ORIGINAL ARTICLE: An Efficient Optimized Method for Isolation of Villous Trophoblast Cells from Human Early Pregnancy Placenta Suitable for Functional and Molecular Studies

First trimester extravillous trophoblast secretes HLA class I molecules via small extracellular vesicles

INTRODUCTION

Human pregnancy requires acceptance and support for the semi-allogeneic embryo and effective protection of both mother and fetus. A failure to adapt, from either side, may cause abortion. The placenta-derived extracellular vesicles (EVs) have a crucial role in human implantation and pregnancy. These are lipid bilayer membrane-delimited, nano-to-micro sized extracellular microvesicles of endosomal origin, containing diverse signaling molecules, and functioning as short and long-distance messengers. We have already shown that first-trimester placenta releases the soluble HLA-C and HLA-G KIR ligands to modulate maternal cytotoxicity via the KIR/HLA axis. This study is to find whether extravillous trophoblast (EVT) secretes these HLA class I molecules via small EVs.

METHODS

sEVs were isolated by ultrafiltration or precipitation from serum-free conditioned media from primary trophoblast-derived EVT, and non-tumor EVT-like model Sw71 cell line, cultured as monolayer and spheroids. sEVs from cultured placental explants served as a positive control. Combined data from several methods was used for their characterization including BCA, DLS, TEM, IEM, Dot blot, and FACS.

RESULTS

Primary trophoblast-derived EVT and Sw71 EVT-like cells produced intact and well-visible CD63+, HLA-G- and HLA-C-bearing sEVs, regardless of culture mode and type of isolation. Both methods yielded sEVs sized 30-100 nm.

DISCUSSION

We show original data on the HLA-C secretion via sEVs by early pregnancy EVT and confirm the production of HLA-G-positive sEVs. A new asset to the usefulness of the Sw71 spheroid model as an implanting blastocyst surrogate is added as a tool to elucidate the sEV-based signalization in the implantation.

The modeling of human implantation and early placentation: achievements and perspectives

BACKGROUND

Successful implantation is a critical step for embryo survival. The major losses in natural and assisted human reproduction appeared to occur during the peri-implantation period. Because of ethical constraints, the fascinating maternal-fetal crosstalk during human implantation is difficult to study and thus, the possibility for clinical intervention is still limited.

OBJECTIVE AND RATIONALE

This review highlights some features of human implantation as a unique, ineffective and difficult-to-model process and summarizes the pros and cons of the most used in vivo, ex vivo and in vitro models. We point out the variety of cell line-derived models and how these data are corroborated by well-defined primary cells of the same nature. Important aspects related to the handling, standardization, validation, and modus operandi of the advanced 3D in vitro models are widely discussed. Special attention is paid to blastocyst-like models recapitulating the hybrid phenotype and HLA profile of extravillous trophoblasts, which are a unique yet poorly understood population with a major role in the successful implantation and immune mother-embryo recognition. Despite raising new ethical dilemmas, extended embryo cultures and synthetic embryo models are also in the scope of our review.

SEARCH METHODS

We searched the electronic database PubMed from inception until March 2024 by using a multi-stage search strategy of MeSH terms and keywords. In addition, we conducted a forward and backward reference search of authors mentioned in selected articles.

OUTCOMES

Primates and rodents are valuable in vivo models for human implantation research. However, the deep interstitial, glandular, and endovascular invasion accompanied by a range of human-specific factors responsible for the survival of the fetus determines the uniqueness of the human implantation and limits the cross-species extrapolation of the data. The ex vivo models are short-term cultures, not relevant to the period of implantation, and difficult to standardize. Moreover, the access to tissues from elective terminations of pregnancy raises ethical and legal concerns. Easy-to-culture cancer cell lines have many limitations such as being prone to spontaneous transformation and lacking decent tissue characteristics. The replacement of the original human explants, primary cells or cancer cell lines with cultures of immortalized cell lines with preserved stem cell characteristics appears to be superior for in vitro modeling of human implantation and early placentation. Remarkable advances in our understanding of the peri-implantation stages have also been made by advanced three dimensional (3D) models i.e. spheroids, organoids, and assembloids, as placental and endometrial surrogates. Much work remains to be done for the optimization and standardization of these integrated and complex models. The inclusion of immune components in these models would be an asset to delineate mechanisms of immune tolerance. Stem cell-based embryo-like models and surplus IVF embryos for research bring intriguing possibilities and are thought to be the trend for the next decade for in vitro modeling of human implantation and early embryogenesis. Along with this research, new ethical dilemmas such as the moral status of the human embryo and the potential exploitation of women consenting to donate their spare embryos have emerged. The careful appraisal and development of national legal and ethical frameworks are crucial for better regulation of studies using human embryos and embryoids to reach the potential benefits for human reproduction.

