Prenatal hypoxia leads to hypertension, renal renin-angiotensin system activation and exacerbates salt-induced pathology in a sex-specific manner

Fat-Diets in Perinatal Stages Altered Nr3c2-Mediated Ca2+ Currents in Mesenteric Arteries of Offspring Rats

SCOPE

Perinatal high-fat diets (PHF) can influence fetal/neonate development, resulting in cardiovascular pathogenesis, but precise mechanisms remain unclear. This study tests aldosterone receptor-mediated Ca2+ influx and the underlying mechanisms influenced by PHF.

METHODS AND RESULTS

Maternal S.D. rats receive PHF during pregnancy and lactation periods. Their male offspring are fed normal diets after weaning for four months. Mesenteric arteries (MA) are for electrophysiological testing, Ca2+ imaging, target gene expression, and promotor methylation. PHF increases aldosterone receptor gene Nr3c2-mediated Ca2+ currents in the smooth muscle cells (SMCs) of the MA via L-type Ca2+ channels (LTCC) in the offspring. The increased expression of aldosterone-receptors and LTCC are responsible for an activated Nr3c2-LTCC pathway in the vasculature, eventually predisposes an increase of Ca2+ influx in the myocytes of resistance arteries. The inhibitor of aldosterone-receptors suppresses the increased Ca2+ currents in the SMCs. Nr3c2 and LTCC are upregulated through the transcriptional mechanism in methylation, which can be reversed in the functional changes by methylation inhibitor 5AZA.

CONCLUSION

The results firstly demonstrate that aldosterone-receptor activation can stimulate Ca2+ currents via LTCC in vascular myocytes, which can be altered by perinatal foods via epigenetic changes of DNA methylation in the promoters of Nr3c2 and LTCC.

Perinatal intermittent hypoxia increases early susceptibility to ANG II-induced hypertension in adult male but not in female Sprague-Dawley rats

Prenatal, perinatal, and adulthood exposure to chronic intermittent hypoxia (IH) increases blood pressure in rodents. Males exposed to chronic IH have higher blood pressure versus females. However, it is unknown if this same-sex difference exists with acute perinatal IH. We tested the hypothesis that acute perinatal IH increases baseline blood pressure and enhances sensitivity to angiotensin II (ANG II)-induced hypertension in male Sprague-Dawley rats. Male and female pups were randomized to control (room air) or IH (10 min of ∼10% O2 for 3 times/day) for the first 8 days of life. IH decreased oxygen saturation, as confirmed via a pulse oximeter. Pups were weaned at postnatal day 21. Blood pressure was measured via telemetry beginning at 14 wk of age and analyzed separately into light and dark phases to assess circadian rhythm. Osmotic minipumps to deliver ANG II were implanted at 15 wk of age. Perinatal IH exposure did not alter baseline blood pressure. One week of ANG II treatment increased blood pressure in light and dark periods in males exposed to IH versus control; there was no effect in females. Blood pressure among the groups was comparable following 2 wk of ANG II infusion. Perinatal IH did not change the circadian rhythm. Following ANG II treatment, indexes of renal injury were measured. Perinatal IH did not alter kidney size, structure, nephron number, or creatinine clearance. These data indicate that acute perinatal IH enhances early ANG II-induced hypertension in males, independent of nephron loss or decreases in body weight or kidney function.NEW & NOTEWORTHY The impact of acute intermittent hypoxia (IH) in early life on blood pressure in adulthood is unknown. This study used a new model exposing female and male rat pups to acute IH in the first 8 days of life, without exposing the dam. Although baseline blood pressure was not altered in adulthood, IH increased susceptibility to angiotensin II hypertension only in males, supporting increased susceptibility of males exposed to IH to a second cardiovascular stressor.

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.

Perspectives on frailty as a total life-course disease with consideration of the fetal environment

Frailty attracts research as it represents a significant target for intervention to extend the healthy life span. An unanswered question in this field is the time point during the life-course at which an individual becomes predisposed to frailty. Here, we propose that frailty has a fetal origin and should be regarded as part of the spectrum of the developmental origins of health and disease. The developmental origins of health and disease theory originated from findings linking the fetal environment to lifestyle-related disorders such as hypertension and diabetes. Coincidentally, a recent trend in frailty research also centers on vascular dysfunction and metabolic alterations as the causality of lifestyle-related disorders such as sarcopenia and dementia. Here, we explore the relationship between fetal programming, frailty-related disorders (sarcopenia and dementia), and other age-related diseases mainly based on reports on intrauterine growth restriction. We propose a "total" life-course approach to combat frailty. With this viewpoint, not only physicians and gerontologists but also obstetricians and pediatricians should team up to overcome age-related diseases in the elderly. Geriatr Gerontol Int 2023; ••: ••-••.

