Protection of porcine oocytes against cell damage caused by oxidative stress during in vitro maturation: role of superoxide dismutase activity in porcine follicular fluid

Exploring melatonin's multifaceted role in female reproductive health: From follicular development to lactation and its therapeutic potential in obstetric syndromes

BACKGROUND

Melatonin is mainly secreted by the pineal gland during darkness and regulates biological rhythms through its receptors in the suprachiasmatic nucleus of the hypothalamus. In addition, it also plays a role in the reproductive system by affecting the function of the hypothalamic-pituitary-gonadal axis, and by acting as a free radical scavenger thus contributing to the maintenance of the optimal physiological state of the gonads. Besides, melatonin can freely cross the placenta to influence fetal development. However, there is still a lack of overall understanding of the role of melatonin in the reproductive cycle of female mammals.

AIM OF REVIEW

Here we focus the role of melatonin in female reproduction from follicular development to delivery as well as the relationship between melatonin and lactation. We further summarize the potential role of melatonin in the treatment of preeclampsia, polycystic ovary syndrome, endometriosis, and ovarian aging.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Understanding the physiological role of melatonin in female reproductive processes will contribute to the advancement of human fertility and reproductive medicine research.

Revealing Changes in Ovarian and Hemolymphatic Metabolites Using Widely Targeted Metabolomics between Newly Emerged and Laying Queens of Honeybee (Apis mellifera)

The queen bee is a central and pivotal figure within the colony, serving as the sole fertile female responsible for its reproduction. The queen possesses an open circulatory system, with her ovaries immersed in hemolymph. A continuous and intricate transportation and interchange of substances exist between the ovaries and hemolymph of queen bees. To determine the characteristic metabolites in the hemolymph and ovary, as well as understand how their rapid metabolism contributes to the process of egg-laying by queens, we reared Apis mellifera queens from three different age groups: newly emerged queen (NEQ), newly laying queen (NLQ), and old laying queen (OLQ). Using widely targeted metabolomics, our study revealed that the laying queen (NLQ and OLQ) exhibited faster fatty acid metabolism, up-regulated expression of antioxidants, and significant depletion of amino acids compared to the NEQ. This study revealed that the levels of carnitine and antioxidants (GSH, 2-O-α-D-glucopyranosyl-L-ascorbic acid, L-ascorbic acid 2-phosphate, etc.) in the NLQ and OLQ were significantly higher compared to NEQ. However, most of the differentially expressed amino acids, such as L-tryptophan, L-tyrosine, L-aspartic acid, etc., detected in NLQ and OLQ were down-regulated compared to the NEQ. Following egg-laying, pathways in the queens change significantly, e.g., Tryptophan metabolism, Tyrosine metabolism, cAMP signaling pathway, etc. Our results suggest that carnitine and antioxidants work together to maintain the redox balance of the queen. Additionally, various amino acids are responsible for maintaining the queen's egg production.

The strong anti-hyaluronidase effect of ellagic acid markedly decreases polyspermy during in vitro fertilization, resulting in sustainment of the developmental potency in porcine oocytes

The present study investigated the effects of ellagic acid, a type of polyphenol that does not have a glycan and is composed of four hydroxyl groups and two lactone functional groups, on porcine in vitro fertilization (IVF) by focusing on its anti-hyaluronidase activity. A comparative analysis of ellagic acid and apigenin, which is commonly used as a hyaluronidase inhibitor, was performed. It compared the effects of ellagic acid and apigenin on hyaluronidase activity at different concentrations. The results showed that 10, 20, and 40 μM ellagic acid strongly reduced hyaluronidase activity (P < 0.05). The addition of 20 μM ellagic acid, but not apigenin, to porcine IVF medium effectively reduced polyspermy without decreasing sperm penetration or the formation rates of male pronuclei in cumulus-free oocytes. However, neither ellagic acid nor apigenin affected the number of sperm that bound to zona pellucida (ZP) or the induction of zona hardening and protease resistance. The percentage of acrosome-reacting sperm that bound to the ZP was markedly lower in the presence of 20 μM ellagic acid than in the untreated and apigenin-treated groups, even though the antioxidant capacity of ellagic acid was weaker than that of apigenin. Furthermore, a markedly higher percentage of embryos developed to the blastocyst stage in the ellagic acid-treated group, and the apoptotic indexes of expanded blastocysts produced by the ellagic acid treatment during IVF were significantly low. Therefore, the anti-hyaluronidase effect of ellagic acid markedly suppressed the induction of the acrosome reaction in sperm that bound to the ZP, resulting in a marked decrease in polyspermy under conditions that maintained high sperm penetrability during IVF and sustainment of the developmental potency in porcine oocytes.

Increasing sperm production and improving cryosurvival of semen in aged Thai native roosters as affected by selenium supplementation

OBJECTIVE

Aging roosters typically exhibit subfertility with decreasing semen quality, furthermore Thai native roosters reared in rural areas are raised for a longer duration than their usual lifespan. The present study therefore aimed to assess the effect of selenium supplementation as an antioxidative substance in diets to improve the semen cryopreservation of aged roosters.

METHODS

Semen samples were collected from young (n = 20) and aged (n = 20) Thai native roosters (Pradu Hang Dum) at 36 and 105 weeks of age when starting the experiment, respectively. They were fed diets either non-supplemented or supplemented with selenium (0.75 ppm). Fresh semen quality and lipid peroxidation of fresh semen was evaluated before cryopreservation using the traditional liquid nitrogen vapor method. Post-thaw sperm quality and fertility potential were determined.

RESULTS

Advancing age is unrelated to decreasing fresh semen quality (p>0.05). However, lipid peroxidation in rooster semen depended on age, and the malondialdehyde (MDA) concentration increased in aged roosters (p<0.05). Selenium supplementation in diets significantly decreased the MDA concentration and increased the sperm concentration (p<0.05). In contrast, cryopreserved semen was affected by advancing rooster age, and selenium influenced sperm quality (p<0.05). Younger roosters had higher post-thaw sperm quality and fertility potential than aged roosters (p<0.05). Likewise, diet selenium supplements improved post-thaw sperm quality and fertility compared with the non-supplement group.

CONCLUSION

Rooster's age does not influence the rooster sperm quality of fresh semen, while sperm cryotolerance and fertility were greater in young roosters than in aged roosters. However, sperm of aged roosters could be improved by dietary selenium supplementation.

Does the addition of follicular fluid in the in vitro maturation medium increase the oocyte maturation and embryo production in alpacas?

In alpacas (Vicugna pacos), the high cost of in vitro embryo production is also a consequence of the use of several substances in the culture medium. In addition, embryo production rates in this species are still considered low. Thus, in attempt to reduce the cost and to improve the in vitro embryo production rates, this study evaluates the effect of adding follicular fluid (FF) in the in vitro maturation medium on oocyte maturation and subsequent embryo production. After ovary collection at the local slaughterhouse, the oocytes were recovered, selected, and allocated in experimental groups: standard maturation medium (G1) and simplified medium added by 10% FF (G2). The FF was acquired from follicles between 7- and 12-mm diameter. The cumulus cell expansion and the embryo production rates were analyzed by chi-square with p < 0.05. No differences (p > 0.05) were observed in maturation rate between G1 (66.36%) and G2 (63.12%) groups. Likewise, no significant difference (p > 0.05) was verified between G1 and G2 for morula (40.85 vs 38.45%), blastocyst (7.01 vs 6.93%), and total number of embryos (47.87 vs 45.38%). In conclusion, it was possible to simplify the medium used for in vitro maturation of alpaca oocytes resulting in embryo production rates similar to the standard medium.

