Renal glomeruli and tubular injury following indomethacin, ibuprofen, and gentamicin exposure in a neonatal rat model

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.

Impact of nephrotoxic drugs on urinary biomarkers of renal function in very preterm infants

BACKGROUND

Following preterm birth, the immature kidney is exposed to several harmful conditions, with an increased risk of renal impairment. We aimed to assess urinary biomarkers of renal function in very preterm infants during early nephrotoxic treatments.

METHODS

Infants ≤32 weeks' gestation and ≤1500 g were enrolled in this observational prospective study. Urine samples were collected on day 1(T1), 2-4(T2), 5-7(T3), 8-10(T4), 11-13(T5). The following urinary biomarkers were determined: osteopontin (uOPN), epidermal growth factor (uEGF), neutrophil gelatinase-associated lipocalin (uNGAL), cystatin C (uCysC). The infants were grouped according to their exposure to amikacin or ibuprofen during the study period and a between-group comparison of urinary biomarkers at each time point was performed.

RESULTS

Thirty-six infants were included. Urinary CysC, uOPN, and uNGAL rose significantly during ibuprofen or amikacin treatment, while no difference was observed for uEGF. After adjustment for possible influencing factors, amikacin administration was associated with higher uCysC at T1 (p = 0.007) and T2 (p = 0.016), whereas ibuprofen increased uOPN (p = 0.001) and uNGAL concentration (p = 0.009) at T3.

CONCLUSION

Nephrotoxic therapies induce molecule-specific change patterns of renal function biomarkers in treated preterm infants. Serial assessments of these biomarkers may aid to identify neonates at risk of renal impairment and to develop tailored therapeutic approaches.

IMPACT

Despite the wide use of nephrotoxic therapies in neonatal settings, little is known on their effect on renal function biomarkers in preterm infants. This study describes molecule-specific change patterns of urinary biomarkers during ibuprofen and amikacin administration, suggesting underlying pathophysiological effects on renal function. Given their low analytical costs and non-invasive collection, the urinary biomarkers investigated in this study represent a promising strategy for serial monitoring of renal function in at-risk neonates and may aid the early detection of renal function impairment at different kidney levels during nephrotoxic treatments.

Drug toxicity in the proximal tubule: new models, methods and mechanisms

The proximal tubule (PT) reabsorbs most of the glomerular filtrate and plays an important role in the uptake, metabolism and excretion of xenobiotics. Some therapeutic drugs are harmful to the PT, and resulting nephrotoxicity is thought to be responsible for approximately 1 in 6 of cases of children hospitalized with acute kidney injury (AKI). Clinically, PT dysfunction leads to urinary wasting of important solutes normally reabsorbed by this nephron segment, leading to systemic complications such as bone demineralization and a clinical scenario known as the renal Fanconi syndrome (RFS). While PT defects can be diagnosed using a combination of blood and urine markers, including urinary excretion of low molecular weight proteins (LMWP), standardized definitions of what constitutes clinically significant toxicity are lacking, and identifying which patients will go on to develop progressive loss of kidney function remains a major challenge. In addition, much of our understanding of cellular mechanisms of drug toxicity is still limited, partly due to the constraints of available cell and animal models. However, advances in new and more sophisticated in vitro models of the PT, along with the application of high-content analytical methods that can provide readouts more relevant to the clinical manifestations of nephrotoxicity, are beginning to extend our knowledge. Such technical progress should help in discovering new biomarkers that can better detect nephrotoxicity earlier and predict its long-term consequences, and herald a new era of more personalized medicine.

Premature differentiation of nephron progenitor cell and dysregulation of gene pathways critical to kidney development in a model of preterm birth

Preterm birth is a leading cause of neonatal morbidity. Survivors have a greater risk for kidney dysfunction and hypertension. Little is known about the molecular changes that occur in the kidney of individuals born preterm. Here, we demonstrate that mice delivered two days prior to full term gestation undergo premature cessation of nephrogenesis, resulting in a lower glomerular density. Kidneys from preterm and term groups exhibited differences in gene expression profiles at 20- and 27-days post-conception, including significant differences in the expression of fat-soluble vitamin-related genes. Kidneys of the preterm mice exhibited decreased proportions of endothelial cells and a lower expression of genes promoting angiogenesis compared to the term group. Kidneys from the preterm mice also had altered nephron progenitor subpopulations, early Six2 depletion, and altered Jag1 expression in the nephrogenic zone, consistent with premature differentiation of nephron progenitor cells. In conclusion, preterm birth alone was sufficient to shorten the duration of nephrogenesis and cause premature differentiation of nephron progenitor cells. These candidate genes and pathways may provide targets to improve kidney health in preterm infants.

Effect of Quercetin on Injury to Indomethacin-Treated Human Embryonic Kidney 293 Cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to treat inflammation and pain and even to prevent the progression of cardiovascular disease. They have become widely used because of their effectiveness, especially among athletes performing high-intensity training. Indomethacin is used for pain management in sports medicine and is highly effective and versatile. However, several clinical studies have reported that indomethacin induces acute renal damage. In the present study, we determined that indomethacin reduced human embryonic kidney 293 (HEK293) cell viability in a concentration-dependent manner by triggering apoptosis. In addition, we demonstrated the effect of quercetin on indomethacin-treated HEK293 cells by inactivating the caspase-3 and caspase-9 signals. Furthermore, quercetin reduced ROS production and increased mitochondrial membrane potential (ΔΨm) in indomethacin-treated HEK293 cells. Our results indicate that quercetin can interrupt the activated caspase and mitochondrial pathway induced by indomethacin in HEK293 cells and affect apoptotic mRNA expression. Quercetin can protect against indomethacin-induced HEK293 cell apoptosis by regulating abnormal ΔΨm and apoptotic mRNA expression.

