Prenatal glucocorticoid exposure in the sheep alters renal development in utero: implications for adult renal function and blood pressure control

Impact of preterm birth on kidney health and development

Preterm birth, defined as birth before the gestational age of 37 weeks, affects 11% of the newborns worldwide. While extensive research has focused on the immediate complications associated with prematurity, emerging evidence suggests a link between prematurity and the development of kidney disease later in life. It has been demonstrated that the normal course of kidney development is interrupted in infants born prematurely, causing an overall decrease in functional nephrons. Yet, the pathogenesis leading to the alterations in kidney development and the subsequent pathophysiological consequences causing kidney disease on the long-term are incompletely understood. In the present review, we discuss the current knowledge on nephrogenesis and how this process is affected in prematurity. We further discuss the epidemiological evidence and experimental data demonstrating the increased risk of kidney disease in these individuals and highlight important knowledge gaps. Importantly, understanding the intricate interplay between prematurity, abnormal kidney development, and the long-term risk of kidney disease is crucial for implementing effective preventive and therapeutic strategies.

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.

Ambulatory Blood Pressure Monitoring in Children and Adults Prenatally Exposed to Dexamethasone Treatment

CONTEXT

The clinical use of dexamethasone (DEX) prenatally to reduce virilization of external genitalia in female fetuses with congenital adrenal hyperplasia (CAH) is efficient but still controversial. It remains challenging to prevent the excessive exposure of DEX in unborn healthy babies during the first trimester of pregnancy.

OBJECTIVE

Since endogenous glucocorticoids contribute to the maintenance of blood pressure (BP) and since events during fetal life may program the fetus and affect future metabolic health, the aim of this study was to analyze ambulatory BP measurements in CAH-unaffected children and adults that were prenatally exposed to DEX treatment.

METHODS

Ambulatory BP measurements were analyzed in 33 (16 female) DEX-treated participants aged 5.1 to 26.3 years (19 participants aged ≤ 18 years) and in 54 (28 female) age- and sex-matched apparently healthy controls aged 5.5 to 25.3 years (27 participants aged ≤ 18 years) with ambulatory normotension.

RESULTS

Participants' age, height, weight, and body mass index were similar between the DEX-treated group and the control group. Heart rate, 24-hour BP, pulse pressure, and nighttime dipping did not statistically significantly differ between DEX-treated participants and controls.

CONCLUSION

Our study suggests that prenatal DEX treatment in CAH-unaffected children and adults does not appear to adversely affect ambulatory BP later in life. Our observations need to be confirmed in larger studies.

Postnatal glucocorticoid use impacts renal function in VLBW neonates

BACKGROUND

Preterm neonates often require glucocorticoids to manage refractory hypotension, prevent, and treat bronchopulmonary dysplasia. We have investigated the effect of cumulative dose and duration of glucocorticoids on blood pressure and renal function in VLBW infants.

METHODS

In this retrospective cohort study, medical records of infants (GA ≤ 35 weeks) born January 2015 to December 2019 were reviewed to extract demographic and clinical characteristics, dose and duration of steroids, blood pressure (BP), and creatinine at the time of discharge from the neonatal intensive care unit.

RESULTS

Two hundred and eighty-three neonates with average GA (28 ± 3 weeks) and birthweight (1060±381 g). Twenty-eight percent (33/116) of infants who received postnatal steroids developed hypertension versus 16% (27/167) of controls (OR = 2.0, p = 0.011). There was a correlation between the cumulative dosage of postnatal steroids and systolic BP (R² = 0.06, p < 0.001). With increasing steroid dose and total steroid days, there was a significant increase in creatinine clearance at the time of discharge (R² = 0.13, p < 0.001; R² = 0.13, p < 0.001, respectively).

CONCLUSIONS

Cumulative dose of postnatal steroids and duration of use is associated with increased systolic BP in premature infants. Postnatal steroids should be used prudently to prevent long-term cardiovascular and renal morbidity.

IMPACT

Preterm neonates are exposed to a high dose of glucocorticoids during their neonatal intensive care stay. The dose and duration of use of postnatal glucocorticoids was associated with significant increase in blood pressure at the time of discharge in preterm neonates. Postnatal glucocorticoid use is associated with improved creatinine clearance likely due to a state of hyperfiltration and may lead to chronic kidney disease later in life. Postnatal glucocorticoids should be used prudently in this highly vulnerable population.

A mouse model of prenatal exposure to Interleukin-6 to study the developmental origin of health and disease

Systemic inflammation in pregnant obese women is associated with 1.5- to 2-fold increase in serum Interleukin-6 (IL-6) and newborns with lower kidney/body weight ratio but the role of IL-6 in increased susceptibility to chronic kidney (CKD) in adult progeny is not known. Since IL-6 crosses the placental barrier, we administered recombinant IL-6 (10 pg/g) to pregnant mice starting at mid-gestation yielded newborns with lower body (p < 0.001) and kidney (p < 0.001) weights. Histomorphometry indicated decreased nephrogenic zone width (p = 0.039) with increased numbers of mature glomeruli (p = 0.002) and pre-tubular aggregates (p = 0.041). Accelerated maturation in IL-6 newborns was suggested by early expression of podocyte-specific protein podocin in glomeruli, increased 5-methyl-cytosine (LC–MS analysis for CpG DNA methylation) and altered expression of certain genes of cell-cycle and apoptosis (RT-qPCR array-analysis). Western blotting showed upregulated pJAK2/pSTAT3. Thus, treating dams with IL-6 as a surrogate provides newborns to study effects of maternal systemic inflammation on future susceptibility to CKD in adulthood.

Maternal selenium deficiency in mice promotes sex-specific changes to urine flow and renal expression of mitochondrial proteins in adult offspring

Selenium deficiency during pregnancy can impair fetal development and predispose offspring to thyroid dysfunction. Given that key selenoproteins are highly expressed in the kidney and that poor thyroid health can lead to kidney disease, it is likely that kidney function may be impaired in offspring of selenium-deficient mothers. This study utilized a mouse model of maternal selenium deficiency to investigate kidney protein glycation, mitochondrial adaptations, and urinary excretion in offspring. Female C57BL/6 mice were fed control (>190 µg selenium/kg) or low selenium (<50 µg selenium/kg) diets four weeks prior to mating, throughout gestation, and lactation. At postnatal day (PN) 170, offspring were placed in metabolic cages for 24 hr prior to tissue collection at PN180. Maternal selenium deficiency did not impact selenoprotein antioxidant activity, but increased advanced glycation end products in female kidneys. Male offspring had reduced renal Complex II and Complex IV protein levels and lower 24 hr urine flow. Although renal aquaporin 2 (Aqp2) and arginine vasopressin receptor 2 (Avpr2) mRNA were not altered by maternal selenium deficiency, a correlation between urine flow and plasma free T4 concentrations in male but not female offspring suggests that programed thyroid dysfunction may be mediating impaired urine flow. This study demonstrates that maternal selenium deficiency can lead to long-term deficits in kidney parameters that may be secondary to impaired thyroid dysfunction. Considering the significant burden of renal dysfunction as a comorbidity to metabolic diseases, improving maternal selenium intake in pregnancy may be one simple measure to prevent lifelong disease.

