Mitochondria remodeling during endometrial stromal cell decidualization.

Upon hormonal stimulation, uterine endometrial stromal cells undergo a dramatic morpho-functional metamorphosis that allows them to secrete large amounts of matrix proteins, cytokines, and growth factors. This step, known as decidualization, is crucial for embryo implantation. We previously demonstrated how the secretory pathway is remodelled during this process. Here we show that hormonal stimulation rapidly induces the expression of many mitochondrial genes, encoded in both the mitochondrial and the nuclear genomes. Altogether, the mitochondrial network quadruples its size and establishes more contacts with the ER. This new organization results in the increased respiratory capacity of decidualized cells. These findings reveal how achieving an efficient secretory phenotype requires a radical metabolic rewiring.

High androgen level during controlled ovarian stimulation cycle impairs endometrial receptivity in PCOS patients.

PCOS is one of the most common endocrine disorders among women of reproductive age. While the mechanism involved is not yet fully characterized. Our study aims to examine the pregnancy outcomes of embryo transfers in women with PCOS after pretreatment, and to explore the possible effect of high androgen levels on endometrial receptivity. Retrospective cohort study was conducted to analyze pregnancy outcomes among 2714 infertile women with tubal factor and 452 PCOS women. Endometrium samples were collected from 6 controls and 6 PCOS patients to detect the expression of endometrial receptivity marks. The implantation rate, clinical and ongoing pregnancy rates and live birth rate in women with PCOS followed fresh embryo transfers were obviously decreased even after the pretreatment. Similar pregnancy outcomes were found in frozen-thawed embryo transfer cycles between women with or without PCOS. Strikingly, serum total testosterone (TT) levels on trigger day were significantly higher in PCOS women. Women with high TT levels presented significantly lower clinical and ongoing pregnancy rates, and the expression of insulin-like growth factor binding protein 1 (IGFBP-1), and leukemia inhibitory factor (LIF) in the endometria decreased significantly as well. High doses of testosterone significantly down-regulated the expression of IGFBP-1 and LIF in Ishikawa cells. Although endocrine abnormalities had been improved before the controlled ovarian stimulation (COS) cycle started, higher serum TT levels were detected on the trigger day of the COS cycle in PCOS patients, which may contribute to the decreased fresh embryo implantation by impairing endometrial receptivity.

Dysregulated miR-124-3p in endometrial epithelial cells reduces endometrial receptivity by altering polarity and adhesion.

The endometrium undergoes substantial remodeling in each menstrual cycle to become receptive to an implanting embryo. Abnormal endometrial receptivity is one of the major causes of embryo implantation failure and infertility. MicroRNA-124-3p is elevated in both the serum and endometrial tissue of women with chronic endometritis, a condition associated with infertility. MicroRNA-124-3p also has a role in cell adhesion, a key function during receptivity to allow blastocysts to adhere and implant. In this study, we aimed to determine the function of microRNA-124-3p on endometrial epithelial adhesive capacity during receptivity and effect on embryo implantation. Using a unique inducible, uterine epithelial-specific microRNA overexpression mouse model, we demonstrated that elevated uterine epithelial microRNA-124-3p impaired endometrial receptivity by altering genes associated with cell adhesion and polarity. This resulted in embryo implantation failure. Similarly in a second mouse model, increasing microRNA-124-3p expression only in mouse uterine surface (luminal) epithelium impaired receptivity and led to implantation failure. In humans, we demonstrated that microRNA-124-3p was abnormally increased in the endometrial epithelium of women with unexplained infertility during the receptive window. MicroRNA-124-3p overexpression in primary human endometrial epithelial cells (HEECs) impaired primary human embryo trophectoderm attachment in a 3-dimensional culture model of endometrium. Reduction of microRNA-124-3p in HEECs from infertile women normalized HEEC adhesive capacity. Overexpression of microRNA-124-3p or knockdown of its direct target IQGAP1 reduced fertile HEEC adhesion and its ability to lose polarity. Collectively, our data highlight that microRNA-124-3p and its protein targets contribute to endometrial receptivity by altering cell polarity and adhesion.

Spatiotemporally distinct roles of cyclooxygenase-1 and cyclooxygenase-2 at fetomaternal interface in mice.

