Inhibition of Trophoblast Cell Invasion by TGFB1, 2, and 3 Is Associated with a Decrease in Active Proteases1

Immune Cells and Infectious Diseases in Preeclampsia Susceptibility

Preeclampsia is a severe pregnancy disorder, affecting approximately 10% of pregnancies worldwide, characterised by hypertension and proteinuria after the 20th week of gestation. The condition poses significant risks to both maternal and fetal health, including cardiovascular complications and impaired fetal development. Recent trends indicate a rising incidence of preeclampsia, correlating with factors such as advanced maternal age and cardiovascular comorbidities. Emerging evidence also highlights a notable increase in the association between autoimmune and infectious diseases with preeclampsia. Autoimmune conditions, such as type 1 diabetes and systemic lupus erythematosus, and infections triggered by global health challenges, including leptospirosis, Zika, toxoplasmosis, and Chagas disease, are now recognised as significant contributors to preeclampsia susceptibility by affecting placental formation and function. This review focuses on the immunologic mechanisms underpinning preeclampsia, exploring how immune system dysregulation and infectious triggers exacerbate the condition. It also discusses the pathologic mechanisms, including galectins, that preeclampsia shares with autoimmune and infectious diseases, and their significant risk for adverse pregnancy outcomes. We emphasise the necessity for accurate diagnosis and vigilant monitoring of immune and infectious diseases during pregnancy to optimise management and reduce risks. By raising awareness about these evolving risks and their impact on pregnancy, we aim to enhance diagnostic practices and preventive strategies, ultimately improving outcomes for pregnant women, especially in regions affected by environmental changes and endemic diseases.

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.

Endometrial TGFβ signaling fosters early pregnancy development by remodeling the fetomaternal interface

The endometrium is a unique and highly regenerative tissue with crucial roles during the reproductive lifespan of a woman. As the first site of contact between mother and embryo, the endometrium, and its critical processes of decidualization and immune cell recruitment, play a leading role in the establishment of pregnancy, embryonic development, and reproductive capacity. These integral processes are achieved by the concerted actions of steroid hormones and a myriad of growth factor signaling pathways. This review focuses on the roles of the transforming growth factor β (TGFβ) pathway in the endometrium during the earliest stages of pregnancy through the lens of immune cell regulation and function. We discuss how key ligands in the TGFβ family signal through downstream SMAD transcription factors and ultimately remodel the endometrium into a state suitable for embryo implantation and development. We also focus on the key roles of the TGFβ signaling pathway in recruiting uterine natural killer cells and their collective remodeling of the decidua and spiral arteries. By providing key details about immune cell populations and TGFβ signaling within the endometrium, it is our goal to shed light on the intricate remodeling that is required to achieve a successful pregnancy.

The Role of TGF-β during Pregnancy and Pregnancy Complications

Transforming growth factor beta (TGF-β), a multifunctional cytokine, is one of the most important inflammatory cytokines closely related to pregnancy. It plays significant roles in hormone secretion, placental development, and embryonic growth during pregnancy. TGF-β is implicated in embryo implantation and inhibits the invasion of extraepithelial trophoblast cells. It also moderates the mother-fetus interaction by adjusting the secretion pattern of immunomodulatory factors in the placenta, consequently influencing the mother's immune cells. The TGF-β family regulates the development of the nervous, respiratory, and cardiovascular systems by regulating gene expression. Furthermore, TGF-β has been associated with various pregnancy complications. An increase in TGF-β levels can induce the occurrences of pre-eclampsia and gestational diabetes mellitus, while a decrease can lead to recurrent miscarriage due to the interference of the immune tolerance environment. This review focuses on the role of TGF-β in embryo implantation and development, providing new insights for the clinical prevention and treatment of pregnancy complications.

Tspan5 promotes the EMT process to regulate the syncytialization of trophoblast cells by activating Notch signalling

Placental trophoblastic cells play important roles in placental development and fetal health. However, the mechanism of trophoblastic cell fusion is still not entirely clear. The level of Tspan5 in the embryo culture medium was detected using enzyme-linked immunosorbent assay (ELISA). Fusion of BeWo cells was observed by immunofluorescence. Cell fusion-related factors and EMT-related factors were identified by qRT-PCR and western blotting. Notch protein repressor DAPT was used to verify the role of Tspan5 in BeWo cells. The expression of Tspan5 was significantly increased in embryo culture medium. The fusion of BeWo cells was observed after treatment with forskolin (FSK). Cell fusion-related factors (i.e. β-hCG and syncytin 1/2) and Tspan5 were significantly increased after FSK treatment. In addition, FSK treatment promoted EMT-related protein expression in BeWo cells. Knockdown of Tspan5 inhibited cell fusion and EMT-related protein levels. Notch-1 and Jagged-1 protein levels were significantly upregulated, and the EMT process was activated by overexpression of Tspan5 in FSK-treated BeWo cells. Interestingly, blocking the Notch pathway by the repressor DAPT had the opposite results. These results indicated that Tspan5 could promote the EMT process by activating the Notch pathway, thereby causing cell fusion. These findings contribute to a better understanding of trophoblast cell syncytialization and embryonic development. Tspan5 may be used as a therapeutic target for normal placental development.

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.

The function of decidua natural killer cells in physiology and pathology of pregnancy

The role of decidual natural killer (dNK) cells in maintaining immune tolerance at the maternal-fetal interface during pregnancy is a significant topic in reproductive health. Immune tolerance is essential for a successful pregnancy and involves a complex immune response involving various immune cells and molecules. DNK cells comprise the largest population of lymphocyte subsets found in the decidua and play important roles in maintaining immune tolerance. These cells exert multiple functions to maintain homeostasis of the decidual microenvironment, including modulation of trophoblast invasion, promotion of fetal development, regulation of endometrial decidualization and spiral artery remodeling. DNK cells can also be divided into different subsets based on their functions as NKtolerant , NKcytotoxic , and NKregulatory cells. However, the relationship between dNK cells function and pregnancy outcomes is complex and poorly understood. In this review, we will focus on the physiological role of dNK cells during pregnancy and highlight the potential role in pathological pregnancies and therapeutic approaches.

Decidual lymphatic endothelial cell-derived granulocyte-macrophage colony-stimulating factor induces M1 macrophage polarization via the NF-κB pathway in severe pre-eclampsia

PROBLEM

Direct interactions between macrophages and lymphatic vessels have been shown previously. In pre-eclampsia (PE), macrophages are dominantly polarized into a proinflammatory M1 phenotype and lymphangiogenesis is defective in the decidua. Here, we investigated whether decidual lymphatic endothelial cells (dLECs) affect macrophage polarization in PE.

METHOD OF STUDY

THP-1 macrophages were cocultured with dLECs or cultured in the conditioned medium (CM) of dLECs. Macrophage polarization was measured using flow cytometry. Granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in dLECs was measured using qRT-PCR and ELISA. The activation of nuclear translocation of nuclear factor-κ (NF-κB), an upstream signaling molecule of GM-CSF, was assessed by immunocytochemical localization of p65. Through GM-CSF knockdown and NF-κB inhibition in dLEC, we evaluated whether the GM-CSF/NF-κB pathway of PE dLEC affects decidual macrophage polarization.

