Origins and manifestations of oocyte maturation competencies

CAPA-IVM improves the cytoplasmic quality of in vitro-matured oocytes from unstimulated mice

Ovarian tissue oocyte (OTO) in vitro maturation (IVM) is a strategy to improve fertility preservation efficiency. Here, the effects of capacitation IVM (CAPA-IVM) on OTO function were investigated. Immature cumulus-oocyte complexes (COCs) from unstimulated 28-day-old mouse ovaries (mimicking OTOs) underwent CAPA-IVM, standard IVM (S-IVM) or in vivo maturation following ovarian stimulation (OS; positive control), and oocyte meiotic maturation and cytoplasmic quality were assessed. CAPA-IVM resulted in improved oocyte meiotic maturation (P < 0.05) and cumulus expansion (P < 0.0001) compared to S-IVM, with expansion comparable to the OS group. MII OTO ROS was lower after CAPA-IVM than S-IVM (P < 0.0001) but not as low as in the OS group (P = 0.036). CAPA-IVM resulted in a better oocyte mitochondrial distribution than S-IVM (P < 0.05) and was similar to the OS group (P > 0.05). Mitochondrial membrane potential in MII OTOs was higher after CAPA-IVM than S-IVM and OS (P < 0.0001). Compared with S-IVM, CAPA-IVM resulted in lower rates of spindle/chromosome configuration and cortical granule distribution abnormalities (P < 0.05), which were similar to OS levels (P > 0.05). MII OTO intracellular Ca2+ levels were similar in the CAPA-IVM and OS groups (P > 0.05), while S-IVM decreased intracellular Ca2+ (P < 0.05). CAPA-IVM and S-IVM decreased mitochondrial Ca2+ levels (P < 0.05). CAPA-IVM increased expression of antioxidant genes (Sod2 and Sirt1) and Egfr (P < 0.05) but not apoptotic genes (Bcl2, Bax and Bcl2/Bax; P > 0.05). CAPA-IVM increased the OTO maturation rate and quality of oocytes from unstimulated mice to the extent that many features of oocyte cytoplasmic quality were comparable to superovulated in vivo matured oocytes.

The Effect of In Vitro Maturation (IVM) Protocol Changes on Measures of Oocyte/Embryo Competence

Purpose: In vitro maturation (IVM) continues its evolution as new ideas are introduced with the objective of making the IVM procedure easier and more effective. This study combines ideas believed likely to improve the IVM outcome or make the IVM oocyte identification process easier. Methods: A cohort of 45 women underwent an IVM cycle in which letrozole was used with the theoretical objective of improving the competence of small antral follicles, the oocyte aspiration technique was modified to minimize the time between oocyte aspiration and oocyte identification, and blastocysts were transferred during a subsequent cycle with controlled endometrial development. Results: Measures of oocyte competence used for these prospectively followed cycles were as follows: the maturation rate was 90.5%, the fertilization rate was 92.4%, the cleavage rate was 94.6%, the usable blastulation rate per zygote was 50.2%, and the implantation rate was 34.2%. Per transfer, the biochemical pregnancy rate was 63.2%, the clinical pregnancy rate was 55.3% and the ongoing/delivered pregnancy rate at the end of the first trimester was 47.4%. The miscarriage rate for clinical pregnancies in the first trimester was 14.3% and the ongoing twinning rate was 11.1%.

Oocyte maturity, oocyte fertilization and cleavage-stage embryo morphology are better in natural compared with high-dose gonadotrophin stimulated IVF cycles

RESEARCH QUESTION

Does high-dose gonadotrophin stimulation have an effect on oocyte and early-stage embryo development?

DESIGN

This was a retrospective study including 616 natural cycle IVF (NC-IVF) and 167 conventional IVF (cIVF) cycles. In total, 2110 oocytes were retrieved and analysed in fresh cycles. In NC-IVF, only human chorionic gonadotrophin was applied to trigger ovulation. In cIVF, antagonist protocols with daily 150-300 IU of human menopausal gonadotrophins were performed. The effect of gonadotrophins on oocyte and early-stage embryo development was analysed. Primary outcomes were the occurrence of mature (metaphase II) oocytes, zygotes and embryos with good morphology at the cleavage stage 2 days after oocyte retrieval.

RESULTS

The mature oocyte rate (number of mature oocytes/number of retrieved oocytes) was higher in NC-IVF than cIVF cycles (89% versus 82%, adjusted odds ratio [aOR] 1.79, P = 0.001), as was the zygote rate per oocyte retrieved (70% versus 58%, aOR 1.76, P = 0.001) and the zygote rate per mature oocyte (79% versus 71%, aOR 1.62, P = 0.001). The percentage of zygotes that developed into cleavage-stage embryos was no different. For the transferred embryos, the probability of having a good embryo morphology with four blastomeres and a fragmentation of <10% (score 0) in cleavage-stage embryos was found to be higher in NC-IVF (proportional aOR for four blastomeres 2.00, P < 0.001; aOR 1.87 for a fragmentation score of 0, P = 0.003).

CONCLUSIONS

Oocyte maturity, oocyte fertilization and morphology of the cleavage-stage embryo are affected by high-dose gonadotrophin stimulation in fresh IVF cycles.

Correlation of the position and status of the polar body from the fertilized oocyte to the euploid status of blastocysts

Polar bodies are tiny cells that are extruded during oocyte meiosis and are generally considered not essential for embryonic development. Therefore, polar bodies have been widely used as important materials for the preimplantation genetic diagnosis of human embryos. Recent studies have shown that polar bodies mediate embryonic development and that their morphology is related to embryo quality and developmental potential. However, the relationship between the emission of the polar body and embryonic euploidy remains unclear. In this study, a total of 1,360 blastocyst trophectoderm (TE) biopsies were performed, and blastocyst ploidy results were correlated with the state of polar bodies. The results showed that polar body angle size and polar body status are not directly related to whether the blastocysts are euploid, aneuploid, or mosaic (p > 0.05). Therefore, in the process of clinical embryo selection, embryologists should not predict the euploidy of blastocysts based on the state of polar bodies, thus affecting embryo selection.

Physiological parameters related to oocyte nuclear differentiation for the improvement of IVM/IVF outcomes in women and cattle

In vitro maturation (IVM) has been applied in numerous different contexts and strategies in humans and animals, but in both cases it represents a challenge still far from being overcome. Despite the large dataset produced over the last two decades on the mechanisms that govern antral follicular development and oocyte metabolism and differentiation, IVM outcomes are still unsatisfactory. This review specifically focuses on data concerning the potential consequences of using supraphysiological levels of FSH during IVM, as well as on the regulation of oocyte chromatin dynamics and its utility as a potential marker of oocyte developmental competence. Taken together, the data revisited herein indicate that a significant improvement in IVM efficacy may be provided by the integration of pre-OPU patient-specific protocols preparing the oocyte population for IVM and more physiological culture systems mimicking more precisely the follicular environment that would be experienced by the recovered oocytes until completion of metaphase II.

