Intrauterine Growth Restriction Females Research Articles

Fetal sex and the relative reactivity of human umbilical vein and arteries are key determinants in potential beneficial effects of phosphodiesterase inhibitors.

Intrauterine growth restriction (IUGR) is a common complication of pregnancy. We previously demonstrated that IUGR is associated with an impaired nitric oxide (NO)-induced relaxation in the human umbilical vein (HUV) of growth-restricted females compared to appropriate for gestational age (AGA) newborns. We found that phosphodiesterase (PDE) inhibition improved NO-induced relaxation in HUV, suggesting that PDEs could represent promising targets for therapeutic intervention. This study aimed to investigate the effects of PDE inhibition on human umbilical arteries (HUAs) compared to HUV. Umbilical vessels were collected in IUGR and AGA term newborns. NO-induced relaxation was studied using isolated vessel tension experiments in the presence or absence of the nonspecific PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX). PDE1B, PDE1C, PDE3A, PDE4B, and PDE5A were investigated by Western blot. NO-induced vasodilation was similar between IUGR and AGA HUAs. In HUAs precontracted with serotonin, IBMX enhanced NO-induced relaxation only in IUGR females, whereas in HUV IBMX increased NO-induced relaxation in all groups except IUGR males. In umbilical vessels preconstricted with the thromboxane A2 analog U46619, IBMX improved NO-induced relaxation in all groups to a greater extent in HUV than HUAs. However, the PDE protein content was higher in HUAs than HUV in all study groups. Therefore, the effects of PDE inhibition depend on the presence of IUGR, fetal sex, vessel type, and vasoconstrictors implicated. Despite a higher PDE protein content, HUAs are less sensitive to IBMX than HUV, which could lead to adverse effects of PDE inhibition in vivo by impairment of the fetoplacental hemodynamics.NEW & NOTEWORTHY The effects of phosphodiesterase inhibition on the umbilical circulation depend on the presence of intrauterine growth restriction, the fetal sex, vessel type, and vasoconstrictors implicated. The human umbilical vascular tone regulation is complex and depends on the amount and activity of specific proteins but also probably on the subcellular organization mediating protein interactions. Therefore, therapeutic interventions using phosphodiesterase inhibitors to improve the placental-fetal circulation should consider fetal sex and both umbilical vein and artery reactivity.

Abstract 028: Sex Differences In Hypertension And Cerebral Oxidative Stress Of Preeclamptic Rat Offspring

Intrauterine growth restriction (IUGR) occurs when the fetus doesn’t receive adequate nutrients. The leading cause of IUGR is placental ischemia, often seen in preeclampsia (PE). Adult IUGR offspring have an increased risk of HTN and oxidative stress (OS), with sex differences. Studies have shown that IUGR males have HTN, cerebrovascular dysfunction (CVD), and cerebral OS at 17 wks; IUGR females are NT with limited CVD and no significant OS. Our study aims to characterize the sex differences in timing and changes of cerebral OS in IUGR offspring. HTN and OS are both present in adult IUGR males, however, the order and timing is unknown. We hypothesize that OS leads to HTN. To test this, we examined the changes in brain OS in 12 wk IUGR and control (CON) males (before HTN), and 17 wk IUGR males (which have HTN) vs CON males. We investigated the same time points in NT females. We divided pups from normal pregnant and PE Sprague-Dawley rats into groups based on pregnancy status and sex. Pups were aged to 12 and 17 wks. We collected brains to measure OS via western blot (Manganese superoxide dismutase) and colorimetric assays: hydrogen peroxide (H 2 O 2 ) and total antioxidant capacity (TAC). 12 wk IUGR and CON offspring were NT with no changes between groups or sex. There were no changes in cerebral H 2 O 2 , TAC, and MnSOD for IUGR offspring compared to their CON. At 17 wks, IUGR males had elevated mean arterial pressure (MAP; 143.0 ± 1.7 vs 133.0 ± 2.7 mmHg; p < 0.01). IUGR females were NT. Cerebral H2O2 levels in IUGR males were elevated (20.5 ± 8.0 vs 3.7 ± 1.0 uM/ mg Protein; p < 0.05) and unchanged in IUGR females. TAC in IUGR males was decreased (157.7 ±21.9 vs 234.9 ± 22.0 mM Trolox/mg Protein; p < 0.05) and unchanged in IUGR females. MnSOD was elevated in females with no differences between groups (150.4 ± 3.8 vs 110.9 ±7.1 IU/Protein/CON%; p < 0.002). All 12 wk rats were NT with no changes in cerebral OS. At 17 wks, IUGR males were HTN with elevated cerebral OS, with no changes in females. The lack of increase in OS at 12 wks, suggest that it’s not a precursor to HTN in males, but rather OS is a downstream effect from HTN. Future studies will look at factors that contribute to HTN and CVD in in IUGR offspring. Studies will also examine why 17 wk female IUGR are protected from HTN and cerebral OS.