Perinatal iron deficiency causes sex-dependent alterations in renal retinoic acid signaling and nephrogenesis

Long-term alterations in kidney structure and function have been observed in offspring exposed to perinatal stressors such as iron deficiency (ID), albeit the mechanisms underlying these changes remain unclear. Here, we assessed how perinatal ID alters renal vitamin A metabolism, an important contributor to nephrogenesis, in the developing kidney. Pregnant Sprague Dawley rats were fed either an iron-restricted or -replete diet throughout gestation, and offspring were studied on postnatal day (PD)1 and 28. Maternal iron restriction results in reduced renal retinoid concentrations in male and female offspring on PD1 (P=.005). Nephron endowment was reduced by 21% in male perinatal ID offspring (P<.001), whereas it was unaffected in perinatal ID females. Perinatal ID resulted in sex-dependent changes in kidney retinoid synthesis and metabolism, whereby male offspring exhibited increased expression of Raldh2 and Rar/Rxr isoforms, while females exhibited unchanged or decreased expression (all interaction P<.05). Male perinatal ID offspring exhibit sex-specific enhancements of retinoic acid pathway signaling components on PD1, including Gdnf (P<.01) and Ctnnb1 (P<.01), albeit robust upregulation of RA transcriptional target Stra6 was observed in both sexes (P=.006). On PD28, perinatal ID resulted in elevated renal retinoid concentrations (P=.02) coinciding with enhanced expression of Raldh2 (P=.04), but not any Rar isoform or Rxr. Further, perinatal ID resulted in robust upregulation of Gdnf, Ret, Ctnnb1, associated with further increases in both Cxcr4 and Stra6 (all P<.01) at PD28. Together, these data suggest perinatal ID results in sustained sex-dependent perturbations in vitamin A metabolism, which likely underlie sex-specific reductions in nephron endowment.

Nephron deficit and low podocyte density increase risk of albuminuria and glomerulosclerosis in a model of diabetes

Podocytes are terminally differentiated epithelial cells in glomeruli. Podocyte injury and loss are features of many diseases leading to chronic kidney disease (CKD). The developmental origins of health and disease hypothesis propose an adverse intrauterine environment can lead to CKD later in life, especially when a second postnatal challenge is experienced. The aim of this study was to examine whether a suboptimal maternal environment would result in reduced podocyte endowment, increasing susceptibility to diabetes-induced renal injury. Female C57BL/6 mice were fed a low protein diet (LPD) to induce growth restriction or a normal protein diet (NPD) from 3 weeks before mating until weaning (postnatal Day 21, P21) when nephron and podocyte endowment were assessed in one male and one female offspring per litter. Littermates were administered streptozotocin or vehicle at 6 weeks of age. Urinary albumin excretion, glomerular size, and podometrics were assessed following 18 weeks of hyperglycemia. LPD offspring were growth restricted and had lower nephron and podocyte number at P21. However, by 24 weeks the podocyte deficit was no longer evident and despite low nephron endowment neither albuminuria nor glomerulosclerosis were observed. Podocyte number was unaffected by 18 weeks of hyperglycemia in NPD and LPD offspring. Diabetes increased glomerular volume reducing podocyte density, with more pronounced effects in LPD offspring. LPD and NPD diabetic offspring developed mild albuminuria with LPD demonstrating an earlier onset. LPD offspring also developed glomerular pathology. These findings indicate that growth-restricted LPD offspring with low nephron number and normalized podocyte endowment were more susceptible to alterations in glomerular volume and podocyte density leading to more rapid onset of albuminuria and renal injury than NPD offspring.

Treatment with Ginkgo biloba supplement modulates oxidative disturbances, inflammation and vascular functions in oxygen deprived hypothyroid mice: Involvement of endothelin-1/NO signaling pathways

A double-hit biological alteration involving exposure to oxygen deprivation in hypothyroid condition may exacerbate cellular oxidative and inflammatory disturbances comparative to a one-hit biological exposure. This study investigated the therapeutic effect of Ginkgo biloba as cardioprotective against aortic oxido-inflammatory disturbances following oxygen deprivation in hypothyroid mice. Male Swiss mice were partitioned into 5 groups (n = 6) for hypothyroidism (Carbimazole 1.2 mg/kg) and hypoxia induction. Group 1 (normal control), group 2 (hypoxic stress control), group 3 (hypoxic and hypothyroid stress), group 4 (hypoxic and hypothyroid stress and Ginkgo biloba 20 mg/kg; p.o) and group 5 (hypoxic and hypothyroid stress and Levothyroxine 10 μg/kg; p.o) for 14 days. Thereafter, serum and aorta was collected for biochemical evaluation. GBS did not up-regulate the serum thyroid hormone imbalances (tri-iodothyronine (T3), thyroxin (T4)) but maintains the TSH levels. The blood glucose level was reduced with decrease oxidative stress and inflammatory mediators in the serum/aorta indicated by inhibited redox status following treatment with GBS. Moreover, endothelin-1/nitric oxide signaling pathways were markedly regulated in the aorta. Conclusively, GBS acts as a therapeutic agent and may be consider as a potential vasodilator candidate in the management and control of hypoxic stress in hypothyroid condition. PRACTICAL APPLICATIONS: Treatment with Gingko biloba supplement abated endothelial abnormalities via elevation of nitric oxide release and suppression of endothelin activity in hypothyroid mice exposed to hypoxic hypoxia. The activity of myeloperoxidase enzyme and redo-inflammatory status was downregulated following treatment with Gingko biloba supplement in hypothyroid mice exposed to hypoxic hypoxia. Treatment with Gingko biloba supplement modulates hypothalamic-pituitary-adrenal (HPA) axis by inhibiting corticosterone release in hypothyroid mice exposed to hypoxic hypoxia.

