Preimplantation Embryo Quality Research Articles

84 Characterization and effect of endometriosomes on the development and quality of pre-implantation bovine embryos

84 Characterization and effect of endometriosomes on the development and quality of pre-implantation bovine embryos

Elevated intracellular pH of zygotes during mouse aging causes mitochondrial dysfunction associated with poor embryo development

The mortality of preimplantation embryos is positively correlated with maternal age. However, the underlying mechanism for the poor quality of embryos remains unclear. Here, we found that aging caused elevated intracellular pH (pHi) in zygotes, which could trigger aberrant mitochondrial membrane potential, increased reactive oxygen species (ROS) levels, and poor embryo development. Moreover, single-cell transcriptome sequencing of mouse zygotes identified 120 genes that were significantly differentially expressed (DE) between young and older zygotes. These include genes such as Slc14a1, Fxyd5, CD74, and Bst, which are related to cell division, ion transporter, and cell differentiation. Further analysis indicated that these DE genes were enriched in apoptosis, the NF-kappa B signaling pathway, and the chemokine signaling pathway, which might be the key regulatory pathway affecting the quality of zygotes and subsequent embryo development. Taken together, our study helps elucidate the poor quality and development of older preimplantation embryos.

Comprehensive Analysis of the Effect of Maternal and Paternal Demographics and Lifestyle Factors on the Embryo Quality and In Vitro Fertilization Outcomes: A Retrospective Study in North Eastern India.

Background Lifestyle habits and demographic characteristics are strongly associated with sperm and oocyte quality and are important co-variates in fertility. However, their effect on the pre-implantation embryo quality in in vitro fertilization (IVF) has not been explored widely. The present retrospective study aimed to explore the effect of maternal and paternal demographic and lifestyle factors on the pre-implantation embryo quality in IVF. Methodology Women in the age group of 21 to 40 years undergoing IVF (n=105) in the Department of Reproductive Medicine, Indira Gandhi Institute of Medical Sciences, Patna, Bihar, and their partners were recruited in the study. Maternal and paternal charts were reviewed, and the demographic, lifestyle habit related data, and data related to oocyte retrieval, oocyte quality, and embryo quality were retrieved in a predesigned spreadsheet. Appropriate statistical analysis was conducted using SPSS Version 21 to evaluate the association of the studied maternal and paternal factors with oocyte and embryo quality. P-values less than 0.05 were considered to be significant. Results Maternal factors such as tubal blockage (p=0.02) and residence in an industrial locality (p=0.001) were found to be significantly associated with the quality of oocytes. None of the maternal factors studied were associated with embryo quality; however, day 3 and day 5 embryo quality was significantly associated with educational status of the male partners (p=0.02), smoking (p=0.05), and chewing tobacco (p=0.01). Day 5 embryo quality was also associated with residence in an industrial locality of the male partners (p=0.04). Conclusions Paternal lifestyle habits such as smoking, chewing tobacco, and demographic characteristics such as education and proximity to an industrial area were all related to poor embryo quality. Maternal factors such as tubal blockage and residence of industrial locality were found to be significantly associated with the quality of oocytes.

Current status of genome-wide epigenetic profiling of mammalian preimplantation embryos.

Genome-wide information on epigenetic modifications in mammalian preimplantation embryos was an unexplored sanctuary of valuable research insights protected by the difficulty of its analysis. However, that is no longer the case, and many epigenome maps are now available for sightseeing there. This review overviews the current status of genome-wide epigenetic profiling in terms of DNA methylome and histone modifications in mammalian preimplantation embryos. As the sensitivity of methods for analyzing epigenetic modifications increased, pioneering work began to explore the genome-wide epigenetic landscape in the mid-2010s, first for DNA methylation and then for histone modifications. Since then, a huge amount of data has accumulated, revealing typical epigenetic profiles in preimplantation development and, more recently, changes in response to environmental interventions. These accumulating data may be used to improve the quality of preimplantation embryos, both in terms of their short-term developmental competence and their subsequent long-term health implications.

