Fetal toxic effects and angiotensin-II-receptor antagonists

The genetics and pathogenesis of CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) comprise a large variety of malformations that arise from defective kidney or urinary tract development and frequently lead to kidney failure. The clinical spectrum ranges from severe malformations, such as renal agenesis, to potentially milder manifestations, such as vesicoureteral reflux. Almost 50% of cases of chronic kidney disease that manifest within the first three decades of life are caused by CAKUT. Evidence suggests that a large number of CAKUT are genetic in origin. To date, mutations in ~54 genes have been identified as monogenic causes of CAKUT, contributing to 12-20% of the aetiology of the disease. Pathogenic copy number variants have also been shown to cause CAKUT and can be detected in 4-11% of patients. Furthermore, environmental and epigenetic factors can increase the risk of CAKUT. The discovery of novel CAKUT-causing genes is challenging owing to variable expressivity, incomplete penetrance and variable genotype-phenotype correlation. However, such a discovery could ultimately lead to improvements in the accurate molecular genetic diagnosis, assessment of prognosis and multidisciplinary clinical management of patients with CAKUT, potentially including personalized therapeutic approaches.

Clinical and pathological investigation of oligomeganephronia

BACKGROUND

Oligomeganephronia (OMN) is a rare congenital anomaly involving the kidney and urinary tract, characterized by decreased number and compensatory hypertrophy of the nephron. It is caused by abnormal kidney development during the embryonic period, especially in patients with low birth weight; however, the actual etiology and clinical features remain unknown. We aim to reveal the clinical and pathological characteristics, treatment, and outcome.

METHODS

Ten patients diagnosed with OMN between 2013 and 2020 were retrospectively investigated. The data were presented as the median ± interquartile range, and statistical significance was set at p < 0.05.

RESULTS

The age at diagnosis was 14.1 years, the male-to-female ratio was 6:4, and only four cases were born with low birth weight. The estimated glomerular filtration rate (eGFR) was 62.2 mL/min/1.73 m². The glomerulus diameter of OMN patients was significantly larger (217 vs. 154 µm, p < 0.001) in OMN patients, and the number of glomeruli of OMN patients was lower (0.89 vs. 2.05/mm², p < 0.001) than the control group. Eight of the ten cases were identified by urinary screening. Nine patients were treated with renin-angiotensin system (RAS) inhibitors, following which proteinuria successfully decreased or disappeared. Their median eGFR was also stable, 53.3 mL/min/1.73 m².

CONCLUSIONS

As few symptoms can lead to OMN discovery, most patients were found during urine screening at school. Kidney dysfunction was observed in all patients at the time of kidney biopsy. Proteinuria has been significantly reduced and the decline rate of eGFR might be improved by RAS inhibitors. "A higher resolution version of the Graphical abstract is available as Supplementary information".

Obesity-associated cardiometabolic complications in polycystic ovary syndrome: The potential role of sodium-glucose cotransporter-2 inhibitors

Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder in reproductive-age women. PCOS is characterized by androgen excess, oligo/anovulation, and polycystic appearance of the ovaries. Women with PCOS have an increased prevalence of multiple cardiovascular risk factors such as insulin resistance, hypertension, renal injury, and obesity. Unfortunately, there is a lack of effective, evidence-based pharmacotherapeutics to target these cardiometabolic complications. Sodium-glucose cotransporter-2 (SGLT2) inhibitors provide cardiovascular protection in patients with and without type 2 diabetes mellitus. Although the exact mechanisms of how SGLT2 inhibitors confer cardiovascular protection remains unclear, numerous mechanistic hypotheses for this protection include modulation of the renin-angiotensin system and/or the sympathetic nervous system and improvement in mitochondrial function. Data from recent clinical trials and basic research show a potential role for SGLT2 inhibitors in treating obesity-associated cardiometabolic complications in PCOS. This narrative review discusses the mechanisms of the beneficial effect of SGLT2 inhibitors in cardiometabolic diseases in PCOS.

Anatomy and embryology of congenital surgical anomalies: Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract or "CAKUT" describes a spectrum of developmental disorders with a range of associated clinical presentations and functional consequences. CAKUT underlies the majority of chronic kidney disease and kidney replacement therapy requirement in children, but functional deterioration can also emerge in adulthood. Understanding the normal embryological processes involved in kidney development allows us to appreciate the timing and sequence of critical events implicated when things go wrong. In this review, we will describe the normal developmental mechanisms and relate this to what we currently know about the pathological processes involved in various forms of CAKUT. We will also review the proposed etiological factors, in particular genetics, involved in CAKUT.

Intact prostaglandin signaling through EP2 and EP4 receptors in stromal progenitor cells is required for normal development of the renal cortex in mice

Cyclooxygenase (Cox) inhibitors are known to have severe side effects during renal development. These consist of reduced renal function, underdeveloped subcapsular glomeruli, interstitial fibrosis, and thinner cortical tissue. Global genetic deletion of Cox-2 mimics the phenotype observed after application of Cox inhibitors. This study aimed to investigate which cell types express Cox-2 and prostaglandin E2 receptors and what functions are mediated through this pathway during renal development. Expression of EP2 and EP4 mRNA was detected by RNAscope mainly in descendants of FoxD1+ stromal progenitors; EP1 and EP3, on the other hand, were expressed in tubules. Cox-2 mRNA was detected in medullary interstitial cells and macula densa cells. Functional investigations were performed with a cell-specific approach to delete Cox-2, EP2, and EP4 in FoxD1+ stromal progenitor cells. Our data show that Cox-2 expression in macula densa cells is sufficient to drive renal development. Deletion of EP2 or EP4 in FoxD1+ cells had no functional effect on renal development. Codeletion of EP2 and EP4 in FoxD1+ stromal cells, however, led to severe glomerular defects and a strong decline of glomerular filtration rate (1.316 ± 69.7 µL/min/100 g body wt in controls vs. 644.1 ± 64.58 µL/min/100 g body wt in FoxD1+/Cre EP2-/- EP4ff mice), similar to global deletion of Cox-2. Furthermore, EP2/EP4-deficient mice showed a significant increase in collagen production with a strong downregulation of renal renin expression. This study shows the distinct localization of EP receptors in mice. Functionally, we could identify EP2 and EP4 receptors in stromal FoxD1+ progenitor cells as essential receptor subtypes for normal renal development.NEW & NOTEWORTHY Cyclooxygenase-2 (Cox-2) produces prostaglandins that are essential for normal renal development. It is unclear in which cells Cox-2 and the receptors for prostaglandin E2 (EP receptors) are expressed during late nephrogenesis. This study identified the expression sites for EP subtypes and Cox-2 in neonatal mouse kidneys. Furthermore, it shows that stromal progenitor cells may require intact prostaglandin E2 signaling through EP2 and EP4 receptors for normal renal development.

