Clinical consequences of developmental programming of low nephron number

The boundaries of normal kidney tissue for biomedical research

PURPOSE OF REVIEW

In this review, we highlight the importance of understanding the inherent biological variability in normal kidney, or healthy reference tissue, to establish an accurate reference point for biomedical research. We explore this and the advantages and limitations of various sources of healthy reference tissue suitable for structural and omics-level studies.

RECENT FINDINGS

Several large consortia are employing omic technologies for diseased and normal kidney tissue, underscoring the importance of utilizing healthy reference tissue in these studies. Emerging approaches, such as artificial intelligence and multiomic analyses, are expanding our understanding of structural and molecular heterogeneity in healthy reference kidney tissue and uncovering new insights.

SUMMARY

Biological variability in healthy reference tissue at the functional, structural, and molecular level is complex and remains an active area of study. Thoughtful selection of healthy reference tissue sources is critical, providing the greatest potential for producing high-quality research outcomes.

Association of perinatal exposition to xenobiotics with kidney volume at birth

BACKGROUND

The state of Aguascalientes has the highest prevalence of kidney failure in young adults globally. A low nephron endowment has been suggested as a possible aetiology. This study aims to evaluate the association between exposure to xenobiotics and low kidney volume (KV) at birth.

METHODS

This is a cross-sectional, observational, descriptive study of at-term pregnant women with no comorbidities. We collected the mother's urine (MU) and amniotic fluid (AF) and the neonate's urine (NU). Metals and non-metals were measured with inductively coupled plasma mass spectrometry, pesticides with high-performance liquid chromatography and fluoride with ion-selective potentiometry. The total KV adjusted by body surface area (TKVBS) was calculated based on the kidney ultrasound.

RESULTS

Between March 2022 and July 2023, we included 299 women with an average age of 24.2 years [standard deviation (SD) 5.1]. A total of 54.2% of neonates were male with an average weight of 3266 g (SD 399). Factors associated with TKVBS ≤5th percentile were female sex, weight gain during pregnancy, glomerular filtration rate, methomyl concentration in AF {odds ratio [OR] 7.41 [95% confidence interval (CI) 2.31-23.8], P = .001}, 2,4-dichlorophenoxyacetic (2,4-D) >10 ng/ml in AF [OR 4.99 (95% CI 1.58-15.7), P = .002], MU [OR 6.1 (95% CI 1.9-19.7), P = 0.002] and NU [OR 5.1 (95% CI 1.10-26.2), P = .023] and fluoride in MU [OR 5.1 (95% CI 1.10-23.5), P = .010] and AF [OR 6.76 (95% CI 1.28-35.7), P = .024]. In all matrices (MU, AF and NU), exposure to pesticides was also significantly associated with greater concentrations of electrolytes (sodium, potassium, calcium, phosphate and magnesium) and trace elements (zinc and iron).

CONCLUSIONS

In neonates born to at-term women with no comorbidities, the presence of pesticides and fluoride was associated with low KV. The significant loss of electrolytes and trace elements associated with pesticides suggests proximal tubulopathy.

Nephron number variability in Japanese subjects: an autopsy-based study and its implications for chronic kidney disease: clinical scientist award address 2024

The number of nephrons is a key determinant of blood pressure regulation and chronic kidney disease (CKD) progression. Although traditional estimates suggest approximately one million nephrons per kidney, modern stereological approaches reveal substantial variability, that is influenced by ethnicity, birth weight, and other early life factors. This review evaluates the century-long evolution of nephron number research, variations across racial and ethnic groups, and explores how factors, such as body size, aging, and lifestyle risks, influence nephron endowment. Techniques for nephron quantification, from design-based stereology to emerging in vivo imaging, are also discussed. Recent research suggests markedly lower nephron counts in Japanese populations, especially among individuals with hypertension or CKD. The autopsy-based investigation in the present study included 27 middle-aged to older Japanese men (9 normotensive, 9 hypertensive, and 9 participants with CKD) who underwent dissector-fractionator stereology to quantify non-sclerosed glomeruli. Normotensive men had an average of approximately 640,399 non-sclerosed glomeruli. In contrast, the hypertensive participants had approximately 392,108 non-sclerosed glomeruli and those with CKD had only 268, 043. These findings underscore the potential influence of limited nephron reserves on hypertension and CKD in Japan. Current evidence suggests that nephron number estimates can guide therapeutic decisions and predict CKD outcomes, while advancements in real-time imaging offer potential avenues for non-invasive nephron assessment. Collectively, these developments highlight the central importance of nephron quantity in nephrology and enable targeted interventions aimed at preserving kidney function and mitigating the CKD burden.

GWAS for Defining the Pathogenesis of Hypertension: Have They Delivered?

Genome-wide association studies have identified >3500 associated single nucleotide polymorphisms and over 1000 independent loci associated with hypertension. These individually have small effect sizes, and few associated loci have been experimentally tested for causal roles in hypertension using animal models or in humans. Thus, methods to prioritize and maximize the relevance of identified single nucleotide polymorphisms and associated loci are critical to determine their importance in hypertension. We propose several approaches to aid in these efforts, including: (1) integration of genome-wide association study data with multiomic data sets, including proteomics, transcriptomics, and epigenomics, (2) utilizing linked clinical and genetic data sets to determine genetic contributions to hypertension subphenotypes with distinct drivers, and (3) performing whole exome/genome sequencing on cohorts of individuals with severe hypertension to enrich for rare variants with larger effect sizes. Rather than creating longer lists of hypertension-associated single nucleotide polymorphisms, these approaches are needed to identify key mediators of hypertension pathophysiology.

Ultrasound Doppler renal pulsatility index is a predictive marker of arterial stiffness in children with solitary functioning kidney

INTRODUCTION

Patients with solitary functioning kidney (SFK) have glomerular hyperfiltration, hypertension, proteinuria and impaired renal function resulting in microvascular atherosclerotic abnormalities. This condition leads to an increase in arterial stiffness. In this study, we aimed to investigate the usefulness of non-invasive renal Doppler ultrasonography hemodynamic parameters in demonstrating arterial stiffness in pediatric patients with SFK.

METHODS

The study included 59 children aged 6-18 years who were diagnosed with SFK. Demographic, biochemical, anthropometric, and blood pressure data were recorded. The renal Doppler ultrasound hemodynamic parameters renal resistive index (RRI), renal pulsatility index (RPI), carotid-femoral pulse wave velocity (cfPWV), central augmentation index (cAIx) and carotid intima media thickness (cIMT) were evaluated.

RESULTS

Eighteen (30.5%) cases with acquired SFK and 41 (64.5%) cases with congenital SFK were detected. Central augmentation indices were higher in children with congenital SFK than in children with acquired SFK (p = 0.038). CkiD-eGFR-SCr-CysC was lower in patients with acquired SFK (p = 0.011). LDL cholesterol levels were higher in children with acquired SFK (p = 0.018). We found a significant correlation between RPI and cfPWV with a correlation coefficient (r) of 0.321 and a statistically significant p-value of 0.013.

CONCLUSIONS

Congenital SFK is associated with increased microvascular atherosclerotic burden. RPI assessment with renal Doppler ultrasound may be a non-invasive method to identify arterial stiffness.

Neonatal Kidney Function, Injury and Drug Dosing: A Contemporary Review

In neonates, estimation of the glomerular filtration rate is problematic, and assessment of renal impairment is challenging. Serum creatinine is a widely used marker, and urine output is an important vital parameter monitored in intensive care settings, particularly in unwell neonates. However, the rapid changes after birth with adaptation to the extrauterine environment is a unique situation in which absolute serum creatinine is not a reliable indicator of renal function. A rise in serum creatinine from the previous value during the neonatal period can be a result of worsening renal function in neonates but is dependent on many other factors. In addition, urine output can be difficult to measure in sick neonates during their intensive care stay. Despite a high prevalence of acute kidney injury (AKI) in preterm and/or unwell infants, the current definitions are not straightforward and do not take postnatal adaptation processes into account. The management of AKI is challenging in very young and small patients because the assessment of fluid status as well as balancing nutritional needs with fluid restriction can be problematic. The Australian Neonatal Medicines Formulary provides advice on drug dosing in the face of reduced renal function in neonates. Predictors (or long-term outcome, or recovery) after AKI diagnosis are still poorly described. Therefore, the diagnosis of neonatal AKI needs to be documented and transferred to the paediatrician responsible for the follow-up of the child. This educational review aims to give a perspective on neonatal kidney function and AKI, the relation of fluid balance and creatinine, the management of neonatal AKI and the consequences for drug dosing and long-term outcomes.

