Role of Lectin-like Oxidized LDL Receptor-1 and Syncytiotrophoblast Extracellular Vesicles in the Vascular Reactivity of Mouse Uterine Arteries During Pregnancy.

Vascular complications in pregnancy (e.g. preeclampsia) are a major source of maternal and foetal morbidity and mortality, and may be due to excessive release of placental syncytiotrophoblast-derived extracellular vesicles (STBEVs) into the maternal circulation. Increased activity of the multi-ligand scavenger receptor Lectin-like Oxidized LDL Receptor-1 (LOX-1) is associated with vascular dysfunction, and LOX-1 has been shown to interact with angiotensin II receptor type 1 (AT1). We hypothesized that STBEVs contribute to vascular dysfunction via LOX-1 and AT1 receptors during pregnancy. Uterine arteries from late pregnant wildtype and LOX-1 overexpressing mice were incubated overnight with or without STBEVs and vascular function was assessed using wire myography. STBEV-incubation decreased angiotensin II responsiveness only in wildtype mice, which coincided with decreased AT1 contribution and expression. Thus, STBEVs reduced angiotensin II responsiveness in normal pregnancy, but not in conditions of increased LOX-1 expression, suggesting that STBEVs (via LOX-1) play a role in normal adaptations to pregnancy. Oxidized LDL (a LOX-1 ligand) increased angiotensin II-induced vasoconstriction in STBEV-incubated arteries from both mouse strains, suggesting that the LOX-1 pathway may be involved in complicated pregnancies with elevated STBEVs and oxidized LDL levels (such as preeclampsia). These data increase our understanding of vascular complications during pregnancy.

In vitro placenta barrier model using primary human trophoblasts, underlying connective tissue and vascular endothelium.

Fetal development may be compromised by adverse events at the placental interface between mother and fetus. However, it is still unclear how the communication between mother and fetus occurs through the placenta. In vitro - models of the human placental barrier, which could help our understanding and which recreate three-dimensional (3D) structures with biological functionalities and vasculatures, have not been reported yet. Here we present a 3D-vascularized human primary placental barrier model which can be constructed in 1 day. We illustrate the similarity of our model to first trimester human placenta, both in its structure and in its ability to respond to altered oxygen and to secrete factors that cause damage cells across the barrier including embryonic cortical neurons. We use this model to highlight the possibility that both the trophoblast and the endothelium within the placenta might play a role in the fetomaternal dialogue.

Alterations in vascular function by syncytiotrophoblast extracellular vesicles via lectin-like oxidized low-density lipoprotein receptor-1 in mouse uterine arteries.

Syncytiotrophoblast extracellular vesicles (STBEVs), released into the maternal circulation during pregnancy, have been shown to affect vascular function; however, the mechanism remains unknown. In rats, STBEVs were shown to reduce endothelium-mediated vasodilation via lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a multi-ligand scavenger receptor that has been associated with vascular dysfunction. Recently, LOX-1 was shown to interact with the angiotensin II type 1 receptor (AT-1). We hypothesized that, in pregnant mice, STBEVs would impair vascular function via LOX-1 and would specifically affect angiotensin II responses. Uterine arteries from pregnant control (C57BL/6) and LOX-1 knockout (LOX-1KO) mice were isolated on gestational day (GD) 18.5. Endothelium-dependent (methylcholine (MCh); ± N(G)-Nitro-L-arginine methyl ester to assess nitric oxide (NO) contribution), and -independent (sodium nitroprusside) vasodilation, and vasoconstriction (angiotensin II; ± AT-1 [candesartan] or angiotensin II type 2 receptor (AT-2) [PD123.319] receptor antagonists; high potassium salt solution) responses were assessed using wire myography. AT-1 and AT-2 expression was analyzed using fluorescence microscopy. Human umbilical vein endothelial cells (HUVECs) were stimulated with STBEVs ± LOX-1 blocking antibody, and superoxide and peroxynitrite production were analyzed. Although MCh-induced vasodilation was decreased (P=0.0012), NO contribution to vasodilation was greater in LOX-1KO mice (P=0.0055). STBEVs delayed angiotensin II tachyphylaxis in arteries from control but not LOX-1KO mice (P<0.0001), while AT-1 and AT-2 expression was unchanged. STBEVs increased peroxynitrite production in HUVECs via LOX-1 (P=0.0091). In summary, LOX-1 deletion altered endothelium-mediated vasodilation, suggesting that LOX-1 contributes to vascular adaptations in pregnancy. STBEVs increased angiotensin II responsiveness and oxidative stress levels via LOX-1, suggesting that increased LOX-1 expression/activation or STBEVs could adversely affect vascular function and contribute to vascular complications of pregnancy.

