Oxidative stress impairs oocyte quality and melatonin protects oocytes from free radical damage and improves fertilization rate

Acrylamide impairs the developmental potential of germinal vesicle oocytes by inducing mitochondrial dysfunction and autophagy/apoptosis in mice

Background: Acrylamide (ACR), an important endogenous contaminant in carbohydrate-rich foods, has been involved in various negative effects on multiple organ networks, including the reproductive system. Previous studies have reported that ACR affects oocyte quality and fertility. Purpose: This study aimed to explore the toxic effects and regulatory mechanisms of ACR on mouse germinal vesicle (GV) oocytes. Research Design: In this study, adult female mice were exposed to ACR at 10 mg/kg/day/body weight through their drinking water continuously for 4 weeks. Study Sample and Data Analysis: The mitochondrial function, autophagy/apoptosis, and development potential of GV oocytes were investigated. Results: The results showed that ACR reduced the oocyte diameter, sperm-binding ability, parthenogenetic activation and in vitro fertilization (IVF) rate, and development potential of pre-implantation embryos. We also found that ACR exposure disrupted chromatin configuration, mitochondrial distribution, and membrane potential (Δφm) of oocytes. Actin filament expression was significantly reduced in both the membrane and cytoplasm of mouse oocytes. Moreover, ACR exposure increased LC3-positive signals, early apoptosis rate, aberrant ATG3, ATG5, LC3, Beclin1, and mTOR mRNA expression. Conclusions: These results suggest that ACR exposure can affect the developmental potential of GV oocytes by inducing mitochondrial dysfunction, actin filament assembly, and autophagy/apoptosis.

Mogroside V Alleviates Oocyte Meiotic Defects and Quality Deterioration in Benzo(a)pyrene-Exposed Mice

Accumulating evidence has demonstrated that benzo(a)pyrene (BaP) exposure adversely affects female reproduction, especially oocyte meiotic maturation and subsequent embryo development. Although we previously found that mogroside V (MV), a major bioactive component of S. grosvenorii, can protect oocytes from quality deterioration caused by certain stresses, whether MV can alleviate BaP exposure-mediated oocyte meiotic defects remains unknown. In this study, female mice were exposed to BaP and treated concomitantly with MV by gavage. We found that BaP exposure reduced the oocyte maturation rate and blastocyst formation rate, which was associated with increased abnormalities in spindle formation and chromosome alignment, reduced acetylated tubulin levels, damaged actin polymerization and reduced Juno levels, indicating that BaP exposure results in oocyte nucleic and cytoplasmic damage. Interestingly, MV treatment significantly alleviated all the BaP exposure-mediated defects mentioned above, indicating that MV can protect oocytes from BaP exposure-mediated nucleic and cytoplasmic damage. Additionally, BaP exposure increased intracellular ROS levels, meanwhile induced DNA damage and early apoptosis in oocytes, but MV treatment ameliorated these defective parameters, therefore it is possible that MV restored BaP-mediated oocyte defects by reducing oxidative stress. In summary, our findings demonstrate that MV might alleviate oocyte meiotic defects and quality deterioration in BaP-exposed mice.

Antioxidants Present in Reproductive Tract Fluids and Their Relevance for Fertility

Nowadays, infertility is classified as a disease of the reproductive system. Although it does not compromise the life of the individual, it can have detrimental effects on the physiological and psychological health of the couple. Male fertility evaluation is mainly focused on the analysis of sperm parameters. However, the ejaculated fluid is also composed of seminal plasma, and the study of this fluid can provide crucial information to help in the assessment of male fertility status. Total antioxidant capacity of the seminal plasma has been positively correlated with the fertility of men. Moreover, evidence highlights to a similar importance as that of female reproductive tract fluid antioxidant capabilities and female fertility. Herein, we describe the functions of seminal plasma and female reproductive tract fluids, as well as their main antioxidant components and their relationships with fertility outcomes. Additionally, this review contains the most up to date information regarding the mechanisms of the interaction between the male and the female reproductive fluids and the importance of proper antioxidant capacity for fertilization.

Effects of multicycle gonadotropin-releasing hormone antagonist protocols on oxidative stress of follicular fluid and ovarian granulosa cells

The effect of repeated multicycle gonadotropin-releasing hormone antagonist (GnRH-ant) protocols on oxidative stress (OS) in follicular fluid (FF) and ovarian granulosa cells (GCs) remains unclear. This study investigated the effects of repeated multicycle GnRH-ant protocols on OS markers of FF and ovarian GCs. A total of 145 patients were enrolled and divided into four groups: 1 cycle group (n = 42), 2 cycles group (n = 37), 3 cycles group (n = 45), and 4-5 cycles group (n = 21). The FF and ovarian GCs of the patients were collected on the day of last oocyte retrieval and the levels of 8-hydroxy-2-deoxyguanosine (8-OHdG), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were tested by ELISA. The results showed that the serum estradiol levels on hCG injection day in the 3 and 4-5 cycles were significantly (P < 0.05) lower than in the 1 and 2 cycles. The number of retrieved oocytes (12.1 ± 3.3 in cycle 1, 11.7 ± 3.1 in cycle 2, 10.4 ± 2.4 in cycle 3, and 9.4 ± 2.4 in cycles 4-5), embryos with two pronuclei (7.6 ± 3.0 in cycle 1, 7.0 ± 2.5 in cycle 2, 6.2 ± 2.6 in cycle 3, and 5.5 ± 2.1 in cycles 4-5), and the rates of high-quality embryos (52.2% in cycle 1, 47.9% in cycle 2, 38.6% in cycle 3, and 36.5% in cycles 4-5), implantation (35.4% in cycle 1, 32.4% in cycle 2, 23.8% in cycle 3, and 22.9% in cycles 4-5) and clinical pregnancy (50.0% in cycle 1, 43.2% in cycle 2, 33.3% in cycle 3, and 23.8% in cycles 4-5) in cycles 3 and 4-5 were significantly (P < 0.05) lower than those in cycles 1 and 2. Compared with 1 and 2 cycles, the 8-OHdG and SOD were significantly increased in the 3-5 cycles, while the CAT and GSH-Px levels were significantly decreased. Together, this study reveals repeated COS with the use of GnRH-ant protocols results in OS and changes the follicle microenvironment of FF and GCs, possibly leading to poor IVF outcomes in patients with 3-5 cycles of COS.

Adipose-Derived Mesenchymal Stem Cells: A Promising Tool in the Treatment of pre mature ovarian failure

Despite being rare, primary ovarian insufficiency (POI) is a significant cause of infertility and deficiency of ovarian hormone in women. Several health risks are also associated with POI, which include dry eye syndrome, reduced density of bones and enhanced fracture risks, troublesome menopausal symptoms, early development of cardiovascular disease, and psychological effects such as declined cognition, reduced perceived psychological support, anxiety, and depression. Replacing premenopausal levels of ovarian sex steroids through proper hormone replacement therapy could improve the quality of life for POI women and ameliorate related health risks. Herein, POI and its complications, in addition to hormone replacement therapies, which are safe and effective, are discussed. It is proposed that the use of HRT) Hormone replacement therapy (formulations which mimic normal production of ovarian hormones could reduce POI-associated morbidity rates if they are continued by the age 50, which is approximately the natural age of menopause. Particular populations of POI women are also addressed, which include those with enhanced risk of ovarian or breast cancer, those with Turner syndrome, those approaching natural menopause, and those who are breastfeeding. It is generally predicted that stem cell-based therapies would be both safe and effective. In fact, several types of cells have been described as safe, though their effectiveness and therapeutic application are yet to be defined. Several factors exist which could affect the results of treatment, such as cell handling, ex-vivo preparation strategies, variations in tissue of origin, potency, and immunocompatibility. Accordingly, cell types potentially effective in regenerative medicine could be recognized. Notably, products of MSCs from various sources of tissues show different levels of regenerative capabilities. The ultimate focus of the review is on adipose tissue-derive MCSs (ADMSCs), which possess exceptional features such as general availability, great ability to proliferate and differentiate, immunomodulatory capabilities, and low immunogenicity.

