HB-EGF directs stromal cell polyploidy and decidualization via cyclin D3 during implantation

MiR-135a-5p regulates window of implantation by suppressing pinopodes development and decidualization of endometrial stromal cells

PURPOSE

The window of implantation (WOI) is a brief period during which the endometrium is receptive to embryo implantation. This study investigated the relationship between miR-135a-5p and endometrial receptivity.

METHODS

Peripheral blood was collected on the day of ovulation and the 5th day after ovulation for high-throughput sequencing from women who achieved clinical pregnancy through natural cycle frozen embryo transfer. RT-qPCR assessed miR-135a-5p expression in the endometrium tissue or cells during the mouse implantation window or decidualization. Scanning electron microscopy was utilized to observe pinopode morphology and quantity in mice overexpressing miR-135a-5p during the WOI. Human endometrial stromal cells (HESC) and artificial induction of mouse uterine decidualization were used to explore whether miR-135a-5p overexpression inhibits decidualization by regulating HOXA10 and BMPR2. Furthermore, the impact of miR-135a-5p on HESC proliferation and HTR8/SVneo invasion was explored.

RESULTS

A total of 54 women were enrolled in the study. bioinformatics analysis and animal models demonstrated that miR-135a-5p was significantly downregulated during the WOI, and its high expression can lead to abnormal pregnancy outcomes. Overexpression of miR-135a-5p resulted in the absence of pinopode in mouse endometrial tissue during the WOI. High miR-135a-5p levels were found to potentially inhibit endometrial tissue decidualization by downregulating HOXA10 and BMPR2 expression. Finally, CEBPD was identified as a potential regulator of miR-135a-5p, which would explain the decreased miR-135a-5p expression during the WOI.

CONCLUSION

MiR-135a-5p expression is significantly downregulated during the WOI. High miR-135a-5p levels suppress pinopode development and endometrial tissue decidualization through HOXA10 and BMPR2, contributing to inadequate endometrial receptivity.

A Novel Method to Repair Thin Endometrium and Restore Fertility Based on Menstruation-Derived Stem Cell

Thin endometrium (TE), which mainly occurs as a result of severe damage to the endometrial basalis, is one of the prominent etiologies of menstrual abnormalities, infertility, and recurrent miscarriage in women. Previous studies have demonstrated that mesenchymal stem cells (MSCs) are considered ideal cells with multipotency for regenerative medicine and exhibit therapeutic effects on TE through their cellular secretions. However, there is limited research on strategies to enhance MSC secretion to improve their therapeutic efficacy. Herein, we isolated menstrual blood-derived mesenchymal stem cells (MenSCs) from menstruation and transformed them into decidualized stromal cells (DSCs), which are specialized cells with enhanced secretory functions. To assess the therapeutic potential of DSCs compared to MenSCs, we conducted a series of experiments in cells and animals. The results demonstrated that DSCs exhibited changes in morphology compared to MenSCs, with a decrease in cell proliferation but a significant improvement in secretion function. Furthermore, DSCs facilitated the restoration of endometrial thickness and increased the number of glands and blood vessel formation. Most importantly, the pregnancy rates in rats were effectively restored, bringing them closer to normal levels. These findings greatly contribute to our understanding of stem cell therapy for TE and strongly suggest that DSCs could hold significant promise as a potential treatment option for TE.

Tryptophan in the mouse diet is essential for embryo implantation and decidualization

Introduction

Nutritional deficiency occurs frequently during pregnancy and breastfeeding. Tryptophan (Trp), an essential amino acid which is critical for protein synthesis, serves as the precursor for serotonin, melatonin, and kynurenine (Kyn). The imbalance between serotonin and kynurenine pathways in Trp metabolism is closely related to inflammation and depression. This study assessed the effects of Trp deficiency on mouse early pregnancy.

Methods

Embryo implantation and decidualization were analyzed after female mice had been fed diets containing 0.2% Trp (for the control group), 0.062% Trp (for the low Trp group) and 0% Trp (for the Trp-free group) for two months. The uteri of the mice were collected on days 4, 5, and 8 of pregnancy for further analysis.

Results

On day 8 of pregnancy, the number of implantation sites were found to be similar between the control and the low Trp groups. However, no implantation sites were detected in the Trp-free group. On day 5 of pregnancy, plane polarity- and decidualization-related molecules showed abnormal expression pattern in the Trp-free group. On day 4 of pregnancy, there was no significant difference in uterine receptivity molecules between the low-Trp group and the control group, but uterine receptivity was abnormal in the Trp-free group. At implantation sites of the Trp-free group, IDO and AHR levels were markedly elevated. This potentially increased levels of Kyn, 2-hydroxy estradiol, and 4-hydroxy estradiol to affect decidualization.

Conclusions

Trp-free diet may impair decidualization via the IDO-KYN-AHR pathway.

The Multiple Functions of HB-EGF in Female Reproduction and Related Cancer: Molecular Mechanisms and Targeting Strategies

Heparin-binding growth factor (HB-EGF) is a member of the epidermal growth factor (EGF) ligand family which has a crucial role in women's health. However, there is a lack of comprehensive review to summarize the significance of HB-EGF. Therefore, this work first described the expression patterns of HB-EGF in the endometrium and ovary of different species and gestational time. Then, the focus was on exploring how it promotes the successful implantation and regulates the process of decidualization and the function of ovarian granulosa cells as an intermediate molecule. Otherwise, we also focused on the clinical and prognostic significance of HB-EGF in female-related cancers (including ovarian cancer, cervical cancer, and endometrial cancer) and breast cancer. Lastly, the article also summarizes the current drugs targeting HB-EGF in the treatment of ovarian cancer and breast cancer. Overall, these studies found that the expression of HB-EGF in the endometrium is spatiotemporal and species-specific. And it mediates the dialogue between the blastocyst and endometrium, promoting synchronous development of the blastocyst and endometrium as an intermediate molecule. HB-EGF may serve as a potentially valuable prognostic clinical indicator in tumors. And the specific inhibitor of HB-EGF (CRM197) has a certain anti-tumor ability, which can exert synergistic anti-tumor effects with conventional chemotherapy drugs. However, it also suggests that more research is needed in the future to elucidate its specific mechanisms and to accommodate clinical studies with a larger sample size to clarify its clinical value.

A Potential Role of CD82/KAI1 during Uterine Decidualization in Mice

The tumor metastasis suppressor gene CD82/KAI1 has been demonstrated to impact human trophoblast invasion and migration. Communication between trophoblasts and decidual stromal cells plays a crucial role in controlling the normal invasiveness of trophoblasts. However, whether CD82/KAI1 is involved in decidualization and what role it plays remain unclear. CD82/KAI1 demonstrates specific spatiotemporal expression patterns in stromal cells undergoing decidualization during pregnancy. This is observed in both naturally pregnant females post-implantation and pseudopregnant mice undergoing induced decidualization, as detected through in situ hybridization and immunofluorescence. CD82/KAI1 expression showed a significant time-dependent increase in cultured stromal cells after 24 and 48 h of progesterone (P4) and estrogen (E2) treatment. This was accompanied by a notable upregulation of decidualization markers, including cyclin D3 and PR. After transducing stromal cells with the adenovirus-overexpressing CD82/KAI1 for 48 h, the expression of cyclin D3 protein increased. Meanwhile, there was an attenuated expression of CD82/KAI1 due to an adenovirus siRNA knockdown, whereas cyclin D3 and PR expressions were not affected. Our findings suggest a potential role of CD82/KAI1 in regulating the process of decidualization, providing insights into stromal cell differentiation.

