The maturing kidney: development and susceptibility

Late-Onset Hyponatremia in Premature Infants

Late-onset hyponatremia (LOH) frequently affects premature infants 2 or more weeks of age due to inadequate sodium intake and excessive kidney loss. Late-onset hyponatremia typically occurs in infants who are physiologically stable and is defined as serum sodium of 132 mEq/L or less or between 133 and 135 mEq/L if receiving sodium supplementation. Recent evidence suggests that spot urine sodium levels may improve the recognition of LOH, as low levels of excreted urine reflect a total body sodium deficit and negative balance. Untreated LOH may result in poor somatic growth, neurodevelopmental delay, higher incidence of bronchopulmonary dysplasia, and more severe retinopathy of prematurity. The primary prevention of LOH is to maintain serum sodium between 135 and 145 mEq/L; however, there are currently no formal protocols guiding sodium supplementation. The purpose of this article is to present on overview of LOH pathophysiology and its effect on somatic growth, neurodevelopment outcomes, and other related sequelae. We further discuss general management strategies and describe a protocol for sodium supplementation that is presently undergoing an evaluation for effectiveness.

Current and Novel Biomarkers of Progression Risk in Children with Chronic Kidney Disease

BACKGROUND

Due to the complexity of chronic kidney disease (CKD) pathophysiology, biomarkers representing different mechanistic pathways have been targeted for the study and development of novel biomarkers. The discovery of clinically useful CKD biomarkers would allow for the identification of those children at the highest risk of kidney function decline for timely interventions and enrollment in clinical trials.

SUMMARY

Glomerular filtration rate and proteinuria are traditional biomarkers to classify and prognosticate CKD progression in clinical practice but have several limitations. Over the recent decades, novel biomarkers have been identified from blood or urine with metabolomic screening studies, proteomic screening studies, and an improved knowledge of CKD pathophysiology. This review highlights promising biomarkers associated with the progression of CKD that could potentially serve as future prognostic markers in children with CKD.

KEY MESSAGES

Further studies are needed in children with CKD to validate putative biomarkers, particularly candidate proteins and metabolites, for improving clinical management.

Biomarkers for acute kidney injury in children - where are we now?

PURPOSE OF REVIEW

Review the literature over the last 2 years on commonly evaluated biomarkers of acute kidney injury (AKI) and highlight the findings of these biomarkers.

RECENT FINDINGS

Among several studied AKI biomarkers, urine neutrophil gelatinase-associated lipocalin (NGAL) and the combination of urine tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) have been recently studied most frequently as diagnostic biomarkers of AKI and for AKI risk stratification. Urine NGAL has continued to show good discriminative value to predict and diagnose AKI in childhood. Urine TIMP-2∗IGFBP7 can provide modest improvement to clinical models of AKI.

SUMMARY

Prior research supports that AKI biomarkers may identify AKI at an earlier time point and indicate clinically meaningful tubular injury. More effort should be made to understand if AKI biomarkers can guide treatments and improve outcomes.

Characterization of the pattern of expression of Gas1 in the kidney during postnatal development in the rat

Growth Arrest-Specific 1 (Gas1) is a pleiotropic protein with different functions, in the adult kidney Gas1 acts as an endogenous inhibitor of cell proliferation but it is also necessary for the maintenance and proliferation of Renal Progenitor Cells (RPC) during early development, thus it fulfills important functions in the adult kidney. However, it is not known whether or not Gas1 is expressed during postnatal development, a critical stage for renal maturation. For this reason, the main objective of this work was to characterize the expression pattern of Gas1 in the different regions of the kidney by immunofluorescence and Western blot analysis during the postnatal development of the rat. We found that Gas1 is present and has a differential expression pattern in the various regions of the nephron during postnatal development. We observed that the highest levels of expression of Gas1 occur in the adult, however, Gas1 is also expressed in RPC and interestingly, the expression of RPC markers such as the Neural cell adhesion molecule (NCAM) and Cluster of differentiation 24 (CD24) were found to have an inverse pattern of expression to Gas1 (decreases as the kidney matures) during postnatal renal maturation, this indicates a role for Gas1 in the regulation of renal cell proliferation at this stage of development.

