Disordered IL-33/ST2 activation in decidualizing stromal cells prolongs uterine receptivity in women with recurrent pregnancy loss

Meta-analysis of endometrial transcriptome data reveals novel molecular targets for recurrent implantation failure

PURPOSE

Gene expression analysis of the endometrium has been shown to be a useful approach for identifying the molecular signatures and pathways involved in recurrent implantation failure (RIF). Nevertheless, individual studies have limitations in terms of study design, methodology and analysis to detect minor changes in expression levels or identify novel gene signatures associated with RIF.

METHOD

To overcome this, we conducted an in silico meta-analysis of nine studies, the systematic collection and integration of gene expression data, utilizing rigorous selection criteria and statistical techniques to ensure the robustness of our findings.

RESULTS

Our meta-analysis successfully unveiled a meta-signature of 49 genes closely associated with RIF. Of these genes, 38 were upregulated and 11 downregulated in RIF patients' endometrium and believed to participate in key processes like cell differentiation, communication, and adhesion. GADD45A, IGF2, and LIF, known for their roles in implantation, were identified, along with lesser-studied genes like OPRK1, PSIP1, SMCHD1, and SOD2 related to female infertility. Many of these genes are involved in MAPK and PI3K-Akt pathways, indicating their role in inflammation. We also investigated to look for key miRNAs regulating these 49 dysregulated mRNAs as potential diagnostic biomarkers. Along with this, we went to associate protein-protein interactions of 49 genes, and we could recognize one cluster consisting of 11 genes (consisted of 22 nodes and 11 edges) with the highest score (p = 0.001). Finally, we validated some of the genes by qRT-PCR in our samples.

CONCLUSION

In summary, the meta-signature genes hold promise for improving RIF patient identification and facilitating the development of personalized treatment strategies, illuminating the multifaceted nature of this complex condition.

Celecoxib attenuates interleukin 33-induced expression of vascular cell adhesion molecule-1 in human ovarian endometriotic stromal cells

OBJECTIVE

Endometriosis is an estrogen-dependent chronic inflammatory disease in women of reproductive age. A review of the literature revealed that cytokines and inflammatory factors are associated with endometriosis-associated infertility. Interleukin 33 (IL-33) is a strong inducer of other pro-inflammatory cytokines. Vascular cell adhesion molecule-1 (VCAM-1) plays a central role in recruiting inflammatory cells, whose expression facilitates leukocyte adhesion and is rapidly induced by pro-inflammatory cytokines. Many studies have indicated that VCAM-1 expression is high in endometriosis; however, whether the expression of VCAM-1 is related to IL-33 is unclear.

MATERIALS AND METHODS

Human ovarian endometriotic stromal cells (hOVEN-SCs) were treated with IL-33 to enable investigation of cell characterization, gene and protein expression, and signal pathways. Proliferation potential was measured using an MTT assay. Gene expression was analyzed using reverse transcription-polymerase chain reaction. Protein expression assay was performed using western blot analysis.

RESULTS

This study investigated the effects of IL-33 on VCAM-1 and COX-2 expression in hOVEN-SCs. First, the results revealed that the IL-33/ST2/mitogen-activated protein kinase (MAPK) signaling pathway could increase the expression of VCAM-1 and COX-2 in hOVEN-SCs. Second, we discovered that COX-2 expression was essential for IL-33-induced VCAM-1 expression because the effects could be negated through NS398, a selective COX-2 inhibitor. Finally, treatment of IL-33-treated hOVEN-SCs with celecoxib significantly and dose-responsively decreased VCAM-1 expression.

CONCLUSION

Taken together, these results indicate that IL-33 can upregulate VCAM-1 expression in hOVEN-SCs through the IL-33/ST2/MAPK/COX-2 signaling pathway and thereby contribute to endometriosis.

Alterations in the pro-resolving lipid mediator machinery within first trimester maternal tissue: Implications in decidualization and miscarriage risk

A pivotal event in uterine receptivity and human reproduction is the differentiation of endometrial stromal cells into decidual cells, known as decidualization. Decidualization is interlinked with its inflammatory environment. Our study aimed to investigate the presence and role of pro-resolving lipid mediators in first trimester maternal tissue. We assessed the levels of LXA4 and RvD1, along with their metabolic LOX enzymes, in elective (control) and sporadic miscarriage samples. We investigated the effects of LXA4 and RvD1 on decidualization using primary endometrial stromal cells and the immortalized endometrial stromal St-T1b cell line. The upregulation of 12- and 15-LOX expression was observed in pregnancy tissue after sporadic miscarriage, suggesting an inflammatory imbalance. Furthermore, incubation with these lipid mediators led to a decrease in decidualization biomarkers PRL and IGFBP-1, accompanied by morphological changes indicative of aberrant differentiation. The expression of LOX enzymes in decidual natural killer cells suggests their involvement in regulating the inflammatory surroundings and the extent of decidualization.

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.

A biomarker for bacteremia in pregnant women with acute pyelonephritis: soluble suppressor of tumorigenicity 2 or sST2

Objective: Sepsis is a leading cause of maternal death, and its diagnosis during the golden hour is critical to improve survival. Acute pyelonephritis in pregnancy is a risk factor for obstetrical and medical complications, and it is a major cause of sepsis, as bacteremia complicates 15-20% of pyelonephritis episodes in pregnancy. The diagnosis of bacteremia currently relies on blood cultures, whereas a rapid test could allow timely management and improved outcomes. Soluble suppression of tumorigenicity 2 (sST2) was previously proposed as a biomarker for sepsis in non-pregnant adults and children. This study was designed to determine whether maternal plasma concentrations of sST2 in pregnant patients with pyelonephritis can help to identify those at risk for bacteremia.Study design: This cross-sectional study included women with normal pregnancy (n = 131) and pregnant women with acute pyelonephritis (n = 36). Acute pyelonephritis was diagnosed based on a combination of clinical findings and a positive urine culture. Patients were further classified according to the results of blood cultures into those with and without bacteremia. Plasma concentrations of sST2 were determined by a sensitive immunoassay. Non-parametric statistics were used for analysis.Results: The maternal plasma sST2 concentration increased with gestational age in normal pregnancies. Pregnant patients with acute pyelonephritis had a higher median (interquartile range) plasma sST2 concentration than those with a normal pregnancy [85 (47-239) ng/mL vs. 31 (14-52) ng/mL, p < .001]. Among patients with pyelonephritis, those with a positive blood culture had a median plasma concentration of sST2 higher than that of patients with a negative blood culture [258 (IQR: 75-305) ng/mL vs. 83 (IQR: 46-153) ng/mL; p = .03]. An elevated plasma concentration of sST2 ≥ 215 ng/mL had a sensitivity of 73% and a specificity of 95% (area under the receiver operating characteristic curve, 0.74; p = .003) with a positive likelihood ratio of 13.8 and a negative likelihood ratio of 0.3 for the identification of patients who had a positive blood culture.Conclusion: sST2 is a candidate biomarker to identify bacteremia in pregnant women with pyelonephritis. Rapid identification of these patients may optimize patient care.

Soluble suppression of tumorigenicity-2 in pregnancy with a small-for-gestational-age fetus and with preeclampsia

OBJECTIVE

Preeclampsia and fetal growth disorders are pregnancy-specific conditions that share common pathophysiological mechanisms. Yet, why some patients develop preeclampsia while others experience fetal growth restriction, or a combination of both clinical presentations, is unknown. We propose that the difference in severity of the maternal inflammatory response can contribute to the clinical phenotypes of preeclampsia vs. small for gestational age (SGA). To assess this hypothesis, we measured maternal plasma concentrations of the soluble isoform of suppression of tumorigenicity-2 (sST2), a member of the interleukin-1 receptor family that buffers proinflammatory responses. Previous reports showed that serum sST2 concentrations rise in the presence of intravascular inflammation and Th1-type immune responses and are significantly higher in patients with preeclampsia compared to those with normal pregnancy. The behavior of sST2 in pregnancies complicated by SGA has not been reported. This study was conducted to compare sST2 plasma concentrations in normal pregnancies, in those with preeclampsia, and in those with an SGA fetus.

METHODS

This retrospective cross-sectional study included women with an SGA fetus (n = 52), women with preeclampsia (n = 106), and those with normal pregnancy (n = 131). Maternal plasma concentrations of sST2 were determined by enzyme-linked immunosorbent assay. Doppler velocimetry of the uterine and umbilical arteries was available in a subset of patients with SGA (42 patients and 43 patients, respectively).

RESULTS

(1) Women with an SGA fetus had a significantly higher median plasma concentration of sST2 than normal pregnant women (p = .008); (2) women with preeclampsia had a significantly higher median plasma concentration of sST2 than those with normal pregnancy (p < .001) and those with an SGA fetus (p < .001); (3) patients with SGA and abnormal uterine artery Doppler velocimetry had a higher median plasma concentration of sST2 than controls (p < .01) and those with SGA and normal uterine artery Doppler velocimetry (p = .02); (4) there was no significant difference in the median plasma sST2 concentration between patients with SGA who had normal uterine artery Doppler velocimetry and controls (p = .4); (5) among patients with SGA, those with abnormal and those with normal umbilical artery Doppler velocimetry had higher median plasma sST2 concentrations than controls (p = .001 and p = .02, respectively); and (6) there was no significant difference in the median plasma sST2 concentrations between patients with SGA who did and those who did not have abnormal umbilical artery Doppler velocimetry (p = .06).