Regulation of nephron progenitor cell lifespan and nephron endowment

Low nephron number - resulting, for example, from prematurity or developmental anomalies - is a risk factor for the development of hypertension, chronic kidney disease and kidney failure. Considerable interest therefore exists in the mechanisms that regulate nephron endowment and contribute to the premature cessation of nephrogenesis following preterm birth. The cessation of nephrogenesis in utero or shortly after birth is synchronized across multiple niches in all mammals, and is coupled with the exhaustion of nephron progenitor cells. Consequently, no nephrons are formed after the cessation of developmental nephrogenesis, and lifelong renal function therefore depends on the complement of nephrons generated during gestation. In humans, a tenfold variation in nephron endowment between individuals contributes to differences in susceptibility to kidney disease; however, the mechanisms underlying this variation are not yet clear. Salient advances in our understanding of environmental inputs, and of intrinsic molecular mechanisms that contribute to the regulation of cessation timing or nephron progenitor cell exhaustion, have the potential to inform interventions to enhance nephron endowment and improve lifelong kidney health for susceptible individuals.

Prenatal Hypoxia Affects Foetal Cardiovascular Regulatory Mechanisms in a Sex- and Circadian-Dependent Manner: A Review

Prenatal hypoxia during the prenatal period can interfere with the developmental trajectory and lead to developing hypertension in adulthood. Prenatal hypoxia is often associated with intrauterine growth restriction that interferes with metabolism and can lead to multilevel changes. Therefore, we analysed the effects of prenatal hypoxia predominantly not associated with intrauterine growth restriction using publications up to September 2021. We focused on: (1) The response of cardiovascular regulatory mechanisms, such as the chemoreflex, adenosine, nitric oxide, and angiotensin II on prenatal hypoxia. (2) The role of the placenta in causing and attenuating the effects of hypoxia. (3) Environmental conditions and the mother's health contribution to the development of prenatal hypoxia. (4) The sex-dependent effects of prenatal hypoxia on cardiovascular regulatory mechanisms and the connection between hypoxia-inducible factors and circadian variability. We identified that the possible relationship between the effects of prenatal hypoxia on the cardiovascular regulatory mechanism may vary depending on circadian variability and phase of the days. In summary, even short-term prenatal hypoxia significantly affects cardiovascular regulatory mechanisms and programs hypertension in adulthood, while prenatal programming effects are not only dependent on the critical period, and sensitivity can change within circadian oscillations.

Early-Life Origins of Metabolic Syndrome: Mechanisms and Preventive Aspects

One of the leading global public-health burdens is metabolic syndrome (MetS), despite the many advances in pharmacotherapies. MetS, now known as "developmental origins of health and disease" (DOHaD), can have its origins in early life. Offspring MetS can be programmed by various adverse early-life conditions, such as nutrition imbalance, maternal conditions or diseases, maternal chemical exposure, and medication use. Conversely, early interventions have shown potential to revoke programming processes to prevent MetS of developmental origins, namely reprogramming. In this review, we summarize what is currently known about adverse environmental insults implicated in MetS of developmental origins, including the fundamental underlying mechanisms. We also describe animal models that have been developed to study the developmental programming of MetS. This review extends previous research reviews by addressing implementation of reprogramming strategies to prevent the programming of MetS. These mechanism-targeted strategies include antioxidants, melatonin, resveratrol, probiotics/prebiotics, and amino acids. Much work remains to be accomplished to determine the insults that could induce MetS, to identify the mechanisms behind MetS programming, and to develop potential reprogramming strategies for clinical translation.

Prenatal hypoxia increases blood pressure in male rat offspring and affects their response to artificial light at night

Prenatal hypoxia (PH) has negative consequences on the cardiovascular system in adulthood and can affect the responses to additional insults later in life. We explored the effects of PH imposed during embryonic day 20 (10.5% O2 for 12 h) on circadian rhythms of systolic blood pressure (BP) and heart rate (HR) in mature male rat offspring measured by telemetry. We evaluated: (1) stability of BP and HR changes after PH; (2) circadian variability of BP and HR after 2 and 5 weeks of exposure to artificial light at night (ALAN; 1-2 lx); and (3) response of BP and HR to norepinephrine. PH increased BP in the dark (134 ± 2 mmHg vs. control 127 ± 2 mmHg; p = 0.05) and marginally in the light (125 ± 1 mmHg vs. control 120 ± 2 mmHg) phase of the day but not HR. The effect of PH was highly repeatable between 21- and 27-week-old PH male offspring. Two weeks of ALAN decreased the circadian variability of HR (p < 0.05) and BP more in control than PH rats. After 5 weeks of ALAN, the circadian variability of HR and BP were damped compared to LD and did not differ between control and PH rats (p < 0.05). Responses of BP and HR to norepinephrine did not differ between control and PH rats. Hypoxia at the end of the embryonic period increases BP and affects the functioning of the cardiovascular system in mature male offspring. ALAN in adulthood decreased the circadian variability of cardiovascular parameters, more in control than PH rats.

Animal Models for DOHaD Research: Focus on Hypertension of Developmental Origins

Increasing evidence suggests that fetal programming through environmental exposure during a critical window of early life leads to long-term detrimental outcomes, by so-called developmental origins of health and disease (DOHaD). Hypertension can originate in early life. Animal models are essential for providing convincing evidence of a causal relationship between diverse early-life insults and the developmental programming of hypertension in later life. These insults include nutritional imbalances, maternal illnesses, exposure to environmental chemicals, and medication use. In addition to reviewing the various insults that contribute to hypertension of developmental origins, this review focuses on the benefits of animal models in addressing the underlying mechanisms by which early-life interventions can reprogram disease processes and prevent the development of hypertension. Our understanding of hypertension of developmental origins has been enhanced by each of these animal models, narrowing the knowledge gap between animal models and future clinical translation.