Non-invasive evaluation of embryo quality for the selection of transferable embryos in human in vitro fertilization-embryo transfer.

The ultimate goal of human assisted reproductive technology is to achieve a healthy pregnancy and birth, ideally from the selection and transfer of a single competent embryo. Recently, techniques for efficiently evaluating the state and quality of preimplantation embryos using time-lapse imaging systems have been applied. Artificial intelligence programs based on deep learning technology and big data analysis of time-lapse monitoring system during in vitro culture of preimplantation embryos have also been rapidly developed. In addition, several molecular markers of the secretome have been successfully analyzed in spent embryo culture media, which could easily be obtained during in vitro embryo culture. It is also possible to analyze small amounts of cell-free nucleic acids, mitochondrial nucleic acids, miRNA, and long non-coding RNA derived from embryos using real-time polymerase chain reaction (PCR) or digital PCR, as well as next-generation sequencing. Various efforts are being made to use non-invasive evaluation of embryo quality (NiEEQ) to select the embryo with the best developmental competence. However, each NiEEQ method has some limitations that should be evaluated case by case. Therefore, an integrated analysis strategy fusing several NiEEQ methods should be urgently developed and confirmed by proper clinical trials.

P-475 Similar fertilization rates and preimplantation embryo development among testosterone-treated transgender men and cisgender women

Abstract Study question What are the effects of testosterone treatment on fertilization rates and preimplantation embryo development among transgender men who underwent fertility preservation? Summary answer Testosterone exposure among transgender men has no adverse impacts on fertilization rates and preimplantation embryo development and quality. What is known already Transmen are assigned female sex at birth but identify as men. This mismatch might induce distress that is termed gender dysphoria. Testosterone therapy induces “masculine” physical traits, suppresses “feminine” ones, and relieves gender dysphoria. More transmen present for testosterone therapy, their average age is decreasing, and many express the desire to have biological children. Therefore, understanding the effects of testosterone on fertility is crucial. Previous data suggest that despite testosterone treatment, the ovarian reserve and the in-vitro oocyte maturation are preserved among transmen. However, the fertility potential in terms of fertilization rate and early embryo development was not explored. Study design, size, duration This retrospective cohort study included 7 testosterone-treated transgender men and 34 cisgender women between April 2016 and November 2021. Participants/materials, setting, methods Testosterone-treated transgender men who cryopreserved embryos were compared to 10 fertile women who cryopreserved embryos and to 24 women who underwent IVF treatment due to unexplained or mechanical infertility. Statistical analyses compared assisted reproductive technology data and outcomes between the transgender men group and the two cisgender women groups. Morphokinetic and morphological parameters were compared between 210 embryos of transgender men and 411 embryos of cisgender women. Main results and the role of chance The transgender men (30.2±3.59 years) were significantly younger than the cisgender women who cryopreserved embryos (35.1±1.85 years; P = 0.005) and the cisgender women who underwent fertility treatment (33.8±3.23 years; P = 0.017). Among the transgender men, the mean length of testosterone exposure was 99.7±49.24 months (range 14-156 months) and the mean time of discontinuation of testosterone prior to stimulation was 6.57±2.14 months (range 4-10 months). After adjusting for the patient’s age, the fertilization rate was comparable between the transgender men and both cisgender women groups (P = 0.391 and 0.659). No significant differences in the number of cryopreserved embryos (7.2±5.09 and 3.5±2.66; P = 0.473) and the days on which they were frozen (P = 0.576) were observed between the transgender men and the fertile cisgender women. All morphokinetic parameters that were evaluated using time-lapse imaging, as well as the morphological characteristics, were comparable between transgender men and both groups of cisgender women. Limitations, reasons for caution All transgender men in our study discontinued the testosterone treatment before starting ovarian stimulation. Stopping hormonal therapy might cause considerable anguish and gender dysphoria. Therefore, further studies that include subjects who did not stop testosterone before fertility preservation are needed. Wider implications of the findings Transgender men have acceptable fertilization rates and normal preimplantation embryo development and quality after long-term testosterone treatment. Embryo cryopreservation is, therefore, a feasible and effective way for them to preserve their fertility for future biological parenting. Trial registration number Not applicable

