Age-Associated Changes in Mouse Oocytes During Postovulatory In Vitro Culture: Possible Role for Meiotic Kinases and Survival Factor BCL21

The Scavenging Activity of Coenzyme Q10 Plus a Nutritional Complex on Human Retinal Pigment Epithelial Cells

Age-related macular degeneration (AMD) and diabetic retinopathy (DR) are common retinal diseases responsible for most blindness in working-age and elderly populations. Oxidative stress and mitochondrial dysfunction play roles in these pathogenesis, and new therapies counteracting these contributors could be of great interest. Some molecules, like coenzyme Q10 (CoQ10), are considered beneficial to maintain mitochondrial homeostasis and contribute to the prevention of cellular apoptosis. We investigated the impact of adding CoQ10 (Q) to a nutritional antioxidant complex (Nutrof Total®; N) on the mitochondrial status and apoptosis in an in vitro hydrogen peroxide (H2O2)-induced oxidative stress model in human retinal pigment epithelium (RPE) cells. H2O2 significantly increased 8-OHdG levels (p < 0.05), caspase-3 (p < 0.0001) and TUNEL intensity (p < 0.01), and RANTES (p < 0.05), caspase-1 (p < 0.05), superoxide (p < 0.05), and DRP-1 (p < 0.05) levels, and also decreased IL1β, SOD2, and CAT gene expression (p < 0.05) vs. control. Remarkably, Q showed a significant recovery in IL1β gene expression, TUNEL, TNFα, caspase-1, and JC-1 (p < 0.05) vs. H2O2, and NQ showed a synergist effect in caspase-3 (p < 0.01), TUNEL (p < 0.0001), mtDNA, and DRP-1 (p < 0.05). Our results showed that CoQ10 supplementation is effective in restoring/preventing apoptosis and mitochondrial stress-related damage, suggesting that it could be a valid strategy in degenerative processes such as AMD or DR.

PrG protects postovulatory oocytes aging in mice through the putrescine pathway

Postovulatory aging of oocytes involves a series of deleterious molecular and cellular changes, which adversely affect oocyte maturation, fertilization, and early embryonic development. Petunidin-3-O-(6-O-pcoumaroyl)-rutinoside-5-O-glucoside (PrG), the main active ingredient of anthocyanin, exerts antioxidant effects. This study investigated whether PrG supplementation could delay postovulatory oocyte aging by alleviating oxidative stress. Our results showed that PrG supplementation decreased the number of abnormal morphology oocytes and improved the oxidative stress of aged oocytes by facilitating the reduction of the reactive oxygen species, the increase in glutathione content, and the recovery of expression of antioxidant-related gene expression. In addition, PrG treatment recovered mitochondrial dysfunction, including mitochondrial distribution, mitochondrial membrane potential and adenosine triphosphate in aged oocytes. PrG-treated oocytes returned to normal levels of cytoplasmic and mitochondrial calcium. Notably, PrG inhibited early apoptosis in aged oocytes. RNA-seq and qRT-PCR results revealed that PrG ameliorated oxidative stress injury in postovulatory aging oocytes of mice via the putrescine pathway. In conclusion, in vitro PrG supplementation is a potential therapy for delaying postovulatory oocyte aging.

Evaluation of viability, developmental competence, and apoptosis-related transcripts during in vivo post-ovulatory oocyte aging in zebrafish Danio rerio (Hamilton, 1822)

Introduction

Post-ovulatory aging is a time-dependent deterioration of ovulated oocytes and a major limiting factor reducing the fitness of offspring. This process may lead to the activation of cell death pathways like apoptosis in oocytes.

Methodology

We evaluated oocyte membrane integrity, egg developmental competency, and mRNA abundance of apoptosis-related genes by RT-qPCR. Oocytes from zebrafish Danio rerio were retained in vivo at 28.5°C for 24 h post-ovulation (HPO). Viability was assessed using trypan blue (TB) staining. The consequences of in vivo oocyte aging on the developmental competence of progeny were determined by the embryo survival at 24 h post fertilization, hatching, and larval malformation rates.

Results

The fertilization, oocyte viability, and hatching rates were 91, 97, and 65% at 0 HPO and dropped to 62, 90, and 22% at 4 HPO, respectively. The fertilizing ability was reduced to 2% at 8 HPO, while 72% of oocytes had still intact plasma membranes. Among the apoptotic genes bcl-2 (b-cell lymphoma 2), bada (bcl2-associated agonist of cell death a), cathepsin D, cathepsin Z, caspase 6a, caspase 7, caspase 8, caspase 9, apaf1, tp53 (tumor protein p53), cdk1 (cyclin-dependent kinase 1) studied, mRNA abundance of anti-apoptotic bcl-2 decreased and pro-apoptotic cathepsin D increased at 24 HPO. Furthermore, tp53 and cdk1 mRNA transcripts decreased at 24 HPO compared to 0 HPO.

Discussion

Thus, TB staining did not detect the loss of oocyte competency if caused by aging. TB staining, however, could be used as a simple and rapid method to evaluate the quality of zebrafish oocytes before fertilization. Taken together, our results indicate the activation of cell death pathways in the advanced stages of oocyte aging in zebrafish.

Cellular senescence in reproduction: a two-edged sword†

Cellular senescence (CS) is the state when cells are no longer capable to divide even after stimulation with grown factors. Cells that begin to undergo CS stop in the cell cycle and enter a suspended state without committing to programmed cell death. These cells assume a specific phenotype and influence their microenvironment by secreting molecules and extracellular vesicles that are part of the so-called senescent cell-associated secretory phenotype (SASP). Cellular senescence is intertwined with physiological and pathological conditions in the human organism. In terms of reproduction, senescent cells are present from reproductive tissues and germ cells to gestational tissues, and participate from fertilization to delivery, going through adverse reproductive outcomes such as pregnancy losses. Furthermore, various SASP molecules are enriched in gestational tissues throughout pregnancy. Thus, the aim of this review is to provide a basis about the features and potential roles played by CS throughout the reproductive process, encompassing its implication in each step of it and proposing a way to manage it in adverse reproductive contexts.

Diminished NAD+ levels and activation of retrotransposons promote postovulatory aged oocyte (POAO) death

Death is the fate of postovulatory aged or unfertilized oocytes (POAO) in many animals. However, precise molecular mechanisms are yet to be discovered. Here, we demonstrate that increased amounts of reactive oxygen species (ROS), calcium ion (Ca+2) channels, and retrotransposon activity induce apoptosis, which in turn causes POAO death. Notably, suppression of ROS, Ca+2 channels, and retrotransposons delayed POAO death. Further, we found that the histone H4K12 and K16 acetylation increased via downregulation of NAD+ and NAD+ -dependent histone deacetylase SIRT3. Furthermore, adding NMN, sodium pyruvate, or CD38 inhibition delayed the death of postovulatory aged oocytes. Finally, we demonstrate the conservation of retrotransposon-induced DNA damage-dependent POAO death in higher-order vertebrates. Our findings suggest that POAO mortality is caused by cyclic cascade metabolic interactions in which low NAD+ levels increase histone acetylation by inhibiting histone deacetylases, resulting in an increase in retrotransposons, ROS, and Ca+2 channel activity and thus contributing to DNA damage-induced apoptosis.

