Marker genes of decidualization: activation of the decidual prolactin gene

Decreased thrombospondin-1 impairs endometrial stromal decidualization in unexplained recurrent spontaneous abortion†

Inappropriate endometrial stromal decidualization has been implied as an important reason of many pregnancy-related complications, such as unexplained recurrent spontaneous abortion, preeclampsia, and intrauterine growth restriction. Here, we observed that thrombospondin-1, an adhesive glycoprotein, was significantly downregulated in endometrial decidual cells from patients with unexplained recurrent spontaneous abortion. The immortalized human endometrial stromal cell line was used to investigate the possible THBS1-mediated regulation of decidualization. In vitro experiments found that the expression level of THBS1 increased with the normal decidualization process. Knockdown of THBS1 could decrease the expression levels of prolactin and insulin-like growth factor binding protein-1, two acknowledged human decidualization markers, whereas THBS1 overexpression could reverse these effects. The RNA sequencing results demonstrated that the extracellular regulated protein kinases signaling pathway was potentially affected by the knockdown of THBS1. We further confirmed that the regulation of THBS1 on decidualization was achieved through the ERK signaling pathway by the treatment of inhibitors. Moreover, knockdown of THBS1 in pregnant mice could impair decidualization and result in an increased fetus resorption rate. Altogether, our study demonstrated a crucial role of THBS1 in the pathophysiological process of unexplained recurrent spontaneous abortion and provided some new insights into the research of pregnancy-related complications.

Deficiency of UCHL1 results in insufficient decidualization accompanied by impaired dNK modulation and eventually miscarriage

BACKGROUND

Miscarriage is a frustrating complication of pregnancy that is common among women of reproductive age. Insufficient decidualization which not only impairs embryo implantation but disturbs fetomaternal immune-tolerance, has been widely regarded as a major cause of miscarriage; however, the underlying mechanisms resulting in decidual impairment are largely unknown.

METHODS

With informed consent, decidual tissue from patients with spontaneous abortion or normal pregnant women was collected to detect the expression profile of UCHL1. Human endometrial stromal cells (HESCs) were used to explore the roles of UCHL1 in decidualization and dNK modulation, as well as the mechanisms involved. C57/BL6 female mice (7-10 weeks old) were used to construct pregnancy model or artificially induced decidualization model to evaluate the effect of UCHL1 on mice decidualization and pregnancy outcome.

RESULTS

The Ubiquitin C-terminal hydrolase L1 (UCHL1), as a deubiquitinating enzyme, was significantly downregulated in decidua from patients with miscarriage, along with impaired decidualization and decreased dNKs. Blockage of UCHL1 led to insufficient decidualization and resultant decreased expression of cytokines CXCL12, IL-15, TGF-β which were critical for generation of decidual NK cells (dNKs), whereas UCHL1 overexpression enhanced decidualization accompanied by increase in dNKs. Mechanistically, the promotion of UCHL1 on decidualization was dependent on its deubiquitinating activity, and intervention of UCHL1 inhibited the activation of JAK2/STAT3 signaling pathway, resulting in aberrant decidualization and decreased production of cytokines associated with dNKs modulation. Furthermore, we found that inhibition of UCHL1 also disrupted the decidualization in mice and eventually caused adverse pregnancy outcome.

CONCLUSIONS

UCHL1 plays significant roles in decidualization and dNKs modulation during pregnancy in both humans and mice. Its deficiency indicates a poor pregnancy outcome due to defective decidualization, making UCHL1 a potential target for the diagnosis and treatment of miscarriage.

Quantitative Analysis of Cellular Morphology During In Vitro Decidualization

Decidualization is a differentiation process involving shape reorganization from a fibroblast to an epithelioid-like appearance characteristic of endometrial stromal cells. For the study of in vitro decidualization, one needs to check that the cells have undergone this process effectively. Verification is usually done by analyzing the expression of decidual markers, but changes in morphology are a more comprehensive feature. However, morphological specificities (i.e., flatness) of endometrial cells prevent the use of existing automated tools. A simple and accurate methodology was developed to quantify the phenotypic changes that occur in an in vitro decidualization system. This approach analyzes cell circularity directly from light microscopy images to follow the effects of progesterone or progestin R5020 in combination with estradiol (E2) and cAMP in inducing the decidualization of human endometrial cells. A statistical model to detect the differences in the kinetics of decidualization of the two hormonal stimuli before all the cell population acquire the decidual phenotype was implemented. It was found that statistical differences in morphology between decidualized and control cells could be detected 2 days after the treatments. Here we detail the model applied, scripts, and input files in order to provide a useful, practical, and low-cost tool to evaluate morphological aspects of endometrial stromal differentiation. This method allows the verification of the effectiveness of the decidualization process of the stromal endometrial cells without having to use cell replicates, as other methods such as immunofluorescence and RT-qPCR assays require. Consequently, this approach can follow the kinetics of a living single replicate throughout the experiment. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Cell circularity quantification of human stromal endometrial cells using ImageJ Basic Protocol 2: Statistical analysis of cell circularity of human stromal endometrial cells.

Advances in understanding canine pregnancy: Endocrine and morpho-functional regulation

Canine pregnancy relies on luteal steroidogenesis for progesterone (P4) production. The canine placenta responds to P4, depending on the nuclear P4 receptor (PGR). This has sparked interest in investigating the interaction between ovarian luteal steroids and the placenta in dogs. Canine placentation is characterized by restricted (shallow) trophoblast invasion, making the dog an interesting model for studying decidua-derived modulation of trophoblast invasion, compared with the more invasive (hemochorial) placentation. The PGR is expressed in maternally derived decidual cells and plays a crucial role in feto-maternal communication during pregnancy maintenance. Understanding PGR-mediated signalling has clinical implications for improving reproductive performance control in dogs. Altering the PGR signalling induces the release of PGF2α from the foetal trophoblast, hindering placental homeostasis, which can also be achieved with antigestagens like aglepristone. Consequently, luteolysis, both natural and antigestagen-induced, involves apoptosis, vascular lesion, and immune cell infiltration in the placenta, resulting in placentolysis and foetal membranes expulsion. Our laboratory developed the immortalized dog uterine stromal (DUS) cell line to study canine-specific decidualization. We study canine reproduction by observing physiological processes and investigating evidence-based mechanisms of decidualization and feto-maternal interaction. Our focus on morphology, function and molecular aspects enhances understanding and enables targeted and translational studies.

Exploring the presence of markers of decidualization in the fallopian tubes: a systematic review

The fallopian tubes (FTs) are part of the female upper genital tract. The healthy FT provides the biological environment for successful fertilization and facilitates the subsequent movement of the conceptus to the endometrial cavity. However, when the FT is damaged, as with salpingitis, pyosalpinx, and hydrosalpinx, it may increase the risk of an ectopic pregnancy, a life-threatening condition. Decidualization refers to a multifactorial process by which the endometrium changes to permit blastocyst implantation. The decidualization reaction is vital for endometrial receptivity during the window of implantation. To date, no comprehensive review that collates evidence on decidualization in the human FT has been conducted. Therefore, the aim of this review is to compile the current evidence on cellular decidualization occurring in the healthy and pathological FT in women of reproductive age. A literature search was conducted using five databases and identified 746 articles, 24 of which were analyzed based on inclusion and exclusion criteria. The available evidence indicates that the FT are able to undergo decidual changes under specific circumstances; however, the exact mechanism by which this occurs is poorly understood. Further research is needed to elucidate the mechanism by which decidualization can occur in the FT.

Single-cell RNA-seq reveals developmental deficiencies in both the placentation and the decidualization in women with late-onset preeclampsia

Preeclampsia (PE) is a leading cause of maternal and fetal morbidity and mortality. Although increasing lines of evidence suggest that both the placenta and the decidua likely play roles in the pathogenesis of PE, the molecular mechanism of PE remains elusive partly because of the heterogeneity nature of the maternal-fetal interface. In this study, we perform single-cell RNA-seq on the placenta and the decidual from patients with late-onset PE (LOPE) and women in normal pregnancy. Analyses of single-cell transcriptomes reveal that in LOPE, there are likely a global development deficiency of trophoblasts with impaired invasion of extravillous trophoblasts (EVT) and increased maternal immune rejection and inflammation in the placenta, while there are likely insufficient decidualization of decidual stromal cells (DSC), increased inflammation, and suppressed regulatory functions of decidual immune cells. These findings improve our understanding of the molecular mechanisms of PE.

