Frequency and distribution of chromosome abnormalities in human oocytes

State of the art in assisted reproductive technologies for patients with advanced maternal age

According to the World Health Organization, the female reproductive age lasts up to 49 years, but problems with the realization of women's reproductive rights may arise much earlier. Significant numbers of factors affect the state of reproductive health: socioeconomic, ecological, lifestyle features, the level of medical literacy, and the state of the organization and medical care quality. Among the reasons for fertility decline in advanced reproductive age are the loss of cellular receptors for gonadotropins, an increase in the threshold of sensitivity of the hypothalamic-pituitary system to the action of hormones and their metabolites, and many others. Furthermore, negative changes accumulate in the oocyte genome, reducing the possibility of fertilization, normal development and implantation of the embryo and healthy offspring birth. Another theory of ageing causing changes in oocytes is the mitochondrial free radical theory of ageing. Taking into account all these age-related changes in gametogenesis, this review considers modern technologies aimed at the preservation and realization of female fertility. Among the existing approaches, two main ones can be distinguished: methods allowing the preservation of reproductive cells at a younger age using ART intervention and cryobanking, as well as methods aimed at improving the basic functional state of advanced-age women's oocytes and embryos.

Unraveling female reproductive senescence to enhance healthy longevity

In a society where women often want successful careers and equal opportunities to men, the early nature of ovarian aging often forces women to make difficult life choices between career and family development. Fertility in women begins to decline after the age of 37 years and it is rare for pregnancies to occur after 45. This reproductive decline in women is inevitable and culminates in menopause, which is a major driver of age-related diseases. In a world where biomedical advances are leading to modifiable biological outcomes, it is time to focus on mitigating female reproductive senescence to maintain fertility and preserve age-related hormonal functions, with the goal of providing increased life choices and enhancing healthspan. To date, reproductive longevity research remains an understudied field. More needs to be done to unravel the biology of the ovarian follicles, which are the functional units of reproductive lifespan and are comprised of cell types including the oocyte (female gamete) and a group of specialized supporting somatic cells. Biological attempts to maintain the quality and quantity of follicles in animal models through manipulating pathways involved in aging can potentially prolong female reproductive lifespan and healthspan. Here, we summarize the molecular events driving ovarian aging and menopause and the interventional strategies to offset these events. Developing solutions to female reproductive senescence will open doors to discover ways to enhance true healthy longevity for both men and women.

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.

MicroRNA-Mediated Gene Regulatory Mechanisms in Mammalian Female Reproductive Health

Mammalian reproductive health affects the entire reproductive cycle starting with the ovarian function through implantation and fetal growth. Various environmental and physiological factors contribute to disturbed reproductive health status leading to infertility problems in mammalian species. In the last couple of decades a significant number of studies have been conducted to investigate the transcriptome of reproductive tissues and organs in relation to the various reproductive health issues including endometritis, polycystic ovarian syndrome (PCOS), intrauterine growth restriction (IUGR), preeclampsia, and various age-associated reproductive disorders. Among others, the post-transcriptional regulation of genes by small noncoding miRNAs contributes to the observed transcriptome dysregulation associated with reproductive pathophysiological conditions. MicroRNAs as a class of non-coding RNAs are also known to be involved in various pathophysiological conditions either in cellular cytoplasm or they can be released to the extracellular fluid via membrane-bounded extracellular vesicles and proteins. The present review summarizes the cellular and extracellular miRNAs and their association with the etiology of major reproductive pathologies including PCOS, endometritis, IUGR and age-associated disorders in various mammalian species.

Increasing ovarian NAD+ levels improve mitochondrial functions and reverse ovarian aging

Loss of follicles together with decreased oocyte quality and quantity contribute to age-associated ovarian senescence and infertility. Although underlying mechanisms for ovarian senescence are still unknown, mitochondrial dysfunctions have been reported. Here, we showed age-dependent decreases in ovarian Nicotinamide Adenine Dinucleotide (NAD⁺) levels in mice whereas supplementing aging mice with nicotinamide riboside (NR), an NAD⁺ precursor, increased ovarian NAD⁺ content. We found that increases in ovarian NAD⁺ levels in aging mice led to increased number of ovarian follicles and ovulatory potential as well as increased live birth rate. NR supplementation also reduced levels of reactive oxygen species and decreased spindle anomalies in aging oocytes, together with increased mitochondrial membrane potential (ΔΨm) and decreased mitochondrial clustering. In addition, NR supplementation improved ovarian mitochondrial energy metabolism. Our data suggested that supplementation with NAD⁺ precursors in vivo and in vitro could be potential therapeutic approaches for treating age-related ovarian infertility.

Comparison of Efficiencies of Non-invasive Prenatal Testing, Karyotyping, and Chromosomal Micro-Array for Diagnosing Fetal Chromosomal Anomalies in the Second and Third Trimesters

In this study, we aimed to compare the efficiency of non-invasive prenatal testing (NIPT), karyotyping, and chromosomal micro-array (CMA) for the diagnosis of fetal chromosomal anomalies in the second and third trimesters. Pregnant women, who underwent amniocenteses for prenatal genetic diagnoses during their middle and late trimesters, were recruited at the Prenatal Diagnosis Center of Taizhou City. Maternal blood was separated for NIPT, and amniotic fluid cells were cultured for karyotyping and CMA. The diagnostic efficiency of NIPT for detecting fetal imbalanced anomalies was compared with karyotyping and CMA. A total of 69 fetal chromosomal imbalances were confirmed by CMA, 37 were diagnosed by NIPT and 35 were found by karyotyping. The sensitivities of NIPT and karyotyping for diagnosing aneuploidy were 96.3% and 100% respectively. Only one mosaic sexual chromosome monosomy was misdiagnosed by NIPT, whereas the sensitivity of NIPT and karyotyping was 70% and 30%, respectively, for detecting pathogenic deletions and duplications sized from 5-20 Mb. Taken together, our results suggest that the efficiency of NIPT was similar to the formula karyotyping for detecting chromosome imbalance in the second and third trimesters.

