Search Results (48)

Recurrent implantation failure (RIF) remains a challenging clinical problem. Growth hormone (GH) co-treatment has been explored as an adjunct in poor responders and RIF patients, with inconsistent evidence of benefit. This prospective cohort study assessed the impact of GH supplementation in 91 RIF patients undergoing in vitro fertilization, stratified by FSHR (follicular stimulating hormone receptor) genotype Asn680Ser with or without GH supplementation. Patients were stratified by FSHR genotype into homozygous Ser/Ser versus Ser/Asn or Asn/Asn groups. Overall, GH co-treatment conferred modest benefits in the unselected RIF cohort, limited to a higher cumulative live birth rate compared to controls and elevated leukemia inhibitory factor (LIF) levels (p < 0.05 both). When stratified by FSHR genotype, the Ser/Ser subgroup exhibited markedly better outcomes with GH. These patients showed a higher (0.5 vs. 0.33, p = 0.003), produced more embryos (2.88 vs. 1.53, p = 0.02), and had a markedly improved cumulative live birth rate—50% with GH versus 13% without—highlighting a clinically meaningful benefit of GH in the Ser/Ser subgroup. No significant benefit was observed in Asn allele carriers. These findings suggest that FSHR genotyping may help optimize treatment selection in RIF patients by identifying those most likely to benefit from GH supplementation. Full article

Understanding the molecular basis of endometrial receptivity is crucial for improving implantation outcomes in assisted reproduction, especially for patients with recurrent implantation failure (RIF). This study investigates the timing relationship between microRNA (miRNA) and messenger RNA (mRNA) profiles in the endometrium using simultaneously the endometrial receptivity array (ERA) and the microRNA receptivity assay (MIRA) in 100 RIF patients undergoing euploid blastocyst transfer. The concordance rate between ERA and MIRA was 72% (Kappa = 0.50), suggesting partial overlap in profiling. Patients were stratified by the timing sequence of miRNA relative to mRNA into Fast, Equal, and Slow groups. Those with delayed miRNA expression (Slow group) had significantly lower pregnancy rates (54.5%) than those with synchronous or leading miRNA expression (81.9% and 94.1%, respectively; p = 0.031). Moreover, the Slow group exhibited higher prior implantation failure counts and altered expression in 15 miRNAs, many involved in aging-related pathways. These findings highlight that asynchronous miRNA–mRNA profiles may reflect impaired receptivity and suggest that miRNA-based staging adds valuable diagnostic insight beyond mRNA profiling alone. Dual assessment of mRNA and miRNA profiles may offer additional diagnostic insight into endometrial receptivity but requires further validation before clinical application. Full article

Background: Recurrent implantation failure (RIF) poses a major challenge in assisted reproductive technologies, with thin endometrium (≤7 mm) being a frequently observed yet poorly understood condition. Emerging evidence implicates nuclear factor-kappa B (NF-κB), a key transcription factor in inflammatory signaling, in impaired endometrial receptivity. However, its clinical relevance and prognostic value for live birth outcomes still need to be fully elucidated. Objective: We aim to evaluate the expression levels of endometrial NF-κB in patients with RIF and thin endometrium and to determine its potential as a predictive biomarker for live birth outcomes following IVF treatment. Methods: In this prospective case–control study, 158 women were categorized into three groups: Group 1 (RIF with thin endometrium, ≤7 mm, n = 52), Group 2 (RIF with normal endometrium, >7 mm, n = 38), and fertile controls (n = 68). NF-κB levels were assessed using ELISA and immunohistochemical histoscore. Pregnancy outcomes were compared across groups. ROC analysis and multivariable logistic regression were performed to assess the predictive value of NF-κB. Results: NF-κB expression was significantly elevated in Group 1 compared to Group 2 and controls (p = 0.0017). ROC analysis identified a cut-off value of 7.8 ng/mg for live birth prediction (AUC = 0.72, sensitivity 74%, specificity 75%). Multivariable analysis confirmed NF-κB is an independent predictor of live birth (p = 0.045). Histological findings revealed increased NF-κB staining in luminal and glandular epithelial cells in the thin endometrium group. Conclusions: Increased endometrial NF-κB expression is associated with thin endometrium and reduced live birth rates in RIF patients. NF-κB may serve not only as a biomarker of pathological inflammation but also as a prognostic tool for treatment stratification in IVF. Based on findings in the literature, the therapeutic targeting of NF-κB may represent a promising strategy to improve implantation outcomes. Full article

