Endometrial receptivity and pregnancy outcome

The effects of GnRH analogues on endometrial receptivity: a comprehensive study

PURPOSE

Endometrial receptivity is a critical determinant of successful embryo implantation and pregnancy. Gonadotropin-releasing hormone (GnRH) analogues are widely used in in vitro fertilization (IVF) but their effects on endometrial receptivity remain incompletely understood. This study aims to investigate the impact of GnRH analogues on endometrial receptivity through various in vitro models.

METHODS

Endometrial samples were collected across various stages of the menstrual cycle. The expression of the gonadotropin-releasing hormone receptor (GnRHR) was analyzed and quantified. A 3D endometrial model was constructed, and effects of GnRH analogues on trophoblast adhesion, as well as on the expression of markers related to endometrial receptivity, were assessed.

RESULTS

The results indicate that GnRHR expression is higher in epithelium in the secretory phase. However, no significant difference in the adhesion of trophoblast cell spheres to endometrial cells across different GnRH analogue concentrations was observed. GnRH analogues did not affect gene mRNAs expressions or protein levels either. Proteomic analysis revealed a downregulation of ITGAE in the antagonist regimen and an upregulation of FAAH2 in the agonist regimen.

CONCLUSIONS

This study suggests that GnRH analogues at different physiological concentrations used in IVF protocols do not significantly impact primary markers of endometrial receptivity. However, the use of antagonist may have an adverse effect on endometrial receptivity. Further research is required to elucidate indirect mechanisms by which GnRH analogues might affect endometrial receptivity and IVF outcomes.

Maternal Tryptophan Supplementation Enhances Sow Reproductive Performance by Influencing Hormones, Tryptophan Metabolism, and Gut Microbiome

BACKGROUND

Enhancing the early embryo survival rate is important for increasing sow reproductive efficiency. Whether and how tryptophan influences early embryo survival and pregnancy outcomes in sows remains unknown.

OBJECTIVES

The objective of this study was to investigate the effects of dietary tryptophan supplementation on the reproductive performance of sows.

METHODS

A total of 128 multiparous Large White × Landrace sows were randomly assigned to 4 groups including the control group (dietary tryptophan concentration was 0.18% from weaning to estrus and 0.10% from day 1 to day 28 of pregnancy) or the low, medium, and high dose of tryptophan supplementation groups (dietary tryptophan levels were 0.27%, 0.36%, and 0.45% from weaning to estrus and 0.15%, 0.20%, and 0.25% from day 1 to day 28 of pregnancy). Primary porcine granulosa cells were isolated from porcine ovaries and treated with selected tryptophan metabolites to assess hormone levels in the cell supernatant.

RESULTS

Compared with the control group, the dietary high levels of tryptophan group increased the litter weight (P < 0.05) and showed an increasing trend in the born alive per litter (P = 0.06). Serum concentration of progesterone and estradiol and levels of tryptophan, kynurenine, xanthurenic acid, 2-aminobenzoic acid, and indoleamine 2,3-dioxygenase on day 28 of pregnancy were increased in the high concentration of tryptophan group (P < 0.05). In vitro experiments using primary porcine granulosa cell culture showed that tryptophan and 2-aminobenzoic acid increased progesterone and estradiol levels in the cell supernatant (P < 0.05). Dietary tryptophan supplementation increased the abundances of fecal beneficial bacteria such as Hydrogenoanaerobacterium and Lachnospiraceae in sows (P < 0.05).

CONCLUSIONS

Dietary tryptophan supplementation may enhance the pregnancy outcome of sows through the increase of tryptophan metabolites to strengthen steroid hormone secretion and the abundance of beneficial microbes.

A Comprehensive Comparison of PICSI and ICSI Techniques Through a Triple-Blinded Trial: Effects on Embryo Quality, Cumulative Pregnancy Rate, and Live Birth Rate

Background: Sperm selection is critical in assisted reproduction, typically relying on swim-up and centrifugation density gradients. New methods, such as PICSI (physiological intracytoplasmic sperm selection), aim to enhance outcomes by selecting mature sperm based on hyaluronic acid (HA) binding and have generated interest due to their potential impact on the clinical outcomes of patients who undergo assisted reproductive treatments. Methods: A single-center, prospective, and triple-blinded study was conducted with 277 couples in the egg donation program. The oocytes of each recipient patient were randomly microinjected using the ICSI or PICSI technique and maintained in culture in time-lapse incubators until blastocyst formation. Biological and clinical outcomes were analyzed, including fertilization and blastocyst formation rates, embryo morphokinetics, pregnancy, miscarriage, and live birth rates, and artificial intelligence-assigned embryo quality scores. Results: Clinical outcomes were comparable between the two groups, but a higher pregnancy rate was observed in the PICSI group than in the ICSI group (74.04% vs. 70.87%). Although blastocyst formation rates were similar on both day 5 (D5) and day 6 of development, the proportion of good-quality embryos on D5 was higher in the PICSI group (68.27%) than in the ICSI group (63.47%) (p > 0.05). Finally, the cumulative pregnancy rate was significantly higher in the experimental group than in the control group (88% vs. 72%) after four embryo transfers (p < 0.05). Conclusions: Utilizing HA to perform sperm selection during ICSI procedures does not increase live birth rates. However, it may enhance the quality of the selected sperm. This could be beneficial for patients in egg donation programs, particularly for those who have experienced repeated pregnancy loss.

Identification of Differentially Expressed mRNAs and lncRNAs Contributes to Elucidation of Underlying Pathogenesis and Therapeutic Strategy of Recurrent Implantation Failure

Recurrent implantation failure (RIF) is a complex and poorly understood clinical disorder characterized by failure to conceive after repeated embryo transfers. Endometrial receptivity (ER) is a prerequisite for implantation, and ER disorders are associated with RIF. However, little is known regarding the molecular mechanisms underlying ER in RIF. In the present study, RNA sequencing data from the mid-secretory endometrium of patients with and without RIF were analyzed to explore the potential long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) involved in RIF. The analysis revealed 213 and 1485 differentially expressed mRNAs and lncRNAs, respectively (fold change ≥ 2 and p < 0.05). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses indicated that these genes were mostly involved in processes related to immunity or inflammation. 5 key genes (TTR, ALB, TF, AFP, and CFTR) and a key module including 14 hub genes (AFP, ALB, APOA1, APOA2, APOB, APOH, FABP1, FGA, FGG, GC, ITIH2, SERPIND1, TF and TTR) were identified in the protein-protein interaction (PPI) network. The 5 key genes were used to further explore the lncRNA-miRNA-mRNA regulatory network. Finally, the drug ML-193 based on the 14 hub genes was identifed through the CMap. After ML-193 treatment, endometrial cell proliferation was increased, the hub genes were mostly down-regulated, and the ER marker HOXA10 was up-regulated. These results offer insights into the regulatory mechanisms of lncRNAs and mRNAs and suggest ML-193 as a therapeutic agent for RIF by enhancing ER.

