Governing the invasive trophoblast: current aspects on intra- and extracellular regulation

Korean mistletoe lectin promotes proliferation and invasion of trophoblast cells through regulation of Akt signaling

Recently, Viscum album var. coloratum agglutinin (VCA) was shown to have various effects on cancer cells. However, most researchers are focused on high concentrations (1-1000 ng/ml) of VCA and its anti-cancer effects. Therefore, we wanted to know whether low concentrations of VCA have an effect on proliferation and invasion of human trophoblast cells (HTR-8/SVneo cell line). Cell proliferations at low concentration of VCA (1-10 pg/ml) were increased over 2-fold relative to the control. Also, gelatinolytic activities of matrix metalloproteinase-2 were increased after VCA treatment, while TIMP-1 expression was reduced. Furthermore, the expression of integrin subunits α5 and β1 were increased 1.5-fold when cells were treated with low dose of VCA (10 pg/ml). Lastly, VCA was able to promote trophoblast invasion through activation of the Akt signaling pathway. In conclusion, low concentrations of VCA can stimulate the ability of trophoblast cells to invade through the extracellular matrix in vitro.

The placenta in toxicology. Part IV: Battery of toxicological test systems based on human placenta

This review summarizes the potential and also some limitations of using human placentas, or placental cells and structures for toxicology testing. The placenta contains a wide spectrum of cell types and tissues, such as trophoblast cells, immune cells, fibroblasts, stem cells, endothelial cells, vessels, glands, membranes, and many others. It may be expected that in many cases the relevance of results obtained from human placenta will be higher than those from animal models due to species specificity of metabolism and placental structure. For practical and economical reasons, we propose to apply a battery of sequential experiments for analysis of potential toxicants. This should start with using cell lines, followed by testing placenta tissue explants and isolated placenta cells, and finally by application of single and dual side ex vivo placenta perfusion. With each of these steps, the relative workload increases while the number of feasible repeats decreases. Simultaneously, the predictive power enhances by increasing similarity with in vivo human conditions. Toxic effects may be detected by performing proliferation, vitality and cell death assays, analysis of protein and hormone expression, immunohistochemistry or testing functionality of signaling pathways, gene expression, transport mechanisms, and so on. When toxic effects appear at any step, the subsequent assays may be cancelled. Such a system may be useful to reduce costs and increase specificity in testing questionable toxicants. Nonetheless, it requires further standardization and end point definitions for better comparability of results from different toxicants and to estimate the respective in vivo translatability and predictive value.

The Lipid Transfer Protein StarD7: Structure, Function, and Regulation

The steroidogenic acute regulatory (StAR) protein-related lipid transfer (START) domain proteins constitute a family of evolutionarily conserved and widely expressed proteins that have been implicated in lipid transport, metabolism, and signaling. The 15 well-characterized mammalian START domain-containing proteins are grouped into six subfamilies. The START domain containing 7 mRNA encodes StarD7, a member of the StarD2/phosphatidylcholine transfer protein (PCTP) subfamily, which was first identified as a gene overexpressed in a choriocarcinoma cell line. Recent studies show that the StarD7 protein facilitates the delivery of phosphatidylcholine to the mitochondria. This review summarizes the latest advances in StarD7 research, focusing on the structural and biochemical features, protein-lipid interactions, and mechanisms that regulate StarD7 expression. The implications of the role of StarD7 in cell proliferation, migration, and differentiation are also discussed.

Control of extravillous trophoblast function by the eotaxins CCL11, CCL24 and CCL26

STUDY QUESTION

What are the effects of the eotaxin group of chemokines (CCL11, CCL24 and CCL26) on extravillous trophoblast (EVT) functions important during uterine decidual vessel remodelling?

SUMMARY ANSWER

CCL11, CCL24 and CCL26 can regulate EVT migration, invasion and adhesion, highlighting a potential regulatory role for these chemokines during uterine decidual spiral arteriole remodelling in the first trimester of human pregnancy.

WHAT IS KNOWN ALREADY

A successful human pregnancy depends on adequate remodelling of the uterine decidual spiral arterioles, a process carried out by EVT which invade from the placenta. The invasion by EVT into the maternal uterine decidual vessels is regulated by the interaction of many factors including members of the chemokine subfamily of cytokines.

