MicroRNA-16 inhibits feto-maternal angiogenesis and causes recurrent spontaneous abortion by targeting vascular endothelial growth factor

Recurrent spontaneous abortion (RSA) is a common health problem that affects women of reproductive age. Recent studies have indicated that microRNAs are important factors in miscarriage. This study investigated the role of miR-16 in regulating vascular endothelial growth factor (VEGF) expression and the pathogenesis of RSA. In this report, clinical samples revealed that miR-16 expression was significantly elevated in the villi and decidua of RSA patients. In vitro, miR-16 upregulation inhibited human umbilical vein endothelial cell proliferation, migration and tube formation. Conversely, the downregulation of miR-16 reversed these effects. In vivo, we demonstrated that abnormal miR-16 levels affect the weights of the placenta and embryo and the number of progeny and microvascular density, as well as cause recurrent abortions by controlling VEGF expression in pregnant mice. VEGF, a potential target gene of miR-16, was inversely correlated with miR-16 expression in the decidua of clinical samples. Furthermore, the luciferase reporter system demonstrated that miR-16 was found to directly downregulate the expression of VEGF by binding a specific sequence of its 3′-untranslated region (3′UTR). Collectively, these data strongly suggest that miR-16 regulates placental angiogenesis and development by targeting VEGF expression and is involved in the pathogenesis of RSA.

Molecular and cellular effects of vitamin B12 forms on human trophoblast cells in presence of excessive folate

Folic acid (FA) and iron are essential supplements during pregnancy. Similarly effects of vitamin B12 (B12) inadequacy and high folate and low B12 status, on pregnancy outcome are available. However there are no mandatory recommendations for B12. There are many forms of B12 viz. Cyanocobalamin (Cbl), Methylcobalamin (MeCbl), Adenosylcobalamin (AdCbl), and Hydroxycobalamin (HCbl) though there is limited consensus on which form has better efficacy. In the present study we have determined effect of various forms of B12 in the presence of two FA concentrations namely normal physiological (20ng/mL; NPFA) and supra-physiological (2000ng/mL; SPFA) concentration to mimic real time situation where FA is in excess due to supplementation. We assessed trophoblastic proliferation, viability, TNFα and EGFr mRNA expression, homocysteine, β-hCG and MDA levels. Trophoblastic viability was significantly suppressed at SPFA concentration and was restored by B12 treatment with Cbl, AdCbl and combination of MeCbl+AdCbl. The mRNA expressions of TNFα were up-regulated, while EGFr were down-regulated at SPFA concentrations, as validated by RT-PCR. Treatment with MeCbl+AdCbl significantly decreased homocysteine and MDA levels at SPFA concentrations. High levels of FA alone had a detrimental effect on placental health and functions as reflected by decreased viability, EGFr expression and increased TNFα expression, homocysteine and MDA levels. Combination of B12 active forms i.e. MeCbl+AdCbl was found to be most effective in neutralising excess folate effect in-vitro.

Effect of folic acid supplementation during pregnancy on gestational hypertension/preeclampsia: A systematic review and meta-analysis

OBJECTIVE

To evaluate the effect of folic acid supplementation during pregnancy on the risk of gestational hypertension/preeclampsia.

METHODS

A systematic review and meta-analysis were conducted. Medline, Embase, Scopus, and the Web of Science were searched from inception to December 2014.

RESULTS

Out of 1224 potentially relevant studies, 13 studies met our inclusion criteria (2 randomized controlled trials (RCTs), 10 cohort studies, and 1 case-control study). The pooled relative risk (RR) and 95% confidence interval (CI) of the two RCTs were 0.62 (0.45-0.87) in the trial arm as compared with the placebo arm. The pooled RR was 0.92 (95% CI: 0.79-1.08) for nine cohort studies with available data on folic acid supplementation in pregnancy and gestational hypertension/preeclampsia. Pooled RR was 0.88 (95% CI: 0.76-1.02) for eight cohort studies with available data on folic acid supplementation and preeclampsia.