Impact of maternal prenatal stress by glucocorticoids on metabolic and cardiovascular outcomes in their offspring: A systematic scoping review

Background

“Stress” is an emerging problem in our society, health care system as well as patient care, worldwide. Especially by focusing on pre-gestational, gestational but also lactation phases “stress” is to be considered as an own trans-generational risk factor which is associated with adverse metabolic as well cardiovascular outcomes in mothers and their children. Hence, the maternal hypothalamic-pituitary-adrenotrophic (HPA) axis may be stimulated by various “stress” mechanisms as well as risk factors leading to an adverse in utero environment, e.g. by excess exposure of glucocorticoids, contributing to cardio-metabolic disorders in mothers and their offspring.

Objective

To review the evidence of in utero programming by focusing on the impact of maternal “stress”, on adverse cardio-metabolic outcomes on their offspring later in life, by identifying underlying (patho-) physiological mechanisms (1) as well as adverse short and long-term cardio-metabolic outcomes (2).

Methods

We conducted a systematic scoping review to identify publications systematically including reviews, interventional, observational, experimental studies as well as human and animal model studies. MEDLINE (PubMed) and EMBASE databases and reference lists were searched. Peer-reviewed articles from January 2000 until August 2020 were included.

Results

Overall, n = 2.634 citations were identified, n = 45 eligible studies were included and synthesized according to their key findings. In brief, maternal hypothalamic-pituitary-adrenotrophic (HPA) axis might play a key role modifying in utero milieu leading to cardio-metabolic diseases in the offspring later in life. However, maternal risk factor “stress”, is clearly linked to adverse cardio-metabolic offspring outcomes, postnatally, such as obesity, hyperglycemia, insulin resistance, diabetes mellitus (DM), Metabolic Syndrome (MetS), cardiovascular disease (CD), hypertension, restricted fetal growth as well as reduced birth, adrenal, and pancreas weights.

Conclusions

Women who experienced “stress” as risk factor, as well as their offspring, clearly have a higher risk of adverse short- as well as long-term cardio-metabolic outcomes. Future research work is needed to understand complex transgenerational mechanisms.

Role of the renin-angiotensin system in kidney development and programming of adult blood pressure

Adverse events during fetal life such as insufficient protein intake or elevated transfer of glucocorticoid to the fetus may impact cardiovascular and metabolic health later in adult life and are associated with increased incidence of type 2 diabetes, ischemic heart disease and hypertension. Several adverse factors converge and suppress the fetal renin-angiotensin-aldosterone system (RAAS). The aim of this review is to summarize data on the significance of RAAS for kidney development and adult hypertension. Genetic inactivation of RAAS in rodents at any step from angiotensinogen to angiotensin II (ANGII) type 1 receptor (AT1) receptors or pharmacologic inhibition leads to complex developmental injury to the kidneys that has also been observed in human case reports. Deletion of the 'protective' arm of RAAS, angiotensin converting enzyme (ACE) 2 (ACE-2) and G-protein coupled receptor for Angiotensin 1-7 (Mas) receptor does not reproduce the AT1 phenotype. The changes comprise fewer glomeruli, thinner cortex, dilated tubules, thicker arterioles and arteries, lack of vascular bundles, papillary atrophy, shorter capillary length and volume in cortex and medulla. Altered activity of systemic and local regulators of fetal-perinatal RAAS such as vitamin D and cyclooxygenase (COX)/prostaglandins are associated with similar injuries. ANGII-AT1 interaction drives podocyte and epithelial cell formation of vascular growth factors, notably vascular endothelial growth factor (VEGF) and angiopoietins (Angpts), which support late stages of glomerular and cortical capillary growth and medullary vascular bundle formation and patterning. RAAS-induced injury is associated with lower glomerular filtration rate (GFR), lower renal plasma flow, kidney fibrosis, up-regulation of sodium transporters, impaired sodium excretion and salt-sensitive hypertension. The renal component and salt sensitivity of programmed hypertension may impact dietary counseling and choice of pharmacological intervention to treat hypertension.

Programming of Renal Development and Chronic Disease in Adult Life

Chronic kidney disease (CKD) can have an insidious onset because there is a gradual decline in nephron number throughout life. There may be no overt symptoms of renal dysfunction until about two thirds or more of the nephrons have been destroyed and glomerular filtration rate (GFR) falls to below 25% of normal (often in mid-late life) (Martinez-Maldonaldo et al., 1992). Once End Stage Renal Disease (ESRD) has been reached, survival depends on renal replacement therapy (RRT). CKD causes hypertension and cardiovascular disease; and hypertension causes CKD. Albuminuria is also a risk factor for cardiovascular disease. The age of onset of CKD is partly determined during fetal life. This review describes the mechanisms underlying the development of CKD in adult life that results from abnormal renal development caused by an adverse intrauterine environment. The basis of this form of CKD is thought to be mainly due to a reduction in the number of nephrons formed in utero which impacts on the age dependent decline in glomerular function. Factors that affect the risk of reduced nephron formation during intrauterine life are discussed and include maternal nutrition (malnutrition and obesity, micronutrients), smoking and alcohol, use of drugs that block the maternal renin-angiotensin system, glucocorticoid excess and maternal renal dysfunction and prematurity. Since CKD, hypertension and cardiovascular disease add to the disease burden in the community we recommend that kidney size at birth should be recorded using ultrasound and those individuals who are born premature or who have small kidneys at this time should be monitored regularly by determining GFR and albumin:creatinine clearance ratio. Furthermore, public health measures aimed at limiting the prevalence of obesity and diabetes mellitus as well as providing advice on limiting the amount of protein ingested during a single meal, because they are all associated with increased glomerular hyperfiltration and subsequent glomerulosclerosis would be beneficial.

In vivo High-Content Screening in Zebrafish for Developmental Nephrotoxicity of Approved Drugs

Despite widespread drug exposure, for example during gestation or in prematurely born children, organ-specific developmental toxicity of most drugs is poorly understood. Developmental and functional abnormalities are a major cause of kidney diseases during childhood; however, the potential causal relationship to exposure with nephrotoxic drugs during nephrogenesis is widely unknown. To identify developmental nephrotoxic drugs in a large scale, we established and performed an automated high-content screen to score for phenotypic renal alterations in the Tg(wt1b:EGFP) zebrafish line. During early nephrogenesis, embryos were exposed to a compound library of approved drugs. After treatment, embryos were aligned within microtiter plates using 3D-printed orientation tools enabling the robust acquisition of consistent dorsal views of pronephric kidneys by automated microscopy. To qualitatively and quantitatively score and visualize phenotypes, we developed software tools for the semi-automated analysis, processing and visualization of this large image-based dataset. Using this scoring scheme, we were able to categorize compounds based on their potential developmental nephrotoxic effects. About 10% of tested drugs induced pronephric phenotypes including glomerular and tubular malformations, or overall changes in kidney morphology. Major chemical compound groups identified to cause glomerular and tubular alterations included dihydropyridine derivatives, HMG CoA reductase inhibitors, fibrates, imidazole, benzimidazole and triazole derivatives, corticosteroids, glucocorticoids, acetic acid derivatives and propionic acid derivatives. In conclusion, the presented study demonstrates the large-scale screening of kidney-specific toxicity of approved drugs in a live vertebrate embryo. The associated technology and tool-sets can be easily adapted for other organ systems providing a unique platform for in vivo large-scale assessment of organ-specific developmental toxicity or other biomedical applications. Ultimately, the presented data and associated visualization and browsing tools provide a resource for potentially nephrotoxic drugs and for further investigations.

