Uterine-specific p53 deficiency confers premature uterine senescence and promotes preterm birth in mice

Chenodeoxycholic Acid Fortified Diet Drives Ovarian Steroidogenesis to Improve Embryo Implantation through Enhancing Uterine Receptivity via Progesterone Receptor Signaling Pathway in Rats

Infertility is a worldwide reproductive health problem influenced by the embryo implantation efficiency. We previously revealed that dietary chenodeoxycholic acid (CDCA) positively influence the early embryo implantation. But how CDCA regulate embryo implantation is largely unexplored. Herein, we investigated the mechanism behind CDCA's regulation on embryo implantation in rats. Results showed that CDCA promoted uterine receptivity, leading to increased number of implantation sites. Mechanistically, CDCA reshaped maternal amino acid metabolism and enhanced serum progesterone levels. CDCA enhanced ovarian progesterone synthesis by improving steroidogenesis-related protein (StAR and CYP11A1) expression via Takeda G-protein-coupled receptor 5. Elevated progesterone exaggerated uterine progesterone but weakened the estradiol signaling in the CDCA group, contributing to better uterine receptive for embryo implantation. Additionally, elevated transcription repressor Stat5b induced the down-regulation of progesterone-metabolizing enzyme 20-hydroxysteroid dehydrogenase 20α-HSD, complementally explained uterine progesterone signaling enhancement. Overall, our data revealed that CDCA drove ovarian steroidogenesis to improve embryo implantation through enhancing uterine receptivity via progesterone receptor pathway in rats. Therefore, CDCA diet may be a potential favorable nutritional strategy for infertility and pregnancy management.

Uterine prostaglandin DP receptor-induced upon implantation contributes to decidualization together with EP4 receptor

To investigate the yet-unknown roles of prostaglandins (PGs) in the uterus, we analyzed the expression of various PG receptors in the uterus. We found that three types of Gs-coupled PG receptors, DP, EP2, and EP4, were expressed in luminal epithelial cells from the peri-implantation period to late pregnancy. DP expression was also induced in stromal cells within the mesometrial region, whereas EP4 was expressed in stromal cells within the anti-mesometrial region during the peri-implantation period. The timing of DP induction after embryo attachment correlated well with that of cyclooxygenase-2 (COX-2); however, COX-2-expressing stromal cells were located in the vicinity of the embryo, whereas DP-expressing stromal cells surrounded these cells on the mesometrial side. Specific [3H]PGD2-binding activity was detected in the decidua of uteri, with PGD2 synthesis comparable to that of PGE2 detected in the uteri during the peri-implantation period. Administration of the COX-2-specific inhibitor celecoxib caused adverse effects on decidualization, as demonstrated by the attenuated weight of the implantation sites, which was recovered by the simultaneous administration of a DP agonist. Such a rescuing effect of the DP agonist was mimicked by an EP4 agonist, but not an EP2 agonist. While the importance of DP signaling was shown pharmacologically, DP/EP2 double deficiency did not affect implantation and decidualization, suggesting the contribution of EP4 to these processes. Indeed, administration of an EP4 antagonist substantially affected decidualization in DP/EP2-deficient mice. These results suggest that COX-2-derived PGD2 and PGE2 contribute to decidualization via a coordinated pathway of DP and EP4 receptors.

Targeting a mTOR/autophagy axis: a double-edged sword of rapamycin in spontaneous miscarriage

Immune dysfunction is a primary culprit behind spontaneous miscarriage (SM). To address this, immunosuppressive agents have emerged as a novel class of tocolytic drugs, modulating the maternal immune system's tolerance towards the embryo. Rapamycin (PubChem CID:5284616), a dual-purpose compound, functions as an immunosuppressive agent and triggers autophagy by targeting the mTOR pathway. Its efficacy in treating SM has garnered significant research interest in recent times. Autophagy, the cellular process of self-degradation and recycling, plays a pivotal role in numerous health conditions. Research indicates that autophagy is integral to endometrial decidualization, trophoblast invasion, and the proper functioning of decidual immune cells during a healthy pregnancy. Yet, in cases of SM, there is a dysregulation of the mTOR/autophagy axis in decidual stromal cells or immune cells at the maternal-fetal interface. Both in vitro and in vivo studies have highlighted the potential benefits of low-dose rapamycin in managing SM. However, given mTOR's critical role in energy metabolism, inhibiting it could potentially harm the pregnancy. Moreover, while low-dose rapamycin has been deemed safe for treating recurrent implant failure, its potential teratogenic effects remain uncertain due to insufficient data. In summary, rapamycin represents a double-edged sword in the treatment of SM, balancing its impact on autophagy and immune regulation. Further investigation is warranted to fully understand its implications.

Deciphering decidual deficiencies in recurrent spontaneous abortion and the therapeutic potential of mesenchymal stem cells at single-cell resolution

BACKGROUND

Recurrent spontaneous abortion (RSA) is a challenging condition that affects the health of women both physically and mentally, but its pathogenesis and treatment have yet to be studied in detail. In recent years, Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) have been shown to be effective in treating various diseases. Current understanding of RSA treatment using WJ-MSCs is limited, and the exact mechanisms of WJ-MSCs action in RSA remains largely unclear. In this study, we explored the decidual deficiencies in RSA and the therapeutic potential of WJ-MSCs at single-cell resolution.

METHODS

Three mouse models were established: a normal pregnancy group, an RSA group, and a WJ-MSC treatment group. Decidual tissue samples were collected for single-cell RNA sequencing (scRNA-seq) and functional verification, including single-cell resolution in situ hybridization on tissues (SCRINSHOT) and immunofluorescence.

RESULTS

We generated a single-cell atlas of decidual tissues from normal pregnant, RSA, and WJ-MSC-treated mice and identified 14 cell clusters in the decidua on day 14. Among these cell populations, stromal cells were the most abundant cell clusters in the decidua, and we further identified three novel subclusters (Str_0, Str_1, and Str_2). We also demonstrated that the IL17 and TNF signaling pathways were enriched for upregulated DEGs of stromal cells in RSA mice. Intriguingly, cell-cell communication analysis revealed that Str_1 cell-related gene expression was greatly reduced in the RSA group and rescued in the WJ-MSC treatment group. Notably, the interaction between NK cells and other cells in the RSA group was attenuated, and the expression of Spp1 (identified as an endometrial toleration-related marker) was significantly reduced in the NK cells of the RSA group but could be restored by WJ-MSC treatment.

CONCLUSION

Herein, we implemented scRNA-seq to systematically evaluate the cellular heterogeneity and transcriptional regulatory networks associated with RSA and its treatment with WJ-MSCs. These data revealed potential therapeutic targets of WJ-MSCs to remodel the decidual subpopulations in RSA and provided new insights into decidua-derived developmental defects at the maternal-foetal interface.

Autophagy genes and signaling pathways in endometrial decidualization and pregnancy complications

Autophagy is a process that occurs in almost all eukaryotic cells and this process is controlled by several molecular processes. Its biological roles include the provision of energy, the maintenance of cell homeostasis, and the promotion of aberrant cell death. The importance of autophagy in pregnancy is gradually becoming recognized. In literature, it has been indicated that autophagy has three different effects on the onset and maintenance of pregnancy: embryo (embryonic development), feto-maternal immune crosstalk, and maternal (decidualization). In humans, proper decidualization is a major predictor of pregnancy accomplishment and it can be influenced by different factors. This review highlights the genes, pathways, regulation, and function of autophagy in endometrial decidualization and other involved factors in this process.

BMP4 in Human Endometrial Stromal Cells Can Affect Decidualization by Regulating FOXO1 Expression

CONTEXT

Recurrent spontaneous abortion (RSA) is defined as the loss of 2 or more consecutive intrauterine pregnancies with the same sexual partner in the first trimester. Despite its significance, the etiology and underlying mechanisms of RSA remain elusive. Defective decidualization is proposed as one of the potential causes of RSA, with abnormal decidualization leading to disturbances in trophoblast invasion function.

OBJECTIVE

To assess the role of bone morphogenetic protein 4 (BMP4) in decidualization and RSA.

METHODS

Decidual samples were collected from both RSA patients and healthy controls to assess BMP4 expression. In vitro cell experiments utilized the hESC cell line to investigate the impact of BMP4 on decidualization and associated aging, as well as its role in the maternal-fetal interface communication. Subsequently, a spontaneous abortion mouse model was established to evaluate embryo resorption rates and BMP4 expression levels.

RESULTS

Our study identified a significant downregulation of BMP4 expression in the decidua of RSA patients compared to the normal control group. In vitro, BMP4 knockdown resulted in inadequate decidualization and inhibited associated aging processes. Mechanistically, BMP4 was implicated in the regulation of FOXO1 expression, thereby influencing decidualization and aging. Furthermore, loss of BMP4 hindered trophoblast migration and invasion via FOXO1 modulation. Additionally, BMP4 downregulation was observed in RSA mice.

