Animal models of fetal growth restriction: Considerations for translational medicine

Selective Targeting of a Novel Vasodilator to the Uterine Vasculature to Treat Impaired Uteroplacental Perfusion in Pregnancy

Fetal growth restriction (FGR) in pregnancy is commonly caused by impaired uteroplacental blood flow. Vasodilators enhance uteroplacental perfusion and fetal growth in humans and animal models; however, detrimental maternal and fetal side effects have been reported. We hypothesised that targeted uteroplacental delivery of a vasodilator would enhance drug efficacy and reduce the risks associated with drug administration in pregnancy. Phage screening identified novel peptides that selectively accumulated in the uteroplacental vasculature of pregnant mice. Following intravenous injection, the synthetic peptide CNKGLRNK selectively bound to the endothelium of the uterine spiral arteries and placental labyrinth in vivo; CNKGLRNK-decorated liposomes also selectively bound to these regions. The nitric oxide donor 2-[[4-[(nitrooxy)methyl]benzoyl]thio]-benzoic acid methyl ester (SE175) induced significant relaxation of mouse uterine arteries and human placental arteries in vitro; thus, SE175 was encapsulated into these targeted liposomes and administered to healthy pregnant C57BL/6J mice or endothelial nitric oxide synthase knockout (eNOS-/-) mice, which exhibit impaired uteroplacental blood flow and FGR. Liposomes containing SE175 (0.44mg/kg) or PBS were administered on embryonic (E) days 11.5, 13.5, 15.5 and 17.5; fetal and placental weights were recorded at term and compared to mice injected with free PBS or SE175. Targeted uteroplacental delivery of SE175 had no effect on fetal weight in C57BL/6J mice, but significantly increased fetal weight and mean spiral artery diameter, and decreased placental weight, indicative of improved placental efficiency, in eNOS-/- mice; free SE175 had no effect on fetal weight or spiral artery diameter. Targeted, but not free SE175 also significantly reduced placental expression of 4-hydroxynonenal, cyclooxygenase-1 and cyclooxygenase-2, indicating a reduction in placental oxidative stress. These data suggest that exploiting vascular targeting peptides to selectively deliver SE175 to the uteroplacental vasculature may represent a novel treatment for FGR resulting from impaired uteroplacental perfusion.

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.

Maternal Choline Supplementation Alters Fetal Growth Patterns in a Mouse Model of Placental Insufficiency

Impairments in placental development can adversely affect pregnancy outcomes. The bioactive nutrient choline may mitigate some of these impairments, as suggested by data in humans, animals, and human trophoblasts. Herein, we investigated the effects of maternal choline supplementation (MCS) on parameters of fetal growth in a Dlx3+/− (distal-less homeobox 3) mouse model of placental insufficiency. Dlx3+/− female mice were assigned to 1X (control), 2X, or 4X choline intake levels during gestation. Dams were sacrificed at embryonic days E10.5, 12.5, 15.5, and 18.5. At E10.5, placental weight, embryo weight, and placental efficiency were higher in 4X versus 1X choline. Higher concentrations of hepatic and placental betaine were detected in 4X versus 1X choline, and placental betaine was positively associated with embryo weight. Placental mRNA expression of Igf1 was downregulated by 4X (versus 1X) choline at E10.5. No differences in fetal growth parameters were detected at E12.5 and 15.5, whereas a small but significant reduction in fetal weight was detected at E18.5 in 4X versus 1X choline. MCS improved fetal growth during early pregnancy in the Dlx3+/− mice with the compensatory downregulation of Igf1 to slow growth as gestation progressed. Placental betaine may be responsible for the growth-promoting effects of choline.