Neonatal glucocorticoid overexposure alters cardiovascular function in young adult horses in a sex-linked manner

Prenatal glucocorticoid overexposure has been shown to programme adult cardiovascular function in a range of species, but much less is known about the long-term effects of neonatal glucocorticoid overexposure. In horses, prenatal maturation of the hypothalamus-pituitary-adrenal axis and the normal prepartum surge in fetal cortisol occur late in gestation compared to other precocious species. Cortisol levels continue to rise in the hours after birth of full-term foals and increase further in the subsequent days in premature, dysmature and maladapted foals. Thus, this study examined the adult cardiovascular consequences of neonatal cortisol overexposure induced by adrenocorticotropic hormone administration to full-term male and female pony foals. After catheterisation at 2-3 years of age, basal arterial blood pressures (BP) and heart rate were measured together with the responses to phenylephrine (PE) and sodium nitroprusside (SNP). These data were used to assess cardiac baroreflex sensitivity. Neonatal cortisol overexposure reduced both the pressor and bradycardic responses to PE in the young adult males, but not females. It also enhanced the initial hypotensive response to SNP, slowed recovery of BP after infusion and reduced the gain of the cardiac baroreflex in the females, but not males. Basal diastolic pressure and cardiac baroreflex sensitivity also differed with sex, irrespective of neonatal treatment. The results show that there is a window of susceptibility for glucocorticoid programming during the immediate neonatal period that alters cardiovascular function in young adult horses in a sex-linked manner.

Prematurity and Dysmaturity Are Associated With Reduced Height and Shorter Distal Limb Length in Horses

The long-term effects of gestational immaturity in the premature (defined as < 320 days gestation) and dysmature (normal term but showing some signs of prematurity) foal have not been thoroughly investigated. Studies have reported that a high percentage of gestationally immature foals with related orthopedic issues such as incomplete ossification may fail to fulfill their intended athletic purpose, particularly in Thoroughbred racing. In humans, premature birth is associated with shorter stature at maturity and variations in anatomical ratios, linked to alterations in metabolism and timing of physeal closure in the long bones. We hypothesized that gestational immaturity in horses might similarly be associated with reduced height and different anatomical ratios at maturity. In this preliminary study, the skeletal ratios of horses with a history of gestational immaturity, identified through veterinary and breeder records, were compared with those of unaffected, closely related horses (i.e., sire, dam, sibling). External measurements were taken from conformation photographs of cases (n = 19) and related horses (n = 28), and these were then combined into indices to evaluate and compare metric properties of conformation. A principal component analysis showed that the first two principal components account for 43.8% of the total conformational variation of the horses' external features, separating horses with a rectangular conformation (body length > height at the withers), from those that are more square (body length = height at the withers). Varimax rotation of PC1 and analysis of different gestational groups showed a significant effect of gestational immaturity (P = .001), with the premature group being more affected than the dysmature group (P = .009, P = .012). Mean values for the four dominant indices showed that these groups have significantly lower distal limb to body length relationships than controls. The observed differences suggest that gestational immaturity may affect anatomical ratios at maturity, which, in combination with orthopedic issues arising from incomplete ossification, may have a further impact on long-term athletic potential.

Combined Antioxidant and Glucocorticoid Therapy for Safer Treatment of Preterm Birth

Ante- and postnatal glucocorticoid therapy reduces morbidity and mortality in the preterm infant, and it is therefore one of the best examples of the successful translation of basic experimental science into human clinical practice. However, accruing evidence derived from human clinical studies and from experimental studies in animal models raise serious concerns about potential long-term adverse effects of treatment on growth and neurological and cardiovascular function in the offspring. This review explores whether combined antioxidant and glucocorticoid therapy may be safer than glucocorticoid therapy alone for the treatment of preterm birth.

Uteroplacental insufficiency temporally exacerbates salt-induced hypertension associated with a reduced natriuretic response in male rat offspring

KEY POINTS

Low weight at birth increases the risk of developing chronic diseases in adulthood A diet that is high in salt is known to elevate blood pressure, which is a major risk factor for cardiovascular and kidney diseases The present study demonstrates that growth restricted male rats have a heightened sensitivity to high dietary salt, in the context of raised systolic blood pressure, reduced urinary sodium excretion and stiffer mesenteric resistance vessels Other salt-induced effects, such as kidney hyperfiltration, albuminuria and glomerular damage, were not exacerbated by being born small The present study demonstrates that male offspring born small have an increased cardiovascular susceptibility to high dietary salt, such that that minimizing salt intake is probably of particular benefit to this at-risk population ABSTRACT: Intrauterine growth restriction increases the risk of developing chronic diseases in adulthood. Lifestyle factors, such as poor dietary choices, may elevate this risk. We determined whether being born small increases the sensitivity to a dietary salt challenge, in the context of hypertension, kidney disease and arterial stiffness. Bilateral uterine vessel ligation or sham surgery (offspring termed Restricted and Control, respectively) was performed on 18-day pregnant Wistar Kyoto rats. Male offspring were allocated to receive a diet high in salt (8% sodium chloride) or remain on standard rat chow (0.52% sodium chloride) from 20 to 26 weeks of age for 6 weeks. Systolic blood pressure (tail-cuff), renal function (24 h urine excretions) and vascular stiffness (pressure myography) were assessed. Restricted males were born 15% lighter than Controls and remained smaller throughout the study. Salt-induced hypertension was exacerbated in Restricted offspring, reaching a peak systolic pressure of ∼175 mmHg earlier than normal weight counterparts. The natriuretic response to high dietary salt in Restricted animals was less than in Controls and may explain the early rise in arterial pressure. Growth restricted males allocated to a high salt diet also had increased passive arterial stiffness of mesenteric resistance arteries. Other aspects of renal function, including salt-induced hyperfiltration, albuminuria and glomerular damage, were not exacerbated by uteroplacental insufficiency. The present study demonstrates that male offspring exposed to uteroplacental insufficiency and born small have an increased sensitivity to salt-induced hypertension and arterial remodelling.

Prenatal Steroids and Metabolic Dysfunction: Lessons from Sheep

Prenatal exposure to excess steroids or steroid mimics can disrupt the normal developmental trajectory of organ systems, culminating in adult disease. The metabolic system is particularly susceptible to the deleterious effects of prenatal steroid excess. Studies in sheep demonstrate that prenatal exposure to excess native steroids or endocrine-disrupting chemicals with steroidogenic activity, such as bisphenol A, results in postnatal development of numerous cardiometabolic perturbations, including insulin resistance, increased adiposity, altered adipocyte size and distribution, and hypertension. The similarities in the phenotypic outcomes programmed by these different prenatal insults suggest that common mechanisms may be involved, and these may include hormonal imbalances (e.g., hyperandrogenism and hyperinsulinemia), oxidative stress, inflammation, lipotoxicity, and epigenetic alterations. Animal models, including the sheep, provide mechanistic insight into the metabolic repercussions associated with prenatal steroid exposure and represent valuable research tools in understanding human health and disease. Focusing on the sheep model, this review summarizes the cardiometabolic perturbations programmed by prenatal exposure to different native steroids and steroid mimics and discusses the potential mechanisms underlying the development of adverse outcomes.

