Embryo Developmental Potential Research Articles

Boric acid supplementation promotes the development of in vitro-produced mouse embryos by related pluripotent and antioxidant genes.

Boric acid (BA) is an important mineral for plants, animals and humans that assists metabolic function and has both positive and negative effects on biological systems. The present study aimed to investigate the effects of different concentrations of BA added to the culture media, the quality and in vitro development potential of mouse embryos. Superovulated C57Bl6/6j female mice were sacrificed ∼18 hours after human chorionic gonadotropin (hCG) injection. Single-cell-stage embryos were collected from the oviduct, divided into experiment groups and cultured in embryo medium with supplemented BA+ in 5% CO2 at 37 °C until 96 hours at the blastocyst stage. The blastocyst development rates of 0, 1.62 × 10-1, 1.62 × 10-2, 1.62 × 10-3 and 1.62 × 10-4 µM BA were 51.52%, 73.47%, 77.36% and 81.13%, respectively. The in vitro development rates were significantly higher in the 1.62 × 10-3 (p < 0.05) and 1.62 × 10-4 µM BA groups than in the control group (p < 0.001). These results indicated that low BA doses influenced embryo development by positively affecting in vitro development rates, embryo cell numbers, biochemical parameters and development at the molecular level by pluripotent and antioxidant genes. Therefore, BA seems to play an important role on in vitro embryo development.

Multi-omics approach to reveal follicular metabolic changes and their effects on oocyte competence in PCOS patients.

Polycystic ovary syndrome (PCOS) is a common heterogeneous disorder linked with endocrine and metabolic disturbances. The underlying mechanism of PCOS, especially its effect on oocyte competence, remains unclear. The study aimed to identify abnormal follicular metabolic changes using a multi-omics approach in follicular fluid from PCOS patients and to determine their effects on oocyte competence. A total of 36 women with PCOS and 35 women without PCOS who underwent in vitro fertilization and embryo transfer were included in the study. Cumulus cells and follicular fluid samples were collected. Follicular fluid samples underwent metabolomic analysis, while cumulus cell clusters from the same patients were assessed using transcriptomic analysis. Clinical information of patients and assisted reproductive technology (ART) results were recorded. Transcriptomics and metabolomics were integrated to identify disrupted pathways, and receiver operation characteristics (ROC) analysis was conducted to identify potential diagnostic biomarkers for PCOS. Pearson correlation analysis was conducted to assess the relationship between metabolites in follicular fluid and oocyte competence (fertilization and early embryo development potential). Through multi-omics analysis, we identified aberrantly expressed pathways at both transcriptional and metabolic levels, such as the citrate cycle (TCA cycle), oxidative phosphorylation, the cAMP signaling pathway, the mTOR signaling pathway, and steroid hormone biosynthesis. Ten candidate metabolites were identified based on metabolic profiling data from these altered pathways. Phytic acid, succinic acid, 2'-deoxyinosine triphosphate, and 4-trimethylammoniobutanoic acid in the follicular fluid exhibited high specificity and sensitivity in distinguishing PCOS. Among these metabolites, L-arginine showed a negative correlation with the 2PN fertilization rate and cleavage rate, while estrone sulfate showed a negative correlation with the high-quality embryo rate in the in-vitro fertilization (IVF) cycle. We have conducted a preliminary study of a novel metabolic signature in women with PCOS using a multi-omics approach. The alterations in key metabolic pathways may enhance our understanding of the pathogenesis of PCOS.

Morphological quality on Day 3 affects the pregnancy outcomes of low-quality euploid blastocysts: a retrospective cohort study.

Does the morphological quality on Day 3 influence the pregnancy outcomes of euploid blastocysts? The morphological quality on Day 3 affects the clinical pregnancy rate (CPR) and live birth rate (LBR) of low-quality euploid blastocysts. The morphological grading of Day 3 embryos affects the pregnancy outcome of cleavage-stage embryos and is an excellent indicator to predict embryo development potential. However, it is still unclear whether morphological quality on Day 3 is associated with pregnancy outcomes of the euploid blastocyst. This retrospective cohort study comprised 1275 patients who received single euploid blastocyst transfer between January 2016 and August 2021 at a tertiary teaching hospital. Patients were grouped into two groups according to the morphological grading on Day 3 of transferred blastocysts: high-quality (HQ, including Grades I and II) Day 3 embryos and low-quality (LQ, Grade III) Day 3 embryos. The primary outcomes were CPR and LBR. Interactions of development days (Day 5 and Day 6) and morphological quality (high- and low-quality) of blastocysts with morphological quality of Day 3 embryos on pregnancy outcomes were tested in the stratified analysis and logistic regression models. The multivariate logistic regression analysis was conducted to investigate the independent effect of the morphological quality of Day 3 embryos on pregnancy outcomes after adjusting for potentially confounding factors. The CPR and LBR of the HQ Day 3 embryos group were statistically higher than those of the LQ Day 3 embryos group (CPR: 59.73% versus 49.70%, respectively, P = 0.015; LBR: 49.73% versus 41.21%, respectively, P = 0.041). The development days of blastocysts did not exhibit a multiplicative interaction with the morphological quality of Day 3 embryos on the CPR (P for interaction = 0.648) and LBR (P for interaction = 0.925). The morphological quality of blastocysts exhibits a multiplicative interaction with the morphological quality of Day 3 embryos on the CPR (P for interaction = 0.020) and LBR (P for interaction = 0.012). After adjusting for potential confounders, the HQ Day 3 embryo group was positively associated with the CPR (adjusted odds ratio (aOR): 2.10, 95% CI: 1.31-3.36, P = 0.002) and LBR (aOR: 1.97, 95% CI: 1.20-3.25, P = 0.008) of LQ blastocysts. However, the morphological quality on Day 3 was not significantly associated with the CPR (aOR: 0.95, 95% CI: 0.58-1.55, P = 0.835) and LBR (aOR: 0.86, 95% CI: 0.53-1.40, P = 0.550) of HQ blastocysts. Selection and confounding bias introduced by the retrospective design cannot be completely eliminated in this study, although multivariable logistic analysis was conducted to adjust for potential confounders. Also, some subgroups had small sample sizes, which may reduce statistical power. Moreover, participants in our study only received single euploid blastocyst transfer, and whether the results could apply to blastocysts with unknown ploidy status is unclear. This study found that the morphological quality on Day 3 was significantly associated with the CPR and LBR of LQ blastocysts; Therefore, when only LQ euploid blastocysts are available for transfer, blastocysts derived from HQ Day 3 embryos are recommended. No external funding was obtained. The authors have no conflicts of interest to declare. N/A.

