Search Results (200)

Successful embryo implantation requires dynamic, bidirectional communication between a developmentally competent blastocyst and a receptive endometrium, integrating hormonal, molecular, and immunologic signals. Increasing evidence indicates that endometrial receptivity is critically dependent on a specialized immune microenvironment that supports trophoblast invasion while maintaining maternal tolerance. This review synthesizes current knowledge on the immunologic regulation of implantation, with emphasis on uterine natural killer (uNK) cells, regulatory T cells (Tregs), macrophages, dendritic cells, and cytokine networks. We further examine intracellular signaling pathways—including JAK/STAT, PI3K/AKT, NF-κB, and MAPK—that integrate immune and decidual responses. The bidirectional embryo–endometrium dialogue is explored through embryo-derived mediators such as human chorionic gonadotropin (hCG), cytokines, growth factors, and extracellular vesicles. The endometrium is increasingly recognized as a biosensor of embryo quality, selectively supporting viable embryos. Disruption of this complex communication network is implicated in recurrent implantation failure and early pregnancy loss. Despite substantial mechanistic advances, clinical translation remains limited. Emerging strategies, including immune profiling, microbiome modulation, and extracellular vesicle-based diagnostics, hold promise for precision reproductive medicine. Full article

The supply of amino acids is essential to embryo survival and successful pregnancy. The accumulating evidence indicates that arginine, a semi-essential amino acid, plays a key role during early pregnancy. Arginase (ARG2) is a key enzyme for catalyzing arginine into ornithine and urea. However, the expression, regulation, and role of arginase during early mouse pregnancy are still unknown. In our study, ARG1 immunofluorescence is mainly detected in uterine epithelium and gradually decreases from days 1 to 5 of pregnancy. From days 1 to 4 of pregnancy, there is no detectable ARG2 immunofluorescence in the mouse uterus. On day 5 of pregnancy, ARG2 signals are strongly seen in the primary decidua surrounding the implanting blastocyst at the implantation site, but not at the inter-implantation site. There is a temporary increase for ARG2 levels under mouse in vitro decidualization, suggesting ARG2 may be involved in the initiation of mouse decidualization. Prl8a2, a marker of mouse in vitro decidualization, is significantly decreased after ARG levels are suppressed. However, Arg2 overexpression obviously increases Prl8a2 levels. Mouse in vitro decidualization is downregulated by arginine and ornithine but stimulated by a low dose of urea. Urea has a beneficial effect on uterine receptivity and antioxidative enzymes. Our results indicate that ARG2 plays an important role during mouse decidualization by balancing the levels of arginine, ornithine, and urea. Full article

Objective: To investigate the relationship between the number of previous implantation failures (IFs) and embryo ploidy status, as well as subsequent clinical outcomes, in women with recurrent implantation failure (RIF) undergoing preimplantation genetic testing for aneuploidy (PGT-A). Methods: This retrospective cohort study included 422 women with RIF who underwent their first PGT-A cycle between 2017 and 2022. Participants were stratified by maternal age (<38 years, n = 292; ≥38 years, n = 130) and by the number of previous IFs, categorized as 3, 4, or ≥5. The primary outcomes were embryo ploidy rates (euploidy, aneuploidy, and mosaicism). Secondary outcomes included reproductive outcomes after single euploid blastocyst transfer (biochemical pregnancy, clinical pregnancy, ongoing pregnancy, live birth, and pregnancy loss) and neonatal birth weight. Results: Women aged ≥38 years had a significantly lower euploidy rate than those <38 years (24.8% vs. 47.3%, p < 0.001). Ploidy distribution did not differ significantly across IF categories. Among women aged <38 years with ≥5 IFs, a greater number of previous embryo transfer attempts was independently associated with higher odds of live birth after euploid embryo transfer (adjusted OR = 1.258, 95% CI: 1.051–1.505; p = 0.012). Neonatal weight did not differ significantly across IF categories. Conclusions: The number of previous IFs was not independently associated with embryo ploidy or clinical outcomes after euploid transfer, whereas advanced maternal age was strongly associated with a lower likelihood of obtaining euploid embryos. In younger women with ≥5 IFs, a greater number of previous embryo transfer attempts was associated with live birth after euploid transfer; however, this exploratory subgroup finding should be interpreted cautiously and requires prospective validation. Because this study did not directly evaluate therapeutic strategies, any potential role for individualized endometrial evaluation or optimization should be considered as hypothesis-generating rather than supported by the present data. Full article