Peroxiredoxin 6 Plays Essential Role in Mediating Fertilization and Early Embryonic Development in Rabbit Oviduct

The oviduct is a site for early reproductive events including gamete maturation, fertilization, and early embryo development. Secretory cells lining the oviduct lumen synthesize and secrete proteins that interact with gametes and developing embryos. Although previous studies have identified some of the secretory proteins in the oviduct, however, knowledge and their precise specific functions in the oviduct are poorly understood. In this study, by using proteomic approach, we identified a secretory protein, Peroxiredoxin 6 (PRDX6), and evaluated its role in mediating early pregnancy events, fertilization, and embryo development in rabbit oviduct. The expression of PRDX6 was significantly higher in ampulla and isthmus sections of the oviduct in mated animal groups compared to non-mated controls. Furthermore, significant reduction in number of embryos recovered from PRDX6 siRNA-transfected oviductal horn was observed compared to the control contralateral horn. Moreover, in animals receiving PRDX6 siRNA in their oviductal horn, the number of implanted blastocysts was significantly less in the uterus as observed on day 9 post-coital (p.c.). Further, during embryo-rabbit oviduct epithelial cell (ROEC) co-culture, siRNA-mediated PRDX6 silencing attenuated the early embryonic development. Mechanistically, increased levels of ROS and expression of oxidative stress- and inflammation-related proteins were found in PRDX6 siRNA-treated ROEC cells as compared to control cells, implicating that ablation of PRDX6 in the oviduct creates a stress-induced micro-environment detrimental to early embryonic development in oviduct. Taken together, our data suggest that PRDX6 maintains an optimal micro-environment conducive to successful embryo development and can be considered as a candidate to evaluate its therapeutic potential in IVF strategies.

Reproductive Longevity and Aging: Geroscience Approaches to Maintain Long-Term Ovarian Fitness

Increases in delayed childbearing worldwide have elicited the need for a better understanding of the biological underpinnings and implications of age-related infertility. In women 35 years and older the incidences of infertility, aneuploidy, and birth defects dramatically increase. These outcomes are a result of age-related declines in both ovarian reserve and oocyte quality. In addition to waning reproductive function, the decline in estrogen secretion at menopause contributes to multisystem aging and the initiation of frailty. Both reproductive and hormonal ovarian function are limited by the primordial follicle pool, which is established in utero and declines irreversibly until menopause. Because ovarian function is dependent on the primordial follicle pool, an understanding of the mechanisms that regulate follicular growth and maintenance of the primordial follicle pool is critical for the development of interventions to prolong the reproductive life span. Multiple pathways related to aging and nutrient-sensing converge in the mammalian ovary to regulate quiescence or activation of primordial follicles. The PI3K/PTEN/AKT/FOXO3 and associated TSC/mTOR pathways are central to the regulation of the primordial follicle pool; however, aging-associated systems such as the insulin-like growth factor-1/growth hormone pathway, and transsulfuration/hydrogen sulfide pathways may also play a role. Additionally, sirtuins aid in maintaining developmental metabolic competence and chromosomal integrity of the oocyte. Here we review the pathways that regulate ovarian reserve and oocyte quality, and discuss geroscience interventions that leverage our understanding of these pathways to promote reproductive longevity.

Melatonin and Myo-Inositol: Supporting Reproduction from the Oocyte to Birth

Human pregnancy is a sequence of events finely tuned by several molecular interactions that come with a new birth. The precise interlocking of these events affecting the reproductive system guarantees safe embryo formation and fetal development. In this scenario, melatonin and myo-inositol seem to be pivotal not only in the physiology of the reproduction process, but also in the promotion of positive gestational outcomes. Evidence demonstrates that melatonin, beyond the role of circadian rhythm management, is a key controller of human reproductive functions. Similarly, as the most representative member of the inositol’s family, myo-inositol is essential in ensuring correct advancing of reproductive cellular events. The molecular crosstalk mediated by these two species is directly regulated by their availability in the human body. To date, biological implications of unbalanced amounts of melatonin and myo-inositol in each pregnancy step are growing the idea that these molecules actively contribute to reduce negative outcomes and improve the fertilization rate. Clinical data suggest that melatonin and myo-inositol may constitute an optimal dietary supplementation to sustain safe human gestation and a new potential way to prevent pregnancy-associated pathologies.

Applications of Melatonin in Female Reproduction in the Context of Oxidative Stress

Oxidative stress has been recognized as one of the causal mediators of female infertility by affecting the oocyte quality and early embryo development. Improving oxidative stress is essential for reproductive health. Melatonin, a self-secreted antioxidant, has a wide range of effects by improving mitochondrial function and reducing the damage of reactive oxygen species (ROS). This minireview illustrates the applications of melatonin in reproduction from four aspects: physiological ovarian aging, vitrification freezing, in vitro maturation (IVM), and oxidative stress homeostasis imbalance associated with polycystic ovary syndrome (PCOS), emphasising the role of melatonin in improving the quality of oocytes in assisted reproduction and other adverse conditions.

Melatonin promotes in vitro maturation of vitrified-warmed mouse GV oocytes potentially by modulating MAD2 protein expression of SAC component through MTRs

Previous studies have shown that melatonin (MT) can ameliorate vitrification-inflicted damage in mouse germinal vesicle (GV) oocytes, however, the key mechanistic basis of this improvement still remains poorly understood. This study was conducted to investigate whether MT can improve in vitro developmental potential of vitrified-warmed GV oocytes through its receptors. The fresh oocytes were randomly divided into four groups: untreated (control group, F), vitrified by open-pulled straw method (vitrification group, V), vitrification group with 100 nmol/L MT supplementation (vitrification + MT group, VM), and with 100 nmol/L MT plus 100 nmol/L luzindole administration (vitrification + MT + luzindole group, VML) or with 50 nmol/L ramelteon addition (vitrification + ramelteon group; VR). After warming, oocytes were cultured in vitro, and MT receptors (MTRs), MAD2 (mitotic arrest deficient 2), Securin and CyclinB1 protein levels and spindle morphology were evaluated. The ratio of oocytes developed to the metaphase I (MI) and metaphase II (MII) stages was also assessed. The results showed that after vitrification-warming, the in vitro maturation rate of GV oocytes was significantly lower compared to the control (F) group. Vitrification also significantly impaired the spindle morphology, decreased the protein level of MTRs and Securin, and decreased MAD2 levels in MI oocytes. However, when MT or ramelteon (MTRs agonist) were added (group wise) to warming and maturation media, the maturation rate of GV oocytes was significantly increased, the normal proportion of the spindle morphology increased, and the expression level of MAD2 increased in their resulting MI oocytes compared to the vitrification group. However, following addition of both MT and ramelteon, the maturation rate of GV oocyte showed no significant difference between VML and vitrification groups. The spindle morphology and MAD2 levels in MI oocytes were comparable to the vitrification group but differed significantly from the VM group. Taken together, finding of the present study shows that MT (100 nmol/L) can ameliorate the in vitro maturation of vitrified-warmed mouse GV oocytes, potentially by improving the spindle morphology, modulating MAD2 protein level and promoting the development of MI stage oocytes through MTRs.

Two melatonin treatments improve the conception rate after fixed-time artificial insemination in beef heifers following synchronisation of oestrous cycles using the CoSynch-56 protocol

OBJECTIVE

This study investigated the effect of melatonin administration in combination with the CoSynch-56 protocol on the conception rate after artificial insemination (AI) in beef heifers.

METHODS

Eighty-six beef heifers were allocated to four treatments in combination with CoSynch-56 treatment. All heifers, excluding the control group (CTR = 25), were injected with melatonin on day 1. The melatonin (MT = 20) and MT + human chorionic gonadotropin (MT + hCG = 21) groups received no further treatment with melatonin. Each heifer was treated with gonadotropin-releasing hormone (GnRH) on day 4, prostaglandin F2α (PGF2α) on day 11, and GnRH and AI 56 h later. The fourth group (2MT = 20) was injected again with melatonin concurrent with AI, and the MT + hCG group received hCG on day 19. Pregnancy diagnosis was performed using transrectal ultrasonography 45 days after AI and blood samples were collected via caudal venipuncture on days 0-1, 14-15, 24 and 59. Concentrations of progesterone (P4) and the activities of oxidative stress-related enzymes were determined using enzyme-linked immunosorbent assay.

RESULTS

The conception rate was greater in the 2MT group (75%) than in the other groups, while there was no significant difference among the CTR (44%), MT (45%) and MT + hCG (38.1%) groups. Treatment with melatonin increased superoxide dismutase and glutathione peroxidase activities and decreased malondialdehyde concentrations but did not significantly affect the concentration of P4.

CONCLUSION

Our results indicate that the administration of melatonin twice during the CoSynch-56 protocol may increase conception rates in beef heifers.

Does maternal exposure to nicotine affect the oocyte quality and reproductive capacity in adult offspring?

