C/EBPbeta is a critical mediator of steroid hormone-regulated cell proliferation and differentiation in the uterine epithelium and stroma

Unraveling the Dynamics of Estrogen and Progesterone Signaling in the Endometrium: An Overview

The endometrium is crucial for the perpetuation of human species. It is a complex and dynamic tissue lining the inner wall of the uterus, regulated throughout a woman's life based on estrogen and progesterone fluctuations. During each menstrual cycle, this multicellular tissue undergoes cyclical changes, including regeneration, differentiation in order to allow egg implantation and embryo development, or shedding of the functional layer in the absence of pregnancy. The biology of the endometrium relies on paracrine interactions between epithelial and stromal cells involving complex signaling pathways that are modulated by the variations of estrogen and progesterone levels across the menstrual cycle. Understanding the complexity of estrogen and progesterone receptor signaling will help elucidate the mechanisms underlying normal reproductive physiology and provide fundamental knowledge contributing to a better understanding of the consequences of hormonal imbalances on gynecological conditions and tumorigenesis. In this narrative review, we delve into the physiology of the endometrium, encompassing the complex signaling pathways of estrogen and progesterone.

Nuclear actin assembly is an integral part of decidualization in human endometrial stromal cells

Decidualization of the human endometrium is critical for establishing pregnancy and is entailed by differentiation of endometrial stromal cells (ESCs) into decidual cells. During decidualization, the actin cytoskeleton is dynamically reorganized for the ESCs' morphological and functional changes. Although actin dynamically alters its polymerized state upon external stimuli not only in the cytoplasm, but also in the nucleus, nuclear actin dynamics during decidualization have not been elucidated. Here, we show that nuclear actin was specifically assembled during decidualization of human ESCs. This decidualization-specific formation of nuclear actin filaments was disassembled following the withdrawal of the decidualization stimulus, suggesting its reversible process. Mechanistically, RNA-seq analyses revealed that the forced disassembly of nuclear actin resulted in the suppression of decidualization, accompanied with the abnormal upregulation of cell proliferation genes, leading to incomplete cell cycle arrest. CCAAT/enhancer-binding protein beta (C/EBPβ), an important regulator for decidualization, was responsible for downregulation of the nuclear actin exporter, thus accelerating nuclear actin accumulation and its assembly for decidualization. Taken together, we demonstrate that decidualization-specific nuclear actin assembly induces cell cycle arrest for establishing the decidualized state of ESCs. We propose that not only the cytoplasmic actin, but also nuclear actin dynamics profoundly affect decidualization process in humans for ensuring pregnancy.

Genetic and epigenetic alterations in precursor lesions of endometrial endometrioid carcinoma

The hyperplasia-carcinoma sequence is a stepwise tumourigenic programme towards endometrial cancer in which normal endometrial epithelium becomes neoplastic through non-atypical endometrial hyperplasia (NAEH) and atypical endometrial hyperplasia (AEH), under the influence of unopposed oestrogen. NAEH and AEH are known to exhibit polyclonal and monoclonal cell growth, respectively; yet, aside from focal PTEN protein loss, the genetic and epigenetic alterations that occur during the cellular transition remain largely unknown. We sought to explore the potential molecular mechanisms that promote the NAEH-AEH transition and identify molecular markers that could help to differentiate between these two states. We conducted target-panel sequencing on the coding exons of 596 genes, including 96 endometrial cancer driver genes, and DNA methylome microarrays for 48 NAEH and 44 AEH lesions that were separately collected via macro- or micro-dissection from the endometrial tissues of 30 cases. Sequencing analyses revealed acquisition of the PTEN mutation and the clonal expansion of tumour cells in AEH samples. Further, across the transition, alterations to the DNA methylome were characterised by hypermethylation of promoter/enhancer regions and CpG islands, as well as hypo- and hyper-methylation of DNA-binding regions for transcription factors relevant to endometrial cell differentiation and/or tumourigenesis, including FOXA2, SOX17, and HAND2. The identified DNA methylation signature distinguishing NAEH and AEH lesions was reproducible in a validation cohort with modest discriminative capability. These findings not only support the concept that the transition from NAEH to AEH is an essential step within neoplastic cell transformation of endometrial epithelium but also provide deep insight into the molecular mechanism of the tumourigenic programme. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

High incidence of decidualization failure in infertile women

Purpose

Decidualization is an important event for embryo implantation and successful pregnancy. Impaired decidualization leads to implantation failure and miscarriage. However, it is unclear how often decidualization failure occurs in infertile women. By analyzing the endometrium at late-secretory phase, we investigated the incidence and pathogenesis of decidualization failure among infertile women.

Methods

Endometrial dating was performed on the endometria obtained in the late-secretory phase from 33 infertile women. Endometrial dating of more than 2 days delay was taken as an indication of decidualization failure. The expression of essential transcription factors for decidualization (FOXO1, WT1, and C/EBPβ) was examined by immunohistochemistry.

Results

Among 32 cases, 20 cases (62.5%) showed decidualization failure. These patients tended to have a history of more frequent miscarriages than those without decidualization failure. The percentage of cells that immunostained positive for the expression of three transcription factors was significantly lower in the patients with decidualization failure than in those without decidualization failure. Serum progesterone levels measured in the mid- and late-secretory phase were not significantly different between the cases with and without decidualization failure.

Conclusions

The incidence of decidualization failure is high in infertile women.

Exposure to di-isononyl phthalate during early pregnancy disrupts decidual angiogenesis and placental development in mice

Di-isononyl phthalate (DiNP), an endocrine-disrupting chemical, is found in numerous consumer products and human exposure to this phthalate is becoming inevitable. The impact of DiNP exposure on the establishment and maintenance of pregnancy remains largely unknown. Thus, we conducted studies in which pregnant mice were exposed to an environmentally relevant dose (20 µg/kg BW/day) of DiNP on days 1-7 of gestation, then analyzed the effects of this exposure on pregnancy outcome. Our studies revealed that exposure to DiNP during this window led to fetal loss towards the end of gestation. Further studies showed that, although embryos were able to attach to the uterus, implantation sites in DiNP-exposed uteri exhibited impaired differentiation of stromal cells to decidual cells and an underdeveloped angiogenic network in the decidual bed. We also found that exposure to this phthalate has a significant effect on trophoblast differentiation and causes disorganization of the placental layers. The labyrinth was significantly reduced, resulting in compromised expression of nutrient transporters in the placentas of mice exposed to DiNP. These placental defects in DiNP-exposed females were the cause of fetal loss during the later stages of gestation.

The role of mesenchymal estrogen receptor 1 in mouse uterus in response to estrogen

Estrogens play important roles in uterine growth and homeostasis through estrogen receptors (ESR1 and ESR2). To address the role of ESR1-mediated tissue events in the murine uterus, we analyzed mice with a mesenchymal tissue-specific knockout of Esr1. Isl1-driven Cre expression generated Esr1 deletion in the uterine stroma and endometrium (Isl-Esr1KO). We showed that overall structure of the Isl1-Esr1KO mouse uterus developed normally, but estrogen responsiveness and subsequent growth were defective, suggesting that mesenchymal ESR1 is necessary for both epithelial and mesenchymal cell proliferation. Furthermore, RNA-seq analysis revealed that the majority of estrogen-induced genes were regulated by stromal ESR1. In control mice, E2 administration induced 9476 up-regulated differentially expressed genes (DEGs), whereas only 1801 up-regulated DEGs were induced by E2 in Isl1-Esr1KO mice. We further showed that stromal ESR1-regulated genes in the mouse uterus included several growth factors and cytokines, which are potential factors that regulate epithelial and stromal tissue interaction, and also genes involved in lipid homeostasis. Therefore, we infer that stromal ESR1 expression is indispensable for most estrogen actions in the mouse uterus and the current results provide new insights into estrogen-mediated homeostasis in female reproductive organs.

Runx1 regulates critical factors that control uterine angiogenesis and trophoblast differentiation during placental development

During early pregnancy in humans and rodents, uterine stromal cells undergo a remarkable differentiation to form the decidua, a transient maternal tissue that supports the growing fetus. It is important to understand the key decidual pathways that orchestrate the proper development of the placenta, a key structure at the maternal-fetal interface. We discovered that ablation of expression of the transcription factor Runx1 in decidual stromal cells in a conditional Runx1-null mouse model (Runx1^d/d) causes fetal lethality during placentation. Further phenotypic analysis revealed that uteri of pregnant Runx1^d/d mice exhibited severely compromised decidual angiogenesis and a lack of trophoblast differentiation and migration, resulting in impaired spiral artery remodeling. Gene expression profiling using uteri from Runx1^d/d and control mice revealed that Runx1 directly controls the decidual expression of the gap junction protein connexin 43 (also known as GJA1), which was previously shown to be essential for decidual angiogenesis. Our study also revealed that Runx1 controls the expression of insulin-like growth factor (IGF) 2 and IGF-binding protein 4 (IGFBP4) during early pregnancy. While Runx1 deficiency drastically reduced the production of IGF2 by the decidual cells, we observed concurrent elevated expression of the IGFBP4, which regulates the bioavailability of IGFs, thereby controlling trophoblast differentiation. We posit that dysregulated expression of GJA1, IGF2, and IGFBP4 in Runx1^d/d decidua contributes to the observed defects in uterine angiogenesis, trophoblast differentiation, and vascular remodeling. This study therefore provides unique insights into key maternal pathways that control the early phases of maternal-fetal interactions within a critical window during placental development.

