The placental pursuit for an adequate oxidant balance between the mother and the fetus

Epigenetic regulation by hypoxia, N-acetylcysteine and hydrogen sulphide of the fetal vasculature in growth restricted offspring: A study in humans and chicken embryos

Fetal growth restriction (FGR) is a common outcome in human suboptimal gestation and is related to prenatal origins of cardiovascular dysfunction in offspring. Despite this, therapy of human translational potential has not been identified. Using human umbilical and placental vessels and the chicken embryo model, we combined cellular, molecular, and functional studies to determine whether N-acetylcysteine (NAC) and hydrogen sulphide (H2S) protect cardiovascular function in growth-restricted unborn offspring. In human umbilical and placental arteries from control or FGR pregnancy and in vessels from near-term chicken embryos incubated under normoxic or hypoxic conditions, we determined the expression of the H2S gene CTH (i.e. cystathionine γ-lyase) (via quantitative PCR), the production of H2S (enzymatic activity), the DNA methylation profile (pyrosequencing) and vasodilator reactivity (wire myography) in the presence and absence of NAC treatment. The data show that FGR and hypoxia increased CTH expression in the embryonic/fetal vasculature in both species. NAC treatment increased aortic CTH expression and H2S production and enhanced third-order femoral artery dilator responses to the H2S donor sodium hydrosulphide in chicken embryos. NAC treatment also restored impaired endothelial relaxation in human third-to-fourth order chorionic arteries from FGR pregnancies and in third-order femoral arteries from hypoxic chicken embryos. This NAC-induced protection against endothelial dysfunction in hypoxic chicken embryos was mediated via nitric oxide independent mechanisms. Both developmental hypoxia and NAC promoted vascular changes in CTH DNA and NOS3 methylation patterns in chicken embryos. Combined, therefore, the data support that the effects of NAC and H2S offer a powerful mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy. KEY POINTS: Gestation complicated by chronic fetal hypoxia and fetal growth restriction (FGR) increases a prenatal origin of cardiovascular disease in offspring, increasing interest in antenatal therapy to prevent against a fetal origin of cardiovascular dysfunction. We investigated the effects between N-acetylcysteine (NAC) and hydrogen sulphide (H2S) in the vasculature in FGR human pregnancy and in chronically hypoxic chicken embryos. Combining cellular, molecular, epigenetic and functional studies, we show that the vascular expression and synthesis of H2S is enhanced in hypoxic and FGR unborn offspring in both species and this acts to protect their vasculature. Therefore, the NAC/H2S pathway offers a powerful therapeutic mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy.

Prenatal environmental adversity and child neurodevelopmental delay: the role of maternal low-grade systemic inflammation and maternal anti-inflammatory diet

Maternal inflammation has been proposed as a possible pathway connecting prenatal environmental adversity (PEA), which includes maternal overweightness or obesity, diabetes, hypertensive disorders, and mood or anxiety disorders, to child neurodevelopmental delay. However, effective preventive measures have not yet been reported. Herein, we aimed to investigate whether a maternal anti-inflammatory diet reduced the risk of PEA-induced neurodevelopmental delay, by inhibiting inflammation. This prospective study included 7438 mother-child pairs. Maternal overweightness or obesity, diabetes, and hypertensive disorders were diagnosed before 28 week gestation. Maternal depression disorders were identified using the Edinburgh postnatal depression survey (EPDS) during mid-pregnancy. During mid- and late pregnancy, maternal high-sensitivity C-reactive protein (hs-CRP) levels were measured to evaluate systemic inflammation. The inflammatory potential of the diet was evaluated using the food-based empirical dietary inflammatory pattern (EDIP) score during mid-pregnancy. Pregnant women were classified into high- or low-score groups based on the median EDIP score. The outcomes of neurodevelopmental delay at 6-36 month postpartum were extracted from the Register of Child Healthcare. Among the 7438 mother-child pairs, 2937 (39.5%) were exposed to PEA, and neurodevelopmental delay occurred in 540 (7.3%). Children exposed to PEA had a higher risk of neurodevelopmental delay than those not exposed. PEA exposure was associated with increased hs-CRP during pregnancy in a PEA monotonic manner, an interquartile range increase in hs-CRP in mid- and late pregnancy was associated with an increased risk of child neurodevelopmental delay. Higher maternal persistent inflammation partially mediated the effect of PEA exposure on child neurodevelopmental delay by 17.19%. An increased risk of PEA-related neurodevelopmental delay was observed only in the children of mothers with high-EDIP rather than low-EDIP. These results suggest that increased systemic inflammation through mid- and late pregnancy mediates the association between PEA and child neurodevelopmental delay. A maternal anti-inflammatory diet may improve PEA-induced neurodevelopmental delay, by inhibiting inflammation.

Exploring the Role of Mediterranean and Westernized Diets and Their Main Nutrients in the Modulation of Oxidative Stress in the Placenta: A Narrative Review

Oxidative stress is a major cellular event that occurs in the placenta, fulfilling critical physiological roles in non-pathological pregnancies. However, exacerbated oxidative stress is a pivotal feature of different obstetric complications, like pre-eclampsia, fetal growth restriction, and other diseases. Compelling evidence supports the relevant role of diet during pregnancy, with pleiotropic consequences for maternal well-being. The present review aims to examine the complex background between oxidative stress and placental development and function in physiological conditions, also intending to understand the relationship between different dietary patterns and the human placenta, particularly how this could influence oxidative stress processes. The effects of Westernized diets (WDs) and high-fat diets (HFDs) rich in ultra-processed foods and different additives are compared with healthy patterns such as a Mediterranean diet (MedDiet) abundant in omega 3 polyunsaturated fatty acids, monounsaturated fatty acids, polyphenols, dietary fiber, and vitamins. Although multiple studies have focused on the role of specific nutrients, mostly in animal models and in vitro, further observational and intervention studies focusing on the placental structure and function in women with different dietary patterns should be conducted to understand the precise influence of diet on this organ.

GPR65 inhibits human trophoblast cell adhesion through upregulation of MYLK and downregulation of fibronectin via cAMP-ERK signaling in a low pH environment

BACKGROUND

Extravillous trophoblasts (EVTs) are essential cells during the formation of the placenta, with the major function of invading the maternal decidua, anchoring the developing placenta to the uterus, remodeling uterine arteries, and regulating immune responses to prevent rejection. During early pregnancy, the decidua undergoes a hypoxic and acidic microenvironment, which has been shown to participate in tumor cell migration, invasion, growth, and angiogenesis. Nevertheless, the mechanisms by which EVTs sense and respond to the acidic microenvironment, thereby executing their functions, remain poorly understood.

METHODS

The effects of G protein-coupled receptor 65 (GPR65) on cell adhesion and other cellular functions were tested using JAR spheroids, mouse blastocysts, and HTR-8/SVneo cells. Specifically, we employed HTR-8/SVneo cells for gene overexpression and silencing to investigate the underlying mechanism of GPR65's impact on trophoblast cell function under acidic conditions. Additionally, villus tissue samples obtained from early pregnancy loss patients were utilized to explore the potential association between GPR65 and its related signaling pathway molecules with the disease.

RESULTS

This study identified GPR65 expression widely in trophoblasts, with the highest level in EVTs. Importantly, optimal GPR65 levels are required for maintaining normal adhesion, migration, and invasion, whereas overexpression of GPR65 inhibits these functions by activating the cAMP-ERK signaling pathway, upregulating myosin light chain kinase (MYLK) and MYLK3 expression, and subsequently downregulating fibronectin. Consistently, elevated expression of GPR65, MYLK, and MYLK3 is observed in patients suffering from early pregnancy loss.

CONCLUSIONS

This work offers insights into the suppressive effects of GPR65 on EVT function under acidic conditions and highlights a putative target for therapeutic intervention in early pregnancy complications. Video Abstract.

Decreased Vitamin D Levels and Altered Placental Vitamin D Gene Expression at High Altitude: Role of Genetic Ancestry

High-altitude hypoxia challenges reproduction; particularly in non-native populations. Although high-altitude residence is associated with vitamin D deficiency, the homeostasis and metabolism of vitamin D in natives and migrants remain unknown. We report that high altitude (3600 m residence) negatively impacted vitamin D levels, with the high-altitude Andeans having the lowest 25-OH-D levels and the high-altitude Europeans having the lowest 1α,25-(OH)2-D levels. There was a significant interaction of genetic ancestry with altitude in the ratio of 1α,25-(OH)2-D to 25-OH-D; with the ratio being significantly lower in Europeans compared to Andeans living at high altitude. Placental gene expression accounted for as much as 50% of circulating vitamin D levels, with CYP2R1 (25-hydroxylase), CYP27B1 (1α-hydroxylase), CYP24A1 (24-hydroxylase), and LRP2 (megalin) as the major determinants of vitamin D levels. High-altitude residents had a greater correlation between circulating vitamin D levels and placental gene expression than low-altitude residents. Placental 7-dehydrocholesterol reductase and vitamin D receptor were upregulated at high altitude in both genetic-ancestry groups, while megalin and 24-hydroxylase were upregulated only in Europeans. Given that vitamin D deficiency and decreased 1α,25-(OH)2-D to 25-OH-D ratios are associated with pregnancy complications, our data support a role for high-altitude-induced vitamin D dysregulation impacting reproductive outcomes, particularly in migrants.

