PLAC8, a new marker for human interstitial extravillous trophoblast cells, promotes their invasion and migration

The multifaceted roles of the transcriptional coactivator TAZ in extravillous trophoblast development of the human placenta

Insights into the molecular processes that drive early development of the human placenta is crucial for our understanding of pregnancy complications such as preeclampsia and fetal growth restriction, since defects in maturation of its epithelial cell, the trophoblast, have been detected in the severe forms of these diseases. However, key regulators specifying the differentiated trophoblast subtypes of the placenta are only slowly emerging. By using diverse trophoblast cell models, we herein show that the transcriptional coactivator of HIPPO signaling, TAZ, plays a pivotal role in the development of invasive extravillous trophoblasts (EVTs), cells that are essential for decidual vessel remodeling and adaption of maternal blood flow to the placenta. Ribonucleic acid sequencing (RNA-seq) or protein analyses upon TAZ gene silencing or CRISPR-Cas9-mediated knockout in differentiating trophoblast stem cells, organoids, primary EVTs, choriocarcinoma cells, or villous explant cultures unraveled that the coactivator promoted expression of genes associated with EVT identity, motility, and survival. Accordingly, depletion or chemical inhibition of TAZ, interacting with TEA domain family member 1 (TEAD1), impaired EVT differentiation, invasion, and migration and triggered apoptosis in the different trophoblast models. Notably, the coactivator also suppressed cell cycle genes and regulators of trophoblast self-renewal and prevented EVTs from cell fusion in organoids and primary cultures. Moreover, TAZ promoted human leukocyte antigen G (HLA-G) surface expression and increased NUAK1 kinase in EVTs thereby maintaining its own expression. In summary, the transcriptional coactivator TAZ plays a multifaceted role in the development of the EVT cell lineage by controlling different biological processes that initiate and preserve differentiation.

Cystatin 6 (CST6) and Legumain (LGMN) are potential mediators in the pathogenesis of preeclampsia

Preeclampsia results from placental insufficiency and causes maternal endothelial dysfunction and multi-organ damage. Our in-silico analysis identified Cystatin 6 (CST6), a cysteine protease inhibitor, as located on the placental surface where it might be released into maternal circulation. This study aimed to characterise CST6 and one of its high affinity targets, Legumain (LGMN), in preeclampsia and assess its biomarker potential by measuring levels in maternal circulation. Placental CST6 mRNA expression was significantly increased in 78 pregnancies complicated by early-onset preeclampsia (delivering at < 34 weeks' gestation) relative to 30 gestation matched controls (P < 0.0001). LGMN mRNA expression was significantly decreased (P = 0.0309). Circulating CST6 was increased in 35 pregnancies complicated by early-onset preeclampsia (< 34 weeks' gestation) relative to 27 gestation matched controls (P = 0.0261), and LGMN levels remained unchanged. At 36 weeks' gestation, circulating CST6 was significantly increased (P = 0.001), while LGMN was significantly decreased (P = 0.0135) in 21 pregnancies preceding diagnosis of preeclampsia at term, compared to 184 pregnancies that did not develop preeclampsia. Human trophoblast stem cells (hTSC) were differentiated into syncytiotrophoblast or extravillous trophoblast (EVT) to evaluate CST6 and LGMN expression in these trophoblast lineages. CST6 and LGMN mRNA expression were significantly increased across 96 h after syncytiotrophoblast (P = 0.0066 and P = 0.0010 respectively) and EVT differentiation (P = 0.0618 and P = 0.0016 respectively), with the highest expression in syncytiotrophoblast. Computational analysis of two publicly available single-cell and single-nuclei RNA sequencing datasets correlated with the expression pattern observed in vitro. When syncytiotrophoblast cells were exposed to hypoxia (1% O2 vs. 8% O2), CST6 expression significantly increased (P = 0.0079), whilst LGMN expression was unchanged. The vascular endothelium may serve as an additional source of circulating CST6 and LGMN in preeclampsia.  Induction of dysfunction in endothelial cells by TNFα, caused reduced CST6 expression (P = 0.0036), whilst LGMN expression remained unchanged. Administering recombinant CST6 to endothelial cells enhanced markers of endothelial dysfunction and LGMN expression in the presence of TNFα. These findings indicate an inverse relationship between CST6 and LGMN in the placenta and maternal circulation in preeclampsia. We suggest elevated circulating levels of CST6 may be induced by placental hypoxia. This study provides novel insight into the dysregulation of CST6 and LGMN in preeclampsia and introduces their potential roles in human pregnancy and associated pathology.

Stem Cell Markers LGR5, LGR4 and Their Immediate Signalling Partners are Dysregulated in Preeclampsia

Leucine-rich repeat-containing G protein-coupled receptors 5/4 (LGR5/LGR4) are critical stem cell markers in epithelial tissues including intestine. They agonise wingless-related integration site (WNT) signalling. Until now, LGR5/LGR4 were uncharacterised in placenta, where analogous functions may exist. We characterised LGR5/LGR4, their ligands/targets in human placenta, with further assessments on dysregulation in preeclampsia/fetal growth restriction (FGR). LGR5 mRNA was unaltered in first trimester (n = 11), preterm (n = 9) and term (n = 11) placental lysate. LGR5 was enriched in human trophoblast stem cells (hTSCs) and downregulated with differentiation to extravillous trophoblasts (p < 0.0215) and syncytiotrophoblasts (p < 0.0350). In situ hybridisation localised LGR5 to unique, proliferative MKI67 + mononuclear trophoblasts underlying syncytium which concurred with proposed progenitor identities in single-cell transcriptomics. LGR5 expression was significantly reduced in placentas from early-onset preeclampsia (p < 0.0001, n = 81 versus n = 19 controls), late-onset preeclampsia (p = 0.0046, n = 20 versus n = 33 controls) and FGR (p = 0.0031, n = 34 versus n = 17 controls). LGR4 was elevated in first trimester versus preterm and term placentas (p = 0.0412), in placentas with early-onset preeclampsia (p = 0.0148) and in FGR (p = 0.0417). Transcriptomic analysis and in vitro hTSC differentiation to both trophoblast lineages suggested LGR4 increases with differentiation. Single-nucleus RNA sequencing of placental villous samples supported LGR5 and LGR4 localisation findings. Hypoxia/proinflammatory cytokine treatment modelling elements experienced by the placenta in placental insufficiency pathogenesis did not significantly alter LGR5/LGR4. Ligands R-spondins 1/3/4, and neutralising targets ring finger protein 43 (RNF43) and zinc and ring finger 3 (ZNRF3) were also reduced in placentas from preeclamptic pregnancies. This study is the first to describe LGR5/LGR4 and their signalling partner expression in human placenta. Their dysregulations in the preeclamptic placenta allude to disruptions to integral trophoblast stem cell function/differentiation that may occur during placental development related to WNT signalling.

NOTUM-mediated WNT silencing drives extravillous trophoblast cell lineage development

Trophoblast stem (TS) cells have the unique capacity to differentiate into specialized cell types, including extravillous trophoblast (EVT) cells. EVT cells invade into and transform the uterus where they act to remodel the vasculature facilitating the redirection of maternal nutrients to the developing fetus. Disruptions in EVT cell development and function are at the core of pregnancy-related disease. WNT-activated signal transduction is a conserved regulator of morphogenesis of many organ systems, including the placenta. In human TS cells, activation of canonical WNT signaling is critical for maintenance of the TS cell stem state and its downregulation accompanies EVT cell differentiation. We show that aberrant WNT signaling undermines EVT cell differentiation. Notum, palmitoleoyl-protein carboxylesterase (NOTUM), a negative regulator of canonical WNT signaling, was prominently expressed in first-trimester EVT cells developing in situ and up-regulated in EVT cells derived from human TS cells. Furthermore, NOTUM was required for optimal human TS cell differentiation to EVT cells. Activation of NOTUM in EVT cells is driven, at least in part, by endothelial Per-Arnt-Sim (PAS) domain 1 (also called hypoxia-inducible factor 2 alpha). Collectively, our findings indicate that canonical Wingless-related integration site (WNT) signaling is essential for maintenance of human trophoblast cell stemness and regulation of human TS cell differentiation. Downregulation of canonical WNT signaling via the actions of NOTUM is required for optimal EVT cell differentiation.