P-239 Embryonic quality assessment from microRNA profiling

Abstract Study question Does the microRNA expression profile in blastocysts change with different embryonic quality parameters? Summary answer MicroRNA expression showed significant changes when aneuploidy was present, in day-6 compared to day-5 blastocysts and with different trophectoderm (TE) morphology grades. What is known already MicroRNA (miRNA) is a gene expression regulatory mechanism used as a diagnostic marker for some conditions. Despite the great magnitude of studies investigating the miRNA role in implantation and pregnancy complications, limited work has been done to evaluate it as a potential marker for preimplantation embryo quality. With the accelerated changes in gene expression at early embryos, the miRNA profile is a potential indicator of embryo quality. This study investigates the blastocyst miRNA profile in relation to three quality parameters: aneuploidy, the day of blastocyst formation and morphology. Study design, size, duration We collected 122 surplus embryos donated for research by 46 consenting couples from Centre for Reproductive and Genetic Health, London. All samples were ICSI derived blastocysts (day5/6) with PGT-A results. For aneuploidy status comparison, samples were categorized according to the number of chromosomes affected (single/multiple) and type of aneuploidy (gain/loss/partial), compared to euploid. The day of blastocyst development has (day5/day6) groups, and finally samples were compared based on TE morphology (excellent/good/fair). Participants/materials, setting, methods Frozen human embryos were individually thawed and transferred to a lysis buffer. The miRNAs were extracted from each sample then sequenced by next generation sequencing (NGS) using miRNA Library Kit (QIAGEN) with NextSeqTM 500 (illumina). The differential expression analysis was conducted using DESeq2 via GeneGlobe (QIAGEN). We set the significance cut-offs to (-2> foldchange >2) and (<0.05 FDR p-value). For gene ontology and pathway annotation, we used miRTargetLink 2.0 and miRPathDB 2.0 platforms. Main results and the role of chance Compared to the euploid blastocysts, all aneuploid categories, except the single chromosome aneuploidy, had significant differences in miRNA expression. Nine miRNAs were altered in the group with multiple aneuploidies, and one was highly upregulated in embryos with partial losses or gains. The majority of differentially expressed (DE) miRNAs in samples with whole chromosomal gain or loss were downregulated. Conversely, four miRNAs showed a significant increase in day-6 blastocysts compared to day-5. Morphology grade comparisons showed no differences between excellent and good TE; however, six miRNAs were significantly changed in fair TE compared to good. The frequently altered miRNAs in these comparisons were ( hsa-let-7c-5p, hsa-miR-206, hsa-miR-184 and hsa-miR-203a-3p ). Unsurprisingly, pathway annotation of the DE miRNAs showed an involvement of key biological processes, like apoptosis, cell-cycle and differentiation, signalling and gene expression regulation, in all groups. The pathways of note in aneuploid blastocysts included DNA damage response, intrinsic and extrinsic apoptotic signalling, and regulation of cell-cycle G1/S associated events. In blastocyst day5/day6 comparison, embryonic and organ development were the most involved pathways, while in TE morphology, kinase activity and phosphorylation along with apoptosis and DNA damage response were significant. Limitations, reasons for caution Differential expression analysis based on inner cell mass (ICM) morphology and blastocyst expansion were not applicable due to the inadequate number of embryos per group; as all the samples collected were in excellent or good quality. Wider implications of the findings Gene expression profiling of miRNAs in human blastocysts will potentially identify biomarkers predictive of implantation success. Trial registration number not applicable

P-252 Oolemma surface area impacts human pre-implantation embryo development and usage: The Rotterdam Periconception Cohort