Sick Day Management Plans for Aboriginal and/or Torres Strait Islander Peoples With Chronic Kidney Disease on the Cape York Peninsula of Australia: Health Workers' Perspectives

OBJECTIVE

This study aimed to explore the perspectives of healthcare professionals on the utility of sick day management plans for people with chronic kidney disease (CKD) in remote communities and collaboratively design a sick day management plan resource.

DESIGN

This qualitative study utilised two phases of data collection: preliminary observational data and semi-structured interviews. The research design and analysis were guided by the normalisation process theory (NPT) framework, tailored for complex interventions in healthcare.

SETTING

Three First Nations communities and one remote mining community in Cape York, Australia.

PARTICIPANTS

In-person semi-structured interviews were conducted with 23 primary healthcare workers; 40% identified as Aboriginal and/or Torres Strait Islander.

RESULTS

The study identified three themes relating to feasibility of implementation: (1) resource coherence and readability, (2) suitability for integration into the care model and (3) safety and risk associated with sick day management plans. Iterative development of resources followed, incorporating feedback from the participants. Recommendations emerged for enhanced readability and coherence, including further co-design with individual communities and consumers, content simplification, incorporation of Aboriginal and/or Torres Strait Islander artwork and language and a flow chart structure.

CONCLUSION

The study underscores the importance of culturally sensitive resource design and the active involvement of Aboriginal and/or Torres Strait Islander communities in healthcare improvement. Future research should explore cost-effective methods for personalised sick day management plans.

The Impact of Gestational Diabetes on Kidney Development: is There an Epigenetic Link?

PURPOSE OF REVIEW

This review explores the mechanisms through which gestational diabetes mellitus GDM impacts fetal kidney development, focusing on epigenetic alterations as mediators of these effects. We examine the influence of GDM on nephrogenesis and kidney maturation, exploring how hyperglycemia-induced intrauterine stress can reduce nephron endowment and compromise renal function via dysregulation of normal epigenetic mechanisms.

RECENT FINDINGS

In addition to metabolic impacts, emerging evidence suggests that GDM exerts its influence through epigenetic modifications, including DNA methylation, histone modifications, and non-coding RNA expression, which disrupt gene expression patterns critical for kidney development. Recently, specific epigenetic modifications observed in offspring exposed to GDM were implicated in aberrant activation or repression of genes essential for kidney development. Key pathways influenced by these epigenetic changes, such as oxidative stress response, inflammatory regulation, and metabolic pathways, are discussed to illustrate the broad molecular impact of GDM on renal development. Finally, we consider potential intervention strategies that could mitigate the adverse effects of GDM on kidney development. These include optimizing maternal glycemic control, dietary modifications, dietary supplementation, and pharmacological agents targeting epigenetic pathways. Through a comprehensive synthesis of current research, this review underscores the importance of early preventive strategies to reduce the burden of kidney disease in individuals exposed to GDM and highlights key epigenetic mechanisms altered during GDM that impact kidney development.

Multi-Organ Phenotypes of Offspring Born Following Hypertensive Disorders of Pregnancy: A Systematic Review

BACKGROUND

Hypertensive pregnancies are associated with an increased risk of cardiovascular and neurological diseases in the offspring during later life. However, less is known about the potential impact on multi-organ phenotypes in offspring before disease symptoms occur. The objective of this systematic review was to determine the associations of fetal exposure to maternal hypertensive pregnancy with multi-organ phenotypes across developmental stages.

METHODS AND RESULTS

Ovid MEDLINE, EMBASE, CENTRAL (Cochrane Central Register of Controlled Trials), WoS, Scopus, CINAHL, and ClinicalTrials.gov were systematically searched until February 2024. Records were independently screened by 2 authors. Studies reporting on the structure or function of the heart, blood vessels, brain, liver, and kidneys in offspring of hypertensive pregnancies compared with a normotensive control population were included. Risk of bias was assessed using the Newcastle-Ottawa Scale. Extracted data were presented using harvest plots. Seventy-three studies including 7091 offspring of hypertensive pregnancies and 42 164 controls were identified that met the inclusion criteria. Thirty-two studies were investigations in fetuses, 24 in neonates and infants, 12 in children, 2 in adolescents, and 3 in adults. Offspring of hypertensive pregnancies had structural and functional changes in the heart compared with controls in some studies across developmental stages. Offspring of hypertensive pregnancies also had smaller occipital and parietal vessels, higher aortic intima-media thickness, and lower retinal arteriolar-to-venular ratio. Some conflicting evidence existed for other phenotypical alterations.

CONCLUSIONS

There is still inconsistent evidence of multi-organ structural and functional differences in offspring of hypertensive pregnancies. The evidence base could therefore be further strengthened through well-designed and conducted prospective studies.

REGISTRATION INFORMATION

www.crd.york.ac.uk. Unique Identifier: CRD42023387550.

Morphometric analysis of the intergenerational effects of protein restriction on nephron endowment in mice

Background

Parental nutritional status is crucial in shaping offspring's kidney development. However, the association between a protein-restrictive diet and its intergenerational impact on kidney development remains unclear.

Methods

We conducted multigenerational morphometric measurements to investigate the effects of parental protein deprivation on offspring kidney development across four generations. F0 mice were divided into two groups and fed a normal protein diet (NPD) or a low-protein diet (LPD) for three weeks before mating and continued these diets throughout gestation and lactation. Body weight (BW), kidney weight (KW), KW/BW ratio, nephron counts, and blood pressure were assessed in F1 pups. To examine paternal effects, we bred CD1 females on an NPD with males on an LPD. BW, KW, KW/BW, and nephron counts were measured at P20. To measure the transgenerational effect of parental LPD on kidney development, F1 offspring (from parents on LPD) were fed NPD upon weaning. These F1 offspring were bred at 6 weeks of age to produce F2, F3 and F4 generations. Kidney metrics were evaluated across generations.

Results

The average body weight of P0 pups from parents on NPD was 1.61g, while pups from parental LPD weighed an average of 0.869g, a decrease of 54 % (p = 6.9e-11, Wilcoxon test). F1 from parental LPD have significantly smaller kidneys than the control, with an average combined kidney weight of 0.0082g versus 0.0129g, a 37 % decrease (p = 3.2e-02, Wilcoxon test). P20 BW and KW remained low in LPD offspring. These effects persisted for 4 generations (F1 to F4) with an average glomerular count reduction of roughly 20 %. F3 and F4 showed wider variability in glomerular counts but were not statistically significant compared to controls.

Conclusions

Both maternal and paternal LPD significantly affected offspring nephron endowment. Our study underscores the complex nature of nutritional transgenerational effects on kidney development, emphasizing the importance of both maternal and paternal dietary impacts on kidney development and the developmental origin of adult disease.

Early metabolic and hemodynamic indicators of kidney dysfunction in mice offspring from parental low protein diet

BACKGROUND

Parental malnutrition, particularly a low-protein diet (LPD), causes oligonephropathy at birth and predisposes offspring to hypertension and chronic kidney disease later in life. The onset of adult kidney disease varies based on genetics and environmental factors, often with subclinical alterations in kidney function being overlooked. This study aimed to examine changes in kidney morphology before significant kidney function decline in the offspring of mice fed a low-protein diet.

METHODS

Using a combination of histological analysis, kidney metabolic and hemodynamic panel assessments, and advanced statistical techniques such as Linear Discriminant Analysis (LDA) and Principal Component Analysis (PCA), we investigated the initial impact of a maternal low-protein diet (LPD) on kidney development and function. Our study utilized 12-week-old F1 mice from F0 parents fed either a low-protein diet (LPD) or a normal-protein diet (NPD) before the onset of hypertension.

RESULTS

The offspring (F1 generation) of parents (F0 generation) fed an LPD show reduced body weight from birth to P20. The kidney weight was also reduced compared to F1 offspring from parents fed an NPD. At 12 weeks of age, body weight normalized, but kidney weight remained low. Offspring of parents fed an LPD displayed abnormal kidney morphology, including dilated tubules, oligonephropathy, and fluid-filled cysts which had worsened with age. A kidney metabolic panel analysis at 12 weeks revealed a slight but consistent increase in urine albumin, plasma creatinine, mean urea, and BUN concentrations. Although no significant changes in hemodynamic variables were observed, 2/12 mice, both males, showed alterations in systolic blood pressure, suggesting sex-specific effects when comparing F1 mice from F0 fed either diet. Overall, kidney metabolic changes were strongly correlated to parental LPD.

