Absolute and Relative Quantification of Placenta-Specific MicroRNAs in Maternal Circulation with Placental Insufficiency–Related Complications

Differential miR-346 and miR-582-3p Expression in Association with Selected Maternal and Fetal Complications

Several miRNAs are expressed in human gestational tissue, and some have been shown to be associated with placental dysfunction and complicated pregnancy outcomes. To investigate the roles of miR-346 and miR-582-3p in adverse obstetric events, we analyzed these 2 miRNAs in three samples (maternal blood, umbilical cord blood and placenta) obtained from pregnant women in four groups, including healthy control (n = 60), preeclampsia (n = 31), preterm delivery (n = 29) and small for gestational age (n = 19) patients. The expression levels of miR-346 and miR-582-3p in all included adverse obstetric outcome groups were significantly higher in the maternal plasma samples but lower in the placenta samples (all p value < 0.05). In addition, the miR-346 expression levels in fetal cord blood were also significantly lower in all of the included adverse obstetric outcome groups (all p < 0.05). Multivariate analysis of the three specimens after adjusting for maternal age and gestational age at delivery gave the same results. In conclusion, aberrant miR-346 and miR-582-3p expression level in pregnancy was associated with multiple maternal and fetal complications. Their differential expression in maternal blood, umbilical cord blood and placenta could be potential biomarkers or therapeutic targets for adverse obstetric outcomes

Dysregulation of Placental miRNA in Maternal Obesity Is Associated With Pre- and Postnatal Growth

CONTEXT

Human placenta exhibits a specific microRNA (miRNA) expression pattern. Some of these miRNAs are dysregulated in pregnancy disorders such as preeclampsia and intrauterine growth restriction and are potential biomarkers for these pathologies.

OBJECTIVE

To study the placental miRNA profile in pregnant women with pregestational overweight/obesity (preOB) or gestational obesity (gestOB) and explore the associations between placental miRNAs dysregulated in maternal obesity and prenatal and postnatal growth.

METHODS

TaqMan Low Density Arrays and real-time polymerase chain reaction were used to profile the placental miRNAs in 70 pregnant women (20 preOB, 25 gestOB, and 25 control). Placentas and newborns were weighed at delivery, and infants were weighed at 1, 4, and 12 months of age.

RESULTS

Eight miRNAs were decreased in placentas from preOB or gestOB (miR-100, miR-1269, miR-1285, miR-181, miR-185, miR-214, miR-296, and miR-487) (all P < 0.05). Among them, miR-100, miR-1285, miR-296, and miR-487 were associated with maternal metabolic parameters (all P < 0.05) and were predictors of lower birth weight (all P < 0.05; R2 > 30%) and increased postnatal weight gain (all P < 0.05; R2 > 20%). In silico analysis showed that these miRNAs were related to cell proliferation and insulin signaling pathways. miR-296 was also present in plasma samples and associated with placental expression and prenatal and postnatal growth parameters (all P < 0.05).

CONCLUSIONS

We identified a specific placental miRNA profile in maternal obesity. Placental miRNAs dysregulated in maternal obesity may be involved in mediation of growth-promoting effects of maternal obesity on offspring and could be used as early markers of prenatal and postnatal growth.

Small Molecule, Big Prospects: MicroRNA in Pregnancy and Its Complications

MicroRNAs are small, noncoding RNA molecules that regulate target gene expression in the posttranscriptional level. Unlike siRNA, microRNAs are "fine-tuners" rather than "switches" in the regulation of gene expression; thus they play key roles in maintaining tissue homeostasis. The aberrant microRNA expression is implicated in the disease process. To date, numerous studies have demonstrated the regulatory roles of microRNAs in various pathophysiological conditions. In contrast, the study of microRNA in pregnancy and its associated complications, such as preeclampsia (PE), fetal growth restriction (FGR), and preterm labor, is a young field. Over the last decade, the knowledge of pregnancy-related microRNAs has increased and the molecular mechanisms by which microRNAs regulate pregnancy or its associated complications are emerging. In this review, we focus on the recent advances in the research of pregnancy-related microRNAs, especially their function in pregnancy-associated complications and the potential clinical applications. Here microRNAs that associate with pregnancy are classified as placenta-specific, placenta-associated, placenta-derived circulating, and uterine microRNA according to their localization and origin. MicroRNAs offer a great potential for developing diagnostic and therapeutic targets in pregnancy-related disorders.

MicroRNAs in Pregnancy and Gestational Diabetes Mellitus: Emerging Role in Maternal Metabolic Regulation

PURPOSE OF THE REVIEW

This review focuses on the recent emergence of microRNAs (miRNAs) as metabolic and developmental regulators in pregnancy and their role in the development of gestational diabetes mellitus (GDM). MiRNAs are short and stable RNA sequences that repress protein synthesis through interference with messenger RNA translation.