Bifenthrin (BF) is a widely used pyrethroid pesticide recognized as an endocrine-disrupting chemical (EDC). Previous studies have confirmed that chronic exposure to BF is associated with various health risks. However, its potential association with recurrent implantation failure (RIF) and recurrent pregnancy loss (RPL) remains unclear. In this study, the potential targets of BF were identified using several databases, including the Comparative Toxicogenomics Database (CTD), TargetNet, GeneCards, SwissTargetPrediction, and STITCH. Differentially expressed genes (DEGs) associated with RIF were obtained from bulk RNA-seq datasets in the GEO database. Candidate targets were identified by intersecting the predicted BF-related targets with the RIF-associated DEGs, followed by functional enrichment analysis using the DAVID and g:Profiler platforms. Subsequently, hub genes were identified based on the STRING database and Cytoscape. A diagnostic model was then constructed based on these hub genes in the RIF cohort and validated in an independent recurrent pregnancy loss (RPL) cohort. Additionally, we performed single-cell type distribution analysis and immune infiltration profiling based on single-cell RNA-seq and bulk RNA-seq data, respectively. Molecular docking analysis using AutoDock Vina was conducted to evaluate the binding affinity between BF and the four hub proteins, as well as several hormone-related receptors. Functional enrichment results indicated that the candidate genes were mainly involved in apoptotic and oxidative stress-related pathways. Ultimately, four hub genes—BCL2, HMOX1, CYCS, and PTGS2—were identified. The diagnostic model based on these genes exhibited good predictive performance in the RIF cohort and was successfully validated in the RPL cohort. Single-cell transcriptomic analysis revealed a significant increase in the proportion of myeloid cells in RPL patients, while immune infiltration analysis showed a consistent downregulation of M2 macrophages in both RIF and RPL. Moreover, molecular docking analysis revealed that BF exhibited high binding affinity to all four hub proteins and demonstrated strong binding potential with multiple hormone receptors, particularly pregnane X receptor (PXR), estrogen receptor α (ESRα), and thyroid hormone receptors (TR). In conclusion, the association of BF with four hub genes and multiple hormone receptors suggests a potential link to immune and endocrine dysregulation observed in RIF and RPL. However, in vivo and in vitro experimental evidence is currently lacking, and further studies are needed to elucidate the mechanisms by which BF may contribute to RIF and RPL. Full article

Background: Endometrial receptivity is crucial for successful embryo implantation in assisted reproductive technologies (ARTs). MicroRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) have emerged as important post-transcriptional regulators of endometrial function, although their diagnostic and molecular functions are poorly understood. Methods: A systematic review was conducted following PRISMA 2020 principles and registered in PROSPERO (CRD420251001811). We looked at 28 peer-reviewed publications published between 2010 and 2025 that used endometrial tissue, blood, uterine fluid, saliva, and embryo culture medium to study miRNAs and other non-coding RNAs in endometrial receptivity, recurrent implantation failure (RIF), and infertility. Results: MiRNAs like miR-145, miR-30d, miR-223-3p, and miR-125b influence implantation-related pathways such as HOXA10, LIF-STAT3, PI3K-Akt, and Wnt/β-catenin. Dysregulated expression profiles were linked to inadequate decidualization, immunological imbalance, and poor angiogenesis. CeRNA networks that include lncRNAs (e.g., H19 and NEAT1) and circRNAs (e.g., circ_0038383) further regulate miRNA activity. Non-invasive biomarkers derived from plasma, uterine fluid, and embryo media showed high prediction accuracy for implantation outcomes. Conclusions: MiRNA signatures offer a functional and diagnostic blueprint for endometrial receptivity. This systematic review provides a timely and thorough synthesis of the existing literature, with the goal of bridging the gap between molecular discoveries and therapeutic applications. By emphasizing both the mechanistic importance and diagnostic value of certain miRNA signatures, it paves the way for future precision-based techniques in embryo transfer and endometrial assessment in ART. Full article