WIDER IMPLICATIONS

We believe that our data provide a systematization of the available information on the modeling of human implantation and early placentation and will facilitate further research in this field. A strict classification of the advanced 3D models with their pros, cons, applicability, and availability would help improve the research quality to provide reliable outputs.

Validation of the Sw71-spheroid model with primary trophoblast cells

PROBLEM

Human implantation is a limiting factor for the success of natural and IVF reproduction since about 60% of pregnancy losses occur in the peri-implantation period. The in vitro modeling of human implantation challenges the researchers in accurate recreation of the complex in vivo differentiation and function of human blastocyst in the peri-implantation period. In previous studies, we constructed Sw71-spheroid models, which like human blastocyst undergo compactization, attaches to the endometrial epithelium, invade, and migrate. The aim of this study was to validate the trophoblast Sw71-spheroid model with primary trophoblast cells, derived from healthy women in early pregnancy.

METHOD OF STUDY

We performed a direct comparison of Sw71-spheroid model with placenta-derived primary trophoblasts regarding their hybrid phenotype and HLA status, as well as the ability to generate spheroids able to migrate and invade. From the primary trophoblast cells, isolated by mild enzymatic treatment and Percoll gradient separation, were generated long-lived clones, which phenotype was assessed by FACS and immunocytochemistry.

RESULTS

Our results showed that cultured primary trophoblasts have the EVT phenotype (Vim+/CK7+/HLA-C+/HLA-G+), like Sw71 cells. In both 3D culture settings, we obtained stable, round-shaped, multilayered spheroids. Although constructed from the same number of cells, the primary trophoblast spheroids were smaller. The primary trophoblast spheroids migrate successfully, and in term of invasion are equally potent but less stable as compared to Sw71 spheroids.

CONCLUSIONS

The Sw71 cell line and cultured native trophoblast cells are interchangeable regarding their EVT phenotype (HLA-C+/HLA-G+/Vim+/CK7+). The blastocyst-like spheroids sourced by both types of cells differentiate in the same time frame and function similarly. We strongly advise the use of Sw71 spheroids as blastocyst surrogate for observation on trophectoderm differentiation and function during early human implantation.

A comprehensive review of human trophoblast fusion models: recent developments and challenges

As an essential component of the maternal-fetal interface, the placental syncytiotrophoblast layer contributes to a successful pregnancy by secreting hormones necessary for pregnancy, transporting nutrients, mediating gas exchange, balancing immune tolerance, and resisting pathogen infection. Notably, the deficiency in mononuclear trophoblast cells fusing into multinucleated syncytiotrophoblast has been linked to adverse pregnancy outcomes, such as preeclampsia, fetal growth restriction, preterm birth, and stillbirth. Despite the availability of many models for the study of trophoblast fusion, there exists a notable disparity from the ideal model, limiting the deeper exploration into the placental development. Here, we reviewed the existing models employed for the investigation of human trophoblast fusion from several aspects, including the development history, latest progress, advantages, disadvantages, scope of application, and challenges. The literature searched covers the monolayer cell lines, primary human trophoblast, placental explants, human trophoblast stem cells, human pluripotent stem cells, three-dimensional cell spheres, organoids, and placenta-on-a-chip from 1938 to 2023. These diverse models have significantly enhanced our comprehension of placental development regulation and the underlying mechanisms of placental-related disorders. Through this review, our objective is to provide readers with a thorough understanding of the existing trophoblast fusion models, making it easier to select most suitable models to address specific experimental requirements or scientific inquiries. Establishment and application of the existing human placental trophoblast fusion models.

Cyclosporin A Promotes Invasion and Migration of Extravillous Trophoblast Cells Derived from Human-Induced Pluripotent Stem Cells and Human Embryonic Stem Cells

Extravillous trophoblast (EVT) cells play an essential role in the maternal-fetal interaction. Although abnormal development and function of EVT cells, including impaired migration and invasion capability, are believed to be etiologically linked to severe pregnancy disorders including pre-eclampsia, the associated molecular mechanisms are not clear due to the lack of an appropriate cell model in vitro. Cyclosporin A (CsA) is a macrolide immunosuppressant and also used in clinic to improve pregnancy outcomes. However, whether CsA has any effects on the function of EVT cells has not been well investigated. In this study, we induced differentiation of human-induced pluripotent stem cells (hiPSCs) and human embryonic stem cells (hESCs) into EVT cells (hiPSC-EVT and hESC-EVT cells, respectively) by Y27632, neuregulin-1 (NRG1), A83-01, and matrigel, and collected these derived EVT cells by flow cytometry for sorting cells positive for double human leukocyte antigen-G (HLA-G) and Cytokeratin7 (KRT7), both of which are EVT markers. We then investigated the effects of CsA on the invasion and migration of these derived EVT cells. We found that the hiPSC-EVT and hESC-EVT cells expressed high levels of the EVT markers such as KRT7, integrin alpha 5 (ITGA5), and HLA-G but low levels of OCT4, a stem cell marker, and that CsA significantly promoted the invasion and migration of hiPSC-EVT and hESC-EVT cells compared with HTR-8/SVneo cells. These results represent a possible cell model for studying the function of EVT cells and mechanism of pregnancy-related disorders associated with EVT. In addition, CsA may be used to treat pregnancy complications in clinic associated with deficient EVT function.

