Sildenafil citrate treatment enhances amino acid availability in the conceptus and fetal growth in an ovine model of intrauterine growth restriction

Maternal tadalafil treatment does not increase uterine artery blood flow or oxygen delivery in the pregnant ewe

Increasing placental perfusion (PP) could improve outcomes of growth-restricted fetuses. One way of increasing PP may be by using phosphodiesterase (PDE)-5 inhibitors, which induce vasodilatation of vascular beds. We used a combination of clinically relevant magnetic resonance imaging (MRI) techniques to characterize the impact that tadalafil infusion has on maternal, placental and fetal circulations. At 116-117 days' gestational age (dGA; term, 150 days), pregnant ewes (n = 6) underwent fetal catheterization surgery. At 120-123 dGA ewes were anaesthetized and MRI scans were performed during three acquisition windows: a basal state and then ∼15-75 min (TAD 1) and ∼75-135 min (TAD 2) post maternal administration (24 mg; intravenous bolus) of tadalafil. Phase contrast MRI and T2 oximetry were used to measure blood flow and oxygen delivery. Placental diffusion and PP were assessed using the Diffusion-Relaxation Combined Imaging for Detailed Placental Evaluation-'DECIDE' technique. Uterine artery (UtA) blood flow when normalized to maternal left ventricular cardiac output (LVCO) was reduced in both TAD periods. DECIDE imaging found no impact of tadalafil on placental diffusivity or fetoplacental blood volume fraction. Maternal-placental blood volume fraction was increased in the TAD 2 period. FetalD O 2 ${D_{{{\mathrm{O}}_2}}}$ andV ̇ O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ were not affected by maternal tadalafil administration. Maternal tadalafil administration did not increase UtA blood flow and thus may not be an effective vasodilator at the level of the UtAs. The increased maternal-placental blood volume fraction may indicate local vasodilatation of the maternal intervillous space, which may have compensated for the reduced proportion of UtAD O 2 ${D_{{{\mathrm{O}}_2}}}$ .

Childhood outcomes after maternal antenatal sildenafil treatment for severe early-onset fetal growth restriction: a randomized trial (STRIDER NZAus)

In this follow-up at 2.5 years of children from the STRIDER NZAus Trial (N = 112), in which women with singleton pregnancies affected by severe early fetal growth restriction were randomized to sildenafil citrate 75 mg daily or placebo until 32 weeks, there was no difference between groups in survival without neurosensory impairment, defined as any of cerebral palsy, deafness, blindness, cognitive delay (Bayley III cognition or language score >1 SD below mean) or motor delay: 30/56[54%] vs. 34/56[61%]; aOR = 0.74, 95%CI: 0.31, 1.77. However, children exposed to sildenafil appeared to be more likely to have cognitive delay (13/45[29%] vs. 4/40[10%]; aOR = 3.71, 95% CI: 1.01, 13.63) but less likely to have emotional-behavioural difficulties (2/43[5%] vs. 8/38[21%]; aOR = 0.19, 95%CI: 0.03, 1.00). Conclusion: maternal sildenafil treatment for severe early-onset FGR was not associated with altered survival free of neurosensory impairment at 2.5 years' corrected age.

Interventions affecting the nitric oxide pathway versus placebo or no therapy for fetal growth restriction in pregnancy

BACKGROUND

Fetal growth restriction (FGR) is a condition of poor growth of the fetus in utero. One of the causes of FGR is placental insufficiency. Severe early-onset FGR at < 32 weeks of gestation occurs in an estimated 0.4% of pregnancies. This extreme phenotype is associated with a high risk of fetal death, neonatal mortality, and neonatal morbidity. Currently, there is no causal treatment, and management is focused on indicated preterm birth to prevent fetal death. Interest has risen in interventions that aim to improve placental function by administration of pharmacological agents affecting the nitric oxide pathway causing vasodilatation.

OBJECTIVES

The objective of this systematic review and aggregate data meta-analysis is to assess the beneficial and harmful effects of interventions affecting the nitric oxide pathway compared with placebo, no therapy, or different drugs affecting this pathway against each other, in pregnant women with severe early-onset FGR.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (16 July 2022), and reference lists of retrieved studies.

SELECTION CRITERIA

We considered all randomised controlled comparisons of interventions affecting the nitric oxide pathway compared with placebo, no therapy, or another drug affecting this pathway in pregnant women with severe early-onset FGR of placental origin, for inclusion in this review.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane Pregnancy and Childbirth methods for data collection and analysis.

MAIN RESULTS

We included a total of eight studies (679 women) in this review, all of which contributed to the data and analysis. The identified studies report on five different comparisons: sildenafil compared with placebo or no therapy, tadalafil compared with placebo or no therapy, L-arginine compared with placebo or no therapy, nitroglycerin compared with placebo or no therapy and sildenafil compared with nitroglycerin. The risk of bias of included studies was judged as low or unclear. In two studies the intervention was not blinded. The certainty of evidence for our primary outcomes was judged as moderate for the intervention sildenafil and low for tadalafil and nitroglycerine (due to low number of participants and low number of events). For the intervention L-arginine, our primary outcomes were not reported. Sildenafil citrate compared to placebo or no therapy (5 studies, 516 women) Five studies (Canada, Australia and New Zealand, the Netherlands, the UK and Brazil) involving 516 pregnant women with FGR were included. We assessed the certainty of the evidence as moderate. Compared with placebo or no therapy, sildenafil probably has little or no effect on all-cause mortality (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.80 to 1.27, 5 studies, 516 women); may reduce fetal mortality (RR 0.82, 95% CI 0.60 to 1.12, 5 studies, 516 women), and increase neonatal mortality (RR 1.45, 95% CI 0.90 to 2.33, 5 studies, 397 women), although the results are uncertain for fetal and neonatal mortality as 95% confidence intervals are wide crossing the line of no effect. Tadalafil compared with placebo or no therapy (1 study, 87 women) One study (Japan) involving 87 pregnant women with FGR was included. We assessed the certainty of the evidence as low. Compared with placebo or no therapy, tadalafil may have little or no effect on all-cause mortality (risk ratio 0.20, 95% CI 0.02 to 1.60, one study, 87 women); fetal mortality (RR 0.11, 95% CI 0.01 to 1.96, one study, 87 women); and neonatal mortality (RR 0.89, 95% CI 0.06 to 13.70, one study, 83 women). L-Arginine compared with placebo or no therapy (1 study, 43 women) One study (France) involving 43 pregnant women with FGR was included. This study did not assess our primary outcomes. Nitroglycerin compared to placebo or no therapy (1 studies, 23 women) One study (Brazil) involving 23 pregnant women with FGR was included. We assessed the certainty of the evidence as low. The effect on the primary outcomes is not estimable due to no events in women participating in both groups. Sildenafil citrate compared to nitroglycerin (1 study, 23 women) One study (Brazil) involving 23 pregnant women with FGR was included. We assessed the certainty of the evidence as low. The effect on the primary outcomes is not estimable due to no events in women participating in both groups.

AUTHORS' CONCLUSIONS

Interventions affecting the nitric oxide pathway probably do not seem to influence all-cause (fetal and neonatal) mortality in pregnant women carrying a baby with FGR, although more evidence is needed. The certainty of this evidence is moderate for sildenafil and low for tadalafil and nitroglycerin. For sildenafil a fair amount of data are available from randomised clinical trials, but with low numbers of participants. Therefore, the certainty of evidence is moderate. For the other interventions investigated in this review there are insufficient data, meaning we do not know whether these interventions improve perinatal and maternal outcomes in pregnant women with FGR.

Placental vascular alterations are associated with early neurodevelopmental and pulmonary impairment in the rabbit fetal growth restriction model

Fetal growth restriction is one of the leading causes of perinatal mortality and morbidity and has consequences that extend well beyond the neonatal period. Current management relies on timely delivery rather than improving placental function. Several prenatal strategies have failed to show benefit in clinical trials after promising results in animal models. Most of these animal models have important developmental and structural differences compared to the human and/or are insufficiently characterized. We aimed to describe placental function and structure in an FGR rabbit model, and to characterize the early brain and lung developmental morbidity using a multimodal approach. FGR was induced in time-mated rabbits at gestational day 25 by partial uteroplacental vessel ligation in one horn. Umbilical artery Doppler was measured before caesarean delivery at gestational day 30, and placentas were harvested for computed microtomography and histology. Neonates underwent neurobehavioral or pulmonary functional assessment the day after delivery, followed by brain or lung harvesting, respectively. Neuropathological assessment included multiregional quantification of neuron density, apoptosis, astrogliosis, cellular proliferation, and oligodendrocyte progenitors. Brain region volumes and diffusion metrics were obtained from ex-vivo brain magnetic resonance imaging. Lung assessment included biomechanical tests and pulmonary histology. Fetal growth restriction was associated with labyrinth alterations in the placenta, driven by fetal capillary reduction, and overall reduced vessels volume. FGR caused altered neurobehavior paralleled by regional neuropathological deficits and reduced fractional anisotropy in the cortex, white matter, and hippocampus. In addition, FGR kittens presented functional alterations in the peripheral lung and structurally underdeveloped alveoli. In conclusion, in a uteroplacental insufficiency FGR rabbit model, placental vascular alterations coincide with neurodevelopmental and pulmonary disruption.