Acrylamide Exposure Impairs Ovarian Tricarboxylic Acid Cycle and Reduces Oocyte Quality in Mouse.

Acrylamide (AAM), a compound extensively utilized in various industrial applications, has been reported to induce toxic effects across multiple tissues in living organisms. Despite its widespread use, the impact of AAM on ovarian function and the mechanisms underlying these effects remain poorly understood. Here, we established an AAM-exposed mouse toxicological model using 21 days of intragastric AAM administration. AAM exposure decreased ovarian coefficient and impaired follicle development. Further investigations revealed AAM would trigger apoptosis and disturb tricarboxylic acid cycle in ovarian tissue, thus affecting mitochondrial electron transport function. Moreover, AAM exposure decreased oocyte and embryo development potential, mechanically associated with pericentrin and phosphorylated Aurora A cluster failure, leading to meiotic spindle assembly defects. Collectively, these results suggest that AAM exposure may lead to apoptosis, glucose metabolic disorders, and mitochondrial dysfunction in ovary tissue, ultimately compromising oocyte quality.

O-195 Decreased embryo developmental potential and lower cumulative pregnancy rate in males with multiple morphological abnormalities of the sperm flagella

Abstract Study question Is there any association between the multiple morphological abnormalities of the sperm flagella (MMAF) patients and the comprehensive outcomes of assisted reproductive technology (ART) cycles? Summary answer Patients with MMAF presented compromised ART outcomes, including lower embryo developmental potential and impaired clinical outcomes, compared with the cohort of oligoasthenospermia. What is known already Several studies have reported a positive intracytoplasmic sperm injection (ICSI) outcome in the MMAF cohort, and others have opposite opinions. The association between MMAF and ART outcomes is still controversial and open for debate. Furthermore, the neonatal outcomes and the information regarding the mutations of MMAF patients were incomplete. Study design, size, duration A retrospective cohort study of MMAF patients was performed at a reproductive medicine center in China between January 2014 and July 2022. Participants/materials, setting, methods Thirty-eight MMAF individuals were recruited based on a typical MMAF phenotype (abnormal sperm flagella, including short, absent, coiled, bent, and/or irregular flagella) and 131 couples with male infertility undergoing in vitro fertilization (IVF)/ICSI treatments over the same period were included as the control pool. Whole exome sequencing (WES) was performed to confirm the genetic pathogenesis of MMAF. Main results and the role of chance Pathogenic variants in known genes of DNAH1, DNAH11, CFAP43, FSIP2, and SPEF2 were identified in MMAF patients. The ART outcomes, including the fertilization rate, 2PN cleavage rate, blastocyst formation rate, and available blastocyte rate, were all significantly lower in the MMAF group than those in the control group (P&amp;lt;0.05). Moreover, the CLPR in the MMAF group was lower than that in the control group according to the embryo transfer times (68.6% vs. 86.5%, P=0.033) and complete cycles (66.7% vs. 84.2%, P=0.020), while no significant differences were found in the neonatal outcomes. Limitations, reasons for caution The sample size was limited due to the low incidence of MMAF and WES was not performed in all MMAF patients. Further exploration of the potential genetic mutations or underlying mechanisms in patients without identified mutations was needed. Moreover, long-term follow-up of neonates needs to be addressed in the future. Wider implications of the findings The current study identified the causative genetic mutations which were partly obligated to the pathogenesis of MMAF and presented the relationship between MMAF and compromised ART outcomes. These results may provide evidence support for clinicians in genetic counseling and clinical instruction in specific MMAF patients. Trial registration number the National Key Research &amp; Development Program of China (2021YFC2700603)

O-020 Investigating the effect of advanced sperm preparation techniques on embryo developmental potential and clinical outcomes: a network meta-analysis of randomized controlled trials

