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

Purinergic system molecules: expression and regulation of enzymes, transporters, and adenosine triphosphate receptors and the role of adenosine triphosphate at the maternal-conceptus interface in pigs†

The purinergic system is composed of purine nucleotides, enzymes, transporters, and receptors and is involved in a variety of physiological processes in the body, including development, metabolism, immunity, tumorigenesis, and reproduction. The importance of the purinergic system for embryo implantation in the endometrium and in pathophysiological conditions has been shown in some species. However, the expression, regulation, and function of purinergic system molecules at the maternal-conceptus interface in pigs is not fully understood. Therefore, we determined the expression of purinergic system molecules in the endometrium during the estrous cycle and pregnancy and in the conceptus and chorioallantoic tissues during pregnancy in pigs. The expression of many purinergic system molecules in the endometrium changed dynamically during pregnancy, with the expression of several components in the endometrium greater on day 15 of pregnancy than day 15 of the estrous cycle, and it was regulated by conceptus-derived interleukin-1beta and interferon-gamma. Purinergic system molecules were also expressed in conceptuses during early pregnancy and in chorioallantoic tissues during mid- to term pregnancy. Furthermore, adenosine triphosphate, a major purinergic signaling molecule, increased migration of endometrial epithelial and conceptus trophectoderm cells, the expression of prostaglandin synthetic enzymes, and the secretion of prostaglandin F2alpha in endometrial epithelial cells in vitro. These data suggest that the purinergic system molecules expressed in the endometrium, conceptus, and chorioallantoic tissues might play an important role in the establishment and maintenance of pregnancy by regulating various cellular functions at the maternal-conceptus interface in pigs.

Effect of Diethylstilbestrol on Implantation and Decidualization in Mice

Diethylstilbestrol (DES) is a synthetic non-steroidal estrogen, which was widely used to prevent preterm birth and abortion from the 1940s to the 1970s. DES can increase the incidence of infertility, the abnormal reproductive tract, and autoimmune diseases. However, the mechanism underlying DES on early pregnancy in mice is unclear. This study evaluated the effects of DES on early pregnancy in mice, especially on uterine receptivity and decidualization. Newborn female mice were subcutaneously injected with 0.1 mg/kg DES, 1 mg/kg DES, or sesame oil as controls for 5 consecutive days. At 6 weeks old, these female mice were mated with 8-12-week-old fertile males to obtain pregnancy. The uteri of these mice were collected on days 4, 5, and 8 of pregnancy for further analysis. On days 5 and 8 of pregnancy, the number of implantation sites in 0.1 mg/kg DES group is similar to the control group, while almost no implantation sites are detected in the 1 mg/kg DES group. On day 4 of pregnancy, there was no significant difference in uterine receptive molecules between the control group and the 0.1 mg/kg DES group. However, the levels of uterine receptive molecules in the 1 mg/kg DES group are abnormal. In addition, 6 μM DES significantly inhibits mouse in vitro decidualization. The excessive activation of pyroptosis may lead to pregnancy failure. The pyroptosis-related molecules in the 1 mg/kg DES group were significantly up-regulated, suggesting that DES may contribute to pregnancy failure by over-activating pyroptosis.

Regulation and function of inosine monophosphate dehydrogenase 2 cytoophidia during mouse and human decidualization

Decidualization is essential for establishing pregnancy in both mice and humans. Cellular stresses, including nucleolar stress and DNA damage, are involved in this process. Inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme for de novo guanosine triphosphate (GTP) synthesis, forms membrane-free macromolecular structures called "cytoophidia" under specific conditions. However, whether IMPDH cytoophidia are present during decidualization remains unknown. In this study, we found that IMPDH2 cytoophidia are primarily detected in mouse decidual cells during early pregnancy. On day 5 of pregnancy, more IMPDH2 cytoophidia are observed at implantation sites than at inter-implantation sites. Physiologically, uteri activated by estrogen exhibit more IMPDH2 cytoophidia than those maintained in a delayed state by progesterone. Although GTP is required for in vitro decidualization in mice, elevated GTP level impairs this process. Furthermore, IMPDH2 cytoophidia can induce nucleolar stress and DNA damage in mice. In the human endometrium, IMPDH2 cytoophidia are observed during the menstrual cycle, particularly enriched in the secretory phase. They promote human decidualization and naturally enhance cellular senescence. Our findings highlight the physiological relevance of IMPDH2 cytoophidia during early pregnancy in mice and humans.

