Protein composition of microparticles shed from human placenta during placental perfusion: Potential role in angiogenesis and fibrinolysis in preeclampsia

Mitochondrial-targeted antioxidant attenuates preeclampsia-like phenotypes induced by syncytiotrophoblast-specific Gαq signaling

Syncytiotrophoblast stress is theorized to drive development of preeclampsia, but its molecular causes and consequences remain largely undefined. Multiple hormones implicated in preeclampsia signal via the Gαq cascade, leading to the hypothesis that excess Gαq signaling within the syncytiotrophoblast may contribute. First, we present data supporting increased Gαq signaling and antioxidant responses within villous and syncytiotrophoblast samples of human preeclamptic placenta. Second, Gαq was activated in mouse placenta using Cre-lox and DREADD methodologies. Syncytiotrophoblast-restricted Gαq activation caused hypertension, kidney damage, proteinuria, elevated circulating proinflammatory factors, decreased placental vascularization, diminished spiral artery diameter, and augmented responses to mitochondrial-derived superoxide. Administration of the mitochondrial-targeted antioxidant Mitoquinone attenuated maternal proteinuria, lowered circulating inflammatory and anti-angiogenic mediators, and maintained placental vascularization. These data demonstrate a causal relationship between syncytiotrophoblast stress and the development of preeclampsia and identify elevated Gαq signaling and mitochondrial reactive oxygen species as a cause of this stress.

Missing links in preeclampsia cell model systems of endothelial dysfunction

Preeclampsia, one of the main hypertensive disorders of pregnancy, is associated with circulating factors released by the ischemic placenta accompanied by systemic endothelial dysfunction. The etiology of preeclampsia remains poorly understood although it is associated with high maternal and fetal mortality and increased cardiovascular disease risk. Most cell model systems used for studying endothelial dysfunction have not taken into account hemodynamic physical factors such as shear-stress forces which may prevent extrapolation of cell data to in vivo settings. We overview the role of hemodynamic forces in modulating endothelial cell function and discuss strategies to reproduce this biological characteristic in vitro to improve our understanding of endothelial dysfunction associated with preeclampsia.

Pre-eclampsia

Pre-eclampsia is a life-threatening disease of pregnancy unique to humans and a leading cause of maternal and neonatal morbidity and mortality. Women who survive pre-eclampsia have reduced life expectancy, with increased risks of stroke, cardiovascular disease and diabetes, while babies from a pre-eclamptic pregnancy have increased risks of preterm birth, perinatal death and neurodevelopmental disability and cardiovascular and metabolic disease later in life. Pre-eclampsia is a complex multisystem disease, diagnosed by sudden-onset hypertension (>20 weeks of gestation) and at least one other associated complication, including proteinuria, maternal organ dysfunction or uteroplacental dysfunction. Pre-eclampsia is found only when a placenta is or was recently present and is classified as preterm (delivery <37 weeks of gestation), term (delivery ≥37 weeks of gestation) and postpartum pre-eclampsia. The maternal syndrome of pre-eclampsia is driven by a dysfunctional placenta, which releases factors into maternal blood causing systemic inflammation and widespread maternal endothelial dysfunction. Available treatments target maternal hypertension and seizures, but the only 'cure' for pre-eclampsia is delivery of the dysfunctional placenta and baby, often prematurely. Despite decades of research, the aetiology of pre-eclampsia, particularly of term and postpartum pre-eclampsia, remains poorly defined. Significant advances have been made in the prediction and prevention of preterm pre-eclampsia, which is predicted in early pregnancy through combined screening and is prevented with daily low-dose aspirin, starting before 16 weeks of gestation. By contrast, the prediction of term and postpartum pre-eclampsia is limited and there are no preventive treatments. Future research must investigate the pathogenesis of pre-eclampsia, in particular of term and postpartum pre-eclampsia, and evaluate new prognostic tests and treatments in adequately powered clinical trials.

The role of extracellular vesicles in intercellular communication in human reproduction

Embryo-maternal cross-talk has emerged as a vitally important process for embryo development and implantation, which is driven by secreted factors and extracellular vesicles (EVs). The EV cargo of bioactive molecules significantly influences target cells and primes them for critical stages of reproductive biology, including embryo development, adhesion, and implantation. Recent research has suggested that EVs and their cargo represent a powerful non-invasive tool that can be leveraged to assess embryo and maternal tissue quality during assisted reproduction treatments. Here, we review the current scientific literature regarding the intercellular cross-talk between embryos and maternal tissues from fertilization to implantation, focusing on human biology and signaling mechanisms identified in animal models.

Preeclampsia and syncytiotrophoblast membrane extracellular vesicles (STB-EVs)

Preeclampsia (PE) is a hypertensive complication of pregnancy that affects 2-8% of women worldwide and is one of the leading causes of maternal deaths and premature birth. PE can occur early in pregnancy (<34 weeks gestation) or late in pregnancy (>34 weeks gestation). Whilst the placenta is clearly implicated in early onset PE (EOPE), late onset PE (LOPE) is less clear with some believing the disease is entirely maternal whilst others believe that there is an interplay between maternal systems and the placenta. In both types of PE, the syncytiotrophoblast (STB), the layer of the placenta in direct contact with maternal blood, is stressed. In EOPE, the STB is oxidatively stressed in early pregnancy (leading to PE later in gestation- the two-stage model) whilst in LOPE the STB is stressed because of villous overcrowding and senescence later in pregnancy. It is this stress that perturbs maternal systems leading to the clinical manifestations of PE. Whilst some of the molecular species driving this stress have been identified, none completely explain the multisystem nature of PE. Syncytiotrophoblast membrane vesicles (STB-EVs) are a potential contributor to this multisystem disorder. STB-EVs are released into the maternal circulation in increasing amounts with advancing gestational age, and this release is further exacerbated with stress. There are good in vitro evidence that STB-EVs are taken up by macrophages and liver cells with additional evidence supporting endothelial cell uptake. STB-EV targeting remains in the early stages of discovery. In this review, we highlight the role of STB-EVs in PE. In relation to current research, we discuss different protocols for ex vivo isolation of STB-EVs, as well as specific issues involving tissue preparation, isolation (some of which may be unique to STB-EVs), and methods for their analysis. We suggest potential solutions for these challenges.

Pre-Existing Diabetes Mellitus, Hypertension and KidneyDisease as Risk Factors of Pre-Eclampsia: A Disease of Theories and Its Association with Genetic Polymorphism

Pre-existing diabetes, hypertension and kidney disorders are prominent risk factors of pre-eclampsia (PE). It is a multifactorial pregnancy disorder associated with high blood pressure, proteinuria, and multiorgan failure, which develops after the 20th week of pregnancy. It is one of the most feared pregnancy disorders, as it consumes thousands of fetomaternal lives per annum. According to clinical and pathological studies, the placenta appears to be a key player in the pathogenesis of PE; however, the exact origin of this disorder is still under debate. Defective placentation and angiogenesis are the hallmarks of PE progression. This angiogenic imbalance, together with maternal susceptibility, might determine the severity and clinical presentation of PE. This article comprehensively examines the mechanisms of pathogenesis of PE and current evidence of the factors involved in its progression. Finally, this article will explore the genetic association of PE, various candidate genes, their proposed mechanisms and variants involved in its pathogenesis.