Abstract Study question Does oolemma area change before the 2-cell stage? Is oolemma area associated with fertilization rate, embryo usage rate and preimplantation embryo development? Summary answer Oolemma area is associated with preimplantation embryo development, the odds of fertilizing and developing into a used or discarded embryo. What is known already Current morphological grading systems are based on embryo morphology and omit oocyte morphology. Fertilization and embryo potential are largely determined by the maturation and quality of the oocyte. Oocyte quality correlates to morphology, and the very early stages of embryo development are critical to changes in oocyte size. Larger oocyte size associates with higher quality blastocyst. This suggests that oocyte size can be a morphological marker of preimplantation embryo quality and assisted reproductive treatment (ART) outcomes. Study design, size, duration This study is embedded in the Rotterdam Periconceptional Cohort, an ongoing prospective tertiary hospital-based birth cohort study. From May 2017 to July 2020, a subcohort of 378 women that underwent ART was included comprising of 124 pregnancies after in vitro fertilization (IVF) and 254 after intracytoplasmic sperm injection (ICSI). Participants/materials, setting, methods Health, lifestyle and treatment factors were collected from detailed self-reported questionnaires and medical records. Oolemma area was measured at the time of fertilization (t0), pronuclear appearance (tPNa) and fading (tPNf). Oolemma area trajectories (slope surface t0-tPNf) were calculated with linear regression. Fertilization rate, embryo usage rate, and embryo morphokinetics were analyzed in association with oolemma area and trajectories. Analyses were performed with linear mixed models, mixed effects logistic regression, and adjusted for relevant confounders. Main results and the role of chance Oolemma area decreased from t0 to tPNf for oocytes that developed into both used or discarded embryos. Oolemma area at t0 was strongly associated with the rate of area shrinking, as larger oolemma areas had faster shrinking rates (Bshrinking -12.55 µm²/hour, 95%CI -14.55; -10.55, p < 0.001). Oocytes that resulted in a usable embryo were larger and reached tPNf faster than oocytes that resulted in a discarded embryo (tPNf 9855±595 µm2 vs 9690±721 µm2, p < 0.001, 24.4±3.6 h vs 26.5±5.8 h, p < 0.001). Oolemma area at tPNf did not differ between ICSI and IVF oocytes, however ICSI oocytes reached tPNf faster than IVF oocytes (23.6±3.2h and 25.9±3.8h, p < 0.001, respectively). In ICSI only, larger oolemma area showed lower odds of a successful fertilization (t0 OR 0.57, 95%CI 0.48; 0.67, p < 0.001), but higher odds of being cryopreserved or transferred (tPNf OR 1.66, 95%CI 1.33; 2.08, p < 0.001). For IVF and ICSI, larger oolemma area at tPNF was associated with faster preimplantation development up to the morula stage (t7 B -1.41, 95%CI -2.18; -0.63, p < 0.001). Oolemma area shrinking rate was not associated with embryo morphokinetics. Limitations, reasons for caution Small number of embryos measured at the blastocyst stage, and oolemma area measurements were not possible at t0 and tPNa for IVF oocytes. Wider implications of the findings Oolemma area is a suggested morphological marker for oocyte competence and an early marker for the success of fertilization and embryo development. The relevance of oolemma area as predictor of ART success requires further research. Cryopreservation and PCOS, which influence oocyte size, could be studied in association with oolemma area. Trial registration number not applicable

Division behaviours and their effects on pre-implantation development of pig embryos.

The quality of pre-implantation embryos could affect developmental efficiency after embryo transfer. However, the assessment of pre-implantation embryos was unsatisfactory, especially in pig embryos to date. Therefore, this study was designed to investigate available and applicable parameters that indicate developmental potential and quality of porcine pre-implantation embryos produced by handmade cloning (HMC), and parthenogenetic activation without zona pellucida (PAZF) and with zona pellucida (PAZI). Firstly, a common division behaviour was detected, that is the formation of uneven division with two unequal size blastomeres (UD 2-cell), especially in HMC embryos; then, the proportion of UD 2-cell was found to be significantly higher than that of even division with equal size blastomeres (ED 2-cell) (72.56 ± 4.56 vs. 24.57 ± 1.92). The formation of UD 2-cell might be due to the spindle migration along the long axis in 1-cell stage, and the cleavage furrow was not formed in the centre of cytoplasm. In the two sister blastomeres of UD 2-cell, uneven distribution of organelles (mitochondria and lipid droplet) was observed with lower proportion in the smaller one (p<.05). Although no difference in blastocyst rate was observed between UD and ED 2-cell embryos, the cell number per blastocyst from UD 2-cell embryos was lower than that from ED 2-cell embryos (44.15 ± 2.05 vs. 51.55 ± 1.83). Besides, because of non-synchronized division of each blastomere, the following three cleavage routes were observed in all HMC/PAZF/PAZI embryos: T1 (2-cell → 3-cell → 4-cell → ≥5-cell → morula → blastocyst), T2 (2-cell → 3-cell → 4-cell → morula → blastocyst) and T3 (2-cell → 3-cell/4-cell → morula → blastocyst). Therefore, in pig in vitro-produced embryos, division behaviours of uneven volume of cytoplasm and non-synchronized cell cycles were observed at the early embryonic developmental stage, which might be another potential factor to evaluate embryonic development.