Fresh Versus Frozen Embryo Transfer in Women with Repeated Implantation Failure

Background

To compare the outcomes of fresh embryo transfer (ET) versus frozen ET (FET) in women with recurrent implantation failure (RIF).

Materials and Methods

This retrospective cohort study was performed at Yazd Reproductive Sciences Institute. A total of 498 cycles, including 418 FET cycles and 80 fresh cycles, from women with RIF were reviewed between February 2020 and February 2023. The chemical and clinical pregnancy rates and live birth rate were compared.

Results

FET cycles demonstrated significantly higher rates of both chemical (29.7% vs 13.8%, P = 0.002) and clinical pregnancy (20.6% vs 10.0%, P = 0.027) compared to fresh ET cycles. The live birth rate in the frozen transfer group was higher compared to the fresh transfer group, but the difference was not statistically significant (8.7% vs 4.9%, P value = 0.127).

Conclusions

Our findings showed that FET cycles may be associated with improved pregnancy rates in women with RIF.

The Role of Hypoxia-Inducible Factor-1α (HIF-1α) in the Progression of Ovarian Cancer: Perspectives on Female Infertility

Hypoxia-Inducible Factor-1α (HIF-1α) is crucial in the progression of ovarian cancer, especially in influencing its tumor microenvironment and promoting pathogenic pathways that worsen female infertility. In hypoxic settings, HIF-1α is stabilized and activates the transcription of genes associated with angiogenesis, metabolic reprogramming, epithelial-to-mesenchymal transition, and therapeutic resistance. Angiogenesis and glycolytic reprogramming mediated by HIF-1 tumor proliferation, survival, and metastasis. Its dysfunction concurrently impairs ovarian homeostasis, undermining follicular growth, hormone synthesis, and the ovarian vascular network, consequently contributing to infertility. Moreover, HIF-1α induces persistent inflammation and oxidative stress, promoting an environment damaging to reproductive health. Due to its dual function in ovarian cancer growth and infertility, HIF-1α is a potential therapeutic target. Strategies including small molecule inhibitors and nanoparticle-mediated delivery of drugs possess the potential to reduce HIF-1α activity, hence reducing cancer progression while protecting fertility. This review seeks to clarify the molecular basis of HIF-1α in ovarian cancer and its effects on female infertility, providing insights into novel treatment approaches that target both controlling the disease and preserving fertility.

METTL14-mediated m6A modification regulates endometrial receptivity by inhibiting SLC39A14

Endometrial receptivity is a complex process that prepares the endometrium for embryo implantation. Inadequate endometrial receptivity is one cause of implantation failure. This study aimed to explore the impact of METTL14-mediated m6A modification of SLC39A14 on endometrial stromal cells (ESCs). ESCs were transfected and subjected to CCK-8 viability assay, EdU proliferation assay, and flow cytometry cell cycle and apoptosis analyses. Autophagy-related proteins LC3, p62, and Beclin-1 were detected through western blotting. RIP was used to detect the interaction between METTL14 protein and SLC39A14 mRNA. Me-RIP was used to measure the m6A level of SLC39A14. Actinomycin D was used to assess the stability of SLC39A14 mRNA. METTL14 overexpression or SLC39A14 knockdown enhanced viability, promoted proliferation and cell cycle progression, restrained apoptosis, reduced LC3II/LC3I and Beclin-1 levels, and increased p62 expression in ESCs. METTL14 bound to SLC39A14 mRNA and increased SLC39A14 m6A modification, reducing SLC39A14 mRNA stability and SLC39A14 protein expression. SLC39A14 overexpression eliminated the effect of METTL14 overexpression on ESCs. In conclusion, METTL14 promotes proliferation and inhibits apoptosis and autophagy activation in ESCs by inhibiting SLC39A14.

Obesity and recurrent spontaneous abortion: the crucial role of weight management in pregnancy

Recurrent spontaneous abortion (RSA), characterized by the loss of two or more pregnancies, impacts approximately 1-2% of couples and poses a significant challenge for individuals of childbearing age. The precise mechanisms underlying RSA remain incompletely understood. Concurrently, the global prevalence of obesity is on the rise, with obesity being closely associated with female reproductive disorders and infertility. This study initially examines the pathways through which obesity contributes to RSA, encompassing factors such as embryonic euploid miscarriage, endometrial development, immune function, among others. Furthermore, adipokines and the fat mass and obesity-related (FTO) are identified as potential contributors to RSA. The study also explores the enhancement of pregnancy outcomes through various weight management strategies, with a particular focus on the roles of dietary interventions, physical activity, and weight control during pregnancy. Obesity is closely related to RSA in multiple aspects. Additional clinical prospective and experimental studies are required to explore its precise pathogenesis. Through this review, we aim to provide strategies for improvement and treatment approaches for RSA related to obesity. Through this review, we suggest potential clinical management strategies and research avenues aimed at offering enhancements and therapeutic insights for miscarriages linked to obesity and its associated risk factors.

Investigating the role of oviductal mucosa-endometrial co-culture in modulating factors relevant to embryo implantation

Background

Intrauterine adhesions (IUAs) are a significant clinical challenge, affecting reproductive health and leading to infertility or recurrent pregnancy loss. Understanding the molecular mechanisms underlying IUA prevention is crucial for developing effective treatment strategies.

Objective

To investigate the interaction between oviductal mucosal cells and endometrial cells and their effects on the expression of key molecules involved in embryo implantation, specifically leukemia inhibitory factor (LIF), avβ3, estrogen receptor (ER), and progesterone receptor (PR).

