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

C-Phycocyanin improves the quality of goat oocytes after in vitro maturation and vitrification

In vitro maturation (IVM) and cryopreservation of goat oocytes are important for establishing a valuable genetic bank for domesticated female animals and improving livestock reproductive efficiency. C-Phycocyanin (PC) is a Spirulina extract with antioxidant, antiinflammatory, and radical scavenging properties. However, whether PC has positive effect on goat oocytes IVM or developmental competence after vitrification is still unknown. In this study, we found that first polar body extrusion (n = 293), cumulus expansion index (n = 269), and parthenogenetic blastocyst formation (n = 281) were facilitated by adding 30 μg/mL PC to the oocyte maturation medium when compared with the control groups and that supplemented with 3, 10, 100 or 300 μg/mL PC (P < 0.05). Although PC supplementation did not affect spindle formation or chromosome alignment (n = 115), it facilitated or improved cortical granules migration (n = 46, P < 0.05), mitochondria distribution (n = 39, P < 0.05), and mitochondrial membrane potential (n = 46, P < 10-4). Meanwhile, supplementation with 30 μg/mL PC in the maturation medium could significantly inhibit the reactive oxygen species accumulation (n = 65, P < 10-4), and cell apoptosis (n = 42, P < 0.05). In addition, PC increased the oocyte mRNA levels of GPX4 (P < 0.01), and decreased the mRNA and protein levels of BAX (P < 0.01). Next, we investigated the effect of PC supplementation in the vitrification solution on oocyte cryopreservation. When compared with the those equilibrate in the vitrification solution without PC, recovered oocytes in the 30 μg/mL PC group showed higher ratios of normal morphology (n = 85, P < 0.05), survival (n = 85, P < 0.05), first polar body extrusion (n = 62, P < 0.05), and parthenogenetic blastocyst formation (n = 107, P < 0.05). Meanwhile, PC supplementation of the vitrification solution increased oocyte mitochondrial membrane potential (n = 53, P < 0.05), decreased the reactive oxygen species accumulation (n = 73, P < 0.05), promoted mitochondria distribution (n = 58, P < 0.05), and inhibited apoptosis (n = 46, P < 10-3). Collectively, our findings suggest that PC improves goat oocyte IVM and vitrification by reducing oxidative stress and early apoptosis, which providing a novel strategy for livestock gamete preservation and utilization.

Treatment of spontaneously hypertensive rats during pregnancy and lactation with the antioxidant tempol lowers blood pressure and reduces oxidative stress

Genetic and environmental factors interact in a complex manner in the pathogenesis of essential hypertension in humans. Oxidative stress is considered one of the more important environmental factors. We used the spontaneously hypertensive rat (SHR) model to test whether continuous feeding with the antioxidant tempol reduces maternal oxidative stress during pregnancy and potentially contributes to the prevention of cardiovascular disease onset. Pregnant female rats were divided into control and tempol-treated groups. Tempol was continuously administered in drinking water. The administration period lasted approximately 40 days, from the confirmation of a vaginal plug until birth of the pups and their subsequent weaning. The blood pressure (BP) of each adult female was measured three times during pregnancy and post parturition. Milk was collected three times from nursing mother rats in the immediate postpartum period. Markers of oxidative stress were measured: 8-hydroxyl-2'-deoxyguanosine (8-OHdG) levels in milk during the experimental period and 8-OHdG and corticosterone levels in urine of adult and neonatal rats. The urinary level of 8-OHdG in the tempol-treated group was significantly lower than that in the control group. Corticosterone levels were significantly lower in urine of neonatal rats from the tempol-treated group compared with the levels of the control group. The levels of total antioxidant in milk were significantly greater in the tempol-treated group than in the control group. This study demonstrated that continuous administration of tempol to pregnant SHRs reduced maternal oxidative stress and contributed to reduced oxidative stress in neonatal rats.

Mechanisms of female reproductive toxicity in pigs induced by exposure to environmental pollutants

Environmental pollutants, including endocrine disruptors, heavy metals, nanomaterials, and pesticides, have been detected in various ecosystems and are of growing global concern. The potential for toxicity to non-target organisms has consistently been raised and is being studied using various animal models. In this review, we focus on pesticides frequently detected in the environment and investigate their potential exposure to livestock. Owing to the reproductive similarities between humans and pigs, various in vitro porcine models, such as porcine oocytes, trophectoderm cells, and luminal epithelial cells, are used to verify reproductive toxicity. These cell lines are being used to study the toxic mechanisms induced by various environmental toxicants, including organophosphate insecticides, pyrethroid insecticides, dinitroaniline herbicides, and diphenyl ether herbicides, which persist in the environment and threaten livestock health. Collectively, these results indicate that these pesticides can induce female reproductive toxicity in pigs and suggest the possibility of adverse effects on other livestock species. These results also indicate possible reproductive toxicity in humans, which requires further investigation.

Evaluation of Oxidative and Nitrosative Stress Markers Related To Inflammation in The Cumulus Cells and Follicular Fluid of Women Undergoing Intracytoplasmic Sperm Injection: A Prospective Study

BACKGROUND

Oxidative/nitrosative stress in the oocyte microenvironment could have an impact on intracytoplasmic sperm injection (ICSI) outcomes. The presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) can stimulate the secretion of pro-inflammatory cytokines, leading to chronic inflammation and potentially affecting embryo as well as oocyte quality. This study aimed to examine the relationship of lipid peroxidation [measured by the malondialdehyde (MDA) assay] with protein carbonyl [measured by the 2,4 dinitrophenylhydrazine (DNPH) assay] levels in cumulus cells (CCs), as well as nitric oxide (NO), peroxynitrite (ONOO-), and C-reactive protein (CRP) levels in follicular fluid (FF). The potential relationship of these levels with ICSI outcome was also evaluated.

MATERIALS AND METHODS

In this prospective study, 63 FF samples and their corresponding CCs were collected for ICSI procedures. Spectrophotometry was used to assess levels of DNPH, MDA, NO, and ONOO-. CRP levels were evaluated using an immunoturbidimetric assay.

RESULTS

The patients under 37 years with normal ovarian reserve had significantly lower levels of MDA, DNPH, NO, ONOO-, and CRP compared to those over 37 years. Additionally, we observed higher levels of MDA, DNPH, NO, ONOO-, and CRP in the group with an oocyte maturity rate of less than 60%. No significant difference was observed between the DNPH levels and factors such as infertility duration, embryo quality, pregnancy, or the number of retrieved oocytes. A higher level of MDA, NO, ONOO-, and CRP was found to be significantly related to the lower number of retrieved oocytes, longer periods of infertility, poor embryo quality, and negative pregnancy outcomes.

CONCLUSION

Oxidative/nitrosative stress, linking to inflammation in the oocyte microenvironment, can be considered as a potentially useful biomarker for assessing the development and competence of oocytes and embryos and predicting ICSI outcomes.

Oxidative Stress in Pregnancy

Recent years have seen an increased interest in the role of oxidative stress (OS) in pregnancy. Pregnancy inherently heightens susceptibility to OS, a condition fueled by a systemic inflammatory response that culminates in an elevated presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the circulatory system. The amplified OS in pregnancy can trigger a series of detrimental outcomes such as underdevelopment, abnormal placental function, and a host of pregnancy complications, including pre-eclampsia, embryonic resorption, recurrent pregnancy loss, fetal developmental anomalies, intrauterine growth restriction, and, in extreme instances, fetal death. The body's response to mitigate the uncontrolled increase in RNS/ROS levels requires trace elements that take part in non-enzymatic and enzymatic defense processes, namely, copper (Cu), zinc (Zn), manganese (Mn), and selenium (Se). Determination of ROS concentrations poses a challenge due to their short half-lives, prompting the use of marker proteins, including malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), and glutathione (GSH). These markers, indicative of oxidative stress intensity, can offer indirect assessments of pregnancy complications. Given the limitations of conducting experimental studies on pregnant women, animal models serve as valuable substitutes for in-depth research. This review of such models delves into the mechanism of OS in pregnancy and underscores the pivotal role of OS markers in their evaluation.

Protective effect of onion peel extract on ageing mouse oocytes

Mammalian oocytes not fertilized immediately after ovulation can undergo ageing and a rapid decline in quality. The addition of antioxidants can be an efficient approach to delaying the oocyte ageing process. Onion peel extract (OPE) contains quercetin and other flavonoids with natural antioxidant activities. In this study, we investigated the effect of OPE on mouse oocyte ageing and its mechanism of action. The oocytes were aged in vitro in M16 medium for 16 h after adding OPE at different concentrations (0, 50, 100, 200, and 500 μg/ml). The addition of 100 μg/ml OPE reduced the oocyte fragmentation rate, decreased the reactive oxygen species (ROS) level, increased the glutathione (GSH) level, and improved the mitochondrial membrane potential compared with the control group. The addition of OPE also increased the expression of SOD1, CAT, and GPX3 genes, and the caspase-3 activity in OPE-treated aged oocytes was significantly lower than that in untreated aged oocytes and similar to that in fresh oocytes. These results indicated that OPE delayed mouse oocyte ageing by reducing oxidative stress and apoptosis and enhancing mitochondrial function.