Update on COVID-19 Therapy in Pediatric Age

With the extension of the COVID-19 pandemic, the large use of COVID-19 vaccines among adults and the emergence of SARS-CoV-2 variants means that the epidemiology of COVID-19 in pediatrics, particularly among younger children, has substantially changed. The prevalence of pediatric COVID-19 significantly increased, several severe cases among children were reported, and long-COVID in pediatric age was frequently observed. The main aim of this paper is to discuss which types of treatment are presently available for pediatric patients with COVID-19, which of them are authorized for the first years of life, and which are the most important limitations of COVID-19 therapy in pediatric age. Four different antivirals, remdesivir (RVD), the combination nirmatrelvir plus ritonavir (Paxlovid), molnupiravir (MPV), and the monoclonal antibody bebtelovimab (BEB), are presently approved or authorized for emergency use for COVID-19 treatment by most of the national health authorities, although with limitations according to the clinical relevance of disease and patient's characteristics. Analyses in the literature show that MPV cannot be used in pediatric age for the risk of adverse events regarding bone growth. The other antivirals can be used, at least in older children, and RDV can be used in all children except in neonates. However, careful research on pharmacokinetic and clinical data specifically collected in neonates and children are urgently needed for the appropriate management of pediatric COVID-19.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Dog

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions) Project (www.toxpath.org/inhand.asp) is a joint initiative of the societies of toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in most tissues and organs from the dog used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions, lesions induced by exposure to test materials, and relevant infectious and parasitic lesions. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

The Impact of Functional and Structural Maturation of the Kidney on Susceptibility to Drug and Chemical Toxicity in Neonatal Rodents

Drug responses are often unpredictable in juvenile animal toxicity studies; hence, optimizing dosages is challenging. Renal functional differences based on age of development will often result in vastly different toxicologic responses. Developmental changes in renal function can alter plasma clearance of compounds with extensive renal elimination. Absorption, distribution, metabolism, and excretion of drugs vary depending on animal age and kidney maturation. Toxicity can result in malformations or renal degeneration. Although renal morphologic development in humans generally occurs in utero, maximal levels of tubular secretion, acid-base equilibrium, concentrating ability, or glomerular filtration rate (GFR) are reached postnatally in humans and animals and subject to drug effects. Maturation of renal metabolism and transporters occurs postnatally and plays a critical role in detoxification and excretion. Maturation times must be considered when designing juvenile toxicity studies and may require cohorts of animals of specific ages to achieve optimal dosing schemes and toxicokinetics. In recent years, critical end points and windows of susceptibility have been established comparatively between species to better model pharmacokinetics and understand pediatric nephrotoxicity. There are examples of agents where toxicity is enhanced in neonates, others where it is diminished, and others where rat nephrotoxicity is expressed as juvenile toxicity, but in humans as gestational toxicity.

DNA Damage and Expression Profile of Genes Associated with Nephrotoxicity Induced by Butralin and Ameliorating Effect of Arabic Gum in Female Rats

Nephrotoxicity induced by exposure to environmental pollution, including herbicides, is becoming a global problem. Natural products are the prime alternative scientific research as they express better medicinal activity and minor side effects compared with a variety of synthetic drugs. This study was performed to evaluate the nephroprotective proficiency of Arabic gum against butralin-induced nephrotoxicity. Adult female rats were supplemented with Arabic gum (4.3 g/kg b.wt) and/or butralin (312 mg/L) in drinking water for 30 days. The results found that markers of serum kidney function, oxidative stress biomarkers, DNA damage, and expression of kidney specific genes (Acsm2, Ace, and Ace2) as well as histopathological examination in treated rats were conducted. Butralin-treated rats showed a rise in serum creatinine (41%), BUN (47.3%), and MDA (140.9%) as well as decrease in activity of the antioxidant markers (CAT (-21%); GPx (-70.7%); and TAC (43.2%)) in comparison with the control group. In addition, butralin treatment increased the DNA damage (221%); altered the expression levels of Acsm2, Ace, and Ace2 (-51.6%, 141.6%, and 143% respectively); and elevated histopathological lesions in the kidney tissues. Pretreatment of Arabic gum prevented butralin-prompted degenerative changes of kidney tissues. The results suggested that the protective effect provided by Arabic gum on renal tissues exposed to the herbicide butralin could be attributed to enhancement of antioxidants and increase the free radical scavenging activity in vivo.