Metformin promotes in vitro maturation of oocytes from aged mice by attenuating mitochondrial oxidative stress via SIRT3-dependent SOD2ac

Human female fecundity decreases irreversibly as chronological age rises, adversely affecting oocyte quality, consequently worsening pregnancy outcomes and increasing the extent of birth defects. The first-line type 2 diabetes treatment metformin has been associated with delayed aging and reduction of oxidative stress; yet it remains unclear if metformin confers any benefits for oocytes from aged mice, particularly in the context of the assisted human reproductive technology (ART) known as in vitro maturation (IVM). Here, we found that adding metformin into the M16 culture medium of oocytes from aged mice significantly improved both oocyte maturation and early embryonic development. This study showed that metformin reduced the extent of meiotic defects and maintained a normal distribution of cortical granules (CGs). RNA-seq analysis of metformin-treated oocytes revealed genes apparently involved in the reduction of mitochondrial ROS. Further, the results supported that the metformin improved mitochondrial function, reduced apoptosis, increased the extent of autophagy, and reduced mitochondrial ROS via SIRT3-mediated acetylation status of SOD2K68 in oocytes from aged mice. Thus, this finding demonstrated a protective effect for metformin against the decreased quality of oocytes from aged mice to potentially improve ART success rates and illustrated a potential strategy to prevent or delay reproductive aging.

Importance of Antioxidant Supplementation during In Vitro Maturation of Mammalian Oocytes

The in vitro embryo production (IVEP) technique is widely used in the field of reproductive biology. In vitro maturation (IVM) is the first and most critical step of IVEP, during which, the oocyte is matured in an artificial maturation medium under strict laboratory conditions. Despite all of the progress in the field of IVEP, the quality of in vitro matured oocytes remains inferior to that of those matured in vivo. The accumulation of substantial amounts of reactive oxygen species (ROS) within oocytes during IVM has been regarded as one of the main factors altering oocyte quality. One of the most promising approaches to overcome ROS accumulation within oocytes is the supplementation of oocyte IVM medium with antioxidants. In this article, we discuss recent advancements depicting the adverse effects of ROS on mammalian oocytes. We also discuss the potential use of antioxidants and their effect on both oocyte quality and IVM rate.

Lycopene Reduces the In Vitro Aging Phenotypes of Mouse Oocytes by Improving Their Oxidative Status

Postovulatory aging is a major problem that limits the success of many assisted reproductive technologies (ARTs). Oxidative stress is a leading cause of oocyte aging. This study investigated the effects of lycopene supplementation of in vitro maturation (IVM) medium during the aging of mouse oocytes on the oocytes' morphology and oxidative stress status. Mouse cumulus-oocyte complexes (COCs) were collected and cultured in the IVM medium either for 17 h, (freshly matured oocytes), or for 48 h, (in vitro-aged oocytes), with or without lycopene. The rate of fragmented and degenerated oocytes and the oocyte levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), total antioxidant capacity (TAC), reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) were estimated and compared. Oocytes aged with 200 nM lycopene revealed significantly less fragmentation and degeneration, lower H2O2 and MDA levels, and higher TAC, GSH and SOD levels than those aged without lycopene. CAT levels were unchanged by lycopene treatment. Taken together, our data showed beneficial effects of lycopene during in vitro aging of mouse oocytes by reducing the oxidative stress damages that lead to their apoptosis. The present study introduces lycopene as a natural supplement to reduce the postovulatory aging-dependent abnormalities of mammalian oocytes.

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.

The boosting effects of melatonin on the expression of related genes to oocyte maturation and antioxidant pathways: a polycystic ovary syndrome- mouse model

Background

Melatonin, as a free radical scavenger exhibiting genomic actions, regulates the antioxidant genes expression and apoptosis mechanisms. In polycystic ovary syndrome (PCOS) patients, an imbalance between free radicals and antioxidants in follicular fluid leads to oxidative stress, aberrant folliculogenesis, and intrinsic defects in PCOS oocytes. In this experimental mouse model study, oocytes of PCOS and the control groups were cultured in different melatonin concentrations (10− 5, 10− 6, and 10− 7 M) to investigate the expression of oocyte maturation-related genes (Gdf9/Bmp15), antioxidant-related genes (Gpx1/Sod1), apoptotic biomarkers (Bcl2/Bax) and total intracellular ROS levels.

Results

Gdf9 and Bmp15, Gpx1 and Sod1 were up-regulated in PCOS and control oocytes cultured in all melatonin concentrations compared to those cultured in IVM basal medium (P < 0.05). A significant decrease in the total ROS level was observed in all groups cultured in the supplemented cultures. Melatonin increased Bcl2 and decreased Bax gene expression in PCOS and control oocytes compared to non-treated oocytes.

Conclusions

Melatonin increased antioxidant gene expression and regulated the apoptosis pathway, effectively reducing the adverse effects of culture conditions on PCOS oocytes. Furthermore, it influenced the expression of oocyte maturation-related genes in PCOS, providing valuable support during the IVM process.

Impact of Oxidative Stress on Embryogenesis and Fetal Development

Multiple cellular processes are regulated by oxygen radicals or reactive oxygen species (ROS) where they play crucial roles as primary or secondary messengers, particularly during cell proliferation, differentiation, and apoptosis. Embryogenesis and organogenesis encompass all these processes; therefore, their role during these crucial life events cannot be ignored, more so when there is an imbalance in redox homeostasis. Perturbed redox homeostasis is responsible for damaging the biomolecules such as lipids, proteins, and nucleic acids resulting in leaky membrane, altered protein, enzyme function, and DNA damage which have adverse impact on the embryo and fetal development. In this article, we attempt to summarize the available data in literature for an in-depth understanding of redox regulation during development that may help in optimizing the pregnancy outcome both under natural and assisted conditions.

Delaying Effects of Prolactin and Growth Hormone on Aging Processes in Bovine Oocytes Matured In Vitro

Aging processes accelerate dramatically in oocytes that have reached the metaphase-II (M-II) stage. The present work aimed to study the patterns and intracellular pathways of actions of prolactin (PRL) and growth hormone (GH) on age-associated changes in bovine M-II oocytes aging in vitro. To this end, we analyzed spontaneous parthenogenetic activation (cytogenetic assay), apoptosis (TUNEL assay), and the developmental capacity (IVF/IVC) of in vitro-matured oocytes after prolonged culturing. Both PRL and GH reduced the activation rate of aging cumulus-enclosed oocytes (CEOs) and denuded oocytes (DOs), and their respective hormone receptors were revealed in the ova. The inhibitor of Src-family tyrosine kinases PP2 eliminated the effects of PRL and GH on meiotic arrest in DOs, whereas the MEK inhibitor U0126 only abolished the PRL effect. Furthermore, PRL was able to maintain the apoptosis resistance and developmental competence of aging CEOs. The protein kinase C inhibitor calphostin C suppressed both the actions of PRL. Thus, PRL and GH can directly support meiotic arrest in aging M-II oocytes by activating MAP kinases and/or Src-family kinases. The effect of PRL in maintaining the developmental capacity of aging oocytes is cumulus-dependent and related to the pro-survival action of the protein kinase C-mediated signal pathway.

17β-estradiol improves the developmental ability, inhibits reactive oxygen species levels and apoptosis of porcine oocytes by regulating autophagy events

OBJECTIVES

Estrogen plays a critical role in the development and apoptosis of oocytes. Autophagy is an evolutionarily conserved and exquisitely regulated self-eating cellular process with important biological functions including the regulation of reproduction. This study aimed to determine the effect of autophagy regulated by the biologically active form of estrogen (17β-estradiol) in porcine oocyte maturation in vitro.

MATERIALS AND METHODS

We measured the effects of oocyte developmental competencies and autophagic activity in the porcine oocyte regulated by 17β-estradiol using autophagic inhibitor (Autophinib). In addition, we studied the role of autophagy in reactive oxygen species (ROS) levels, mitochondrial distribution, Ca²⁺ production, mitochondrial membrane potential (ΔΨm), and early apoptosis by caspase-3, -8 activity in the mature oocytes.

