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

Decidual Cells Block Inflammation-Mediated Inhibition of 15-Hydroxyprostaglandin Dehydrogenase in Trophoblasts

Chorioamnionitis generates prostaglandin (PG) E2 and F2α, promoting fetal membrane rupture, cervical ripening, and uterine contractions. 15-Hydroxyprostaglandin dehydrogenase (HPGD) contributes to pregnancy maintenance by inactivating PGs. The role of decidual cells in regulating HPGD expression at the maternal-fetal interface was investigated. HPGD immunostaining was primarily detected in anchoring villi and choriodecidual extravillous trophoblasts (EVTs) in the first, second, and third trimesters. Chorionic EVTs adjacent to decidua parietalis exhibited significantly higher HPDG levels than those adjacent to amnion. HPGD histologic score levels were significantly lower in choriodecidua from chorioamnionitis versus gestational age-matched controls (means ± SEM, 132.6 ± 3.8 versus 31.2 ± 7.9; P < 0.05). Conditioned media supernatant (CMS) from in vitro decidualized term decidual cells (TDCs) up-regulated HPGD levels in EVTs differentiated from human trophoblastic stem cells, primary trophoblasts, and HTR8/SVneo cells. However, CMS from 5 μg/mL lipopolysaccharide or 10 ng/mL IL-1β pretreated TDC cultures down-regulated HPGD levels in HTR8/SVneo cultures. Similarly, direct treatment of HTR8/SVneo cultures with lipopolysaccharide or IL-1β significantly reduced HPGD levels versus control (0.57 ± 0.1 or 0.47 ± 0.1 versus 1.03 ± 0.03; P < 0.05) but not in TDC-CMS pretreated HTR8/SVneo cultures. Collectively, the results uncover a novel decidual cell-mediated paracrine mechanism that stimulates levels of trophoblastic HPGD, whose function is to inactivate labor-inducing PGs, thereby promoting uterine quiescence during pregnancy. However, infectious/inflammatory stimuli in decidual cells cause a paracrine inhibition of trophoblastic HPGD expression, increasing PGE2/PGF2α levels, thereby contributing to preterm birth.

Ancient and modern mechanisms compete in progesterone receptor activation

The progesterone receptor (PR) belongs to the steroid receptor family of ligand-regulated transcription factors, controlling genes important for development, metabolism, and reproduction. Understanding how diverse ligands bind and modulate PR activity will illuminate the design of ligands that control PR-driven signaling pathways. Here, we use molecular dynamics simulations to investigate how PR dynamics are altered by functionally diverse ligands. Using a library of 33 steroidal ligands that range from inactive to EC50 < 0.1 nM, we reveal an unexpected evolutionary basis for the wide gamut of activation. While other oxosteroid receptors employ an evolutionarily conserved mechanism dependent on a hydrogen bond between the receptor and ligand, extant PR has evolved a preference for activation that is not reliant on this polar interaction. We demonstrate that potent ligands utilize the modern PR mechanism while weaker ligands coopt the defunct ancestral mechanism by forming hydrogen bonds with Asn719. Based on their structures and dynamic signatures, ligands partition into four classes (inactive, weak, moderate and high potency) that interact distinctly with the PR binding pocket. Further, we use luciferase reporter assays and PR mutants to probe the roles of pocket residues in mediating distinct PR mechanisms. This combination of MD simulations and in vitro studies provide insight into how the evolutionary history of PR shapes its response to diverse ligands.

Exposure to topiramate and acetazolamide causes endocrine disrupting effects in female rats during estrus

BACKGROUND

Idiopathic intracranial hypertension (IIH) is a disease characterized by elevated intracranial pressure (ICP) and is a disease of young females. The first line pharmacological treatments include acetazolamide and topiramate and given the nature of IIH patients and the dosing regimen of these drugs, their effect on the endocrine system is important to evaluate. We aimed to assess the effects of acetazolamide and topiramate on steroid profiles in relevant endocrine tissues.

METHODS

Female Sprague Dawley rats received chronic clinically equivalent doses of acetazolamide or topiramate by oral gavage and were sacrificed in estrus. Tissue specific steroid profiles of lateral ventricle CP, 4th ventricle CP, CSF, serum, uterine horn and fundus, ovaries, adrenal glands and pituitary glands were assessed by quantitative targeted LC-MS/MS. We determined luteinizing hormone (LH) and follicle stimulating hormones (FSH) levels in paired serum by ELISA.

RESULTS

Topiramate increased the concentration of estradiol and decreased the concentration of DHEA in lateral choroid plexus. Moreover, it decreased the concentration of androstenediol in the pituitary gland. Topiramate increased serum LH. Acetazolamide decreased progesterone levels in serum and uterine fundus and increased corticosteroid levels in the adrenal glands.

CONCLUSION

These results demonstrate that both acetazolamide and topiramate have endocrine disrupting effects in rats. Topiramate primarily targeted the choroid plexus and the pituitary gland while acetazolamide had broader systemic effects. Furthermore, topiramate predominantly targeted sex hormones, whereas acetazolamide widely affected all classes of hormones. A similar effect in humans has not yet been documented but these concerning findings warrants further investigations.

Blastocyst-Derived Lactic Acid May Regulate S100A6 Expression and Function in Mouse Decidualization via Stimulation of Uterine Epithelial Arachidonic Acid Secretion

(1) Background: Inflammatory responses are implicated in embryo implantation, decidualization, pregnancy maintenance and labor. Both embryo implantation and decidualization are essential to successful pregnancy in rodents and primates. S100A6 is involved in inflammation, tumor development, apoptosis and calcium homeostasis. S100A6 is strongly expressed in mouse decidua, but the underlying mechanisms of how S100A6 regulates implantation and decidualization are poorly defined. (2) Methods: Mouse endometrial stromal and epithelial cells are isolated from day 4 pseudopregnant mouse uteri. Both immunofluorescence and Western blotting are used to analyze the expression and localization of proteins. The molecular mechanism is verified in vitro by Western blotting and the quantitative polymerase chain reaction. (3) Results: From days 4 to 8 of pregnancy, S100A6 is specifically expressed in mouse subluminal stromal cells. Blastocyst-derived lactic acid induces AA secretion by activating the luminal epithelial p-cPLA2. The epithelial AA induces stromal S100A6 expression through the COX2/PGI2/PPAR δ pathway. Progesterone regulates S100A6 expression through the progesterone receptor (PR). S100A6/RAGE signaling can regulate decidualization via EGFR/ERK1/2 in vitro. (4) Conclusions: S100A6, as an inflammatory mediator, is important for mouse implantation and decidualization.

