Stress In Oocytes Research Articles

SCM-198 ameliorates the quality of postovulatory and maternally aged oocytes by reducing oxidative stress

Oocyte aging is a key constraint on oocyte quality, leading to fertilization failure and abnormal embryonic development. In addition, it is likely to generate unfavorable assisted reproductive technology (ART) outcomes. SCM-198, a synthetic form of leonurine, was found to rescue the rate of oocyte fragmentation caused by postovulatory aging. Therefore, the aim of this study was to conduct a more in-depth investigation of SCM-198 by exploring its relationship with aged oocytes after ovulation or maternal aging and clarifying whether it affects cell quality. The results indicate that, compared to the postovulatory aged group, the 50 µM SCM-198 group significantly improved sperm-egg binding and increased fertilization of aged oocytes, restoring the spindle apparatus/chromosome structure, cortical granule distribution, and ovastacin and Juno protein distribution. The 50 µM SCM-198 group showed significantly normal mitochondrial distribution, low levels of reactive oxygen species (ROS), and a small quantity of early oocyte apoptosis compared to the postovulatory aged group. Above all, in vivo supplementation with SCM-198 effectively eliminated excess ROS and reduced the spindle/chromosome structural defects in aged mouse oocytes. In summary, these findings indicate that SCM-198 inhibits excessive oxidative stress in oocytes and alters oocyte quality both in vitro and in vivo.Graphical

Loss of AMPK activity induces organelle dysfunction and oxidative stress during oocyte aging

BackgroundOocyte quality is critical for the mammalian reproduction due to its necessity on fertilization and early development. During aging, the declined oocytes showing with organelle dysfunction and oxidative stress lead to infertility. AMP-activated protein kinase (AMPK) is a serine/threonine protein kinase which is important for energy homeostasis for metabolism. Little is known about the potential relationship between AMPK with oocyte aging.ResultsIn present study we reported that AMPK was related with low quality of oocytes under post ovulatory aging and the potential mechanism. We showed the altered AMPK level during aging and inhibition of AMPK activity induced mouse oocyte maturation defect. Further analysis indicated that similar with its upstream regulator PKD1, AMPK could reduce ROS level to avoid oxidative stress in oocytes, and this might be due to its regulation on mitochondria function, since loss of AMPK activity induced abnormal distribution, reduced ATP production and mtDNA copy number of mitochondria. Besides, we also found that the ER and Golgi apparatus distribution was aberrant after AMPK inhibition, and enhanced lysosome function was also observed.ConclusionsTaken together, these data indicated that AMPK is important for the organelle function to reduce oxidative stress during oocyte meiotic maturation.

Peptide derived from RAGE efficiently improves oocyte development through attenuating oxidative stress in oocytes of mice with polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is a common and complex endocrine disorder in reproductive-aged women that frequently leads to infertility due to poor oocyte quality. In this study, we identified a new active peptide (advanced glycation end products receptors RAGE344-355 ) from PCOS follicular fluid using mass spectrometry. We found that supplementing PCOS-like mouse oocytes with RAGE344-355 attenuated both meiotic defects and oxidative stress levels, ultimately preventing developmental defects. Additionally, our results suggest that RAGE344-355 may interact with eEF1a1 to mitigate oxidative meiotic defects in PCOS-like mouse oocytes. These findings highlight the potential for further clinical development of RAGE344-355 as a potent supplement and therapeutic option for women with PCOS. This research addresses an important clinical problem and offers promising opportunities for improving oocyte quality in PCOS patients.