Role of COX-2/PGE2 signaling pathway in the apoptosis of rat ovarian granulosa cells induced by MEHP

OBJECTIVE

MEHP, as the metabolite of DEHP, is a widely used environmental endocrine disruptor. Ovarian granulosa cells participate in maintaining the function of ovary and COX2/PGE2 pathway may regulate the function of granulosa cells. We aimed to explore how COX-2/PGE2 pathway affects cell apoptosis in ovarian granulosa cells caused by MEHP.

METHODS

Primary rat ovarian granulosa cells were treated with MEHP (0, 200, 250, 300 and 350 μM) for 48 h. Adenovirus was used for over-expression of COX-2 gene. The cell viability was tested with CCK8 kits. The apoptosis level was tested by flow cytometry. The levels of PGE2 were tested with ELISA kits. The expression levels of COX-2/PGE2 pathway related genes, ovulation-related genes and apoptosis-related genes, were measured with RT-qPCR and Western blot.

RESULTS

MEHP decreased the cell viability. After MEHP exposure, the cell apoptosis level increased. The level of PGE2 markedly decreased. The expression levels of COX-2/PGE2 pathway related genes, ovulation-related genes and anti-apoptotic genes decreased; the expression levels of pro-apoptotic genes increased. The apoptosis level was alleviated after over-expression of COX-2, and the level of PGE2 slightly increased. The expression levels of PTGER2 and PTGER4, and the levels of ovulation-related genes increased; the levels of pro-apoptotic genes decreased.

CONCLUSION

MEHP can cause cell apoptosis by down-regulating the levels of ovulation-related genes via COX-2/PGE2 pathway in rat ovarian granulosa cells.

Human Follicular Fluid and Mesenchymal Stem Cell Conditioned Medium Improves in Vitro Development of Vitrified-Warmed Mouse Oocytes

BACKGROUND: In vitro maturation (IVM) and oocyte cryopreservation are therapeutic options in assisted reproductive technology which is used to preserve fertility in patients with different causes of infertility. OBJECTIVE: To analyze in vitro development of vitrified-warmed oocytes in the presence of human follicular fluid (FF) and bone marrow mesenchymal stem cell-conditioned medium (BMSC- CM) as a rescue strategy in fertility preservation. MATERIALS AND METHODS: BMSC-CM and FF media were used as two natural media. Not only osteogenic and adipogenic differentiation but also flow cytometry was carried out to confirm the nature of mesenchymal stem cells. A total of 327 vitrified-warmed oocytes were randomly assigned to three groups with different maturation media. After 24 h the maturation rate was evaluated. In vitro fertilization and also embryo development were also assessed. RESULTS: Oocytes matured in the BMSC-CM and FF groups showed a significant increase compared to the control group (76.6±2.9, 53.2±1.0 , and 40.8±6.1, respectively) (P < 0.05). Embryo cleavage rates in the BMSC-CM were dramatically higher than FF and control groups (85.6±2.2, 70.5±2.2, and 60.7±1.5, respectively). Blastocyst formation rates in the BMSC-CM group were statically different compared to FF and control groups (73.6±1.0, 58.5±1.0, and 45.8±4.2, respectively). CONCLUSION: BMSC-CM and FF media not only improve the maturation rate of vitrified warmed oocytes but also significantly increase embryo cleavage and blastocyst rates.

Effects of alpha lipoic acid treatment during in vitro maturation on the development of porcine somatic cell nuclear transfer embryos

Oxidative stress influences the embryo production efficiency in vitro. We investigated the effects of alpha lipoic acid (ALA) treatment during the in vitro maturation (IVM) period on the porcine somatic cell nuclear transfer (SCNT) embryo production. After IVM, maturation rates of the 12.5- and 25-μM ALA-treated groups were not significantly different from those of the 0-μM ALA-treated group. Compared to those in the 0-μM ALA-treated group, the reactive oxygen species and glutathione levels were significantly decreased and increased, respectively, in the cytoplasm of matured oocytes in the 12.5-50-μM ALA-treated groups. Apoptosis rate in cumulus cells after IVM was significantly lower in the 12.5-50-μM ALA-treated groups than in the 0-μM ALA-treated group. Blastocyst formation rate was significantly higher in parthenogenetic oocytes treated with 12.5-μM ALA than in the 0-, 25-, and 50-μM ALA-treated groups. Similarly, in SCNT embryos, the 12.5-μM ALA-treated group showed a significantly higher blastocyst formation rate than the 0-μM ALA-treated group. Apoptosis rate in SCNT blastocysts was significantly decreased by 12.5-μM ALA treatment. The results showed that treatment with 12.5-μM ALA during IVM improves porcine SCNT embryo development and partial quality.

Supplementation of SDF1 during Pig Oocyte In Vitro Maturation Improves Subsequent Embryo Development

The quality of in vitro matured oocytes is inferior to that of in vivo matured oocytes, which translates to low developmental capacity of embryos derived from in vitro matured oocytes. The developmental potential of in vitro matured oocytes is usually impaired due to oxidative stress. Stromal cell-derived factor-l (SDF1) can reduce oxidative stress and inhibit apoptosis. The aim of this study was to investigate the effects of SDF1 supplementation during pig oocyte in vitro maturation (IVM) on subsequent embryo development, and to explore the acting mechanisms of SDF1 in pig oocytes. We found that the IVM medium containing 20 ng/mL SDF1 improved the maturation rate of pig oocytes, as well as the cleavage rate and blastocyst rate of embryos generated by somatic cell nuclear transfer, in vitro fertilization, and parthenogenesis. Supplementation of 20 ng/mL SDF1 during IVM decreased the ROS level, increased the mitochondrial membrane potential, and altered the expression of apoptosis-related genes in the pig oocytes. The porcine oocyte transcriptomic data showed that SDF1 addition during IVM altered the expression of genes enriched in the purine metabolism and TNF signaling pathways. SDF1 supplementation during pig oocyte IVM also upregulated the mRNA and protein levels of YY1 and TET1, two critical factors for oocyte development. In conclusion, supplementation of SDF1 during pig oocyte IVM reduces oxidative stress, changes expression of genes involved in regulating apoptosis and oocyte growth, and enhances the ability of in vitro matured pig oocytes to support subsequent embryo development. Our findings provide a theoretical basis and a new method for improving the developmental potential of pig in vitro matured oocytes.

Supplementation of porcine in vitro maturation medium with FGF2, LIF, and IGF1 enhances cytoplasmic maturation in prepubertal gilts oocytes and improves embryo quality

In porcine in vitro production (IVP) systems, the use of oocytes derived from prepubertal gilts, whilst being commercially attractive, remains challenging due to their poor developmental competence following in vitro maturation (IVM). Follicular fluid contains important growth factors and plays a key role during oocyte maturation; therefore, it is a common supplementation for porcine IVM medium. However, follicular fluid contains many poorly characterized components, is batch variable, and its use raises biosecurity concerns. In an effort to design a defined IVM system, growth factors such as cytokines have been previously tested. These include leukaemia inhibitory factor (LIF), fibroblast growth factor 2 (FGF2), and insulin-like growth factor 1 (IGF1), the combination of which is termed 'FLI'. Here, using abattoir-derived oocytes in a well established porcine IVP system, we compared follicular fluid and FLI supplementation during both IVM and embryo culture to test the hypothesis that FLI can substitute for follicular fluid without compromising oocyte nuclear and cytoplasmic maturation. We demonstrate that in oocytes derived from prepubertal gilts, FLI supplementation enhances oocyte meiotic maturation and has a positive effect on the quality and developmental competence of embryos. Moreover, for the first time, we studied the effects of follicular fluid and FLI combined showing no synergistic effects.