RECENT FINDINGS

The placenta produces numerous miRNAs with some of them being released in the maternal circulation. These miRNA genes are encoded into specific clusters and expressed preferentially by placental cells, in a time-dependent manner. They were shown to be dysregulated in plasma and placenta from women suffering from GDM and associated with pregnancy and birth-related outcomes. The discovery of pregnancy-related miRNAs and their respective characterization will provide us with important information as to their function in maternal and placental metabolic regulation. More studies are needed to determine whether they will be useful for early screening of GDM.

Follow-up of gestational trophoblastic disease/neoplasia via quantification of circulating nucleic acids of placental origin using C19MC microRNAs, hypermethylated RASSF1A, and SRY sequences

The aim of the study was to evaluate the effectiveness of placental-specific markers, extracellular fetal DNA (sex-determining region Y and hypermethylated RASSF1A sequences) and circulating C19MC microRNAs (miR-516-5p, miR-517-5p, miR-518b, miR-520a-5p, miR-520h, miR-525, and miR-526a) for the diagnosis and consecutive follow-up of gestational trophoblastic disease/neoplasia. Increased levels of extracellular fetal DNA and C19MC microRNAs were detected in patients with active disease when compared with the period when the patients reached remission of the disease. The positive correlation between plasma levels of hypermethylated RASSF1A sequence, C19MC microRNAs, and human chorionic gonadotropin serum levels was found. MiR-520a-5p had the best performance to detect patients with active disease (a positive predictive value of 100% at a null false positive ratio (FPR)). MiR-516-5p and miR-525 were able to diagnose 100% of women with active disease at the FPR 3.9%/7.7%. The overall predictive capacity of single miR-526a (81.8% at null FPR), miR-517-5p (90.9% at 15.4% FPR), miR-518b (100% at 38.5% FPR), and miR-520h (90.9% at 26.9% FPR) biomarkers to detect active disease cases was slightly lower. Transient increase in C19MC microRNA plasma levels after the first cycle of chemotherapy indicated the decay of placental trophoblast residual tissue. The increased levels of extracellular fetal DNA and placental-specific C19MC microRNAs are associated with gestational trophoblastic disease/neoplasia. Screening of extracellular placental-specific biomarkers may represent an additional option to identify a significant proportion of women with active disease and to monitor the therapy response. Non-invasive follow-up of the decomposing residual tissue in the form of extracellular nucleic acids of placental origin packed into apoptotic bodies derived from placental trophoblasts is available.

Do miRNAs Play a Role in Fetal Growth Restriction? A Fresh Look to a Busy Corner

Placenta is the crucial organ for embryo and fetus development and plays a critical role in the development of fetal growth restriction (FGR). There are increasing evidences on the role of microRNAs (miRNAs) in a variety of pregnancy-related complications such as preeclampsia and FGR. More than 1880 miRNAs have been reported in humans and most of them are expressed in placenta. In this paper, we aimed to review the current evidence about the topic. According to retrieved data, controversial results about placental expression of miRNAs could be due (at least in part) to the different experimental methods used by different groups. Despite the fact that several authors have demonstrated a relatively easy and feasible detection of some miRNAs in maternal whole peripheral blood, costs of these tests should be reduced in order to increase cohorts and have stronger evidence. In this regard, we take the opportunity to solicit future studies on large cohort and adequate statistical power, in order to identify a panel of biomarkers on maternal peripheral blood for early diagnosis of FGR.

The expression level of C19MC miRNAs in early pregnancy and in response to viral infection

INTRODUCTION

We have previously shown that miRNAs produced from the Chromosome 19 MiRNA Cluster (C19MC), which are expressed almost exclusively in primate trophoblasts and are released into the maternal circulation, reduce viral replication in non-placental cells and can modulate migratory behavior of extravillous trophoblast. We sought to define the expression pattern of C19MC miRNA in early pregnancy and in response to viral infection in vitro and in vivo.

METHODS

We prospectively followed women undergoing in vitro fertilization (IVF) and determined their blood level of C19MC miRNA using RT-qPCR. To examine the effect of viral exposure on C19MC miRNAs expression, we used three systems: (1) a transgenic mouse overexpressing the C19MC cluster and exposed to Togaviridae during pregnancy, (2) cultured primary human trophoblasts exposed to Vesicular Stomatitis Virus in vitro, and (3) amniotic fluid from women exposed to cytomegalovirus during pregnancy.

RESULTS

In 27 IVF pregnancies, C19MC miRNAs were detected as early as 2 weeks after implantation, and their levels increased thereafter. There was no change in C19MC miRNA expression levels in the mouse placenta in response to viral exposure. Similarly, Vesicular Stomatitis Virus infection of primary human trophoblast did not selectively increase C19MC miRNA expression. C19MC miRNA expression in the amniotic fluid was not affected by vertical transmission of cytomegalovirus.