CONCLUSION

Whether folic acid supplementation in pregnancy can prevent the occurrence of gestational hypertension/preeclampsia remains uncertain.

Folic acid supplementation in pregnancy to prevent preterm birth: a systematic review and meta-analysis of randomized controlled trials

Folic acid (FA) may have a role in the prevention of pregnancy complications. However, the efficacy of FA supplementation in reducing the risk of preterm birth (PTB) is still unclear. The aim of this systematic review with meta-analysis was to evaluate the efficacy of folic acid supplementation during pregnancy to prevent preterm birth (PTB). The research protocol was designed a priori, defining methods for searching the literature in electronic databases, including and examining articles, and extracting and analyzing data. We included all randomized trials (RCTs) of asymptomatic singleton gestations without prior PTB who were randomized to prophylactic treatment with either FA supplementation or control (placebo or no treatment). The primary outcome was the incidence of PTB <37 weeks. Five randomized trials including 5,332 asymptomatic singleton gestations without prior PTB were included in the analysis. Women who received FA supplementation had a similar rate of PTB <37 weeks (22.6% vs 22.9%; RR 0.99, 95% CI 0.82-1.18), PTB<34 weeks (7.1% vs 8.7%; RR 0.77, 95% CI 0.55-1.09) and of preterm premature rupture of membranes (2.4% vs 2.9%; RR 0.81, 95% CI 0.44-1.50) compared with control group. Regarding neonatal outcome we found no significant differences in birth weight (mean difference 85.58g, 95% CI -55.17-226.34), low birth weight (21.0% vs 15.1%; RR 0.79, 95% CI 0.49 to 1.28) and perinatal death (2.9% vs 2.4%; RR 0.90, 95% CI 0.60-1.34). In summary, FA supplementation during pregnancy does not prevent PTB <37 weeks. Daily FA supplementation remains the most important intervention to reduce the risk of neural tube defects.

Effect of folic acid on human trophoblast health and function in vitro

INTRODUCTION

The combined intake of folic acid (FA) from prenatal multivitamin supplements and fortified foods can result in FA intake values that exceed the tolerable upper intake level (UL). It is unclear what impact FA intake above the UL may have on the feto-placental unit. Our objective was to determine the effects of increasing concentrations of FA on trophoblast health and function in vitro.

METHODS

Two human placental cell lines [HTR-8/SVneo (n = 5 experiments) and BeWo (n = 5 experiments)] and human placenta tissue explants (n = 6 experiments) were exposed to increasing concentrations of FA (2-2000 ng/mL) for 48-h. Intracellular total folate concentration, trophoblast proliferation, viability, apoptosis, placenta cell invasion and β-hCG hormone release were assessed.

RESULTS

Exposure to increasing FA concentrations resulted in higher intracellular total folate in placental cell lines and tissue explants (p < 0.05); yet, only minimal effects of excess folic acid were observed on the primary indicators of placental health and function studied. Specifically, treatment with excess folic acid (2000 ng/mL) resulted in reduced cellular viability in the villous trophoblast BeWo cell line and increased rates of proliferation in the HT8-8/SVneo extravillous trophoblast cell line (p < 0.05). Further, deficient concentrations of folic acid (2 ng/mL) resulted in decreased cell viability and invasive capabilities of the HTR-8/SVneo extravillous trophoblast cell line (p < 0.05).

DISCUSSION

Our results demonstrate that placental health and function may be compromised in conditions of folate deficiency, and not necessarily in conditions of excess FA. This finding supports the recommendation of prenatal folic acid supplementation in the North American population. Further work aimed at clarifying the therapeutic window of FA intake in the obstetrical population is warranted.