Background/Objectives: Laser-assisted zona pellucida (ZP) drilling on day 4 embryos is routinely performed in IVF laboratories to facilitate trophectoderm (TE) herniation for blastocyst biopsy. Nevertheless, inner cell mass (ICM) herniation through the initial ZP opening occasionally occurs and may interfere with standard TE biopsy. Methods: This retrospective study assessed the clinical and obstetric safety of a double ZP drilling strategy for TE biopsy in preimplantation genetic testing for aneuploidy (PGT-A) cycles. A total of 560 single euploid embryo transfer cycles were analyzed. Blastocysts were categorized (Groups 1–6) based on ICM/TE herniation patterns and the corresponding biopsy approach. Clinical outcomes were compared between cycles undergoing TE biopsy through a single ZP opening (TE hatching with ICM remaining within the ZP) and cycles requiring a second opening to relocate the biopsy site when the ICM herniated through the original opening or was positioned externally. Results: The single-opening approach of Group 1 accounted for 295 cycles (52.7%), with implantation, miscarriage, and live birth rates of 65.4%, 14.0%, and 56.3%, respectively. The double-opening approach of Group 3 was applied in 21 cycles (3.8%), yielding implantation, miscarriage, and live birth rates of 66.7%, 0%, and 66.7%, respectively. No significant differences were observed between the two strategies in implantation, miscarriage, or live birth rates. Obstetric and neonatal outcomes, including gestational age, birth weight, and monozygotic twinning incidence, were comparable. Fifteen healthy infants were delivered following TE biopsy using the double-opening strategy. Conclusions: These data support incorporating ICM position into TE biopsy decision-making and suggest that creating a second ZP opening to reposition the biopsy site is clinically feasible and does not compromise reproductive or obstetric outcomes in PGT-A cycles. Full article

Multimorbidity is a key global trend across healthcare fields, including gynecology. It is strongly associated with an overall poorer health status. Statistics indicate that in the 21st century most women experience at least one gynecological disease. Meanwhile, there is a consistent increase in the prevalence of obesity associated with chronic inflammation and hyperestrogenism. Alongside other factors, it leads to a growing prevalence of hyperproliferative diseases of the female reproductive system (FRS), encompassing both benign and malignant conditions. While advanced-stage malignant tumors can be linked to missed detection and wrong checkup strategies, benign neoplasms can compromise the ovarian reserve and thus cause major concerns. The prevailing benign FRS tumors are uterine fibroids (UFs) and benign ovarian tumors (BOTs), including serous and mucinous cystadenomas. It appears that an increase in certain benign FRS tumors is occurring in parallel with a rise in infertility (especially “unexplained infertility”) and reproduction failures, potentially associated with endometrial dysfunction. Thus, the endometrium is currently considered a critical area of research due to its vital role as the site of blastocyst adhesion and implantation, especially in patients with comorbidities. In this context, this article highlights the significance and pathophysiological characteristics of UFs and BOTs and their impact on defective endometrial receptivity. Full article

