Manipulation of the oocyte: possible damage to the spindle apparatus

Clinical effectiveness of spindle-view intracytoplasmic sperm injection compared to conventional intracytoplasmic sperm injection in patients with poor ovarian response and previous implantation failure

OBJECTIVE

This study aimed to determine the clinical advantage of spindle-view intracytoplasmic sperm injection (SVICSI; a novel technology) over conventional intracytoplasmic sperm injection (cICSI) in patients with poor ovarian response (POR) and previous implantation failure.

METHODS

The study included 37 patients who underwent SVICSI followed by fresh embryo transfer (FET) at a single fertility clinic from January to December 2022, 58 patients who underwent cICSI followed by FET at the same fertility clinic from January to December 2021 as a control group. All study participants met the Bologna criteria for POR and had at least three or more previous failed embryo transfers.

RESULTS

The number of blastocyst transfers was significantly higher in the SVICSI group than in the cICSI group. A good-quality cleavage embryo rate, blastocyst rate, and good-quality blastocyst rate were also significantly higher in the SVICSI group than in the cICSI group. There were no significant differences in the rates of fertilization, implantation, clinical pregnancy, or clinical abortion between the two groups.

CONCLUSION

In patients with POR, those who underwent SVICSI appeared to have better embryos than those who underwent cICSI. However, whether SVICSI improved clinical outcomes such as implantation and pregnancy rates cannot be proven.

Design and implementation of a lab-on-a-chip for assisted reproductive technologies

Introduction

The microfluidic device is highly optimized to remove oocytes from the cumulus-corona cell mass surrounding them. Additionally, it effectively captures and immobilizes the oocytes, aiding in assessing their quality and facilitating the injection of sperm into the oocyte. In this study, a novel microfluidic chip was designed and manufactured using conventional soft lithography methods.

Methods

This research proposes the utilization of a microfluidic chip as a substitute for the conventional manual procedures involved in oocyte denudation, trapping, and immobilization. The microfluidic chip was modeled and simulated using COMSOL Multiphysics® 5.2 software to optimize and enhance its design and performance. The microfluidic chip was fabricated using conventional injection molding techniques on a polydimethylsiloxane substrate by employing soft lithography methods.

Results

A hydrostatic force was applied to guide the oocyte through predetermined pathways to eliminate the cumulus cells surrounding the oocyte. The oocyte was subsequently confined within the designated trap region by utilizing hydraulic resistance along the paths and immobilized by applying vacuum force.

Conclusion

The application of this chip necessitates a lower level of operator expertise compared to enzymatic and mechanical techniques. Moreover, it is feasible to continuously monitor the oocyte's state throughout the procedure. There is a reduced need for cultural media compared to more standard approaches.

Noninvasive autologous mitochondria transport improves the quality and developmental potential of oocytes from aged mice

OBJECTIVE

To establish an optimized autologous mitochondria transport technique for oocyte-aging rescue, which minimizes both the patient's pains and the damage to oocytes.

DESIGN

Experimental laboratory study.

SETTING

Laboratory.

ANIMAL(S)

Institute of Cancer Research mice.

INTERVENTION(S)

The murine umbilical cord mesenchymal stem cells were isolated from the female pup and cryopreserved. After the female aged, its germinal vesicle (GV) oocytes were collected and treated to weaken the zona pellucida. Its autologous umbilical cord mesenchymal stem cells were induced into granulosa cells (iGCs). The zona-weakened GV oocytes were aggregated with iGCs into iGC-oocyte complexes. Then, these complexes were cultured in growth-differentiation factor 9-containing media for 3 days. Next, they were subjected to in vitro maturation and fertilization. Presumptive zygotes were cultured for 24 hours, and the cleaved 2-cell embryos were selected for embryo transfer.

MAIN OUTCOME MEASURE(S)

The oocyte quality was determined by examining mitochondrial ultrastructure using transmission electron microscopy, the adenosine triphosphate content using a luminometer, and intracellular reactive oxygen species levels by confocal microscopy. The spindle organization in mature oocytes was examined by confocal microscopy. The developmental potential of oocytes was evaluated by monitoring the in vitro embryo development and the birth rate after embryo transfer.

RESULT(S)

Mitochondria migrated from iGCs into the GV oocyte via transzonal filopodia. The maturation rate, quality, and developmental potential of these oocytes were substantially increased. Furthermore, the birth rate after embryo transfer has been improved.

CONCLUSION(S)

This approach used noninvasive procedures to collect mitochondria donor cells and optimized mitochondria transfer manipulations; thus, it may have potential in ameliorating oocyte-aging-related subfertility.

Glycine ameliorates MBP-induced meiotic abnormalities and apoptosis by regulating mitochondrial-endoplasmic reticulum interactions in porcine oocytes