Abstract Study question Are embryological and clinical outcomes affected when employing Magnetic-Activated Cell-Sorting (MACS), Density Gradient Centrifuge (DGC)-Zeta and Microfluidic Sperm Selection (MSS) instead of DGC and Swim-Up? Summary answer MACS and MSS enhance both laboratory and clinical outcomes, while DGC-Zeta seems to improve only clinical outcomes, in comparison to conventional sperm preparation techniques. What is known already Sperm preparation techniques have been developed to enhance sperm selection process towards improving IVF laboratory and clinical outcomes. Based on centrifugation and sperm migration, DGC and swim-up constitute the standard methods for improving sperm parameters, nonetheless disregarding molecular aspects. Certain techniques, namely MACS, DCG/Zeta and MSS have been proposed to effectively select non-apoptotic sperm with intact chromatin and high DNA integrity claiming their place in routine clinical practice. Concurring on the efficacy of these adjunct methods from the standpoint of embryo developmental dynamic and clinical outcomes is both pertinent and imperative. Study design, size, duration A systematic search of the literature was performed in the database Pubmed/Medline up to December 2023. Only full-text manuscripts published in English where randomization was performed on oocytes or patients were eligible. Studies reporting on semen samples obtained by surgical techniques were excluded. A total of 20 RCTs were included in this network meta-analysis. Other reported sperm preparation techniques were excluded due to the limited number of available Randomized Controlled Trials (RCTs). Participants/materials, setting, methods All RCTs providing results on the aforementioned sperm preparation techniques were included. The outcome measures were fertilization, cleavage, blastocyst formation, clinical pregnancy, and live-birth rates. To evaluate the network estimate both direct and indirect effects were assessed. When heterogeneity was I2=0% the fixed-effects model was preferred. In any other case the random-effects model was employed. To rank the sperm preparation techniques' efficiency, the frequentist method employing the P-score was opted for. Main results and the role of chance The 20 included RCTs presented with a total of 17 different designs and 8 different combinations of sperm preparation techniques. Seventeen studies reported on fertilization rate providing no statistically significant difference between the sperm preparation techniques albeit with high heterogeneity I2=69%. Regarding cleavage rate (n = 10 studies), only MACS/DGC presented with an improved outcome when compared to DGC (RR: 1.43; 95%CI: 1.16-1.76; I2=96%). MACS/DGC presented with the highest efficiency (P-Score=0.90), followed by combination of MACS/DGC/swim-up (P-Score=0.83). Both MSS and MACS/DGC presented with significantly higher blastocyst formation rate compared to DGC (MSS: RR:1.14;95%CI:1.02-1.29; MACS: RR: 1.37; 95%CI: 1.04-1.82; I2=0%). According to P-Score, MACS/DGC was presented as the most efficient technique (P-Score=0.89) followed by MSS (P-Score=0.44). Regarding clinical pregnancy rates, the 12 studies featured low heterogeneity (I2=0). MACS/DGC presented with higher clinical pregnancy rates compared to DGC (RR: 1.30; 95%CI: 1.09-1.36) and the combination of DGC/swim-up (RR: 1.55; 95%CI: 1.12-1.95). MSS presented with enhanced results compared to swim-up (RR: 1.37; 95%CI: 1.11-1.69) and DGC-Zeta presented with higher clinical pregnancy rates compared to DGC (RR: 1.76; 95%CI: 1.28-1.92). The most efficient technique was DGC-Zeta (P-Score=0.98), followed by MACS/DGC (P-Score=0.82). Regarding live-birth rates no statistically significant difference was observed, albeit high heterogeneity was observed (I2=51%). Limitations, reasons for caution The blastocyst formation rate and the live-birth rate outcomes should be interpreted with caution due to the limited number of RCTs. The indirect effect estimates may pose as an intrinsic limitation of the network meta-analysis, especially in cases with limited direct data. Wider implications of the findings This data demonstrates that the combination of MACS/DGC provided enhanced laboratory and clinical outcomes compared to conventional techniques. Investigating sperm selection techniques that assess advanced sperm characteristics rather than parameters alone is timely and essential. To concur on optimal practice further RCTs directly comparing MSS, MACS and DGC-Zeta are required. Trial registration number Not applicable

P-299 The influence of ovarian endometriomas surgery or not and the iron overload in follicular fluid on the outcome of IVF-ET

Abstract Study question To investigate the influence of ovarian endometriomas(OEM) surgery or not on the outcome of in vitro fertilization and embryo transfer. Summary answer Laparoscopic surgery can not significantly improve the outcome of IVF-ET in OEM patients, but may decrease the ovarian reserve. What is known already Despite the great advantages of ovarian endometriomas surgery treatment in endometriosis-linked infertility, the impact of laparoscopic cystectomy on outcomes of infertility management with ART is controversial. Numerous mechanisms have been proposed in an effort to delineate the multifaceted pathophysiology that induces impairment of reproductive dynamics in patients with OEM. Reactive oxygen species, dysregulation of the immune system and iron overload constitute the crucial mechanisms that detrimentally affect oocyte and embryo developmental potential. Study design, size, duration This study retrospectively included 882 cycles in our reproductive center from January 2018 to December 2020, and the patients were divided into operation group (n = 386) and OEM group (n = 496) according to whether they underwent laparoscopic cystectomy before IVF-ET. Participants/materials, setting, methods The baseline data of age, infertility duration, basic FSH, AFC, and BMI were used as matching factors, and Propensity score matching was carried out according to the sample ratio of 1:1, and 327 cycles in the operation group and 327 cycles in the OEM group were finally included. Follicular fluid was collected under ultrasound guidance during oocyte retrieval. A total of 74 follicular fluid samples meeting the study conditions were collected. Main results and the role of chance (1)The clinical pregnancy rate of fresh embryo transfer cycle in the OEM group was significantly higher than that in the operation group (77.4% Vs 52.9%), and the difference was statistically significant (P = 0.039). There was no significant difference in pregnancy outcome in frozen embryo transfer cycle (P &amp;gt; 0.05). (2) The results of Multi-factor logistic regression model showed the clinical pregnancy rate of patients in the OEM group was 3.048 times than that of patients in the operation group in fresh cycle, and the difference was significant (OR 3.029 95%CI 1.017-9.018, P = 0.047), while early abortion and live birth pregnancy outcomes were not significantly affected in both groups. For the frozen embryo transfer cycle, there were no significant effects on clinical pregnancy, early abortion and live birth pregnancy outcomes in both groups. (3) There was no significant difference in follicular fluid iron concentration between OEM group and control group(11.53±3.38 Vs 12.18±4.37μg/dl, P = 0.112). The concentration of ferritin in follicle fluid in OEM group (57.38±139.90) was significantly higher than that in control group (24.88±13.76 μg/ml), the difference was statistically significant (P = 0.032). Limitations, reasons for caution The present study being of a retrospective and monocentric study, may not come to a very convincing conclusion, and some unknown biases might still exist due to possible underestimation of some confounders. Wider implications of the findings Collectively, our results indicate that laparoscopic ovarian cystectomy couldn’t significantly improve the IVF-ET outcomes in patients with OEM, but rather increased the risk of reduced ovarian reserve function. Ovarian reserve function was the main factor affecting the IVF-ET outcomes for infertile patients with OEM. Trial registration number /