Roles of lipid mediators in early pregnancy events

Background

Early pregnancy events, including embryo implantation, are critical for maintaining a healthy pregnancy and facilitating childbirth. Despite numerous signaling pathways implicated in establishing early pregnancy, a comprehensive understanding of implantation remains elusive.

Methods

This paper provides a comprehensive review of the current research on lipids in the context of early pregnancy, with a particular focus on feto-maternal communications.

Main Findings

Embryo implantation entails direct interaction between uterine tissues and embryos. Introducing embryos triggers significant changes in uterine epithelial morphology and stromal differentiation, facilitating embryo implantation through communication with uterine tissue. Studies employing genetic models and chemical compounds targeting enzymes and receptors have elucidated the crucial roles of lipid mediators-prostaglandins, lysophosphatidic acid, sphingosine-1-phosphate, and cannabinoids-in early pregnancy events.

Conclusion

Given the high conservation of lipid synthases and receptors across species, lipid mediators likely play pivotal roles in rodents and humans. Further investigations into lipids hold promise for developing novel diagnostic and therapeutic approaches for infertility in humans.

Embryo-derive TNF promotes decidualization via fibroblast activation

Decidualization is a process in which endometrial stromal fibroblasts differentiate into specialized secretory decidual cells and essential for the successful establishment of pregnancy. The underlying mechanism during decidualization still remains poorly defined. Because decidualization and fibroblast activation share similar characteristics, this study was to examine whether fibroblast activation is involved in decidualization. In our study, fibroblast activation-related markers are obviously detected in pregnant decidua and under in vitro decidualization. ACTIVIN A secreted under fibroblast activation promotes in vitro decidualization. We showed that arachidonic acid released from uterine luminal epithelium can induce fibroblast activation and decidualization through PGI₂ and its nuclear receptor PPARδ. Based on the significant difference of fibroblast activation-related markers between pregnant and pseudopregnant mice, we found that embryo-derived TNF promotes CPLA_2α phosphorylation and arachidonic acid release from luminal epithelium. Fibroblast activation is also detected under human in vitro decidualization. Similar arachidonic acid-PGI₂-PPARδ-ACTIVIN A pathway is conserved in human endometrium. Collectively, our data indicate that embryo-derived TNF promotes CPLA_2α phosphorylation and arachidonic acid release from luminal epithelium to induce fibroblast activation and decidualization.

Uterine deficiency of Dnmt3b impairs decidualization and causes consequent embryo implantation defects

Uterine deficiency of Dnmt3b impairs decidualization and consequent embryo implantation defects. Recent advances in molecular technologies have allowed the unprecedented mapping of epigenetic modifications during embryo implantation. DNA methyltransferase 3a (DNMT3A) and DNMT3B are responsible for establishing DNA methylation patterns produced through their de novo-type DNA methylation activity in implantation stage embryos and during germ cell differentiation. It was reported that conditional knockout of Dnmt3a in the uterus does not markedly affect endometrial function during embryo implantation, but the tissue-specific functions of Dnmt3b in the endometrium during embryo implantation remain poorly understood to investigate the role of Dnmt3b during peri-implantation period. Here, we generated Dnmt3b conditional knockout (Dnmt3bd/d) female mice using progesterone receptor-Cre mice and examined the role of Dnmt3b during embryo implantation. Dnmt3bd/d female mice exhibited compromised fertility, which was associated with defective decidualization, but not endometrial receptivity. Furthermore, results showed loss of Dnmt3b did not lead to altered genomic methylation patterns of the decidual endometrium during early pregnancy. Transcriptome sequencing analysis of uteri from day 6 pregnant mice identified phosphoglycerate kinase 1 (Pgk1) as one of the most variable genes in Dnmt3bd/d decidual endometrium. Potential roles of PGK1 in the decidualization process during early pregnancy were confirmed. Lastly, the compromised decidualization upon the downregulation of Dnmt3b could be reversed by overexpression of Pgk1. Collectively, our findings indicate that uterine deficiency of Dnmt3b impairs decidualization and consequent embryo implantation defects.

Rhythm of the First Language: Dynamics of Extracellular Vesicle-Based Embryo-Maternal Communication in the Pre-Implantation Microenvironment

One of the most critical steps in mammalian reproduction is implantation. Embryos with an impaired capacity for embryo-maternal crosstalk are thought to have a reduced potential for implantation. One agent of embryo-maternal communication is extracellular vesicles (EV). EVs are lipid bilayer-bound biological nanoparticles implicated in intercellular communication between many of the known cell types. In the current study, we isolated EVs from trophoblast analogue JAr spheroids and supplemented the EVs with receptive endometrium analogue RL95-2 cells to simulate pre-implantation embryo-maternal dialogue. The transcriptome of the endometrial cells was examined at 30 min, 4 h and 48 h intervals using Oxford Nanopore^® technology. At the time points, 30 min, 4 h and 48 h, the endometrial cells showed a significantly altered transcriptome. It seems trophoblast EVs induce a swift and drastic effect on the endometrial transcriptome. The effect peaks at around 4 h of EV supplementation, indicating a generalized effect on cell physiology. Alterations are especially apparent in biological pathways critical to embryonic implantation, such as extracellular matrix-receptor interactions and cytokine-receptor interactions. These observations can be helpful in elucidating the dynamics of embryo-maternal communication in the pre-implantation period.

Dysregulated glycolysis underpins high-fat-associated endometrial decidualization impairment during early pregnancy in mice

Pregnancy complications are more likely to occur in obese women because of defective decidualization. However, the specific mechanism of glycolysis in decidual modulation associated with obesity remains unknown. Therefore, we explored the role of glycolysis in the endometrium of obese pregnant mice during decidualization. C57BL/6J mice were fed a high-fat diet (HFD) to induce obesity. All obesity related parameters were significantly higher in the HFD mice than control. Furthermore, the HFD mice had fewer implantation sites, a smaller decidual area growth, and decreased decidualization marker protein expression than control. The HFD mice also had significantly decreased lactate production and glycolytic enzyme expression. To confirm the functional role of glycolysis during the decidual period in obese pregnant mice, we extracted endometrial stromal cells (ESCs) and treated them with oleic acid (OA) and palmitic acid (PA) to mimic a high-fat environment. Decidualization and glycolysis were significantly restricted in the OA-and PA-treated groups. Moreover, we administered a glycolytic inhibitor, 2-DG, and an agonist, pioglitazone. 2-DG treatment considerably decreased the cells' glycolysis and decidualization. However, pioglitazone treatment improved glycolysis and alleviated defective decidualization. In conclusion, obesity-induced endometrial glycolysis modifications and key glycolytic enzyme downregulation during early pregnancy might cause abnormal decidualization, leading to an unsustainable pregnancy.

