Implantation Window Research Articles

Development of a New Personalized Molecular Test Based on Endometrial Receptivity and Maternal-Fetal Dialogue: Adhesio.

Successful embryo implantation relies on a receptive endometrium and a maternofetal dialogue. Abnormal receptivity is a common cause of implantation failure in assisted reproductive techniques. This study aimed to develop a novel transcriptomic-based diagnostic assay, Adhesio, for assessing endometrial receptivity and guiding personalized embryo transfer. Adhesio was developed based on an initial dataset of 74 endometrial biopsies. Two types of biopsy samples were involved: 45 endometrial biopsies collected during the optimal theoretical window of implantation (WOI) and 29 endometrial biopsies which cells have been cultured with or without an autologous embryo. Microarray analysis was performed to identify differentially expressed genes associated with endometrial receptivity and selected candidate genes were assessed using quantitative real-time polymerase chain reaction (RT-qPCR) on biopsy samples. Statistical analyses were conducted to assess the performance and accuracy of Adhesio. The microarray analysis identified three distinct clusters of endometrial samples with differential gene expression patterns. Cluster 1 exhibited 1717 differentially expressed genes involved in biological processes associated with endometrial receptivity. A specific transcriptomic signature of 60 genes associated with endometrial co-culture was obtained using class prediction approach. Thereafter, an original panel of 10 genes was selected as potential biomarkers for endometrial receptivity based on their expression profiles in both endometrial biopsies and co-cultured cells. This article outlines the methodology employed to develop Adhesio, a test that assesses endometrial receptivity using an original panel of 10 genes. These genes are not only involved during the WOI but are also influenced by the maternal-fetal dialogue.

The endoplasmic reticulum protein HSPA5/BiP is essential for decidual transformation of human endometrial stromal cells

Decidualization denotes the process of inflammatory reprogramming of endometrial stromal cells (EnSC) into specialized decidual cells (DC). During this process, EnSC are subjected to endoplasmic reticulum (ER) stress as well as acute cellular senescence. Both processes contribute to the proinflammatory mid-luteal implantation window and their dysregulation has been implicated in reproductive failure. Here, we evaluated the link between ER stress, decidual differentiation and senescence. In-silico analysis identified HSPA5 gene, codifying the ER chaperone BiP, as a potentially critical regulator of cell fate divergence of decidualizing EnSC into anti-inflammatory DC and pro-inflammatory senescent decidual cells (snDC). Knockdown of HSPA5 in primary EnSC resulted both in decreased expression of DC marker genes and attenuated induction of senescence associated β-galactosidase activity, a marker of snDC. Stalling of the decidual reaction upon HSPA5 knockdown was apparent at 8 days of differentiation and was preceded by the upregulation of ER stress associated proteins IRE1α and PERK. Further, HSPA5 knockdown impaired colony-forming unit activity of primary EnSC, indicative of loss of cellular plasticity. Together, our results point to a key role for HSPA5/BiP in decidual transformation of EnSCs and highlight the importance of constraining ER stress levels during this process.

Improving pregnancy outcomes in patients with recurrent implantation failure: The power of RNA-seq-based endometrial receptivity testing.

To evaluate whether RNA-seq-based endometrial receptivity testing (rsERT) can improve pregnancy outcomes in personalized frozen-thawed embryo transfer (pFET) during hormone replacement therapy (HRT) cycles among patients with recurrent implantation failure (RIF). We conducted a retrospective cohort study involving 98 RIF patients undergoing HRT for FET. The experimental group consisted of 58 patients who underwent pFET after rsERT, while the control group included 40 patients who refused rsERT and underwent conventional ET. We recorded and examined the subsequent pregnancy outcomes from all cycles. The results of rsERT revealed that 67.24% of the experimental group were out of the "window of implantation" (WOI), with all cases showing a delay. The HCG-positive rate, implantation rate, and clinical pregnancy rate (CPR) in the experimental group were significantly higher than those in the control group, at 75.86% versus 50.00% (P = .030), 56.38% versus 31.43% (P = .002), and 68.97% versus 47.50% (P = .033), respectively. Our study demonstrated that utilizing rsERT technology to guide pFET in HRT cycles significantly enhances implantation and CPRs in RIF patients. Importantly, our findings confirm the effectiveness of rsERT technology and establish a scientific rationale for personalized reproductive medical interventions.

