Variations in expression of copper/zinc superoxide dismutase in villous trophoblast of the human placenta with gestational age

Disrupted Balance of the Oxidant-Antioxidant System in the Pathophysiology of Female Reproduction: Oxidative Stress and Adverse Pregnancy Outcomes

The significance of oxidative stress in the pathophysiology of male reproductive processes has been closely studied in the last two decades. Recently, it has become clear that oxidative stress can lead to numerous pathological conditions during female reproductive processes as well, contributing to the development of endometriosis, polycystic ovary syndrome and various forms of infertility. During pregnancy, physiological generation of reactive oxygen species (ROS) occurs in association with several developmental processes including oocyte maturation and implantation. An overproduction of ROS can lead to disturbances in fetal development and increases the risk for missed abortion, intrauterine growth restriction, pre-eclampsia, premature delivery and gestational diabetes. Our review focuses on the etiological role of the disrupted oxidant-antioxidant system during human gestation as it relates to adverse pregnancy outcomes.

Oxidative Stress in Assisted Reproductive Techniques, with a Focus on an Underestimated Risk Factor

Based on current findings, the presence of oxidative stress has a significant impact on the quality of gametes and embryos when performing assisted reproductive techniques (ART). Unfortunately, in vitro manipulation of these cells exposes them to a higher level of reactive oxygen species (ROS). The primary goal of this review is to provide a comprehensive overview of the development of oxidative stress in female and male reproductive systems, as well as in the case of the pre-implantation embryo and its environment. This review also focuses on the origins of ROS and the mechanisms of oxidative stress-induced damage during ART procedures. A well-known but underestimated hazard, light exposure-related photo-oxidation, is particularly concerning. The effect of oxidative stress on ART outcomes, as well as the various strategies for preventing it, are also discussed. We emphasize the role and significance of antioxidants and light protection including forms, functions, and mechanisms in the development of gametes and embryos in vivo and in vitro.

Placental Malfunction, Fetal Survival and Development Caused by Sow Metabolic Disorder: The Impact of Maternal Oxidative Stress

The energy and metabolic state of sows will alter considerably over different phases of gestation. Maternal metabolism increases dramatically, particularly in late pregnancy. This is accompanied by the development of an increase in oxidative stress, which has a considerable negative effect on the maternal and the placenta. As the only link between the maternal and the fetus, the placenta is critical for the maternal to deliver nutrients to the fetus and for the fetus' survival and development. This review aimed to clarify the changes in energy and metabolism in sows during different pregnancy periods, as well as the impact of maternal oxidative stress on the placenta, which affects the fetus' survival and development.

Evaluation of oxidative stress markers in subtypes of preeclampsia: A systematic review and meta-analysis

Studies about oxidative stress biomarkers revealed different phenotypes between early and late preeclampsia (PE). Despite that, there is extensive evidence of oxidative stress in investigations that combinate forms different of preeclampsia. This study reviews the oxidative stress profile in the PE subtypes and evaluates which markers are altered in the blood and placental tissue. A search was conducted in databases such as MEDLINE, EMBASE, LILACS, and Web of Science without restricting the year and language of publication. The quality of the studies was evaluated by the Newcastle-Ottawa scale and Joanna Briggs Institute for analytical Cross-Sectional Studies. After 13,319 screened records, 65 were included in the systematic review. The markers of stress oxidative of damage and reactive species were those selected, such as malondialdehyde (MDA), lipid peroxide, advanced protein oxidation products, carbonyl protein, 8-hydroxy-2'-deoxyguanosine, total oxidant status, hydrogen peroxide, nitric oxide (NO). We described the antioxidant activity, including the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase, free glutathione, and total antioxidant capacity (TAC). We results demonstrated that oxidative stress is related to pathophysiology of PE, there were increased lipid peroxidation in the blood and placenta, and in blood a reduction of NO levels and of TAC, like lower enzymatic activity of GPx, CAT in PE, and SOD in mild PE. In addition, altered levels of MDA in the placenta and blood show that placental changes have repercussions on the clinical syndrome and are related to the severity of the disease.

Human Chorionic Villous Differentiation and Placental Development

In humans, the placenta provides the only fetomaternal connection and is essential for establishing a pregnancy as well as fetal well-being. Additionally, it allows maternal physiological adaptation and embryonic immunological acceptance, support, and nutrition. The placenta is derived from extra-embryonic tissues that develop rapidly and dynamically in the first weeks of pregnancy. It is primarily composed of trophoblasts that differentiate into villi, stromal cells, macrophages, and fetal endothelial cells (FEC). Placental differentiation may be closely related to perinatal diseases, including fetal growth retardation (FGR) and hypertensive disorders of pregnancy (HDP), and miscarriage. There are limited findings regarding human chorionic villous differentiation and placental development because conducting in vivo studies is extremely difficult. Placental tissue varies widely among species. Thus, experimental animal findings are difficult to apply to humans. Early villous differentiation is difficult to study due to the small tissue size; however, a detailed analysis can potentially elucidate perinatal disease causes or help develop novel therapies. Artificial induction of early villous differentiation using human embryonic stem (ES) cells/induced pluripotent stem (iPS) cells was attempted, producing normally differentiated villi that can be used for interventional/invasive research. Here, we summarized and correlated early villous differentiation findings and discussed clinical diseases.

Mitochondrial dysfunction-induced high hCG associated with development of fetal growth restriction and pre-eclampsia with fetal growth restriction

Fetal growth restriction (FGR) and pre-eclampsia with fetal growth restriction (PE/FGR) are high-risk perinatal diseases that may involve high levels of human chorionic gonadotropin (hCG) and mitochondrial dysfunction. However, little is known about how these factors affect placental function. We investigated how mitochondrial dysfunction and high hCG expression affected placental function in unexplained FGR and PE/FGR. We observed elevated expression of hCGβ and growth differentiation factor 15 mRNA and protein levels in the placenta with both diseases. Likewise, antiangiogenic factors, such as Ang2, IP10, sFlt1, IL8, IL1B, and TNFα, were also upregulated at the mRNA level. In addition, the expression of COXI and COXII which encoded by mitochondrial DNA were significantly decreased in both diseases, suggesting that mitochondrial translation was impaired. Treatment with hCG increased Ang2, IP10, IL8, and TNFα mRNA levels in a dose-dependent manner via the p38 and JNK pathways. Mitochondrial translation inhibitors increased hCGβ expression through stabilization of HIF1α, and increased IL8 and TNFα mRNA expression. These results revealed that high expression of hCG due to mitochondrial translational dysfunction plays an important role in the pathogenesis of FGR and PE/FGR.

