The role of mitochondrial activity in female fertility and assisted reproductive technologies: overview and current insights

Association between mitochondrial DNA genotype and sperm motility in humans

The relationship between genetic alterations in mitochondrial DNA (mtDNA) and progressive motility (PR) and rapid progressive motility (grade A) of ejaculated human spermatozoa remains unclear. In this study, we explored the association between human mtDNA genotype and sperm PR and grade A by analyzing mtDNA copy number, loci, haplogroup, rearrangement, deletions, and duplications and sperm motility parameters. Human sperm mtDNA copy number, loci and haplogroups were not associated with human sperm motility PR or A grade. However, the cumulative frequency of human sperm mtDNA rearrangements (including deletions and duplications) in participants with high PR and grade A ratio was higher than in participants with low PR and grade A ratio. Additional studies are needed to understand the relationship between mtDNA genotypes, including deletions and duplications, and human sperm motility.

The role of mitochondrial dynamics in oocyte and early embryo development

Mitochondrial dysfunction is widely implicated in various human diseases, through mechanisms that go beyond mitochondria's well-established role in energy generation. These dynamic organelles exert vital control over numerous cellular processes, including calcium regulation, phospholipid synthesis, innate immunity, and apoptosis. While mitochondria's importance is acknowledged in all cell types, research has revealed the exceptionally dynamic nature of the mitochondrial network in oocytes and embryos, finely tuned to meet unique needs during gamete and pre-implantation embryo development. Within oocytes, both the quantity and morphology of mitochondria can significantly change during maturation and post-fertilization. These changes are orchestrated by fusion and fission processes (collectively known as mitochondrial dynamics), crucial for energy production, content exchange, and quality control as mitochondria adjust to the shifting energy demands of oocytes and embryos. The roles of proteins that regulate mitochondrial dynamics in reproductive processes have been primarily elucidated through targeted deletion studies in animal models. Notably, impaired mitochondrial dynamics have been linked to female reproductive health, affecting oocyte quality, fertilization, and embryo development. Dysfunctional mitochondria can lead to fertility problems and can have an impact on the success of pregnancy, particularly in older reproductive age women.

Mitochondrial replacement techniques for treating infertility

Mitochondrial replacement techniques (MRTs) usually aim to prevent the genetic transmission of maternally inherited mitochondrial diseases. Until now, only the UK and Australia have implemented specific legal regulations of MRTs. In both countries, clinical trials on these techniques are only permissible for cases with a high risk of severe mitochondrial disease in the offspring. However, these techniques can also be applied to treat infertility, especially for older women with impaired oocyte quality. In some countries without legal regulation of these techniques, MRTs are already offered for this purpose. Yet, this application of MRTs has received insufficient attention in the bioethical literature so far.In this paper, I examine whether there are ethical reasons to prohibit trials on MRTs in the context of infertility when they are permitted for preventing mitochondrial disease. Allowing MRTs in one context but not the other might be justified either because their application in the context of mitochondrial disease (1) is supported by a more convincing evidence base, (2) has a higher potential benefit or (3) has a lower risk. I compare both applications of MRTs with respect to these three factors. I conclude that there is no convincing reason to prohibit clinical trials on MRTs for infertility when they are permitted in the context of mitochondrial disease.

Impact of endometriosis on the ovarian follicles

A significant body of evidence has supported a negative impact of endometriosis on ovarian follicles; however, the origin and relevance of this ovarian impairment in endometriosis is still a matter of debate. The ovarian damage can be caused by endometriosis itself or by surgeries aiming to remove endometriotic lesions. In this review, we summarized the existing knowledge on the mechanisms by which endometriosis can impact the ovarian follicles, from molecular to clinical points of view. From a molecular standpoint, the presence of endometriosis or its consequences can induce oxidative stress, inflammation, aberrant mitochondrial energy metabolism and inappropriate steroid production in granulosa cells, phenomena that may impair the quality of oocytes to variable degrees. These alterations may have clinical relevance on the accelerated exhaustion of the ovarian reserve, on the ovarian response to gonadotrophin stimulation in IVF cycles and on the competence of the oocytes. Critical points to be considered in current clinical practices related to fertility issues in endometriosis are discussed.

KAT8 functions in redox homeostasis and mitochondrial dynamics during mouse oocyte meiosis progression

As a histone acetyltransferase, lysine acetyltransferase 8 (KAT8) participates in diverse biological processes. However, the effect of KAT8 on oocyte maturation in mice remains unclear. In this study, we found that mouse oocytes overexpressing Kat8-OE induced maturation failure manifested reduced rates of GVBD and first polar body emission. In addition, immunostaining results revealed that Kat8 overexpressing oocytes showed inappropriate mitochondrial distribution patterns, overproduction of reactive oxygen species (ROS), accumulation of phosphorylated γH2AX, hyperacetylation of α-tubulin, and severely disrupted spindle/chromosome organization. Moreover, we revealed that Kat8 overexpression induced a decline in SOD1 proteins and KAT8's interaction with SOD1 in mouse ovaries via immunoprecipitation. Western blotting data confirmed that Kat8-OE induced downregulation of SOD1 expression, which is a key factor for the decline of oocyte quality in advanced maternal age. Also, the injection of Myc-Sod1 cRNA could partially rescue maternal age-induced meiotic defects in oocytes. In conclusion, our data demonstrated that high level of KAT8 inhibited SOD1 activity, which in turn induced defects of mitochondrial dynamics, imbalance of redox homeostasis, and spindle/chromosome disorganization during mouse oocyte maturation.

