Indian hedgehog as a progesterone-responsive factor mediating epithelial-mesenchymal interactions in the mouse uterus

Progesterone in frozen embryo transfer cycles: assays, circulating concentrations, metabolites, and molecular action

Programmed or medicated frozen embryo transfer cycles rely on exogenous progesterone (P) administration to prepare the endometrium for implantation and maintain pregnancy. Presently, the optimal route and dose of P replacement for frozen embryo transfer are not known. In addition, there is a paucity of data and insufficient understanding regarding the metabolism and actions of P in implantation and pregnancy maintenance. In the present review, we discuss how different P assay methodologies affect the determination of P thresholds for implantation and pregnancy maintenance. In addition, we discuss the importance of free P and its regulation in the endometrium and show the complexity of molecular signaling that is required for P-dependent endometrial receptivity. We concluded that future studies should focus on defining accurate circulating and endometrial P concentrations, both for total and free P, and how these concentrations correlate with endometrial receptivity and clinical outcomes.

Molecular approaches to mammalian uterine receptivity for conceptus implantation

Mammalian reproduction is more inefficient than expected and embryo/conceptus implantation into the maternal endometrium is considered to be a rate-limiting process. Although extensive physiological and structural diversity exists among mammalian species, the basic molecular mechanisms underlying successful implantation are conserved. The extensive use of genetically engineered mouse models has provided considerable information on uterine receptivity for embryo implantation. The molecular mechanisms and cellular processes identified thus far require further validation in other mammalian species. In this review, representative ovarian steroid hormone-induced signaling pathways controlling uterine adaptation are presented based on the results of rodent studies. Selected examples of functional conservation in mammals, such as humans and cattle, are briefly described. To date, molecular therapeutic trials for fertility improvement have not been conducted. Considerable efforts are required to provide further understanding of these molecular mechanisms. Such understanding will contribute to the development of reliable clinical diagnostics and therapeutics for implantation failure, leading to reproductive success in a wide variety of mammals in the future.

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.

Structure, function, and research progress of primary cilia in reproductive physiology and reproductive diseases

Primary cilia, serving as the central hub for cellular signal transduction, possess the remarkable ability to translate diverse extracellular signals, both chemical and mechanical, into intracellular responses. Their ubiquitous presence in the reproductive system underscores their pivotal roles in various cellular processes including development, differentiation, and migration. Emerging evidence suggests primary cilia as key players in reproductive physiology and associated pathologies. Notably, primary cilia have been identified in granulosa cells within mouse ovaries and uterine stromal cells, and perturbations in their structure and function have been implicated in a spectrum of reproductive dysfunctions and ciliary-related diseases. Furthermore, disruptions in primary cilia-mediated signal transduction pathways under pathological conditions exacerbate the onset and progression of reproductive disorders. This review provides a comprehensive overview of current research progress on primary cilia and their associated signaling pathways in reproductive physiology and diseases, with the aim of furnishing theoretical groundwork for the prevention and management of primary cilia-related structural and functional abnormalities contributing to reproductive system pathologies.

Progesterone signaling in uterine leiomyoma biology: Implications for potential targeted therapy

Uterine leiomyomas (ULs) are the most common benign smooth muscle cell steroid-dependent tumors that occur in women of reproductive age. Progesterone (P4) is a major hormone that promotes the ULs development and growth. P4 action in ULs is mediated mainly by its nuclear progesterone receptors (PGRs), although rapid non-genomic responses have also been observed. Data on the membrane progesterone receptors (mPRs) regulated signaling pathways in ULs in the available literature is still very limited. One of the essential characteristics of ULs is the excessive production of extracellular matrix (ECM). P4 has been shown to stimulate ECM production and collagen synthesis in ULs. Recent research demonstrated that, despite their benign nature, ULs may present with abnormal vasculature. P4 has been shown to regulate angiogenesis in ULs through the upregulation of vascular endothelial growth factor (VEGF) and by controlling the secretion of permeability factors. This review summarizes the key findings regarding the role of PGRs and mPRs in ULs, especially highlighting the potential ECM and angiogenesis modulation by P4. An increased understanding of this mechanistic role of nuclear and specifically mPRs in the biology of P4-modulated ECM and angiogenesis in the growth of ULs could turn out to be fundamental for developing effective targeted therapies for ULs.

The presence of blastocyst within the uteri facilitates lumenal epithelium transformation for implantation via upregulating lysosome proteostasis activity

ABBREVIATIONS

ACTB: actin beta; AREG: amphiregulin; ATP6V0A4: ATPase, H+ transporting, lysosomal V0 subunit A4; Baf A1: bafilomycin A1; BSA: bovine serum albumin; CLDN1: claudin 1; CTSB: cathepsin B; DEGs: differentially expressed genes; E2: 17β-estradiol; ESR: estrogen receptor; GATA2: GATA binding protein 2; GLA: galactosidase, alpha; GO: gene ontology; HBEGF: heparin-binding EGF-like growth factor; IGF1R: insulin-like growth factor 1 receptor; Ihh: Indian hedgehog; ISH: in situ hybridization; LAMP1: lysosomal-associated membrane protein 1; LCM: laser capture microdissection; Le: lumenal epithelium; LGMN: legumain; LIF: leukemia inhibitory factor; LIFR: LIF receptor alpha; MSX1: msh homeobox 1; MUC1: mucin 1, transmembrane; P4: progesterone; PBS: phosphate-buffered saline; PCA: principal component analysis; PPT1: palmitoyl-protein thioesterase 1; PGR: progesterone receptor; PSP: pseudopregnancy; PTGS2/COX2: prostaglandin-endoperoxide synthase 2; qPCR: quantitative real-time polymerase chain reaction; SP: pregnancy; TFEB: transcription factor EB.

Transcriptome profiling of gonad-stimulating factors in thoracic ganglia and a potential role of Indian hedgehog gene in vitellogenesis of banana shrimp Fenneropenaeus merguiensis

Shrimp reproduction is controlled by several factors. Central nervous tissues, especially thoracic ganglia and brain, are known sources of gonad stimulating factors (GSFs) in crustaceans, but the GSFs in shrimp have not yet been clarified. Hence, we aimed to characterize and study putative GSFs from thoracic ganglia of adult female Fenneropenaeus merguiensis. An analysis of thoracic ganglia transcriptome revealed 3224 putative GSFs of a total 77,681 unigenes. Only 376 putative GSFs were differentially expressed during ovarian developmental stages. Eight candidate GSFs were validated for their expression patterns in thoracic ganglia, including the Indian hedgehog gene. F. merguiensis Indian hedgehog (FmIHH) was then investigated for its role in vitellogenesis. The obtained full-length cDNA of FmIHH was similar to other crustacean IHHs rather than Sonic and Desert HHs. The FmIHH was dominantly expressed in thoracic ganglia, and its expression was significantly increased in the vitellogenic stages before being downregulated at the mature stage of ovarian development. Injection of the recombinant FmIHH (His-TF-IHH) protein stimulated vitellogenin expression in ovaries on day 3 and 7, and also increased the gonadosomatic index. In addition, crustacean hyperglycemic hormone expression and total sugar were significantly decreased in eyestalks and hemolymph, respectively, after injection of His-TF-IHH, while lactic acid was increased. Both total sugar and lactic acid were unchanged in ovaries of His-TF-IHH injected shrimp. These results suggested that FmIHH plays a crucial role in vitellogenesis and regulate sugar uptake during ovarian development.

