TLR8-activating miR-146a-3p is an intermediate signal contributing to fetal membrane inflammation in response to bacterial LPS.

Preterm birth is the largest contributor to neonatal morbidity and is often associated with chorioamnionitis, defined as inflammation/infection of the fetal membranes (FMs). Chorioamnionitis is characterised by neutrophil infiltration of the FMs and is associated with elevated levels of the neutrophil chemoattractant, interleukin (IL)-8 and the proinflammatory cytokine, IL-1ß. While FMs can respond to infections through innate immune sensors, such as toll-like receptors (TLRs), the downstream mechanisms by which chorioamnionitis arises are not fully understood. A novel group of non-classical microRNAs (miR-21a, miR-29a, miR-146a-3p, Let-7b) function as endogenous danger signals by activating the ssRNA viral sensors TLR7 and TLR8. In this study, the pro-inflammatory roles of TLR7/TLR8-activating miRs were examined as mediators of FM inflammation in response to bacterial lipopolysaccharide (LPS) using an in vitro human FM explant system, an in vivo mouse model of pregnancy, and human clinical samples. Following LPS exposure, miR-146a-3p was significantly increased in both human FM explants and wild-type mouse FMs. Expression of miR-146a-3p was also significantly elevated in FMs from women with preterm birth and chorioamnionitis. FM IL-8 and inflammasome-mediated IL-1ß production in response to LPS was dependent on miR-146a-3p and TLR8 downstream of TLR4 activation. In wild-type mice, LPS exposure increased FM IL-8 and IL-1ß production and induced preterm birth. In TLR7-/-/TLR8-/- mice, LPS exposure was able to initiate but not sustain preterm birth, and FM inflammation was reduced. Together, we demonstrate a novel signalling mechanism at the maternal-fetal interface in which TLR8-activating miR-146a-3p acts as an intermediate danger signal to drive FM inflammasome-dependent and -independent mechanisms of inflammation and, thus, may play a role in chorioamnionitis and subsequent preterm birth.

Decidualization dampens toll-like receptor mediated inflammatory responses in human endometrial stromal cells by upregulating IκBα.

Endometrial stromal cells (EnSCs) are the major cell type of the human endometrium and they undergo dramatic differentiation, termed decidualization, every month that enables them to be receptive to implantation. Appropriate decidualization and EnSC function is key for a successful pregnancy. EnSC function may be affected when the uterus is exposed to bacterial and viral infection. However, how human EnSCs respond to viral and bacterial components have not been well-studied and it remains unclear whether uterine innate immune responses change during decidualization. This study demonstrated that viral double-stranded RNA [Poly(I:C)] and bacterial lipopolysaccharide (LPS) upregulated undecidualized human EnSC production of a large array of proinflammatory cytokines and chemokines, and revealed that these immune responses were significantly dampened during decidualization in vitro and in vivo. This dampened response was associated with increased NFKBIA transcription during decidualization that leads to the accumulation of this negative regulator in decidualizing EnSCs that can bind to NFκB p65 and prevents its nuclear translocation and downstream Toll-like receptor signaling. These findings highlight that endometrial responses to infection may vary at different stages of the menstrual cycle which may be important for preparing the endometrium to support the growth of the semi-allogenic blastocyst. This work emphasizes the need to consider menstrual cycle stage, sex hormone levels and the differentiation status of cells when examining inflammatory responses in the future.

Endometrial responses to bacterial and viral infection: a scoping review.