MMP-1, MMP-2, MMP-9, TIMP-1, TIMP-2, MUC1 and CD29 Expression in Endometrial Polyps at Implantation Window Compared to Neighbouring Normal Endometrium

MMP-1, MMP-2, MMP-9, TIMP-1, TIMP-2, MUC1 and CD29 Expression in Endometrial Polyps at Implantation Window Compared to Neighbouring Normal Endometrium

Taurine is essential for mouse uterine luminal fluid resorption during implantation window via the SCNN1A and AQP8 signaling.

Uterine fluid homeostasis during peri-implantation is crucial for successful embryo implantation. Taurine (Tau) plays a crucial role in regulating osmotic pressure and ion transport. However, the precise mechanisms underlying Tau-mediated regulation of uterine fluid homeostasis during peri-implantation in mice remain unclear. In this study, we generated a Tau-deficient mouse model by administering Tau-free diet to Csad knockout (Csad-/-) mice to block endogenous Tau synthesis and exogenous Tau absorption (Csad-/--Tau free). Our findings demonstrated that Csad-/-Tau free mice with diminished level of Tau exhibited decreased rates of embryo implantation and impaired fertility. Further analysis revealed that the expression of Scnn1a was down-regulated during the implantation window, while Aqp8 was upregulated in Csad-/-Tau free mice, leading to uterine luminal fluid retention and defects in luminal closure, resulting in failed embryo implantation. Additionally, it was also found that E2 inhibited uterine Csad expression and Tau synthesis, while P4 promoted them. Therefore, our findings suggest that ovarian steroid hormones regulate Csad expression and Tau synthesis, thereby affecting release and resorption of uterine luminal fluid, ultimately impacting embryo implantation success.

Altered Expressions of IL-15, IFNG, and HPRT1 Genes in the Thin Endometria of Patients with Reproductive Disorders: A Prospective Comparative Study

Reproductive disorders are common events in modern reproductive medicine, occurring both in spontaneous and assisted pregnancies. Studies on the molecular mechanisms of implantation disorders in thin endometria, including the study of gene transcriptional activities, have shed light on the identification of the potential biological markers of endometrial receptivity. Background/Objectives: The goal of this study was to reveal the significantly dysregulated selected gene expressions between RIF and RPL patients with thin endometria. Methods: Endometrial samples were collected from RIF patients (n = 20) and RPL patients (n = 19) during the implantation window days (LH + 7—LH + 10) of their natural menstrual cycles. Ten genes were chosen as the target genes regarding their possible relations with the implantation process. The total RNA was purified and reverse-transcribed, and gene expressions were quantified by RT-PCR. Results: The expressions of the IL-15, INFG, and HPRT1 genes were significantly decreased in the RIF patients with thin endometria compared to the RPL patients (log2 fold change = 0.92, p = 0.023 for IL-15; log2 fold change = 1.24, p = 0.046 for INFG; and log2 fold change = 0.579, p = 0.046 for HPRT1). There were no significant differences in the expressions of the CXCL8, CXCL1, MMP10, C4BPA, TNC, VEGFB, and HAND2 genes between the groups. Conclusions: Decreased expressions of the IL-15, INFG, and HPRT1 genes were found in patients with RIF with thin endometria compared to the endometria of women with RPL. This has practical significance for clinicians for the differentiated prescription of immunomodulatory therapy in patients undergoing ART programs.