O-215 Copper oxide nanoparticles (CuONPs) impairs mitophagy and promotes DNA methylation to suppress mouse embryonic pluripotency

Abstract Study question Does exposure to copper oxide nanoparticle (CuONPs) have adverse effects on early embryonic development? What is the potential mechanism? Summary answer CuONPs exposure can damage mitophagy and lead to α-KG reduction, resulting DNA hypermethylation, thereby reducing the pluripotency of pre-implantation embryos in mice. What is known already Environmental nanomaterials contamination is a great concern for organisms including human. Exposure to nanomaterials have been associated with fecundity and fertility in couples conceiving via assisted reproduction technology. Among these bio-effects, nanomaterials induced epigenetic changes are of particular interest. Copper oxide nanoparticles (CuONPs) are widely used in a huge range of applications which might pose potential risk to organisms. Recent studies reported that CuONPs exposure resulted in transgenerational toxicity in Caenorhabditis elegans associated with possible epigenetic regulation. However, whether CuONPs exposure affect mammalian embryonic development, and if so the underlying mechanisms, are unclear. Study design, size, duration For the human experiments, we measured the copper ion content in women’s urine, and assessed the expression of pluripotent genes in 3PN embryos treated with CuONPs. For the embryo experiments, we collected zygotes from ICR mice and cultured them in KSOM medium with CuONPs (10 μg/mL) until blastocyst stage. For the cell experiments, we treated mouse embryonic stem cells (mESCs) with CuONPs (2 μg/mL) for four days to detect cell proliferation and pluripotency. Participants/materials, setting, methods The ICP-MS method was used to detect copper ion content in women’s urine. Time–lapse incubator was used to document the developmental potential of embryos. To quantify the metabolites of embryo, we employed metabolomics. Single-cell multiomics sequencing that enables profiling of genome-wide chromatin accessibility, DNA methylation and RNA expression were performed to detect genes expression and epigenetic modification. We used real-time PCR, immunofluorescence, and western blot to measure the expression of pluripotency related genes. Main results and the role of chance In human, we discovered a significant negative relationship between the urine’s copper ion content and clinical pregnancy rate. In embryo experiments, CuONPs exposure has been shown to have adverse effects on embryo developmental potential, resulting morula and blastocyst transformation arrest, as well as reduction in blastocyst rate and live birth rate. Furthermore, CuONPs treatment led to a reduction in blastocyst quality, indicating a decrease in blastocyst cell count, particularly in ICM cells. CuONPs also inhibited the pluripotency of blastocysts and mESCs, showing down-regulated expression of pluripotent genes. Mechanistically, CuONPs aggregated in lysosomes and decreased the mitophagic flux of embryos, which caused damaged mitochondria to accumulate and ultimately caused mitochondrial dysfunction. Notably, in embryos treated with CuONPs, there was a decrease in α-ketoglutarate (α-KG) due to the disruption of the tricarboxylic acid (TCA) cycle. α-KG is an essential cofactor for α-KG dependent dioxygenases such as the ten-eleven translocation (TET) family of DNA demethylase. The lack of α-KG in CuONPs-treated embryos led to DNA hypermethylation, which reduced chromatin accessibility, and suppressed the expression of pluripotent genes like sox2, klf2, and klf4. The poor pluripotency ultimately leads to abnormal embryonic development in CuONPs-treated embryos. Limitations, reasons for caution The molecular mechanism by which CuONPs arrest the development of pre-implantation embryos remains to be determined. In addition, future work should be extended to human embryos to determine whether this mechanism is conserved between mice and humans. Wider implications of the findings The findings of this work indicated the relationship between CuONPs and epigenetic modification. The results will support a more thorough understanding into the biosafety of CuONPs, and offer fresh perspectives on the potential uses of nanomaterials in the field of reproductive medicine in the future. Trial registration number Not Applicable

O-261 Frozen gametes differ in post-insemination dynamics to their fresh sibling counterparts in cycles using testicular sperm

