Expression pattern and phosphorylation status of Smad2/3 in different subtypes of human first trimester trophoblast

TGFβ signalling: a nexus between inflammation, placental health and preeclampsia throughout pregnancy

BACKGROUND

The placenta is a unique and pivotal organ in reproduction, controlling crucial growth and cell differentiation processes that ensure a successful pregnancy. Placental development is a tightly regulated and dynamic process, in which the transforming growth factor beta (TGFβ) superfamily plays a central role. This family of pleiotropic growth factors is heavily involved in regulating various aspects of reproductive biology, particularly in trophoblast differentiation during the first trimester of pregnancy. TGFβ signalling precisely regulates trophoblast invasion and the cell transition from cytotrophoblasts to extravillous trophoblasts, which is an epithelial-to-mesenchymal transition-like process. Later in pregnancy, TGFβ signalling ensures proper vascularization and angiogenesis in placental endothelial cells. Beyond its role in trophoblasts and endothelial cells, TGFβ signalling contributes to the polarization and function of placental and decidual macrophages by promoting maternal tolerance of the semi-allogeneic foetus. Disturbances in early placental development have been associated with several pregnancy complications, including preeclampsia (PE) which is one of the severe complications. Emerging evidence suggests that TGFβ is involved in the pathogenesis of PE, thereby offering a potential target for intervention in the human placenta.

OBJECTIVE AND RATIONALE

This comprehensive review aims to explore and elucidate the roles of the major members of the TGFβ superfamily, including TGFβs, bone morphogenetic proteins (BMPs), activins, inhibins, nodals, and growth differentiation factors (GDFs), in the context of placental development and function. The review focusses on their interactions within the major cell types of the placenta, namely trophoblasts, endothelial cells, and immune cells, in both normal pregnancies and pregnancies complicated by PE throughout pregnancy.

SEARCH METHODS

A literature search was carried out using PubMed and Google Scholar, searching terms: 'TGF signalling preeclampsia', 'pregnancy TGF signalling', 'preeclampsia tgfβ', 'preeclampsia bmp', 'preeclampsia gdf', 'preeclampsia activin', 'endoglin preeclampsia', 'endoglin pregnancy', 'tgfβ signalling pregnancy', 'bmp signalling pregnancy', 'gdf signalling pregnancy', 'activin signalling pregnancy', 'Hofbauer cell tgfβ signalling', 'placental macrophages tgfβ', 'endothelial cells tgfβ', 'endothelium tgfβ signalling', 'trophoblast invasion tgfβ signalling', 'trophoblast invasion Smad', 'trophoblast invasion bmp', 'trophoblast invasion tgfβ', 'tgfβ preeclampsia', 'tgfβ placental development', 'TGFβ placental function', 'endothelial dysfunction preeclampsia tgfβ signalling', 'vascular remodelling placenta TGFβ', 'inflammation pregnancy tgfβ', 'immune response pregnancy tgfβ', 'immune tolerance pregnancy tgfβ', 'TGFβ pregnancy NK cells', 'bmp pregnancy NK cells', 'bmp pregnancy tregs', 'tgfβ pregnancy tregs', 'TGFβ placenta NK cells', 'TGFβ placenta tregs', 'NK cells preeclampsia', 'Tregs preeclampsia'. Only articles published in English until 2023 were used.

OUTCOMES

A comprehensive understanding of TGFβ signalling and its role in regulating interconnected cell functions of the main placental cell types provides valuable insights into the processes essential for successful placental development and growth of the foetus during pregnancy. By orchestrating trophoblast invasion, vascularization, immune tolerance, and tissue remodelling, TGFβ ligands contribute to the proper functioning of a healthy maternal-foetal interface. However, dysregulation of TGFβ signalling has been implicated in the pathogenesis of PE, where the shallow trophoblast invasion, defective vascular remodelling, decreased uteroplacental perfusion, and endothelial cell and immune dysfunction observed in PE, are all affected by an altered TGFβ signalling.

WIDER IMPLICATIONS

The dysregulation of TGFβ signalling in PE has important implications for research and clinical practice. Further investigation is required to understand the underlying mechanisms, including the role of different ligands and their regulation under pathophysiological conditions, in order to discover new therapeutic targets. Distinguishing between clinically manifested subtypes of PE and studying TGFβ signalling in different placental cell types holistically is an important first step. To put this knowledge into practice, pre-clinical animal models combined with new technologies are needed. This may also lead to improved human research models and identify potential therapeutic targets, ultimately improving outcomes for affected pregnancies and reducing the burden of PE.

