Glutathione content and glutathione peroxidase expression in in vivo and in vitro matured equine oocytes

Effects of holding and the addition of naloxone on vitrification of equine immature oocytes

This study investigates the effects of overnight holding and naloxone (Nx) supplementation on the vitrification outcomes of equine immature oocytes. Oocytes were divided into six experimental groups based on treatment combinations: fresh (F) and held (H) control oocytes, oocytes vitrified with or without Nx (10-8 M) (VIT and VIT-Nx), oocytes vitrified after overnight holding with or without Nx (10-8 M) (H-VIT and H-VIT-Nx). They were assessed for survival, meiotic competence, intracellular oxidative stress, mitochondrial activity and distribution, apoptosis, and apoptotic gene expression. At survival rate determination, the degeneration rate was higher in VIT and VIT-Nx compared to F (P < 0.05). The highest maturation rate was observed in VIT-Nx. A significant reduction in ROS levels was observed in H compared to F (P < 0.05). ROS levels were similar between F and VIT, while the Nx supplementation tended to increase them (VIT-Nx vs F: P = 0.053; VIT-Nx vs VIT: P = 0.069). Conversely, in oocytes vitrified after overnight holding, vitrification induced an increase in ROS levels (H vs VIT: P < 0.05), which was not observed in H-VIT-Nx. GSH intracellular levels showed significant differences only in held oocytes, with higher GH levels in H compared to H-VIT and H-VIT-Nx (P < 0.05). All treatments induced an increase in HMMP levels compared to F (P < 0.05). In H oocytes, mitochondria were distributed throughout the entire oolemma (TOMM20) and active mitochondria (D-LAT) were detected in the outermost region. Incontrast, in H-VIT-Nx, potentially active mitochondria were spread throughout the cytoplasm. AnnexinV/PI staining revealed that the percentage of viable oocytes was higher (P < 0.05) in F and H than in all vitrified/warmed oocytes, and H-VIT-Nx had the highest degeneration rate (P < 0.05). RT-PCR analysis confirmed the detection for both reference genes, and target genes BCL2 and Survivin in all samples. In contrast, BAX and p53 transcripts were consistently undetectable. No significant differences were observed in the expression of BCL2 and Survivin between groups. In conclusion, overnight holding at uncontrolled room temperature can alter oocyte characteristics and lead to variable results after vitrification. Nx demonstrated contrasting antioxidant effects depending on the vitrification timing, but it appeared to improve IVM outcomes in oocytes vitrified immediately after collection.

Building a Human Ovarian Antioxidant ceRNA Network "OvAnOx": A Bioinformatic Perspective for Research on Redox-Related Ovarian Functions and Dysfunctions

The ovary is a major determinant of female reproductive health. Ovarian functions are mainly related to the primordial follicle pool, which is gradually lost with aging. Ovarian aging and reproductive dysfunctions share oxidative stress as a common underlying mechanism. ROS signaling is essential for normal ovarian processes, yet it can contribute to various ovarian disorders when disrupted. Therefore, balance in the redox system is crucial for proper ovarian functions. In the present study, by focusing on mRNAs and ncRNAs described in the ovary and taking into account only validated ncRNA interactions, we built an ovarian antioxidant ceRNA network, named OvAnOx ceRNA, composed of 5 mRNAs (SOD1, SOD2, CAT, PRDX3, GR), 10 miRNAs and 5 lncRNAs (XIST, FGD5-AS1, MALAT1, NEAT1, SNHG1). Our bioinformatic analysis indicated that the components of OvAnOx ceRNA not only contribute to antioxidant defense but are also involved in other ovarian functions. Indeed, antioxidant enzymes encoded by mRNAs of OvAnOx ceRNA operate within a regulatory network that impacts ovarian reserve, follicular dynamics, and oocyte maturation in normal and pathological conditions. The OvAnOx ceRNA network represents a promising tool to unravel the complex dialog between redox potential and ovarian signaling pathways involved in reproductive health, aging, and diseases.

Use of green microalgae Chlorella as a nutritional supplement to support oocyte and embryo production in goats

This study aimed to evaluate the use of green microalgae as a nutritional supplement for oocyte and embryo production in goats. Two experiments were performed on adult goats to obtain oocytes (EVO; n = 14) and in vivo embryos (IVD; n = 14). In both, the donors were divided into control (n = 7) and Chlorella (n = 7) groups. All goats received a base diet, and donors were orally supplemented with Chlorella pyrenoidosa (CH) in the Chlorella groups. For EVO, donors received 10 g CH for 14 days, and for IVD, 20 g CH was given for six days before embryo recovery. In EVO and IVD, food intake in the CH group was comparatively low, and it showed relatively high subcutaneous adipose deposition. In addition, the CH group exhibited an increase in triglyceride, cholesterol, and plasma glucose levels. In IVD, a significant increase in peripheral glutathione peroxidase levels was noticed. In EVO, the CH group showed relatively large follicular size and an increase in intrafollicular levels of triglycerides, glucose, and glutathione peroxidase. No differences were observed in the oocyte collected, and CH oocytes showed a low intensity of MitoTracker fluorescence (MT). In IVD, the CH group had a high proportion of transferable embryos, and these structures exhibited high fluorescence intensities for MT and H2DCFDA probes. We concluded that under these conditions, CH did not enhance the quality of the recovered oocytes. However, a daily dose of 20 g CH improved the quality of embryos and stimulated their mitochondrial functionality.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Reactive oxygen species in the mammalian pre-implantation embryo

In brief

Reactive oxygen species are generated throughout the pre-implantation period and are necessary for normal embryo formation. However, at pathological levels, they result in reduced embryo viability which can be mediated through factors delivered by sperm and eggs at conception or from the external environment.

Abstract

Reactive oxygen species (ROS) occur naturally in pre-implantation embryos as a by-product of ATP generation through oxidative phosphorylation and enzymes such as NADPH oxidase and xanthine oxidase. Biological concentrations of ROS are required for crucial embryonic events such as pronuclear formation, first cleavage and cell proliferation. However, high concentrations of ROS are detrimental to embryo development, resulting in embryo arrest, increased DNA damage and modification of gene expression leading to aberrant fetal growth and health. In vivo embryos are protected against oxidative stress by oxygen scavengers present in follicular and oviductal fluids, while in vitro, embryos rely on their own antioxidant defence mechanisms to protect against oxidative damage, including superoxide dismutase, catalase, glutathione and glutamylcysteine synthestase. Pre-implantation embryonic ROS originate from eggs, sperm and embryos themselves or from the external environment (i.e. in vitro culture system, obesity and ageing). This review examines the biological and pathological roles of ROS in the pre-implantation embryo, maternal and paternal origins of embryonic ROS, and from a clinical perspective, we comment on the growing interest in combating increased oxidative damage in the pre-implantation embryo through the addition of antioxidants.