The role of melatonin, a multitasking molecule, in retarding the processes of ageing

Biological ageing is generally accompanied by a gradual loss of cellular functions and physiological integrity of organ systems, the consequential enhancement of vulnerability, senescence and finally death. Mechanisms which underlie ageing are primarily attributed to an array of diverse but related factors including free radical-induced damage, dysfunction of mitochondria, disruption of circadian rhythms, inflammaging, genomic instability, telomere attrition, loss of proteostasis, deregulated sensing of nutrients, epigenetic alterations, altered intercellular communication, and decreased capacity for tissue repair. Melatonin, a prime regulator of human chronobiological and endocrine physiology, is highly reputed as an antioxidant, immunomodulatory, antiproliferative, oncostatic, and endocrine-modulatory molecule. Interestingly, several recent reports support melatonin as an anti-ageing agent whose multifaceted functions may lessen the consequences of ageing. This review depicts four categories of melatonin's protective effects on ageing-induced molecular and structural alterations. We also summarize recent findings related to the function of melatonin during ageing in various tissues and organs.

CoQ10 Supplementation in Patients Undergoing IVF-ET: The Relationship with Follicular Fluid Content and Oocyte Maturity

Background: The target of the reduced fecundity with aging is the oocyte. The follicular fluid and its components are strongly linked with the environment of the maturing oocyte. The aim of the present study was to evaluate CoQ10 bioavailability in follicular fluids after oral supplementation and its possible implication in oocyte maturation. Methods: Fifteen female partners of infertile couples, aged 31–46, undergoing IVF-ET and taking 200 mg/day oral CoQ10 were compared to unsupplemented patients. CoQ10 content, its oxidative status and total antioxidant capacity were evaluated also in relation to oocyte maturation indexes. Results: CoQ10 supplementation produced a significant increase in follicular content and a significant improvement of its oxidative status. Follicular fluid total antioxidant capacity highlighted a significant decrease in patients supplemented with CoQ10, specially in women >35 years. CoQ10 supplementation was associated with a significant decrease in total antioxidant capacity of fluid from follicles containing mature oocyte, moreover CoQ10 oxidative status was also significantly reduced but in follicles containing immature oocyte. Conclusions: Our observation leads to the hypothesis that the oral supplementation of CoQ10 may improve follicular fluid oxidative metabolism and oocyte quality, specially in over 35-year-old women.

Do patients who achieve pregnancy using IVF-PGS do the recommended genetic diagnostic testing in pregnancy?

PURPOSE

Patients undergoing in-vitro fertilization (IVF) with preimplantation genetic screening (PGS) are counseled about the limitations of this technique. As part of the consent process for PGS, physicians recommend diagnostic genetic testing performed in early pregnancy to definitively rule out chromosomal abnormalities. We have noted anecdotally, however, that few patients undergo the recommended diagnostic testing. In this study, we are examining if women who conceived using IVF-PGS did early pregnancy chromosomal testing, and if they did, what type of testing they had.

METHODS

This study was performed from 2015 to 2017 in the Division of Reproductive Endocrinology and Infertility at Northwestern University. We included patients who became pregnant after IVF-PGS who were seen by the Division of Reproductive Genetics and non-PGS control group.

RESULTS

Sixty-eight patients were included. A total of 50 patients (73.5%) opted for non-invasive prenatal screening; 5 (7.4%) had invasive testing (4 had chorionic villus sampling and 1 had amniocentesis). A total of 13 patients (19%) declined further genetic testing. When comparing demographic data, the mean age was significantly higher in the group of patients who pursued non-invasive testing than in the group who declined further testing (37.15 vs 34.05 years old, p < 0.05). Control group declined invasive diagnostic testing.

CONCLUSIONS

Most patients who conceive using IVF-PGS do not pursue diagnostic prenatal chromosomal testing. Future studies focusing on decision making in this patient group are warranted to further elucidate why a small percentage of patients opt for diagnostic testing, even when adequately counseled about the inherent limitations of PGS.

Effect of next-generation sequencing in preimplantation genetic testing on live birth ratio

The present study analysed live birth ratios in frozen embryo transfer (FET) cycles where embryo ploidy status was determined with preimplantation genetic testing (PGT) using next-generation sequencing (NGS). PGT was performed on trophectoderm cells biopsied at the blastocyst stage. The present prospective cohort study included 112 women undergoing frozen embryo transfer, with NGS PGT. The control group consisted of 85 patients who underwent the IVF procedure with FET planned for a subsequent cycle. The live birth rate per cycle was higher by ~18.5 percentage points in the investigated compared with control group (42.0% vs 23.5% respectively; P = 0.012). The differences between the study and control groups were also significant for clinical pregnancy (42.0% vs 23.5% respectively; P = 0.012), implantation (41.2% vs 22.2% respectively; P = 0.001) and pregnancy loss rates (9.6% vs 28.6% respectively; P = 0.027). The results show that PGT NGS is a useful method for embryo selection and it may be implemented in routine clinical practice with propitious results.

Ovarian Aging and Osteoporosis

Osteoporosis is the most common bone metabolic disease with a very high morbidity, and women usually got a higher risk of osteoporosis than men. The high incidence rate of osteoporosis in women was mainly caused by (1) women having fewer skeletons and bone mass, (2) pregnancy consuming a large amount of calcium and other nutrients, and most importantly (3) the cease of estrogen secretion by ovaries after menopause. Along with ovarian aging, the follicle pool gradually declines and the oocyte quality reduced, accompanied with decline in serum estrogen. Estrogen deficiency plays an important role in the pathogenesis of postmenopausal osteoporosis; it is mainly a result of the recognition that estrogen regulates bone remodeling by modulating the production of cytokines and growth factors from bone marrow and bone cells. This review will summarize current knowledge concerning ovarian aging and postmenopause osteoporosis and also discuss clinical treatment and new ideas of drug development for osteoporosis.

Loss of Centromere Cohesion in Aneuploid Human Oocytes Correlates with Decreased Kinetochore Localization of the Sac Proteins Bub1 and Bubr1

In human eggs, aneuploidy increases with age and can result in infertility and genetic diseases. Studies in mouse oocytes suggest that reduced centromere cohesion and spindle assembly checkpoint (SAC) activity could be at the origin of chromosome missegregation. Little is known about these two features in humans. Here, we show that in human eggs, inter-kinetochore distances of bivalent chromosomes strongly increase with age. This results in the formation of univalent chromosomes during metaphase I (MI) and of single chromatids in metaphase II (MII). We also investigated SAC activity by checking the localization of BUB1 and BUBR1. We found that they localize at the kinetochore with a similar temporal timing than in mitotic cells and in a MPS1-dependent manner, suggesting that the SAC signalling pathway is active in human oocytes. Moreover, our data also suggest that this checkpoint is inactivated when centromere cohesion is lost in MI and consequently cannot inhibit premature sister chromatid separation. Finally, we show that the kinetochore localization of BUB1 and BUBR1 decreases with the age of the oocyte donors. This could contribute to oocyte aneuploidy.

