididymal duct is crucial for proper function and, therefore, male fertility. The development of the epididymis is complex; the initial stages form as a transient embryonic kidney; then the mesonephros is formed, which in turn undergoes extensive morphogenesis under the influence of androgens and growth factors. Thus, understanding of its full development requires a wide and multidisciplinary view. This review focuses on mouse models that display abnormalities of the Wolffian duct and mesonephric development, the importance of these mouse models toward understanding male reproductive tract development, and how these models contribute to our understanding of clinical abnormalities in humans such as congenital anomalies of the kidney and urinary tract (CAKUT).

Genetic Basis of Posterior Urethral Valves Inheritance

OBJECTIVE

To highlight genetic pattern of posterior urethral valves (PUVs), we performed a genetic study on 2 siblings affected. PUVs are the most common congenital cause of lower urinary tract obstruction and an important cause of renal failure in infants (50% progress to end-stage renal disease in 10 years). PUVs occur in 1 of 5000-8000 male infants, but real incidence is arduous to determine because of the wide spectrum of possible clinical presentation. A different recurrence rate is reported in African Americans and children with Down syndrome, although usually PUVs are not found in syndromic conditions but constitute an isolated disorder. Although most cases appear to be sporadic, some reports in literature suggest a partial genetic etiology.

MATERIALS AND METHODS

We report 2 brothers with PUVs. The children's mother was a healthy woman but had a history of urinary tract infections of unknown etiology. We investigated possible familial genetic anomalies using a DNA array comparative genomic hybridization technique.

RESULTS

We identified 2 partial duplications in the short arm of chromosome 11 recurring in both children and mother.

CONCLUSION

This finding, not previously reported to our knowledge, adds new data to support the hypothesis of the presence of a hereditary component in the occurrences of PUVs.

Genetic Basis of Ureterocele

Congenital anomalies of the kidney and urinary tract (CAKUT) form a group of heterogeneous disorders that affect the kidneys, ureters and bladder, with frequent asynchronous presentations and multiple CAKUT associations in the same individual. Urinary tract formation is a complex process, dependent of the interaction of multiple genes and their sub-product. The same genic alterations can lead to different molecular expressions and different morphological anomalies. The ureterocele is a cystic dilation of the distal intramural ureter, resulting in obstruction of urine flow, dilation of the ureter and renal pelvis and loss of renal function. Two key steps in the urinary tract ontogenesis may be related to ureterocele development: formation and migration of the ureteric bud and its incorporation in the bladder. This review aims to describe the morphological, cellular and biochemical steps, as well as the genes involved in the occurrence of this anomaly.

Genetic, environmental, and epigenetic factors involved in CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) refer to a spectrum of structural renal malformations and are the leading cause of end-stage renal disease in children. The genetic diagnosis of CAKUT has proven to be challenging due to genetic and phenotypic heterogeneity and incomplete genetic penetrance. Monogenic causes of CAKUT have been identified using different approaches, including single gene screening, and gene panel and whole exome sequencing. The majority of the identified mutations, however, lack substantial evidence to support a pathogenic role in CAKUT. Copy number variants or single nucleotide variants that are associated with CAKUT have also been identified. Numerous studies support the influence of epigenetic and environmental factors on kidney development and the natural history of CAKUT, suggesting that the pathogenesis of this syndrome is multifactorial. In this Review we describe the current knowledge regarding the genetic susceptibility underlying CAKUT and the approaches used to investigate the genetic basis of CAKUT. We outline the associated environmental risk factors and epigenetic influences on CAKUT and discuss the challenges and strategies used to fully address the involvement and interplay of these factors in the pathogenesis of the disease.

Detection of recurrent transmission of 17q12 microdeletion by array comparative genomic hybridization in a fetus with prenatally diagnosed hydronephrosis, hydroureter, and multicystic kidney, and variable clinical spectrum in the family

OBJECTIVE

This study was aimed at detection of recurrent transmission of the 17q12 microdeletion in a fetus with congenital anomalies of the kidney and urinary tract.