An update on placental drug transport and its relevance to fetal drug exposure

Pregnant women are often complicated with diseases that require treatment with medication. Most drugs administered to pregnant women are off-label without the necessary dose, efficacy, and safety information. Knowledge concerning drug transfer across the placental barrier is essential for understanding fetal drug exposure and hence drug safety and efficacy to the fetus. Transporters expressed in the placenta, including adenosine triphosphate (ATP)-binding cassette efflux transporters and solute carrier uptake transporters, play important roles in determining drug transfer across the placental barrier, leading to fetal exposure to the drugs. In this review, we provide an update on placental drug transport, including in vitro cell/tissue, ex vivo human placenta perfusion, and in vivo animal studies that can be used to determine the expression and function of drug transporters in the placenta as well as placental drug transfer and fetal drug exposure. We also describe how the knowledge of placental drug transfer through passive diffusion or active transport can be combined with physiologically based pharmacokinetic modeling and simulation to predict systemic fetal drug exposure. Finally, we highlight knowledge gaps in studying placental drug transport and predicting fetal drug exposure and discuss future research directions to fill these gaps.

Melatonin Hormone Acts on Cells of Maternal Blood and Placenta From Diabetic Mothers

Changes in glucose metabolism of diabetic mothers affect immunological components, proinflammatory factors, and placental hypervascularization that can induce cell death. The hormone melatonin has been identified as a potential modulating agent. The aim of this study was to analyze the oxidative process and the apoptosis in maternal blood and placental cells modulated by melatonin from diabetic mothers. The groups were 40 pregnant women divided into non-diabetic (ND) and type 2 diabetes mellitus (T2DM) groups. Blood and placental cells were obtained by density gradient and maintained in culture treated or not with melatonin (100 ng/mL) for 24 h (37°C, 5% CO2). Oxidative stress was evaluated by superoxide release and CuZn superoxide dismutase (SOD). Apoptosis was assessed by flow cytometry. Maternal hyperglycemia increased superoxide release and apoptosis in MN cells from maternal blood and reduced SOD level and SOD/O2- ratio. Melatonin reduced oxidative stress and apoptosis rates in MN cells in the blood of diabetic mothers. There was a reduction in SOD and SOD/O2- ratio in the placental extravillous layer, and melatonin restored the concentrations of this enzyme. There was greater superoxide release, reduced SOD/O2- ratio, and apoptosis in MN cells placental villous layer. Melatonin increased apoptosis rates in the placental villous layer from hyperglycemic mothers. These data suggest that hyperglycemia altered the processes oxidative in blood and placenta from hyperglycemic mothers. These changes reflected in the mechanisms of induction of apoptosis, especially in the vascularized layers of the placenta, and were modulated by melatonin.

NPFF increases fusogenic proteins syncytin 1 and syncytin 2 via GCM1 in first trimester primary human cytotrophoblast cells

Neuropeptide FF (NPFF) is well-known for its roles in the central nervous system. Despite studies demonstrating that NPFF receptor 2 (NPFFR2) mRNA is highest in placenta, nothing is known about NPFF-NPFFR2 functions in placental development. Here, we investigated the effects of NPFF-NPFFR2 on expression of syncytial [human chorionic gonadotropin (hCG) β] and fusogenic [syncytin 1, syncytin 2, and glial cells missing 1 (GCM1)] genes in first trimester primary human cytotrophoblast cells. By analyzing two publicly available microarray data sets, we found that NPFF is consistently expressed throughout gestation whereas NPFFR2 increases in first trimester and is elevated in placenta samples from women with preeclampsia. Immunohistochemistry showed that NPFFR2, syncytin 1/2, and GCM1 each displayed unique patterns of expression among different trophoblast populations in first trimester placenta. Treatment of primary human cytotrophoblast cells with NPFF increased the mRNA and protein levels of hCG β, syncytin 1, syncytin 2, and GCM1; and knockdown of NPFFR2 abolished these effects. Interestingly, GCM1 mediated NPFF-induced upregulation of syncytin 1 and syncytin 2, but not hCG β, in primary human cytotrophoblasts. Our results demonstrate that NPFF acts via NPFFR2 to enhance production of hCG β and promote GCM1-dependent expression of syncytin 1 and 2 in human cytotrophoblasts.