Embryo implantation is crucial for ensuring a successful pregnancy outcome and subsequent child health. The intrauterine environment during the peri-implantation period shows drastic changes in gene expression and cellular metabolism in response to hormonal stimuli and reciprocal communication with embryos. Here, we performed spatial transcriptomic analysis to elucidate the mechanisms underlying embryo implantation. Transcriptome data revealed that lipid metabolism pathways, especially arachidonic acid-related (AA-related) ones, were enriched in the embryo-receptive luminal epithelia. Cyclooxygenases (COXs), rate-limiting enzymes involved in prostaglandin production by AA, were spatiotemporally regulated in the vicinity of embryos during implantation, but the role of each COX isozyme in the uterus for successful pregnancy was unclear. We established uterine-specific COX2-knockout (uKO) and COX1/uterine COX2-double-KO (COX1/COX2-DKO) mice. COX2 uKO caused deferred implantation with failed trophoblast invasion, resulting in subfertility with reduced pregnancy rates and litter sizes. COX1/COX2 DKO induced complete infertility, owing to abrogated embryo attachment. These results demonstrate that both isozymes have distinct roles during embryo implantation. Spatial transcriptome and lipidome analyses revealed unique profiles of prostaglandin synthesis by each COX isozyme and spatiotemporal expression patterns of downstream receptors throughout the endometrium. Our findings reveal previously unappreciated roles of COXs at the fetomaternal interface to establish early pregnancy.

Impact of blastocyst grading and blastocyst biopsy dates on the clinical outcomes of patients undergoing preimplantation genetic testing.

Background: Preimplantation genetic testing (PGT) allows for the evaluation of embryo genetic information prior to implantation, enabling the selection of normal embryos for transfer and ultimately leading to better pregnancy outcomes. In this study, we explored factors that influence clinical outcomes of patients undergoing PGT. The effects of blastocyst grading and biopsy dates on clinical outcomes were also analyzed. Methods: The clinical data and pregnancy outcomes of 428 PGT cycles performed in the Reproductive Medicine Department of the Northern Theater General Hospital between January 2017 and December 2022 were retrospectively analyzed. Multifactorial logistic regression analysis and nomograms were used to determine factors influencing pregnancy outcomes. The impact of D5 blastocysts (290 cycles) and D6 blastocysts (138 cycles) with different quality levels on clinical outcomes was also compared. Results: Multifactorial logistic regression analysis showed that age, BMI, endometrial thickness, and embryo quality of women affected PGT clinical outcomes. Women aged <40 years or with a body mass index (BMI) >18.5 and endometrial thickness>1.0 cm had a significantly higher pregnancy success rate. Compared to that of D6 blastocyst biopsy, D5 blastocyst biopsy was associated with a higher pregnancy success rate but a similar live birth rate. No significant differences were observed in the pregnancy and live birth rates of D5 and D6 high-quality blastocysts. Conclusion: To achieve better pregnancy outcomes after PGT, considering blastocyst grading and biopsy dates when transferring embryos is essential for improving pregnancy outcomes. Furthermore, patients should adjust their BMI, endometrial receptivity, and endometrial thickness and pattern.

The Role of the Endometrium in Implantation: A Modern View.

According to the current data, the endometrium acts as a "sensor" of embryo quality, which promotes the implantation of euploid embryos and prevents the implantation and/or subsequent development of genetically abnormal embryos. The present review addresses the nature of the "sensory function" of the endometrium and highlights the necessity for assessing its functional status. The first section examines the evolutionary origin of the "sensory" ability of the endometrium as a consequence of spontaneous decidualization that occurred in placental animals. The second section details the mechanisms for implementing this function at the cellular level. In particular, the recent findings of the appearance of different cell subpopulations during decidualization are described, and their role in implantation is discussed. The pathological consequences of an imbalance among these subpopulations are also discussed. Finally, the third section summarizes information on currently available clinical tools to assess endometrial functional status. The advantages and disadvantages of the approaches are emphasized, and possible options for developing more advanced technologies for assessing the "sensory" function of the endometrium are proposed.

Correlation of hysteroscopic findings of chronic endometritis with CD138 immunohistochemistry and their correlation with pregnancy outcomes.