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.

Redox imbalance in age-related ovarian dysfunction and perspectives for its prevention

The age at which women have their first child is increasing. This change represents a major health problem to society because advanced maternal age is related with a decay in fertility and an increase in the incidence of a variety of pregnancy complications and offspring health issues. The ovary stands as the main contributor for female reproductive ageing because of the progressive age-related decrease in follicle number and oocyte quality. Loss of redox homeostasis and establishment of an ovarian oxidative microenvironment are seen as major underlying causes for such downfall and impairment of ovarian function. Thus, the use of antioxidants to preserve fertility became an important field of research. In this review, new insights on mechanisms underlying the establishment of oxidative stress and its repercussions on ovarian ageing are addressed, along with the current state of knowledge on antioxidant supplementation and its contribution for healthy ageing and extension of ovarian lifespan.

Effect of oxygen and glucose availability during in vitro maturation of bovine oocytes on development and gene expression

PURPOSE

Oxygen tension during the in vitro maturation (IVM) of oocytes is important for oocyte developmental competence. A conflict exists in the literature as to whether low oxygen during IVM is detrimental or beneficial to the oocyte. Many research and clinical labs use higher than physiological oxygen tension perhaps believing that low-oxygen tension is detrimental to oocyte development. Other studies show that glucose is important if low-oxygen tension is used during maturation. In this study, we look at the link between low oxygen and glucose availability during IVM to resolve misconceptions around low-oxygen tension during IVM.

METHODS

Bovine cumulus oocyte complexes (COCs) were matured at 20% vs 7% oxygen in media containing differing glucose concentrations or varying availability. Cleavage and blastocyst rates were recorded. RT-PCR determined expression levels of metabolic, oxygen, and stress-responsive genes following IVM.

RESULTS

Embryo development in 7% oxygen groups with 2.3mM glucose/low glucose availability was lower than 20% oxygen groups. Under 7% oxygen with 5.6mM glucose or higher glucose availability, rates were restored to those seen in 20% oxygen. Expressions of BNIP3, ENO1, GAPDH, and SLC2A1, were upregulated in 7% oxygen/low glucose, compared to 20% oxygen groups. BNIP3 expression was higher in 7% oxygen group with low glucose availability compared to the 20% groups.

CONCLUSION

Oocyte developmental competence is negatively impacted following IVM in low oxygen when glucose availability is limited. Glucose concentration and physical culture conditions need to be considered when comparing the effects of different oxygen concentrations during IVM.

The effect of denudation and injection timing in the reproductive outcomes of ICSI cycles: new insights into the risk of in vitro oocyte ageing

STUDY QUESTION

Does the time elapsed between oocyte pick-up (OPU) and denudation or injection affect the probability of achieving a live birth (LB) in ICSI cycles?

SUMMARY ANSWER

Prolonged oocyte culture before denudation (>4 h) was associated with an increase in clinical pregnancy (CP), LB and cumulative LB (CLB) rates when compared with earlier denudation timings.

WHAT IS KNOWN ALREADY

Oocyte maturation is a complex and dynamic process involving structural and biochemical modifications in the cell necessary to support fertilization and early embryo development. While meiotic competence is easily identifiable by the presence of an extruded first polar body, cytoplasmic maturation cannot be assessed microscopically. Culturing oocytes with their surrounding cumulus cells (CCs) prior to ICSI can enhance the completion of in vitro cytoplasmic maturation; conversely, prolonged culture may induce cell degeneration. The optimal culture intervals prior to oocyte denudation and/or injection have not yet been established and may prove relevant for the improvement of ICSI reproductive outcomes.

STUDY DESIGN, SIZE, DURATION

This is a single-centre retrospective cohort analysis of 1378 ICSI cycles performed between January 2005 and October 2018. Data were categorized according to: (i) the time interval between OPU and denudation (<3 h, 3-4 h and ≥4 h), (ii) the time interval between denudation and ICSI (<1.5 h, 1.5-2 h, ≥2 h) and (iii) the time interval between OPU and ICSI (<5 h, 5-6 h and ≥6 h). The effect of these timings on fertilization, CP, LB and CLB rates were compared. The culture intervals between different procedures were dependent exclusively on laboratory workload.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ICSI cycles performed in women younger than 40 years old using autologous gametes with at least one metaphase II injected oocyte were included. The effect of oocyte culture duration prior to denudation and injection of the oocytes was compared using multivariable regression accounting for potential confounding variables.

MAIN RESULTS AND THE ROLE OF CHANCE

Fertilization and oocyte damage rate after ICSI was found to be independent of the time interval to denudation (<3 h, 3-4 h and ≥4 h) and/or injection (<5 h, 5-6 h and ≥6 h). Extending oocyte culture before denudation significantly improved CP (29.5%, 42.7% and 50.6%, respectively), LB (25.1%, 34.4% and 40.7%, respectively) and CLB rates (26.0%, 36.1% and 42.2%, respectively), particularly if the time interval was at least 4 h. Additionally, LB (31.7%, 35.8% and 27.4%, respectively) and CLB rates (34.2%, 36.6% and 27.7%, respectively) were also dependent on the time from OPU to injection.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by its retrospective nature and potential unmeasured confounding cannot be excluded. Furthermore, the effect of even shorter or longer periods of culture before denudation and/or injection were not evaluated and should not be extrapolated from these results.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings propose new evidence of a previously unrecognized protective effect of the CCs-oocyte interactions in human ART, raising the question of a possible downstream effect in embryogenesis which significantly affects LB rates. Additionally, this is the first study to suggest a negative effect of further extending culture before ICSI on LB and CLB rates, thus potentially allowing for the narrowing of an optimal ICSI time interval. Simple strategies such as the establishment of more effective time frames to perform these procedures and adjusting laboratory practice may prove beneficial, ultimately improving ICSI reproductive outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

Cryopreservation and oxidative stress in porcine oocytes

Several vitrification protocols have been established for porcine oocytes so as to facilitate gene banking of female germplasm. Although live piglets have been successfully produced from pig oocytes vitrified at the germinal vesicle (GV) stage, the competence of vitrified oocytes to develop into the blastocyst stage is greatly compromised following cryopreservation. The focus of this review is to elucidate the impact of cryopreservation on the redox balance of pig oocytes, making special reference to the relevance of non-enzymatic and enzymatic antioxidant defences. Besides, the regulation of gene expression in response to oxidative stress is also considered. Finally, we discuss the effects of supplementing maturation and vitrification media with the exogenous non-enzymatic antioxidants that have hitherto yielded the most relevant results.

Molecular characteristics of oocytes and somatic cells of follicles at different sizes that influence in vitro oocyte maturation and embryo production

During the last 10 to 15 yr, in vitro research to predict antral follicle growth and oocyte maturation has delivered interesting advances in the knowledge of processes regulating follicle growth and developmental competence of oocytes. This review discusses the contribution of cumulus and mural granulosa cells in the process of oocyte maturation and cumulus expansion in cumulus-oocyte complexes (COCs) from follicles of different sizes and shows that differences in gene expression in oocytes, granulosa, and theca cells of small and large follicles impact the success of in vitro blastocyst development. In addition, the molecular mechanisms by which COC metabolism and antioxidant defense provide oocyte competence are highlighted. Furthermore, new insights and perspectives on molecular and cellular regulation of in vitro oocyte maturation are emphasized.