Temporal Trends of Acute Kidney Injury and Associated Risk Exposures in Extremely Preterm Infants

BACKGROUND AND OBJECTIVES

Neonatal AKI in the preterm population is an under-recognized morbidity. Detecting AKI in preterm infants is important for their long-term kidney health. We aimed to examine the yearly trends of incidence and the related morbidities and care practices affecting the occurrence of neonatal AKI in extremely preterm (gestational age <29 weeks) and very preterm (gestational age 29-32 weeks) infants.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The trends and the related risk factors and care practices of AKI were examined in the extremely preterm (n=434) and very preterm (n=257) infants who were admitted within 14 days after birth from 2005 to 2018 to the University Hospital and had at least two serum creatinine measurements during hospitalization. We defined AKI as a serum creatinine rise of 0.3 mg/dl or more within 48 hours or a 1.5-fold increase within 7 days.

RESULTS

The extremely preterm group had a three-fold higher incidence of AKI (30% versus 10%) than the very preterm group. Among preterm infants with AKI, 92% had one episode of AKI, and 45% experienced stage 2 or 3 AKI; the mean duration of AKI was 12±9 days. Across the 14-year period, the crude incidence of AKI declined markedly from 56% to 17% in the extremely preterm group and from 23% to 6% in the very preterm group. After adjustment, a significant decline of AKI incidence was still observed in the extremely preterm group. The declining AKI in the extremely preterm infants was related to the trends of decreasing incidences of neonatal transfer, prolonged aminoglycoside exposure, prophylactic use of nonsteroidal anti-inflammatory drugs, and sepsis.

CONCLUSIONS

We observed a declining trend in the incidence of neonatal AKI among extremely preterm infants from 2005 to 2018, which may be related to improvement of care practices.

Exposure of human fetal kidneys to mild analgesics interferes with early nephrogenesis

Acetaminophen, aspirin, and ibuprofen are mild analgesics commonly used by pregnant women, the sole current recommendation being to avoid ibuprofen from the fifth month of gestation. The nephrotoxicity of these three analgesics is well documented in adults, as is their interference with prostaglandins biosynthesis. Here we investigated the effect of these analgesics on human first trimester kidneys ex vivo. We first evaluated prostaglandins biosynthesis functionality by performing a wide screening of prostaglandin expression patterns in first trimester human kidneys. We demonstrated that prostaglandins biosynthesis machinery is functional during early nephrogenesis. Human fetal kidney explants aged 7-12 developmental weeks were exposed ex vivo to ibuprofen, aspirin or acetaminophen for 7 days, and analyzed by histology, immunohistochemistry, and flow cytometry. This study has revealed that these analgesics induced a spectrum of abnormalities within early developing structures, ranging from cell death to a decline in differentiating glomeruli density. These results warrant caution for the use of these medicines during the first trimester of pregnancy.

Pediatric Renal Ontogeny and Applications in Drug Development

The clinical applications of renal ontogeny mainly include renal function evaluation and optimal dosing of renally eliminated drugs in pediatric patients, which rely on pharmacometric models and/or bedside estimated glomerular filtration rate equations. However, these applications in drug development are based on an understanding of renal function development, especially when considering premature infants, and the renal biomarkers that can be used for renal function assessment. This review provides a general overview on (1) renal function development, (2) the biomarkers that are used to assess renal function, and (3) the practical application of this knowledge to drug dosing for renally eliminated drugs during pediatric development. While pharmacometric approaches for estimating renal function during development have improved considerably, the number of drug development programs that have studied premature infants is small and suggests that caution should be taken in estimating doses for renally eliminated drugs during periods of rapid change in renal function.

A Multiparametric Assay Platform for Simultaneous In Vivo Assessment of Pronephric Morphology, Renal Function and Heart Rate in Larval Zebrafish

Automated high-throughput workflows allow for chemical toxicity testing and drug discovery in zebrafish disease models. Due to its conserved structural and functional properties, the zebrafish pronephros offers a unique model to study renal development and disease at larger scale. Ideally, scoring of pronephric phenotypes includes morphological and functional assessments within the same larva. However, to efficiently upscale such assays, refinement of existing methods is required. Here, we describe the development of a multiparametric in vivo screening pipeline for parallel assessment of pronephric morphology, kidney function and heart rate within the same larva on a single imaging platform. To this end, we developed a novel 3D-printed orientation tool enabling multiple consistent orientations of larvae in agarose-filled microplates. Dorsal pronephros imaging was followed by assessing renal clearance and heart rates upon fluorescein isothiocyanate (FITC)-inulin microinjection using automated time-lapse imaging of laterally positioned larvae. The pipeline was benchmarked using a set of drugs known to induce developmental nephrotoxicity in humans and zebrafish. Drug-induced reductions in renal clearance and heart rate alterations were detected even in larvae exhibiting minor pronephric phenotypes. In conclusion, the developed workflow enables rapid and semi-automated in vivo assessment of multiple morphological and functional parameters.

The Effect of Preterm Birth on Renal Development and Renal Health Outcome

Preterm birth is associated with adverse renal health outcomes including hypertension, chronic kidney disease, and an increased rate of progression to end-stage renal failure. This review explores the antenatal, perinatal, and postnatal factors that affect the functional nephron mass of an individual and contribute to long-term kidney outcome. Health-care professionals have opportunities to increase their awareness of the risks to kidney health in this population. Optimizing maternal health around the time of conception and during pregnancy, providing kidney-focused supportive care in the NICU during postnatal nephrogenesis, and avoiding accelerating nephron loss throughout life may all contribute to improved long-term outcomes. There is a need for ongoing research into the long-term kidney outcomes of preterm survivors in mid-to-late adulthood as well as a need for further research into interventions that may improve ex utero nephrogenesis.