Control of mitochondrial integrity influences oocyte quality during reproductive aging

Reduced quality in oocytes from women of advanced maternal age (AMA) is associated with dysfunctional mitochondria. The objective of this study was to investigate the mechanisms controlling mitochondrial quality during maternal aging in mouse and human oocytes. We first evaluated the expression of proteins involved in the mitochondrial unfolded protein response (UPRmt) and mitophagy in in vivo matured metaphase II (MII) oocytes collected from young and aged mice. Expression of UPRmt proteins, HSPD1 and LONP1, and mitophagy proteins, total-PRKN and phosphorylated-PRKN, was significantly decreased in aged compared to young oocytes. Treatment of aged oocytes during in vitro maturation with the mitochondrially targeted antioxidant mitoquinone (MQ) specifically restored total-PRKN and phosphorylated-PRKN expression to levels seen in young oocytes. We next investigated whether maturing young oocytes under a high-oxygen environment would mimic the effects observed in oocytes from aged females. Phosphorylated-PRKN expression in oxidatively stressed young oocytes was reduced compared to that in oocytes matured under normal oxygen levels, and the mitochondrial DNA (mtDNA) copy number was increased. Treating oxidatively challenged young oocytes with MQ restored the phosphorylated-PRKN expression and mtDNA copy numbers. Treatment of oxidatively challenged oocytes with MQ also increased the co-localization of mitochondria and lysosomes, suggesting increased mitophagy. These data correlated with the developmental potential of the oocytes, as blastocyst development and hatching of oxidatively stressed oocytes were reduced, while treatment with MQ resulted in a significant increase in blastocyst development and hatching, and in the percentage of inner cell mass. Consistent with our results in mice, MII oocytes from women of AMA exhibited a significant decrease in phosphorylated-PKRN and total-PRKN compared to those of young women. Our findings suggest that the protein machinery to control the health of the mitochondria via UPRmt and mitophagy may be compromised in oocytes from aged females, which may result in inefficient clearance of dysfunctional mitochondria and reduced oocyte quality.

Nonerythroid hemoglobin promotes human cumulus cell viability and the developmental capacity of the human oocyte

OBJECTIVE

To determine the relationship between the levels of cumulus cell (CC) hemoglobin messenger ribonucleic acid (mRNA) and the developmental potential of the associated oocyte and whether hemoglobin protects the CCs from oxidative stress-induced apoptosis.

DESIGN

Laboratory-based study.

SETTING

University laboratory and university-affiliated in vitro fertilization center.

PATIENT(S)

Cumulus cells from the oocytes of patients who underwent in vitro fertilization with intracytoplasmic sperm injection with and without preimplantation genetic testing between 2018 and 2020.

INTERVENTION(S)

Studies on individual and pooled CCs collected at the time of oocyte retrieval or cultured under 20% or 5% O2.

MAIN OUTCOME MEASURE(S)

Quantitative polymerase chain reaction analysis of individual and pooled patient CC samples were used to monitor the hemoglobin mRNA levels. Reverse transcription-polymerase chain reaction arrays were used to assess genes that regulate oxidative stress in CCs associated with aneuploid and euploid blastocysts. Studies were conducted to assess the effect of oxidative stress on the rate of apoptosis, level of reactive oxygen species, and gene expression in CCs in vitro.

RESULT(S)

Compared with CCs associated with arrested and aneuploid blastocysts, the mRNA levels encoding the alpha and beta chains of hemoglobin increased by 2.9- and 2.3-fold in CCs associated with euploid blastocysts, respectively. The mRNA levels encoding the alpha and beta chains of hemoglobin also increased by 3.8- and 4.5-fold in CCs cultured under 5% O2 vs. 20% O2, respectively, and multiple regulators of oxidative stress were overexpressed in cells cultured under 20% O2 compared with those under 5% O2. However, the rate of apoptosis and amount of mitochondrial reactive oxidative species increased by 1.25-fold in CCs cultured under 20% O2 compared with those under 5% O2. Variable amounts of the alpha and beta chains of hemoglobin were also detected within the zona pellucida and oocytes.

CONCLUSION(S)

Higher levels of nonerythroid hemoglobin in CCs are associated with oocytes that result in euploid blastocysts. Hemoglobin may protect CCs from oxidative stress-induced apoptosis, which may enhance cumulus-oocyte interactions. Moreover, CC-derived hemoglobin may be transferred to the oocytes and protect it from the adverse effects of oxidative stress that occurs in vivo and in vitro.

Reactive oxygen species and ovarian diseases: Antioxidant strategies

Reactive oxygen species (ROS) are mainly produced in mitochondria and are involved in various physiological activities of the ovary through signaling and are critical for regulating the ovarian cycle. Notably, the imbalance between ROS generation and the antioxidant defense system contributes to the development of ovarian diseases. These contradictory effects have critical implications for potential antioxidant strategies that aim to scavenge excessive ROS. However, much remains to be learned about how ROS causes various ovarian diseases to the application of antioxidant therapy for ovarian diseases. Here, we review the mechanisms of ROS generation and maintenance of homeostasis in the ovary and its associated physiological effects. Additionally, we have highlighted the pathological mechanisms of ROS in ovarian diseases and potential antioxidant strategies for treatment.

Oxidative Stress as a Potential Underlying Cause of Minimal and Mild Endometriosis-Related Infertility

Oxidative stress (OS) plays an important role in a variety of physiological and pathological processes of the female reproductive system. In recent years the relationship between OS and endometriosis has been of particular interest, and a theory has been suggested that OS may be a cause of endometriosis development. While the link between endometriosis and infertility is well established, minimal or mild stages of endometriosis are not considered to cause infertility. Increasing evidence of OS as a leading agent in the development of endometriosis has brought up a theory of minimal/mild endometriosis itself being one of the manifestations of high OS rather than a separate disease which directly causes infertility. Moreover, further development of the disease is thought to contribute to an increased production of reactive oxygen species (ROS) thus leading to the progression of endometriosis itself as well as to other pathological processes in the female reproductive system. Therefore, in case of minimal or mild endometriosis, the less invasive treatment could be offered in order to stop the ongoing cycle of endometriosis-reinforced excess ROS production and to reduce their harmful effects. In this article the existing connection between OS, endometriosis, and infertility is explored.

Mechanisms of action of non-enzymatic antioxidants to control oxidative stress during in vitro follicle growth, oocyte maturation, and embryo development

In vitro follicle growth and oocyte maturation still has a series of limitations, since not all oocytes matured in vitro have the potential to develop in viable embryos. One of the factors associated with low oocyte quality is the generation of reactive oxygen species (ROS) during in vitro culture. Therefore, this review aims to discuss the role of non-enzymatic antioxidants in the control of oxidative stress during in vitro follicular growth, oocyte maturation and embryonic development. A wide variety of non-enzymatic antioxidants (melatonin, resveratrol, L-ascorbic acid, L-carnitine, N-acetyl-cysteine, cysteamine, quercetin, nobiletin, lycopene, acteoside, mogroside V, phycocyanin and laminarin) have been used to supplement culture media. Some of them, like N-acetyl-cysteine, cysteamine, nobiletin and quercetin act by increasing the levels of glutathione (GSH), while melatonin and resveratrol increase the expression of antioxidant enzymes and minimize oocyte oxidative stress. L-ascorbic acid reduces free radicals and reactive oxygen species. Lycopene positively regulates the expression of many antioxidant genes. Additionally, L-carnitine protects DNA against ROS-induced damage, while acteoside and laminarin reduces the expression of proapoptotic genes. Mogrosides increases mitochondrial function and reduces intracellular ROS levels, phycocyanin reduces lipid peroxidation, and lycopene neutralizes the adverse effects of ROS. Thus, it is very important to know their mechanisms of actions, because the combination of two or more antioxidants with different activities has great potential to improve in vitro culture systems.

[When to Stop Contraception - Reasons and Consequences of Delaying Parenthood]

When to Stop Contraception - Reasons and Consequences of Delaying Parenthood Abstract. Women are delaying motherhood for many reasons. However, knowledge on age-related decline of fertility is limited. Many patients and even physicians are not aware that female fertility starts to diminish significantly after the age of thirty-two years, and success rates of in vitro treatment are overestimated in the general population. Apart from maternal age there is no predictor for future fecundity. Physicians should actively discuss reasons for delaying motherhood and options for improving fecundity. During the reproductive life span, women need reliable counselling on contraception and fertility.

Analysis of cumulative outcomes and influencing factors of patients with discrepancies between age and AMH levels in the early follicular phase prolonged protocol

OBJECTIVE

To explore the cumulative outcomes and influencing factors of patients with discrepancies between age and Anti-Müllerian hormone (AMH) levels in the early follicular phase prolonged protocol.

METHODS

A total of 1282 cycles of in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) assisted pregnancy with the early follicular phase prolonged protocol in the Reproductive Medicine Center of the Third Affiliated Hospital of Zhengzhou University from September 2015 to December 2020 were retrospectively analyzed. They were divided into the young low-AMH group (n=1076) and the older high-AMH group (n=206). The primary outcomes included cumulative clinical pregnancy rate (CCPR) and cumulative live birth rate (CLBR). Secondary outcomes included the number of oocytes retrieved, number of available embryos, clinical pregnancy rate (CPR), live birth rate (LBR), miscarriage rate (MR), pregnancy complications, and neonatal outcomes.