Respiratory depression in a neonate born to mother on maximum dose sertraline: a case report

BACKGROUND

Mood and anxiety disorders are common in women of childbearing age, especially during the peripartum period. As more women seek medical management for these conditions, there is an increasing need for studies to better examine the effects of exposure to selective serotonin reuptake inhibitors (SSRIs), and other antidepressants, on newborns at the time of delivery.

CASE PRESENTATION

We report the case of a term Caucasian infant born to a 17-year-old white female taking 100 mg of sertraline daily for depression and anxiety who exhibited respiratory depression and hypoxia after an uncomplicated vaginal delivery. The neonate was treated with the use of continuous positive airway pressure (CPAP) and supplemental oxygen and subsequently the symptoms resolved without complication.

CONCLUSIONS

We present this case with the suspicion of poor neonatal adjustment syndrome as the possible cause of the respiratory depression and hypoxia in this newborn.

Expression of Acsm2, a kidney-specific gene, parallels the function and maturation of proximal tubular cells

The acyl-CoA synthetase medium-chain family member 2 (Acsm2) gene was first identified and cloned by our group as a kidney-specific "KS" gene. However, its expression pattern and function remain to be clarified. In the present study, we found that the Acsm2 gene was expressed specifically and at a high level in normal adult kidneys. Expression of Acsm2 in kidneys followed a maturational pattern: it was low in newborn mice and increased with kidney development and maturation. In situ hybridization and immunohistochemistry revealed that Acsm2 was expressed specifically in proximal tubular cells of adult kidneys. Data from the Encyclopedia of DNA Elements database revealed that the Acsm2 gene locus in the mouse has specific histone modifications related to the active transcription of the gene exclusively in kidney cells. Following acute kidney injury, partial unilateral ureteral obstruction, and chronic kidney diseases, expression of Acsm2 in the proximal tubules was significantly decreased. In human samples, the expression pattern of ACSM2A, a homolog of mouse Acsm2, was similar to that in mice, and its expression decreased with several types of renal injuries. These results indicate that the expression of Acsm2 parallels the structural and functional maturation of proximal tubular cells. Downregulation of its expression in several models of kidney disease suggests that Acms2 may serve as a novel marker of proximal tubular injury and/or dysfunction.

Rethinking furosemide use for infants with bronchopulmonary dysplasia

Diuretics are commonly administered to infants with bronchopulmonary dysplasia (BPD) to improve respiratory function despite the absence of prospective data demonstrating long term benefits. While many potentially adverse effects of furosemide are known to clinicians, its direct and indirect impact on multiple pathophysiological processes need to be understood. While furosemide likely has a role in the management of infants with BPD, clinicians are encouraged to recognize these potential complications associated with furosemide administration. Specifically, a deeper understanding of the impact of diuretics on sodium metabolism neurohumoral regulation of cardiopulmonary physiology is required.