2,4,6-triiodophenol exhibits embryotoxicity to pre-implantation mouse embryos in an in vitro exposure model

2,4,6-triiodophenol (TIP), a novel type of halophenolic disinfection byproducts, has been widely detected in water bodies, even in drinking water. Recently, TIP has drawn increasing concerns on account of considerable developmental toxicity towards lower organisms and cytotoxicity for mammalian cells. However, it remains unknown about its toxicity on mammalian pre-implantation embryos. Here, by exposing mouse zygotes derived in vitro fertilization to TIP, which ranged from 5 to 50 μM, we found that TIP impaired the quality of pre-implantation mouse embryos in a dose-dependent manner, inducing decline of both total and trophectoderm cell numbers, enhancing caspase 3/7 activity and reactive oxygen species generation, though it did not decrease blastocyst formation efficiency. For the sake that only high qualified embryos are able to implant in endometrium and generate health body finally, we applied a previously modified in vitro culture system to assess TIP-exposed blastocysts’ further developmental potency beyond pre-implantation stage. Surprisingly, although the exposed dose was only 5 μM and TIP was removed as soon as the zygotes reached blastocyst stage, these blastocysts still nearly lost their implantation and egg cylinder formation ability, exhibiting abnormal embryonic lineage differentiation pattern as well. Therefore, our study not only entirely shows TIP embryonic toxicity on mouse pre-implantation embryos, but also proposes a model to evaluate embryotoxicity from the zygote to egg cylinder stage.

Similar fertilization rates and preimplantation embryo development among testosterone-treated transgender men and cisgender women

What are the effects of testosterone treatment on oocyte fertilization and preimplantation embryo development among transgender men who have undergone fertility preservation? A retrospective study was undertaken in a university-affiliated tertiary hospital between April 2016 and November 2021. Embryos were divided into three groups by source: 210 embryos from 7 testosterone-exposed transgender men, 135 from 10 cisgender women who cryopreserved embryos, and 276 from 24 cisgender women who underwent fertility treatment. Statistical analyses compared assisted reproductive technology outcomes between the group of transgender men and both groups of cisgender women. Morphokinetic and morphological parameters were compared between the embryos derived from these three groups. The transgender men (30.2±3.5 years of age) were significantly younger than the cisgender women who cryopreserved embryos (35.1±1.8 years; P=0.005) and the cisgender women who underwent fertility treatment (33.8±3.2 years; P=0.017). After adjusting for participant age, the fertilization rate was comparable between the transgender men and both groups of cisgender women (P=0.391 and 0.659). There were no significant differences between the transgender men and the cisgender women who preserved fertility in terms of number of cryopreserved embryos (7.2±5.1 and 3.5±2.6; P=0.473) or the distribution of embryo age at cryopreservation (P=0.576). All morphokinetic parameters evaluated by time-lapse imaging, as well as the morphological characteristics, were comparable for the embryos in all three groups. Testosterone exposure among transgender men has no adverse impact upon fertilization rates or preimplantation embryo development and quality.