Identification of miRNAs and associated pathways regulated by Leukemia Inhibitory Factor in trophoblastic cell lines

INTRODUCTION

Leukemia Inhibitory Factor (LIF) regulates behavior of trophoblast cells and their interaction with immune and endothelial cells. In vitro, trophoblast cell response to LIF may vary depending on the cell model. Reported differences in the miRNA profile of trophoblastic cells may be responsible for these observations. Therefore, miRNA expression was investigated in four trophoblastic cell lines under LIF stimulation followed by in silico analysis of altered miRNAs and their associated pathways.

METHODS

Low density TaqMan miRNA assays were used to quantify levels of 762 mature miRNAs under LIF stimulation in three choriocarcinoma-derived (JEG-3, ACH-3P and AC1-M59) and a trophoblast immortalized (HTR-8/SVneo) cell lines. Expression of selected miRNAs was confirmed in primary trophoblast cells and cell lines by qPCR. Targets and associated pathways of the differentially expressed miRNAs were inferred from the miRTarBase followed by a KEGG Pathway Enrichment Analysis. HTR-8/SVneo and JEG-3 cells were transfected with miR-21-mimics and expression of miR-21 targets was assessed by qPCR.

RESULTS

A similar number of miRNAs changed in each tested cell line upon LIF stimulation, however, low coincidence of individual miRNA species was observed and occurred more often among choriocarcinoma-derived cells (complete data set at http://www.ncbi.nlm.nih.gov/geo/ under GEO accession number GSE130489). Altered miRNAs were categorized into pathways involved in human diseases, cellular processes and signal transduction. Six cascades were identified as significantly enriched, including JAK/STAT and TGFB-SMAD. Upregulation of miR-21-3p was validated in all cell lines and primary cells and STAT3 was confirmed as its target.

DISCUSSION

Dissimilar miRNA responses may be involved in differences of LIF effects on trophoblastic cell lines.

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 Oncostatin M on Invasion of Primary Trophoblasts under Normoxia and Hypoxia Conditions

PURPOSE

To investigate the effect of oncostatin M (OSM) on protein expression levels and enzymatic activities of matrix metalloprotainase (MMP)-2 and MMP-9 in primary trophoblasts and the invasiveness thereof under normoxia and hypoxia conditions.

MATERIALS AND METHODS

Protein expression levels and enzymatic activities of MMP-2 and MMP-9 in primary trophoblasts under normoxia and hypoxia conditions were examined by Western blot and zymography, respectively. Effects of exogenous OSM on the in vitro invasion activity of trophoblasts according to oxygen concentration were also determined. Signal transducer and activator of transcription 3 (STAT3) siRNA was used to determine whether STAT3 activation in primary trophoblasts was involved in the effect of OSM.

RESULTS

OSM enhanced protein expression levels and enzymatic activities of MMP-2 and MMP-9 in term trophoblasts under hypoxia condition, compared to normoxia control (p<0.05). OSM-induced MMP-2 and MMP-9 enzymatic activities were significantly suppressed by STAT3 siRNA silencing under normoxia and hypoxia conditions (p<0.05). Hypoxia alone or OSM alone did not significantly increase the invasiveness of term trophoblasts. However, the invasion activity of term trophoblasts was significantly increased by OSM under hypoxia, compared to that without OSM treatment under normoxia.

CONCLUSION

OSM might be involved in the invasiveness of extravillous trophoblasts under hypoxia conditions via increasing MMP-2 and MMP-9 enzymatic activities through STAT3 signaling. Increased MMP-9 activity by OSM seems to be more important in primary trophoblasts.

Characteristics of Trophoblasts in Long-Term Culture

We analyzed more than 40 cytotrophoblast cultures derived from cell islets that grew from trypsinized tissue fragments of placental microvilli. Phenotypic variability of trophoblasts was demonstrated. Changes in trophoblast morphology from epithelium-like or oval cells to bipolar and spindle-shaped or twisted and then to mesenchymal-like cells as well as intensive expression of cytokeratin-7 and vimentin attested to epithelial-mesenchymal transition of trophoblasts during in vitro culturing. Analysis of the expression of specific markers in long-term trophoblast culture (≥7 passages) revealed the possibility of culture contamination with other non-trophoblast cells including fibroblasts. High risk of trophoblast culture contamination with rapidly growing cells necessitates regular control of the cultures used in fundamental studies. Our experiments confirmed the possibility of long-term culturing of cells maintaining trophoblast properties. The identity and purity of 4 trophoblast cultures free from contamination and retaining the properties of pure culture during long-term (>10 passages) culturing in vitro were confirmed.