PURPOSE: To investigate the correlation between hysteroscopic findings of chronic endometritis and CD138 immunohistochemistry positive in endometritis and to analyze the pregnancy outcomes and associated risk factors following embryo transfer in women diagnosed with chronic endometritis via hysteroscopy. METHODS: A retrospective observational study carried out at the Reproductive Medicine Center of Tangdu Hospital of Air Force Medical University, from January 2021 to December 2021, was performed by obtaining data from 194 medical records of women who underwent hysteroscopies for infertility and were diagnosed with chronic endometritis based on Delphi criteria. Spearman correlation analysis was used to evaluate the correlation between hysteroscopic findings and endometrial CD138 immunohistochemistry. The study also observed the differences in relevant indexes between the CD138-positive and CD138-negative groups after embryo transfer and analyzed factors influencing implantation failure using logistic regression analysis. RESULTS: The correlation analysis between hysteroscopic findings and CD138 immunohistochemistry showed that micropolyps were correlated with CD138 immunohistochemistry positivity. The correlation coefficient was 0.32 (P < 0.01). After embryo transfer, the clinical pregnancy rate of the CD138-positive group was lower compared to that of the CD138-negative group [64.79% (46/71) vs. 81.30% (100/123), P < 0.05]. The results of the multivariate logistic regression analysis revealed that age (P = 0.43) and CD138 immunohistochemistry positivity (P = 0.008) were the independent risk factors for predicting whether or not embryo implantation was successful. CONCLUSION: Hysteroscopic findings do not correlate strongly with endometrial CD138 immunohistochemistry, and chronic endometritis cannot be diagnosed by hysteroscopy alone. CD138 immunohistochemistry positivity is an independent factor contributing to the decrease in clinical pregnancy rate following embryo transfer.

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.

Angiogenic factor-driven improvement of refractory thin endometrium with autologous platelet-rich plasma intrauterine infusion in frozen embryo transfer cycles.

Objective: A beneficial effect on endometrial thickness (EMT) and improvement of pregnancy outcome after intrauterine infusion of platelet-rich plasma (PRP) has been suggested. This study assessed the effect of intrauterine PRP infusion on live birth rate and obstetrical outcomes and analyzed cytokines that can potentially improve pregnancy outcomes through PRP. Method: This study was a prospective cohort study conducted in a university hospital fertility center. The study included ninety-one patients who had a history of two or more failed in vitro fertilization (IVF) attempts and refractory thin endometrium that remained unresponsive after at least two conventional treatments for thin endometrium. Patients were treated with an intrauterine infusion of autologous PRP between days 7 and 14 of their hormone replacement therapy-frozen embryo transfer (HRT-FET) cycle. PRP was administered at 3-day intervals until their EMT reached 7mm. After a maximum of three PRP administrations, embryo transfer (ET) was performed. The primary outcome was the live birth rate. Secondary outcomes included the implantation rate and increase in EMT compared to the previous cycle. We compared the cytokines related to angiogenesis in a patient's whole blood (WB) and PRP by utilizing a commercial screening kit. Results: The live birth rate in the PRP treatment cycle was 20.9% (19 of 91 patients), significantly superior to the previous cycle without PRP infusion (p < 0.001). The implantation rate was also significantly higher during the PRP treatment cycle (16.4%) compared to the previous cycle (3.1%) (p < 0.001). The mean EMT post-PRP treatment was 6.1 mm, showing a significant increase of 0.8 mm (p < 0.001). Nonetheless, an increase in EMT was also observed in the non-pregnancy group. No adverse effects were reported by patients treated with autologous PRP. Cytokine array analysis confirmed marked increases in well-known pro-angiogenic factors such as Ang-1, EGF, LAP (TGF-b1), MMP-8, PDGF-AA, and PDGF-AB/PDGF-BB. Conclusion: Intrauterine PRP infusion offers a safe and effective treatment for patients with refractory thin endometrium and implantation failures. The angiogenic cytokines present in PRP are the primary drivers of this improvement.

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

Background: 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. Objective: To develop and validate an ML model that employs radiomic features derived from multimodal transvaginal ultrasound images, focusing on improving ER evaluation in RPL. Methods: 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. Results: 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. Conclusion: 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.

Exogenous melatonin ameliorates embryo-maternal cross-talk in early pregnancy in sheep.