CONCLUSION

Our findings highlighted the downregulation of BMP4 in both RSA patients and mice. BMP4 in human endometrial stromal cells was shown to modulate decidualization by regulating FOXO1 expression. Loss of BMP4 may contribute to the pathogenesis of RSA, suggesting potential avenues for abortion prevention strategies.

Multiomics insights into the female reproductive aging

The human female reproductive lifespan significantly diminishes with age, leading to decreased fertility, reduced fertility quality and endocrine function disorders. While many aspects of aging in general have been extensively documented, the precise mechanisms governing programmed aging in the female reproductive system remain elusive. Recent advancements in omics technologies and computational capabilities have facilitated the emergence of multiomics deep phenotyping. Through the application and refinement of various high-throughput omics methods, a substantial volume of omics data has been generated, deepening our comprehension of the pathogenesis and molecular underpinnings of reproductive aging. This review highlights current and emerging multiomics approaches for investigating female reproductive aging, encompassing genomics, epigenomics, transcriptomics, proteomics, metabolomics, and microbiomics. We elucidate their influence on fundamental cell biology and translational research in the context of reproductive aging, address the limitations and current challenges associated with multiomics studies, and offer a glimpse into future prospects.

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.

Uterine Aging and Reproduction: Dealing with a Puzzle Biologic Topic

Uterine aging is the process of the senescence of uterine tissue, observed in all middle-aged mammals. Since the aging-related changes in the uterus are associated with infertility and poor pregnancy outcomes, with a lack of studies discussing uterine aging, authors reviewed uterine aging and its consequences on reproduction. MEDLINE, Scopus, and PubMed searches during the years 1990-2023 were performed using a combination of keywords and terms on such topics. According to the author's evaluation, articles were identified, selected, and included in this narrative review. The aging process has an unfavorable impact on the uterus of mammals. There are different and selected molecular pathways related to uterine aging in humans and animals. Uterine aging impairs the function of the uterine myometrium, neurofibers of the human uterus, and human endometrium. These biological pathways modulate oxidative stress, anti-inflammatory response, inflammation, mitochondrial function, DNA damage repair, etc. All these dysregulations have a role in poorer reproductive performance and pregnancy outcomes in older mammals. The most recent data suggest that uterine aging is accompanied by genetic, epigenetic, metabolic, and immunological changes. Uterine aging has a negative impact on the reproductive performance in mammalian species, but it could be potentially modulated by pharmacological agents, such as quercetin and dasatinib.

Progesterone Activates the Histone Lactylation-Hif1α-glycolysis Feedback Loop to Promote Decidualization

Decidualization is a progesterone-dependent cellular differentiation process that is essential for establishing pregnancy. Robust activation of glycolysis and lactate synthesis during decidualization is remarkable, but their developmental functions remain largely unknown. Herein, we identify that endometrial lactate production plays a critical role in establishing local histone lactylation, a newly identified histone modification, and is important for ensuring normal decidualization. Enhanced endometrial glycolysis is the hallmark metabolic change and is tightly coupled with H4K12la during decidualization. Inhibition of histone lactylation impaired decidualization, in either physiological conception or in vivo and in vitro induced decidualization models. Mechanistic study based on CUT&Tag and ATAC-seq revealed that a transcriptional factor hypoxia-inducible factor 1 α (Hif1α) is the critical regulatory target of H4K12la, and in turn forms an H4K12la-Hif1α-glycolysis feedback loop to drive decidualization. Moreover, we demonstrate that the loop is directly activated by progesterone during decidualization. Our study not only advances the current knowledge of the role of lactate in regulating uterine function, but also establishes a novel functional link among the major endocrine factors, endometrial metabolic change, and epigenetic modification during endometrial remodeling. These findings present valuable clues to develop clinical intervention strategies to improve pregnancy outcomes following both natural conception and assisted reproduction.

Deciphering a critical role of uterine epithelial SHP2 in parturition initiation at single cell resolution

The timely onset of female parturition is a critical determinant for pregnancy success. The highly heterogenous maternal decidua has been increasingly recognized as a vital factor in setting the timing of labor. Despite the cell type specific roles in parturition, the role of the uterine epithelium in the decidua remains poorly understood. This study uncovers the critical role of epithelial SHP2 in parturition initiation via COX1 and COX2 derived PGF2α leveraging epithelial specific Shp2 knockout mice, whose disruption contributes to delayed parturition initiation, dystocia and fetal deaths. Additionally, we also show that there are distinct types of epithelium in the decidua approaching parturition at single cell resolution accompanied with profound epithelium reformation via proliferation. Meanwhile, the epithelium maintains the microenvironment by communicating with stromal cells and macrophages. The epithelial microenvironment is maintained by a close interaction among epithelial, stromal and macrophage cells of uterine stromal cells. In brief, this study provides a previously unappreciated role of the epithelium in parturition preparation and sheds lights on the prevention of preterm birth.

Stromal cells-specific retinoic acid determines parturition timing at single-cell and spatial-temporal resolution

The underlying mechanisms governing parturition remain largely elusive due to limited knowledge of parturition preparation and initiation. Accumulated evidences indicate that maternal decidua plays a critical role in parturition initiation. To comprehensively decrypt the cell heterogeneity in decidua approaching parturition, we investigate the roles of various cell types in mouse decidua process and reveal previously unappreciated insights in parturition initiation utilizing single-cell RNA sequencing (scRNA-seq). We enumerate the cell types in decidua and identity five different stromal cells populations and one decidualized stromal cells. Furthermore, our study unravels that stromal cells prepare for parturition by regulating local retinol acid (RA) synthesis. RA supplement decreases expression of extracellular matrix-related genes in vitro and accelerates the timing of parturition in vivo. Collectively, the discovery of contribution of stromal cells in parturition expands current knowledge about parturition and opens up avenues for the intervention of preterm birth (PTB).

Mechanism of BLIMP1/TRIM66/COX2 in human decidua participates in parturition†

The mechanism underlying the initiation of parturition remains unclear. Cyclooxygenase 2 and prostaglandins in decidual membrane tissue play an important role in the "parturition cascade." With the advancement of gestation, the expression of the transcriptional suppressor B lymphocyte-induced maturation protein 1 in the decidual membrane gradually decreases. Through chromatin immunoprecipitation sequencing, we found that B lymphocyte-induced maturation protein 1 has a binding site in the distal intergenic of PTGS2(COX2). Tripartite motif-containing protein 66 is a chromatin-binding protein that usually performs transcriptional regulatory functions by "reading" histone modification sites in chromatin. In this study, tripartite motif-containing protein 66 exhibits the same trend of expression as B lymphocyte-induced maturation protein 1 in the decidua during gestation. Moreover, the co-immunoprecipitation assay revealed that tripartite motif-containing protein 66 combined with B lymphocyte-induced maturation protein 1. This finding indicated that tripartite motif-containing protein 66 formed a transcription complex with B lymphocyte-induced maturation protein 1, which coregulated the expression of COX2. In animal experiments, we injected si-Blimp1 adenoviruses (si-Blimp1), Blimp1 overexpression plasmid (Blimp1-OE), and Trim66 overexpression plasmid (Trim66-OE) through the tail vein of mice. The results showed that B lymphocyte-induced maturation protein 1 and tripartite motif-containing protein 66 affected the initiation of parturition in mice. Therefore, the present evidence suggests that B lymphocyte-induced maturation protein 1 and tripartite motif-containing protein 66 partially participate in the initiation of labor, which may provide a new perspective for exploring the mechanism of term labor.

Identification and Imaging of Prostaglandin Isomers Utilizing MS3 Product Ions and Silver Cationization

Prostaglandins (PGs) are important lipid mediators involved in physiological processes, such as inflammation and pregnancy. The pleiotropic effects of the PG isomers and their differential expression from cell types impose the necessity for studying individual isomers locally in tissue to understand the molecular mechanisms. Currently, mass spectrometry (MS)-based analytical workflows for determining the PG isomers typically require homogenization of the sample and a separation method, which results in a loss of spatial information. Here, we describe a method exploiting the cationization of PGs with silver ions for enhanced sensitivity and tandem MS to distinguish the biologically relevant PG isomers PGE2, PGD2, and Δ12-PGD2. The developed method utilizes characteristic product ions in MS3 for training prediction models and is compatible with direct infusion approaches. We discuss insights into the fragmentation pathways of Ag+ cationized PGs during collision-induced dissociation and demonstrate the high accuracy and robustness of the model to predict isomeric compositions of PGs. The developed method is applied to mass spectrometry imaging (MSI) of mouse uterus implantation sites using silver-doped pneumatically assisted nanospray desorption electrospray ionization and indicates localization to the antimesometrial pole and the luminal epithelium of all isomers with different abundances. Overall, we demonstrate, for the first time, isomeric imaging of major PG isomers with a simple method that is compatible with liquid-based extraction MSI methods.

