Phagocytosis of apoptotic trophoblastic debris protects endothelial cells against activation

Therapeutic potential of miRNAs in placental extracellular vesicles in ovarian and endometrial cancer

There is a cross-link between the placenta and cancer development, as the placenta is grown as a highly invasive tumour-like organ. However, placental development is strictly controlled. Although the underlying mechanism of this control is largely unknown, it is now well-recognised that extracellular vesicles (EVs) released from the placenta play an important role in controlling placenta proliferation and invasion, as placental EVs have shown their effect on regulating maternal adaptation. Better understanding the tumour-like mechanism of the placenta could help to develop a therapeutic potential in cancers. In this study, by RNA sequencing of placental EVs, 20 highly expressed microRNAs (miRNAs) in placental EVs were selected and analysed for their functions on ovarian and endometrial cancer. There were up to seven enriched miRNAs, including miRNA-199a-3p, miRNA-143-3p, and miRNA-519a-5p in placental EVs showing effects on the inhibition of ovarian and endometrial cancer cell proliferation and migration, and promotion of cancer cell death, reported in the literature. Most of these miRNAs have been reported to be downregulated in ovarian and endometrial cancer. Transfection of ovarian and endometrial cancer cells with mimics of miRNA-199a-3p, miRNA-143-3p, and miRNA-519a-5p significantly reduced the cell viability. Our findings could provide strategies for using these naturally occurring miRNAs to develop a novel method to treat ovarian and endometrial cancer in the future.

Normotensive placental extracellular vesicles provide long-term protection against hypertension and cardiovascular disease

BACKGROUND

Women with normotensive pregnancy are at a reduced risk of developing cardiovascular disease postpartum compared with those who experience hypertensive conditions during pregnancy. However, the underlying mechanisms remain poorly understood. During normotensive pregnancy, vast numbers of placental extracellular vesicles are released into the maternal circulation, which protect endothelial cells from activation and alter maternal vascular tone. We hypothesized that placental extracellular vesicles play a mechanistic role in lowering the risk of cardiovascular disease following normotensive pregnancy.

OBJECTIVE

This study aimed to investigate the long-term effects of placental extracellular vesicles derived from normotensive term placentae on the cardiovascular system and explore the mechanisms underlying their biological effects.

STUDY DESIGN

Spontaneously hypertensive rats were injected with placental extracellular vesicles from normotensive term pregnancies (2 mg/kg each time, n=8) or vehicle control (n=9) at 3 months of age. Blood pressure and cardiac function were regularly monitored from 3 months to 15 months of age. The response of mesenteric resistance arteries to vasoactive substances was investigated to evaluate vascular function. Cardiac remodeling, small artery remodeling, and renal function were investigated to comprehensively assess the impact of placental extracellular vesicles on cardiovascular and renal health.

RESULTS

Compared with vehicle-treated control animals, rats treated with normotensive placental extracellular vesicles exhibited a significantly lower increase in blood pressure and improved cardiac function. Furthermore, the vasodilator response to the endothelium-dependent agonist acetylcholine was significantly enhanced in the normotensive placental extracellular vesicle-treated spontaneously hypertensive rats compared with the control. Moreover, treatment with placental extracellular vesicles reduced wall thickening of small renal vessels and attenuated renal fibrosis.

CONCLUSION

Placental extracellular vesicles from normotensive term pregnancies have long-lasting protective effects reducing hypertension and mitigating cardiovascular damage in vivo.

A pilot in vivo study: potential ovarian cancer therapeutic by placental extracellular vesicles

The biological links between cancer and pregnancy are of interest due to parallel proliferative, immunosuppressive, and invasive mechanisms between tumour and placental cells. However, the proliferation and invasion of placental cells are strictly regulated. The understanding of this regulation is largely unknown. Placental extracellular vesicles (EVs) may play an important role in this regulation, as placental EVs are known to contribute to maternal adaptation, including adaptation of the vascular and immune systems. We have previously reported that placental EVs significantly inhibited ovarian cancer cell proliferation by delaying the progression of the cell cycle. We, therefore, performed this pilot in vivo study to investigate whether placental EVs can also inhibit ovarian tumour growth in a SKOV-3 human tumour xenograft model. A single intraperitoneal injection of placental EVs at 15 days post tumour implantation, significantly inhibited the growth of the tumours in our in vivo model. Signs of cellular necrosis were observed in the ovarian tumour tissues, but not in other organs collected from mice that had been treated with placental EVs. Expression of receptor-interacting kinase 1 (RIPK1) and mixed linkage kinase domain-like (MLKL), which are mediators of necroptosis were not observed in our xenografted tumours. However, extensive infiltration of CD169+ macrophages and NK cells in ovarian tumour tissues collected from placental micro-EVs treated mice were observed. We demonstrate here that inhibition of ovarian tumour growth in our xenograft model by placental EVs involves cellular necrosis and infiltration of CD169+ macrophages and NK cells into the tumour tissues.

Recent insight into autophagy and immunity at the maternal-fetal interface

Autophagy is a lysosomal degradation pathway that supports metabolic adaptation and energy cycling. It is essential for cell homeostasis, differentiation, development, and survival. Recent studies have shown that autophagy could influence immune responses by regulating immune cell functions. Reciprocally, immune cells strongly influence autophagy. Immune cells at the maternal-fetal interface are thought to play essential roles in pregnancy. Here, we review the induction of autophagy at the maternal-fetal interface and its role in decidualization and placental development. Additionally, we emphasize the role of autophagy in the immune microenvironment at the maternal-fetal interface, including innate immunity, adaptive immunity, and immune tolerance molecules. It also suggests new research directions and prospects.