Research advances in endometriosis-related signaling pathways: A review

Endometriosis (EM) is characterized by the existence of endometrial mucosa outside the uterine cavity, which causesinfertility, persistent aches, and a decline in women's quality of life. Both hormone therapies and nonhormone therapies, such as NSAIDs, are ineffective, generic categories of EM drugs. Endometriosis is a benign gynecological condition, yet it shares a number of features with cancer cells, including immune evasion, survival, adhesion, invasion, and angiogenesis. Several endometriosis-related signaling pathways are comprehensively reviewed in this article, including E2, NF-κB, MAPK, ERK, PI3K/Akt/mTOR, YAP, Wnt/β-catenin, Rho/ROCK, TGF-β, VEGF, NO, iron, cytokines and chemokines. To find and develop novel medications for the treatment of EM, it is essential to implicitly determine the molecular pathways that are disordered during EM development. Additionally, research on the shared pathways between EM and tumors can provide hypotheses or suggestions for endometriosis therapeutic targets.

Establishment of the fetal-maternal interface: developmental events in human implantation and placentation

Early pregnancy is a complex and well-orchestrated differentiation process that involves all the cellular elements of the fetal-maternal interface. Aberrant trophoblast-decidual interactions can lead to miscarriage and disorders that occur later in pregnancy, including preeclampsia, intrauterine fetal growth restriction, and preterm labor. A great deal of research on the regulation of implantation and placentation has been performed in a wide range of species. However, there is significant species variation regarding trophoblast differentiation as well as decidual-specific gene expression and regulation. Most of the relevant information has been obtained from studies using mouse models. A comprehensive understanding of the physiology and pathology of human implantation and placentation has only recently been obtained because of emerging advanced technologies. With the derivation of human trophoblast stem cells, 3D-organoid cultures, and single-cell analyses of differentiated cells, cell type-specific transcript profiles and functions were generated, and each exhibited a unique signature. Additionally, through integrative transcriptomic information, researchers can uncover the cellular dysfunction of embryonic and placental cells in peri-implantation embryos and the early pathological placenta. In fact, the clinical utility of fetal-maternal cellular trafficking has been applied for the noninvasive prenatal diagnosis of aneuploidies and the prediction of pregnancy complications. Furthermore, recent studies have proposed a viable path toward the development of therapeutic strategies targeting placenta-enriched molecules for placental dysfunction and diseases.

IHH, SHH, and primary cilia mediate epithelial-stromal cross-talk during decidualization in mice

The establishment of pregnancy depends on interactions between the epithelial and stromal cells of the endometrium that drive the decidual reaction that remodels the stroma and enables embryo implantation. Decidualization in mice also depends on ovarian hormones and the presence of a blastocyst. Hedgehog signaling is transduced by primary cilia in many tissues and is involved in epithelial-stromal cross-talk during decidualization. We found that primary cilia on mouse uterine stromal cells increased in number and length during early pregnancy and were required for decidualization. In vitro and in vivo, progesterone promoted stromal ciliogenesis and the production of Indian hedgehog (IHH) in the epithelium and Sonic hedgehog (SHH) in the stroma. Blastocyst-derived TNF-α also induced epithelial IHH, which stimulated the production of SHH in the stroma through a mechanism that may involve the release of arachidonic acid from epithelial cells. In the stroma, SHH activated canonical Hedgehog signaling through primary cilia and promoted decidualization through a mechanism that depended on interleukin-11 (IL-11) and primary cilia. Our findings identify a primary cilia-dependent network that controls endometrial decidualization and suggest primary cilia as a candidate therapeutic target for endometrial diseases.

Cysteine dioxygenase and taurine are essential for embryo implantation by involving in E2-ERα and P4-PR signaling in mouse

BACKGROUND

Taurine performs multiple physiological functions, and the maintenance of taurine level for most mammals relies on active uptake from diet and endogenous taurine synthesis through its synthesis enzymes, including cysteine dioxygenase (CDO). In addition, uterus tissue and uterus fluid are rich in taurine, and taurine synthesis is regulated by estrogen (E₂) and progesterone (P₄), the key hormones priming embryo-uterine crosstalk during embryo implantation, but the functional interactions and mechanisms among which are largely unknown. The present study was thus proposed to identify the effects of CDO and taurine on embryo implantation and related mechanisms by using Cdo knockout (KO) and ovariectomy (OVX) mouse models.

RESULTS

The uterine CDO expression was assayed from the first day of plugging (d 1) to d 8 and the results showed that CDO expression level increased from d 1 to d 4, followed by a significant decline on d 5 and persisted to d 8, which was highly correlated with serum and uterine taurine levels, and serum P₄ concentration. Next, Cdo KO mouse was established by CRISPER/Cas9. It was showed that Cdo deletion sharply decreased the taurine levels both in serum and uterus tissue, causing implantation defects and severe subfertility. However, the implantation defects in Cdo KO mice were partly rescued by the taurine supplementation. In addition, Cdo deletion led to a sharp decrease in the expressions of P₄ receptor (PR) and its responsive genes Ihh, Hoxa10 and Hand2. Although the expression of uterine estrogen receptor (ERα) had no significant change, the levels of ERα induced genes (Muc1, Ltf) during the implantation window were upregulated after Cdo deletion. These accompanied by the suppression of stroma cell proliferation. Meanwhile, E₂ inhibited CDO expression through ERα and P₄ upregulated CDO expression through PR.

CONCLUSION

The present study firstly demonstrates that taurine and CDO play prominent roles in uterine receptivity and embryo implantation by involving in E₂-ERα and P₄-PR signaling. These are crucial for our understanding the mechanism of embryo implantation, and infer that taurine is a potential agent for improving reproductive efficiency of livestock industry and reproductive medicine.

CRC Therapy Identifies Indian Hedgehog Signaling in Mouse Endometrial Epithelial Cells and Inhibition of Ihh-KLF9 as a Novel Strategy for Treating IUA

Intrauterine adhesion (IUA) causes menstrual disturbance and infertility. There is no effective treatment available for moderate to severe IUA cases. Stem cell-based therapy has been investigated for treating IUA but is limited in clinical applications due to issues including the precise induction of differentiation, tumorigenesis, and unclear molecular mechanisms. In our recent study, we isolated and expanded the long-term cultures of conditional reprogrammed (CR) mouse endometrial epithelial cells. Treating IUA mice with these CR cells (CRCs) restored the morphology and structure of the endometrium and significantly improved the pregnancy rate. In this study, our data with high-throughput sequencing, CRISPR knockout Ihh^-/-CRCs, and transplantation identified for the first time that the Indian hedgehog (Ihh) gene plays a critical role in the regulation of endometrial epithelial cell proliferation. We also found that aberrant activated Ihh-krüppel-like factor 9 (KLF9) signaling contributes to the inhibition of normal progesterone receptor (PR) function in IUA mice. Thus, we hypothesized that inhibition of the Ihh-KLF9 pathway may be a novel strategy to treat IUA. Our data demonstrated that treatment with the hedgehog signaling inhibitor Vismodegib restored the morphology, structure, and microenvironment of the endometrium, and greatly improved the pregnancy rate in IUA mice. This study suggests a promising application of hedgehog inhibitors as a targeted drug in the IUA clinic.