Early and late anti nociceptive effects of sucrose on neonatal inflammatory pain in rats: Comparison to a non-steroidal anti-inflammatory drug

Management of neonatal pain is not only ethical but is also essential. Barriers to pain management in infants include lack of safe and effective medications and fear of adverse effects of conventional pain medications. Sweet solutions given intraorally have been shown to reduce pain behaviors and associated symptoms. Sucrose and other sweet solutions are being increasingly used at the NICUs and immunization clinics. Sucrose for mild invasive procedures is effective and safe for those procedures that need to be repeated multiple times during the day. Only few studies examine the efficacy of sucrose for the management of inflammatory pain during infancy. In this study, Complete Freund's Adjuvant (CFA) was used to induce inflammation in 5-day-old rat pups; CFA also produces inflammation that lasts for more than a day, thus can also be a model for chronic pain. Sucrose or ibuprofen was given to subset of pups shortly after CFA intraplantar injections. Thermal as well as mechanical pain sensitivity was assessed on subsequent days as well as during adolescence and early adulthood. Sucrose and ibuprofen were both effective in preventing hyperalgesia and allodynia produced by CFA. Interestingly, sucrose was even more effective than ibuprofen, and the analgesic effects continued further to adolescence and adult life of the rats. Thus, and according to the results of this study, sucrose seems to be just as effective for inflammatory pain as Ibuprofen. In addition, sucrose protects against later-in-life hypersensitivity consequences to neonatal pain.

Comparative effect of indomethacin (IndoM) on the enzymes of carbohydrate metabolism, brush border membrane and oxidative stress in the kidney, small intestine and liver of rats

Indomethacin (IndoM) has prominent anti-inflammatory and analgesic-antipyretic properties. However, high incidence and severity of side-effects on the structure and functions of the kidney, liver and intestine limits its clinical use. The present study tested the hypothesis that IndoM causes multi-organ toxicity by inducing oxidative stress that alters the structure of various cellular membranes, metabolism and hence functions. The effect of IndoM was determined on the enzymes of carbohydrate metabolism, brush border membrane (BBM) and oxidative stress in the rat kideny, liver and intestine to understand the mechanism of IndoM induced toxicity. Adult male Wister rats were given IndoM (20 mg/kg) intra-peritoneally in sodium bicarbonate twice a day for 3 d. The body weights of the rats were recorded before and after experimental procedure. IndoM administration significantly increased blood urea nitrogen, serum creatinine, cholesterol and alkaline phosphatase but inorganic phosphate indicating IndoM induced renal, hepatic and intestinal toxicity. Activity of lactate dehydrogenase along with glucose-6- and fructose-1, 6-bis phosphatase, glucose-6-phosphate dehydrogenase and NADP-malic enzyme increased but malate dehydrogenase decreased in all tissues. Lipid peroxidation (LPO) significantly increased whereas the antioxidant enzymes decreased in all rat tissues studied. The results indicate that IndoM administration caused severe damage to kidney, liver and intestine by icreasing LPO, suppressing antioxidant enzymes and inhibiting oxidative metablolism. The energy dependence was shifted to anaerobic glycolysis due to mitochondrial damage supported by increased gluconeogenesis to provide more glucose to meet energy requirements.

Urinary acute kidney injury biomarkers in very low-birth-weight infants on indomethacin for patent ductus arteriosus

BACKGROUND

Serum creatinine (SCr)- or urine output-based definitions of acute kidney injury (AKI) have important limitations in neonates. This study evaluates the diagnostic value of urinary biomarkers in very low-birth-weight (VLBW) infants receiving indomethacin for closure of a patent ductus arteriosus (PDA).

METHODS

Prospective cohort study in 14 indomethacin-treated VLBW infants and 18 VLBW infants without indomethacin as controls. Urinary biomarkers were measured before, during, and after indomethacin administration.

RESULTS

Indomethacin therapy was associated with significantly higher SCr concentrations at 36, 84, and 120 h compared to controls. At 36 h, three indomethacin-treated patients met the criteria for neonatal modified Kidney Disease: Improving Global Outcomes (KDIGO) AKI. The product of urinary tissue inhibitor of metalloproteinase-2 and insulin-like growth factor-binding protein 7 ([TIMP-2]•[IGFBP7]) was significantly elevated in the AKI subgroup at 12 h (P < 0.05), hence 24 h earlier than the increase in SCr. Urinary neutrophil gelatinase-associated lipocalin (NGAL) and calprotectin were significantly increased in the indomethacin group at 12 h (P < 0.05), irrespective of fulfillment of the AKI criteria. Urinary kidney injury molecule-1 (KIM-1) was not significantly altered.

CONCLUSION

While urinary [TIMP-2]•[IGFBP7] proves valuable for the early diagnosis of neonatal modified KDIGO-defined AKI, elevated urinary NGAL and calprotectin concentrations in indomethacin-treated VLBW infants not fulfilling the AKI criteria may indicate subclinical kidney injury.

Early postnatal gentamicin and ceftazidime treatment in normal and food restricted neonatal wistar rats: Implications for kidney development

BACKGROUND

Up to two-thirds of premature born neonates are treated for infections with aminoglycosides such as gentamicin. Although acute toxicities are well described, there is uncertainty on developmental changes after treatment of premature born neonates. We studied the effect of gentamicin and ceftazidime on kidney development in the rat. Additionally, we evaluated the modulating effect of extrauterine growth restriction.

METHODS

On postnatal day (PND) 2, Wistar rats were cross-fostered into normal sized litters (12 pups) or large litters (20 pups) to create normal food (NF) or food restricted (FR) litters to simulate growth restriction and dosed daily intraperitoneally with placebo, 4 mg/kg of gentamicin or 50 mg/kg ceftazidime until PND 8. Gentamicin pharmacokinetics were studied in a separate group of animals. Kidneys were weighed. Renal expression of 18 developmental genes was evaluated by quantitative PCR on PND 8. On PND 35, glomerular number was assessed by stereology and glomerular generations were counted.