Potential role of folate in pre-eclampsia

Dietary deficiencies of folate and other B vitamin cofactors involved in one-carbon metabolism, together with genetic polymorphisms in key folate-methionine metabolic pathway enzymes, are associated with increases in circulating plasma homocysteine, reduction in DNA methylation patterns, and genome instability events. All of these biomarkers have also been associated with pre-eclampsia. The aim of this review was to explore the literature and identify potential knowledge gaps in relation to the role of folate at the genomic level in either the etiology or the prevention of pre-eclampsia. A systematic search strategy was designed to identify citations in electronic databases for the following terms: folic acid supplementation AND pre-eclampsia, folic acid supplementation AND genome stability, folate AND genome stability AND pre-eclampsia, folic acid supplementation AND DNA methylation, and folate AND DNA methylation AND pre-eclampsia. Forty-three articles were selected according to predefined selection criteria. The studies included in the present review were not homogeneous, which made pooled analysis of the data very difficult. The present review highlights associations between folate deficiency and certain biomarkers observed in various tissues of women at risk of pre-eclampsia. Further investigation is required to understand the role of folate in either the etiology or the prevention of pre-eclampsia.

Altered folate metabolism modifies cell proliferation and progesterone secretion in human placental choriocarcinoma JEG-3 cells

Folate is an essential B vitamin required for de novo purine and thymidylate synthesis, and for the remethylation of homocysteine to form methionine. Folate deficiency has been associated with placenta-related pregnancy complications, as have SNP in genes of the folate-dependent enzymes, methionine synthase (MTR) and methylenetetrahydrofolate dehydrogenase 1 (MTHFD1). We aimed to determine the effect of altered folate metabolism on placental cell proliferation, viability and invasive capacity and on progesterone and human chorionic gonadotropin (hCG) secretion. Human placental choriocarcinoma (JEG-3) cells cultured in low folic acid (FA) (2 nM) demonstrated 13% (P<0.001) and 26% (P<0.001) lower proliferation, 5.5% (P=0.025) and 7.5% (P=0.004) lower invasion capacity, and 5 to 7.5% (P=0.004-0.025) lower viability compared with control (20 nM) or supplemented (100 nM) cells, respectively. FA concentration had no effect on progesterone or hCG secretion. Small interfering RNA (siRNA) knockdown of MTR gene and protein expression resulted in 17.7% (P<0.0001) lower proliferation and 61% (P=0.014) higher progesterone secretion, but had no effect on cell invasion and hCG secretion. siRNA knockdown of MTHFD1 gene expression in the absence of detectable changes in protein expression resulted in 10.3% (P=0.001) lower cell proliferation, but had no effect on cell invasion and progesterone or hCG secretion. Our data indicate that impaired folate metabolism can result in lower trophoblast proliferation, and could alter viability, invasion capacity and progesterone secretion, which may explain in part the observed associations between folate and placenta-related complications.

Molecular mechanisms underlying the anti-proliferative and anti-migratory effects of folate on homocysteine-challenged rat aortic smooth muscle cells

BACKGROUND AND PURPOSE

Homocysteine is an intermediate product formed during the metabolism of methionine, and is increased in cells with folate deficiency. Patients with hyperhomocysteinemia tend to develop cardiovascular disease. Here, we have examined the molecular mechanisms underlying the anti-proliferative and anti-migratory effects of folate on homocysteine-challenged rat aortic smooth muscle cells (RASMCs).

EXPERIMENTAL APPROACH

Cultures of RASMC were challenged with homocysteine and then incubated with folate added. Changes in p21/p27, AKT and RhoA were followed by RT-PCR, Western blotting and immunocytochemistry. Transfection and anti-sense techniques were also used. Cell viability, growth and migration were measured.

KEY RESULTS

Folate up-regulated p21/p27 through a Src/ERK-dependent mechanism that accounted for its anti-proliferative effects on RASMC. Folate protected RASMC from the effects of homocysteine by reducing AKT1, focal adhesion kinase (FAK), paxillin, and p190RhoGAP activation/phosphorylation, along with cytosolic levels of p21 and p27, and increasing RhoA activation. Overexpression of AKT1, but not of AKT2, induced p21/p27 phosphorylation and increased cytosolic p21/p27 levels, as did homocysteine treatment. By contrast, and similarly to folate treatment, transfection with dominant negative (DN) AKT1 counteracted these effects. Additionally, AKT was shown to be an upstream target of FAK activation. In RASMC overexpressing constitutively active RhoA, activation of RhoA mediated the anti-migratory effects of folate. Addition of Y27632 (a RhoA inhibitor) and DNRhoA counteracted the anti-migratory effects, confirming RhoA involvement.

