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

BACKGROUND

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

OBJECTIVE AND RATIONALE

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

SEARCH METHODS

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

OUTCOMES

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

WIDER IMPLICATIONS

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

Molecular mechanism of aberrant decidualization in adenomyosis leading to reduced endometrial receptivity

Patients with adenomyosis not only experience a decrease in quality of life as a result of dysmenorrhea and severe monthly flow but they are also rendered infertile. Pregnancy rates are still low among women with adenomyosis, even with assisted reproduction. According to the current study, endometrial receptivity is primarily responsible for the lower conception rate among patients with adenomyosis. Decidualization of endometrial stromal cells is the fundamental requirement for endometrial receptivity and the maintenance of a normal pregnancy, even though endometrial receptivity is made up of a variety of cells, including immune cells, endometrial epithelial cells, and endometrial stromal cells. Our overview reveals that endometriosis deficiencies are present in patients with adenomyosis. These flaws may be linked to aberrant pathways in endometrial stromal cells, such as PI3K/Akt, JAK2/STAT3, and hedgehog. Correcting the abnormal expression of molecules in endometrial stromal cells in the endometrium of patients with adenomyosis may become the focus of research to improve endometrial receptivity and increase the pregnancy rate.

Deciphering the role of rapamycin in modulating decidual senescence: implications for decidual remodeling and implantation failure

PURPOSE

Physiological decidual senescence promotes embryo implantation, whereas pathological decidual senescence causes many pregnancy pathologies. The aim of this study was to evaluate the effect of rapamycin on decidual cell subpopulations and endometrial function in physiological and induced senescence and to investigate the decidual cell subpopulations present in physiological conditions during early pregnancy and implantation in mice.

METHODS

Control, physiological decidualization (0.5 mM cAMP and 1 μM MPA added), and induced senescence (0.1 mM HU added) models with and without 200 nM rapamycin treatment were established using a human endometrial stromal cell line, and decidual cell subpopulations were analyzed by immunofluorescence and flow cytometry. The human extravillous trophoblast cell line AC-1M88 was also cultured in decidualization models, and spheroid expansion analysis was performed. In in vivo studies, decidual cell subpopulations were analyzed by immunofluorescence during early mouse pregnancy.

RESULTS

The results revealed that rapamycin decreased DIO2 and β-GAL expressions in physiological and induced senescence without FOXO1. Notably, in induced senescence, increased fragmentation was observed in AC-1M88 cells, and rapamycin treatment successfully attenuated the fragmentation of spheroids. We showed that the FOXO1-DIO2 signaling axis can trigger decidual senescence during early gestation and days of implantation in mice.

CONCLUSIONS

Our study underlines the importance of rapamycin in modulating decidual cell subpopulations and endometrial tissue function during decidual senescence. The information obtained may provide insight into the pathologies of pregnancy seen due to decidual senescence and guide better treatment strategies for reproductive problems.

The Multiple Functions of HB-EGF in Female Reproduction and Related Cancer: Molecular Mechanisms and Targeting Strategies

Heparin-binding growth factor (HB-EGF) is a member of the epidermal growth factor (EGF) ligand family which has a crucial role in women's health. However, there is a lack of comprehensive review to summarize the significance of HB-EGF. Therefore, this work first described the expression patterns of HB-EGF in the endometrium and ovary of different species and gestational time. Then, the focus was on exploring how it promotes the successful implantation and regulates the process of decidualization and the function of ovarian granulosa cells as an intermediate molecule. Otherwise, we also focused on the clinical and prognostic significance of HB-EGF in female-related cancers (including ovarian cancer, cervical cancer, and endometrial cancer) and breast cancer. Lastly, the article also summarizes the current drugs targeting HB-EGF in the treatment of ovarian cancer and breast cancer. Overall, these studies found that the expression of HB-EGF in the endometrium is spatiotemporal and species-specific. And it mediates the dialogue between the blastocyst and endometrium, promoting synchronous development of the blastocyst and endometrium as an intermediate molecule. HB-EGF may serve as a potentially valuable prognostic clinical indicator in tumors. And the specific inhibitor of HB-EGF (CRM197) has a certain anti-tumor ability, which can exert synergistic anti-tumor effects with conventional chemotherapy drugs. However, it also suggests that more research is needed in the future to elucidate its specific mechanisms and to accommodate clinical studies with a larger sample size to clarify its clinical value.

Losartan impairs HTR-8/SVneo trophoblast migration through inhibition of angiotensin II-induced pro-inflammatory profile in human endometrial stromal cells

A deep interaction between the endometrium and the invading trophoblast occurs during implantation in humans, with the acquisition of uterine receptivity to the invading embryo promoted by an elevation of pro-inflammatory cytokines in the endometrium, and the invasiveness of decidualizing endometrial stromal cells, augmented by trophoblast-derived signals. Considering that usage of angiotensin II type 1 (AT1) receptor blockers, among other renin-angiotensin system (RAS) antagonists, is associated with adverse pregnancy outcomes, here we aim to analyse the involvement of AT1 receptor in the reciprocal dialogue occurring between endometrial stroma and trophoblast cells. In human endometrial stromal cells (T-HESC) pre-incubated with a decidualization cocktail, angiotensin (Ang) II increased protein expression of prolactin and FOXO1, markers of endometrial decidualization, while promoting nuclear translocation of FOXO1. In addition, Ang II treatment increased CXCL8, and matrix metalloprotease (MMP)-2 levels in T-HESC. Incubation with the AT1 receptor blocker losartan or with an NFAT signalling inhibitor, decreased Ang II-induced secretion of prolactin, CXCL8, and MMP-2 in T-HESC. In a wound healing assay, conditioned medium (CM) obtained from Ang II-treated T-HESC, but not CM from losartan-pre-incubated T-HESC, increased migration of HTR-8/SVneo trophoblasts, effect that was inhibited in the presence of a CXCL8-neutralizing antibody. An increased secretion of CXCL8 and MMP-2 was observed after treatment of T-HESC with CM obtained from HTR-8/SVneo cells, which was not observed in T-HESC pre-incubated with losartan or with the NFAT inhibitor. This study evidenced a reciprocal RAS-coded messaging between trophoblast and ESC which is affected by the AT1 receptor blocker losartan.

Doxorubicin resistant choriocarcinoma cell line derived spheroidal cells exhibit stem cell markers but reduced invasion

Cell cycle-specific cancer chemotherapy is based on the ability of a drug to halt, minimise or destroy rapidly dividing cells. However, their efficacy is limited by the emergence of a self-renewing cell pool called “cancer stem cells” (CSC). Choriocarcinoma is a tumour of trophoblastic tissue. We, in this study, analysed whether spheroids generated from doxorubicin-treated and non-treated choriocarcinoma cell lines exhibit markers of stem cells. Two choriocarcinoma cell lines, namely JEG-3 and BeWo, were used in this study. Spheroids were generated from doxorubicin-treated cells and the non-treated cells under non-adherent condition, followed by analysis of stem-cell markers’ expression, namely NANOG, OCT4 and SOX2. Immunofluorescence analysis suggested a general increase in the markers’ concentration in spheroids relative to the parental cells. RT-qPCR and immunoblots showed an increase in the stem-cell marker expression in spheroids generated from doxorubicin-treated when compared to non-treated cells. In spheroids, Sox2 was significantly upregulated in doxorubicin-treated spheroids, whereas Nanog and Oct4 were generally downregulated when compared to non-treated spheroids. Both 2D and 3D invasion assays showed that the spheroids treated with doxorubicin exhibited reduced invasion. Our data suggest that choriocarcinoma cell lines may have the potential to produce spheroidal cells, yet the drug-treatment affected the invasion potential of spheroids.