Human Placental Intracellular Cholesterol Transport: A Focus on Lysosomal and Mitochondrial Dysfunction and Oxidative Stress

The placenta participates in cholesterol biosynthesis and metabolism and regulates exchange between the maternal and fetal compartments. The fetus has high cholesterol requirements, and it is taken up and synthesized at elevated rates during pregnancy. In placental cells, the major source of cholesterol is the internalization of lipoprotein particles from maternal circulation by mechanisms that are not fully understood. As in hepatocytes, syncytiotrophoblast uptake of lipoprotein cholesterol involves lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SR-BI). Efflux outside the cells requires proteins such as the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. However, mechanisms associated with intracellular traffic of cholesterol in syncytiotrophoblasts are mostly unknown. In hepatocytes, uptaken cholesterol is transported to acidic late endosomes (LE) and lysosomes (LY). Proteins such as Niemann–Pick type C 1 (NPC1), NPC2, and StAR related lipid transfer domain containing 3 (STARD3) are required for cholesterol exit from the LE/LY. These proteins transfer cholesterol from the lumen of the LE/LY into the LE/LY-limiting membrane and then export it to the endoplasmic reticulum, mitochondria, or plasma membrane. Although the production, metabolism, and transport of cholesterol in placental cells are well explored, there is little information on the role of proteins related to intracellular cholesterol traffic in placental cells during physiological or pathological pregnancies. Such studies would be relevant for understanding fetal and placental cholesterol management. Oxidative stress, induced by generating excess reactive oxygen species (ROS), plays a critical role in regulating various cellular and biological functions and has emerged as a critical common mechanism after lysosomal and mitochondrial dysfunction. This review discusses the role of cholesterol, lysosomal and mitochondrial dysfunction, and ROS in the development and progression of hypercholesterolemic pregnancies.

Bioenergetics adaptations and redox homeostasis in pregnancy and related disorders

Pregnancy is a challenging physiological process that involves maternal adaptations to the increasing energetics demands imposed by the growing conceptus. Failure to adapt to these requirements may result in serious health complications for the mother and the baby. The mitochondria are biosynthetic and energy-producing organelles supporting the augmented energetic demands of pregnancy. Evidence suggests that placental mitochondria display a dynamic phenotype through gestation. At early stages of pregnancy placental mitochondria are mainly responsible for the generation of metabolic intermediates and reactive oxygen species (ROS), while at later stages of gestation, the placental mitochondria exhibit high rates of oxygen consumption. This review describes the metabolic fingerprint of the placental mitochondria at different stages of pregnancy and summarises key signs of mitochondrial dysfunction in pathological pregnancy conditions, including preeclampsia, gestational diabetes and intrauterine growth restriction (IUGR). So far, the effects of placental-driven metabolic changes governing the metabolic adaptations occurring in different maternal tissues in both, healthy and pathological pregnancies, remain to be uncovered. Understanding the function and molecular aspects of the adaptations occurring in placental and maternal tissue's mitochondria will unveil potential targets for further therapeutic exploration that could address pregnancy-related disorders. Targeting mitochondrial metabolism is an emerging approach for regulating mitochondrial bioenergetics. This review will also describe the potential therapeutic use of compounds with a recognised effect on mitochondria, for the management of preeclampsia.

Rosiglitazone augments antioxidant response in the human trophoblast and prevents apoptosis†

Insufficient perfusion of the trophoblast by maternal blood is associated with an increased generation of reactive oxygen species and complications of the placenta. In this study, we first examined whether rosiglitazone, an agonist of the peroxisome proliferator-activated receptor-γ (PPARγ), protects the human trophoblast from oxidative injury by regulating key antioxidant proteins, catalase (CAT) and the superoxide dismutases (SOD1 and SOD2). In first trimester placental explants, localization of CAT was limited to cytotrophoblasts, whereas SOD1 was expressed in both the cyto- and syncytiotrophoblasts. In first trimester placental explants, hypoxia decreased the expression of both SOD1 and SOD2, and increased apoptosis. Treatment with rosiglitazone dose-dependently upregulated anti-oxidative CAT and SOD2, and rescued hypoxic injury in first trimester villous explants and JEG-3 cells, strongly suggesting the involvement of the PPARγ in regulating their expressions. Rosiglitazone facilitated transcription activity of PPARγ, and enhanced promotor binding, increased transcriptional activity at the CAT promoter, and elevated protein expression/activity. Treatment of hypoxic JEG-3 cells with rosiglitazone resulted in mitochondrial membrane potential increase and a reduction of caspase 9 and caspase 3 activity which is consistent with improved cell survival. To complement PPARγ activation data, we also utilized the antagonist (SR-202) and siRNA to suppress PPARγ expression and demonstrate the specific role of PPARγ in reducing ROS and oxidative stress. Ex vivo examination of term human placenta revealed lower expression of antioxidant proteins in pathologic compared to healthy placental tissues, which could be rescued by rosiglitazone, indicating that rosiglitazone can improve survival of the trophoblast under pathological conditions. These findings provide evidence that the PPARγ pathway directly influences cellular antioxidants production and the pathophysiology of placental oxidative stress.

Protein kinase CK2 contributes to placental development: physiological and pathological implications

Preeclampsia (PE) is the most threatening pathology of human pregnancy. Its development is thought to be due to a failure in the invasion of trophoblast cells that establish the feto-maternal circulation. Protein kinase CK2 is a ubiquitous enzyme reported to be involved in the control of cell invasion. CK2 consists of two subunits, a catalytic subunit, CK2α, and a regulatory subunit, CK2β. To date, no data exist regarding the expression and role of this enzyme in normal and PE pregnancies. We performed studies, at the clinical level using distinctive cohorts from early pregnancy (n = 24) and from PE (n = 23) and age-matched controls (n = 28); in vitro, using trophoblast cell lines; ex vivo, using placental explants; and in vivo, using PE mouse models. We demonstrated that (i) CK2 is more expressed during the late first trimester of pregnancy and is mainly localized in differentiated trophoblast cells, (ii) the inhibition of its enzymatic activity decreased the proliferation, migration, invasion, and syncytialization of trophoblast cells, both in 2D and 3D culture systems, and (iii) CK2 activity and the CK2α/CK2β protein ratio were increased in PE human placentas. The pattern and profile of CK2 expression were confirmed in gravid mice along with an increase in the PE mouse models. Altogether, our results demonstrate that CK2 plays an essential role in the establishment of the feto-maternal circulation and that its deregulation is associated with PE development. The increase in CK2 activity in PE might constitute a compensatory mechanism to ensure proper pregnancy progress.

Modification of endothelial nitric oxide synthase by 4-oxo-2(E)-nonenal(ONE) in preeclamptic placentas

Preeclampsia (PE) is a leading cause of pregnancy complications, affecting 3-7% of pregnant women worldwide. The pathophysiology of preeclampsia involves a redox imbalance, oxidative stress and a reduced nitric oxide (NO) bioavailability. The molecular and cellular mechanisms leading to the dysfunction of the placental endothelial NO synthase (eNOS) are not clarified. This study was designed to investigate whether aldehydes generated by lipid peroxidation products (LPP), may contribute to placental eNOS dysfunction in PE. The analysis of placentas from PE-affected patients and normal pregnancies, showed a significant increase in protein carbonyl content, indicative of oxidative stress-induced protein modification, as shown by the accumulation of acrolein, 4-hydroxynonenal (HNE), and 4-oxo-2(E)-nonenal (ONE) adducts in PE placentas. In contrast, the levels of these LPP-adducts were low in placentas from normal pregnancies. Immunofluorescence and confocal experiments pointed out a colocalization of eNOS with ONE-Lys adducts, whereas eNOS was not modified in normal placentas. LC-MS/MS analysis of recombinant eNOS preincubated with ONE, allowed to identify several ONE-modified Lys-containing peptides, confirming that eNOS may undergo post-translational modification by LPP. The preincubation of HTR-8/SVneo human trophoblasts (HTR8) with ONE, resulted in ONE-Lys modification of eNOS and a reduced generation of NO. ONE inhibited the migration of HTR8 trophoblasts in the wound closure model, and this was partly restored by the NO donor, NOC-18, which confirmed the important role of NO in the invasive potential of trophoblasts. In conclusion, placental eNOS is modified by ONE in PE placentas, which emphasizes the sensitivity of this protein to oxidative stress in the disturbed redox environment of preeclamptic pregnancies.