Fertility is a dynamic, multifactorial process governed by hormonal, immune, metabolic, and environmental factors. Recent evidence highlights the gut microbiota as a key systemic regulator of reproductive health, with notable impacts on endometrial function, implantation, pregnancy maintenance, and the timing of birth. This review examines the gut–endometrial axis, focusing on how gut microbial communities influence reproductive biology through molecular signaling pathways. We discuss the modulatory roles of microbial-derived metabolites—including short-chain fatty acids, bile acids, and tryptophan catabolites—in shaping immune tolerance, estrogen metabolism, and epithelial integrity at the uterine interface. Emphasis is placed on shared mechanisms such as β-glucuronidase-mediated estrogen recycling, Toll-like receptor (TLR)-driven inflammation, Th17/Treg cell imbalance, and microbial translocation, which collectively implicate dysbiosis in the etiology of gynecological disorders including endometriosis, polycystic ovary syndrome (PCOS), recurrent implantation failure (RIF), preeclampsia (PE), and preterm birth (PTB). Although most current evidence remains correlational, emerging insights from metagenomic and metabolomic profiling, along with microbiota-depletion models and Mendelian randomization studies, underscore the biological significance of gut-reproductive crosstalk. By integrating concepts from microbiology, immunology, and reproductive molecular biology, this review offers a systems-level perspective on host–microbiota interactions in female fertility. Full article

Microorganisms play an important role in regulating various biological processes in our bodies. In women, abnormal changes in the reproductive tract microbiome are associated with various gynecological diseases and infertility. Recent studies suggest that patients with recurrent implantation failure (RIF) have a reduced genus Lactobacillus population, a predominant bacterial species in the vagina and uterus that protects the reproductive tract from pathogenic bacterial growth via the production of various metabolites (e.g., lactic acid, bacteriocin, and H₂O₂). Moreover, a higher percentage of pathogenic bacteria genera, including Atopobium, Gardnerella, Prevotella, Pseudomonas, and Streptococcus, was found in the uterus of RIF patients. This review aimed to examine the role of pathogenic bacteria in RIF, determine the factors altering the endometrial microbiome, and assess the impact of the microbiome on embryo implantation in RIF. Several factors can influence microbial balance, including the impact of extrinsic elements such as semen and antibiotics, which can lead to dysbiosis in the female reproductive tract and affect implantation. Additionally, probiotics such as Lacticaseibacillus rhamnosus were reported to have clinical potential in RIF patients. Future studies are needed to develop targeted probiotic therapies to restore microbial balance and enhance fertility outcomes. Research should also focus on understanding the mechanisms by which microorganisms generate metabolites to suppress pathogenic bacteria for embryo implantation. Identifying these interactions may contribute to innovative microbiome-based interventions for reproductive health. Full article

Background: Vascular Endothelial Growth Factor (VEGF) is a key regulator in angiogenesis and contributes to a successful implantation. The current study has the following objective: to perform genotyping and haplotyping analysis to confirm whether the VEGF-936C/T, VEGF-634C/G, and VEGF-2578C/A gene polymorphisms are associated with the susceptibility for recurrent implantation failure (RIF) in Romanian females at reproductive age. Materials and Methods: In total, 41 infertile women experiencing recurrent implantation failure and 44 women with minor infertility were genotyped for VEGF polymorphisms using PCR-RFLP analysis. Results: The VEGF-936C/T polymorphism in the dominant model, (C/T+T/T), represents an increased risk factor for recurrent implantation failure, the odds being 2.70 (95% CI: [1.04, 7.00]). Also, VEGF-2578C/A gene polymorphism represents the risk factor of RIF under the codominant (adjusted-OR = 5.28, 95% CI: [1.42, 19.65]) and recessive models (adjusted-OR = 5.15, 95% CI: [1.55, 17.09]). Patients carrying the VEGF-T936 allele or VEGF-C2578 allele had 2.25-fold and 2.36-fold increased odds of implantation failure (95% CI: [1.05, 4.81], p = 0.034) and 95% CI: [1.27, 4.39], p = 0.006), respectively. The results of the haplotype-based regression analysis reveal that patient carriers of the VEGF-936/-634/-2578 T-C-A haplotype had 12.39 increased odds of RIF. Also, carriers of the VEGF-936/-2578 T-A haplotype had 9.56-fold (p = 0.0113) increased odds of RIF after adjusting for age. Conclusions: We found a significant association between VEGF-936C/T and VEGF-2578C/A polymorphisms and the odds of RIF in this cohort of Romanian infertile women. Haplotype analysis suggested the role of VEGF-936/-634/-2578 T-C-A and VEGF-936/-2578 T-A haplotypes as a risk factors for RIF. Full article