Maternal underweight does not adversely affect the outcomes of IVF/ICSI and frozen embryo transfer cycles or early embryo development

Objective To compare assisted reproductive technology (ART) outcomes and preimplantation embryo development between underweight and normal-weight women. Methods This retrospective cohort study included 26 underweight women (body mass index [BMI] < 18.50 kg/m2) and 104 normal-weight women (BMI >20 and <24.9 kg/m2) who underwent a total of 204 in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles and 358 fresh/frozen embryo transfers (ET) in our institution between January 2016 and December 2018. Statistical analyses compared selected ART outcomes (ovarian stimulation, fertilization, and pregnancy) between both weight groups. Morphokinetic and morphological parameters were also compared between 346 and 1467 embryos of underweight and normal-weight women, respectively. Results The mean ± standard deviation age of the underweight and normal-weight women was similar (31.6 ± 4.17 vs 32.4 ± 3.59 years; p = .323). There were no differences in the peak estradiol levels, the number of retrieved oocytes, the number of metaphase II oocytes, and the oocyte maturity rates between the two groups. The IVF/ICSI fertilization rates and the number of embryos suitable for transfer or cryopreservation were similar for both groups. All morphokinetic parameters that were evaluated by means of time-lapse imaging as well as the morphological characteristics were comparable between low and normal BMI categories. There were no significant differences in pregnancy achievement, clinical pregnancy, live births, and miscarriage rates between the suboptimal and optimal weight women. Conclusion Underweight status has no adverse impacts on the outcomes of IVF/ICSI with either fresh or frozen ET or on preimplantation embryo development and quality.

Involvement of extracellular vesicle-encapsulated miRNAs in human reproductive disorders: a systematic review.

In recent years, extracellular vesicles (EVs) have emerged as essential players in cell-to-cell communication, particularly having an active regulating role in biological systems. Because reproductive-associated processes are not exempt of this communication, multiple studies have been devoted to this realm, focusing on gamete maturation, embryo implantation or fetal development. The aim of the present review was to comprehensively and systematically collect evidence about the function of the microRNA (miRNA) encapsulated in EVs isolated from different reproductive tissues or fluids in reproductive-related diseases. Following PRISMA guidelines, we conducted a systematic search of the literature published in MEDLINE-PubMed until the end of February 2021. After selection, 32 studies were included in the qualitative review comparing the miRNA expression profile in EVs between different pathological disorders. Most reports showed the potential of the miRNAs carried by EVs to be used as putative biomarkers of reproductive disorders, including pregnancy affections, disease progression and quality of preimplantation embryos. The most relevant miRNAs were found to be highly heterogeneous among studies, with some conflicting results. Further research is thus warranted to address whether cofounding factors, such as the methods to isolate EVs and miRNAs, the subset of EVs, the criteria of patient selection, the timing of sample retrieval, or any other factor, may explain the inconsistencies between studies.

Parameters to identify good quality oocytes and embryos in cattle

Oocyte/embryo selection methodologies are either invasive or noninvasive and can be applied at various stages of development from the oocyte to cleaved embryos and up to the blastocyst stage. Morphology and the proportion of embryos developing to the blastocyst stage are important criteria to assess developmental competence. Evaluation of morphology remains the method of choice for selecting viable oocytes for IVP or embryos prior to transfer. Although non-invasive approaches are improving, invasive ones have been extremely helpful in finding candidate genes to determine oocyte/embryo quality. There is still a strong need for further refinement of existing oocyte and embryo selection methods and quality parameters. The development of novel, robust and non-invasive procedures will ensure that only embryos with the highest developmental potential are chosen for transfer. In the present review, various methods for assessing the quality of oocytes and preimplantation embryos, particularly in cattle, are considered. These methods include assessment of morphology including different staining procedures, transcriptomic and proteomic analyses, metabolic profiling, as well as the use of artificial intelligence technologies.