CEBP-β and PLK1 as Potential Mediators of the Breast Cancer/Obesity Crosstalk: In Vitro and In Silico Analyses

Over the last two decades, obesity has reached pandemic proportions in several countries, and expanding evidence is showing its contribution to several types of malignancies, including breast cancer (BC). The conditioned medium (CM) from mature adipocytes contains a complex of secretes that may mimic the obesity condition in studies on BC cell lines conducted in vitro. Here, we report a transcriptomic analysis on MCF-7 BC cells exposed to adipocyte-derived CM and focus on the predictive functional relevance that CM-affected pathways/processes and related biomarkers (BMs) may have in BC response to obesity. CM was demonstrated to increase cell proliferation, motility and invasion as well as broadly alter the transcript profiles of MCF-7 cells by significantly modulating 364 genes. Bioinformatic functional analyses unraveled the presence of five highly relevant central hubs in the direct interaction networks (DIN), and Kaplan-Meier analysis sorted the CCAAT/enhancer binding protein beta (CEBP-β) and serine/threonine-protein kinase PLK1 (PLK1) as clinically significant biomarkers in BC. Indeed, CEBP-β and PLK1 negatively correlated with BC overall survival and were up-regulated by adipocyte-derived CM. In addition to their known involvement in cell proliferation and tumor progression, our work suggests them as a possible "deus ex machina" in BC response to fat tissue humoral products in obese women.

Runx1 regulates critical factors that control uterine angiogenesis and trophoblast differentiation during placental development

During early pregnancy in humans and rodents, uterine stromal cells undergo a remarkable differentiation to form the decidua, a transient maternal tissue that supports the growing fetus. It is important to understand the key decidual pathways that orchestrate the proper development of the placenta, a key structure at the maternal-fetal interface. We discovered that ablation of expression of the transcription factor Runx1 in decidual stromal cells in a conditional Runx1 -null mouse model ( Runx1 ^d/d ) causes fetal lethality during placentation. Further phenotypic analysis revealed that uteri of pregnant Runx1 ^d/d mice exhibited severely compromised decidual angiogenesis, and a lack of trophoblast differentiation and migration, resulting in impaired spiral artery remodeling. Gene expression profiling using uteri from Runx1 ^d/d and control mice revealed that Runx1 directly controls the decidual expression of the gap junction protein connexin 43 (also known as GJA1), which was previously shown to be essential for decidual angiogenesis. Our study also revealed a critical role of Runx1 in controlling insulin-like growth factor (IGF) signaling at the maternal-fetal interface. While Runx1-deficiency drastically reduced the production of IGF2 by the decidual cells, we observed concurrent elevated expression of the IGF-binding protein 4 (IGFBP4), which regulates the bioavailability of IGFs thereby controlling trophoblast differentiation. We posit that dysregulated expression of GJA1, IGF2, and IGFBP4 in Runx1 ^d/d decidua contributes to the observed defects in uterine angiogenesis, trophoblast differentiation, and vascular remodeling. This study therefore provides unique insights into key maternal pathways that control the early phases of maternal-fetal interactions within a critical window during placental development.

SIGNIFICANCE

A clear understanding of the maternal pathways that ensure coordination of uterine differentiation and angiogenesis with embryonic growth during the critical early stages of placenta formation still eludes us. The present study reveals that the transcription factor Runx1 controls a set of molecular, cellular, and integrative mechanisms that mediate maternal adaptive responses controlling uterine angiogenesis, trophoblast differentiation, and resultant uterine vascular remodeling, which are essential steps during placenta development.

Progress on the Role of Estrogen and Progesterone Signaling in Mouse Embryo Implantation and Decidualization

Embryo implantation and decidualization are key steps in establishing a successful pregnancy. Defects in embryo implantation and decidualization can cause a series of adverse chain reactions which can contribute to harmful pregnancy outcomes, such as embryo growth retardation, preeclampsia, miscarriage, premature birth, and so on. Approximately 75% of failed pregnancies are considered to be due to embryo implantation failure or defects. Decidualization, characterized by proliferation and differentiation of uterine stromal cells, is one of the essential conditions for blastocyst implantation, placental formation, and maintenance of pregnancy and is indispensable for the establishment of pregnancy in many species. Embryo implantation and decidualization are closely regulated by estrogen and progesterone secreted by the ovaries. Many cellular events and molecular signaling network pathways are involved in this process. This article reviews the recent advances in the molecular mechanisms of estrogen- and progesterone-regulating uterine receptivity establishment, blastocyst implantation, and decidualization, in order to better understand the underlying molecular mechanisms of hormonal regulation of embryo implantation and to develop new strategies for preventing or treating embryo implantation defects and improving the pregnancy rate of women.

Circadian gene Rev-erbα influenced by sleep conduces to pregnancy by promoting endometrial decidualization via IL-6-PR-C/EBPβ axis

BACKGROUND

Sleep disturbance can cause adverse pregnancy outcomes by changing circadian gene expression. The potential mechanisms remain unclear. Decidualization is critical for the establishment and maintenance of normal pregnancy, which can be regulated by circadian genes. Whether Rev-erbα, a critical circadian gene, affects early pregnancy outcome by regulating decidualization needs to be explored.

METHODS

QPCR, western blot and artificial decidualization mouse model were used to confirm the effect of sleep disturbance on Rev-erbα expression and decidualization. The regulatory mechanism of Rev-erbα on decidualization was assessed using QPCR, western blot, RNA-Seq, and Chip-PCR. Finally, sleep disturbance mouse model was used to investigate the effect of therapeutic methods targeting Rev-erbα and interleukin 6 (IL-6) on improving adverse pregnancy outcomes induced by sleep disturbance.

RESULTS

Dysregulation of circadian rhythm due to sleep disturbance displayed abnormal expression profile of circadian genes in uterine including decreased level of Rev-erbα, accompanied by defective decidualization. Rev-erbα could regulate decidualization by directly repressing IL-6, which reduced the expression of CCAAT/enhancer-binding protein β (C/EBPβ) and its target insulin-like growth factor binding protein 1 (IGFBP1), the marker of decidualization, by inhibiting progesterone receptors (PR) expression. Moreover, deficient decidualization, higher abortion rate and lower implantation number were exhibited in the mouse models with sleep disturbance compared with those in normal mouse. Pharmacological activation of Rev-erbα or neutralization of IL-6 alleviated the adverse effect of sleep disturbance on pregnancy outcomes.

CONCLUSIONS

Taken together, Rev-erbα regulated decidualization via IL-6-PR-C/EBPβ axis and might be a connector between sleep and pregnancy outcome. Therapies targeting Rev-erbα and IL-6 might help improving adverse pregnancy outcomes induced by sleep disturbance.

Extracellular Vesicles Secreted by Mouse Decidual Cells Carry Critical Information for the Establishment of Pregnancy

The mouse decidua secretes many factors that act in a paracrine/autocrine manner to critically control uterine decidualization, neovascularization, and tissue remodeling that ensure proper establishment of pregnancy. The precise mechanisms that dictate intercellular communications among the uterine cells during early pregnancy remain unknown. We recently reported that conditional deletion of the gene encoding the hypoxia-inducible transcription factor 2 alpha (Hif2α) in mouse uterus led to infertility. Here, we report that HIF2α in mouse endometrial stromal cells (MESCs) acts via the cellular trafficking regulator RAB27b to control the secretion of extracellular vesicles (EVs) during decidualization. We also found that Hif2α-regulated pathways influence the biogenesis of EVs. Proteomic analysis of EVs secreted by decidualizing MESCs revealed that they harbor a wide variety of protein cargoes whose composition changed as the decidualization process progressed. The EVs enhanced the differentiation capacity of MESCs and the production of angiogenic factors by these cells. We also established that matrix metalloproteinase-2, a prominent EV cargo protein, modulates uterine remodeling during decidualization. Collectively, our results support the concept that EVs are central to the mechanisms by which the decidual cells communicate with each other and other cell types within the uterus to facilitate successful establishment of pregnancy.

The Regulators of Human Endometrial Stromal Cell Decidualization

Several factors are important for implantation and subsequent placentation in the endometrium, including immunity, angiogenesis, extracellular matrix, glucose metabolism, reactive oxidative stress, and hormones. The involvement or abnormality of these factors can impair canonical decidualization. Unusual decidualization can lead to perinatal complications, such as disruption of trophoblast invasion. Drastic changes in the morphology and function of human endometrial stromal cells (hESCs) are important for decidualization of the human endometrium; hESCs are used to induce optimal morphological and functional decidualization in vitro because they contain estrogen and progesterone receptors. In this review, we will focus on the studies that have been conducted on hESC decidualization, including the results from our laboratory.