Abstract P210: Sex Specific Changes In Cerebral Proinflammatory Cytokines In Intrauterine Growth Restricted Offspring

Background: Intrauterine growth restriction (IUGR) often times results from placental ischemia, which restricts the distribution of nutrients and oxygen to meet the metabolic demand of the growing fetus. IUGR offspring (OS) have an increased risk for developing cerebrovascular diseases (CVD) later in life. Factors for development of CVDs are HTN and inflammation. Our lab has shown 17 week IUGR male rats from preeclamptic pregnancies have HTN and elevated inflammation via systemic IL-17, while our females show no change. The role of inflammation to cause HTN in IUGR offspring in a sex specific manner is unknown and the major focus of this study which examines the changes in cerebral inflammation IUGR offspring at 12 weeks. We hypothesize that cerebral inflammation in IUGR males will be elevated, while no change in female IUGR offspring will be observed. Methods: IUGR offspring originate from preeclamptic Sprague Dawley dams. OS weaned for 3 weeks and were separated by sex and IUGR status. At 12 weeks, the rats underwent carotid catheterization to measure BP. Brains were collected to measure pro-inflammatory cytokines, such as TNF-α and IL-17 via ELISAs. Results: At 12 weeks, all OS were normotensive. Brain TNF-α increased in female IUGR (17,366± 1,500 vs 8,116± 1,341 pg/mL, p<0.05) and was elevated in male IUGR (20,845±7571 vs 8,516±1712 pg/mL, ns). Brain IL-17 increased in male IUGR (13,580± 945 vs 9,620± 945 pg/mL, p<0.05) and was elevated in female IUGR (13,143± 1613 vs 10,930± 696 pg/mL, ns). Systemic IL-17 was increased in IUGR male OS (112±16.8vs100±3.9 IU/Protein/CON %, ns). Conclusion: At 12 weeks, brain TNF-α and IL-17 were elevated in IUGR males and females. The differences in expression of each cytokine between the sexes suggest that IL-17 contributes to the increase in BP, especially in males. Understanding the timing of these developments could help to elucidate the role of inflammation in the development of CVD with or without HTN. This study is clinically relevant as it provides a sex specific inflammatory target for therapeutics, to help prevent hypertension and CVD in IUGR offspring. In the future, we will evaluate the role of inflammation in IUGR offspring in a sex specific manner.

Sexual Dimorphism in the Closure of the Hippocampal Postnatal Critical Period of Synaptic Plasticity after Intrauterine Growth Restriction: Link to Oligodendrocyte and Glial Dysregulation