RESULTS

The results showed that the oocyte meiotic progression and early embryonic development were gradually decreased with Autophinib treatment, which was improved by 17β-estradiol. Immunofluorescence experiments revealed that 17β-estradiol primarily could promote the autophagy in the mature oocytes, and block the reduced-autophagic events by Autophinib. Moreover, 17β-estradiol improved the Autophinib induced high ROS levels, abnormal mitochondrial distribution and low Ca²⁺ production in mature oocytes. Analyses of early apoptosis and ΔΨm showed that autophagy inhibition was accompanied by increased cellular apoptosis, and 17β-estradiol reduced apoptosis rates of mature oocytes. Importantly, autophagy was downregulated by treatment with Autophinib, an activation of caspase-8 and cleaved caspase-3 increased. Those effects were abolished by 17β-estradiol, which could upregulate autophagy.

CONCLUSIONS

Our study have showed important implications that 17β-estradiol could promote efficacy of the development of porcine oocytes, enhance the autophagy, reduce ROS levels and apoptosis activity in vitro maturation.

Meiosis Resumption of Immature Human Oocytes following Treatment with Calcium Ionophore In Vitro

Objective:

In vitro maturation (IVM) of human oocytes is used to induce meiosis progression in immature retrieved oocytes. Calcium (Ca2+) has a central role in oocyte physiology. Passage through meiosis phase to another phase is controlled by increasing intracellular Ca2+. Therefore, the current research was conducted to evaluate the role of calcium ionophore (CI) on human oocyte IVM.

Materials and Methods:

In this clinical trial study, immature human oocytes were obtained from 216 intracytoplasmic sperm injection (ICSI) cycles. After ovarian stimulation, germinal vesicle (GV) stage oocytes were collected and categorized into two groups: with and without 10 µM CI treatment. Next, oocyte nuclear maturation was assessed after 24–28 hours of culture. Real-time reverse transcription polymerase chain reaction (RT-PCR) was used to assess the transcript profile of several oocyte maturation-related genes (MAPK3, CCNB1, CDK1, and cyclin D1 [CCND1]) and apoptotic-related genes (BCL-2, BAX, and Caspase-3). Oocyte glutathione (GSH) and reactive oxygen species (ROS) levels were assessed using Cell Tracker Blue and 2’,7’-dichlorodihydrofluorescein diacetate (H2DCFDA) fluorescent dye staining. Oocyte spindle configuration and chromosome alignment were analysed by immunocytochemistry.

Results:

The metaphase II (MII) oocyte rate was higher in CI‐treated oocytes (73.53%) compared to the control (67.43%) group, but this difference was not statistically significant (P=0.13). The mRNA expression profile of oocyte maturation-related genes (MAPK3, CCNB1, CDK1, and CCND1) (P<0.05) and the anti-apoptotic BCL-2 gene was remarkably up-regulated after treatment with CI (P=0.001). The pro-apoptotic BAX and Caspase-3 relative expression levels did not change significantly. The CI‐treated oocyte cytoplasm had significantly higher GSH and lower ROS (P<0.05). There was no statistically significant difference in meiotic spindle assembly and chromosome alignment between CI treatment and the control group oocytes.

Conclusion:

The finding of the current study supports the role of CI in meiosis resumption of human oocytes. (Registration Number: IRCT20140707018381N4)

Treatment of in vitro-Matured Bovine Oocytes With Tauroursodeoxycholic Acid Modulates the Oxidative Stress Signaling Pathway

In several species, oocyte and embryo competence are improved by the addition of endoplasmic reticulum (ER) stress inhibitors to in vitro maturation (IVM) medium and/or in vitro culture (IVC) medium. This study aimed to evaluate the effects of three concentrations of tauroursodeoxycholic acid (TUDCA; 50, 200, and 1,000 μM), a chemical chaperone for relieving ER stress, during IVM of bovine cumulus-oocyte complexes (COCs) for 24 h. Treated oocytes were analyzed for nuclear maturation, reactive oxygen species (ROS) production, mitochondrial activity, and abundance of target transcripts. In addition, the number of pronuclei in oocytes was evaluated after 18-20 h of insemination, and the rates of blastocyst and hatched blastocyst formation were evaluated after 7 and 8/9 days of culture, respectively. We further evaluated the transcript abundance of embryonic quality markers. Our findings showed that supplementation of IVM medium with 200 μM of TUDCA decreased ROS production and increased abundance of transcripts related to antioxidant activity in oocytes (CAT, GPX1, and HMOX1) and embryos (GPX1 and PRDX3). Interestingly, high concentration of TUDCA (1,000 μM) was toxic to oocytes, reducing the nuclear maturation rate, decreasing mitochondrial activity, and increasing the abundance of ER stress (HSPA5) and cellular apoptosis (CASP3 and CD40) related transcripts. The results of this study suggest that treatment with 200 μM of TUDCA is associated with a greater resistance to oxidative stress and indirectly with ER stress relief in bovine oocytes.

IGF2 improves the developmental competency and meiotic structure of oocytes from aged mice

Advanced maternal-age is a major factor adversely affecting oocyte quality, consequently worsening pregnancy outcomes. Thus, developing strategies to reduce the developmental defects associated with advanced maternal-age would benefit older mothers. Multiple growth factors involved in female fertility have been extensively studied; however, the age-related impacts of various growth factors remain poorly studied. In the present study, we identified that levels of insulin-like growth factor 2 (IGF2) are significantly reduced in the serum and oocytes of aged mice. We found that adding IGF2 in culture medium promotes oocyte maturation and significantly increases the proportion of blastocysts: from 41% in the untreated control group to 64% (50 nM IGF2) in aged mice (p < 0.05). Additionally, IGF2 supplementation of the culture medium reduced reactive oxygen species production and the incidence of spindle/chromosome defects. IGF2 increases mitochondrial functional activity in oocytes from aged mice: we detected increased ATP levels, elevated fluorescence intensity of mitochondria, higher mitochondrial membrane potentials, and increased overall protein synthesis, as well as increased autophagy activity and decreased apoptosis. Collectively, our findings demonstrate that IGF2 supplementation in culture media improves oocyte developmental competence and reduces meiotic structure defects in oocytes from aged mice.

Performing ICSI within 4 hours after denudation optimizes clinical outcomes in ICSI cycles

BACKGROUND

The study aimed to investigate whether and how general and partial time intervals between processes, from human chorionic gonadotrophin (HCG) trigger to intracytoplasmic sperm injection (ICSI), affected the laboratory and reproductive outcomes in ICSI cycles.

METHODS

This was a retrospective data analysis of 3602 women who underwent ICSI treatment cycles using partner or donor sperms, performed at Reproduction Medicine Center of Tongji Hospital of Tongji Medical College of Huazhong University of Science and Technology (Wuhan, China) between October 2016 and September 2018. The clinical pregnancy rate was the major outcome in the study. The fertilization and available embryo rates were secondary outcomes.

RESULTS

Data from 3602 consecutive fresh ICSI cycles was analysed. Multivariate linear regression and logistic regression analysis of factors related to fertilization and clinical pregnancy rates showed that fertilization rate (P = 0.001) and clinical pregnancy rate (P = 0.037) were significantly associated with denudation (DN)-ICSI interval. Long DN-ICSI interval was associated with higher rate of fertilization than short DN-ICSI interval but significantly decreased clinical pregnancy rate when the interval is over 4 h (P < 0.05).

CONCLUSIONS

DN-ICSI time interval can act as an independent predictor for clinical outcomes in ICSI cycles. The optimal time for ICSI is within 4 h after oocyte denudation for excellent laboratory and reproductive outcomes in ICSI cycles.