New insights on mitochondrial heteroplasmy observed in ovarian diseases

BACKGROUND

The reportedly high mutation rate of mitochondrial DNA (mtDNA) may be attributed to the absence of histone protection and complete repair mechanisms. Mitochondrial heteroplasmy refers to the coexistence of wild-type and mutant mtDNA. Most healthy individuals carry a low point mutation load (<1 %) in their mtDNA, typically without any discernible phenotypic effects. However, as it exceeds a certain threshold, it may cause the onset of various diseases. Since the ovary is a highly energy-intensive organ, it relies heavily on mitochondrial function. Mitochondrial heteroplasmy can potentially contribute to a variety of significant ovarian disorders.

AIM OF REVIEW

In this review, we have elucidated the close relationship between mtDNA heteroplasmy and ovarian diseases, and summarized novel avenues and strategies for the potential treatment of these ovarian diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Mitochondrial heteroplasmy can potentially contribute to a variety of significant ovarian disorders, including polycystic ovary syndrome, premature ovarian insufficiency, and endometriosis. Current strategies related to mitochondrial heteroplasmy are untargeted and have low bioavailability. Nanoparticle delivery systems loaded with mitochondrial modulators, mitochondrial replacement/transplantation therapy, and mitochondria-targeted gene editing therapy may offer promising paths towards potentially more effective treatments for these diseases, despite ongoing challenges.

Facilitation of Ovarian Response by Mechanical Force-Latest Insight on Fertility Improvement in Women with Poor Ovarian Response or Primary Ovarian Insufficiency

The decline in fertility in aging women, especially those with poor ovarian response (POR) or primary ovarian insufficiency (POI), is a major concern for modern IVF centers. Fertility treatments have traditionally relied on gonadotropin- and steroid-hormone-based IVF practices, but these methods have limitations, especially for women with aging ovaries. Researchers have been motivated to explore alternative approaches. Ovarian aging is a complicated process, and the deterioration of oocytes, follicular cells, the extracellular matrix (ECM), and the stromal compartment can all contribute to declining fertility. Adjunct interventions that involve the use of hormones, steroids, and cofactors and gamete engineering are two major research areas aimed to improve fertility in aging women. Additionally, mechanical procedures including the In Vitro Activation (IVA) procedure, which combines pharmacological activators and fragmentation of ovarian strips, and the Whole Ovary Laparoscopic Incision (WOLI) procedure that solely relies on mechanical manipulation in vivo have shown promising results in improving follicle growth and fertility in women with POR and POI. Advances in the use of mechanical procedures have brought exciting opportunities to improve fertility outcomes in aging women with POR or POI. While the lack of a comprehensive understanding of the molecular mechanisms that lead to fertility decline in aging women remains a major challenge for further improvement of mechanical-manipulation-based approaches, recent progress has provided a better view of how these procedures promote folliculogenesis in the fibrotic and avascular aging ovaries. In this review, we first provide a brief overview of the potential mechanisms that contribute to ovarian aging in POI and POR patients, followed by a discussion of measures that aim to improve ovarian folliculogenesis in aging women. At last, we discuss the likely mechanisms that contribute to the outcomes of IVA and WOLI procedures and potential future directions.

Are epigenetic mechanisms and nutrition effective in male and female infertility?

This review discusses epigenetic mechanisms and the relationship of infertility in men and women in relation to parameters pertaining to nutrition. The prevalence of infertility worldwide is 8-12 %, and one out of every eight couples receives medical treatment. Epigenetic mechanisms, aging, environmental factors, dietary energy and nutrients and non-nutrient compounds; more or less energy intake, and methionine come into play in the occurrence of infertility. It also interacts with vitamins B12, D and B6, biotin, choline, selenium, zinc, folic acid, resveratrol, quercetin and similar factors. To understand the molecular mechanisms regulating the expression of genes that affect infertility, the environment, the role of genotype, age, health, nutrition and changes in the individual's epigenotype must first be considered. This will pave the way for the identification of the unknown causes of infertility. Insufficient or excessive intake of energy and certain macro and micronutrients may contribute to the occurrence of infertility as well. In addition, it is reported that 5-10 % of body weight loss, moderate physical activity and nutritional interventions for improvement in insulin sensitivity contribute to the development of fertility. Processes that pertain to epigenetics carry alterations which are inherited yet not encoded via the DNA sequence. Nutrition is believed to have an impact over the epigenetic mechanisms which are effective in the pathogenesis of several diseases like infertility. Epigenetic mechanisms of individuals with infertility are different from healthy individuals. Infertility is associated with epigenetic mechanisms, nutrients, bioactive components and numerous other factors.

Design of a gradient-rheotaxis microfluidic chip for sorting of high-quality Sperm with progressive motility

Assisted reproductive technology (ART) is an important invention for the treatment of human infertility, and the isolation of high-quality sperm with progressive motility is one of the most critical steps that eventually affect the fertilization rate. Conventional sperm separation approaches include the swim-up method and density gradient centrifugation. However, the quality of isolated sperm obtained from both approaches can still be improved by improving sorted sperm motility, minimizing the DNA fragmentation rate, and removing abnormal phenotypes. Here, we report a Progressive Sperm Sorting Chip (PSSC) for high-quality sperm isolation. Based on the rheotaxis behavior of sperm, a gradient flow field is created in the chip for progressive sperm sorting. Clinical experiment results for 10 volunteers showed that greater than 90% of isolated sperm exhibit high motility (> 25 μm/s), high linearity (0.8), and a very low DNA fragmentation rate (< 5%). In addition, the whole process is label and chemical free. These features aid in gentle sperm sorting to obtain healthy sperm. This device uniquely enables the selection of high-quality sperm with progressive motility and might be clinically applied for infertility treatment in the near future.

Decreased oocyte quality in patients with endometriosis is closely related to abnormal granulosa cells

Infertility and menstrual abnormalities in endometriosis patients are frequently caused by aberrant follicular growth or a reduced ovarian reserve. Endometriosis typically does not directly harm the oocyte, but rather inhibits the function of granulosa cells, resulting in a decrease in oocyte quality. Granulosa cells, as oocyte nanny cells, can regulate meiosis, provide the most basic resources required for oocyte development, and influence ovulation. Endometriosis affects oocyte development and quality by causing granulosa cells apoptosis, inflammation, oxidative stress, steroid synthesis obstacle, and aberrant mitochondrial energy metabolism. These aberrant states frequently interact with one another, however there is currently relatively little research in this field to understand the mechanism of linkage between abnormal states.

