Increased serine synthesis in cumulus cells of young infertile women with diminished ovarian reserve

STUDY QUESTION

What are the differences in gene expression of cumulus cells (CCs) between young women with diminished ovarian reserve (DOR) and those of similar age with normal ovarian reserve (NOR)?

SUMMARY ANSWER

Gene expression and metabolome profiling analysis demonstrate that the de novo serine synthesis pathway (SSP) is increased in the CCs of young women with DOR.

WHAT IS KNOWN ALREADY

The incidence of DOR has risen, tending to present at younger ages. Its mechanisms and aetiologies are still poorly understood. Abnormal metabolism is present in luteinized CCs of patients with DOR. Previous studies have revealed that mitochondrial dysfunction and impaired oxidative phosphorylation in CCs are related to DOR in women of advanced age. The pathogenic mechanisms likely differ between young women with DOR and cases associated with advanced maternal age. Several studies have examined amino acid metabolism in the follicle, with a focus on embryo development, but less information is available about CCs. The physiological significance of de novo serine synthesis in follicles and oocytes remains largely unknown.

STUDY DESIGN, SIZE, DURATION

CC samples were obtained from 107 young infertile women (age <38 years) undergoing ICSI, from July 2017 to June 2019, including 54 patients with DOR and 53 patients with NOR.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Oocyte development data were analysed retrospectively. Comprehensive genome-wide transcriptomics of CCs was performed. Differentially expressed genes (DEGs) were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to categorize the functions of the DEGs and identify significantly enriched pathways. The transcript and protein levels of key enzymes involved in serine synthesis were verified in additional samples using quantitative real-time PCR (qRT-PCR) (n = 10) and capillary western blotting (n = 36). Targeted metabolomics of amino acids in CC extracts was performed by ultrahigh-performance liquid MS (UHPLC-MS/MS).

MAIN RESULTS AND THE ROLE OF CHANCE

The number of oocytes (2.4 ± 2.2 versus 12.1 ± 5.3) and metaphase II oocytes (2.1 ± 2.0 versus 9.9 ± 4.9) retrieved was significantly decreased in the DOR versus the NOR group, respectively (P < 0.0001). The rates of fertilization (80.7% versus 78.8%), viable embryos (73.7% versus 72.5%), and high-quality embryos (42.8% versus 49.0%) did not differ between the DOR and NOR groups, respectively (P > 0.05). A total of 95 DEGs were found by transcriptome sequencing. GO and KEGG analyses demonstrated that the DEGs were linked to amino acid metabolism and suggested significantly higher activity of the de novo SSP in the CCs of young women with DOR. Further qRT-PCR and capillary western blotting revealed that key enzymes (PHGDH, PSAT1, PSPH, and SHMT2) involved in de novo serine synthesis were upregulated, and UHPLC-MS/MS analysis showed increases in serine and glycine (a downstream product of serine) levels in the CCs of young patients with DOR. Our data clearly demonstrate that the de novo SSP, which diverts 3-phosphoglycerate from glycolysis to serine synthesis, was upregulated in young DOR CCs.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Regarding the reproductive capacity of young patients DOR, the pregnancy outcomes were not analysed. The sample size was limited, and only women undergoing ICSI were examined since this was a prerequisite for the acquisition of CCs, which may cause selection bias. The exact mechanisms by which the SSP in CCs regulates ovarian reserve still require further study.

WIDER IMPLICATIONS OF THE FINDINGS

Our research presents new evidence that alterations of the SSP in CCs of young infertile women are associated with DOR. We believe this is a significant contribution to the field, which should be key for understanding the cause and mechanisms of ovarian hypofunction in young women.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the Ministry of Science and Technology of China (2018YFC1005001) and National Natural Science Foundation of China (31601197). There were no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Antimüllerian hormone is not associated with embryo ploidy in patients with and without infertility undergoing in vitro fertilization with preimplantation genetic testing

OBJECTIVE

To assess the association between antimüllerian hormone (AMH) and embryo ploidy rates in 2 cohorts of patients undergoing in vitro fertilization (IVF) with trophectoderm biopsy for preimplantation genetic testing for aneuploidy (PGT-A): the general population of women pursuing IVF with PGT-A (Infertile cohort) and women pursuing IVF with preimplantation genetic testing for monogenic disorders (PGT-M) owing to the risk of hereditary monogenic diseases (Non-infertile cohort).

DESIGN

Retrospective cohort study.

SETTING

Academic center.

PATIENT(S)

Patients undergoing their first cycle of IVF with trophectoderm biopsy and PGT-A or PGT-A and PGT-M in our center between March 2012 and June 2020. Patients of advanced maternal age according to the Bologna criteria (age ≥40 years) and patients who underwent fresh embryo transfers were excluded.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Proportion of euploid, mosaic, and aneuploid embryos per cycle.

RESULT(S)

"Infertile" (n = 926) and "Non-infertile" (n = 214) patients were stratified on the basis of AMH levels, with low-AMH defined as <1.1 ng/mL in accordance with the Bologna criteria. Age-adjusted regression models showed no relationship between AMH classification and proportion of euploid, mosaic, and aneuploid embryos in the Infertile or Non-infertile cohorts. In the Infertile cohort, no association between AMH classification and embryo ploidy rates was identified in a subgroup analysis of patients aged <35 years, 35-37 years, and 38-39 years. These findings persisted in a sensitivity analysis of infertile patients stratified into AMH (ng/mL) quartile categories.

CONCLUSION(S)

No association was found between AMH and the proportion of euploid, mosaic, or aneuploid embryos in 2 large cohorts of patients undergoing IVF with PGT-A (Infertile patients) or PGT-A and PGT-M (Non-infertile patients), suggesting that a quantitative depletion of ovarian reserve does not predict the ploidy status of the embryo cohort.

