Roles of Resveratrol in Improving the Quality of Postovulatory Aging Oocytes In Vitro

Chemical reversion of age-related oocyte dysfunction fails to enhance embryo development in a bovine model of postovulatory aging

PURPOSE

There are no clinical treatments to prevent/revert age-related alterations associated with oocyte competence decline in the context of advanced maternal age. Those alterations have been attributed to oxidative stress and mitochondrial dysfunction. Our study aimed to test the hypothesis that in vitro maturation (IVM) medium supplementation with antioxidants (resveratrol or phloretin) may revert age-related oocyte competence decline.

METHODS

Bovine immature oocytes were matured in vitro for 23 h (young) and 30 h (aged). Postovulatory aged oocytes (control group) and embryos obtained after fertilization were examined and compared with oocytes supplemented with either 2 μM of resveratrol or 6 μM phloretin (treatment groups) during IVM.

RESULTS

Aged oocytes had a significantly lower mitochondrial mass and proportion of mitochondrial clustered pattern, lower ooplasmic volume, higher ROS, lower sirtuin-1 protein level, and a lower blastocyst rate in comparison to young oocytes, indicating that postovulatory oocytes have a lower quality and developmental competence, thus validating our experimental model. Supplementation of IVM medium with antioxidants prevented the generation of ROS and restored the active mitochondrial mass and pattern characteristic of younger oocytes. Moreover, sirtuin-1 protein levels were also restored but only following incubation with resveratrol. Despite these findings, the blastocyst rate of treatment groups was not significantly different from the control group, indicating that resveratrol and phloretin could not restore the oocyte competence of postovulatory aged oocytes.

CONCLUSION

Resveratrol and phloretin can both revert the age-related oxidative stress and mitochondrial dysfunction during postovulatory aging but were insufficient to enhance embryo developmental rates under our experimental conditions.

Mitochondria as therapeutic targets in assisted reproduction

Mitochondria are essential organelles with specialized functions, which play crucial roles in energy production, calcium homeostasis, and programmed cell death. In oocytes, mitochondrial populations are inherited maternally and are vital for developmental competence. Dysfunction in mitochondrial quality control mechanisms can lead to reproductive failure. Due to their central role in oocyte and embryo development, mitochondria have been investigated as potential diagnostic and therapeutic targets in assisted reproduction. Pharmacological agents that target mitochondrial function and show promise in improving assisted reproduction outcomes include antioxidant coenzyme Q10 and mitoquinone, mammalian target of rapamycin signaling pathway inhibitor rapamycin, and nicotinamide mononucleotide. Mitochondrial replacement therapies (MRTs) offer solutions for infertility and mitochondrial disorders. Autologous germline mitochondrial energy transfer initially showed promise but failed to demonstrate significant benefits in clinical trials. Maternal spindle transfer (MST) and pronuclear transfer hold potential for preventing mitochondrial disease transmission and improving oocyte quality. Clinical trials of MST have shown promising outcomes, but larger studies are needed to confirm safety and efficacy. However, ethical and legislative challenges complicate the widespread implementation of MRTs.

Mitochondrial Quality Control in Ovarian Function: From Mechanisms to Therapeutic Strategies

Mitochondrial quality control plays a critical role in cytogenetic development by regulating various cell-death pathways and modulating the release of reactive oxygen species (ROS). Dysregulated mitochondrial quality control can lead to a broad spectrum of diseases, including reproductive disorders, particularly female infertility. Ovarian insufficiency is a significant contributor to female infertility, given its high prevalence, complex pathogenesis, and profound impact on women's health. Understanding the pathogenesis of ovarian insufficiency and devising treatment strategies based on this understanding are crucial. Oocytes and granulosa cells (GCs) are the primary ovarian cell types, with GCs regulated by oocytes, fulfilling their specific energy requirements prior to ovulation. Dysregulation of mitochondrial quality control through gene knockout or external stimuli can precipitate apoptosis, inflammatory responses, or ferroptosis in both oocytes and GCs, exacerbating ovarian insufficiency. This review aimed to delineate the regulatory mechanisms of mitochondrial quality control in GCs and oocytes during ovarian development. This study highlights the adverse consequences of dysregulated mitochondrial quality control on GCs and oocyte development and proposes therapeutic interventions for ovarian insufficiency based on mitochondrial quality control. These insights provide a foundation for future clinical approaches for treating ovarian insufficiency.

Could polyphenols be an effective treatment in the management of polycystic ovary syndrome?

Polycystic ovary syndrome (PCOS), is a health problem observed in women of reproductive age. Different diets, physical activity recommendations and lifestyle changes can be effective in dealing with the symptoms of PCOS. Nutrition is indeed an essential part of the treatment of the disease as it directly affects body weight loss, insulin resistance, lipid profile, hormones, and dermatological complaints such as acne. Polyphenols, simply classified as flavonoids and non-flavonoids, are bioactive components found in plant-based foods. The most common polyphenols in the diet are flavanols, flavonols, flavanone, anthocyanins. In particular, polyphenols which are compounds naturally found in foods, have antioxidant, anticancer, anti-inflammatory, antimutagenic benefits along with many other ones. In the treatment of PCOS, polyphenols may help reduce the symptoms, improve insulin resistance and poor lipid profile, and cure hormonal disorders. It has been reported that polyphenols are influential in menstrual cycle disorders and enable a decrease in body weight, hyperandrogenism, estrogen, testosterone, luteinizing hormone (LH)/follicle stimulating hormone (FSH) ratios and LH. For adequate daily intake of polyphenols, which are found in high amounts in fruits and vegetables, at least 5 portions of fruits and vegetables should be consumed in addition to a healthy nutrition pattern. In this review, the effects of various polyphenols on polycystic ovary syndrome are discussed.