Ovine uteroplacental and fetal metabolism during and after fetal cortisol overexposure in late gestation

Cortisol modifies fetal metabolism in preparation for delivery, but whether preterm cortisol exposure programs persisting changes in fetoplacental metabolism remains unknown. This study infused fetal sheep with saline ( n = 36) or cortisol ( n = 27) to raise fetal plasma cortisol to normal prepartum concentrations for 5 days from day 125 of gestation (term: ≈145 days). Fetal uptake and uteroplacental metabolism of glucose, oxygen, and lactate, together with fetal hepatic glucogenic capacity, were measured on the final day of infusion or 5 days later. Cortisol reduced adrenal weight and umbilical glucose uptake during infusion but increased fetal glucose concentrations, hepatic glycogen content, and hepatic glucogenic enzyme activity (fructose-1,6-bisphosphatase and glucose-6-phosphatase) and gene expression ( PC and G6PC) compared with saline infusion. Postcortisol infusion, umbilical glucose uptake, and hepatic glucose-6-phosphatase activity remained low and high, respectively, whereas fetal glucose levels normalized and hepatic glycogen was lower with higher adrenal weights than in controls. Cortisol infusion increased the proportion of total uterine glucose uptake consumed by the uteroplacental tissues, irrespective of age. Placental tracer glucose transport capacity was also increased after, but not during, cortisol infusion, without changes in placental glucose transporter gene expression. Blood lactate concentration and Pco2 were higher, whereas pH and O2 content were lower in cortisol-infused than saline-infused fetuses, although uteroplacental metabolism and fetal uptake of oxygen and lactate were unaltered. The results suggest that preterm cortisol overexposure alters fetoplacental metabolism and adrenal function subsequently with persisting increases in uteroplacental glucose consumption at the expense of the fetal supply.

Constitutive metanephric mesenchyme-specific expression of interferon-gamma causes renal dysplasia by regulating Sall1 expression

Transplacental viral and parasitic infections have been shown to initiate an innate response in the mammalian embryo by increasing the expression of pro-inflammatory cytokines such as interferon-gamma (Ifng). However, the developmental consequences of an activated innate immunity and, in particular, the effects of induction of Ifng expression independent of infection have been largely overlooked. Here, we demonstrate in vivo that the conditional overexpression of Ifng in metanephric mesenchymal (MM) progenitors results in renal agenesis or hypoplasia. Cell death was observed in and around the MM region of E10.5-11.5 mutants where Ifng was constitutively expressed during early kidney development and resulted in a retardation of branching morphogenesis. Furthermore, isolated mutant or normal Ifng-treated metanephroi replicated this phenotype in culture, demonstrating the inherent nature of the aberrant morphogenesis. The expression of renal progenitor marker Sall1 was significantly decreased in the MM of mutant kidneys, suggesting that a reduction in Sall1 may be the cause of cell death in the MM during early kidney development and that, in turn, retards UB branching in the mutants. Therefore, the aberrant induction of Ifng expression, as part of an innate immune response, may contribute to renal agenesis or hypoplasia during early metanephric development by regulating the MM progenitor population.

Tubuloglomerular feedback responses in offspring of dexamethasone-treated ewes

Via developmental programming, prenatal perturbations, such as exposure to glucocorticoids and maternal malnutrition alter kidney development and contribute to the development of hypertension. To examine the possibility that alterations in tubuloglomerular feedback (TGF) contribute to the development of hypertension in offspring following maternal dexamethasone treatment (Dex) in early gestation, studies were conducted in fetal sheep and lambs. Pregnant ewes were infused with dexamethasone (0.48 mg/h) at 26-28 days gestation. No differences were observed in mean arterial pressure, glomerular filtration rate. or electrolyte excretion rates between the Dex and Untreated fetuses or lambs. Gestational exposure to Dex markedly enhanced TGF sensitivity, as the turning point in Dex-treated fetuses was significantly lower (12.9 ± 0.9 nl/min; P < 0.05) compared with Untreated fetuses (17.0 ± 1.0 nl/min). This resetting of TGF sensitivity persisted after birth (P < 0.01). TGF reactivity did not differ between the groups in fetuses or lambs. In response to nitric oxide inhibition, TGF sensitivity increased (the turning point decreased) and reactivity increased in Untreated fetuses and lambs, but these effects were blunted in the Dex-treated fetuses and lambs. Our data suggest that an altered TGF response may be an underlying renal mechanism contributing to the development of hypertension in the Dex model of fetal programming. The lower tonic level of NO production in these dexamethasone-exposed offspring may contribute to the development of hypertension as adults.

Preterm birth and ventilation decrease surface density of glomerular capillaries in lambs, regardless of postnatal respiratory support mode

BACKGROUND

Prematurity is often complicated by respiratory support, including invasive mechanical ventilation (IMV) and noninvasive support (NIS). Compared with IMV, NIS reduces injury to the lung and brain. Prematurity may also disrupt glomerular architecture. Whether NIS differentially affects glomerular architecture is incompletely understood. We hypothesized that IMV would lead to greater disruption of glomerular architecture than NIS.

METHODS

This is a secondary analysis of kidneys from moderately preterm lambs delivered at ~131 d gestation (term ~150 d) that had antenatal steroid exposure and surfactant treatment before resuscitation by IMV. At ~3 h of age, half of the lambs were switched to NIS. Support was for 3 d or 21 d. Structural indices of glomerular architecture were quantified.

RESULTS

The number of glomerular generations was unaffected by moderate preterm birth and respiratory support, either IMV or NIS. At 3 d and 21 d of IMV or NIS, glomerular capillary surface density was not different. Glomerular capillary surface density was significantly lower in the inner and outer cortex compared with unventilated gestation age-matched or postnatal age-matched reference lambs.

CONCLUSION

Moderate preterm birth and invasive or noninvasive respiratory support decreases glomerular capillarization in the lamb kidney. This adverse effect on glomerular development may contribute to increased risk for adult-onset hypertension and renal dysfunction.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

Incubation relative humidity induces renal morphological and physiological remodeling in the embryo of the chicken (Gallus gallus domesticus)

The metanephric kidneys of the chicken embryo, along with the chorioallantoic membrane, process water and ions to maintain osmoregulatory homeostasis. We hypothesized that changes in relative humidity (RH) and thus osmotic conditions during embryogenesis would alter the developmental trajectory of embryonic kidney function. White leghorn chicken eggs were incubated at one of 25-30% relative humidity, 55-60% relative humidity, and 85-90% relative humidity. Embryos were sampled at days 10, 12, 14, 16, and 18 to examine embryo and kidney mass, glomerular characteristics, body fluid osmolalities, hematological properties, and whole embryo oxygen consumption. Low and especially high RH elevated mortality, which was reflected in a 10-20% lower embryo mass on D18. Low RH altered several glomerular characteristics by day 18, including increased numbers of glomeruli per kidney, increased glomerular perfusion, and increased total glomerular volume, all indicating potentially increased functional kidney capacity. Hematological variables and plasma and amniotic fluid osmolalities remained within normal physiological values. However, the allantoic, amniotic and cloacal fluids had a significant increase in osmolality at most developmental points sampled. Embryonic oxygen consumption increased relative to control at both low and high relative humidities on Day 18, reflecting the increased metabolic costs of osmotic stress. Major differences in both renal structure and performance associated with changes in incubation humidity occurred after establishment of the metanephric kidney and persisted into late development, and likely into the postnatal period. These data indicate that the avian embryo deserves to be further investigated as a promising model for fetal programming of osmoregulatory function, and renal remodeling during osmotic stress.