Monobutyl phthalate (MBP) is the main metabolite of dibutyl phthalate (DBP) in vivo. MBP has a stable structure, can continuously accumulate in living organisms, and has the potentially to harm animal and human reproductive function. In the ovarian follicle microenvironment, MBP may lead to defects in follicular development and steroid production, abnormal meiotic maturation, impaired ovarian function and other reproductive deficits. In this study, SMART-seq was used to investigate the effects of MBP exposure on the in vitro maturation (IVM) and development of porcine oocytes. The results showed that differentially expressed genes after MBP exposure were enriched in the biological processes cytoskeleton, cell apoptosis, endoplasmic reticulum (ER) and mitochondria. Glycine (Gly) improved the developmental potential of porcine oocytes by regulating mitochondrial and ER function. The effect of Gly in protecting oocytes against MBP-induced damage was studied. The results showed that the addition of Gly significantly decreased the rate of MBP-induced spindle abnormalities, decreased the frequency of MBP-induced mitochondria-associated ER membrane (MAM) interactions, and downregulated the protein and gene expression of the linkage molecules Mitofusin 1 (MFN1) and Mitofusin 2 (MFN2) in the MAM. Additionally, treatment with Gly restored the distribution of the 1,4,5-triphosphate receptor 1 (IP₃R1) and voltage-dependent anion channel 1 (VDAC1), further decreasing the intracellular free calcium concentration ([Ca²⁺]_i) levels and mitochondrial Ca²⁺ ([Ca²⁺]_m) , increasing the ER Ca²⁺ ([Ca²⁺]_ER) levels, and thus significantly increasing the ER levels and mitochondrial membrane potential (ΔΨ m). Gly also decreased the levels of reactive oxygen species (ROS) and increased the levels of Glutathione (GSH), oocyte apoptosis-related indicators (Caspase-3 activity and Annexin V) and oocyte apoptosis-related genes (BAX, Caspase 3 and AIFM1). Our results suggest that Gly can ameliorate microtubule cytoskeleton abnormalities and improve oocyte maturation by reducing the defective mitochondrial-ER interactions caused by MBP exposure in vitro.

Oocyte quality and aging

It is well known that female reproduction ability decreases during the forth decade of life due to age-related changes in oocyte quality and quantity; although the number of women trying to conceive has today increased remarkably between the ages of 36 to 44. The causes of reproductive aging and physiological aspects of this phenomenon are still elusive. With increase in the women's age, during Assisted Reproductive Technologies (ART) we have perceived a significant decline in the number and quality of retrieved oocytes, as well as in ovarian follicle reserves. This is because of increased aneuploidy due to factors such as spindle apparatus disruption; oxidative stress and mitochondrial damage. The aim of this review paper is to study data on the potential role of the aging process impacting oocyte quality and female reproductive ability. We present the current evidence that show the decreased oocyte quality with age, related to reductions in female reproductive outcome. The aging process is complicated and it is caused by many factors that control cellular and organism life span. Although the factors responsible for reduced oocyte quality remain unknown, the present review focuses on the potential role of ovarian follicle environment, oocyte structure and its organelles. To find a way to optimize oocyte quality and ameliorate clinical outcomes for women with aging-related causes of infertility.

Selection of competent oocytes by morphological criteria for assisted reproductive technologies

Invasive and noninvasive methods are commonly used to select developmentally competent oocytes that can improve the take-home baby rates in assisted reproductive technology (ART) centers. One of the noninvasive methods conventionally utilized to determine competent oocytes is the morphological analysis of cumulus complex, first polar body, zona pellucida, perivitelline space, meiotic spindle, and ooplasm. Successful fertilization, early embryo development, uterine implantation, and healthy pregnancy depend on the quality of oocytes, and morphological evaluation is one of the options used to predict quality levels. In this review, the morphological criteria being utilized in certain ART centers are comprehensively evaluated with special references to their predictive values and potential contributions to selecting high-quality oocytes.

Quality of Blastocysts Created by Embryo Splitting: A Time-Lapse Monitoring and Chromosomal Aneuploidy Study

Objective

The aim of this study was to screen the potential of human embryos to develop into expanding blastocysts following in vitro embryo splitting and then assess the quality of the generated blastocysts based on chromosomal characteristics and using morphokinetics.

Materials and Methods

In this experimental study, a total of 82 good quality cleavage-stage donated embryos (8- 14 cells) were used (24 embryos were cultured to the blastocyst stage as controls and 58 embryos underwent in vitro splitting). After in vitro splitting, the blastomere donor and blastomere recipient embryos were named twin A and twin B, respectively. Morphokinetics and morphological parameters were evaluated using a time-lapse system in the blastocysts developed from twin embryos. Aneuploidy of chromosomes 13, 15, 16, 18, 21, 22, X and Y were analyzed in the twin blastocysts.

Results

Following in vitro splitting, of the 116 resulting twin embryos, 80 (69%) developed to the expanded blastocyst (EBL) stage compared to 21 (87.5%) embryos in the control group (P>0.05). The morphokinetics analysis suggested that the developmental time-points were influenced by the in vitro splitting. Moreover, the blastocysts developed from A and B twins had impaired morphology compared to controls. Regarding chromosome abnormalities, there was no significant difference in the rate of aneuploidy or mosaicism between the different groups.

Conclusion

This study showed that while no chromosomal abnormalities were seen, in vitro embryo splitting may affect the embryo morphokinetics.

Di(n-butyl) phthalate exposure impairs meiotic competence and development of mouse oocyte

Di(n-butyl) phthalate (DBP) is extensively used in industrial applications as plasticizer and stabilizer and its presence in the environment may present health risks for human. Previous studies have demonstrated its mutagenic, teratogenic, and carcinogenic ability. However, its effect on mammalian oocyte maturation remains unknown. In this study, we examined the effect of DBP on oocyte maturation both in vitro and in vivo. Our results showed that DBP could significantly reduce mice oocyte germinal vesicle breakdown (GVBD) and polar body extrusion (PBE) rates. In addition, oocyte cytoskeleton was damaged and cortical granule-free domains (CGFDs) were also disrupted. Finally, DBP induced early apoptosis of oocyte and granulosa cells (GCs). Collectively, these data demonstrate that DBP could reduce meiosis competence and mouse oocyte development.

pH: the silent variable significantly impacting meiotic spindle assembly in mouse oocytes

RESEARCH QUESTION

Temperature fluctuation negatively impacts the assembly and function of the meiotic spindle, but does pH have a similar effect?