Therapeutic effects of resveratrol on epigenetic mechanisms in age-related diseases: A comprehensive review

Recently, various studies have shown that epigenetic changes are associated with aging and age-related diseases. Both animal and human models have revealed that epigenetic processes are involved in aging mechanisms. These processes happen at multiple levels and include histone modification, DNA methylation, and changes in noncoding RNA expression. Consequently, changes in the organization of chromatin and DNA accessibility lead to the regulation of gene expression. With increasing awareness of the pivotal function of epigenetics in the aging process, researchers' attention has been drawn to how these epigenetic changes can be modified to prevent, stop, or reverse aging, senescence, and age-related diseases. Among various agents that can affect epigenetic, polyphenols are well-known phytochemicals found in fruits, vegetables, and plants. Polyphenols are found to modify epigenetic-related mechanisms in various diseases and conditions, such as metabolic disorders, obesity, neurodegenerative diseases, cancer, and cardiovascular diseases. Resveratrol (RSV) is a member of the stilbene subgroup of polyphenols which is derived from various plants, such as grapes, apples, and blueberries. Therefore, herein, we aim to summarize how RSV affects different epigenetic processes to change aging-related mechanisms. Furthermore, we discuss its roles in age-related diseases, such as Alzheimer's, Parkinson's, osteoporosis, and cardiovascular diseases.

Time elapsed between ovulation and insemination determines the quality of fertilized rat oocytes

Genetically modified rats are valuable models in human disease research. We recently developed an improved system for rat sperm cryopreservation and in vitro fertilization (IVF) that facilitates the efficient production and preservation of genetically modified rats. In the IVF procedure performed using frozen-thawed rat sperm, the IVF schedule is fixed to ensure timely hormone administration and oocyte collection. To enhance the flexibility of the IVF schedule, possible periods of postovulated rat oocytes with normal fertility and developmental abilities should be determined. Therefore, in this study, we examined the fertilization and developmental ability of incubated oocytes 1-13 h after oocyte collection at 9:00 AM. The fertilization rate decreased 7 h after oocyte collection, and abnormally fertilized oocytes appeared 10 h after oocyte collection. The developmental rate also decreased 7 h after oocyte collection; however, live pups were obtained from oocytes 12 h after oocyte collection. In summary, ovulated rat oocytes exhibited a high developmental ability after IVF for up to 4 h after oocyte collection.

The multiple actions of grape and its polyphenols on female reproductive processes with an emphasis on cell signalling

Grapes are an economically important fruit crop, and their polyphenols (mainly phenolic acids, flavanols, flavonols, anthocyanins, proanthocyanidins, and stilbenes) can exert a wide range of health benefits as an interesting and valuable dietary supplement for natural complementary therapy. However, their potential physiological and therapeutic actions on reproductive processes have not been sufficiently elucidated. This evidence-based study presents current knowledge of grape extracts and polyphenols, as well as their properties and therapeutical actions in relation to female reproduction in a nutshell. Grape extract, and its polyphenols such as resveratrol, proanthocyanidin B2 or delphinidin may influence female reproductive physiology and pathology, as well as regulate multiple signaling pathways related to reproductive hormones, steroid hormones receptors, intracellular regulators of oxidative stress and subsequent inflammation, apoptosis, and proliferation. Their role in the management of ovarian cancer, age-related reproductive insufficiency, ovarian ischemia, PCOS, or menopausal syndrome has been indicated. In particular, the potential involvement of grapeseed extracts and/or proanthocyanidin B2 and delphinidin on ovarian steroidogenesis, oocyte maturation, and developmental capacity has been implicated, albeit at different regulatory levels. Grape polyphenols exert a wide range of health benefits posing grape extract as an interesting and valuable dietary supplement for natural complementary therapy. This evidence-based study focuses on the actions of grapeseed extract and grape polyphenols on female reproductive processes at various regulatory levels and multiple signalling pathways by regulating reproductive hormones (GnRH, gonadotropins, prolactin, steroid hormones, IGFBP), steroid receptors, markers of proliferation and apoptosis. However, lack of knowledge of standardized dosages so far limits their clinical application despite the wide range of their biological and therapeutic potentials.

Mammalian embryo culture media: now and into the future

For over 70years, since the culture of the first mammalian embryo in vitro , scientists have undertaken studies to devise and optimise media to support the manipulation and culture of gametes and embryos. This area of research became especially active in the late 1970s onwards following the successful birth of the first human in vitro fertilised embryo. This review summarises some of the key advances in mammalian embryo culture media over time based on a greater understanding of the biochemical milieu of the reproductive tract. It highlights how learnings from studies in mice and agricultural species have informed human culture media compositions, in particular the inclusion of albumin, growth factors, cytokines, and antioxidants into contemporary culture media formulations, and how these advances may then in turn help to inform and guide development of in vitro culture systems used in other arenas, in particular agriculture. Additionally, it will highlight how the introduction of new technologies, such as timelapse, can influence current trends in media composition and usage that may see a return to a single step medium.

Ferulic Acid Enhances Oocyte Maturation and the Subsequent Development of Bovine Oocytes

Improving the quality of oocytes matured in vitro is integral to enhancing the efficacy of in vitro embryo production. Oxidative stress is one of the primary causes of quality decline in oocytes matured in vitro. In this study, ferulic acid (FA), a natural antioxidant found in plant cell walls, was investigated to evaluate its impact on bovine oocyte maturation and subsequent embryonic development. Bovine cumulus-oocyte complexes (COCs) were treated with different concentrations of FA (0, 2.5, 5, 10, 20 μM) during in vitro maturation (IVM). Compared to the control group, supplementation with 5 μM FA significantly enhanced the maturation rates of bovine oocytes and the expansion of the cumulus cells area, as well as the subsequent cleavage and blastocyst formation rates after in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT). Furthermore, FA supplementation was observed to effectively decrease the levels of ROS in bovine oocytes and improve their mitochondrial function. Our experiments demonstrate that FA can maintain the levels of antioxidants (GSH, SOD, CAT) in oocytes, thereby alleviating the oxidative stress induced by H2O2. RT-qPCR results revealed that, after FA treatment, the relative mRNA expression levels of genes related to oocyte maturation (GDF-9 and BMP-15), cumulus cell expansion (HAS2, PTX3, CX37, and CX43), and embryo pluripotency (OCT4, SOX2, and CDX2) were significantly increased. In conclusion, these findings demonstrate that FA supplementation during bovine oocyte IVM can enhance oocyte quality and the developmental potential of subsequent embryos.