RESULTS

The CPR (68.7% vs. 59.4%) and the LBR (60.7% vs. 43.1%) in the young low-AMH group were higher than those in the older high-AMH group. In contrast, the number of oocytes retrieved (11 vs. 17), number of available embryos (5 vs. 8), and MR (10.6% vs. 18.3%) in the young low-AMH group were lower. There was no significant difference between the two groups in the CCPR, CLBR, pregnancy complications, and neonatal outcomes. Logistic regression analysis showed that infertility duration, basal follicle-stimulating hormone (FSH), and antral follicle count (AFC) correlated with CCPR, while maternal age, type of infertility, basal FSH, AFC, and infertility duration correlated with CLBR. The area under the receiver operating characteristic curves (ROC) curve for the combined model of infertility duration, AFC, and basal FSH to predict cumulative pregnancy was 0.629 (95%CI:0.592-0.666), while the combined model of maternal age, AFC, basal FSH, infertility duration, and type of infertility to predict cumulative live birth was 0.649 (95%CI:0.615-0.682).

CONCLUSION

Although AMH levels are low by contrast, young patients have a favorable outcome after IVF/ICSI. In patients with discrepancies between age and AMH levels in the early follicular phase prolonged protocol, maternal age correlates better with cumulative live birth. The model that combines maternal age and other factors can help predict cumulative live birth, but its value is limited.

The association between serum sex hormone-binding globulin changes during progestin-primed ovarian stimulation and embryo outcomes: a retrospective cohort study

Objective: This study is aimed to examine the associations between embryo outcomes and serum sex hormone-binding globulin (SHBG) changes during progestin-primed ovarian stimulation (PPOS) protocols in IVF/ICSI cycles.Research methods: This study included 2790 eligible consecutive cycles of patients aged 21-53 years undergoing PPOS treatment. Multivariable linear regression analysis was performed to explore the association between SHBG changes and embryo outcomes.Results of the study: Our results showed that the SHBG-increase rate on the HCG day and in the late follicular phase were positively and linearly correlated with available embryos in day3, with adjusted regression coefficients (β) for the SHBG-increase rate on the HCG day, in the late follicular phase were 0.6 (0.4, 0.9), 0.4 (0.2, 0.6), but in the middle follicular phase and in the early follicular phase, this correlation was not significant (p > 0.05).Conclusion: Our results indicate that serum SHBG increment may serve as a biomarker of the developmental potential of the oocytes from patients undergoing the PPOS protocol.

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

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

Transcriptome-wide N6-methyladenine methylation in granulosa cells of women with decreased ovarian reserve

Background

The emerging epitranscriptome plays an essential role in female fertility. As the most prevalent internal mRNA modification, N6-methyladenine (m6A) methylation regulate mRNA fate and translational efficiency. However, whether m6A methylation was involved in the aging-related ovarian reserve decline has not been investigated. Herein, we performed m6A transcriptome-wide profiling in the ovarian granulosa cells of younger women (younger group) and older women (older group).

Results

m6A methylation distribution was highly conserved and enriched in the CDS and 3’UTR region. Besides, an increased number of m6A methylated genes were identified in the older group. Bioinformatics analysis indicated that m6A methylated genes were enriched in the FoxO signaling pathway, adherens junction, and regulation of actin cytoskeleton. A total of 435 genes were differently expressed in the older group, moreover, 58 of them were modified by m6A. Several specific genes, including BUB1B, PHC2, TOP2A, DDR2, KLF13, and RYR2 which were differently expressed and modified by m6A, were validated using qRT-PCR and might be involved in the decreased ovarian functions in the aging ovary.

Conclusions

Hence, our finding revealed the transcriptional significance of m6A modifications and provide potential therapeutic targets to promote fertility reservation for aging women.

DNA damage in preimplantation embryos and gametes: specification, clinical relevance and repair strategies

BACKGROUND

DNA damage is a hazard that affects all cells of the body. DNA-damage repair (DDR) mechanisms are in place to repair damage and restore cellular function, as are other damage-induced processes such as apoptosis, autophagy and senescence. The resilience of germ cells and embryos in response to DNA damage is less well studied compared with other cell types. Given that recent studies have described links between embryonic handling techniques and an increased likelihood of disease in post-natal life, an update is needed to summarize the sources of DNA damage in embryos and their capacity to repair it. In addition, numerous recent publications have detailed novel techniques for detecting and repairing DNA damage in embryos. This information is of interest to medical or scientific personnel who wish to obtain undamaged embryos for use in offspring generation by ART.

OBJECTIVE AND RATIONALE

This review aims to thoroughly discuss sources of DNA damage in male and female gametes and preimplantation embryos. Special consideration is given to current knowledge and limits in DNA damage detection and screening strategies. Finally, obstacles and future perspectives in clinical diagnosis and treatment (repair) of DNA damaged embryos are discussed.

SEARCH METHODS

Using PubMed and Google Scholar until May 2021, a comprehensive search for peer-reviewed original English-language articles was carried out using keywords relevant to the topic with no limits placed on time. Keywords included ‘DNA damage repair’, ‘gametes’, ‘sperm’, ‘oocyte’, ‘zygote’, ‘blastocyst’ and ‘embryo’. References from retrieved articles were also used to obtain additional articles. Literature on the sources and consequences of DNA damage on germ cells and embryos was also searched. Additional papers cited by primary references were included. Results from our own studies were included where relevant.

OUTCOMES

DNA damage in gametes and embryos can differ greatly based on the source and severity. This damage affects the development of the embryo and can lead to long-term health effects on offspring. DDR mechanisms can repair damage to a certain extent, but the factors that play a role in this process are numerous and altogether not well characterized. In this review, we describe the multifactorial origin of DNA damage in male and female gametes and in the embryo, and suggest screening strategies for the selection of healthy gametes and embryos. Furthermore, possible therapeutic solutions to decrease the frequency of DNA damaged gametes and embryos and eventually to repair DNA and increase mitochondrial quality in embryos before their implantation is discussed.

WIDER IMPLICATIONS

Understanding DNA damage in gametes and embryos is essential for the improvement of techniques that could enhance embryo implantation and pregnancy success. While our knowledge about DNA damage factors and regulatory mechanisms in cells has advanced greatly, the number of feasible practical techniques to avoid or repair damaged embryos remains scarce. Our intention is therefore to focus on strategies to obtain embryos with as little DNA damage as possible, which will impact reproductive biology research with particular significance for reproductive clinicians and embryologists.

In vitro maturation medium supplementation: utilization of repaglinide, L-carnitine, and mesenchymal stem cell-conditioned medium to improve developmental competence of oocytes derived from endometriosis mouse models

Endometriosis (EMS) is one of the most prevalent causes for female infertility. Herein, we investigated the effect of the repaglinide (RG), L-carnitine (LC), and bone marrow mesenchymal stem cell-conditioned medium (BMSC-CM) supplementation during in vitro maturation (IVM) on the quality, maturation, and fertilization rates, as well as embryonic quality and development of oocytes derived from normal and EMS mouse model. Immature oocytes were collected from two groups of normal and EMS-induced female NMRI mice at 6-8 weeks of age. Oocytes were cultured in IVM medium unsupplemented (control group), or supplemented with 1 M RG, 0.3 and 0.6 mg/mL LC, and 25 and 50% BMSC-CM. After 24 h of oocyte incubation, IVM rate and antioxidant status were assessed. Subsequently, the rates of fertilization, cleavage, blastulation, and embryonic development were assessed. Our results demonstrated that supplementation of IVM medium with LC and BMSC-CM, especially 50% BMSC-CM, significantly enhanced IVM and fertilization rates, and markedly improved blastocyst development and total blastocyst cell numbers in EMS-induced mice compared to the control group (53.28±0.24 vs 18.09±0.10%). Additionally, LC and BMSC-CM were able to significantly modulate EMS-induced nitro-oxidative stress by boosting total antioxidant capacity (TAC) and mitigating nitric oxide (NO) levels. Collectively, LC and BMSC-CM supplementation improved oocyte quality and IVM rates, pre-implantation developmental competence of oocytes after in vitro fertilization, and enhanced total blastocyst cell numbers probably by attenuating nitro-oxidative stress and accelerating nuclear maturation of oocytes. These outcomes may provide novel approaches to refining the IVM conditions that can advance the efficiency of assisted reproductive technologies in infertile couples.

The putative roles of FSH and AMH in the regulation of oocyte developmental competence: from fertility prognosis to mechanisms underlying age-related subfertility

BACKGROUND

Fertility loss during female ageing is associated with increasing basal FSH and decreasing anti-Müllerian hormone (AMH) concentrations, together with compromised oocyte quality, presumably due to increased oxidative stress (OS) and DNA damage, as well as reduced metabolic and meiotic competences. Basal FSH and AMH circulatory concentrations have been broadly utilized as IVF success predictors, regardless of fluctuations in prognostic accuracy; basal FSH and AMH perform better in pre-advanced maternal age (AMA: >35 years) and AMA patients, respectively. The relationships between FSH and AMH intrafollicular levels and IVF outcomes suggest, nevertheless, that both hormones regulate oocyte competence, supporting the hypothesis that changes in FSH/AMH levels cause, at least in part, oocyte quality degradation during ageing. To understand the reasons behind the fluctuations in FSH and AMH prognostic accuracies and to clarify their participation in mechanisms determining oocyte competence and age-related subfertility, a deeper knowledge of the regulation of FSH and AMH intrafollicular signalling during the female reproductive lifespan, and of their effects on the cumulus-oocyte complex, is required.