Prenatal interventions for fetal growth restriction in animal models: A systematic review

Fetal growth restriction (FGR) in human pregnancy is associated with perinatal mortality, short- and long-term morbidities. No prenatal therapy is currently established despite decades of research. We aimed to review interventions in animal models for prenatal FGR treatment, and to seek the next steps for an effective clinical therapy. We registered our protocol and searched MEDLINE, Embase, and The Cochrane Library with no language restrictions, in accordance with the PRISMA guideline. We included all studies that reported the effects of any prenatal intervention in animal models of induced FGR. From 3257 screened studies, 202 describing 237 interventions were included for the final synthesis. Mice and rats were the most used animals (79%) followed by sheep (16%). Antioxidants (23%), followed by vasodilators (18%), nutrients (14%), and immunomodulators (12%) were the most tested therapy. Two-thirds of studies only reported delivery or immediate neonatal outcomes. Adverse effects were rarely reported (11%). Most studies (73%), independent of the intervention, showed a benefit in fetal survival or birthweight. The risk of bias was high, mostly due to the lack of randomization, allocation concealment, and blinding. Future research should aim to describe both short- and long-term outcomes across various organ systems in well-characterized models. Further efforts must be made to reduce selection, performance, and detection bias.

Effect of Maternal Sildenafil Supplementation During Gestation on the Reproductive Performance of Sows/Gilts and Growth Performance of Neonatal Piglets

Sildenafil, a phosphodiesterase 5 (PDE-5) inhibitor, provides an alternative and effective strategy to increase uterine blood flow and vascular development, thus improving fetal development. Previous studies have shown that sildenafil attenuates fetal growth restriction in rodents, sheep, and humans. However, the effect of sildenafil intervention on fetal growth in pigs remains unclear. This study aims to evaluate the effect of dietary supplementation with sildenafil on the reproductive performance of sows and gilts. Over 700 Landrace × Large White crossbred sows in the 3rd or 4th parity were randomly assigned to the control group and the sildenafil treatment groups. In brief, sows in the treatment groups were given a basic diet supplemented with sildenafil (0.32 g/day) during different stages of gestation: (1) gestation day (GD) 0–110; (2) GD 0–30; (3) GD 30–80; (4) GD 80–110; and (5) GD 30–110. At parturition, the total number of piglets born per litter, the number of piglets born alive or dead, the average birth weight, the number of weaned piglets, and the average weaning weights were recorded and analyzed. Sildenafil supplementation throughout gestation (GD 0–110) increased both the litter size and the average birth weight. To reduce the cost of extended sildenafil supplementation, time-phased strategies were further tested. Sildenafil supplementation during early gestation (GD 0–30), mid-gestation (GD 30–80), and late gestation (GD 80–110) partially improved litter performance. Notably, sows fed sildenafil supplementation from the mid-to-late gestation period (GD 30–110) showed significantly improved litter performance, approaching the levels in the sows supplemented with sildenafil throughout the whole gestation period. Taken together, our results showed that maternal sildenafil supplementation during gestation can effectively improve the reproductive performance of sows and gilts, and enhance the growth performance of neonatal piglets, thus providing a promising and practical intervention strategy to improve reproductive management in pig farming.

Placental Transcriptome Adaptations to Maternal Nutrient Restriction in Sheep

Placental development is modified in response to maternal nutrient restriction (NR), resulting in a spectrum of fetal growth rates. Pregnant sheep carrying singleton fetuses and fed either 100% (n = 8) or 50% (NR; n = 28) of their National Research Council (NRC) recommended intake from days 35–135 of pregnancy were used to elucidate placentome transcriptome alterations at both day 70 and day 135. NR fetuses were further designated into upper (NR NonSGA; n = 7) and lower quartiles (NR SGA; n = 7) based on day 135 fetal weight. At day 70 of pregnancy, there were 22 genes dysregulated between NR SGA and 100% NRC placentomes, 27 genes between NR NonSGA and 100% NRC placentomes, and 22 genes between NR SGA and NR NonSGA placentomes. These genes mediated molecular functions such as MHC class II protein binding, signaling receptor binding, and cytokine activity. Gene set enrichment analysis (GSEA) revealed significant overrepresentation of genes for natural-killer-cell-mediated cytotoxicity in NR SGA compared to 100% NRC placentomes, and alterations in nutrient utilization pathways between NR SGA and NR NonSGA placentomes at day 70. Results identify novel factors associated with impaired function in SGA placentomes and potential for placentomes from NR NonSGA pregnancies to adapt to nutritional hardship.

Transplacental Transfer and Fetal Pharmacodynamics of Sildenafil in the Pregnant Sheep Model

BACKGROUND

Sildenafil is a phosphodiesterase-5 inhibitor considered for antenatal use for a variety of indications. We sought to assess sildenafil pharmacokinetics in the pregnant ewe and fetus and evaluate its physiological fetal effects.

METHODS

Twelve fetal lambs (127-133 days GA, term 145) were chronically catheterized in utero. Ewes received different doses of sildenafil, either via subcutaneous injection (1.6, 2.0 mg/kg/day) or intravenous (IV) infusion (3, 5, 7, 10, and 12 mg/kg/day). Maternal and fetal sildenafil concentrations and metabolic status (blood gas analysis) were measured at given intervals. The fetal heart rate, pulmonary blood flow, systemic and aortic pressure, and maternal uterine artery pressure were continuously monitored.

RESULTS

The transplacental sildenafil transfer was 2.9% (range: 1.4-7.8%), preventing attainment of fetal target concentrations without toxic maternal levels. IV sildenafil infusion induced an immediate, temporary, dose-dependent reduction of pulmonary vascular resistance (38-78%) and increased both pulmonary blood flow (32-132%) and heart rate (13-49%), with limited nonlinear dose-dependent effects on systemic and pulmonary pressures. Fetal and maternal blood gases and maternal uterine artery pressures were unaffected by sildenafil infusion.

CONCLUSION

In sheep, transplacental transfer of sildenafil is extremely low. Though, minimal fetal sildenafil concentrations induce an acute transient pulmonary vasodilation, well-tolerated by the fetus and ewe.

Effects of mid-gestational l-citrulline supplementation to twin-bearing ewes on umbilical blood flow, placental development, and lamb production traits

The objective of the study was to examine how l-citrulline supplementation to ewes during mid-gestation influences placental activity, placental blood flow, lamb body weight, and carcass characteristics. Two studies were completed. A pharmacokinetic study to compare circulating plasma amino acid concentrations after a single intravenous injection of 155 µmol/kg BW l-citrulline or after an isonitrogenous amount of l-alanine (control; 465 µmol/kg BW). Increases (P < 0.05) in circulating citrulline concentrations were detected for 8 h after l-citrulline injection versus the control. Similarly, increases (P < 0.05) in circulating arginine concentrations were detected for 24 h after l-citrulline treatment. The second study used 12 ewes with twin pregnancies. Daily intravenous injections of either l-citrulline or l-alanine were administered for 39 d from d 42–45 to 81–84 of gestation. Ewes were limit-fed at 85% daily energy requirements during the injection period. A decrease (P < 0.0001) in body weight was observed in both treatment groups during this period. No treatment differences were observed in circulating pregnancy-specific protein B concentrations or placental blood flow during the treatment and post-treatment gestational period. No treatment differences were observed in lamb survival nor in lamb birth, weaning and slaughter weights. Treatment did not influence lamb carcass composition or organ weights. However, there was a tendency (P = 0.10) for an increase in antral follicle numbers in ovaries from ewe lambs derived from ewes treated with l-citrulline. In summary, a daily l-citrulline injection increased both circulating citrulline and arginine concentrations in ewes, but daily l-citrulline injections during mid-gestation did not produce any detectable changes in placental activity and blood flow, neonatal and postnatal lamb development, and lamb carcass composition at slaughter. In conclusion, no benefits in placental function and lamb development were observed after providing l-citrulline during mid-gestation in ewes exposed to a mild energy restriction, but there was an indication that follicle numbers in ewe lambs were positively influenced by l-citrulline treatment during fetal development.

Role of Dietary Amino Acids and Nutrient Sensing System in Pregnancy Associated Disorders

Defective implantation is related to pregnancy-associated disorders such as spontaneous miscarriage, intrauterine fetal growth restriction and others. Several factors proclaimed to be involved such as physiological, nutritional, environmental and managemental that leads to cause oxidative stress. Overloading of free radicals promotes oxidative stress, and the internal body system could not combat its ability to encounter the damaging effects and subsequently leading to pregnancy-related disorders. During pregnancy, essential amino acids display important role for optimum fetal growth and other necessary functions for continuing fruitful pregnancy. In this context, dietary amino acids have received much attention regarding the nutritional concerns during pregnancy. Arginine, glutamine, tryptophan and taurine play a crucial role in fetal growth, development and survival while ornithine and proline are important players for the regulation of gene expression, protein synthesis and angiogenesis. Moreover, amino acids also stimulate the mammalian target of rapamycin (mTOR) signaling pathway which plays a central role in the synthesis of proteins in placenta, uterus and fetus. This review article explores the significances of dietary amino acids in pregnancy development, regulation of nutrient-sensing pathways such as mTOR, peroxisome proliferator-activated receptors (PPARs), insulin/insulin-like growth factor signaling pathway (IIS) and 5' adenosine monophosphate-activated protein kinase (AMPK) which exhibit important role in reproduction and its related problems. In addition, the antioxidant function of dietary amino acids against oxidative stress triggering pregnancy disorders and their possible outcomes will also be enlightened. Dietary supplementation of amino acids during pregnancy could help mitigate reproductive disorders and thereby improving fertility in animals as well as humans.