House dust mite-induced Akt-ERK1/2-C/EBP beta pathway triggers CCL20-mediated inflammation and epithelial-mesenchymal transition for airway remodeling

House dust mite (HDM) allergens cause inflammatory responses and chronic allergic diseases such as bronchial asthma and atopic dermatitis. Here, we investigate the mechanism by which HDM induces C-C chemokine ligand 20 (CCL20) expression to promote chronic inflammation and airway remodeling in an HDM-induced bronchial asthma mouse model. We showed that HDM increased CCL20 levels via the Akt-ERK1/2-C/EBPβ pathway. To investigate the role of CCL20 in chronic airway inflammation and remodeling, we made a mouse model of CCL20-induced bronchial asthma. Treatment of anti-CCL20Ab in this mouse model showed the reduced airway hyper-responsiveness and inflammatory cell infiltration into peribronchial region by neutralizing CCL20. In addition, CCL20 induced the Nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation through NLRP3 deubiquitination and transcriptional upregulation in BEAS-2B cells. As expected, anti-CCL20Ab markedly suppressed NLRP3 activation induced by CCL20. Moreover, HDM-induced CCL20 leads to epithelial-mesenchymal transition in the lung epithelium which appears to be an important regulator of airway remodeling in allergic asthma. We also found that anti-CCL20Ab attenuates airway inflammation and remodeling in an HDM-induced mouse model of bronchial asthma. Taken together, our results suggest that HDM-induced CCL20 is required for chronic inflammation that contributes airway remodeling in a mouse model of asthma.

A novel lncRNA lncSAMD11-1: 1 interacts with PIP4K2A to promote endometrial decidualization by stabilizing FoxO1 nuclear localization

Decidualization is essential for a successful pregnancy and determines embryo implantation and pregnancy maintenance. Abnormal decidualization is one of the main causes of recurrent implantation failure (RIF). Studies have shown that large amounts of long noncoding RNAs (lncRNAs) are abnormally expressed in endometrial samples from patients with RIF. However, the functional contributions of lncRNAs to decidualization in RIF have not been explored. In this study, we found that lncSAMD11-1:1 was significantly declined in the endometria of patients with RIF. The knockdown of lncSAMD11-1:1 in human endometrial stromal cells (hESCs) restrained decidualization and embryo implantation in vitro, while the overexpression of lncSAMD11-1:1 facilitated hESC decidualization and embryo implantation in vitro and ameliorated decidualization in RIF patients. Mechanistically, lncSAMD11-1:1 and phosphatidylinositol-5-phosphate 4-kinase type 2 alpha (PIP4K2A) translocated out of nucleus and bound to each other during decidualization, thereby inhibiting the phosphorylation of AKT and promoting FoxO1 nuclear localization. These data suggest that lncSAMD11-1:1 might be a critical novel lncRNA functionally required for human decidualization, and the dysregulation of lncSAMD11-1:1 in the endometrium may be a new predisposing factor of RIF.

Deficiency of RARα Suppresses Decidualization via Downregulating CEBPB Transcription in Women With Recurrent Implantation Failure

Background

Recurrent implantation failure (RIF) is a disease associated with endometrial receptivity dysfunction. Retinoic acid receptor alpha (RARα) is an important protein in many biological processes, such as differentiation and development. However, the exact underlying mechanism whereby RARα affects RIF remains unknown. This study investigated RARα expression and its contribution in the mid-luteal phase endometria of patients with RIF.

Methods

The expression levels of RARα and CCAAT/enhancer-binding protein (C/EBP) β in the endometria of the RIF and normal group were investigated using western blotting and immunohistochemistry. In in vitro experiments, immortal telomerase-transformed human endometrial stromal cells (T-HESCs) were incubated with medroxyprogesterone-17-acetate (MPA) and cyclic adenosine monophosphate (cAMP) for 4 days to induce decidualization. The expression levels of the decidualization markers prolactin (PRL) and insulin-like growth factor-binding protein-1 (IGFBP-1) were determined using quantitative polymerase chain reaction. RARα was knocked down using a small interfering RNA, and C/EBPβ was overexpressed from an adenoviral vector. The transcriptional regulation of CEBPB by RARα was determined by chromatin immunoprecipitation (ChIP) assay and luciferase assays.

Results

We found that the expression levels of RARα decreased in the mid-luteal endometria of RIF patients. After 4 days of decidualization induction in vitro, RARα knockdown impaired the decidualization of T-HESCs and downregulated the expression of C/EBPβ. The restoration of C/EBPβ expression rescued the RARα knockdown-induced suppression of T-HESC decidualization. In ChIP analysis of lysates from decidualized T-HESCs, the CEBPB promoter region was enriched in chromatin fragments pulled down using an anti-RARα antibody. However, the relationship between CEBPB transcription and RARα expression levels was only observed when the decidualization of T-HESCs was induced by the addition of cAMP and MPA. To identify the binding site of RARα/retinoid X receptor α, we performed luciferase assays. Mutation of the predicted binding site in CEBPB (-2,009/-1,781) decreased the transcriptional activity of the reporter. To confirm this mechanism, the expression levels of C/EBPβ in the mid-luteal endometria of RIF patients were determined and found to decrease with decreased RARα expression levels.

Conclusion

A deficiency of RARα expression in the mid-luteal endometrium inhibits decidualization due to the downregulation of CEBPB transcription. This is a potential mechanism contributing to RIF.

Cyanidin-3-O-glucoside ameliorates cadmium induced uterine epithelium proliferation in mice

Cadmium (Cd) is an environmental pollutant and endocrine disrupter, abundantly present in water, food, and soil. Accumulation of Cd in the body can negatively affect female reproduction; especially the uterus is exceptionally sensitive to the toxic actions of Cd. The anthocyanin cyanidin-3-O-glucoside (C3G) is a naturally occurring phenolic compound in fruits and plants that can antagonize the toxic effects of Cd. This capacity makes C3G a possible candidate to prevent Cd-induced female infertility. The present study aimed to investigate: 1) whether C3G intake could prevent Cd-induced female reproductive toxicity, and 2) the underlying mechanisms responsible for this protective effect. The results of our study indicated that Cd exposure did not affect ovarian function, but induced hypertrophy of the uterine endometrium. Oral intake of C3G markedly reduced the effects of Cd exposure on the thickness of the uterine epithelium cells. Transcriptomic analysis of the endometrium revealed that C3G intake had anti-estrogenic effects, attenuating Cd-induced endometrial epithelial cell proliferation by inhibiting estrogen-responsive genes, enhancing epithelial progesterone receptor expression, and regulating Klf4 expression. The current findings implicate that C3G has the potential to be used as a dietary supplement based on its capacity to intervene in Cd-induced female reproductive toxicity.

Increased expression of HOXA11-AS attenuates endometrial decidualization in recurrent implantation failure patients

Endometrial decidualization is a prerequisite for implantation, and impaired decidualization is associated with recurrent implantation failure (RIF). Coding genes of the HOX family have been clarified as critical regulators in endometrial decidualization, but the role of long non-coding RNAs (lncRNAs) in the HOX gene family has yet to be determined. The aim of this study was to clarify the possible roles of lncRNAs in the HOX gene family in decidualization. In this study, we identified that HOXA11-AS was the most reduced lncRNA in the HOX family in the human endometrium during the window of implantation, and it was elevated in RIF patients. Mechanistically, HOXA11-AS negatively regulated decidualization through competitive interaction with PTBP1, an RNA-binding protein. Binding of PTBP1 to HOXA11-AS limited PTBP1 availability to regulate PKM1/2 alternative splicing, resulting in enhanced PKM1 and diminished PKM2 expression, thus attenuating decidualization. The pattern of high HOXA11-AS expression and impaired PKM2 splicing was consistently observed in RIF patients. Collectively, our study indicates that the increase of HOXA11-AS is detrimental to endometrial decidualization, likely contributing to RIF. Our study may shed light on the pathogenesis and treatment of RIF.

Regulation and Function of Laminin A5 during Mouse and Human Decidualization

Decidualization is essential to the establishment of pregnancy in rodents and primates. Laminin A5 (encoding by Laminin α5) is a member of the laminin family, which is mainly expressed in the basement membranes. Although laminins regulate cellular phenotype maintenance, adhesion, migration, growth, and differentiation, the expression, function, and regulation of laminin A5 during early pregnancy are still unknown. Therefore, we investigated the expression and role of laminin A5 during mouse and human decidualization. Laminin A5 is highly expressed in mouse decidua and artificially induced deciduoma. Laminin A5 is significantly increased under in vitro decidualization. Laminin A5 knockdown significantly inhibits the expression of Prl8a2, a marker for mouse decidualization. Progesterone stimulates the expression of laminin A5 in ovariectomized mouse uterus and cultured mouse stromal cells. We also show that progesterone regulates laminin A5 through the PKA-CREB-C/EBPβ pathway. Laminin A5 is also highly expressed in human pregnant decidua and cultured human endometrial stromal cells during in vitro decidualization. Laminin A5 knockdown by siRNA inhibits human in vitro decidualization. Collectively, our study reveals that laminin A5 may play a pivotal role during mouse and human decidualization via the PKA-CREB-C/EBPβ pathway.