β-hydroxybutyrate impairs bovine oocyte maturation via pyruvate dehydrogenase (PDH) associated energy metabolism abnormality

Background: Ketosis is one of the most frequent and costly metabolic disorders in high-producing dairy cows, and negatively associated with the health and reproductive performance of bovine. Ketosis is mainly caused by the accumulation of ketone body β-hydroxybutyric acid and its diagnosis is based on β-hydroxybutyrate (βHB) concentration in blood. Methods: In this study, we investigated the effects of βHB on bovine oocyte maturation in the concentration of subclinical (1.2 mM) βHB and clinical (3.6 mM). Results: The results showed βHB disrupted bovine oocyte maturation and development capacity. Further analysis showed that βHB induced oxidative stress and mitochondrial dysfunction, as indicated by the increased level of reactive oxygen species (ROS), disrupted mitochondrial structure and distribution, and depolarized membrane potential. Furthermore, oxidative stress triggered early apoptosis, as shown by the enhanced levels of Caspase-3 and Annexin-V. Moreover, 3.6 mM βHB induced the disruption of the pyruvate dehydrogenase (PDH) activity, showing with the decrease of the global acetylation modification and the increase of the abnormal spindle rate. Conclusion: Our study showed that βHB in subclinical/clinical concentration had toxic effects on mitochondrial function and PDH activity, which might affect energy metabolism and epigenetic modification of bovine oocytes and embryos.

Cardiovascular prevention in childhood: a consensus document of the Italian Society of Cardiology Working Group on Congenital Heart Disease and Cardiovascular Prevention in Paediatric Age

Cardiovascular diseases (CVD) may be manifested from a very early age. Genetic and environmental (epigenetic) factors interact to affect development and give rise to an abnormal phenotypical expression of genetic information, although not eliciting changes in the nucleotide sequence of DNA. It has been scientifically proven that increased oxidative stress (OS) caused by disease (overweight, obesity, diabetes), nutritional imbalances, unhealthy lifestyles (smoking, alcohol, substance abuse) in the mother during pregnancy may induce placental dysfunction, intrauterine growth restriction, prematurity, low birth weight, postnatal adiposity rebound, metabolic alterations and consequent onset of traditional cardiovascular risk factors. OS represents the cornerstone in the onset of atherosclerosis and manifestation of CVD following an extended asymptomatic period. OS activates platelets and monocytes eliciting the release of pro-inflammatory, pro-atherogenic and pro-oxidising substances resulting in endothelial dysfunction, decrease in flow-mediated arterial dilatation and increase in carotid intima-media thickness. The prevention of CVD is defined as primordial (aimed at preventing risk factors development), primary (aimed at early identification and treatment of risk factors), secondary (aimed at reducing risk of future events in patients who have already manifested a cardiovascular event), and tertiary (aimed at limiting the complex outcome of disease). Atherosclerosis prevention should be implemented as early as possible. Appropriate screening should be carried out to identify children at high risk who are apparently healthy and implement measures including dietary and lifestyle changes, addition of nutritional supplements and, lastly, pharmacological treatment if risk profiles fail to normalise. Reinstating endothelial function during the reversible stage of atherosclerosis is crucial.

Mitochondrial DNA quantification correlates with the developmental potential of human euploid blastocysts but not with that of mosaic blastocysts

PURPOSE

We aimed to study the association between adjusted mtDNA levels in human trophectoderm biopsy samples and the developmental potential of euploid and mosaic blastocysts.

METHODS

We analyzed relative mtDNA levels in 2,814 blastocysts obtained from 576 couples undergoing preimplantation genetic testing for aneuploidy from June 2018 to June 2021. All patients underwent in vitro fertilization in a single clinic; the study was blinded-mtDNA content was unknown at the time of single embryo transfer. The fate of the euploid or mosaic embryos transferred was compared with mtDNA levels.

RESULTS

Euploid embryos had lower mtDNA than aneuploid and mosaic embryos. Embryos biopsied on Day 5 had higher mtDNA than those biopsied on Day 6. No difference was detected in mtDNA scores between embryos derived from oocytes of different maternal ages. Linear mixed model suggested that blastulation rate was associated with mtDNA score. Moreover, the specific next-generation sequencing platform used have a significant effect on the observed mtDNA content. Euploid embryos with higher mtDNA content presented significantly higher miscarriage rates and lower live birth rates, while no significant difference was observed in the mosaic cohort.

CONCLUSION

Our results will aid in improving methods for analyzing the association between mtDNA level and blastocyst viability.

Dihydromyricetin supplementation during in vitro culture improves porcine oocyte developmental competence by regulating oxidative stress

Dihydromyricetin (DHM), a dihydroflavonoid compound, exhibits a variety of biological activities, including antitumor activity. However, the effects of DHM on mammalian reproductive processes, especially during early embryonic development, remain unclear. In this study, we added DHM to porcine zygotic medium to explore the influence and underlying mechanisms of DHM on the developmental competence of parthenogenetically activated porcine embryos. Supplementation with 5 μM DHM during in vitro culture (IVC) significantly improved blastocyst formation rate and increased the total number of cells in porcine embryos. Further, DHM supplementation also improved glutathione levels and mitochondrial membrane potential; reduced natural reactive oxygen species levels in blastomeres and apoptosis rate; upregulated Nanog, Oct4, SOD1, SOD2, Sirt1, and Bcl2 expression; and downregulated Beclin1, ATG12, and Bax expression. Collectively, DHM supplementation regulated oxidative stress during IVC and could act as a potential antioxidant during in vitro porcine oocytes maturation.