Neuropilin-1 is uniquely expressed on small syncytiotrophoblast extracellular vesicles but not on medium/large vesicles from preeclampsia and normal placentae

Preeclampsia (PE) is a multisystem progressive hypertensive disorder unique to human pregnancy. The placenta is fundamental to its pathogenesis and releases placental factors as well as extracellular vesicles (small and medium/large syncytiotrophoblast extracellular vesicles (STB-EVs)) as a response to syncytiotrophoblast stress such as tissue factor and plasminogen activator inhibitors 1. Neuropilin 1 (NRP-1) is an anti-angiogenic factor involved in development, angiogenesis, arteriogenesis, and vascular permeability. NRP-1 acts as a co-receptor for growth factors such as vascular endothelial growth factor (VEGF), placenta growth factor (PLGF), and epidermal growth factor (EGF). Given the documented pro and anti-angiogenic roles of STB-EVs, we hypothesized that 1) STB-EVs might express NRP-1; and 2) the expression of NRP-1 might differ between normal and preeclampsia STB-EVs.

METHODS

We isolated STB-EVs (both small and medium/large) from PE and NP placentae using the physiologic ex vivo dual lobe perfusion model. The enriched STB-EVs were characterized by Western blot, transmission electron microscopy (TEM), and nanoparticle tracking analysis (NTA) according to the international society of extracellular vesicles (ISEV) guidelines. We assessed for NRP-1 expression with Western blot (placenta and STB-EVs) and immunohistochemistry (placenta). We performed co-expression analysis for placenta alkaline phosphatase (PLAP - a known STB-EV marker) and NRP-1 with immunoprecipitation followed by Western blot.

RESULTS

We confirmed NRP-1 expression in NP and PE placenta. We showed that NRP-1 Expression was limited to small syncytiotrophoblast membrane extracellular vesicles (S STB-EVs) but not medium/large STB-EVs and that NRP-1 is co-expressed with PLAP.

CONCLUSION

Neuropilin-1 is uniquely expressed on small syncytiotrophoblast extracellular vesicles but not on medium/large vesicles from preeclampsia and normal placentae.

In sickness and in health: The functional role of extracellular vesicles in physiology and pathology in vivo: Part I: Health and Normal Physiology: Part I: Health and Normal Physiology

Previously thought to be nothing more than cellular debris, extracellular vesicles (EVs) are now known to mediate physiological and pathological functions throughout the body. We now understand more about their capacity to transfer nucleic acids and proteins between distant organs, the interaction of their surface proteins with target cells, and the role of vesicle-bound lipids in health and disease. To date, most observations have been made in reductionist cell culture systems, or as snapshots from patient cohorts. The heterogenous population of vesicles produced in vivo likely act in concert to mediate both beneficial and detrimental effects. EVs play crucial roles in both the pathogenesis of diseases, from cancer to neurodegenerative disease, as well as in the maintenance of system and organ homeostasis. This two-part review draws on the expertise of researchers working in the field of EV biology and aims to cover the functional role of EVs in physiology and pathology. Part I will outline the role of EVs in normal physiology.

Trophoblasts Modulate the Ca2+ Oscillation and Contraction of Myometrial Smooth Muscle Cells by Small Extracellular Vesicle- (sEV-) Mediated Exporting of miR-25-3p during Premature Labor

The placenta could transmit information to the maternal circulation via the secretion of small extracellular vesicles (sEVs), but little is known about whether and how these sEVs participate in premature labor (PTL). We speculate that miRNA plays an important role in sEV-mediated fetal-maternal information transmission. The present study was aimed at investigating whether the placenta can regulate the contraction of the maternal myometrium via sEV-mediated transmit of miR-25-3p during PTL. The expression of miR-25-3p and its targets Cav3.2 and SERCA2a in clinical samples, cells, and animal specimens was detected. The role of miR-25-3p was observed in the LPS-induced preterm labor mouse model. The sEVs from HTR-8/SVneo cells were characterized by transmission electron microscopy and nanoparticle tracking analysis. The Ca²⁺ oscillation in HMSMs was analyzed by an intracellular Ca²⁺ change tracking assay on a confocal microscope. The contraction of HMSMs was detected by a collagen matrix contraction assay. We found that miR-25-3p can directly bind to the 3′UTR of Cav3.2 and SERCA2a. The miR-25-3p level was decreased, and the expression of its targets Cav3.2 and SERCA2a was increased in the placenta and myometrium tissues of PTL patients. Forced upregulation of miR-25-3p reduced the oxidative stress and inflammation responses and the incidence of PTL in LPS-treated mice. The expression of miR-25-3p was not changed in LPS-stimulated human myometrial smooth muscle cells (HMSMs) but was strongly reduced in the trophoblast cell and its sEVs. Additionally, the trophoblast cell line HTR-8/SVneo could transmit miR-25-3p into HMSMs via sEVs. The sEVs derived from LPS-stimulated trophoblasts upregulated the expression of Cav3.2 and SERCA2a and triggered Ca²⁺ oscillation as well as the contraction of HMSMs; these effects were partially reversed by the overexpression of miR-25-3p in the trophoblasts. Further, the upregulation of miR-25-3p induced changes of Ca²⁺ oscillation and contraction of HMSMs mediated by sEVs which were also abrogated by the knockdown of miR-25-3p in HMSMs. The results demonstrated that miR-25-3p plays a crucial role in PTL via Cav3.2- and SERCA2a-mediated Ca²⁺ oscillation and contraction of HMSMs. PTL seems to be related to the decreased exosomal miR-25-3p content transmitted by the trophoblasts under inflammatory conditions.

Extracellular Vesicles and Antiphospholipid Syndrome: State-of-the-Art and Future Challenges

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by thromboembolism, obstetric complications, and the presence of antiphospholipid antibodies (aPL). Extracellular vesicles (EVs) play a key role in intercellular communication and connectivity and are known to be involved in endothelial and vascular pathologies. Despite well-characterized in vitro and in vivo models of APS pathology, the field of EVs remains largely unexplored. This review recapitulates recent findings on the role of EVs in APS, focusing on their contribution to endothelial dysfunction. Several studies have found that APS patients with a history of thrombotic events have increased levels of EVs, particularly of endothelial origin. In obstetric APS, research on plasma levels of EVs is limited, but it appears that levels of EVs are increased. In general, there is evidence that EVs activate endothelial cells, exhibit proinflammatory and procoagulant effects, interact directly with cell receptors, and transfer biological material. Future studies on EVs in APS may provide new insights into APS pathology and reveal their potential as biomarkers to identify patients at increased risk.

The promise of placental extracellular vesicles: models and challenges for diagnosing placental dysfunction in utero†

Monitoring the health of a pregnancy is of utmost importance to both the fetus and the mother. The diagnosis of pregnancy complications typically occurs after the manifestation of symptoms, and limited preventative measures or effective treatments are available. Traditionally, pregnancy health is evaluated by analyzing maternal serum hormone levels, genetic testing, ultrasonographic imaging, and monitoring maternal symptoms. However, researchers have reported a difference in extracellular vesicle (EV) quantity and cargo between healthy and at-risk pregnancies. Thus, placental EVs (PEVs) may help to understand normal and aberrant placental development, monitor pregnancy health in terms of developing placental pathologies, and assess the impact of environmental influences, such as infection, on pregnancy. The diagnostic potential of PEVs could allow for earlier detection of pregnancy complications via noninvasive sampling and frequent monitoring. Understanding how PEVs serve as a means of communication with maternal cells and recognizing their potential utility as a readout of placental health have sparked a growing interest in basic and translational research. However, to date, PEV research with animal models lags behind human studies. The strength of animal pregnancy models is that they can be used to assess placental pathologies in conjunction with isolation of PEVs from fluid samples at different time points throughout gestation. Assessing PEV cargo in animals within normal and complicated pregnancies will accelerate the translation of PEV analysis into the clinic for potential use in prognostics. We propose that appropriate animal models of human pregnancy complications must be established in the PEV field.