Functional tests to guide management in an adult with loss of function of type-1 angiotensin II receptor

BACKGROUND

Genetic loss of function of AGT (angiotensinogen), REN (renin), ACE (angiotensin-converting enzyme), or AGTR1 (type-1 angiotensin II receptor) leads to renal tubular dysgenesis (RTD). This syndrome is almost invariably lethal. Most surviving patients reach stage 5 chronic kidney disease at a young age.

METHODS

Here, we report a 28-year-old male with a homozygous truncating mutation in AGTR1 (p.Arg216*), who survived the perinatal period with a mildly impaired kidney function. In contrast to classic RTD, kidney biopsy showed proximal tubules that were mostly normal. During the subsequent three decades, we observed evidence of both tubular dysfunction (hyperkalemia, metabolic acidosis, salt-wasting and a urinary concentrating defect) and glomerular dysfunction (reduced glomerular filtration rate, currently ~30 mL/min/1.73 m², accompanied by proteinuria). To investigate the recurrent and severe hyperkalemia, we performed a patient-tailored functional test and showed that high doses of fludrocortisone induced renal potassium excretion by 155%. Furthermore, fludrocortisone lowered renal sodium excretion by 39%, which would have a mitigating effect on salt-wasting. In addition, urinary pH decreased in response to fludrocortisone. Opposite effects on urinary potassium and pH occurred with administration of amiloride, further supporting the notion that a collecting duct is present and able to react to fludrocortisone.

CONCLUSIONS

This report provides living proof that even truncating loss-of-function mutations in AGTR1 are compatible with life and relatively good GFR and provides evidence for the prescription of fludrocortisone to treat hyperkalemia and salt-wasting in such patients.

Prenatal Diagnosis of Autosomal Recessive Renal Tubular Dysgenesis with Anhydramnios Caused by a Mutation in the AGT Gene

Autosomal recessive renal tubular dysgenesis (ARRTD) is a rare and lethal disorder that causes stillbirth or early neonatal death. Most of the reported cases are diagnosed postnatally by a histopathological hallmark of the absence or paucity of differentiated proximal tubules in kidneys. Prenatal diagnosis of ARRTD is challenging because only a few fetal features (e.g., oligohydramnios/anhydramnios, anuria) are associated with this condition. In this study, we report a fetus with ARRTD, which showed anhydramnios and invisible urinary bladder since the second trimester, followed by growth restriction and reversed end diastolic flow in the middle cerebral artery (MCA-REDF). No morphological anomaly was detected on the fetal kidneys during an ultrasound scan. The baby died of refractory hypotension the day after their birth. Genetic analysis of genes that are involved in the renin-angiotensin-aldosterone system (RAAS), which are the known genetic causes of ARRTD, identified a novel, biparental-origin homozygous c.857-619_1269+243delinsTTGCCTTGC mutation in the AGT gene. The mutation is considered as pathogenic because it is cosegregated with ARRTD and detected in other unrelated ARRTD families. Our findings link the fetal ultrasound manifestations to the ARRTD, highlighting clues that are useful for prenatal diagnosis, which warrants confirmatory genotyping of the RAAS genes including oligohydramnios/anhydramnios, anuria (absent filling of a fetal urinary bladder), MCA-REDF, and a morphologically normal kidney.

Apparently normal kidney development in mice with conditional disruption of ANG II-AT1 receptor genes in FoxD1-positive stroma cell precursors

An intact renin-angiotensin system involving ANG II type 1 (AT₁) receptors is crucial for normal kidney development. It is still unclear in which cell types AT₁ receptor signaling is required for normal kidney development, maturation, and function. Because all kidney cells deriving from stroma progenitor cells express AT₁ receptors and because stromal cells fundamentally influence nephrogenesis and tubular maturation, we investigated the relevance of AT₁ receptors in stromal progenitors and their descendants for renal development and function. For this aim, we generated and analyzed mice with conditional deletion of AT_1A receptor in the FoxD1 cell lineage in combination with global disruption of the AT_1B receptor gene. These FoxD1-AT1ko mice developed normally. Their kidneys showed neither structural nor functional abnormalities compared with wild-type mice, whereas in isolated perfused FoxD1-AT1ko kidneys, the vasoconstrictor and renin inhibitory effects of ANG II were absent. In vivo, however, plasma renin concentration and renal renin expression were normal in FoxD1-AT1ko mice, as were blood pressure and glomerular filtration rate. These findings suggest that a strong reduction of AT₁ receptors in renal stromal progenitors and their descendants does not disturb normal kidney development.