Sulforaphane alleviates the meiosis defects induced by 3-nitropropionic acid in mouse oocytes

3-Nitropropionic acid (3-NP) is a mycotoxin commonly found in plants and fungi that has been linked to mammalian intoxication. Previously, we found 3-NP treatment exhibited reproductive toxicity by inducing oxidative stress in mouse ovary; however, the toxic effects of 3-NP on mouse oocyte maturation have not been investigated. Sulforaphane (SFN) is a naturally bioactive phytocompound derived from cruciferous vegetables that has been shown to possess cytoprotective properties. The present study was designed to investigate the cytotoxicity of 3-NP during mouse oocyte maturation and the protective effects of SFN on oocytes challenged with 3-NP. The results showed 3-NP had a dose-dependent inhibitory effect on oocyte maturation, and SFN significantly alleviated the defects caused by 3-NP, including failed first polar body extrusion and abnormal spindle assembly. Furthermore, 3-NP caused abnormal mitochondrial distribution in oocytes and disrupted mitochondrial functions, including mitochondrial depolarization, decreased ATP levels, and increased mitochondrial-derived ROS. Finally, 3-NP induced oxidative stress in oocytes, leading to increased apoptosis and autophagy, while SFN supplementation had significant cytoprotective effects on these damages. Collectively, our results provide insight on the mechanism of 3-NP toxicity in mouse oocytes and suggest the application of SFN may be a viable intervention strategy to mitigate 3-NP-induced reproductive toxicity.

Equine maternal aging affects the metabolomic profile of oocytes and follicular cells during different maturation time points.

Introduction: Oocyte quality and fertility decline with advanced maternal age. During maturation within the ovarian follicle, the oocyte relies on the associated somatic cells, specifically cumulus and granulosa cells, to acquire essential components for developmental capacity. Methods: A nontargeted metabolomics approach was used to investigate the effects of mare age on different cell types within the dominant, follicular-phase follicle at three time points during maturation. Metabolomic analyses from single oocytes and associated cumulus and granulosa cells allowed correlations of metabolite abundance among cell types. Results and Discussion: Overall, many of the age-related changes in metabolite abundance point to Impaired mitochondrial metabolic function and oxidative stress in oocytes and follicular cells. Supporting findings include a higher abundance of glutamic acid and triglycerides and lower abundance of ceramides in oocytes and somatic follicular cells from old than young mares. Lower abundance of alanine in all follicular cell types from old mares, suggests limited anaerobic energy metabolism. The results also indicate impaired transfer of carbohydrate and free fatty acid substrates from cumulus cells to the oocytes of old mares, potentially related to disruption of transzonal projections between the cell types. The identification of age-associated alterations in the abundance of specific metabolites and their correlations among cells contribute to our understanding of follicular dysfunction with maternal aging.

Effect of heat exposure on the growth and developmental competence of bovine oocytes derived from early antral follicles

In dairy cows, low fertility caused by summer heat stress continues into the cooler autumn season. This can be caused by impaired oocyte quality in small growing follicles during summer. Here, we subjected oocyte–cumulus–granulosa complexes (OCGCs) derived from early antral follicles (0.5–1 mm) to in vitro growth (IVG) culture under two different temperature settings (the control and heat shock groups), and evaluated effects of heat exposure on growth and developmental competence of oocytes, factors affecting the developmental competence of oocytes (steroidogenesis of granulosa cells, oxidative stress in oocytes, and cell-to-cell communication between oocytes and somatic cells). Oocyte diameters after culture were smaller in the heat shock group. Although nuclear maturation and cleavage rates were similar between the groups, blastocyst rates were lower in the heat shock group (0.0%) than in the control group (27.7%), and reduced glutathione (GSH) levels in oocytes were lower in the heat shock group. Supplementation of cysteine, which stimulates GSH synthesis, increased GSH level and improved blastocyst rate of heat shocked oocytes (27.9%). These results suggest that heat exposure impairs the growth and developmental competence of oocytes in early antral follicles through GSH depletion, which can induce low fertility during summer and the following autumn.

Toxicological impacts of nanopolystyrene on zebrafish oocyte with insight into the mechanism of action: An expression-based analysis