Roles of bone morphogenetic proteins in endometrial remodeling during the human menstrual cycle and pregnancy

BACKGROUND

During the human menstrual cycle and pregnancy, the endometrium undergoes a series of dynamic remodeling processes to adapt to physiological changes. Insufficient endometrial remodeling, characterized by inadequate endometrial proliferation, decidualization and spiral artery remodeling, is associated with infertility, endometriosis, dysfunctional uterine bleeding, and pregnancy-related complications such as preeclampsia and miscarriage. Bone morphogenetic proteins (BMPs), a subset of the transforming growth factor-β (TGF-β) superfamily, are multifunctional cytokines that regulate diverse cellular activities, such as differentiation, proliferation, apoptosis, and extracellular matrix synthesis, are now understood as integral to multiple reproductive processes in women. Investigations using human biological samples have shown that BMPs are essential for regulating human endometrial remodeling processes, including endometrial proliferation and decidualization.

OBJECTIVE AND RATIONALE

This review summarizes our current knowledge on the known pathophysiological roles of BMPs and their underlying molecular mechanisms in regulating human endometrial proliferation and decidualization, with the goal of promoting the development of innovative strategies for diagnosing, treating and preventing infertility and adverse pregnancy complications associated with dysregulated human endometrial remodeling.

SEARCH METHODS

A literature search for original articles published up to June 2023 was conducted in the PubMed, MEDLINE, and Google Scholar databases, identifying studies on the roles of BMPs in endometrial remodeling during the human menstrual cycle and pregnancy. Articles identified were restricted to English language full-text papers.

OUTCOMES

BMP ligands and receptors and their transduction molecules are expressed in the endometrium and at the maternal-fetal interface. Along with emerging technologies such as tissue microarrays, 3D organoid cultures and advanced single-cell transcriptomics, and given the clinical availability of recombinant human proteins and ongoing pharmaceutical development, it is now clear that BMPs exert multiple roles in regulating human endometrial remodeling and that these biomolecules (and their receptors) can be targeted for diagnostic and therapeutic purposes. Moreover, dysregulation of these ligands, their receptors, or signaling determinants can impact endometrial remodeling, contributing to infertility or pregnancy-related complications (e.g. preeclampsia and miscarriage).

WIDER IMPLICATIONS

Although further clinical trials are needed, recent advancements in the development of recombinant BMP ligands, synthetic BMP inhibitors, receptor antagonists, BMP ligand sequestration tools, and gene therapies have underscored the BMPs as candidate diagnostic biomarkers and positioned the BMP signaling pathway as a promising therapeutic target for addressing infertility and pregnancy complications related to dysregulated human endometrial remodeling.

Gene-network based analysis of human placental trophoblast subtypes identifies critical genes as potential targets of therapeutic drugs

During early pregnancy, extravillous trophoblasts (EVTs) play a crucial role in modifying the maternal uterine environment. Failures in EVT lineage formation and differentiation can lead to pregnancy complications such as preeclampsia, fetal growth restriction, and pregnancy loss. Despite recent advances, our knowledge on molecular and external factors that control and affect EVT development remains incomplete. Using trophoblast organoid in vitro models, we recently discovered that coordinated manipulation of the transforming growth factor beta (TGFβ) signaling is essential for EVT development. To further investigate gene networks involved in EVT function and development, we performed weighted gene co-expression network analysis (WGCNA) on our RNA-Seq data. We identified 10 modules with a median module membership of over 0.8 and sizes ranging from 1005 (M1) to 72 (M27) network genes associated with TGFβ activation status or in vitro culturing, the latter being indicative for yet undiscovered factors that shape the EVT phenotypes. Lastly, we hypothesized that certain therapeutic drugs might unintentionally interfere with placentation by affecting EVT-specific gene expression. We used the STRING database to map correlations and the Drug-Gene Interaction database to identify drug targets. Our comprehensive dataset of drug-gene interactions provides insights into potential risks associated with certain drugs in early gestation.

