Decline In Oocyte Quality Research Articles

P-154 growth hormone supplementation decline quality of maternally aged oocytes via reducing aneuploidy

Abstract Study question Does growth hormone (GH) supplementation ameliorate the quality of oocytes in aged mice via reducing aneuploidy? Summary answer Daily injections of growth hormone for 2 months improve the age-related decline in ovarian reserve, and promote oocyte quality by reducing the aneuploidy rate. What is known already Women of advanced maternal age, particular over 35 years, could consequently bear poor quality oocytes, which are mainly caused by chromosomal aneuploidy. Age-related decline in GH levels may be related to the insufficient reproductive potential in women of advanced maternal age. To date, the role of GH in in vitro fertilization remains controversial. GH has been reported to affect oocyte quality, and studies in vivo have shown that intraperitoneal administration of GH reduces the occurrence rate of spindle/chromosome defects. Study design, size, duration The young (6-week-old) and aged (8-month-old) C57BL/6J mice were used in the study. In the in vivo experiment, aged mice were intraperitoneally injected daily with GH (1.6 mg/kg body weight, n = 85) or the equivalent volume of NS (n = 81) for consecutive for two months. In the in vitro experiment, GV oocytes from aged mice were treated with GH (Gene Science Pharmaceuticals, Changchun, China) (200ng/ml) in M16 medium for 14∼16 hours. Participants/materials, setting, methods We analyzed the number of oocytes and hormone levels to assess ovarian reserve, by immunohistochemistry and ELISA methods. The expression of GHR was measured by real-time quantitative RT-PCR and immunofluorescence. Time–lapse incubator was utilized to record the developmental potential of oocytes and embryos. Immunofluorescence was performed to assess parameters of oocyte quality (mitochondrial functions, ROS level, spindle/chromosome defects, and DNA damage). Chromosome spread and single-cell DNA sequencing were used to analyze chromosome aneuploidy rate. Main results and the role of chance The expression of GHR decreased in aged oocyte (21.68±1.08) and increased after GH treatment(30.64±0.70, P < 0.001). GH ameliorated decline in ovarian reserve of aged mice, with increased ovarian index (0.040%±0.0031 vs 0.023%±0.0019, P < 0.01), number of preantral follicles (7.33±0.89 vs 4.12±0.58, P < 0.05) and antral follicles (8.67±1.2 vs 3.33±0.88, P < 0.05) compared to the aged controls, but no other hormonal differences were detected. After GH supplementation, aged oocyte showed better quality and developmental potential, including restored mitochondrial functions (P < 0.05) and decreased ROS level (19.83±1.50 vs 23.6±1.72, P < 0.05). As expected, GH effectively promoted the fertilization rate (39.9%±1.10 vs 14.4%±0.62, P < 0.001) and early embryo development (P < 0.01). In addition, the spindle/chromosome defects (31.6%±2.12 vs 48.9%±1.83, P < 0.01), DNA damage (16.37±1.76 vs 49.35±2.52, P < 0.001) and aneuploidy rate (21.5%±1.61 vs 34.6%±1.84, P < 0.01) were lower in GH group than that in control group. Overall, GH treatment restored age-related decline in ovarian reserve, and decreased the occurrence rate of aneuploidy caused by spindle/chromosome defects, inducing a better oocyte quality in aged mice. Limitations, reasons for caution The molecular and mechanism of GH to regulate spindle/chromosome function remains to be determined. Besides, future work should be extended to human oocyte to determine whether this mechanism is conserved between mice and humans. Wider implications of the findings Our work expounds a theoretical basis for application of GH to improve the fertility of aged women. Besides, the results also feed new ideas for the prevention and treatment of oocyte quality decline in assisted reproductive technology. Trial registration number not applicable

Aflatoxin B1 exposure disrupts organelle distribution in mouse oocytes.