Exposure to Benzo(a)pyrene promotes proliferation and inhibits differentiation of stromal cells in mice during decidualization

The environmental pollutant Benzo(a)pyrene (BaP) has an adverse effect on the reproductive performance of mammals. We previously showed that BaP treatment during early pregnancy damages endometrial morphology and impairs embryo implantation. Endometrial decidualization at the implantation site (IS) after embryo implantation is crucial for pregnancy maintenance and placental development. The balance between proliferation and differentiation in endometrial stromal cells (ESCs) is a crucial event of decidualization, which is regulated by the cell cycle. Here, we report that abnormal decidualization caused by BaP is associated with cell cycle disturbance of stromal cells. The mice in the treatment group were gavaged with 0.2 mg/kg/day BaP from day 1-8 of pregnancy, while those in control were gavaged with corn oil in parallel. BaP damaged the decidualization of ESCs and reduced the number of polyploid cells. Meanwhile, BaP up-regulated the expression of Ki67 and PCNA, affecting the differentiation of stromal cells. The cell cycle progression analysis during decidualization in vivo and in vitro showed that BaP induced polyploid cells deficiency with enhanced expressions of CyclinA(E)/CDK2, CyclinD/CDK4 and CyclinB/CDK1, which promote the transformation of cells from G₁ to S phase and simultaneously activate the G₂/M phase. The above results indicated that BaP exposure accelerates cell cycle progression, promotes ESC proliferation, inhibits differentiation, and impedes proper decidualization and polyploidy development. Thus, the imbalance of ESC proliferation and differentiation would be an important mechanism for BaP-induced defective decidualization.

Egr3 as an important regulator of uterine decidualization through targeting Hand2

Early growth response 3 (Egr3) is required for embryogenesis, but little understanding is usable about its function in embryo implantation and decidualization. The present study exhibited an obvious localization of Egr3 in luminal epithelium and subluminal stroma at implantation sites. Administration of estrogen brought about a distinct gather of Egr3 mRNA in uterine luminal and glandular epithelia. Meanwhile, Egr3 was visualized in the decidua where it might facilitate the proliferation of stromal cells via Ccnd3 and accelerate stromal differentiation, testifying the significance of Egr3 in decidualization. In ovariectomized mice uteri or stromal cells, progesterone advanced the expression of Egr3 whose obstruction counteracted the inducement of stromal differentiation by progesterone. Consistently, Egr3 mediated the influence of cAMP and heparin-binding EGF-like growth factor (HB-EGF) on the differentiation program. Additionally, cAMP-protein kinase A (PKA) signaling mediated the adjustment of progesterone on Egr3. Impediment of HB-EGF antagonized the ascendance of Egr3 conferred by cAMP. In stromal cells, Egr3 activated the transcription of Hand2 whose promoter region exhibited the binding enrichment of Egr3. Activation of Hand2 relieved the weakness of stromal differentiation by Egr3 hinderance, whereas knockdown of Hand2 neutralized the guidance of Egr3 overexpression on the differentiation program. Collectively, Egr3 was identified as an important regulator of uterine decidualization through targeting Hand2 in response to progesterone/cAMP/HB-EGF pathway.

The regulation and function of acetylated high-mobility group box 1 during implantation and decidualization

Introduction

High-mobility group box 1 (HMGB1) is a non-histone nuclear protein and can be extracellularly secreted to induce sterile inflammation. Although uterine deletion of HMGB1 causes implantation and decidualization defects, how secreted HMGB1 is involved in mouse early pregnancy is still unknown.

Methods

Mouse models, mouse primary endometrial cells and human endometrial cell lines were used in this study. Both immunofluorescence and Western blot were performed to show the localization and relative level of HMGB1 and acetylated HMGB1, respectively. Relative mRNA levels were analyzed by real time RT-PCR.

Results

The secreted HMGB1 was detected in uterine lumen fluid in mouse periimplantation uterus. There is an obvious difference for secreted HMGB1 levels in uterine fluid between day 4 of pregnancy and day 4 of pseudopregnancy, suggesting the involvement of blastocysts during HMGB1 secretion. Trypsin is clearly detected in mouse blastocyst cavity and in the supernatant of cultured blastocysts. Trypsin significantly stimulates HB-EGF production through activating PAR2 and ADAM17. Uterine injection of PAR2 inhibitor into day 4 pregnant mice significantly reduces the number of implantation sites. HB-EGF released from luminal epithelium can induce mouse in vitro decidualization. The conditioned medium collected from trypsin-treated luminal epithelium is able to induce in vitro decidualization, which is suppressed by EGFR inhibitor. Intrauterine injection of glycyrrhizin (HMGB1 inhibitor) can significantly inhibit mouse embryo implantation. We also showed that exogenous HMGB1 released from human epithelial cells are able to induce human in vitro decidualization.

Conclusion

Trypsin can induce decidualization of stromal cells via PAR2-HMGB1-ADAM17-HB-EGF from luminal epithelium.

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.

Distinguish Characters of Luminal and Glandular Epithelium from Mouse Uterus Using a Novel Enzyme-Based Separation Method

The uterine luminal epithelium, glandular epithelium, and stromal cells are vital for the establishment of pregnancy. Previously studies have shown various methods to isolate mouse uterine epithelium and stromal cells, including laser capture microdissection (LCM), enzyme digestion, and immunomagnetic beads. Despite the importance of the endometrial epithelium as the site of implantation and nutritional support for the conceptus, there is no isolated method to separate the luminal epithelium and glandular epithelium. Here, we establish a novel enzyme-based way to separate two types of epithelium and keep their viability. In this article, we analyzed their purity by mRNA level, immunostaining, and transcriptome analysis. Our isolation method revealed several unstudied luminal and glandular epithelial markers in transcriptome analysis. We further demonstrated the viability of the isolated epithelium by 2D and 3D cultures. The results showed that we successfully separated the endometrial luminal epithelium and glandular epithelium. We also provided an experimental model for the following study of the physiological function of the different parts of the uterus and related diseases.

Follistatin is a crucial chemoattractant for mouse decidualized endometrial stromal cell migration by JNK signalling

Follistatin (FST) and activin A as gonadal proteins exhibit opposite effects on follicle-stimulating hormone (FSH) release from pituitary gland, and activin A-FST system is involved in regulation of decidualization in reproductive biology. However, the roles of FST and activin A in migration of decidualized endometrial stromal cells are not well characterized. In this study, transwell chambers and microfluidic devices were used to assess the effects of FST and activin A on migration of decidualized mouse endometrial stromal cells (d-MESCs). We found that compared with activin A, FST exerted more significant effects on adhesion, wound healing and migration of d-MESCs. Similar results were also seen in the primary cultured decidual stromal cells (DSCs) from uterus of pregnant mouse. Simultaneously, the results revealed that FST increased calcium influx and upregulated the expression levels of the migration-related proteins MMP9 and Ezrin in d-MESCs. In addition, FST increased the level of phosphorylation of JNK in d-MESCs, and JNK inhibitor AS601245 significantly attenuated FST action on inducing migration of d-MESCs. These data suggest that FST, not activin A in activin A-FST system, is a crucial chemoattractant for migration of d-MESCs by JNK signalling to facilitate the successful uterine decidualization and tissue remodelling during pregnancy.

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.