Maternal Macronutrient Consumption and the Developmental Origins of Metabolic Disease in the Offspring

Recent research aimed at understanding the rise in obesity and cardiometabolic disease in children suggests that suboptimal maternal nutrition conditions organ systems and physiological responses in the offspring contributing to disease development. Understanding the mechanisms by which the macronutrient composition of the maternal diet during pregnancy or lactation affects health outcomes in the offspring may lead to new maternal nutrition recommendations, disease prevention strategies and therapies that reduce the increasing incidence of cardiometabolic disease in children. Recent mechanistic animal model research has identified how excess fats and sugars in the maternal diet alter offspring glucose tolerance, insulin signaling and metabolism. Maternal nutrition appears to influence epigenetic alterations in the offspring and the programming of gene expression in key metabolic pathways. This review is focused on experimental studies in animal models that have investigated mechanisms of how maternal consumption of macronutrients affects cardiometabolic disease development in the offspring. Future research using "-omic" technologies is essential to elucidate the mechanisms of how altered maternal macronutrient consumption influences the development of disease in the offspring.

Description of a method for inducing fetal growth restriction in the spiny mouse

Intrauterine or fetal growth restriction (IUGR) is a major complication of pregnancy and leads to significant perinatal morbidities and mortality. Typically, induction of IUGR in animals involves the complete occlusion or ablation of vessels to the uterus or placenta, acutely impairing blood flow and fetal growth, usually with high fetal loss. We aimed to produce a model of reduced fetal growth in the spiny mouse with minimal fetal loss. At 27 days gestational age (term is 38-39 days), a piece of silastic tubing was placed around the left uterine artery to prevent the further increase of uterine blood flow with advancing gestation to induce IUGR (occluded). Controls were generated from sham surgeries without placement of the tubing. Dams were humanely euthanized at 37 days gestational age and all fetuses and placentas were weighed and collected. Of the 17 dams that underwent surgery, 15 carried their pregnancies to 37 days gestational age and 95% of fetuses survived to this time. The difference in fetal body weight between occluded and control was ~21% for fetuses in the left uterus side: there were no differences for fetuses in the right uterus side. Offspring from the occluded group had significantly lower brain, liver, lung, kidney and carcass weights compared with shams. Preventing the gestation-related increase of uterine blood flow induced significant growth restriction in the fetal spiny mouse, with minimal fetal loss. This technique could be readily adapted for other small animal.

Antecedents and correlates of blood concentrations of neurotrophic growth factors in very preterm newborns

AIM

To identify the antecedents and very early correlates of low concentrations of neurotrophic growth factors in the blood of extremely preterm newborns during the first postnatal month.

METHODS

Using an immunobead assay, we measured the concentrations of neurotrophin 4 (NT4), brain-derived neurotrophic factor (BDNF), and basic fibroblast growth factor (bFGF) in blood spots collected on postnatal days 1 (N=1062), 7 (N=1087), 14 (N=989), 21 (N=940) and 28 (N=880) from infants born before the 28th week of gestation. We then sought the correlates of measurements in the top and bottom quartiles for gestational age and day the specimen was collected.

RESULTS

The concentrations of 2 neurotrophic proteins, NT4 and BDNF, were low among children delivered for medical (maternal or fetal) indications, and among those who were growth restricted. Children who had top quartile concentrations of NT4, BDNF, and bFGF tended to have elevated concentrations of inflammation-related proteins that day. This pattern persisted for much of the first postnatal month.

CONCLUSIONS

Delivery for medical indications and fetal growth restriction are associated with a relative paucity of NT4 and BDNF concentrations during the first 24 h after very preterm birth. Elevated blood concentrations of NT4, BDNF, and bFGF tended to co-occur with indicators of systemic inflammation on the same day.