Aflatoxin B1 (AFB1) is a secondary metabolite produced by the fungus Aspergillus, which is ubiquitous in moldy grain products. Aflatoxin B1 has been reported to possess hepatotoxicity, renal toxicity, and reproductive toxicity. Previous studies have shown that AFB1 is toxic to mammalian oocytes. However, the potential toxicity of AFB1 on the organelles of mouse oocytes is unknown. In this study, we found that exposure to AFB1 significantly reduced mouse oocyte development capacity. Further analysis showed that the endoplasmic reticulum (ER) failed to accumulate around the spindle, and scattered in the cytoplasm under AFB1 exposure. Similar to the ER, the Golgi apparatus showed a uniform localization pattern following AFB1 treatment. In addition, we found that AFB1 exposure caused the condensation of lysosomes in the cytoplasm, presenting as a clustered or spindle peripheral-localization pattern, which indicated that protein modification, transport, and degradation were affected. Mitochondrial distribution was also altered by AFB1 treatment. In summary, our study showed that AFB1 exposure had toxic effects on the distribution of mouse oocyte organelles, which further led to a decline in oocyte quality.

Idiopathic early ovarian ageing: risk of miscarriage and chance of delivery following ART in a nationwide cohort study.

Is idiopathic reduced ovarian reserve in young women, quantified as low response to ovarian stimulation in ART, associated with a concomitant loss of oocyte quality as determined by risk of pregnancy loss and chance of clinical pregnancy and live birth? Young women with idiopathic accelerated loss of follicles exhibit a similar risk of pregnancy loss as young women with normal ovarian reserve. Normal ovarian ageing is described as a concomitant decline in oocyte quantity and quality with increasing age. Conflicting results exist with regard to whether a similar decline in oocyte quality also follows an accelerated loss of follicles in young women. This national register-based, historical cohort study included treatment cycles from young women (≤37 years) after ART treatment in Danish public or private fertility clinics during the period 1995-2014. The women were divided into two groups dependent on their ovarian reserve status: early ovarian ageing (EOA) group and normal ovarian ageing (NOA) group. There were 2734 eligible cycles in the EOA group and 22573 in the NOA group. Of those, 1874 (n = 1213 women) and 19526 (n = 8814 women) cycles with embryo transfer were included for analyses in the EOA and NOA group, respectively. EOA was defined as ≤5 oocytes harvested in both the first and second cycle stimulated with FSH. The NOA group should have had at least two FSH-stimulated cycles with ≥8 oocytes harvested in either the first or the second cycle. Cases with known causes influencing the ovarian reserve (endometriosis, ovarian surgery, polycystic ovary syndrome, chemotherapy, etc.) were excluded. The oocyte quality was evaluated by the primary outcome defined as the overall risk of pregnancy loss (gestational age (GA) ≤22 weeks) following a positive hCG and further stratified into: non-visualized pregnancy loss, early miscarriage (GA ≤ 12 weeks) and late miscarriage (GA > 12 weeks). Secondary outcomes were chance of clinical pregnancy and live birth per embryo transfer. Cox regression models were used to assess the risk of pregnancy loss. Time-to-event was measured from the day of embryo transfer from the second cycle and subsequent cycles. Logistic regression models were used to assess the chance of clinical pregnancy and live birth. The overall risk of pregnancy loss for the EOA group was comparable with the NOA group (adjusted hazard ratio: 1.04, 95% CI: 0.86; 1.26). Stratifying by pregnancy loss types showed comparable risks in the EOA and NOA group. The odds of achieving a clinical pregnancy or live birth per embryo transfer was lower in the EOA group compared to the NOA group (adjusted odds ratio: 0.77 (0.67; 0.88) and 0.78 (0.67; 0.90), respectively). Only women with at least two ART cycles were included. We had no information on the total doses of gonadotropin administered in each cycle. The present findings may indicate that mechanism(s) other than aneuploidy may explain the asynchrony between the normal-for-age risk of miscarriage and the reduced chance of implantation found in our patients with EOA. The results of this study could be valuable when counselling young patients with low ovarian reserve. The study was funded by the Health Research Fund of Central Denmark Region. The authors have no conflict of interest to declare. N/A.

