The Role of Oocyte Quality in Explaining "Unexplained" Infertility

Treatment With a Patented 3.6:1 Myo-Inositol to D-chiro-Inositol Ratio, Antioxidants, Vitamins and Minerals Food Supplement in Women With a History of Assisted Reproductive Technique (ART) Failures: A Series of Case Reports

Infertility affects 15% of couples in reproductive age worldwide. In women in particular, infertility can be caused by various abnormalities, with polycystic ovary syndrome (PCOS) being the most common. Currently, there are many assisted reproductive techniques (ART) available to combat the burden of infertility. However, positive results are not guaranteed. The administration of inositol has been shown to increase positive reproductive outcomes in women undergoing ART. Here we present a series of clinical cases in which women with a history of infertility and previously failed ART, supplemented with a specific 3.6:1 MYO:DCI ratio, antioxidants, vitamins, and minerals for a period of 1 to 3 months before undergoing in vitro fertilization (IVF). In this series of case reports, we provide preliminary evidence that supplementation with a specific 3.6:1 MYO to DCI ratio, as well as antioxidants, vitamins, and minerals may contribute positively to female fertility in women undergoing IVF, with a history of primary or secondary infertility and previously failed ART.

Minerals and the Menstrual Cycle: Impacts on Ovulation and Endometrial Health

The role of minerals in female fertility, particularly in relation to the menstrual cycle, presents a complex area of study that underscores the interplay between nutrition and reproductive health. This narrative review aims to elucidate the impacts of minerals on key aspects of the reproductive system: hormonal regulation, ovarian function and ovulation, endometrial health, and oxidative stress. Despite the attention given to specific micronutrients in relation to reproductive disorders, there is a noticeable absence of a comprehensive review focusing on the impact of minerals throughout the menstrual cycle on female fertility. This narrative review aims to address this gap by examining the influence of minerals on reproductive health. Each mineral's contribution is explored in detail to provide a clearer picture of its importance in supporting female fertility. This comprehensive analysis not only enhances our knowledge of reproductive health but also offers clinicians valuable insights into potential therapeutic strategies and the recommended intake of minerals to promote female reproductive well-being, considering the menstrual cycle. This review stands as the first to offer such a detailed examination of minerals in the context of the menstrual cycle, aiming to elevate the understanding of their critical role in female fertility and reproductive health.

Similar pregnancy outcomes from fresh and frozen donor oocytes transferred to gestational carriers: a SART database analysis isolating the effects of oocyte vitrification

PURPOSE

This work aimed to study clinical and neonatal outcomes of embryos derived from frozen compared to fresh donor oocytes in gestational carrier cycles.

METHODS

This is a retrospective cohort study using the Society for Assisted Reproductive Technology Clinic Outcome Reporting System database between 2014 and 2015, comprising of 1284 fresh transfer cycles to gestational carrier recipients of embryos resulting from fresh (n = 1119) and vitrified/thawed (n = 165) donor oocytes. Models were adjusted for gestational carrier age, preimplantation genetic testing (PGT-A), number of embryos transferred, multiple gestation, and fetal heart reduction. As our models were part of a larger analysis, intended parent BMI, smoking status, and parity were also adjusted for, but did not influence outcomes in this analysis.

RESULTS

There was no significant difference in probability of live birth rates when comparing embryos derived from fresh and frozen donor oocytes in gestational carrier cycles. There were also no significant differences in biochemical pregnancy losses or clinical miscarriage. There were no significant differences noted in low birthweight or high birthweight infants derived from fresh versus frozen donor oocyte after transfer into a gestational carrier.

CONCLUSIONS

The analysis of fresh and frozen donor oocytes in gestational carrier cycles provides the opportunity to assess for a possible effect of vitrification on the oocyte by controlling for differences in the uterine environment. We observed no significant differences in live birth, pregnancy loss, low birthweight or high birthweight infants when comparing fresh and frozen donor oocytes in gestational carrier cycles.