Cumulus cells of euploid versus whole chromosome 21 aneuploid embryos reveal differentially expressed genes

Research questionCan cumulus cells be used as a non-invasive target for the study of determinants of preimplantation embryo quality? DesignCumulus cells were collected from monosomy 21, trisomy 21 and euploid embryos and subjected to RNA sequencing analysis and real-time polymerase chain reaction assays. The differential gene expression was analysed for different comparisons. ResultsA total of 3122 genes in monosomy 21 cumulus cells and 19 genes in trisomy 21 cumulus cells were differentially expressed compared with euploid cumulus cells. Thirteen of these genes were differentially expressed in both monosomy and trisomy 21, compared with euploid, including disheveled segment polarity protein 2 (DVL2), cellular communication network factor 1 (CCN1/CYR61) and serum response factor (SRF), which have been previously implicated in embryo developmental competence. In addition, ingenuity pathway analysis revealed cell–cell contact function to be affected in both monosomy and trisomy 21 cumulus cells. ConclusionsThese findings support the use of cumulus cell gene expression analysis for the development of biomarkers evaluating oocyte quality for patients undergoing fertility preservation of oocytes.

Male Factors: the Role of Sperm in Preimplantation Embryo Quality.

Few studies have been conducted on the paternal effects on embryogenesis as compared with studies on maternal effects. The fertility potential of sperm decreases with genomic material abnormalities. Damaged DNA of sperm has been correlated with poor fertilization, reduced implantation and pregnancy rates, and increased production of aneuploid embryos. Evidence suggests that the role of sperm in embryogenesis goes beyond genomic material transfer, and centrosomes, sperm-derived cytoplasmic factors, paternal mRNA, and small RNAs are essential for early embryonic development. Epigenetic factors like histone modification and DNA methylation participate in the regulation of gene expression in sperm. The etiology of sperm chromatin abnormalities is important in male fertility and may affect reproductive outcomes. Success in implantation depends on the quality of the fertilized sperm and oocyte as well as the type of assisted reproductive techniques. Therefore, male factors affecting development of embryo can play a role in the failure of assisted reproductive techniques. Further studies are needed to evaluate clinical aspects and the risks of transmitting genetic or epigenetic disorders to provide safe therapies for infertility.

Preconceptional Maternal Vegetable Intake and Paternal Smoking Are Associated with Pre-implantation Embryo Quality

Inadequate nutrition and lifestyle behaviors, particularly during the periconception period, are associated with a negative impact on embryonic and subsequent fetal development. We investigated the associations between parental nutritional and lifestyle factors and pre-implantation embryo development. A total of 113 women and 41 partners, with a corresponding 490 embryos, who underwent intracytoplasmic sperm injection (ICSI) treatment subscribed to the mHealth coaching platform “Smarter Pregnancy.” At baseline, nutrition and lifestyle behaviors (intake of fruits, vegetables, folic acid, and smoking and alcohol use) were identified and risk scores were calculated. A lower risk score represents healthier behavior. As outcome measure, a time-lapse morphokinetic selection algorithm (KIDScore) was used to rank pre-implantation embryo quality on a scale from 1 (poor) to 5 (good) after being cultured in the Embryoscope™ time-lapse incubator until embryonic day 3. To study the association between the nutritional and lifestyle risk scores and the KIDScore in men and women, we used a proportional odds model. In women, the dietary risk score (DRS), a combination of the risk score of fruits, vegetables, and folic acid, was negatively associated with the KIDScore (OR 0.86 (95% CI 0.76 to 0.98), p = 0.02). This could mainly be attributed to an inadequate vegetable intake (OR 0.76 (95% CI 0.59 to 0.96), p = 0.02). In men, smoking was negatively associated with the KIDscore (OR 0.53 (95% CI 0.33 to 0.85), p < 0.01). We conclude that inadequate periconceptional maternal vegetable intake and paternal smoking significantly reduce the implantation potential of embryos after ICSI treatment. Identifying modifiable lifestyle risk factors can contribute to directed, personalized, and individual recommendations that can potentially increase the chance of a healthy pregnancy.

Inverse relationship between autophagy and CTSK is related to bovine embryo quality.