Macromolecules Influence Cellular Competence and Expression Level of IGFs Genes in Bovine Oocytes In Vitro

In vitro maturation (IVM) of mammalian oocytes, which influences subsequent in vitro development of embryos, is affected by the macromolecule content in culture media for the success of oocyte maturation competence, in which the cytoplasmic and nuclear reprogramming events occur. The insulin-like growth factor family (IGFs) promotes the maturation of bovine oocytes and the expansion of cumulus cells and also inhibits apoptosis. This study was, therefore, designed to examine the effects of macromolecules (bovine serum albumin, BSA; fetal calf serum, FCS; and polyvinyl alcohol, PVA) on in vitro nuclear maturation, total cellular protein, glutathione peroxidase (GPx) enzyme activity, and the gene expression level of IGF1, IGF2, and their receptor in bovine oocytes. Oocytes obtained from bovine ovaries were cultured in bicarbonate-buffered medium 199 supplemented with 4 mg/mL BSA, 10% FCS, 1 mg/mL PVA, and without macromolecule supplement (control) during 22 h in the air with a humidified atmosphere and 5% CO2 at 38.5 °C temperature. Supplementation of BSA and FCS increased (χ2 = 9.84; p < 0.05) the percentages of oocytes that reached metaphase II compared to the control and PVA. The amount of protein per ml of cell extracts of oocytes matured in FCS supplemented culture media was higher (p < 0.05) than the oocytes in the PVA and control. The levels of GPx enzyme activity in cell extracts isolated from oocytes in each experimental group did not change over time, but the GPx enzyme activity in oocytes matured in PVA-supplemented culture media was lower (p < 0.05) than in oocytes in the other experimental groups. Transcript for the IGF1 gene was not detected in all experimental groups, but the supplementation of BSA and FCS significantly elevated the transcript level of the IGF2 gene. In addition, the maturation of oocytes with BSA-supplemented media increased the transcript level of the IGF1R gene, whereas the transcript level of the IGF2R gene was similar among macromolecule supplementation groups. The current study concluded that BSA and FCS could improve in vitro bovine oocyte development due to supporting nuclear maturation and increasing the total cellular protein content, GPx enzyme, and transcript activity.

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.

Effect of lycopene supplementation to bovine oocytes exposed to heat shock during in vitro maturation

We investigated the effect of the antioxidant lycopene supplemented into the in vitro maturation medium (TCM-199 with 20 ng/mL epidermal growth factor and 50 mg/mL gentamycin) in a heat shock (HS) model to mimic in vivo heat stress conditions. Bovine cumulus-oocyte complexes were supplemented with 0.2 μM lycopene (or not supplemented; control) under HS (40.5 °C) and non-HS (NHS; 38.5 °C) during maturation. After 22 h of maturation, we evaluated the nuclear status of the oocytes, the level of reactive oxygen species (ROS) production, and the respective blastocyst development and quality (via differential staining). Data were fitted in logistic and linear regression models, and the replicates were set as a random effect. The nuclear maturation was higher in NHS (84.0 ± 3.2%; least square mean ± standard error) than HS control (60.4 ± 4.3%; P < 0.001). Remarkably, the nuclear maturation in HS lycopene (71.7 ± 4.1%) was similar to NHS control (P = 0.7). Under HS conditions lycopene reduced ROS production (27.4 ± 4.8; relative fluorescence units (RFU)) in comparison to HS control (33.8 ± 1.8 RFU; P = 0.009). However, the ROS production in NHS lycopene (18.9 ± 2.0 RFU) was similar to NHS control (18.7 ± 1.8 RFU; P = 0.9). The cleavage rate in HS lycopene (76.1 ± 3.3%) was not lower than NHS lycopene (83.3 ± 2.5%; P > 0.1). On the day 8 of embryo development, the blastocyst rate was higher for NHS lycopene (55.2 ± 4.7%) versus NHS control (44.5 ± 4.7%; P = 0.04), but under HS the day 8 blastocyst rate was similar between control (29.9 ± 4.2%) and lycopene (32.3 ± 4.2%; P = 0.9). Lycopene supplementation increased the cell number of the embryos (total cell, trophectoderm, and inner cell mass numbers) under NHS conditions (P > 0.03). The apoptotic cell ratio was lower in lycopene (NHS and HS) versus control (NHS and HS) (P > 0.04). Lycopene has the ability to scavenge oocyte ROS and improved the cleavage rate of embryos under HS conditions. However, this could not be translated to a higher blastocyst development, which remained lower under HS. Results of our study indicate that antioxidant supplementation like lycopene during the maturation of bovine cumulus-oocyte complexes may be routinely used to improve blastocyst rate and quality under standard maturation conditions.

A Nuclear and Cytoplasmic Characterization of Bovine Oocytes Reveals That Cysteamine Partially Rescues the Embryo Development in a Model of Low Ovarian Reserve

Simple Summary

Women’s reproductive performance starts declining in the mid-30s, and by age 40–45, the possibility of becoming pregnant becomes very small. Reproductive aging is a physiological process of fertility decline characterized by a decrease in quality and stockpile of eggs (also called ovarian reserve) in most mammals. However, young individuals too can show an accelerated reproductive aging that similarly results in a low ovarian reserve and hypofertility. This syndrome, called premature ovarian failure (POF), is becoming a relevant problem due to the general tendency to postpone the first pregnancy. In this study, we used bovine ovaries that were classified in two categories, according to the number of follicles visible on the ovarian surface, and analyzed some parameters of egg maturation. We observed that eggs from the ‘aging-like’ ovaries carry several defects that impair maturation. However, one of the parameters was improved upon supplementation with a scavenger of free radicals, providing a proof of concept that in-depth knowledge of the cellular mechanisms is essential to find solutions to everyday-life problems.

Abstract

Decreased oocyte quality is a major determinant of age-associated fertility decline. Similarly, individuals affected by early ovarian aging carry low-quality oocytes. Using an established bovine model of early ovarian aging, we investigated key features of ‘quality’ oocyte maturation, associated with the onset of egg aneuploidy and reproductive aging, such as histone modifications, mitochondria distribution and activity, reduced glutathione (GSH) content, and gap junction functionality. Bovine ovaries were classified according to the antral follicle count (AFC), and the retrieved oocytes were processed immediately or matured in vitro. We observed alterations in several cellular processes, suggesting a multifactorial etiology of the reduced oocyte quality. Furthermore, we performed a rescue experiment for one of the parameters considered. By adding cysteamine to the maturation medium, we experimentally increased the free radical scavenger ability of the ‘low competence’ oocytes and obtained a higher embryo development. Our findings show that adopting culture conditions that counteract the free radicals has a positive impact on the quality of ‘compromised’ oocytes. Specifically, cysteamine treatment seems to be a promising option for treating aging-related deficiencies in embryo development.

