Extracellular signal-regulated kinase 1/2 signaling pathway is required for endometrial decidualization in mice and human

Rapid generation of functional nanovesicles from human trophectodermal cells for embryo attachment and outgrowth

Extracellular vesicles (EVs) are important mediators of embryo attachment and outgrowth critical for successful implantation. While EVs have garnered immense interest in their therapeutic potential in assisted reproductive technology by improving implantation success, their large-scale generation remains a major challenge. Here, we report a rapid and scalable production of nanovesicles (NVs) directly from human trophectoderm cells (hTSCs) via serial mechanical extrusion of cells; these NVs can be generated in approximately 6 h with a 20-fold higher yield than EVs isolated from culture medium of the same number of cells. NVs display similar biophysical traits (morphologically intact, spherical, 90-130 nm) to EVs, and are laden with hallmark players of implantation that include cell-matrix adhesion and extracellular matrix organisation proteins (ITGA2/V, ITGB1, MFGE8) and antioxidative regulators (PRDX1, SOD2). Functionally, NVs are readily taken up by low-receptive endometrial HEC1A cells and reprogram their proteome towards a receptive phenotype that support hTSC spheroid attachment. Moreover, a single dose treatment with NVs significantly enhanced adhesion and spreading of mouse embryo trophoblast on fibronectin matrix. Thus, we demonstrate the functional potential of NVs in enhancing embryo implantation and highlight their rapid and scalable generation, amenable to clinical utility.

Enhancing endometrial receptivity: the roles of human chorionic gonadotropin in autophagy and apoptosis regulation in endometrial stromal cells

Inadequate endometrial receptivity often results in embryo implantation failure and miscarriage. Human chorionic gonadotropin (hCG) is a key signaling molecule secreted during early embryonic development, which regulates embryonic maternal interface signaling and promotes embryo implantation. This study aimed to examine the impact of hCG on endometrial receptivity and its underlying mechanisms. An exploratory study was designed, and endometrial samples were obtained from women diagnosed with simple tubal infertility or male factor infertile (n = 12) and recurrent implantation failure (RIF, n = 10). Using reverse transcription-quantitative PCR and western blotting, luteinizing hormone (LH)/hCG receptor (LHCGR) levels and autophagy were detected in the endometrial tissues. Subsequently, primary endometrial stromal cells (ESCs) were isolated from these control groups and treated with hCG to examine the presence of LHCGR and markers of endometrial receptivity (HOXA10, ITGB3, FOXO1, LIF, and L-selectin ligand) and autophagy-related factors (Beclin1, LC3, and P62). The findings revealed that the expressions of receptivity factors, LHCGR, and LC3 were reduced in the endometrial tissues of women with RIF compared with the control group, whereas the expression of P62 was elevated. The administration of hCG to ESCs specifically activated LHCGR, stimulating an increase in the endometrial production of HOXA10, ITGB3, FOXO1, LIF and L-selectin ligands. Furthermore, when ESCs were exposed to 0.1 IU/mL hCG for 72 h, the autophagy factors Beclin1 and LC3 increased within the cells and P62 decreased. Moreover, the apoptotic factor Bax increased and Bcl-2 declined. However, when small interfering RNA was used to knock down LHCGR, hCG was less capable of controlling endometrial receptivity and autophagy molecules in ESCs. In addition, hCG stimulation enhanced the phosphorylation of ERK1/2 and mTOR proteins. These results suggest that women with RIF exhibit lower levels of LHCGR and compromised autophagy function in their endometrial tissues. Thus, hCG/LHCGR could potentially improve endometrial receptivity by modulating autophagy and apoptosis.

Applying a novel kinomics approach to study decidualization and the effects of antigestagens using a canine model†

Maternal decidual cells are crucial for the maintenance of canine pregnancy as they are the only cells expressing the nuclear progesterone (P4) receptor (PGR) in the placenta. Interfering with P4/PGR signaling adversely affects decidual cells and terminates pregnancy. Although immortalized dog uterine stromal (DUS) cells can be decidualized in vitro using cAMP, the involvement of cAMP-dependent kinases in canine decidualization had not been investigated. Therefore, the present project investigated changes in the kinome of DUS cells following in vitro decidualization, using the serine/threonine kinase (STK) PamChip assay (PamGene). Decidualization led to a predicted activation of 85 STKs in DUS cells, including protein kinase (PK) A, PKC, extracellular signal-regulated kinase (ERK)1/2 and other mitogen-activated protein kinases (MAPKs), calcium/calmodulin-dependent protein kinases (CAMKs), and Akt1/2. In addition, blocking PGR with type 2 antigestagens (aglepristone or mifepristone) decreased the activity of virtually all kinases modulated by decidualization. The underlying transcriptional effects were inferred from comparison with available transcriptomic data on antigestagen-mediated effects in DUS cells. In targeted studies, interfering with PKA or MAPK kinase (MEK)1/2 resulted in downregulation of important decidualization markers (e.g., insulin-like growth factor 1 (IGF1), prostaglandin E2 synthase (PTGES), prolactin receptor (PRLR), PGR, and prostaglandin-endoperoxide synthase 2 (PTGS2/COX2)). Conversely, blocking of PKC decreased the mRNA availability of IGF1, PGR, and PTGS2, but not of PTGES and PRLR. Moreover, suppressing PKA decreased the phosphorylation of the transcription factors cJUN and CREB, whereas blocking of PKC affected only cJUN. This first kinomics analysis to target decidualization showed an increased activity of a wide range of STKs, which could be hindered by disrupting P4/PGR signaling. Decidualization appears to be regulated in a kinase-dependent manner, with PKA and PKC evoking different effects.

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.

Polycystic ovary syndrome and adverse pregnancy outcomes: potential role of decidual function

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting fertility and mental health among women of reproductive age. In addition to anovulation and hyperandrogenism, patients also experience metabolic issues, such as insulin resistance, obesity, and dyslipidemia, as well as chronic low-grade inflammation throughout the body. Recent studies have shown that even with assisted reproductive technology to treat anovulatory issues, patients with PCOS still have higher rates of adverse pregnancy outcomes and abortion compared to normal pregnancies. These findings suggest that PCOS may impair the endometrium and disrupt the onset and maintenance of healthy pregnancies. Decidualization is a crucial step in the process of healthy pregnancy, during which endometrial stromal cells (ESCs) differentiate into secretory decidual stromal cells (DSCs) regulated by hormones and local metabolism. This article comprehensively reviews the pathological processes of PCOS and the mechanisms involved in its impaired decidualization. In addition, we explore how PCOS increases the incidence of adverse pregnancy outcomes (APO). By gaining a better understanding of the adverse effects of PCOS on pregnancy and its specific mechanisms, we hope to provide a theoretical basis for reducing APO and improving the live birth rate among women with PCOS.

