Dynamic chromatin remodeling in cycling human endometrium at single-cell level.

Estrogen-dependent proliferation followed by progesterone-dependent differentiation of the endometrium culminates in a short implantation window. We performed single-cell assay for transposase-accessible chromatin with sequencing on endometrial samples obtained across the menstrual cycle to investigate the regulation of temporal gene networks that control embryo implantation. We identify uniquely accessible chromatin regions in all major cellular constituents of the endometrium, delineate temporal patterns of coordinated chromatin remodeling in epithelial and stromal cells, and gain mechanistic insights into the emergence of a receptive state through integrated analysis of enriched transcription factor (TF) binding sites in dynamic chromatin regions, chromatin immunoprecipitation sequencing analyses, and gene expression data. We demonstrate that the implantation window coincides with pervasive cooption of transposable elements (TEs) into the regulatory chromatin landscape of decidualizing cells and expression of TE-derived transcripts in a spatially defined manner. Our data constitute a comprehensive map of the chromatin changes that control TF activities in a cycling endometrium at cellular resolution.

Human embryo implantation.

Embryo implantation in humans is interstitial, meaning the entire conceptus embeds in the endometrium before the placental trophoblast invades beyond the uterine mucosa into the underlying inner myometrium. Once implanted, embryo survival pivots on the transformation of the endometrium into an anti-inflammatory placental bed, termed decidua, under homeostatic control of uterine natural killer cells. Here, we examine the evolutionary context of embryo implantation and elaborate on uterine remodelling before and after conception in humans. We also discuss the interactions between the embryo and the decidualising endometrium that regulate interstitial implantation and determine embryo fitness. Together, this Review highlights the precarious but adaptable nature of the implantation process.

JAZF1-SUZ12 dysregulates PRC2 function and gene expression during cell differentiation.

Polycomb repressive complex 2 (PRC2) methylates histone H3 lysine 27 (H3K27me3) to maintain gene repression and is essential for cell differentiation. In low-grade endometrial stromal sarcoma (LG-ESS), the PRC2 subunit SUZ12 is often fused with the NuA4/TIP60 subunit JAZF1. We show that JAZF1-SUZ12 dysregulates PRC2 composition, genome occupancy, histone modification, gene expression, and cell differentiation. Loss of the SUZ12 N terminus in the fusion protein abrogates interaction with specific PRC2 accessory factors, reduces occupancy at PRC2 target genes, and diminishes H3K27me3. Fusion to JAZF1 increases H4Kac at PRC2 target genes and triggers recruitment to JAZF1 binding sites during cell differentiation. In human endometrial stromal cells, JAZF1-SUZ12 upregulated PRC2 target genes normally activated during decidualization while repressing genes associated with immune clearance, and JAZF1-SUZ12-induced genes were also overexpressed in LG-ESS. These results reveal defects in chromatin regulation, gene expression, and cell differentiation caused by JAZF1-SUZ12 that may underlie its role in oncogenesis.

EndoTime: non-categorical timing estimates for luteal endometrium.