Targeted Deletion of Mitofusin 1 and Mitofusin 2 Causes Female Infertility and Loss of Follicular Reserve

Mitochondria are dynamic organelles that regulate their size, shape, and morphology through mechanisms called fusion and fission, to continually adapt themselves to their bioenergetic environment. These mechanisms play a critical role to maintain the mitochondrial function under metabolic and environmental stress. Mitofusin 1 (MFN1) and mitofusin 2 (MFN2) are transmembrane GTPases that regulate mitochondrial fusion mechanism and are required for the maintenance of cellular homeostasis. In this study, we aimed to determine the role of mitofusins in female reproductive competence and senescence using a mouse model with oocyte-specific double deletion of Mfn1 and Mfn2, eliminating the potential functional redundancy of these two proteins. Oocyte-specific targeted double deletion of Mfn1 and Mfn2 in mice resulted in female infertility associated with impaired follicular development and oocyte maturation. It also resulted in altered mitochondrial dynamics and mitochondrial dysfunction. Lack of Mfn1 and Mfn2 in oocytes resulted in accelerated follicular depletion and impaired oocyte quality which are consistent with phenotype of reproductive aging.

Bisphenol A exposure modulates reproductive and endocrine system, mitochondrial function and cellular senescence in female adult rats: A hallmarks of polycystic ovarian syndrome phenotype

Bisphenol A (BPA) mimics estrogen and consequently suspected to be detrimental to female reproductive system. Biomonitoring confirms the BPA burden in body leading to a complex condition called polycystic ovarian syndrome (PCOS) which is frequently attributed to female infertility. Due to unclear precise molecular pathomechanisms of BPA in PCOS, we intend to examine the molecular mechanisms of the reproductive, endocrine, mitochondrial features, and cellular senescence in BPA-treated rats. We analyzed vaginal smears and ovarian follicles using microscope, assessed sex hormones by ELISA, analyzed BPA target gene expression by semi-quantitative RT-PCR, assessed senescence induction by β-galactosidase staining and immunofluorescence in BPA-treated rats. Our data showed hormonal imbalance, impaired folliculogenesis, abnormal expression patterns of target genes, CDKN2A overexpression and enhanced ROS levels in BPA-treated rats. This study provides insights on the effects of BPA exposure on ovulatory, hormonal, mitochondrial dysfunction, and senescence that benefit in better understanding of PCOS induced by BPA.

Miro1 regulates mitochondrial homeostasis and meiotic resumption of mouse oocyte

Miro1, a mitochondrial Rho GTPase1, is a kind of mitochondrial outer membrane protein involved in the regulation of mitochondrial anterograde transport and its subcellular distribution. Mitochondria influence reproductive processes of mammals in some aspects. Mitochondria are important for oocyte maturation, fertilization and embryonic development. The purpose of this study was to evaluate whether Miro1 regulates mouse oocyte maturation by altering mitochondrial homeostasis. We showed that Miro1 was expressed in mouse oocyte at different maturation stages. Miro1 mainly distributed in the cytoplasm and around the spindle during oocyte maturation. Small interference RNA-mediated Miro1 depletion caused significantly abnormal distribution of mitochondria and endoplasmic reticulum as well as mitochondrial dysfunction, resulting in severely impaired germinal vesicle breakdown (GVBD) of mouse oocytes. For those oocytes which went through GVBD in the Miro1-depleted group, part of them were inhibited in meiotic prophase I stage with abnormal chromosome arrangement and scattered spindle length. Our results suggest that Miro1 is essential for maintaining the maturation potential of mouse oocyte.

Leukemia inhibitory factor enhances the development and subsequent blastocysts quality of yak oocytes in vitro

Leukemia inhibitory factor (LIF) is a multipotent cytokine of the IL-6 family which plays a critical role in the maturation and development of oocytes. This study evaluated the influence of LIF on the maturation and development ability of yak oocytes, and the quality of subsequent blastocysts under in vitro culture settings. Different concentrations of LIF (0, 25, 50, and 100 ng/mL) were added during the in vitro culture of oocytes to detect the maturation rate of oocytes, levels of mitochondria, reactive oxygen species (ROS), actin, and apoptosis in oocytes, mRNA transcription levels of apoptosis and antioxidant-related genes in oocytes, and total cell number and apoptosis levels in subsequent blastocysts. The findings revealed that 50 ng/mL LIF could significantly increase the maturation rate (p < 0.01), levels of mitochondria (p < 0.01) and actin (p < 0.01), and mRNA transcription levels of anti-apoptotic and antioxidant-related genes in yak oocytes. Also, 50 ng/mL LIF could significantly lower the generation of ROS (p < 0.01) and apoptosis levels of oocytes (p < 0.01). In addition, blastocysts formed from 50 ng/mL LIF-treated oocytes showed significantly larger total cell numbers (p < 0.01) and lower apoptosis rates (p < 0.01) than the control group. In conclusion, the addition of LIF during the in vitro maturation of yak oocytes improved the quality and the competence of maturation and development in oocytes, as well as the quality of subsequent blastocysts. The result of this study provided some insights into the role and function of LIF in vitro yak oocytes maturation, as well as provided fundamental knowledge for assisted reproductive technologies in the yak.