Research progress on the STAT signaling pathway in pregnancy and pregnancy-associated disorders

Signal transducer and activator of transcription (STAT) proteins, pivotal regulators of signaling cascades, undergo activation in response to the stimulation of cytokines and growth factors, and participate in biological processes, including inflammation, immune responses, cell proliferation, and differentiation. During the process of pregnancy, STAT signaling is involved in regulating embryonic implantation, endometrial decidualization, and establishing and maintaining maternal-fetal immune tolerance. Increasing evidence suggests that aberrant STAT signaling contributes to the occurrence and development of pregnancy disorders, including repeated implantation failure (RIF), preeclampsia (PE), recurrent spontaneous abortion (RSA), preterm birth (PTB) and gestational diabetes mellitus (GDM). Elucidating the molecular mechanisms of the STAT signaling pathway holds promise for further understanding the establishment and maintenance of normal pregnancy, and thereby providing potent targets and strategic avenues for the prevention and management of ailments associated with pregnancy. In this review, we summarized the roles of the STAT signaling pathway and its related regulatory function in embryonic implantation, endometrial decidualization, and maternal-fetal immune tolerance. In conclusion, in-depth research on the mechanism of the STAT signaling pathway not only enhances our understanding of normal pregnancy processes but also offers STAT-based therapeutic approaches to protect women from the burden of pregnancy-related disorders.

Temporal changes in cyclinD-CDK4/CDK6 and cyclinE-CDK2 pathways: implications for the mechanism of deficient decidualization in an immune-based mouse model of unexplained recurrent spontaneous abortion

BACKGROUND

Deficient endometrial decidualization has been associated with URSA. However, the underlying mechanism is poorly understood. This study aimed to investigate the temporal cytokine changes and the involvement of CyclinD-CDK4/6 and CyclinE-CDK2 pathways in the regulation of the G1 phase of the cell cycle during decidualization in a murine model of URSA.

METHODS

Serum and decidual tissues of mice were collected from GD4 to GD8. The embryo resorption and abortion rates were observed on GD8 and the decidual tissue status was assessed. In addition, PRL, Cyclin D, CDK6, CDK4, Cyclin E, CDK2 expression in mice were measured.

RESULTS

URSA mice showed high embryo resorption rate and PRL, Cyclin D, Cyclin E CDK2, CDK4, CDK6 down-regulation during decidualization. The hyperactivated Cyclin D-CDK4/CDK6 and cyclin E/CDK2 pathways inhibit the decidualization process and leading to deficient decidualization.

CONCLUSION

Insufficient decidualization is an important mechanism of URSA. which is related to the decrease of Cyclin D、Cyclin E、 CDK2、CDK4 and CDK6 in decidualization process of URSA.

Loss of MIG-6 results in endometrial progesterone resistance via ERBB2

Female subfertility is highly associated with endometriosis. Endometrial progesterone resistance is suggested as a crucial element in the development of endometrial diseases. We report that MIG-6 is downregulated in the endometrium of infertile women with endometriosis and in a non-human primate model of endometriosis. We find ERBB2 overexpression in the endometrium of uterine-specific Mig-6 knockout mice (Pgr^cre/+Mig-6^f/f; Mig-6^d/d). To investigate the effect of ERBB2 targeting on endometrial progesterone resistance, fertility, and endometriosis, we introduce Erbb2 ablation in Mig-6^d/d mice (Mig-6^d/dErbb2^d/d mice). The additional knockout of Erbb2 rescues all phenotypes seen in Mig-6^d/d mice. Transcriptomic analysis shows that genes differentially expressed in Mig-6^d/d mice revert to their normal expression in Mig-6^d/dErbb2^d/d mice. Together, our results demonstrate that ERBB2 overexpression in endometrium with MIG-6 deficiency causes endometrial progesterone resistance and a nonreceptive endometrium in endometriosis-related infertility, and ERBB2 targeting reverses these effects.

Female subfertility is highly associated with endometriosis. Here the authors show that progesterone-induced MIG-6 is reduced in endometrium of infertile women and non-human primates with endometriosis, and in a mouse model find that Erbb2 is the key mediator of Mig-6 loss induced endometriosis-related infertility.

Fructose-1,6-bisphosphate prevents pregnancy loss by inducing decidual COX-2+ macrophage differentiation

Decidualization is an intricate biological process in which extensive remodeling of the endometrium occurs to support the development of an implanting blastocyst. However, the immunometabolic mechanisms underlying this process are still largely unknown. We found that the decidualization process is accompanied by the accumulation of fructose-1,6-bisphosphate (FBP). The combination of FBP with pyruvate kinase M stimulated IL-27 secretion by endometrial stromal cells in an ERK/c-FOS-dependent manner. IL-27 induced decidual COX-2⁺ M2-like macrophage differentiation, which promotes decidualization, trophoblast invasion, and maternal-fetal tolerance. Transfer of Ptgs2⁺/COX-2⁺ macrophages prevented fetal loss in Il27ra-deleted pregnant mice. FBP levels were low in plasma and decidual tissues of patients with unexplained recurrent spontaneous abortion. In therapeutic studies, FBP supplementation significantly improved embryo loss by up-regulation of IL-27-induced COX-2⁺ macrophage differentiation in a mouse model of spontaneous abortion. These findings collectively provide a scientific basis for a potential therapeutic strategy to prevent pregnancy loss.

Shp2 in uterine stromal cells critically regulates on time embryo implantation and stromal decidualization by multiple pathways during early pregnancy

Approximately 75% of failed pregnancies are considered to be due to embryo implantation failure or defects. Nevertheless, the explicit signaling mechanisms governing this process have not yet been elucidated. Here, we found that conditional deletion of the Shp2 gene in mouse uterine stromal cells deferred embryo implantation and inhibited the decidualization of stromal cells, which led to embryonic developmental delay and to the death of numerous embryos mid-gestation, ultimately reducing female fertility. The absence of Shp2 in stromal cells increased the proliferation of endometrial epithelial cells, thereby disturbing endometrial epithelial remodeling. However, Shp2 deletion impaired the proliferation and polyploidization of stromal cells, which are distinct characteristics of decidualization. In human endometrial stromal cells (hESCs), Shp2 expression gradually increased during the decidualization process. Knockout of Shp2 blocked the decidual differentiation of hESCs, while Shp2 overexpression had the opposite effect. Shp2 knockout inhibited the proliferation of hESCs during decidualization. Whole gene expression profiling analysis of hESCs during the decidualization process showed that Shp2 deficiency disrupted many signaling transduction pathways and gene expression. Analyses of hESCs and mouse uterine tissues confirmed that the signaling pathways extracellular regulated protein kinases (ERK), protein kinase B (AKT), signal transducer and activator of transcription 3 (STAT3) and their downstream transcription factors CCAAT/enhancer binding protein β (C/EBPβ) and Forkhead box transcription factor O1 (FOXO-1) were involved in the Shp2 regulation of decidualization. In summary, these results demonstrate that Shp2 plays a crucial role in stromal decidualization by mediating and coordinating multiple signaling pathways in uterine stromal cells. Our discovery possibly provides a novel key regulator of embryo implantation and novel therapeutic target for pregnancy failure.

Embryo implantation includes the establishment of uterine receptivity, blastocyst attachment, and endometrial decidualization. Disorders of this process usually induce pregnancy failure, resulting in women infertility. But the signaling mechanisms governing this process remain unclear. Here, using gene knockout mouse model and human endometrial stromal cells (hESCs), we identified a novel key regulator of embryo implantation, Shp2, which plays a crucial role in stromal decidualization by mediating and coordinating multiple signaling pathways in uterine stromal cells. Shp2 deficiency in mouse uterine stromal cells inhibited the uterine stromal decidualization, disturbing embryo implantation and embryonic development, ultimately reducing female fertility. The absence of Shp2 in hESCs also blocked the decidual differentiation. Our findings not only promote the understanding of peri-implantation biology, but may also provide a critical target for more effectively diagnose and/or treat women with recurrent implantation failure or early pregnancy loss.

