FOXO1A differentially regulates genes of decidualization

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.

The Long Non-Coding RNA Gene AC027288.3 Plays a Role in Human Endometrial Stromal Fibroblast Decidualization

During the secretory phase of the menstrual cycle, endometrial fibroblast cells begin to change into large epithelial-like cells called decidual cells in a process called decidualization. This differentiation continues more broadly in the endometrium and forms the decidual tissue during early pregnancy. The cells undergoing decidualization as well as the resulting decidual cells, support successful implantation and placentation during early pregnancy. This study was carried out to identify new potentially important long non-coding RNA (lncRNA) genes that may play a role in human endometrial stromal fibroblast cells (hESF) undergoing decidualization in vitro, and several were found. The expression of nine was further characterized. One of these, AC027288.3, showed a dramatic increase in the expression of hESF cells undergoing decidualization. When AC027288.3 expression was targeted, the ability of the cells to undergo decidualization as determined by the expression of decidualization marker protein-coding genes was significantly altered. The most affected markers of decidualization whose expression was significantly reduced were FOXO1, FZD4, and INHBA. Therefore, AC027288.3 may be a major upstream regulator of the WNT-FOXO1 pathway and activin-SMAD3 pathways previously shown as critical for hESF decidualization. Finally, we explored possible regulators of AC027288.3 expression during human ESF decidualization. Expression was regulated by cAMP and progesterone. Our results suggest that AC027288.3 plays a role in hESF decidualization and identifies several other lncRNA genes that may also play a role.

The involvement of RNA N6-methyladenosine and histone methylation modification in decidualization and endometriosis-associated infertility

Defective decidualization of endometrial stromal cells (ESCs) in endometriosis (EM) patients leads to inadequate endometrial receptivity and EM-associated infertility. Hypoxia is an inevitable pathological process of EM and participates in deficient decidualization of the eutopic secretory endometrium. Enhancer of zeste homology 2 (EZH2) is a methyltransferase which catalyses H3K27Me3, leading to decreased expression levels of target genes. Although EZH2 expression is low under normal decidualization, it is abundantly increased in the eutopic secretory endometrium of EM and is induced by hypoxia. Chromatin immunoprecipitation-PCR results revealed that decidua marker IGFBP1 is a direct target of EZH2, partially explaining the increased levels of histone methylation modification in defected decidualization of EM. To mechanism controlling this, we examined the effects of hypoxia on EZH2 and decidualization. EZH2 mRNA showed decreased m6 A modification and increased expression levels under hypoxia and decidualization combined treatment. Increased EZH2 expression was due to the increased expression of m6 A demethylase ALKBH5 and decreased expression of the m6 A reader protein YTHDF2. YTHDF2 directly bind to the m6 A modification site of EZH2 to promote EZH2 mRNA degradation in ESCs. Moreover, selective Ezh2 depletion in mouse ESCs increased endometrial receptivity and improved mouse fertility by up-regulating decidua marker IGFBP1 expression. This is the first report showing that YTHDF2 can act as a m6 A reader to promote decidualization by decreasing the stability of EZH2 mRNA and further increasing the expression of IGFBP1 in ESCs. Taken together, our findings highlight the critical role of EZH2/H3K27Me3 in decidualization and reveal a novel epigenetic mechanism by which hypoxia can suppress EM decidualization by decreasing the m6 A modification of EZH2 mRNA.

ATOH8 Expression Is Regulated by BMP2 and Plays a Key Role in Human Endometrial Stromal Cell Decidualization

During the secretory phase of the menstrual cycle, elongated fibroblast-like mesenchymal cells in the uterine endometrium begin to transdifferentiate into polygonal epithelioid-like (decidual) cells. This decidualization process continues more broadly during early pregnancy, and the resulting decidual tissue supports successful embryo implantation and placental development. This study was carried out to determine if atonal basic helix-loop-helix transcription factor 8 (ATOH8) plays a role in human endometrial stromal fibroblast (ESF) decidualization. ATOH8 messenger RNA and protein expression levels significantly increased in human ESF cells undergoing in vitro decidualization, with the protein primarily localized to the nucleus. When ATOH8 expression was silenced, the ability of the cells to undergo decidualization was significantly diminished. Overexpression of ATOH8 enhanced the expression of many decidualization markers. Silencing the expression of ATOH8 reduced the expression of FZD4, FOXO1, and several known FOXO1-downstream targets during human ESF cell decidualization. Therefore, ATOH8 may be a major upstream regulator of the WNT/FZD-FOXO1 pathway, previously shown to be critical for human endometrial decidualization. Finally, we explored possible regulators of ATOH8 expression during human ESF decidualization. BMP2 significantly enhanced ATOH8 expression when cells were stimulated to undergo decidualization, while an ALK2/3 inhibitor reduced ATOH8 expression. Finally, although the steroids progesterone plus estradiol did not affect ATOH8 expression, the addition of cyclic adenosine monophosphate (cAMP) analogue alone represented the major effect of ATOH8 expression when cells were stimulated to undergo decidualization. Our results suggest that ATOH8 plays a crucial role in human ESF decidualization and that BMP2 plus cAMP are major regulators of ATOH8 expression.

Calpain7 negatively regulates human endometrial stromal cell decidualization in EMs by promoting FoxO1 nuclear exclusion via hydrolyzing AKT1

Endometrial receptivity damage caused by impaired decidualization may be one of the mechanisms of infertility in endometriosis (EMs). Our previous study demonstrated that Calpain-7 (CAPN7) is abnormally overexpressed in EMs. Whether CAPN7 affects the regulation of decidualization and by what mechanism CAPN7 regulates decidualization remains to be determined. In this study, we found CAPN7 expression decreased during human endometrial stromal cell (HESC) decidualization in vitro. CAPN7 negatively regulated decidualization in vitro and in vivo. We also identified one conserved potential PEST sequence in the AKT1 protein and found that CAPN7 was able to hydrolyse AKT1 and enhance AKT1's phosphorylation. Correspondingly, CAPN7 notably promoted the phosphorylation of Forkhead Box O1 (FoxO1), the downstream of AKT1 protein, at Ser319, leading to increased FoxO1 exclusion from nuclei and attenuated FoxO1 transcriptional activity in decidualized HESC. In addition, we detected endometrium CAPN7, p-AKT1 and p-FoxO1 expressions were increased in EMs. These data demonstrate that CAPN7 negatively regulates HESC decidualization in EMs probably by promoting FoxO1's phosphorylation and FoxO1 nuclear exclusion via hydrolyzing AKT1. The dysregulation of CAPN7 may be a novel cause of EMs.

Notch signaling in reproduction

The Notch signaling pathway is conserved among mammalian species and controls proliferation, differentiation, and cell death in many organs throughout the body including the reproductive tract. Notch signaling plays critical roles in the development and function of both the male and female reproductive systems. Specifically, within the female reproductive tract, Notch signaling is hormone regulated and mediates key reproductive events important for ovarian and uterine function. In this review, we highlight the tissues that express Notch receptors, ligands, and downstream effectors and distinguish how these molecules regulate reproductive function in male and female mice, non-human primates, and humans. Finally, we describe some of the aberrations in Notch signaling in female reproductive pathologies and identify opportunities for future investigation.

PPP2R2A affects embryonic implantation by regulating the proliferation and apoptosis of Hu sheep endometrial stromal cells

Embryonic implantation is a complex reproductive physiological process in mammals. Although several endometrial proteins affecting embryonic implantation have been reported in the past, there are still potential endometrial proteins that have been neglected, and their specific regulatory mechanisms are unclear. This study demonstrated that protein phosphatase 2A regulatory subunit B55α (PPP2R2A) served as a novel regulator in medication of sheep embryonic implantation in vitro. Our results showed that sheep PPP2R2A encoded 447 amino acids and shared 91.74%-92.36% amino acid sequences with its orthologs compared with other species. Meanwhile, PPP2R2A was widely expressed in sheep uterine tissues, and it could regulate the expression levels of key regulators of embryonic implantation in endometrial stromal cells (ESCs). Knockdown of PPP2R2A significantly inhibited cell proliferation by blocking cell cycle transfer G0/G1 into S phase accompanied by downregulation of CDK2, CDK4, CCND1, CCNE1 and upregulation of P21. In contrast to PPP2R2A overexpression, PPP2R2A interference greatly promoted cell apoptosis and the expression of BAX, CASP3, CASP9 and BAX/BCL-2. Taken together, these results suggest that PPP2R2A, as a novel regulatory factor, affects embryonic implantation via regulating the proliferation and apoptosis of Hu sheep ESCs in vitro.

