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

Quantitative Proteomics Analysis Reveals XDH Related with Ovarian Oxidative Stress Involved in Broodiness of Geese

Studies have demonstrated significant alterations in ovarian oxidative stress levels, ovarian degeneration, and follicular atresia during the broody period in geese. The results of this study showed that during the broody period, geese exhibited degraded ovarian tissues, disrupted follicular development, a thinner granulosa cell layer, and lower levels of ovarian hormones E2, P4, and AMH. Antioxidant activity (GSH, CAT, SOD, T-AOC, and the content of H2O2) and the mRNA expression levels of antioxidant genes (GPX, SOD-1, SOD-2, CAT, COX-2, and Hsp70) were significantly higher in pre-broody geese compared to laying geese, while the expression of apoptosis-related genes (p53, Caspase-3, and Caspase-9) increased and the anti-apoptotic gene Bcl-2 decreased. Additionally, proteomic analysis identified 703 differentially expressed proteins (DEPs), primarily concentrated in the GO categories of the biological process (biological regulation, response to stimulus, etc.) and enriched in the KEGG pathways (PI3K-Akt signaling pathway, etc.). Among them, XDH was central to the regulatory network. Furthermore, Western blotting revealed higher expression of XDH in the ovaries of pre-broody geese than those of laying geese. Pearson correlation analysis indicated a significant correlation between XDH expression and oxidative stress markers in the ovaries of geese (r > 0.75). Overall, these results demonstrated that geese experience ovarian atrophy and remarkably increased oxidative stress during the broody period, suggesting that XDH may be a key driver of broodiness in geese.

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.

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.

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.

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

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

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.

Research on the Mechanism of Asperosaponin VI for Treating Recurrent Spontaneous Abortion by Bioinformatics Analysis and Experimental Validation

Asperosaponin VI (AS6), as the quality marker of Dipsaci Radix, is verified to exert therapeutic effect on alleviating recurrent spontaneous abortion (RSA). However, due to the lack of relevant research, its molecular mechanism is still unclear. We retrieved targets for AS6 and RSA, and then used their overlapped targets for PPI analysis. In addition, we used GO and KEGG enrichment analyses, and molecular docking to investigate the anti-RSA mechanisms of AS6. Furthermore, we conducted in vitro experiments to validate the predictions of network pharmacology. Results showed that a total of 103 AS6-associated targets and 2084 RSA-associated targets, with 49 targets overlapped. GO enrichment analysis showed 845 significant biological processes like decidualization, while KEGG pathway enrichment analysis revealed 76 significant entries including 18 signaling pathways, which were closely linked to PI3K-Akt, HIF-1, TNF, IL-17, and VEGF signaling pathways, etc. Molecular docking findings verified that AS6 had tight link with the key targets including JUN, CASP3, STAT3, SRC, and PTGS2. Notably, in vitro experiments revealed that AS6 treatment could exert lower expressions of JUN, pro-CASP3, CASP3, STAT3, SRC, and PTGS2 in decidual cells compared with progesterone despite the expressions of STAT3, SRC, and PTGS2 with no significant difference, and mifepristone could interfere with the effects. In general, numerous targets and multiple pathways involve during the process of AS6 treatment against RSA. Moreover, our in vitro research first reported that AS6 may regulate the expressions of key targets (JUN, CASP3, STAT3, SRC, and PTGS2) in decidual cells to promote decidualization, thus treating RSA.