2-bromoacetamide exposure impairs oocyte maturation in mice and humans primarily via disrupting the cytoskeleton

2-bromoacetamide (BAcAm) is an emerging class of unregulated disinfection by-products (DBPs), with potent cytogenetic and developmental toxicity in animals. However, whether BAcAm exerts toxic effects on mammalian oocyte quality remains to be elucidate. In this research, we investigated the effect of BAcAm on mouse and human oocyte maturation with an in vitro culture system. Our results revealed that BAcAm exposure hindered the extrusion of the first polar body, disrupted the spindle organization and reduced the competence of embryo development after fertilization in the mouse oocytes. Results of single-cell RNA sequencing (scRNA-seq) showed that 605 differentially expressed genes (DEGs) were identified in the BAcAm exposed mouse oocytes, among which 366 were up-regulated and 239 were down-regulated. Gene Ontology (GO) analysis further revealed that DEGs were mainly enriched in mitochondrial functions, oxidative stress, cytoskeleton, endoplasmic reticulum (ER), Golgi and protein synthesis, DNA damage and apoptosis. We then conducted further tests in these aspects and discovered that BAcAm exposure principally perturbed the function of microtubule and actin cytoskeleton. This finding was confirmed in human oocytes. Overall, our data suggest that BAcAm exposure disturbs the cytoskeleton function, thus impairing oocyte maturation. These data, for the first time, provide a comprehensive view for the toxic effects of BAcAm on oocyte maturation.

Association of infertility with type and timing of menopause: a prospective cohort study

STUDY QUESTION

What is the association between past infertility and the type and timing of menopause in midlife women?

SUMMARY ANSWER

Women with a history of infertility were more likely to experience surgical menopause overall and had elevated risk of earlier surgical menopause until age 43 years but experienced no differences in the timing of natural menopause.

WHAT IS KNOWN ALREADY

Infertility is experienced by 12-25% of women and is thought to reveal a propensity for poor health outcomes, such as chronic illness, later in life. However, little is known about whether infertility is linked with characteristics of the menopausal transition as women age, despite possible shared underlying pathways involving ovarian function and gynecologic disease.

STUDY DESIGN, SIZE, DURATION

Secondary analysis of a prospective cohort study of 13 243 midlife females recruited in Phase 1 of the Alberta's Tomorrow Project (Alberta, Canada) and followed approximately every 4 years (2000-2022).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were collected through standardized self-report questionnaires. History of infertility, defined as ever trying to become pregnant for more than 1 year without conceiving, was measured at baseline. Menopause characteristics were measured at each study follow-up. Menopause type was defined as premenopause, natural menopause, surgical menopause (bilateral oophorectomy), or indeterminate menopause (premenopausal hysterectomy with ovarian conservation). Timing of natural menopause was defined as the age at 1 full year after the final menstrual period, and timing of surgical and indeterminate menopause was defined as the age at the time of surgery. We used flexible parametric survival analysis for the outcome of menopause timing with age as the underlying time scale and multinomial logistic regression for the outcome of menopause type. Multivariable models controlled for race/ethnicity, education, parity, previous pregnancy loss, and smoking. Sensitivity analyses additionally accounted for birth history, menopausal hormone therapy, body mass index, chronic medical conditions, and age at baseline.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, 18.2% of women reported a history of infertility. Past infertility was associated with earlier timing of surgical menopause exclusively before age 43 years (age 35: adjusted hazard ratio 3.13, 95% CI 1.95-5.02; age 40: adjusted hazard ratio 1.83, 95% CI 1.40-2.40; age 45: adjusted hazard ratio 1.13, 95% CI 0.87-1.46) as well as greater odds of experiencing surgical menopause compared to natural menopause (adjusted odds ratio 1.40, 95% CI 1.18-1.66). Infertility was not associated with the timing of natural or indeterminate menopause.

LIMITATIONS, REASONS FOR CAUTION

Information on the underlying cause of infertility and related interventions was not collected, which precluded us from disentangling whether associations differed by infertility cause and treatment. Residual confounding is possible given that some covariates were measured at baseline and may not have temporally preceded infertility.