Oxidative Stress as Cause, Consequence, or Biomarker of Altered Female Reproduction and Development in the Space Environment

Oxidative stress has been implicated in the pathophysiology of numerous terrestrial disease processes and associated with morbidity following spaceflight. Furthermore, oxidative stress has long been considered a causative agent in adverse reproductive outcomes. The purpose of this review is to summarize the pathogenesis of oxidative stress caused by cosmic radiation and microgravity, review the relationship between oxidative stress and reproductive outcomes in females, and explore what role spaceflight-induced oxidative damage may have on female reproductive and developmental outcomes.

Estimation of the burden of human placental micro- and nano-vesicles extruded into the maternal blood from 8 to 12 weeks of gestation

BACKGROUND

The human placenta extrudes a variety of extracellular vesicles (EVs) into the maternal blood daily. These vesicles may be crucial to the adaptation of the maternal cardiovascular and immune systems to pregnancy. Quantifying the EVs that are released in early gestation is important to our understanding of how placental EVs may contribute to the regulation of maternal physiology.

METHODS

EVs were isolated from first trimester placental explants and separated into micro- and nano-vesicles by differential centrifugation. The numbers of each type of EVs extruded from each milligram of placentae between gestational weeks 8 and 12 was determined by Nanoparticle Tracking Analysis. The total protein or DNA content of the vesicles was determined by BCA assay or Qubit^® 2.0.

RESULTS

Neither the number of micro- nor nano-EVs/mg explant (n = 49), nor the total protein (n = 19) and DNA content (n = 29) of these EVs changed significantly between 8 and 12 weeks of gestation. When the increasing placental weight with gestation was accounted for, the daily number of placental EVs extruded into the maternal blood increased by more than 100 fold between 8 and 12 weeks (micro-EVs 6.23 X 10¹⁴ and nano-EVs 1.84 X 10¹⁴ at 12 weeks, p = 0.0003).

DISCUSSION

Constant production of micro- and nano-EVs per-milligram placenta, regardless of gestational age, and the increased daily burden of EVs across gestational age indicate these EVs have the potential to regulate maternal physiology from early pregnancy. Since total EV protein content, like EV numbers was, constant, this is a potentially reliable surrogate for quantifying EVs.

Early Gestational Hypoxia and Adverse Developmental Outcomes

Hypoxia is a normal and essential part of embryonic development. However, this state may leave the embryo vulnerable to damage when oxygen supply is disturbed. Embryofetal response to hypoxia is dependent on duration and depth of hypoxia, as well as developmental stage. Early postimplantation rat embryos were resilient to hypoxia, with many surviving up to 1.5 hr of uterine clamping, while most mid-gestation embryos were dead after 1 hour of clamping. Survivors were small and many had a range of defects, principally terminal transverse limb reduction defects. Similar patterns of malformations occurred when embryonic hypoxia was induced by maternal hypoxia, interruption of uteroplacental flow, or perfusion and embryonic bradycardia. There is good evidence that high altitude pregnancies are associated with smaller babies and increased risk of some malformations, but these results are complicated by increased risk of pre-eclampsia. Early onset pre-eclampsia itself is associated with small for dates and increased risk of atrio-ventricular septal defects. Limb defects have clearly been associated with chorionic villus sampling, cocaine, and misoprostol use. Similar defects are also observed with increased frequency among fetuses who are homozygous for thalassemia. Drugs that block the potassium current, whether as the prime site of action or as a side effect, are highly teratogenic in experimental animals. They induce embryonic bradycardia, hypoxia, hemorrhage, and blisters, leading to transverse limb defects as well as craniofacial and cardiovascular defects. While evidence linking these drugs to birth defects in humans is not compelling, the reason may methodological rather than biological. Birth Defects Research 109:1358-1376, 2017.© 2017 Wiley Periodicals, Inc.

Oxidative stress in placental pathology

The most important function of the placenta is the exchange of nutrients and oxygen between a mother and her fetus. To establish a healthy functioning placenta, placentation needs to occur with adequate remodelling of spiral arteries by extravillous trophoblasts. When this process is impaired, the resulting suboptimal and inadequate placenta function results in the manifestation of pregnancy complications. Impaired placenta function can cause preeclampsia and leads to fetal growth restriction due to hypoxia. Presence of hypoxia leads to oxidative stress due to an imbalance between reactive oxygen species and antioxidants, thereby causing damage to proteins, lipids and DNA. In the placenta, signs of morphological adaptation in response to hypoxia can be found. Different placental lesions like maternal or fetal vascular malperfusion or chronic villitis lead to a decreased exchange of oxygen between the mother and the fetus. Clinically, several biomarkers indicative for oxidative stress, e.g. malondialdehyde and reduced levels of free thiols are found. This review aims to give an overview of the causes and (potential) role of placental oxidative stress in the development of placental parenchymal pathology and its clinical consequences. Also, therapeutic options aiming at prevention or treatment of hypoxia of the placenta and fetus are described.

Evaluation of Malondialdehyde, Superoxide Dismutase and Catalase Activity in Fetal Cord Blood of Depressed Mothers

Objective

The umbilical cord consists of two arteries and one vein and it functions in the transport between the maternal and fetal circulation. Biochemical analysis of fetal cord blood (FCB) during delivery could be beneficial in terms of understanding the fetal environment. In this study, we aimed to investigate oxidative parameters like malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels in FCB during delivery.

Methods

We collected FCB samples during caesarean section. Our study included 33 depressed mothers and 37 healthy controls. We investigated MDA, SOD, and CAT levels in FCB samples.

Results

We found no significant difference between groups in terms of MDA (p=0.625), SOD (p=0.940), and CAT (p=0.413) levels.

Conclusion

Our study reveals probable protective effects of the placenta from oxidative stress. Future studies should include larger samples.

Placental Oxidative Stress: From Miscarriage to Preeclampsia

OBJECTIVE

To review the role of oxidative stress in two common placental-related disorders of pregnancy, miscarriage and preeclampsia.

METHODS

Review of published literature.

RESULTS

Miscarriage and preeclampsia manifest at contrasting stages of pregnancy, yet both have their roots in deficient trophoblast invasion during early gestation. Early after implantation, endovascular trophoblast cells migrate down the lumens of spiral arteries, and are associated with their physiological conversion into flaccid conduits. Initially these cells occlude the arteries, limiting maternal blood flow into the placenta. The embryo therefore develops in a low oxygen environment, protecting differentiating cells from damaging free radicals. Once embryogenesis is complete, the maternal intervillous circulation becomes fully established, and intraplacental oxygen concentration rises threefold. Onset of the circulation is normally a progressive periphery-center phenomenon, and high levels of oxidative stress in the periphery may induce formation of the chorion laeve. If trophoblast invasion is severely impaired, plugging of the spiral arteries is incomplete, and onset of the maternal intervillous circulation is premature and widespread throughout the placenta. Syncytiotrophoblastic oxidative damage is extensive, and likely a major contributory factor to miscarriage. Between these two extremes will be found differing degrees of trophoblast invasion compatible with ongoing pregnancy but resulting in deficient conversion of the spiral arteries and an ischemia-reperfusion-type phenomenon. Placental perfusion will be impaired to a greater or lesser extent, generating commensurate placental oxidative stress that is a major contributory factor to preeclampsia.