Immunology of Pregnancy and Systemic Consequences

Pregnancy is an immunological paradox, with renowned Nobel Prize winning transplantation biologist Sir Peter Brian Medawar being the first to introduce this concept back in 1953. This concept considers how the maternal immune system can tolerate the developing fetus, which is 50% antigenically foreign to the uterus. There have been significant advances in our understanding of the immune system in regulating fertility, pregnancy and in complications of these, and what was once considered a paradox can be seen as a highly evolved system. Indeed, the complexity of the maternal-fetal interface along with our ever-advancing knowledge of immune cells and mediators means that we have a better understanding of these interactions, with gaps still present.  This chapter will summarise the key aspects of the role of the immune system at each stage of pregnancy and highlight the recent advances in our knowledge.

Glucose and fatty acids catabolism during in vitro decidualization of human endometrial stromal cells

The differentiation of endometrial stromal cells, named decidualization, is essential for the proper formation of the materno-fetal interphase. One important feature of decidualization is the increased glucose consumption and its utilization by endometrial cells to produce energy. Besides glucose, fatty acids are another important energy source for living cells and it has been described that endometrial stromal cells rely on the proper function of the oxidation of fatty acids for the correct decidualization. It is, however, unknown whether the turn-over of fatty acid degradation is modified during decidualization. Furthermore, it is also unknown how the final products of glucose and fatty acid catabolism are related to the function of the tricarboxylic acid cycle for the efficient ATP production. In this study, we evaluated the content levels of different intermediate metabolites and the expression of the key enzymes related to the degradation of glucose and fatty acids during the in vitro decidualization of human endometrial stromal cells. Our results suggest that human endometrial stromal cells undergo energetic metabolic changes during decidualization and that decidualizing and non-decidualizing cells differ in the level of activation of different metabolic pathways and, probably, in the use of intermediate metabolites.

Inserting Cre recombinase into the Prolactin 8a2 gene for decidua-specific recombination in mice

An estimated 75% of unsuccessful pregnancies are due to implantation failure. Investigating the causes of implantation failure is difficult as decidualization and embryo implantation is a dynamic process. Here, we describe a new decidua-specific iCre recombinase mouse strain. Utilizing CRISPR/Cas9-based genome editing, a mouse strain was developed that expresses iCre recombinase under the control of the endogenous prolactin family 8, subfamily a, member 2 (Prl8a2) promoter. iCre recombinase activity was examined by crossing with mTmG/+ or Sun1-GFP reporter alleles. iCre activity initiated reporter expression at gestational day 5.5 in the primary decidual zone and continued into mid-gestation (gestational day 9.5), with expression highly concentrated in the anti-mesometrial region. No reporter expression was observed in the ovary, oviduct, pituitary, or skeletal muscle, supporting the tissue specificity of the Prl8a2iCre in the primary decidual zone. This novel iCre line will be a valuable tool for in vivo genetic manipulation and lineage tracing to investigate functions of genetic networks and cellular dynamics associated with decidualization and infertility.

Proteome-defined changes in cellular pathways for decidua and trophoblast tissues associated with location and viability of early-stage pregnancy

BACKGROUND

In early pregnancy, differentiating between a normal intrauterine pregnancy (IUP) and abnormal gestations including early pregnancy loss (EPL) or ectopic pregnancy (EP) is a major clinical challenge when ultrasound is not yet diagnostic. Clinical treatments for these outcomes are drastically different making early, accurate diagnosis imperative. Hence, a greater understanding of the biological mechanisms involved in these early pregnancy complications could lead to new molecular diagnostics.

METHODS

Trophoblast and endometrial tissue was collected from consenting women having an IUP (n = 4), EPL (n = 4), or EP (n = 2). Samples were analyzed by LC-MS/MS followed by a label-free proteomics analysis in an exploratory study. For each tissue type, pairwise comparisons of different pregnancy outcomes (EPL vs. IUP and EP vs. IUP) were performed, and protein changes having a fold change ≥ 3 and a Student's t-test p-value ≤ 0.05 were defined as significant. Pathway and network classification tools were used to group significantly changing proteins based on their functional similarities.

RESULTS

A total of 4792 and 4757 proteins were identified in decidua and trophoblast proteomes. For decidua, 125 protein levels (2.6% of the proteome) were significantly different between EP and IUP, whereas EPL and IUP decidua were more similar with only 68 (1.4%) differences. For trophoblasts, there were 66 (1.4%) differences between EPL and IUP. However, the largest group of 344 differences (7.2%) was observed between EP and IUP trophoblasts. In both tissues, proteins associated with ECM remodeling, cell adhesion and metabolic pathways showed decreases in EP specimens compared with IUP and EPL. In trophoblasts, EP showed elevation of inflammatory and immune response pathways.

CONCLUSIONS

Overall, differences between an EP and IUP are greater than the changes observed when comparing ongoing IUP and nonviable intrauterine pregnancies (EPL) in both decidua and trophoblast proteomes. Furthermore, differences between EP and IUP were much higher in the trophoblast than in the decidua. This observation is true for the total number of protein changes as well as the extent of changes in upstream regulators and related pathways. This suggests that biomarkers and mechanisms of trophoblast function may be the best predictors of early pregnancy location and viability.

Impairment of Decidualization of Endometrial Stromal Cells by hsa-miR-375 Through NOX4 Targeting

Decidualization of the endometrial stromal cells (ESCs) is essential for successful embryo implantation. It involves the transformation of fibroblastic cells into epithelial-like cells that secrete cytokines, growth factors, and proteins necessary for implantation. Previous studies have revealed altered expression of miR-375 in the endometrium of patients with recurrent implantation failure and the ectopic stromal cells of patients with endometriosis. However, the exact molecular mechanisms, particularly the role of microRNAs (miRNAs) in the regulation of decidualization, remain elusive. In this study, we investigated whether decidualization is affected by miR-375 and its potential target(s). The findings demonstrated the downregulation of the expression of miR-375 in the secretory phase compared to its expression in the proliferative phase of the endometrium in normal donors. In contrast, it was upregulated in the secretory phase of the endometrium in infertility patients. Furthermore, during decidualization of ESCs in vitro, overexpression of miR-375 significantly reduced the transcript-level expression of forkhead box protein O1 (FOXO1), prolactin (PRL), and insulin-like growth factor binding protein-1 (IGFBP1), the well-known decidual cell markers. Overexpression of miR-375 also resulted in reduced decidualization-derived intracellular and mitochondrial reactive oxygen species (ROS) levels. Using the luciferase assay, we confirmed that NADPH oxidase 4 (NOX4) is a direct target of miR-375. Collectively, the study showed that the miR-375-mediated NOX4 downregulation reduced ROS production and attenuated the decidualization of ESCs. It provides evidence that miR-375 is a negative regulator of decidualization and could serve as a potential target for combating infertility.

Decorin production by the human decidua: role in decidual cell maturation

Decidualization involves the proliferation and differentiation of fibroblast-like endometrial stromal cells into epithelioid-shaped and secretory 'decidual' cells in response to steroid hormones. Human decidual cells produce insulin-like growth factor-binding protein-1 and prolactin (PRL), two well-recognized markers of decidual cell maturation and a proteoglycan decorin (DCN). We reported that DCN restrains the human trophoblast renewal, migration, invasion and endovascular differentiation needed for uterine arterial remodeling during normal pregnancy. DCN overproduction by the decidua is associated with a hypo-invasive placenta and a serious pregnancy disorder, pre-eclampsia (PE). Furthermore, elevated maternal plasma DCN levels during the second trimester is a predictive biomarker of PE. While these paracrine roles of decidua-derived DCN on trophoblast physiology and pathology have been well-defined, it remains unknown whether DCN plays any autocrine role in decidual cell development. The objectives of this study were to examine: the kinetics of DCN production during decidualization of human endometrial stromal cells; gestational age-related changes in DCN production by the first trimester decidua; and a possible autocrine role of DCN on decidual cell maturation. We found that DCN production is enhanced during decidualization of both primary and immortalized human endometrial stromal cells in vitro and during early gestation in decidual samples tested ex vivo, and that it is important for endometrial stromal cell maturation into a decidual phenotype. Decorin-depleted human endometrial stromal cells exposed to decidualizing stimuli failed to mature fully, as evidenced by fibroblastoid morphology, reduced insulin-like growth factor-binding protein-1 and PRL expression, and reduction in cellular ploidy. We identified heart and neural crest derivatives-expressed protein 2, and progesterone receptor as potential downstream mediators of DCN effects.