TAZ as a novel regulator of oxidative damage in decidualization via Nrf2/ARE/Foxo1 pathway

TAZ, as a crucial effector of Hippo pathway, is required for spermatogenesis and fertilization, but little is known regarding its physiological function in uterine decidualization. In this study, we showed that TAZ was localized in the decidua, where it promoted stromal cell proliferation followed by accelerated G1/S phase transition via Ccnd3 and Cdk4 and induced the expression or activity of stromal differentiation markers Prl8a2, Prl3c1 and ALP, indicating the importance of TAZ in decidualization. Knockdown of TAZ impeded HB-EGF induction of stromal cell proliferation and differentiation. Under oxidative stress, TAZ protected stromal differentiation against oxidative damage by reducing intracellular ROS and enhancing cellular antioxidant capacity dependent on the Nrf2/ARE/Foxo1 pathway. TAZ strengthened the transcriptional activity of Nrf2 which directly bound to the antioxidant response element (ARE) of Foxo1 promoter region. Additionally, silencing TAZ caused accumulation of intracellular ROS through heightening NOX activity whose blockade by APO reversed the disruption in stromal differentiation. Further analysis revealed that TAZ might restore mitochondrial function, as indicated by the increase in ATP level, mtDNA copy number and mitochondrial membrane potential with the reduction in mitochondrial superoxide. Additionally, TAZ modulated the activities of mitochondrial respiratory chain complexes I and III whose suppression by ROT and AA resulted in the inability of TAZ to defend against oxidative damage to stromal differentiation. Moreover, TAZ prevented stromal cell apoptosis by upregulating Bcl2 expression and inhibiting Casp3 activity and Bax expression. In summary, TAZ might mediate HB-EGF function in uterine decidualization through Ccnd3 and ameliorate oxidative damage to stromal cell differentiation via Nrf2/ARE/Foxo1 pathway.

A protein known to regulate cell proliferation plays a key role in preparing a woman’s uterus for pregnancy, a finding that could inform future treatments for female infertility. A team led by Zhan-Peng Yue and Bin Guo from Jilin University, Changchun, China, examined the role of a co-activator protein called TAZ in decidualization, the process in which the uterine lining changes hormonally and biochemically following ovulation. The researchers showed that TAZ levels build up in the mucosal lining of the uterus, where the protein works with various regulators of the cell cycle to promote the proliferation of connective tissue cells known as stromal cells, which support early embryonic development. The researchers demonstrated that in the face of oxidative stress TAZ helps orchestrate molecular detoxification mechanisms that protect these stromal cells from damage.

Exposure to butylated hydroxytoluene compromises endometrial decidualization during early pregnancy

Butylated hydroxytoluene (BHT), one of the most widely used synthetic phenolic antioxidants, is a popular food additive. Previous studies have reported the possible health hazards of BHT. However, BHT effects on female reproduction, especially on endometrial decidualization, are still unknown. During early pregnancy, decidualization plays important roles for embryo implantation and pregnancy establishment. This study aimed to explore the effects of BHT on endometrial decidualization in pregnant mice. The pregnant mice received BHT via intraperitoneal injection at doses of 0, 200, and 400 mg/kg/day from day 1 (D1) of pregnancy until sacrifice. Under BHT exposure, maternal body weight was significantly decreased during early pregnancy. Compared with the control group, the number of implantation sites and uterine weight were significantly reduced in the BHT groups. The uterine lumen failed to close after BHT exposure, and the decidual morphology of endometrial stromal cells was inhibited by BHT. Furthermore, BHT significantly decreased the expression of endometrial decidual markers including COX2, HOXA10, and MMP9. Notably, the levels of serum estrogen (E2) and progesterone (P4) and expression levels of uterus estrogen receptor α (ERα) and progesterone receptor (PR) during early pregnancy were significantly upregulated following BHT exposure. In conclusion, these results demonstrated that gestational BHT exposure could inhibit decidualization of mouse endometrium during early pregnancy. The disorders of reproductive hormones and changes of hormone receptor signals could be responsible for the impaired decidualization. This study provided new evidence for the deleterious effects of BHT on female reproduction and revealed the potential reproductive toxicity of synthetic phenolic antioxidants.

AMPK/mTOR downregulated autophagy enhances aberrant endometrial decidualization in folate-deficient pregnant mice

Existing evidence suggests that adverse pregnancy outcomes are closely related to dietary factors. Folate plays an important role in neural tube formation and fetal growth, folate deficiency is a major risk factor of birth defects. Our early studies showed that folate deficiency could impair enddecidualization, however, the mechanism is still unclear. Dysfunctional autophagy is associated with many diseases. Here, we aimed to evaluate the adverse effect of folate deficiency on endometrial decidualization, with a particular focus on endometrial cell autophagy. Mice were fed with no folate diet in vivo and the mouse endometrial stromal cell was cultured in a folate-free medium in vitro. The decrease of the number of endometrial autophagosomes and the protein expressions of autophagy in the folate-deficient group indicated that autophagosome formation, autophagosome-lysosome fusion, and lysosomal degradation were inhibited. Autophagic flux examination using mCherry-GFP-LC3 transfection showed that the fusion of autophagosomes with lysosomes was inhibited by folate deficiency. Autophagy inducer rapamycin could reverse the impairment of folate deficiency on endometrial decidualization. Moreover, folate deficiency could reduce autophagy by disrupting AMPK/mTOR signaling, resulting in aberrant endometrial decidualization and adverse pregnancy outcomes. Further co-immunoprecipitation examination showed that decidual marker protein Hoxa10 could interact with autophagic marker protein Cathepsin L, and the interaction was notably reduced by folate deficiency. In conclusion, AMPK/mTOR downregulated autophagy was essential for aberrant endometrial decidualization in early pregnant mice, which could result in adverse pregnancy outcomes. This provided some new clues for understanding the causal mechanisms of birth defects induced by folate deficiency.

Low-dose bisphenol A impairs the function of mouse decidual stromal cells by activating LUMAN-mediated unfolded protein response

The nonsteroidal estrogenic compound bisphenol A (BPA) is widely present in several industrial and medical products including plastic food containers and sealants in dentistry. There are growing concerns on the toxic effects of this compounds since BPA is known to have reproductive toxicity. This study evaluated the effects of low-dose BPA exposure on decidual stromal cells (DSCs) of mice. The results showed that although 10 nM of BPA have no significant effect on the cell viability, it alters the expression of decidualization-related genes including Prl8a2, Prl3c1, Ptgs2, and Mmp2. Moreover, we found that low-dose BPA exposure induces UPR response in DSCs. However, the expression of the three major UPR receptors (Perk, Ire 1, and Xbp1) did not change significantly. Interestingly, the expression of Luman, a novel receptor of UPR, was significantly upregulated in a dose-dependent manner. Lentivirus containing shLuman sequence was used to generate stable Luman silencing DSCs. It's showed that Luman knockdown could affect the expression of decidualization-related genes in decidual cells after BPA treatment. In summary, these results suggest that Luman plays a key role in low dose BPA-induced decidual toxicity of DSCs in mouse.

Cytokine imbalance at materno-embryonic interface as a potential immune mechanism for recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a prominent reproductive disease that distresses about 2%-5% of couples. RPL is the loss of two or more successive spontaneous pregnancies prior to the 20th week of embryo development. The commencement of pregnancy necessitates implantation of the embryo into responsive maternal decidua synchronized with the process of placentation, decidual and myometrial trophoblast incursion as well as refashioning of spiral blood arteries of uterus. The collapse of any of the processes fundamental for pregnancy success may result into an array of pregnancy problems including spontaneous pregnancy loss. Endometrium of human female manufactures an extensive range of cytokines during the proliferative and secretory stage of the menstrual cycle. These endometrial cytokines are thought as major players for making the uterus ready for embryo implantation and placental development during pregnancy. Decidual cytokines regulate the invasion of trophoblast and remodeling of spiral arteries as well as take part in immune suppression to accomplish the pregnancy. Deterrence of maternal rejection of embryo needs a regulated milieu, which takes place essentially at the embryo-maternal interface and the tissues of the uterus. The reasons of RPL remain anonymous in a large number of cases that lead to difficulties in management and severe trauma in couples. Cytokine modulatory therapies have been shown promising for preventing RPL. Further study of novel factors is wanted to establish more effective RPL treatment protocols. The present study aims to review the outcome of cytokine breach at materno-embryonic interface and the efficacy of cytokine modulatory therapies in RPL.