Methods

Tubal mucosa and endometrium specimens were collected from 22 patients undergoing surgical interventions. Cells were cultured alone and co-cultured at ratios of 1:1, 1:0.5, and 1:0.1. LIF, avβ3, ER, and PR expression levels were measured using real-time fluorescence quantitative polymerase chain reaction and enzyme-linked immunosorbent assay.

Results

Our results demonstrated that LIF expression was significantly augmented in co-culture conditions, particularly in the 1:1 ratio, compared to oviductal mucosa monoculture (P < 0.05). Although LIF expression was also elevated in 1:0.5 and 1:0.1 co-culture ratios, these increases were not statistically significant (P > 0.05). For avβ3, increased expression was observed in the 1:1 co-culture group (P < 0.05), but no significant differences were detected in 1:0.5 and 1:0.1 co-culture groups. ER expression showed a downward trend in co-culture, but without statistical significance (P > 0.05), and PR expression remained stable across all groups.

Conclusion

Co-culture modulates key molecules involved in embryo implantation, particularly LIF and avβ3. These findings highlight the potential roles of LIF and avβ3 in IUA prevention strategies and provide important insights for future clinical interventions. Tubal mucosal cells can not only grow in the endometrial cell microenvironment, but also the tolerance of tubal mucosal cells can be improved when they are co-cultured.

MicroRNAs, endometrial receptivity and molecular pathways

MicroRNAs (miRNAs) are a type of specific molecules that control the activities of the uterus, such as the process of cellular maturing and evolution. A lot of substances like growth factors, cytokines, and transcription factors play a role in embryo-endometrial interaction. MiRNAs could regulate various these factors by attaching to the 3' UTR of their mRNAs. Moreover, current research show that miRNAs participate in formation of blood vessels in endometrium (miR-206, miR-17-5p, miR-16-5p…), decidualization (miR-154, miR-181, miR-9…), epithelial-mesenchymal transition (miR-30a-3p), immune response (miR-888, miR-376a, miR-300…) embryo attachment (miR-145, miR-27a,451…) and pinopod formation (mir-223-3p, mir-449a, mir-200c). In this study, the focus is on the role of miRNAs in managing the uterus' receptivity to an embryo and its ability to facilitate attachment. More specifically, we are exploring the mechanisms by which miRNAs regulate the presence of specific molecules involved in this crucial physiological process.

Irisin in Reproduction: Its Roles and Therapeutic Potential in Male and Female Fertility Disorders

The current study focused on identifying the potential of irisin in mammalian reproduction. The established role of irisin, a proteolytic product of FNDC5, in adipose tissue browning, energy metabolism, and thermogenesis suggests its role in reproductive health, often disturbed by metabolic imbalances. Various studies on mice demonstrated irisin's role in improving spermatogenesis, sperm count, and testosterone levels by influencing the hypothalamus-pituitary-gonadal axis. Moreover, in females, there is a fluctuation in levels of irisin during critical reproductive stages, including menstrual cycles, puberty, and pregnancy. Conditions like pregnancy complications, precocious puberty, and polycystic ovary syndrome (PCOS) are found to have an association with abnormal irisin levels. The potential role of irisin in endometrial receptivity and preventing endometritis is also discussed in this review. Overall, the influence of irisin on female and male reproduction is evident from various studies. However, further research is needed to elucidate irisin mechanism in reproduction and its potential as a therapeutic or diagnostic tool for reproductive dysfunctions and infertility.

Monoamine oxidases activity maintains endometrial monoamine homeostasis and participates in embryo implantation and development

BACKGROUND

Monoamine oxidases (MAOs) is an enzyme that catalyzes the deamination of monoamines. The current research on this enzyme is focused on its role in neuropsychiatric, neurodevelopmental, and neurodegenerative diseases. Indeed, MAOs with two isoforms, namely, A and B, are located on the outer mitochondrial membrane and are widely distributed in the central nervous system and peripheral tissues. Several reports have described periodic changes in the levels of this enzyme in the human endometrial tissue.

RESULTS

The novel role of MAOs in endometrial receptivity establishment and embryonic development by maintaining monoamine homeostasis was investigated in this study. MAOs activity was observed to be enhanced during the first trimester in both humans and mice under normal conditions. However, under pathological conditions, MAOs activity was reduced and was linked to early pregnancy failure. During the secretory phase, the endometrial stromal cells differentiated into decidual cells with a stronger metabolism of monoamines by MAOs. Excessive monoamine levels cause monoamine imbalance in decidual cells, which results in the activation of the AKT signal, decreased FOXO1 expression, and decidual dysfunction.

CONCLUSIONS

The findings suggest that endometrial receptivity depends on the maintenance of monoamine homeostasis via MAOs activity and that this enzyme participates in embryo implantation and development.

The Molecular Link between Obesity and the Endometrial Environment: A Starting Point for Female Infertility

Female infertility constitutes a growing health problem in developing countries and could be associated with several possible causes including reproductive disorders, congenital malformations, infections and hormonal dysfunction. Nonetheless, a series of additional factors can also negatively impact female fertility and are represented by chronic exposure to environmental pollutants, stress, unhealthy lifestyle choices such as cigarette smoking and, among others, obesity. Excess weight is associated with several chronic diseases, and growing evidence demonstrates that it can compromise reproductive physiology due to its influence on endometrial gene expression and receptivity. Thus, the current review of the literature mainly focused on how obesity can impair uterine receptivity, mostly from a molecular point of view throughout the window of implantation (WOI) period at an endometrial level. It was also highlighted that an obesity-related increase in adipose tissue may lead to a modulation in the expression of multiple pathways, which could cause a hostile endometrial environment with a consequent negative impact on the uterine receptivity and the establishment of pregnancy. Thanks to the use of the endometrial receptivity assay (ERA), a specific microarray that studies the expression of a series of genes, it is now possible to evaluate the endometrial status of patients with infertility problems in a more detailed manner. Moreover, female fertility and endometrial receptivity could be affected by endometriosis, a chronic benign gynecological disease, whose cause-and-effect relationship to obesity is still uncertain. Therefore, further investigations would be required to better elucidate these mechanisms that govern embryo implantation and could be potentially useful for the generation of new strategies to overcome implantation failure and improve the pregnancy rates in obese women.