CONCLUSIONS

Preeclampsia and disorders of fetal growth are conditions characterized by intravascular inflammation, as reflected by maternal plasma concentrations of sST2. The severity of intravascular inflammation is highest in patients with preeclampsia.

DHT and Insulin Upregulate Secretion of the Soluble Decoy Receptor of IL-33 From Decidualized Endometrial Stromal Cells

Interleukin 33 (IL-33) signaling regulates most of the key processes of pregnancy, including decidualization, trophoblast proliferation and invasion, vascular remodeling, and placental growth. Accordingly, dysregulation of IL-33, its membrane-bound receptor (ST2L, transducer of IL-33 signaling), and its soluble decoy receptor (sST2, inhibitor of IL-33 signaling) has been linked to a wide range of adverse pregnancy outcomes that are common in women with obesity and polycystic ovary syndrome, that is, conditions associated with hyperandrogenism, insulin resistance, and compensatory hyperinsulinemia. To reveal if androgens and insulin might modulate uteroplacental IL-33 signaling, we investigated the effect of dihydrotestosterone (DHT) and/or insulin on the expression of ST2L and sST2 (along with the activity of their promoter regions), IL-33 and sIL1RAP (heterodimerization partner of sST2), during in vitro decidualization of endometrial stromal cells from 9 healthy women. DHT and insulin markedly upregulated sST2 secretion, in addition to the upregulation of its messenger RNA (mRNA) expression, while the proximal ST2 promoter, from which the sST2 transcript originates, was upregulated by insulin, and in a synergistic manner by DHT and insulin combination treatment. On the other hand, sIL1RAP was slightly downregulated by insulin and IL-33 mRNA expression was not affected by any of the hormones, while ST2L mRNA expression and transcription from its promoter region (distal ST2 promoter) could not be detected or showed a negligibly low level. We hypothesize that high levels of androgens and insulin might lead to subfertility and pregnancy complications, at least partially, through the sST2-dependent downregulation of uteroplacental IL-33 signaling.

miRNAs associated with endoplasmic reticulum stress and unfolded protein response during decidualization

RESEARCH QUESTION

Do microRNAs (miRNAs) play a role in regulating endoplasmic reticulum stress (ERS) and unfolded protein response (UPR) in decidualized cells and endometrium associated with reproductive failures?

DESIGN

Endometrial stromal cell line St-T1b was decidualized in vitro with 8-Br-cAMP over 5 days, or treated with the ERS inducer thapsigargin. Expression of ERS sensors, UPR markers and potential miRNA regulators was analysed by quantitative PCR. Endometrial biopsies from patients with recurrent pregnancy loss (RPL) and recurrent implantation failure (RIF) were investigated for the location of miRNA expression.

RESULTS

Decidualization of St-T1b cells resulted in increased expression of ERS sensors including ATF6α, PERK and IRE1α, and the UPR marker, CHOP. TXNIP, which serves as a link between the ERS pathway and inflammation, as well as inflammasome NLRP3 and interleukin 1β expression increased in decidualized cells. An in-silico analysis identified miR-17-5p, miR-21-5p and miR-193b-3p as miRNAs potentially involved in regulation of the ERS/UPR pathways and inflammation associated with embryo implantation. Their expression decreased significantly (P ≤ 0.0391) in non-decidualized cells in the presence of thapsigargin. Finally, expression of the selected miRNAs was localized by in-situ hybridization in stromal and glandular epithelial cells in endometrial samples from patients with RPL and RIF. Expression in stroma cells from patients with RPL was lower in comparison with stroma cells from patients with RIF.

CONCLUSIONS

Decidualization in St-T1b cells is accompanied by ERS/UPR processes, associated with an inflammatory response that is potentially influenced by miR-17-5p, miR-21-5p and miR-193b-3p. These miRNAs are expressed differentially in stromal cells from patients with RPL and RIF, indicating an alteration in regulation of the ERS/UPR pathways.

Endometrial responses to bacterial and viral infection: a scoping review

BACKGROUND

The endometrium is a highly dynamic tissue that undergoes dramatic proliferation and differentiation monthly in order to prepare the uterus for implantation and pregnancy. Intrauterine infection and inflammation are being increasingly recognized as potential causes of implantation failure and miscarriage, as well as obstetric complications later in gestation. However, the mechanisms by which the cells of the endometrium respond to infection remain understudied and recent progress is slowed in part owing to similar overlapping studies being performed in different species.

OBJECTIVE AND RATIONALE

The aim of this scoping review is to systematically summarize all published studies in humans and laboratory animals that have investigated the innate immune sensing and response of the endometrium to bacteria and viruses, and the signaling mechanisms involved. This will enable gaps in our knowledge to be identified to inform future studies.

SEARCH METHODS

The Cochrane Library, Ovid Embase/Medline, PubMed, Scopus, Google Scholar, and Web of Science databases were searched using a combination of controlled and free text terms for uterus/endometrium, infections, and fertility to March 2022. All primary research papers that have reported on endometrial responses to bacterial and viral infections in the context of reproduction were included. To focus the scope of the current review, studies in domesticated animals, included bovine, porcine, caprine, feline, and canine species were excluded.

OUTCOMES

This search identified 42 728 studies for screening and 766 full-text studies were assessed for eligibility. Data was extracted from 76 studies. The majority of studies focused on endometrial responses to Escherichia coli and Chlamydia trachomatis, with some studies of Neisseria gonorrhea, Staphylococcus aureus, and the Streptococcus family. Endometrial responses have only been studied in response to three groups of viruses thus far: HIV, Zika virus, and the herpesvirus family. For most infections, both cellular and animal models have been utilized in vitro and in vivo, focusing on endometrial production of cytokines, chemokines, and antiviral/antimicrobial factors, and the expression of innate immune signaling pathway mediators after infection. This review has identified gaps for future research in the field as well as highlighted some recent developments in organoid systems and immune cell co-cultures that offer new avenues for studying endometrial responses to infection in more physiologically relevant models that could accelerate future findings in this area.

WIDER IMPLICATIONS

This scoping review provides an overarching summary and benchmark of the current state of research on endometrial innate immune responses to bacterial and viral infection. This review also highlights some exciting recent developments that enable future studies to be designed to deepen our understanding of the mechanisms utilized by the endometrium to respond to infection and their downstream effects on uterine function.

The function of decidua natural killer cells in physiology and pathology of pregnancy

The role of decidual natural killer (dNK) cells in maintaining immune tolerance at the maternal-fetal interface during pregnancy is a significant topic in reproductive health. Immune tolerance is essential for a successful pregnancy and involves a complex immune response involving various immune cells and molecules. DNK cells comprise the largest population of lymphocyte subsets found in the decidua and play important roles in maintaining immune tolerance. These cells exert multiple functions to maintain homeostasis of the decidual microenvironment, including modulation of trophoblast invasion, promotion of fetal development, regulation of endometrial decidualization and spiral artery remodeling. DNK cells can also be divided into different subsets based on their functions as NKtolerant , NKcytotoxic , and NKregulatory cells. However, the relationship between dNK cells function and pregnancy outcomes is complex and poorly understood. In this review, we will focus on the physiological role of dNK cells during pregnancy and highlight the potential role in pathological pregnancies and therapeutic approaches.

Impaired secretion of C-X-C motif chemokine ligand 10 by stimulation with a Toll-like receptor 4 ligand in endometrial epithelium of infertile patients with minimal-to-mild endometriosis

Successful embryo implantation requires transient, well-controlled inflammation in decidualizing cells. In mice, Toll-like receptor (TLR) 4 signaling in endometrial epithelial cells (EECs) by stimulation with factors present in seminal fluids has been shown to be a key upstream driver of a controlled inflammatory response. Clinical evidence supports that exposure of the female reproductive tract to seminal plasma promotes implantation success. We investigated the response of EECs to TLR2 (Pam3Csk4), TLR 3 (Poly I:C), and TLR4 (lipopolysaccharides [LPS]) ligands with respect to secretion of C-X-C motif chemokine ligand (CXCL) 10 (CXCL10) and interleukin-6 (IL-6) in infertile patients with minimal-to-mild endometriosis (EECs-endo) (n = 38) and those of healthy, fertile women (EECs-healthy) (n = 30). Stimulation with either Pam3Csk4, Poly I:C or LPS, significantly induced CXCL10 and IL-6 in EECs-healthy (p < 0.05). In EECs-endo, either Pam3Csk4 or Poly I:C significantly induced CXCL10 (p < 0.05), whereas no significant response was observed after stimulation with LPS. Neither LPS, Poly I:C, nor Pam3Csk4 significantly induced IL-6 secretion in EECs-endo. Secretion of CXCL10 in EECs-healthy after stimulation with LPS was significantly higher (p < 0.05) than that in EECs-endo. CXCL10 decreased cell proliferation of EECs from both groups. Activation of nuclear factor kappa light chain enhancer of activated B cells and signal transducer and activator of transcription 3 signalings was not impaired, but activation of p38 mitogen-activated protein kinases signaling by LPS stimulation was impaired in EECs-endo. The present findings suggested that an insufficient response of EECs to a TLR4 ligand may be involved in molecular mechanisms of endometriosis-associated infertility.