Prenatal hypocalvaria after prolonged intrauterine exposure to angiotensin II receptor antagonists

We report a case of prenatal exposure to angiotensin II receptor antagonists (ARA II) from the beginning of pregnancy in a patient with a hypokinetic dilated cardiomyopathy. This case report emphasizes the fetal renal impact of prolonged intrauterine exposure to renin-angiotensin system (RAS) blockers, and highlights that this exposure can cause severe prenatal hypocalvaria. This delayed ossification can be reversible after birth, but the presence of anhydramnios indicates an early and irreversible block of RAS blockers in the fetus that is responsible for fetal kidney development abnormalities. This association carries a high risk of neonatal death. Prolonged exposure to ARA II or other RAS blockers remains prohibited throughout pregnancy.

Enhanced angiotensinogen expression in neonates during kidney development

BACKGROUND

We recently demonstrated that preterm neonates have higher urinary angiotensinogen (AGT) levels than full-term neonates. Here, we tested the hypothesis that enhanced neonatal AGT expression is associated with intrarenal renin-angiotensin system (RAS) status during kidney development.

METHODS

We prospectively recruited neonates born at our hospital and healthy children with minor glomerular abnormalities between April 2013 and March 2017. We measured neonatal plasma and urinary AGT levels at birth and 1 year later and assessed renal AGT expression in kidney tissues from neonates and healthy children using immunohistochemical (IHC) analysis.

RESULTS

Fifty-four neonates and eight children were enrolled. Although there were no changes in plasma AGT levels, urinary AGT levels were significantly decreased 1 year after birth. Urinary AGT levels at birth were inversely correlated with gestational age, and urinary AGT levels at birth and 1 year later were inversely correlated with estimated glomerular filtration rate 1 year after birth. IHC analysis showed that renal AGT expression in neonates was higher than that in healthy children and inversely correlated with gestational age.

CONCLUSIONS

Enhanced AGT expression and urinary AGT excretion may reflect intrarenal RAS activation associated with kidney development in utero.

Chronic captopril treatment reveals the role of ANG II in cardiovascular function of embryonic American alligators (Alligator mississippiensis)

Angiotensin II (ANG II) is a powerful vasoconstrictor of the renin-angiotensin system (RAS) that plays an important role in cardiovascular regulation in adult and developing vertebrates. Knowledge of ANG II's contribution to developmental cardiovascular function comes from studies in fetal mammals and embryonic chickens. This is the first study to examine the role of ANG II in cardiovascular control in an embryonic reptile, the American alligator (Alligator mississippiensis). Using chronic low (~ 5-mg kg embryo^-1), or high doses (~ 450-mg kg embryo^-1) of captopril, an angiotensin-converting enzyme (ACE) inhibitor, we disrupted the RAS and examined the influence of ANG II in cardiovascular function at 90% of embryonic development. Compared to embryos injected with saline, mean arterial pressure (MAP) was significantly reduced by 41 and 72% under low- and high-dose captopril treatments, respectively, a greater decrease in MAP than observed in other developing vertebrates following ACE inhibition. Acute exogenous ANG II injection produced a stronger hypertensive response in low-dose captopril-treated embryos compared to saline injection embryos. However, ACE inhibition with the low dose of captopril did not change adrenergic tone, and the ANG II response did not include an α-adrenergic component. Despite decreased MAP that caused a left shifted baroreflex curve for low-dose captopril embryos, ANG II did not influence baroreflex sensitivity. This study demonstrates that ANG II contributes to cardiovascular function in a developing reptile, and that the RAS contributes to arterial blood pressure maintenance during development across multiple vertebrate groups.

(Pro)renin and (pro)renin receptor expression during kidney development in neonates

Although a recent study demonstrated that the (pro)renin receptor ((P)RR) was highly expressed in the developing kidney during the mouse embryonic development, the mechanism by which (P)RR supports renal development in humans is not fully understood. In this study, we examined the plasma levels of (pro)renin and soluble (P)RR (s(P)RR) in cord blood and neonates as well as (P)RR expression in human kidney tissues. Samples were collected from 57 preterm and 67 full-term human neonates. (Pro)renin and s(P)RR levels were measured using enzyme-linked immunosorbent assays. Additionally, we performed an immunohistochemical (IHC) analysis of kidney tissues from neonates and minor glomerular abnormalities in order to assess (P)RR expression in the kidney. Plasma (pro)renin and s(P)RR levels in cord blood were significantly higher in preterm neonates than in full-term neonates. Four weeks after birth, these differences were no longer evident for either plasma (pro)renin or s(P)RR levels between the two groups. Importantly, plasma (pro)renin and s(P)RR levels in cord blood were inversely correlated with gestational age. Furthermore, IHC indicated that renal expression levels of (P)RR in neonates were stronger than those in minor glomerular abnormalities.

CONCLUSION

(P)RR may play a pivotal role in prenatal renal development in humans. What is Known: • Renal renin-angiotensin system (RAS) has several pathophysiologic functions not only in blood pressure regulation but also in pediatric renal disease. • Renal RAS activation plays a key role of renal development during gestation. What is New : • Plasma (pro)renin and soluble (pro)renin receptor (s(P)RR) levels in cord blood were significantly higher in preterm neonates than in full-term neonates. • Immunohistochemical analysis of kidney tissue indicated that renal expression levels of (P)RR in neonates were stronger than in minor glomerular abnormalities.

Placental transfer and mammary excretion of a novel angiotensin receptor blocker fimasartan in rats

Background

Fimasartan (FMS) is a potent angiotensin receptor blocker for the treatment of mild to moderate hypertension. This study aimed to evaluate the transfer of FMS to fetus and breast milk in rats.

Methods

In order to study the transfer to the fetus and nursing pup, pregnant and nursing maternal rats were administered with FMS by a constant intravenous infusion to reach target plasma concentrations of 200 ng/mL and 100 ng/mL. The concentrations of FMS in plasma, placenta, amniotic fluid, fetus, and milk were determined by a validated LC-MS/MS assay.