The TGF-β/UCHL5/Smad2 Axis Contributes to the Pathogenesis of Placenta Accreta

Placenta accreta is a high-risk condition causing obstetric crisis and hemorrhage; however, its pathogenesis remains unknown. We aimed to identify the factors contributing to trophoblast invasiveness and angiogenic potential, which in turn drive the pathogenesis of placenta accreta. We focused on the transforming growth factor (TGF)-β1-Smad pathway and investigated the intrinsic relationship between the time- and dose-dependent inhibition of the ubiquitinating enzyme UCHL5 using bAP15, a deubiquitinase inhibitor, after TGF-β1 stimulation and the invasive and angiogenic potential of two cell lines, gestational choriocarcinoma cell line JEG-3 and trophoblast cell line HTR-8/SVneo. UCHL5 inhibition negatively regulated TGF-β1-induced Smad2 activation, decreasing extravillous trophoblast invasiveness. Smad1/5/9 and extracellular signal-regulated kinase (ERK) were simultaneously activated, and vascular endothelial growth factor was secreted into the trophoblast medium. However, extravillous trophoblast culture supernatant severely impaired the vasculogenic potential of human umbilical vein endothelial cells. These results suggest that the downstream ERK pathway and Smad1/5/9 potentially regulate the TGF-β1-Smad pathway in extravillous trophoblasts, whereas Smad2 contributes to their invasiveness. The abnormal invasive and angiogenic capacities of extravillous cells, likely driven by the interaction between TGF-β1-Smad and ERK pathways, underlie the pathogenesis of placenta accreta.

Laminin switches terminal differentiation fate of human trophoblast stem cells under chemically defined culture conditions

Human trophoblast stem cells (hTSCs) have emerged as a powerful tool to model early placental development in vitro. Analogous to the epithelial cytotrophoblast in the placenta, hTSCs can differentiate into cells of the extravillous trophoblast (EVT) lineage or the multinucleate syncytiotrophoblast (STB). Here we present a chemically defined culture system for STB and EVT differentiation of hTSCs. Notably, in contrast to current approaches, we neither utilize forskolin for STB formation nor transforming growth factor-beta (TGFβ) inhibitors or a passage step for EVT differentiation. Strikingly, the presence of a single additional extracellular cue-laminin-111-switched the terminal differentiation of hTSCs from STB to the EVT lineage under these conditions. In the absence of laminin-111, STB formation occurred, with cell fusion comparable to that obtained with differentiation mediated by forskolin; however, in the presence of laminin-111, hTSCs differentiated to the EVT lineage. Protein expression of nuclear hypoxia-inducible factors (HIF1α and HIF2α) was upregulated during EVT differentiation mediated by laminin-111 exposure. A heterogeneous mixture of Notch1+ EVTs in colonies and HLA-G+ single-cell EVTs were obtained without a passage step, reminiscent of heterogeneity in vivo. Further analysis showed that inhibition of TGFβ signaling affected both STB and EVT differentiation mediated by laminin-111 exposure. TGFβ inhibition during EVT differentiation resulted in decreased HLA-G expression and increased Notch1 expression. On the other hand, TGFβ inhibition prevented STB formation. The chemically defined culture system for hTSC differentiation established herein facilitates quantitative analysis of heterogeneity that arises during hTSC differentiation and will enable mechanistic studies in vitro.

Exosomes: New regulators of reproductive development

Exosomes are a subtype of extracellular vesicles (EVs) with a size range between 30 and 150 ​nm, which can be released by the majority of cell types and circulate in body fluid. They function as a long-distance cell-to-cell communication mechanism that modulates the gene expression profile and fate of target cells. Increasing evidence has indicated exosomes' central role in regulating various complex reproductive processes. However, to our knowledge, a review that focally and vividly describes the role of exosomes in reproductive development is still lacking. This review highlights our knowledge about the contribution of exosomes to early mammalian reproduction, such as gametogenesis, fertilization, early embryonic development, implantation, placentation and pregnancy. The discussion is primarily drawn from literature pertaining to the mammalian lineage with emphasis on the roles of exosomes in human reproduction and laboratory and livestock models.