The association of gut microbiome with recurrent pregnancy loss: A comprehensive review

The steady-state gut microbiome not only promotes the metabolism and absorption of nutrients that are difficult to digest by the host itself, but also participates in systemic metabolism. Once the dynamic balance is disturbed, the gut microbiome may lead to a variety of diseases. Recurrent pregnancy loss (RPL) affects 1-2% of women of reproductive age, and its prevalence has increased in recent years. According to the literature review, the gut microbiome is a new potential driver of the pathophysiology of recurrent abortion, and the gut microbiome has emerged as a new candidate for clinical prevention and treatment of RPL. However, few studies have concentrated on the direct correlation between RPL and the gut microbiome, and the mechanisms by which the gut microbiome influences recurrent miscarriage need further investigation. In this review, the effects of the gut microbiome on RPL were discussed and found to be associated with inflammatory response, the disruption of insulin signaling pathway and the formation of insulin resistance, maintenance of immunological tolerance at the maternal-fetal interface due to the interference with the immune imbalance of Treg/Th17 cells, and obesity.

IL-33/ST2 axis of human amnion fibroblasts participates in inflammatory reactions at parturition

BACKGROUND

Inflammation of the fetal membranes is an indispensable event of labor onset at both term and preterm birth. Interleukin-33 (IL-33) is known to participate in inflammation via ST2 (suppression of tumorigenicity 2) receptor as an inflammatory cytokine. However, it remains unknown whether IL-33/ST2 axis exists in human fetal membranes to promote inflammatory reactions in parturition.

METHODS

The presence of IL-33 and ST2 and their changes at parturition were examined with transcriptomic sequencing, quantitative real-time polymerase chain reaction, Western blotting or immunohistochemistry in human amnion obtained from term and preterm birth with or without labor. Cultured primary human amnion fibroblasts were utilized to investigate the regulation and the role of IL-33/ST2 axis in the inflammation reactions. A mouse model was used to further study the role of IL-33 in parturition.

RESULTS

Although IL-33 and ST2 expression were detected in both epithelial and fibroblast cells of human amnion, they are more abundant in amnion fibroblasts. Their abundance increased significantly in the amnion at both term and preterm birth with labor. Lipopolysaccharide, serum amyloid A1 and IL-1β, the inflammatory mediators pertinent to labor onset, could all induce IL-33 expression through NF-κB activation in human amnion fibroblasts. In turn, via ST2 receptor, IL-33 induced the production of IL-1β, IL-6 and PGE2 in human amnion fibroblasts via the MAPKs-NF-κB pathway. Moreover, IL-33 administration induced preterm birth in mice.

CONCLUSION

IL-33/ST2 axis is present in human amnion fibroblasts, which is activated in both term and preterm labor. Activation of this axis leads to increased production of inflammatory factors pertinent to parturition, and results in preterm birth. Targeting the IL-33/ST2 axis may have potential value in the treatment of preterm birth.

Endometrial and placental stem cells in successful and pathological pregnancies

The endometrium is a dynamic tissue that undergoes extensive remodeling during the menstrual cycle and further gets modified during pregnancy. Different kinds of stem cells are reported in the endometrium. These include epithelial stem cells, endometrial mesenchymal stem cells, side population stem cells, and very small embryonic-like stem cells. Stem cells are also reported in the placenta which includes trophoblast stem cells, side population trophoblast stem cells, and placental mesenchymal stem cells. The endometrial and placental stem cells play a pivotal role in endometrial remodeling and placental vasculogenesis during pregnancy. The dysregulation of stem cell function is reported in various pregnancy complications like preeclampsia, fetal growth restriction, and preterm birth. However, the mechanisms by which it does so are yet elusive. Herein, we review the current knowledge of the different type of stem cells involved in pregnancy initiation and also highlight how their improper functionality leads to pathological pregnancy.

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

OBJECTIVE AND DESIGN

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

MATERIAL OR SUBJECTS

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

TREATMENT

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

METHODS

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

RESULTS

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

CONCLUSION

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

Upregulation of IL-33, CCL2, and CXCL16 levels in Brazilian pregnant women infected by Toxoplasma gondii

Congenital toxoplasmosis can cause neurological and eye damage, behavioral alterations, or death in fetuses or babies born to Toxoplasma gondii-infected women. Several pieces of evidence suggest that socioeconomic, environmental, and inflammatory patterns linked to the maternal immune response partly drive the pathogenesis of this disease. However, immunoregulation induced by T. gondii infection during gestation is not completely understood. The aim of this study was to assess the association between T. gondii seropositivity and concentrations of plasma markers (CCL2, CXCL16, IL-17, and IL-33) in Brazilian pregnant women. Inflammatory markers were measured by immunoassays in the plasma of 131 pregnant women (13 to 46 years old). The prevalence of T. gondii infections was 45.8% (n = 60) in this population. The concentrations of CCL2, CXCL16, and IL-33 were higher in T. gondii-seropositive than in seronegative pregnant women, while the opposite was observed for IL-17 levels. In IgG+ women, a strong correlation between IL-17 and IL-33 (r = 0.7508, p = 0.0001) and a moderate correlation between CXCL16/IL-17 (r = 0.7319, p = 0.0001) and CXCL16/CCL2 (r = 0.3519, p = 0.0098) was observed. In uninfected women, a strong correlation was found between IL-17 and CXCL16 (r = 0.6779, p = 0.0001) but moderate between IL-17 and IL-33 (r = 0.4820, p = 0.0001). In summary, our data suggest that plasma upregulation of CCL2, CXCL16, and IL-33 might exert a potential protective role in the mother/fetus/parasite axis and, in addition, multiparous women are more likely to be infected with T. gondii than primiparous women.

Tacrolimus improved the pregnancy outcomes of patients with refractory recurrent spontaneous abortion and immune bias disorders: a randomized controlled trial

OBJECTIVE

To investigate the effect of tacrolimus treatment on refractory recurrent spontaneous abortion (RSA) patients with elevated serum IL-33/ST2 levels.

METHODS

This study was a randomized controlled trial (RCT) of refractory RSA patients with elevated peripheral blood IL-33/ST2 levels or an elevated Th1/Th2 cell ratio. A total of 149 women were enrolled, each of whom had had at least 3 serial miscarriages and was confirmed to have elevated peripheral blood IL-33/ST2 levels or an elevated Th1/Th2 cell ratio. These women were randomly divided into two groups. The tacrolimus group (n = 75) received basic therapy with the addition of tacrolimus (Prograf). Tacrolimus was administered at a dose of 0.05 ~ 0.1 mg/kg/day from the end of the menstrual period to the beginning of the next menstrual period or to the 10th week of pregnancy. In contrast, basic therapy with the addition of placebo was given to the placebo group (n = 74). The main study outcome was the delivery of healthy newborns without deformities.

RESULTS

A total of 60 (80.00%) patients in the tacrolimus group and 47 (63.51%) patients in the placebo group delivered healthy newborns [P = 0.03, odds ratio = 2.30; 95% confidence interval (1.10 ~ 4.81)]. The peripheral blood IL-33/ST2 levels and Th1/Th2 cell ratio of the tacrolimus group were much lower than those of the placebo group (P < 0.05).

CONCLUSION

We validated our previous finding that serum IL-33 and sST2 concentrations are related to RSA. Immunosuppressive treatment with tacrolimus was demonstrated to be a promising method to treat refractory RSA with immune bias disorders.

Defects in protective cytokine profiles in spontaneous miscarriage in the first trimester

OBJECTIVE

To study differences in cytokine expression profiles between women with ongoing pregnancy and those experiencing spontaneous miscarriage, among women who presented with threatened miscarriage before week 16 of gestation.

DESIGN

Prospective cohort study.

SETTING

Academic hospital.

PATIENT(S)

In this prospective cohort study, 155 pregnant women, comprising normal pregnant women recruited from antenatal clinics (n = 97) and women with threatened miscarriage recruited from an emergency walk-in clinic (n = 58).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Sixty-five serum cytokines quantified using multiplex immunoassay correlated with miscarriage outcomes.