Presence of Endometrioma Does Not Impair Embryo Quality and Assisted Reproductive Technology (ART) Cycle Outcome in Diminished Ovarian Reserve (DOR) Patients

This study aims to assess the impact of endometrioma on embryo quality and cycle outcome in patients who undergo assisted reproductive technology (ART) treatment due to diminished ovarian reserve (DOR). Retrospective case-control study was conducted in women ≤ 40 years of age who underwent ART treatment caused by DOR, defined according to POSEIDON criteria, at a university-based infertility clinic between January 2015 and December 2020. Three groups of patients were selected: group A included patients with an idiopathic DOR, group B included patients with endometrioma(s) who underwent ovarian cystectomy, and group C included patients with endometrioma(s) without surgical treatment. A total of 351 women with DOR were included in the final analysis. Demographic characteristics, including age and AMH, were similar between the groups. Significant differences were observed among groups on mean number of MII oocytes retrieved (1.88 ± 1.59 vs. 2.84 ± 2.89 vs. 2.78 ± 2.41, respectively; p < 0.001) and mean number of embryos (1.04 ± 1.18 vs. 1.87 ± 2.01 vs. 1.66 ± 1.81, respectively; p < 0.001). However, the mean number of top-quality embryos, cycle cancellation, and live birth rates were similar between the groups. Clinical pregnancy (35 (26.5%) vs. 8 (18.2%) vs. 18 (42.9%), respectively; p = 0.038) and miscarriage rates (12 (9.1%) vs. 0 vs. 8 (19.0%), respectively; p = 0.009) were higher in endometrioma group without surgery. Women with DOR appear to have similar ART cycle outcomes regardless of the etiology, in terms of live birth rates. Infertility of endometrioma patients might be related to altered endometrium rather than to decreased oocyte quality. Cystectomy for endometrioma before IVF did not seem to affect the LBR.

Single-cell RNA-seq analysis and cell-cluster deconvolution of the human preovulatory follicular fluid cells provide insights into the pathophysiology of ovarian hyporesponse

Reduction in responsiveness to gonadotropins or hyporesponsiveness may lead to the failure of in vitro fertilization (IVF), due to a low number of retrieved oocytes. The ovarian sensitivity index (OSI) is used to reflect the ovarian responsiveness to gonadotropin stimulation before IVF. Although introduced to clinical practice already years ago, its usefulness to predict clinical outcomes requires further research. Nevertheless, pathophysiological mechanisms of ovarian hyporesponse, along with advanced maternal age and in younger women, have not been fully elucidated. Follicles consist of multiple cell types responsible for a repertoire of biological processes including responding to pituitary gonadotropins necessary for follicle growth and oocyte maturation as well as ovulation. Encouraging evidence suggests that hyporesponse could be influenced by many contributing factors, therefore, investigating the variability of ovarian follicular cell types and their gene expression in hyporesponders is highly informative for increasing their prognosis for IVF live birth. Due to advancements in single-cell analysis technologies, the role of somatic cell populations in the development of infertility of ovarian etiology can be clarified. Here, somatic cells were collected from the fluid of preovulatory ovarian follicles of patients undergoing IVF, and RNA-seq was performed to study the associations between OSI and gene expression. We identified 12 molecular pathways differentially regulated between hypo- and normoresponder patient groups (FDR<0.05) from which extracellular matrix organization, post-translational protein phosphorylation, and regulation of Insulin-like Growth Factor (IGF) transport and uptake by IGF Binding Proteins were regulated age-independently. We then generated single-cell RNA-seq data from matching follicles revealing 14 distinct cell clusters. Using cell cluster-specific deconvolution from the bulk RNA-seq data of 18 IVF patients we integrated the datasets as a novel approach and discovered that the abundance of three cell clusters significantly varied between hypo- and normoresponder groups suggesting their role in contributing to the deviations from normal ovarian response to gonadotropin stimulation. Our work uncovers new information regarding the differences in the follicular gene expression between hypo- and normoresponders. In addition, the current study fills the gap in understanding the inter-patient variability of cell types in human preovulatory follicles, as revealed by single-cell analysis of follicular fluid cells.

Prdm9 deficiency of rat oocytes causes synapsis among non-homologous chromosomes and aneuploidy

Aneuploidy (abnormal chromosome number) accompanies reduced ovarian function in humans and mice, but the reasons behind this concomitance remain underexplored. Some variants in the human gene encoding histone-3-lysine-4,36-trimethyltransferase PRDM9 are associated with aneuploidy, and other variants with ovarian function reduced by premature ovarian failure (POF), but no link between POF and aneuploidy has been revealed. SHR/OlaIpcv rat females lacking PRDM9 manifest POF-a reduced follicle number, litter size, and reproductive age. Here, we explored this model to test how POF relates to oocyte euploidy. The mutant rat females displayed increased oocyte aneuploidy and embryonic death of their offspring compared to controls. Because rat PRDM9 positions meiotic DNA breaks, we investigated the repair of these breaks. Fertile control rodents carry pachytene oocytes with synapsed homologous chromosomes and repaired breaks, while sterile Prdm9-deficient mice carry pachytene-like oocytes with many persisting breaks and asynapsed chromosomes. However, most PRDM9-lacking rat oocytes displayed a few persisting breaks and non-homologous synapsis (NHS). HORMAD2 protein serves as a barrier to sister-chromatid repair and a signal for the synapsis and DNA repair checkpoints. NHS but not asynapsis was associated with HORMAD2 levels similar to the levels on rat pachytene chromosomes with homologous synapsis. NHS was accompanied by crossing-over decreased below the minimum that is essential for euploidy. We argue that the increased mutant rat aneuploidy is due to NHS, which allows some oocytes to pass meiotic checkpoints without one crossing-over per chromosomal pair, leading to segregation errors, and thereby NHS links POF to aneuploidy.

Prospects of Germline Nuclear Transfer in Women With Diminished Ovarian Reserve

Diminished ovarian reserve (DOR) is associated with a reduced quantity and quality of the retrieved oocytes, usually leading to poor reproductive outcomes which remain a great challenge for assisted reproduction technology (ART). Women with DOR often have to seek for oocyte donation, precluding genetically related offspring. Germline nuclear transfer (NT) is a novel technology in ART that involves the transfer of the nuclear genome from an affected oocyte/zygote of the patient to the cytoplast of an enucleated donor oocyte/zygote. Therefore, it offers opportunities for the generation of genetically related embryos. Currently, although NT is clinically applied only in women with serious mitochondrial DNA disorders, this technology has also been proposed to overcome certain forms of female infertility, such as advanced maternal age and embryo developmental arrest. In this review, we are proposing the NT technology as a future treatment option for DOR patients. Strikingly, the application of different NT strategies will result in an increase of the total number of available reconstituted embryos for DOR patients.

Diminished ovarian reserve is associated with reduced euploid rates via preimplantation genetic testing for aneuploidy independently from age: evidence for concomitant reduction in oocyte quality with quantity

OBJECTIVE(S)

To determine whether women with diminished ovarian reserve (DOR) (quantitatively) had lower rates of euploid blastocysts, as a proxy for oocyte quality.

DESIGN

Retrospective cohort study.

SETTING

University reproductive health clinic.

PATIENT(S)

A total of 1,152 women aged 19-42 years underwent 1,675 IVF cycles yielding 8,073 blastocysts for biopsy from 2010 to 2019.