Placental Origins of Chronic Disease

Epidemiological evidence links an individual's susceptibility to chronic disease in adult life to events during their intrauterine phase of development. Biologically this should not be unexpected, for organ systems are at their most plastic when progenitor cells are proliferating and differentiating. Influences operating at this time can permanently affect their structure and functional capacity, and the activity of enzyme systems and endocrine axes. It is now appreciated that such effects lay the foundations for a diverse array of diseases that become manifest many years later, often in response to secondary environmental stressors. Fetal development is underpinned by the placenta, the organ that forms the interface between the fetus and its mother. All nutrients and oxygen reaching the fetus must pass through this organ. The placenta also has major endocrine functions, orchestrating maternal adaptations to pregnancy and mobilizing resources for fetal use. In addition, it acts as a selective barrier, creating a protective milieu by minimizing exposure of the fetus to maternal hormones, such as glucocorticoids, xenobiotics, pathogens, and parasites. The placenta shows a remarkable capacity to adapt to adverse environmental cues and lessen their impact on the fetus. However, if placental function is impaired, or its capacity to adapt is exceeded, then fetal development may be compromised. Here, we explore the complex relationships between the placental phenotype and developmental programming of chronic disease in the offspring. Ensuring optimal placentation offers a new approach to the prevention of disorders such as cardiovascular disease, diabetes, and obesity, which are reaching epidemic proportions.

Intrauterine Growth Restriction: Hungry for an Answer

Intrauterine growth restriction (IUGR) has been defined in several ways, but in general describes a condition in which the fetus exhibits poor growth in utero. This complication of pregnancy poses a significant public health burden as well as increased morbidity and mortality for the offspring. In human IUGR, alteration in fetal glucose and insulin homeostasis occurs in an effort to conserve energy and survive at the expense of fetal growth in an environment of inadequate nutrient provision. Several animal models of IUGR have been utilized to study the effects of IUGR on fetal glucose handling, as well as the postnatal reprogramming of energy metabolite handling, which may be unmasked in adulthood as a maladaptive propensity for cardiometabolic disease. This developmental programming may be mediated in part by epigenetic modification of essential regulators of glucose homeostasis. Several pharmacological therapies and nonpharmacological lifestyle modifications have shown early promise in mitigating the risk for or severity of adult metabolic phenotypes but still require further study of unanticipated and/or untoward side effects.

Sox21 deletion in mice causes postnatal growth deficiency without physiological disruption of hypothalamic-pituitary endocrine axes

The hypothalamic-pituitary axes are the coordinating centers for multiple endocrine gland functions and physiological processes. Defects in the hypothalamus or pituitary gland can cause reduced growth and severe short stature, affecting approximately 1 in 4000 children, and a large percentage of cases of pituitary hormone deficiencies do not have an identified genetic cause. SOX21 is a protein that regulates hair, neural, and trophoblast stem cell differentiation. Mice lacking Sox21 have reduced growth, but the etiology of this growth defect has not been described. We studied the expression of Sox21 in hypothalamic-pituitary development and examined multiple endocrine axes in these mice. We find no evidence of reduced intrauterine growth, food intake, or physical activity, but there is evidence for increased energy expenditure in mutants. In addition, despite changes in pituitary hormone expression, hypothalamic-pituitary axes appear to be functional. Therefore, SOX21 variants may be a cause of non-endocrine short stature in humans.

Role of hypoxia during nephrogenesis

Mammals develop in a physiologically hypoxic state, and the oxygen tension of different tissues in the embryo is precisely controlled. Deviation from normal oxygenation, such as what occurs in placental insufficiency, can disrupt fetal development. Several studies demonstrate that intrauterine hypoxia has a negative effect on kidney development. As nascent nephrons are forming from nephron progenitors in the nephrogenic zone, they are exposed to varying oxygen tension by virtue of the development of the renal vasculature. Thus, nephrogenesis may be linked to oxygen tension. However, the mechanism(s) by which this occurs remains unclear. This review focuses on what is known about molecular mechanisms active in physiological and pathological hypoxia and their effects on kidney development.