Podometrics in Japanese Living Donor Kidneys: Associations with Nephron Number, Age, and Hypertension

BACKGROUND

Podocyte depletion, low nephron number, aging, and hypertension are associated with glomerulosclerosis and CKD. However, the relationship between podometrics and nephron number has not previously been examined.

METHODS

To investigate podometrics and nephron number in healthy Japanese individuals, a population characterized by a relatively low nephron number, we immunostained single paraffin sections from 30 Japanese living-kidney donors (median age, 57 years) with podocyte-specific markers and analyzed images obtained with confocal microscopy. We used model-based stereology to estimate podometrics, and a combined enhanced-computed tomography/biopsy-specimen stereology method to estimate nephron number.

RESULTS

The median number of nonsclerotic nephrons per kidney was 659,000 (interquartile range [IQR], 564,000-825,000). The median podocyte number and podocyte density were 518 (IQR, 428-601) per tuft and 219 (IQR, 180-253) per 10⁶μm³, respectively; these values are similar to those previously reported for other races. Total podocyte number per kidney (obtained by multiplying the individual number of nonsclerotic glomeruli by podocyte number per glomerulus) was 376 million (IQR, 259-449 million) and ranged 7.4-fold between donors. On average, these healthy kidneys lost 5.63 million podocytes per kidney per year, with most of this loss associated with glomerular loss resulting from global glomerulosclerosis, rather than podocyte loss from healthy glomeruli. Hypertension was associated with lower podocyte density and larger podocyte volume, independent of age.

CONCLUSIONS

Estimation of the number of nephrons, podocytes, and other podometric parameters in individual kidneys provides new insights into the relationships between these parameters, age, and hypertension in the kidney. This approach might be of considerable value in evaluating the kidney in health and disease.

COVID-19 During Development: A Matter of Concern

A new infectious disease, COVID-19, has spread around the world. The most common symptoms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are cough and fever, but severe cases can develop acute respiratory distress syndrome. The main receptor for SARS-CoV-2 in human tissue is angiotensin-converting enzyme 2, and the lungs, heart, and kidneys are the most affected organs. Besides the inflammatory process and tissue damage, the presence of a cytokine "storm" has been related to a higher mortality rate. Other infectious viral diseases, such as Zika, chikungunya, and influenza, were associated with complications in pregnant women, such as growth restriction, malformation, preterm birth, low birth weight, miscarriage, and death, although they can also cause developmental disorders in infants and adolescents. Evidence points out that stressors during pregnancy and infancy may lead to the development of obesity, diabetes, and cardiovascular disease. Therefore, we hypothesize that COVID-19 infection during the critical phases of development can program the individual to chronic diseases in adulthood. It is important that COVID-19 patients receive proper monitoring as a way to avoid expensive costs to public health in the future.

Targeting the Renin-Angiotensin-Aldosterone System to Prevent Hypertension and Kidney Disease of Developmental Origins

The renin-angiotensin-aldosterone system (RAAS) is implicated in hypertension and kidney disease. The developing kidney can be programmed by various early-life insults by so-called renal programming, resulting in hypertension and kidney disease in adulthood. This theory is known as developmental origins of health and disease (DOHaD). Conversely, early RAAS-based interventions could reverse program processes to prevent a disease from occurring by so-called reprogramming. In the current review, we mainly summarize (1) the current knowledge on the RAAS implicated in renal programming; (2) current evidence supporting the connections between the aberrant RAAS and other mechanisms behind renal programming, such as oxidative stress, nitric oxide deficiency, epigenetic regulation, and gut microbiota dysbiosis; and (3) an overview of how RAAS-based reprogramming interventions may prevent hypertension and kidney disease of developmental origins. To accelerate the transition of RAAS-based interventions for prevention of hypertension and kidney disease, an extended comprehension of the RAAS implicated in renal programming is needed, as well as a greater focus on further clinical translation.

Perinatal iron deficiency and a high salt diet cause long-term kidney mitochondrial dysfunction and oxidative stress

AIMS

Perinatal iron deficiency (ID) alters developmental trajectories of offspring, predisposing them to cardiovascular dysfunction in later life. The mechanisms underlying this long-term programming of renal function have not been defined. We hypothesized perinatal ID causes hypertension and alters kidney metabolic function and morphology in a sex-dependent manner in adult offspring. Furthermore, we hypothesized these effects are exacerbated by chronic consumption of a high salt diet.

METHODS AND RESULTS

Pregnant Sprague Dawley rats were fed either an iron-restricted or replete diet prior to and throughout pregnancy. Adult offspring were fed normal or high salt diets for 6 weeks prior to experimentation at 6 months of age. Blood pressure (BP) was assessed via indwelling catheters in anaesthetized offspring; kidney mitochondrial function was assessed via high-resolution respirometry; reactive oxygen species and nitric oxide were quantified via fluorescence microscopy. Adult males, but not females, exhibited increased systolic BP due to ID (P = 0.01) and high salt intake (P = 0.02). In males, but not in females, medullary mitochondrial content was increased by high salt (P = 0.003), while succinate-dependent respiration was reduced by ID (P < 0.05). The combination of perinatal ID and high salt reduced complex IV activity in the cortex of males (P = 0.01). Perinatal ID increased cytosolic superoxide generation (P < 0.001) concomitant with reduced nitric oxide bioavailability (P < 0.001) in male offspring, while high salt increased mitochondrial superoxide in the medulla (P = 0.04) and cytosolic superoxide within the cortex (P = 0.01). Male offspring exhibited glomerular basement membrane thickening (P < 0.05), increased collagen deposition (P < 0.05), and glomerular hypertrophy (interaction, P = 0.02) due to both perinatal ID and high salt. Female offspring exhibited no alterations in mitochondrial function or morphology due to either high salt or ID.