Evolutionary transcriptomics implicates HAND2 in the origins of implantation and regulation of gestation length

The developmental origins and evolutionary histories of cell types, tissues, and organs contribute to the ways in which their dysfunction produces disease. In mammals, the nature, development and evolution of maternal-fetal interactions likely influence diseases of pregnancy. Here we show genes that evolved expression at the maternal-fetal interface in Eutherian mammals play essential roles in the evolution of pregnancy and are associated with immunological disorders and preterm birth. Among these genes is HAND2, a transcription factor that suppresses estrogen signaling, a Eutherian innovation allowing blastocyst implantation. We found dynamic HAND2 expression in the decidua throughout the menstrual cycle and pregnancy, gradually decreasing to a low at term. HAND2 regulates a distinct set of genes in endometrial stromal fibroblasts including IL15, a cytokine also exhibiting dynamic expression throughout the menstrual cycle and gestation, promoting migration of natural killer cells and extravillous cytotrophoblasts. We demonstrate that HAND2 promoter loops to an enhancer containing SNPs implicated in birth weight and gestation length regulation. Collectively, these data connect HAND2 expression at the maternal-fetal interface with evolution of implantation and gestational regulation, and preterm birth.

Immune Tolerance of the Human Decidua

The endometrium is necessary for implantation, complete development of the placenta, and a successful pregnancy. The endometrium undergoes repeated cycles of proliferation, decidualization (differentiation), and shedding during each menstrual cycle. The endometrium—including stromal, epithelial, vascular endothelial, and immune cells—is both functionally and morphologically altered in response to progesterone, causing changes in the number and types of immune cells. Immune cells make up half of the total number of endometrial cells during implantation and menstruation. Surprisingly, immune tolerant cells in the endometrium (uterine natural killer cells, T cells, and macrophages) have two conflicting functions: to protect the body by eliminating pathogenic microorganisms and other pathogens and to foster immunological change to tolerate the embryo during pregnancy. One of the key molecules involved in this control is the cytokine interleukin-15 (IL-15), which is secreted by endometrial stromal cells. Recently, it has been reported that IL-15 is directly regulated by the transcription factor heart- and neural crest derivatives-expressed protein 2 in endometrial stromal cells. In this review, we outline the significance of the endometrium and immune cell population during menstruation and early pregnancy and describe the factors involved in immune tolerance and their involvement in the establishment and maintenance of pregnancy.

Thyroid Hormone Facilitates in vitro Decidualization of Human Endometrial Stromal Cells via Thyroid Hormone Receptors

Endometrial stromal cells differentiate into decidual cells through the process of decidualization. This differentiation is critical for embryo implantation and the successful establishment of pregnancy. Recent epidemiological studies have suggested that thyroid hormone is important in the endometrium during implantation, and it is commonly believed that thyroid hormone is essential for proper development, differentiation, growth, and metabolism. This study aimed to investigate the impact of thyroid hormone on decidualization in human endometrial stromal cells (hESCs) and define its physiological roles in vitro by gene targeting. To identify the expression patterns of thyroid hormone, we performed gene expression profiling of hESCs during decidualization after treating them with the thyroid hormone levothyroxine (LT4). A major increase in decidual response was observed after combined treatment with ovarian steroid hormones and thyroid hormone. Moreover, LT4 treatment also affected the regulation of many transcription factors important for decidualization. We found that type 3 deiodinase, which is particularly important in fetal and placental tissues, was upregulated during decidualization in the presence of thyroid hormone. Further, it was observed that progesterone receptor, an ovarian steroid hormone receptor, was involved in thyroid hormone-induced decidualization. In the absence of thyroid hormone receptor (TR), due to the simultaneous silencing of TRα and TRβ, thyroid hormone expression was unchanged during decidualization. In summary, we demonstrated that thyroid hormone is essential for decidualization in the endometrium. This is the first in vitro study to find impaired decidualization as a possible cause of infertility in subclinical hypothyroidism (SCH) patients.

Insulin Signaling Via Progesterone-Regulated Insulin Receptor Substrate 2 is Critical for Human Uterine Decidualization

Decidualization, the process by which fibroblastic human endometrial stromal cells (HESC) differentiate into secretory decidual cells, is a critical event during the establishment of pregnancy. It is dependent on the steroid hormone progesterone acting through the nuclear progesterone receptor (PR). Previously, we identified insulin receptor substrate 2 (IRS2) as a factor that is directly regulated by PR during decidualization. IRS2 is an adaptor protein that functionally links receptor tyrosine kinases, such as insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF1R), and their downstream effectors. IRS2 expression was induced in HESC during in vitro decidualization and siRNA-mediated downregulation of IRS2 transcripts resulted in attenuation of this process. Further use of siRNAs targeted to IR or IGF1R transcripts showed that downregulation of IR, but not IGF1R, led to impaired decidualization. Loss of IRS2 transcripts in HESC suppressed phosphorylation of both ERK1/2 and AKT, downstream effectors of insulin signaling, which mediate gene expression associated with decidualization and regulate glucose uptake. Indeed, downregulation of IRS2 resulted in reduced expression and membrane localization of the glucose transporters GLUT1 and GLUT4, resulting in lowered glucose uptake during stromal decidualization. Collectively, these data suggest that the PR-regulated expression of IRS2 is necessary for proper insulin signaling for controlling gene expression and glucose utilization, which critically support the decidualization process to facilitate pregnancy. This study provides new insight into the mechanisms by which steroid hormone signaling intersects with insulin signaling in the uterus during decidualization, which has important implications for pregnancy complications associated with insulin resistance and infertility.

Molecular Signaling Regulating Endometrium-Blastocyst Crosstalk

Implantation of the embryo into the uterine endometrium is one of the most finely-regulated processes that leads to the establishment of a successful pregnancy. A plethora of factors are released in a time-specific fashion to synchronize the differentiation program of both the embryo and the endometrium. Indeed, blastocyst implantation in the uterus occurs in a limited time frame called the "window of implantation" (WOI), during which the maternal endometrium undergoes dramatic changes, collectively called "decidualization". Decidualization is guided not just by maternal factors (e.g., estrogen, progesterone, thyroid hormone), but also by molecules secreted by the embryo, such as chorionic gonadotropin (CG) and interleukin-1β (IL-1 β), just to cite few. Once reached the uterine cavity, the embryo orients correctly toward the uterine epithelium, interacts with specialized structures, called pinopodes, and begins the process of adhesion and invasion. All these events are guided by factors secreted by both the endometrium and the embryo, such as leukemia inhibitory factor (LIF), integrins and their ligands, adhesion molecules, Notch family members, and metalloproteinases and their inhibitors. The aim of this review is to give an overview of the factors and mechanisms regulating implantation, with a focus on those involved in the complex crosstalk between the blastocyst and the endometrium.

Development and utilization of human decidualization reporter cell line uncovers new modulators of female fertility

Failure of embryo implantation accounts for a significant percentage of female infertility. Exquisitely coordinated molecular programs govern the interaction between the competent blastocyst and the receptive uterus. Decidualization, the rapid proliferation and differentiation of endometrial stromal cells into decidual cells, is required for implantation. Decidualization defects can cause poor placentation, intrauterine growth restriction, and early parturition leading to preterm birth. Decidualization has not yet been systematically studied at the genetic level due to the lack of a suitable high-throughput screening tool. Herein we describe the generation of an immortalized human endometrial stromal cell line that uses yellow fluorescent protein under the control of the prolactin promoter as a quantifiable visual readout of the decidualization response (hESC-PRLY cells). Using this cell line, we performed a genome-wide siRNA library screen, as well as a screen of 910 small molecules, to identify more than 4,000 previously unrecognized genetic and chemical modulators of decidualization. Ontology analysis revealed several groups of decidualization modulators, including many previously unappreciated transcription factors, sensory receptors, growth factors, and kinases. Expression studies of hits revealed that the majority of decidualization modulators are acutely sensitive to ovarian hormone exposure. Gradient treatment of exogenous factors was used to identify EC₅₀ values of small-molecule hits, as well as verify several growth factor hits identified by the siRNA screen. The high-throughput decidualization reporter cell line and the findings described herein will aid in the development of patient-specific treatments for decidualization-based recurrent pregnancy loss, subfertility, and infertility.