Effect of supplementation of unprotected or protected arginine to prolific ewes on maternal amino acids profile, lamb survival at birth, and pre- and post-weaning lamb growth

This research determined the effects of dietary supplementation with rumen-protected arginine (Pro-Arg) on metabolites and amino acids in maternal plasma and lamb survival rate at birth (LSRAB) in prolific Afec-Assaf ewes. The hypothesis was that Pro-Arg, the precursor for nitric oxide and polyamines, would increase placental development and vascularity, uteroplacental blood flow, and nutrient transport and reduce oxidative stress to increase LSRAB. Ewes were fed either their basal diet, basal diet with Pro-Arg, or basal diet with unprotected arginine (Unp-Arg; 18 g/head/d). The supplemental arginine was about 1% of the dry matter intake from day 40 or 60 of gestation until parturition. Ninety-two of 98 ewes produced live lambs. Ewes fed Pro-Arg had greater (P = 0.002) concentrations of arginine and other amino acids in plasma, whereas Unp-Arg did not affect concentrations of arginine, but decreased (P < 0.05) concentrations of some amino acids. There was no effect of treatments on gestation length (144 ± 2 d), prolificacy (2.65 lambs born per ewe), LSRAB (0.80), body weight (88.8 ± 10.8 kg), and body condition score (2.8 ± 0.6) of ewes, or birth weight and crown-rump length of lambs. The GI (BW/CRL1.5) was affected by sex of lamb (P = 0.008), parity of ewe (P = 0.002), litter size (P = 0.0001), and lamb status (P = 0.003). Of 229 lambs born, 32 were dead and 16 died before 5 mo of age, leaving 181 lambs with records on weights at birth and 5 mo of age. Interestingly, lambs born to ewes fed the Unp-Arg and Pro-Arg weighed 3.6 kg less at postnatal day 150 than lambs from control ewes.

Maternal sildenafil impairs the cardiovascular adaptations to chronic hypoxaemia in fetal sheep

KEY POINTS

Fetal growth restriction induces a haemodynamic response that aims to maintain blood flow to vital organs such as the brain, in the face of chronic hypoxaemia Maternal sildenafil treatment impairs the hypoxaemia-driven haemodynamic response and potentially compromises fetal development.

ABSTRACT

Inadequate substrate delivery to a fetus results in hypoxaemia and fetal growth restriction (FGR). In response, fetal cardiovascular adaptations redirect cardiac output to essential organs to maintain oxygen delivery and sustain development. However, FGR infants remain at risk for cardiovascular and neurological sequelae. Sildenafil citrate (SC) has been examined as a clinical therapy for FGR, but also crosses the placenta and may exert direct effects on the fetus. We investigated the effects of maternal SC administration on maternal and fetal cardiovascular physiology in growth-restricted fetal sheep. Fetal sheep (0.7 gestation) underwent sterile surgery to induce growth restriction by single umbilical artery ligation (SUAL) or sham surgery (control, AG). Fetal catheters and flow probes were implanted to measure carotid and femoral arterial blood flows. Ewes containing SUAL fetuses were randomized to receive either maternal administration of saline or SC (36 mg i.v. per day) beginning 4 days after surgery, and continuing for 20 days. Physiological recordings were obtained throughout the study. Antenatal SC treatment reduced body weight by 32% and oxygenation by 18% in SUAL compared to AG. SC did not alter maternal or fetal heart rate or blood pressure. Femoral blood flow and peripheral oxygen delivery were increased by 49% and 30% respectively in SUALSC compared to SUAL, indicating impaired cardiovascular adaptation to chronic hypoxaemia. Antenatal SC directly impairs the fetal haemodynamic response to chronic hypoxaemia. Consideration of the consequences upon the fetus should be paramount when administering interventions to the mother during pregnancy.

Effect of maternal nutrient restriction on skeletal muscle mass and associated molecular pathways in SGA and Non-SGA sheep fetuses

Maternal nutrient restriction causes small for gestational age (SGA) offspring, which exhibit a higher risk for metabolic syndrome in adulthood. Fetal skeletal muscle is particularly sensitive to maternal nutrient restriction, which impairs muscle mass and metabolism. Using a 50% nutrient restriction treatment from gestational day (GD) 35 to GD 135 in sheep, we routinely observe a spectral phenotype of fetal weights within the nutrient-restricted (NR) group. Thus, our objective was to evaluate the effect of maternal NR on muscle mass, myofiber hypertrophy, myonuclear dotation, and molecular markers for protein synthesis and degradation, while accounting for the observed fetal weight variation. Within the NR group, we classified upper-quartile fetuses into NR(Non-SGA) (n = 11) and lower-quartile fetuses into NR(SGA) (n = 11). A control group (n = 12) received 100% of nutrient requirements throughout pregnancy. At GD 135, fetal plasma and organs were collected, and gastrocnemius and soleus muscles were sampled for investigation. Results showed decreased (P < 0.05) absolute tissue/organ weights, including soleus and gastrocnemius muscles, in NR(SGA) fetuses compared to NR(Non-SGA) and control. Myofiber cross-sectional area was smaller in NR(SGA) vs control for gastrocnemius (P = 0.0092) and soleus (P = 0.0097) muscles. Within the gastrocnemius muscle, the number of myonuclei per myofiber was reduced (P = 0.0442) in NR(SGA) compared to control. Cortisol may induce protein degradation. However, there were no differences in fetal cortisol among groups. Nevertheless, for gastrocnemius muscle, cortisol receptor (NR3C1; P = 0.0124), and FOXO1 (P = 0.0131) were upregulated in NR(SGA) compared to control while NR(Non-SGA) did not differ from the other 2 groups. KLF15 was upregulated (P = 0.0002) in both NR(SGA) and NR(Non-SGA); while FBXO32, TRIM63, BCAT2 or MSTN did not differ. For soleus muscle, KLF15 mRNA was upregulated (P = 0.0145) in NR(SGA) compared to control, and expression of MSTN was increased (P = 0.0259) in NR(SGA) and NR(Non-SGA) compared to control. At the protein level, none of the mentioned molecules nor total ubiquitin-labeled proteins differed among groups (P > 0.05). Indicators of protein synthesis (total and phosphorylated MTOR, EI4EBP1, and RPS6KB1) did not differ among groups in either muscle (P > 0.05). Collectively, results highlight that maternal NR unequally affects muscle mass in NR(SGA) and NR(Non-SGA) fetuses, and alterations in myofiber cross-sectional area and myonuclei number partially explain those differences.

Development of a surgical procedure for removal of a placentome from a pregnant ewe during gestation

Background

In recent decades, there has been a growing interest in the impact of insults during pregnancy on postnatal health and disease. It is known that changes in placental development can impact fetal growth and subsequent susceptibility to adult onset diseases; however, a method to collect sufficient placental tissues for both histological and gene expression analyses during gestation without compromising the pregnancy has not been described. The ewe is an established biomedical model for the study of fetal development. Due to its cotyledonary placental type, the sheep has potential for surgical removal of materno-fetal exchange tissues, i.e., placentomes. A novel surgical procedure was developed in well-fed control ewes to excise a single placentome at mid-gestation.

Results

A follow-up study was performed in a cohort of nutrient-restricted ewes to investigate rapid placental changes in response to undernutrition. The surgery averaged 19 min, and there were no viability differences between control and sham ewes. Nutrient restricted fetuses were smaller than controls (4.7 ± 0.1 kg vs. 5.6 ± 0.2 kg; P < 0.05), with greater dam weight loss (− 32.4 ± 1.3 kg vs. 14.2 ± 2.2 kg; P < 0.01), and smaller placentomes at necropsy (5.7 ± 0.3 g vs. 7.2 ± 0.9 g; P < 0.05). Weight of sampled placentomes and placentome numbers did not differ.

Conclusions

With this technique, gestational studies in the sheep model will provide insight into the onset and complexity of changes in gene expression in placentomes resulting from undernutrition (as described in our study), overnutrition, alcohol or substance abuse, and environmental or disease factors of relevance and concern regarding the reproductive health and developmental origins of health and disease in humans and in animals.

Adaptive responses to maternal nutrient restriction alter placental transport in ewes

INTRODUCTION

Maternal nutrient partitioning, uteroplacental blood flow, transporter activity, and fetoplacental metabolism mediate nutrient delivery to the fetus. Inadequate availability or delivery of nutrients results in intrauterine growth restriction (IUGR), a leading cause of neonatal morbidity and mortality. Maternal nutrient restriction can result in IUGR, but only in an unforeseeable subset of individuals.