1-Nitropyrene exposure impairs embryo implantation through disrupting endometrial receptivity genes expression and producing excessive ROS

Haze problem is an important factor threatening human health. PM2.5 is the main culprit haze. 1-Nitropyrene (1-NP) is the main nitrated polycyclic aromatic hydrocarbon, the toxic component of PM2.5 particles. The effects of 1-NP on various organs and reproductive health have been extensively and deeply studied, but the effects of 1-NP on embryo implantation and endometrial receptivity remain to be determined. The purpose of this study was to investigate the adverse effects of 1-NP on mouse embryo implantation and human endometrial receptivity. In early pregnancy, CD1 mice were given 2 mg/kg 1-NP by oral gavage, which resulted in a decreased embryo implantation number on day 5, inhibited leukemic inhibitory factor (LIF)/STAT3 pathway, decreased expression of estrogen receptor and progesterone receptor, and disrupted regulation of uterine cell proliferation. In addition, in a human in vitro implantation model, 1-NP was found to significantly inhibit the adhesion rate between trophoblast spheroids and endometrial epithelial cells, possibly by inhibiting the expression of receptivity molecules in Ishikawa cells. Promoting reactive oxygen species (ROS) production may be an additional mechanism by which it inhibits trophoblast spheroid adhesion. In this study, we used an in vivo mouse pregnancy model and an in vitro human embryo implantation model to demonstrate that 1-NP can impair endometrial receptivity and compromise embryo implantation.

The essential glucose transporter GLUT1 is epigenetically upregulated by C/EBPβ and WT1 during decidualization of the endometrium

Human endometrial stromal cells (ESCs) differentiate into decidual cells by the action of progesterone, which is essential for implantation and maintenance of pregnancy. We previously reported that glucose uptake by human ESCs increases during decidualization and that glucose is indispensable for decidualization. Although glucose transporter 1 (GLUT1) is upregulated during decidualization, it remains unclear whether it is involved in glucose uptake. Here, we attempted to determine the role of GLUT1 during decidualization as well as the factors underlying its upregulation. ESCs were incubated with cAMP to induce decidualization. Knockdown of GLUT1 suppressed cAMP-increased glucose uptake and the expressions of specific markers of decidualization, IGF-binding protein-1 (IGFBP-1), and prolactin (PRL). To investigate the regulation of GLUT1 expression, we focused on CCAAT enhancer-binding protein β (C/EBPβ) and Wilms' tumor 1 (WT1) as the upstream transcription factors regulating GLUT1 expression. Knockdown of either C/EBPβ or WT1 suppressed cAMP-increased GLUT1 expression and glucose uptake. cAMP treatment also increased the recruitment of C/EBPβ and WT1 to the GLUT1 promoter region. Interestingly, cAMP increased the H3K27 acetylation (H3K27ac) and p300 recruitment in the GLUT1 promoter region. Knockdown of C/EBPβ or WT1 inhibited these events, indicating that both C/EBPβ and WT1 contribute to the increase of H3K27ac by recruiting p300 to the GLUT1 promoter region during decidualization. These findings indicate that GLUT1 is involved in glucose uptake in ESCs during decidualization, thus facilitating the establishment of pregnancy.

C/EBP β Mediates the Aberrant Inflammatory Response and Cell Cycle Arrest in Lps-stimulated Human Renal Tubular Epithelial Cells by Regulating NF-κB Pathway

BACKGROUND AND AIMS

The main cause of sepsis-induced Acute kidney injury (AKI) is acute infection after surgery and subsequent progression. However, the mechanism by which AKI is caused and developed from sepsis are not completely known. Herein, we determined the role of CCAAT/enhancer-binding protein β (C/EBP β) in sepsis-induced AKI METHODS: C/EBP β expression was up or down-regulated in LPS-stimulated human renal tubular epithelial cells in vitro by recombinant adenoviruses or siRNA. Subsequent analyses included the test of TNF-α and IL-6 levels by ELISA, cell cycle assay by flow cytometry.

RESULTS

C/EBP β was aberrantly expressed in renal tubular epithelial HK-2 cells exposed to LPS. C/EBP β overexpression significantly enhanced, but C/EBP β silencing obviously decreased the production and secretion of inflammatory cytokines TNF-α and IL-6 induced by LPS stimulus in HK-2 cells. And the cell cycle arrest of HK-2 cells induced by LPS was also enhanced after C/EBP β overexpression while attenuated after C/EBP β silencing. Consistent pattern of changes in Cyclin D1 and p21 expression were observed in LPS-stimulated HK-2 cells after C/EBP β silencing and C/EBP β overexpression. Additionally, the increased p-NF-κB levels induced by LPS were found to be obviously decreased after C/EBP β silencing in HK-2 cells. And the enhanced TNF-α and IL-6 secretion as well as cell cycle arrest by C/EBP β overexpression were blocked by BAY11-7082 inhibitor of NF-κB pathway.

CONCLUSIONS

C/EBP β could mediate the LPS-induced aberrant inflammatory response and cell cycle arrest in tubular epithelial cells by NF-κB pathway.

Transcription factor C/EBPβ induces genome-wide H3K27ac and upregulates gene expression during decidualization of human endometrial stromal cells

We previously reported that H3K27 acetylation (H3K27ac) increases throughout the genome during decidualization of human endometrial stromal cells (ESCs). However, its mechanisms have not been clarified. We also reported that C/EBPβ acts as a pioneer factor initiating chromatin remodeling by increasing H3K27ac of IGFBP-1 and PRL promoters. Therefore, C/EBPβ may be involved in the genome-wide increase of H3K27ac during decidualization. In this study, we investigated whether C/EBPβ causes genome-wide H3K27ac modifications and regulates gene expressions during decidualization. cAMP was used to induce decidualization. Three types of cells (control cells, cAMP-treated cells, and cAMP-treated + C/EBPβ-knockdowned cells by siRNA) were generated. Of 4190 genes that were upregulated by cAMP, C/EBPβ knockdown inhibited these upregulation in 2239 genes (53.4%), indicating that they are under the regulation of C/EBPβ. cAMP increased H3K27ac in 1272 of the 2239 genes. C/EBPβ knockdown abolished the increase of H3K27ac in almost all genes (1263 genes, 99.3%), suggesting that C/EBPβ can upregulate gene expression by increasing H3K27ac. To investigate how C/EBPβ regulates H3K27ac throughout the genome, we tested the hypothesis that C/EBPβ binds to its binding regions and recruits cofactors with histone acetyltransferase activities. To do this, we collated our ChIP-sequence data with public ChIP-sequence database of transcription factors, and found that p300 is the most likely cofactor that binds to the H3K27ac-increased-regions with C/EBPβ. ChIP-qPCR of several genes confirmed that C/EBPβ binds to the target regions, recruits p300, and increases H3K27ac. Our genome-wide analysis revealed that C/EBPβ induces H3K27ac throughout the genome and upregulates gene expressions during decidualization by recruiting p300 to the promoters.

Mating to Intact, but Not Vasectomized, Males Elicits Changes in the Endometrial Transcriptome: Insights From the Bovine Model

An appropriate female reproductive environment is essential for pregnancy success. In several species, including mice, pigs and horses, seminal plasma (SP) components have been shown to modulate this environment, leading to increased embryo viability and implantation. Due to the characteristics of mating in the aforementioned species, SP comes into direct contact with the uterus. However, it is questionable whether any SP reaches the uterus in species that ejaculate inside the vagina, such as humans and cattle. Hence, we hypothesized that sperm, perhaps acting as a vehicle for SP factors, play a more important role in the modulation of the maternal uterine environment in these species. In addition, changes elicited by SP and/or sperm may originate in the vagina and propagate to more distal regions of the female reproductive tract. To test these hypotheses, a bovine model in which heifers were mated to intact or vasectomized bulls or were left unmated was used. RNA-sequencing of endometrial samples collected 24 h after mating with a vasectomized bull did not reveal any differentially expressed genes (DEGs) in comparison with control samples. However, the endometrium of heifers mated with intact bulls exhibited 24 DEGs when compared to heifers mated with vasectomized bulls, and 22 DEGs when compared to unmated control heifers. The expression of a set of cytokines (IL6, IL1A, IL8, and TNFA) and candidate genes identified in the endometrial RNA-sequencing (PLA2G10, CX3CL1, C4BPA, PRSS2, BLA-DQB, and CEBPD) were assessed by RT-qPCR in the vagina and oviductal ampulla. No differences in expression of these genes were observed between treatments in any region. However, mating to both intact and vasectomized bulls induced an increase in IL1A and TNFA expression in the vagina compared to the oviduct. These data indicate that sperm, but not secretions from the accessory glands alone, induce modest changes in endometrial gene expression after natural mating in cattle. However, it is not clear whether this effect is triggered by inherent sperm proteins or SP proteins bound to sperm surface at the time of ejaculation.

Human Endometrial Transcriptome and Progesterone Receptor Cistrome Reveal Important Pathways and Epithelial Regulators

CONTEXT

Poor uterine receptivity is one major factor leading to pregnancy loss and infertility. Understanding the molecular events governing successful implantation is hence critical in combating infertility.

OBJECTIVE

To define Progesterone Receptor (PGR)-regulated molecular mechanisms and epithelial roles in receptivity.