Enrichment and characterization of extracellular vesicles from ex vivo one-sided human placenta perfusion

PROBLEM

Extracellular vesicles (EVs) released by the placenta are packed with biological information and play a major role in fetomaternal communication. Here, we describe a comprehensive set-up for the enrichment and characterization of EVs from human placenta perfusion and their application in further assays.

METHOD OF STUDY

Human term placentas were used for 3 h ex vivo one-sided perfusions to simulate the intervillous circulation. Thereafter, populations of small (sEVs) and large EV (lEVs) were enriched from placental perfusate via serial ultracentrifugation. Following, EV populations were characterized regarding their size, protein concentration, RNA levels, expression of surface markers as well as their uptake and miRNA transfer to recipient cells.

RESULTS

The sEV and lEV fractions from an entire perfusate yielded, respectively, 294 ± 32 µg and 525 ± 96 µg of protein equivalents and 2.6 ± 0.5 µg and 3.6 ± 0.9 µg of RNA. The sEV fraction had a mean diameter of 117 ± 47 nm, and the lEV fraction presented 236 ± 54 nm. CD63 was strongly detected by dot blot in sEVs, whereas only traces of this marker were found in lEVs. Both EV fractions were positive for the trophoblast marker PLAP (placental alkaline phosphatase) and annexin A1. EV internalization in immune cells was visualized by confocal microscopy, and the transfer of placental miRNAs was detected by quantitative real-time PCR (qPCR).

CONCLUSIONS

Enriched EV populations showed characteristic features of sEVs and lEVs. EV uptake and transfer of miRNAs to recipient cells demonstrated their functional integrity. Therefore, we advocate the ex vivo one-sided placenta perfusion as a robust approach for the collection of placental EVs.

Association of placenta-derived extracellular vesicles with pre-eclampsia and associated hypercoagulability: a clinical observational study

OBJECTIVE

Pre-eclampsia (PE) is a pregnancy-associated condition initiated by placental factors. We have demonstrated that placental extracellular vesicles (pcEVs) cause hypertension and proteinuria in pregnant and non-pregnant mice.

STUDY DESIGN

An observational study with both case-control and longitudinal designs.

SETTING

A single centre at the Department of Obstetrics and Gynaecology, Tianjin Medical University.

POPULATION

We collected blood samples and clinical information from 54 PE patients, 33 normally pregnant women at 30-36 gestational weeks and on postpartum days 1 and 4 for the cross-sectional study, and at 22-31, 32-35 and 36-40 weeks for the longitudinal study. Non-pregnant women were also recruited.

METHODS

Blood samples were analysed using flow cytometry, coagulation tests and ELISA.

MAIN OUTCOME MEASURES

The primary outcome was plasma pcEV and other extracellular vesicles (EVs), and their expressions of anionic phospholipids and von Willebrand factor (VWF). Secondary variables included coagulation, ADAMTS-13 and the anionic phospholipid-binding proteins.

RESULTS

Plasma pcEVs progressively increased from pregnant women during non-menstrual period (NW) to PE patients (interquartile range [IQR] for NW: 206/microlitre [116-255], normal pregnancy [NP]: 1108/microlitre [789-1969] and PE: 8487/microlitre [4991-16 752]) and predicted PE. EVs from endothelial cells, platelets and erythrocytes accounted for <10% of pcEVs. VWF became hyper-adhesive in PE patients and contributed to the pregnancy-associated hypercoagulability.

CONCLUSION

Placental, platelet- and endothelial cell-derived EVs were significantly elevated in PE patients, but only pcEVs predicted PE. These EVs played a causal role in the pregnancy-induced hypercoagulability.

TWEETABLE ABSTRACT

Placenta-derived extracellular vesicles predict pre-eclampsia and the associated hypercoagulability.

Laboratory options for risk assessment of pregnancy pathologies

The most effective method of screening for chromosomal abnormalities and evaluating the risk of pregnancy pathologies in the first trimester is combined screening. The algorithm of screening is based on the combination of maternal age, measuring of the nuchal translucency and the fetal heart rate and analysis of the placental products of free ß-hCG and PAPP-A. For the screening of preeclampsia, placental growth factor (PlGF) is added. To distinguish between preeclampsia and other pathologies caused by placental dysfunction it is recommended to also extend the screening with selected immunological markers. We concluded that elevated biochemical and immunological markers can help to predict the threat of preeclampsia in the third trimester. Some markers can probably predict the development of particularly severe pathological conditions.

Antiphospholipid antibodies and extracellular vesicles in pregnancy

Antiphospholipid antibodies (aPL) are autoantibodies that target phospholipid-binding proteins, such as β2 glycoprotein I (β2GPI), and can induce thrombosis systemically, as well as increase the risk of obstetric complications such as recurrent miscarriage and preeclampsia. Due to the expression of β2GPI by placental trophoblasts, aPL readily target the maternal-fetal interface during pregnancy and many studies have investigated the deleterious effects of aPL on placental trophoblast function. This review will focus on studies that have examined the effects of aPL on the production and modification of extracellular vesicles (EVs) from trophoblasts, as EVs are a key mode of feto-maternal communication in both normal and pathological pregnancy. A more comprehensive understanding of the effects of aPL on the quantity and cargo of EVs extruded by the human placenta may contribute to our current knowledge of how aPL induce both systemic and obstetric disease.

Mechanisms of Key Innate Immune Cells in Early- and Late-Onset Preeclampsia

Preeclampsia is a complex cardiovascular disorder of pregnancy with underlying multifactorial pathogeneses; however, its etiology is not fully understood. It is characterized by the new onset of maternal hypertension after 20 weeks of gestation, accompanied by proteinuria, maternal organ damage, and/or uteroplacental dysfunction. Preeclampsia can be subdivided into early- and late-onset phenotypes (EOPE and LOPE), diagnosed before 34 weeks or from 34 weeks of gestation, respectively. Impaired placental development in early pregnancy and subsequent growth restriction is often associated with EOPE, while LOPE is associated with maternal endothelial dysfunction. The innate immune system plays an essential role in normal progression of physiological pregnancy and fetal development. However, inappropriate or excessive activation of this system can lead to placental dysfunction or poor maternal vascular adaptation and contribute to the development of preeclampsia. This review aims to comprehensively outline the mechanisms of key innate immune cells including macrophages, neutrophils, natural killer (NK) cells, and innate B1 cells, in normal physiological pregnancy, EOPE and LOPE. The roles of the complement system, syncytiotrophoblast extracellular vesicles and mesenchymal stem cells (MSCs) are also discussed in the context of innate immune system regulation and preeclampsia. The outlined molecular mechanisms, which represent potential therapeutic targets, and associated emerging treatments, are evaluated as treatments for preeclampsia. Therefore, by addressing the current understanding of innate immunity in the pathogenesis of EOPE and LOPE, this review will contribute to the body of research that could lead to the development of better diagnosis, prevention, and treatment strategies. Importantly, it will delineate the differences in the mechanisms of the innate immune system in two different types of preeclampsia, which is necessary for a more personalized approach to the monitoring and treatment of affected women.