The Blocking of Integrin-Mediated Interactions with Maternal Endothelial Cells Reversed the Endothelial Cell Dysfunction Induced by EVs, Derived from Preeclamptic Placentae

Placental extracellular vesicles (EVs) have increasingly been recognized as a major mediator of feto-maternal communication. However, the cellular and molecular mechanisms of the uptake of placental EVs by recipient cells are still not well-understood. We previously reported that placental EVs target a limited number of organs in vivo. In the current study, we investigated the mechanisms underlying the uptake of placental EVs into target cells. Placental EVs were derived from explant cultures of normal or preeclamptic placentae. The mechanisms underlying the uptake of placental EVs were elucidated, using the phagocytosis or endocytosis inhibitor, trypsin-treatment or integrin-blocking peptides. The endothelial cell activation was studied using the monocyte adhesion assay after the preeclamptic EVs exposure, with and/or without treatment with the integrin blocking peptide, YIGSR. The cellular mechanism of the uptake of the placental EVs was time, concentration and energy-dependent and both the phagocytosis and endocytosis were involved in this process. Additionally, proteins on the surface of the placental EVs, including integrins, were involved in the EV uptake process. Furthermore, inhibiting the uptake of preeclamptic EVs with YIGSR, reduced the endothelial cell activation. The interaction between the placental EVs and the recipient cells is mediated by integrins, and the cellular uptake is mediated by a combination of both phagocytosis and endocytosis.

Loss of E-Cadherin Staining Continuity in the Trophoblastic Basal Membrane Correlates with Increased Resistance in Uterine Arteries and Proteinuria in Patients with Pregnancy-Induced Hypertension

Pregnancy-induced hypertension (PIH), especially when complicated with pre-eclampsia (PE), could be a life-threatening complication of pregnancy. Pre-eclampsia is one of the leading causes of perinatal morbidity and mortality in women. Pre-eclampsia is mainly characterized by hypertension and kidney damage with proteinuria. Abnormal placentation and altered structure of the placental barrier are believed to participate in the pathogenesis of pregnancy-induced hypertension, leading to PE. In the current study, we aimed to analyze the immunohistochemical expression pattern of E-cadherin and p120, two markers of epithelial–mesenchymal transition, in placental samples derived from a group of 55 patients with pregnancy-induced hypertension, including pre-eclampsia and 37 healthy pregnant controls. The results were correlated with the presence of an obtained early uterine artery flow notching during diastole on Doppler ultrasound. We observed a higher frequency of discontinuous E-cadherin staining in the basement membrane of syncytiotrophoblast in patients with PIH/PE compared to controls (p < 0.001, Fisher’s exact test). Moreover, the loss of continuity of E-cadherin expression correlated with the presence of a bilateral early diastolic notch on Doppler ultrasound (p < 0.001, Fisher’s exact test) and the presence of proteinuria (p = 0.013, Fisher’s exact test). These findings suggest that E-cadherin contributes to the integrity of the placental barrier, and its loss could be an immunohistochemical marker of PE.

Placental extracellular vesicles retain biological activity after short-term storage (14 days) at 4 °C or room temperature

INTRODUCTION

To investigate the role of placental extracellular vesicles (EVs), especially in pathological pregnancy, the use of freshly isolated EVs is often limited due to the sporadic and unpredictable availability of placental samples. Therefore, it is important to understand and use optimised storage conditions for placental EVs. In this study, we investigated different conditions for the short-term storage of placental micro- and nano-EVs and examined their biological activity.

METHODS

Placental EVs were collected from first trimester placentae. EVs were suspended in PBS and aliquoted, and then stored for up to 14 days at room temperature, 4 °C or -20 °C. Total protein and DNA levels were measured at various time points. The ability of stored placental EVs to alter endothelial cell activation was quantified by monocyte adhesion assays.

RESULTS

There was no difference in the concentration of placental micro- or nano-EVs between each time point, when stored at either room temperature or 4 °C. However, there was a significant loss of placental EVs after storage at -20 °C. There was no difference in protein or DNA levels of placental EVs when stored at either room temperature or 4 °C. Biological activity of placental EVs was retained for up to 14 days at either room temperature or 4 °C measured by monocyte adhesion assays.

DISCUSSION

We have shown that placental micro- and nano-EVs are stable and retain biological activities following storage in PBS or media for 14 days at either room temperature or 4 °C.

Downregulation of Ribosomal Contents and Kinase Activities Is Associated with the Inhibitive Effect on the Growth of Group B Streptococcus Induced by Placental Extracellular Vesicles

BACKGROUND

Like many other cell types, the human placenta produces large amounts of extracellular vesicles (EVs). Increasing evidence has shown that placental EVs contribute to the regulation of maternal immune and vascular systems during pregnancy via the transfer of their cargos. In this study, we investigated the effect of placental EVs on the growth of opportunistic pathogens that commonly colonise the female reproductive tract.

METHODS

Gram-positive bacterium Group B Streptococcus (GBS) and Gram-negative bacterium Escherichia coli (E. coli) were treated with placental EVs that were collected from placental explant cultures, and the growth, susceptibility, and resistance to antibiotics of the bacteria were measured. In addition, comparative proteomics analysis was also performed for the GBS with or without exposure to placental EVs.