BACKGROUND: The endometrium is a highly dynamic tissue that undergoes dramatic proliferation and differentiation monthly in order to prepare the uterus for implantation and pregnancy. Intrauterine infection and inflammation are being increasingly recognized as potential causes of implantation failure and miscarriage, as well as obstetric complications later in gestation. However, the mechanisms by which the cells of the endometrium respond to infection remain understudied and recent progress is slowed in part owing to similar overlapping studies being performed in different species. OBJECTIVE AND RATIONALE: The aim of this scoping review is to systematically summarize all published studies in humans and laboratory animals that have investigated the innate immune sensing and response of the endometrium to bacteria and viruses, and the signaling mechanisms involved. This will enable gaps in our knowledge to be identified to inform future studies. SEARCH METHODS: The Cochrane Library, Ovid Embase/Medline, PubMed, Scopus, Google Scholar, and Web of Science databases were searched using a combination of controlled and free text terms for uterus/endometrium, infections, and fertility to March 2022. All primary research papers that have reported on endometrial responses to bacterial and viral infections in the context of reproduction were included. To focus the scope of the current review, studies in domesticated animals, included bovine, porcine, caprine, feline, and canine species were excluded. OUTCOMES: This search identified 42 728 studies for screening and 766 full-text studies were assessed for eligibility. Data was extracted from 76 studies. The majority of studies focused on endometrial responses to Escherichia coli and Chlamydia trachomatis, with some studies of Neisseria gonorrhea, Staphylococcus aureus, and the Streptococcus family. Endometrial responses have only been studied in response to three groups of viruses thus far: HIV, Zika virus, and the herpesvirus family. For most infections, both cellular and animal models have been utilized in vitro and in vivo, focusing on endometrial production of cytokines, chemokines, and antiviral/antimicrobial factors, and the expression of innate immune signaling pathway mediators after infection. This review has identified gaps for future research in the field as well as highlighted some recent developments in organoid systems and immune cell co-cultures that offer new avenues for studying endometrial responses to infection in more physiologically relevant models that could accelerate future findings in this area. WIDER IMPLICATIONS: This scoping review provides an overarching summary and benchmark of the current state of research on endometrial innate immune responses to bacterial and viral infection. This review also highlights some exciting recent developments that enable future studies to be designed to deepen our understanding of the mechanisms utilized by the endometrium to respond to infection and their downstream effects on uterine function.

Antiphospholipid Antibodies Increase Endometrial Stromal Cell Decidualization, Senescence, and Inflammation via Toll-like Receptor 4, Reactive Oxygen Species, and p38 MAPK Signaling.

OBJECTIVE: Miscarriage affects 1 in 7 pregnancies, and antiphospholipid autoantibodies (aPLs) are one of the biggest risk factors for recurrent pregnancy loss. While aPLs target the endometrial stroma, little is known about their impact. Endometrial stromal cells (EnSCs) undergo decidualization each menstrual cycle, priming the uterus to receive implanting embryos. Thus, appropriate decidualization and EnSC function is key for establishment of a successful pregnancy. This study was undertaken to explore the effects of aPL on EnSC decidualization, senescence, and inflammation. METHODS: EnSCs under decidualizing conditions were exposed to aPL or control IgG alone or in the presence of either a Toll-like receptor 4 (TLR-4) antagonist, a p38 MAPK inhibitor, a reactive oxygen species (ROS) inhibitor, low molecular weight heparin (LMWH), or acetyl salicylic acid. Secretion of decidualization markers and inflammatory interleukin-8 were quantified by enzyme-linked immunosorbent assay, and senescence-associated ß-galactosidase activity was evaluated. In a mouse model of decidualization, aPL or control IgG was administered, and uterine expression levels of decidualization and inflammatory markers were quantified by real-time quantitative polymerase chain reaction. RESULTS: Antiphospholipid antibodies increased human EnSC decidualization, senescence, and inflammation. This phenotype was recapitulated in the mouse model. The decidualization and inflammatory responses were partially mediated by TLR-4 and p38 MAPK, while the decidualization and senescence responses were ROS-dependent. LMWH, commonly used to treat aPL-positive women at risk of obstetric complications, reduced the ability of aPL to increase EnSC decidualization and inflammation. CONCLUSION: These findings shed new light on the pathogenesis of pregnancy complications in women with aPLs and underscore the benefit of heparin in preventing pregnancy loss in this high-risk population.

A Comparison of Treatment Options for Type 1 and Type 2 Caesarean Scar Pregnancy: A Retrospective Case Series Study.