Compartmentalized localization of 11β-HSD 1 and 2 at the feto-maternal interface in the first trimester of human pregnancy

Glucocorticoids are engaged in a number of actions at the feto-maternal interface for the establishment of early pregnancy. However, excessive glucocorticoids can be deleterious to fetal development. Therefore, compartmentalized distribution of 11β-hydroxysteroid dehydrogenase 1 and 2 (11β-HSD1 and 2), which regenerates and inactivates cortisol respectively, would ensure an optimal cortisol concentration at the feto-maternal interface for the establishment of early gestation. However, the distribution pattern of 11β-HSD1 and 2 at the feto-maternal interface in early human pregnancy is not clearly defined. Here we showed that 11β-HSD1 distributed extensively on the maternal side including decidual stromal cells and epithelial cells but scarcely on the fetal side except for localization in the fetal blood vessels of the chorionic villi. In contrast, 11β-HSD2 was abundantly localized in syncytial layer of the chorionic villi and the decidual epithelium. In primary cultures, cortisol upregulated not only 11β-HSD1 expression in decidual stromal cells but also 11β-HSD2 expression in villous trophoblasts of early pregnancy. Further studies revealed that cortisol inhibited the expression of interleukin-1β and 6 in decidual stromal cells and villous trophoblasts, and stimulated expression of human chorionic gonadotropin in villous trophoblasts. Collectively, this study has revealed a compartmentalized distribution pattern of 11β-HSD 1 and 2 at the feto-maternal interface, both of which can be upregulated by glucocorticoids, suggesting that a coordinated interaction between 11β-HSD 1 and 2 may exist to ensure an optimal cortisol concentration at discrete locations at the feto-maternal interface for the establishment of early pregnancy.

Human Primary Trophoblast Cell Culture Model to Study the Protective Effects of Melatonin Against Hypoxia/reoxygenation-induced Disruption

This protocol describes how villous cytotrophoblast cells are isolated from placentas at term by successive enzymatic digestions, followed by density centrifugation, media gradient isolation and immunomagnetic purification. As observed in vivo, mononucleated villous cytotrophoblast cells in primary culture differentiate into multinucleated syncytiotrophoblast cells after 72 hr. Compared to normoxia (8% O2), villous cytotrophoblast cells that undergo hypoxia/reoxygenation (0.5% / 8% O2) undergo increased oxidative stress and intrinsic apoptosis, similar to that observed in vivo in pregnancy complications such as preeclampsia, preterm birth, and intrauterine growth restriction. In this context, primary villous trophoblasts cultured under hypoxia/reoxygenation conditions represent a unique experimental system to better understand the mechanisms and signalling pathways that are altered in human placenta and facilitate the search for effective drugs that protect against certain pregnancy disorders. Human villous trophoblasts produce melatonin and express its synthesizing enzymes and receptors. Melatonin has been suggested as a treatment for preeclampsia and intrauterine growth restriction because of its protective antioxidant effects. In the primary villous cytotrophoblast cell model described in this paper, melatonin has no effect on trophoblast cells in normoxic state but restores the redox balance of syncytiotrophoblast cells disrupted by hypoxia/reoxygenation. Thus, human villous trophoblast cells in primary culture are an excellent approach to study the mechanisms behind the protective effects of melatonin on placental function during hypoxia/reoxygenation.

Characterization of Natural Killer Cells and Cytokines in Maternal Placenta and Fetus of Diabetic Mothers

The present study characterized natural killer cells and cytokines in diabetic mothers, their placenta, and fetus. In the maternal blood from the hyperglycemic groups, the CD16⁺CD56⁻ NK cells increased, whereas that of CD16⁺CD56⁺ decreased in gestational diabetes mellitus [GDM] group. Cord blood from type 2 diabetes [DM-2] showed a higher proportion of CD16⁺CD56⁻ and CD16⁻CD56⁺. The placental extravillous layer of GDM and DM-2 showed an increase of CD16⁺CD56⁻ cells and, irrespective of region, the proportion of CD16⁻CD56⁺ cells was higher in mild gestational hyperglycemia [MGH] and GDM and lower in DM-2. IL-2 was lower in maternal blood and IFN-γ higher in maternal and cord blood from the GDM group. IL-17 was higher in maternal and cord blood from the DM-2 group. The placental extravillous layer of the MGH showed high levels of IL-4, IL-6, IL-10, IL-17, and IFN-γ and low levels of IL-1β and IL-8, whereas the placental villous layer contained high levels of IL-17 and IFN-γ. The GDM group, irrespective of region, showed higher levels of IL-8. The DM-2 group, irrespective of region, placenta showed high levels of TNF-α, IL-17, and IFN-γ. The hyperglycemia produces an inflammatory environment with a high content of inflammatory cytokines and cells expressing CD16⁺.