Generation of Progesterone-Responsive Endometrial Stromal Fibroblasts from Human Induced Pluripotent Stem Cells: Role of the WNT/CTNNB1 Pathway

Defective endometrial stromal fibroblasts (EMSFs) contribute to uterine factor infertility, endometriosis, and endometrial cancer. Induced pluripotent stem cells (iPSCs) derived from skin or bone marrow biopsies provide a patient-specific source that can be differentiated to various cells types. Replacement of abnormal EMSFs is a potential novel therapeutic approach for endometrial disease; however, the methodology or mechanism for differentiating iPSCs to EMSFs is unknown. The uterus differentiates from the intermediate mesoderm (IM) to form coelomic epithelium (CE) followed by the Müllerian duct (MD). Here, we successfully directed the differentiation of human iPSCs (hiPSCs) through IM, CE, and MD to EMSFs under molecularly defined embryoid body culture conditions using specific hormonal treatments. Activation of CTNNB1 was essential for expression of progesterone receptor that mediated the final differentiation step of EMSFs before implantation. These hiPSC-derived tissues illustrate the potential for iPSC-based endometrial regeneration for future cell-based treatments.

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We developed a molecularly defined system for differentiating hiPSCs to EMSFs

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hiPSC-derived EMSFs undergo decidualization in response to hormonal stimulation

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D14 embryoid bodies recapitulate the molecular signature of primary EMSFs

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The WNT/CTNNB1 pathway is required for induction of EMSF from hiPSCs

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.

FKBP51 regulates decidualization through Ser473 dephosphorylation of AKT

Defective decidualization of human endometrial stromal cells (ESCs) has recently been highlighted as an underlying cause of implantation failure. FK-506-binding protein 51 (FKBP51) has been shown to participate in the steroid hormone response and the protein kinase B (AKT) regulation process, both of which are important pathways involved in decidualization. The objective of the present study was to investigate the potential effects and mechanisms of FKBP51 in the regulation of ESC decidualization. By performing immunohistochemical staining on an endometrial tissue microarray (TMA) derived from normal females, we found that FKBP51 expression was much higher in the luteal phase than in the follicular phase in ESCs. Primary ESCs were isolated from patients to build an in vitro decidualization model through co-culture with medroxyprogesterone acetate (MPA) and 8-bromoadenosine (cAMP). SC79, a specific AKT activator in various physiological and pathological conditions, and shRNA-FKBP51 were used to examine the roles of AKT and FKBP51 in decidualization. The Western blot and RT-PCR results showed that FKBP51, insulin-like growth factor-binding protein 1 (IGFBP1) and prolactin (PRL) expression increased in ESCs treated with MPA + cAMP; meanwhile, the level of p-Ser473 AKT (p-S473 AKT) decreased and forkhead box protein O1 (FOXO1A) expression increased. Decidualization was inhibited by the AKT activator SC79 and the transfection of FKBP51-shRNA by affecting protein synthesis, cell morphology, cell growth and cell cycle. Furthermore, this inhibition was rescued by FKBP51-cDNA transfection. The results supported that FKBP51 promotes decidualization by reducing the Ser473 phosphorylation levels in AKT.

Dysregulation of In Vitro Decidualization of Human Endometrial Stromal Cells by Insulin via Transcriptional Inhibition of Forkhead Box Protein O1

Insulin resistance and compensatory hyperinsulinemia are characteristic features of obesity and polycystic ovary syndrome, and both are associated with reduced fertility and implantation. There is little knowledge about the effect of insulin on the decidualization process and previous findings are contradictory. We investigated the effect of insulin on the regulation of forkhead box protein O1 (FOXO1), one of the most important transcription factors during decidualization. Endometrial stromal cells were isolated from six healthy, regularly menstruating women and decidualized in vitro. Gene expression levels of six putative FOXO1 target genes (including insulin-like growth factor binding protein-1 (IGFBP1) and prolactin (PRL)) were measured with Real-Time PCR following FOXO1 inhibition or insulin treatment. PI3K inhibition was used to identify the possible mechanism behind regulation. Subcellular localization of FOXO1 was analyzed with immunofluorescence. All the genes (IGFBP1, CTGF, INSR, DCN, LEFTY2), except prolactin, were evaluated as FOXO1 target genes in decidualizing stromal cells. Insulin caused a significant dose-dependent inhibition of the verified FOXO1 target genes. It was also demonstrated that insulin regulated FOXO1 target genes by transcriptional inactivation and nuclear export of FOXO1 via PI3K pathway. However, insulin did not inhibit the morphological transformation of endometrial stromal cells via transcriptional inactivation of FOXO1. This study provides new insights on the action of insulin on the endometrium via regulation of FOXO1. It is suggested that hyperinsulinemia results in dysregulation of a high number of FOXO1 controlled genes that may contribute to endometrial dysfunction and reproductive failure. Our findings may illuminate possible reasons for unexplained infertility.

Progesterone Resistance in Endometriosis Is Modulated by the Altered Expression of MicroRNA-29c and FKBP4

CONTEXT

Endometriosis results in aberrant gene expression in the eutopic endometrium (EuE) and subsequent progesterone resistance. MicroRNA (miR) microarray data in a baboon model of endometriosis showed an increased expression of miR-29c.

OBJECTIVES

To explore the role of miR-29c in progesterone resistance in a subset of women with endometriosis.

DESIGN

MiR-29c expression was analyzed in the endometrium of baboons and women with or without endometriosis. The role in progesterone resistance and decidualization was analyzed by transfecting human uterine fibroblast cells with miR-29c.

PATIENTS

Subjects diagnosed with deep infiltrative endometriosis (DIE) by transvaginal ultrasound with bowel preparation underwent surgical excision of endometriosis. Eutopic secretory endometrium was collected pre- and postoperatively. Women with normal EuE and without DIE served as controls.

RESULTS

Quantitative reverse transcription polymerase chain reaction demonstrated that miR-29c expression increased, while the transcript levels of its target, FK506-binding protein 4 (FKBP4), decreased in the EuE of baboons following the induction of endometriosis. FKBP4 messenger RNA and decidual markers were statistically significantly decreased in decidualized human uterine fibroblast cells transfected with a miR-29c mimic compared with controls. Human data corroborated our baboon data and demonstrated higher expression of miR-29c in endometriosis EuE compared with normal EuE. MiR-29c was significantly decreased in endometriosis EuE postoperatively compared with preoperative tissues, and FKBP4 showed an inverse trend following radical laparoscopic resection surgery.

CONCLUSIONS

We demonstrate that miR-29c expression is increased in EuE of baboons and women with endometriosis, which might contribute to a compromised progesterone response by diminishing the levels of FKBP4. Resection of DIE is likely to reverse the progesterone resistance associated with endometriosis in women.

Phosphatidic acid induces decidualization by stimulating Akt-PP2A binding in human endometrial stromal cells

Decidualization of human endometrial stromal cells (hESCs) is crucial for successful uterine implantation and maintaining pregnancy. We previously reported that phospholipase D1 (PLD1) is required for cAMP-induced decidualization of hESCs. However, the mechanism by which phosphatidic acid (PA), the product of PLD1 action, might regulate decidualization is not known. We confirmed that PA induced decidualization of hESCs by observing morphological changes and measuring increased levels of decidualization markers such as IGFBP1 and prolactin transcripts (P < 0.05). Treatment with PA reduced phosphorylation of Akt and consequently that of FoxO1, which led to the increased IGFBP1 and prolactin mRNA levels (P < 0.05). Conversely, PLD1 knockdown rescued Akt phosphorylation. Binding of PP2A and Akt increased in response to cAMP or PA, suggesting that their binding is directly responsible for the inactivation of Akt during decidualization. Consistent with this observation, treatment with okadaic acid, a PP2A inhibitor, also inhibited cAMP-induced decidualization by blocking Akt dephosphorylation.