Cardiovascular Dysfunction in Intrauterine Growth Restriction

PURPOSE OF REVIEW

We highlight important new findings on cardiovascular dysfunction in intrauterine growth restriction.

RECENT FINDINGS

Intrauterine growth restriction (IUGR) is a multifactorial condition which negatively impacts neonatal growth during pregnancy and is associated with health problems during the lifespan. It affects 5-15% of all pregnancies in the USA and Europe with varying percentages in developing countries. Epidemiological studies have reported that IUGR is associated with the pathogenesis of hypertension, activation of the renin-angiotensin system (RAS), disruption in placental-mTORC and TGFβ signaling cascades, and endothelial dysfunction in IUGR fetuses, children, adolescents, and adults resulting in the development of cardiovascular diseases (CVD). Experimental studies are needed to investigate therapeutic measures to treat increased blood pressure (BP) and long-term CVD problems in people affected by IUGR. We outline the mechanisms mediating fetal programming of hypertension in developing CVD. We have reviewed findings from different experimental models focusing on recent studies that demonstrate CVD in IUGR.

Regulation of Placental Efflux Transporters during Pregnancy Complications

The placenta is essential for regulating the exchange of solutes between the maternal and fetal circulations. As a result, the placenta offers support and protection to the developing fetus by delivering crucial nutrients and removing waste and xenobiotics. ATP-binding cassette transporters, including multidrug resistance protein 1, multidrug resistance-associated proteins, and breast cancer resistance protein, remove chemicals through active efflux and are considered the primary transporters within the placental barrier. Altered transporter expression at the barrier could result in fetal exposure to chemicals and/or accumulation of xenobiotics within trophoblasts. Emerging data demonstrate that expression of these transporters is changed in women with pregnancy complications, suggesting potentially compromised integrity of placental barrier function. The purpose of this review is to summarize the regulation of placental efflux transporters during medical complications of pregnancy, including 1) placental inflammation/infection and chorioamnionitis, 2) hypertensive disorders of pregnancy, 3) metabolic disorders including gestational diabetes and obesity, and 4) fetal growth restriction/altered fetal size for gestational age. For each disorder, we review the basic pathophysiology and consider impacts on the expression and function of placental efflux transporters. Mechanisms of transporter dysregulation and implications for fetal drug and toxicant exposure are discussed. Understanding how transporters are up- or downregulated during pathology is important in assessing possible exposures of the fetus to potentially harmful chemicals in the environment as well as the disposition of novel therapeutics intended to treat placental and fetal diseases. SIGNIFICANCE STATEMENT: Diseases of pregnancy are associated with reduced expression of placental barrier transporters that may impact fetal pharmacotherapy and exposure to dietary and environmental toxicants.

Quantitative longitudinal T2* mapping for assessing placental function and association with adverse pregnancy outcomes across gestation

Existing methods for evaluating in vivo placental function fail to reliably detect pregnancies at-risk for adverse outcomes prior to maternal and/or fetal morbidity. Here we report the results of a prospective dual-site longitudinal clinical study of quantitative placental T2* as measured by blood oxygen-level dependent magnetic resonance imaging (BOLD-MRI). The objectives of this study were: 1) to quantify placental T2* at multiple time points across gestation, and its consistency across sites, and 2) to investigate the association between placental T2* and adverse outcomes. 797 successful imaging studies, at up to three time points between 11 and 38 weeks of gestation, were completed in 316 pregnancies. Outcomes were stratified into three groups: (UN) uncomplicated/normal pregnancy, (PA) primary adverse pregnancy, which included hypertensive disorders of pregnancy, birthweight <5th percentile, and/or stillbirth or fetal death, and (SA) secondary abnormal pregnancy, which included abnormal prenatal conditions not included in the PA group such as spontaneous preterm birth or fetal anomalies. Of the 316 pregnancies, 198 (62.6%) were UN, 70 (22.2%) PA, and 48 (15.2%) SA outcomes. We found that the evolution of placental T2* across gestation was well described by a sigmoid model, with T2* decreasing continuously from a high plateau level early in gestation, through an inflection point around 30 weeks, and finally approaching a second, lower plateau in late gestation. Model regression revealed significantly lower T2* in the PA group than in UN pregnancies starting at 15 weeks and continuing through 33 weeks. T2* percentiles were computed for individual scans relative to UN group regression, and z-scores and receiver operating characteristic (ROC) curves calculated for association of T2* with pregnancy outcome. Overall, differences between UN and PA groups were statistically significant across gestation, with large effect sizes in mid- and late- pregnancy. The area under the curve (AUC) for placental T2* percentile and PA pregnancy outcome was 0.71, with the strongest predictive power (AUC of 0.76) at the mid-gestation time period (20–30 weeks). Our data demonstrate that placental T2* measurements are strongly associated with pregnancy outcomes often attributed to placental insufficiency.

Trial registration: ClinicalTrials.gov: NCT02749851.

Glucosamine enhances proliferation, barrier, and anti-oxidative functions in porcine trophectoderm cells

Trophectoderm (TE) is the first epithelium that appears during mammalian embryogenesis, and is a polarized transporting single cell layer that comprises the wall of the blastocyst. Previous studies have revealed the functional roles of glucose (Gluc), fructose (Fruc), and glutamine (Gln), which play a positive role in porcine trophectoderm (pTr) cell proliferation and migration, suggesting the importance of nutrients for normal development of the conceptus and implantation. This work was conducted to test the hypothesis that glucosamine (GlcN), which is synthesized from Gln and Fruc-6-phosphate through the hexosamine biosynthesis pathway (HBP), can stimulate proliferation and sustain the barrier and anti-oxidative functions of pTr cells. Cells were treated with 0, 0.25, or 0.5 mmol L^-1 GlcN in the presence or absence of adiquat (DQ) for the indicated time points. The results showed that 0.25 or 0.5 mmol L^-1 GlcN stimulated pTr cell viability and DNA replication compared to the control group. The addition of 0.25 mmol L^-1 GlcN enhanced the phosphorylation of mTOR signaling proteins, which can be inhibited by the inhibitor of phosphatidylinositol 3-kinase (PI3K), LY294002. Transepithelial electrical resistance (TEER) was increased, and paracellular permeability was correspondingly reduced in GlcN treatment. GlcN attenuated DQ-induced cell death and reduced the level of reactive oxygen species (ROS). The decreased TEER values and increased paracellular permeability caused by DQ treatment were also inhibited by GlcN treatment. The addition of 0.5 mmol L^-1 GlcN increased the protein expression of zonula occludens-3 (ZO-3), claudin-3, and claudin-4 in pTr cells, while inhibited the downregulation protein of claudin-1 and claudin-3 brought about by oxidative stress. Collectively, GlcN plays an important role in promoting proliferation and stimulating the mTOR cell signaling pathway, as well as ameliorating oxidative stress and augmenting barrier functions in pTr cells.

High Altitude Pregnancies and Vascular Dysfunction: Observations From Latin American Studies

An estimated human population of 170 million inhabit at high-altitude (HA, above 2,500 m). The potential pathological effects of HA hypobaric hypoxia during gestation have been the focus of several researchers around the world. The studies based on the Himalayan and Central/South American mountains are particularly interesting as these areas account for nearly 70% of the HA world population. At present, studies in human and animal models revealed important alterations in fetal development and growth at HA. Moreover, vascular responses to chronic hypobaria in the pregnant mother and her fetus may induce marked cardiovascular impairments during pregnancy or in the neonatal period. In addition, recent studies have shown potential long-lasting postnatal effects that may increase cardiovascular risk in individuals gestated under chronic hypobaria. Hence, the maternal and fetal adaptive responses to hypoxia, influenced by HA ancestry, are vital for a better developmental and cardiovascular outcome of the offspring. This mini-review exposes and discusses the main determinants of vascular dysfunction due to developmental hypoxia at HA, such as the Andean Mountains, at the maternal and fetal/neonatal levels. Although significant advances have been made from Latin American studies, this area still needs further investigations to reveal the mechanisms involved in vascular dysfunction, to estimate complications of pregnancy and postnatal life adequately, and most importantly, to determine potential treatments to prevent or treat the pathological effects of being developed under chronic hypobaric hypoxia.

Endothelial Dysfunction in Pregnancy Complications

The endothelium, which constitutes the inner layer of blood vessels and lymphatic structures, plays an important role in various physiological functions. Alterations in structure, integrity and function of the endothelial layer during pregnancy have been associated with numerous gestational complications, including clinically significant disorders, such as preeclampsia, fetal growth restriction, and diabetes. While numerous experimental studies have focused on establishing the role of endothelial dysfunction in pathophysiology of these gestational complications, their mechanisms remain unknown. Numerous biomarkers of endothelial dysfunction have been proposed, together with the mechanisms by which they relate to individual gestational complications. However, more studies are required to determine clinically relevant markers specific to a gestational complication of interest, as currently most of them present a significant overlap. Although the independent diagnostic value of such markers remains to be insufficient for implementation in standard clinical practice at the moment, inclusion of certain markers in predictive multifactorial models can improve their prognostic value. The future of the research in this field lies in the fine tuning of the clinical markers to be used, as well as identifying possible therapeutic techniques to prevent or reverse endothelial damage.