Factors related to follicular oxidative stress in intracytoplasmic sperm injection cycles and its effects on granulosa cells

The aim of the present study was to investigate several common conditions that may potentially be correlated with follicular oxidative status during an intracytoplasmic sperm injection (ICSI) cycle and that include the serum oestrogen level on the day of oocyte pick-up, maternal age and pregnancy outcome. Patients that were enrolled in the study were classified randomly into three groups using their numerical order. The first group were classified based on maternal age (<35 and ≥35 years) (n = 398), the second group on the serum oestradiol (E2) level on the day of human chorionic gonadotropin (hCG) administration (levels >90th percentile and ≤ 90th percentile) (n = 491) and the third group on pregnancy outcome (positive/negative) (n = 376). The groups were matched for the other variables (stimulation protocol, dose of gonadotropin, duration of stimulation, antral follicle count, body mass index, basal follicle stimulating hormone (FSH), and E2 levels and day of hCG trigger) to prevent the possible contribution of those parameters to the results. Each group was matched for other variables (stimulation protocol, dose of gonadotrophin, duration of stimulation, antral follicle count, body mass index, basal FSH and E2 levels and day of hCG trigger) that may have affected the outcome, except for the parameter under investigation. Maternal age (P = 0.044,168 r = 0.418), oestrogen level on day of hCG administration (P = 0.001, r = 0.436) and pregnancy outcome (AUC = 0.65, P = 0.071) were found to be correlated with follicular oxidative status. The results obtained will help us to shield patients from possible situations that may cause oxidative stress and therefore adverse outcomes of an ICSI cycle.

The antioxidant dimethylthiourea improves IVF efficiency and decreases cumulus cell apoptosis in pigs

Abattoir ovaries, which are the main source of oocytes for reproductive biotechnologies, arrive at the laboratory under ischaemic conditions. Reoxygenation generates reactive oxygen species (ROS) in ischaemic tissues, which could affect oocyte quality. The aim of this study was to evaluate the effect of supplementation of media with dimethylthiourea (DMTU) during the collection and washing of cumulus-oocyte complexes (COC) on ROS levels, COC apoptosis and oocyte nuclear and cytoplasmic maturation. Thus, the collection (TCM-199) and washing (TCM-199 with 10% porcine follicular fluid, sodium pyruvate and antibiotics) media were supplemented with 1 and 10mM DMTU. In the control group, the media were not supplemented with DMTU. Intracellular ROS levels decreased significantly in the DMTU-treated groups (P<0.05). Although no effects on rate of nuclear maturation were observed, DMTU significantly increased sperm penetration rates without increasing polyspermy (P<0.05). The addition of 10mM DMTU to the collection and washing media enhanced IVF efficiency. DMTU did not modify the early or late apoptosis of oocytes. Both concentrations of DMTU significantly increased viability and decreased the apoptosis of cumulus cells (P<0.05). These results suggest that the addition of 1 or 10mM of DMTU to the media during the collection and washing of porcine COCs is useful for decreasing cumulus apoptosis mediated by ROS and for optimising the IVF of porcine oocytes.

Phytanic acid-derived peroxisomal lipid metabolism in porcine oocytes

Lipid metabolism plays an important role in oocyte maturation. The peroxisome is the fundamental mediator for this mechanism. In this study, we investigated the peroxisomal lipid metabolism in porcine oocytes. Phytanic acid (PA) was chosen as an activator of alpha-oxidation in peroxisomes. Oocyte maturation, embryo development, immunocytochemistry of peroxisomal lipid activities, and staining of mitochondrial potentials were assessed. We found that 40 μM PA not only increased porcine oocyte maturation and embryonic development, but also upregulated the expression of genes and proteins related to activities of the peroxisomal lipid metabolism (PHYH, PEX19, and PEX subfamilies) and mitochondrial potentials (NRF1 and PGC1α). Moreover, PA upregulated the lipid droplet and fatty acid content in the oocytes. Moreover, mitochondria were activated and the mitochondrial membrane potential was increased after PA treatment, resulting in the production of more ATPs in the oocytes. Our findings suggest that the degradation of PA via alpha-oxidation in the peroxisome may potentiate oocyte maturation processes, peroxisomal lipid oxidation, and mitochondria activities.

Effects o follicular fluid oxidative status on human mural granulosa cells, oocyte competency and ICSI parameters

PURPOSE

The aim of the present study was to understand the molecular and genetic alterations involved in follicular fluid oxidative process by investigating human mural granulosa cells and to find possible biomarkers for oocyte competency and ICSI outcome measures.

METHODS

A total of 166 patients were included in the study. Total antioxidant and oxidant levels of follicular fluids were measured on the day of oocyte pick-up and oxidative status were calculated. Expression profiles of three potential target proteins in cases of oxidative stress (Hsp70, Tgf-β, Notch1), DNA status and chromatin integrity of mural granulosa cells were analyzed.

RESULTS

TAS levels were positively correlated with the Hsp70 and Tgf-β expression patterns of mural granulosa cells. Mature oocyte rate and fertilization rates were affected negatively by the presence of oxidative stress and a significant positive correlation was found with the oxidative status and the fertilization rate, whereas no correlation with the remaining ICSI parameters in the overall group.

CONCLUSIONS

Oxidative stress detected in follicular fluid adversely affects fertilization rates post-ICSI however no effect on the remaining parameters including embryo quality, pregnancy, and implantation rates. DNA damage, chromatin integrity were increased, whereas Hsp70 and Tgf-ß were decreased in mural granulosa cells in cases of oxidative stress which may indirectly reflect the oocyte competency and may be used as biomarkers for ICSI outcome measures.

Controlling chronic low-grade inflammation to improve follicle development and survival

Chronic low-grade inflammation is one cause of follicle development disturbance. Chronic inflammation exists in pathological conditions such as premature ovarian failure, physiological aging of the ovaries, and polycystic ovary syndrome. Inflammation of the whole body can affect oocytes via the follicle microenvironment, oxidative stress, and GM-CSF. Many substances without toxic side-effects extracted from natural organisms have gradually gained researchers' attention. Recently, chitosan oligosaccharide, resveratrol, anthocyanin, and melatonin have been found to contribute to an improvement in inflammation. This review discusses the interrelationships between chronic low-grade inflammation and follicle development, the underlying mechanisms, and methods that may improve follicle development by controlling the level of chronic low-grade inflammation.

Effects of melatonin on morphology and development of primordial follicles during in vitro culture of bovine ovarian tissue

This study aims to investigate the effect of melatonin on activation, growth and morphology of bovine primordial follicles, as well as on stromal cells density in ovarian tissues after in vitro culture. Ovarian fragments were cultured in α-MEM⁺ alone or supplemented with melatonin (250, 500, 1,000 or 2,000 pM) for a period of six days. Non-cultured and cultured tissues were processed for histological analysis; according to developmental stages, follicles were classified as primordial or growing follicles. These follicles were further classified as morphologically normal or degenerated. Ovarian stromal cell density was also evaluated. The percentages of primordial and developing follicles, as well as those classified of normal follicles, were compared by Fisher's exact test, and the differences were considered significant when p < .05. The results showed that the presence of 1,000 and 2,000 pM melatonin in culture medium promoted a reduction in the percentage of primordial follicles and an increase in the percentage of development follicles, when compared to follicles cultured in control medium. On the other hand, the presence of 250 or 500 pM melatonin did not show a significant effect on the percentage of primordial and developing follicles. Besides that, the presence of 500, 1,000 and 2,000 pM melatonin maintained the percentage of normal follicles similar to those seen uncultured control. Moreover, tissues cultured in presence of 1,000 pM melatonin showed a higher percentage of normal follicles when compared to follicles cultured in the presence of 250 pM melatonin. It was observed a similar profile of stromal density in both uncultured tissues and those cultured in vitro in the presence of melatonin. In conclusion, melatonin (1,000 and 2,000 pM) promotes bovine primordial follicles activation and maintains the stromal cell density during in vitro culture of ovarian cortical tissue.

