Is perivitelline space morphology of the oocyte associated with pregnancy outcome in intracytoplasmic sperm injection cycles?

Ex ovo omnia-why don't we know more about egg quality via imaging?

Determining egg quality is the foremost challenge in assisted reproductive technology (ART). Although extensive advances have been made in multiple areas of ART over the last 40 years, oocyte quality assessment tools have not much evolved beyond standard morphological observation. The oocyte not only delivers half of the nuclear genetic material and all of the mitochondrial DNA to an embryo but also provides complete developmental support during embryonic growth. Oocyte mitochondrial numbers far exceed those of any somatic cell, yet little work has been done to evaluate the mitochondrial bioenergetics of an oocyte. Current standard oocyte assessment in in vitro fertilization (IVF) centers include the observation of oocytes and their surrounding cell complex (cumulus cells) via stereomicroscope or inverted microscope, which is largely primitive. Additional oocyte assessments include polar body grading and polarized light meiotic spindle imaging. However, the evidence regarding the aforementioned methods of oocyte quality assessment and IVF outcomes is contradictory and non-reproducible. High-resolution microscopy techniques have also been implemented in animal and human models with promising outcomes. The current era of oocyte imaging continues to evolve with discoveries in artificial intelligence models of oocyte morphology selection albeit at a slow rate. In this review, the past, current, and future oocyte imaging techniques will be examined with the goal of drawing attention to the gap which limits our ability to assess oocytes in real time. The implications of improved oocyte imaging techniques on patients undergoing IVF will be discussed as well as the need to develop point of care oocyte assessment testing in IVF labs.

Segmentation of mature human oocytes provides interpretable and improved blastocyst outcome predictions by a machine learning model

Within the medical field of human assisted reproductive technology, a method for interpretable, non-invasive, and objective oocyte evaluation is lacking. To address this clinical gap, a workflow utilizing machine learning techniques has been developed involving automatic multi-class segmentation of two-dimensional images, morphometric analysis, and prediction of developmental outcomes of mature denuded oocytes based on feature extraction and clinical variables. Two separate models have been developed for this purpose-a model to perform multiclass segmentation, and a classifier model to classify oocytes as likely or unlikely to develop into a blastocyst (Day 5-7 embryo). The segmentation model is highly accurate at segmenting the oocyte, ensuring high-quality segmented images (masks) are utilized as inputs for the classifier model (mask model). The mask model displayed an area under the curve (AUC) of 0.63, a sensitivity of 0.51, and a specificity of 0.66 on the test set. The AUC underwent a reduction to 0.57 when features extracted from the ooplasm were removed, suggesting the ooplasm holds the information most pertinent to oocyte developmental competence. The mask model was further compared to a deep learning model, which also utilized the segmented images as inputs. The performance of both models combined in an ensemble model was evaluated, showing an improvement (AUC 0.67) compared to either model alone. The results of this study indicate that direct assessments of the oocyte are warranted, providing the first objective insights into key features for developmental competence, a step above the current standard of care-solely utilizing oocyte age as a proxy for quality.

Human metaphase II oocytes with narrow perivitelline space have poor fertilization, developmental, and pregnancy potentials

PURPOSE

To analyze the fertilization, developmental, and pregnancy potentials in oocytes with narrow perivitelline space.

METHODS

Perivitelline space (PVS) of oocytes was evaluated at the time of ICSI, and those without sufficient PVS were judged as oocytes with narrow PVS (NPVS oocytes), and those with sufficient PVS formation were judged as oocytes with non-narrow PVS (non-NPVS oocytes). The analysis included 634 NPVS oocytes from 278 cycles and 12,121 non-NPVS oocytes from 1698 cycles. The fertilization and developmental potentials of NPVS and non-NPVS oocytes were compared by calculating odds ratios using a mixed-effects logistic regression model. We also compared the embryo transfer outcomes of those used for single vitrified-warmed blastocyst transfer after developing into the blastocyst stage.

RESULTS

NPVS oocytes had higher odds ratios for degeneration (adjusted odds ratio [aOR], 1.555; 95% confidence interval [CI], 1.096-2.206; p = 0.0133) and 0PN (aOR, 1.387; 95% CI, 1.083-1.775; p = 0.0095), resulting in a lower 2PN rate (aOR, 0.761; 95% CI, 0.623-0.929; p = 0.0072). Even embryos with confirmed 2PN had lower odds ratios for cleavage (aOR, 0.501; 95% CI, 0.294-0.853; p = 0.0109) and blastocyst development (Gardner criteria; CC-AA) rates (aOR, 0.612; 95% CI, 0.476-0.788; p = 0.0001). Blastocysts developed from NPVS oocytes had significantly lower odds ratios for clinical pregnancy (aOR, 0.435; 95% CI, 0.222-0.854; p = 0.0156) than those developed from non-NPVS oocytes.

CONCLUSIONS

Oocytes with NPVS have low fertilization and developmental potential, as well as low likelihood of pregnancy.