STUDY OF THE ENDOMETRIAL GLANDULAR COMPONENT IN WOMEN WITH FERTILITY AND POST-COVID SYNDROME IN ANAMNESIS

The aim. To increase the effectiveness of the endometrial endometrial glandular component study in women with infertility and post-COVID syndrome. Materials and methods. A study was conducted at the State institution "Carpathian Human Reproduction Centre" of the Ministry of Health of Ukraine in the period from 2022 to the end of the first half-year of 2024. There were included 80 women in the experimental group and 40 women in the control group. The selection criterion for the study group was the presence of documented post-COVID syndrome (COVID-19 symptoms lasted longer than 12 weeks). The selection criterion for the control group was the absence of confirmed SARS-CoV-2 virus in the anamnesis. The following characteristics were common for both groups: diagnosed infertility, age – 25-42 years, written informed consent of the patient to participate in the study. The criteria for exclusion from the study for patients of both groups were: detection of human immunodeficiency virus, viral hepatitis, other sexually transmitted infections, tuberculosis of the genitourinary system, malignant diseases, mental disorders that make communication with person impossible or the awareness of written consent is questioned. General clinical and laboratory examinations and transvaginal sonographic examination of the pelvic organs were performed in the middle stage of proliferation and the middle stage of secretion according to the calendar calculation the menstrual cycle. A visually guided diagnostic office hysteroscopy was performed with the collection of biological material from the most changed areas (biopsies were collected in the middle stage of proliferation and the middle stage of secretion in different menstrual cycles). A routine staining of samples with hematoxylin-eosin, morphometry of the endometrial glandular component, optical determination of the number of glands and measurement of the diameter of the lumen of the studied glands, considering the possible measurement error, glandular-stromal ratio, functional activity of the glands, were performed. A histochemical PAS-reaction to identify the glycoproteins of gland secretions and immunohistochemical staining of the glandular epithelium to express the receptivity of the glands to estrogen and progesterone were carried out. The results. After conducting the PAS-reaction, a higher secretion was noted in the glands than in the stroma of the endometrium during the period of the implantation window in both cohorts. No statistically significant difference between the groups in the amount of glycogen of the middle proliferative phase in the glands (p=0.315) or stroma (p=0.486). Glycogen in this phase was visualized of very small granules and coarse granules, without their formation in clusters. A decrease in secretion was established in 16 (40%) patients of the control group and 49 (61.3%) women of the experimental group in the middle secretory phase, which was statistically significant (p=0.028). A decrease in the expression level of the progesterone receptor in the middle secretory phase was found to be significantly more pronounced in the experimental group than in the control group (р=0.044). Conclusions. In the middle secretory phase, a decrease in the secretion of glycogen by the endometrial glands and a decrease in the level of expression of the progesterone receptor in endometrial biopsies were detected by the routine histological, histochemical techniques and immunohistochemical stude in women with infertility and a history of post-COVID syndrome.

Supraphysiological Dose of Testosterone Impairs the Expression and Distribution of Sex Steroid Receptors during Endometrial Receptivity Development in Female Sprague-Dawley Rats.

This study aims to investigate the effect of a supraphysiological dose of testosterone on the levels of sex steroid hormones and the expression and distribution of sex steroid receptors in the uterus during the endometrial receptivity development period. In this study, adult female Sprague-Dawley rats (n = 24) were subcutaneously administered 1 mg/kg/day of testosterone alone or in combination with the inhibitors (finasteride or anastrozole or both) from day 1 to day 3 post-coitus, while a group of six untreated rats served as a control group. The rats were sacrificed on the evening of post-coital day 4 of to measure sex steroid hormone levels by ELISA. Meanwhile, gene expression and protein distribution of sex steroid receptors were analysed by quantitative polymerase chain reaction (qPCR) and immunohistochemistry (IHC), respectively. In this study, treatment with a supraphysiological dose of testosterone led to a significant reduction in oestrogen and progesterone levels compared to the control. The mRNA expression of the androgen receptor increased significantly in all treatment groups, while the mRNA expression of both the progesterone receptor and the oestrogen receptor-α decreased significantly in all treatment groups. The IHC findings of all sex steroid receptors were coherent with all mRNAs involved. This study shows that a supraphysiological dose of testosterone was able to interrupt the short period of the implantation window. This finding could serve as a basis for understanding the role of testosterone in endometrial receptivity in order to develop further therapeutic approaches targeting androgen-mediated disorders of endometrial receptivity.

Personalized embryo transfer guided by rsERT with hourly precision improves pregnancy outcomes in patients with a receptive window of implantation: a pilot study.

To investigate whether personalized embryo transfer (pET) predicted by a modified RNA-sequencing-based endometrial receptivity test (rsERT) model can improve intrauterine pregnancy rate (IPR) in patients with a receptive window of implantation (WOI). A retrospective pilot study was conducted in the Center for Reproductive Medicine, Central South University, from January 2018 to December 2023. A total of 524 patients with receptive WOI results from rsERT were assigned into two groups based on whether they underwent conventional embryo transfer (conventional ET) or pET. Patients in the conventional ET were matched with those in the pET group at a 1:1 ratio using propensity score matching (PSM). Before PSM, the IPR (55.73% vs. 46.19%, P = 0.032) and implantation rate (IR) (47.51% vs. 34.03%, P = 0.000) in the pET group were significantly higher than that in the conventional ET group. However, the number and types of transferred embryos differed significantly between the two groups. After adjusting for confounding factors, IPR (57.38% vs. 44.81, P = 0.016) and IR (46.81% vs. 33.10%, P = 0.001) remained significantly higher in the pET group compared to the conventional ET group. The implantation failure rate was significantly lower in the pET group compared to controls (42.62% vs. 55.19%, P = 0.016). Additionally, the multiple-pregnancy rate was significantly higher in the pET group compared to the conventional ET group (10.29% vs. 1.68%, P = 0.001). Women with receptive WOI results could benefit from the receptivity-timed pET predicted by the newly refined rsERT. These findings provide a basis for future research in precision medicine for embryo transfer.