Psychological Stress and Functional Endometrial Disorders: Update of Mechanism Insights

The human endometrium plays a vital role in providing the site for embryo implantation and maintaining the normal development and survival of the embryo. Recent studies have shown that stress is a common factor for the development of unexplained reproductive disorders. The nonreceptive endometrium and disturbed early maternal-fetal interaction might lead to infertility including the repeated embryo implantation failure and recurrent spontaneous abortion, or late pregnancy complications, thereby affecting the quality of life as well as the psychological status of the affected individuals. Additionally, psychological stress might also adversely affect female reproductive health. In recent years, several basic and clinical studies have tried to investigate the harm caused by psychological stress to reproductive health, however, the mechanism is still unclear. Here, we review the relationship between psychological stress and endometrial dysfunction, and its consequent effects on female infertility to provide new insights for clinical therapeutic interventions in the future.

Chronic endometritis and altered embryo implantation: a unified pathophysiological theory from a literature systematic review

PURPOSE

Chronic endometritis (CE) is a frequent hysteroscopic and histological finding which affects embryo transfer implantation during IVF-ICSI cycles. In particular, CE impairs proper decidualization and, subsequently, implantation. Although this correlation has been clearly clarified, a pathophysiological explanation assembling all the studies performed has not been elucidated yet. For this reason, we have structured a systematic review considering all the original articles that evaluated a pathological element involved in CE and implantation impairment.

METHODS

The authors searched electronic databases and, after screening, collected 15 original articles. These were fully scanned and used to create a summary pathway.

RESULTS

CE is primarily caused by infections, which lead to a specific cytokine and leukocyte pattern in order to prepare the uterus to fight the noxa. In particular, the immunosuppression requested for a proper semi-allogenic embryo transfer implantation is converted into an immunoreaction, which hampers correct embryo implantation. Moreover, endometrial vascularization is affected and both irregular vessel density and luminal thickening and thrombosis reduce what we have first identified as endometrial flow reserve. Finally, incorrect uterine wave propagation could affect embryo contact with decidua.

CONCLUSION

This is the first summary of evidence on CE pathophysiology and its relationship with infertility. Understanding the CE pathophysiology could improve our knowledge in embryo transfer success.

Circulating pregnancy hormone relaxin as a first trimester biomarker for preeclampsia

OBJECTIVE

Preeclampsia, a multi-system hypertensive disorder, is associated with perturbations in the maternal cardiovascular system during early pregnancy. The corpus luteal hormone relaxin, a potent vasodilator, may contribute to physiological circulatory changes especially in early gestation when circulating levels are highest. This study investigated whether first trimester circulating relaxin may be a suitable biomarker for the early prediction of preeclampsia.

METHODS

Relaxin was initially measured in first-trimester samples of women who developed late-onset preeclamptic (LO-PE; delivery ≥ 34 weeks; n = 33) and uncomplicated pregnancies (n = 25) in Pittsburgh, USA. Subsequently, to expand the group numbers, relaxin was measured in women who developed LO-PE (n = 95), early-onset preeclamptic (EO-PE; delivery < 34 weeks; n = 57), and uncomplicated pregnancies (n = 469) in Utrecht, the Netherlands.

RESULTS

In the Pittsburgh subjects, low relaxin levels (lowest centile: <p10) showed an adjusted odds ratio (OR) of 5.29 (95%CI 1.10-25.5) for LO-PE. In the Utrecht population, low relaxin levels (<p10) demonstrated adjusted ORs of 1.45 (95%CI 0.54-3.90) and 2.03 (95%CI 1.06-3.88) for EO-PE and LO-PE respectively, the latter increasing to an adjusted OR of 3.18 (95%CI 1.41-7.20) when newborn weight was < 10%. Serum relaxin concentrations slightly improved the detection rate of a previously derived prediction model for LO-PE from 42.5% to 45.1% at a fixed 10% false-positive rate.

CONCLUSION

Relaxin shows little improvement in the performance of first trimester prediction models, which does not support its clinical implementation as a biomarker. Although this study was only correlational, the results point to a possible pathophysiologic role for low relaxin levels in pregnancies that later develop LO-PE.

Decreased Autophagy Impairs Decidualization of Human Endometrial Stromal Cells: A Role for ATG Proteins in Endometrial Physiology

During the menstrual cycle, the endometrium undergoes cyclic changes of cellular proliferation, differentiation, and death, an essential preparation of the endometrium for its interaction with the implanting embryo. In particular, the differentiation of endometrial stromal cells, named decidualization, ensures the formation of a proper feto-maternal interface for a regulated trophoblast invasion and correct placental orientation and growth. Interestingly, autophagy, an intracellular degradation process of great importance for the maintenance of cellular homeostasis, plays an important role in cell proliferation, differentiation, and growth. In the endometrium, increased detection of autophagy markers correlates with the progression of the menstrual cycle. However, until now, it was unknown whether autophagy contributes to the proper function of the endometrium. In this study, we show that autophagy is increased during in vitro decidualization of human endometrial stromal cells. Furthermore, we demonstrate that the knockdowns of two important autophagy-related (ATG) proteins, ATG7 and ATG5, impaired decidualization, confirming a positive role of these proteins and of autophagy for the correct decidualization of human endometrial stromal cells. In conclusion, in this work, we describe a previously unknown functional connection between autophagy and endometrial physiology.

CDKN1C (P57): one of the determinants of human endometrial stromal cell decidualization

Decidualization is regulated by crosstalk of progesterone and the cAMP pathway. It involves extensive reprogramming of gene expression and includes a wide range of functions. To investigate how cell cycle regulatory genes drive the human endometrial stromal cell (ESC) exit cell cycle and enter differentiation, primary cultured ESC was treated with 8-Br-cAMP and MPA and cell cycle distribution was investigated by flow cytometry. High-throughput cell cycle regulatory gene expression was also studied by microarray. To validate the results of microarray chip, immunohistochemistry and semi-quantitative method of optical density were used to analyze the expression of cell cycle regulator proteins in proliferative phase of endometrium (n = 6) and early pregnancy decidua (n = 6). In addition, we selected cyclin-dependent kinase inhibitor 1c (CDKN1C, also known as P57) and cyclin-dependent kinase inhibitor 2b (CDKN2B, also known as P15) in order to study their role in the process of decidualization by the RNAi method. ESC was arrested at G0/G1 checkpoints during decidualization. Cell cycle regulatory genes P57 and P15 were upregulated, while cyclin D1 (CCND1), cyclin-dependent kinase 2 (CDK2), and cell division cycle protein 2 homolog (CDC2) were downregulated during ESC differentiation both in vitro and vivo. P57 siRNA impaired ESC decidualization and caused different morphological and ultrastructural changes as well as a relatively low secretion of prolactin, but P15 siRNA had no effects. We concluded that P15, CCND1, CDK2, and CDC2 may participate in ESC withdraw from the cell cycle and go into differentiation both in vitro and in vivo. P57 is one of the key determinants of ESC differentiation due to its effect on the cell cycle distribution, but its association with the decidua-specific transcription factor needs further investigation.

Protective role of GPR120 in the maintenance of pregnancy by promoting decidualization via regulation of glucose metabolism

Background

Intake of ω-3 PUFAs have been demonstrated to have positive effects on pregnancy outcome, whose receptor, GPR120, regulates several cellular functions including differentiation, metabolism and immune reaction. However, whether GPR120 is involved in decidualization and pregnancy remains unknown.

Methods

Decidua tissue from women with normal pregnancy and spontaneous abortion were collected to determine the expression profile of GPR120. Abortion mouse models and artificially induced deciduoma in mice were established to evaluate the effect of GPR120 on pregnancy outcome and in vivo decidualization. HESCs and primary DSCs were used to explore the roles of GPR120 in decidualization and mechanisms involved.

Findings

We found that GPR120 functioned to promote decidualization by upregulating glucose uptake and pentose-phosphate pathway (PPP) of human endometrial stromal cells. Firstly, the expression of GPR120 in decidua of spontaneous abortion was downregulated compared to normal decidua. Lack of GPR120 predisposed mice to LPS or RU486 induced abortion. Decidualization was augmented by GPR120 via improving GLUT1-mediated glucose uptake and G6PD- mediated PPP. FOXO1 was upregulated by GPR120 via activation of ERK1/2 and AMPK signaling and increased the expression of GLUT1. Furthermore, the expression of chemokines and cytokines in decidual stromal cells was enhanced by GPR120. Lastly, GPR120 agonist ameliorated LPS-induced abortion in the mice.