Progesterone triggers Rho kinase-cofilin axis during in vitro and in vivo endometrial decidualization

STUDY QUESTION

Can a combination of the focussed protein kinase assays and a wide-scale proteomic screen pinpoint novel, clinically relevant players in decidualization in vitro and in vivo?

SUMMARY ANSWER

Rho-dependent protein kinase (ROCK) activity is elevated in response to the combined treatment with progesterone and 8-Br-cAMP during in vitro decidualization, mirrored by increase of ROCK2 mRNA and protein levels and the phosphorylation levels of its downstream target Cofilin-1 (CFL1) in secretory versus proliferative endometrium.

WHAT IS KNOWN ALREADY

Decidualization is associated with extensive changes in gene expression profile, proliferation, metabolism and morphology of endometrium, yet only a few underlying molecular pathways have been systematically explored. In vitro decidualization of endometrial stromal cells (ESCs) can be reportedly induced using multiple protocols with variable physiological relevance. In our previous studies, cyclic AMP (cAMP)/cAMP-dependent protein kinase (PKA)/prolactin axis that is classically upregulated during decidualization showed dampened activation in ESCs isolated from polycystic ovary syndrome (PCOS) patients as compared to controls.

STUDY DESIGN, SIZE, DURATION

In vitro decidualization studies were carried out in passage 2 ESCs isolated from controls (N = 15) and PCOS patients (N = 9). In parallel, lysates of non-cultured ESCs isolated from proliferative (N = 4) or secretory (N = 4) endometrial tissue were explored. The observed trends were confirmed using cryo-cut samples of proliferative (N = 3) or secretory endometrium (N = 3), and in proliferative or secretory full tissue samples from controls (N = 8 and N = 9, respectively) or PCOS patients (N = 10 for both phases).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The activities of four target kinases were explored using kinase-responsive probes and selective inhibitors in lysates of in vitro decidualized ESCs and non-cultured ESCs isolated from tissue at different phases of the menstrual cycle. In the latter lysates, wide-scale proteomic and phosphoproteomic studies were further carried out. ROCK2 mRNA expression was explored in full tissue samples from controls or PCOS patients. The immunofluorescent staining of phosphorylated CFL1 was performed in full endometrial tissue samples, and in the in vitro decidualized fixed ESCs from controls or PCOS patients. Finally, the cellular migration properties were explored in live in vitro decidualized ESCs.

MAIN RESULTS AND THE ROLE OF CHANCE

During in vitro decidualization, the activities of PKA, protein kinase B (Akt/PKB), and ROCK are increased while the activity of casein kinase 2 (CK2) is decreased; these initial trends are observable after 4-day treatment (P < 0.05) and are further augmented following the 9-day treatment (P < 0.001) with mixtures containing progesterone and 8-Br-cAMP or forskolin. The presence of progesterone is necessary for activation of ROCK, yet it is dispensable in the case of PKA and Akt/PKB; in comparison to controls, PCOS patient-derived ESCs feature dampened response to progesterone. In non-cultured ESCs isolated from secretory vs proliferative phase tissue, only activity of ROCK is increased (P < 0.01). ROCK2 protein levels are slightly elevated in secretory versus proliferative ESCs (relative mean standard deviation < 50%), and ROCK2 mRNA is elevated in mid-secretory versus proliferative full tissue samples (P < 0.05) obtained from controls but not PCOS patients. Activation of ROCK2 downstream signalling results in increase of phospho-S3 CFL1 in secretory endometrium (P < 0.001) as well as in vitro decidualized ESCs (P < 0.01) from controls but not PCOS patients. ROCK2-triggered alterations in the cytoskeleton are reflected by the significantly decreased motility of in vitro decidualized ESCs (P < 0.05).

LARGE SCALE DATA

Proteomic and phosphoproteomic data are available via ProteomeXchange with identifier PXD026243.

LIMITATIONS, REASONS FOR CAUTION

The number of biological samples was limited. The duration of protocol for isolation of non-cultured ESCs from tissue can potentially affect phosphorylation pathways in cells, yet the possible artefacts were minimized by the identical treatment of proliferative and secretory samples.

WIDER IMPLICATIONS OF THE FINDINGS

The study demonstrated the benefits of combining the focussed kinase activity assay with wide-scale phosphoproteomics and showed the need for detailed elaboration of the in vitro decidualization protocols. ROCK was identified as the novel target of interest in decidualization, which requires closer attention in further studies-including the context of decidualization-related subfertility and infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Estonian Ministry of Education and Research, and the Estonian Research Council (PRG1076, PRG454, PSG230 and PSG608), Enterprise Estonia (EU48695), Horizon 2020 innovation grant (ERIN, Grant no. EU952516) of the European Commission, the COMBIVET ERA Chair, H2020-WIDESPREAD-2018-04 (Grant agreement no. 857418), the Academy of Finland (Project grants 315921 and 321763), the Finnish Medical Foundation and The Sigrid Juselius Foundation. The authors confirm that they have no conflict of interest with respect to the content of this article.

Psychological Stress and Functional Endometrial Disorders: Update of Mechanism Insights

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

Treatment of pregnancies complicated by intrauterine growth restriction with nitric oxide donors increases placental expression of Epidermal Growth Factor-Like Domain 7 and improves fetal growth: A pilot study

Intrauterine growth restriction (IUGR) is a pathological condition of pregnancy with high perinatal mortality and morbidity, characterized by inadequate fetal growth associated to altered maternal hemodynamics with impaired uteroplacental blood flow and placental insufficiency. To date, iatrogenic premature delivery remains the elective therapeutic strategy. However, in recent years the possibility of a therapeutic approach with vasodilators and myorelaxants, such as nitric oxide (NO) donors, has gained interest. NO controls many endothelial cell functions, including angiogenesis and vascular permeability, by regulating the expression of angiogenic factors, such as Vascular Endothelial Growth Factor. In the present study, we investigated if treatment of pregnancies complicated by IUGR with NO donors affects the expression of Epidermal Growth Factor-Like Domain 7 (EGFL7), a secreted endothelial factor, previously demonstrated to be expressed by both endothelial and trophoblast cells and involved in proper placental development. NO donor treatment induced placental levels of EGFL7 and, in association with oral fluids, significantly improved fetal growth. Ex vivo experiments confirmed that NO donors increased expression and secretion of EGFL7 by villous explants. To specifically investigate the potential response of trophoblast cells to NO, we treated HTR8-sVneo cells with NO donors and observed induction of EGFL7 expression. Altogether, our findings indicate that NO induces endothelial and trophoblast expression of EGFL7 in the placenta and improves fetal growth, suggesting a correlation between placental levels of EGFL7 and pregnancy outcome.