IFNT-induced IRF1 enhances bovine endometrial receptivity by transactivating LIFR

Interferon-τ (IFN-τ) participates in the establishment of endometrial receptivity in ruminants. However, the precise mechanisms by which IFN-τ establishes bovine endometrial receptivity remain largely unknown. Interferon regulatory factor 1 (IRF1) is a classical interferon-stimulated gene (ISG) induced by type I interferon, including IFN-τ. Leukemia inhibitory factor receptor (LIFR) is a transmembrane receptor for leukemia inhibitory factor (LIF), which is a key factor in regulating embryo implantation in mammals. This study aimed to investigate the roles of IRF1 and LIFR in the regulation of bovine endometrial receptivity by IFN-τ. In vivo, we found IRF1 and LIFR were upregulated in the bovine endometrial luminal epithelium on Day 18 of pregnancy compared to Day 18 of the estrous cycle. In vitro, IFN-τ could upregulate IRF1, LIFR, and endometrial receptivity markers (LIF, HOXA10, ITGAV, and ITGB3) expression, downregulate E-cadherin expression and reduce the quantity of microvilli of bovine endometrial epithelial cells (bEECs). Overexpression of IRF1 had similar effects to IFN-τ on endometrial receptivity, and interference of LIFR could block these effects, suggesting the positive effects of IRF1 on endometrial receptivity were mediated by LIFR. Dual luciferase reporter assay verified that IRF1 could transactivate LIFR transcription by binding to its promoter. In conclusion, IFN-τ can induce IRF1 expression in bovine endometrial epithelial cells, and IRF1 upregulates LIFR expression by binding to LIFR promoter, contributing to the enhancement of bovine endometrial receptivity.

Analysis of predictors of clinical pregnancy and live birth in patients with RIF treated with IVF-ET technology: a cohort study based on a propensity score approach

Objective

To investigate the predictors of clinical pregnancy and live birth rate in patients with recurrent embryo implantation failure (RIF) treated with in vitro fertilization-embryo transfer (IVF-ET) technique.

Method

This retrospective cohort study was conducted in Jinjiang District Maternal and Child Health Hospital, Chengdu City, Sichuan Province, China. Patients were recruited who were enrolled at this hospital between November 1, 2019 and August 31, 2022, and who met the following criteria: a frozen embryo transfer (FET) at day 5 or 6 blastocyst stage was performed and the number of transfer cycles was not less than two. We collected information on age, height, weight, number of embryo transfer cycles, and information related to clinical outcomes. We used the group of patients who underwent ERA testing as the study group and those who underwent FET only as the control group, and matched baseline characteristics between the two groups by propensity score to make them comparable. We compared the differences in clinical outcomes between the two groups and further explored predictors of pregnancy and live birth using survival analysis and COX regression modeling.

Results

The success rate of clinical pregnancy in RIF patients was 50.74% and the live birth rate was 33.09%. Patients in the FET group were less likely to achieve clinical pregnancy compared to the ERA group (HR = 0.788, 95%CI 0.593-0.978, p < 0.05). Patients with >3 previous implantation failures had a lower probability of achieving a clinical pregnancy (HR = 0.058, 95%CI 0.026-0.128, p < 0.05) and a lower likelihood of a live birth (HR = 0.055, 95%CI 0.019-0.160, p < 0.05), compared to patients with ≤3 previous implantation failures. Patients who had two embryos transferred were more likely to achieve a clinical pregnancy (HR = 1.357, 95%CI 1.079-1.889, p < 0.05) and a higher likelihood of a live birth (HR = 1.845, 95%CI 1.170-2.910, p < 0.05) than patients who had a single embryo transfer. Patients with concomitant high-quality embryo transfer were more likely to achieve a clinical pregnancy compared to those without high-quality embryo transfer (HR = 1.917, 95%CI 1.225-1.863, p < 0.05).

Conclusion

Not receiving an ERA, having >3 previous implantation failures, using single embryo transfer and not transferring quality embryos are predictors for clinical pregnancy in patients with RIF. Having>3 previous implantation failures and using single embryo transfer were predictors for live birth in patients with RIF.

Meta-analysis of trigger timing in normal responders undergoing GnRH antagonist ovarian hyperstimulation protocol

IMPORTANCE

The first meta-analysis focused only on gonadotropin-releasing hormone (GnRH) antagonists, which helped determine the effect of delay trigger on pregnancy outcomes.

OBJECTIVE

To evaluate the impact of delay trigger compared with standard trigger in normal responders undergoing GnRH antagonist protocol in improving pregnancy outcomes.

METHODS

Studies published before April 2023 in PubMed, EMBASE, Cochrane Library, Web of Science, CNKI, Wanfang, VIP and CBM databases were searched. Randomized controlled trials (RCTs) and cohort studies conducted in normal responders reporting the efficacy of delay trigger using GnRH antagonist protocol were included. Data were combined to calculate mean differences (MD) for continuous variables and odd ratios (OR) for categorical variables with their corresponding 95% confidence intervals (CIs). Heterogeneity was assessed using Cochran's Q test.

RESULTS

Endpoints, including clinical pregnancy rate (CPR), live birth rate (LBR), the number of oocyte retrievals and embryos, and fertilization rate, were analyzed. Six (6) clinical studies (4 RCTs and 2 cohort studies) with 1,360 subjects were included. The pooled results showed that the number of oocyte retrievals (MD: 1.20, 95% CI: 1.10, 1.30, p < 0.01), fertilization rate (MD: 0.64, 95% CI: 0.29, 0.99, p < 0.01) and days of stimulation (MD: 0.95; 95% CI: 0.54, 1.37; p < 0.01) in the delay trigger group was significantly higher than that in the standard trigger group. However, there was no significant difference in the number of embryos (MD: 0.19, 95% CI: -0.29, 0.67, p = 0.44), CPR (OR: 1.12; 95% CI: 0.72, 1.75; p = 0.062), and LBR (OR: 1.23; 95% CI: 0.90, 1.66; p = 0.19) between the two trigger groups.

CONCLUSION

Delaying trigger time in GnRH antagonist protocol increased the number of oocytes retrieved but not the number of embryos. Furthermore, delay trigger shot was not associated with a clinical benefit towards CPR and LBR in women who underwent fresh embryo transfer cycles.

TRIAL REGISTRATION

The International Prospective Register of Systematic Reviews (PROSPERO), registration number: CRD42023413217.