Interpretation

GPR120 plays significant roles in decidualization and the maintenance of pregnancy, which might be a potential target for diagnosis and treatment of spontaneous abortion.

Fund

Ministry of Science and Technology of China, National Natural Science Foundation of China, the Program of Science and Technology Commission of Shanghai Municipality.

Metformin inhibits estradiol and progesterone-induced decidualization of endometrial stromal cells by regulating expression of progesterone receptor, cytokines and matrix metalloproteinases

BACKGROUND

Polycystic ovary syndrome (PCOS) is a serious threat for reproductive-aged women. Metformin has been used for the treatment of PCOS. However, its molecular mechanism in decidualization process of PCOS has not been well featured.

METHODS

RT-qPCR analysis was used to detect expression patterns of progesterone receptor (PGR), estradiol receptor alpha (ERα), Cytokeratin 8 and Vimentin in endometrial tissues of PCOS and non-PCOS patients. RT-qPCR assay was also employed to determine mRNA expression of prolactin, Insulin-like growth factor-binding protein 1 (IGFBP-1), matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP9). Cytokine secretion were measured by matching ELISA kits. Protein expression of p-ERK1/2, ERK1/2, p-p38 MAPK, p38 MAPK, and PGR (PGRA and PGRB) was tested by western blot assay.

RESULTS

PGR expression was upregulated in PCOS patients. Metformin alleviated estradiol (E2) and progesterone (P4) (EP)-induced decidualization of endometrial stromal cells. Abnormal cytokine secretion was observed in EP-stimulated endometrial stromal cells in the absence or presence of metfromin. Metformin suppressed EP-induced MMP-2 and MMP-9 upregulation. Metformin alleviated EP-triggered p38 MAPK inactivation and PGR (PGRA and PGRB) expression. Metfromin had no effect on ERK1/2 signaling in EP-stimulated endometrial stromal cells.

CONCLUSION

Metformin alleviated EP-induced decidualization of endometrial stromal cells by modulating secretion of multiple cytokines, inhibiting expression of MMP-2 and MMP-9, activating p38-MAPK signaling and reducing PGR expression, providing a deep insight into the molecular basis of metfromin therapy for PCOS patients.

A single-cell survey of the human first-trimester placenta and decidua

The placenta and decidua interact dynamically to enable embryonic and fetal development. Here, we report single-cell RNA sequencing of 14,341 and 6754 cells from first-trimester human placental villous and decidual tissues, respectively. Bioinformatic analysis identified major cell types, many known and some subtypes previously unknown in placental villi and decidual context. Further detailed analysis revealed proliferating subpopulations, enrichment of cell type-specific transcription factors, and putative intercellular communication in the fetomaternal microenvironment. This study provides a blueprint to further the understanding of the roles of these cells in the placenta and decidua for maintenance of early gestation as well as pathogenesis in pregnancy-related disorders.

Isolation of Human Endometrial Stromal Cells for In Vitro Decidualization

The differentiation of human endometrial stromal cells (HESC) from fibroblast-like appearance into secretory decidua is a transformation required for embryo implantation into the uterine lining of the maternal womb. Improper decidualization has been established as a root cause for implantation failure and subsequent early embryo miscarriage. Therefore, understanding the molecular mechanisms underlying decidualization is advantageous to improving the rate of successful births. In vivo based studies of artificial decidualization are often limiting due to ethical dilemmas associated with human research, as well as translational complications within animal models. As a result, in vitro assays through primary cell culture are often utilized to explore the modulation of decidualization via hormones. This study provides a detailed protocol for the isolation of HESC and subsequent artificial decidualization via the supplementation of hormones to the culturing medium. Further, this study provides a well-designed method to knockdown any gene of interest by utilizing lipid-based siRNA transfections. This protocol permits the optimization of culture purity as well as product yield, thereby maximizing the ability to utilize this model as a reliable method to understand the molecular mechanisms underlying decidualization, and the subsequent quantification of secreted agents by decidualized endometrial stromal cells.

Human chorionic gonadotropin induces decidualization of ectopic human endometrium more effectively than forskolin in an in-vivo endometriosis model

Endometriosis, characterized by the presence of endometrial tissue at ectopic sites, is a leading cause of pelvic pain and subfertility in women. The stromal compartment of the endometrium is considered to play a pivotal role in the establishment and persistence of endometriotic lesions, thus impaired decidualization of these cells may result in enhanced invasion capacity at ectopic sites. Consequently, stimulation of decidualization may alleviate this disease. To analyze the effect of systemically applied compounds on decidualization of ectopic endometrial tissue, endometriosis was induced by suturing human eutopic endometrium to the peritoneum of 22 NOD/SCID mice. Each mouse received four tissue fragments from the same patient. Mice were randomly allocated either to one control and three experimental groups ( n = 4/group) which were treated with progesterone alone or in combination with forskolin or human chorionic gonadotropin for seven days or to one control and one experimental group ( n = 3/group) which was treated with progesterone and human chorionic gonadotropin for 10 days followed by 7 days without treatment. At the end of the experiments, lesions were measured and analyzed for markers of decidualization (FOXO-1, prolactin) and proliferation (Ki-67). Decidualization was induced in the ectopic lesions by systemic treatment in vivo. This induction was significantly stronger after treatment with progesterone in combination with human chorionic gonadotropin than with forskolin or with progesterone alone. Only the combination with human chorionic gonadotropin led to induction of FOXO1 protein expression and a significant physiologic transformation of the ectopic endometrial stromal cells after seven days of treatment. After termination of human chorionic gonadotropin treatment, the decidualization process continued, leading to a significant inhibition of proliferation. Thus, decidualization of human ectopic endometrial tissue can be induced in a humanized endometriosis mouse model in vivo. This model may help to decipher the signal pathways involved in this decidualization process and to develop novel therapeutical approaches to alleviate this painful disease. Impact statement Impaired decidualization of endometrial stromal cells may contribute to the development of endometriosis, and an increased decidualization reaction may prevent or alleviate this prevalent gynecological disease. Human chorionic gonadotropin (hCG) has been shown to promote decidualization in eutopic endometrium. Up to now in vitro studies mainly used cAMP for successful induction of decidualization of isolated endometrial stromal cells. Here, for the first time, decidualization of ectopic endometrial lesions is induced in an experimental endometriosis mouse model, comparing the effectiveness of hCG with that of the direct adenylyl cyclase activator Forskolin. In this 3D-organ structure in vivo, hCG proved to be more effective in the induction of decidualization than forskolin. Particularly in case of progesterone resistance, alternative pathways inducing decidualization could alleviate endometriosis, and the sophisticated hCG action could constitute a therapeutical tool to induce terminal differentiation in ectopic endometrial lesions.

WNK lysine deficient protein kinase 1 regulates human endometrial stromal cell decidualization, proliferation, and migration in part through mitogen-activated protein kinase 7

The differentiation of endometrial stromal cells into decidual cells, termed decidualization, is an integral step in the establishment of pregnancy. The mitogen-activated protein kinase homolog, WNK lysine deficient protein kinase 1 (WNK1), is activated downstream of epidermal growth factor receptor during decidualization. Primary human endometrial stromal cells (HESCs) were subjected to small interfering RNA knockdown of WNK1 followed by in vitro decidualization. This abrogated expression of the decidual marker genes, insulin like growth factor binding protein 1 (IGFBP1) and prolactin (PRL), and prevented adoption of decidual cell morphology. Analysis of the WNK1-dependent transcriptome by RNA-Seq demonstrated that WNK1 regulates the expression of 1858 genes during decidualization. Gene ontology and upstream regulator pathway analysis showed that WNK1 regulates cell migration, differentiation, and proliferation. WNK1 was required for many of the gene expression changes that drive decidualization, including the induction of the inflammatory cytokines, C-C motif chemokine ligand 8 (CCL8), interleukin 1 beta (IL1B), and interleukin 15 (IL15), and the repression of transforming growth factor-beta (TGF-beta) pathway genes, including early growth response 2 (EGR2), SMAD family member 3 (SMAD3), integrin subunit alpha 2 (ITGA2), integrin subunit alpha 4 (ITGA4), and integrin subunit beta 3 (ITGB3). In addition to abrogating decidualization, WNK1 knockdown decreased the migration and proliferation of HESCs. Furthermore, mitogen-activated protein kinase 7 (MAPK7), a known downstream target of WNK1, was activated during decidualization in a WNK1-dependent manner. Small interfering RNA knockdown of MAPK7 demonstrated that MAPK7 regulates a subset of WNK1-regulated genes and controls the migration and proliferation of HESCs. These results indicate that WNK1 and MAPK7 promote migration and proliferation during decidualization and regulate the expression of inflammatory cytokines and TGF-beta pathway genes in HESCs.

