Oocyte aneuploidy mechanisms are different in two situations of increased chromosomal risk: older patients and patients with recurrent implantation failure after in vitro fertilization

Determining diagnostic criteria and cause of recurrent implantation failure

PURPOSE OF REVIEW

Recurrent implantation failure (RIF) refers to the absence of implantation after repeated transfer of good embryos into a normal uterus. This review discusses the diagnostic criteria and cause of RIF.

RECENT FINDINGS

Regardless of the advancements in IVF practice, RIF is still a challenge that has to be solved. Exact definition of RIF is lacking today. For the initial evaluation, a rigorous algorithmic evaluation should be compromised with an individualized principle. Factors that might affect the number and quality of the oocyte and sperm cells should be investigated in order to obtain a good-quality embryo. Embryo assessment should be performed under ideal laboratory circumstances. The uterine environment should be carefully evaluated and the embryo should be transferred into the uterus at the most receptive time. Some of the newly introduced diseases and empirical treatment strategies, such as chronic endometritis, vaginal microbiota, immunologic profile and immunomodulator treatments, can be discussed with the couple under the light of adequate evidence-based information.

SUMMARY

New diagnostic and treatment modalities are needed to be introduced, which would be safe, efficient and efficacious after well-designed randomized controlled trials.

The Effects of Acupuncture on Pregnancy Outcomes of Recurrent Implantation Failure: A Systematic Review and Meta-Analysis

Objective

To systematically evaluate the efficacy and safety of acupuncture for patients with recurrent implantation failure (RIF) undergoing in vitro fertilization-embryo transfer (IVF-ET) and hopefully provide reliable guidance for clinicians and patients.

Methods

Through searching domestic and foreign medical journals, the literature of randomized controlled trials (RCTs) of acupuncture for RIF undergoing IVF-ET was collected. RevMan 5.3 software was used for meta-analysis and Cochrane's risk of bias assessment tool was used to evaluate the quality of the included studies.

Results

Seven documents meeting the criteria were finally included. The results showed that the intervention group contributes more in outcomes including clinical pregnancy rate (RR = 1.90, 95% CI (1.51, 2.40), P < 0.05), biochemical pregnancy rate (RR = 1.59, 95% CI (1.27, 1.99), P < 0.05), embryo implantation rate (RR = 1.89, 95% CI (1.47, 2.45), P < 0.05), and endometrial thickness (MD = 1.11, 95% CI (0.59, 1.63), P < 0.05) when compared with the control group, and the difference is statistically significant. In terms of the number of embryo transfers and the type of endometrium, the difference between the acupuncture group and the control group was not statistically significant.

Conclusion

Acupuncture therapy on patients with RIF can improve the pregnancy outcome of patients. It is a relatively effective treatment with satisfactory safety and suitable for clinical application. However, as the quality of the included studies is not good enough, the conclusion of this meta-analysis should be treated with caution. More double-blind RCTs equipped with high quality and large samples are expected for the improvement of the level of evidence.

Effects of endometrial preparations and transferred embryo types on pregnancy outcome from patients with advanced maternal age