Human placental development and function

The placenta is a transient fetal organ that plays a critical role in the health and wellbeing of both the fetus and its mother. Functionally, the placenta sustains the growth of the fetus as it facilitates delivery of oxygen and nutrients and removal of waste products. Not surprisingly, defective early placental development is the primary cause of common disorders of pregnancy, including recurrent miscarriage, fetal growth restriction, pre-eclampsia and stillbirth. Adverse pregnancy conditions will also affect the life-long health of the fetus via developmental programming[1]. Despite its critical importance in reproductive success and life-long health, our understanding of placental development is not extensive, largely due to ethical limitations to studying early or chronological placental development, lack of long-term in vitro models, or comparative animal models. In this review, we examine current knowledge of early human placental development, discuss the critical role of the maternal endometrium and of the fetal-maternal dialogue in pregnancy success, and we explore the latest models of trophoblast and endometrial stem cells. In addition, we discuss the role of oxygen in placental formation and function, how nutrient delivery is mediated during the periods of histotrophic nutrition (uptake of uterine secretions) and haemotrophic nutrition (exchange between the maternal and fetal circulations), and how placental endocrine function facilitates fetal growth and development.

Transforming growth factor-β signaling governs the differentiation program of extravillous trophoblasts in the developing human placenta

Abnormal placentation has been noticed in a variety of pregnancy complications such as miscarriage, early-onset preeclampsia, and fetal growth restriction. Defects in the developmental program of extravillous trophoblasts (EVTs), migrating from placental anchoring villi into the maternal decidua and its vessels, is thought to be an underlying cause. Yet, key regulatory mechanisms controlling commitment and differentiation of the invasive trophoblast lineage remain largely elusive. Herein, comparative gene expression analyses of HLA-G-purified EVTs, isolated from donor-matched placenta, decidua, and trophoblast organoids (TB-ORGs), revealed biological processes and signaling pathways governing EVT development. In particular, bioinformatics analyses and manipulations in different versatile trophoblast cell models unraveled transforming growth factor-β (TGF-β) signaling as a crucial pathway driving differentiation of placental EVTs into decidual EVTs, the latter showing enrichment of a secretory gene signature. Removal of Wingless signaling and subsequent activation of the TGF-β pathway were required for the formation of human leukocyte antigen-G⁺ (HLA-G⁺) EVTs in TB-ORGs that resemble in situ EVTs at the level of global gene expression. Accordingly, TGF-β-treated EVTs secreted enzymes, such as DAO and PAPPA2, which were predominantly expressed by decidual EVTs. Their genes were controlled by EVT-specific induction and genomic binding of the TGF-β downstream effector SMAD3. In summary, TGF-β signaling plays a key role in human placental development governing the differentiation program of EVTs.

(Dis)similarities between the Decidual and Tumor Microenvironment

Placenta-specific trophoblast and tumor cells exhibit many common characteristics. Trophoblast cells invade maternal tissues while being tolerated by the maternal immune system. Similarly, tumor cells can invade surrounding tissues and escape the immune system. Importantly, both trophoblast and tumor cells are supported by an abetting microenvironment, which influences invasion, angiogenesis, and immune tolerance/evasion, among others. However, in contrast to tumor cells, the metabolic, proliferative, migrative, and invasive states of trophoblast cells are under tight regulatory control. In this review, we provide an overview of similarities and dissimilarities in regulatory processes that drive trophoblast and tumor cell fate, particularly focusing on the role of the abetting microenvironments.

Roles of TGF-β Superfamily Proteins in Extravillous Trophoblast Invasion

Following embryo implantation, extravillous trophoblasts (EVTs) invade the maternal decidua to a certain extent during early pregnancy, which is critical for normal placentation and successful pregnancy in humans. Although sharing a similar protein structure, the transforming growth factor-β (TGF-β) superfamily members exert divergent functions in regulating EVT invasion, which contributes to a relative balance of TGF-β superfamily proteins in precisely modulating this process at the maternal-fetal interface during the first trimester of pregnancy. This review details recent advances in our understanding of the functions of TGF-β superfamily members and their corresponding receptors, signaling pathways, and downstream molecular targets in regulating human EVT invasion from studies using various in vitro or ex vivo experimental models. Also, the relevance of these discoveries about TGF-β superfamily members to adverse pregnancy outcomes is summarized. The application of 3D culture trophoblast organoids, single-cell sequencing, and microfluidic assays in EVT invasion studies will help better reveal the molecular mechanisms through which TGF-β superfamily members regulate human EVT invasion, shedding light on the development of innovative strategies for predicting, diagnosing, treating, and preventing adverse human pregnancy outcomes related to EVT invasion dysfunction.