RESULT(S)

Among women presenting with threatened miscarriage, those who eventually miscarried had significantly lower levels of interleukin (IL)-2, IL-12p70, IL-17A, B-cell-activating factor, B lymphocyte chemoattractant, basic nerve growth factor, interferon-γ, tumor necrosis factor-related apoptosis-inducing ligand, thymic stromal lymphopoietin, and tumor necrosis factor-α and higher levels of vascular endothelial growth factor A, IL-21, and stromal cell-derived factor 1α than those with ongoing pregnancy. Comparisons between normal pregnancies and women with threatened miscarriage who eventually miscarried revealed significant differences across 7 cytokines: B-cell-activating factor; B lymphocyte chemoattractant; basic nerve growth factor; IL-17A; fractalkine/CX3CL1; vascular endothelial growth factor A; and CCL22. Vascular endothelial growth factor A exhibited a negative correlation with the progesterone level (r = -0.270). The cluster of significant cytokines alludes to T cell proliferation, B-cell proliferation, natural killer cell-mediated cytotoxicity, and apoptosis as important pathways that determine pregnancy outcomes. Bioinformatic analysis further revealed alteration of the suppressor of cytokine signaling proteins family of Janus kinase-signal transducer and activator of transcription signaling axis by cytokines as a plausible key molecular mechanism in spontaneous miscarriage.

CONCLUSION(S)

This study demonstrates that the regulated balance between the proinflammatory and anti-inflammatory pathways is crucial to maintaining pregnancy. A better understanding of the cytokines associated with immunomodulatory effects may lead to novel targets for the prediction and treatment of spontaneous miscarriage.

Towards reproducible research in recurrent pregnancy loss immunology: Learning from cancer microenvironment deconvolution

The most recent international guidelines regarding recurrent pregnancy loss (RPL) exclude most of the immunological tests recommended for RPL since they do not reach an evidence-based level. Comparisons for metanalysis and systematic reviews are limited by the ambiguity in terms of RPL definition, etiological and risk factors, diagnostic work-up, and treatments applied. Therefore, cohort heterogeneity, the inadequacy of numerosity, and the quality of data confirm a not standardized research quality in the RPL field, especially for immunological background, for which potential research application remains confined in a separate single biological layer. Innovative sequencing technologies and databases have proved to play a significant role in the exploration and validation of cancer research in the context of dataset quality and bioinformatics tools. In this article, we will investigate how bioinformatics tools born for large-scale cancer immunological research could revolutionize RPL immunological research but are limited by the nature of current RPL datasets.

The Update Immune-Regulatory Role of Pro- and Anti-Inflammatory Cytokines in Recurrent Pregnancy Losses

Recurrent pregnancy losses (RPL) is a common reproductive disorder with various underlying etiologies. In recent years, rapid progress has been made in exploring the immunological mechanisms for RPL. A propensity toward Th2 over Th1 and regulatory T (Treg) over Th17 immune responses may be advantageous for reproductive success. In women with RPL and animals prone to abortion, an inordinate expression of cytokines associated with implantation and early embryo development is present in the endometrium or decidua secreted from immune and non-immune cells. Hence, an adverse cytokine milieu at the maternal-fetal interface assaults immunological tolerance, leading to fetal rejection. Similar to T cells, NK cells can be categorized based on the characteristics of cytokines they secrete. Decidual NK (dNK) cells of RPL patients exhibited an increased NK1/NK2 ratio (IFN-γ/IL-4 producing NK cell ratios), leading to pro-inflammatory cytokine milieu and increased NK cell cytotoxicity. Genetic polymorphism may be the underlying etiologies for Th1 and Th17 propensity since it alters cytokine production. In addition, various hormones participate in cytokine regulations, including progesterone and estrogen, controlling cytokine balance in favor of the Th2 type. Consequently, the intricate regulation of cytokines and hormones may prevent the RPL of immune etiologies. Local or systemic administration of cytokines or their antagonists might help maintain adequate cytokine milieu, favoring Th2 over Th1 response or Treg over Th17 immune response in women with RPL. Herein, we provided an updated comprehensive review regarding the immune-regulatory role of pro- and anti-inflammatory cytokines in RPL. Understanding the roles of cytokines involved in RPL might significantly advance the early diagnosis, monitoring, and treatment of RPL.

Maternal selection of human embryos in early gestation: Insights from recurrent miscarriage

Compared to most mammals, human pregnancy is unusual in that it involves chromosomally diverse embryos, cyclical breakdown and regeneration of the uterine mucosa, and intimate integration of fetal and maternal cells at the uteroplacental interface. Not surprisingly, pregnancy often falters in early gestation. Whether these losses result in clinical miscarriages depends on the origins and impacts of chromosomal errors on fetal development and the ability of the decidualizing endometrium to engage in embryo biosensing and selection. Aneuploidy originating in oocytes during meiosis drives the age-related risk of miscarriage. By contrast, the frequency of endometrial cycles with an impaired decidual response may account for the stepwise increase in miscarriage rates with each pregnancy loss independently of maternal age. Additional physiological mechanisms operate in early gestation to ensure that most failing pregnancies are lost before vascular maternal-fetal connections are established by the end of the first trimester. Here, we summarise how investigations into the mechanisms that cause miscarriage led to new insights into the processes that govern maternal selection of human embryos in early gestation.

Maternal IL-33 critically regulates tissue remodeling and type 2 immune responses in the uterus during early pregnancy in mice

The pregnant uterus is an immunologically rich organ, with dynamic changes in the inflammatory milieu and immune cell function underlying key stages of pregnancy. Recent studies have implicated dysregulated expression of the interleukin-1 (IL-1) family cytokine, IL-33, and its receptor, ST2, in poor pregnancy outcomes in women, including recurrent pregnancy loss, preeclampsia, and preterm labor. How IL-33 supports pregnancy progression in vivo is not well understood. Here, we demonstrate that maternal IL-33 signaling critically regulates uterine tissue remodeling and immune cell function during early pregnancy in mice. IL-33-deficient dams exhibit defects in implantation chamber formation and decidualization, and abnormal vascular remodeling during early pregnancy. These defects coincide with delays in early embryogenesis, increased resorptions, and impaired fetal and placental growth by late pregnancy. At a cellular level, myometrial fibroblasts, and decidual endothelial and stromal cells, are the main IL-33⁺ cell types in the uterus during decidualization and early placentation, whereas ST2 is expressed by uterine immune populations associated with type 2 immune responses, including ILC2s, Tregs, CD4⁺ T cells, M2- and cDC2-like myeloid cells, and mast cells. Early pregnancy defects in IL-33-deficient dams are associated with impaired type 2 cytokine responses by uterine lymphocytes and fewer Arginase-1⁺ macrophages in the uterine microenvironment. Collectively, our data highlight a regulatory network, involving crosstalk between IL-33-producing nonimmune cells and ST2⁺ immune cells at the maternal-fetal interface, that critically supports pregnancy progression in mice. This work has the potential to advance our understanding of how IL-33 signaling may support optimal pregnancy outcomes in women.

Multiomics Studies Investigating Recurrent Pregnancy Loss: An Effective Tool for Mechanism Exploration

Patients with recurrent pregnancy loss (RPL) account for approximately 1%-5% of women aiming to achieve childbirth. Although studies have shown that RPL is associated with failure of endometrial decidualization, placental dysfunction, and immune microenvironment disorder at the maternal-fetal interface, the exact pathogenesis remains unknown. With the development of high-throughput technology, more studies have focused on the genomics, transcriptomics, proteomics and metabolomics of RPL, and new gene mutations and new biomarkers of RPL have been discovered, providing an opportunity to explore the pathogenesis of RPL from different biological processes. Bioinformatics analyses of these differentially expressed genes, proteins and metabolites also reflect the biological pathways involved in RPL, laying a foundation for further research. In this review, we summarize the findings of omics studies investigating decidual tissue, villous tissue and blood from patients with RPL and identify some possible limitations of current studies.

Decidualization resistance in the origin of preeclampsia

Preeclampsia is a major obstetrical complication with short- and long-term life-threatening consequences for both mother and child. Shallow cytotrophoblast invasion through the uterine decidua into the spiral arteries is implicated in the pathogenesis of preeclampsia, although the cause of deficient arterial invasion remains unknown. Research that is focused on the "soil"-the maternal decidua-highlights the importance of this poorly understood but influential uterine layer. Decidualization of endometrial cells regulates embryo invasion, which is essential for spiral artery remodeling and establishing the maternal-fetal interface. Exploration of the association between impaired decidualization and preeclampsia revealed suboptimal endometrial maturation and uterine natural killer cells present in the decidua before preeclampsia development. Furthermore, decidualization defects in the endometrium of women with severe preeclampsia, characterized by impaired cytotrophoblast invasion, were detected at the time of delivery and persisted 5 years after the affected pregnancy. Recently, a maternal deficiency of annexin A2 expression was found to influence aberrant decidualization and shallow cytotrophoblast invasion, suggesting that decidualization resistance, which is a defective endometrial cell differentiation during the menstrual cycle, could underlie shallow trophoblast invasion and the poor establishment of the maternal-fetal interface. Based on these findings, the transcriptional signature in the endometrium that promotes decidualization deficiency could be detected before (or after) conception. This would serve to identify women at risk of developing severe preeclampsia and aid the development of therapies focused on improving decidualization, perhaps also preventing severe preeclampsia. Here, we discuss decidualization deficiency as a contributor to the pathogenesis of pregnancy disorders with particular attention to severe preeclampsia. We also review current diagnostic strategies and discuss future directions in diagnostic methods based on decidualization.