Systemic oxidative stress as a possible mechanism underlying the pathogenesis of mild endometriosis-related infertility

RESEARCH QUESTION

Does systemic oxidative stress occur during the early follicular phase of the menstrual cycle in infertile women with minimal (stage I) or mild (stage II) endometriosis? Are serum oxidative stress markers during the early follicular phase of the menstrual cycle good predictors of successful gestation in these women who undergo ovarian stimulation for intracytoplasmic sperm injection (ICSI)?

MATERIALS AND METHODS

A pilot study (prospective case-control study) was conducted in a University Hospital. Serum samples were obtained during the early follicular phase of the natural cycle preceding ovarian stimulation for ICSI of infertile women (with and without stage I and II endometriosis, the latter having male factor infertility). Total hydroperoxides (FOX1), malondialdehyde, advanced oxidation protein products, reduced glutathione, superoxide dismutase, total antioxidant capacity (TAC), 8-hydroxy-2'-deoxyguanosine (8OHdG) and vitamin E were analysed in serum from 35 women with stage I or II endometriosis and 60 control women. The accuracy of oxidative stress markers for predicting clinical pregnancy and live births was determined by receiver operator characteristic curves.

RESULTS

Women with stage I and II endometriosis showed lower serum 8OHdG concentrations (16.02 ng/ml) compared with the control group (22.08 ng/ml). The best predictor for clinical pregnancy and live births was TAC, whereas FOX1 was the best predictor of clinical pregnancy in the control group.

CONCLUSIONS

Infertile women with stage I and II endometriosis present systemic oxidative stress during the early follicular phase of the menstrual cycle. Some oxidative stress markers were good predictors of clinical pregnancy and live births after ICSI. Serum TAC was predictive of clinical pregnancy and live births after ICSI in women with stage I or II endometriosis.

Effects of manganese on maturation of porcine oocytes in vitro and their subsequent embryo development after parthenogenetic activation and somatic cell nuclear transfer

This study was carried out to examine the effects of manganese (Mn) on the developmental competence of porcine oocytes during in vitro maturation (IVM) after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT). Upon treatment of porcine oocytes with different concentrations (0, 3, 6, and 12 ng/ml) of Mn during IVM, PA was performed to determine the optimum concentration. Following PA, the rate of blastocyst formation was higher significantly in treated porcine oocytes at 6 ng/ml of Mn than in other groups (P < 0.05). However, there was no substantial difference in the cleavage rate and total blastocyst cell numbers among all groups. SCNT was performed using the optimal concentration of Mn from PA, which showed an improved blastocyst formation rate in treated oocytes compared to that in control group (P < 0.05). However, the cleavage rate and total cell numbers per blastocyst were not different between the control and the Mn treated groups after SCNT. Additionally, oocyte nuclear maturation, intracellular glutathione (GSH), and reactive oxygen species (ROS) levels were assessed. There was no significant difference observed in nuclear maturation among all the groups. However, enhanced intracellular GSH levels while lower levels of ROS were seen in the Mn treated group compared to the control group (P < 0.05). Thus, these results indicate that Mn supplementation can improve the developmental competence of porcine PA and SCNT embryos by increasing GSH and decreasing ROS levels.

Impact of Oxidative Stress on Age-Associated Decline in Oocyte Developmental Competence

Reproductive capacity in women starts to decline beyond their mid-30s and pregnancies in older women result in higher rates of miscarriage with aneuploidy. Age-related decline in fertility is strongly attributed to ovarian aging, diminished ovarian reserves, and decreased developmental competence of oocytes. In this review, we discuss the underlying mechanisms of age-related decline in oocyte quality, focusing on oxidative stress (OS) in oocytes. The primary cause is the accumulation of spontaneous damage to the mitochondria arising from increased reactive oxygen species (ROS) in oocytes, generated by the mitochondria themselves during daily biological metabolism. Mitochondrial dysfunction reduces ATP synthesis and influences the meiotic spindle assembly responsible for chromosomal segregation. Moreover, reproductively aged oocytes produce a decline in the fidelity of the protective mechanisms against ROS, namely the ROS-scavenging metabolism, repair of ROS-damaged DNA, and the proteasome and autophagy system for ROS-damaged proteins. Accordingly, increased ROS and increased vulnerability of oocytes to ROS lead to spindle instability, chromosomal abnormalities, telomere shortening, and reduced developmental competence of aged oocytes.

Melatonin Improves Oocyte Maturation and Mitochondrial Functions by Reducing Bisphenol A-Derived Superoxide in Porcine Oocytes In Vitro

Bisphenol A (BPA) is synthetic organic compound that exhibits estrogen-like properties and it induces mitochondrial superoxide production. Melatonin (Mela) protects against BPA-mediated cell damage and apoptosis. However, the antioxidative effects of Mela against BPA-induced superoxide production in porcine oocytes are still not known. In this study, we investigated the antioxidative effects of Mela against BPA-derived superoxide on oocyte maturation in pigs. To investigate the effects of the superoxide specific scavenger, Mito-TEMPO, on porcine oocyte maturation in response to BPA exposure apoptosis proteins, we treated the oocytes with Mito-TEMPO (0.1 µM) after pre-treating them with BPA (75 µM) for 22 h. As expected, the reduction in meiotic maturation and cumulus cell expansion of cumulus-oocyte-complexes (COCs) in the BPA (75 µM) treated group was recovered (p < 0.01) by treatment with Mito-TEMPO (0.1 µM). An increase in the levels of mitochondrial apoptotic proteins (AIF, cleaved Cas 3 and cleaved Parp1) in response to BPA-induced damage was also reduced by Mito-TEMPO treatment in porcine COCs. Interestingly, we confirmed the positive effects of Mela with respect to superoxide production upon BPA exposure during oocyte maturation and also confirmed the reduction in mitochondrial apoptosis in Mela (0.1 µM)-treated porcine COCs. These results provide evidence for the first time that antioxidative effects of Mela on BPA-derived superoxide improve porcine oocyte maturation.

Selenium (Na2SeO3) Upregulates Expression of Immune Genes and Blood-Testis Barrier Constituent Proteins of Bovine Sertoli Cell In Vitro

Sertoli cells were isolated from newborn calves and cultured in a medium supplemented with 0, 0.25, 0.50, 0.75, and 1.00 mg/L of sodium selenite to study their immune stimulatory effect, influence on cell's viability, and expression of blood-testis barrier proteins (occludin, connexin-43, zonula occluden, E-cadherin) using quantitative PCR and western blot analyses. Results showed that medium supplemented with 0.50 mg/L of selenium significantly (P < 0.05) promoted cell viability, upregulated toll-like receptor gene (TLR4), anti-inflammatory cytokines (IL-4, IL-10, TGFβ1), and expressions of blood-testis barrier proteins, and modulated expressions of pro-inflammatory cytokines (TNF-α, IL-1β, IFN-γ). Sertoli cells grown in culture medium supplemented with 0.25 mg/L of selenium significantly upregulated TLR4, IL-4, IL-10, TGFβ1, and blood-testis barrier proteins compared to the control group. Sodium selenite supplementation at 0.75 and 1.00 mg/L levels was cytotoxic and temporarily downregulated the expression of blood-testis barrier protein within 24 h after culture; however, commencing from 72 h post culture, increased cell viability and upregulation of expression of blood-testis barrier proteins were observed. In conclusion, the results of this study showed that selenium supplementation in the culture medium up to 0.50 mg/L concentration upregulates immune genes and blood-testis barrier constituent proteins of bovine Sertoli cells.