The formation and expansion capacity of blastocysts plays a very important role in successful implantation. During mammalian embryo development derived from in vitro production (IVP), early embryos are highly susceptible to various cellular stresses, including endoplasmic reticulum (ER) stress, which has been identified in IVP embryos, suggesting that ER stress modulation is crucial for IVP embryo development. In this study, we aimed to evaluate the influences of ER stress on preimplantation embryos during blastocyst formation and expansion potential in pigs. Tunicamycin (TM), an ER stress inducer, was employed in porcine embryos, significantly increasing the mRNA levels of ER stress-related markers ATF6, CHOP, and GRP78. When one-cell embryos were cultured in the presence of TM, the blastocyst formation and diameter (reflecting the blastocyst expansion capacity) were significantly inhibited in a dose-dependent manner. When morula-stage porcine embryos were cultured in TM, the blastocyst formation rate, blastocyst diameter, total cells and EdU-positive cell numbers were significantly lower than the TM-free control group. TM reduced the potential of blastocoel recovery (ex-expansion) in blastocysts collapsed by cytochalasin D and impeded blastocyst expansion. In addition, TM reduced the mRNA levels of CDH1 and TJP1 and affected the normal expression pattern of E-cadherin, Oct4, Sox2 and Cdx2 in porcine blastocysts. Taken together, these findings suggest that TM treatment during embryo development in vitro interferes with the formation and expansion capacity of the blastocoel in pigs. Full article

Embryo implantation presents a cell biological paradox: contact formation between the trophoblast of the blastocyst and the epithelial lining of the endometrium contradicts typical epithelial cell behaviour, as does the subsequent invasion needed for placenta formation in most species (including the human). Explaining this conundrum became a challenge for investigation since its recognition about 40 years ago and it receives increasing interest because implantation failure appears to be a major cause for low success in assisted reproduction. The present article reviews the main findings that have directed attention of researchers on epithelial cell polarity and on the theoretical concept of epithelial–mesenchymal transition (EMT). Apart from trophoblast attachment competence, a special focus is on endometrial receptivity. Comparison with epithelial fusion processes (EFPs) in development and with tumour cell invasion has been and is still considered helpful in order to take advantage of the progress made in those fields. Concerning the mechanisms involved, it must be emphasized that trophoblast and uterine luminal epithelium (ULE) do not undergo a complete switch to a mesenchymal programme (do not undergo a complete EMT) but make use of partial changes in the epithelial programme. The large number of data accumulated recently should allow us to now make progress in identifying what these partial programme changes are exactly and how they are regulated; also, they may offer chances for obtaining deeper insights into the regulation of implantation. Full article

Background/Objectives: Cryopreservation technology used in assisted reproductive technology (ART) has significantly improved live birth rates by enabling multiple embryo transfers with frozen embryos from a single ovarian stimulation cycle. However, there is conflicting data on the effect of prolonged cryopreservation of human blastocysts. Methods: This Danish nationwide cohort study includes all frozen embryo transfers (FETs) from 1 January 2012 to 31 March 2019. Biochemical pregnancy, clinical pregnancy, and live births were analyzed based on blastocyst storage time. Blastocyst storage time was stratified into five groups, ≤3 month, 4–6 months, 7–12 months, 13–24 months, and ≥25 months, with the shortest (≤3 months) as the reference. We also examined the risk of preterm birth, small and large for gestational age (SGA and LGA), and congenital malformations among live-born children. Multivariable analysis was used to estimate the odd ratios of the reproductive outcomes, accounting for potential confounders. Results: We identified 7042 women with 12,599 FETs. Characteristics of women at embryo transfer did not vary significantly by storage time, except for polycystic ovarian syndrome (PCOS), which increased from 2.6% in the reference group to 6.7% in the ≥25-month group. The clinical pregnancy rate was 35.7%. Blastocyst storage time did not significantly affect biochemical pregnancy rates, with adjusted odds ratios (aORs) of 0.94 (95% CI: 0.80–1.11) to 0.96 (95% CI: 0.82–1.12) for the 13–24-month and ≥25-month groups, respectively. Clinical pregnancy rates also did not decrease with storage time (aOR 0.96, 95% CI: 0.82–1.13) for ≥25 months. The live birth rate was 28.6%, with no significant decrease during storage (aOR 0.89, 95% CI: 0.75–1.06). However, the risk of LGA was slightly, but non-significantly, increased (aOR: 1.42, 95% CI: 0.84–2.42) in the ≥25-month group, whereas the aOR of SGA and congenital malformations was not increased. Conclusions: Our data indicates that storing blastocysts for a period of 25 months does not significantly affect pregnancy chances following assisted reproductive technology treatment. Full article