A review of fundamental principles for animal models of DOHaD research: an Australian perspective

Epidemiology formed the basis of ‘the Barker hypothesis’, the concept of ‘developmental programming’ and today’s discipline of the Developmental Origins of Health and Disease (DOHaD). Animal experimentation provided proof of the underlying concepts, and continues to generate knowledge of underlying mechanisms. Interventions in humans, based on DOHaD principles, will be informed by experiments in animals. As knowledge in this discipline has accumulated, from studies of humans and other animals, the complexity of interactions between genome, environment and epigenetics, has been revealed. The vast nature of programming stimuli and breadth of effects is becoming known. As a result of our accumulating knowledge we now appreciate the impact of many variables that contribute to programmed outcomes. To guide further animal research in this field, the Australia and New Zealand DOHaD society (ANZ DOHaD) Animals Models of DOHaD Research Working Group convened at the 2nd Annual ANZ DOHaD Congress in Melbourne, Australia in April 2015. This review summarizes the contributions of animal research to the understanding of DOHaD, and makes recommendations for the design and conduct of animal experiments to maximize relevance, reproducibility and translation of knowledge into improving health and well-being.

Maternal corticosterone exposure in the mouse programs sex-specific renal adaptations in the renin-angiotensin-aldosterone system in 6-month offspring

Short‐term maternal corticosterone (Cort) administration at mid‐gestation in the mouse reduces nephron number in both sexes while programming renal and cardiovascular dysfunction in 12‐month male but not female offspring. The renal renin–angiotensin–aldosterone system (RAAS), functions in a sexually dimorphic manner to regulate both renal and cardiovascular physiology. This study aimed to identify if there are sex‐specific differences in basal levels of the intrarenal RAAS and to determine the impact of maternal Cort exposure on the RAAS in male and female offspring at 6 months of age. While intrarenal renin concentrations were higher in untreated females compared to untreated males, renal angiotensin II concentrations were higher in males than females. Furthermore, basal plasma aldosterone concentrations were greater in females than males. Cort exposed male but not female offspring had reduced water intake and urine excretion. Cort exposure increased renal renin concentrations and elevated mRNA expression of Ren1, Ace2, and Mas1 in male but not female offspring. In addition, male Cort exposed offspring had increased expression of the aldosterone receptor, Nr3c2 and renal sodium transporters. In contrast, Cort exposure increased Agtr1a mRNA levels in female offspring only. This study demonstrates that maternal Cort exposure alters key regulators of renal function in a sex‐specific manner at 6 months of life. These finding likely contribute to the disease outcomes in male but not female offspring in later life and highlights the importance of renal factors other than nephron number in the programming of renal and cardiovascular disease.

Glucocorticoid programming of intrauterine development

Glucocorticoids (GCs) are important environmental and maturational signals during intrauterine development. Toward term, the maturational rise in fetal glucocorticoid receptor concentrations decreases fetal growth and induces differentiation of key tissues essential for neonatal survival. When cortisol levels rise earlier in gestation as a result of suboptimal conditions for fetal growth, the switch from tissue accretion to differentiation is initiated prematurely, which alters the phenotype that develops from the genotype inherited at conception. Although this improves the chances of survival should delivery occur, it also has functional consequences for the offspring long after birth. Glucocorticoids are, therefore, also programming signals that permanently alter tissue structure and function during intrauterine development to optimize offspring fitness. However, if the postnatal environmental conditions differ from those signaled in utero, the phenotypical outcome of early-life glucocorticoid receptor overexposure may become maladaptive and lead to physiological dysfunction in the adult. This review focuses on the role of GCs in developmental programming, primarily in farm species. It examines the factors influencing GC bioavailability in utero and the effects that GCs have on the development of fetal tissues and organ systems, both at term and earlier in gestation. It also discusses the windows of susceptibility to GC overexposure in early life together with the molecular mechanisms and long-term consequences of GC programming with particular emphasis on the cardiovascular, metabolic, and endocrine phenotype of the offspring.

In Utero Origins of Hypertension: Mechanisms and Targets for Therapy

The developmental origins of health and disease theory is based on evidence that a suboptimal environment during fetal and neonatal development can significantly impact the evolution of adult-onset disease. Abundant evidence exists that a compromised prenatal (and early postnatal) environment leads to an increased risk of hypertension later in life. Hypertension is a silent, chronic, and progressive disease defined by elevated blood pressure (>140/90 mmHg) and is strongly correlated with cardiovascular morbidity/mortality. The pathophysiological mechanisms, however, are complex and poorly understood, and hypertension continues to be one of the most resilient health problems in modern society. Research into the programming of hypertension has proposed pharmacological treatment strategies to reverse and/or prevent disease. In addition, modifications to the lifestyle of pregnant women might impart far-reaching benefits to the health of their children. As more information is discovered, more successful management of hypertension can be expected to follow; however, while pregnancy complications such as fetal growth restriction, preeclampsia, preterm birth, etc., continue to occur, their offspring will be at increased risk for hypertension. This article reviews the current knowledge surrounding the developmental origins of hypertension, with a focus on mechanistic pathways and targets for therapeutic and pharmacologic interventions.

Compensatory responses to nephron deficiency: adaptive or maladaptive?

Compensatory renal growth is a characteristic adaptation to reduced renal mass that appears to recapitulate the normal pattern of maturation of the kidney during the postnatal period. Hypertrophy of tubules (predominantly the proximal tubule) and glomeruli is accompanied by increased single nephron glomerular filtration rate and tubular reabsorption of sodium. We propose that the very factors, which contribute to the increase in growth and function of the renal tubular system, are, in the long term, the precursors to the development of hypertension in those with a nephron deficit. The increase in single nephron glomerular filtration rate is dependent on multiple factors, including reduced renal vascular resistance associated with an increased influence of nitric oxide, and a rightward shift in the tubuloglomerular feedback curve, both of which contribute to the normal maturation of renal function. The increased influence of nitric oxide appears to contribute to the reduction in tubuloglomerular feedback sensitivity and facilitate the initial increase in glomerular filtration rate. The increased single-nephron filtered load associated with nephron deficiency may promote hypertrophy of the proximal tubule and so increased reabsorption of sodium, and thus a rightward shift in the pressure natriuresis relationship. Normalization of sodium balance can then only occur at the expense of chronically increased arterial pressure. Therefore, alterations/adaptations in tubules and glomeruli in response to nephron deficiency may increase the risk of hypertension and renal disease in the long-term.

Prospective evaluation of associations between prenatal cortisol and adulthood coronary heart disease risk: the New England family study

OBJECTIVE

Increasing evidence suggests that early life factors may influence coronary heart disease (CHD) risk; however, little is known about the contributions of prenatal cortisol. Objectives were to prospectively assess the associations of maternal cortisol levels during pregnancy with offspring's 10-year CHD risk during middle age.

METHODS

Participants were 262 mother-offspring dyads from the New England Family Study. Maternal free cortisol was assessed in third-trimester maternal serum samples. Ten-year CHD risk was calculated in offspring at a mean age of 42 years, using the validated Framingham risk algorithm incorporating diabetes, systolic and diastolic blood pressure, total and high-density lipoprotein cholesterol, smoking, age, and sex.