Putrescine delays postovulatory aging of mouse oocytes by upregulating PDK4 expression and improving mitochondrial activity

If fertilization does not occur for a prolonged period in vivo or in vitro, the postovulatory oocytes will deteriorate, which called the postovulatory aging. This process disrupts the developmental competence. In the present study, we showed that the reactive oxygen species (ROS) was accumulated in oocytes during the postovulatory aging. ROS inhibited Sirt1 expression, and then increased oxidative stress by downregulating the intracellular Sirt1-FOXO3a-SOD2 axis. Moreover, the inhibited Sirt1 expression was related to the decreased mitochondrial function and the lowered level of autophagy. The mitochondrial-related apoptosis was increased by inhibiting the AKT and ERK1/2 pathways, due to the accumulation of ROS in the postovulatory oocytes. The mitochondrial pyruvate dehydrogenase kinase-4 (PDK4) can reduce ROS by inhibiting the tricarboxylic acid (TAC) cycle. We found that PDK4 was significantly decreased in the postovulatory aging oocytes. Putrescine, one of the abundant biogenic amines, ameliorated the effects of ROS and therefore improved the quality of the postovulatory aging oocytes by increasing the expression of PDK4. When PDK4 was downregulated using siRNAs, the effects of putrescine were significantly receded. We concluded that putrescine delayed the aging process of postovulatory oocytes by upregulating PDK4 expression and improving mitochondrial activity.

Coenzyme Q10 ameliorates the quality of postovulatory aged oocytes by suppressing DNA damage and apoptosis

Postovulatory aging is known to compromise the oocyte quality as well as subsequent embryo development in many different animal models, and becomes one of the most intractable issues that limit the outcome of human assisted reproductive technology (ART). However, the strategies to prevent the deterioration of aged oocytes and relevant mechanisms are still underexplored. Here, we find that supplementation of CoQ10, a natural antioxidant present in human follicular fluids, is able to restore the postovulatory aging-induced fragmentation of oocytes and decline of fertilization. Importantly, we show that CoQ10 supplementation recovers postovulatory aging-caused meiotic defects such as disruption of spindle assembly, misalignment of chromosome, disappearance of actin cap, and abnormal distribution patterns of mitochondria and cortical granules. In addition, CoQ10 protects aged oocytes from premature exocytosis of ovastacin, cleavage of sperm binding site ZP2, and loss of localization of Juno, to maintain the fertilization potential. Notably, CoQ10 suppresses the aging-induced oxidative stress by reducing the levels of superoxide and DNA damage, ultimately inhibiting the apoptosis. Taken together, our findings demonstrate that CoQ10 supplementation is a feasible and effective way to prevent postovulatory aging and preserve the oocyte quality, potentially contributing to improve the successful rate of IVF (in vitro fertilization) and ICSI (intracytoplasmic sperm injection) during human ART.

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

After ovulation, mammalian oocytes will undergo a time-dependent process of aging if they are not fertilized. This postovulatory aging (POA) seriously affects the oocyte quality and then impairs the subsequent fertilization and early embryo development, which should be avoided especially in assisted reproductive technology (ART). Resveratrol is an antioxidant substance that can scavenge free radicals and is effective in improving ovary functions. Here, mouse oocytes were used to investigate the effects and mechanisms of resveratrol on POA oocytes in vitro. With 1.0 µM resveratrol treatment during aging process, the rates of fertilization and blastocyst in POA oocytes increased significantly compared with those in the POA group. Resveratrol can reduce the loss of sperm binding sites by stabilizing Juno. Resveratrol can maintain the normal morphology of spindle and mitochondrion distribution and alleviate the levels of ROS and early apoptosis. Additionally, resveratrol can reduce the changes of H3K9me2. Therefore, resveratrol can significantly improve the quality of POA oocytes in vitro to enhance the rates of fertilization and blastocyst, which may be very helpful during the ART process.

Postovulatory ageing modifies sperm-induced Ca2+ oscillations in mouse oocytes through a conditions-dependent, multi-pathway mechanism

Postovulatory ageing of mammalian oocytes occurs between their ovulation and fertilization and has been shown to decrease their developmental capabilities. Aged oocytes display numerous abnormalities, including altered Ca²⁺ signalling. Fertilization-induced Ca²⁺ oscillations are essential for activation of the embryonic development, therefore maintaining proper Ca²⁺ homeostasis is crucial for the oocyte quality. In the present paper, we show that the mechanism underlying age-dependent alterations in the pattern of sperm-triggered Ca²⁺ oscillations is more complex and multifaceted than previously believed. Using time-lapse imaging accompanied by immunostaining and molecular analyses, we found that postovulatory ageing affects the amount of Ca²⁺ stored in the cell, expression of Ca²⁺ pump SERCA2, amount of available ATP and distribution of endoplasmic reticulum and mitochondria in a manner often strongly depending on ageing conditions (in vitro vs. in vivo). Importantly, those changes do not have to be caused by oxidative stress, usually linked with the ageing process, as they occur even if the amount of reactive oxygen species remains low. Instead, our results suggest that aberrations in Ca²⁺ signalling may be a synergistic result of ageing-related alterations of the cell cycle, cytoskeleton, and mitochondrial functionality.

SIRT2 functions in aging, autophagy, and apoptosis in post-maturation bovine oocytes

AIMS

Sirtuins have been implicated in the aging process, however, the functions of SIRT2 in post-maturation aging of oocytes are not fully understood. The purpose of the present investigation was to assess the roles of SIRT2 in aged oocytes and mechanisms involved.

MAIN METHODS

The fresh MII oocytes were aging in vitro, and treated with SIRT2 inhibitor (SirReal2), autophagy activator (Rapamycin), and autophagy inhibitor (3-Ma) for 24 h, respectively. Oocyte activation, cytoplasmic fragmentation, and spindle defects, mitochondrial distribution, ROS levels, ATP production, mitochondrial membrane potential, and early apoptosis were investigated. Western blotting was performed to determine LC3-II accumulation, SQSTM1 degradation, and caspase-3 activity.

KEY FINDINGS

SIRT2 expression gradually decreased in a time-dependent manner during oocyte aging. Treatment with SirReal2 significantly increased the rates of oocyte activation, cytoplasmic fragmentation, and spindle defects. In particular, the high ROS levels, abnormal mitochondrial distribution, low ATP production, and lost ΔΨm were observed in SirReal2-exposed oocytes. Further analysis revealed that LC3-II accumulation and SQSTM1 degradation were induced by SIRT2 inhibition. By performing early apoptosis analysis showed that oocyte aging was accompanied with cellular apoptosis, and SIRT2 inhibition increased apoptosis rates of aged oocytes. Importantly, upregulating autophagy with Rapamycin could mimic the effects of SIRT2 inhibition on apoptosis by increasing caspase-3 activation, whereas downregulating autophagy with 3-MA could abolish those effects by blocking caspase-3 activation.

SIGNIFICANCE

Our results suggest that SIRT2 inactivation is a key mechanism underlying of cellular aging, and SIRT2 inhibition contributes to autophagy-dependent cellular apoptosis in post-maturation oocytes.