WIDER IMPLICATIONS OF THE FINDINGS

Women with a history of infertility were more likely to experience early surgical menopause and may therefore benefit from preemptive screening and treatment for gynecologic diseases to reduce bilateral oophorectomy, where clinically appropriate, and its associated health risks in midlife. Moreover, the lack of association between infertility and timing of natural menopause adds to the emerging knowledge that diminishing ovarian reserve does not appear to be a primary biological mechanism of infertility nor its downstream implications for women's health.

STUDY FUNDING/COMPETING INTEREST(S)

Alberta's Tomorrow Project is only possible due to the commitment of its research participants, its staff and its funders: Alberta Health, Alberta Cancer Foundation, Canadian Partnership Against Cancer and Health Canada, and substantial in-kind funding from Alberta Health Services. The views expressed herein represent the views of the author(s) and not of Alberta's Tomorrow Project or any of its funders. This secondary analysis is funded by Project Grant Priority Funding in Women's Health Research from the Canadian Institutes of Health Research (Grant no. 491439). N.V.S. is supported by a Banting Postdoctoral Fellowship from the Canadian Institutes of Health Research. H.K.B. is supported by the Canada Research Chairs Program. E.A.B. is supported by an Early Career Investigator Award in Maternal, Reproductive, Child and Youth Health from the Canadian Institutes of Health Research. A.K.S. has received honoraria from Pfizer, Lupin, Bio-Syent, and Eisai and has received grant funding from Pfizer. N.V.S., H.K.B., and E.A.B. have no conflicts of interest to report.

TRIAL REGISTRATION NUMBER

N/A.

Associations between exposure to cadmium, lead, mercury and mixtures and women's infertility and long-term amenorrhea

BACKGROUND

Cadmium (Cd), lead (Pb), and mercury (Hg) have been shown to exhibit endocrine disrupting properties. Their effects on women's reproductive health, however, remain elusive. Here, we investigated associations between blood concentrations of Pb, Cd, Hg, and their mixture and infertility and long-term amenorrhea in women aged 20-49 years using the US National Health and Nutrition Examination Survey (NHANES) 2013-2018 cross-sectional survey.

METHODS

A total of 1,990 women were included for the analysis of infertility and 1,919 women for long-term amenorrhea. The methods of log-transformation and use of quartiles were used to analyze blood heavy metal concentrations. Statistical differences in the covariates between the outcome groups were evaluated using a chi-squared test for categorical variables and a t-test for continuous variables. Multiple logistic regression models were used to examine the associations.

RESULTS

The blood concentrations of Pb and heavy metal mixtures were significantly higher in ever-infertile women than pregnant women, but the concentrations of Cd and Hg were comparable. After full adjustment, multiple logistic regression analyses revealed a significant and dose-dependent positive association between blood Pb concentrations and women's historical infertility, a negative association between Cd and women's long-term amenorrhea, and no associations between Hg and heavy metal mixture and women's infertility or long-term amenorrhea.

CONCLUSIONS

Our study suggests that exposure to heavy metals exhibit differential associations with history of infertility and amenorrhea, and Pb may adversely impact women's reproduction and heighten the risks of infertility and long-term amenorrhea.

Using Hormone Data and Age to Pinpoint Cycle Day within the Menstrual Cycle

Background and Objectives: Menstrual cycle tracking is essential for reproductive health and overall well-being. However, there is still an over-reliance on estimations that standard cycles are 28 days long, divided evenly between the follicular and luteal phases. Due to the variability of cycle length and cycle phase lengths, common methods of identifying where an individual is in their cycle are often inaccurate. This study used daily hormone monitoring obtained through a remote hormone-monitoring platform to evaluate hormone levels across a menstrual cycle to identify nuances in the follicular and luteal phases in individuals of different age groups. Materials and Methods: This study used a remote fertility testing system that quantitatively tracks luteinizing hormone (LH) and pregnanediol-3-glucuronide (PdG) through urine tests read by an AI-powered smartphone app. The study analyzed cycle data from 1233 users with a total of 4123 evaluated cycles. Daily levels for LH and PdG were monitored across multiple cycles. Results: This study determined that calculated cycle lengths tended to be shorter than user-reported cycle lengths. Significant differences were observed in cycle phase lengths between age groups, indicating that follicular phase length declines with age while luteal phase length increases. Finally, the study found that if an individual's age, first cycle day, and current hormone levels are known, population-level hormone data can be used to pinpoint which cycle phase and cycle day they are in with 95% confidence. Conclusions: At-home hormone monitoring technologies can allow patients and clinicians to track their cycles with greater precision than when relying on textbook estimations. The study's findings have implications for fertility planning, clinical management, and general health monitoring. Prior to this study, no standard existed for pinpointing where a person was in their cycle through only one measure of LH and PdG. These findings have the potential to fill significant gaps within reproductive healthcare and beyond.

