Human placental explants in culture: approaches and assessments

Toxicity of anticancer drugs in human placental tissue explants and trophoblast cell lines

The application of anticancer drugs during pregnancy is associated with placenta-related adverse pregnancy outcomes. Therefore, it is important to study placental toxicity of anticancer drugs. The aim of this study was to compare effects on viability and steroidogenesis in placental tissue explants and trophoblast cell lines. Third trimester placental tissue explants were exposed for 72 h (culture day 4–7) to a concentration range of doxorubicin, paclitaxel, cisplatin, carboplatin, crizotinib, gefitinib, imatinib, or sunitinib. JEG-3, undifferentiated BeWo, and syncytialised BeWo cells were exposed for 48 h to the same drugs and concentrations. After exposure, tissue and cell viability were assessed and progesterone and estrone levels were quantified in culture medium. Apart from paclitaxel, all compounds affected both cell and tissue viability at clinically relevant concentrations. Paclitaxel affected explant viability moderately, while it reduced cell viability by 50% or more in all cell lines, at 3–10 nM. Doxorubicin (1 µM) reduced viability in explants to 83 ± 7% of control values, whereas it fully inhibited viability in all cell types. Interference with steroid release in explants was difficult to study due to large variability in measurements, but syncytialised BeWo cells proved suitable for this purpose. We found that 1 µM sunitinib reduced progesterone release to 76 ± 6% of control values, without affecting cell viability. While we observed differences between the models for paclitaxel and doxorubicin, most anticancer drugs affected viability significantly in both placental explants and trophoblast cell lines. Taken together, the placenta should be recognized as a potential target organ for toxicity of anticancer drugs.

Cholesterol Crystals and NLRP3 Mediated Inflammation in the Uterine Wall Decidua in Normal and Preeclamptic Pregnancies

Preeclampsia is a hypertensive and inflammatory pregnancy disorder associated with cholesterol accumulation and inflammation at the maternal-fetal interface. Preeclampsia can be complicated with fetal growth restriction (FGR) and shares risk factors and pathophysiological mechanisms with cardiovascular disease. Cholesterol crystal mediated NLRP3 inflammasome activation is central to cardiovascular disease and the pathway has been implicated in placental inflammation in preeclampsia. Direct maternal-fetal interaction occurs both in the uterine wall decidua and at the placental surface and these aligned sites constitute the maternal-fetal interface. This study aimed to investigate cholesterol crystal accumulation and NLRP3 inflammasome expression by maternal and fetal cells in the uterine wall decidua of normal and preeclamptic pregnancies. Pregnant women with normal (n = 43) and preeclamptic pregnancies with (n = 28) and without (n = 19) FGR were included at delivery. Cholesterol crystals were imaged in decidual tissue by both second harmonic generation microscopy and polarization filter reflected light microscopy. Quantitative expression analysis of NLRP3, IL-1β and cell markers was performed by immunohistochemistry and automated image processing. Functional NLRP3 activation was assessed in cultured decidual explants. Cholesterol crystals were identified in decidual tissue, both in the tissue stroma and near uterine vessels. The cholesterol crystals in decidua varied between pregnancies in distribution and cluster size. Decidual expression of the inflammasome components NLRP3 and IL-1β was located to fetal trophoblasts and maternal leukocytes and was strongest in areas of proximity between these cell types. Pathway functionality was confirmed by cholesterol crystal activation of IL-1β in cultured decidual explants. Preeclampsia without FGR was associated with increased trophoblast dependent NLRP3 and IL-1β expression, particularly in the decidual areas of trophoblast and leukocyte proximity. Our findings suggest that decidual accumulation of cholesterol crystals may activate the NLRP3 inflammasome and contribute to decidual inflammation and that this pathway is strengthened in areas with close maternal-fetal interaction in preeclampsia without FGR.

Exploiting the placenta for nanoparticle-mediated drug delivery during pregnancy

A major challenge to treating diseases during pregnancy is that small molecule therapeutics are transported through the placenta and incur toxicities to the developing fetus. The placenta is responsible for providing nutrients, removing waste, and protecting the fetus from toxic substances. Thus, the placenta acts as a biological barrier between the mother and fetus that can be exploited for drug delivery. Nanoparticle technologies provide the opportunity for safe drug delivery during pregnancy by controlling how therapeutics interact with the placenta. In this Review, we present nanoparticle drug delivery technologies specifically designed to exploit the placenta as a biological barrier to treat maternal, placental, or fetal diseases exclusively, while minimizing off-target toxicities. Further, we discuss opportunities, challenges, and future directions for implementing drug delivery technologies during pregnancy.

Schinus terebenthifolius Raddi extracts: From sunscreen activity toward protection of the placenta to Zika virus infection, new uses for a well-known medicinal plant

Schinus terebinthifolius Raddi is a well-known medicinal plant native of South America. This species has demonstrated important biological activities such as antihypertensive and vasodilator, antimicrobial, anti-inflammatory and antioxidant. However, no studies have been, so far, reported with the fruits of S. terebinthifolius as a protector of the placenta against Zika virus infection and as sunscreen agents. The present study aimed to investigate new uses for the ethanolic fruit extracts of S. terebinthifolius, from fruits'peel (STPE) and from the whole fruits (STWFE). Zika virus (ZIKV) has been linked to several fetal malformations, such as microcephaly and other central nervous system abnormalities. Thus, the potential of these natural extracts against ZIKV infection was evaluated, using an in vitro method. The photoprotective potential, determined by spectrometry, along with phenolic content, antioxidant capacity, and chemical composition of both extracts were also evaluated. The chemical composition of the extracts was evaluated by HPLC-UV / vis. The cytotoxicity of peel and whole fruit extracts in vero E6 cell lines, in placental cell lines and placental explant cultures were evaluated by the MTT assay. The infectivity of placental cells and explants was evaluated by qRT-PCR and the effects of extracts on ZIKV infection were investigated using HTR-8/SVneo cells, pre-treated with 100 μg mL^-1 of STWFE for 1 h, and infected with MR766 (AD) or PE243 (EH) ZIKV strains. STFE and STWFE were well-tolerated by both placental-derived trophoblast cell line HTR-8/SVneo as well as by term placental chorionic villi explants, which indicate absence of cytotoxicity in all analysed concentrations. Two strains of ZIKV were tested to access if pre-treatment of trophoblast cells with the STWFE would protect them against infection. Flow cytometry analysis revealed that STWFE extract greatly reduced ZIKV infection. The extracts were also photoprotective with SPF values equivalent to the standard, benzophenone-3. The formulations prepared in different concentrations of the extracts (5-10 %) had shown maximum SPF values of 32.21. STWFE represents a potential natural mixture to be used in pregnancy in order to restrain placental infection by ZIKV and might potentially protect fetus against ZIKV-related malformations. The extracts exhibited photoprotective activity and some of the phenolic compounds, mainly resveratrol, catechin and epicatechin, are active ingredients in all assayed activities. The development of biotechnological/medical products, giving extra value to products from family farming, is expected, with strong prospects for success.

Sulforaphane improves vascular reactivity in mouse and human arteries after "preeclamptic-like" injury

INTRODUCTION

The widespread maternal endothelial dysfunction that underlies the manifestations of preeclampsia is thought to arise from excessive placental production of antiangiogenic factors and enhanced oxidative stress. Therefore, we assessed whether the natural antioxidant sulforaphane could improve vascular function.