DISCUSSION

The expression of C19MC miRNAs in maternal circulation very early in pregnancy suggests a role in the establishment of the maternal-fetal interface. The levels of C19MC miRNA are not influenced by diverse types of viral infection.

First trimester screening of circulating C19MC microRNAs and the evaluation of their potential to predict the onset of preeclampsia and IUGR

Objectives

A nested case control study of a longitudinal cohort comparing pregnant women enrolled at 10 to 13 gestational weeks was carried out to evaluate risk assessment for preeclampsia and IUGR based on circulating placental specific C19MC microRNAs in early pregnancy.

Methods

The expression of placental specific C19MC microRNAs (miR-516b-5p, miR-517-5p, miR-518b, miR-520a-5p, miR-520h, and miR-525-5p) was determined in plasma samples from pregnancies that subsequently developed preeclampsia (n = 21), IUGR (n = 18), and 58 normal pregnancies using real-time PCR and comparative Ct method relative to synthetic Caenorhabditis elegans microRNA (cel-miR-39).

Results

Circulating C19MC microRNAs were up-regulated (miR-517-5p, p = 0.005; miR-518b, p = 0.013; miR-520h, p = 0.021) or showed a trend toward up-regulation in patients destined to develop preeclampsia (miR-520a-5p, p = 0.067; miR-525-5p, p = 0.073). MiR-517-5p had the best predictive performance for preeclampsia with a sensitivity of 42.9%, a specificity of 86.2%, a PPV of 52.9% and a NPV of 80.6%. The combination of all examined circulating C19MC microRNAs had no advantage over using only the miR-517-5p biomarker to predict the occurrence of preeclampsia (a sensitivity of 20.6%, a specificity of 90.8%, a PPV of 44.8%, and a NPV of 76.0%).

Conclusions

Up-regulation of miR-517-5p, miR-518b and miR-520h was associated with a risk of later development of preeclampsia. First trimester screening of extracellular miR-517-5p identified a proportion of women with subsequent preeclampsia. No circulating C19MC microRNA biomarkers were identified that could predict later occurrence of IUGR.

Systematic Review of Micro-RNA Expression in Pre-Eclampsia Identifies a Number of Common Pathways Associated with the Disease

Background

Pre-eclampsia (PE) is a complex, multi-systemic condition of pregnancy which greatly impacts maternal and perinatal morbidity and mortality. MicroRNAs (miRs) are differentially expressed in PE and may be important in helping to understand the condition and its pathogenesis.

Methods

Case-control studies investigating expression of miRs in PE were collected through a systematic literature search. Data was extracted and compared from 58 studies to identify the most promising miRs associated with PE pathogenesis and identify areas of methodology which could account for often conflicting results.

Results

Some of the most frequently differentially expressed miRs in PE include miR-210, miR-223 and miR-126/126* which associate strongly with the etiological domains of hypoxia, immunology and angiogenesis. Members of the miR-515 family belonging to the imprinted chromosome 19 miR cluster with putative roles in trophoblast invasion were also found to be differentially expressed. Certain miRs appear to associate with more severe forms of PE such as miR-210 and the immune-related miR-181a and miR-15 families. Patterns of miR expression may help pinpoint key pathways (e.g. IL-6/miR-223/STAT3) and aid in untangling the heterogeneous nature of PE. The detectable presence of many PE-associated miRs in antenatal circulatory samples suggests their usefulness as predictive biomarkers. Further progress in ascertaining the clinical value of miRs and in understanding how they might contribute to pathogenesis is predicated upon resolving current methodological challenges in studies. These include differences in diagnostic criteria, cohort characteristics, sampling technique, RNA isolation and platform-dependent variation in miR profiling.

Conclusion

Reviewing studies of PE-associated miRs has revealed their potential as informants of underlying target genes and pathways relating to PE pathogenesis. However, the incongruity in results across current studies hampers their capacity to be useful biomarkers of the condition.

Role of Extracellular Vesicles and microRNAs on Dysfunctional Angiogenesis during Preeclamptic Pregnancies

Preeclampsia is a syndrome characterized by hypertension during pregnancy, which is a leading cause of morbidity and mortality in both mother and newborn in developing countries. Some advances have increased the understanding of pathophysiology of this disease. For example, reduced utero-placental blood flow associated with impaired trophoblast invasion may lead to a hypoxic placenta that releases harmful materials into the maternal and feto-placental circulation and impairs endothelial function. Identification of these harmful materials is one of the hot topics in the literature, since these provide potential biomarkers. Certainty, such knowledge will help us to understand the miscommunication between mother and fetus. In this review we highlight how placental extracellular vesicles and their cargo, such as small RNAs (i.e., microRNAs), might be involved in endothelial dysfunction, and then in the angiogenesis process, during preeclampsia. Currently only a few reports have addressed the potential role of endothelial regulatory miRNA in the impaired angiogenesis in preeclampsia. One of the main limitations in this area is the variability of the analyses performed in the current literature. This includes variability in the size of the particles analyzed, and broad variation in the exosomes considered. The quantity of microRNA targets genes suggest that practically all endothelial cell metabolic functions might be impaired. More studies are required to investigate mechanisms underlying miRNA released from placenta upon endothelial function involved in the angiogenenic process.