Altered Expression of C4BPA and CXCL1 Genes in the Endometrium of Patients with Recurrent Implantation Failure after In Vitro Fertilization and Thin Endometrium.

Currently, recurrent implantation failure (RIF) after in vitro fertilization is a problem that is commonly faced by reproductive specialists. The phenomenon of a thin endometrium in RIF patients is not yet completely understood or sufficiently treated. This study aimed to reveal the dysregulated expression of selected genes between RIF patients with a thin endometrium and fertile women. Endometrial samples were collected in the implantation window (21-24 days of the natural menstrual cycle) from RIF patients (n = 20) and fertile women (n = 14). Ten genes were chosen as target genes regarding their possible relations with the implantation process. The endometrial gene expression levels showed differences in RIF samples compared to fertile samples. Significant downregulation was observed for the CXCL1 (p = 0.005) and C4BPA (p = 0.03) genes. There was no statistically significant difference between the RIF group and the fertile group in the expression of eight genes: CXCL8, HPRT1, MMP10, INFG, VEGFB, HAND2, IL-15, and TNC (p > 0.05). The use of a combination of two markers (C4BPA + CXCL1) allows for the good discrimination of RIF patients from fertile women (AUC 0.806).

A Comprehensive Review of the Endometrial Receptivity Array in Embryo Transfer: Advancements, Applications, and Clinical Outcomes.

Embryo transfer is a pivotal procedure in assisted reproductive technologies (ART). Yet, the success of this process hinges on multiple factors, with endometrial receptivity playing a critical role in determining the likelihood of successful implantation. The endometrial receptivity array (ERA) is an advanced diagnostic tool designed to personalize embryo transfer timing by assessing the endometrium's receptivity. This review comprehensively examines the ERA, exploring its biological foundation, technological development, and clinical applications. The ERA's ability to analyze the expression of genes associated with endometrial receptivity offers a tailored approach to identifying the optimal window of implantation (WOI), particularly benefiting patients with recurrent implantation failure (RIF) or repeated unsuccessful in vitro fertilization (IVF) cycles. Clinical outcomes from ERA-guided embryo transfers indicate improvements in implantation rates and overall pregnancy success, although challenges such as result variability and cost-effectiveness persist. This review also discusses the latest advancements in ERA technology, including integrating genomic and transcriptomic analyses, non-invasive techniques, and using artificial intelligence (AI). Controversies regarding the widespread application of ERA and its necessity in all IVF cases are critically examined. By summarizing the current state of ERA in embryo transfer, this review aims to inform clinicians, researchers, and patients about its potential to enhance ART outcomes and to highlight areas for future research and innovation.

Optimizing evaluation of endometrial receptivity in recurrent pregnancy loss: a preliminary investigation integrating radiomics from multimodal ultrasound via machine learning.

Recurrent pregnancy loss (RPL) frequently links to a prolonged endometrial receptivity (ER) window, leading to the implantation of non-viable embryos. Existing ER assessment methods face challenges in reliability and invasiveness. Radiomics in medical imaging offers a non-invasive solution for ER analysis, but complex, non-linear radiomic-ER relationships in RPL require advanced analysis. Machine learning (ML) provides precision for interpreting these datasets, although research in integrating radiomics with ML for ER evaluation in RPL is limited. To develop and validate an ML model that employs radiomic features derived from multimodal transvaginal ultrasound images, focusing on improving ER evaluation in RPL. This retrospective, controlled study analyzed data from 346 unexplained RPL patients and 369 controls. The participants were divided into training and testing cohorts for model development and accuracy validation, respectively. Radiomic features derived from grayscale (GS) and shear wave elastography (SWE) images, obtained during the window of implantation, underwent a comprehensive five-step selection process. Five ML classifiers, each trained on either radiomic, clinical, or combined datasets, were trained for RPL risk stratification. The model demonstrating the highest performance in identifying RPL patients was selected for further validation using the testing cohort. The interpretability of this optimal model was augmented by applying Shapley additive explanations (SHAP) analysis. Analysis of the training cohort (242 RPL, 258 controls) identified nine key radiomic features associated with RPL risk. The extreme gradient boosting (XGBoost) model, combining radiomic and clinical data, demonstrated superior discriminatory ability. This was evidenced by its area under the curve (AUC) score of 0.871, outperforming other ML classifiers. Validation in the testing cohort of 215 subjects (104 RPL, 111 controls) confirmed its accuracy (AUC: 0.844) and consistency. SHAP analysis identified four endometrial SWE features and two GS features, along with clinical variables like age, SAPI, and VI, as key determinants in RPL risk stratification. Integrating ML with radiomics from multimodal endometrial ultrasound during the WOI effectively identifies RPL patients. The XGBoost model, merging radiomic and clinical data, offers a non-invasive, accurate method for RPL management, significantly enhancing diagnosis and treatment.