RESULTS

When treated with placental micro-EVs or nano-EVs, the GBS growth curve entered the stationary phase earlier, compared to untreated GBS. Treatment with placental EVs also inhibited the growth of GBS on solid medium, compared to untreated GBS. However, these biological activities were not seen in E. coli. This attenuative effect required interaction of placental EVs with GBS but not phagocytosis. In addition, the susceptibility or resistance to antibiotics of GBS or E. coli was not directly affected by treatment with placental EVs. The proteomic and Western blotting analysis of GBS that had been treated with placental EVs suggested that the downregulation of cellular components and proteins associated with phosphorylation and cell energy in GBS may contribute to these attenuative effects.

CONCLUSION

We demonstrated the attenuative effect of the growth of GBS treated with placental EVs. Downregulation of cellular components and proteins associated with phosphorylation and cell energy may contribute to the physiological changes in GBS treated with placental EVs.

Complications of Pregnancy and the Risk of Developing Endometrial or Ovarian Cancer: A Case-Control Study

BACKGROUND

The association of complications of pregnancy and the risk of developing gynecological cancer is controversial with the limited study. In this study, we investigated the association of preeclampsia, or gestational diabetes mellitus (GDM), or large for gestational age (LGA), or intrauterine growth restriction (IUGR) and the risk of endometrial or ovarian cancer.

METHODS

In this case-control study, 189 women with endometrial cancer and 119 women with ovarian cancer were included. 342 women without gynecological cancers were randomly selected as a control group. Data on the history of pregnancy and age at diagnosis of gynecological cancer as well as the use of intrauterine devices (IUDs) were collected.

RESULTS

Women with a history of preeclampsia or IUGR did not have an increased risk of developing endometrial or ovarian cancer. While women with a history of GDM or with the delivery of LGA infant increased the risk of developing endometrial cancer but not ovarian cancer. The odds of women with a history of GDM or with the delivery of LGA infant developing endometrial cancer was 2.691 (95% CI: 1.548, 4.3635, p=0.0003), or 6.383 (95% CI: 2.812, 13.68, p<0.0001) respectively, compared to the controls. The odds ratio of women who did not use IUDs developing ovarian cancer was 1.606 (95% CI: 1.057, 2.434), compared to the controls. There was no association of age at first birth and developing endometrial or ovarian cancer.

CONCLUSION

Our observational data suggested that GDM and delivery of an LGA infant are associated with an increased risk of endometrial cancer.

Endoplasmic reticulum stress occurs in association with the extrusion of toxic extracellular vesicles from human placentae treated with antiphospholipid antibodies

Antiphospholipid autoantibodies (aPLs), a major maternal risk factor for preeclampsia, are taken into the syncytiotrophoblast where they bind intracellular vesicles and mitochondria. Subsequently, large quantities of extracellular vesicles (EVs) extruded from syncytiotrophoblast into the maternal circulation are altered such that they cause maternal endothelial cell activation. However, the mechanism driving this change is unknown. First trimester placental explants were treated with aPL for 18 h. The EVs were then collected by different centrifugation. The levels of HSP 70, misfolded proteins, caspase 8 activity, and Mixed Lineage Kinase domain-Like (MLKL) were measured in placental explants and EVs. In addition, the levels of TNF-α and CD95 in conditioned medium were also measured. Treating placental explants with aPL caused an increase in levels of HSP 70, misfolded proteins and MLKL in placental explants and EVs. Increased activity of caspase 8 was also seen in placental explants. Higher levels of TNF-α were seen conditioned medium from aPL-treated placental explant cultures. aPLs appear to induce endoplasmic reticulum stress in the syncytiotrophoblast in a manner that involved caspase 8 and TNF-α. To avoid accumulation of the associated misfolded proteins and MLKL, the syncytiotrophoblast exports these potentially dangerous proteins in EVs. It is likely that the dangerous proteins that are loaded into placental EVs in preeclampsia contribute to dysfunction of the maternal cells.

Role of the NLRP3 Inflammasome in Preeclampsia

Reproduction involves tightly regulated series of events and the immune system is involved in an array of reproductive processes. Disruption of well-controlled immune functions leads to infertility, placental inflammation, and numerous pregnancy complications, including preeclampsia (PE). Inflammasomes are involved in the process of pathogen clearance and sterile inflammation. They are large multi-protein complexes that are located in the cytosol and play key roles in the production of the pivotal inflammatory cytokines, interleukin (IL)-1β and IL-18, and pyroptosis. The nucleotide-binding oligomerization domain, leucine-rich repeat-, and pyrin domain-containing 3 (NLRP3) inflammasome is a key mediator of sterile inflammation induced by various types of damage-associated molecular patterns (DAMPs). Recent evidence indicates that the NLRP3 inflammasome is involved in pregnancy dysfunction, including PE. Many DAMPs (uric acid, palmitic acid, high-mobility group box 1, advanced glycation end products, extracellular vesicles, cell-free DNA, and free fatty acids) are increased and associated with pregnancy complications, especially PE. This review focuses on the role of the NLRP3 inflammasome in the pathophysiology of PE.

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.

Role of the Monocyte-Macrophage System in Normal Pregnancy and Preeclampsia

The proper functioning of the monocyte-macrophage system, an important unit of innate immunity, ensures the normal course of pregnancy. In this review, we present the current data on the origin of the monocyte-macrophage system and its functioning in the female reproductive system during the ovarian cycle, and over the course of both normal and complicated pregnancy. Preeclampsia is a crucial gestation disorder characterized by pronounced inflammation in the maternal body that affects the work of the monocyte-macrophage system. The effects of inflammation at preeclampsia manifest in changes in monocyte counts and their subset composition, and changes in placental macrophage counts and their polarization. Here we summarize the recent data on this issue for both the maternal organism and the fetus. The influence of estrogen on macrophages and their altered levels in preeclampsia are also discussed.