STUDY QUESTION: Can the accuracy of timing of luteal phase endometrial biopsies based on urinary ovulation testing be improved by measuring the expression of a small number of genes and a continuous, non-categorical modelling approach? SUMMARY ANSWER: Measuring the expression levels of six genes (IL2RB, IGFBP1, CXCL14, DPP4, GPX3 and SLC15A2) is sufficient to obtain substantially more accurate timing estimates and to assess the reliability of timing estimates for each sample. WHAT IS KNOWN ALREADY: Commercially available endometrial timing approaches based on gene expression require large gene sets and use a categorical approach that classifies samples as pre-receptive, receptive or post-receptive. STUDY DESIGN, SIZE, DURATION: Gene expression was measured by RTq-PCR in different sample sets, comprising a total of 664 endometrial biopsies obtained 4-12 days after a self-reported positive home ovulation test. A further 36 endometrial samples were profiled by RTq-PCR as well as RNA-sequencing. PARTICIPANTS/MATERIALS, SETTING, METHODS: A computational procedure, named 'EndoTime', was established that models the temporal profile of each gene and estimates the timing of each sample. Iterating these steps, temporal profiles are gradually refined as sample timings are being updated, and confidence in timing estimates is increased. After convergence, the method reports updated timing estimates for each sample while preserving the overall distribution of time points. MAIN RESULTS AND THE ROLE OF CHANCE: The Wilcoxon rank-sum test was used to confirm that ordering samples by EndoTime estimates yields sharper temporal expression profiles for held-out genes (not used when determining sample timings) than ordering the same expression values by patient-reported times (GPX3: P < 0.005; CXCL14: P < 2.7e-6; DPP4: P < 3.7e-13). Pearson correlation between EndoTime estimates for the same sample set but based on RTq-PCR or RNA-sequencing data showed a high degree of congruency between the two (P = 8.6e-10, R2 = 0.687). Estimated timings did not differ significantly between control subjects and patients with recurrent pregnancy loss or recurrent implantation failure (P > 0.05). LARGE SCALE DATA: The RTq-PCR data files are available via the GitHub repository for the EndoTime software at https://github.com/AE-Mitchell/EndoTime, as is the code used for pre-processing of RTq-PCR data. The RNA-sequencing data are available on GEO (accession GSE180485). LIMITATIONS, REASONS FOR CAUTION: Timing estimates are informed by glandular gene expression and will only represent the temporal state of other endometrial cell types if in synchrony with the epithelium. Methods that estimate the day of ovulation are still required as these data are essential inputs in our method. Our approach, in its current iteration, performs batch correction such that larger sample batches impart greater accuracy to timing estimations. In theory, our method requires endometrial samples obtained at different days in the luteal phase. In practice, however, this is not a concern as timings based on urinary ovulation testing are associated with a sufficient level of noise to ensure that a variety of time points will be sampled. WIDER IMPLICATIONS OF THE FINDINGS: Our method is the first to assay the temporal state of luteal-phase endometrial samples on a continuous domain. It is freely available with fully shared data and open-source software. EndoTime enables accurate temporal profiling of any gene in luteal endometrial samples for a wide range of research applications and, potentially, clinical use. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by a Wellcome Trust Investigator Award (Grant/Award Number: 212233/Z/18/Z) and the Tommy's National Miscarriage Research Centre. None of the authors have any competing interests. J.L. was funded by the Biotechnology and Biological Sciences Research Council (UK) through the Midlands Integrative Biology Training Partnership (MIBTP, BB/M01116X/1).

Evolutionary transcriptomics implicates new genes and pathways in human pregnancy and adverse pregnancy outcomes.

Evolutionary changes in the anatomy and physiology of the female reproductive system underlie the origins and diversification of pregnancy in Eutherian ('placental') mammals. This developmental and evolutionary history constrains normal physiological functions and biases the ways in which dysfunction contributes to reproductive trait diseases and adverse pregnancy outcomes. Here, we show that gene expression changes in the human endometrium during pregnancy are associated with the evolution of human-specific traits and pathologies of pregnancy. We found that hundreds of genes gained or lost endometrial expression in the human lineage. Among these are genes that may contribute to human-specific maternal-fetal communication (HTR2B) and maternal-fetal immunotolerance (PDCD1LG2) systems, as well as vascular remodeling and deep placental invasion (CORIN). These data suggest that explicit evolutionary studies of anatomical systems complement traditional methods for characterizing the genetic architecture of disease. We also anticipate our results will advance the emerging synthesis of evolution and medicine ('evolutionary medicine') and be a starting point for more sophisticated studies of the maternal-fetal interface. Furthermore, the gene expression changes we identified may contribute to the development of diagnostics and interventions for adverse pregnancy outcomes.