Endocrine disrupting chemicals interfere with decidualization of human primary endometrial stromal cells in vitro

Multiple studies have shown associations between exposure to endocrine disrupting chemicals (EDCs) and reduced fertility in women. However, little is known about the target organs of chemical disruption of female fertility. Here, we focus on the hormone-sensitive uterine lining, the endometrium, as a potential target. Decidualization is the morphological and functional change that endometrial stromal cells undergo to support endometrial receptivity, which is crucial for successful implantation, placentation, and pregnancy. We investigated the effect of nine selected EDCs on primary human endometrial stromal cell decidualization in vitro. The cells were exposed to a decidualization-inducing mixture in the presence or absence of 1 μM of nine different EDCs for nine days. Extent of decidualization was assessed by measuring the activity of cAMP dependent protein kinase, Rho-associated coiled-coil containing protein kinase, and protein kinase B in lysates using photoluminescent probes, and secretion of prolactin into the media by using ELISA. Decidualization-inducing mixture upregulated activity of protein kinases and prolactin secretion in cells derived from all women. Of the tested chemicals, dichlorodiphenyldichloroethylene (p,p'-DDE), hexachlorobenzene (HCB) and perfluorooctanesulfonic acid (PFOS) significantly reduced decidualization as judged by the kinase markers and prolactin secretion. In addition, bisphenol A (BPA) reduced prolactin secretion but did not significantly affect activity of the kinases. None of the EDCs was cytotoxic, based on the assessment of total protein content or activity of the viability marker casein kinase 2 in lysates. These results indicate that EDCs commonly present in the blood circulation of reproductive-aged women can reduce decidualization of human endometrial stromal cells in vitro. Future studies should focus on detailed hazard assessment to define possible risks of EDC exposure to endometrial dysfunction and implantation failure in women.

Understanding menstrual blood-derived stromal/stem cells: Definition and properties. Are we rushing into their therapeutic applications?

Cells with mesenchymal stem cell properties have been identified in menstrual blood and termed menstrual blood-derived stem/stromal cells (MenSCs). MenSCs have been proposed as ideal candidates for cell-based therapy in regenerative medicine and immune-related diseases. However, MenSCs identity has been loosely defined so far and there is controversy regarding their cell markers and differentiation potential. In this review, we outline the origin of MenSCs in the context of regenerating human endometrium, with attention to endometrial eMSCs as reference cells to understand MenSCs. We summarize the cell identity markers analyzed and the immunomodulatory and reparative properties reported. We also address the recent use of MenSCs in cell reprogramming. The main goal of this review is to contribute to the understanding of the identity and properties of MenSCs as well as to identify potential caveats and new venues that deserve to be explored to strengthen their potential applications.

Interaction between insulin and androgen signalling in decidualization, cell migration and trophoblast invasion in vitro

Finely tuned decidualization of endometrial stromal fibroblasts into decidual cells is crucial for successful implantation and a healthy pregnancy. Both insulin and androgens are known to modulate decidualization, however, their complex effect on this process has not been fully elucidated. As hyperinsulinemia and hyperandrogenism are associated in clinical conditions, we aimed to investigate the interaction between insulin and androgens on decidualization. Primary human endometrial stromal cells were decidualized in vitro in the presence of insulin and/or androgens (dihydrotestosterone (DHT), testosterone). Gene or protein expressions of decidualization markers were measured, and cells size characteristics were determined. Migration of decidualizing endometrial stromal cells and invasion of HTR‐8/SVneo trophoblast spheroids were assessed. We found that insulin and androgens in combination enhanced the upregulation of several decidualization markers including prolactin, tissue factor, tissue inhibitor of matrix metalloproteinase 3 and connexin‐43, and also interacted in modulating cell size characteristics resulting in enlarged decidualizing cells. However, insulin and DHT together restricted the migration of decidualizing cells and invasion of trophoblast spheroids. Our findings suggest that insulin and androgens interact to potentiate the process of decidualization. On the other hand, inhibited cell migration and trophoblast invasion might negatively impact the function of decidualizing endometrial stromal cells.

Building a stem cell-based primate uterus

The uterus is the organ for embryo implantation and fetal development. Most current models of the uterus are centred around capturing its function during later stages of pregnancy to increase the survival in pre-term births. However, in vitro models focusing on the uterine tissue itself would allow modelling of pathologies including endometriosis and uterine cancers, and open new avenues to investigate embryo implantation and human development. Motivated by these key questions, we discuss how stem cell-based uteri may be engineered from constituent cell parts, either as advanced self-organising cultures, or by controlled assembly through microfluidic and print-based technologies.

Embryo implantation in the laboratory: an update on current techniques

BACKGROUND

The embryo implantation process is crucial for the correct establishment and progress of pregnancy. During implantation, the blastocyst trophectoderm cells attach to the epithelium of the endometrium, triggering intense cell-to-cell crosstalk that leads to trophoblast outgrowth, invasion of the endometrial tissue, and formation of the placenta. However, this process, which is vital for embryo and foetal development in utero, is still elusive to experimentation because of its inaccessibility. Experimental implantation is cumbersome and impractical in adult animal models and is inconceivable in humans.

OBJECTIVE AND RATIONALE

A number of custom experimental solutions have been proposed to recreate different stages of the implantation process in vitro, by combining a human embryo (or a human embryo surrogate) and endometrial cells (or a surrogate for the endometrial tissue). In vitro models allow rapid high-throughput interrogation of embryos and cells, and efficient screening of molecules, such as cytokines, drugs, or transcription factors, that control embryo implantation and the receptivity of the endometrium. However, the broad selection of available in vitro systems makes it complicated to decide which system best fits the needs of a specific experiment or scientific question. To orient the reader, this review will explore the experimental options proposed in the literature, and classify them into amenable categories based on the embryo/cell pairs employed.The goal is to give an overview of the tools available to study the complex process of human embryo implantation, and explain the differences between them, including the advantages and disadvantages of each system.

SEARCH METHODS

We performed a comprehensive review of the literature to come up with different categories that mimic the different stages of embryo implantation in vitro, ranging from initial blastocyst apposition to later stages of trophoblast invasion or gastrulation. We will also review recent breakthrough advances on stem cells and organoids, assembling embryo-like structures and endometrial tissues.

OUTCOMES

We highlight the most relevant systems and describe the most significant experiments. We focus on in vitro systems that have contributed to the study of human reproduction by discovering molecules that control implantation, including hormones, signalling molecules, transcription factors and cytokines.