DESIGN

RNA-sequencing and PGR-ChIP-seq were conducted in parallel to identify PGR-regulated pathways during the Window of implantation (WOI) in endometrium of fertile women.

SETTING

Endometrial biopsies from the proliferative and mid-secretory phases were analyzed.

PATIENTS OR OTHER PARTICIPANTS

Participants were fertile, reproductive aged (18-37 years) women with normal cycle length, and without any history of dysmenorrhea, infertility, or irregular cycles. In total, 42 endometrial biopsies obtained from 42 women were analyzed in this study.

INTERVENTIONS

There were no interventions during this study.

MAIN OUTCOME MEASURES

Here we measured the alterations in gene expression and PGR occupancy in the genome during the WOI, based on the hypothesis that PGR binds uterine chromatin cycle dependently to regulate genes involved in uterine cell differentiation and function.

RESULTS

653 genes were identified with regulated PGR binding and differential expression during the WOI. These were involved in regulating inflammatory response, xenobiotic metabolism, epithelial mesenchymal transition, cell death, interleukin/Signal Transducer And Activator Of Transcription (STAT) signaling, estrogen response, and Mammalian target of rapamycin complex 1 (MTORC1) response. Transcriptome of the epithelium identified 3052 differentially expressed genes, of which 658 were uniquely regulated. Transcription factors Interferon Regulatory Factor 8 (IRF8) and Myocyte Enhancer Factor 2C (MEF2C) were found to be regulated in the epithelium during the WOI at the protein level, suggesting potentially important functions that are previously unrecognized.

CONCLUSION

PGR binds the genomic regions of genes regulating critical processes in uterine receptivity and function.

Regulatory mechanisms of endometrial decidualization and pregnancy-related diseases

Endometrial decidualization is one of the earliest changes by which the uterus adapts to pregnancy. During this period, the endometrium undergoes complex changes in its biochemistry, physiology, and function at various levels, providing a suitable microenvironment for embryo implantation and development. Favorable decidualization lays an essential foundation for subsequent gestation, without which pregnancy failure or pregnancy complications may occur. The interaction between pregnancy-related hormones and cytokines produced by embryonic and uterine cells is known to be essential for decidualization, in which some transcription factors also play pivotal roles. Increasing evidence has revealed the importance of metabolism in regulating decidualization. Here, we summarize and discuss these crucial elements in decidualization and the relationship between decidualization and pregnancy complications. A better comprehension of these issues should help to improve the prediction of pregnancy outcomes and the use of appropriate intervention.

Exploring the role of Luman/CREB3 in regulating decidualization of mice endometrial stromal cells by comparative transcriptomics

Background

Luman is a member of CREB3 (cAMP responsive element-binding) subfamily of the basic leucine-zipper (bZIP) transcription factors. It may play an important regulatory role during the decidualization process since Luman was highly expressed in the decidual cells. However, the exact molecular mechanisms of how Luman regulating decidualization is unknown.

Results

Using an in vitro model, we prove that Luman knockdown significantly affects the decidualization process of mice endometrial stromal cells (ESCs) as the expression of two decidual markers PRL8a2 and PRL3c1 were repressed. We employed massively parallel RNA sequencing (RNA-Seq) to understand the changes in the transcriptional landscape associated with knockdown of Luman in ESCs during in vitro decidualization. We found significant dysregulation of genes related to protein processing in the endoplasmic reticulum (ER). Several genes involved in decidualization including bone morphogenetic proteins (e.g. BMP1, BMP4, BMP8A, BMP2, and BMP8B), growth factor-related genes (e.g. VEGFB, FGF10, and FGFR2), and transcription factors (IF4E, IF4A2, WNT4, WNT9A, ETS1, NOTCH1, IRX1, IDB1, IDB2, and IDB3), show altered expression. We also found that the knockdown of Luman is associated with increased expression of cell cycle-related genes including cycA1, cycB1, cycB2, CDK1, CDK2, and PLPK1, which resulted in an increased proportion of ESCs in the G1 phase. Differentially expressed genes (DEGs) were highly enriched on ECM-receptor interaction signaling, endoplasmic reticulum protein processing, focal adhesion, and PI3K-Akt signaling pathways.

Conclusions

Luman knockdown results in widespread gene dysregulation during decidualization of ESCs. Genes involved in protein processing in ER, bone morphogenetic protein, growth factor, and cell cycle progression were identified as particularly important for explaining the decidual deficiency observed in this in vitro model. Therefore, this study provides clues as to the underlying mechanisms that may expand our understanding of gene regulation during decidualization.

Estradiol-17β-Induced Changes in the Porcine Endometrial Transcriptome In Vivo

Estradiol-17β (E2) is a key hormone regulating reproductive functions in females. In pigs, E2, as the main conceptus signal, initiates processes resulting in prolonged corpus luteum function, embryo development, and implantation. During early pregnancy the endometrium undergoes morphological and physiological transitions that are tightly related to transcriptome changes. Recently, however, the importance of E2 as a primary conceptus signal in the pig has been questionable. Thus, the aim of the present study was to determine the effects of E2 on the porcine endometrial transcriptome in vivo and to compare these effects with transcriptome profiles on day 12 of pregnancy. Microarray analysis revealed differentially expressed genes (DEGs) in response to E2 with overrepresented functional terms related to secretive functions, extracellular vesicles, cell adhesion, proliferation and differentiation, tissue rearrangements, immune response, lipid metabolism, and many others. Numerous common DEGs and processes for the endometrium on day 12 of pregnancy and E2-treated endometrium were identified. In summary, the present study is the first evidence for the effect of E2 on transcriptome profiles in porcine endometrium in vivo in the period corresponding to the maternal recognition of pregnancy. The presented results provide a valuable resource for further targeted studies considering genes and pathways regulated by conceptus-derived estrogens and their role in pregnancy establishment.

Malic enzyme 1 is important for uterine decidualization in response to progesterone/cAMP/PKA/HB-EGF pathway

Malic enzyme 1 (Me1), a member of the malic enzymes involving in glycolytic pathway and citric acid cycle, is essential for the energy metabolism and maintenance of intracellular redox balance state, but its physiological role and regulatory mechanism in the uterine decidualization are still unknown. Current study showed that Me1 was strongly expressed in decidual cells, and could promote the proliferation and differentiation of stromal cells followed by an accelerated cell cycle transition, indicating an importance of Me1 in the uterine decidualization. Silencing of Me1 attenuated NADPH generation and reduced GR activity, while addition of NADPH improved the defect of GR activity elicited by Me1 depletion. Further analysis found that Me1 modulated intracellular GSH content via GR. Meanwhile, Me1 played a role in maintaining mitochondrial function as indicated by these observations that blockadge of Me1 led to the accumulation of mitochondrial O 2 - level and decreased ATP production and mtDNA copy numbers accompanied with defective mitochondrial membrane potential. In uterine stromal cells, progesterone induced Me1 expression through PR-cAMP-PKA pathway. Knockdown of HB-EGF might impede the regulation of progesterone and cAMP on Me1. Collectively, Me1 is essential for uterine decidualization in response to progesterone/cAMP/PKA/HB-EGF pathway and plays an important role in preventing mitochondrial dysfunction.

HB-EGF Ameliorates Oxidative Stress-Mediated Uterine Decidualization Damage

HB-EGF is essential for uterine decidualization, but its antioxidant function remains largely unclear. Here, we found that HB-EGF promoted the proliferation of stromal cells followed by the accelerated transition of the cell cycle from G1 to S phase and enhanced the expression or activity of Prl8a2, Prl3c1, and ALP which were well-established markers for uterine stromal cell differentiation during decidualization. Under oxidative stress, stromal cell differentiation was impaired, but this impairment was abrogated by rHB-EGF accompanied with the reduced levels of ROS and MDA which were regarded as the biomarkers for oxidative stress, indicating an antioxidant role of HB-EGF. Further analysis revealed that HB-EGF enhanced the activities of antioxidant enzymes SOD, CAT, and GPX, where addition of GPX inhibitor MS attenuated the induction of rHB-EGF on Prl8a2, Prl3c1, and ALP. Meanwhile, HB-EGF rescued the content of GSH and restored the ratio of GSH/GSSG after exposure to H2O2 but did not alter NOX activity. Along with a decline for mitochondrial superoxide, exogenous rHB-EGF improved the damage of oxidative stress on mtDNA copy number, ATP level, mitochondrial membrane potential, and activities of mitochondrial respiratory chain complex I and III whose blockage by ROT and AA led to a failure of rHB-EGF in protecting stromal cell differentiation against injury. Moreover, HB-EGF prevented stromal cell apoptosis by inhibiting Caspase-3 activity and Bax expression and recovering the level of Bcl-2 mRNA. Collectively, HB-EGF might ameliorate oxidative stress-mediated uterine decidualization damage.