Intrauterine growth restriction (IUGR) resulting from hypertensive disease of pregnancy (HDP) leads to sexually dimorphic hippocampal-dependent cognitive and memory impairment in humans. In our translationally relevant mouse model of IUGR incited by HDP, we have previously shown that the synaptic development in the dorsal hippocampus including GABAergic development, NPTX2⁺ excitatory synaptic formation, axonal myelination, and perineural net (PNN) formation were perturbed by IUGR at adolescent equivalence in humans (P40). The persistence of these disturbances through early adulthood and the potential upstream mechanisms are currently unknown. Thus, we hypothesized that NPTX2⁺ expression, PNN formation, axonal myelination, all events closing synaptic development in the hippocampus, will be persistently perturbed, particularly affecting IUGR female mice through P60 given the fact that they had worse short-term recognition memory in this model. We additionally hypothesized that such sexual dimorphism is linked to persistent glial dysregulation. We induced IUGR by a micro-osmotic pump infusion of a potent vasoconstrictor U-46619, a thromboxane A₂-analog, in the last week of the C57BL/6 mouse gestation to precipitate HDP. Sham-operated mice were used as controls. At P60, we assessed hippocampal and hemispheric volumes, NPTX2 expression, PNN formation, as well as myelin basic protein (MBP), Olig2, APC/CC1, and M-NF expression. We also evaluated P60 astrocytic (GFAP) reactivity and microglial (Iba1 and TMEM119) activation using immunofluorescent-immunohistochemistry and Imaris morphological analysis plus cytokine profiling using Meso Scale Discovery platform. IUGR offspring continued to have smaller hippocampal volumes at P60 not related to changes in hemisphere volume. NPTX2⁺ puncta counts and volumes were decreased in IUGR hippocampal CA subregions of female mice compared to sex-matched shams. Intriguingly, NPTX2⁺ counts and volumes were concurrently increased in the dentate gyrus (DG) subregion. PNN volumes were smaller in CA1 and CA3 of IUGR female mice along with PNN intensity in CA3 but they had larger volumes in the CA3 of IUGR male mice. The myelinated axon (MBP⁺) areas, volumes, and lengths were all decreased in the CA1 of IUGR female mice compared to sex-matched shams, which correlated with a decrease in Olig2 nuclear expression. No decrease in the number of APC/CC1⁺ mature oligodendrocytes was identified. We noted an increase in M-NF expression in the mossy fibers connecting DG to CA3 only in IUGR female mice. Reactive astrocytes denoted by GFAP areas, volumes, lengths, and numbers of branching were increased in IUGR female CA1 but not in IUGR male CA3 compared to sex-matched shams. Lastly, activated microglia were only detected in IUGR female CA1 and CA3 subregions. We detected no difference in the cytokine profile between sham and IUGR adult mice of either sex. Collectively, our data support a sexually dimorphic impaired closure of postnatal critical period of synaptic plasticity in the hippocampus of young adult IUGR mice with greater effects on females. A potential mechanism supporting such dimorphism may include oligodendrocyte dysfunction in IUGR females limiting myelination, allowing axonal overgrowth followed by a reactive glial-mediated synaptic pruning.

Placental insufficiency contributes to fatty acid metabolism alterations in aged female mouse offspring.

Intrauterine growth restriction (IUGR) is an accepted risk factor for metabolic disorders in later life, including obesity and type 2 diabetes. The level of metabolic dysregulation can vary between subjects and is dependent on the severity and the type of IUGR insult. Classical IUGR animal models involve nutritional deprivation of the mother or uterine artery ligation. The latter aims to mimic a placental insufficiency, which is the most frequent cause of IUGR. In this study, we investigated whether IUGR attributable to placental insufficiency impacts the glucose and lipid homeostasis at advanced age. Placental insufficiency was achieved by deletion of the transcription factor AP-2y ( Tfap2c), which serves as one of the major trophoblast differentiation regulators. TdelT-IUGR mice were obtained by crossing mice with a floxed Tfap2c allele and mice with Cre recombinase under the control of the Tpbpa promoter. In advanced adulthood (9-12 mo), female and male IUGR mice are respectively 20% and 12% leaner compared with controls. At this age, IUGR mice have unaffected glucose clearance and lipid parameters (cholesterol, triglycerides, and phospholipids) in the liver. However, female IUGR mice have increased plasma free fatty acids (+87%) compared with controls. This is accompanied by increased mRNA levels of fatty acid synthase and endoplasmic reticulum stress markers in white adipose tissue. Taken together, our results suggest that IUGR by placental insufficiency may lead to higher lipogenesis in female mice in advanced adulthood, at least indicated by greater Fasn expression. This effect was sex specific for the aged IUGR females.

Role of fetal nutrient restriction and postnatal catch-up growth on structural and mechanical alterations of rat aorta.