Pregnancy is a complicated process. It has three phases: the body recognizes the embryo, it maintains the pregnancy, and finally, it induces labor. These stages happen in all mammals, but the details are different in humans. Human pregnancy and labor last longer. We menstruate. Our placentas invade deeper into the uterus, and the cues that signal pregnancy is done and induce labor are different than in most other mammals. We are also more likely to have pregnancy complications, including infertility, a dangerous rise in blood pressure called preeclampsia, and premature birth. The reasons for these differences are unknown. Human pregnancy relies on close communication between the placenta and the uterus. The immune system must allow the placenta to grow large enough to support the developing embryo, and blood vessels need to adapt to supply gases and nutrients and to remove waste. Understanding how the genes used by the human uterus are different to those used in other species could help explain why human pregnancies are so unusual. Mika, Marinic et al. compared the genes used by the pregnant human uterus to those used in 32 other species, including monkeys, marsupials and other mammals, birds, and reptiles. The analysis revealed that the humans use almost a thousand genes that other animals do not. These genes have roles in the invasion of the placenta, the growth of blood vessels, and control of the immune system. Several have links to the hormone serotonin, which had not been connected with the uterus before. Mika, Marinic et al. suggest that it might control the length of pregnancy, the timing of labor, and communication between parent and baby. The genes identified here provide a starting point for further investigation of human pregnancy. In the future, this may help to prevent or treat infertility, preeclampsia, or premature birth. A possible next step is to examine our closest living relatives, the great apes. Performing similar experiments using tissues or cells from chimpanzees, gorillas, and orangutans could reveal more about the genes unique to human pregnancy.

Embryo biosensing by uterine natural killer cells determines endometrial fate decisions at implantation.

Decidualizing endometrial stromal cells (EnSC) critically determine the maternal response to an implanting conceptus, triggering either menstruation-like disposal of low-fitness embryos or creating an environment that promotes further development. However, the mechanism that couples maternal recognition of low-quality embryos to tissue breakdown remains poorly understood. Recently, we demonstrated that successful transition of the cycling endometrium to a pregnancy state requires selective elimination of pro-inflammatory senescent decidual cells by activated uterine natural killer (uNK) cells. Here we report that uNK cells express CD44, the canonical hyaluronan (HA) receptor, and demonstrate that high molecular weight HA (HMWHA) inhibits uNK cell-mediated killing of senescent decidual cells. In contrast, low molecular weight HA (LMWHA) did not attenuate uNK cell activity in co-culture experiments. Killing of senescent decidual cells by uNK cells was also inhibited upon exposure to medium conditioned by IVF embryos that failed to implant, but not successful embryos. Embryo-mediated inhibition of uNK cell activity was reversed by recombinant hyaluronidase 2 (HYAL2), which hydrolyses HMWHA. We further report a correlation between the levels of HYAL2 secretion by human blastocysts, morphological scores, and implantation potential. Taken together, the data suggest a pivotal role for uNK cells in embryo biosensing and endometrial fate decisions at implantation.

The Role of Decidual Subpopulations in Implantation, Menstruation and Miscarriage.

In each menstrual cycle, the endometrium becomes receptive to embryo implantation while preparing for tissue breakdown and repair. Both pregnancy and menstruation are dependent on spontaneous decidualization of endometrial stromal cells, a progesterone-dependent process that follows rapid, oestrogen-dependent proliferation. During the implantation window, stromal cells mount an acute stress response, which leads to the emergence of functionally distinct decidual subsets, reflecting the level of replication stress incurred during the preceding proliferative phase. Progesterone-dependent, anti-inflammatory decidual cells (DeC) form a robust matrix that accommodates the conceptus whereas pro-inflammatory, progesterone-resistant stressed and senescent decidual cells (senDeC) control tissue remodelling and breakdown. To execute these functions, each decidual subset engages innate immune cells: DeC partner with uterine natural killer (uNK) cells to eliminate senDeC, while senDeC co-opt neutrophils and macrophages to assist with tissue breakdown and repair. Thus, successful transformation of cycling endometrium into the decidua of pregnancy not only requires continuous progesterone signalling but dominance of DeC over senDeC, aided by recruitment and differentiation of circulating NK cells and bone marrow-derived decidual progenitors. We discuss how the frequency of cycles resulting in imbalanced decidual subpopulations may determine the recurrence risk of miscarriage and highlight emerging therapeutic strategies.

Impact of Sustained Transforming Growth Factor-ß Receptor Inhibition on Chromatin Accessibility and Gene Expression in Cultured Human Endometrial MSC.