AngiomiRs: Potential Biomarkers of Pregnancy's Vascular Pathologies

In recent years, microRNAs (miRNAs) have been the focus of research for their role in posttranscriptional regulation and as potential biomarkers of risk for disease development. Their identification in specific physiological processes, like angiogenesis, a key pathway in placental vascular development in pregnancy, suggests an important role of miRNAs that regulate angiogenesis (angiomiRs). Many complications of pregnancy have in common placental vascular alterations, involving an imbalance in the angiogenesis process in the development of conditions such as preeclampsia, intrauterine growth restriction, and gestational diabetes, complications with the highest rates of morbimortality in pregnancy. Many studies have identified angiomiRs with differential expression profiles in each of these diseases; however, this evidence requires further studies focused on evaluating their potential as biomarkers of risk for the angiomiRs detected, to establish correlations between placental tissue and serum/plasma expression profiles. Therefore, the objective of this review is to highlight the best angiomiRs detected in placental tissue and serum/plasma in each of these three pathologies to show the current data available for potential biomarkers and to propose future research strategies on this topic.

Noninvasive nucleic acid-based approaches to monitor placental health and predict pregnancy-related complications

During pregnancy, the placenta releases a variety of nucleic acids (including deoxyribonucleic acid, messenger ribonucleic acid, or microribonucleic acids) either as a result of cell turnover or as an active messaging system between the placenta and cells in the maternal body. The profile of released nucleic acids changes with the gestational age and has been associated with maternal and fetal parameters. It also can directly reflect pathological changes in the placenta. Nucleic acids may therefore provide a rich source of novel biomarkers for the prediction of pregnancy complications. However, their utility in the clinical setting depends, first, on overcoming some technical considerations in their quantification, and, second, on developing a better understanding of the factors that influence their function and abundance.

Quantification of preeclampsia-related microRNAs in maternal serum

To identify the specific serum preeclampsia (PE)-related biomarkers, 10 microRNAs (miRNAs) were selected based on their reported aberrant (4 upregulated and 6 downregulated) expression in PE placenta. A total of 1,035 pregnant patients were enrolled. Finally, 32 pregnancies with PE and 32 healthy pregnancies were incorporated in the study. The expression of these 10 miRNAs in the different trimesters was determined by SYBR-Green reverse transcription-quantitative polymerase chain reaction. Compared with that in the healthy controls, the expression levels of miR-152, miR-183 and miR-210 in PE serum were higher in the second and third trimester, whereas the expression of miR-182 was only higher in the third trimester. The expression levels of 6 miRNAs (miR-1, miR-328, miR-363, miR-377, miR-500 and miR-584) that were downregulated in PE placenta showed no significant differences between pregnancies complicated by PE and healthy pregnancies throughout the 3 trimesters. Areas under the receiver operating characteristic [standard error (SE)] during the 20-24th gestational week for predicting PE were miR-152: 0.94 (SE, 0.026), miR-183: 0.97 (SE, 0.031) and miR-210: 0.93 (SE, 0.018). In conclusion, the expression levels of serum miR-152, miR-183 and miR-210 were elevated since the second trimester in pregnancies complicated with PE, indicating their potentials as serum biomarkers for forecasting PE.

Differential expression of plasma microRNA in preeclamptic patients at delivery and 1 year postpartum

OBJECTIVE

Preeclampsia (PE) is a hypertensive disorder of pregnancy characterized by widespread maternal endothelial dysfunction. Although clinical signs subside following delivery, long-term risks associated with PE include hypertension, stroke, and cardiovascular disease. MicroRNAs (miRNAs) are emerging as critical regulators of biological function, and while alterations to the miRNAome have been described in the context of pregnancy and PE, the postpartum implications of PE on miRNA expression is unknown. The goal of this study was to characterize circulating miRNA profiles at the time of delivery and at 1 year postpartum for women who did and did not develop PE.

STUDY DESIGN

Using a targeted reverse transcription polymerase chain reaction approach, selected miRNAs putatively involved in the pathophysiology of PE were examined in 17 normotensive control and 13 PE maternal plasma samples at the time of delivery and 1 year postpartum. Ingenuity Pathway Analysis was used to map putative messenger RNA targets of differentially expressed miRNA to global molecular networks based on gene function.