Background: There is currently no agreement on the optimal management of caesarean scar pregnancy. Caesarean scar pregnancy is currently categorised into two subtypes according to the site of implantation. This may consequently result in the difference in treatment options. However, the comparison of the success rate of each treatment option according to the subtypes has not been fully investigated. Methods: 71 patients who were treated by uterine curettage (D and C), or uterine artery embolization with curettage (UAE) or hysteroscopy in conjunction with laparoscopy between January 2016 and March 2020 were included. Data on maternal age, gestational sac age, the sac diameter, the interval between two pregnancies, the number of previous caesarean sections, amount of bleeding and ß-hCG levels were collected and analysed dependent on the subtypes. Results: There was no difference in the clinical parameters of the cases who received different options of treatment, as well as no difference in the clinical parameters between type 1 and type 2 caesarean scar pregnancy. The primary success rate for type 1 caesarean scar pregnancy by D and C, or UAE, or hysteroscopy in conjunction with laparoscopy was 95, or 100 or 100%, respectively. The primary success rate for type 2 caesarean scar pregnancy by D and C, or UAE, or hysteroscopy in conjunction with laparoscopy was 27, or 67, or 95% respectively. Conclusion: Our data demonstrates that hysteroscopy in conjunction with laparoscopy for type 2 caesarean scar pregnancy was the most successful compared to other options, but for type 1 caesarean scar pregnancy, D and C could be the cost-effective option.

Visualization and Quantification of Neutrophil Extracellular Traps.

Neutrophils are innate immune cells that play important roles in many physiological and pathological processes, including immune defense and cancer metastasis. In addition to the release of proinflammatory cytokines, chemokines, and cytoplasmic granules containing digestive proteins, in recent years, neutrophils have been observed to release neutrophil extracellular traps (NETs) that consist of extracellular DNA associated with antimicrobial proteins, such as histones and myeloperoxidase. These NETs are increasingly being recognized as an important mechanism of neutrophil host defense and function. This chapter will summarize the current literature on the known processes of NET formation and describe in detail an immunofluorescence approach that can be employed to visualize and quantify NETs in vitro.

Active Management Reduces the Incidence of Recurrent Pre-eclampsia and Improves Maternal and Fetal Outcomes in Women With Recurrent Pre-eclampsia.

Background: Women with previous pre-eclampsia are at an increased risk of developing recurrent pre-eclampsia. Intervention with low dose aspirin had been recommended to reduce the incidence of recurrent pre-eclampsia. However, the association between interventions and maternal and neonatal outcomes in subsequent pregnancies in women with previous pre-eclampsia has not been fully studied. Methods: In this prospective study, a total of 41 patients with previous pre-eclampsia received low dose aspirin and active management (including psychological and physiological intervention), between 10 to 28 weeks until 32 to 34 weeks in our regional referral hospital. The recurrence of pre-eclampsia, and maternal and neonatal outcomes in this pregnancy were analyzed and compared to our previous study which reported a 60% recurrence of pre-eclampsia in our regional referral hospital. Results: Thirteen women with previous pre-eclampsia developed recurrent pre-eclampsia. The time of onset or severity of pre-eclampsia in the previous pregnancy was not associated with the incidence of recurrent pre-eclampsia. The time of onset of previous pre-eclampsia was also not associated with the time of onset in subsequent pre-eclampsia. However, the number of severe recurrent pre-eclampsia was significantly reduced, compared to their first pregnancies. The number of SGA and stillbirth/neonatal death was also significantly reduced in recurrent pre-eclampsia that was actively managed, compared to their first pregnancies. Conclusion: Despite the small sample size included in this study, our study demonstrates that active obstetric management reduces the incidence of recurrent pre-eclampsia, compared to our previous study, and reduces the severity of recurrent pre-eclampsia. It also improves neonatal outcomes in recurrent pre-eclampsia. However, because of no controls in this study, our findings need to confirmed by a case-control or randomized clinical trial study.

Polymicrobial stimulation of human fetal membranes induce neutrophil activation and neutrophil extracellular trap release.