Syncytiotrophoblast-Derived Extracellular Vesicles in Pathophysiology of Preeclampsia

Preeclampsia is a common obstetric complication associated with pregnancy and it endangers lives of the mother and the infant. The histopathological changes associated with preeclampsia include systemic endothelial dysfunction, persistent inflammatory state, and coagulation and fibrinolysis dysregulations. Preeclampsia is considered to be caused by the systemic vasoconstriction of small arteries and disruption of the endothelial integrity, resulting in hypertension, proteinuria, and multiple organ dysfunction. However, mediators that trigger or propagate the pathology of preeclampsia remain poorly defined. Syncytiotrophoblast-derived extracellular vesicles (SDEVs) are increasingly recognized as a key mediator for the development of preeclampsia, but the underlying mechanisms through which these SDEVs are released and induce systemic responses are not fully understood. This review focuses on multiple roles of SDEVs in the pathogenesis of preeclampsia.

SerpinB2 inhibits migration and promotes a resolution phase signature in large peritoneal macrophages

SerpinB2 (plasminogen activator inhibitor type 2) has been called the "undecided serpin" with no clear consensus on its physiological role, although it is well described as an inhibitor of urokinase plasminogen activator (uPA). In macrophages, pro-inflammatory stimuli usually induce SerpinB2; however, expression is constitutive in Gata6+ large peritoneal macrophages (LPM). Interrogation of expression data from human macrophages treated with a range of stimuli using a new bioinformatics tool, CEMiTool, suggested that SerpinB2 is most tightly co- and counter-regulated with genes associated with cell movement. Using LPM from SerpinB2-/- and SerpinB2R380A (active site mutant) mice, we show that migration on Matrigel was faster than for their wild-type controls. Confocal microscopy illustrated that SerpinB2 and F-actin staining overlapped in focal adhesions and lamellipodia. Genes associated with migration and extracellular matrix interactions were also identified by RNA-Seq analysis of migrating RPM from wild-type and SerpinB2R380A mice. Subsequent gene set enrichment analyses (GSEA) suggested SerpinB2 counter-regulates many Gata6-regulated genes associated with migration. These data argue that the role of SerpinB2 in macrophages is inhibition of uPA-mediated plasmin generation during cell migration. GSEA also suggested that SerpinB2 expression (likely via ensuing modulation of uPA-receptor/integrin signaling) promotes the adoption of a resolution phase signature.

Placenta-derived extracellular vesicles induce preeclampsia in mouse models

Preeclampsia is a pregnancy-induced condition that impairs the mother’s health and results in pregnancy termination or premature delivery. Elevated levels of placenta-derived extracellular vesicles (pcEV) in the circulation have been consistently associated with preeclampsia, but whether these vesicles induce preeclampsia or are the product of preeclampsia is not known. Guided by a small cohort study of preeclamptic patients, we examined the impact of pcEV on the pathogenesis of preeclampsia in mouse models. We detected pcEV in pregnant C56BL/6J mice with a peak level of 3.8±0.9×10⁷/mL at 17-18 days post-coitum. However, these pregnant mice developed hypertension and proteinuria only after being infused with vesicles purified from injured placenta. These extracellular vesicles released from injured placenta disrupted endothelial integrity and induced vasoconstriction. Enhancing the clearance of extracellular vesicles prevented the development of the extracellular vesicle-induced preeclampsia in mice. Our results demonstrate a causal role of pcEV in preeclampsia and identify microvesicle clearance as a new therapeutic strategy for the treatment of this pregnancy-associated complication.

Deletion of Prl7d1 causes placental defects at mid-pregnancy in mice

Prolactin family 7, subfamily d, member 1 (Prl7d1), a member of the expanding prolactin family, is mainly expressed in the placental junctional zone (including trophoblast giant cells and spongiotrophoblast cells) with peak expression observed at 12 days postcoitum (dpc) in mice. Previous studies have shown that PRL7D1 is a key mediator of angiogenesis in vitro; however, its physiological roles in placental development in vivo have not been characterized. To address this issue, we deleted Prl7d1 in mice and demonstrated that its absence results in reduced litter size and fertility. Histologically, Prl7d1 mutants exhibited striking placental abnormalities at 12.5 dpc, including a reduction in the proportion of labyrinth layers and a significant increase in decidual natural killer cells, glycogen trophoblasts, and trophoblast giant cells in the junctional zone. Moreover, placentas from Prl7d1-null mice displayed a thickened decidual spiral artery. Notably, these negative effects were more pronounced in male fetuses. Further RNA-sequencing analysis showed that Prl7d1 deletion results in significant differences in the placental transcriptome profile between the two sexes of fetuses. Together, this study demonstrates that Prl7d1 possesses antiangiogenic properties in deciduas and inhibits the development of junctional zone, which potentially alters the functional capacity of the placenta to support optimal fetal growth. Moreover, of note, the role of Prl7d1 in the placenta is regulated in a fetal sex-specific manner.

Human vitreous in proliferative diabetic retinopathy: Characterization and translational implications

Diabetic retinopathy (DR) is one of the leading causes of visual impairment in the working-age population. DR is a progressive eye disease caused by long-term accumulation of hyperglycaemia-mediated pathological alterations in the retina of diabetic patients. DR begins with asymptomatic retinal abnormalities and may progress to advanced-stage proliferative diabetic retinopathy (PDR), characterized by neovascularization or preretinal/vitreous haemorrhages. The vitreous, a transparent gel that fills the posterior cavity of the eye, plays a vital role in maintaining ocular function. Structural and molecular alterations of the vitreous, observed during DR progression, are consequences of metabolic and functional modifications of the retinal tissue. Thus, vitreal alterations reflect the pathological events occurring at the vitreoretinal interface. These events are caused by hypoxic, oxidative, inflammatory, neurodegenerative, and leukostatic conditions that occur during diabetes. Conversely, PDR vitreous can exert pathological effects on the diabetic retina, resulting in activation of a vicious cycle that contributes to disease progression. In this review, we recapitulate the major pathological features of DR/PDR, and focus on the structural and molecular changes that characterize the vitreal structure and composition during DR and progression to PDR. In PDR, vitreous represents a reservoir of pathological signalling molecules. Therefore, in this review we discuss how studying the biological activity of the vitreous in different in vitro, ex vivo, and in vivo experimental models can provide insights into the pathogenesis of PDR. In addition, the vitreous from PDR patients can represent a novel tool to obtain preclinical experimental evidences for the development and characterization of new therapeutic drug candidates for PDR therapy.

SerpinB2 deficiency in mice reduces bleeding times via dysregulated platelet activation

SerpinB2, also known as plasminogen activation inhibitor type 2 (PAI-2), is classically viewed as an inhibitor of fibrinolysis. However, we show herein a distinct, hitherto unrecognized role for SerpinB2 in hemostasis. Mice deficient in SerpinB2 expression and mice with an active site mutation in SerpinB2, both showed significant reductions in tail bleeding times. This hemostatic phenotype was associated with platelets, with SerpinB2 and SerpinB2-urokinase complexes clearly present in platelet fractions, and immunohistochemistry of blood clots suggesting SerpinB2 is associated with platelet aggregates. Thromboelastography illustrated faster onset of clot formation in blood from SerpinB2 deficient mice, whereas clotting of platelet-free plasma was unaffected. The results appear consistent with the low circulating SerpinB2 levels and hypercoagulation seen during pre-eclampsia; however, SerpinB2 was not detected in human platelets.