Melatonin Reduces Oxidative Stress in the Right Ventricle of Newborn Sheep Gestated under Chronic Hypoxia

Pulmonary arterial hypertension of newborns (PAHN) constitutes a critical condition involving both severe cardiac remodeling and right ventricle dysfunction. One main cause of this condition is perinatal hypoxia and oxidative stress. Thus, it is a public health concern for populations living above 2500 m and in cases of intrauterine chronic hypoxia in lowlands. Still, pulmonary and cardiac impairments in PAHN lack effective treatments. Previously we have shown the beneficial effects of neonatal melatonin treatment on pulmonary circulation. However, the cardiac effects of this treatment are unknown. In this study, we assessed whether melatonin improves cardiac function and modulates right ventricle (RV) oxidative stress. Ten lambs were gestated, born, and raised at 3600 m. Lambs were divided in two groups. One received daily vehicle as control, and another received daily melatonin (1 mg·kg^-1·d^-1) for 21 days. Daily cardiovascular measurements were recorded and, at 29 days old, cardiac tissue was collected. Melatonin decreased pulmonary arterial pressure at the end of the experimental period. In addition, melatonin enhanced manganese superoxide dismutase and catalase (CAT) expression, while increasing CAT activity in RV. This was associated with a decrease in superoxide anion generation at the mitochondria and NADPH oxidases in RV. Finally, these effects were associated with a marked decrease of oxidative stress markers in RV. These findings support the cardioprotective effects of an oral administration of melatonin in newborns that suffer from developmental chronic hypoxia.

Gestational Hypoxia and Blood-Brain Barrier Permeability: Early Origins of Cerebrovascular Dysfunction Induced by Epigenetic Mechanisms

Fetal chronic hypoxia leads to intrauterine growth restriction (IUGR), which is likely to reduce oxygen delivery to the brain and induce long-term neurological impairments. These indicate a modulatory role for oxygen in cerebrovascular development. During intrauterine hypoxia, the fetal circulation suffers marked adaptations in the fetal cardiac output to maintain oxygen and nutrient delivery to vital organs, known as the "brain-sparing phenotype." This is a well-characterized response; however, little is known about the postnatal course and outcomes of this fetal cerebrovascular adaptation. In addition, several neurodevelopmental disorders have their origins during gestation. Still, few studies have focused on how intrauterine fetal hypoxia modulates the normal brain development of the blood-brain barrier (BBB) in the IUGR neonate. The BBB is a cellular structure formed by the neurovascular unit (NVU) and is organized by a monolayer of endothelial and mural cells. The BBB regulates the entry of plasma cells and molecules from the systemic circulation to the brain. A highly selective permeability system achieves this through integral membrane proteins in brain endothelial cells. BBB breakdown and dysfunction in cerebrovascular diseases lead to leakage of blood components into the brain parenchyma, contributing to neurological deficits. The fetal brain circulation is particularly susceptible in IUGR and is proposed to be one of the main pathological processes deriving BBB disruption. In the last decade, several epigenetic mechanisms activated by IU hypoxia have been proposed to regulate the postnatal BBB permeability. However, few mechanistic studies about this topic are available, and little evidence shows controversy. Therefore, in this mini-review, we analyze the BBB permeability-associated epigenetic mechanisms in the brain exposed to chronic intrauterine hypoxia.

Structural changes, increased hypoxia, and oxidative DNA damage in placenta due to maternal smokeless tobacco use

BACKGROUND

Smokeless tobacco (SLT) consumption during pregnancy is a well-recognized health risk that causes placental damage including hypoxia and oxidative damage. Although consumption of SLT by women varies from region to region, majority of tea leave pluckers consume SLT for relieving stress and pain. Still, the effects of SLT consumption have not been evaluated in tea garden workers (TGW). While previous studies have attempted to report effects of cigarette smoke using in vitro model, hypoxia-inducible factor (HIF)-1α expression in human placentae from pregnant women exposed to SLT has not been previously studied. This study was aimed to explore the effects of SLT consumption on placental structure, expression of HIF-1α and oxidative DNA damage in sample population of TGW.

METHODS

A total of 51 placentae were collected from SLT users and nonusers (n = 30 and 21, respectively) with full-term normal delivery, who were involved in the plucking of tea leaves during pregnancy in tea plantation. Low birth weight (LBW, i.e., weight <2,500 g) and normal birth weight (NBW) groups among both SLT user and nonuser were compared for the stated parameters. Placental tissues were processed for transmission electron microscopy (TEM) study and immunohistochemical analysis for the expression of HIF-1α and 8-hydroxy-2'-deoxyguanosine (8-OHdG).

RESULTS

Altered ultrastructural characteristics were observed in the tertiary villi of LBW group among SLT users which included endothelial cells protrusion into capillary lumen, degenerated nuclei, significant thickening of trophoblast basement membrane and vasculo-syncytial membrane, abnormalities of the microvilli, swollen or damaged mitochondria, and dilatation in endoplasmic reticulum cisternae. Furthermore, significant reduction in the perimeter, area, and number of the stromal capillary of the tertiary villi of placenta were found in LBW group as compared with NBW group from the SLT users. Enhanced expression for HIF-1α and oxidative DNA damage (8-OHdG) biomarker was observed in SLT users as compared with nonusers.

CONCLUSIONS

Maternal SLT exposure during pregnancy may be associated with villus hypoxia and consequently oxidative DNA damage. It is presumed that deleterious effect of SLT exposure on placenta could result in impairment of placental barrier, and restrict nutrient and oxygen supply from mother to fetus, and thus could be a cause of fetal growth restriction.

The newborn sheep translational model for pulmonary arterial hypertension of the neonate at high altitude

Chronic hypoxia during gestation induces greater occurrence of perinatal complications such as intrauterine growth restriction, fetal hypoxia, newborn asphyxia, and respiratory distress, among others. This condition may also cause a failure in the transition of the fetal to neonatal circulation, inducing pulmonary arterial hypertension of the neonate (PAHN), a syndrome that involves pulmonary vascular dysfunction, increased vasoconstrictor tone and pathological remodeling. As this syndrome has a relatively low prevalence in lowlands (~7 per 1000 live births) and very little is known about its prevalence and clinical evolution in highlands (above 2500 meters), our understanding is very limited. Therefore, studies on appropriate animal models have been crucial to comprehend the mechanisms underlying this pathology. Considering the strengths and weaknesses of any animal model of human disease is fundamental to achieve an effective and meaningful translation to clinical practice. The sheep model has been used to study the normal and abnormal cardiovascular development of the fetus and the neonate for almost a century. The aim of this review is to highlight the advances in our knowledge on the programming of cardiopulmonary function with the use of high-altitude newborn sheep as a translational model of PAHN.

Novel insights for the role of nitric oxide in placental vascular function during and beyond pregnancy

More than 30 years have passed since endothelial nitric oxide synthesis was described using the umbilical artery and vein endothelium. That seminal report set the cornerstone for unveiling the molecular aspects of endothelial function. In parallel, the understanding of placental physiology has gained growing interest, due to its crucial role in intrauterine development, with considerable long-term health consequences. This review discusses the evidence for nitric oxide (NO) as a critical player of placental development and function, with a special focus on endothelial nitric oxide synthase (eNOS) vascular effects. Also, the regulation of eNOS-dependent vascular responses in normal pregnancy and pregnancy-related diseases and their impact on prenatal and postnatal vascular health are discussed. Recent and compelling evidence has reinforced that eNOS regulation results from a complex network of processes, with novel data concerning mechanisms such as mechano-sensing, epigenetic, posttranslational modifications, and the expression of NO- and l-arginine-related pathways. In this regard, most of these mechanisms are expressed in an arterial-venous-specific manner and reflect traits of the fetal systemic circulation. Several studies using umbilical endothelial cells are not aimed to understand placental function but general endothelial function, reinforcing the influence of the placenta on general knowledge in physiology.

Beneficial effects of melatonin on prostanoids pathways in pulmonary hypertensive neonates

Pulmonary arterial hypertension of the newborn (PAHN) is a syndrome caused by chronic hypoxia, characterized by decreased vasodilator function, a marked vasoconstrictor activity, proliferation of smooth muscle cells (SMC) and thickening of the extracellular matrix in the pulmonary circulation, among other characteristics. Prostaglandins are derived from the arachidonic acid (AA) metabolism and are important regulators of pulmonary vascular tone. Since hypoxia induces oxidative stress and has been related to PAHN, a postnatal treatment with melatonin has been proposed due to its antioxidant properties. Here, we determined the effects of melatonin on pulmonary vascular homeostasis given by prostanoids. Ten PAHN newborn lambs were divided in two groups and treated either with vehicle or melatonin. After 1 week of treatment, we assessed pulmonary vascular prostanoids function and expression by wire myography, RT-PCR, Western Blot and immunohistochemistry. Melatonin improved in vivo and ex vivo pulmonary vasodilation. This was associated with an increased function and expression of vasodilator prostanoids at the expense of vasoconstrictor prostanoids. Our study demonstrates for the first time that melatonin may enhance the vasodilator prostanoid pathway in PAHN.