Preterm birth is a major contributor to neonatal mortality and morbidity. While the causes of preterm birth remain incompletely understood, infection is a major risk factor, and chorioamnionitis is commonly observed. Chorioamnionitis is characterized by inflammation and neutrophil infiltration of the fetal membranes (FM). We recently reported that human FMs which had been exposed to low levels of bacterial lipopolysaccharide (LPS) recruit neutrophils and activate them, increasing their secretion of pro-inflammatory cytokines, degranulation of myeloperoxidase (MPO), and release of neutrophil extracellular traps (NETs). Herein, we demonstrate that conditioned media (CM) from viral dsRNA (Poly(I:C))-stimulated FMs also increased neutrophil migration, and induced the secretion of inflammatory IL-8 and the release of NETs. Furthermore, CM from FMs stimulated by a combination of bacterial LPS and Poly(I:C) augmented neutrophil NET release, compared to CM from FMs stimulated with either Poly(I:C) or LPS alone. NETs induced by FMs exposed to Poly(I:C), with or without LPS, were released and degraded quicker than those induced by resting or LPS-stimulated FM-CM. These findings indicate that FMs exposed to viral dsRNA promote neutrophil recruitment, activation and NET formation, similar to FMs exposed to bacterial LPS alone. However, in response to FM polymicrobial stimulation the levels and kinetics of NET release are augmented. This work builds upon our understanding of how infections at the maternal-fetal interface may affect neutrophil function.

Activated Neutrophils Propagate Fetal Membrane Inflammation and Weakening through ERK and Neutrophil Extracellular Trap-Induced TLR-9 Signaling.

Preterm birth is associated with significant neonatal mortality and morbidity worldwide. Chorioamnionitis, inflammation of the fetal membranes (FMs), is a major risk factor and is characterized by neutrophil infiltration. However, the role of neutrophils at the FMs remains unclear. We recently reported that FMs exposed to bacterial LPS recruited more neutrophils compared with resting FMs and activated them to degranulate and release reactive oxygen species, chemokines/cytokines, and neutrophil extracellular traps. We posit that under resting conditions, neutrophils play a protective surveillance role, whereas during infection/inflammation, they induce FM tissue injury. To test this, human FM explants were exposed to neutrophil conditioned media (CM). We demonstrate that CM from neutrophils exposed to resting FM-CM did not affect FM viability or function. Conversely, CM from neutrophils activated by LPS-stimulated FM-CM significantly increased FM secretion of inflammatory IL-6, IL-8, GRO-α, and the markers of membrane weakening, MMP-9 and PGE2 This FM response was partially mediated by ERK signaling and neutrophil extracellular traps through the activation of the DNA sensor, TLR-9. Thus, neutrophils recruited by FMs during infection can propagate FM inflammation and weakening, acting in a feed-forward mechanism to propagate tissue injury at the maternal-fetal interface, increasing the risk of premature FM rupture and preterm birth in women with intrauterine infection.

Antiphospholipid antibodies and extracellular vesicles in pregnancy.

Antiphospholipid antibodies (aPL) are autoantibodies that target phospholipid-binding proteins, such as ß2 glycoprotein I (ß2GPI), 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 ß2GPI 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.

Neutrophils in preterm birth: Friend or foe?

Preterm birth is a serious global health problem that affects 5-18% of pregnancies worldwide. In addition to being the major cause of neonatal mortality and morbidity, preterm birth is associated with short term and long term complications in the offspring. Despite this, the causes and pathogenesis of preterm birth remain unclear. Neutrophils are innate immune cells that infiltrate the maternal-fetal interface during normal parturition and their accumulation is dramatically increased during preterm birth, especially in the presence of an infection. Indeed, a defining feature of chorioamnionitis (inflammation of the chorioamnionic fetal membranes) that is associated with more than 40% of preterm births, is neutrophil accumulation. While these cells may play an important role during normal term parturition as well as preterm birth, their functions at the maternal-fetal interface are unclear. This review will provide a broad overview of the relevant studies to enable a better understanding of the roles of neutrophils during normal parturition and preterm birth.

Is body mass index associated with irregular menstruation: a questionnaire study?