Phagocytosis of Extracellular Vesicles Extruded From the Placenta by Ovarian Cancer Cells Inhibits Growth of the Cancer Cells

OBJECTIVE

Ovarian cancer is a common gynecological cancer, and parity is negatively associated with the incidence of this disease. This negative association is hypothesized to be due in part to shifting the balance of estrogen and progesterone toward more progesterone and reduced ovulation during pregnancy. However, studies suggested that parity is also associated with estrogen-independent gynecological cancers suggesting balance of hormones may not be the only protective factor. Extracellular vesicles (EVs) play an important role in cell-to-cell communication in physiological and pathological conditions. During pregnancy, large amounts of EVs are extruded from the placenta, and they seem to be involved in the remarkable adaptation of a woman's body to normal pregnancy. We hypothesized that EVs extruded from the placenta play a role in this protective effect.

METHODS

Placental EVs were collected from first-trimester placentae, and cancer cell EVs were isolated from ovarian cancer cells. The EVs were exposed to ovarian cancer cells for 48 hours. The proliferation of cancer cells and the cell cycle were measured. In addition, phagocytosis of deported placental EVs by cancer cells was also measured.

RESULTS

The proliferation of cancer cells was significantly reduced by treatment with placental EVs (P = 0.001, analysis of variance), but not EVs from monocytes (P = 0.195), compared with untreated cancer cells. Furthermore, placental EVs also prevented the proliferation of cancer cells induced by cancer cell-derived EVs (P = 0.001). This inhibition of proliferation of ovarian cancer cells was partially due to phagocytosis of placental EVs by cancer cells. Phagocytosis of placental EVs delayed progression through the cell cycle. Calreticulin, a phagocytic "eat me" signal carried by placental EVs significantly inhibited ovarian cancer growth (P = 0.001).

CONCLUSIONS

Our data demonstrated that EVs extruded from the placenta prevented ovarian cancer cell growth by a mechanism that involved delaying progression of the cell cycle after phagocytosis of the EVs.

Placental Nano-vesicles Target to Specific Organs and Modulate Vascular Tone In Vivo

STUDY QUESTION

How do nano-vesicles extruded from normal first trimester human placentae affect maternal vascular function?

SUMMARY ANSWER

Placental nano-vesicles affect the ability of systemic mesenteric arteries to undergo endothelium- and nitric oxide- (NO-) dependent vasodilation in vivo in pregnant mice.

WHAT IS KNOWN ALREADY

Dramatic cardiovascular adaptations occur during human pregnancy, including a substantial decrease in total peripheral resistance in the first trimester. The human placenta constantly extrudes extracellular vesicles that can enter the maternal circulation and these vesicles may play an important role in feto-maternal communication.

STUDY DESIGN, SIZE, DURATION

Human placental nano-vesicles were administered into CD1 mice via a tail vein and their localization and vascular effects at 30 min and 24 h post-injection were investigated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Nano-vesicles from normal first trimester human placentae were collected and administered into pregnant (D12.5) or non-pregnant female mice. After either 30 min or 24 h of exposure, all major organs were dissected for imaging (n = 7 at each time point) while uterine and mesenteric arteries were dissected for wire myography (n = 6 at each time point). Additional in vitro studies using HMEC-1 endothelial cells were also conducted to investigate the kinetics of interaction between placental nano-vesicles and endothelial cells.

MAIN RESULTS AND THE ROLE OF CHANCE

Nano-vesicles from first trimester human placentae localized to the lungs, liver and kidneys 24 h after injection into pregnant mice (n = 7). Exposure of pregnant mice to placental nano-vesicles for 30 min in vivo increased the vasodilatory response of mesenteric arteries to acetylcholine, while exposure for 24 h had the opposite effect (P < 0.05, n = 6). These responses were prevented by L-NAME, an NO synthase inhibitor. Placental nano-vesicles did not affect the function of uterine arteries or mesenteric arteries from non-pregnant mice. Placental nano-vesicles rapidly interacted with endothelial cells via a combination of phagocytosis, endocytosis and cell surface binding in vitro.

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

As it is not ethical to administer labelled placental nano-vesicles to pregnant women, pregnant CD1 mice were used as a model of pregnancy.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to report the localization of placental nano-vesicles and their vascular effects in vivo. This work provides new insight into how the dramatic maternal cardiovascular adaptations to pregnancy may occur and indicates that placental extracellular vesicles may be important mediators of feto-maternal communication in a healthy pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the Faculty of Medical and Health Science (FMHS) School of Medicine PBRF research fund to L.W.C. M.T. is a recipient of a University of Auckland Health Research Doctoral Scholarship and the Freemasons Postgraduate Scholarship. No authors have any competing interests to disclose.

Immunological effects of placental extracellular vesicles

Extracellular vesicles (EVs) extruded by the human placenta are increasingly being recognized as an essential mode of feto-maternal communication. In the past two decades, there has been an explosion of research into the roles that placental EVs play in modulating the maternal immune and cardiovascular systems during healthy pregnancies, as well as how this communication is altered in obstetric diseases. This review aims to introduce readers to the processes of placental EV formation and the cargos they carry, and also to collate and summarize the published literature that investigates the immunological effects of placental EVs throughout human pregnancy.