Trophoblast Side-Population Markers are Dysregulated in Preeclampsia and Fetal Growth Restriction

Dysregulated progenitor cell populations may contribute to poor placental development and placental insufficiency pathogenesis. Side-population cells possess progenitor properties. Recent human trophoblast side-population isolation identified enrichment of 8 specific genes (CXCL8, ELL2, GATA6, HK2, HLA-DPB1, INTS6, SERPINE3 and UPP1) (Gamage et al. 2020, Stem Cell Rev Rep). We characterised these trophoblast side-population markers in human placenta and in placental insufficiency disorders: preeclampsia and fetal growth restriction (FGR). Trophoblast side-population markers localised to mononuclear trophoblasts lining the placental villous basement membrane in preterm control, preeclamptic and FGR placental sections (n = 3, panel of 3 markers/serial section). Analysis of single-cell transcriptomics of an organoid human trophoblast stem cell (hTSC) to extravillous trophoblast (EVT) differentiation model (Shannon et al. 2022, Development) identified that all side-population genes were enriched in mononuclear trophoblast and trophoblasts committed to differentiation under hTSC culture conditions. In vitro validation via 96 h time course hTSC differentiation to EVTs or syncytiotrophoblasts (n = 5) demonstrated ELL2 and HK2 increased with differentiation (p < 0.0024, p < 0.0039 respectively). CXCL8 and HLA-DPB1 were downregulated (p < 0.030, p < 0.011 respectively). GATA6 and INTS6 increased with EVT differentiation only, and UPP1 reduced with syncytialisation. SERPINE3 was undetectable. Trophoblast side-population marker mRNA was measured in human placentas (< 34-weeks' gestation; n = 78 preeclampsia, n = 30 FGR, and n = 18 gestation-matched controls). ELL2, HK2 and CXCL8 were elevated in preeclamptic (p = 0.0006, p < 0.0001, p = 0.0335 respectively) and FGR placentas (p = 0.0065, p < 0.0001, p = 0.0001 respectively) versus controls. Placental GATA6 was reduced in pregnancies with preeclampsia and FGR (p = 0.0014, p = 0.0146 respectively). Placental INTS6 was reduced with FGR only (p < 0.0001). This study identified the localisation of a unique trophoblast subset enriched for side-population markers. Aberrant expression of some side-population markers may indicate disruptions to unique trophoblast subtypes in placental insufficiency.

Cell type and cell signaling innovations underlying mammalian pregnancy

How fetal and maternal cell types have co-evolved to enable mammalian placentation poses a unique evolutionary puzzle. Here, we present a multi-species atlas integrating single-cell transcriptomes from six species bracketing therian mammal diversity. We find that invasive trophoblasts share a gene-expression signature across eutherians, and evidence that endocrine decidual cells evolved stepwise from an immunomodulatory cell type retained in Tenrec with affinity to human decidua of menstruation. We recover evolutionary patterns in ligand-receptor signaling: fetal and maternal cells show a pronounced tendency towards disambiguation, but a predicted arms race dynamic between them is limited. We reconstruct cell communication networks of extinct mammalian ancestors, finding strong integration of fetal trophoblast into maternal networks. Together, our results reveal a dynamic history of cell type and signaling evolution.

Synopsis

The fetal-maternal interface is one of the most intense loci of cell-cell signaling in the human body. Invasion of cells from the fetal placenta into the uterus, and the corresponding transformation of maternal tissues called decidualization, first evolved in the stem lineage of eutherian mammals( 1 , 2 ). Single-cell studies of the human fetal-maternal interface have provided new insight into the cell type diversity and cell-cell interactions governing this chimeric organ( 3-5 ). However, the fetal-maternal interface is also one of the most rapidly evolving, and hence most diverse, characters among mammals( 6 ), and an evolutionary analysis is missing. Here, we present and compare single-cell data from the fetal-maternal interface of species bracketing key events in mammal phylogeny: a marsupial (opossum, Monodelphis domestica ), the afrotherian Tenrec ecaudatus, and four Euarchontoglires - guinea pig and mouse (Rodentia) together with recent macaque and human data (primates) ( 4 , 5 , 7 ). We infer cell type homologies, identify a gene-expression signature of eutherian invasive trophoblast conserved over 99 million years, and discover a predecidual cell in the tenrec which suggests stepwise evolution of the decidual stromal cell. We reconstruct ancestral cell signaling networks, revealing the integration of fetal cell types into the interface. Finally, we test two long-standing theoretical predictions, the disambiguation hypothesis( 8 ) and escalation hypothesis( 9 ), at transcriptome-wide scale, finding divergence between fetal and maternal signaling repertoires but arms race dynamics restricted to a small subset of ligand-receptor pairs. In so doing, we trace the co-evolutionary history of cell types and their signaling across mammalian viviparity.

NOTUM-MEDIATED WNT SILENCING DRIVES EXTRAVILLOUS TROPHOBLAST CELL LINEAGE DEVELOPMENT

Trophoblast stem (TS) cells have the unique capacity to differentiate into specialized cell types, including extravillous trophoblast (EVT) cells. EVT cells invade into and transform the uterus where they act to remodel the vasculature facilitating the redirection of maternal nutrients to the developing fetus. Disruptions in EVT cell development and function are at the core of pregnancy-related disease. WNT-activated signal transduction is a conserved regulator of morphogenesis of many organ systems, including the placenta. In human TS cells, activation of canonical WNT signaling is critical for maintenance of the TS cell stem state and its downregulation accompanies EVT cell differentiation. We show that aberrant WNT signaling undermines EVT cell differentiation. Notum, palmitoleoyl-protein carboxylesterase (NOTUM), a negative regulator of canonical WNT signaling, was prominently expressed in first trimester EVT cells developing in situ and upregulated in EVT cells derived from human TS cells. Furthermore, NOTUM was required for optimal human TS cell differentiation to EVT cells. Activation of NOTUM in EVT cells is driven, at least in part, by endothelial PAS domain 1 (also called hypoxia-inducible factor 2 alpha). Collectively, our findings indicate that canonical WNT signaling is essential for maintenance of human trophoblast cell stemness and regulation of human TS cell differentiation. Downregulation of canonical WNT signaling via the actions of NOTUM is required for optimal EVT cell differentiation.

Revealing the molecular landscape of human placenta: a systematic review and meta-analysis of single-cell RNA sequencing studies

BACKGROUND

With increasing significance of developmental programming effects associated with placental dysfunction, more investigations are devoted to improving the characterization and understanding of placental signatures in health and disease. The placenta is a transitory but dynamic organ adapting to the shifting demands of fetal development and available resources of the maternal supply throughout pregnancy. Trophoblasts (cytotrophoblasts, syncytiotrophoblasts, and extravillous trophoblasts) are placental-specific cell types responsible for the main placental exchanges and adaptations. Transcriptomic studies with single-cell resolution have led to advances in understanding the placenta's role in health and disease. These studies, however, often show discrepancies in characterization of the different placental cell types.

OBJECTIVE AND RATIONALE

We aim to review the knowledge regarding placental structure and function gained from the use of single-cell RNA sequencing (scRNAseq), followed by comparing cell-type-specific genes, highlighting their similarities and differences. Moreover, we intend to identify consensus marker genes for the various trophoblast cell types across studies. Finally, we will discuss the contributions and potential applications of scRNAseq in studying pregnancy-related diseases.

SEARCH METHODS

We conducted a comprehensive systematic literature review to identify different cell types and their functions at the human maternal-fetal interface, focusing on all original scRNAseq studies on placentas published before March 2023 and published reviews (total of 28 studies identified) using PubMed search. Our approach involved curating cell types and subtypes that had previously been defined using scRNAseq and comparing the genes used as markers or identified as potential new markers. Next, we reanalyzed expression matrices from the six available scRNAseq raw datasets with cell annotations (four from first trimester and two at term), using Wilcoxon rank-sum tests to compare gene expression among studies and annotate trophoblast cell markers in both first trimester and term placentas. Furthermore, we integrated scRNAseq raw data available from 18 healthy first trimester and nine term placentas, and performed clustering and differential gene expression analysis. We further compared markers obtained with the analysis of annotated and raw datasets with the literature to obtain a common signature gene list for major placental cell types.

OUTCOMES

Variations in the sampling site, gestational age, fetal sex, and subsequent sequencing and analysis methods were observed between the studies. Although their proportions varied, the three trophoblast types were consistently identified across all scRNAseq studies, unlike other non-trophoblast cell types. Notably, no marker genes were shared by all studies for any of the investigated cell types. Moreover, most of the newly defined markers in one study were not observed in other studies. These discrepancies were confirmed by our analysis on trophoblast cell types, where hundreds of potential marker genes were identified in each study but with little overlap across studies. From 35 461 and 23 378 cells of high quality in the first trimester and term placentas, respectively, we obtained major placental cell types, including perivascular cells that previously had not been identified in the first trimester. Importantly, our meta-analysis provides marker genes for major placental cell types based on our extensive curation.

WIDER IMPLICATIONS

This review and meta-analysis emphasizes the need for establishing a consensus for annotating placental cell types from scRNAseq data. The marker genes identified here can be deployed for defining human placental cell types, thereby facilitating and improving the reproducibility of trophoblast cell annotation.