Placental treatment improves cardiac tolerance to ischemia/reperfusion insult in adult male and female offspring exposed to prenatal hypoxia

Offspring born from complicated pregnancies are at greater risk of cardiovascular disease in adulthood. Prenatal hypoxia is a common pregnancy complication that results in placental oxidative stress and impairs fetal development. Adult offspring exposed to hypoxia during fetal life are more susceptible to develop cardiac dysfunction, and show decreased cardiac tolerance to an ischemia/reperfusion (I/R) insult. To improve offspring cardiac outcomes, we have assessed the use of a placenta-targeted intervention during hypoxic pregnancies, by encapsulating the mitochondrial antioxidant MitoQ into nanoparticles (nMitoQ). We hypothesized that maternal nMitoQ treatment during hypoxic pregnancies improves cardiac tolerance to I/R insult in adult male and female offspring. Pregnant Sprague-Dawley rats were exposed to normoxia (21 % O²) or hypoxia (11 % O²) from gestational day 15-20, after injection with 100 μL saline or nMitoQ (125 μM) on GD15 (n=6-8/group). Male and female offspring were aged to 4 months. Both male and female offspring from hypoxic pregnancies showed reduced cardiac tolerance to I/R (assessed ex vivo using the isolated working heart technique) which was ameliorated by nMitoQ treatment. To identify potential molecular mechanisms for the changes in cardiac tolerance to I/R, cardiac levels/phosphorylation of proteins important for intracellular Ca²⁺ cycling were assessed with Western blotting. In prenatally hypoxic male offspring, improved cardiac recovery from I/R by nMitoQ was accompanied by increased cardiac phospholamban and phosphatase 2Ce levels, and a trend to decreased Ca²⁺/calmodulin-dependent protein kinase IIδ phosphorylation. In contrast, in female offspring, nMitoQ treatment in hypoxic pregnancies increased phospholamban and protein kinase Cε phosphorylation. Maternal nMitoQ treatment improves cardiac tolerance to I/R insult in adult offspring and thus has the potential to improve the later-life trajectory of cardiovascular health of adult offspring born from pregnancies complicated by prenatal hypoxia.

Adaptations of the human placenta to hypoxia: opportunities for interventions in fetal growth restriction

BACKGROUND

The placenta is the functional interface between the mother and the fetus during pregnancy, and a critical determinant of fetal growth and life-long health. In the first trimester, it develops under a low-oxygen environment, which is essential for the conceptus who has little defense against reactive oxygen species produced during oxidative metabolism. However, failure of invasive trophoblasts to sufficiently remodel uterine arteries toward dilated vessels by the end of the first trimester can lead to reduced/intermittent blood flow, persistent hypoxia and oxidative stress in the placenta with consequences for fetal growth. Fetal growth restriction (FGR) is observed in ∼10% of pregnancies and is frequently seen in association with other pregnancy complications, such as preeclampsia (PE). FGR is one of the main challenges for obstetricians and pediatricians, as smaller fetuses have greater perinatal risks of morbidity and mortality and postnatal risks of neurodevelopmental and cardio-metabolic disorders.

OBJECTIVE AND RATIONALE

The aim of this review was to examine the importance of placental responses to changing oxygen environments during abnormal pregnancy in terms of cellular, molecular and functional changes in order to highlight new therapeutic pathways, and to pinpoint approaches aimed at enhancing oxygen supply and/or mitigating oxidative stress in the placenta as a mean of optimizing fetal growth.

SEARCH METHODS

An extensive online search of peer-reviewed articles using PubMed was performed with combinations of search terms including pregnancy, placenta, trophoblast, oxygen, hypoxia, high altitude, FGR and PE (last updated in May 2020).

OUTCOMES

Trophoblast differentiation and placental establishment are governed by oxygen availability/hypoxia in early pregnancy. The placental response to late gestational hypoxia includes changes in syncytialization, mitochondrial functions, endoplasmic reticulum stress, hormone production, nutrient handling and angiogenic factor secretion. The nature of these changes depends on the extent of hypoxia, with some responses appearing adaptive and others appearing detrimental to the placental support of fetal growth. Emerging approaches that aim to increase placental oxygen supply and/or reduce the impacts of excessive oxidative stress are promising for their potential to prevent/treat FGR.

WIDER IMPLICATIONS

There are many risks and challenges of intervening during pregnancy that must be considered. The establishment of human trophoblast stem cell lines and organoids will allow further mechanistic studies of the effects of hypoxia and may lead to advanced screening of drugs for use in pregnancies complicated by placental insufficiency/hypoxia. Since no treatments are currently available, a better understanding of placental adaptations to hypoxia would help to develop therapies or repurpose drugs to optimize placental function and fetal growth, with life-long benefits to human health.

Medicines prescribed for asthma, discontinuation and perinatal outcomes, including breastfeeding: A population cohort analysis

OBJECTIVES

To explore associations between exposures to medicines prescribed for asthma and their discontinuation in pregnancy and preterm birth [<37 or <32 weeks], SGA [<10th and <3rd centiles], and breastfeeding at 6-8 weeks.

METHODS

Design. A population-based cohort study. Setting. The Secure Anonymised Information Linkage [SAIL] databank in Wales, linking maternal primary care data with infant outcomes. Population. 107,573, 105,331, and 38,725 infants born 2000-2010 with information on premature birth, SGA and breastfeeding respectively, after exclusions. Exposures. maternal prescriptions for asthma medicines or their discontinuation in pregnancy. Methods. Odds ratios for adverse pregnancy outcomes were calculated for the exposed versus the unexposed population, adjusted for smoking, parity, age and socio-economic status.

RESULTS

Prescriptions for asthma, whether continued or discontinued during pregnancy, were associated with birth at<32 weeks' gestation, SGA <10th centile, and no breastfeeding (aOR 1.33 [1.10-1.61], 1.10 [1.03-1.18], 0.93 [0.87-1.01]). Discontinuation of asthma medicines in pregnancy was associated with birth at<37 weeks' and <32 weeks' gestation (aOR 1.22 [1.06-1.41], 1.53 [1.11-2.10]). All medicines examined, except ICS and SABA prescribed alone, were associated with SGA <10th centile.

CONCLUSIONS

Prescription of asthma medicines before or during pregnancy was associated with higher prevalence of adverse perinatal outcomes, particularly if prescriptions were discontinued during pregnancy. Women discontinuing medicines during pregnancy could be identified from prescription records. The impact of targeting close monitoring and breastfeeding support warrants exploration.

MiR-21-5p directly contributes to regulating eNOS expression in human artery endothelial cells under normoxia and hypoxia

Clinical conditions associated with hypoxia and oxidative stress, such as fetal growth restriction (FGR), results in endothelial dysfunction. Previous reports show that changes in eNOS expression under these conditions are tightly controlled by DNA methylation and histone posttranslational modifications. However, the contribution of an orchestrating epigenetic mechanism, such as miRNAs, on the NO-related genes expression has not been addressed. We aimed to determine the levels of miRNAs highly expressed in normal endothelial cells (EC), miR-21 and miR-126, in FGR human umbilical artery EC (HUAEC), and their effects on hypoxia-dependent regulation of both, NO-related and oxidative stress-related genes. Results were validated by transcriptome analysis of HUAEC cultured under chronic low oxygen conditions. Cultured FGR-HUAEC showed decreased hsa-miR-21, DDAH1, SOD1, and NRF2, but increased miR-126, NOX4, and eNOS levels, compared with controls. MiR-21-5p levels in FGR were associated with increased hg-miR-21 gene promoter methylation, with no changes in hg-miR-126 gene promoter methylation. HUAEC exposed to hypoxia showed a transient increase in eNOS and DDAH11, paralleled by decrease miR-21-5p levels, but no changes in miR-126-3p and the other genes under study. Transcriptome profiling showed an inverse relationship among miR-21 and several transcripts targeted by miR-21 in HUAEC exposed to hypoxia, meanwhile miR-21-5p-mimic decreased eNOS and DDAH1 transcripts stability, blocking their induction by hypoxia. Consequently, FGR programs a hypoxia-related miRNA that contributes to the regulation of the NO pathway, involving a direct effect of miR-21-5p on eNOS transcript stability, not previously reported. Moreover, hypoxia downregulates miR-21-5p, contributing to increasing the expression of NO-related genes in arterial endothelial cells.