HB-EGF Ameliorates Oxidative Stress-Mediated Uterine Decidualization Damage

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

Elevated insulin levels compromise endometrial decidualization in mice with decrease in uterine apoptosis in early-stage pregnancy

Women with hyperinsulinism and insulin resistance have reduced fertility, but the underlying mechanism is still poorly understood. Aberrant endometrial decidualization in early pregnancy was linked to pregnancy complications. In this study, we aimed to test whether elevated insulin levels compromise decidualization in early-stage pregnancy. C57BL/6J mice in high insulin-exposed group were given a subcutaneous injection of recombinant insulin at a concentration of 0.05 IU daily. During decidualization in early pregnancy, serum levels of insulin, E2, P4, LH, FSH and blood glucose were significantly altered in mice treated with high insulin levels. The number of embryo implantation sites and endometrial decidual markers BMP2, ER, PR was significantly decreased by high insulin levels in vivo. Artificial decidual induction in primary mouse endometrial stromal cells and immortal human endometrial stromal cells line were all compromised after treated with 100 nmol/L insulin levels. All these results on flow cytometry, transmission electron microscopy and western blotting of Bax, Bcl2, cleaved Caspase3, cleaved PARP proteins level showed that decidual cells apoptosis was significantly decreased. Mitochondrial transmembrane potential also significantly increased by the influence of high insulin levels. PI3K and p-Akt were much higher after insulin exposure and the compromised decidualization by high insulin treatment was rescued by PI3K/Akt inhibitor LY294002 both in vitro and in vivo. In conclusion, we demonstrated that elevated insulin levels could compromise mice decidualization in early-stage pregnancy and PI3K/p-Akt-regulated apoptosis was essential for this role. It provides a clue for future investigation on compromised reproduction in women with hyperinsulinemia.

Oncostatin M expression in the mouse uterus during early pregnancy promotes embryo implantation and decidualization

Oncostatin M (OSM) is a member of the interleukin-6 (IL-6) family, which functions in embryo implantation and decidualization. The expression, function and regulation of Osm in mouse uteri during early pregnancy remain unknown. We show that Osm is mainly expressed in the uterine epithelium from days 1 to 4 of pregnancy and in decidual cells on day 5 of pregnancy. Osm promotes the attachment of Osm-soaked blue beads, which mimic blastocysts, to a pseudopregnant mouse uterus. Prostaglandin E2 (PGE₂ )-induced Osm in mouse uterine epithelial cells upregulates the levels of Il-33 expression and phosphorylates Stat3. In vitro decidualization is significantly promoted by Osm. Our results indicate that PGE₂ -induced Osm may mediate embryo implantation through Il-33 and participate in decidualization via the Stat3-Egr1 pathway.

Homeobox genes for embryo implantation: From mouse to human

The proper development of uterus to a state of receptivity and the attainment of implantation competency for blastocyst are 2 indispensable aspects for implantation, which is considered to be a critical event for successful pregnancy. Like many developmental processes, a large number of transcription factors, such as homeobox genes, have been shown to orchestrate this complicated but highly organized physiological process during implantation. In this review, we focus on progress in studies of the role of homeobox genes, especially the Hox and Msx gene families, during implantation, together with subsequent development of post-implantation uterus and related reproductive defects in both mouse models and humans, that have led to better understanding of how implantation is precisely regulated and provide new insights into infertility.

The endocannabinoid anandamide impairs in vitro decidualization of human cells

Endocannabinoids (eCBs) are endogenous mediators that along with the cannabinoid receptors (CB1 and CB2), a membrane transporter and metabolic enzymes form the endocannabinoid system (ECS). Several eCBs have been discovered with emphasis on anandamide (AEA). They are involved in several biological processes such as energy balance, immune response and reproduction. Decidualization occurs during the secretory phase of human menstrual cycle, which involves proliferation and differentiation of endometrial stromal cells into decidual cells and is crucial for the establishment and progression of pregnancy. In this study, a telomerase-immortalized human endometrial stromal cell line (St-T1b) and non-differentiated primary cultures of human decidual fibroblasts from term placenta were used to characterize the ECS using immunoblotting and qRT-PCR techniques. It was shown that St-T1b cells express CB1, but not CB2, and that both receptors are expressed in HdF cells. Furthermore, the expression of fatty acid amide hydrolase (FAAH), the main degrading enzyme of AEA, increased during stromal cell differentiation. AEA inhibited cell proliferation, through deregulation of cell cycle progression and induced polyploidy. Moreover, through CB1 binding receptor, AEA also impaired cell differentiation. Therefore, AEA is proposed as a modulator of human decidualization. Our findings may provide wider implications, as deregulated levels of AEA, due to Cannabis sativa consumption or altered expression of the metabolic enzymes, may negatively regulate human endometrial stromal cell decidualization with an impact on human (in)fertility.Free Portuguese abstract: A Portuguese translation of this abstract is freely available at http://www.reproduction-online.org/content/152/4/351/suppl/DC1.

Decidualisation and placentation defects are a major cause of age-related reproductive decline

Mammalian reproductive performance declines rapidly with advanced maternal age. This effect is largely attributed to the exponential increase in chromosome segregation errors in the oocyte with age. Yet many pregnancy complications and birth defects that become more frequent in older mothers, in both humans and mice, occur in the absence of karyotypic abnormalities. Here, we report that abnormal embryonic development in aged female mice is associated with severe placentation defects, which result from major deficits in the decidualisation response of the uterine stroma. This problem is rooted in a blunted hormonal responsiveness of the ageing uterus. Importantly, a young uterine environment can restore normal placental as well as embryonic development. Our data highlight the pivotal, albeit under-appreciated, impact of maternal age on uterine adaptability to pregnancy as major contributor to the decline in reproductive success in older females.Advanced maternal age has been associated with lower reproductive success and higher risk of pregnancy complications. Here the authors show that maternal ageing-related embryonic abnormalities in mouse are caused by decidualisation and placentation defects that can be rescued by transferring the embryo from an old to a young uterus.

Decidual Stromal Cell Necroptosis Contributes to Polyinosinic-Polycytidylic Acid-Triggered Abnormal Murine Pregnancy

Infectious agents can reach the placenta either via the maternal blood or by ascending the genito-urinary tract, and then initially colonizing the maternal decidua. Decidual stromal cells (DSCs) are the major cellular component of the decidua. Although DSCs at the maternal–fetal interface contribute to the regulation of immunity in pregnancy in the face of immunological and physiological challenges, the roles of these DSCs during viral infection remain ill defined. Here, we characterized the response of DSCs to a synthetic double-stranded RNA molecule, polyinosinic-polycytidylic acid [poly(I:C)], which is a mimic of viral infection. We demonstrated that both transfection of cells with poly(I:C) and addition of extracellular (non-transfected) poly(I:C) trigger the necroptosis of DSCs and that this response is dependent on RIG-I-like receptor/IPS-1 signaling and the toll-like receptor 3/TIR-domain-containing adapter-inducing interferon-β pathway, respectively. Furthermore, following poly(I:C) challenge, pregnant mixed lineage kinase domain-like protein-deficient mice had fewer necrotic cells in the mesometrial decidual layer, as well as milder pathological changes in the uterine unit, than did wild-type mice. Collectively, our results establish that necroptosis is a contributing factor in poly(I:C)-triggered abnormal pregnancy and thereby indicate a novel therapeutic strategy for reducing the severity of the adverse effects of viral infections in pregnancy.