Primary Cilia Restrain PI3K-AKT Signaling to Orchestrate Human Decidualization

Endometrial decidualization plays a pivotal role during early pregnancy. Compromised decidualization has been tightly associated with recurrent implantation failure (RIF). Primary cilium is an antenna-like sensory organelle and acts as a signaling nexus to mediate Hh, Wnt, TGFβ, BMP, FGF, and Notch signaling. However, whether primary cilium is involved in human decidualization is still unknown. In this study, we found that primary cilia are present in human endometrial stromal cells. The ciliogenesis and cilia length are increased by progesterone during in vitro and in vivo decidualization. Primary cilia are abnormal in the endometrium of RIF patients. Based on data from both assembly and disassembly of primary cilia, it has been determined that primary cilium is essential to human decidualization. Trichoplein (TCHP)-Aurora A signaling mediates cilia disassembly during human in vitro decidualization. Mechanistically, primary cilium modulates human decidualization through PTEN-PI3K-AKT-FOXO1 signaling. Our study highlights primary cilium as a novel decidualization-related signaling pathway.

Contribution of the Wolffian duct mesenchyme to the formation of the female reproductive tract

The female reproductive tract develops from its embryonic precursor, the Müllerian duct. In close proximity to the Müllerian duct lies the precursor for the male reproductive tract, the Wolffian duct, which is eliminated in the female embryo during sexual differentiation. We discovered that a component of the Wolffian duct, its mesenchyme, is not eliminated after sexual differentiation. Instead, the Wolffian duct mesenchyme underwent changes in transcriptome and chromatin accessibility from male tract to female tract identity, and became a unique mesenchymal population in the female reproductive tract with localization and transcriptome distinct from the mesenchyme derived from the Müllerian duct. Partial ablation of the Wolffian duct mesenchyme stunted the growth of the fetal female reproductive tract in ex vivo organ culture. These findings reveal a new fetal origin of mesenchymal tissues for female reproductive tract formation and reshape our understanding of sexual differentiation of reproductive tracts.

Effects of an inhibitor of the SHH signaling pathway on endometrial cells of patients with endometriosis

BACKGROUND

Endometriosis is one of the most common gynecological diseases, and seriously reduces the quality of life of patients. However, the pathogenesis of this disease is unclear. Therefore, more studies are needed to elucidate its pathogenesis. Our previous publication found that the Sonic Hedgehog (SHH) signaling pathway was activated in endometriosis. This study tested whether SHH signaling in endometrial stromal cells (ESCs) was critical for the pathogenesis of endometriosis.

METHODS

To examine the effect of inhibiting the SHH signaling pathway on endometriosis, we first isolated ESCs from eutopic endometrial tissues of patients with or without endometriosis and identified the extracted cells by morphological observation and immunofluorescence. Then, we treated ESCs with the GLI inhibitor GANT61 and used CCK-8, wound healing and invasion assays to detect cell activities, such as proliferation, invasion and metastasis. Furthermore, we detected the expression of key proteins and proliferation markers of the SHH signaling pathway in the lesions of nude mice using immunochemistry.

RESULTS

We demonstrated that higher concentrations of GANT61 decreased the proliferation rate and migration distance of ESCs. We observed that GANT61 inhibited the invasion of ESCs. In addition, blockage of the SHH signaling pathway significantly reduced cell proliferation in vitro.

CONCLUSIONS

Our study suggested that inhibition of the SHH pathway is involved in cell proliferation and invasive growth in the pathogenesis of endometriosis.

Ovarian Transcriptomic Analysis of Ninghai Indigenous Chickens at Different Egg-Laying Periods

Egg production is an essential indicator of poultry fertility. The ovary is a crucial organ involved in egg production; however, little is known about the key genes and signaling pathways involved in the whole egg-laying cycle of hens. In order to explore the mechanism of egg production at different stages of the egg-laying process, ovarian tissues from four chickens were randomly selected for transcriptome analysis at each of the three ages (145 d, 204 d, and 300 d in the early, peak, and late stages of egg laying). A total of 12 gene libraries were constructed, and a total of 8433 differential genes were identified from NH145d vs. NH204d, NH145d vs. NH300d and NH300d vs. NH204d (Ninghai 145-day-old, Ninghai 204-day-old, and Ninghai 300-day-old), with 1176, 1653 and 1868 up-regulated genes, and 621, 1955 and 1160 down-regulated genes, respectively. In each of the two comparison groups, 73, 1004, and 1030 differentially expressed genes were found to be co-expressed. We analyzed the differentially expressed genes and predicted nine genes involved in egg production regulation, including LRP8, BMP6, ZP4, COL4A1, VCAN, INHBA, LOX, PTX3, and IHH, as well as several essential egg production pathways, such as regulation adhesion molecules (CAMs), calcium signaling pathways, neuroactive ligand–receptor interaction, and cytokine–cytokine receptor interaction. Transcriptional analysis of the chicken ovary during different phases of egg-lay will provide a useful molecular basis for study of the development of the egg-laying ovary.

Progesterone Actions and Resistance in Gynecological Disorders

Estrogen and progesterone and their signaling mechanisms are tightly regulated to maintain a normal menstrual cycle and to support a successful pregnancy. The imbalance of estrogen and progesterone disrupts their complex regulatory mechanisms, leading to estrogen dominance and progesterone resistance. Gynecological diseases are heavily associated with dysregulated steroid hormones and can induce chronic pelvic pain, dysmenorrhea, dyspareunia, heavy bleeding, and infertility, which substantially impact the quality of women's lives. Because the menstrual cycle repeatably occurs during reproductive ages with dynamic changes and remodeling of reproductive-related tissues, these alterations can accumulate and induce chronic and recurrent conditions. This review focuses on faulty progesterone signaling mechanisms and cellular responses to progesterone in endometriosis, adenomyosis, leiomyoma (uterine fibroids), polycystic ovary syndrome (PCOS), and endometrial hyperplasia. We also summarize the association with gene mutations and steroid hormone regulation in disease progression as well as current hormonal therapies and the clinical consequences of progesterone resistance.

Uterine Receptivity is Reflected by LIF Expression in the Cervix

Recurrent implantation failure is a major problem in assisted reproductive technology (ART). Although ART systems have evolved rapidly over the decades, it is still difficult to diagnose uterine conditions suitable for embryo transfer (ET) without the use of invasive endometrial procedures. Previous studies in mice showed that leukemia inhibitory factor (LIF) is a well-known endometrial biomarker for uterine implantation capacity, also known as uterine receptivity. This study focused on LIF in the mouse and human cervix as a possible biomarker of implantation capacity. We found that high expression of LIF in the cervical epithelium is strongly correlated with that of the uterine epithelium during the peri-implantation period in mice. Likewise, human cervical epithelia also exhibit elevated levels of LIF in the peri-implantation period. In addition, cervical LIF is downregulated in mice with defective implantation caused by pharmacological treatments. These results indicated that cervical LIF is a possible biomarker that detected uterine receptivity without invasive endometrial damage.