Endoplasmic reticulum stress stimulates the release of extracellular vesicles carrying danger-associated molecular pattern (DAMP) molecules.

Disturbances in endoplasmic reticulum (ER) function lead to ER stress which, when severe or prolonged, may result in apoptosis. Severe ER stress has been implicated in several pathological conditions including pre-eclampsia, a multisystem disorder of pregnancy associated with the release of pro-inflammatory factors from the placenta into the maternal circulation. Here, we show that severe ER stress induced by two distinct mechanisms in BeWo choriocarcinoma cells leads to the release of extracellular vesicles (EVs) carrying pro-inflammatory damage-associated molecular pattern (DAMP) molecules. Co-treatment with the antioxidant pyrrolidine dithiocarbamate results in a reduction in ER stress-induced EV-associated DAMP release. We further demonstrate that severe ER stress is associated with changes in the expression of several stress-related proteins, notably Cited-2 and phosphorylated JNK. Together, these data indicate that severe ER stress-mediated release of EV-associated DAMPs may contribute to the heightened systemic maternal inflammatory response characteristic of pre-eclampsia and may also be relevant to other chronic inflammatory diseases which display elevated ER stress.

Syncytiotrophoblast extracellular vesicles impair rat uterine vascular function via the lectin-like oxidized LDL receptor-1.

Syncytiotrophoblast extracellular vesicles (STBEVs) are placenta derived particles that are released into the maternal circulation during pregnancy. Abnormal levels of STBEVs have been proposed to affect maternal vascular function. The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a multi-ligand scavenger receptor. Increased LOX-1 expression and activation has been proposed to contribute to endothelial dysfunction. As LOX-1 has various ligands, we hypothesized that, being essentially packages of lipoproteins, STBEVs are able to activate the LOX-1 receptor thereby impairing vascular function via the production of superoxide and decreased nitric oxide bioavailability. Uterine arteries were obtained in late gestation from Sprague-Dawley rats and incubated for 24h with or without human STBEVs (derived from a normal pregnant placenta) in the absence or presence of a LOX-1 blocking antibody. Vascular function was assessed using wire myography. Endothelium-dependent maximal vasodilation to methylcholine was impaired by STBEVs (MCh Emax: 57.7±5.9% in STBEV-incubated arteries vs. 77.8±2.9% in controls, p<0.05). This was prevented by co-incubation of STBEV-incubated arteries with LOX-1 blocking antibodies (MCh Emax: 78.8±4.3%, p<0.05). Pre-incubation of the vessels with a nitric oxide synthase inhibitor (L-NAME) demonstrated that the STBEV-induced impairment in vasodilation was due to decreased nitric oxide contribution (ΔAUC 12.2±11.7 in STBEV-arteries vs. 86.5±20 in controls, p<0.05), which was abolished by LOX-1 blocking antibody (ΔAUC 98.9±17, p<0.05). In STBEV-incubated vessels, LOX-1 inhibition resulted in an increased endothelial nitric oxide synthase expression (p<0.05), to a level similar to control vessels. The oxidant scavenger, superoxide dismutase, did not improve this impairment, nor were vascular superoxide levels altered. Our data support an important role for STBEVs in impairment of vascular function via activation of LOX-1 and reduced nitric oxide mediated vasodilation. Moreover, we postulate that the LOX-1 pathway could be a potential therapeutic target in pathologies associated with vascular dysfunction during pregnancy.