Many studies have investigated the negative impacts of microplastics on teleost fishes with very little or no evidence of their mechanism of action. This scenario entreats us to investigate the toxicities of nanopolystyrene in zebrafish oocyte with emphasis on the mechanism of action. In the present study, the cellular levels of mRNA transcripts of different genetic markers (such as: sod, gpx, nrf2, inos, ucp2, and atp6 (redox-sensitive markers); nfkβ, tnfα, il-10, ikβ, gdf9, and bmp15 (immune markers); gadd45, rad51, p53 and bcl2 (DNA damage and apoptotic)) have been quantified by real-time PCR after 6 h of incubation of isolated oocyte with different doses of nanopolystyrene viz. P0 (control i.e. no polystyrene in culture medium), P1 (100 ng/ml), and P2 (400 ng/ml). Results showed that both the treatment concentrations of nanopolystyrene induce oxidative stress with % DPPH = 30.75, 31.61, and 32.43% for P0, P1, and P2, respectively. Increase in oxidative stress in oocytes with increasing doses of nanopolystyrene was also observed in TBARS assay with MDA content 0.12 and 0.21 μM for P1 and P2, respectively as compaired to the control 0.08 μM. This increased oxidative stress can regulate the expression pattern (upregulation/downregulation) of selected genes leading to different toxic effects like – oxidative stress, immunotoxicity, and apoptosis in oocytes, which suggests the impairment of reproductive functions by nanopolystyrene.

Effects of BPA, BPS, and BPF on Oxidative Stress and Antioxidant Enzyme Expression in Bovine Oocytes and Spermatozoa.

Bisphenol A (BPA) and its analogs, bisphenol S (BPS) and bisphenol F (BPF), might impact fertility by altering oxidative stress pathways. Here, we hypothesize that bisphenols-induced oxidative stress is responsible for decreased gamete quality. In both female (cumulus-oocyte-complexes—COCs) and male (spermatozoa), oxidative stress was measured by CM-H2DCFDA assay and key ROS scavengers (SOD1, SOD2, GPX1, GPX4, CAT) were quantified at the mRNA and protein levels using qPCR and Western blot (COCs)/immunofluorescence (sperm). Either gamete was treated in five groups: control, vehicle, and 0.05 mg/mL of BPA, BPS, or BPF. Our results show elevated ROS in BPA-treated COCs but decreased production in BPS- and BPF-treated spermatozoa. Additionally, both mRNA and protein expression of SOD2, GPX1, and GPX4 were decreased in BPA-treated COCs (p < 0.05). In sperm, motility (p < 0.03), but not morphology, was significantly altered by bisphenols. SOD1 mRNA expression was significantly increased, while GPX4 was significantly reduced. These results support BPA’s ability to alter oxidative stress in oocytes and, to a lesser extent, in sperm. However, BPS and BPF likely act through different mechanisms.

Redox Regulation and Oxidative Stress in Mammalian Oocytes and Embryos Developed In Vivo and In Vitro.

Oocytes and preimplantation embryos require careful regulation of the redox environment for optimal development both in vivo and in vitro. Reactive oxygen species (ROS) are generated throughout development as a result of cellular metabolism and enzyme reactions. ROS production can result in (i) oxidative eustress, where ROS are helpful signalling molecules with beneficial physiological functions and where the redox state of the cell is maintained within homeostatic range by a closely coupled system of antioxidants and antioxidant enzymes, or (ii) oxidative distress, where excess ROS are deleterious and impair normal cellular function. in vitro culture of embryos exacerbates ROS production due to a range of issues including culture-medium composition and laboratory culture conditions. This increase in ROS can be detrimental not only to assisted reproductive success rates but can also result in epigenetic and genetic changes in the embryo, resulting in transgenerational effects. This review examines the effects of oxidative stress in the oocyte and preimplantation embryo in both the in vivo and in vitro environment, identifies mechanisms responsible for oxidative stress in the oocyte/embryo in culture and approaches to reduce these problems, and briefly examines the potential impacts on future generations.

NAMPT reduction-induced NAD+ insufficiency contributes to the compromised oocyte quality from obese mice.

Maternal obesity is associated with multiple adverse reproductive outcomes, whereas the underlying molecular mechanisms are still not fully understood. Here, we found the reduced nicotinamide phosphoribosyl transferase (NAMPT) expression and lowered nicotinamide adenine dinucleotide (NAD+) content in oocytes from obese mice. Next, by performing morpholino knockdown assay and pharmacological inhibition, we revealed that NAMPT deficiency not only severely disrupts maturational progression and meiotic apparatus, but also induces the metabolic dysfunction in oocytes. Furthermore, overexpression analysis demonstrated that NAMPT insufficiency induced NAD+ loss contributes to the compromised developmental potential of oocytes and early embryos from obese mice. Importantly, in vitro supplement and in vivo administration of nicotinic acid (NA) was able to ameliorate the obesity‐associated meiotic defects and oxidative stress in oocytes. Our results indicate a role of NAMPT in modulating oocyte meiosis and metabolism, and uncover the beneficial effects of NA treatment on oocyte quality from obese mice.