Harvesting and Characterization of Syncytial Nuclear Aggregates Following Culture of First Trimester Human Placental Explants

There is currently no effective method to study multinucleated trophoblast debris extruded from the syncytiotrophoblast into the maternal circulation. In Chapter 9 , an in vitro placental explant culture model to generate trophoblast debris was described. Here, we detail the method utilized to isolate individual large multinucleated syncytial nuclear aggregates (SNAs) that are extruded from the syncytiotrophoblast following the culture of first trimester human placental explants. Syncytial nuclear aggregates have been observed in the peripheral maternal circulation as early as 6 weeks' gestation and may play a role in tolerating the maternal immune system during pregnancy. Conversely, aberrant cell death processes in the syncytiotrophoblast due to various maternal factors leading to the extrusion of SNAs that are altered in nature have been implicated in the development of preeclampsia. The methods described herein allow for the isolation and harvest of SNAs without other types of extruded trophoblast debris and can be used to investigate the effect of various maternal factors on the nature of SNAs extruded from the placenta in vitro.

Melatonin prevents preeclamptic sera and antiphospholipid antibodies inducing the production of reactive nitrogen species and extrusion of toxic trophoblastic debris from first trimester placentae

BACKGROUND

The exact cause of preeclampsia is unknown. However a "toxin" from the placenta triggers the condition via activation of the maternal endothelium. Extracellular vesicles (EVs) from the syncytiotrophoblast, may be an endothelial-activating toxin. Antiphospholipid antibodies (aPL) and preeclamptic sera both induce the production of endothelial cell-activating EVs by mechanisms which may produce excess free-radicals in the placenta. Melatonin is produced by the human placenta and has both direct and indirect anti-free-radical properties and may therefore counter the effects of aPL and preeclamptic sera.

METHODS

First trimester placental explants were exposed to preeclamptic sera or aPL in the presence or absence of melatonin. Nitrosylative damage was assessed in the explants by immunohistochemistry and the effect of EVs from these explants on endothelial cell activation determined by ICAM-1. Release of nitrosylated proteins from the explants was also measured.

RESULTS

Placental explants showed reduced secretion of melatonin after treatment with preeclamptic sera. Nitrosylated proteins were more abundant in placentae that had been treated with aPL or preeclamptic sera and EVs from such placentae induced endothelial cell activation. Adding melatonin to the aPL or preeclamptic sera reversed the protein nitrosylation and production of endothelial-activating EVs.

DISCUSSION

Our data are consistent with reports that the levels of circulating melatonin are reduced in preeclampsia and suggest that aPL and factors in preeclamptic sera induce free-radical-mediated damage in the placenta leading to the production of endothelial-activating EVs. Melatonin reversing production of endothelial-activating EVs indicates that melatonin may have therapeutic benefits in women with preeclampsia and/or aPL.

Neutrophil Extracellular Traps Drive Endothelial-to-Mesenchymal Transition

OBJECTIVE

An excessive release and impaired degradation of neutrophil extracellular traps (NETs) leads to the continuous exposure of NETs to the endothelium in a variety of hematologic and autoimmune disorders, including lupus nephritis. This study aims to unravel the mechanisms through which NETs jeopardize vascular integrity.

APPROACH AND RESULTS

Microvascular and macrovascular endothelial cells were exposed to NETs, and subsequent effects on endothelial integrity and function were determined in vitro and in vivo. We found that endothelial cells have a limited capacity to internalize NETs via the receptor for advanced glycation endproducts. An overflow of the phagocytic capacity of endothelial cells for NETs resulted in the persistent extracellular presence of NETs, which rapidly altered endothelial cell-cell contacts and induced vascular leakage and transendothelial albumin passage through elastase-mediated proteolysis of the intercellular junction protein VE-cadherin. Furthermore, NET-associated elastase promoted the nuclear translocation of junctional β-catenin and induced endothelial-to-mesenchymal transition in cultured endothelial cells. In vivo, NETs could be identified in kidney samples of diseased MRL/lpr mice and patients with lupus nephritis, in whom the glomerular presence of NETs correlated with the severity of proteinuria and with glomerular endothelial-to-mesenchymal transition.

CONCLUSIONS

These results indicate that an excess of NETs exceeds the phagocytic capacity of endothelial cells for NETs and promotes vascular leakage and endothelial-to-mesenchymal transition through the degradation of VE-cadherin and the subsequent activation of β-catenin signaling. Our data designate NET-associated elastase as a potential therapeutic target in the prevention of endothelial alterations in diseases characterized by aberrant NET release.

Treating normal early gestation placentae with preeclamptic sera produces extracellular micro and nano vesicles that activate endothelial cells

OBJECTIVES

Preeclampsia is characterised by systemic endothelial cell dysfunction thought to be triggered by toxic/dangerous factors from the placenta, including placental extracellular vesicles (EVs). Why placental EVs become toxic is unknown. We previously reported that preeclamptic sera produced toxic/dangerous placental macrovesicles but whether small EVs are also toxic/dangerous in preeclampsia is unknown.

STUDY DESIGN

First trimester placental explants were treated with 10% preeclamptic or control sera (n=10) for 24h. Micro- and nano-vesicles were harvested by sequential centrifugation. Micro- or nano-vesicles were also exposed to monolayers of endothelial cells in the presence or absence of nifedipine (50μg/ml) or labetalol (0.5μg/ml) which are well-known anti-hypertensives in clinical practices.