MiRNAs Regulating Oxidative Stress: A Correlation with Doppler Sonography of Uteroplacental Complex and Clinical State Assessments of Newborns in Fetal Growth Restriction

Overproduction of reactive oxygen species (ROS) and, as a result, uncontrolled oxidative stress (OS) can play a central role in disorders of fetal hemodynamics and subsequent development of adverse perinatal outcomes in newborns with fetal growth restriction (FGR). Given the epigenetic nature of such disorders, the aim of our study was to evaluate the expression of miRNAs associated with OS and endothelial dysfunction (miR-27a-3p, miR-30b-5p, miR-125b-5p, miR-221-3p, miR-451a and miR-574-3p) in umbilical cord blood using real-time quantitative RT-PCR. ΜiRNA expression was evaluated in patients with FGR delivery before (n = 9 pregnant) and after 34 weeks of gestation (n = 13 pregnant), and the control groups corresponding to the main groups by gestational age (13 pregnant women in each group, respectively). A significant increase in miR-451a expression was detected in late-onset FGR and correlations with fetoplacental and cerebral circulation were established (increase of resistance in the umbilical artery (pulsatility index, PI UA (umbilical artery): r = −0.59, p = 0.001) and a decrease in cerebral blood flow (CPR: r = 0.48, p = 0.009)). The change in miR-125b-5p expression in the placenta is associated with reduced Doppler of cerebral hemodynamics (CPR: r = 0.73, p = 0.003; PI MCA (middle cerebral artery): r = 0.79, p = 0.0007), and newborn weight (r = 0.56, p = 0.04) in early-onset FGR. In addition, significant changes in miR-125b-5p and miR-451a expression in umbilical cord blood plasma were found in newborns with neonatal respiratory distress syndrome (NRDS) (in early-onset FGR) and very low birth weight (VLBW) (in late-onset FGR). A number of key signaling pathways have been identified in which the regulation of the studied miRNAs is involved, including angiogenesis, neurotrophin signaling pathway and oxidative stress response. In general, our study showed that changes of the redox homeostasis in the mother-placenta-fetus system in FGR and subsequent perinatal outcomes may be due to differential expression of oxidative stress-associated miRNAs.

Childhood maltreatment is associated with changes in mitochondrial bioenergetics in maternal, but not in neonatal immune cells

Childhood maltreatment (CM) comprises experiences of abuse and neglect during childhood. CM causes psychological as well as biological alterations in affected individuals. In humans, it is hardly explored whether these CM consequences can be transmitted directly on a biological level to the next generation. Here, we investigated the associations between maternal CM and mitochondrial bioenergetics (mitochondrial respiration and intracellular mitochondrial density) in immune cells of mothers and compared them with those of their newborns. In n = 102 healthy mother-newborn dyads, maternal peripheral blood mononuclear cells and neonatal umbilical cord blood mononuclear cells were collected and cryopreserved shortly after parturition to measure mitochondrial respiration and intracellular mitochondrial density with high-resolution respirometry and spectrophotometric analyses, respectively. Maternal CM was assessed with the Childhood Trauma Questionnaire Maternal and neonatal mitochondrial bioenergetics were quantitatively comparable and positively correlated. Female newborns showed higher mitochondrial respiration compared to male newborns. Maternal CM load was significantly and positively associated with mitochondrial respiration and density in mothers, but not with mitochondrial respiration in newborns. Although maternal and neonatal mitochondrial bioenergetics were positively correlated, maternal CM only had a small effect on mitochondrial density in newborns, which was not significant in this study after adjustment for multiple comparisons. The biological relevance of our finding and its consequences for child development need further investigation in future larger studies. This study reports data on mitochondrial bioenergetics of healthy mother-newborn dyads with varying degrees of CM.

Establishment of a Novel Fetal Growth Restriction Model and Development of a Stem-Cell Therapy Using Umbilical Cord-Derived Mesenchymal Stromal Cells

Fetal growth restriction (FGR) is a major complication of prenatal ischemic/hypoxic exposure and affects 5%-10% of pregnancies. It causes various disorders, including neurodevelopmental disabilities due to chronic hypoxia, circulatory failure, and malnutrition via the placenta, and there is no established treatment. Therefore, the development of treatments is an urgent task. We aimed to develop a new FGR rat model with a gradual restrictive load of uterus/placental blood flow and to evaluate the treatment effect of the administration of umbilical cord-derived mesenchymal stromal cells (UC-MSCs). To create the FGR rat model, we used ameroid constrictors that had titanium on the outer wall and were composed of C-shaped casein with a notch and center hole inside that gradually narrowed upon absorbing water. The ameroid constrictors were attached to bilateral ovarian/uterine arteries on the 17th day of pregnancy to induce chronic mild ischemia, which led to FGR with over 20% bodyweight reduction. After the intravenous administration of 1 × 10⁵ UC-MSCs, we confirmed a significant improvement in the UC-MSC group in a negative geotaxis test at 1 week after birth and a rotarod treadmill test at 5 months old. In the immunobiological evaluation, the total number of neurons counted via the stereological counting method was significantly higher in the UC-MSC group than in the vehicle-treated group. These results indicate that the UC-MSCs exerted a treatment effect for neurological impairment in the FGR rats.

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

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

Prenatal Hypoxia and Placental Oxidative Stress: Insights from Animal Models to Clinical Evidences

Hypoxia is a common form of intrauterine stress characterized by exposure to low oxygen concentrations. Gestational hypoxia is associated with the generation of reactive oxygen species. Increase in oxidative stress is responsible for damage to proteins, lipids and DNA with consequent impairment of normal cellular functions. The purpose of this review is to propose a summary of preclinical and clinical evidences designed to outline the correlation between fetal hypoxia and oxidative stress. The results of the studies described show that increases of oxidative stress in the placenta is responsible for changes in fetal development. Specifically, oxidative stress plays a key role in vascular, cardiac and neurological disease and reproductive function dysfunctions. Moreover, the different finding suggests that the prenatal hypoxia-induced oxidative stress is associated with pregnancy complications, responsible for changes in fetal programming. In this way, fetal hypoxia predisposes the offspring to congenital anomalies and chronic diseases in future life. Several antioxidant agents, such as melatonin, erythropoietin, vitamin C, resveratrol and hydrogen, shown potential protective effects in prenatal hypoxia. However, future investigations will be needed to allow the implementation of these antioxidants in clinical practice for the promotion of health in early intrauterine life, in fetuses and children.

Adult vascular dysfunction in foetal growth-restricted guinea-pigs is associated with a neonate-adult switching in Nos3 DNA methylation

AIM

Foetal growth restriction (FGR) is associated with endothelial dysfunction and cardiovascular diseases in adult subjects. Early vascular remodelling and epigenetic changes occurring on key endothelial genes might precede this altered vascular function. Further, it has been proposed that oxidative stress during development may determine some of these epigenetic modifications. To address this issue, we studied the in vivo and ex vivo vascular function and Nos3 promoter DNA methylation in arteries from eight-month-old guinea-pig born from control, FGR-treated and FGR-NAC-treated pregnancies.

METHODS

Femoral and carotid arteries in vivo vascular function were determined by Doppler, whilst ex vivo vascular function and biomechanical properties were assessed by wire myography. Levels of eNOS mRNA and site-specific DNA methylation in Nos3 promoter in aorta endothelial cells (AEC) were determined by qPCR and pyrosequencing respectively.

RESULTS

FGR adult showed an increased femoral vascular resistance (P < .05), stiffness (P < .05) and arterial remodelling (P < .01), along with an impaired NO-mediated relaxation (P < .001). These effects were prevented by maternal treatment with NAC. Endothelial-NOS mRNA levels were decreased in FGR adult compared with control and FGR-NAC (P < .05), associated with increased DNA methylation levels (P < .01). Comparison of Nos3 DNA methylation in AEC showed a differential methylation pattern between foetal and adult guinea-pigs (P < .05).

CONCLUSION

Altogether, these data suggest that adult vascular dysfunction in the FGR does not result from early changes in Nos3 promoter DNA methylation, but from an altered vessel structure established during foetal development.

Effect of magnesium-degradation products and hypoxia on the angiogenesis of human umbilical vein endothelial cells

Biodegradable magnesium (Mg) metals have been applied in orthopaedic and stent applications due to their biodegradability, bioabsorbability and adaptability to tissue regeneration. However, further investigations are still needed to understand how angiogenesis will respond to high concentrations of Mg and oxygen content differences, which are vital to vascular remodelling and bone fracture regeneration or tissue healing. Human primary endothelial cells were exposed to various concentrations (2-8 mM) of extracellular Mg degradation products under either hypoxia or normoxia. Increased proliferation was measured with Mg extracts under hypoxia but not under normoxia. Under normoxia and with Mg extracts, HUVEC migration exhibited a bell-shaped curve. The same pattern was observed with VEGFB expression, while VEGFA was constantly downregulated. Under hypoxia, migration and VEGFA levels remained constant; however, VEGFB was upregulated. Similarly, under normoxia, tube formation as well as VEGFA and VEGFB levels were downregulated. Nevertheless, under hypoxia, tube formation remained constant while VEGFA and VEGFB levels were upregulated. These results suggest that Mg extracts did not interfere with angiogenesis under hypoxia. STATEMENT OF SIGNIFICANCE: Neoangiogenesis, mediated by (e.g.) hypoxia, is a key factor for proper tissue healing Thus, effect of Mg degradation products under either hypoxia or normoxia on angiogenesis were investigated. Under normoxia and increased Mg concentrations, a general negative effect was measured on early (migration) and late (tubulogenesis) angiogenesis. However, under hypoxia, this effect was abolished. As magnesium degradation is an oxygen-dependant process, hypoxia condition may be a relevant factor to test material cytocompatibility in vitro.