Placenta-derived extracellular vesicles: their cargo and possible functions

The literature on extracellular vesicles consists of rapidly expanding and often contradictory information. In this paper we attempt to review what is currently known regarding extracellular vesicles released specifically from human placental syncytiotrophoblast cells with a focus on the common but complex pregnancy-associated syndrome pre-eclampsia, where the level of syncytiotrophoblast extracellular vesicle release is significantly increased. We review common methods for syncytiotrophoblast extracellular vesicle derivation and isolation and we discuss the cargo of syncytiotrophoblast extracellular vesicles including proteins, RNA and lipids and their possible functions. A meta-analysis of available trophoblast-derived extracellular vesicle proteomic datasets revealed only three proteins in common: albumin, fibronectin-1 and plasminogen activator inhibitor-1, suggesting some variability in vesicle cargo, most likely reflecting stage and cell type of origin. We discuss the possible sources of variability that may have led to the low number of common markers, which has led us to speculate that markers and density in common use may not be strict criteria for identifying and isolating placenta-derived exosomes.

Extracellular Vesicles in Human Reproduction in Health and Disease

Extensive evidence suggests that the release of membrane-enclosed compartments, more commonly known as extracellular vesicles (EVs), is a potent newly identified mechanism of cell-to-cell communication both in normal physiology and in pathological conditions. This review presents evidence about the formation and release of different EVs, their definitive markers and cargo content in reproductive physiological processes, and their capacity to convey information between cells through the transfer of functional protein and genetic information to alter phenotype and function of recipient cells associated with reproductive biology. In the male reproductive tract, epididymosomes and prostasomes participate in regulating sperm motility activation, capacitation, and acrosome reaction. In the female reproductive tract, follicular fluid, oviduct/tube, and uterine cavity EVs are considered as vehicles to carry information during oocyte maturation, fertilization, and embryo-maternal crosstalk. EVs via their cargo might be also involved in the triggering, maintenance, and progression of reproductive- and obstetric-related pathologies such as endometriosis, polycystic ovarian syndrome, preeclampsia, gestational diabetes, and erectile dysfunction. In this review, we provide current knowledge on the present and future use of EVs not only as biomarkers, but also as therapeutic targeting agents, mainly as vectors for drug or compound delivery into target cells and tissues.

Microvesicles in Atherosclerosis and Angiogenesis: From Bench to Bedside and Reverse

Atherosclerosis (AT) is a progressive chronic disease involving lipid accumulation, fibrosis, and inflammation in medium and large-sized arteries, and it is the main cause of cardiovascular disease (CVD). AT is caused by dyslipidemia and mediated by both innate and adaptive immune responses. Despite lipid-lowering drugs have shown to decrease the risk of cardiovascular events (CVEs), there is a significant burden of AT-related morbidity and mortality. Identification of subjects at increased risk for CVE as well as discovery of novel therapeutic targets for improved treatment strategies are still unmet clinical needs in CVD. Microvesicles (MVs), small extracellular plasma membrane particles shed by activated and apoptotic cells have been widely linked to the development of CVD. MVs from vascular and resident cells by facilitating exchange of biological information between neighboring cells serve as cellular effectors in the bloodstream and play a key role in all stages of disease progression. This article reviews the current knowledge on the role of MVs in AT and CVD. Attention is focused on novel aspects of MV-mediated regulatory mechanisms from endothelial dysfunction, vascular wall inflammation, oxidative stress, and apoptosis to coagulation and thrombosis in the progression and development of atherothrombosis. MV contribution to vascular remodeling is also discussed, with a particular emphasis on the effect of MVs on the crosstalk between endothelial cells and smooth muscle cells, and their role regulating the active process of AT-driven angiogenesis and neovascularization. This review also highlights the latest findings and main challenges on the potential prognostic, diagnostic, and therapeutic value of cell-derived MVs in CVD. In summary, MVs have emerged as new regulators of biological functions in atherothrombosis and might be instrumental in cardiovascular precision medicine; however, significant efforts are still needed to translate into clinics the latest findings on MV regulation and function.

Immune-modulatory effects of syncytiotrophoblast extracellular vesicles in pregnancy and preeclampsia

Unique immunologic adaptations exist to successfully establish and maintain pregnancy and to avoid an immune attack against the semi allogenic fetus. These adaptations occur both locally at the maternofetal interface and in the peripheral circulation and affect the innate as well as the adaptive immune system. Pregnancy is characterized by a general inflammatory state with activation of monocytes and granulocytes, but also with suppressive lymphocytes (regulatory T cells), and skewing towards T helper 2 immunity. The pregnancy complication preeclampsia is associated with an exaggerated inflammatory state and predominance of T helper 1 and 17 immunity. The syncytiotrophoblast has been found to secrete extracellular vesicles as communication factors into the maternal circulation. Syncytiotrophoblast extracellular vesicles from normal pregnancy have been shown to interact with monocytes, granulocytes, T cells and natural killer cells and influence the function of these cells. In doing so, they may support the inflammatory state of normal pregnancy as well as the suppressive lymphocyte phenotype. During preeclampsia, syncytiotrophoblast extracellular vesicles are not only increased in numbers but also showed an altered molecular load. Based on data from in vitro studies, it can be suggested that syncytiotrophoblast extracellular vesicles from preeclamptic pregnancies may support the exaggerated inflammatory state during preeclampsia. In this review, we discuss the immunological functions of syncytiotrophoblast extracellular vesicles and their involvement in adapting the maternal peripheral immunological adaptations to pregnancy.

Vitamin D Reduces Oxidative Stress-Induced Procaspase-3/ROCK1 Activation and MP Release by Placental Trophoblasts

CONTEXT

Increased microparticle (MP) shedding by placental trophoblasts contributes to maternal vascular inflammatory response and endothelial dysfunction in preeclampsia. Vitamin D has beneficial effects in pregnancy; however, its effect on trophoblast MP release has not been investigated.

OBJECTIVE

To investigate if vitamin D could protect trophoblasts from oxidative stress-induced MP release.

DESIGN

Placental trophoblasts were isolated from uncomplicated and preeclamptic placentas. Effects of vitamin D on MP release induced by oxidative stress inducer CoCl2 were studied.

MAIN OUTCOME MEASURES

Annexin V+ MPs were assessed by flow cytometry. Expression of caveolin-1, endothelial nitric oxide synthase (eNOS), procaspase-3, cleaved caspase-3, and Rho-associated coiled-coil protein kinase 1 (ROCK1) in trophoblasts and trophoblast-derived MPs were determined by Western blot.

RESULTS

Trophoblasts from preeclamptic pregnancies released significantly more MPs than cells from uncomplicated pregnancies (P < 0.01). CoCl2-induced increase in MP release was associated with upregulation of caveolin-1 and downregulation of eNOS expression in trophoblasts (P < 0.05), which could be attenuated by 1,25(OH)2D3. Moreover, 1,25(OH)2D3 could also inhibit CoCl2-induced procaspase-3 cleavage and ROCK1 activation in trophoblasts. Consistently, CoCl2-induced upregulation of procaspase-3, cleaved caspase-3, and ROCK1 expression in trophoblast-derived MPs were also reduced in cells treated with 1,25(OH)2D3.

CONCLUSIONS

Placental trophoblasts from preeclamptic pregnancies released more MP than cells from uncomplicated pregnancies. Oxidative stress-induced increase in MP shedding is associated with upregulation of caveolin-1 and downregulation of eNOS expression in placental trophoblasts. Inhibition of caspase-3 cleavage and ROCK1 activation, together with upregulation of eNOS expression, could be the potential cellular/molecular mechanism(s) of vitamin D protective effects on placental trophoblasts.