Development of a novel human recellularized endometrium that responds to a 28-day hormone treatment

Three-dimensional (3D) in vitro models have been established to study the physiology and pathophysiology of the endometrium. With emerging evidence that the native extracellular matrix (ECM) provides appropriate cues and growth factors essential for tissue homeostasis, we describe, a novel 3D endometrium in vitro model developed from decellularized human endometrial tissue repopulated with primary endometrial cells. Analysis of the decellularized endometrium using mass spectrometry revealed an enrichment of cell adhesion molecules, cytoskeletal proteins, and ECM proteins such as collagen IV and laminin. Primary endometrial cells within the recellularized scaffolds proliferated and remained viable for an extended period of time in vitro. In order to evaluate the hormonal response of cells within the scaffolds, the recellularized scaffolds were treated with a modified 28-day hormone regimen to mimic the human menstrual cycle. At the end of 28 days, the cells within the endometrial scaffold expressed both estrogen and progesterone receptors. In addition, decidualization markers, IGFBP-1 and prolactin, were secreted upon addition of dibutyryl cyclic AMP indicative of a decidualization response. This 3D model of the endometrium provides a new experimental tool to study endometrial biology and drug testing.

hCG activates Epac-Erk1/2 signaling regulating Progesterone Receptor expression and function in human endometrial stromal cells

STUDY QUESTION

How does hCG signal in human endometrial stromal cells (ESCs) and what is its role in regulating ESC function?

SUMMARY ANSWER

hCG signaling in ESCs activates the extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) pathway through exchange protein activated by cyclic AMP (cAMP) (Epac) and transiently increases progesterone receptor (PR) transcript and protein expression and its transcriptional function.

WHAT IS KNOWN ALREADY

hCG is one of the earliest embryo-derived secreted signals in the endometrium, which abundantly expresses LH/hCG receptors. hCG signals through cAMP/protein kinase A (PKA) in gonadal cells, but in endometrial epithelial cells, hCG induces Erk1/2 activation independent of the cAMP/PKA pathway. Few data exist concerning the signal transduction pathways triggered by hCG in ESCs and their role in regulation of ESC function.

STUDY DESIGN, SIZE, DURATION

This is an in vitro study comprising patients undergoing benign gynecological surgery (n = 46).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Endometrial samples were collected from normal cycling women during the mid-secretory phase for ESCs isolation. The study conducted in an academic research laboratory within a tertiary-care hospital. The activation of the Erk1/2 signal transduction pathway elicited by hCG was evaluated in ESC. Signaling pathway inhibitors were used to examine the roles of PKA, PI3K, PKC, adenylyl cyclase and Epac on the hCG-stimulated up-regulation of phospho-Erk1/2 (pErk1/2). Erk1/2 phosphorylation was determined by immunoblot. siRNA targeting Epac was used to investigate the molecular mechanisms. To assess the role of Erk1/2 signaling induced by hCG on ESC function, gene expression regulation was examined by immunofluorescence and real-time quantitative PCR. The role of PR on the regulation of transcript levels was studied using progesterone and the PR antagonist RU486. All experiments were conducted using at least three different cell culture preparations in triplicate.

MAIN RESULTS AND THE ROLE OF CHANCE

Addition of hCG to ESCs in vitro induced the phosphorylation of Erk1/2 through cAMP accumulation. Such induction could not be blocked by inhibitors for PKA, PKC and PI3K. Epac inhibition and knockdown with siRNA prevented pErk1/2 induction by hCG. ESCs stimulated with hCG for up to 72 h showed a significant increase in PR mRNA and immunofluorescent label at 48 h only; an effect that was abrogated with the mitogen-activated protein kinase kinase inhibitor UO126. In addition, the hCG-activated Erk1/2 pathway significantly decreased the mRNA levels for secreted frizzled-related protein 4 (SFRP4) at 24 h, whereas it increased those for homeobox A10 (HOXA10) at 48 h (P = 0.041 and P = 0.022 versus control, respectively). Prolactin mRNA levels were not significantly modified. HOXA10 mRNA up-regulation by hCG was not enhanced by co-stimulation with progesterone; however, it was completely abolished in the presence of RU486 (P = 0.036 hCG versus hCG + RU486).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study utilizing stromal cell cultures from human endometrial tissues. Furthermore, results obtained should also be confirmed in vivo in the context of the whole human endometrial tissue and hormonal milieu. The in vitro experiments using hCG have been conducted without other hormones/factors that may also modulate the ESCs response to hCG.

WIDER IMPLICATIONS OF THE FINDINGS

We have determined that hCG induces the PR through the Erk1/2 pathway in ESCs which may render them more sensitive to progesterone, increasing our understanding about the effects of hCG at the embryo-maternal interface. The activation of such a pathway in the context of the hormonal milieu during the window of implantation might contribute to a successful dialog between the embryo and the uterus, leading to appropriate endometrial function. Defective hCG signaling in the endometrial stromal tissue may lead to an incomplete uterine response, compromising embryo implantation and early pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Fund for Scientific and Technological Development, Government of Chile (FONDECYT) grants 11100443 and 1140614 (A.T.-P.). The authors have no conflicts of interest to declare.

Integration of Transcriptomic and Metabolomic Data Reveals Enhanced Steroid Hormone Biosynthesis in Mouse Uterus During Decidualization

It has been long recognized that decidualization is accompanied by significant changes in metabolic pathways. In the present study, we used the GC-TOF-MS approach to investigate the global metabolite profile changes associated with decidualization of mouse uterus on day 8 of pregnancy. We identified a total of 20 differentially accumulated metabolites, of which nine metabolites were down-regulated and 11 metabolites were up-regulated. As expected, seven differentially accumulated metabolites were involved in carbohydrate metabolism. We observed statistically significant changes in polyamines, putrescine and spermidine. Interestingly, the pantothenic acid, also known as vitamin B₅ , was up-regulated. Finally, by integrating with transcriptomic data obtained by RNA-seq, we revealed enhanced steroid hormone biosynthesis during decidualization. Our study contributes to an increase in the knowledge on the molecular mechanisms of decidualization.

Crosstalk between human endometrial stromal cells and decidual NK cells promotes decidualization in vitro by upregulating IL‑25

Embryo implantation is essential for a successful pregnancy, and leads to the decidualization of endometrial stromal cells (ESCs) in the secretory phase of the menstrual cycle. It has previously been demonstrated that decidual stromal cells (DSCs) co‑express interleukin (IL)‑25/IL‑17RB and that IL‑25 further promotes the proliferation of DSCs via activating c‑Jun n‑terminal kinase and protein kinase B signals, therefore the present study primarily focused on the role of IL‑25 in the process of decidualization in vitro. It was demonstrated that the expression of IL‑25/IL‑17RB in ESCs was decreased compared with DSCs. In addition, following decidualization, the expression levels of IL‑25/IL‑17RB in ESCs were significantly elevated. Recombinant human (rh) IL‑25 promoted the decidualization of ESCs in the presence of 8‑bromoadenosine 3',5'‑cyclic monophosphate sodium salt and 6α‑methyl17α‑acetoxyprogesterone, which was partially inhibited by anti‑human IL‑25 neutralizing antibody (anti‑IL‑25) or anti‑IL‑17RB. In addition, decidual natural killer (dNK) cells not only secreted IL‑25, however also further accelerated the decidualization in vitro. Therefore, these findings indicated that ESCs differentiate into DSCs in the presence of ovarian hormones, resulting in the upregulation of IL‑25/IL‑17RB expression in ESCs. Furthermore, IL‑25 secreted by ESCs and dNK cells further facilitates the decidualization of ESCs, which may form a positive feedback mechanism at the maternal‑fetal interface and thus contribute to the establishment and maintenance of normal pregnancy.