Tumor Homing Reactive Oxygen Species Nanoparticle for Enhanced Cancer Therapy

Multifunctional nanoparticles that carry chemotherapeutic agents can be innovative anticancer therapeutic options owing to their tumor-targeting ability and high drug-loading capacity. However, the nonspecific release of toxic DNA-intercalating anticancer drugs from the nanoparticles has significant side effects on healthy cells surrounding the tumors. Herein, we report a tumor homing reactive oxygen species nanoparticle (THoR-NP) platform that is highly effective and selective for ablating malignant tumors. Sodium nitroprusside (SNP) and diethyldithiocarbamate (DDC) were selected as an exogenous reactive oxygen species (ROS) generator and a superoxide dismutase 1 inhibitor, respectively. DDC-loaded THoR-NP, in combination with SNP treatment, eliminated multiple cancer cell lines effectively by the generation of peroxynitrite in the cells (>95% cell death), as compared to control drug treatments of the same concentration of DDC or SNP alone (0% cell death). Moreover, the magnetic core (ZnFe₂O₄) of the THoR-NP can specifically ablate tumor cells (breast cancer cells) via magnetic hyperthermia, in conjunction with DDC, even in the absence of any exogenous RS supplements. Finally, by incorporating iRGD peptide moieties in the THoR-NP, integrin-enriched cancer cells (malignant tumors, MDA-MB-231) were effectively and selectively killed, as opposed to nonmetastatic tumors (MCF-7), as confirmed in a mouse xenograft model. Hence, our strategy of using nanoparticles embedded with ROS-scavenger-inhibitor with an exogenous ROS supplement is highly selective and effective cancer therapy.

Nicotine-Induced Oxidative Stress in Human Primary Endometrial Cells

Nicotine is a major component of tobacco plants and is responsible for the development of reproductive problems in smokers. Nicotine has been recognized to result in oxidative stress by inducing the generation of reactive oxygen species (ROS) in some parts of female reproductive system, but the effect of nicotine on endometrium that plays an important role in reproductive biology stays unexplored. The aim of this work was to clarify the direct effects of nicotine administration on the antioxidant defense system and lipid peroxidation in human endometrial cells. Human endometrial stromal primary cells were treated with nicotine (0, 10−11, 10−8, and 10−6 M) for 24 hours. On nicotine administration, the endometrial cells were associated with a decrease in antioxidant defense markers such as Glutathione (GSH) level, glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT) enzymes activity and higher levels of malondialdehyde (MDA) in a dose-dependent manner when compared to the control. We concluded that nicotine as a pro-oxidant affects the oxidative state of the endometrial cells.

Effect of aspartame on the placenta of adult albino rat. A histological and immunohistochemical study

Aspartame is an artificial sweetener usually consumed by hundreds of millions of persons all over the world. Its metabolites can be toxic to many organs and there are only a few studies on the use of aspartame during gestation. The present study was designed to fully evaluate the effect of aspartame on the histological structure of the placenta in the adult albino rat. Twenty pregnant female rats were equally divided into group I that served as control, and group II that received aspartame at a dose 14 mg/kg by gavage on the 9th, 10th and 11th day of pregnancy. Placental specimens were processed for histological and immunohistochemical staining against vascular endothelial growth factor (VEGF). Aspartame induced a significant decrease in the mean placental weight and the mean thickness of both labyrinth and basal zones. Damage in the placenta was detected in the form of rupture of the interhemal membrane, lysis of glycogen trophoblast cells, spongiotrophoblast cells with vacuolated cytoplasm and darkly stained nuclei. A significant increase in vascular endothelial growth factor expression in both labyrinth and basal zones was detected. Ultrastructural examination showed fetal capillaries with condensed nuclei of endothelial cells, cytotrophoblasts with condensed fragmented nuclei and vacuolated cytoplasm, and syncytiotrophoblasts with irregular condensed fragmented nuclei. It could be concluded that aspartame has deeply impacted the normal structure and presumably the function of the placenta, therefore, restrictions are to be imposed on the consumption of aspartame especially during pregnancy.

Association between prenatal particulate air pollution exposure and telomere length in cord blood: Effect modification by fetal sex

INTRODUCTION

In utero particulate matter exposure produces oxidative stress that impacts cellular processes that include telomere biology. Newborn telomere length is likely critical to an individual's telomere biology; reduction in this initial telomere setting may signal increased susceptibility to adverse outcomes later in life. We examined associations between prenatal particulate matter with diameter ≤2.5 µm (PM_2.5) and relative leukocyte telomere length (LTL) measured in cord blood using a data-driven approach to characterize sensitive windows of prenatal PM_2.5 effects and explore sex differences.

METHODS

Women who were residents of Mexico City and affiliated with the Mexican Social Security System were recruited during pregnancy (n = 423 for analyses). Mothers' prenatal exposure to PM_2.5 was estimated based on residence during pregnancy using a validated satellite-based spatio-temporally resolved prediction model. Leukocyte DNA was extracted from cord blood obtained at delivery. Duplex quantitative polymerase chain reaction was used to compare the relative amplification of the telomere repeat copy number to single gene (albumin) copy number. A distributed lag model incorporating weekly averages for PM_2.5 over gestation was used in order to explore sensitive windows. Sex-specific associations were examined using Bayesian distributed lag interaction models.

RESULTS

In models that included child's sex, mother's age at delivery, prenatal environmental tobacco smoke exposure, pre-pregnancy BMI, gestational age, birth season and assay batch, we found significant associations between higher PM_2.5 exposure during early pregnancy (4-9 weeks) and shorter LTL in cord blood. We also identified two more windows at 14-19 and 34-36 weeks in which increased PM_2.5 exposure was associated with longer LTL. In stratified analyses, the mean and cumulative associations between PM_2.5 and shortened LTL were stronger in girls when compared to boys.

CONCLUSIONS

Increased PM_2.5 during specific prenatal windows was associated with shorter LTL and longer LTL. PM_2.5 was more strongly associated with shortened LTL in girls when compared to boys. Understanding sex and temporal differences in response to air pollution may provide unique insight into mechanisms.

Preeclampsia link to gestational hypoxia

Complications of pregnancy remain key drivers of morbidity and mortality, affecting the health of both the mother and her offspring in the short and long term. There is lack of detailed understanding of the pathways involved in the pathology and pathogenesis of compromised pregnancy, as well as a shortfall of effective prognostic, diagnostic and treatment options. In many complications of pregnancy, such as in preeclampsia, there is an increase in uteroplacental vascular resistance. However, the cause and effect relationship between placental dysfunction and adverse outcomes in the mother and her offspring remains uncertain. In this review, we aim to highlight the value of gestational hypoxia-induced complications of pregnancy in elucidating underlying molecular pathways and in assessing candidate therapeutic options for these complex disorders. Chronic maternal hypoxia not only mimics the placental pathology associated with obstetric syndromes like gestational hypertension at morphological, molecular and functional levels, but also recapitulates key symptoms that occur as maternal and fetal clinical manifestations of these pregnancy disorders. We propose that gestational hypoxia provides a useful model to study the inter-relationship between placental dysfunction and adverse outcomes in the mother and her offspring in a wide array of examples of complicated pregnancy, such as in preeclampsia.

Antenatal melatonin modulates an enhanced antioxidant/pro-oxidant ratio in pulmonary hypertensive newborn sheep

Chronic hypobaric hypoxia during fetal and neonatal life induces neonatal pulmonary hypertension. Hypoxia and oxidative stress are driving this condition, which implies an increase generation of reactive oxygen species (ROS) and/or decreased antioxidant capacity. Melatonin has antioxidant properties that decrease oxidative stress and improves pulmonary vascular function when administered postnatally. However, the effects of an antenatal treatment with melatonin in the neonatal pulmonary function and oxidative status are unknown. Therefore, we hypothesized that an antenatal therapy with melatonin improves the pulmonary arterial pressure and antioxidant status in high altitude pulmonary hypertensive neonates. Twelve ewes were bred at high altitude (3600 m); 6 of them were used as a control group (vehicle 1.4% ethanol) and 6 as a melatonin treated group (10 mg d-1 melatonin in vehicle). Treatments were given once daily during the last third of gestation (100-150 days). Lambs were born and raised with their mothers until 12 days old, and neonatal pulmonary arterial pressure and resistance, plasma antioxidant capacity and the lung oxidative status were determined. Furthermore, we measured the pulmonary expression and activity for the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase, and the oxidative stress markers 8-isoprostanes, 4HNE and nitrotyrosine. Finally, we assessed pulmonary pro-oxidant sources by the expression and function of NADPH oxidase, mitochondria and xanthine oxidase. Melatonin decreased the birth weight. However, melatonin enhanced the plasma antioxidant capacity and decreased the pulmonary antioxidant activity, associated with a diminished oxidative stress during postnatal life. Interestingly, melatonin also decreased ROS generation at the main pro-oxidant sources. Our findings suggest that antenatal administration of melatonin programs an enhanced antioxidant/pro-oxidant status, modulating ROS sources in the postnatal lung.