Embryo-Derived Cathepsin B Promotes Implantation and Decidualization by Activating Pyroptosis

Embryo implantation and decidualization are crucial for a successful pregnancy. How the inflammatory response is regulated during these processes is undefined. Pyroptosis is an inflammatory form of cell death mediated by gasdermin D (GSDMD). Through in vivo, cultured epithelial cells and organoids, it is shown that pyroptosis occurs in epithelial cells at the implantation site. Compared with those on day 4 of pseudopregnancy and delayed implantation, pyroptosis-related protein levels are significantly increased on day 4 of pregnancy and activated implantation, suggesting that blastocysts are involved in regulating pyroptosis. Blastocyst-derived cathepsin B (CTSB) is stimulated by preimplantation estradiol-17β and induces pyroptosis in epithelial cells. Pyroptosis-induced IL-18 secretion from epithelial cells activates a disintegrin and metalloprotease 12 (ADAM12) to process the epiregulin precursor into mature epiregulin. Epiregulin (EREG) enhances in vitro decidualization in mice. Pyroptosis-related proteins are detected in the mid-secretory human endometrium and are elevated in the recurrent implantation failure endometrium. Lipopolysaccharide treatment in pregnant mice causes implantation failure and increases pyroptosis-related protein levels. Therefore, the data suggest that modest pyroptosis is beneficial for embryo implantation and decidualization. Excessive pyroptosis can be harmful and lead to pregnancy failure.

Histamine promotes mouse decidualization through stimulating epithelial amphiregulin release

Accumulating evidence shows that inflammation is essential for embryo implantation and decidualization. Histamine, a proinflammatory factor that is present in almost all mammalian tissues, is synthesized through decarboxylating histidine by histidine decarboxylase (HDC). Although histamine is known to be essential for decidualization, the underlying mechanism remains undefined. In the present study, histamine had no obvious direct effects on in vitro decidualization in mice. However, the obvious differences in HDC protein levels between day 4 of pregnancy and day 4 of pseudopregnancy, as well as between delayed and activated implantation, suggested that the blastocyst may be involved in regulating HDC expression. Furthermore, blastocyst-derived tumor necrosis factor α (TNFα) significantly increased HDC levels in the luminal epithelium. Histamine increased the levels of amphiregulin (AREG) and disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) proteins, which was abrogated by treatment with famotidine, a specific histamine type 2 receptor (H2R) inhibitor, or by TPAI-1 (a specific inhibitor of ADAM17). Intraluminal injection of urocanic acid (HDC inhibitor) on day 4 of pregnancy significantly reduced the number of implantation sites on day 5 of pregnancy. TNFα-stimulated increases in HDC, AREG and ADAM17 protein levels was abrogated by urocanic acid, a specific inhibitor of HDC. Additionally, AREG treatment significantly promoted in vitro decidualization. Collectively, our data suggests that blastocyst-derived TNFα induces luminal epithelial histamine secretion, and histamine increases mouse decidualization through ADAM17-mediated AREG release.

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.

Expression profile analysis of LncRNAs and mRNAs in pre-receptive endometrium of women with polycystic ovary syndrome undergoing in vitro fertilization-embryo transfer

BACKGROUND

To compare the expression levels of long non-coding RNA (lncRNA) and messenger RNA (mRNA) in pre-receptive endometrium between patients with Polycystic Ovary Syndrome (PCOS)and normal ovulation undergoing in vitro fertilization-embryo transfer (IVF-ET).