MATERIALS AND METHODS

A 35-year-old woman was referred to the hospital at 20 weeks' gestation because of hydronephrosis in the fetus. The mother was normal and healthy. Her second child was a girl who had bilateral dysplastic kidneys that required hemodialysis, and died at the age of 5 years. During this pregnancy, the woman underwent amniocentesis at 18 weeks' gestation because of advanced maternal age. Cytogenetic analysis revealed a karyotype of 46,XY. Prenatal ultrasound showed left hydronephrosis with a tortuous ureter, right hydronephrosis, and increased echogenicity of the kidneys. Fetal magnetic resonance imaging showed right dilated renal calyces, left hydronephrosis, hydroureter, and multicystic kidney. The pregnancy was subsequently terminated. Array comparative genomic hybridization (aCGH) and fluorescence in situ hybridization were applied for genetic analysis using umbilical cord, maternal blood, and cultured amniocytes.

RESULTS

aCGH analysis on umbilical cord detected a 1.75-Mb deletion at 17q12 including haploinsufficiency of LHX1 and HNF1B. aCGH analysis on maternal blood detected a 1.54-Mb deletion at 17q12 including haploinsufficiency of LHX1 and HNF1B. Metaphase fluorescence in situ hybridization analysis on cultured amniocytes and maternal blood lymphocytes using 17q12-specific bacterial artificial chromosome probe showed 17q12 microdeletion in the fetus and the mother.

CONCLUSION

Prenatal diagnosis of recurrent renal and urinary tract abnormalities in the fetus should include a differential diagnosis of familial 17q12 microdeletion.

Smad4 regulates ureteral smooth muscle cell differentiation during mouse embryogenesis

Proper formation of ureteral smooth muscle cells (SMCs) during embryogenesis is essential for ureter peristalsis that propels urine from the kidney to the bladder in mammals. Currently the molecular factors that regulate differentiation of ureteral mesenchymal cells into SMCs are incompletely understood. A recent study has reported that Smad4 deficiency reduces the number of ureteral SMCs. However, its precise role in the ureteral smooth muscle development remains largely unknown. Here, we used Tbx18:Cre knock-in mouse line to delete Smad4 to examine its requirement in the development of ureteral mesenchyme and SMC differentiation. We found that mice with specific deletion of Smad4 in Tbx18-expressing ureteral mesenchyme exhibited hydroureter and hydronephrosis at embryonic day (E) 16.5, and the mutant mesenchymal cells failed to differentiate into SMCs with increased apoptosis and decreased proliferation. Molecular markers for SMCs including alpha smooth muscle actin (α-SMA) and smooth muscle myosin heavy chain (SM-MHC) were absent in the mutant ureters. Moreover, disruption of Smad4 significantly reduced the expression of genes, including Sox9, Tbx18 and Myocardin associated with SMC differentiation. These findings suggest that Smad4 is essential for initiating the SMC differentiation program during ureter development.

Congenital anomalies of the kidney and urinary tract (CAKUT) associated with Hirschsprung's disease: a systematic review

PURPOSE

Congenital anomalies of the kidney and urinary tract (CAKUT), a term introduced in the late 1990 s accounts for 30-50 % of cases of end-stage renal disease in children. The association of urogenital anomalies and Hirschsprung's disease (HSCR) based on the common genetic background of enteric nervous system and human urinary tract development has been well described in the literature. However, the reported prevalence of HSCR associated with CAKUT seems to be underestimated. The aim of this systematic review was to determine the prevalence of this association and show its relationship to other syndromes.

METHODS

A systematic literature search was conducted for relevant articles published between 1955 and 2014. Two online databases were searched for the terms "Hirschsprung's disease", "congenital anomalies of the kidney and urinary tract", "urogenital anomalies" and "urological anomalies". All published studies containing adequate clinical data were included. Resulting publications were reviewed for epidemiology, genetic testing, operative treatment and morbidity. Reference lists were screened for additional cases.