A high level of KLF12 causes folic acid-resistant neural tube defects by activating the Shh signalling pathway in mice

Although adequate periconceptional folic acid (FA) supplementation has reduced the occurrence of pregnancies affected by neural tube defects (NTDs), the mechanisms underlying FA-resistant NTDs are poorly understood, and thus NTDs still remain a global public health concern. A high level of Krüppel-like factor 12 (KLF12) exerts deleterious effects on heath in most cases, but evidence for its roles in development has not been published. We observed KLF12-overexpressing mice showed disturbed neural tube development. KLF12-overexpressing foetuses died in utero at approximately 10.5 days post coitus, with 100% presenting cranial NTDs. Neither FA nor formate promoted normal neural tube closure in mutant foetuses. The RNA-seq results showed that a high level of KLF12 caused NTDs in mice via overactivating the sonic hedgehog (Shh) signalling pathway, leading to the upregulation of patched 1, GLI-Krüppel family member GLI1, hedgehog-interacting protein, etc., while FA metabolism-related enzymes did not express differently. PF-5274857, an antagonist of the Shh signalling pathway, significantly promoted dorsolateral hinge point formation and partially rescued the NTDs. The regulatory hierarchy between a high level of KLF12 and FA-resistant NTDs might provide new insights into the diagnosis and treatment of unexplained NTDs in the future.

Illuminating the "Black Box" of Progesterone-Dependent Embryo Implantation Using Engineered Mice

Synchrony between progesterone-driven endometrial receptivity and the arrival of a euploid blastocyst is essential for embryo implantation, a prerequisite event in the establishment of a successful pregnancy. Advancement of embryo implantation within the uterus also requires stromal fibroblasts of the endometrium to transform into epithelioid decidual cells, a progesterone-dependent cellular transformation process termed decidualization. Although progesterone is indispensable for these cellular processes, the molecular underpinnings are not fully understood. Because human studies are restricted, much of our fundamental understanding of progesterone signaling in endometrial periimplantation biology comes from in vitro and in vivo experimental systems. In this review, we focus on the tremendous progress attained with the use of engineered mouse models together with high throughput genome-scale analysis in disclosing key signals, pathways and networks that are required for normal endometrial responses to progesterone during the periimplantation period. Many molecular mediators and modifiers of the progesterone response are implicated in cross talk signaling between epithelial and stromal cells of the endometrium, an intercellular communication system that is critical for the ordered spatiotemporal control of embryo invasion within the maternal compartment. Accordingly, derailment of these signaling systems is causally linked with infertility, early embryo miscarriage and gestational complications that symptomatically manifest later in pregnancy. Such aberrant progesterone molecular responses also contribute to endometrial pathologies such as endometriosis, endometrial hyperplasia and cancer. Therefore, our review makes the case that further identification and functional analysis of key molecular mediators and modifiers of the endometrial response to progesterone will not only provide much-needed molecular insight into the early endometrial cellular changes that promote pregnancy establishment but lend credible hope for the development of more effective mechanism-based molecular diagnostics and precision therapies in the clinical management of female infertility, subfertility and a subset of gynecological morbidities.

Binding of microRNA-135a (miR-135a) to homeobox protein A10 (HOXA10) mRNA in a high-progesterone environment modulates the embryonic implantation factors beta3-integrin (ITGβ3) and empty spiracles homeobox-2 (EMX2)

Background

Patients with elevated circulating progesterone concentrations on the day of the human chorionic gonadotropin (hCG) trigger had relatively low implantation rates during assisted reproductive treatments. In this study, we assess the hypothesis that different concentrations of progesterone regulate the expression of homeobox protein A10 (HOXA10) and its downstream genes through miRNA-135a.

Methods

MicroRNA-135a (miR-135a), HOXA10, beta3-integrin (ITGβ3), and empty spiracles homeobox-2 (EMX2) expression levels in endometrial tissues from patients with elevated progesterone were measured. To determine the threshold of progesterone level which can impair implantation, Ishikawa cells were used to determine the expression of the aforementioned 4 genes after exposure to 5 graded concentrations of progesterone. The dual-luciferase reporter assay was used to verify whether miR-135a regulated the expression of HOXA10. Furthermore, the effects of HOXA10 on the expression of key endometrial receptivity genes ITGβ3 and EMX2 were confirmed.

Results

High progesterone levels promoted miR-135a expression in vivo, and miR-135a bound to the 3'-untranslated region (3'-UTR) of HOXA10 mRNA to inhibit HOXA10 expression. Reduction of HOXA10 promoted EMX2 expression and inhibited ITG-3 production. Progesterone promoted the expression of HOXA10 in vitro at low concentrations. However, when the concentration was greater than 10⁻⁷ ng/mL, progesterone inhibited HOXA10 by promoting miR-135a expression, thereby altering the expression of related genes and affecting endometrial receptivity.

Conclusions

In vitro, the trend in miR-135a expression (which first decreased and then increased) was in direct contrast to that of HOXA10 expression (which first increased and then decreased) as progesterone levels increased. The key factors regulating endometrial receptivity included ITGβ3 and EMX2, which were confirmed to be regulated by HOXA10. High progesterone levels affected miR-135a expression, and miR-135a inhibited HOXA10 expression, thereby affecting endometrial receptivity.

Secretory phospholipase A2-X (Pla2g10) is a novel progesterone receptor target gene exclusively induced in uterine luminal epithelium for uterine receptivity in mice

BACKGROUND

Aberration of estrogen (E2) and/or progesterone (P4) signaling pathways affects expression of their target genes, which may lead to failure of embryo implantation and following pregnancy. Although many target genes of progesterone receptors (PRs) have been identified in uterine stroma, only a few PR targets have been reported in the epithelium. Secretory phospholipase A2-(PLA2)-X, a member of the PLA2 family that releases arachidonic acids for the synthesis of prostaglandins that are important for embryo implantation, is dysregulated in the endometrium of patients suffering from repeated implantation failure. However, it is not clear whether sPLA2-X is directly regulated by ovarian steroid hormones for embryo implantation in the uterus.

RESULT

P4 induced the Pla2g10 encoding of secretory PLA2-X in the apical region of uterine LE of ovariectomized mice via PR in both time- and dose-dependent manners, whereas E2 significantly inhibited it. This finding is consistent with the higher expression of Pla2g10 at the diestrus stage, when P4 is elevated during the estrous cycle, and at P4-treated delayed implantation. The level of Pla2g10 on day 4 of pregnancy (day 4) was dramatically decreased on day 5, when PRs are absent in the LE. Luciferase assays of mutagenesis in uterine epithelial cells demonstrated that four putative PR response elements in a Pla2g10 promoter region are transcriptionally active for Pla2g10. Intrauterine delivery of small interfering RNA for Pla2g10 on day 3 significantly reduced the number of implantation sites, reinforcing the critical function(s) of Pla2g10 for uterine receptivity in mice.

CONCLUSIONS

Pla2g10 is a novel PR target gene whose expression is exclusively localized in the apical region of the uterine LE for uterine receptivity for embryo implantation in mice.

Cortical Granule Distribution and Expression Pattern of Genes Regulating Cellular Component Size, Morphogenesis, and Potential to Differentiation are Related to Oocyte Developmental Competence and Maturational Capacity In Vivo and In Vitro

Polyspermia is an adverse phenomenon during mammalian fertilization when more than one sperm fuses with a single oocyte. The egg cell is prepared to prevent polyspermia by, among other ways, producing cortical granules (CGs), which are specialized intracellular structures containing enzymes that aim to harden the zona pellucida and block the fusion of subsequent sperm. This work focused on exploring the expression profile of genes that may be associated with cortical reactions, and evaluated the distribution of CGs in immature oocytes and the peripheral density of CGs in mature oocytes. Oocytes were isolated and then processed for in vitro maturation (IVM). Transcriptomic analysis of genes belonging to five ontological groups has been conducted. Six genes showed increased expression after IVM (ARHGEF2, MAP1B, CXCL12, FN1, DAB2, and SOX9), while the majority of genes decreased expression after IVM. Using CG distribution analysis in immature oocytes, movement towards the cortical zone of the oocyte during meiotic competence acquisition was observed. CGs peripheral density decreased with the rise in meiotic competence during the IVM process. The current results reveal important new insights into the in vitro maturation of oocytes. Our results may serve as a basis for further studies to investigate the cortical reaction of oocytes.