Gonadal development begins in the intrauterine phase and females from most species are born with an established oocyte reserve. Exposure to drugs during gestation can compromise the offspring health, also affecting the gametes quality. Nicotine, the main component of cigarettes, is an oxidant agent capable of altering the fertility in men and women. As female gametes are susceptible to oxidative stress, this drug can damage the oolemma and affect oocyte maturation, induce errors during chromosomal segregation and DNA fragmentation. Oocyte mitochondria are particularly susceptible to injuries, contributing to the oocyte quality loss and embryonic development disruption. Thus, considering the high number of women who smoke during pregnancy, while significant events are occurring in the embryo for future fertility of offspring, we seek to verify the quality of the oocytes from adult rats exposed to nicotine during intrauterine phase and breastfeeding. Pregnant Wistar rats received nicotine by osmotic mini-pumps and the female progenies were evaluated in adulthood for oocyte quality (viability, lipid peroxidation, generation of reactive oxygen species and mitochondrial integrity) and reproductive capacity. Embryos (3dpc) and fetuses (20dpc) generated by these rats were also evaluated. The results showed that the dose of 2 mg/kg/day of nicotine through placenta and breast milk does not affect the number of oocytes and the fertility capacity of adult rats. However, it causes some morphological alterations in oocytes, mitochondrial changes, embryonic fragmentation and disruption of fetal development. The malformations in fetuses generated from these gametes can also indicate the occurrence of epigenetic modifications.

Research progress of melatonin (MT) in improving ovarian function: a review of the current status

Melatonin (MT) is an endogenous hormone mainly synthesized by pineal cells, which has strong endogenous effects of eliminating free radicals and resisting oxidative damages. Melatonin (MT) can not only regulate the body’s seasonal and circadian rhythms; but also delay ovarian senescence, regulate ovarian biological rhythm, promote follicles formation, and improve oocyte quality and fertilization rate. This review aimd to provide evidence concerning the synthesis and distribution, ovarian function, and role of MT in development of follicles and oocytes. Moreover, the role of MT as antioxidative, participating in biological rhythm regulation, was also reviewed. Furthermore, the effects of MT on various ovarian related diseases were analyzed, particularly for the ovarian aging and polycystic ovary syndrome (PCOS).

The effect of oral melatonin supplementation on MT-ATP6 gene expression and IVF outcomes in Iranian infertile couples: a nonrandomized controlled trial

This study aims to evaluate the effect of melatonin supplementation on the outcomes of in vitro fertilization (IVF) and mitochondrial adenosine triphosphate production (MT-ATP6) gene expression in Iranian infertile couples. A single-blind nonrandomized controlled trial was conducted, recruiting 90 infertile couples who underwent IVF at an infertility center in Tehran, Iran. Patients who were assigned to the intervention group received melatonin as a supplementation to the standard controlled ovarian stimulation (COS). The control group received a COS protocol only. Primary outcome was the mRNA level of the MT-ATP6 gene in cumulus cells of ovarian follicles. Secondary outcomes were the mean number of mature oocytes retrieved, the embryo quality, and biochemical and clinical pregnancy rates. The mRNA level of the MT-ATP6 gene in cumulus cells between intervention and control groups was not statistically different (0.931 vs.1; P ˃ 0.05). The mean number of poor-quality embryos was significantly lower in the intervention group than that in the control group (0.27 vs. 0.80; P = 0.028). The biochemical and clinical pregnancy rates were higher in the intervention group (24% vs. 14%, P = 0.089, and 14% vs. 7%, P = 0.302, respectively); however, the difference was not significant. Melatonin supplementation did not increase the odds of clinical pregnancy and the number of mature oocytes retrieved, but significantly reduced the number of low-quality embryos. More extensive studies focusing on the level of MT-ATP6 gene expression in the oocyte or blastomere cells may further elucidate the effect of supplementation with melatonin in infertile couples who have poor clinical outcomes. Trial registration: Current Controlled Trials: IRCT2015042912307N4.

Modulation of Intracellular ROS and Senescence-Associated Phenotypes of Xenopus Oocytes and Eggs by Selective Antioxidants

Aging of oocytes and eggs diminishes their reproductive and developmental potential. It has been demonstrated previously that reactive oxygen species (ROS) contribute to accelerated aging of various cells. In the present study, we measured intracellular levels of ROS and investigated effects of several selective antioxidants (AOXs) on the viability and functional activity of aging oocytes and eggs of the African clawed frog Xenopus laevis. The fluorescent cell-permeable dye DCFDA, which is widely employed for ROS detection in cultured mammalian cells, was used to monitor ROS levels in the fresh and bench-aged oocytes and eggs by an optimized protocol. It was found that intracellular ROS contents were increased in frog oocytes and eggs aged for 48 h. It was further demonstrated using selective cell-permeable AOXs targeting different ROS-generating mechanisms, that the major source of ROS in Xenopus oocytes and eggs is the plasma membrane NADPH oxidase, and that mitochondrial generation contributes to the intracellular ROS content to a lesser extent. Targeted inhibition of NADPH oxidase with a natural organic compound apocynin reduced ROS levels significantly in Xenopus oocytes and eggs, maintained their normal phenotype and supported their functional competence. To our knowledge this is the first report concerning beneficial effects of apocynin on the isolated gamete cells, such as oocytes and eggs.

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.

Seasonal Effect on Developmental Competence, Oxidative Status and Tubulin Assessment of Prepubertal Ovine Oocyte

Simple Summary

Oocytes obtained from the ovaries of slaughtered prepubertal ewes can be incorporated into an in vitro embryo production system. The collection of this material is possible at two different times of the year, spring and autumn. The first period is linked to the natural reproductive cycle of the sheep. The second, on the other hand, is linked to the manipulation of the reproductive seasonality which allows the oestrus cycle to be controlled artificially. The analysis highlighted that the collection season influences oocytes quality from prepubertal donors in terms of improved energetic and oxidative status, microtubular organization, and developmental competence in oocytes recovered in spring. Data obtained underline that oocytes seem to be genetically and evolutionarily programmed to give their best in spring, this being the most favorable period for newborns.

Abstract

The reproductive seasonality of domestic animals is often manipulated in order to have more reproductive periods for commercial purposes related to the production of milk and meat. It is scientifically proven that such an alteration of the reproductive activity in sheep entails a deterioration in oocyte quality, leading to an inability to generate embryos. Since oocytes obtained from prepubertal ewes can be incorporated into an in vitro embryo production system and considering that their quality is crucial to the success of in vitro procedures, the aim of this work was to investigate the effect of seasons on the quality of prepubertal ovine oocytes collected in autumn and spring. Ovaries were collected from a local slaughterhouse from 30–40-day-old suckling lambs during both seasons. Following 24 h of in vitro maturation, oocytes developmental competence, reactive oxygen species (ROS) intracellular levels, and mitochondrial activity were evaluated, and a tubulin assessment was performed. The results on embryo production, as a percentage of first divisions and number of blastocysts obtained, were significantly higher in oocytes collected in the spring. Mitochondrial activity in oocytes was higher, and ROS production significantly lower, in spring than in autumn. Tubulin PTMs (tyrosinated and acetylated α-tubulin) showed a higher immunoreactivity in oocytes collected in spring compared with autumn sampling. Our data showed that seasons may affect the developmental competence, energetic status, and tubulin assessment of oocytes recovered from prepubertal ewes. Therefore, special care should be taken when choosing the period of the year for prepuberal ovine oocytes collection aimed at in vitro embryo reproduction programs.

Effect of melatonin supplementation during IVM of dromedary camel oocytes (Camelus dromedarius) on their maturation, fertilization, and developmental rates in vitro

The positive impact of melatonin on in vitro embryo production (IVEP) has been reported in many domestic species; however, no studies have been carried out in camelids. We aimed to evaluate the effects of melatonin supplementation in maturation media on in vitro maturation, fertilization, and preimplantation embryo development of dromedary camel oocytes (experiment 1). We also evaluated the concentrations of total antioxidant capacity (TAC), and malondialdehyde (MDA) in the IVM spent medium in relation to melatonin supplementation. Cumulus oocyte complexes (COCs) were cultured in in vitro maturation media (IVM) supplemented with either 0.0, 25.0, 50.0 or 75.0 μM of melatonin for 30 h. Matured oocytes were then fertilized in vitro with epididymal camel spermatozoa. Following IVF, the resulting embryos were cultured in vitro for seven days. The percentage of maturation, fertilization, cleavage, and embryo developmental rates (morula and blastocyst) was recorded (experiment 1). TAC and MDA levels in the IVM spent maturation media were also evaluated at 30 h post-IVM (experiment 2). The results showed that supplementation of IVM media with 25 μM melatonin significantly improved oocyte nuclear maturation, fertilization (18 h post-insemination; pi), cleavage (day 3 pi), morula (day 5 pi) and blastocyst (day 7 pi) rates as compared with the controls and other melatonin-supplemented groups. Furthermore, the TAC in the IVM spent media was significantly increased (P < 0.05) in 25 μM melatonin supplemented groups than those supplemented with 0.0, 50.0, 75.0 μM melatonin. However, the concentration of MDA was significantly lower (P < 0.05) in IVM media supplemented with 25.0 μM of melatonin when compared with the control and other treatment groups. In conclusion, supplementation of IVM medium with 25 μM of melatonin could enhance the in vitro developmental capacity of dromedary camel oocytes.