Extracellular vesicles in blood, milk and body fluids of the female and male urogenital tract and with special regard to reproduction

Extracellular vesicles (EVs) are released from almost all cells and tissues. They are able to transport substances (e.g. proteins, RNA or DNA) at higher concentrations than in their environment and may adhere in a receptor-controlled manner to specific cells or tissues in order to release their content into the respective target structure. Blood contains high concentrations of EVs mainly derived from platelets, and, at a smaller amount, from erythrocytes. The female and male reproductive tracts produce EVs which may be associated with fertility or infertility and are released into body fluids and mucosas of the urogenital organs. In this review, the currently relevant detection methods are presented and critically compared. During pregnancy, placenta-derived EVs are dynamically detectable in peripheral blood with changing profiles depending upon progress of pregnancy and different pregnancy-associated pathologies, such as preeclampsia. EVs offer novel non-invasive diagnostic tools which may reflect the situation of the placenta and the foetus. EVs in urine have the potential of reflecting urogenital diseases including cancers of the neighbouring organs. Several methods for detection, quantification and phenotyping of EVs have been established, which include electron microscopy, flow cytometry, ELISA-like methods, Western blotting and analyses based on Brownian motion. This review article summarises the current knowledge about EVs in blood and cord blood, in the different compartments of the male and female reproductive tracts, in trophoblast cells from normal and pre-eclamptic pregnancies, in placenta ex vivo perfusate, in the amniotic fluid, and in breast milk, as well as their potential effects on natural killer cells as possible targets.

Syncytiotrophoblast extracellular vesicles - Circulating biopsies reflecting placental health

The ability to directly monitor the status of the placenta throughout pregnancy would be a major advance in both general and personalized obstetric care, allowing treatments to be tailored to the dynamic changes that can occur in gestation. Syncytiotrophoblast extracellular vesicles (STBEV) are membrane bound vesicles, released from the surface of the placenta directly into the maternal circulation, in the form of exosomes, microvesicles and apoptotic bodies. They carry many syncytiotrophoblast derived factors such as proteins, lipids, glycans and nucleic acids, which together could dynamically signal to the mother the status of the placenta. We review STBEV research and discuss the potential for STBEV to be used as circulating syncytiotrophoblast biopsies, accessible via a simple blood sample throughout pregnancy, giving a real-time readout of syncytiotrophoblast health. We also highlight advances in the use of extracellular vesicles as circulating tumour derived biopsies in the field of cancer research, which could prove beneficial to obstetric care.

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Syncytiotrophoblast release extracellular vesicles (STBEV) directly into the maternal circulation, during normal pregnancy and in increased amounts in preeclampsia, in the form of exosomes, microvesicles and apoptotic bodies.

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STBEV carry many syncytiotrophoblast derived factors such as proteins, lipids, glycans and nucleic acids, the composition of which can change with syncytiotrophoblast stress.

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Circulating STBEV are therefore placental “biopsies” accessible throughout gestation, giving a real-time readout of syncytiotrophoblast health.

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STBEV have great potential as biomarkers for monitoring heterogeneous syndromes such as PE and other forms of placental compromise/stress.

Isolation of human trophoblastic extracellular vesicles and characterization of their cargo and antiviral activity

INTRODUCTION

Primary human trophoblasts release a repertoire of extracellular vesicles (EVs). Among them are nano-sized exosomes, which we found to suppress the replication of a wide range of diverse viruses. These exosomes contain trophoblastic microRNAs (miRNAs) that are expressed from the chromosome 19 miRNA cluster and exhibit antiviral properties. Here, we report our investigation of the cargo of placental EVs, focusing on the composition and the antiviral properties of exosomes, microvesicles, and apoptotic blebs.

METHODS

We isolated EVs using ultracentrifugation and defined their purity using immunoblotting, electron microscopy, and nanoparticle tracking. We used liquid chromatography-electrospray ionization-mass spectrometry, protein mass spectrometry, and miRNA TaqMan card PCR to examine the phospholipids, proteins, and miRNA cargo of trophoblastic EVs and an in vitro viral infection assay to assess the antiviral properties of EVs.

RESULTS

We found that all three EV types contain a comparable repertoire of miRNA. Interestingly, trophoblastic exosomes harbor a protein and phospholipid profile that is distinct from that of microvesicles or apoptotic blebs. Functionally, trophoblastic exosomes exhibit the highest antiviral activity among the EVs. Consistently, plasma exosomes derived from pregnant women recapitulate the antiviral effect of trophoblastic exosomes derived from in vitro cultures of primary human trophoblasts.

DISCUSSION

When compared to other trophoblastic EVs, exosomes exhibit a unique repertoire of proteins and phospholipids, but not miRNAs, and a potent viral activity. Our work suggests that human trophoblastic EVs may play a key role in maternal-placental-fetal communication.

PZP and PAI-2: Structurally-diverse, functionally similar pregnancy proteins?

Pregnancy zone protein (PZP) and plasminogen activator inhibitor type 2 (PAI-2) are two multifunctional proteins that are elevated in normal pregnancy and numerous other inflammatory states. Both proteins were originally identified as protease inhibitors, but current evidence supports the notion that they may also function as modulators of T-helper cells and/or extracellular chaperones. Exacerbated inflammation, fibrinolytic disturbances and misfolded proteins are all implicated in the pathology of preeclampsia, a leading cause of maternal and foetal mortality and morbidity. Notably, reduced levels of PZP or PAI-2 are associated with preeclampsia and clarification of their diverse functions in normal pregnancy could provide much needed insight regarding the pathogenesis of this disorder. Given that inflammation and protein misfolding underlie the pathology of a very large number of disorders, the contributions of PZP and PAI-2 to extracellular proteostasis and immunoregulation could be broad-reaching.

Gelsolin is an endogenous inhibitor of syncytiotrophoblast extracellular vesicle shedding in pregnancy

BACKGROUND

Preeclampsia, a pregnancy-specific inflammatory disorder, is characterized by high levels of anti-angiogenic protein, soluble fms-like tyrosine kinase 1 (sFlt1), in the maternal circulation. sFlt1 producing molecular machinery is present in syncytiotrophoblast extracellular vesicles that are released by the placenta into maternal plasma during normal pregnancy, a process greatly accelerated in preeclampsia. We hypothesized that syncytiotrophoblast extracellular vesicles exposes cytoplasmic actin to plasma resulting in depletion of plasma gelsolin (pGSN), an abundant plasma protein that scavenges circulating actin and other pro-inflammatory mediators.

OBJECTIVE

To test whether pGSN levels would be lower in preeclampsia and to assess whether recombinant human plasma gelsolin (rhpGSN) may promote placental health by decreasing shedding of syncytiotrophoblast extracellular vesicles.

METHODS

We tested pGSN levels in third trimester plasma samples from women with preeclampsia and non-hypertensive pregnancies. We then assessed whether rhpGSN may act as a negative regulator of syncytial shedding in placental explant culture and dynamic mechanical stretch studies.

RESULTS

pGSN levels fall in late pregnancy and decline further in preeclampsia patients. Recombinant human pGSN (rhpGSN) at 100μg/ml limits spontaneous syncytiotrophoblast vesicle release and sFlt1 protein dissemination by normal placental explants. Higher rhpGSN doses (500μg/ml) also limit syncytiotrophoblast vesicle and sFlt1 dissemination from preeclamptic placental explants. rhpGSN also mitigates syncytiotrophoblast vesicle during dynamic mechanical stretch.

CONCLUSIONS

1) pGSN, an anti-inflammatory factor of maternal origin is reduced in preeclampsia and may contribute to disease progression and 2) exogenous rhpGSN supplementation can limit the dissemination of toxic syncytiotrophoblast vesicle that characterizes the disease state.