Type of chromosome abnormality affects embryo morphology dynamics

OBJECTIVE

To study the differences in the cleavage time between types of embryo chromosomal abnormalities and elaborate algorithm to exclude aneuploid embryos according to the likelihood to be euploid.

DESIGN

Retrospective cohort study.

SETTING

University affiliated private center.

PATIENT(S)

Preimplantational genetic screening patients (n = 112) including cases of advanced maternal age, repeated implantation failure, and recurrent miscarriage. A total of 485 embryos were analyzed.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

All biopsied embryos were cultured in an incubator with time-lapse technology, cleavage timing from insemination to day 3 and all kinetic parameters that have been described in previous studies by our group.

RESULT(S)

Logistic regression analysis were used to identify morphokinetic parameters and some were strongly associated with complex aneuploid embryos; t3 (odds ratio = 0.590, 95% confidence interval 0.359-0.971) and t5-t2 (odds ratio = 0.151, 95% confidence interval 0.082-0.278).

CONCLUSION(S)

Embryo morphokinetics are affected by chromosome aneuploidy and further analysis of the chromosome content reveals higher differences when the complexity in the chromosome disorders is increased. The use of time-lapse monitoring, although not able to detect an abnormal embryo, may be potentially useful to discard those embryos with high risk of complex chromosomal abnormalities.

A meta-analysis of neonatal health outcomes from oocyte donation

Donated oocytes are a treatment modality for female infertility which is also associated with increased risks of preeclampsia. Subsequently it is important to evaluate if there is concomitant increased risks for adverse neonatal events in donated oocyte neonates. A structured search of the literature using PubMed, EMBASE and Cochrane Reviews was performed to investigate the perinatal health outcomes of offspring conceived from donor oocytes compared with autologous oocytes. Meta-analysis was performed on comparable outcomes data. Twenty-eight studies were eligible and included in the review, and of these, 23 were included in a meta-analysis. Donor oocyte neonates are at increased risk of being born with low birth weight (<2500 g) [risk ratio (RR): 1.18, 95% confidence interval (CI): 1.14–1.22, P-value (P)<0.00001], very low birth weight (<1500 g) (RR: 1.24, CI: 1.15–1.35, P<0.00001), preterm (<37 weeks) (RR: 1.26, CI: 1.23–1.30, P<0.00001), of lower gestational age (mean difference −0.3 weeks, CI: −0.35 weeks to −0.25 weeks, P<0.00001), and preterm with low birth weight (RR: 1.24, CI: 1.19–1.29, P<0.00001), when compared with autologous oocyte neonates. Conversely, low birth weight outcomes were improved in term donor oocyte neonates (RR: 0.86, CI: 0.8–0.93, P=0.0003). These negative outcomes remained significant when controlling for multiple deliveries. The donor oocyte risk rates are higher than those found in general ART outcomes, are important considerations for the counselling of infertile patients and may also influence the long term health of the offspring.

Impact of sperm genome decay on Day-3 embryo chromosomal abnormalities from advanced-maternal-age patients

Infertile male patients often exhibit unconventional semen parameters, including DNA fragmentation, chromatin dispersion, and aneuploidy-collectively referred to as sperm genome decay (SGD). We investigated the correlation of SGD to embryo chromosomal abnormalities and its effect on clinical pregnancy rates in patients with advanced maternal age (AMA) (>40 years) who were undergoing intracytoplasmic sperm injection-preimplantation genetic screening (ICSI-PGS). Three groups were assessed: patients with AMA and male partners with normal sperm (AMA-N); AMA patients and male partners presenting with SGD (AMA-SGD); and young fertile female patients and male partners with SGD (Y-SGD). We found a significant increase in embryonic chromosomal abnormalities-polyploidy, nullisomy, mosaicism, and chaotic anomaly rates-when semen parameters are altered (76% vs. 67% and 66% in AMA-SGD vs. AMA-N and Y-SGD groups, respectively). Statistical analysis showed a correlation between SGD and aneuploidies of embryonic chromosomes 13, 16, 21, X, and Y, as well as negative clinical outcomes. Incorporation of molecular sperm analyses should therefore significantly minimize the risk of transmission of chromosomal anomalies from spermatozoa to embryos, and may provide better predictors of pregnancy than conventional sperm analyses. We also demonstrated that an ICSI-PGS program should be implemented for SGD patients in order to limit transmission of chromosomal paternal anomalies and to improve clinical outcome.

Epidemiological investigation of risk factors of the pregnant women with early spontaneous abortion in Beijing

OBJECTIVE

To determine the risk factors of the pregnant women with early spontaneous abortion in Beijing.

METHODS

A total of 34,417 cases of pregnant women were participated in the survey from January 2000 to December 2013. A questionnaire was informed to each woman. The content of questionnaire includes four parts: general condition, obstetrical history, past history and family history, and living environment and habits. The mental condition was evaluated with Self-Rating Anxiety Scale (SAS) and Self-Rating Depression Scale (SDS).

RESULTS

A total of 32,296 questionnaires were collected. The spontaneous abortion rate in the total sample was 3.0%. There was no significant difference between the normal pregnancy group and spontaneous abortion group in terms of general condition, obstetrical and past history (P>0.05). Significant differences between the two groups were found in terms of decoration during pregnancy, keeping pets, near mobile communication base station within 100 m around the residence, drinking during pregnancy, having a cold during pregnancy and SAS (P<0.05). Having a cold during pregnancy, decoration during pregnancy, near mobile communication base station within 100 m around the residence, keeping pets and high SAS were determined the independent risk factors of spontaneous abortion by Logistic regression analysis.

CONCLUSIONS

Having a cold during pregnancy, decoration, keeping pets, near mobile communication base station within 100 m around the residence and high SAS are the independent risk factors of spontaneous abortion in Beijing.

MicroRNA and implantation

We provide a review of microRNA (miRNA) related to human implantation which shows the potential diagnostic role of miRNAs in impaired endometrial receptivity, altered embryo development, implantation failure after assisted reproduction technology, and in ectopic pregnancy and pregnancies of unknown location. MicroRNAs may be emerging diagnostic markers and potential therapeutic tools for understanding implantation disorders. However, further research is needed before miRNAs can be used in clinical practice for identifying and treating implantation failure.

Would it be too late? A retrospective case-control analysis to evaluate maternal-fetal outcomes in advanced maternal age

PURPOSE

To evaluate maternal-fetal outcomes in women of advanced maternal age (AMA; >35 years old) and women of physiological maternal age as controls (C; <35 years old).