Dynamic chromatin remodeling in cycling human endometrium at single-cell level

Estrogen-dependent proliferation followed by progesterone-dependent differentiation of the endometrium culminates in a short implantation window. We performed single-cell assay for transposase-accessible chromatin with sequencing on endometrial samples obtained across the menstrual cycle to investigate the regulation of temporal gene networks that control embryo implantation. We identify uniquely accessible chromatin regions in all major cellular constituents of the endometrium, delineate temporal patterns of coordinated chromatin remodeling in epithelial and stromal cells, and gain mechanistic insights into the emergence of a receptive state through integrated analysis of enriched transcription factor (TF) binding sites in dynamic chromatin regions, chromatin immunoprecipitation sequencing analyses, and gene expression data. We demonstrate that the implantation window coincides with pervasive cooption of transposable elements (TEs) into the regulatory chromatin landscape of decidualizing cells and expression of TE-derived transcripts in a spatially defined manner. Our data constitute a comprehensive map of the chromatin changes that control TF activities in a cycling endometrium at cellular resolution.

Distinct HAND2/HAND2-AS1 Expression Levels May Fine-Tune Mesenchymal and Epithelial Cell Plasticity of Human Mesenchymal Stem Cells

We previously developed several successful decellularization strategies that yielded porcine cardiac extracellular matrices (pcECMs) exhibiting tissue-specific bioactivity and bioinductive capacity when cultured with various pluripotent and multipotent stem cells. Here, we study the tissue-specific effects of the pcECM on seeded human mesenchymal stem cell (hMSC) phenotypes using reverse transcribed quantitative polymerase chain reaction (RT-qPCR) arrays for cardiovascular related gene expression. We further corroborated interesting findings at the protein level (flow cytometry and immunological stains) as well as bioinformatically using several mRNA sequencing and protein databases of normal and pathologic adult and embryonic (organogenesis stage) tissue expression. We discovered that upon the seeding of hMSCs on the pcECM, they displayed a partial mesenchymal-to-epithelial transition (MET) toward endothelial phenotypes (CD31+) and morphologies, which were preceded by an early spike (~Day 3 onward after seeding) in HAND2 expression at both the mRNA and protein levels compared to that in plate controls. The CRISPR-Cas9 knockout (KO) of HAND2 and its associated antisense long non-coding RNA (HAND2-AS1) regulatory region resulted in proliferation arrest, hypertrophy, and senescent-like morphology. Bioinformatic analyses revealed that HAND2 and HAND2-AS1 are highly correlated in expression and are expressed in many different tissue types albeit at distinct yet tightly regulated expression levels. Deviation (downregulation or upregulation) from these basal tissue expression levels is associated with a long list of pathologies. We thus suggest that HAND2 expression levels may possibly fine-tune hMSCs' plasticity through affecting senescence and mesenchymal-to-epithelial transition states, through yet unknown mechanisms. Targeting this pathway may open up a promising new therapeutic approach for a wide range of diseases, including cancer, degenerative disorders, and aging. Nevertheless, further investigation is required to validate these findings and better understand the molecular players involved, potential inducers and inhibitors of this pathway, and eventually potential therapeutic applications.

Hedgehog signaling is required for endometrial remodeling and myometrial homeostasis in the cycling mouse uterus

Decades of work demonstrate that the mammalian estrous cycle is controlled by cycling steroid hormones. However, the signaling mechanisms that act downstream, linking hormonal action to the physical remodeling of the cycling uterus, remain unclear. To address this issue, we analyzed gene expression at all stages of the mouse estrous cycle. Strikingly, we found that several genetic programs well-known to control tissue morphogenesis in developing embryos displayed cyclical patterns of expression. We find that most of the genetic architectures of Hedgehog signaling (ligands, receptors, effectors, and transcription factors) are transcribed cyclically in the uterus, and that conditional disruption of the Hedgehog receptor smoothened not only elicits a failure of normal cyclical thickening of the endometrial lining but also induces aberrant deformation of the uterine smooth muscle. Together, our data shed light on the mechanisms underlying normal uterine remodeling specifically and cyclical gene expression generally.

Local production of 17β-oestradiol in the endometrium during the implantation window: a pilot study

Graphical abstract

Abstract

Sex steroids are converted to bioactive metabolites and vice versa by endometrial steroid-metabolising enzymes. Studies indicate that alterations in this metabolism might affect endometrial receptivity. This pilot study determined whether the endometrial formation and inactivation of 17β-oestradiol differed between the supposedly embryo-receptive endometrium and non-receptive endometrium of women undergoing IVF/intracytoplasmic sperm injection (ICSI). Endometrial biopsies were obtained from IVF/ICSI patients 5-8 days after ovulation in a natural cycle, prior to their second IVF/ICSI cycle with fresh embryo transfer (ET). Endometrial biopsies from patients who achieved clinical pregnancy after fresh ET (n = 15) were compared with endometrial biopsies from patients that did not conceive after fresh ET (n = 15). Formation of 17β-oestradiol (oxidative 17β-hydroxysteroid dehydrogenases (HSDs)), oestrone (reductive HSD17Bs) and inhibition of HSD17B1 activity were determined by high-performance liquid chromatography. The endometrial transcriptome was profiled using RNA sequencing followed by principal component analysis and differentially expressed gene analysis. The false discovery rate-adjusted P < 0.05 and log fold change >0.5 were selected as the screening threshold. Formation and inactivation of 17β-oestradiol resulted similar between groups. Inhibition of HSD17B1 activity was significantly higher in the non-pregnant group when only primary infertile women (n = 12) were considered (27.1%, n = 5 vs 16.2%, n = 7, P = 0.04). Gene expression analysis confirmed the presence of HSD17B1 (encoding HSD17B1), HSD17B2 (encoding HSD17B2) and 33 of 46 analysed steroid metabolising enzymes in the endometrium. In the primary infertile subgroup (n = 10) 12 DEGs were found including LINC02349 which has been linked to implantation. However, the exact relationship between steroid-metabolising enzyme activity, expression and implantation outcome requires further investigation in larger, well-defined patient groups.

Lay summary

Sex hormones are produced and broken down by enzymes that can be found in the endometrium (the inner lining of the womb). This enzyme activity might influence the chances of becoming pregnant. We compared (i) enzyme activity in the endometrium of 15 women who did and 15 women who did not become pregnant in their second in vitro fertilisation attempt, (ii) how enzyme activity can be blocked by an inhibitor, and (iii) differences in gene expression (the process by which instructions in our DNA are converted into a product). Enzyme activity was similar between groups. We found that in women who have never been pregnant in the past, inhibition of enzyme activity was higher and found differences in a gene that has been linked to the implantation of the embryo, but future studies should be performed in larger, well-defined patient groups to confirm these findings.