CONCLUSION AND IMPLICATIONS

Folate was anti-proliferative and anti-migratory in homocysteine-challenged RASMC. Mechanisms underlying folate-mediated protection against the proatherosclerotic effects of homocysteine have been delineated.

Endometrial stromal cells and decidualized stromal cells: origins, transformation and functions

Decidualization of endometrium, which is characterized by endometrial stromal cell (ESC) decidualization, vascular reconstruction, immune cell recruitment, and plentiful molecule production, is a crucial step for uterus to become receptive for embryo. When implantation takes place, ESCs surround and directly interact with embryo. Decidualized stromal cells (DSCs) are of great importance in endometrial decidualization, having a broad function in regulating immune activity and vascular remodeling of uterus. DSCs are shown to have a higher metabolic level and looser cytoskeleton than ESCs. What's the origin of ESCs and how ESCs successfully transform into DSCs had puzzled scientists in the last decades. Breakthrough had been achieved recently, and many studies had elucidated some of the characters and functions of DSCs. However, several questions still remain unclear. This paper reviews current understanding of where ESCs come from and how ESCs differentiate into DSCs, summarizes some characters and functions of DSCs, analyzes current studies and their limitations and points out research areas that need further investigation.

Mechanism of drug-induced gingival overgrowth revisited: a unifying hypothesis

Drug-induced gingival overgrowth (DIGO) is a disfiguring side effect of anti-convulsants, calcineurin inhibitors, and calcium channel blocking agents. A unifying hypothesis has been constructed which begins with cation flux inhibition induced by all three of these drug categories. Decreased cation influx of folic acid active transport within gingival fibroblasts leads to decreased cellular folate uptake, which in turn leads to changes in matrix metalloproteinases metabolism and the failure to activate collagenase. Decreased availability of activated collagenase results in decreased degradation of accumulated connective tissue which presents as DIGO. Studies supporting this hypothesis are discussed.

Preventive effects of folic acid supplementation on adverse maternal and fetal outcomes

Although there is accumulating evidence regarding the additional protective effect of folic acid against adverse pregnancy outcomes other than neural tube defects, these effects have not been elucidated in detail. We evaluated whether folic acid supplementation is associated with favorable maternal and fetal outcomes. This was a secondary analysis of 215 pregnant women who were enrolled in our prior study. With additional data from telephone interviews regarding prenatal folic acid supplementation, existing demographic, maternal and fetal data were statistically analyzed. The concentration of folic acid in maternal blood was significantly higher following folic acid supplementation (24.6 ng/mL vs.11.8 ng/mL). In contrast, homocysteine level in maternal blood decreased with folic acid supplementation (5.5 µmol/mL vs. 6.8 µmol/mL). The rates of both preeclampsia (odds ratio [OR], 0.27; 95% confidence interval [CI], 0.09–0.76) and small for gestational age (SGA; 9.2% vs. 20.0%; OR, 0.42; 95% CI, 0.18–0.99) were lower in the folic acid supplementation group than those in the control group. Other pregnancy outcomes had no association with folic acid supplementation. The findings indicate that folic acid supplementation may help to prevent preeclampsia and SGA. Further studies are warranted to elucidate the favorable effects of folic acid supplementation on pregnancy outcomes.

Folic acid supplementation and preterm birth: results from observational studies

INTRODUCTION

Folic acid (FA) supplementation is recommended worldwide in the periconceptional period for the prevention of neural tube defects. Due to its involvement in a number of cellular processes, its role in other pregnancy outcomes such as miscarriage, recurrent miscarriage, low birth weight, preterm birth (PTB), preeclampsia, abruptio placentae, and stillbirth has been investigated. PTB is a leading cause of perinatal mortality and morbidity; therefore its association with FA supplementation is of major interest. The analysis of a small number of randomized clinical trials (RCTs) has not found a beneficial role of FA in reducing the rate of PTBs.