RESULTS

Food restricted litters showed 22% less body weight compared with controls by day 35 (p < 0.001), 1.4- to 1.5-fold down regulation of Renin, Oat1, and Agtr1a (p < 0.05) expression and a 12% reduction in glomerular numbers (mean 30841 vs. 35187, p < 0.001), whereas glomerular generation count was unaffected. Gentamicin pharmacokinetic parameters were found to be in a human clinical range (mean maximum concentration in plasma of 4.88 mg/L and mean area under the plasma-concentration time curve up to the last measured concentration after 4 hr of 10.71 mg.h/L for sexes combined) and all endpoints were unaffected. Ceftazidime reduced Renin expression by 1.7-fold (p < 0.01).

CONCLUSION

Our experiments showed that gentamicin at clinical levels did not disturb kidney development, ceftazidime can affect Renin expression, and extrauterine growth restriction impairs kidney development, but did not modulate potential drug toxicity. Birth Defects Research 109:1228-1235, 2017. © 2017 Wiley Periodicals, Inc.

The Impact of Kidney Development on the Life Course: A Consensus Document for Action

Hypertension and chronic kidney disease (CKD) have a significant impact on global morbidity and mortality. The Low Birth Weight and Nephron Number Working Group has prepared a consensus document aimed to address the relatively neglected issue for the developmental programming of hypertension and CKD. It emerged from a workshop held on April 2, 2016, including eminent internationally recognized experts in the field of obstetrics, neonatology, and nephrology. Through multidisciplinary engagement, the goal of the workshop was to highlight the association between fetal and childhood development and an increased risk of adult diseases, focusing on hypertension and CKD, and to suggest possible practical solutions for the future. The recommendations for action of the consensus workshop are the results of combined clinical experience, shared research expertise, and a review of the literature. They highlight the need to act early to prevent CKD and other related noncommunicable diseases later in life by reducing low birth weight, small for gestational age, prematurity, and low nephron numbers at birth through coordinated interventions. Meeting the current unmet needs would help to define the most cost-effective strategies and to optimize interventions to limit or interrupt the developmental programming cycle of CKD later in life, especially in the poorest part of the world.

Drug-induced renal damage in preterm neonates: state of the art and methods for early detection

Only a small fraction of drugs widely used in neonatal intensive care units (NICU) are specifically authorized for this population. Even if unlicensed or off-label use is necessary, it is associated with increased adverse drug reactions, which must be carefully weighed against expected benefits. In particular, renal damage is frequent among preterm babies, and is considered a predisposing factor for the development of chronic kidney disease in adulthood. Apart from specific conditions affecting premature neonates (e.g. respiratory distress syndrome, perinatal asphyxia), drugs play an important role in impairing renal function because of well-known nephrotoxicity and/or interaction with renal developmental factors. From a review of the available studies on drug use in NICU patients, we identified and described the most commonly administered drugs that are correlated to renal damage. Early detection of kidney injury is becoming an essential aspects for clinicians because of the limited number of biomarkers applicable in the neonatal population. Postnatal changes of biochemical processes that influence pharmacokinetic and pharmacodynamic aspects need to be further investigated in order to better understand the mechanisms of drug toxicity in this population. The most promising strategies for dose adjustment and therapeutic schemes are discussed. The purpose of this review was to describe current knowledge on drug use among premature babies and their implication in kidney injury development, as well as to highlight available strategies for early detection of renal damage.

The interplay between drugs and the kidney in premature neonates

The kidney plays a central role in the clearance of drugs. However, renal drug handling entails more than glomerular filtration and includes tubular excretion and reabsorption, and intracellular metabolization by cellular enzyme systems, such as the Cytochrome P450 isoenzymes. All these processes show maturation from birth onwards, which is one of the reasons why drug dosing in children is not simply similar to dosing in small adults. As kidney development normally finishes around the 36th week of gestation, being born prematurely will result in even more immature renal drug handling. Environmental effects, such as extra-uterine growth restriction, sepsis, asphyxia, or drug treatments like caffeine, aminoglycosides, or non-steroidal anti-inflammatory drugs, may further hamper drug handling in the kidney. Dosing in preterm neonates is therefore dependent on many factors that need to be taken into account. Drug treatment may significantly hamper postnatal kidney development in preterm neonates, just like renal immaturity has an impact on drug handling. The restricted kidney development results in a lower number of nephrons that may have several long-term sequelae, such as hypertension, albuminuria, and renal failure. This review focuses on the interplay between drugs and the kidney in premature neonates.

Decreasing podocyte number during human kidney intrauterine development

Nephron number at birth has relevant clinical importance with implications for long-term renal health. In recent years, the podocyte depletion hypothesis has emerged as an important concept in kidney pathology. This study was aimed at verifying whether human podocyte number changes significantly during intrauterine life. To this end, 62 subjects with gestational ages ranging from 20 to 41 wk were examined. Kidney sections were stained with hematoxylin and eosin and digitally scanned at ×400 magnification. Subjects were subdivided into fetuses (gestational age ≤24 wk, n = 5), preterms (gestational age ≥25 and ≤36 wk, n = 39), and full-term newborns (gestational age ≥37 wk, n = 18). The average podocyte number of 1,908 ± 645, 1,394 ± 498, and 1,126 ± 256 was, respectively, observed in fetuses, preterms, and full-term newborns. A significant main effect ( P = 0.0051) of gestational age on podocyte number was observed with a significantly lower number in full-term newborns than in fetuses ( P < 0.01). Intragroup variability was also observed. We speculate that variations in podocyte number could be correlated with factors such as drugs and maternal diet occurring during intrauterine life. In conclusion, this study shows, for the first time, a decreasing trend in podocyte number during gestation.