Sterile inflammation and pregnancy complications: a review

Inflammation is essential for successful embryo implantation, pregnancy maintenance and delivery. In the last decade, important advances have been made in regard to endogenous, and therefore non-infectious, initiators of inflammation, which can act through the same receptors as pathogens. These molecules are referred to as damage-associated molecular patterns (DAMPs), and their involvement in reproduction has only recently been unraveled. Even though inflammation is necessary for successful reproduction, untimely activation of inflammatory processes can have devastating effect on pregnancy outcomes. Many DAMPs, such as uric acid, high-mobility group box 1 (HMGB1), interleukin (IL)-1 and cell-free fetal DNA, have been associated with pregnancy complications, such as miscarriages, preeclampsia and preterm birth in preclinical models and in humans. However, the specific contribution of alarmins to these conditions is still under debate, as currently there is lack of information on their mechanism of action. In this review, we discuss the role of sterile inflammation in reproduction, including early implantation and pregnancy complications. Particularly, we focus on major alarmins vastly implicated in numerous sterile inflammatory processes, such as uric acid, HMGB1, IL-1α and cell-free DNA (especially that of fetal origin) while giving an overview of the potential role of other candidate alarmins.

Maternal Therapy with Ad.VEGF-A165 Increases Fetal Weight at Term in a Guinea-Pig Model of Fetal Growth Restriction

In a model of growth-restricted sheep pregnancy, it was previously demonstrated that transient uterine artery VEGF overexpression can improve fetal growth. This approach was tested in guinea-pig pregnancies, where placental physiology is more similar to humans. Fetal growth restriction (FGR) was attained through peri-conceptual nutrient restriction in virgin guinea pigs. Ad.VEGF-A₁₆₅ or Ad.LacZ (1 × 10¹⁰vp) was applied at mid-gestation via laparotomy, delivered externally to the uterine circulation with thermosensitive gel. At short-term (3-8 days post surgery) or at term gestation, pups were weighed, and tissues were sampled for vector spread analysis, VEGF expression, and its downstream effects. Fetal weight at term was increased (88.01 ± 13.36 g; n = 26) in Ad.VEGF-A₁₆₅-treated animals compared with Ad.LacZ-treated animals (85.52 ± 13.00 g; n = 19; p = 0.028). The brain, liver, and lung weight and crown rump length were significantly larger in short-term analyses, as well as VEGF expression in transduced tissues. At term, molecular analyses confirmed the presence of VEGF transgene in target tissues but not in fetal samples. Tissue histology analysis and blood biochemistry/hematological examination were comparable with controls. Uterine artery relaxation in Ad.VEGF-A₁₆₅-treated dams was higher compared with Ad.LacZ-treated dams. Maternal uterine artery Ad.VEGF-A₁₆₅ increases fetal growth velocity and term fetal weight in growth-restricted guinea-pig pregnancy.

The use of ultrasound to assess fetal growth in a guinea pig model of fetal growth restriction

Fetal growth restriction (FGR) is a common and potentially severe pregnancy complication. Currently there is no treatment available. The guinea pig is an attractive model of human pregnancy as placentation is morphologically very similar between the species. Nutrient restriction of the dam creates growth-restricted fetuses while leaving an intact uteroplacental circulation, vital for evaluating novel therapies for FGR. Growth-restricted fetuses were generated by feeding Dunkin Hartley guinea pig dams 70% of ad libitum intake from four weeks before and throughout pregnancy. The effect of maternal nutrient restriction (MNR) on dams and fetuses was carefully monitored, and ultrasound measurements of pups collected. There was no difference in maternal weight at conception, however by five weeks post conception MNR dams were significantly lighter ( P < 0.05). MNR resulted in significantly smaller pup size from 0.6-0.66 gestation. Ultrasound is a powerful non-invasive tool for assessing the effect of therapeutic interventions on fetal growth, allowing longitudinal measurement of fetuses. This model and method yield data applicable to the human condition without the need for animal sacrifice and will be useful in the translation of therapies for FGR into the clinic.