Antiphospholipid antibodies increase endometrial stromal cell decidualization, senescence and inflammation via TLR4, ROS and p38 MAP kinase signaling

OBJECTIVE

Miscarriage affects one in seven pregnancies and antiphospholipid autoantibodies (aPL) are one of the biggest risk factors for recurrent pregnancy loss. While aPL target the endometrial stroma, little is known about their impact. Endometrial stromal cells (EnSCs) undergo decidualization each menstrual cycle, priming the uterus to receive implanting embryos. Thus, appropriate decidualization and EnSC function is key for establishment of a successful pregnancy.

METHODS

EnSCs under decidualizing conditions were exposed to aPL or control IgG alone or in the presence of either a Toll-like receptor 4 (TLR4) antagonist, a p38 MAPK inhibitor, a reactive oxygen species (ROS) inhibitor, low-molecular weight heparin (LMWH), or acetyl salicylic acid (ASA). Secretion of decidualization markers and inflammatory interleukin (IL)-8 were quantified by ELISA, and senescence-associated β-galactosidase activity was evaluated. In a mouse model of decidualization, aPL or control IgG was administered and uterine expression of decidualization and inflammatory markers quantified by RT-qPCR.

RESULTS

aPL increased human EnSC decidualization, senescence and inflammation. This phenotype was recapitulated in the mouse model. The decidualization and inflammatory responses were partially mediated by TLR4 and p38 MAP kinase, while the decidualization and senescence responses were ROS-dependent. LMWH, commonly used to treat aPL-positive women at risk for obstetric complications, reduced the ability of aPL to increase EnSC decidualization and inflammation.

CONCLUSION

These findings shed new light on the pathogenesis of pregnancy complications in women with aPL and underscore the benefit of heparin for preventing pregnancy loss in this high-risk population.

Decreased intracellular IL-33 impairs endometrial receptivity in women with adenomyosis

Adenomyosis is a common benign uterine lesion that is associated with female infertility, reduced clinical pregnancy rate and high miscarriage risk. While it has been known that the impaired endometrial receptivity is implicated in infertility in patients with adenomyosis, the underlying mechanism remains unclear. In the present study, we showed that intracellular protein level of IL-33 was downregulated in the endometrium of patients with adenomyosis, and IL-33 expression status was shown to be positively correlated with that of HOXA10, an endometrial receptivity marker. The subsequent analysis indicated IL-33 overexpression led to the increase of HOXA10 expression and enhancement of embryo implantation in vitro, which was accompanied with induction of STAT3 phosphorylation. Meanwhile, cryptotanshinone, a potent STAT3 inhibitor, was found to significantly suppress the increase of HOXA10 expression and embryo implantation caused by IL-33 overexpression in vitro, revealing the critical role of STAT3 activity. Consistently, the positive relationship between IL33 and HOXA10 expression in the endometrium was verified in the analysis of adenomyosis mouse model.

Killer Timing: The Temporal Uterine Natural Killer Cell Differentiation Pathway and Implications for Female Reproductive Health

Natural killer (NK) cells are the predominant maternal uterine immune cell component, and they densely populate uterine mucosa to promote key changes in the post-ovulatory endometrium and in early pregnancy. It is broadly accepted that (a) immature, inactive endometrial NK (eNK) cells in the pre-ovulatory endometrium become activated and transition into decidual NK (dNK) cells in the secretory stage, peri-implantation endometrium, and continue to mature into early pregnancy; and (b) that secretory-stage and early pregnancy dNK cells promote uterine vascular growth and mediate trophoblast invasion, but do not exert their killing function. However, this may be an overly simplistic view. Evidence of specific dNK functional killer roles, as well as opposing effects of dNK cells on the uterine vasculature before and after conception, indicates the presence of a transitory secretory-stage dNK cell (s-dNK) phenotype with a unique angiodevelopmental profile during the peri-implantation period, that is that is functionally distinct from the angiomodulatory dNK cells that promote vessel destabilisation and vascular cell apoptosis to facilitate uterine vascular changes in early pregnancy. It is possible that abnormal activation and differentiation into the proposed transitory s-dNK phenotype may have implications in uterine pathologies ranging from infertility to cancer, as well as downstream effects on dNK cell differentiation in early pregnancy. Further, dysregulated transition into the angiomodulatory dNK phenotype in early pregnancy will likely have potential repercussions for adverse pregnancy outcomes, since impaired dNK function is associated with several obstetric complications. A comprehensive understanding of the uterine NK cell temporal differentiation pathway may therefore have important translational potential due to likely NK phenotypic functional implications in a range of reproductive, obstetric, and gynaecological pathologies.

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.

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.

Novel approaches to the management of recurrent pregnancy loss: The OPTIMUM (OPtimization of Thyroid function, Thrombophilia, Immunity, and Uterine Milieu) treatment strategy

PURPOSE

Does the OPtimization of Thyroid function, Thrombophilia, Immunity, and Uterine Milieu (OPTIMUM) treatment strategy, developed for treating repeated implantation failure (RIF), contribute to improving pregnancy outcomes in patients with a history of recurrent pregnancy loss (RPL)?

METHODS

Between 2018 and 2019, women with RPL after two or more clinical pregnancy losses underwent RPL testing. We treated chronic endometritis with antibiotics, high Th1/Th2 cell ratios with vitamin D and/or tacrolimus, overt/subclinical hypothyroidism with levothyroxine, and thrombophilia with low-dose aspirin. Of 168 consecutive women aged ≤43 years, 115 underwent RPL testing. We compared 100 pregnancies (90 women) and 46 pregnancies (41 women) with and without the OPTIMUM treatment strategy, respectively.

RESULTS

RPL testing identified intrauterine abnormalities in 66 (57.4%), elevated Th1/Th2 cell ratios in 50 (43.5%), thyroid dysfunction in 33 (28.7%), and thrombophilia in 33 (28.7%). The live birth rate in the OPTIMUM group was significantly higher than that in the control group among women aged <40 years (78.1% and 42.3%, respectively; p = 0.002), but no significant difference was observed in women aged ≥40 years (55.6% and 30.0%, respectively; p = 0.09).

CONCLUSIONS

The OPTIMUM treatment strategy improved pregnancy outcomes in patients with not only RIF but also RPL.

Single-cell analysis of prostaglandin E2-induced human decidual cell in vitro differentiation: a minimal ancestral deciduogenic signal†

The decidua is a hallmark of reproduction in many placental mammals. Differentiation of decidual stromal cells is known to be induced by progesterone and the cyclic AMP/protein kinase A (cAMP/PKA) pathway. Several candidates have been identified as the physiological stimulus for adenylyl cyclase activation, but their relative importance remains unclear. To bypass this uncertainty, the standard approach for in vitro experiments uses membrane-permeable cAMP and progestin. We phylogenetically infer that prostaglandin E2 (PGE2) likely was the signal that ancestrally induced decidualization in conjunction with progesterone. This suggests that PGE2 and progestin should be able to activate the core gene regulatory network of decidual cells. To test this prediction, we performed a genome-wide study of gene expression in human endometrial fibroblasts decidualized with PGE2 and progestin. Comparison to a cAMP-based protocol revealed shared activation of core decidual genes and decreased induction of senescence-associated genes. Single-cell transcriptomics of PGE2-mediated decidualization revealed a distinct, early-activated state transitioning to a differentiated decidual state. PGE2-mediated decidualization was found to depend upon progestin-dependent induction of PGE2 receptor 2 (PTGER2) which in turn leads to PKA activation upon PGE2 stimulation. Progesterone-dependent induction of PTGER2 is absent in opossum, an outgroup taxon of placental mammals which is incapable of decidualization. Together, these findings suggest that the origin of decidualization involved the evolution of progesterone-dependent activation of the PGE2/PTGER2/PKA axis, facilitating entry into a PKA-dominant rather than AKT-dominant cellular state. We propose the use of PGE2 for in vitro decidualization as an alternative to 8-Br-cAMP.

A 3D endometrial organotypic model simulating the acute inflammatory decidualisation initiation phase with epithelial induction of the key endometrial receptivity marker, integrin αVβ3

STUDY QUESTION

Is it possible to develop a simplified physiological in vitro system representing the key cell-types associated with a receptive endometrial phenotype?

SUMMARY ANSWER

We present a new concept to investigate endometrial receptivity, with a 3D organotypic co-culture model to simulate an early and transient acute autoinflammatory decidual status that resolves in the induction of a receptive endometrial phenotype.

WHAT IS KNOWN ALREADY

Embryo implantation is dependent on a receptive uterine environment. Ovarian steroids drive post-ovulation structural and functional changes in the endometrium, which becomes transiently receptive for an implanting conceptus, termed the ‘window of implantation’, and dysregulation of endometrial receptivity is implicated in a range of reproductive, obstetric, and gynaecological disorders and malignancies. The interactions that take place within the uterine microenvironment during this time are not fully understood, and human studies are constrained by a lack of access to uterine tissue from specific time-points during the menstrual cycle. Physiologically relevant in vitro model systems are therefore fundamental for conducting investigations to better understand the cellular and molecular mechanisms controlling endometrial receptivity.