Expression pattern of ZNF33B in bovine ovaries and the effect of its polymorphism on superovulation traits

ZNF33B belongs to recently duplicated Krüppel-associated box domain zinc finger proteins (KRAB-ZFPs), which is widely present in various organs, and some evidence showed that its expression is altered in the ovary undergoing superovulation. In this study, the expression of ZNF33B in ovary and early embryo was determined by immunohistochemistry and immunofluorescence techniques. Results showed that the expression of ZNF33B in the ovary was mainly in the cytoplasm of oocytes and granulosa luteal cells of ovarian corpus luteum and significantly reduced during follicular ovulation to luteal degeneration. The expression of ZNF33B in the early embryo transferred from the nucleus to the whole cell, suggesting that the expression of ZNF33B is spatiotemporally specific. Then, in combination with the single nucleotide polymorphism (SNP) database, the g.-61G>T mutant of the 5′-untranslated region (5′ UTR) of the ZNF33B gene was screened out from 556 Changbaishan black cattle, and the frequency of the mutant gene was counted. The statistics of superovulation and superovulation traits confirmed significant differences between the two genotypes in the quantity and quality of oocytes obtained after superovulation. This study confirmed, for the first time, the effect of ZNF33B gene polymorphism on superovulation traits and suggested that the mutation could provide a basis for cattle breeding and improving animal fertility.

Effect of season on germinal vesicle stage, quality, and subsequent in vitro developmental competence in bovine cumulus-oocyte complexes

Although the reproductive performance of grazing cattle is lower in summer compared to winter, the effect of season on oocyte developmental competence has not been thoroughly examined. We measured the effect of season on oocyte chromatin compaction, cumulus cell quality, and embryonic development after in vitro fertilization. Cumulus oocytes-complexes (COCs) were collected from abattoir cows' ovaries during the winter and summer months. First, we evaluated the degree of chromatin compaction in germinal vesicle (GV) oocytes (GV1 through GV3), which is associated with different degrees of developmental competence. Then, we determined the apoptotic index in cumulus cells from immature and in vitro matured COCs. Finally, in vitro matured oocytes were fertilized to determine blastocyst rate and embryo quality. During the summer months, we observed a significantly lower proportion of oocytes reaching the GV3 stage and higher levels of DNA fragmentation in cumulus cell. As a result, blastocyst yield and quality were reduced during the summer months. In conclusion, summer negatively affected oocyte GV stage progression, cumulus cell quality, and embryo development. Increased cumulus cell DNA fragmentation during summer, may partially explain the reduced oocyte maturation capacity, considering the relevance of cumulus-oocyte communication during this stage.

Effects of BPA, BPS, and BPF on Oxidative Stress and Antioxidant Enzyme Expression in Bovine Oocytes and Spermatozoa

Bisphenol A (BPA) and its analogs, bisphenol S (BPS) and bisphenol F (BPF), might impact fertility by altering oxidative stress pathways. Here, we hypothesize that bisphenols-induced oxidative stress is responsible for decreased gamete quality. In both female (cumulus-oocyte-complexes-COCs) and male (spermatozoa), oxidative stress was measured by CM-H2DCFDA assay and key ROS scavengers (SOD1, SOD2, GPX1, GPX4, CAT) were quantified at the mRNA and protein levels using qPCR and Western blot (COCs)/immunofluorescence (sperm). Either gamete was treated in five groups: control, vehicle, and 0.05 mg/mL of BPA, BPS, or BPF. Our results show elevated ROS in BPA-treated COCs but decreased production in BPS- and BPF-treated spermatozoa. Additionally, both mRNA and protein expression of SOD2, GPX1, and GPX4 were decreased in BPA-treated COCs (p < 0.05). In sperm, motility (p < 0.03), but not morphology, was significantly altered by bisphenols. SOD1 mRNA expression was significantly increased, while GPX4 was significantly reduced. These results support BPA's ability to alter oxidative stress in oocytes and, to a lesser extent, in sperm. However, BPS and BPF likely act through different mechanisms.

Factors Influencing the In Vitro Maturation (IVM) of Human Oocyte

In vitro maturation (IVM) of oocytes is a promising assisted reproductive technology (ART) deemed as a simple and safe procedure. It is mainly used in patients with impaired oocyte maturation and in fertility preservation for women facing the risk of losing fertility. However, to date, it is still not widely used in clinical practice because of its underperformance. The influencing factors, such as biphasic IVM system, culture medium, and the supplementation, have a marked effect on the outcomes of oocyte IVM. However, the role of different culture media, supplements, and follicular priming regimens in oocyte IVM have yet to be fully clarified and deserve further investigation.

Ovarian activation delays in peripubertal ewe lambs infected with Haemonchus contortus can be avoided by supplementing protein in their diets

BACKGROUND

The ewe lamb nutritional and physiological state interfere with the ovarian environment and fertility. The lack or excess of circulating nutrients reaching the ovary can change its gene expression. A protein deficiency in the blood caused by an Haemonchus contortus abomasal infection is detrimental to the organism's development during puberty. The peripubertal period is a time of intensive growth that requires a high level of nutrients. An essential feature controlling pubertal arousal and female reproductive potential is ovarian follicle growth activation. Protein supplementation improves the sheep's immune response to helminthic infections. We aimed to determine if supplementing protein in infected ewe lambs' diet would impact the ovarian environment leading to earlier ovarian follicle activation than in infected not supplemented animals.

METHODS

We fed 18 Santa Ines ewe lambs (Ovis aries) - bred by the same ram - with either 12% protein (Control groups) or 19% protein (Supplemented groups) in their diets. After 35 days of the diet, they were each artificially infected or not with 10,000 Haemonchus contortus L3 larvae. Following 77 days of the diet and 42 days of infection, we surgically collected their left ovaries and examined their genes expression through RNA sequencing.

RESULTS

We found that protein supplementation in infected animals led to an up-regulation of genes (FDR p-values < 0.05) and biological processes (p-value cut-off = 0.01) linked to meiotic activation in pre-ovulatory follicles and primordial follicle activation, among others. The supplemented not infected animals also up-regulated genes and processes linked to meiosis and others, such as circadian behaviour. The not supplemented animals had these same processes down-regulated while up-regulated processes related to tissue morphogenesis, inflammation and immune response.

CONCLUSION

Diet's protein supplementation of peripubertal infected animals allowed them to express genes related to a more mature ovarian follicle stage than their half-sisters that were not supplemented. These results could be modelling potential effects of the interaction between environmental factors, nutrition and infection on reproductive health. When ovarian activation is achieved in a timely fashion, the ewe may generate more lambs during its reproductive life, increasing sheep breeders' productivity.

Dynamic changes of histone methylation in mammalian oocytes and early embryos

Histone methylation is a key epigenetic mechanism and plays a major role in regulating gene expression during oocyte maturation and early embryogenesis. This mechanism can be briefly defined as the process by which methyl groups are transferred to lysine and arginine residues of histone tails extending from nucleosomes. While methylation of the lysine residues is catalyzed by histone lysine methyltransferases (KMTs), protein arginine methyltransferases (PRMTs) add methyl groups to the arginine residues. When necessary, the added methyl groups can be reversibly removed by histone demethylases (HDMs) by a process called histone demethylation. The spatiotemporal regulation of methylation and demethylation in histones contributes to modulating the expression of genes required for proper oocyte maturation and early embryonic development. In this review, we comprehensively evaluate and discuss the functional importance of dynamic histone methylation in mammalian oocytes and early embryos, regulated by KMTs, PRMTs, and HDMs.