The lncRNA LINC00339-encoded peptide promotes trophoblast adhesion to endometrial cells via MAPK and PI3K-Akt signaling pathways

BACKGROUND

Endometrial receptivity (ER), a pivotal event for successful embryo implantation, refers to the capacity of endometrium to allow the adhesion of the trophectoderm of the blastocyst to endometrial cells. In this paper, we set to elucidate whether the peptides encoded by lncRNAs could influence trophoblast cells' adhesion to endometrial cells.

METHODS

WGCNA construction and bioinformatics were used to find out the ER-related lncRNAs with coding potential. Protein analysis was done by immunoblotting and immunofluorescence (IF) microscopy. CCK-8 and Calcein-AM/PI double staining assays were employed to evaluate cell viability. The effect of the peptide on trophoblast spheroids' adhesion to endometrial cells was evaluated. The RNA sequencing (RNA-seq) analysis was applied to identify downstream molecular processes.

RESULTS

lncRNA LINC00339 was found to be related to ER development and it had been predicted to have protein-coding potential. LINC00339 had high occupancy of ribosomes and was confirmed to encode a 49-aa peptide (named LINC00339-205-49aa). LINC00339-205-49aa could promote the attachment of JAR trophoblast spheroids to Ishikawa endometrial cells in vitro. LINC00339-205-49aa also upregulated the expression of E-cadherin in Ishikawa cells. Mechanistically, MAPK and PI3K-Akt signaling pathways were involved in the modulation of LINC00339-205-49aa, which were activated by LINC00339-205-49aa in Ishikawa cells.

CONCLUSION

These data demonstrate that a previously uncharacterized peptide encoded by lncRNA LINC00339 has the ability to enhance JAR trophoblast spheroids' adhesion to Ishikawa endometrial cells, highlighting a new opportunity for the development of drugs to improve ER.

Pregnancies through oocyte donation. A mini review of pathways involved in placental dysfunction

Pregnancies resulting from assisted reproductive techniques (ART) are increasingly prevalent worldwide. While most pregnancies conceived through in-vitro fertilization (IVF) progress without complications, mounting evidence suggests that these pregnancies are at a heightened risk of adverse perinatal outcomes. Specifically, IVF pregnancies involving oocyte donation have garnered attention due to numerous reports indicating an elevated risk profile for pregnancy-related complications within this subgroup of patients. The precise mechanisms contributing to this increased risk of complications remain incompletely understood. Nonetheless, it is likely that they are mediated by an abnormal immune response at the fetal-maternal interface. Additionally, these outcomes may be influenced by baseline patient characteristics, such as the etiology of infertility, absence of corpus luteum, and variations in endometrial preparation protocols, among other factors. This review aims to succinctly summarize the most widely accepted mechanisms that potentially contribute to the onset of placental dysfunction in pregnancies conceived through oocyte donation.

Ligustilide enhances pregnancy outcomes via improvement of endometrial receptivity and promotion of endometrial angiogenesis in rats

Ligustilide (LIG) is the main active ingredient of Angelica sinensis (Oliv.) Diels, which could promote focal angiogenesis to exert neuroprotection. However, there was no report that verified the exact effects of LIG on endometrial angiogenesis and the pregnancy outcomes. To explore the effects of LIG on low endometrial receptivity (LER) and angiogenesis, pregnancy rats were assigned into Control (saline treatment), LER (hydroxyurea-adrenaline treatment), LIG 20 mg/kg and LIG 40 mg/kg groups. Hematoxylin and eosin (H&E) staining was performed to evaluate endometrial morphology. Quantitative real-time PCR, immunofluorescence staining, western blot and immunohistochemistry staining were employed to assess the expression of endometrial receptivity factors and angiogenesis-related gene/protein, respectively. RNA sequencing was used to analyze the effects of LIG on LER caused by Kidney deficiency and blood stasis. We found that endometrial thickness and the implanted embryo number were substantially reduced in the hydroxyurea-adrenaline-treated pregnancy rats. At the same time, the gene and protein expressions of ERα, LIF, VEGFA and CD31 in the endometrium were markedly reduced, while the expressions of MUC1, E-cadherin were increased in the LER group. Administration of LIG raised the endometrial thickness and implanted embryos, as well as reversed the expressions of these factors. Collectively, our findings revealed that LIG could facilitate embryo implantation via recovery of the endometrium receptivity and promotion of endometrial angiogenesis.

Priming of macrophage by glycosphingolipids from extracellular vesicles facilitates immune tolerance for embryo-maternal crosstalk

Glycosphingolipids (GSLs) display diverse functions during embryonic development. Here, we examined the GSL profiles of extracellular vesicles (EVs) secreted from human embryonic stem cells (hESCs) and investigated their functions in priming macrophages to enhance immune tolerance of embryo implantation. When peripheral blood mononuclear cells were incubated with ESC-secreted EVs, globo-series GSLs (GHCer, SSEA3Cer, and SSEA4Cer) were transferred via EVs into monocytes/macrophages. Incubation of monocytes during their differentiation into macrophages with either EVs or synthetic globo-series GSLs induced macrophages to exhibit phenotypic features that imitate immune receptivity, i.e., macrophage polarization, augmented phagocytic activity, suppression of T cell proliferation, and the increased trophoblast invasion. It was also demonstrated that decidual macrophages in first-trimester tissues expressed globo-series GSLs. These findings highlight the role of globo-series GSLs via transfer from EVs in priming macrophages to display decidual macrophage phenotypes, which may facilitate healthy pregnancy.

Current knowledge on the role of extracellular vesicles in endometrial receptivity

Endometrial receptivity has been widely understood as the capacity of the endometrium to receive implantable embryos. The establishment of endometrial receptivity involves multiple biological processes including decidualization, tissue remodeling, angiogenesis, immune regulation, and oxidative metabolism. Extracellular vesicles (EVs) are lipid-bilayer-membrane nanosized vesicles mediating cell-to-cell communication. Recently, EVs and their cargo have been proven as functional factors in the establishment of endometrial receptivity. In this review, we comprehensively summarized the alteration of endometrium/embryo-derived EVs during the receptive phase and retrospected the current findings which revealed the pivotal role and potential mechanism of EVs to promote successful implantation. Furthermore, we highlight the potentiality and limitations of EVs being translated into clinical applications such as biomarkers of endometrial receptivity or reproductive therapeutic mediators, and point out the direction for further research.