Intrauterine growth restriction (IUGR), induced by maternal undernutrition, leads to impaired aortic development. This is followed by hypertrophic remodelling associated with accelerated growth during lactation. Fetal nutrient restriction is associated with increased aortic compliance at birth and at weaning, but not in adult animals. This mechanical alteration may be related to a decreased perinatal collagen deposition. Aortic elastin scaffolds purified from young male and female IUGR animals also exhibit increased compliance, only maintained in adult IUGR females. These mechanical alterations may be related to differences in elastin deposition and remodelling. Fetal undernutrition induces similar aortic structural and mechanical alterations in young male and female rats. Our data argue against an early mechanical cause for the sex differences in hypertension development induced by maternal undernutrition. However, the larger compliance of elastin in adult IUGR females may contribute to the maintenance of a normal blood pressure level. Fetal undernutrition programmes hypertension development, males being more susceptible. Deficient fetal elastogenesis and vascular growth is a possible mechanism. We investigated the role of aortic mechanical alterations in a rat model of hypertension programming, evaluating changes at birth, weaning and adulthood. Dams were fed ad libitum (Control) or 50% of control intake during the second half of gestation (maternal undernutrition, MUN). Offspring aged 3days, 21days and 6months were studied. Blood pressure was evaluated in vivo. In the thoracic aorta we assessed gross structure, mechanical properties (intact and purified elastin), collagen and elastin content and internal elastic lamina (IEL) organization. Only adult MUN males developed hypertension (systolic blood pressure: MUNmales =176.6±5.6mmHg; Controlmales =136.1±4.9mmHg). At birth MUN rats were lighter, with smaller aortic cross-sectional area (MUNmales =(1.51±0.08)×105 μm2 , Controlmales =(2.8±0.04)×105 μm2 ); during lactation MUN males and females exhibited catch-up growth and aortic hypertrophy (MUNmales =(14.5±0.5)×105 μm2 , Controlmales =(10.4±0.9)×105 μm2 ), maintained until adulthood. MUN aortas were more compliant until weaning (functional stiffness: MUNmales =1.0±0.04; Controlmales =1.3±0.03), containing less collagen with larger IEL fenestrae, returning to normal in adulthood. Purified elastin from young MUN offspring was more compliant in both sexes; only MUN adult females maintained larger elastin compliance (slope: MUNfemales =24.1±1.9; Controlfemales =33.3±2.8). Fetal undernutrition induces deficient aortic development followed by hypertrophic remodelling and larger aortic compliance in the perinatal period, with similar alterations in collagen and elastin in both sexes. The observed alterations argue against an initial mechanical cause for sex differences in hypertension development. However, the maintenance of high elastin compliance in adult females might protect them against blood pressure rise.

Foetal growth restriction in mice modifies postnatal airway responsiveness in an age and sex-dependent manner.

Epidemiological studies demonstrate an association between intrauterine growth restriction (IUGR) and asthma; however the underlying mechanism is unknown. We investigated the impact of maternal hypoxia-induced IUGR on airway responsiveness in male and female mice during juvenility and adulthood. Pregnant BALB/c mice were housed under hypoxic conditions for gestational days 11-17.5 and then returned to normoxic conditions for the remainder of pregnancy. A control group was housed under normoxic conditions throughout pregnancy. Offspring were studied at 2 weeks (juveniles) and 8 weeks (adults), where lung volume was assessed by plethysmography, airway responsiveness to methacholine determined by the forced oscillation technique and lungs fixed for morphometry. IUGR offspring were lighter at birth, exhibited "catch-up growth" by 2 weeks, but were again lighter in adulthood. IUGR males were "hyper-responsive" at 2 weeks and "hypo-responsive" as adults, in contrast with IUGR females who were hyper-responsive in adulthood. IUGR males had increased inner and total wall thickness at 2 weeks which resolved by adulthood, while airways in IUGR females were structurally normal throughout life. There were no differences in lung volume between Control and IUGR offspring at any age. Our data demonstrate changes in airway responsiveness as a result of IUGR that could influence susceptibility to asthma development and contribute to sexual dimorphism in asthma prevalence which switches from a male dominated disease in early life to a female dominated disease in adulthood.

Effect of moderate, 30 percent global maternal nutrient reduction on fetal and postnatal baboon phenotype.