RESULTS

The ratio of inflammatory M1 macrophages with HLA-DR⁺ /CD80⁺ markers significantly increased following coculturing with PE dLECs or culturing in PE dLEC CM, indicating that the PE dLEC-derived soluble factor acts in a paracrine manner. GM-CSF expression was significantly upregulated in PE dLECs. Recombinant human GM-CSF induced macrophage polarization toward an M1-like phenotype, whereas its knockdown in PE dLECs suppressed it, suggesting PE dLECs induce M1 macrophage polarization by secreting GM-CSF. The NF-κB p65 significantly increased in PE dLECs compared to the control, and pretreatment with an NF-κB inhibitor significantly suppressed GM-CSF production from PE dLECs.

CONCLUSIONS

In PE, dLECs expressing high levels of GM-CSF via the NF-κB-dependent pathway play a role in inducing decidual M1 macrophage polarization.

Fetal-maternal interactions during pregnancy: a 'three-in-one' perspective

A successful human pregnancy requires the maternal immune system to recognize and tolerate the semi-allogeneic fetus, allowing for appropriate trophoblasts invasion and protecting the fetus from invading pathogens. Therefore, maternal immunity is critical for the establishment and maintenance of pregnancy, especially at the maternal-fetal interface. Anatomically, the maternal-fetal interface has both maternally- and fetally- derived cells, including fetal originated trophoblasts and maternal derived immune cells and stromal cells. Besides, a commensal microbiota in the uterus was supposed to aid the unique immunity in pregnancy. The appropriate crosstalk between fetal derived and maternal originated cells and uterine microbiota are critical for normal pregnancy. Dysfunctional maternal-fetal interactions might be associated with the development of pregnancy complications. This review elaborates the latest knowledge on the interactions between trophoblasts and decidual immune cells, highlighting their critical roles in maternal-fetal tolerance and pregnancy development. We also characterize the role of commensal bacteria in promoting pregnancy progression. Furthermore, this review may provide new thought on future basic research and the development of clinical applications for pregnancy complications.

Increase in transforming growth factor-β didnot affect trombospondin1 in preeclampsia placentas

Objective

The abnormalities of the placental growth process are a theory causing pre-eclampsia. Antiangiogenic factors contributed to it, such as thrombospondin-1 (TSp-1) that could stimulate transforming growth factor-beta (TGF-β), or vice versa. Some research showed that an increase in TGF-β did not always figurized its signaling. Therefore, we conducted a study to examine the TGF-β signaling proteins through its receptors and TSp-1 expression in preeclampsia placentas.

Materials and Methods

This observational study used 33 normal and 33 pre-eclampsia placental storaged samples, for examination of TGF-β and TGF-βR 1 and 2, SMAD2 using ELISA, and SMAD2 and TSp-1 mRNA using the reverse transcription polymerase chain reaction method. Data were analyzed using SPSS version 20.0, normality test by Kolmogorov-Smirnov, and significancy was analyzed using nonparametric Mann-Whitney test, or t-test for parametric, with confidence interval 95%. Spearman correlation was used for non-parametric data, besides the Pearson correlation for parametric data.

Results

Results showed that there were significant differences between preeclampsia and normal placenta in TGF-β, its receptors, SMAD2, and TSp-1 mRNA. Normal-TGF-β=1.19 (0.713-2.051) pg/mg; preeclampsia-TGFB=2.69 (0.906-10.252) pg/mg; p=0.001; normal-TGFBR1=1.025 (0.622-1.402) ng/mg; preeclampsia-TGFBR1=1.223 (0.372-2.553) ng/mg; p=0.004; Normal-TGF-βR2=0.959 (0.644-1.634) pg/mg; preeclampsia-TGFBR2=1.490 (0.775-3.645) pg/mg; p=0.0001; normal-SMAD2=2.087 (1.279-4.300) ng/mg; preeclampsia-SMAD2=3.508 (1.842-22.489) ng/mg; p=0.0001. The SMAD2 mRNA relative expression (Livax) in the normal placenta was=0.71 (0.03-7.25); pre-eclampsia placenta (PE)=0.49 (0.01-40.71); p=0.075, the normal TSp-1 mRNA expression=1.08 (0.09-5.31); PE=0.21 (0.002-24.06); p=0.002. The correlation test showed a strong correlation between TGF-β with TGFBR1 and 2 in the normal placenta, conversely, there was no correlation in the preeclampsia placenta. There was also no correlation between SMAD2 and TSp-1 mRNA in both normal and pre-eclampsia.

Conclusion

TGF-β signaling in the preeclampsia placenta was changed due to the increased of the protein signaling it self without correlation between TGF-β to its receptors and TSp-1 relative expression.

SERPINA5 may promote the development of preeclampsia by disruption of the uPA/uPAR pathway

Preeclampsia (PE) is the leading cause of maternal and fetal morbidity or mortality but lacks reliable methods for early diagnosis. In a previous study, serum SERPINA5 levels were higher in women with PE before the clinical manifestation of the disease. This study aimed to evaluate the efficacy of SERPINA5 in predicting PE and investigate its role in trophoblast cell biology. A multicenter, 2-stage observational case-control study was performed to develop and validate an early predictive PE model based on SERPINA5, maternal characteristics, and inflammatory factors. To further understand the relationship between SERPINA5 and PE, SERPINA5 was overexpressed or knocked down in extravillous trophoblast cells (EVT) and a pregnant rat model. After development and initial validation, a model that combined SERPINA5 and inflammatory factors had a high predictive ability for PE before 20 weeks gestation with an AUC of 0.90 (95% CI 0.83-0.96). It also demonstrated that SERPINA5 inhibited primary EVT cell invasion by disrupting the urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor (uPA/uPAR) pathway, in turn, is involved in the development of PE. In vivo experiments also proved that overexpression of SERPINA5 induced a PE-like syndrome (hypertension and proteinuria) in pregnant rats. Therefore, serum SERPINA5 is a promising early biomarker of PE, suggesting that it may be involved in placental development through its action on the uPA/uPAR system prior to the clinical manifestation of PE.

Hypoxia induced ALKBH5 prevents spontaneous abortion by mediating m6A-demethylation of SMAD1/5 mRNAs

The molecules induced by hypoxia have been supposed to be important regulators of first trimester trophoblast activity, but the key mechanism mediating invasion of trophoblast cells is not fully illustrated. Here, we found that the expression of RNA demethylase ALKBH5 was upregulated in trophoblast upon hypoxia treatment and decreased in extravillous trophoblast (EVT) of patients with recurrent spontaneous abortion (RSA). Furthermore, we found that trophoblast-specific knockdown of ALKBH5 in mouse placenta suppressed the invasion of trophoblast and significantly led to fetus abortion in vivo. Then ALKBH5 was identified to promote the invasion of trophoblast. Mechanistically, we identified transcripts with altered methylation in trophoblast induced by hypoxia via m⁶A-seq, ALKBH5 translocated from nucleus to cytoplasm upon hypoxia treatment and demethylated certain target transcripts, such as m⁶A-modified SMAD1/SMAD5, consequently enhanced the translation of SMAD1/SMAD5 and then promoted MMP9 and ITGA1 production. Thus, we demonstrated that ALKBH5 promoted the activity of trophoblasts by enhancing SMAD1/5 expression via erasing their m⁶A modifications. Our research revealed a new m⁶A epigenetic way to regulate the invasion of trophoblast, which suggested a novel potential therapeutic target for spontaneous abortion prevention.