METHODS

Single-center, retrospective case-control analysis, from January 1 to December 31, 2013. For each group, we evaluated obstetric history, number of twin pregnancies, delivery mode, incidence of obstetric diseases and neonatal outcomes (5-min Apgar score, neonatal weight, meconium stained fluid rate, admission to the neonatal intensive care unit rate, and incidence of congenital malformations). Data are presented as n (%) and analyzed with χ (2) test and Fisher exact test (when required). A p value < 0.05 was considered statistically significant. Moreover, we calculated the odds ratio (OR), with confidence interval (CI) at 95 %.

RESULTS

We enrolled 1,347 pregnant women, 210 (15.6 %) in AMA and 1,137 (84.4 %) C. AMA patients showed a higher rate of previous (anamnestic) spontaneous abortion (SA; p = 0.001; OR = 2.10) and previous (anamnestic) voluntary pregnancy termination (p = 0.022; OR = 1.59), iterative cesarean section (p = 0.026; OR = 2.33), SA (p = 0.001; OR = 12.82), preterm delivery (p = 0.001; OR = 69.84), congenital malformations (p = 0.036; OR = 3.94). In C there was a greater number of nulliparous (p = 0.009; OR = 0.52) and vaginal deliveries (p = 0.025; OR = 0.41). There were not any statistically significant differences between the two groups for twin pregnancies (p = 0.862; OR = 0.97), first cesarean section (p = 0.145; OR = 0.95), other obstetric diseases and neonatal outcomes.

CONCLUSION

AMA could be considered an important risk factor only for SA and PTD and does not influence neonatal outcomes except for congenital malformations.

Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes

Background

Recent advances in time-lapse monitoring in IVF treatment have provided new morphokinetic markers for embryonic competence. However, there is still very limited information about the relationship between morphokinetic parameters, chromosomal compositions and implantation potential. Accordingly, this study aimed at investigating the effects of selecting competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing on pregnancy and implantation outcomes for patients undergoing preimplantation genetic screening (PGS).

Methods

A total of 1163 metaphase II (MII) oocytes were retrieved from 138 PGS patients at a mean age of 36.6 ± 2.4 years. These sibling MII oocytes were then randomized into two groups after ICSI: 1) Group A, oocytes (n = 582) were cultured in the time-lapse system and 2) Group B, oocytes (n = 581) were cultured in the conventional incubator. For both groups, whole genomic amplification and array CGH testing were performed after trophectoderm biopsy on day 5. One to two euploid blastocysts within the most predictive morphokinetic parameters (Group A) or with the best morphological grade available (Group B) were selected for transfer to individual patients on day 6. Ongoing pregnancy and implantation rates were compared between the two groups.

Results

There were significant differences in clinical pregnancy rates between Group A and Group B (71.1% vs. 45.9%, respectively, p = 0.037). The observed implantation rate per embryo transfer significantly increased in Group A compared to Group B (66.2% vs. 42.4%, respectively, p = 0.011). Moreover, a significant increase in ongoing pregnancy rates was also observed in Group A compared to Group B (68.9% vs. 40.5%. respectively, p = 0.019). However, there was no significant difference in miscarriage rate between the time-lapse system and the conventional incubator (3.1% vs. 11.8%, respectively, p = 0.273).

Conclusions

This is the first prospective investigation using sibling oocytes to evaluate the efficiency of selecting competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for PGS patients. Our data clearly demonstrate that the combination of these two advanced technologies to select competent blastocysts for transfer results in improved implantation and ongoing pregnancy rates for PGS patients.

The frequency of precocious segregation of sister chromatids in mouse female meiosis I is affected by genetic background

Mammalian female gametes frequently suffer from numerical chromosomal aberrations, the main cause of miscarriages and severe developmental defects. The underlying mechanisms responsible for the development of aneuploidy in oocytes are still not completely understood and remain a subject of extensive research. From studies focused on prevalence of aneuploidy in mouse oocytes, it has become obvious that reported rates of aneuploidy are strongly dependent on the method used for chromosome counting. In addition, it seems likely that differences between mouse strains could influence the frequency of aneuploidy as well; however, up till now, such a comparison has not been available. Therefore, in our study, we measured the levels of aneuploidy which has resulted from missegregation in meiosis I, in oocytes of three commonly used mouse strains-CD-1, C3H/HeJ, and C57BL/6. Our results revealed that, although the overall chromosomal numerical aberration rates were similar in all three strains, a different number of oocytes in each strain contained prematurely segregated sister chromatids (PSSC). This indicates that a predisposition for this type of chromosome segregation error in oocyte meiosis I is dependent on genetic background.

Coenzyme Q10 Supplementation and Oocyte Aneuploidy in Women Undergoing IVF-ICSI Treatment

BACKGROUND

The age-related reduction in live-birth rate is attributed to a high rate of aneuploidy and follicle depletion. We showed in an animal model that treatment with Coenzyme Q10 (CoQ10) markedly improved reproductive outcome. The aim of this study was to compare the post-meiotic oocyte aneuploidy rate in in vitro fertilization (IVF) and intra cytoplasmic sperm injection (ICSI) patients treated with CoQ10 or placebo.

METHODS

We conducted a double blind placebo controlled randomized trial that included IVF–ICSI patients 35–43 years of age. The patients were treated with either 600 mg of CoQ10 or an equivalent number of placebo caps. We compared the post-meiotic aneuploidy rate using polar body biopsy (PBBX) and comparative genomic hybridization (CGH). According to the power calculation, 27 patients were needed for each arm.

RESULTS

Owing to safety concerns regarding the effects of polar body biopsy on embryo quality and implantation, the study was terminated before reaching the target number of participants. A total of 39 patients were evaluated and randomized (17 CoQ10, 22 placebo), 27 were given the study medication (12 CoQ10, 15 placebo), and 24 completed an IVF–ICSI cycle including PBBX and embryo transfer (10 CoQ10, 14 placebo). Average age, base line follicle stimulating hormone (FSH), peak estradiol and progesterone serum level, as well as the total number of human menopausal gonadotropin (hMG) units—did not differ between the groups. The rate of aneuploidy was 46.5% in the CoQ10 group compared to 62.8% in the control. Clinical pregnancy rate was 33% for the CoQ10 group and 26.7% for the control group.

CONCLUSION

No significant differences in outcome were detected between the CoQ10 and placebo groups. However, the final study was underpowered to detect a difference in the rate of aneuploidy.