CONCLUSION

Our findings indicate that significant kidney damage must accumulate in the F1 generation from parents fed an LPD before any detectable changes in blood pressure occur. Our study suggests that small variations in kidney metabolic function may point to early kidney damage and should not be overlooked in the offspring of these malnourished mice and likely humans.

[The association between preterm birth and hypertension]

In recent years, the number of premature births worldwide has been increasing, and their long-term prognoses, particularly the cardiovascular outcomes of preterm individuals in adulthood, have become a growing concern. Adults who were born prematurely are at a higher risk for cardiovascular diseases, which may be related to changes in cardiovascular structure, renal structure alterations, changes in body composition, and overactivation of the hypothalamic-pituitary-adrenal axis. To improve the outcomes for preterm individuals, long-term follow-up monitoring and effective prevention and treatment measures are necessary. This article aims to review the relevant literature, summarize the risks and mechanisms of hypertension during childhood and adulthood in those born prematurely, and enhance awareness and understanding of the risk of hypertension in adults who were born prematurely.

Pediatric kidney dimensions and risk of persistent albuminuria in Mexican adolescents

In Mexico, chronic kidney disease of unknown origin is highly prevalent. Screening studies in adolescents have shown persistent microalbuminuria (pACR), adaptive podocytopathy and decreased kidney volume (KV). Here, we sought to develop normality tables of kidney dimensions by ultrasound in the Mexican state of Aguascalientes pediatric population (0 to 18y) and evaluate the relationship between the KV and pACR among the region's adolescents in a cross-sectional study. Kidney length (KL) and KV were determined by ultrasound. Our findings were compared with those in international literature of different populations where tables and graphs of normal kidney dimensions by ultrasound were reported. We compared organ dimensions in individuals above the age of 11 without albuminuria with those in patients with pACR recruited through screening studies in adolescents in Aguascalientes. This included 1068 individuals to construct percentile tables and graphs of the KL. Kidney dimensions were significantly lower when compared with all international comparisons. From a total 14,805 screen individuals, we compared 218 adolescents with pACR and 377 individuals without significant albuminuria. The Total KV adjusted to body surface (TKVBS) was significantly associated with pACR (odds ratio 1.03, 95% confidence interval 1.02-1.03). The upper quartile of TKVBS was highly associated with pACR (7.57, 4.13-13.87), hypertension (2.53, 1.66-3.86), and hyperfiltration (26 vs 11.5%). Thus, TKVBS is directly associated with pACR while greater KV, arterial hypertension, and hyperfiltration in patients with pACR suggest that the increase in volume is secondary to kidney hypertrophy. Additionally, the adaptative podocytopathy with low fibrosis seen on kidney biopsy which was performed in a subset of patients, and the smaller kidney dimensions in our population point to prenatal oligonephronia as the primary cause of the detected kidney disease.

Advances in pediatric acute kidney injury pathobiology: a report from the 26th Acute Disease Quality Initiative (ADQI) conference

BACKGROUND

In the past decade, there have been substantial advances in our understanding of the pathobiology of pediatric acute kidney injury (AKI). In particular, animal models and studies focused on the relationship between kidney development, nephron number, and kidney health have identified a number of heterogeneous pathophysiologies underlying AKI. Despite this progress, gaps remain in our understanding of the pathobiology of pediatric AKI.

METHODS

During the 26th Acute Disease Quality Initiative (ADQI) Consensus conference, a multidisciplinary group of experts discussed the evidence and used a modified Delphi process to achieve consensus on recommendations for opportunities to advance translational research in pediatric AKI. The current state of research understanding as well as gaps and opportunities for advancement in research was discussed, and recommendations were summarized.

RESULTS

Consensus was reached that to improve translational pediatric AKI advancements, diverse teams spanning pre-clinical to epidemiological scientists must work in concert together and that results must be shared with the community we serve with patient involvement. Public and private research support and meaningful partnerships with adult research efforts are required. Particular focus is warranted to investigate the pediatric nuances of AKI, including the effect of development as a biological variable on AKI incidence, severity, and outcomes.

CONCLUSIONS

Although AKI is common and associated with significant morbidity, the biologic basis of the disease spectrum throughout varying nephron developmental stages remains poorly understood. An incomplete understanding of factors contributing to kidney health, the diverse pathobiologies underlying AKI in children, and the historically siloed approach to research limit advances in the field. The recommendations outlined herein identify gaps and outline a strategic approach to advance the field of pediatric AKI via multidisciplinary translational research.

Climate change and its influence in nephron mass

PURPOSE OF REVIEW

The consequences of climate change, including heat and extreme weather events impact kidney function in adults and children. The impacts of climate change on kidney development during gestation and thereby on kidney function later in life have been poorly described. Clinical evidence is summarized to highlight possible associations between climate change and nephron mass.

RECENT FINDINGS

Pregnant women are vulnerable to the effects of climate change, being less able to thermoregulate, more sensitive to the effects of dehydration, and more susceptible to infections. Exposure to heat, wildfire smoke, drought, floods and climate-related infections are associated with low birth weight, preterm birth and preeclampsia. These factors are associated with reduced nephron numbers, kidney dysfunction and higher blood pressures in offspring in later life. Exposure to air pollution is associated with higher blood pressures in children and has variable effects on estimated glomerular filtration rate.

SUMMARY

Climate change has important impacts on pregnant women and their unborn children. Being born too small or too soon is associated with life-time risk of kidney disease. Climate change may therefore have a dual effect of impacting fetal kidney development and contributing to cumulative postnatal kidney injury. The impact on population kidney health of future generations may be significant.

Installation of the developing nephron in the fetal human kidney during advanced pregnancy

BACKGROUND

The kidneys of preterm and low birth weight babies reflect vulnerability, since several noxae can evoke the termination of nephron formation. This again leads to oligonephropathy with severe consequences for health in the later life. While the clinical parameters have been intensely investigated, only little is known about the initial traces left by the noxae. For the fetal human kidney, solely the lack of basophilic S-shaped bodies and the reduction in width of the nephrogenic zone were registered. It is not known in how far also the involved progenitor cells, the earlier nephron stages, the collecting duct (CD) ampullae, and the local interstitium are collaterally harmed.

AIM

The interstitium at the forming nephron is heterogeneously structured. Thereby, it fulfills quite different mastering and integrative tasks. Since data dealing with the installation of a nephron is not available, the microanatomical features were recorded.

RESULTS

The microscopic specimens show that the installation of the transient stages of nephron anlage is not synchronized. Instead, it is controlled within a nephrogenic compartment of the nephrogenic zone. It starts near the renal capsule by positioning the nephrogenic niche so that the nephrogenic progenitor cells face the epithelial progenitor cell at the tip of a CD ampulla. Then, the induced nephrogenic progenitor cells assimilate in the pretubular aggregate. While its medial part remains opposite the head of the CD ampulla, at its proximal end, the primitive renal vesicle is formed. Only a part of it separates to stick to the section border between the head and conus of the CD ampulla. This marks the link with the future connecting tubule at the distal pole of the extending renal vesicle. Meanwhile, the proximal pole is mounted next to the connecting tubule of an earlier developed nephron. The resulting two-point mounting serves a common elongation of the conus at the CD ampulla and the medial aspect of the comma-shaped body. In the S-shaped body, it supports to defoliate the arising glomerulus and to link it with the perforating radiate artery at its deep lateral aspect.

CONCLUSIONS

The investigation depicts that the installation is an interactive process between the stages of nephron anlage and its structural neighbors. A special meaning has the interjacent interstitium. It is vital for the positioning, shaping, and physiological integration. Due to its special location, this is mainly exposed to noxae.