INTERVENTIONS(S)

Preimplantation genetic testing for aneuploidy.

MAIN OUTCOME MEASURE(S)

Euploid rates, defined as the number of euploid blastocysts divided by the number of biopsied blastocysts per cycle.

RESULT(S)

A total of 225 women (20%) had DOR as infertility diagnosis per the Bologna criteria. Age was higher among the women with DOR (39.5 y vs. 37.0 y). Euploid rates were lower among women with vs. without DOR (29.0% vs. 44.9%). In generalized linear models controlling for age, women with DOR had 24% reduced odds of a biopsied blastocyst being euploid versus women without DOR. In a secondary analysis assigning DOR status to women producing the lowest quartile of age-adjusted mature oocyte yield, this relationship remained. No differences were identified in live birth rates between women with and without DOR after euploid single-embryo transfer independently from age (n = 944 transfers; 56.8% vs. 54.8%, respectively).

CONCLUSION(S)

Blastocysts from women with DOR are less likely to be euploid than those from women without DOR after adjustment for age. Given the concomitant reduction in euploid rates with quantity of oocytes observed in this study, quantitative ovarian reserve assessments (i.e., follicular machinery) may yield insight into relative ovarian aging.

Ovarian Sparing Surgery in Mature Ovarian Teratomas in Children: A 20-Year Single-Center Experience

INTRODUCTION

 Despite its benign nature, possible bilateral presentation, and a very good prognosis, ovarian sparing tumorectomy (OST) in mature ovarian teratoma (MOT) is not commonly performed. Unilateral oophorectomy has physiological consequences, while bilateral is devastating. The aim of this study is promotion of OST in MOT among children.

MATERIALS AND METHODS

 We reviewed 120 patients operated for MOT between August 1999 and 2019.

RESULTS

 Ovariectomy was performed in 15 patients (14 between 1999 and 2009 and 1 after 2010). In 105 girls, OST was possible including 32 with ovarian torsion. The approach was laparoscopy in 30 girls (11 conversions) and laparotomy in 94. Intra-abdominal spillage occurred in 30% of laparoscopic dissections. Postoperative morbidity was not associated with surgical approach (p = 0.613) or presence of adnexal torsion (p = 0,608). Follow-up was from 4 months to 9 years (median = 4 years) with access to 90% of patients. Bilateral lesions were observed in six (synchronous in five and metachronous in one) patients. Recurrence appeared in three patients operated via laparotomy and OST (after 12, 46, and 74 months). In one girl, asynchronous contralateral MOT was found 5 years after unilateral oophorectomy. Ovarian regeneration after torsion was observed in sonography in 84.4% of the patients. None of the patients experienced chemical peritonitis or malignant tumor transformation.

CONCLUSION

 OST is safe and effective and should be the first-line procedure in children. Laparoscopy and laparotomy constitute a complementary approach to MOT. Ultrasound follow-up is necessary to monitor recurrence, contralateral disease, and ovarian regeneration.

GnRH Antagonist Protocol With Cessation of Cetrorelix on Trigger Day Improves Embryological Outcomes for Patients With Sufficient Ovarian Reserve

OBJECTIVE

To evaluate the efficiency and validity of cessation of cetrorelix on trigger day during gonadotropin releasing hormone antagonist (GnRH-ant)-controlled ovarian stimulation of in vitro fertilization (IVF) cycles.

METHODS

In this retrospective study, a total of 1271 patients undergoing initial IVF cycles following the GnRH-ant protocol were enrolled; 832 patients received cetrorelix on trigger day (Group A) and 439 patients ceased cetrorelix on trigger day (Group B). We compared demographic characteristics, embryological and clinical outcomes between the two groups. A Poisson regression model was used to identify factors that significantly affected embryological outcomes. Patients were further divided into subgroups according to anti-Mullerian hormone (AMH) and age, to assess associations between ceasing cetrorelix on trigger day and embryological outcomes.

RESULTS

There was a significant improvement on embryological outcomes in patients who ceased cetrorelix on trigger day, and there were no significant differences in clinical outcomes or preovulation rates between the two groups. Furthermore, for patients with 1.1 ≤ AMH ≤ 4.7 ng/ml, all embryological outcomes were significantly higher in Group B compared with Group A. For patients with AMH > 4.7 ng/ml, the number of oocytes retrieved, fertilization rate (2PN) of IVF cycles and proportion of day 3 good quality embryos were all significantly higher in Group B. For patients with age < 35 years, all the embryological outcomes, besides the number of available embryos, were significantly higher in Group B than in Group A. There were no differences in embryological outcomes between the two groups when patients were stratified based on age > 35 years or AMH < 1.1 ng/ml.

CONCLUSION

GnRH-ant protocol with cessation of cetrorelix on trigger day improved embryological outcomes for young patients or patients with sufficient ovarian reserve, and was effective at preventing preovulation.

Conversion of in vitro fertilization cycles to intrauterine inseminations in patients with a poor ovarian response: Risk of multiple pregnancies

PURPOSE

To determine the risk of multiple pregnancies (MP) following conversion of in vitro fertilization (IVF) cycles to intrauterine insemination (IUI) when a poor ovarian response (POR) is diagnosed during controlled ovarian stimulation (COS).

METHODS

We undertook a retrospective study in our teaching hospital from January 2012 to December 2017. We included all IVF cycles with POR that were converted to IUI (<5 follicles ≥ 14 mm and peak estradiol level < 1000 pg/mL on trigger day).

RESULTS

Overall, 205 IVF cycles that were converted to IUI in 128 patients were analyzed. Mean age was 34.1 ± 4.6 years, mean antral follicle count was 11 ± 5.3 and mean AMH was 1.8 ± 2.9 ng/L. The main causes of infertility were unexplained (41 %) (84/205) and diminished ovarian reserve (35 %) (72/205). Of all the cycles converted to IUI, 53 (26 %) had one mature follicle on trigger day, 56 (27 %) had 2, 56 (27 %) had 3, and 40 (20 %) had 4. The live birth rate (LBR) was 7.3 % (15/205), and the miscarriage rate was 28.6 % (6/21). There were 3 twin pregnancies, but no higher order pregnancies; the MP rate was 14.3 % (3/21). There was no significant difference in the MP rate between patients with 1-2 mature follicles and patients with 3-4 mature follicles (18.2 % vs 10 %, p = 0.99, respectively).

CONCLUSION

In IVF cycles converted to IUI for poor response, the risk of MP is acceptable (14 %) with no higher order pregnancies, even with 3 or 4 follicles ≥14 mm on trigger day.