WIDER IMPLICATIONS

The momentum of this field is growing thanks to the use of stem cells to build embryo-like structures and endometrial tissues, and the use of bioengineering to extend the life of embryos in culture. We propose to merge bioengineering methods derived from the fields of stem cells and reproduction to develop new systems covering a wider window of the implantation process.

Molecules and Prostaglandins Related to Embryo Tolerance

It is generally understood that the entry of semen into the female reproductive tract provokes molecular and cellular changes facilitating conception and pregnancy. We show a broader picture of the participation of prostaglandins in the fertilization, implantation and maintenance of the embryo. A large number of cells and molecules are related to signaling networks, which regulate tolerance to implantation and maintenance of the embryo and fetus. In this work, many of those cells and molecules are analyzed. We focus on platelets, polymorphonuclear leukocytes, and group 2 innate lymphoid cells involved in embryo tolerance in order to have a wider view of how prostaglandins participate. The combination of platelets and neutrophil extracellular traps (Nets), uterine innate lymphoid cells (uILC), Treg cells, NK cells, and sex hormones have an important function in immunological tolerance. In both animals and humans, the functions of these cells can be regulated by prostaglandins and soluble factors in seminal plasma to achieve an immunological balance, which maintains fetal-maternal tolerance. Prostaglandins, such as PGI2 and PGE2, play an important role in the suppression of the previously mentioned cells. PGI2 inhibits platelet aggregation, in addition to IL-5 and IL-13 expression in ILC2, and PGE2 inhibits some neutrophil functions, such as chemotaxis and migration processes, leukotriene B4 (LTB4) biosynthesis, ROS production, and the formation of extracellular traps, which could help prevent trophoblast injury and fetal loss. The implications are related to fertility in female when seminal fluid is deposited in the vagina or uterus.

Alterations in Epithelial Cell Polarity During Endometrial Receptivity: A Systematic Review

Background

Abnormal endometrial receptivity is one of the major causes of embryo implantation failure and infertility. The plasma membrane transformation (PMT) describes the collective morphological and molecular alterations occurring to the endometrial luminal epithelium across the mid-secretory phase of the menstrual cycle to facilitate implantation. Dysregulation of this process directly affects endometrial receptivity and implantation. Multiple parallels between these alterations to confer endometrial receptivity in women have been drawn to those seen during the epithelial-mesenchymal transition (EMT) in tumorigenesis. Understanding these similarities and differences will improve our knowledge of implantation biology, and may provide novel therapeutic targets to manage implantation failure.

Methods

A systematic review was performed using the Medline (Ovid), Embase, and Web of Science databases without additional limits. The search terms used were "(plasma membrane* or cell membrane*) and transformation*" and "endometrium or endometrial." Research studies on the PMT or its regulation in women, discussing either the endometrial epithelium, decidualized stroma, or both, were eligible for inclusion.

Results

A total of 198 articles were identified. Data were extracted from 15 studies that matched the inclusion criteria. Collectively, these included studies confirmed the alterations occurring to the endometrial luminal epithelium during the PMT are similar to those seen during the EMT. Such similarities included alterations to the actin cytoskeleton remodeling of adherens junctions, integrin expression and epithelial-stromal communication. These were also some differences between these processes, such as the regulation of tight junctions and mucins, which need to be further researched.

Conclusions

This review raised the prospect of shared and distinct mechanisms existing in PMT and EMT. Further investigation into similarities between the PMT in the endometrium and the EMT in tumorigenesis may provide new mechanistic insights into PMT and new targets for the management of implantation failure and infertility.

The role of mesenchymal-epithelial transition in endometrial function

BACKGROUND

The human uterine endometrium undergoes significant remodeling and regeneration on a rapid and repeated basis, after parturition, menstruation, and in some cases, injury. The ability of the adult endometrium to undergo cyclic regeneration and differentiation/decidualization is essential for successful human reproduction. Multiple key physiologic functions of the endometrium require the cells of this tissue to transition between mesenchymal and epithelial phenotypes, processes known as mesenchymal-epithelial transition (MET) and epithelial-mesenchymal transition (EMT). Although MET/EMT processes have been widely characterized in embryonic development and in the context of malignancy, mounting evidence demonstrates the importance of MET/EMT in allowing the endometrium the phenotypic and functional flexibility necessary for successful decidualization, regeneration/re-epithelialization and embryo implantation.

OBJECTIVE AND RATIONALE

The objective of this review is to provide a comprehensive summary of the observations concerning MET and EMT and their regulation in physiologic uterine functions, specifically in the context of endometrial regeneration, decidualization and embryo implantation.

SEARCH METHODS

Using variations of the search terms 'mesenchymal-epithelial transition', 'mesenchymal-epithelial transformation', 'epithelial-mesenchymal transition', 'epithelial-mesenchymal transformation', 'uterus', 'endometrial regeneration', 'endometrial decidualization', 'embryo implantation', a search of the published literature between 1970 and 2018 was conducted using the PubMed database. In addition, we searched the reference lists of all publications included in this review for additional relevant original studies.

OUTCOMES

Multiple studies demonstrate that endometrial stromal cells contribute to the regeneration of both the stromal and epithelial cell compartments of the uterus, implicating a role for MET in mechanisms responsible for endometrial regeneration and re-epithelialization. During decidualization, endometrial stromal cells undergo morphologic and functional changes consistent with MET in order to accommodate embryo implantation. Under the influence of estradiol, progesterone and multiple other factors, endometrial stromal fibroblasts acquire epithelioid characteristics, such as expanded cytoplasm and rough endoplasmic reticulum required for greater secretory capacity, rounded nuclei, increased expression of junctional proteins which allow for increased cell-cell communication, and a reorganized actin cytoskeleton. During embryo implantation, in response to both maternal and embryonic-derived signals, the maternal luminal epithelium as well as the decidualized stromal cells acquire the mesenchymal characteristics of increased migration/motility, thus undergoing EMT in order to accommodate the invading trophoblast.

WIDER IMPLICATIONS

Overall, the findings support important roles for MET/EMT in multiple endometrial functions required for successful reproduction. The endometrium may be considered a unique wound healing model, given its ability to repeatedly undergo repair without scarring or loss of function. Future studies to elucidate how MET/EMT mechanisms may contribute to scar-free endometrial repair will have considerable potential to advance studies of wound healing mechanisms in other tissues.