Reproductive and transcriptome characteristics of endometrium at the window of im-plantation in patients after fertility-sparing treatment of endometrial intraepithelial neoplasm or cancer

BackgroundProgestin therapy is an option for patients with endometrial carcinoma (EC) or endometrial intraepithelial neoplasm (EIN) who fit specific criteria of fertility-sparing treatment. However, the implantation rate remains low among females receiving in vitro fertilization (IVF) even after the complete reversal of endometrial lesions. MethodsHere, ten patients with EC/EIN achieved complete regression (CR) in histology. Their relevant metabolic and IVF parameters were collected. An endometrial sampling at the window of implantation (WOI) and transcriptome analysis were conducted among them, and four healthy controls were analyzed to analyze endometrial receptivity. ResultsOn average, it took ten patients five months to achieve CR after four curettage procedures. The interquartile range of endometrium thickness on trigger day was between 8.8 and 10.0 mm, while the range was 15.2–18.5 mm for controls. Five patients got pregnant after a frozen-embryo transfer. According to ERA analysis, the endometrial sampling at WOI showed pre-receptive status in four cases. In total, 1458 differential expression genes were identified, and 70 belonged to the ERA genes. ImmuneScore indicated decreased NK cells in the endometrium, affecting endometrial receptivity. ConclusionsEven after EC/EIN reversal in histology, endometrial receptivity has already been compromised regarding altered WOI and immune microenvironment, leading to a low pregnancy rate.

The role of microRNAs in the regulation of critical genes and signalling pathways that determine endometrial receptivity.

Endometrial receptivity is the ability of the endometrium to accept embryos. Thus, endometrial receptivity dysfunction is an important factor leading to embryo implantation failure. A good endometrial receptivity provides a suitable environment for embryo implantation, improving the embryo implantation rate. The "implantation window" stage, or the receptive stage of the endometrium, is regulated by various hormones, genes, proteins and cytokines, among which microRNAs (miRNAs) and their target genes have a regulatory effect on endometrial receptivity. This review outlines the relationship between endometrial receptivity and pregnancy, the mRNAs and related signalling pathways that regulate endometrial receptivity, and the regulatory role of miRNA in endometrial receptivity, providing a deeper understanding of the regulatory mechanisms of miRNA on endometrial receptivity in humans and animals and reference for the endometrial receptivity-related research.

Generation of epithelial-stromal assembloids as an advanced in vitro model of impaired adenomyosis-related endometrial receptivity

ObjectiveTo create a novel, more advanced in vitro model of human endometrium, using so-called assembloids, looking to explore endometrial receptivity in adenomyosis. DesignEvaluation of assembloid responsiveness to hormonal stimulation by immunohistochemistry, ELISA and scanning electron microscopy (SEM). SettingUniversity-based research unit in gynecology. SubjectsTwelve women, 6 of whom were affected by adenomyosis. InterventionOrganoids (in the form of glandular fragments) and stromal fibroblasts were collected from endometrial biopsies. The two populations were combined inside an extracellular matrix to create 3D assembloids, which were then exposed to hormonal stimulation (β-estradiol for 48 hours, followed by β-estradiol/progesterone/cyclic adenosine monophosphate for 72 hours) to mimic the window of implantation. Main outcome measuresGlycodelin, leukemia inhibitory factor (LIF) and homeobox A10 (HOXA10) expression, prolactin secretion and pinopode development. ResultsEndometrial organoids and stromal cells were successfully isolated from women with and without adenomyosis and combined to generate the assembloid model. Upon stimulation, assembloids from both groups acquired a more secretory phase-like phenotype, as demonstrated by histology, and were shown to be positive for glycodelin, LIF and HOXA10 by immunohistochemistry. Adenomyotic assembloids expressed significantly lower levels of LIF and HOXA10 within the stromal compartment after stimulation than did healthy assembloids in the same condition. ELISA revealed prolactin secretion in vitro, showing an upward trend in hormonally treated assembloids from both healthy and affected women. By SEM, fully formed pinopodes were discerned on the epithelial surface of healthy assembloids after stimulation, but they were absent in case of adenomyosis. ConclusionPrimary assembloids can be generated from endometrial biopsies from both healthy subjects and women affected by adenomyosis. These assembloids are amenable to hormonal stimulation and mimic secretory phase-specific characteristics of endometrial tissue in vivo, including glycodelin, LIF and HOXA10 expression, and pinopode formation. Assembloids from adenomyosis appear to be less sensitive to hormonal treatment, showing reduced expression of LIF and HOXA10 in the stromal compartment and failing to form pinopodes. All in all, endometrial assembloids may serve as an advanced preclinical model of adenomyosis-related impaired endometrial receptivity, opening up new horizons in understanding and treating the condition.