RESULTS

In multivariable-adjusted linear regression analyses adjusted for age and race/ethnicity, high versus low maternal cortisol tertile was associated with 36.7% (95% confidence interval [CI] = 8.4% to 72.5%) greater mean 10-year CHD risk score in women. There was no association in men (-2.8%, 95% CI = -23.8% to 24.0%). Further adjustment for in utero socioeconomic position showed 26.1% (95% CI = -0.5% to 59.9%) greater CHD risk in women. Adjustment for maternal age and size for gestational age had little effect on findings.

CONCLUSIONS

Maternal prenatal cortisol levels were positively associated with 10-year CHD risk among female, and not male, offspring. Adjusting for socioeconomic position during pregnancy reduced effect size in women, suggesting that it may be a common prior factor in both maternal cortisol and CHD risk. These findings provide evidence that targeting mothers who have elevated prenatal cortisol levels, including elevated cortisol in the setting of low socioeconomic position, may potentially reduce long-term CHD risk in their offspring.

Excess prenatal corticosterone exposure results in albuminuria, sex-specific hypotension, and altered heart rate responses to restraint stress in aged adult mice

Exposure to excess glucocorticoids programs susceptibility to cardiovascular and renal dysfunction in later life although the mechanisms have not been clearly elucidated. We administered corticosterone (CORT; 33 μg·kg(-1)·h(-1)) to pregnant mice for 60 h from embryonic day (E) 12.5. Prenatal CORT resulted in postnatal growth restriction and reduced nephron endowment at postnatal day 30 in both male and female offspring. The reduction in nephron number was associated with increased expression of apoptotic markers in the kidney at E14.5. In offspring of both sexes at 12 mo of age, there were no differences in kidney weights, urine output, or urinary sodium excretion; however, prenatal CORT exposure increased the urinary albumin/creatinine ratio and 24-h urinary albumin excretion. Surprisingly, at 12 mo male but not female offspring exposed to prenatal CORT were hypotensive, with mean arterial blood pressures ∼10 mmHg lower than untreated controls (P < 0.001). Finally, we examined how offspring responded to a renal or cardiovascular challenge (saline load or restraint stress). When given 0.9% NaCl as drinking water for 7 days, there were no differences in blood pressures or urinary parameters between groups. Restraint stress (15 min) caused a tachycardic response in all animals; however the increase in heart rate was not sustained in male offspring exposed to CORT (P < 0.01), suggesting that autonomic control of cardiovascular function may be altered. These data demonstrate that excess prenatal CORT impairs kidney development and increases the risk of cardiovascular dysfunction especially in males.

Differential mRNA expression and glucocorticoid-mediated regulation of TRPM6 and TRPM7 in the heart and kidney throughout murine pregnancy and development

The transient receptor potential (TRP) channels TRPM6 and TRPM7 are critically involved in maintaining whole body and cellular Mg²⁺ homeostasis and ensuring the normal function of organs such as the heart and kidney. However, we do not know how the expression of TRPM6 and TPRM7 in these organs changes throughout fetal development and adult life, and whether this expression can be hormonally regulated. This study determined the ontogeny of TRPM6 and TRPM7 mRNA expression from mid-gestation through to adulthood in the mouse. In a second series of experiments, we examined how maternal administration of the glucocorticoids corticosterone and dexamethasone between embryonic days 12.5–15 affected TRPM6 and TRPM7 channel mRNA expression in the mother and fetus. Whilst renal TRPM7 expression was relatively constant throughout development, renal TRPM6 expression was markedly upregulated after birth. In contrast, cardiac TRPM7 expression was 2–4 fold higher in the fetus than in the adult. Surprisingly, TRPM6 expression was detected in the fetal heart (qPCR and in situ hybridization). Glucocorticoid administration during gestation increased fetal cardiac expression of both channels without affecting renal expression. In contrast, in the dam renal TRPM6 and TRPM7 expression was increased by glucocorticoids with no change in the cardiac channel expression. These data suggest that TRPM6 and TRPM7 channels are important in organogenesis, and that elevated maternal glucocorticoid levels can alter the expression of these channels. This suggests that perturbations in hormonal regulatory systems during pregnancy may adversely impact upon normal fetal development, at least in part by altering expression of TRPM channels.

Why and how we determine nephron number

The total number of glomeruli (nephrons) in a kidney is an important microanatomical parameter for at least three reasons: it provides an index of the success/extent of nephrogenesis and can thereby provide insights into the roles of specific genes and feto-maternal environmental factors in nephrogenesis; low nephron number has been linked to an increased risk of cardiovascular and renal disease in adulthood; and knowledge of quantitative kidney microanatomy can illuminate our understanding of physiological mechanisms in health and disease. A range of methods has been used to count glomeruli in kidneys over the past 100 years, with design-based stereology (the physical disector/fractionator combination) considered the gold standard. However, this approach is labor-intensive and expensive, and therefore is not utilized by most laboratories. A new method for counting and sizing every glomerulus in the kidney has recently been described. This method involves in vivo labeling of glomeruli with cationic ferritin, and then magnetic resonance imaging (MRI) of the ex vivo kidney. Values are obtained in one sixth of the time of disector-based approaches. This new MRI method holds great promise for studies of glomerular number and size ex vivo and in vivo.

Adverse prenatal environment and kidney development: implications for programing of adult disease

The 'developmental origins of health and disease' hypothesis suggests that many adult-onset diseases can be attributed to altered growth and development during early life. Perturbations during gestation can be detrimental and lead to an increased risk of developing renal, cardiovascular, metabolic, and neurocognitive dysfunction in adulthood. The kidney has emerged as being especially vulnerable to insult at almost any stage of development resulting in a reduction in nephron endowment. In both humans and animal models, a reduction in nephron endowment is strongly associated with an increased risk of hypertension. The focus of this review is twofold: i) to determine the importance of specific periods during development on long-term programing and ii) to examine the effects of maternal perturbations on the developing kidney and how this may program adult-onset disease. Recent evidence has suggested that insults occurring around the time of conception also have the capacity to influence long-term health. Although epigenetic mechanisms are implicated in mediating these outcomes, it is unclear as to how these may impact on kidney development. This presents exciting new challenges and areas for research.

Impaired ability to modulate glomerular filtration rate in aged female sheep following fetal uninephrectomy

Fetal uninephrectomy (uni-x) results in hypertension at a later age in female than male sheep. We hypothesized that dysregulation of tubular sodium handling contributes to the reduced ability to regulate extracellular fluid (ECF) homeostasis in older females born with a congenital nephron deficit. Following renal excretory balance studies, the response to inhibition of the Na(+)K(+)2Cl(-) cotransporter with furosemide (0.5 mg/kg bolus + 1 mg/kg per hour, i.v) or vehicle treatment was examined in conscious 5-year-old female uni-x (n = 7) and sham (n = 7) sheep. Balance studies in meal-fed sheep demonstrated that while average 24 h sodium excretion over 6 days was not different between the groups, the daily variation in sodium excretion was significantly greater in uni-x compared to sham sheep (31 ± 4% vs. 12 ± 2%; P < 0.001). Basal plasma renin activity (PRA) and renal cortical cyclooxygenase-2 (COX-2) gene expression were lower in uni-x sheep (both, P < 0.01). The increases in glomerular filtration rate (GFR) and renal blood flow observed in sham sheep in response to furosemide were significantly attenuated in uni-x sheep (both P GROUP×TREAT < 0.05). However, fractional sodium excretion increased by a greater extent in the uni-x (4.4 ± 1.0%) as compared to the sham sheep (2.0 ± 0.4%; P GROUP×TIME < 0.05) in response to furosemide. In conclusion, fetal uni-x was associated with altered renal sodium handling and hypertension in aged females. The impaired ability to modulate PRA and GFR in the adults with a congenital nephron deficit may reduce the capacity of the kidney to respond to gains or losses in ECF to maintain a stable internal environment.