Bisphenol compounds regulate decidualized stromal cells in modulating trophoblastic spheroid outgrowth and invasion in vitro†

Bisphenol A (BPA) is commonly found in epoxy resins used in the manufacture of plastic coatings in food packaging and beverage cans. There is a growing concern about BPA as a weak estrogenic compound that can affect human endocrine function. Chemicals structurally similar to BPA, such as bisphenol F (BPF) and bisphenol S (BPS), have been developed as substitutes in the manufacturing industry. Whether these bisphenol substitutes have adverse effects on human endocrine and reproductive systems remains largely unknown. This study investigated the effects of BPA, BPF, and BPS on regulating the function of decidualized human primary endometrial stromal cells on trophoblast outgrowth and invasion by indirect and direct co-culture models. All three bisphenols did not affect the stromal cell decidualization process. However, BPA- and BPF-treated decidualized stromal cells stimulated trophoblastic spheroid invasion in the indirect coculture model. The BPA-treated decidualized stromal cells had upregulated expressions of several invasion-related molecules including leukemia inhibitory factor (LIF), whereas both BPA- and BPF-treated decidualized stromal cells had downregulated expressions of anti-invasion molecules including plasminogen activator inhibitor type 1 (PAI-1) and tumor necrosis factor (TNFα) . Taken together, BPA and BPF altered the expression of invasive and anti-invasive molecules in decidualized stromal cells modulating its function on trophoblast outgrowth and invasion, which could affect the implantation process and subsequent pregnancy outcome.

Loss of CDYL Results in Suppression of CTNNB1 and Decreased Endometrial Receptivity

Impaired endometrial receptivity is one of the major causes of recurrent implantation failure (RIF), although the underlying molecular mechanism has not been fully elucidated. In the present study, we demonstrated that chromodomain Y like (CDYL) was highly expressed in the endometrium at mid-secretory phase during the normal menstrual cycles. However, the expression of CDYL was downregulated in the endometrial tissues obtained from women with RIF, consistently with the protein level of LIF, which is a marker of endometrial receptivity. In CDYL-knockdown human endometrial Ishikawa cells, we identified 1738 differentially expressed genes (DEGs). Importantly, the catenin beta 1 (CTNNB1) expression was dramatically reduced responding to the CDYL inhibition, both in Ishikawa cells as well as the primary endometrial epithelial and stromal cells. In addition, the expression of CTNNB1was decreased in the endometrium from RIF patients as well. These results suggested that the expression of CTNNB1 was regulated by CDYL in endometrium. The cell migration was impaired by CDYL-knockdown in Ishikawa cells and primary endometrial stromal cells (ESCs), which could be rescued by CDYL or CTNNB1 overexpression. Collectively, our findings indicated that the decreased expression of CDYL may suppress endometrial cell migration capability by affecting CTNNB1 expression, which would contribute to poor endometrial receptivity in women with RIF.

Marijuana-derived cannabinoids inhibit uterine endometrial stromal cell decidualization and compromise trophoblast-endometrium cross-talk

Marijuana (cannabis) use by pregnant women in the United States is increasing and there is a dire need to understand the beneficial or harmful effects of cannabis during pregnancy. Uterine endometrial stromal cells are fibroblast-like cells that differentiate into secretory cells, a process called decidualization, to create a microenvironment conducive for placenta formation and early embryonic growth. In this study, using model human cell lines, we for the first time demonstrate that Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) inhibit endometrial stromal cell decidualization and have adverse effects on trophoblast-endometrium cross-talk.

Inside the Endometrial Cell Signaling Subway: Mind the Gap(s)

Endometrial cells perceive and respond to their microenvironment forming the basis of endometrial homeostasis. Errors in endometrial cell signaling are responsible for a wide spectrum of endometrial pathologies ranging from infertility to cancer. Intensive research over the years has been decoding the sophisticated molecular means by which endometrial cells communicate to each other and with the embryo. The objective of this review is to provide the scientific community with the first overview of key endometrial cell signaling pathways operating throughout the menstrual cycle. On this basis, a comprehensive and critical assessment of the literature was performed to provide the tools for the authorship of this narrative review summarizing the pivotal components and signaling cascades operating during seven endometrial cell fate “routes”: proliferation, decidualization, implantation, migration, breakdown, regeneration, and angiogenesis. Albeit schematically presented as separate transit routes in a subway network and narrated in a distinct fashion, the majority of the time these routes overlap or occur simultaneously within endometrial cells. This review facilitates identification of novel trajectories of research in endometrial cellular communication and signaling. The meticulous study of endometrial signaling pathways potentiates both the discovery of novel therapeutic targets to tackle disease and vanguard fertility approaches.

Proteomic profiling of human decidual immune proteins during Toxoplasma gondii infection

A Toxoplasma gondii infection during pregnancy can result in spontaneous abortion, preterm labor, or congenital fetal defects. The decidual immune system plays a critical role in regulating the immune micro-environment and in the induction of immune tolerance. To better understand the factors that mediate the decidual immune response associated with the T. gondii infection, a large-scale study employing TMT proteomics was conducted to characterize the differential decidual immune proteomes from infected and uninfected human decidual immune cells samples. The decidual immune cells from 105 human voluntary abortion tissues were purified, and of the 5510 unique proteins identified, 181 proteins were found to be differentially abundant (>1.2-fold cutoff, p < 0.05) in the T. gondii-infected decidual immune cells. 11 proteins of 181 differentially expressed proteins associated with trophoblast invasion, placental development, intrauterine fetal growth, and immune tolerance were verified using a quantitative real-time polymerase chain reaction and western blotting. This systematic analysis for the proteomics of decidual immune cells identified a broad range of immune factors in human decidual immune cells, shedding a new insight into the decidual immune molecular mechanism for abnormal pregnancy outcomes associated with T. gondii infection.

Selective estrogen receptor modulator ormeloxifene suppresses embryo implantation via inducing miR-140 and targeting insulin-like growth factor 1 receptor in rat uterus

Ormeloxifene, the non-steroidal SERM contraceptive, inhibits endometrial receptivity and embryo implantation via countering nidatory estrogen. However, the molecular mechanism of ormeloxifene action responsible for its contraceptive efficacy still remains unclear. Herein, we aimed to identify the miRNAs modulated under the influence of ormeloxifene and to explore their role in endometrial receptivity and embryo implantation. By doing microRNA sequencing analysis, a total of 168 miRNAs were found to be differentially expressed in uterine tissue of ormeloxifene-treated rats, on day 5 (10:00 h) of pregnancy i.e. peri-implantation period. Out of differentially expressed miRNAs, miR-140 expression was found to be elevated in ormeloxifene administered groups and was selected for detailed investigation. In-vivo gain-of-function of miR-140 resulted in a significant reduction of implantation sites indicating its role in embryo implantation. The experiment on delayed implantation showed that estradiol caused down-regulation of miR-140. It also suppressed the attachment and outgrowth of BeWo spheroids to RL95-2 endometrial cells. In transwell migration assay, miR-140 was found to be involved in suppression of migration and invasion of endometrial epithelial cells. The ormeloxifene treatment caused up-regulation of miR-140 along with down-regulated expression of its target IGF1R in endometrial epithelial and stromal cells which also led to the suppression of downstream effectors integrin β3 and FAK. In mimic miR-140 receiving horn, the reduced expression of IGF1R was observed along with suppressed downstream integrin β3 and FAK similar to that observed in uteri of ormeloxifene- treated rats. Taken together, these findings suggest that ormeloxifene-induced inhibition of embryo implantation occurs via inducing miR-140 and altering its target IGF1R in rat uterus.