The Promyelocytic Leukemia Zinc Finger Transcription Factor Is Critical for Human Endometrial Stromal Cell Decidualization

Progesterone, via the progesterone receptor (PGR), is essential for endometrial stromal cell decidualization, a cellular transformation event in which stromal fibroblasts differentiate into decidual cells. Uterine decidualization supports embryo implantation and placentation as well as subsequent events, which together ensure a successful pregnancy. Accordingly, impaired decidualization results not only in implantation failure or early fetal miscarriage, but also may lead to potential adverse outcomes in all three pregnancy trimesters. Transcriptional reprogramming on a genome-wide scale underlies progesterone dependent decidualization of the human endometrial stromal cell (hESC). However, identification of the functionally essential signals encoded by these global transcriptional changes remains incomplete. Importantly, this knowledge-gap undercuts future efforts to improve diagnosis and treatment of implantation failure based on a dysfunctional endometrium. By integrating genome-wide datasets derived from decidualization of hESCs in culture, we reveal that the promyelocytic leukemia zinc finger (PLZF) transcription factor is rapidly induced by progesterone and that this induction is indispensable for progesterone-dependent decidualization. Chromatin immunoprecipitation followed by next generation sequencing (ChIP-Seq) identified at least ten progesterone response elements within the PLZF gene, indicating that PLZF may act as a direct target of PGR signaling. The spatiotemporal expression profile for PLZF in both the human and mouse endometrium offers further support for stromal PLZF as a mediator of the progesterone decidual signal. To identify functional targets of PLZF, integration of PLZF ChIP-Seq and RNA Pol II RNA-Seq datasets revealed that the early growth response 1 (EGR1) transcription factor is a PLZF target for which its level of expression must be reduced to enable progesterone dependent hESC decidualization. Apart from furnishing essential insights into the molecular mechanisms by which progesterone drives hESC decidualization, our findings provide a new conceptual framework that could lead to new avenues for diagnosis and/or treatment of adverse reproductive outcomes associated with a dysfunctional uterus.

Excess Maternal Fructose Consumption Increases Fetal Loss and Impairs Endometrial Decidualization in Mice

The most significant increase in metabolic syndrome over the previous decade occurred in women of reproductive age, which is alarming given that metabolic syndrome is associated with reproductive problems including subfertility and early pregnancy loss. Individuals with metabolic syndrome often consume excess fructose, and several studies have concluded that excess fructose intake contributes to metabolic syndrome development. Here, we examined the effects of increased fructose consumption on pregnancy outcomes in mice. Female mice fed a high-fructose diet (HFrD) for 6 weeks developed glucose intolerance and mild fatty liver but did not develop other prominent features of metabolic syndrome such as weight gain, hyperglycemia, and hyperinsulinemia. Upon mating, HFrD-exposed mice had lower pregnancy rates and smaller litters at midgestation than chow-fed controls. To explain this phenomenon, we performed artificial decidualization experiments and found that HFrD consumption impaired decidualization. This appeared to be due to decreased circulating progesterone as exogenous progesterone administration rescued decidualization. Furthermore, HFrD intake was associated with decreased bone morphogenetic protein 2 expression and signaling, both of which were restored by exogenous progesterone. Finally, expression of forkhead box O1 and superoxide dismutase 2 [Mn] proteins were decreased in the uteri of HFrD-fed mice, suggesting that HFrD consumption promotes a prooxidative environment in the endometrium. In summary, these data suggest that excess fructose consumption impairs murine fertility by decreasing steroid hormone synthesis and promoting an adverse uterine environment.

In silico, in vitro and in vivo analysis identifies a potential role for steroid hormone regulation of FOXD3 in endometriosis-associated genes

STUDY QUESTION

Can bioinformatics analysis of publically available microarray datasets be utilized in identifying potentially important transcription factors (TF) in the hormonal regulation of the endometrium?

SUMMARY ANSWER

Systems integration and analysis of existing complex (published) datasets, predicted a role for the novel transcription factor, Forkhead Box D3 (FOXD3) in healthy endometrium and in endometriosis, which was followed by the demonstration of decreased levels of the protein upon decidualisation of normal human endometrial stromal cells in vitro and differential endometrial expression in the stroma in endometriosis.

WHAT IS KNOWN ALREADY

The reported endometriosis-associated endometrial aberrations are most pronounced in the progesterone-dominant secretory phase and progesterone resistance is a proposed causative factor.

STUDY DESIGN, SIZE, DURATION

The study was initially an 'in silico' study, with confirmatory 'wet lab' data from western blotting (WB), qPCR and Immunohistochemistry (IHC) on endometrial biopsies obtained from 142 women undergoing gynaecological surgery.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study was conducted at a University Research Institute. Bioinformatic analysis of selected published microarray datasets identified differentially regulated genes for the early and mid-secretory phases relative to the proliferative phase. Diseases and Functions categories were identified with Ingenuity (IPA) 'core analysis' software. The key transcription factors controlling secretory phase gene changes were revealed with oPOSSUM software. FOXD3 expression levels were examined in human endometrial samples from women aged 18-55 years by WB, IHC, and qPCR. The progesterone regulation of endometrial FOXD3 levels was examined in vivo and in cultured primary human endometrial stromal cells in vitro.

MAIN RESULTS AND THE ROLE OF CHANCE

Initial data mining and subsequent bioinformatics analysis of human endometrial microarray datasets identified FOXD3 to be a key regulator of gene expression specific to secretory phase/endometriosis. FOXD3 was dynamically expressed in healthy endometrium and differentially expressed in endometriosis. In vitro decidualisation of primary endometrial stromal cells significantly decreased FOXD3 protein (P = 0.0005) and progestagen (Levonorgestrel) treatment also reduced the high endometrial FOXD3 protein (P = 0.0001) and mRNA levels (P = 0.04) seen in untreated women with endometriosis, with a shift of FOXD3 from the nucleus to the cytoplasm.

LIMITATIONS, REASONS FOR CAUTION

The quality of Bioinformatics analysis and results depends on the published micro-array data.

WIDER IMPLICATIONS OF THE FINDINGS

An in depth analysis of FOXD3 function and its relationship with estrogen and progesterone might provide insights into its potential deregulation in proliferative disorders of the endometrium including endometrial cancer where its expression is also deregulated. Further, FOX transcription factors are increasingly seen as novel therapeutic targets in disease.

STUDY FUNDING/COMPETING INTERESTS

We acknowledge the support by Wellbeing of Women project grant RG1073 (D.K.H., A.J.V.). We also acknowledge the support of Liverpool Women's Hospital Foundation Trust (J.A.D.), Institute of Translational Medicine (D.M., A.J.V., D.K.H.) and the Institute of Integrative Biology (O.V.), University of Liverpool. All authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

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.

Decreased Notch pathway signaling in the endometrium of women with endometriosis impairs decidualization

CONTEXT

Endometriosis is a common gynecological disease affecting one in 10 women of reproductive age and is a major cause of pelvic pain and impaired fertility. Endometrial stromal cells of women with endometriosis exhibit a reduced response to in vitro decidualization. NOTCH1 is critical for decidualization of both mouse and human uterine stromal cells.

OBJECTIVE

This study aimed to determine whether decidualization failure in women with endometriosis is a consequence of impaired Notch signaling.

SETTING AND DESIGN

We investigated expression levels of Notch signaling components in the endometrium of women and baboons with or without endometriosis. We identified NOTCH1-regulated genes during decidualization of human uterine fibroblast (HuF) cells by microarray and quantified their expression levels in in vitro-decidualized endometrial stromal cells isolated from women with or without endometriosis.

RESULTS

Notch signaling receptors NOTCH1 and NOTCH4, ligands JAGGED2 and DLL4, as well as direct target genes HES5 and HEY1 were decreased in the eutopic endometrium of women and baboons with endometriosis. Notch signaling was decreased in stromal cells isolated from women with endometriosis, which was associated with impaired in vitro decidualization. Genes that were down-regulated by NOTCH1 silencing in decidualized HuF cells were also decreased in decidualized endometrial stromal cells of women with endometriosis. FOXO1 acts as a downstream target of Notch signaling and endometriosis is associated with decreased expression of NOTCH1-regulated, FOXO1-responsive genes during decidualization.

CONCLUSIONS

Decreased Notch signaling is associated with endometriosis and contributes to impaired decidualization through the down-regulation of FOXO1.