Proteomic characterization of macro-, micro- and nano-extracellular vesicles derived from the same first trimester placenta: relevance for feto-maternal communication

STUDY QUESTION

What proteins are carried by extracellular vesicles (EVs) released from normal first trimester placentae?

SUMMARY ANSWER

One thousand five hundred and eighty-five, 1656 and 1476 proteins were characterized in macro-, micro- and nano-vesicles, respectively, from first trimester placentae, with all EV fractions being enriched for proteins involved in vesicle transport and inflammation.

WHAT IS KNOWN ALREADY

Placental EVs are being increasingly recognized as important mediators of both healthy and pathological pregnancies. However, current research has focused on detecting changes in specific proteins in particular fractions of vesicles during disease. This is the first study to investigate the full proteome of different-sized fractions of EVs from the same first trimester placenta and highlights the differences/similarities between the vesicle fractions.

STUDY DESIGN, SIZE, DURATION

A well-established ex vivo placental explant culture model was used to generate macro-, micro- and nano-vesicles from 56 first trimester placentae. Vesicle fractions were collected by differential ultracentrifugation, quantified and characterized.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Placental macro-, micro- and nano-vesicles were characterized by microscopy, dynamic light scattering and nanoparticle tracking analysis. The proteome of each EV fraction was interrogated using liquid chromatography-coupled tandem mass spectrometry. Results were validated by semi-quantitative western blotting.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1585, 1656 and 1476 proteins were identified in macro-, micro- and nano-vesicles, respectively. One thousand one hundred and twenty-five proteins were shared between all three fractions while up to 223 proteins were unique to each fraction. Gene Ontology pathway analysis showed an enrichment of proteins involved in vesicle transport and inflammation in all three fractions of EVs. The expression levels of proteins involved in internalization of vesicles (annexin V, calreticulin, CD31, CD47), the complement pathway [C3, decay-accelerating factor (DAF), membrane cofactor protein (MCP), protectin] and minor histocompatibility antigens [ATP-dependent RNA helicase (DDX3), ribosomal protein S4 (RPS4)] were different between different-sized EVs.

LIMITATIONS, REASONS FOR CAUTION

This study is largely hypothesis-generating in nature. It is important to validate these findings using EVs isolated from maternal plasma and the function of the different EV fractions would need further investigation.

WIDER IMPLICATIONS OF THE FINDINGS

Our results support the concept that various EV factions can interact with different maternal cells and have unique effects to mediate feto-maternal communication during early pregnancy. This study also provides a list of candidate proteins, which may inform the identification of robust markers that can be used to isolate placental vesicles from the maternal blood in the future.

STUDY FUNDING/COMPETING INTERESTS

M.T. is a recipient of the University of Auckland Health Research Doctoral Scholarship and the Freemasons Postgraduate Scholarship. This project was supported by a School of Medicine Performance-based research fund (PBRF) grant awarded to L.W.C. No authors have any conflicts of interest to disclose.

Placental Microparticles and MicroRNAs in Pregnant Women with Plasmodium falciparum or HIV Infection

Background

During pregnancy, syncytiotrophoblast vesicles contribute to maternal tolerance towards the fetus, but also to pathologies such as pre-eclampsia. The aim of the study was to address whether Plasmodium falciparum and HIV infections in pregnancy affect the secretion, microRNA content and function of trophoblast microparticles.

Methods

Microparticles were isolated and characterized from 122 peripheral plasmas of Mozambican pregnant women, malaria- and/or HIV-infected and non-infected. Expression of placenta-related microRNAs in microparticles was analysed by qPCR and the effect of circulating microparticles on dendritic cells assessed by phenotype analysis and cytokine/chemokine measurement.

Results

Concentrations of total and trophoblast microparticles detected by flow cytometry were higher in HIV-positive (P = 0.005 and P = 0.030, respectively) compared to non-infected mothers, as well as in women delivering low birthweight newborns (P = 0.032 and P = 0.021, respectively). miR-517c was overexpressed in mothers with placental malaria (P = 0.034), compared to non-infected. Microparticles from HIV-positive induced a higher expression of MHCII (P = 0.021) and lower production of MCP1 (P = 0.008) than microparticles from non-infected women.

Conclusions

In summary, alterations in total and trophoblast microparticles associated with malaria and HIV in pregnant women may have an immunopathogenic role. The potential for placental-derived vesicles and microRNAs as biomarkers of adverse outcomes during pregnancy and malaria infection should be confirmed in future studies.

Role of exosomes and microvesicles in hypoxia-associated tumour development and cardiovascular disease

Exosomes and microvesicles, collectively referred to as extracellular vesicles (EVs), can transfer complex biological information and induce a diverse signalling response in recipient cells with potential relevance in a wide array of pathological conditions. Tissue hypoxia constitutes a stress-associated phenotype that is central to the malignant state of aggressive tumours as well as to ischaemic tissue in cardiovascular disorders. The adaptive response to hypoxic stress is largely dependent on intercellular communication in which EVs, and cellular exchange of EV cargo molecules, have recently been implicated. The results of numerous studies indicate that hypoxia-dependent shaping of the molecular profile of EVs may mediate the biological response to hypoxia. EVs have been shown to induce tumour angiogenesis and hypercoagulation as well as tissue remodelling and protective effects in ischaemic cardiovascular conditions. Recent findings report increased levels of circulating EVs in patients with hypoxia-associated disorders such as myocardial infarction, stroke and pre-eclampsia, indicating a role of EVs as biomarkers in these pathophysiological states. Here, we discuss the intriguing role of EVs in tumour development and cardiovascular disease, focusing on the paracrine transfer of the hypoxic response to neighbouring cells and to distant cells at the systemic level, with wide implications for biomarker discovery and therapeutic intervention.

Endoglin in HIV-associated preeclamptic placentae

OBJECTIVE

To examine the placental immunoexpression of endoglin (Eng), in HIV-negative and HIV-positive normotensive (N- and N+) and preeclamptic (P- and P+) pregnancies at term, using immunohistochemistry and immunoelectron microscopy.

RESULTS

Strong Eng immunoreactivity was observed within endothelial cells, syncytio- and cyto-trophoblast cell populations. All extravillous trophoblast cells were immunopositive for Eng. Subcellularly, gold particles were immunolocalised within the endoplasmic reticulum, and mitochondria. Immunoexpression of Eng differed significantly between exchange (p = 0.02) and conducting villi (p < 0.001). A higher Eng immunoexpression was observed in both villi types of the preeclamptic compared to normotensive groups. Irrespective of pregnancy type (normotensive versus PE), there was no significant effect of HIV status on Eng immunoexpression within the exchange and conducting villi.

CONCLUSION

The immunostaining of Eng within the endothelial cells, syncytio-, cyto- and extravillous trophoblast cell populations of HIV-associated preeclamptic placentae is novel. Endoglin and its soluble component remains an area for dynamic placental exploration in preeclampsia development.

Linking the old and new -- do angiotensin II type 1 receptor antibodies provide the missing link in the pathophysiology of preeclampsia?

Preeclampsia remains a leading cause of maternal and neonatal morbidity and mortality. The pathophysiology of preeclampsia remains poorly understood with various pathological mechanisms being implicated including the renin angiotensin system (RAAS), angiogenic pathways and various components of the immune system. Recently a pathogenic autoimmune factor has been identified in the form of auto-agonistic angiotensin II type 1 receptor antibodies (AT1-AA). AT1-AA have been studied in vitro and in vivo in various human and animal models and these data have provided compelling evidence for their role in preeclampsia. This review summarises the current literature surrounding the role of AT1-AA in preeclampsia and draws links between this relatively novel antibody to well-established pathological mechanisms including the immune system, the RAAS, angiogenic pathways and placental ischaemia.