AIM OF THE STUDY

The aim of this review was to examine the results from recent observational studies about the effect of FA supplementation on PTB.

MATERIALS AND METHODS

We carried out a search on Medline and by manual search of the observational studies from 2009 onwards that analyzed the rate of PTB in patients who received supplementation with FA before and/or throughout pregnancy.

RESULTS

The results from recent observational studies suggest a slight reduction of PTBs that is not consistent with the results from RCTs. Further research is needed to better understand the role of FA supplementation before and during pregnancy in PTB.

Absence of association between serum folate and preeclampsia in women exposed to food fortification

OBJECTIVE

To evaluate serum folate concentration early in pregnancy and any association with hypertensive disorders of pregnancy in a population exposed to folic acid supplementation and food fortification.

METHODS

This is a nested case-control study based on a prospective cohort of 7,929 pregnant women recruited in the Quebec City metropolitan area, including 214 participants who developed a hypertensive disorder of pregnancy and 428 normotensive participants in the control group matched for parity, multiple pregnancy, smoking status, gestational, and maternal age at inclusion, and duration of blood sample storage. Serum folate levels were measured at a mean of 14 weeks of gestation.

RESULTS

More than 98% of the participants took folic acid or multivitamins before the end of the first trimester. Mean serum folate levels were accordingly high and there were no differences between women who further developed a hypertensive disorder of pregnancy compared with women in the control group (60.1 nmol/L compared with 57.9 nmol/L; P=.51). The proportion of participants with serum folate below the 10th percentile (less than 22.3 nmol/L) of age-matched women in our outpatient population was similar between groups (P=.66) and no participant had levels generally defined as folate deficiency (less than 10 nmol/L).

CONCLUSION

In a general cohort of pregnant women benefiting from a national policy of folic acid food fortification combined with a high adherence to folic acid supplementation, serum folate levels are high and do not differ between women who develop a hypertensive disorder of pregnancy and women who remain normotensive. Further supplementation with higher doses is unlikely to be beneficial in such populations.

LEVEL OF EVIDENCE

II.

Lessons from the one-carbon metabolism: passing it along to the next generation

During development, a fetus and its placenta must respond to a changing maternal environment to ensure normal growth is achieved and survival is maintained. The mechanisms behind developmental programming involve complex interactions between epigenetic and physiological processes, which are not well understood. Importantly, when programming goes awry, it puts the fetus at risk for disease later in life and may, in some instances, affect subsequent generations via epigenetic processes including DNA methylation. The one-carbon metabolism, which includes the folate, methionine and choline pathways, provides methyl groups necessary for DNA methylation and a normal epigenetic landscape. Accordingly, disruptions in this pathway affect placental development and function leading to altered fetal programming. Remarkably, recent studies have revealed that abnormal folate metabolism causes transgenerational effects probably through epigenetic inheritance. The epigenetic mechanisms behind this phenomenon are not well understood but they have important implications for the influence of the metabolic environment on epigenetic stability and non-genetic inheritance of disease. Importantly, there are increasing concerns that assisted reproductive technologies cause aberrant epigenetic profiles in embryos leading to abnormal fetal programming. How the negative epigenetic consequences of assisted reproduction treatment affect subsequent generations requires further investigation.

Maternal soluble fms-like tyrosine kinase-1, placental growth factor, plasminogen activator inhibitor-2, and folate concentrations and early fetal size: the Generation R study

OBJECTIVE

Fetal growth is dependent on adequate development of the placenta. Impaired angiogenesis and vasculogenesis in early pregnancy compromises placental and embryonic development. The proteins soluble fms-like tyrosine kinase (sFlt)-1, placental growth factor (PlGF), and plasminogen activator inhibitor (PAI)-2, and the B vitamin folate are determinants of placental development. This study aims to identify associations between these maternal biomarkers and early fetal size.

