Circulating mRNA for epidermal growth factor-like domain 7 (EGFL7) in maternal blood and early intrauterine growth restriction. A preliminary analysis

Evaluation Of Epidermal Growth Factor-Like Domain (EGFL7) mRNA Expression and its Protein Level in Preeclampsia

Objectives

To evaluate the mRNA expression of epidermal growth factor-like domain 7 (EGFL7) in maternal blood and its protein level in sera of pregnant women complicated with preeclampsia (PE).

Method

Case-control study involving 25 pregnant women diagnosed with PE (cases) and 25 gestational age-matched normal pregnant women (controls). EGFL7 mRNA expression in normal and PE patients was quantified by (qRT-PCR), and EGFL7 protein level was estimated using ELISA.

Results

The RQ values of EGFL7 in the PE group were significantly higher than in the NC group (P < 0.001). Pregnancies affected with PE showed higher serum EGFL7 protein compared with matched controls (P < 0.001). EGFL7 serum level cutoff value ≥ 38.25 µg/ml could be used in the diagnosis of PE with sensitivity = 92%, and specificity = 88%.

Conclusion

EGFL7 mRNA is overexpressed in maternal blood of pregnancies complicated with preeclampsia. Serum EGFL7 protein is elevated in PE cases and can be used as a diagnostic marker for preeclampsia.

Epigenetics Beyond Fetal Growth Restriction: A Comprehensive Overview

Fetal growth restriction is a pathological condition occurring when the fetus does not reach the genetically determined growth potential. The etiology of fetal growth restriction is expected to be multifactorial and include fetal, maternal, and placental factors, the latter being the most frequent cause of isolated fetal growth restriction. Severe fetal growth restriction has been related to both an increased risk of perinatal morbidity and mortality, and also a greater susceptibility to developing diseases (especially cardio-metabolic and neurological disorders) later in life. In the last decade, emerging evidence has supported the hypothesis of the Developmental Origin of Health and Disease, which states that individual developmental 'programming' takes place via a delicate fine tuning of fetal genetic and epigenetic marks in response to a large variety of 'stressor' exposures during pregnancy. As the placenta is the maternal-fetal interface, it has a crucial role in fetal programming, such that any perturbation altering placental function interferes with both in-utero fetal growth and also with the adult life phenotype. Several epigenetic mechanisms have been highlighted in modulating the dynamic placental epigenome, including alterations in DNA methylation status, post-translational modification of histones, and non-coding RNAs. This review aims to provide a comprehensive and critical overview of the available literature on the epigenetic background of fetal growth restriction. A targeted research strategy was performed using PubMed, MEDLINE, Embase, and The Cochrane Library up to January 2022. A detailed and fully referenced synthesis of available literature following the Scale for the Assessment of Narrative Review Articles guidelines is provided. A variety of epigenetic marks predominantly interfering with placental development, function, and metabolism were found to be potentially associated with fetal growth restriction. Available evidence on the role of environmental exposures in shaping the placental epigenome and the fetal phenotype were also critically discussed. Because of the highly dynamic crosstalk between epigenetic mechanisms and the extra level of complexity in interpreting the final placental transcriptome, a full comprehension of these phenomenon is still lacking and advances in multi-omics approaches are urgently needed. Elucidating the role of epigenetics in the developmental origins of health and disease represents a new challenge for the coming years, with the goal of providing early interventions and prevention strategies and, hopefully, new treatment opportunities.

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.

Blood-based biomarkers in the maternal circulation associated with fetal growth restriction

Fetal growth restriction (FGR) is associated with threefold to fourfold increased risk of stillbirth. Identifying FGR, through its commonly used surrogate-the small-for-gestational-age (SGA, estimated fetal weight and/or abdominal circumference <10th centile) fetus-and instituting fetal surveillance and timely delivery decrease stillbirth risk. Methods available to clinicians for antenatal identification of SGA fetuses have surprisingly poor sensitivity. About 80% of cases remain undetected. Measuring the symphysis-fundal height detects only 20% of SGA fetuses, and even universal third trimester ultrasound detects, at best, 57% of those born SGA. There is an urgent need to find better ways to identify this at-risk cohort. This review summarises efforts to identify molecular biomarkers (proteins, metabolites, or ribonucleic acids) that could be used to better predict FGR. Most studies examining potential biomarkers to date have utilised case-control study designs without proceeding to validation in independent cohorts. To develop a robust test for FGR, large prospective studies are required with a priori validation plans and cohorts. Given that current clinical care detects 20% of SGA fetuses, even a screening test with ≥60% sensitivity at 90% specificity could be clinically useful, if developed. This may be an achievable aspiration. If discovered, such a test may decrease stillbirth.

EGFL7 gene expression is regulated by hypoxia in trophoblast and altered in the plasma of patients with early preeclampsia

INTRODUCTION

Preeclampsia is a severe complication of pregnancy, and likely arises from abnormal placental development in early pregnancy. Persistent placental hypoxia is thought to trigger the release of anti-angiogenic factors into the maternal circulation leading to widespread endothelial dysfunction. Epidermal growth factor-like domain 7 (EGFL7) is a secreted angiogenic factor that may play a key role in the disrupted angiogenesis seen in response to placental hypoxia that characterizes preeclampsia.