DESIGN

Polarized light microscopy was used to study the spindle in living mouse oocytes under different pH conditions. Female mice (n = 53) were superovulated, and oocytes collected, denuded and allocated to treatment groups. All experiments were performed at 37°C, and standard bicarbonate-buffered medium was used either pre-equilibrated in 6% CO₂ or unequilibrated (in ambient CO₂). Mean oocyte spindle retardance was measured over time in response to changing pH. Spindles were also assessed to understand whether this effect was reversible, by using a fixed pH in a zwitterionic buffer.

RESULTS

The data show the spindle is impacted by pH fluctuation, with mean retardance significantly higher at pH 7.4-7.5 than at the point of media equilibration (P < 0.001). This effect was found to be reversible; retardance significantly decreased after transition of the oocytes from pH 7.43 or pH 7.53 back to the original pre-equilibration pH of 7.32 (P < 0.05).

CONCLUSIONS

This study has shown that the meiotic spindle in mouse oocytes is highly sensitive to changes in oocyte culture media pH. If comparable in humans, this has significance as to the pH level of culture media currently used in assisted reproductive technology clinics worldwide, and reinforces the requirement for stringent control over extrinsic variables in the IVF laboratory.

Andrographolide disrupts meiotic maturation by blocking cytoskeletal reorganisation and decreases the fertilisation potential of mouse oocytes

Andrographolide (AG) is a diterpenoid lactone isolated from the stem and leaves of Andrographis paniculata Nees that is used for the effective treatment of infectious diseases in Asian countries. Previous studies have reported adverse effects of AG on female fertility in rodents; however, the underlying mechanisms are unknown. The aim of the present study was to investigate the effects of AG on the IVM of mouse oocytes and their fertilisation potential. Immature oocytes incubated for 6, 14 or 24h in medium containing 5, 10 or 20μM AG showed time- and dose-dependent decreases in maturation rates compared with the control group. Immunostaining revealed that AG exposure disrupted spindle organisation and migration, as well as actin cap formation and cytokinesis. Furthermore, most oocytes exposed to 20μM AG underwent apoptosis, and the few oocytes exposed to 5 or 10μM AG that reached MII exhibited lower fertilisation rates after intracytoplasmic sperm injection. The findings of the present study suggest that AG may disrupt mouse oocyte meiotic maturation by blocking cytoskeletal reorganisation, and may thus have an adverse effect on female fertility.

DNA methylation signatures in cord blood of ICSI children

STUDY QUESTION

Does ICSI induce specific DNA methylation changes in the resulting offspring?

SUMMARY ANSWER

Although several thousand analyzed CpG sites (throughout the genome) displayed significant between-group methylation differences, both ICSI and spontaneously conceived children varied within the normal range of methylation variation.

WHAT IS KNOWN ALREADY

Children conceived by ART have increased risks for medical problems at birth and to the extent of present knowledge also in later life (i.e. impaired metabolic and cardiovascular functions). One plausible mechanism mediating these ART effects are epigenetic changes originating in the germ cells and/or early embryos and persisting during further development.

STUDY DESIGN, SIZE, DURATION

We compared the cord blood methylomes and candidate gene methylation patterns of newborns conceived through ICSI or spontaneously.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Umbilical cord bloods were obtained from healthy newborn singletons conceived spontaneously (53 samples), through ICSI (89) or IVF (34). Bisulfite-converted DNA samples of 48 ICSI and 46 control pregnancies were used for genome-wide analyses with Illumina's 450K methylation arrays. Candidate genes from the methylation screen were analyzed in all three groups by bisulfite pyrosequencing.

MAIN RESULTS AND THE ROLE OF CHANCE

Altogether, 4730 (0.11%) of 428 227 analyzed CpG sites exhibited significant between-group methylation differences, but all with small (β < 10%) or very small (β < 1%) effect size. ICSI children showed a significantly decreased DNA methylation age at birth, lagging approximately half a week behind the controls. ART-susceptible CpGs were enriched in CpG islands with low methylation values (0-20%) and in imprinting control regions (ICRs). Eighteen promoter regions (six in microRNA and SNORD RNA genes), four CpG islands (three in genes including one long non-coding RNA), and two ICRs contained multiple significant sites. Three differentially methylated regions were studied in more detail by bisulfite pyrosequencing. ATG4C and SNORD114-9 could be validated in an independent ICSI group, following adjustment for maternal age and other confounding factors. ATG4C was also significant in the IVF group.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The observed epigenetic effects are small and there are numerous potential confounding factors such as parental age and infertility. Although our study meets current standards for epigenetic screens, sample size is still two orders of magnitude below that of genome-wide association studies.

WIDER IMPLICATIONS OF THE FINDINGS

Our study suggests an impact of ICSI on the offspring's epigenome(s), which may contribute to phenotypic variation and disease susceptibility in ART children. Epigenetic regulation of gene expression by different classes of non-coding RNAs may be a key mechanism for developmental programming through ART.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a research grant (no. 692185) from the European Union (ERA of ART). There are no competing interests.

Endometriosis Is a Cause of Infertility. Does Reactive Oxygen Damage to Gametes and Embryos Play a Key Role in the Pathogenesis of Infertility Caused by Endometriosis?