Correlation between Serum Levels of HLA-G and Recurrent Implantation Failure During Implantation Window in Women Undergoing In Vitro Fertilization

Background: Recurrent implantation failure (RIF) during artificial reproductive techniques (ARTs) remains a health problem. Many physiopathological pathways have been proposed for RIF, but the causes are not yet clear. Thus, the purpose of the current study was to evaluate the possible correlation between human leucocyte antigen-G (HLA-G) serum levels and recurrent implantation failure during the implantation window in women undergoing In vitro fertilization (IVF). Materials and Methods: In this prospective case-control study, 39 patients with RIF and 20 cases with successful implantation were enrolled as the control group. HLA-G serum levels were measured using the sandwich ELISA method in both groups. Results: HLA-G serum levels in the RIF group were significantly higher than in controls (0.085 ± 0.019 compared to 0.073 ± 0.005, p = 0.024). Furthermore, by grouping patients based on age and BMI, we found that in the cases with ages above 30 years and with BMI more than 25 (kg/m2), HLA-G serum levels in the RIF group were remarkably greater than controls (0.088 ± 0.019 compared to 0.072 ± 0.004, p = 0.002 and 0.083 ± 0.012 compared to 0.072 ± 0.003, p = 0.021, respectively). Conclusion: Serum levels of HLA-G increase in the RIF patients, especially in cases of patients above 30 years old and those with BMI ≥ 25, which remains significant after eliminating confounding variables. These results may indicate the involvement of physiopathological pathways of HLA-G in the increasing risk of RIF.

Effect of electroacupuncture pre-conditioning on the expression rhythm of core clock gene Bmal1 in uterine tissue of controlled hyperstimulation rats.

To observe the effect of electroacupuncture (EA) pre-conditioning on the expression rhythm of clock gene Bmal1 in the uterine tissue of rats with controlled ovarian hyperstimulation(COH), so as to explore its mechanisms underlying improvement of the endometrial receptivity of ovarian superovulation during implantation. Seventy-two female SD rats with typical estrous cycles were randomly divided into normal control, model and EA pre-conditioning (pre-EA) groups, with 24 rats in each group. The COH model was established by giving the rats with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) by intraperitoneal injection. The rats of the pre-EA group received EA stimulation (1 Hz/5 Hz, a tolerable strength) of "Guanyuan"(CV4) and "Sanyinjiao"(SP6) for 15 min each time, once daily (at 21：00 every day). After successive EA intervention during the first two estrous cycles, the modeling began in the third estrus cycle and the EA intervention was continued till the end of modeling, followed by raising the rats with superovulation induction and male rats undergoing vasoligation in one cage (1∶1). The rats during the estrum in the normal control group or those of the model group at the end of modeling were raised together with the male rats undergoing vasoligation in one cage. On the 5th day (04：00 AM) after raising in one cage, the rats in the three groups were sacrificed in six batches every 4 hours, with 4 rats in each group in each batch. The H.E. staining was used for revealing alterations of the endometrial thickness, number of glands and blood vessels and tissue histology, and ELISA employed to ascertain the contents of estradiol (E2) and progesterone (Pg) in serum. The expression rhythm of core clock gene Bmal1 ［In the present study, Zeitgeber time (ZT) is an artificially set laboratory time, i.e., ZT7 (07：00) is light on and ZT19 (19：00) is light off.］ and the expression of endometrial HoxA10 and leukemia inhibitory factor (LIF) mRNAs were detected by quantitative real-time PCR. The Western blot was employed to detect the expression levels of HoxA10 and LIF proteins. Findings of the clock gene Bmal1 level showed that the expression peak was at ZT12 and the valley value at ZT20 in the normal control group, and that of the peak value was at ZT20 and valley value at ZT12 in the model group, while in the pre-EA group, the peak value was at ZT8, and the valley value at ZT4. The difference of Bmal1 levels among the three groups was most significant at ZT12 (12：00), therefore, the tissue samples were taken at ZT12 in this study for comparison of the levels of different indexes among the 3 groups. Compared with the control group, the endometrial thickness, number of glands and blood vessels, HoxA10 and LIF mRNAs and proteins were significantly down-regulated (P<0.01, P<0.05), and contents of serum E2 and Pg were considerably up-regulated in the model group (P<0.01, P<0.05). Relevant to the model group, the pre-EA group had an apparent increase in the endometrial thickness, number of glands and blood vessels, and expression levels of HoxA10 and LIF mRNAs and proteins (P<0.05, P<0.01), and a marked decrease in the serum Pg (P<0.05). At the ZT12 (12：00 noon), compared with the normal control group, the mRNA level of Bmal1 was significantly decreased in the model group (P<0.01)；and compared with the model group, the level of Bmal1 mRNA was significantly increased in the pre-EA group (P<0.05). In addition, at the node of ZT16, the mRNA level of Bmal1 was significantly decreased in the model group in comparison with the normal control group (P<0.01). EA preconditioning can improve the endometrial receptivity during the implantation window period in rats with COH, which may be related to its functions in regulating the expression of clock gene Bmal1 in the uterine tissue and in correcting the disturbance of clock gene rhythm.