METHODS

Cell viability of human umbilical vein endothelial cells (HUVECs) was assessed after 24 or 48 h in normoxia (20% O₂) or hypoxia (1% O₂) with or without sulforaphane. To model vascular dysfunction associated with preeclampsia, mouse mesenteric arteries were incubated in trophoblast conditioned media (TCM), and human omental arteries incubated in preeclamptic explant media (PEM) with or without sulforaphane. Both media are rich in antiangiogenic compounds associated with preeclampsia. TCM was generated from primary cytotrophoblast cells from term placentae of normotensive, while PEM was generated from explants from preeclamptic women. Reactivity was assessed by wire myography. sulforaphane's actions as a vasodilator were also investigated.

RESULTS

Under conditions of hypoxia, sulforaphane improved HUVEC viability. In mouse mesenteric arteries, sulforaphane reduced contraction evoked by potassium (p < 0.001), phenylephrine and endothelin 1 (all p < 0.001). Sulforaphane also inhibited Ca²⁺-induced contraction (p = 0.014). Sulforaphane prevented TCM-induced augmentation of phenylephrine and angiotensin II-mediated contraction of mouse mesenteric arteries. In human omental arteries, sulforaphane induced vasodilation (p < 0.001), and prevented PEM-induced endothelial dysfunction by restoring arterial sensitivity to the endothelium-dependent vasodilator bradykinin (p = 0.008).

DISCUSSION

Sulforaphane causes relaxation in arteries and protects against arterial dysfunction induced by placental-derived antiangiogenic factors, which are known to contribute to the preeclampsia.

The unique applicability of the human placenta to the Adverse Outcome Pathway (AOP) concept: the placenta provides fundamental insights into human organ functions at multiple levels of biological organization

Despite the short lifespan of the human placenta, the proper formation and function of the organ is of crucial importance for fetal development. Placental dysfunction increases the risk of complications for mother and child during pregnancy and childbirth and beyond as it predisposes to fetal programming. The placenta is an upstream organ of the fetus. It performs the functions of fetal lungs, liver, intestines, kidneys and glands as long as these organs are not fully functional. Furthermore, it is the only human organ that is non-invasively available either after elective abortion or after birth. This is a crucial point given that the conceptual framework of Adverse Outcome Pathway (AOP) requires data on organ function. In vitro and ex vivo placental studies, combined with epidemiological and clinical data on pregnant women, newborns, and infants can uniquely cover all levels of information needed to develop new AOPs and complement existing AOPs related to reproductive toxicity and beyond. To stimulate further research in this area and to support researchers in future studies dealing with the development of AOPs related to the placenta, this review first gives a brief description of placental structure, placental development and relevant pregnancy diseases. The state of knowledge about the available placental models, their particularities and limitations are briefly discussed. Finally, the use of placental research for the development of AOPs is presented with an illustrative example.

Maternal Immunization: Nature Meets Nurture

Vaccinating women in pregnancy (i.e., maternal immunization) has emerged as a promising tool to tackle infant morbidity and mortality worldwide. This approach nurtures a 'gift of nature,' whereby antibody is transferred from mother to fetus transplacentally during pregnancy, or postnatally in breast milk, thereby providing passive, antigen-specific protection against infections in the first few months of life, a period of increased immune vulnerability for the infant. In this review, we briefly summarize the rationale for maternal immunization programs and the landscape of vaccines currently in use or in the pipeline. We then direct the focus to the underlying biological phenomena, including the main mechanisms by which maternally derived antibody is transferred efficiently to the infant, at the placental interface or in breast milk; important research models and methodological approaches to interrogate these processes, particularly in the context of recent advances in systems vaccinology; the potential biological and clinical impact of high maternal antibody titres on neonatal ontogeny and subsequent infant vaccine responses; and key vaccine- and host-related factors influencing the maternal-infant dyad across different environments. Finally, we outline important gaps in knowledge and suggest future avenues of research on this topic, proposing potential strategies to ensure optimal testing, delivery and implementation of maternal vaccination programs worldwide.

Modeling human trophoblast, the placental epithelium at the maternal fetal interface

Appropriate human trophoblast lineage specification and differentiation is crucial for the establishment of normal placentation and maintenance of pregnancy. However, due to the lack of proper modeling systems, the molecular mechanisms of these processes are still largely unknown. Much of the early studies in this area have been based on animal models and tumor-derived trophoblast cell lines, both of which are suboptimal for modeling this unique human organ. Recent advances in regenerative and stem cell biology methods have led to development of novel in vitro model systems for studying human trophoblast. These include derivation of human embryonic and induced pluripotent stem cells and establishment of methods for the differentiation of these cells into trophoblast, as well as the more recent derivation of human trophoblast stem cells. In addition, advances in culture conditions, from traditional two-dimensional monolayer culture to 3D culturing systems, have led to development of trophoblast organoid and placenta-on-a-chip model, enabling us to study human trophoblast function in context of more physiologically accurate environment. In this review, we will discuss these various model systems, with a focus on human trophoblast, and their ability to help elucidate the key mechanisms underlying placental development and function. This review focuses on model systems of human trophoblast differentiation, including advantages and limitations of stem cell-based culture, trophoblast organoid, and organ-on-a-chip methods and their applications in understanding placental development and disease.

TLR3 expression by maternal and fetal cells at the maternal-fetal interface in normal and preeclamptic pregnancies

Inflammation and oxidative stress at the maternal-fetal interface characterize the placental dysfunction that underlies the pregnancy disorder preeclampsia. Specialized fetal trophoblasts directly interact with leukocytes at both sites of the maternal-fetal interface; the uterine wall decidua; and the placenta. TLR3 has been implicated in the harmful inflammation at the maternal-fetal interface in preeclampsia, but the cellular involvement in the decidua and placenta has not been determined. This study aimed to characterize and quantify cell-specific TLR3 expression and function at the maternal-fetal interface in normal and preeclamptic pregnancies. TLR3 expression was assessed by immunohistochemistry and quantified by a novel image-based and cell-specific quantitation method. TLR3 was expressed at the maternal-fetal interface by all decidual and placental trophoblast types and by maternal and fetal leukocytes. Placental, but not decidual, TLR3 expression was significantly higher in preeclampsia compared to normal pregnancies. This increase was attributed to placental intravillous tissue and associated with both moderate and severe placental dysfunction. TLR3 pathway functionality in the decidua and placenta was confirmed by TLR3 ligand-induced cytokine response, but the TLR3 expression levels did not correlate between the two sites. In conclusion, functional TLR3 was broadly expressed by maternal and fetal cells at both sites of the maternal-fetal interface and the placental intravillous expression was increased in preeclampsia. This suggests TLR3-mediated inflammatory involvement with local regulation at both sites of the maternal-fetal interface in normal and preeclamptic pregnancies.

Upregulation of pannexin-1 hemichannels explains the apparent death of the syncytiotrophoblast during human placental explant culture

BACKGROUND

It has been reported that during the culture of human placental explants, the syncytiotrophoblast dies between 3 and 24 h and is then replaced within 48 h by a new syncytiotrophoblast layer formed by the fusion of underlying cytotrophoblasts. Most frequently the death of the syncytiotrophoblast is indicated by the uptake of nuclear stains such as propidium iodide (PI). This process is reportedly similar in both early and late gestation placental explants.