METHODS

To elucidate potential mechanisms regulating fetal nutrient availability, singleton sheep pregnancies were generated by embryo transfer. Pregnant ewes received either a 50% NRC (NR; n = 24) or 100% NRC (n = 7) diet from gestational Day 35 until necropsy on Day 125. Maternal weight did not correlate with fetal weight; therefore, the six heaviest (NR Non-IUGR) and five lightest (NR IUGR) fetuses from nutrient-restricted ewes, and seven 100% NRC fetuses, were compared to investigate differences in nutrient availability.

RESULTS

Insulin, multiple amino acids, and their metabolites, were reduced in fetal circulation of NR IUGR compared to NR Non-IUGR and 100% NRC pregnancies. In contrast, glucose in fetal fluids was not different between groups. There was a nearly two-fold reduction in placentome volume and fetal/maternal interface length in NR IUGR compared to NR Non-IUGR and 100% NRC pregnancies. Changes in amino acid concentrations were associated with altered expression of cationic (SLC7A2, SLC7A6, and SLC7A7) and large neutral (SLC38A2) amino acid transporters in placentomes.

DISCUSSION

Results establish a novel approach to study placental adaptation to maternal undernutrition in sheep and support the hypothesis that amino acids and polyamines are critical mediators of placental and fetal growth in sheep.

Maternal low molecular weight heparin versus sildenafil citrate for fetal growth restriction: a randomized, parallel groups, open-label clinical trial

OBJECTIVES

To compare the effect of sildenafil citrate (SC) and low molecular weight heparin (LMWH) on neonatal birth weight (BW) and the fetoplacental blood flow in pregnancies with FGR.

STUDY DESIGN

A parallel groups, randomized clinical trial was conducted at a university hospital, between June 2017 and September 2018, involving 100 pregnant women with placental mediated FGR between 28 and 35 weeks of gestation who were randomly assigned to receive either SC or LMWH started at FGR diagnosis till delivery.

RESULTS

The neonatal BW in LMWH group was higher than SC group (p < 0.000) with a longer time from randomization till delivery, LMWH group had significant improvement in Ut A PI, UA PI, and MCA PI compared with SC treated group with p values 0.005, <0.000001, and 0.014, respectively.

CONCLUSION

The neonatal BW, time from randomization to delivery, and fetoplacental blood flow indices were significantly better with LMWH use compared with SC.

Effects of Maternal Sildenafil Treatment on Vascular Function in Growth-Restricted Fetal Sheep

Objective- The objective of this study was to investigate the effect of intravenous maternal sildenafil citrate (SC) administration on vascular function in growth-restricted fetal sheep. Approach and Results- Fetal growth restriction (FGR) results in cardiovascular adaptations that redistribute cardiac output to optimize suboptimal intrauterine conditions. These adaptations result in structural and functional cardiovascular changes, which may underlie postnatal neurological and cardiovascular sequelae. Evidence suggests SC, a potent vasodilator, may improve FGR. In contrast, recent clinical evidence suggests potential for adverse fetal consequence. Currently, there is limited data on SC effects in the developing fetus. We hypothesized that SC in utero would improve vascular development and function in an ovine model of FGR. Preterm lambs (0.6 gestation) underwent sterile surgery for single umbilical artery ligation or sham (control, appropriately grown) surgery to replicate FGR. Ewes received continuous intravenous SC (36 mg/24 h) or saline from surgery until 0.83 gestation. Fetuses were delivered and immediately euthanized for collection of femoral and middle cerebral artery vessels. Vessel function was assessed via in vitro wire myography. SC exacerbated growth restriction in growth-restricted fetuses and resulted in endothelial dysfunction in the cerebral and femoral vasculature, irrespective of growth status. Dysfunction in the cerebral circulation is endothelial, whereas smooth muscle in the periphery is the origin of the deficit. Conclusions- SC crosses the placenta and alters key fetal vascular development. Extensive studies are required to investigate the effects of SC on fetal development to address safety before additional use of SC as a treatment.

Maternal Nutrient Restriction and Skeletal Muscle Development: Consequences for Postnatal Health

Severe undernutrition and famine continue to be a worldwide concern, as cases have been increasing in the past 5 years, particularly in developing countries. The occurrence of nutrient restriction (NR) during pregnancy affects fetal growth, leading to small for gestational age (SGA) or intrauterine growth restricted (IUGR) offspring. During adulthood, SGA and IUGR offspring are at a higher risk for the development of metabolic syndrome. Skeletal muscle is particularly sensitive to prenatal NR. This tissue plays an essential role in oxidation and glucose metabolism because roughly 80% of insulin-mediated glucose uptake occurs in muscle, and it represents around 40% of body weight. Alterations in myofiber number, hypertrophy and myofiber type composition, decreased protein synthesis, lower mitochondrial content and activity of oxidative enzymes, and increased accumulation of intramuscular triglycerides are among the described programming effects of maternal NR on skeletal muscle. Together, these features would add to a phenotype that is prone to insulin resistance, type 2 diabetes, obesity, and metabolic syndrome. Insights from diverse animal models (i.e. ovine, swine, and rodent) have provided valuable information regarding the molecular mechanisms behind those altered developmental pathways. Understanding those molecular signatures supports the development of efficient treatments to counteract the effects of maternal NR on skeletal muscle, and its negative implications for postnatal health.

Antenatal sildenafil citrate treatment increases offspring blood pressure in the placental-specific Igf2 knockout mouse model of FGR

Fetal growth restriction (FGR), where a fetus fails to reach its genetic growth potential, affects up to 8% of pregnancies and is a major risk factor for stillbirth and adulthood morbidity. There are currently no treatments for FGR, but candidate therapies include the phosphodiesterase-5 inhibitor sildenafil citrate (SC). Randomized clinical trials in women demonstrated no effect of SC on fetal growth in cases of severe early onset FGR; however, long-term health outcomes on the offspring are unknown. This study aimed to assess the effect of antenatal SC treatment on metabolic and cardiovascular health in offspring by assessing postnatal weight gain, glucose tolerance, systolic blood pressure, and resistance artery function in a mouse model of FGR, the placental-specific insulin-like growth factor 2 (PO) knockout mouse. SC was administered subcutaneously (10 mg/kg) daily from embryonic day (E)12.5. Antenatal SC treatment did not alter fetal weight or viability but increased postnatal weight gain in wild-type (WT) female offspring (P < 0.05) and reduced glucose sensitivity in both WT (P < 0.01) and P0 (P < 0.05) female offspring compared with controls. Antenatal SC treatment increased systolic blood pressure in both male (WT vs. WT-SC: 117 ± 2 vs. 140 ± 3 mmHg, P < 0.0001; P0 vs. P0-SC: 113 ± 3 vs. 140 ± 4 mmHg, P < 0.0001; means ± SE) and female (WT vs. WT-SC: 121 ± 2 vs. 140 ± 2 mmHg, P < 0.0001; P0 vs. P0-SC: 117 ± 2 vs. 144 ± 4 mmHg, P < 0.0001) offspring at 8 and 13 wk of age. Increased systolic blood pressure was not attributed to altered mesenteric artery function. In utero exposure to SC may result in metabolic dysfunction and elevated blood pressure in later life.

NEW & NOTEWORTHY Sildenafil citrate (SC) is currently used to treat fetal growth restriction (FGR). We demonstrate that SC is ineffective at treating FGR, and leads to a substantial increase systolic blood pressure and alterations in glucose homeostasis in offspring. We therefore urge caution and suggest that further studies are required to assess the safety and efficacy of SC in utero, in addition to the implications on long-term health.

Safety Evaluation of Tadalafil Treatment for Fetuses with Early-Onset Growth Restriction (TADAFER): Results from the Phase II Trial

Tadalafil is a phosphodiesterase 5 (PDE5) inhibitor with a long half-life, high selectivity, and rapid onset of action. Because the safety of using PDE5 inhibitors as therapeutic agents for fetal growth restriction (FGR) has been a problem worldwide, this paper primarily focuses on the safety assessments performed in the Tadalafil Treatment for Fetuses with Early-Onset Growth Restriction (TADAFER) II population. Neonatal and maternal adverse events were analyzed, in addition to fetal, neonatal, and infant death cases, six months after stopping the trial. Eighty-nine pregnant women with FGR were studied between September 2016 and March 2018 (45 and 44 in the tadalafil and conventional treatment groups, respectively). Seven (16%) deaths (four fetal, one neonatal, and two infant) in the control group, whereas only one neonatal death occurred in the tadalafil group. Although headache, facial flushing, and nasal hemorrhage occurred more frequently in the tadalafil group, these symptoms were Grade 1 and transient. In conclusion, this trial showed that tadalafil decreased the fetal and infant deaths associated with FGR. This is thought to be primarily due to pregnancy prolongation. Further studies are warranted to evaluate the efficacy of tadalafil in treating early-onset FGR.