The transcriptome landscapes of allantochorion and vitelline-chorion in equine day 30 conceptus

During equine early gestation, trophectoderm forms chorion tissue, which is composed of two parts that one is covering allantoin, called allantochorion (AC) and another is covering yolk sac, which here we call vitelline-chorion (VC). Given that little is known about the equine trophoblast-derived chorion differentiation at an early stage, we first compared the transcriptome of AC and VC of day 30 equine conceptus based on RNA-sequencing. As a result, we found that compared to VC, there are 484 DEGs, including 305 up- and 179 down-regulated genes in AC. GO and KEGG analysis indicated that up-regulated genes in AC are mainly cell proliferation and cell adhesion-related genes, participating in allantois expansion and allantochorionic-placenta formation; dominant genes in VC are extracellular exosome and other cell adhesion-related genes implicated in direct and indirect conceptus-maternal communication. Additionally, as for the progenitor chorion tissue of equine chorionic gonadotropin secreting endometrium cup-the chorionic girdle (CG), which locates at the junction of the dilating AC and regressing VC, we revealed its unique gene expression pattern and the gene regulation during its further differentiation in vitro. Collectively, this study sheds light on the molecular events regarding the trophoblast differentiation and function at an early stage of the equine preimplantation conceptus.

The Role of Cytokines in Maintaining the Dynamics of Cell-Cell Interaction between Natural Killer Cells and Trophoblast Cells

We analyzed the effect of individual cytokines that are secretory products of placenta typical of the uteroplacental bed. The proinflammatory cytokines IL-6, IFNγ, and IL-1β increased the expression of TGFβR2 molecule by trophoblast cells, while VEGF and PLGF increased the expression of CD45, CD29, and CD54 adhesion molecule by trophoblast cells. The antiinflammatory cytokine IL-4 increased LeptinR expression by trophoblast cells. PMA and TNFα also enhanced the adhesion of NK cells to trophoblast cells. Our findings suggest that NK cells involved CD11a, CD11b, and CD18 molecules during their transmigration through trophoblast, as well as during their transendothelial migration.

TGF-β1 inhibits human trophoblast cell invasion by upregulating kisspeptin expression through ERK1/2 but not SMAD signaling pathway

BACKGROUND

Tightly regulation of extravillous cytotrophoblast (EVT) cell invasion is critical for the placentation and establishment of a successful pregnancy. Insufficient EVT cell invasion leads to the development of preeclampsia (PE) which is a leading cause of maternal and perinatal mortality and morbidity. Transforming growth factor-beta1 (TGF-β1) and kisspeptin are expressed in the human placenta and have been shown to inhibit EVT cell invasion. Kisspeptin is a downstream target of TGF-β1 in human breast cancer cells. However, whether kisspeptin is regulated by TGF-β1 and mediates TGF-β1-suppressed human EVT cell invasion remains unclear.

METHODS

The effect of TGF-β1 on kisspeptin expression and the underlying mechanisms were explored by a series of in vitro experiments in a human EVT cell line, HTR-8/SVneo, and primary cultures of human EVT cells. Serum levels of TGF-β1 and kisspeptin in patients with or without PE were measured by ELISA.

RESULTS

TGF-β1 upregulates kisspeptin expression in HTR-8/SVneo cells and primary cultures of human EVT cells. Using pharmacological inhibitor and siRNA, we demonstrate that the stimulatory effect of TGF-β1 on kisspeptin expression is mediated via the ALK5 receptor. Treatment with TGF-β1 activates SMAD2/3 canonical pathways as well as ERK1/2 and PI3K/AKT non-canonical pathways. However, only inhibition of ERK1/2 activation attenuates the stimulatory effect of TGF-β1 on kisspeptin expression. In addition, siRNA-mediated knockdown of kisspeptin attenuated TGF-β1-suppressed EVT cell invasion. Moreover, we report that serum levels of TGF-β1 and kisspeptin are significantly upregulated in patients with PE.

CONCLUSIONS

By illustrating the potential physiological role of TGF-β1 in the regulation of kisspeptin expression, our results may serve to improve current strategies used to treat placental diseases.

Epithelial-mesenchymal transition process during embryo implantation

The epithelial to mesenchymal transition (EMT) in endometrial epithelial and trophectoderm cells is essential for the progression of embryo implantation and its impairment could cause implantation failure. Therefore, EMT should be tightly regulated in both embryonic and endometrial cells during implantation. Studies reported the involvement of numerous factors in EMT regulation, including hormones, growth factors, transcription factors, microRNAs, aquaporins (AQPs), and ion channels. These factors act through different signaling pathways to affect the expression of epithelial and mesenchymal markers as well as the cellular cytoskeleton. Although the mechanisms involved in cancer cell EMT have been well studied, little is known about EMT during embryo implantation. Therefore, we comprehensively reviewed different factors that regulate the EMT, a key event required for the conceptus implantation to the endometrium.Summary sentence: Abnormal epithelial-mesenchymal transition (EMT) process within endometrial epithelial cells (EECs) or trophoblast cells can cause implantation failure. This process is regulated by various factors. Thus, the objective of this review was to summarize the effective factors on the EMT process during implantation.

Role of clusterin in the regulation of trophoblast development and preeclampsia

Preeclampsia (PE) threatens the safety of mothers and fetuses, and its pathogenesis is still unclear. Our previous study has found the relationship between PE and serum Clusterin (CLU). This study aimed to investigate the role of CLU on PE. Firstly, levels of CLU in serum and placental tissue from PE patients and healthy pregnancies were compared. Then, RNA sequencing, cell counting kit-8, matrigel invasion, cell apoptosis, and angiogenesis assay were performed to evaluate the role of CLU on primary isolation trophoblast cells. We found the expression of CLU was increased before the clinical syndrome occurred, whereas its level was positively related to the severity of PE. CLU significantly inhibited the expression of matrix metalloproteinase-9 and Vimentin and enhanced E-cadherin to inhibit epithelial-mesenchymal transition of trophoblast cells, further reducing its migration and invasion. Our results suggested that CLU may play a role in regulating trophoblast invasion and migration during placental development, which may be one of the risk factors for PE.

CD93 a potential player in cytotrophoblast and endothelial cell migration

CD93, also known as complement component C1q receptor, is expressed on the surface of different cellular types such as monocytes, neutrophils, platelets, microglia, and endothelial cells, and it plays a pivotal role in cell proliferation, cell migration, and formation of capillary-like structures. These processes are strictly regulated, and many fetal and maternal players are involved during placental development. At present, there are no studies in literature regarding CD93 in placental development, so we investigated CD93 expression in first and third trimester and PE placentas by immunohistochemistry and western blotting analysis. In addition, we performed in vitro experiments under oxidative stress conditions to demonstrate how oxidative stress acts on CD93 protein expression. Our data showed that CD93 was expressed in villous cytotrophoblast cells, in some fetal vessels of first and third trimester and PE placentas and in the extravillous cytotrophoblast of cell columns in the first trimester placentas. Moreover, we detected a significant decrease of CD93 expression in third trimester and PE placentas compared to first trimester placentas, while no differences were detected between third and PE placentas. No differences of CD93 expression were detected in oxidative stress conditions. We suggest that CD93 can guide extravillous cytotrophoblast migration through β1-integrin in uterine spiral arteries during placentation in the first trimester of pregnancy and that the decrease of CD93 expression in third trimester and PE placentas could be linked to the poor extravillous cytotrophoblast cells migration. So, it might be interesting to understand the role of CD93 in the first phases of PE onset.