RESULTS

Significant increases (P < .05) in 7 miRNAs with antiangiogenic, inflammatory, and apoptotic functions (miR-98-5p, miR-222-3p, miR-210-3p, miR-155-5p, miR-296-3p, miR-181a-5p, miR-29b-3p) were evident in maternal plasma at the time of severe PE compared to time-matched controls. Plasma samples from individuals who developed mild PE exhibited no changes compared to control samples for the subset of miRNAs analyzed here. Differential expression of plasma miRNA at the time of delivery for women with PE were largely resolved at 1 year postpartum, and reduced expression of only miR-221-3p (P < .05) was evident. Network analysis of putative targets of differentially regulated miRNA identified 11 interacting networks with enrichment for proteins involved in cardiovascular disease, organ system development and function, and cell signaling and interaction.

CONCLUSION

The systemic effect of PE on maternal systems is evident in the circulating miRNAome with substantial alterations in miRNA expression in women who develop severe PE. In addition we provide novel evidence of disruption to miR-221 expression 1 year postpartum following a pregnancy complicated by PE compared to normotensive time-matched controls, which may allude to persistent inflammation in these women after delivery.

Combined Screening for Early Detection of Pre-Eclampsia

Although the precise pathophysiology of pre-eclampsia remains unknown, this condition continues to be a major cause of maternal and fetal mortality. Early prediction of pre-eclampsia would allow for timely initiation of preventive therapy. A combination of biophysical and biochemical markers are superior to other tests for early prediction of the development of pre-eclampsia. Apart from the use of parameters in first-trimester aneuploidy screening, cell-free fetal DNA quantification is emerging as a promising marker for prediction of pre-eclampsia. This article reviews the current research of the most important strategies for prediction of pre-eclampsia, including the use of maternal risk factors, mean maternal arterial pressure, ultrasound parameters, and biomarkers.

Potential role of circulating microRNAs as early markers of preeclampsia

OBJECTIVE

To identify microRNAs (miRNAs) differentially expressed at early stages of gestation (12-14 weeks) in the serum of pregnant women, who later developed severe preeclampsia (sPE) in the third trimester of pregnancy (n = 24) compared to women with normal pregnancy (n = 24).

MATERIALS AND METHODS

Sera from 12-14-week-gestation whole blood were subjected to microarray analysis with TaqMan Low Density Array chips (human microRNA panel V3.0), and to quantitative real-time polymerase chain reaction.

RESULTS

By using the TaqMan Low Density Array chip technology, 19 mature miRNAs appeared differentially expressed in the group of women who later developed sPE as compared to normal women. The expression of four miRNAs (miR-1233, miR-520, miR-210, miR-144) was validated by quantitative real-time polymerase chain reaction analysis. MiR-1233 was the most overexpressed in the serum of women who later developed sPE.

CONCLUSION

Circulating miRNAs deserve further investigation in order to explore their potential role in the pathogenesis of preeclampsia. In particular, miR-1233 might represent a potential marker of early sPE.

The Function of TrophomiRs and Other MicroRNAs in the Human Placenta

In eutherian organisms, the placenta interfaces the fetal and maternal environments. Located at the placental villous surface, in direct contact with maternal blood, is the trophoblast layer, which mediates the crucial maternal-fetal exchange of gases, nutrients, and waste products, produces hormones that support the pregnancy, and provides immunologic defense. Discovery of microRNAs (miRNAs) and their role in development, differentiation, and homeostatic resilience has increased our understanding of genomic and epigenomic networks that regulate placental function. Moreover, unique miRNA species, which are expressed by human trophoblasts and are termed "trophomiRs," may show specialized functions during normal and pathological pregnancies. Placental miRNAs, packaged within exosomes and other vesicles or bound in protein complexes, are capable of communicating distinctive signals to maternal and/or fetal tissues. Additional research may usher in the use of circulating miRNAs as pregnancy-related disease biomarkers, providing new diagnostic and therapeutic options during pregnancy.

Expression profile of C19MC microRNAs in placental tissue in pregnancy-related complications

To demonstrate that pregnancy-related complications are associated with alterations in placental microRNA expression. Gene expression of 15 C19MC microRNAs (miR-512-5p, miR-515-5p, miR-516-5p, miR-517-5p, miR-518b, miR-518f-5p, miR-519a, miR-519d, miR-519e-5p, miR-520a-5p, miR-520h, miR-524-5p, miR-525, miR-526a, and miR-526b) was assessed in placental tissues, compared between groups (21 gestational hypertension [GH], 63 preeclampsia, 36 fetal growth restriction [FGR], and 42 normal pregnancies), and correlated with the severity of the disease with respect to clinical signs, delivery date, and Doppler ultrasound parameters. The expression profile of microRNAs was different between pregnancy-related complications and controls. The downregulation of 4 of 15 (miR-517-5p, miR-519d, miR-520a-5p, and miR-525), 6 of 15 (miR-517-5p, miR-518f-5p, miR-519a, miR-519d, miR-520a-5p, and miR-525), and 11 of 15 (miR-515-5p, miR-517-5p, miR-518b, miR-518f-5p, miR-519a, miR-519d, miR-520a-5p, miR-520h, miR-524-5p, miR-525, and miR-526a) microRNAs was associated with GH, FGR, and preeclampsia, respectively. Sudden onset of severe preeclampsia requiring immediate termination of gestation and mild forms of preeclampsia (persisting for several weeks) were associated with similar microRNA expression profile (downregulation of miR-517-5p, miR-520a-5p, miR-524-5p, and miR-525). In addition, miR-519a was found to be associated with severe preeclampsia. The longer the pregnancy-related disorder lasted, the more extensive was the downregulation of microRNAs (miR-515-5p, miR-518b, miR-518f-5p, miR-519d, and miR-520h). The downregulation of some C19MC microRNAs is a common phenomenon shared between GH, preeclampsia, and FGR. On the other hand, some of the C19MC microRNAs are only downregulated just in preeclampsia.