CONCLUSION

Miscarriage, missed miscarriage, and early- and late-onset preeclampsia represent a spectrum of disorders secondary to deficient trophoblast invasion.

Depression in pregnancy is associated with decreased glutathione peroxidase activity in fetal cord blood

The investigation of fetal cord blood (FCB) during child delivery has created a novel topic in the field of psychiatric research. The umbilical vein receives nutrients and oxygen from the mother's circulation and transports them to the fetal circulation. Investigating fetal cord blood during delivery is beneficial for understanding the fetal environment. Depression in pregnancy is associated with medical and emotional burdens. In this study, we aimed to investigate glutathione peroxidase (Gpx) and myeloperoxidase (MPO) activity in the FCB of depressed mothers and healthy controls. Our study included 45 depressed mothers and 59 healthy controls. The FCB samples were collected from the umbilical vein during delivery. We found that Gpx levels were significantly decreased in the FCB of depressed mothers than healthy controls, medians were 0.14 U/ml and 0.16 U/ml respectively, Z: -3.567 and p < 0.001. MPO levels were similar in both groups, medians were 1.0 U/L and 1.2 U/L respectively, Z: -1.837 and p:0.066. Depression in pregnancy may be associated with decreased antioxidant levels, and this condition may cause an oxidative load, which may lead to improper brain development. Future studies should be performed in larger samples to clarify our preliminary results.

Probable preventive effects of placenta from oxidative stress; Evaluation of total antioxidant status, total oxidant status and oxidative stress index in fetal cord blood during the delivery

Depression in pregnancy may have negative effects on birth outcomes. It may also effect the intrauterine environment of the fetus. The umbilical cord is the conduit between the fetus and placenta, and functions in the transport between fetus and mother. Investigating biochemical parameters in fetal cord blood (FCB) during delivery may be helpful to understanding to what the fetus is exposed to, at least in the last trimester. In this study, we aimed to investigate total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) in the FCB of depressed mothers and healthy controls during delivery. Our study included 33 depressed mothers and 37 healthy controls. TAS, TOS, and OSI were measured according to Erel's method. We found that TAS, TOS, and OSI levels were similar in patients and healthy controls; however, the birth weights of depressed patients were significantly lower than those of healthy controls. Our results suggest that the placental barrier may prevent from oxidative stress. Future studies should include blood samples collected simultaneously from mothers during delivery.

Circulating and myometrial markers of oxidative stress in pregnant women with fetal growth restriction

AIM

The objective of this study was to identify the relationship between fetal growth restriction (FGR) and oxidative stress. The mechanisms that protect against oxidative stress in the local microenvironment were investigated by comparing the activities of the markers, both in the circulation and myometrium.

MATERIALS AND METHODS

Myometrial tissue and serum levels of malondialdehyde (MDA), xanthine oxidase (XO), catalase (CAT) and superoxide dismutase (SOD) markers were measured in 20 FGR and 20 healthy pregnancies.

RESULTS

The mean duration of gestation at delivery was shorter (P = 0003) and the mean birthweight was lower P < 0001) in the FGR study group compared with the control group, as expected. While MDA and CAT concentrations were higher in the serum (P < 0.02 and P < 0.01, respectively), but lower in the myometrial samples (P < 0.01) in the FGR versus the control group, XO and myometrial SOD values were comparable in both groups.

CONCLUSIONS

Although our data demonstrated that FGR is associated with oxidative stress, the exact role and mechanism of the oxidant and antioxidant imbalance is obscure. We speculate that despite limited local synthesis of CAT, effective and efficient removal of MDA in the uterine environment explains high MDA and CAT serum concentrations in women with FGR. Alternatively, a well-functioning myometrial system could rescue the fetus from reactive oxygen species, as demonstrated by lowered MDA and depleted CAT resulting from hyperconsumption. Elevated serum MDA and CAT levels in the serum may reflect the 'spillover' of these markers from the uterus to the circulation.

Assessment of lipid and protein peroxidation markers in non-pregnant and pregnant female dogs

The aim of the study was to investigate oxidative stress during normal pregnancy in female dogs based on an evaluation of plasma markers for lipid and protein peroxidation. Twenty clinically healthy female dogs (10 non-pregnant and 10 pregnant) were used in the study. Blood samples from the pregnant animals were collected at 19-21, 38-40, and 56-58 days of pregnancy. Blood samples from non-pregnant female dogs were obtained between 20 and 35 days after ineffective breeding. As indicators of oxidative stress, we measured the following using spectrophotometric and spectrof- luorimetric methods: thiobarbituric acid reactive substances (TBARS), radical cations of N,N, diethylparaphenylene diamine (RC-DEPPD), sulfhydryl groups (SH groups), bityrosine and formylkynurenine. The mean plasma TBARS concentration in the pregnant dogs (0.486 ± 0.071-0.581 ± 0.191 μmol/g protein) was significantly higher (p < 0.05) than that found in the non-pregnant animals (0.274 ± 0.111 μmol/g protein). A marked, although not significant, decrease in SH group content, as well as an increase in bityrosine and formylkynurenine concentration were concurrently observed in the pregnant dogs. No significant differences were found in terms of the studied markers in the pregnant animals when comparing the values obtained during the investigated periods of pregnancy, although there was a progressive decrease in TBARS concentration and a progressive increase in RC-DEPPD, bityrosine and formylkynurenine contents. Our findings suggest that normal pregnancy in female dogs is associated with oxidative stress. Further studies are necessary to establish the physiological ranges of antioxidative/oxidative profiles in pregnant dogs and to explain if and how the intensity of oxidative stress might contribute to the risk of the complications of pregnancy.

Improving asthma during pregnancy with dietary antioxidants: the current evidence

The complication of asthma during pregnancy is associated with a number of poor outcomes for the mother and fetus. This may be partially driven by increased oxidative stress induced by the combination of asthma and pregnancy. Asthma is a chronic inflammatory disease of the airways associated with systemic inflammation and oxidative stress, which contributes to worsening asthma symptoms. Pregnancy alone also intensifies oxidative stress through the systemic generation of excess reactive oxidative species (ROS). Antioxidants combat the damaging effects of ROS; yet antioxidant defenses are reduced in asthma. Diet and nutrition have been postulated as potential factors to combat the damaging effects of asthma. In particular, dietary antioxidants may play a role in alleviating the heightened oxidative stress in asthma. Although there are some observational and interventional studies that have shown protective effects of antioxidants in asthma, assessment of antioxidants in pregnancy are limited and there are no antioxidant intervention studies in asthmatic pregnancies on asthma outcomes. The aims of this paper are to (i) review the relationships between oxidative stress and dietary antioxidants in adults with asthma and asthma during pregnancy, and (ii) provide the rationale for which dietary management strategies, specifically increased dietary antioxidants, might positively impact maternal asthma outcomes. Improving asthma control through a holistic antioxidant dietary approach might be valuable in reducing asthma exacerbations and improving asthma management during pregnancy, subsequently impacting perinatal health.