Dendrobine enhances bovine oocyte maturation and subsequent embryonic development and quality

Strategies for improving the quality of oocytes have important theoretical and practical significance for increasing the efficiency of livestock breeding. In this respect, the accumulation of reactive oxygen species (ROS) is a major factor affecting the development of oocytes and embryos. This study investigated the effects of Dendrobium nobile extract (DNE) on the in vitro maturation of bovine oocytes and embryonic development after IVF. DNE is an extract from Dendrobium rhizomes that contains alkaloids with anti-inflammatory, anti-cancer and anti-ageing functions. Various concentrations of DNE (0, 5, 10, 20 and 50 μmol/L) were added during oocyte maturation in vitro, and we found that 10 μmol/L of DNE remarkably increased the oocyte maturation rate, the subsequent blastocyst formation rate and embryo quality. Further, we found that DNE treatment decreased the frequency of spindle/chromosome defects and ROS and increased the oocyte glutathione and mitochondrial membrane potential in oocytes. Moreover, DNE upregulated the expression of oxidative stress-related genes (Sirt1, Sirt2, Sirt3 and Sod1) in oocytes and apoptosis-related genes (Caspase-3, Caspase-4, Bax, Bcl-xl and Survivin) in blastocysts. These results suggest that DNE supplementation can promote oocyte maturation and subsequent embryonic development by regulating redox reactions and inhibiting embryonic apoptosis.

Evaluation of Dysfunctional HDL by Myeloperoxidase/Paraoxonase Ratio in Unexplained Infertility Patients Undergoing IVF/ICSI

The relationship between oxidative stress and unexplained infertility (UEI) has not been studied in detail. This is the first study to evaluate dysfunctional high-density lipoprotein (HDL) by the myeloperoxidase (MPO) and paraoxonase (PON) ratio to investigate the role of oxidative stress in UEI.

MATERIALS AND METHODS

Patients with UEI (study group, n = 40) and male factor infertility (control group, n = 36) were included in this prospective study. Demographics and laboratory assessments were analyzed.

RESULTS

Total dosages of gonadotropin were higher in UEI when compared to the control group (p = 0.033). Number of Grade 1 embryos and the quality of blastocysts were lower in UEI than in the control group (p = 0.024, p = 0.020, respectively), whereas serum MPO/PON ratio was higher in UEI (p = 0.042). Stepwise linear regression analysis revealed that serum MPO/PON ratio levels could significantly predict the duration of infertility (p = 0.012).

CONCLUSIONS

Serum MPO/PON ratio increased in patients with UEI, whereas the number of Grade 1 embryos and the quality of blastocysts decreased. Similar clinical pregnacy rates were found in both groups but the ET on day five is associated with higher clinical pregnancy rate in the male factor infertility.