Aging and oocyte competence: A molecular cell perspective

Follicular microenvironment is paramount in the acquisition of oocyte competence, which is dependent on two interconnected and interdependent processes: nuclear and cytoplasmic maturation. Extensive research conducted in human and model systems has provided evidence that those processes are disturbed with female aging. In fact, advanced maternal age (AMA) is associated with a lower chance of pregnancy and live birth, explained by the age-related decline in oocyte quality/competence. This decline has largely been attributed to mitochondria, essential for oocyte maturation, fertilization, and embryo development; with mitochondrial dysfunction leading to oxidative stress, responsible for nuclear and mitochondrial damage, suboptimal intracellular energy levels, calcium disturbance, and meiotic spindle alterations, that may result in oocyte aneuploidy. Nuclear-related mechanisms that justify increased oocyte aneuploidy include deoxyribonucleic acid (DNA) damage, loss of chromosomal cohesion, spindle assembly checkpoint dysfunction, meiotic recombination errors, and telomere attrition. On the other hand, age-dependent cytoplasmic maturation failure is related to mitochondrial dysfunction, altered mitochondrial biogenesis, altered mitochondrial morphology, distribution, activity, and dynamics, dysmorphic smooth endoplasmic reticulum and calcium disturbance, and alterations in the cytoskeleton. Furthermore, reproductive somatic cells also experience the effects of aging, including mitochondrial dysfunction and DNA damage, compromising the crosstalk between granulosa/cumulus cells and oocytes, also affected by a loss of gap junctions. Old oocytes seem therefore to mature in an altered microenvironment, with changes in metabolites, ribonucleic acid (RNA), proteins, and lipids. Overall, understanding the mechanisms implicated in the loss of oocyte quality will allow the establishment of emerging biomarkers and potential therapeutic anti-aging strategies. This article is categorized under: Reproductive System Diseases > Molecular and Cellular Physiology.

Luteolin regulates the distribution and function of organelles by controlling SIRT1 activity during postovulatory oocyte aging

The quality of oocytes determines their development competence, which will be rapidly lost if the oocytes are not fertilized at the proper time after ovulation. SIRT1, one of the sirtuin family members, has been proven to protect the quality of oocytes during postovulatory oocyte aging. However, evidence of the effect of SIRT1 on the activity of organelles including the mitochondria, the endoplasmic reticulum (ER), the Golgi apparatus, and the lysosomes in postovulatory aging oocyte is lacking. In this study, we investigated the distribution and function of organelles in postovulatory aged oocytes and discovered abnormalities. Luteolin, which is a natural flavonoid contained in vegetables and fruits, is an activator of SIRT1. When the oocytes were treated with luteolin, the abnormal distribution of mitochondria, ER, and Golgi complex were restored during postovulatory oocyte aging. The ER stress protein GRP78 and the lysosome protein LAMP1 increased, while the mitochondrial membrane potential and the Golgi complex protein GOLPH3 decreased in aged oocytes, and these were restored by luteolin treatment. EX-527, an inhibitor of SIRT1, disrupted the luteolin-mediated normal distribution and function of mitochondria, ER, Golgi apparatus, and lysosomes. In conclusion, we demonstrate that luteolin regulates the distribution and function of mitochondria, ER, Golgi apparatus, and lysosomes during postovulatory oocyte aging by activating SIRT1.

Potential Synergistic Supplementation of NAD+ Promoting Compounds as a Strategy for Increasing Healthspan

Disrupted biological function, manifesting through the hallmarks of aging, poses one of the largest threats to healthspan and risk of disease development, such as metabolic disorders, cardiovascular ailments, and neurodegeneration. In recent years, numerous geroprotectors, senolytics, and other nutraceuticals have emerged as potential disruptors of aging and may be viable interventions in the immediate state of human longevity science. In this review, we focus on the decrease in nicotinamide adenine dinucleotide (NAD+) with age and the supplementation of NAD+ precursors, such as nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR), in combination with other geroprotective compounds, to restore NAD+ levels present in youth. Furthermore, these geroprotectors may enhance the efficacy of NMN supplementation while concurrently providing their own numerous health benefits. By analyzing the prevention of NAD+ degradation through the inhibition of CD38 or supporting protective downstream agents of SIRT1, we provide a potential framework of the CD38/NAD+/SIRT1 axis through which geroprotectors may enhance the efficacy of NAD+ precursor supplementation and reduce the risk of age-related diseases, thereby potentiating healthspan in humans.

The Antioxidant Auraptene Improves Aged Oocyte Quality and Embryo Development in Mice

Decrease in quality of postovulatory aged oocytes occurs due to oxidative stress and leads to low fertilization and development competence. It is one of the main causes that exerting detrimental effect on the success rate in assisted reproductive technology (ART). Auraptene (AUR), a citrus coumarin, has been reported to possess an antioxidant effects in other tissues. In this study, we aimed to confirm the potential of AUR to delay the oocyte aging process by alleviating oxidative stress. Superovulated mouse oocytes in metaphase of second meiosis (MII) were exposed to 0, 1 or 10 μM AUR for 12 h of in vitro aging. AUR addition to the culture medium recovered abnormal spindle and chromosome morphology and mitigated mitochondrial distribution and mitochondrial membrane potential (ΔΨ) in aged oocytes. AUR-treated aged oocytes also showed suppressed oxidative stress, with lower reactive oxygen species (ROS) levels, higher glutathione (GSH) levels and increased expression of several genes involved in antioxidation. Furthermore, AUR significantly elevated the fertilization and embryo developmental rates. Oocytes aged with 1 μM AUR exhibited morphokinetics that were very similar to those of the control group. Altogether, these data allowed us to conclude that AUR improved the quality of aged oocytes and suggest AUR as an effective clinical supplement candidate to prevent postovulatory aging.