Dendritic Cells and the Establishment of Fetomaternal Tolerance for Successful Human Pregnancy

Pregnancy is a remarkable event where the semi-allogeneic fetus develops in the mother's uterus, despite genetic and immunological differences. The antigen handling and processing at the maternal-fetal interface during pregnancy appear to be crucial for the adaptation of the maternal immune system and for tolerance to the developing fetus and placenta. Maternal antigen-presenting cells (APCs), such as macrophages (Mφs) and dendritic cells (DCs), are present at the maternal-fetal interface throughout pregnancy and are believed to play a crucial role in this process. Despite numerous studies focusing on the significance of Mφs, there is limited knowledge regarding the contribution of DCs in fetomaternal tolerance during pregnancy, making it a relatively new and growing field of research. This review focuses on how the behavior of DCs at the maternal-fetal interface adapts to pregnancy's unique demands. Moreover, it discusses how DCs interact with other cells in the decidual leukocyte network to regulate uterine and placental homeostasis and the local maternal immune responses to the fetus. The review particularly examines the different cell lineages of DCs with specific surface markers, which have not been critically reviewed in previous publications. Additionally, it emphasizes the impact that even minor disruptions in DC functions can have on pregnancy-related complications and proposes further research into the potential therapeutic benefits of targeting DCs to manage these complications.

Evaluation of Molecular Interactions and Cellular Dynamics at the Maternal-Fetal Interface During Placental Morphogenesis

Molecular events at the maternal-fetal interface establish successful pregnancies. Identifying and characterizing the heterogeneous cell population and their cross-talk at the cellular and molecular levels are essential to expand our knowledge on the progression and maintenance of pregnancy. In this chapter, we briefly discuss the organization of maternal-fetal interface in mice/rats and humans. We illustrate methods for studying the cell composition using flow cytometry, immunocytochemical and biochemical studies, intercellular interaction using co-culture system and spheroid assay, and function of trophoblast cells using ELISA, RNA sequencing, mass spectrometry (MS) to analyze the proteome, invasion assay, and scratch wound assay.

Generation of Human Trophoblast Stem Cell-Dependent Placental In Vitro Models

Currently, human trophoblast stem cell (hTSC) is considered to be the most promising laboratory model stimulating trophoblast criteria. Our group has established hTSCs allowing differentiation to syncytiotrophoblast (STB) and extravillous trophoblast (EVT). Further, hTSC-based three-dimensional (3D) trophoblast organoid (hTSC-organoid) provides a transformative model for studying human placental development and the interaction between trophoblast and maternal environment. Here, we present a protocol to obtain different types of placental trophoblast cells and trophoblast organoids using hTSCs. The generation of hTSC-organoids takes 6 days. hTSC-organoids permit passaging and can differentiate into EVT lineage.

Low m6A modification-mediated upregulation of PLAC8 promotes trophoblast cell invasion and migration in preeclampsia

BACKGROUND

The main symptoms of preeclampsia (PE), a specific ailment that develops during pregnancy, are proteinuria and hypertension. The pathological root of the onset and progression of PE is widely regarded as abnormal placental trophoblast cell function. This study aimed to look into the character and mechanism of Placenta-specific 8 (PLAC8) in trophoblast cell invasion and migration.

METHODS

Expressions of PLAC8 and AlkB homologue 5 (ALKBH5) were examined by western blot and quantitative real-time PCR. The m6A level of PLAC8 mRNA was detected by methylated RNA Immunoprecipitation. Using Transwell experiments, cell invasion and migration were examined. The enzyme-linked immunosorbent assay was utilized to analyze the MMP-2 and MMP-9 secretion levels. RNA pull-down and RNA immunoprecipitation were conducted to detect the binding between ALKBH5 and PLAC8.

RESULTS

In PE tissue and hypoxia-treated HTR-8/SVneo cells, levels of ALKBH5 and PLAC8 were increased, and PLAC8 m6A methylation levels were decreased. There was a positive correlation between PLAC8 and ALKBH5 expression in clinical tissues. In addition, overexpressing PLAC8 promoted HTR-8/SVneo cell migration and invasion, and so as the levels of MMP-2 and MMP-9; while interference with PLAC8 reduced the migration and invasion of hypoxia-treated HTR-8/SVneo cells, and so as the levels of MMP-2 and MMP-9. Moreover, the PLAC8 mRNA's m6A modification site was GAACU (Position 1449, Site 2). Increased levels of MMP-2 and MMP-9, as well as migration and invasion of HTR-8/SVneo cells exposed to hypoxia, were all facilitated by the m6A Site2 mutation. Furthermore, ALKBH5 could bind to PLAC8, reduce its m6A modification, and promote its expression.

CONCLUSION

High-expressed ALKBH5 inhibits the m6A level of PLAC8 mRNA and promotes PLAC8 expression, while PLAC8 overexpression can promote hypoxia-induced invasion and migration of HTR-8/Svneo cells, indicating its potential protective function in PE.

Trophoblast Differentiation: Mechanisms and Implications for Pregnancy Complications

Placental development is a tightly controlled event, in which cell expansion from the trophectoderm occurs in a spatiotemporal manner. Proper trophoblast differentiation is crucial to the vitality of this gestational organ. Obstructions to its development can lead to pregnancy complications, such as preeclampsia, fetal growth restriction, and preterm birth, posing severe health risks to both the mother and offspring. Currently, the only known treatment strategy for these complications is delivery, making it an important area of research. The aim of this review was to summarize the known information on the development and mechanistic regulation of trophoblast differentiation and highlight the similarities in these processes between the human and mouse placenta. Additionally, the known biomarkers for each cell type were compiled to aid in the analysis of sequencing technologies.

Spatial multiomics map of trophoblast development in early pregnancy

The relationship between the human placenta-the extraembryonic organ made by the fetus, and the decidua-the mucosal layer of the uterus, is essential to nurture and protect the fetus during pregnancy. Extravillous trophoblast cells (EVTs) derived from placental villi infiltrate the decidua, transforming the maternal arteries into high-conductance vessels1. Defects in trophoblast invasion and arterial transformation established during early pregnancy underlie common pregnancy disorders such as pre-eclampsia2. Here we have generated a spatially resolved multiomics single-cell atlas of the entire human maternal-fetal interface including the myometrium, which enables us to resolve the full trajectory of trophoblast differentiation. We have used this cellular map to infer the possible transcription factors mediating EVT invasion and show that they are preserved in in vitro models of EVT differentiation from primary trophoblast organoids3,4 and trophoblast stem cells5. We define the transcriptomes of the final cell states of trophoblast invasion: placental bed giant cells (fused multinucleated EVTs) and endovascular EVTs (which form plugs inside the maternal arteries). We predict the cell-cell communication events contributing to trophoblast invasion and placental bed giant cell formation, and model the dual role of interstitial EVTs and endovascular EVTs in mediating arterial transformation during early pregnancy. Together, our data provide a comprehensive analysis of postimplantation trophoblast differentiation that can be used to inform the design of experimental models of the human placenta in early pregnancy.

Monosodium Glutamate Perturbs Human Trophoblast Invasion and Differentiation through a Reactive Oxygen Species-Mediated Pathway: An In-Vitro Assessment

The overproduction of reactive oxygen species (ROS) has been associated with various human diseases. ROS exert a multitude of biological effects with both physiological and pathological consequences. Monosodium glutamate (MSG), a sodium salt of the natural amino acid glutamate, is a flavor-enhancing food additive, which is widely used in Asian cuisine and is an ingredient that brings out the “umami” meat flavor. MSG consumption in rats is associated with ROS generation. Owing to its consumption as part of the fast-food culture and concerns about its possible effects on pregnancy, we aimed to study the impact of MSG on placental trophoblast cells. MSG exposure influenced trophoblast invasion and differentiation, two of the most critical functions during placentation through enhanced production of ROS. Similar findings were also observed on MSG-treated placental explants, as confirmed by elevated Nrf2 levels. Ultrastructural studies revealed signs of subcellular injury by MSG exposure. Mechanistically, MSG-induced oxidative stress with endoplasmic reticulum stress pathways involving Xbp1s and IRE1α was observed. The effect of MSG through an increased ROS production indicates that its long-term exposure might have adverse health effect by compromising key trophoblast functions.

Ezrin and Its Phosphorylated Thr567 Form Are Key Regulators of Human Extravillous Trophoblast Motility and Invasion

The protein ezrin has been shown to enhance cancer cell motility and invasion leading to malignant behaviours in solid tumours, but a similar regulatory function in the early physiological reproduction state is, however, much less clear. We speculated that ezrin may play a key role in promoting first-trimester extravillous trophoblast (EVT) migration/invasion. Ezrin, as well as its Thr567 phosphorylation, were found in all trophoblasts studied, whether primary cells or lines. Interestingly, the proteins were seen in a distinct cellular localisation in long, extended protrusions in specific regions of cells. Loss-of-function experiments were carried out in EVT HTR8/SVneo and Swan71, as well as primary cells, using either ezrin siRNAs or the phosphorylation Thr567 inhibitor NSC668394, resulting in significant reductions in both cell motility and cellular invasion, albeit with differences between the cells used. Our analysis further demonstrated that an increase in focal adhesion was, in part, able to explain some of the molecular mechanisms involved. Data collected using human placental sections and protein lysates further showed that ezrin expression was significantly higher during the early stage of placentation and, importantly, clearly seen in the EVT anchoring columns, further supporting the potential role of ezrin in regulating migration and invasion in vivo.