Flip a coin: cell senescence at the maternal-fetal interface†

During pregnancy, cell senescence at the maternal-fetal interface is required for maternal well-being, placental development, and fetal growth. However, recent reports have shown that aberrant cell senescence is associated with multiple pregnancy-associated abnormalities, such as preeclampsia, fetal growth restrictions, recurrent pregnancy loss, and preterm birth. Therefore, the role and impact of cell senescence during pregnancy requires further comprehension. In this review, we discuss the principal role of cell senescence at the maternal-fetal interface, emphasizing its "bright side" during decidualization, placentation, and parturition. In addition, we highlight the impact of its deregulation and how this "dark side" promotes pregnancy-associated abnormalities. Furthermore, we discuss novel and less invasive therapeutic practices associated with the modulation of cell senescence during pregnancy.

Hypoxia-inducible factor 1 signaling drives placental aging and can provoke preterm labor

Most cases of preterm labor have unknown cause, and the burden of preterm birth is immense. Placental aging has been proposed to promote labor onset, but specific mechanisms remain elusive. We report findings stemming from unbiased transcriptomic analysis of mouse placenta, which revealed that hypoxia-inducible factor 1 (HIF-1) stabilization is a hallmark of advanced gestational timepoints, accompanied by mitochondrial dysregulation and cellular senescence; we detected similar effects in aging human placenta. In parallel in primary mouse trophoblasts and human choriocarcinoma cells, we modeled HIF-1 induction and demonstrated resultant mitochondrial dysfunction and cellular senescence. Transcriptomic analysis revealed that HIF-1 stabilization recapitulated gene signatures observed in aged placenta. Further, conditioned media from trophoblasts following HIF-1 induction promoted contractility in immortalized uterine myocytes, suggesting a mechanism by which the aging placenta may drive the transition from uterine quiescence to contractility at the onset of labor. Finally, pharmacological induction of HIF-1 via intraperitoneal administration of dimethyloxalyl glycine (DMOG) to pregnant mice caused preterm labor. These results provide clear evidence for placental aging in normal pregnancy, and demonstrate how HIF-1 signaling in late gestation may be a causal determinant of the mitochondrial dysfunction and senescence observed within the trophoblast as well as a trigger for uterine contraction.

Uterine-specific Ezh2 deletion enhances stromal cell senescence and impairs placentation, resulting in pregnancy loss

Maternal uterine remodeling facilitates embryo implantation, stromal cell decidualization and placentation, and perturbation of these processes may cause pregnancy loss. Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase that epigenetically represses gene transcription; loss of uterine EZH2 affects endometrial physiology and induces infertility. We utilized a uterine Ezh2 conditional knockout (cKO) mouse to determine EZH2's role in pregnancy progression. Despite normal fertilization and implantation, embryo resorption occurred mid-gestation in Ezh2cKO mice, accompanied by compromised decidualization and placentation. Western blot analysis revealed Ezh2-deficient stromal cells have reduced amounts of the histone methylation mark H3K27me3, causing upregulation of senescence markers p21 and p16 and indicating that enhanced stromal cell senescence likely impairs decidualization. Placentas from Ezh2cKO dams on gestation day (GD) 12 show architectural defects, including mislocalization of spongiotrophoblasts and reduced vascularization. In summary, uterine Ezh2 loss impairs decidualization, increases decidual senescence, and alters trophoblast differentiation, leading to pregnancy loss.

The EZH2-PRC2-H3K27me3 axis governs the endometrial cell cycle and differentiation for blastocyst invasion

Infertility occurs in 15% of couples worldwide. Recurrent implantation failure (RIF) is one of the major problems in in vitro fertilization and embryo transfer (IVF-ET) programs, and how to manage patients with RIF to achieve successful pregnancy outcomes remains unresolved. Here, a uterine polycomb repressive complex 2 (PRC2)-regulated gene network was found to control embryo implantation. Our RNA-seq analyses of the human peri-implantation endometrium obtained from patients with RIF and fertile controls revealed that PRC2 components, including its core enzyme enhancer of zeste homolog 2 (EZH2)-catalyzing H3K27 trimethylation (H3K27me3) and their target genes are dysregulated in the RIF group. Although fertility of uterine epithelium-specific knockout mice of Ezh2 (eKO mice) was normal, Ezh2-deleted mice in the uterine epithelium and stroma (uKO mice) exhibited severe subfertility, suggesting that stromal Ezh2 plays a key role in female fertility. The RNA-seq and ChIP-seq analyses revealed that H3K27me3-related dynamic gene silencing is canceled, and the gene expression of cell-cycle regulators is dysregulated in Ezh2-deleted uteri, causing severe epithelial and stromal differentiation defects and failed embryo invasion. Thus, our findings indicate that the EZH2-PRC2-H3K27me3 axis is critical to preparing the endometrium for the blastocyst invasion into the stroma in mice and humans.

Establishment of the fetal-maternal interface: developmental events in human implantation and placentation

Early pregnancy is a complex and well-orchestrated differentiation process that involves all the cellular elements of the fetal-maternal interface. Aberrant trophoblast-decidual interactions can lead to miscarriage and disorders that occur later in pregnancy, including preeclampsia, intrauterine fetal growth restriction, and preterm labor. A great deal of research on the regulation of implantation and placentation has been performed in a wide range of species. However, there is significant species variation regarding trophoblast differentiation as well as decidual-specific gene expression and regulation. Most of the relevant information has been obtained from studies using mouse models. A comprehensive understanding of the physiology and pathology of human implantation and placentation has only recently been obtained because of emerging advanced technologies. With the derivation of human trophoblast stem cells, 3D-organoid cultures, and single-cell analyses of differentiated cells, cell type-specific transcript profiles and functions were generated, and each exhibited a unique signature. Additionally, through integrative transcriptomic information, researchers can uncover the cellular dysfunction of embryonic and placental cells in peri-implantation embryos and the early pathological placenta. In fact, the clinical utility of fetal-maternal cellular trafficking has been applied for the noninvasive prenatal diagnosis of aneuploidies and the prediction of pregnancy complications. Furthermore, recent studies have proposed a viable path toward the development of therapeutic strategies targeting placenta-enriched molecules for placental dysfunction and diseases.

An unanticipated discourse of HB-EGF with VANGL2 signaling during embryo implantation

Implantation is the first direct encounter between the embryo and uterus during pregnancy, and Hbegf is the earliest known molecular signaling for embryo-uterine crosstalk during implantation. The downstream effectors of heparin-binding EGF (HB-EGF) in implantation remain elusive due to the complexity of EGF receptor family. This study shows that the formation of implantation chamber (crypt) triggered by HB-EGF is disrupted by uterine deletion of Vangl2, a key planar cell polarity component (PCP). We found that HB-EGF binds to ERBB2 and ERBB3 to recruit VANGL2 for tyrosine phosphorylation. Using in vivo models, we show that uterine VAGL2 tyrosine phosphorylation is suppressed in Erbb2/Erbb3 double conditional knockout mice. In this context, severe implantation defects in these mice lend support to the critical role of HB-EGF-ERBB2/3-VANGL2 in establishing a two-way dialogue between the blastocyst and uterus. In addition, the result addresses an outstanding question how VANGL2 is activated during implantation. Taken together, these observations reveal that HB-EGF regulates the implantation process by influencing uterine epithelial cell polarity comprising VANGL2.

BAFF and APRIL counterregulate susceptibility to inflammation-induced preterm birth

Clinical evidence points to a function for B cell-activating factor (BAFF) in pregnancy. However, direct roles for BAFF-axis members in pregnancy have not been examined. Here, via utility of genetically modified mice, we report that BAFF promotes inflammatory responsiveness and increases susceptibility to inflammation-induced preterm birth (PTB). In contrast, we show that the closely related A proliferation-inducing ligand (APRIL) decreases inflammatory responsiveness and susceptibility to PTB. Known BAFF-axis receptors serve a redundant function in signaling BAFF/APRIL presence in pregnancy. Treatment with anti-BAFF/APRIL monoclonal antibodies or BAFF/APRIL recombinant proteins is sufficient to manipulate susceptibility to PTB. Notably, macrophages at the maternal-fetal interface produce BAFF, while BAFF and APRIL presence divergently shape macrophage gene expression and inflammatory function. Overall, our findings demonstrate that BAFF and APRIL play divergent inflammatory roles in pregnancy and provide therapeutic targets for mitigating risk of inflammation-induced PTB.