The ratio of exogenous Luteinizing hormone to Follicle stimulating hormone administered for controlled ovarian stimulation is associated with oocytes' number and competence

We performed a retrospective study aiming to study the relationship between the ratio of the exogenous luteinizing hormone to follicle stimulating hormone (LH/FSH) administrated for controlled ovarian stimulation (COS) and the number and competence of the oocytes retrieved for in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Eight hundred sixty-eight consecutive infertile patients (mean age 34.54 ± 4.01 years, mean anti-Müllerian hormone (AMH) 2.94 ± 2.07 ng/ml) treated with long agonist protocol and a mixed gonadotropin protocol (human menopausal gonadotropin in association with recombinant FSH (recFSH)) who performed IVF/ICSI between January 2013 and February 2016, were included. Patients with severe male factor were excluded. LH/FSH was calculated based on total doses of the two gonadotropins. We found, after adjustment for confounders, a positive relationship between LH/FSH and the retrieved oocytes’ (β = 0.229, P<0.0001) and zygotes’ number (β = 0.144, P<0.0001) in the entire study group and in subgroups according to age (<35 and ≥35 years) and ovarian reserve (AMH < 1.1 and ≥ 1.1 ng/ml). The fertilization rate was positively associated with LH/FSH in patients with LH/FSH in the lowest three quartiles (below 0.77) (β = 0.096, P=0.034). However, patients in the fourth quartile of LH/FSH had a lower fertilization rate as compared with patients in quartiles 1–3 which, after adjustment for covariates, was only marginally negatively related with LH/FSH (β = −0.108, P=0.05). In conclusion, our results suggest that the adequate LH/FSH administrated during COS can improve the oocytes’ and zygotes’ number in IVF/ICSI cycles, but also the fertilization rate when a certain proportion of LH/FSH is not exceeded.

Novel Insights on the Role of Nitric Oxide in the Ovary: A Review of the Literature

Nitric oxide (NO) is formed during the oxidation of L-arginine to L-citrulline by the action of multiple isoenzymes of NO synthase (NOS): neuronal NOS (nNOS), endotelial NOS (eNOS), and inducible NOS (iNOS). NO plays a relevant role in the vascular endothelium, in central and peripheral neurons, and in immunity and inflammatory systems. In addition, several authors showed a consistent contribution of NO to different aspects of the reproductive physiology. The aim of the present review is to analyse the published data on the role of NO within the ovary. It has been demonstrated that the multiple isoenzymes of NOS are expressed and localized in the ovary of different species. More to the point, a consistent role was ascribed to NO in the processes of steroidogenesis, folliculogenesis, and oocyte meiotic maturation in in vitro and in vivo studies using animal models. Unfortunately, there are few nitric oxide data for humans; there are preliminary data on the implication of nitric oxide for oocyte/embryo quality and in-vitro fertilization/embryo transfer (IVF/ET) parameters. NO plays a remarkable role in the ovary, but more investigation is needed, in particular in the context of human ovarian physiology.

Collection and in vitro maturation of Mazama gouazoubira (brown brocket deer) oocytes obtained after ovarian stimulation

In vitro production of embryos has gained prominence as a tool for use in wildlife conservation programmes in situ and ex situ. However, the development of this technique depends on steps that include ovarian stimulation, collection and oocyte maturation. The purpose of this study was to assess the feasibility of an ovarian stimulation protocol for follicular aspiration, the efficiency of videolaparoscopy for follicular aspiration and test a medium for in vitro oocyte maturation for the species Mazama gouazoubira. Five females were submitted to repeated ovarian stimulation (hormone protocol using controlled internal drug release), and estradiol benzoate on D0 and eight injections of follicle-stimulating hormone, once every 12 h, from D4 onwards at 30-day intervals. Fourteen surgical procedures were performed in superstimulated females, resulting in the collection of 94 oocytes and an average of 17.1 ± 9.1 follicles observed, 13.5 ± 6.6 follicles aspirated and 7.2 ± 3.7 oocytes collected per surgery. After collection, the oocytes were submitted to in vitro maturation for 24 h and stained with Hoechst 33342 dye to evaluate their nuclear status; 64.5% of the oocytes reached MII and 16.1% were spontaneously activated by parthenogenesis. The nuclear status of oocytes that did not undergo in vitro maturation was evaluated; 80.9% were found to be immature.

High dose of d-chiro-inositol improves oocyte quality in women with polycystic ovary syndrome undergoing ICSI: a randomized controlled trial

The aim of this study was to evaluate the effect of two doses of d-chiro-inositol (DCI) in combination with Myo-inositol (MYO) on the oocyte quality (OQ) of women with polycystic ovarian syndrome (PCOS) undergoing intracytoplasmic sperm injection (ICSI). Methods: This was a controlled, randomized, double-blind, parallel group study on 172 oocytes from 11 women. The study compared the effect of two MYO-DCI formulations given over 12 weeks on OQ. Five women received 550 mg of MYO + 300 mg of DCI daily (high DCI content group), while 6 women were given a daily dose of 550 mg of MYO with the only 27.6 mg of DCI (low DCI content group). Results: According to a multivariate analysis using linear mixed effect models, high doses of DCI have a positive influence on the quality of the cytoplasm of the oocyte (β = 1.631, χ² = 7.347, d.f. = 1, p = .00672). Zona pellucida, plasma membrane, cytoplasm, and sperm reception have also been improved with any combination of MYO/DCI by decreasing testosterone or improving insulin sensitivity, regardless of age and body mass index. Conclusion: The combination of MYO with high doses of DCI improved oocyte cytoplasm quality in women with PCOS undergoing ICSI.

Polycystic Ovary Syndrome: Impact of Lipotoxicity on Metabolic and Reproductive Health

Importance

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy of reproductive-aged women. Women with PCOS are at increased risk of developing several metabolic and reproductive abnormalities, including metabolic syndrome. Underlying the combined metabolic and reproductive dysfunction is lipotoxicity, defined as the ectopic deposition of lipid in nonadipose tissue where it induces oxidative stress linked with insulin resistance and inflammation.

Objective

To examine what metabolic components underlie insulin resistance in PCOS, how lipotoxicity through insulin resistance impairs metabolism and reproduction in these women, and why evidence-based, individualized management is essential for their care.

Evidence Acquisition

PubMed search was performed using relevant terms to identify journal articles related to the subject. Relevant textbook chapters were also used.

Results

Polycystic ovary syndrome by Rotterdam criteria represents a complex syndrome of heterogeneous expression with variable adverse metabolic and reproductive implications. Women with classic PCOS are often insulin resistant and at greatest risk of developing metabolic syndrome with preferential fat accumulation and weight gain. Moreover, PCOS women may also have an altered capacity to properly store fat, causing ectopic lipid accumulation in nonadipose tissue, including the ovaries, where it can perpetuate insulin resistance and inflammation and harm the oocyte.

Conclusions and Relevance

A personalized approach to managing PCOS is essential to improve the health of all PCOS women through cost-effective prevention and/or treatment, to minimize the risk of pregnancy complications in those individuals wishing to conceive, and to optimize the long-term health of PCOS women and their offspring.