OBJECTIVE AND RATIONALE

An extensive body of information on the regulation of FSH and AMH intrafollicular availability and signalling, as well as on the control of folliculogenesis and oocyte metabolism, has been accumulated. However, these datasets have been explored within the relatively narrow boundaries of their specific subjects. Given the aforementioned gaps in knowledge and their clinical relevance, herein we integrate clinical and basic data, within a wide biological perspective, aiming to shed light on (i) the reasons for the variability in the accuracy of serum FSH and AMH as fertility markers, and on (ii) the potential roles of these hormones in mechanisms regulating oocyte quality, particularly those associated with ageing.

SEARCH METHODS

The PubMed database encompassing the period between 1960 and 2021 was searched. Principal search terms were FSH, FSH receptor, AMH, oocyte, maternal age, cumulus, transzonal projections (TZPs), actin, OS, redox, reactive oxygen species, mitochondria, DNA damage, DNA repair, aneuploidy, spindle, meiosis, gene expression, transcription, translation, oocyte secreted factors (OSFs), cAMP, cyclic guanosine monophosphate, natriuretic peptide C, growth differentiation factor 9, bone morphogenetic protein 15 and fibroblast growth factor.

OUTCOMES

Our analysis suggests that variations in the accuracy of fertility prognosis reflect a modest association between circulatory AMH levels and oocyte quality as well as increasing basal FSH inter-cycle variability with age. In addition, the basic and clinical data articulated herein support the hypothesis that increased intrafollicular FSH levels, as maternal age advances, may override the physiological protective influences of AMH and OSFs against excessive FSH signalling in cumulus cells. This would result in the disruption of oocyte homeostasis via reduced TZP-mediated transfer of cumulus-derived molecules essential for meiotic competence, gene expression, redox activity and DNA repair.

WIDER IMPLICATIONS

In-depth data analysis, encompassing a wide biological perspective has revealed potential causative mechanisms of age-related subfertility triggered by alterations in FSH/AMH signalling during the female reproductive life. Insights from new mechanistic models arising from this analysis should contribute to advancing our comprehension of oocyte biology in humans and serve as a valuable reference for novel AMA subfertility treatments aimed at improving oocyte quality through the modulation of AMH/FSH action.

Use of platelet-rich plasma in the treatment of infertility in poor responders in assisted human reproduction procedures

Couple infertility is a pathology with an absolute number of cases growing markedly over the last decade in connection mainly with the increased age of couples wishing to conceive. Platelet-rich plasma (PRP) is an alternative treatment used for several years for experimental purposes. Yet, this method is not yet defined as a standard therapeutic option in the infertility protocol for poor responders in assisted human reproduction procedures. Thus, the present study is a retrospective study conducted between February 2019 and February 2020 to evaluate the effect of ovarian PRP injection in patients with a poor ovarian response (POR) to ovarian stimulation. Women (n=20; age 31-44 years) diagnosed with POR based on the European Society of Human Reproduction and Embryology criteria underwent ovarian injection with autologous PRP injection. Markers of ovarian reserve before, during the following two menstrual cycles, and at six months after treatment were followed as well as stimulation and fertilisation parameters before and post-treatment. PRP treatment resulted in increased antral follicle count and serum anti-Mullerian hormone, while levels of serum follicle-stimulating hormone and luteinising hormone were decreased. These changes were more pronounced during the 2nd menstrual cycle following treatment. By six months following the injection, their values return to pre-treatment levels and any small differences were not considered statistically significant. The average dose of gonadotropin used and duration remained statistically unchanged, but a significant increase in estradiol achieved by the day of the human chorionic gonadotropin trigger day was achieved. The cancellation rate decreased following PRP treatment while the number of collected oocytes, number of oocytes in metaphase II rose. The number of embryos (of A and B quality) resulting also increased but fell short of the significance level set (α=0.073). Following the PRP injection, two singleton pregnancies were achieved, resulting in live births at term without complications during pregnancy. Another pregnancy was achieved spontaneously 45 months following the PRP and a failed assisted human reproduction procedure. Although the group included a small number of women, the results indicate the potential benefits of an ovarian autologous PRP injection in women with POR. Positive results appear to be short-term for 2-6 months after the procedure.

The impact of maternal age on gene expression during the GV to MII transition in euploid human oocytes

STUDY QUESTION

Are there age-related differences in gene expression during the germinal vesicle (GV) to metaphase II (MII) stage transition in euploid human oocytes?

SUMMARY ANSWER

A decrease in mitochondrial-related transcripts from GV to MII oocytes was observed, with a much greater reduction in MII oocytes with advanced age.

WHAT IS KNOWN ALREADY

Early embryonic development is dependent on maternal transcripts accumulated and stored within the oocyte during oogenesis. Transcriptional activity of the oocyte, which dictates its ultimate developmental potential, may be influenced by age and explain the reduced competence of advanced maternal age (AMA) oocytes compared with the young maternal age (YMA). Gene expression has been studied in human and animal oocytes; however, RNA sequencing could provide further insights into the transcriptome profiling of GV and in vivo matured MII euploid oocytes of YMA and AMA patients.

STUDY DESIGN, SIZE, DURATION

Fifteen women treated for infertility in a single IVF unit agreed to participate in this study. Five GV and 5 MII oocytes from 6, 21-26 years old women (YMA cohort) and 5 GV and 6 MII oocytes from 6, 41-44 years old women (AMA cohort) undergoing IVF treatment were donated. The samples were collected within a time frame of 4 months. RNA was isolated and deep sequenced at the single-cell level. All donors provided either GV or MII oocytes.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Cumulus dissection from donated oocytes was performed 38 h after hCG injection, denuded oocytes were inserted into lysis buffer supplemented with RNase inhibitor. The samples were stored at -80°C until further use. Isolated RNA from GV and MII oocytes underwent library preparation using an oligo deoxy-thymidine (dT) priming approach (SMART-Seq v4 Ultra Low Input RNA assay; Takara Bio, Japan) and Nextera XT DNA library preparation assay (Illumina, USA) followed by deep sequencing. Data processing, quality assessment and bioinformatics analysis were performed using source-software, mainly including FastQC, HISAT2, StringTie and edgeR, along with functional annotation analysis, while scploid R package was employed to determine the ploidy status.

MAIN RESULTS AND THE ROLE OF CHANCE

Following deep sequencing of single GV and MII oocytes in both YMA and AMA cohorts, several hundred transcripts were found to be expressed at significantly different levels. When YMA and AMA MII oocyte transcriptomes were compared, the most significant of these were related to mitochondrial structure and function, including biological processes, mitochondrial respiratory chain complex I assembly and mitochondrial translational termination (false discovery rate (FDR) 6.0E-10 to 1.2E-7). These results indicate a higher energy potential of the YMA MII cohort that is reduced with ageing. Other biological processes that were significantly higher in the YMA MII cohort included transcripts involved in the translation process (FDR 1.9E-2). Lack of these transcripts could lead to inappropriate protein synthesis prior to or upon fertilisation of the AMA MII oocytes.

LARGE SCALE DATA

The RNA sequencing data were deposited in the Gene Expression Omnibus (https://www.ncbi.nlm.nih.gov/geo), under the accession number: GSE164371.

LIMITATIONS, REASONS FOR CAUTION

The relatively small sample size could be a reason for caution. However, the RNA sequencing results showed homogeneous clustering with low intra-group variation and five to six biological replicates derived from at least three different women per group minimised the potential impact of the sample size.

WIDER IMPLICATIONS OF THE FINDINGS

Understanding the effects of ageing on the oocyte transcriptome could highlight the mechanisms involved in GV to MII transition and identify biomarkers that characterise good MII oocyte quality. This knowledge has the potential to guide IVF regimes for AMA patients.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Medical Research Council (MRC Grant number MR/K020501/1).

Local DNA synthesis is critical for DNA repair during oocyte maturation

Mammalian oocytes can be very long-lived cells and thereby are very likely to encounter DNA damage during their lifetime. Defective DNA repair may result in oocytes that are developmentally incompetent or give rise to progeny with congenital disorders. During oocyte maturation, damaged DNA is repaired primarily by non-homologous end joining (NHEJ) or homologous recombination (HR). Although these repair pathways have been studied extensively, the associated DNA synthesis is poorly characterized. Here, using porcine oocytes, we demonstrate that the DNA synthesis machinery is present during oocyte maturation and dynamically recruited to sites of DNA damage. DNA polymerase δ is identified as being crucial for oocyte DNA synthesis. Furthermore, inhibiting synthesis causes DNA damage to accumulate and delays the progression of oocyte maturation. Importantly, inhibition of the spindle assembly checkpoint (SAC) bypassed the delay of oocyte maturation caused by DNA synthesis inhibition. Finally, we found that ∼20% of unperturbed oocytes experienced spontaneously arising damage during maturation. Cumulatively, our findings indicate that oocyte maturation requires damage-associated DNA synthesis that is monitored by the SAC. This article has an associated First Person interview with the first author of the paper.