Unveiling uterine aging: Much more to learn

Uterine aging is an important factor that impacts fertility, reproductive health, and uterus-related diseases; however, it remains poorly explored. Functionally, these disturbances have been associated with an abnormal hormonal response in the endometrium and decreased endometrial receptivity. Based on emerging evidence, these alterations are mediated via the senescence of endometrial stem cells and impaired decidualization of endometrial stromal cells. Multiple molecular activities may participate in uterine aging, including oxidative stress, inflammation, fibrosis, DNA damage response, and cellular senescence. Over the past decade, several protective strategies targeting these biological processes have afforded promising results, including stem cell therapy, anti-aging drugs, and herbal medicines. However, the currently available evidence is fragmented and scattered. Here, we summarize the most recent findings regarding uterine aging, including functional and structural alterations and potential cellular and molecular mechanisms, and discuss potential protective interventions against uterine aging. Thereby, we hope to provide a comprehensive understanding of the pathophysiological processes and underlying mechanisms associated with uterine aging, as well as improve fecundity and reproductive outcomes in females of advanced reproductive age.

Characterization of methylation profiles in spontaneous preterm birth placental villous tissue

Preterm birth is a global public health crisis which results in significant neonatal and maternal mortality. Yet little is known regarding the molecular mechanisms of idiopathic spontaneous preterm birth, and we have few diagnostic markers for adequate assessment of placental development and function. Previous studies of placental pathology and our transcriptomics studies suggest a role for placental maturity in idiopathic spontaneous preterm birth. It is known that placental DNA methylation changes over gestation. We hypothesized that if placental hypermaturity is present in our samples, we would observe a unique idiopathic spontaneous preterm birth DNA methylation profile potentially driving the gene expression differences we previously identified in our placental samples. Our results indicate the idiopathic spontaneous preterm birth DNA methylation pattern mimics the term birth methylation pattern suggesting hypermaturity. Only seven significant differentially methylated regions fitting the idiopathic spontaneous preterm birth specific (relative to the controls) profile were identified, indicating unusually high similarity in DNA methylation between idiopathic spontaneous preterm birth and term birth samples. We identified an additional 1,718 significantly methylated regions in our gestational age matched controls where the idiopathic spontaneous preterm birth DNA methylation pattern mimics the term birth methylation pattern, again indicating a striking level of similarity between the idiopathic spontaneous preterm birth and term birth samples. Pathway analysis of these regions revealed differences in genes within the WNT and Cadherin signaling pathways, both of which are essential in placental development and maturation. Taken together, these data demonstrate that the idiopathic spontaneous preterm birth samples display a hypermature methylation signature than expected given their respective gestational age which likely impacts birth timing.

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.

Oxidative stress on vessels at the maternal-fetal interface for female reproductive system disorders: Update

Considerable evidence shows that oxidative stress exists in the pathophysiological process of female reproductive system diseases. At present, there have been many studies on oxidative stress of placenta during pregnancy, especially for preeclampsia. However, studies that directly focus on the effects of oxidative stress on blood vessels at the maternal-fetal interface and their associated possible outcomes are still incomplete and ambiguous. To provide an option for early clinical prediction and therapeutic application of oxidative stress in female reproductive system diseases, this paper briefly describes the composition of the maternal-fetal interface and the molecular mediators produced by oxidative stress, focuses on the sources of oxidative stress and the signaling pathways of oxidative stress at the maternal-fetal interface, expounds the adverse consequences of oxidative stress on blood vessels, and deeply discusses the relationship between oxidative stress and some pregnancy complications and other female reproductive system diseases.

Spontaneous preterm birth: Involvement of multiple feto-maternal tissues and organ systems, differing mechanisms, and pathways

Survivors of preterm birth struggle with multitudes of disabilities due to improper in utero programming of various tissues and organ systems contributing to adult-onset diseases at a very early stage of their lives. Therefore, the persistent rates of low birth weight (birth weight < 2,500 grams), as well as rates of neonatal and maternal morbidities and mortalities, need to be addressed. Active research throughout the years has provided us with multiple theories regarding the risk factors, initiators, biomarkers, and clinical manifestations of spontaneous preterm birth. Fetal organs, like the placenta and fetal membranes, and maternal tissues and organs, like the decidua, myometrium, and cervix, have all been shown to uniquely respond to specific exogenous or endogenous risk factors. These uniquely contribute to dynamic changes at the molecular and cellular levels to effect preterm labor pathways leading to delivery. Multiple intervention targets in these different tissues and organs have been successfully tested in preclinical trials to reduce the individual impacts on promoting preterm birth. However, these preclinical trial data have not been effectively translated into developing biomarkers of high-risk individuals for an early diagnosis of the disease. This becomes more evident when examining the current global rate of preterm birth, which remains staggeringly high despite years of research. We postulate that studying each tissue and organ in silos, as how the majority of research has been conducted in the past years, is unlikely to address the network interaction between various systems leading to a synchronized activity during either term or preterm labor and delivery. To address current limitations, this review proposes an integrated approach to studying various tissues and organs involved in the maintenance of normal pregnancy, promotion of normal parturition, and more importantly, contributions towards preterm birth. We also stress the need for biological models that allows for concomitant observation and analysis of interactions, rather than focusing on these tissues and organ in silos.

The Regulators of Human Endometrial Stromal Cell Decidualization

Several factors are important for implantation and subsequent placentation in the endometrium, including immunity, angiogenesis, extracellular matrix, glucose metabolism, reactive oxidative stress, and hormones. The involvement or abnormality of these factors can impair canonical decidualization. Unusual decidualization can lead to perinatal complications, such as disruption of trophoblast invasion. Drastic changes in the morphology and function of human endometrial stromal cells (hESCs) are important for decidualization of the human endometrium; hESCs are used to induce optimal morphological and functional decidualization in vitro because they contain estrogen and progesterone receptors. In this review, we will focus on the studies that have been conducted on hESC decidualization, including the results from our laboratory.

PGRMC1 Regulates Cellular Senescence via Modulating FOXO1 Expression in Decidualizing Endometrial Stromal Cells

The appropriate differentiation of endometrial stromal cells (ESCs) into decidual cells is required for embryo implantation and subsequent placentation into humans. Decidualization is accompanied by the appearance of senescent-like cells. We recently reported the secretory phase-specific downregulation of endometrial progesterone receptor membrane component 1 (PGRMC1) and enhanced decidualization upon PGRMC1 knockdown and inhibition in cultured ESCs. However, it remains unknown whether PGRMC1 is involved in cellular senescence during decidualization. Here, we showed that the small interfering RNA (siRNA)-mediated knockdown of PGRMC1 and the inhibition of PGRMC1 by AG-205 increased the expression of the transcription factor forkhead box protein O1 (FOXO1) and the senescence-associated β-galactosidase activity in cAMP analog- and progesterone-treated ESCs. Furthermore, the knockdown of FOXO1 repressed the decidual senescence induced by siRNA-based PGRMC1 knockdown or AG-205 treatment. Taken together, the decreased PGRMC1 expression in ESCs may accelerate decidualization and cellular senescence via the upregulation of FOXO1 expression for appropriate endometrial remodeling and embryo implantation during the secretory phase.

The immunobiology of preterm labor and birth: intra-amniotic inflammation or breakdown of maternal-fetal homeostasis

In brief

The syndrome of preterm labor comprises multiple established and novel etiologies. This review summarizes the distinct immune mechanisms implicated in preterm labor and birth and highlights potential strategies for its prevention.

Abstract

Preterm birth, the leading cause of neonatal morbidity and mortality worldwide, results from preterm labor, a syndrome that includes multiple etiologies. In this review, we have summarized the immune mechanisms implicated in intra-amniotic inflammation, the best-characterized cause of preterm labor and birth, as well as novel etiologies non-associated with intra-amniotic inflammation (i.e. formally known as idiopathic). While the intra-amniotic inflammatory responses driven by microbes (infection) or alarmins (sterile) have some overlap in the participating cellular and molecular processes, the distinct natures of these two conditions necessitate the implementation of specific approaches to prevent adverse pregnancy and neonatal outcomes. Intra-amniotic infection can be treated with the correct antibiotics, whereas sterile intra-amniotic inflammation could potentially be treated by administering a combination of anti-inflammatory drugs (e.g. betamethasone, inflammasome inhibitors, etc.). Recent evidence also supports the role of fetal T-cell activation as a newly described trigger for preterm labor and birth in a subset of cases diagnosed as idiopathic. Moreover, herein we also provide evidence of two maternally-driven immune mechanisms responsible for preterm births formerly considered to be idiopathic. First, the impairment of maternal Tregs can lead to preterm birth, likely due to the loss of immunosuppressive activity resulting in unleashed effector T-cell responses. Secondly, homeostatic macrophages were shown to be essential for maintaining pregnancy and promoting fetal development, and the adoptive transfer of homeostatic M2-polarized macrophages shows great promise for preventing inflammation-induced preterm birth. Collectively, in this review, we discuss the established and novel immune mechanisms responsible for preterm birth and highlight the potential targets for novel strategies aimed at preventing the multi-etiological syndrome of preterm labor leading to preterm birth.