Circulating microRNAs as clinical biomarkers in the predictions of pregnancy complications

Predicting pregnancy complications is a major topic for clinicians and biologists for maternal and fetal monitoring. Noninvasive biomarkers in maternal blood such as circulating microRNAs (miRNAs) are promising molecules to predict pregnancy disorders. miRNAs are noncoding short RNAs that regulate mRNA expression by repressing the translation or cleaving the transcript. miRNAs are released to the extracellular systemic circulation via exosomes. The discovery of plasma- or serum-derived miRNAs and of free-circulating exosomes that contain miRNAs provides useful information about the physiological or pathophysiological roles of the miRNAs. Specific placental miRNAs are present in maternal plasma in different ways depending on whether the pregnancy is normal or pathological or if there is no pregnancy. This paper focuses on placental miRNAs and extracellular miRNAs to the placenta whose misregulation could lead to pregnancy complications.

First trimester screening of circulating C19MC microRNAs can predict subsequent onset of gestational hypertension

OBJECTIVE

The objective of the study was to evaluate risk assessment for gestational hypertension based on the profile of circulating placental specific C19MC microRNAs in early pregnancy.

STUDY DESIGN

The prospective longitudinal cohort study of women enrolled at first trimester screening at 10 to 13 weeks was carried out (n = 267). Relative quantification of placental specific C19MC microRNAs (miR-516-5p, miR-517*, miR-518b, miR-520a*, miR-520h, miR-525 and miR-526a) was determined in 28 normal pregnancies and 18 pregnancies which developed gestational hypertension using real-time PCR and a comparative Ct method relative to synthetic C. elegans microRNA (cel-miR-39).

RESULTS

Increased extracellular C19MC microRNA plasmatic levels (miR-516-5p, p<0.001; miR-517*, p = 0.007; miR-520h, p<0.001; miR-518b, p = 0.002) were detected in patients destined to develop gestational hypertension. MiR-520h had the best predictive performance with a PPV of 84.6% at a 7.1% false positive rate. The combination of miR-520h and miR-518b was able to predict 82.6% of women at the same false positive rate. The overall predictive capacity of single miR-518b (73.3% at 14.3% FPR), miR-516-5p (70.6% at 17.9% FPR) and miR-517* (57.9% at 28.6% FPR) biomarkers was lower.

CONCLUSION

The study brought interesting finding that the up-regulation of miR-516-5p, miR-517*, miR-520h and miR-518b is associated with a risk of later development of gestational hypertension. First trimester screening of extracellular miR-520h alone or in combination with miR-518b identified a significant proportion of women with subsequent gestational hypertension.

Human exosomal placenta-associated miR-517a-3p modulates the expression of PRKG1 mRNA in Jurkat cells

During pregnancy, human placenta-associated microRNAs (miRNAs) derived from the miRNA cluster in human chromosome 19 are expressed in villous trophoblasts and secreted into maternal circulation via exosomes; however, little is known about whether circulating placenta-associated miRNAs are transferred into maternal immune cells via exosomes, and modulate expression of target genes in the recipient cells. We employed an in vitro model of trophoblast-immune cell communication using BeWo cells (a human trophoblast cell line) and Jurkat cells (a human leukemic T-cell line) and investigated whether BeWo exosomal placenta-associated miRNAs can suppress expression of target genes in the recipient Jurkat cells. Using this system, we identified PRKG1 as a target gene of placenta-associated miRNA miR-517a-3p. Moreover, we demonstrated that BeWo exosomal miR-517a-3p was internalized into Jurkat cells and subsequently suppressed the expression of PRKG1 in recipient Jurkat cells. Furthermore, using peripheral blood natural killer (NK) cells in vivo, we confirmed that circulating miR-517a-3p was delivered into maternal NK cells as it was into Jurkat cells in vitro. Placenta-associated miR-517a-3p was incorporated into maternal NK cells in the third trimester, and it was rapidly cleared after delivery. Expression levels of miR-517a-3p and its target mRNA PRKG1 were inversely correlated in NK cells before and after delivery. These in vitro and in vivo results suggest that exosome-mediated transfer of placenta-associated miRNAs and subsequent modulation of their target genes occur in maternal NK cells. The present study provides novel insight into our understanding of placenta-maternal communication.