Updating the markers for oocyte quality evaluation: intracellular temperature as a new index

BACKGROUND

The developmental competence of an embryo is principally dictated by the oocyte. Usually, oocyte selection is based on morphological properties; however, all morphological criteria that are currently used for the grading and screening of oocytes are not able to eliminate the subjectivity. Despite recent studies of the molecular factors related to oocyte quality, it is technically difficult to develop an index based on these factors, and new indices that reflect intracellular conditions are necessary.

METHODS

Morphological and molecular factors influencing developmental competence were comprehensively reviewed, and intracellular temperature was evaluated as a new marker of oocyte quality.

MAIN FINDINGS

The intracellular temperature of mature oocytes was high in fresh oocytes and decreased with time after polar body release. Under the same conditions, the intracellular temperature and its distribution differed among oocytes, suggesting that temperature represents the state of each oocyte.

CONCLUSION

Intracellular temperature is advantageous as an objective and quantitative indicator of oocyte quality. Further studies should evaluate the link between temperature and cellular phenomena to establish its use as an indicator of quality.

Mesenchymal Stem Cell-Conditioned Medium Modulates Apoptotic and Stress-Related Gene Expression, Ameliorates Maturation and Allows for the Development of Immature Human Oocytes after Artificial Activation

The aim of the present study was to determine whether mesenchymal stem cell-conditioned medium (MSC-CM) modulates apoptotic and stress-related gene expression, and ameliorates maturation and developmental potential of immature human oocytes after artificial activation. A total of 247 surplus immature germinal vesicle (GV) oocytes obtained from infertile women were allocated into two in vitro maturation (IVM) groups: 1: GV oocytes (n = 116) matured in vitro (fIVM), and 2: GV oocytes (n = 131) that were vitrified, then in vitro matured (vIVM). Also, two maturation media were used: Alpha-minimum essential medium (α-MEM) and human umbilical cord-derived MSCs (hUCM). After 36 h of incubation, the IVM oocytes were examined for nuclear maturation. In IVM-matured oocytes, cytoplasmic maturation was evaluated after artificial activation through Ionomycin. Moreover, the quantitative expressions of B-cell CLL/lymphoma 2 (BCL2), BCL2-associated X protein (BAX), superoxide dismutase (SOD), and Heat shock proteins (HSP70) in matured oocytes were assessed by quantitative Real-time polymerase chain reaction (qRT-PCR) and compared with fresh and vitrified in vivo matured oocytes, which were used as fIVM and vIVM controls, respectively. The highest maturation rate was found in hUCM in fIVM, and the lowest maturation rate was found using α-MEM in vIVM (85.18% and 71.42%, respectively). The cleavage rate in fIVM was higher than that in vIVM (83.4% vs. 72.0%). In addition, the cleavage rate in α-MEM was lower than that in the hUCM (66.0% vs. 89.4%). Furthermore, the difference between parthenote embryo arrested in 4-8 cells (p < 0.04) and the quality of embryo arrested in 8-cell (p < 0.007) were significant. The developmental stages of parthenote embryos in hUCM versus α-MEM were as follows: 2-4 cell (89.45% vs. 66.00%, respectively), 4-8 cell (44.31% vs. 29.11%, respectively), morula (12.27% vs. 2.63%, respectively), and blastocysts (2.5% vs. 0%, respectively). The messenger RNA (mRNA) expression levels of BCL2, BAX and SOD were significantly different (p < 0.05) between the matured IVM oocytes. Overall, hUCM showed potential efficacy in terms of ameliorating oocyte maturation and in promoting the development and mRNA expression of BAX, BCL2, and SOD.

Molecular Mechanisms Responsible for Increased Vulnerability of the Ageing Oocyte to Oxidative Damage

In their midthirties, women experience a decline in fertility, coupled to a pronounced increase in the risk of aneuploidy, miscarriage, and birth defects. Although the aetiology of such pathologies are complex, a causative relationship between the age-related decline in oocyte quality and oxidative stress (OS) is now well established. What remains less certain are the molecular mechanisms governing the increased vulnerability of the aged oocyte to oxidative damage. In this review, we explore the reduced capacity of the ageing oocyte to mitigate macromolecular damage arising from oxidative insults and highlight the dramatic consequences for oocyte quality and female fertility. Indeed, while oocytes are typically endowed with a comprehensive suite of molecular mechanisms to moderate oxidative damage and thus ensure the fidelity of the germline, there is increasing recognition that the efficacy of such protective mechanisms undergoes an age-related decline. For instance, impaired reactive oxygen species metabolism, decreased DNA repair, reduced sensitivity of the spindle assembly checkpoint, and decreased capacity for protein repair and degradation collectively render the aged oocyte acutely vulnerable to OS and limits their capacity to recover from exposure to such insults. We also highlight the inadequacies of our current armoury of assisted reproductive technologies to combat age-related female infertility, emphasising the need for further research into mechanisms underpinning the functional deterioration of the ageing oocyte.

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.

Meiotic arrest with roscovitine and follicular fluid improves cytoplasmic maturation of porcine oocytes by promoting chromatin de-condensation and gene transcription

The developmental capacity of in vitro matured oocytes is inferior to that of the in vivo matured ones due to insufficient cytoplasmic maturation. Although great efforts were made to accomplish better cytoplasmic maturation by meiotic arrest maintenance (MAM) before in vitro maturation (IVM), limited progress has been achieved in various species. This study showed that MAM of porcine oocytes was better achieved with roscovitine than with dibutyryl cyclic adenosine monophosphate (db-cAMP) or 3-isobutyl-1-methylxanthine. Oocyte developmental competence after IVM was significantly improved following MAM in 199 + FF medium (TCM-199 containing 10% porcine follicular fluid and 25 µM roscovitine) to a level even higher than that in control oocytes matured without pre-MAM. Observations on other markers further confirmed the positive effects of MAM in 199 + FF on oocyte cytoplasmic maturation. During MAM culture in 199 + FF, re-decondensation (RDC) of condensed chromatin occurred, and transcription of genes beneficial to cytoplasmic maturation was evident in some of the oocytes with surrounded nucleoli (SN). However, MAM with db-cAMP neither induced RDC nor improved oocyte developmental potential. Together, the results suggest that MAM in the presence of FF and roscovitine improved the developmental competence of porcine oocytes by promoting a pre-GVBD chromatin de-condensation and expression of beneficial genes.

Follicular Fluid redox involvement for ovarian follicle growth

As the human ovarian follicle enlarges in the course of a regular cycle or following controlled ovarian stimulation, the changes in its structure reveal the oocyte environment composed of cumulus oophorus cells and the follicular fluid (FF).

In contrast to the dynamic nature of cells, the fluid compartment appears as a reservoir rich in biomolecules. In some aspects, it is similar to the plasma, but it also exhibits differences that likely relate to its specific localization around the oocyte. The chemical composition indicates that the follicular fluid is able to detect and buffer excessive amounts of reactive oxygen species, employing a variety of antioxidants, some of them components of the intracellular milieu.

An important part is played by albumin through specific cysteine residues. But the fluid contains other molecules whose cysteine residues may be involved in sensing and buffering the local oxidative conditions. How these molecules are recruited and regulated to intervene such process is unknown but it is a critical issue in reproduction.

In fact, important proteins in the FF, that regulate follicle growth and oocyte quality, exhibit cysteine residues at specific points, whose untoward oxidation would result in functional loss. Therefore, preservation of controlled oxidative conditions in the FF is a requirement for the fine-tuned oocyte maturation process. In contrast, its disturbance enhances the susceptibility to the establishment of reproductive disorders that would require the intervention of reproductive medicine technology.