Background and Objectives: Aneuploidy is the leading cause of implantation failure and miscarriage, with prevalence increasing with maternal age. Embryos classified as chaotic, characterized by the presence of five or more chromosomal abnormalities, and those with complex aneuploidies, defined by two to four abnormalities, represent a controversial category in preimplantation genetic testing for aneuploidy (PGT-A), as the potential for misclassification remains a significant concern. Materials and Methods: We performed a retrospective study at the Calla IVF Center, Oradea, analyzing 230 blastocysts grouped by maternal age (25–30, 31–35, 36–40, and 41–50 years). A trophoblast biopsy was performed on days 5–7, and the samples were analyzed by next-generation sequencing (NGS). Embryos were classified as euploid, aneuploid, mosaic, or chaotic. The 19 embryos initially diagnosed as chaotic were thawed and subjected to re-biopsy. Statistical analysis included descriptive statistics (chi-square tests and ANOVA) and multivariable regression models, with p < 0.05 as the criterion for statistical significance. Results: Aneuploidy increased with maternal age, from 29.6% in women aged 25–30 years to 68.7% in those aged 41–50 (p = 0.002). Poor-quality blastocysts exhibited higher aneuploidy rates (72.4%) than good-quality embryos (34.6%; p = 0.004). Chaotic embryos comprised 8.3% of the cohort. Upon re-biopsy, none were confirmed as euploid; all remained abnormal and were reassigned to aneuploid, mosaic, or persistently chaotic categories. This finding suggests that apparent euploid results reported elsewhere may reflect technical variability and sampling limitations in PGT-A rather than accurate chromosomal normalization. Conclusions: The prevalence of aneuploid embryos showed a progressive increase with advancing maternal age. Chaotic embryos are heterogeneous, and re-biopsy may help refine the interpretation of complex PGT-A profiles, supporting its role as a diagnostic and quality control tool rather than a strategy to identify euploid embryos. Our study offers novel insights through age-stratified analysis, the integration of morphology with genetics in a Romanian IVF cohort, and a detailed evaluation of chaotic embryos, providing clinical recommendations for patient counseling and embryo selection. Full article

Background: The success of in vitro fertilization (IVF) is influenced by multiple patient- and laboratory-related factors, including maternal age, body mass index (BMI), ovarian stimulation, and embryo quality. Laboratory illumination may induce photo-oxidative stress, potentially impairing embryo development and implantation. This study evaluated the clinical impact of introducing a light-protection protocol in an IVF laboratory. Methods: We retrospectively analyzed 2125 IVF cycles with fresh embryo transfer performed at the Assisted Reproduction Centre of the University of Pécs between 1 March 2016 and 30 November 2020. A light-protection protocol was implemented on 1 March 2017, while all other laboratory and clinical parameters remained unchanged. Pregnancy outcomes before and after implementation were compared, with additional subgroup analyses focusing on cycles with low blastocyst-formation rates. Results: After implementation of light protection, overall pregnancy rates increased by approximately 5%; however, this difference was not statistically significant. In contrast, subgroup analyses demonstrated a markedly greater improvement in pregnancy outcomes—up to 37%—in cycles characterized by low blastocyst-formation rates. Conclusions: Although light protection did not significantly improve overall pregnancy rates, the findings suggest a clinically relevant benefit in selected cases with reduced embryonic developmental competence. Minimizing photo-oxidative stress may therefore represent a targeted laboratory intervention to improve IVF outcomes in vulnerable embryo populations. Full article