Oroxin A reduces oxidative stress, apoptosis, and autophagy and improves the developmental competence of porcine embryos in vitro

Oroxin A (OA) is a flavonoid isolated from Oroxylum indicum (L.) Kurz that has various biological activities, including antioxidant activities. This study aimed to examine the viability of using OA in an in vitro culture (IVC) medium for its antioxidant effects and related molecular mechanisms on porcine blastocyst development. In this study, we investigated the effects of OA on early porcine embryo development via terminal deoxynucleotidyl transferase dUTP nick-end labeling, 5-ethynyl-2'-deoxyuridine labeling, quantitative reverse transcription PCR, and immunocytochemistry. Embryos cultured in the IVC medium supplemented with 2.5 μM of OA had an increased blastocyst formation rate, total cell number, and proliferation capacity, along with a low apoptosis rate. OA supplementation decreased reactive oxygen species levels, while increasing glutathione levels. OA-treated embryos exhibited an improved intracellular mitochondrial membrane potential and reduced autophagy. Moreover, levels of pluripotency- and antioxidant-related genes were upregulated, whereas those of apoptosis- and autophagy-related genes were downregulated by OA addition. In conclusion, OA improves preimplantation embryonic development by reducing oxidative stress and enhancing mitochondrial function.

Protective Effects of Antioxidants on Cyclophosphamide-Induced Ovarian Toxicity

The most common limitation of anticancer chemotherapy is the injury to normal cells. Cyclophosphamide, which is one of the most widely used alkylating agents, can cause premature ovarian insufficiency and infertility since the ovarian follicles are extremely sensitive to their effects. Although little information is available about the pathogenic mechanism of cyclophosphamide-induced ovarian damage, its toxicity is attributed to oxidative stress, inflammation, and apoptosis. The use of compounds with antioxidant and cytoprotective properties to protect ovarian function from deleterious effects during chemotherapy would be a significant advantage. Thus, this article reviews the mechanism by which cyclophosphamide exerts its toxic effects on the different cellular components of the ovary, and describes 24 cytoprotective compounds used to ameliorate cyclophosphamide-induced ovarian injury and their possible mechanisms of action. Understanding these mechanisms is essential for the development of efficient and targeted pharmacological complementary therapies that could protect and prolong female fertility.

Assessment of Telomere Length and Mitochondrial DNA Copy Number in Granulosa Cells as Predictors of Aneuploidy Rate in Young Patients

Background: To identify the correlation among female age, cellular aging markers, and aneuploidy rate in in vitro fertilization (IVF) and the preimplantation genetic test for aneuploidy (PGT-A) cycles. Methods: This is a prospective cohort study recruiting 110 infertile women between August 2017 and July 2018. They were divided into young-age (<38 years, n = 60) and advanced-age (≥38 years, n = 50) groups. Peripheral leukocytes were assessed, and the granulosa cells were pooled during oocyte pickup. Mitochondrial DNA (mtDNA) copy number and telomere length (TL) were measured using real-time polymerase chain reaction. PGT-A was performed on the NGS platform. Results: mtDNA copy number and TL were positively correlated in both leukocytes (rho = 0.477, p < 0.001) and granulosa cells (rho = 0.361, p < 0.001), but the two parameters in leukocytes were not correlated with those in granulosa cells. In the young-age group, TL in the granulosa cells was the only factor correlated with the aneuploidy rate (rho = −0.283, p = 0.044), whereas in the advanced-age group, age was the main factor (rho = 0.358, p = 0.018). Conclusions: TL in the granulosa cells was negatively correlated with the aneuploidy rate in the young-age group, supporting the application of PGT-A in younger women.

Mitochondrial hijacking: A potential mechanism for SARS-CoV-2 to impair female fertility

As well as causing respiratory lesions, the multi-organ complications caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are also well known. Combined with the epidemiological characteristics of SARS-CoV-2 with high transmission rate and low lethality, the impact of complications caused by its infection on infected individuals seems to be of greater concern. There has been evidence that viral infection is complicated by female reproductive impairment, but the mechanism by which SARS-CoV-2 impairs female fertility is unclear. In addition, RNA-GPS technology has revealed that the SARS-CoV-2 genome resides in mitochondria of the host cells and affects mitochondrial function. Considering the close relationship between mitochondria and female fertility, this paper takes mitochondrial hijacking as an entry point to elucidate the possible mechanisms by which SARS-CoV-2 affects female fertility through the mitochondrial hijacking pathway, which will be important for timely preventive measures and identification of therapeutic targets for infected women with reproductive needs, especially those with asymptomatic infection.

Therapeutic options for premature ovarian insufficiency: an updated review

Primary ovarian insufficiency (POI) is a rare gynecological condition. This disease causes menstrual disturbances, infertility, and various health problems. Historically, hormone replacement therapy is the first-line treatment for this disorder. Women diagnosed with POI are left with limited therapeutic options. In order to remedy this situation, a new generation of therapeutic approaches, such as in vitro activation, mitochondrial activation technique, stem cell and exosomes therapy, biomaterials strategies, and platelet-rich plasma intra-ovarian infusion, is being developed. However, these emerging therapies are yet in the experimental stage and require precise design components to accelerate their conversion into clinical treatments. Thus, each medical practitioner bears responsibility for selecting suitable therapies for individual patients. In this article, we provide a timely analysis of the therapeutic strategies that are available for POI patients and discuss the prospects of POI therapy.

Mitofusins: from mitochondria to fertility

Germ cell formation and embryonic development require ATP synthesized by mitochondria. The dynamic system of the mitochondria, and in particular, the fusion of mitochondria, are essential for the generation of energy. Mitofusin1 and mitofusin2, the homologues of Fuzzy onions in yeast and Drosophila, are critical regulators of mitochondrial fusion in mammalian cells. Since their discovery mitofusins (Mfns) have been the source of significant interest as key influencers of mitochondrial dynamics, including membrane fusion, mitochondrial distribution, and the interaction with other organelles. Emerging evidence has revealed significant insight into the role of Mfns in germ cell formation and embryonic development, as well as the high incidence of reproductive diseases such as asthenospermia, polycystic ovary syndrome, and gestational diabetes mellitus. Here, we describe the key mechanisms of Mfns in mitochondrial dynamics, focusing particularly on the role of Mfns in the regulation of mammalian fertility, including spermatogenesis, oocyte maturation, and embryonic development. We also highlight the role of Mfns in certain diseases associated with the reproductive system and their potential as therapeutic targets.