Reprogramming of ovarian aging epigenome by resveratrol

Resveratrol is an antiaging, antioxidant, and anti-inflammatory natural polyphenolic compound. Growing evidence indicates that resveratrol has potential therapeutic effects for improving aging ovarian function. However, the mechanisms underlying prolonged reproductive longevity remain elusive. We found that resveratrol ameliorates ovarian aging transcriptome, some of which are associated with specific changes in methylome. In addition to known aging transcriptome of oocytes and granulosa cells such as decline in oxidoreductase activity, metabolism and mitochondria function, and elevated DNA damage and apoptosis, actin cytoskeleton are notably downregulated with age, and these defects are mostly rescued by resveratrol. Moreover, the aging-associated hypermethylation of actin cytoskeleton is decreased by resveratrol. In contrast, deletion of Tet2, involved in DNA demethylation, abrogates resveratrol-reprogrammed ovarian aging transcriptome. Consistently, Tet2 deficiency results in additional altered pathways as shown by increased mTOR and Wnt signaling, as well as reduced DNA repair and actin cytoskeleton with mouse age. Moreover, genes associated with oxidoreductase activity and oxidation-reduction process were hypermethylated in Tet2-deficient oocytes from middle-age mice treated with resveratrol, indicating that loss of Tet2 abolishes the antioxidant effect of resveratrol. Taking together, our finding provides a comprehensive landscape of transcriptome and epigenetic changes associated with ovarian aging that can be reprogrammed by resveratrol administration, and suggests that aberrantly increased DNA methylation by Tet2 deficiency promotes additional aging epigenome that cannot be effectively restored to younger state by resveratrol.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Oxidative stress and in vitro ageing of the post-ovulatory oocyte: an update on recent advances in the field

In brief

Post-ovulatory ageing of oocytes leads to poor oocyte and embryo quality as well as abnormalities in offspring. This review provides an update on the contributions of oxidative stress to this process and discusses the current literature surrounding the use of antioxidant media to delay post-ovulatory oocyte ageing.

Abstract

Following ovulation, the metaphase II stage oocyte has a limited functional lifespan before succumbing to a process known as post-ovulatory oocyte ageing. This progressive demise occurs both in vivo and in vitro and is accompanied by a deterioration in oocyte quality, leading to a well-defined sequelae of reduced fertilisation rates, poor embryo quality, post-implantation errors, and abnormalities in the offspring. Although the physiological consequences of post-ovulatory oocyte ageing have largely been characterised, less is known regarding the molecular mechanisms that drive this process. This review presents an update on the established relationships between the biochemical changes exhibited by the ageing oocyte and the myriad of symptoms associated with the ageing phenotype. In doing so, we consider the molecular events that are potentially involved in orchestrating post-ovulatory ageing with a particular focus on the role of oxidative stress. We highlight the mounting evidence that oxidative stress acts as an initiator for a cascade of events that create the aged oocyte phenotype. Specifically, oxidative stress has the capacity to disrupt mitochondrial function and directly damage multiple intracellular components of the oocyte such as lipids, proteins, and DNA. Finally, this review addresses emerging strategies for delaying post-ovulatory oocyte ageing with emphasis placed on the promise afforded by the use of selected antioxidants to guide the development of media tailored for the preservation of oocyte integrity during in vitro fertilisation procedures.

Quercetin protects porcine oocytes from in vitro aging by reducing oxidative stress and maintaining the mitochondrial functions

Quercetin (QUE) is a component of the flavonoid family that shows various therapeutic properties, such as antioxidant effects. However, whether QUE affects porcine oocyte in vitro aging has not yet been investigated. Therefore, in this study, we applied various doses of QUE to freshly isolated porcine oocytes and found that 10 µM QUE improved the oocyte maturation rate in vitro, as reflected by the increased degree of cumulus cell expansion and first polar body extrusion. More importantly, we found that QUE reduced in vitro aging and improved the maturity level of porcine oocytes after another 24 h of culturing, accompanied by the upregulated expression levels of bone morphogenetic protein 15, growth differentiation factor 9, Moloney sarcoma oncogene, and cyclin-dependent kinase 2. In addition, we found that QUE treatment significantly reduced the intracellular reactive oxygen species levels, apoptosis, and autophagy and upregulated the expression levels of superoxide dismutase 2 and catalase in aged porcine oocytes. In addition, QUE restored impaired mitochondrial membrane potential and spindle assembly in aged porcine oocytes. Our findings demonstrate that QUE can protect porcine oocytes from in vitro aging by reducing oxidative stress and maintaining mitochondrial function.

RA33, an analogue of resveratrol, improves the development of in vitro-fertilized bovine embryos

Oxidative stress is an undesirable effect of in vitro culture, which requires antioxidant supplementation. This study investigated the analogue of resveratrol (RA33) as an alternative to resveratrol, an antioxidant molecule, for the in vitro culture of in vitro-fertilized bovine embryos. The effect of different concentrations of RA33 on embryo development was evaluated and a comparison between RA33 and resveratrol was performed. The cleavage rate was higher (P < 0.05) with 2.5 μM (69.0 ± 4.4%) than at 0, 0.1 or 0.5 μM RA33 (62.1 ± 2.0%, 60.7 ± 5.9% and 56.7 ± 5.8%, respectively). The blastocyst rates on days 7 and 8 post-fertilization with 2.5 μM RA33 (19.4 ± 3.3% and 24.6 ± 3.3%, respectively) were higher (P < 0.05) than for 0 μM (12.4 ± 2.5% and 15.2±2.5%, respectively). When 2.5 μM RA33 was compared with 0.5 μM resveratrol, similar (P > 0.05) cleavage and blastocyst rates were found between them, but the cleavage rate was higher (P < 0.05) in the control (80.8 ± 3.4%) than for the resveratrol treatment (76.4 ± 3.6%). The numbers of apoptotic cells and the apoptotic index were lower (P < 0.05) with RA33 (6.5 ± 0.6 cells and 6.4 ± 0.7%, respectively) and resveratrol (5 ± 0.8 cells and 5.5 ± 1.0%, respectively) than in the control group (9.8 ± 1.2 cells and 8.9 ± 1.1%, respectively). In conclusion, RA33 can enhance the preimplantation development of in vitro-fertilized bovine embryos and be an alternative to resveratrol in embryo culture medium.