Prospective study of a Swedish infertile cohort 2005-08: population characteristics, treatments and pregnancy rates

BACKGROUND

We here report on results from a prospective study comprising 380 infertile couples undergoing infertility work-up and various treatments for infertility in our clinic. The aim was to investigate the overall birth rate as a result of different treatments, as well as spontaneous pregnancies.

METHODS

Three hundred and eighty couples were consecutively included between December 2005 and May 2008. All couples underwent a fertility work-up, including hysterosalpingogram, hormonal characterization, clinical examination, screening for infectious diseases and semen analysis. The mean age of the women at the time of inclusion was 33.2 years. The mean duration of infertility prior to inclusion was 1.8 years. And 46.6% (n = 177) of the women had been pregnant prior to their first visit to the clinic and 30.0% (n = 114) had been pregnant earlier in their present relationship.

RESULTS

As of November 2010, 57.3% (n = 218) of the women had given birth to a child when they were lost to follow up by the study. Spontaneous conception was observed in 11.3% (n = 43) of the women, 14.5% (n = 64) conceived after intrauterine insemination (IUI), 4.2% (n = 16) conceived after ovarian hyperstimulation and ovulation induction (OH/OI) and 28.4% (n = 113) after in vitro fertilization. There were 280 pregnancies and 58 spontaneous abortions (22.3%) in the group. Mean anti-mullerian hormone significantly correlated with antral follicle count and age and was significantly higher in the subgroup that became pregnant after IUI.

CONCLUSIONS

Spontaneous pregnancies and IUI + OH/OI contributed significantly to the pregnancies observed in the total population. Predictive factors for pregnancy were anti-mullerian hormone in the group undergoing IUI treatment and in the age group ≥38-duration of infertility. Previous pregnancies, body mass index, estradiol, follicle stimulating hormone or having given birth prior to the infertility period were not predictive of pregnancy for the infertile couples in this study.

Shortened estrous cycle length, increased FSH levels, FSH variance, oocyte spindle aberrations, and early declining fertility in aging senescence-accelerated mouse prone-8 (SAMP8) mice: concomitant characteristics of human midlife female reproductive aging

Women experience a series of specific transitions in their reproductive function with age. Shortening of the menstrual cycle begins in the mid to late 30s and is regarded as the first sign of reproductive aging. Other early changes include elevation and increased variance of serum FSH levels, increased incidences of oocyte spindle aberrations and aneuploidy, and declining fertility. The goal of this study was to investigate whether the mouse strain senescence-accelerated mouse-prone-8 (SAMP8) is a suitable model for the study of these midlife reproductive aging characteristics. Midlife SAMP8 mice aged 6.5-7.85 months (midlife SAMP8) exhibited shortened estrous cycles compared with SAMP8 mice aged 2-3 months (young SAMP8, P = .0040). Midlife SAMP8 mice had high FSH levels compared with young SAMP8 mice, and mice with a single day of high FSH exhibited statistically elevated FSH throughout the cycle, ranging from 1.8- to 3.6-fold elevation on the days of proestrus, estrus, metestrus, and diestrus (P < .05). Midlife SAMP8 mice displayed more variance in FSH than young SAMP8 mice (P = .01). Midlife SAMP8 ovulated fewer oocytes (P = .0155). SAMP8 oocytes stained with fluorescently labeled antitubulin antibodies and scored in fluorescence microscopy exhibited increased incidence of meiotic spindle aberrations with age, from 2/126 (1.59%) in young SAMP8 to 38/139 (27.3%) in midlife SAMP8 (17.2-fold increase, P < .0001). Finally, SAMP8 exhibited declining fertility from 8.9 pups/litter in young SAMP8 to 3.5 pups/litter in midlife SAMP8 mice (P < .0001). The age at which these changes occur is younger than for most mouse strains, and their simultaneous occurrence within a single strain has not been described previously. We propose that SAMP8 mice are a model of midlife human female reproductive aging.

Selection of euploid blastocysts for cryopreservation with array comparative genomic hybridization (aCGH) results in increased implantation rates in subsequent frozen and thawed embryo transfer cycles

BACKGROUND

In assisted reproductive treatments, embryos remaining after fresh embryo transfer are usually selected for cryopreservation based on traditional morphology assessment. Our previous report has demonstrated that array comparative genomic hybridization (aCGH) screening for IVF patients with good prognosis significantly improves clinical and ongoing pregnancy rates in fresh embryo transfer cycles. The current study further investigates the efficiency of applying aCGH in the selection of euploid embryos for cryopreservation as related to pregnancy and implantation outcomes in subsequent frozen embryo transfer (FET) cycles.

METHODS

First-time IVF patients with good prognosis undergoing fresh single embryo transfer and having at least one remaining blastocyst for cryopreservation were prospectively randomized into two groups: 1) Group A patients had embryos assessed by morphology first and then by aCGH screening of trophectoderm cells and 2) Group B patients had embryos evaluated by morphology alone. All patients had at least one blastocyst available for cryopreservation after fresh embryo transfer. There were 15 patients in Group A and 23 patients in Group B who failed to conceive after fresh embryo transfer and completed the FET cycles. Blastocyst survival and implantation rates were compared between the two groups.

RESULTS

There were no significant differences in blastocyst survival rates between Group A and Group B (90.9% vs. 91.3%, respectively; p >0.05). However, a significantly higher implantation rate was observed in the morphology assessment plus aCGH screening group compared to the morphology assessment alone group (65.0% vs. 33.3%, respectively; p = 0.038). There was no miscarriage observed in Group A while a 16.7% miscarriage rate was recorded in Group B (0% vs. 16.7%, respectively; p >0.05).

CONCLUSIONS

While aCGH screening has been recently applied to select euploid blastocysts for fresh transfer in young, low-risk IVF patients, this is the first prospective study on the impact of aCGH specifically on blastocyst survival and implantation outcomes in the subsequent FET cycles of IVF patients with good prognosis. The present study demonstrates that aCGH screening of blastocysts prior to cryopreservation significantly improves implantation rates and may reduce the risk of miscarriage in subsequent FET cycles. Further randomized clinical studies with a larger sample size are needed to validate these preliminary findings.

Single thawed euploid embryo transfer improves IVF pregnancy, miscarriage, and multiple gestation outcomes and has similar implantation rates as egg donation

PURPOSE

The objective of our study was to determine if trophectoderm biopsy, vitrification, array-comparative genomic hybridization and single thawed euploid embryo transfer (STEET) can reduce multiple gestations and yield high pregnancy and low miscarriage rates.