Sperm donation: an alternative to improve post-ICSI live birth rates in advanced maternal age patients

STUDY QUESTION

Can sperm donation increase live birth rates following ICSI in advanced maternal age (AMA) patients?

SUMMARY ANSWER

Sperm donation increases the live birth rate in AMA ICSI cycles.

WHAT IS KNOWN ALREADY

In ICSI practice, sperm donation has been predominantly applied to overcome male infertility. The involvement of paternal age and lower sperm quality in the severe reduction in fertility observed in AMA patients remains to be clarified.

STUDY DESIGN, SIZE, DURATION

Retrospective multicenter cohort study including data generated between 2015 and 2019 from 755 ICSI cycles achieving a fresh embryo transfer, of which 337 were first homologous cycles (normozoospermic partner sperm and homologous oocytes) and 418 were first sperm donation cycles (donor sperm and homologous oocytes). The association of sperm origin (partner vs donor) with live birth was assessed by multivariate analysis in non-AMA (<37 years, n = 278) and AMA (≥37 years, n = 477) patients, separately, including in the model all variables previously found to be associated with live birth in a univariate analysis (number of MII oocytes recovered, number of embryos transferred, and maternal age). ICSI outcomes were compared between sperm donation and homologous cycles in overall, non-AMA and AMA patients.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study was conducted in three fertility clinics and included 755 Caucasian patients aged 24-42 years undergoing their first homologous or sperm donation ICSI cycle achieving a fresh embryo transfer.

MAIN RESULTS AND THE ROLE OF CHANCE

The multivariate analysis revealed that sperm donation was positively associated with the likelihood of a live birth independently of all other variables tested in AMA (P = 0.02), but not in non-AMA patients. Live birth, delivery, and miscarriage rates differed substantially between sperm donation and homologous AMA cycles; live birth and delivery rates were 70-75% higher (25.4% vs 14.5% and 22.5% vs 13.5%, respectively; P < 0.01), while miscarriage occurrence was less than half (18.0% vs 39.5%; P < 0.01) in sperm donation compared to homologous AMA cycles.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by its retrospective nature, differences in patients profiles between sperm donation and homologous-control groups and varying proportion of donor cycles between fertility centers, although these variations have been controlled for in the statistical analysis.

WIDER IMPLICATIONS OF THE FINDINGS

The findings suggest that sperm donation increases live birth rates while reducing miscarriage occurrence in AMA patients, and thus may be a valid strategy to improve ICSI outcomes in this growing and challenging patient group.

STUDY FUNDING/COMPETING INTEREST(S)

N/A.

TRIAL REGISTRATION NUMBER

N/A.

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.

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.

Physiological factors influencing female fertility in birds

Fertility is fundamental to reproductive success, but not all copulation attempts result in a fertilized embryo. Fertilization failure is especially costly for females, but we still lack a clear understanding of the causes of variation in female fertility across taxa. Birds make a useful model system for fertility research, partly because their large eggs are easily studied outside of the female's body, but also because of the wealth of data available on the reproductive productivity of commercial birds. Here, we review the factors contributing to female infertility in birds, providing evidence that female fertility traits are understudied relative to male fertility traits, and that avian fertility research has been dominated by studies focused on Galliformes and captive (relative to wild) populations. We then discuss the key stages of the female reproductive cycle where fertility may be compromised, and make recommendations for future research. We particularly emphasize that studies must differentiate between infertility and embryo mortality as causes of hatching failure, and that non-breeding individuals should be monitored more routinely where possible. This review lays the groundwork for developing a clearer understanding of the causes of female infertility, with important consequences for multiple fields including reproductive science, conservation and commercial breeding.

Maternal age at birth and daughter's fecundability

STUDY QUESTION

Do daughters of older mothers have lower fecundability?

SUMMARY ANSWER

In this cohort study of North American pregnancy planners, there was virtually no association between maternal age ≥35 years and daughters' fecundability.

WHAT IS KNOWN ALREADY

Despite suggestive evidence that daughters of older mothers may have lower fertility, only three retrospective studies have examined the association between maternal age and daughter's fecundability.

STUDY DESIGN, SIZE, DURATION

Prospective cohort study of 6689 pregnancy planners enrolled between March 2016 and January 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Pregnancy Study Online (PRESTO) is an ongoing pre-conception cohort study of pregnancy planners (age, 21-45 years) from the USA and Canada. We estimated fecundability ratios (FR) for maternal age at the participant's birth using multivariable proportional probabilities regression models.

MAIN RESULTS AND THE ROLE OF CHANCE

Daughters of mothers ≥30 years were less likely to have previous pregnancies (or pregnancy attempts) or risk factors for infertility, although they were more likely to report that their mother had experienced problems conceiving. The proportion of participants with prior unplanned pregnancies, a birth before age 21, ≥3 cycles of attempt at study entry or no follow-up was greater among daughters of mothers <25 years. Compared with maternal age 25-29 years, FRs (95% CI) for maternal age <20, 20-24, 30-34, and ≥35 were 0.72 (0.61, 0.84), 0.92 (0.85, 1.00), 1.08 (1.00, 1.17), and 1.00 (0.89, 1.12), respectively.

LIMITATIONS, REASONS FOR CAUTION

Although the examined covariates did not meaningfully affect the associations, we had limited information on the participants' mother. Differences by maternal age in reproductive history, infertility risk factors and loss to follow-up suggest that selection bias may partly explain our results.

WIDER IMPLICATIONS OF THE FINDINGS

Our finding that maternal age 35 years or older was not associated with daughter's fecundability is reassuring, considering the trend towards delayed childbirth. However, having been born to a young mother may be a marker of low fecundability among pregnancy planners.

STUDY FUNDING/COMPETING INTEREST(S)

PRESTO was funded by NICHD Grants (R21-HD072326 and R01-HD086742) and has received in-kind donations from Swiss Precision Diagnostics, FertilityFriend.com, Kindara.com, and Sandstone Diagnostics. Dr Wise is a fibroid consultant for AbbVie, Inc.

TRIAL REGISTRATION NUMBER

n/a.

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.

Oocytes mount a noncanonical DNA damage response involving APC-Cdh1-mediated proteolysis

In mitotic cells, DNA damage induces temporary G2 arrest via inhibitory Cdk1 phosphorylation. In contrast, fully grown G2-stage oocytes readily enter M phase immediately following chemical induction of DNA damage in vitro, indicating that the canonical immediate-response G2/M DNA damage response (DDR) may be deficient. Senataxin (Setx) is involved in RNA/DNA processing and maintaining genome integrity. Here we find that mouse oocytes deleted of Setx accumulate DNA damage when exposed to oxidative stress in vitro and during aging in vivo, after which, surprisingly, they undergo G2 arrest. Moreover, fully grown wild-type oocytes undergo G2 arrest after chemotherapy-induced in vitro damage if an overnight delay is imposed following damage induction. Unexpectedly, this slow-evolving DDR is not mediated by inhibitory Cdk1 phosphorylation but by APC-Cdh1–mediated proteolysis of the Cdk1 activator, cyclin B1, secondary to increased Cdc14B-dependent APC-Cdh1 activation and reduced Emi1-dependent inhibition. Thus, oocytes are unable to respond immediately to DNA damage, but instead mount a G2/M DDR that evolves slowly and involves a phosphorylation-independent proteolytic pathway.

Asiatic acid protects oocytes against in vitro aging-induced deterioration and improves subsequent embryonic development in pigs

As a pentacyclic triterpene in Centella asiatica, asiatic acid (AA) is a powerful antioxidant with many bioactivities. In the present research, we investigated whether AA has the potential to rescue the decrease in porcine oocyte quality that occurs during in vitro aging (IVA). Mature porcine oocytes were collected and then continuously cultured for an additional 24 h or 48 h with or without AA in maturation medium as an IVA model. The results revealed that AA supplementation reduced the percentage of abnormal aged porcine oocytes during IVA. Furthermore, AA supplementation effectively maintained aged porcine oocyte developmental competence, both parthenogenetic activation and in vitro fertilization. The number of sperm that bound to the zona pellucida on aged porcine oocytes was higher in the AA-supplemented group than in the non-supplemented group. Moreover, AA supplementation not only blocked IVA-induced oxidative stress but also maintained intracellular GSH levels and reduced the percentage of early apoptosis aged porcine oocytes. Mitochondrial functions were disordered during the IVA process. The intracellular ATP levels and mitochondrial membrane potential in aged porcine oocytes were dramatically increased by AA supplementation. Therefore, AA has beneficial effects on porcine oocyte quality and developmental potential maintenance during IVA.