2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-Glucoside improves female ovarian aging

Reduced fertility associated with normal aging may reflect the over-maturity of oocytes. It is increasingly important to reduce aging-induced infertility since recent trends show people marrying at later ages. 2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-glucoside (THSG), a polyphenol extracted from Polygonum multiflorum, has been reported to have anti-inflammatory and anti-aging properties. To evaluate whether THSG can reduce aging-related ovarian damage in a female mouse model of aging, THSG was administered by gavage at a dose of 10 mg/kg twice weekly, starting at 4 weeks of age in a group of young mice. In addition, the effect of THSG in a group of aged mice was also studied in mice starting at 24 weeks of age. The number of oocytes in the THSG-fed group was higher than in the untreated control group. Although the percentage of secondary polar bodies (PB2) decreased during aging in the THSG-fed group, it decreased much more slowly than in the age-matched control group. THSG administration increased the quality of ovaries in young mice becoming aged. Western blotting analyses also indicated that CYP19, PR-B, and ER-β expressions were significantly increased in 36-week-old mice. THSG also increased oocyte numbers in aged mice compared to mice without THSG fed. Studies of qPCR and immunohistochemistry (IHC) analyses of ovaries in the aged mice groups were conducted. THSG increased gene expression of anti-Müllerian hormone (AMH), a biomarker of oocyte number, and protein accumulation in 40-week-old mice. THSG increased the expression of pgc1α and atp6, mitochondrial biogenesis-related genes, and their protein expression. THSG also attenuated the fading rate of CYP11a and CYP19 associated with sex hormone synthesis. And THSG maintains a high level of ER-β expression, thereby enhancing the sensitivity of estrogen. Our findings indicated that THSG increased or extended gene expression involved in ovarian maintenance and rejuvenation in young and aged mice. On the other hand, THSG treatments significantly maintained oocyte quantity and quality in both groups of young and aged mice compared to each age-matched control group. In conclusion, THSG can delay aging-related menopause, and the antioxidant properties of THSG may make it suitable for preventing aging-induced infertility.

Protective effect of resveratrol against cadmium-induced toxicity on ovine oocyte in vitro maturation and fertilization

Background

Heavy metal cadmium (Cd) is a widespread environmental contaminant with a potential toxicity that might negatively affect female reproduction and fertility. It has been reported that Cd exposure impaired the quality of oocytes and led to a defective maturation and fertilization, through oxidative stress induction. Resveratrol (Res) is a natural polyphenol with strong antioxidant properties that exhibited protective role in preventing oocyte redox homeostasis disruption and quality decline. Here, we explored whether the addition of Res to in vitro maturation (IVM) medium might act as a protection against Cd-induced toxicity on ovine oocyte maturation and fertilization. Firstly, we evaluated the effect of supplementing IVM medium with two different Res concentrations (1 and 2 μmol/L) on nuclear maturation and fertilization of oocytes matured under CdCl₂ (2 μmol/L) exposure. Therefore, the concentration of 1 μmol/L Res was selected to analyse the effects of this compound on intracellular ROS levels, mitochondrial (mt) distribution and activity, chromatin configuration, cytoskeleton morphology, cortical granules (CGs) distribution and mRNA expression of genes associated with cellular response to oxidative stress (i.e. SIRT1, SOD 1, GPX1, GSR, CAT) in Cd-exposed in vitro matured oocytes.

Results

We found that 1 μmol/L Res restored the reduced oocyte meiotic competence induced by Cd exposure as well as, Res sustained oocyte ability to be normally fertilized and decreased polyspermic fertilization at both tested concentrations. Moreover, we demonstrated that 1 μmol/L Res mitigated Cd-induced alterations of oocyte cytoplasmic maturation by reducing reactive oxygen species (ROS) accumulation, preventing mt dysfunction, maintaining the correct meiotic spindle and cortical F-actin assembly and the normal cortical granule distribution as well as up-regulating SIRT1, SOD1 and GPX1 genes.

Conclusions

Taken together, our findings highlighted the beneficial influence exerted by Res in preventing Cd-induced disturbance of nuclear and cytoplasmic maturation and subsequent fertilization in ovine oocytes. Res treatment may help to establish defence strategies counteracting Cd-induced toxicity on the female gamete.

Melatonin improves meiosis maturation against diazinon exposure in mouse oocytes

AIMS

Organophosphorus pesticide diazinon (DZN) has adverse effects on animals and humans by direct contact or the spread of food chain. The antioxidant melatonin has protective effects on female reproduction. This study aimed to explore the effects of DZN on meiosis maturation in mouse cumulus oocyte complexes (COCs) and the effects of melatonin.

MAIN METHODS

Different concentrations of DZN and melatonin were added during the in vitro maturation of COCs. Then we detected the extrusion rate of the first polar body, the number of sperms binding to oocyte, mitochondrial membrane potential, reactive oxygen species (ROS), early apoptosis. Subsequently, the expression of Juno, CX37, CX43 and ERK1/2 were detected by immunofluorescence staining and Western blotting.

KEY FINDINGS

DZN exposure results in the failure of nuclear and cytoplasmic maturation of oocyte meiosis. Destruction of repositioning and function of mitochondria increases the levels of ROS and early apoptosis. The DZN-exposed oocytes express less Juno resulting to bind less sperms than normal. The loss of gap junctions and failure to activate ERK1/2 also contribute to the failure of cytoplasmic maturation. All these ultimately lead to the poor oocyte quality and low fertility. Appropriate melatonin can effectively restore all these defects.

SIGNIFICANCE

Under DZN exposure, melatonin can significantly improve the quality of oocytes, and melatonin promotes oocyte maturation by protecting gap junction and restoring ERK1/2 pathway, which is a new breakthrough for improving female fertility.

Aged mice ovaries harbor stem cells and germ cell nests but fail to form follicles

BACKGROUND

We recently published evidence to suggest that two populations of stem cells including very small embryonic-like stem cells (VSELs) and ovarian stem cells (OSCs) in ovary surface epithelium (OSE) undergo proliferation/differentiation, germ cell nests (GCN) formation, meiosis and eventually differentiate into oocytes that assemble as primordial follicles on regular basis during estrus cycle. Despite presence of stem cells, follicles get exhausted with advancing age in mice and result in senescence equivalent to menopause in women. Stem cells in aged ovaries can differentiate into oocytes upon transplantation into young ovaries, however, it is still not well understood why follicles get depleted with advancing age despite the presence of stem cells. The aim of the present study was to study stem cells and GCN in aged ovaries.