Gallic acid promotes the in vitro development of sheep secondary isolated follicles involving the phosphatidylinositol 3-kinase pathway

This study was conducted to evaluate the effect of addition of gallic acid as the single antioxidant to the base medium for in vitro culture of sheep secondary follicles and if the phosphatidylinositol 3-kinase (PI3K) pathway is involved in the action of gallic acid. Secondary follicles were isolated and cultured for 12 days in α-MEM supplemented with bovine serum albumin (BSA), insulin, glutamine, hypoxanthine, transferrin, selenium, and ascorbic acid (control medium: α-MEM⁺) or in α-MEM supplemented with BSA, insulin, glutamine, hypoxanthine and different concentrations of gallic acid (25, 50 or 100 μM), thus replacing transferrin, selenium and ascorbic acid in the medium. Follicle morphology, glutathione (GSH), and mitochondrial activity, and meiotic resumption were evaluated. Furthermore, inhibition of PI3K pathway was performed by pretreatment with LY294002. After 12 days of culture, the follicle survival in a medium containing 100 μM gallic acid was similar (P > 0.05) to α-MEM⁺ and greater (P < 0.05) compared with other gallic acid concentrations. Antrum formation, follicle diameter, GSH, and mitochondrial activity, and meiotic resumption, however, were greater (P < 0.05) when 100 μM gallic acid was included in the α-MEM⁺ culture medium compared with the control medium. Furthermore, LY294002 inhibited (P < 0.05) follicle survival, development, and meiotic resumption stimulated by 100 μM gallic acid. In conclusion, concentration of 100 μM of gallic acid can be a substitute for transferrin, selenium, and ascorbic acid in the base medium during in vitro culture of sheep secondary follicles, inducing follicle development likely through the PI3K pathway.

Psychological aspects of infertility. A systematic review

Objective

Fertility may be defined as a capacity to conceive and produce offspring. Infertility is characterized by failure to establish a clinical pregnancy after 12 months of regular and unprotected sexual intercourse. Infertility concerns an estimated 8–12% of the global population, and is associated with factors including time of unwanted non-conception, age of female partner and number of diseases impacting fertility. Unexplained infertility is described as idiopathic. This study aimed to analyse and evaluate the influence of mental disorders, often considered as reasons for idiopathic infertility, on female and male fertility, including stress, depression, sleep and eating disorders, and addictions.

Methods

This systematic review comprised a search of MEDLINE, Cochrane and PubMed databases for relevant articles that were analysed by two independent reviewers.

Results

A total of 106 articles published between 1955–2019 were included. Mental disorders modify endocrine gland and immune system functioning at both the tissue and cellular level, and are negatively associated with female and male fertility.

Conclusion

Mental disorders may negatively impact female and male fertility. Further studies are required to explain the exact role and contribution of mental disorders to fertility.

Novel therapeutic targets to improve IVF outcomes in endometriosis patients: a review and future prospects

BACKGROUND

Patients with endometriosis often experience infertility and have poor IVF outcomes, with low fertilization and pregnancy rates. Although many theories have tried to explain the mechanisms underlying infertility in these patients, none of them is conclusive.

OBJECTIVE AND RATIONALE

In this review, we discuss the pathologic mechanisms through which endometriosis likely leads to infertility along with the therapeutic options used to date to treat endometriosis-related infertility and, thereby, to improve IVF outcomes in patients with endometriosis.

SEARCH METHODS

We performed a comprehensive literature search of clinical outcomes in endometriosis and the molecular mechanisms contributing to oocyte quality using the PubMed database to identify human and animal studies published from 1992 until September 2020. In total, 123 manuscripts were included.

OUTCOMES

While some theories propose that endometriosis patients may have fertility problems as a result of decreased endometrial receptivity, others reinforce the idea that infertility could be associated with oocyte alterations and lower implantation rates. Single-cell RNA sequencing of oocytes from patients with endometriosis has identified dysregulated mechanisms involved in steroid metabolism and biosynthesis, response to oxidative stress and cell cycle regulation. Dysregulation of these mechanisms could result in the poor IVF outcomes observed in patients with endometriosis. Further, impaired steroidogenesis may directly affect oocyte and embryo quality. Increased oxidative stress in patients with endometriosis also has a detrimental effect on the follicular microenvironment, inducing cell cycle dysregulation in oocytes, poor oocyte quality, and infertility. Moreover, granulosa cells in the context of endometriosis undergo increased apoptosis and have an altered cell cycle that could adversely affect folliculogenesis, oocyte and embryo quality, and IVF outcomes. Endometriosis is also associated with inflammatory damage and impaired angiogenesis, which could be directly correlated with poor IVF outcomes. While therapeutic options using GnRH analogues, progestins and aromatase inhibitors do not improve endometriosis-related infertility, anti-inflammatory agents and antioxidant supplementation could improve oocyte quality as well as implantation and clinical pregnancy rates in patients with endometriosis.

WIDER IMPLICATIONS

Endometriosis is a heterogeneous disease whose pathogenesis is complex and could affect fertility by altering a collection of molecular mechanisms in oocytes. Thus, a single model is not sufficient to describe endometriosis-related infertility. Dysregulation of steroidogenesis, oxidative stress, cell cycle progression, inflammation and angiogenesis in the follicular environment and oocytes in individuals with endometriosis are all possible contributors to endometriosis-related infertility. Therefore, treatments targeting these mechanisms could be therapeutic alternatives to improve IVF outcomes for these patients.

Melatonin alleviates deoxynivalenol-induced apoptosis of human granulosa cells by reducing mutually accentuated FOXO1 and ER stress‡

Deoxynivalenol (DON) is one of the most prevalent Fusarium mycotoxins, which cause detrimental effects on human and animal reproductive systems by inducing oxidative stress. Increasing evidence has suggested the potential roles of melatonin in protecting granulosa cells from oxidative injury, but the underlying mechanisms remain largely elusive. Here, we demonstrated that suppression of FOXO1 and endoplasmic reticulum (ER) stress was engaged in melatonin-mediated protection against oxidative damage in human granulosa cells upon DON exposure in vitro. DON induced excess reactive oxygen species accumulation, cells viability loss, reduced estradiol-17β, and progesterone production in human granulosa cells, whereas melatonin ameliorated these phenotypes. Next, we found that the protective effect of melatonin against apoptosis was via reducing ER stress because the inhibition of ER stress displayed similar protective effects during DON treatment. Moreover, melatonin provided no additional protection when ER stress was inhibited. We further found that FOXO1 is a pivotal downstream effector of melatonin and ER stress in regulating DON-induced apoptosis in human granulosa cells. Blocking of FOXO1 reduced DON-induced cells death and FOXO1 activation could be suppressed by melatonin or ER stress inhibitor. However, melatonin failed to further restore cells viability in the presence of FOXO1 inhibitor. Collectively, our results reveal a new mechanism of melatonin in protecting against DON-induced apoptosis and dysfunction by suppressing ER stress and FOXO1 in human granulosa cells.

Maternal Supplementation with Herbal Antioxidants during Pregnancy in Swine

The effects of a combined supplementation with herbal antioxidants during pregnancy on reproductive traits and piglet performance (number of live, dead, and mummified newborns and litter weight at birth and individual body weight at both birth and weaning) were assessed in a total of 1027 sows (504 treated and 523 control females) kept under commercial breeding conditions. The supplementation increased the number of live-born piglets (13.64 ± 0.11 vs. 12.96 ± 0.13 in the controls; p = 0.001) and the total litter weight, decreasing the incidence of low-weight piglets without affecting the number of stillbirths and mummified newborns. Such an effect was modulated by the number of parity and the supplementation, with supplementation increasing significantly the number of living newborns in the first, second, sixth, and seventh parities (0.87, 1.10, 1.49, and 2.51 additional piglets, respectively; p < 0.05). The evaluation of plasma vitamin concentration and biomarkers of oxidative stress (total antioxidant capacity, TAC, and malondialdehyde concentration, MDA) performed in a subset of farrowing sows and their lighter and heavier piglets showed that plasma levels of both vitamins were significantly higher in the piglets than in their mothers (p < 0.05 for vitamin C and p < 0.005 for vitamin E), with antioxidant supplementation increasing significantly such concentrations. Concomitantly, there were no differences in maternal TAC but significantly higher values in piglets from supplemented sows (p < 0.05). On the other hand, supplementation decreased plasma MDA levels both in the sows and their piglets (p < 0.05). Finally, the piglets from supplemented mothers showed a trend for a higher weaning weight (p = 0.066) and, specifically, piglets with birth weights above 1 kg showed a 7.4% higher weaning weight (p = 0.024). Hence, the results of the present study, with high robustness and translational value by offering data from more than 1000 pregnancies under standard breeding conditions, supports that maternal supplementation with herbal antioxidants during pregnancy significantly improves reproductive efficiency, litter traits, and piglet performance.