Thymoquinone reduces intracytoplasmic oxidative stress and improves epigenetic modification in polycystic ovary syndrome mice oocytes, during in-vitro maturation

Although in-vitro maturation (IVM) of oocytes has been presented as an alternative treatment to traditional stimulated in-vitro fertilization, the culture condition can be improved by natural antioxidants. Thus, we investigated the protective effect of Thymoquinone (TQ) during IVM in the polycystic ovary syndrome (PCOS) mice model. The induction of PCOS was made by dehydroepiandrosterone via subcutaneous injection, in prepubertal female B6D2F1-mice. After 21 days later, germinal vesicle (GV)-stage-oocytes were extracted and incubated in IVM media containing 0, 1.0, 10.0, and 100.0 μM of TQ. To assess fertilization and blastulation rates, after 22-24 hr, the treated oocytes were fertilized in-vitro with epididymal spermatozoa. Some other oocytes were evaluated for maturation, epigenetic, and oxidative stress markers. Similarly, the mRNA expression of epigenetic enzymes genes (Dnmt1 and Hdac1), three maternally derived genes (Mapk, CyclinB, and Cdk1) and apoptosis-related genes (Bax and Bcl2) were assessed. Our results showed that the maturation, fertilization, and blastulation rates were significantly higher in the 10.0 μM TQ-treated group compared with the untreated group and likewise with in-vivo matured oocytes. The Bax expression was reduced in 10.0 μM TQ matured oocytes, but Bcl2, Dnmt1, Hdac1, Cdk1, and Mapk were upregulated in this group compared to other groups. Furthermore, dimethylation of histone-3 at lysine-9 (H3K9m2) and DNA methylation were significantly increased whereas H4K12 acetylation (H4K12ac) was decreased in the 10.0 μM TQ-treated group in comparison with control and in-vivo matured oocytes. Therefore, our results are suggesting that 10.0 μM TQ may enhance the developmental competence of PCOS oocytes via the modulation of oxidative stress and epigenetic alterations.

Effects of Heyan Kuntai Capsule () on Follicular Development and Oocyte Cohesin Levels in Aged Mice

OBJECTIVE

To evaluate the effect of Heyan Kuntai Capsule (, HYKT) on the ovarian function of aged mice and expressions of cohesion complexes in oocytes.

METHODS

Twenty-five 9-month-old female C57BL/6J mice were randomly divided into 5 groups by block randomization method (n=5 per group), including the control group (saline), 17β-estradiol group [E2, 100 μg/(kg•d)], and low-, medium-, and highdose of HYKT groups [0.3, 0.9, 2.7 g/(kg•d), respectively]. All mice were treated by intragastric administration for 4 weeks. Hematoxylin and eosin staining and anti-VASA staining were used to detect the amounts of follicles. The apoptosis of follicles was measured by anti-gamma H2A histone family member X (γH2AX) staining and TdT-mediated dUTP Nick-End Labeling (TUNEL) assay. The density of cohesin subunits, REC8 meiotic recombination protein (REC8), structural maintenance of chromosome (SMC) 1β and SMC3 in oocytes were evaluated by immunofluorescent staining.

RESULTS

After administration of E2 and high-dose of HYKT, the total number of follicles as well as the number of primordial and primary follicles were significantly increased (P<0.05). Anti-γH2AX staining and TUNEL assay demonstrated that high-dose of HYKT and E2 partly suppressed the apoptosis of follicles (P<0.05). Furthermore, it showed an increased trend in the levels of REC8 and SMC1β, after administration with E2 and HYKT, and no obvious change in the level of SMC3.

CONCLUSION

HYKT could enhance the number of follicles, suppress apoptosis of oocytes and have a trend to elevate the meiotic-specific cohesin subunits (REC8 and SMC1β) in oocytes of aged mice, indicating a beneficial effect on the ovarian function in terms of the quantity and quality of follicles.

Functions and dysfunctions of the mammalian centrosome in health, disorders, disease, and aging

Since its discovery well over 100 years ago (Flemming, in Sitzungsber Akad Wissensch Wien 71:81-147, 1875; Van Beneden, in Bull Acad R Belg 42:35-97, 1876) the centrosome is increasingly being recognized as a most impactful organelle for its role not only as primary microtubule organizing center (MTOC) but also as a major communication center for signal transduction pathways and as a center for proteolytic activities. Its significance for cell cycle regulation has been well studied and we now also know that centrosome dysfunctions are implicated in numerous diseases and disorders including cancer, Alstrom syndrome, Bardet-Biedl syndrome, Huntington's disease, reproductive disorders, and several other diseases and disorders. The present review is meant to build on information presented in the previous review (Schatten, in Histochem Cell Biol 129:667-686, 2008) and to highlight functions of the mammalian centrosome in health, and dysfunctions in disorders, disease, and aging with six sections focused on (1) centrosome structure and functions, and new insights into the role of centrosomes in cell cycle progression; (2) the role of centrosomes in tumor initiation and progression; (3) primary cilia, centrosome-primary cilia interactions, and consequences for cell cycle functions in health and disease; (4) transitions from centrosome to non-centrosome functions during cellular polarization; (5) other centrosome dysfunctions associated with the pathogenesis of human disease; and (6) centrosome functions in oocyte germ cells and dysfunctions in reproductive disorders and reproductive aging.

Quercetin delays postovulatory aging of mouse oocytes by regulating SIRT expression and MPF activity

If no fertilization occurs at an appropriate time after ovulation, oocyte quality deteriorates rapidly as a process called postovulatory aging. Because the postovulatory aging of oocytes has detrimental effects on embryo development and offspring, many efforts have been made to prevent oocyte aging. Here we showed that quercetin prevented the decline in oocyte quality during postovulatory aging of oocytes. Quercetin treatment reduced aging-induced morphological changes and reactive oxygen species accumulation. Moreover, quercetin attenuated the aging-associated abnormalities in spindle organization and mitochondrial distribution, preventing decrease of SIRT expression and histone methylation. Quercetin also ameliorated the decrease in maturation-promoting factor activity and the onset of apoptosis during postovulatory aging. Furthermore, quercetin treatment during postovulatory aging improves early embryo development. Our results demonstrate that quercetin relieves deterioration in oocyte quality and improves subsequent embryo development.

Inhibition of cathepsin B activity prevents deterioration in the quality of in vitro aged porcine oocytes

The activity of cathepsin B, a member of the lysosomal protease family, directly correlates with oocyte quality and subsequent embryonic development. However, its biological function during the progression of in vitro aging of oocytes in pigs has not been demonstrated. Here, we showed that cathepsin B activity was dramatically increased during in vitro aged oocytes. The inhibition of cathepsin B activity prevented the decline of the quality of aged oocytes and improved their subsequent developmental competence. Moreover, the inhibition of cathepsin B activity reduced aging-induced mitochondrial dysfunction and attenuated oxidative stress. The inhibition of cathepsin B activity also markedly decreased early apoptosis levels and the frequency of spindle anomalies during in vitro aging of oocytes. These results demonstrate that in vitro aging of oocytes induces cathepsin B activity, which is associated with a decline in oocyte quality. The inhibition of cathepsin B activity has a beneficial effect on oocytes during the process of in vitro aging.

Role of BCL2L10 in regulating buffalo (Bubalus bubalis) oocyte maturation

It has been reported that BCL2L10 is abundantly and specifically expressed in adult human and mouse oocytes and played a very important role in oocytes maturation and early embryonic development. This study is to investigate the expression pattern of BCL2L10 in buffalo ovaries and its effect on the in vitro maturation of buffalo oocytes, so as to dissect mechanism of oocytes maturation and provide theoretical guidance for improvement of the in vitro maturation of buffalo oocytes. The results showed that BCL2L10 gene was enriched in ovary and the expression of BCL2L10 was oocyte specific and up-regulated during oocyte maturation. BCL2L10 protein and mRNA were detectable in buffalo early embryos, upregulated at 2-cell to 8-cell stages and down-regulated in the later stages. Knockdown of BCL2L10 by RNA interference resulted in a significant decrease in the maturation rate (33.5%) and cleavage rate (37.52%) of buffalo oocytes coupled with up-regulation of apoptosis-related gene Caspase-9. We concluded that BCL2L10 is a candidate associated with buffalo oocyte maturation.