METHODS

We performed a retrospective observational study comparing single thawed euploid embryo to routine age matched in vitro fertilization (IVF) patients that underwent blastocyst transfer from 2008 to 2011 and to our best prognosis group donor oocyte recipients (Donor). Our main outcome measures were implantation rate, clinical pregnancy rate, spontaneous abortion rate and multiple gestation rate.

RESULTS

The STEET group had a significantly higher implantation rate (58 %, 53/91) than the routine IVF group (39 %, 237/613) while the Donor group (57 %, 387/684) had a similar implantation rate. The clinical pregnancy rates were not statistically different between the STEET and IVF groups. However, the multiple gestation rate was significantly lower in the STEET group (STEET 2 % versus IVF 34 %, Donor 47 %).

CONCLUSIONS

STEET results in a high pregnancy rate, low multiple gestation rate and miscarriage rates. Despite the older age of STEET patients and transfer of twice as many embryos, the implantation rate for STEET was indistinguishable from that for egg donation. STEET offers an improvement to IVF, lowering risks without compromising pregnancy rate.

Bone morphogenetic protein-15 in follicle fluid combined with age may differentiate between successful and unsuccessful poor ovarian responders

BACKGROUND

The counselling of poor ovarian responders about the probability of pregnancy remains a puzzle for gynaecologists. The aim of this study was to optimise the management of poor responders by investigating the role of the oocyte-derived factor bone morphogenetic protein-15 (BMP-15) combined with chronological age in the prediction of the outcome of in-vitro fertilisation-embryo transfer (IVF-ET) in poor responders.

METHODS

A retrospective study conducted in a university hospital. A total of 207 poor ovarian responders who reached the ovum pick-up stage undergoing IVF/intracytoplasmic sperm injection (ICSI) with three or fewer follicles no less than 14 mm on the day of oocyte retrieval were recruited from July 1, 2008 to December 31, 2009. Another 215 coinstantaneous cycles with normal responses were selected as controls. The BMP-15 levels in the follicular fluid (FF) of the 207 poor responders were analysed by western blot. Based on the FF BMP-15 level and age, poor responders were sub-divided into four groups. The main outcome measures were the FF BMP-15 level, implantation rate, pregnancy rate, and live birth rate.

RESULTS

The implantation rate (24.2% vs. 15.3%), chemical pregnancy rate (40% vs. 23.7%), clinical pregnancy rate (36.5% vs. 20.4%) and live birth rate (29.4% vs. 15.1%) in the high BMP-15 group were significantly higher than those in the low BMP-15 group. Furthermore, poor responders aged less than or equal to 35 years with a higher FF BMP-15 level had the best implantation, pregnancy and live birth rates, which were comparable with those of normal responders.

CONCLUSIONS

Our study suggests a potential role of BMP-15 in the prediction of the IVF outcome. A high FF BMP-15 combined with an age less than or equal to 35 years may be used as a potential indicator for repeating IVF cycles in poor ovarian responders.

A review of, and commentary on, the ongoing second clinical introduction of preimplantation genetic screening (PGS) to routine IVF practice

PURPOSE

Current re-introduction of "improved" preimplantation genetic screening (PGS#2) raises the question whether PGS#2 is ready for routine clinical application.

METHODS

We assessed available evidence via review of published data for years 2005-2012, and review of currently ongoing registered clinical trials, based on searches under appropriate key words in PubMed, MEDLINE, Cochrane Database System Review and Google Scholar and http://www.ClinicalTrials.gov . In absence of prospective clinical trials, and due to limited available data, individual publications/ongoing studies are assessed.

RESULTS

PGS#2 offers significant improvements in accuracy of aneuploidy diagnosis over PGS#1. By moving embryo biopsy from day-3 after fertilization (6-8 cell stage) to trophectoderm biopsy at blastocyst stage (day 5-6), PGS#2, however, adds additional co-variables to the analysis of efficacy of the procedure, which have special relevance for women with diminished ovarian reserve (DOR), who usually produce small egg and embryo numbers. Limited published data, claiming efficacy of PGS#2, as well as ongoing clinical trials, do not consider these additional co-variables, do not analyze outcomes by intent to treat and, therefore, have to be considered biased in patient selection.

CONCLUSIONS

Here reached conclusions are based on absence of adequate data rather than affirmative outcome assessments. They, therefore, are subject to change at any future date with generation of significant new data. Premature introduction of PGS#1 caused significant damage to patients. As currently no reliable PGS#2 data are available to suggest improvements in IVF outcomes, to avoid a repeat of the PGS#1 experience, PGS#2 should be considered experimental until data show otherwise.

Current understanding of ovarian aging

The reproductive system of human female exhibits a much faster rate of aging than other body systems. Ovarian aging is thought to be dominated by a gradual decreasing numbers of follicles, coinciding with diminished quality of oocytes. Menopause is the final step in the process of ovarian aging. This review focuses on the mechanisms underlying the ovarian aging involving a poor complement of follicles at birth and a high rate of attrition each month, as well as the alternated endocrine factors. We also discuss the possible causative factors that contribute to ovarian aging, e.g., genetic factors, accumulation of irreparable damage of microenvironment, pathological effect and other factors. The appropriate and reliable methods to assess ovarian aging, such as quantification of follicles, endocrine measurement and genetic testing have also been discussed. Increased knowledge of the ovarian aging mechanisms may improve the prevention of premature ovarian failure.

Array comparative genomic hybridization screening in IVF significantly reduces number of embryos available for cryopreservation

Objective

During IVF, non-transferred embryos are usually selected for cryopreservation on the basis of morphological criteria. This investigation evaluated an application for array comparative genomic hybridization (aCGH) in assessment of surplus embryos prior to cryopreservation.

Methods

First-time IVF patients undergoing elective single embryo transfer and having at least one extra non-transferred embryo suitable for cryopreservation were offered enrollment in the study. Patients were randomized into two groups: Patients in group A (n=55) had embryos assessed first by morphology and then by aCGH, performed on cells obtained from trophectoderm biopsy on post-fertilization day 5. Only euploid embryos were designated for cryopreservation. Patients in group B (n=48) had embryos assessed by morphology alone, with only good morphology embryos considered suitable for cryopreservation.