METHODS

We cultured first trimester placental explants for up to 48 h and tested membrane intactness by exposure to PI. Connexin and pannexin mRNAs were quantified by RT-PCR and protein levels determined by immunofluorescence. The syncytiotrophoblast membrane leak was determined by culturing explants in the presence of hemichannel blockers. Extrusion of extracellular vesicles from the syncytiotrophoblast was quantified.

RESULTS

Nuclei of the syncytiotrophoblast were stained with PI following approximately 4 h of culture and this was prevented by culturing the explants with pannexin-1 blockers. Expression of pannexin-1 hemichannels increased during explant culture (p = 0.0027). Extracellular vesicles were most abundantly extruded from the explants during the first 3 h of culture and the temporal pattern of extrusion was unaltered by blocking hemichannels.

DISCUSSION

We show the mechanism of uptake of nuclear non-viability stains into the syncytiotrophoblast during explant culture is via upregulation of pannexin 1 hemichannels. Contrary to suggestions by some, the production of extracellular vesicles from cultured placental explants is not an in vitro artefact resulting from the apparent death of the syncytiotrophoblast in explant cultures.

In Vitro Anti-Prostate Cancer Activity of Two Ebselen Analogues

Scientific research has been underway for decades in order to develop an effective anticancer drug, and it has become crucial to find a novel and effective chemotherapeutics in the case of prostate cancer treatment. Ebselen derivatives have been shown to possess a variety of biological activities, including cytostatic and cytotoxic action against tumor cells. In this study, the cytotoxic effect and anticancer mechanism of action of two organoselenium compounds— (N-allyl-1,2-benzisoselenazol-3(2H)-one (N-allyl-BS) and N-(3-methylbutyl)-1,2-benzisoselenazol-3(2H)-one) (N-(3-mb)-BS)—were investigated on two phenotypically different prostate cancer cell lines DU 145 and PC-3. The influence of analyzed compounds on the viability parameter was also assessed on normal prostate cell line PNT1A. The results showed that both organoselenium compounds (OSCs) efficiently inhibited cancer cell proliferation, whereas normal PNT1A cells were less sensitive to the analazyed ebselen analouges. Both OSCs induced G2/M cell cycle arrest and prompted cell death through apoptosis. The detection of cleaved Poly (ADP-ribose) Polymerase (PARP) confirmed this. In addition, N-allyl-BS and N-(3-m)-b-BS increased the level of reactive oxygen species (ROS) formation, however only N-allyl-BS induced DNA damage. Based on our data, we assume that OSCs’ anticancer action can be associated with oxidative stress induction and inactivation of the Akt- dependent signalling pathway. In conclusion, our data demonstrate that ebselen derivatives showed strong cytotoxic efficiency towards prostate cancer cells and may be elucidated as a novel, potent anticancer agent.

Placenta as a target of trichloroethylene toxicity

Trichloroethylene (TCE) is an industrial solvent and a common environmental contaminant detected in thousands of hazardous waste sites. Risk of exposure is a concern for workers in occupations that use TCE as well as for residents who live near industries that use TCE or who live near TCE-contaminated sites. Although renal, hepatic and carcinogenic effects of TCE have been documented, less is known about TCE impacts on reproductive functions despite epidemiology reports associating maternal TCE exposure with adverse pregnancy outcomes. Toxicological evidence suggests that the placenta mediates at least some of the adverse pregnancy outcomes associated with TCE exposure. Toxicology studies show that the TCE metabolite, S-(1,2-dichlorovinyl)-l-cysteine (DCVC) generates toxic effects such as mitochondrial dysfunction, apoptosis, oxidative stress, and release of prostaglandins and pro-inflammatory cytokines in placental cell lines. Each of these mechanisms of toxicity have significant implications for placental functions and, thus, ultimately the health of mother and developing child. Despite these findings there remain significant gaps in our knowledge about effects of TCE on the placenta, including effects on specific placental cell types and functions as well as sex differences in response to TCE exposure. Due to the critical role that the placenta plays in pregnancy, future research addressing some of these knowledge gaps could lead to significant gains in public health.

Experimental models of maternal-fetal interface and their potential use for nanotechnology applications

During pregnancy, the placenta regulates the transfer of oxygen, nutrients, and residual products between the maternal and fetal bloodstreams and is a key determinant of fetal exposure to xenobiotics from the mother. To study the disposition of substances through the placenta, various experimental models are used, especially the perfused placenta, placental villi explants, and cell lineage models. In this context, nanotechnology, an area of study that is on the rise, enables the creation of particles on nanometric scales capable of releasing drugs aimed at specific tissues. An important reason for furthering the studies on transplacental transfer is to explore the potential of nanoparticles (NPs), in new delivery strategies for drugs that are specifically aimed at the mother, the placenta, or the fetus and that involve less toxicity. Due to the fact that the placental barrier is essential for the interaction between the maternal and fetal organisms as well as the possibility of NPs being used in the treatment of various pathologies, the aim of this review is to present the main experimental models used in studying the maternal-fetal interaction and the action of NPs in the placental environment.

Analysis of the capacity of Salmonella enterica Typhimurium to infect the human Placenta

INTRODUCTION

Salmonella species are gram-negative facultative intracellular bacteria that are common causes of foodborne illness in North America. Infections by Salmonella during pregnancy are a significant cause of fetal loss in domestic livestock, and fetal and maternal mortality in mice. Furthermore, Salmonella infection is associated with miscarriage, stillbirth and preterm birth in pregnant women. Despite these collective associations, the extent to which Salmonella can infect the human placenta has not been investigated.

METHODS

Human placental villous explants from several gestational ages were exposed to Salmonella enterica serovar Typhimurium (STm) ex vivo. Infection was assessed by colony forming unit assay and whole mount immunofluorescence (WMIF).

RESULTS

Viable bacteria were recovered from placental villous explants of all gestational ages tested, but the bacterial burden was highest in 1st trimester explants. Bacterial numbers did not change appreciably with time post-infection in explants from any gestational age examined, suggesting that STm does not proliferate in placental villi. Exposure of villous explants to STm strains defective for the type III secretion systems revealed that Salmonella pathogenicity island 1 is essential for optimal invasion. In contrast to placental explants, STm infected and proliferated within villous cytotrophoblast cells isolated from term placentas. WMIF demonstrated that STm was restricted primarily to the syncytiotrophoblast layer in infected placentas.

DISCUSSION

Our study demonstrates that STm can invade into the syncytiotrophoblast but does not subsequently proliferate. Thus, the syncytiotrophoblast may function as a barrier to STm infection of the fetus.

Developing novel in vitro methods for the risk assessment of developmental and placental toxicants in the environment

During pregnancy, the placenta is critical for the regulation of maternal homeostasis and fetal growth and development. Exposures to environmental chemicals during pregnancy can be detrimental to the health of the placenta and therefore adversely impact maternal and fetal health. Though research on placental-derived developmental toxicity is expanding, testing is limited by the resources required for traditional test methods based on whole animal experimentation. Alternative strategies utilizing in vitro methods are well suited to contribute to more efficient screening of chemical toxicity and identification of biological mechanisms underlying toxicity outcomes. This review aims to summarize methods that can be used to evaluate toxicity resulting from exposures during the prenatal period, with a focus on newer in vitro methods centered on placental toxicity. The following key aspects are reviewed: (i) traditional test methods based on animal developmental toxicity testing, (ii) in vitro methods using monocultures and explant models, as well as more recently developed methods, including co-cultures, placenta-on-a-chip, and 3-dimensional (3D) cell models, (iii) endpoints that are commonly measured using in vitro designs, and (iv) the translation of in vitro methods into chemical evaluations and risk assessment applications. We conclude that findings from in vitro placental models can contribute to the screening of potentially hazardous chemicals, elucidation of chemical mechanism of action, incorporation into adverse outcome pathways, estimation of doses eliciting toxicity, derivation of extrapolation factors, and characterization of overall risk of adverse outcomes, representing key components of chemical regulation in the 21^st century.