Activated mutant p110α causes endometrial carcinoma in the setting of biallelic Pten deletion

PTEN and PIK3CA mutations occur with high frequency in uterine endometrioid carcinoma (UEC). Although PTEN mutations are present in complex atypical hyperplasia and carcinoma, PIK3CA mutations are restricted to carcinoma. We generated mouse models harboring Pten loss and/or activated Pik3ca in the endometrial epithelium to investigate their respective roles in the pathogenesis of UEC. Presence of an activated mutant Pik3ca on the background of Pten loss led to aggressive disease, with 100% of mice exhibiting carcinoma. Expression of Pik3ca with E545K mutation alone was unable to cause hyperplasia or cancer in the uterus and did not activate Akt as effectively as Pten deletion in short-term cultures of mouse endometrial epithelium, likely explaining the lack of phenotype in vivo. We also report that nuclear localization of FOXO1 correlated with PTEN mutational status irrespective of the PIK3CA status in endometrial cancer cell lines. Furthermore, gene expression profiles resulting from Pten loss or activation of Pik3ca in primary mouse endometrial epithelial cells exhibit minimal overlap. Thus, Pten and Pik3ca have distinct consequences on the activation of the phosphatidylinositol 3-kinase pathway in endometrial epithelium and are likely to affect other nonoverlapping cellular mechanisms involved in the development and progression of the most common type of uterine cancer.

FOXO1 is required for binding of PR on IRF4, novel transcriptional regulator of endometrial stromal decidualization

The forkhead box O1A (FOXO1) is an early-induced target of the protein kinase A pathway during the decidualization of human endometrial stromal cells (HESCs). In this study we identified the cistrome and transcriptome of FOXO1 and its role as a transcriptional regulator of the progesterone receptor (PR). Direct targets of FOXO1 were identified by integrating RNA sequencing with chromatin immunoprecipitation followed by deep sequencing. Gene ontology analysis demonstrated that FOXO1 regulates a subset of genes in decidualization such as those involved in cancer, p53 signaling, focal adhesions, and Wnt signaling. An overlap of the FOXO1 and PR chromatin immunoprecipitation followed by deep sequencing intervals revealed the co-occupancy of FOXO1 in more than 75% of PR binding intervals. Among these intervals were highly enriched motifs for the interferon regulatory factor member 4 (IRF4). IRF4 was determined to be a genomic target of both FOXO1 and PR and also to be differentially regulated in HESCs treated with small interfering RNA targeting FOXO1 or PR prior to decidualization stimulus. Ablation of FOXO1 was found to abolish binding of PR to the shared binding interval downstream of the IRF4 gene. Finally, small interfering RNA-mediated ablation of IRF4 was shown to compromise morphological transformation of decidualized HESCs and to attenuate the expression of the decidual markers IGFBP1, PRL, and WNT4. These results provide the first evidence that FOXO1 is functionally required for the binding of PR to genomic targets. Most notably, FOXO1 and PR are required for the regulation of IRF4, a novel transcriptional regulator of decidualization in HESCs.

Implantation and Establishment of Pregnancy in Human and Nonhuman Primates

Implantation and the establishment of pregnancy are critical for the propagation of the species, but yet remain the limiting steps in human and primate reproduction. Successful implantation requires a competent blastocyst and a receptive endometrium during a specific window of time during the menstrual cycle to initiate the bilateral communication required for the establishment of a successful pregnancy. This chapter provides an overview of these processes and discusses the molecular mechanisms associated with implantation of the blastocyst and decidualization of the uterus in primates.

Influence of AKT on progesterone action in endometrial diseases

Progesterone plays an essential role in the maintenance of the endometrium; it prepares the endometrium for pregnancy, promotes decidualization, and inhibits estrogen-dependent proliferation. Progesterone function is often dysregulated in endometrial disease states. In addition, the PI3K/AKT signaling pathway is often overactive in endometrial pathologies and promotes the survival and proliferation of the diseased cells. Understanding how AKT influences progesterone action is critical in improving hormone-based therapies in endometrial pathologies. Here, we summarize recent studies investigating the crosstalk between the AKT pathway and progesterone receptor function in endometriosis and endometrial cancer.

Requirement of heart and neural crest derivatives-expressed transcript 2 during decidualization of human endometrial stromal cells in vitro

OBJECTIVE

To investigate the role of heart and neural crest derivatives-expressed transcript 2 (HAND2) during decidualization of human endometrial stromal cells (ESCs).

DESIGN

In vitro experiment.

SETTING

Research laboratory.

PATIENT(S)

Twenty-six patients undergoing hysterectomy for benign reasons.

INTERVENTION(S)

ESCs were cultured for 12 days with HAND2 small interfering RNA (siRNA) or nonsilencing RNA during decidualization by medroxyprogesterone acetate (MPA) and E2.

MAIN OUTCOME MEASURE(S)

Decidualization was monitored by changes in cellular morphology and the expression of several decidual-specific genes.

RESULT(S)

HAND2 siRNA effectively suppressed HAND2 levels in ESCs after 12 days of E2 + MPA treatment. ESCs cultured with HAND2 siRNA retained a long fibroblast-like shape, whereas the cells cultured with control siRNA transformed into enlarged polygonal cells. Silencing of HAND2 expression significantly reduced connexin-43 involved in the morphologic changes. HAND2 silencing significantly reduced the mRNA levels of fibulin-1, prolactin, tissue inhibitor of metalloproteinase 3, interleukin-15, and forkhead box O1A (FOXO1A), but had no effect on the mRNA levels of dickkopf-1, serum glucocorticoid kinase 1, and insulin-like growth factor-binding protein 5. HAND2 siRNA effectively suppressed the levels of nuclear FOXO1A protein as a regulator of decidualization.

CONCLUSION(S)

These results suggest that HAND2 plays a key role in the regulation of progestin-induced decidualization of human ESCs.

Differential expression and anti-oxidant function of glutathione peroxidase 3 in mouse uterus during decidualization

Glutathione peroxidase 3 (GPX3) is an important member of antioxidant enzymes for reducing reactive oxygen species and maintaining the oxygen balance. Gpx3 mRNA is strongly expressed in decidual cells from days 5 to 8 of pregnancy. After pregnant mice are treated with GPX inhibitor for 3 days, pregnancy rate is significantly reduced. Progesterone stimulates Gpx3 expression through PR/HIF1α in mouse endometrial stromal cells. In the decidua, the high level of GPX3 expression is closely associated with the reduction of hydrogen peroxide (H2O2). Based on our data, GPX3 may play a major role in reducing H2O2 during decidualization.

Genome-wide DNA methylation analysis predicts an epigenetic switch for GATA factor expression in endometriosis

Endometriosis is a gynecological disease defined by the extrauterine growth of endometrial-like cells that cause chronic pain and infertility. The disease is limited to primates that exhibit spontaneous decidualization, and diseased cells are characterized by significant defects in the steroid-dependent genetic pathways that typify this process. Altered DNA methylation may underlie these defects, but few regions with differential methylation have been implicated in the disease. We mapped genome-wide differences in DNA methylation between healthy human endometrial and endometriotic stromal cells and correlated this with gene expression using an interaction analysis strategy. We identified 42,248 differentially methylated CpGs in endometriosis compared to healthy cells. These extensive differences were not unidirectional, but were focused intragenically and at sites distal to classic CpG islands where methylation status was typically negatively correlated with gene expression. Significant differences in methylation were mapped to 403 genes, which included a disproportionally large number of transcription factors. Furthermore, many of these genes are implicated in the pathology of endometriosis and decidualization. Our results tremendously improve the scope and resolution of differential methylation affecting the HOX gene clusters, nuclear receptor genes, and intriguingly the GATA family of transcription factors. Functional analysis of the GATA family revealed that GATA2 regulates key genes necessary for the hormone-driven differentiation of healthy stromal cells, but is hypermethylated and repressed in endometriotic cells. GATA6, which is hypomethylated and abundant in endometriotic cells, potently blocked hormone sensitivity, repressed GATA2, and induced markers of endometriosis when expressed in healthy endometrial cells. The unique epigenetic fingerprint in endometriosis suggests DNA methylation is an integral component of the disease, and identifies a novel role for the GATA family as key regulators of uterine physiology-aberrant DNA methylation in endometriotic cells correlates with a shift in GATA isoform expression that facilitates progesterone resistance and disease progression.