Transcriptional profiling with a pathway-oriented analysis in the placental villi of unexplained miscarriage

INTRODUCTION

Miscarriage is the most common placental-related complication of pregnancy. It has been extensively investigated to discover the underlying mechanism(s) by which miscarriage occurs, but in many cases the etiology still remains unclear. The aim of this study was to analyze genome-wide expression profiles of placental villi (PV) from unexplained miscarriage with a pathway-oriented method for identifying underlying mechanism(s) of unexplained miscarriage.

METHODS

We investigated PV of 18 women with unexplained miscarriage and 11 women underwent normal pregnancy. Each PV was obtained through dilatation & evacuation and chorionic villous sampling, respectively. Genome-wide expression profiles of PV were analyzed by Gene Set Enrichment Analysis (GSEA) to find dysregulated signaling pathways in PV of unexplained miscarriage.

RESULTS

Unsupervised hierarchical clustering showed heterogeneity of expression profiles between PV of normal developing pregnancy and unexplained miscarriage. GSEA, a supervised analysis, with KEGG pathways revealed that several gene sets associated with mitochondrial function including glutathione metabolism and oxidative phosphorylation are dysregulated in PV from unexplained miscarriage. RT-PCR, real-time RT-PCR and/or immunohistochemistry reinforced that expression of genes constituting these gene sets enriched in normal pregnancy and Cu/Zn-superoxide dismutase was down-regulated in PV of unexplained miscarriage.

DISCUSSION

Structural vulnerability of placental villi for reactive oxygen species (ROS), which is caused by systemic down-regulation of mitochondrial pathways involved in mitochondrial redox balance and functions, aggravates oxidative stress with increased ROS production in PV of unexplained miscarriage.

CONCLUSION

Systemic vulnerability for ROS in PV could be a major cause of unexplained miscarriage.

Comparative expression of hCG β-genes in human trophoblast from early and late first-trimester placentas

Human chorionic gonadotropin (hCG) displays a major role in pregnancy initiation and progression and is involved in trophoblast differentiation and fusion. However, the site and the type of dimeric hCG production during the first trimester of pregnancy is poorly known. At that time, trophoblastic plugs present in the uterine arteries disappear, allowing unrestricted flow of maternal blood to the intervillous space. The consequence is an important modification of the trophoblast environment, including a rise of oxygen levels from about 2.5% before 10 wk of amenorrhea (WA) to ∼8% after 12 WA. Two specific β-hCG proteins that differ from three amino acids have been described: type 1 (CGB7) and type 2 (CGB3, -5, and -8). Here, we demonstrated in situ and ex vivo on placental villi and in vitro in primary cultures of human cytotrophoblasts that type 1 and 2 β-hCG RNAs and proteins were expressed by trophoblasts and that these expressions were higher before blood enters in the intervillous space (8-9 vs. 12-14 WA). hCG was immunodetected in villous mononucleated cytotrophoblasts (VCT) and syncytiotrophoblast (ST) at 8-9 WA but only in ST at 12-14 WA. Furthermore, hCG secretion was fourfold higher in VCT cultures from 8-9 WA compared with 12-14 WA. Interestingly, VCT from 8-9 WA placentas were found to exhibit more fusion features. Taken together, we showed that type 1 and type 2 β-hCG are highly expressed by VCT in the early first trimester, contributing to the high levels of hCG found in maternal serum at this term.

Review: Human trophoblast fusion and differentiation: lessons from trisomy 21 placenta

The syncytiotrophoblast layer plays a major role throughout pregnancy, since it is the site of numerous placental functions, including ion and nutrient exchange and the synthesis of steroid and peptide hormones required for fetal growth and development. Inadequate formation and regeneration of this tissue contributes to several pathologies of pregnancy such as intrauterine growth restriction and preeclampsia, which may lead to iatrogenic preterm delivery in order to prevent fetal death and maternal complications. Syncytiotrophoblast formation can be reproduced in vitro using different models. For the last ten years we have routinely purified villous cytotrophoblastic cells (CT) from normal first, second and third trimester placentas and from gestational age-matched Trisomy 21 placentas. We cultured villous CT on plastic dishes to follow the molecular and biochemical aspects of their morphological and functional differentiation. Taking advantage of this unique collection of samples, we here discuss the concept that trophoblast fusion and functional differentiation may be two differentially regulated processes, which are linked but quite distinct. We highlight the major role of mesenchymal-trophoblast cross talk in regulating trophoblast cell fusion. We suggest that the oxidative status of the trophoblast may regulate glycosylation of proteins, including hCG, and thereby modulate major trophoblast cell functions.

Amniotic fluid eicosanoids in preterm and term births: effects of risk factors for spontaneous preterm labor

OBJECTIVE

To evaluate amniotic fluid arachidonic acid metabolites using enzymatic and nonenzymatic (lipid peroxidation) pathways in spontaneous preterm birth and term births, and to estimate whether prostanoid concentrations correlate with risk factors (race, cigarette smoking, and microbial invasion of amniotic cavity) associated with preterm birth.

METHODS

In a case-control study, amniotic fluid was collected at the time of labor or during cesarean delivery. Amniotic fluid samples were subjected to gas chromatography, negative ion chemical ionization, and mass spectrometry for prostaglandin (PG) E2, PGF2α, and PGD2 and for 6-keto-PGF1α (thromboxane 2 and F2-isoprostane). Primary analysis examined differences between prostanoid concentrations in preterm birth (n=133) compared with term births (n=189). Secondary stratified analyses (by race, cigarette smoking, and microbial invasion of amniotic cavity) compared eicosanoid concentrations in three epidemiological risk factors.

RESULTS

Amniotic fluid F2-isoprostane, PGE2, and PGD2 were significantly higher at term than in preterm birth, whereas PGF2α was higher in preterm birth 6-keto-PGF1α and thromboxane 2 concentrations were not different. Data stratified by race (African American or white) showed no significant disparity among prostanoid concentrations. Regardless of gestational age status, F2-isoprostane was threefold higher in smokers, and other eicosanoids were also higher in smokers compared with nonsmokers. Preterm birth with microbial invasion of amniotic cavity had significantly higher F2-isoprostane compared with preterm birth without microbial invasion of amniotic cavity.

CONCLUSION

Most amniotic fluid eicosanoid concentrations (F2-isoprostane, PGE2, and PGD2), are higher at term than in preterm births. The only amniotic fluid eicosanoid that is not higher at term is PGF2α.

Oxidative stress

Considerable evidence implicates oxidative stress in the pathophysiology of many complications of human pregnancy, and this topic has now become a major focus of both clinical and basic science research. Oxidative stress arises when the production of reactive oxygen species overwhelms the intrinsic anti-oxidant defences. Reactive oxygen species play important roles as second messengers in many intracellular signalling cascades aimed at maintaining the cell in homeostasis with its immediate environment. At higher levels, they can cause indiscriminate damage to biological molecules, leading to loss of function and even cell death. In this chapter, we will review how reactive oxygen species are generated and detoxified in the human placenta, and what roles they may play at homeostatic concentrations. We will then consider their involvement in normal placental development, and in complications ranging from miscarriage to pre-eclampsia and premature rupture of the membranes.