Sexual dimorphism of mitochondrial function in the hypoxic guinea pig placenta

Placental hypoxia can stimulate oxidative stress and mitochondrial dysfunction reducing placental efficiency and inducing fetal growth restriction (FGR). We hypothesized that chronic hypoxia inhibits mitochondrial function in the placenta as an underlying cause of cellular mechanisms contributing to FGR. Pregnant guinea pigs were exposed to either normoxia (NMX) or hypoxia (HPX; 10.5% O2) at 25 day gestation until term (65 day). Guinea pigs were anesthetized, and fetuses and placentas were excised at either mid (40 day) or late gestation (64 day), weighed, and placental tissue stored at -80°C until assayed. Mitochondrial DNA content, protein expression of respiratory Complexes I-V, and nitration and activity rates of Complexes I and IV were measured in NMX and HPX male (N = 6 in each treatment) and female (N = 6 in each treatment) placentas. Mitochondrial density was not altered by HPX in either mid- or late-term placentas. In mid gestation, HPX slightly increased expression of Complexes I-III and V in male placentas only, but had no effect on either Complex I or IV activity rates or nitrotyrosine expression. In late gestation, HPX significantly decreased CI/CIV activity rates and increased CI/CIV nitration in male but not female placentas exhibiting a sexual dimorphism. Complex I-V expression was reduced from mid to late gestation in both male and female placentas regardless of treatment. We conclude that chronic HPX decreases mitochondrial function by inhibiting Complex I/IV activity via increased peroxynitrite in a sex-related manner. Further, there may be a progressive decrease in energy metabolism of placental cell types with gestation that increases the vulnerability of placental function to intrauterine stress.

The role of nitric oxide in the cardiopulmonary response to hypoxia in highland and lowland newborn llamas

KEY POINTS

Perinatal hypoxia causes pulmonary hypertension in neonates, including humans. However, in species adapted to hypoxia, such as the llama, there is protection against pulmonary hypertension. Nitric oxide (NO) is a vasodilatator with an established role in the cardiopulmonary system of many species, but its function in the hypoxic pulmonary vasoconstrictor response in the newborn llama is unknown. Therefore, we studied the role of NO in the cardiopulmonary responses to acute hypoxia in high- and lowland newborn llamas. We show that high- compared to lowland newborn llamas have a reduced pulmonary vasoconstrictor response to acute hypoxia. Protection against excessive pulmonary vasoconstriction in the highland llama is mediated via enhancement of NO pathways, including increased MYPT1 and reduced ROCK expression as well as Ca2+ desensitization. Blunting of pulmonary hypertensive responses to hypoxia through enhanced NO pathways may be an adaptive mechanism to withstand life at high altitude in the newborn llama.

ABSTRACT

Llamas are born in the Alto Andino with protection against pulmonary hypertension. The physiology underlying protection against pulmonary vasoconstrictor responses to acute hypoxia in highland species is unknown. We determined the role of nitric oxide (NO) in the cardiopulmonary responses to acute hypoxia in high- and lowland newborn llamas. The cardiopulmonary function of newborn llamas born at low (580 m) or high altitude (3600 m) was studied under acute hypoxia, with and without NO blockade. In pulmonary arteries, we measured the reactivity to potassium and sodium nitroprusside (SNP), and in lung we determined the content of cGMP and the expression of the NO-related proteins: BKCa, PDE5, PSer92-PDE5, PKG-1, ROCK1 and 2, MYPT1, PSer695-MYPT1, PThr696-MYPT1, MLC20 and PSer19-MLC20. Pulmonary vascular remodelling was evaluated by morphometry and based on α-actin expression. High- compared to lowland newborn llamas showed lower in vivo pulmonary arterial pressor responses to acute hypoxia. This protection involved enhanced NO function, as NO blockade reverted the effect and the pulmonary arterial dilatator response to SNP was significantly enhanced in highland neonates. The pulmonary expression of ROCK2 and the phosphorylation of MLC20 were lower in high-altitude llamas. Conversely, MYPT1 was up-regulated whilst PSer695-MYPT1 and PThr695-MYPT1 did not change. Enhanced NO-dependent mechanisms were insufficient to prevent pulmonary arterial remodelling. Combined, the data strongly support that in the highland newborn llama reduced ROCK, increased MYPT1 expression and Ca2+ desensitization in pulmonary tissue allow an enhanced NO biology to limit hypoxic pulmonary constrictor responses. Blunting of hypoxic pulmonary hypertensive responses may be an adaptive mechanism to life at high altitude.

Hypoxia and Oxidative Stress Are Associated with Reduced Fetal Growth in Twin and Undernourished Sheep Pregnancies

Low birth weight has profound implications for perinatal mortality and morbidity in lambs, causing higher mortality and lower growth potential. Low birth weight, as a consequence of fetal growth restriction, occurs in undernourished and multiple pregnancies, where hypoxia and oxidative stress could play a critical role. Our aim was to establish the effects of nutritional deprivation and pregnancy rank on fetal growth, oxygenation, and oxidative status in sheep pregnancies under extensive Patagonian conditions. At 30 days after mating, single- and twin-bearing ewes were offered only natural pasture (undernutrition group) or natural pasture plus concentrate supplementation (well-nourished group). At day 140 of gestation, blood gases and redox status were evaluated in venous cord blood, and fetal biometric characteristics were obtained after cesarean section. Both maternal undernutrition and twinning led to decreased oxygen supply to the fetuses (p = 0.016 and p = 0.050, respectively), which was associated with decreased intrauterine growth (r = 0.446, p < 0.01). Moreover, twinning increased oxidative stress in cord blood (p < 0.05), which might also contribute to fetal growth restriction. These results reinforce the importance of maternal nutrition, especially for those ewes bearing multiples, and opens new possibilities for nutritional or antioxidant interventions for preventing fetal hypoxia and oxidative stress.

Recent advances in antenatal factors predisposing to bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) remains a major cause of late morbidities and death after preterm birth. BPD is characterized by an arrest of vascular and alveolar growth and high risk for pulmonary hypertension; yet mechanisms contributing to its pathogenesis and early strategies to prevent BPD are poorly understood. Strong epidemiologic studies have shown that the "new BPD" reflects the long-lasting impact of antenatal factors on lung development, partly due to placental dysfunction, as reflected in recent data from animal models. Improved understanding of mechanisms through which antenatal stress alters placental function and contributes to BPD may lead to preventive therapies.

Investigation of elevation as a risk factor for hypertensive disorders of pregnancy among Colorado women between 2007 and 2015

OBJECTIVE

The purpose of this study is to determine the association between high elevation and hypertensive disorders of pregnancy (HDP).

METHODS

Retrospective cohort study using Colorado birth certificate data to compare HDP at high (≥8,000 ft), moderate (4,501-7,999 ft), or low (≤4,500 ft) elevation using logistic regression.

RESULTS

Among the cohort (n = 314,431), 3.4% of women developed a HDP. High or moderate elevation was not significantly associated with HDP relative to low elevation (adjusted odds ratio [aOR] 1.16, 95% confidence interval [CI] 0.93-1.43; aOR 1.14, 95% CI 0.98-1.31, respectively).

CONCLUSION

Women living at high or moderate elevation do not have higher odds of HDP.

Evidence establishing a link between prenatal and early-life stress and asthma development

PURPOSE OF REVIEW

The objective of this review is to provide an update on our evolving understanding of the effects of stress in pregnancy and during early development on the onset of asthma-related phenotypes across childhood, adolescence, and into early adulthood.

RECENT FINDINGS

Accumulating evidence over the past 2 decades has established that prenatal and early-life psychological stress and stress correlates (e.g., maternal anxiety or depression) increase the risk for childhood respiratory disorders. Recent systematic reviews and meta-analyses including numerous prospective epidemiological and case-control studies substantiate a significant effect of prenatal stress and stress in early childhood on the development of wheeze, asthma, and other atopic-related disorders (eczema and allergic rhinitis), with many studies showing an exposure-response relationship. Offspring of both sexes are susceptible to perinatal stress, but effects differ. The impact of stress on child wheeze/asthma can also be modified by exposure timing. Moreover, coexposure to prenatal stress can enhance the effect of chemical stressors, such as prenatal traffic-related air pollution, on childhood respiratory disease risk. Understanding complex interactions among exposure dose, timing, child sex, and concurrent environmental exposures promises to more fully characterize stress effects and identify susceptible subgroups. Although the link between perinatal stress and childhood asthma-related phenotypes is now well established, pathways by which stress predisposes children to chronic respiratory disorders are not as well delineated. Mechanisms central to the pathophysiology of wheeze/asthma and lung growth and development overlap and involve a cascade of events that include disrupted immune, neuroendocrine, and autonomic function as well as oxidative stress. Altered homeostatic functioning of these integrated systems during development can enhance vulnerability to asthma and altered lung development.