Reproductive actions of prolactin mediated through short and long receptor isoforms

Prolactin (PRL) is a polypeptide hormone with a wide range of physiological functions, and is critical for female reproduction. PRL exerts its action by binding to membrane bound receptor isoforms broadly classified as the long form and the short form receptors. Both receptor isoforms are highly expressed in the ovary as well as in the uterus. Although signaling through the long form is believed to be more predominant, it remains unclear whether activation of this isoform alone is sufficient to support reproductive functions or whether both types of receptor are required. The generation of transgenic mice selectively expressing either the short or the long form of PRL receptor has provided insight into the differential signaling mechanisms and physiological functions of these receptors. This review describes the essential finding that both long and short receptor isoforms are crucial for ovarian functions and female fertility, and highlights novel mechanisms of action for these receptors.

Liver receptor homolog-1 is essential for pregnancy

Successful pregnancy requires coordination of an array of signals and factors from multiple tissues. One such element, the liver receptor homolog-1 (Lrh-1, NR5A2), is an orphan nuclear receptor that regulates metabolism and hormone synthesis¹. It is strongly expressed in granulosa cells of ovarian follicles and in the corpus luteum of rodents² and humans. Germline ablation of the Lrh-1 gene in mice is embryo-lethal at gastrulation³. Depletion of Lrh-1 in the ovarian follicle demonstrates that it regulates genes required for both steroid synthesis and ovulation⁴. To study the effects of Lrh-1 on mouse gestation, we disrupted its expression in the corpus luteum, resulting in luteal insufficiency. Hormone replacement permitted embryo implantation but was followed by gestational failure with impaired endometrial decidualization, compromised placental formation, fetal growth retardation, and fetal death. Lrh-1 is expressed in the mouse and human endometrium. In a human model of primary culture of endometrial stromal cells, depletion of Lrh-1 by siRNA abrogated decidualization. These findings demonstrate that Lrh-1 is necessary for maintenance of the corpus luteum, for promotion of decidualization and for placental formation. It therefore plays multiple, indispensible roles in establishing and sustaining pregnancy.

Tissue inhibitor of metalloproteinases (TIMPs) in heart failure

Remodeling of the myocardium and the extracellular matrix (ECM) occurs in heart failure irrespective of its initial cause. The ECM serves as a scaffold to provide structural support as well as housing a number of cytokines and growth factors. Hence, disruption of the ECM will result in structural instability as well as activation of a number of signaling pathways that could lead to fibrosis, hypertrophy, and apoptosis. The ECM is a dynamic entity that undergoes constant turnover, and the integrity of its network structure is maintained by a balance in the function of matrix metalloproteinases (MMPs) and their inhibitors, the tissue inhibitor of metalloproteinases (TIMPs). In heart disease, levels of MMPs and TIMPs are altered resulting in an imbalance between these two families of proteins. In this review, we will discuss the structure, function, and regulation of TIMPs, their MMP-independent functions, and their role in heart failure. We will review the knowledge that we have gained from clinical studies and animal models on the contribution of TIMPs in the development and progression of heart disease. We will further discuss how ECM molecules and regulatory genes can be used as biomarkers of disease in heart failure patients.

The mesenchymal-epithelial transition during in vitro decidualization

The epithelial-mesenchymal transition plays a critical role in embryonic development, cancer progression, and metastasis. Decidualization is the process by which the fibroblast-like endometrial stromal cells differentiate into polygonal epithelial-like cells. However, it is still unclear whether mesenchymal-epithelial transition (MET) occurs during decidualization. The aim of this study was to examine whether decidualization causes the downregulation of some mesenchymal markers and upregulation of some epithelial markers in cultured uterine stromal cells. We showed that decidualization causes the downregulation of snail and vimentin expression, and upregulation of E-cadherin and cytokeratin expression. During in vitro decidualization, cultured stromal cells lose elongated shape and show epithelium-like characteristics. Our data suggest that the process of MET may exist during decidualization.

WNT4 acts downstream of BMP2 and functions via β-catenin signaling pathway to regulate human endometrial stromal cell differentiation

Differentiation of endometrial stromal cells into decidual cells is a prerequisite for successful embryo implantation. Our previous studies in the mouse have shown that bone morphogenetic protein 2 (BMP2), a morphogen belonging to the TGFβ superfamily, is essential for this differentiation process. BMP2 is markedly induced in human primary endometrial stromal cells (HESCs) as they undergo differentiation in response to steroid hormones and cAMP. The present study was undertaken to identify the BMP2-mediated molecular pathways in primary cultures of HESCs during decidualization. Using gene expression profiling, we identified wingless-related murine mammary tumor virus integration site 4 (WNT4) as a target of BMP2 regulation during decidualization. Attenuation of WNT4 expression in HESCs by small interfering RNA administration greatly reduced BMP2-induced stromal differentiation. Additionally, adenovirus-mediated overexpression of WNT4 in HESCs markedly advanced the differentiation program, indicating that it is a key regulator of decidualization. The stimulatory effect of WNT4 was accompanied by the accumulation of active β-catenin in the nuclei of decidualizing stromal cells, indicating the involvement of the canonical WNT signaling pathway. Functional inhibition of WNT4/β-catenin pathway by Dickkopf-1, an inhibitor of the canonical WNT signaling, or small interfering RNA-mediated silencing of β-catenin expression, greatly reduced the BMP2- and WNT4-induced decidualization. Gene expression profiling revealed that Forkhead box protein O1, a forkhead family transcription factor and previously reported regulator of HESC differentiation, is a common downstream mediator of both BMP2 and WNT4 signaling. Taken together, these studies uncovered a linear pathway involving BMP2, WNT4/β-catenin, and Forkhead box protein O1 that operates in human endometrium to critically control decidualization.

Progestin-induced heart and neural crest derivatives expressed transcript 2 is associated with fibulin-1 expression in human endometrial stromal cells

OBJECTIVE

To investigate whether heart and neural crest derivatives expressed transcript 2 (HAND2) regulates fibulin-1 (FBLN1) expression during decidualization of human endometrial stromal cells (ESCs).

DESIGN

In vitro experiment.

SETTING

Research laboratory.

PATIENT(S)

Twenty-four patients undergoing hysterectomy for benign reasons.

INTERVENTION(S)

ESCs were cultured with various progestins (medroxyprogesterone acetate [MPA], norethisterone, levonorgestrel, dienogest, and P), E(2), dexamethasone, and/or 8-bromoadenosine 3', 5'-cyclic monophosphate (8-Br-cAMP). HAND2 and FBLN1 were silenced by small interfering RNA technology.

MAIN OUTCOME MEASURE(S)

HAND2 and FBLN1 expression levels were assessed by real-time polymerase chain reaction and Western blot analysis.

RESULT(S)

MPA or E(2) + MPA increased HAND2 mRNA levels in ESCs in a time- and dose-dependent manner, and this stimulatory effect was blocked by RU-486 (P receptor antagonist). HAND2 was increased by E(2) + MPA earlier than FBLN1. Simultaneous MPA and 8-Br-cAMP treatment synergistically enhanced HAND2 mRNA levels. P and all the progestins significantly increased HAND2 mRNA levels, whereas E(2), 8-Br-cAMP, or dexamethasone alone had no effect. Silencing of HAND2 expression significantly reduced FBLN1 expression, whereas FBLN1 silencing had no effect on HAND2 expression.

CONCLUSION(S)

These results suggest that progestin-induced HAND2 contributes to FBLN1 expression in human ESCs.