STUDY DESIGN

From a prospective birth cohort study in The Netherlands, 1491 pregnant women were selected for this study. At a mean gestational age (GA) of 12.4 weeks (SD 0.8) maternal venous blood samples were obtained to determine the concentrations of sFlt-1, PlGF, PAI-2, and folate. Early fetal size was assessed with measurement of the crown-to-rump length (CRL) at a mean of 12.4 weeks' GA (SD 0.8). Analyses were performed using multivariable linear regression analyses with the biomarkers (continuous, quintiles) as regressors and CRL as main outcome measure.

RESULTS

Linear trend analysis showed positive associations between maternal sFlt-1 (P < .001), PlGF (P = .042), PAI-2 (P < .001), and folate (P = .039) and CRL. These associations were independent of GA, maternal age, height, body mass index, ethnicity, fetal sex, parity, educational level, smoking, and folic acid supplement use (folate not adjusted).

CONCLUSION

sFlt-1, PlGF, PAI-2, and folate are positively associated with first-trimester fetal size.

AP-2α suppresses invasion in BeWo cells by repression of matrix metalloproteinase-2 and -9 and up-regulation of E-cadherin

Preeclampsia complicates 5-10% of pregnancies and is a leading cause of maternal/fetal morbidity and mortality. Although the cause is unknown, the reduced migration/invasion of extravillous trophoblasts is generally regarded as a key feature of preeclampsia genesis. The present study examined the expression of activator protein-2α (AP-2α), tissue inhibitor of metalloproteinase 2 (TIMP-2), matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and E-cadherin in severe preeclamptic placentas and normal placentas using real-time PCR and immunohistochemistry. The expression levels of AP-2α, TIMP-2, and E-cadherin were elevated, while MMP-2 and MMP-9 levels were decreased in severe preeclamptic placentas when compared with normal placentas. To explore the underlying molecular mechanisms, BeWo cells were transfected with an AP-2α-expression construct as well as a siRNA against AP-2α. The over-expression of AP-2α decreased the invasive abilities of BeWo cells. AP-2α induction was followed by the induction of TIMP-2 and E-cadherin and a significant reduction of MMP-2 and MMP-9. Whereas in AP-2α-silencing BeWo cells, we observed the decreased expression of TIMP-2 and E-cadherin and the increased expression of MMP-2 and MMP-9. We presume that AP-2α may suppress trophoblast invasion by repression of MMP-2 and MMP-9 and up-regulation of E-cadherin, thus leading to shallow placentation in severe preeclampsia.

Review of the inhibition of biological activities of food-related selected toxins by natural compounds

There is a need to develop food-compatible conditions to alter the structures of fungal, bacterial, and plant toxins, thus transforming toxins to nontoxic molecules. The term 'chemical genetics' has been used to describe this approach. This overview attempts to survey and consolidate the widely scattered literature on the inhibition by natural compounds and plant extracts of the biological (toxicological) activity of the following food-related toxins: aflatoxin B1, fumonisins, and ochratoxin A produced by fungi; cholera toxin produced by Vibrio cholerae bacteria; Shiga toxins produced by E. coli bacteria; staphylococcal enterotoxins produced by Staphylococcus aureus bacteria; ricin produced by seeds of the castor plant Ricinus communis; and the glycoalkaloid α-chaconine synthesized in potato tubers and leaves. The reduction of biological activity has been achieved by one or more of the following approaches: inhibition of the release of the toxin into the environment, especially food; an alteration of the structural integrity of the toxin molecules; changes in the optimum microenvironment, especially pH, for toxin activity; and protection against adverse effects of the toxins in cells, animals, and humans (chemoprevention). The results show that food-compatible and safe compounds with anti-toxin properties can be used to reduce the toxic potential of these toxins. Practical applications and research needs are suggested that may further facilitate reducing the toxic burden of the diet. Researchers are challenged to (a) apply the available methods without adversely affecting the nutritional quality, safety, and sensory attributes of animal feed and human food and (b) educate food producers and processors and the public about available approaches to mitigating the undesirable effects of natural toxins that may present in the diet.