Nanotechnology-based strategies for the detection and quantification of microRNA

MicroRNAs (miRNAs) are important regulators of gene expression, and many pathological conditions, including cancer, are characterized by altered miRNA expression levels. Therefore, accurate and sensitive quantification of miRNAs may result in correct disease diagnosis establishing these small noncoding RNA transcripts as valuable biomarkers. Aiming at overcoming some limitations of conventional quantification strategies, nanotechnology is currently providing numerous significant alternatives to miRNA sensing. In this review an up-to-date account of nanotechnology-based strategies for miRNA detection and quantification is given. The topics covered are: nanoparticle-based approaches in solution, sensing based on nanostructured surfaces, combined nanoparticle/surface sensing approaches, and single-molecule approaches.

Circulating C19MC microRNAs in preeclampsia, gestational hypertension, and fetal growth restriction

The objective of the study was to identify the profile of circulating C19MC microRNAs (miR-516-5p, miR-517*, miR-518b, miR-520a*, miR-520h, miR-525, and miR-526a) in patients with established preeclampsia (n = 63), fetal growth restriction (n = 27), and gestational hypertension (n = 23). We examined the correlation between plasmatic concentrations and expression levels of microRNAs and the severity of the disease with respect to clinical signs, requirements for the delivery, and Doppler ultrasound parameters. Using absolute and relative quantification approaches, increased extracellular C19MC microRNA levels (miR-516-5p, P = 0.037, P = 0.009; miR-517*, P = 0.033, P = 0.043; miR-520a*, P = 0.001, P = 0.009; miR-525, P = 0.026, P = 0.01; miR-526a, P = 0.03, P = 0.035) were detected in patients with preeclampsia. The association analysis pointed to no relationship between C19MC microRNA plasmatic concentrations and expression profile and identified risk factors for a poorer perinatal outcome. However, the dependence between the levels of plasmatic C19MC microRNAs and the pulsatility index in the middle cerebral artery and the values of cerebroplacental ratio was demonstrated. The study brought the interesting finding that the upregulation of miR-516-5p, miR-517*, miR-520a*, miR-525, and miR-526a is a characteristic phenomenon of established preeclampsia.

Pregnancy-associated miRNA-clusters

MicroRNAs (miRNAs) are expressed in the placenta and can be detected in maternal plasma. An increasing number of studies have been published on the cellular origin, distribution and function of miRNAs in pregnancy. Specific miRNA profiles have been described for the placenta, maternal plasma and several pregnancy disorders. It has been observed that numerous miRNAs, which are predominantly or exclusively expressed during pregnancy, are clustered in chromosomal regions, may be controlled by the same promoters, may have similar seed regions and targets, and work synergistically. The three most eminent clusters are the chromosome 19 miRNA cluster (C19MC), C14MC and miR-371-3 cluster, which is also localized on chromosome 19. MiRNA members of these clusters are not only detected in the placenta, but also in other compartments, e.g. in serum where they have the potential to become novel biomarkers of pregnancy disorders. Additionally, some members are also expressed in a variety of tumors. Antagonism of selected miRNAs or their targets may lead to novel strategies for the development of new drug classes in pregnancy disorders or other diseases. This review summarizes current knowledge on the pregnancy-related miRNA clusters - the C19MC, C14MC and miR-371-3 cluster - in regard to pregnancy and also other, mostly pathological circumstances.

Maternal predictors of intrauterine growth restriction

PURPOSE OF REVIEW

Intrauterine growth restriction (IUGR) occurs when fetal growth rate falls below the genetic potential and affects a significant number of pregnancies, but still no therapy has been developed for this pregnancy disease. This article reviews the most recent findings concerning maternal characteristics and behaviours predisposing to IUGR as well as maternal early markers of the disease. A comprehensive understanding of factors associated with IUGR will help in providing important tools for preventing and understanding adverse outcomes.

RECENT FINDINGS

Maternal nutritional status, diet and exposure to environmental factors are increasingly acknowledged as potential factors affecting fetal growth both by altering nutrient availability to the fetus and by modulating placental gene expression, thus modifying placental function.

SUMMARY

Assessing nutritional and environmental factors associated with IUGR, and the molecular mechanisms by which they may have a role in the disease onset, is necessary to provide comprehensive and common guidelines for maternal care and recommended behaviours. Moreover, maternal genetic predispositions and early serum markers may allow a better and more specific monitoring of high risk pregnancies, optimizing the timing of delivery.

