Usefulness of circulating microRNAs for the prediction of early preeclampsia at first-trimester of pregnancy

Circulating miRNAs and Preeclampsia: From Implantation to Epigenetics

In this review, we comprehensively present the literature on circulating microRNAs (miRNAs) associated with preeclampsia, a pregnancy-specific disease considered the primary reason for maternal and fetal mortality and morbidity. miRNAs are single-stranded non-coding RNAs, 20-24 nt long, which control mRNA expression. Changes in miRNA expression can induce a variation in the relative mRNA level and influence cellular homeostasis, and the strong presence of miRNAs in all body fluids has made them useful biomarkers of several diseases. Preeclampsia is a multifactorial disease, but the etiopathogenesis remains unclear. The functions of trophoblasts, including differentiation, proliferation, migration, invasion and apoptosis, are essential for a successful pregnancy. During the early stages of placental development, trophoblasts are strictly regulated by several molecular pathways; however, an imbalance in these molecular pathways can lead to severe placental lesions and pregnancy complications. We then discuss the role of miRNAs in trophoblast invasion and in the pathogenesis, diagnosis and prediction of preeclampsia. We also discuss the potential role of miRNAs from an epigenetic perspective with possible future therapeutic implications.

Discovery and verification of extracellular microRNA biomarkers for diagnostic and prognostic assessment of preeclampsia at triage

We report on the identification of extracellular miRNA (ex-miRNA) biomarkers for early diagnosis and prognosis of preeclampsia (PE). Small RNA sequencing of maternal serum prospectively collected from participants undergoing evaluation for suspected PE revealed distinct patterns of ex-miRNA expression among different categories of hypertensive disorders in pregnancy. Applying an iterative machine learning method identified three bivariate miRNA biomarkers (miR-522-3p/miR-4732-5p, miR-516a-5p/miR-144-3p, and miR-27b-3p/let-7b-5p) that, when applied serially, distinguished between PE cases of different severity and differentiated cases from controls with a sensitivity of 93%, specificity of 79%, positive predictive value (PPV) of 55%, and negative predictive value (NPV) of 89%. In a small independent validation cohort, these ex-miRNA biomarkers had a sensitivity of 91% and specificity of 57%. Combining these ex-miRNA biomarkers with the established sFlt1:PlGF protein biomarker ratio performed better than either set of biomarkers alone (sensitivity of 89.4%, specificity of 91.3%, PPV of 95.5%, and NPV of 80.8%).

Circulating miRNAs in the first trimester and pregnancy complications: a systematic review

Most pregnancy complications originate with early placentation. MicroRNAs (miRNAs) may play an important role in placentation and function as biomarkers of future pregnancy complications. We summarized from the literature all first trimester circulating miRNAs associated with pregnancy complications of placental origin and further identified the miRNAs which have the most evidence as potential early biomarkers for pregnancy complications. We conducted a systematic review following PRISMA reporting guidelines (PROSPERO CRD42020183421). We identified all first trimester serum or plasma miRNAs associated with a pregnancy complication of placental origin (preeclampsia, intrauterine growth restriction (IUGR), gestational hypertension, preterm delivery) and the number of times those miRNAs were identified, as a measure of replication. Twenty-one studies examined 118 unique miRNAs, and 87 were associated with at least one pregnancy complication; preeclampsia was the most common. Seven miRNAs were significantly associated with a pregnancy complication in at least two studies: miR-125b, miR-518b, miR-628-3p, miR-365a-3p, miR-520h, miR-374a-5p, miR-191-5p. Few miRNAs were associated with more than one pregnancy complication: miR-518b and miR-520h with preeclampsia and gestational hypertension, miR-374a-5p and miR-191-5p with preterm birth and preeclampsia. Our systematic review suggests seven miRNAs as potential biomarkers of pregnancy complications. These complications are thought to originate with early placental defects and these miRNAs may also be biomarkers of placental pathology. First-trimester biomarkers of pregnancy complications can facilitate early detection and interventions.

Role of microRNAs regulating trophoblast cell function in the pathogenesis of pre‑eclampsia (Review)

Pre-eclampsia (PE) is a complicated pregnancy-specific disease and is considered the primary reason for maternal and foetal mortality and morbidity. PE has a multifactorial pathogenesis but the causes of PE remain unclear. The functions of trophoblasts, including differentiation, proliferation, migration, invasion and apoptosis, are essential for successful pregnancy. During the early stages of placental development, trophoblasts are strictly regulated by several molecular pathways; however, an imbalance of these molecular pathways can lead to severe placental lesions and pregnancy complications. Certain microRNAs (miRs) are abnormally expressed in PE, with several miRs involved in the regulation of pregnancy-associated genes. The present review discusses the miRs regulating trophoblast function, how they affect the pathogenesis of PE and evaluating the possibility of miRs in screening, diagnosis and treatment of PE.

Detection of Embryonic Trisomy 21 in the First Trimester Using Maternal Plasma Cell-Free RNA

Prenatal trisomy 21 (T21) screening commonly involves testing a maternal blood sample for fetal DNA aneuploidy. It is reliable but poses a cost barrier to universal screening. We hypothesized maternal plasma RNA screening might provide similar reliability but at a lower cost. Discovery experiments used plasma cell-free RNA from 20 women 11−13 weeks tested by RNA and miRNA microarrays followed by qRT-PCR. Thirty-six mRNAs and 18 small RNAs of the discovery cDNA were identified by qPCR as potential markers of embryonic T21. The second objective was validation of the RNA predictors in 998 independent pregnancies at 11−13 weeks including 50 T21. Initial analyses identified 9−15 differentially expressed RNA with modest predictive power (AUC < 0.70). The 54 RNAs were then subjected to machine learning. Eleven algorithms were trained on one partition and tested on an independent partition. The three best algorithms were identified by Kappa score and the effects of training/testing partition size and dataset class imbalance on prediction were evaluated. Six to ten RNAs predicted T21 with AUCs up to 1.00. The findings suggest that maternal plasma collected at 11−13 weeks, tested by qRT-PCR, and classified by machine learning, may accurately predict T21 for a lower cost than plasma DNA, thus opening the door to universal screening.

Epigenetic Profiling in the Saliva of Obese Pregnant Women

Maternal obesity is associated with inflammation and oxidative stress, strongly impacting the intrauterine environment with detrimental consequences for both mother and offspring. The saliva is a non-invasive biofluid reflecting both local and systemic health status. This observational study aimed to profile the epigenetic signature in the saliva of Obese (OB) and Normal-Weight (NW) pregnant women. Sixteen NW and sixteen OB Caucasian women with singleton spontaneous pregnancies were enrolled. microRNAs were quantified by the OpenArray Platform. The promoter region methylation of Suppressor of Cytokine Signaling 3 (SOCS3) and Transforming Growth Factor Beta 1 (TGF-Beta1) was assessed by pyrosequencing. There were 754 microRNAs evaluated: 20 microRNAs resulted in being differentially expressed between OB and NW. microRNA pathway enrichment analysis showed a significant association with the TGF-Beta signaling pathway (miTALOS) and with fatty acids biosynthesis/metabolism, lysine degradation, and ECM–receptor interaction pathways (DIANA–miRPath). Both SOCS3 and TGF-Beta1 were significantly down-methylated in OB vs. NW. These results help to clarify impaired mechanisms involved in obesity and pave the way for the understanding of specific damaged pathways. The characterization of the epigenetic profile in saliva of pregnant women can represent a promising tool for the identification of obesity-related altered mechanisms and of possible biomarkers for early diagnosis and treatment of pregnancy-adverse conditions.

miR-146b-5p and miR-520h Expressions Are Upregulated in Serum of Women with Recurrent Spontaneous Abortion