Minding the gender gap in fertility: The rationale, obstacles, and strategies to improve utilization of fertility preservation

The aim of this commentary is to describe the sex differences in reproductive capacity and specifically the decline in oocyte quality and quantity with advancing age. Furthermore, the use of oocyte vitrification as a strategy to circumvent ovarian aging is discussed, as are disparities in access to fertility preservation.

Improvement of ovarian insufficiency from alginate oligosaccharide in mice

• In this study, the premature ovarian insufficiency model of female mice was established by the treatment of busulfan. • AOS treatment resulted in the recovery of reproductive hormone levels, follicular development and oocyte maturation. • The premature ovarian insufficiency induced by busulfan was significantly improved after AOS administration in mice. In the present society, owing to environmental and psychological pressure, female reproductive health issues are becoming increasingly prominent. Statistics report that approximately 15% childbearing age couples suffer from infertility worldwide. Alginate oligosaccharides (AOS) have recently attracted increased attention for their roles in the reproductive system, particularly in males. However, the role of AOS on ovarian development have not been previously reported. This study is aimed to investigate the effects of AOS on ovarian function disorder. In this study, female mice were treated with busulfan to establish a premature ovarian insufficiency model. Through comparative analysis of the ovarian function and follicular development in the control, busulfan treatment and AOS treated groups, the rescuing effect and mechanisms of AOS on ovarian insufficiency were explored. Our results for the first time revealed that the phenotype of premature ovarian insufficiency induced by busulfan treatment, in mice, was significantly improved after AOS administration. AOS treatment resulted in the recovery of reproductive hormone levels, up-regulated expression of follicular development-related key proteins, and the restoration of oocyte maturation and histone methylation modification. This provides a theoretical therapeutic approach for the prevention of ovarian and oocyte quality decline.

Role of Granulosa Cells in the Aging Ovarian Landscape: A Focus on Mitochondrial and Metabolic Function.

Mitochondria are at the intersection of aging and fertility, with research efforts centered largely on the role that these specialized organelles play in the relatively rapid decline in oocyte quality that occurs as females approach reproductive senescence. In addition to various roles in oocyte maturation, fertilization, and embryogenesis, mitochondria are critical to granulosa cell function. Herein, we provide a review of the literature pertaining to the role of mitochondria in granulosa cell function, with emphasis on how mitochondrial aging in granulosa cells may impact reproduction in female mammals.

FAM111A Is a Novel Molecular Marker for Oocyte Aging.

Aging is the main cause of decline in oocyte quality, which can further trigger the failure of assisted reproductive technology (ART). Exploring age-related genes in oocytes is an important way to investigate the molecular mechanisms involved in oocyte aging. To provide novel insight into this field, we performed a pooled analysis of publicly available datasets, using the overlapping results of two statistical methods on two Gene Expression Omnibus (GEO) datasets. The methods utilized in the current study mainly include Spearman rank correlation, the Wilcoxon signed-rank test, t-tests, Venn diagrams, Gene Ontology (GO), Protein–Protein Interaction (PPI), Gene Set Enrichment Analysis (GSEA), Gene Set Variation Analysis (GSVA), and receiver operating characteristic (ROC) curve analysis. We identified hundreds of age-related genes across different gene expression datasets of in vitro maturation-metaphase II (IVM-MII) oocytes. Age-related genes in IVM-MII oocytes were involved in the biological processes of cellular metabolism, DNA replication, and histone modifications. Among these age-related genes, FAM111A expression presented a robust correlation with age, seen in the results of different statistical methods and different datasets. FAM111A is associated with the processes of chromosome segregation and cell cycle regulation. Thus, this enzyme is potentially an interesting novel marker for the aging of oocytes, and warrants further mechanistic study.