The NR2F2-HAND2 signaling axis regulates progesterone actions in the uterus at early pregnancy

Endometrial function is dependent on a tight crosstalk between the epithelial and stromal cells of the endometrium. This communication is critical to ensure a fertile uterus and relies on progesterone and estrogen signaling to prepare a receptive uterus for embryo implantation in early pregnancy. One of the key mediators of this crosstalk is the orphan nuclear receptor NR2F2, which regulates uterine epithelial receptivity and stromal cell differentiation. In order to determine the molecular mechanism regulated by NR2F2, RNAseq analysis was conducted on the uterus of PgrCre;Nr2f2f/f mice at Day 3.5 of pregnancy. This transcriptomic analysis demonstrated Nr2f2 ablation in Pgr-expressing cells leads to a reduction of Hand2 expression, increased levels of Hand2 downstream effectors Fgf1 and Fgf18, and a transcriptome manifesting suppressed progesterone signaling with an altered immune baseline. ChIPseq analysis conducted on the Day 3.5 pregnant mouse uterus for NR2F2 demonstrated the majority of NR2F2 occupies genomic regions that have H3K27ac and H3K4me1 histone modifications, including the loci of major uterine transcription regulators Hand2, Egr1, and Zbtb16. Furthermore, functional analysis of an NR2F2 occupying site that is conserved between human and mouse was capable to enhance endogenous HAND2 mRNA expression with the CRISPR activator in human endometrial stroma cells. These data establish the NR2F2 dependent regulation of Hand2 in the stroma and identify a cis-acting element for this action. In summary, our findings reveal a role of the NR2F2-HAND2 regulatory axis that determines the uterine transcriptomic pattern in preparation for the endometrial receptivity.

Chromatin architectural factor CTCF is essential for progesterone-dependent uterine maturation

Receptors for estrogen and progesterone frequently interact, via Cohesin/CTCF loop extrusion, at enhancers distal from regulated genes. Loss-of-function CTCF mutation in >20% of human endometrial tumors indicates its importance in uterine homeostasis. To better understand how CTCF-mediated enhancer-gene interactions impact endometrial development and function, the Ctcf gene was selectively deleted in female reproductive tissues of mice. Prepubertal Ctcfd/d uterine tissue exhibited a marked reduction in the number of uterine glands compared to those without Ctcf deletion (Ctcff/f mice). Post-pubertal Ctcfd/d uteri were hypoplastic with significant reduction in both the amount of the endometrial stroma and number of glands. Transcriptional profiling revealed increased expression of stem cell molecules Lif, EOMES, and Lgr5, and enhanced inflammation pathways following Ctcf deletion. Analysis of the response of the uterus to steroid hormone stimulation showed that CTCF deletion affects a subset of progesterone-responsive genes. This finding indicates (1) Progesterone-mediated signaling remains functional following Ctcf deletion and (2) certain progesterone-regulated genes are sensitive to Ctcf deletion, suggesting they depend on gene-enhancer interactions that require CTCF. The progesterone-responsive genes altered by CTCF ablation included Ihh, Fst, and Errfi1. CTCF-dependent progesterone-responsive uterine genes enhance critical processes including anti-tumorigenesis, which is relevant to the known effectiveness of progesterone in inhibiting progression of early-stage endometrial tumors. Overall, our findings reveal that uterine Ctcf plays a key role in progesterone-dependent expression of uterine genes underlying optimal post-pubertal uterine development.

An integrative analysis of endometrial steroid metabolism and transcriptome in relation to endometrial receptivity in in vitro fertilization patients

OBJECTIVE

To study the relationship between the steroid concentration in the endometrium, in serum, and the gene expression level of steroid-metabolizing enzymes in the context of endometrial receptivity in in vitro fertilization (IVF) patients.

DESIGN

Case-control study of 40 IVF patients recruited in the SCRaTCH study (NTR5342), a randomized controlled trial investigating pregnancy outcome after "endometrial scratching." Endometrial biopsies and serum were obtained from patients with a first failed IVF cycle randomized to the endometrial scratch in the midluteal phase of the natural cycle before the next fresh embryo transfer during the second IVF cycle.

SETTING

University hopsital.

PATIENTS

Twenty women with clinical pregnancy were compared with 20 women who did not conceive after fresh embryo transfer. Cases and controls were matched for primary vs. secondary infertility, embryo quality, and age.

INTERVENTION

None.

MAIN OUTCOME MEASURE(S)

Steroid concentrations in endometrial tissue homogenates and serum were measured with liquid chromatography-mass spectrometry. The endometrial transcriptome was profiled by RNA-sequencing, followed by principal component analysis and differential expression analysis. False discovery rate-adjusted and log-fold change >|0.5| were selected as the threshold for differentially expressed genes.

RESULT(S)

Estrogen levels were comparable in both serum (n = 16) and endometrium (n = 40). Androgens and 17-hydroxyprogesterone were higher in serum than that in endometrium. Although steroid levels did not vary between pregnant and nonpregnant groups, subgroup analysis of primary women with infertility showed a significantly lower estrone concentration and estrone:androstenedione ratio in serum of the pregnant group (n = 5) compared with the nonpregnant group (n = 2). Expression of 34 out of 46 genes encoding the enzymes controlling the local steroid metabolism was detected, and estrogen receptor β gene was differentially expressed between pregnant and nonpregnant women. When only the primary infertile group was considered, 28 genes were differentially expressed between pregnant and nonpregnant women, including HSD11B2, that catalyzes the conversion of cortisol into cortisone.

CONCLUSION(S)

Steroidomic and transcriptomic analyses show that steroid concentrations are regulated by the local metabolism in the endometrium. Although no differences were found in endometrial steroid concentration in the pregnant and nonpregnant IVF patients, primary women with infertility showed deviations in steroid levels and gene expression, indicating that a more homogeneous patient group is required to uncover the exact role of steroid metabolism in endometrial receptivity.

CLINICAL TRIAL REGISTRATION NUMBER

The study was registered in the Dutch trial registry (www.trialregister.nl), registration number NL5193/NTR5342, available at https://trialsearch.who.int/Trial2.aspx?TrialID=NTR6687. The date of registration is July 31, 2015. The first enrollment is on January 1, 2016.

Androgen signalling in the ovaries and endometrium

Currently, our understanding of hormonal regulation within the female reproductive system is largely based on our knowledge of estrogen and progesterone signalling. However, while the important functions of androgens in male physiology are well known, it is also recognized that androgens play critical roles in the female reproductive system. Further, androgen signalling is altered in a variety of gynaecological conditions, including endometriosis and polycystic ovary syndrome, indicative of regulatory roles in endometrial and ovarian function. Co-regulatory mechanisms exist between different androgens, estrogens, and progesterone, resulting in a complex network of steroid hormone interactions. Evidence from animal knockout studies, in vitro experiments, and human data indicate that androgen receptor expression is cell-specific and menstrual cycle stage-dependent, with important regulatory roles in the menstrual cycle, endometrial biology, and follicular development in the ovaries. This review will discuss the expression and co-regulatory interactions of androgen receptors, highlighting the complexity of the androgen signalling pathway in the endometrium and ovaries, and the synthesis of androgens from additional alternative pathways previously disregarded as male-specific. Moreover, it will illustrate the challenges faced when studying androgens in female biology, and the need for a more in-depth, integrative view of androgen metabolism and signalling in the female reproductive system.