Effects of hydroxychloroquine on the human placenta-Findings from in vitro experimental data and a systematic review

Hydroxychloroquine (HCQ), a toll like receptor (TLR) 7 and 9 antagonist, is used during pregnancy for inflammatory conditions with limited understanding of its placental toxicology. We hypothesized that HCQ does not have toxic effects on the placenta and can modulate cytokine release in response to TLR7/9 activation. A systematic review was conducted and no studies of HCQ on multicellular human placental tissue were identified. Accordingly, placental villous explants were cultured for 7 days with HCQ +/- TLR7/9 agonists. HCQ did not affect cell turnover, nutrient transport or cytokine release but increased IL-10 (anti-inflammatory) secretion and promoted syncytiotrophoblast regeneration. Cytokine release stimulated by TLR7/9 agonists was unaffected by HCQ. In conclusion, HCQ did not adversely affect placental tissue and may have a protective anti-inflammatory function. Further research is needed to determine the mechanisms of HCQ actions on human placenta and whether they could be utilized to improve pregnancy outcomes.

Increased circulating levels of Epidermal Growth Factor-like Domain 7 in pregnant women affected by preeclampsia

Proper placental development is crucial to establish a successful pregnancy. Defective placentation is the major cause of several pregnancy complications, including preeclampsia (PE). We have previously demonstrated that the secreted factor Epidermal Growth Factor-like Domain 7 (EGFL7) is expressed in trophoblast cells of the human placenta and that it regulates trophoblast migration and invasion, suggesting a role in placental development. In the present study, we demonstrate that circulating levels of EGFL7 are undetectable in nonpregnant women, increase during pregnancy and decline toward term. Close to term, circulating levels of EGFL7 are significantly higher in patients affected by PE when compared to normal pregnancies. Consistent with these results, villus explant cultures obtained from placentas affected by PE display increased release of EGFL7 in the culture medium when compared to those from normal placentas. Our results suggest that increased release of placenta-derived EGFL7 and increased circulating levels of EGFL7 are associated with the clinical manifestation of PE.

Low-dose aspirin reduces hypoxia-induced sFlt1 release via the JNK/AP-1 pathway in human trophoblast and endothelial cells

Pre-eclampsia (PE) is a serious hypertensive disorder of pregnancy that remains a leading cause of perinatal and maternal morbidity and mortality worldwide. Placental ischemia/hypoxia and the secretion of soluble fms-like tyrosine kinase 1 (sFlt1) into maternal circulation are involved in the pathogenesis of PE. Although low-dose aspirin (LDA) has beneficial effects on the prevention of PE, the exact mechanisms of action of LDA, particularly on placental dysfunction, and sFlt1 release, have not been well investigated. This study aimed to determine whether LDA exists the protective effects on placental trophoblast and endothelial functions and prevents PE-associated sFlt1 release. First, we observed that LDA mitigated hypoxia-induced trophoblast apoptosis, showed positive effects on trophoblast cells migration and invasion activity, and increased the tube-forming activity of human umbilical vein endothelial cells (HUVECs). In addition, LDA decreased hypoxia-induced sFlt1 production, and the c-Jun NH₂ -terminal kinase/activator protein-1 (JNK/AP-1) pathway was shown to mediate the induction of sFlt1. Moreover, the transcription factor AP-1 was confirmed to regulate the Flt1 gene expression by directly binding to the Flt1 promoter in luciferase assays. The result of chromatin immunoprecipitation assays further demonstrated that LDA could directly decrease the expression of the transcription factor AP-1, and thus decrease sFlt1 production. Finally, the effects of LDA on sFlt1 production were proved in human placental explants. Taken together, our data show the protective effects of LDA against trophoblast and endothelial cell dysfunction and reveal that the LDA-mediated inhibition of sFlt1 via the JNK/AP-1 pathway may be a potential cellular/molecular mechanism for the prevention of PE.

Lymphocytic Choriomeningitis Virus Infection Demonstrates Higher Replicative Capacity and Decreased Antiviral Response in the First-Trimester Placenta

Lymphocytic choriomeningitis virus (LCMV) is a rodent disease that can be transmitted to humans. A majority of persons infected with LCMV have only minor symptoms; however, it can cross the placental barrier during pregnancy and cause congenital defects in the fetus. Some viral infections early in gestation are hypothesized to lead to worse outcomes compared to those acquired during late gestation; however, LCMV has not been studied in this context. In the present study, differences in immunomodulation between the first- and third-trimester placental explants infected with LCMV were measured. LCMV replication was observed in the first-trimester chorionic villi, but not in term. The term placenta exhibited a robust innate immune response to infection by LCMV, marked by induction of ifn-α, il-6, and tnf-α gene expression which was not seen in the first-trimester explants. Cytokine secretion was also only seen in term explants. The results indicate that the first-trimester and term placentas differ in their permissiveness for LCMV infection, inversely correlating with the innate antiviral responses. This has implications for developing effective mechanisms that protect the fetus from infection based on stage of development.

Effects of cannabis tetrahydrocannabinol on endocannabinoid homeostasis in human placenta

Cannabis use has become a hot topic in several countries due to the debate about its legalization for medical purposes. However, data are limited regarding adverse events, safety and potential impact on reproductive health. Cannabis consumption during pregnancy has been associated with gestational disorders such as preterm birth, intrauterine growth restriction, low birth weight and increased risk of miscarriage, though the underlying biochemical mechanisms are still unknown. Given that the endocannabinoid system (ECS) is involved in several reproductive processes, we tested the hypothesis that the negative outcomes may result from the impact on the ECS homeostasis caused by the main psychoactive compound of cannabis, Δ⁹-tetrahydrocannabinol (THC). We demonstrate that THC (10-40 µM) impairs placental endocannabinoid system by disrupting the endocannabinoid anandamide (AEA) levels and the expression of AEA synthetic and degrading enzymes N-arachidonoylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD) and fatty acid amide hydrolase (FAAH), respectively. Although, no alterations in cannabinoid receptors CB1 and CB2 expression were observed. Thus, long-term local AEA levels are associated with a shift in the enzymatic profile to re-establish ECS homeostasis. In chronic cannabis users, high AEA levels in placenta may disturb the delicate balance of trophoblast cells turnover leading to alterations in normal placental development and foetal growth.