Exchange protein directly activated by cAMP (EPAC) promotes transcriptional activation of the decidual prolactin gene via CCAAT/enhancer-binding protein in human endometrial stromal cells

Protein kinase A (PKA) signalling accompanies elevated intracellular cAMP levels during endometrial stromal cell (ESC) decidualisation. Exchange protein directly activated by cAMP (EPAC), an alternate mediator of cAMP signalling, promotes PKA analogue-induced decidualisation; however, the precise mechanism by which EPAC and PKA co-operatively stimulate decidualisation has not been characterised. To examine the role of CCAAT/enhancer-binding protein (C/EBP) in EPAC- and PKA-mediated decidualisation of primary human ESCs, a reporter plasmid containing the 332bp region upstream from the transcription initiation site of the decidual prolactin (dPRL) gene was generated and the promoter activity was evaluated using a luciferase assay. The dPRL promoter activity was increased by treatment of transfected ESCs with the PKA-selective cAMP analogue N6-phenyl-cAMP (Phe) and enhanced further by co-treatment with the EPAC-selective cAMP analogue 8-(4-chlorophenyltio)-2'-O-methyl cAMP (CPT). Treatment with forskolin, an adenylyl cyclase activator, had a similar effect on reporter activity. Site-directed mutagenesis of the C/EBPβ- and/or C/EBPδ-binding site in the dPRL promoter abolished Phe/CPT-mediated elevation of the reporter activity. EPAC2 knockdown markedly reduced Phe-stimulated C/EBPβ and C/EBPδ mRNA levels, as well as forkhead box O1 (FOXO1) protein levels. These results suggest that EPAC signalling enhances PKA-mediated dPRL expression in ESCs by acting on C/EBP response elements in the promoter region of the gene.

Progesterone and Estrogen Signaling in the Endometrium: What Goes Wrong in Endometriosis?

In the healthy endometrium, progesterone and estrogen signaling coordinate in a tightly regulated, dynamic interplay to drive a normal menstrual cycle and promote an embryo-receptive state to allow implantation during the window of receptivity. It is well-established that progesterone and estrogen act primarily through their cognate receptors to set off cascades of signaling pathways and enact large-scale gene expression programs. In endometriosis, when endometrial tissue grows outside the uterine cavity, progesterone and estrogen signaling are disrupted, commonly resulting in progesterone resistance and estrogen dominance. This hormone imbalance leads to heightened inflammation and may also increase the pelvic pain of the disease and decrease endometrial receptivity to embryo implantation. This review focuses on the molecular mechanisms governing progesterone and estrogen signaling supporting endometrial function and how they become dysregulated in endometriosis. Understanding how these mechanisms contribute to the pelvic pain and infertility associated with endometriosis will open new avenues of targeted medical therapies to give relief to the millions of women suffering its effects.

Impaired decidualization caused by downregulation of circadian clock gene BMAL1 contributes to human recurrent miscarriage†

Recurrent miscarriage (RM) is characterized by two or more consecutive losses of a clinically established intrauterine pregnancy at early gestation. To date, the etiology of RM remains poorly understood. Impaired decidualization is thought to predispose women to subsequent pregnancy failure. The transcriptional factor brain and muscle aryl hydrocarbon receptor nuclear translocator-like (BMAL1) controls circadian rhythms and regulates a very large diversity of physiological processes. BMAL1 is essential for fertility. Here, we investigated the expression and function of BMAL1 in human decidualization and its relation with RM. A total of 39 decidua samples were collected. We also examined human endometrial stromal cells (HESCs) and primary endometrial stromal cells (ESCs), and primary decidual stromal cells (DSCs) isolated from decidua of first-trimester pregnancies. Compared to normal pregnant women, the expression of BMAL1 was reduced in the decidual tissues from individuals with RM. After in vitro induction of decidualization, the transcription of BMAL1 in both HESCs and primary ESCs was increased. This is in line with the relatively higher expression of BMAL1 in DSCs than in ESCs. Silencing of BMAL1 resulted in impaired decidualization. Moreover, levels of tissue inhibitors of metalloproteinases (TIMPs) increased significantly upon decidualization. Further experiments demonstrated that BMAL1 silencing curtails the ability of DSCs to restrict excessive trophoblast invasion via downregulation of TIMP3. Our study demonstrates a functional role for BMAL1 during decidualization: the downregulation of BMAL1 in RM leads to impaired decidualization and aberrant trophoblast invasion by regulating TIMP3 and consequently predisposing individuals for RM.

Identification of Gene Expression Changes Associated With Uterine Receptivity in Mice

The mouse is a widely used animal model for studying human reproduction. Although global gene expression changes associated with human uterine receptivity have been determined by independent groups, the same studies in the mouse are scarce. The extent of similarities/differences between mice and humans on uterine receptivity at the molecular level remains to be determined. In the present study, we analyzed global gene expression changes in receptive uterus on day 4 of pregnancy compared to non-receptive uterus on day 3 of pregnancy in mice. A total of 541 differentially expressed genes were identified, of which 316 genes were up-regulated and 225 genes were down-regulated in receptive uterus compared to non-receptive uterus. Gene ontology and gene network analysis highlighted the activation of inflammatory response in the receptive uterus. By analyzing the promoter sequences of differentially expressed genes, we identified 12 causal transcription factors. Through connectivity map (CMap) analysis, we revealed several compounds with potential anti-receptivity activity. Finally, we performed a cross-species comparison against human uterine receptivity from a published dataset. Our study provides a valuable resource for understanding the molecular mechanism underlying uterine receptivity in mice.

The mammalian decidual cell evolved from a cellular stress response

Among animal species, cell types vary greatly in terms of number and kind. The number of cell types found within an organism differs considerably between species, and cell type diversity is a significant contributor to differences in organismal structure and function. These observations suggest that cell type origination is a significant source of evolutionary novelty. The molecular mechanisms that result in the evolution of novel cell types, however, are poorly understood. Here, we show that a novel cell type of eutherians mammals, the decidual stromal cell (DSC), evolved by rewiring an ancestral cellular stress response. We isolated the precursor cell type of DSCs, endometrial stromal fibroblasts (ESFs), from the opossum Monodelphis domestica. We show that, in opossum ESFs, the majority of decidual core regulatory genes respond to decidualizing signals but do not regulate decidual effector genes. Rather, in opossum ESFs, decidual transcription factors function in apoptotic and oxidative stress response. We propose that rewiring of cellular stress responses was an important mechanism for the evolution of the eutherian decidual cell type.

Construction of implantation failure related lncRNA-mRNA network and identification of lncRNA biomarkers for predicting endometrial receptivity

Insufficient endometrial receptivity is a major factor leading to implantation failure (IF), and the traditional way of morphological observation of endometrium cannot determine the condition of receptivity sufficiently. Considering that long-noncoding RNAs (lncRNAs) regulate endometrial receptivity and competing endogenous RNA (ceRNA) mechanism works in plenty of biological processes, ceRNA is likely to function in the pathology of IF. In the present study, we aim to construct an implantation failure related lncRNA-mRNA network (IFLMN), and to identify the key lncRNAs as the candidates for predicting endometrial receptivity. The global background network was constructed based on the presumed lncRNA-miRNA and miRNA-mRNA pairs obtained from lncRNASNP and miRTarBase. Differentially expressed genes (DEGs) of IF were calculated using the data of GSE26787, and then re-annotated as differentially expressed mRNAs (DEMs) and lncRNAs (DELs). IFLMN was constructed by hypergeometric test, including 255 lncRNA-mRNA pairs, 10 lncRNAs, and 212 mRNAs. Topological analysis determined the key lncRNAs with the highest centroid. Functional enrichment analyses were performed by unsupervised clustering, GO classification, KEGG pathway, and co-expression module analyses, achieving six key lncRNAs and their ceRNA sub-networks, which were involved in immunological activity, growth factor binding, vascular proliferation, apoptosis, and steroid biosynthesis in uterus and prepared endometrium for embryo implantation. Sixteen endometrial samples were collected during mid-luteal phase, including 8 recurrent implantation failure (RIF) or recurrent miscarriage (RM) women and 8 controls who conceived successfully. Quantitative real-time PCR was performed to compare the expression of the above six lncRNAs, which validated that the expression of all these lncRNAs was significantly elevated in endometrium of RIF/RM patients. Further studies are needed to investigate the underlying mechanism, and the lncRNAs may be developed into predictive biomarkers for endometrial receptivity.

Uterine glands coordinate on-time embryo implantation and impact endometrial decidualization for pregnancy success

Uterine glands are essential for pregnancy establishment. By employing forkhead box A2 (FOXA2)-deficient mouse models coupled with leukemia inhibitory factor (LIF) repletion, we reveal definitive roles of uterine glands in embryo implantation and stromal cell decidualization. Here we report that LIF from the uterine glands initiates embryo-uterine communication, leading to embryo attachment and stromal cell decidualization. Detailed histological and molecular analyses discovered that implantation crypt formation does not involve uterine glands, but removal of the luminal epithelium is delayed and subsequent decidualization fails in LIF-replaced glandless but not gland-containing FOXA2-deficient mice. Adverse ripple effects of those dysregulated events in the glandless uterus result in embryo resorption and pregnancy failure. These studies provide evidence that uterine glands synchronize embryo-endometrial interactions, coordinate on-time embryo implantation, and impact stromal cell decidualization, thereby ensuring embryo viability, placental growth, and pregnancy success.