Role of Decidual Natural Killer Cells in Human Pregnancy and Related Pregnancy Complications

Pregnancy is a unique type of immunological process. Healthy pregnancy is associated with a series of inflammatory events: implantation (inflammation), gestation (anti-inflammation), and parturition (inflammation). As the most abundant leukocytes during pregnancy, natural killer (NK) cells are recruited and activated by ovarian hormones and have pivotal roles throughout pregnancy. During the first trimester, NK cells represent up to 50–70% of decidua lymphocytes. Differently from peripheral-blood NK cells, decidual natural killer (dNK) cells are poorly cytolytic, and they release cytokines/chemokines that induce trophoblast invasion, tissue remodeling, embryonic development, and placentation. NK cells can also shift to a cytotoxic identity and carry out immune defense if infected in utero by pathogens. At late gestation, premature activation of NK cells can lead to a breakdown of tolerance of the maternal–fetal interface and, subsequently, can result in preterm birth. This review is focused on the role of dNK cells in normal pregnancy and pathological pregnancy, including preeclampsia, recurrent spontaneous abortion, endometriosis, and recurrent implantation failure. dNK cells could be targets for the treatment of pregnancy complications.

Prokineticin 1-prokineticin receptor 1 signaling in trophoblast promotes embryo implantation and placenta development

Successful pregnancy establishment in mammals depends on proper embryo-maternal communication. Prokineticin 1 (PROK1) is a secretory protein that exerts pleiotropic functions in various tissues. Despite the studies that have primarily been performed with human cell lines and mice, the function of PROK1 in trophoblasts has still not been fully elucidated. Hence, the aim of this study was to establish the role of PROK1 in trophoblasts during implantation and placentation. Prokineticin 1 mRNA was elevated in porcine trophoblasts during implantation and the early placentation period. Furthermore, we reveal that PROK1–PROKR1 signaling induces the expression of genes involved in the regulation of angiogenesis, immunological response, trophoblast cell adhesion, invasion, and proliferation, as well as stimulating phosphorylation of MAPK and PTK2. Ingenuity Pathway Analysis identified the aforementioned and also other functions associated with PROK1-regulated genes/proteins, such as cell-to-cell contact, epithelial tissue differentiation, Ca2+ release, lipid synthesis, and chemotaxis. We also showed evidence that PROK1 acting via PROKR1 increased trophoblast cell proliferation and adhesion. The PROK1-stimulated cell proliferation was mediated by PI3K/AKT/mTOR, MAPK, and cAMP, whereas adhesion was mediated by MAPK and/or PI3K/AKT signaling pathways. Concluding, our study suggests that PROK1 plays a pleiotropic role in trophoblast function during implantation and early placentation.

Regulation of placentation by the transforming growth factor beta superfamily†

During pregnancy, there is increased expression of some cytokines at the fetal-maternal interface; and the clarification of their roles in trophoblast-endometrium interactions is crucial to understanding the mechanism of placentation. This review addresses the up-to-date reported mechanisms by which the members of the transforming growth factor beta superfamily regulate trophoblast proliferation, differentiation, and invasion of the decidua, which are the main phases of placentation. The available information shows that these cytokines regulate placentation in somehow a synergistic and an antagonistic manner; and that dysregulation of their levels can lead to aberrant placentation. Nevertheless, prospective studies are needed to reconcile some conflicting reports; and identify some unknown mediators involved in the actions of these cytokines before their detailed mechanistic regulation of human placentation could be fully characterized. The TGF beta superfamily are expressed in the placenta, and regulate the process of placentation through the activation of several signaling pathways.

The role of decidual natural killer cell derived soluble factors in early pregnancy

Decidual natural killer cell (dNK), the predominant decidual lymphocytes in early pregnancy, are primarily identified based on their CD56^bright CD16^- phenotype and play an important role in maintaining immune tolerance at the maternal-fetal interface. dNK dysfunction reportedly leads to pathological pregnancy. Indeed, various dNK-derived soluble factors are involved in a series of key processes related to pregnancy outcomes. In this review, we summarize the roles of these dNK-derived factors in immune tolerance and embryonic development to improve the current understanding regarding the physiological and pathological mechanisms that occur during pregnancy, while potentially informing the development of effective therapeutics.

Extracellular vesicles derived from M1 macrophages deliver miR-146a-5p and miR-146b-5p to suppress trophoblast migration and invasion by targeting TRAF6 in recurrent spontaneous abortion

Rationale: Emerging evidence demonstrates that insufficient migration and invasion of trophoblasts play critical roles in the pathogenesis of recurrent spontaneous abortion (RSA). Cell-to-cell communication at the maternal-fetal interface is essential to maintain the invasion and migration of trophoblasts. M1 macrophages, important immune cellular components at the maternal-fetal interface, have been reported to be elevated in decidua tissues from patients with RSA. Recent studies indicate that M1 macrophages modulate trophoblast biological behaviors; however, the underlying mechanisms remain poorly understood. Methods: Extracellular vesicles (EVs) were isolated from the supernatant of M1 macrophages inducted from THP-1 cells (M1-EVs) by ultracentrifugation, identified by transmission electron microscopy, nanoparticle tracking analysis, and western blotting, and their miRNA profile was characterized by miRNA sequencing. Scratch wound healing and transwell assays were used to investigate the effect of M1-EVs on trophoblast migration and invasion. RT-PCR, western blotting, and luciferase reporter assays were conducted to uncover the underlying mechanism. Finally, animal experiments were employed to explore the effect of M1-EVs on embryo absorption in mice. Results: M1 macrophages suppressed trophoblast EMT to reduce their migration and invasion abilities in vitro by secreting EVs. Through miRNA sequencing, miR-146a-5p and miR-146b-5p were identified as the most upregulated miRNAs in trophoblasts treated with M1-EVs. Further functional experiments showed that M1-EVs inhibited trophoblast migration and invasion by transferring miR-146a-5p and miR-146b-5p. Mechanistically, EV miR-146a-5p and miR-146b-5p inhibited EMT of trophoblasts by directly suppressing TNF receptor-associated factor 6 (TRAF6) expression at the post-transcriptional level. Furthermore, M1-EVs aggravated embryo absorption in mice. Clinically, expression of miR-146a-5p, miR-146b-5p, and TRAF6 were aberrant in placental villous tissues from patients with RSA, and negative correlations were found between miR-146a-5p/miR-146b-5p and TRAF6 expression levels. Conclusions: Our findings indicate that miR-146a-5p and miR-146b-5p derived from EVs play important roles in intercellular communication between M1 macrophages and trophoblasts, illuminating a novel mechanism in M1 macrophage regulation of trophoblasts and their role in RSA.

A crossroad between placental and tumor biology: What have we learnt?

Placenta in certain species including the human has evolved as a highly invasive tumor-like organ invading the uterus aned its vasculature to derive oxygen and nutrients for the fetus and exchange waste products. While several excellent reviews have been written comparing hemochorial placentation with tumors, no comprehensive review is available dealing with mechanistic insights into what makes them different, and what tumor biologists can learn from placental biologists, and vice versa. In this review, we analyze the structure-function relationship of the human placenta, emphasizing the functional need of the spatio-temporally orchestrated trophoblast invasiveness for fetal development and growth, and pathological consequences of aberrant invasiveness for fetal and maternal health. We then analyze similarities and differences between the placenta and invasive tumors in terms of hallmarks of cancer, some key molecules regulating their invasive functions, and how placental cancers (choriocarcinomas) or other cancers become refractory or even addicted to these invasion-restraining molecules. We cite in vitro models of human trophoblast and choriocarcinoma cell lines utilized to study mechanisms in normal placental development as well as those responsible for tumor progression. We discuss the pathobiology of hyper-invasive placentas and show thattrophoblastic neoplasias are a unique and heterogeneous class of tumors. We delve into the questions as to why metastasis from other organs rarely occurs at the placental site and whether pregnancy makes the mother more or less vulnerable to cancer-related morbidity/mortality. We attempt to compare trophoblast stem cells and cancer stem cells. Finally, we leave the readers with some thoughts as foods of future investigations.