Abstract Study question Are there differences in post-insemination events between fresh and frozen-derived gametes when testicular sperm extraction (TESE) is used? Summary answer Frozen-TESE leads to decreased fertilization, but not blastocyst euploidy rates; 2PN-lag time is significantly longer when frozen gametes are utilized compared to their fresh counterparts What is known already Studies indicate that the origin of testicular sperm influences the development potential of cleavage-stage embryos into blastocysts. Recent morphokinetic analysis suggest that embryos from frozen-TESE exhibit prolonged pronuclear stages and more frequent uneven cleavage compared to those from ejaculated sperm. Notably, no comparison with fresh-TESE was performed. To date, no studies have explored analysis in embryo morphokinetic parameters comparing fresh and frozen-TESE, especially when derived from the same patient.Such comparisons could provide a more accurate understanding of potential differences. Given that TESE occasionally involves the use of vitrified oocytes, it is essential to thoroughly examine outcomes across all combinations. Study design, size, duration Retrospective cohort study in a tertiary referral IVF centre including 72 cycles of 30 couples between January 2017 to September 2023. Following insemination by TESE-sperm, embryos were cultured in time-lapse (TL) incubator. Blastocysts ≥BL3CC (Gardner’s) underwent trophectoderm (TE) biopsy for Preimplantation Genetic Testing for aneuploidy (PGT-A) by next generation sequency (NGS). Participants/materials, setting, methods Gamete sources were fresh (fresh-TESE) or frozen-thawed-TESE (frozen-TESE) from the same patients with non-obstructive azoospermia (NOA), and fresh or vitrified (frozen) oocytes from the same female partner. Fertilization, usable blastocysts, and euploidy rates were recorded. Morphokinetics were annotated for time (t) of PB2 (tPB2), tPNa (PN-appearance), tPNf (PN-fading), t2-t9, CP (compaction), tM (Morula), tSB (start blastulation), tB (blastocyst) and timings between each developmental event. Main results and the role of chance Among included 980 oocyte/TESE dyads, 253 (25.8%) used fresh oocyte/sperm, 141 (14.4%) frozen oocyte/fresh sperm, 558 (56.9%) fresh oocyte/frozen sperm and 28 (2.9%) frozen oocyte/sperm. In oocyte/sperm dyads using fresh-TESE, normal fertilization (2PN) (52.0% vs. 44.5%) were higher compared to dyads using frozen-TESE (P &amp;lt; 0.01). Mixed-effects logistic-regression accounting for dependency structure between oocytes/sperm dyads of the same couple, showed an association of frozen-TESE with lower fertilization (OR: 0.64, 95%CI: 0.45-0.89, P = 0.008) and lower blastulation (³BL3CC)/MII (OR: 0.53, 95%CI: 0.37-0.77, P = 0.001), but similar blastulation (³BL3CC)/2PN (OR: 0.69, 95%CI: 0.45-1.07, P = 0.09). After accounting for female age, euploidy per tested blastocyst was similar whether fresh or frozen sperm was used (OR: 0.91, 95% CI: 0.46-1.79, P = 0.788). Frozen oocyte use on the other hand was not significantly associated with these outcomes (P &amp;gt; 0.05 for all). Analysis of morphokinetic parameters revealed that use of frozen dyads was associated with longer duration of 2PN after tPNa to tPNf: in frozen-TESE, 2.10h longer (95%CI: 0.55-3.64, P = 0.008); and in frozen oocytes, 2.34h longer (95%CI: 0.31-4.36, P = 0.024). Among embryos reaching blastulation, frozen-TESE embryos reached 6-cell stage earlier (tPNf to t6, 2.4h earlier, P = 0.009) but they were somewhat delayed in reaching expansion from there on (t6 to tEB, 4.4 hours later, P = 0.059). Limitations, reasons for caution In certain oocytes, insemination was conducted using either fresh or frozen immotile sperm that showed unresponsiveness to activation methods. However, the samples size hinders a comprehensive comparison. Wider implications of the findings Use of frozen-thawed TESE from NOA-patients may decrease fertilization and consequently lower blastocyst yield, but not euploidy rates. Synchronizing fresh-TESE with oocyte retrieval appears safer to maximize fertilization. Regardless of the gamete type, frozen-sourced sperm or oocyte impact 2PN-lag time, possibly indicating nuclear repair mechanisms post-freezing, requiring further investigation. Trial registration number 2310-ABU-020-VF

P-515 The morphokinetic signature of high-level mosaic embryos in time-lapse ART analysis

Abstract Study question Do high-level mosaic embryos exhibit differences in developmental speed compared to euploid or low-level mosaic embryos? Summary answer High-level mosaic embryos exhibit slower development than euploid and low-level mosaic embryos during the blastulation and blastocyst formation stages. What is known already Time-lapse technology (TLT) has facilitated the real-time observation of human embryo development without disrupting culture conditions, generating a wealth of morphokinetic data linked to outcomes such as implantation potential, blastocyst development, and ploidy status. However, the developmental patterns of mosaic embryos based on their aneuploidy level using TLT remain not well understood. Consequently, we aimed to assess the clinical significance of morphokinetic parameters in human embryo development, with a specific focus on embryos categorized by their mosaic status. Study design, size, duration This retrospective study examined 385 blastocysts undergoing preimplantation genetic testing for aneuploidy (PGT-A) between January and December 2022. Out of the total, 191 expansion blastocysts underwent PGT-A biopsy on day 5. The PGT-A results, which categorized embryos into euploid, aneuploid, and mosaic based on their genetic composition, were determined through next-generation sequencing (NGS) by an analysis company. Mosaic embryos were further categorized into two groups: high-level mosaicism (&amp;gt;30% aneuploidy cells) and low-level mosaicism (≤30%). Participants/materials, setting, methods Differences in development rates were assessed through the examination of morphological and morphokinetic parameters. These parameters included the time to second polar body extrusion (tPB2), time to pronuclei appearance and fading (tPNa, tPNf), time to reach 2–8 cells (t2, t3, t4, t5, t6, t7, t8, t9), and time to the onset of blastulation and blastocyst formation (tSB, tB). Statistical analyses, incorporating ANOVA and post-hoc tests, were employed to compare developmental timings across different groups. Main results and the role of chance When categorizing mosaic embryos based on their level, high-level mosaic embryos showed a significantly slower developmental rate than low-level mosaic embryos, evident at both the blastulation stage (tsB, high-level vs. low-level: 101.80h vs. 97.3h, p=0.003) and blastocyst stage (tB, high-level vs. low-level: 109.98h vs. 105.92h, p=0.005). In comparison to euploid embryos, low-level mosaic embryos demonstrated comparable outcomes. Conversely, high-level embryos exhibited a significant difference in both blastulation (tsB, euploidy vs. high-level: 98.85h vs. 101.80h, p=0.026) and blastocyst (tB, euploidy vs. high-level: 106.73h vs. 109.98h, p=0.011) stages. These findings suggested that the mosaic level of embryos might influence developmental kinetics, proposing this approach as an additional tool for the selection of mosaic embryos in the context of embryo transfer. Limitations, reasons for caution This study focused on morphokinetic parameters captured using time-lapse imaging, which may not fully represent the complex cellular dynamics within embryos. Furthermore, the categorization of mosaic embryos into high-level and low-level groups based on the percentage of mosaicism (&amp;gt;30% and ≤30%, respectively) might not capture all embryo developmental potential. Wider implications of the findings The findings suggest valuable predictive potential in assessing the development of aneuploid and mosaic embryos. Further research into the development of euploid, aneuploid, and mosaic embryos, as well as high-level and low-level mosaic embryos, could provide valuable insights for ART practices. This could significantly impact ART decision-making and patient outcomes. Trial registration number not applicable