Bezafibrate prevents aging in in vitro-matured porcine oocytes.

Bezafibrate, a fibrate drug used as a lipid-lowering agent to treat hyperlipidemia, is a pan-agonist of peroxisome proliferator-activated receptor alpha. It can enhance mitochondrial fatty acid oxidation, oxidative phosphorylation, and mitochondrial biogenesis. After ovulation, oocytes may get arrested at the metaphase II (MII) stage until fertilization beyond optimal timing, which is termed as post-ovulatory aging. Post-ovulatory aging is a disease that degrades DNA, mitochondria, and oxidative system, and has a negative impact on embryo development and quality; however, the impact of bezafibrate during post-ovulatory aging has not been fully defined. In the present study, we assessed the ability of bezafibrate to prevent the progression of aging in in vitro conditions as well as the underlying mechanisms in pigs. An appropriate concentration of this drug (50 μM) was added, and then oxidative stress, reactive oxygen species downstream, mitochondrial biogenesis, and mitochondrial function were analyzed via immunofluorescence staining and real-time polymerase chain reaction. Bezafibrate significantly alleviated reactive oxygen species and ameliorated glutathione production simultaneously in oocytes and embryos. Moreover, it diminished H2A.X and attenuated CASPASE 3 expression produced by oxidative stress in oocytes and embryos. Furthermore, bezafibrate remarkably improved the mitochondrial function and blastocyst quality as well as markedly reduced the mitochondria/TOM20 ratio and mtDNA copy number. The elevated PARKIN level indicated that mitophagy was induced by bezafibrate treatment after post-ovulatory aging. Collectively, these results suggest that bezafibrate beneficially affects against porcine post-ovulatory oocyte aging in porcine by its antioxidant property and mitochondrial protection.

Oxidative Stress in Oocytes and Embryo Development: Implications for In Vitro Systems.

Significance: To improve the outcomes of in vitro culture of human oocytes and embryos, the dynamic balance and roles of reactive oxygen species (ROS) in folliculogenesis and embryo development merit further consideration. Recent Advances: ROS have been demonstrated to participate in various signaling processes and act as mediators in various physiological events in germ cells. An imbalance between pro-oxidants and antioxidants seems to explain the high failure rate of assisted reproduction. Critical Issues: Oxidative stress induced by excessive ROS or insufficient antioxidant protection can cause detrimental effects on both male and female reproduction. In this study, oxidative stress in folliculogenesis and embryo development are summarized and the multiple modifiable factors of in vitro culture systems in relation to ROS are discussed. Future Directions: More studies are needed to establish an optimal redox state in in vitro culture systems for human oocytes and embryos.

Mice born to females with oocyte-specific deletion of mitofusin 2 have increased weight gain and impaired glucose homeostasis.

Offspring born to obese and diabetic mothers are prone to metabolic diseases, a phenotype that has been linked to mitochondrial dysfunction and endoplasmic reticulum (ER) stress in oocytes. In addition, metabolic diseases impact the architecture and function of mitochondria-ER contact sites (MERCs), changes which associate with mitofusin 2 (MFN2) repression in muscle, liver and hypothalamic neurons. MFN2 is a potent modulator of mitochondrial metabolism and insulin signaling, with a key role in mitochondrial dynamics and tethering with the ER. Here, we investigated whether offspring born to mice with MFN2-deficient oocytes are prone to obesity and diabetes. Deletion of Mfn2 in oocytes resulted in a profound transcriptomic change, with evidence of impaired mitochondrial and ER function. Moreover, offspring born to females with oocyte-specific deletion of Mfn2 presented increased weight gain and glucose intolerance. This abnormal phenotype was linked to decreased insulinemia and defective insulin signaling, but not mitochondrial and ER defects in offspring liver and skeletal muscle. In conclusion, this study suggests a link between disrupted mitochondrial/ER function in oocytes and increased risk of metabolic diseases in the progeny. Future studies should determine whether MERC architecture and function are altered in oocytes from obese females, which might contribute toward transgenerational transmission of metabolic diseases.