Understanding Progestins: From Basics to Clinical Applicability

Progestin is a term used to describe a synthetic progestogen. The activity and potency of synthetic progestins are mostly evaluated via parameters associated with their endometrial effects, which are related to their interactions with progesterone, estrogen, androgen, glucocorticoid, and mineralocorticoid receptors. The chemical structure of progestins is the key to understanding their interactions with these receptors and predicting the other effects associated with these drugs. Due to their endometrial effect, progestins are used for different gynecological conditions, such as endometriosis, contraception, hormonal replacement therapy, and artificial reproduction techniques. This review is focused on improving our knowledge of progestins (from their history and biochemical effects related to their chemical structures to clinical applications in gynecological conditions) in order to improve clinical practice.

The history and future of in vitro fertilization in the United States: the complex interrelationships among basic science, human medicine, and politics

Although much of the foundational basic scientific and clinical research was conducted in the United States, the first in vitro fertilization (IVF) birth occurred in the United Kingdom. Why? For centuries, all research surrounding the field of "reproduction" has elicited bipolar passionate responses by the American public, and the issue of "test tube babies" has been no different. The history of conception in the United States is defined by complex interrelationships among scientists, clinicians, and politically charged decisions by various branches of the US government. With a focus on research in the United States, this review summarizes the early scientific and clinical advances important to the development of IVF and then addresses the potential future developments in IVF. We also consider what future advances are possible in the United States given the current regulations, laws, and funding.

Progesterone: A Neuroprotective Steroid of the Intestine

The enteric nervous system (ENS) is an intrinsic network of neuronal ganglia in the intestinal tube with about 100 million neurons located in the myenteric plexus and submucosal plexus. These neurons being affected in neurodegenerative diseases, such as Parkinson's disease, before pathological changes in the central nervous system (CNS) become detectable is currently a subject of discussion. Understanding how to protect these neurons is, therefore, particularly important. Since it has already been shown that the neurosteroid progesterone mediates neuroprotective effects in the CNS and PNS, it is now equally important to see whether progesterone has similar effects in the ENS. For this purpose, the RT-qPCR analyses of laser microdissected ENS neurons were performed, showing for the first time the expression of the different progesterone receptors (PR-A/B; mPRa, mPRb, PGRMC1) in rats at different developmental stages. This was also confirmed in ENS ganglia using immunofluorescence techniques and confocal laser scanning microscopy. To analyze the potential neuroprotective effects of progesterone in the ENS, we stressed dissociated ENS cells with rotenone to induce damage typical of Parkinson's disease. The potential neuroprotective effects of progesterone were then analyzed in this system. Treatment of cultured ENS neurons with progesterone reduced cell death by 45%, underscoring the tremendous neuroprotective potential of progesterone in the ENS. The additional administration of the PGRMC1 antagonist AG205 abolished the observed effect, indicating the crucial role of PGRMC1 with regard to the neuroprotective effect of progesterone.

Membrane Progesterone Receptors (mPRs/PAQRs) Are Going beyond Its Initial Definitions

Progesterone (PRG) is a key cyclical reproductive hormone that has a significant impact on female organs in vertebrates. It is mainly produced by the corpus luteum of the ovaries, but can also be generated from other sources such as the adrenal cortex, Leydig cells of the testes and neuronal and glial cells. PRG has wide-ranging physiological effects, including impacts on metabolic systems, central nervous systems and reproductive systems in both genders. It was first purified as an ovarian steroid with hormonal function for pregnancy, and is known to play a role in pro-gestational proliferation during pregnancy. The main function of PRG is exerted through its binding to progesterone receptors (nPRs, mPRs/PAQRs) to evoke cellular responses through genomic or non-genomic signaling cascades. Most of the existing research on PRG focuses on classic PRG-nPR-paired actions such as nuclear transcriptional factors, but new evidence suggests that PRG also exerts a wide range of PRG actions through non-classic membrane PRG receptors, which can be divided into two sub-classes: mPRs/PAQRs and PGRMCs. The review will concentrate on recently found non-classical membrane progesterone receptors (mainly mPRs/PAQRs) and speculate their connections, utilizing the present comprehension of progesterone receptors.

Uterine administration of C-X-C motif chemokine ligand 12 increases the pregnancy rates in mice with induced endometriosis

OBJECTIVE

To study the effect of intrauterine injection of C-X-C motif chemokine ligand 12 (CXCL12), also known as a stem cell chemoattractant (stromal cell-derived factor 1), on fertility and endometrial receptivity in mice with endometriosis.

DESIGN

Laboratory study.

SETTING

Academic Medical Center.

ANIMAL(S)

Fifty-six mice underwent chemotherapy and bone marrow transplantation. Thirty-six of these mice underwent either surgery to induce endometriosis (n = 20) or sham surgery (n = 16).

INTERVENTION(S)

Injection of CXCL12 as a potential therapeutic agent to improve fertility in endometriosis.

MAIN OUTCOME MEASURE(S)

Pregnancy rate, bone marrow-derived cell (BMDC) recruitment and endometrial receptivity markers.

RESULT(S)

The mice with or without endometriosis received a single uterine injection of either CXCL12 or placebo. Uterine injection of CXCL12 increased the pregnancy rates in a mouse model of endometriosis. Mice were euthanized after delivery, and implantation markers homeobox A11, alpha-v beta-3 integrin, and progesterone receptor were analyzed by immunohistochemistry, whereas green fluorescent protein positive BMDC recruitment was quantified by immunohistochemistry and immunofluorescence. The sham surgery groups without endometriosis had the highest cumulative pregnancy rate (100%) regardless of CXCL12 treatment. The endometriosis group treated with placebo had the lowest pregnancy rate. An increased pregnancy rate was noted in the endometriosis group after treatment with CXCL12. There was also an increase in BMDC recruitment and endometrial expression of progesterone receptor and alpha-v beta-3 integrin in the endometriosis group that received CXCL12 compared with that in the endometriosis group that received placebo.

CONCLUSION(S)

Uterine injection of CXCL12 increased the pregnancy rates in a mouse model of endometriosis. These results suggest that CXCL12 has a potential role as a therapeutic agent in women with infertility related to endometriosis and potentially other endometrial receptivity defects.