Germinal stage vitrification is superior to MII stage vitrification in prepubertal mouse oocytes

This study investigated if in vitro maturation (IVM) before or after vitrification would be more successful for prepubertal oocytes. To mimic prepubertal conditions in an experimental setup, oocytes were collected from healthy 14, 21 and 28day old Swiss albino mice. The germinal vesicle (GV) stage oocytes and in vitro matured MII oocytes were subjected to vitrification-warming. Both structural (meiotic spindle morphology, mitochondrial integrity, cortical granules) and functional (sperm zona binding, fertilization) characteristics were assessed in oocytes after warming. This study demonstrated that IVM was more detrimental to prepubertal oocytes than to young adults. Further, vitrification of the IVM oocytes resulted in an increase in the number of abnormal meiotic spindles, a change in the cortical distribution pattern, a reduction in sperm zona binding and the fertilization rate. Importantly, oocyte integrity was better when prepubertal oocytes were vitrified before, rather than after, IVM. The above observations support GV stage vitrification for prepubertal oocytes requiring fertility preservation. Understanding the mechanisms behind the differing outcomes for oocytes from immature females will help in refining current protocol, thereby retaining the oocytes' maximum structural and functional integrity Further investigation is necessary to determine whether human prepubertal oocytes also behave in a similar way. It is to be noted here, with great emphasis, that a major limitation of this study is that the oocytes' abilities were tested only until fertilisation, as a consequence of which the study cannot reveal the developmental potentials of the embryos beyond fertilisation.

Ligands, Receptors, and Transcription Factors that Mediate Inter-Cellular and Intra-Cellular Communication during Ovarian Follicle Development

Reliably producing a competent oocyte entails a deeper comprehension of ovarian follicle maturation, a very complex process that includes meiotic maturation of the female gamete, the oocyte, together with the mitotic divisions of the hormone-producing somatic cells. In this report, we investigate murine ovarian folliculogenesis in vivo using publicly available time-series microarrays from primordial to antral stage follicles. Manually curated protein interaction networks were employed to identify autocrine and paracrine signaling between the oocyte and the somatic cells (granulosa and theca cells) at multiple stages of follicle development. We established plausible protein-binding interactions between expressed genes that encode secreted factors and expressed genes that encode cellular receptors. Some computationally identified signaling interactions are well established, such as the paracrine signaling from the oocyte to the somatic cells through the oocyte-secreted growth factor Gdf9, while others are novel connections in term of ovarian folliculogenesis, such as the possible paracrine connection from somatic-secreted factor Ntn3 to the oocyte receptor Neo1. Additionally, we identified several of the likely transcription factors that might control the dynamic transcriptome during ovarian follicle development, noting that the YAP/TAZ signaling pathway is very active in vivo. This novel dynamic model of signaling and regulation can be employed to generate testable hypotheses regarding follicle development that could be validated experimentally, guiding the improvement of culture media to enhance in vitro ovarian follicle maturation and possibly novel therapeutic targets for reproductive diseases.

Luteinizing Hormone Action in Human Oocyte Maturation and Quality: Signaling Pathways, Regulation, and Clinical Impact

The ovarian follicle luteinizing hormone (LH) signaling molecules that regulate oocyte meiotic maturation have recently been identified. The LH signal reduces preovulatory follicle cyclic nucleotide levels which releases oocytes from the first meiotic arrest. In the ovarian follicle, the LH signal reduces cyclic nucleotide levels via the CNP/NPR2 system, the EGF/EGF receptor network, and follicle/oocyte gap junctions. In the oocyte, reduced cyclic nucleotide levels activate the maturation promoting factor (MPF). The activated MPF induces chromosome segregation and completion of the first and second meiotic divisions. The purpose of this paper is to present an overview of the current understanding of human LH signaling regulation of oocyte meiotic maturation by identifying and integrating the human studies on this topic. We found 89 human studies in the literature that identified 24 LH follicle/oocyte signaling proteins. These studies show that human oocyte meiotic maturation is regulated by the same proteins that regulate animal oocyte meiotic maturation. We also found that these LH signaling pathway molecules regulate human oocyte quality and subsequent embryo quality. Remarkably, in vitro maturation (IVM) prematuration culture (PMC) protocols that manipulate the LH signaling pathway improve human oocyte quality of cultured human oocytes. This knowledge has improved clinical human IVM efficiency which may become a routine alternative ART for some infertile patients.

Spindle abnormalities and chromosome misalignment in bovine oocytes after exposure to low doses of bisphenol A or bisphenol S

STUDY QUESTION

What are the effects of exposure to bisphenol A (BPA) or bisphenol S (BPS) during IVM on bovine oocyte maturation, spindle morphology and chromosome alignment?

SUMMARY ANSWER

Exposure to BPA or BPS during IVM resulted in increased spindle abnormalities and chromosome misalignment, even at very low concentrations.

WHAT IS KNOWN ALREADY

BPA is an endocrine disrupting chemical that alters oocyte maturation, spindle morphology and chromosome alignment in a range of species. The use of BPA substitutes, such as BPS, is increasing and these substitutes often display different potencies and mechanisms of action compared with BPA.

STUDY DESIGN, SIZE, DURATION

Bovine cumulus-oocyte complexes (COCs) underwent IVM with BPA or BPS for 24 h, together with vehicle-only controls. Overall, 10 different concentrations of BPA or BPS were used ranging from 1 fM to 50 μM in order to detect low dose or non-monotonic effects. An incomplete block design was utilized for the study, with at least three replicates per block. A total of 939 oocytes (250 of which were controls) were used for the BPA experiments, and 432 (110 controls) for the BPS experiments. Following the IVM period, the oocytes were denuded and fixed for immunocytochemistry.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Immunocytochemistry was used to label the chromatin, actin, and microtubules in the fixed oocytes. The meiotic stage was assessed using immunofluorescence, and the metaphase-II (MII) oocytes were further assessed for spindle morphology and chromosome alignment (in all MII oocytes regardless of spindle morphology) using immunofluorescence and confocal microscopy. Significant differences between the treatment and control groups were determined using chi-square and Fisher's exact tests.

MAIN RESULTS AND THE ROLE OF CHANCE

There was no effect of BPA or BPS on the proportion of bovine oocytes that reached MII (P > 0.05). BPA and BPS increased spindle abnormalities in MII oocytes at almost all concentrations tested, including those as low as 1 fM (P = 0.013) or 10 fM (P < 0.0001), respectively, compared to control. Oocytes with flattened spindles with broad poles were observed at a higher frequency at some concentrations of BPA (P = 0.0002 and P = 0.002 for 10 nM and 50 μM, respectively) or BPS (P = 0.01 for 100 nM BPS), while this spindle phenotype was absent in the controls. BPA increased chromosome misalignment at concentrations of 10 fM, 10 nM and 50 μM (P < 0.0001 to P = 0.043 depending on the dose). BPS increased chromosome misalignment at concentrations of 10 fM, 100 pM, 10 nM, 100 nM and 50 μM (P < 0.0001 to P = 0.013 depending on the dose).

LIMITATIONS REASONS FOR CAUTION

Exposures to BPA or BPS were performed during the IVM of COCs to allow for determination of direct effects of these chemicals on oocyte maturation. Whole follicle culture or in vivo studies will confirm whether follicular cell interactions modify the effects of BPA or BPS on oocyte meiotic maturation. Investigation into the effects of BPA or BPS on other oocyte functions will determine whether these chemicals alter oocyte quality via mechanisms independent of the meiotic endpoints characterized here.