Indomethacin administered early in the postnatal period results in reduced glomerular number in the adult rat

Indomethacin and ibuprofen are administered to close a patent ductus arteriosus (PDA) during active glomerulogenesis. Light and electron microscopic glomerular changes with no change in glomerular number were seen following indomethacin and ibuprofen treatment during glomerulogenesis at 14 days after birth in a neonatal rat model. This present study aimed to determine whether longstanding renal structural changes are present at 30 days and 6 mo (equivalent to human adulthood). Rat pups were administered indomethacin or ibuprofen antenatally on days 18-20 (0.5 mg·kg(-1)·dose(-1) indomethacin; 10 mg·kg(-1)·dose(-1) ibuprofen) or postnatally intraperitoneally from day 1 to 3 or day 1 to 5 (0.2 mg·kg(-1)·dose(-1) indomethacin; 10 mg·kg(-1)·dose(-1) ibuprofen). Control groups received no treatment or normal saline intraperitoneally. Pups were killed at 30 days of age and 6 mo of age. Tissue blocks from right kidneys were prepared for light and electron microscopic examination, while total glomerular number was determined in left kidneys using unbiased stereology. Eight pups were included in each group from 14 maternal rats. At 30 days and 6 mo, there were persistent electron microscopy abnormalities of the glomerular basement membrane in those receiving postnatal indomethacin and ibuprofen. There were no significant light microscopy findings at 30 days or 6 mo. At 6 mo, there were significantly fewer glomeruli in those receiving postnatal indomethacin but not ibuprofen (P = 0.003). In conclusion, indomethacin administered during glomerulogenesis appears to reduce the number of glomeruli in adulthood. Alternative options for closing a PDA should be considered including ibuprofen as well as emerging therapies such as paracetamol.

Long-term renal consequences of preterm birth

The normal development of the kidney may be affected by several factors, including abnormalities in placental function, resulting in fetal growth restriction, exposure to maternal disease states, including hypertension and diabetes, antenatal steroids, chorioamnionitis, and preterm delivery. After preterm birth, several further insults may occur that may influence nephrogenesis and renal health, including exposure to nephrotoxic medications, postnatal growth failure, and obesity after growth restriction. In this review article, common clinical neonatal scenarios are used to highlight these renal risk factors, and the animal and human evidence on which these risk factors are based are discussed.

Assessment of renal functional maturation and injury in preterm neonates during the first month of life

Worldwide, approximately 10% of neonates are born preterm. The majority of preterm neonates are born when the kidneys are still developing; therefore, during the early postnatal period renal function is likely reflective of renal immaturity and/or injury. This study evaluated glomerular and tubular function and urinary neutrophil gelatinase-associated lipocalin (NGAL; a marker of renal injury) in preterm neonates during the first month of life. Preterm and term infants were recruited from Monash Newborn (neonatal intensive care unit at Monash Medical Centre) and Jesse McPherson Private Hospital, respectively. Infants were grouped according to gestational age at birth: ≤28 wk (n = 33), 29-31 wk (n = 44), 32-36 wk (n = 32), and term (≥37 wk (n = 22)). Measures of glomerular and tubular function were assessed on postnatal days 3-7, 14, 21, and 28. Glomerular and tubular function was significantly affected by gestational age at birth, as well as by postnatal age. By postnatal day 28, creatinine clearance remained significantly lower among preterm neonates compared with term infants; however, sodium excretion was not significantly different. Pathological proteinuria and high urinary NGAL levels were observed in a number of neonates, which may be indicative of renal injury; however, there was no correlation between the two markers. Findings suggest that neonatal renal function is predominantly influenced by renal maturity, and there was high capacity for postnatal tubular maturation among preterm neonates. There is insufficient evidence to suggest that urinary NGAL is a useful marker of renal injury in the preterm neonate.

Effect of NSAIDs and diuretics on nephrogenesis in an ex vivo embryogenic kidney model

The kidney is one of the key organs in clearing foreign compounds. The effects of drugs on the developing kidney are relatively unknown. We studied the direct effect of furosemide, hydrochlorothiazide, ibuprofen, and indomethacin on kidney development in an ex vivo embryonic kidney model. At embryonic day 13, metanephroi were dissected from mice and cultured in control media or media supplemented with various clinically relevant concentrations of drugs. The ureteric tree was visualized by whole-mount staining and branching was evaluated by counting. Additionally, gene expression levels of Wt1, Sox9, Bmp7, Fgf8, and Gdnf were investigated. No distinct differences were noted on either ureteric tip development or gene expression analysis for each drug after 24 hr of exposure. Even though short-term exposure to clinically relevant concentrations seems not to disturb renal development, future research is needed to study prolonged or repeated exposures.

Development of an automated imaging pipeline for the analysis of the zebrafish larval kidney

The analysis of kidney malformation caused by environmental influences during nephrogenesis or by hereditary nephropathies requires animal models allowing the in vivo observation of developmental processes. The zebrafish has emerged as a useful model system for the analysis of vertebrate organ development and function, and it is suitable for the identification of organotoxic or disease-modulating compounds on a larger scale. However, to fully exploit its potential in high content screening applications, dedicated protocols are required allowing the consistent visualization of inner organs such as the embryonic kidney. To this end, we developed a high content screening compatible pipeline for the automated imaging of standardized views of the developing pronephros in zebrafish larvae. Using a custom designed tool, cavities were generated in agarose coated microtiter plates allowing for accurate positioning and orientation of zebrafish larvae. This enabled the subsequent automated acquisition of stable and consistent dorsal views of pronephric kidneys. The established pipeline was applied in a pilot screen for the analysis of the impact of potentially nephrotoxic drugs on zebrafish pronephros development in the Tg(wt1b:EGFP) transgenic line in which the developing pronephros is highlighted by GFP expression. The consistent image data that was acquired allowed for quantification of gross morphological pronephric phenotypes, revealing concentration dependent effects of several compounds on nephrogenesis. In addition, applicability of the imaging pipeline was further confirmed in a morpholino based model for cilia-associated human genetic disorders associated with different intraflagellar transport genes. The developed tools and pipeline can be used to study various aspects in zebrafish kidney research, and can be readily adapted for the analysis of other organ systems.