90 YEARS OF PROGESTERONE: New insights into progesterone receptor signaling in the endometrium required for embryo implantation

Progesterone's ability to maintain pregnancy in eutherian mammals highlighted this steroid as the 'hormone of pregnancy'. It was the unique 'pro-gestational' bioactivity of progesterone that enabled eventual purification of this ovarian steroid to crystalline form by Willard Myron Allen in the early 1930s. While a functional connection between normal progesterone responses ('progestational proliferation') of the uterus with the maintenance of pregnancy was quickly appreciated, an understanding of progesterone's involvement in the early stages of pregnancy establishment was comparatively less well understood. With the aforementioned as historical backdrop, this review focuses on a selection of key advances in our understanding of the molecular mechanisms by which progesterone, through its nuclear receptor (the progesterone receptor), drives the development of endometrial receptivity, a transient uterine state that allows for embryo implantation and the establishment of pregnancy. Highlighted in this review are the significant contributions of advanced mouse engineering and genome-wide transcriptomic and cistromic analytics which reveal the pivotal molecular mediators and modifiers that are essential to progesterone-dependent endometrial receptivity and decidualization. With a clearer understanding of the molecular landscape that underpins uterine responsiveness to progesterone during the periimplantation period, we predict that common gynecologic morbidities due to abnormal progesterone responsiveness will be more effectively diagnosed and/or treated in the future.

Interleukin-13 receptor subunit alpha-2 is a target of progesterone receptor and steroid receptor coactivator-1 in the mouse uterus†

The endometrium, composed of epithelial and stromal cell compartments, is tightly regulated by the ovarian steroid hormones estrogen (E2) and progesterone (P4) during early pregnancy. Through the progesterone receptor (PGR), steroid receptor coactivators, and other transcriptional coregulators, progesterone inhibits E2-induced cell proliferation and induces the differentiation of stromal cells in a process called decidualization to promote endometrial receptivity. Although interleukin-13 receptor subunit alpha-2 (Il13ra2) is expressed in the human and mouse endometrium, its potential role in the steroid hormone regulation of the endometrium has not been thoroughly examined. In this study, we employed PGR knockout mice and steroid receptor coactivator-1 knockout mice (SRC-1-/-) to profile the expression of Il13ra2 in the murine endometrium and determine the role of these transcriptional regulators in the hormone-responsiveness of Il13ra2 expression. Furthermore, we utilized a well-established decidualization-inducing steroidogenic cocktail and a siRNA-based knockdown of IL13RA2 to determine the importance of IL13RA2 in the decidualization of primary human endometrial stromal cells. Our findings demonstrate that Il13ra2 is expressed in the subepithelial stroma of the murine endometrium in response to ovarian steroid hormones and during early pregnancy in a PGR- and SRC-1-dependent manner. Furthermore, we show that knockdown of IL13RA2 before in vitro decidualization of primary human endometrial stromal cells partially compromises the full decidualization response. We conclude that Il13ra2 is a downstream target of progesterone through PGR and SRC-1 and plays a role in mediating the stromal action of ovarian steroid hormones.

Endometrial Decidualization: The Primary Driver of Pregnancy Health

Interventions to prevent pregnancy complications have been largely unsuccessful. We suggest this is because the foundation for a healthy pregnancy is laid prior to the establishment of the pregnancy at the time of endometrial decidualization. Humans are one of only a few mammalian viviparous species in which decidualization begins during the latter half of each menstrual cycle and is therefore independent of the conceptus. Failure to adequately prepare (decidualize) the endometrium hormonally, biochemically, and immunologically in anticipation of the approaching blastocyst—including the downregulation of genes involved in the pro- inflammatory response and resisting tissue invasion along with the increased expression of genes that promote angiogenesis, foster immune tolerance, and facilitate tissue invasion—leads to abnormal implantation/placentation and ultimately to adverse pregnancy outcome. We hypothesize, therefore, that the primary driver of pregnancy health is the quality of the soil, not the seed.

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.

The processes of cellular growth, aging, and programmed cell death are involved in lifespan of ovarian granulosa cells during short-term IVC - Study based on animal model

The oogenesis and folliculogenesis are closely linked and occur simultaneously in the growing ovarian follicles. Biochemical and morphological changes in oocytes (OC) and surrounding granulosa cells (GCs) are highly complex and depend on many factors, including intercellular communication. GCs are cells with many functions, often crucial for the proper viability of the oocyte and subsequent positive fertilization. The purpose of this study was to analyze gene expression in porcine GCs, to define differentially expressed genes belongs to the "cell growth", "aging", "positive regulation of cell death", "apoptotic process", "regulation of cell death", "cell death" and "negative regulation of cell death" ontology groups during the short - term primary in vitro culture. Microarrays were employed to study the transcriptome contained in the total RNA of the cultured GCs. Ovaries were obtained after slaughter, from 40 gilts of swine aged 170 days. The cells were obtained through puncture of the ovaries, collection of follicular fluid, removal of the cumulus - oocyte complexes and centrifugation. The cells were then cultured in vitro. The RNA material was obtained before the culture was established (0h) and then after 48h, 96h and 144h of its course. From 182 differently expressed genes belonging to the these ontology groups, we have selected POSTN, FN1, FMOD, ITGB3, DCN, SERPINB2, SFRP2, IGFBP5, EMP1, and CCL2 which were upregulated, as well as DAPL1, ESR1, IHH, TGFBR3, PPARD, PDK4, TXNIP, IFIT3, CSRNP3, and TNFSF10 genes whose expression was downregulated during the time of in vitro culture of the GCs. The significance of the differential gene expression is to provide new information on the molecular aspects of in vitro granulosa cell culture.

Hedgehog Signaling for Urogenital Organogenesis and Prostate Cancer: An Implication for the Epithelial-Mesenchyme Interaction (EMI)

Hedgehog (Hh) signaling is an essential growth factor signaling pathway especially in the regulation of epithelial-mesenchymal interactions (EMI) during the development of the urogenital organs such as the bladder and the external genitalia (EXG). The Hh ligands are often expressed in the epithelia, affecting the surrounding mesenchyme, and thus constituting a form of paracrine signaling. The development of the urogenital organ, therefore, provides an intriguing opportunity to study EMI and its relationship with other pathways, such as hormonal signaling. Cellular interactions of prostate cancer (PCa) with its neighboring tissue is also noteworthy. The local microenvironment, including the bone metastatic site, can release cellular signals which can affect the malignant tumors, and vice versa. Thus, it is necessary to compare possible similarities and divergences in Hh signaling functions and its interaction with other local growth factors, such as BMP (bone morphogenetic protein) between organogenesis and tumorigenesis. Additionally, this review will discuss two pertinent research aspects of Hh signaling: (1) the potential signaling crosstalk between Hh and androgen signaling; and (2) the effect of signaling between the epithelia and the mesenchyme on the status of the basement membrane with extracellular matrix structures located on the epithelial-mesenchymal interface.