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

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

Uterine epithelial Gp130 orchestrates hormone response and epithelial remodeling for successful embryo attachment in mice

Leukemia inhibitory factor (LIF) receptor, an interleukin 6 cytokine family signal transducer (Il6st, also known as Gp130) that is expressed in the uterine epithelium and stroma, has been recognized to play an essential role in embryo implantation. However, the molecular mechanism underlying Gp130-mediated LIF signaling in the uterine epithelium during embryo implantation has not been elucidated. In this study, we generated mice with uterine epithelium specific deletion of Gp130 (Gp130 ecKO). Gp130 ecKO females were infertile due to the failure of embryo attachment and decidualization. Histomorphological observation revealed that the endometrial shape and embryo position from Gp130 ecKO were comparable to those of the control, and uterine epithelial cell proliferation, whose attenuation is essential for embryo implantation, was controlled in Gp130 ecKO. Comprehensive gene expression analysis using RNA-seq indicates that epithelial Gp130 regulates the expression of estrogen- and progesterone-responsive genes in conjunction with immune response during embryo implantation. We also found that an epithelial remodeling factor, snail family transcriptional repressor 1 (Snai1), was markedly reduced in the pre-implantation uterus from Gp130 ecKO. These results suggest that not only the suppression of uterine epithelial cell proliferation, but also Gp130-mediated epithelial remodeling is required for successful implantation in mice.

iTRAQ-based Proteomic Analysis Unveils ACSL4 as a Novel Potential Regulator of Human Endometrial Receptivity

Competent endometrial receptivity is a prerequisite for successful embryo implantation. Identification of novel key molecules involved in endometrial receptivity is essential to better interpret human implantation and improve pregnancy rates in assisted reproduction treatment. Isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics was performed to profile the proteomes of the prereceptive (luteinizing hormone [LH] + 2, n = 4) and receptive (LH + 7, n = 4) endometrial tissues. A total of 173 differentially expressed proteins (DEPs) between LH + 2 and LH + 7 endometrial samples were identified. Integrated analysis of the proteomic data and published transcriptomic data was performed to identify the concordant DEPs with differential expression at both the messenger RNA and protein levels. Protein-protein interaction (PPI) network analysis was performed on concordant DEPs. We first identified 63 novel concordant DEPs and 5 hub proteins (ACSL4, ACSL5, COL1A1, PTGS1, and PLA2G4F) between LH + 2 and LH + 7 endometrial samples. ACSL4 was predominantly expressed in endometrial epithelial cells and its expression was significantly upregulated by progesterone in the LH + 7 endometrium and significantly downregulated in repeated implantation failure patients. Knockdown of ACSL4 in endometrial epithelial cells induced the downregulation of endometrial receptivity markers (HOXA10, COX2, and LIF) and the significant decrease of implantation rate during in vitro implantation analysis. This study provides the first gel-independent quantitative proteomes of the LH + 2 and LH + 7 human endometrium using iTRAQ technology. The identified concordant DEPs and hub proteins open a new avenue for future studies aimed at elucidating the underlying mechanisms governing endometrial receptivity. ACSL4 was identified as a novel regulatory molecule in the establishment of endometrial receptivity and might play important roles during implantation.

GOLPH3 modulates expression and alternative splicing of transcription factors associated with endometrial decidualization in human endometrial stromal cells

Endometrial decidualization is a decidual tissue formed by the proliferation and re-differentiation of endometrial stroma stimulated by decidualization inducing factors. It is very important for the proper maintenance of pregnancy. Previous studies speculated that Golgi phosphoprotein 3 (GOLPH3) may have a regulatory role in the process of endometrial decidualization, while the specific molecular mechanisms of GOLPH3 is unclear. In this part, GOLPH3 was silenced in human endometrial stromal cells (hESCs), and the transcriptome data (RNA-seq) by GOLPH3 knockdown (siGOLPH3) was obtained by high-throughput sequencing technology so as to analyze the potential targets of GOLPH3 at expression and alternative splicing levels in hESCs. Through bioinformatics analysis, we found that siGOLPH3 can significantly affect the overall transcriptional level of hESCs. A total of 6,025 differentially expressed genes (DEGs) and 4,131 differentially alternative splicing events (DASEs) were identified. Through functional cluster analysis of these DEGs and genes where differential alternative splicing events are located, it is found that they are enriched in the PI3K/Akt signaling pathway, RNA splicing and processing, transcription factors and other pathways related to endometrial decidualization and important biological processes, indicating the important biological function of GOLPH3. At the same time, we focused on the analysis of the transcription factors regulated by GOLPH3, including gene expression regulation and the regulation of variable splicing. We found that GOLPH3can regulate the expression of transcription factors such as LD1, FOSL2, GATA2, CSDC2 and CREB3L1. At the same time, it affects the variable splicing mode of FOXM1 and TCF3. The function of these transcription factors is directly related to decidualization of endometrium. Therefore, we infer that GOLPH3 may participate in endometrial de membrane by regulating expression and alternative splicing levels of transcription factors. We further identified the role of GOLPH3 in the transcriptional mechanism. At the same time, it also expands the function mode of GOLPH3 protein molecule, and provides a theoretical basis for downstream targeted drug research and development and clinical application.

An In Vivo Screening Model for Investigation of Pathophysiology of Human Implantation Failure

To improve current infertility treatments, it is important to understand the pathophysiology of implantation failure. However, many molecules are involved in the normal biological process of implantation and the roles of each molecule and the molecular mechanism are not fully understood. This review highlights the hemagglutinating virus of Japan (HVJ; Sendai virus) envelope (HVJ-E) vector, which uses inactivated viral particles as a local and transient gene transfer system to the murine uterus during the implantation period in order to investigate the molecular mechanism of implantation. In vivo screening in mice using the HVJ-E vector system suggests that signal transducer and activator of transcription-3 (Stat-3) could be a diagnostic and therapeutic target for women with a history of implantation failure. The HVJ-E vector system hardly induces complete defects in genes; however, it not only suppresses but also transiently overexpresses some genes in the murine uterus. These features may be useful in investigating the pathophysiology of implantation failure in women.

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.

Spatial definition of the human progesterone receptor-B transcriptional complex

We report the quaternary structure of core transcriptional complex for the full-length human progesterone receptor-B (PR-B) homodimer with primary coactivator steroid receptor coactivator-2 (SRC-2) and the secondary coactivator p300/CREB-binding protein (CBP). The PR-B homodimer engages one SRC-2 mainly through its activation function 1 (AF1) in N-terminus. SRC-2 is positioned between PR-B and p300 leaving space for direct interaction between PR-B and p300 through PR-B's C-terminal AF2 and its unique AF3. Direct AF3/p300 interaction provides long-desired structural insights into the known functional differences between PR-B and the PR-A isoform lacking AF3. We reveal the contributions of each AF and demonstrate their structural basis in forming the PR-B dimer interface and PR-B/coactivator complex. Comparison of the PR-B/coactivator complex with other steroid receptor (estrogen receptor and androgen receptor) complexes also shows that each receptor has its unique mechanism for recruiting coactivators due to the highly variable N-termini among receptors.