[The role of oxidative stress in placental-related diseases of pregnancy]

In normal pregnancies, the earliest stages of development take place in a low oxygen (O₂) environment. This physiological hypoxia of the early gestational sac protects the developing fetus against the deleterious and teratogenic effects of O₂free radicals. Oxidative stress is manifested at the maternal-fetal interface from early pregnancy onwards. In early pregnancy, a well-controlled oxidative stress plays a role in modulating placental development, functions and remodelling. Focal trophoblastic oxidative damage and progressive villous degeneration trigger the formation of the fetal membranes, which is an essential developmental step enabling vaginal delivery. Our data have demonstrated that the first trimester placenta in humans is histiotrophic and not haemochorial. The development and maintenance of a physiological O₂ gradient between the uterine and fetal circulations is also essential for placental functions, such as transport and hormonal synthesis. Pathological oxidative stress arises when the production of reactive O₂ species overwhelms the intrinsic anti-oxidant defences causing indiscriminate damage to biological molecules, leading to loss of function and cell death. We here review the role of oxidative stress in the pathophysiology of miscarriage, pre-eclampsia and fetal growth restriction.

Regulation of fetal liver growth in a model of diet restriction in the pregnant rat

Limited nutrient availability is a cause of intrauterine growth restriction (IUGR), a condition that has important implications for the well being of the offspring. Using the established IUGR model of maternal fasting in the rat, we investigated mechanisms that control gene expression and mRNA translation in late-gestation fetal liver. Maternal fasting for 48 h during the last one-third of gestation was associated with a 10-15% reduction in fetal body weight and a disproportionate one-third reduction in total fetal liver protein. The fetal liver transcriptome showed only subtle changes consistent with reduced cell proliferation and enhanced differentiation in IUGR. Effects on the transcriptome could not be attributed to specific transcription factors. We purified translating polysomes to profile the population of mRNAs undergoing active translation. Microarray analysis of the fetal liver translatome indicated a global reduction of translation. The only targeted effect was enhanced translation of mitochondrial ribosomal proteins in IUGR, consistent with enhanced mitochondrial biogenesis. There was no evidence for attenuated signaling through the mammalian target of rapamycin (mTOR). Western blot analysis showed no changes in fetal liver mTOR signaling. However, eukaryotic initiation factor 2α (eIF2α) phosphorylation was increased in livers from IUGR fetuses, consistent with a role in global translation control. Our data indicate that IUGR-associated changes in hepatic gene expression and mRNA translation likely involve a network of complex regulatory mechanisms, some of which are novel and distinct from those that mediate the response of the liver to nutrient restriction in the adult rat.

Stimulatory Effects of Coumestrol on Embryonic and Fetal Development Through AKT and ERK1/2 MAPK Signal Transduction

Successful establishment of pregnancy is required for fetal-maternal interactions regulating implantation, embryonic development and placentation. A uterine environment with insufficient growth factors and nutrients increases the incidence of intrauterine growth restriction (IUGR) leading to an impaired uterine environment. In the present study, we demonstrated the effects of the phytoestrogen coumestrol on conceptus development in the pig that is regarded as an excellent biomedical animal model for research on IUGR. Results of this study indicated that coumestrol induced migration of porcine trophectoderm (pTr) cells in a concentration-dependent manner. In response to coumestrol, the phosphorylation of AKT, P70S6K, S6, ERK1/2 MAPK, and P90RSK proteins were activated in pTr cells and ERK1/2 MAPK and P90RSK phosphorylation was prolonged for a longer period than for the other proteins. To identify the signal transduction pathway induced by coumestrol, pharmacological inhibitors U0126 (an ERK1/2 inhibitor) and LY294002 (a PI3K inhibitor) were used to pretreat pTr cells. The results showed that coumestrol-induced phosphorylation of ERK1/2 MAPK and P90RSK was blocked by U0126. In addition, the increased phosphorylation in response to coumestrol was completely inhibited following pre-treatment incubation of pTr cells in the presence of LY294002 and U0126. Furthermore, these two inhibitors suppressed the ability of coumestrol to induce migration of pTr cells. Collectively, these findings suggest that coumestrol affects embryonic development through activation of the PI3K/AKT and ERK1/2 MAPK cell signal transduction pathways and improvement in the uterine environment through coumestrol supplementation may provide beneficial effects of enhancing embryonic and fetal survival and development. J. Cell. Physiol. 231: 2733-2740, 2016. © 2016 Wiley Periodicals, Inc.