Regulatory T cells (Tregs), particularly their phenotypically distinct subpopulations, are critical for the establishment of maternal immune tolerance during embryo implantation. Despite advances in assisted reproductive technologies, implantation failure remains a frequent and often unexplained clinical challenge. Variations in Treg frequency and phenotype have been proposed to influence implantation success, particularly under differing hormonal conditions. This study aimed to investigate peripheral blood Treg levels and their subpopulations on the day of blastocyst transfer in both stimulated in vitro fertilization (IVF/ICSI) cycles involving controlled ovarian hyperstimulation (COH) and true natural cycles with frozen embryo transfer (FET), and to examine their associations with systemic hormone levels and anti-Müllerian hormone (AMH). A prospective observational study was conducted including women undergoing IVF/ICSI with fresh embryo transfer (ET) and women undergoing natural cycle FET. Peripheral blood samples were collected on the day of ET and analyzed using 13-colour flow cytometry, enabling detailed subdivision of Tregs into multiple subpopulations based on the expression of differentiation and chemokine markers, including CXCR5. In addition, because common $\gamma$-chain cytokines may influence pregnancy success by modulating the balance between suppressive Treg and non-Treg subsets, intracellular STAT5 signaling was assessed using phospho-specific flow cytometry. Serum estradiol, progesterone, FSH, LH, and AMH levels were measured in parallel. Significant differences were observed in Treg subpopulation distributions between women who conceived and those who did not. Higher frequencies of naïve CXCR5⁻ Tregs were associated with clinical pregnancy, independent of age, and correlated with serum progesterone levels. Moreover, both naïve Treg frequency and enhanced IL-7-dependent STAT5 signaling in naïve Tregs from women undergoing COH were associated with AMH levels, suggesting a link between ovarian reserve and Treg homeostasis mediated by signal transducer and activator of transcription 5 (STAT5) signaling. In conclusion, Treg subpopulations, particularly CXCR5⁻ naïve Tregs, appear to play a central role in implantation success following ET. Their distribution differs between stimulated and natural cycles and is influenced by systemic progesterone levels and STAT5 signaling. These findings suggest that peripheral Treg profiling may represent a potential biomarker of implantation competence and could inform personalized approaches in assisted reproduction. Full article

Reactive oxygen species (ROS) are essential regulators of fertilization and early embryo development in mammals, including humans and various animal models, but they exert detrimental effects when produced in excess. In assisted reproductive technologies (ART), particularly in vitro fertilization (IVF), exposure to non-physiological conditions increases oxidative stress (OS), impairing gamete quality, embryo viability, and clinical outcomes. This review synthesizes experimental and clinical studies describing the endogenous and exogenous sources of ROS relevant to embryo development in IVF. Endogenous ROS arise from intrinsic metabolic pathways such as oxidative phosphorylation, NADPH oxidase, and xanthine oxidase. Exogenous sources include suboptimal laboratory conditions characterized by factors such as high oxygen tension, temperature shifts, pH instability, light exposure, media composition, osmolarity, and cryopreservation procedures. Elevated ROS disrupt oocyte fertilization, embryonic cleavage, compaction, blastocyst formation, and implantation by inducing DNA fragmentation, lipid peroxidation, mitochondrial dysfunction, and apoptosis. In addition, the review highlights how parental health factors establish the initial redox status of gametes, which influences subsequent embryo development in vitro. While antioxidant supplementation and optimized culture conditions can mitigate oxidative injury, the precise optimal redox environment remains a subject of ongoing research. This review emphasizes that future research should focus on defining specific redox thresholds and developing reliable, non-invasive indicators of embryo oxidative status to improve the success rates of ART. Full article

Anthocyanin is a flavonoid known for its strong antioxidant and anti-inflammatory activities in both in vitro and in vivo systems. This study investigated whether anthocyanin supplementation could improve the developmental competence, hatching rate, and the expression of development- and proliferation-related markers in ICR mouse blastocysts cultured in vitro. Mouse embryos were cultured in KSOM medium supplemented with 2, 4, or 8 μM anthocyanin. Among these, 4 μM was selected as the working concentration within the tested range. Morphological assessment was used to evaluate blastocyst development and hatching, while quantitative real-time polymerase chain reaction (qPCR) was performed to measure the expression of GLUT4 and PI3K. Anthocyanin supplementation significantly enhanced blastocyst quality, as reflected by higher developmental competence and increased hatching rates compared with the control group. In addition, anthocyanin-treated blastocysts displayed elevated mRNA expression of GLUT4 and PI3K, indicating a potential association with enhanced metabolic readiness and cellular proliferation. Overall, these findings indicate that anthocyanin supports embryo quality during preimplantation development in vitro, with potential relevance to implantation-related processes. Further research is needed to clarify the underlying mechanisms and explore the potential applications of anthocyanin in reproductive medicine. Full article