METHODS

Primary trophoblasts were isolated and cultured in both normoxic and hypoxic conditions. Under hypoxia HIF1α was silenced and EGFL7 mRNA expression was assessed. EGFL7 mRNA expression was measured in placentas obtained from women with early (<34 weeks) and late onset preeclampsia; and in peripheral whole blood maternal samples from women with preeclampsia and gestation matched controls. EGFL7 plasma levels were assessed in plasma from women with preeclampsia, compared to gestation-matched controls.

RESULTS

EGFL7 expression was significantly upregulated in primary human trophoblasts cultured in hypoxia (>2-fold, p < 0.0001), however this was not regulated via a HIF1α dependent manner. EGFL7 mRNA expression was not altered in placenta from women with early or late onset preeclampsia. Circulating EGFL7 protein levels were not different in women with severe preeclampsia. In contrast, EGFL7 mRNA expression was increased in maternal blood in women with early onset preeclampsia (∼1.6-fold, p < 0.05).

DISCUSSION

EGFL7 mRNA expression is increased with hypoxia in human trophoblast and is increased in the maternal circulation in women with preeclampsia. Further studies aimed at understanding the role and regulation of EGLF7 in the pathophysiology of preeclampsia are required.

Altered feto-placental vascularization, feto-placental malperfusion and fetal growth restriction in mice with Egfl7 loss of function

EGFL7 is a secreted angiogenic factor produced by embryonic endothelial cells. To understand its role in placental development, we established a novel Egfl7 knockout mouse. The mutant mice have gross defects in chorioallantoic branching morphogenesis and placental vascular patterning. Microangiography and 3D imaging revealed patchy perfusion of Egfl7^-/- placentas marked by impeded blood conductance through sites of narrowed vessels. Consistent with poor feto-placental perfusion, Egfl7 knockout resulted in reduced placental weight and fetal growth restriction. The placentas also showed abnormal fetal vessel patterning and over 50% reduction in fetal blood space. In vitro, placental endothelial cells were deficient in migration, cord formation and sprouting. Expression of genes involved in branching morphogenesis, Gcm1, Syna and Synb, and in patterning of the extracellular matrix, Mmrn1, were temporally dysregulated in the placentas. Egfl7 knockout did not affect expression of the microRNA embedded within intron 7. Collectively, these data reveal that Egfl7 is crucial for placental vascularization and embryonic growth, and may provide insight into etiological factors underlying placental pathologies associated with intrauterine growth restriction, which is a significant cause of infant morbidity and mortality.

The expression of epidermal growth factor-like domain 7 regulated by oxygen tension via hypoxia inducible factor (HIF)-1α activity

OBJECTIVE

Hypoxia inducible factor-1α (HIF-1α) regulates many genes involved in angiogenesis during embryonic development. Epidermal growth factor-like domain 7 (Egfl7) is a specific marker for human arterial endothelial cells that are in an activated state of proliferation, migration, and remodeling. This study evaluates the intricate relationship between HIF-1α and Egfl7 under both hyperoxia and hypoxia states.

METHODS

The neonatal mice were exposed to either hyperoxia or hypoxia in order to detect the pulmonary and cardiac Egfl7 messenger RNA (mRNA) or protein expression regulated by oxygen tension in vivo by reverse transcriptase polymerase chain reaction or immunohistochemistry staining. Egfl7 expression in HIF-1α null pulmonary endothelial cells in hypoxia conditions and effects of overexpression or knockdown of HIF-1α on Egfl7 expression in human umbilical vein endothelial cells would be clarified in vitro by reverse transcriptase polymerase chain reaction and Western blot, respectively.

RESULTS

Hyperoxia exposure significantly reduced Egfl7 expression in neonatal mice lungs by 36% compared with age-matched normoxia control mice (P < 0.05, n = 6). The pulmonary Egfl7 transcription levels were increased by 1.7- and 1.9-fold in 24 hours and by day 8 in hypoxia groups compared with the normoxia control values (P < 0.05, n = 6). The cardiac Egfl7 mRNA expression was significantly increased by 4.5-fold in the day 8 group compared with the normoxia control values (P < 0.05, n = 6). The expression of Egfl7 decreased significantly in the HIF-1α(-/-) endothelial cells (ECs), which was only 26% of wild-type HIF-1α(+/+) ECs (P < 0.05, n = 3). Hypoxia caused a mild but significant increase of Egfl7 expression in HIF-1α(+/+) ECs (P < 0.05). In vitro, overexpression of HIF-1α enhanced Egfl7 expression, whereas knockdown of HIF-1α reduced Egfl7 expression.

CONCLUSIONS

Overexpression of HIF-1α enhanced Egfl7 expression, whereas knockdown of HIF-1α reduced Egfl7 expression. Egfl7 could be a HIF-1α responsive gene regulated by oxygen tension.

The Role of RNAs and microRNAs in Non-Invasive Prenatal Diagnosis

In this paper, all possible clinical applications of circulating mRNA and miRNA for non-invasive prenatal diagnosis appearing in the medical literature so far are described. Data from the literature have also been reported and commented on along with some possible future applications.