Results

Upon constant intravenous infusion, the plasma FMS concentration reached the target steady state concentrations (C_ss = 200 ng/mL and 100 ng/mL) in 24 h. The tissue-to-plasma partition coefficients (K_p) for placenta, amniotic fluid, and milk were obtained based on the observed FMS concentrations in the tissues and C_ss. The K_p values for all tissues were not different between high (C_ss = 200 ng/mL) and low (C_ss = 100 ng/mL) dose groups. While the mean K_p of the placenta was 44.6–59.0 %, the mean K_p was 1.3–1.7 % for the amniotic fluid and 14.9–17.0 % for fetus. The mean K_p of milk was 10.4–15.2 %.

Conclusions

Placental transfer and milk excretion of FMS was relatively lower compared to other angiotensin receptor blockers.

Acute Kidney Injury Recognition and Management: A Review of the Literature and Current Evidence

Acute renal failure is defined as a rapid decrease in the glomerular filtration rate, occurring over a period of hours to days and by the inability of the kidney to regulate fluid and electrolyte homeostasis appropriately. AKI is a catastrophic, life-threatening event in critically ill patients. AKI can be divided into pre-renal injury, intrinsic kidney disease (including vascular insults) and obstructive uropathies. The prognosis of AKI is highly dependent on the underlying cause of the injury. Children who have AKI as a component of multisystem failure have a much higher mortality rate than children with intrinsic renal disease. Treatment of AKI is subjected to risk stratification and ongoing damage control measures, such as patients with sepsis, exposure to nephrotoxic agents, ischemia, bloody diarrhea, or volume loss, could be helped by optimizing the fluid administrations, antibiotics possessing least nephrotoxic potential, blood transfusion where hemoglobin is dangerously low, limiting the use of nephrotoxic agents including radio contrast use, while maximize the nutrition. Acute kidney injury remains a complex disorder with an apparent differentiation in pathology between septic and nonseptic forms of the disease. Although more studies are still required, progress in this area has been steady over the last decade with purposeful international collaboration.

Postnatal acute renal failure after fetal exposure to angiotensin receptor blockers

Maternal hypertensive treatment with angiotensin receptor blockers (ARBs) during the second and third trimester of pregnancy is associated with several fetal and neonatal complications, and potential adverse outcomes. We report a neonate presenting with transient renal acute failure during the first days of life after maternal treatment with ARBs. Women who became pregnant while taking one of these drugs must modify antihypertensive therapy with a different class drug as soon as pregnancy is recognised.

Resolution of refractory hypotension and anuria in a premature newborn with loss-of-function of ACE

We present the investigation and management of a premature, hypotensive neonate born after a pregnancy complicated by anhydramnios to highlight the impact of early and informed management for rare kidney disease. Vasopressin was used to successfully treat refractory hypotension and anuria in the neonate born at 27 weeks of gestation. Next generation sequencing of a targeted panel of genes was then performed in the neonate and parents. Subsequently, two compound heterozygous deletions leading to frameshift mutations were identified in the angiotensin 1-converting enzyme gene ACE; exon 5:c.820_821delAG (p.Arg274Glyfs*117) and exon24: c.3521delG (p.Gly1174Alafs*12), consistent with a diagnosis of renal tubular dysgenesis. In light of the molecular diagnosis, identification, and treatment of associated low aldosterone level resulted in further improvement in renal function and only mild residual chronic renal failure is present at 14 months of age. Truncating alterations in ACE most often result in fetal demise during gestation or in the first days of life and typically as a result of the Potter sequence. The premature delivery, and serendipitous early treatment with vasopressin, and then later fludrocortisone, resulted in an optimal outcome in an otherwise lethal condition.

Prenatal Exposure to Angiotensin II Receptor Blockers and Hemodynamic Effects on the Newborn

Angiotensin II receptor blockers (ARBs) are potent antihypertensive agents that block the renin angiotensin aldosterone system (RAS). Their use in pregnancy may cause malformations, oligoanuria, hypotension, and death. Hypotension is observed up to 15% of cases and is described as refractory to volume and inotropic support, although its pathophysiology is unknown. We present a case of prenatal exposure to ARBs in order to characterize the hemodynamic compromise in the newborn, help in decision-making, and guide the therapeutic approach to these patients.

Prenatal exposure to lipopolysaccharide results in local RAS activation in the adipose tissue of rat offspring

BACKGROUND

Adult metabolic syndrome may originate in part during fetal or early life. This study was designed to investigate the effects of prenatal exposure to lipopolysaccharide (LPS) on adipose development and local renin-angiotensin system (RAS) activation in rat offspring.

METHODS

Pregnant rats were randomly divided into three groups (n = 8 in each), including an NS group (pregnant rats were only treated with 0.5 ml normal saline from the 8th to the 14th day of gestation); an LPS group (pregnant rats were injected intraperitoneally with 0.79 mg/kg LPS on the 8th, 10th and 12th days of pregnancy); and an LPS+pyrrolidine dithiocarbamate (PDTC) group (identical to the LPS group except that 100 mg/kg PDTC was administered from the 8th to the 14th day of gestation).

RESULTS

Prenatal exposure to LPS resulted in increased blood pressure, adipose coefficient and body weight in rat offspring. Specifically, during the infancy of the offspring rats, the LPS stimulus promoted the differentiation of adipose cells, diminishing their diameters and proportions while simultaneously increasing cell number. In contrast, once the rats were grown, adipose cell differentiation was inhibited, and the diameters and proportions of the cells were increased. Moreover, each component of the RAS was changed and was shown to be activated. PDTC, an inhibitor of NF-κB, could reverse the influence of the stimulus during pregnancy.

CONCLUSION

Prenatal exposure to LPS in rats results in increased blood pressure, adipose coefficient, body weight and activation of adipose RAS in offspring.