Most developmental programming studies on maternal nutrient reduction (MNR) are in altricial rodents whose maternal nutritional burden and offspring developmental trajectory differ from precocial non-human primates and humans. Control (CTR) baboon mothers ate ad libitum; MNR mothers ate 70% global control diet in pregnancy and lactation. We present offspring morphometry, blood cortisol, and adrenocorticotropin (ACTH) during second half of gestation (G) and first three postnatal years. Moderate MNR produced intrauterine growth restriction (IUGR). IUGR males (n=43) and females (n=28) were smaller than CTR males (n=50) and females (n=47) in many measurements at many ages. In CTR, fetal ACTH increased 228% and cortisol 48% between 0.65G and 0.9G. IUGR ACTH was elevated at 0.65G and cortisol at 0.9G. 0.9G maternal gestational weight gain, fetal weight, and placenta weight were correlated. Moderate IUGR decreased body weight and morphometric measurements at key time points and altered hypothalamo-pituitary-adrenal function.

Fatty Acid de Novo Synthesis in Adult Intrauterine Growth‐Restricted Offspring, and Adult Male Response to a High Fat Diet

Intrauterine growth restriction (IUGR) with rapid catch-up growth leads to adult obesity and insulin resistance. We have previously shown that IUGR male rats demonstrated increased de novo fatty acid synthesis in the subcutaneous (SC) fat, but not the visceral fat, during the nursing period prior to the onset of obesity. Young IUGR females do not exhibit the same increase. We further hypothesized that in male IUGR offspring, de novo synthesis is a programmed intrinsic effect that persists to adulthood and does not suppress in response to a high fat diet. We measured fatty acid de novo synthesis in IUGR adult males (6months) using deuterium-enriched drinking water as a stable isotope tracer, then further studied the response after consumption of an isocaloric high fat diet. Baseline de novo synthesis in adult females was also studied at age 9months. Males demonstrated increased baseline de novo synthesis in both SC fat and visceral fat. Correspondingly, SC and visceral fat protein expression of lipogenic enzymes acetyl-coA carboxylase-α (ACCα) and fatty acid synthase were upregulated. After the isocaloric high fat diet, de novo synthesis was suppressed such that no differences remained between the two groups, although, IUGR SC fat demonstrated persistently increased lipogenic protein expression. In contrast, de novo synthesis among adult females is not impacted in IUGR. In conclusion, enhancement of male IUGR SC fat de novo synthesis appears to be an early consequence of metabolic programming, whereas enhancement in visceral fat appears to be a later consequence.

IUGR prevents IGF-1 upregulation in juvenile male mice by perturbing postnatal IGF-1 chromatin remodeling.

Intrauterine growth restriction (IUGR) offspring with rapid catch-up growth are at increased risk for early obesity especially in males. Persistent insulin-like growth factor-1 (IGF-1) reduction is an important risk factor. Using a mouse model of maternal hypertension-induced IUGR, we examined IGF-1 levels, promoter DNA methylation, and histone H3 covalent modifications at birth (D1). We additionally investigated whether prenatal perturbations could reset at preadolescence (D21). IUGR was induced via maternal thromboxane A2-analog infusion in mice. IUGR uniformly decreased D1 IGF-1 mRNA and protein levels with reduced promoter 1 (P1) transcription and increased P1 DNA methylation. IUGR males also had increased H3K4ac at exon 5 and 3' distal UTR. At D21, IUGR males continued to have decreased IGF-1 levels, originating from both P1 and P2 with reduced 1A variant. IUGR males also had decreased activation mark of H3K4me3 at P1 compared with sham males. In contrast, D21 IUGR females normalized their IGF-1 levels, in association with an increased activation mark of H3K4me3 at P1 compared with sham females. IUGR uniformly affected D1 hepatic IGF-1 epigenetic modifications in both sexes. However, at preadolescence, IUGR males are unable to correct for the prenatal reduction possibly due to a more perturbed IGF-1 chromatin structure.