Histology Atlas of the Developing Mouse Urinary System With Emphasis on Prenatal Days E10.5-E18.5

Congenital abnormalities of the urinary tract are some of the most common human developmental abnormalities. Several genetically engineered mouse models have been developed to mimic these abnormalities and aim to better understand the molecular mechanisms of disease. This atlas has been developed as an aid to pathologists and other biomedical scientists for identification of abnormalities in the developing murine urinary tract by cataloguing normal structures at each stage of development. Hematoxylin and eosin- and immunohistochemical-stained sections are provided, with a focus on E10.5-E18.5, as well as a brief discussion of postnatal events in urinary tract development. A section on abnormalities in the development of the urinary tract is also provided, and molecular mechanisms are presented as supplementary material. Additionally, overviews of the 2 key processes of kidney development, branching morphogenesis and nephrogenesis, are provided to aid in the understanding of the complex organogenesis of the kidney. One of the key findings of this atlas is the histological identification of the ureteric bud at E10.5, as previous literature has provided conflicting reports on the initial point of budding. Furthermore, attention is paid to points where murine development is significantly distinct from human development, namely, in the cessation of nephrogenesis.

A brief review of kidney development, maturation, developmental abnormalities, and drug toxicity: juvenile animal relevancy

Nonclinical juvenile animal tests perform a valuable role in determining adverse drug effects during periods of organogenesis and/or functional maturation. Developmental anatomic and functional maturation time points are important to consider between juveniles and adults when regarding different organ toxicities in response to drug administration. The kidney is an example of a major organ that has differences in these time points in comparing juveniles to adults and in contrasting humans to laboratory animal species. Toxicologic pathologists, involved in juvenile studies, need to be aware of these time points which are age-related exposure periods of sensitivity to drug toxicity. Age-related developmental anatomic and functional maturation are factors which can affect the way that a drug is absorbed, distributed, metabolized, and excreted (ADME). Changes to any component of ADME may alter drug toxicity resulting in kidney abnormalities, nephrotoxicity, or maturational disorders. Juvenile animal kidneys may either be less resistant or more resistant to known adult nephrotoxic drug effects. Furthermore, drug toxicity observed in juvenile animal kidneys may not always correspond to similar toxicities in humans. Juvenile animal nonclinical toxicology studies targeting the kidneys have to be carefully planned to attain the maximum knowledge from each study.

Kidney Dysfunction in Adult Offspring Exposed In Utero to Type 1 Diabetes Is Associated with Alterations in Genome-Wide DNA Methylation

Background

Fetal exposure to hyperglycemia impacts negatively kidney development and function.

Objective

Our objective was to determine whether fetal exposure to moderate hyperglycemia is associated with epigenetic alterations in DNA methylation in peripheral blood cells and whether those alterations are related to impaired kidney function in adult offspring.

Design

Twenty nine adult, non-diabetic offspring of mothers with type 1 diabetes (T1D) (case group) were matched with 28 offspring of T1D fathers (control group) for the study of their leukocyte genome-wide DNA methylation profile (27,578 CpG sites, Human Methylation 27 BeadChip, Illumina Infinium). In a subset of 19 cases and 18 controls, we assessed renal vascular development by measuring Glomerular Filtration Rate (GFR) and Effective Renal Plasma Flow (ERPF) at baseline and during vasodilatation produced by amino acid infusion.

Results

Globally, DNA was under-methylated in cases vs. controls. Among the 87 CpG sites differently methylated, 74 sites were less methylated and 13 sites more methylated in cases vs. controls. None of these CpG sites were located on a gene known to be directly involved in kidney development and/or function. However, the gene encoding DNA methyltransferase 1 (DNMT1)—a key enzyme involved in gene expression during early development–was under-methylated in cases. The average methylation of the 74 under-methylated sites differently correlated with GFR in cases and controls.

Conclusion

Alterations in methylation profile imprinted by the hyperglycemic milieu of T1D mothers during fetal development may impact kidney function in adult offspring. The involved pathways seem to be a nonspecific imprinting process rather than specific to kidney development or function.