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.

Angiopoietin 2 stimulates trophoblast invasion via a mechanism associated with JNK signaling

Extravillous trophoblast cell (EVT) invasion is tightly controlled, and its dysregulation can lead to altered spiral artery remodeling and contribute to a number of different pregnancy complications. Angiopoietin-2 (Ang-2) is expressed by trophoblast cells and various cells in the decidua, and trophoblast cells express its receptor, Tie2. Ang-2 has been shown to play roles in tumor progression and metastasis but it is not known if it also regulates EVT invasion. Here, we show that both the HTR-8/SVneo cell line and primary isolates of human EVT expressed various integrins and the Tie2 receptor, and Ang-2 stimulated their migration and/or invasion. Ang-2 increased expression of matrix metalloproteinase (MMP)2 and MMP9, altered the cytoskeleton of HTR-8/SVneo cells and also induced phosphorylation of Tie2, JNK and c-Jun. Inhibition of p-JNK (using SP600125) blocked the Ang-2 induced invasion of HTR-8/SVneo cells. In addition, inhibition of Tie2 (pexmetinib) and integrin signaling (RGDS and ATN-161) also blocked Ang-2-induced invasion. In conclusion, we demonstrate that Ang-2 can stimulate EVT invasion via a mechanism associated with activation of both the Tie2 receptor and integrins, which appear to work through different pathways; Tie2 through the JNK/c-JUN pathway and integrins through an as yet unidentified pathway(s). We therefore propose that any alterations in Ang-2 expression in the decidua would lead to an imbalance in pro- and anti-invasive factors, disrupting regulation of EVT invasion and spiral artery remodeling and thereby contribute to the etiology of several complications of pregnancy.

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.

Unconventional Actions of Glycoprotein Hormone Subunits: A Comprehensive Review

The glycoprotein hormones (GPH) are heterodimers composed of a common α subunit and a specific β subunit. They act by activating specific leucine-rich repeat G protein-coupled receptors. However, individual subunits have been shown to elicit responses in cells devoid of the receptor for the dimeric hormones. The α subunit is involved in prolactin production from different tissues. The human chorionic gonadotropin β subunit (βhCG) plays determinant roles in placentation and in cancer development and metastasis. A truncated form of the thyrotropin (TSH) β subunit is also reported to have biological effects. The GPH α- and β subunits are derived from precursor genes (gpa and gpb, respectively), which are expressed in most invertebrate species and are still represented in vertebrates as GPH subunit paralogs (gpa2 and gpb5, respectively). No specific receptor has been found for the vertebrate GPA2 and GPB5 even if their heterodimeric form is able to activate the TSH receptor in mammals. Interestingly, GPA and GPB are phylogenetically and structurally related to cysteine-knot growth factors (CKGF) and particularly to a group of antagonists that act independently on any receptor. This review article summarizes the observed actions of individual GPH subunits and presents the current hypotheses of how these actions might be induced. New approaches are also proposed in light of the evolutionary relatedness with antagonists of the CKGF family of proteins.

Vitamin D Promotes Trophoblast Cell Induced Separation of Vascular Smooth Muscle Cells in Vascular Remodeling via Induction of G-CSF

Vitamin D deficiency is associated with complications of pregnancy such as pre-eclampsia, fetal growth restriction, and miscarriage, all of which are also associated with incomplete spiral artery (SpA) remodeling. We have previously shown that both uterine natural killer (uNK) cells and extravillous trophoblast cells (EVT) are required for successful SpA remodeling, but whether their activity in this process is modulated by vitamin D is not known. In the current study, we use a previously described chorionic plate artery (CPA) ex vivo model of vascular remodeling to determine the effects of 1,25(OH)₂D treated uNK cell, placental explant (PEx), and uNK/PEx conditioned medium (CM) on vascular smooth muscle cell (VSMC) disorganization and phenotypic switching. Significant results were followed up in VSMCs in vitro. We demonstrate that 1,25(OH)₂D can enhance the ability of PEx to induce SpA remodeling, via a mechanism associated with increased secretion of granulocyte-colony stimulating factor (G-CSF). G-CSF appears able to increase VSMC disorganization and phenotypic switching in both an ex vivo vascular model and in vitro VSMC cultures. The clinical relevance of these findings are still to be determined. G-CSF may have differential effects depending on dose and vascular bed, and vitamin D may play a role in potentiating these actions. G-CSF may be an interesting potential therapeutic target for facilitating physiological vascular remodeling for the prevention of adverse obstetric outcomes.

Zika virus infection of first trimester trophoblast cells affects cell migration, metabolism and immune homeostasis control

Zika virus (ZIKV) re-emerged after circulating almost undetected for many years and the last spread in 2015 was the major outbreak reported. ZIKV infection was associated with congenital fetal growth anomalies such as microcephaly, brain calcifications, and low birth weight related to fetal growth restriction. In this study, we investigated the effect of ZIKV infection on first trimester trophoblast cell function and metabolism. We also studied the interaction of trophoblast cells with decidual immune populations. Results presented here demonstrate that ZIKV infection triggered a strong antiviral response in first trimester cytotrophoblast-derived cells, impaired cell migration, increased glucose uptake and GLUT3 expression, and reduced brain derived neurotrophic factor (BDNF) expression. ZIKV infection also conditioned trophoblast cells to favor a tolerogenic response since an increased recruitment of CD14+ monocytes bearing an anti-inflammatory profile, increased CD4+ T cells and NK CD56^Dim and NK CD56^Bright populations and an increment in the population CD4+ FOXP3+ IL-10+ cells was observed. Interestingly, when ZIKV infection of trophoblast cells occurred in the presence of the vasoactive intestinal peptide (VIP) there was lower detection of viral RNA and reduced toll-like receptor-3 and viperin messenger RNA expression, along with reduced CD56^Dim cells trafficking to trophoblast conditioned media. The effects of ZIKV infection on trophoblast cell function and immune-trophoblast interaction shown here could contribute to defective placentation and ZIKV persistence at the fetal-maternal interface. The inhibitory effect of VIP on ZIKV infection of trophoblast cells highlights its potential as a candidate molecule to interfere ZIKV infection during early pregnancy.

Tuning Trophoblast Motility in a Gelatin Hydrogel via Soluble Cues from the Maternal-Fetal Interface

Trophoblast cells play multiple critical roles in pregnancy, notably modulating blastocyst attachment to the endometrium as well as invading into and actively remodeling the endometrium to facilitate biotransport needs of the growing embryo. Despite the importance of trophoblast invasion for processes essential at early stages of pregnancy, much remains unknown regarding the balance of signaling molecules that may influence trophoblast invasion into the endometrium. The goal of this study was to use three-dimensional trophoblast spheroid motility assays to examine the effect of cues from the maternal-fetal interface on trophoblast motility. We report use of a methacrylamide-functionalized gelatin hydrogel to support quantitative analysis of trophoblast outgrowth area and cell viability. We show that this multidimensional model of trophoblast motility can resolve quantifiable differences in outgrowth area and viability in the presence of a known invasion promoter, epidermal growth factor, and a known invasion inhibitor, transforming growth factor β1. We then investigate the sensitivity of trophoblast motility to cortisol, a hormone associated with exogenous stressors. Together, this approach provides a toolset to investigate the coordinated action of physiological and pathophysiological processes on early stages of trophoblast invasion.