A gene network of uterine luminal epithelium organizes mouse blastocyst implantation

Purpose

The receptive endometrium is critical for blastocyst implantation. In mice, after blastocysts enter the uterine cavities on day 4 of pregnancy (day 1 = vaginal plug), blastocyst attachment is completed within 24 h, accompanied by dynamic interactions between the uterine luminal epithelium and the blastocysts. Any failures in this process compromise subsequent pregnancy outcomes. Here, we performed comprehensive analyses of gene expression at the luminal epithelium in the peri-implantation period.

Methods

RNA-seq combined with laser microdissection (LMD) was used to reveal unique gene expression kinetics in the epithelium.

Results

We found that the prereceptive epithelium on day 3 specifically expresses cell cycle-related genes. In addition, days 3 and 4 epithelia express glutathione pathway-related genes, which are protective against oxidative stresses. In contrast, day 5 epithelium expresses genes involved in glycolysis and the regulation of cell proliferation. The genes highly expressed on days 3 and 4 compared to day 5 are related to progesterone receptor signaling, and the genes highly expressed on day 5 compared to days 3 and 4 are associated with the ones regulated by H3K27me3.

Conclusions

These results suggest that specific gene expression patterns govern uterine functions during early pregnancy, contributing to implantation success.

Generation and characterization of human Fetal membrane and Decidual cell lines for reproductive biology experiments†

Human fetal membrane and maternal decidua parietalis form one of the major feto-maternal interfaces during pregnancy. Studies on this feto-maternal interface is limited as several investigators have limited access to the placenta, and experience difficulties to isolate and maintain primary cells. Many cell lines that are currently available do not have the characteristics or properties of their primary cells of origin. Therefore, we created, characterized the immortalized cells from primary isolates from fetal membrane-derived amnion epithelial cells, amnion and chorion mesenchymal cells, chorion trophoblast cells and maternal decidua parietalis cells. Primary cells were isolated from a healthy full-term, not in labor placenta. Primary cells were immortalized using either a HPV16E6E7 retroviral or a SV40T lentiviral system. The immortalized cells were characterized for the morphology, cell type-specific markers, and cell signalling pathway activation. Genomic stability of these cells was tested using RNA seq, karyotyping, and short tandem repeats DNA analysis. Immortalized cells show their characteristic morphology, and express respective epithelial, mesenchymal and decidual markers similar to that of primary cells. Gene expression of immortalized and primary cells were highly correlated (R = 0.798 to R = 0.974). Short tandem repeats DNA analysis showed in the late passage number (>P30) of cell lines matched 84-100% to the early passage number (<P10) of the cell lines revealing there were no genetic drift over the passages. Karyotyping also revealed no chromosomal anomalies. Creation of these cell lines can standardize experimental approaches, eliminate subject to subject variabilities, and benefit the reproductive biological studies on pregnancies by using these cells.

Transcriptomic analysis of human endometrial stromal cells during early embryo invasion

PURPOSE

During early embryo invasion (48 h after embryo attachment), what functional changes accompany dynamic gene expression alterations in human endometrial stromal cells?

METHOD

In the present study, primary human endometrial stromal cells (phESCs) were cultured. After in vitro decidualization, primary human endometrial stromal cells (phESCs) were cultured with blastocysts for 48 h. During this process, blastocysts attached and invaded the phESCs (embryo-invaded primary human endometrial stromal cells, ehESCs). We performed comprehensive transcriptomic profiling of phESCs (two replicates) and ehESCs (five replicates) and analyzed the differentially expressed gene (DEGs) sets for gene ontology (GO) terms and Kyoto encyclopaedia of genes and genomes (KEGG) pathway enrichment. To analyse potential connectivity patterns between the transcripts in these DEG sets, a protein-protein interaction (PPI) network was constructed using the STRING database.

RESULTS

A total of 592 DEGs were identified between phESCs and ehESCs after embryo invasion. Primary human endometrial stromal cells underwent significant transcriptomic changes that occur in a stepwise fashion. Oxidative phosphorylation, mitochondrial organization, and P53 signalling pathways were significantly altered in phESCs after embryo invasion. EP300 may play a key role in regulating transcription via chromatin remodelling to facilitate the adaptive gene expression changes that occur during embryo invasion.

CONCLUSIONS

Our data identify dynamic transcriptome changes that occur in endometrial stromal cells within 48 h after embryo invasion. The pathways that we found to be enriched in phESCs after embryo invasion (oxidative phosphorylation, mitochondrial organization, and P53 signalling) may represent novel mechanisms underlying embryo implantation, and may illuminate the reasons that some women experience reproductive failure.Key messagesHuman endometrial stromal cells have undergone changes in gene expression regulation and signalling pathways during the embryo invasion.Mitochondrial-oxidative phosphorylation changes in human stromal cells manifested as down-regulation of gene expression in the electron transport chain.TP53 signalling pathway and transcriptional regulator EP300 assist stromal cells to get adaptive changes during embryo invasion phase.

The damage effect of heat stress and psychological stress combined exposure on uterus in female rats

AIMS

Explore the effects of heat stress and psychological stress combined exposure on the uterus and its underlying mechanisms.

MAIN METHODS

Sixty female Sprague-Dawley rats were randomly assigned to four groups: control group, psychological stress group, high ambient temperature group, and high ambient temperature combined with psychological stress group. All treatments were administered for two weeks. During this period, the estrous cycle, body weights and rectal temperature were measured regularly. Then, ovarian weight coefficient, serum estradiol (E₂) and progesterone (P) concentration, uterine histomorphological alterations, levels of tumor necrosis factor alpha (TNF-α), malondialdehyde (MDA) and superoxide dismutase (SOD), and the expressions of ovarian hormone receptors, leukemia inhibitory factor (LIF) and its receptor, homeobox gene A10 (HoxA10), Wnt5a, Wnt7a, β-catenin, and P-β-catenin^Y142 in the uterus and endometrium were detected.

KEY FINDINGS

High temperature combined with psychological stress lead to body weight, body temperature, ovarian hormones and estrus cycle disorder, uterine gland ducts expansion and endometrial thickness reduction, and the decreased expression of endometrial receptivity markers (LIF and HoxA10). Further, disturbed expression of E₂ and P receptors in endometrium, elevated MDA and TNF-α levels, and decreased Wnt5a, Wnt7a and P-β-catenin^Y142 content were found. Our data suggested that co-exposure to high temperature and psychological stress could aggravate uterine damage probably by inducing ovarian hormonal disorder and the subsequent oxidative stress and inflammation, and reduce the endometrial function through suppressing Wnt signaling.

SIGNIFICANCE

This will provide the scientific basis for improving female reproductive health, and preventing and treating reproductive disorders.

Bone marrow-derived progenitor cells contribute to remodeling of the postpartum uterus

Endometrial stem/progenitor cells play a role in postpartum uterine tissue regeneration, but the underlying mechanisms are poorly understood. While circulating bone marrow (BM)-derived cells (BMDCs) contribute to nonhematopoietic endometrial cells, the contribution of BMDCs to postpartum uterus remodeling is unknown. We investigated the contribution of BMDCs to the postpartum uterus using 5-fluorouracil-based nongonadotoxic BM transplant from green fluorescent protein (GFP) donors into wild-type C57BL/6J female mice. Flow cytometry showed an influx of GFP+ cells to the uterus immediately postpartum accounting for 28.7% of total uterine cells, followed by a rapid decrease to prepregnancy levels. The majority of uterine GFP+ cells were CD45+ leukocytes, and the proportion of nonhematopoietic CD45-GFP+ cells peaked on postpartum day (PPD) 1 (17.5%). Immunofluorescence colocalization of GFP with CD45 pan-leukocyte and F4/80 macrophage markers corroborated these findings. GFP+ cells were found mostly in subepithelial stromal location. Importantly, GFP+ cytokeratin-positive epithelial cells were found within the luminal epithelium exclusively on PPD1, demonstrating direct contribution to postpartum re-epithelialization. A subset (3.2%) of GFP+ cells were CD31+CD45- endothelial cells, and found integrated within blood vessel endothelium. Notably, BM-derived GFP+ cells demonstrated preferential proliferation (PCNA+) and apoptosis (TUNEL+) on PPD1 vs resident GFP- cells, suggesting an active role for BMDCs in rapid tissue turnover. Moreover, GFP+ cells gradually acquired cell senescence together with decreased proliferation throughout the postpartum. In conclusion, BM-derived progenitors were found to have a novel nonhematopoietic cellular contribution to postpartum uterus remodeling. This contribution may have an important functional role in physiological as well as pathological postpartum endometrial regeneration.