Iodoacetic acid disrupts mouse oocyte maturation by inducing oxidative stress and spindle abnormalities

Disinfection by-products (DBPs) are compounds produced during the water disinfection process. Iodoacetic acid (IAA) is one of the unregulated DBPs in drinking water, with potent cytotoxicity and genotoxicity in animals. However, whether IAA has toxic effects on oocyte maturation remains unclear. Here, we show that IAA exposure resulted in metaphase I (MI) arrest and polar-body-extrusion failure in mouse oocytes, indicating that IAA had adverse effects on mouse oocyte maturation in vitro. Particularly, IAA treatment caused abnormal spindle assembly and chromosome misalignment. Previous studies reported that IAA is a known inducer of oxidative stress in non-germline cells. Correspondingly, we found that IAA exposure increased the reactive oxygen species (ROS) levels in oocytes in a dose-dependent manner, indicating IAA exposure could induce oxidative stress in oocytes. Simultaneously, DNA damage was also elevated in the nuclei of these IAA-exposed mouse oocytes, evidenced by increased γ-H2AX focus number. In addition, the un-arrested oocytes entered metaphase II (MII) with severe defects in spindle morphologies and chromosome alignment after 14-h IAA treatment. An antioxidant, N-acetyl-L-cysteine (NAC), reduced the elevated ROS level and restored the meiotic maturation in the IAA-exposed oocytes, which indicates that IAA-induced maturation failure in oocytes was mainly mediated by oxidative stress. Collectively, our results indicate that IAA exposure interfered with mouse oocyte maturation by elevating ROS levels, disrupting spindle assembly, inducing DNA damage, and causing MI arrest.

DRP1 deficiency induces mitochondrial dysfunction and oxidative stress-mediated apoptosis during porcine oocyte maturation

BackgroundEnvironmental pollution induces oxidative stress and apoptosis in mammalian oocytes, which can cause defects in reproduction; however, the molecular regulation of oxidative stress in oocytes is still largely unknown. In the present study, we identified that dynamin-related protein 1 (DRP1) is an important molecule regulating oocyte mitochondrial function and preventing oxidative stress/apoptosis. DRP1 is a member of the dynamin GTPase superfamily localized at the mitochondrial-endoplasmic reticulum interaction site, where it regulates the fission of mitochondria and other related cellular processes.ResultsOur results show that DRP1 was stably expressed during different stages of porcine oocyte meiosis, and might have a potential relationship with mitochondria as it exhibited similar localization. Loss of DRP1 activity caused failed porcine oocyte maturation and cumulus cell expansion, as well as defects in polar body extrusion. Further analysis indicated that a DRP1 deficiency caused mitochondrial dysfunction and induced oxidative stress, which was confirmed by increased reactive oxygen species levels. Moreover, the incidence of early apoptosis increased as detected by positive Annexin-V signaling.ConclusionsTaken together, our results indicate that DRP1 is essential for porcine oocyte maturation and that a DRP1 deficiency could induce mitochondrial dysfunction, oxidative stress, and apoptosis.

Epigallocatechin-3-gallate (EGCG) protects the oocytes from methyl parathion-induced cytoplasmic deformities by suppressing oxidative and endoplasmic reticulum stress