Exposure to social defeat stress in adolescence improves the working memory and anxiety-like behavior of adult female rats with intrauterine growth restriction, independently of hippocampal neurogenesis

Intrauterine growth restriction (IUGR) is a risk factor for memory impairment and emotional disturbance during growth and adulthood. However, this risk might be modulated by environmental factors during development. Here we examined whether exposing adolescent male and female rats with thromboxane A2-induced IUGR to social defeat stress (SDS) affected their working memory and anxiety-like behavior in adulthood. We also used BrdU staining to investigate hippocampal cellular proliferation and BrdU and NeuN double staining to investigate neural differentiation in female IUGR rats. In the absence of adolescent stress, IUGR female rats, but not male rats, scored significantly lower in the T-maze test of working memory and exhibited higher anxiety-like behavior in the elevated-plus maze test compared with controls. Adolescent exposure to SDS abolished these behavioral impairments in IUGR females. In the absence of adolescent stress, hippocampal cellular proliferation was significantly higher in IUGR females than in non-IUGR female controls and was not influenced by adolescent exposure to SDS. Hippocampal neural differentiation was equivalent in non-stressed control and IUGR females. Neural differentiation was significantly increased by adolescent exposure to SDS in controls but not in IUGR females. There was no significant difference in the serum corticosterone concentrations between non-stressed control and IUGR females; however, adolescent exposure to SDS significantly increased serum corticosterone concentration in control females but not in IUGR females. These results demonstrate that adolescent exposure to SDS improves behavioral impairment independent of hippocampal neurogenesis in adult rats with IUGR.

UCP1 is present in porcine adipose tissue and is responsive to postnatal leptin.

Intrauterine growth restriction (IUGR) may be accompanied by inadequate thermoregulation, especially in piglets that are not considered to possess any brown adipose tissue (BAT) and are thus entirely dependent on shivering thermogenesis in order to maintain body temperature after birth. Leptin can stimulate heat production by promoting non-shivering thermogenesis in BAT, but whether this response occurs in piglets is unknown. Newborn female piglets that were characterised as showing IUGR (mean birth weight of approximately 0.98 kg) were therefore administered injections of either saline or leptin once a day for the first 5 days of neonatal life. The dose of leptin was 0.5 mg/kg, which is sufficient to increase plasma leptin by approximately tenfold and on the day of birth induced a rapid increase in body temperature to values similar to those of normal-sized 'control' piglets (mean birth weight of ∼1.47 kg). Perirenal adipose tissue was then sampled from all offspring at 21 days of age and the presence of the BAT-specific uncoupling protein 1 (UCP1) was determined by immunohistochemistry and immunoblotting. UCP1 was clearly detectable in all samples analysed and its abundance was significantly reduced in the IUGR piglets that had received saline compared with controls, but was raised to the same amount as in controls in those IUGR females given leptin. There were no differences in gene expression between primary markers of brown and white adipose tissues between groups. In conclusion, piglets possess BAT that when stimulated exogenously by leptin can promote increased body temperature.

Gender-specific heart rate dynamics in severe intrauterine growth-restricted fetuses

BackgroundManagement of intrauterine growth restriction (IUGR) remains a major issue in perinatalogy. AimsThe objective of this paper was the assessment of gender-specific fetal heart rate (FHR) dynamics as a diagnostic tool in severe IUGR. SubjectsFHR was analyzed in the antepartum period in 15 severe IUGR fetuses and 18 controls, matched for gestational age, in relation to fetal gender. Outcome measuresLinear and entropy methods, such as mean FHR (mFHR), low (LF), high (HF) and movement frequency (MF), approximate, sample and multiscale entropy. Sensitivities and specificities were estimated using Fisher linear discriminant analysis and the leave-one-out method. ResultsOverall, IUGR fetuses presented significantly lower mFHR and entropy compared with controls. However, gender-specific analysis showed that significantly lower mFHR was only evident in IUGR males and lower entropy in IUGR females. In addition, lower LF/(MF+HF) was patent in IUGR females compared with controls, but not in males. Rather high sensitivities and specificities were achieved in the detection of the FHR recordings related with IUGR male fetuses, when gender-specific analysis was performed at gestational ages less than 34weeks. ConclusionsSevere IUGR fetuses present gender-specific linear and entropy FHR changes, compared with controls, characterized by a significantly lower entropy and sympathetic-vagal balance in females than in males. These findings need to be considered in order to achieve better diagnostic results.

The effect of hypoxia-induced intrauterine growth restriction on renal artery function.