An imbalance between angiogenic and anti-angiogenic factors precedes fetal death in a subset of patients: results of a longitudinal study

OBJECTIVE

Women with a fetal death at the time of diagnosis have higher maternal plasma concentrations of the anti-angiogenic factor, soluble vascular endothelial growth factor receptor (sVEGFR)-1, than women with a normal pregnancy. An important question is whether these changes are the cause or consequence of fetal death. To address this issue, we conducted a longitudinal study and measured the maternal plasma concentrations of selective angiogenic and anti-angiogenic factors before the diagnosis of a fetal death. The anti-angiogenic factors studied were sVEGFR-1 and soluble endoglin (sEng), and the angiogenic factor, placental growth factor (PlGF).

METHODS

This retrospective longitudinal nested case-control study included 143 singleton pregnancies in the following groups: (1) patients with uncomplicated pregnancies who delivered a term infant with an appropriate weight for gestational age (n=124); and (2) patients who had a fetal death (n=19). Blood samples were collected at each prenatal visit, scheduled at 4-week intervals from the first trimester until delivery. Plasma concentrations of sVEGFR-1, sEng, and PlGF were determined by specific and sensitive ELISA. A linear mixed-effects model was used for analysis.

RESULTS

(1) The average profiles of analyte concentrations as a function of gestational age for sVEGFR-1, sEng and PlGF were different between women destined to have a fetal death and those with a normal pregnancy after adjusting for covariates (p<0.05); (2) Plasma sVEGFR-1 concentrations in patients destined to have a fetal death were significantly lower between 7 and 11 weeks of gestation and became significantly higher than those of women with a normal pregnancy between 20 and 37 weeks of gestation (p<0.05); (3) Similarly, plasma sEng concentrations of women destined to have a fetal death were lower at 7 weeks of gestation (p=0.04) and became higher than those of controls between 20 and 40 weeks of gestation (p<0.05); (4) In contrast, plasma PlGF concentrations were higher among patients destined to develop a fetal death between 7 and 14 weeks of gestation and became significantly lower than those in the control group between 22 and 39 weeks of gestation (p<0.05); (5) The ratio of PlGF/(sVEGFR-1 × sEng) was significantly higher in women destined to have a fetal death between 7 and 13 weeks of gestation (94-781%) and significantly lower (44-75%) than those in normal pregnant women between 20 and 40 weeks of gestation (p<0.05); (6) Similar results were obtained when patients with a fetal death were stratified into those who were diagnosed before or after 37 weeks of gestation.

CONCLUSIONS

Fetal death is characterised by higher maternal plasma concentrations of PlGF during the first trimester compared to normal pregnancy. This profile changes into an anti-angiogenic one during the second and third trimesters.

The origin of pre-eclampsia: from decidual "hyperoxia" to late hypoxia

Normal gestation implants on a relatively hypoxic deciduas so that trophoblast deeply invades endometrium and angiogenesis seeks for oxygen supply. If implantation occurs before those hypoxic conditions occur, trophoblast invasion is defective, due to the relatively high oxygen tension in the decidual environment, laying the foundations for subsequent pre-eclampsia.

Beyond oxygen: complex regulation and activity of hypoxia inducible factors in pregnancy

In the first trimester the extravillous cytotrophoblast cells occlude the uterine spiral arterioles creating a low oxygen environment early in pregnancy, which is essential for pregnancy success. Paradoxically, shallow trophoblast invasion and defective vascular remodelling of the uterine spiral arteries in the first trimester may result in impaired placental perfusion and chronic placental ischemia and hypoxia later in gestation leading to adverse pregnancy outcomes. The hypoxia inducible factors (HIFs) are key mediators of the response to low oxygen. We aimed to elucidate mechanisms of regulation of HIFs and the role these may play in the control of placental differentiation, growth and function in both normal and pathological pregnancies. The Pubmed database was consulted for identification of the most relevant published articles. Search terms used were oxygen, placenta, trophoblast, pregnancy, HIF and hypoxia. The HIFs are able to function throughout all aspects of normal and abnormal placental differentiation, growth and function; during the first trimester (physiologically low oxygen), during mid-late gestation (where there is adequate supply of blood and oxygen to the placenta) and in pathological pregnancies complicated by placental hypoxia/ischemia. During normal pregnancy HIFs may respond to complex alterations in oxygen, hormones, cytokines and growth factors to regulate placental invasion, differentiation, transport and vascularization. In the ever-changing environment created during pregnancy, the HIFs appear to act as key mediators of placental development and function and thereby are likely to be important contributors to both normal and adverse pregnancy outcomes.

Effect of docosahexaenoic acid and eicosapentaenoic acid supplementation on oxidative stress levels during pregnancy

Docosahexaenoic acid (DHA) is an indispensable component of cell membranes with high requirements during pregnancy. DHA supplementation is thought to enhance oxidative stress because of increased likelihood of lipid peroxidation. We estimated the oxidative stress levels in two groups of pregnant women who received daily supply of required vitamins with (n = 23) or without (n = 23) 500 mg of DHA and 150 mg of eicosapentaenoic acid (EPA) from 20 weeks of gestation to the time of delivery. Urinary excretions of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage and of malondialdehyde (MDA), a marker of lipid peroxidation, were measured at 20, 30 weeks and at the time of delivery. Urinary MDA excretion remained unchanged throughout the study period in both groups. Urinary 8-OHdG excretion at delivery was significantly higher than at 20 and 30 weeks (p < 0.05), but there were no group differences at the three time points. There were no differences between the two groups in plasma a-tocopherol levels. We conclude that under the conditions studied, a daily supplementation of 500 mg DHA and 150 mg EPA with vitamins to pregnant women did not enhance lipid peroxidation or oxidative DNA damage.

Oxygen, the Janus gas; its effects on human placental development and function

The accumulation of oxygen in the earth's atmosphere enabled metabolic pathways based on high-energy electron transfers that were capable of sustaining complex multicellular organisms to evolve. This advance came at a price, however, for the high reactivity of oxygen posed a major challenge as biological molecules became susceptible to oxidative damage, resulting in potential loss of function. Many extant physiological systems are therefore adapted, and homeostatically regulated, to supply sufficient oxygen to meet energy demands whilst also protecting cells, and mitochondria in particular, from excessive concentrations that could lead to oxidative damage. The invasive form of implantation displayed by the human conceptus presents particular challenges in this respect. During the first trimester, the conceptus develops in a low oxygen environment that favours organogenesis in the embryo, and cell proliferation and angiogenesis in the placenta. Later in pregnancy, higher oxygen concentrations are required to support the rapid growth of the fetus. This transition, which appears unique to the human placenta, must be negotiated safely for a successful pregnancy. Normally, onset of the maternal placental circulation is a progressive periphery-centre phenomenon, and is associated with extensive villous regression to form the chorion laeve. In cases of miscarriage, onset of the circulation is both precocious and disorganized, and excessive placental oxidative stress and villous regression undoubtedly contribute to loss of the pregnancy. Comparison of experimental and in vivo data indicates that fluctuations in placental oxygen concentration are a more powerful stimulus for the generation of oxidative stress than chronic hypoxia alone. Placental oxidative and endoplasmic reticulum stress appear to play key roles in the pathophysiology of complications of pregnancy, such as intrauterine growth restriction and preeclampsia, through their adverse impacts on placental function and growth. Establishing an inviolable maternal blood supply for the second and third trimesters is therefore one of the most crucial aspects of human placentation.