Antioxidant Intervention Attenuates Aging-Related Changes in the Murine Ovary and Oocyte

Advanced maternal age (AMA) is associated with reduced fertility due in part to diminished ovarian follicle quantity, inferior oocyte quality, chromosome aneuploidy, and lower implantation rates. Ovarian aging is accompanied by increased oxidative stress and blunted antioxidant signaling, such that antioxidant intervention could improve reproductive potential. The first aim of this study was to determine the molecular effects of antioxidant intervention in the ovaries and oocytes of aged mice, utilizing a supplement containing only naturally occurring açaí (Euterpe oleracea) with an oxygen radical absorbance capacity of 208,628 μmol Trolox equivalent (TE)/100 g indicating high antioxidant activity. Nine month old female CF-1 mice were administered 80 mg/day antioxidants (n = 12) or standard diet (n = 12) for 12 weeks. In the ovary, antioxidant treatment upregulated β-adrenergic signaling, downregulated apoptosis and proinflammatory signaling, and variably affected cell growth and antioxidant pathways (p < 0.05). Exogenous antioxidants also increased the oocyte expression of antioxidant genes GPX1, SOD2, and GSR (p < 0.05). A feasibility analysis was then conducted on female AMA infertility patients as a proof-of-principle investigation. Patients (n = 121; <45 years old) consented to receiving 600 mg antioxidants three times daily for ≥8 weeks preceding infertility treatment. Preliminary results indicate promising outcomes for AMA patients, warranting further investigation.

The role of honeybee pollen as a natural source of antioxidants in the in vitro maturation medium of sheep oocytes and its effect on gene expression

This study aimed to investigate the effect of honeybee pollen as an antioxidant source in a maturation medium of sheep oocytes on the in vitro maturation rate, glutathione concentration, and gene expression. To our knowledge, this study might be the first of its kind in this field. Sheep oocytes were cultured in vitro with honeybee pollen at four different concentrations (0.0, 1.0, 10.0, and 50.0 μg/ml). The results indicated that the ratio of oocytes that reached metaphase II stage was higher in the honeybee pollen-treated groups than in the control group (p ≤ 0.05). The reduced glutathione (GSH) mean content of matured oocytes was 9.85 nmol/25 oocytes, when honeybee pollen was added to the in vitro maturation (IVM) medium at a concentration of 1.0 μg/ml, compared with 5.84 and 4.44 nmol when using 10.0 and 50.0 μg/ml honeybee pollen, respectively. On the other hand, there was no significant difference in glutathione concentration between the control and 1.0 μg/ml honeybee pollen groups. Expression of candidate genes (GDF-9, BAX, Cyclin B, C-MOS, and IGF1) was upregulated in oocytes cultured with honeybee pollen when compared with oocytes cultured without honeybee pollen. In conclusion, the addition of honeybee pollen at a concentration of 1.0 μg/ml to IVM medium improved the in vitro maturation rate of sheep oocytes, increased the glutathione concentration, and improved gene expression.

Dietary selenium deficiency and supplementation differentially modulate the expression of two ER-resident selenoproteins (selenoprotein K and selenoprotein M) in the ovaries of aged mice: Preliminary data

In the present report, we determined the impact of dietary selenium (Se) deficiency and supplementation on the expression of two ER-resident selenoproteins i.e., Selenok and Selenom in the ovaries of aging mice. The mRNA expression of Selenok and Selenom (RT-qPCR) was significantly higher in the ovaries of mice fed diets supplemented with inorganic (ISe-S: 0.33 mg Se/kg) and organic (OSe-S: 0.33 mg Se/kg) Se compared to those fed a Se-deficient (Se-D: 0.08 mg Se/kg) diet and both Se-adequate (ISe-A: 0.15 mg Se/kg and OSe-A: 0.15 mg Se/kg) diets. Similarly, the protein signals of SELENOK (immunofluorescence assay) were also significantly higher in the Se-supplemented groups compared to those fed Se-D and Se-adequate (ISe-A and OSe-A) diets. Meanwhile, the rate of in vitro-produced blastocysts developing from MII oocytes was also evaluated and it was revealed that this rate was significantly higher in the Se-supplemented mice compared to those fed a Se-D diet. Altogether, the dietary Se supplementation increased the expression of Selenok (also its protein expression) and Selenom in the ovaries of aging mice, potentially contributing to an improved developmental potential of in vitro-matured M II oocytes.

Impact of oxidative stress on oocyte competence for in vitro embryo production programs

Producing high-competent oocytes during the in vitro maturation (IVM) is considered a key step for the success of the in vitro production (IVP) of embryos. One of the known disruptors of oocyte developmental competence on IVP is oxidative stress (OS), which appears due to the imbalance between the production and neutralization of reactive oxygen species (ROS). The in vitro conditions induce supraphysiological ROS levels due to the exposure to an oxidative environment and the isolation of the oocyte from the follicle protective antioxidant milieu. In juvenile in vitro embryo transfer (JIVET), which aims to produce embryos from prepubertal females, the oocytes are more sensitive to OS as they have inherent lower quality. Therefore, the IVM strategies that aim to prevent OS have great interest for both IVP and JIVET programs. The focus of this review is on the effects of ROS on oocyte IVM and the main antioxidants that have been tested for protecting the oocyte from OS. Considering the importance that OS has on oocyte competence, it is crucial to create standardized antioxidant IVM systems for improving the overall IVP success.

Proteomic Analysis in Seminal Plasma of Fertile Donors and Infertile Patients with Sperm DNA Fragmentation

Seminal plasma proteomics studies could represent a new approach for the determination of molecular elements driving male infertility, resulting in a better male infertility characterization. The aim of this study is to investigate proteomic differences in seminal plasma samples from fertile and infertile individuals. For that, semen samples were selected according to semen analysis, clinical pathology, and values of sperm DNA fragmentation (alkaline and neutral Comet assay and Sperm Chromatin Dispersion test). A total of 24 seminal plasma samples classified in four groups were processed: fertile donors (FD), recurrent miscarriage patients (RM), asthenoteratozoospermic patients (ATZ), and asthenoteratozoospermic patients with varicocele (ATZ-VAR). Results obtained by 2D-differential gel electrophoresis (2D-DIGE) revealed 26 spots significantly increased in fertile donors when compared to patient groups. Also, eight spots in the ATZ group and two in the ATZ-VAR group were decreased compared to the other groups. Twenty-eight proteins were identified by mass spectrometry (MS), most of them involved in metabolic and cellular processes and with a catalytic or binding function. Protein-protein interactions through Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) tool suggest that a large part of them were associated with each other. Furthermore, most of them were associated with ubiquitin C, indicating that it could play an important regulation role, resulting in a potential male infertility biomarker.

Placenta-Derived Mesenchymal Stem Cells Restore the Ovary Function in an Ovariectomized Rat Model via an Antioxidant Effect

Oxidative stress is one of the major etiologies of ovarian dysfunction, including premature ovarian failure (POF). Previous reports have demonstrated the therapeutic effects of human placenta-derived mesenchymal stem cells (PD-MSCs) in an ovariectomized rat model (OVX). However, their therapeutic mechanism in oxidative stress has not been reported. Therefore, we investigated to profile the exosome of serum and demonstrate the therapeutic effect of PD-MSCs transplantation for the ovary function. We established an OVX model by ovariectomy and PD-MSCs transplantation was conducted by intravenous injection. Additionally, various factors in the exosome were profiled by LC-MS analysis. As a result, the transplanted PD-MSCs were engrafted into the ovary and the existence of antioxidant factors in the exosome. A decreased expression of oxidative stress markers and increased expression of antioxidant markers were shown in the transplantation (Tx) in comparison to the non-transplantation group (NTx) (* p < 0.05). The apoptosis factors were decreased, and ovary function was improved in Tx in comparison to NTx (* p < 0.05). These results suggest that transplanted PD-MSCs restore the ovarian function in an OVX model via upregulated antioxidant factors. These findings offer new insights for further understanding of stem cell therapy for reproductive systems.

Extracellular vesicles derived from endometrial human mesenchymal stem cells enhance embryo yield and quality in an aged murine model†

Advanced age is a risk factor undermining women's fertility. Hence, the optimization of assisted reproduction techniques is an interdisciplinary challenge that requires the improvement of in vitro culture systems. Here, we hypothesize that supplementation of embryo culture medium with extracellular vesicles from endometrial-derived mesenchymal stem cells (EV-endMSCs) may have a positive impact on the embryo competence of aged oocytes. In this work, 24 weeks old B6D2 female mice were used as egg donors and in vitro fertilization assays were performed using males from the same strain (8-12 weeks); the presumptive zygotes were incubated in the presence of 0, 10, 20, 40, or 80 μg/ml of EV-endMSCs. The results from the proteomic analysis of EV-endMSCs and the classification by Reactome pathways allowed us to identify proteins closely related with the fertilization process. Moreover, in our aged murine model, the supplementation of the embryo culture medium with EV-endMSCs improved the developmental competence of the embryos as well as the total blastomere count. Finally, gene expression analysis of murine blastocysts showed significant changes on core genes related to cellular response to oxidative stress, metabolism, placentation, and trophectoderm/inner cell mass formation. In summary, we demonstrate that EV-endMSCs increase the quality of the embryos, and according to proteomic and genomic analysis, presumably by modulating the expression of antioxidant enzymes and promoting pluripotent activity. Therefore, EV-endMSCs could be a valuable tool in human assisted reproduction improving the developmental competence of aged oocytes and increasing the odds of implantation and subsequent delivery.