Expression of epigenetic machinery genes is sensitive to maternal obesity and weight loss in relation to fetal growth in mice

BACKGROUND

Maternal obesity impacts fetal growth and pregnancy outcomes. To counteract the deleterious effects of obesity on fertility and pregnancy issue, preconceptional weight loss is recommended to obese women. Whether this weight loss is beneficial/detrimental for offspring remains poorly explored. Epigenetic mechanisms could be affected by maternal weight changes, perturbing expression of key developmental genes in the placenta or fetus. Our aim was to investigate the effects of chronic maternal obesity on feto-placental growth along with the underlying epigenetic mechanisms. We also tested whether preconceptional weight loss could alleviate these effects.

RESULTS

Female mice were fed either a control diet (CTRL group), a high-fat diet (obese (OB) group), or a high-fat diet switched to a control diet 2 months before conception (weight loss (WL) group). At mating, OB females presented an obese phenotype while WL females normalized metabolic parameters. At embryonic day 18.5 (E18.5), fetuses from OB females presented fetal growth restriction (FGR; -13 %) and 28 % of the fetuses were small for gestational age (SGA). Fetuses from WL females normalized this phenotype. The expression of 60 epigenetic machinery genes and 32 metabolic genes was measured in the fetal liver, placental labyrinth, and junctional zone. We revealed 23 genes altered by maternal weight trajectories in at least one of three tissues. The fetal liver and placental labyrinth were more responsive to maternal obesity than junctional zone. One third (18/60) of the epigenetic machinery genes were differentially expressed between at least two maternal groups. Interestingly, genes involved in the histone acetylation pathway were particularly altered (13/18). In OB group, lysine acetyltransferases and Bromodomain-containing protein 2 were upregulated, while most histone deacetylases were downregulated. In WL group, the expression of only a subset of these genes was normalized.

CONCLUSIONS

This study highlights the high sensitivity of the epigenetic machinery gene expression, and particularly the histone acetylation pathway, to maternal obesity. These obesity-induced transcriptional changes could alter the placental and the hepatic epigenome, leading to FGR. Preconceptional weight loss appears beneficial to fetal growth, but some effects of previous obesity were retained in offspring phenotype.

The consequences of fetal growth restriction on brain structure and neurodevelopmental outcome

Fetal growth restriction (FGR) is a significant complication of pregnancy describing a fetus that does not grow to full potential due to pathological compromise. FGR affects 3-9% of pregnancies in high-income countries, and is a leading cause of perinatal mortality and morbidity. Placental insufficiency is the principal cause of FGR, resulting in chronic fetal hypoxia. This hypoxia induces a fetal adaptive response of cardiac output redistribution to favour vital organs, including the brain, and is in consequence called brain sparing. Despite this, it is now apparent that brain sparing does not ensure normal brain development in growth-restricted fetuses. In this review we have brought together available evidence from human and experimental animal studies to describe the complex changes in brain structure and function that occur as a consequence of FGR. In both humans and animals, neurodevelopmental outcomes are influenced by the timing of the onset of FGR, the severity of FGR, and gestational age at delivery. FGR is broadly associated with reduced total brain volume and altered cortical volume and structure, decreased total number of cells and myelination deficits. Brain connectivity is also impaired, evidenced by neuronal migration deficits, reduced dendritic processes, and less efficient networks with decreased long-range connections. Subsequent to these structural alterations, short- and long-term functional consequences have been described in school children who had FGR, most commonly including problems in motor skills, cognition, memory and neuropsychological dysfunctions.