Human Placental NADPH Oxidase Mediates sFlt-1 and PlGF Secretion in Early Pregnancy: Exploration of the TGF-β1/p38 MAPK Pathways

Preeclampsia, a hypertensive disorder occurring during pregnancy, is characterized by excessive oxidative stress and trophoblast dysfunction with dysregulation of soluble Fms-like tyrosine kinase 1 (sFlt-1) and placental growth factor (PlGF) production. Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase (Nox) is the major source of placental superoxide in early pregnancy and its activation with the subsequent formation of superoxide has been demonstrated for various agents including Transforming Growth Factor beta-1 (TGF-β1), a well-known p38 MAPK pathway activator. However, the bridge between Nox and sFlt-1 remains unknown. The purpose of this study was to explore the possible signaling pathway of TGF-β1/Nox/p38 induced sFlt-1 production in human chorionic villi (CV). Methods: Human chorionic villi from first trimester placenta (7–9 Gestational Weeks (GW)) were treated with TGF-β1 or preincubated with p38 inhibitor, SB203580. For NADPH oxidase inhibition, CV were treated with diphenyleneiodonium (DPI). The protein levels of phospho-p38, p38, phospho-Mothers Against Decapentaplegic homolog 2 (SMAD2), and SMAD2 were detected by Western blot. The secretion of sFlt-1 and PlGF by chorionic villi were measured with Electrochemiluminescence Immunologic Assays, and NADPH oxidase activity was monitored by lucigenin method. Results: We demonstrate for the first time that NADPH oxidase is involved in sFlt-1 and PlGF secretion in first trimester chorionic villi. Indeed, the inhibition of Nox by DPI decreases sFlt-1, and increases PlGF secretions. We also demonstrate the involvement of p38 MAPK in sFlt-1 secretion and Nox activation as blocking the p38 MAPK phosphorylation decreases both sFlt-1 secretion and superoxide production. Nevertheless, TGF-β1-mediated p38 activation do not seem to be involved in regulation of the first trimester placental angiogenic balance and no crosstalk was found between SMAD2 and p38 MAPK pathways. Conclusions: Thus, the placental NADPH oxidase play a major role in mediating the signal transduction cascade of sFlt-1 production. Furthermore, we highlight for the first time the involvement of p38 activation in first trimester placental Nox activity.

Establishment and differentiation of long-term trophoblast organoid cultures from the human placenta

The human placenta is essential for successful reproduction. There is great variation in the anatomy and development of the placenta in different species, meaning that animal models provide limited information about human placental development and function. Until recently, it has been impossible to isolate trophoblast cells from the human placenta that proliferate in vitro. This has limited our ability to understand pregnancy disorders. Generating an in vitro model that recapitulates the unique features of the human placenta has been challenging. The first in vitro model system of human trophoblast that could be cultured long term and differentiated to syncytiotrophoblast (SCT) and extravillous trophoblast (EVT) was a two-dimensional (2D) culture system of human trophoblast stem cells. Here, we describe a protocol to isolate trophoblast from first-trimester human placentas that can be grown long term in a three-dimensional (3D) organoid culture system. Trophoblast organoids can be established within 2-3 weeks, passaged every 7-10 d, and cultured for over a year. The structural organization of these human trophoblast organoids closely resembles the villous placenta with a layer of cytotrophoblast (VCT) that differentiates into superimposed SCT. Altering the composition of the medium leads to differentiation of the trophoblast organoids into HLA-G+ EVT cells which rapidly migrate and invade through the Matrigel droplet in which they are cultured. Our previous research confirmed that there is similarity between the trophoblast organoids and in vivo placentas in their transcriptomes and ability to produce placental hormones. This organoid culture system provides an experimental model to investigate human placental development and function as well as interactions of trophoblast cells with the local and systemic maternal environment.