METHODS

Endometrial tissues were collected with endometrial vacuum curette in pre-receptive phase (3 days after oocytes retrieval) from PCOS and control groups. LncRNAs and mRNAs of endometrium were identified via RNA sequencing and alignments. A subset of 9 differentially expressed lncRNAs and 11 mRNAs were validated by quantitative reverse transcription polymerase chain reaction(qRT-PCR)in 22 PCOS patients and 18 ovulation patients. The function of mRNAs with differential expression patterns were explored using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG).

RESULTS

We found out 687 up-regulated and 680 down-regulated mRNAs, as well as 345 up-regulated and 63 down-regulated lncRNAs in the PCOS patients in contrast to normal ovulation patients. qRT-PCR was used to detect the expression of 11 mRNAs, and validated that the expression of these 6 mRNAs CXCR4, RABL6, OPN3, SYBU, IDH1, NOP10 were significantly elevated among PCOS patients, and the expression of ZEB1 was significantly decreased. qRT-PCR was performed to detect the expression of 9 lncRNAs, and validated that the expression of these 7 lncRNAs IDH1-AS1, PCAT14, FTX, DANCR, PRKCQ-AS1, SNHG8, TPT1-AS1 were significantly enhanced among PCOS patients. Bioinformatics analysis showed that differentially expressed genes (DEGs) involved KEGG pathway were tyrosine metabolism, PI3K-Akt pathway, metabolic pathway, Jak-STAT pathway, pyruvate metabolism, protein processing in endoplasmic reticulum, oxidative phosphorylation and proteasome. The up-regulation of GO classification was involved in ATP metabolic process, oxidative phosphorylation, RNA catabolic process, and down-regulation of GO classification was response to corticosteroid, steroid hormone, and T cell activation.

CONCLUSION

Our results determined the characteristics and expression profile of endometrial lncRNAs and mRNAs in PCOS patients in pre-receptive phase, which is the day 3 after oocytes retrival. The possible pathways and related genes of endometrial receptivity disorders were found, and those lncRNAs may be developed as a predictive biomarker of endometrium in pre-receptive phase.

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.

Paradoxical expression of NRP1 in decidual stromal and immune cells reveals a novel inflammation balancing mechanism during early pregnancy

OBJECTIVE AND DESIGN

To investigate the balancing mechanisms between decidualization-associated inflammation and pregnancy-related immunotolerance.

MATERIAL OR SUBJECTS

Decidual samples from women with normal pregnancy (n = 58) or unexplained spontaneous miscarriage (n = 13), peripheral blood from normal pregnancy and endometria from non-pregnancy (n = 10) were collected. Primary endometrial stromal cells (ESCs), decidual stromal cells (DSCs), decidual immune cells (DICs) and peripheral blood mononuclear cells (PBMCs) were isolated.

TREATMENT

The plasmid carrying neuropilin-1 (NRP1) gene was transfected into ESC for overexpression. To induce decidualization in vitro, ESCs were treated with a combination of 10 nM estradiol, 100 nM progesterone and 0.5 mM cAMP. Anti-Sema3a and anti-NRP1 neutralizing antibodies were applied to block the ligand-receptor interactions.

METHODS

RNA-seq analysis was performed to identify differentially expressed genes in DSCs and DICs, and NRP1 expression was verified by Western blotting and flow cytometry. The secretion of inflammatory mediators was measured using a multifactor cytometric bead array. The effects of Sema3a-NRP1 pathway on DICs were determined by flow cytometry. Statistical differences between groups were compared using the T test and one way or two-way ANOVA.