Effect of Resveratrol on Pregnancy, Prenatal Complications and Pregnancy-Associated Structure Alterations

Adverse pregnancy outcomes are considered significant health risks for pregnant women and their offspring during pregnancy and throughout their lifespan. These outcomes lead to a perturbated in-utero environment that impacts critical phases of the fetus's life and correlates to an increased risk of chronic pathological conditions, such as diabetes, obesity, and cardiovascular diseases, in both the mother's and adult offspring's life. The dietary intake of naturally occurring antioxidants promotes health benefits and disease prevention. In this regard, maternal dietary intake of polyphenolic antioxidants is linked to a reduced risk of maternal obesity and cardio-metabolic disorders, positively affecting both the fetus and offspring. In this work, we will gather and critically appraise the current literature highlighting the effect/s of the naturally occurring polyphenol antioxidant resveratrol on oxidative stress, inflammation, and other molecular and physiological phenomena associated with pregnancy and pregnancy conditions, such as gestational diabetes, preeclampsia, and preterm labor. The resveratrol impact on prenatal complications and pregnancy-associated structures, such as the fetus and placenta, will also be discussed. Finally, we will draw conclusions from the current knowledge and provide future perspectives on potentially exploiting resveratrol as a therapeutic tool in pregnancy-associated conditions.

High-Fat Diet and Female Fertility across Lifespan: A Comparative Lesson from Mammal Models

Female reproduction focuses mainly on achieving fully grown follicles and competent oocytes to be successfully fertilized, as well as on nourishing the developing offspring once pregnancy occurs. Current evidence demonstrates that obesity and/or high-fat diet regimes can perturbate these processes, leading to female infertility and transgenerational disorders. Since the mechanisms and reproductive processes involved are not yet fully clarified, the present review is designed as a systematic and comparative survey of the available literature. The available data demonstrate the adverse influences of obesity on diverse reproductive processes, such as folliculogenesis, oogenesis, and embryo development/implant. The negative reproductive impact may be attributed to a direct action on reproductive somatic and germinal compartments and/or to an indirect influence mediated by the endocrine, metabolic, and immune axis control systems. Overall, the present review highlights the fragmentation of the current information limiting the comprehension of the reproductive impact of a high-fat diet. Based on the incidence and prevalence of obesity in the Western countries, this topic becomes a research challenge to increase self-awareness of dietary reproductive risk to propose solid and rigorous preventive dietary regimes, as well as to develop targeted pharmacological interventions.

1-Nitropyrene exposure induces mitochondria dysfunction and impairs oocyte maturation in mice

Oocyte quality is essential for a successful pregnancy. 1-Nitropyrene (1-NP) is a widely distributed pollutant in the environment and is well-known for its mutagenicity and carcinogenicity. However, whether 1-NP has toxic effects on mammalian oocyte quality remains unknown. In the present study, we focused on the effect of 1-NP on oocyte maturation using mouse oocytes as an in vitro model. Our study showed that 1-NP exposure disrupted the meiotic spindle assembly and caused chromosome misalignment, further impaired first polar body extrusion, and significantly decreased the fertilization capability in mouse oocytes. Further investigation showed that the mitochondrial membrane potential (MMP) and ATP levels were decreased, and the expression of genes encoding components of the mitochondrial respiratory chain was inhibited in 1-NP exposed oocytes. Meanwhile, 1-NP exposure increased the levels of reactive oxygen species (ROS), inhibited the expression of genes encoding antioxidant enzymes, and increased the frequency of early apoptotic oocytes. Overall, our data suggest that 1-NP exposure disrupts mitochondrial function and intracellular redox balance, ultimately impairing oocyte maturation. These findings reveal the adverse effect of 1-NP exposure on oocyte quality.

Maternal erythrocyte fatty acid composition as a predictive marker for pregnancy health

Pregnancy is accompanied by a surge in demand for fatty acids (FAs) in order to support maternal health, as well as fetal growth and development. Of particular demand is essential for long-chain polyunsaturated FAs. FAs are primarily obtained from dietary sources and are distributed in the body. In comparison with the use of self-reporting approaches, measuring the FA levels within different blood compartments can present a more accurate image of nutritional, and thus tissue, FA composition. Hence, the FA profile of plasma or serum is commonly used for physiological analyses. Nevertheless, plasma and serum FAs are not yet incorporated into cell membranes, and consequently may not be a suitable reflection of the FA status of body tissues. The evaluation of erythrocyte FA levels offers a superior possibility for the following reasons: the biological fluctuation of erythrocyte FA composition is low, phospholipids account for almost all the lipid content of erythrocytes, and the FA profiles of erythrocytes represent those of tissues. Here, we elaborate on whether the status of maternal erythrocyte FAs can serve as a prognostic biomarker for reproductive health and fetomaternal complications, including embryonic and fetoplacental development, gestational length, and preeclampsia. In addition, factors with the potential of altering the maternal erythrocyte FAs such as maternal diet, lifestyle habits, genetics, and body composition are discussed.