Intraovarian vascular enhancement via stromal injection of platelet-derived growth factors: Exploring subsequent oocyte chromosomal status and in vitro fertilization outcomes

The inverse correlation between maternal age and pregnancy rate represents a major challenge for reproductive endocrinology. The high embryo ploidy error rate in failed in vitro fertilization (IVF) cycles reflects genetic misfires accumulated by older oocytes over time. Despite the application of different follicular recruitment protocols during IVF, gonadotropin modifications are generally futile in addressing such damage. Even when additional oocytes are retrieved, quality is frequently poor. Older oocytes with serious cytoplasmic and/or chromosomal errors are often harvested from poorly perfused follicles, and ovarian vascularity and follicular oxygenation impact embryonic chromosomal competency. Because stimulation regimens exert their effects briefly and immediately before ovulation, gonadotropins alone are an ineffective antidote to long-term hypoxic pathology. In contrast, the tissue repair properties (and particularly the angiogenic effects) of platelet-rich plasma (PRP) are well known, with applications in other clinical contexts. Injection of conventional PRP and/or its components (e.g., isolated platelet-derived growth factors as a cell-free substrate) into ovarian tissue prior to IVF has been reported to improve reproductive outcomes. Any derivative neovascularity may modulate oocyte competence by increasing cellular oxygenation and/or lowering concentrations of intraovarian reactive oxygen species. We propose a mechanism to support intrastromal angiogenesis, improved follicular perfusion, and, crucially, embryo ploidy rescue. This last effect may be explained by mRNA upregulation coordinated by PRP-associated molecular signaling, as in other tissue systems. Additionally, we outline an intraovarian injection technique for platelet-derived growth factors and present this method to help minimize reliance on donor oocytes and conventional hormone replacement therapy.

Listening to mother: Long-term maternal effects in mammalian development

The oocyte is a complex cell that executes many crucial and unique functions at the start of each life. These functions are fulfilled by a unique collection of macromolecules and other factors, all of which collectively support meiosis, oocyte activation, and embryo development. This review focuses on the effects of oocyte components on developmental processes that occur after the initial stages of embryogenesis. These include long-term effects on genome function, metabolism, lineage allocation, postnatal progeny health, and even subsequent generations. Factors that regulate chromatin structure, genome programming, and mitochondrial function are elements that contribute to these oocyte functions.

Autophagy in Female Fertility: A Role in Oxidative Stress and Aging

Significance: The precipitous age-related decline in female fertility is intimately associated with a reduction in both the quantity and quality of the germline (oocytes). Although complex etiologies undoubtedly contribute to the deterioration of oocyte quality, increasing attention has focused on the pervasive impact of oxidative stress. Indeed, the prolonged lifespan of the meiotically arrested oocyte places this cell at heightened risk of oxidative lesions, which commonly manifest in dysregulation of protein homeostasis (proteostasis). Although oocytes are able to mitigate this threat via the mobilization of a sophisticated network of surveillance, repair, and proteolytic pathways, these defenses are themselves prone to age-related defects, reducing their capacity to eliminate oxidatively damaged proteins. Recent Advances: Here, we give consideration to the quality control mechanisms identified within the ovary that afford protection to the female germline. Our primary focus is to review recent advances in our understanding of the autophagy pathway and its contribution to promoting oocyte longevity and modulating pathophysiological responses to oxidative stress. In addition, we explore the therapeutic potential of emerging strategies to fortify autophagic activity. Critical Issues: The complex interplay of oxidative stress and autophagy has yet to be fully elucidated within the context of the aging oocyte and surrounding ovarian environment. Future Directions: Emerging evidence provides a strong impetus to resolve the causal link between autophagy and oxidative stress-driven pathologies in the aging oocyte. Such research may ultimately inform novel therapeutic strategies to combat the age-related loss of female fertility via fortification of intrinsic autophagic activity.

Effects of resveratrol, granulocyte-macrophage colony-stimulating factor or dichloroacetic acid in the culture media on embryonic development and pregnancy rates in aged mice

The success rate of assisted reproductive technology is closely correlated with maternal age. Reproductive aging pathologies are frequently caused by impaired DNA repair, genomic instability, and mitochondrial dysfunction. Several reports have shown that resveratrol can prevent age-related diseases by improving mitochondrial function. Improved blastocyst development and mitochondrial output by dichloroacetic acid (DCA) supplementation were reported in aged mice. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has significant effects on implantation rates in women with previous miscarriages. Therefore, this study was conducted to observe how those compounds influence the developmental and the reproductive potential of aged oocytes. BDF1 female mice at 58-62 weeks old were used for this study. MII oocytes were fertilized and cultured in MRC media supplemented with or without resveratrol (0.5 μM), GM-CSF (2 ng/ml) or DCA (1.0 mM). The addition of resveratrol, GM-CSF or DCA tended to increase blastocyst development and pregnancy rates. Supplementation with resveratrol significantly increased the pregnancy and implantation rates (p < 0.05). Moreover, resveratrol decreased reactive oxygen species production and increased mitochondrial membrane potential. These results suggest that the addition of resveratrol can increase pregnancy outcomes in women of advanced maternal age.

The Presence of Immature GV- Stage Oocytes during IVF/ICSI Is a Marker of Poor Oocyte Quality: A Pilot Study

Here we investigate whether the presence of germinal vesicle-stage oocytes (GV- oocytes) reflects poor oocyte developmental competence (or quality). This was a prospective, non-randomised, cohort pilot-study involving 60 patients undergoing in vitro fertilization/ intracytoplasmic sperm injection for whom complete pregnancy outcome data were available. Patients in whom GV- oocytes were retrieved (GV+) at transvaginal oocyte retrieval (TVOR) were compared with those from whom no GVs were retrieved (GV-). We found that GV+ (n = 29) and GV- (n = 31) patients were similarly aged (35.4 vs. 36.4 years; p = 0.446). GV+ patients had a mean of 2.41 ± 2.03 GVs and comparable yields of MII oocytes to GV- patients (11 ± 6.88 vs. 8.26 ± 4.84; p = 0.077). Compared with GV- patients, GV+ patients had markedly lower implantation rates (11.8% vs. 30.2%; p = 0.022) as well as oocyte utilisation rates for clinical pregnancy (2.3% vs. 6.8%; p = 0.018) and live-birth (1.9% vs. 5.7%; p = 0.029). DNA damage levels measured using γH2AX immunostaining were not different in oocytes from women <36 years versus those ≥36 years (p = 0.606). Thus, patients who have GV- stage oocytes at TVOR exhibit poor oocyte quality reflected in reduced per-oocyte pregnancy success rates and uniformly high levels of oocyte DNA damage.

The deteriorating soma and the indispensable germline: gamete senescence and offspring fitness

The idea that there is an impenetrable barrier that separates the germline and soma has shaped much thinking in evolutionary biology and in many other disciplines. However, recent research has revealed that the so-called 'Weismann Barrier' is leaky, and that information is transferred from soma to germline. Moreover, the germline itself is now known to age, and to be influenced by an age-related deterioration of the soma that houses and protects it. This could reduce the likelihood of successful reproduction by old individuals, but also lead to long-term deleterious consequences for any offspring that they do produce (including a shortened lifespan). Here, we review the evidence from a diverse and multidisciplinary literature for senescence in the germline and its consequences; we also examine the underlying mechanisms responsible, emphasizing changes in mutation rate, telomere loss, and impaired mitochondrial function in gametes. We consider the effect on life-history evolution, particularly reproductive scheduling and mate choice. Throughout, we draw attention to unresolved issues, new questions to consider, and areas where more research is needed. We also highlight the need for a more comparative approach that would reveal the diversity of processes that organisms have evolved to slow or halt age-related germline deterioration.

The RXFP3 receptor is functionally associated with cellular responses to oxidative stress and DNA damage

DNA damage response (DDR) processes, often caused by oxidative stress, are important in aging and -related disorders. We recently showed that G protein-coupled receptor (GPCR) kinase interacting protein 2 (GIT2) plays a key role in both DNA damage and oxidative stress. Multiple tissue analyses in GIT2KO mice demonstrated that GIT2 expression affects the GPCR relaxin family peptide 3 receptor (RXFP3), and is thus a therapeutically-targetable system. RXFP3 and GIT2 play similar roles in metabolic aging processes. Gaining a detailed understanding of the RXFP3-GIT2 functional relationship could aid the development of novel anti-aging therapies. We determined the connection between RXFP3 and GIT2 by investigating the role of RXFP3 in oxidative stress and DDR. Analyzing the effects of oxidizing (H₂O₂) and DNA-damaging (camptothecin) stressors on the interacting partners of RXFP3 using Affinity Purification-Mass Spectrometry, we found multiple proteins linked to DDR and cell cycle control. RXFP3 expression increased in response to DNA damage, overexpression, and Relaxin 3-mediated stimulation of RXFP3 reduced phosphorylation of DNA damage marker H2AX, and repair protein BRCA1, moderating DNA damage. Our data suggests an RXFP3-GIT2 system that could regulate cellular degradation after DNA damage, and could be a novel mechanism for mitigating the rate of age-related damage accumulation.