Results

Among biopsied embryos in group A (n=425), euploidy was confirmed in 226 (53.1%). After fresh single embryo transfer, 64 (28.3%) surplus euploid embryos were cryopreserved for 51 patients (92.7%). In group B, 389 good morphology blastocysts were identified and a single top quality blastocyst was selected for fresh transfer. All group B patients (48/48) had at least one blastocyst remaining for cryopreservation. A total of 157 (40.4%) blastocysts were frozen in this group, a significantly larger proportion than was cryopreserved in group A (p=0.017, by chi-squared analysis).

Conclusion

While aCGH and subsequent frozen embryo transfer are currently used to screen embryos, this is the first investigation to quantify the impact of aCGH specifically on embryo cryopreservation. Incorporation of aCGH screening significantly reduced the total number of cryopreserved blastocysts compared to when suitability for freezing was determined by morphology only. IVF patients should be counseled that the benefits of aCGH screening will likely come at the cost of sharply limiting the number of surplus embryos available for cryopreservation.

Preimplantation genetic diagnosis to improve pregnancy outcomes in subfertility

Pre-implantation genetic diagnosis provides prenatal genetic diagnosis before implantation, thus allowing detection of chromosomal abnormalities and their exclusion from embryo transfer in assisted reproductive technologies. Polar body, blastomere or trophectoderm can each be used to obtain requisite genetic or embryonic DNA. Pre-implantation genetic diagnosis for excluding unbalanced translocations is well accepted, and pre-implantation genetic diagnosis aneuploidy testing to avoid repeated pregnancy losses in couples having recurrent aneuploidy is efficacious in reducing miscarriages. Controversy remains about whether pre-implantation genetic diagnosis aneuploidy testing improves take home pregnancy rates, for which reason adherence to specific indications is recommended while the issue is being adjudicated. Current recommendations are for obligatory 24 chromosome testing, most readily using array comparative genome hybridisation.

Large animal models for the study of ovarian follicular dynamics in women

Initial studies of the ovaries were based on postmortem anatomic descriptions, followed by histologic and endocrine approaches. The introduction of high-resolution ultrasonography provided a long-awaited tool to image the reproductive tissues in situ in both animals and humans. Critical studies of the characteristics and control of ovarian follicular and luteal dynamics in nonhuman primates, rodents, and domestic farm animals have involved frequent (i.e., daily or multiple times a day) blood sampling and ultrasonography. Studies of this nature in women are difficult, and often unethical to conduct. Differences in antral folliculogenesis between humans and animals appear to be more in detail rather than in essence, and may reflect differences in intrinsic physiology or merely differences in our ability to detect changes in a given species. In women, the presence of endometrial shedding and symmetric luteal and follicular phases are different from that observed during the estrous cycles of domestic farm animals but despite these differences, general similarities in antral follicular dynamics exist. A continuous pattern of antral follicle development was originally proposed in domestic livestock species; however, the use of frequent serial ultrasonography and simultaneous endocrine profiling in these animal species has resulted in a broad understanding of follicular wave dynamics. Follicular waves have now been described in every species in which this approach has been used, including humans. The relatively large diameters of antral follicles in cows and mares, compared with monkeys, sheep, and rodents provide greater feasibility for characterizing antral follicular dynamics ultrasonographically. While the use of large animal models has increased our understanding of ovarian function and provides the hypothetical basis for studies in women, differences in vocabulary, culture, and research methodologies has hampered knowledge translation. These differences represent a systemic impediment to a broad understanding of ovarian function and limits progress and innovation in the development of safer and more efficacious treatments for infertility and contraception.

Selection of single blastocysts for fresh transfer via standard morphology assessment alone and with array CGH for good prognosis IVF patients: results from a randomized pilot study

BACKGROUND

Single embryo transfer (SET) remains underutilized as a strategy to reduce multiple gestation risk in IVF, and its overall lower pregnancy rate underscores the need for improved techniques to select one embryo for fresh transfer. This study explored use of comprehensive chromosomal screening by array CGH (aCGH) to provide this advantage and improve pregnancy rate from SET.

METHODS

First-time IVF patients with a good prognosis (age <35, no prior miscarriage) and normal karyotype seeking elective SET were prospectively randomized into two groups: In Group A, embryos were selected on the basis of morphology and comprehensive chromosomal screening via aCGH (from d5 trophectoderm biopsy) while Group B embryos were assessed by morphology only. All patients had a single fresh blastocyst transferred on d6. Laboratory parameters and clinical pregnancy rates were compared between the two groups.

RESULTS

For patients in Group A (n = 55), 425 blastocysts were biopsied and analyzed via aCGH (7.7 blastocysts/patient). Aneuploidy was detected in 191/425 (44.9%) of blastocysts in this group. For patients in Group B (n = 48), 389 blastocysts were microscopically examined (8.1 blastocysts/patient). Clinical pregnancy rate was significantly higher in the morphology + aCGH group compared to the morphology-only group (70.9 and 45.8%, respectively; p = 0.017); ongoing pregnancy rate for Groups A and B were 69.1 vs. 41.7%, respectively (p = 0.009). There were no twin pregnancies.

CONCLUSION

Although aCGH followed by frozen embryo transfer has been used to screen at risk embryos (e.g., known parental chromosomal translocation or history of recurrent pregnancy loss), this is the first description of aCGH fully integrated with a clinical IVF program to select single blastocysts for fresh SET in good prognosis patients. The observed aneuploidy rate (44.9%) among biopsied blastocysts highlights the inherent imprecision of SET when conventional morphology is used alone. Embryos randomized to the aCGH group implanted with greater efficiency, resulted in clinical pregnancy more often, and yielded a lower miscarriage rate than those selected without aCGH. Additional studies are needed to verify our pilot data and confirm a role for on-site, rapid aCGH for IVF patients contemplating fresh SET.

Delay in oocyte aging in mice by the antioxidant N-acetyl-L-cysteine (NAC)

BACKGROUND

Ovarian aging is associated with declining numbers and quality of oocytes and follicles. Oxidative stress by reactive oxygen species (ROS) contributes to somatic aging in general, and also has been implicated in reproductive aging. Telomere shortening is also involved in aging, and telomeres are particularly susceptible to ROS-induced damage. Previously, we have shown that antioxidant N-acetyl-L-cysteine (NAC) effectively rescues oocytes and embryos from ROS-induced telomere shortening and apoptosis in vitro. Using mice as models, we tested the hypothesis that reducing oxidative stress by NAC might prevent or delay ovarian aging in vivo.

METHODS

Initially, young females were treated with NAC in drinking water for 2 months and the quality of fertilized oocytes and early embryo development were evaluated. Next, young mice 1-1½ months old were treated for 1 year with NAC added in drinking water, and their fertility was analyzed starting at 6 months, as indicated by litter size, oocyte number and quality. The ovaries were also examined for telomere activity and length and the expression of selected genes related to aging and DNA damage.