Deficiency of PARP-1 and PARP-2 in the mouse uterus results in decidualization failure and pregnancy loss

Miscarriage is a common complication of pregnancy for which there are few clinical interventions. Deficiency in endometrial stromal cell decidualization is considered a major contributing factor to pregnancy loss; however, our understanding of the underlying mechanisms of decidual deficiency are incomplete. ADP ribosylation by PARP-1 and PARP-2 has been linked to physiological processes essential to successful pregnancy outcomes. Here, we report that the catalytic inhibition or genetic ablation of PARP-1 and PARP-2 in the uterus lead to pregnancy loss in mice. Notably, the absence of PARP-1 and PARP-2 resulted in increased p53 signaling and an increased population of senescent decidual cells. Molecular and histological analysis revealed that embryo attachment and the removal of the luminal epithelium are not altered in uterine Parp1, Parp2 knockout mice, but subsequent decidualization failure results in pregnancy loss. These findings provide evidence for a previously unknown function of PARP-1 and PARP-2 in mediating decidualization for successful pregnancy establishment.

Single-cell transcriptome analysis reveals defective decidua stromal niche attributes to recurrent spontaneous abortion

Objectives

Successful pregnancy involves the homeostasis between maternal decidua and fetoplacental units, whose disruption contributes to compromised pregnancy outcomes, including recurrent spontaneous abortion (RSA). The role of cell heterogeneity of maternal decidua in RSA is yet to be illustrated.

Materials and methods

A total of 66,078 single cells from decidua samples isolated from patients with RSA and healthy controls were analysed by unbiased single‐cell RNA sequencing (scRNA‐seq).

Results

Our scRNA‐seq results revealed that stromal cells are the most abundant cell type in decidua during early pregnancy. RSA samples are accompanied by aberrant decidualization and obviously obstructed communication between stromal cells and other cell types, such as abnormal activation of macrophages and NK cells. In addition, the over‐activated TNF superfamily member 12 (TNFSF12, TWEAK) and FASLG in RSA are closely related to stromal cell demise and pregnancy failure.

Conclusions

Our research reveals that the cell composition and communications in normal and RSA decidua at early pregnancy and provides insightful information for the pathology of RSA and will pave the way for pregnancy loss prevention.

In situ imaging reveals disparity between prostaglandin localization and abundance of prostaglandin synthases

Prostaglandins are important lipids involved in mediating many physiological processes, such as allergic responses, inflammation, and pregnancy. However, technical limitations of in-situ prostaglandin detection in tissue have led researchers to infer prostaglandin tissue distributions from localization of regulatory synthases, such as COX1 and COX2. Herein, we apply a novel mass spectrometry imaging method for direct in situ tissue localization of prostaglandins, and combine it with techniques for protein expression and RNA localization. We report that prostaglandin D₂, its precursors, and downstream synthases co-localize with the highest expression of COX1, and not COX2. Further, we study tissue with a conditional deletion of transformation-related protein 53 where pregnancy success is low and confirm that PG levels are altered, although localization is conserved. Our studies reveal that the abundance of COX and prostaglandin D₂ synthases in cellular regions does not mirror the regional abundance of prostaglandins. Thus, we deduce that prostaglandins tissue localization and abundance may not be inferred by COX or prostaglandin synthases in uterine tissue, and must be resolved by an in situ prostaglandin imaging.

Duncan et al. use a mass spectrometry imaging method to assess the localization and concentration of prostaglandins (PGs) in mouse tissues during pregnancy. This study brings new biological insights into the spatial evaluation of PGs in tissues, which could reveal the functional significance of each PGs during different stages of embryo development/pregnancy.

Functional changes in decidual mesenchymal stem/stromal cells are associated with spontaneous onset of labour

Ageing and parturition share common pathways, but their relationship remains poorly understood. Decidual cells undergo ageing as parturition approaches term, and these age-related changes may trigger labour. Mesenchymal stem/stromal cells (MSCs) are the predominant stem cell type in the decidua. Stem cell exhaustion is a hallmark of ageing, and thus ageing of decidual MSCs (DMSCs) may contribute to the functional changes in decidual tissue required for term spontaneous labour. Here, we determine whether DMSCs from patients undergoing spontaneous onset of labour (SOL-DMSCs) show evidence of ageing-related functional changes compared with those from patients not in labour (NIL-DMSCs), undergoing Caesarean section. Placentae were collected from term (37-40 weeks of gestation), SOL (n = 18) and NIL (n = 17) healthy patients. DMSCs were isolated from the decidua basalis that remained attached to the placenta after delivery. DMSCs displayed stem cell-like properties and were of maternal origin. Important cell properties and lipid profiles were assessed and compared between SOL- and NIL-DMSCs. SOL-DMSCs showed reduced proliferation and increased lipid peroxidation, migration, necrosis, mitochondrial apoptosis, IL-6 production and p38 MAPK levels compared with NIL-DMSCs (P < 0.05). SOL- and NIL-DMSCs also showed significant differences in lipid profiles in various phospholipids (phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylserine), sphingolipids (ceramide, sphingomyelin), triglycerides and acyl carnitine (P < 0.05). Overall, SOL-DMSCs had altered lipid profiles compared with NIL-DMSCs. In conclusion, SOL-DMSCs showed evidence of ageing-related reduced functionality, accumulation of cellular damage and changes in lipid profiles compared with NIL-DMSCs. These changes may be associated with term spontaneous labour.

Comparison of the fertility of tumor suppressor gene-deficient C57BL/6 mouse strains reveals stable reproductive aging and novel pleiotropic gene

Tumor suppressor genes are involved in maintaining genome integrity during reproduction (e.g., meiosis). Thus, deleterious alleles in tumor suppressor-deficient mice would exhibit higher mortality during the perinatal period. A recent aging model proposes that perinatal mortality and age-related deleterious changes might define lifespan. This study aimed to quantitatively understand the relationship between reproduction and lifespan using three established tumor suppressor gene (p53, APC, and RECQL4)-deficient mouse strains with the same C57BL/6 background. Transgenic mice delivered slightly reduced numbers of 1st pups than wild-type mice [ratio: 0.81–0.93 (p = 0.1–0.61)] during a similar delivery period, which suggest that the tumor suppressor gene-deficient mice undergo relatively stable reproduction. However, the transgenic 1st pups died within a few days after birth, resulting in a further reduction in litter size at 3 weeks after delivery compared with that of wild-type mice [ratio: 0.35–0.68 (p = 0.034–0.24)] without sex differences, although the lifespan was variable. Unexpectedly, the significance of reproductive reduction in transgenic mice was decreased at the 2nd or later delivery. Because mice are easily affected by environmental factors, our data underscore the importance of defining reproductive ability through experiments on aging-related reproduction that can reveal a trade-off between fecundity and aging and identify RECQL4 as a novel pleiotropic gene.

Extracellular vesicle mediated feto-maternal HMGB1 signaling induces preterm birth

Preterm birth (PTB; <37 weeks of gestation) impacts ∼11% of all pregnancies and contributes to 1 million neonatal deaths worldwide annually. An understanding of the feto-maternal (F-M) signals that initiate birthing (parturition) at term is critical to design strategies to prevent their premature activation, resulting in PTB. Although endocrine and immune cell signaling are well-reported, fetal-derived paracrine signals capable of transitioning quiescent uterus to an active state of labor are poorly studied. Recent reports have suggested that senescence of the fetal amnion membrane coinciding with fetal growth and maturation generates inflammatory signals capable of triggering parturition. This is by increasing the inflammatory load at the feto-maternal interface (FMi) tissues (i.e., amniochorion-decidua). High mobility group box 1 protein (HMGB1), an alarmin, is one of the inflammatory signals released by senescent amnion cells via extracellular vesicles (exosomes; 40-160 nm). Increased levels of HMGB1 in the amniotic fluid, cord and maternal blood are associated with term and PTB. This study tested the hypothesis that senescent amnion cells release HMGB1, which is fetal signaling capable of increasing FMi inflammation, predisposing them to parturition. To test this hypothesis, exosomes from amnion epithelial cells (AECs) grown under normal conditions were engineered to contain HMGB1 by electroporation (eHMGB1). eHMGB1 was characterized (quantity, size, shape, markers and loading efficiency), and its propagation through FMi was tested using a four-chamber microfluidic organ-on-a-chip device (FMi-OOC) that contained four distinct cell types (amnion and chorion mesenchymal, chorion trophoblast and decidual cells) connected through microchannels. eHMGB1 propagated through the fetal cells and matrix to the maternal decidua and increased inflammation (receptor expression [RAGE and TLR4] and cytokines). Furthermore, intra-amniotic injection of eHMGB1 (containing 10 ng) into pregnant CD-1 mice on embryonic day 17 led to PTB. Injecting carboxyfluorescein succinimidyl ester (CFSE)-labeled eHMGB1, we determined in vivo kinetics and report that eHMGB1 trafficking resulting in PTB was associated with increased FMi inflammation. This study determined that fetal exosome mediated paracrine signaling can generate inflammation and induce parturition. Besides, in vivo functional validation of FMi-OOC experiments strengthens the reliability of such devices to test physiologic and pathologic systems.