Detailed statistical analysis plan for the Dutch STRIDER (Sildenafil TheRapy In Dismal prognosis Early-onset fetal growth Restriction) randomised clinical trial on sildenafil versus placebo for pregnant women with severe early onset fetal growth restriction

OBJECTIVE

The objective of the Dutch Sildenafil therapy in dismal prognosis early onset fetal growth restriction (STRIDER) randomised clinical trial is to assess the beneficial and harmful effects of sildenafil versus placebo on fetal and neonatal mortality in pregnant women with severe early-onset fetal growth restriction. The objective of this detailed statistical analysis plan is to minimize the risks of selective reporting and data-driven analysis.

SETTING

The setting is 10 tertiary care hospitals and one secondary care hospital in The Netherlands.

PARTICIPANTS

The participants will be 360 pregnant women with severe early-onset fetal growth restriction.

INTERVENTIONS

The intervention is sildenafil 25 mg or placebo orally three times a day.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome is a composite of death or major neonatal morbidity assessed at hospital discharge. The secondary outcomes are neurodevelopmental impairment; mean scores of the Bayley III cognitive and motor assessment; the proportion of patients experiencing either preeclampsia or haemolysis, elevated liver enzymes, and low platelets syndrome; pulsatility index of uterine arteries, umbilical artery, and middle cerebral artery; birthweight; and gestational age at either delivery or intra-uterine death.

RESULTS

A detailed statistical analysis is presented, including pre-defined exploratory outcomes and planned subgroup analyses. One interim analysis after 180 patients had completed the study was planned and a strategy to minimise the risks of type I errors due to repetitive testing is presented. During review of this manuscript the interim analysis was performed by the Data Safety Monitoring Board and early stopping of the trial was recommended. Final analyses will be conducted independently by two statistically qualified persons following the present plan.

CONCLUSION

This pre-specified statistical analysis plan was written and submitted without knowledge of the unblinded data and updated after stopping of the trial at interim analysis.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02277132 . Registered on 29 September 2014. Original protocol for the study: doi: https://doi.org/10.5281/zenodo.56148.

Effect of sildenafil citrate treatment in the eNOS knockout mouse model of fetal growth restriction on long-term cardiometabolic outcomes in male offspring

Fetal growth restriction (FGR) is associated with an increased risk of hypertension, insulin resistance, obesity and cardiovascular disease in adulthood. Currently there are no effective treatments to reverse the course of FGR. This study used the eNOS knockout mouse (eNOS^-/-), a model of FGR, to determine the ability of sildenafil, a potential new treatment for FGR, to improve cardiovascular and metabolic outcomes in adult offspring following a complicated pregnancy. Pregnant eNOS^-/- and C57BL/6J control dams were randomised to sildenafil treatment (0.2 mg/ml in drinking water) or placebo at day 12.5 of gestation until birth. After weaning, male offspring were randomised to either a high fat (HFD; 45% kcal from fat) or normal chow diet (ND), and raised to either postnatal day 90 or 150. Growth and body composition, glucose tolerance, insulin resistance, systolic blood pressure and vascular function were analysed at both time-points. eNOS^-/- offspring were significantly smaller than their C57BL/6J controls at weaning and P90 (p < 0.01); at P150 they were a similar weight. Total adipose tissue deposition at P90 was significantly increased only in eNOS^-/- mice fed a HFD (p < 0.001). At P150 both C57BL/6J and eNOS^-/- offspring fed a HFD demonstrated significant adipose tissue deposition (p < 0.01), regardless of maternal treatment. Both diet and maternal sildenafil treatment had a significant effect on glucose tolerance. Glucose tolerance was significantly impaired in eNOS^-/- mice fed a HFD (p < 0.01); this was significant in offspring from both sildenafil and vehicle treated mothers at P90 and P150. Glucose tolerance was also impaired in C57BL/6J mice fed a HFD at both P90 and P150 (p < 0.01), but only in those also exposed to sildenafil. In these C57BL/6J mice, sildenafil was associated with impaired insulin sensitivity at P90 (p = 0.020) but increased insulin resistance at P150 (p = 0.019). Exposure to sildenafil was associated with a significant increase in systolic blood pressure in eNOS^-/- mice compared with their C57BL/6J diet controls at P150 (p < 0.05). Exposure to sildenafil had differing effects on vascular function in mesenteric arteries; it increased vasodilation in response to ACh in C57BL/6J mice, but was associated with a more constrictive phenotype in eNOS^-/- mice. eNOS^-/- mice demonstrate a number of impaired outcomes consistent with programmed cardiometabolic disease, particularly when faced with the 'second hit' of a HFD. Exposure to sildenafil treatment during pregnancy did not increase fetal growth or significantly improve adult metabolic or cardiac outcomes. Maternal sildenafil treatment was, however, associated with small impairments in glucose handling and an increase in blood pressure. This study highlights the importance of understanding the long-term effects of treatment during pregnancy in offspring from both complicated and healthy control pregnancies.

The effects of sildenafil citrate on feto-placental development and haemodynamics in a rabbit model of intrauterine growth restriction

The present study evaluated the effectiveness of sildenafil citrate (SC) to improve placental and fetal growth in a diet-induced rabbit model of intrauterine growth restriction (IUGR). Pregnant rabbits were fed either ad libitum (Group C) or restricted to 50% of dietary requirements (Group R) or restricted and treated with SC (Group SC). The treatment with SC improved placental development by increasing vascularity and vessel hypertrophy in the decidua. The assessment of feto-placental haemodynamics showed higher resistance and pulsatility indices at the middle cerebral artery (MCA) in fetuses treated with SC when compared with Group R, which had increased systolic peak and time-averaged mean velocities at the MCA. Furthermore, fetuses in the SC group had significantly higher biparietal and thoracic diameters and longer crown-rump lengths than fetuses in Group R. Hence, the SC group had a reduced IUGR rate and a higher kit size at birth compared with Group R. In conclusion, SC may provide potential benefits in pregnancies with placental insufficiency and IUGR, partially counteracting the negative effects of food restriction on placental development and fetal growth. However, the present study also found evidence of a possible blood overflow in the brain that warrants further investigation.

Evaluation of Sildenafil and Tadalafil for Reversing Constriction of Fetal Arteries in a Human Placenta Perfusion Model

Fetal growth restriction resulting from reduced placental blood perfusion is a major cause of neonatal morbidity and mortality. Aside from intense surveillance and early delivery, there is no treatment for fetal growth restriction. A potential treatment associated with placental vasoconstriction is the class of PDE5 (phosphodiesterase type 5) inhibitors such as sildenafil, which is known to cross the placenta. In contrast, tadalafil, a more potent and selective PDE5 inhibitor has not been studied in pregnancy or experimental models of fetal growth restriction. Therefore, we compared the efficacy of these 2 PDE5 inhibitors for reversing vasoconstriction in an ex vivo human placental model and evaluating molecular and physiological responses. Sildenafil and tadalafil were infused into the intervillous space in a preconstricted human placental dual cotyledon, dual perfusion assay for the comparison of arteriole pressures and molecular indicators of drug inhibition. Results indicate a decrease arterial pressure with sildenafil citrate compared with controls, whereas tadalafil showed no difference. PDE5 and endothelial nitric oxide synthase activity were altered with sildenafil but not tadalafil. Sildenafil citrate improved preconstricted placental arterial perfusion in a human placental model, whereas tadalafil showed no response. It is possible that tadalafil did not cross the human placental barrier or was degraded by trophoblasts. This study supports human clinical trials exploring sildenafil as a potential treatment for improving fetal blood flow in fetal growth restriction associated with vasoconstriction.

STRIDER (Sildenafil TheRapy in dismal prognosis early onset fetal growth restriction): an international consortium of randomised placebo-controlled trials

Background

Severe, early-onset fetal growth restriction due to placental insufficiency is associated with a high risk of perinatal mortality and morbidity with long-lasting sequelae. Placental insufficiency is the result of abnormal formation and function of the placenta with inadequate remodelling of the maternal spiral arteries. There is currently no effective therapy available. Some evidence suggests sildenafil citrate may improve uteroplacental blood flow, fetal growth, and meaningful infant outcomes. The objective of the Sildenafil TheRapy In Dismal prognosis Early onset fetal growth Restriction (STRIDER) collaboration is to evaluate the effectiveness of sildenafil versus placebo in achieving healthy perinatal survival through the conduct of randomised clinical trials and systematic review including individual patient data meta-analysis.

Methods

Five national/bi-national multicentre randomised placebo-controlled trials have been launched. Women with a singleton pregnancy between 18 and 30 weeks with severe fetal growth restriction of likely placental origin, and where the likelihood of perinatal death/severe morbidity is estimated to be significant are included. Participants will receive either sildenafil 25 mg or matching placebo tablets orally three times daily from recruitment to 32 weeks gestation.

Discussion

The STRIDER trials were conceived and designed through international collaboration. Although the individual trials have different primary outcomes for reasons of sample size and feasibility, all trials will collect a standard set of outcomes including survival without severe neonatal morbidity at time of hospital discharge. This is a summary of all the STRIDER trial protocols and provides an example of a prospectively planned international clinical research collaboration. All five individual trials will contribute to a pre-planned systematic review of the topic including individual patient data meta-analysis.

Trial registrations

New Zealand and Australia: ACTRN12612000584831. Registered 30/05/2012.

Canada: NCT02442492. Registered 05/05/2015.

Ireland: CT 900/572/1. Registered 15/07/2015.

