Current controversies in prenatal diagnosis 4: pregnancy complications due to placental vascular disease (pre-eclampsia, FGR): are we ready for prevention?

Extracellular Vesicles and Preeclampsia: Current Knowledge and Future Research Directions

Preeclampsia (PE) is associated with long-term morbidity in mothers and lifelong morbidities for their children, ranging from cerebral palsy and cognitive delay in preterm infants, to hypertension, diabetes and obesity in adolescents and young adults. There are several processes that are critical for development of materno-fetal exchange, including establishing adequate perfusion of the placenta by maternal blood, and the formation of the placental villous vascular tree. Recent studies provide persuasive evidence that placenta-derived extracellular vesicles (EVs) represent a significant intercellular communication pathway, and that they may play an important role in placental and endothelial cell (both fetal and maternal) function. These functions are known to be altered in PE. EVs can carry and transport a wide range of bioactive molescules that have potential to be used as biomarkers and therapeutic delivery tools for PE. EV content is often parent cell specific, thus providing an insight or "thumbprint" of the intracellular environment of the originating cell (e.g., human placenta). EV have been identified in plasma under both normal and pathological conditions, including PE. The concentration of EVs and their content in plasma has been reported to increase in association with disease severity and/or progression. Placenta-derived EVs have been identified in maternal plasma during normal pregnancy and PE pregnancies. They contain placenta-specific proteins and miRNAs and, as such, may be differentiated from maternally-derived EVs. The aim of this review, thus, is to describe the potential roles of EVs in preecmpatic pregnancies, focussing on EVs secreted from placental cells. The biogenesis, specificity of placental EVs, and methods used to characterise EVs in the context of PE pregnancies will be also discussed.

Molecular Targets of Aspirin and Prevention of Preeclampsia and Their Potential Association with Circulating Extracellular Vesicles during Pregnancy

Uncomplicated healthy pregnancy is the outcome of successful fertilization, implantation of embryos, trophoblast development and adequate placentation. Any deviation in these cascades of events may lead to complicated pregnancies such as preeclampsia (PE). The current incidence of PE is 2–8% in all pregnancies worldwide, leading to high maternal as well as perinatal mortality and morbidity rates. A number of randomized controlled clinical trials observed the association between low dose aspirin (LDA) treatment in early gestational age and significant reduction of early onset of PE in high-risk pregnant women. However, a substantial knowledge gap exists in identifying the particular mechanism of action of aspirin on placental function. It is already established that the placental-derived exosomes (PdE) are present in the maternal circulation from 6 weeks of gestation, and exosomes contain bioactive molecules such as proteins, lipids and RNA that are a “fingerprint” of their originating cells. Interestingly, levels of exosomes are higher in PE compared to normal pregnancies, and changes in the level of PdE during the first trimester may be used to classify women at risk for developing PE. The aim of this review is to discuss the mechanisms of action of LDA on placental and maternal physiological systems including the role of PdE in these phenomena. This review article will contribute to the in-depth understanding of LDA-induced PE prevention.

Unmethylated-maspin DNA in maternal plasma is associated with severe preeclampsia

INTRODUCTION

Cell-free fetal DNA in maternal plasma is associated with complications of pregnancy, including preeclampsia. Determination of levels is affected by fetal gender and genetic polymorphisms. Unmethylated maspin (u-maspin) is present in the placenta, and is placental-specific. The purpose of this study was to determine whether u-maspin DNA in maternal blood could serve as a marker of preeclampsia by measuring levels in different trimesters of normal pregnancies and in those complicated by preeclampsia.

MATERIAL AND METHODS

This case-control study was set in a tertiary care hospital. The population consisted of 45 women with normal pregnancies (15 in the 1st trimester, 15 in the 2nd trimester, 15 in the 3rd trimester), 20 women with mild preeclampsia, 25 women with severe preeclampsia, and six women with gestational trophoblastic disease. Peripheral blood was collected and methylation-specific PCR and fluorescence quantitative PCR were performed to measure the content of u-maspin DNA in maternal blood.

RESULTS

U-maspin DNA was 5.5-fold higher in women with severe preeclampsia than in those with a normal 3rd trimester pregnancy (p < 0.05). During normal pregnancy, u-maspin DNA in maternal plasma tended to increase with advancing gestational age (p = 0.06). U-maspin DNA was not detected in healthy non-pregnant women or those with gestational trophoblastic disease.

CONCLUSION

U-maspin DNA in maternal blood is associated with severe preeclampsia.

New directions in the prediction of pre-eclampsia

Pre-eclampsia remains an important worldwide cause of maternal and perinatal morbidity and mortality. Improved prediction of those destined to develop this condition would allow for timely initiation of prophylactic therapy, appropriate antenatal surveillance and better targeted research into preventive interventions. This paper reviews recent research into strategies for the prediction of pre-eclampsia, including the use of maternal risk factors, mean maternal arterial pressure, ultrasound parameters and biomarkers. The most promising strategies involve multiparametric approaches, which use a variety of individual parameters in combination, as has been established in first-trimester aneuploidy screening. The paper concludes with a discussion of the issues around the introduction of such testing into clinical practice.