Approximately, 10-15% of women of reproductive age are affected by endometriosis, which often leads to infertility. Endometriosis often has an inherited component, and several causative predisposing factors are hypothesized to underlie the pathogenesis of endometriosis. One working hypothesis is the theory of retrograde menstruation. According to the theory of retrograde menstruation, components of refluxed blood, including apoptotic endometrial tissue, desquamated menstrual cells, lysed erythrocytes, and released iron, induce inflammation in the peritoneal cavity. This in turn activates macrophage release of reactive oxygen species (ROS), leading to oxidative stress via the respiratory burst. Refluxed blood promotes the Fenton reaction, terminating in the production of hydroxyl radical, the most potently destructive ROS. In this article, we review the papers that demonstrate decreased quantity and quality of oocytes and embryos retrieved from IVF/ICSI patients with endometriosis. We discuss literature data demonstrating that ROS are generated in endometriotic tissues that have physical proximity to gametes and embryos, and demonstrating adverse impacts on oocyte, sperm and embryo microtubule apparatus, chromosomes, and DNA. Data that addresses the notions that endometriosis causes oocyte and fetal aneuploidy and that these events are mediated by ROS species are also discussed. Literature data are also discussed that employ use of anti-oxidant molecules to evaluate the importance of ROS-mediated oxidative damage in the pathogenesis of endometriosis. Studies are discussed that have employed anti-oxidants compounds as therapeutics to improve oocyte and embryo quality in infertile subjects, and improve fertility in patients with endometriosis.

Evidence of Oocyte Polarity in Bovine; Implications for Intracytoplasmic Sperm Injection and Somatic Cell Nuclear Transfer

Objective

We recently demonstrated spatial regionalization of maternal transcripts and proteins within unfertilized ovine oocyte. Here, we investigated the likelihood of oocyte polarity for the first time in bovine.

Materials and Methods

In this experimental study, in vitro matured bovine oocytes were used for manual bisection [into oocyte halve that were near-to (HNS) and far-from (FS) spindle] or trisection [into MII-spindle (S), the spindle-side half (NS), and the distal half unassociated with the spindle (FS)]. Prepared pools of oocyte substructures were used for comparative quantitative real-time polymerase chain reaction (RT-qPCR). To map the possible preferential sperm entry point (SEP), the spatial relationship between SEP and MII-spindle was measured 5 hours post-fertilization.

Results

The proportional amount of maternal mRNA in S oocyte fragment was estimated to be 6 to 11-fold higher than NS and FS counterparts. The relative abundances of Nanog, Oct4, Fgf4 and Tead4 were significantly higher in HNS oocyte fragment compared t0 FS. The relative abundances of Ctnb, Carm1, Rex1, Sox2 and Cdx2 were comparable between HNS and NS oocyte fragments. FS oocyte fragment possessed significantly higher transcripts of Gata4 compared to HNS. The distribution of certain transcripts related to pluripotency and lineage commitment were different depending upon the region of the oocyte; either enriched at S (Tead4, Nanog, Ctnb and Sox2), NS (Oct4), or FS (Gata6). The SEP in almost (90%) fertilized oocytes was located in MII-hemisphere.

Conclusion

The observation of spatial restriction of mRNAs and SEP within MII-oocyte may indicate that the principal forces of oocyte polarity are evolutionary conserved. This may in turn highlight the need for refinements in the methodology of intracytoplasmic sperm injection (where a sperm is injected far from the MII-spindle) and somatic cell nuclear transfer (where a major amount of regulative mRNAs that are associated with MIIspindle is removed during enucleation).

Relationship between meiotic spindles visualization and intracytoplasmic sperm injection outcomes in human oocytes

In assisted reproductive techniques, the operator attempts to select morphologically best embryos to predict embryo viability. Development of polarized light microscope, which evaluates the oocytes' spindles according to birefringence of living cells, had been helpful in oocyte selection. The aim of this study is evaluating the relationship between meiotic spindles visualization and intracytoplasmic sperm injection (ICSI) outcomes in human oocytes. In this study, 264 oocytes from 24 patients with an average age of 30.5±7.5 years with infertility duration of 1 to 10 years were collected. The oocytes were randomly allocated to the control injection group (n=126) and the oocyte imaging group (spindle-aligned group) (n=138). In the spindle-aligned group, the meiotic spindle was identified by means of polarized light microscope to align the spindle at 6 or 12 o'clock. Then the spindle-aligned group was divided into three sub-groups based on spindle morphology: fine, average, and (poor). After ICSI, embryos were checked every 24 hours and scored; 72 hours later, high-grade embryos were transferred intravaginally to uterus. This study showed that the fertilization rate in the spindle-aligned group was higher than the control group (P<0.05). After cleavage, a positive correlation was observed between spindle morphology and embryo morphology. Among the sub-groups of spindle-aligned group, the embryos' morphology of the fine group was better than the other subgroups and embryos of the poor group had lower quality and more fragmentation. The results revealed that the selection of oocytes based on meiotic spindle imaging can significantly improve the rate of fertilization and embryo cleavage and certainly increase the rate of implantation.

Relationship between pre-ICSI meiotic spindle angle, ovarian reserve, gonadotropin stimulation, and pregnancy outcomes

PURPOSE

The goals of this study are to analyze the clinical pregnancy rate as a function of the pre-intracytoplasmic sperm injection (ICSI) oocyte spindle angle and determine factors which can be associated with different spindle angles, if clinically relevant.

METHODS

Fifty-eight patients, who underwent their first ICSI cycle from January to December 2013, were included. Eight hundred thirty oocytes were collected, and 648 were metaphase II (MII) on retrieval day. Spindles were characterized in terms of visibility and position in relation to the first polar body (PB). Oocytes were separated into four groups based on angle: (group 1, n = 297) 0°-29°; (group 2 n = 212) 30°-89°; (group 3, n = 72) ≥90°; and those with no visible spindle (group 4, n = 67).

RESULTS

The rate of blastocyst development was associated with the spindle angle (p = 0.002). The rate of good quality blastocysts were as follows: group 1 (42%), group 2 (30%), group 3 (35%), and group 4 (19%) (p = 0.02). Pregnancy and live birth rates were also affected (p = 0.007 and p = 0.046, respectively). Antral follicle count (AFC) (p = 0.001), total FSH stimulating dose (p = 0.0001), and peak serum estradiol level (p = 0.0001) were associated with spindle angle grouping. Miscarriage rates trended different (p = 0.07). On the other hand, day 3 follicle-stimulating hormone (FSH) levels and female and male age were not associated with spindle angle grouping.