The risk of developing cardiovascular diseases is known to begin before birth and the impact of the intrauterine environment on subsequent adult health is currently being investigated from many quarters. Following our studies demonstrating the impact of hypoxia in utero and consequent intrauterine growth restriction (IUGR) on the rat cardiovascular system, we hypothesized that changes extend throughout the vasculature and alter function of the renal artery. In addition, we hypothesized that hypoxia induces renal senescence as a potential mediator of altered vascular function. We demonstrated that IUGR females had decreased responses to the adrenergic agonist phenylephrine (PE; pEC50 6.50 ± 0.05 control v. 6.17 ± 0.09 IUGR, P < 0.05) and the endothelium-dependent vasodilator methylcholine (MCh; E max 89.8 ± 7.0% control v. 41.0 ± 6.5% IUGR, P < 0.001). In IUGR females, this was characterised by increased basal nitric oxide (NO) modulation of vasoconstriction (PE pEC50 6.17 ± 0.09 IUGR v. 6.42 ± 0.08 in the presence of the NO synthase inhibitor N-nitro-l-arginine methyl ester hydrochloride (l-NAME; P < 0.01) but decreased activated NO modulation (no change in MCh responses in the presence of l-NAME), respectively. In contrast, IUGR males had no changes in PE or MCh responses but demonstrated increased basal NO (PE pEC50 6.29 ± 0.06 IUGR v. 6.42 ± 0.12 plus l-NAME, P < 0.01) and activated NO (E max 37.8 ± 9.4% control v. -0.8 ± 13.0% plus l-NAME, P < 0.05) modulation. No significant changes were found in gross kidney morphology, proteinuria or markers of cellular senescence in either sex. In summary, renal vascular function was altered by hypoxia in utero in a sex-dependent manner but was unlikely to be mediated by premature renal senescence.

Novel thromboxane A2 analog-induced IUGR mouse model.

Rodents, particularly rats, are used in the majority of intrauterine growth restriction (IUGR) research. An important tool that is lacking in this field is the ability to impose IUGR on transgenic mice. We therefore developed a novel mouse model of chronic IUGR using U-46619, a thromboxane A2 (TXA2) analog, infusion. TXA2 overproduction is prevalent in human pregnancies complicated by cigarette smoking, diabetes mellitus and preeclampsia. In this model, U-46619 micro-osmotic pump infusion in the last week of C57BL/6J mouse gestation caused maternal hypertension. IUGR pups weighed 15% less, had lighter brain, lung, liver and kidney weights, but had similar nose-to-anus lengths compared with sham pups at birth. Metabolically, IUGR pups showed increased essential branched-chain amino acids. They were normoglycemic yet hypoinsulinemic. They showed decreased hepatic mRNA levels of total insulin-like growth factor-1 and its variants, but increased level of peroxisome proliferator-activated receptor-gamma coactivator-1 alpha. IUGR offspring were growth restricted from birth (P1) through postnatal day 21 (P21). IUGR males caught up with sham males in weight by P28, whereas IUGR females caught up with sham females by P77. IUGR males surpassed sham males in weight by P238. In summary, we have a non-brain sparing IUGR mouse model that has a relative ease of surgical IUGR induction and exhibits features similar to the chronic IUGR offspring of humans and other animal models. As transgenic technology predominates in mice, this model now permits the imposition of IUGR on transgenic mice to interrogate mechanisms of fetal origins of adult disease.

Intrauterine Growth Restriction Alters Hippocampal Expression and Chromatin Structure of Cyp19a1 Variants

We evaluated the impact of uteroplacental insufficiency (UPI), and subsequent intrauterine growth restriction (IUGR), on serum testosterone and hippocampal expression of Cyp19a1 variants and aromatase in rats. Additionally, we determined UPI induced histone modification of the promoter regions of Cyp19a1 variants using chromatin immunoprecipitation. Cyp19a1 is the gene encoding the protein aromatase, that catalyzes the biosynthesis of estrogens from androgens and is necessary for masculinization of the brain. IUGR was induced via bilateral uterine artery. UPI increased serum testosterone in day of life 0 (D0) and day of life 21 (D21) IUGR males to 224% and 299% of control values, respectively. While there was no significant impact of UPI on testosterone in D0 females, testosterone in D21 IUGR females was 187% of controls. Cyp19a1 variant 1.f and variant II are expressed in the rat hippocampus at D0 and D21. UPI significantly reduced expression of Cyp19a1 variant 1.f in D0 males, with no impact in females. Similarly at D0, UPI reduced expression of aromatase, the protein encoded by Cyp19a1, in males. Dimethylation of H3K4 was increased in the promoter region of variant 1.f (P1.f) and trimethylation of H3K4 was decreased in the promoter region of variant II (PII). At D21, dimethylation of H3K4 is significantly reduced in PII of IUGR males. We conclude that UPI increases serum testosterone and reduces Cyp19a1 variant 1.f expression in the hippocampus of D0 IUGR males. Additionally, UPI alters the chromatin structure of CYP19a1 at both D0 and D21.