Long-term treatment of Nicotinamide mononucleotide improved age-related diminished ovary reserve through enhancing the mitophagy level of granulosa cells in mice

Ovarian aging affects the reproductive health of elderly women due to decline in oocyte quality, which is closely related to mitochondrial dysfunction. Nicotinamide mononucleotide (NMN), as a precursor of NAD+, effectively regulate mitochondria metabolism in mice. However, roles of NMN in improving age-related diminished ovary reserve remain to be determined. In present study, 4, 8, 12, 24, 40-week old female ICR mice were collected and a 20-week-long administration of NMN was conducted to 40-week-old mice (60WN), meanwhile the control group is given water (60WC). First, we found that 20-week-long administration of NMN to 40-week-old mice exhibited anti-aging and anti-inflammatory effects on organ structures, along with the improvement of estrus cycle condition and endocrine function. The number of primordial, primary, secondary, antral follicles and corpora luteum of ovaries in 60WN group was significantly increased compared with those in 60WC group. Additionally, the protein and gene expressions of P16 of ovaries were significantly reduced in 60WN group than in 60WC group. the mitochondria biogenesis, autophagy level, and proteases activity enhanced in granulosa cells after 20-week-administration of NMN. Present results indicate that NMN has the potential to save diminished ovary reserve by long-term treatment, providing a basis for exploring the role of NMN in anti-ovarian aging by enhancing the mitophagy level of granulosa cells.

Oogenesis Arrest Prior to Birth: A Trade-off between Possible Evolutionary Advantages and Age-Related Oocyte Dysfunction?

Oogenesis in mammalian females, including humans, is arrested prior to birth. Females, therefore, are born with a limited number of primary oocytes. This is in direct contrast to males in whom spermatogenesis continues during the entire lifespan following puberty. Here, we discuss possible evolutionary advantages that this confers and contrast this with age-related decline in oocyte quality that results in diminished fertility with advancing maternal age. We believe that a better understanding of these processes would be helpful in developing strategies to preserve fertility as maternal age increases, especially in the context of the current demographic shift with more and more women seeking fertility treatment at advanced age.

Anti-Aging Effect of Urolithin A on Bovine Oocytes In Vitro.

Simple SummaryPost-ovulatory and maternal oocyte aging impair female reproductive capacity through several mechanisms that are not fully understood. Urolithin A (UA) is a natural compound previously identified to exert an anti-aging effects in several cells, which has never been used in bovine germinal cells. Our goal was to study UA effect on the developmental potential of the female gamete and the surround cumulus cells obtained from young and adult cows. A model for in vitro aging of female gametes was implemented to study different problems associated with reproductive aging and fertility impairment. Results confirmed that aging exerts a harmful effect on oocyte quality measured by using different parameters and gene expression levels of cumulus cells. Moreover, UA supplementation was an effective way to prevent oocyte aging, improving the subsequent bovine embryonic development.Oxidative stress and mitochondrial dysfunction have been associated with the age-related decline of oocyte quality and strategies for their prevention are currently quested. Urolithin A (UA) is a natural metabolite with pro-apoptotic and antioxidant effects, capable of preventing the accumulation of dysfunctional mitochondria in different aged cells. UA has never been tested in bovine oocytes. Our aim was to study the effect of UA on the developmental potential of cumulus-oocyte-complexes (COCs) and granulosa cells’ (GCs) expression of important genes related to reproductive competence. Nuclear maturation progression, mitochondrial membrane potential (MMP) and developmental competence of physiologically mature (22 h) and in vitro aged oocytes (30 h of IVM) obtained from prepubertal and adult females, either supplemented with UA or not were assessed. Additionally, the amount of mRNA of several genes (NFE2L2, NQO1, and mt-DN5) and the number of mt-ND5 DNA copies were quantified in cultured GCs from prepubertal and adult females, either supplemented with UA or not. Our study confirmed the harmful effect of oocyte aging on the nuclear maturation progression, MMP, developmental competence and gene expression levels. UA treatment during in vitro maturation enhanced (p < 0.05) the maturation rate and subsequent developmental capacity of aged oocytes. A positive effect (p < 0.05) of UA on physiological maturation, MMP and embryonic development was also identified. UA also interfered on the expression profile of NFE2L2 and NQO1 genes in GCs cultures. Our findings demonstrate that UA supplementation is an effective way to prevent oocyte aging and improves the subsequent bovine embryonic development.

Constitutive Expression of TERT Enhances β-Klotho Expression and Improves Age-Related Deterioration in Early Bovine Embryos.