BACKGROUND: Irregular menstrual cycles including the length of cycles and menses, and heavy menstrual blood loss are linked to many gynaecological diseases. Obesity has been reported to be associated with irregular menstrual cycles. However, to date, most studies investigating this association are focused on adolescence or university students. Whether this association is also seen in adult women, especially women who had a history of birth has not been fully investigated. METHODS: Questionnaire data were collected from 1012 women aged 17 to 53 years. Data on age, weight and height, gravida, the length of menstrual cycles and menses, and the number of pads used during menses were collected. Factors associated with menstrual cycle according to BMI categories were analysed. RESULTS: There were no differences in the length of menstrual cycles and menses in women of different body mass index (BMI) groups. However, there was a significant difference in menstrual blood loss in women of different BMI categories. The odds ratio of having heavy menstrual blood loss in obese women was 2.28 (95% CL: 1.244, 4.193), compared to women with normal weight, while there was no difference in the odds ratio of having heavy menstrual blood loss in overweight, compared to normal weight, women. In contrast, the odds ratio of having heavy menstrual blood loss in underweight women was 0.4034 (95% CL: 0.224, 0.725), compared to women with normal weight. CONCLUSION: Although BMI was not correlated with the length of menstrual cycle and menses, BMI is positively associated with menstrual blood loss. Our data suggest that BMI influences menstrual blood loss in women of reproductive age and weight control is important in women's reproductive years.

Viral infection dampens human fetal membrane type I interferon responses triggered by bacterial LPS.

The maternal-fetal interface possesses innate immune strategies to protect against infections. We previously reported that prior viral infection of human fetal membranes (FMs) in vitro and mouse FMs in vivo sensitized the tissue to low dose bacterial LPS leading to augmented inflammation. The objective of this study was to examine FM production of type I interferons (IFNs) and IFN-stimulated genes (ISGs) in the context of this polymicrobial model. Human FM explants and pregnant C57BL/6 mice were treated with or without low dose LPS following exposure to media or the γ-herpes virus, MHV-68. FM RNA was analyzed by qRT-PCR for type I IFNs, ISGs, upstream signaling, and MHV-68 open reading frames (ORFs). Pre-exposure to MHV-68 followed by LPS treatment inhibited the ability of LPS to induce human FM type I IFNs (IFNA, IFNB); ISGs (OAS, MxA, APOBEC3G) and upstream signaling mediators (RIG-I, TBK-1). Signaling mediators IRF-3 and IRF-7 were also reduced. In mouse FMs, pre-exposure to MHV-68 followed by LPS treatment reduced the ability of LPS to upregulate Ifna, Ifnb, Mxa, Irf7, and also reduced Irf3. MHV-68 infection of FMs induced ORF45 which targets IRF-7, and this was further augmented in response to a combination of MHV-68 and LPS. Together, these findings indicate that a viral infection blunts FM type I IFN production and signaling in response to LPS leading to a suppressed ISG response. Our studies suggest that a viral infection inhibits this protective FM response by negatively regulating IRF-7 through ORF45, leaving the maternal-fetal interface vulnerable to further viral attack.

Immunology of the Placenta.

In this article, the authors provide a general overview of the major immune cells present at the maternal-fetal interface, describe the key mechanisms used by the placenta to promote maternal immune regulation, tolerance, and adaptation, and discuss how dysregulation of these pathways could lead to obstetric complications such as pregnancy loss and preeclampsia. Finally, they conclude with a description of the innate immune properties of the human placenta that not only serve to protect the pregnancy from infection but also contribute to pregnancy complications such as preterm birth.

Are maternal and neonatal outcomes different in placental abruption between women with and without preeclampsia?

INTRODUCTION: Placental abruption is a serious pregnancy complication that causes maternal and neonatal mortality and morbidity. Whether maternal and neonatal outcomes differ between patients who concurrently presented with preeclampsia and those who did not, have not been fully investigated. METHODS: A total number of 158 patients with placental abruption were included. Of them, 66 concurrently had preeclampsia. Maternal and neonatal characteristics including delivery weeks, time of onset and birthweight as well as the grade of placental abruption were collected and analysed. RESULTS: The time at diagnosis of placental abruption in patients who concurrently presented preeclampsia was significantly earlier than that in patients who did not. The number of patients with grade III placental abruption was significantly higher in patients who concurrently presented with preeclampsia, compared to patients who did not. The odds ratio of an increase in grade III placental abruption in patients who concurrently presented preeclampsia was 5.27 (95%CL: 2.346, 12.41), compared to patients who did not. The numbers of infants who were born pre-term and the numbers of stillbirth/neonatal deaths as well as the number of fetal distress were significantly higher in patients who concurrently presented with preeclampsia, compared to patients who did not. The fetal birthweight was significantly lower in patients who concurrently presented with preeclampsia compared to patients who did not. DISCUSSION: Our study demonstrates that women with preeclampsia experiencing placental abruption had worse maternal, fetal and neonatal outcomes, compared to women experiencing placental abruption alone.