The role of progesterone receptor isoforms in the myometrium

Myometrial contraction is stringently controlled throughout pregnancy and parturition. Progesterone signaling, effecting through the progesterone receptor (PR), is pivotal in modulating uterine activity. Evidence has shown that two major PR isoforms, PR-A and PR-B, have distinct activities on gene regulation, and the ratio between these isoforms determines the contractility of the myometrium at different gestational stages. Herein, we focus on the regulation of PR activity in the myometrium, especially the differential actions of the two PR isoforms, which maintain uterine quiescence during pregnancy and regulate the switch to a contractile state at the onset of labor. To demonstrate the PR regulatory network and its mechanisms of actions on myometrial activity, we summarized the findings into three parts: Regulation of PR Expression and Isoform Levels, Progesterone Receptor Interacting Factors, and Biological Processes Regulated by Myometrial Progesterone Receptor Isoforms. Recent genomic and epigenomic data, from human specimens and mouse models, are recruited to support the existing knowledge and offer new insights and future directions in myometrial biology.

PRMT1, a Key Modulator of Unliganded Progesterone Receptor Signaling in Breast Cancer

The progesterone receptor (PR) is a key player in major physiological and pathological responses in women, and the signaling pathways triggered following hormone binding have been extensively studied, particularly with respect to breast cancer development and progression. Interestingly, growing evidence suggests a fundamental role for PR on breast cancer cell homeostasis in hormone-depleted conditions, with hormone-free or unliganded PR (uPR) involved in the silencing of relevant genes prior to hormonal stimulation. We herein identify the protein arginine methyltransferase PRMT1 as a novel actor in uPR signaling. In unstimulated T47D breast cancer cells, PRMT1 interacts and functions alongside uPR and its partners to target endogenous progesterone-responsive promoters. PRMT1 helps to finely tune the silencing of responsive genes, likely by promoting a proper BRCA1-mediated degradation and turnover of unliganded PR. As such, PRMT1 emerges as a key transcriptional coregulator of PR for a subset of relevant progestin-dependent genes before hormonal treatment. Since women experience periods of hormonal fluctuation throughout their lifetime, understanding how steroid receptor pathways in breast cancer cells are regulated when hormones decline may help to determine how to override treatment failure to hormonal therapy and improve patient outcome.

Catalpol attenuates polycystic ovarian syndrome by regulating sirtuin 1 mediated NF-κB signaling pathway

Oxidative stress plays a central role in polycystic ovary syndrome (PCOS). Catalpol (CAT) is the active ingredient of Rehmannia glutinosa Libosch which has therapeutic effect on PCOS. However, little is known about the mechanism of CAT in PCOS. PCOS rats were induced by subcutaneous injection of dehydroepiandrosteronec for four weeks and then were treated with CAT (50 mg/kg) or carboxyl methyl cellulose (the solvent of CAT) or normal saline for another 4 weeks. Histopathological observation of ovarian tissues, the levels of testosterone, estradiol and progesterone in rat plasma samples, the oxidative stress related-indexes and the expressions of NF-κB pathway-related proteins were determined. KGN cell (human ovarian granulosa cell line) was used as PCOS cell model and was transfected with siSIRT1 in the presence of CAT. The viability, proliferation and apoptosis of cells and the levels of SIRT1 and NF-κB pathway-related proteins were measured. CAT lessened the anthropometric indices and improved ovarian damage in PCOS model rats, and reduced the levels of testosterone, estradiol, progesterone and MDA, increased GSH content, and elevated the activities of catalase, GSH-Px and SOD in ovarian tissues of PCOS model rats. CAT up-regulated SIRT1 level and inhibited the activation of NF-κB signaling pathway in PCOS rat model and KGN cells. Silencing SIRT1 increased the viability and proliferation, whilst decreased the apoptosis of CAT-treated KGN cells. Silencing SIRT1 counteracted the effect of CAT on the level of oxidative stress-related factors and NF-κB signaling pathway in KGN cells. CAT attenuated PCOS by regulating SIRT1 mediated NF-κB signaling pathway.

Progesterone Signaling in Endometrial Epithelial Organoids

For pregnancy to be established, uterine cells respond to the ovarian hormones, estrogen, and progesterone, via their nuclear receptors, the estrogen receptor (ESR1) and progesterone receptor (PGR). ESR1 and PGR regulate genes by binding chromatin at genes and at distal enhancer regions, which interact via dynamic 3-dimensional chromatin structures. Endometrial epithelial cells are the initial site of embryo attachment and invasion, and thus understanding the processes that yield their receptive state is important. Here, we cultured and treated organoids derived from human epithelial cells, isolated from endometrial biopsies, with estrogen and progesterone and evaluated their transcriptional profiles, their PGR cistrome, and their chromatin conformation. Progesterone attenuated estrogen-dependent gene responses but otherwise minimally impacted the organoid transcriptome. PGR ChIPseq peaks were co-localized with previously described organoid ESR1 peaks, and most PGR and ESR1 peaks were in B (inactive) compartment regions of chromatin. Significantly more ESR1 peaks were assigned to estrogen-regulated genes by considering chromatin loops identified using HiC than were identified using ESR1 peak location relative to closest genes. Overall, the organoids model allowed a definition of the chromatin regulatory components governing hormone responsiveness.

Lipid metabolism and endometrial receptivity

BACKGROUND

Obesity has now been recognized as a high-risk factor for reproductive health. Although remarkable advancements have been made in ART, a considerable number of infertile obese women still suffer from serial implantation failure, despite the high quality of embryos transferred. Although obesity has long been known to exert various deleterious effects on female fertility, the underlying mechanisms, especially the roles of lipid metabolism in endometrial receptivity, remain largely elusive.

OBJECTIVE AND RATIONALE

This review summarizes current evidence on the impacts of several major lipids and lipid-derived mediators on the embryonic implantation process. Emerging methods for evaluating endometrial receptivity, for example transcriptomic and lipidomic analysis, are also discussed.

SEARCH METHODS

The PubMed and Embase databases were searched using the following keywords: (lipid or fatty acid or prostaglandin or phospholipid or sphingolipid or endocannabinoid or lysophosphatidic acid or cholesterol or progesterone or estrogen or transcriptomic or lipidomic or obesity or dyslipidemia or polycystic ovary syndrome) AND (endometrial receptivity or uterine receptivity or embryo implantation or assisted reproductive technology or in vitro fertilization or embryo transfer). A comprehensive literature search was performed on the roles of lipid-related metabolic pathways in embryo implantation published between January 1970 and March 2022. Only studies with original data and reviews published in English were included in this review. Additional information was obtained from references cited in the articles resulting from the literature search.