Prokineticin 1 is up-regulated by insulin in decidualizing human endometrial stromal cells

Prokineticin 1 (PROK1), a hypoxia‐regulated angiogenic factor, has emerged as a crucial regulator of embryo implantation and placentation. Dysregulation of PROK1 has been linked to recurrent pregnancy loss, pre‐eclampsia, foetal growth restriction and preterm birth. These pregnancy complications are common in women with obesity and polycystic ovary syndrome, i.e. conditions associated with insulin resistance and compensatory hyperinsulinaemia. We investigated the effect of insulin on PROK1 expression during in vitro decidualization. Endometrial stromal cells were isolated from six healthy, regularly menstruating women and decidualized in vitro. Insulin induced a significant dose‐dependent up‐regulation of PROK1 on both mRNA and protein level in decidualizing endometrial stromal cells. This up‐regulation was mediated by hypoxia‐inducible factor 1‐alpha (HIF1α) via the phosphatidylinositol 3‐kinase (PI3K) pathway. Furthermore, we demonstrated that PROK1 did not affect the viability, but significantly inhibited the migration of endometrial stromal cells and the migratory and invasive capacity of trophoblast cell lines. This in vitro study provides new insights into the regulation of PROK1 by insulin in human decidualizing endometrial stromal cells, the action of PROK1 on migration of endometrial stromal cells, as well as migration and invasion of trophoblasts. We speculate that hyperinsulinaemia may be involved in the mechanisms by which PROK1 is linked to placenta‐related pregnancy complications.

Human extravillous trophoblast invasion: intrinsic and extrinsic regulation

During the establishment of pregnancy, a human blastocyst implants into the uterine endometrium to facilitate the formation of a functional placenta. Implantation involves the blastocyst adhering to the uterine luminal epithelium before the primitive syncytiotrophoblast and subsequently specialised cells, the extravillous trophoblast (EVT), invade into the decidua in order to engraft and remodel uterine spiral arteries, creating the placental blood supply at the end of the first trimester. Defects in EVT invasion lead to abnormal placentation and thus adverse pregnancy outcomes. The local decidual environment is thought to play a key role in regulating trophoblast invasion. Here we describe the major cell types present in the decidua during the first trimester of pregnancy and review what is known about their regulation of EVT invasion. Overall, the evidence suggests that in a healthy pregnancy almost all cell types in the decidua actively promote EVT invasion and, further, that reduced EVT invasion towards the end of the first trimester is regulated, in part, by the reduced invasive capacity of EVTs shown at this time.

Tetraspanin CD82: a suppressor of solid tumors and a modulator of membrane heterogeneity

Tetraspanin CD82 suppresses the progression and metastasis of a wide range of solid malignant tumors. However, its roles in tumorigenesis and hematopoietic malignancy remain unclear. Ubiquitously expressed CD82 restrains cell migration and cell invasion by modulating both cell-matrix and cell-cell adhesiveness and confining outside-in pro-motility signaling. This restraint at least contributes to, if not determines, the metastasis-suppressive activity and, also likely, the physiological functions of CD82. As a modulator of cell membrane heterogeneity, CD82 alters microdomains, trafficking, and topography of the membrane by changing the membrane molecular landscape. The functional activities of membrane molecules and the cytoskeletal interaction of the cell membrane are subsequently altered, followed by changes in cellular functions. Given its pathological and physiological importance, CD82 is a promising candidate for clinically predicting and blocking tumor progression and metastasis and also an emerging model protein for mechanistically understanding cell membrane organization and heterogeneity.

Endometrial androgen signaling and decidualization regulate trophoblast expansion and invasion in co-culture: A time-lapse study

INTRODUCTION

To elucidate whether trophoblast expansion and invasion are modulated by androgen signaling in an in vitro co-culture model system with decidualizing endometrial stromal cells (ESCs).

METHODS

We employed an in vitro co-culture model of early embryo implantation, consisting of human ESCs (EtsT499 cells) and spheroids generated by extravillous trophoblast (EVT) derived HTR8/Svneo. The ESCs were decidualized with 8-bromo-cAMP (8-br-cAMP) in the presence or absence of dihydrotestosterone (DHT) at various concentrations for 5 days before co-culture with EVT spheroids. Trophoblast expansion was monitored by fluorescent time-lapse imaging microscopy. ESCs motility was visualized by using CellTracker™ Orange CMRA fluorescent probe. Apoptosis of ESCs was detected by CellEvent™ Caspase-3/7^® green detection reagent. Invasion assays were performed to quantify EVT invasion through a chemotaxis cell membrane.

RESULTS

Expansion of EVT spheroids was significantly enhanced by decidualized compared to undifferentiated ESCs. This process was further stimulated if ESCs were first decidualized in the presence of DHT. In contrast to decidualized ESCs, undifferentiated cells actively migrated away from expanding EVT spheroids. Invasiveness of EVT toward decidualized ESCs was significantly attenuated in comparison to undifferentiated ESCs. DHT had no effect on EVT invasion. However, an inhibitor of intercellular gap junction communication significantly enhanced EVT invasion towards decidualized ESCs.

CONCLUSIONS

These results indicate distinct roles for androgen signaling and gap junction formation in decidual cells in regulating trophoblast expansion and invasion.

Impaired function of trophoblast cells derived from translocated hESCs may explain pregnancy loss in women with balanced translocation (11;22)

PURPOSE

The aim of the study was to study whether the trophoblasts carrying unbalanced translocation 11,22 [t(11;12)] display abnormal expression of trophoblastic genes and impaired functional properties that may explain implantation failure.

METHODS

t(11;22) hESCs and control hESCs were differentiated in vitro into trophoblast cells in the presence of BMP4, and trophoblast vesicles (TBVs) were created in suspension. The expression pattern of extravillous trophoblast (EVT) genes was compared between translocated and control TBVs. The functional properties of the TBVs were evaluated by their attachment to endometrium cells (ECC1) and invasion through trans-well inserts.

RESULTS

TBVs derived from control hESCs expressed EVT genes from functioning trophoblast cells. In contrast, TBVs differentiated from the translocated hESC line displayed impaired expression of EVT genes. Moreover, the number of TBVs that were attached to endometrium cells was significantly lower compared to the controls. Correspondingly, invasiveness of trophoblast-differentiated translocated cells was also significantly lower than that of the control cells.

CONCLUSIONS

These results may explain the reason for implantation failure in couple carriers of t(11;22). They also demonstrate that translocated hESCs comprise a valuable in vitro human model for studying the mechanisms underlying implantation failure.