Methyl parathion (MP) is a commonly used organophosphorus insecticide in commercial farming. It is well known that MP exposure can affect the function of nervous, respiratory, cardiovascular and reproductive systems. In our previous report we have demonstrated that MP exposure results in poor oocyte maturation and defective embryo development which is mainly mediated through oxidative stress. The present investigation was designed to explore whether using a potent free radical scavenger like Epigallocatechin-3-gallate (EGCG) can help in reducing the detrimental effects of MP on the oocytes. For the study, germinal vesicle (GV) stage oocytes collected from the ovaries of adult Swiss albino mice were subjected to in vitro maturation (IVM) in the presence or absence of MP (100 μg/mL) and/or EGCG (0.25 μM). MP significantly reduced the nuclear maturation rate, and resulted in poor cytoplasmic organization which was evident from the altered distribution pattern of mitochondria, endoplasmic reticulum and abnormal spindle organization. These changes were associated with significant elevation in oxidative stress and expression of ER stress markers such as 78 kDa Glucose regulated protein (GRP78) as well as X-box binding protein-1 (XBP1) in the oocytes. Further, the oocytes exposed to MP had lower activation rate and developmental potential. Supplementation of EGCG during IVM not only improved the nuclear maturation rate but also reduced the cytoplasmic abnormalities. These beneficial effects appear to be due to mitigation of oxidative and ER stress in oocytes. In conclusion, results of our study indicate that EGCG can help in alleviating MP-induced oocyte abnormalities.

High-fat diet leads to elevated lipid accumulation and endoplasmic reticulum stress in oocytes, causing poor embryo development.

The present study was designed to investigate the effect of diet-induced obesity on endoplasmic reticulum (ER) stress in oocytes. Swiss albino mice (3 weeks old) were fed with a high-fat diet (HFD) for 8 weeks. Oocytes were assessed for lipid droplet accumulation, oxidative stress, ER stress and their developmental potential invitro. High lipid accumulation (P<0.01) and elevated intracellular levels of reactive oxygen species were observed in both germinal vesicle and MII oocytes of HFD-fed mice (P<0.05 and P<0.01 respectively compared with control). Further, expression of the ER stress markers X-box binding protein 1 (XBP1), glucose-regulated protein 78 (GRP78), activating transcription factor 4 (ATF4) and activating transcription factor 6 (ATF6) was significantly (P<0.001) higher in oocytes of the HFD than control group. Oocytes from HFD-fed mice exhibited poor fertilisation and blastocyst rates, a decrease in total cell number and high levels of DNA damage (P<0.01) compared with controls. In conclusion, diet-induced obesity resulted in elevated lipid levels and higher oxidative and ER stress in oocytes, which contributed to the compromised developmental potential of embryos.

Ibuprofen at environmentally relevant concentrations alters embryonic development, induces teratogenesis and oxidative stress in Cyprinus carpio

Ibuprofen (IBU) is a non-steroidal anti-inflammatory (NSAIDs) that is used in various conditions. The prescriptions and the global consumption of this drug are very high and its annual production oscillates in millions of tons, this generates that the IBU is present in many waterbodies because it is discharged through the municipal, hospital and industrial effluents. For the above, the purpose of this work was to determine if IBU at environmentally relevant concentrations was capable of inducing alterations to embryonic development, teratogenic effects and oxidative stress in oocytes and embryos of Cyprinus carpio. Oocytes of common carp were exposed to IBU concentrations between 1.5 and 11.5 μg L−1 (environmentally relevant). LC50 and EC50 of malformations were determined to calculate the teratogenic index (TI). Also, main alterations to embryonic development and teratogenic effects were evaluated. Oxidative stress was evaluated by determining biomarkers of cellular oxidation and antioxidation using the same concentrations at 72 and 96 hpf in embryos of Cyprinus carpio. The results showed a LC50 of 4.17 μg L−1, EC50 of 1.39 μg L−1 and TI of 3.0. The main embryonic development disorders and teratogenic effects were delayed hatching, hypopigmentation, pericardial edema, yolk deformation, and developmental delay. Biomarkers of cellular oxidation and antioxidants were increased with respect to the control in a concentration-dependent manner. The results of the study allow us to conclude that IBU at environmentally relevant concentrations is capable of inducing embryotoxicity and teratogenicity in a fish of commercial interest like Cyprinus carpio.