Expression of mmu-miR-96 in the endometrium during early pregnancy and its regulatory effects on stromal cell apoptosis via Bcl2

Decidualization of endometrial stromal cells is an important feature of implantation and pregnancy. The molecular mechanism underlying decidualization remains unclear, particularly regarding the microRNA (miRNA/miR) regulation of this process. The present study revealed the temporal and spatial distribution of mmu-miR-96 in the mouse uterus during early pregnancy by reverse transcription-quantitative polymerase chain reaction and in situ hybridization. In addition, primary stromal cells were isolated from the mouse uterus and used to explore the role of mmu-miR-96 in decidualization. The results demonstrated that mmu-miR-96 was highly expressed in stromal cells during pregnancy, and was upregulated at implantation sites. In addition, mmu-miR-96 was strongly expressed during decidualization, which indicates that it may serve a role in the decidualization of stromal cells. Based on existing reports, mmu-miR-96 participates in apoptosis; therefore the present study investigated its effects on the apoptosis of primary endometrial stromal cells. The results indicated that overexpression of mmu-miR-96 may induce apoptosis of stromal cells. In further studies regarding the underlying mechanism, the target genes of mmu-miR-96 were screened by bioinformatics analysis, and it was confirmed that B-cell lymphoma 2, an anti-apoptotic gene, was the target of mmu-miR-96, as determined using a reporter gene assay. In conclusion, the present study suggested that mmu-miR-96 participates in the decidualization of endometrial stromal cells in mice, thereby serving a key role in pregnancy.

Proliferation of mouse endometrial stromal cells in culture is highly sensitive to lysophosphatidic acid signaling

Endometrial stromal cells (ESCs) proliferate rapidly both in vivo and in vitro. Here we show that proliferation of ESCs in vitro is strongly dependent on lysophosphatidic acid (LPA) signaling. LPA is produced by autotaxin (ATX) and induces various kinds of cellular processes including migration, proliferation and inhibition of cell death possibly through six G protein-coupled receptors (LPA_1-6). We found that ESCs proliferated rapidly in vitro in an autocrine manner and that the proliferation was prominently suppressed by either an ATX inhibitor (ONO-8430506) or an LPA_1/3 antagonist (Ki16425). Among the cells lines tested, mouse ESCs were the most sensitive to these inhibitors. Proliferation of ESCs isolated from either LPA₁- or LPA₃-deficient mice was comparable to proliferation of ESCs isolated from control mice. An LPA receptor antagonist (AM095), which was revealed to be a dual LPA₁/LPA₃ antagonist, also suppressed the proliferation of ESCs. The present results show that LPA signaling has a critical role in the proliferation of ESCs, and that this role is possibly mediated redundantly by LPA₁ and LPA₃.

Positive Regulation of Decidualization by l-Type Amino Acid Transporter 1 (lat1) in Pregnant Mice

Amino acids have an important role in the pre and post implantation of placenta and embryo development. l-type amino-acid transporter 1 (lat1) is responsible for the transportation of large neutral amino acids and is mainly expressed in human fetal liver, placenta, brain, etc. This study is the first to investigate the expression of lat1 in the early pregnancy of mouse uteri and its role in the process of decidualization. Endometrial stromal cells of a mouse model were used to evaluate decidualization from Day 4–8 of pregnancy in vitro followed by lat1 knock down by small interfering RNA and by a competitive inhibitor of Leucine transport 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH). The effects of lat1 on decidualization in vivo were assessed by injecting BCH into the uterine horns. The mRNA and protein expressions of lat1 in the implantation sites were higher than that in the inter-implantation sites and were localized in the luminal and gland epithelium, stromal and decidual cells. Its increased expression (p < 0.05) was associated with artificial decidualization as well as activation of prl expression. Down-regulation of lat1 expression in these cells by siRNA and BCH inhibited the decidual progression in vitro. Inhibition of lat1 transportation by BCH controlled decidual progression in vivo also accompanied the down-regulation of prl, lat1 expression in the decidual area and embryo size on Day 8 of pregnancy. In conclusion, these results revealed that lat1 might play an important role in the decidual progression both in vitro and in vivo.

nm23 regulates decidualization through the PI3K-Akt-mTOR signaling pathways in mice and humans

STUDY QUESTION

Does nm23 have functional significance in decidualization in mice and humans?

SUMMARY ANSWER

nm23 affects decidualization via the phosphoinositide 3 kinase/mammalian target of rapamycin (PI3K-Akt-mTOR) signaling pathways in mouse endometrial stromal cells (ESCs; mESCs) and human ESCs.

WHAT IS KNOWN ALREADY

The function of nm23 in suppressing metastasis has been demonstrated in a variety of cancer types. nm23 also participates in the control of DNA replication and cell proliferation and differentiation.

STUDY DESIGN, SIZE AND DURATION

We first analyzed the expression profile of nm23 in mice during early pregnancy (n = 6/group), pseudopregnancy (n = 6/group) and artificial decidualization (n = 6/group) and in humans during the menstrual cycle phases and the first trimester. We then used primary cultured mESCs and a human ESC line, T-HESC, to explore the hormonal regulation of nm23 and the roles of nm23 in in vitro decidualization, and as a possible mediator of downstream PI3K-Akt-mTOR signaling pathways.

PARTICIPANTS/MATERIALS, SETTINGS AND METHODS

We evaluated the dynamic expression of nm23 in mice and humans using immunohistochemistry, western blot and real-time quantitative RT-PCR (RT-qPCR). Regulation of nm23 by steroid hormones was investigated in isolated primary mESCs and T-HESCs by western blot. The effect of nm23 knockdown (using siRNA) on ESC proliferation was analyzed by 5-ethynyl-2'-deoxyuridine staining (EdU) and proliferating cell nuclear antigen protein (PCNA) expression. The influence of nm23 expression on the differentiation of ESCs was determined by RT-qPCR using the mouse differentiation markers decidual/trophoblast PRL-related protein (dtprp, also named prl8a2) and prolactin family 3 subfamily c member 1 (prl3c1) and the human differentiation markers insulin-like growth factor binding protein 1 (IGFBP1) and prolactin (PRL). The effects of nm23 siRNA (si-nm23) and the PI3K inhibitor LY294002 on the downstream effects of nm23 on the PI3K-Akt-mTOR signaling pathway were estimated by western blot.

MAIN RESULTS AND THE ROLE OF CHANCE

NM23-M1 was specifically expressed in the decidual zone during early pregnancy and in artificially induced deciduoma, and NM23-H1 was strongly expressed in human first trimester decidua. The expression of nm23 was upregulated by oestradiol and progesterone (P < 0.05 versus control) in vitro in mESCs and T-HESC, and this was inhibited by their respective receptor antagonists, ICI 182,780 and RU486. Mouse and human nm23 knockdown decreased ESC proliferation and differentiation (P < 0.05 versus control). The PI3K-Akt-mTOR signaling pathways were downstream mediators of nm23 in mESCs and T-HESCs decidualization.