Age-associated decline in oocyte quality is one of the dominant factors of low fertility. Aging alters several key processes, such as telomere lengthening, cell senescence, and cellular longevity of granulosa cells surrounding oocyte. To investigate the age-dependent molecular changes, we examined the expression, localization, and correlation of telomerase reverse transcriptase (TERT) and β-Klotho (KLB) in bovine granulosa cells, oocytes, and early embryos during the aging process. Herein, cumulus-oocyte complexes (COCs) obtained from aged cows (>120 months) via ovum pick-up (OPU) showed reduced expression of β-Klotho and its co-receptor fibroblast growth factor receptor 1 (FGFR1). TERT plasmid injection into pronuclear zygotes not only markedly enhanced day-8 blastocysts’ development competence (39.1 ± 0.8%) compared to the control (31.1 ± 0.5%) and D-galactose (17.9 ± 1.0%) treatment groups but also enhanced KLB and FGFR1 expression. In addition, plasmid-injected zygotes displayed a considerable enhancement in blastocyst quality and implantation potential. Cycloastragenol (CAG), an extract of saponins, stimulates telomerase enzymes and enhances KLB expression and alleviates age-related deterioration in cultured primary bovine granulosa cells. In conclusion, telomerase activation or constitutive expression will increase KLB expression and activate the FGFR1/β-Klotho pathway in bovine granulosa cells and early embryos, inhibiting age-related malfunctioning.

Longevity pathways are associated with human ovarian ageing.

STUDY QUESTIONAre genes known to be involved in somatic cell ageing, particularly related to longevity pathways, associated with the accelerated ageing process of the ovary?SUMMARY ANSWERGrowth, metabolism, and cell-cycle progression-related pathways that are involved in somatic cell ageing are also associated with ovarian ageing.WHAT IS KNOWN ALREADYOvarian ageing is characterized by a gradual decline in ovarian follicle quantity, a decline in oocyte quality, and lower chances of pregnancy. Genetic pathways modulating the rate of somatic cell ageing have been researched intensively. Ovarian ageing does not follow the same timeline as somatic cell ageing, as signs of ovarian ageing occur at a younger female age, while the somatic cells are still relatively young. It is not known whether the generally recognized somatic cell longevity genes also play a role during ovarian ageing. Looking at somatic cell longevity genes can lead to new hypotheses and possible treatment options for subfertility caused by ovarian ageing.STUDY DESIGN, SIZE, DURATIONIn this observational study, we analysed a dataset of individual gene expression profiles of 38 germinal vesicle (GV) oocytes from 38 women aged between 25 and 43 years. We correlated female age (calendar age in years) and biological age (factors known to be associated with ovarian ageing such as dosage of FSH needed for ovarian hyperstimulation, and antral follicle count (AFC)) with gene expression signatures of longevity pathways.PARTICIPANTS/MATERIALS, SETTING, METHODSTranscripts of 38 GV oocytes were used for individual gene expression analysis. R version 3.5.1 was used to process and analyse data. The GeneAge database (build 19) was used to obtain mouse ageing-related genes. Human to mouse orthologues were obtained using the R package biomaRt. Correlations and significance between gene expression data and age were tested for using Pearson's product moment correlation coefficient using ranked expression data. Distributions were compared with an ANOVA, and the Tukey Honest Significant Difference method was used to control for the Type I error rate across multiple comparisons.MAIN RESULTS AND THE ROLE OF CHANCEOf the 136 genes in the GeneAge database, the expression of 15 anti-longevity genes identified in oocytes showed a positive correlation with female calendar age and FSH dosage administered during ICSI treatment, and a negative correlation with AFC. Expression of 32 pro-longevity genes was negatively correlated with calendar age and FSH dosage, and positively correlated with AFC. In general, anti- and pro-longevity genes changed in opposing directions with advancing maternal age in oocytes. Notably, the anti-longevity genes include many ‘growth’-related genes involved in the mechanistic target of rapamycin (mTOR) Complex 1 pathway, such as EIF5A2, EIF3H, EIF4E, and mTOR. The pro-longevity genes include many cell-cycle progression-related genes involved in DNA damage repair (e.g. XRCC6, ERCC2, and MSH2) or cell-cycle checkpoint regulation genes (e.g. ATM, BRCA1, TP53, TP63, TP73, and BUB1B).LIMITATIONS, REASONS FOR CAUTIONUsing mature oocytes instead of GV-stage oocytes discarded from ICSI treatments may provide different results. No correction for multiple testing was carried out on individual genes because a small set of longevity-related genes was selected a priori for the analysis. The global trend was corrected for multiple testing and remained significant. This work was an observational study and, as no additional experimental work was performed, the associations described do not directly demonstrate the involvement of such genes in oocyte ageing.WIDER IMPLICATIONS OF THE FINDINGSGrowth, metabolism, and cell-cycle progression-related pathways that are known to be involved in somatic cell ageing were associated with ovarian ageing. If experimental data are obtained to support these associations, we suggest that interventions known to modulate these processes could benefit women suffering from ovarian ageing.STUDY FUNDING/COMPETING INTEREST(S)G.E.J. is supported by a VENI grant from ZonMw (https://www.zonmw.nl). Work in the Houtkooper group is financially supported by an ERC Starting grant (No. 638290), a VIDI grant from ZonMw (No. 91715305), and the Velux Stiftung (No. 1063). M.G. declares several research and educational grants from Guerbet, Merck and Ferring (all location VUmc), outside the scope of the submitted work. The other authors report no competing interestTRIAL REGISTRATION NUMBERN/A.