The effects of melatonin on bovine uniparental embryos development in vitro and the hormone secretion of COCs

Melatonin is a unique multifunctional molecule that mediates reproductive functions in animals. In this study, we investigated the effects of melatonin on bovine parthenogenetic and androgenetic embryonic development, oocyte maturation, the reactive oxygen species (ROS) levels in parthenogenetic and androgenetic embryos and cumulus—oocyte complexes (COCs) hormone secretion with melatonin supplementation at four concentrations (0, 10, 20, and 30 pmol/mL), respectively. The results showed that melatonin significantly promoted the rates of bovine parthenogenetic and androgenetic embryonic cleavage and morula and blastocysts development (P < 0.05). The rate of cleavage was higher in the androgenetic embryo than that in the parthenogenetic embryo. Compared with the parthenogenetic embryos, the androgenetic embryos had a poor developmental competence from morula to blastocyst stage. Moreover, the levels of ROS were significantly lower in the parthenogenetic and androgenetic embryoes with melatonin-treated group than that of the control group (P < 0.05). Melatonin supplemented significantly increased the maturation rate of oocyte in vitro (P < 0.05). More importantly, melatonin significantly promoted the secretion of progesterone and estradiol by COCs (P < 0.05). To reveal the regulatory mechanism of melatonin on steroids synthesis, we found that steroidogenic genes (CYP11A1, CYP19A1 and StAR) were upregulated, suggesting that melatonin regulated estradiol and progesterone secretion through mediating the expression of steroidogenic genes (CYP11A1, CYP19A1 and StAR). In addition, MT1 and MT2 were identified in bovine early parthenogenetic and androgenetic embryos using western blot. It could be concluded that melatonin had beneficial effects on bovine oocyte in vitro maturation, COC hormone secretion, early development of subsequent parthenogenetic and androgenetic embryos. It is inferred that melatonin could be used to enhance the efficiency of in vitro developed embryos.

Role of oxidant–antioxidant balance in reproduction of domestic animals

Reproductive process leads to dynamic changes in metabolism and energy consumption, which may be responsible for the excessive production of free radicals (oxidants) that are generated during the physiological process of oxygen consumption. As the ovary is a metabolically active organ, it produces oxidants. Growing follicles, granulose cells of Graffian follicles and ovulated follicles all produce both enzymatic and non-enzymatic antioxidants to preserve themselves from the oxidative damage of oxidants. Oxidants and antioxidants are involved in several reproductive functions such as the regulation of follicular fluid environment, folliculogenesis, steroidogenesis, corpus luteum function, and luteolysis. In this article, the currently available literature is reviewed in relation to the roles of oxidants and oxidative stress in both normal and abnormal reproductive physiological processes.

Equilibrium between anti-oxidants and reactive oxygen species: a requisite for oocyte development and maturation

Reactive oxygen species (ROS) are required for cellular functioning and are controlled by anti‐oxidants. The ROS influence the follicles, oocytes, endometrium, and their environment. The luteinizing hormone surge initiates a massive recruitment of ROS that modulates major reproductive functions namely, oocyte maturation, ovarian steroidogenesis, corpus luteal function, and luteolysis. The anti‐oxidant system balances ROS generation and maintains the cellular functions. Both enzymatic and non‐enzymatic anti‐oxidants namely, vitamins and minerals are present in the follicles and protect the oocytes from the damaging effects of ROS. The overproduction of ROS leads to oxidative stress that affects the quality of oocytes and subsequent anovulation. Although researchers have tried to establish the role of ROS and anti‐oxidants in oocyte development, still this aspect needs to be revisited. This review discusses the importance of the ROS and anti‐oxidant balance that is required for the development and maturation of oocytes. There are increasing data on the activity of ROS and anti‐oxidants in supporting oocyte development and maturation. However, extensive research is required to identify the safe physiological concentration and duration of both the ROS and anti‐oxidants that are required to facilitate oocyte development and maturation during in vitro and in vivo conditions.

Effect of insulin-transferrin-selenium (ITS) and l-ascorbic acid (AA) during in vitro maturation on in vitro bovine embryo development

The aim of this study was to evaluate the effect of adding a combination of insulin, transferrin and selenium (ITS) and l-ascorbic acid (AA) during in vitro maturation (IVM) and in vitro culture (IVC) on in vitro embryo production. To verify the effect of the supplements, cleavage and blastocyst rates, embryo size and total cell number were performed. Embryonic development data, embryo size categorization and kinetics of maturation were analyzed by chi-squared test, while the total cell number was analyzed by a Kruskal-Wallis test (P < 0.05). When ITS was present during IVM, IVC or the entire culture, all treatments had a cleavage and blastocyst rates and embryo quality, similar to those of the control group (P < 0.05). Supplementation of IVM medium with ITS and AA for 12 h or 24 h showed that the last 12 h increased embryo production (51.6%; n = 220) on D7 compared with the control (39.5%; n = 213). However, no improvement was observed in blastocyst rate when less competent oocytes, obtained from 1-3 mm follicles, were exposed to ITS + AA for the last 12 h of IVM, with a blastocyst rate of 14.9% (n = 47) compared with 61.0% (n = 141) in the control group. The results suggest that the addition of ITS alone did not affect embryo production; however, when combined with AA in the last 12 h of maturation, there was improvement in the quantity and quality of embryos produced. Furthermore, the use of ITS and AA during IVM did not improve the competence of oocytes obtained from small follicles.

NADPH oxidase-4 and MATER expressions in granulosa cells: Relationships with ovarian aging

AIMS

Relevant roles in follicular development and ovulation are played by maternal antigen that embryos require (MATER), product of a maternal effect gene, and by reactive oxygen species (ROS), indispensable for the induction of ovulatory genes. At the moment, the relationship between these two biological systems and their involvement in the ovarian aging have not been still clarified. The aim of the current experimental study was to analyse the age-related changes of the MATER and NOX proteins.

MATERIALS AND METHODS

MATER and ROS homeostasis was studied in granulosa cells (GCs) and cumulus cells (CCs) of infertile patients who undergone oocyte retrieval for in vitro fertilization cycles using Western blot and confocal immunofluorescence analysis. Samples were obtained from subjects with age≥40years (cases) and with age≤37years (controls).

KEY FINDINGS

The expression pattern of MATER and NOX observed in GCs was not different from that observed in CCs. High levels of both proteins were detected in the control samples. A significant lower expression of both MATER and NOX4 was observed in the case versus control samples.

SIGNIFICANCE

The expression of MATER and NOX4 proteins are closely related to the follicular development and ovulation with particular regard for ovarian aging.

Increased concentration of 8-hydroxy-2'-deoxyguanosine in follicular fluid of infertile women with endometriosis

Impaired oocyte quality and oxidative stress might be involved in the pathogenesis of endometriosis-related infertility. To improve our understanding of the role of oxidative stress in this condition, we compare eight oxidative stress markers from each stage, including the simultaneous analysis of lipids, proteins and DNA damage, in the serum and follicular fluid of infertile women with endometriosis and infertile controls undergoing controlled ovarian stimulation for intracytoplasmic sperm injection. In total, 87 serum samples (43 with endometriosis, 44 controls) and 61 follicular fluid samples (29 with endometriosis, 32 controls) free of blood contamination upon visual inspection and presenting granulosa cells alone or granulosa cells plus a retrieved mature oocyte were collected on the day of oocyte retrieval. Total hydroperoxides, malondialdehyde, advanced oxidation protein products, glutathione, superoxide dismutase (SOD) and total antioxidant capacity (TAC) were determined by spectrophotometry, vitamin E by high-performance liquid chromatography and 8-hydroxy-2'-deoxyguanosine (8OHdG) by enzyme-linked immunosorbent assay. The endometriosis group showed higher serum concentrations of glutathione and SOD, lower serum concentrations of TAC and higher follicular concentrations of 8OHdG and vitamin E compared with infertile controls. These data indicate both systemic and follicular oxidative stress in infertile patients with endometriosis. For the first time, we demonstrate the presence of oxidative DNA damage, represented by higher 8OHdG concentrations in the follicular microenvironment of these patients, possibly related to compromised oocyte quality and associated with the pathogenesis of endometriosis-related infertility.