TGFβ superfamily signaling and uterine decidualization

Decidualization is an intricate biological process where extensive morphological, functional, and genetic changes take place in endometrial stromal cells to support the development of an implanting blastocyst. Deficiencies in decidualization are associated with pregnancy complications and reproductive diseases. Decidualization is coordinately regulated by steroid hormones, growth factors, and molecular and epigenetic mechanisms. Transforming growth factor β (TGFβ) superfamily signaling regulates multifaceted reproductive processes. However, the role of TGFβ signaling in uterine decidualization is poorly understood. Recent studies using the Cre-LoxP strategy have shed new light on the critical role of TGFβ signaling machinery in uterine decidualization. Herein, we focus on reviewing exciting findings from studies using both mouse genetics and in vitro cultured human endometrial stromal cells. We also delve into emerging mechanisms that underlie decidualization, such as non-coding RNAs and epigenetic modifications. We envision that future studies aimed at defining the interrelationship among TGFβ signaling circuitries and their potential interactions with epigenetic modifications/non-coding RNAs during uterine decidualization will open new avenues to treat pregnancy complications associated with decidualization deficiencies.

Establishment and characterization of cell lines derived from complete hydatidiform mole

Gestational trophoblastic diseases (GTDs) are a group of diseases characterized by abnormal cellular proliferation of atypical trophoblasts. A hydatidiform mole is an abnormal pregnancy caused by genetic fertilization disorders, and it can be classified as a complete hydatidiform mole (CHM) or a partial hydatidiform mole. The aim of this study was to establish cell lines from CHMs and to characterize the cells for future studies concerning GTD. HMol1-2C, HMol1-3B, HMol1-8 and HMol3-1B were established from primary cultures of CHM explants following the introduction of different combinations of genes including human telomerase reverse transcriptase (hTERT), a mutant form of CDK (CDK4R24C), cyclin D1, p53C234, MYC and HRAS. HMol1-2C, HMol1-3B, and HMol3-1B were confirmed to originate from trophoblasts of androgenic, homozygous CHMs. These three cell lines exhibited low human chorionic gonadotropin secretion, low migration and invasion abilities, and the potential to differentiate into syncytiotrophoblastic cells via forskolin treatment. These results suggest that these cells exhibit characteristics of trophoblastic cells, especially cytotrophoblastic cells. HMol1-8 was found to consist of diploid cells and originated from maternal cells, suggesting that they were derived from decidual cells. In conclusion, we successfully established three cell lines from CHMs by introduction of hTERT and other genes. Analysis revealed that the genetic origin of each cell line was identical with that of the original molar tissue, and the cell lines exhibited characteristics of trophoblastic cells, which are similar to undifferentiated cytotrophoblasts.

Functional implications of the utero-placental relaxin (RLN) system in the dog throughout pregnancy and at term

Relaxin (RLN) is a key hormone of pregnancy in mammals best known for its involvement in connective tissue remodeling. In the domestic dog, placental RLN is the only known endocrine marker of pregnancy. However, knowledge is sparse regarding the spatio-temporal expression of RLN and its receptors (RXFP1 and RXFP2) in the canine uterus and placenta. Here, their expression was investigated in the pre-implantation uterus and utero-placental compartments (UtPl) at selected time points during gestation: post-implantation, mid-gestation, and at normal and antigestagen-induced luteolysis/abortion. Immunohistochemistry with newly generated, canine-specific antisera, in situ hybridization and semi-quantitative PCR were applied. In compartmentalization studies, placental and endometrial RLN increased continuously toward prepartum. The placental RXFP1 was time-related and highest during post-implantation and decreased together with RXFP2 at prepartum luteolysis. The endometrial levels of both receptors did not vary greatly, but myometrial RXFP2 decreased from mid-gestation to prepartum luteolysis. Antigestagen treatment resulted in suppression of RLN in UtPl and decreased RXFP1 and RXFP2 in the uterus. The placental RLN was localized mainly in the cytotrophoblast. Additionally, RXFP1 stained strongly in placental endothelial cells while RXFP2 was found mainly in maternal decidual cells. Uterine staining for all targets was found in epithelial cellular constituents and in myometrium. Finally, besides its endocrine functions, RLN seems to be involved in auto-/paracrine regulation of utero-placental functions in dogs in a time-dependent manner. New insights into feto-maternal communication was provided, in particular regarding the localization of RXFP2 in the maternal decidual cells, implying functional roles of RLN during the decidualization process.

Regulation of the PI3K/Akt pathway during decidualization of endometrial stromal cells

Infertility is constantly increasing in Canada, where 16% of Canadian couples are experiencing difficulty conceiving. It is thought that infertility can emanate from the dysregulated communication between the embryo and the maternal endometrium. In order to allow for this window of implantation to be open at the right moment, endometrial stromal cells proliferate and differentiate by a mechanism called decidualization. Intracellular and molecular mechanisms involved in the regulation of apoptosis and cell proliferation during decidualization of the endometrium are yet to be fully understood. It has been well demonstrated previously that Akt is importantly involved in cell survival and glycogen synthesis. Akt1, Akt2 and Akt3 isoforms have distinct physiological roles; this could also be the case during decidualization and pregnancy. The aim of this study is to investigate the regulation of PI3K/Akt pathway during the decidualization process of endometrial stromal cells. Expression of Akt isoforms, Akt activity (phospho-Akt), pIκB and substrates of Akt during decidualization were measured. To our knowledge, these results are the first to suggest a decrease in levels of Akt isoforms as well as a downregulation of Akt activity in the process of decidualization of human endometrial stromal cells. We also uncovered that decidualization induced nuclear localization of p65 through the phosphorylation of IκB, its inhibitory subunit; however, Par-4, a recently uncovered regulator of cell differentiation, was displaced from the nucleus upon decidualization. Our results also suggest that HIESC cells exhibit decreased motility during decidualization and that PI3K pathway inhibition could be involved in this process. Finally, we demonstrate that specific Akt isoforms present unique effects on the successful induction of decidualization. Further analyses will involve investigations to understand the precise signaling mechanisms by which this pathway is regulated.

Chronic endometritis modifies decidualization in human endometrial stromal cells

BACKGROUND

Chronic endometritis (CE) is a continuous inflammation of uterine endometrium, and it is usually symptomless. As CE has been thought not to affect the reproductive status and general health of affected women, its significance has not been explored. However, recent studies have shown that CE is related with repeated implantation failures after in vitro fertilization-embryo transfer, unexplained infertility, and recurrent miscarriages. As decidua differentiates to support the implantation process and maintains the pregnancy, we hypothesized that CE may influence the process of decidualization.

METHODS

Seventeen patients were employed in the experiment involving culture of endometrial stromal cells (ESCs). After obtaining endometrial samples, ESCs were harvested and cultured for 13 days. The concentrations in culture media and the protein expressions in ESCs of prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1), two well known decidualization markers used in a large number of in vitro models, were analyzed by ELISA and Western blotting, respectively, and the cell numbers were also counted. The mRNA levels of PRL and IGFBP-1 were tested by quantitative real time polymerase chain reaction (RT-PCR). Since sex hormone induce proliferation and differentiation to decidua via binding to the sex hormone receptors (ERα, ERβ, PRA, and PRB), their expression was assessed in another 17 patients' paraffin-embedded endometrial tissue specimens by immunohistochemistry and semi-quantified by H-score.

RESULTS

Increased cell numbers and reduced secretion of PRL and IGFBP-1 were detected by ELISA in the ESCs of CE patients after culture for 13 days compared with non-CE patients. The decreased protein expression of IGFBP-1 in ESCs of CE patients was detected by Western blotting. The decreased expression of PRL mRNA and IGFBP-1 mRNA were detected by RT-PCR. Increased expressions of ERα, ERβ, PRA, and PRB were observed in the stromal cells of CE patients in comparison to non-CE patients, whereas increased expressions of ERα and ERβ were detected in the glandular cells of CE.

CONCLUSION

Our data suggests that CE modifies decidualization of human ESC through untuning the function of sex steroid hormone receptor.

A study on regional differences in decidualization of the mouse uterus

Although regional differences in mouse decidualization have been recognized for decades, the molecular mechanisms remain understudied. In the present study, by using RNA-seq, we compared transcriptomic differences between the anti-mesometrial (AM) region and the mesometrial (M) region of mouse uterus on day 8 of pregnancy. A total of 1423 differentially expressed genes were identified, of which 811 genes were upregulated and 612 genes were downregulated in the AM region compared to those in the M region. Gene ontology analysis showed that upregulated genes were generally involved in cell metabolism and differentiation, whereas downregulated genes were associated with lymphocyte themes and immune response. Through network analysis, we identified a total of 6 hub genes. These hub genes are likely more important than other genes due to their key positions in the network. We also examined the promoter regions of differentially expressed genes for the enrichment of transcription factor-binding sites. In the end, we demonstrated that a similar regional gene expression pattern can be observed in the artificial decidualization model. Our study contributes to an increase in the knowledge on the molecular mechanisms underlying regional decidualization in mice.