SGK1 is essential for meiotic resumption in mammalian oocytes

In mammalian females, oocytes are stored in the ovary and meiosis is arrested at the diplotene stage of prophase I. When females reach puberty oocytes are selectively recruited in cycles to grow, overcome the meiotic arrest, complete the first meiotic division and become mature (ready for fertilization). At a molecular level, the master regulator of prophase I arrest and meiotic resumption is the maturation-promoting factor (MPF) complex, formed by the active form of cyclin dependent kinase 1 (CDK1) and Cyclin B1. However, we still do not have complete information regarding the factors implicated in MPF activation. In this study we document that out of three mammalian serum-glucocorticoid kinase proteins (SGK1, SGK2, SGK3), mouse oocytes express only SGK1 with a phosphorylated (active) form dominantly localized in the nucleoplasm. Further, suppression of SGK1 activity in oocytes results in decreased CDK1 activation via the phosphatase cell division cycle 25B (CDC25B), consequently delaying or inhibiting nuclear envelope breakdown. Expression of exogenous constitutively active CDK1 can rescue the phenotype induced by SGK1 inhibition. These findings bring new insights into the molecular pathways acting upstream of MPF and a better understanding of meiotic resumption control by presenting a new key player SGK1 in mammalian oocytes.

Obesity and risk of female reproductive conditions: A Mendelian randomisation study

BACKGROUND

Obesity is observationally associated with altered risk of many female reproductive conditions. These include polycystic ovary syndrome (PCOS), abnormal uterine bleeding, endometriosis, infertility, and pregnancy-related disorders. However, the roles and mechanisms of obesity in the aetiology of reproductive disorders remain unclear. Thus, we aimed to estimate observational and genetically predicted causal associations between obesity, metabolic hormones, and female reproductive disorders.

METHODS AND FINDINGS

Logistic regression, generalised additive models, and Mendelian randomisation (MR) (2-sample, non-linear, and multivariable) were applied to obesity and reproductive disease data on up to 257,193 women of European ancestry in UK Biobank and publicly available genome-wide association studies (GWASs). Body mass index (BMI), waist-to-hip ratio (WHR), and WHR adjusted for BMI were observationally (odds ratios [ORs] = 1.02-1.87 per 1-SD increase in obesity trait) and genetically (ORs = 1.06-2.09) associated with uterine fibroids (UF), PCOS, heavy menstrual bleeding (HMB), and pre-eclampsia. Genetically predicted visceral adipose tissue (VAT) mass was associated with the development of HMB (OR [95% CI] per 1-kg increase in predicted VAT mass = 1.32 [1.06-1.64], P = 0.0130), PCOS (OR [95% CI] = 1.15 [1.08-1.23], P = 3.24 × 10-05), and pre-eclampsia (OR [95% CI] = 3.08 [1.98-4.79], P = 6.65 × 10-07). Increased waist circumference posed a higher genetic risk (ORs = 1.16-1.93) for the development of these disorders and UF than did increased hip circumference (ORs = 1.06-1.10). Leptin, fasting insulin, and insulin resistance each mediated between 20% and 50% of the total genetically predicted association of obesity with pre-eclampsia. Reproductive conditions clustered based on shared genetic components of their aetiological relationships with obesity. This study was limited in power by the low prevalence of female reproductive conditions among women in the UK Biobank, with little information on pre-diagnostic anthropometric traits, and by the susceptibility of MR estimates to genetic pleiotropy.