Developmental origins of chronic renal disease: an integrative hypothesis

Cardiovascular diseases are one of the leading causes of mortality. Hypertension (HT) is one of the principal risk factors associated with death. Chronic kidney disease (CKD), which is probably underestimated, increases the risk and the severity of adverse cardiovascular events. It is now recognized that low birth weight is a risk factor for these diseases, and this relationship is amplified by a rapid catch-up growth or overfeeding during infancy or childhood. The pathophysiological and molecular mechanisms involved in the “early programming” of CKD are multiple and partially understood. It has been proposed that the developmental programming of arterial hypertension and chronic kidney disease is related to a reduced nephron endowment. However, this mechanism is still discussed. This review discusses the complex relationship between birth weight and nephron endowment and how early growth and nutrition influence long term HT and CKD. We hypothesize that fetal environment reduces moderately the nephron number which appears insufficient by itself to induce long term diseases. Reduced nephron number constitutes a “factor of vulnerability” when additional factors, in particular a rapid postnatal growth or overfeeding, promote the early onset of diseases through a complex combination of various pathophysiological pathways.

Prenatal exposure to dexamethasone in the mouse alters cardiac growth patterns and increases pulse pressure in aged male offspring

Exposure to synthetic glucocorticoids during development can result in later cardiovascular and renal disease in sheep and rats. Although prenatal glucocorticoid exposure is associated with impaired renal development, less is known about effects on the developing heart. This study aimed to examine the effects of a short-term exposure to dexamethasone (60 hours from embryonic day 12.5) on the developing mouse heart, and cardiovascular function in adult male offspring. Dexamethasone (DEX) exposed fetuses were growth restricted compared to saline treated controls (SAL) at E14.5, but there was no difference between groups at E17.5. Heart weights of the DEX fetuses also tended to be smaller at E14.5, but not different at E17.5. Cardiac AT_1aR, Bax, and IGF-1 mRNA expression was significantly increased by DEX compared to SAL at E17.5. In 12-month-old offspring DEX exposure caused an increase in basal blood pressure of ∼3 mmHg. In addition, DEX exposed mice had a widened pulse pressure compared to SAL. DEX exposed males at 12 months had an approximate 25% reduction in nephron number compared to SAL, but no difference in cardiomyocyte number. Exposure to DEX in utero appears to adversely impact on nephrogenesis and heart growth but is not associated with a cardiomyocyte deficit in male mice in adulthood, possibly due to compensatory growth of the myocardium following the initial insult. However, the widened pulse pressure may be indicative of altered vascular compliance.

Improvement in renal hemodynamics following combined angiotensin II infusion and AT1R blockade in aged female sheep following fetal unilateral nephrectomy

Renin-angiotensin system (RAS) is a powerful modulator of renal hemodynamic and fluid homeostasis. Up-regulation in components of intra-renal RAS occurs with ageing. Recently we reported that 2 year old uninephrectomised (uni-x) female sheep have low renin hypertension and reduced renal function. By 5 years of age, these uni-x sheep had augmented decrease in renal blood flow (RBF) compared to sham. We hypothesised that this decrease in RBF in 5 year old uni-x sheep was due to an up-regulation in components of the intra-renal RAS. In this study, renal responses to angiotensin II (AngII) infusion and AngII type 1 receptor (AT1R) blockade were examined in the same 5 year old sheep. We also administered AngII in the presence of losartan to increase AngII bioavailability to the AT2R in order to understand AT2R contribution to renal function in this model. Uni-x animals had significantly lower renal cortical content of renin, AngII (∼40%) and Ang 1-7 (∼60%) and reduced cortical expression of AT1R gene than sham animals. In response to both AngII infusion and AT1R blockade via losartan, renal hemodynamic responses and tubular sodium excretion were significantly attenuated in uni-x animals compared to sham. However, AngII infusion in the presence of losartan caused ∼33% increase in RBF in uni-x sheep compared to ∼14% in sham (P<0.05). This was associated with a significant decrease in renal vascular resistance in the uni-x animals (22% vs 15%, P<0.05) without any changes in systemic blood pressure. The present study shows that majority of the intra-renal RAS components are suppressed in this model of low renin hypertension. However, increasing the availability of AngII to AT2R by AT1R blockade improved renal blood flow in uni-x sheep. This suggests that manipulation of the AT2R maybe a potential therapeutic target for treatment of renal dysfunction associated with a congenital nephron deficit.

Short- and long-term effects of exposure to natural and synthetic glucocorticoids during development

1.Glucocorticoids (GCs) are necessary for fetal development, but clinical and experimental studies suggest that excess exposure may be detrimental to health in both the short and longer term. 2.Exposure of the fetus to synthetic GCs can occur if the mother has a medical condition requiring GC therapy (e.g. asthma) or if she threatens to deliver her baby prematurely. Synthetic GCs can readily cross the placenta and treatment is beneficial, at least in the short term, for maternal health and fetal survival. 3.Maternal stress during pregnancy can raise endogenous levels of the natural GC cortisol. A significant proportion of the cortisol is inactivated by the placental 'GC barrier'. However, exposure to severe stress during pregnancy can result in increased risk of miscarriage, low birth weight and behavioural deficits in children. 4.Animal studies have shown that excess exposure to both synthetic and natural GCs can alter normal organ development, including that of the heart, brain and kidney. The nature and severity of the organ impairment is dependent upon the timing of exposure and, in some cases, the type of GC used and the sex of the fetus. 5.In animal models, exposure to elevated GCs during pregnancy has been associated with adult-onset diseases, including elevated blood pressure, impaired cardiac and vascular function and altered metabolic function.

Thermoregulatory deficits in adult Long Evans rat exposed perinatally to the antithyroidal drug, propylthiouracil

Developmental exposure to endocrine disrupting drugs and environmental toxicants has been shown to alter a variety of physiological processes in mature offspring. Body (core) temperature (T(c)) is a tightly regulated homeostatic system but is susceptible to disruptors of the hypothalamic pituitary thyroid (HPT) axis. We hypothesized that thermoregulation would be disrupted in adult offspring exposed perinatally to an HPT disruptor. Propylythiouracil (PTU) was used as a prototypical compound because of its well known antithyroidal properties. PTU was added to the drinking water of pregnant rats in concentrations of 0, 1, 2, 3, and 10 ppm from gestational day (GD) 6 through postnatal day (PND) 21. Adult male offspring were implanted with radiotransmitters to monitor Tc and motor activity (MA) and were observed undisturbed at an ambient temperature of 22 °C for 12 consecutive days. Data were averaged into a single 24 hour period to minimize impact of ultradian changes in T(c) and MA. All treatment groups showed a distinct circadian temperature rhythm. Rats exposed to 10 ppm PTU exhibited a marked deviation in their regulated T(c) with a reduction of approximately 0.4 °C below that of controls throughout the daytime period and a smaller reduction at night. Rats exposed to 1 or 2 ppm also had smaller but significant reductions in T(c). MA was unaffected by PTU. Overall, developmental exposure to moderate doses of an antithyroidal drug led to an apparent permanent reduction in T(c) of adult offspring that was independent of changes in MA.