Placental Vesicles Carry Active Endothelial Nitric Oxide Synthase and Their Activity is Reduced in Preeclampsia.

Preeclampsia, a multisystem hypertensive disorder of pregnancy, is associated with increased systemic vascular resistance. Placentae from patients with preeclampsia have reduced levels of endothelial nitric oxide synthase (eNOS) and, thus, less nitric oxide (NO). Syncytiotrophoblast extracellular vesicles (STBEV), comprising microvesicles (STBMV) and exosomes, carry signals from the syncytiotrophoblast to the mother. We hypothesized that STBEV-bound eNOS (STBEV-eNOS), capable of producing NO, are released into the maternal circulation. Dual-lobe ex vivo placental perfusion and differential centrifugation was used to isolate STBEV from preeclampsia (n=8) and normal pregnancies (NP; n=11). Plasma samples of gestational age-matched preeclampsia and NP (n=6) were used to isolate circulating STBMV. STBEV expressed placental alkaline phosphatase, confirming placental origin. STBEV coexpressed eNOS, but not inducible nitric oxide synthase, confirmed using Western blot, flow cytometry, and immunodepletion. STBEV-eNOS produced NO, which was significantly inhibited by N G-nitro-l-arginine methyl ester (eNOS inhibitor; P<0.05) but not by N-(3-(aminomethyl) bezyl) acetamidine) (inducible nitric oxide synthase inhibitor). STBEV-eNOS catalytic activity was confirmed by visualizing eNOS dimerization. STBEV-eNOS was more abundant in uterine vein compared with peripheral blood, indicating placental origin. STBEV isolated from preeclampsia-perfused placentae had lower levels of STBEV-eNOS (STBMV; P<0.05) and overall lower NO activity (STBMV, not significant; syncytiotrophoblast extracellular exosomes, P<0.05) compared with those from NP. Circulating plasma STBMV from preeclampsia women had lower STBEV-eNOS expression compared with that from NP women (P<0.01). This is the first observation of functional eNOS expressed on STBEV from NP and preeclampsia placentae, as well as in plasma. The lower STBEV-eNOS NO production seen in preeclampsia may contribute to the decreased NO bioavailability in this disease.

Syncytiotrophoblast Extracellular Vesicles from Pre-Eclampsia Placentas Differentially Affect Platelet Function.

Pre-eclampsia (PE) complicates around 3% of all pregnancies and is one of the most common causes of maternal mortality worldwide. The pathophysiology of PE remains unclear however its underlying cause originates from the placenta and manifests as raised blood pressure, proteinuria, vascular or systemic inflammation and hypercoagulation in the mother. Women who develop PE are also at significantly higher risk of subsequently developing cardiovascular (CV) disease. In PE, the failing endoplasmic reticulum, oxidative and inflammatory stressed syncytiotrophoblast layer of the placenta sheds increased numbers of syncytiotrophoblast extracellular vesicles (STBEV) into the maternal circulation. Platelet reactivity, size and concentration are also known to be altered in some women who develop PE, although the underlying reasons for this have not been determined. In this study we show that STBEV from disease free placenta isolated ex vivo by dual placental perfusion associate rapidly with platelets. We provide evidence that STBEV isolated from normal placentas cause platelet activation and that this is increased with STBEV from PE pregnancies. Furthermore, treatment of platelets with aspirin, currently prescribed for women at high risk of PE to reduce platelet aggregation, also inhibits STBEV-induced reversible aggregation of washed platelets. Increased platelet reactivity as a result of exposure to PE placenta derived STBEVs correlates with increased thrombotic risk associated with PE. These observations establish a possible direct link between the clotting disturbances of PE and dysfunction of the placenta, as well as the known increased risk of thromboembolism associated with this condition.

Measurement of refractive index by nanoparticle tracking analysis reveals heterogeneity in extracellular vesicles.