CONCLUSIONS

Embryos resulting from oocytes with pre-ICSI spindle angles between 0° and 29° were associated with better blastocyst, pregnancy, live birth, and miscarriage rates when compared to oocytes that had no visible spindle. Low ovarian reserve and excessive stimulation were also associated with lack of spindle and therefore lower pregnancy outcomes.

Exposure to Aroclor-1254 impairs spindle assembly during mouse oocyte maturation

Polychlorinated biphenyls (PCBs), as typical environmental estrogen disruptors, are a structurally-related group of halogenated aromatic hydrocarbons that are composed of 209 isomers and present as a mixture in the environment. PCBs congener with different numbers and positions of chlorine atoms substituted on the biphenyl moiety. Aroclor-1254 is a mixture of more than 60 PCB congeners. Previous studies have provided the evidence that PCBs have severe negative effects on reproductive functions, but the effects of PCBs on spindle assembly during mouse oocyte maturation in vitro have not been reported. In the present study, female ICR mouse immature oocytes were cultured in M2 medium with 1 and 10 μg mL^-1 Aroclor-1254 separately in vitro. The percentage of germinal vesicle breakdown (GVBD) and the first polar body extrusion were recorded. The results showed no significant difference in the percentage of GVBD or the first polar body extrusion between control oocytes and Aroclor-1254-treated oocytes. Further studies showed that the normal localization of γ-tubulin and Aurora-A kinase was interfered and α-tubulin assembling into spindle was affected when mouse oocytes were exposed to Aroclor-1254. The length of spindle from 10 μg mL^-1 Aroclor-1254-treated oocytes was longer than that from control oocytes, and the spindle area in the Aroclor-1254-treated groups were decreased. Furthermore, the percentage of DNA damage in cumulus cells revealed an increase after exposed to Aroclor-1254. These results will provide the important reference for the prevention of reproductive disorders caused by PCBs. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1652-1662, 2016.

N-Acetyl-Cysteine and l-Carnitine Prevent Meiotic Oocyte Damage Induced by Follicular Fluid From Infertile Women With Mild Endometriosis

This study evaluated the potential protective effect of the antioxidants, l-carnitine (LC) and N-acetyl-cysteine (NAC), in preventing meiotic oocyte damage induced by follicular fluid (FF) from infertile women with mild endometriosis (ME). We performed an experimental study. The FF samples were obtained from 22 infertile women undergoing stimulated cycles for intracytoplasmic sperm injection (11 with ME and 11 without endometriosis). Immature bovine oocytes were submitted to in vitro maturation (IVM) divided into 9 groups: no-FF (No-FF); with FF from control (CFF) or ME (EFF) groups; and with LC (C + LC and E + LC), NAC (C + NAC and E + NAC), or both antioxidants (C + 2Ao and E + 2Ao). After IVM, oocytes were immunostained for visualization of microtubules and chromatin by confocal microscopy. The percentage of meiotically normal metaphase II (MII) oocytes was significantly lower in the EFF group (51.35%) compared to No-FF (86.36%) and CFF (83.52%) groups. The E + NAC (62.22%), E + LC (80.61%), and E + 2Ao (61.40%) groups showed higher percentage of normal MII than EFF group. The E + LC group showed higher percentage of normal MII than E + NAC and E + 2Ao groups and a similar percentage to No-FF and CFF groups. Therefore, FF from infertile women with ME causes meiotic abnormalities in bovine oocytes, and, for the first time, we demonstrated that the use of NAC and LC prevents these damages. Our findings elucidate part of the pathogenic mechanisms involved in infertility associated with ME and open perspectives for further studies investigating whether the use of LC could improve the natural fertility and/or the results of in vitro fertilization of women with ME.

Zearalenone exposure affects mouse oocyte meiotic maturation and granulosa cell proliferation

Zearalenone (ZEN) is a metabolite of Fusarium and is a common contaminant of grains and foodstuffs. ZEN acts as a xenoestrogen and is considered to be cytotoxic, tissue toxic, and genotoxic, which causes abortions and stillbirths in humans and animals. Since estrogens affect oocyte maturation during meiosis, in this study we investigated the effects of ZEN on mouse oocyte meiotic maturation and granulosa cell proliferation. Our results showed that ZEN-treated oocyte maturation rates were decreased, which might be due to the disrupted cytoskeletons: (1) ZEN treatment resulted in significantly more oocytes with abnormal spindle morphologies; (2) actin filament expression and distribution were also disrupted after ZEN treatment, which was confirmed by the aberrant distribution of actin regulatory proteins. In addition, cortical granule-free domains (CGFDs) were disrupted after ZEN treatment, which indicated that ZEN may affect mouse oocyte fertilization capability. ZEN reduced mouse granulosa cell proliferation in a dose-dependent manner as determined by MTT assay and TUNEL apoptosis analysis, which may be another cause for the decreased oocyte maturation. Thus, our results demonstrated that exposure to zearalenone affected oocyte meiotic maturation and granulosa cell proliferation in mouse.