Endometrial mesenchymal stem cells (eMSC) drive the extraordinary regenerative capacity of the human endometrium. Clinical application of eMSC for therapeutic purposes is hampered by spontaneous differentiation and cellular senescence upon large-scale expansion in vitro. A83-01, a selective transforming growth factor-ß receptor (TGFß-R) inhibitor, promotes expansion of eMSC in culture by blocking differentiation and senescence, but the underlying mechanisms are incompletely understood. In this study, we combined RNA-seq and ATAC-seq to study the impact of sustained TGFß-R inhibition on gene expression and chromatin architecture of eMSC. Treatment of primary eMSC with A83-01 for 5 weeks resulted in differential expression of 1,463 genes. Gene ontology analysis showed enrichment of genes implicated in cell growth whereas extracellular matrix genes and genes involved in cell fate commitment were downregulated. ATAC-seq analysis demonstrated that sustained TGFß-R inhibition results in opening and closure of 3,555 and 2,412 chromatin loci, respectively. Motif analysis revealed marked enrichment of retinoic acid receptor (RAR) binding sites, which was paralleled by the induction of RARB, encoding retinoic acid receptor beta (RARß). Selective RARß inhibition attenuated proliferation and clonogenicity of A83-01 treated eMSC. Taken together, our study provides new insights into the gene networks and genome-wide chromatin changes that underpin maintenance of an undifferentiated phenotype of eMSC in prolonged culture.

Acute atherosis and diffuse lipid infiltration of the placental bed: A review of historical lipid studies.

Based on a variety of tissue samples, including Caesarean hysterectomy specimens with the placenta in situ, a detailed map of uteroplacental vascular lesions was established in over a century of research. One such lesion is acute atherosis of unremodelled basal and uteroplacental arteries, defined by the presence of fibrinoid necrosis, subendothelial macrophage foam cells, and perivascular lymphocytic infiltration. Two studies conducted over 50 years ago used Oil Red O staining of frozen tissue sections to visualise lipid infiltration of placental bed vessels and document the presence of lipid-laden foam cells in acute atherosis. These studies also demonstrated that significant amounts of intracellular and extracellular lipids can accumulate in the decidua basalis, often extending into the superficial layer of the myometrium. This phenomenon, termed diffuse lipid infiltration (DLI), was found not only to be prevalent in hypertensive and preeclamptic pregnancies but also associated with postterm pregnancies. Despite being a potential pathognomonic sign of placental malfunction, DLI has been neglected in the context placental bed pathophysiology. To renew interest in this putative pathological feature, and stimulate mechanistic investigations, we review here the original and, to our knowledge, only lipid studies on frozen placental bed tissue sections.

Recurrent pregnancy loss is associated with a pro-senescent decidual response during the peri-implantation window.

During the implantation window, the endometrium becomes poised to transition to a pregnant state, a process driven by differentiation of stromal cells into decidual cells (DC). Perturbations in this process, termed decidualization, leads to breakdown of the feto-maternal interface and miscarriage, but the underlying mechanisms are poorly understood. Here, we reconstructed the decidual pathway at single-cell level in vitro and demonstrate that stromal cells first mount an acute stress response before emerging as DC or senescent DC (snDC). In the absence of immune cell-mediated clearance of snDC, secondary senescence transforms DC into progesterone-resistant cells that abundantly express extracellular matrix remodelling factors. Additional single-cell analysis of midluteal endometrium identified DIO2 and SCARA5 as marker genes of a diverging decidual response in vivo. Finally, we report a conspicuous link between a pro-senescent decidual response in peri-implantation endometrium and recurrent pregnancy loss, suggesting that pre-pregnancy screening and intervention may reduce the burden of miscarriage.

Impact of sitagliptin on endometrial mesenchymal stem-like progenitor cells: A randomised, double-blind placebo-controlled feasibility trial.