Caffeic Acid Phenethyl Ester Reduces the Adverse Effects of Nicotine on the Endometrium

Background

Tobacco smoke contains various toxins that negatively affect the human reproductive system. Caffeic acid phenethyl ester (CAPE), a potent antioxidant, has protective effects on the reproductive system against oxygen-free radicals, methotrexate, and pesticides. Herein, the effect of CAPE on some key markers of endometrial receptivity has been evaluated.

Methods

A cross-sectional study was conducted during 2018-2019 in the Department of Clinical Biochemistry, School of Medicine, Fasa University of Medical Sciences (Fasa, Iran). Primary endometrial cells were divided into five groups, namely control, nicotine, CAPE, vehicle, and nicotine+CAPE. Real-time polymerase chain reaction (PCR) and methylation-specific PCR were performed to evaluate gene expressions and methylation, respectively. Appropriate doses of CAPE and nicotine were determined using the MTT assay. Data were analyzed using SPSS software (version 16.0) with a one-way analysis of variance. P<0.01 was considered statistically significant. The fold change was calculated using the 2-∆ΔCT method.

Results

Treatment of cells with nicotine significantly reduced the expression of C-X-C motif chemokine ligand 12 (CXCL12), fibroblast growth factor 2 (FGF2), and vascular endothelial growth factor A (VEGF-A) genes (P<0.0001). However, the expression levels increased significantly when treated with nicotine+CAPE (P<0.0001). Despite the reduced CXCL12 gene expression in cells treated with nicotine, CXCL12 was unmethylated in all study groups, indicating that the methylation status of the CXCL12 gene was not affected by nicotine or CAPE.

Conclusion

CAPE can be a suitable agent to protect female smokers from the harmful effects of nicotine. This manuscript is available as a preprint on the Research Gate website.

A novel therapeutic approach for endometriosis using adipose-derived stem cell-derived conditioned medium- A new hope for endometriotic patients in improving fertility

Introduction

Endometriosis is defined as the growth of endometrial glands and stromal cells in a heterotopic location with immune dysregulation. It usually leads to chronic pelvic pain and subfertility. Although various treatments are available, the recurrence rate remains high. Adipose tissue is an abundant source of multipotent mesenchymal adipose-derived stem cells (ADSCs). ADSCs display effects on not only tissue regeneration, but also immune regulation. Thus, the current study aims to test the effects of ADSCs on the growth of endometriosis.

Methods

ADSCs isolated from lipoaspiration-generated adipose tissue and their conditioned medium (ADSC-CM) were subjected to quality validation, including karyotyping as well as growth promotion and sterility tests for microbial contamination under Good Tissue Practice and Good Manufacturing Practice regulations. An autologous endometriosis mouse model was established by suturing endometrial tissue to peritoneal wall followed by treating with DMEM/F12 medium, ADSC-CM, ADSCs or ADSC-CM+ADSCs for 28 days. The area of endometriotic cysts and the degree of pelvic adhesion were measured. ICAM-1, VEGF and caspase 3 expression was assessed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry. Moreover, the mice were allowed to mate and deliver. The pregnancy outcomes were recorded. The ADSC-CM was subjected to proteomics analysis with further data mining with Ingenuity Pathway Analysis (IPA).

Results

Both ADSC-CM and ADSCs passed quality validation. ADSC-CM reduced the area of endometriotic cysts. The inhibition by ADSC-CM was obliterated by adding ADSCs. The presence of ADSCs with or without ADSC-CM increased the peritoneal adhesion. ADSC-CM inhibited ICAM-1 and VEGF mRNA and protein expression, whereas the addition of ADSCs not only did not inhibit by itself, but also blocked the inhibition by ADSC-CM. The resorption rate was reduced by ADSC-CM. The number of live birth/dam and the survival rate of pup at 1 week-old were both increased by ADSC-CM in mice with endometriosis. IPA demonstrated that PTX3 was potentially critical for the inhibition of endometriosis by ADSC-CM due to its anti-inflammatory and antiangiogenic properties as well as its importance in implantation.

Conclusion

ADSC-CM inhibited endometriosis development and improved pregnancy outcomes in mice. Potential translation to clinical treatment for human endometriosis is expected.

Impact of Endometrial Receptivity Analysis on Pregnancy Outcomes In Patients Undergoing Embryo Transfer: A Systematic Review and Meta-Analysis

To analyze the influence of endometrial receptivity analysis (ERA) on embryo transfer (ET) results in patients undergoing in vitro fertilization (IVF) treatment. PubMed, Embase, Cochrane Central Register of Controlled Trials, and BioMed Central databases were searched from inception up to December 2022 for studies comparing pregnancy outcomes in patients undergoing personalized embryo transfer (pET) by ERA versus standard ET. Data were pooled by meta-analysis using a random effects model. We identified twelve studies, including 14,224 patients. No differences were observed between patients undergoing ERA test and those not undergoing ERA test prior to ET in terms of live birth (OR 1.00, 95% CI 0.63-1.58, I2 = 92.7%), clinical pregnancy (OR 1.20, 95% CI 0.90-1.61, I2 = 86.5%), biochemical pregnancy (OR 0.83, 95% CI 0.46-1.49, I2 = 87%), positive pregnancy test (OR 0.99, 95% CI 0.80-1.22, I2 = 0%), miscarriage (OR 0.91, 95% CI 0.62-1.34, I2 = 67.1%), and implantation rate (OR 1.18, 95% CI 0.44-3.14, I2 = 93.2%). pET with ERA is not associated with any significant differences in pregnancy outcomes as compared to standard ET protocols. Therefore, the utility of ERA in patients undergoing IVF should be revisited.