Evaluation of uterine receptivity after gonadotropin releasing hormone agonist administration as an oocyte maturation trigger: a rodent model

In natural cycle or minimal stimulation cycle IVF, buserelin acetate (buserelin), a gonadotropin-releasing hormone agonist, is often used as a maturation trigger; however, its effect on pregnancy outcomes remains unclear. Therefore, in the present study, we compared uterine receptivity in buserelin-administered mice with that in human chorionic gonadotropin (hCG)-administered mice during the peri-implantation period. Implantation, decidualisation, and term-pregnancy were impaired following hCG, but not buserelin administration. hCG stimulated the synthesis and secretion of progesterone and oestradiol, whereas ovarian steroidogenesis in the buserelin-treated group was comparable with that in the control group. Furthermore, similar to the observation in controls, the buserelin-treated group exhibited activation of progesterone receptor signalling and inhibition of oestrogen receptor signalling in the endometrial epithelium on the day of implantation. However, epithelial progesterone signalling was not detected, and a high expression of genes downstream to oestrogen was observed on day 4 following hCG administration. These results suggest that buserelin administration does not impact uterine receptivity as it did not affect ovarian steroidogenesis and endometrial steroid signalling. Therefore, buserelin is preferred as an oocyte maturation trigger to optimise uterine receptivity during treatments involving timed intercourse, intrauterine insemination, or fresh embryo transfer following in vitro fertilisation.

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.

Myometrial progesterone hyper-responsiveness associated with increased risk of human uterine fibroids

BACKGROUND

Uterine Fibroids (UFs) growth is ovarian steroid-dependent. Previous studies have shown that estrogen and progesterone play an important role in UF development. However, the mechanism underlying progesterone induced UF pathogenesis is largely unknown. In this study, we determined the expression of progesterone receptor and compared the expression level of progesterone-regulated genes (PRGs) in human myometrial cells from normal uteri (MyoN) versus uteri with UFs (MyoF) in response to progesterone.

METHODS

Primary human myometrial cells were isolated from premenopausal patients with structurally normal uteri (PrMyoN). Primary human myometrial cells were also isolated from uterus with UFs (PrMyoF). Isolated tissues were excised at least 2 cm from the closest UFs lesion(s). Progesterone receptor (PR) expression was assessed using Western blot (WB). Expression levels of 15 PRGs were measured by qRT-PCR in PrMyoN and PrMyoF cells in the presence or absence of progesterone.

RESULTS

WB analysis revealed higher expression levels of PR in PrMyoF cells as compared to PrMyoN cells. Furthermore, we compared the expression patterns of 15 UF-related PRGs in PrMyoN and PrMyoF primary cells in response to progesterone hormone treatment. Our studies demonstrated that five PRGs including Bcl2, FOXO1A, SCGB2A2, CYP26a1 and MMP11 exhibited significant progesterone-hyper-responsiveness in human PrMyoF cells as compared to PrMyoN cells (P < 0.05). Another seven PRGs, including CIDEC, CANP6, ADHL5, ALDHA1, MT1E, KIK6, HHI showed gain in repression in response to progesterone treatment (P > 0.05). Importantly, these genes play crucial roles in cell proliferation, apoptosis, cell cycle, tissue remodeling and tumorigenesis in the development of UFs.

CONCLUSION

These data support the idea that progesterone acts as contributing mechanism in the origin of UFs. Identification and analysis of these PRGs will help to further understand the role of progesterone in UF development.

Uterine receptivity, embryo attachment, and embryo invasion: Multistep processes in embryo implantation

BACKGROUND

Recurrent implantation failure is a critical issue in IVF-ET treatment. Successful embryo implantation needs appropriate molecular and cellular communications between embryo and uterus. Rodent models have been used intensively to understand these mechanisms.

METHODS

The molecular and cellular mechanisms of embryo implantation were described by referring to the previous literature investigated by us and others. The studies using mouse models of embryo implantation were mainly cited.

RESULTS

Progesterone (P4) produced by ovarian corpus luteum provides the uterus with receptivity to the embryo, and uterine epithelial growth arrest and stromal proliferation, what we call uterine proliferation-differentiation switching (PDS), take place in the peri-implantation period before embryo attachment. Uterine PDS is a hallmark of uterine receptivity, and several genes such as HAND2 and BMI1, control uterine PDS by modulating P4-PR signaling. As the next implantation process, embryo attachment onto the luminal epithelium occurs. This process is regulated by FOXA2-LIF pathway and planar cell polarity signaling. Then, the luminal epithelium at the embryo attachment site detaches from the stroma, which enables trophoblast invasion. This process of embryo invasion is regulated by HIF2α in the stroma.

CONCLUSION

These findings indicate that embryo implantation contains multistep processes regulated by specific molecular pathways.

Progesterone governs endometrial proliferation-differentiation switching and blastocyst implantation

Blastocyst implantation contains the following three processes: apposition, attachment, and invasion of the blastocyst. Ovarian hormone progesterone (P₄) regulates these processes exquisitely. P₄-induced molecular communications between the endometrial epithelium and stroma as well as endometrial proliferation-differentiation switching (PDS) until blastocyst attachment are fundamental steps in blastocyst implantation. Based on the knowledge obtained from the previous studies of mouse models by my group and others, this article outlines how P₄ directs the uterus to complete blastocyst implantation.

New Gene Markers of Angiogenesis and Blood Vessels Development in Porcine Ovarian Granulosa Cells during Short-Term Primary Culture In Vitro

The physiological processes that drive the development of ovarian follicle, as well as the process of oogenesis, are quite well known. Granulosa cells are major players in this occurrence, being the somatic element of the female gamete development. They participate directly in the processes of oogenesis, building the cumulus-oocyte complex surrounding the ovum. In addition to that, they have a further impact on the reproductive processes, being a place of steroid sex hormone synthesis and secretion. It is known that the follicle development creates a major need for angiogenesis and blood vessel development in the ovary. In this study, we use novel molecular approaches to analyze markers of these processes in porcine granulosa cultured primarily in vitro. The cells were recovered from mature sus scrofa specimen after slaughter. They were then subjected to enzymatic digestion and culture primarily for a short term. The RNA was extracted from cultures in specific time periods (0h, 24h, 48h, 96h, and 144h) and analyzed using expression microarrays. The genes that exhibited fold change bigger than |2|, and adjusted p-value lower than 0.05, were considered differentially expressed. From these, we have chosen the members of “angiogenesis,” “blood vessel development,” “blood vessel morphogenesis,” “cardiovascular system development,” and “vasculature development” for further selection. CCL2, FGFR2, SFRP2, PDPN, DCN, CAV1, CHI3L1, ITGB3, FN1, and LOX which are upregulated, as well as CXCL10, NEBL, IHH, TGFBR3, SCUBE1, IGF1, EDNRA, RHOB, PPARD, and SLITRK5 genes whose expression is downregulated through the time of culture, were chosen as the potential markers, as their expression varied the most during the time of culture. The fold changes were further validated with RT-qPCR. The genes were described, with special attention to their possible function in GCs during culture. The results broaden the general knowledge about GC's in vitro molecular processes and might serve as a point of reference for further in vivo and clinical studies.

Molecular mechanisms of embryonic implantation in mammals: Lessons from the gene manipulation of mice

BACKGROUND

Human infertility has become a serious and social issue all over the world, especially in developed countries. Numerous types of assisted reproductive technology have been developed and are widely used to treat infertility. However, pregnancy outcomes require further improvement. It is essential to understand the cross-talk between the uterus (mother) and the embryo (fetus) in pregnancy, which is a very complicated event.