Celastrol Prevents Oxidative Stress Effects on FSHR, PAPP, and CYP19A1 Gene Expression in Cultured Human Granulosa-Lutein Cells

Regulation of oxidative stress (OS) is important to prevent damage to female reproductive physiology. While normal OS levels may have a regulatory role, high OS levels may negatively affect vital processes such as folliculogenesis or embryogenesis. The aim of this work was to study OS induced by glucose, a reactive oxygen species generator, or peroxynitrite, a reactive nitrogen species generator, in cultured human granulosa-lutein (hGL) cells from oocyte donors, analyzing expression of genes involved in oocyte maturation (FSHR, PAPP, and CYP19A1) and OS damage response (ALDH3A2). We also evaluated the effect of celastrol as an antioxidant. Our results showed that although both glucose and peroxynitrite produce OS increments in hGL cells, only peroxynitrite treatment increases ALDH3A2 and PAPP gene expression levels and decreases FSHR gene expression levels. Celastrol pre-treatment prevents this effect of peroxynitrite. Interestingly, when celastrol alone was added, we observed a reduction of the expression of all genes studied, which was independent of both OS inductors. In conclusion, regulation of OS imbalance by antioxidant substances such as celastrol may prevent negative effects of OS in female fertility. In addition to the antioxidant activity, celastrol may well have an independent role on regulation of gene expression in hGL cells.

Mitochondria: emerging therapeutic strategies for oocyte rescue

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

Reprogramming of glucose metabolism of cumulus cells and oocytes and its therapeutic significance

The aim of this review is to summarize our current understanding of the molecular mechanism for the glucose metabolism, especially pyruvate dehydrogenase (PDH), during oocyte maturation, as well as future perspectives of therapeutic strategies for aging focusing on metabolic regulation between aerobic glycolysis and the tricarboxylic acid (TCA) cycle/oxidative phosphorylation (OXPHOS). Each keyword alone or in combination was used to search from PubMed. Glucose metabolism is a dynamic process involving "On" and "Off" switches by the pyruvate dehydrogenase kinase (PDK)-PDH axis, which is crucial for energy metabolism and mitochondrial efficiency in cumulus cell differentiation and oocyte maturation. Activation of PDK suppresses the conversion of pyruvate to acetyl-coenzyme A (acetyl-CoA) through the inactivation of PDH, which allows the cumulus cells to supply sufficient amounts of pyruvate, lactate, and nicotinamide adenine dinucleotide phosphate (NADPH) to the oocytes. On the other hand, inactivation of PDK in oocytes can produce adenosine triphosphate (ATP) through a metabolic shift from aerobic glycolysis to the TCA cycle/OXPHOS. The metabolic balance between aerobic glycolysis and TCA cycle/OXPHOS presents us with a number of enzymes, ligands, receptors, and antioxidants that are potential therapeutic targets, some of which have already been successfully pursued to improve fertility outcomes. However, there are also many reports that question their efficacy. In conclusion, understanding the molecular mechanisms involved in the PDK-PDH axis is a crucial step to advance in novel therapeutic strategies to improve oocyte quality.

Cellular and molecular alterations of buffalo oocytes cultured under two different levels of oxygen tension during in vitro maturation

This study was conducted to monitor the cellular and molecular changes of buffalo cumulus-oocytes complexes (COCs) cultured under high or low oxygen levels. Morphologically good quality COCs (n = 1627) were screened using brilliant cresyl blue (BCB) staining and placed into three groups (BCB+, BCB- and control). All groups of COCs were cultured under low (5%) or high (20%) oxygen tensions. Intracellular and molecular changes including oocyte ultrastructure, lipid contents, mitochondrial activity and transcript abundance of genes regulating different pathways were analyzed in the matured oocyte groups. The results revealed that oxygen tension did not affect cumulus expansion rates, however the BCB+ group had a higher (P ≤ 0.05) expansion rate compared with the BCB- group. BCB- oocytes recorded the lowest meiotic progression rate (P ≤ 0.05) under high oxygen levels that was linked with an increased level of reactive oxygen species (ROS) compared with the BCB+ oocytes. Ultrastructure examination indicated that BCB+ oocytes had a higher rate of cortical granules migration compared with BCB- under low oxygen tension. In parallel, our results indicated the upregulation of NFE2L2 in groups of oocytes cultured under high oxygen tension that was coupled with reduced mitochondrial activity. In contrast, the expression levels of MAPK14 and CPT2 genes were increased (P ≤ 0.05) in groups of oocytes cultured under low compared with high oxygen tension that was subsequently associated with increased mitochondrial activity. In conclusion, data from the present investigation indicated that low oxygen tension is a favourable condition for maintaining the mitochondrial activity required for nuclear maturation of buffalo oocytes. However, low-quality oocytes (BCB-) responded negatively to high oxygen tension by reducing the expression of gene-regulating metabolic activity (CPT2). This action was an attempt by BCB- oocytes to reduce the increased levels of endogenously produced ROS that was coupled with decreased expression of the gene controlling meiotic progression (MAPK14) in addition to nuclear maturation rate.

Detection of Polymorphisms in the MTNR1A Gene and Their Association with Reproductive Performance in Awassi Ewes

Simple Summary

The purpose of the study was to explore the influence of MTNR1A gene polymorphisms on the reproductive performance in Awassi sheep, which is an important and widespread breed in developing Mediterranean countries. A total of 31 SNPs was detected, 5 of which caused amino acid changes. Two of the found SNPs were found to be totally linked and associated with an advanced reproductive recovery in ewes carrying the C allele. The obtained results could be useful for improving reproductive management in developing Mediterranean areas.

Abstract

The economy in Mediterranean areas is tightly linked to the evolution of the sheep-farming system; therefore, improvement in ewe’s reproductive performance is essential in the developing countries of this area. MTNR1A is the gene coding for Melatonin receptor 1 (MT1), and it is considered to be involved in the reproductive activity in sheep. The aims of this study were: (1) identifying the polymorphisms from the entire MTNR1A coding region and promoter in Lebanese Awassi sheep flocks, and (2) investigating the association between the found polymorphisms and the reproductive performance, assessed as lambing rate, litter size, and days to lambing (DTL). The study was conducted in two districts of Lebanon, where 165 lactating ewes, aged 5.2 ± 1.5 years, with body condition score (BCS) 3.3 ± 0.4, were chosen and exposed to adult and fertile rams. From 150 to 220 days after ram introduction, lambing dates and litter sizes were registered. This study provided the entire coding region of the MTNR1A receptor gene in the Awassi sheep breed. Thirty-one single nucleotide polymorphisms (SNPs) were detected, five of which were missense mutations. The H2, H3, and H4 haplotypes were associated with lower DTL (p < 0.05), as well as the SNPs rs430181568 and rs40738822721, named from now on SNP20 and SNP21, respectively. These SNPs were totally linked and can be considered as a single marker. The ewes carrying the C allele at both these polymorphic sites advanced their reproductive recovery (p < 0.05). These results are essential for improving reproductive management and obtaining advanced lambing in Awassi ewes.

Melatonin in Mitochondria: Mitigating Clear and Present Dangers

In cancer cells, glucose is primarily metabolized to pyruvate and then to lactate in the cytosol. By allowing the conversion of pyruvate to acetyl-CoA in mitochondria, melatonin reprograms glucose metabolism in cancer cells to a normal cell phenotype. Acetyl-CoA in the mitochondria also serves as a necessary co-factor for the rate-limiting enzyme in melatonin synthesis, thus ensuring melatonin production in mitochondria of normal cells.

The presence of microorganisms in follicular fluid and its effect on the outcome of in vitro fertilization-embryo transfer (IVF-ET) treatment cycles

Objectives

To determine if the presence of microorganisms in follicular fluid of women undergoing in vitro fertilization-embryo transfer (IVF-ET) adversely affects the outcome of the treatment cycles.