Using RT-PCR and glutathione level to study the effect of follicular fluid on in vitro maturation and gene expression of sheep oocytes

The aim of this study is to evaluate the effect of sheep follicular fluid (SFF) supplementation of the in vitro maturation (IVM) media of sheep oocytes on the resumption of meiosis, glutathione (GSH) level, and expression of apoptosis (Bax, Bcl-2) as well as heat shock protein beta-1 (HSPB1) genes. Sheep ovaries were collected from the central slaughterhouse of Riyadh city, KSA. Oocytes were aspirated from 3 to 8 mm follicles. Sheep oocytes were cultured in maturation medium with different concentrations of sheep follicular fluid: 0% (control), 10%, 20% and 40% for 24 h. The results indicated that the maturation rate of oocytes was significantly (p ≤ .05) decreased in 40% SFF (36.87%) versus the control (61.3%), 10% SFF (63.95%) and 20% SFF (64.08%). The supplementation of the IVM medium with 10% SFF induced an intra-oocyte GSH concentration that was significantly higher than in sheep oocytes cultured with 20% and 40% SFF and similar to the GSH content in oocytes cultured without SFF. Real-time polymerase chain reaction analysis of gene expression revealed no significant differences in the Bax and HSPB1 genes between the control and 10% SFF, whereas they were significantly higher in 40% FF (p ≤ .05) compared to the control. The expression of Bax:Bcl-2 was significantly higher in 20% and 40% SFF compared to the control group. In conclusion, the addition of SFF to the IVM culture of sheep oocytes is recommended to support nuclear maturation and increase oocyte competence.

TCTP regulates spindle assembly during postovulatory aging and prevents deterioration in mouse oocyte quality

If no fertilization occurs for a prolonged time following ovulation, oocytes experience a time-dependent deterioration in quality both in vivo and in vitro due to processes called postovulatory aging. Because the postovulatory aging of oocytes has marked detrimental effects on embryo development and offspring, many efforts have been made to unveil the underlying mechanisms. Here we showed that translationally controlled tumor protein (TCTP) regulates spindle assembly during postovulatory aging and prevents deterioration in mouse oocyte quality. Spindle dynamics decreased with reduced TCTP level during aging of mouse oocytes. Knockdown of TCTP accelerated the reduction of spindle dynamics, accompanying with aging-related deterioration of oocyte quality. Conversely, overexpression of TCTP prevented aging-associated decline of spindle dynamics. Moreover, the aging-related abnormalities in oocytes were rescued after TCTP overexpression, thereby improving fertilization competency and subsequent embryo development. Therefore, our results demonstrate that TCTP-mediated spindle dynamics play a key role in maintaining oocyte quality during postovulatory aging and overexpression of TCTP is sufficient to prevent aging-associated abnormalities in mouse oocytes.

Centrosome and microtubule functions and dysfunctions in meiosis: implications for age-related infertility and developmental disorders

The effects of oocyte aging on meiotic spindle dynamics have been well recognised, but the mechanisms underlying the effects are not well understood. In this paper we review the role of centrosomes and the microtubule cytoskeleton in meiotic spindle formation and maintenance, and the impact of oocyte aging on spindle integrity resulting in centrosome and microtubule dysfunctions that are associated with aneuploidy. Loss of spindle integrity includes dispersion of proteins from the centrosome core structure and loss of attachment of microtubules to centrosomes and kinetochores, which will result in abnormal chromosome separation. The inability of centrosomal proteins to accurately associate with the centrosome structure may be the result of destabilisation of the core structure itself or of microtubule destabilisation at the centrosome-facing microtubule areas that are acetylated in fresh oocytes but may not be acetylated in aging oocytes. Microtubule destabilisation prevents accurate motor-driven transport of centrosomal proteins along microtubules to form and maintain a functional centrosome. Other factors to form and maintain the MII spindle include signal transductions that affect microtubule dynamics and stability. Understanding the mechanisms underlying centrosome and microtubule dysfunctions during oocyte aging will allow diagnosis and analysis of oocyte quality and abnormalities as important aspects for targeted treatment of aging oocytes to extend or restore viability and developmental capacity. New therapeutic approaches will allow improvements in reproductive success rates in IVF clinics, as well as improvements in reproductive success rates in farm animals. This review is focused on: (1) centrosome and microtubule dynamics in fresh and aging oocytes; (2) regulation of centrosome and/or microtubule dynamics and function; and (3) possible treatments to extend the oocyte's reproductive capacity and viability span.

Theory about the Embryo Cryo-Treatment

Background

To create hypothesis, which can give a logical explanation related to the benefits of freezing/thawing embryos. Cryopreservation is not only a technology used for storing embryos, but also a method of embryo treatment that can potentially improve the success rate in infertile couples.

Methods

From the analysis of multiple results in assisted reproductive technology, which have no satisfactory explanation to date, we found evidence to support a 'therapeutic' effect of the freezing/thawing of embryos on the process of recovery of the embryo and its subsequent implantation.

Results

Freezing/thawing is a way to activate the endogenous survival and repair responses in preimplantation embryos. Several molecular mechanisms can explain the higher success rate of ET using thawed embryos compared to fresh ET in women of advanced reproductive age, the higher miscarriage rate in cases of thawed blastocyst ET compared to thawed ET at early cleavage embryo, and the higher perinatal parameters of born children after thawed ET. Embryo thawing induces a stress. Controlled stress is not necessarily detrimental, because it generates a phenomenon that is counteracted by several known biological responses aimed to repair mitochondrial damage of membrane and protein misfolding. The term for favorable biological responses to low exposures to stress is called hormesis.

Conclusions

This thesis will summarize the role of cryopreservation in the activation of a hormetic response, preserving the mitochondrial function, improving survival, and having an impact on the process of implantation, miscarriage, and the development of pregnancy.

Impact of prolonged oocyte incubation time before vitrification on oocyte survival, embryo formation, and embryo quality in mice

Oocyte incubation time before freezing is one of the factors affecting oocyte vitrification. In the assisted reproductive technology (ART) clinics, it is sometimes decided to perform oocyte vitrification after a long period of incubation time due to various conditions, such as inability to collect semen samples, unsuccessful urological interventions (PESA, TESE, etc.), or unexpected conditions. A time factor of up to 6 h has been studied in the available reports. Therefore, this study was designed to evaluate oocyte incubation time before freezing at 0, 6, 12, 18, and 24 h after retrieval. Metaphase II (MII) oocytes were obtained from NMRI female mice after being randomly divided into the five groups of 0, 6, 12, 18, and 24 h of freezing via hormonal stimulation following retrieval and entered into the vitrification-warming process. The thawed oocytes were evaluated according to the survival criteria and then inseminated with the sperms of male mice for in vitro fertilization. The next day, the embryo formation rate and embryo quality were assessed. Our results demonstrated that even after 24 h of incubation, the survival rate of oocytes was 51.35% with the embryo formation rate of 73.21%. However, the survival and embryo formation rates significantly decreased within 12, 18, and 24 h after retrieval compared to the groups vitrified at 0 h. The embryo quality was significantly reduced by vitrification at 0 to 24 h after retrieval. According to our data, although a prolonged incubation time before freezing reduced the survival rate, there was still a chance for oocytes to stay alive with acceptable embryo formation and quality rates after vitrification warming of oocytes.