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.

Melatonin: a "Higgs boson" in human reproduction

As the Higgs boson could be a key to unlocking mysteries regarding our Universe, melatonin, a somewhat mysterious substance secreted by the pineal gland primarily at night, might be a crucial factor in regulating numerous processes in human reproduction. Melatonin is a powerful antioxidant which has an essential role in controlling several physiological reactions, as well as biological rhythms throughout human reproductive life. Melatonin, which is referred to as a hormone, but also as an autocoid, a chronobiotic, a hypnotic, an immunomodulator and a biological modifier, plays a crucial part in establishing homeostatic, neurohumoral balance and circadian rhythm in the body through synergic actions with other hormones and neuropeptides. This paper aims to analyze the effects of melatonin on the reproductive function, as well as to shed light on immunological and oncostatic properties of one of the most powerful hormones.

Development of mouse preantral follicle after in vitro culture in a medium containing melatonin

Objective

Improvements in cancer treatment have allowed more young women to survive. However, many cancer patients suffer from ovarian failure. Cryopreservation is one of the solutions for fertility restoration in these patients. The cryopreservation of isolated follicles is a more attractive approach in the long term. Many endocrine and paracrine factors can stimulate the granulosa cells of preantral follicles to proliferate. Melatonin acts as direct free radical scavenger and indirect antioxidant. In this study, we investigated the direct effects of melatonin on follicle development and oocyte maturation by exposing in vitro cultured mouse vitrified-warmed ovarian follicles to melatonin.

Materials and Methods

In an experimental study, preantral follicles with diameter of 150-180 µm were isolated from prepubertal mouse ovaries. Follicles were vitrified and thawed using cryolock method. They were then cultured individually for 7 days in droplets supplemented with 0, 10 and 100 pM melatonin, while ovulation was induced using epidermal growth factor (EGF) and human chorionic gonadotropin (hCG). The survival rate of follicles and nuclear maturation of ovulated oocytes were determined.

Results

At the end of culture, significant increases in follicle survival (p<0.001) and in diameter (p<0.05) were noticed in 10 pM melatonin group compared to control group. In the 100 pM group, survival rate was not affected by melatonin. It was revealed that after induction of ovulation, total number of metaphase II oocytes in treatment groups were not influenced by melatonin (p>0.05).

Conclusion

Culture of mouse vitrified-warmed preantral follicles in a medium supplemented with 10 pM melatonin increased the number of surviving follicles.

Nitric oxide synthase (NOS) inhibition during porcine in vitro maturation modifies oocyte protein S-nitrosylation and in vitro fertilization

Nitric oxide (NO) is a molecule involved in many reproductive processes. Its importance during oocyte in vitro maturation (IVM) has been demonstrated in various species although sometimes with contradictory results. The objective of this study was to determine the effect of NO during IVM of cumulus oocyte complexes and its subsequent impact on gamete interaction in porcine species. For this purpose, IVM media were supplemented with three NOS inhibitors: NG-nitro-L-arginine methyl ester (L-NAME), NG-monomethyl-L-arginine (L-NMMA) and aminoguanidine (AG). A NO donor, S-nitrosoglutathione (GSNO), was also used. The effects on the cumulus cell expansion, meiotic resumption, zona pellucida digestion time (ZPdt) and, finally, on in vitro fertilization (IVF) parameters were evaluated. The oocyte S-nitrosoproteins were also studied by in situ nitrosylation. The results showed that after 42 h of IVM, AG, L-NAME and L-NMMA had an inhibitory effect on cumulus cell expansion. Meiotic resumption was suppressed only when AG was added, with 78.7% of the oocytes arrested at the germinal vesicle state (P<0.05). Supplementation of the IVM medium with NOS inhibitors or NO donor did not enhance the efficiency of IVF, but revealed the importance of NO in maturation and subsequent fertilization. Furthermore, protein S-nitrosylation is reported for the first time as a pathway through which NO exerts its effect on porcine IVM; therefore, it would be important to determine which proteins are nitrosylated in the oocyte and their functions, in order to throw light on the mechanism of action of NO in oocyte maturation and subsequent fertilization.

The control of reactive oxygen species influences porcine oocyte in vitro maturation

The aim of this study was to examine the effect of varying intracellular reactive oxygen species (ROS) levels during oocyte in vitro maturation with enzymatic ROS production systems (xanthine + xanthine oxidase or xanthine + xanthine oxidase + catalase), scavenger systems (catalase or superoxide dismutase + catalase) or cysteine on porcine oocyte maturation. Oocyte ROS levels showed an increase when H2O2 or O2∙(-) production systems were added to the culture medium (p < 0.05). On the other hand, the presence of ROS scavengers in the maturation medium did not modify oocyte ROS levels compared with the control after 48 h of maturation, but the addition of cysteine induced a decrease in oocyte ROS levels (p < 0.05). The ROS production systems used in this work did not modified the percentage of oocyte nuclear maturation, but increased the decondensation of sperm head (p < 0.05) and decreased the pronuclear formation (p < 0.05). In turn, the addition of O2∙(-) and H2O2 scavenging systems during in vitro maturation did not modify the percentage of oocytes reaching metaphase II nor the oocytes with decondensed sperm head or pronuclei after fertilization. However, both parameters increased in the presence of cysteine (p < 0.05). The exogenous generation of O2∙(-) and H2O2 during oocyte in vitro maturation would not affect nuclear maturation or later sperm penetration, but most of the spermatozoa cannot progress to form the pronuclei after fusion with the oocyte. The decrease in endogenous ROS levels by the addition of cysteine would improve pronuclear formation after sperm penetration.

The effects of superoxide dismutase addition to the transport medium on cumulus-oocyte complex apoptosis and IVF outcome in cats (Felis catus)

The aim of the present study was to examine the effects of superoxide dismutase (SOD) addition to the ovary transport medium (4°C, 3-72 h) on ovarian cell viability and apoptosis and in vitro embryo production (IVEP) in domestic cats. The ovaries collected from 76 mixed-breed domestic queens were randomly assigned to the control or SOD-treated groups and incubated for 3, 24, 48 or 72 h. The ovaries were then subjected to the following: (1) fixed in formalin to assess the incidence of apoptosis (fragmented DNA in situ detection kit), (2) stored at -196°C in liquid nitrogen to evaluate the expression of the pro-apoptotic Bax gene and the anti-apoptotic Bcl-2 gene (RT-PCR), and (3) used to obtain the cumulus-oocyte complexes (COCs) in order to test the cell viability (carboxyfluorescein or trypan blue staining) and IVEP. The incidence of apoptosis appeared to be higher in the control compared with the SOD-treated ovaries. The ovarian expression of Bax was lower and the Bcl-2 expression was higher in the SOD-treated group compared with the control group. The presence of SOD in the transport medium increased the viability of COCs and IVEP compared with the control medium. In summary, the supplementation of the ovary transport medium with SOD reduced cellular apoptosis and enhanced COC survival and IVEP in domestic cats.