INTRODUCTION: Optical techniques are routinely used to size and count extracellular vesicles (EV). For comparison of data from different methods and laboratories, suitable calibrators are essential. A suitable calibrator must have a refractive index (RI) as close to that of EV as possible but the RI of EV is currently unknown. To measure EV, RI requires accurate knowledge of size and light scattering. These are difficult to measure as most EVs cannot be resolved by light microscopy and their diameter is smaller than the wavelength of visible light. However, nanoparticle tracking analysis (NTA) provides both size and relative light scattering intensity (rLSI) values. We therefore sought to determine whether it was possible to use NTA to measure the RI of individual EVs. METHODS: NTA was used to measure the rLSI and size of polystyrene and silica microspheres of known size and RI (1.470 and 1.633, respectively) and of EV isolated from a wide range of cells. We developed software, based on Mie scattering code, to calculate particle RI from the rLSI data. This modelled theoretical scattering intensities for polystyrene and silica microspheres of known size (100 and 200 nm) and RI. The model was verified using data from the polystyrene and silica microspheres. Size and rLSI data for each vesicle were processed by the software to generate RI values. RESULTS: The following modal RI measurements were obtained: fresh urinary EV 1.374, lyophilised urinary EV 1.367, neuroblastoma EV 1.393, blood EV 1.398, EV from activated platelets 1.390, small placental EV 1.364-1.375 and 1.398-1.414 for large placental EV (>200 nm). Large placental EV had a significantly higher RI than small placental EV (p<0.0001). The spread of RI values was narrower for small EV than for the more heterogeneous large EV. DISCUSSION: Using NTA and Mie scattering theory, we have demonstrated that it is possible to estimate the RI of sub-micron EV using NTA data. EV typically had a modal RI of 1.37-1.39, whereas values of >1.40 were observed for some large (>200 nm) microvesicles. CONCLUSION: This method for measuring EV RI will be useful for developing appropriate calibrators for EV measurement.

Secretions from placenta, after hypoxia/reoxygenation, can damage developing neurones of brain under experimental conditions.

Some psychiatric diseases in children and young adults are thought to originate from adverse exposures during foetal life, including hypoxia and hypoxia/reoxygenation. The mechanism is not understood. Several authors have emphasised that the placenta is likely to play an important role as the key interface between mother and foetus. Here we have explored whether a first trimester human placenta or model barrier of primary human cytotrophoblasts might secrete factors, in response to hypoxia or hypoxia/reoxygenation, that could damage neurones. We find that the secretions in conditioned media caused an increase of [Ca(2+)]i and mitochondrial free radicals and a decrease of dendritic lengths, branching complexity, spine density and synaptic activity in dissociated neurones from embryonic rat cerebral cortex. There was altered staining of glutamate and GABA receptors. We identify glutamate as an active factor within the conditioned media and demonstrate a specific release of glutamate from the placenta/cytotrophoblast barriers invitro after hypoxia or hypoxia/reoxygenation. Injection of conditioned media into developing brains of P4 rats reduced the numerical density of parvalbumin-containing neurones in cortex, hippocampus and reticular nucleus, reduced immunostaining of glutamate receptors and altered cellular turnover. These results show that the placenta is able to release factors, in response to altered oxygen, that can damage developing neurones under experimental conditions.

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.

Investigation of the actin scavenging system in pre-eclampsia.

OBJECTIVES: Cell injury releases actin, the most abundant cell protein. Gelsolin and vitamin D binding protein (VDBP) together depolymerise and clear cell-free actin. Impaired actin clearance is associated with several diseases and correlates with clinical outcome. The actin scavenging system was investigated in pre-eclampsia (PE), a procoagulant and proinflammatory state with placental and vascular damage. STUDY DESIGN: Plasma gelsolin and actin free VDBP (AFVDBP) were measured in PE (early onset <33weeks; late onset ≥36weeks), matched normal pregnant (normP) and non-pregnant (nonPr) women, using commercially available ELISAs. Longitudinal samples from normP and women who subsequently developed PE were also analysed. RESULTS: Plasma gelsolin fell during pregnancy (p=0.0002), with a concomitant rise in actin-free VDBP (p<0.001). Gelsolin concentrations were only significantly lower in established PE (p<0.05) when compared to non-pregnant controls. CONCLUSIONS: We have shown that the components of the actin clearance system, gelsolin and AFVDBP, are altered in normal pregnancy and further changes occur in established PE, suggesting depleted actin clearance in PE. Whether this is a cause or consequence of PE pathophysiology requires further investigation.