The role of Rad51 in safeguarding mitochondrial activity during the meiotic cell cycle in mammalian oocytes

Rad51 is a conserved eukaryotic protein that mediates the homologous recombination repair of DNA double-strand breaks that occur during mitosis and meiosis. In addition, Rad51 promotes mitochondrial DNA synthesis when replication stress is increased. Rad51 also regulates cell cycle progression by preserving the G2/M transition in embryonic stem cells. In this study, we report a novel function of Rad51 in regulating mitochondrial activity during in vitro maturation of mouse oocytes. Suppression of Rad51 by injection of Rad51 dsRNA into germinal vesicle-stage oocytes resulted in arrest of meiosis in metaphase I. Rad51-depleted oocytes showed chromosome misalignment and failures in spindle aggregation, affecting the completion of cytokinesis. We found that Rad51 depletion was accompanied by decreased ATP production and mitochondrial membrane potential and increased DNA degradation. We further demonstrated that the mitochondrial defect activated autophagy in Rad51-depleted oocytes. Taken together, we concluded that Rad51 functions to safeguard mitochondrial integrity during the meiotic maturation of oocytes.

Effect of medium additives during liquid storage on developmental competence of in vitro matured bovine oocytes

Our aim was to improve the developmental competence of bovine oocytes during their liquid storage by using additives. In vitro matured oocytes were stored for 20 h at 25°C in HEPES buffered TCM 199 medium (base medium). After storage, in vitro embryo development after in vitro fertilization was compared to those of non-stored (control) ones. Addition of 10% (v/v) newborn calf serum or 10.27 mmol/L pyruvate alone to the base medium did not improve blastocyst formation rates in stored oocytes; however, their simultaneous addition significantly improved the rate compared with those stored in base medium (P < 0.05). Supplementation of the holding medium with dithiothreitol (DTT) at any concentrations did not improve embryo development from stored oocytes. Although supplementation with cyclosporine A (CsA) significantly reduced apoptosis and membrane damage rates during storage, it did not improve the developmental competence of oocytes. 1,2-bis(2-aminophenoxy) ethane N,N,N',N'-tetraacetic acid tetrakis-acetoxymethyl ester and ruthenium red had no effect on oocyte apoptotic rates. Blastocyst formation rates in all stored groups remained significantly lower than that of the control. In conclusion, pyruvate and serum had a synergic effect to moderate the reduction of oocyte quality during storage, whereas mitochondrial membrane pore inhibitor CsA and the antioxidant DTT did not affect their developmental competence.

Oocyte aging in a marine protostome worm: The roles of maturation-promoting factor and extracellular signal regulated kinase form of mitogen-activated protein kinase

The roles of maturation-promoting factor (MPF) and an extracellular signal regulated kinase form of mitogen-activated protein kinase (ERK MAPK) are analyzed during oocyte aging in the marine protostome worm Cerebratulus. About a day after removal from the ovary, unfertilized metaphase-I-arrested oocytes of Cerebratulus begin to flatten and swell before eventually lysing, thereby exhibiting characteristics of a necroptotic mode of regulated cell death. Based on immunoblots probed with phospho-specific antibodies, MPF and ERK are initially active in freshly mature specimens. However, as oocytes age, both kinase activities decline, with ERK deactivation occurring well before MPF downregulation. Experiments using pharmacological modulators indicate that oocyte degradation is promoted by the maturation-initiated activation of ERK as well as by the deactivation of MPF that occurs in extensively aged specimens. The potential significance of these findings is discussed relative to previously published results for apoptotic eggs and oocytes of echinoderm and vertebrate deuterostomes.

The effect of temperature during liquid storage of in vitro-matured bovine oocytes on subsequent embryo development

The aim of the present study was to optimize the temperature for the temporal storage of matured bovine oocytes. In vitro-matured bovine oocytes were preserved in HEPES-buffered TCM199 medium supplemented with 10% newborn calf serum at different temperatures (4 °C, 15 °C, 25 °C, and 38.5 °C) for 20 hours. Embryo development and blastocyst quality after in vitro fertilization, cytoplasmic ATP and glutathione levels in oocytes, and the frequency of apoptotic oocytes were compared among storage groups and a control group without storage. Among the storage groups, those at 25 °C and 38.5 °C showed the highest rates of blastocyst development (19.3% and 24.5%, respectively) compared with those stored at 4 °C and 15 °C (8.5% and 14.9%, respectively); however, blastocyst formation rates in all storage groups were lower than that in the control group (39.8%; P < 0.05). Storage at 38.5 °C and 15 °C was associated with reduced cell numbers in resultant blastocysts compared with the control and the 25 °C storage groups. Storage at 4 °C reduced metabolic activity of oocytes characterized by their lower ATP levels compared with the other groups. Storage for 20 hours significantly reduced the glutathione content in oocytes in all groups in a similar manner, irrespective of the temperature. Storage at 4 °C or 15 °C but not at 25 °C and 38.5 °C significantly increased the percentage of apoptotic oocytes compared with the control group. In conclusion, 25 °C was found to be the most suitable temperature for the temporal storage of matured bovine oocytes regarding both the developmental competence of oocytes and the quality of resultant blastocysts.

Prolactin and growth hormone affect metaphase-II chromosomes in aging oocytes via cumulus cells using similar signaling pathways

General senescence of the adult organism is closely connected with reproductive one. Meanwhile, the age-related reduction in the female fertility is primarily associated with a decline in the gamete quality. Molecular and cellular changes in oocytes of old mammalian females are very similar to those occurring during aging of matured ova of their young counterparts, suggesting similarities in underlying mechanisms. The aim of the present work was to study actions of two related pituitary hormones, prolactin (PRL) and growth hormone (GH), on age-associated modifications of metaphase-II (M-II) chromosomes in bovine oocytes using a model of the prolonged culture. We analyzed: (1) effects of PRL and GH on abnormal changes in the chromosome morphology in aging matured oocytes and the role of cumulus cells in these effects and (2) signaling pathways involved in the hormone actions. During the prolonged culture of oocytes, a gradual rise in the frequency of destructive modifications of M-II chromosomes was revealed. In the case of cumulus-enclosed oocytes (CEOs), PRL and GH exerted dose-dependent biphasic effects on the frequency of these modifications. Both PRL (50 ng/ml) and GH (10 ng/ml) decelerated the abnormal chromosome changes in CEOs, but did not affect the chromosome configuration in denuded oocytes. Concurrently, the presence of PRL and GH receptors in cumulus cells surrounding matured oocytes was demonstrated. Attenuating effects of both hormones on the chromosome modifications in aging CEOs were abolished by PP2 (an inhibitor of Src-family tyrosine kinases), triciribine (an inhibitor of Akt kinase), and calphostin C (a protein kinase C inhibitor). Our findings indicate that PRL and GH can exert the similar decelerating action on age-associated alterations in the M-II chromosome morphology in bovine ova, which is mediated by cumulus cells and may be related to activation of Src-family tyrosine kinases as well as Akt- and protein kinase C-dependent signal pathways.

Extended in vitro maturation affects gene expression and DNA methylation in bovine oocytes

To mimic post-ovulatory ageing, we have extended the in vitro maturation (IVM) phase to 48 h and examined effects on (i) developmental potential, (ii) expression of a panel of developmentally important genes and (iii) gene-specific epigenetic marks. Results were compared with the 24 h IVM protocol (control) usually employed for bovine oocytes. Cleavage rates and blastocyst yields were significantly reduced in oocytes after extended IVM. No significant differences were observed in the methylation of entire alleles in oocytes for the genes bH19, bSNRPN, bZAR1, bOct4 and bDNMT3A. However, we found differentially methylated CpG sites in the bDNMT3Ls locus in oocytes after extended IVM and in embryos derived from them compared with controls. Moreover, embryos derived from the 48 h matured oocyte group were significantly less methylated at CpG5 and CpG7 compared with the 24 h group. CpG7 was significantly hypermethylated in embryos produced from the control oocytes, but not in oocytes matured for 48 h. Furthermore, methylation for CpG5-CpG8 of bDNMT3Ls was significantly lower in oocytes of the 24 h group compared with embryos derived therefrom, whereas no such difference was found for oocytes and embryos of the in vitro aged group. Expression of most of the selected genes was not affected by duration of IVM. However, transcript abundance for the imprinted gene bIGF2R was significantly reduced in oocytes analyzed after extended IVM compared with control oocytes. Transcript levels for bPRDX1, bDNMT3A and bBCLXL were significantly reduced in 4- to 8-cell embryos derived from in vitro aged oocytes. These results indicate that extended IVM leads to ageing-like alterations and demonstrate that epigenetic mechanisms are critically involved in ageing of bovine oocytes, which warrants further studies into epigenetic mechanisms involved in ageing of female germ cells, including humans.