Unexplained recurrent spontaneous abortion (URSA) is characterized by two or more consecutive pregnancy losses before the 20th week of gestation with unknown etiology. Dysregulation of microRNAs (miRNAs) expression has been reported in reproductive diseases. This study aimed to compare differentially expressed miRNAs in the serum samples between URSA patients and healthy individuals. URSA cases were confirmed by a gynecologist. Peripheral blood sample was‏ gathered from 9 URSA patients, 15 normal pregnant, and 10 non-pregnant women without abortion history. After separating serum, the expression levels of the miR-101-3p, miR-517c-3p, miR-146b-5p, miR-221-3p, and miR-520 h were measured by qRT-PCR assay. The circulating level of miR-520 h in URSA patients was significantly up-regulated compared with healthy pregnant (P < 0.01) and healthy non-pregnant (P = 0.002) women. Furthermore, miR-520 h expression was significantly different between healthy non-pregnant and pregnant women (P = 0.002). Statistical analysis indicated miR-146b-5p expression was significantly up-regulated in URSA patients compared to normal pregnant women (P = 0.018). However, the transcription level of miR-146b-5p was insignificantly different between normal non-pregnant women and the other two groups. Also, circulating levels of miR-101-3p, miR-221-3p, and miR-517c-3p were not significantly different in the studied groups. Statistical analysis showed significant correlations between both miR-221-3p and miR-517c-3p and other miRNAs (P < 0.05). The circulating levels of miR-520 h and miR-146b-5p could be considered biomarkers for URSA diagnosis. Also, miR-517c-3p and miR-221-3p might play a regulatory role in other miRNAs expressions during pregnancy. Previous work, in contrary to our findings, claims that the expression levels of miR-221-3p, miR-101-3p, and miR-517c-3p increased in plasma and tissue samples of patients with URSA. However, our research for the first time indicates that the expression level of miR-520 h and miR-146b-5p in the serum of these patients has increased. Future investigations are necessary to confirm these findings.

Uncovering serum placental-related non-coding RNAs as possible biomarkers of preeclampsia risk, onset and severity revealed MALAT-1, miR-363 and miR-17

New predictors that could boost early detection of preeclampsia (PE) and prognosticate its severity are urgently needed. We examined serum miR-17, miR-363, MALAT-1 and HOTAIR as potential biomarkers of PE risk, onset and severity. This prospective study included 160 pregnant females; 82 PE cases and 78 healthy pregnancies. Serum samples were collected between 20 to 40 weeks of gestation. Early-onset PE was defined as developing clinical manifestations at ≤ 34 gestational weeks. Severe PE was defined as systolic blood pressure ≥ 160 mmHg and/or diastolic blood pressure ≥ 110 mmHg and proteinuria (≥ 2 g/24 h or ≥ 2+ dipstick). Selection of PE-related non-coding RNAs and functional target gene analysis were conducted using bioinformatics analysis. Expression profiles were assessed by RT-qPCR. Serum miR-363 and MALAT-1 were downregulated, meanwhile miR-17 was upregulated, and HOTAIR was not significantly altered in PE compared with healthy pregnancies. miR-17 was elevated while miR-363 and MALAT-1 were reduced in severe versus mild PE. miR-363 was lower in early-onset versus late-onset PE. MALAT-1, miR-17 and miR-363 showed diagnostic potential and discriminated severe PE, whereas miR-363 distinguished early-onset PE in the receiver-operating-characteristic analysis. miR-363 and MALAT-1 were significantly associated with early and severe PE, respectively in multivariate logistic analysis. In PE, miR-17 and MALAT-1 were significantly correlated with gestational age (r = - 0.328 and r = 0.322, respectively) and albuminuria (r = 0.312, and r = - 0.35, respectively). We constructed the MALAT-1, miR-363, and miR-17-related protein-protein interaction networks linked to PE. Serum miR-17, miR-363 and MALAT-1 could have utility as new biomarkers of PE diagnosis. miR-363 may be associated with early-onset PE and MALAT-1 downregulation correlates with PE severity.

Preeclamptic Women Have Disrupted Placental microRNA Expression at the Time of Preeclampsia Diagnosis: Meta-Analysis

Introduction: Preeclampsia (PE) is a pregnancy-associated, multi-organ, life-threatening disease that appears after the 20th week of gestation. The aim of this study was to perform a systematic review and meta-analysis to determine whether women with PE have disrupted miRNA expression compared to women who do not have PE. Methods: We conducted a systematic review and meta-analysis of studies that reported miRNAs expression levels in placenta or peripheral blood of pregnant women with vs. without PE. Studies published before October 29, 2021 were identified through PubMed, EMBASE and Web of Science. Two reviewers used predefined forms and protocols to evaluate independently the eligibility of studies based on titles and abstracts and to perform full-text screening, data abstraction and quality assessment. Standardized mean difference (SMD) was used as a measure of effect size. Results: 229 publications were included in the systematic review and 53 in the meta-analysis. The expression levels in placenta were significantly higher in women with PE compared to women without PE for miRNA-16 (SMD = 1.51,95%CI = 0.55-2.46), miRNA-20b (SMD = 0.89, 95%CI = 0.33-1.45), miRNA-23a (SMD = 2.02, 95%CI = 1.25-2.78), miRNA-29b (SMD = 1.37, 95%CI = 0.36-2.37), miRNA-155 (SMD = 2.99, 95%CI = 0.83-5.14) and miRNA-210 (SMD = 1.63, 95%CI = 0.69-2.58), and significantly lower for miRNA-376c (SMD = -4.86, 95%CI = -9.51 to -0.20). An increased level of miRNK-155 expression was found in peripheral blood of women with PE (SMD = 2.06, 95%CI = 0.35-3.76), while the expression level of miRNA-16 was significantly lower in peripheral blood of PE women (SMD = -0.47, 95%CI = -0.91 to -0.03). The functional roles of the presented miRNAs include control of trophoblast proliferation, migration, invasion, apoptosis, differentiation, cellular metabolism and angiogenesis. Conclusion: miRNAs play an important role in the pathophysiology of PE. The identification of differentially expressed miRNAs in maternal blood creates an opportunity to define an easily accessible biomarker of PE.

Circulating MicroRNAs in the Second Trimester From Pregnant Women Who Subsequently Developed Preeclampsia: Potential Candidates as Predictive Biomarkers and Pathway Analysis for Target Genes of miR-204-5p

MicroRNAs (miRNAs) play an important role in the pathophysiology of preeclampsia (PE). However, the expression of circulating miRNAs was not analyzed in the second trimester of pregnancy, a period of major relevance to identify predictive biomarkers for PE. Therefore, we examined the expression profiles of 84 circulating miRNAs using a PCR array in plasma collected between 20 and 25 weeks of gestation from pregnant women, who subsequently developed PE and those who remained healthy during pregnancy, randomly selected from a prospective cohort. Overall, 23 miRNAs had a fold change > 2.0 and were considered to be upregulated in plasma from pregnant women who subsequently developed PE, even before the onset of clinical symptoms of PE. However, only miR-204-5p was statistically significant (P = 0.0082). Experimentally validated interactions for the target genes of miR-204-5p extracted from miRTarBase were used in the gene set functional enrichment analysis to identify Reactome pathways. The network connecting the 37 target genes for miR-204-5p revealed pathways of known pathophysiological relevance during the early development of PE and included key genes related to PE, such as BDNF, MMP-9, MALAT1, TGFBR2, and SIRT1. We further depicted downstream targets of SIRT1 that are related to the vascular endothelial function or implicated in the pathophysiology of PE, namely, FOXO1, NFκB, HIF-1α, NOS3, and PPAR-γ. Our novel findings provide for circulating miRNAs upregulated in the second trimester on plasma from pregnant women who subsequently developed PE that is potentially related to the early development of PE, which may guide further studies focused on the validation of potential predictive biomarkers in PE.