The transcription factor FOXA2 is specifically expressed in uterine glands. Here, using two conditional FOXA2 knockout mouse models, the authors show that glandular epithelia of the endometrium are required for timely embryo implantation and subsequent endometrial decidualization during successful pregnancy establishment.

Physiological and pathological implications of retinoid action in the endometrium

Retinol (vitamin A) and its derivatives, collectively known as retinoids, are required for maintaining vision, immunity, barrier function, reproduction, embryogenesis and cell proliferation and differentiation. Despite the fact that most events in the endometrium are predominantly regulated by steroid hormones (estrogens and progesterone), accumulating evidence shows that retinoid signaling is also involved in the development and maintenance of the endometrium, stromal decidualization and blastocyst implantation. Moreover, aberrant retinoid metabolism seems to be a critical factor in the development of endometriosis, a common gynecological disease, which affects up to 10% of reproductive age women and is characterized by the ectopic localization of endometrial-like tissue in the pelvic cavity. This review summarizes recent advances in research on the mechanisms and molecular actions of retinoids in normal endometrial development and physiological function. The potential roles of abnormal retinoid signaling in endometriosis are also discussed. The objectives are to identify limitations in current knowledge regarding the molecular actions of retinoids in endometrial biology and to stimulate new investigations toward the development potential therapeutics to ameliorate or prevent endometriosis symptoms.

Estrogen induces EGR1 to fine-tune its actions on uterine epithelium by controlling PR signaling for successful embryo implantation

The harmonized actions of ovarian E₂ and progesterone (P₄) regulate the proliferation and differentiation of uterine cells in a spatiotemporal manner. Imbalances between these hormones often lead to infertility and gynecologic diseases. Whereas numerous factors that are involved in P₄ signaling have been identified, few local factors that mediate E₂ actions in the uterus have been revealed. Here, we demonstrate that estrogen induces the transcription factor, early growth response 1 ( Egr1), to fine-tune its actions in uterine epithelial cells (ECs) that are responsible for uterine receptivity for embryo implantation. In the presence of exogenous gonadotrophins, ovulation, fertilization, and embryonic development normally occur in Egr1^-/- mice, but these animals experience the complete failure of embryo implantation with reduced artificial decidualization. Although serum levels of E₂ and P₄ were comparable between Egr1^+/+ and Egr1^-/- mice on d 4 of pregnancy, aberrantly reduced levels of progesterone receptor in Egr1^-/- uterine ECs caused enhanced E₂ activity and impaired P₄ response. Ultrastructural analyses revealed that Egr1^-/- ECs are not fully able to provide proper uterine receptivity. Uterine mRNA landscapes in Egr1^-/- mice revealed that EGR1 controls the expression of a subset of E₂-regulated genes. In addition, P₄ signaling was unable to modulate estrogen actions, including those that are involved in cell-cycle progression, in ECs that were deficient in EGR1. Furthermore, primary coculture of Egr1^-/- ECs with Egr1^+/+ stromal cells, and vice versa, supported the notion that Egr1 is required to modulate E₂ actions on ECs to prepare the uterine environment for embryo implantation. In contrast to its role in ECs, loss of Egr1 in stroma significantly reduced stromal cell proliferation. Collectively, our results demonstrate that E₂ induces EGR1 to streamline its actions for the preparation of uterine receptivity for embryo implantation in mice.-Kim, H.-R., Kim, Y. S., Yoon, J. A., Yang, S. C., Park, M., Seol, D.-W., Lyu, S. W., Jun, J. H., Lim, H. J., Lee, D. R., Song, H. Estrogen induces EGR1 to fine-tune its actions on uterine epithelium by controlling PR signaling for successful embryo implantation.

The TGF-β Family in the Reproductive Tract

The transforming growth factor β (TGF-β) family has a profound impact on the reproductive function of various organisms. In this review, we discuss how highly conserved members of the TGF-β family influence the reproductive function across several species. We briefly discuss how TGF-β-related proteins balance germ-cell proliferation and differentiation as well as dauer entry and exit in Caenorhabditis elegans. In Drosophila melanogaster, TGF-β-related proteins maintain germ stem-cell identity and eggshell patterning. We then provide an in-depth analysis of landmark studies performed using transgenic mouse models and discuss how these data have uncovered basic developmental aspects of male and female reproductive development. In particular, we discuss the roles of the various TGF-β family ligands and receptors in primordial germ-cell development, sexual differentiation, and gonadal cell development. We also discuss how mutant mouse studies showed the contribution of TGF-β family signaling to embryonic and postnatal testis and ovarian development. We conclude the review by describing data obtained from human studies, which highlight the importance of the TGF-β family in normal female reproductive function during pregnancy and in various gynecologic pathologies.

Novel Function of a Transcription Factor WT1 in Regulating Decidualization in Human Endometrial Stromal Cells and Its Molecular Mechanism

The Wilms tumor suppressor gene (WT1) encodes an essential transcription factor regulating mammalian urogenital development. However, the function of WT1 in human endometrium is still unclear. The current study examined the involvement of WT1 in the regulation of IGF-binding protein-1 (IGFBP-1) and prolactin (PRL), which are specific markers of decidualization, in human endometrial stromal cells (ESCs) undergoing decidualization. ESCs isolated from proliferative-phase endometrium were incubated with cyclic adenosine monophosphate (cAMP) to induce decidualization. cAMP increased WT1 expression with the induction of IGFBP-1 and PRL. Knockdown of WT1 by small interfering RNA inhibited cAMP-induced expression of IGFBP-1 and PRL. cAMP also induced the recruitment of WT1 to the IGFBP-1 and PRL promoters. To investigate the mechanism by which WT1 is upregulated by cAMP, we focused on C/EBPβ, a gene that regulates the expression of many genes during decidualization. Knockdown of C/EBPβ decreased cAMP-increased WT1 expression. cAMP increased the recruitment of C/EBPβ to the WT1 enhancer that is located approximately 14,000 bp downstream from the transcription start site. To test the endogenous function of the WT1 enhancer region on WT1 expression, the endogenous WT1 enhancer region was deleted by CRISPR/Cas9 system in HEK293 cells. The increase of WT1 expression by cAMP was not observed in the enhancer-deleted clones. Chromatin immunoprecipitation assay revealed that this enhancer region has high levels of H3K27ac and H3K4me1, which are active enhancer marks. These results show the role of WT1 in regulating decidualization in human ESCs. C/EBPβ is an upstream gene that regulates WT1 expression by binding to the novel enhancer region.

Juxtacrine Activity of Estrogen Receptor α in Uterine Stromal Cells is Necessary for Estrogen-Induced Epithelial Cell Proliferation

Aberrant regulation of uterine cell growth can lead to endometrial cancer and infertility. To understand the molecular mechanisms of estrogen-induced uterine cell growth, we removed the estrogen receptor α (Esr1) from mouse uterine stromal cells, where the embryo is implanted during pregnancy. Without ESR1 in neighboring stroma cells, epithelial cells that line the inside of the uterus are unable to grow due to a lack of growth factors secreted from adjacent stromal cells. Moreover, loss of stromal ESR1 caused mice to deliver fewer pups due in part due to inability of some embryos to implant in the uterus, indicating that stromal ESR1 is crucial for uterine cell growth and pregnancy.

Combined transcriptome and metabolome analyses of metformin effects reveal novel links between metabolic networks in steroidogenic systems

Metformin is an antidiabetic drug, which inhibits mitochondrial respiratory-chain-complex I and thereby seems to affect the cellular metabolism in many ways. It is also used for the treatment of the polycystic ovary syndrome (PCOS), the most common endocrine disorder in women. In addition, metformin possesses antineoplastic properties. Although metformin promotes insulin-sensitivity and ameliorates reproductive abnormalities in PCOS, its exact mechanisms of action remain elusive. Therefore, we studied the transcriptome and the metabolome of metformin in human adrenal H295R cells. Microarray analysis revealed changes in 693 genes after metformin treatment. Using high resolution magic angle spinning nuclear magnetic resonance spectroscopy (HR-MAS-NMR), we determined 38 intracellular metabolites. With bioinformatic tools we created an integrated pathway analysis to understand different intracellular processes targeted by metformin. Combined metabolomics and transcriptomics data analysis showed that metformin affects a broad range of cellular processes centered on the mitochondrium. Data confirmed several known effects of metformin on glucose and androgen metabolism, which had been identified in clinical and basic studies previously. But more importantly, novel links between the energy metabolism, sex steroid biosynthesis, the cell cycle and the immune system were identified. These omics studies shed light on a complex interplay between metabolic pathways in steroidogenic systems.