METHODS

OSE cells from aged mice (> 18 months equivalent to > 55 years old women) were enzymatically separated and used to study stem cells. Viable (7-AAD negative) VSELs in the size range of 2-6 µm with a surface phenotype of Lin-CD45-Sca-1+ were enumerated by flow cytometry. Immuno-fluorescence and RT-PCR analysis were done to study stem/progenitor cells (OCT-4, MVH, SCP3) and transcripts specific for VSELs (Oct-4A, Sox-2, Nanog), primordial germ cells (Stella), germ cells (Oct-4, Mvh), early meiosis (Mlh1, Scp1) and ring canals (Tex14).

RESULTS

Putative VSELs and OSCs were detected as darkly stained, spherical cells with high nucleo-cytoplasmic ratio along with germ cells nests (GCN) in Hematoxylin & Eosin stained OSE cells smears. Germ cells in GCN with distinct cytoplasmic continuity expressed OCT-4, MVH and SCP3. Transcripts specific for stem cells, early meiosis and ring canals were detected by RT-PCR studies.

CONCLUSION

Rather than resulting as a consequence of accelerated loss of primordial follicle and their subsequent depletion, ovarian senescence/menopause occurs as a result of stem cells dysfunction. VSELs and OSCs exist along with increased numbers of GCNs arrested in pre-meiotic or early meiotic stage in aged ovaries and primordial follicle assembly is blocked possibly due to age-related changes in their microenvironment.

In vivo and in vitro postovulatory aging: when time works against oocyte quality?

In mammalian species an optimal fertilization window during which successful fertilization occurs. In the majority of mammals estrus marks ovulation time and coincident with mating, thereby allowing the synchronized meeting in the fallopian tubes, between freshly ejaculated sperm and freshly ovulated oocytes. Conversely, women do not show natural visual signs of ovulation such that fertilization can occur hours later involving an aged oocyte and freshly ejaculated spermatozoa. During this time, the oocyte undergoes a rapid degradation known as “postovulatory aging” (POA). POA may become particularly important in the human-assisted reproductive technologies, as the fertilization of retrieved mature oocytes can be delayed due to increased laboratory workload or because of unforeseeable circumstances, like the delayed availability of semen samples. This paper is an updated review of the consequences of POA, either in vivo or in vitro, on oocyte quality with particular attention to modifications caused by POA on oocyte nuclear, cytoplasmic, genomic, and epigenetic maturation, and embryo development.

Antioxidant Effects of Resveratrol in Intervertebral Disk

Intervertebral disk (IVD) degeneration (IVDD) can cause various spinal degenerative diseases. Cumulative evidence has indicated that IVDD can result from inflammation, apoptosis, autophagy, biomechanical changes and other factors. Currently, lack of conservative treatment for degenerative spinal diseases leads to an urgent demand for clinically applicable medication to ameliorate the progression of IVDD. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a polyphenol compound extracted from red wine or grapes, has shown protective effects on IVD, alleviating the progression of IVDD. Resveratrol has been demonstrated as a scavenger of free radicals both in vivo and in vitro. The antioxidant effects of resveratrol are likely attributed to its regulation on mitochondrial dysfunction or the elimination of reactive oxygen species. This review will summarize the mechanisms of the reactive oxygen species production and elaborate the mechanisms of resveratrol in retarding IVDD progression, providing a comprehensive understanding of the antioxidant effects of resveratrol in IVD.

Effects and Mechanisms of Resveratrol on Aging and Age-Related Diseases

The aging of population has become an issue of great concern because of its rapid increase. Aging is an important risk factor of many chronic diseases. Resveratrol could be found in many foods, such as grapes, red wine, peanuts, and blueberries. Many studies reported that resveratrol possessed various bioactivities, such as antioxidant, anti-inflammatory, cardiovascular protection, anticancer, antidiabetes mellitus, antiobesity, neuroprotection, and antiaging effects. The antiaging mechanisms of resveratrol were mainly ameliorating oxidative stress, relieving inflammatory reaction, improving mitochondrial function, and regulating apoptosis. Resveratrol could be an effective and safe compound for the prevention and treatment of aging and age-related diseases. In this review, we summarize the effects of resveratrol on aging, life extension, and several age-related diseases, with special attention paid to the mechanisms of antiaging action.

Co-encapsulation of tertinoin and resveratrol by solid lipid nanocarrier (SLN) improves mice in vitro matured oocyte/ morula-compact stage embryo development

As a promising strategy in overcoming drug resistance, the nano drug co-delivery system (NDCDS) can transport two or more drugs into the cell. In this study, we sought to compare the dual and single drug-delivery system, to deliver the optimal dose of Resveratrol (RES) and Tretinoin (TTN) into the in vitro matured oocyte and morula-compact stage embryonic cells. The formation of single (RES/TTN) and dual-drug (RES + TTN)-SLN were confirmed by Uv-vis spectrophotometery, dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) technologies. In two experiments, the oocytes/presumptive zygotes were cultured under various concentrations of the single (RES/TTN) and dual-drug (RES + TTN)-SLN. In vitro toxicity studies, including nuclear staining (Aceto-orcein and Hoechst 33342), H2DCFDA fluorescent staining, chemiluminescence assay, and quantitative reverse transcription-PCR (qRT-PCR) techniques, indicated an excellent oocyte/embryo internalization of RES and TTN. Moreover, when oocytes/embryos were treated with the lowest concentration of RES + TTN-SLN, antioxidants-related genes were upregulated, apoptotic-related genes were downregulated, and intra/extracellular ROS production was reduced. In vitro cytotoxicity studies also demonstrated that single/dual-encapsulation of RES or TTN were safe even at the highest concentration (10 and 5 μM) compared to the control group. To sum it up, both delivery systems of RES and TTN by SLN (dual or single encapsulation) can deliver the optimal dose of RES and TTN into the oocyte/embryo. Where the dual-delivery of RES and TTN even at the lowest concentration (0.25 μM + 0.1 μm) showed a synergistic anti-oxidative effect in oocyte/embryo with a better inhibition of intra/extra-cellular ROS production by an enhanced/controlled intracellular penetration.

Coenzyme Q10 supplement rescues postovulatory oocyte aging by regulating SIRT4 expression

BACKGROUND

High-quality of the oocyte is crucial for embryo development and the success of human assisted reproduction. The postovulatory aged oocytes lose the developmental competence with mitochondrial dysfunction and oxidative stress. Coenzyme Q10 (CoQ10) is widely distributed in the membranes of cells, and has an important role in the mitochondrial respiration chain, against oxidative stress and modulation of gene expression.