TLR2 mediates renal apoptosis in neonatal mice subjected experimentally to obstructive nephropathy

Urinary tract obstruction during renal development leads to inflammation, tubular apoptosis, and interstitial fibrosis. Toll like receptors (TLRs) expressed on leukocytes, myofibroblasts and renal cells play a central role in acute inflammation. TLR2 is activated by endogenous danger signals in the kidney; its contribution to renal injury in early life is still a controversial topic. We analyzed TLR2 for a potential role in the neonatal mouse model of congenital obstructive nephropathy. Inborn obstructive nephropathies are a leading cause of end-stage kidney disease in children. Thus, newborn Tlr2-/- and wild type (WT) C57BL/6 mice were subjected to complete unilateral ureteral obstruction (UUO) or sham-operation on the 2nd day of life. The neonatal kidneys were harvested and analyzed at days 7 and 14 of life. Relative expression levels of TLR2, caspase-8, Bcl-2, Bax, GSDMD, GSDME, HMGB1, TNF, galectin-3, α-SMA, MMP-2, and TGF-β proteins were quantified semi-quantitatively by immunoblot analyses. Tubular apoptosis, proliferation, macrophage- and T-cell infiltration, tubular atrophy, and interstitial fibrosis were analyzed immunohistochemically. Neonatal Tlr2-/- mice kidneys exhibited less tubular and interstitial apoptosis as compared to those of WT C57BL/6 mice after UUO. UUO induced neonatally did trigger pyroptosis in kidneys, however to similar degrees in Tlr2-/- and WT mice. Also, tubular atrophy, interstitial fibrosis, tubular proliferation, as well as macrophage and T-cell infiltration were unremarkable. We conclude that while TLR2 mediates apoptosis in the kidneys of neonatal mice subjected to UUO, leukocyte recruitment, interstitial fibrosis, and consequent neonatal obstructive nephropathy might lack a TLR2 involvement.

Acetyl-CoA is a key molecule for nephron progenitor cell pool maintenance

Nephron endowment at birth impacts long-term renal and cardiovascular health, and it is contingent on the nephron progenitor cell (NPC) pool. Glycolysis modulation is essential for determining NPC fate, but the underlying mechanism is unclear. Combining RNA sequencing and quantitative proteomics we identify 267 genes commonly targeted by Wnt activation or glycolysis inhibition in NPCs. Several of the impacted pathways converge at Acetyl-CoA, a co-product of glucose metabolism. Notably, glycolysis inhibition downregulates key genes of the Mevalonate/cholesterol pathway and stimulates NPC differentiation. Sodium acetate supplementation rescues glycolysis inhibition effects and favors NPC maintenance without hindering nephrogenesis. Six2Cre-mediated removal of ATP-citrate lyase (Acly), an enzyme that converts citrate to acetyl-CoA, leads to NPC pool depletion, glomeruli count reduction, and increases Wnt4 expression at birth. Sodium acetate supplementation counters the effects of Acly deletion on cap-mesenchyme. Our findings show a pivotal role of acetyl-CoA metabolism in kidney development and uncover new avenues for manipulating nephrogenesis and preventing adult kidney disease.

Burden and predictors of diabetic kidney disease in an adult Ugandan population with new-onset diabetes

BACKGROUND

Despite the growing evidence of diabetic kidney disease (DKD) in adult patients with long-standing diabetes in sub-Saharan Africa, data on its burden and correlates in adult African patients with new-onset diabetes are limited. We, therefore, undertook this study to determine the burden and predictors of DKD in an adult population with new-onset diabetes in Uganda.

METHODS

We collected data on the relevant sociodemographic, clinical, anthropometric, and metabolic characteristics in 519 participants with newly diagnosed diabetes recruited from seven tertiary hospitals. A spot mid-stream urine sample was collected for determination of the urine albumin creatinine ratio (UACR) using Clinitek® microalbumin strips and a point-of-care Clinitek® status analyser. The estimated glomerular filtration rate (e-GFR) was determined using the Chronic Kidney Disease Epidemiology formula. The presence of DKD was defined as a spot UACR ≥ 3 mg/mmol with or without an e-GFR < 60 ml/min/1.73m2.

RESULTS

The median (IQR) age, UACR, and e-GFR of the participants were 48 years (39-57), 2.27 mg/mmol (1.14-3.41), and 121.8 ml/min/1.73m2 (105.4-133.9). UACR ≥ 3 mg/mmol and e-GFR < 60 ml/min/1.73m2 was noted in 175 (33.7%) and 7 (1.4%) participants, respectively. DKD was documented in 175 participants (33.7%). Compared with those without DKD, participants with DKD were more likely to be ≥ 50 years of age (53.7% vs. 43%, p = 0.02) and to have co-existing hypertension at the time of diagnosis (40.6% vs. 30.1%, p = 0.02). On multivariate analysis, self-reported hypertension comorbidity (OR 1.76 95% CI 1.24-2.48, p = 0.002) and body mass index (BMI) ≥ 30 kg/m2 (OR 0.61 95% CI 0.41-0.91, p = 0.02) were noted to independently predict DKD.

CONCLUSION

In this study population, DKD was relatively common and was independently associated with self-reported hypertension comorbidity and BMI ≥ 30 kg/m2.

Sex Differences in Offspring of Preeclamptic Pregnancies

A poor uterine environment causes changes in fetal development that affect the health of offspring long-term. Although there are multiple pathways that contribute to the development of cardiovascular and neurological disease, low birth weight or fetal growth restriction (FGR) predisposes offspring to these diseases. There is a link between fetal exposure to adverse influences and hypertension later in life. Many epidemiological studies support the link between fetal life and the risk of disease later in life. Experimental models have sought to provide mechanistic proof of this link while simultaneously investigating potential therapeutics or treatment pathways. Preeclampsia (PE), one of several hypertensive disorders in pregnancy, is a leading cause of morbidity and mortality for both the mother and fetus. Studies have shown that PE is a state of chronic inflammation and there is an imbalance between pro-inflammatory and regulatory immune cells and mediators. There is no cure for PE beyond the delivery of the fetal-placental unit, and many PE pregnancies result in FGR and preterm birth. Epidemiological data demonstrate that the sex of the offspring is correlated with the degree of cardiovascular disease that develops with the age of the offspring yet few studies examine the effect of sex on the development of neurological disorders. Even fewer studies examine the effects of therapeutics on offspring of different genders following a PE pregnancy. Moreover, there remain significant gaps in knowledge concerning the role the immune system plays in FGR offspring developing hypertension or neurovascular disorders later in life. Therefore, the purpose of this review is to highlight current research on sex differences in the developmental programming of hypertension and neurological disorders following a PE pregnancy.

Pathomechanisms of Prenatally Programmed Adult Diseases

Based on epidemiological observations Barker et al. put forward the hypothesis/concept that an adverse intrauterine environment (involving an insufficient nutrient supply, chronic hypoxia, stress, and toxic substances) is an important risk factor for the development of chronic diseases later in life. The fetus responds to the unfavorable environment with adaptive reactions, which ensure survival in the short run, but at the expense of initiating pathological processes leading to adult diseases. In this review, the major mechanisms (including telomere dysfunction, epigenetic modifications, and cardiovascular-renal-endocrine-metabolic reactions) will be outlined, with a particular emphasis on the role of oxidative stress in the fetal origin of adult diseases.

Renal Functional Response-Association With Birth Weight and Kidney Volume

Introduction

Renal functional response (RFR) is the acute increase in glomerular filtration rate (GFR) after a protein load. Low RFR is a marker of single nephron hyperfiltration. Low birth weight (LBW) is associated with reduced number of nephrons, lower kidney function, and smaller kidneys in adults. In the present study, we investigate the associations among LBW, kidney volume, and RFR.

Methods

We studied adults aged 41 to 52 years born with either LBW (≤2300 g) or normal birth weight (NBW; 3500-4000 g). GFR was measured using plasma clearance of iohexol. A stimulated GFR (sGFR) was measured on a separate day after a protein load of 100 g using a commercially available protein powder, and RFR was calculated as delta GFR. Kidney volume was estimated from magnetic resonance imaging (MRI) images using the ellipsoid formula.

Results

A total of 57 women and 48 men participated. The baseline mean ± SD GFR was 118 ± 17 ml/min for men and 98 ± 19 ml/min for women. The overall mean RFR was 8.2 ± 7.4 ml/min, with mean RFR of 8.3 ± 8.0 ml/min and 8.1 ± 6.9 ml/min in men and women, respectively (P = 0.5). No birth-related variables were associated with RFR. Larger kidney volume was associated with higher RFR, 1.9 ml/min per SD higher kidney volume (P = 0.009). Higher GFR per kidney volume was associated with a lower RFR, -3.3ml/min per SD (P < 0.001).