Consumption of a high-salt diet by ewes during pregnancy alters nephrogenesis in 5-month-old offspring

Maternal nutrition during pregnancy can affect kidney development in the foetus, which may lead to adverse consequences in the mature kidney. It was expected that high-salt intake by pregnant ewes would lead to a reduction in foetal glomerular number but that the ovine kidney would adapt to maintain homoeostasis, in part by increasing the size of each glomerulus. Merino ewes that were fed either a control (1.5% NaCl) or high-salt (10.5% NaCl) diet during pregnancy, as well as their 5-month-old offspring, were subjected to a dietary salt challenge, and glomerular number and size and sodium excretion were measured. The high-salt offspring had 20% fewer glomeruli compared with the control offspring (P < 0.001), but they also had larger glomerular radii compared with the control offspring (P < 0.001). Consequently, the cross-sectional area of glomeruli was 18% larger in the high-salt offspring than in the control offspring (P < 0.05). There was no difference in the daily urinary sodium excretion between the two offspring groups (P > 0.05), although the high-salt offspring produced urine with a higher concentration of sodium. Our results demonstrated that maternal high-salt intake during pregnancy affected foetal nephrogenesis, altering glomerular number at birth. However, the ability to concentrate and excrete salt was not compromised, which indicates that the kidney was able to adapt to the reduction in the number of glomeruli.

Hemodynamic and hormonal changes to dual renin-angiotensin system inhibition in experimental hypertension

We examined the antihypertensive effects of valsartan, aliskiren, or both drugs combined on circulating, cardiac, and renal components of the renin-angiotensin system in congenic mRen2.Lewis hypertensive rats assigned to: vehicle (n=9), valsartan (via drinking water, 30 mg/kg per day; n=10), aliskiren (SC by osmotic mini-pumps, 50 mg/kg per day; n=10), or valsartan (30 mg/kg per day) combined with aliskiren (50 mg/kg per day; n=10). Arterial pressure and heart rate were measured by telemetry before and during 2 weeks of treatment; trunk blood, heart, urine, and kidneys were collected for measures of renin-angiotensin system components. Arterial pressure and left-ventricular weight/tibia length ratio were reduced by monotherapy of valsartan, aliskiren, and further reduced by the combination therapy. Urinary protein excretion was reduced by valsartan and further reduced by the combination. The increases in plasma angiotensin (Ang) II induced by valsartan were reversed by the treatment of aliskiren and partially suppressed by the combination. The decreases in plasma Ang-(1-7) induced by aliskiren recovered in the combination group. Kidney Ang-(1-12) was increased by the combination therapy whereas the increases in urinary creatinine mediated by valsartan were reversed by addition of aliskiren. The antihypertensive and antiproteinuric actions of the combined therapy were associated with marked worsening of renal parenchymal disease and increased peritubular fibrosis. The data show that despite improvements in the surrogate end points of blood pressure, ventricular mass, and proteinuria, dual blockade of Ang II receptors and renin activity is accompanied by worsening of renal parenchymal disease reflecting a renal homeostatic stress response attributable to loss of tubuloglomerular feedback by Ang II.

Environmental exposure to lead and mercury in Mexican children: a real health problem

Exposure to lead (Pb) and mercury (Hg) remains a world public health problem, particularly for young children in developing countries. In Mexico, the main sources of exposure to Pb and Hg are wastes from human activities that increase the natural sources of these metals. Pb and Hg are highly toxic during development and maturation periods of the central nervous system (CNS); these effects are associated with the risk for neurodegenerative diseases. Mexico has numerous exposure sources to Pb and Hg; nevertheless, information on exposure in children is limited, particularly for Hg. Therefore, we conducted a review of the studies performed in children exposed to Pb and Hg. Data presented support that an important proportion of Mexican children have Pb levels above values associated with dangerous effects. On the other hand, studies on Hg-exposure are scarce, so we need more studies to estimate the magnitude of the problem and to determine exposure levels in Mexican children. Available data support the urgent need for coordinated actions among researchers, and health and environmental government authorities to implement education and nutritional campaigns, as well as to decrease exposure and effects of Pb and Hg. In addition, there must be a priority for the implementation of educational campaigns directed to the general population, but with emphasis in parents, education staff and health care providers to decrease both the risk of exposure of children to Pb and Hg and the effects of the exposure to these metals.