BHLHE40 plays a pathological role in pre-eclampsia through upregulating SNX16 by transcriptional inhibition of miR-196a-5p

Pre-eclampsia (PE), which results from abnormal placentation, is a primary cause of maternal and neonatal morbidity and mortality. However, the causes of abnormal development of the placenta remain poorly understood. BHLHE40 is a transcriptional repressor in response to hypoxia. Bioinformatics analysis demonstrated that BHLHE40 negatively regulates miR-196a-5p expression, which may decrease miR-196a-5p to target SNX16. Since SNX16 exerts an inhibitory effect on cell migration, it may disrupt trophoblast cell migration in placentation. Therefore, the objective of this study was to explore a possible role of the BHLHE40/miR-196a-5p/SNX16 axis in PE pathogenesis. BHLHE40, miR-196a-5p and SNX16 mRNA and/or protein levels were detected in PE and normal placenta tissues. PE models in vitro and in vivo were constructed by culturing trophoblasts under hypoxia and reducing the uterine perfusion pressure in pregnant C57/BL6N mice, respectively. BHLHE40 and SNX16 were upregulated in PE placenta, while miR-196a-5p was downregulated. Knockdown of BHLHE40 reversed miR-196a-5p expression in trophoblasts under hypoxia, and upregulation of miR-196a-5p inhibited SNX16 expression. As indicated by ChIP assay, BHLHE40 bound to the promoter of the miR-196a-5p gene; luciferase reporter analysis showed that miR-196a-5p could bind to the 3'-untranslated region of SNX16 mRNA. Knockdown of either BHLHE40 or SNX16, or an increase in miR-196a-5p, restored cell viability, migration, invasion and matrix metalloprotein (MMP)-2 and MMP-9 expression under hypoxia. BHLHE40 knockdown also alleviated PE symptoms in pregnant C57/BL6N mice. This study supports involvement of the BHLHE40/miR-196a-5p/SNX16 axis in PE pathogenesis; Proper adjustment of the BHLHE40/miR-196a-5p/SNX16 axis is able to attenuate PE symptoms.

Circulating Nucleic Acids in Maternal Plasma and Serum in Pregnancy Complications: Are They Really Useful in Clinical Practice? A Systematic Review

OBJECTIVE

A systematic review was carried out to summarize the available evidence to assess whether circulating nucleic acids in maternal plasma and serum (CNAPS) have the potential to serve as extra and independent markers for the prediction and/or progression monitoring of the most common and severe complications of pregnancy, including preeclampsia, intrauterine growth restriction, preterm delivery, morbidly adherent placenta, gestational diabetes, antiphospholipid syndrome, threatened abortion, intrahepatic cholestasis of pregnancy, and hyperemesis gravidarum.

METHOD

A comprehensive literature search of the MEDLINE (PubMed), EMBASE, and ISI Web of Knowledge databases was conducted to identify relevant studies that included amounts of CNAPS in the abovementioned pregnancy complications.

RESULTS

Eighty-three studies met the eligibility criteria. The vast majority of studies were conducted on the quantity of total circulating cell free DNA (cfDNA) and cell free fetal DNA (cffDNA), and some were conducted on messenger RNA (mRNA) species. A few studies have instead evaluated the cell free DNA fetal fraction (cfDNAff), but only in a limited number of pregnancy complications. Despite the growing interest and the abundance of the papers available, little information is available for other new CNAPS, including microRNA (miRNA), long noncoding RNA (lncRNA), mitochondrial DNA (mtDNA), and circular RNA.

CONCLUSION

Due to the heterogeneity of the populations enrolled, the scarcity of the studies that adjusted the CNAPS values for possible confounding factors, and the difficulty in interpreting the published data, no conclusion regarding the statistical robustness and clinical relevance of the data can be made at present. If assayed at the third trimester, the CNAPS have, however, shown better performance, and could be used in populations already at risk of developing complications as suggested by the presence of other clinical features. Other CNAPS, including miRNA, are under investigation, especially for the screening of gestational diabetes mellitus, but no data about their clinical utility are available. Circulating DNA (cfDNA, cffDNA, and cfDNAff) and mRNA have not been properly evaluated yet, especially in patients asymptomatic early in pregnancy but who developed complications later, perhaps because of the high cost of these techniques and the availability of other predictors of pregnancy complications (biochemical, biophysical, and ultrasound markers). Therefore, from the analysis of the data, the positive predictive value is not available. As regards the new CNAPS, including miRNA, there are still no sufficient data to understand if they can be promising markers for pregnancy complications monitoring and screening, since CNAPS are statistically weak and expensive. It is reasonable to currently conclude that the use of the CNAPS in clinical practice is not recommended.

Analysis of Circulating microRNA Signatures and Preeclampsia Development

microRNAs are important regulators of cell processes and have been proposed as potential preeclampsia biomarkers. We evaluated serum microRNA expression profiling to identify microRNAs involved in preeclampsia development. Serum microRNA expression profiling was evaluated at 12, 16, and 20 weeks of gestation (WG), and at the time of preeclampsia diagnosis. Two groups were evaluated using TaqMan low-density array plates: a control group with 18 normotensive pregnant women and a case group with 16 patients who developed preeclampsia during the follow-up period. Fifty-three circulating microRNAs were differentially expressed between groups (p < 0.05). Compared with controls, hsa-miR-628-3p showed the highest relative quantity values (at 12 WG = 7.7 and at 20 WG = 3.45) and the hsa-miRs -151a-3p and -573 remained differentially expressed from 16 to 20 WG (p < 0.05). Signaling pathways including cancer-related, axon guidance, Neurotrophin, GnRH, VEGF, and B/T cell receptor, were most commonly altered. Further target gene prediction revealed that nuclear factor of activated T-cells 5 gene was included among the transcriptional targets of preeclampsia-modulated microRNAs. Specific microRNAs including hsa-miRs -628-3p, -151a-3p, and -573 were differentially expressed in serum of pregnant women before they developed preeclampsia compared with controls and their participation in the preeclampsia development should be considered.

MicroRNA-mRNA Networks in Pregnancy Complications: A Comprehensive Downstream Analysis of Potential Biomarkers

Pregnancy complications are a major cause of fetal and maternal morbidity and mortality in humans. The majority of pregnancy complications initiate due to abnormal placental development and function. During the last decade, the role of microRNAs (miRNAs) in regulating placental and fetal development has become evident. Dysregulation of miRNAs in the placenta not only affects placental development and function, but these miRNAs can also be exported to both maternal and fetal compartments and affect maternal physiology and fetal growth and development. Due to their differential expression in the placenta and maternal circulation during pregnancy complications, miRNAs can be used as diagnostic biomarkers. However, the differential expression of a miRNA in the placenta may not always be reflected in maternal circulation, which makes it difficult to find a reliable biomarker for placental dysfunction. In this review, we provide an overview of differentially expressed miRNAs in the placenta and/or maternal circulation during preeclampsia (PE) and intrauterine growth restriction (IUGR), which can potentially serve as biomarkers for prediction or diagnosis of pregnancy complications. Using different bioinformatics tools, we also identified potential target genes of miRNAs associated with PE and IUGR, and the role of miRNA-mRNA networks in the regulation of important signaling pathways and biological processes.