The Relevant Participation of Prolactin in the Genesis and Progression of Gynecological Cancers

Prolactin (PRL) is a hormone produced by the pituitary gland and multiple non-pituitary sites, vital in several physiological processes such as lactation, pregnancy, cell growth, and differentiation. However, PRL is nowadays known to have a strong implication in oncogenic processes, making it essential to delve into the mechanisms governing these actions. PRL and its receptor (PRLR) activate a series of effects such as survival, cellular proliferation, migration, invasion, metastasis, and resistance to treatment, being highly relevant in developing certain types of cancer. Because women produce high levels of PRL, its influence in gynecological cancers is herein reviewed. It is interesting that, other than the 23 kDa PRL, whose mechanism of action is endocrine, other variants of PRL have been observed to be produced by tumoral tissue, acting in a paracrine/autocrine manner. Because many components, including PRL, surround the microenvironment, it is interesting to understand the hormone's modulation in cancer cells. This work aims to review the most important findings regarding the PRL/PRLR axis in cervical, ovarian, and endometrial cancers and its molecular mechanisms to support carcinogenesis.

miR223-3p, HAND2, and LIF expression regulated by calcitonin in the ERK1/2-mTOR pathway during the implantation window in the endometrium of mice

PROBLEM

Approximately one-third of infertility cases are related to the female partner, and implantation failure is the primary reason for female infertility. The current research was established to assess the impact of calcitonin on endometrial receptivity.

METHODS OF STUDY

64 female BALB/c mice were assigned to 2 groups as follows: mice with regular ovarian cycle and mice with stimulated ovarian cycle. The two groups were further divided into four subgroups as follows: control (Ctrl), calcitonin (CT), pp242, and CT + pp242 groups. Calcitonin and pp242 were injected on days 3, 4, and 5 of pregnancy. On day 5 of gestation, all of the animals were sacrificed, and their uterine was removed for the morphological analysis, as well as the expression assessment genes and proteins.

RESULTS

The results demonstrated that ovarian stimulation increased the rate of phosphorylation of ERK1/2 and mTOR proteins, and resulted in the upregulation of miR-223-3p. The administration of calcitonin also elevated the expression levels of LIF and HAND2 gene in both regular ovarian and ovarian-stimulated cycles. In ovarian-stimulated groups, the administration of calcitonin led to a decrease in the expression of miR-223-3p. Calcitonin administration also markedly increased the phosphorylation of 4EBP1 and ERK1/2 in the regular ovarian cycle.

CONCLUSION

It seems that calcitonin is capable of enhancing the endometrial receptivity of the uterine, thereby the overexpression of HAND2 and LIF and downregulation of miR-223-3p through the ERK1/2-mTOR signaling pathway.

WNK1 regulates uterine homeostasis and its ability to support pregnancy

WNK1 (with no lysine [K] kinase 1) is an atypical kinase protein ubiquitously expressed in humans and mice. A mutation in its encoding gene causes hypertension in humans, which is associated with abnormal ion homeostasis. WNK1 is critical for in vitro decidualization in human endometrial stromal cells, thereby demonstrating its importance in female reproduction. Using a mouse model, WNK1 was ablated in the female reproductive tract to define its in vivo role in uterine biology. Loss of WNK1 altered uterine morphology, causing endometrial epithelial hyperplasia, adenomyotic features, and a delay in embryo implantation, ultimately resulting in compromised fertility. Combining transcriptomic, proteomic, and interactomic analyses revealed a potentially novel regulatory pathway whereby WNK1 represses AKT phosphorylation through protein phosphatase 2A (PP2A) in endometrial cells from both humans and mice. We show that WNK1 interacted with PPP2R1A, the alpha isoform of the PP2A scaffold subunit. This maintained the levels of PP2A subunits and stabilized its activity, which then dephosphorylated AKT. Therefore, loss of WNK1 reduced PP2A activity, causing AKT hypersignaling. Using FOXO1 as a readout of AKT activity, we demonstrate that there was escalated FOXO1 phosphorylation and nuclear exclusion, leading to a disruption in the expression of genes that are crucial for embryo implantation.

Blastocyst-induced ATP release from luminal epithelial cells initiates decidualization through the P2Y2 receptor in mice

Embryo implantation involves a sterile inflammatory reaction that is required for the invasion of the blastocyst into the decidua. Adenosine triphosphate (ATP) released from stressed or injured cells acts as an important signaling molecule to regulate many key physiological events, including sterile inflammation. We found that the amount of ATP in the uterine luminal fluid of mice increased during the peri-implantation period, and this depended on the presence of an embryo. We further showed that the release of ATP from receptive epithelial cells was likely stimulated by lactate released from the blastocyst through connexin hemichannels. The ATP receptor P2y2 was present on uterine epithelial cells during the preimplantation period and increased in the stromal cells during the time at which decidualization began. Pharmacological inhibition of P2y2 compromised decidualization and implantation. ATP-P2y2 signaling stimulated the phosphorylation of Stat3 in uterine luminal epithelial cells and the expression of early growth response 1 (Egr1) and prostaglandin-endoperoxide synthase 2 (Ptgs2, also known as Cox-2), all of which are required for decidualization and/or implantation, in stromal cells. Short exposure to high concentrations of ATP promoted decidualization of primary stromal cells, but longer exposures or lower ATP concentrations did not. The expression of genes encoding ATP-degrading ectonucleotidases increased in the decidua during the peri-implantation period, suggesting that they may limit the duration of the ATP signal. Together, our results indicate that the blastocyst-induced release of ATP from uterine epithelial cells during the peri-implantation period may be important for the initiation of stromal cell decidualization.

Bisphenol A-induced mechanistic impairment of decidualization

Decidualization is a crucial precedent to embryo implantation, as its impairment is a major contributor to female infertility and pregnancy complications. Unraveling the molecular mechanisms involved in the impairment of decidualization has been a subject of interest in the field of reproductive medicine. Evidence from several experimental settings show that exposure to bisphenol A (BPA), an endocrine-disrupting chemical, affects the expression of several molecules that are involved in decidualization. Both low and high doses of BPA impair decidualization through the dysregulation of estrogen (ER) and progesterone (PR) receptors. Exposure to low doses of BPA leads to decreased levels and activities of several antioxidant enzymes, increased activity of endothelial nitric oxide synthase (eNOS), and increased production of nitric oxide (NO) via the upregulation of ER and PR. Consequently, oxidative stress is induced and decidualization becomes impaired. On the other hand, exposure to high doses of BPA downregulates ER and PR and impairs decidualization through two distinct pathways. One is through the upregulation of early growth response-1 (EGR1) via increased phosphorylation of extracellular signal-regulated protein kinases 1 and 2; and the other is through a reduced serum glucocorticoid-induced kinase-1 (SGK1)-mediated downregulation of epithelial sodium channel-α and the induction of oxidative stress. Thus, regardless of the dose, BPA can impair decidualization to trigger infertility and pregnancy complications. This warrants the need to adopt lifestyles that will decrease the tendency of getting exposed to BPA.

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.

Shared Molecular Features Linking Endometriosis and Obstetric Complications

Recent epidemiological research has shown the increased risk of adverse pregnancy outcomes in women with endometriosis compared with the general population. The aim of this review is to explore common pathophysiologic mechanisms between endometriosis and obstetric complications. A computerized literature search was performed to identify relevant studies. The search covered the period between January 2008 and October 2018. One of the potential mechanisms driving the initiation and progression of endometriosis is the accumulation of a variety of epigenetic changes in endometrial cells. Epigenetic control of gene expression which is considered to be responsible for the development of endometriosis is commonly seen in patients with preeclampsia, small for gestational age (SGA), or preterm birth. DLX5 and GATA3, paternally imprinted genes, and CDKN1C, a maternally imprinted gene, were aberrantly expressed in placenta tissues of the preeclampsia; CDKN1C, the growth inhibitor gene, was upregulated in human SGA placentas; and hypomethylation of PTGER2 would be associated with preterm birth. Preeclampsia, SGA, or preterm birth may share common epigenetic alterations with endometriosis, which raises the possibility that the occurrence of two conditions might be nonrandom. To date, however, there is a lack of evidence that links endometriosis and other obstetric complications, such as postpartum hemorrhage or placental abruption, at the epigenetic level. In conclusion, epigenetic changes may be a common hallmark of two conditions: endometriosis and obstetrical complications, such as preeclampsia, SGA, or preterm birth.