FOXO1 transcription factor inhibits luteinizing hormone β gene expression in pituitary gonadotrope cells

Synthesis of luteinizing hormone (LH) is tightly controlled by a complex network of hormonal signaling pathways that can be modulated by metabolic cues, such as insulin. One group of candidate genes that may be regulated by insulin signaling in pituitary gonadotrope cells is the FOXO subfamily of forkhead transcription factors. In this study we investigated whether FOXO1 is expressed in gonadotropes and if it can modulate LH β-subunit (Lhb) gene expression. We demonstrated that FOXO1 is expressed in murine gonadotrope cells and that insulin signaling increased FOXO1 phosphorylation and cytoplasmic localization in a PI3K-dependent manner. We also showed that FOXO1 repressed basal transcription and gonadotropin-releasing hormone (GnRH) induction of both the murine and human LHB genes in LβT2 cells, suggesting that FOXO1 regulation of LHB transcription may be conserved between rodents and humans. Although we did not detect FOXO1 binding to the proximal Lhb promoter, the FOXO1 DNA binding domain was necessary for the suppression, suggesting that FOXO1 exerts its effect through protein-protein interactions with transcription factors/cofactors required for Lhb gene expression. FOXO1 repression mapped to the proximal Lhb promoter containing steroidogenic factor 1 (SF1), pituitary homeobox 1 (PTX1), and early growth response protein 1 (EGR1) binding elements. Additionally, FOXO1 blocked induction of the Lhb promoter with overexpressed SF1, PTX1, and EGR1, indicating that FOXO1 repression occurs via these transcription factors but not through regulation of their promoters. In summary, we demonstrate that FOXO1 phosphorylation and cellular localization is regulated by insulin signaling in gonadotropes and that FOXO1 inhibits Lhb transcription. Our study also suggests that FOXO1 may play an important role in controlling LH levels in response to metabolic cues.

Biological characterization of non-steroidal progestins from botanicals used for women's health

Progesterone plays a central role in women's reproductive health. Synthetic progestins, such as medroxyprogesterone acetate (MPA) are often used in hormone replacement therapy (HRT), oral contraceptives, and for the treatment of endometriosis and infertility. Although MPA is clinically effective, it also promiscuously binds to androgen and glucocorticoid receptors (AR/GR) leading to many undesirable side effects including cardiovascular diseases and breast cancers. Therefore, identifying alternative progestins is clinically significant. The purpose of this study was to biologically characterize non-steroidal progestins from botanicals by investigating theirinteraction and activation of progesterone receptor (PR). Eight botanicals commonly used to alleviate menopausal symptoms were investigated to determine if they contain progestins using a progesterone responsive element (PRE) luciferase reporter assay and a PR polarization competitive binding assay. Red clover extract stimulated PRE-luciferase and bound to PR. A library of purified compounds previously isolated from red clover was screened using the luciferase reporter assay. Kaempferol identified in red clover and a structurally similar flavonoid, apigenin, bound to PR and induced progestegenic activity and P4 regulated genes in breast epithelial cells and human endometrial stromal cells (HESC). Kaempferol and apigenin demonstrated higher progestegenic potency in the HESC compared to breast epithelial cells. Furthermore, phytoprogestins were able to activate P4 signaling in breast epithelial cells without downregulating PR expression. These data suggest that botanical extracts used for women's health may contain compounds capable of activating progesterone receptor signaling.

Increased activation of the PI3K/AKT pathway compromises decidualization of stromal cells from endometriosis

CONTEXT

Endometriosis affects approximately 10% of women in the United States and causes pain and infertility. Decidualization of endometrial stromal cells from women with endometriosis is aberrant.

OBJECTIVE

The objective of this study was to investigate a potential mechanism for the inadequate decidual response in stromal cells from ovarian endometriomas.

DESIGN

Stromal cells of the endometrium from women without endometriosis (HSC) or from ovarian endometriomas (OsisSC) were grown in culture and treated with 10 μm LY294002 or 250 nm MK2206, 100 nm medroxyprogesterone acetate (M), and 0.5 mm dibutyryl cAMP (A) or infection with 100 multiplicity of infection adenoviral constructs containing wild-type Forkhead box O1 or triple-mutant FOXO1. Real-time PCR was used to measure the expression of FOXO1, IGF binding protein-1 (IGFBP1), and prolactin (PRL) mRNA, and Western blot and immunohistochemical staining were used to detect the levels of progesterone receptor (PR), FOXO1, AKT, and p(Ser473)-AKT protein in vitro or in vivo.

RESULTS

Expression of the decidua-specific genes, IGFBP1 and PRL, were significantly lower in OsisSC compared with normal HSC in response to M+A treatment. Basal expression levels of PRA, PRB, and FOXO1 proteins were dramatically lower in OsisSC. Overexpression of triple-mutant FOXO1 increased mRNA levels of IGFBP1 and PRL in OsisSC in the presence of M+A, whereas the overexpression of wild-type FOXO1 had no effect. AKT was highly phosphorylated in OsisSC compared with HSC and inhibition of phosphatidylinositol 3-kinase, with LY294002, increased levels of FOXO1 protein as well as IGFBP1 mRNA in the presence of M+A. Moreover, inhibition of AKT with MK2206, an allosteric AKT inhibitor, dramatically increased the accumulation of nuclear FOXO1 as well as expression of IGFBP1. Finally, immunohistochemical staining demonstrated higher p(Ser473)-AKT and lower FOXO1 levels in endometriosis tissues, compared with normal endometrial tissues.

CONCLUSIONS

In endometriotic stromal cells, overactivation of the phosphatidylinositol 3-kinase/AKT signaling pathway contributes to the reduced expression of the decidua-specific gene, IGFBP1, potentially through reduced levels of nuclear FOXO1.

Notch1 mediates uterine stromal differentiation and is critical for complete decidualization in the mouse

Uterine receptivity implies a dialogue between the hormonally primed maternal endometrium and the free-floating blastocyst. Endometrial stromal cells proliferate, avert apoptosis, and undergo decidualization in preparation for implantation; however, the molecular mechanisms that underlie differentiation into the decidual phenotype remain largely undefined. The Notch family of transmembrane receptors transduce extracellular signals responsible for cell survival, cell-to-cell communication, and differentiation, all fundamental processes for decidualization and pregnancy. Using a murine artificial decidualization model, pharmacological inhibition of Notch signaling by γ-secretase inhibition resulted in a significantly decreased deciduoma. Furthermore, a progesterone receptor (PR)-Cre Notch1 bigenic (Notch1(d/d)) confirmed a Notch1-dependent hypomorphic decidual phenotype. Microarray and pathway analysis, following Notch1 ablation, demonstrated significantly altered signaling repertoire. Concomitantly, hierarchical clustering demonstrated Notch1-dependent differences in gene expression. Uteri deprived of Notch1 signaling demonstrated decreased cellular proliferation; namely, reduced proliferation-specific antigen, Ki67, altered p21, cdk6, and cyclinD activity and an increased apoptotic-profile, cleaved caspase-3, Bad, and attenuated Bcl2. The results demonstrate that the preimplantation uterus relies on Notch signaling to inhibit apoptosis of stromal fibroblasts and regulate cell cycle progression, which together promotes successful decidualization. In summary, Notch1 signaling modulates multiple signaling mechanisms crucial for decidualization and these studies provide additional perspectives to the coordination of multiple signaling modalities required during decidualization.

Transposon-mediated rewiring of gene regulatory networks contributed to the evolution of pregnancy in mammals

A fundamental challenge in biology is explaining the origin of novel phenotypic characters such as new cell types; the molecular mechanisms that give rise to novelties are unclear. We explored the gene regulatory landscape of mammalian endometrial cells using comparative RNA-Seq and found that 1,532 genes were recruited into endometrial expression in placental mammals, indicating that the evolution of pregnancy was associated with a large-scale rewiring of the gene regulatory network. About 13% of recruited genes are within 200 kb of a Eutherian-specific transposable element (MER20). These transposons have the epigenetic signatures of enhancers, insulators and repressors, directly bind transcription factors essential for pregnancy and coordinately regulate gene expression in response to progesterone and cAMP. We conclude that the transposable element, MER20, contributed to the origin of a novel gene regulatory network dedicated to pregnancy in placental mammals, particularly by recruiting the cAMP signaling pathway into endometrial stromal cells.

Expression and function of fatty acid-binding protein 4 during mouse decidualization

Fatty acid-binding protein 4 (Fabp4) is highly expressed in the secondary decidual zone of mouse decidua and deciduoma and stromal cells under in vitro decidualization. Dtprp, a well-known marker of in vitro decidualization, is diminished by small interfering RNA against Fabp4 and FABP4 inhibitor and stimulated through Fabp4 overexpression.