OUTCOMES

Recent studies have shown that a fatty acids-related pro-inflammatory response in the embryo-endometrium boundary facilitates pregnancy via mediation of prostaglandin signaling. Phospholipid-derived mediators, for example endocannabinoids, lysophosphatidic acid and sphingosine-1-phosphate, are associated with endometrial receptivity, embryo spacing and decidualization based on evidence from both animal and human studies. Progesterone and estrogen are two cholesterol-derived steroid hormones that synergistically mediate the structural and functional alterations in the uterus ready for blastocyst implantation. Variations in serum cholesterol profiles throughout the menstrual cycle imply a demand for steroidogenesis at the time of window of implantation (WOI). Since 2002, endometrial transcriptomic analysis has been serving as a diagnostic tool for WOI dating. Numerous genes that govern lipid homeostasis have been identified and, based on specific alterations of lipidomic signatures differentially expressed in WOI, lipidomic analysis of endometrial fluid provides a possibility for non-invasive diagnosis of lipids alterations during the WOI.

WIDER IMPLICATIONS

Given that lipid metabolic dysregulation potentially plays a role in infertility, a better understanding of lipid metabolism could have significant clinical implications for the diagnosis and treatment of female reproductive disorders.

SOX4 facilitates PGR protein stability and FOXO1 expression conducive for human endometrial decidualization

The establishment of pregnancy in human necessitates appropriate decidualization of stromal cells, which involves steroids regulated periodic transformation of endometrial stromal cells during the menstrual cycle. However, the potential molecular regulatory mechanism underlying the initiation and maintenance of decidualization in humans is yet to be fully elucidated. In this investigation, we document that SOX4 is a key regulator of human endometrial stromal cells decidualization by directly regulating FOXO1 expression as revealed by whole genomic binding of SOX4 assay and RNA sequencing. Besides, our immunoprecipitation and mass spectrometry results unravel that SOX4 modulates progesterone receptor (PGR) stability through repressing E3 ubiquitin ligase HERC4-mediated degradation. More importantly, we provide evidence that dysregulated SOX4–HERC4–PGR axis is a potential cause of defective decidualization and recurrent implantation failure in in-vitro fertilization (IVF) patients. In summary, this study evidences that SOX4 is a new and critical regulator for human endometrial decidualization, and provides insightful information for the pathology of decidualization-related infertility and will pave the way for pregnancy improvement.

Comparison of lncRNA Expression in the Uterus between Periods of Embryo Implantation and Labor in Mice

Simple Summary

Progesterone has been proven to play an important role in female mammals during pregnancy. In this study, the uteri of pregnant mice were collected to compare mRNA and lncRNA expression between periods of embryo implantation and labor. The results show that 19 known differentially expressed lncRNAs and 31 novel differentially lncRNAs were commonly expressed between the two stages, indicating that these lncRNAs’ function is related to progesterone.

Abstract

Uterine function during pregnancy is regulated mainly by progesterone (P4) and estrogen (E2). Serum P4 levels are known to fluctuate significantly over the course of pregnancy, especially during embryo implantation and labor. In this study, pregnant mice at E0.5, E4.5, E15.5, and E18.5 (n = 3/E) were used for an RNA-Seq-based analysis of mRNA and lncRNA expression. In this analysis, 1971 differentially expressed (DE) mRNAs, 493 known DE lncRNAs, and 1041 novel DE lncRNAs were found between E0.5 and E4.5 at the embryo implantation stage, while 1149 DE mRNAs, 192 known DE lncRNAs, and 218 novel DE lncRNAs were found between E15.5 and E18.5 at the labor stage. The expression level of lncRNA-MMP11 was significantly downregulated by P4 treatment on MSM cells, while lncRNA-ANKRD37 was significantly upregulated. Notably, 117 DE mRNAs, 19 known DE lncRNAs, and 31 novel DE lncRNAs were commonly expressed between the two stages, indicating that these mRNAs and lncRNAs may be directly or indirectly regulated by P4.

How Protein Methylation Regulates Steroid Receptor Function

Steroid receptors (SRs) are members of the nuclear hormonal receptor family, many of which are transcription factors regulated by ligand binding. SRs regulate various human physiological functions essential for maintenance of vital biological pathways, including development, reproduction, and metabolic homeostasis. In addition, aberrant expression of SRs or dysregulation of their signaling has been observed in a wide variety of pathologies. SR activity is tightly and finely controlled by post-translational modifications (PTMs) targeting the receptors and/or their coregulators. Whereas major attention has been focused on phosphorylation, growing evidence shows that methylation is also an important regulator of SRs. Interestingly, the protein methyltransferases depositing methyl marks are involved in many functions, from development to adult life. They have also been associated with pathologies such as inflammation, as well as cardiovascular and neuronal disorders, and cancer. This article provides an overview of SR methylation/demethylation events, along with their functional effects and biological consequences. An in-depth understanding of the landscape of these methylation events could provide new information on SR regulation in physiology, as well as promising perspectives for the development of new therapeutic strategies, illustrated by the specific inhibitors of protein methyltransferases that are currently available.

Female Reproductive Systems: Hormone Dependence and Receptor Expression

The female reproductive system which consists of the ovaries, uterus (myometrium, endometrium), Fallopian tubes, cervix and vagina is exquisitely sensitive to the actions of steroid hormones. The ovaries play a key role in the synthesis of bioactive steroids (oestrogens, androgens, progestins) that act both within the tissue (intracrine/paracrine) as well as on other reproductive organs following release into the blood stream (endocrine action). Sex steroid receptors encoded by the oestrogen (ESR1, ESR2), progesterone (PR) and androgen (AR) receptor genes, which are members of the superfamily of ligand activated transcription factors are widely expressed within these tissues. These receptors play critical role(s) in regulation of cell proliferation, ovulation, endometrial receptivity, myometrial cell function and inflammatory cell infiltration. Our understanding of their importance has been informed by studies on human tissues and cells, which have employed immunohistochemistry as well as a wide range of molecular and genetic methods to identify which processes are dependent steroid ligand activation. The development of mice with targeted deletions of each of these receptors has provided complementary data that has extended our appreciation of cell-cell interactions in the fine tuning of reproductive tissue function. This large body of work has formed the basis of new and improved therapeutics to treat conditions such as infertility.