In brief: Melatonin plays a crucial role in enhancing reproductive performance in small ruminants. This paper reveals the effects of exogenous melatonin on the placental and endometrial rearrangement in early pregnancy in sheep. Abstract: Early pregnancy losses cause 25% of pregnancy failures in small ruminants because of asynchrony between conceptus and uterine signals. In this context, melatonin plays a crucial role in sheep reproductive dynamics, but little is known about its effects during the peri-implantation period. We hypothesized that melatonin supports embryo implantation by modulating the uterine microenvironment. This study aimed to assess the effects of exogenous melatonin on the endometrial and early placental rearrangement. Ten multiparous ewes either did (MEL, n = 5) or did not (CTR, n = 5) receive a subcutaneous melatonin implant (18 mg) 50 days before a synchronized mating. On day 21 of pregnancy, the sheep were euthanized. MEL ewes exhibited a higher prolificity rate (2.8 vs 2.0 embryos/ewe) and plasma progesterone levels (3.84 vs 2.96 ng/mL, P < 0.05) than did CTR ewes. Groups did not differ significantly in embryo crown-rump length. MEL placentas had significantly (P < 0.001) more binucleated trophoblast cells in the chorion region, and ovine placental lactogen expression was significantly (P < 0.05) more strongly upregulated than in CTR. Exogenous melatonin increased significantly (P < 0.05) gene expression of angiogenic factors (VEGFA, VEGFR1, IGF1R), IFNAR2, and PR in the caruncular endometrium. Expression of the MT2 receptor in the endometrium and placenta was significantly (P < 0.05) higher in the MEL group. These results indicate that melatonin implants acted differentially on uterine and placental rearrangement. Melatonin increases differentiation in the placenta and induces changes that could promote vessel maturation in the endometrium, suggesting that it enhances the uterine microenvironment in the early stage of pregnancy in sheep.

Protective effects of engineered Lactobacillus crispatus strains expressing G-CSF on thin endometrium of mice.

STUDY QUESTION: Does recombinant Lactobacillus expressing granulocyte colony-stimulating factor (G-CSF) have a better protective effect than the current treatment of thin endometrium (TE)? SUMMARY ANSWER: This study suggested that the intrauterine injection of Lactobacillus crispastus (L. crispastus)-pPG612-G-CSF has a positive effect on preventing TE induced by 95% alcohol in mice. WHAT IS KNOWN ALREADY: TE has a negative impact on the success rate of ART in patients, and is usually caused by intrauterine surgery, endometrial infection, or hormone drugs. Exogenous G-CSF can promote endometrial vascular remodelling and increase endometrial receptivity and the embryo implantation rate. Moreover, Lactobacillus plays a crucial role in maintaining and regulating the local microecological balance of the reproductive tract, and it could be a delivery carrier of the endometrial repair drug G-CSF. STUDY DESIGN, SIZE, DURATION: We constructed engineered L. crispastus strains expressing G-CSF. The mice were divided into five groups: (i) Control group (C, n = 28), uteri were treated with preheated saline solution via intrauterine injection on the third and sixth day of oestrus; (ii) Model group (M, n = 35), where uteri were treated with 95% alcohol on the third day of oestrus and preheated saline solution on the sixth day of oestrus via intrauterine injection; (iii) L. crispatus-pPG612-treatment group (L, n = 45), where uteri were treated with 95% alcohol on the third day of oestrus and 0.1 ml × 108 CFU/ml L. crispatus-pPG612 on the sixth day of oestrus via intrauterine injection; (iv) L. crispatus-pPG612-treatment group (LG, n = 45), where uteri were treated with 95% alcohol on the third day of oestrus and 0.1 ml × 108 CFU/ml L. crispatus-pPG612-G-CSF on the sixth day of oestrus via intrauterine injection; (v) G-CSF-treatment group (G, n = 52), where uteri were treated with 95% alcohol on the third day of oestrus and 30 µg/kg G-CSF on the sixth day of oestrus via intrauterine injection. Then, we compared the effects of L. crispastus, L. crispatus-pPG612-G-CSF and G-CSF on endometrial thickness, angiogenesis, fibrosis, and inflammation in the TE mouse. PARTICIPANTS/MATERIALS, SETTING, METHODS: We collected uterine tissues for haematoxylin-eosin staining, immunohistochemical staining, Western blot and RT-PCR, as well as serum for ELISA and uterine flushing solution for high-throughput sequencing. MAIN RESULTS AND THE ROLE OF CHANCE: Compared with those in the M group (the mice of the group were intrauterine injected 95% alcohol and treated with saline solution), the L. crispatus-pPG612-G-CSF strain increased the thickness of the endometrium (P < 0.001) and the number of blood vessels and glands (both P < 0.001), enhanced the expression of cytokeratin 19 (CK19) (P < 0.001), vimentin (Vim) (P < 0.001), vascular endothelial growth factor-A (P < 0.001), and CD34 (P < 0.001), and decreased fibrosis levels (P = 0.004). In addition, the high-throughput sequencing results indicated that the L. crispatus-pPG612-G-CSF strain could decrease the abundance of Pseudomonas (P = 0.044) and Actinomyces spp. (P = 0.094) in TE mice and increased the average number of embryos (P = 0.036). Finally, the L. crispatus-pPG612-G-CSF strain was preliminarily confirmed to activate the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) signalling pathway and enhance the mRNA expression of hypoxia-inducible factor-1α (P < 0.001), vascular endometrial growth factor (P = 0.003), and endothelial cell nitric oxide synthase (P = 0.003) in mouse uterine tissue. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Therapy with the L. crispatus-pPG612-G-CSF strain has tremendous potential to accelerate the reparative processes of TE. However, we have reported only the expression of genes and proteins related to the PI3K/AKT pathway, and numerous other mechanisms may also be involved in the restoration of the endometrium by L. crispatus-pPG612-G-CSF. WIDER IMPLICATIONS OF THE FINDINGS: The results from the study provide new ideas and suggest new methods for TE treatment. STUDY FUNDING/COMPETING INTEREST(S): This work was financially supported by the Project of Science and Technology Development Plan of Jilin Province (grant number 20210101232JC), the Science and Technology Plan Item of Jilin Provincial Education Department (grant number JT53101022010), and the Doctoral Research Start-up Fund of Jilin Medical University (grant numbers JYBS2021014LK and 2022JYBS006KJ). The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.