STUDY DESIGN, SIZE, DURATION

We conducted an in vitro cell culture study using human cell lines and primary human cells isolated from endometrial biopsy tissue. The biopsy tissue samples were obtained from three women attending gynaecological outpatient departments in NHS Lothian. The work was carried out between December 2016 and April 2019, at the MRC Centre for Reproductive Health, Queen’s Medical Research Institute, University of Edinburgh.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An endometrial stromal cell (ESC) line, and endometrial epithelial cells (EECs) isolated from endometrial biopsy tissue and expanded in vitro by conditional reprogramming, were used throughout the study. Immunocytochemical and flow cytometric analyses were used to confirm epithelial phenotype following conditional reprogramming of EECs. To construct an endometrial organotypic co-culture model, ESCs were embedded within a 3D growth factor-reduced Matrigel structure, with a single layer of conditionally reprogrammed EECs seeded on top. Cells were stimulated with increasing doses of medroxyprogesterone acetate, cAMP and oestradiol, in order to induce ESC decidual transformation and endometrial receptivity. Decidual response and the induction of a receptive epithelial phenotype were assessed by immunocytochemical detection and quantitative in-cell western analyses, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

A transient up-regulation of the interleukin-33 receptor protein, ST2L, was observed in ESCs, indicating a transient autoinflammatory decidual response to the hormonal stimulation, known to induce receptivity gene expression in the overlying epithelium. Hormonal stimulation increased the EEC protein levels of the key marker of endometrial receptivity, integrin αVβ3 (n = 8; *P < 0.05; ***P < 0.0001). To our knowledge, this is the first demonstration of a dedicated endometrial organotypic model, which has been developed to investigate endometrial receptivity, via the recapitulation of an early decidual transitory acute autoinflammatory phase and induction of an epithelial phenotypic change, to represent a receptive endometrial status.

LIMITATIONS, REASONS FOR CAUTION

This simplified in vitro ESC-EEC co-culture system may be only partly representative of more complex in vivo conditions.

WIDER IMPLICATIONS OF THE FINDINGS

The 3D endometrial organotypic model presented here may offer a valuable tool for investigating a range of reproductive, obstetric, and gynaecological disorders, to improve outcomes for assisted reproductive technologies, and for the development of advances in contraceptive methods.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by a Medical Research Council Centre Grant (project reference MR/N022556/1). R.F. was the recipient of a Moray Endowment award and a Barbour Watson Trust award. C.-J.L. is a Royal Society of Edinburgh Personal Research Fellow, funded by the Scottish Government. The authors have no conflicts of interest to declare.

Infertility and subsequent recurrent miscarriage: Current state of the literature and future considerations for practice and research

Background: Recurrent miscarriage (RM) and infertility are independently associated with adverse pregnancy outcomes, in addition to psychological sequelae. Experiencing pregnancy loss alongside infertility is particularly difficult. International guidance regarding RM is conflicting, and applicability to women with infertility is undetermined. The aim of this study was to: (i) establish if women/couples with a history of infertility are recognised in the literature on the investigation and management of RM, and (ii) determine if the specific needs of women/couples experiencing RM and infertility are ascertained and incorporated into clinical management strategies. Methods: We examined the wide-ranging literature to ascertain what gaps existed. Studies were retrieved through searches of PubMed and Google Scholar up to 21 January 2021 using appropriate controlled vocabulary and combinations of key words. No language or study design restrictions were applied. Results: While women/couples experiencing RM after infertility appear in studies evaluating investigations and proposed treatments, high-quality studies are lacking. Furthermore, they are largely excluded from international clinical guidance and qualitative research. Conclusions: The experiences of women/couples with RM and infertility and their specific care needs within maternity and fertility services are underexplored. It is unclear from current RM guidelines how best to manage and support this complex cohort. Women/couples with infertility and RM are underserved in the literature and in clinical guidance. Further robust studies are warranted to examine pregnancy outcomes, investigations and treatments currently used. Qualitative research is also required to identify their medical and psychological needs to better support this vulnerable group.

Modelling the impact of decidual senescence on embryo implantation in human endometrial assembloids

Decidual remodelling of midluteal endometrium leads to a short implantation window after which the uterine mucosa either breaks down or is transformed into a robust matrix that accommodates the placenta throughout pregnancy. To gain insights into the underlying mechanisms, we established and characterized endometrial assembloids, consisting of gland-like organoids and primary stromal cells. Single-cell transcriptomics revealed that decidualized assembloids closely resemble midluteal endometrium, harbouring differentiated and senescent subpopulations in both glands and stroma. We show that acute senescence in glandular epithelium drives secretion of multiple canonical implantation factors, whereas in the stroma it calibrates the emergence of anti-inflammatory decidual cells and pro-inflammatory senescent decidual cells. Pharmacological inhibition of stress responses in pre-decidual cells accelerated decidualization by eliminating the emergence of senescent decidual cells. In co-culture experiments, accelerated decidualization resulted in entrapment of collapsed human blastocysts in a robust, static decidual matrix. By contrast, the presence of senescent decidual cells created a dynamic implantation environment, enabling embryo expansion and attachment, although their persistence led to gradual disintegration of assembloids. Our findings suggest that decidual senescence controls endometrial fate decisions at implantation and highlight how endometrial assembloids may accelerate the discovery of new treatments to prevent reproductive failure.

Endometrial Receptivity Testing and Therapy in Assisted Reproductive Treatment

Assisted reproductive treatment (ART) gave numerous couples the chance to have their biological child. Improvement in laboratory and culture conditions allows for selection of embryos with the best developmental potential, although replacement of these top-quality embryos does not, however, guarantee reproductive success. Endometrial receptivity is essential for pregnancy establishment and may be the limiting factor for the observed pregnancy rates with ART. Multiple modalities have been in use to assess endometrial receptivity, with ultrasound assessment of the endometrial morphology most commonly used due to its noninvasive nature and availability. Utilization of various "omics" increases our understanding of endometrial receptivity and selectivity; however, significantly more work is required to develop clinically relevant and validated tests of endometrial receptivity and treatments which could improve a suboptimal endometrial milieu. Current evidence for and against use of various tests of endometrial receptivity in women undergoing ART is presented in this article.

Senolytic treatment modulates decidualization in human endometrial stromal cells

Decidualization - the differentiation of endometrial stromal cells (ESCs) into decidual cells - is a crucial step for successful embryo implantation and placentation that is initiated in the secretory phase of the menstrual cycle. During decidualization, ESCs undergo proliferation arrest and secrete inflammatory mediators, including senescence-associated secretory phenotype (SASP). Although several senolytic agents improve age-related diseases, their effects on cellular senescence in decidualizing ESCs has not been explored. To do this, we treated decidualized ESCs with the senolytic agents Quercetin (Que), Dasatinib (Das), and BPTES. Que decreased the number of senescence-associated β-galactosidase (SA-β-Gal) positive cells and expression of senescence markers in ESCs treated with the decidual stimulus (dibutyryl-cAMP plus progesterone: DP). Concomitantly, Que markedly increased the expression of the decidualization markers IGFBP1, PRL, and FOXO1, in decidualizing ESCs. Similar to Que, Das also stimulated decidualization. Treatment with a combination of Que and Das synergistically increased the expression of decidualization markers and senescence markers compared with treatment with Que or Das alone. However, BPTES did not enhance the expression of decidualization markers. These results imply that treatment with Que and/or Das can remove senescent decidual cells and enhance the decidualization of the rest of ESCs. Thus, senolytic modulation of abnormal ESC decidualization could alleviate infertility caused by dysfunctions of endometrial receptivity and embryo implantation.

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.

Interleukin-33 promotes invasiveness of human ovarian endometriotic stromal cells through the ST2/MAPK/MMP-9 pathway activated by 17β-estradiol

OBJECTIVE

Endometriosis is an estrogen-dependent, benign, and chronic gynecological disorder occurring in women of reproductive age. Although the pathogenesis of endometriosis is poorly understood, implantation theory indicates that viable endometrial cells shed from the endometrium into the pelvic peritoneum or ovaries, possibly through retrograde menstruation, and then reattach, invade, and damage other tissues. Interleukin (IL)-33, a new member of the IL-1 superfamily, is mainly upregulated by stromal cells following proinflammatory stimulation. Matrix metalloproteinases (MMPs) are involved in the degradation and reconstruction of the extracellular matrix. MMP-9 participates in the pathogenesis of endometriosis by promoting the invasion of endometriotic cells. This study investigated the effect of IL-33 on the cell invasion ability of and MMP-9 expression in human stromal cells derived from ovarian endometrioma (hOVEN-SCs).

MATERIALS AND METHODS

We isolated hOVEN-SCs from human ovarian endometrioma. Gene expression was analyzed using the Illumina Human WG-6 v2 Expression BeadChips microarray platform and through reverse transcription-polymerase chain reaction. Cell migration and invasion were examined by performing the transwell chamber assay.

RESULTS

We found that 17β-estradiol could increase the expression of IL-33 and ST2 through the estrogen receptor pathway in hOVEN-SCs. Moreover, IL-33 upregulated MMP-9 expression in and enhanced the invasion ability of hOVEN-SCs through the ST2/MAPK signaling pathway. Our results showed that MMP-9 expression was essential for IL-33-induced cell invasion.