Pivotal role of the transcriptional co-activator YAP in trophoblast stemness of the developing human placenta

Various pregnancy complications, such as severe forms of preeclampsia or intrauterine growth restriction, are thought to arise from failures in the differentiation of human placental trophoblasts. Progenitors of the latter either develop into invasive extravillous trophoblasts, remodeling the uterine vasculature, or fuse into multinuclear syncytiotrophoblasts transporting oxygen and nutrients to the growing fetus. However, key regulatory factors controlling trophoblast self-renewal and differentiation have been poorly elucidated. Using primary cells, three-dimensional organoids, and CRISPR-Cas9 genome-edited JEG-3 clones, we herein show that YAP, the transcriptional coactivator of the Hippo signaling pathway, promotes maintenance of cytotrophoblast progenitors by different genomic mechanisms. Genetic or chemical manipulation of YAP in these cellular models revealed that it stimulates proliferation and expression of cell cycle regulators and stemness-associated genes, but inhibits cell fusion and production of syncytiotrophoblast (STB)-specific proteins, such as hCG and GDF15. Genome-wide comparisons of primary villous cytotrophoblasts overexpressing constitutively active YAP-5SA with YAP KO cells and syncytializing trophoblasts revealed common target genes involved in trophoblast stemness and differentiation. ChIP-qPCR unraveled that YAP-5SA overexpression increased binding of YAP-TEAD4 complexes to promoters of proliferation-associated genes such as CCNA and CDK6 Moreover, repressive YAP-TEAD4 complexes containing the histone methyltransferase EZH2 were detected in the genomic regions of the STB-specific CGB5 and CGB7 genes. In summary, YAP plays a pivotal role in the maintenance of the human placental trophoblast epithelium. Besides activating stemness factors, it also directly represses genes promoting trophoblast cell fusion.

Comparative Study of PPARγ Targets in Human Extravillous and Villous Cytotrophoblasts

Trophoblasts, as the cells that make up the main part of the placenta, undergo cell differentiation processes such as invasion, migration, and fusion. Abnormalities in these processes can lead to a series of gestational diseases whose underlying mechanisms are still unclear. One protein that has proven to be essential in placentation is the peroxisome proliferator-activated receptor γ (PPARγ), which is expressed in the nuclei of extravillous cytotrophoblasts (EVCTs) in the first trimester and villous cytotrophoblasts (VCTs) throughout pregnancy. Here, we aimed to explore the genome-wide effects of PPARγ on EVCTs and VCTs via treatment with the PPARγ-agonist rosiglitazone. EVCTs and VCTs were purified from human chorionic villi, cultured in vitro, and treated with rosiglitazone. The transcriptomes of both types of cells were then quantified using microarray profiling. Differentially expressed genes (DEGs) were filtered and submitted for gene ontology (GO) annotation and pathway analysis with ClueGO. The online tool STRING was used to predict PPARγ and DEG protein interactions, while iRegulon was used to predict the binding sites for PPARγ and DEG promoters. GO and pathway terms were compared between EVCTs and VCTs with clusterProfiler. Visualizations were prepared in Cytoscape. From our microarray data, 139 DEGs were detected in rosiglitazone-treated EVCTs (RT-EVCTs) and 197 DEGs in rosiglitazone-treated VCTs (RT-VCTs). Downstream annotation analysis revealed the similarities and differences between RT-EVCTs and RT-VCTs with respect to the biological processes, molecular functions, cellular components, and KEGG pathways affected by the treatment, as well as predicted binding sites for both protein-protein interactions and transcription factor-target gene interactions. These results provide a broad perspective of PPARγ-activated processes in trophoblasts; further analysis of the transcriptomic signatures of RT-EVCTs and RT-VCTs should open new avenues for future research and contribute to the discovery of possible drug-targeted genes or pathways in the human placenta.

Differential Role of Smad2 and Smad3 in the Acquisition of an Endovascular Trophoblast-Like Phenotype and Preeclampsia