Anandamide down-regulates placental transporter expression through CB2 receptor-mediated inhibition of cAMP synthesis

The BCRP/ABCG2 efflux transporter is expressed on the membrane of placental syncytiotrophoblasts and protects the fetus from toxicant exposure. Syncytiotrophoblasts arise from the fusion of cytotrophoblasts, a process negatively regulated by the endocannabinoid, anandamide (AEA). It is unknown whether AEA can influence fetal concentrations of xenobiotics by modulating the expression of transporters in syncytiotrophoblasts. Here, we sought to characterize and identify the mechanism(s) responsible for AEA-mediated down-regulation of the BCRP transporter in human placental explants and BeWo trophoblasts. Treatment of human placental explants with AEA (1 μM, 24 h) reduced hCGα, syncytin-1, and BCRP mRNAs by ˜30%. Similarly, treatment of BeWo trophoblasts with AEA (0-10 μM, 3-24 h) coordinately down-regulated mRNAs for hCGß, syncytin-2, and BCRP. In turn, AEA increased the sensitivity of trophoblasts to the cytotoxicity of mitoxantrone, a known BCRP substrate, and environmental and dietary contaminants including mycoestrogens and perfluorinated chemicals. AEA-treated trophoblasts also demonstrated reduced BCRP transport of the mycoestrogen zearalenone and the diabetes drug glyburide, labeled with BODIPY. The AEA-mediated reduction of BCRP mRNA was abrogated when placental cells were co-treated with AM630, a CB2 receptor inhibitor, or 8-Br-cAMP, a cAMP analog. AEA reduced intracellular cAMP levels in trophoblasts by 75% at 1 h, and completely inhibited forskolin-induced phosphorylation of the cAMP response element binding protein (CREB). AEA also decreased p-CREB binding to the BCRP promoter. Taken together, our data indicate that AEA down-regulates placental transporter expression and activity via CB2-cAMP signaling. This novel mechanism may explain the repression of placental BCRP expression observed during diseases of pregnancy.

The Effect of Maternal Obesity on Placental Cell-Free DNA Release in a Mouse Model

BACKGROUND

The fetal fraction of cell-free DNA (cfDNA) in maternal plasma is decreased in obese women. The underlying mechanism is not well understood. The amount of cfDNA released from the placenta has not been directly examined in maternal obesity.

OBJECTIVE

We sought to quantify release of cfDNA from the placenta and fetal membranes in maternal diet-induced obesity using explant cultures in an established mouse model.

STUDY DESIGN

C57BL6/J females were fed either 60% high-fat diet or 10% fat-matched control diet for 14 weeks prepregnancy and throughout gestation. Placentas and fetal membranes were collected on e18 and randomly allocated to time 0-, 1-, or 6-hour culture times. The CfDNA was isolated from culture media, quantified, and normalized to tissue weight.

RESULTS

Placentas from obese dams released significantly less cfDNA compared to those of lean dams at time 0 (45.8 ± 4.3 ng/mg vs 65.6 ± 7.9 ng/mg, P = .02). Absolute cfDNA levels increased with longer placental culture, with no significant differences between obese and lean dams at 1 and 6 hours. Membranes released significantly less cfDNA than did placentas at every time point.

CONCLUSIONS

Maternal obesity is associated with decreased release of cfDNA from the placenta compared to lean controls immediately after tissue harvest. This may provide an alternative explanation for the lower fetal fraction of cfDNA noted in maternal obesity.

Placental inflammation by HMGB1 activation of TLR4 at the syncytium

INTRODUCTION

Normal pregnancy is characterized by an elevated inflammatory state involving the placenta. The placental inflammation is further increased in preeclampsia, resulting in release of harmful danger signals to the maternal circulation. Activation of toll-like receptors (TLR)2 and TLR4 by endogenous danger signals plays a role in inflammatory diseases. Placental TLR2 and TLR4 expression has been reported, and high mobility group box 1 (HMGB1) is a likely endogenous activator of these receptors. We aimed to examine HMGB1 activation of TLR2 and TLR4 as mechanisms of placental inflammation in normal and preeclamptic pregnancies, by combined analysis of expression and function of the ligand HMGB1, the receptors TLR2 and TLR4, and the cytokine responder interleukin (IL)-8.

METHODS

Protein expression was analyzed in placental tissue from normal and preeclamptic pregnancies, and cytokine responses to two distinct HMGB1 isoforms were examined in placental explants and trophoblasts. Inflammatory and anti-angiogenic markers were measured in maternal serum.

RESULTS

We demonstrated strong co-localized expression of HMGB1, TLR4 and IL-8 in the syncytium layer of the placenta. Syncytium TLR4 expression and maternal serum levels of IL-8 were significantly increased in preeclamptic compared to normal pregnancies. Functionality was confirmed by TLR4-dependent release of IL-8 from placental explants and trophoblasts in response to the inflammatory isoform of HMGB1.

DISCUSSION

This demonstrates a role for the HMGB1-TLR4 pathway at the syncytium layer and suggests involvement in placental inflammation and preeclampsia.

Progesterone and cyclic adenosine monophosphate down-regulate CD90 in the stromal cells of human decidua. In vitro evidence and in situ findings

OBJECTIVE

CD90 is a glycoprotein involved in leukocyte relocation and cell differentiation. CD90 is expressed in endothelial and stromal cells in human endometrium; however, its role in the remodeling of the decidual tissue during pregnancy is poorly understood. Here, we investigate how CD90 expression in decidual stromal cells (DSCs) is regulated.

METHOD OF STUDY

The native CD90 receptor in stromal cells in decidua was investigated via histology. We further develop in vitro culture of DSCs which allows us to test the effects of hormones and paracrine signals on CD90 expression.

RESULTS

Stromal cells in first-trimester human decidua display heterogeneous levels of CD90 expression. In vitro analyses reveal that progesterone, a factor normally secreted by trophoblast cells in the placenta, and extracellular cyclic adenosine monophosphate, a known downstream signaling messenger of progesterone, reduce CD90 expression in DSCs by ~30%. This reduction in CD90 expression correlates with a change toward a more highly differentiated cell state.

CONCLUSION

DSCs in early pregnancy show different levels of CD90 expression, suggesting different DSC differentiation and selective interactions with cells during decidual morphogenesis.

Extracellular vesicles generated by placental tissues ex vivo: A transport system for immune mediators and growth factors

PROBLEM

To study the mechanisms of placenta function and the role of extracellular vesicles (EVs) in pregnancy, it is necessary to develop an ex vivo system that retains placental cytoarchitecture and the primary metabolic aspects, in particular the release of EVs and soluble factors. Here, we developed such a system and investigated the pattern of secretion of cytokines, growth factors, and extracellular vesicles by placental villous and amnion tissues ex vivo.

METHODS OF STUDY

Placental villous and amnion explants were cultured for 2 weeks at the air/liquid interface and their morphology and the released cytokines and EVs were analyzed. Cytokines were analyzed with multiplexed bead assays, and individual EVs were analyzed with recently developed techniques that involved EV capture with magnetic nanoparticles coupled to anti-EV antibodies and flow cytometry.

RESULTS

Ex vivo tissues (i) remained viable and preserved their cytoarchitecture; (ii) maintained secretion of cytokines and growth factors; (iii) released EVs of syncytiotrophoblast and amnion epithelial cell origins that contain cytokines and growth factors.

CONCLUSION

A system of ex vivo placental villous and amnion tissues can be used as an adequate model to study placenta metabolic activity in normal and complicated pregnancies, in particular to characterize EVs by their surface markers and by encapsulated proteins. Establishment and benchmarking the placenta ex vivo system may provide new insight in the functional status of this organ in various placental disorders, particularly regarding the release of EVs and cytokines. Such EVs may have a prognostic value for pregnancy complications.