Effects of maternal ageing on ICSI outcomes and embryo development in relation to oocytes morphological characteristics of birefringent structures

The aim of this study was to determine the morphological characteristics of the older reproductive aged women's oocytes and to reveal the influence of these characteristics on intra-cytoplasmic sperm injection (ICSI) outcomes. The oocytes of women older than 35 years of age were evaluated retrospectively. Non-invasive polarization microscopy (PolScope) examinations of mature oocytes were performed by measurement of meiotic spindles’ length, area and retardance and zona pellucida thickness and retardance. Fertilization and conception competence and the correlation with the birefringent structures were assessed. Two hundred and thirteen mature oocytes from 54 women were evaluated with a PolScope. Length of the meiotic spindle was shown to be related to fertilization success of women with advanced maternal age. In conclusion, the PolScope is a useful device used to identify the oocyte quality. Quantitative measurements of meiotic spindle parameters may be valuable for the selection of high-quality oocytes that have the potential for embryo development in the in vitro fertilization (IVF) laboratory of women older than 35 years of age who are mostly poor responders.

The impact of examining the meiotic spindle by polarization microscopy on assisted reproduction outcomes

OBJECTIVE

To examine the effect of submitting oocytes to polarization microscopy (PM) before intracytoplasmic sperm injection (ICSI).

DESIGN

Retrospective observational study.

SETTING

University hospital in Brazil.

PATIENT(S)

Couples undergoing ICSI.

INTERVENTION(S)

PM before ICSI (PM group) compared with no PM before ICSI (No-PM group)

MAIN OUTCOMES MEASURE(S)

Fertilization and cleavage rates, formation of top-quality embryos (TQEs), and implantation, clinical pregnancy, miscarriage, and live-birth rates.

RESULT(S)

The PM group consisted of 1,000 consecutive oocytes from 201 couples submitted to PM during the year of 2008. The No-PM group consisted of 1,400 oocytes from 249 couples: 700 consecutive oocytes were retrieved before we started using PM and 700 consecutive oocytes were retrieved after we stopped using PM. In the PM group, we observed an increased fertilization rate (79.7% vs. 72.5%, PM group vs. No-PM group, respectively) but reduced cleavage rate (86.2% vs. 92.5%) and TQE formation (33.1% vs. 49.9%). Implantation (18.7% vs. 20.6%), clinical pregnancy (31.8% vs. 33.3%), miscarriage (21.9% vs. 15.7%), and live-birth (24.9% vs. 28.1%) rates were not significantly different between groups.

CONCLUSION(S)

Use of PM was associated with increased fertilization rate but reduced cleavage rate and TQE formation; no significant difference was observed for implantation, clinical pregnancy, or live-birth rates.

Follicular fluid from infertile women with mild endometriosis may compromise the meiotic spindles of bovine metaphase II oocytes

STUDY QUESTION

What is the potential impact of follicular fluid (FF) from infertile women with mild endometriosis (ME) on oocyte quality, especially on nuclear maturation and the meiotic spindle?

SUMMARY ANSWER

FF from infertile women with ME may compromise nuclear maturation and the meiotic spindles of in vitro matured bovine oocytes.

WHAT IS KNOWN ALREADY

Controversial studies have suggested that impaired oocyte quality may be involved in the pathogenesis of endometriosis-related infertility. Moreover, some studies have demonstrated alterations in the composition of FF from infertile women with endometriosis. However, to date no study has evaluated the effect of FF from infertile women with ME on the genesis of meiotic oocyte anomalies.

STUDY DESIGN, SIZE, DURATION

We performed an experimental study. Samples of FF were obtained from February 2009 to February 2011 from 22 infertile women, 11 with ME and 11 with tubal or male factors of infertility (control group), who underwent ovarian stimulation for ICSI at our university IVF Unit. From March 2011 to February 2012 we performed in vitro maturation (IVM) experiments using immature bovine oocytes as described below.

PARTICIPANTS/MATERIALS, SETTING, METHODS

FF free of blood and containing a mature oocyte was obtained from 22 infertile women during oocyte retrieval for ICSI. Immature bovine oocytes underwent IVM in the absence of FF (No-FF) and in the presence of four concentrations (1, 5, 10 and 15%) of FF from infertile women without endometriosis (C-FF) and with ME (ME-FF). Eleven replicates were performed, each one using FF from a control patient and a patient with ME. Each FF sample was used in only one experiment. After 22-24 h of IVM, oocytes were denuded, fixed and immunostained for morphological visualization of microtubules and chromatin by confocal microscopy.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1324 cumulus-oocyte complexes were matured in vitro. Of these, 1128 were fixed and 1048 were analyzed by confocal microscopy. The percentage of meiotically normal oocytes was significantly higher for oocytes that underwent IVM in the absence of FF (No-FF; 76.5%) and in the presence of 1% (80.9%), 5% (76.6%), 10% (75%) and 15% (76.2%) C-FF than in oocytes that underwent IVM in the presence of 1% (44.4%), 5% (36.7%), 10% (45.5%) and 15% (51.2%) ME-FF (P < 0.01). No differences were observed among FF concentrations within each group. When the four concentrations from each group were pooled, the number of oocytes in metaphase I stage was significantly higher in the ME-FF (50 oocytes) than in the C-FF (29 oocytes) group and the percentage of meiotic abnormalities was significantly higher when oocytes were matured with ME-FF (55.8%) than with C-FF (23.1%), P < 0.01.

LIMITATIONS, REASONS FOR CAUTION

Owing to the strict selection criteria for FF donors, this study had a small sample size (11 cases and 11 controls), and thus further investigations using a large cohort of patients are needed to confirm these results. In addition, data obtained from studies using animal models may not necessarily be extrapolated to humans and studies evaluating in vivo matured oocytes from infertile women with ME are important to confirm our results.

WIDER IMPLICATIONS OF THE FINDINGS

Our results open new insights into the pathogenic mechanisms of infertility related to mild endometriosis, suggesting that FF from infertile women with mild endometriosis may be involved in the worsening of oocyte quality of these women.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Council for Scientific and Technological Development (CNPq), Brazil. The authors declare no conflicts of interest.