CONCLUSION

Perinatal ID causes long-term sex-dependent alterations in renal metabolic function and morphology, potentially contributing to hypertension and increased cardiovascular disease risk.

Sex differences and the effects of intrauterine hypoxia on growth and in vivo heart function of fetal guinea pigs

We hypothesized that the physiological adaptations of the fetus in response to chronic intrauterine hypoxia depend on its sex and the gestational age of exposure. Pregnant guinea pigs were exposed to room air (normoxia, NMX) or 10.5% O₂ (hypoxia, HPX) at either 25 days (early onset) or 50 days (late onset) of gestation until term (~65 days). We evaluated the effects of HPX on hemodynamic and cardiac function indices using Doppler ultrasound and determined sex-related differences in near-term fetuses. Indices of uterine/umbilical artery pulsatility (PI index) and fetal heart systolic and diastolic function [Tei index and passive filling (E-wave) to filling due to atrial contraction (A-wave) (E/A ratios), respectively] were measured in utero and fetal body (FBW) and organ weights measured from extracted fetuses. Both early- and late-onset HPX decreased FBW in both males and females, had no effect on placenta weights, and increased placenta weight-to-FBW ratios. Early- but not late-onset HPX increased uterine artery PI, but neither HPX condition affected umbilical artery PI. Early-onset HPX increased left ventricle E/A ratios in both males and females, whereas late-onset HPX increased the right ventricle E/A ratio in females only. Hypoxia had no effect on the Tei index in either sex. Early- and late-onset HPX induce placental insufficiency and fetal growth restriction and increase diastolic filling depending on the sex, with female fetuses having a greater capacity than males to compensate for intrauterine hypoxia.

Physiology and Pathophysiology of Compensatory Adaptations of a Solitary Functioning Kidney

Children born with a solitary functioning kidney (SFK) have an increased risk of hypertension and kidney disease from early in adulthood. In response to a reduction in kidney mass, the remaining kidney undergoes compensatory kidney growth. This is associated with both an increase in size of the kidney tubules and the glomeruli and an increase in single nephron glomerular filtration rate (SNGFR). The compensatory hypertrophy and increase in filtration at the level of the individual nephron results in normalization of total glomerular filtration rate (GFR). However, over time these same compensatory mechanisms may contribute to kidney injury and hypertension. Indeed, approximately 50% of children born with a SFK develop hypertension by the age of 18 and 20–40% require dialysis by the age of 30. The mechanisms that result in kidney injury are only partly understood, and early biomarkers that distinguish those at an elevated risk of kidney injury are needed. This review will outline the compensatory adaptations to a SFK, and outline how these adaptations may contribute to kidney injury and hypertension later in life. These will be based largely on the mechanisms we have identified from our studies in an ovine model of SFK, that implicate the renal nitric oxide system, the renin angiotensin system and the renal nerves to kidney disease and hypertension associated with SFK. This discussion will also evaluate current, and speculate on next generation, prognostic factors that may predict those children at a higher risk of future kidney disease and hypertension.

Fetal renal artery impedance in pregnancies affected by preeclampsia

Background Preeclampsia (PE) is a pregnancy-specific vascular endothelial disorder characterized by multi-organ system involvement. This includes the maternal kidneys, with changes such as continuous vasospasm of renal arteries and reduced renal blood flow. However, it is unclear whether similar renal vascular changes are seen in the fetus. This study sought to compare renal artery impedance in fetuses of women with and without PE. Methods This was a prospective Doppler assessment study of the fetal renal artery impedance in 48 singleton fetuses. The group with PE consisted of 24 appropriately grown fetuses in pregnancy complicated by both mild and severe PE and a control group of 24 uncomplicated pregnancies. Doppler studies included renal artery systolic/diastolic (S/D) ratio, pulsatility index (PI), resistance index (RI), and identification of end-diastolic blood flow. Results Fetuses of mothers with PE were more likely to have a lower renal artery Doppler S/D ratio (7.85 [6.4-10.2] vs. 10.8 [7.75-22.5], P = 0.03) and lower RI (0.875 [0.842-0.898] vs. 0.905 [0.872-0.957], P = 0.03). However, there was no statistically significant difference in PI. There was also no difference in the incidence of absent end-diastolic flow. Conclusion This study suggests that PE results in changes in blood flow to the renal arteries of the fetus. This may be associated with long-term adverse health effects later in adulthood.