Placental inflammation in pre-eclampsia by Nod-like receptor protein (NLRP)3 inflammasome activation in trophoblasts

Pre-eclampsia is associated with increased levels of cholesterol and uric acid and an inflamed placenta expressing danger-sensing pattern recognition receptors (PRRs). Crystalline cholesterol and uric acid activate the PRR Nod-like receptor protein (NLRP)3 inflammasome to release interleukin (IL)-1β and result in vigorous inflammation. We aimed to characterize crystal-induced NLRP3 activation in placental inflammation and examine its role in pre-eclampsia. We confirmed that serum total cholesterol and uric acid were elevated in pre-eclamptic compared to healthy pregnancies and correlated positively to high sensitivity C-reactive protein (hsCRP) and the pre-eclampsia marker soluble fms-like tyrosine kinase-1 (sFlt-1). The NLRP3 inflammasome pathway components (NLRP3, caspase-1, IL-1β) and priming factors [complement component 5a (C5a) and terminal complement complex (TCC)] were co-expressed by the syncytiotrophoblast layer which covers the placental surface and interacts with maternal blood. The expression of IL-1β and TCC was increased significantly and C5a-positive regions in the syncytiotrophoblast layer appeared more frequent in pre-eclamptic compared to normal pregnancies. In-vitro activation of placental explants and trophoblasts confirmed NLRP3 inflammasome pathway functionality by complement-primed crystal-induced release of IL-1β. This study confirms crystal-induced NLRP3 inflammasome activation located at the syncytiotrophoblast layer as a mechanism of placental inflammation and suggests contribution of enhanced NLRP3 activation to the harmful placental inflammation in pre-eclampsia.

MicroRNAs: crucial regulators of placental development

MicroRNAs (miRNAs) are small non-coding single-stranded RNAs that are integral to a wide range of cellular processes mainly through the regulation of translation and mRNA stability of their target genes. The placenta is a transient organ that exists throughout gestation in mammals, facilitating nutrient and gas exchange and waste removal between the mother and the fetus. miRNAs are expressed in the placenta, and many studies have shown that miRNAs play an important role in regulating trophoblast differentiation, migration, invasion, proliferation, apoptosis, vasculogenesis/angiogenesis and cellular metabolism. In this review, we provide a brief overview of canonical and non-canonical pathways of miRNA biogenesis and mechanisms of miRNA actions. We highlight the current knowledge of the role of miRNAs in placental development. Finally, we point out several limitations of the current research and suggest future directions.

Trophoblast differentiation, invasion and hormone secretion in a three-dimensional in vitro implantation model with rhesus monkey embryos

BACKGROUND

The initiation of primate embryo invasion into the endometrium and the formation of the placenta from trophoblasts, fetal mesenchyme, and vascular components are essential for the establishment of a successful pregnancy. The mechanisms which direct morphogenesis of the chorionic villi, and the interactions between trophectoderm-derived trophoblasts and the fetal mesenchyme to direct these processes during placentation are not well understood due to a dearth of systems to examine and manipulate real-time primate implantation. Here we describe an in vitro three-dimensional (3-D) model to study implantation which utilized IVF-generated rhesus monkey embryos cultured in a Matrigel explant system.

METHODS

Blastocyst stage embryos were embedded in a 3-D microenvironment of a Matrigel carrier and co-cultured with a feeder layer of cells generating conditioned medium. Throughout the course of embryo co-culture embryo growth and secretions were monitored. Embedded embryos were then sectioned and stained for markers of trophoblast function and differentiation.

RESULTS

Signs of implantation were observed including enlargement of the embryo mass, and invasion and proliferation of trophoblast outgrowths. Expression of chorionic gonadotropin defined by immunohistochemical staining, and secretion of chorionic gonadotropin and progesterone coincident with the appearance of trophoblast outgrowths, supported the conclusion that a trophoblast cell lineage formed from implanted embryos. Positive staining for selected markers including Ki67, MHC class I, NeuN, CD31, vonWillebrand Factor and Vimentin, suggest growth and differentiation of the embryo following embedding.

CONCLUSIONS

This 3-D in vitro system will facilitate further study of primate embryo biology, with potential to provide a platform for study of genes related to implantation defects and trophoblast differentiation.

In Vitro Human Placental Studies to Support Adenovirus-Mediated VEGF-DΔNΔC Maternal Gene Therapy for the Treatment of Severe Early-Onset Fetal Growth Restriction

Severe fetal growth restriction (FGR) affects 1 in 500 pregnancies, is untreatable, and causes serious neonatal morbidity and death. Reduced uterine blood flow (UBF) is one cause. Transduction of uterine arteries in normal and FGR animal models using an adenovirus (Ad) encoding VEGF isoforms increases UBF and improves fetal growth in utero. Understanding potential adverse consequences of this therapy before first-in-woman clinical application is essential. The aims of this study were to determine whether Ad.VEGF-D^ΔNΔC (1) transfers across the human placental barrier and (2) affects human placental morphology, permeability and primary indicators of placental function, and trophoblast integrity. Villous explants from normal term human placentas were treated with Ad.VEGF-D^ΔNΔC (5 × 10^7-10 virus particles [vp]/mL), or virus formulation buffer (FB). Villous structural integrity (hematoxylin and eosin staining) and tissue accessibility (LacZ immunostaining) were determined. Markers of endocrine function (human chorionic gonadotropin [hCG] secretion) and cell death (lactate dehydrogenase [LDH] release) were assayed. Lobules from normal and FGR pregnancies underwent ex vivo dual perfusion with exposure to 5 × 10¹⁰ vp/mL Ad.VEGF-D^ΔNΔC or FB. Perfusion resistance, para-cellular permeability, hCG, alkaline phosphatase, and LDH release were measured. Ad.VEGF-D^ΔNΔC transfer across the placental barrier was assessed by quantitative polymerase chain reaction in DNA extracted from fetal-side venous perfusate, and by immunohistochemistry in fixed tissue. Villous explant structural integrity and hCG secretion was maintained at all Ad.VEGF-D^ΔNΔC doses. Ad.VEGF-D^ΔNΔC perfusion revealed no effect on placental permeability, fetoplacental vascular resistance, hCG secretion, or alkaline phosphatase release, but there was a minor elevation in maternal-side LDH release. Viral vector tissue access in both explant and perfused models was minimal, and the vector was rarely detected in the fetal venous perfusate and at low titer. Ad.VEGF-D^ΔNΔC did not markedly affect human placental integrity and function in vitro. There was limited tissue access and transfer of vector across the placental barrier. Except for a minor elevation in LDH release, these test data did not reveal any toxic effects of Ad.VEGF-D^ΔNΔC on the human placenta.