RESULTS

Combined with five RNA-seq datasets, NRP1 was the only immune checkpoint changing oppositely between DSCs and DICs. The decreased expression of NRP1 in DSCs allowed intrinsic inflammatory responses required for decidualization, while its increased expression in DICs enhanced tolerant phenotypes beneficial to pregnancy maintenance. DSC-secreted Sema3a promoted immunosuppression in DICs via NRP1 binding. In women with miscarriage, NRP1 was abnormally elevated in DSCs but diminished in decidual macrophages and NK cells.

CONCLUSION

NRP1 is a multifunctional controller that balances the inflammatory states of DSCs and DICs in gravid uterus. Abnormal expression of NRP1 is implicated in miscarriage.

Oryzalin impairs maternal-fetal interaction during early pregnancy via ROS-mediated P38 MAPK/AKT and OXPHOS downregulation

Oryzalin is a dinitroaniline pesticide for the control of weed growth via suppression of microtubule synthesis. There are studies about the deleterious effects of dinitroaniline pesticides on the reproductive system. Therefore, we attempted to demonstrate the toxic mechanisms of oryzalin on early pregnancy using porcine uterine epithelial cells (pLE) and trophectoderm (pTr) cells. According to our results, the viability and proliferation of pLE and pTr cells were suppressed in response to oryzalin exposure, and cell cycle progression was affected. Additionally, oryzalin induced apoptotic cell death and impaired mitochondrial membrane polarity in pLE and pTr cells. Moreover, we confirmed that oryzalin significantly downregulated adenosine triphosphate (ATP) production via the oxidative phosphorylation system and upregulated reactive oxygen species (ROS) generation in both pLE and pTr cells. The oryzalin-induced ROS generation was mitigated by N-acetylcysteine, a ROS scavenger, and further upregulation of phosphor-P38 MAPK/AKT/P70S6K protein expression was ameliorated in both pLE and pTr cells. We also confirmed that the suppression of migration and proliferation in oryzalin-treated pLE and pTr cells was restored upon oxidative stress mitigation. In summary, we revealed that the cytotoxic mechanisms of oryzalin-induced implantation failure were mediated by ROS-induced intracellular signaling regulation and migratory potential in pLE and pTr cells.

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

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

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.

Effects of Cadmium Exposure on Leydig Cells and Blood Vessels in Mouse Testis

Environmental exposure to cadmium (Cd) contributes to a decline in the quality of human semen. Although the testis is sensitive to Cd exposure, the mechanism underlying how cadmium affects the testis remains to be defined. In this study, male mice were treated with intraperitoneal injections of 0, 0.5, 1.5 and 2.5 mg CdCl₂/kg/day for 10 days, respectively. Both the testicular weight and the 3β-HSD activity of Leydig cells were significantly reduced with the administration of 2.5 mg CdCl₂/kg/day. The height of endothelial cells in the interstitial blood vessels significantly increased with the use of 2.5 mg CdCl₂/kg/day compared with the control. Western blot data showed that the protein levels of CD31, αSMA, caveolin and Ng2 increased with cadmium exposure, and this increase was particularly significant with the administration of 2.5 mg CdCl₂/kg/day. CD31, αSMA, caveolin and Ng2 are related to angiogenesis. Based on our data, cadmium exposure may stimulate the proliferation of the mural cells and endothelial cells of blood vessels, which may lead to abnormal function of the testis.

Regulation and Function of Laminin A5 during Mouse and Human Decidualization

Decidualization is essential to the establishment of pregnancy in rodents and primates. Laminin A5 (encoding by Laminin α5) is a member of the laminin family, which is mainly expressed in the basement membranes. Although laminins regulate cellular phenotype maintenance, adhesion, migration, growth, and differentiation, the expression, function, and regulation of laminin A5 during early pregnancy are still unknown. Therefore, we investigated the expression and role of laminin A5 during mouse and human decidualization. Laminin A5 is highly expressed in mouse decidua and artificially induced deciduoma. Laminin A5 is significantly increased under in vitro decidualization. Laminin A5 knockdown significantly inhibits the expression of Prl8a2, a marker for mouse decidualization. Progesterone stimulates the expression of laminin A5 in ovariectomized mouse uterus and cultured mouse stromal cells. We also show that progesterone regulates laminin A5 through the PKA-CREB-C/EBPβ pathway. Laminin A5 is also highly expressed in human pregnant decidua and cultured human endometrial stromal cells during in vitro decidualization. Laminin A5 knockdown by siRNA inhibits human in vitro decidualization. Collectively, our study reveals that laminin A5 may play a pivotal role during mouse and human decidualization via the PKA-CREB-C/EBPβ pathway.