METHODS

The mammalian uterus requires many physiological and morphological changes for pregnancy-associated events, including implantation, decidualization, placentation, and parturition, to occur. Here is discussed recent advances in the knowledge of the molecular mechanisms underlying these reproductive events - in particular, embryonic implantation and decidualization - based on original and review articles.

MAIN FINDINGS RESULTS

In mice, embryonic implantation and decidualization are regulated by two steroid hormones: estrogen and progesterone. Along with these hormones, cytokines, cell-cycle regulators, growth factors, and transcription factors have essential roles in implantation and decidualization in mice.

CONCLUSION

Recent studies using the gene manipulation of mice have given considerable insight into the molecular mechanisms underlying embryonic implantation and decidualization. However, as most of the findings are based on mice, comparative research using different mammalian species will be useful for a better understanding of the species-dependent differences that are associated with reproductive events, including embryonic implantation.

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

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

A historical review of blastocyst implantation research

Research development on blastocyst implantation was reviewed in three sections: primate implantation, ungulate farm animal implantation, and the general process of blastocyst implantation in small rodents. Future research directions of this area are suggested.

Heparan Sulfate Proteoglycan Sulfation Regulates Uterine Differentiation and Signaling During Embryo Implantation

To prepare for embryo implantation, the uterus must undergo a series of reciprocal interactions between the uterine epithelium and the underlying stroma, which are orchestrated by ovarian hormones. During this process, multiple signaling pathways are activated to direct cell proliferation and differentiation, which render the uterus receptive to the implanting blastocysts. One important modulator of these signaling pathways is the cell surface and extracellular matrix macromolecules, heparan sulfate proteoglycans (HSPGs). HSPGs play crucial roles in signal transduction by regulating morphogen transport and ligand binding. In this study, we examine the role of HSPG sulfation in regulating uterine receptivity by conditionally deleting the N-deacetylase/N-sulfotransferase (NDST) 1 gene (Ndst1) in the mouse uterus using the Pgr-Cre driver, on an Ndst2- and Ndst3-null genetic background. Although development of the female reproductive tract and subsequent ovarian function appear normal in Ndst triple-knockout females, they are infertile due to implantation defects. Embryo attachment appears to occur but the uterine epithelium at the site of implantation persists rather than disintegrates in the mutant. Uterine epithelial cells continued to proliferate past day 4 of pregnancy, accompanied by elevated Fgf2 and Fgf9 expression, whereas uterine stroma failed to undergo decidualization, as evidenced by lack of Bmp2 induction. Despite normal Indian hedgehog expression, transcripts of Ptch1 and Gli1, both components as well as targets of the hedgehog (Hh) pathway, were detected only in the subepithelial stroma, indicating altered Hh signaling in the mutant uterus. Taken together, these data implicate an essential role for HSPGs in modulating signal transduction during mouse implantation.

Oestrogen, progesterone and stem cells: the discordant trio in endometriosis?

Oestrogen–progesterone signalling is highly versatile and critical for the maintenance of healthy endometrium in humans. The genomic and nongenomic signalling cascades initiated by these hormones in differentiated cells of endometrium have been the primary focus of research since 1920s. However, last decade of research has shown a significant role of stem cells in the maintenance of a healthy endometrium and the modulatory effects of hormones on these cells. Endometriosis, the growth of endometrium outside the uterus, is very common in infertile patients and the elusiveness in understanding of disease pathology causes hindrance in selection of treatment approaches to enhance fertility. In endometriosis, the stem cells are dysfunctional as it can confer progesterone resistance to their progenies resulting in disharmony of hormonal orchestration of endometrial homeostasis. The bidirectional communication between stem cell signalling pathways and oestrogen–progesterone signalling is found to be disrupted in endometriosis though it is not clear which precedes the other. In this paper, we review the intricate connection between hormones, stem cells and the cross-talks in their signalling cascades in normal endometrium and discuss how this is deregulated in endometriosis. Re-examination of the oestrogen–progesterone dependency of endometrium with a focus on stem cells is imperative to delineate infertility associated with endometriosis and thereby aid in designing better treatment modalities.

The high concentration of progesterone is harmful for endometrial receptivity and decidualization

Progesterone is required for the establishment and maintenance of mammalian pregnancy and widely used for conservative treatment of luteal phase deficiency in clinics. However, there are limited solid evidences available for the optimal timing and dose of progesterone therapy, especially for the possible adverse effects on implantation and decidualization when progesterone is administrated empirically. In our study, mouse models were used to examine effects of excess progesterone on embryo implantation and decidualization. Our data indicate that excess progesterone is not only harmful for mouse implantation, but also impairs mouse decidualization. In excess progesterone-treated mice, the impaired LIF/STAT3 pathway and dysregulated endoplasmic reticulum stress may lead to the inhibition of embryo implantation and decidualization. It is possible that the decrease in birth weight of excess progesterone-treated mice is due to a compromised embryo implantation and decidualization. Furthermore, excess progesterone compromises in vitro decidualization of human endometrial stromal cells.

Hormone dependent uterine epithelial-stromal communication for pregnancy support

Human fertility is a relatively inefficient process. Despite the presence of visibly healthy embryos, 30% of pregnancies generated by assisted reproductive technology (ART) fail before the second trimester. The uterine microenvironment plays a critical role in establishing and maintaining a successful pregnancy that requires coordinated communication between the epithelial and stromal cells of the endometrium. The epithelial cells must cease proliferation and become permissive for the conceptus (embryo and associated extraembryonic membranes), while the stromal cells undergoes mesenchymal-to-epithelioid transformation to form the decidua in support of subsequent embryo development. The ovarian steroids Estrogen (E2) and Progesterone (P4) are the major hormones governing these processes. These hormones act via their nuclear receptors, the estrogen receptor, ESR1, and progesterone receptor, PGR, to direct the transcription of genes that orchestrate epithelial and stromal cell communication. This review will discuss the molecular mechanisms utilized by steroid hormones that regulate uterine receptivity, as well, establish and maintain pregnancy.

Genetic Intersection of Tsix and Hedgehog Signaling during the Initiation of X-Chromosome Inactivation

X-chromosome inactivation (XCI) silences one X chromosome in the female mammal and is essential to peri-implantation development. XCI is thought to be cell autonomous, with all factors required being produced within each cell. Nevertheless, external cues may exist. Here, we search for such developmental signals by combining bioinformatic, biochemical, and genetic approaches. Using ex vivo and in vivo models, we identify the Hedgehog (HH) paracrine system as a candidate signaling cascade. HH signaling keeps XCI in check in pluripotent cells and is transduced by GLI transcription factors to binding sites in Tsix, the antisense repressor of XCI. GLI potentiates Tsix expression and impedes XCI. In vivo, mutating Indian Hedgehog results in a sex ratio bias against females, and the female lethality is rescued by a second-site mutation in Tsix. These data demonstrate a genetic and functional intersection between HH and XCI and support a role for intercellular signaling during XCI.