RESULTS

A total of 32 articles reported 222 cases of HSCR associated with either CAKUT, "urological" or "urogenital" anomalies from 1955 to 2014. Gender was reported in a total of 68 cases, with 54 (79 %) males and 14 (21 %) females. Extent of aganglionosis was reported in 67 cases and included classical rectosigmoid disease in 38, long-segment aganglionosis in 12, total colonic aganglionosis in 12 and total intestinal aganglionosis in 5 patients. 18 articles reported 204 cases of either CAKUT, "urological" or "urogenital" anomalies in a case series of 5.693 HSCR patients, resulting in an overall prevalence of 3.6 % of this association. Within this collective of 18 studies only seven were, regardless of the date of publication compatible with CAKUT criteria introduced and published in the late 1990 s. These seven studies reported a total of 72 patients with associated CAKUT among 757 HSCR patients resulting in a prevalence of 9.5 %. After introduction of the CAKUT acronym, only three studies specifically investigated the association of HSCR and CAKUT stating a prevalence of 14.3 % resulting in an almost fivefold increase compared to the reported prevalence of HSCR and associated urological and urogenital anomalies. The remaining 14 publications reported 18 single cases of HSCR patients with associated CAKUT phenotypes. Of these 18 cases, 11 (61 %) cases were associated with other syndromes or syndromatic features or reported chromosomal anomalies.

CONCLUSION

This review confirms that the recognition of CAKUT in HSCR patients has been underestimated in the past. The results suggest that when confronted with HSCR in a patient, a thorough urological investigation may be indicated. The high prevalence of associated syndromes in HSCR with CAKUT may further suggest a syndromic association.

Estimation of total glomerular number using an integrated disector method in embryonic and postnatal kidneys

Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) are a polymorphic group of clinical disorders comprising the major cause of renal failure in children. Included within CAKUT is a wide spectrum of developmental malformations ranging from renal agenesis, renal hypoplasia and renal dysplasia (maldifferentiation of renal tissue), each characterized by varying deficits in nephron number. First presented in the Brenner Hypothesis, low congenital nephron endowment is becoming recognized as an antecedent cause of adult-onset hypertension, a leading cause of coronary heart disease, stroke, and renal failure in North America. Genetic mouse models of impaired nephrogenesis and nephron endowment provide a critical framework for understanding the origins of human kidney disease. Current methods to quantitate nephron number include (i) acid maceration (ii) estimation of nephron number from a small number of tissue sections (iii) imaging modalities such as MRI and (iv) the gold standard physical disector/fractionator method. Despite its accuracy, the physical disector/fractionator method is rarely employed because it is labour-intensive, time-consuming and costly to perform. Consequently, less rigourous methods of nephron estimation are routinely employed by many laboratories. Here we present an updated, digitized version of the physical disector/fractionator method using free open source Fiji software, which we have termed the integrated disector method. This updated version of the gold standard modality accurately, rapidly and cost-effectively quantitates nephron number in embryonic and post-natal mouse kidneys, and can be easily adapted for stereological measurements in other organ systems.

Role of Wnt5a-Ror2 signaling in morphogenesis of the metanephric mesenchyme during ureteric budding

Development of the metanephric kidney begins with the induction of a single ureteric bud (UB) on the caudal Wolffian duct (WD) in response to GDNF (glial cell line-derived neurotrophic factor) produced by the adjacent metanephric mesenchyme (MM). Mutual interaction between the UB and MM maintains expression of GDNF in the MM, thereby supporting further outgrowth and branching morphogenesis of the UB, while the MM also grows and aggregates around the branched tips of the UB. Ror2, a member of the Ror family of receptor tyrosine kinases, has been shown to act as a receptor for Wnt5a to mediate noncanonical Wnt signaling. We show that Ror2 is predominantly expressed in the MM during UB induction and that Ror2- and Wnt5a-deficient mice exhibit duplicated ureters and kidneys due to ectopic UB induction. During initial UB formation, these mutant embryos show dysregulated positioning of the MM, resulting in spatiotemporally aberrant interaction between the MM and WD, which provides the WD with inappropriate GDNF signaling. Furthermore, the numbers of proliferating cells in the mutant MM are markedly reduced compared to the wild-type MM. These results indicate an important role of Wnt5a-Ror2 signaling in morphogenesis of the MM to ensure proper epithelial tubular formation of the UB required for kidney development.

Vesicoureteric reflux and reflux nephropathy: from mouse models to childhood disease

Vesicoureteric reflux (VUR) is a common congenital urinary tract defect that predisposes children to recurrent kidney infections. Kidney infections can result in renal scarring or reflux nephropathy defined by the presence of chronic tubulo-interstitial inflammation and fibrosis that is a frequent cause of end-stage renal failure. The discovery of mouse models with VUR and with reflux nephropathy has provided new opportunities to understand the pathogenesis of these conditions and may provide insight on the genes and the associated phenotypes that need to be examined in human studies.