Pre-eclampsia predictive ability of maternal miR-125b: a clinical and experimental study

Pre-eclampsia (PE) is a systemic maternal syndrome affecting 2-8% of pregnancies worldwide and involving poor placental perfusion and impaired blood supply to the foetus. It manifests after the 20th week of pregnancy as new-onset hypertension and substantial proteinuria and is responsible for severe maternal and newborn morbidity and mortality. Identifying biomarkers that predict PE onset prior to its establishment would critically help treatment and attenuate outcome severity. MicroRNAs are ubiquitous gene expression modulators found in blood and tissues. Trophoblast cell surface antigen (Trop)-2 promotes cell growth and is involved in several cancers. We assessed the PE predictive ability of maternal miR-125b in the first trimester of pregnancy by measuring its plasma levels in women with normal pregnancies and with pregnancies complicated by PE on the 12th week of gestation. To gain insight into PE pathogenesis we investigated whether Trop-2 is targeted by miR-125b in placental tissue. Data analysis demonstrated a significant association between plasma miR-125b levels and PE, which together with maternal body mass index before pregnancy provided a predictive model with an area under the curve of 0.85 (95% confidence interval, 0.70-1.00). We also found that Trop-2 is a target of miR-125b in placental cells; its localization in the basal part of the syncytiotrophoblast plasma membrane suggests a role for it in the early onset of PE. Altogether, maternal miR-125b proved a promising early biomarker of PE, suggesting that it may be involved in placental development through its action on Trop-2 well before the clinical manifestations of PE.

Elevated microRNA-125b inhibits cytotrophoblast invasion and impairs endothelial cell function in preeclampsia

Preeclampsia (PE) is a life-threatening disorder of human pregnancy affecting 5-8% of all pregnancies. Currently, PE remains an elusive complicated and heterogenous medical condition with no early marker or symptoms is recognized for this serious pregnancy complications. Here, we profiled the plasma miRNA expression patterns associated with preeclampsia and found 16 miRNAs were deregulated (p < 0.01) in patients who later developed PE. Circulating hsa-miR-125b was aberrantly upregulated in early pregnancy and significantly reduced after delivery in preeclampsia. We then investigated the underlying molecular mechanisms between miR-125b and PE in vitro. We found that upregulated miR-125b can target KCNA1 to inhibit trophoblast invasion in human trophoblast cells. Moreover, overexpression of miR-125b in HUVECs impaired endothelial cell function through GPC1. The findings indicated that upregulated miR-125b leads to impaired placentation, and an increased risk of preeclampsia, Our studies provide novel insights into the underlying mechanisms on the association of miR-125b in early pregnancy and risk of PE, miR-125b might be a more specific predictive marker and a safe therapeutic target for treating patients with PE.

Discovery and Verification of Extracellular miRNA Biomarkers for Non-invasive Prediction of Pre-eclampsia in Asymptomatic Women

Development of effective prevention and treatment strategies for pre-eclampsia is limited by the lack of accurate methods for identification of at-risk pregnancies. We performed small RNA sequencing (RNA-seq) of maternal serum extracellular RNAs (exRNAs) to discover and verify microRNAs (miRNAs) differentially expressed in patients who later developed pre-eclampsia. Sera collected from 73 pre-eclampsia cases and 139 controls between 17 and 28 weeks gestational age (GA), divided into separate discovery and verification cohorts, are analyzed by small RNA-seq. Discovery and verification of univariate and bivariate miRNA biomarkers reveal that bivariate biomarkers verify at a markedly higher rate than univariate biomarkers. The majority of verified biomarkers contain miR-155-5p, which has been reported to mediate the pre-eclampsia-associated repression of endothelial nitric oxide synthase (eNOS) by tumor necrosis factor alpha (TNF-α). Deconvolution analysis reveals that several verified miRNA biomarkers come from the placenta and are likely carried by placenta-specific extracellular vesicles.

Small RNA-seq of maternal serum in women who later developed pre-eclampsia

Bioinformatic analyses identify univariate and bivariate miRNA biomarkers

Many bivariate biomarkers contain miR-155-5p

Deconvolution analyses verify several miRNAs to be placenta specific

Placenta-specific plasma miR518b is a potential biomarker for preeclampsia

INTRODUCTION

MicroRNAs have a significant role in the pathogenesis of preeclampsia. Circulating microRNAs could represent a potential biomarker for preeclampsia. The aim of this study was to evaluate plasma miR210-3p and miR518b in preeclampsia and healthy pregnancy for the first time by digital droplet PCR (ddPCR).

METHODS

Thirty-six pregnant women (seventeen healthy pregnancies, nineteen preeclampsia patients) were involved from the Clinic for Gynaecology and Obstetrics "Narodni front" in Belgrade, Serbia. Plasma miR210-3p, miR518b and cel-miR-39 as a spike-in control were measured by ddPCR.

RESULTS

MiR518b was significantly elevated in preeclampsia compared to a healthy pregnancy (P = 0.034; 0.302(0.217-0.421) vs. 0.171(0.110-0.266)). MiR210-3p showed no significant difference between the two groups (P = 0.951). The adjustment of miR518b was made for a gestational age and smoking status and the difference between the preeclampsia and healthy pregnancy group was more significant (P = 0.026; 0.300(0.216-0.419) vs. 0.172(0.121-0.245)). Plasma miR-518b was significantly higher in the group of preeclampsia patients with proteinuria above the 75th percentile for the group (P = 0.033), in women who smoked (P = 0.039), and was positively related to uric acid in preeclampsia (P = 0.018, r = 0.536). Plasma miR518b was able to significantly discriminate between preeclampsia and healthy pregnancy, yielding AUC of 0.712 (95%CI:0.539-0.891), P = 0.028.

CONCLUSIONS

In this study plasma microRNA were measured for the first time in preeclampsia and healthy pregnancies with ddPCR. Placenta-specific miR-518b could serve as a potential biomarker for discriminating preeclampsia and healthy pregnancy, which should be confirmed on a larger study population. This study has failed to confirm the same potential for miR210-3p.

Preeclampsia – Prediction and Monitoring Factors

Preeclampsia is one of the leading causes of maternal and perinatal morbidity and mortality, usually characterized by hypertension and proteinuria. Despite high incidence of preeclampsia the pathophysiological basis of preeclampsia is still not clear and there are a number of mechanisms and signaling pathways that intertwine. It is very important to develop specific and reliable predictive algorithms in order to enable early initiation of therapy due to facts that incidence of preeclampsia has upward trend and that cause adverse maternal and fetal outcome. Some of the most commonly used methods for prediction of preeclampsia include uterine artery Doppler velocimetry, determination of some microRNA, such as miR-210, and assessment of various pro-angiogenic and anti-angiogenic factors from blood. Angiogenic factors that possibly have most important role in pathogenesis of preeclampsia are vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), which promote angiogenesis, and soluble fms-like tyrosine kinase-1 (sFlt1) and soluble form of endoglin (s-Eng), which exhibit anti-angiogenic properties. Aggravating circumstance is that preeclampsia has heterogeneous origin, and due to this fact, the value of individual markers can vary significantly. There is a constant tendency for creating comprehensive algorithm for prediction of preeclampsia which would be sufficiently specific and sensitive, and in the same time cheap and available. In that sense, new clinical studies are needed to show the most effective combination of parameters in the predeclampsia prediction.

MicroRNAs: Small molecules with a large impact on pre-eclampsia

As critical mediators in biological processes, microRNAs (miRNAs) which are small and endogenous noncoding RNAs have been associated with disease progression, cell proliferation, and development. Pre-eclampsia (PE), a pregnancy-related disorder with no early markers or symptoms is recognized as the main reason for fetal and maternal mortality and morbidity in the initial steps or even during pregnancy, worldwide. Clinical symptoms usually appear in the third trimester of the pregnancy. Although numerous research have unraveled several aspects of placenta development abnormalities associated with abnormal trophoblastic invasion and angiogenesis modification, many questions about the PE pathogenesis remains unanswered. A large number of studies have shown the important role of miRNAs as potential biomarkers in the PE prognosis and diagnosis. Here, the latest investigations about the PE and placental miRNAs expression, as well as, the crucial role of miRNA molecules including miR-210 and miR-155 which are deregulated in patients with PE, will be argued.