Objective: The aim of this study was to evaluate whether intrauterine administration of autologous peripheral blood mononuclear cells (PBMCs) activated with interferon tau (IFN-τ) before embryo transfer improves implantation and pregnancy outcomes in IVF patients. Methods: This single-center, prospective, randomized, controlled trial was conducted at Nadezhda Women’s Health Hospital (Approval No.: 6/28022023). The study was registered at ClinicalTrials.gov (NCT05775198). Randomization was computer-generated with allocation concealed via sealed envelopes. Participants and statisticians were blinded to group assignment; clinicians were not. Women aged 21–50 undergoing frozen–thawed embryo transfer with euploid embryos were included. Exclusion criteria included uterine anomalies, autoimmune, oncologic conditions, infections, or use of immunosuppressants. Participants (n = 340) were randomized 1:1 to receive either intrauterine infusion of autologous PBMCs activated in vitro with IFN-τ or standard IVF care without PBMC treatment. PBMCs were cultured with recombinant IFN-τ, washed, and infused 24 h prior to single euploid blastocyst transfer. A total of 14 patients were excluded from analysis because of early dropout, leaving 326 (n = 167; n = 159) patients for modified intention-to-treat analysis. Primary outcomes included implantation rate (elevated urinary or blood hCG), clinical pregnancy (fetal heartbeat at 6–8 weeks), and live birth rates. Miscarriage rate and safety were secondary objectives. Patients were followed up until 6 weeks post pregnancy resolution. Results: In the intervention group, 38.3% of patients achieved implantation, compared to 27.7% in the controls (OR 1.6, 95% CI: 1.0–2.6, p = 0.04). Live birth rates were also significantly higher in the IFN-τ-modulated PBMC group (28.7% vs. 17.6%, OR 1.9, 95% CI: 1.1–3.2; p = 0.02). While the clinical pregnancy rate was higher, it did not reach statistical significance (34.7% vs. 25.8%, p = 0.08). There was no difference between the groups in terms of miscarriage (p = 0.4). No serious adverse events were reported after treatment, during pregnancy or in the postnatal period. Conclusions: Intrauterine treatment with IFN-τ-activated PBMCs before ET significantly improves implantation and live birth rates in IVF patients. Full article

A predominant etiological factor in implantation failure and early pregnancy loss is embryonic chromosomal abnormalities. The current clinical standard for determining embryonic ploidy is invasive preimplantation genetic testing. This procedure imposes mechanical stress on embryonic cells during trophectoderm biopsy and fails to significantly improve live birth rates per transfer, likely due to its inability to evaluate the embryo’s implantation potential. Consequently, there is a clear need to develop a non-invasive method, suitable for routine clinical practice, that can simultaneously assess both the ploidy and implantation competence of a blastocyst prior to uterine transfer. Our research group was the first to achieve this by quantifying specific piwiRNAs (piR_016677, piR_017716, piR_020497, piR_015462) in spent culture medium. These data served as the foundation for logistic regression models tailored for day 5 blastocysts, day 6 blastocysts, and blastocysts irrespective of their developmental rate. These models demonstrated high diagnostic accuracy, with specificity ranging from 68% to 100% and sensitivity from 71% to 100%. The rationale for employing these molecules as biomarkers lies in their potential biological roles, which encompass maintaining genomic stability through LINE-1 regulation, as well as direct involvement in critical processes such as cell cycle control, spindle assembly, and cellular adhesion—all of which are imperative for successful implantation. Full article