CONCLUSION

Our main finding is that 17β-estradiol could increase IL-33 expression through the estrogen receptor pathway and activate MMP-9 expression in and invasion ability of hOVEN-SCs through the IL-33/ST2/MAPK signaling pathway. The results of this study and further related studies may provide new strategies for the prevention and treatment of endometriosis.

Protective role of IL33 signaling in negative pregnancy outcomes associated with lipopolysaccharide exposure

Interleukin 33 (IL33) signaling has been implicated in the establishment and maintenance of pregnancy and in pregnancy disorders. The goal of this project was to evaluate the role of IL33 signaling in rat pregnancy. The rat possesses hemochorial placentation with deep intrauterine trophoblast invasion; features also characteristic of human placentation. We generated and characterized a germline mutant rat model for IL33 using CRISPR/Cas9 genome editing. IL33 deficient rats exhibited deficits in lung responses to an inflammatory stimulus (Sephadex G-200) and to estrogen-induced uterine eosinophilia. Female rats deficient in IL33 were fertile and exhibited pregnancy outcomes (gestation length and litter size) similar to wild-type rats. Placental weight was adversely affected by the disruption of IL33 signaling. A difference in pregnancy-dependent adaptations to lipopolysaccharide (LPS) exposure was observed between wild-type and IL33 deficient pregnancies. Pregnancy in wild-type rats treated with LPS did not differ significantly from pregnancy in vehicle-treated wild-type rats. In contrast, LPS treatment decreased fetal survival rate, fetal and placental weights, and increased fetal growth restriction in IL33 deficient rats. In summary, a new rat model for investigating IL33 signaling has been established. IL33 signaling participates in the regulation of placental development and protection against LPS-induced fetal and placental growth restriction.

Clinical consequences of defective decidualization

Decidualization is characterized by a series of genetic, metabolic, morphological, biochemical, vascular and immune changes occurring in the endometrial stroma in response to the implanting embryo or even before conception and involves the stromal cells of the endometrium. It is a fundamental reproductive event occurring in mammalian species with hemochorial placentation. A growing body of experimental and clinical evidence strongly suggests that defective or disrupted decidualization contributes to the establishment of an inappropriate maternal-fetal interface. This has relevant clinical consequences, ranging from recurrent implantation failure and recurrent pregnancy loss in early pregnancy to several significant complications of advanced gestation. Moreover, recent evidence indicates that selected diseases of the endometrium, such as chronic endometritis and endometriosis, can have a detrimental impact on the decidualization response in the endometrium and may help explain some aspects of the reduced reproductive outcome associated with these conditions. Further research efforts are needed to fully understand the biomolecular mechanisms ans events underlying an abnormal decidualization response. This will permit the development of new diagnostic and therapeutic strategies aimed to improve the likelihood of achieveing a successful pregnancy.

Evolution of Embryo Implantation Was Enabled by the Origin of Decidual Stromal Cells in Eutherian Mammals

Mammalian pregnancy evolved in the therian stem lineage, that is, before the common ancestor of marsupials and eutherian (placental) mammals. Ancestral therian pregnancy likely involved a brief phase of attachment between the fetal and maternal tissues followed by parturition-similar to the situation in most marsupials including the opossum. In all eutherians, however, embryo attachment is followed by implantation, allowing for a stable fetal-maternal interface and an extended gestation. Embryo attachment induces an attachment reaction in the uterus that is homologous to an inflammatory response. Here, we elucidate the evolutionary mechanism by which the ancestral inflammatory response was transformed into embryo implantation in the eutherian lineage. We performed a comparative uterine transcriptomic and immunohistochemical study of three eutherians, armadillo (Dasypus novemcinctus), hyrax (Procavia capensis), and rabbit (Oryctolagus cuniculus); and one marsupial, opossum (Monodelphis domestica). Our results suggest that in the eutherian lineage, the ancestral inflammatory response was domesticated by suppressing one of its modules detrimental to pregnancy, namely, neutrophil recruitment by cytokine IL17A. Further, we propose that this suppression was mediated by decidual stromal cells, a novel cell type in eutherian mammals. We tested a prediction of this model in vitro and showed that decidual stromal cells can suppress the production of IL17A from helper T cells. Together, these results provide a mechanistic understanding of early stages in the evolution of eutherian pregnancy.

The proliferative phase endometrium in IVF/ICSI: an in-cycle molecular analysis predictive of the outcome following fresh embryo transfer

STUDY QUESTION

Does an early proliferative phase endometrial biopsy harvested during ovarian stimulation harbour information predictive of the outcome following fresh embryo transfer (ET) in that same cycle?

SUMMARY ANSWER

Transcriptome analysis of the whole-tissue endometrium did not reveal significant differential gene expression (DGE) in relation to the outcome; however, the secretome profile of isolated, cultured and in vitro decidualized endometrial stromal cells (EnSCs) varied significantly between patients who had a live birth compared to those with an implantation failure following fresh ET in the same cycle as the biopsy.

WHAT IS KNOWN ALREADY

In the majority of endometrial receptivity research protocols, biopsies are harvested during the window of implantation (WOI). This, however, precludes ET in that same cycle, which is preferable as the endometrium has been shown to adapt over time. Endometrial biopsies taken during ovarian stimulation have been reported not to harm the chances of implantation, and in such biopsies DGE has been observed between women who achieve pregnancy versus those who do not. The impact of the endometrial proliferative phase on human embryo implantation remains unclear, but deserves further attention, especially since in luteal phase endometrial biopsies, a transcriptional signature predictive for repeated implantation failure has been associated with reduced cell proliferation, possibly indicating proliferative phase involvement. Isolation, culture and in vitro decidualization (IVD) of EnSCs is a frequently applied basic research technique to assess endometrial functioning, and a disordered EnSC secretome has previously been linked with failed implantation.

STUDY DESIGN, SIZE, DURATION

This study was nested in a randomized controlled trial (RCT) investigating the effect of endometrial scratching during the early follicular phase of ovarian stimulation on clinical pregnancy rates after IVF/ICSI. Of the 96 endometrial biopsies available, after eliminating those without fresh ET and after extensive matching in order to minimize the risk of potential confounding, 18 samples were retained to study two clinical groups: nine biopsies of patients with a live birth versus nine biopsies of patients with an implantation failure, both following fresh ET performed in the same cycle as the biopsy. We studied the proliferative endometrium by analysing its transcriptome and by isolating, culturing and decidualizing EnSCs in vitro. We applied this latter technique for the first time on proliferative endometrial biopsies obtained during ovarian stimulation for in-cycle outcome prediction, in an attempt to overcome inter-cycle variability.

PARTICIPANTS/MATERIALS, SETTING, METHODS

RNA-sequencing was performed for 18 individual whole-tissue endometrial biopsies on an Illumina HiSeq1500 machine. DGE was analysed three times using different approaches (DESeq2, EdgeR and the Wilcoxon rank-sum test, all in R). EnSC isolation and IVD was performed (for 2 and 4 days) for a subset of nine samples, after which media from undifferentiated and decidualized cultures were harvested, stored at -80°C and later assayed for 45 cytokines using a multiplex suspension bead immunoassay. The analysis was performed by partial least squares regression modelling.

MAIN RESULTS AND THE ROLE OF CHANCE

After correction for multiple hypothesis testing, DGE analysis revealed no significant differences between endometrial samples from patients who had a live birth and those with an implantation failure following fresh ET. However secretome analysis after EnSC isolation and culture, showed two distinct clusters that clearly corresponded to the two clinical groups. Upon IVD, the secretome profiles shifted from that of undifferentiated cells but the difference between the two clinical groups remained yet were muted, suggesting convergence of cytokine profiles after decidualization.

LIMITATIONS, REASONS FOR CAUTION

Caution is warranted due to the limited sample size of the study and the in vitro nature of the EnSC experiment. Validation on a larger scale is necessary, however, hard to fulfil given the very limited availability of in-cycle proliferative endometrial biopsies outside a RCT setting.

WIDER IMPLICATIONS OF THE FINDINGS

These data support the hypothesis that the endometrium should be assessed not only during the WOI and that certain endometrial dysfunctionalities can probably be detected early in a cycle by making use of the proliferative phase. This insight opens new horizons for the development of endometrial tests, whether diagnostic or predictive of IVF/ICSI treatment outcome.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by Fonds Wetenschappelijk Onderzoek (FWO, Flanders, Belgium, 11M9415N, 1 524 417N), Wetenschappelijk Fonds Willy Gepts (WFWG G160, Universitair Ziekenhuis Brussel, Belgium) and the National Medicine Research Council (NMRC/CG/M003/2017, Singapore). There are no conflicts of interests.

TRIAL REGISTRATION NUMBER

NCT02061228.

Seminal plasma promotes decidualization of endometrial stromal fibroblasts in vitro from women with and without inflammatory disorders in a manner dependent on interleukin-11 signaling

STUDY QUESTION

Do seminal plasma (SP) and its constituents affect the decidualization capacity and transcriptome of human primary endometrial stromal fibroblasts (eSFs)?