Recurrent pregnancy loss (RPL) is defined as the occurrence of two or more consecutive pregnancy losses before 24 weeks of gestation. It affects 3–5% of women who are attempting to conceive. RPL can stem from a variety of causes and is frequently associated with psychological distress and a diminished quality of life. By contrast, recurrent implantation failure (RIF) refers to the inability to achieve a successful pregnancy after three or more high-quality embryo transfers or at least two instances of egg donation. RIF shares several causative factors with RPL. The immunological underpinnings of these conditions involve alterations in uterine NK cells, reductions in M2 macrophages and myeloid-derived suppressor cells, an increased Th1/Th2 ratio, a decreased Treg/Th17 ratio, the presence of shared ≥3 HLA alleles between partners, and autoimmune disorders. Various therapeutic approaches have been employed to address these immunological concerns, achieving varying degrees of success, although some therapies remain contentious within the medical community. This review intends to explore the immunological factors implicated in RPL and RIF and to analyze the immunological treatments employed for these conditions, which may include steroids, intravenous immunoglobulins, calcineurin inhibitors, anti-TNF antibodies, intralipid infusions, granulocyte colony-stimulating factor, and lymphocyte immunotherapy. Full article

Objectives: The downregulation of anti-adhesive regulatory proteins and upregulation of adhesive genes are critical for the receptive endometrium. This study was designed to determine whether switching between the anti-adhesive podocalyxin (PDX) and adhesive HOXA10 receptivity modulator occurs in the endometrium of women with recurrent implantation failure (RIF). Methods: Twenty-four patients with RIF who could not conceive for three or more cycles despite good-quality embryo transfer constituted the study group. Twenty-four patients with unexplained infertility (UEI) matched for age, BMI, and infertility duration were included in the control group. Twenty women scheduled to undergo intrauterine device (IUD) placement for birth control were included in the comparative group. Endometrial tissue was collected from patients with RIF and UEI during egg retrieval after ovarian stimulation using the GnRH antagonist protocol. In the fertile group, endometrial tissues were collected during IUD insertion. HOXA10 mRNA expression was analyzed by qRT-PCR and PDX protein expression was analyzed by ELISA. The relative expression of endometrial HOXA10 mRNA was calculated using the 2^−ΔΔCt equation. Results: The relative expression of HOXA10 mRNA in the RIF group was significantly lower than that in the UEI group (p < 0.001). HOXA10 mRNA expression in the fertile group was significantly higher than that in the RIF group and was similar to that in the UEI group. PDX expression in the RIF group was significantly higher than that in the UEI group (p < 0.001). PDX expression in the fertile group was significantly lower than in the RIF and UEI groups. A negative correlation was detected between the anti-adhesive PDX protein and adhesive HOXA10 (r = −0.797, p < 0.001). Although there was a positive correlation between endometrial thickness recorded on the day of hCG administration and HOXA10 (r = 0.590, p < 0.01), endometrial thickness was negatively correlated with PDX (r = −0.529, p < 0.01). Conclusions: The failed physiological downregulation of the anti-adhesive PDX protein in patients with RIF prevented the upregulation of adhesive HOXA10 mRNA. Full article

Background: This prospective study aims to identify the effect of the dienogest 2 mg/day and aspirin 150 mg/day combined treatment for two months before frozen ET on the assisted reproduction outcome in women with adenomyosis and recurrent implantation failure (RIF). Methods: Patients were selected based on specific criteria and divided into two groups (with and without treatment). Preimplantation biochemical parameters and ultrasonographic features (endometrial thickness, uterine peristalsis, and junctional zone thickness) were compared with pregnancy rate in a non-natural cycle frozen embryo transfer technique. A comparison between the two study groups indicated an increased successful implantation rate and clinical pregnancy rate (25% vs. 7.4%). Results: These results were attributed to the reduced uterine peristalsis and the reduction in thickness of the junctional zone following treatment. Available data were limited due to the nature of the study though maximal effort was exerted for the selected patients between groups to be as demographically similar and free from other potential pathology that may affect the results. Conclusions: In conclusion, it appears that the above stated treatment improves outcomes in women with adenomyosis and RIF; the parameters used may provide an insight as to the reasons why this occurs, though an explanation of the molecular mechanisms is still elusive. Full article