Diminished ovarian reserve and poor response to stimulation in patients <38 years old: a quantitative but not qualitative reduction in performance

STUDY QUESTION

Do infertile women aged <38 years with quantitative evidence of diminished ovarian reserve and/or poor response to stimulation also exhibit poor oocyte quality as measured by blastulation rates, aneuploidy rates, and live birth rates?

SUMMARY ANSWER

Young women with evidence of accelerated follicular depletion, either by precycle ovarian reserve testing or postcycle evidence of low oocyte yield, exhibit equivalent blastulation rates, aneuploidy rates and live birth rates per euploid embryo transfer as age-matched controls with normal precycle and postcycle parameters.

WHAT IS KNOWN ALREADY

Previous studies are conflicted as to whether women with evidence of diminished ovarian reserve and/or poor ovarian response are also at increased risk of exhibiting evidence of poor oocyte quality. Most prior studies have failed to adequately control for the confounding effect of female age on typical markers of oocyte quality in poor responders. The rate of follicular depletion occurs at around 38 years on average; thus, evidence of quantitative depletion before this would indicate a premature diminution of ovarian reserve and allow evaluation of whether markers of oocyte quality are tied to quantitative markers.

STUDY DESIGN, SIZE, DURATION

This was a retrospective cohort study at a single center between 2012 and 2016. This time frame was specifically chosen as all embryos were cultured to the blastocyst stage at this center during the study period (no cleavage stage transfers were performed). Two comparisons were made: precycle assessment of ovarian reserve (based on anti-mullerian hormone (AMH) level) and postcycle oocyte yield results. For each comparison, patients in <10th percentile were compared to patients in the interquartile range (IQR) with respect to blastulation rate, aneuploidy rate and live birth rate. A mixed effects model was created to control for female age (in the <38 year old range) and correlation among oocytes from a given cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS

For the precycle blastulation analysis, only patients with AMH data available were included (345 patients with AMH in the <10th percentile versus 1758 patients with AMH in the 25th to 75th percentile (IQR)). To compare aneuploidy rates, the subset of these patients who pursued preimplantation genetic testing for aneuploidy (PGT-A) was then analyzed (124 patients in the <10th percentile versus 782 patients in the IQR). For the postcycle blastulation analysis, all patients who proceeded to retrieval (whether or not they also had AMH data available) were included (535 patients with oocyte yield in the <10th percentile versus 2675 patients in the IQR). To compare aneuploidy rates, the subset of these patients who pursued PGT-A was then analyzed (156 patients in the <10th percentile versus 1100 patients in the IQR).

MAIN RESULTS AND THE ROLE OF CHANCE

The adjusted odds of a given fertilized oocyte developing to a blastocyst, being aneuploid or leading to a live birth after euploid transfer were no different if the oocyte was retrieved from a cycle with ovarian reserve parameters or oocyte yield in the <10th percentile compared to an oocyte retrieved in a cycle with those parameters in the 25-75th percentile. An AMH level in the <10th percentile did more commonly result in cycle cancellation prior to retrieval and after retrieval prior to transfer due to global arrest of embryos.

LIMITATIONS, REASONS FOR CAUTION

The timing of retrieval in patients with fewer oocytes may be more optimal given the greater ability to discern the overall maturity of the cohort, thus enhancing performance per retrieved oocyte. Analyses included only first cycles. Subsequent adjustment of protocol due to prior performance may mean that some patients in the <10th percentile for oocyte yield are actually better prognosis patients than their first cycle indicates. Data on whether or not patients were on oral contraceptives at time that AMH level drawn was not available. Other unknown biases are also likely to be present given retrospective nature of the study.

WIDER IMPLICATIONS OF THE FINDINGS

While young women with evidence of quantitative depletion of ovarian reserve have lower live birth rates per stimulation cycle, this not attributable to poor oocyte quality because the blastulation rate per fertilized oocyte and live birth rate per embryo transfer are equivalent to that in women with normal quantitative markers of ovarian reserve. Thus, the pathophysiology mediating a premature quantitative decline in ovarian reserve appears different than that which mediates markers of oocyte quality, such as aneuploidy. Young poor responders may use this information to help guide embryo accumulation strategies when considering their family building plans.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

Correlation between aneuploidy pregnancy and the concentration of various hormones and vascular endothelial factor in follicular fluid as well as the number of acquired oocytes

Objective To investigate the correlation between aneuploidy pregnancy and the concentration of various hormones and vascular endothelial factor in follicular fluid as well as the number of acquired oocytes and to provide a scientific basis for improving ovulation induction programs. Methods In total, we collected 277 follicular fluid specimens from patients undergoing in vitro fertilization (IVF) treatment in our hospital. Eighteen cases of aneuploidy embryos were identified. The follicular fluid of these aneuploidy embryos was used for the study. According to the case and control 1:5 paired design, we selected five age-matched controls with healthy births following IVF for each aneuploidy case. Concentrations of anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estrogen (E2) and vascular endothelial growth factor (VEGF) in the follicular fluid were measured. Conditional logistic regression was used to analyze the relationship between aneuploidy pregnancy and the concentrations of various hormones and VEGF in the follicular fluid as well as the number of acquired oocytes. Results Multivariate conditional logistic regression showed that of all the factors analyzed, only FSH [odds ratio (OR) = 1.300, 95% confidence interval (CI), 1.091-1.548, P = 0.003] level in the follicular fluid and the number of acquired oocytes (OR = 1.179, 95% CI, 1.070-1.299, P = 0.001) were closely related to aneuploidy pregnancy. No other factors were found to be associated with aneuploidy pregnancy. Conclusion FSH concentrations in the follicular fluid are risk factors for aneuploidy pregnancies. The higher the number of eggs, the higher the risk of aneuploidy. These findings may help improve ovulation induction programs.

Low oocyte yield during IVF treatment and the risk of a trisomic pregnancy

A low number of antral follicles may result in the selection of suboptimal oocytes that are prone to meiotic errors. The aim of this case-control study was to evaluate women receiving IVF treatment with low oocyte yield (defined as three or fewer oocytes retrieved after ovarian stimulation) who are at an increased risk of a trisomic pregnancy. Data were obtained from Danish and Dutch medical registries between 1983 and 2011. Analyses were carried out in 105 cases and 442 controls matched by age and year of IVF treatment. Cases were women with a trisomic pregnancy (trisomies 13, 18 or 21) resulting from fresh IVF treatment and confirmed by karyotyping. Cases were included regardless of pregnancy outcome. Controls were women with a live born child without a trisomy, resulting from fresh IVF treatment. Low oocyte yield was observed in 6.6% (29/440) of the women, of which 8.4% (7/83) were cases and 6.2% (22/357) controls. Low oocyte yield in IVF treatment was not associated with a higher risk of trisomic pregnancy (OR 1.43, 95% CI 0.64 to 3.19). Stratification for female age, adjustment for history of ovarian surgery, and gonadotrophin-releasing hormone protocol used did not change the results.