Conclusion

Larger kidney size and lower GFR per kidney volume were associated with higher RFR. Birth weight was not shown to associate with RFR in mainly healthy middle-aged men and women.

The impact of intrauterine growth restriction and prematurity on nephron endowment

In humans born at term, maximal nephron number is reached by the time nephrogenesis is completed - at approximately 36 weeks' gestation. The number of nephrons does not increase further and subsequently remains stable until loss occurs through ageing or disease. Nephron endowment is key to the functional capacity of the kidney and its resilience to disease; hence, any processes that impair kidney development in the developing fetus can have lifelong adverse consequences for renal health and, consequently, for quality and length of life. The timing of nephrogenesis underlies the vulnerability of developing human kidneys to adverse early life exposures. Indeed, exposure of the developing fetus to a suboptimal intrauterine environment during gestation - resulting in intrauterine growth restriction (IUGR) - and/or preterm birth can impede kidney development and lead to reduced nephron endowment. Furthermore, emerging research suggests that IUGR and/or preterm birth is associated with an elevated risk of chronic kidney disease in later life. The available data highlight the important role of early life development in the aetiology of kidney disease and emphasize the need to develop strategies to optimize nephron endowment in IUGR and preterm infants.

The renin-angiotensin system modulates endotoxic postconditioning of exacerbated renal vasoconstriction in preeclamptic offspring

We recently reported exacerbated endotoxic signs of neuroinflammation and autonomic defects in offspring of preeclamptic (PE) dams. Here, we investigated whether PE programming similarly modifies hemodynamic and renal vasoconstrictor responsiveness to endotoxemia in PE offspring and whether this interaction is modulated by gestational angiotensin 1-7 (Ang1-7). Preeclampsia was induced by gestational treatment with L-NAME. Adult offspring was challenged with lipopolysaccharides (LPS, 5 mg/kg) and systolic blood pressure (SBP) and renal vasoconstrictions were assessed 4 h later. Male, but not female, offspring of PE rats exhibited SBP elevations that were blunted by LPS. Renal vasoconstrictions induced by angiotensin II (Ang II), but not phenylephrine, were intensified in perfused kidneys of either sex. LPS blunted the heightened Ang II responses in male, but not female, kidneys. While renal expressions of AT1-receptors and angiotensin converting enzyme (ACE) were increased in PE offspring of both sexes, ACE2 was upregulated in female offspring only. These molecular effects were diminished by LPS in male offspring. Gestational Ang1-7 caused sex-unrelated attenuation of phenylephrine vasoconstrictions and preferentially downregulated Ang II responses and AT1-receptor and nuclear factor-kB (NFkB) expressions in females. Together, endotoxemia and Ang1-7 offset in sexually-related manners imbalances in renal vasoconstriction and AT1/ACE/ACE2 signaling in PE offspring.

Persistent high blood pressure and renal dysfunction in preterm infants during childhood

BACKGROUND

Infants born very preterm (≤32 weeks gestational age, GA) and very-low birth weight (≤1500 g; PT-VLBW) demonstrate high systolic blood pressure (SBP), renal dysfunction, and obesity at 6 months-3 years and in early adulthood. Their parallel measurement and progression during childhood is unclear.

METHODS

We reenrolled 62/120 patients originally seen at 1-3 years at 10-13 years and remeasured anthropometric indices, SBP, and serum creatinine (Cr) and cystatin C (cysC) to determine estimated glomerular filtration rate (eGFR). We selected Term-matched Controls at 10-13 years from the 2015-2016 NHANES database at a ratio of 2 Controls:1 Case (124:62).

RESULTS

Reenrolled patients were predominantly Hispanic, birth weight 1073 ± 251 g, and GA at birth 28 ± 2 weeks. At 10-13 years, 45% were classified overweight/obese, 48% had SBP ≥ 90th centile (77% considered hypertensive), and 34% had low eGFR (<90 mL min^-1 [1.73 m²]^-1). Notably, 57% of reenrolled PT-VLBW Cases had low eGFR_cysC at both 1-3 and 10-13 years, P < 0.03. Compared to Controls, Cases had four times the adjusted odds for having an elevated SBP and low eGFR_Cr despite similar proportions with overweight/obesity among Cases and Controls.

CONCLUSIONS

PT-VLBW infants seen at 1-3 years exhibit obesity, elevated SBP, and low eGFR in infancy and 10-13 years. Although the small sample size may limit conclusions, pediatricians should consider serial evaluations of PT-VLBW throughout childhood.

IMPACT

The association between preterm birth and elevated blood pressure, renal dysfunction, and obesity in young adults begins as early as 1 year and persists at 10-13 years of age. This is the first study reporting serial measurements of blood pressure, renal function, and obesity from infancy to preadolescence in children born very preterm. Fifty-seven percent of preterm 1-3 year olds have persistent low estimated glomerular filtration rate associated with hypertension at 10-13 years. Clinicians should consider serial evaluations of blood pressure, renal function, and obesity throughout infancy and childhood in all preterm births.

Postnatal persistence of nonhuman primate sex-dependent renal structural and molecular changes programmed by intrauterine growth restriction

BACKGROUND

Poor nutrition during fetal development programs postnatal kidney function. Understanding postnatal consequences in nonhuman primates (NHP) is important for translation to our understanding the impact on human kidney function and disease risk. We hypothesized that intrauterine growth restriction (IUGR) in NHP persists postnatally, with potential molecular mechanisms revealed by Western-type diet challenge.

METHODS

IUGR juvenile baboons were fed a 7-week Western diet, with kidney biopsies, blood, and urine collected before and after challenge. Transcriptomics and metabolomics were used to analyze biosamples.

RESULTS

Pre-challenge IUGR kidney transcriptome and urine metabolome differed from controls. Post-challenge, sex and diet-specific responses in urine metabolite and renal signaling pathways were observed. Dysregulated mTOR signaling persisted postnatally in female pre-challenge. Post-challenge IUGR male response showed uncoordinated signaling suggesting proximal tubule injury.

CONCLUSION

Fetal undernutrition impacts juvenile offspring kidneys at the molecular level suggesting early-onset blood pressure dysregulation.

Low birth weight, nephron number and chronic kidney disease

Chronic kidney diseases have a significant impact on morbidity and mortality worldwide. Low birth weight, fetal growth restriction and prematurity are indicators of fetal growth and development disorders associated with a congenital reduction in nephron number, which predisposes to an increased risk for chronic kidney disease. On an individual basis, a small nephron number at birth is not always enough to determine the onset of chronic kidney disease, but it decreases the ability of the kidneys to resist any insults to renal tissue that may occur later in life, such as exposure to nephrotoxic drugs or episodes of acute kidney injury. The high incidence of low birth weight and preterm birth globally suggests that, at the population level, the impact of alterations in fetal development on the subsequent onset of chronic kidney disease could be significant. The implementation of strategies aimed at reducing the incidence of prematurity, fetal growth restriction, as well as other conditions that lead to low birth weight and a reduced nephron number at birth, provides an opportunity to prevent the development of chronic kidney disease in adulthood. For these purposes the coordinated intervention of several specialists, including obstetricians, gynecologists, neonatologists, nephrologists, and family doctors, is necessary. Such strategies can be particularly useful in resource-poor countries, which are simultaneously burdened by maternal, fetal and child malnutrition; poor health; epidemics caused by communicable diseases; and little access to screening and primary care.