Placental extracellular vesicles and feto-maternal communication

The human placenta is an anatomically unique structure that extrudes a variety of extracellular vesicles into the maternal blood (including syncytial nuclear aggregates, microvesicles, and nanovesicles). Large quantities of extracellular vesicles are produced by the placenta in both healthy and diseased pregnancies. Since their first description more than 120 years ago, placental extracellular vesicles are only now being recognized as important carriers for proteins, lipids, and nucleic acids, which may play a crucial role in feto-maternal communication. Here, we summarize the current literature on the cargos of placental extracellular vesicles and the known effects of such vesicles on maternal cells/systems, especially those of the maternal immune and vascular systems.

Balance of antiangiogenic and angiogenic factors in the context of the etiology of preeclampsia

The "two-stage disorder" theory that is assumed for the etiology of preeclampsia hypothesizes that antiangiogenic and angiogenic factors and/or placental debris play an important role in this disorder. The physiological actions of placental debris occur via the balance between antiangiogenic and angiogenic factors. Accordingly, this balance between antiangiogenic and angiogenic factors should be investigated to elucidate the various pathological features of preeclampsia. Their accurate evaluation is needed to investigate not only antiangiogenic factors (such as sFlt-1 and sEng) and angiogenic factors (such as vascular endothelial growth factor, placental growth factor and transforming growth factor-β) but also the expression level of their receptors such as Flt-1 and Eng. However, it is ethically and technically difficult to investigate the above-mentioned factors at antepartum in human patients. The examination of the ratios of sFlt-1/vascular endothelial growth factor receptor ligands and sEng/transforming vascular endothelial growth factor-β and the use of experimental animal models may help in elucidating various unresolved issues in preeclampsia.

Placental disease and the maternal syndrome of preeclampsia: missing links?

Preeclampsia remains a significant obstetric risk worldwide. The pathophysiology of preeclampsia is complex, with multiple stages involving maladaptations in both placental and maternal physiology. The placenta links the pre-clinical stage of impaired remodeling of the uterine vasculature, occurring in early pregnancy, to the later clinical stages characterised by the maternal syndrome of hypertension and proteinuria. This review focuses on some of the recent candidates for the missing links in this process.

Docosahexaenoic acid supplementation early in pregnancy may prevent deep placentation disorders

Uteroplacental ischemia may cause preterm birth, either due to preterm labor, preterm premature rupture of membranes, or medical indication (in the presence of preeclampsia or fetal growth restriction). Uteroplacental ischemia is the product of defective deep placentation, a failure of invasion, and transformation of the spiral arteries by the trophoblast. The failure of normal placentation generates a series of clinical abnormalities nowadays called "deep placentation disorders"; they include preeclampsia, fetal growth restriction, preterm labor, preterm premature rupture of membranes, in utero fetal death, and placental abruption. Early reports suggested that a LC-PUFAs (long chain polyunsaturated fatty acids) rich diet reduces the incidence of deep placentation disorders. Recent randomized controlled trials are inconsistent to show the benefit of docosahexaenoic acid (DHA) supplementation during pregnancy to prevent deep placentation disorders, but most of them showed that DHA supplementation was associated with lower risk of early preterm birth. We postulate that DHA supplementation, early in pregnancy, may reduce the incidence of deep placentation disorders. If our hypothesis is correct, DHA supplementation, early in pregnancy, will become a safe and effective strategy for primary prevention of highly relevant pregnancy diseases, such as preterm birth, preeclampsia, and fetal growth restriction.

Placental alkaline phosphatase de-phosphorylates insulin-like growth factor (IGF)-binding protein-1

BACKGROUND

Insulin-like growth factors (IGF) regulate fetal growth through their effects on placenta. Their actions are influenced by IGF binding protein-1. Phosphorylated IGFBP-1 (pIGFBP-1) has high affinity for IGF-I and usually inhibits IGF-I activity but during pregnancy, it is de-phosphorylated to generate lower affinity isoforms and consequently, increased IGF bioavailability. Here we investigate the role of placenta in this process.

RESULTS

Our data show that term human placental explants, but not their conditioned medium, can de-phosphorylate IGFBP-1 through the action of placental alkaline phosphatase (PLAP).

DISCUSSION

PLAP-mediated de-phosphorylation of IGFBP-1 may provide a mechanism for controlling IGF-I bioavailability and action at the maternal/fetal interface.

Tumor cell-expressed SerpinB2 is present on microparticles and inhibits metastasis

Expression of SerpinB2 (plasminogen activator inhibitor type 2/PAI-2) by certain cancers is associated with a favorable prognosis. Although tumor-associated host tissues can express SerpinB2, no significant differences in the growth of a panel of different tumors in SerpinB2(-/-) and SerpinB2(+/+) mice were observed. SerpinB2 expression by cancer cells (via lentiviral transduction) also had no significant effect on the growth of panel of mouse and human tumor lines in vivo or in vitro. SerpinB2 expression by cancer cells did, however, significantly reduce the number of metastases in a B16 metastasis model. SerpinB2-expressing B16 cells also showed reduced migration and increased length of invadopodia-like structures, supporting the classical view that that tumor-derived SerpinB2 is inhibiting extracellular urokinase. Importantly, although SerpinB2 is usually poorly secreted, we found that SerpinB2 effectively reaches the extracellular milieu on the surface of 0.5-1 μm microparticles (MPs), where it was able to inhibit urokinase. We also provide evidence that annexins mediate the binding of SerpinB2 to phosphatidylserine, a lipid characteristically exposed on the surface of MPs. The presence of SerpinB2 on the surface of MPs provides a physiological mechanism whereby cancer cell SerpinB2 can reach the extracellular milieu and access urokinase plasminogen activator (uPA). This may then lead to inhibition of metastasis and a favorable prognosis.

Syncytiotrophoblast vesicles show altered micro-RNA and haemoglobin content after ex-vivo perfusion of placentas with haemoglobin to mimic preeclampsia

Background

Cell-free foetal haemoglobin (HbF) has been shown to play a role in the pathology of preeclampsia (PE). In the present study, we aimed to further characterize the harmful effects of extracellular free haemoglobin (Hb) on the placenta. In particular, we investigated whether cell-free Hb affects the release of placental syncytiotrophoblast vesicles (STBMs) and their micro-RNA content.

Methods

The dual ex-vivo perfusion system was used to perfuse isolated cotyledons from human placenta, with medium alone (control) or supplemented with cell-free Hb. Perfusion medium from the maternal side of the placenta was collected at the end of all perfusion phases. The STBMs were isolated using ultra-centrifugation, at 10,000×g and 150,000×g (referred to as 10K and 150K STBMs). The STBMs were characterized using the nanoparticle tracking analysis, identification of surface markers and transmission electron microscopy. RNA was extracted and nine different micro-RNAs, related to hypoxia, PE and Hb synthesis, were selected for analysis by quantitative PCR.

Results

All micro-RNAs investigated were present in the STBMs. Mir-517a, mir-141 and mir-517b were down regulated after Hb perfusion in the 10K STBMs. Furthermore, Hb was shown to be carried by the STBMs.

Conclusion

This study showed that Hb perfusion can alter the micro-RNA content of released STBMs. Of particular interest is the alteration of two placenta specific micro-RNAs; mir-517a and mir-517b. We have also seen that STBMs may function as carriers of Hb into the maternal circulation.