Mechanisms of endothelium-dependent vasodilation in male and female, young and aged offspring born growth restricted

Numerous epidemiological studies have shown that cardiovascular dysfunction in adult life may be programmed by compromised growth in utero. Aging is a risk factor for vascular endothelial-dependent dysfunction. After birth, the impact of intrauterine growth restriction (IUGR) on normal aging mechanisms of vascular dysfunction is not known. We hypothesized that IUGR would cause changes in vascular function that would affect the mechanisms of endothelium-dependent vasodilation later in life in an age- or sex-dependent manner. To create an IUGR model, pregnant Sprague-Dawley rats were placed in a hypoxic (12% O(2)) or control (room air, 21% O(2)) environment from days 15 to 21 of the pregnancy, and both male and female offspring were investigated at 4 or 12 mo of age. Endothelial function was assessed in small mesenteric arteries using methacholine (MCh)-induced vasodilation in a wire myograph system. The involvement of nitric oxide (NO), prostaglandins, and endothelium-derived hyperpolarizing factor (EDHF) was assessed using the inhibitors N(omega)-nitro-l-arginine methyl ester hydrochloride, meclofenamate, or a combination of apamin and TRAM-34 (SK(Ca) and IK(Ca) blockers), respectively. EDHF-induced vasodilation was further investigated by using inhibitors of P450 epoxygenases [N-methylsulfonyl-6-(2-propargyloxyphenyl) hexanamide] and gap junctions (18alpha-glycyrrhetinic acid). NO-mediated vasodilation was significantly reduced in aged controls and both young and aged IUGR females. EDHF-mediated vasodilation was maintained in all groups; however, an additional involvement of gap junctions was found in females exposed to hypoxia in utero, which may represent a compensatory mechanism. A change in the mechanisms of vasodilation occurring at an earlier age in IUGR offspring may predispose them to adult cardiovascular diseases.

Uteroplacental insufficiency affects kidney VEGF expression in a model of IUGR with compensatory glomerular hypertrophy and hypertension

Low nephron endowment secondary to intrauterine growth restriction (IUGR) results in compensatory hypertrophy of the remaining glomeruli, which in turn is associated with hypertension. However, gender differences exist in the response of the kidney to injury, and IUGR female offspring seems protected from an unfavorable outcome. We previously reported differences in gender-specific gene expression in the IUGR kidney as well as increased circulating corticosterone levels following uteroplacental insufficiency (UPI). Vascular endothelial growth factor (VEGF), which is critical for renal development, is an important candidate in the IUGR kidney since its expression can be regulated by sex-steroids and glucocorticoids. We hypothesize that IUGR leads to altered kidney VEGF expression in a gender-specific manner. Following uterine ligation in the pregnant rat, UPI decreases renal VEGF levels in male and female IUGR animals at birth and through postnatal day 21. However, by day 120 of life, IUGR females have increased kidney VEGF expression, not present in the IUGR males. In addition, IUGR males exhibit increased serum testosterone levels as well as proteinuria. These findings are intriguing in light of the difference in glomerular hypertrophy observed: IUGR males show increased glomerular area when compared to IUGR females. In this model characterized by decreased nephron number and adult onset hypertension, UPI decreases renal VEGF expression during nephrogenesis. Our most intriguing finding is the increased renal VEGF levels in adult IUGR females, associated with a more benign phenotype. We suggest that the mechanisms underlying renal disease in response to IUGR are most likely regulated in a gender specific manner.