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). Full article

Recurrent Pregnancy Loss (RPL) affects 1–2% of women, and its triggering factors are unclear. Several studies have shown that the vaginal, endometrial, and gut microbiota may play a role in RPL. A decrease in the quantity of Lactobacillus crispatus in local microbiota has been associated with an increase in local (vaginal and endometrial) inflammatory response and immune cell activation that leads to pregnancy loss. The inflammatory response may be triggered by gram-negative bacteria, lipopolysaccharides (LPS), viral infections, mycosis, or atypia (tumor growth). Bacterial structures and metabolites produced by microbiota could be involved in immune cell modulation and may be responsible for immune cell activation and molecular mimicry. Gut microbiota metabolic products may increase the amount of circulating pro-inflammatory lymphocytes, which, in turn, will migrate into vaginal or endometrial tissues. Local pro-inflammatory Th1 and Th17 subpopulations and a decrease in local Treg and tolerogenic NK cells are accountable for the increase in pregnancy loss. Local microbiota may modulate the local inflammatory response, increasing pregnancy success. Analyzing local and gut microbiota may be necessary to characterize some RPL patients. Although oral supplementation of probiotics has not been shown to modify vaginal or endometrial microbiota, the metabolites produced by it may benefit patients. Lactobacillus crispatus transplantation into the vagina may enhance the required immune tolerogenic response to achieve a normal pregnancy. The effect of hormone stimulation and progesterone to maintain early pregnancy on microbiota has not been adequately studied, and more research is needed in this area. Well-designed clinical trials are required to ascertain the benefit of microbiota modulation in RPL. Full article

Background and Objectives: Recurrent implantation failure (RIF) affects 10% of couples undergoing in vitro fertilization (IVF), spurring exploration into tailored treatments to enhance implantation rates. Maternal immune tolerance towards embryos, particularly killer-cell immunoglobulin-like receptors (KIRs) on natural killer (NK) cells, is a focal point in RIF research. Materials and Methods: This retrospective cohort study, conducted at fertility clinic in Oradea, Romania, involved 65 infertile couples undergoing IVF treatment between January 2022 and December 2023. Couples were divided into two groups: KIR AA (Group A) and KIR Bx (Group B). Results: Factors such as age, type of infertility, oocytes retrieved, embryos produced, pregnancy rates in Group A without and with immunomodulatory treatment were documented. Group A, receiving immunomodulatory treatment, achieved a pregnancy rate of 47.8%, significantly higher than the 23.73% rate without treatment (p = 0.008). Group B had a higher mean patient age than Group A. However, miscarriage rates did not significantly differ between Group A with treatment and Group B (p = 0.2457), suggesting comparable outcomes with immunomodulation. Conclusions: The impact of immunological factors on recurrent implantation failure is being more and more emphasized and warrants the attention of specialists in human reproduction. Uterine natural killers and their function though KIR receptors deserve particular attention as immunomodulatory treatment may improve pregnancy rates in patients with KIR AA haplotype. Full article

Recurrent implantation failure (RIF) poses a significant challenge in assisted reproductive technology (ART) outcomes. The endometrium plays a crucial role in embryo implantation, and its protein expression profile is integral in determining receptivity. Proteomics has emerged as a valuable tool in unraveling the molecular intricacies underlying endometrial receptivity and RIF. The aim of the present review is to analyze the contribution of proteomics to the understanding of endometrial protein expression in women with RIF, based on the results of significant proteomic studies. Medline/Pubmed databases were searched using keywords pertaining to proteomics combined with terms related to RIF. 15 studies were included in the present review. Several proteins have been found to exbibit differential expression in endometrial biopsies and fluid samples between fertile women and women with RIF during the receptive endometrial phase. The profile of endometrial proteins varied significantly among the studies. Nevertheless, similar changes in the expression levels of annexin-6, progesterone receptor, MMP-2, and MMP-9 in the endometrium of women with RIF, were found in more than one study indicating that certain proteins could potentially be effective biomarkers of endometrial receptivity. Proteomics contributes significantly to the understanding of protein expression in the endometrium of women with RIF and the analysis of proteins in endometrial fluid are promising for improving the clinical management of RIF. Full article