Multicolor flow cytometry and nanoparticle tracking analysis of extracellular vesicles in the plasma of normal pregnant and pre-eclamptic women.

Excessive release of syncytiotrophoblast extracellular vesicles (STBMs) from the placenta into the maternal circulation may contribute to the systemic inflammation that is characteristic of pre-eclampsia (PE). Other intravascular cells types (platelets, leukocytes, red blood cells [RBCs], and endothelium) may also be activated and release extracellular vesicles (EVs). We developed a multicolor flow cytometry antibody panel to enumerate and phenotype STBMs in relation to other EVs in plasma from nonpregnant (NonP) and normal pregnant (NormP) women, and women with late-onset PE. Nanoparticle tracking analysis (NTA) was used to determine EV size and concentration. In vitro-derived STBMs and EVs from platelets, leukocytes, RBCs, and endothelial cells were examined to select suitable antibodies to analyze the corresponding plasma EVs. Flow cytometry analysis of plasma from NonP, NormP, and PE showed that STBMs comprised the smallest group of circulating EVs, whereas most were derived from platelets. The next most abundant group comprised unidentified orphan EVs (which did not label with any of the antibodies in the panel), followed by EVs from RBCs and leukocytes. NTA showed that the total number of EVs in plasma was significantly elevated in NormP and late-onset PE women compared to NonP controls, and that EVs were smaller in size. In general, EVs were elevated in pregnancy plasma apart from platelet EVs, which were reduced. These studies did not show any differences in EVs between NormP and PE, probably because late-onset PE was studied.

Extracellular vesicle sizing and enumeration by nanoparticle tracking analysis.

Nanoparticle tracking analysis (NTA) is a light-scattering technique that is useful for the rapid sizing and enumeration of extracellular vesicles (EVs). As a relatively new method, NTA has been criticised for a lack of standardisation. We propose the use of silica microspheres for the calibration of NTA measurements and describe in detail a protocol for the analysis of EVs by NTA which should minimise many of the sources of variability and imprecision associated with this technique.

Detection of soluble ST2 in human follicular fluid and luteinized granulosa cells.

Follicular fluid (FF) contains various cytokines that are involved with folliculogenesis, some of which have been shown to be associated with oocyte quality and the implantation potential of a resulting embryo. Several IL-1 family members have previously been identified in FF. This study investigates a newly identified member of the family, IL-33, and its receptor ST2, comparing values to those of FF Granulocyte-Colony Stimulating Factor (G-CSF)--a known predictor of Assisted Reproductive Technology (ART) success. FF was collected from patients undergoing in vitro fertilisation/intra-cytoplasmic sperm injection (IVF/ICSI) at oocyte retrieval to analyse IL-33 and sST2 expression in human follicles. sST2, but not IL-33, is highly increased in the FF compared to plasma levels (up to 7.9-fold), with higher levels in larger follicles (p<0.05). Furthermore, we identify that human luteinised granulosa cells are one possible source of the FF sST2, as these cells express and secrete sST2 when cultured ex vivo. FF associated with oocytes which when fertilised develop into good quality embryos have higher sST2 levels than those which are graded average (p<0.01). These embryos were transferred to the patient and levels of FF sST2 compared between successful and unsuccessful ICSI cycles. However unlike G-CSF, sST2 levels cannot be used to predict cycle outcome.

Characterisation of syncytiotrophoblast vesicles in normal pregnancy and pre-eclampsia: expression of Flt-1 and endoglin.