Effect of single post-ovulatory administration of mifepristone (RU486) on transcript profile during the receptive period in human endometrium

Progesterone regulates uterine function during the luteal phase and is essential for the acquisition of endometrial receptivity. The objective of the present study was to identify endometrial transcripts whose expression is altered during the window of implantation after the administration of 200 mg of the antiprogestin mifepristone, 48 h after the LH peak (LH+2, LH+0=LH peak), and to determine the relationship of these transcripts with those regulated during the acquisition of receptivity. Endometrial samples were obtained in LH+7 from seven women of proven fertility, each one contributing with one cycle treated with placebo and another with mifepristone. Additionally, endometrial samples were obtained in LH+2 and LH+7 during a single untreated spontaneous cycle from seven normal fertile women as a reference. DNA microarrays were used to identify transcripts significantly regulated (defined as ≥2.0-fold change with false discovery rate below 1% usingt-test) with the administration of mifepristone vs placebo, or during the transition from pre-receptive to receptive (LH+2 vs LH+7). Approximately 2000 transcripts were significantly regulated in both comparisons (mifepristone vs placebo and LH+2 vs LH+7), but only 777 of them were coincident and displayed opposite regulation except for 25. The mRNA level for eight selected genes regulated by mifepristone was confirmed by real-time RT-PCR. We conclude that not all changes in endometrial transcript levels occurring in the transition from LH+2 to LH+7 seem to be regulated by the progesterone receptor and ∼37% of the genes whose transcript levels changed by effect of mifepristone could be associated with the acquisition of receptivity.

Effects of low doses of mifepristone on human embryo implantation process in a three-dimensional human endometrial in vitro co-culture system

OBJECTIVES

We wanted to explore the effects of two different low doses (0.5μM and 0.05μM) of mifepristone, exposed during the receptive period, on the human embryo implantation process, using a well-established three-dimensional in vitro cell culture model, specifically developed to study this process.

METHODS

An in vitro three-dimensional cell culture model was constructed using human endometrial cells isolated from the endometrium of proven fertile women, collected on cycle day LH+4. After 5 days of culture, supernumerary human embryos were added and cultured for another 5 days with mifepristone 0.5μM (n=8) or 0.05μM (n=10) or vehicle as control (n=10). The cultures were checked for embryo attachment and terminated. We studied the expression of 16 reported endometrial receptivity markers in the endometrial constructs using real-time polymerase chain reaction.

RESULTS

None of the embryos in 0.5μM of mifepristone attached to the endometrial constructs (p=.004), whereas 4 out of 10 in 0.05μM (p=.3698) and 7 out of 10 embryos in the control group attached to the cultures. We found that most of the studied receptivity markers were significantly altered with mifepristone exposure in a similar direction in both treatment groups. Only IL6 was significantly differentially expressed between the treatment groups (p=.017).

CONCLUSION

We report for the first time that exposure to a low concentration (0.5μM) of mifepristone during the receptive period successfully inhibits human embryo implantation process in vitro. Further, we observed a dose-dependent effect of mifepristone on endometrial receptivity at the functional level.

IMPLICATION

This study contributes new knowledge that low dose of mifepristone during the short period of receptive phase can inhibit endometrial receptivity, which further promotes mifepristone as a contraceptive agent. This could give women a treatment choice to avoid unwanted pregnancy with high efficacy and minimal side effects.

Identification of target genes for a prolactin family paralog in mouse decidua

Prolactin family 8, subfamily a, member 2 (PRL8A2; also called decidual prolactin-related protein; dPRP) is a member of the expanded prolactin family. PRL8A2 is expressed in the uterine decidua and contributes to pregnancy-dependent adaptations to hypoxia. The purpose of this study was to identify gene targets for PRL8A2 action within the uteroplacental compartment. Affymetrix DNA microarray analysis was performed for RNA samples from WT and Prl8a2 null tissues. Validation of the DNA microarray was performed using quantitative RT-PCR. Nine genes were confirmed with decreased expression in Prl8a2 null tissues (e.g., Klk7, Rimklb, Arhgef6, Calm4, Sprr2h, Prl4a1, Ccl27, Lipg, and Htra3). These include potential decidual, endothelial and trophoblast cell targets positively regulated by PRL8A2. A significant upregulation of Derl3, Herpud1, Creld2, Hsp90b1, Ddit3 and Hspa5 was identified in Prl8a2 null tissues, reflecting an increased endoplasmic reticulum (ER) stress response. ER stress genes were prominently expressed in the uterine decidua. We propose that PRL8A2 is a mediator of progesterone-dependent modulation of intrauterine responses to physiological stressors.

International Union of Basic and Clinical Pharmacology. XCV. Recent advances in the understanding of the pharmacology and biological roles of relaxin family peptide receptors 1-4, the receptors for relaxin family peptides

Relaxin, insulin-like peptide 3 (INSL3), relaxin-3, and INSL5 are the cognate ligands for the relaxin family peptide (RXFP) receptors 1-4, respectively. RXFP1 activates pleiotropic signaling pathways including the signalosome protein complex that facilitates high-sensitivity signaling; coupling to Gα(s), Gα(i), and Gα(o) proteins; interaction with glucocorticoid receptors; and the formation of hetero-oligomers with distinctive pharmacological properties. In addition to relaxin-related ligands, RXFP1 is activated by Clq-tumor necrosis factor-related protein 8 and by small-molecular-weight agonists, such as ML290 [2-isopropoxy-N-(2-(3-(trifluoromethylsulfonyl)phenylcarbamoyl)phenyl)benzamide], that act allosterically. RXFP2 activates only the Gα(s)- and Gα(o)-coupled pathways. Relaxin-3 is primarily a neuropeptide, and its cognate receptor RXFP3 is a target for the treatment of depression, anxiety, and autism. A variety of peptide agonists, antagonists, biased agonists, and an allosteric modulator target RXFP3. Both RXFP3 and the related RXFP4 couple to Gα(i)/Gα(o) proteins. INSL5 has the properties of an incretin; it is secreted from the gut and is orexigenic. The expression of RXFP4 in gut, adipose tissue, and β-islets together with compromised glucose tolerance in INSL5 or RXFP4 knockout mice suggests a metabolic role. This review focuses on the many advances in our understanding of RXFP receptors in the last 5 years, their signal transduction mechanisms, the development of novel compounds that target RXFP1-4, the challenges facing the field, and current prospects for new therapeutics.

Regulation of inflammatory and angiogenesis mediators in a functional model of decidualized endometrial stromal cells

The mechanisms involving the expression of interleukin (IL) 1 family members in the process of preparing the endometrium to receive an embryo remain unclear. In this study, decidualization differentially skewed the balance of IL1 family receptor expression in a pattern that increases endometrial stromal cell receptivity to IL1, IL18 and IL33. Additionally, endometrial cells showed increased expression of homeobox HOXA10 and HOXA11 and LIFR, which are known to be involved in endometrial embryo receptivity. Further analyses of decidual endometrial cells revealed a significant increase in the release of potent proinflammatory, remodelling and angiogenic factors implicated in the embryo invasion process, such as VEGF (P = 0.0305), MMP9 (P = 0.0003), TIMP3 (P = 0.0001), RANTES (P = 0.0020), MCP1 (P = 0.0001) and MIF (P = 0.0068). No significant changes in endogenous IL1B secretion were observed. Decreased secretion of IL18 and decidualization increased secretion of IL33. These findings reveal a significant modulation of endometrial cell receptivity to IL1 family members during endometrial stromal cell decidualization, and suggest that the involvement of IL1 family members is important in physiological processes of endometrial receptivity, including adaptive immunology. This may be relevant to establishing a favourable uterine microenvironment for embryo implantation.

Systematic Analysis of the Molecular Mechanism Underlying Decidualization Using a Text Mining Approach

Decidualization is a crucial process for successful embryo implantation and pregnancy in humans. Defects in decidualization during early pregnancy are associated with several pregnancy complications, such as pre-eclampsia, intrauterine growth restriction and recurrent pregnancy loss. However, the mechanism underlying decidualization remains poorly understood. In the present study, we performed a systematic analysis of decidualization-related genes using text mining. We identified 286 genes for humans and 287 genes for mice respectively, with an overlap of 111 genes shared by both species. Through enrichment test, we demonstrated that although divergence was observed, the majority of enriched gene ontology terms and pathways were shared by both species, suggesting that functional categories were more conserved than individual genes. We further constructed a decidualization-related protein-protein interaction network consisted of 344 nodes connected via 1,541 edges. We prioritized genes in this network and identified 12 genes that may be key regulators of decidualization. These findings would provide some clues for further research on the mechanism underlying decidualization.