Deletion of hypoxia-responsive microRNA-210 results in a sex-specific decrease in nephron number

Low nephron number results in an increased risk of developing hypertension and chronic kidney disease. Intrauterine growth restriction is associated with a nephron deficit in humans, and is commonly caused by placental insufficiency, which results in fetal hypoxia. The underlying mechanisms by which hypoxia impacts kidney development are poorly understood. microRNA-210 is the most consistently induced microRNA in hypoxia and is known to promote cell survival in a hypoxic environment. In this study, the role of microRNA-210 in kidney development was evaluated using a global microRNA-210 knockout mouse. A male-specific 35% nephron deficit in microRNA-210 knockout mice was observed. Wnt/β-catenin signaling, a pathway crucial for nephron differentiation, was misregulated in male kidneys with increased expression of the canonical Wnt target lymphoid enhancer binding factor 1. This coincided with increased expression of caspase-8-associated protein 2, a known microRNA-210 target and apoptosis signal transducer. Together, these data are consistent with a sex-specific requirement for microRNA-210 in kidney development.

Prenatal hypoxia increases susceptibility to kidney injury

Prenatal hypoxia is a gestational stressor that can result in developmental abnormalities or physiological reprogramming, and often decreases cellular capacity against secondary stress. When a developing fetus is exposed to hypoxia, blood flow is preferentially redirected to vital organs including the brain and heart over other organs including the kidney. Hypoxia-induced injury can lead to structural malformations in the kidney; however, even in the absence of structural lesions, hypoxia can physiologically reprogram the kidney leading to decreased function or increased susceptibility to injury. Our investigation in mice reveals that while prenatal hypoxia does not affect normal development of the kidneys, it primes the kidneys to have an increased susceptibility to kidney injury later in life. We found that our model does not develop structural abnormalities when prenatally exposed to modest 12% O2 as evident by normal histological characterization and gene expression analysis. Further, adult renal structure and function is comparable to mice exposed to ambient oxygen throughout nephrogenesis. However, after induction of kidney injury with a nephrotoxin (cisplatin), the offspring of mice housed in hypoxia exhibit significantly reduced renal function and proximal tubule damage following injury. We conclude that exposure to prenatal hypoxia in utero physiologically reprograms the kidneys leading to increased susceptibility to injury later in life.

Maternal hypoxia developmentally programs low podocyte endowment in male, but not female offspring

Fetal hypoxia is a common complication of pregnancy. We have previously reported that maternal hypoxia in late gestation in mice gives rise to male offspring with reduced nephron number, while females have normal nephron number. Male offspring later develop proteinuria and renal pathology, including glomerular pathology, whereas female offspring are unaffected. Given the central role of podocyte depletion in glomerular and renal pathology, we examined whether maternal hypoxia resulted in low podocyte endowment in offspring. Pregnant CD1 mice were allocated at embryonic day 14.5 to normoxic (21% oxygen) or hypoxic (12% oxygen) conditions. At postnatal day 21, kidneys from mice were immersion fixed, and one mid-hilar slice per kidney was immunostained with antibodies directed against p57 and synaptopodin for podocyte identification. Slices were cleared and imaged with a multiphoton microscope for podometric analysis. Male hypoxic offspring had significantly lower birth weight, nephron number, and podocyte endowment than normoxic male offspring (podocyte number; normoxic 62.86 ± 2.26 podocytes per glomerulus, hypoxic 53.38 ± 2.25; p < .01, mean ± SEM). In contrast, hypoxic female offspring had low birth weight but their nephron and podocyte endowment was the same as normoxic female offspring (podocyte number; normoxic 62.38 ± 1.86 podocytes per glomerulus, hypoxic 61.81 ± 1.80; p = .88). To the best of our knowledge, this is the first report of developmentally programmed low podocyte endowment. Given the well-known association between podocyte depletion in adulthood and glomerular pathology, we postulate that podocyte endowment may place offspring at risk of renal disease in adulthood, and explain the greater vulnerability of male offspring.

Moderate prenatal ethanol exposure in the rat promotes kidney cell apoptosis, nephron deficits, and sex-specific kidney dysfunction in adult offspring

Alcohol during pregnancy can impair fetal development and result in offspring with neurodevelopmental deficits. Less is known about how low to moderate alcohol exposure can affect other organs, such as the kidney. Here, the effects of moderate ethanol exposure throughout pregnancy on kidney development were examined using a rat model. Rats were fed a liquid diet containing 6% ethanol (vol/vol) or control (0% ethanol) throughout pregnancy. Kidneys were collected at embryonic day (E) 20 or postnatal day (PN) 30 and total glomerular (nephron) number determined using unbiased stereology. Kidney function was examined in offspring at 8 and 19 months. At E20, fetuses exposed to ethanol had fewer nephrons with increased apoptosis. Alcohol exposure caused kidney dysregulation of pro- (Bax) and anti- (Bcl-2) apoptotic factors, and reduced expression of the cell proliferation marker, Ki67. Prenatal alcohol decreased expression of Gdnf and Tgfb1, important regulators of branching morphogenesis, in male fetuses. At PN30, kidney volume and nephron number were lower in offspring exposed to prenatal alcohol. Urine flow and osmolality were normal in offspring exposed to alcohol however sodium excretion tended to be lower in females prenatally exposed to alcohol. Findings suggest exposure to moderate levels of alcohol during pregnancy results in impaired kidney development and leads to a permanent nephron deficit. Although the impact on adult kidney function was relatively minor, these data highlight that even at moderate levels, alcohol consumption during pregnancy can have deleterious long-term outcomes and should be avoided.