STUDY DESIGN, SIZE, DURATION

This study used the HTR8/SVneo cell line as a model for invasive EVT. All experiments were repeated on at least three separate occasions.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effect of recombinant human CCL11, CCL24 and CCL26 on EVT migration and invasive potential was measured using the xCELLigence real-time system, wound-healing and Matrigel invasion assays, zymography to measure MMP activity and reverse zymography to measure TIMP activity. A commercially available adhesion assay was used to assess EVT adhesion to extracellular matrix proteins.

MAIN RESULTS AND THE ROLE OF CHANCE

All the three eotaxins were found to significantly stimulate migration of the EVT-derived cell line HTR8/SVneo (P < 0.05) with no significant changes in cell number following treatment with each chemokine (P > 0.05). All the three eotaxins significantly increased HTR8/SVneo invasion (P < 0.05) and MMP2 activity (P < 0.05) without any effects on TIMP2 activity (P > 0.05). All the three eotaxins significantly increased HTR8/SVneo cell binding to collagen IV (P < 0.05) and fibronectin (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This work has been conducted in vitro with a commonly used cell line model of EVT, HTR8/SVneo.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the first to comprehensively examine the effects of the eotaxin group of chemokines on EVT functions and demonstrates that all the three eotaxins have the ability to regulate EVT functions critical to their role in vessel remodelling. This identifies a new role for the eotaxin group of chemokines during placentation.

Differential expression of β-catenin and Dickkopf-1 in the third trimester placentas from normal and preeclamptic pregnancies: a comparative study

BACKGROUND

Beta-catenin is a key nuclear effector of Wnt signaling which could be antagonized by dickkopf-1(DKK1). Beta-catenin and DKK1 are involved in a variety of biological processes; however, their expression in the placenta with severe preeclampsia (PE) has not been elucidated. This study was aimed to detect the localization and compare the expression of beta-catenin and DKK1 in normal and preeclamptic placenta.

METHODS

Sixty pregnant women who underwent cesarean section were enrolled in this study, including 30 healthy pregnant women in the control group and 30 preeclamptic women in the severe PE group. Real-time polymerase chain reaction (real-time-PCR) and western blot were employed to detect the beta-catenin and DKK1 mRNA and protein expression levels, respectively, and their locations were evaluated by immunohistochemistry (IHC).

RESULTS

Our results indicated that beta-catenin and DKK1 were expressed predominantly in the syncytiotrophoblast and the extravillous trophoblast (EVT). The beta-catenin mRNA and protein expressions were significantly decreased, whereas the DKK1 significantly increased in preeclamptic placental tissues compared to normal placental controls.

CONCLUSIONS

In conclusion, decreased beta-catenin expression, as well as DKK1 over-expression might be associated with the process of the pathogenesis of PE. Further studies would elucidate their exact roles in the pathogenesis of PE.

Tolerance induction at the early maternal-placental interface through selective cell recruitment and targeting by immune polypeptides

Pregnancy challenges immune cells and immunomodulatory circuits of the mother and the developing fetus to dynamically adapt to each other in an homeostatic and tolerant environment for fetal growth. This entails the coordination of multiple cellular processes all devoted to accommodate and nourish the fetus while protecting the mother from endogenous and exogenous threatens. From the earliest stages of pregnancy, several strategies to efficiently communicate immune and trophoblast cells within the interface or at a distance were identified and chemokines might act at on different targets through direct or indirect mechanisms. Here, we briefly review some mechanisms of T regulatory cell recruitment to the early maternal-placental interfaces to accomplish immunotolerance and homeostatic control and we discuss evidence on two locally released polypeptides, RANTES (regulated on activation, normal, T-cell expressed, and secreted) and vasoactive intestinal peptide (VIP), as novel contributors to the multiplicity of immune tolerant responses and uterine quiescence requirements.

Association of Wnt2 and sFRP4 expression in the third trimester placenta in women with severe preeclampsia

BACKGROUND

The Wnt signaling pathway is a conserved pathway and plays a crucial role in regulating trophoblast functions. Abnormal expression of the Wnt pathway may result in the dysfunction of the trophoblast that can contribute to the pathogenesis of preeclampsia (PE). However, published data regarding the association between Wnt pathway and PE in human pregnancy is rare.