Less is more: combination antibiotic therapy for the treatment of gram-negative bacteremia in pediatric patients

IMPORTANCE

Definitive combination antibiotic therapy with a β-lactam and an aminoglycoside for the treatment of gram-negative bacteremia is commonly prescribed in pediatric patients; however, its efficacy and toxicity relative to β-lactam monotherapy are unknown.

OBJECTIVE

To determine whether definitive combination antibiotic therapy affects mortality and nephrotoxicity in pediatric patients with gram-negative bacteremia.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study including pediatric patients (aged ≤18 years) with gram-negative bacteremia hospitalized at the Johns Hopkins Children's Center between 2002 and 2011.

MAIN OUTCOMES AND MEASURES

Outcomes included 30-day mortality and nephrotoxicity classified according to the pediatric RIFLE (risk for renal dysfunction, injury to the kidney, failure of kidney function, loss of kidney function, and end-stage renal disease) criteria. To account for nonrandom assignment of combination therapy, propensity score weighting was combined with multivariable logistic regression to estimate the effect of combination therapy on mortality and nephrotoxicity.

RESULTS

Of the 879 eligible pediatric patients with bacteremia, 537 (61.1%) received combination therapy. After propensity score adjustment, baseline demographic and clinical characteristics between the groups were well balanced. There was no association between combination therapy and 30-day mortality (odds ratio, 0.98; 95% CI, 0.93-1.02; P = .27). There were 170 patients (19.3%) with evidence of acute kidney injury, including 135 (25.1%) and 35 (10.2%) in the combination therapy and monotherapy arms, respectively. Patients receiving combination therapy had approximately twice the odds of nephrotoxicity compared with those receiving monotherapy (odds ratio, 2.15; 95% CI, 2.09-2.21).

CONCLUSIONS AND RELEVANCE

The use of β-lactam monotherapy for gram-negative bacteremia in pediatric patients reduces subsequent nephrotoxicity without compromising survival.

Developmental origins of health and adult disease: what should neonatologists/paediatricians be considering about the long-term health of their patients?

The developmental origins of health and disease hypothesis is now strongly supported by both animal and human evidence, and as a consequence, obstetricians, neonatologists and paediatricians need to consider the impact that the in utero and early post-natal environment can have on later renal, cardiovascular and metabolic health. Four common clinical scenarios were provided along with animal and human evidence identifying long-term health implications. Suggestions as to how we should translate this growing body of evidence into practice are provided.

Increased urinary podocytes following indomethacin suggests drug-induced glomerular injury

BACKGROUND

Preterm infants are delivered while glomerulogenesis is ongoing and may be exposed to insults, including medications that may affect renal development. Podocytes detected in the urine are an indicator of glomerular injury. The aims of this study were to determine whether preterm and term infants excrete podocytes in their urine and whether exposure to gentamicin and indomethacin increase podocyte excretion in their urine.

METHODS

Preterm infants <33 weeks gestation had urine collected each day while receiving either gentamicin or indomethacin. Preterm and term control infants had urine collected for 3 days. The number of casts and podocytes present in the urine of infants receiving indomethacin and gentamicin were compared with preterm and term control infants.

RESULTS

Forty-two neonates were included in the study. Podocytes were present in small numbers (< 2) in the urine of both preterm and term control neonates. The number of podocytes in the preterm group receiving indomethacin was significantly higher than in all other groups (p=0.02) ,as was urinary albumin (p=0.02).

CONCLUSIONS

Increased number of podocytes in preterm neonates receiving indomethacin and higher excretion of albumin suggest glomerular injury is occurring. It is unknown whether injury to glomeruli during glomerulogenesis in preterm neonates has long-term sequelae for renal development and function into adulthood.

Effects of ibuprofen treatment on the developing preterm baboon kidney

Preterm neonates are commonly exposed postnatally to pharmacological treatments for a patent ductus arteriosus. Exposure of the developing kidney to nephrotoxic medications may adversely impact renal development. This study aimed to determine the effect of early postnatal ibuprofen treatment, both alone and in combination with a nitric oxide synthase inhibitor (NOSi), on renal development and morphology. Baboon neonates were delivered prematurely at 125-day (125d) gestation (term = 185d) and were euthanized at birth or postnatal day 6. Neonates were divided into four groups: 125d gestational controls (n = 8), Untreated (n = 8), Ibuprofen (n = 6), and ibuprofen (Ibu)+NOSi (n = 4). Animals in the Ibuprofen and Ibu+NOSi groups received five doses of ibuprofen, with the Ibuprofen+NOSi animals additionally administered a NOS inhibitor (N(G)-monomethyl-l-arginine). There was no difference among groups in body weight, kidney weight, or glomerular generation number. Nephrogenic zone width was significantly reduced in the Ibuprofen group (123.5 ± 7.4 μm) compared with the 125d gestational control (176.1 ± 6.9 μm) and Untreated animals (169.7 ± 78.8 μm). In the Ibu+NOSi group, nephrogenic zone width averaged 152.7 ± 3.9 μm, which was not significantly different from any other group. Morphologically abnormal glomeruli were present at a range of 0.0-22.9% in the Untreated group, 0.0-6.1% in the Ibuprofen group, and 0.0-1.4% in the Ibu+NOSi group. In conclusion, early postnatal ibuprofen exposure is associated with a reduced nephrogenic zone width, which may suggest the early cessation of nephrogenesis following treatment. Ultimately, this may impact the number of nephrons formed in the preterm kidney.