The effect of sperm DNA fragmentation on ICSI outcomes depending on oocyte quality

BACKGROUND

Sperm deoxyribonucleic acid (DNA) fragmentation is commonly encountered in spermatozoa, and the oocyte assumes responsibility for repairing sperm DNA fragmentation during the oocyte-embryo transition.

OBJECTIVES

This study aimed to investigate whether the effect of sperm DNA fragmentation on intracytoplasmic sperm injection outcomes depends on the incidence of oocyte dimorphisms.

MATERIALS AND METHODS

For the present cohort, 2942 fertilized oocytes from 525 patients submitted to intracytoplasmic sperm injection cycles were assessed. The present study was conducted in a private in vitro fertilization center affiliated to a university from June 2016 to July 2019. Semen samples were divided into the following two groups depending on the sperm DNA fragmentation index: a low fragmentation index group (<30% sperm DNA fragmentation, n = 1468) and a high fragmentation index group (≥30% sperm DNA fragmentation, n = 486). In addition, mature oocytes were examined before sperm injection, and intracytoplasmic and extracytoplasmic defects were recorded. The effect of the sperm DNA fragmentation index on laboratory and clinical intracytoplasmic sperm injection outcomes (depending on the presence of oocyte defects) was evaluated.

RESULTS

Significant increases in the rates of fertilization, high-quality embryo, implantation, and pregnancy were noted for cycles with <30% sperm DNA fragmentation than cycles with ≥30% sperm DNA fragmentation (regardless of the presence of oocyte dimorphisms). The presence of dimorphisms significantly impacted laboratory and clinical outcomes. The lowest fertilization and high-quality embryo rates were observed when a high sperm DNA fragmentation index was associated with the presence of dark cytoplasm, vacuoles, resistant membrane, and non-resistant membrane. The lowest implantation and pregnancy rates were observed when a high sperm DNA fragmentation index was associated with the presence of vacuoles, defective perivitelline space, and fragmented polar body. The effect of sperm DNA fragmentation on miscarriage rates was significantly influenced by the presence of centrally located cytoplasmic granulation, a defective perivitelline space and non-resistant membrane.

CONCLUSION

A high sperm DNA fragmentation index increases the likelihood of miscarriage in intracytoplasmic sperm injection cycles, an effect that may potentially be magnified by the presence of oocyte dysmorphisms.

DYSMORPHISMS OF OOCYTES IN ART PROCEDURES: A LITERATURE REVIEW

Relevance: Assisted reproductive technologies (ART) are rapidly developing and in recent decades have become increasingly important due to the growing number of infertile couples around the world. Human oocytes are the main objects used in ART procedures. Consequently, the quality of oocytes can determine the key parameters of ART. The purpose of this review was to analyze the literature and the results of studies in the field of ART devoted to extracytoplasmic dysmorphisms of human oocytes – morphological changes outside the cytoplasmic structure of oocytes, their effect on fertilization, cleavage, implantation frequency, clinical pregnancy rate, as well as the possibility of their use as biomarkers for predicting the quality of embryos, blastocysts, and their further implantation potential. Materials and Methods: This literature review was based on a search conducted among domestic and foreign publications for 2000-2020 available in Russian and international search systems (PubMed, eLibrary) using the keywords «infertility,” “IVF,” «oocyte,” “morphological assessment of oocytes,” “dysmorphisms of oocytes ,” and “ assisted reproductive technologies.” Results: This literature review contains literature data and the analysis of research results in the field of ART devoted to the morphological qualities and abnormalities (dysmorphisms) of human oocytes. It describes the types of extracytoplasmic abnormalities encountered in the clinical practice of in-vitro fertilization, their effect on fertilization, cleavage, implantation rate, and clinical pregnancy rate, as well as the possibility of their use as biomarkers to predict the quality of embryos and blastocysts and their further implantation potential.

Stratifying Cumulus Cell Samples Based on Molecular Profiling to Help Resolve Biomarker Discrepancies and to Predict Oocyte Developmental Competence

To increase the efficiency of assisted reproductive techniques (ART), molecular studies have been performed to identify the best predictive biomarkers for selecting the most suitable germ cells for fertilization and the best embryo for intra-uterine transfer. However, across different studies, no universal markers have been found. In this study, we addressed this issue by generating gene expression and CpG methylation profiles of outer cumulus cells obtained during intra-cytoplasmic sperm injection (ICSI). We also studied the association of the generated genomic data with the clinical parameters (spindle presence, zona pellucida birefringence, pronuclear pattern, estrogen level, endometrium size and lead follicle size) and the pregnancy result. Our data highlighted the presence of several parameters that affect analysis, such as inter-individual differences, inter-treatment differences, and, above all, specific treatment protocol differences. When comparing the pregnancy outcome following the long protocol (GnRH agonist) of ovarian stimulation, we identified the single gene markers (NME6 and ASAP1, FDR < 5%) which were also correlated with endometrium size, upstream regulators (e.g., EIF2AK3, FSH, ATF4, MKNK1, and TP53) and several bio-functions related to cell death (apoptosis) and cellular growth and proliferation. In conclusion, our study highlighted the need to stratify samples that are very heterogeneous and to use pathway analysis as a more reliable and universal method for identifying markers that can predict oocyte development potential.