Growth hormone ameliorates the age-associated depletion of ovarian reserve and decline of oocyte quality via inhibiting the activation of Fos and Jun signaling.

Oocyte quality typically begins to decline with aging, which contributes to subfertility and infertility. However, there is still no effective treatment to restore the ovarian reserve and improve aged-oocyte quality. According to the present study, growth hormone (GH) secretion changes with maternal age in female mice. After intraperitoneal injection with GH (1 mg/kg body weight) every two days for two months, the 10-month-old mice showed a better ovarian reserve and oocyte quality than control mice. GH treatment decreased the occurrence rate of aneuploidy caused by spindle/chromosome defects. Additionally, the single oocyte transcriptome analysis indicated that GH decreased the expression of apoptosis-related genes in oocytes. It was also observed that GH treatment reduced the expression of γH2AX and apoptosis of aged oocytes via decreasing the activation of Fos and Jun. Collectively, our results indicate that GH treatment is an effective way to reverse the age-associated depletion of ovarian reserve and the decline of oocyte quality by decreasing apoptosis.

Particulate Matter Exposure During Oocyte Maturation: Cell Cycle Arrest, ROS Generation, and Early Apoptosis in Mice.

Particulate matter (PM) is a general atmospheric pollutant released into the air by an anthropogenic and naturally derived mixture of substances. Current studies indicate that fine dust can result in different health defects, including endothelial dysfunction, asthma, lung cancer, cardiovascular diseases, uterine leiomyoma, deterioration in sperm quality, and overall birth impairment. However, the most prominent effects of PM10 (diameter < 10 μM) exposure on the female reproductive system, especially with respect to oocyte maturation, remain unclear. In the present study, maturing mouse oocytes were treated with PM10 and the phenotypes of the resulting toxic effects were investigated. Exposure to PM10 led to impairment of maturation capacity by inducing cell cycle arrest and blocking normal polar body extrusion during in vitro maturation and activation of fertilization of mouse oocytes. Additionally, defects in tubulin formation and DNA alignment were observed in PM10-treated oocytes during metaphase I to anaphase/telophase I transition. Moreover, PM10 induced reactive oxygen species generation, mitochondrial dysfunction, DNA damage, and early apoptosis. Taken together, these results indicate that PM10 exposure leads to a decline in oocyte quality and affects the subsequent embryonic development potential of mammalian oocytes.

Melatonin Attenuates Peroxynitrite-Induced Meiosis Dysfunction in Porcine Oocytes.