The actions of the renin-angiotensin system on cardiovascular and osmoregulatory function in embryonic chickens (Gallus gallus domesticus)

Using embryonic chickens (Gallus gallus domesticus), we examined the role of the renin-angiotensin system (RAS) in cardiovascular and osmotic homeostasis through chronic captopril, an angiotensin-converting enzyme (ACE) inhibitor. Captopril (5 mg kg⁻¹ embryo wet mass) or saline (control) was delivered via the egg air cell daily from embryonic day 5-18. Mean arterial pressure (MAP), heart rate (ƒ(H)), fluid osmolality and ion concentration, and embryonic and organ masses were measured on day 19. Exogenous angiotensin I (ANG I) injection did not change MAP or ƒ(H) in captopril-treated embryos, confirming ACE inhibition. Captopril-treated embryos were significantly hypotensive, with MAP 15% lower than controls, which we attributed to the loss of vasoconstrictive ANG II action. Exogenous ANG II induced a relatively greater hypertensive response in captopril-treated embryos compared to controls. Changes in response to ANG II following pre-treatment with phentolamine (α-adrenergic antagonist) indicated a portion of the ANG II response was due to circulating catecholamines in captopril-treated embryos. An increase in MAP and ƒ(H) in response to hexamethonium indicated vagal tone was also increased in the absence of ACE activity. Captopril-treated embryos had lower osmolality, lower Na⁺ and higher K⁺ concentration in the blood, indicating osmoregulatory changes. Larger kidney mass in captopril-treated embryos suggests disrupting the RAS may stimulate kidney growth by decreasing resistance at the efferent arteriole and increasing the fraction of cardiac output to the kidneys. This study suggests that the RAS, most likely through ANG II action, influences the development of the cardiovascular and osmoregulatory systems.

Fetal renin-angiotensin-system blockade syndrome: renal lesions

BACKGROUND

Fetuses exposed to angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists during the second and/or third trimesters of gestation are at high risk of developing severe complications. They consist in fetal hypotension, and anuria/oligohydramnios leading to Potter sequence, frequently associated with hypocalvaria. Most fetuses die during the pre- or postnatal period, whereas others recover normal or subnormal renal function. However, the secondary occurrence of renal failure or hypertension has been reported in children after apparent complete recovery.

METHODS

In this context, we analyzed renal lesions in 14 fetus/neonates who died soon after exposure to renin-angiotensin-system (RAS) blockers. Our objective was to determine the causes for the persistence or the secondary occurrence of renal complications reported in some of the survivors.

RESULTS

As previously described, renal tubular dysgenesis is usually observed. Additional lesions, such as thickening of the muscular wall of arterioles and interlobular arteries, glomerular cysts, and interstitial fibrosis, develop early during fetal life.

CONCLUSION

We suggest that renal lesions that develop before birth may persist after withdrawal of the causative drugs and normalization of blood and renal perfusion pressure. Their persistence could explain the severe long-term outcome of some of these patients. Long-term study of children exposed to RAS blockers during fetal life is strongly recommended.

Renal tubular dysgenesis

Renal tubular dysgenesis (RTD) is a severe foetal disorder characterised by the absence or poor development of proximal tubules, early onset and persistent anuria (leading to oligohydramnios and the Potter sequence) and ossification defects of the skull. In most cases, early death occurs from pulmonary hypoplasia, anuria and refractory arterial hypotension. RTD may be acquired during foetal development or inherited as an autosomal recessive disease. Inherited RTD is genetically heterogeneous and linked to mutations in the genes encoding the major components of the renin-angiotensin system (RAS): angiotensinogen, renin, angiotensin-converting enzyme or angiotensin II receptor type 1. Mutations result in either the absence of production or lack of efficacy of angiotensin II. Secondary RTD has been observed in various situations, particularly in the donor twin of severe twin-to-twin transfusion syndrome, in foetuses affected with congenital haemochromatosis or in foetuses exposed to RAS blockers. All cases result in renal hypoperfusion. These examples illustrate the importance of a functional RAS in the maintenance of blood pressure and renal blood flow for humans during foetal life. The diagnosis of RTD in an anuric foetus with normal renal sonography results is important for the management of the foetus or neonate. Depending on the genetic or secondary cause of the disease, such findings can lead to genetic counselling or the prevention of recurrence in subsequent pregnancies.

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.

Deletion of von Hippel-Lindau protein converts renin-producing cells into erythropoietin-producing cells

States of low perfusion pressure of the kidney associate with hyperplasia or expansion of renin-producing cells, but it is unknown whether hypoxia-triggered genes contribute to these changes. Here, we stabilized hypoxia-inducible transcription factors (HIFs) in mice by conditionally deleting their negative regulator, Vhl, using the Cre/loxP system with renin-1d promoter-driven Cre expression. Vhl (−/−(REN)) mice were viable and had normal BP. Deletion of Vhl resulted in constitutive accumulation of HIF-2α in afferent arterioles and glomerular cells and HIF-1α in collecting duct cells of the adult kidney. The preglomerular vascular tree developed normally, but far fewer renin-expressing cells were present, with more than 70% of glomeruli not containing renin cells at the typical juxtaglomerular position. Moreover, these mice had an attenuated expansion of renin-producing cells in response to a low-salt diet combined with an ACE inhibitor. However, renin-producing cells of Vhl (−/−(REN)) mice expressed the erythropoietin gene, and they were markedly polycythemic. Taken together, these results suggest that hypoxia-inducible genes, regulated by VHL, are essential for normal development and physiologic adaptation of renin-producing cells. In addition, deletion of Vhl shifts the phenotype of juxtaglomerular cells from a renin- to erythropoietin-secreting cell type, presumably in response to HIF-2 accumulation.

Prognosis and outcome of pregnancies exposed to renin-angiotensin system blockers

OBJECTIVE

To study pregnancy outcomes and fetal renal prognosis markers in cases of exposure to renin-angiotensin system blockers.