MicroRNA-181a is involved in the regulation of human endometrial stromal cell decidualization by inhibiting Krüppel-like factor 12

BACKGROUND

The transformation of endometrium into decidua is essential for normal implantation of the blastocyst. However, the post-transcriptional regulation and the miRNAs involved in decidualization remain poorly understood. Here, we examined microRNA-181a (miR-181a) expression in decidualized human endometrial stromal cell (hESC). In addition, we investigated the functional effect of miR-181a on hESC decidualization in vitro.

METHODS

Quantitative real-time PCR (qRT-PCR) was used to detect the profile of miR-181a in decidualized hESC. qRT-PCR, enzyme-linked fluorescent assay, and immunofluorescence assay were performed to investigate decidualization marker genes' expression after enhancing or inhibition of miR-181a expression in hESC. Luciferase reporter assay, western blotting, qRT-PCR, and immunofluorescence assay were carried out to identify the relationship between miR-181a and Krüppel-like factor 12 (KLF12).

RESULTS

miR-181a expression levels increased dramatically in hESC treated with 8-Br-cAMP and MPA. Increased miR-181a expression promoted hESC decidualization-related gene expression and morphological transformation; conversely, inhibition of miR-181a expression compromised hESC decidualization in vitro. Further analysis confirmed that miR-181a interacted with the 3' untranslated region of the transcription factor KLF12 and down-regulated KLF12 at the transcriptional and translational levels. KLF12 overexpression abolished miR-181a-induced decidualization.

CONCLUSIONS

Our findings suggest that miR-181a plays a functionally important role in human endometrial stromal cell decidualization in vitro by inhibiting KLF12.

Effects of ulipristal acetate on human embryo attachment and endometrial cell gene expression in an in vitro co-culture system

STUDY QUESTION

Does ulipristal acetate (UPA) used for emergency contraception (EC) interfere with the human embryo implantation process?

SUMMARY ANSWER

UPA, at the dosage used for EC, does not affect human embryo implantation process, in vitro.

WHAT IS KNOWN ALREADY

A single pre-ovulatory dose of UPA (30 mg) acts by delaying or inhibiting ovulation and is recommended as first choice among emergency contraceptive pills due to its efficacy. The compound has also been demonstrated to have a dose-dependent effect on the endometrium, which theoretically could impair endometrial receptivity but its direct action on human embryo implantation has not yet been studied.

STUDY DESIGN, SIZE, DURATION

Effect of UPA on embryo implantation process was studied in an in vitro endometrial construct. Human embryos were randomly added to the cultures and cultured for 5 more days with UPA (n = 10) or with vehicle alone (n = 10) to record the attachment of embryos.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Endometrial biopsies were obtained from healthy, fertile women on cycle day LH+4 and stromal and epithelial cells were isolated. A three-dimensional in vitro endometrial co-culture system was constructed by mixing stromal cells with collagen covered with a layer of epithelial cells and cultured in progesterone containing medium until confluence. The treatment group received 200 ng/ml of UPA. Healthy, viable human embryos were placed on both control and treatment cultures. Five days later the cultures were tested for the attachment of embryos and the 3D endometrial constructs were analysed for endometrial receptivity markers by real-time PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

There was no significant difference in the embryo attachment rate between the UPA treated group and the control group as 5 out of 10 human embryos exposed to UPA and 7 out of 10 embryos in the control group attached to the endometrial cell surface (P = 0.650). Out of 17 known receptivity genes studied here, only 2 genes, HBEGF (P = 0.009) and IL6 (P = 0.025) had a significant up-regulation and 4 genes, namely HAND2 (P = 0.003), OPN (P = 0.003), CALCR (P = 0.016) and FGF2 (P = 0.023) were down-regulated with the exposure of UPA, compared with control group.

LIMITATIONS, REASONS FOR CAUTION

This proof of concept study was conducted with a few human embryos, as their availability was limited. Although the 3D model used for this study is well established and the artificial endometrial luminal epithelium shown to express progesterone regulated markers of endometrial receptivity it is still an in vitro model, lacking all cell types that constitute the receptive endometrium in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides new insights on the mechanism of action of UPA on human embryo implantation, demonstrating that UPA in a dosage used for EC does not affect embryo viability and the implantation process of embryo. Progesterone receptor modulators (PRMs) hold the potential to be attractive estrogen- and gestagen-free contraceptives and thus may be made available to a larger proportion of women globally due to these findings.

STUDY FUNDING/COMPETING INTERESTS

Swedish Research Council (K2010-54X-14212-09-3) and support provided through the regional agreement on medical training and clinical research (ALF) between Stockholm County Council and Karolinska University Hospital.

The clock protein period 2 synchronizes mitotic expansion and decidual transformation of human endometrial stromal cells

Implantation requires coordinated interactions between the conceptus and surrounding decidual cells, but the involvement of clock genes in this process is incompletely understood. Circadian oscillations are predicated on transcriptional-translational feedback loops, which balance the activities of the transcriptional activators CLOCK (circadian locomotor output cycles kaput) and brain muscle arnt-like 1 and repressors encoded by PER (Period) and Cryptochrome genes. We show that loss of PER2 expression silences circadian oscillations in decidualizing human endometrial stromal cells (HESCs). Down-regulation occurred between 12 and 24 hours following differentiation and coincided with reduced CLOCK binding to a noncanonical E-box enhancer in the PER2 promoter. RNA sequencing revealed that premature inhibition of PER2 by small interfering RNA knockdown leads to a grossly disorganized decidual response. Gene ontology analysis highlighted a preponderance of cell cycle regulators among the 1121 genes perturbed upon PER2 knockdown. Congruently, PER2 inhibition abrogated mitotic expansion of differentiating HESCs by inducing cell cycle block at G2/M. Analysis of 70 midluteal endometrial biopsies revealed an inverse correlation between PER2 transcript levels and the number of miscarriages in women suffering reproductive failure (Spearman rank test, ρ = −0.3260; P = 0.0046). Thus, PER2 synchronizes endometrial proliferation with initiation of aperiodic decidual gene expression; uncoupling of these events may cause recurrent pregnancy loss.—Muter, J., Lucas, E. S., Chan, Y.-W., Brighton, P. J., Moore, J. D., Lacey, L., Quenby, S., Lam, E. W.-F., Brosens, J. J. The clock protein period 2 synchronizes mitotic expansion and decidual transformation of human endometrial stromal cells.

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.

Endometrial stromal cells and decidualized stromal cells: origins, transformation and functions

Decidualization of endometrium, which is characterized by endometrial stromal cell (ESC) decidualization, vascular reconstruction, immune cell recruitment, and plentiful molecule production, is a crucial step for uterus to become receptive for embryo. When implantation takes place, ESCs surround and directly interact with embryo. Decidualized stromal cells (DSCs) are of great importance in endometrial decidualization, having a broad function in regulating immune activity and vascular remodeling of uterus. DSCs are shown to have a higher metabolic level and looser cytoskeleton than ESCs. What's the origin of ESCs and how ESCs successfully transform into DSCs had puzzled scientists in the last decades. Breakthrough had been achieved recently, and many studies had elucidated some of the characters and functions of DSCs. However, several questions still remain unclear. This paper reviews current understanding of where ESCs come from and how ESCs differentiate into DSCs, summarizes some characters and functions of DSCs, analyzes current studies and their limitations and points out research areas that need further investigation.

Ion/Water Channels for Embryo Implantation Barrier

Successful implantation involves three distinct processes, namely the embryo apposition, attachment, and penetration through the luminal epithelium of the endometrium to establish a vascular link to the mother. After penetration, stromal cells underlying the epithelium differentiate and surround the embryo to form the embryo implantation barrier, which blocks the passage of harmful substances to the embryo. Many ion/water channel proteins were found to be involved in the process of embryo implantation. First, ion/water channel proteins play their classical role in establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ions across the cell membrane. Second, most of ion/water channel proteins are regulated by steroid hormone (estrogen or progesterone), which may have important implications to the embryo implantation. Last but not least, these proteins do not limit themselves as pure channels but also function as an initiator of a series of consequences once activated by their ligand/stimulator. Herein, we discuss these new insights in recent years about the contribution of ion/water channels to the embryo implantation barrier construction during early pregnancy.