Differential expression of serum proteins before 20 weeks gestation in women with hypertensive disorders of pregnancy: A potential role for SH3BGRL3

INTRODUCTION

The objective of this study was to explore serum levels of differentially abundant proteins between women with hypertensive disorders of pregnancy (HDP) and women with normal-term pregnancy, and to explore the contribution of SH3BGRL3 to the pathogenesis of HDP.

METHODS

At 6-20 weeks gestation 48 pregnant women who later developed HDP (HDP group) and 48 women with normal-term pregnancy (normal group) were recruited based on maternal age and gestational age at a 1:1 ratio. Total serum protein was extracted, denatured, deoxidized, and subjected to enzymolysis. The sample was labeled with Tandem Mass Tags and analyzed via mass spectroscopy to identify differentially abundant proteins. The role of SH3BGRL3 in trophoblast invasion, proliferation and apoptosis was examined using the HTR-8/SVneo cell line and primary isolates of extravillous trophoblast (EVT) cells.

RESULTS

In the proteomic profiling analysis, there were 19 proteins that showed significant differential abundance (P < 0.05). Among them, 13 proteins were more abundant and 6 proteins were less abundant in the serum from the HDP group compared with the normal group. The function of one of the more abundant proteins, SH3BGRL3, in trophoblast cell invasion, proliferation and apoptosis was investigated. Treatment of the EVT cells or the HTR-8/SVneo cell line with anti-SH3BGRL3 inhibited proliferation, but stimulated both apoptosis and invasion. MMP2 and p-ERK levels were also decreased in EVT after anti-SH3BGRL3 treatment.

DISCUSSION

The SH3BGRL3 protein can regulate various aspects of trophoblast biology, and may be useful in the clinical diagnosis of HDP.

Tuning trophoblast motility in a gelatin hydrogel via soluble cues from the maternal-fetal interface

Trophoblast cells play multiple critical roles in pregnancy, notably modulating blastocyst attachment to the endometrium as well as invading into and actively remodeling the endometrium to facilitate biotransport needs of the growing embryo. Despite the importance of trophoblast invasion for processes essential at early stages of pregnancy, much remains unknown regarding the balance of signaling molecules that may influence trophoblast invasion into the endometrium. The goal of this study was to use three-dimensional trophoblast spheroid motility assays to examine the effect of cues from the maternal-fetal interface on trophoblast motility. We report use of a methacrylamide-functionalized gelatin (GelMA) hydrogel to support quantitative analysis of trophoblast outgrowth area and cell viability. We show this multidimensional model of trophoblast motility can resolve quantifiable differences in outgrowth area and viability in the presence of a known invasion promoter, epidermal growth factor, and a known invasion inhibitor, transforming growth factor β1. We then investigate the sensitivity of trophoblast motility to cortisol, a hormone associated with exogenous stressors. Together, this approach provides a toolset to investigate the coordinated action of physiological and pathophysiological processes on early stages of trophoblast invasion.

MicroRNA-27a inhibits trophoblast cell migration and invasion by targeting SMAD2: Potential role in preeclampsia

Preeclampsia (PE) is a severe idiopathic obstetric complication that occurs worldwide. Insufficient trophoblast invasion is a characteristic of the pathogenesis of PE. MicroRNA-27a (miR-27a) has been reported to be highly expressed in PE placentas. The aim of the present study was to investigate the role and underlying mechanisms of miR-27a in the pathogenesis of PE. The expression level of miR-27a was evaluated in the placenta and serum from patients with PE and healthy pregnant women. Cell Counting Kit-8 and flow cytometry assays were performed to detect human HTR-8/SVneo trophoblast proliferation and apoptosis after miR-27a overexpression or inhibition. In addition, Transwell assays were used to measure cell migration and invasion. A luciferase reporter assay was performed to determine the interaction between miR-27a and SMAD2. The present results suggested that miR-27a expression level was significantly increased in PE placentas and serum. In addition, miR-27a overexpression suppressed cell migratory and invasive abilities, impaired proliferation and promoted apoptosis in human trophoblasts. It was demonstrated that miR-27a may target SMAD and contribute to trophoblast invasion. Collectively, the results of the present study suggested that miR-27a inhibited trophoblast cell migration and invasion by targeting SMAD2, thus presenting a promising therapeutic target for PE.

Matrix metalloproteinase 15 plays a pivotal role in human first trimester cytotrophoblast invasion and is not altered by maternal obesity

Adequate anchoring of the placenta in the uterus through invasion of first trimester cytotrophoblasts (CTB) is required for a successful pregnancy. This process is mediated by matrix metalloproteinases (MMPs) and regulated by the maternal environment. Obesity is known to alter the intrauterine milieu and has been related to impaired invasion. We hypothesized that placental MMP15, a novel membrane‐type MMP, is involved in CTB invasion and regulated by maternal obesity in early pregnancy. Thus, in this study MMP15 was immunolocalized to invasive extravillous and interstitial CTB. MMP15 silencing in chorionic villous explants using two different siRNAs reduced trophoblast outgrowth length (−35%, P ≤ .001 and −26%, P < .05) and area (−43%, P ≤ .001 and −36%, P ≤ .01) without altering trophoblast proliferation or apoptosis. Short‐term treatment of primary first trimester trophoblasts with IL‐6 (10 ng/mL), interleukin 10 (IL‐10) (50 ng/mL), and tumor necrosis factor α (TNF‐α) (10 ng/mL) did not affect MMP15 protein levels. Likewise, MMP15 mRNA and protein levels were unaltered between human first trimester placentas from control pregnancies vs those complicated with maternal obesity. Overall, our results suggest that the role of MMP15 in placental development and function in early pregnancy is limited to CTB invasion without being affected by short‐ and long‐term inflammation.

Regulatory T Cells in Pregnancy: It Is Not All About FoxP3

In pregnancy, the semi-allogeneic fetus needs to be tolerated by the mother's immune system. Regulatory T cells (Tregs) play a prominent role in this process. Novel technologies allow for in-depth phenotyping of previously unidentified immune cell subsets, which has resulted in the appreciation of a vast heterogeneity of Treg subsets. Similar to other immunological events, there appears to be great diversity within the Treg population during pregnancy, both at the maternal-fetal interface as in the peripheral blood. Different Treg subsets have distinct phenotypes and various ways of functioning. Furthermore, the frequency of individual Treg subsets varies throughout gestation and is altered in aberrant pregnancies. This suggests that distinct Treg subsets play a role at different time points of gestation and that their role in maintaining healthy pregnancy is crucial, as reflected for instance by their reduced frequency in women with recurrent pregnancy loss. Since pregnancy is essential for the existence of mankind, multiple immune regulatory mechanisms and cell types are likely at play to assure successful pregnancy. Therefore, it is important to understand the complete microenvironment of the decidua, preferably in the context of the whole immune cell repertoire of the pregnant woman. So far, most studies have focused on a single mechanism or cell type, which often is the FoxP3 positive regulatory T cell when studying immune regulation. In this review, we instead focus on the contribution of FoxP3 negative Treg subsets to the decidual microenvironment and their possible role in pregnancy complications. Their phenotype, function, and effect in pregnancy are discussed.