METHODS

We conducted a retrospective study of a series of 21 patients exposed to blockers of the renin-angiotensin system during pregnancy. Two markers were prenatally studied, fetal serum β2-microglobulin and amniotic fluid volume. Poor renal prognosis evaluation was based on postnatal glomerular filtration rate or on the presence of renal histologic lesions.

RESULTS

Of the 21 fetuses, only one had a normal postnatal renal function at birth (oligohydramnios regression and normal β2-microglobulin). All fetuses with persistent oligohydramnios or β2-microglobulin ≥ 5 mg/L presented an adverse renal outcome.

CONCLUSION

Exposure to renin-angiotensin system blockers complicated by oligohydramnios is associated with a very poor outcome. We propose a prenatal management based on amniotic fluid volume monitoring and fetal serum β2-microglobulin. However, our preliminary results have to be confirmed by a larger study.

Is there an embryopathy associated with first-trimester exposure to angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists? A critical review of the evidence

Drugs that interfere with the renin-angiotensin system, such as angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), are widely used to manage hypertension and heart failure. Adequate functioning of the RAS is essential for normal fetal kidney development. The potential for ACEIs and ARBs to impair fetal and neonatal renal function if taken after the first trimester of pregnancy has been well documented. Although these drugs were not found to be teratogenic in animals, until recently little was known about the teratogenic effects of ACEIs and ARBs in humans when exposure was limited to the first trimester of pregnancy. New evidence from epidemiologic studies indicates that there may be an elevated teratogenic risk when these drugs are taken during the first trimester of pregnancy. However, this elevated risk does not appear to be specific to ACEIs and ARBs, but is instead related to maternal factors and diseases that typically coexist with hypertension in pregnancy, such as diabetes, advanced maternal age, and obesity. Women who become pregnant while being treated with an ACEI or ARB should be advised to avoid exposure to these drugs during the second and third trimesters of pregnancy by switching to a different class of antihypertensive drugs between weeks 8 and 10 after conception.

Spectrum of mutations in the renin-angiotensin system genes in autosomal recessive renal tubular dysgenesis

Autosomal recessive renal tubular dysgenesis (RTD) is a severe disorder of renal tubular development characterized by early onset and persistent fetal anuria leading to oligohydramnios and the Potter sequence, associated with skull ossification defects. Early death occurs in most cases from anuria, pulmonary hypoplasia, and refractory arterial hypotension. The disease is linked to mutations in the genes encoding several components of the renin-angiotensin system (RAS): AGT (angiotensinogen), REN (renin), ACE (angiotensin-converting enzyme), and AGTR1 (angiotensin II receptor type 1). Here, we review the series of 54 distinct mutations identified in 48 unrelated families. Most of them are novel and ACE mutations are the most frequent, observed in two-thirds of families (64.6%). The severity of the clinical course was similar whatever the mutated gene, which underlines the importance of a functional RAS in the maintenance of blood pressure and renal blood flow during the life of a human fetus. Renal hypoperfusion, whether genetic or secondary to a variety of diseases, precludes the normal development/ differentiation of proximal tubules. The identification of the disease on the basis of precise clinical and histological analyses and the characterization of the genetic defects allow genetic counseling and early prenatal diagnosis.

The Fetal Safety of Angiotensin Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers

Angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) are known to cause fetal renal damage in pregnancy. Due to conflicting reports in the literature, their safety after first trimester exposure has been debated. Our aim was to determine whether the use of ACE inhibitors or ARBs in the first trimester of pregnancy is associated with an increased risk for major malformations or other adverse outcomes. All subjects were prospectively enrolled from among women contacting a teratogen information service. At initial contact, details of maternal medical history and exposures were collected and follow-up interviews were conducted to ascertain pregnancy outcomes. Two comparator groups, women with hypertension treated with other antihypertensives, and healthy controls were also recruited. Baseline maternal characteristics were not different among the three groups. There were no differences in rates of major malformations. Both the ACE-ARBs and disease-matched groups exhibited significantly lower birth weight and gestational ages than the healthy controls (P < 0.001 for both variables). There was a significantly higher rate of miscarriage noted in the ACE/ARB group (P < 0.001). These results suggest that ACE inhibitors/ARBs are not major human teratogens; however, they may be associated with an increased risk for miscarriage.

Autosomal dominant mutation in the signal peptide of renin in a kindred with anemia, hyperuricemia, and CKD

Homozygous or compound heterozygous mutations in renin (REN) cause renal tubular dysgenesis, which is characterized by death in utero due to kidney failure and pulmonary hypoplasia. The phenotype resembles the fetopathy caused by angiotensin-converting enzyme inhibitor or angiotensin receptor blocker intake during pregnancy. Recently, heterozygous REN mutations were shown to result in early-onset hyperuricemia, anemia, and chronic kidney disease (CKD). To date, only 3 different heterozygous REN mutations have been published. We report mutation analysis of the REN gene in 39 kindreds with hyperuricemia and CKD who previously tested negative for mutations in the UMOD (uromodulin) and HNF1B (hepatocyte nuclear factor 1β) genes. We identified one kindred with a novel thymidine to cytosine mutation at position 28 in the REN complementary DNA, corresponding to a tryptophan to arginine substitution at amino acid 10, which is found within the signal sequence (c.28T>C; p.W10R). On this basis, we conclude that REN mutations are rare events in patients with CKD. Within the kindred, we found affected individuals over 4 generations who carried the novel REN mutation and were characterized by significant anemia, hyperuricemia, and CKD. Anemia was severe and disproportional to the degree of decreased kidney function. Because all heterozygous REN mutations that have been described are localized in the signal sequence, screening of the REN gene for patients with CKD with hyperuricemia and anemia may best be focused on sequencing of exon 1, which encodes the signal peptide.