[Construction of competitive endogenous RNA regulatory network and clinical verification for repeated implantation failure].

Objective: To construct a repetitive implantation failure (RIF)-related competitive endogenous RNA (ceRNA) regulatory network and validate with clinical samples. Methods: RIF-related long non-coding RNA (lncRNA), microRNA (miRNA) and messenger RNA (mRNA) from the high-throughput gene expression omnibus (GEO) database Expression profile data set were obtained to construct a ceRNA regulatory network of lncRNA-miRNA-mRNA. At the same time, weighted gene co-expression network analysis (WGCNA) was used to explore hub genes in the network. This retrospective study collected RIF patients and controls (at least one pregnancy history after assisted conception) who underwent in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) for assisted pregnancy from 2020 to 2021 at the Reproductive Medicine Center of the First Affiliated Hospital of Zhengzhou University. In the endometrial tissue of patients with 1 pregnancy history, real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) was used to verify the mRNA expression levels of RIF-related hub genes, and Western blotting and immunohistochemistry were used to verify protein expression levels of vascular cell adhesion molecule-1 (VCAM1). Results: A RIF-related ceRNA regulatory network consisting of 32 lncRNAs, 31 miRNAs and 88 mRNAs was constructed, and 7 RIF-related hub genes were identified using WGCNA. By intersecting 88 mRNAs and hub genes in the ceRNA network, two RIF-related key genes were obtained, i.e., VCAM1 and interleukin-2 receptor α (interleukin-2 receptor α, IL-2RA). In clinical verification, the ages of the control group and RIF group [M (Q1, Q3)] were 26.50 (25.00, 34.00) and 30.50 (25.75, 35.25) years old, respectively (P>0.05). Compared with the control group, the mRNA [0.30 (0.15, 0.42) vs 0.99 (0.69, 1.34), P=0.001] and protein expression [0.44 (0.16, 1.27) vs 2.39 (1.58, 2.58), P<0.001] of VCAM1 in the endometrium of the RIF group were both reduced. Conclusions: This study uses bioinformatics analysis methods to construct a RIF-related ceRNA regulatory network, and it is confirmed through clinical samples that the expression level of VCAM1 in the endometrial tissue of RIF patients is significantly reduced.