Chitosan nanoparticles enhance developmental competence of in vitro-matured porcine oocytes

Oxidative stress is inevitable as it is derived from the handling, culturing, inherent metabolic activities and medium supplementation of embryos. This study was performed to investigate the protective effect of chitosan nanoparticles (CNPs) on oxidative damage in porcine oocytes. For this purpose, cumulus-oocyte complexes (COCs) derived from porcine slaughterhouse ovaries were exposed to different concentrations of CNPs (0, 10, 25 and 50 µg/ml) during in vitro maturation (IVM). Oocytes treated with 25 µg/ml CNPs showed significantly higher levels of GSH, along with a significant reduction in ROS levels compared to control, CNPs10 and CNPs50 groups. In parthenogenetic embryo production, the maturation rate was significantly higher in the CNPs25 group than that in the control and all other treated groups. In addition, when compared to the CNPs50 and control groups, CNPs25-treated oocytes showed significantly higher cleavage and blastocyst development rates. The highest concentration of CNPs reduced the total cell number and ratio of ICM: TE cells in parthenogenetic embryos, suggesting that there is a threshold where benefits are lost if exceeded. In cloned embryos, the CNPs25 group, as compared to all other treated groups, showed significantly higher maturation and cleavage rates. Furthermore, the blastocyst development rate in the CNPs25-treated group was significantly higher than that in the CNPs50-treated group, as was the total cell number. Moreover, we found that cloned embryos derived from the CNPs25-treated group showed significantly higher expression levels of Pou5f1, Dppa2, and Ndp52il genes, compared with those of the control and other treated groups. Our results demonstrated that 25 µg/ml CNPs treatment during IVM improves the developmental competence of porcine oocytes by reducing oxidative stress.

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

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

Transferrin and antioxidants partly prevented mouse oocyte oxidative damage induced by exposure of cumulus-oocyte complexes to endometrioma fluid

Background

Exposure of oocytes to the endometrioma fluid has an adverse effect on embryonic quality. To determine whether adding transferrin and antioxidants to culture medium could counteract detrimental effects on mouse cumulus-oocyte complexes (COCs) induced by exposure to endometrioma fluid or not, we conducted an in vitro cross-sectional study using human and mouse COCs.

Methods

Eighteen women who had their oocytes exposed to endometrioma fluid during oocyte retrieval were enrolled. COCs from superovulated ICR female mice were collected. They were first exposed to human endometrioma fluid and then treated by transferrin and/or antioxidants (cysteamine + cystine). Subsequently, COCs function was assessed by molecular methods.

Results

This study observed that human COCs inadvertently exposed to endometrioma fluid in the in vitro fertilization (IVF) group led to a lower good quality embryo rate compared to intracytoplasmic sperm injection (ICSI) group. Exposure of mouse COCs to endometrioma fluid accelerated oocyte oxidative damage, evidenced by significantly reduced CCs viability, defective mitochondrial function, decreased GSH content and increased ROS level, associated with the significantly higher pro-portion of abnormal spindles and lower blastocyst formation (p < 0.05, respectively). This damage could be recovered partly by treating COCs with transferrin and antioxidants (cysteamine + cystine).

Conclusions

Transferrin and antioxidants could reduce the oxidative damage caused by COCs exposure to endometrioma fluid. This finding provides a promising new possibility for intervention in the human oocyte oxidative damage process induced by endometrioma fluid during oocyte pick-up.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-020-00738-0.

A prematuration approach to equine IVM: considering cumulus morphology, seasonality, follicle of origin, gap junction coupling and large-scale chromatin configuration in the germinal vesicle

Several studies report that a two-step culture where mammalian oocytes are first kept under meiosis-arresting conditions (prematuration) followed by IVM is beneficial to embryo development. The most promising results were obtained by stratifying the oocyte population using morphological criteria and allocating them to different culture conditions to best meet their metabolic needs. In this study, horse oocytes were characterised to identify subpopulations that may benefit from prematuration. We investigated gap-junction (GJ) coupling, large-scale chromatin configuration and meiotic competence in compact and expanded cumulus-oocyte complexes (COCs) according to follicle size (<1, 1-2, >2cm) and season. Then we tested the effect of cilostamide-based prematuration in compact COCs collected from follicles <1 and 1-2cm in diameter on embryo development. Meiotic competence was not affected by prematuration, whereas COCs from follicles 1-2cm in diameter yielded embryos with a higher number of cells per blastocyst than oocytes that underwent direct IVM (P<0.01, unpaired Mann-Whitney test), suggesting improved developmental competence. Oocytes collected from follicles <1cm in diameter were not affected by prematuration. This study represents an extensive characterisation of the functional properties of immature horse oocytes and is the first report of the effects of cilostamide-based prematuration in horse oocyte IVM on embryo development.

Severity of prepregnancy diabetes on the fetal malformations and viability associated with early embryos in rats†

Preexisting/pregestational diabetes enhances the risk of birth defects. Several factors have been involved during the implantation process, such as cytokines (granulocyte-macrophage-colony-stimulating factor [GM-CSF]). The objective was to evaluate the effects of two levels of diabetes on the redox status of preimplantation embryos during the implantation process to comprehend how both are involved in embryo and fetal viability against maternal diabetes. Female Sprague-Dawley rats received streptozotocin at birth (mild diabetes [MD]) or at adulthood (severe diabetes [SD]) to obtain two experimental diabetes intensities. After confirming the diabetic status, the nondiabetic and diabetic groups were mated around day 110 of life. At gestational day (GD) 21, fetuses were assessed for viability and malformations and ovaries for embryo loss before implantation. Other pregnant nondiabetic and diabetic rats were sacrificed at GD2-4 for maternal and preimplantation embryo oxidative stress markers, maternal serum insulin, uterine fluid GM-CSF, and preimplantation embryo morphological analysis. MD and SD caused abnormal redox levels, lower GM-CSF and insulin levels during the preimplantation period, and embryonic loss before implantation. SD caused lower fetal viability and higher fetal malformation percentages at GD21. The SD dam-derived preimplantation embryos presented lower glutathione levels and higher thiobarbituric acid reactive substances concentration at GD3 and an increased frequency of abnormal preimplantation embryos at GD4. In conclusion, preexisting diabetes leads to complications in the implantation process. Furthermore, maternal oxidative stress and other metabolic changes alter the redox state and morphological structure of preimplantation embryos, contributing to damaged growth and development in late pregnancy.