Increased incidence of ectopic pregnancy after in vitro fertilization in women with decreased ovarian reserve

The incidence of ectopic pregnancy after assisted reproductive technology is increased approximately 2.5-5-fold compared with natural conceptions.Strategies were used to decrease the incidence of ectopic pregnancy, but ectopic pregnancy still occurs. In the present study, women were selected with decreased ovarian reserve (defined as FSH > 10 IU/L) aged 20 to 38 years who underwent IVF-ET between 2009 and 2014. These 2,061 women were age-matched with an equal number of women with normal ovarian reserve (defined as FSH ≤ 10 IU/L). During cycles following fresh embryo transfer, 93 patients were diagnosed with ectopic pregnancy. The incidence of ectopic pregnancy in clinical pregnancies was significantly higher in the decreased ovarian reserve than in the normal ovarian reserve group (5.51% vs. 2.99%). After adjusting for confounding factors, the incidence of ectopic pregnancy was significantly associated with decreased ovarian reserve. Our results showed that decreased ovarian reserve is an independent risk factor for ectopic pregnancy after in vitro fertilization-embryo transfer.

A putative role for anti-Müllerian hormone (AMH) in optimising ovarian reserve expenditure

The mammalian ovary has a finite supply of oocytes, which are contained within primordial follicles where they are arrested in a dormant state. The number of primordial follicles in the ovary at puberty is highly variable between females of the same species. Females that enter puberty with a small ovarian reserve are at risk of a shorter reproductive lifespan, as their ovarian reserve is expected to be depleted faster. One of the roles of anti-Müllerian hormone (AMH) is to inhibit primordial follicle activation, which slows the rate at which the ovarian reserve is depleted. A simple interpretation is that the function of AMH is to conserve ovarian reserve. However, the females with the lowest ovarian reserve and the greatest risk of early reserve depletion have the lowest levels of AMH. In contrast, AMH apparently strongly inhibits primordial follicle activation in females with ample ovarian reserve, for reasons that remain unexplained. The rate of primordial follicle activation determines the size of the developing follicle pool, which in turn, determines how many oocytes are available to be selected for ovulation. This review discusses the evidence that AMH regulates the size of the developing follicle pool by altering the rate of primordial follicle activation in a context-dependent manner. The expression patterns of AMH across life are also consistent with changing requirements for primordial follicle activation in the ageing ovary. A potential role of AMH in the fertility of ageing females is proposed herein.

Morphokinetic Characteristics and Developmental Potential of In Vitro Cultured Embryos from Natural Cycles in Patients with Poor Ovarian Response

Background. Patients with poor ovarian response to ovarian hyperstimulation represent an interesting group for studying the impact of embryo cleavage irregularities on clinical outcome since all embryos, regardless of their quality, are usually transferred to the uterus. The aim of our study was to follow the morphokinetics of fertilized oocytes from natural cycles in poor responders. Methods. Zygotes from 53 cycles were cultured in vitro for 3 days. The morphokinetics of their development and transfer outcomes were retrospectively analyzed for the normally and irregularly cleaved embryos. Results. Of all embryos, 30.2% had single and 20.8% multiple cleavage irregularities with the following prevalence: developmental arrest 30.2%, direct cleavage to more than two cells 24.5%, chaotic cleavage 13.2%, and reverse cleavage 11.3%. These embryos had longer pronuclear phases, first cytokinesis, second embryo cell cycles, and less synchronized divisions. The transfer of normally developing embryos resulted in an implantation rate of 30.8% and a delivery rate of 23.1%, but irregularly cleaved embryos did not implant. Conclusions. The use of time-lapse microscopy in poor responder patients identified embryos with cleavage abnormalities that are related with no or extremely low implantation potential. Gained information about embryo quality is important for counselling patients about their expectations.

Maternal antimullerian hormone as a predictor of fetal aneuploidy occurring in an early pregnancy loss

Objective

The purpose of the study was to examine the relationship between the parameter representing ovarian reserve and the fetal aneuploidy in early spontaneous miscarriage.

Methods

A multicenter retrospective cohort study was performed in patients who were diagnosed with early pregnancy loss (≤13 gestational weeks) and examined for fetal karyotype at the CHA Gangnam Medical Center, CHA Bundang Medical Center, and CHA Gumi Medical Center between January 2011 and December 2012. Karyotyping was performed by the Genetic Laboratory of the Fertility Center of CHA Gangnam Medical Center. Medical records were reviewed for demographics, karyotype analysis and hormonal assay of ovarian reserve including antimullerian hormone (AMH) and follicle stimulating hormone. Statistical analysis was performed using SPSS software.

Results

A total 462 patients were included in this study. The mean age of the patients was 35.31±4.12 years and the mean AMH level was 3.88±3.50 ng/mL (n=195). Two hundred eleven conceptuses (45.7%) of patients showed the euploid and 251 (54.3%) showed the aneuploid. There are significant differences in maternal age, AMH and gestational age between fetal euploid and aneuploid groups (34.46±4.35 vs. 36.04±3.78 years, P<0.001; 4.60±3.86 vs. 3.43±3.18 ng/mL, P=0.022; 7.67±1.54 vs. 8.27±1.46 weeks, P<0.001, respectively). Multivariate analysis revealed that low AMH level and early gestational age were maternal age-independent markers for fetal aneuploid (P<0.001 and P=0.045, respectively).

Conclusion

Low maternal AMH level might be a predicting marker for fetal aneuploid in early pregnancy loss.

Follicle pool, ovarian surgery and the risk for a subsequent trisomic pregnancy

STUDY QUESTION

Is there an association between trisomic pregnancy, a marker for decreased oocyte quality, and the reduced oocyte quantity that follows ovarian surgery?

SUMMARY ANSWER

Previous ovarian surgery is not associated with an increased risk for a subsequent trisomic pregnancy.

WHAT IS KNOWN ALREADY

Ovarian surgery diminishes the number of oocytes. The risk for a trisomic pregnancy is suggested to be higher in women with fewer oocytes, independent of their chronological age.