Osteoprotegerin interacts with syndecan-1 to promote human endometrial stromal decidualization by decreasing Akt phosphorylation

STUDY QUESTION

Does osteoprotegerin (OPG) promote human endometrial stromal decidualization?

SUMMARY ANSWER

OPG is essential for human endometrial stromal decidualization through its interaction with syndecan-1 to decrease Akt phosphorylation.

WHAT IS KNOWN ALREADY

OPG (a cytokine receptor) levels are significantly increased in the circulation of pregnant women. However, the role and mechanism of OPG in human endometrial stromal cell (ESC) decidualization remain elusive.

STUDY DESIGN, SIZE, DURATION

We analyzed the endometrial expression of OPG in endometrial tissue samples collected from women with regular menstrual cycles (ranging from 25 to 35 days), and decidual tissue samples collected from woman with normal early pregnancy or recurrent pregnancy loss (RPL) who visited the Department of Gynecology and Obstetrics at a tertiary care center from January to October 2018. None of the subjects had hormonal treatment for at least 3 months prior to the procedure. In total, 16 women with normal early pregnancy and 15 with RPL were selected as subjects for this study. The function of OPG in decidualization was explored in a human endometrial stromal cell (HESC) line and primary cultures of HESCs.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We collected endometrial tissues (by biopsy) from the subjects during their menstrual cycle and decidual tissues from subjects with a normal early pregnancy and those with RPL at the time of dilation and curettage. The control group comprised randomly selected women who underwent termination of an apparently normal early pregnancy. The endometrial OPG expression was analyzed using immunohistochemical staining and quantitative RT-PCR (qRT-PCR). Immunofluorescence staining and western blot, and qRT-PCR were used to explore the mRNA and protein expression, respectively, of OPG in an immortalized HESC line and in primary cultures of HESC during proliferation and decidualization. siRNA-mediated knockdown experiments were performed to examine the function of OPG in HESC proliferation and decidualization. Flow cytometry and the cell proliferation MTS assay were performed to further examine the role of OPG in HESC proliferation. We also analyzed decidual marker gene expression by qRT-PCR to assess the consequences of OPG loss for HESC decidualization. A co-immunoprecipitation (IP) assay was used to determine the potential interaction between the OPG and Syndecan-1. Western blot analysis of the rescue experiments performed using the phosphatidylinositol 3-kinase (PI3K) signaling-specific inhibitor LY294002 was used to investigate the downstream signaling pathways through which OPG could mediate HESC decidualization.

MAIN RESULTS AND THE ROLE OF CHANCE

OPG was expressed in both the human endometrium and in vitro decidualized ESCs. Knockdown experiments revealed that OPG loss impaired the expression of IGF-binding protein-1 (IGFBP-1) (P < 0.05) and prolactin (PRL) (P < 0.05), two specific markers of decidualization, in HESC undergoing decidualization. We also uncovered that OPG knockdown induced the aberrant activation of Akt (protein kinase B) during HESC decidualization (P < 0.05). The inhibition of Akt activation could rescue the impaired expression of the decidual markers PRL (P < 0.05) and IGFBP-1 (P < 0.05) in response to OPG knockdown. Syndecan-1 was considered a potential receptor candidate, as it was expressed in both the endometrium and in vitro cultured stromal cells. Subsequent co-IP experiments demonstrated the interaction between OPG and Syndecan-1 during decidualization. In addition, Syndecan-1 knockdown not only clearly attenuated the decidualization markers PRL (P < 0.05) and IGFBP-1 (P < 0.05) but also induced the aberrant enhancement of Akt phosphorylation in decidualized cells, consistent with the phenotype of OPG knockdown cells. Finally, we revealed that the transcript and protein expression of both OPG and Syndecan-1 was significantly lower in the decidual samples of women with RPL than in those of women with normal pregnancy (P < 0.05).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

In this study, based on a number of approaches, it was demonstrated that OPG mediated the repression of Akt that occurs during human stromal cell decidualization, however, the molecular link between OPG and Akt signaling was not determined, and still requires further exploration.

WIDER IMPLICATIONS OF THE FINDINGS

OPG is required for decidualization, and a decrease in OPG levels is associated with RPL. These findings provide a new candidate molecule for the diagnosis and potential treatment of RPL.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by the National Natural Science Foundation of China U1605223 (to G.S.), 81701457 (to Y.J.) and 81601349 (to Y.J.). The authors have no conflicts of interest to disclose.

RNA Sequencing Reveals Distinct Immune Responses in the Chorioamniotic Membranes of Women with Preterm Labor and Microbial or Sterile Intra-amniotic Inflammation

Preterm labor precedes premature birth, the leading cause of neonatal morbidity and mortality worldwide. Preterm labor can occur in the context of either microbe-associated intra-amniotic inflammation (i.e., intra-amniotic infection) or intra-amniotic inflammation in the absence of detectable microorganisms (i.e., sterile intra-amniotic inflammation). Both intra-amniotic infection and sterile intra-amniotic inflammation trigger local immune responses that have deleterious effects on fetal life. Yet, the extent of such immune responses in the fetal tissues surrounding the amniotic cavity (i.e., the chorioamniotic membranes) is poorly understood. By using RNA sequencing (RNA seq) as a discovery approach, we found that there were significant transcriptomic differences involving host response to pathogens in the chorioamniotic membranes of women with intra-amniotic infection compared to those from women without inflammation. In addition, the sterile or microbial nature of intra-amniotic inflammation was associated with distinct transcriptomic profiles in the chorioamniotic membranes. Moreover, the immune response in the chorioamniotic membranes of women with sterile intra-amniotic inflammation was milder in nature than that induced by microbes and involved the upregulation of alarmins and inflammasome-related molecules. Lastly, the presence of maternal and fetal inflammatory responses in the placenta was associated with the upregulation of immune processes in the chorioamniotic membranes. Collectively, these findings provide insight into the immune responses against microbes or alarmins that take place in the fetal tissues surrounding the amniotic cavity, shedding light on the immunobiology of preterm labor and birth.

Retinoblastoma protein promotes uterine epithelial cell cycle arrest and necroptosis for embryo invasion

Retinoblastoma protein (RB) encoded by Rb1 is a prominent inducer of cell cycle arrest (CCA). The hormone progesterone (P₄ ) promotes CCA in the uterine epithelium and previous studies indicated that P₄ activates RB by reducing the phosphorylated, inactive form of RB. Here, we show that embryo implantation is impaired in uterine-specific Rb1 knockout mice. We observe persistent cell proliferation of the Rb1-deficient uterine epithelium until embryo attachment, loss of epithelial necroptosis, and trophoblast phagocytosis, which correlates with subsequent embryo invasion failure, indicating that Rb1-induced CCA and necroptosis of uterine epithelium are involved in embryo invasion. Pre-implantation P₄ supplementation is sufficient to restore these defects and embryo invasion. In Rb1-deficient uterine epithelial cells, TNFα-primed necroptosis is impaired, which is rescued by the treatment with a CCA inducer thymidine or P₄ through the upregulation of TNF receptor type 2. TNFα is expressed in the luminal epithelium and the embryo at the embryo attachment site. These results provide evidence that uterine Rb1-induced CCA is involved in TNFα-primed epithelial necroptosis at the implantation site for successful embryo invasion.

Activation of Autophagy in Human Uterine Myometrium During Labor

OBJECTIVE

The purpose of this study was to analyze the autophagy of the human uterine myometrium during the labor.

METHODS

We collected uterine myometrium strips from term, singleton, nulliparous healthy women undergoing cesarean delivery before labor (nonlabor group, n = 10) or during normal labor (in-labor group, n = 10) without rupturing of membrane. The indications for cesarean delivery were breech presentation or maternal request. Transmission electron microscopy was used to observe autophagosomes. Reverse transcriptase polymerase chain reaction, immunofluorescence, and Western blot were used to quantify the messenger RNA (mRNA) and protein level of the autophagy markers LC3B, P62, and Beclin-1 in the uterine muscle strips.