Effects of DEHP on endometrial receptivity and embryo implantation in pregnant mice

Di-(2-ethylhexyl)-phthalate (DEHP) is a ubiquitous environmental pollutant and endocrine disruptor (ED) that causes serious adverse effects on animal and human health. The harmful effects of DEHP on human reproduction are increasingly recognized, especially in women. However, it is not known how endometrial receptivity and embryo implantation, which play important roles in the establishment of pregnancy, are affected by DEHP. This study was aimed towards investigating the effects of DEHP on endometrial receptivity and embryo implantation in pregnant mice. The pregnant mice received DEHP at 0, 250, 500 and 1000 mg/kg/day from day 1 (D1) of gestation until sacrifice. Administration of DEHP led to compromised endometrial receptivity and decreased number of implantation sites. The mRNA and protein expression levels of ERα, PR and E-cadherin, but not those of HoxA10 and MMP-2, were up-regulated by DEHP in the mouse endometrium. The results further suggested that DEHP disrupts the MAPK and NF-κB signaling pathways. This was maybe one of paths which influenced the E-cadherin expression. In conclusion, DEHP reduced endometrial receptivity and impaired embryo implantation by influencing the expression of hormone receptors and E-cadherin. Therefore, determining the full extent of the hazards of DEHP to human reproduction will be vital to developing and implementing effective protective measures.

Plasmodium falciparum parasitaemia in the first half of pregnancy, uterine and umbilical artery blood flow, and foetal growth: a longitudinal Doppler ultrasound study

BACKGROUND

During early pregnancy, the placenta develops to meet the metabolic demands of the foetus. The objective of this analysis was to examine the effect of malaria parasitaemia prior to 20 weeks' gestation on subsequent changes in uterine and umbilical artery blood flow and intrauterine growth restriction.

METHODS

Data were analysed from 548 antenatal visits after 20 weeks' gestation of 128 women, which included foetal biometric measures and interrogation of uterine and umbilical artery blood flow. Linear mixed effect models estimated the effect of early pregnancy malaria parasitaemia on uterine and umbilical artery resistance indices. Log-binomial models with generalized estimating equations estimated the effect of early pregnancy malaria parasitaemia on the risk of intrauterine growth restriction.

RESULTS

There were differential effects of early pregnancy malaria parasitaemia on uterine artery resistance by nutritional status, with decreased uterine artery resistance among nourished women with early pregnancy malaria and increased uterine artery resistance among undernourished women with early pregnancy malaria. Among primigravidae, early pregnancy malaria parasitaemia decreased umbilical artery resistance in the late third trimester, likely reflecting adaptive villous angiogenesis. In fully adjusted models, primigravidae with early pregnancy malaria parasitaemia had 3.6 times the risk of subsequent intrauterine growth restriction (95% CI: 2.1, 6.2) compared to the referent group of multigravidae with no early pregnancy malaria parasitaemia.

CONCLUSIONS

Early pregnancy malaria parasitaemia affects uterine and umbilical artery blood flow, possibly due to alterations in placentation and angiogenesis, respectively. Among primigravidae, early pregnancy malaria parasitaemia increases the risk of intrauterine growth restriction. The findings support the initiation of malaria parasitaemia prevention and control efforts earlier in pregnancy.

Naturally occurring variation in trophoblast invasion as a source of novel (epigenetic) biomarkers