LIMITATIONS AND REASONS FOR CAUTION

Whether the nm23 regulates decidualization via the activation of AMPK, RAS, PKA, STAT3 or other signaling molecules remains to be determined. The role of nm23 in decidualization was tested in vitro only.

WIDER IMPLICATIONS OF THE FINDINGS

Results demonstrate that nm23 plays a vital role in decidualization in mice and humans and that nm23 gene expression is hormonally regulated. The downregulation of nm23 in decidua during the first trimester may be associated with infertility in women.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by the National Natural Science Foundation of China (grant nos. 81370731, 31571551 and 31571190), the Science and Technology Project of Chongqing Education Committee (KJ130309), open funding by the Chongqing Institute for Family Planning (1201) and the Excellent Young Scholars of Chongqing Medical University (CQYQ201302). The authors have no conflicts of interest to declare.

Hoxa-10 and Cyclin D3 Overexpression in the Decidual Reaction in a Superovulation Protocol in Young Adult C57BL/6J Mice

Following the performance of a superovulation protocol, multiple nodules were observed bilaterally in the uterine horns of 31 of 276 (11.2%) C57BL/6 J female mice aged 8.5 ± 0.6 (mean and standard error of mean) weeks. These lesions prevented embryo collection, and the uterine decidual reaction was suspected. Samples of pathological uteri (n = 20) and the normal genital tracts of donors treated with a similar superovulation protocol (control group, n = 10) were collected. Immunohistochemistry was performed to evaluate pancytokeratin, desmin, vimentin, progesterone receptor (PR), estrogen receptor α (ERα), Ki-67, cyclin D3 and c-Myc expression, as well as quantitative polymerase chain reaction to assess cyclin D3, Hoxa-10 and heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA expression. The uterine decidual reaction presented a high degree of structural organization and specifically affected the antimesometrial region of the endometrium. The abnormal decidual cells were large polygonal cells that were frequently polyploid or binucleated and strongly positive for desmin. Immunohistochemistry showed higher Ki-67 proliferation index and higher expression of PR and cyclin D3 in decidual cells in the antimesometrial aspect of the endometrium, compared to nondecidualized endometrial stromal cells in the mesometrial aspect of affected uteri, and compared to endometrial stromal cells in healthy uteri. High expression of cyclin D3 and Hoxa-10 mRNA was also observed in uteri affected by the decidual reaction. These results suggest that PR overexpression in endometrial stromal cells, likely due to high progesterone levels, triggers cyclin D3 and Hoxa-10 overexpression, which may be involved in the pathological mechanisms of the mouse uterine decidual reaction.

Polycomb repressive complex 1 controls uterine decidualization

Uterine stromal cell decidualization is an essential part of the reproductive process. Decidual tissue development requires a highly regulated control of the extracellular tissue remodeling; however the mechanism of this regulation remains unknown. Through systematic expression studies, we detected that Cbx4/2, Rybp, and Ring1B [components of polycomb repressive complex 1 (PRC1)] are predominantly utilized in antimesometrial decidualization with polyploidy. Immunofluorescence analyses revealed that PRC1 members are co-localized with its functional histone modifier H2AK119ub1 (mono ubiquitination of histone-H2A at lysine-119) in polyploid cell. A potent small-molecule inhibitor of Ring1A/B E3-ubiquitin ligase or siRNA-mediated suppression of Cbx4 caused inhibition of H2AK119ub1, in conjunction with perturbation of decidualization and polyploidy development, suggesting a role for Cbx4/Ring1B-containing PRC1 in these processes. Analyses of genetic signatures by RNA-seq studies showed that the inhibition of PRC1 function affects 238 genes (154 up and 84 down) during decidualization. Functional enrichment analyses identified that about 38% genes primarily involved in extracellular processes are specifically targeted by PRC1. Furthermore, ~15% of upregulated genes exhibited a significant overlap with the upregulated Bmp2 null-induced genes in mice. Overall, Cbx4/Ring1B-containing PRC1 controls decidualization via regulation of extracellular gene remodeling functions and sheds new insights into underlying molecular mechanism(s) through transcriptional repression regulation.

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.

Control of regional decidualization in implantation: Role of FoxM1 downstream of Hoxa10 and cyclin D3

Appropriate regulation of regional uterine stromal cell decidualization in implantation, at the mesometrial triangle and secondary decidual zone (SDZ) locations, is critical for successful pregnancy, although the regulatory mechanisms remain poorly understood. In this regard, the available animal models that would specifically allow mechanistic analysis of site-specific decidualization are strikingly limited. Our study found that heightened expression of FoxM1, a Forkhead box transcription factor, is regulated during decidualization, and its conditional deletion in mice reveals failure of implantation with regional decidualization defects such as a much smaller mesometrial decidua with enlarged SDZ. Analysis of cell cycle progression during decidualization both in vivo and in vitro demonstrates that the loss of FoxM1 elicits diploid cell deficiency with enhanced arrests prior to mitosis and concomitant upregulation of polyploidy. We further showed that Hoxa10 and cyclin D3, two decidual markers, control transcriptional regulation and intra-nuclear protein translocation of FoxM1 in polyploid cells, respectively. Overall, we suggest that proper regional decidualization and polyploidy development requires FoxM1 signaling downstream of Hoxa10 and cyclin D3.

Expression of KRAS in the endometrium of early pregnant mice and its effect during embryo implantation

This study investigated the expression pattern of Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) in the endometrium of early-stage pregnant mice and its function during embryo implantation. The expression of KRAS was measured at the mRNA level using real-time polymerase chain reaction (PCR) and at the protein level using immunohistochemistry and western blotting. The expressions of KRAS mRNA and protein were not significantly different in the endometrium of pseudopregnant and early-stage pregnant mice. However, the immunohistochemistry results showed that KRAS was highly expressed in the decidualizing stromal cells on days 5-7 of mouse pregnancy and was enhanced in the epithelial cells as pregnancy progressed. The expression of KRAS protein was higher after the stromal cell was artificially decidualized in vivo and in vitro. Stromal cell proliferation was attenuated after down-regulating KRAS expression. After silencing KRAS in the mouse uterus, the embryo implantation rate was significantly reduced (P < 0.005). We speculate that KRAS may regulate the stromal cell proliferation and differentiation progress and then affect the embryo implantation process. This study reveals that KRAS plays an important role in regulating the embryo implantation process.

IFN-γ induces aberrant CD49b⁺ NK cell recruitment through regulating CX3CL1: a novel mechanism by which IFN-γ provokes pregnancy failure

Interferon-γ (IFN-γ), a pleiotropic lymphokine, has important regulatory effects on many cell types. Although IFN-γ is essential for the initiation of uterine vascular modifications and maintenance of decidual integrity, IFN-γ administration can also cause pregnancy failure in many species. However, little is known about the effector mechanisms involved. In this study, using an IFN-γ-induced abortion mouse model, we reported that no Dolichos biflorus agglutinin lectin-positive uterine natural killer (uNK) cells were observed in the uteri from IFN-γ-induced abortion mice. By contrast, the percentage of CD3⁻CD49b⁺ NK cells in the uterus and blood from a foetal resorption group was significantly higher than that of the control group. Similarly, significantly upregulated expression of CD49b (a pan-NK cell marker), CX3CL1 and CX3CR1 (CX3CL1 receptor) was detected in the uteri of IFN-γ-induced abortion mice. Using isolated uterine stromal cells, we showed that upregulated expression of CX3CL1 by IFN-γ was dependent on a Janus family kinase 2-signal transducers and activators of transcription 1 (JAK2-STAT1) pathway. We further demonstrated the chemotactic activity of CX3CL1 in uterine stromal cell conditioned medium on primary splenic NK cells. Finally, we observed increased recruitment of CD49b⁺ NK cells into the endometrium after exogenous CX3CL1 administration. Collectively, our findings indicate that IFN-γ can significantly increase uterine CX3CL1 expression via activation of the JAK2-STAT1 pathway, thus inducing CD49b⁺ NK cell uterine homing, and eventually provoke foetal loss. Thus, we provide a new line of evidence correlating the deleterious effects of IFN-γ on pregnancy with the aberrant regulation of CX3CL1 and CD49b⁺ NK cells.