OBJECTIVE

To investigate the functions and mechanisms of CoQ10 on delaying postovulatory oocyte aging.

METHODS

Quantitative real-time PCR and Immunofluorescence staining were used to determine the expression patterns of the biogenesis genes of CoQ10 in postovulatory aged oocytes compared with fresh oocytes. The mitochondrial function, apoptosis, reactive oxygen species (ROS) accumulation and spindle abnormalities were investigated after treatment with 10 μM CoQ10 in aged groups. SIRT4 siRNA or capped RNA was injected into oocytes to investigate the function of SIRT4 on postovulatory oocyte aging and the relationship between CoQ10 and SIRT4.

RESULTS

Multiple CoQ10 biosynthesis enzymes are insufficient, and supplement of CoQ10 can improve oocyte quality and elevate the development competency of postovulatory aged oocytes. CoQ10 can attenuate the aging-induced abnormalities including mitochondrial dysfunction, ROS accumulation, spindle abnormalities, and apoptosis in postovulatory aged oocytes. Furthermore, SIRT4, which was first found to be up-regulated in postovulatory aged oocytes, decreased following CoQ10 treatment. Finally, knockdown of SIRT4 can rescue aging-induced dysfunction of mitochondria, and the efficiency of CoQ10 rescuing dysfunction of mitochondria can be weakened by SIRT4 overexpression.

CONCLUSION

Supplement of CoQ10 protects oocytes from postovulatory aging by inhibiting SIRT4increase.

Polyphenols: Natural compounds with promising potential in treating polycystic ovary syndrome

Polyphenols are natural compounds used by plants as a defense system against various stresses. In recent years, the importance of these polyhydroxyphenols has extensively increased due to their potent cardioprotection, anti-carcinogenic, anti-oxidant, anti-apoptotic, and anti-inflammatory properties. Therefore, various studies have reported promising results from the studies investigating their efficacy as a therapeutic strategy in various disorders such as human malignancies, cardiovascular diseases, nervous system impairments, diabetes, metabolic syndrome, aging, and inflammation-associated disorders, as well as a polycystic ovarian syndrome (PCOS). Since oxidative stress, hormonal, metabolic, and endocrine disturbances have been shown to play a crucial role in the initiation/progression of PCOS, polyphenols are suggested to be an effective treatment for this disorder. Therefore, this study aimed to discuss the therapeutic potential of multiple polyphenols in PCOS.

Mitochondria: emerging therapeutic strategies for oocyte rescue

As the vital organelles for cell energy metabolism, mitochondria are essential for oocyte maturation, fertilization, and embryo development. Abnormalities in quantity, quality, and function of mitochondria are closely related to poor fertility and disorders, such as decreased ovarian reserve (DOR), premature ovarian aging (POA), and ovarian aging, as well as maternal mitochondrial genetic disease caused by mitochondrial DNA (mtDNA) mutations or deletions. Mitochondria have begun to become a therapeutic target for infertility caused by factors such as poor oocyte quality, oocyte aging, and maternal mitochondrial genetic diseases. Mitochondrial replacement therapy (MRT) has attempted to use heterologous or autologous mitochondria to rebuild healthy state of oocyte by increasing the amount of mitochondria (e.g., partial ooplasm transfer, autologous mitochondrial transfer), or to stop the transmission of mtDNA diseases by replacing abnormal maternal mitochondria (e.g., pronuclei transfer, spindle transfer, polar body transfer). Among them, autologous mitochondrial transfer is the most promising therapeutic technology as of today which does not involve using a third party, but its clinical efficacy is controversial due to many factors such as the aging phenomenon of germ line cells, the authenticity of the existence of ovarian stem cells (OSC), and secondary damage caused by invasive surgery to patients with poor ovarian function. Therefore, the research of optimal autologous cell type that can be applied in autologous mitochondrial transfer is an area worthy of further exploration. Besides, the quality of germ cells can also be probably improved by the use of compounds that enhance mitochondrial activity (e.g., coenzyme Q10, resveratrol, melatonin), or by innovative gene editing technologies which have shown capability in reducing the risk of mtDNA diseases (e.g., CRISPR/Cas9, TALENTs). Though the current evidences from animal and clinical trials are not sufficient, and some solutions of technical problems are still needed, we believe this review will guide a new direction in the possible clinical applied mitochondrial-related therapeutic strategies in reproductive medicine.

Paraquat Reduces the Female Fertility by Impairing the Oocyte Maturation in Mice

Paraquat (PQ) is a widely used non-selective and oxidizing herbicide in farmland, orchards, flower nursery, and grassland. Overuse of PQ will accumulate in the body and affect the reproduction in mammals. In this study, we found that PQ could reduce the female fertility by oral administration for 21 days in mice. PQ exposure could impair the nuclear maturation by perturbing the spindle assembly and kinetochore–microtubule attachment to cause the misaligned chromosomes during meiosis. In the meantime, PQ exposure disturbed the mitochondrial distribution and enhanced the level of reactive oxygen species and early apoptosis, which thereby deteriorated the early embryo development. Also, PQ administration could cause some changes in epigenetic modifications such as the level of H3K9me2 and H3K27me3. Therefore, PQ administration reduces the female fertility by impairing the nuclear and cytoplasmic maturation of oocytes in mice.

The Role of Oxidative Stress and Natural Antioxidants in Ovarian Aging

The ovarian system comprises vital organs in females and is of great significance for the maintenance of reproductive potential and endocrine stability. Although complex pathogenesis undoubtedly contributes to ovarian aging, increasing attention is being paid to the extensive influence of oxidative stress. However, the role of oxidative stress in ovarian aging is yet to be fully elucidated. Exploring oxidative stress-related processes might be a promising strategy against ovarian aging. In this review, compelling evidence is shown that oxidative stress plays a role in the etiology of ovarian aging and promotes the development of other ovarian aging-related etiologies, including telomere shortening, mitochondrial dysfunction, apoptosis, and inflammation. In addition, some natural antioxidants such as quercetin, resveratrol, and curcumin have a protective role in the ovaries through multiple mechanisms. These findings raise the prospect of oxidative stress modulator-natural antioxidants as therapeutic interventions for delaying ovarian aging.