PLAC8 contributes to the malignant behaviors of cervical cancer cells by activating the SOX4-mediated AKT pathway

Cervical cancer (CC) is the primary cancer-related cause of morbidity and mortality in women. Previous studies have shown that placenta-specific 8 (PLAC8) has different functions in multiple malignancies. This study aimed to explore the function and regulatory mechanism of PLAC8 in CC. Bioinformatics and immunohistochemical analyses demonstrated that PLAC8 was significantly upregulated in CC tissues compared with normal tissues. Gain/loss-of-function experiments showed that siRNA-mediated knockdown of PLAC8 suppressed cell migration and invasion, while PLAC8 overexpression promoted cell motility. Moreover, PLAC8 was revealed to affect the epithelial-mesenchymal transition (EMT) process by upregulating epithelial (E)-cadherin and decreasing the expression of mesenchymal markers of EMT, including vimentin, zinc finger E-box binding homeobox 1 (ZEB1), neural (N)-cadherin, matrix metalloproteinase-9 (MMP-9), and MMP-2 in PLAC8-silenced cells. PLAC8 activated the AKT pathway, as proven by the downregulation of p-AKT_Ser473 and p-AKT_Thr308 expression after PLAC8 knockdown. Furthermore, PLAC8 overexpression upregulated the expression of sex-determining region Y-related high-mobility group box transcription factor 4 (SOX4), which is reported to mediate the activation of the AKT pathway, and SOX4 deficiency reversed the cellular functions caused by PLAC8 overexpression. Overall, the present study indicates that PLAC8 may facilitate CC development by activating the SOX4-mediated AKT pathway, suggesting that PLAC8 may serve as a potential biomarker for CC treatment.

Feto-placental Unit: From Development to Function

The placenta is an intriguing organ that allows us to survive intrauterine life. This essential organ connects both mother and fetus and plays a crucial role in maternal and fetal well-being. This chapter presents an overview of the morphological and functional aspects of human placental development. First, we describe early human placental development and the characterization of the cell types found in the human placenta. Second, the human placenta from the second trimester to the term of gestation is reviewed, focusing on the morphology and specific pathologies that affect the placenta. Finally, we focus on the placenta's primary functions, such as oxygen and nutrient transport, and their importance for placental development.

Hippo signaling cofactor, WWTR1, at the crossroads of human trophoblast progenitor self-renewal and differentiation

Healthy progression of human pregnancy relies on cytotrophoblast (CTB) progenitor self-renewal and its differentiation toward multinucleated syncytiotrophoblasts (STBs) and invasive extravillous trophoblasts (EVTs). However, the underlying molecular mechanisms that fine-tune CTB self-renewal or direct its differentiation toward STBs or EVTs during human placentation are poorly defined. Here, we show that Hippo signaling cofactor WW domain containing transcription regulator 1 (WWTR1) is a master regulator of trophoblast fate choice during human placentation. Using human trophoblast stem cells (human TSCs), primary CTBs, and human placental explants, we demonstrate that WWTR1 promotes self-renewal in human CTBs and is essential for their differentiation to EVTs. In contrast, WWTR1 prevents induction of the STB fate in undifferentiated CTBs. Our single-cell RNA sequencing analyses in first-trimester human placenta, along with mechanistic analyses in human TSCs revealed that WWTR1 fine-tunes trophoblast fate by directly regulating WNT signaling components. Importantly, our analyses of placentae from pathological pregnancies show that extreme preterm births (gestational time ≤28 wk) are often associated with loss of WWTR1 expression in CTBs. In summary, our findings establish the critical importance of WWTR1 at the crossroads of human trophoblast progenitor self-renewal versus differentiation. It plays positive instructive roles in promoting CTB self-renewal and EVT differentiation and safeguards undifferentiated CTBs from attaining the STB fate.

Development and Validation of a 6-Gene Hypoxia-Related Prognostic Signature For Cholangiocarcinoma

Cholangiocarcinoma (CHOL) is highly malignant and has a poor prognosis. This study is committed to creating a new prognostic model based on hypoxia related genes. Here, we established a novel tumor hypoxia-related prognostic model consisting of 6 hypoxia-related genes by univariate Cox regression and the least absolute shrinkage and selection operator (LASSO) algorithm to predict CHOL prognosis and then the risk score for each patient was calculated. The results showed that the patients with high-risk scores had poor prognosis compared with those with low-risk scores, which was verified as an independent predictor by multivariate analysis. The hypoxia-related prognostic model was validated in both TCGA and GEO cohorts and exhibited excellent performance in predicting overall survival in CHOL. The PPI results suggested that hypoxia-related genes involved in the model may play a central role in regulating the hypoxic state. In addition, the presence of IDH1 mutations in the high-risk group was high, and GSEA results showed that some metabolic pathways were upregulated, but immune response processes were generally downregulated. These factors may be potential reasons for the high-risk group with worse prognosis. The analysis of different immune regulation-related processes in the high- and low-risk groups revealed that the expression of genes related to immune checkpoints would show differences between these two groups. We further verified the expression of the oncogene PPFIA4 in the model, and found that compared with normal samples, CHOL patients were generally highly expressed, and the patients with high-expression of PPFIA4 had a poor prognosis. In summary, the present study may provide a valid prognostic model for bile duct cancer to inform better clinical management of patients.

Early human trophoblast development: from morphology to function

Human pregnancy depends on the proper development of the embryo prior to implantation and the implantation of the embryo into the uterine wall. During the pre-implantation phase, formation of the morula is followed by internalization of blastomeres that differentiate into the pluripotent inner cell mass lineage, while the cells on the surface undergo polarization and differentiate into the trophectoderm of the blastocyst. The trophectoderm mediates apposition and adhesion of the blastocyst to the uterine epithelium. These processes lead to a stable contact between embryonic and maternal tissues, resulting in the formation of a new organ, the placenta. During implantation, the trophectoderm cells start to differentiate and form the basis for multiple specialized trophoblast subpopulations, all of which fulfilling specific key functions in placentation. They either differentiate into polar cells serving typical epithelial functions, or into apolar invasive cells that adapt the uterine wall to progressing pregnancy. The composition of these trophoblast subpopulations is crucial for human placenta development and alterations are suggested to result in placenta-associated pregnancy pathologies. This review article focuses on what is known about very early processes in human reproduction and emphasizes on morphological and functional aspects of early trophoblast differentiation and subpopulations.

Transcription factor networks in trophoblast development

The placenta sustains embryonic development and is critical for a successful pregnancy outcome. It provides the site of exchange between the mother and the embryo, has immunological functions and is a vital endocrine organ. To perform these diverse roles, the placenta comprises highly specialized trophoblast cell types, including syncytiotrophoblast and extravillous trophoblast. The coordinated actions of transcription factors (TFs) regulate their emergence during development, subsequent specialization, and identity. These TFs integrate diverse signaling cues, form TF networks, associate with chromatin remodeling and modifying factors, and collectively determine the cell type-specific characteristics. Here, we summarize the general properties of TFs, provide an overview of TFs involved in the development and function of the human trophoblast, and address similarities and differences to their murine orthologs. In addition, we discuss how the recent establishment of human in vitro models combined with -omics approaches propel our knowledge and transform the human trophoblast field.

Primary Trophoblast Cultures: Characterization of HLA Profiles and Immune Cell Interactions

Introduction

Trophoblasts are essential in fetal-maternal interaction during pregnancy. The goal was to study HLA profiles of primary trophoblasts derived from placentas, and to investigate their usefulness in studying interaction with immune cells.

Methods

After enzymatic digestion of first-trimester placental tissue from seven donors (6-9 weeks gestation) and trophoblast enrichment we cultured cytotrophoblasts (CTB) in stem cell medium. CTB were differentiated into EVT in a Matrigel-containing medium. A subset of CTB/EVT was profiled for microRNA levels. Expression of classical HLA molecules and of HLA-G was studied by flow cytometry, qPCR, and ELISA. Secondary trophoblast cell lines JAR and JEG-3 were studied as controls. Lymphocytes were investigated during co-culturing with EVT.

Results

The trophoblasts could be easily maintained for several passages, upregulated classical trophoblast markers (GATA3, TFAP2C, chromosome-19 microRNAs), and upon differentiation to EVT they were selective in expressing HLA-C. EVT showed increasing expression of total HLA-G, an increasing proportion of HLA-G1 over G2- and G3 isoforms, and elevated excretion of soluble HLA-G. These features were distinct from those of the secondary trophoblast cell lines. TNF-α and IL-8 represented the most abundantly secreted cytokines by CTB, but their levels were minimal in EVT cultures. As proof of principle, we showed that EVT affect lymphocytes in three-day co-cultures (n=4) by decreasing activation marker HLA-DR.

Conclusion

We verified the possibility culturing trophoblasts from first-term placentas, and their capability of differentiating to HLA-G expressing EVT. This culture model better represents the in-vivo situation than previously studied secondary trophoblast cell lines and enables mechanistic studies of fetal-maternal interactions.