Mapping of long interspersed element-1 (L1) insertions by TIPseq provides information about sub chromosomal genetic variation in human embryos.

Retrotransposons play important roles during early development when they are transiently de-repressed during epigenetic reprogramming. Long interspersed element-1 (L1), the only autonomous retrotransposon in humans, comprises 17% of the human genome. We applied the Single Cell Transposon Insertion Profiling by Sequencing (scTIPseq) to characterize and map L1 insertions in human embryos. Sixteen cryopreserved, genetically tested, human blastocysts, were accessed from consenting couples undergoing IVF at NYU Langone Fertility Center. Additionally, four trios (father, mother, and embryos) were also evaluated. scTIPseq was applied to map L1 insertions in all samples, using L1 locations reported in the 1000 Genomes as controls. Twenty-nine unknown and unique insertions were observed in the sixteen embryos. Most were intergenic; no insertions were located in exons or immediately upstream of genes. The location or number of unknown insertions did not differ between euploid and aneuploid embryos, suggesting they are not merely markers of aneuploidy. Rather, scTIPseq provides novel information about sub-chromosomal structural variation in human embryos. Trio analyses showed a parental origin of all L1 insertions in embryos. Several studies have measured L1 expression at different stages of development in mice, but this study for the first time reports unknown insertions in human embryos that were inherited from one parent, confirming no de novo L1 insertions occurred in parental germline or during embryogenesis. Since one-third of euploid embryo transfers fail, future studies would be useful for understanding whether these sub-chromosomal genetic variants or de novo L1 insertions affect embryo developmental potential.

The timing of pronuclear transfer critically affects the developmental competence and quality of embryos.

Pronuclear transfer has been successfully used in human-assisted reproduction to suppress the adverse effects of a defective oocyte cytoplasm or to bypass an idiopathic developmental arrest. However, the effects of the initial parental genome remodelling in a defective cytoplasm on the subsequent development after pronucleus transfer have not been systematically studied. By performing pronuclear transfer in pre-replication and post-replication mouse embryos, we show that the timing of the procedure plays a critical role. Although apparently morphologically normal blastocysts were obtained in both pre- and post-replication pronuclear transfer groups, post-replication pronuclear transfer led to a decrease in developmental competence and profound changes in embryonic gene expression. By inhibiting the replication in the abnormal cytoplasm before pronuclear transfer into a healthy cytoplasm, the developmental potential of embryos could be largely restored. This shows that the conditions under which the first embryonic replication occurs strongly influence developmental potential. Although pronuclear transfer is the method of choice for mitigating the impact of a faulty oocyte cytoplasm on early development, our results show that the timing of this intervention should be restricted to the pre-replication phase.

Impact of culture media pre-equilibration methods on embryo development

This study investigates the influence of four culture media pre-equilibration methods on embryo development and clinical pregnancy outcomes. The methods are as follows: Method A involved covering media with fresh mineral oil in humid-type incubators for 24 h. Method B replicated Method A in dry-type incubators. Method C utilized pre-equilibrated (humidified) mineral oil to cover the media, also in humid-type incubators for 24 h. Method D followed the same process as Method C but in dry-type incubators. Subsequently, media from all groups were transferred to dry-type incubators for 72 h. Osmolality was measured at 24, 48, 72, and 96 h. For G1 PLUS, no significant differences were observed among groups at 24, 48, and 72 h. However, at 96 h, Groups B and D exhibited significantly higher osmolality than Groups A and C (A vs B, p = 0.043; A vs D: p = 0.046; B vs C, p = 0.043; C vs D, p = 0.046). No significant variations were found between Groups A and C or B and D. Similar results were obtained for G2 PLUS. A retrospective analysis of embryo development and clinical outcomes using Methods A revealed significant improvements in good blastocysts and available embryos compared with Method B for all (p = 0.005 and 0.004) and IVF cycles (p = 0.025 and 0.017). Method A also enhanced blastocyst formation in ICSI cycles (p = 0.017). However, clinical pregnancy outcomes did not significantly differ between Methods A and B. Pre-equilibrating culture media overnight in humid-type incubators, even when covered with fresh mineral oil, significantly mitigates osmolality rise and improves embryo development potential during embryo culture in dry-type incubators.

Decreased embryo developmental potential and lower cumulative pregnancy rate in men with multiple morphological abnormalities of the sperm flagella.