Methods

Follicular fluid was collected from 86 women enrolled for IVF-ET at the National Hospital, Abuja from June 1, 2018 to December 1, 2018. Microscopy imaging and cultures were performed to identify bacteria and fungi in the follicular fluid and the vagina. Women with follicular fluid microorganisms were the test group while the controls were those without follicular fluid microorganisms. Fertilization and pregnancy rates were subsequently determined and their association with the presence of follicular fluid microorganisms was assessed using univariable and multivariable logistic regression modelling.

Results

The mean age and mean Body Mass Index (BMI) of the participants were 35(± 3.5) years and 28(± 4.9) kg/m² respectively. Bacteria and fungi were isolated in 17% of the follicular fluid samples collected (n = 15/86). Most common isolates were Streptococcus spp. (n = 4/15), Staphylococcus aureus (n = 7/15), Enterococcus spp. (n = 4/15), Lactobacillus species (n = 2/15) and Candida albicans (n = 2/15). There was no statistically significant difference in the fertilization rates (adjusted odds ratio [AdjOR] 0.55, 95% confidence interval [CI] 0.04–7.34; P = 0.10) and pregnancy rates (AdjOR 4.02, 95% CI 0.56–28.92; P = 0.19) between the group of women with positive follicular fluid bacterial /fungal colonization as compared against those with negative follicular fluid colonization.

Conclusion

Isolation of microorganisms from follicular fluid did not adversely affect fertilization and pregnancy rates following IVF-ET treatment cycles at the fertility centre of National Hospital, Abuja.

First evidence of the protective role of melatonin in counteracting cadmium toxicity in the rat ovary via the mTOR pathway

Herein, the first evidence of the ability of melatonin (MLT) to counteract cadmium (Cd) toxic effects on the rat ovary is reported. Cd treatment, enhancing oxidative stress, provoked clear morphological, histological and biomolecular alterations, i.e. in the estrous cycle duration, in the ovarian and serum E2 concentration other than in the steroidogenic and folliculogenic genes expression. Results demonstrated that the use of MLT, in combination with Cd, avoided the changes, strongly suggesting that it is an efficient antioxidant for preventing oxidative stress in the rat ovary. Moreover, to explore the underlying mechanism involved, at molecular level, in the effects of Cd-MLT interaction, the study focused on the mTOR and ERK1/2 pathways. Interestingly, data showed that Cd influenced the phosphorylation status of mTOR, of its downstream effectors and of ERK1/2, inducing autophagy and apoptosis, while cotreatment with MLT nullified these changes. This work highlights the beneficial role exerted by MLT in preventing Cd-induced toxicity in the rat ovary, encouraging further studies to confirm its action on human ovarian health with the aim to use this indolamine to ameliorate oocyte quality in women with fertility disorders.

Molecular Mechanisms of Melatonin-Mediated Cell Protection and Signaling in Health and Disease

Melatonin, an endogenously synthesized indolamine, is a powerful antioxidant exerting beneficial action in many pathological conditions. Melatonin protects from oxidative stress in ischemic/reperfusion injury, neurodegenerative diseases, and aging, decreases inflammation, modulates the immune system, inhibits proliferation, counteracts the Warburg effect, and promotes apoptosis in various cancer models. Melatonin stimulates antioxidant enzymes in the cells, protects mitochondrial membrane phospholipids, especially cardiolipin, from oxidation thus preserving integrity of the membranes, affects mitochondrial membrane potential, stimulates activity of respiratory chain enzymes, and decreases the opening of mitochondrial permeability transition pore and cytochrome c release. This review will focus on the molecular mechanisms of melatonin effects in the cells during normal and pathological conditions and possible melatonin clinical applications.

Roles of melatonin in the teleost ovary: A review of the current status

Melatonin, the neurohormone mainly synthesized in and secreted from the pineal gland of vertebrates following a circadian rhythm, is an important factor regulating various physiological processes, including reproduction. Recent data indicate that melatonin is also synthesized in the ovary and that it acts directly at the level of the ovary to modulate ovarian physiology. In some teleosts, melatonin is reported to affect ovarian steroidogenesis. The direct action of melatonin on the ovary could be a possible factor promoting oocyte maturation in teleosts. A role for melatonin in follicle rupture during ovulation in the teleost medaka has recently emerged. In addition, melatonin is suggested to affect oocyte maturation by its antioxidant activity. However, the molecular mechanisms underlying these direct effects of melatonin are largely unknown.

Melatonin and CIDR improved the follicular and luteal haemodynamics, uterine and ovarian arteries vascular perfusion, ovarian hormones and nitric oxide in cyclic cows

This study hypothesizes that melatonin with exogenous progesterone (CIDR) can improve follicular, luteal, ovarian and uterine haemodynamic of heat-stressed cows. Holstein cows (N = 12) studied for two spontaneous oestrous cycles during winter then divided equally during summer into the CIDR group received CIDR for 7 days and the melatonin group (Mel) received three injections of melatonin (75 mg/head) at the CIDR insertion, removal and ovulation days. Blood samples were collected to assay oestradiol (E2), progesterone (P4) and nitric oxide (NO). On day 0 (Ovulation), Mel had more small follicles (p < .05), higher ipsilateral and contralateral ovarian arteries (Ov.A.) peak systolic velocity (PSV), higher ipsilateral uterine artery (Ut.A.) PSV (p = .031) and blood flow volume (BFV), also Mel elevated contralateral Ut.A. PSV and BFV (p < .0001) but lowered contra Ut.A. pulsatility index (PI, p < .0001), E2 (p < .01) and NO (p < .0001). Mel increased the corpus luteum diameter (CL, p < .001), coloured area (p < .007) and P4 (p < .0001) on day 5 and reduced them (p < .05; p < .01) on Day 14. On day 10, Mel obtained CL diameter (p < .03) and coloured area (p < .002) of spontaneous that was higher than CIDR and decreased P4 (p < .003). Mel increased CL diameter, area and coloured area and decreased them thereafter. Mel increased the ipsilateral ovarian and uterine arteries PSV and BFV before ovulation and until day 8. Mel increased P4 and decreased NO until days 6 and 14. In conclusion, the improvement in follicular, luteal, ovarian and uterine haemodynamic and the decrease of NO production proved our hypothesis Melatonin doses higher than 75 mg/head is recommended to improve the heat-stressed cow's fertility.

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.

Lead exposure activates the Nrf2/Keap1 pathway, aggravates oxidative stress, and induces reproductive damage in female mice

Lead, a common metallic contaminant, is widespread in the living environment, and has deleterious effects on the reproductive systems of humans and animals. Although numerous toxic effects of lead have been reported, the effects and underlying mechanisms of the impacts of lead exposure on the female reproductive system, especially oocyte maturation and fertility, remain unknown. In this study, mice were treated by gavage for seven days to evaluate the reproductive damage and role of Nrf2-mediated defense responses during lead exposure. Lead exposure significantly reduced the maturation and fertilization of oocytes in vivo. Additionally, lead exposure triggered oxidative stress with a decreased glutathione level, increased amount of reactive oxygen species, and abnormal mitochondrial distribution. Moreover, lead exposure caused histopathological and ultrastructural changes in oocytes and ovaries, along with decreases in the activities of catalase, glutathione peroxidase, total superoxide dismutase, and glutathione-S transferase, and increases in the levels of malonaldehyde in mouse ovaries. Further experiments demonstrated that lead exposure activated the Nrf2 signaling pathway to protect oocytes against oxidative stress by enhancing the transcription levels of antioxidant enzymes. In conclusion, our study demonstrates that lead activates the Nrf2/Keap1 pathway and impairs oocyte maturation and fertilization by inducing oxidative stress, leading to a decrease in the fertility of female mice.

Maternal pineal melatonin in gestation and lactation physiology, and in fetal development and programming

Pregnancy and lactation are reproductive processes that rely on physiological adaptations that should be timely and adequately triggered to guarantee both maternal and fetal health. Pineal melatonin is a hormone that presents daily and seasonal variations that synchronizes the organism's physiology to the different demands across time through its specific mechanisms and ways of action. The reproductive system is a notable target for melatonin as it actively participates on reproductive physiology and regulates the hypothalamus-pituitary-gonads axis, influencing gonadotropins and sexual hormones synthesis and release. For its antioxidant properties, melatonin is also vital for the oocytes and spermatozoa quality and viability, and for blastocyst development. Maternal pineal melatonin blood levels increase during pregnancy and triggers the maternal physiological alterations in energy metabolism both during pregnancy and lactation to cope with the energy demands of both periods and to promote adequate mammary gland development. Moreover, maternal melatonin freely crosses the placenta and is the only source of this hormone to the fetus. It importantly times the conceptus physiology and influences its development and programing of several functions that depend on neural and brain development, ultimately priming adult behavior and energy and glucose metabolism. The present review aims to explain the above listed melatonin functions, including the potential alterations observed in the progeny gestated under maternal chronodisruption and/or hypomelatoninemia.