Does attendance of a prenatal education course reduce rates of caesarean section on maternal request? A questionnaire study in a tertiary women hospital in Shanghai, China.

OBJECTIVE: Caesarean section rates have significantly increased worldwide. China has a caesarean rate of 46%, with a moderate contribution of caesarean section on maternal request. In this study, we investigated the association between maternal characteristics, attendance at a prenatal education course and caesarean section on maternal request. DESIGN: Questionnaire study. SETTING: Tertiary hospital in China. SAMPLE: 564 questionnaires. METHODS: On postpartum day 42, questionnaire data were collected. Data including age, parity, gravida, delivery mode, educational level, residence status, living condition and attendance of prenatal education course were analysed. PRIMARY AND SECONDARY OUTCOME MEASURES: Factors associated with caesarean section on maternal request. RESULTS: 46% of women were delivered by caesarean section on maternal request. Maternal age and residence status were all significantly associated with having a caesarean section on maternal request. The OR of an increase in caesarean section on maternal request in women over 30 years was 2.42 (95%confidence limits 1.597 to 3.666), compared with women under 30 years. 75% more women who resided in Shanghai had caesarean section on maternal request, compared with women who resided outside of Shanghai. However, there was a significant reduction (35%) in the number of caesarean sections on maternal request in women who attended a prenatal education course (p=0.029). There was no significant association between attendance of a prenatal education course and the other maternal characteristics studied. CONCLUSION: Maternal age is associated with an increased risk of caesarean section on maternal request. For women of all age, attendance of a prenatal education course significantly reduced the rate of caesarean section on maternal request. Our data suggest that promotion of a prenatal education course is an important tool in China to reduce the rate of caesarean section.

Lipopolysaccharide-Stimulated Human Fetal Membranes Induce Neutrophil Activation and Release of Vital Neutrophil Extracellular Traps.

Preterm birth is a major contributor to neonatal mortality and morbidity, and infection is a major risk factor. Chorioamnionitis, inflammation of the placenta, and fetal membranes (FMs) are commonly observed in preterm birth and are characterized by neutrophil infiltration. However, interactions between FMs and neutrophils remain incompletely understood. The objectives of this study were to determine how FMs, with or without bacterial LPS stimulation, affect neutrophil recruitment, activation, and the formation of neutrophil extracellular traps (NETs) and to elucidate the signaling mechanisms involved. Using a combination of in vitro, ex vivo, and in vivo approaches, we show that human resting FMs can directly recruit neutrophils and induce them to produce proinflammatory factors. Furthermore, neutrophils release vital NETs in response to FM-derived factors. LPS-stimulated FMs further augmented neutrophil recruitment, inflammatory cytokine/chemokine secretion, and vital NET release and also induced reactive oxygen species production and degranulation. We demonstrate a role for FM-derived TNF-α in mediating these effects through activation of neutrophil p38 MAPK. We propose that, during infection, neutrophil recruitment and activation may neutralize pathogens, vital NET formation, and prolonged neutrophil viability, and in combination with degranulation, reactive oxygen species production and inflammatory chemokine/cytokine production may contribute to tissue injury at the maternal/fetal interface.

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.

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.

Isolation and Characterization of Extracellular Vesicles from Ex Vivo Cultured Human Placental Explants.

Ex vivo culture of human placental explants has long allowed placentologists to study the milieu of soluble factors secreted by the human placenta throughout gestation while retaining the correct three-dimensional structure of the placental villi. Here, we detail the placental explant culture method employed in our laboratory to collect extracellular vesicles which are known to be released by the human placenta throughout pregnancy from 6 weeks of gestation. Using this method, at least three different populations of placental extracellular vesicles can be simultaneously collected from each placental sample, allowing for comparative analysis of the cargos and downstream effects of the different types of extracellular vesicles produced by the human placenta.