LRRK2 regulates actin assembly for spindle migration and mitochondrial function in mouse oocyte meiosis

Leucine-rich-repeat kinase 2 (LRRK2) belongs to the Roco GTPase family and is a large multidomain protein harboring both GTPase and kinase activities. LRRK2 plays indispensable roles in many processes, such as autophagy and vesicle trafficking in mitosis. In this study, we showed the critical roles of LRRK2 in mammalian oocyte meiosis. LRRK2 is mainly accumulated at the meiotic spindle periphery during oocyte maturation. Depleting LRRK2 led to the polar body extrusion defects and also induced large polar bodies in mouse oocytes. Mass spectrometry analysis and co-immunoprecipitation results showed that LRRK2 was associated with several actin-regulating factors, such as Fascin and Rho-kinase (ROCK), and depletion of LRRK2 affected the expression of ROCK, phosphorylated cofilin, and Fascin. Further analysis showed that LRRK2 depletion did not affect spindle organization but caused the failure of spindle migration, which was largely due to the decrease of cytoplasmic actin filaments. Moreover, LRRK2 showed a similar localization pattern to mitochondria, and LRRK2 was associated with several mitochondria-related proteins. Indeed, mitochondrial distribution and function were both disrupted in LRRK2-depleted oocytes. In summary, our results indicated the critical roles of LRRK2 in actin assembly for spindle migration and mitochondrial function in mouse oocyte meiosis.

Mitochondria-related changes and metabolic dysfunction in low prognosis patients under the POSEIDON classification

STUDY QUESTION

What is the relationship between mitochondria of granulosa cells (GCs) and age and ovarian function in the patients under the POSEIDON classification?

SUMMARY ANSWER

Our results revealed obvious abnormal mitochondrial-related changes in low prognosis IVF population, where age and the function of ovarian reserve exerted a divergent effect on mitochondrial content and function.

WHAT IS KNOWN ALREADY

Mitochondria have an important role in the cross-talk between GCs and oocytes. However, factors affecting mitochondria of GCs and related mechanisms are still poorly understood.

STUDY DESIGN, SIZE, DURATION

GCs samples were obtained from 119 infertile women undergoing IVF from September 2020 to February 2021. Six groups were investigated by the POSEIDON stratification: young with normal prognosis (C1), aging with normal prognosis (C2), young and low prognosis group with normal ovarian reserve (NOR) (G1), aging and low prognosis group with NOR (G2), young and low prognosis group with diminished ovarian reserve (DOR) (G3), and aging and low prognosis group with DOR (G4).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The morphology of GC mitochondria was observed by transmission electron microscopy. MtDNA copy number and mitochondrial replication-related genes were detected by real-time quantitative PCR (qPCR). Mitochondrial membrane potential (MMP) and cytosolic reactive oxygen species (ROS) were detected by confocal microscopy. Cellular glycolysis and aerobic respiratory capacity were analyzed by Seahorse XFe96 Analyzer, and related gene expression and protein levels were assessed by qPCR and Western blot.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared to the normal prognosis groups, mitochondrial morphology was impaired in the low prognosis groups, where the young groups (G1, G3) with low prognosis showed phenotypes undergoing oxidative stress (round, vacuolated, swollen with decreased matrix density) and the aging groups (G2, G4) revealed typical aging characteristics (an irregular shape with heterogeneous matrix density and cord-like cristae). Additionally, the degree of corresponding change and damage was more obvious in patients with DOR (G3, G4) regardless of age. For mitochondrial content, the mtDNA copy number in GCs was significantly negatively correlated with age in the low prognosis groups (β = -0.373, P = 0.005). Interestingly, the relationship between mtDNA copy number and anti-Mullerian hormone score differed between the two age groups with low prognosis, with a negative correlation in the young groups (β = -0.639, P = 0.049) and a positive correlation in the aging groups (β = 0.505, P = 0.039). In addition, significantly reduced mitochondrial activity (MMP, ROS) and cell metabolism (both glycolysis and OXPHOS) were observed in the low prognosis groups, with the most obvious decrease being observed in the DOR population. However, the metabolism of the GCs in normal prognosis aging women (C2) shifted from OXPHOS to anaerobic glycolysis.

LIMITATIONS, REASONS FOR CAUTION

Owing to the difficulties involved in primary GC collection and culture, the sample size was limited.

WIDER IMPLICATIONS OF THE FINDINGS

Mitochondrial abnormality is closely linked to the low prognostic outcome in IVF patients. Supplementing the functional mitochondrial content or improving mitochondrial function by autologous mitochondrial transfer or mitochondrial-related regulating drugs may help improve the clinical outcomes in patients with a low prognosis, especially for those with DOR.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China (No. 21737001), the Peking University Clinical Medicine + X Youth Project (PKU2020LCXQ011), the Research and Development Program of Peking University People's Hospital (No. RDH2017-03; No. RDX2019-06) and the Application of Clinical Features of Capital Special Subject (Z171100001017130). There were no competing interests.

TRIAL REGISTRATION NUMBER

This study was registered with the Chinese Clinical Trial Register (Clinical Trial Number: ChiCTR2100045531).

Reproductive senescence impairs the energy metabolism of human luteinized granulosa cells

RESEARCH QUESTION

Female age is the single greatest factor influencing reproductive performance and granulosa cells are considered as potential biomarkers of oocyte quality. Is there an age effect on the energy metabolism of human mural granulosa cells?

DESIGN

Observational prospective cohort and experimental study including 127 women who had undergone IVF cycles. Women were allocated to two groups: a group of infertile patients aged over 38 years and a control group comprising oocyte donors aged less than 35 years. Individuals with pathologies that could impair fertility were excluded from both groups. Following oocyte retrieval, cumulus and granulosa cells were isolated and their bioenergetic properties (oxidative phosphorylation parameters, rate of aerobic glycolysis and adenine nucleotide concentrations) were analysed and compared.