Morphological, cellular and molecular changes during postovulatory egg aging in mammals

Postovulatory aging is associated with several morphological, cellular and molecular changes that deteriorate egg quality either by inducing abortive spontaneous egg activation (SEA) or by egg apoptosis. The reduced egg quality results in poor fertilization rate, embryo quality and reproductive outcome. Although postovulatory aging-induced abortive SEA has been reported in several mammalian species, the molecular mechanism(s) underlying this process remains to be elucidated. The postovulatory aging-induced morphological and cellular changes are characterized by partial cortical granules exocytosis, zona pellucida hardening, exit from metaphase-II (M-II)arrest and initiation of extrusion of second polar body in aged eggs. The molecular changes include reduction of adenosine 3',5'- cyclic monophosphate (cAMP) level, increase of reactive oxygen species (ROS) and thereby cytosolic free calcium (Ca²⁺) level. Increased levels of cAMP and/or ROS trigger accumulation of Thr-14/Tyr-15 phosphorylated cyclin-dependent kinase 1 (Cdk1) on one hand and degradation of cyclin B1 through ubiquitin-mediated proteolysis on the other hand to destabilize maturation promoting factor (MPF). The destabilized MPF triggers postovulatory aging-induced abortive SEA and limits various assisted reproductive technologies (ARTs) outcome in several mammalian species. Use of certain drugs that can either increase cAMP or reduce ROS level would prevent postovulatory aging-induced deterioration in egg quality so that more number of good quality eggs can be made available to improve ART outcome in mammals including human.

Reduction of phosphorylated Thr-161 Cdk1 level participates in roscovitine-induced Fas ligand-mediated apoptosis in rat eggs cultured in vitro

The present study was aimed to find out whether roscovitine reduces phosphorylated Thr-161 of cyclin-dependent kinase 1 (Cdk1) level and induces egg apoptosis through Fas ligand (FasL)-mediated pathway. For this purpose, ovulated eggs were cultured in media 199 with or without various concentrations of roscovitine (0, 25, 50, 100, 200 μM) for 3 h in vitro. The morphological apoptotic changes, phosphorylation status of Cdk1, FasL concentration, caspase-8 and caspase-3 activities, and DNA fragmentation were analyzed. Data of the present study suggest that roscovitine significantly reduced Thr-161 phosphorylated Cdk1 level without altering the total level of Cdk1 and induced cytoplasmic fragmentation, a morphological apoptotic feature in a concentration-dependent manner. The roscovitine-induced cytoplasmic fragmentation was associated with increased FasL concentration. The increased FasL concentration induced caspase-8 followed by caspase-3 activities. The increased caspases activity finally induced DNA fragmentation in eggs that showed cytoplasmic fragmentation. Taken together, these results suggest that roscovitine reduced phosphorylated Thr-161 of Cdk1 level and induces apoptosis through FasL-mediated pathway in rat eggs cultured in vitro.

Maternal age effect on mouse oocytes: new biological insight from proteomic analysis

The long-standing view of ‘immortal germline vs mortal soma’ poses a fundamental question in biology concerning how oocytes age in molecular terms. A mainstream hypothesis is that maternal ageing of oocytes has its roots in gene transcription. Investigating the proteins resulting from mRNA translation would reveal how far the levels of functionally available proteins correlate with mRNAs and would offer novel insights into the changes oocytes undergo during maternal ageing. Gene ontology (GO) semantic analysis revealed a high similarity of the detected proteome (2324 proteins) to the transcriptome (22 334 mRNAs), although not all proteins had a cognate mRNA. Concerning their dynamics, fourfold changes of abundance were more frequent in the proteome (3%) than the transcriptome (0.05%), with no correlation. Whereas proteins associated with the nucleus (e.g. structural maintenance of chromosomes and spindle-assembly checkpoints) were largely represented among those that change in oocytes during maternal ageing; proteins associated with oxidative stress/damage (e.g. superoxide dismutase) were infrequent. These quantitative alterations are either impoverishing or enriching. Using GO analysis, these alterations do not relate in any simple way to the classic signature of ageing known from somatic tissues. Given the lack of correlation, we conclude that proteome analysis of mouse oocytes may not be surrogated with transcriptome analysis. Furthermore, we conclude that the classic features of ageing may not be transposed from somatic tissues to oocytes in a one-to-one fashion. Overall, there is more to the maternal ageing of oocytes than mere cellular deterioration exemplified by the notorious increase of meiotic aneuploidy.

Oxidative stress and redox regulation of gametogenesis, fertilization, and embryonic development

Oxidative stress caused by elevated reactive oxygen species (ROS) is one of the predominant causes of both male and female infertility. Oxidative stress conditions cause either cell death or senescence by oxidation of cellular molecules including nucleic acid, proteins, and lipids. It is particularly important to minimize oxidative stress when in vitro fertilization is performed for the purpose of assisted reproduction. The problems associated with assisted reproductive technology are becoming evident, and it is now the time to clarify its mechanisms and cope with them. On the other hand, the beneficial roles of ROS, such as intracellular signaling, have become evident. The antithetical functions of ROS make it more difficult to overcome the problems caused by oxidative stress. Despite the difficulty in understanding mammalian reproduction, the mechanisms and problems can be gradually unveiled by advanced technology such as genetic modification of animals.

Mechanistic action of mesenchymal stem cell injection in the treatment of chemically induced ovarian failure in rabbits

BACKGROUND

No curative treatment is known for primary ovarian failure; however, mesenchymal stem cells (MSCs), through self-renewal and regeneration, push the trial to evaluate their role in the treatment of ovarian failure. The aim of this study was to explore the impact of MSCs on cyclophosphamide (CTX)-induced ovarian failure in rabbits and to clarify the mechanism(s) by which MSCs exert their action.

METHODS

Thirty-five adult female rabbits were injected with CTX to induce ovarian failure. Five rabbits were euthanized after the last injection of CTX for histological examination. The others (30 rabbits) were further subdivided into two groups: group 1 (ovarian failure group, 15 rabbits) received no treatment; group 2 (ovarian failure and MSC recipient group, 15 rabbits) received MSCs isolated from extracted bone marrow of male rabbits.

RESULTS

A decrease of follicle-stimulating hormone and an increase of estrogen and vascular endothelial growth factor (VEGF) levels in the MSC recipient group versus the ovarian failure group were found. Weak caspase-3 expression and +ve proliferating cell nuclear antigen staining after MSC injection were detected. Cytological and histological examinations showed increased follicle numbers with apparent normal structure of ovarian follicles in the MSC recipient group. Moreover, Y chromosome-containing cells from male donors were present within the ovarian tissues in group 2.

CONCLUSIONS

The current study suggests that intravenous injection of MSCs into rabbits with chemotherapy-induced ovarian damage improved ovarian function. MSCs accomplish this function by direct differentiation into specific cellular phenotypes and by secretion of VEGF, which influence the regeneration of the ovary.