Dissimilar microRNA-21 functions and targets in trophoblastic cell lines of different origin

Trophoblast cells express a singular miRNA expression profile which varies during pregnancy and whose alteration may be associated with pregnancy complications. miR-21, a widely known oncomir, is highly expressed in human placenta but its role in regulating trophoblast cells remains unclear. The aim of this study was to investigate miR-21 functions and targets in HTR-8/SVneo immortalized trophoblast and JEG-3 choriocarcinoma cells, which are trophoblast cell models that differ in their cellular origin. Cells were transfected with miR-21-antagomir, -mimic or their respective controls. Following, cell proliferation (BrdU), migration (Transwell and scratch wound-healing assays), invasion (Matrigel assays) and apoptosis (flow cytometry, TUNEL assay and Western blotting) were assessed. Expression of the potential miR-21 targets phosphatase and tensin homolog (PTEN) and programmed cell death 4 (PDCD4) were analyzed by Western blotting. Inhibition of miR-21 decreased cell proliferation, migration, and invasion in JEG-3 and HTR-8/SVneo cells and additionally, induced apoptosis in JEG-3 cells. Silencing of miR-21 enhanced PDCD4 expression only in JEG-3 cells, and PTEN expression only in HTR-8/SVneo cells. Inhibition of miR-21 significantly increased phosphorylation of AKT in HTR-8/SVneo cells. In conclusion, miR-21 has cell-specific targets depending upon the origin of trophoblastic cells. Furthermore, miR-21 regulates major cellular processes including cell growth, migration, invasion and apoptosis suggesting that its impairment may lead to placental disorders.

Isolation, purification and in vitro differentiation of cytotrophoblast cells from human term placenta

BACKGROUND

The syncytialization of cytotrophoblast cells to syncytiotrophoblast is central to human placental transport and hormone production. Many techniques for in vitro study of this process have been proposed and new investigators to the field may find the literature in the field daunting. Here, we present a straightforward and reliable method to establish this important model using modern but readily available tools and reagents.

METHODS

Villous cytotrophoblast cells are obtained from term placenta using mild enzymatic degradation, Percoll gradient centrifugation, negative magnetic cell sorting using an antibody against classical major histocompatibility complex molecules and in vitro culture on a matrix-coated growth surface.

RESULTS

The purity of isolated cytotrophoblast cells exceeds 98 % as assessed by cytokeratin-7 expression using flow cytometry. Contamination by mesenchymal cells, extravillous trophoblast cells, leukocytes, Hofbauer and endothelial cells is minimized (less than 2 % when analyzed for vimentin, HLA-G, CD45, CD163 and CD31 using flow cytometry). Isolated cytotrophoblast cells began to aggregate into monolayers of mononucleated cells within about 12 h of plating. By 72 h in culture, most cytotrophoblast cells have differentiated into syncytiotrophoblast as demonstrated by a loss of intercellular E-cadherin expression upon fusion into multinucleated syncytia. After 72 h in culture, nearly every cultured cell expresses syncytiotrophoblast markers, including cytokeratin-7, human chorionic gonadotropin-β (β-hCG) and the fusion-related proteins glial cell missing-1 (GCM-1) and syncytin.

CONCLUSIONS

We present an efficient and reliable method for isolating of cytotrophoblast cells with high purity and complete differentiation into syncytiotrophoblast in vitro.

STAT5 is Activated by Epidermal Growth Factor and Induces Proliferation and Invasion in Trophoblastic Cells

Epidermal growth factor (EGF) is expressed by decidual and trophoblast cells and influences manifold cellular functions during embryo implantation. Thus far, signaling of EGF via Signal Transducer and Activator of Transcription 5 (STAT5) has been only partially investigated. STAT5 stimulates proliferation and cell cycle progression in several cell types. Its dysregulation is associated with pregnancy. The aim of this study was to investigate STAT5 activation and function mediated by EGF in 2 trophoblastic cell lines, namely, HTR8/SVneo and JAR. Additionally, expression of STAT5B messenger RNA (mRNA) in trophoblast models has been compared to that of primary cells isolated from term placentas. Our results demonstrate the highest STAT5B mRNA expression in isolated trophoblast cells, lower expression in HTR8/SVneo cells, and the significantly lowest in JAR cells. Moreover, EGF-mediated STAT5 activation increases cell proliferation and viability in both cell lines. The STAT5 knockdown results in significant decrease in cell viability induced by EGF. Only in HTR8/SVneo cells, invasion decreases after STAT5 silencing and this effect cannot be rescued by further addition of EGF. These results demonstrate that STAT5 activated by EGF constitutes an important cascade for the regulation of cell proliferation and invasion in trophoblast cells.