RESULTS

There were no differences between both groups in maternal age, body mass index, gestational week, neonatal weight, operative bleeding, and postpartum bleeding. Transmission electron micrographs showed that autophagosomes existed in myometrial tissue in both groups. There were more autophagosomes in the in-labor group than in the nonlabor group, and the difference had significance. The in-labor group had significantly greater LC3B mRNA expression but significantly lower P62 mRNA expression compared with the nonlabor group. Semiquantitative immunofluorescence in uterine myometrial cells in the in-labor group showed increased LC3B puncta formation and greater Beclin-1 expression but reduced P62 puncta formation compared with the nonlabor group. The ratio of LC3BII/I proteins was significantly higher, but P62 protein was significantly lower in the in-labor group compared with the nonlabor group. The Beclin-1 mRNA and protein expressions were not significantly different between the 2 groups.

CONCLUSION

Autophagy was activated in human uterine myometrium during labor and might play an important role in maintaining uterine contraction function.

Notch1 is crucial for decidualization and maintaining the first pregnancy in the mouse†

The endometrium undergoes a pregnancy-delivery-repair cycle multiple times during the reproductive lifespan in females. Decidualization is one of the critical events for the success of this essential process. We have previously reported that Notch1 is essential for artificial decidualization in mice. However, in a natural pregnancy, the deletion of Notch1 (PgrCre/+Notch1f/f, or Notch1d/d) only affects female fertility in the first 30 days of a 6-month fertility test, but not the later stages. In the present study, we undertook a closer evaluation at the first pregnancy of these mice to attempt to understand this puzzling phenomenon. We observed a large number of pregnancy losses in Notch1d/d mice in their first pregnancy, which led to the subfertility observed in the first 30 days of the fertility test. We then demonstrated that the initial pregnancy loss is a consequence of impaired decidualization. Furthermore, we identified a group of genes that contribute to Notch1 regulated decidualization in a natural pregnancy. Gene ontogeny analysis showed that these differentially expressed genes in the natural pregnancy are involved in cell-cell and cell-matrix interactions, different from genes that have been previously identified from the artificial decidualization model, which contribute to cell proliferation and apoptosis. In summary, we determined that Notch1 is essential for normal decidualization in the mouse uterus only in the first pregnancy but not in subsequent ones.

Maternal regulation of inflammatory cues is required for induction of preterm birth

Infection-driven inflammation in pregnancy is a major cause of spontaneous preterm birth (PTB). Both systemic infection and bacterial ascension through the vagina/cervix to the amniotic cavity are strongly associated with PTB. However, the contribution of maternal or fetal inflammatory responses in the context of systemic or localized models of infection-driven PTB is not well defined. Here, using intraperitoneal or intraamniotic LPS challenge, we examined the necessity and sufficiency of maternal and fetal Toll-like receptor (TLR) 4 signaling in induction of inflammatory vigor and PTB. Both systemic and local LPS challenge promoted induction of inflammatory pathways in uteroplacental tissues and induced PTB. Restriction of TLR4 expression to the maternal compartment was sufficient for induction of LPS-driven PTB in either systemic or intraamniotic challenge models. In contrast, restriction of TLR4 expression to the fetal compartment failed to induce LPS-driven PTB. Vav1-Cre-mediated genetic deletion of TLR4 suggested a critical role for maternal immune cells in inflammation-driven PTB. Further, passive transfer of WT in vitro-derived macrophages and dendritic cells to TLR4-null gravid females was sufficient to induce an inflammatory response and drive PTB. Cumulatively, these findings highlight the critical role for maternal regulation of inflammatory cues in induction of inflammation-driven parturition.

Effect of culture conditions and method of conception on mouse live birth rate

OBJECTIVE

To understand in a mouse model whether there are differences in the decidua and live birth rate after transfer of blastocysts generated by in vitro fertilization (IVF) or by superovulation with spontaneous mating into unstimulated recipients.

DESIGN

Animal experiment.

SETTING

University-affiliated tertiary hospital.

ANIMAL(S)

Mice.

INTERVENTION(S)

IVF embryos were generated and cultured in either Whitten medium (WM, suboptimal conditions) and 20% O₂ or KSOM medium with amino acids (KAA, optimal conditions) and 5% O₂. The control blastocysts from superovulated mice were flushed out of the uterus 3.5 days (E3.5) after mating (FB group). The resulting blastocysts were transferred to nonsuperovulated CF1 recipients mated to vasectomized males. To understand whether anomalies of decidua were present, the expression of genes involved in decidual development and inflammation was analyzed at E7.5 and E18.5. Similarly, immunostaining was used to evaluate whether the pathways involved in activation of mTORC1 (p-S6) and Cox2 signaling (Cox 2 staining) were altered.

MAIN OUTCOME MEASURE(S)

Live birth rate, gene expression, and immunostaining of decidua.

RESULT(S)

Implantation rates at E7.5 were similar, but in vivo embryos (FB groups) were predicted to result in live births 3.3 times higher (2.2-5.1) and 6.6 times higher (4.7-9.3) compared with optimal and suboptimal cultures, respectively. Expression of genes involved in decidual development and inflammation or localization and intensity of staining for p-S6 (mTOR pathway), or inflammation (Cox 2 pathway) were not different among the groups.

CONCLUSION(S)

The predicted live birth rate was decreased in mouse embryos generated by IVF compared with embryos generated by mating, whereas the implantation rate was not different. Suboptimal culture conditions resulted in lower birth rate. We did not find evidence of abnormalities in decidualization that could explain these findings. These data indicate that blastocysts cultured in stressful conditions are less competent, suggesting that decreasing the number of embryonic manipulations may result in higher live birth rates.

Long non-coding RNA SNHG29 regulates cell senescence via p53/p21 signaling in spontaneous preterm birth

INTRODUCTION

Spontaneous preterm birth affects>5-18% of pregnancies and causes infant morbidity and mortality. Long non-coding RNAs can regulate gene expression and have been associated with preterm birth. In this study, we investigated whether the long non-coding RNA SNHG29 was associated with spontaneous preterm birth.

METHODS

We collected the placentas from women who underwent preterm/full-term birth with/without labor. We determined the levels of expression of SNHG29 in the placental tissues using quantitative real-time polymerase chain reaction. We generated a senescence model by treating HTR8/SVneo cells with 200 μM H2O2 for 2 h. The degree of senescence induced in cells depleted of or overexpressing SNHG29 was determined by measuring senescence-associated gene expression and β-galactosidase activity.

RESULTS

SNHG29 was overexpressed in the placentas of women who delivered preterm with labor and in HTR8/SVneo cells treated with H2O2 (p < 0.05). The levels of mRNA of p53 and p21, protein levels of p53, phospho-p53, p21and phospho-p21, and β-galactosidase activity was decreased in HTR8/SVneo cells depleted of SNHG29, while the opposite trend was observed in HTR8/SVneo cells overexpressing SNHG29 (p < 0.05). We observed an increase in the expression of IL-8 and TNF-α in senescent HTR8/SVneo cells (p < 0.05).

DISCUSSION

SNHG29 was overexpressed in placentas from women who delivered preterm with labor compared to those in women who underwent preterm birth without labor and full-term birth with/without labor. High levels of SNHG29 enhanced senescence in vivo. The increase in pro-inflammatory cytokine expression and release by senescent cells may be pivotal to the pathophysiology of spontaneous preterm birth.

Novel pathways of inflammation in human fetal membranes associated with preterm birth and preterm pre-labor rupture of the membranes

Spontaneous preterm birth (PTB) and preterm pre-labor rupture of the membranes (pPROM) are major pregnancy complications. Although PTB and pPROM have common etiologies, they arise from distinct pathophysiologic pathways. Inflammation is a common underlying mechanism in both conditions. Balanced inflammation is required for fetoplacental growth; however, overwhelming inflammation (physiologic at term and pathologic at preterm) can lead to term and preterm parturition. A lack of effective strategies to control inflammation and reduce the risk of PTB and pPROM suggests that there are several modes of the generation of inflammation which may be dependent on the type of uterine tissue. The avascular fetal membrane (amniochorion), which provides structure, support, and protection to the intrauterine cavity, is one of the key contributors of inflammation. Localized membrane inflammation helps tissue remodeling during pregnancy. Two unique mechanisms that generate balanced inflammation are the progressive development of senescence (aging) and cyclic cellular transitions: epithelial to mesenchymal (EMT) and mesenchymal to epithelial (MET). The intrauterine build-up of oxidative stress at term or in response to risk factors (preterm) can accelerate senescence and promote a terminal state of EMT, resulting in the accumulation of inflammation. Inflammation degrades the matrix and destabilizes membrane function. Inflammatory mediators from damaged membranes are propagated via extracellular vesicles (EV) to maternal uterine tissues and transition quiescent maternal uterine tissues into an active state of labor. Membrane inflammation and its propagation are fetal signals that may promote parturition. This review summarizes the mechanisms of fetal membrane cellular senescence, transitions, and the generation of inflammation that contributes to term and preterm parturitions.