Conditional ablation of glycogen synthase kinase 3β in postnatal mouse kidney

Glycogen synthase kinase (GSK)3 is a ubiquitously expressed serine/threonine kinase existing in two isoforms, namely GSK3α and GSK3β. Aside from the long-recognized role in insulin signal transduction and glycogen biosynthesis, GSK3β has been recently coined as a master control molecule in nuclear factor-κB activation and inflammatory kidney injury. Nevertheless, previous studies are less conclusive because they relied greatly on small molecule inhibitors, which lack selectivity and barely distinguish between the GSK3 isoforms. In addition, early embryonic lethality after global knockout of GSK3β precludes interrogation of the biological role of GSK3β in the adult kidney. To circumvent these issues, the Cre/loxP system was used to generate a conditional knockout mouse model in which the GSK3β gene was specifically deleted in kidney cortical tubules at postnatal mature stage. Kidney-specific ablation of GSK3β resulted in a phenotype no different from control littermates. Knockout mice (KO) were viable and exhibited normal development and normal kidney physiology in terms of kidney function, urine albumin excretion, and urine-concentrating ability. It is noteworthy that apart from normal glomerular and tubulointerstitial morphology, the kidneys from KO demonstrated more glycogen accumulation in the renal cortical tubules as assessed by both periodic acid-Schiff staining for light microscopy and direct biochemical assay, consistent with an elevated glycogen synthetic activity as evidenced by diminished inhibitory phosphorylation of glycogen synthase that occurred subsequent to GSK3β ablation. This finding was further validated by electron microscopic observations of increased deposition of glycogen particles in the renal tubules of KO, suggesting that GSK3α could not fully compensate for the loss of GSK3β in regulating glycogen metabolism in the kidney. Collectively, our study suggests that kidney-specific ablation of GSK3β barely affects kidney function and histology under normal circumstances. Extended examinations of these KO under diseased conditions are merited to understand the role of GSK3β in renal pathophysiology.

Long-term effects of high lipid and high energy diet on serum lipid, brain fatty acid composition, and memory and learning ability in mice

OBJECTIVE

It is well known that high lipid and high energy diet is harmful to health. But the different effects of high lipid diet composed of either saturated fatty acids or unsaturated fatty acids have not been distinguished.

METHOD

Eighteen pregnant C57BL/6j (22-25g) mice were randomly divided into three groups of six each and fed with chow or high lipid diet composed of either flaxseed oil (chow diet 84%, cholesterol 0.2%, flaxseed oil 15.8%) or lard fat (chow diet 84%, cholesterol 0.2%, lard fat 15.8%). After weaning, the offspring were fed the same diet as their mothers were fed during the experiment, and their spatial memory and learning ability were evaluated by Morris water maze when they were 8 weeks old. Next, the blood and tissues were sampled when they were 9 weeks old. Serum lipids were determined using kits, and brain fatty acids were measured using a gas chromatograph.

RESULTS

Compared to chow diet (control), high flaxseed oil diet (HFO) increased high density lipoprotein cholesterol level (HDL-C) in the mothers but not in offspring; high lard fat diet (HLF) increased serum total cholesterol level (TC) and low density lipoprotein cholesterol level (LDL-C) both in mothers and offspring. Brain fatty acids profile was altered by HLF compared with chow diet. Polyunsaturated fatty acids and long-chain polyunsaturated fatty acids content were significantly lower in the HLF group than in the control group, but saturated fatty acids content were significantly higher in HLF group than those in control group. The changed fatty acids composition affected the spatial memory and learning ability of adult offspring.

CONCLUSIONS

A long-term high lard diet increased offspring serum TC and LDL-C levels and affected the brain's fatty acid composition, and memory and learning ability. The polyunsaturated fatty acid content of the brain may be correlated with serum cholesterol levels.