Enhancing uterine receptivity for embryo implantation through controlled collagenase intervention.

Ineffective endometrial matrix remodeling, a key factor in infertility, impedes embryo implantation in the uterine wall. Our study reveals the cellular and molecular impact of human collagenase-1 administration in mouse uteri, demonstrating enhanced embryo implantation rates. Collagenase-1 promotes remodeling of the endometrial ECM, degrading collagen fibers and proteoglycans. This process releases matrix-bound bioactive factors (e.g., VEGF, decorin), facilitating vascular permeability and angiogenesis. Collagenase-1 elevates embryo implantation regulators, including NK cell infiltration and the key cytokine LIF. Remarkably, uterine tissue maintains structural integrity despite reduced endometrial collagen fiber tension. In-utero collagenase-1 application rescues implantation in heat stress and embryo transfer models, known for low implantation rates. Importantly, ex vivo exposure of human uterine tissue to collagenase-1 induces collagen de-tensioning and VEGF release, mirroring remodeling observed in mice. Our research highlights the potential of collagenases to induce and orchestrate cellular and molecular processes enhancing uterine receptivity for effective embryo implantation. This innovative approach underscores ECM remodeling mechanisms critical for embryo implantation.

Differential expression of ion channel coding genes in the endometrium of women experiencing recurrent implantation failures.

Our study probed the differences in ion channel gene expression in the endometrium of women with Recurrent Implantation Failure (RIF) compared to fertile women. We analyzed the relative expression of genes coding for T-type Ca2+, ENaC, CFTR, and KCNQ1 channels in endometrial samples from 20 RIF-affected and 10 control women, aged 22-35, via microarray analysis and quantitative real-time PCR. Additionally, we examined DNA methylation in the regulatory region of KCNQ1 using ChIP real-time PCR. The bioinformatics component of our research included Gene Ontology analysis, protein-protein interaction networks, and signaling pathway mapping to identify key biological processes and pathways implicated in RIF. This led to the discovery of significant alterations in the expression of ion channel genes in RIF women's endometrium, most notably an overexpression of CFTR and reduced expression of SCNN1A, SCNN1B, SCNN1G, CACNA1H, and KCNQ1. A higher DNA methylation level of KCNQ1's regulatory region was also observed in RIF patients. Gene-set enrichment analysis highlighted a significant presence of genes involved with ion transport and membrane potential regulation, particularly in sodium and calcium channel complexes, which are vital for cation movement across cell membranes. Genes were also enriched in broader ion channel and transmembrane transporter complexes, underscoring their potential extensive role in cellular ion homeostasis and signaling. These findings suggest a potential involvement of ion channels in the pathology of implantation failure, offering new insights into the mechanisms behind RIF and possible therapeutic targets.

Adiponectin receptor 1 regulates endometrial receptivity via the adenosine monophosphate­activated protein kinase/E­cadherin pathway.

Endometrial receptivity is essential for successful embryo implantation and pregnancy initiation and is regulated via various signaling pathways. Adiponectin, an important adipokine, may be a potential regulator of reproductive system functions. The aim of the present study was to elucidate the regulatory role of adiponectin receptor 1 (ADIPOR1) in endometrial receptivity. The endometrial receptivity between RL95­2 and AN3CA cell lines was confirmed using an in vitro JAr spheroid attachment model. 293T cells were transfected with control or short hairpin (sh)ADIPOR1 vectors and RL95­2 cells were transduced with lentiviral particles targeting ADIPOR1. Reverse transcription­quantitative PCR and immunoblot assays were also performed. ADIPOR1 was consistently upregulated in the endometrium during the mid­secretory phase compared with that in the proliferative phase and in receptive RL95­2 cells compared with that in non­receptive AN3CA cells. Stable cell lines with diminished ADIPOR1 expression caused by shRNA showed reduced E­cadherin expression and attenuated in vitro endometrial receptivity. ADIPOR1 regulated AMP­activated protein kinase (AMPK) activity in endometrial epithelial cells. Regulation of AMPK activity via dorsomorphin and 5­aminoimidazole­4­carboxamide ribonucleotide affected E­cadherin expression and in vitro endometrial receptivity. The ADIPOR1/AMPK/E­cadherin axis is vital to endometrial receptivity. These findings can help improve fertility treatments and outcomes.