Effects of Melatonin on Early Pregnancy in Mouse: Involving the Regulation of StAR, Cyp11a1, and Ihh Expression

To test whether melatonin plays an important role in the process of early pregnancy, melatonin was given in drinking water to pregnant mice at different gestation stages. These included mice who were given melatonin 14 days prior to their successful mating (confirmed by vaginal plug) (Group A), after successful mating (Group B), and 14 days prior to and until after successful mating (Group C). Melatonin administration significantly enhanced serum as well as ovarian melatonin levels in the mice. It was observed that melatonin did not affect the natural estrous of mice. On day 0.5 of gestation (D0.5), melatonin not only elevated progesterone (P) secretion, but also upregulated expressions of StAR and Cyp11a1, the two marker genes of corpus luteum in ovaries (p < 0.05). Group A had a significantly lower estradiol (E₂) secretion and a higher number of implantation sites as well as litter size than controls (p < 0.05) and also had an increased Ihh expression in endometrium of D7.5 gestation. Melatonin treatment after successful mating improved the progesterone (P) secretion at D7.5 of gestation (p < 0.05) and significantly induced leukaemia inhibitory factor (LIF) expression (p < 0.05). Our study indicates that melatonin treatment up-regulated the genes involved in pregnenolone synthesis in ovary and Ihh expression in uterine endometrium. The mechanisms of melatonin to improve embryo implantation related to their actions on promoting the development of corpus luteum before gestation and helping to specify uterine receptivity in early pregnant mice.

The regulation of Hh/Gli1 signaling cascade involves Gsk3β- mediated mechanism in estrogen-derived endometrial hyperplasia

The present study was undertaken to explore the functional involvement of Hh signaling and its regulatory mechanism in endometrial hyperplasia. Differential expression of Hh signaling molecules i.e., Ihh, Shh, Gli1 or Gsk3β was observed in endometrial hyperplasial (EH) cells as compared to normal endometrial cells. Estradiol induced the expression of Hh signaling molecules and attenuated the expression of Gsk3β whereas anti-estrogen (K1) or progestin (MPA) suppressed these effects in EH cells. Cyclopamine treatment or Gli1 siRNA knockdown suppressed the growth of EH cells and reduced the expression of proliferative markers. Estradiol also induced the nuclear translocation of Gli1 which was suppressed by both MPA and K1 in EH cells. While exploring non-canonical mechanism, LY-294002 (Gsk3β activator) caused a decrease in Gli1 expression indicating the involvement of Gsk3β in Gli1 regulation. Further, Gsk3β silencing promoted the expression and nuclear translocation of Gli1 demonstrating that Gsk3β serves as a negative kinase regulator of Gli1 in EH cells. Similar attenuation of Hh signaling molecules was observed in rats with uterine hyperplasia undergoing anti-estrogen treatment. The study suggested that Hh/Gli1 cascade (canonical pathway) as well as Gsk3β-Gli1 crosstalk (non-canonical pathway) play crucial role in estrogen-dependent cell proliferation in endometrial hyperplasia.

Molecular and cellular events during blastocyst implantation in the receptive uterus: clues from mouse models

The success of implantation is an interactive process between the blastocyst and the uterus. Synchronized development of embryos with uterine differentiation to a receptive state is necessary to complete pregnancy. The period of uterine receptivity for implantation is limited and referred to as the “implantation window”, which is regulated by ovarian steroid hormones. Implantation process is complicated due to the many signaling molecules in the hierarchical mechanisms with the embryo-uterine dialogue. The mouse is widely used in animal research, and is uniquely suited for reproductive studies, i.e., having a large litter size and brief estrous cycles. This review first describes why the mouse is the preferred model for implantation studies, focusing on uterine morphology and physiological traits, and then highlights the knowledge on uterine receptivity and the hormonal regulation of blastocyst implantation in mice. Our recent study revealed that selective proteolysis in the activated blastocyst is associated with the completion of blastocyst implantation after embryo transfer. Furthermore, in the context of blastocyst implantation in the mouse, this review discusses the window of uterine receptivity, hormonal regulation, uterine vascular permeability and angiogenesis, the delayed-implantation mouse model, morphogens, adhesion molecules, crosslinker proteins, extracellular matrix, and matricellular proteins. A better understanding of uterine and blastocyst biology during the peri-implantation period should facilitate further development of reproductive technology.

Gain-of-function β-catenin in the uterine mesenchyme leads to impaired implantation and decidualization

Embryo implantation and endometrial decidualization are critical events that occur during early pregnancy in humans and mice, and perturbation in either can result in infertility. WNT signaling through the canonical β-catenin pathway plays a pivotal role in embryonic Müllerian duct development, postnatal uterine maturation and establishment of pregnancy. Loss of β-catenin in the Müllerian duct mesenchyme (MDM)-derived stroma and myometrium results in impaired decidualization and infertility, whereas gain-of-function (GOF) results in the formation of mesenchymal tumors and sub-fertility attributed to malformed oviducts. We hypothesized that GOF β-catenin further contributes to sub-fertility through improper stromal and epithelial cell signaling during embryo implantation and decidualization. We show that mice with GOF β-catenin in MDM-derived stroma and myometrium have reduced implantation sites after embryo transfer and decreased decidualization. On day 4.5 of pseudopregnancy or in mice treated with progesterone and estrogen to mimic early pregnancy, the estrogen-LIF-ERK and progesterone-IHH pathways remain predominantly intact in GOF β-catenin mice; however, JAK/STAT signaling is altered. pSTAT3 is significantly reduced in GOF β-catenin mice and expression of downstream epithelial junctional complex factors, Ctnna1 and Cldn1, is increased. We also show that purified stromal cells from GOF β-catenin uteri, when removed from epithelial cell influence and provided with the appropriate hormonal stimuli, are able to decidualize in vitro indicating that the cells are intrinsically capable of decidualization. Taken together, these results suggest that dysregulated β-catenin activity in the stroma affects epithelial cell STAT3 signaling and ultimately embryo implantation and stromal decidualization.

Epithelial and non-epithelial Ptch1 play opposing roles to regulate proliferation and morphogenesis of the mouse mammary gland

Patched 1 (Ptch1) has epithelial, stromal and systemic roles in murine mammary gland organogenesis, yet specific functions remain undefined. Cre-recombinase-mediated Ptch1 ablation in mammary epithelium increased proliferation and branching, but did not phenocopy transgenic expression of activated smoothened (SmoM2). The epithelium showed no evidence of canonical hedgehog signaling, and hyperproliferation was not blocked by smoothened (SMO) inhibition, suggesting a non-canonical function of PTCH1. Consistent with this possibility, nuclear localization of cyclin B1 was increased. In non-epithelial cells, heterozygous Fsp-Cre-mediated Ptch1 ablation increased proliferation and branching, with dysplastic terminal end buds (TEB) and ducts. By contrast, homozygous Ptch1 ablation decreased proliferation and branching, producing stunted ducts filled with luminal cells showing altered ovarian hormone receptor expression. Whole-gland transplantation into wild-type hosts or estrogen/progesterone treatment rescued outgrowth and hormone receptor expression, but not the histological changes. Bone marrow transplantation failed to rescue outgrowth. Ducts of Fsp-Cre;Ptch1^fl/fl mice were similar to Fsp-Cre;SmoM2 ducts, but Fsp-Cre;SmoM2 outgrowths were not stunted, suggesting that the histology might be mediated by Smo in the local stroma, with systemic Ptch1 required for ductal outgrowth and proper hormone receptor expression in the mammary epithelium.

Summary: Systemic and tissue-specific depletion of patched 1 in epithelial and stromal compartments of the mammary gland defines functions in ductal patterning, proliferation and gene expression.