Development of a micro-array to detect human and mouse microRNAs and characterization of expression in human organs

MicroRNAs (miRNAs) are believed to play important roles in developmental and other cellular processes by hybridizing to complementary target mRNA transcripts. This results in either cleavage of the hybridized transcript or negative regulation of translation. Little is known about the regulation or pattern of miRNA expression. The predicted presence of numerous miRNA sequences in higher eukaryotes makes it highly likely that the expression levels of individual miRNA molecules themselves should play an important role in regulating multiple cellular processes. Therefore, determining the pattern of global miRNA expression levels in mammals and other higher eukaryotes is essential to help understand both the mechanism of miRNA transcriptional regulation as well as to help identify miRNA regulated gene expression. Here, we describe a novel method to detect global processed miRNA expression levels in higher eukaryotes, including human, mouse and rats, by using a high-density oligonucleotide array. Array results have been validated by subsequent confirmation of mir expression using northern-blot analysis. Major differences in mir expression have been detected in samples from diverse sources, suggesting highly regulated mir expression, and specific gene regulatory functions for individual miRNA transcripts. For example, five different miRNAs were found to be preferentially expressed in human kidney compared with other human tissues. Comparative analysis of surrounding genomic sequences of the kidney-specific miRNA clusters revealed the occurrence of specific transcription factor binding sites located in conserved phylogenetic foot prints, suggesting that these may be involved in regulating mir expression in kidney.

A functional immature model of chronic partial ureteral obstruction

BACKGROUND

The most common nonlethal congenital anomaly of the urinary tract is ureteral obstruction without dysplasia. Although rarely progressive, the morbidity associated with metabolic and surgical management is considerable. Our study was designed to measure local and systemic pathophysiologic mechanisms in an immature model of chronic partial unilateral ureteral obstruction (UUO) after completion of glomerulogenesis.

METHODS

A partial UUO was created by the method of "psoas wrap" in young male weanling rats. Control animals were sham operated. Three groups were divided as follows: sham (N= 15), UUO (N= 18), and UUO + angiotensin-converting enzyme (ACE) (N= 16) inhibitor, enalapril. Renal glomerular and tubular functions were determined by creatinine and uric acid clearances. Diuresis was assessed by urine volume, osmolality, and fractional solute excretions from samples above and below the obstruction. Proteinuria was determined by the urine protein/creatinine ratio (Up/c).

RESULTS

Proteinuria was attenuated in UUO + ACE-treated animals. The hyperuricemia of the immature UUO animals was avoided by an increase in the clearance of uric acid in the UUO + ACE-treated group. Fractional solute excretions suggested a diversion of diuresis to the contralateral unobstructed kidney.

CONCLUSION

Angiotensin blockade during chronic UUO in young rats affords protection by attenuating proteinuria, promoting uricosuria, and diverting solute diuresis. These data suggest a complex interaction of local and systemic mechanisms unique to the maturing kidney.

Effects of maternal hypercholesterolemia on pregnancy and development of offspring

The effect of maternal hypercholesterolemia on the course of pregnancy and the development of offspring was investigated. Rats were fed either an enriched-cholesterol diet (HC) or a standard diet (control) from 1 week before mating until weaning of offspring. Compared with the control group, HC dams showed a fourfold increase in abortions, a twofold increase in neonatal mortality, smaller litter size, and lower birth weight of pups. At weaning, Na(+),K(+)-ATPase activity in the outer renal medulla was reduced in HC pups compared with control pups, suggesting retarded or impaired development of medullary nephron segments. At this point, to better examine the adverse effects of maternal hypercholesterolemia, the HC pups were divided into two groups: one fed a cholesterol-enriched diet (HC/hc) and the other a standard diet (HC/nc), while control pups were maintained on the standard diet. In adulthood, the HC/hc group showed growth impairment and reduced renal function, demonstrated by low creatinine clearance (0.24+/-0.04 ml/min per 100 g body weight) and high fractional excretion of sodium, potassium, and water ( P<0.05 vs. control). These effects were partially reversed in the HC/nc group. In this study, neither dams nor offspring developed hypertension. Thus, maternal hypercholesterolemia adversely affected pregnancy outcomes and the development of offspring by inducing abnormalities and thereby reducing renal function.