STUDY DESIGN, SIZE, DURATION

This is a matched case-control study. Cases are women with a confirmed trisomic pregnancy occurring between 1 January 2000 and 31 December 2010 regardless of pregnancy outcome and controls are women that had a live born child without a trisomy. In total, there were 8573 participants in the study; 1723 cases and 6850 controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were obtained from Danish medical registries. Matching criteria were maternal age and year of conception. Number of controls matched per case ranged from one to four. Among cases and controls with a trisomic pregnancy, 2.7% (46/1723) versus 2.5% (172/6850) had undergone ovarian surgery before pregnancy.

MAIN RESULTS AND ROLE OF CHANCE

History of ovarian surgery is not associated with a higher risk for a subsequent trisomic pregnancy (odds ratio = 1.00, 95% confidence interval 0.99-1.01). Subgroup analyses by indication of surgery and interval between ovarian surgery and pregnancy do not show an effect on trisomic pregnancy risk.

LIMITATIONS, REASONS FOR CAUTION

The medical registries used to select cases and controls did not contain information on surgical technique nor volume of ovarian tissue resected, previous trisomic pregnancy prior to the ovarian surgery or long-term use of oral contraceptives. Therefore, correction for these factors was not performed.

WIDER IMPLICATIONS OF THE FINDINGS

We did not confirm the hypothesis that ovarian surgery, a marker for decreased oocyte quantity, is related to trisomic pregnancy, a marker for decreased oocyte quality. This suggests that ovarian surgery, which has a direct reductive effect on the size of the follicle pool, may affect oocyte quality differently when compared with the reduction in follicle pool size due to ageing.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by grants from the Gratama Stichting, University of Groningen and the University Medical Center Groningen, The Netherlands. Ø.L. has within the last 3 years received honoraria for speeches in pharmacoepidemiological issues, not related to this study. The Department of Obstetrics and Gynaecology receives unrestricted educational grants from Ferring Pharmaceuticals. A.H. received a grant from ZonMW (i.e. National Dutch Scientific funding) for a RCT not related to this publication. Dr A.H. received speakers fee from MSD for an educational presentation. All other authors have no conflict of interest.

Mitochondrial SIRT3 and its target glutamate dehydrogenase are altered in follicular cells of women with reduced ovarian reserve or advanced maternal age

STUDY QUESTION

Is the activity of sirtuin 3 (SIRT3) altered in granulosa and cumulus cells from young women with reduced ovarian reserve or women of advanced maternal age?

SUMMARY ANSWER

SIRT3 mRNA and active protein in granulosa and cumulus cells were decreased in women with reduced ovarian reserve and advanced maternal age.

WHAT IS KNOWN ALREADY

Young women with reduced ovarian reserve or women of advanced maternal age have reduced oocyte viability, possibly due to altered granulosa and cumulus cell metabolism. The mitochondrial SIRT3 protein may be implicated in these processes as it is able to sense the metabolic state of the cell and alter mitochondrial protein function post-translationally.

STUDY DESIGN, SIZE, DURATION

This is a prospective cohort study, in which women (n = 72) undergoing routine IVF/ICSI were recruited and allocated to one of three cohorts based on age and ovarian reserve (as assessed by serum anti-Mullerian hormone level). Women were classified as young (≤35 years) or of advanced maternal age (≥40 years).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Granulosa and cumulus cells were collected. SIRT3 mRNA and protein levels and protein activity was analysed in granulosa and cumulus cells via quantitative PCR, immunohistochemistry and western blotting, and deacetylation activity, respectively. Activity of the glutamate dehydrogenase (GDH) enzyme, a known target of SIRT3, was assessed, and acetylated proteins in mitochondria isolated from granulosa and cumulus cells were separated by immunoprecipitation and acetylation of GDH assessed by western blotting. Data for women with good prognosis (young women with normal ovarian reserve) were compared with those from young women with reduced ovarian reserve and those of advanced maternal age.

MAIN RESULTS AND THE ROLE OF CHANCE

SIRT3 mRNA and active protein were present in granulosa and cumulus cells and co-localized to the mitochondria. SIRT3 mRNA in granulosa cells was decreased in young women with reduced ovarian reserve and advanced maternal age versus young women with normal ovarian reserve (P < 0.05). SIRT3 mRNA in cumulus cells was decreased in women of advanced maternal age versus young women with normal ovarian reserve only (P < 0.05). Granulosa cell GDH activity was decreased in young women with reduced ovarian reserve and in women of advanced maternal age (P < 0.05), whereas cumulus cell GDH activity was reduced in the advanced maternal age group only (P < 0.05). The acetylation profile of GDH in mitochondria revealed increased acetylation of GDH in granulosa and cumulus cells from women of advanced maternal age (P < 0.05) while young women with reduced ovarian reserve had increased GDH acetylation in granulosa cells only (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

Although patients were allocated to groups based on maternal age and ovarian reserve and matched for BMI, other maternal factors may also alter the 'molecular health' of ovarian cells.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that SIRT3 post-translational modification of mitochondrial enzymes in human granulosa and cumulus cells may regulate GDH activity, thus altering the metabolic milieu surrounding the developing oocyte. Owing to the association between the decline in oocyte quality and pregnancy rates in women of advanced maternal age and the possible association with reduced ovarian reserve, knowledge of perturbed SIRT3 function in granulosa and cumulus cells may lead to novel therapies to improve mitochondrial metabolism in the oocyte and follicular cells in women undergoing IVF treatment.

STUDY FUNDING/COMPETING INTEREST(S)

No conflicts of interest to declare. Research was funded by an NHMRC project grant.

Association between response to ovarian stimulation and miscarriage following IVF: an analysis of 124 351 IVF pregnancies

STUDY QUESTION

Is there a relationship between ovarian reserve, quantified as ovarian response to stimulation, and miscarriage rate following IVF treatment?

SUMMARY ANSWER

There is a strong association between the number of oocytes retrieved and miscarriage rate following IVF treatment, with the miscarriage rate decreasing with an increasing number of oocytes and then levelling off: poor responders have a higher miscarriage rate across all age groups.

WHAT IS ALREADY KNOWN

Poor ovarian response is a manifestation of a decline in the quantity of the primordial follicle pool. Whether poor ovarian response is associated with a decline in oocyte quality contributing to miscarriage is however debated.

STUDY DESIGN, SIZE, DURATION

Anonymous data were obtained from the Human Fertilization and Embryology Authority (HFEA), the statutory regulator of assisted reproduction treatment (ART) in the UK. The HFEA has collected data on all ART performed in the UK since 1991. Data from 1991 to June 2008 involving 402 185 stimulated fresh IVF cycles and 124 351 pregnancy outcomes were analysed.