Impaired female fertility in tubulointerstitial antigen-like 1-deficient mice

Tubulointerstitial nephritis antigen-like 1 (Tinagl1, also known as adrenocortical zonation factor 1 [AZ-1] or lipocalin 7) is a matricellular protein. Previously, we demonstrated that Tinagl1 expression was restricted to extraembryonic regions during the postimplantation period and detected marked expression in mouse Reichert's membranes. In uteri, Tinagl1 is markedly expressed in the decidual endometrium during the postimplantation period, suggesting that it plays a physical and physiological role in embryo development and/or decidualization of the uterine endometrium during pregnancy. In the present study, in order to determine the role of Tinagl1 during embryonic development and pregnancy, we generated Tinagl1-deficient mice. Although Tinagl1(-/-) embryos were not lethal during development to term, homologous matings of Tinagl1(-/-) females and Tinagl1(-/-) males showed impaired fertility during pregnancy, including failure to carry pregnancy to term and perinatal lethality. To examine ovarian function, ovulation was induced with equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG); the number of ovulated oocytes did not differ between Tinagl1(-/-) and Tinagl1(flox/flox). In vitro fertilization followed by embryo culture also demonstrated the normal developmental potential of Tinagl1-null embryos during the preimplantation period. Our results demonstrate that Tinagl1 deficiency affects female mice and results in subfertility phenotypes, and they suggest that although the potential of Tinagl1(-/-) oocytes is normal, Tinagl1 is related to fertility in adult females but is not essential for either fertilization or preimplantation development in vitro.

Cyclic decidualization of the human endometrium in reproductive health and failure

Decidualization denotes the transformation of endometrial stromal fibroblasts into specialized secretory decidual cells that provide a nutritive and immunoprivileged matrix essential for embryo implantation and placental development. In contrast to most mammals, decidualization of the human endometrium does not require embryo implantation. Instead, this process is driven by the postovulatory rise in progesterone levels and increasing local cAMP production. In response to falling progesterone levels, spontaneous decidualization causes menstrual shedding and cyclic regeneration of the endometrium. A growing body of evidence indicates that the shift from embryonic to maternal control of the decidual process represents a pivotal evolutionary adaptation to the challenge posed by invasive and chromosomally diverse human embryos. This concept is predicated on the ability of decidualizing stromal cells to respond to individual embryos in a manner that either promotes implantation and further development or facilitates early rejection. Furthermore, menstruation and cyclic regeneration involves stem cell recruitment and renders the endometrium intrinsically capable of adapting its decidual response to maximize reproductive success. Here we review the endocrine, paracrine, and autocrine cues that tightly govern this differentiation process. In response to activation of various signaling pathways and genome-wide chromatin remodeling, evolutionarily conserved transcriptional factors gain access to the decidua-specific regulatory circuitry. Once initiated, the decidual process is poised to transit through distinct phenotypic phases that underpin endometrial receptivity, embryo selection, and, ultimately, resolution of pregnancy. We discuss how disorders that subvert the programming, initiation, or progression of decidualization compromise reproductive health and predispose for pregnancy failure.

Decidualization induces a secretome switch in perivascular niche cells of the human endometrium

The endometrial perivascular microenvironment is rich in mesenchymal stem-like cells that express type 1 integral membrane protein Sushi domain containing 2 (SUSD2) but the role of these cells in the decidual transformation of this tissue in pregnancy is unknown. We used an antibody directed against SUSD2 (W5C5) to isolate perivascular (W5C5(+)) and nonperivascular (W5C5(-)) fibroblasts from mid-luteal biopsies. We show that SUSD2 expression, and hence the ratio of W5C5(+):W5C5(-) cells, changes in culture depending on cell-cell contact and activation of the Notch signaling pathway. RNA sequencing revealed that cultures derived from W5C5(+) progenitor cells remain phenotypically distinct by the enrichment of novel and established endometrial perivascular signature genes. In an undifferentiated state, W5C5(+)-derived cells produced lower levels of various chemokines and inflammatory modulators when compared with their W5C5(-) counterparts. This divergence in secretomes was switched and became more pronounced upon decidualization, which transformed perivascular W5C5(+) cells into the dominant source of a range of chemokines and cytokines, including leukemia inhibitory factor and chemokine (C-C motif) ligand 7. Our findings suggest that the decidual response is spatially organized at the embryo-maternal interface with differentiating perivascular cells establishing distinct cytokine and chemokine profiles that could potentially direct trophoblast toward maternal vessels and govern local immune responses in pregnancy.

The human endometrium as a sensor of embryo quality

Human reproduction is characterized by a high degree of embryo wastage, which is largely ascribed to a high prevalence of embryo aneuploidy. It is proposed that maternal strategies have evolved that prevent inappropriate investment in invasive, but poorly viable embryos. Key to this is the emerging concept of the endometrium as biosensor, first identified in human in vitro embryo/decidualized stromal cell coculture systems and recently confirmed in an in vivo mouse model. In this review, the growing supporting experimental evidence for the biosensor component of decidualized endometrium is outlined, and recent insights into the nature of the embryo-derived signal detected by the endometrium and the biological processes by which this signal is thought to be converted into a go or no-go endometrial response are described. Finally, the clinical implications of this new paradigm of the choosy uterus are addressed.

Functional antagonism between high temperature requirement protein A (HtrA) family members regulates trophoblast invasion

Human trophoblast invasion of decidualized endometrium is essential for placentation and is tightly regulated and involves trophoblast-decidual cell interaction. High temperature requirement A4 (HtrA4) is a secreted serine protease highly expressed in the invasive extravillous trophoblasts that invade decidua. In contrast, both HtrA1 and HtrA3 have been shown to inhibit trophoblast invasion. Here we provide evidence that decidua-secreted HtrA1 and HtrA3 antagonize HtrA4-mediated trophoblast invasion. We demonstrated that HtrA1 and HtrA3 interact with and degrade HtrA4 and thereby inhibit trophoblast-like JAR cell invasion. Specifically, HtrA1 and HtrA3 expression is up-regulated under decidualization conditions in endometrial stromal and epithelial cells, T-HESCs and Ishikawa cells, respectively. Conditioned media from these two cell lines after decidualization treatment suppress HtrA4-expressing JAR cell invasion in an HtrA1- or HtrA3-dependent manner. Co-culture of the HtrA4-expressing JAR cells with decidualization stimuli-treated T-HESC or Ishikawa monolayer also impairs JAR cell invasion, which can be reversed by HtrA1 or HtrA3 knockdown, supporting that HtrA1 and HtrA3 are crucial for trophoblast-decidual cell interaction in the control of trophoblast invasion. Our study reveals a novel regulatory mechanism of trophoblast invasion through physical and functional interaction between HtrA family members.

In-vitro model systems for the study of human embryo-endometrium interactions

Implantation requires highly orchestrated interactions between the developing embryo and maternal endometrium. The association between abnormal implantation and reproductive failure is evident, both in normal pregnancy and in assisted reproduction patients. Failure of implantation is the pregnancy rate-limiting step in assisted reproduction, but, as yet, empirical interventions have largely failed to address this problem. Better understanding of the mechanisms underlying human embryo-endometrium signalling is a prerequisite for the further improvement of assisted reproduction outcomes and the development of effective interventions to prevent early pregnancy loss. Studying human embryo implantation is challenging since in-vivo experiments are impractical and unethical, and studies in animal models do not always translate well to humans. However, in recent years in-vitro models have been shown to provide a promising way forward. This review discusses the principal models used to study early human embryo development and initial stages of implantation in vitro. While each model has limitations, exploiting these models will improve understanding of the molecular mechanisms and embryo-endometrium cross-talk at the early implantation site. They provide valuable tools to study early embryo development and pathophysiology of reproductive disorders and have revealed novel disease mechanisms such as the role of epigenetic modifications in recurrent miscarriage.