Improving the quality and the developmental competence of in vitro produced (IVP) embryos is an indispensable goal for assisted reproductive technology. Autophagy is a major protective mechanism for intracellular degradation of unnecessary cytoplasmic components. Autophagy ends by the fusion between autophagic vacuoles and lysosomes, allowing the degradation of the cargo by lysosomal enzymes, especially the cathepsins (CTSs). However, it is still unclear how autophagy and cathepsin K (CTSK) relate to embryo development. This study evaluated (1.) the activities of autophagy and CTSK in relation to bovine embryo quality and (2.) the effect of autophagy induction and/or CTSK inhibition on preimplantation embryo development and quality. We show here that good-quality embryos exhibited a greater autophagic activity and less CTSK activity compared to poor-quality embryos. Blastomeres of an individual embryo may vary in their quality. Good quality blastomeres showed an increased autophagic activity and decreased CTSK activity compared to poor-quality blastomeres within the same embryo at different developmental stages. Importantly, induction of autophagy and/or inhibition of CTSK improved the developmental rate (increased blastocyst and hatching rates) and the quality (increased total cell number and decreased the percentage of apoptotic cells) of IVP bovine embryos. These results demonstrate a promising approach to selectively isolate good-quality embryos and improve the efficiency of IVEP of cattle embryos.

Low-dose Roundup induces developmental toxicity in bovine preimplantation embryos in vitro.

Roundup is a widely used glyphosate-based herbicide worldwide. Roundup residues can be detected in the organs and urine of animals. However, its toxicity on mammalian preimplantation embryos has not been well investigated. Here, we show Roundup impairs the development and quality of bovine preimplantation embryos in a dose-dependent manner. Exposure to the agricultural recommended doses of Roundup caused in vitro developmental arrest and quick death of bovine embryos. Furthermore, even a very low concentration (0.9ppm) of Roundup was harmful to bovine preimplantation development. In addition, Roundup increases intracellular calcium levels and induces oxidative stress and apoptosis in bovine embryos. Even if the embryos developed to morphologically normal blastocysts when cultured with low concentrations of Roundup, abnormal intracellular calcium and oxidative stress could be detected inside the embryos and led to an increased incidence of apoptosis in the blastocysts. These data suggest Roundup residues from the agricultural application are potentially dangerous to mammalian preimplantation embryos.

Hyaluronic acid and epidermal growth factor improved the bovine embryo quality by regulating the DNA methylation and expression patterns of the focal adhesion pathway.

Focal adhesion pathway is one of the key molecular pathways affected by suboptimal culture conditions during embryonic development. The epidermal growth factor (EGF) and hyaluronic acid (HA) are believed to be involved in the focal adhesion pathway function by regulating the adherence of the molecules to the extracellular matrix. However, regulatory and molecular mechanisms through which the EGF and HA could influence the embryo development is not clear. Therefore, this study aimed to investigate the effect of continued or stage specific supplementation of EGF and/or HA on the developmental competence and quality of bovine preimplantation embryos and the subsequent consequences on the expression and DNA methylation patterns of genes involved in the focal adhesion pathway. The results revealed that, the supplementation of EGF or HA from zygote to the blastocysts stage reduced the level of reactive oxygen species and increased hatching rate after thawing. On the other hand, HA decreased the apoptotic nuclei and increased blastocyst compared to EGF supplemented group. Gene expression and DNA methylation analysis in the resulting blastocysts indicated that, combined supplementation of EGF and HA increased the expression of genes involved in focal adhesion pathway while supplementation of EGF, HA or a combination of EGF and HA during the entire preimplantation period changed the DNA methylation patterns of genes involved in focal adhesion pathway. On the other hand, blastocysts developed in culture media supplemented with EGF + HA until the 16-cell stage exhibited higher expression level of genes involved in focal adhesion pathway compared to those supplemented after the 16-cell stage. Conversely, the DNA methylation level of candidate genes was increased in the blastocysts obtained from embryos cultured in media supplemented with EGF + HA after 16-cell stage. In conclusion, supplementation of bovine embryos with EGF and/or HA during the entire preimplantation period or in a stage specific manner altered the DNA methylation and expression patterns of candidate genes involved in the focal adhesion pathway which was in turn associated with the observed embryonic developmental competence and quality.