The TGFβ Family in Human Placental Development at the Fetal-Maternal Interface

Emerging data suggest that a trophoblast stem cell (TSC) population exists in the early human placenta. However, in vitro stem cell culture models are still in development and it remains under debate how well they reflect primary trophoblast (TB) cells. The absence of robust protocols to generate TSCs from humans has resulted in limited knowledge of the molecular mechanisms that regulate human placental development and TB lineage specification when compared to other human embryonic stem cells (hESCs). As placentation in mouse and human differ considerably, it is only with the development of human-based disease models using TSCs that we will be able to understand the various diseases caused by abnormal placentation in humans, such as preeclampsia. In this review, we summarize the knowledge on normal human placental development, the placental disease preeclampsia, and current stem cell model systems used to mimic TB differentiation. A special focus is given to the transforming growth factor-beta (TGFβ) family as it has been shown that the TGFβ family has an important role in human placental development and disease.

Innate Lymphoid Cells at the Maternal-Fetal Interface in Human Pregnancy

Pregnancy constitutes a major challenge to the maternal immune system, which must tolerate fetal alloantigen encoded by paternal genes. In addition to their role in inducing maternal-fetal immune tolerance, accumulating evidence indicates that decidual immune cells are involved in several processes required for a successful pregnancy, including trophoblast invasion as well as tissue and spiral artery remodeling. Innate lymphoid cells (ILCs), an important branch of the innate immune system, which has expanded rapidly in recent years, are strong actors in mucosal immunity, tissue homeostasis and metabolism regulation. With the recent identification of ILCs in the human decidua, the role of ILCs at the maternal-fetal interface raises concern. Herein, we review the presence and characterization of ILCs in the human decidua, as well as their function in normal pregnancy and pathological pregnancy, including reproductive failure, preeclampsia and others.

Altered decidual and placental catabolism of vitamin D may contribute to the aetiology of spontaneous miscarriage

INTRODUCTION

Vitamin D catabolizing enzymes, along with vitamin D receptor (VDR) and vitamin D binding protein (DBP) are expressed in the decidua and placenta during pregnancy and capable of synthesizing active vitamin D. Vitamin D plays roles in immunoregulation and trophoblast invasion, key features of a successful pregnancy. Epidemiological data suggests that vitamin D deficiency is associated with both spontaneous and recurrent miscarriage but few studies have investigated the expression of the key vitamin D catabolizing enzymes in miscarriage.

METHODS

Placenta and decidua were collected after termination of apparently normal pregnancies (controls, n = 22) or spontaneous miscarriage (n = 20). Immunohistochemical staining, Western Blot and qRT-PCR were performed for CYP27B1, CYP24A1, CYP2R1, VDR and DBP (not qRT-PCR). HTR-8/SVneo cells were cultured in CoCL₂ (hypoxic mimetic) or LPS (bacterial infection mimetic) for 24 h, RNA extracted and qRT-PCR performed for CYP27B1, CYP24A1, CYP2R1 and VDR.

RESULTS

In spontaneous miscarriage, placental and decidual expression of CYP27B1 was reduced, while expression of CYP24A1, VDR and DBP was increased. When a trophoblast cell line was treated with CoCL₂ expression of CYP27B1 was increased and CYP24A1 was reduced, while LPS induced expression of VDR.

DISCUSSION

This is the first report of altered utero-placental vitamin D catabolism in spontaneous miscarriage. It is becoming accepted that women who are undergoing assisted reproductive technologies should ensure they have sufficient vitamin D levels prior to pregnancy, these data support that all women should ensure they are vitamin D replete before planning to get pregnant.

HTR-8/SVneo: A model for epithelial to mesenchymal transition in the human placenta

INTRODUCTION

The placenta is a transitory organ essential for proper fetal maturation and growth. Trophoblasts, the main cell type of the placenta, differentiate along the villous or extravillous pathways. The ability of villous cytotrophoblasts to undergo an epithelial-to-mesenchymal transition to form the invasive extravillous trophoblasts is vital for a successful pregnancy outcome. Many trophoblastic cell lines, including HTR-8/SVneo, have been widely used to investigate extravillous trophoblast biology and functions. We have previously reported that HTR-8/SVneo cell line contains a mixed populations of epithelial and mesenchymal cells. Uncovering the mechanisms underlying this heterogeneity is essential for the proper study of normal and pathological placental function.

METHODS

HTR-8/SVneo was subjected to monoclonal isolation, spheroid formation assay and cell sorting to isolate pure epithelial and mesenchymal populations. These fractions were maintained in culture and assessed for expression of epithelial and mesenchymal markers using quantitative real-time PCR and immunofluorescence. In addition, the implication of TGFβ in the EMT process was investigated using a selective inhibitor of TGF-βR1 (A83-01).

RESULTS

Passaging of the pure epithelial population maintained under normal culture condition resulted in a shift to a mesenchymal phenotype. This transition was reduced upon inhibiting TGF-βR1. Similarly, E-cadherin positive HTR-8/SVneo spheroids plated in 2D culture resulted in the emergence of streams of invading mesenchymal cells.

DISCUSSION

HTR-8/SVneo cell line is undergoing EMT under normal culture condition and TGFβ is a key mediator of this process. Our results raise the possibility of using HTR-8/SVneo cell line as a model to investigate EMT in extravillous trophoblast cells.

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.

Hyperglycosylated human chorionic gonadotropin as a predictor of ongoing pregnancy

BACKGROUND

Hyperglycosylated human chorionic gonadotropin, the predominant human chorionic gonadotropin variant secreted following implantation, is associated with trophoblast invasion.

OBJECTIVE

To determine whether the initial serum hyperglycosylated human chorionic gonadotropin differs between ongoing and failed pregnancies, and to compare it to total serum human chorionic gonadotropin as a predictor of ongoing pregnancy.

MATERIALS AND METHODS

Women undergoing fresh/frozen in vitro fertilization cycles at a university-based infertility clinic with an autologous day 5 single embryo transfer resulting in serum human chorionic gonadotropin >3 mIU/mL (n = 115) were included. Human chorionic gonadotropin was measured 11 days after embryo transfer in a single laboratory (coefficient of variation <6%). Surplus frozen serum (-80^oC) was shipped to Quest Laboratories for measurement of hyperglycosylated human chorionic gonadotropin (coefficient of variation <9.1%). Linear regression analyses adjusted for oocyte age a priori were used to compare human chorionic gonadotropin and hyperglycosylated human chorionic gonadotropin in ongoing pregnancies (>8 weeks of gestation) and failed pregnancies (clinical pregnancy loss, biochemical and ectopic pregnancies).

RESULTS

A total of 85 pregnancies (73.9%) were ongoing. Hyperglycosylated human chorionic gonadotropin and human chorionic gonadotropin values were highly correlated (Pearson correlation coefficient 92.14, P < .0001), and mean values of both were positively correlated with blastocyst expansion score (P value test for trend < .0004). Mean human chorionic gonadotropin and hyperglycosylated human chorionic gonadotropin were significantly higher in ongoing vs failed pregnancies. Among ongoing pregnancies vs clinical losses, mean hyperglycosylated human chorionic gonadotropin, but not human chorionic gonadotropin, was significantly higher (19.0 vs 12.2 ng/mL, β -8.1, 95% confidence interval -13.0 to -3.2), and hyperglycosylated human chorionic gonadotropin comprised a higher proportion of total human chorionic gonadotropin (4.6% vs 4.1%; risk ratio, 0.79; 95% confidence interval, 0.66-0.94).