A high level of reactive oxygen species (ROS) is widely considered one of the major causes of oocyte quality decline. Peroxynitrite is known as a powerful oxidant, which could induce multiple physical diseases. Recently, emerging pieces of evidences indicate that melatonin effectively promotes the development of oocytes, although the specific work mechanism remains to be further clarified. In this study, it was shown that peroxynitrite increased the level of ROS in porcine oocytes, which induced the apoptosis of oocytes, thereby leading to the obstruction of spindle assembly, depolymerization of actin, and decrease of polar body expulsion. These negative effects contributed to the failure of meiosis and ultimately blocked the maturation of porcine oocytes. As expected, it was found that melatonin effectively removed the accumulated ROS in oocytes, preventing oocytes from peroxynitrite-induced oocyte maturation failure, which might provide a novel approach to improve female livestock reproduction and cure female infertility in clinical practice.

Pachymic acid protects oocyte by improving the ovarian microenvironment in polycystic ovary syndrome mice†.

Women with polycystic ovary syndrome (PCOS) are characterized by endocrine disorders accompanied by a decline in oocyte quality. In this study, we generated a PCOS mice model by hypodermic injection of dehydroepiandrosterone, and metformin was used as a positive control drug to study the effect of pachymic acid (PA) on endocrine and oocyte quality in PCOS mice. Compared with the model group, the mice treated with PA showed the following changes (slower weight gain, improved abnormal metabolism; increased development potential of GV oocytes, reduced number of abnormal MII oocytes, and damaged embryos; lower expression of ovarian-related genes in ovarian tissue and pro-inflammatory cytokines in adipose tissue). All these aspects show similar effects on metformin. Most notably, PA is superior to metformin in improving inflammation of adipose tissue and mitochondrial abnormalities. It is suggested that PA has the similar effect with metformin, which can improve the endocrine environment and oocyte quality of PCOS mice. These findings suggest that PA has the similar effect with metformin, which can improve the endocrine environment and oocyte quality of PCOS mice.

Procyanidin B2 Improves Oocyte Maturation and Subsequent Development in Type 1 Diabetic Mice by Promoting Mitochondrial Function.

Type 1 diabetes (T1D) results in decreased oocyte quality and compromised early embryonic development. Procyanidin B2 (PB2) is a natural compound extracted from grape seeds and has strong antioxidant activity in vivo. This study evaluated the effect of PB2 on oocyte maturation in diabetic mice. Diabetic mice were induced by streptozotocin (STZ) injection. PB2 was supplemented in the in vitro maturation medium, and the ratio of germinal vesicle breakdown (GVBD) and polar body extrusion (PBE), reactive oxygen species (ROS) levels, mitochondrial function, developmental ability, as well as crotonylation at H4K5 were determined in oocytes. PB2 can promote the extrusion of PBE (88.34% vs. 75.02%, P < 0.05); reduce the generation of ROS (1.12 vs. 1.96, P < 0.05); and improve the level of mitochondrial membrane potential (0.87 vs. 0.79 Δφm, P < 0.05), ATP level (1.31 vs. 0.71pmol, P < 0.05), and mitochondria temperature (618.25 vs. 697.39pixels, P < 0.05). The addition of PB2 also improved the level of oocyte crotonylation at H4K5 (crH4K5) (47.26 vs. 59.68pixels, P < 0.05) and increased the blastocyst rate (61.51% vs. 36.07%, P < 0.05) after parthenogenetic activation. Our results are the first to reveal a role for PB2 in promoting the viability of oocytes by regulating the mitochondrial function. Moreover, we uncover that PB2 can improve the level of crH4K5, which provides a new strategy to combat the decline in oocyte quality of diabetic.