The motile and invasive capacity of human endometrial stromal cells: implications for normal and impaired reproductive function

BACKGROUND Mechanisms underlying early reproductive loss in the human are beginning to be elucidated. The migratory and invasive capacity of human endometrial stromal cells (ESCs) is increasingly recognized to contribute to the intense tissue remodelling associated with embryo implantation, trophoblast invasion and endometrial regeneration. In this review, we examine the signals and mechanisms that control ESC migration and invasion and assess how deregulation of these cell functions contributes to common reproductive disorders. METHODS The PubMed database was searched for publications on motility and invasiveness of human ESCs in normal endometrial function and in reproductive disorders including implantation failure, recurrent pregnancy loss (RPL), endometriosis and adenomyosis, covering the period 2000-2012. RESULTS Increasing evidence suggests that implantation failure and RPL involve abnormal migratory responses of decidualizing ESCs to embryo and trophoblast signals. Numerous reports indicate that endometriosis, as well as adenomyosis, is associated with increased basal and stimulated invasiveness of ESCs and their progenitor cells, suggesting a link between a heightened menstrual repair response and the formation of ectopic implants. Migration and invasiveness of ESCs are controlled by a complex array of hormones, growth factors, chemokines and inflammatory mediators, and involve signalling through Rho GTPases, phosphatidylinositol-3-kinase and mitogen-activated protein kinase pathways. CONCLUSIONS Novel concepts are extending our understanding of the key functions of ESCs in effecting tissue repair imposed by cyclic menstruation and parturition. Migration of decidualizing ESCs also serves to support blastocyst implantation and embryo selection through discriminate motile responses directed by embryo quality. Targeting regulatory molecules holds promise for developing new strategies for the treatment of reproductive disorders such as endometriosis and recurrent miscarriage; and harnessing the migratory capacity of progenitor mesenchymal stem cells in the endometrium may offer new opportunities in regenerative medicine.

Control of human endometrial stromal cell motility by PDGF-BB, HB-EGF and trophoblast-secreted factors

Human implantation involves extensive tissue remodeling at the fetal-maternal interface. It is becoming increasingly evident that not only trophoblast, but also decidualizing endometrial stromal cells are inherently motile and invasive, and likely contribute to the highly dynamic processes at the implantation site. The present study was undertaken to further characterize the mechanisms involved in the regulation of endometrial stromal cell motility and to identify trophoblast-derived factors that modulate migration. Among local growth factors known to be present at the time of implantation, heparin-binding epidermal growth factor-like growth factor (HB-EGF) triggered chemotaxis (directed locomotion), whereas platelet-derived growth factor (PDGF)-BB elicited both chemotaxis and chemokinesis (non-directed locomotion) of endometrial stromal cells. Supernatants of the trophoblast cell line AC-1M88 and of first trimester villous explant cultures stimulated chemotaxis but not chemokinesis. Proteome profiling for cytokines and angiogenesis factors revealed neither PDGF-BB nor HB-EGF in conditioned media from trophoblast cells or villous explants, while placental growth factor, vascular endothelial growth factor and PDGF-AA were identified as prominent secretory products. Among these, only PDGF-AA triggered endometrial stromal cell chemotaxis. Neutralization of PDGF-AA in trophoblast conditioned media, however, did not diminish chemoattractant activity, suggesting the presence of additional trophoblast-derived chemotactic factors. Pathway inhibitor studies revealed ERK1/2, PI3 kinase/Akt and p38 signaling as relevant for chemotactic motility, whereas chemokinesis depended primarily on PI3 kinase/Akt activation. Both chemotaxis and chemokinesis were stimulated upon inhibition of Rho-associated, coiled-coil containing protein kinase. The chemotactic response to trophoblast secretions was not blunted by inhibition of isolated signaling cascades, indicating activation of overlapping pathways in trophoblast-endometrial communication. In conclusion, trophoblast signals attract endometrial stromal cells, while PDGF-BB and HB-EGF, although not identified as trophoblast-derived, are local growth factors that may serve to fine-tune directed and non-directed migration at the implantation site.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Endometrial stromal cells of women with recurrent miscarriage fail to discriminate between high- and low-quality human embryos

Background

The aetiology of recurrent miscarriage (RM) remains largely unexplained. Women with RM have a shorter time to pregnancy interval than normally fertile women, which may be due to more frequent implantation of non-viable embryos. We hypothesized that human endometrial stromal cells (H-EnSCs) of women with RM discriminate less effectively between high-and low-quality human embryos and migrate more readily towards trophoblast spheroids than H-EnSCs of normally fertile women.

Methodology/Principal Findings

Monolayers of decidualized H-EnSCs were generated from endometrial biopsies of 6 women with RM and 6 fertile controls. Cell-free migration zones were created and the effect of the presence of a high-quality (day 5 blastocyst, n = 13), a low-quality (day 5 blastocyst with three pronuclei or underdeveloped embryo, n = 12) or AC-1M88 trophoblast cell line spheroid on H-ESC migratory activity was analyzed after 18 hours. In the absence of a spheroid or embryo, migration of H-EnSCs from fertile or RM women was similar. In the presence of a low-quality embryo in the zone, the migration of H-EnSCs of control women was inhibited compared to the basal migration in the absence of an embryo (P<0.05) and compared to the migration in the presence of high-quality embryo (p<0.01). Interestingly, the migratory response H-EnSCs of women with RM did not differ between high- and low-quality embryos. Furthermore, in the presence of a spheroid their migration was enhanced compared to the H-EnSCs of controls (p<0.001).

Conclusions

H-EnSCs of fertile women discriminate between high- and low-quality embryos whereas H-EnSCs of women with RM fail to do so. H-EnSCs of RM women have a higher migratory response to trophoblast spheroids. Future studies will focus on the mechanisms by which low-quality embryos inhibit the migration of H-EnSCs and how this is deregulated in women with RM.

The role of interleukin-1β in human trophoblast motility

The pleiotropic cytokine interleukin-1β (IL-1β) can promote physiological cell migration, as well as cancer cell invasion and metastasis. Its role in human trophoblast invasion, however, has not been satisfactorily answered since direct, indirect as well as no effects on trophoblast motility have been published. Therefore, the role of IL-1β has been re-evaluated by exclusively using human primary trophoblast model systems. Immunofluorescence of first trimester placentae indicated IL-1 receptor 1 (IL-1R1) protein expression in first trimester villous cytotrophoblasts (vCTB) and extravillous trophoblasts (EVT). The latter expressed higher mRNA levels of the receptor as shown by comparative gene chip data of vCTB and EVT. Similarly, Western blot analyses and immunofluorescence revealed a time- and differentiation-dependent increase of IL-1R1 in primary EVT seeded on fibronectin. IL-1β dose-dependently elevated migration of isolated first trimester EVT through fibronectin-coated transwells, which was inhibited in the presence of IL-1R antagonist (IL-1Ra), whereas proliferation of these cells was not affected. Similarly, the interleukin did not alter proliferation of vCTB and cell column trophoblasts in floating villi of early pregnancy, but promoted migration in villous explant cultures seeded on collagen I. Western blot analyses of supernatants of primary EVT and first trimester villous explant cultures revealed IL-1β induced secretion of urokinase plasminogen activator (uPA), plasminogen activator inhibitor (PAI)-1 and PAI-2, which was diminished upon combined IL-1β/IL-1Ra treatment. In conclusion, these data suggest that IL-1β directly promotes trophoblast motility of first trimester EVT involving the uPA/PAI system.