Effects of ibuprofen treatment on the developing preterm baboon kidney

Preterm neonates are commonly exposed postnatally to pharmacological treatments for a patent ductus arteriosus. Exposure of the developing kidney to nephrotoxic medications may adversely impact renal development. This study aimed to determine the effect of early postnatal ibuprofen treatment, both alone and in combination with a nitric oxide synthase inhibitor (NOSi), on renal development and morphology. Baboon neonates were delivered prematurely at 125-day (125d) gestation (term = 185d) and were euthanized at birth or postnatal day 6. Neonates were divided into four groups: 125d gestational controls (n = 8), Untreated (n = 8), Ibuprofen (n = 6), and ibuprofen (Ibu)+NOSi (n = 4). Animals in the Ibuprofen and Ibu+NOSi groups received five doses of ibuprofen, with the Ibuprofen+NOSi animals additionally administered a NOS inhibitor (N(G)-monomethyl-l-arginine). There was no difference among groups in body weight, kidney weight, or glomerular generation number. Nephrogenic zone width was significantly reduced in the Ibuprofen group (123.5 ± 7.4 μm) compared with the 125d gestational control (176.1 ± 6.9 μm) and Untreated animals (169.7 ± 78.8 μm). In the Ibu+NOSi group, nephrogenic zone width averaged 152.7 ± 3.9 μm, which was not significantly different from any other group. Morphologically abnormal glomeruli were present at a range of 0.0-22.9% in the Untreated group, 0.0-6.1% in the Ibuprofen group, and 0.0-1.4% in the Ibu+NOSi group. In conclusion, early postnatal ibuprofen exposure is associated with a reduced nephrogenic zone width, which may suggest the early cessation of nephrogenesis following treatment. Ultimately, this may impact the number of nephrons formed in the preterm kidney.

Current evidence on the safety profile of NSAIDs for the treatment of PDA

Patent ductus arteriosus (PDA) complicates the clinical course of preterm infants. Nonsteroidal anti-inflammatory drugs, especially Indomethacin and Ibuprofen, have been widely used for both prevention and treatment of PDA. Short-term efficacy of Indomethacin or Ibuprofen is equivalent, while Ibuprofen results show a higher safety profile. Ibuprofen is associated with fewer clinical gastrointestinal and renal side effects with respect to Indomethacin even if subclinical potential effects are reported. When administered as prophylaxis, Ibuprofen has no effects on prevention of intraventricular haemorrhage unlike Indomethacin. Considering the potential adverse effects of both these drugs, a careful monitoring during and after the treatment period is highly recommended.

Preterm birth and the kidney: implications for long-term renal health

Although the majority of preterm neonates now survive infancy, there is emerging epidemiological evidence to demonstrate that individuals born preterm exhibit an elevated risk for the development of hypertension and renal impairment later in life, thus supporting the developmental origins of health and disease hypothesis. The increased risk may potentially be attributed to a negative impact of preterm birth on nephron endowment. Indeed, at the time when most preterm neonates are delivered, nephrogenesis in the kidney is still ongoing with the majority of nephrons normally formed during the third trimester of pregnancy. A number of clinical studies have provided evidence of altered renal function during the neonatal period, but to date there have been limited studies describing the consequences of preterm birth on kidney structure. Importantly, studies in the preterm baboon have shown that nephrogenesis is clearly ongoing following preterm birth; however, the presence of abnormal glomeruli (up to 18% in some cases) is of concern. Similar glomerular abnormalities have been described in autopsied preterm infants. Prenatal and postnatal factors such as exposure to certain medications, hyperoxia and intrauterine and/or extrauterine growth restriction are likely to have a significant influence on nephrogenesis and final nephron endowment. Further studies are required to determine the factors contributing to renal maldevelopment and to identify potential interventional strategies to maximize nephron endowment at the start of life, thereby optimizing long-term renal health for preterm individuals.

Accelerated maturation and abnormal morphology in the preterm neonatal kidney

Nephrogenesis is ongoing at the time of birth for the majority of preterm infants, but whether postnatal renal development follows a similar trajectory to normal in utero growth is unknown. Here, we examined tissue collected at autopsy from 28 kidneys from preterm neonates, whose postnatal survival ranged from 2 to 68 days, including 6 that had restricted intrauterine growth. In addition, we examined kidneys from 32 still-born gestational controls. We assessed the width of the nephrogenic zone, number of glomerular generations, cross-sectional area of the renal corpuscle, and glomerular maturity and morphology. Renal maturation accelerated after preterm birth, with an increased number of glomerular generations and a decreased width of the nephrogenic zone in the kidneys of preterm neonates. Of particular concern, compared with gestational controls, preterm kidneys had a greater percentage of morphologically abnormal glomeruli and a significantly larger cross-sectional area of the renal corpuscle, suggestive of renal hyperfiltration. These observations suggest that the preterm kidney may have fewer functional nephrons, thereby increasing vulnerability to impaired renal function in both the early postnatal period and later in life.

Long-term effects of neonatal drugs on the kidney

Several drugs have been shown to produce an adverse affect on kidneys, mainly when exposure occurred during active nephrogenesis (pregnancy or prematurity). Several experimental studies on drug-related renal injury have been done on animal models. Observational reports on early drug-related nephrotoxicity in humans are increasing. The investigations regard nephrotoxicity from antibiotics (particularly aminoglycosides), angiotensin-converting enzyme (ACE) inhibitors, non-steroidal anti-inflammatory drugs and antifungins. Few reports have been specifically on the long-term effects on kidneys of drugs given to newborns during active nephrogenesis. Most observations were targeted to investigate long-term renal effects of prematurity and intrauterine growth retardation (IUGR). Nephrotoxic medication taken during fetal life and during postnatal nephrogenesis could interfere with nephron generation contributing to a particular magnitude of damage. Such adjunctive damage could further increase the risk of renal failure in the adulthood of children born prematurely.