Assessment of in vivo fetal growth and placental vascular function in a novel intrauterine growth restriction model of progressive uterine artery occlusion in guinea pigs

Intra-uterine growth restriction (IUGR) is associated with short and long-term metabolic and cardiovascular alterations. Mice and rats have been extensively used to study the effects of IUGR, but there are notable differences in fetal and placental physiology relative to those of humans that argue for alternative animal models. This study proposes that gradual occlusion of uterine arteries from mid-gestation in pregnant guinea pigs produces a novel model to better assess human IUGR. Fetal biometry and in vivo placental vascular function were followed by sonography and Doppler of control pregnant guinea pigs and sows submitted to surgical placement of ameroid constrictors in both uterine arteries (IUGR) at mid-gestation (35 days). The ameroid constrictors induced a reduction in the fetal abdominal circumference growth rate (0.205 cm day(-1) ) compared to control (0.241 cm day(-1) , P < 0.001) without affecting biparietal diameter growth. Umbilical artery pulsatility and resistance indexes at 10 and 20 days after surgery were significantly higher in IUGR animals than controls (P < 0.01). These effects were associated with a decrease in the relative luminal area of placental chorionic arteries (21.3 ± 2.2% vs. 33.2 ± 2.7%, P < 0.01) in IUGR sows at near term. Uterine artery intervention reduced fetal (∼30%), placental (∼20%) and liver (∼50%) weights (P < 0.05), with an increased brain to liver ratio (P < 0.001) relative to the control group. These data demonstrate that the ameroid constrictor implantations in uterine arteries in pregnant guinea pigs lead to placental vascular dysfunction and altered fetal growth that induces asymmetric IUGR.

Ventilation-induced lung injury is not exacerbated by growth restriction in preterm lambs

Intrauterine growth restriction (IUGR) and preterm birth are frequent comorbidities and, combined, increase the risk of adverse respiratory outcomes compared with that in appropriately grown (AG) infants. Potential underlying reasons for this increased respiratory morbidity in IUGR infants compared with AG infants include altered fetal lung development, fetal lung inflammation, increased respiratory requirements, and/or increased ventilation-induced lung injury. IUGR was surgically induced in preterm fetal sheep (0.7 gestation) by ligation of a single umbilical artery. Four weeks later, preterm lambs were euthanized at delivery or delivered and ventilated for 2 h before euthanasia. Ventilator requirements, lung inflammation, early markers of lung injury, and morphological changes in lung parenchymal and vascular structure and surfactant composition were analyzed. IUGR preterm lambs weighed 30% less than AG preterm lambs, with increased brain-to-body weight ratio, indicating brain sparing. IUGR did not induce lung inflammation or injury or alter lung parenchymal and vascular structure compared with AG fetuses. IUGR and AG lambs had similar oxygenation and respiratory requirements after birth and had significant, but similar, increases in proinflammatory cytokine expression, lung injury markers, gene expression, and surfactant phosphatidylcholine species compared with unventilated controls. IUGR does not induce pulmonary structural changes in our model. Furthermore, IUGR and AG preterm lambs have similar ventilator requirements in the immediate postnatal period. This study suggests that increased morbidity and mortality in IUGR infants is not due to altered lung tissue or vascular structure, or to an altered response to early ventilation.

From Pre-Clinical Studies to Clinical Trials: Generation of Novel Therapies for Pregnancy Complications

Complications of pregnancy represent a significant disease burden, with both immediate and lasting consequences for mother and baby. Two key pregnancy complications, fetal growth restriction (FGR) and preeclampsia (PE), together affect around 10%–15% of all pregnancies worldwide. Despite this high incidence, there are currently no therapies available to treat these pregnancy disorders. Early delivery remains the only intervention to reduce the risk of severe maternal complications and/or stillbirth of the baby; however early delivery itself is associated with increased risk of neonatal mortality and morbidity. As such, there is a pressing need to develop new and effective treatments that can prevent or treat FGR and PE. Animal models have been essential in identifying and screening potential new therapies in this field. In this review, we address recent progress that has been made in developing therapeutic strategies for pregnancy disorders, some of which are now entering clinical trials.