A proteomic atlas of ligand-receptor interactions at the ovine maternal-fetal interface reveals the role of histone lactylation in uterine remodeling

Well-orchestrated maternal–fetal cross talk occurs via secreted ligands, interacting receptors, and coupled intracellular pathways between the conceptus and endometrium and is essential for successful embryo implantation. However, previous studies mostly focus on either the conceptus or the endometrium in isolation. The lack of integrated analysis impedes our understanding of early maternal–fetal cross talk. Herein, focusing on ligand–receptor complexes and coupled pathways at the maternal–fetal interface in sheep, we provide the first comprehensive proteomic map of ligand–receptor pathway cascades essential for embryo implantation. We demonstrate that these cascades are associated with cell adhesion and invasion, redox homeostasis, and the immune response. Candidate interactions and their physiological roles were further validated by functional experiments. We reveal the physical interaction of albumin and claudin 4 and their roles in facilitating embryo attachment to endometrium. We also demonstrate a novel function of enhanced conceptus glycolysis in remodeling uterine receptivity by inducing endometrial histone lactylation, a newly identified histone modification. Results from in vitro and in vivo models supported the essential role of lactate in inducing endometrial H3K18 lactylation and in regulating redox homeostasis and apoptotic balance to ensure successful implantation. By reconstructing a map of potential ligand–receptor pathway cascades at the maternal–fetal interface, our study presents new concepts for understanding molecular and cellular mechanisms that fine-tune conceptus–endometrium cross talk during implantation. This provides more direct and accurate insights for developing potential clinical intervention strategies to improve pregnancy outcomes following both natural and assisted conception.

In situ Synthesized Monosodium Urate Crystal Enhances Endometrium Decidualization via Sterile Inflammation During Pregnancy

High level of uric acid (UA) is the major origin of gout, and is highly associated with various pregnant complications, such as preeclampsia and gestational diabetes. However, UA’s level and role in the very early stage of pregnancy has not been uncovered. This study aims to investigate the relevance of serum UA and decidualization, an essential process for the establishment and maintenance of pregnancy in women and mice during the early stage of pregnancy. In this study, we first proved that expression level of UA synthase xanthine dehydrogenase (XDH) is highly increased along with decidualization of endometrial stromal cells in both in vitro and in vivo models. Furthermore, serum and endometrial levels of UA are higher in mice with decidualized uterin horn and in vitro decidualized stromal cells. The existence of monosodium urate (MSU) crystal was also confirmed by immunostaining. Next, the roles of MSU on decidualization were explored by both in vitro and in vivo models. Our data shows MSU crystal but not UA enhances the decidualization response of endometrial stromal cells, via the upregulation of inflammatory genes such Ptgs2 and Il11. inhibiting of Cox-2 activity abolishes MSU crystal induced higher expression of decidualization marker Prl8a2. At last, in women, we observed enriched expression of XDH in decidua compare to non-decidualized endometrium, the serum level of UA is significantly increased in women in very early stage of pregnancy, and drop down after elective abortion. In summary, we observed an increased serum UA level in the early stage of women’s pregnancy, and proved that the increased level of UA results from the expressed XDH in decidualizing endometrium of both human and mouse, leading to the formation of MSU crystal. MSU crystal can enhance the decidualization response via inflammatory pathways. Our study has uncovered the association between UA, MSU, and decidualization during the early stage of pregnancy.