Proteomic Analysis on the Alteration of Protein Expression in the Placental Villous Tissue of Early Pregnancy Loss

Early pregnancy loss is the most common complication of human reproduction. Given the complexities of early development, it is likely that many mechanisms are involved. Knowledge of differences in protein expression in parallel profiling is essential to understand the comprehensive pathophysiological mechanism underlying early pregnancy loss. To identify proteins with different expression profiles related to early pregnancy loss, we applied a proteomic approach and performed two-dimensional gel electrophoresis (2-DE) on six placental villous tissues from patients with early pregnancy loss and six from normal pregnant women, followed by comparison of the silver-stained 2-DE profiles. It was found that 13 proteins were downregulated and 5 proteins were upregulated significantly (P < 0.05) in early pregnancy loss as determined by spot volume. Among them, 10 downregulated and 2 upregulated spots were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Anomalies of these proteins, including three principal antioxidant enzymes (copper/zinc-superoxide dismutase, peroxiredoxin 3, and thioredoxin-like 1 protein), S100 calcium binding protein, galectin-1, chorionic somatomammotropin hormone 1, transthyretin, fas inhibitory molecule, eukaryotic translation elongation factor, RNA-binding protein, ubiquitin-conjugating enzyme E2N, and proteasome beta-subunit, indicate widespread failure in cell regulations and processes such as antioxidative defense, differentiation, cell proliferation, metabolism, apoptosis, transcription, and proteolysis in early pregnancy loss. This study has identified several proteins that are associated with placentation and early development, shedding a new insight into the proteins that may be potentially involved in the pathophysiological mechanisms underlying early pregnancy loss.

Cytotrophoblast differentiation in the first trimester of pregnancy: evidence for separate progenitors of extravillous trophoblasts and syncytiotrophoblast

It is commonly accepted that a single pool of villous cytotrophoblasts are precursors of both syncytiotrophoblast and extravillous trophoblasts during the first trimester. Here we present evidence that these two trophoblast subpopulations arise from separate progenitors that have different survival characteristics when studied in villous explant cultures. Dual staining with chloromethylfluorescin diacetate and ethidium bromide revealed degeneration of the syncytiotrophoblast by non-apoptotic mechanisms within 4 h of culture. The syncytiotrophoblast had regenerated within 48 h but at this point the vast majority of the cytotrophoblast and cells of the mesenchymal core were dead. Despite this extensive cytotrophoblast death, explants are able to produce extravillous trophoblast outgrowth for up to 3 weeks in culture. We believe that the villous cytotrophoblasts in the tips of anchoring villi are resistant to the factors that cause the death of the majority of villous cytotrophoblasts in culture. We speculate that as early as 8 weeks of gestation there are two separate villous cytotrophoblast populations, one committed to differentiate into syncytiotrophoblast and the second committed to the extravillous differentiation pathway.

The regulation of trophoblast differentiation by oxygen in the first trimester of pregnancy

In the first trimester of human pregnancy villous cytotrophoblasts are able to differentiate to form either the overlying syncytiotrophoblast layer or, in anchoring villi, extravillous trophoblasts which grow out from the villi and invade into the maternal decidua, acting to both physically attach the placenta to the decidua, and modify the maternal spiral arteries to sustain pregnancy. During the first 10-12 weeks of gestation, extravillous trophoblast plugs block the spiral arteries and prevent maternal blood flow entering the intervillous space, thereby creating an environment of physiological hypoxia in which placental and fetal development occur. As extravillous trophoblasts migrate away from the villus they differentiate from a proliferative to an invasive phenotype. The hypoxic environment of the first trimester is believed to play an important role in the regulation of trophoblast differentiation. However, there is currently a large body of conflicting experimental evidence concerning this topic. This review examines the experimental evidence to date on the role of oxygen in trophoblast differentiation.

Pathophysiological basis for the prophylaxis of preeclampsia through early supplementation with antioxidant vitamins

Preeclampsia (PE) is a multisystem disorder that remains a major cause of maternal and foetal morbidity and death. To date, no treatment has been found that prevents the development of the disease. Endothelial dysfunction is considered to underlie its clinical manifestations, such as maternal hypertension, proteinuria, and edema; however, the precise biochemical pathways involved remain unclear. A current hypothesis invokes the occurrence of oxidative stress as pathogenically important, as suggested by the fact that in PE, the placental and circulating levels of lipid peroxidation products (F2-isoprostanes and malondialdehyde [MDA]) are increased and endothelial cells are activated. A potential mechanism for endothelial dysfunction may occur via nuclear transcription factor kappa B (NF-kappaB) activation by oxidative stress. Alternatively, the idea that the antiangiogenic placental soluble fms-like tyrosine kinase 1 factor (sFlt1) is involved in the pathogenesis of this disease is just emerging; however, other pathophysiological events seem to precede its increased production. This review is focused on evidence providing a pathophysiological basis for the beneficial effect of early antioxidant therapy in the prevention of PE, mainly supported by the biological effects of vitamins C and E.

The role of ultrasound imaging in diagnosing and investigating early pregnancy failure

The advent of high-resolution transvaginal ultrasound (TVS) has revolutionized our understanding of the pathophysiology and the management of early pregnancy failure. Knowledge of the ultrasound appearances of normal early pregnancy development and a good understanding of its pitfalls are essential for the diagnosis and management of early pregnancy failure. Ultrasound imaging has rapidly replaced all other techniques used to study normal human development in the first trimester, and ultrasound features of the early gestational sac have corroborated anatomical studies showing that the first structures to appear are the celomic cavity and the secondary yolk sac. No single ultrasound measurement of the different anatomical features in the first trimester has been shown to have a high predictive value for determining early pregnancy outcome. Similarly, Doppler studies have failed to demonstrate abnormal blood flow indices in the first-trimester uteroplacental circulation of pregnancies that subsequently end in miscarriage. Ultrasound parameters combined with maternal serum hormone levels, maternal age, smoking habits, obstetric history and the occurrence of vaginal bleeding have all been combined in multivariate analyses, with mixed results. Combined ultrasound and in-vitro experiments have demonstrated that the maternal circulation inside the placenta starts at the periphery at around 9 weeks of gestation and that this is associated with a physiological oxidative stress which could be the trigger for the formation of the placental membranes. Abnormal development of these membranes can result in subchorionic hemorrhage and threatened miscarriage with subsequent long-term consequences such as preterm rupture of the membranes and preterm labor, irrespective of the finding of a hematoma on ultrasound. In both euploid and aneuploid missed miscarriages there is clear ultrasound evidence for excessive entry of maternal blood at a very early stage inside the developing placenta resulting in oxidative stress and subsequent degeneration of villous tissue. The finding of blood flow in the intervillous space in cases of first-trimester miscarriage using color Doppler also appears to be useful in the prediction of success of expectant management. Miscarriages with blood flow within the intervillous space are up to four times more likely to complete with expectant management. TVS is considered the gold standard in the diagnosis and management of incomplete miscarriage. Expectant management of miscarriage, using ultrasound parameters to determine eligibility, could significantly reduce the number of unnecessary evacuations of the retained products of conception, depending on the criteria used.