The key long non-coding RNA screening and validation between germinal vesicle and metaphase II of porcine oocyte in vitro maturation

Oocyte maturation plays a vitally important role in the reproduction of pigs. However, the roles of messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs) in the developmental process of porcine oocyte maturation are still largely unclear. In this study, a transcriptome analysis of germinal vesicle (GV) and metaphase II (MII) of oocytes from Chinese Duroc pigs was performed. A total of 1,753,030 and 2,486 differentially expressed (DE) mRNAs, 22,811 and 9,868 DE lncRNAs were identified between GV and MII stages, respectively. Furthermore, functional enrichment analysis showed that the common DE mRNAs and DE lncRNAs during the process of maturation were mainly involved in biological process and cellular components. Our study provides new insights of the expression changes of mRNAs and lncRNAs during GV and MII stages, which might contribute to the maturation of oocytes. These results greatly improve our understanding of the molecular mechanisms regulating the maturation of oocytes in pigs.

Cellular and molecular mechanisms of the preovulatory follicle differenciation and ovulation: What do we know in the mare relative to other species

Terminal follicular differentiation and ovulation are essential steps of reproduction. They are induced by the increase in circulating LH, and lead to the expulsion from the ovary of oocytes ready to be fertilized. This review summarizes our current understanding of cellular and molecular pathways that control ovulation using a broad mammalian literature, with a specific focus to the mare, which is unique in some aspects of ovarian function in some cases. Essential steps and key factors are approached. The first part of this review concerns LH, receptors and signaling, addressing the description of the equine gonadotropin and cloning, signaling pathways that are activated following the binding of LH to its receptors, and implication of transcription factors which better known are CCAAT-enhancer-binding proteins (CEBP) and cAMP response element-binding protein (CREB). The second and major part is devoted to the cellular and molecular actors within follicular cells during preovulatory maturation. We relate to 1) molecules involved in vascular permeability and vasoconstriction, 2) involvement of neuropeptides, such as kisspeptin, neurotrophins and neuronal growth factor, neuropeptide Y (NPY), 3) the modification of steroidogenesis, steroids intrafollicular levels and enzymes activity, 4) the local inflammation, with the increase in prostaglandins synthesis, and implication of leukotrienes, cytokines and glucocorticoids, 5) extracellular matrix remodelling with involvement of proteases, antiproteases and inhibitors, as well as relaxin, and finaly 6) the implication of oxytocine, osteopontin, growth factors and reactive oxygen species. The third part describes our current knowledge on molecular aspect of in vivo cumulus-oocyte-complexe maturation, with a specific focus on signaling pathways, paracrine factors, and intracellular regulations that occur in cumulus cells during expansion, and in the oocyte during nuclear and cytoplasmic meiosis resumption. Our aim was to give an overall and comprehensive map of the regulatory mechanisms that intervene within the preovulatory follicle during differentiation and ovulation.

In vitro maturation affects chromosome segregation, spindle morphology and acetylation of lysine 16 on histone H4 in horse oocytes

Implantation failure and genetic developmental disabilities in mammals are caused by errors in chromosome segregation originating mainly in the oocyte during meiosis I. Some conditions, like maternal ageing or in vitro maturation (IVM), increase the incidence of oocyte aneuploidy. Here oocytes from adult mares were used to investigate oocyte maturation in a monovulatory species. Experiments were conducted to compare: (1) the incidence of aneuploidy, (2) the morphology of the spindle, (3) the acetylation of lysine 16 on histone H4 (H4K16) and (4) the relative amount of histone acetyltransferase 1 (HAT1), K(lysine) acetyltransferase 8 (KAT8, also known as MYST1), histone deacetylase 1 (HDAC1) and NAD-dependent protein deacetylase sirtuin 1 (SIRT1) mRNA in metaphase II stage oocytes that were in vitro matured or collected from peri-ovulatory follicles. The frequency of aneuploidy and anomalies in spindle morphology was increased following IVM, along with a decrease in H4K16 acetylation that was in agreement with our previous observations. However, differences in the amount of the transcripts investigated were not detected. These results suggest that the degradation of transcripts encoding for histone deacetylases and acetyltransferases is not involved in the changes of H4K16 acetylation observed following IVM, while translational or post-translational mechanisms might have a role. Our study also suggests that epigenetic instabilities introduced by IVM may affect the oocyte and embryo genetic stability.

The Role of Antioxidant Enzymes in the Ovaries

Proper physiological function of the ovaries is very important for the entire female reproductive system and overall health. Reactive oxygen species (ROS) are generated as by-products during ovarian physiological metabolism, and antioxidants are indicated as factors that can maintain the balance between ROS production and clearance. A disturbance in this balance can induce pathological consequences in oocyte maturation, ovulation, fertilization, implantation, and embryo development, which can ultimately influence pregnancy outcomes. However, our understanding of the molecular and cellular mechanisms underlying these physiological and pathological processes is lacking. This article presents up-to-date findings regarding the effects of antioxidants on the ovaries. An abundance of evidence has confirmed the various significant roles of these antioxidants in the ovaries. Some animal models are discussed in this review to demonstrate the harmful consequences that result from mutation or depletion of antioxidant genes or genes related to antioxidant synthesis. Disruption of antioxidant systems may lead to pathological consequences in women. Antioxidant supplementation is indicated as a possible strategy for treating reproductive disease and infertility by controlling oxidative stress (OS). To confirm this, further investigations are required and more antioxidant therapy in humans has to been performed.

Maternal age and in vitro culture affect mitochondrial number and function in equine oocytes and embryos

Advanced maternal age and in vitro embryo production (IVP) predispose to pregnancy loss in horses. We investigated whether mare age and IVP were associated with alterations in mitochondrial (mt) DNA copy number or function that could compromise oocyte and embryo development. Effects of mare age (<12 vs ≥12 years) on mtDNA copy number, ATP content and expression of genes involved in mitochondrial replication (mitochondrial transcription factor (TFAM), mtDNA polymerase γ subunit B (mtPOLB) and mitochondrial single-stranded DNA-binding protein (SSB)), energy production (ATP synthase-coupling factor 6, mitochondrial-like (ATP-synth_F6)) and oxygen free radical scavenging (glutathione peroxidase 3 (GPX3)) were investigated in oocytes before and after in vitro maturation (IVM), and in early embryos. Expression of TFAM, mtPOLB and ATP-synth-F6 declined after IVM (P<0.05). However, maternal age did not affect oocyte ATP content or expression of genes involved in mitochondrial replication or function. Day 7 embryos from mares ≥12 years had fewer mtDNA copies (P=0.01) and lower mtDNA:total DNA ratios (P<0.01) than embryos from younger mares, indicating an effect not simply due to lower cell number. Day 8 IVP embryos had similar mtDNA copy numbers to Day 7 in vivo embryos, but higher mtPOLB (P=0.013) and a tendency to reduced GPX3 expression (P=0.09). The lower mtDNA number in embryos from older mares may compromise development, but could be an effect rather than cause of developmental retardation. The general down-regulation of genes involved in mitochondrial replication and function after IVM may compromise resulting embryos.