The Netherlands: NCT02277132. Registered 29/09/2014.

United Kingdom: ISRCTN39133303. Registered 31/07/2014.

The impact of IUGR on pancreatic islet development and β-cell function

Placental insufficiency is a primary cause of intrauterine growth restriction (IUGR). IUGR increases the risk of developing type 2 diabetes mellitus (T2DM) throughout life, which indicates that insults from placental insufficiency impair β-cell development during the perinatal period because β-cells have a central role in the regulation of glucose tolerance. The severely IUGR fetal pancreas is characterized by smaller islets, less β-cells, and lower insulin secretion. Because of the important associations among impaired islet growth, β-cell dysfunction, impaired fetal growth, and the propensity for T2DM, significant progress has been made in understanding the pathophysiology of IUGR and programing events in the fetal endocrine pancreas. Animal models of IUGR replicate many of the observations in severe cases of human IUGR and allow us to refine our understanding of the pathophysiology of developmental and functional defects in islet from IUGR fetuses. Almost all models demonstrate a phenotype of progressive loss of β-cell mass and impaired β-cell function. This review will first provide evidence of impaired human islet development and β-cell function associated with IUGR and the impact on glucose homeostasis including the development of glucose intolerance and diabetes in adulthood. We then discuss evidence for the mechanisms regulating β-cell mass and insulin secretion in the IUGR fetus, including the role of hypoxia, catecholamines, nutrients, growth factors, and pancreatic vascularity. We focus on recent evidence from experimental interventions in established models of IUGR to understand better the pathophysiological mechanisms linking placental insufficiency with impaired islet development and β-cell function.

Treating the dysfunctional placenta

Placental dysfunction underlies major obstetric diseases such as pre-eclampsia and fetal growth restriction (FGR). Whilst there has been a little progress in prophylaxis, there are still no treatments for placental dysfunction in normal obstetric practice. However, a combination of increasingly well-described in vitro systems for studying the human placenta, together with the availability of more appropriate animal models of pre-eclampsia and FGR, has facilitated a recent surge in work aimed at repurposing drugs and therapies, developed for other conditions, as treatments for placental dysfunction. This review: (1) highlights potential candidate drug targets in the placenta - effectors of improved uteroplacental blood flow, anti-oxidants, heme oxygenase induction, inhibition of HIF, induction of cholesterol synthesis pathways, increasing insulin-like growth factor II availability; (2) proposes an experimental pathway for taking a potential drug or treatment for placental dysfunction from concept through to early phase clinical trials, utilizing techniques for studying the human placenta in vitro and small animal models, particularly the mouse, for in vivo studies; (3) describes the data underpinning sildenafil citrate and adenovirus expressing vascular endothelial growth as potential treatments for placental dysfunction and summarizes recent research on other potential treatments. The importance of sharing information from such studies even when no effect is found, or there is an adverse outcome, is highlighted. Finally, the use of adenoviral vectors or nanoparticle carriers coated with homing peptides to selectively target drugs to the placenta is highlighted: such delivery systems could improve efficacy and reduce the side effects of treating the dysfunctional placenta.

Functional amino acids in the development of the pig placenta

The mammalian placenta is essential for supplying nutrients (e.g., amino acids and water) and oxygen from the mother to fetus and for removing fetal metabolites (e.g., ammonia and CO₂ ) from fetus to mother. Thus, placental growth and development are determinants of fetal survival, growth, and development. Indeed, low birth weight is closely associated with reduced placental growth. Providing gestating gilts or sows with dietary supplementation of arginine and glutamine, increases placental growth (including vascular growth), improves embryonic/fetal growth and survival, and reduces the large variation in birth weight among litters. These two amino acids serve as building blocks for tissue protein as well as substrates for the production of polyamines and nitric oxide, which stimulate DNA and protein synthesis and angiogenesis and vascular growth in the placenta. These recent findings not only greatly advance the field of mammalian amino acid metabolism and nutrition, but also provide practical, mechanism-based methods to enhance reproductive efficiency in swine. These results may also help improve embryonic/fetal survival and growth in other livestock species (e.g., sheep and cattle) and in humans.

Dietary -carbamylglutamate and rumen-protected -arginine supplementation ameliorate fetal growth restriction in undernourished ewes

This study was conducted with an ovine intrauterine growth restriction (IUGR) model to test the hypothesis that dietary -carbamylglutamate (NCG) and rumen-protected -Arg (RP-Arg) supplementation are effective in ameliorating fetal growth restriction in undernourished ewes. Beginning on d 35 of gestation, ewes were fed a diet providing 100% of NRC-recommended nutrient requirements, 50% of NRC recommendations (50% NRC), 50% of NRC recommendations supplemented with 20 g/d RP-Arg (providing 10 g/d of Arg), and 50% of NRC recommendations supplemented with 5 g/d NCG product (providing 2.5 g/d of NCG). On d 110, maternal, fetal, and placental tissues and fluids were collected and weighed. Ewe weights were lower ( < 0.05) in nutrient-restricted ewes compared with adequately fed ewes. Maternal RP-Arg or NCG supplementation did not alter ( = 0.26) maternal BW in nutrient-restricted ewes. Weights of most fetal organs were increased ( < 0.05) in RP-Arg-treated and NCG-treated underfed ewes compared with 50% NRC-fed ewes. Supplementation of RP-Arg or NCG reduced ( < 0.05) concentrations of β-hydroxybutyrate, triglycerides, and ammonia in serum of underfed ewes but had no effect on concentrations of lactate and GH. Maternal RP-Arg or NCG supplementation markedly improved ( < 0.05) concentrations of AA (particularly arginine-family AA and branched-chain AA) and polyamines in maternal and fetal plasma and in fetal allantoic and amniotic fluids within nutrient-restricted ewes. These novel results indicate that dietary NCG and RP-Arg supplementation to underfed ewes ameliorated fetal growth restriction, at least in part, by increasing the availability of AA in the conceptus and provide support for its clinical use to ameliorate IUGR in humans and sheep industry production.

Dietary interventions for fetal growth restriction - therapeutic potential of dietary nitrate supplementation in pregnancy

Fetal growth restriction (FGR) affects around 5% of pregnancies and is associated with significant short- and long-term adverse outcomes. A number of factors can increase the risk of FGR, one of which is poor maternal diet. In terms of pathology, both clinically and in many experimental models of FGR, impaired uteroplacental vascular function is implicated, leading to a reduction in the delivery of oxygen and nutrients to the developing fetus. Whilst mechanisms underpinning impaired uteroplacental vascular function are not fully understood, interventions aimed at enhancing nitric oxide (NO) bioavailability remain a key area of interest in obstetric research. In addition to endogenous NO production from the amino acid l-arginine, via nitric oxide synthase (NOS) enzymes, research in recent years has established that significant NO can be derived from dietary nitrate, via the 'alternative NO pathway'. Dietary nitrate, abundant in green leafy vegetables and beetroot, can increase NO bioactivity, conferring beneficial effects on cardiovascular function and blood flow. Given the beneficial effects of dietary nitrate supplementation to date in non-pregnant humans and animals, current investigations aim to assess the therapeutic potential of this approach in pregnancy to enhance NO bioactivity, improve uteroplacental vascular function and increase fetal growth.

Invited review: impact of specific nutrient interventions during mid-to-late gestation on physiological traits important for survival of multiple-born lambs

To improve production efficiency, the sheep meat industry has increased flock prolificacy. However, multiple-born lambs have lower birth weights, increased mortality and reduced growth rate compared with single-born lambs. Lamb mortality is a major issue for livestock farming globally and solutions are required to increase survival to realise the value of increased flock fecundity. Nutrition during gestation can influence maternal-foetal placental nutrient transfer and thus foetal growth and organ/tissue development, as well as improve postnatal productivity. This review covers the challenges and opportunities associated with increased prolificacy, highlights gaps in our knowledge and identifies some opportunities for how targeted intervention with specific nutrients during mid-to-late pregnancy may influence lamb survival and productivity with a specific focus on pasture-based systems. This time frame was selected as intervention strategies in short-time windows post-pregnancy scanning and before lambing to improve lamb survival in high-risk groups (e.g. triplets) are likely to be the most practical and economically feasible options for pasture-based extensive farming systems.