WIDER IMPLICATIONS OF THE FINDINGS

The findings of this study show that both BPA and BPS induce spindle abnormalities and chromosome misalignment in bovine in a non-monotonic manner, and at concentrations that are orders of magnitude below those measured in humans. Taken in context with previous studies on the effects of BPA in a range of species, our data support the literature that BPA may reduce oocyte quality and lead to subsequent infertility. Additionally, these results contribute to the burgeoning field of research on BPS and suggest that BPS may indeed be a 'regrettable substitution' for BPA.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by funding from the National Institutes of Health (NIH) (Grant 1R15ES024520-01). The authors declare no conflict of interest.

Low dose clomiphene citrate as a mild stimulation protocol in women with unsuspected poor in vitro fertilization result can generate more oocytes with optimal cumulative pregnancy rate

BACKGROUND

The use of long protocol during controlled ovarian stimulation for assisted reproduction attracts high dosage of gonadotropins. High dose of gonadotropins can be detrimental to oocyte development, which affects its quality and compromises the treatment outcome. Mild stimulation protocols that attract low dose gonadotropins could be useful alternative regimen to address such problems. This study evaluated the efficacy of low dose clomiphene citrate based protocol plus low dose gonadotropins on predicted normal responder patients who had unsuspected poor in vitro fertilization (IVF) result, following an initial stimulation with long gonadotropin-releasing hormone (GnRH) agonist protocol.

METHODS

This a retrospective study of 65 infertile women who underwent 130 cycles in our center from January 2011 to December 2014. The initial IVF cycle (Group 1) was treated with long GnRH-a protocol plus a high dose of gonadotropins (≥150 IU/d), while second IVF cycle (Group 2) had low dose clomiphene citrate based protocol plus low dose gonadotropins (75-112.5 IU/d).

RESULTS

The rate of cumulative pregnancy/started cycle (9.2% [6/65] vs. 51% [33/65]; P < 0001) was significantly better in CC protocol than the long GnRH agonist protocol. The number of oocytes retrieved was also higher in CC protocol compared to the long protocol (7.26 ± 1.95 vs. 5.98 ± 1.31; P = 0.03). There was a lower number of patients without embryos (12.31% vs. 33.85%; p < 0.0001) in CC protocol than long protocol.

CONCLUSIONS

This study showed a better cumulative pregnancy rate in the low dose CC based protocol. There was a higher number of oocytes retrieved after using a lower total dose of recombinant FSH in CC protocol. Thus, clomiphene treatment plus low dose rFSH can be an alternative option for such patients in second cycle stimulation instead of repeating long protocol regimen. Randomized controlled studies with larger number of patients will be needed for more accurate evidence.

The Phosphatase Dusp7 Drives Meiotic Resumption and Chromosome Alignment in Mouse Oocytes

Mammalian oocytes are stored in the ovary, where they are arrested in prophase for prolonged periods. The mechanisms that abrogate the prophase arrest in mammalian oocytes and reinitiate meiosis are not well understood. Here, we identify and characterize an essential pathway for the resumption of meiosis that relies on the protein phosphatase DUSP7. DUSP7-depleted oocytes either fail to resume meiosis or resume meiosis with a significant delay. In the absence of DUSP7, Cdk1/CycB activity drops below the critical level required to reinitiate meiosis, precluding or delaying nuclear envelope breakdown. Our data suggest that DUSP7 drives meiotic resumption by dephosphorylating and thereby inactivating cPKC isoforms. In addition to controlling meiotic resumption, DUSP7 has a second function in chromosome segregation: DUSP7-depleted oocytes that enter meiosis show severe chromosome alignment defects and progress into anaphase prematurely. Altogether, these findings establish the phosphatase DUSP7 as an essential regulator of multiple steps in oocyte meiosis.

CoQ10 increases mitochondrial mass and polarization, ATP and Oct4 potency levels, and bovine oocyte MII during IVM while decreasing AMPK activity and oocyte death

PURPOSE

We tested whether mitochondrial electron transport chain electron carrier coenzyme Q10 (CoQ10) increases ATP during bovine IVM and increases %M2 oocytes, mitochondrial polarization/mass, and Oct4, and decreases pAMPK and oocyte death.

METHODS

Bovine oocytes were aspirated from ovaries and cultured in IVM media for 24 h with 0, 20, 40, or 60 μM CoQ10. Oocytes were assayed for ATP by luciferase-based luminescence. Oocyte micrographs were quantitated for Oct4, pAMPK (i.e., activity), polarization by JC1 staining, and mitochondrial mass by MitoTracker Green staining.

RESULTS

CoQ10 at 40 μM was optimal. Oocytes at 40 μM enabled 1.9-fold more ATP than 0 μM CoQ10. There was 4.3-fold less oocyte death, 1.7-fold more mitochondrial charge polarization, and 3.1-fold more mitochondrial mass at 40 μM than at 0 μM CoQ10. Increased ATP was associated with 2.2-fold lower AMPK thr172P activation and 2.1-fold higher nuclear Oct4 stemness/potency protein at 40 μM than at 0 μM CoQ10. CoQ10 is hydrophobic, and at all doses, 50% was lost from media into oil by ~ 12 h. Replenishing CoQ10 at 12 h did not significantly diminish dead oocytes.

CONCLUSIONS

The data suggest that CoQ10 improves mitochondrial function in IVM where unwanted stress, higher AMPK activity, and Oct4 potency loss are induced.

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.

A review of fundamental principles for animal models of DOHaD research: an Australian perspective

Epidemiology formed the basis of ‘the Barker hypothesis’, the concept of ‘developmental programming’ and today’s discipline of the Developmental Origins of Health and Disease (DOHaD). Animal experimentation provided proof of the underlying concepts, and continues to generate knowledge of underlying mechanisms. Interventions in humans, based on DOHaD principles, will be informed by experiments in animals. As knowledge in this discipline has accumulated, from studies of humans and other animals, the complexity of interactions between genome, environment and epigenetics, has been revealed. The vast nature of programming stimuli and breadth of effects is becoming known. As a result of our accumulating knowledge we now appreciate the impact of many variables that contribute to programmed outcomes. To guide further animal research in this field, the Australia and New Zealand DOHaD society (ANZ DOHaD) Animals Models of DOHaD Research Working Group convened at the 2nd Annual ANZ DOHaD Congress in Melbourne, Australia in April 2015. This review summarizes the contributions of animal research to the understanding of DOHaD, and makes recommendations for the design and conduct of animal experiments to maximize relevance, reproducibility and translation of knowledge into improving health and well-being.

The role of in-vivo and in-vitro maturation time on ooplasmic dysmaturity

This study investigates whether the timing of in-vivo and in-vitro maturation influences ooplasmic dysmaturity. This is a retrospective comparison of intracytoplasmic sperm injection (ICSI) cycles (index cycles) complicated by complete fertilization failure (CFF) to cycles with successful fertilization in the same patient. The cycle following the index cycle was modified intentionally to increase fertilization. The times between human chorionic gonadotrophin (HCG) trigger and oocyte retrieval, HCG trigger and removal of cumulus cells, and HCG trigger and sperm injection were recorded. Fifteen patients were included. Compared with successful fertilization cycles, index (CFF) cycles showed a shorter time interval between HCG trigger and oocyte retrieval (2029.0 ± 16 versus 2195.0 ± 10 min; P < 0.001), HCG trigger and removal of cumulus cells (2201.4 ± 15 versus 2309.0 ± 23 min; P < 0.001) and oocyte retrieval and removal of cumulus cells (114.0 ± 13 versus 171.8 ± 15 min; P < 0.001). The interval between HCG trigger and ICSI was comparable between groups. Findings reveal novel patterns in time intervals between HCG trigger, oocyte retrieval, removal of cumulus cells and ICSI. Thus, modulating time intervals between HCG trigger, oocyte retrieval, removal of cumulus cells and ICSI to grant fertilization seems feasible.