MAIN OUTCOMES MEASURES

The number and size of micro- and nano-vesicles were counted. Endothelial cell-surface intercellular adhesion molecule 1 (ICAM-1) and high mobility group box 1 (HMGB1) levels in micro- or nano-vesicles were measured by immunoassays.

RESULTS

Neither the amount nor size of both micro- and nano-vesicles was different after treating placental explants with preeclamptic or control sera. The levels of HMGB1 were significantly increased in both micro- and nano-vesicles from preeclamptic sera treated placental explants (p<0.03). Exposing endothelial cells to micro- or nano-vesicles from preeclamptic sera-treated placental explants induced endothelial activation, but it was reversed by co-incubation with nifedipine (p=0.004) or labetalol (p=0.002).

CONCLUSION

Our data demonstrate that preeclamptic sera produce toxic/dangerous micro- and nano-placental EVs which activated endothelial cells. This effect was reversed by antihypertensives. The increased levels of HMGB1 in EVs may contribute to endothelial cell activation.

In vivo targets of human placental micro-vesicles vary with exposure time and pregnancy

Throughout human gestation, the placenta extrudes vast quantities of extracellular vesicles (EVs) of different sizes into the maternal circulation. Although multinucleated macro-vesicles are known to become trapped in the maternal lungs and do not enter the peripheral circulation, the maternal organs and cells that smaller placental micro-vesicles interact with in vivo remain unknown. This study aimed to characterise the interaction between placental micro-vesicles and endothelial cells in vitro and to elucidate which organs placental micro-vesicles localise to in vivo Placental macro- and micro-vesicles were isolated from cultured human first trimester placental explants by sequential centrifugation and exposed to human microvascular endothelial cells for up to 72 h. In vivo, placental macro- and micro-vesicles were administered to both non-pregnant and pregnant CD1 mice, and after two or 30 min or 24 h, organs were imaged on an IVIS Kinetic Imager. Placental EVs rapidly interacted with endothelial cells via phagocytic and clathrin-mediated endocytic processes in vitro, with over 60% of maximal interaction being achieved by 30 min of exposure. In vivo, placental macro-vesicles were localised exclusively to the lungs regardless of time of exposure, whereas micro-vesicles were localised to the lungs, liver and kidneys, with different distribution patterns depending on the length of exposure and whether the mouse was pregnant or not. The fact that placental EVs can rapidly interact with endothelial cells and localise to different organs in vivo supports that different size fractions of placental EVs are likely to have different downstream effects on foeto-maternal communication.

Pregnancy in the liver transplant recipient

During gestation, the woman's body undergoes various changes, and the line between physiology and pathology is very thin even in healthy women. Today, many of the liver transplant recipients are young women, who at one point in their lives may consider the possibility of pregnancy. Clinicians have to counsel them about the time of conception, the risk of miscarriage, the deterioration of the mother's health status, and the risk of birth defects. This review, based on our 20 years of clinical experience and up-to-date literature, provides comprehensive guidelines on pregnancy management in liver transplant recipients. Pregnancy in liver transplant recipients is possible but never physiological. Proper management and pharmacotherapy lowers the incidence of complications and birth defects. Critical factors for perinatal success include stable graft function before pregnancy, proper preparation for pregnancy, and cautious observation during its course. Liver Transplantation 22 1408-1417 2016 AASLD.

Increased levels of HMGB1 in trophoblastic debris may contribute to preeclampsia

Preeclampsia is triggered by an as yet unknown toxin from the placenta. Antiphospholipid antibodies (aPL), a strong risk factor for preeclampsia, have been shown to induce the production of toxic trophoblastic debris from the placenta. High mobility group box 1 (HMGB1) is a proinflammatory danger signal, and the expression of it has been reported to be increased in preeclampsia. This study examined whether aPL or preeclamptic sera increase the expression of HMGB1 in the syncytiotrophoblast or trophoblastic debris. Trophoblastic debris from normal placental explants that had been cultured with aPL or preeclamptic sera was exposed to endothelial cells. Endothelial cell activation was quantified by cell-surface ICAM-1 expression and U937 monocyte adhesion. The expression of HMGB1 in placental explants and trophoblastic debris that had been treated with aPL or preeclamptic sera was measured by immunohistochemistry and western blotting. The expression of the receptor for advanced glycation end products (RAGE) in endothelial cells was quantified by western blotting. Compared with controls, the expression of HMGB1 in the cytoplasm of the syncytiotrophoblast and trophoblastic debris was increased by treating placental explants with aPL or preeclamptic sera. The increased levels of HMGB1 contributed to endothelial cell activation, mediated in part by the RAGE. Preeclamptic sera and aPL both induced an increase in the cytoplasmic levels of the danger signal HMGB1 in trophoblastic debris. This increased HMGB1 in trophoblastic debris may be one of the toxic factors released from the placenta in preeclampsia.

Update of syncytiotrophoblast derived extracellular vesicles in normal pregnancy and preeclampsia

The release of extracellular vesicles (EV) by the syncytiotrophoblast (STB) may be an important mechanism by which the placenta signals to the mother. STB derived EV (STBEV) are comprised predominantly of exosomes (50-150nm) and microvesicles (100-1000nm) that contain bioactive mediators such as proteins, nucleic acids and lipids. They, along with larger syncytial nuclear aggregates are released by the STB into the maternal circulation throughout gestation in normal pregnancy where they appear to have an immunoregulatory role, inhibiting T cell and NK cell responses. In pre-eclampsia (PE) STBEV are released in significantly increased numbers and have pro-inflammatory, anti-angiogenic and procoagulant activity, implicating them in the maternal systemic inflammation, endothelial dysfunction and activation of the clotting system which typifies the disorder. Research has focused on understanding the biological significance of STBEV by measuring their size and repertoire of molecules carried and how they differ in normal pregnancy and PE, using techniques such as Nanoparticle Tracking Analysis, flow cytometry and mass spectrometry. We have also found alterations in STBEV surface glycans associated with PE. The goal is to better understand the role STBEV play in normal pregnancy and PE and whether they are potential biomarkers of placental pathology and therapeutic targets in PE.