PARTICIPANTS/ MATERIALS, SETTING, METHODS

Data on all women undergoing a stimulated fresh IVF treatment cycle with at least one oocyte retrieved during the period from 1991 to June 2008 were analysed for their early pregnancy outcomes.

MAIN RESULTS AND THE ROLE OF CHANCE

There was a strong association between the number of oocytes retrieved and the clinical miscarriage rate. The miscarriage rate fell from 20 to 13% with an increasing number of oocytes before levelling off. Stepwise logistic regression identified three cut-off points (4, 10 and 15 oocytes) at or beyond which the probability of clinical miscarriage fell. There was no increase in miscarriage rate with very high oocyte numbers (>20 oocytes). The lowest risk of miscarriage (9.9%) was for women under 38 years of age, with primary infertility without a female cause and producing more than three oocytes.

LIMITATIONS, REASONS FOR CAUTION

Although the analysis was performed only on stimulated IVF cycles (excluding unstimulated cycles), the data had the limitation that there was no information on the total gonadotrophin consumption. The model was adjusted for age and type of infertility, but the dataset contained no information on other confounders such as body mass index (BMI) of the women to allow adjustment.

WIDER IMPLICATIONS FOR THE FINDINGS

Analysis of this extensive dataset suggests that poor responders have a higher risk of clinical miscarriage, indicating that poor ovarian response is associated with a parallel decline in both oocyte quantity and quality. The miscarriage rate is also higher with advanced age, secondary infertility and a female cause of infertility compared with a younger age, male factor infertility and unexplained cause.

The association between the oocyte pool and aneuploidy: a comparative study of the reproductive potential of young and aged mice

PURPOSE

The present study examined the effect of aging on female reproductive potential.

METHODS

Six-week-old and 9-month-old CD1 mice were referred to as the 'young' and 'aged' groups, respectively. Oocytes were collected after superovulation, and their viability were compared using parthenogenetic activation. The aneuploidy of the oocytes (MII) was assessed using chromosome spread, and the whole ovarian follicle number was counted using an unbiased stereological method. Serum hormone levels were measured using the radio-immunity method, and the expression of the Cohesin subunit genes in the oocytes (GV) were assessed using RT-PCR.

RESULTS

The mean number of recovered (25.8 vs. 16.2; P < 0.05) and live oocytes (24.0 vs. 11.73; P <0.01) per head in the young-mice group (6-week-old) was significantly higher than that of the aged group (9-month-old). The aneuploidy rate of the ovulated oocytes in the aged group was significantly higher than that of the young group (36.8% vs. 10%; P < 0.01), and the rate of blastocyst formation in the young group (85.23%) was significantly higher than that of the aged group (81.2%; P <0.05). The number of primordial follicles (the oocyte pool) per ovary in the aged group was significantly decreased compared with the young group (330 ± 33.51 vs. 2079.6 ± 420.70; P < 0.01), and the level of AMH in the aged group was significantly higher than that of the young group (4.66 ± 0.11 ng/ml vs. 4.07 ± 0.18 ng/ml; P < 0.01).

CONCLUSIONS

We propose that maternal aging significantly reduces the oocyte pool, superovulation efficiency and developmental potential and increases the oocyte aneuploidy rate.

Biomarkers of ovarian reserve

Although it is widely appreciated that age is the primary determinant of the number of primordial follicles remaining within the ovary, it is now also recognized that for any given age two women can have a 100-fold difference in their ovarian reserve. Consequently, age alone has relatively poor accuracy in determining the reproductive potential for young women, and this has led to the development of additional biomarkers that more accurately reflect the ovarian reserve. In this review we discuss the strengths and limitations of the classical and novel biomarkers and provide a rationale for the adoption of biomarkers to facilitate the individualization of reproductive health.

Serum anti-Mullerian hormone levels affect the rate of ongoing pregnancy after in vitro fertilization

We used logistic regression analysis to investigate the relationship between serum anti-Mullerian hormone (AMH) levels and the rate of ongoing pregnancy. Retrospective data were collected from 1043 women who had undergone their first cycle of in vitro fertilization (IVF), including 540 cycles of fresh embryo transfer and 503 cycles of frozen-thawed embryo transfer. The patients were divided into 4 groups based on the cutoff values from a receiver-operating characteristic curve: 0.0 to 12.4, 12.5 to 25.5, 25.6 to 44.1, and >44.2 pmol/L. After adjustment for multiple confounders, the serum AMH group was found to be significantly related to the rate of ongoing pregnancy in total cycles (0.0-12.4 vs 12.5-25.5 pmol/L; P = .0088, odds ratio, 1.909: vs 25.6-44.1 pmol/L; P = .0281, odds ratio, 2.109: vs >44.2 pmol/L; P = .0008, odds ratio, 2.840). In conclusion, there appears to be a significant relationship between serum AMH levels and the ongoing pregnancy rate in first IVF treatment cycles after adjustment for multiple confounders.

The poor responder in IVF: is the prognosis always poor?: a systematic review

BACKGROUND In IVF treatment a considerable proportion of women are faced with a low number of oocytes retrieved. These poor responders have reduced pregnancy rates compared with normal responders. However, this may not be applicable to all poor responders. This review aims at identifying patient characteristics and ovarian reserve tests (ORT) that will determine prognosis for pregnancy in poor responders. METHODS A systematic search was conducted in PubMed, Embase, Cochrane and SCOPUS databases in April 2010. Studies regarding patient characteristics or ORT in poor responders and their pregnancy prospects were included. All included papers were summarized in descriptive tables. RESULTS Nineteen studies were included. Pooled data of six studies comparing poor and normal responders demonstrated clearly lower pregnancy rates in poor responders (14.8 versus 34.5%). Ten studies indicated that older poor responders have a lower range of pregnancy rates compared with younger (1.5-12.7 versus 13.0-35%, respectively). Four studies showed that pregnancy prospects become reduced when fewer oocytes are retrieved (0-7% with 1 oocyte versus 11.5-18.6% with 4 oocytes). Five studies concerning pregnancy rates in subsequent cycles suggested a more favourable outcome in unexpected poor responders, and if ≥2 oocytes were retrieved. CONCLUSIONS Poor responders are not a homogeneous group of women with regards to pregnancy prospects. Female age and number of oocytes retrieved in particular will modulate the chances for pregnancy in current and subsequent cycles. Applying these criteria will allow the identification of couples with a reasonable prognosis and balanced decision-making on the management of poor responders.