PLAC8 Overexpression Promotes Lung Cancer Cell Growth via Wnt/β-Catenin Signaling

The PLAC8 expression in lung cancer tissues and in vitro grown lung cancer cells, as well as the involvement of the Wnt/β-Catenin signaling pathway, was investigated in this process. PLAC8 protein expression in human lung cancer tissues and lung tumor cells of different strains was discovered using immunohistochemistry staining and Western blot, respectively. Animal models of PLAC8 overexpression and knockdown were created using lentivirus. The development in tumor tissue was seen both in vitro and vivo. The Wnt/β-Catenin signaling pathway played an important part in this process, as shown by the dual luciferase reporter gene system. PLAC8 expression was elevated in lung cancer tissues and plasma and decreased in plasma after lung tumor resection. PLAC8 upregulation promotes cell proliferation in vivo and in vitro, while PLAC8 downregulation inhibits cell viability and proliferation. The results of the dual luciferase reporter gene system suggest that PLAC8 can significantly activate the Wnt/β-Catenin signaling pathway in cells and can conduct signaling through it. A potential treatment targeting the prognosis of lung cancer patients may be PLAC8 overexpression, which promotes the lung cancer cell proliferation through controlling the Wnt/β-Catenin signaling pathway.

Evaluation of the PLAC8 Gene in Mexican Women With and Without Preeclampsia and Obesity

Preeclampsia (PE) is a leading cause of maternal-fetal mortality worldwide, and obesity is an important risk factor. Genes associated with pathophysiological events common to preeclampsia and obesity, such as PLAC8, remain to be studied; therefore, the aim of the present study was to evaluate this gene in the placentas of women affected with preeclampsia and healthy pregnant women. This case-controlled study included 71 healthy and 64 preeclampsia pregnancies. Gene expression was evaluated in primary human cytotrophoblasts (PHCT) from six normal and six preeclampsia pregnancies, and protein expression was verified in placentas from five healthy and six preeclampsia pregnancies. The whole coding and 5′ regions of the PLAC8 gene were sequenced from healthy (n = 10) and preeclamptic (n = 10) pregnancies. The presence of the observed nucleotide variations was analyzed by RT-PCR in the total population. Statistical analyses were performed accordingly. Obesity was associated with severe preeclampsia (SPE) (OR = 3.34; CI 95% 1.3–8.2, p < 0.01). Significantly higher mRNA and protein expression was observed in preeclamptic vs. healthy placentas (p < 0.05). After sequencing, a single nucleotide variation was identified in 10 cases and one control (p < 0.01), which was then evaluated in the total population showing no association with preeclampsia. This preliminary study confirms the association of SPE with obesity and suggests higher expression of PLAC8 mRNA and protein in placentas from preeclampsia. No differences in nucleotide variations between cases and controls of the whole population were observed. Further research is required to evaluate the implications of higher gene/protein expression in preeclampsia and the causes of such variation.

Placenta-specific 8 (PLAC8) mediates inflammation and mobility of the hPDLCs via MEK/ERK signaling pathway

BACKGROUND

Placenta-specific 8 (PLAC8) is reported to regulate cellular functions in the progression of various diseases. However, its role in periodontitis is still unclear.

METHODS

Human periodontal ligament cells (hPDLCs) were treated with lipopolysaccharide of Porphyromonas Gingivalis (LPS-PG) to mimic periodontitis in vitro. Real-time quantitative polymerase chain reaction (RT-qPCR) was performed to measure the mRNA expression levels and western blot was for protein levels. Wound healing and transwell migration assays were performed to assess the cell mobility of hPDLCs. Both mRNA and protein levels of inflammatory cytokines including IFN-γ, IL-17, TNF-α, IL-4, IL-10 and IL-13 were accessed to evaluated process of periodontitis in vitro. Furthermore, the protein expressions of mitogen-activated protein kinase kinase (MEK), extracellular regulated protein kinase (ERK) and their phosphorylated products quantified by western blotting assay were determined to confirm the activation of the MEK/ERK signaling pathway.

RESULTS

The microarray analysis results showed that PLAC8 was most significantly downregulated in periodontium samples of patients with periodontitis, which participates in blood coagulation and integrin-mediated signaling pathway. PLAC8 was also markedly downregulated in the LPS-PG-treated hPDLCs. Moreover, overexpression of PLAC8 ameliorated inflammation and promoted cell mobility of LPS-PG-treated hPDLCs, while inhibition of PLAC8 exhibited the opposite effects. MEK/ERK was selected based on analyses of the protein-protein interaction (PPI) network as the potential signaling pathway interacted with PLAC8, and PLAC8 showed regulatory function on activation of the MEK/ERK pathway. Additionally, U0126, the inhibitor of MEK, abrogated the effects of PLAC8 on inflammation and cell mobility of LPS-PG-treated hPDLCs.

CONCLUSION

Overexpression of PLAC8 protected hPDLCs from dysfunction of inflammation and cell mobility via activating MEK/ERK pathway, indicating a novel therapeutic target for periodontitis.

Abnormal Circulating Maternal miRNA Expression Is Associated with a Low (<4%) Cell-Free DNA Fetal Fraction

The present pilot study investigates whether an abnormal miRNA profile in NIPT plasma samples can explain the finding of a low cell-free DNA (cfDNA) fetal fraction (cfDNAff) in euploid fetuses and non-obese women. Twelve women who underwent neoBona^® NIPT with a normal fetal karyotype were studied. Six with a cfDNAff < 4% were matched with a control group with normal levels of cfDNAff > 4%. Samples were processed using the nanostring nCounter^® platform with a panel of 800 miRNAs. Four of the maternal miRNAs, miR-579, miR-612, miR-3144 and miR-6721, had a significant abnormal expression in patients. A data filtering analysis showed that miR-579, miR-612, miR-3144 and miR-6721 targeted 169, 1, 48 and 136 placenta-specific genes, respectively. miR-579, miR-3144 and miR-6721 shared placenta-specific targeted genes involved in trophoblast invasion and migration pathways (IGF2R, PTCD2, SATB2, PLAC8). Moreover, the miRNA target genes encoded proteins localized in the placenta and involved in the pathogenesis of pre-eclampsia, including chorion-specific transcription factor GCMa, PRG2, Lin-28 Homolog B and IGFBP1. In conclusion, aberrant maternal miRNA expression in circulating plasma could be a source of dysregulating trophoblast invasion and migration and could represent a novel cause of a low cfDNAff in the sera of pregnant women at the time of NIPT analysis.

Characterization of primary models of human trophoblast

Two recently developed models, trophoblast organoids and trophoblast stem cells (TSCs), are useful tools to further the understanding of human placental development. Both differentiate from villous cytotrophoblast (VCT) to either extravillous trophoblast (EVT) or syncytiotrophoblast (SCT). Here, we compare the transcriptomes and miRNA profiles of these models to identify which trophoblast they resemble in vivo. Our findings indicate that TSCs do not readily undergo SCT differentiation and closely resemble cells at the base of the cell columns from where EVT derives. In contrast, organoids are similar to VCT and undergo spontaneous SCT differentiation. A defining feature of human trophoblast is that VCT and SCT are human leukocyte antigen (HLA) null, whereas EVT expresses HLA-C, -G and -E molecules. We find that trophoblast organoids retain these in vivo characteristics. In contrast, TSCs express classical HLA-A and HLA-B molecules, and maintain their expression after EVT differentiation, with upregulation of HLA-G. Furthermore, HLA expression in TSCs differs when grown in 3D rather than in 2D, suggesting that mechanical cues are important. Our results can be used to select the most suitable model for the study of trophoblast development, function and pathology.

Summary: Characterization of trophoblast organoids and trophoblast stem cells as exciting models of human placentation enables the selection of the most suitable system to address specific research questions.

Cellular Complexity of Hemochorial Placenta: Stem Cell Populations, Insights from scRNA-seq, and SARS-CoV-2 Susceptibility

Purpose of Review

The placenta is a transient organ that forms de novo and serves a critical role in supporting fetal growth and development. Placental oxygen, nutrients, and waste are transported through processes that depend on vascular structure and cell type-specific expression and localization of membrane transporters. Understanding how the placenta develops holds great significance for maternal-fetal medicine. The purpose of this review is to examine current information regarding placental progenitor populations.

Recent Findings

Recent advancements in single-cell RNA sequencing (scRNA-seq) provide unprecedented depth for the investigation of cell type-specific gene expression patterns in the placenta. Thus far, several mouse placenta scRNA-seq studies have been conducted which produced and analyzed transcriptomes of placental progenitors and cells of the fully developed placenta between embryonic day (E) 7.0 and E12.5. Together with human placenta scRNA-seq data which, in part, has been produced through coordinated research campaigns in the scientific community to understand the potential for SARS-CoV-2 infection, these mammalian studies lend fundamental insight into the cellular and molecular composition of hemochorial placentae found in both mouse and human.