Multiple morphological abnormalities of the sperm flagella (MMAF) is characterized by abnormal flagellar phenotypes, which is a particular kind of asthenoteratozoospermia. Previous studies have reported a comparable intracytoplasmic sperm injection (ICSI) outcome in terms of fertilization rate and clinical pregnancy rate in patients with MMAF compared with those with no MMAF; however, others have conflicting opinions. Assisted reproductive technology (ART) outcomes in individuals with MMAF are still controversial and open to debate. A total of 38 patients with MMAF treated at an academic reproductive center between January 2014 and July 2022 were evaluated in the current retrospective cohort study and followed up until January 2023. Propensity score matching was used to adjust for the baseline clinical characteristics of the patients and to create a comparable control group. The genetic pathogenesis of MMAF was confirmed by whole exome sequencing. The main outcomes were the embryo developmental potential, the cumulative pregnancy rate (CLPR), and the cumulative live birth rate (CLBR). Pathogenic variants in known genes of DNAH1, DNAH11, CFAP43, FSIP2, and SPEF2 were identified in patients with MMAF. Laboratory outcomes, including the fertilization rate, 2PN cleavage rate, blastocyst formation rate, and available blastocyst rate, followed a trend of decline in the MMAF group (p < 0.05). Moreover, according to the embryo transfer times and complete cycles, the CLPR in the cohort of MMAF was lower compared with the oligoasthenospermia pool (p = 0.033 and p = 0.020, respectively), while no statistical differences were observed in the neonatal outcomes. The current study presented decreased embryo developmental potential and compromised clinical outcomes in the MMAF cohort. These findings may provide clinicians with evidence to support genetic counseling and clinical guidance in specific patients with MMAF.

Evaluating the developmental potential of 2.1PN-derived embryos and associated chromosomal analysis.

Zygotes with 2.1 pronuclei (2.1PN) present with two normal-sized pronuclei, and an additional smaller pronucleus, that is approximately smaller thantwo thirds the size of a normal pronucleus. It remains unclear whether the additional pronucleus causes embryonic chromosome abnormalities. In the majority of cases, in vitro fertilization (IVF) clinics discarded 2.1PN zygotes. Thus, the present study aimed to evaluate the developmental potential and value of 2.1PN zygotes. 2.1PN-derived embryos from 164 patients who underwent IVF or intracytoplasmic sperm injection (ICSI) treatment between January 2021 and December 2022 were included in the present study. All embryos were monitored using a time-lapse system, and blastocyst formation was used to assess 2.1PN-derived embryo developmental potential. The blastocyst formation was quantified using generalized estimating equations, and chromosome euploidy was analyzed using next-generation sequencing (NGS). In addition, the potential association between age and occurrence of 2.1PN zygotes was determined. The present study demonstrated that numerous 2.1PN zygotes developed into blastocysts. Early cleavage patterns and embryo quality on Day 3 were the independent predictors for the blastocyst formation of 2.1PN-derived embryos. The 2.1PN zygotes displayed a comparable developmental potential compared to 2PN zygotes in advanced age patients (≥ 38). Moreover, there was a tendency that 2.1PN-derived blastocysts showed a similar euploidy rate compared to 2PN-derived blastocysts. Clinicians should consider using 2.1PN-derived euploid embryos for transfer after preimplantation genetic testing in the absence of available 2PN embryo cycles. 2.1PN-derived embryos could be a candidate, particularly beneficial for patients at advanced age.

Progestins for pituitary suppression during ovarian stimulation in artificial reproductive technology

Background: Progestins can suppress endogenous luteinizing hormone secretion from the pituitary gland. Progestins can be used orally and are less expensive than gonadotrophin-releasing hormone (GnRH) analogs. However, early endometrial exposure to progestin precludes fresh embryo transfer (ET), but the emergence of vitrification for oocyte cryopreservation cycles allows more opportunities for using progestins for pituitary suppression.&#x0D; Objective: To assess the mechanism of pituitary suppression by progestins, the effectiveness of progestins compared with GnRH analogs, the effect of progestins on oocyte and embryo developmental potential and euploidy status, and the cost-effectiveness of progestin-primed stimulation. &#x0D; Methods: A literature search using the keywords “multiple waves of antral ovarian follicular development, In Vitro Fertilization, Ovarian stimulation ” was performed in the PubMed database.&#x0D; Results: The duration of stimulation, gonadotrophin consumption, and oocyte yield were similar in progestins and GnRH analogs. However, progestins were associated with significantly lower gonadotrophin consumption than their analogs. Overall, live birth and clinical pregnancy rates per ET were similar to those of progestins and GnRH analogs. Studies comparing medroxyprogesterone acetate, dydrogesterone, and micronized progesterone suggest similar ovarian responses and pregnancy outcomes. The euploidy status of embryos and obstetric and neonatal outcomes from progestin-primed cycles are similar to those of embryos from conventional stimulation cycles. Despite the lower cost of progestins than GnRH analogs, the mandatory cryopreservation of all embryos followed by a deferred transfer may increase the cost per live birth with progestins compared with an artificial reproductive technology cycle culminating in a fresh ET.&#x0D; Conclusion: Progestins present an effective option for women who do not contemplate a fresh ET, e.g., fertility preservation, anticipated hyper responders, preimplantation genetic testing, oocyte donors, and double stimulation cycles.

Glutathione safeguards TET-dependent DNA demethylation and is critical for the acquisition of totipotency and pluripotency during preimplantation development.