RESULTS

Human mural luteinized granulosa and cumulus cells present high rates of aerobic glycolysis that cannot be increased further when mitochondrial ATP synthesis is inhibited. Addition of follicular fluid to the experimental media is necessary to reach the full respiratory capacity of the cells. Granulosa cells from aged women present lower mitochondrial respiration (12.8 ± 1.6 versus 11.2 ± 1.6 pmol O₂/min/mg; P = 0.046), although mitochondrial mass is not decreased, and lower aerobic glycolysis, than those from young donors (12.9 ± 1.3 versus 10.9 ± 0.5 mpH/min/mg; P = 0.009). The concurrent decrease in the two energy supply pathways leads to a decrease in the cellular energy charge (0.87 ± 0.01 versus 0.83 ± 0.02; P < 0.001).

CONCLUSIONS

Human mural luteinized granulosa cells exhibit a reduction in their energy metabolism as women age that is likely to influence female reproductive potential.

Bezafibrate prevents aging in in vitro-matured porcine oocytes

Bezafibrate, a fibrate drug used as a lipid-lowering agent to treat hyperlipidemia, is a pan-agonist of peroxisome proliferator-activated receptor alpha. It can enhance mitochondrial fatty acid oxidation, oxidative phosphorylation, and mitochondrial biogenesis. After ovulation, oocytes may get arrested at the metaphase II (MII) stage until fertilization beyond optimal timing, which is termed as post-ovulatory aging. Post-ovulatory aging is a disease that degrades DNA, mitochondria, and oxidative system, and has a negative impact on embryo development and quality; however, the impact of bezafibrate during post-ovulatory aging has not been fully defined. In the present study, we assessed the ability of bezafibrate to prevent the progression of aging in in vitro conditions as well as the underlying mechanisms in pigs. An appropriate concentration of this drug (50 μM) was added, and then oxidative stress, reactive oxygen species downstream, mitochondrial biogenesis, and mitochondrial function were analyzed via immunofluorescence staining and real-time polymerase chain reaction. Bezafibrate significantly alleviated reactive oxygen species and ameliorated glutathione production simultaneously in oocytes and embryos. Moreover, it diminished H2A.X and attenuated CASPASE 3 expression produced by oxidative stress in oocytes and embryos. Furthermore, bezafibrate remarkably improved the mitochondrial function and blastocyst quality as well as markedly reduced the mitochondria/TOM20 ratio and mtDNA copy number. The elevated PARKIN level indicated that mitophagy was induced by bezafibrate treatment after post-ovulatory aging. Collectively, these results suggest that bezafibrate beneficially affects against porcine post-ovulatory oocyte aging in porcine by its antioxidant property and mitochondrial protection.

Potential of Mitochondrial Genome Editing for Human Fertility Health

Mitochondrial DNA (mtDNA) encodes vital proteins and RNAs for the normal functioning of the mitochondria. Mutations in mtDNA leading to mitochondrial dysfunction are relevant to a large spectrum of diseases, including fertility disorders. Since mtDNA undergoes rather complex processes during gametogenesis and fertilization, clarification of the changes and functions of mtDNA and its essential impact on gamete quality and fertility during this process is of great significance. Thanks to the emergence and rapid development of gene editing technology, breakthroughs have been made in mitochondrial genome editing (MGE), offering great potential for the treatment of mtDNA-related diseases. In this review, we summarize the features of mitochondria and their unique genome, emphasizing their inheritance patterns; illustrate the role of mtDNA in gametogenesis and fertilization; and discuss potential therapies based on MGE as well as the outlook in this field.

Pigment epithelium-derived factor negates oxidative stress in mouse oocytes

Molecular changes, caused by various environmental factors, affect the quality and developmental potential of oocytes. Oxidative stress (OS) is a major factor involved in various gynecologic disorders and/or in aging. Recent studies suggest that elevated reactive oxygen species (ROS) hamper oocyte quality and future embryonic development. Pigment epithelium-derived factor (PEDF) is a pleiotropic protein, known for its antiangiogenic, anti-inflammatory, and antioxidative properties. Our previous findings demonstrate the antioxidative role of rPEDF in maintaining granulosa cell viability. In the current study, we examined the ability of PEDF to negate the adverse impact of OS on oocytes. Maturation rate of oocytes exposed to OS was significantly lower than that of control oocytes. The number of mtDNA copies in OS-exposed oocytes was significantly higher than in control oocytes (>3 times), whereas ATP concentration was significantly lower. Oocytes exposed to OS demonstrated impaired chromosome arrangement at the metaphase plate. PEDF significantly improved maturation rate of untreated OS-exposed oocytes. Moreover, mtDNA copy number, ATP concentration, and chromosome arrangement at the metaphase plate in rPEDF-treated OS-exposed oocytes were restored to the level of control oocytes. Our findings demonstrate that OS hampers the ability of oocytes to undergo proper in vitro maturation. The energetic balance of OS-exposed oocyte is characterized by excessive mtDNA replication and reduced ATP concentration; it hampers the ability of oocytes to perform high fidelity chromosome segregation. PEDF alleviates this damage, improves the rate of oocyte maturation, and preserves mtDNA level and ATP content, thus enabling oocytes to form proper metaphase plate and improve oocyte competence.