Chronic hypertension with related drug treatment of pregnant women and congenital abnormalities in their offspring: a population-based study

Chronic hypertension (CH) is a common chronic disease and occurs frequently in pregnant women. The teratogenic/fetotoxic effect of certain antihypertensive drugs has been shown. The objective of this study was to investigate the association between pregnant women with CH and the possible risk of congenital abnormalities (CAs) among their offspring. The prevalence of medically recorded CH in the prenatal maternity logbook was compared between 1030 pregnant women who later had offspring with CA (case group) and 1579 pregnant women with CH who later delivered newborn infants without CA (control group). Control newborn infants were matched to cases in the population-based data set of the Hungarian Case-Control Surveillance System of Congenital Abnormalities during 1980-1996. Of 23 different CA groups with informative offspring, esophageal atresia/stenosis was a greater risk in pregnant women with CH (adjusted odds ratios with 95% confidence intervals: 3.1, 1.4-6.8). In conclusion, a higher risk of esophageal atresia/stenosis was found in the offspring of pregnant women with severe CH, which could not be explained by related drug treatments. This finding requires confirmation or lack thereof by future studies.

Efficacy and safety of angiotensin II receptor type 1 antagonists in children and adolescents

Our purpose was to evaluate the effects of angiotensin II receptor type 1 antagonists (ARAs) in children and adolescents with hypertension or/and several kinds of nephropathies on blood pressure (BP) and proteinuria and to evaluate related safety issues. Data sources were Medline, Embase, The Cochrane Library, BIOSIS Previews, contact with investigators and manufacturers, personal bibliography of the lead author, and manual searches. We selected randomized controlled trials (RCTs), uncontrolled trials, and case series investigating ARAs in children and adolescents, as well as case reports about adverse events and the embryotoxic effects of ARAs in children. In four RCTs with 698 individuals, mean systolic blood pressure (BP) decreased by 10.5 mmHg [95% confidence interval (CI) 9.8-11.2] and mean diastolic BP by 6.4 mmHg (95% CI 5.8-7.0). Proteinuria decreased by 30-64% (range) in two RCTs and four case series. Safety data were comparable with adult safety data. ARAs can be considered effective and safe in lowering BP and proteinuria in the pediatric age group. The correlation between the surrogate parameters BP and proteinuria with clinical endpoints is documented to a large degree. The evidence is based on RCTs and also on lower evidence levels, such as case series. In some conditions, RCTs in children are not feasible. Registers could provide more evidence in the future.

[Mutations in renin-angiotensin system genes and kidney developmental anomalies]

Autosomal recessive renal tubular dysgenesis (RTD) is a clinical disorder observed in fetuses, characterized by absence or poor development of proximal tubules and early onset and persistent oligohydramnios leading to the Potter sequence, associated with skull ossification defect. The disease is uniformly severe resulting in low blood pressure and perinatal death in most cases or in chronic renal disease in the few surviving patients. Based on the phenotype and the finding of striking changes in renal renin expression (absent or massive), we hypothesized and demonstrated that genetic defects in the renin-angiotensin system (RAS) components are the underlying causes of the disease. At the present time, molecular screening has been performed in 46 families (F) and homozygous or compound heterozygous mutations have been detected in 41. They affect the genes encoding renine (9F), angiotensinogen (3F), AT1 receptor (3F) and angiotensin converting enzyme (26F). These findings highlight the importance of the RAS during human kidney development. Moreover, the identification of the disease based on precise histological and immunohistological analysis, and the research of the genetic defect, now allow genetic counseling and early prenatal diagnosis.

Renin-angiotensin system in kidney development: renal tubular dysgenesis

Autosomal recessive renal tubular dysgenesis (RTD) is a severe disorder of renal tubular development characterized by early onset and persistent fetal anuria leading to oligohydramnios and the Potter sequence. At birth, blood pressure is dramatically low and perinatal death occurs in most cases. Skull ossification defects are frequently associated with RTD. The disease is genetically heterogeneous and linked to mutations in the genes encoding any of the components of the renin-angiotensin system (RAS). An intense stimulation of renin production is noted in the kidneys of patients with mutations in the genes encoding angiotensinogen, angiotensin-converting enzyme, or AT1 receptor, whereas absence or increased renin production is associated with REN defects depending on the type of mutation. The severity of the disease underlines the importance of a functional RAS in the maintenance of blood pressure and renal blood flow during fetal life. The absence or poor development of proximal tubules, as well as renal vascular changes, may be attributable to renal hypoperfusion rather than to a morphogenic property of the RAS. The less severe phenotype in mice devoid of RAS may be linked to differences between mice and humans in the time of nephrogenesis and maturation of the RAS. The identification of the disease on the basis of precise clinical and histological analyses and the characterization of the genetic defects allow genetic counseling and early prenatal diagnosis.

Fetal and neonatal consequences of antenatal exposure to type 1 angiotensin II receptor-antagonists

Sartans are selective type 1 angiotensin II receptor-antagonists that are used in the treatment of arterial hypertension. Few reports are available concerning the use of sartans during pregnancy. We report two cases of adverse fetal outcome in hypertensive pregnancies exposed to sartans. In the first case, anamnios and fetal renal failure due to severe tubular dysgenesia led to termination of pregnancy in the 27th week. The second patient presented with hypocalvaria and developed fetal renal failure. The use of sartans during the two last trimesters of pregnancy should be strictly avoided.

Angiotensin II Receptor Blockers in Pregnancy: A Case Report and Systematic Review of the Literature

OBJECTIVE

To describe the case of a woman exposed to angiotensin-II receptor blockers (ARBs) in the preconceptional period and to systematically review the literature on the safety of these drugs when used by pregnant women.

METHODS

The case was identified at the Korean Motherisk Program (Seoul). For the systematic review, we searched the PubMed for case reports, case series, and post-marketing surveys.