ATP mediates the interaction between human blastocyst and endometrium

OBJECTIVE

Embryo implantation needs a reciprocal interaction between competent embryo and receptive endometrium. Adenosine triphosphate (ATP) produced by stressed or injured cells acts as an important signalling molecule. This study aims to investigate whether adenosine triphosphate (ATP) plays an important role in the dialogue of human blastocyst-endometrium.

MATERIALS AND METHODS

The concentration of lactate was analysed in culture medium from human embryos collected from in vitro fertilization patients. Extracellular ATP was measured by ATP Bioluminescent Assay Kit. Ishikawa cells and T-HESCs were treated with ATP, ATP receptor antagonist, ATP hydrolysis enzyme or inhibitors of ATP metabolic enzymes. The levels of gene expression were evaluated by real-time PCR and immunoassay.

RESULTS

We showed that injured human endometrial epithelial cells could rapidly release ATP into the extracellular environment as an important signalling molecule. In addition, blastocyst-derived lactate induces the release of non-lytic ATP from human endometrial receptive epithelial cells via connexins. Extracellular ATP stimulates the secretion of IL8 from epithelial cells to promote the process of in vitro decidualization. Extracellular ATP could also directly promote the decidualization of human endometrial stromal cells via P2Y-purinoceptors. More importantly, the supernatants of injured epithelial cells clearly induce the decidualization of stromal cells in time-dependent manner.

CONCLUSION

Our results suggest that ATP should play an important role in human blastocyst-endometrium dialogue for the initiation of decidualization.

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

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

Molecular Signaling Regulating Endometrium-Blastocyst Crosstalk

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

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.

Administration of dexamethasone disrupts endometrial receptivity by alteration of expression of miRNA 223, 200a, LIF, Muc1, SGK1, and ENaC via the ERK1/2-mTOR pathway

Successful implantation of embryos requires endometrial receptivity. Glucocorticoids are one of the factors influencing the implantation window. In this study, 40 female BALB/c mice were used to study the impacts of dexamethasone administration on endometrial receptivity markers during implantation window. The mice mated and were randomly divided into four groups: control (vehicle), dexamethasone (100 μg/kg, IP), PP242 (30 mg/kg, IP), and dexamethasone + PP242 (Dex + PP242). On the Day 4th and 5th of gestation, mice received their respective treatments and were killed on the 5th day. To assess the expression of Muc1, leukemia inflammatory inhibitor (LIF), serum/glucocorticoid-inducible kinase 1 (SGK1), epithelial Na+ channel (ENaC), miRNA 200a, and miRNA 223-3p in the endometrium real-time polymerase chain reaction was performed. Furthermore, using Western blot analysis protein expressions of extracellular signal-regulated kinase 1/2 (ERK1/2), mammalian target of rapamycin (mTOR), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) were evaluated. Periodic Acid-Schiff staining was used to examine the histomorphological changes of the uterus. According to the results dexamethasone declined the expression of LIF, whereas upregulated expression of Muc1, SGK1, ENaC mRNA, miRNA 200a, and miRNA 223-3p in the endometrium. In addition, PP242, an mTOR inhibitor, induced mRNA expression of Muc1, miRNA200a, and miRNa223-3p whereas it declined the expression of LIF. Moreover, activity of the ERK1/2-mTOR pathway in the endometrial cells was deterred by dexamethasone and PP242. Nonstop epithelium proliferation and elevated surface glycoproteins layer on epithelium of dexamethasone and/or PP242-received groups were divulged through histochemical analysis. According to the above mentioned results, uterine receptivity during implantation period was declined by dexamethasone, at least in part, through modulation of involved genes in endometrial receptivity and inhibition of the ERK1/2-mTOR pathway.

The effect of fludrocortisone on the uterine receptivity partially mediated by ERK1/2-mTOR pathway

Implantation of embryos needs endometrial receptivity. Mineralocorticoids is one of the causes influencing the implantation window. This study targeted to evaluation fludrocortisone different properties on endometrial receptivity. The objective of this study was to assess whether treatment with fludrocortisone could impact the expression of diverse genes and proteins that are involved in uterine receptivity in mice. In this study, 40 female adult BALB/c mice were used. The samples were allocated to four groups of ten. Control group (C) received: vehicle; fludrocortisone group (FCA): received 1.5 mg/kg fludrocortisone; PP242 group (PP242): received 30 mg/kg PP242; fludrocortisone+PP242 group (FCA+PP242): received fludrocortisone and PP242. Mice were killed on window implantation day after mating and confirmed pregnancy. The endometrial epithelium of mouse was collected to assess mRNA expression of leukemia inhibitory factor (LIF), mucin-1 (MUC1), heparin-binding epidermal growth factor (HB-EGF), (Msx.1), miRNA Let-7a, and miRNA 223-3p as well as protein expression of extracellular signal-regulated kinase 1/2 (ERK1/2), mammalian target of rapamycin (mTOR), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) in the uterine using real-time PCR and western blot, respectively. In comparison with the control group, fludrocortisone administration upregulated the expression of LIF, HB-EGF, Msx.1, miRNA Let-7a, ERK1/2, and mTOR in the epithelial endometrium. The PP242-treated group demonstrated a significant rise in the expression of MUC1, miRNA 223-3p and a remarkable decline in ERK1/2 and p-4E-BP1 levels in comparison with the control group. Combination therapy of (FCA+PP242) resulted in a remarkable rise in LIF, Msx-1, HB-EGF, ERK1/2, and mTOR levels, in comparison with the PP242 group. Furthermore, combination therapy of (FCA+PP242) downregulated the expression of MUC1 in comparison with the PP242-treated group. According to the results, fludrocortisone affected uterine receptivity possibly by means of modulating the expression of genes involved in the uterine receptivity and activation of the ERK1/2-mTOR pathway.

The Modified Bushen Antai Recipe Upregulates Estrogen and Progesterone Receptors at the Maternal-Fetal Interface in Pregnant Rats with Mifepristone-Induced Pregnancy Loss

Background

The modified Bushen Antai recipe (BSAT) is a centuries-old traditional Chinese medicine that we use in our center as a therapy against pregnancy loss. Our study aimed to explore the potential benefit and mechanism of BSAT in pregnant rats with mifepristone-induced pregnancy loss.

Materials and Methods

The signature compounds of the eight BSAT ingredients were analyzed by high-performance liquid chromatography (HPLC). The BSAT group (n = 8) was treated daily with 6.3 ml/kg BSAT from gestation day (D) 0.5 to 10.5 and once with 1.25 mg/kg mifepristone on D 10.5. Normal saline replaced BSAT in the model group (n = 8), and both BSAT and mifepristone in the control group (n = 8). Morphological and histological analyses were performed on D 13.5.