BMP signaling and its modifiers in kidney development

The kidney develops through mutual interactions between the metanephric mesenchyme and the ureteric bud, the former of which contains nephron progenitors that give rise to glomeruli and renal tubules. Bone morphogenetic protein (BMP) signaling and its modifiers play important roles in many steps of kidney development. BMP4 inhibits ureteric bud attraction, and the BMP antagonist Gremlin is essential for the initial stage of ureteric budding. During mid-gestation, BMP7 maintains the nephron progenitors and, at the same time, sensitizes them to the ureteric bud-derived differentiation signal. Crossveinless2 is a pro-BMP factor, and its absence leads to kidney hypoplasia. After birth, when nephron progenitors have disappeared, Dullard, a phosphatase that inactivates BMP receptors, keeps BMP signaling at an appropriate level. Deletion of Dullard results in excessive BMP signaling and apoptosis of the postnatal nephrons. In this review I discuss the similarities and differences of BMP functions in kidney development, as well as in diseases.

Whole-exome resequencing reveals recessive mutations in TRAP1 in individuals with CAKUT and VACTERL association

Congenital abnormalities of the kidney and urinary tract (CAKUT) account for approximately half of children with chronic kidney disease and they are the most frequent cause of end-stage renal disease in children in the US. However, its genetic etiology remains mostly elusive. VACTERL association is a rare disorder that involves congenital abnormalities in multiple organs including the kidney and urinary tract in up to 60% of the cases. By homozygosity mapping and whole-exome resequencing combined with high-throughput mutation analysis by array-based multiplex PCR and next-generation sequencing, we identified recessive mutations in the gene TNF receptor-associated protein 1 (TRAP1) in two families with isolated CAKUT and three families with VACTERL association. TRAP1 is a heat-shock protein 90-related mitochondrial chaperone possibly involved in antiapoptotic and endoplasmic reticulum stress signaling. Trap1 is expressed in renal epithelia of developing mouse kidney E13.5 and in the kidney of adult rats, most prominently in proximal tubules and in thick medullary ascending limbs of Henle's loop. Thus, we identified mutations in TRAP1 as highly likely causing CAKUT or VACTERL association with CAKUT.

Adult-onset renal failure in a family with Alagille syndrome with proteinuria and a novel JAG1 mutation

Alagille syndrome (AGS) is an autosomal-dominant multi-organ disorder involving the liver, heart, eyes, face and skeleton. In addition, various renal abnormalities have also been reported in several cases. We describe a patient with a novel frameshift mutation in exon 12 of the JAG1 gene who presented with chronic renal failure. In this family, five members of three generations had clinical features implicated in AGS. Three members had adult-onset renal dysfunction with proteinuria, and two of them required haemodialysis therapy. AGS should be considered in the differential diagnosis of proteinuric renal disease, even in adult patients.

Islet1 deletion causes kidney agenesis and hydroureter resembling CAKUT

Islet1 (Isl1) is a transcription factor transiently expressed in a subset of heart and limb progenitors. During studies of limb development, conditional Isl1 deletion produced unexpected kidney abnormalities. Here, we studied the renal expression of Isl1 and whether it has a role in kidney development. In situ hybridization revealed Isl1 expression in the mesenchymal cells surrounding the base of the ureteric bud in mice. Conditional deletion of Isl1 caused kidney agenesis or hypoplasia and hydroureter, a phenotype resembling human congenital anomalies of the kidney and urinary tract (CAKUT). The absence of Isl1 led to ectopic branching of the ureteric bud out from the nephric duct or to the formation of accessory buds, both of which could lead to obstruction of the ureter-bladder junction and consequent hydroureter. The abnormal elongation and poor branching of the ureteric buds were the likely causes of the kidney agenesis or hypoplasia. Furthermore, the lack of Isl1 reduced the expression of Bmp4, a gene implicated in the CAKUT-like phenotype, in the metanephric region before ureteric budding. In conclusion, Isl1 is essential for proper development of the kidney and ureter by repressing the aberrant formation of the ureteric bud. These observations call for further studies to investigate whether Isl1 may be a causative gene for human CAKUT.