Lefty inhibits in vitro decidualization by regulating P57 and cyclin D1 expressions

Endometrial decidualization is highly important for successful construction and maintenance of embryo implantation and pregnancy. Lefty gene at different menstrual cycle phases has different expressions, indicating its regulatory significance. To study the mechanism of Lefty in decidualization, human endometrial stromal cells (hESCs) were cultured and induced with medroxyprogesterone acetate (MPA) and 8-bromoadenosine-cAMP (8-Br-cAMP) in vitro as a research model. Our results showed that Lefty1 overexpression inhibited MPA- and 8-Br-cAMP-induced hESC decidualization and significantly reduced the secretion of prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP-1). With the inhibition of Lefty1 expression, hESC decidualization induced by MPA and 8-Br-cAMP became more remarkable, and the secretions of PRL and IGFBP-1 were higher too. Further tests indicated that during the process of decidualization, P57 expression increased, whereas cyclin D1 expression decreased. Although Lefty1 overexpression did not significantly change the expressions of P57 and cyclin D1, inhibition of Lefty1 expression resulted in more evident changes in P57 and cyclin D1 expressions. Meanwhile, cell cycle examination showed that Lefty1 overexpression reduced the cell cycle arrest at G1/S phase in the in vitro hESC decidualization model. Therefore, Lefty1 could regulate the cell cycle via modulating the expressions of P57 and cyclin D1 and then inhibit the decidualization in vitro.

Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy

We have determined uterine glycogen content, metabolizing enzyme expression and activity in the mink, a species that exhibits obligatory embryonic diapause, resulting in delayed implantation. Gross uterine glycogen concentrations were highest in estrus, decreased 50% by diapause and 90% in pregnancy (P ≤ 0.05). Endometrial glycogen deposits, which localized primarily to glandular and luminal epithelia, decreased 99% between estrus and diapause (P ≤ 0.05) and were nearly undetectable in pregnancy. Glycogen synthase and phosphorylase proteins were most abundant in the glandular epithelia. Glycogen phosphorylase activity (total) in uterine homogenates was higher during estrus and diapause, than pregnancy. While glycogen phosphorylase protein was detected during estrus and diapause, glycogen synthase was almost undetectable after estrus, which probably contributed to a higher glycogenolysis/glycogenesis ratio during diapause. Uterine glucose-6-phosphatase 3 gene expression was greater during diapause, when compared to estrus (P ≤ 0.05) and supports the hypothesis that glucose-6-phosphate resulting from phosphorylase activity was dephosphorylated in preparation for export into the uterine lumen. The relatively high amount of hexokinase-1 protein detected in the luminal epithelia during estrus and diapause may have contributed to glucose trapping after endometrial glycogen reserves were depleted. Collectively, our findings suggest to us that endometrial glycogen reserves may be an important source of energy, supporting uterine and conceptus metabolism up to the diapausing blastocyst stage. As a result, the size of uterine glycogen reserves accumulated prior to mating may in part, determine the number of embryos that survive to the blastocyst stage, and ultimately litter size.

Mammalian target of rapamycin complex 1 and cyclooxygenase 2 pathways cooperatively exacerbate endometrial cancer

The underlying causes of endometrial cancer (EMC) are poorly understood, and treatment options for patients with advanced stages of the disease are limited. Mutations in the phosphatase and tensin homologue gene are frequently detected in EMC. Cyclooxygenase 2 (Cox2) and mammalian target of rapamycin complex 1 (mTORC1) are known downstream targets of the phosphatase and tensin homologue protein, and their activities are up-regulated in EMC. However, it is not clear whether Cox2 and mTORC1 are crucial players in cancer progression or whether they work in parallel or cooperatively. In this study, we used a Cox2 inhibitor, celecoxib, and an mTORC1 inhibitor, rapamycin, in mouse models of EMC and in human EMC cell lines to explore the interactive roles of Cox2 and mTORC1 signaling. We found that a combined treatment with celecoxib and rapamycin markedly reduces EMC progression. We also observed that rapamycin reduces Cox2 expression, whereas celecoxib reduces mTORC1 activity. These results suggest that Cox2 and mTORC1 signaling is cross-regulated and cooperatively exacerbate EMC.

The epidermal growth factor receptor critically regulates endometrial function during early pregnancy

Infertility and adverse gynecological outcomes such as preeclampsia and miscarriage represent significant female reproductive health concerns. The spatiotemporal expression of growth factors indicates that they play an important role in pregnancy. The goal of this study is to define the role of the ERBB family of growth factor receptors in endometrial function. Using conditional ablation in mice and siRNA in primary human endometrial stromal cells, we identified the epidermal growth factor receptor (Egfr) to be critical for endometrial function during early pregnancy. While ablation of Her2 or Erbb3 led to only a modest reduction in litter size, mice lacking Egfr expression are severely subfertile. Pregnancy demise occurred shortly after blastocyst implantation due to defects in decidualization including decreased proliferation, cell survival, differentiation and target gene expression. To place Egfr in a genetic regulatory hierarchy, transcriptome analyses was used to compare the gene signatures from mice with conditional ablation of Egfr, wingless-related MMTV integration site 4 (Wnt4) or boneless morphogenic protein 2 (Bmp2); revealing that not only are Bmp2 and Wnt4 key downstream effectors of Egfr, but they also regulate distinct physiological functions. In primary human endometrial stromal cells, marker gene expression, a novel high content image-based approach and phosphokinase array analysis were used to demonstrate that EGFR is a critical regulator of human decidualization. Furthermore, inhibition of EGFR signaling intermediaries WNK1 and AKT1S1, members identified in the kinase array and previously unreported to play a role in the endometrium, also attenuate decidualization. These results demonstrate that EGFR plays an integral role in establishing the cellular context necessary for successful pregnancy via the activation of intricate signaling and transcriptional networks, thereby providing valuable insight into potential therapeutic targets.

Approximately 10% of reproductive aged women are considered infertile. While great strides have been made in assisted reproductive technologies, overall success rates, especially considering the cost, remain low. Studies indicate that due to its sequential nature, nearly 75% of pregnancy failures are due to defects that occur very early in gestation. Therefore, understanding the physiological changes that occur in the endometrium during this period and how those changes are regulated is of paramount importance if we are to improve our ability to address female reproductive health concerns. We investigated a family of growth factor receptors and identified one that critically regulates the growth and survival of the endometrium in response to the implanting embryo. Furthermore, we used unbiased approaches to identify which signaling pathways and genetic networks are activated downstream of this receptor to execute each of the processes necessary for a successful pregnancy. Understanding the mechanisms and genetic networks with which pregnancy is regulated is a prerequisite to the development of effective pharmaceutical therapeutics.