Summary

Single-cell placenta research has advanced understanding of tissue-resident stem cells and molecules that are poised to support maternal-fetal communication and nutrient transport. Herein, we provide context for these recent findings by reviewing placental anatomy and cell populations, and discuss recent scRNA-seq mouse placenta findings. Further research is needed to evaluate the utility of placental stem cells in the development of new therapeutic approaches for the treatment of wound healing and disease.

PLAC8 promotes EV71 infected inflammatory lesion by disturbing Th-cell-related cytokines release in neonatal mouse

Enterovirus 71 can cause severe hand, foot, and mouth disease (HFMD) in children. However, little is known about the mechanism of inflammatory disorders caused by EV71 infection and why severe cases are mainly children aged under-three. In current study, using mRNA microarray assay, the differential expression of Placenta-specific 8 (PLAC8) was identified in mice brain. In addition, we found that PLAC8 expression was down-regulated with age in mice lung tissues and human peripheral blood. Then, we further proved that PLAC8 could promote inflammation progress and disturb Th1/Th2/Th17/Treg related cytokines release after EV71 infection using PLAC8 plasmid over-expressed neonatal mouse model. Our data suggest that PLAC8 might play a crucial role in Th cell differentiation and inflammatory damage caused by EV71 infection in infants. Thus, our findings would help understand the causes of severe inflammatory injury in infants during EV71 infection, and provide new insights into the prevention and control of severe HFMD.

Multifaced roles of PLAC8 in cancer

The role of PLAC8 in tumorigenesis has been gradually elucidated with the development of research. Although there are common molecular mechanisms that enforce cell growth, the impact of PLAC8 is varied and can, in some instances, have opposite effects on tumorigenesis. To systematically understand the role of PLAC8 in tumors, the molecular functions of PLAC8 in cancer will be discussed by focusing on how PLAC8 impacts tumorigenesis when it arises within tumor cells and how these roles can change in different stages of cancer progression with the ultimate goal of suppressing PLAC8-relevant cancer behavior and related pathologies. In addition, we highlight the diversity of PLAC8 in different tumors and its functional output beyond cancer cell growth. The comprehension of PLAC8's molecular function might provide new target and lead to the development of novel anticancer therapies.

Oxidative stress-induced impairment of trophoblast function causes preeclampsia through the unfolded protein response pathway

Pre-eclampsia (PE) is a pregnancy-specific disorder, characterized by hypertension and proteinuria. In PE, trophoblasts mediated inadequate remodeling of uterine spiral arteries seem to interrupt uteroplacental blood flow, one of the hallmarks in the early onset of PE (EO-PE). This, in turn, results in placental ischemia–reperfusion injury during hypoxia and reoxygenation episodes, leading to the generation of reactive oxygen species (ROS) and oxidative stress (OS). But still it is debatable if OS is a cause or consequence of PE. In this present study, we have investigated the effects of OS on PE placentae and trophoblast cell functions using BeWo and HTR8/SVneo cell lines. PE placental tissues showed abnormal ultrastructure, high level of reactive oxygen species (ROS) with altered unfolded protein responses (UPR) in compare with term placental tissues. Similar to PE placentae, during OS induction, the trophoblast cells showed altered invasion and migration properties with significantly variable expression of differentiation and invasion markers, e.g., syncytin and MMPs. The effect was rescued by antioxidant, N-acetyl cysteine, thereby implying a ROS-specific effect and in the trophoblast cells, OS triggers UPR pathway through IRE1α-XBP1 axis. Taken together, these findings highlight the harmful effect of unfolded protein response, which was induced due to OS on trophoblast cells and deformed invasion and differentiation programme and can be extended further to clinical settings to identify clinically approved antioxidants during pregnancy as a therapeutic measure to reduce the onset of PE.

PLAC8 promotes the autophagic activity and improves the growth priority of human trophoblast cells

Autophagy plays an important role in the normal development and function of trophoblast cells and is precisely regulated during pregnancy. Dysregulated autophagy contributes to the abnormal proliferation of trophoblasts, which is closely related to the occurrence of pregnancy-related diseases. Placenta specific 8 (PLAC8, Onzin) is a multifaceted protein proven to promote autophagy and potentiate various tumor progression. Its role in trophoblasts remains elusive. In our present study, PLAC8 expression was detected in tissues of first-trimester placentas (n = 5), term placentas (n = 5), choriocarcinoma (n = 5), and placental site trophoblastic tumor (n = 5). PLAC8 expression was increased in gestational neoplasms compared with normal pregnancies. mCherry-EGFP-LC3B reporter and transmission electron microscopy confirmed PLAC8 promoted the autophagic flux of human trophoblast cells. Both gain-of-function and loss-of-function experiments demonstrated PLAC8-regulated autophagy-related genes, including ATG5, ATG12, and Beclin-1. In addition, our data showed that PLAC8 co-localized with p53 and promoted its degradation, and p53 re-expression partially abrogated the PLAC8-induced autophagy activity. Furthermore, the overexpression of PLAC8 promoted cell viability and proliferation, acting as a protective mechanism of trophoblasts against the cytotoxicity of etoposide (VP-16). Such a phenomenon was effectively abrogated by autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ). In conclusion, PLAC8-induced autophagy to promote the proliferation of trophoblasts. This study provided insights into the mechanism of PLAC8-induced autophagy in trophoblasts, which is significant for a wide range of gestational diseases and may contribute to developing novel treatment strategies for trophoblastic diseases.

Central role of the placenta during viral infection: Immuno-competences and miRNA defensive responses

Pregnancy is a unique immunological condition in which an "immune-diplomatic" dialogue between trophoblasts and maternal immune cells is established to protect the fetus from rejection, to create a privileged environment in the uterus and to simultaneously be alert to any infectious challenge. The maternal-placental-fetal interface (MPFI) performs an essential role in this immunological defense. In this review, we will address the MPFI as an active immuno-mechanical barrier that protects against viral infections. We will describe the main viral infections affecting the placenta and trophoblasts and present their structure, mechanisms of immunocompetence and defensive responses to viral infections in pregnancy. In particular, we will analyze infection routes in the placenta and trophoblasts and the maternal-fetal outcomes in both. Finally, we will focus on the cellular targets of the antiviral microRNAs from the C19MC cluster, and their effects at both the intra- and extracellular level.

Molecular Signatures of Placentation and Secretion Uncovered in Poeciliopsis Maternal Follicles

Placentation evolved many times independently in vertebrates. Although the core functions of all placentas are similar, we know less about how this similarity extends to the molecular level. Here, we study Poeciliopsis, a unique genus of live-bearing fish that have independently evolved complex placental structures at least three times. The maternal follicle is a key component of these structures. It envelops yolk-rich eggs and is morphologically simple in lecithotrophic species but has elaborate villous structures in matrotrophic species. Through sequencing, the follicle transcriptome of a matrotrophic, Poeciliopsis retropinna, and lecithotrophic, P. turrubarensis, species we found genes known to be critical for placenta function expressed in both species despite their difference in complexity. Additionally, when we compare the transcriptome of different river populations of P. retropinna, known to vary in maternal provisioning, we find differential expression of secretory genes expressed specifically in the top layer of villi cells in the maternal follicle. This provides some of the first evidence that the placental structures of Poeciliopsis function using a secretory mechanism rather than direct contact with maternal circulation. Finally, when we look at the expression of placenta proteins at the maternal–fetal interface of a larger sampling of Poeciliopsis species, we find expression of key maternal and fetal placenta proteins in their cognate tissue types of all species, but follicle expression of prolactin is restricted to only matrotrophic species. Taken together, we suggest that all Poeciliopsis follicles are poised for placenta function but require expression of key genes to form secretory villi.

Autophagy Process in Trophoblast Cells Invasion and Differentiation: Similitude and Differences With Cancer Cells

Early human placental development begins with blastocyst implantation, then the trophoblast differentiates and originates the cells required for a proper fetal nutrition and placental implantation. Among them, extravillous trophoblast corresponds to a non-proliferating trophoblast highly invasive that allows the vascular remodeling which is essential for appropriate placental perfusion and to maintain the adequate fetal growth. This process involves different placental cell types as well as molecules that allow cell growth, cellular adhesion, tissular remodeling, and immune tolerance. Remarkably, some of the cellular processes required for proper placentation are common between placental and cancer cells to finally support tumor growth. Indeed, as in placentation trophoblasts invade and migrate, cancer cells invade and migrate to promote tumor metastasis. However, while these processes respond to a controlled program in trophoblasts, in cancer cells this regulation is lost. Interestingly, it has been shown that autophagy, a process responsible for the degradation of damaged proteins and organelles to maintain cellular homeostasis, is required for invasion of trophoblast cells and for vascular remodeling during placentation. In cancer cells, autophagy has a dual role, as it has been shown both as tumor promoter and inhibitor, depending on the stage and tumor considered. In this review, we summarized the similarities and differences between trophoblast cell invasion and cancer cell metastasis specifically evaluating the role of autophagy in both processes.