Trophoblastic debris modifies endothelial cell transcriptome in vitro: a mechanism by which fetal cells might control maternal responses to pregnancy

The mechanisms by which the fetus induces maternal physiological adaptations to pregnancy are unclear. Cellular debris, shed from the placental syncytiotrophoblast into the maternal blood and phagocytosed by maternal endothelial and immune cells, may be one of these mechanisms. Here we show that trophoblastic debris from normal first trimester placentae induces changes in the transcriptome and proteome of endothelial cells in vitro, which might contribute to the adaptation of the maternal cardiovascular system to pregnancy. Trophoblastic debris also induced endothelial cells to transcribe placenta-specific genes, including the vasodilator hormone CSH1, thereby expanding the effective functional size of the placenta. Our data suggest that the deportation of trophoblastic debris is an important part of the complex network of feto-maternal communication.

The role of anti-phospholipid antibodies in autoimmune reproductive failure

Anti-phospholipid antibodies (aPL) are autoantibodies that are associated with thrombosis and a range of pregnancy complications including recurrent pregnancy loss and pre-eclampsia. The three clinically relevant, well-characterized aPL are anti-cardiolipin antibodies, lupus anticoagulant and anti-beta-2-glycoprotein I (β2GPI) antibodies. aPL do not bind directly to phospholipids but instead bind to a plasma-binding ‘cofactor’. The most extensively studied cofactor is β2GPI, whose role in pregnancy is not fully elucidated. Although the pathogenicity of aPL in recurrent pregnancy loss is well established in humans and animal models, the association of aPL with infertility does not appear to be causative. aPL may exert their detrimental effects during pregnancy by directly binding trophoblast cells of the placenta, altering trophoblast signalling, proliferation, invasion and secretion of hormones and cytokines, and by increasing apoptosis. Heparin is commonly used to treat pregnant women with aPL; however, as thrombotic events do not occur in the placentae of all women with aPL, it may exert a protective effect by preventing the binding of aPL to β2GPI or by acting through non-thrombotic pathways. The aim of this review is to present evidence summarizing the current understanding of this field.

Antiphospholipid antibodies bind syncytiotrophoblast mitochondria and alter the proteome of extruded syncytial nuclear aggregates

INTRODUCTION

Antiphospholipid antibodies (aPL) are autoantibodies that increase the risk of women developing the hypertensive disorder pre-eclampsia. aPL are internalised by the syncytiotrophoblast and increase extrusion of necrotic multinucleated syncytial nuclear aggregates (SNAs), which may trigger endothelial dysfunction in pre-eclampsia. The mechanisms by which aPL alter death processes in the syncytiotrophoblast leading to extrusion of SNAs are unknown.

METHODS

First trimester human placentae (n = 10) were dissected into explants and cultured either with aPL (50 μg/mL), isotype-matched control antibody (50 μg/mL), or media for 24 h. Harvested SNAs underwent iTRAQ proteomic analysis. Mitochondria in syncytiotrophoblast treated with aPL labelled with FluoroNanogold were visualised using transmission electron microscopy (TEM).

RESULTS

aPL altered the expression of 72 proteins in SNAs. Thirteen proteins were involved in mitochondrial function. TEM demonstrated that aPL bind to mitochondria in the syncytiotrophoblast and may cause mitochondrial swelling.

DISCUSSION

aPL disrupt mitochondria increasing the extrusion of SNAs with an altered proteome from the syncytiotrophoblast. These altered SNAs may trigger endothelial dysfunction and pre-eclampsia in these pregnancies.

IL-1 beta but not the NALP3 inflammasome is an important determinant of endothelial cell responses to necrotic/dangerous trophoblastic debris

INTRODUCTION

Necrotic but not apoptotic trophoblastic debris can induce endothelial cell activation but the mechanism by which endothelial cells distinguish apoptotic from necrotic debris is unclear. The NALP3 inflammasome is a pattern recognition receptor that macrophages employ to recognise "danger signals" in necrotic cell corpses. In this study, we hypothesized that endothelial cells can identify and respond to necrotic trophoblastic debris via the NALP3 inflammasome.

METHODS

The effect of trophoblastic debris on endothelial expression of NALP3 inflammasome components was investigated using qRT-PCR, immunoassays and fluorescent caspase 1 activity assay. IL-1β in was quantified by ELISA. Endothelial cell activation was measured by cell surface ICAM expression and monocytes adhesion assay.

RESULTS

The NALP3 inflammasome was expressed in resting vascular endothelial cells and is involved in endothelial response to danger signals. However, exposure to necrotic trophoblastic debris did not significantly alter the expression of any of the three components of the NALP3 inflammasome at the mRNA level, nor was caspase-1 activation increased. Conditioned media from endothelial cells exposed to necrotic trophoblastic debris contained elevated levels of IL-1β which was derived from the necrotic debris and which contributed to endothelial cell activation.