During the first trimester of pregnancy fetal trophoblasts invade the maternal decidua, thereby remodeling the maternal spiral arteries. This process of trophoblast invasion is very similar to cancer cell invasion, with multiple signaling pathways shared between the two. Pregnancy-related diseases, e.g., pre-eclampsia, and cancer metastasis start with a decrease or increase in cellular invasion, respectively. Here, we investigate if first trimester placental explants can be used to identify epigenetic factors associated with changes in cellular invasion and their potential use as biomarkers. We show that the outgrowth potential of first trimester explants significantly correlates with promoter methylation of PRKCDBP and MMP2, two genes known to be differentially methylated in both placenta and cancer. The increase in methylation percentage of placental cells coincides with an increase in invasion potential. Subsequently, as a non-invasive marker must be detectable in blood, plasma samples of pregnant and non-pregnant women were analyzed. The MMP2 promoter showed high methylation levels in non-pregnant plasma samples, which decreased in pregnant plasma samples which also contain placental DNA. The decrease in methylated plasma DNA during pregnancy is most likely due to the fractional increase in unmethylated placental DNA. This suggests that the level of unmethylated DNA has the potential to be used as an invasion marker, where higher levels of unmethylated DNA indicate a lower invasion potential of trophoblasts. These proof of principle data provide evidence that human first trimester placental explants are an excellent ex vivo model system to identify (epigenetic) factors and thus potential biomarkers associated with changes in cellular invasion, e.g., to detect pregnancy-related diseases or cancer metastasis. To identify novel biomarkers the next step is to correlate naturally occurring variation in invasion potential to changes in (epigenetic) factors by genome-wide approaches such as massively parallel sequencing.

Folate transporter expression decreases in the human placenta throughout pregnancy and in pre-eclampsia

The transport of folate across the placenta involves a number of different receptors including folate receptor-alpha (FR-α), reduced folate carrier (RFC) and proton coupled folate transporter (PCFT). In addition there are a number of ATP-dependent transporters which have also recently been shown to be involved in folate transport; these include ABCB1, ABCC2 and BCRP (ABCG2). The aim of the current study was to characterise the placental mRNA and protein expression of these folate transporters throughout gestation and also to see if expression is altered in pre-eclampsia. Placental tissue was collected from women undergoing termination of pregnancy (TOP) and from women undergoing elective Caesarean section. To investigate mRNA expression quantitative real time PCR was used with gene specific oligonucleotide primers to FR-α, RFC, PCFT, ABCB1, ABCC2, BCRP and the reference gene YWHAZ. Protein expression was also characterised using immunohistochemistry of paraffin embedded placental tissue. Both protein and mRNA expression of all transporters examined decreased as the gestation progressed. Expression of FR-α and PCFT mRNA and protein were decreased in pre-eclampsia compared with normal term pregnancy. The higher levels of expression of FR-α, RFC, PCFT, ABCB1, ABCC2 and BCRP in early pregnancy indicate that these transporters may have an important role in the establishment and development of the placenta, with expression reducing in preparation for parturition. Reductions in FR-α and PCFT in pre-eclampsia may be a mechanism involved in the pathogenesis of pre-eclampsia by limiting placental folate uptake resulting in reduced levels of angiogenesis, cell proliferation and antioxidant protection.

Angiogenic growth factors in the diagnosis and prediction of pre-eclampsia

The pathogenesis of pre-eclampsia is still not completely known; however, in the recent decade, there have been tremendous research efforts leading to impressive results highlighting the role of a disturbed angiogenic balance as one of the key features of the disease. Numerous studies have shown the key role of the placenta in the pathogenesis of pre-eclampsia. A shift in the sFlt-1 (soluble Fms-like tyrosine kinase-1)/PlGF (placental growth factor) ratio is associated with the disease. Although pre-eclampsia seems to be a clearly defined disease, clinical presentation, and particularly the dynamics of the clinical course, can vary enormously. The only available tools to diagnose pre-eclampsia are blood pressure measurement and urine protein sampling. However, these tools have a low sensitivity and specificity regarding the prediction of the course of the disease or maternal and perinatal outcomes. The only cure for the disease is delivery, although a timely diagnosis helps in decreasing maternal and fetal morbidity and mortality. The sFlt1/PlGF ratio is able to give additional valuable information on the status and progression of the disease and is apt to be implemented in the diagnostic algorithm of pre-eclampsia. In the present review, we aim to provide an overview of the vast literature on angiogenesis and anti-angiogenesis factors in pre-eclampsia that have been published over the last decade. We introduce work from basic research groups who have focused on the pathophysiological basis of the disease. Furthermore, we review studies with a clinical focus in which the sFlt-1/PlGF ratio has been analysed along with other candidates for routine clinical assessment of pre-eclampsia.