Reactive Oxygen Species Generation and Use of Antioxidants during In Vitro Maturation of Oocytes

In vitro maturation (IVM) is emerging as a popular technology at the forefront of fertility treatment and preservation. However, standard in vitro culture (IVC) conditions usually increase reactive oxygen species (ROS), which have been implicated as one of the major causes for reduced embryonic development. It is well-known that higher than physiological levels of ROS trigger granulosa cell apoptosis and thereby reduce the transfer of nutrients and survival factors to oocytes, which leads to apoptosis. ROS are neutralized by an elaborate defense system that consists of enzymatic and non-enzymatic antioxidants. The balance between ROS levels and antioxidants within IVM media are important for maintenance of oocytes that develop to the blastocyst stage. The effects of antioxidant supplementation of IVM media have been studied in various mammalian species. Therefore, this article reviews and summarizes the effects of ROS on oocyte quality and the use of antioxidant supplementations for IVM, in addition to its effects on maturation rates and further embryo development.

Cerium oxide nanoparticles (CeO2 NPs) improve the developmental competence of in vitro-matured prepubertal ovine oocytes

The present study investigated whether supplementation with different doses of cerium dioxide nanoparticles (CeO2 NPs) during in vitro maturation (IVM) of prepubertal ovine oocytes influenced their embryonic development in vitro. Cumulus–oocyte complexes derived from the ovaries of slaughtered prepubertal sheep underwent IVM with CeO2NPs (0, 44, 88 or 220 µg mL–1). Matured oocytes were fertilised in vitro and zygotes were cultured for 7 days. The results demonstrated that CeO2NPs were internalised in the cumulus cells and not in the oocyte. The treatment with CeO2NPs did not affect nuclear maturation or intracellular levels of reactive oxygen species of the oocytes. The percentage of oocytes with regular chromatin configuration and cytoskeleton structures when treated with 44 µg mL–1 CeO2NPs was similar to oocytes matured in the absence of CeO2NPs and significantly higher than those treated with 88 or 220 µg mL–1 CeO2NPs. The relative quantification of transcripts in the cumulus cells of oocytes matured with 44 µg mL–1 CeO2NPs showed a statistically lower mRNA abundance of BCL2-associated X protein (BAX), B-cell CLL/lymphoma 2 (BCL2) and superoxide dismutase 1 (SOD1) compared with the 0 µg mL–1 CeO2 NPs group. A concentration of 44 µg mL–1 CeO2NPs significantly increased the blastocyst yield and their total, inner cell mass and trophectoderm cell numbers, compared with the 0 and 220 µg mL–1 groups. A low concentration of CeO2NPs in the maturation medium enhanced in vitro embryo production of prepubertal ovine oocytes.

Influence of transvaginal ultrasound-guided follicular punctures in the mare on heart rate, respiratory rate, facial expression changes, and salivary cortisol as pain scoring

Transvaginal ultrasound-guided follicular punctures are widely used in the mare for diagnosis, research, and commercial applications. The objective of our study was to determine their influence on pain, stress, and well-being in the mare, by evaluating heart rate, breath rate, facial expression changes, and salivary cortisol before, during, and after puncture. For this experiment, 21 pony mares were used. Transvaginal ultrasound-guided aspirations were performed on 11 mares. After injections for sedation, analgesia, and antispasmodia, the follicles from both ovaries were aspirated with a needle introduced through the vagina wall into the ovary. In the control group, 10 mares underwent similar treatments and injections, but no follicular aspiration. Along the session, heart rate and breath rate were evaluated by a trained veterinarian, ears position, eyelid closure, and contraction of facial muscles were evaluated, and salivary samples were taken for evaluation of cortisol concentration. A significant relaxation was observed after sedative injection in the punctured and control mares, according to ear position, eyelid closure, and contraction of facial muscles, but no difference between punctured and control animals was recorded. No significant modification of salivary cortisol concentration during puncture and no difference between punctured and control mares at any time were observed. No significant modification of the breath rate was observed along the procedure for the punctured and the control mares. Heart rate increased significantly but transiently when the needle was introduced in the ovary and was significantly higher at that time for the punctured mares than that for control mares. None of the other investigated parameters were affected at that time, suggesting discomfort is minimal and transient. Improving analgesia, e.g., through a multimodal approach, during that possibly more sensitive step could be recommended. The evaluation of facial expression changes and heart rate is easy-to-use and accurate tools to evaluate pain and well-being of the mare.

Beta-mercaptoethanol supplementation of in vitro maturation medium does not influence nuclear and cytoplasmic maturation of equine oocytes

In vitro embryo production in the horse is still not as efficient as in other species. Oxidative stress negatively affects oocyte and embryo culture. To attenuate/minimize the oxidative stress, antioxidants such as low-molecular thiol compounds can be added to culture media. Beta-mercaptoethanol (BME) has been shown to improve maturation and embryo development in different species. The aim of this study was to investigate whether the addition to maturation medium of BME at common (0.1 mM) and high (0.7 mM) concentration could improve oocyte maturation also in the horse. Equine oocytes recovered from slaughterhouse ovaries were used. Meiotic configuration after in vitro maturation (IVM) and early embryo production after intracytoplasmic sperm injection (ICSI) were considered as criteria for assessing nuclear and cytoplasmic maturation, respectively. A total of 1,076 oocytes were analysed over two experiments: 848 (control n = 293, BME 0.1 n = 270, BME 0.7 n = 285) were stained with Hoechst 33342 and examined for nuclear stage after 26 hr of IVM, and 228 MII oocytes were fertilized by ICSI (control n = 83, BME 0.1 n = 65, BME 0.7 n = 80). Cleavage rates were determined after 60 hr of culture. Unlike results obtained in other species, the addition of BME did not influence maturation rates (51.9% control vs 55.6% BME 0.1 mM and 55.1% BME 0.7 mM), nor cleavage rates after ICSI (38.6% vs 38.5% and 41.3%, respectively). In conclusion, the addition of BME at 0.1 and 0.7 mM to the maturation medium, in our culture conditions, has no effect on nuclear and cytoplasmic maturation of equine oocytes.