Evaluating the value of day 0 of an ICSI cycle on indicating laboratory outcome

A number of oocyte characteristics have been associated with fertilization, implantation and live-birth rates, albeit without reaching a consensus. This study aims to delineate possible associations between oocyte characteristics, oocyte behavior during intracytoplasmic sperm injection (ICSI), fertilization potential, and laboratory outcomes. Four-hundred and seventy-seven patients, yielding 3452 oocytes, were enrolled in this prospective observational study from 2015 to 2018. Οoplasm granularity was associated with poor embryo quality and higher probabilities of post-ICSI oocytes and embryos discarded in any developmental stage and never selected for embryo transfer or cryopreservation (p < 0.001). Both sudden or difficult ooplasm aspiration, and high or lack of resistance during ICSI were associated with either a poor Zygote-Score or fertilization failure (p < 0.001). Sudden or difficult ooplasm aspiration and high resistance during ICSI penetration were positively associated with resulting to a post-ICSI oocyte or embryo that would be selected for discard. Evaluation of oocyte characteristics and oocyte behavior during ICSI may provide early information regarding laboratory and cycle outcomes. Particularly, ooplasm granularity, and fragmentation of polar body, along with sudden or difficult ooplasm aspiration and high or lack of resistance during ICSI penetration may hinder the outcome of an ICSI cycle. The associations presented herein may contribute towards development of a grading system or a prediction model. Taking into account information on oocytes and ICSI behavior may effectively assist in enhancing IVF outcome rates.

Effects of Short-Term Inhibition of Rho Kinase on Dromedary Camel Oocyte In Vitro Maturation

Simple Summary

Our results revealed, for the first time, that short-term inhibition of Rho-associated protein kinases (ROCK) for 4 h prior to in vitro maturation (IVM) in a biphasic IVM approach improved oocyte nuclear maturation, producing more MII oocyte, through modulating the expression of cytokinesis- and antiapoptosis-related mRNA transcripts. This positive result suggests ROCK inhibitor as a potential candidate molecule to exploit in the control of oocyte meiotic maturation.

Abstract

This is the first report on a biphasic in vitro maturation (IVM) approach with a meiotic inhibitor to improve dromedary camel IVM. Spontaneous meiotic resumption poses a major setback for in vitro matured oocytes. The overall objective of this study was to improve in vitro maturation of dromedary camel oocytes using ROCK inhibitor (Y-27632) in a biphasic IVM to prevent spontaneous meiotic resumption. In the first experiment, we cultured immature cumulus–oocyte complexes (COCs, n = 375) in a prematuration medium supplemented with ROCK inhibitor (RI) for 2 h, 4 h, 6 h, and 24 h before submission to normal in vitro maturation to complete 28 h. The control was cultured for 28 h in the absence of RI. In the first phase of experiment two, we cultured COCs (n = 480) in the presence or absence (control) of RI for 2 h, 4 h, 6 h, and 24 h, and conducted real-time relative quantitative PCR (qPCR) on selected mRNA transcripts. The same was done in the second phase, but qPCR was done after completion of normal IVM. Assessment of nuclear maturation showed that pre-IVM for 4 h yielded an increase in MII oocyte (54.67% vs. 26.6% of control; p < 0.05). As expected, the same group showed the highest degree (2) of cumulus expansion. In experiment 2, qPCR results showed significantly higher expression of ACTB and BCL2 in the RI group treated for 4 h when compared with the other groups. However, their relative quantification after biphasic IVM did not reveal any significant difference, except for the positive response of BCL2 and BAX/BCL2 ratio after 4 and 6 h biphasic IVM. In conclusion, RI prevents premature oocyte maturation and gave a significantly positive outcome during the 4 h treatment. This finding is a paradigm for future investigation on dromedary camel biphasic IVM and for improving the outcome of IVM in this species.

Blastulation of a zygote to a hatched blastocyst without any clear cell division: an observational finding in a time-lapse system after in vitro fertilization

PURPOSE

To describe an interesting not previously described morphokinetic finding.

METHODS

Retrospective case report of a couple undergoing controlled ovarian stimulation (COS) followed by in vitro fertilization and blastocyst transfer.

RESULTS

We identified a unique finding of blastulation of a fertilized human zygote after conventional in vitro fertilization. The fertilized zygote did not show any clear cytokinesis until approximately 107 h post insemination, when it started dividing into a blastocyst. By 113 h post insemination, inner cell mass and trophectoderm cells could be clearly distinguished and the blastocyst was completely hatched by 136 h post insemination.

CONCLUSION

Time-lapse systems offer more detailed observations of embryonic development. Here, we report an atypical development of an embryo that was not described previously. We hope to become an insightful discussion among peers and incentive the publication of such findings in the future.