Mechanism of human chorionic gonadotropin in endometrial receptivity via the miR-126-3p/PI3K/Akt/eNOS axis

Human chorionic gonadotropin (hCG) might affect endometrial receptivity, exerting integral roles in embryo implantation. This study explored the action of hCG in endometrial receptivity via the miR-126-3p/PIK3R2/PI3K/Akt/eNOS axis. The embryo implantation dysfunction (EID) mouse models were established by administrating mifepristone and human endometrial epithelial cells (EECs) were used for in vivo experiments, both followed by hCG treatment. Expression level of CD105 and protein levels of cadherin CD144 and CD146 in mice were determined by immunohistochemistry and Western blot. The levels of miR-126-3p and PIK3R2 mRNA and PIK3R2, p-PI3K p85 α, PI3K p110 α, p-Akt, Akt, p-eNOS, and eNOS protein levels were measured. Cell proliferation was evaluated by CCK-8 and EdU assays. The binding sites of miR-126-3p and PIK3R2 were predicted and verified. hCG-treated EECs were further transfected with miR-126-inhibitor for functional rescue experiments. hCG ameliorated endometrial receptivity in EID mice. Moreover, hCG promoted miR-126-3p and suppressed PIK3R2 in EID mice and EECs. miR-126-3p targeted PIK3R2. EEC proliferation was enhanced after hCG treatment but inhibited by miR-126-3p downregulation. Both in vivo and in vitro experiments validated that hCG activated the PI3K/Akt/eNOS pathway through the miR-126-3p/PIK3R2 axis. Collectively, hCG improves endometrial receptivity by activating the PI3K/Akt/eNOS pathway via regulating miR-126-3p/PIK3R2.

Expression profile of genes related to pregnancy maintenance in Dromedary Camel during the first trimester

So far, few signals involved in embryo-maternal dialogue have been identified in pregnant she-camel. Our objective was to investigate expression profiles of genes relevant to uterine extracellular matrix remodeling (ITGB4, SLCO2A1, FOS, and JUN), uterine tissue vascularization, and placental formation (VEGFA, PGF, and PDGFA), embryonic growth and development (IGF1 and PTEN), plus cell death of uterine tissue (BCL2) in early pregnant versus non-pregnant she-camels. Forty genital tracts (20 pregnant and 20 non-pregnant) and blood samples were collected from abattoirs. Total RNA was extracted from uterine tissues and qRT-PCR was conducted for candidate genes. Serum concentrations of progesterone (P4) and estradiol17-β (E2) were measured. Expression of ITGB4, FOS, and PGF genes increased (P < 0.001) in the right uterine horn of pregnant versus non-pregnant she-camels. Moreover, JUN, SLCO2A1, VEGFA, and PTEN mRNAs were up-regulated (P < 0.001) in various segments of uterine tissues in pregnant groups. The PDGFA transcript was over-expressed (P < 0.001) in both uterine horns of pregnant groups. Additionally, IGF1 was higher (P < 0.001) in the right horn and the uterine body of pregnant groups, and expression of BCL2 was increased (P < 0.001) in the pregnant uterine body. Moreover, serum concentrations of P4 were higher (P < 0.001) and E2 lower (P < 0.05) in pregnant she-camels. Taken together, the fine-tuning of genes related to implantation, matrix formation, vascularization, and placental formation is highly required for successful pregnancy in she-camels.

Acupuncture Improves Endometrial Angiogenesis by Activating PI3K/AKT Pathway in a Rat Model with PCOS

Background. Acupuncture, a treatment derived from traditional Chinese medicine, can effectively relieve the symptoms and improve pregnancy outcome in patients with polycystic ovary syndrome (PCOS); however, its mechanism remains unclear. This study aimed at investigating whether acupuncture could improve endometrial angiogenesis and thus endometrial receptivity via activating PI3K/AKT pathway in PCOS rats. Methods. We established a rat model with PCOS, which was induced by DHEA. Acupuncture was performed every other day for 15 days, and the PI3K inhibitor (LY294002) was intraperitoneal injected 30 mins before acupuncture treatment. Females rats were mated with male SPF SD rats in a ratio of 2 : 1 after treatment and sacrificed on the 5th day when the vaginal plug was identified. The number of implantation sites was observed, followed by ovarian and endometrial morphology detected with hematoxylin-eosin staining and a scanning electron microscope, estrous cycle detected with vaginal smear analysis, and sex hormones and angiogenesis-related PI3K/AKT gene/protein expression detected with enzyme-linked immunosorbent assay, western blotting, immune histochemistry, and quantitative real-time PCR. Results. Acupuncture notably improved implantation sites’ number, endometrial receptivity factors including endometrial morphology, pinopodes, HOX-10, and LIF protein expression, as well as angiogenesis and PI3K/AKT pathway factors such as VEGF, VEGFR2, Ang-1, PI3K, AKT, and P-AKT gene/protein expression and the level of eNOS and NO in the endometrium of rats with PCOS; PCOS-like symptoms were alleviated as well. The efficacy of acupuncture on a rat model with PCOS was counteracted by the combination with the PI3K inhibitor. Conclusion. Acupuncture improves endometrial angiogenesis by activating the PI3K/AKT pathway, thus promoting endometrial receptivity and the number of implantation sites in rats with PCOS.

The newly non-uniform endometrial echogenicity on transvaginal ultrasound do not impact in vitro fertilization and embryo transfer success: A retrospective cohort study

OBJECTIVE

To evaluate the effect of newly non-uniform endometrial echogenicity diagnosed by transvaginal ultrasound on the outcome of pregnancy in vitro fertilization-embryo transfer (IVF-ET) during controlled ovarian hyperstimulation (COH) by retrospective cohort analysis.

METHODS

A retrospective cohort study of a total of 604 patients with newly non-uniform endometrial echogenicity from January 2013 to June 2017, each woman was matched with three control subjects of similar age (±1 year), type of infertility (primary or secondary), the protocol used for COH, and the number of ET cycles in our unit. The patients in the study group and control group were matched according to the strict 1:3 matching principle. Baseline characteristics and pregnancy outcomes were compared.

RESULTS

There were no statistically significant difference in baseline characteristics, live birth rate, biochemical pregnancy rate, clinical pregnancy rate, clinical pregnancy miscarriage rate and ectopic pregnancy rate between the two groups. But there were significant statistical differences in past history of uterine cavity surgery between the two groups (35.26% VS 21.19%), especially in history of endometrial polyp surgery (94.84% VS 90.10%).

CONCLUSIONS

Our results demonstrate the newly diagnosed non-uniform endometrial echogenicity during controlled ovarian hyperstimulation does not affect the pregnancy outcome of in vitro fertilization-embryo transfer, and fresh embryo transfer can be continued.