Ex vivo modeling of chemical synergy in prenatal kidney cystogenesis

Cyclic adenosine monophosphate (cAMP) drives genetic polycystic kidney disease (PKD) cystogenesis. Yet within certain PKD families, striking differences in disease severity exist between affected individuals, and genomic and/or environmental modifying factors have been evoked to explain these observations. We hypothesized that PKD cystogenesis is accentuated by an aberrant fetal milieu, specifically by glucocorticoids. The extent and nature of cystogenesis was assessed in explanted wild-type mouse embryonic metanephroi, using 8-Br-cAMP as a chemical to mimic genetic PKD and the glucocorticoid dexamethasone as the environmental modulator. Cysts and glomeruli were quantified by an observer blinded to culture conditions, and tubules were phenotyped using specific markers. Dexamethasone or 8-Br-cAMP applied on their own produced cysts predominantly arising in proximal tubules and descending limbs of loops of Henle. When applied together, however, dexamethasone over a wide concentration range synergized with 8-Br-cAMP to generate a more severe, glomerulocystic, phenotype; we note that prominent glomerular cysts have been reported in autosomal dominant PKD fetal kidneys. Our data support the idea that an adverse antenatal environment exacerbates renal cystogenesis.

Blunted sodium excretion in response to a saline load in 5 year old female sheep following fetal uninephrectomy

Previously, we have shown that fetal uninephrectomy (uni-x) causes hypertension in female sheep by 2 years of age. Whilst the hypertension was not exacerbated by 5 years of age, these uni-x sheep had greater reductions in renal blood flow (RBF). To further explore these early indications of a decline in renal function, we investigated the renal response to a saline load (25 ml/kg/40 min) in 5-year old female uni-x and sham sheep. Basal mean arterial pressure was ∼15 mmHg greater (P(Group)<0.001), and sodium excretion (∼50%), glomerular filtration rate (∼30%, GFR) and RBF (∼40%) were all significantly lower (P(Group)<0.01) in uni-x compared to sham animals. In response to saline loading, sodium excretion increased significantly in both groups (P(Time)<0.001), however this response was blunted in uni-x sheep (P(GroupxTime)<0.01). This was accompanied with an attenuated increase in GFR and fractional sodium excretion (both P(GroupxTime)<0.05), and reduced activation of the renin-angiotensin system (both P<0.05), as compared to the sham group. The reduction in sodium excretion was associated with up-regulations in the renal gene expression of NHE3 and Na(+)/K(+) ATPase α and β subunits in the kidney cortex of the uni-x compared to the sham animals (P<0.05). Notably, neither group completely excreted the saline load within the recovery period, but the uni-x retained a higher percentage of the total volume (uni-x: 48±7%; sham: 22±9%, P<0.05). In conclusion, a reduced ability to efficiently regulate extracellular fluid homeostasis is evident in female sheep at 5 years of age, which was exacerbated in animals born with a congenital nephron deficit. Whilst there was no overt exacerbation of hypertension and renal insufficiency with age in the uni-x sheep, these animals may be more vulnerable to secondary renal insults.

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.

Lack of renal 11 beta-hydroxysteroid dehydrogenase type 2 at birth, a targeted temporal window for neonatal glucocorticoid action in human and mice

Background

Glucocorticoid hormones play a major role in fetal organ maturation. Yet, excessive glucocorticoid exposure in utero can result in a variety of detrimental effects, such as growth retardation and increased susceptibility to the development of hypertension. To protect the fetus, maternal glucocorticoids are metabolized into inactive compounds by placental 11beta-hydroxysteroid dehydrogenase type2 (11βHSD2). This enzyme is also expressed in the kidney, where it prevents illicit occupation of the mineralocorticoid receptor by glucocorticoids. We investigated the role of renal 11βHSD2 in the control of neonatal glucocorticoid metabolism in the human and mouse.

Methods

Cortisol (F) and cortisone (E) concentrations were measured in maternal plasma, umbilical cord blood and human newborn urine using HPLC. 11βHSD2 activity was indirectly assessed by comparing the F/E ratio between maternal and neonatal plasma (placental activity) and between plasma and urine in newborns (renal activity). Direct measurement of renal 11βHSD2 activity was subsequently evaluated in mice at various developmental stages. Renal 11βHSD2 mRNA and protein expression were analyzed by quantitative RT-PCR and immunohistochemistry during the perinatal period in both species.

Results

We demonstrate that, at variance with placental 11βHSD2 activity, renal 11βHSD2 activity is weak in newborn human and mouse and correlates with low renal mRNA levels and absence of detectable 11βHSD2 protein.

Conclusions

We provide evidence for a weak or absent expression of neonatal renal 11βHSD2 that is conserved among species. This temporal and tissue-specific 11βHSD2 expression could represent a physiological window for glucocorticoid action yet may constitute an important predictive factor for adverse outcomes of glucocorticoid excess through fetal programming.

Mechanisms of fetal programming in hypertension

Events that occur in the early fetal environment have been linked to long-term health and lifespan consequences in the adult. Intrauterine growth restriction (IUGR), which may occur as a result of nutrient insufficiency, exposure to hormones, or disruptions in placental structure or function, may induce the fetus to alter its developmental program in order to adapt to the new conditions. IUGR may result in a decrease in the expression of genes that are responsible for nephrogenesis as nutrients are rerouted to the development of more essential organs. Fetal survival under these conditions often results in low birth weight and a deficit in nephron endowment, which are associated with hypertension in adults. Interestingly, male IUGR offspring appear to be more severely affected than females, suggesting that sex hormones may be involved. The processes of fetal programming of hypertension are complex, and we are only beginning to understand the underlying mechanisms.

Cell biology of ischemia/reperfusion injury

Disorders characterized by ischemia/reperfusion (I/R), such as myocardial infarction, stroke, and peripheral vascular disease, continue to be among the most frequent causes of debilitating disease and death. Tissue injury and/or death occur as a result of the initial ischemic insult, which is determined primarily by the magnitude and duration of the interruption in the blood supply, and then subsequent damage induced by reperfusion. During prolonged ischemia, ATP levels and intracellular pH decrease as a result of anaerobic metabolism and lactate accumulation. As a consequence, ATPase-dependent ion transport mechanisms become dysfunctional, contributing to increased intracellular and mitochondrial calcium levels (calcium overload), cell swelling and rupture, and cell death by necrotic, necroptotic, apoptotic, and autophagic mechanisms. Although oxygen levels are restored upon reperfusion, a surge in the generation of reactive oxygen species occurs and proinflammatory neutrophils infiltrate ischemic tissues to exacerbate ischemic injury. The pathologic events induced by I/R orchestrate the opening of the mitochondrial permeability transition pore, which appears to represent a common end-effector of the pathologic events initiated by I/R. The aim of this treatise is to provide a comprehensive review of the mechanisms underlying the development of I/R injury, from which it should be apparent that a combination of molecular and cellular approaches targeting multiple pathologic processes to limit the extent of I/R injury must be adopted to enhance resistance to cell death and increase regenerative capacity in order to effect long-lasting repair of ischemic tissues.