Precise hourly personalized embryo transfer significantly improves clinical outcomes in patients with repeated implantation failure.

This study investigated whether RNA-Seq-based endometrial receptivity test (rsERT)-which provides precision for the optimal hour of the window of implantation (WOI)-can improve clinical outcomes of frozen embryo transfer (FET) cycles in patients with a history of repeated implantation failure (RIF). Patients with a history of RIF who received at least one autologous high-quality blastocyst during the subsequent FET cycle were retrospectively enrolled and divided into two groups: rsERT and FET, comprising patients who underwent rsERT-guided pET (n=115) and standard FET without rsERT (n=272), respectively. In the rsERT group, 39.1% (45/115) of patients were receptive. rsERT patients showed a higher probability of achieving both positive human chorionic gonadotropin (63.5% vs. 51.5%, P=0.03) and clinical pregnancy (54.8% vs. 38.6%, P=0.003) rates. In subgroup analysis, rsERT patients with non-receptive results had higher clinical pregnancy rates than patients undergoing FET (58.6% vs. 38.6%, P=0.003). rsERT patients with receptive results guided by rsERT with a precise WOI time had higher, although non-significant, clinical pregnancy rates (48.9% vs. 38.6%, P=0.192) than patients who underwent standard-time FET. Hourly precise rsERT can significantly improve the probability of achieving clinical pregnancy in patients with RIF, especially in those with non-receptive rsERT results.

P-517 The effects of various female infertility factors on endometrial receptivity