Results

BSAT contains eight medicinal ingredients including Cuscuta chinensis and Dipsacus asperoides. The HPLC analysis detected the signature compounds of seven medicinal ingredients in the extract. Embryo resorption rate in the BSAT group was significantly lower than that in the model group, although the number of surviving embryos was similar between the two groups. Hematoxylin and eosin (HE) staining suggested that the maximum cross-sectional area of the placenta and the area ratio of the placental labyrinth in the BSAT group were higher than those in the model group. Immunohistochemical (IHC) staining indicated that the expression of ki67, estrogen receptor alpha (ERα), and progesterone receptor (PR) in the placental labyrinth of the BSAT group was higher than that of the model group. Furthermore, the protein levels of ERα, PR, phospho-Akt/Akt, and phospho-Erk1/2/Erk1/2 in the BSAT group were higher than those in the control group. The mRNA levels of ERα and PR in the BSAT group were higher than those in the control group.

Conclusions

BSAT may induce estrogen and progesterone receptors by phosphorylation via the classic Akt and Erk1/2 signaling pathways in the maternal-fetal interface of pregnant rats, thereby reducing the pregnancy loss rate and improving the live birth rate.

How does toxoplasmosis affect the maternal-foetal immune interface and pregnancy?

Toxoplasma gondii is a zoonotic parasite which, depending on the geographical location, can infect between 10% and 90% of humans. Infection during pregnancy may result in congenital toxoplasmosis. The effects on the foetus vary depending on the stage of gestation in which primary maternal infection arises. A large body of research has focused on understanding immune response to toxoplasmosis, although few studies have addressed how it is affected by pregnancy or the pathological consequences of infection at the maternal-foetal interface. There is a lack of knowledge about how maternal immune cells, specifically macrophages, are modulated during infection and the resulting consequences for parasite control and pathology. Herein, we discuss the potential of T. gondii infection to affect the maternal-foetal interface and the potential of pregnancy to disrupt maternal immunity to T. gondii infection.

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

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

Uterine progesterone signaling is a target for metformin therapy in PCOS-like rats

Impaired progesterone (P4) signaling is linked to endometrial dysfunction and infertility in women with polycystic ovary syndrome (PCOS). Here, we report for the first time that elevated expression of progesterone receptor (PGR) isoforms A and B parallels increased estrogen receptor (ER) expression in PCOS-like rat uteri. The aberrant PGR-targeted gene expression in PCOS-like rats before and after implantation overlaps with dysregulated expression of Fkbp52 and Ncoa2, two genes that contribute to the development of uterine P4 resistance. In vivo and in vitro studies of the effects of metformin on the regulation of the uterine P4 signaling pathway under PCOS conditions showed that metformin directly inhibits the expression of PGR and ER along with the regulation of several genes that are targeted dependently or independently of PGR-mediated uterine implantation. Functionally, metformin treatment corrected the abnormal expression of cell-specific PGR and ER and some PGR-target genes in PCOS-like rats with implantation. Additionally, we documented how metformin contributes to the regulation of the PGR-associated MAPK/ERK/p38 signaling pathway in the PCOS-like rat uterus. Our data provide novel insights into how metformin therapy regulates uterine P4 signaling molecules under PCOS conditions.

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

STUDY QUESTION

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

SUMMARY ANSWER

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

WHAT IS KNOWN ALREADY

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

STUDY DESIGN, SIZE, DURATION

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

PARTICIPANTS/MATERIALS, SETTING, METHODS

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

MAIN RESULTS AND THE ROLE OF CHANCE

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

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

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

WIDER IMPLICATIONS OF THE FINDINGS

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

STUDY FUNDING/COMPETING INTEREST(S)

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

G-protein coupled receptor 64 is required for decidualization of endometrial stromal cells

Although GPR64 has an important role for male fertility, its physiological roles in the female reproductive system are still unknown. In the present study, immunohistochemical analysis reveals a spatiotemporal expression of GPR64 in the uterus during early pregnancy. Observation of remarkable induction of GPR64 expression in uterine decidual cells points to its potential physiological significance on decidualization. The decidualization of uterine stromal cells is a key event in implantation. Progesterone (P4) signaling is crucial for the decidualization of the endometrial stromal cells for successful pregnancy. Therefore, we examined ovarian steroid hormone regulation of GPR64 expression in the murine uterus. P4 induced GPR64 expression in the epithelial and stromal cells of the uterus in ovariectomized wild-type mice, but not in PRKO mice. ChIP analysis confirmed that PGR proteins were recruited on progesterone response element of Gpr64 gene in the uteri of wild-type mice treated with P4. Furthermore, the expression of GPR64 was increased in human endometrial stromal cells (hESCs) during in vitro decidualization. Interestingly, small interfering RNA (siRNA)-mediated knockdown of GPR64 in hESCs remarkably reduced decidualization. These results suggest that Gpr64 has a crucial role in the decidualization of endometrial stromal cells.

Endometrial receptivity in the eutopic endometrium of women with endometriosis: it is affected, and let me show you why

The endometrium maintains complex controls on proliferation and apoptosis as part of repetitive menstrual cycles that prepare the endometrium for the window of implantation and pregnancy. The reliance on inflammatory mechanisms for both implantation and menstruation creates the opportunity in the setting of endometriosis for establishment of chronic inflammation that is disruptive to endometrial receptivity, causing both infertility and abnormal bleeding. Clinically, there can be little doubt that the endometrium of women with endometriosis is less receptive to embryo implantation, and strong evidence exists to suggest that endometrial changes are associated with decreased cycle fecundity as a result of this disease. Here we provide unifying concepts regarding those changes and how they are coordinated to promote progesterone resistance and estrogen dominance through aberrant cell signaling pathways and reduced expression of key homeostatic proteins in eutopic endometrium of women with endometriosis.

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.

cAMP-Response Element-Binding 3-Like Protein 1 (CREB3L1) is Required for Decidualization and its Expression is Decreased in Women with Endometriosis

Endometriosis is a major cause of infertility and pelvic pain, affecting more than 10% of reproductive-aged women. Progesterone resistance has been observed in the endometrium of women with this disease, as evidenced by alterations in progesterone-responsive gene and protein expression. cAMPResponse Element-Binding 3-like protein 1 (Creb3l1) has previously been identified as a progesterone receptor (PR) target gene in mouse uterus via high density DNA microarray analysis. However, CREB3L1 function has not been studied in the context of endometriosis and uterine biology. In this study, we validated progesterone (P4) regulation of Creb3l1 in the uteri of wild-type and progesterone receptor knockout (PRKO) mice. Furthermore, we observed that CREB3L1 expression was significantly higher in secretory phase human endometrium compared to proliferative phase and that CREB3L1 expression was significantly decreased in the endometrium of women with endometriosis. Lastly, by transfecting CREB3L1 siRNA into cultured human endometrial stromal cells (hESCs) prior to hormonal induction of in vitro decidualization, we showed that CREB3L1 is required for the decidualization process. Interestingly, phosphorylation of ERK1/2, critical factor for decidualization, was also significantly reduced in CREB3L1-silenced hESCs. It is known that hESCs from patients with endometriosis show impaired decidualization and that dysregulation of the P4-PR signaling axis is linked to a variety of endometrial diseases including infertility and endometriosis. Therefore, these results suggest that CREB3L1 is required for decidualization in mice and humans and may be linked to the pathogenesis of endometriosis in a P4-dependent manner.