CONCLUSIONS

We found that common indices of overall and central obesity were associated with increased risks of reproductive disorders to heterogenous extents in a systematic, large-scale genetics-based analysis of the aetiological relationships between obesity and female reproductive conditions. Our results suggest the utility of exploring the mechanisms mediating the causal associations of overweight and obesity with gynaecological health to identify targets for disease prevention and treatment.

Isolation and in vitro Culture of Mouse Oocytes

Females are endowed at birth with a fixed reserve of oocytes, which declines both in quantity and quality with advancing age. Understanding the molecular mechanisms regulating oocyte quality is crucial for improving the chances of pregnancy success in fertility clinics. In vitro culture systems enable researchers to analyse important molecular and genetic regulators of oocyte maturation and fertilisation. Here, we describe in detail a highly reproducible technique for the isolation and culture of fully grown mouse oocytes. We include the considerations and precautionary measures required for minimising the detrimental effects of in vitro culture conditions. This technique forms the starting point for a wide range of experimental approaches such as post-transcriptional gene silencing, immunocytochemistry, Western blotting, high-resolution 4D time-lapse imaging, and in vitro fertilization, which are instrumental in dissecting the molecular determinants of oocyte quality. Hence, this protocol serves as a useful, practical guide for any oocyte researcher beginning experiments aimed at investigating important oocyte molecular factors. Graphic abstract: A step-by-step protocol for the isolation and in vitro culture of oocytes from mice.

Senataxin: A New Guardian of the Female Germline Important for Delaying Ovarian Aging

Early decline in ovarian function known as premature ovarian aging (POA) occurs in around 10% of women and is characterized by a markedly reduced ovarian reserve. Premature ovarian insufficiency (POI) affects ~1% of women and refers to the severe end of the POA spectrum in which, accelerated ovarian aging leads to menopause before 40 years of age. Ovarian reserve refers to the total number of follicle-enclosed oocytes within both ovaries. Oocyte DNA integrity is a critical determinant of ovarian reserve since damage to DNA of oocytes within primordial-stage follicles triggers follicular apoptosis leading to accelerated follicle depletion. Despite the high prevalence of POA, very little is known regarding its genetic causation. Another little-investigated aspect of oocyte DNA damage involves low-grade damage that escapes apoptosis at the primordial follicle stage and persists throughout oocyte growth and later follicle development. Senataxin (SETX) is an RNA/DNA helicase involved in repair of oxidative stress-induced DNA damage and is well-known for its roles in preventing neurodegenerative disease. Recent findings uncover an important role for SETX in protecting oocyte DNA integrity against aging-induced increases in oxidative stress. Significantly, this newly identified SETX-mediated regulation of oocyte DNA integrity is critical for preventing POA and early-onset female infertility by preventing premature depletion of the ovarian follicular pool and reducing the burden of low-grade DNA damage both in primordial and fully-grown oocytes.

Understanding oocyte ageing: can we influence the process as clinicians?

PURPOSE OF REVIEW

Oocyte quality is rate-limiting for pregnancy success and declines with age. Here, I review animal-study evidence showing dramatic reversal of oocyte ageing with mitochondrial nutrients and explore clinical evidence related to their usage.

RECENT FINDINGS

Oocyte ageing is strongly tied to mitochondrial dysfunction and oxidative stress. Quality-defining events occur over a protracted period (2-3 months in humans) when oocyte volume increases over 100-fold. Treating mice during the growth phase with mitochondrial modifiers such as CoQ10 combats oocyte ageing. Exciting new work shows that raising oocyte NAD+ levels also dramatically rejuvenate aged oocytes. However, evidence that any of these agents can reproducibly improve quality in humans is lacking. This is largely because there has been a focus on patients with poor ovarian response during IVF and/or low ovarian follicular pool size, rather than patients with poor oocyte quality. In addition, studies have used short-term treatment during ovarian stimulation after oocyte growth is already complete.

SUMMARY

Mitochondrial therapeutics such as NAD+-boosting used during the oocyte's growth phase markedly improve oocyte quality in mice. Evaluating them in humans should focus on patients with poor oocyte quality and utilise per-oocyte (rather than per-cycle) endpoints after adequate treatment that captures the growth phase when quality is defined.