Pathophysiology of histological changes in early pregnancy loss

An early pregnancy loss (EPL) or first-trimester miscarriage is the most common complication of human reproduction, with an incidence ranging between 50 and 70% of all conceptions. Two-thirds of EPL cases present with a thinner and fragmented trophoblastic shell, and reduced cytotrophoblast invasion of the tips of the spiral arteries. This leads to incomplete plugging during early pregnancy, and premature onset of the maternal circulation throughout the placenta. The excessive entry of maternal blood into the intervillous space has a direct mechanical effect on the villous tissue, and an indirect oxidative stress effect that contributes to cellular dysfunction and/or damage. Correlation of in vivo and in vitro data suggests that overwhelming oxidative stress of the placental tissues represents a common pathophysiological mechanism for the different etiologies of EPL. Autosomal trisomies are the most frequent karyotypic abnormalities found in EPL, but the comparison of data from different cytogenetic studies is difficult because of the lack of clinical information in many cases on maternal age, gestational age, time of fetal demise and the cytogenetic methodology employed. The majority of authors did find a weak association between villous morphologic features and chromosomal abnormalities, with the exception of partial mole triploidy. The comparison of ultrasound findings and placental histological data indicates that villous changes following fetal demise in utero could explain the overall low predictive value of placental histology alone in identifying an aneuploidy or another non-chromosomal etiology. By contrast, the histological features of complete and partial hydatidiform molar EPL are so distinctive that most cases of molar EPL are correctly diagnosed by histological examination alone. Overall, histopathology when correlated with in vivo ultrasound/Doppler has provided novel clues to the pathophysiology of EPL. Prospective studies are needed to evaluate the impact of these findings on routine histopathologic examination in first-trimester miscarriages.

Intralobular differences in antioxidant enzyme expression and activity reflect the pattern of maternal arterial bloodflow within the human placenta

The aim was to determine whether the activities and mRNA concentrations of antioxidant enzymes in human placental tissues reflect the prevailing oxygen tension or developmental maturity of the villi. Advantage was taken of contrasting gradients within lobules of the mature placenta. The central region is well-oxygenated compared to the periphery, owing to the direction of maternal blood flow. However, central villi are morphologically and enzymatically immature compared to peripheral villi. Activity of catalase (t=8.72, P< 0.001) and glutathione peroxidase (t=2.17,P< 0.05) was higher in central than peripheral villi, but no difference was detected for total superoxide dismutase (t=1.08, P> 0.05). The degree of change in catalase activity across the lobule correlated closely with the radius (r=-0.70, P< 0.01). The mRNA concentration was higher in the centre for catalase (t=2.81, P< 0.05) and for glutathione peroxidase (t=3.33, P< 0.05), but no differences were found for copper/zinc or manganese superoxide dismutase. In separate experiments, first trimester villi cultured under 10 per cent oxygen contained higher concentrations of catalase mRNA than controls maintained under 2.5 per cent oxygen. We conclude that the activities of catalase and glutathione peroxidase reflect gradients established by the pattern of maternal intralobular bloodflow, and that oxygen tension is one regulatory factor in vitro.

Iron and oxidative stress in pregnancy

Pregnancy, mostly because of the mitochondria-rich placenta, is a condition that favors oxidative stress. Transitional metals, especially iron, which is particularly abundant in the placenta, are important in the production of free radicals. Protective mechanisms against free radical generation and damage increase throughout pregnancy and protect the fetus, which, however, is subjected to a degree of oxidative stress. Oxidative stress peaks by the second trimester of pregnancy, ending what appears to be a vulnerable period for fetal health and gestational progress. Conditions restricted to pregnancy, such as gestational hypertension, insulin resistance and diabetes, exhibit exaggerated indications of free radical damage. Antioxidants as well as avoidance of iron excess ameliorate maternal and early fetal damage. In rats both iron deficiency and excess result in free radical mitochondrial damage. Estimates of gestational iron requirements and of the proportion of iron absorbed from different iron supplemental doses suggest that with present supplementation schemes the intestinal mucosal cells are constantly exposed to unabsorbed iron excess and oxidative stress. Unpublished work carried out in Mexico City with nonanemic women at midpregnancy indicates that 60 mg/d of iron increases the risk of hemoconcentration, low birth weight and premature birth and produces a progressive decline in plasma copper. These risks are not observed in women supplemented with 120 mg iron once or twice per week. Studies on the influence of iron supplementation schemes on oxidative stress are needed.

The human first trimester gestational sac limits rather than facilitates oxygen transfer to the foetus--a review

Oxygen (O2) free radicals are a potential teratologic threat to the foetal tissues and are known to be involved in the pathophysiology of common human pregnancy disorders such as miscarriage and pre-eclampsia. During the first two months of human gestation, the placenta surrounds the whole gestational sac, the villi contain only a few capillaries located mainly within the centre of the mesenchymal core, the trophoblastic layer is twice the thickness it will be in the second trimester, the foetal red cells are nucleated and the exocoelomic cavity (ECC) occupies most of the space inside the gestational sac. The ECC contains no oxygen transport system, but anti-oxidant molecules that may provide additional protection to the embryo from oxidative damage are present. Ultrasound and anatomical studies have also demonstrated that the intervillous circulation starts in the periphery of the placenta at around 9 weeks of gestation, and that it becomes continuous and diffuse in the entire placenta only after 12 weeks. Overall, these anatomical features provide indirect evidence that the architecture of the human first trimester gestational sac limits foetal exposure to O2 to what is strictly necessary for its development. These results are in agreement with the concept that the placenta and foetus develop in a physiologically low O2 environment and that its metabolism must be essentially anaerobic. Because of these anatomical arrangements, different nutritional pathways to those operating during most of pregnancy must serve the first-trimester foetus. Up to 9 weeks of gestation, foetal nutrition appears to depend on uterine glandular secretions that are delivered into the intervillous space, supplemented by maternal plasma proteins and other molecules that may percolate through the trophoblastic shell. These molecules diffuse through, or are transported by, the trophoblast of the villi and the chorionic plate into the ECC. From here they are absorbed by the secondary yolk sac (SYS), in which the extraembryonic circulation is probably first established. At the end of the first trimester, the SYS and two-thirds of the placental mass degenerate, and the ECC is progressively obliterated by the enlarging amniotic cavity. The trophoblastic plugs occluding the utero-placental arteries are gradually dislocated, allowing maternal blood to flow into the intervillous space, and the uterine glands involute. These major anatomical transformations modify considerably the spatial relationships between the maternal tissues and the developing embryo, and, consequently, the materno-embryonic exchange pathways. Overall the comparison of morphological features with physiological findings reveals that the architecture of the human first trimester gestational sac is designed to limit foetal exposure to oxygen to that which is strictly necessary for its development, and that during early pregnancy alternative nutritional pathways are in use.