Signal transducer and activator of transcription-3 licenses Toll-like receptor 4-dependent interleukin (IL)-6 and IL-8 production via IL-6 receptor-positive feedback in endometrial cells

Interleukin 6 (IL-6), acting via the IL-6 receptor (IL6R) and signal transducer and activator of transcription-3 (STAT3), limits neutrophil recruitment once bacterial infections are resolved. Bovine endometritis is an exemplar mucosal disease, characterized by sustained neutrophil infiltration and elevated IL-6 and IL-8, a neutrophil chemoattractant, following postpartum Gram-negative bacterial infection. The present study examined the impact of the IL6R/STAT3 signaling pathway on IL-8 production by primary endometrial cells in response to short- or long-term exposure to lipopolysaccharide (LPS) from Gram-negative bacteria. Tyrosine phosphorylation of STAT3 is required for DNA binding and expression of specific targets genes. Immunoblotting indicated constitutive tyrosine phosphorylation of STAT3 in endometrial cells was impeded by acute exposure to LPS. After 24 h exposure to LPS, STAT3 returned to a tyrosine phosphorylated state, indicating cross-talk between the Toll-like receptor 4 (TLR4) and the IL6R/STAT3 signaling pathways. This was confirmed by short interfering RNA targeting the IL6R, which abrogated the accumulation of IL-6 and IL-8, induced by LPS. Furthermore, there was a differential endometrial cell response, as the accumulation of IL-6 and IL-8 was dependent on STAT3, suppressor of cytokine signaling 3, and Src kinase signaling in stromal cells, but not epithelial cells. In conclusion, positive feedback through the IL6R amplifies LPS-induced IL-6 and IL-8 production in the endometrium. These findings provide a mechanistic insight into how elevated IL-6 concentrations in the postpartum endometrium during bacterial infection leads to marked and sustained neutrophil infiltration.

Molecular cues to the anti-implantation effect of nano-puerarin in rats

Puerarin, a selective oestrogen receptor modulator, intercepts implantation in rats, albeit at unacceptably higher doses. We developed poly lactic-co-glycolic acid-encapsulated nano-puerarin (PN) and mapped the molecular pathway underlying its anti-implantation effects. Smooth-surfaced and spherical PN having a mean diameter of ∼147nm was obtained with good yield, efficient encapsulation, and optimum drug loading. In culture, PN slowly and steadily released puerarin, which was readily taken up by the decidual cells. PN exerted a dose-dependent anti-implantation effect. As marked by attenuated expression of stromal cell desmin, alkaline phosphatase, IGFBP1, and decidual prolactin-related protein, the anti-implantation effect of PN seemed secondary to compromised decidualization. Usingin vivo(pregnant and pseudopregnant rats) andin vitro(endometrial stromal cell culture) treatment models, we document that PN enforced inhibition of uterine expression ofHbegfandHoxa10and their downstream signalling molecules, Cyclin D3 (CCND3)/CDK4. PN also efficiently ablated theIhh-Nr2f2-Bmp2signalling pathway and invited the loss of uterine potential for decidualization. There was a dose-dependent up-regulation of RHOA and its effector protein kinase, ROCK1, leading to the promotion of MLC phosphorylation and actin–myosin interaction. PN also down-regulated the stromal cell activation of ERK½ and expression of MMP9. These effects acting together stabilized the stroma and inhibited the stromal cell migration. Central to this array of events was the adversely altered endometrial expression of oestrogen receptor subtypes and repression of progesterone receptor that indulged endless proliferation of luminal epithelia and distorted the precisely choreographed stroma–epithelia crosstalk. Thus, PN dismantles the endometrial bed preparation and prevents implantation.

Involvement of atypical transcription factor E2F8 in the polyploidization during mouse and human decidualization

Polyploid decidual cells are specifically differentiated cells during mouse uterine decidualization. However, little is known about the regulatory mechanism and physiological significance of polyploidization in pregnancy. Here we report a novel role of E2F8 in the polyploidization of decidual cells in mice. E2F8 is highly expressed in decidual cells and regulated by progesterone through HB-EGF/EGFR/ERK/STAT3 signaling pathway. E2F8 transcriptionally suppresses CDK1, thus triggering the polyploidization of decidual cells. E2F8-mediated polyploidization is a response to stresses which are accompanied by decidualization. Interestingly, polyploidization is not detected during human decidualization with the down-regulation of E2F8, indicating differential expression of E2F8 may lead to the difference of decidual cell polyploidization between mice and humans.

ARID1A Is Essential for Endometrial Function during Early Pregnancy

AT-rich interactive domain 1A gene (ARID1A) loss is a frequent event in endometriosis-associated ovarian carcinomas. Endometriosis is a disease in which tissue that normally grows inside the uterus grows outside the uterus, and 50% of women with endometriosis are infertile. ARID1A protein levels were significantly lower in the eutopic endometrium of women with endometriosis compared to women without endometriosis. However, an understanding of the physiological effects of ARID1A loss remains quite poor, and the function of Arid1a in the female reproductive tract has remained elusive. In order to understand the role of Arid1a in the uterus, we have generated mice with conditional ablation of Arid1a in the PGR positive cells (Pgrcre/+Arid1af/f; Arid1ad/d). Ovarian function and uterine development of Arid1ad/d mice were normal. However, Arid1ad/d mice were sterile due to defective embryo implantation and decidualization. The epithelial proliferation was significantly increased in Arid1ad/d mice compared to control mice. Enhanced epithelial estrogen activity and reduced epithelial PGR expression, which impedes maturation of the receptive uterus, was observed in Arid1ad/d mice at the peri-implantation period. The microarray analysis revealed that ARID1A represses the genes related to cell cycle and DNA replication. We showed that ARID1A positively regulates Klf15 expression with PGR to inhibit epithelial proliferation at peri-implantation. Our results suggest that Arid1a has a critical role in modulating epithelial proliferation which is a critical requisite for fertility. This finding provides a new signaling pathway for steroid hormone regulation in female reproductive biology and furthers our understanding of the molecular mechanisms that underlie dysregulation of hormonal signaling in human reproductive disorders such as endometriosis.

Mig-6 suppresses endometrial cancer associated with Pten deficiency and ERK activation

PTEN mutations are the most common genetic alterations in endometrial cancer. Loss of PTEN and subsequent AKT activation stimulate estrogen receptor α-dependent pathways that play an important role in endometrial tumorigenesis. The major pathologic phenomenon of endometrial cancer is the loss of ovarian steroid hormone control over uterine epithelial cell proliferation and apoptosis. However, the precise mechanism of PTEN/AKT signaling in endometrial cancer remains poorly understood. The progesterone signaling mediator MIG-6 suppresses estrogen signaling and it has been implicated previously as a tumor suppressor in endometrial cancer. In this study, we show that MIG-6 also acts as a tumor suppressor in endometrial cancers associated with PTEN deficiency. Transgenic mice, where Mig-6 was overexpressed in progesterone receptor-expressing cells, exhibited a relative reduction in uterine tumorigenesis caused by Pten deficiency. ERK1/2 was phosphorylated in uterine tumors and administration of an ERK1/2 inhibitor suppressed cancer progression in PR(cre/+)Pten(f/f) mice. In clinical specimens of endometrial cancer, MIG-6 expression correlated inversely with ERK1/2 phosphorylation during progression. Taken together, our findings suggest that Mig-6 regulates ERK1/2 phosphorylation and that it is crucial for progression of PTEN-mutant endometrial cancers, providing a mechanistic rationale for the evaluation of ERK1/2 inhibitors as a therapeutic treatment in human endometrial cancer.