Prenatal Metal Exposures and Associations with Kidney Injury Biomarkers in Children

Prenatal exposure to arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) may be nephrotoxic, yet limited studies have examined subclinical kidney injury biomarkers in children. We assessed whether metal exposure in the second trimester (2T), a crucial time of kidney development, is associated with altered urine kidney injury and function biomarkers in preadolescent children. Analyses included 494 children participating in a birth cohort study in Mexico City. Concentrations of As, Cd, and Pb were measured from pregnant women in 2T blood and urine, and Hg in urine only. Kidney biomarkers were measured from children in urine at age 8-12 years. We assessed the associations between individual metals and (1) kidney biomarkers using linear regression and (2) a multi-protein kidney mixture using weighted quantile sum (WQS) regression. Associations of separate urine and blood metal mixtures with individual kidney biomarkers were assessed via WQS. Within the multi-protein mixture, the association with increased urinary As was predominated by urine alpha-1-microglobulin (A1M), interferon gamma-induced protein 10 (IP10), and fatty acid binding protein 1; the association with increased urinary Cd was predominated by A1M, clusterin, and albumin. The urine metal mixture was associated with increased albumin (0.23 ng/mL; 95% confidence interval (CI): 0.10, 0.37), IP10 (0.15 ng/mL; 95% CI: 0.02, 0.28), and cystatin C (0.17 ng/mL; 95% CI: 0.04, 0.31); these associations were mainly driven by urinary As and Cd. We observed null associations between prenatal blood or urine metal mixtures and estimated glomerular filtration rate. Higher prenatal urinary metals, individually and as a mixture were associated with altered kidney injury biomarkers in children. Further research and longer participant follow-up are required to ascertain the risk of kidney disease later in life.

Cardiovascular Risks of Hypertension: Lessons from Children with Chronic Kidney Disease

Hypertension is the most common complication of chronic kidney disease (CKD) in children, having a strong association with subsequential cardiovascular disease (CVD). In pediatric CKD, a considerable percentage of children with hypertension are undiagnosed or undertreated. Prior research has evaluated structural and functional markers of subclinical CVD and biomarkers in adults with CKD, while ideal biomarkers in pediatrics are still insufficiently studied. The ultimate goal of this review is to summarize what is currently known about state of hypertension, cardiovascular risk factors, and potential CVD markers/biomarkers in children with pre-dialysis CKD. We discuss omics-related biomarkers and the pathophysiologic processes of endothelial dysfunction, kidney injury, oxidative stress and inflammation that are classified by specific biomarkers. Moreover, we illustrate the existing challenges and highlight the paucity of pediatric CKD research to evaluate these CVD biomarkers for future clinical pediatric practice. Thus, achieving clinical utility of CVD biomarkers for use in pediatric CKD remains a significant challenge requiring additional efforts.

Principles of human and mouse nephron development

The mechanisms underlying kidney development in mice and humans is an area of intense study. Insights into kidney organogenesis have the potential to guide our understanding of the origin of congenital anomalies and enable the assembly of genetic diagnostic tools. A number of studies have delineated signalling nodes that regulate positional identities and cell fates of nephron progenitor and precursor cells, whereas cross-species comparisons have markedly enhanced our understanding of conserved and divergent features of mammalian kidney organogenesis. Greater insights into the complex cellular movements that occur as the proximal-distal axis is established have challenged our understanding of nephron patterning and provided important clues to the elaborate developmental context in which human kidney diseases can arise. Studies of kidney development in vivo have also facilitated efforts to recapitulate nephrogenesis in kidney organoids in vitro, by providing a detailed blueprint of signalling events, cell movements and patterning mechanisms that are required for the formation of correctly patterned nephrons and maturation of physiologically functional apparatus that are responsible for maintaining human health.

The interstitium at the developing nephron in the fetal kidney during advanced pregnancy - a microanatomical inventory

Background

A series of noxae can evoke the termination of nephron formation in preterm and low birth weight babies. This results in oligonephropathy with severe consequences for health in the later life. Although the clinical parameters have been extensively investigated, little is known about the initial damage. Previous pathological findings indicate the reduction in width of the nephrogenic zone and the lack of S-shaped bodies. Current morphological investigations suggest that due to the mutual patterning beside the forming nephron, also its structural neighbors, particularly the interjacent interstitium, must be affected. However, beside the findings on integrative and mastering functions, systematic microanatomical data explaining the configuration of the interstitium at the developing nephron in the fetal kidney during advanced pregnancy is not available. Therefore, this work explains the typical features.

Results

The generated data depicts that the progenitor cells, nephrogenic niche, pretubular aggregate, and mesenchymal-to-epithelial transition are restricted to the subcapsular interstitium. During the proceeding development, only the distal pole of the renal vesicles and comma- and S-shaped bodies stays in further contact with it. The respective proximal pole is positioned opposite the peritubular interstitium at the connecting tubule of an underlying but previously formed nephron. The related medial aspect faces the narrow peritubular interstitium of a collecting duct (CD) ampulla first only at its tip, then at its head, conus, and neck, and finally at the differentiating CD tubule. The lateral aspect starts at the subcapsular interstitium, but then it is positioned along the wide perivascular interstitium of the neighboring ascending perforating radiate artery. When the nephron matures, the interstitial configuration changes again.

Conclusions

The present investigation illustrates that the interstitium at the forming nephron in the fetal kidney consists of existing, transient, stage-specific, and differently far matured compartments. According to the developmental needs, it changes its shape by formation, degradation, fusion, and rebuilding.

Prenatal and early childhood critical windows for the association of nephrotoxic metal and metalloid mixtures with kidney function

INTRODUCTION

As renal development and maturation processes begin in utero and continue through early childhood, sensitive developmental periods arise during which metal exposures can program subclinical nephrotoxicity that manifests later in life. We used novel dentine biomarkers of established nephrotoxicants including arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr), and lithium (Li), and their mixtures, to identify critical windows of exposure-associated kidney function alterations in preadolescents.

METHODS

Participants included 353 children in the Programming Research in Obesity Growth, Environment and Social Stressors (PROGRESS) longitudinal birth cohort study based in Mexico City. Estimated glomerular filtration rate (eGFR) was assessed in 8-12 year old children using serum cystatin C measures. Pre- and postnatal metal(loid) concentrations were assessed in weekly increments by analyzing deciduous teeth with laser ablation-inductively coupled plasma-mass spectrometry. We used reverse distributed lag models (rDLMs) and lagged Weighted Quantile Sum (L-WQS) regression to examine time-varying associations between weekly perinatal metal(loid) exposure or metal(loid) mixtures and preadolescent eGFR while adjusting for age, sex, BMI z-score, SES and prenatal tobacco smoke exposure.

RESULTS

We identified a critical window of susceptibility to Pb exposure, in the late 3rd trimester (5 weeks prior to birth) during which higher Pb exposure was associated with children's increased eGFR. When all elements were assessed as a mixture, we identified late 2nd/early 3rd trimester (weeks 8-17 of gestation) as a window of vulnerability associated with decreased eGFR, with Li and Cr contributing the greatest weights to the association. When stratified by sex, we observed stronger effects among boys than girls.

CONCLUSIONS

Using tooth-matrix biomarkers, we identified discrete developmental exposure windows wherein Pb and metal(loid) mixtures were associated with altered preadolescent kidney function.

What a paediatric nephrologist should know about preeclampsia and why it matters

Preeclampsia is a protean syndrome causing a kidney disease characterised by hypertension and proteinuria, usually considered transitory and reversible after delivery. Its prevalence ranges from 3-5 to 10% if all the related disorders are considered. This narrative review, on behalf of the Kidney and Pregnancy Study Group of the Italian Society of Nephrology, focuses on three reasons why preeclampsia should concern paediatric nephrologists and how they can play an important role in its prevention, as well as in the prevention of future kidney and cardiovascular diseases. Firstly, all diseases of the kidney and urinary tract diagnosed in paediatric age are associated with a higher risk of adverse pregnancy-related outcomes, including preeclampsia. Secondly, babies with low birth weights (small for gestational age, born preterm, or both) have an increased risk of developing the full panoply of metabolic diseases (obesity, hypertension, early-onset cardiopathy and chronic kidney disease) and girls are at higher risk of developing preeclampsia when pregnant. The risk may be particularly high in cases of maternal preeclampsia, highlighting a familial aggregation of this condition. Thirdly, pregnant teenagers have a higher risk of developing preeclampsia and the hypertensive disorders of pregnancy, and should be followed up as high risk pregnancies. In summary, preeclampsia has come to be seen as a window on the future health of both mother and baby. Identification of subjects at risk, early counselling and careful follow-up can contribute to reducing the high morbidity linked with this disorder.