Evidence for a conserved function of heart and neural crest derivatives expressed transcript 2 in mouse and human decidualization

Previously, we showed that heart and neural crest derivatives expressed transcript 2 (Hand2) mRNA levels dramatically increase in mouse uterine endometrial stromal cells (ESCs) as they undergo decidualization in vivo. However, to date, little is known about the expression and function of this transcription factor in mouse or human uterus decidualization. Therefore, this study was conducted to provide a more detailed assessment of Hand2 gene expression and function in the mouse uterus during the peri-implantation period and also in mouse plus human ESCs during decidualization in vitro. The results show that Hand2 mRNA and protein levels increase in the mouse uterus during decidualization and this does not depend on the presence of a conceptus. Interestingly, Hand2 mRNA and protein are present in ESCs adjacent to the luminal epithelium in the uterus prior to the onset of implantation. We find that progesterone is likely a regulator of Hand2 expression during uterine sensitization of the mouse uterus. Finally, Hand2 expression increases in mouse and human fibroblast cells as they undergo decidualization in vitro. This expression is significantly increased in response to prostaglandin E(2). In particular, reduction of Hand2 expression in these cells using small hairpin RNA or small interfering RNA approaches results in the reduced extent of decidualization as shown by the reduced expression of a subset of decidualization markers. The results of this study support the hypothesis that Hand2 expression not only plays an important role in decidualization but may also play a role in obtaining proper progesterone-dependent uterine sensitization required for implantation to begin.

Parathyroid hormone-like hormone (PTHLH) represses decidualization of human uterine fibroblast cells by an autocrine/paracrine mechanism

CONTEXT

Parathyroid hormone-like hormone (PTHLH) is abundantly expressed by human endometrial stromal cells during decidualization. However, the role for PTHLH in the decidualization process is unknown.

OBJECTIVE

To examine the effects of PTHLH on the induction and maintenance of decidualization of human uterine fibroblast (HUF) cells in vitro.

DESIGN

HUF cells were treated with a PTHLH siRNA or a PTHLH receptor antagonist (bPTH(7-34)) before or after decidualization with medroxyprogesterone acetate (MPA), estradiol (E(2)), and prostaglandin E(2) (PGE(2)). Decidualization was monitored by immunocytochemistry and the induction of decidualization-specific marker genes, including IGFBP-1, prolactin, lefty, and transcription factor FOXO1.

RESULTS

HUF cells decidualized after pretreatment with a PTHLH siRNA showed greater morphologic changes of decidualization, greater IGFBP-1 protein, and two- to threefold more IGFBP-1, prolactin, lefty, and FOXO1 mRNAs than cells pretreated with a nonsilencing RNA. The PTHLH siRNA pretreated cells also had 31% less DNA fragmentation (TUNEL assay) and 30-35% less caspase 3 levels during decidualization than cells pretreated treated with nonsilencing RNA. Treatment of HUF cells with PTHLH siRNA or bPTH(7-34) at 9 d after the induction of decidualization also resulted in 2.1- to 3.2-fold greater IGFBP-1, prolactin, lefty, and FOXO1 mRNA levels than that noted in control cells treated with nonsilencing RNA.

CONCLUSIONS

These finding strongly suggest that PTHLH represses the induction of human decidualization, stimulates stromal cell apoptosis, and limits the extent of uterine stromal cell differentiation. Because PTHLH and its receptor are expressed by HUF cells and placental cells, the inhibitory effect of PTHLH on decidualization appears to be due, at least in part, to an autocrine/paracrine mechanism.

The orphan nuclear receptor Nur77 regulates decidual prolactin expression in human endometrial stromal cells

Prolactin (PRL) is synthesized and released by several extrapituitary tissues, including decidualized stromal cells. Despite the important role of decidual PRL during pregnancy, little is understood about the factors involved in the proper regulation of decidual PRL expression. Here we present evidence that the transcription factor Nur77 plays an active role in decidual prolactin expression in human endometrial stromal cells (hESCs). Nur77 mRNA expression in hESCs was significantly increased after decidualization stimulated by 8-Br-cAMP and medroxyprogesterone acetate (MPA). Adenovirus-mediated overexpression of Nur77 in hESCs markedly increased PRL mRNA expression and enhanced decidual PRL promoter (dPRL/-332Luc) activity in a concentration-dependent manner. Furthermore, knockdown of Nur77 in hESCs significantly decreased decidual PRL promoter activation and substantially attenuated PRL mRNA expression and PRL secretion (P < 0.01) induced by 8-Br-cAMP and MPA. These results demonstrate that Nur77 is a novel transcription factor that contributes significantly to the regulation of prolactin gene expression in human endometrial stromal cells.

LEFTY, a member of the transforming growth factor-beta superfamily, inhibits uterine stromal cell differentiation: a novel autocrine role

LEFTY is expressed in normal endometrium in cells that decidualize. To understand the importance of this expression, we have studied the effect of LEFTY on decidualization in vitro and in vivo. Exposure of human uterine fibroblast (HuF) cells to recombinant LEFTY blocked the induction of the decidual differentiation-specific marker genes, IGFBP1 (IGF-binding protein 1) and PRL (prolactin) in response to medroxyprogesterone acetate, estradiol, and prostaglandin E2. The inhibitory effect was associated with decreased induction of the transcription factors ETS1 and FOXO1, both of which are essential for decidualization. Overexpression of LEFTY in decidualized HuF cells with an adenovirus that transduced LEFTY caused a marked decrease in IGFBP1 secretion, and withdrawal of medroxyprogesterone acetate from decidualized cells resulted in a decrease in IGFBP1 secretion and an increase in LEFTY expression. Moreover, overexpression of LEFTY in decidualized cells reprogrammed the cells to a less differentiated state and attenuated expression of decidual markers. Uterine decidualization was markedly attenuated and litter size was significantly reduced by retroviral transduction of LEFTY in the uterine horns of pregnant mice or by induction of LEFTY expression by doxycycline treatment in Tet-On conditional LEFTY transgenic pregnant mice. In addition, administration of the contraceptive agent drospirenone to ovariectomized mice induced a marked increase in LEFTY expression and inhibited decidualization. Taken together, these finding indicate that LEFTY acts as a molecular switch that modulates both the induction of decidual differentiation and the maintenance of a decidualized state. Because decidual cells express abundant amounts of LEFTY, the action of LEFTY on decidualization occurs by an autocrine mechanism.

The protein kinase A pathway-regulated transcriptome of endometrial stromal fibroblasts reveals compromised differentiation and persistent proliferative potential in endometriosis

Intrinsic abnormalities in transplanted eutopic endometrium are believed to contribute to the pathogenesis of pelvic endometriosis. Herein we investigated transcriptomic differences in human endometrial stromal fibroblasts (hESFs) from women with (hESF(endo)) vs. without (hESF(nonendo)) endometriosis, in response to activation of the protein kinase A (PKA) pathway with 8-bromoadenosine-cAMP (8-Br-cAMP). hESF(nonendo) (n = 4) and hESF(endo) (n = 4) were isolated from eutopic endometrium and treated +/- 0.5 mm 8-Br-cAMP for 96 h. Purified total RNA was subjected to microarray analysis using the whole-genome Gene 1.0 ST Affymetrix platform. A total of 691 genes were regulated in cAMP-treated hESF(nonendo) vs. 158 genes in hESF(endo), suggesting a blunted response to cAMP/PKA pathway activation in women with disease. Real-time PCR and ELISA validated the decreased expression of decidualization markers in hESF(endo) compared with hESF(nonendo). In the absence of disease, 8-Br-cAMP down-regulated progression through the cell cycle via a decrease in cyclin D1, cyclin-dependent kinase 6, and cell division cycle 2 and an increase in cyclin-dependent kinase inhibitor 1A. However, cell cycle components in hESF(endo) were not responsive to 8-Br-cAMP, resulting in persistence of a proliferative phenotype. hESF(endo) treated with 8-Br-cAMP exhibited altered expression of immune response, extracellular matrix, cytoskeleton, and apoptosis genes. Changes in phosphodiesterase expression and activity were not different among experimental groups. These data support that eutopic hESF(endo) with increased proliferative potential can seed the pelvic cavity via retrograde menstruation and promote establishment, survival, and proliferation of endometriosis lesions, independent of hydrolysis of cAMP and likely due to an inherent abnormality in the PKA pathway.