Fertilization and pregnancy potential of immature oocytes from stimulated intracytoplasmic sperm injection cycles

OBJECTIVE

We evaluated the fertilization potential of immature oocytes obtained from controlled ovarian hyperstimulation cycles of patients undergoing ICSI.

METHODS

We retrospectively analyzed 463 ICSI cycles containing at least one immature oocyte at oocyte denudation. ICSI was performed on mature oocytes at oocyte denudation (metaphase-II [MII] oocytes) and the oocytes that extruded the first polar body between oocyte denudation and ICSI (MI-MII oocytes). Fertilization and early embryonic development were compared between MII and MI-MII oocytes. To investigate the pregnancy potential of MI-MII oocytes, the pregnancy outcome was analyzed in 24 ICSI cycles containing only immature oocytes at retrieval.

RESULTS

The fertilization rate of MI-MII oocytes (37.0%) was significantly lower than that of MII oocytes (72.3%). The rates of delayed embryos and damaged embryos did not significantly differ. Eighty-one immature oocytes were retrieved in 24 cycles that retrieved only immature oocytes and 61 (75.3%) of them were in the MI stage. ICSI was performed on 36 oocytes (59.0%) that extruded the first polar body before ICSI and nine MI-MII oocytes (25.0%) were fertilized. Embryo transfers were performed in five cycles. Pregnancy was observed in one cycle, but it ended in biochemical pregnancy.

CONCLUSION

In ICSI cycles, oocytes that extruded the first polar body between denudation and ICSI can be used as a source of oocytes for sperm injection. However, their fertilization and pregnancy potential are lower than that of mature oocytes. Therefore, ovarian stimulation should be performed carefully for mature oocytes obtained at retrieval, especially in cycles with a small number of retrieved oocytes.

The in vitro MN assay in 2011: origin and fate, biological significance, protocols, high throughput methodologies and toxicological relevance

Micronuclei (MN) are small, extranuclear bodies that arise in dividing cells from acentric chromosome/chromatid fragments or whole chromosomes/chromatids lagging behind in anaphase and are not included in the daughter nuclei at telophase. The mechanisms of MN formation are well understood; their possible postmitotic fate is less evident. The MN assay allows detection of both aneugens and clastogens, shows simplicity of scoring, is widely applicable in different cell types, is internationally validated, has potential for automation and is predictive for cancer. The cytokinesis-block micronucleus assay (CBMN) allows assessment of nucleoplasmic bridges, nuclear buds, cell division inhibition, necrosis and apoptosis and in combination with FISH using centromeric probes, the mechanistic origin of the MN. Therefore, the CBMN test can be considered as a "cytome" assay covering chromosome instability, mitotic dysfunction, cell proliferation and cell death. The toxicological relevance of the MN test is strong: it covers several endpoints, its sensitivity is high, its predictivity for in vivo genotoxicity requires adequate selection of cell lines, its statistical power is increased by the recently available high throughput methodologies, it might become a possible candidate for replacing in vivo testing, it allows good extrapolation for potential limits of exposure or thresholds and it is traceable in experimental in vitro and in vivo systems. Implementation of in vitro MN assays in the test battery for hazard and risk assessment of potential mutagens/carcinogens is therefore fully justified.

In vitro fertilization on a single-oocyte positioning system integrated with motile sperm selection and early embryo development

In vitro fertilization (IVF) technology has been broadly applied to solve human infertility in recent years. However, the physical tools for IVF remain unchanged over several decades before microfluidic technology was introduced in this field. Here, we report a novel microdevice that integrates each step of IVF, including oocyte positioning, sperm screening, fertilization, medium replacement, and embryo culture. Oocytes can be singly positioned in a 4 × 4 array of octacolumn units. The four symmetrical straight channels, crossing at the oocyte positioning region, allowed efficient motile sperm selection and facilitated rapid medium replacement. The fertilization process and early embryonic development of the individual zygote was traced with microscopic recording and analyzed by in situ fluorescent staining. The murine sperm motility was increased from 60.8 ± 3.4% to 96.1 ± 1.9% through the screening channels. The embryo growth rate and blastocyst formation were similar between the routine Petri dish group and the microdevice group. The healthy blastocysts developed in the microdevice could be conveniently retrieved through a routine pipetting operation and used for further embryo transfer.

Time course of meiotic spindle development in MII oocytes

The aim of this study was to examine changes in meiotic spindle morphology over time to potentially optimize timing for ICSI. Using polarized light microscopy, images of MII oocytes were captured after retrieval of oocytes in stimulated cycles at six time intervals in culture: 36–36.5 h, 36.5–37.0 h, 38–38.5 h, 39–39.5 h, 40–40.5 h and 40.5–41 h post hCG. Captured images were analysed for spindle presence and their retardance. Results showed that spindles were detected in 58% (45/78) of oocytes at 36–36.5 h. This percentage rose to a peak (96% vs. 58%, p < 0.001) at 39–39.5 h and stabilized between 39–40.5 h post trigger then significantly declined at 40.5–41 h post hCG (96% vs. 77%, p < 0.001). Average spindle retardance increased from 36–36.5 h (1.8 ± 0.7 nm) until it peaked at 39–40.5 h (3.8 ± 0.8 nm, p < 0.0001) and then declined significantly after 40.5–41 h (3.2 ± 0.9 nm, p = 0.0001). These results show that the meiotic spindle appearance is time dependent with the majority of oocytes having detectable spindles and highest retardance between 39–40.5 h post hCG under currently used stimulation protocol after which they start to disaggregate. 39–40.5 h post hCG may be the optimal time for ICSI.