Regulation of tamoxifen sensitivity by the PLAC8/MAPK pathway axis is antagonized by curcumin-induced protein stability change

Tamoxifen resistance remains the major obstacle to the estrogen receptor positive breast cancer endocrine therapy. Placenta-specific 8 (PLAC8) has been implicated in epithelial-mesenchymal transition and tumorigenesis. However, the molecular mechanisms underlying PLAC8 function in the context of tamoxifen resistance are unclear. Curcumin has attracted considerable attention in the last decades. It is isolated from Curcuma longa and has beneficial effects in cancer therapy. We studied this property by using MCF-7 and tamoxifen-resistant breast cancer cells (MCF-7/TAM) cell lines. PLAC8 can regulate MCF-7/TAM cell drug sensitivity through the MAPK/ERK pathway and shows the potential effects of curcumin or as a possible druggable target against tamoxifen failure.

Integrating LCM-Based Spatio-Temporal Transcriptomics Uncovers Conceptus and Endometrial Luminal Epithelium Communication that Coordinates the Conceptus Attachment in Pigs

Attachment of conceptus to the endometrial luminal epithelium (LE) is a critical event for early placentation in Eutheria. Since the attachment occurs at a particular site within the uterus, a coordinated communication between three spatially distinct compartments (conceptus and endometrial LE from two anatomical regions of the uterus to which conceptus attaches and does not attach) is essential but remains to be fully characterized. Using the laser capture microdissection (LCM) technique, we firstly developed an approach that can allow us to pair the pig conceptus sample with its nearby endometrial epithelium sample without losing the native spatial information. Then, a comprehensive spatio-temporal transcriptomic profile without losing the original conceptus-endometrium coordinates was constructed. The analysis shows that an apparent difference in transcriptional responses to the conceptus exists between the endometrial LE from the two anatomically distinct regions in the uterus. In addition, we identified the communication pathways that link the conceptus and endometrial LE and found that these pathways have important roles in conceptus attachment. Furthermore, a number of genes whose expression is spatially restricted in the two different anatomical regions within the uterus were characterized for the first time and two of them (SULT2A1 and MEP1B) may cooperatively contribute to establish conceptus attachment in pigs. The results from our study have implications in understanding of conceptus/embryo attachment in pigs and other large polytocous species.

Placentation in the Human and Higher Primates

Placentation in humans is precocious and highly invasive compared to other mammals. Implantation is interstitial, with the conceptus becoming completely embedded within the endometrium towards the end of the second week post-fertilization. Villi initially form over the entire surface of the chorionic sac, stimulated by histotrophic secretions from the endometrial glands. The secondary yolk sac never makes contact with the chorion, and a choriovitelline placenta is never established. However, recent morphological and transcriptomic analyses suggest that the yolk sac plays an important role in the uptake of nutrients from the coelomic fluid. Measurements performed in vivo demonstrate that early development takes place in a physiological, low-oxygen environment that protects against teratogenic free radicals and maintains stem cells in a multipotent state. The maternal arterial circulation to the placenta is only fully established around 10-12 weeks of gestation. By then, villi have regressed over the superficial, abembryonic pole, leaving the definitive discoid placenta, which is of the villous, hemochorial type. Remodeling of the maternal spiral arteries is essential to ensure a high-volume but low-velocity inflow into the mature placenta. Extravillous trophoblast cells migrate from anchoring villi and surround the arteries. Their interactions with maternal immune cells release cytokines and proteases that are key to remodeling, and a successful pregnancy.

Nuclear receptor coactivator 6 promotes HTR-8/SVneo cell invasion and migration by activating NF-κB-mediated MMP9 transcription

Objectives

NCOA6 is a transcription coactivator; its deletion in mice results in growth retardation and lethality between 8.5 and 12.5 dpc with defects in the placenta. However, the transcription factor(s) and the mechanism(s) involved in the function of NCOA6 in placentation have not been elucidated. Here, the roles of NCOA6 in human cytotrophoblast invasion and migration were studied.

Materials and Methods

Human placenta tissues were collected from normal pregnancies and pregnancies complicated by early‐onset severe preeclampsia (sPE). Immunofluorescence, RT‐qPCR and Western blotting were used to determine NCOA6 expression. Transwell invasion/migration assays were performed to explore whether NCOA6 knockdown affected human placenta‐derived HTR‐8/SVneo cell invasion/migration. Gelatin zymography was performed to examine the change in the gelatinolytic activities of secreted MMP2 and MMP9. Luciferase reporter assays were used to explore whether NCOA6 coactivated NF‐κB‐mediated MMP9 transcription.

Results

NCOA6 is mainly expressed in the human placental trophoblast column, as well as in the EVTs. HTR‐8/SVneo cell invasion and migration were significantly attenuated after NCOA6 knockdown, and the secretion of MMP9 was decreased due to transcriptional suppression. NCOA6 was further found to coactivate NF‐κB‐mediated MMP9 transcription. Moreover, expression of NCOA6 was impaired in placentas of patients complicated by early‐onset sPE.

Conclusions

Thus, we demonstrated that NCOA6 is important for cytotrophoblast invasion/migration, at least partially, by activating NF‐κB‐mediated MMP9 transcription; the downregulation of NCOA6 may contribute to the pathogenesis of early‐onset sPE.

TEAD4 ensures postimplantation development by promoting trophoblast self-renewal: An implication in early human pregnancy loss

Early pregnancy loss affects ∼15% of all implantation-confirmed human conceptions. However, evolutionarily conserved molecular mechanisms that regulate self-renewal of trophoblast progenitors and their association with early pregnancy loss are poorly understood. Here, we provide evidence that transcription factor TEAD4 ensures survival of postimplantation mouse and human embryos by controlling self-renewal and stemness of trophoblast progenitors within the placenta primordium. In an early postimplantation mouse embryo, TEAD4 is selectively expressed in trophoblast stem cell-like progenitor cells (TSPCs), and loss of Tead4 in postimplantation mouse TSPCs impairs their self-renewal, leading to embryonic lethality before embryonic day 9.0, a developmental stage equivalent to the first trimester of human gestation. Both TEAD4 and its cofactor, yes-associated protein 1 (YAP1), are specifically expressed in cytotrophoblast (CTB) progenitors of a first-trimester human placenta. We also show that a subset of unexplained recurrent pregnancy losses (idiopathic RPLs) is associated with impaired TEAD4 expression in CTB progenitors. Furthermore, by establishing idiopathic RPL patient-specific human trophoblast stem cells (RPL-TSCs), we show that loss of TEAD4 is associated with defective self-renewal in RPL-TSCs and rescue of TEAD4 expression restores their self-renewal ability. Unbiased genomics studies revealed that TEAD4 directly regulates expression of key cell cycle genes in both mouse and human TSCs and establishes a conserved transcriptional program. Our findings show that TEAD4, an effector of the Hippo signaling pathway, is essential for the establishment of pregnancy in a postimplantation mammalian embryo and indicate that impairment of the Hippo signaling pathway could be a molecular cause for early human pregnancy loss.

TBC1D20 deficiency induces Sertoli cell apoptosis by triggering irreversible endoplasmic reticulum stress in mice

Male 'blind sterile' mice with the causative TBC1 domain family member 20 (TBC1D20) deficiency are infertile with excessive germ cell apoptosis and spermatogenesis arrest at the spermatid stage. Sertoli cells are characterised as 'nurse cells' essential for normal spermatogenesis, but the role and corresponding molecular mechanisms of TBC1D20 deficiency in Sertoli cells of mice are not clear to date. In the present study, the histopathology of the testis and Sertoli cell proliferation and apoptosis were determined, and the corresponding molecular mechanisms were investigated by western blotting. Our data showed that TBC1D20 exhibits a testis-abundant expression pattern, and its expression level is positively associated with spermatogenesis. TBC1D20 is assembled in the Golgi and endoplasmic reticulum and is widely expressed by various germ cell subtypes and Sertoli cells. TBC1D20 deficiency in Sertoli cells led to an excessive apoptosis ratio and G1/S arrest. The increased apoptosis of TBC1D20-deficient Sertoli cells resulted from caspase-12 activation. TBC1D20-deficient Sertoli cells had an abnormal Golgi-endoplasmic reticulum structure, which led to endoplasmic reticulum stress, resulting in cell cycle arrest and excessive apoptosis. It suggested that TBC1D20 deficiency triggers irreversible endoplasmic reticulum stress resulting in G1/S arrest and excessive apoptosis in TBC1D20-deficient Sertoli cells, and TBC1D20 deficiency in Sertoli cells may also contribute to the infertility phenotype in 'blind sterile' male mice.