Eccentric localization of catalase to protect chromosomes from oxidative damages during meiotic maturation in mouse oocytes

The maintenance of genomic integrity and stability is essential for the survival of every organism. Unfortunately, DNA is vulnerable to attack by a variety of damaging agents. Oxidative stress is a major cause of DNA damage because reactive oxygen species (ROS) are produced as by-products of normal cellular metabolism. Cells have developed eloquent antioxidant defense systems to protect themselves from oxidative damage along with aerobic metabolism. Here, we show that catalase (CAT) is present in mouse oocytes to protect the genome from oxidative damage during meiotic maturation. CAT was expressed in the nucleus to form unique vesicular structures. However, after nuclear envelope breakdown, CAT was redistributed in the cytoplasm with particular focus at the chromosomes. Inhibition of CAT activity increased endogenous ROS levels, but did not perturb meiotic maturation. In addition, CAT inhibition produced chromosomal defects, including chromosome misalignment and DNA damage. Therefore, our data suggest that CAT is required not only to scavenge ROS, but also to protect DNA from oxidative damage during meiotic maturation in mouse oocytes.

Changes in histone H4 acetylation during in vivo versus in vitro maturation of equine oocytes

Epigenetic modifications are established during gametogenesis and preimplantation embryonic development. Any disturbance of the normal natural environment during these critical phases could cause alterations of the epigenetic signature. Histone acetylation is an important epigenetic modification involved in the regulation of chromatin organization and gene expression. The present study was aimed to determine whether the proper establishment of post-translational histone H4 acetylation at lysine 8 (AcH4K8), 12 (AcH4K12) and 16 (AcH4K16) of equine oocytes is adversely affected during in vitro maturation (IVM) when compared with in vivo matured oocytes collected from naturally cycling mares not undergoing ovarian hyperstimulation. The acetylation patterns were investigated by means of indirect immunofluorescence staining with specific antibodies directed against the acetylated lysine residues. Our results indicate that the acetylation state of H4 is dependent on the chromatin configuration in immature germinal vesicle (GV) stage oocytes and it changes in a residue-specific manner along with the increase of chromatin condensation. In particular, the levels of AcH4K8 and AcH4K12 increased significantly, while AcH4K16 decreased significantly from the fibrillar to the condensed state of chromatin configuration within the GV. Moreover, during meiosis, K8 and K12 were substantially deacetylated without any differences between in vivo and in vitro conditions, while K16 displayed a strong acetylation in oocytes matured in vivo, and in contrast, it was markedly deacetylated following IVM. Although the functional meaning of residue-specific acetylation during oocyte differentiation and meiotic resumption needs further investigation, our results support the hypothesis that IVM conditions can adversely affect oocyte ability to regulate the epigenetic reprogramming, critical for successful meiosis and subsequent embryonic development.

The effect of raw soybean on oxidative status of digestive organs in mice

The present study was undertaken to specify the effect of raw soybean on oxidative status of digestive organs in mice. For this purpose, thirty male (C57BL/6J) mice were randomly divided into three groups and fed on different diets as follows: Group 1 was fed on control diet, Group 2 was fed on raw soybean diet and Group 3 was fed on raw soybean diet supplemented with 30 mg/kg cysteamine. After two weeks of feeding, duodenum, liver and pancreas samples were collected to measure oxidative and antioxidative parameters. The results show that ingestion of raw soybean markedly increased contents of superoxide anion and malondialdehyde (MDA) and activity of inducible nitric oxide synthase (iNOS), decreased activity of superoxide dismutase (SOD), T-AOC and content of reduced glutathione (GSH) in digestive organs of mice (P < 0.05). In the group fed with raw soybean diet supplemented with cysteamine, oxidative stress was mitigated. However, oxidative parameter levels were still higher than those of control diet-fed group. The present study indicates that ingestion of raw soybean could result in an imbalance between oxidant and antioxidant, and thus induce oxidative stress in digestive organs of mice.

Proteomic analysis of mare follicular fluid during late follicle development

Background

Follicular fluid accumulates into the antrum of follicle from the early stage of follicle development. Studies on its components may contribute to a better understanding of the mechanisms underlying follicular development and oocyte quality. With this objective, we performed a proteomic analysis of mare follicular fluid. First, we hypothesized that proteins in follicular fluid may differ from those in the serum, and also may change during follicle development. Second, we used four different approaches of Immunodepletion and one enrichment method, in order to overcome the masking effect of high-abundance proteins present in the follicular fluid, and to identify those present in lower abundance. Finally, we compared our results with previous studies performed in mono-ovulant (human) and poly-ovulant (porcine and canine) species in an attempt to identify common and/or species-specific proteins.

Methods

Follicular fluid samples were collected from ovaries at three different stages of follicle development (early dominant, late dominant and preovulatory). Blood samples were also collected at each time. The proteomic analysis was carried out on crude, depleted and enriched follicular fluid by 2D-PAGE, 1D-PAGE and mass spectrometry.

Results

Total of 459 protein spots were visualized by 2D-PAGE of crude mare follicular fluid, with no difference among the three physiological stages. Thirty proteins were observed as differentially expressed between serum and follicular fluid. Enrichment method was found to be the most powerful method for detection and identification of low-abundance proteins from follicular fluid. Actually, we were able to identify 18 proteins in the crude follicular fluid, and as many as 113 in the enriched follicular fluid. Inhibins and a few other proteins involved in reproduction could only be identified after enrichment of follicular fluid, demonstrating the power of the method used. The comparison of proteins found in mare follicular fluid with proteins previously identified in human, porcine and canine follicular fluids, led to the identification of 12 common proteins and of several species-specific proteins.

Conclusions

This study provides the first description of mare follicular fluid proteome during the late follicle development stages. We identified several proteins from crude, depleted and enriched follicular fluid. Our results demonstrate that the enrichment method, combined with 2D-PAGE and mass spectrometry, can be successfully used to visualize and further identify the low-abundance proteins in the follicular fluid.

In vitro developmental potential of macaque oocytes, derived from unstimulated ovaries, following maturation in the presence of glutathione ethyl ester

BACKGROUND

The inadequacies of oocyte in vitro maturation (IVM) systems for both non-human primates and humans are evidenced by reduced fertilization and poor embryonic development, and may be partly explained by significantly lower glutathione (GSH) contents compared with in vivo matured (IVO) oocytes. As this influence has not been fully explored, this study investigated the effect of the GSH donor, glutathione ethyl ester (GSH-OEt), on the IVM and development of macaque oocytes as a model of human oocyte IVM.