Effects of tris (2-carboxyethyl) phosphine hydrochloride treatment on porcine oocyte in vitro maturation and subsequent in vitro fertilized embryo developmental capacity

Oocyte in vitro maturation (IVM) is a crucial process that determines subsequent in vitro embryo production. The present study investigated the effects of the antioxidant tris (2-carboxyethyl) phosphine hydrochloride (TCEP-HCL) on the in vitro maturation of porcine oocytes and in vitro developmental competence of fertilized embryos. Oocytes were matured in IVM medium based on four concentration groups of TCEP-HCL (0, 50, 100, and 200 μM) treatment. 100 μM TCEP-HCL treatment significantly increased the oocyte first polar body extrusion rate, monospermy rate and subsequent in vitro fertilized embryo developmental capacity (cleavage rate, blastocyst formation rate, and blastocyst total cell number) compared to those in the control group. Furthermore, 100 μM TCEP-HCL treatment significantly reduced the levels of reactive oxygen species, significantly increased glutathione levels and mitochondrial content compared to those in the control group. Moreover, 100 μM TCEP-HCL treatment significantly decreased the oocyte apoptosis, blastocyst apoptosis compared to that in the controls. In summary, these results indicate that 100 μM TCEP-HCL treatment improves the quality and developmental capacity of in vitro-fertilized embryos by decreasing oxidative stress in porcine oocytes.

Inhibitory effects of astaxanthin on postovulatory porcine oocyte aging in vitro

Mammalian oocytes represent impaired quality after undergoing a process of postovulatory aging, which can be alleviated through various effective ways such as reagent treatment. Accumulating evidences have revealed the beneficial effects of astaxanthin (Ax) as a potential antioxidant on reproductive biology. Here, porcine matured oocytes were used as a model to explore whether Ax supplement can protect against oocyte aging in vitro and the underlying mechanism, and therefore they were cultured with or without 2.5 μM Ax for an additional 24 h. Aged oocytes treated with Ax showed improved yield and quality of blastocysts as well as recovered expression of maternal genes. Importantly, oxidative stress in aged oocytes was relieved through Ax treatment, based on reduced reactive oxygen species and enhanced glutathione and antioxidant gene expression. Moreover, inhibition in apoptosis and autophagy of aged oocyte by Ax was confirmed through decreased caspase-3, cathepsin B and autophagic activities. Ax could also maintain spindle organization and actin expression, and rescue functional status of organelles including mitochondria, endoplasmic reticulum, Golgi apparatus and lysosomes according to restored fluorescence intensity. In conclusion, Ax might provide an alternative for ameliorating the oocyte quality following aging in vitro, through the mechanisms mediated by its antioxidant properties.

A grape seed extract maternal dietary supplementation improves egg quality and reduces ovarian steroidogenesis without affecting fertility parameters in reproductive hens

In broiler hens, the genetic selection increased susceptibility to metabolic disorders and reproductive dysfunctions. In human ovarian cells, grape seed extracts (GSE) improved steroid production. Here, we investigated the effects of a GSE dietary supplementation on egg production and quality, fertility parameters, Reactive Oxygen Species (ROS) and steroid content in yolk egg associated to plasma adipokines in broiler hens. For this, we designed two in vivo experiments, the first one included three groups of hens: A (control), B and C (supplemented with GSE at 0.5% and 1% of the total diet composition, respectively, since week 4), and the second one used two groups of hens: A (control) and D (supplemented with GSE at 1% of the total diet composition since hatching). We assessed the egg production from 23^th to 40^th weeks and quality at 33^th week. After artificial inseminations, the fertility parameters were calculated. In egg yolk, Reactive Oxygen Species (ROS) level and steroid production were evaluated by Ros-Glo H202 and ELISA assay, respectively. Expression of steroidogenic enzymes and adipokines and their receptors was determined by RT-qPCR in ovarian cells and plasma adipokines (RARRES2, ADIPOQ and NAMPT) were evaluated by specific ELISA assays. The fertility parameters and egg production were unaffected by GSE supplementation whatever the experiment (exp.). However, the rate of double-yolk eggs decreased for all GSE supplemented groups (exp. 1 P <0.01, exp.2, P<0.02). In exp.1, C group eggs were bigger and larger (P<0.0001) and the shell elasticity was higher for both B and C (P<0.0003) as compared to control. In the egg yolk, GSE supplementation in both exp. reduced ROS content and steroidogenesis consistent with a decrease in P450 aromatase and StAR mRNA expression and basal in vitro progesterone secretion in granulosa cells (P<0.001). Interestingly, in both exp. RARRES2 plasma levels were positively correlated while ADIPOQ and NAMPT plasma levels were negatively correlated, with steroids and ROS in yolk (P<0.0001). Taken together, maternal dietary GSE supplementation did not affect egg production and fertility parameters whereas it reduced ROS content and steroidogenesis in yolk egg. Furthermore, it ameliorated egg quality by decreasing the number of double-yolk eggs and by improving the size of normal eggs and the elasticity of the shell. Taken together, our data suggest the possibility of using dietary maternal GSE to improve egg quality.

Resveratrol delays postovulatory aging of mouse oocytes through activating mitophagy

Resveratrol (3,5,4'-trihydroxystilbene, RSV) is a natural potential anti-aging polyphenolic compound frequently used as a nutritional supplement against several diseases. However, the underlying mechanisms by which resveratrol regulates postovulatory aging of oocytes are still insufficiently known. In this study, we found that resveratrol could delay postovulatory aging and improve developmental competence of oocytes through activating selective mitophagy in the mouse. Resveratrol could maintain spindle morphology but it disturbed cortical granule (CG) distribution during oocyte aging. This might be due to upregulated mitophagy, since blocking mitophagy by cyclosporin A (CsA) treatment affected oocyte quality by damaging mitochondrial function and it decreased embryonic development. In addition, we also observed an involvement of FoxO3a in regulating mitophagy in aging oocytes following resveratrol treatment. Taken together, our results provide evidence that mitophagy induced by resveratrol is a potential mechanism to protect against postovulatory oocyte aging.