DISCUSSION

Necrotic trophoblastic debris induced endothelial cell activation through the IL-1β/IL-1R pathway. However, the NALP3 inflammasome in endothelial cells was not involved in this process.

The anti-inflammatory effect of calcium for preventing endothelial cell activation in preeclampsia

Preeclampsia is a disorder of pregnancy characterized by endothelial activation. It is believed to be a response to a 'toxin(s)' from the placenta including trophoblastic debris and inflammatory cytokines. Calcium is known to reduce the risk of preeclampsia but the mechanism of its protective effect remains unknown. In this study, we investigated the potential mechanism(s) of calcium supplementation for preventing endothelial activation induced by trophoblastic debris. Trophoblastic debris was harvested from preeclamptic placentae and also from first-trimester placentae, which had been treated with preeclamptic sera. Endothelial cells were then cultured with trophoblastic debris in the presence of calcium. Endothelial activation was measured by quantifying endothelial cell-surface intercellular adhesion molecule-1 (ICAM-1) and by U937 monocyte adhesion to endothelial cells. The expression of ICAM-1 and U937 adhesion to endothelial cells were significantly reduced following exposure of endothelial cells to trophoblastic debris from preeclamptic placenta or from first-trimester placentae treated with preeclamptic sera in the presence of calcium compared with treatment without calcium. The expression of ICAM-1 was also significantly reduced following exposure of endothelial cells to trophoblastic debris with the nitric oxide donor or following treatment of endothelial cells with interleukin (IL)-1β in the presence of calcium. Our study demonstrated that calcium supplementation prevented endothelial cell activation induced by trophoblastic debris from preeclamptic placentae. The nitric oxide synthase (NOS) pathway and anti-inflammatory effects are involved in the action of calcium on endothelial cell activation. These findings may suggest, at least in part, the protective mechanism of calcium supplementation on preeclampsia.

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.

Calcium supplementation prevents endothelial cell activation: possible relevance to preeclampsia

OBJECTIVES

Preeclampsia is a leading cause of maternal and fetal mortality and morbidity. A hallmark of preeclampsia is endothelial cell dysfunction/activation in response to 'toxins' from the placenta. Necrotic trophoblastic debris (NTD) is one possible placental toxin and other activators of endothelial cells include inflammatory cytokines. Calcium supplementation appears to protect 'at-risk' women from developing preeclampsia but how is unclear.

METHODS

Placental explants were cultured with interleukin-6 (IL-6) in varied concentrations of calcium. The resultant trophoblastic debris was exposed to endothelial cells. Endothelial cells were exposed to activators including NTD, IL-6, and preeclamptic sera in the presence of varied concentrations of calcium and activation monitored by quantifying cell surface markers by ELISA.

RESULTS

Raising the levels of calcium did not prevent the IL-6-induced shedding of NTD from placental explants but did prevent the activation of endothelial cells in response to IL-6, preeclamptic sera, or NTD. Reducing the level of calcium directly induced the activation of endothelial cells. Inhibiting nitric oxide synthetase ablated the ability of high calcium levels to protect endothelial cell activation. The activity of endothelial cell nitric oxide synthetase was blocked with L-N-nitroarginine methyl ester.

CONCLUSION

Our results demonstrate calcium levels do not affect the shedding of trophoblastic debris but are important to endothelial cell activation and supplemental calcium may reverse the activation of the endothelium in preeclamptic women. These results may in part explain the benefits of calcium supplementation in the reduction of risk for developing preeclampsia and provide in-vitro mechanistic support for the use of calcium supplementation in at-risk women.

Fetal-maternal interactions in the synepitheliochorial placenta using the eGFP cloned cattle model

Background

To investigate mechanisms of fetal-maternal cell interactions in the bovine placenta, we developed a model of transgenic enhanced Green Fluorescent Protein (t-eGFP) expressing bovine embryos produced by nuclear transfer (NT) to assess the distribution of fetal-derived products in the bovine placenta. In addition, we searched for male specific DNA in the blood of females carrying in vitro produced male embryos. Our hypothesis is that the bovine placenta is more permeable to fetal-derived products than described elsewhere.

Methodology/Principal Findings

Samples of placentomes, chorion, endometrium, maternal peripheral blood leukocytes and blood plasma were collected during early gestation and processed for nested-PCR for eGFP and testis-specific Y-encoded protein (TSPY), western blotting and immunohistochemistry for eGFP detection, as well as transmission electron microscopy to verify the level of interaction between maternal and fetal cells. TSPY and eGFP DNA were present in the blood of cows carrying male pregnancies at day 60 of pregnancy. Protein and mRNA of eGFP were observed in the trophoblast and uterine tissues. In the placentomes, the protein expression was weak in the syncytial regions, but intense in neighboring cells on both sides of the fetal-maternal interface. Ultrastructurally, our samples from t-eGFP expressing NT pregnancies showed to be normal, such as the presence of interdigitating structures between fetal and maternal cells. In addition, channels-like structures were present in the trophoblast cells.

Conclusions/Significance

Data suggested that there is a delivery of fetal contents to the maternal system on both systemic and local levels that involved nuclear acids and proteins. It not clear the mechanisms involved in the transfer of fetal-derived molecules to the maternal system. This delivery may occur through nonclassical protein secretion; throughout transtrophoblastic-like channels and/or by apoptotic processes previously described. In conclusion, the bovine synepitheliochorial placenta displays an intimate fetal-maternal interaction, similar to other placental types for instance human and mouse.