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 Current Understanding of Molecular Mechanisms in Adenomyosis-Associated Infertility and the Treatment Strategy for Assisted Reproductive Technology.

Adenomyosis, endometriosis of the uterus, is associated with an increased likelihood of abnormal endometrial molecular expressions thought to impair implantation and early embryo development, resulting in disrupted fertility, including the local effects of sex steroid and pituitary hormones, immune responses, inflammatory factors, and neuroangiogenic mediators. In the recent literature, all of the proposed pathogenetic mechanisms of adenomyosis reduce endometrial receptivity and alter the adhesion molecule expression necessary for embryo implantation. The evidence so far has shown that adenomyosis causes lower pregnancy and live birth rates, higher miscarriage rates, as well as adverse obstetric and neonatal outcomes. Both pharmaceutical and surgical treatments for adenomyosis seem to have a positive impact on reproductive outcomes, leading to improved pregnancy and live birth rates. In addition, adenomyosis has negative impacts on reproductive outcomes in patients undergoing assisted reproductive technology. This association appears less significant after patients follow a long gonadotropin-releasing hormone agonist (GnRHa) protocol, which improves implantation rates. The pre-treatment of GnRHa can also be beneficial before engaging in natural conception attempts. This review aims to discover adenomyosis-associated infertility and to provide patient-specific treatment options.

Vaginal and endometrial microbiome dysbiosis associated with adverse embryo transfer outcomes.

BACKGROUND: Assisted reproductive technology (ART) is the most effective method to treat infertility and the pathogenesis of implantation failure after in vitro fertilization-embryo transfer (IVF-ET) is a challenging filed in infertility. Microbes in the female reproductive tract are considered to be associated with gynecological and obstetric diseases. However, its effects on embryo implantation failure are unsured. PURPOSE: This study aimed to investigate reproductive tract dysbiosis, identify different bacteria in reproductive tract as potential biomarkers of embryo implantation failure and demonstrate the pathogenesis through metabolites analysis. METHODS: We compared the data from 16S rRNA gene and metagenome in reproductive tracts through QIIME2 and HUMAnN2 by the times of embryo implantation failure on 239 infertile patients and 17 healthy women. RESULTS: Our study revealed a strong positive correlation between Lactobacillus abundance and embryo implantation success (IS) after IVF-ET. The microbial community composition and structure in reproductive tract showed substantially difference between the embryo implantation failure (IF) and healthy control. Moreover, we established a diagnostic model through receiver operating characteristic (ROC) with 0.913 area under curve (AUC) in IS and multiple implantation failures (MIF), verified its effectiveness with an AUC = 0.784 demonstrating microbial community alterations could efficiently discriminate MIF patients. Metagenome functional analyses of vaginal samples from another independent infertile patients after IVF-ET revealed the L-lysine synthesis pathway enriched in IF patients, along with ascended vaginal pH and decreased Lactobacillus abundance. CONCLUSIONS: This study clarifies several independent relationships of bacteria in vagina and endometrial fluid on embryo implantation failure and undoubtedly broadens the understanding about female reproductive health.

Decidualized Endometrial Stromal Cells Promote Mitochondrial Beta-Oxidation to Produce the Octanoic Acid Required for Implantation.

Decidualization denotes the morphological and biological differentiating process of human endometrial stromal cells (HESCs). Fatty acid pathways are critical for endometrial decidualization. However, the participation of fatty acids as an energy source and their role in endometrial decidualization have received little attention. To identify fatty acids and clarify their role in decidualization, we comprehensively evaluated free fatty acid profiles using liquid chromatography/Fourier transform mass spectrometry (LC/FT-MS). LC/FT-MS analysis detected 26 kinds of fatty acids in the culture medium of decidualized or un-decidualized HESCs. Only the production of octanoic acid, which is an essential energy source for embryonic development, was increased upon decidualization. The expressions of genes related to octanoic acid metabolism including ACADL, ACADM, and ACADS; genes encoding proteins catalyzing the first step of mitochondrial fatty acid beta-oxidation; and ACSL5 and ACSM5; genes encoding fatty acid synthesis proteins were significantly altered upon decidualization. These results suggest that decidualization promotes lipid metabolism, implying that decidualized HESCs require energy metabolism of the mitochondria in embryo implantation.