SUMMARY ANSWER

SP promotes decidualization of eSFs from women with and without inflammatory disorders (polycystic ovary syndrome (PCOS), endometriosis) in a manner that is not mediated through semen amyloids and that is associated with a potent transcriptional response, including the induction of interleukin (IL)-11, a cytokine important for SP-induced decidualization.

WHAT IS KNOWN ALREADY

Clinical studies have suggested that SP can promote implantation, and studies in vitro have demonstrated that SP can promote decidualization, a steroid hormone-driven program of eSF differentiation that is essential for embryo implantation and that is compromised in women with the inflammatory disorders PCOS and endometriosis.

STUDY DESIGN, SIZE, DURATION

This is a cross-sectional study involving samples treated with vehicle alone versus treatment with SP or SP constituents. SP was tested for the ability to promote decidualization in vitro in eSFs from women with or without PCOS or endometriosis (n = 9). The role of semen amyloids and fractionated SP in mediating this effect and in eliciting transcriptional changes in eSFs was then studied. Finally, the role of IL-11, a cytokine with a key role in implantation and decidualization, was assessed as a mediator of the SP-facilitated decidualization.

PARTICIPANTS/MATERIALS, SETTING, METHODS

eSFs and endometrial epithelial cells (eECs) were isolated from endometrial biopsies from women of reproductive age undergoing benign gynecologic procedures and maintained in vitro. Assays were conducted to assess whether the treatment of eSFs with SP or SP constituents affects the rate and extent of decidualization in women with and without inflammatory disorders. To characterize the response of the endometrium to SP and SP constituents, RNA was isolated from treated eSFs or eECs and analyzed by RNA sequencing (RNAseq). Secreted factors in conditioned media from treated cells were analyzed by Luminex and ELISA. The role of IL-11 in SP-induced decidualization was assessed through Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas-9-mediated knockout experiments in primary eSFs.

MAIN RESULTS AND THE ROLE OF CHANCE

SP promoted decidualization both in the absence and presence of steroid hormones (P < 0.05 versus vehicle) in a manner that required seminal proteins. Semen amyloids did not promote decidualization and induced weak transcriptomic and secretomic responses in eSFs. In contrast, fractionated SP enriched for seminal microvesicles (MVs) promoted decidualization. IL-11 was one of the most potently SP-induced genes in eSFs and was important for SP-facilitated decidualization.

LARGE SCALE DATA

RNAseq data were deposited in the Gene Expression Omnibus repository under series accession number GSE135640.

LIMITATIONS, REASONS FOR CAUTION

This study is limited to in vitro analyses.

WIDER IMPLICATIONS OF THE FINDINGS

Our results support the notion that SP promotes decidualization, including within eSFs from women with inflammatory disorders. Despite the general ability of amyloids to induce cytokines known to be important for implantation, semen amyloids poorly signaled to eSFs and did not promote their decidualization. In contrast, fractionated SP enriched for MVs promoted decidualization and induced a transcriptional response in eSFs that overlapped with that of SP. Our results suggest that SP constituents, possibly those associated with MVs, can promote decidualization of eSFs in an IL-11-dependent manner in preparation for implantation.

STUDY FUNDING/COMPETING INTEREST(S)

This project was supported by NIH (R21AI116252, R21AI122821 and R01AI127219) to N.R.R. and (P50HD055764) to L.C.G. The authors declare no conflict of interest.

Characterization of highly proliferative decidual precursor cells during the window of implantation in human endometrium

Pregnancy depends on the wholesale transformation of the endometrium, a process driven by differentiation of endometrial stromal cells (EnSC) into specialist decidual cells. Upon embryo implantation, decidual cells impart the tissue plasticity needed to accommodate a rapidly growing conceptus and invading placenta, although the underlying mechanisms are unclear. Here we characterize a discrete population of highly proliferative mesenchymal cells (hPMC) in midluteal human endometrium, coinciding with the window of embryo implantation. Single-cell transcriptomics demonstrated that hPMC express genes involved in chemotaxis and vascular transmigration. Although distinct from resident EnSC, hPMC also express genes encoding pivotal decidual transcription factors and markers, most prominently prolactin. We further show that hPMC are enriched around spiral arterioles, scattered throughout the stroma, and occasionally present in glandular and luminal epithelium. The abundance of hPMC correlated with the in vitro colony-forming unit activity of midluteal endometrium and, conversely, clonogenic cells in culture express a gene signature partially conserved in hPMC. Cross-referencing of single-cell RNA-sequencing data sets indicated that hPMC differentiate into a recently discovered decidual subpopulation in early pregnancy. Finally, we demonstrate that recurrent pregnancy loss is associated with hPMC depletion. Collectively, our findings characterize midluteal hPMC as novel decidual precursors that are likely derived from circulating bone marrow-derived mesenchymal stem/stromal cells and integral to decidual plasticity in pregnancy.

Intralipid infusion at time of embryo transfer in women with history of recurrent implantation failure: A systematic review and meta-analysis

AIM

Recurrent implantation failure (RIF) affects 10% of couples undergoing assisted conception, often due to poor endometrial receptivity. We conducted a systematic review and meta-analysis to evaluate the effectiveness of Intra-venous intralipid (IVI) in improving pregnancy rates in women with history of RIF using.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL for any randomized trials evaluating the use of IVI at the time of embryo transfer in women undergoing assisted conception until September 2020. We extracted data in duplicate and assessed risk of bias using the Cochrane Risk of Bias tools. We meta-analyzed data using a random effect model.

RESULTS

We included five randomized trials reporting on 843 women with an overall moderate risk of bias. All trials used 20% IVI solution at the time of embryo transfer compared to normal saline infusion or no intervention (routine care). The IVI group had a higher chance of clinical pregnancy (172 vs 119, risk ratio [RR] 1.55, 95% confidence interval [CI] 1.16-2.07, I² 44.2%) and live birth (132 vs 73, RR 1.83, 95% CI 1.42-2.35, I² 0%) post treatment compared to no intervention. Our findings are limited by the small sample size and the variations in treatment protocols and population characteristics.

CONCLUSION

There is limited evidence to support the use of IVI at the time of embryo transfer in women with the history of RIF. More research is needed before adopting it in clinical practice.

Exometabolomic Analysis of Decidualizing Human Endometrial Stromal and Perivascular Cells

Differentiation of endometrial fibroblasts into specialized decidual cells controls embryo implantation and transforms the cycling endometrium into a semi-permanent, immune-protective matrix that accommodates the placenta throughout pregnancy. This process starts during the midluteal phase of the menstrual cycle with decidual transformation of perivascular cells (PVC) surrounding the terminal spiral arterioles and endometrial stromal cells (EnSC) underlying the luminal epithelium. Decidualization involves extensive cellular reprogramming and acquisition of a secretory phenotype, essential for coordinated placental trophoblast invasion. Secreted metabolites are an emerging class of signaling molecules, collectively known as the exometabolome. Here, we used liquid chromatography-mass spectrometry to characterize and analyze time-resolved changes in metabolite secretion (exometabolome) of primary PVC and EnSC decidualized over 8 days. PVC were isolated using positive selection of the cell surface marker SUSD2. We identified 79 annotated metabolites differentially secreted upon decidualization, including prostaglandin, sphingolipid, and hyaluronic acid metabolites. Secreted metabolites encompassed 21 metabolic pathways, most prominently glycerolipid and pyrimidine metabolism. Although temporal exometabolome changes were comparable between decidualizing PVC and EnSC, 32 metabolites were differentially secreted across the decidualization time-course. Further, targeted metabolomics demonstrated significant differences in secretion of purine pathway metabolites between decidualized PVC and EnSC. Taken together, our findings indicate that the metabolic footprints generated by different decidual subpopulations encode spatiotemporal information that may be important for optimal embryo implantation.

Recurrent pregnancy loss

Recurrent pregnancy loss is a distressing pregnancy disorder experienced by ~2.5% of women trying to conceive. Recurrent pregnancy loss is defined as the failure of two or more clinically recognized pregnancies before 20-24 weeks of gestation and includes embryonic and fetal losses. The diagnosis of an early pregnancy loss is relatively straightforward, although progress in predicting and preventing recurrent pregnancy loss has been hampered by a lack of standardized definitions, the uncertainties surrounding the pathogenesis and the highly variable clinical presentation. The prognosis for couples with recurrent pregnancy loss is generally good, although the likelihood of a successful pregnancy depends on maternal age and the number of previous losses. Recurrent pregnancy loss can be caused by chromosomal errors, anatomical uterine defects, autoimmune disorders and endometrial dysfunction. Available treatments target the putative risk factors of pregnancy loss, although the effectiveness of many medical interventions is controversial. Regardless of the underlying aetiology, couples require accurate information on their chances of having a baby and appropriate support should be offered to reduce the psychological burden associated with multiple miscarriages. Future research must investigate the pathogenesis of recurrent pregnancy loss and evaluate novel diagnostic tests and treatments in adequately powered clinical trials.