METHODS

Macaque oocytes derived from unstimulated ovaries were cultured in mCMRL-1066 alone or supplemented with 3 or 5 mM GSH-OEt. In vitro matured oocytes were subjected to the GSH assay, fixed for the assessment of spindle morphology or prepared ICSI. Embryo development of zygotes cultured in mHECM-9 was assessed up to Day 9 post-ICSI. RESULTS Supplementation of the maturation medium with GSH-OEt significantly increased oocyte maturation and normal fertilization rates compared with control oocytes, but only 5 mM GSH-OEt significantly increased the oocyte and cumulus cell GSH content. Confocal microscopy revealed significant differences in the spindle morphology between IVO and control in vitro matured metaphase II oocytes. Oocytes matured with 5 mM GSH-OEt exhibited spindle area and spindle pole width similar to that seen in the IVO oocyte. While no significant differences were observed in blastocyst rates, addition of 3 mM GSH-OEt during IVM significantly increased the proportion of embryos developing to the 5-8 cell stage while 5 mM GSH-OEt significantly increased the proportion of morula-stage embryos compared with controls.

CONCLUSIONS

Supplementation of the IVM medium with GSH-OEt promotes better maturation and normal fertilization of macaque oocytes compared with non-supplemented medium. However, further improvement of the primate oocyte IVM culture system is required to support better blastocyst development of oocytes derived from unstimulated ovaries.

Could oxidative stress influence the in-vitro maturation of oocytes?

In the efforts aimed at improving the quality of in-vitro-matured human oocytes, the dynamic balance and roles of pro-/antioxidants merit further consideration. In-vitro maturation (IVM) is emerging as a popular technology at the forefront of fertility treatment and preservation. However, standard in-vitro culture conditions exert oxidative stress or an imbalance between oxidants and antioxidants. Reactive oxygen species (ROS) are oxygen-derived molecules formed as intermediary products of cellular metabolism. By acting as powerful oxidants, ROS can oxidatively modify any molecule, resulting in structural and functional alterations. ROS are neutralized by an elaborate defence system consisting of enzymatic and nonenzymatic antioxidants. This review captures the inherent and external factors that may modulate the oxidative stress status of oocytes. It discusses the suspected impacts of oxidative stress on the gamut of events associated with IVM, including prematuration arrest, meiotic progression, chromosomal segregation, cytoskeletal architecture and gene expression. In-vivo and in-vitro strategies that may overcome the potential influences of oxidative stress on oocyte IVM are presented. Future studies profiling the oxidative stress status of the oocyte may permit not only the formulation of a superior IVM medium that maintains an adequate pro-/antioxidant balance, but also the identification of predictors of oocyte quality.

Influence of cysteamine on in vitro maturation, in vitro and in vivo fertilization of equine oocytes

Contents The effect of cysteamine on in vitro nuclear and cytoplasmic maturation of equine oocytes collected by transvaginal ultrasound guided follicular aspiration was assessed. Oocytes were matured in vitro with (cysteamine group) or without (control group) cysteamine. The nuclear stage after DNA Hoechst staining, penetration rates after two different in vitro fertilization (IVF) techniques (IVF media with ionophore and Hepes buffer with heparin) and the embryo yield following oocyte intra-oviductal transfer were used as a criterion for assessing nuclear and cytoplasmic maturation, respectively. Contrary to the data described in other domestic species, there was no effect of cysteamine on in vitro nuclear maturation, IVF or in vivo embryonic development under our conditions. Ovum pick up yields (52%) and maturation rates (control group: 47% and cysteamine group: 55%) were similar to those previously reported. From 57 oocytes transferred to the oviduct in each group, the number of embryos collected was 10 (17%) in the control group and five in the cysteamine group (9%). Those two percentages were not statistically different (p > 0.05). No effect of IVF technique was seen on the success rate (6%) in each group.

Heat shock-derived reactive oxygen species induce embryonic mortality in in vitro early stage bovine embryos

Heat shock is known to increase the mortality of early stage embryos, but the exact mechanism is unclear. In the present study, we investigated the possibility that the increased mortality is caused by heat shock-generated reactive oxygen species (ROS). The level of ROS was controlled by using beta-mercaptoethanol (beta-ME), a scavenger of ROS. In vitro-produced 8-cell stage embryos were cultured at 38.5 C or heat-shocked by exposure to 41 C for 6 h with 0, 10 and 50 microM beta-ME. Intracellular ROS levels were measured by a fluorescent dye, 2',7'-dichlorodihydrofluorescein diacetate (DCHFDA), and intracellular reduced form of glutathione (GSH) contents were estimated by another fluorescent dye, 4-chloromethyl-6,8-difluoro-7-hydroxycoumarin. Total glutathione content was estimated by the glutathione recycling assay. On day 8 after insemination, heat shock decreased the percentage of embryos that developed to the blastocyst stage and increased intracellular ROS levels, but there was no significant effect on the GSH and total glutathione contents. In contrast, beta-ME significantly decreased ROS levels in heat-shocked embryos and increased the GSH and total glutathione concentrations. Ten microM beta-ME significantly improved the viability of heat-shocked embryos. beta-ME caused no detrimental effects when it was added at normal culture temperature (38.5 C). These results indicate that ROS is the primary cause of increased embryonic mortality in heat-shocked early stage embryos.

Expression profiling of a high-fertility mouse line by microarray analysis and qPCR

Background

In a recent study it was demonstrated that a largely increased ovulation number is responsible for high prolificacy in two mouse lines selected for fertility performance. The objective of the present study was to identify genes that are involved in increasing the ovulation number in one of these lines, FL1. For differential expression profiling, ovaries of FL1 and of a non-selected control line, DUKsi, both lines derived from the same genetic pool, were analyzed with microarray analysis and quantitative polymerase chain reaction (qPCR). Ovaries from 30 animals of each line were collected at the metestrous stage, combined to 6 pools each, and processed for microarray analysis.

Results

The actual number of ova shed in FL1 exceeded that of the DUKsi control line more than twofold (26.6 vs. 12.9). 148 differentially expressed ovarian transcripts could be identified, 74 of them up- and 74 down-regulated. Of these, 47 significantly mapped to specific Gene Ontology (GO) terms representing different biological processes as steroid metabolism, folliculogenesis, immune response, intracellular signal transduction (particularly of the G protein signaling cascade), regulation of transcription and translation, cell cycle and others. qPCR was used to re-evaluate selected transcripts and to estimate inter-individual variation of expression levels. These data significantly correlated with microarray data in 12 out of 15 selected transcripts but revealed partly large variations of expression levels between individuals.