Central and peripheral actions of melatonin on reproduction in seasonal and continuous breeding mammals

Under field conditions, especially for mammals that inhabit high latitudes, the regulation of seasonal breeding activity to ensure delivery of the young at the time most conducive to their survival is essential. This is most frequently accomplished by the annual reproductive cycle being linked to seasonal photoperiod changes which determine the nocturnal duration of the pineal melatonin signal. Mating can occur during any season that ensures spring/early summer delivery of the offspring. Thus, the season of mating is determined by the duration of pregnancy. The precise hormonal control of the annual cycle of reproduction by melatonin is accomplished at the level of the hypothalamo-pituitary axis which, in turn, determines the physiological state of the gonad and adnexa due to the regulation of pituitary gonadotrophin release. Many species are continuous rather than seasonal breeders. In these species, melatonin has a minor hormonal influence on the central regulation of reproduction but, nevertheless, its antioxidant functions at the level of the gonads support optimal reproductive physiology. Possibly like all cells, those in the ovary, e.g., granulosa cells and oocytes (less is known about melatonin synthesis by the testes or spermatogenic cells), synthesize melatonin which is used locally to combat free radicals and reactive nitrogen species which would otherwise cause oxidative/nitrosative stress to these critically important cells. Oxidative damage to the oocyte, zygote, blastocyst, etc., results in an abnormal fetus which is either sloughed or gives rise to an unhealthy offspring. The importance of the protection of the gametes (both oocytes and sperm) from oxidative molecular mutilation cannot be overstated. Fortunately, as a highly effective free radical scavenger and indirect antioxidant (by upregulating antioxidant enzyme), locally-produced melatonin is in the optimal location to protect the reproductive system from such damage.

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.

Clinical Application of Antioxidants to Improve Human Oocyte Mitochondrial Function: A Review

Mitochondria produce adenosine triphosphate (ATP) while also generating high amounts of reactive oxygen species (ROS) derived from oxygen metabolism. ROS are small but highly reactive molecules that can be detrimental if unregulated. While normally functioning mitochondria produce molecules that counteract ROS production, an imbalance between the amount of ROS produced in the mitochondria and the capacity of the cell to counteract them leads to oxidative stress and ultimately to mitochondrial dysfunction. This dysfunction impairs cellular functions through reduced ATP output and/or increased oxidative stress. Mitochondrial dysfunction may also lead to poor oocyte quality and embryo development, ultimately affecting pregnancy outcomes. Improving mitochondrial function through antioxidant supplementation may enhance reproductive performance. Recent studies suggest that antioxidants may treat infertility by restoring mitochondrial function and promoting mitochondrial biogenesis. However, further randomized, controlled trials are needed to determine their clinical efficacy. In this review, we discuss the use of resveratrol, coenzyme-Q10, melatonin, folic acid, and several vitamins as antioxidant treatments to improve human oocyte and embryo quality, focusing on the mitochondria as their main hypothetical target. However, this mechanism of action has not yet been demonstrated in the human oocyte, which highlights the need for further studies in this field.

Melatonin levels and microRNA (miRNA) relative expression profile in the follicular ambient microenvironment in patients undergoing in vitro fertilization process

PURPOSE

Intrafollicular fluid (IFF) melatonin plays a decisive role in maintaining granulosa cells' DNA integrity and protects them against apoptosis. It reduces oxidative stress and improves the oocyte quality with a higher fertilization rate.

METHOD

This prospective study investigated the antioxidant property of IFF melatonin and its impact on IVF outcome parameters. We also explored the relative expression of five microRNAs (miR-663b, miR-320a, miR-766-3p, miR-132-3p, miR-16-5p) and levels of cell-free DNA (cfDNA) by real-time PCR in unexplained infertile patients. We collected 425 follicular fluid (FF) samples containing mature oocytes from 295 patients undergoing IVF.

RESULTS

Patients were subgrouped based on IFF melatonin concentration (group A ≤ 30 pg/mL, group B > 70 to ≤ 110 pg/mL, group C > 111 to ≤ 385 pg/mL). Our results showed that patients with ≤ 30 pg/mL IFF melatonin levels have significantly higher oxidative stress markers, cfDNA levels, and lower relative expression of miR-663b, miR-320a, miR-766-3p, miR-132-3p, and miR-16-5p compared to other subgroups (p < 0.001). Similarly, they have a low fertilization rate and a reduced number of high-quality day 3 embryos.

CONCLUSION

Findings suggest that the therapeutic use of melatonin produces a considerable rise in the number of mature oocytes retrieved, fertilization rate, and good-quality embryo selection. Furthermore, miRNA signature enhances the quality of embryo selection, thus, may allow us to classify them as non-invasive biomarkers to identify good-quality embryos.

Melatonin inhibits the apoptosis of rooster Leydig cells by suppressing oxidative stress via AKT-Nrf2 pathway activation

Oxidative stress has been described as a key driver of Leydig cell apoptosis. Melatonin has antioxidative and antiapoptotic effects, but the potential effects and mechanism of melatonin on oxidative stress and apoptosis in rooster Leydig cells remain unclear. Our results showed that melatonin biosynthetic enzymes and melatonin receptors were expressed in rooster Leydig cells and their expression were locally inhibited as rooster sexual maturation. We found that melatonin inhibited H₂O₂-induced apoptosis of rooster Leydig cell by activating the melatonin receptors Mel-1a and Mel-1b. Additionally, melatonin protects mitochondria from damage by reducing the level of oxidative stress in Leydig cells. Melatonin relieved H₂O₂-induced oxidative stress by significantly reducing intracellular ROS, MDA and 8-OHdG levels and increasing SOD and GSH-Px activities. Simultaneously, melatonin significantly reduced H₂O₂-induced depolarization of ΔΨm and decreased the release of Cytochrome C and Ca²⁺. We also observed that melatonin activated the Nrf2 pathway, while Nrf2 silencing abrogated the anti-oxidative and anti-apoptotic effects of melatonin in rooster Leydig cells. Furthermore, melatonin promoted the phosphorylation of AKT, while AKT inhibitor suppressed the Nrf2 pathway activated by melatonin and alleviated the inhibitory effects of melatonin on apoptosis and oxidative stress. In conclusion, melatonin could inhibit apoptosis in rooster Leydig cells by suppressing oxidative stress via activation of the AKT-Nrf2 pathway.

Is Melatonin the Cornucopia of the 21st Century?

Melatonin, an indoleamine hormone produced and secreted at night by pinealocytes and extra-pineal cells, plays an important role in timing circadian rhythms (24-h internal clock) and regulating the sleep/wake cycle in humans. However, in recent years melatonin has gained much attention mainly because of its demonstrated powerful lipophilic antioxidant and free radical scavenging action. Melatonin has been proven to be twice as active as vitamin E, believed to be the most effective lipophilic antioxidant. Melatonin-induced signal transduction through melatonin receptors promotes the expression of antioxidant enzymes as well as inflammation-related genes. Melatonin also exerts an immunomodulatory action through the stimulation of high-affinity receptors expressed in immunocompetent cells. Here, we reviewed the efficacy, safety and side effects of melatonin supplementation in treating oxidative stress- and/or inflammation-related disorders, such as obesity, cardiovascular diseases, immune disorders, infectious diseases, cancer, neurodegenerative diseases, as well as osteoporosis and infertility.