An Update on the Progress of Endometrial Receptivity in Women with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a significant public health issue with diverse presentations, including reproductive, metabolic, and psychological disorders. Although problems with ovulation, metabolism, and hormonal imbalance can be pharmacologically improved, even the excellent quality of transferred embryos does not necessarily increase the pregnancy rate. Poor endometrial receptivity in women with PCOS perturbs endometrial decidualization and blastocyst implantation, increasing adverse pregnancy outcomes, such as miscarriage and poor embryonic development. The etiological and pathophysiological mechanisms involved in defective endometrial receptivity in women with PCOS have not been fully elucidated to date. Various contributing factors have been reported as primary causes of defective endometrial receptivity in women with PCOS, including metabolic alterations, inflammatory events, and some abnormally expressed endometrial molecular markers. However, few studies to date have investigated in depth the complex mechanisms underlying the compromised endometrial receptivity in women with PCOS. This article reviews recent reports mainly on metabolic alterations and some new endometrial molecular markers in order to collate the existing data and improve our understanding in this field. The aim was to discuss current novel insights on defective endometrial receptivity in women with PCOS in order to provide a theoretical basis for reducing adverse pregnancy outcomes and improving the live birth rate in PCOS.

Construction of circRNA-miRNA-mRNA network in the pathogenesis of recurrent implantation failure using integrated bioinformatics study

This research attempted to elucidate the molecular components are involved in the pathogenesis of recurrent implantation failure (RIF). We initially identified that 386 mRNAs, 144 miRNAs and 2548 circRNAs were differentially expressed (DE) in RIF and then investigated the genetic cause of the observed abnormal expression by constructing a circRNA‐miRNA‐mRNA network considering the competing endogenous RNA theory. We further analysed the upstream transcription factors and related kinases of DEmRNAs (DEMs) and demonstrated that SUZ12, AR, TP63, NANOG, and TCF3 were the top five TFs binding to these DEMs. Besides, protein‐protein interaction analysis disclosed that ACTB, CXCL10, PTGS2, CXCL12, GNG4, AGT, CXCL11, SST, PENK, and FOXM1 were the top 10 hub genes in the acquired network. Finally, we performed the functional enrichment analysis and found that arrhythmogenic right ventricular cardiomyopathy (ARVC), hypertrophic cardiomyopathy (HCM), pathways in cancer, TNF signalling pathway and steroid hormone biosynthesis were the potentially disrupted pathways in RIF patients. Optimistically, our findings may deepen our apprehensions about the underlying molecular and biological causes of RIF and provide vital clues for future laboratory and clinical experiments that will ultimately bring a better outcome for patients with RIF.

Deficiency of Sirtuin 1 Impedes Endometrial Decidualization in Recurrent Implantation Failure Patients

Decidualization is driven by differentiation of human endometrial stromal cells (ESCs), and is a prerequisite for successful implantation and establishment of pregnancy. The critical role of impaired decidualization in women suffered recurrent implantation failure (RIF) has been established, while the underlying mechanism is poorly understood. In the present study, we verified the essential role of Sirtuin1 (SIRT1) in regulating differentiation and maintaining reactive oxygen species (ROS) homeostasis of human ESCs during decidualization. The abundance of SIRT1 was decreased in RIF patients both in the endometria during window of implantation phase and in the decidualized ESCs. Downregulation of SIRT1 disrupted the intracellular ROS homeostasis during decidualization of ESC, manifested as the accumulation of intracellular ROS level and the reduction of antioxidant stress molecules. Elimination of ROS with N-acetyl-L-cysteine (NAC) could rescued the decidualization inhibition caused by SIRT1 knockdown. Further, we explored the insufficient expression of SIRT1 in ESC affected the deacetylation of forkhead box O1 (FOXO1), and thus inhibited the transcriptional activity of FOXO1. This could account for the dysregulation of intracellular ROS homeostasis during decidualization and decreased expression of decidual markers. Collectively, our findings provided insight into the role of down-regulated SIRT1 in the poor decidual response of ESCs in RIF patients.

Current and Future Roles of Circular RNAs in Normal and Pathological Endometrium

The uterine endometrium, which lines the mammalian uterus, is essential for embryo implantation. This lining undergoes significant changes during sexual and menstrual cycles. The endometrium is also associated with hormone-related diseases such as endometriosis and endometrial cancer. Circular RNAs (circRNAs) play a role in various biological processes. Recent studies have determined that circRNAs function in both normal and pathological endometrial environments. Here, we review high-throughput studies pertaining to circRNAs as well as individual circRNAs active in the endometrium, in order to explore the myriad functions of circRNAs in the endometrium and mechanisms underlying these functions, from panoramic and individual perspectives. Owing to their abundant expression, stability, and small size, circRNAs have displayed potential usefulness as diagnostic markers and treatment targets for endometrial-related diseases. Therefore, the specific role of circRNAs in the endometrium warrants systematic investigation in the future.

Interaction of sperm with endometrium can regulate genes involved in endometrial receptivity pathway in mice: An experimental study

Background

Many researchers consider implantation and endometrial receptivity as pertinent issues in reproductive science. Although, several experiments have been performed and their results evaluated, yet there is no confirmed evidence about the related factors and the role of sperm in endometrial receptivity.

Objective

To investigate the effect of the sperm-endometrium interaction in regulating genes involved in the endometrial receptivity pathway.

Materials and Methods

In this experimental study, 10 male and 30 female NMRI mice were included, and half of the male cases were vasectomized. The subjects were divided into two groups as follows; group 1 (case) comprised of 15 females mated with 5 non-vasectomized male mice, while group 2 (control) consisted of 15 females mated with 5 vasectomized males. Cases were sacrificed and assessed after 36 hr and the endometrial tissue was extracted and kept at -80°C until the next use. The expression of the endometrial receptivity pathway genes, including VEGF, HBEGF, FGF2, EGF, LIF, LIFR, HOXA10, MUC1, PGR, and CSF, was examined in both groups. For statistical analysis, an independent samples test (Mean ± SD) was used.

Results

The mRNA levels of LIF (p = 0.045), LIFR (p = 0.040), MUC1 (p = 0.032), VEGF (p = 0.022), EFG (p = 0.035), and FGF2 (p = 0.040) were significantly upregulated in the case group compared with the control group.

Conclusion

Finally, seminal plasma was observed to be effective in expressing the involved genes in the successful implantation pathway, including LIF, LIFR, MUC1, VEGF, EGF, and FGF2.