Spindle and chromosome configurations of human oocytes matured in vitro in two different culture media

In-vitro maturation can have deleterious effects on spindle formation and proper chromosome alignment in human oocytes and can be profoundly affected by culture conditions. This study compared the spindle presence and location with the maturation rate of germinal vesicle (GV) oocytes cultured in two different media: G1.2 and G1.2 supplemented with follicle-stimulating hormone, human chorionic gonadotrophin and 17beta-oestradiol. A total of 304 oocytes were retrieved from 101 women undergoing IVF treatment with intracytoplasmic sperm injection. Spindle presence was recorded using the Polscope. Spindle morphology was evaluated with immunocytological staining for alpha-tubulin and chromatin. Twenty-one in-vitro matured oocytes with the presence of spindle and ten of their corresponding polar bodies (PB) were also assessed for aneuploidy. A significantly increased maturation rate (69.7%) was observed after 24h in the supplemented culture media compared with the G1.2 media (56.6%; P<0.05). The proportions of metaphase II (MII) oocytes with spindle presence and abnormal spindle morphology were similar in the two culture media. Also, 76.9% of MII and 70% of PB had chromosomal abnormalities. In conclusion, supplementing culture media may increase the oocyte maturation rate in vitro, but does not necessarily indicate the presence of a birefringent spindle, or normal spindle and chromosomal alignment.

Zona pellucida birefringence in in vivo and in vitro matured oocytes

OBJECTIVE

To evaluate zona pellucida birefringence (ZPB) in immature and mature oocytes collected after controlled ovarian stimulation and to assess the influence of ZPB on oocyte development.

DESIGN

Prospective study.

SETTING(S)

Private assisted reproduction centre.

PATIENT(S)

Thirty patients undergoing intracytoplasmic sperm injection.

INTERVENTION(S)

The ZPB of mature and immature oocytes was evaluated using a polarization imaging software module, and the oocytes were classified as high birefringence (HB) or low birefringence.

MAIN OUTCOME MEASURE(S)

The ZPB of in vivo and in vitro matured oocytes and its influence on spontaneous nuclear maturation in vitro, fertilization, and embryo quality.

RESULT(S)

The percentage of HB oocytes was higher in immature than in mature oocytes (40.1 vs. 23.6%). Among immature oocytes, an increased percentage of HB in prophase-I stage oocytes compared to metaphase I stage oocytes was also observed (50.7 vs. 25.0%). However, the percentage of HB oocytes did not change when comparing oocytes before and after in vitro maturation for both prophase I and metaphase I oocytes. No influence of ZPB was observed on the spontaneous in vitro maturation potential. Exclusively for metaphase II retrieved oocytes, a positive influence of ZPB on fertilization (odds ratio [OR], 1.78; 95% confidence interval [CI], 1.27-2.49) and embryo quality (OR, 2.28; 95% CI, 1.04-4.99) was noted.

CONCLUSION(S)

ZPB may be a useful tool to predict embryo quality for metaphase-II oocytes. Moreover, the completion of nuclear changes in the production of metaphase-II oocytes in vitro may not reflect their molecular maturity.

Relationship between visualization of meiotic spindle in human oocytes and ICSI outcomes: a meta-analysis

The objective of this meta-analysis was to investigate the influence of meiotic spindle visualization in human oocytes on intracytoplasmic sperm injection (ICSI) outcomes. Search strategies included on-line surveys of databases (MEDLINE, EMBASE, Science Citation Index, Cochrane Controlled Trials Register and Ovid). The fixed effect was used for odds ratio. Ten trials fulfilled the inclusion criteria comparing in-vitro and clinical ICSI outcomes with or without visualization of meiotic spindle in fresh and in-vivo matured oocytes. According to the meta-analysis, the results showed statistically significant higher fertilization rate (P < 0.0001) when the meiotic spindle was viewed than when it was not. Moreover, the percentage of pro-nuclear-stage embryos with good morphology (P = 0.003), cleavage rate (P < 0.0001), percentage of day-3 top-quality embryos (P = 0.003) and percentage of embryos that reached the blastocyst stage (P < 0.0001) were statistically significantly better among embryos derived from oocytes in which meiotic spindle was viewed compared with those in which meiotic spindle was not observed. However, these differences were not observed in the clinical pregnancy or implantation rates. This observation has clinical relevance mainly in countries where there is a legal limit on the number of oocytes to be fertilized. However, additional controlled trials are needed to further confirm these results.

Rhesus macaque embryos derived from MI oocytes maturing after retrieval display high rates of chromosomal anomalies

BACKGROUND

Rhesus macaque and human preimplantation embryos display similar rates of chromosomal abnormalities. The aim of this study was to determine whether embryos developing from MI oocytes that mature post-retrieval display more chromosomal anomalies than those embryos that are generated from oocytes that are at MII at the time of retrieval.

METHODS

Rhesus macaque oocytes were obtained after hormonal ovarian stimulation. Immediately after retrieval, the oocytes were classified according to their maturational status. Following in vitro fertilization, Day 3 embryos with good morphology and development derived from oocytes maturing post-retrieval and those from oocytes that were mature at the time of retrieval were cytogenetically assessed using a five-color fluorescent in situ fluorescent hybridization assay developed for rhesus macaque chromosomes homologous to human chromosomes 13, 16, 18, X and Y.

RESULTS

Blastomeres from 53 embryos were analyzed. Of the 27 embryos that developed from oocytes that were mature at collection, 18 embryos were chromosomally normal (66.7%), while from the 26 embryos that developed from oocytes that matured post-retrieval, only 9 embryos were chromosomally normal (34.6%).

CONCLUSIONS

These results indicate that embryos developing from oocytes maturing post-retrieval display high rates of chromosomal abnormalities and have therefore a reduced developmental competence. As a result, the clinical relevance of using immature oocytes that are retrieved after stimulated cycles in human IVF warrants further investigation.