Nicotinamide Mononucleotide Supplementation Reverses the Declining Quality of Maternally Aged Oocytes

Advanced maternal age is highly associated with a decline in oocyte quality, but effective approaches to improve it have still not been fully determined. Here, we report that invivo supplementation of nicotinamide mononucleotide (NMN) efficaciously improves the quality of oocytes from naturally aged mice by recovering nicotinamide adenine dinucleotide (NAD+) levels. NMN supplementation not only increases ovulation of aged oocytes but also enhances their meiotic competency and fertilization ability by maintaining the normal spindle/chromosome structure and the dynamics of the cortical granule component ovastacin. Moreover, single-cell transcriptome analysis shows that the beneficial effect of NMN on aged oocytes is mediated by restoration of mitochondrial function, eliminating the accumulated ROS to suppress apoptosis. Collectively, our data reveal that NMN supplementation is a feasible approach to protect oocytes from advanced maternal age-related deterioration, contributing to the improvement of reproductive outcome of aged women and assisted reproductive technology.

Sirt1 sustains female fertility by slowing age-related decline in oocyte quality required for post-fertilization embryo development.

The NAD+‐dependent sirtuin deacetylase, Sirt1, regulates key transcription factors strongly implicated in ageing and lifespan. Due to potential confounding effects secondary to loss of Sirt1 function from the soma in existing whole‐animal mutants, the in vivo role of Sirt1 in oocytes (oocyte‐Sirt1) for female fertility remains unknown. We deleted Sirt1 specifically in growing oocytes and study how loss of oocyte‐Sirt1 affects a comprehensive range of female reproductive parameters including ovarian follicular reservoir, oocyte maturation, oocyte mitochondrial abundance, oxidative stress, fertilization, embryo development and fertility during ageing. Surprisingly, eliminating this key sirtuin from growing oocytes has no effect in young females. During a 10‐month‐long breeding trial, however, we find that 50% of females lacking oocyte‐Sirt1 become prematurely sterile between 9 and 11 months of age when 100% of wild‐type females remain fertile. This is not due to an accelerated age‐related decline in oocyte numbers in the absence of oocyte‐Sirt1 but to reduced oocyte developmental competence or quality. Compromised oocyte quality does not impact in vivo oocyte maturation or fertilization but leads to increased oxidative stress in preimplantation embryos that inhibits cleavage divisions. Our data suggest that defects emerge in aged females lacking oocyte‐Sirt1 due to concurrent age‐related changes such as reduced NAD+ and sirtuin expression levels, which compromise compensatory mechanisms that can cover for Sirt1 loss in younger oocytes. In contrast to evidence that increasing Sirt1 activity delays ageing, our data provide some of the only in vivo evidence that loss of Sirt1 induces premature ageing.

Subcortical maternal complex (SCMC) expression during folliculogenesis is affected by oocyte donor age in sheep

The age-associated decline in female fertility is largely ascribable to the decrease in oocyte quality. The subcortical maternal complex (SCMC) is a multiprotein complex essential for early embryogenesis and female fertility and functionally conserved across mammals. The present work evaluated expression dynamics of its components during folliculogenesis in relation to maternal age in sheep. The expression of the SCMC components (KHDC3/FILIA, NLRP2, NLRP5/MATER, OOEP/FLOPED, PADI6, TLE6 and ZBED3) was analyzed by real-time PCR in pools of growing oocytes (GO) of different diameters (70-90 μm (S), 90-110 μm (M), or 110-130 μm (L)) derived from non-hormonally treated adult (Ad; age < 4 years), prepubertal (Pr; age 40 days), or aged ewes (age > 6 years). Specific expression patterns associated with donor age were observed during folliculogenesis for all genes, except ZBED3. In oocytes of adult donors, the synthesis of NLRP2, NLRP5, PADI6, and ZBED3 mRNAs was complete in S GO, while FILIA, TLE6, and OOEP were actively transcribed at this stage. Conversely, Pr GO showed active transcription of all mRNAs, except for ZBED3, during the entire window of oocyte growth. Notably, aged GO showed a completely inverse pattern, with a decrease of NLRP2, TLE6, FILIA, and PADI6 mRNA abundance during the latest stage of oocyte growth (L GO). Interestingly, MATER showed high expression variability, suggesting large inter-oocyte differences. Our study describes the SCMC expression dynamics during sheep oogenesis and reports age-specific patterns that are likely involved in the age-related decline of oocyte quality.