BACKGROUND: The placental syncytiotrophoblast releases micro and nanovesicles (STBM), into the maternal circulation in normal pregnancy and in increased amounts in pre-eclampsia (PE), which have proinflammatory and antiangiogenic activity and are implicated in PE pathophysiology. Better characterisation of STBM is essential to understand their role in PE. METHODS AND RESULTS: STBM prepared by placental lobe dual perfusion (pSTBM) and mechanical disruption (mSTBM) were analysed by four colour flow cytometry (4CFC), nanoparticle tracking analysis (NTA) and Western blotting to determine vesicle size, purity and Flt-1 and endoglin (Eng) expression. Biological activity of STBM associated Flt-1 and endoglin was assessed by the ability of VEGF, PlGF and TGFß to bind to mSTBM and inhibit mSTBM induced endothelial monolayer disruption. STBM content was consistently high (~87-95%) across the different preparations. However, surface antigen intensities differed, with significantly lower placental alkaline phosphatase (P<0.05) and Eng (P<0.05) expression on mSTBM, and Flt-1 (P<0.05) expression on pSTBM. For PE placenta derived preparations, pSTBM contained lower Eng positive STBM (P<0.05) and mSTBM Eng expression was increased (P<0.05). Western blotting revealed increased Flt-1/sFlt-1 (P<0.02) and decreased placental alkaline phosphatase (P = 0.0002) content of PE placenta pSTBM. Using NTA, perfused PE placentas released significantly larger MV (P<0.001). Finally, VEGF, PlGF and TGFß bound to mSTBM at physiologically relevant concentrations and inhibited mSTBM induced endothelial disruption (P<0.05-P<0.001). CONCLUSIONS: This study has found differences in physical and antigenic characteristics of normal and PE placenta STBM preparations produced by placental perfusion or mechanical disruption. We have also demonstrated that large quantities of biologically active STBM associated endoglin and Flt-1/sFlt-1 could contribute to the increased circulating levels measured in PE patients and add to the perturbation of the maternal vascular endothelium, normally attributed to non-membrane bound sFlt-1 and sEndoglin.

Measurement of sST2 is comparable to PlGF in the diagnosis of early-onset pre-eclampsia.

A diagnostic test to confirm pre-eclampsia would be beneficial for the clinical management of the syndrome. The Triage PlGF test is able to confirm pre-eclampsia with high accuracy, with the greatest efficacy at <35weeks gestation. We recently found that the anti-inflammatory protein sST2 is elevated in the plasma of pre-eclamptic women compared to normal controls. Here sST2 and PlGF are compared in early-onset and late-onset pre-eclamptic women. sST2 was found to be an equally good diagnostic tool for early-onset (sST2 AUC 0.944 versus PlGF AUC 0.995; not significant) but not late-onset disease.

Exosome-mediated delivery of siRNA in vitro and in vivo.

The use of small interfering RNAs (siRNAs) to induce gene silencing has opened a new avenue in drug discovery. However, their therapeutic potential is hampered by inadequate tissue-specific delivery. Exosomes are promising tools for drug delivery across different biological barriers. Here we show how exosomes derived from cultured cells can be harnessed for delivery of siRNA in vitro and in vivo. This protocol first describes the generation of targeted exosomes through transfection of an expression vector, comprising an exosomal protein fused with a peptide ligand. Next, we explain how to purify and characterize exosomes from transfected cell supernatant. Next, we detail crucial steps for loading siRNA into exosomes. Finally, we outline how to use exosomes to efficiently deliver siRNA in vitro and in vivo in mouse brain. Examples of anticipated results in which exosome-mediated siRNA delivery is evaluated by functional assays and imaging are also provided. The entire protocol takes ~3 weeks.

RhoE is regulated by cyclic AMP and promotes fusion of human BeWo choriocarcinoma cells.