We explored the strategy of frozen-thawed embryo transfer (FET) in the women with advanced maternal age (AMA). We first determined the age cut-off point of AMA by retrospective analysis of pregnancy outcomes in the patients undergoing FET. The patients with AMA were divided into 3 groups including natural cycle (NC) group, controlled ovarian stimulation (COS) group, and hormone replacement therapy (HRT) group, and simultaneously were divided into 2 groups including cleavage-stage embryo transfer (CET) group and blastocyst-stage embryo transfer (BET) group. The clinical pregnancy, embryo implantation, abortion and live birth rates were compared between the 3 groups and the 2 groups, respectively. We found that in the women aged 38 years or over, the clinical pregnancy rate and live birth rate were all significantly decreased as compared with the younger than 38-year-old women (all P < 0.05), so the women aged 38 years or over were regarded as the patients with AMA in this study. In the patients with AMA, the clinical pregnancy rate and live birth rate were 22.95% and 18.03% in NC group, 23.68% and 15.79% % in COS group as well as 24.58% and 15.92% in HRT group, and there were no significant differences in the clinical pregnancy rate and live birth rate between the 3 groups. However, the clinical pregnancy rate (42.96% vs 15.87%) and embryo implantation rate (32.26% vs 9.67%) were all significantly higher in the BET group than in the CET group (all P < 0.01). We conclude that in the women aged 38 years or over, the choice of endometrial preparation protocols may depend on the individual specific conditions because the endometrial preparation protocols do not affect FET outcome, but BET can obtain better FET outcomes as compared with CET. Abbreviations: AMA: advanced maternal age; FET: frozen-thawed embryo transfer; NC: natural cycle; COS: controlled ovarian stimulation; HRT: hormone replacement therapy; CET: cleavage-stage embryo transfer; BET: blastocyst-stage embryo transfer; LH: luteinizing hormone; HCG: human chorionic gonadotropin; HMG: human menopausal gonadotropin; FSH: follicle-stimulating hormone; BMI: body mass index.

Age-associated alterations in the micromechanical properties of chromosomes in the mammalian egg

PURPOSE

The incidence of aneuploidy in eggs from women of advanced reproductive age can exceed 60%, making the mammalian egg a unique model system to study the mechanisms of chromosome segregation errors.

METHODS

Here we applied a novel biophysical chromosome stretching approach to quantify mechanical stiffness of meiotic chromosomes in the mammalian egg and then documented how these properties changed in a mouse model of physiologic reproductive aging.

RESULTS

We found significant differences in chromosome micromechanics, and thus in higher order chromosome structure, coincident with advanced reproductive age, a time that is also unequivocally associated with an increase in egg aneuploidy.

CONCLUSIONS

These findings have important implications for both reproductive and cancer biology where aneuploidy plays a central role in aging related disease states.

Follicular fluid protein content (FSH, LH, PG4, E2 and AMH) and polar body aneuploidy

PURPOSE

Our objective was to identify a marker for oocyte aneuploidy in follicular fluid (FF) in women with an increased risk of oocyte aneuploidy after controlled ovarian hyperstimulation.

MATERIALS AND METHODS

Three groups of oocytes were constituted for polar body screening by FISH (chromosomes 13, 16, 18, 21 and 22): Group 1, advanced maternal age (n = 156); Group 2, implantation failure (i.e. no pregnancy after the transfer of more than 10 embryos; n = 101) and Group 3, implantation failure and advanced maternal age (n = 56). FSH and other proteins were assayed in the corresponding FF samples.

RESULTS

Of the 313 oocytes assessed, 35.78 % were abnormal. We found a significant difference between the follicular FSH levels in normal oocytes and abnormal oocytes (4.85 ± 1.75 IU/L vs. 5.41 ± 2.47 IU/L, respectively; p = 0.021). We found that the greater the number of chromosomal abnormalities per oocyte (between 0 and 3), the higher the follicular FSH level.

CONCLUSION

High FF FSH levels were associated with oocyte aneuploidy in women having undergone controlled ovarian hyperstimulation.

Meiotic origins of maternal age-related aneuploidy

Chromosome segregation errors in female meiosis lead to aneuploidy in the resulting egg and embryo, making them one of the leading genetic causes of spontaneous abortions and developmental disabilities in humans. It is known that aneuploidy of meiotic origin increases dramatically as women age, and current evidence suggests that most errors occur in meiosis I. Several hypotheses regarding the cause of maternal age-related aneuploidy have been proposed, including recombination errors in early meiosis, a defective spindle assembly checkpoint in meiosis I, and deterioration of sister chromatid cohesion with age. This review discusses findings in each area, and focuses especially on recent studies suggesting that deterioration of cohesion with increasing maternal age is a leading cause of age-related aneuploidy.