Prenatal caffeine exposure induced renal developmental toxicity and transgenerational effect in rat offspring

Epidemiological studies revealed that prenatal caffeine exposure (PCE) is associated with adverse gestational outcomes and susceptibility to chronic diseases in offspring, yet the effects of PCE on glomerulosclerosis susceptibility in adult female offspring and its intergenerational transmission remain to be further investigated. Here, we found that PCE caused fetal kidney dysplasia and glomerulosclerosis of the female offspring. Besides, the kidney of F1 offspring in PCE group exhibited the "low expressional programming of AT2R" and "GC-IGF1 programming" alteration. Intergenerational genetic studies revealed that the renal defect and GC-IGF1 programming alteration was inherited to F2 adult female offspring derived from the female germ line, but Low expression of AT2R did not extend to the F2 female offspring. Taken together, PCE caused renal dysplasia and adult glomerulosclerosis in the F1 female offspring, which might be mediated by renal AT2R low expressional programming and GC-IGF1 axis alteration. Furthermore, PCE induced transgenerational toxicity on kidney, and GC-IGF1 programming alteration might be the potential molecular mechanism. This study provided experimental evidence for the mechanism study of the intergenerational inheritance of kidney developmental toxicity caused by PCE.

Salt sensitivity of blood pressure in childhood and adolescence

Although moderation of sodium intake is recommended population-wide, it remains uncertain who benefits from salt restriction. Salt sensitivity refers to changes in blood pressure in response to sodium intake and may occur with or without hypertension. Unfortunately, there is no practical way to assess salt sensitivity in daily practice. Assessment of salt sensitivity even in research studies is challenging with varying protocols utilized which may contribute to differing results. Building on studies in animals and adults, risk factors and conditions associated with salt sensitivity have been identified in the pediatric and young adult populations. This review presents the limited evidence linking obesity, low birth weight, diabetes, chronic kidney disease, and race/ethnicity with salt sensitivity in children, adolescents, and young adults. The impact of stress on sodium handling is also reviewed. The influence of age on the timing of introduction of dietary salt restriction and the long-term influence of salt sensitivity on risk for hypertension are considered. Lastly, interventions other than salt restriction that may improve salt sensitivity and may inform recommendations to families are reviewed.

Healthy and unhealthy aging on kidney structure and function: human studies

PURPOSE OF REVIEW

This review is intended to provide an up-to-date analysis of the structural and functional alterations of the kidneys that accompany healthy and unhealthy aging in humans. Macro- and micro- structural changes and glomerular filtration rate (whole kidney and single nephron) accompanying aging will be stressed.

RECENT FINDINGS

Comparative findings concerning distribution of anatomic changes of the kidney healthy and unhealthy aging are reviewed. Challenges concerning definition of chronic kidney disease (CKD) in otherwise healthy aging patients are discussed. The complex interactions of CKD and aging are discussed. The role of podocyte dysbiosis in kidney aging is reviewed.

SUMMARY

Kidney aging is a complex phenomenon often difficult to distinguish from CKD. Nonetheless, phenotypes of healthy and unhealthy aging are evident. Much more information concerning the molecular characteristics of normal kidney aging and its relevance to chronic kidney disease is needed.

Growth control of the kidney

The functional mass of kidney tissue in an adult is an important determinant of human health. Kidney formation during development is an essential determinant of the final nephron endowment of the adult organ, and no evidence has been reported that mice or humans are able to generate new nephrons after the developmental period. Mechanisms controlling organ growth after development are essential to establish the final adult organ size. The potential for organ growth is maintained in adult life and the size of one kidney may be significantly increased by loss of the contralateral kidney. The mouse has provided a model system for investigators to critically explore genetic, cell biological, and hormonal control of developmental and juvenile kidney growth. This article reviews three basic aspects of kidney size regulation: (1) Mechanisms that control nephron formation and how these are altered by the cessation of nephrogenesis at the end of the developmental period. (2) Applicability of the general model for growth hormone-insulin like growth factor control to kidney growth both pre- and postnatally. (3) Commonalities between mechanisms of juvenile kidney growth and the compensatory growth that is stimulated in adult life by reduction of kidney mass. Understanding the mechanisms that determine set-points for cell numbers and size in the kidney may inform ongoing efforts to generate kidney tissue from stem cells.

Glomerular hyperfiltration

Circulating blood is filtered across the glomerular barrier to form an ultrafiltrate of plasma in the Bowman's space. The volume of glomerular filtration adjusted by time is defined as the glomerular filtration rate (GFR), and the total GFR is the sum of all single-nephron GFRs. Thus, when the single-nephron GFR is increased in the context of a normal number of functioning nephrons, single glomerular hyperfiltration results in 'absolute' hyperfiltration in the kidney. 'Absolute' hyperfiltration can occur in healthy people after high protein intake, during pregnancy and in patients with diabetes, obesity or autosomal-dominant polycystic kidney disease. When the number of functioning nephrons is reduced, single-nephron glomerular hyperfiltration can result in a GFR that is within or below the normal range. This 'relative' hyperfiltration can occur in patients with a congenitally reduced nephron number or with an acquired reduction in nephron mass consequent to surgery or kidney disease. Improved understanding of the mechanisms that underlie 'absolute' and 'relative' glomerular hyperfiltration in different clinical settings, and of whether and how the single-nephron haemodynamic and related biomechanical forces that underlie glomerular hyperfiltration promote glomerular injury, will pave the way toward the development of novel therapeutic interventions that attenuate glomerular hyperfiltration and potentially prevent or limit consequent progressive kidney injury and loss of function.

Systemic Hypertension in Infants with Bronchopulmonary Dysplasia

PURPOSE OF REVIEW

Neonatal hypertension is increasingly recognized as improvements in neonatal intensive care have led to increased survival of premature infants. Among infants with bronchopulmonary dysplasia (BPD), the rates of hypertension are much higher than the general neonatal population. However, the etiology and pathophysiology of this increased risk of hypertension in neonates with lung disease remain unclear.

RECENT FINDINGS

Among infants with bronchopulmonary dysplasia, the rates of hypertension are much higher than the general neonatal population. New studies suggest outcomes in neonates with BPD with hypertension are usually good, with resolution of hypertension in most infants with lung disease. Several potential mechanisms of hypertension in this patient population have been recently proposed. This review focuses on the recent epidemiologic data on prevalence of hypertension in neonates with bronchopulmonary dysplasia, reviews the typical clinical course, and discusses available strategies for management of infants with bronchopulmonary dysplasia that develop hypertension.

Low Birthweight as a Risk Factor for Non-communicable Diseases in Adults

According to studies undertaken over the past 40 years, low birthweight (LBW) is not only a significant predictor of perinatal death and morbidity, but also increases the risk of chronic non-communicable diseases (NCDs) in adulthood. The purpose of this paper is to summarize the research on LBW as a risk factor for NCDs in adults. The Barker hypothesis was based on the finding that adults with an LBW or an unhealthy intrauterine environment, as well as a rapid catch-up, die due to NCDs. Over the last few decades, terminology such as thrifty genes, fetal programming, developmental origins of health and disease (DOHaD), and epigenetic factors have been coined. The most common NCDs include cardiovascular disease, diabetes mellitus type 2 (DMT2), hypertension (HT), dyslipidemia, proteinuria, and chronic kidney disease (CKD). Studies in mothers who experienced famine and those that solely reported birth weight as a risk factor for mortality support the concept. Although the etiology of NCD is unknown, Barry Brenner explained the notion of a low glomerular number (nGlom) in LBW children, followed by the progression to hyperfiltration as the physiopathologic etiology of HT and CKD in adults based on Guyton's renal physiology work. Autopsies of several ethnic groups have revealed anatomopathologic evidence in fetuses and adult kidneys. Because of the renal reserve, demonstrating renal function in proportion to renal volume in vivo is more difficult in adults. The greatest impact of these theories can be seen in pediatrics and obstetrics practice.

BET Proteins Regulate Expression of Osr1 in Early Kidney Development

In utero renal development is subject to maternal metabolic and environmental influences affecting long-term renal function and the risk of developing chronic kidney failure and cardiovascular disease. Epigenetic processes have been implicated in the orchestration of renal development and prenatal programming of nephron number. However, the role of many epigenetic modifiers for kidney development is still unclear. Bromodomain and extra-terminal domain (BET) proteins act as histone acetylation reader molecules and promote gene transcription. BET family members Brd2, Brd3 and Brd4 are expressed in the nephrogenic zone during kidney development. Here, the effect of the BET inhibitor JQ1 on renal development is evaluated. Inhibition of BET proteins via JQ1 leads to reduced growth of metanephric kidney cultures, loss of the nephron progenitor cell population, and premature and disturbed nephron differentiation. Gene expression of key nephron progenitor transcription factor Osr1 is downregulated after 24 h BET inhibition, while Lhx1 and Pax8 expression is increased. Mining of BRD4 ChIP-seq and gene expression data identify Osr1 as a key factor regulated by BRD4-controlled gene activation. Inhibition of BRD4 by BET inhibitor JQ1 leads to downregulation of Osr1, thereby causing a disturbance in the balance of nephron progenitor cell self-renewal and premature differentiation of the nephron, which ultimately leads to kidney hypoplasia and disturbed nephron development. This raises questions about the potential teratogenic effects of BET inhibitors for embryonic development. In summary, our work highlights the role of BET proteins for prenatal programming of nephrogenesis and identifies Osr1 as a potential target of BET proteins.