Research progress of endometrial receptivity in patients with polycystic ovary syndrome: a systematic review

Polycystic ovary syndrome (PCOS) is a neuroendocrine heterogeneous disease that frequently occurs in women of reproductive age, causing serious damage to the fertility, quality of life, and physical and mental health of patients. The current studies have proved that satisfactory endometrial receptivity is one of the conditions that must be met during the process of spermatovum position, adhesion and invasion, as well as the subsequent blastocyst division and embryo development. Women with PCOS may suffer a series of pathological processes such as changes in the expression levels of hormones and related receptors, imbalances in the proportion of miscellaneous cytokines, insulin resistance, low-grade chronic inflammation and endometrial morphological changes, which will damage endometrial receptivity from various aspects and obstruct fertilized egg nidation and embryonic development, thus causing adverse reproductive health events including infertility and abortion. This article reviews the research progress about characteristics and related influencing factors of endometrial receptivity in PCOS patients.

Thicker endometrium on hCG trigger day improves the live birth rate of fresh cleavage embryo transfer in GnRH-agonist regimen of normogonadotrophic women

Background

Luteinizing hormone (LH) and progesterone (PROG) on human chorionic gonadotropin (hCG) trigger day are significantly correlated with assisted reproductive technology (ART) outcome. Moreover, LH and PROG are also involved in the functional preparation of the endometrium during the implantation window; however, whether they are related to endometrial thickness (EMT) is still unknown. The aim of the present study was to assess whether EMT has a positive correlation on the live birth rate following fresh embryo transfer (ET), and whether LH and PROG have an impact on EMT.

Methods

A total of 2,260 normogonadotrophic women were treated with a GnRH agonist for in vitro fertilization (IVF)/intracytoplasmic sperm injection. Patients with advanced age and poor ovarian reserve were excluded. The levels of LH, PROG, and EMT on the hCG trigger day were divided into binary variables, respectively, by the cutoff values, and which were obtained based on receiver operating characteristic curve analysis of live birth among LH, PROG and EMT levels on the hCG trigger day, respectively. Multivariate binary logistic regression was used to confirm the role of LH, PROG, and EMT on the live birth, and stratified analysis was used to determine whether LH and PROG have an impact on EMT.

Results

EMT and LH were protective factors for live births, with odds ratios (OR) of 1.11 [95% confidence interval (CI): 1.066–1.157] and 1.696 (95% CI: 1.345–2.139), respectively. However, PROG was a risk factor for live birth, with an OR of 0.635 (95% CI: 0.526–0.766). The hierarchical cross-table analysis indicated that EMT had no significant difference for live birth in the combination of low LH and high PROG group. In the other subgroups, thick EMT was associated with a higher live birth rate (P<0.05).

Conclusions

On hCG trigger day, EMT, LH, and PROG all were independent factors that affected the live birth of fresh ETs. Thick EMT can significantly increase the live birth rate. However, multivariate logistic regression analysis showed that EMT does not affect the live birth rate in combination of low LH and high PROG environment.

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.

Therapeutic Potentials of Low-Dose Tacrolimus for Aberrant Endometrial Features in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a major anovulatory infertility affecting a great proportion of women of childbearing age and is associated with obesity, insulin resistance and chronic inflammation. Poor endometrial receptivity and recurrent implantation failure are major hurdles to the establishment of pregnancy in women with PCOS. The accumulating body of evidence obtained from experimental and clinical studies suggests a link between inherent adaptive and innate immune irregularities and aberrant endometrial features in PCOS. The use of conventional therapeutic interventions such as lifestyle modification, metformin and ovarian stimulation has achieved limited clinical success in restoring ovulation and endometrial receptivity in women with PCOS. Unlike other immunosuppressive drugs prescribed in the clinical management of autoimmune and inflammatory disorders that may have deleterious effects on fertility and fetal development, preclinical studies in mice and in women without PCOS but with repeated implantation failure revealed potential therapeutic benefits for the use of low-dose tacrolimus in treating female infertility. Improved systemic and ovarian immune functions, endometrial progesterone receptor and coreceptor expressions and uterine vascular adaptation to pregnancy were among features of enhanced progesterone-receptor sensitivity in the low-dose tacrolimus-treated mouse model of the disease. In this review, we have compiled available experimental and clinical data in literature on endometrial progesterone resistance and current therapeutic options, as well as mechanisms of actions and reported outcomes relevant to the potential therapeutic benefits for the use of low-dose tacrolimus in treating PCOS-associated female infertility.

Endometrial receptivity and embryo implantation in carnivores-commonalities and differences with other mammalian species

Endometrial receptivity and embryo implantation processes are a major point of pregnancy failure in many mammalian species, including humans. Although reproductive biology in many carnivore species remains enigmatic, the few that have been studied so far are invaluable comparative models. The goals of this review are to (1) summarize current data on the mechanisms involved in uterine receptivity and embryo implantation in carnivores, including commonalities and differences with other mammalian species and (2) identify research priorities to better understand a key phenomenon in a critical group of mammals. Besides unique reproductive traits in some carnivores (induced vs. spontaneous ovulation in cats, ovulation at the germinal vesicle stage in dogs), preimplantation embryo development is comparable with other orders. However, the timing of implantation varies, especially in species having an embryonic diapause. Mechanisms involved in endometrial receptivity and decidualization still remain to be fully understood, but specific markers have already been identified. Importantly, the use of endogenous hormones to control the ovarian activity may impact endometrial receptivity and subsequent embryo implantation. Next, research efforts should take advantage of advanced technologies to further study embryo implantation in carnivores and to provide more relevant models to reproductive medicine or for the conservation of rare and endangered species.

Huperzine-A administration recovers rat ovary function after sympathetic stress

Chronic cold stress affects ovarian morphology and impairs fertility in rats. It causes an ovarian polycystic ovary (PCOS)-like phenotype, which resembles PCOS in women. The mechanism of cold stress action involves increased ovarian noradrenaline (NA) levels, which remain elevated after cessation of cold stress. By contrast, ovarian acetylcholine (ACh) levels are only transiently elevated and returned to control levels after a 28-day post stress period. Because ACh can exert trophic actions in the ovary, we hypothesised that a sustained elevation of ovarian ACh levels by intraovarian exposure to the ACh-esterase blocker huperzine-A (Hup-A) may interfere with cold stress-induced ovarian changes. This possibility was examined in female Sprague-Dawley rats exposed to cold stress (4°C for 3 h day^-1 for 28 days), followed by a 28-day period without stress. To elevate ACh, in a second group Hup-A was delivered into the ovary of cold stress-exposed rats. A third group was not exposed to cold stress. As expected, cold stress elevated ovarian NA, reduced the number of corpora lutea and increased the number of follicular cysts. It increased plasma testosterone and oestradiol but decreased plasma levels of progesterone. In the Hup-A group, ovarian levels of both, NA and ACh, were elevated, there were fewer cysts and normal testosterone and oestradiol plasma levels were found. However, progesterone levels remained low. Most likely, low progesterone was associated with impaired mating behaviour and low pregnancy rate. We propose that elevated intraovarian levels of ACh are involved in the rescue of ovarian function, opening a target to control ovarian diseases affecting follicular development.