OBJECTIVE

The aims of this study were to investigate the expression pattern of Wnt2 and secreted frizzled-related protein 4 (sFRP4) in the third trimester human placenta and to evaluate the relationship between changes in placental Wnt2 and sFRP4 expression and severe PE.

METHODS

The expression of Wnt2 and sFRP4 in normal and severe PE placentas was examined using immunohistochemistry (IHC), real-time polymerase chain reaction, and Western blot.

RESULTS

Compared to the controls, the relative expression of Wnt2 messenger RNA was remarkably downregulated in the PE placentas, while there was no significant difference in sFRP4 between the 2 groups. The IHC indicated that Wnt2 and sFRP4 were expressed predominantly in the villous syncytiotrophoblast and the extravillous trophoblast, whereas Wnt2 in the control group showed higher staining intensity than in the PE group, and sFRP4 in the PE group had a higher staining intensity than in the control group. Furthermore, the results of the Western blots were consistent with the IHC.

CONCLUSIONS

The Wnt signaling pathway was detected in human third trimester placentas, and the decreased placental expression of Wnt2 and increased placental expression of sFRP4 may be associated with the pathogenesis of severe PE.

Kisspeptin-10 inhibits cell migration in vitro via a receptor-GSK3 beta-FAK feedback loop in HTR8SVneo cells

Kisspeptin inhibits cancer cell metastasis and placental trophoblast cell migration. Kisspeptin gene expression in the placenta and circulating kisspeptin levels change during normal pregnancy and they are altered in preeclampsia. We therefore assessed the effect of kisspeptin-10 on the in vitro migration of a human placental cell line derived from first trimester extravillious trophoblasts (HTR8SVneo). HTR8SVneo cells specifically bound 125I-Kisspeptin-10 but kisspeptin-10 did not induce inositol phosphate production. Cell migration was inhibited by kisspeptin-10 with a maximal inhibition at 100nM. The signaling pathways involved in inhibition of cell migration were examined. Treatment with kisspeptin-10 elicited phosphorylation of GSK3 beta at Ser9 (which inhibits activity), with a 3-fold increase at 5 min. Transient phosphorylation of ERK1/2 and p38MAPK peaked at 10min. Phosphorylation of focal adhesion kinase (FAK) at Tyr925 increased 3-fold at 10 min. Inhibition of GSK3 beta correlated with release of beta-catenin into the cytoplasm. These signaling events were differentially blocked by inhibitors of G(q/11), Src, EGFR, PI(3)K, PKC and MEK. The data suggest that kisspeptin/GPR54 EGF-receptor transactivation leads to phosphorylation of ERK1/2, causing activation of p90rsk which in turn inhibits GSK3 beta via Ser9 phosphorylation. Inactivation of GSK3 beta results in release of beta-catenin into the cytoplasm, affecting cell-cell adhesion and Tyr925 phosphorylation of FAK, which increases phosphorylation of ERK1/2 via RAS/Raf-1 creating a feedback loop to enhance the effects on migration. These findings indicate that kisspeptin-10 inhibits the migration of human placental trophoblast-derived HTR8SVneo cells by stimulating complex ERK1/2-p90rsk-GSK3 beta-FAK feedback interactions.

Thymic stromal lymphopoietin promotes the proliferation of human trophoblasts via phosphorylated STAT3-mediated c-Myc upregulation

Our previous study has demonstrated that thymic stromal lymphopoietin (TSLP) stimulates trophoblast proliferation and invasion, suggesting TSLP plays an important role in the placentation in early human pregnancy, but the intracellular molecular mechanism is currently unknown. The present study is undertaken to investigate whether the STAT3-c-Myc signaling pathway is involved in TSLP-mediated trophoblast proliferation. Primary human first-trimester trophoblasts were treated with TSLP only, or TSLP combined with different signaling inhibitors (STAT3, STAT5, AKT, and ERK). The levels of STAT3 tyrosine phosphorylation and c-Myc expression were determined by using Western blot analysis, and the proliferation of trophoblasts was analyzed by BrdU cell proliferation assay. JEG-3 cells were transfected with siRNA targeting to c-Myc, and the proliferation was determined in JEG-3 cells treated with TSLP only, or TSLP combined with c-Myc silencing. It was revealed that treatment with TSLP significantly enhanced STAT3 phosphorylation and c-Myc expression in human trophoblasts. The effect of TSLP upregulation on trophoblast proliferation was abrogated completely by either STAT3 inhibitor or c-Myc siRNA silence. We further found that the upregulation of TSLP on c-Myc expression was abrogated completely by the STAT3 inhibitor, which suggests that the intracellular STAT3 phosphorylation is an upstream signal of c-Myc expression in the TSLP-stimulated trophoblast proliferation. These results suggest that TSLP may upregulate c-Myc expression through activation of STAT3 pathway, thereby inducing trophoblast proliferation.