Current model systems for the study of preeclampsia

Preeclampsia (PE) is a pregnancy complex disease, distinguished by high blood pressure and proteinuria, diagnosed after the 20th gestation week. Depending on the values of blood pressure, urine protein concentrations, symptomatology, and onset of disease there is a wide range of phenotypes, from mild forms developing predominantly at the end of pregnancy to severe forms developing in the early stage of pregnancy. In the worst cases severe forms of PE could lead to systemic endothelial dysfunction, eclampsia, and maternal and/or fetal death. Worldwide the fetal morbidity and mortality related to PE is calculated to be around 8% of the total pregnancies. PE still being an enigma regarding its etiology and pathophysiology, in general a deficient trophoblast invasion during placentation at first stage of pregnancy, in combination with maternal conditions are accepted as a cause of endothelial dysfunction, inflammatory alterations and appearance of symptoms. Depending on the PE multifactorial origin, several in vitro, in vivo, and in silico models have been used to evaluate the PE pathophysiology as well as to identify or test biomarkers predicting, diagnosing or prognosing the syndrome. This review focuses on the most common models used for the study of PE, including those related to placental development, abnormal trophoblast invasion, uteroplacental ischemia, angiogenesis, oxygen deregulation, and immune response to maternal-fetal interactions. The advances in mathematical and computational modeling of metabolic network behavior, gene prioritization, the protein-protein interaction network, the genetics of PE, and the PE prediction/classification are discussed. Finally, the potential of these models to enable understanding of PE pathogenesis and to evaluate new preventative and therapeutic approaches in the management of PE are also highlighted. Impact statement This review is important to the field of preeclampsia (PE), because it provides a description of the principal in vitro, in vivo, and in silico models developed for the study of its principal aspects, and to test emerging therapies or biomarkers predicting the syndrome before their evaluation in clinical trials. Despite the current advance, the field still lacking of new methods and original modeling approaches that leads to new knowledge about pathophysiology. The part of in silico models described in this review has not been considered in the previous reports.

Dendritic polyglycerol nanoparticles show charge dependent bio-distribution in early human placental explants and reduce hCG secretion

A thorough understanding of nanoparticle bio-distribution at the feto-maternal interface will be a prerequisite for their diagnostic or therapeutic application in women of childbearing age and for teratologic risk assessment. Therefore, the tissue interaction of biocompatible dendritic polyglycerol nanoparticles (dPG-NPs) with first- trimester human placental explants were analyzed and compared to less sophisticated trophoblast-cell based models. First-trimester human placental explants, BeWo cells and primary trophoblast cells from human term placenta were exposed to fluorescence labeled, ∼5 nm dPG-NPs, with differently charged surfaces, at concentrations of 1 µM and 10 nM, for 6 and 24 h. Accumulation of dPGs was visualized by fluorescence microscopy. To assess the impact of dPG-NP on trophoblast integrity and endocrine function, LDH, and hCG releases were measured. A dose- and charge-dependent accumulation of dPG-NPs was observed at the early placental barrier and in cell lines, with positive dPG-NP-surface causing deposits even in the mesenchymal core of the placental villi. No signs of plasma membrane damage could be detected. After 24 h we observed a significant reduction of hCG secretion in placental explants, without significant changes in trophoblast apoptosis, at low concentrations of charged dPG-NPs. In conclusion, dPG-NP’s surface charge substantially influences their bio-distribution at the feto-maternal interface, with positive charge facilitating trans-trophoblast passage, and in contrast to more artificial models, the first-trimester placental explant culture model reveals potentially hazardous influences of charged dPG-NPs on early placental physiology.

Derivation of Human Trophoblast Stem Cells

Trophoblast cells play an essential role in the interactions between the fetus and mother. Mouse trophoblast stem (TS) cells have been derived and used as the best in vitro model for molecular and functional analysis of mouse trophoblast lineages, but attempts to derive human TS cells have so far been unsuccessful. Here we show that activation of Wingless/Integrated (Wnt) and EGF and inhibition of TGF-β, histone deacetylase (HDAC), and Rho-associated protein kinase (ROCK) enable long-term culture of human villous cytotrophoblast (CT) cells. The resulting cell lines have the capacity to give rise to the three major trophoblast lineages, which show transcriptomes similar to those of the corresponding primary trophoblast cells. Importantly, equivalent cell lines can be derived from human blastocysts. Our data strongly suggest that the CT- and blastocyst-derived cell lines are human TS cells, which will provide a powerful tool to study human trophoblast development and function.

Enrofloxacin and Toltrazuril Are Able to Reduce Toxoplasma gondii Growth in Human BeWo Trophoblastic Cells and Villous Explants from Human Third Trimester Pregnancy

Classical treatment for congenital toxoplasmosis is based on combination of sulfadiazine and pyrimethamine plus folinic acid. Due to teratogenic effects and bone marrow suppression caused by pyrimethamine, the establishment of new therapeutic strategies is indispensable to minimize the side effects and improve the control of infection. Previous studies demonstrated that enrofloxacin and toltrazuril reduced the incidence of Neospora caninum and Toxoplasma gondii infection. The aim of the present study was to evaluate the efficacy of enrofloxacin and toltrazuril in the control of T. gondii infection in human trophoblast cells (BeWo line) and in human villous explants from the third trimester. BeWo cells and villous were treated with several concentrations of enrofloxacin, toltrazuril, sulfadiazine, pyrimethamine, or combination of sulfadiazine+pyrimethamine, and the cellular or tissue viability was verified. Next, BeWo cells were infected by T. gondii (2F1 clone or the ME49 strain), whereas villous samples were only infected by the 2F1 clone. Then, infected cells and villous were treated with all antibiotics and the T. gondii intracellular proliferation as well as the cytokine production were analyzed. Finally, we evaluated the direct effect of enrofloxacin and toltrazuril in tachyzoites to verify possible changes in parasite structure. Enrofloxacin and toltrazuril did not decrease the viability of cells and villous in lower concentrations. Both drugs were able to significantly reduce the parasite intracellular proliferation in BeWo cells and villous explants when compared to untreated conditions. Regardless of the T. gondii strain, BeWo cells infected and treated with enrofloxacin or toltrazuril induced high levels of IL-6 and MIF. In villous explants, enrofloxacin induced high MIF production. Finally, the drugs increased the number of unviable parasites and triggered damage to tachyzoite structure. Taken together, it can be concluded that enrofloxacin and toltrazuril are able to control T. gondii infection in BeWo cells and villous explants, probably by a direct action on the host cells and parasites, which leads to modifications of cytokine release and tachyzoite structure.

Placental control of drug delivery

The placenta serves as the interface between the maternal and fetal circulations and regulates the transfer of oxygen, nutrients, and waste products. When exogenous substances are present in the maternal bloodstream-whether from environmental contact, occupational exposure, medication, or drug abuse-the extent to which this exposure affects the fetus is determined by transport and biotransformation processes in the placental barrier. Advances in drug delivery strategies are expected to improve the treatment of maternal and fetal diseases encountered during pregnancy.

Cell-free DNA release by mouse placental explants

Although suggested that “fetal” cell-free DNA (cfDNA) is derived from trophoblast cells, the exact origin is unclear. The studies in this report sought to demonstrate that placental tissue releases cfDNA in parallel with cell death, that the size range of cfDNA is similar to that found in maternal plasma, and that the cfDNA fragments are able to stimulate a proinflammatory cytokine response. Placentas were harvested from near term pregnant CD-1 mice and cultured in DMEM/Ham’s F12/FBS media in 8% or 21% O₂. After centrifugation to remove cells and cellular debris, the cfDNA was extracted from the media and quantified by DNA spectrophotometry. The cfDNA fragments were sized using a 1.5% TAE gel. Cell death was quantified by lactate dehydrogenase assay; and tissue homogenates were used to quantify caspase activity and BAX expression. Cultured RAW-264.7 macrophage cells were used to determine IL6 stimulation by cfDNA. The cfDNA levels released in 8% O₂ (placental normoxia) were not significantly different from explants cultured in 21% O₂ (placental hyperoxia). The cfDNA fragments ranged in size from < 100 –< 400 bp. The cfDNA release increased when cultured with LPS, whereas it decreased with trolox (vitamin E analog). Explant release of cfDNA increased in parallel with cell death. The cfDNA release and cell death of trophoblast appears to involve components of the apoptosis signaling pathway as suggested by LPS enhancement of placental caspase activity, suppression of cfDNA release by a pan-caspase inhibitor and the trend toward increased Bax protein expression. Studies with cultured macrophage cells confirmed the ability of cfDNA to stimulate an IL6 response. In summary, these studies have confirmed the ability of placental tissue to release significant amounts of cfDNA, a phenomenon that appears to be mediated, at least in part, by apoptosis; and that the cfDNA released by the placental explants is able to stimulate a significant proinflammatory response. Thus, these studies provide support for the hypothesis that cell-free fetal DNA released by placental tissue potentially plays a mechanistically important role during the events leading to the onset of parturition.