MicroRNA expression studies: challenge of selecting reliable reference controls for data normalization

Accurate determination of microRNA expression levels is a prerequisite in using these small non-coding RNA molecules as novel biomarkers in disease diagnosis and prognosis. Quantitative PCR is the method of choice for measuring the expression levels of microRNAs. However, a major obstacle that affects the reliability of results is the lack of validated reference controls for data normalization. Various non-coding RNAs have previously been used as reference controls, but their use may lead to variations and lack of comparability of microRNA data among the studies. Despite the growing number of studies investigating microRNA profiles to discriminate between healthy and disease stages, robust reference controls for data normalization have so far not been established. In the present article, we provide an overview of different reference controls used in various diseases, and highlight the urgent need for the identification of suitable reference controls to produce reliable data. Our analysis shows, among others, that RNU6 is not an ideal normalizer in studies using patient material from different diseases. Finally, our article tries to disclose the challenges to find a reference control which is uniformly and stably expressed across all body tissues, fluids, and diseases.

Placental exosomes viewed from an 'omics' perspective: implications for gestational diabetes biomarkers identification

Exosomes are defined as extracellular vesicles that are released from cells upon fusion of an intermediate endocytic compartment - the multivesicular body - with the plasma membrane. Recently, placenta-derived exosomes have gained special attention, since they play a crucial role in the communication between the mother and fetus. It is known that the concentration of placenta-derived exosomes in the maternal bloodstream is higher in patients with preeclampsia or gestational diabetes mellitus. However, their composition in terms of the content of proteins, nucleic acids or lipids is uncertain. In this work, we reviewed the recent advances in placental exosomes characterization through omics-based methods, and their potential to predict gestational diabetes mellitus.

Serum levels of miR-628-3p and miR-628-5p during the early pregnancy are increased in women who subsequently develop preeclampsia

OBJECTIVE

Preeclampsia pathogenesis involves imbalances of oxidative stress networks including the heat shock protein (HSP) pathway. Micro-RNAs regulate gene networks associated with preeclampsia. Hsp90 and Runx2 are transcriptional targets of miR-628-3p. Considering that potential participation of hsa-miR-628-3p in PE development is still not elucidated, the aim of this study was to evaluate serum microRNA expression of hsa-miR-628-3p and hsa-miR-628-5p and their association with the preeclampsia development.

STUDY DESIGN

A retrospective nested cohort case-control study was conducted. Serum samples from 16 pregnant women who developed preeclampsia (WWD-PE) during the follow-up period were selected and individually matched to that from 18 women in the cohort who had healthy pregnancies without complications (controls).

MAIN OUTCOME MEASURES

The levels of hsa-miR-628-3p and hsa-miR-628-5p were measured in serum samples from study groups at 12, 16, and 20 weeks of gestation (WG) using TaqMan probes. Additionally serum levels were measured at the moment of diagnosis, in women with preeclampsia.

RESULTS

Serum levels of hsa-miR-628-3p were higher than controls in WWD-PE at 12 WG (RQ = 7.7; P = 0.020), and of hsa-miR-628-5p at 20 WG (RQ = 3.4; P = 0.008). An increase in hsa-miR-628-3p serum levels at 12 WG (RQ = 12.01; P = 0.001) and of hsa-miR-628-5p at 20 WG (RQ = 2.95; P = 0.033) was also observed in women who developed mild preeclampsia, and severe preeclampsia, respectively.

CONCLUSIONS

Serum hsa-miR-628-3p and hsa-miR-628-5p were differentially expressed between WWD-PE and controls, suggesting a participation of these miRNAs in the development of preeclampsia. Future studies are needed to validate hsa-miR628-3p and -5p as early predictors of preeclampsia.

Quantification of circulating miR-517c-3p and miR-210-3p levels in preeclampsia

MicroRNAs (miRNAs, miRs) are small regulatory non-coding RNAs that regulate gene expression by incomplete complementary attachment to the 3'UTR, 5'UTR, ORF and promoter regions of target mRNAs. We compared plasma levels of miR-210-3p and miR-517c-3p as cell-free microRNAs (cfmiRNAs) in preeclamptic (n = 20) and healthy women (n = 20). These miRs are responsible for cell growth and proliferation, placental hypoxia, immune response and apoptosis. We found higher expression levels of miR-210 and miR-517c in preeclamptic cases (+3.34 and +2.27 fold change, respectively). This is the first study that evaluates the plasma levels of miR-517c in preeclamptic cases by real time PCR (RT-PCR) technique. This study can lead to new opportunities for research about the roles of miRNAs in preeclampsia etiology or new biomarkers.

MiR-221-3p is down-regulated in preeclampsia and affects trophoblast growth, invasion and migration partly via targeting thrombospondin 2

Preeclampsia (PE) is a common obstetrical disorder characterized by hypertension and proteinuria. The aberrant expression of miR-221-3p in placental tissues has been implicated in the pathogenesis of PE. This study examined the role of miR-221-3p in trophoblast growth, invasion and migration, and explored the underlying mechanisms. Our results showed that miR-221-3p was down-regulated in placental tissues from PE patients compared to heathy controls as measured by quantitative real-time PCR assay. CCK-8 assay, Transwell invasion assay and wound healing assay showed that miR-221-3p overexpression promoted trophoblast (HTR-8/SVneo cells) growth, invasion and migration, and knockdown of miR-221-3p exerted the opposite effects. Flow cytometry experiments further demonstrated that miR-221-3p overexpression inhibited apoptosis, increased cell population at S phase, and decreased cell population at G₀/G₁ phase of HTR-8/SVneo cells; while miR-221-3p knockdown exerted the opposite effects. Bioinformatics prediction and luciferase reporter assay showed that miR-221-3p targeted the 3' untranslated region of thrombospondin 2 (THBS2), and qRT-PCR and western blot assays revealed that miR-221-3p negatively regulated the expression of THBS2 in HTR-8/SVneo cells. Furthermore, overexpression of THBS2 attenuated the in vitro effects of miR-221-3p overexpression on cell growth, invasion and migration of HTR-8/SVneo cells. The clinical sample analysis showed that the mRNA expression levels of THBS2 was significantly increased in placental tissues from PE patients and was negatively correlated with expression levels of miR-221-3p. In summary, our results demonstrated that miR-221-3p was down-regulated in PE, and the in vitro functional assays revealed that miR-221-3p promoted trophoblast growth, invasion and migration partly via targeting THBS2.

Molecular determinants of microvascular dysfunction in hypertensive pregnancy and preeclampsia

Preeclampsia is a pregnancy-related disorder characterized by hypertension and often fetal intrauterine growth restriction, but the underlying mechanisms are unclear. Defective placentation and apoptosis of invasive cytotrophoblasts cause inadequate remodeling of spiral arteries, placental ischemia, and reduced uterine perfusion pressure (RUPP). RUPP causes imbalance between the anti-angiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the pro-angiogenic vascular endothelial growth factor and placental growth factor, and stimulates the release of proinflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors target the vascular endothelium, smooth muscle and various components of the extracellular matrix. Generalized endotheliosis in systemic, renal, cerebral, and hepatic vessels causes decreases in endothelium-derived vasodilators such as nitric oxide, prostacyclin and hyperpolarization factor, and increases in vasoconstrictors such as endothelin-1 and thromboxane A2. Enhanced mechanisms of vascular smooth muscle contraction, such as intracellular Ca2+ , protein kinase C, and Rho-kinase cause further increases in vasoconstriction. Changes in matrix metalloproteinases and extracellular matrix cause inadequate vascular remodeling and increased arterial stiffening, leading to further increases in vascular resistance and hypertension. Therapeutic options are currently limited, but understanding the molecular determinants of microvascular dysfunction could help in the design of new approaches for the prediction and management of preeclampsia.