An in vitro model for the study of human implantation

PROBLEM

Implantation remains the rate-limiting step for the success of in vitro fertilization. Appropriate models to study the molecular aspects of human implantation are necessary in order to improve fertility.

METHODS

First trimester trophoblast cells are differentiated into blastocyst-like spheroids (BLS) by culturing them in low attachment plates. Immortalized human endometrial stromal cells and epithelial cells (ECC-1) were stably transfected with GFP or tdTomato. Co-culture experiments were monitored using Volocity imaging analysis system.

RESULTS

This method demonstrates attachment and invasion of BLS, formed by trophoblast cells, into stromal cells, but not to uterine epithelial cells.

CONCLUSION

We have developed an in vitro model of uterine implantation. The manipulation of this system allows for dual color monitoring of the cells over time. Additionally, specific compounds can be added to the culture media to test how this may affect implantation and invasion. This model is a helpful tool in understanding the complexity of human implantation.

Leukaemia inhibitory factor mediated proliferation of HTR-8/SVneo trophoblast cells is dependent on activation of extracellular signal-regulated kinase 1/2

Leukaemia inhibitory factor (LIF) is one of the cytokines that is indispensable for embryo implantation. The aim of the present study was to investigate the role of activation of extracellular signal-regulated kinase (ERK) 1/2 in LIF-mediated proliferation of HTR-8/SVneo cells. Stimulation of HTR-8/SVneo cells with LIF (50 ng mL(-1)) resulted in an increase in cell proliferation (P < 0.05) via increased transition of cells to the G(2)/M phase of cell cycle. Stimulation with LIF resulted in the activation of both signal transducer and activator of transcription (STAT) 3 Tyr(705) and ERK1/2, but inhibition of ERK1/2 signalling by pretreatment of cells with U0126 (10 µM) for 2h resulted in abrogation of LIF-mediated increases in G(2)/M transition, with a significant decrease (P < 0.05) in absolute cell numbers compared with control. Although STAT3 silencing had no effect on LIF-dependent proliferation of HTR-8/SVneo cells, it did result in an increase in cell apoptosis, which increased further upon inhibition of ERK1/2 activation irrespective of LIF stimulation. Stimulation of cells with LIF increased the Bcl-2/Bax ratio, whereas ERK1/2 inhibition decreased the Bcl-2/Bax ratio, even after LIF stimulation. Hence, it can be inferred that ERK1/2 activation is essential for LIF-mediated increases in proliferation and that both STAT3 and ERK1/2 activation are important for the survival of HTR-8/SVneo cells.

Does metformin influence the insulin-, IGF I- and IGF II-receptor gene expression and Akt phosphorylation in human decidualized endometrial stromal cells?

OBJECTIVE

To assess the effects of metformin on insulin-, IGF I-, and IGF II-receptor gene expression and Akt phosphorylation in decidualized human endometrial stromal cells (ESC) after stimulation with insulin, IGF I and II.

STUDY DESIGN

ESC were isolated from healthy, regularly cycling women and after two passages decidualized with estrogen/progesterone±metformin. Cells were incubated with insulin, IGF I or IGF II for 1, 5, and 10 min to assess Akt phosphorylation by Western blot. To investigate the insulin-, IGF I- and IGF II-receptor gene expression ESC were incubated with insulin, IGF I or IGF II for 6 and 24h.