Transcriptomic and ChIP-seq Integrative Analysis Reveals Important Roles of Epigenetically Regulated lncRNAs in Placental Development in Meishan Pigs

The development of the placental fold, which increases the maternal–fetal interacting surface area, is of primary importance for the growth of the fetus throughout the whole pregnancy. However, the mechanisms involved remain to be fully elucidated. Increasing evidence has revealed that long non-coding RNAs (lncRNAs) are a new class of RNAs with regulatory functions and could be epigenetically regulated by histone modifications. In this study, 141 lncRNAs (including 73 up-regulated and 68 down-regulated lncRNAs) were identified to be differentially expressed in the placentas of pigs during the establishment and expanding stages of placental fold development. The differentially expressed lncRNAs and genes (DElncRNA-DEgene) co-expression network analysis revealed that these differentially expressed lncRNAs (DElncRNAs) were mainly enriched in pathways of cell adhesion, cytoskeleton organization, epithelial cell differentiation and angiogenesis, indicating that the DElncRNAs are related to the major events that occur during placental fold development. In addition, we integrated the RNA-seq (RNA sequencing) data with the ChIP-seq (chromatin immunoprecipitation sequencing) data of H3K4me3/H3K27ac produced from the placental samples of pigs from the two stages (gestational days 50 and 95). The analysis revealed that the changes in H3K4me3 and/or H3K27ac levels were significantly associated with the changes in the expression levels of 37 DElncRNAs. Furthermore, several H3K4me3/H3K27ac-lncRNAs were characterized to be significantly correlated with genes functionally related to placental development. Thus, this study provides new insights into understanding the mechanisms for the placental development of pigs.

Trophoblast lineage-specific differentiation and associated alterations in preeclampsia and fetal growth restriction

The human placenta is a poorly-understood organ, but one that is critical for proper development and growth of the fetus in-utero. The epithelial cell type that contributes to primary placental functions is called "trophoblast," including two main subtypes, villous and extravillous trophoblast. Cytotrophoblast and syncytiotrophoblast comprise the villous compartment and contribute to gas and nutrient exchange, while extravillous trophoblast invade and remodel the uterine wall and vessels, in order to supply maternal blood to the growing fetus. Abnormal differentiation of trophoblast contributes to placental dysfunction and is associated with complications of pregnancy, including preeclampsia (PE) and fetal growth restriction (FGR). This review describes what is known about the cellular organization of the placenta during both normal development and in the setting of PE/FGR. It also explains known trophoblast lineage-specific markers and pathways regulating their differentiation, and how these are altered in the setting of PE/FGR, focusing on studies which have used human placental tissues. Finally, it also highlights remaining questions and needed resources to advance this field.

Intermittent Hypoxia Impairs Trophoblast Cell Viability by Triggering the Endoplasmic Reticulum Stress Pathway

Intermittent hypoxia (IH) is a prominent characteristic of many clinical complications such as obstructive sleep apnea syndrome (OSAS). OSAS is related to a higher incidence of adverse pregnancy outcomes, and IH has been suggested as the preliminary physiological etiology. However, further studies remain to be performed on the underlying cellular and molecular pathogenic mechanisms of OSAS-related IH on adverse pregnancy outcomes. Here, we used a trophoblast cell line (HTR8/SVneo), primary extravillous trophoblast cells (EVTs), and a normal-term placenta villi explant culture model in vitro in this research. The effects and possible molecular mechanisms of IH on trophoblast motility, cell cycle progression, and apoptosis were investigated. IH reduced HTR8/SVneo cell and EVT motility significantly, which could be partially attributed to the reduced secretion of matrix metalloproteinase 2. IH treatment blocked HTR8/SVneo cell proliferation significantly by modulating the expression of D-type Cyclins. IH also induced significant trophoblast cell apoptosis. Moreover, our study supports the premise that IH attenuates trophoblast cell motility and proliferation and induces excessive trophoblast cell apoptosis by specifically triggering the endoplasmic reticulum (ER) stress signaling pathway. Briefly, differing from the mechanism of trophoblast motility and proliferation inhibition, and apoptosis induction by hypoxia, IH is apt to weaken trophoblast viability mainly by activating the ER stress signaling pathway with a time-dependent pattern, which is further implicated in OSAS-associated adverse pregnancy outcomes.

Involvement of the Endocrine-Disrupting Chemical Bisphenol A (BPA) in Human Placentation

Background: Endocrine-disrupting chemicals (EDCs) are environmental chemicals/toxicants that humans are exposed to, interfering with the action of multiple hormones. Bisphenol A (BPA) is classified as an EDC with xenoestrogenic activity with potentially adverse effects in reproduction. Currently, a significant knowledge gap remains regarding the complete spectrum of BPA-induced effects on the human placenta. As such, the present study examined the effects of physiologically relevant doses of BPA in vitro. Methods: qRT-PCR, Western blotting, immunofluorescence, ELISA, microarray analyses, and bioinformatics have been employed to study the effects of BPA using nonsyncytialised (non-ST) and syncytialised (ST) BeWo cells. Results: Treatment with 3 nM BPA led to an increase in cell number and altered the phosphorylation status of p38, an effect mediated primarily via the membrane-bound estrogen receptor (GPR30). Nonbiased microarray analysis identified 1195 and 477 genes that were differentially regulated in non-ST BeWo cells, whereas in ST BeWo cells, 309 and 158 genes had altered expression when treated with 3 and 10 nM, respectively. Enriched pathway analyses in non-ST BeWo identified a leptin and insulin overlap (3 nM), methylation pathways (10 nM), and differentiation of white and brown adipocytes (common). In the ST model, most significantly enriched were the nuclear factor erythroid 2-related factor 2 (NRF2) pathway (3 nM) and mir-124 predicted interactions with cell cycle and differentiation (10 nM). Conclusion: Collectively, our data offer a new insight regarding BPA effects at the placental level, and provide a potential link with metabolic changes that can have an impact on the developing fetus.

TBC1D20 Is Essential for Mouse Blood-Testis Barrier Integrity Through Maintaining the Epithelial Phenotype and Modulating the Maturation of Sertoli Cells

Sertoli cells are important for spermatogenesis not only by directly interacting with germ line cells in the seminiferous epithelium but also by constituting the blood-testis barrier (BTB) structure to create a favorable environment for spermatogenesis. Blind sterile (bs) male mice are infertile, with excessive germ cell apoptosis and spermatogenesis arrest. TBC1D20 (TBC1 domain family member 20) deficiency has been identified as the causative mutation in bs mice. However, whether TBC1D20 loss of function also impairs BTB integrity, which further contributes to the failed spermatogenesis of bs male mice, remains unclear. In the present study, biotin tracer assay and transmission electron microscopy showed severely disrupted BTB integrity in bs testes. Compared to the wild-type Sertoli cells, BTB components of cultured bs Sertoli cells in vitro was perturbed with downregulation of E-cadherin, ZO-1, β-catenin, and Claudin 11. The obvious rearrangement of F-actin indicated disrupted epithelial-mesenchymal balance in TBC1D20-deficient Sertoli cells. The ability of bs Sertoli cells to maintain the clone formation of spermatogonia stem cells was also obviously limited. Furthermore, the decreasing of SOX9 (sex-determining region Y box 9) and WT1 (Wilms' tumor 1) and increasing of vimentin in bs Sertoli cells indicated that TBC1D20 loss of function attenuated the differentiation progression of bs Sertoli cells. In summary, TBC1D20 loss of function impedes the maturation of adult Sertoli cells and resulted in impaired BTB integrity, which is further implicated in the infertile phenotype of bs male mice.

Expression pattern of placenta specific 8 and keratin 20 in different types of gastrointestinal cancer

The aim of the present study was to investigate the expression of keratin 20 (KRT20) and placenta specific 8 (PLAC8) in gastrointestinal (GI) cancer with various differentiation phenotypes. The present study retrospectively investigated archived formalin-fixed paraffin-embedded tissue samples from 12 patients at different stages of GI cancer [four with gastric cancer, four with pancreatic cancer and four with colorectal cancer (CRC)]. The stages were pre-determined, according to differentiation phenotypes, by a pathologist of the Department of Pathology at Sijhih Cathay General Hospital. KRT20 and PLAC8 expression levels were assessed using immunohistochemistry. The CRC cell lines SW620 and Caco-2 were used to assess interactions between KRT20 and PLAC8 via reverse transcription-quantitative PCR. PLAC8 and KRT20 expression was observed consistently only in the well-differentiated CRC tissue samples. Low KRT20 expression levels were observed in the PLAC8 knockdown SW620 cells. In addition, there was a positive association between PLAC8 and KRT20 expression in the differentiated Caco-2 cells. According to the results of the present study, the differentiation status of GI cancer influenced KRT20 expression, particularly in CRC, which may explain why patients with well-differentiated CRC display better clinical outcomes. Therefore, the prognostic significance of KRT20 and PLAC8 may be particularly crucial for patients with CRC displaying a well-differentiated phenotype.

Development of the human placenta

The placenta is essential for normal in utero development in mammals. In humans, defective placental formation underpins common pregnancy disorders such as pre-eclampsia and fetal growth restriction. The great variation in placental types across mammals means that animal models have been of limited use in understanding human placental development. However, new tools for studying human placental development, including 3D organoids, stem cell culture systems and single cell RNA sequencing, have brought new insights into this field. Here, we review the morphological, molecular and functional aspects of human placental formation, with a focus on the defining cell of the placenta - the trophoblast.