Competition for Materno-Fetal Resource Partitioning in a Rabbit Model of Undernourished Pregnancy

The major goal of animal production is to obtain abundant and healthy meat for consumers. Maternal food restriction (MFR) is often applied in farms to reduce production costs. However, the suitability of MFR in livestock animals is questionable, as this management may compromise maternal fitness due to a severe negative energetic balance and can induce Intrauterine Growth Restriction (IUGR) and prenatal programming in the offspring. Here, we sought to determine, using pregnant rabbits, the consequences of MFR on maternal endocrine and metabolic status and conceptus development. Pregnant dams were distributed into three groups: CONTROL (ad libitum feeding throughout the entire pregnancy; mean pregnancy length being around 31 days), UNDERFED (50% MFR during the entire pregnancy) and EARLY-UNDERFED (50% MFR only during the preimplantation period, Days 0–7). Maternal leptin concentrations and glycemic and lipid profiles were determined throughout pregnancy, whilst conceptus development was assessed ex-vivo at Day 28. Placental parameters were determined by macroscopic and histological evaluations and apoptotic assessments (TUNEL and Caspase-3). The main results of the study showed that, despite MFR altered maternal plasma lipid concentration (P<0.05), there were no effects on maternal bodyweight, plasma leptin concentration or glycemic profile. Fetal crown-rump lengths were reduced in both undernourished groups (P<0.001), but a significant reduction in fetal weight was only observed in the UNDERFED group (P<0.001). Growth in both undernourished groups was asymmetrical, with reduced liver weight (P<0.001) and significantly increased brain: fetal weight-ratio (P<0.001) and brain: liver weight-ratio (P<0.001) when compared to the CONTROL group. A significant reduction in placental weight was only observed in the UNDERFED group (P<0.001), despite both undernourished groups showing higher apoptotic rates at decidua and labyrinth zone (P<0.05) than the CONTROL group. Thus, these groups evidenced signs of placental degeneration, necrosis and stromal collapse. In summary, MFR may encourage the mother to make strategic decisions to safeguard her metabolic status and fitness at the expense of growth reduction in the litter, resulting in enhanced apoptotic and pathological processes at placental level and IUGR.

Sildenafil therapy for fetal cardiovascular dysfunction during hypoxic development: studies in the chick embryo

KEY POINTS

Common complications of pregnancy, such as chronic fetal hypoxia, trigger a fetal origin of cardiovascular dysfunction and programme cardiovascular disease in later life. Sildenafil treatment protects placental perfusion and fetal growth, but whether the effects of sildenafil transcend the placenta to affect the fetus is unknown. Using the chick embryo model, here we show that sildenafil treatment directly protects the fetal cardiovascular system in hypoxic development, and that the mechanisms of sildenafil protection include reduced oxidative stress and increased nitric oxide bioavailability; Sildenafil does not protect against fetal growth restriction in the chick embryo, supporting the idea that the protective effect of sildenafil on fetal growth reported in mammalian studies, including humans, is secondary to improved placental perfusion. Therefore, sildenafil may be a good candidate for human translational antioxidant therapy to protect the chronically hypoxic fetus in adverse pregnancy.

ABSTRACT

There is a need for developing clinically translatable therapy for preventing fetal origins of cardiovascular disease in pregnancy complicated by chronic fetal hypoxia. Evidence shows that sildenafil protects placental perfusion and fetal growth. However, whether beneficial effects of sildenafil transcend onto the fetal heart and circulation in complicated development is unknown. We isolated the direct effects of sildenafil on the fetus using the chick embryo and hypothesised that sildenafil also protects fetal cardiovascular function in hypoxic development. Chick embryos (n = 11 per group) were incubated in normoxia or hypoxia (14% O₂ ) from day 1 and treated with sildenafil (4 mg kg^-1  day^-1 ) from day 13 of the 21-day incubation. Hypoxic incubation increased oxidative stress (4-hydroxynonenal, 141.1 ± 17.6% of normoxic control), reduced superoxide dismutase (60.7 ± 6.3%), increased phosphodiesterase type 5 expression (167 ± 13.7%) and decreased nitric oxide bioavailability (54.7 ± 6.1%) in the fetal heart, and promoted peripheral endothelial dysfunction (70.9 ± 5.6% AUC of normoxic control; all P < 0.05). Sildenafil treatment after onset of chronic hypoxia prevented the increase in phosphodiesterase expression (72.5 ± 22.4%), protected against oxidative stress (94.7 ± 6.2%) and normalised nitric oxide bioavailability (115.6 ± 22.3%) in the fetal heart, and restored endothelial function in the peripheral circulation (89.8 ± 2.9%). Sildenafil protects the fetal heart and circulation directly in hypoxic development via mechanisms including decreased oxidative stress and enhanced nitric oxide bioavailability. Sildenafil may be a good translational candidate for human antioxidant therapy to prevent fetal origins of cardiovascular dysfunction in adverse pregnancy.

Maternal Administration of Sildenafil Citrate Alters Fetal and Placental Growth and Fetal–Placental Vascular Resistance in the Growth-Restricted Ovine Fetus

Intrauterine growth restriction (IUGR) causes short- and long-term morbidity. Reduced placental perfusion is an important pathogenic component of IUGR; substances that enhance vasodilation in the uterine circulation, such as sildenafil citrate (sildenafil), may improve placental blood flow and fetal growth. This study aimed to examine the effects of sildenafil in the growth-restricted ovine fetus. Ewes carrying singleton pregnancies underwent insertion of vascular catheters, and then, they were randomized to receive uterine artery embolization (IUGR) or to a control group. Ewes in the IUGR group received a daily infusion of sildenafil (IUGR+SC; n=10) or vehicle (IUGR+V; n=8) for 21 days. The control group received no treatment (n=9). Umbilical artery blood flow was measured using Doppler ultrasound and the resistive index (RI) calculated. Fetal weight, biometry, and placental weight were obtained at postmortem after treatment completion. Umbilical artery RI in IUGR+V fell less than in controls; the RI of IUGR+SC was intermediate to that of the other 2 groups (mean±SEM for control versus IUGR+V versus IUGR+SC: ∆RI, 0.09±0.03 versus −0.01±0.02 versus 0.03±0.02; F (2, 22)=4.21; P =0.03). Compared with controls, lamb and placental weights were reduced in IUGR+V but not in IUGR+SC (control versus IUGR+V versus IUGR+SC: fetal weight, 4381±247 versus 3447±235 versus 3687±129 g; F (2, 24)=5.49; P =0.01 and placental weight: 559.7±35.0 versus 376.2±32.5 versus 475.2±42.5 g; F (2, 24)=4.64; P =0.01). Sildenafil may be a useful adjunct in the management of IUGR. An increase in placental weight and fall in fetal–placental resistance suggests that changes to growth are at least partly mediated by changes to placental growth rather than alterations in placental efficiency.

Intrauterine growth restriction: impact on cardiovascular development and function throughout infancy

Intrauterine growth restriction (IUGR) refers to the situation where a fetus does not grow according to its genetic growth potential. One of the main causes of IUGR is uteroplacental vascular insufficiency. Under these circumstances of chronic oxygen and nutrient deprivation, the growth-restricted fetus often displays typical circulatory changes, which in part represent adaptations to the suboptimal intrauterine environment. These fetal adaptations aim to preserve oxygen and nutrient supply to vital organs such as the brain, the heart, and the adrenals. These prenatal circulatory adaptations are thought to lead to an altered development of the cardiovascular system and "program" the fetus for life long cardiovascular morbidities. In this review, we discuss the alterations to cardiovascular structure, function, and control that have been observed in growth-restricted fetuses, neonates, and infants following uteroplacental vascular insufficiency. We also discuss the current knowledge on early life surveillance and interventions to prevent progression into chronic disease.

Reprogramming: A Preventive Strategy in Hypertension Focusing on the Kidney

Adulthood hypertension can be programmed in response to a suboptimal environment in early life. However, developmental plasticity also implies that one can prevent hypertension in adult life by administrating appropriate compounds during early development. We have termed this reprogramming. While the risk of hypertension has been assessed in many mother-child cohorts of human developmental programming, interventions necessary to prove causation and provide a reprogramming strategy are lacking. Since the developing kidney is particularly vulnerable to environmental insults and blood pressure is determined by kidney function, renal programming is considered key in developmental programming of hypertension. Common pathways, whereby both genetic and acquired developmental programming converge into the same phenotype, have been recognized. For instance, the same reprogramming interventions aimed at shifting nitric oxide (NO)-reactive oxygen species (ROS) balance, such as perinatal citrulline or melatonin supplements, can be protective in both genetic and developmentally programmed hypertension. Furthermore, a significantly increased expression of gene Ephx2 (soluble epoxide hydrolase) was noted in both genetic and acquired animal models of hypertension. Since a suboptimal environment is often multifactorial, such common reprogramming pathways are a practical finding for translation to the clinic. This review provides an overview of potential clinical applications of reprogramming strategies to prevent programmed hypertension. We emphasize the kidney in the following areas: mechanistic insights from human studies and animal models to interpret programmed hypertension; identified risk factors of human programmed hypertension from mother-child cohorts; and the impact of reprogramming strategies on programmed hypertension from animal models. It is critical that the observed effects on developmental reprogramming in animal models are replicated in human studies.