RESULTS

Insulin- and IGF I-receptor gene expression in ESC changed significantly after incubation with insulin, IGF I or IGF II. This was further augmented in metformin pretreated cells, while IGF II-receptor gene expression changed particularly after pretreatment with metformin. Akt phosphorylation peaked after 5 min insulin, IGF I and IGF II stimulation in ESC in both control (control 0.08 ± 0.03 vs. insulin 0.74 ± 0.19, IGF I 0.68 ± 0.22, IGF II 0.53 ± 0.13, p<0.05) and metformin pretreated cells (control 0.03 ± 0.01 vs. insulin 0.75 ± 0.11, IGF I 0.74 ± 0.15, IGF II 0.67 ± 0.09, p<0.005). However, there was no significant difference between the control and metformin pretreated group.

CONCLUSION

Insulin, IGF I and IGF II lead to changes in their receptor gene expression and induced Akt phosphorylation in ESC. These effects were further highlighted in the presence of metformin.

StarD7 gene expression in trophoblast cells: contribution of SF-1 and Wnt-beta-catenin signaling

Steroidogenic acute regulatory protein-related lipid transfer domain containing 7 (StarD7) is a poorly characterized member of the steroidogenic acute regulatory protein-related lipid transfer proteins, up-regulated in JEG-3 cells, involved in intracellular transport and metabolism of lipids. Previous studies dealing with the mechanisms underlying the human StarD7 gene expression led us to define the cis-acting regulatory sequences in the StarD7 promoter using as a model JEG-3 cells. These include a functional T cell-specific transcription factor 4 (TCF4) site involved in Wnt-β-catenin signaling. To understand these mechanisms in more depth, we examined the steroidogenic factor 1 (SF-1) contribution to StarD7 expression. Cotransfection experiments in JEG-3 cells point out that the StarD7 promoter is activated by SF-1, and this effect is increased by forskolin. EMSA using JEG-3 nuclear proteins demonstrated that SF-1 binds to the StarD7 promoter. Additionally, chromatin immunoprecipitation analysis indicated that SF-1 and β-catenin are bound in vivo to the StarD7 promoter. Reporter gene assays in combination with mutations in the SF-1 and TCF4 binding sites revealed that the StarD7 promoter is synergistically activated by SF-1 and β-catenin and that the TCF4 binding site (-614/-608) plays an important role in this activation. SF-1 amino acid mutations involved in the physical interaction with β-catenin abolished this activation; thus demonstrating that the contact between the two proteins is necessary for an efficient StarD7 transcriptional induction. Finally, these data suggest that β-catenin could function as a bridge between SF-1 and TCF4 forming a ternary complex, which would stimulate StarD7 expression. The SF-1 and β-catenin pathway convergence on StarD7 expression may have important implications in the phospholipid uptake and transport, contributing to the normal trophoblast development.

Human decidua and invasive trophoblasts are rich sources of nearly all human matrix metalloproteinases

Trophoblast cell (CTB) invasion into the maternal endometrium plays a crucial role during human embryo implantation and placentation. As for all invasive cell types, the ability of CTB to infiltrate the uterine wall is facilitated by the activity of matrix metalloproteinases (MMPs), which is regulated by tissue inhibitors of MMPs (TIMPs). There is evidence for the expression of several MMPs and TIMPs in decidua. However, published data are limited. Therefore, to set a foundation for future research, we screened a panel of healthy human deciduas obtained during first, second and third trimester of pregnancy in addition to isolated decidual cell populations for the expression of all known human MMPs and TIMPs by RT-PCR, western blot and immunohistochemistry. In the decidual samples, we detected almost all MMPs and all four TIMPs at mRNA level. While the expression of proMMP-3 and active MMP-13 and -23 was down-regulated in the course of pregnancy, the pro forms of MMP-8, -19 and -23, active MMP-9, -10, -12, -15, -16, -26 and -28, and pro- and active MMP-14 increased towards the end of gestation. All MMPs and TIMPs were expressed in uterine natural killer cells, decidual fibroblasts and/or trophoblasts, with the exception of MMP-20 and -25. In summary, a remarkably broad spectrum of MMPs was expressed at the human feto-maternal interface, reflecting the highly invasive and remodelling effect on placenta formation. It can be speculated that expression of MMPs correlates with the invasive potential of CTBs together with a crucial role in activation of labour at term.