Abstract Study question Is there a correlation between different female infertility factors and displaced window of implantation? Summary answer Patients with decreased ovarian reserve and endometriosis have higher risk in experiencing displaced window of implantation. What is known already Numerous studies substantiate that infertility stems from various etiology, including ovulatory dysfunction, male factors, tubal disease, endometriosis, uterine factors...etc. MicroRNAs (miRNAs) play a crucial role in initiating these infertility-related disorders and influencing biological processes like gametogenesis, embryogenesis, ovarian, uterine or endometrial condition. Notably, miRNAs regulate endometrial receptivity, suggesting optimal embryo transfer timing during IVF treatment by identifying the window of implantation (WOI). In recognition of this significant function, MIRA, a molecular testing solution that predicts endometrial receptivity for patients undergoing frozen embryo transfer (FET) by targeting miRNA biomarkers, was developed in hopes of bolstering success rate for personalized embryo transfer. Study design, size, duration This study aims to identify if there is a correlation seen between female infertility factors and the WOI. We enrolled a total of 96 patients who demonstrated successful pregnancy outcomes following personalized embryo transfer. The patients’ personalized embryo transfer timing recommendations were assessed based on their miRNA expression profiles using MIRA. Concurrently, the participants’ underlining infertility diseases were classified according to diagnoses guidelines provided by Taiwan’s Ministry of Health and Welfare. Participants/materials, setting, methods Six categories of female infertility diseases were included: decreased ovarian reserve, tubal, endometriosis, uterine abnormalities (excluding myoma and adenomyosis), polycystic ovary syndrome (PCOS), and myoma factors. Infertile factors such as unexplained, aneuploid oocyte (PGT), male factors, and adenomyosis were excluded due to limited sample size. Statistical analysis of endometrial stages and disease categories involved calculating percentage of the window of implantation (WOI) versus displaced WOI (either pre- or post-receptive) within the six types of diseases. Main results and the role of chance Our result showed that overall, 64.58% of 96 patients have a receptive window of implantation. Compared to this baseline, polycystic ovary syndrome (66.67%) does not elevate the risk of displaced endometrial stages. However, patients with decreased ovarian reserve and endometriosis are more likely to display displaced window of implantation, with average rates of 57.14% and 55.56% WOI respectively. Notably, patients with uterine abnormalities (84.62%) and myoma (87.5%) factors exhibit a lower likelihood of having a displaced WOI. The WOI percentage caused by tubal factors is slightly lower at 76.19%. In conclusion, these preliminary findings establishes that categories of female infertility diseases have discernible effects on patients’ WOI. As patients with certain infertility factors, such as decreased ovarian reserve and endometriosis, demonstrated a greater risk in experiencing displaced WOI, patients that fall under these categories could further benefit from utilizing endometrial receptivity testing to determine the optimal timing for their embryo transfer to potentially improve their reproductive outcomes and facilitate shared decision-making (SDM) in patient’s embryo transfer process. Limitations, reasons for caution While this result offers a preliminary overview for the correlation between endometrial stages and female infertility diseases, we cannot confirm whether these conclusions reached statistical significance due to the limitation of data. Wider implications of the findings Further investigation into the specific reasons for the discernable WOI patterns in different diseases is warranted in larger sample sizes to offer more personalized and robust clinical information supporting IVF treatments. Trial registration number ’not applicable’

P-802 Exploring the effects of phthalate mixtures on human endometrial organoids: Insights into transcriptomic and proteomic profiles throughout the menstrual cycle

Abstract Study question Does the exposure of human endometrial organoids (hEOs) to phthalates influence their transcriptomic and proteomic profiles, particularly during the window of implantation? Summary answer The mixture of phthalates altered the expression of several genes which are essential during the window of implantation. What is known already hEOs display a robust responsiveness to steroid hormones and accurately reproduce essential morphological features observed in the receptive endometrium in vivo. The conventional approach to evaluating chemical health risks has predominantly been centered on the assessment of individual substances, overlooking the reality that individuals are regularly exposed to diverse mixtures of phthalates, a class of Endocrine Disrupting Chemicals (EDCs). There is a limited number of studies indicating that phthalates and their combinations can have a negative impact on the endometrium. To this purpose, we explore the effect of this mixture on endometrial receptivity during the Window Of Implantation (WOI). Study design, size, duration Endometrial tissues (n = 6) used for this study were obtained, with written informed consent from all participants. The endometrial organoids were generated from the biopsies and treated with hormones to mimic the WOI. Samples were then exposed with a mixture of phthalates in order to study the transcriptomic and proteomic changes on these cells throughout the menstrual cycle, especially the WOI. Participants/materials, setting, methods hEOs were generated from endometrial biopsies of healthy volunteers (n = 6). Organoids were cultured for 4 days and then divided into: untreated without any hormonal treatment; stimulated with 10 nM estrogen (E2); treated with 10 nM estrogen, 1μM progesterone (P4) and 1μM cyclic adenosine monophosphate (cAMP). EOs were further on exposed to the phthalate mixture. Proteomic profiling was performed using 2-D electrophoresis and Mass spectrometry. Samples were also subject to transcriptomic analysis, by RNA sequencing. Main results and the role of chance hEOs present a suitable in vitro model for the screening of the impact of phthalate mixtures on the endometrium throughout the menstrual cycle. Cytotoxicity test confirmed that the chosen concentration (100x of the value referring to the geometrical means in urine) of the mixture is not toxic for the cells. The transcriptomic and proteomic analyses revealed several up-regulated or down-regulated genes which are involved into pivotal pathways implicated to the WOI. Limitations, reasons for caution This study represents a preliminary experiment. All results need to be validated on an enlarged number of samples to provide more statistical strength. Wider implications of the findings hEOs offer a robust in vitro model to simulate and gain a more profound comprehension of the consequences arising from the combinatory effects of EDCs, on the endometrium. This model proves valuable in examining the impact of various EDCs across different phases of the menstrual cycle. Trial registration number not applicable