Live birth and miscarriage rate following intracytoplasmic morphologically selected sperm injection vs intracytoplasmic sperm injection: An updated systematic review and meta-analysis

INTRODUCTION

Intracytoplasmic morphologically selected sperm injection (IMSI) is one of the sperm selection techniques used for assisted reproduction which has been applied for a variety of indications including previously failed fertilization with intracytoplasmic sperm injection (ICSI). A Cochrane review¹ found no difference in outcomes between either modality of sperm selection. Since the Cochrane review was published there have been a further two randomized controlled trials comparing IMSI and ICSI. This systematic review and meta-analysis aims to compare IMSI with ICSI as insemination methods regarding live birth rate and miscarriage rate.

MATERIAL AND METHODS

Systematic review of randomized controlled trials, observational studies and similar reviews in electronic databases published before January 2018.

RESULTS

We found nine randomized controlled trials, evaluating 1610 cycles of in vitro fertilization and 15 observational studies evaluating 1243 cycles of in vitro fertilization. Meta-analysis of the included randomized controlled trials showed no difference in the live birth rate or miscarriage rate between the ICSI and IMSI groups. Meta-analysis of five observational studies showed a significantly higher number of live births in the IMSI group than ICSI group (live birth rate odds ratio 1.47, 95% confidence interval 1.16-4.07), with a moderate degree of heterogeneity (I²  = 41%). Additionally, from six observational studies, a significantly lower miscarriage rate was observed in the IMSI group than in the ICSI group (odds ratio 0.51, 95% confidence interval 0.37-0.70, I²  = 0%).

CONCLUSIONS

Meta-analysis of randomized studies comparing IMSI to ICSI has not shown any difference in live birth rate and miscarriage rate. Meta-analysis of observational studies, which must be interpreted with caution, revealed an increased live birth rate and decreased miscarriage rate with IMSI vs ICSI.

Oxidative homeostasis in oocyte competence for in vitro embryo development

The objective of this study was to evaluate the levels of reactive oxygen species (ROS) and glutathione (GSH) in oocytes from follicles of different diameters and their relevance in the in vitro production of embryos (IVPE). Bovine ovaries were aspirated according to the diameter of the follicle [2-8 (general), 4-8 (large), and 2 < 4 mm (small)]. The oocytes were evaluated for levels of ROS, GSH, in vitro maturation, and IVPE. Higher levels of ROS and GSH were observed (p < 0.05) in oocytes of the large group (85.6 ± 7.2 and 140.0 ± 9.6) followed by those in the general (81.1 ± 10.5 and 134.3 ± 7.8) and small (73.5 ± 10.1 and 125.0 ± 10.6) groups. However, the proportion of ROS/GSH did not differ (p > 0.05) between the general, large, and small groups. The maturation was higher (p < 0.05) in the large group (87.8 ± 3.0%) than in the small group (72.2 ± 5.8%), but both were similar (p > 0.05) to that in the general group (82.2 ± 2.5%), whereas the IVPE of the large group (57.3 ± 3.0%) was higher (p < 0.05) than those in the general (44.7 ± 4.4%) and small (34.0 ± 4.0%) groups. We report that oocytes from large follicles are more competent for IVPE, whereas higher levels of ROS and GSH appear to be correlated with oocyte competence, as long as oxidative homeostasis is retained.

Natural antioxidants in the vitrification solution improve the ovine ovarian tissue preservation

The present study evaluated the effect of the addition of antioxidants anethole (AN) and robinin (RO) in the vitrification solution, and the in vitro incubation (IVI) medium of ovine ovarian tissue. Ovarian fragments were vitrified without antioxidant (VWA) or with different concentrations of AN (30, 300 and 2000 μg/mL) or RO (0.125, 0.25 and 0.50 mg/mL), followed by IVI (24 h). Histological analyses showed that the percentage of morphologically normal preantral follicles (MNPF) in AN 2000 did not differ from RO 0.125 or fresh ovarian tissue (CTR). Subsequently, ovarian fragments were vitrified in the presence of AN 2000 and RO 0.125 followed by IVI without or with (AN 2000+ and RO 0.125+) the same antioxidants. The follicular activation in all treatments was significantly increased as compared to the CTR. The stroma cell density (SCD) in all the vitrified fragments was significantly lower than the CTR. However, in the AN 2000 and RO 0.125 this parameter was significantly higher when compared to the VWA. The reactive oxygen species (ROS) in the ovarian cortex of the AN 2000 or AN 2000+ were significantly reduced in comparison with the CTR while the intracellular ROS levels of AN 2000 and CTR were similar. The total antioxidant capacity (TAC) in RO 0.125 was significantly higher than that of VWA, AN 2000 and AN 2000+. According to the results, the use of antioxidants (AN or RO) only in the vitrification solution of ovine ovarian tissue is recommended, due to their better preservation of the SCD. Moreover, AN 2000 best maintains the follicular morphology, while RO 0.125 has a high TAC.

β-carotene improves oocyte development and maturation under oxidative stress in vitro

Recently, the mean maternal age at first birth has been continuing to increase. The decline in the age-related fertility is due to the reduction in the number and the quality of the oocyte. An elevation in intra-ovarian reactive oxygen species (ROS) is correlated with the increase in maternal age, and the oxidative stress is involved in the decline in oocyte quality. Although β-carotene, a very effective quencher of ROS, has been found to have the beneficial contribution to the ovarian development and steroidogenesis, it is unknown the effect of β-carotene on the oocyte development especially oocyte maturation. This investigation aimed to explore the beneficial contribution of β-carotene on oocyte maturation under oxidative stress and the underlying mechanism. We found that the oxidative stress induced by ROS reagent Rosup inhibited oocyte development/maturation and parthenogenetic activation which could be dramatically rescued by β-carotene (57.1 ± 4.7% vs 78.9 ± 3.8%; p < 0.05) in vitro. The underlying mechanisms include that β-carotene not only reduces ROS formation and cell apoptosis, but also it can restore actin expression, cortical granule-free domain (CGFD) formation, mitochondria homogeneous distribution, and nuclear maturation. The data suggest that β-carotene acts as a potential antioxidant in the oocyte. Therefore, the findings from this investigation provide the fundamental 7knowledge for using β-carotene as an antioxidant to improve the oocyte quality and even the ovarian function.

Impacts of cannabinoid epigenetics on human development: reflections on Murphy et. al. 'cannabinoid exposure and altered DNA methylation in rat and human sperm' epigenetics 2018; 13: 1208-1221

Recent data from the Kollins lab (‘Cannabinoid exposure and altered DNA methylation in rat and human sperm’ Epigenetics 2018; 13: 1208–1221) indicated epigenetic effects of cannabis use on sperm in man parallel those in rats and showed substantial shifts in both hypo- and hyper-DNA methylation with the latter predominating. This provides one likely mechanism for the transgenerational transmission of epigenomic instability with sperm as the vector. It therefore contributes important pathophysiological insights into the probable mechanisms underlying the epidemiology of prenatal cannabis exposure potentially explaining diverse features of cannabis-related teratology including effects on the neuraxis, cardiovasculature, immune stimulation, secondary genomic instability and carcinogenesis related to both adult and pediatric cancers. The potentially inheritable and therefore multigenerational nature of these defects needs to be carefully considered in the light of recent teratological and neurobehavioural trends in diverse jurisdictions such as the USA nationally, Hawaii, Colorado, Canada, France and Australia, particularly relating to mental retardation, age-related morbidity and oncogenesis including inheritable cancerogenesis. Increasing demonstrations that the epigenome can respond directly and in real time and retain memories of environmental exposures of many kinds implies that the genome-epigenome is much more sensitive to environmental toxicants than has been generally realized. Issues of long-term multigenerational inheritance amplify these concerns. Further research particularly on the epigenomic toxicology of many cannabinoids is also required.

The small non-coding RNA profile of mouse oocytes is modified during aging

Oocytes are reliant on messenger RNA (mRNA) stores to support their survival and integrity during a protracted period of transcriptional dormancy as they await ovulation. Oocytes are, however, known to experience an age-associated alteration in mRNA transcript abundance, a phenomenon that contributes to reduced developmental potential. Here we have investigated whether the expression profile of small non-protein-coding RNAs (sRNAs) is similarly altered in aged mouse oocytes. The application of high throughput sequencing revealed substantial changes to the global sRNA profile of germinal vesicle stage oocytes from young (4-6 weeks) and aged mice (14-16 months). Among these, 160 endogenous small-interfering RNAs (endo-siRNAs) and 10 microRNAs (miRNAs) were determined to differentially accumulate within young and aged oocytes. Further, we revealed decreased expression of two members of the kinesin protein family, Kifc1 and Kifc5b, in aged oocytes; family members selectively targeted for expression regulation by endo-siRNAs of elevated abundance. The implications of reduced Kifc1 and Kifc5b expression were explored using complementary siRNA-mediated knockdown and pharmacological inhibition strategies, both of which led to increased rates of aneuploidy in otherwise healthy young oocytes. Collectively, our data raise the prospect that altered sRNA abundance, specifically endo-siRNA abundance, could influence the quality of the aged oocyte.