A microfluidics assay to study invasion of human placental trophoblast cells

Pre-eclampsia, fetal growth restriction and stillbirth are major pregnancy disorders throughout the world. The underlying pathogenesis of these diseases is defective placentation characterized by inadequate invasion of extravillous placental trophoblast cells into the uterine arteries. How trophoblast invasion is controlled remains an unanswered question but is influenced by maternal uterine immune cells called decidual natural killer cells. Here, we describe an in vitro microfluidic invasion assay to study the migration of primary human trophoblast cells. Each experiment can be performed with a small number of cells making it possible to conduct research on human samples despite the challenges of isolating primary trophoblast cells. Cells are exposed to a chemical gradient and tracked in a three-dimensional microenvironment using real-time high-resolution imaging, so that dynamic readouts on cell migration such as directionality, motility and velocity are obtained. The microfluidic system was validated using isolated trophoblast and a gradient of granulocyte-macrophage colony-stimulating factor, a cytokine produced by activated decidual natural killer cells. This microfluidic model provides detailed analysis of the dynamics of trophoblast migration compared to previous assays and can be modified in future to study in vitro how human trophoblast behaves during placentation.

Oxygen and tissue culture affect placental gene expression

INTRODUCTION

Placental explant culture is an important model for studying placental development and functions. We investigated the differences in placental gene expression in response to tissue culture, atmospheric and physiologic oxygen concentrations.

METHODS

Placental explants were collected from normal term (38-39 weeks of gestation) placentae with no previous uterine contractile activity. Placental transcriptomic expressions were evaluated with GeneChip^® Human Genome U133 Plus 2.0 arrays (Affymetrix).

RESULTS

We uncovered sub-sets of genes that regulate response to stress, induction of apoptosis programmed cell death, mis-regulation of cell growth, proliferation, cell morphogenesis, tissue viability, and protection from apoptosis in cultured placental explants. We also identified a sub-set of genes with highly unstable pattern of expression after exposure to tissue culture. Tissue culture irrespective of oxygen concentration induced dichotomous increase in significant gene expression and increased enrichment of significant pathways and transcription factor targets (TFTs) including HIF1A. The effect was exacerbated by culture at atmospheric oxygen concentration, where further up-regulation of TFTs including PPARA, CEBPD, HOXA9 and down-regulated TFTs such as JUND/FOS suggest intrinsic heightened key biological and metabolic mechanisms such as glucose use, lipid biosynthesis, protein metabolism; apoptosis, inflammatory responses; and diminished trophoblast proliferation, differentiation, invasion, regeneration, and viability.

DISCUSSION

These findings demonstrate that gene expression patterns differ between pre-culture and cultured explants, and the gene expression of explants cultured at atmospheric oxygen concentration favours stressed, pro-inflammatory and increased apoptotic transcriptomic response.

Downregulation of peroxiredoxin-3 by hydrophobic bile acid induces mitochondrial dysfunction and cellular senescence in human trophoblasts

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific disorder characterised by raised bile acids in foetal-maternal circulation, which threatens perinatal health. During the progression of ICP, the effect of oxidative stress is underscored. Peroxiredoxin-3 (PRDX3) is a mitochondrial antioxidant enzyme that is crucial to balance intracellular oxidative stress. However, the role of PRDX3 in placental trophoblast cells under ICP is not fully understood. We demonstrated that the level of PRDX3 was downregulated in ICP placentas as well as bile acids–treated trophoblast cells and villous explant in vitro. Toxic levels of bile acids and PRDX3 knockdown induced oxidative stress and mitochondrial dysfunction in trophoblast cells. Moreover, silencing of PRDX3 in trophoblast cell line HTR8/SVneo induced growth arrest and cellular senescence via activation of p38-mitogen-activated protein kinase (MAPK) and induction of p21^WAF1/CIP and p16^INK4A. Additionally, enhanced cellular senescence, determined by senescence-associated beta-galactosidase staining, was obviously attenuated by p38-MAPK inhibitor SB203580. Our data determined that exposure to bile acid decreased PRDX3 level in human trophoblasts. PRDX3 protected trophoblast cells against mitochondrial dysfunction and cellular senescence induced by oxidative stress. Our results suggest that decreased PRDX3 by excessive bile acids in trophoblasts plays a critical role in the pathogenesis and progression of ICP.

The xenoestrogens, bisphenol A and para-nonylphenol, decrease the expression of the ABCG2 transporter protein in human term placental explant cultures

Many endogenous and xenobiotic compounds are substrates and regulators of human placental ABC transporters. ABCG2 is protecting fetus against foreign chemicals. Environmental xenoestrogens, like bisphenol A (BPA) and p-nonylphenol (p-NP), mimic natural estrogens and can affect hormonal systems. Effects of BPA, p-NP, DES (diethylstilbestrol) and estradiol (E2), on ABCG2 expression were studied using human first trimester and term placental explants. Role of estrogen receptors (ER) in the effects of chemicals was studied by ER antagonist. Term placenta expressed less ABCG2 protein. In term placentas BPA (p < 0.05), p-NP (p < 0.01) and E2 (p < 0.05) decreased the ABCG2 protein expression after 48 h exposure while after 24 h exposure, only E2 decreased the expression (p < 0.05). The chemicals did not affect ABCG2 in first trimester placentas. The ER antagonist affected differently the responses of chemicals. In conclusion, environmental xenoestrogens downregulate placental ABCG2 protein expression depending on gestational age.

Comparison of syncytiotrophoblast generated from human embryonic stem cells and from term placentas

Human embryonic stem cells (ESCs) readily commit to the trophoblast lineage after exposure to bone morphogenetic protein-4 (BMP-4) and two small compounds, an activin A signaling inhibitor and a FGF2 signaling inhibitor (BMP4/A83-01/PD173074; BAP treatment). During differentiation, areas emerge within the colonies with the biochemical and morphological features of syncytiotrophoblast (STB). Relatively pure fractions of mononucleated cytotrophoblast (CTB) and larger syncytial sheets displaying the expected markers of STB can be obtained by differential filtration of dispersed colonies through nylon strainers. RNA-seq analysis of these fractions has allowed them to be compared with cytotrophoblasts isolated from term placentas before and after such cells had formed syncytia. Although it is clear from extensive gene marker analysis that both ESC- and placenta-derived syncytial cells are trophoblast, each with the potential to transport a wide range of solutes and synthesize placental hormones, their transcriptome profiles are sufficiently dissimilar to suggest that the two cell types have distinct pedigrees and represent functionally different kinds of STB. We propose that the STB generated from human ESCs represents the primitive syncytium encountered in early pregnancy soon after the human trophoblast invades into the uterine wall.