BACKGROUND: Recurrent pregnancy loss (RPL) is associated with the loss of endometrial mesenchymal stem-like progenitor cells (eMSC). DPP4 inhibitors may increase homing and engraftment of bone marrow-derived cells to sites of tissue injury. Here, we evaluated the effect of the DPP4 inhibitor sitagliptin on eMSC in women with RPL, determined the impact on endometrial decidualization, and assessed the feasibility of a full-scale clinical trial. METHODS: A double-blind, randomised, placebo-controlled feasibility trial on women aged 18 to 42 years with a history of 3 or more miscarriages, regular menstrual cycles, and no contraindications to sitagliptin. Thirty-eight subjects were randomised to either 100 mg sitagliptin daily for 3 consecutive cycles or identical placebo capsules. Computer generated, permuted block randomisation was used to allocate treatment packs. Colony forming unit (CFU) assays were used to quantify eMSC in midluteal endometrial biopsies. The primary outcome measure was CFU counts. Secondary outcome measures were endometrial thickness, study acceptability, and first pregnancy outcome within 12 months following the study. Tissue samples were subjected to explorative investigations. FINDINGS: CFU counts following sitagliptin were higher compared to placebo only when adjusted for baseline CFU counts and age (RR: 1.52, 95% CI: 1.32-1.75, P<0.01). The change in CFU count was 1.68 in the sitagliptin group and 1.08 in the placebo group. Trial recruitment, acceptability, and drug compliance were high. There were no serious adverse events. Explorative investigations showed that sitagliptin inhibits the expression of DIO2, a marker gene of senescent decidual cells. INTERPRETATION: Sitagliptin increases eMSCs and decreases decidual senescence. A large-scale clinical trial evaluating the impact of preconception sitagliptin treatment on pregnancy outcome in RPL is feasible and warranted. FUNDING: Tommy's Baby Charity. CLINICAL TRIAL REGISTRATION: EU Clinical Trials Register no. 2016-001120-54.

Resveratrol inhibits decidualization by accelerating downregulation of the CRABP2-RAR pathway in differentiating human endometrial stromal cells.

Pregnancy critically depends on the transformation of the human endometrium into a decidual matrix that controls embryo implantation and placenta formation, a process driven foremost by differentiation and polarization of endometrial stromal cells into mature and senescent decidual cells. Perturbations in the decidual process underpin a spectrum of prevalent reproductive disorders, including implantation failure and early pregnancy loss, emphasizing the need for new therapeutic interventions. Resveratrol is a naturally occurring polyphenol, widely used for its antioxidant and anti-inflammatory properties. Using primary human endometrial stromal cell (HESC) cultures, we demonstrate that resveratrol has anti-deciduogenic properties, repressing not only the induction of the decidual marker genes PRL and IGFBP1 but also abrogating decidual senescence. Knockdown of Sirtuin 1, a histone deacetylase activated by resveratrol, restored the expression of IGFBP1 but not the induction of PRL or senescence markers in decidualizing HESCs, suggesting involvement of other pathways. We demonstrate that resveratrol interferes with the reprogramming of the retinoic acid signaling pathway in decidualizing HESCs by accelerating down-regulation of cellular retinoic acid-binding protein 2 (CRABP2) and retinoic acid receptor (RAR). Notably, knockdown of CRABP2 or RAR in HESCs was sufficient to recapitulate the anti-deciduogenic effects of resveratrol. Thus, while resveratrol has been advanced as a potential fertility drug, our results indicate it may have detrimental effects on embryo implantation by interfering with decidual remodeling of the endometrium.

Preeclampsia: the role of persistent endothelial cells in uteroplacental arteries.

We explore the potential role of the endothelial lining of uteroplacental arteries in the pathogenesis of preeclampsia, a severe pregnancy disorder characterized by incomplete invasion of the uterine vasculature by extravillous trophoblast and angiogenic imbalance. In normal pregnancy, the endothelium disappears progressively from the uteroplacental arteries and is replaced by trophoblast and deposition of fibrofibrinoid structure, underpinning the so-called physiological transformation of uterine spiral arteries. We hypothesize that partial persistence of the endothelium, albeit injured, initiates a chain of events leading to the emergence of preeclampsia in 3 sequential stages. The first stage results in retention of the endothelium in uteroplacental arteries secondary to incomplete physiological transformation of the vessels. Consequently, the uteroplacental vessels are reactive to pathological cues, which drives local arteriopathy. The second stage starts with progressive reduction in uteroplacental blood flow, generating oxidative stress in the whole placenta, and heightened maternal inflammation in response to circulating trophoblastic debris. In the third stage, generalized endotheliosis causes systemic angiogenic imbalance, hypertension, and other clinical manifestation of preeclampsia.