Role of mesenchymal stem cells exosomes derived microRNAs; miR-136, miR-494 and miR-495 in pre-eclampsia diagnosis and evaluation

BACKGROUND

Pre-eclampsia (PE) is one of the most threatening pregnancy complications. So far neither a secure, competent therapy for PE nor effective biomarkers for a premature discovery has been achieved. However, currently, the use of released microRNAs (miRNAs) as potential biomarkers and therapy targets for various diseases is the dominating area of research. The aim of our study was to identify miRNAs 136, 494 and 495 genes expression in exosomes of peripheral blood compared to umbilical cord mesenchymal stem cells (UCMSCs) conditioned media released exososomes in patients with PE, as valuable markers for PE early prediction.

METHODS

Blood samples were collected from 100 patients with PE and 100 control with normal pregnancies. Thirty fresh umbilical cord samples of women with healthy pregnancies (n = 15) and PE patients (n = 15) were retrieved during caesarean deliveries and UCMSCs were isolated from Wharton jelly. The expression of miRNAs 136, 494 and 495 in exosomes of peripheral blood and UCMSCs conditioned media was measured using quantitative real-time PCR method. Unpaired t-test, Pearson correlation test and Receiver operator characteristic (ROC) analysis were used for data analysis.

RESULTS

Our study revealed a significantly higher expression levels of miRNAs 136, 494 and 495 in exosomes of peripheral blood and matched with UCMSCs released exosomes from patients with PE compared to normal pregnancies (p = 0.000). In peripheral blood of PE, they were 6.4, 3.9 and 2.1 folds higher, respectively. ROC analysis revealed that the sensitivity and specificity values of miRNA-136 were 95% and 100%, respectively, with a cut-off value of 2.55. The sensitivity and specificity values of miRNA-494 were 86% and 95%, respectively, with a cut-off value of 0.47. The sensitivity and specificity values of miRNA-495 were 90% and 83%, respectively, with a cut-off value of 1.287.

CONCLUSION

Our findings suggest that exosomes derived miRNA-136, miRNA-494 and miRNA-495 could be promising circulating biomarkers in early detection of PE. Furthermore, UCMSCs released exosomes miRNA-136, miRNA-494 and miRNA-495 genes expression confirmed peripheral blood results analysis.

Roles of microRNAs in preeclampsia

Preeclampsia (PE) is a complex disorder that is characterized by hypertension and proteinuria after the 20th week of pregnancy, and it causes most neonatal morbidity and perinatal mortality. Most studies suggest that placental dysfunction is the main cause of PE. However, genetic factors, immune factors, and systemic inflammation are also related to the pathophysiology of this syndrome. Thus far, the exact pathogenesis of PE is not yet fully understood, and intense research efforts are focused on PE to elucidate the pathophysiological mechanisms. MicroRNAs (miRNAs) refer to small single-stranded and noncoding molecules that can negatively regulate gene expression, and miRNA regulatory networks play an important role in diverse pathological processes. Many studies have confirmed deregulated miRNA in pregnant patients with PE, and the function and mechanism of these differentially expressed miRNA are gradually being revealed. In this review, we summarize the current research about miRNA involved in PE, including placenta-specific miRNA, their predictive value, and their function in the development of PE. This review will provide fundamental evidence of miRNA in PE, and further studies are necessary to explore the roles of miRNA in the early diagnosis and treatment of PE.

Cardiac remodeling and pre-eclampsia: an overview of microRNA expression patterns

Pre-eclampsia (PE) is strongly associated with heart failure (HF) later in life. During PE pregnancy, the left ventricle undergoes concentric remodeling which often persists after delivery. This aberrant remodeling can induce a molecular signature that can be evaluated in terms of microRNAs (miRNAs) and which may help to explain the associated increased risk of HF. For this review, we performed a literature search of PubMed (National Center for Biotechnology Information), identifying studies on miRNA expression in concentric remodeling and on miRNA expression in PE. The miRNA data were stratified based on origin (isolated from humans or animals and from tissue or the circulation) and both datasets compared in order to generate a list of miRNA expression patterns in concentric remodeling and in PE. The nine miRNAs identified in both concentric remodeling and PE-complicated pregnancy were: miR-1, miR-18, miR-21, miR-29b, miR-30, miR-125b, miR-181b, miR-195 and miR-499-5p. We found five of these miRNAs (miR-18, miR-21, miR-125b, miR-195 and miR-499-5p) to be upregulated in both PE pregnancy and cardiac remodeling and two (miR-1 and miR-30) to be downregulated in both; the remaining two miRNAs (miR-29b and miR-181b) showed upregulation during PE but downregulation in cardiac remodeling. This innovative approach may be a step towards finding relevant biomarkers for complicated pregnancy and elucidating their relationship with remote cardiovascular disease. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Differentially expressed microRNAs in experimental cerebral malaria and their involvement in endocytosis, adherens junctions, FoxO and TGF-β signalling pathways

Cerebral malaria (CM) is the most severe manifestation of infection with Plasmodium, however its pathogenesis is still not completely understood. microRNA (miRNA) have been an area of focus in infectious disease research, due to their ability to affect normal biological processes, and have been shown to play roles in various viral, bacterial and parasitic infections, including malaria. The expression of miRNA was studied following infection of CBA mice with either Plasmodium berghei ANKA (causing CM), or Plasmodium yoelii (causing severe but non-cerebral malaria (NCM)). Using microarray analysis, miRNA expression was compared in the brains of non-infected (NI), NCM and CM mice. Six miRNA were significantly dysregulated between NCM and CM mice, and four of these, miR-19a-3p, miR-19b-3p, miR-142-3p and miR-223-3p, were further validated by qPCR assays. These miRNA are significantly involved in several pathways relevant to CM, including the TGF-β and endocytosis pathways. Dysregulation of these miRNA during CM specifically compared with NCM suggests that these miRNA, through their regulation of downstream targets, may be vitally involved in the neurological syndrome. Our data implies that, at least in the mouse model, miRNA may play a regulatory role in CM pathogenesis.

Correlation of miRNA and VEGF expression with the outcome of early-onset severe preeclampsia in patients receiving expectant treatment

The present study was planned to explore the relationship between miRNA and VEGF expression in serum as well as placenta tissue with the outcome of early-onset severe preeclampsia (EOSP) in patients receiving expectant treatment. Sixty EOSP patients who had expectant treatment indications were divided into the success group (n = 46) and the failure group (n = 14) according to the pregnancy outcomes. miR-210 and miR-155 expression levels were studied in serum, ante partum, and in placenta tissue. The vascular endothelial growth factor (VEGF) and soluble VEGF receptor 1 (sFlt-1) expression levels were also explored. miR-210 and miR-155 expression levels in serum and placenta tissue before treatment, ante partum, and after accouchement of the success group were significantly lower than those of the failure group. Further, VEGF expression levels in serum and placenta tissue before treatment, ante partum, and after accouchement of the success group were significantly higher than those of the failure group. However, sFlt-1 expression levels in the success group showed a decrease in comparison to the failure group. The increase of miR-210, miR-155 levels, sFlt-1 levels, and the decrease of VEGF levels in EOSP patients might be correlated with the failure of expectant treatment.

Differential expression profiles of circulating microRNAs in newborns associated to maternal pregestational overweight and obesity

BACKGROUND

The perinatal environment has a role in the establishment of altered metabolic and inflammatory responses, and could be modulated by microRNAs regulating immune and metabolic processes.

OBJECTIVE

To analyze the expression profile of four circulating microRNAs and cytokine serum concentrations in neonates born to overweight and obese women.

METHODS

Pregnant women were included and grouped by pregestational body mass index (21 with normal weight, 10 overweight and 10 obese women). A peripheral blood sample was obtained from newborn infants and used to determine circulating miRNAs expression and cytokine serum concentrations.