Conclusion

(1) The abundance of numerous ovarian transcripts was significantly different in FL1 compared to the non-selected control line DUKsi thus suggesting that at least some of the respective genes and corresponding biological processes are involved in improving reproductive traits, particularly by increasing the number of ovulation. (2) Selective qPCR re-evaluation largely confirmed the microarray data and in addition demonstrated that sample pooling can be beneficial to find out group-specific expression profiles despite of large inter-individual variation. (3) The present data will substantially help ongoing genetic association studies to identify candidate genes and causative mutations responsible for increased fertility performance in mice.

Bovine in vitro oocyte maturation as a model for manipulation of the γ-glutamyl cycle and intraoocyte glutathione

Glutathione (GSH) is the main non-enzymatic defence against oxidative stress and is a critical intracellular component required for oocyte maturation. In the present study, several modulators of intracellular GSH were assessed for their effect on the in vitro maturation (IVM) and intracellular GSH content of bovine metaphase (MII) oocytes. Of the five GSH modulators tested, only the cell-permeable GSH donor glutathione ethyl ester (GSH-OEt) significantly increased the GSH content of IVM MII oocytes in a concentration-dependent manner without adversely affecting oocyte maturation rate. The GSH level in IVM MII oocytes was greatly influenced by the presence or absence of cumulus cells and severely restricted when oocytes were cultured in the presence of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. The addition of GSH-OEt to cumulus-denuded or BSO-treated oocytes increased the GSH content of bovine MII oocytes. Supplementation of the maturation medium with bovine serum albumin (BSA) or fetal calf serum (FCS) affected the GSH content of IVM MII oocytes, with greater levels attained under BSA culture conditions. The addition of GSH-OEt to the maturation medium increased the GSH content of IVM MII oocytes, irrespective of protein source. Spindle morphology, as assessed by immunocytochemistry and confocal microscopy, displayed distinct alterations in response to changes in oocyte GSH levels. GSH depletion caused by BSO treatment tended to widen spindle poles and significantly increased spindle area. Supplementation of the IVM medium with GSH-OEt increased spindle length, but did not significantly alter spindle area or spindle morphology. GSH-OEt represents a novel oocyte-permeable and cumulus cell-independent approach for effective elevation of mammalian oocyte GSH levels.

Selenium improves the developmental ability and reduces the apoptosis in porcine parthenotes

Selenium is an essential trace element in conventional tissue culture media to guarantee adequate biosynthesis of selenoprotein in cellular antioxidant system to protect the cells from oxidative damage and apoptosis. This study investigated the effect of selenium, in the form of sodium selenite (SS), on developmental ability and quality of in vitro produced porcine parthenotes. For this, parthenogenetic presumptive diploid zygotes were produced by electroactivation and cultured in the absence or presence of SS at different concentrations (0, 2.5, 25, 250 ng/ml) in a serum-free defined culture medium supplemented with polyvinyl alcohol (PVA) or bovine serum albumin (BSA). Results showed that, development rate of 2-4 cell stage parthenotes to blastocyst and their cell number was increased while TUNEL index was decreased, in a dose-dependent manner, when SS was supplemented to NCSU23 + PVA. Interestingly, the blastocyst rate and their quality approached to those cultured in NCSU23 + BSA (P < 0.05), thereby suggesting PVA + 25 ng/ml SS to be a partial replacement of BSA. In the presence of PVA, supplementation of SS at a concentration of 25 ng/ml did not improve the cleavage rate of in vitro matured oocytes but there was significant improvement in the blastocyst rate (45.4 +/- 8.8% vs. 12.7 +/- 4.8%), total nuclei number (42.1 +/- 3.5 vs. 31.3 +/- 2.9) and inner cell mass (ICM) rate (29.4 +/- 1.5% vs. 21.3 +/- 1.2%) and decrease in TUNEL index (5.6 +/- 0.5 vs. 12.9 +/- 1.3) compared to nonsupplemented controls. The SS supplementation also decreased the BAX:BCL-xL transcript ratio, increased the expression of ERK1/2 and glutathione peroxidase (GPX) and reduced the level of Caspase 3 proteins (P < 0.05). These data thus suggest that SS improves the development rate and quality of porcine parthenotes by preventing oxidative damage and apoptosis.

An epigenetic perspective on the free radical theory of development

The development of organisms requires concerted changes in gene activity. The free radical theory of development proposes that oxygen serves as a morphogen to educe development by influencing the production of metabolic oxidants such as free radicals and reactive oxygen species. One of the central tenets of this theory is that these metabolic oxidants influence development by altering the antioxidant capacity of cells by changing their production of glutathione (GSH). Here we extend on these principles by linking GSH production and oxygen sensing in the control of gene expression to establish the epigenotype of cells during development. We prescribe this novel role to GSH and oxygen during development because these metabolites influence the activity of enzymes responsible for initiating and perpetuating epigenetic control of gene expression. Increased GSH production influences epigenetic processes including DNA and histone methylation by limiting the availability of S-adenosylmethionine, the cofactor utilized during epigenetic control of gene expression by DNA and histone methyltransferases. Moreover, the recent discovery of histone demethylases that require oxygen as a cofactor directly links epigenetic processes to oxygen gradients during development.

Localization of cystathionine beta synthase in mice ovaries and its expression profile during follicular development

BACKGROUND

In vitro fertilization (IVF) researches have suggested that cystathionine beta synthase (CBS) is involved in oocyte development. However, little is known about the regional and cellular expression patterns of CBS in the ovary. The purpose of this study was to analyze the localization of CBS in mice ovaries and to investigate the expression profile during follicular development.

METHODS

We used in situ hybridization and immunohistochemical analysis to determine CBS expression in the ovaries of female Balb/c mice. Then the follicles were collected from F1 (C57BL x Balb/c) mice and cultured in vitro. With the method of semi-quantitative RT-PCR, we also investigated the expression profile of CBS during follicular development.

RESULTS

CBS was absent in the oocytes, although it was ubiquitously expressed in the ovary with the strongest expression in follicular cells at all stages. In late antral follicles, CBS expression was markedly higher in granulosa cells located close to the antrum and in cumulus cells around the oocyte. The semi-quantitative RT-PCR showed that CBS mRNA was detected in follicles at all stages in vitro. In cumulus-oocyte complexes superovulated, CBS expression also increased rapidly.

CONCLUSIONS

CBS was located mainly in the follicular cells in the ovaries. The level of CBS expression is high in follicles during folliculogenesis in mice. Differences in the CBS expression profile between oocyte and follicular cells suggest a role for CBS as a mediator in interactions between oocyte and granulosa cells.