Ptn functions downstream of C/EBPβ to mediate the effects of cAMP on uterine stromal cell differentiation through targeting Hand2 in response to progesterone

Ptn is a pleiotropic growth factor involving in the regulation of cellular proliferation and differentiation, but its biological function in uterine decidualization remains unknown. Here, we showed that Ptn was highly expressed in the decidual cells, and could induce the proliferation of uterine stromal cells and expression of Prl8a2 and Prl3c1 which were two well-established differentiation markers for decidualization, suggesting an important role of Ptn in decidualization. In the uterine stromal cells, progesterone stimulated the expression of Ptn accompanied with an accumulation of intracellular cAMP level. Silencing of Ptn impeded the induction of progesterone and cAMP on the differentiation of uterine stromal cells. Administration of PKA inhibitor H89 resulted in a blockage of progesterone on Ptn expression. Further analysis evidenced that regulation of progesterone and cAMP on Ptn was mediated by C/EBPβ. During in vitro decidualization, knockdown of Ptn could weaken the up-regulation of Prl8a2 and Prl3c1 elicited by C/EBPβ overexpression, while constitutive activation of Ptn reversed the repressive effects of C/EBPβ siRNA on the expression of Prl8a2 and Prl3c1. Meanwhile, Ptn might mediate the regulation of C/EBPβ on Hand2 which was a downstream target of Ptn in the differentiation of uterine stromal cells. Attenuation of Ptn or C/EBPβ by specific siRNA blocked the stimulation of Hand2 by progesterone and cAMP. Collectively, Ptn may play a vital role in the progesterone-induced decidualization pathway.

CCAAT/enhancer binding protein β negatively regulates progesterone receptor expression in human glioblastoma cells

Many progesterone (P4) actions are mediated by its intracellular receptor (PR), which has two isoforms (PR-A and PR-B) differentially transcribed from separate promoters of a single gene. In glioblastomas, the most frequent and aggressive brain tumors, PR-B is the predominant isoform. In an in silico analysis we showed putative CCAAT/Enhancer Binding Protein (C/EBP) binding sites at PR-B promoter. We evaluated the role of C/EBPβ in PR-B expression regulation in glioblastoma cell lines, which expressed different ratios of PR and C/EBPβ isoforms (LAP1, LAP2, and LIP). ChIP assays showed a significant basal binding of C/EBPβ, specific protein 1 (Sp1) and estrogen receptor alpha (ERα) to PR-B promoter. C/EBPβ knockdown increased PR-B expression and treatment with estradiol (E2) reduced C/EBPβ binding to the promoter and up-regulated PR-B expression. P4 induced genes were differently regulated when CEBP/β was silenced. These data show that C/EBPβ negatively regulates PR-B expression in glioblastoma cells.

An essential developmental function for murine phosphoglycolate phosphatase in safeguarding cell proliferation

Mammalian phosphoglycolate phosphatase (PGP) is thought to target phosphoglycolate, a 2-deoxyribose fragment derived from the repair of oxidative DNA lesions. However, the physiological role of this activity and the biological function of the DNA damage product phosphoglycolate is unknown. We now show that knockin replacement of murine Pgp with its phosphatase-inactive Pgp^D34N mutant is embryonically lethal due to intrauterine growth arrest and developmental delay in midgestation. PGP inactivation attenuated triosephosphate isomerase activity, increased triglyceride levels at the expense of the cellular phosphatidylcholine content, and inhibited cell proliferation. These effects were prevented under hypoxic conditions or by blocking phosphoglycolate release from damaged DNA. Thus, PGP is essential to sustain cell proliferation in the presence of oxygen. Collectively, our findings reveal a previously unknown mechanism coupling a DNA damage repair product to the control of intermediary metabolism and cell proliferation.

Hmgn1 acts downstream of C/EBPβ to regulate the decidualization of uterine stromal cells in mice

Although Hmgn1 is involved in the regulation of gene expression and cellular differentiation, its physiological roles on the differentiation of uterine stromal cells during decidualization still remain unknown. Here we showed that Hmgn1 mRNA was highly expressed in the decidua on days 6-8 of pregnancy. Simultaneously, increased expression of Hmgn1 was also observed in the artificial and in vitro induced decidualization models. Hmgn1 induced the proliferation of uterine stromal cells and expression of Ccna1, Ccnb1, Ccnb2 and Cdk1 in the absence of estrogen and progesterone. Overexpression of Hmgn1 could enhance the expression of Prl8a2 and Prl3c1 which were 2 well-known differentiation markers for decidualization, whereas inhibition of Hmgn1 with specific siRNA could reduce their expression. Further studies found that Hmgn1 could mediate the effects of C/EBPβ on the expression of Prl8a2 and Prl3c1 during in vitro decidualization. In the uterine stromal cells, cAMP analog 8-Br-cAMP could stimulate the expression of Hmgn1 via C/EBPβ. Moreover, siRNA-mediated down-regulation of Hmgn1 could attenuate the effects of cAMP on the differentiation of uterine stromal cells. During in vitro decidualization, Hmgn1 might act downstream of C/EBPβ to regulate the expression of Cox-2, mPGES-1 and Vegf. Progesterone could up-regulate the expression of Hmgn1 in the ovariectomized mouse uterus, uterine epithelial cells and stromal cells. Knockdown of C/EBPβ with siRNA alleviated the up-regulation of progesterone on Hmgn1 expression. Collectively, Hmgn1 may play an important role during mouse decidualization.

Decreased expression of NR4A nuclear receptors in adenomyosis impairs endometrial decidualization

STUDY QUESTION

How do NR4A receptors drive decidualization of human endometrial stromal cells (hESCs)?

SUMMARY ANSWER

NR4A receptors modulate endometrial decidualization by transcriptional activation of FOXO1A, and in adenomyosis patients, the reduced expression of NR4A receptors in the eutopic endometrium may represent a novel mechanism to explain impaired decidualization and subfertility.

WHAT IS KNOWN ALREADY

A close relationship between impaired decidualization and subfertility has been established. In human endometrial stromal cells, orphan nuclear receptor NR4A is a novel regulator of decidualization.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Eutopic endometrial tissues and hESCs from fertile controls (n = 56) and adenomyosis patients (n = 27) were collected for in vitro analysis. Primary hESCs isolated from eutopic endometrial tissues were used to evaluate the biological function of NR4A receptors. Adenovirus-mediated overexpression of NR4A and small interfering RNAs targeting NR4A, and FOXO1A were used to investigate the molecular mechanisms. Gene expression regulation was examined by real-time-quantitative PCR, immunostaining, and luciferase reporter assay. Artificial decidualization assay was performed to investigate the role of NR4A1 during decidualization in vivo.

MAIN RESULTS AND THE ROLE OF CHANCE

NR4A modulates the decidualization of hESCs by upregulating prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1) expression and transformation in vitro. Loss of uterine Nr4a1 results in female subfertility due to impaired decidualization. Mechanistically, NR4A binds to the nerve growth factor 1B (NGFI-B) -responsive element (NBRE) (-843 to -813) within the FOXO1A promoter region and regulates FOXO1A expression. Loss of FOXO1A significantly inhibits PRL and IGFBP-1 expression, as induced by NR4A. Moreover, the expression of NR4A and FOXO1A was lower in adenomyosis endometrial tissues compared to fertile controls, especially in stroma compartments. Ectopic NR4A expression rescued PRL and IGFBP-1 expression in adenomyotic hESCs to near-normal levels. Furthermore, PI3K/AKT signaling pathway involved in inducing NR4A expression under decidualization stimuli in hESCs and the level of p(Ser473)-AKT was significantly higher in stroma in endometrium from patients with adenomyosis.

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study with a small sample size, utilizing stromal cell cultures from endometrial tissues of adenomyosis patients. Furthermore, results obtained should also be confirmed in a larger data set and with adenomyosis mouse models in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

Identification of a positive agonist of NR4A receptors will be critical for the improved treatment of patients with conditions of insufficient decidualization-associated infertility, such as adenomyosis and endometriosis.

LARGE SCALE DATA

N/A.

STUDY FUNDING AND COMPETING INTERESTS

This study was supported by the National Natural Science Foundation of China (81170570, G.J.Y. 81370683, G.J.Y. 81501251, Y.J. 31571189, H.X.S. and 81571402, G.J.Y.), and a special grant for clinical medicine science of Jiangsu Province (BL2014003, H.X.S.). The authors have no conflicts of interest to declare.

Runx2 acts downstream of C/EBPβ to regulate the differentiation of uterine stromal cells in mice

Although Runx2 is involved in the regulation of cellular differentiation, its physiological roles in the differentiation of uterine stromal cells during decidualization still remain unknown. The aim of this study was to examine the expression, regulation and function of Runx2 in mouse uterus during decidualization. The results showed that Runx2 was highly expressed in the decidua and oil-induced decidualized cells. In the uterine stromal cells, recombinant human Runx2 (rRunx2) could induce the expression of Prl8a2 and Prl3c1 which are two well-known differentiation markers for decidualization, while inhibition of Runx2 with specific siRNA reduced their expression. Further study found that rRunx2 could improve the expression of Prl8a2 and Prl3c1 in the C/EBPβ siRNA-transfected stromal cells. In the stromal cells, cAMP analogue 8-Br-cAMP could induce the expression of Runx2. Moreover, the induction was blocked by PKA inhibitor H89. Simultaneously, attenuation of C/EBPβ with siRNA could also reduce the cAMP-induced Runx2 expression. Furthermore, siRNA-mediated silencing of Runx2 expression alleviated the effects of cAMP on the differentiation of stromal cells. Runx2 might act downstream of C/EBPβ to regulate the expression of Cox-2, Vegf and Mmp9 in the uterine stromal cells. Collectively, Runx2 may play an important role during mouse decidualization.