Differentially expressed microRNAs and affected biological pathways revealed by modulated modularity clustering (MMC) analysis of human preeclamptic and IUGR placentas

INTRODUCTION

This study focuses on the implementation of modulated modularity clustering (MMC) a new cluster algorithm for the identification of molecular signatures of preeclampsia and intrauterine growth restriction (IUGR), and the identification of affected microRNAs

METHODS

Eighty-six human placentas from normal (40), growth-restricted (27), and preeclamptic (19) term pregnancies were profiled using Illumina Human-6 Beadarrays. MMC was utilized to generate modules based on similarities in placental transcriptome. Gene Set Enrichment Analysis (GSEA) was used to predict affected microRNAs. Expression levels of these candidate microRNAs were investigated in seventy-one human term placentas as follows: control (29); IUGR (26); and preeclampsia (16).

RESULTS

MMC identified two modules, one representing IUGR placentas and one representing preeclamptic placentas. 326 differentially expressed genes in the module representing IUGR and 889 differentially expressed genes in a module representing preeclampsia were identified. Functional analysis of molecular signatures associated with IUGR identified P13K/AKT, mTOR, p70S6K, apoptosis and IGF-1 signaling as being affected. Analysis of variance of GSEA-predicted microRNAs indicated that miR-194 was significantly down-regulated both in preeclampsia (p = 0.0001) and IUGR (p = 0.0304), and miR-149 was significantly down-regulated in preeclampsia (p = 0.0168).

DISCUSSION

Implementation of MMC, allowed identification of genes disregulated in IUGR and preeclampsia. The reliability of MMC was validated by comparing to previous linear modeling analysis of preeclamptic placentas.

CONCLUSION

MMC allowed the elucidation of a molecular signature associated with preeclampsia and a subset of IUGR samples. This allowed the identification of genes, pathways, and microRNAs affected in these diseases.

Differential expression of plasma miR-146a in sepsis patients compared with non-sepsis-SIRS patients

Sepsis is a subtype of systemic inflammatory response syndrome (SIRS), which is characterized by infection. Circulating microRNAs (miRNAs), including miR-150, miR-146a and miR-223, are potential biomarkers of sepsis. In this study, we demonstrated that measuring the relative expression of miR-146a/U6 in plasma, using the 2^−ΔΔCt method, provides a method for differentiating between sepsis and non-sepsis-SIRS. We observed a significant increase in miR-146a expression in the initial cohort of 6 non-sepsis-SIRS patients compared to the 4 sepsis patients (P=0.01) and in the second cohort of 8 non-sepsis-SIRS patients compared to the 10 sepsis patients (P=0.027). Additionally, we identified that sodium citrate and ethylenediaminetetraacetic acid (EDTA) K₂ may be used as anticoagulant reagents. Generation of a standard curve is not necessary in these diagnostic tests, unless the standard of normalization is carefully selected. Thus we provide more detailed guidance for the clinical use of circulating miRNA biomarkers.

microRNA-29b contributes to pre-eclampsia through its effects on apoptosis, invasion and angiogenesis of trophoblast cells

PE (pre-eclampsia), a pregnancy-specific disorder, is characterized by increased trophoblast cell death and deficient trophoblast invasion and reduced trophoblast-mediated remodelling of spiral arteries. The present study was performed to determine the function of miR-29b (microRNA-29b) in trophoblast cells and its underlying role in the pathogenesis of PE. The prediction of miR-29b target genes was performed using computer-based programs, including Targetscan, Pictar and miRBase. The function of these target genes was analysed further by gene ontology (GO). The effects of miR-29b on apoptosis, and invasion and angiogenesis of trophoblast cell lines (HTR-8/SVneo, BeWo and JAR) were examined by flow cytometry and Matrigel assay respectively. We found that miR-29b induced apoptosis and inhibited invasion and angiogenesis of trophoblast cells. Further studies confirmed that miR-29b regulated the expression of MCL1 (myeloid cell leukaemia sequence 1), MMP2 (encoding matrix metallproteinase 2), VEGFA (vascular endothelial growth factor A) and ITGB1 (integrin β1) genes by directly binding to their 3'-UTRs (untranslated regions). Moreover, we identified that there was an inverse correlation between miR-29b and its target genes in subjects with PE. Taken together, these findings support a novel role for miR-29b in invasion, apoptosis and angiogenesis of trophoblast cells, and miR-29b may become a new potential therapeutic target for PE.

Extracellular nucleic acids in maternal circulation as potential biomarkers for placental insufficiency

Since the placenta is being continuously remodeled during normal placental development, extracellular nucleic acids of both fetal and placental origin, packed into either trophoblast-derived apoptotic bodies or shedding syncytiotrophoblast microparticles, may be detected in maternal circulation during the course of normal gestation. Placental-insufficiency-related pregnancy complications have been shown to be associated with excessive placental trophoblast apoptosis and shedding of placenta debris. Recent advances in the field are reviewed with a focus on the diagnostic potential of particular molecular biomarkers and their eventual implementation in the currently used predictive and diagnostic algorithms for placental-insufficiency-related pregnancy complications.