Serum amyloid A in the placenta and its role in trophoblast invasion

The serum amyloid A (SAA) protein is known to function in the acute phase response and immunoregulation. Recently, SAA has been shown to be involved in cell proliferation, differentiation and migratory behavior in different cell types. Here, we evaluated whether exogenous SAA could influence trophoblast invasion and differentiation using both the trophoblast-like BeWo cell line and fully differentiated human extravillous trophoblast cells (EVT) isolated from term placentae. SAA stimulated BeWo cell invasion, as measured in Matrigel invasion assays, and induced metalloprotease mRNA expression and activity. Given that BeWo cells express Toll-like receptor 4 (TLR4), a known receptor for SAA, we examined the role of TLR4 in SAA-induced invasion using a TLR4 neutralizing antibody. We also tested whether SAA could affect markers of trophoblast syncytialization in BeWo cells. We observed that SAA decreased βhCG secretion and did not influence trophoblast syncytialization. Using EVT cells isolated from human term basal plates, we confirmed that SAA at 1 and 10 µg/mL doubled EVT invasion in a TLR4-dependent manner, but at 20 µg/mL inhibited EVT cells invasiveness. In addition, we observed that SAA was expressed in both BeWo cells and human term placentae, specifically in the syncytiotrophoblast, decidual cells and EVT. In conclusion, SAA was identified as a molecule that functions in the placental microenvironment to regulate metalloprotease activity and trophoblast invasion, which are key processes in placentation and placental homeostasis.

The term basal plate of the human placenta as a source of functional extravillous trophoblast cells

BACKGROUND

Extravillous trophoblast (EVT) cells are of pivotal importance in human embryo implantation and homeostasis of the maternal fetal interface. Invasion of the endometrium by EVT contributes to placental anchorage, spiral artery remodeling, immunological defense, tolerogenic responses, and several collaborative cross talks involved in establishing and maintaining a successful pregnancy. We report here an improved protocol for the isolation of fully differentiated EVT cells from the basal plate of the human term placenta.

METHODS

The basal plate was carefully dissected from the villous tissue and the amniochorion membrane prior to enzymatic digestion. Term basal EVT cells were isolated using a 30 and 60% Percoll gradient. A panel of markers and characteristics of the isolated cells were used to confirm the specificity and efficiency of the method so that their potential as an investigative tool for placental research could be ascertained.

RESULTS

Isolated cells were immunoreactive for cytokeratin-7 (CK-7), placental growth factor, placental alkaline phosphatase, human leukocyte antigen G1 (HLA-G1), and α1 and α5 integrins, similarly to the EVT markers from first trimester placental villi. Around 95% of the isolated cells labeled positively for CK-7 and 82% for HLA-G1. No significant change in viability was observed during 48 h of EVT culture as indicated by propidium iodide incorporation and trypan blue test exclusion. Genes for metalloproteinases MMP-2 and MMP9 (positive regulators of trophoblast invasiveness) were expressed up to 48 h of culturing, as also the gelatinolytic activity of the isolated cells. Transforming growth factor (TGF)-beta, which inhibits proliferation, migration, and invasiveness of first-trimester EVT cells, also reduced invasion of isolated term EVT cells in transwell assays, whereas epidermal growth factor was a positive modulator.

CONCLUSIONS

Term basal plate may be a viable source of functional EVT cells that is an alternative to villous explant-derived EVT cells and cell lines. Isolated term EVT cells may be particularly useful in investigation of the role of trophoblast cells in pathological gestations, in which the precise regulation and interactive ability of extravillous trophoblast has been impaired.

Effect of baicalein on the expression of VIP in extravillous cytotrophoblasts infected with human cytomegalovirus in vitro

This paper aimed to study the ability of baicalein to block human cytomegalovirus (HCMV) infection in extravillous cytotrophoblasts (EVT) and its effect on the vasoactive intestinal peptide (VIP) expression in HCMV-infected EVT in vitro. A human trophoblast cell line (HPT-8) was chosen in this study. HCMV with 100 TCID50 was added into culture medium to infect HPT-8 cells, and then HCMV pp65 antigen was assayed by immunofluorescence staining. The infection status was determined by virus titration. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect virus DNA load in the infected cells. The expression of VIP mRNA and protein in the infected cells was measured by qRT-PCR, immunocytochemistry and Western blotting. Concentration of VIP secreted in supernatants was determined by ELISA. Red-stained HCMV pp65 antigens were found in infected HPT-8 cells 48 h after infection. HCMV replicated in large quantity in infected HPT-8 cells 4 days after infection, reaching a peak at day 6 post-infection. After treatment with baicalein, virus DNA load in infected HPT-8 cells was decreased (P<0.05), and the levels of VIP mRNA and protein, and the concentration were raised to the normal (P>0.05). Our study suggested that baicalein exerts a positive effect on the VIP expression in HCMV-infected EVT at maternal-fetal interface.