Expression and intracytoplasmic distribution of staufen and calreticulin in maturing human oocytes

PURPOSE

In this study we hypothesized that the mRNA vector Staufen mediates RNA relocalization during meiotic maturation, and by virtue of its interactions with endoplasmic reticulum, provides a possible mechanism by which protein synthesis is regulated.

METHODS

We assessed the expression of staufen (STAU) and calreticulin (CALR), the latter adopted as a marker of the endoplasmic reticulum, in human oocytes at different stages of maturation: GV, metaphase MI and MII. Oocytes were subjected to polymerase chain reaction in order to investigate the expression of STAU and CALR. The corresponding protein products were identified by immunofluorescence and confocal laser scanning microscopy.

RESULTS

STAU and CALR were constantly expressed and selectively localized during oocyte maturation. At the GV stage the both proteins displayed a dispersed distribution localization throughout the cytoplasm. Progressing to the MII stage, STAU tended to compartmentalize towards the cortical area of the oocyte clustering in granules of larger sizes. At the MII stage, CALR assumed a pattern reminiscent and possibly coincident with the position of the meiotic spindle.

CONCLUSIONS

The changing pattern of STAU distribution during meiotic maturation of human oocytes implicates a novel mechanism for the regulation of protein synthesis based on mRNA localization. Moreover, the unique disposition of CALR at the MII spindle uncovers a physical interaction with endoplasmic reticulum that may mediate cytoskeletal remodelling during oocyte maturation.

Microfluidic method of pig oocyte quality assessment in relation to different follicular size based on lab-on-chip technology

Since microfollicular environment and the size of the follicle are important markers influencing oocyte quality, the aim of this study is to present the spectral characterization of oocytes isolated from follicles of various sizes using lab-on-chip (LOC) technology and to demonstrate how follicle size may affect oocyte quality. Porcine oocytes (each, n = 100) recovered from follicles of different sizes, for example, from large (>5 mm), medium (3–5 mm), and small (<3 mm), were analyzed after preceding in vitro maturation (IVM). The LOC analysis was performed using a silicon-glass sandwich with two glass optical fibers positioned “face-to-face.” Oocytes collected from follicles of different size classes revealed specific and distinguishable spectral characteristics. The absorbance spectra (microspectrometric specificity) for oocytes isolated from large, medium, and small follicles differ significantly (P < 0.05) and the absorbance wavelengths were between 626 and 628 nm, between 618 and 620 nm, and less than 618 nm, respectively. The present study offers a parametric and objective method of porcine oocyte assessment. However, up to now this study has been used to evidence spectral markers associated with follicular size in pigs, only. Further investigations with functional-biological assays and comparing LOC analyses with fertilization and pregnancy success and the outcome of healthy offspring must be performed.

Effects of Aroclor 1254 on in vivo oocyte maturation in the mouse

Polychlorinated biphenyls (PCBs) are stable, lipophilic compounds that accumulate in the environment and in the food chain. Though some studies provided evidence that PCBs had adverse effects on reproductive function, most of these results were from in vitro models. Therefore we investigated the effect of Aroclor 1254 (a commercial PCBs mixture) treatments on in vivo maturation and developmental potential of mouse oocytes. In the present study, female ICR mice were treated with different doses (12.5, 25 and 50 mg/kg) of Aroclor 1254 (a commercial PCB mixture) once every 72 hours by intraperitoneal injection for 9 days. After three treatments of Aroclor 1254, the mice were superovulated to collect oocytes one day after the last exposure. The effects of Aroclor 1254 on oocyte maturation, fertilization, and preimplantation embryonic development were investigated. Immunofluorescence-stained oocytes were observed under a confocal microscope to assess the effects of Aroclor 1254 on spindle morphology. Parthenogenic activation and the incidence of cumulus apoptosis in cumulus-oocyte complexes were observed as well. Oocytes exposed to different doses of Aroclor 1254 in vivo were associated with a significant decrease in outgrowth potential, abnormal spindle configurations, and the inhibition of parthenogenetic activation of ovulated oocytes. Furthermore, the incidence of apoptosis in cumulus cells was increased after exposed to Aroclor 1254. These results may provide reference for the treatment of reproductive diseases such as infertility or miscarriage caused by environmental contaminants.

First polar body morphology affects potential development of porcine parthenogenetic embryo in vitro

Previous studies have reported that the first polar body (PB1) morphology reflects embryo development competence, but the effects of PB1 on porcine embryo development remain unknown. This study aims to determine whether the ability of porcine embryo development is related to oocytes' PB1 in vitro. The distribution of type II cortical granules (CGs) of porcine matured oocytes in grade B PB1 is significantly greater compared with those in grades A and C PB1 (71.43% versus 52.46% and 50%; P 0.05). The acetylation level of porcine embryos in the group with grade B PB1 is significantly greater compared with those in the other groups (P < 0.05), and is almost 2.5 times higher than that in grade A. Therefore, porcine oocytes with PB1 in grade B are more competitive in cytoplasmic maturation and further embryo development in vitro.

Changes in large-scale chromatin structure and function during oogenesis: a journey in company with follicular cells

The mammalian oocyte nucleus or germinal vesicle (GV) exhibits characteristic chromatin configurations, which are subject to dynamic modifications through oogenesis. Aim of this review is to highlight how changes in chromatin configurations are related to both functional and structural modifications occurring in the oocyte nuclear and cytoplasmic compartments. During the long phase of meiotic arrest at the diplotene stage, the chromatin enclosed within the GV is subjected to several levels of regulation. Morphologically, the chromosomes lose their individuality and form a loose chromatin mass. The decondensed configuration of chromatin then undergoes profound rearrangements during the final stages of oocyte growth that are tightly associated with the acquisition of meiotic and developmental competence. Functionally, the discrete stages of chromatin condensation are characterized by different level of transcriptional activity, DNA methylation and covalent histone modifications. Interestingly, the program of chromatin rearrangement is not completely intrinsic to the oocyte, but follicular cells exert their regulatory actions through gap junction mediated communications and intracellular messenger dependent mechanism(s). With this in mind and since oocyte growth mostly relies on the bidirectional interaction with the follicular cells, a connection between cumulus cells gene expression profile and oocyte developmental competence, according to chromatin configuration is proposed. This analysis can help in identifying candidate genes involved in the process of oocyte developmental competence acquisition and in providing non-invasive biomarkers of oocyte health status that can have important implications in treating human infertility as well as managing breeding schemes in domestic mammals.