SUMMARY

Mechanistic studies that more comprehensively assess biomarkers reflecting alterations across interrelated stress response systems and associated regulatory processes, in both pregnant women and young children, could be highly informative. Leveraging high-throughput systems-wide technologies to include epigenomics (e.g., DNA methylation, microRNAs), transcriptomics, and microbiomics as well as integrated multiomics are needed to advance this field of science. Understanding stress-induced physiological changes occurring during vulnerable life periods that contribute to chronic respiratory disease risk could lead to the development of preventive strategies and novel therapeutic interventions.

Humanin (HN) and glucose transporter 8 (GLUT8) in pregnancies complicated by intrauterine growth restriction

Background

Intrauterine growth restriction (IUGR) results from a lack of nutrients transferred to the developing fetus, particularly oxygen and glucose. Increased expression of the cytoprotective mitochondrial peptide, humanin (HN), and the glucose transporter 8, GLUT8, has been reported under conditions of hypoxic stress. However, the presence and cellular localization of HN and GLUT8 in IUGR-related placental pathology remain unexplored. Thus, we undertook this study to investigate placental expression of HN and GLUT8 in IUGR-affected versus normal pregnancies.

Results

We found 1) increased HN expression in human IUGR-affected pregnancies on the maternal aspect of the placenta (extravillous trophoblastic (EVT) cytoplasm) compared to control (i.e. appropriate for gestational age) pregnancies, and a concomitant increase in GLUT8 expression in the same compartment, 2) HN and GLUT8 showed a protein-protein interaction by co-immunoprecipitation, 3) elevated HN and GLUT8 levels in vitro under simulated hypoxia in human EVT cells, HTR8/SVneo, and 4) increased HN expression but attenuated GLUT8 expression in vitro under serum deprivation in HTR8/SVneo cells.

Conclusions

There was elevated HN expression with cytoplasmic localization to EVTs on the maternal aspect of the human placenta affected by IUGR, also associated with increased GLUT8 expression. We found that while hypoxia increased both HN and GLUT8, serum deprivation increased HN expression alone. Also, a protein-protein interaction between HN and GLUT8 suggests that their interaction may fulfill a biologic role that requires interdependency. Future investigations delineating molecular interactions between these proteins are required to fully uncover their role in IUGR-affected pregnancies.

SLC9B1 methylation predicts fetal intolerance of labor

Fetal intolerance of labor is a common indication for delivery by Caesarean section. Diagnosis is based on the presence of category III fetal heart rate tracing, which is an abnormal heart tracing associated with increased likelihood of fetal hypoxia and metabolic acidemia. This study analyzed data from 177 unique women who, during their prenatal visits (7-15 weeks and/or 24-32 weeks) to Atlanta area prenatal care clinics, consented to provide blood samples for DNA methylation (HumanMethylation450 BeadChip) and gene expression (Human HT-12 v4 Expression BeadChip) analyses. We focused on 57 women aged 18-36 (mean 25.4), who had DNA methylation data available from their second prenatal visit. DNA methylation patterns at CpG sites across the genome were interrogated for associations with fetal intolerance of labor. Four CpG sites (P value <8.9 × 10^-9, FDR <0.05) in gene SLC9B1, a Na⁺/H⁺ exchanger, were associated with fetal intolerance of labor. DNA methylation and gene expression were negatively associated when examined longitudinally during pregnancy using a linear mixed-effects model. Positive predictive values of methylation of these four sites ranged from 0.80 to 0.89, while negative predictive values ranged from 0.91 to 0.92. The four CpG sites were also associated with fetal intolerance of labor in an independent cohort (the Johns Hopkins Prospective PPD cohort). Therefore, fetal intolerance of labor could be accurately predicted from maternal blood samples obtained between 24-32 weeks gestation. Fetal intolerance of labor may be accurately predicted from maternal blood samples obtained between 24-32 weeks gestation by assessing DNA methylation patterns of SLC9B1. The identification of pregnant women at elevated risk for fetal intolerance of labor may allow for the development of targeted treatments or management plans.

Maternal Lifetime Stress and Prenatal Psychological Functioning and Decreased Placental Mitochondrial DNA Copy Number in the PRISM Study

Psychosocial stress contributes to placental oxidative stress. Mitochondria are vulnerable to oxidative stress, which can lead to changes in mitochondrial DNA copy number (mtDNAcn). We examined associations of maternal lifetime stress, current negative life events, and depressive and posttraumatic-stress-disorder symptom scores with placental mtDNAcn in a racially/ethnically diverse sample (n = 147) from the Programming of Intergenerational Stress Mechanisms (PRISM) study (Massachusetts, March 2011 to August 2012). In linear regression analyses adjusted for maternal age, race/ethnicity, education, prenatal fine particulate matter exposure, prenatal smoking exposure, and the sex of the child, all measures of stress were associated with decreased placental mtDNAcn (all P values < 0.05). Weighted-quantile-sum (WQS) regression showed that higher lifetime stress and depressive symptoms accounted for most of the effect on mtDNAcn (WQS weights: 0.25 and 0.39, respectively). However, among white individuals, increased lifetime stress and posttraumatic stress disorder symptoms explained the majority of the effect (WQS weights: 0.20 and 0.62, respectively) while among nonwhite individuals, lifetime stress and depressive symptoms accounted for most of the effect (WQS weights: 0.27 and 0.55, respectively). These analyses are first to link increased maternal psychosocial stress with reduced placental mtDNAcn and add to literature documenting racial/ethnic differences in the psychological sequelae of chronic stress that may contribute to maternal-fetal health.

Prenatal hypoxia and placental oxidative stress: linkages to developmental origins of cardiovascular disease

Intrauterine growth restriction (IUGR, a pregnancy complication where the fetus does not reach its genetic growth potential) is a leading cause of fetal morbidity and mortality with a significant impact on population health. IUGR is associated with gestational hypoxia; which can lead to placental oxidative stress and fetal programming of cardiovascular disease. Mitochondria are a major source of placental oxidative stress and may provide a therapeutic target to mitigate the detrimental effects of placental oxidative stress on pregnancy outcomes. A nanoparticle-mediated delivery of a mitochondrial antioxidant to the placenta is a potential novel approach that may avoid unwanted off-target effects on the developing offspring.

Maternal chronic hypoxia increases expression of genes regulating lung liquid movement and surfactant maturation in male fetuses in late gestation

KEY POINTS

Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth restriction that may influence respiratory outcome at birth. We investigated the effect of maternal chronic hypoxia for a month in late gestation on signalling pathways regulating fetal lung maturation and the transition to air-breathing at birth using isobaric hypoxic chambers without alterations to maternal food intake. Maternal chronic hypoxia in late gestation increases fetal lung expression of genes regulating hypoxia signalling, lung liquid reabsorption and surfactant maturation, which may be an adaptive response in preparation for the successful transition to air-breathing at birth. In contrast to other models of chronic fetal hypoxaemia, late gestation onset fetal hypoxaemia promotes molecular regulation of fetal lung maturation. This suggests a differential effect of timing and duration of fetal chronic hypoxaemia on fetal lung maturation, which supports the heterogeneity observed in respiratory outcomes in newborns following exposure to chronic hypoxaemia in utero.

ABSTRACT

Chronic fetal hypoxaemia is a common pregnancy complication that may arise from maternal, placental and/or fetal factors. Respiratory outcome of the infant at birth likely depends on the duration, timing and severity of the hypoxaemic insult. We have isolated the effect of maternal chronic hypoxia (MCH) for a month in late gestation on fetal lung development. Pregnant ewes were exposed to normoxia (21% O2 ) or hypoxia (10% O2 ) from 105 to 138 days of gestation (term ∼145 days). At 138 days, gene expression in fetal lung tissue was determined by quantitative RT-PCR. Cortisol concentrations were determined in fetal plasma and lung tissue. Numerical density of surfactant protein positive cells was determined by immunohistochemistry. MCH reduced maternal PaO2 (106 ± 2.9 vs. 47 ± 2.8 mmHg) and fetal body weight (4.0 ± 0.4 vs. 3.2 ± 0.9 kg). MCH increased fetal lung expression of the anti-oxidant marker CAT and decreased expression of the pro-oxidant marker NOX-4. MCH increased expression of genes regulating hypoxia signalling and feedback (HIF-3α, KDM3A, SLC2A1, EGLN-3). There was no effect of MCH on fetal plasma/lung tissue cortisol concentrations, nor genes regulating glucocorticoid signalling (HSD11B-1, HSD11B-2, NR3C1, NR3C2). MCH increased expression of genes regulating sodium (SCNN1-B, ATP1-A1, ATP1-B1) and water (AQP-4) movement in the fetal lung. MCH promoted surfactant maturation (SFTP-B, SFTP-D, ABCA3) at the molecular level, but did not alter the numerical density of surfactant positive cells in lung tissue. MCH in late gestation promotes molecular maturation of the fetal lung, which may be an adaptive response in preparation for the successful transition to air-breathing at birth.

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.