Trophoblast differentiation of human embryonic stem cells

Molecular mechanisms regulating human trophoblast differentiation remain poorly understood due to difficulties in obtaining primary tissues from very early developmental stages in humans. Therefore, the use of human embryonic stem cells (hESCs) as a source for generating trophoblast tissues is of significant interest. Trophoblast-like cells have been obtained through treatment of hESCs with bone morphogenetic protein (BMP) or inhibitors of activin/nodal/transforming growth factor-β signaling, or through protocols involving formation of embryoid bodies (EBs); however, there is controversy over whether hESC-derived cells are indeed analogous to true trophoblasts found in vivo. In this review, we provide an overview of previously described efforts to obtain trophoblasts from hESCs. We also discuss the merits and limitations of hESCs as a source of trophoblast derivatives.

Wide-ranging DNA methylation differences of primary trophoblast cell populations and derived cell lines: implications and opportunities for understanding trophoblast function

Difficulties associated with long-term culture of primary trophoblasts have proven to be a major hurdle in their functional characterization. In order to circumvent this issue, several model cell lines have been established over many years using a variety of different approaches. Due to their differing origins, gene expression profiles and behaviour in vitro, different model lines have been utilized to investigate specific aspects of trophoblast biology. However, generally speaking, the molecular mechanisms underlying functional differences remain unclear. In this study, we profiled genome-scale DNA methylation in primary first trimester trophoblast cells and seven commonly used trophoblast-derived cell lines in an attempt to identify functional pathways differentially regulated by epigenetic modification in these cells. We identified a general increase in DNA promoter methylation levels in four choriocarcinoma (CCA)-derived lines and transformed HTR-8/SVneo cells, including hypermethylation of several genes regularly seen in human cancers, while other differences in methylation were noted in genes linked to immune responsiveness, cell morphology, development and migration across the different cell populations. Interestingly, CCA-derived lines show an overall methylation profile more similar to unrelated solid cancers than to untransformed trophoblasts, highlighting the role of aberrant DNA methylation in CCA development and/or long-term culturing. Comparison of DNA methylation and gene expression in CCA lines and cytotrophoblasts revealed a significant contribution of DNA methylation to overall expression profile. These data highlight the variability in epigenetic state between primary trophoblasts and cell models in pathways underpinning a wide range of cell functions, providing valuable candidate pathways for future functional investigation in different cell populations. This study also confirms the need for caution in the interpretation of data generated from manipulation of such pathways in vitro.

Lactobacillus rhamnosus GR-1 stimulates colony-stimulating factor 3 (granulocyte) (CSF3) output in placental trophoblast cells in a fetal sex-dependent manner

Bacterial vaginosis is associated with a 1.4-fold increased risk of preterm birth. We have shown previously that Lactobacillus rhamnosus GR-1 supernatant up-regulates interleukin 10 and down-regulates tumor necrosis factor-alpha output in lipopolysaccharide (LPS)-treated human primary placenta cultures in a fetal sex-dependent manner. We hypothesize that lactobacilli also exert their anti-inflammatory effect by up-regulation of colony-stimulating factor 3 (granulocyte) (CSF3), which is secreted from both immune and placental trophoblast cells, and that this activity is dependent on the sex of the fetus. Placental trophoblast cells were isolated from term elective cesarean section placentae using a Percoll gradient and separated from CD45(+) cells using magnetic purification. Cells were treated with LPS in the presence or absence of pretreatments with L. rhamnosus GR-1 supernatant or chemical inhibitors of the intracellular signaling pathways. Phosphorylations of mitogen-activated protein kinase 14 (MAPK14, previously known as p38) and signal transducer and activator of transcription (STAT) 3 were measured by Western blot analysis, and levels of CSF3 were determined by ELISA. CSF3 output was increased only in the placental trophoblast cells of female fetuses treated with LPS, GR-1 supernatant, and a combination of both treatments. The GR-1 supernatant up-regulated the phosphorylation of STAT3 and MAPK14. CSF3 output was inhibited by both Janus kinases (JAK) and MAPK14 inhibitors. None of the treatments was able to increase CSF3 output in either the pure trophoblast or the CD45(+) cell preparations alone. These results suggest an underlying mechanism for the sex difference in incidence of preterm birth and provide potential evidence for a therapeutic benefit of lactobacilli in reducing the risk of preterm labor.