RESULTS

There were significant differences in the expression of three microRNAs between newborns of pregestational obese women and newborns from pregestational normal weight women: miR-155 (p = 0.03), miR-181a (p = 0.02) and miR-221 (p = 0.04). A significant reduction in IL-1β (p = 0.005) expression was also found in newborns of overweight women; although this cytokine was also diminished in newborns of obese women, this was not statistically significant. An association between IL-1β concentrations and miR-146a and miR-221 expression was also observed.

CONCLUSIONS

Expression of miR-155, miR-181a and miR-221 differs in infants born to obese women compared with infants born to normal weight women. Changes in microRNA expression could participate in the epigenetic foetal programming of metabolic disorders in children born to obese women.

MicroRNA expression profiling in placenta and maternal plasma in early pregnancy loss

Early pregnancy loss (EPL), also termed early miscarriage, is determined as the unintentional expulsion of an embryo or fetus prior to the 12th week of gestation. EPL frequency is ~15% in pregnancies. Fetal development and growth is associate with placental function and vessel development; therefore, the placental genome would represent a useful miscarriage model for (epi)genetic and genomic studies. An important factor of placental development and function is epigenetic regulation of gene expression. microRNAs (miRNAs) are the primary epigenetic regulators which have an important role in placental development and function. In the present study, maternal plasma and villous tissue were collected from 16 EPL cases in 6th-8th gestational weeks (GWs) and 8 abortions (control group) in 6th-8th GWs. Detection of the differences in miRNA expression was performed using microarrays and dysregulated miRNAs were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). miRNA microarray findings revealed that four miRNAs, including hsa-miRNA (miR)-125a-3p, hsa-miR-3663-3p, hsa-miR-423-5p and hsa-miR-575 were upregulated in tissue samples. In maternal plasma, two miRNAs (hsa-let-7c, hsa-miR-122) were upregulated and one miRNA (hsa-miR-135a) was downregulated. A total of 6 out of 7 dysregulated miRNAs were validated using RT-qPCR. The target genes of these dysregulated miRNAs were detected using the GeneSpring database. The aim of the present study was to detect dysregulated miRNAs in maternal plasma and villous cells and identify the target genes of dysregulated miRNAs and their associated pathways. The target gene analyses have revealed that the affected genes are primarily associated with cell migration, proliferation, implantation, adhesion, angiogenesis and differentiation and all are involved with EPL pathogenesis. Therefore, the present study may contribute to the understanding of the molecular mechanisms which lead to EPL.

Circulating levels of specific members of chromosome 19 microRNA cluster are associated with preeclampsia development

PURPOSE

To perform serum microRNA expression profiling to identify members of chromosome 19 miRNA cluster involved in preeclampsia development.

METHODS

Serum chromosome 19 miRNA cluster microRNA expression profiling was evaluated at 12, 16, and 20 gestational weeks and at the time of preeclampsia diagnosis, in women who developed preeclampsia (WWD-PE; n = 16) and controls (n = 18) using TaqMan low density array plates.

RESULTS

A total of 51 chromosome 19 microRNA cluster members were evaluated. The circulating hsa-miRs 512-3p, 518f-3p, 520c-3p, and 520d-3p, were differentially expressed between groups (P < 0.05). Compared with controls, serum levels of hsa-miR-518f-3p at 20 GW were useful for identifying WWD-Mild-PE (P = 0.035) and WWD-Severe-PE (P = 0.007).

CONCLUSIONS

Serum hsa-miRs 512-3p, 518f-3p, 520c-3p, and 520d-3p, are differentially expressed between WWD-PE and controls and their role in the development of preeclampsia should be investigated further.

Maternal Circulating microRNAs and Pre-Eclampsia: Challenges for Diagnostic Potential

Pre-eclampsia (PE) is a common hypertensive disorder of pregnancy with a significant impact on maternal and neonatal mortality and morbidity. While the pathogenesis of PE has been well described, identification of a biomarker(s) with robust predictive utility in identifying women at the highest risk of developing the condition has yet to be identified. In the search for diagnostic markers, those that may be obtained from the circulation are preferred alternatives to those derived from organ tissue samples. Because of their stability in plasma, microRNAs (miRNAs) have been explored as biomarkers in a host of disease states, although there is comparably little literature available on the circulating miRNAome of PE. This article provides a narrative review on the current state of knowledge on miRNAs associated with PE. Literature on circulating miRNAs is presented and the challenges to developing the diagnostic and prognostic utility of miRNAs in this context is discussed.

Second trimester extracellular microRNAs in maternal blood and fetal growth: An exploratory study

Healthy feto-maternal communication is critical during pregnancy and is orchestrated by the placenta. Dysfunction of the placenta leads to fetal growth complications; however, the underlying biological mechanisms have yet to be fully elucidated. Circulating extracellular microRNAs (exmiRNAs) in the blood have been implicated in cell-to-cell communication. Therefore, exmiRNAs may provide useful biological information about communication between the mother, the fetus, and the placenta during pregnancy. We used logistic regression to determine the association of exmiRNAs with abnormal fetal growth by comparing mothers of infants classified as small-for-gestational age (SGA) (n = 36) and large-for-gestational age (LGA) (n = 13) to appropriate-for-gestational age (AGA), matched by gestational age at delivery and infant sex. In addition, we used linear regression to determine associations between exmiRNAs and birth weight-for-gestational age (BWGA) z-score (n = 100), adjusting for maternal age, body mass index, and parity. We found that higher levels of miR-20b-5p, miR-942-5p, miR-324-3p, miR-223-5p, and miR-127-3p in maternal serum were associated with lower odds for having a SGA vs. AGA infant, and higher levels of miR-661, miR-212-3p, and miR-197-3p were associated with higher odds for having a LGA vs. AGA infant. We also found associations between miR-483-5p, miR-10a-5p, miR-204-5p, miR-202-3p, miR-345-5p, miR-885-5p, miR-127-3p, miR-148b-3p, miR-324-3p, miR-1290, miR-597-5p, miR-139-5p, miR-215-5p, and miR-99b-5p and BWGA z-score. We also found sex-specific associations with exmiRNAs and fetal growth. Our findings suggest that exmiRNAs circulating in maternal blood at second trimester are associated with fetal growth. Validation of our findings may lead to the development of minimally-invasive biomarkers of fetal growth during pregnancy.

Placental Exosomes as Early Biomarker of Preeclampsia: Potential Role of Exosomal MicroRNAs Across Gestation

CONTEXT

There is a need to develop strategies for early prediction of patients who will develop preeclampsia (PE) to establish preventive strategies to reduce the prevalence and severity of the disease and their associated complications.

OBJECTIVE

The objective of this study was to investigate whether exosomes and their microRNA cargo present in maternal circulation can be used as early biomarker for PE.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

A retrospective stratified study design was used to quantify total exosomes and placenta-derived exosomes present in maternal plasma of normal (n = 32 per time point) and PE (n = 15 per time point) pregnancies. Exosomes present in maternal circulation were determined by nanoparticle tracking analysis. An Illumina TruSeq® Small RNA Library Prep Kit was used to construct a small RNA library from exosomal RNA obtained from plasma samples.

RESULTS

In presymptomatic women, who subsequently developed PE, the concentration of total exosomes and placenta-derived exosomes in maternal plasma was significantly greater than those observed in controls, throughout pregnancy. The area under the receiver operating characteristic curves for total exosome and placenta-derived exosome concentrations were 0.745 ± 0.094 and 0.829 ± 0.077, respectively. In total, over 300 microRNAs were identified in exosomes across gestation, where hsa-miR-486-1-5p and hsa-miR-486-2-5p were identified as the candidate microRNAs.

CONCLUSIONS

Although the role of exosomes during PE remains to be fully elucidated, we suggest that the concentration and content of exosomes may be of diagnostic utility for women at risk for developing PE.