Interaction of the conceptus and endometrium to establish pregnancy in mammals: role of interleukin 1β

Implantation and the establishment of pregnancy in mammals involves an intricate interplay of hormones, cytokines, growth factors, proteins, lipids, ions and the extracellular matrix between the uterine epithelium, stroma, immune cells and the conceptus trophectoderm. The divergent nature of implantation in the mouse, human and pig provides not only an interesting contrast in the establishment of pregnancy and early embryonic development but also intriguing similarities with regard to early endometrial-conceptus signaling. An interesting pro-inflammatory cytokine expressed in a number of mammalian species during the period of implantation is interleukin-1β (IL1B). The presence of IL1B might be involved with immunotolerance at the maternal-placental interface and has been proposed as one of the mediators in placental viviparity. The production of IL1B and other proinflammatory cytokines might play a role in establishing pregnancy through modulation of the nuclear factor kappa-B (NFKB) system in a number of species. A model for the regulation of cellular progesterone receptor expression and NFKB activation for endometrial receptivity and conceptus attachment is continuing to evolve and is discussed in the present review.

Decidual-secreted factors alter invasive trophoblast membrane and secreted proteins implying a role for decidual cell regulation of placentation

Inadequate or inappropriate implantation and placentation during the establishment of human pregnancy is thought to lead to first trimester miscarriage, placental insufficiency and other obstetric complications. To create the placental blood supply, specialized cells, the ‘extravillous trophoblast’ (EVT) invade through the differentiated uterine endometrium (the decidua) to engraft and remodel uterine spiral arteries. We hypothesized that decidual factors would regulate EVT function by altering the production of EVT membrane and secreted factors. We used a proteomics approach to identify EVT membrane and secreted proteins regulated by decidual cell factors. Human endometrial stromal cells were decidualized in vitro by treatment with estradiol (10⁻⁸ M), medroxyprogesterone acetate (10⁻⁷ M) and cAMP (0.5 mM) for 14 days. Conditioned media (CM) was collected on day 2 (non-decidualized CM) and 14 (decidualized CM) of treatment. Isolated primary EVT cultured on Matrigel™ were treated with media control, non-decidualized or decidualized CM for 16 h. EVT CM was fractionated for proteins <30 kDa using size-exclusion affinity nanoparticles (SEAN) before trypsin digestion and HPLC-MS/MS. 43 proteins produced by EVT were identified; 14 not previously known to be expressed in the placenta and 12 which had previously been associated with diseases of pregnancy including preeclampsia. Profilin 1, lysosome associated membrane glycoprotein 1 (LAMP1), dipeptidyl peptidase 1 (DPP1/cathepsin C) and annexin A2 expression by interstitial EVT in vivo was validated by immunhistochemistry. Decidual CM regulation in vitro was validated by western blotting: decidualized CM upregulated profilin 1 in EVT CM and non-decidualized CM upregulated annexin A2 in EVT CM and pro-DPP1 in EVT cell lysate. Here, non-decidualized factors induced protease expression by EVT suggesting that non-decidualized factors may induce a pro-inflammatory cascade. Preeclampsia is a pro-inflammatory condition. Overall, we have demonstrated the potential of a proteomics approach to identify novel proteins expressed by EVT and to uncover the mechanisms leading to disease states.

IFPA Award in Placentology lecture: molecular regulation of human trophoblast invasion

Invasion of extravillous trophoblast cell types into maternal uterine tissues is essential for successful human placental development and progression of pregnancy. Whereas endovascular trophoblasts migrate into the maternal spiral arteries, interstitial trophoblasts invade the decidual stroma, colonize the vessels from outside and communicate with diverse uterine cell types such as decidual stromal cells, macrophages and uterine NK cells. For example, interstitial trophoblasts expressing polymorphic human leukocyte antigen-C interact with uterine NK cells through binding to their killer immunoglobulin-like receptors which likely plays a role in trophoblast invasion and reproductive success of pregnancy. Both extravillous trophoblast subtypes are critically involved in the vascular transformation of the spiral arteries into dilated conduits ensuring appropriate blood flow into the intervillous space. Failures in this remodeling process are thought to be associated with severe forms of fetal growth restriction, preeclampsia and other pregnancy complications warranting studies on the molecular regulation of extravillous trophoblast differentiation. Moreover, interstitial trophoblast-derived hormones may regulate diverse biological functions in the decidua. In particular, human chorionic gonadotrophin has been shown to promote angiogenesis and to suppress apoptosis of endometrial stromal cells. In return, decidual cells produce a plethora of soluble factors controlling trophoblast invasion in a time- and distance-dependent manner. However, the underlying mechanisms have not been fully elucidated. Here, we will summarize autocrine as well as paracrine factors regulating invasion of extravillous trophoblasts and discuss critical signaling cascades involved. In addition, we will focus on key regulatory transcription factors controlling cell column proliferation and differentiation of the human extravillous trophoblast.

CD82 gene suppression in endometrial stromal cells leads to increase of the cell invasiveness in the endometriotic milieu

Tetraspanin CD82 is a wide-spectrum tumor metastasis suppressor that inhibits motility and invasiveness of cancer cells. Endometriosis is a benign gynecological disorder, but appears malignant behaviors including invasion, ectopic implantation and recurrence. This study is to elucidate the role of CD82 expression regulation in the pathogenesis of endometriosis. The short interfering RNA silence was established to analyze the roles of CD82, chemokine CCL2, and its receptor CCR2 in the invasiveness of endometrial stromal cells (ESCs). We have found that the mRNA and protein levels of CD82 in the primary normal ESCs from endometrium without endometriosis are significantly higher than that of the primary ESCs from eutopic endometrium and ectopic tissue. CD82 inhibits the invasiveness of ESCs by downregulating CCL2 secretion and CCR2 expression via mitogen-activated protein kinase (MAPK) and integrinβ1 signal pathway, and in turn upregulating the expression of TIMP1 and TIMP2 in an autocrine manner. The combination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) with 17β-estradiol can promote the invasion of ESCs via suppressing CD82 expression and stimulating CCL2 secretion and CCR2 expression, and the enhanced interaction of CCL2-CCR2 recruits more macrophages into the ectopic milieu in a paracrine manner, which further downregulates CD82 expression in the ectopic ESCs. Our study has demonstrated for the first time that the abnormal lower CD82 expression in ESCs induced by TCDD and estrogen may be an important molecular basis of endometriosis pathogenesis through enhancing the CCL2 secretion and CCR2 expression and the invasion of ESCs via MAPK and integrinβ1 signal pathway.