RESULTS

A hypertensive woman was exposed to irbesartan prior to conception. The embryo had delayed development of upper and lower extremities and decreased digital groove. A karyotype identified a 45,XO Turner syndrome. The patient had a spontaneous abortion. Including the case reported here, 64 published cases were identified in total; 57.8% had favorable and 42.2% had unfavorable outcomes. Duration of treatment during pregnancy among women who had adverse fetal outcomes was 26.3 +/- 10.5 weeks (mean +/- SD), compared with 17.3 +/- 11.6 weeks in those who had favorable outcomes (p = 0.04).

CONCLUSIONS

Exposure to ARBs for a period longer than the first trimester of pregnancy appears to be associated with a high risk for adverse fetal outcomes.

Olmesartan medoxomil-induced acute renal failure in a premature newborn following maternal exposure during pregnancy: a case report and review of the literature

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (AT II) receptor blockers (ARBs) are widely used antihypertensives with well-recognized renoprotective and cardioprotective effects. Although treatment with these agents generally does not result in adverse metabolic consequences, their use during human pregnancy has been associated with negative reactions. Here we report a premature baby with a history of oligohydramnios and maternal exposure to the ARB olmesartan medoxomil who was transferred to our institution with acute renal failure. Conservative treatment with diuretics and meticulous management of fluids and electrolytes resulted in an improvement in renal function in the patient. We conclude that olmesartan medoxomil may cause reversible renal failure in premature neonates.

Management of acute kidney injury in children: a guide for pediatricians

Acute kidney injury (AKI; previously called acute renal failure) is characterized by a usually reversible increase in the blood concentration of creatinine and nitrogenous waste products and by the inability of the kidney to appropriately regulate fluid and electrolyte homeostasis. The incidence of AKI in children appears to be increasing and the etiology of AKI over the past decades has shifted from primary renal disease to multifactorial causes, particularly in hospitalized children. Renal failure can be divided into prerenal failure, intrinsic renal disease including vascular insults, and obstructive uropathies. The history, physical examination, and laboratory studies including a urinalysis and radiographic studies can establish the likely cause(s) of AKI. Once intrinsic renal failure has become established, management of the metabolic complications of AKI requires meticulous attention to fluid balance, electrolyte status, acid-base balance, and nutrition. Many children with AKI will need renal replacement therapy to remove endogenous and exogenous toxins and to maintain fluid, electrolyte, and acid-base balance until renal function improves. Renal replacement therapy may be provided by peritoneal dialysis (PD), intermittent hemodialysis (HD), or hemofiltration with or without a dialysis circuit. Many factors--including the age and size of the child, the cause of renal failure, the degree of metabolic derangements, blood pressure, and nutritional needs--are considered in deciding when to initiate renal replacement therapy and which modality of therapy to use. The prognosis of AKI is highly dependent on the underlying etiology of the AKI. Children who have AKI as a component of multisystem failure have a much higher mortality rate than children with intrinsic renal disease. Recovery from intrinsic renal disease is also highly dependent on the underlying etiology of the AKI. Children who have experienced AKI from any cause are at risk for late development of renal failure long after the initial insult. Such children need life-long monitoring of their renal function, blood pressure, and urinalysis.

Acute kidney injury in children

Acute kidney injury (AKI) (previously called acute renal failure) is characterized by a reversible increase in the blood concentration of creatinine and nitrogenous waste products and by the inability of the kidney to regulate fluid and electrolyte homeostasis appropriately. The incidence of AKI in children appears to be increasing, and the etiology of AKI over the past decades has shifted from primary renal disease to multifactorial causes, particularly in hospitalized children. Genetic factors may predispose some children to AKI. Renal injury can be divided into pre-renal failure, intrinsic renal disease including vascular insults, and obstructive uropathies. The pathophysiology of hypoxia/ischemia-induced AKI is not well understood, but significant progress in elucidating the cellular, biochemical and molecular events has been made over the past several years. The history, physical examination, and laboratory studies, including urinalysis and radiographic studies, can establish the likely cause(s) of AKI. Many interventions such as 'renal-dose dopamine' and diuretic therapy have been shown not to alter the course of AKI. The prognosis of AKI is highly dependent on the underlying etiology of the AKI. Children who have suffered AKI from any cause are at risk for late development of kidney disease several years after the initial insult. Therapeutic interventions in AKI have been largely disappointing, likely due to the complex nature of the pathophysiology of AKI, the fact that the serum creatinine concentration is an insensitive measure of kidney function, and because of co-morbid factors in treated patients. Improved understanding of the pathophysiology of AKI, early biomarkers of AKI, and better classification of AKI are needed for the development of successful therapeutic strategies for the treatment of AKI.

Use of antihypertensive drugs during pregnancy and lactation

The decision to treat elevated arterial pressure in pregnancy depends on the risk and benefits imposed on the mother and the fetus. Treatment for mild-to-moderate hypertension during pregnancy may not reduce maternal or fetal risk. Severe hypertension, on the other hand, should be treated to decrease maternal risk. Methyldopa and beta-adrenoceptor antagonists have been used most extensively. In acute severe hypertension, intravenous labetalol or oral nifedipine are reasonable choices.

Toxicité fœtale des antagonistes des récepteurs de l'angiotensine II. À propos d'un cas

The fetal toxicity of angiotensin-converting enzyme inhibitors (ACEI) is now well known. Sartans which are angiotensin II inhibitors, are supposed to have the same side effects on the fetus as ACEI because of their similar mechanism of action. This is supported by experimental and clinical data. Clinical presentation of fetal exposition to sartans varies from transient oligamnios to permanent renal failure, potentially complicated by Potter syndrome. According to previously reported cases, we report a case of transitory fetal oliguria secondary to the exposure to an angiotensin-II-receptor inhibitor (valsartan) between 19 and 21 weeks' gestation. We discuss the management of pregnancies exposed to angiotensin II inhibitors.