Early first trimester peripheral blood cell microRNA predicts risk of preterm delivery in pregnant women: Proof of concept

Objective

We investigated the capacity of first trimester peripheral blood mononuclear cell (PBMC) microRNA to determine risk of spontaneous preterm birth among pregnant women.

Study design

The study included 39 pregnant women with the following delivery outcomes: 25 with a full term delivery (38–42 weeks gestation) 14 with spontaneous preterm birth (<38 weeks gestation). Of the 14 women experiencing spontaneous preterm birth, 7 delivered at 34-<38 weeks gestation (late preterm) and 7 delivered at <34 weeks gestation (early preterm). Samples were collected at a mean of 7.9±3.0 weeks gestation. Quantitative rtPCR was performed on 30 selected microRNAs. MicroRNA Risk Scores were calculated and Area-Under the Curve-Receiver-Operational-Characteristic (AUC-ROC) curves derived.

Results

The AUC-ROC for the group delivering preterm (<38 weeks) was 0.95 (p>0.0001). The AUC-ROC for early preterm group (<34 weeks) was 0.98 (p<0.0001) and the AUC-ROC for the late preterm group (34-<38 weeks) was 0.92 (p<0.0001).

Conclusion

Quantification of first trimester peripheral blood PBMC MicroRNA may provide sensitive and specific prediction of spontaneous preterm birth in pregnant women. Larger studies are needed for confirmation.

Circulating microRNA expression as predictor of preeclampsia and its severity

Preeclampsia (PE) is a pregnancy syndrome characterized by hypertension and proteinuria, and a leading cause of maternal and fetal morbidity and mortality, with poorly defined pathophysiological mechanisms remain. Circulating microRNAs (miRNAs) are small, noncoding RNA molecules, which negatively regulate gene expression, and considered as promising biomarkers for PE. The objective of the study was to evaluate circulating miRNA signatures in women with PE compared to healthy women, and in women sub-grouped per PE severity. This study assessed miRNA expression profile in the plasma of 15 women with PE (7 mild and 8 severe) compared to 7 women with uncomplicated pregnancies. Circulating miRNA was extracted from maternal plasma, and the differential expression of 84 miRNA species were determined using customized pathway-focused miRNA profiler kits. A set of 7 miRNAs that were differentially expressed in PE patients and in mild vs. severe PE cases subgroups. These included miR-215, miR-155, miR-650, miR-210, miR-21 which were upregulated, and miR-18a, miR-19b1 were downregulated in women with PE compared to control women, and between women with severe PE compared to mild PE. In addition, four novel miRNAs comprising miR-518b and miR-29a which were upregulated, and miR-144, miR-15b which were downregulated in severe PE compared to mild PE. This study for the first time presents the differential expression profile of circulating miRNAs according to the severity of the disease. The results confirm the contribution of miRNA to PE pathogenesis, as well as being predictors of the severity of PE.

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.

Matrix Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy is associated with marked hemodynamic and uterine changes that allow adequate uteroplacental blood flow and uterine expansion for the growing fetus. These pregnancy-associated changes involve significant uteroplacental and vascular remodeling. Matrix metalloproteinases (MMPs) are important regulators of vascular and uterine remodeling. Increases in MMP-2 and MMP-9 have been implicated in vasodilation, placentation, and uterine expansion during normal pregnancy. The increases in MMPs could be induced by the increased production of estrogen and progesterone during pregnancy. MMP expression/activity may be altered during complications of pregnancy. Decreased vascular MMP-2 and MMP-9 may lead to decreased vasodilation, increased vasoconstriction, hypertensive pregnancy, and preeclampsia. Abnormal expression of uteroplacental integrins, cytokines, and MMPs may lead to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate remodeling of spiral arteries, and reduced uterine perfusion pressure (RUPP). RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic vascular endothelial growth factor and placental growth factor, or stimulate the release of inflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could target MMPs in the extracellular matrix as well as endothelial and vascular smooth muscle cells, causing generalized vascular dysfunction, increased vasoconstriction and hypertension in pregnancy. MMP activity can also be altered by endogenous tissue inhibitors of metalloproteinases (TIMPs) and changes in the MMP/TIMP ratio. In addition to their vascular effects, decreases in expression/activity of MMP-2 and MMP-9 in the uterus could impede uterine growth and expansion and lead to premature labor. Understanding the role of MMPs in uteroplacental and vascular remodeling and function could help design new approaches for prediction and management of preeclampsia and premature labor.

Blood laboratory testing for early prediction of preeclampsia: chasing the finish line or at the starting blocks?

Preeclampsia (PE) affects 2-8% of pregnancies worldwide, thus representing an important cause of maternal and neonatal morbidity, up to death. Many studies have been designed to identify putative biomarkers for accurate and timely diagnosing PE, but only some of them were focused on specific and sensitive biomarkers for early prediction of this life-threatening condition. In particular, some prospective studies aimed to investigate the predictive role of circulating biomarkers before 20 weeks of gestation in the general pregnant population yielded conflicting results. This article is hence centered on results obtained in studies investigating the predictive performances of angiogenic, anti-angiogenic, inflammatory, endocrine, and epigenetic biomarkers. The available evidence suggests that angiogenic and anti-angiogenic molecules, in particular the sFlt1:PlGF ratio, may be considered the biomarkers with the best diagnostic performance in the second trimester. However, doubts remain about their use in clinical settings before the 20th gestational week. Even lower evidence is available for other biomarkers, due to the fact that some positive results have not been confirmed in ensuing investigations, whereas unresolved analytical issues still contribute to make their clinical reliability rather questionable. Differential expression of microRNAs seems also a promising evidence for early prediction of PE, but additional research and well-designed prospective studies are needed to identify and validate routine predictive tests. KEY MESSAGES Preeclampsia affects 2-8% of pregnant women worldwide, thus remaining one of the leading causes of maternal and neonatal morbidity and mortality. Several studies have investigated the predictive role of circulating biomarkers before 20th week of gestation with conflicting results. Additional research and well-designed prospective studies are needed to identify and validate predictive tests in clinical practice.

MiR-942 decreased before 20 weeks gestation in women with preeclampsia and was associated with the pathophysiology of preeclampsia in vitro

OBJECTIVE

To investigate the possible relationship between miR-942 levels and the pathogenesis of preeclampsia using in vitro assays and to investigate circulating miR-942 levels in the early phase of mid-of pregnancy in women who later developed preeclampsia and in women with uncomplicated pregnancies.

METHODS

Plasma samples were collected from pregnant women between 12 and 20 weeks of gestation. MiR-942 levels were determined by stem-loop real-time PCR for 26 cases who subsequently developed preeclampsia as well as for 52 controls. Bioinformatics software was used to predict the target genes of miR-942, and a dual-luciferase reporter system was utilized to validate target gene regulation. Finally, MTT proliferation assays, transwell invasion assays, and endothelial cell tube formation assays were performed to further explore the function of miR-942 using a human extravillous trophoblast cell line (TEV-1).

RESULT

Circulating miR-942 levels were significantly lower in mid-pregnancy (12-20 weeks gestation) in women who later developed preeclampsia compared with those with an uncomplicated pregnancy (p < 0.05). Endoglin (ENG) is an miR-942 target gene. MiR-942 had a sensitivity of 0.673, a specificity of 0.875, and an area under the receiver operating characteristic curve (AUC) of 0.718 [95% CI, 0.594-0.822] for the possible screening of preeclampsia. In vitro, decreased miR-942 expression decreased the invasive ability of TEV-1 cells, and inhibited the HUVEC angiogenesis assay, both effects that are similar to what is observed in preeclampsia (both p <0.05).

CONCLUSION

MiR-942 may be involved in the pathogenesis of preeclampsia via the regulation of its target gene ENG. Multicenter studies must be performed and a greater number of samples must be analyzed to ascertain whether circulating miR-942 levels can serve as a novel early diagnostic marker for preeclampsia.

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.