During early development, both genome-wide epigenetic reprogramming and metabolic remodeling are hallmark changes of normal embryogenesis. However, little is known about their relationship and developmental functions during the preimplantation window, which is essential for the acquisition of totipotency and pluripotency. Herein, we reported that glutathione (GSH), a ubiquitous intracellular protective antioxidant that maintains mitochondrial function and redox homeostasis, plays a critical role in safeguarding postfertilization DNA demethylation and is essential for establishing developmental potential in preimplantation embryos. By profiling mitochondria-related transcriptome that coupled with different pluripotency, we found GSH is a potential marker that is tightly correlated with full pluripotency, and its beneficial effect on prompting developmental potential was functionally conformed using invitro fertilized mouse and bovine embryos as the model. Mechanistic study based on preimplantation embryos and embryonic stem cells further revealed that GSH prompts the acquisition of totipotency and pluripotency by facilitating ten-eleven-translocation (TET)-dependent DNA demethylation, and ascorbic acid (AsA)-GSH cycle is implicated in the process. In addition, we also reported that GSH serves as an oviductal paracrine factor that supports development potential of preimplantation embryos. Thus, our results not only advance the current knowledge of functional links between epigenetic reprogramming and metabolic remodeling during preimplantation development but also provided a promising approach for improving current invitro culture system for assisted reproductive technology.

Overexpression of BRG1 improves early development of porcine somatic cell nuclear transfer embryos

The epigenetic modification levels of donor cells directly affect the developmental potential of somatic cell nuclear transfer (SCNT) embryos. BRG1, as an epigenetic modifying enzyme, has not yet been studied in donor cells and SCNT embryos. In this study, BRG1 was overexpressed in porcine fetal fibroblasts (PFFs), its effect on chromatin openness and gene transcription was examined, subsequently, the development potential of porcine SCNT embryos was investigated. The results showed that compared with the control group, the percentage of G1 phase cells was significantly increased (32.3 % ± 0.87 vs 25.7 % ± 0.81, P < 0.05) in the experimental group. The qRT-PCR results showed that the expression of H3K9me3-related genes was significantly decreased (P < 0.05), HAT1 was significantly increased (P < 0.05). Assay of Transposase Accessible Chromatin sequencing (ATAC-seq) results revealed that SMARCA4、NANOG、SOX2、MAP2K6 and HIF1A loci had more open chromatin peaks in the experimental group. The RNA-seq results showed that the upregulated genes were mainly enriched in PI3K/AKT and WNT signaling pathways, and the downregulated genes were largely focused on disease development. Interestingly, the developmental rate of porcine SCNT embryos was improved (27.33 % ± 1.40 vs 17.83 % ± 2.02, P < 0.05), the expression of zygotic gene activation-related genes in 4-cell embryos, and embryonic development-related genes in blastocysts was significantly upregulated in the experimental group (P < 0.05). These results suggest that overexpression of BRG1 in donor cells is benefit for the developmental potential of porcine SCNT embryos.

Understanding the implications of follicular output rate (FORT) and follicle to oocyte index (FOI) on human embryo morphokinetics

Objective To study if there are any effects of follicular output rate (FORT) and follicle to oocyte index (FOI) on embryos morphokinetics. Study design Kinetic data of 8,376 embryos, cultured in a time-lapse imaging incubator, derived from 2,470 patients undergoing ICSI cycles were analysed. Embryos were split into groups according to FOI value: Low FOI (n=247 cycles and 894 embryos) and High FOI (n=2,223 cycles and 7,482 embryos) and according to the FORT value: Low FORT (n= 753 cycle and 2,556 embryos), Medium FORT (n=874 cycles and 2,970 embryos), and High FORT (n=843 cycles and 2,850 embryos). Morphokinetic data were compared among the groups. Results Embryos derived from cycles with a low FOI presented slower development, a significantly lower KID score D5, blastocyst formation, and implantation rates when compared with those from cycles with high FOI. For the FORT, an increased time to complete morphokinetic events, significantly lower rates of blastocyst formation and implantation was observed among embryos derived from cycles with low FORT, followed by those with medium FORT, while embryos derived from cycles with high FORT presented a better development competence. However, no significant differences were noted in clinical pregnancy, miscarriage, or livebirth rates when the low, medium, and high FORT groups were compared. Conclusion FORT and FOI correlate with faster embryo development and may be a valuable approach to predict embryo developmental potential.

Morphological assessment of oocyte quality during assisted reproductive technology cycle.

Following the advancement of medically assisted reproduction (MAR) technology, and the rationale to extend the culture to the blastocyst stage, performing elective single embryo transfer (eSET), gamete quality and assessment have acquired large relevance in ART. Embryo quality is strictly correlated with gametes quality and culture conditions. Oocyte maturity assessment is therefore imperative for fertilization and embryo evolution. Mature oocytes at the metaphase II stage result in a higher fertilization rate compared to immature oocytes. Indeed, oocyte morphology evaluation represents an important and challenging task that may serve as a valuable prognostic tool for future embryo development and implantation potential. Different grading systems have been reported to assess human embryos, however, in many cases, it is still a major challenge to select the single embryo to transfer with the highest implantation potential. Further, eSET has conferred a challenge to embryologists, who must try to enhance embryo culture and selection to provide an adequate success rate, whilst reducing the overall number of embryos transferred. Above the standard morphological assessment, there are several invasive or non-invasive approaches for embryo selection such as preimplantation genetic testing, time-lapse technology, proteomics and metabolomics, as well as oxygen utilization and analysis of oxidative stress in culture medium. This short review is not designed to be a comprehensive review of all possible features that may influence oocyte quality. It does give, however, a brief overview and describes the prognostic value of the morphological characteristics of human oocytes on their developmental capacity following ART treatments.