A Scoping Review of Life-Course Psychosocial Stress and Kidney Function

Increased exposure to maternal psychosocial stress during gestation and adverse neonatal environments has been linked to alterations in developmental programming and health consequences in offspring. A programmed low nephron endowment, among other altered pathways of susceptibility, likely increases the vulnerability to develop chronic kidney disease in later life. Our aim in this scoping review was to identify gaps in the literature by focusing on understanding the association between life-course exposure to psychosocial stress, and the risk of reduced kidney function. A systematic search in four databases (PubMed, ProQuest, Wed of Science, and Scopus) was performed, yielding 609 articles. Following abstract and full-text review, we identified 19 articles meeting our inclusion criteria, reporting associations between different psychosocial stressors and an increase in the prevalence of kidney disease or decline in kidney function, mainly in adulthood. There are a lack of studies that specifically evaluated the association between gestational exposure to psychosocial stress and measures of kidney function or disease in early life, despite the overall evidence consistent with the independent effects of prenatal stress on other perinatal and postnatal outcomes. Further research will establish epidemiological studies with clear and more comparable psychosocial stressors to solve this critical research gap.

Clinical Management of Children with a Congenital Solitary Functioning Kidney: Overview and Recommendations

CONTEXT

A congenital solitary functioning kidney (cSFK) is a common developmental defect that predisposes to hypertension and chronic kidney disease (CKD) as a consequence of hyperfiltration. Every urologist takes care of patients with a cSFK, since some will need lifelong urological care or will come with clinical problems or questions to an adult urologist later in life.

OBJECTIVE

We aim to provide clear recommendations for the initial clinical management and follow-up of children with a cSFK.

EVIDENCE ACQUISITION

PubMed and EMBASE were searched to identify relevant publications, which were combined with guidelines on related topics and expert opinion.

EVIDENCE SYNTHESIS

Initially, cSFK diagnosis should be confirmed and risk factors for kidney injury should be identified using ultrasound. Although more research into early predictors of kidney injury is needed, additional congenital anomalies of the kidney or urinary tract and absence of compensatory kidney hypertrophy have repeatedly been associated with a worse prognosis. The role of voiding cystourethrography and antibiotic prophylaxis remains controversial, and is complicated by the exclusion of children with a cSFK from studies. A yearly follow-up for signs of kidney injury is recommended for children with a cSFK. As masked hypertension is prevalent, annual ambulatory blood pressure measurement should be considered. During puberty, an increasing incidence of kidney injury is seen, indicating that long-term follow-up is necessary. If signs of kidney injury are present, angiotensin converting enzyme inhibitors are the first-line drugs of choice.

CONCLUSIONS

This overview points to the urological and medical clinical aspects and long-term care guidance for children with a cSFK, who are at risk of hypertension and CKD. Monitoring for signs of kidney injury is therefore recommended throughout life. Large, prospective studies with long-term follow-up of clearly defined cohorts are still needed to facilitate more risk-based and individualized clinical management.

PATIENT SUMMARY

Many children are born with only one functioning kidney, which could lead to kidney injury later in life. Therefore, a kidney ultrasound is made soon after birth, and other investigations may be needed as well. Urologists taking care of patients with a solitary functioning kidney should realize the long-term clinical aspects, which might need medical management.

Preterm birth and neonatal acute kidney injury: implications on adolescent and adult outcomes

As a result of preterm birth, immature kidneys are exposed to interventions in the NICU that promote survival, but are nephrotoxic. Furthermore, the duration of renal development may be truncated in these vulnerable neonates. Immaturity and nephrotoxic exposures predispose preterm newborns to acute kidney injury (AKI), particularly in the low birth weight and extremely preterm gestational age groups. Several studies have associated preterm birth as a risk factor for future chronic kidney disease (CKD). However, only a few publications have investigated the impact of neonatal AKI on CKD development. Here, we will review the evidence linking preterm birth and AKI in the NICU to CKD and highlight the knowledge gaps and opportunities for future research. For neonatal intensive care studies, we propose the inclusion of AKI as an important short-term morbidity outcome and CKD findings such as a reduced glomerular filtration rate in the assessment of long-term outcomes.

The polycomb proteins EZH1 and EZH2 co-regulate chromatin accessibility and nephron progenitor cell lifespan in mice

SIX2 (SIX homeobox 2)-positive nephron progenitor cells (NPCs) give rise to all epithelial cell types of the nephron, the filtering unit of the kidney. NPCs have a limited lifespan and are depleted near the time of birth. Epigenetic factors are implicated in the maintenance of organ-restricted progenitors such as NPCs, but the chromatin-based mechanisms are incompletely understood. Here, using a combination of gene targeting, chromatin profiling, and single-cell RNA analysis, we examined the role of the murine histone 3 Lys-27 (H3K27) methyltransferases EZH1 (enhancer of zeste 1) and EZH2 in NPC maintenance. We found that EZH2 expression correlates with NPC growth potential and that EZH2 is the dominant H3K27 methyltransferase in NPCs and epithelial descendants. Surprisingly, NPCs lacking H3K27 trimethylation maintained their progenitor state but cycled slowly, leading to a smaller NPC pool and formation of fewer nephrons. Unlike Ezh2 loss of function, dual inactivation of Ezh1 and Ezh2 triggered overexpression of the transcriptional repressor Hes-related family BHLH transcription factor with YRPW motif 1 (Hey1), down-regulation of Six2, and unscheduled activation of Wnt4-driven differentiation, resulting in early termination of nephrogenesis and severe renal dysgenesis. Double-mutant NPCs also overexpressed the SIX family member Six1 However, in this context, SIX1 failed to maintain NPC stemness. At the chromatin level, EZH1 and EZH2 restricted accessibility to AP-1-binding motifs, and their absence promoted a regulatory landscape akin to differentiated and nonlineage cells. We conclude that EZH2 is required for NPC renewal potential and that tempering of the differentiation program requires cooperation of both EZH1 and EZH2.

Whole genome sequencing and novel candidate genes for CAKUT and altered nephrogenesis in the HSRA rat

The HSRA rat is a model of congenital abnormalities of the kidney and urogenital tract (CAKUT). Our laboratory has used this model to investigate the role of nephron number (functional unit of the kidney) in susceptibility to develop kidney disease as 50-75% offspring are born with a single kidney (HSRA-S), while 25-50% are born with two kidneys (HSRA-C). HSRA-S rats develop increased kidney injury and hypertension with age compared with nephrectomized two-kidney animals (HSRA-UNX), suggesting that even slight differences in nephron number can be an important driver in decline in kidney function. The HSRA rat was selected and inbred from a family of outbred heterogeneous stock (NIH-HS) rats that exhibited a high incidence of CAKUT. The HS model was originally developed from eight inbred strains (ACI, BN, BUF, F344, M520, MR, WKY, and WN). The genetic make-up of the HSRA is therefore a mosaic of these eight inbred strains. Interestingly, the ACI progenitor of the HS model exhibits CAKUT in 10-15% of offspring with the genetic cause being attributed to the presence of a long-term repeat (LTR) within exon 1 of the c-Kit gene. Our hypothesis is that the HSRA and ACI share this common genetic cause, but other alleles in the HSRA genome contribute to the increased penetrance of CAKUT (75% HSRA vs. 15% in ACI). To facilitate genetic studies and better characterize the model, we sequenced the whole genome of the HSRA to a depth of ~50×. A genome-wide variant analysis of high-impact variants identified a number of novel genes that could be linked to CAKUT in the HSRA model. In summary, the identification of new genes/modifiers that lead to CAKUT/loss of one kidney in the HSRA model will provide greater insight into association between kidney development and susceptibility to develop cardiovascular disease later in life.