Mitochondrial function, blastocyst development and live foals born after ICSI of immature vitrified/warmed equine oocytes matured with or without melatonin

Oocyte vitrification is considered experimental in the horse with only three live foals reported. The oxidative conditions induced by vitrification could in part explain the poor results and melatonin, a powerful antioxidant, could stimulate ROS metabolization and restore mitochondrial function in these oocytes. Our objective was to determine the oxidative status of vitrified equine oocytes and to analyze the effect of melatonin on mitochondrial-specific ROS (mROS), oocyte maturation, ICSI embryo development and viability. Immature, abattoir-derived oocytes were held for 15 h and vitrified in a final concentration of 20% EG, 20% DMSO and 0.65 M trehalose. In Experiment 1, overall ROS was determined by DCHF-DA; vitrification increased ROS production compared to non-vitrified controls (1.29 ± 0.22 vs 0.74 ± 0.25 a. u.; P = 0.0156). In Experiment 2, mROS was analyzed by MitoSOX™ in vitrified/warmed oocytes matured with (+) or without (-) supplementation of 10^-9 M melatonin; mROS decreased in vitrified and non-vitrified oocytes matured in presence of melatonin (P < 0.05). In Experiment 3, we assessed the effect of melatonin supplementation on oocyte maturation, embryo development after ICSI, and viability by pregnancy establishment. Melatonin did not improve oocyte maturation, cleavage or blastocyst rate of non-vitrified oocytes. However, vitrified melatonin (+) oocytes reached similar cleavage (61, 75 and 77%, respectively) and blastocyst rate (15, 29 and 26%, respectively) than non-vitrified, melatonin (+) and (-) oocytes. Vitrified, melatonin (-) oocytes had lower cleavage (46%) and blastocyst rate (9%) compared to non-vitrified groups (P < 0.05), but no significant differences were observed when compared to vitrified melatonin (+). Although the lack of available recipients precluded the transfer of every blastocyst produced in our study, transferred embryos from non-vitrified oocytes resulted in 50 and 83% pregnancy rates while embryos from vitrified oocytes resulted in 17 and 33% pregnancy rates, from melatonin (+) and (-) treatments respectively. Two healthy foals, one colt from melatonin (+) and one filly from melatonin (-) treatment, were born from vitrified/warmed oocytes. Gestation lengths (considering day 0 = day of ICSI) were 338 days for the colt and 329 days for the filly, respectively. Our work showed for the first time that in the horse, as in other species, intracellular reactive oxygen species are increased by the process of vitrification. Melatonin was useful in reducing mitochondrial-related ROS and improving ICSI embryo development, although the lower pregnancy rate in presence of melatonin should be further analyzed in future studies. To our knowledge this is the first report of melatonin supplementation to an in vitro embryo culture system and its use to improve embryo developmental competence of vitrified oocytes following ICSI.

Melatonin Reverses 10-Hydroxycamptothecin-Induced Apoptosis and Autophagy in Mouse Oocyte

10-Hydroxycamptothecin (HCPT) is a widely used anticancer drug that induces cytotoxicity by triggering the cell apoptotic pathway. Studies have shown that HCPT has harmful effects on normal cells, but whether HCPT affects the development of mouse oocytes in vitro has not been reported. First, this study investigated the development of oocytes exposed to 60 μM HCPT in vitro. In the HCPT-treated group, the first polar body extrusion (PBE) rate of oocytes decreased, spindle morphology was abnormal, DNA double-strand break, oxidative stress level increased, and mitochondrial distribution was abnormal. The apoptosis and autophagy levels of oocytes in the HCPT-treated group were detected by qRT-PCR and western blot. Compared with the control group, the expressions of key regulators of oocyte apoptosis (bax, caspase-3) and autophagy (lc3, beclin, ATG12) pathway were increased in the HCPT-treated group. HCPT treatment induced apoptosis and autophagy in oocytes. Melatonin (MT) can protect cell structure, prevent DNA damage, and reduce the content of peroxides. So we wondered whether MT could ameliorate the harmful effects of mouse oocytes induced by HCPT. Interestingly, the addition of 1 mM MT can protect oocytes from HCPT toxicity to some extent. Compared with the HCPT group, the addition of 1 mM MT increased the PBE ratio of oocytes, decreased ROS levels, and decreased spindle abnormalities and DNA breakage ratio. In summary, these results revealed that HCPT exhibited adverse effects on mouse oocyte maturation and quality, and MT administration alleviated the negative influence of HCPT.

Effect of mitophagy in oocytes and granulosa cells on oocyte quality†

Mitophagy is the process by which cells selectively remove supernumerary or damaged mitochondria through autophagy, and is crucial for mitochondrial homeostasis and cell survival. Mitochondria play vital roles in determining the developmental competence of oocytes. During the early stages of oogenesis, aberrant mitochondria can be removed by mitophagy. After oocyte formation, mitophagy is not actively initiated to clear damaged mitochondria despite the presence of mitophagy regulators in oocytes, which leads to the transmission of dysfunctional mitochondria from the oocyte to the embryo. However, granulosa cells around oocytes can improve mitochondrial function through mitophagy, thereby improving oocyte developmental capacity. Furthermore, this review discusses recent work on the substances and environmental conditions that affect mitophagy in oocytes and granulosa cells, thus providing new directions for improving oocyte quality during assisted reproductive technology treatment.

Elevation of MPF and MAPK gene expression, GSH content and mitochondrial distribution quality induced by melatonin promotes porcine oocyte maturation and development in vitro

The MPF and MAPK genes play crucial roles during oocyte maturation processes. However, the pattern of MPF and MAPK gene expression induced by melatonin (MT) and its correlation to oocyte maturation quality during the process of porcine oocyte maturation in vitro remains unexplored. To unravel it, in this study, we cultured the porcine oocytes in maturation medium supplemented with 0, 10⁻⁶, 10⁻⁹, and 10⁻¹² mol/L melatonin. Later, we analyzed the MPF and MAPK gene expression levels by RT-PCR and determined the maturation index (survival and maturation rate of oocytes). The GSH content in the single oocyte, and cytoplasmic mitochondrial maturation distribution after porcine oocyte maturation in vitro was also evaluated. We also assessed the effects of these changes on parthenogenetic embryonic developmental potential. The oocytes cultured with 10⁻⁹mol/L melatonin concentration showed higher oocyte maturation rate, and MPF and MAPK genes expression levels along with better mitochondrial distribution than the 0, 10⁻⁶, and 10⁻¹² mol/L melatonin concentrations (p < 0.05). No significant difference was observed in the survival rates when the oocytes were cultured with different melatonin concentrations. The expression of the MPF gene in the oocytes cultured with 10⁻⁶ mol/L melatonin was higher than with 10⁻¹² and 0 mol/L melatonin, and the expression of the MAPK gene in 10⁻⁶ and 10⁻¹² group was higher than the control (p < 0.05). As far as the embryonic developmental potential is concerned, the cleavage and blastocyst rate of oocytes cultured with 10⁻⁶ and 10⁻⁹ mol/L melatonin was significantly higher than the 10⁻¹² mol/L melatonin and control. In conclusion, 10⁻⁹–10⁻⁶ mol/L melatonin significantly induced the MPF and MAPK gene expression; besides, it could also be correlated with GSH content of single oocyte, mitochondrial maturation distribution, and the first polar body expulsion. These changes were also found to be associated with parthenogenetic embryo developmental potential in vitro.

Melatonin slightly alleviates the effect of heat shock on bovine oocytes and resulting blastocysts

Heat stress is associated with increased production of reactive oxygen species (ROS) and disruption of bovine oocyte function. Here, we examined whether the antioxidant melatonin can alleviate the deleterious effects of heat stress on oocyte developmental competence. Cumulus-oocyte complexes were matured for 22 h at 38.5 °C (control) or for 22 h at 41.5 °C (heat shock) with or without 1.0 × 10^-7 M melatonin. At the end of maturation, a subgroup of oocytes was examined for nuclear and cytoplasmic maturation, ROS level and mitochondrial membrane potential. A second subgroup of oocytes underwent fertilization (18 h), and putative zygotes were cultured in an incubator equipped with a time-lapse system for ∼190 h. Cleavage rate and the proportion of blastocysts, as well as embryo kinetics were recorded. Expanded blastocysts were collected and their transcript abundance was evaluated. Heat shock increased ROS and reduced the proportion of oocytes that resumed meiosis and reached the metaphase-II stage. Exposing oocytes to heat shock with melatonin alleviated these effects to some extent, expressed by a marginal reduction in ROS level and increased proportion of metaphase-II stage oocytes. Neither the distribution of oocyte cortical granules nor polarization of the mitochondrial membrane differed between control and heat-shocked oocytes cultured with or without melatonin. Heat shock reduced the proportion of embryos that cleaved and developed to blastocysts, characterized by alterations in kinetics of the developed embryos expressed by a delay in the first cleavage, second cleavage and blastocyst formation for heat-shock vs. control groups. Melatonin did not restore the competence or kinetics of embryos developed from heat-shocked oocytes. However, expanded blastocysts developed from heat-shocked oocytes treated with melatonin expressed a higher transcript abundance of genes associated with mitochondrial function, relative to the control and heat-shock group. In summary, melatonin improved the oxidative status of heat-shocked oocytes to some extent and had a beneficial effect on maternal mitochondrial transcripts in the developed blastocysts.