Birth of healthy offspring following ICSI in in vitro-matured common marmoset (Callithrix jacchus) oocytes

Intracytoplasmic sperm injection (ICSI), an important method used to treat male subfertility, is applied in the transgenic technology of sperm-mediated gene transfer. However, no study has described successful generation of offspring using ICSI in the common marmoset, a small non-human primate used as a model for biomedical translational research. In this study, we investigated blastocyst development and the subsequent live offspring stages of marmoset oocytes matured in vitro and fertilized by ICSI. To investigate the optimal timing of performing ICSI, corrected immature oocytes were matured in vitro and ICSI was performed at various time points (1–2 h, 2–4 h, 4–6 h, 6–8 h, and 8–10 h after extrusion of the first polar body (PB)). Matured oocytes were then divided randomly into two groups: one was used for in vitro fertilization (IVF) and the other for ICSI. To investigate in vivo development of embryos followed by ICSI, 6-cell- to 8-cell-stage embryos and blastocysts were nonsurgically transferred into recipient marmosets. Although no significant differences were observed in the fertilization rate of blastocysts among ICSI timing after the first PB extrusion, the blastocyst rate at 1–2 h was lowest among groups at 2–4 h, 4–6 h, 6–8 h, and 8–10 h. Comparing ICSI to IVF, the fertilization rates obtained in ICSI were higher than in IVF (p>0.05). No significant difference was noted in the cleaved blastocyst rate between ICSI and IVF. Following the transfer of 37 ICSI blastocysts, 4 of 20 recipients became pregnant, while with the transfer of 21 6-cell- to 8-cell-stage ICSI embryos, 3 of 8 recipients became pregnant. Four healthy offspring were produced and grew normally. These are the first marmoset offspring produced by ICSI, making it an effective fertilization method for marmosets.

Understanding fertilization through intracytoplasmic sperm injection (ICSI)

Since the establishment of in vitro fertilization, it became evident that almost half of the couples failed to achieve fertilization and this phenomenon was attributed to a male gamete dysfunction. The adoption of assisted fertilization techniques particularly ICSI has been able to alleviate male factor infertility by granting the consistent ability of a viable spermatozoon to activate an oocyte. Single sperm injection, by pinpointing the beginning of fertilization, has been an invaluable tool in clarifying the different aspects of early fertilization and syngamy. However, even with ICSI some couples fail to fertilize due to ooplasmic dysmaturity in relation to the achieved nuclear maturation marked by the extrusion of the first polar body. More uncommon are cases where the spermatozoa partially or completely lack the specific oocyte activating factor. In this work, we review the most relevant aspects of fertilization and its failure through assisted reproductive technologies. Attempts at diagnosing and treating clinical fertilization failure are described.

Role of gap junction-mediated communications in regulating large-scale chromatin configuration remodeling and embryonic developmental competence acquisition in fully grown bovine oocyte

PURPOSE

This study was aimed to test the hypothesis that gap junction mediated communications (GJC) are required to allow the progressive chromatin configuration remodeling (from GV1 to GV3) process to occur in fully grown oocytes in order to gain the final step of developmental competence acquisition, and that a premature disruption of GJC can alter this process.

METHODS

Bovine cumulus-oocytes complexes collected from medium antral follicles were cultured for 2, 4, 6 and 8 h in the presence of 10(-4) IU/ml of r-hFSH and with 2 mM of the non-selective PDE inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) to prevent meiotic resumption. GJC functionality and chromatin configuration were monitored during the culture period. After meiotic arrest, the developmental capability of oocytes was assessed after IVM and IVF.

RESULTS

IBMX was effective in significantly sustaining GJC up to 6 h and maintaining meiotic arrest, when compared to control group. Moreover, the percentage of oocytes with less condensed chromatin (GV1) decreased within 4 h of culture, while the proportion of GV2 oocytes gradually increased up to 6 h. Interestingly, a decline in the proportion of GV2 oocytes and an increase in the proportion of GV3 oocytes were observed after 6 h of culture, when the major drop of GJC occurred. On the contrary, when GJC were uncoupled by adding 3 mM of 1-heptanol or through cumulus cells removal, chromatin condensation occurred rapidly throughout the culture period, more promptly in denuded oocytes. Moreover, the maintenance of GJC during meiotic arrest was accompanied by a significant increase of developmental competence compared to the control, as indicated by a higher percentage of hatched blastocysts and blastocyst cell number.

CONCLUSIONS

Altogether, our data indicate that both paracrine and junctional mechanisms are involved in modulating large-scale chromatin structure during the final phase of oocyte differentiation.

The dynamics of in vitro maturation of germinal vesicle oocytes

OBJECTIVE

To evaluate the dynamics of the nuclear maturation (NM) of in vitro-matured (IVM) oocytes and to determine the most favorable duration of meiosis II (MII) arrest in relation to the normal activation response.

DESIGN

Experimental.

SETTING

University-affiliated infertility clinic.

PATIENT(S)

Donated immature germinal vesicle oocytes (GV).

INTERVENTION(S)

The GV underwent spontaneous IVM and the dynamics of NM studied by real-time monitoring. The IVM oocytes were parthenogenetically activated at different MII arrest points and their response assessed.

MAIN OUTCOME MEASURE(S)

Moment of GV breakdown; extrusion of the first polar body; duration of MI and MII arrest; activation rate (AR) and type.

RESULT(S)

Two GV populations-early (E-IVM, 18.4 ± 2.7 hours) and late (L-IVM, 26.3 ± 3.8 hours) maturing-were defined according to the time required for extrusion of the first polar body. Significantly more E-IVM than L-IVM exhibited a normal activation response (61.3% vs. 34.6%), but AR were similar (average, 88.6%) in both groups. Duration of the GV stage differed between the two groups, but MI arrest (14.0 ± 0.3 hours) was constant. The E-IVM arrested at MII for at least 4.3 hours displayed significantly lower AR and similar normal activation rates (61.3%) to E-IVM arrested for a shorter time (83.9% vs. 100%). The L-IVM displayed a similar AR (80.8%), but lower normal activation rates than E-IVM (34.6%), regardless of when activation took place.

CONCLUSION(S)

The success of IVM depends on the NM timing rather than on the length of MII arrest.

Large-scale chromatin morpho-functional changes during mammalian oocyte growth and differentiation

Mammalian oocyte development is characterized by impressive changes in chromatin structure and function within the germinal vesicle (GV). These changes are crucial to confer the oocyte with meiotic and developmental competencies. In cow, oocytes collected from early and middle antral follicles present four patterns of chromatin configuration, from GV0 to GV3, and its progressive condensation has been related to the achievement of developmental potential. During oogenesis, follicular cells are essential for the acquisition of meiotic and developmental competencies and communicate with the oocyte by paracrine and gap junction mediated mechanisms. We recently analyzed the role of gap junction communications (GJC) on chromatin remodeling process during the specific phase of folliculogenesis that coincides with the transcriptional silencing and sequential acquisition of meiotic and developmental capabilities. Our studies demonstrated that GJC between germinal and somatic compartments plays a fundamental role in the regulation of chromatin remodeling and transcription activities during the final oocyte differentiation, throughout cAMP dependent mechanism(s).