Adolescent Preeclampsia: Pathological Drivers and Clinical Prevention.

Preeclampsia is an important cause of maternal and perinatal morbidity, especially in first-time pregnant adolescent women. Although prevention of preeclampsia has been attempted for many decades, effective intervention can only be achieved upon the full elucidation of the risk factors and mechanisms of disease. As the pathogenesis of preeclampsia during adolescence may differ from that in older women, preventive interventions should be tailored accordingly. During adolescence, 4 putative drivers of preeclampsia can be identified. First, uterine immaturity in very young teenagers is likely a major cause of defective deep placentation and adverse reproductive outcome, underscoring the importance of educational programs and public health initiatives focused on teen pregnancy prevention. Second, the association between adolescent obesity and preeclampsia merits further studies on the benefits of weight loss and dietary interventions to improve pregnancy outcome. Third, there is a need for greater awareness of the link between cardiovascular risk factors in young women and early-onset preeclampsia associated with atherosclerosis of the uteroplacental arteries. Finally, infrequent menstruations may prolong uterine immaturity because of lack of "menstrual preconditioning." This risk factor may be amenable to pharmacological/hormonal preconditioning prior to conception.

Covalent Attachment of Fibronectin onto Emulsion-Templated Porous Polymer Scaffolds Enhances Human Endometrial Stromal Cell Adhesion, Infiltration, and Function.

A novel strategy for the surface functionalization of emulsion-templated highly porous (polyHIPE) materials as well as its application to in vitro 3D cell culture is presented. A heterobifunctional linker that consists of an amine-reactive N-hydroxysuccinimide ester and a photoactivatable nitrophenyl azide, N-sulfosuccinimidyl-6-(4'-azido-2'-nitrophenylamino)hexanoate (sulfo-SANPAH), is utilized to functionalize polyHIPE surfaces. The ability to conjugate a range of compounds (6-aminofluorescein, heptafluorobutylamine, poly(ethylene glycol) bis-amine, and fibronectin) to the polyHIPE surface is demonstrated using fluorescence imaging, FTIR spectroscopy, and X-ray photoelectron spectroscopy. Compared to other existing surface functionalization methods for polyHIPE materials, this approach is facile, efficient, versatile, and benign. It can also be used to attach biomolecules to polyHIPE surfaces including cell adhesion-promoting extracellular matrix proteins. Cell culture experiments demonstrated that the fibronectin-conjugated polyHIPE scaffolds improve the adhesion and function of primary human endometrial stromal cells. It is believed that this approach can be employed to produce the next generation of polyHIPE scaffolds with tailored surface functionality, enhancing their application in 3D cell culture and tissue engineering whilst broadening the scope of applications to a wider range of cell types.

EVI1 carboxy-terminal phosphorylation is ATM-mediated and sustains transcriptional modulation and self-renewal via enhanced CtBP1 association.

The transcriptional regulator EVI1 has an essential role in early hematopoiesis and development. However, aberrantly high expression of EVI1 has potent oncogenic properties and confers poor prognosis and chemo-resistance in leukemia and solid tumors. To investigate to what extent EVI1 function might be regulated by post-translational modifications we carried out mass spectrometry- and antibody-based analyses and uncovered an ATM-mediated double phosphorylation of EVI1 at the carboxy-terminal S858/S860 SQS motif. In the presence of genotoxic stress EVI1-WT (SQS), but not site mutated EVI1-AQA was able to maintain transcriptional patterns and transformation potency, while under standard conditions carboxy-terminal mutation had no effect. Maintenance of hematopoietic progenitor cell clonogenic potential was profoundly impaired with EVI1-AQA compared with EVI1-WT, in particular in the presence of genotoxic stress. Exploring mechanistic events underlying these observations, we showed that after genotoxic stress EVI1-WT, but not EVI1-AQA increased its level of association with its functionally essential interaction partner CtBP1, implying a role for ATM in regulating EVI1 protein interactions via phosphorylation. This aspect of EVI1 regulation is therapeutically relevant, as chemotherapy-induced genotoxicity might detrimentally sustain EVI1 function via stress response mediated phosphorylation, and ATM-inhibition might be of specific targeted benefit in EVI1-overexpressing malignancies.