RESULTS

Short-term treatment of mice for 2 months with NAC demonstrated that NAC improved the quality of fertilized oocytes and early embryo development. Mice treated with a long-term low concentration (0.1 mM) of NAC had increased litter sizes at the ages of 7-10 months compared with age-matched controls without NAC treatment. NAC also increased the quality of the oocytes from these older mice. Moreover, the expression of sirtuins was increased, telomerase activity was higher and telomere length was longer in the ovaries of mice treated with NAC compared with those of the control group.

CONCLUSIONS

These data suggest that appropriate treatment with the antioxidant NAC postpones the process of oocyte aging in mice.

Intra-age, intercenter, and intercycle differences in chromosome abnormalities in oocytes

OBJECTIVE

To determine the extent of intra-age and intercycle variations in the frequency of first polar body aneuploidy in two consecutive cycles of oocyte retrieval undertaken by the same patient within 1 year.

DESIGN

Retrospective study.

SETTING

Fertility centers.

PATIENT(S)

Infertile couples undergoing IVF.

INTERVENTION(S)

Patients underwent two consecutive cycles of preimplantation genetic screening through first polar body biopsy within 1 year.

MAIN OUTCOME MEASURE(S)

Meiosis I aneuploidy.

RESULT(S)

A total of 226 patients underwent 452 cycles of preimplantation genetic screening. Differences within age groups were wide, with 0-100% of oocytes being chromosomally normal in all age groups. Euploidy rates between centers were significantly different (48% vs. 25%). Intercycle differences for the same patient were also wide (0-100%), but with 68.5% of patients having less than ±2 euploid eggs of difference between cycles.

CONCLUSION(S)

Although euploidy rate decreased on average with advancing maternal age, the high intra-age and intercenter variation in oocyte chromosome abnormalities emphasize the difficulty in estimating how many euploid oocytes a specific woman will have. This may have repercussions for fertility preservation where a defined number of eggs are currently frozen just based on maternal age.

Five chromosome segregation in polar bodies and the corresponding oocyte

For a comprehensive picture of the meiotic process and to follow up its products, five chromosomes were tested by fluorescent in-situ hybridization in both polar bodies (PB) and corresponding 145 oocytes. Results were obtained in 143 sets and the prediction of euploidy or aneuploidy based on PB analysis was confirmed by direct analysis in 140 oocytes (98%). Concordance for all chromosomes was found in 132 oocytes, while in the remaining eight, at least one chromosome did not reflect the prediction made by the corresponding PB. When restricting the analysis to the 132 fully concordant oocytes, 215 errors were found in PB: 58% in PB1 and 42% in PB2. Premature separation of chromatids occurred in 89% of aneuploid PB1, whereas only 11% of errors derived from bivalent non-disjunction. In 19% of meiosis-I errors, a complementary error in meiosis II compensated the error originated in the first meiotic division. In conclusion, the testing of PB predicted reliably the oocyte’s chromosome condition. Although limited to five chromosomes, the follow up of meiosis by fluorescent in-situ hybridization provided a full description of chromosome allocation during the two divisions characterizing the nuclear maturation of the oocyte.

Similar rates of chromosomal aberrant secondary oocytes in two indigenous cattle (Bos taurus) breeds as determined by dual-color FISH

In vitro-matured metaphase II (MII) oocytes with corresponding first polar bodies (I pb) from two indigenous cattle (Bos taurus) breeds have been investigated to provide specific data upon the incidence of aneuploidy. A total of 165 and 140 in vitro-matured MII oocytes of the Podolian (PO) and Maremmana (MA) breeds, respectively, were analyzed by fluorescence in situ hybridization using Xcen and five chromosome-specific painting probes. Oocytes with unreduced chromosome number were 13.3% and 6.4% in the two breeds, respectively, averaging 10.2%. In the PO, out of 100 MII oocytes + I pb analyzed, two oocytes were nullisomic for chromosome 5 (2.0%) and one disomic for the same chromosome (1.0%). In the MA, out of 100 MII oocytes + I pb, one oocyte was found nullisomic for chromosome 5 (1.0%) and one was disomic for the X chromosome (1.0%). Out of 200 MII oocytes + I pb, the mean rate of aneuploidy (nullisomy + disomy) for the two chromosomes scored was 2.5%, of which 1.5% was due to nullisomy and 1.0% due to disomy. By averaging these data with those previously reported on dairy cattle, the overall incidence of aneuploidy in cattle, as a species, was 2.25%, of which 1.25% was due to nullisomy and 1.0% due to disomy. The results so far achieved indicate similar rates of aneuploidy among the four cattle breeds investigated. Interspecific comparison between cattle (Xcen-5 probes) and pig (Sus scrofa domestica) (1-10 probes) also reveal similar rates. Further studies are needed that use more probes to investigate the interchromosomal effect. Establishing a baseline level of aneuploidy for each species/breed could also be useful for improving the in vitro production of embryos destined to the embryo transfer industry as well as for monitoring future trends of the reproductive health of domestic animals in relation to management errors and/or environmental hazards.

Beta- and gamma-cytoplasmic actins are required for meiosis in mouse oocytes

In mammals, female meiosis consists of two asymmetric cell divisions, which generate a large haploid oocyte and two small polar bodies. Asymmetric partitioning of the cytoplasm results from migration of the meiotic spindle toward the cortex and requires actin filaments. However, the subcellular localization and the role of the existing two cytoplasmic actin (CYA) isoforms, beta and gamma, have not been characterized. We show that beta- and gamma-CYA are differentially distributed in the maturing oocyte from late metaphase I as well as in preimplantation embryos. Gamma-CYA is preferentially enriched in oocyte cortices and is absent from all cell-cell contact areas from metaphase II until the blastocyst stage. Beta-CYA is enriched in contractile structures, at cytokinesis, at cell-cell contacts, and around the forming blastocoel. Alteration of beta- or gamma-CYA function by isoform-specific antibody microinjection suggests that gamma-CYA holds a major and specific role in the establishment and/or maintenance of asymmetry in meiosis I and in the maintenance of overall cortical integrity. In contrast, beta- and gamma-CYA, together, appear to participate in the formation and the cortical anchorage of the second meiotic spindle in waiting for fertilization. Finally, differences in gamma-CYA expression are amongst the earliest markers of cell fate determination in development.