During placental development, cytotrophoblast progenitor cells differentiate into the syncytiotrophoblast and invasive extravillous trophoblasts (EVTs). Some EVTs further differentiate into endovascular trophoblasts (enEVTs) which exhibit endothelial-like properties. Abnormal placental development, including insufficient enEVT-mediated remodeling of the uterine spiral arteries, is thought to be a precipitating factor in the onset of preeclampsia (PE), a pregnancy-related hypertensive disorder. Several members of the transforming growth factor-β (TGF-β) superfamily, such as TGF-βs, Nodal, and Activin have been reported to either promote or inhibit the invasive EVT pathway. These ligands signal through serine/threonine receptor complexes to activate downstream signaling mediators, Smad2 and Smad3. In this study, we determined Smad2 and Smad3 expression pattern in placenta and their effects on trophoblast invasion and differentiation. Total Smad2/3 levels were relatively constant across gestation while the ratio of active phosphorylated forms to their total levels varied with gestational stages, with a higher pSmad2/total Smad2 in later gestation and a higher pSmad3/total Smad3 in early gestation. Immunofluorescent staining revealed that pSmad3 was localized in nuclei of EVTs in anchoring villi. On the other hand, pSmad2 was mostly absent in this invasive EVT population. In addition, pSmad3/total Smad3, but not pSmad2/total Smad2, was significantly lower in both early onset and late onset PE cases, as compared to gestational age-matched controls. Functional studies carried out using a first trimester trophoblast cell line, HTR-8/SVneo, and first trimester human placental explants showed that Smad2 and Smad3 had differential roles in the invasive pathway. Specifically, siRNA-mediated knockdown of Smad2 resulted in an increase in trophoblast invasion and an upregulation of mRNA levels of enEVT markers while the opposite was observed with Smad3 knockdown. In addition, Smad2 siRNA accelerated the EVT outgrowth in first trimester placental explants while the Smad3 siRNA reduced the outgrowth of EVTs when compared to the control. Furthermore, knockdown of Smad2 enhanced, whereas overexpression of Smad2 suppressed, the ability of trophoblasts to form endothelial-like networks. Conversely, Smad3 had opposite effects as Smad2 on network formation. These findings suggest that Smad2 and Smad3 have opposite functions in the acquisition of an enEVT-like phenotype and defects in Smad3 activation are associated with PE.

Platelet-derived factors impair placental chorionic gonadotropin beta-subunit synthesis

Abstract

During histiotrophic nutrition of the embryo, maternal platelets may be the first circulating maternal cells that find their way into the placental intervillous space through narrow intertrophoblastic gaps within the plugs of spiral arteries. Activation of platelets at the maternal-fetal interface can influence trophoblast behavior and has been implicated in serious pregnancy pathologies. Here, we show that platelet-derived factors impaired expression and secretion of the human chorionic gonadotropin beta-subunit (βhCG) in human first trimester placental explants and the trophoblast cell line BeWo. Impaired βhCG synthesis was not the consequence of hampered morphological differentiation, as assessed by analysis of differentiation-associated genes and electron microscopy. Platelet-derived factors did not affect intracellular cAMP levels and phosphorylation of CREB, but activated Smad3 and its downstream-target plasminogen activator inhibitor (PAI)-1 in forskolin-induced BeWo cell differentiation. While TGF-β type I receptor inhibitor SB431542 did not restore impaired βhCG production in response to platelet-derived factors, Smad3 inhibitor SIS3 interfered with CREB activation, suggesting an interaction of cAMP/CREB and Smad3 signaling. Sequestration of transcription co-activators CBP/p300, known to bind both CREB and Smad3, may limit βhCG production, since CBP/p300 inhibitor C646 significantly restricted its forskolin-induced upregulation. In conclusion, our study suggests that degranulation of maternal platelets at the early maternal-fetal interface can impair placental βhCG production, without substantially affecting morphological and biochemical differentiation of villous trophoblasts.

Key messages

Maternal platelets can be detected on the surface of the placental villi and in intercellular gaps of trophoblast cell columns from gestational week 5 onwards.

Platelet-derived factors impair hCG synthesis in human first trimester placenta.

Platelet-derived factors activate Smad3 in trophoblasts.

Smad3 inhibitor SIS3 interferes with forskolin-induced CREB signaling.

Sequestration of CBP/p300 by activated Smad3 may limit placental hCG production.

Electronic supplementary material

The online version of this article (10.1007/s00109-019-01866-x) contains supplementary material, which is available to authorized users.