The effects of substituting glassware for plasticware and the use of an ethanol vector on oocyte maturation in vitro

The intent of this study was to evaluate specific technical aspects of in vitro oocyte maturation (IVM), which included container material and solvent delivery vector. Oocytes were matured in oil-free, open-well systems contained in either plastic or glass dishes and compared to control oocytes matured in media droplets on plastic dishes overlaid with mineral oil. Open-well experiments were repeated with ethanol in a quantity sufficient for delivery of nonmiscible compounds. Cleavage rates were significantly decreased in the glassware system when compared to controls. The plasticware open-well system did not differ from either the controls or the glassware groups. Cleavage in glassware with ethanol was significantly lower than controls or plasticware with ethanol. Blastocyst rates were only decreased in the glassware-ethanol treatment when compared to plasticware-ethanol treatment. Cell counts and percentage of TUNEL-positive cells did not differ significantly. Unexpectedly, sex ratio was significantly decreased (34% male) from the expected value of 50% male in the glassware group with added ethanol. The current study demonstrates the sensitivity of IVM to subtle technical changes, resulting in significant developmental consequences.

Localization of DNA methyltransferase-1 during oocyte differentiation, in vitro maturation and early embryonic development in cow

DNA methyltransferase-1 (Dnmt1) is involved in the maintenance of DNA methylation patterns and is crucial for normal mammalian development. The aim of the present study was to assess the localization of Dnmt1 in cow, during the latest phases of oocyte differentiation and during the early stages of segmentation. Dnmt1 expression and localization were assessed in oocytes according to the chromatin configuration, which in turn provides an important epigenetic mechanism for the control of global gene expression and represents a morphological marker of oocyte differentiation. We found that the initial chromatin condensation was accompanied by a slight increase in the level of global DNA methylation, as assessed by 5-methyl-cytosine immunostaining followed by laser scanning confocal microscopy analysis (LSCM). RT-PCR confirmed the presence of Dnmt1 transcripts throughout this phase of oocyte differentiation. Analogously, Dnmt1 immunodetection and LSCM indicated that the protein was always present and localized in the cytoplasm, regardless the chromatin configuration and the level of global DNA methylation. Moreover, our data indicate that while Dnmt1 is retained in the cytoplasm in metaphase II stage oocytes and zygotes, it enters the nuclei of 8–16 cell stage embryos. As suggested in mouse, the functional meaning of the presence of Dnmt1 in the bovine embryo nuclei could be the maintainement of the methylation pattern of imprinted genes. In conclusion, the present work provides useful elements for the study of Dnmt1 function during the late stage of oocyte differentiation, maturation and early embryonic development in mammals.

Altered expression of Armet and Mrlp51 in the oocyte, preimplantation embryo, and brain of mice following oocyte in vitro maturation but postnatal brain development and cognitive function are normal

Despite the efforts to recapitulate the follicle environment, oocytes from in vitro maturation (IVM) have poorer developmental potential than those matured in vivo and the effects on the resultant offspring are of concern. The aim of this study was to determine altered gene expression in oocytes following IVM and to evaluate the expression of the arginine rich, mutated in early stage of tumors gene (Armet) and mitochondrial ribosomal protein L51 (Mrpl51) in embryos and brains of fetal/postnatal mice and the brain development of IVM offspring. An IVM mouse model was established while oocytes matured in vivo were used as the controls. Suppressive subtractive hybridization (SSH) and RT-PCR/western blot were used to analyze the differential expression of genes/proteins between IVM and the control group. HE staining and water maze were used to assess the histological changes in brain tissue and cognition of the offspring. The rates of fertilization, cleavage, and live birth were significantly decreased in IVM group. Thirteen genes were upregulated in IVM oocytes compared with the control, including Armet and Mrpl51. The higher level of Armet in IVM oocytes was retained in brain of newborn mice, which could be related to the upregulation of activating transcription factor 6 (Atf6) and X-box binding protein 1 (Xbp1), while Mrpl51 was expressed normally in brain of postnatal mice. No significant differences were detected in brain weight, neuronal counts, and the cognition in the offspring between the two groups. The present results suggested that IVM could affect the pregnancy outcome and the Armet and Mrpl51 gene/protein expression. The change in Armet expression lasted while the change of Mrpl51 disappeared after birth. However, the brain development of the offspring seemed to be unaffected by IVM.

Gap junction-mediated communications regulate chromatin remodeling during bovine oocyte growth and differentiation through cAMP-dependent mechanism(s)

Oocyte development is characterized by impressive changes in chromatin structure and function in the germinal vesicle (GV) that are crucial in conferring to the oocyte meiotic and developmental competence. During oogenesis, oocyte and follicular cells communicate by paracrine and junctional mechanisms. In cow, cumulus-enclosed oocytes (CEOs) isolated from early antral follicles have uncondensed chromatin (GV0), functionally open gap junction (GJ)-mediated communications, and limited meiotic competence. The aim of the present study was to analyze the role of GJ communications on the chromatin remodeling process during the specific phase of folliculogenesis that coincides with the transcriptional silencing and the sequential acquisition of meiotic and developmental capability. CEOs were cultured in a follicle-stimulating hormone-based culture system that sustained GJ coupling and promoted oocyte growth and transition from GV0 to higher stages of condensation. When GJ functionality was experimentally interrupted, chromatin rapidly condensed, and RNA synthesis suddenly ceased. These effects were prevented by the addition of cilostamide, a phosphodiesterase 3 inhibitor, indicating that the action of GJ-mediated communication on chromatin structure and function is mediated by cAMP. Prolonging GJ coupling during oocyte culture before in vitro maturation enhanced the ability of early antral oocytes to undergo meiosis and early embryonic development. Altogether, the evidence suggests that GJ-mediated communication between germinal and somatic compartments plays a fundamental role in the regulation of chromatin remodeling and transcription, which in turn are related to competence acquisition.

Does the duration of gonadotropin stımulation affect embryo quality on post-retrieval day 3?

AIM

To determine if the duration of ovarian hyperstimulation affects quality of embryos on the 3rd day.

METHODS

Retrospective cohort study was designed in a University affiliated hospital. Six-hundred fifteen women undergoing first IVF treatment were grouped according to the duration of controlled ovarian hyperstimulation (COH) in long-down regulated cycles. Group A consisted of women with 8 or less days of COH, Group B consisted of women who had between 9 and 10 days of COH and Group C had 11 days or more COH. The degree of fragmentation and asymmetry of blastomeres were compared for the 3rd day after oocyte retrieval.

RESULTS

On day 3, there were more embryos with 10-25% fragmentation in Group A than in Group B. Embryos were also less symmetrical in Group A than in Group B.

CONCLUSIONS

COH cycles which are shorter than 9 days result in more embryos with more than 10% fragmentation on post-retrieval day 3.

What to do when ICSI fails

The refinement of gamete micromanipulation techniques has made conception possible for couples with male factor infertility who otherwise would remain childless. Moreover, intracytoplasmic sperm injection (ICSI) has ensured that such refractory cases can now generate offspring as successfully as in couples that merely require in vitro insemination. However, despite the now sterling record of ICSI it does not assure a successful outcome for every patient. This can be due, for instance, to the inability of the spermatozoon to activate the oocyte, and applies obviously in cases where spermatozoa are absent from the ejaculate or testicular biopsy. In the present paper we describe in detail the reasons for such failure and review the options that may help overcome it. In particular, we outline the treatment protocol for the situation in which spermatozoa are unable to induce oocyte activation. Further, we report on the clinical outcome achieved with spermatozoa retrieved from the testis, and in cases of extreme oligozoospermia we also explore the option of replicating a single spermatozoon while gaining information on its genomic content. For the most extreme situation in which men have no identifiable germ cells, we will discuss the current status of efforts to accomplish neo-gametogenesis through embryonic stem cell differentiation.