Analysis of chromatin accessibility in decidualizing human endometrial stromal cells.

Spontaneous decidualization of the endometrium in response to progesterone signaling is confined to menstruating species, including humans and other higher primates. During this process, endometrial stromal cells (EnSCs) differentiate into specialized decidual cells that control embryo implantation. We subjected undifferentiated and decidualizing human EnSCs to an assay for transposase accessible chromatin with sequencing (ATAC-seq) to map the underlying chromatin changes. A total of 185,084 open DNA loci were mapped accurately in EnSCs. Altered chromatin accessibility upon decidualization was strongly associated with differential gene expression. Analysis of 1533 opening and closing chromatin regions revealed over-representation of DNA binding motifs for known decidual transcription factors (TFs) and identified putative new regulators. ATAC-seq footprint analysis provided evidence of TF binding at specific motifs. One of the largest footprints involved the most enriched motif-basic leucine zipper-as part of a triple motif that also comprised the estrogen receptor and Pax domain binding sites. Without exception, triple motifs were located within Alu elements, which suggests a role for this primate-specific transposable element (TE) in the evolution of decidual genes. Although other TEs were generally under-represented in open chromatin of undifferentiated EnSCs, several classes contributed to the regulatory DNA landscape that underpins decidual gene expression.-Vrljicak, P., Lucas, E. S., Lansdowne, L., Lucciola, R., Muter, J., Dyer, N. P., Brosens, J. J., Ott, S. Analysis of chromatin accessibility in decidualizing human endometrial stromal cells.

The Glycosyltransferase EOGT Regulates Adropin Expression in Decidualizing Human Endometrium.

In pregnancy, resistance of endometrial decidual cells to stress signals is critical for the integrity of the fetomaternal interface and, by extension, survival of the conceptus. O-GlcNAcylation is an essential posttranslational modification that links glucose sensing to cellular stress resistance. Unexpectedly, decidualization of primary endometrial stromal cells (EnSCs) was associated with a 60% reduction in O-linked ß-N-acetylglucosamine (O-GlcNAc)‒modified proteins, reflecting downregulation of the enzyme that adds O-GlcNAc to substrates (O-GlcNAc transferase; OGT) but not the enzyme that removes the modification (O-GlcNAcase). Notably, epidermal growth factor domain-specific O-linked GlcNAc transferase (EOGT), an endoplasmic reticulum-specific OGT that modifies a limited number of secreted and membrane proteins, was markedly induced in differentiating EnSCs. Knockdown of EOGT perturbed a network of decidual genes involved in multiple cellular functions. The most downregulated gene upon EOGT knockdown in decidualizing cells was the energy homeostasis-associated gene (ENHO), which encodes adropin, a metabolic hormone involved in energy homeostasis and glucose and fatty acid metabolism. Analysis of midluteal endometrial biopsies revealed an inverse correlation between endometrial EOGT and ENHO expression and body mass index. Taken together, our findings revealed that obesity impairs the EOGT-adropin axis in decidual cells, which in turn points toward a mechanistic link between metabolic disorders and adverse pregnancy outcome.

Clearance of senescent decidual cells by uterine natural killer cells in cycling human endometrium.

In cycling human endometrium, menstruation is followed by rapid estrogen-dependent growth. Upon ovulation, progesterone and rising cellular cAMP levels activate the transcription factor Forkhead box O1 (FOXO1) in endometrial stromal cells (EnSCs), leading to cell cycle exit and differentiation into decidual cells that control embryo implantation. Here we show that FOXO1 also causes acute senescence of a subpopulation of decidualizing EnSCs in an IL-8 dependent manner. Selective depletion or enrichment of this subpopulation revealed that decidual senescence drives the transient inflammatory response associated with endometrial receptivity. Further, senescent cells prevent differentiation of endometrial mesenchymal stem cells in decidualizing cultures. As the cycle progresses, IL-15 activated uterine natural killer (uNK) cells selectively target and clear senescent decidual cells through granule exocytosis. Our findings reveal that acute decidual senescence governs endometrial rejuvenation and remodeling at embryo implantation, and suggest a critical role for uNK cells in maintaining homeostasis in cycling endometrium.