Tet3 enhances IL-6 expression through up-regulation of 5-hmC in IL-6 promoter in chronic hypoxia induced atherosclerosis in offspring rats

AIMS

Tet1, Tet2, and interleukin-6 (IL-6) have been linked to atherosclerosis. Whether Tet3 has a relationship with atherosclerosis and IL-6 was unknown. This study aims to determine the link between Tet3 and IL-6, and the role of Tet3 in prenatal hypoxia-induced atherosclerosis in offspring rats.

MAIN METHODS

Pregnant rats were divided into hypoxia and control group. Their male offspring were tested at 20 months old. Hematoxylin-eosin staining and transmission electron microscopic staining were used. Gene mRNA and protein levels were measured with q-PCR or Western blotting. Cell viability and migration was tested with MTT or cell scratch assay. 5-hmC and 5-mC expression were obtained by qGlucMS-PCR; 5-hmC and 5-mC activity were obtained by dot blotting.

KEY FINDINGS

Chronic prenatal hypoxia increased Tet3 and IL-6 expression, and decreased Tet3 activity in offspring rats. GlucMS-qPCR showed the percentage of 5-hmC was significantly up-regulated in the promoter of IL-6 in both the rats and cells. Moreover, 5-hmC percentage also was increased in the A7r5 cells transfected with Tet3. Furthermore, Tet3 promoted proliferation and migration of A7r5 cells. However, Tet3 was not sensitive to acute hypoxia, while influenced by HIF-1α DNA element.

SIGNIFICANCE

Tet3 enhanced IL-6 expression though up-regulating 5-hmC percentage in the IL-6 promoter.

The Placental Transcriptome in Late Gestational Hypoxia Resulting in Murine Intrauterine Growth Restriction Parallels Increased Risk of Adult Cardiometabolic Disease

Intrauterine growth restriction (IUGR) enhances risk for adult onset cardiovascular disease (CVD). The mechanisms underlying IUGR are poorly understood, though inadequate blood flow and oxygen/nutrient provision are considered common endpoints. Based on evidence in humans linking IUGR to adult CVD, we hypothesized that in murine pregnancy, maternal late gestational hypoxia (LG-H) exposure resulting in IUGR would result in (1) placental transcriptome changes linked to risk for later CVD, and 2) adult phenotypes of CVD in the IUGR offspring. After subjecting pregnant mice to hypoxia (10.5% oxygen) from gestational day (GD) 14.5 to 18.5, we undertook RNA sequencing from GD19 placentas. Functional analysis suggested multiple changes in structural and functional genes important for placental health and function, with maximal dysregulation involving vascular and nutrient transport pathways. Concordantly, a ~10% decrease in birthweights and ~30% decrease in litter size was observed, supportive of placental insufficiency. We also found that the LG-H IUGR offspring exhibit increased risk for CVD at 4 months of age, manifesting as hypertension, increased abdominal fat, elevated leptin and total cholesterol concentrations. In summary, this animal model of IUGR links the placental transcriptional response to the stressor of gestational hypoxia to increased risk of developing cardiometabolic disease.

Poor Early Growth and Age-Associated Disease

The prevalence of age-associated disease is increasing at a striking rate globally and there is evidence to suggest that the ageing process may actually begin before birth. It has been well-established that the status of both the maternal and early postnatal environments into which an individual is exposed can have huge implications for the risk of developing age-associated disease, including cardiovascular disease (CVD), type-2 diabetes (T2D) and obesity in later life. Therefore, the dissection of underlying molecular mechanisms to explain this phenomenon, known as 'developmental programming' is a highly investigated area of research. This book chapter will examine the epidemiological evidence and the animal models of suboptimal maternal and early postnatal environments and will discuss the progress being made in the development of safe and effective intervention strategies which ultimately could target those 'programmed' individuals who are known to be at-risk of age-associated disease.

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 hypoxia impairs cardiac mitochondrial and ventricular function in guinea pig offspring in a sex-related manner

Adverse intrauterine conditions cause fetal growth restriction and increase the risk of adult cardiovascular disease. We hypothesize that intrauterine hypoxia impairs fetal heart function, is sustained after birth, and manifests as both cardiac and mitochondrial dysfunction in offspring guinea pigs (GPs). Pregnant GPs were exposed to 10.5% O₂ (HPX) at 50 days of gestation (full term = 65 days) or normoxia (NMX) for the duration of the pregnancy. Pups were allowed to deliver vaginally and raised in a NMX environment. At 90 days of age, mean arterial pressure (MAP) was measured in anesthetized GPs. NMX and prenatally HPX offspring underwent echocardiographic imaging for in vivo measurement of left ventricular cardiac morphology and function, and O₂ consumption rates and complex IV enzyme activity were measured from isolated cardiomyocytes and mitochondria, respectively. Prenatal HPX increased ( P < 0.01) MAP (52.3 ± 1.3 and 58.4 ± 1.1 mmHg in NMX and HPX, respectively) and decreased ( P < 0.05) stroke volume (439.8 ± 54.5 and 289.4 ± 15.8 μl in NMX and HPX, respectively), cardiac output (94.4 ± 11.2 and 67.3 ± 3.8 ml/min in NMX and HPX, respectively), ejection fraction, and fractional shortening in male, but not female, GPs. HPX had no effect on left ventricular wall thickness or end-diastolic volume in either sex. HPX reduced mitochondrial maximal respiration and respiratory reserve capacity and complex IV activity rates in hearts of male, but not female, GPs. Prenatal HPX is a programming stimulus that increases MAP and decreases cardiac and mitochondrial function in male offspring. Sex-related differences in the contractile and mitochondrial responses suggest that female GPs are protected from cardiovascular programming of prenatal HPX.