Hepatic and renal toxicities of indomethacin acid, salt form and complexed forms with hydroxypropyl-β-cyclodextrin on Wistar rats after oral administration

Indomethacin (IM), a non-steroidal anti-inflammatory drug, has the capacity to induce hepatic and renal injuries when administrated systemically. The aim of this study is to assess the IM absorption from complexed forms when orally administered to rats, by means of a comparative evaluation of its capacity to induce hepatic and renal injury in different forms, namely IM acid, IM sodium salt or IM complexed with hydroxypropyl-β-cyclodextrin (HP-β-CD), using freeze- and spray-drying methods. A total of 135 Wistar rats weighing 224.4 ± 62.5 g were put into 10 groups. They were allowed free access to water but were maintained on fast for 18 h before the first administration until the end of the experiment. Water and HP-β-CD (control groups) and IM acid form, IM trihydrated-sodium-salt and IM-HP-β-CD spray- and freeze-dried, at normal and toxic doses (test groups), were orally administered once/day for 3 days. Seventy-two hours after the first administration, the animals were sacrificed and a fragment of the liver and one kidney were collected and prepared for histopathological evaluation. Lesion indexes (rated 0/4 for liver and 0/3 for kidney) were developed and the type of injury scored according to the severity of damage. A statistical analysis of the severity and incidence of lesions was carried out. Animals administered with IM complexed forms showed similar hepatic and renal lesions, both in toxic and therapeutic doses, when compared with those observed in animals administered with IM acid or salt forms. This suggests that under the present experimental conditions, IM is equally absorbed from the gastrointestinal tract, independently of the administered IM form.

Effect of drugs on renal development

Many nephrotoxic effects of drugs have been described, whereas the effect on renal development has received less attention. Nephrogenesis ceases at approximately 36 weeks of gestation, indicating that drugs administered to pregnant women and to preterm-born neonates may influence kidney development. Such an effect on renal development may lead to a wide spectrum of renal malformations (congenital anomalies of the kidney and urinary tract [CAKUT]), ranging from renal agenesis to a reduced nephron number. Any of these anomalies may have long-term sequelae, and CAKUT is the primary cause for renal replacement therapy in childhood. This review focuses on research into the effect of drug treatment during active nephrogenesis during pregnancy and in preterm-born infants. Because the effects of many widely used drugs have not been unraveled thus far, more research is needed to study the effect on renal development and long-term renal sequelae after drug treatment during nephrogenesis.

Urinary levels of regenerating islet-derived protein III β and gelsolin differentiate gentamicin from cisplatin-induced acute kidney injury in rats

A key aspect for the clinical handling of acute kidney injury is an early diagnosis, for which a new generation of urine biomarkers is currently under development including kidney injury molecule 1 and neutrophil gelatinase-associated lipocalin. A further diagnostic refinement is needed where one specific cause among several potentially nephrotoxic insults can be identified during the administration of multidrug therapies. In this study we identified increases in regenerating islet-derived protein III beta (reg IIIb) and gelsolin as potential differential urinary markers of gentamicin's nephrotoxicity. Indeed, urinary levels of both reg IIIb and gelsolin distinguish between the nephrotoxicity caused by gentamicin from that caused by cisplatin where these markers were not increased by the latter. Reg IIIb was found to be overexpressed in the kidneys of gentamicin-treated rats and excreted into the urine, whereas urinary gelsolin originated from the blood by glomerular filtration. Our results illustrate an etiological diagnosis of acute kidney injury through analysis of urine. Thus, our results raise the possibility of identifying the actual nephrotoxin in critically ill patients who are often treated with several nephrotoxic agents at the same time, thereby providing the potential for tailoring therapy to an individual patient, which is the aim of personalized medicine.

Indomethacin, ibuprofen and gentamicin administered during late stages of glomerulogenesis do not reduce glomerular number at 14 days of age in the neonatal rat

Premature neonates are frequently administered indomethacin, ibuprofen and gentamicin during the period of active glomerulogenesis. These drugs are known to have nephrotoxic effects, but the morphological effect of these drugs is unknown. The purpose of this study was to determine whether administration of these drugs during the late stages of glomerulogenesis in the rat has an effect on glomerular endowment. Rat pups were given, intraperitoneally, indomethacin, ibuprofen or indomethacin and gentamicin for the first 5 days of their postnatal life. The pups were killed at 14 days of age at completion of glomerulogenesis. The total number of glomeruli in the left kidney was determined by the physical disector/fractionator stereological technique. There was no difference between treatment groups in total number of glomeruli per kidney (P = 0.45). There were significantly fewer glomeruli per gram of kidney in those rat pups that had received indomethacin or ibuprofen (P < 0.0001). The reduction in the number of glomeruli per gram of kidney may indicate augmented growth of nephron tubules and/or collecting ducts, and/or be a consequence of oedema secondary to drug exposure. Further study is required to determine whether reduced glomerular number is seen in older animals or following exposure to these drugs at different time-points in kidney development.

The effects of postnatal retinoic acid administration on nephron endowment in the preterm baboon kidney

Administration of retinoic acid (RA), the active metabolite of vitamin A, is linked to the stimulation of nephrogenesis. The aim of this study was to determine whether early postnatal administration of RA could enhance ongoing nephrogenesis in a baboon model of premature birth. Unbiased stereological methods were used to estimate kidney volume, renal corpuscle volume, and nephron number. The percentage of abnormal glomeruli and the number of glomerular generations was also determined in the kidneys of preterm control (n = 6) and preterm +RA (n = 6) animals that received 500 microg/kg/d of all-trans RA after premature delivery. There was no significant difference between the preterm control and the preterm +RA groups in kidney size, nephron number (preterm control: 329,924 +/- 41,752; preterm +RA: 354,041 +/- 52,095; p = 0.59), renal corpuscle volume, number of glomerular generations, or the percentage of abnormal glomeruli. The proportion of abnormal glomeruli did not appear to be linked to any elements of postnatal care examined. The results of this study indicate that early postnatal administration of RA is unable to stimulate nephrogenesis in the kidney of the preterm baboon. Encouragingly, it does not appear to have any adverse effects on kidney development.