Fusion of placental villous cytotrophoblasts with the overlying syncytiotrophoblast is essential for the maintenance of successful pregnancy, and disturbances in this process have been implicated in pathological conditions such as pre-eclampsia and intra-uterine growth retardation. In this study we examined the role of the Rho GTPase family member RhoE in trophoblast differentiation and fusion using the BeWo choriocarcinoma cell line, a model of villous cytotrophoblast fusion. Treatment of BeWo cells with the cell permeable cyclic AMP analogue dibutyryl cyclic AMP (dbcAMP) resulted in a strong upregulation of RhoE at 24 h, coinciding with the onset of fusion. Using the protein kinase A (PKA)-specific cAMP analogue N(6)-phenyl-cAMP, and a specific inhibitor of PKA (14-22 amide, PKI), we found that upregulation of RhoE by cAMP was mediated through activation of PKA signalling. Silencing of RhoE expression by RNA interference resulted in a significant decrease in dbcAMP-induced fusion. However, expression of differentiation markers human chorionic gonadotrophin and placental alkaline phosphatase was unaffected by RhoE silencing. Finally, we found that RhoE upregulation by dbcAMP was significantly reduced under hypoxic conditions in which cell fusion is impaired. These results show that induction of RhoE by cAMP is mediated through PKA and promotes BeWo cell fusion but has no effect on functional differentiation, supporting evidence that these two processes may be controlled by separate or diverging pathways.

Syncytiotrophoblast microvesicles released from pre-eclampsia placentae exhibit increased tissue factor activity.

BACKGROUND: Pre-eclampsia is a complication of pregnancy associated with activation of coagulation. It is caused by the placenta, which sheds increased amounts of syncytiotrophoblast microvesicles (STBM) into the maternal circulation. We hypothesized that STBM could contribute to the haemostatic activation observed in pre-eclampsia. METHODOLOGY/PRINCIPAL FINDINGS: STBM were collected by perfusion of the maternal side of placentae from healthy pregnant women and women with pre-eclampsia at caesarean section. Calibrated automated thrombography was used to assess thrombin generation triggered by STBM-borne tissue factor in platelet poor plasma (PPP). No thrombin was detected in PPP alone but the addition of STBM initiated thrombin generation in 14/16 cases. Pre-eclampsia STBM significantly shortened the lag time (LagT, P = 0.01) and time to peak thrombin generation (TTP, P = 0.005) when compared to normal STBM. Blockade of tissue factor eliminated thrombin generation, while inhibition of tissue factor pathway inhibitor significantly shortened LagT (p = 0.01) and TTP (P<0.0001), with a concomitant increase in endogenous thrombin potential. CONCLUSIONS/SIGNIFICANCE: STBM triggered thrombin generation in normal plasma in a tissue factor dependent manner, indicating that TF activity is expressed by STBM. This is more pronounced in STBM shed from pre-eclampsia placentae. As more STBM are shed in pre-eclampsia these observations give insight into the disordered haemostasis observed in this condition.

ST2 and IL-33 in pregnancy and pre-eclampsia.

Normal pregnancy is associated with a mild systemic inflammatory response and an immune bias towards type 2 cytokine production, whereas pre-eclampsia is characterized by a more intense inflammatory response, associated with endothelial dysfunction and a type 1 cytokine dominance. Interleukin (IL)-33 is a newly described member of the IL-1 family, which binds its receptor ST2L to induce type 2 cytokines. A soluble variant of ST2 (sST2) acts as a decoy receptor to regulate the activity of IL-33. In this study circulating IL-33 and sST2 were measured in each trimester of normal pregnancy and in women with pre-eclampsia. While IL-33 did not change throughout normal pregnancy, or between non-pregnant, normal pregnant or pre-eclamptic women, sST2 was significantly altered. sST2 was increased in the third trimester of normal pregnancy (p<0.001) and was further increased in pre-eclampsia (p<0.001). This increase was seen prior to the onset of disease (p<0.01). Pre-eclampsia is a disease caused by placental derived factors, and we show that IL-33 and ST2 can be detected in lysates from both normal and pre-eclampsia placentas. ST2, but not IL-33, was identified on the syncytiotrophoblast layer, whereas IL-33 was expressed on perivascular tissue. In an in vitro placental perfusion model, sST2 was secreted by the placenta into the 'maternal' eluate, and placental explants treated with pro-inflammatory cytokines or subjected to hypoxia/reperfusion injury release more sST2, suggesting the origin of at least some of the increased amounts of circulating sST2 in pre-eclamptic women is the placenta. These results suggest that sST2 may play a significant role in pregnancies complicated by pre-eclampsia and increased sST2 could contribute to the type 1 bias seen in this disorder.