Prolonged prenatal hypoxia selectively disrupts collecting duct patterning and postnatal function in male mouse offspring

KEY POINTS

In the present study, we investigated whether hypoxia during late pregnancy impairs kidney development in mouse offspring, and also whether this has long-lasting consequences affecting kidney function in adulthood. Hypoxia disrupted growth of the kidney, particularly the collecting duct network, in juvenile male offspring. By mid-late adulthood, these mice developed early signs of kidney disease, notably a compromised response to water deprivation. Female offspring showed no obvious signs of impaired kidney development and did not develop kidney disease, suggesting an underlying protection mechanism from the hypoxia insult. These results help us better understand the long-lasting impact of gestational hypoxia on kidney development and the increased risk of chronic kidney disease.

ABSTRACT

Prenatal hypoxia is a common perturbation to arise during pregnancy, and can lead to adverse health outcomes in later life. The long-lasting impact of prenatal hypoxia on postnatal kidney development and maturation of the renal tubules, particularly the collecting duct system, is relatively unknown. In the present study, we used a model of moderate chronic maternal hypoxia throughout late gestation (12% O₂ exposure from embryonic day 14.5 until birth). Histological analyses revealed marked changes in the tubular architecture of male hypoxia-exposed neonates as early as postnatal day 7, with disrupted medullary development and altered expression of Ctnnb1 and Crabp2 (encoding a retinoic acid binding protein). Kidneys of the RARElacZ line offspring exposed to hypoxia showed reduced β-galactosidase activity, indicating reduced retinoic acid-directed transcriptional activation. Wild-type male mice exposed to hypoxia had an early decline in urine concentrating capacity, evident at 4 months of age. At 12 months of age, hypoxia-exposed male mice displayed a compromised response to a water deprivation challenge, which was was correlated with an altered cellular composition of the collecting duct and diminished expression of aquaporin 2. There were no differences in the tubular structures or urine concentrating capacity between the control and hypoxia-exposed female offspring at any age. The findings of the present study suggest that prenatal hypoxia selectively disrupts collecting duct patterning through altered Wnt/β-catenin and retinoic acid signalling and this results in impaired function in male mouse offspring in later life.

Modeling heart failure risk in diabetes and kidney disease: limitations and potential applications of transverse aortic constriction in high-fat-fed mice

There is an increased incidence of heart failure in individuals with diabetes mellitus (DM). The coexistence of kidney disease in DM exacerbates the cardiovascular prognosis. Researchers have attempted to combine the critical features of heart failure, using transverse aortic constriction, with DM in mice, but variable findings have been reported. Furthermore, kidney outcomes have not been assessed in this setting; thus its utility as a model of heart failure in DM and kidney disease is unknown. We generated a mouse model of obesity, hyperglycemia, and mild kidney pathology by feeding male C57BL/6J mice a high-fat diet (HFD). Cardiac pressure overload was surgically induced using transverse aortic constriction (TAC). Normal diet (ND) and sham controls were included. Heart failure risk factors were evident at 8-wk post-TAC, including increased left ventricular mass (+49% in ND and +35% in HFD), cardiomyocyte hypertrophy (+40% in ND and +28% in HFD), and interstitial and perivascular fibrosis (Masson's trichrome and picrosirius red positivity). High-fat feeding did not exacerbate the TAC-induced cardiac outcomes. At 11 wk post-TAC in a separate mouse cohort, echocardiography revealed reduced left ventricular size and increased left ventricular wall thickness, the latter being evident in ND mice only. Systolic function was preserved in the TAC mice and was similar between ND and HFD. Thus combined high-fat feeding and TAC in mice did not model the increased incidence of heart failure in DM patients. This model, however, may mimic the better cardiovascular prognosis seen in overweight and obese heart failure patients.

Sex-specific cardiovascular susceptibility to ischaemic myocardial injury following exposure to prenatal hypoxia

Cardiovascular diseases (CVDs) are the leading cause of mortality and hypertension contributes substantially to the incidence of stroke, coronary artery disease, heart failure, atrial fibrillation and peripheral vascular disease. The origin of hypertension is clearly multifactorial, and a complex and multifaceted approach is necessary to decrease its incidence. The most recognizable factors involved in reducing the incidence of hypertension are prevention, early diagnosis and treatment; however, the importance of the foetal environment and early postnatal development has recently been considered. In clinical practice, these factors are still frequently overlooked, probably because of a lack of knowledge about the underlying mechanisms and effective treatment or prevention. Pathophysiological mechanisms underlying the prenatal programming of CVDs were investigated in the study by Shah et al. published recently in Clinical Science (2017) 131(17), 2303–2317. The study explored cardiac susceptibility of adult male and female rat offspring to ischaemic myocardial injury due to prenatal exposure to hypoxia. The results demonstrated significant changes in global cardiac function and left ventricular dilatation following myocardial infarction in rat offspring prenatally exposed to hypoxia. The effects were gender specific and occurred only in males, whereas females were protected. These findings are important from several perspectives. First, they point to the fact that an inadequate foetal environment can increase susceptibility to death from myocardial infarction. Second, during their reproductive life, females are better protected from cardiovascular insult than males, but it is not known if they lose this advantage after menopause, and can be equally at risk as males.