CONCLUSION

Measured 11 days after single blastocyst transfer, hyperglycosylated human chorionic gonadotropin and human chorionic gonadotropin values were highly correlated, but only mean hyperglycosylated human chorionic gonadotropin and its ratio to total human chorionic gonadotropin were significantly higher in ongoing pregnancies vs clinical pregnancy losses. Further evaluation of hyperglycosylated human chorionic gonadotropin, including in multiple embryo transfers and multiple pregnancy, and using serial measurements, is required.

MicroRNAs in Uteroplacental Vascular Dysfunction

Pregnancy complications of preeclampsia and intrauterine growth restriction (IUGR) are major causes of maternal and perinatal/neonatal morbidity and mortality. Although their etiologies remain elusive, it is generally accepted that they are secondary to placental insufficiency conferred by both failure in spiral artery remodeling and uteroplacental vascular malfunction. MicroRNAs (miRNAs) are small no-coding RNA molecules that regulate gene expression at the post-transcriptional level. Increasing evidence suggests that miRNAs participate in virtually all biological processes and are involved in numerous human diseases. Differentially expressed miRNAs in the placenta are typical features of both preeclampsia and IUGR. Dysregulated miRNAs target genes of various signaling pathways in uteroplacental tissues, contributing to the development of both complications. In this review, we provide an overview of how aberrant miRNA expression in preeclampsia and IUGR impacts the expression of genes involved in trophoblast invasion and uteroplacental vascular adaptation.

A gelatin hydrogel to study endometrial angiogenesis and trophoblast invasion

The endometrium is the lining of the uterus and site of blastocyst implantation. Each menstrual cycle, the endometrium cycles through rapid phases of growth, remodelling and breakdown. Significant vascular remodelling is also driven by trophoblast cells that form the outer layer of the blastocyst. Trophoblast invasion and remodelling enhance blood flow to the embryo ahead of placentation. Understanding the mechanisms of endometrial vascular remodelling and trophoblast invasion would provide key insights into endometrial physiology and cellular interactions critical for establishment of pregnancy. The objective of this study was to develop a tissue engineering platform to investigate the processes of endometrial angiogenesis and trophoblast invasion in a three-dimensional environment. We report adaptation of a methacrylamide-functionalized gelatin hydrogel that presents matrix stiffness in the range of the native tissue, supports the formation of endometrial endothelial cell networks with human umbilical vein endothelial cells and human endometrial stromal cells as an artificial endometrial perivascular niche and the culture of an endometrial epithelial cell layer, enables culture of a hormone-responsive stromal compartment and provides the capacity to monitor the kinetics of trophoblast invasion. With these studies, we provide a series of techniques that will instruct researchers in the development of endometrial models of increasing complexity.

New Insights into the Process of Placentation and the Role of Oxidative Uterine Microenvironment

For a successful pregnancy to occur, a predecidualized receptive endometrium must be invaded by placental differentiated cells (extravillous trophoblast cells (EVTs)) and, at the same time, continue decidualization. EVT invasion is aimed at anchoring the placenta to the maternal uterus and ensuring local blood supply increase necessary to provide normal placental and foetal development. The first is achieved by migrating through the maternal endometrium and deeper into the myometrium, while the second by transforming uterine spiral arteries into large vessels. This process is a tightly regulated battle comprising interests of both the mother and the foetus. Invading EVTs are required to perform a scope of functions: move, adhere, proliferate, differentiate, interact, and digest the extracellular matrix (ECM); tolerate hypoxia; transform the maternal spiral arteries; and die by apoptosis. All these functions are modulated by their surrounding microenvironment: oxygen, soluble factors (e.g., cytokines, growth factors, and hormones), ECM proteins, and reactive oxygen species. A deeper comprehension of oxidative uterine microenvironment contribution to trophoblast function will be addressed in this review.

Plausibility of trophoblastic-like regulation of cancer tissue

Background: Thus far, a well-established logical pattern of malignancy does not exist. The current approach to cancer properties is primarily descriptive with usually, for each of them, extensive analyses of the underlying associated biomolecular mechanisms. However, this remains a catalog and it would be valuable to determine the organizational chart that could account for their implementation, hierarchical links and input into tumor regulation.

Hypothesis: Striking phenotypic similarities exist between trophoblast (invasive and expanding early placenta) and cancer regarding cell functions, logistics of development, means of protection and capacity to hold sway over the host organism. The concept of cancer cell trophoblastic-like transdifferentiation appears to be a rational proposal in an attempt to explain this analogy and provide a consistent insight into how cancer cells are functioning. Should this concept be validated, it could pave the way to promising research and therapeutic perspectives given that the trophoblastic properties are vital for the tumor while they are permanently epigenetically turned off in normal cells. Specifically targeting expression of the trophoblastic master genes could thereby be envisaged to jeopardize the tumor and its metastases without, in principle, inducing adverse side effects in the healthy tissues.

Conclusion: A wide set of functional features of cancer tissue regulation, including some apparently paradoxical facts, was reviewed. Cancer cell misuse of physiological trophoblastic functions can clearly account for them, which identifies trophoblastic-like transdifferentiation as a likely key component of malignancy and makes it a potential relevant anticancer target.

Comparative Analysis of the Transcriptome and Proteome during Mouse Placental Development

The condition of the placenta is a determinant of the short- and long-term health of the mother and the fetus. However, critical processes occurring in early placental development, such as trophoblast invasion and establishment of placental metabolism, remain poorly understood. To gain a better understanding of the genes involved in regulating these processes, we utilized a multiomics approach, incorporating transcriptome, proteome, and phosphoproteome data generated from mouse placental tissue collected at two critical developmental time points. We found that incorporating information from both the transcriptome and proteome identifies genes associated with time point-specific biological processes, unlike using the proteome alone. We further inferred genes upregulated on the basis of the proteome data but not the transcriptome data at each time point, leading us to identify 27 genes that we predict to have a role in trophoblast migration or placental metabolism. Finally, using the phosphoproteome data set, we discovered novel phosphosites that may play crucial roles in the regulation of placental transcription factors. By generating the largest proteome and phosphoproteome data sets in the developing placenta, and integrating transcriptome analysis, we uncovered novel aspects of placental gene regulation.

Human trophoblast requires galectin-3 for cell migration and invasion

Invasive extravillous cytotrophoblast of the human placenta expresses galectins-1, -3, and -8 in vivo and in vitro. This study aimed to investigate the potential role of galectin-3 in cell migration and invasion, using recombinant human galectin-3 (rhgalectin-3), small molecule galectin inhibitor I₄₇, and galectin-3 silencing. HTR-8/SVneo cell migration was stimulated by rhgalectin-3 and reduced by I₄₇, which could be neutralised by rhgalectin-3. Inhibitor specificity and selectivity for the galectins expressed in extravillous trophoblast were validated in solid phase assays using recombinant galectin-1, -3, -8, confirming selectivity for galectin-3. HTR-8/SVneo cell migration and invasion, and invasion by isolated trophoblast cells in primary culture were significantly reduced in the presence of I_47, which could be restored by rhgalectin-3. Upon HTR-8/SVneo cell treatment with galectin-3 siRNA both LGALS3 and galectin-3 protein were dramatically decreased. Silencing of galectin-3 induced significant reduction in cell migration and invasion, which was restored by rhgalectin-3. The influence on known mediators of cell invasion, MMP2 and -9, and integrins α₁, α₅, and β₁ was followed in silenced cells, showing lower levels of MMPs and a large reduction in integrin subunit β₁. These results show that galectin-3 acts as a pro-invasive autocrine/paracrine factor in trophoblast in vitro.