Cyclic decidualization of the human endometrium in reproductive health and failure

Decidualization denotes the transformation of endometrial stromal fibroblasts into specialized secretory decidual cells that provide a nutritive and immunoprivileged matrix essential for embryo implantation and placental development. In contrast to most mammals, decidualization of the human endometrium does not require embryo implantation. Instead, this process is driven by the postovulatory rise in progesterone levels and increasing local cAMP production. In response to falling progesterone levels, spontaneous decidualization causes menstrual shedding and cyclic regeneration of the endometrium. A growing body of evidence indicates that the shift from embryonic to maternal control of the decidual process represents a pivotal evolutionary adaptation to the challenge posed by invasive and chromosomally diverse human embryos. This concept is predicated on the ability of decidualizing stromal cells to respond to individual embryos in a manner that either promotes implantation and further development or facilitates early rejection. Furthermore, menstruation and cyclic regeneration involves stem cell recruitment and renders the endometrium intrinsically capable of adapting its decidual response to maximize reproductive success. Here we review the endocrine, paracrine, and autocrine cues that tightly govern this differentiation process. In response to activation of various signaling pathways and genome-wide chromatin remodeling, evolutionarily conserved transcriptional factors gain access to the decidua-specific regulatory circuitry. Once initiated, the decidual process is poised to transit through distinct phenotypic phases that underpin endometrial receptivity, embryo selection, and, ultimately, resolution of pregnancy. We discuss how disorders that subvert the programming, initiation, or progression of decidualization compromise reproductive health and predispose for pregnancy failure.

A pan-cancer modular regulatory network analysis to identify common and cancer-specific network components

Many human diseases including cancer are the result of perturbations to transcriptional regulatory networks that control context-specific expression of genes. A comparative approach across multiple cancer types is a powerful approach to illuminate the common and specific network features of this family of diseases. Recent efforts from The Cancer Genome Atlas (TCGA) have generated large collections of functional genomic data sets for multiple types of cancers. An emerging challenge is to devise computational approaches that systematically compare these genomic data sets across different cancer types that identify common and cancer-specific network components. We present a module- and network-based characterization of transcriptional patterns in six different cancers being studied in TCGA: breast, colon, rectal, kidney, ovarian, and endometrial. Our approach uses a recently developed regulatory network reconstruction algorithm, modular regulatory network learning with per gene information (MERLIN), within a stability selection framework to predict regulators for individual genes and gene modules. Our module-based analysis identifies a common theme of immune system processes in each cancer study, with modules statistically enriched for immune response processes as well as targets of key immune response regulators from the interferon regulatory factor (IRF) and signal transducer and activator of transcription (STAT) families. Comparison of the inferred regulatory networks from each cancer type identified a core regulatory network that included genes involved in chromatin remodeling, cell cycle, and immune response. Regulatory network hubs included genes with known roles in specific cancer types as well as genes with potentially novel roles in different cancer types. Overall, our integrated module and network analysis recapitulated known themes in cancer biology and additionally revealed novel regulatory hubs that suggest a complex interplay of immune response, cell cycle, and chromatin remodeling across multiple cancers.

CRISPLD2 is a target of progesterone receptor and its expression is decreased in women with endometriosis

Endometriosis, defined as the presence of endometrial cells outside of the uterine cavity, is a major cause of infertility and pelvic pain, afflicting more than 10% of reproductive age women. Endometriosis is a chronic inflammatory disease and lipopolysaccharide promotes the proliferation and invasion of endometriotic stromal cells. Cysteine-rich secretory protein LCCL domain-containing 2 (CRISPLD2) has high affinity for lipopolysaccharide and plays a critical role in defense against endotoxin shock. However, the function of CRISPLD2 has not been studied in endometriosis and uterine biology. Herein, we examined the expression of CRISPLD2 in endometrium from patients with and without endometriosis using immunohistochemistry. The expression of CRISPLD2 was higher in the secretory phase in human menstrual cycle compared to proliferative phase. The expression of CRISPLD2 was significantly decreased in the endometrium of women with endometriosis in the early secretory phase compared to women without endometriosis. The increase of CRISPLD2 expression at the early secretory and dysregulation of its expression in endometriosis suggest progesterone (P4) regulation of CRISPLD2. To investigate whether CRISPLD2 is regulated by P4, we examined the expression of the CRISPLD2 in the uteri of wild-type and progesterone receptor knock out (PRKO) mice. The expression of CRISPLD2 was significantly increased after P4 treatment in the wild-type mice. However, CRISPLD2 expression was significantly decreased in the (PRKO) mice treated with P4. During early pregnancy, the expression of CRISPLD2 was increased in decidua of implantation and post-implantation stages. CRISPLD2 levels were also increased in cultured human endometrial stromal cells during in vitro decidualization. These results suggest that the CRISPLD2 is a target of the progesterone receptor and may play an important role in pathogenesis of endometriosis.

Molecular basis of thyrotropin and thyroid hormone action during implantation and early development

BACKGROUND

Implantation and early embryo development are finely regulated processes in which several molecules are involved. Evidence that thyroid hormones (TH: T4 and T3) might be part of this machinery is emerging. An increased demand for TH occurs during gestation, and any alteration in maternal thyroid physiology has significant implications for both maternal and fetal health. Not only overt but also subclinical hypothyroidism is associated with infertility as well as with obstetric complications, including disruptions and disorders of pregnancy, labor, delivery, and troubles in early neonatal life.

METHODS

We searched the PubMed and Google Scholar databases for articles related to TH action on ovary, endometrium, trophoblast maturation and embryo implantation. In addition, articles on the regulation of TH activity at cellular level have been reviewed. The findings are hereby summarized and critically discussed.

RESULTS

TH have been shown to influence endometrial, ovarian and placental physiology. TH receptors (TR) and thyrotropin (thyroid-stimulating hormone: TSH) receptors (TSHR) are widely expressed in the feto-maternal unit during implantation, and both the endometrium and the trophoblast might be influenced by TH either directly or through TH effects on the synthesis and activity of implantation-mediating molecules. Interestingly, due to the multiplicity of mechanisms involved in TH action (e.g. differential expression of TR isoforms, heterodimeric receptor partners, interacting cellular proteins, and regulating enzymes), the TH concentration in blood is not always predictive of their cellular availability and activity at both genomic and nongenomic level.

CONCLUSIONS

In addition to the known role of TH on the hormonal milieu of the ovarian follicle cycle, which is essential for a woman's fertility, evidence is emerging on the importance of TH signaling during implantation and early pregnancy. Based on recent observations, a local action of TH on female reproductive organs and the embryo during implantation appears to be crucial for a successful pregnancy. Furthermore, an imbalance in the spatio-temporal expression of factors involved in TH activity might induce early arrest of pregnancy in women considered as euthyroid, based on their hormonal blood concentration. In conclusion, alterations of the highly regulated local activity of TH may play a crucial, previously underestimated, role in early pregnancy and pregnancy loss. Further studies elucidating this topic should be encouraged.

Diverse roles of prostaglandins in blastocyst implantation

Prostaglandins (PGs), derivatives of arachidonic acid, play an indispensable role in embryo implantation. PGs have been reported to participate in the increase in vascular permeability, stromal decidualization, blastocyst growth and development, leukocyte recruitment, embryo transport, trophoblast invasion, and extracellular matrix remodeling during implantation. Deranged PGs syntheses and actions will result in implantation failure. This review summarizes up-to-date literatures on the role of PGs in blastocyst implantation which could provide a broad perspective to guide further research in this field.