Trisomic pregnancy and elevated FSH: implications for the oocyte pool hypothesis

BACKGROUND

Some studies, but not all, support the hypothesis that trisomy frequency is related to the size of the oocyte pool, with the risk increased for women with fewer oocytes (older ovarian age). We tested this hypothesis by comparing hormonal indicators of ovarian age among women who had trisomic pregnancy losses with indicators among women with non-trisomic losses or chromosomally normal births. The three primary indicators of advanced ovarian age were low level of anti-Müllerian hormone (AMH), high level of follicle-stimulating hormone (FSH) and low level of inhibin B.

METHODS

The analysis drew on data from two hospital-based case-control studies. Data were analyzed separately and the evidence from the two sites was combined. We compared 159 women with trisomic pregnancy losses to three comparison groups: 60 women with other chromosomally abnormal losses, 79 women with chromosomally normal losses and 344 women with live births (LBs) age-matched to women with losses. We analyzed the hormone measures as continuous and as categorical variables. All analyses adjust for age in single years, day of blood draw, interval in storage and site.

RESULTS

AMH and inhibin B did not differ between women with trisomic losses and any of the three comparison groups. Mean ln(FSH) was 0.137 units (95% confidence interval (CI): 0.055, 0.219) higher for trisomy cases compared with LB controls; it was also higher, though not significantly so, for trisomy cases compared with women with other chromosomally abnormal losses or chromosomally normal losses. The adjusted odds ratio in relation to high FSH (≥ 10 mIU/ml) was significantly increased for trisomy cases versus LB controls (adjusted odds ratio (OR): 3.8, 95% CI: 1.6, 8.9).

CONCLUSIONS

The association of trisomy with elevated FSH is compatible with the oocyte pool hypothesis, whereas the absence of an association with AMH is not. Alternative interpretations are considered, including the possibility that elevated FSH may disrupt meiotic processes or allow recruitment of abnormal follicles.

A lower antral follicle count is associated with infertility

OBJECTIVE

To determine whether infertile women have lower antral follicle counts (AFC) than age-matched normal women.

DESIGN

Case-control.

SETTING

Academic center.

PATIENT(S)

A total of 881 infertile women and 771 women from the community.

INTERVENTION(S)

Antral follicle count and basal hormone measurements.

MAIN OUTCOME MEASURE(S)

Median AFCs and FSH levels were compared between the two groups within 5-year age strata by using the median test. A subanalysis was performed by identifying women in the control group with a history of attempting conception without success (subfertile group) and with a spontaneous conception in fewer than 12 months resulting in a live birth (fertile group). Age-specific AFC percentiles were calculated and compared within strata determined by age at the time of attempted conception.

RESULT(S)

AFCs were significantly lower in infertile women than in control women across age groups up to 40 years of age. Average FSH levels were significantly higher in the younger-age infertile group versus the community. AFC percentiles differ significantly between fertile and subfertile women within the community up to 40 years of age.

CONCLUSION(S)

Decreased AFC in infertile women suggests that factors affecting the size of the remaining follicle pool in younger women also affect oocyte quality and the likelihood of conception.

Are poor responders patients at higher risk for producing aneuploid embryos in vitro?

PURPOSE

To test the hypothesis that aged women with poor ovarian response express an increase on embryo chromosomal alterations when compared to aged women who presented normal response.

METHODS

Couples undergoing intracytoplasmic sperm injection cycles with preimplantation genetic screening, were subdivided into two groups: Poor Responder group (n = 34), patients who produced ≤4 oocytes; and Normoresponder group (n = 50), patients who produced ≥5 oocytes. Groups were compared regarding cycles' outcomes and aneuploidy frequency.

RESULTS

There were no significant differences between and groups regarding the fertilization rate (p = 0.6861), clinical pregnancy (p = 0.9208), implantation (p = 0.6863), miscarriage (p = 0.6788) and the percentage of aneuploid embryos (p = 0.270). Embryo transfer rate was significantly lower on poor responder group (p = 0.0128) and logistic regression confirmed the influence of poor response on the chance of embryo transfer (p = 0.016).

CONCLUSIONS

Aged females responding poorly to gonadotrophins are not at a higher risk for producing aneuploid embryos in vitro.

Chromosomal and cytoplasmic context determines predisposition to maternal age-related aneuploidy: brief overview and update on MCAK in mammalian oocytes

It has been known for more than half a century that the risk of conceiving a child with trisomy increases with advanced maternal age. However, the origin of the high susceptibility to nondisjunction of whole chromosomes and precocious separation of sister chromatids, leading to aneuploidy in aged oocytes and embryos derived from them, cannot be traced back to a single disturbance and mechanism. Instead, analysis of recombination patterns of meiotic chromosomes of spread oocytes from embryonal ovary, and of origins and exchange patterns of extra chromosomes in trisomies, as well as morphological and molecular studies of oocytes and somatic cells from young and aged females, show chromosome-specific risk patterns and cellular aberrations related to the chronological age of the female. In addition, analysis of the function of meiotic- and cell-cycle-regulating genes in oogenesis, and the study of the spindle and chromosomal status of maturing oocytes, suggest that several events contribute synergistically to errors in chromosome segregation in aged oocytes in a chromosome-specific fashion. For instance, loss of cohesion may differentially predispose chromosomes with distal or pericentromeric chiasmata to nondisjunction. Studies on expression in young and aged oocytes from human or model organisms, like the mouse, indicate that the presence and functionality/activity of gene products involved in cell-cycle regulation, spindle formation and organelle integrity may be altered in aged oocytes, thus contributing to a high risk of error in chromosome segregation in meiosis I and II. Genes that are often altered in aged mouse oocytes include MCAK (mitotic-centromere-associated protein), a microtubule depolymerase, and AURKB (Aurora kinase B), a protein of the chromosomal passenger complex that has many targets and can also phosphorylate and regulate MCAK localization and activity. Therefore we explored the role of MCAK in maturing mouse oocytes by immunofluorescence, overexpression of a MCAK–EGFP (enhanced green fluorescent protein) fusion protein, knockdown of MCAK by RNAi (RNA interference) and inhibition of AURKB. The observations suggest that MCAK is involved in spindle regulation, chromosome congression and cell-cycle control, and that reductions in mRNA and protein in a context of permissive SAC (spindle assembly checkpoint) predispose to aneuploidy. Failure to recruit MCAK to centromeres and low expression patterns, as well as disturbances in regulation of enzyme localization and activity, e.g. due to alterations in activity of AURKB, may therefore contribute to maternal age-related rises in aneuploidy in mammalian oocytes.