175 Nobiletin enhances the quality of in vitro-matured bovine oocytes and blastocysts by altering the transcription of key developmental genes

One of the problems associated with in vitro production of embryos in bovine is the increase in reactive oxygen species (ROS), which leads to cell alterations and death. Nobiletin is a polymethoxyflavone isolated from citrus fruits with various beneficial effects on cell cycle regulation and inhibition of ROS production. In a preliminary study, we demonstrated that supplementation of 25 or 50 µM nobiletin to the in vitro maturation (IVM) medium reduces oxidative stress and improves oocyte nuclear and cytoplasmic maturation and embryo development. Thus, in this study, we aimed to evaluate the antioxidant activity of nobiletin during IVM on bovine matured oocytes, their cumulus cells (CC), and blastocysts by quantitative changes of gene expression. Immature cumulus oocytes complexes (COC) were aspirated from ovaries of slaughtered heifers. Selected COC underwent IVM in TCM-199+10% FCS and 10ng mL−1 epidermal growth factor (EGF; Control) supplemented with 25 µM (Nob25) or 50 µM (Nob50) nobiletin (MedChemExpress, Monmouth Junction, NJ, USA) or 0.001% dimethyl sulfoxide (DMSO control), a vehicle for nobiletin dilution, in 5% CO2 in air at 38.5°C. After 24h, 50 matured oocytes/group and their CC were snap-frozen in LN2 for gene expression analysis. The remaining oocytes were fertilized (Day 0) and cultured in vitro. Blastocysts (Day 7; n=50/group) were snap-frozen in LN2 for gene expression analysis (5 replicates). The mRNA abundance of candidate genes related with oxidative stress (SOD2, CYP51); apoptosis (BAX); quality (BMP15, BMP7, CLIC1, MAPK1, ABCB1); and cell junction (GJA1) was measured by quantitative PCR; H2AFZ and 18S rRNA were used as housekeeping genes. Statistical significance was assessed by one-way ANOVA. Supplementation of IVM medium with Nob25 or Nob50 produced changes in the expression levels of genes related to oxidative stress and apoptosis during IVM compared with controls. SOD2 and CYP51 were down-regulated in oocytes and CC (P&amp;lt;0.05) but not in blastocysts, whereas BAX was down-regulated only in CC (P&amp;lt;0.05). Nobiletin supplementation in IVM increased the expression of MAPK1 in oocytes and blastocysts (P&amp;lt;0.05); however, no differences were observed in CC. BMP15 for oocytes and their CC and GJA1 for CC were up-regulated in Nob25 and Nob50 groups compared with controls (P&amp;lt;0.05). The relative abundance of CLIC1 decreased in blastocysts from both nobiletin groups compared with controls (P&amp;lt;0.05). No significant differences in the expression in ABCB1 and BMP7 were detected. In conclusion, our results suggest that supplementation of 25 or 50 µM nobiletin to the IVM medium reduces oxidative stress in oocytes and CC, decreases CC apoptosis, and provokes positive changes in the expression of genes related to oocyte and embryo quality. This research was supported by Spanish MINECO (AGL2015-70140-R and AGL2015-66145-R). Y. N. Cajas was supported by a grant from SENESCYT-Ecuador.

SIRT7 functions in redox homeostasis and cytoskeletal organization during oocyte maturation.

SIRT7, a member of the sirtuin family, with coenzyme NAD catalyzes protein deacetylation and has been implicated in multiple biologic processes; however, its function in mammalian oocytes remains to be explored. Here, we report disrupted meiotic maturation upon specific knockdown of SIRT7 in mouse oocytes. In particular, disorganized spindle/chromosomes and the loss of the cortical actin cap are readily observed in SIRT7-depleted oocytes, generating aneuploid eggs. Furthermore, we found that SIRT7 depletion markedly elevated reactive oxygen species levels in oocytes, thereby compromising the developmental competence of early embryos. Of note, SIRT7 protein level is significantly decreased in oocytes from obese mice, and the forced expression of exogenous SIRT7 ameliorates maternal obesity-associated meiotic defects and oxidative stress in oocytes. In summary, our data suggest that SIRT7 is an essential factor in the determination of oocyte quality and may mediate the effects of obesity on female reproduction.-Gao, M., Li, X., He, Y., Han, L., Qiu, D., Ling, L., Liu, H., Liu, J., Gu, L. SIRT7 functions in redox homeostasis and cytoskeletal organization during oocyte maturation.