Preconceptional diagnosis for Robertsonian translocation as an alternative to preimplantation genetic diagnosis in two situations: a pilot study

INTRODUCTION

Preimplantation genetic diagnosis (PGD) is widely used for women heterozygous for a Robertsonian translocation. Preconceptional diagnosis (PCD), performed before fertilization, may be an alternative to PGD, especially in countries where PGD is restricted or prohibited, as in France. It could also give different information and clarify the influence of reproductive and obstetric history.

METHODS

In our study, translocation was diagnosed before ICSI in five cases (group A), and after newborn or fetal aneuploidy or miscarriage in two cases, (group B).

RESULTS

First polar body (PB1) analysis using acrocentric centromeric probes was done for 85 PB1s, and aneuploidy rate was at 42.4%. Oocyte aneuploidy rate differed (p<0.0001) between groups A and B (30% vs 84%). Despite the small group sizes, we demonstrate a correlation (p=0.0358) of aneuploidy rate in polar bodies after 2 or more attempts. Three live births were recorded, all in group A.

DISCUSSION

PCD could thus be an alternative to PGD. This pilot study also provides new prognostic information taking into account the women's natural history, but further confirmation is required.

Gamete cytogenetic study in couples with implantation failure: aneuploidy rate is increased in both couple members

PURPOSE

Implantation failure is known to be associated with an increased risk of aneuploidy in embryos, a situation leading to a pre-implantation genetic screening, not allowed in different countries like France. Our aim was to evaluate the gamete aneuploidy incidence in this context, using first polar body and spermatozoa aneuploidy screening.

METHODS

Three groups were considered: 11 couples with pregnancy obtained after IVF for female infertility (group 1); 20 couples with pregnancy obtained after IVF for male infertility (group 2); and 35 couples with implantation failure (group 3). In group 3, 28 couples treated by ICSI volunteered for first polar body analysis (PB1).

RESULTS

Spermatozoa aneuploidy rate was increased in groups 2 (1.6%) and 3 (2.1%) in comparison to group 1 (0.6%). PB1 aneuploidy rate was 35.4% in group 3. Finally, eight couples (32%) had no particular chromosomal risk in gametes, 15/25 (60%) presented an increased spermatic (>2%) or oocyte (>1/3) aneuploidy rate, and 2/25 (8%) had both.

CONCLUSION

Those results confirm that implantation failure has a heterogeneous origin, that gamete chromosome abnormality rate is one of the major contributing factors, and that 1st Polar body and spermatozoa aneuploidy screening or pre-implantation genetics screening may be indicated for these couples.

Meiosis in oocytes: predisposition to aneuploidy and its increased incidence with age

Mammalian oocytes begin meiosis in the fetal ovary, but only complete it when fertilized in the adult reproductive tract. This review examines the cell biology of this protracted process: from entry of primordial germ cells into meiosis to conception. The defining feature of meiosis is two consecutive cell divisions (meiosis I and II) and two cell cycle arrests: at the germinal vesicle (GV), dictyate stage of prophase I and at metaphase II. These arrests are spanned by three key events, the focus of this review: (i) passage from mitosis to GV arrest during fetal life, regulated by retinoic acid; (ii) passage through meiosis I and (iii) completion of meiosis II following fertilization, both meiotic divisions being regulated by cyclin-dependent kinase (CDK1) activity. Meiosis I in human oocytes is associated with an age-related high rate of chromosomal mis-segregation, such as trisomy 21 (Down's syndrome), resulting in aneuploid conceptuses. Although aneuploidy is likely to be multifactorial, oocytes from older women may be predisposed to be becoming aneuploid as a consequence of an age-long decline in the cohesive ties holding chromosomes together. Such loss goes undetected by the oocyte during meiosis I either because its ability to respond and block division also deteriorates with age, or as a consequence of being inherently unable to respond to the types of segregation defects induced by cohesion loss.