Down-regulation of microRNA-34a-5p promotes trophoblast cell migration and invasion via targetting Smad4

Trophoblastic dysfunction, such as insufficient migration and invasion, is well-known to be correlated with preeclampsia (PE). Recently, microRNAs (miRNAs) have been implicated in diverse biological processes and human diseases, including PE. However, the expression and functions of miRNAs in the progression of PE, especially in the regulation of trophoblast cell migration and invasion remain largely unclear. Here, we compared the miRNAs expression profiles of PE patients with healthy controls using microarray assay and chose a significant increased miRNA-miR-34a-5p for further investigation. Overexpression of miR-34a-5p dramatically reduced migration and invasion in trophoblast HTR-8/SVneo cells, whereas enhanced by its inhibitor. Luciferase activity assay showed that miR-34a-5p directly target Smad family member 4 (Smad4), which is associated with cancer cell invasiveness and metastasis. We also found that Smad4 was down-regulated in PE patients, and an inverse relationship between Smad4 and miR-34a-5p expression levels was observed in placental tissues from PE patients. Further study showed that knockdown of Smad4 effectively attenuated the promoting effects of miR-34a-5p inhibition on the migration and invasion of HTR-8/SVneo cells. Taken together, these findings suggest that inhibition of miR-34a-5p improves invasion and migration of trophoblast cells by directly targetting Smad4, which indicated the potential of miR-34a-5p as a therapeutic target against PE.

Trophoblast organoids as a model for maternal-fetal interactions during human placentation

The placenta is the extraembryonic organ that supports the fetus during intrauterine life. Although placental dysfunction results in major disorders of pregnancy with immediate and lifelong consequences for the mother and child, our knowledge of the human placenta is limited owing to a lack of functional experimental models1. After implantation, the trophectoderm of the blastocyst rapidly proliferates and generates the trophoblast, the unique cell type of the placenta. In vivo, proliferative villous cytotrophoblast cells differentiate into two main sub-populations: syncytiotrophoblast, the multinucleated epithelium of the villi responsible for nutrient exchange and hormone production, and extravillous trophoblast cells, which anchor the placenta to the maternal decidua and transform the maternal spiral arteries2. Here we describe the generation of long-term, genetically stable organoid cultures of trophoblast that can differentiate into both syncytiotrophoblast and extravillous trophoblast. We used human leukocyte antigen (HLA) typing to confirm that the organoids were derived from the fetus, and verified their identities against four trophoblast-specific criteria3. The cultures organize into villous-like structures, and we detected the secretion of placental-specific peptides and hormones, including human chorionic gonadotropin (hCG), growth differentiation factor 15 (GDF15) and pregnancy-specific glycoprotein (PSG) by mass spectrometry. The organoids also differentiate into HLA-G+ extravillous trophoblast cells, which vigorously invade in three-dimensional cultures. Analysis of the methylome reveals that the organoids closely resemble normal first trimester placentas. This organoid model will be transformative for studying human placental development and for investigating trophoblast interactions with the local and systemic maternal environment.

Cord Blood-Derived Stem Cells Suppress Fibrosis and May Prevent Malignant Progression in Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a severe skin fragility disorder caused by mutations in the Col7a1 gene. Patients with RDEB suffer from recurrent erosions in skin and mucous membranes and have a high risk for developing cutaneous squamous cell carcinoma (cSCCs). TGFβ signaling has been associated with fibrosis and malignancy in RDEB. In this study, the activation of TGFβ signaling was demonstrated in col7a1^-/- mice as early as a week after birth starting in the interdigital folds of the paws, accompanied by increased deposition of collagen fibrils and elevated dermal expression of matrix metalloproteinase (MMP)-9 and MMP-13. Furthermore, human cord blood-derived unrestricted somatic stem cells (USSCs) that we previously demonstrated to significantly improve wound healing and prolong the survival of col7a1^-/- mice showed the ability to suppress TGFβ signaling and MMP-9 and MMP-13 expression meanwhile upregulating anti-fibrotic TGFβ3 and decorin. In parallel, we cocultured USSCs in a transwell with RDEB patient-derived fibroblasts, keratinocytes, and cSCC, respectively. The patient-derived cells were constitutively active for STAT, but not TGFβ signaling. Moreover, the levels of MMP-9 and MMP-13 were significantly elevated in the patient derived-keratinocytes and cSCCs. Although USSC coculture did not inhibit STAT signaling, it significantly suppressed the secretion of MMP-9 and MMP-13, and interferon (IFN)-γ from RDEB patient-derived cells. Since epithelial expression of these MMPs is a biomarker of malignant transformation and correlates with the degree of tumor invasion, these results suggest a potential role for USSCs in mitigating epithelial malignancy, in addition to their anti-inflammatory and anti-fibrotic functions. Stem Cells 2018;36:1839-12.