Doppler sonographic examination of uterine and placental perfusion in cows in the last month of gestation and effects of epidural anesthesia and isoxsuprine

The massive increase in size of the fetus and uterus in the last trimester is accompanied by an increasing demand for nutrients and oxygen, and it is assumed that this demand is met by increasing uterine and fetal perfusion. The goals of this study were to measure the perfusion of the uterine arteries and the placentomes in the last month of gestation and to investigate the effect of epidural anesthesia and isoxsuprine on perfusion. During the last month of gestation, eight Braunvieh cows underwent nine color Doppler sonographic examinations of the uterine arteries to determine diameter (DM), pulse rate (PR), resistance index, time-averaged maximum blood flow velocity (TAMV), and blood flow volume (BFV), and power-mode Doppler sonography was used to determine perfusion of placentomes. The PR increased (P < 0.001), and the BFV and TAMV of the ipsilateral uterine artery decreased between 4.5 and 0.5 weeks prepartum (BFV, 236.8 ± 65.80 and 208 ± 41.52 cm(3)/s, P < 0.01; TAMV, 140.0 ± 26.53 cm/s and 125.2 ± 18.46 cm/s, P < 0.05). After sonographic examination, the cows received epidural administration of local anesthetic (100-mg lidocaine) in the sacrococcygeal space or isoxsuprine (200 mg/cow, iv), and the sonographic measurements were repeated 30 minutes later. After epidural anesthesia, the TAMV and BFV of the contralateral uterine artery increased by 5.4% (P < 0.05) and 7.9% (P < 0.01). In the placentomes of the gravid uterine horn, the relative placentome perfusion and the color pixel grading (Cp) increased by 10.1% (P < 0.05) and 11.5% (P < 0.01) after epidural anesthesia. After isoxsuprine, the DM, PR, and BFV increased by 4.7%, 49.3%, and 16.9% in the ipsilateral uterine artery and by 10.8%, 48.7%, and 22.8%, respectively in the contralateral uterine artery. The TAMV of the ipsilateral uterine artery increased by 7.1% (P < 0.01), and the resistance index decreased in both uterine arteries (ipsilateral 24.2%, contralateral 14.9%, both P < 0.00001). Isoxsuprine increased the relative placentome perfusion and the Cp of the placentomes by 18.1% and 18.3% in the gravid horn and by 10.2% and 24.2% in the nongravid horn. Blood flow variables changed little in the last month of gestation. However, epidural anesthesia and isoxsuprine caused changes in uterine and placentome perfusion that suggest improvement of placental nutrient and oxygen supply to the fetus.

Select nutrients and their effects on conceptus development in mammals

The dialogue between the mammalian conceptus (embryo/fetus and associated membranes) involves signaling for pregnancy recognition and maintenance of pregnancy during the critical peri-implantation period of pregnancy when the stage is set for implantation and placentation that precedes fetal development. Uterine epithelial cells secrete and/or transport a wide range of molecules, including nutrients, collectively referred to as histotroph that are transported into the fetal-placental vascular system to support growth and development of the conceptus. The availability of uterine-derived histotroph has long-term consequences for the health and well-being of the fetus and the prevention of adult onset of metabolic diseases. Histotroph includes numerous amino acids, but arginine plays a particularly important role as a source of nitric oxide and polyamines required for fetal-placental development in rodents, swine and humans through mechanisms that remain to be fully elucidated. Mechanisms whereby arginine regulates expression of genes via the mechanistic target of rapamycin cell signaling pathways critical to conceptus development, implantation and placentation are discussed in detail in this review.

Improving amino acid nutrition to prevent intrauterine growth restriction in mammals

Intrauterine growth restriction (IUGR) is one of the most common concerns in human obstetrics and domestic animal production. It is usually caused by placental insufficiency, which decreases fetal uptake of nutrients (especially amino acids) from the placenta. Amino acids are not only building blocks for protein but also key regulators of metabolic pathways in fetoplacental development. The enhanced demands of amino acids by the developing conceptus must be met via active transport systems across the placenta as normal pregnancy advances. Growing evidence indicates that IUGR is associated with a reduction in placental amino acid transport capacity and metabolic pathways within the embryonic/fetal development. The positive relationships between amino acid concentrations in circulating maternal blood and placental amino acid transport into fetus encourage designing new therapies to prevent or treat IUGR by enhancing amino acid availability in maternal diets or maternal circulation. Despite the positive effects of available dietary interventions, nutritional therapy for IUGR is still in its infancy. Based on understanding of the underlying mechanisms whereby amino acids promote fetal growth and of their dietary requirements by IUGR, supplementation with functional amino acids (e.g., arginine and glutamine) hold great promise for preventing fetal growth restriction and improving health and growth of IUGR offspring.

Factors controlling nutrient availability to the developing fetus in ruminants

Inadequate delivery of nutrients results in intrauterine growth restriction (IUGR), which is a leading cause of neonatal morbidity and mortality in livestock. In ruminants, inadequate nutrition during pregnancy is often prevalent due to frequent utilization of exensive forage based grazing systems, making them highly susceptible to changes in nutrient quality and availability. Delivery of nutrients to the fetus is dependent on a number of critical factors including placental growth and development, utero-placental blood flow, nutrient availability, and placental metabolism and transport capacity. Previous findings from our laboratory and others, highlight essential roles for amino acids and their metabolites in supporting normal fetal growth and development, as well as the critical role for amino acid transporters in nutrient delivery to the fetus. The focus of this review will be on the role of maternal nutrition on placental form and function as a regulator of fetal development in ruminants.

The influence of Sildenafil citrate on uterine tissue perfusion and the cardiovascular system during the luteal phase of the ovarian cycle in cows

The aim of the study was to evaluate the influence of the Sildenafil citrate on the blood flow in the uterus of cows during dioestrus. Uterine blood flow was examined in five, healthy, adult cows. Between day 6-8 of the ovarian cycle, each cow received 200mg of sildenafil diluted in 10ml of warm saline into the body of the uterus. Analysis of the blood pressure, ECG and the maximum velocity in m/s (V max) in the aorta was performed and selected parameters of the blood flow (PI, pulsatile index; RI, resistance index; SPV, systolic peak velocity; EDV, end diastolic velocity; FVI, flow velocity integral; SV/DV, systolic peak velocity: end-diastolic velocity ratio) were measured in the uterine artery (Arteria uterine) before and after sildenafil infusion. In addition, Color Doppler examination of the uterine wall perfusion was analyzed. A significant decrease of values of PI and SV/DV ratio as well as an increase of end diastolic velocity and time averaged maximum velocity was noted. With the use of color coded sonography, the increased intensity of the blood flow in the uterine wall was observed. It was concluded that intrauterine administration of sildenafil during dioestrus can increase uterine tissue perfusion.

Parenteral administration of twin-bearing ewes with L-arginine enhances the birth weight and brown fat stores in sheep

The objective of this study was to evaluate the effects of parenteral administration of L-arginine (Arg) to well-fed twin-bearing ewes from day (d) 100 of pregnancy to birth on fetal growth, body composition and neonatal behavior. Ewes received an i.v. bolus of either 345 μmol Arg-HCl/kg bodyweight or saline solution (control) 3 times a day. At d 140 of pregnancy, Arg-supplemented and control ewes were euthanized and fetal weight and fetal organ weight recorded, and maternal and fetal plasma concentrations of amino acids, hormones and metabolites analyzed. A subset of ewes was allowed to lamb and birth weight, body dimensions and behavior of the lambs in the first 2 hours(h) following birth recorded and blood samples collected. At d 140 of pregnancy, fetal weight internal organ weights were unaffected by treatment with the exception of brown fat stores which were increased by 16% in fetuses from Arg-supplemented ewes relative to controls (P < 0.05). At birth, there was an interaction (P = 0.06) between treatment and sex for birth weight of the lamb. The ewe lambs from Arg-supplemented ewes were 12% (P < 0.05) heavier at birth compared with controls whereas birth weight of male lambs did not differ. These results indicate that maternal Arg supplementation enhanced brown fat stores in the fetus and countered some effect of fetal growth restriction due to litter size in female lambs. Increasing birth weight of female lambs and enhancing brown fat stores of all lambs may have important implications for lamb survival and postnatal growth.

Sildenafil citrate increases fetal weight in a mouse model of fetal growth restriction with a normal vascular phenotype

Fetal growth restriction (FGR) is defined as the inability of a fetus to achieve its genetic growth potential and is associated with a significantly increased risk of morbidity and mortality. Clinically, FGR is diagnosed as a fetus falling below the 5(th) centile of customised growth charts. Sildenafil citrate (SC, Viagra™), a potent and selective phosphodiesterase-5 inhibitor, corrects ex vivo placental vascular dysfunction in FGR, demonstrating potential as a therapy for this condition. However, many FGR cases present without an abnormal vascular phenotype, as assessed by Doppler measures of uterine/umbilical artery blood flow velocity. Thus, we hypothesized that SC would not increase fetal growth in a mouse model of FGR, the placental-specific Igf2 knockout mouse, which has altered placental exchange capacity but normal placental blood flow. Fetal weights were increased (by 8%) in P0 mice following maternal SC treatment (0.4 mg/ml) via drinking water. There was also a trend towards increased placental weight in treated P0 mice (P = 0.056). Additionally, 75% of the P0 fetal weights were below the 5(th) centile, the criterion used to define human FGR, of the non-treated WT fetal weights; this was reduced to 51% when dams were treated with SC. Umbilical artery and vein blood flow velocity measures confirmed the lack of an abnormal vascular phenotype in the P0 mouse; and were unaffected by SC treatment. (14)C-methylaminoisobutyric acid transfer (measured to assess effects on placental nutrient transporter activity) per g placenta was unaffected by SC, versus untreated, though total transfer was increased, commensurate with the trend towards larger placentas in this group. These data suggest that SC may improve fetal growth even in the absence of an abnormal placental blood flow, potentially affording use in multiple sub-populations of individuals presenting with FGR.