RAB7 activity is required for the regulation of mitophagy in oocyte meiosis and oocyte quality control during ovarian aging

There is increasing evidence that mitophagy, a specialized form of autophagy to degrade and clear long-lived or damaged mitochondria, is impaired in aging and age-related disease. Previous study has demonstrated the obesity-exposed oocytes accumulate and transmit damaged mitochondria due to an inability to activate mitophagy. However, it remains unknown whether mitophagy functions in oocyte and what's the regulatory mechanism in oocyte aging. In the study, when fully grown oocytes were treated with CCCP, an uncoupling agent to induce mitophagy, we found the activation of the PRKN-mediated mitophagy pathway accompanied the blockage of meiosis at metaphase I stage. Our result then demonstrated its association with the decreased activity of RAB7 and all the observed defects in CCCP treated oocytes could be effectively rescued by microinjection of mRNA encoding active RAB7^Q67L or treatment with the RAB7 activator ML098. Further study indicated PRKN protein level as a rate-limiting factor to facilitate degradation of RAB7 and its GEF (guanine nucleotide exchange factor) complex CCZ1-MON1 through the ubiquitin-proteasome system. In GV oocytes collected during ovarian aging, we found the age-related increase of PINK1 and PRKN proteins and a significant decrease of RAB7 which resulted in defects of mitophagosome formation and the accumulation of damaged mitochondria. The age-related retardation of female fertility was improved after in vivo treatment of ML098. Thus, RAB7 activity is required to maintain the balance between mitophagy and chromosome stability and RAB7 activator is a good candidate to ameliorate age-related deterioration of oocyte quality.Abbreviations: ATG9: autophagy related 9A; ATP: adenosine triphosphate; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; CCZ1: CCZ1 vacuolar protein trafficking and biogenesis associated; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GAPs: GTPase-activating proteins; GEF: guanine nucleotide exchange factor; GV: germinal vesicle; GVBD: germinal vesicle breakdown; LAMP1: lysosomal-associated membrane protein 1; MI: metaphase I stage of meiosis; MII: metaphase II stage of meiosis; Mito: MitoTracker; mtDNA: mitochondrial DNA; MON1: MON1 homolog, secretory trafficking associated; OPTN: optineurin; PINK1: PTEN induced putative kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; RAB7: RAB7, member RAS oncogene family; ROS: reactive oxygen species; TEM: transmission electron microscopy; TOMM20/TOM20: translocase of outer mitochondrial membrane 20; TUBB: tubulin, beta; UB: ubiquitin.

Reproductive senescence and energetic metabolism of human luteinized granulosa cells: is it all about ATP? A prospective cohort and critical view

Mitochondria are known to play a key role in the regulation of reproductive capacity. Senescence is known to impair mitochondrial function and, ultimately, cellular energetic metabolism. Therefore, as women age, a deficient energy supply is likely to affect oocyte quality. The analysis of granulosa cells is considered a valuable noninvasive strategy to assess factors implicated in oocyte competence. Thus, we conducted an observational prospective cohort to evaluate the impact of aging on energy production by luteinized granulosa cells (LGCs). The control group comprised 13 young oocyte donors, whereas the comparison group included 13 infertile women over 38 years of age undergoing in vitro fertilization. Women with diseases that could potentially impact mitochondrial function were excluded. No differences were detected in the ATP levels in LGCs from young donors and infertile patients of advanced reproductive age (1.9 ± 0.99 picomoles in the control group vs. 2.1 ± 0.59 picomoles; p-value = .139). Likewise, the ATP levels in our series did not correlate with either oocyte number or maturity. Despite the similar ATP levels in LGCs, an age effect on the bioenergetic status cannot be excluded. Energy metabolism is very complex, and ATP does not seem to be the most important and reliable parameter.

Exploring reproductive associations of serum polybrominated diphenyl ether and hydroxylated brominated diphenyl ether concentrations among women undergoing in vitro fertilization

STUDY QUESTION

Are serum concentrations of polybrominated diphenyl ethers (PBDEs) and hydroxylated brominated diphenyl ethers (OH-BDEs) associated with IVF endpoints?

SUMMARY ANSWER

Positive associations were observed for BDE153 and several OH-BDEs with IVF endpoints.

WHAT IS KNOWN ALREADY

PBDEs have been voluntarily phased out of production in the USA and EU due to their persistence and toxicity to humans and ecosystems. PBDEs have been associated with implantation failure among women undergoing IVF, yet some animal studies suggest greater toxicity from their metabolites, OH-BDEs.

STUDY DESIGN, SIZE, DURATION

We evaluated a subset of 215 women (contributing 330 IVF cycles) enrolled between 2005 and 2016 in a longitudinal cohort based at Massachusetts General Hospital Fertility Center.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The following PBDEs were quantified: 47, 99, 100, 153 and 154 and the following OH-BDEs: 3-OH-BDE47, 5-OH-BDE47, 6-OH-BDE47 and 4-OH-BDE49. Clinical endpoints of IVF treatments were abstracted from electronic medical records. Associations of log-transformed PBDEs and OH-BDEs with IVF outcomes were assessed using multivariable generalized mixed models and cluster weighted generalized estimating equation models adjusted for lipids, age, BMI, race, year of sample collection, IVF protocol and FSH levels. Outcomes were adjusted to represent a percent change in outcome with an increase equal to the magnitude of the difference between the 75th and 25th percentiles for each specific compound (interquartile range (IQR) increase).

MAIN RESULTS AND THE ROLE OF CHANCE

Detection frequencies were highest for congeners 47 and 153 (82% ≥ method detection limit (MDL)) and metabolites 3 and 5-OH-BDE47 and 4-OH-BDE49 (92% > MDL). PBDE and OH-BDE geometric mean concentrations declined by up to 80% between participants recruited in 2005 and those recruited in 2016. An IQR increase of BDE153 was associated with an increase in the probability of implantation (relative risk (RR) = 1.26, 95% CI: 1.16, 1.36), clinical pregnancy (RR = 1.32, 95% CI: 1.19, 1.46) and live birth (RR = 1.34; 95% CI: 1.15, 1.54). An IQR increase in 3 and 5-OH-BDE47 was associated with increased probabilities of implantation (RR = 1.52; 95% CI: 1.11, 2.09), clinical pregnancy (RR = 1.66; 95% CI: 1.17, 2.36), and live birth (RR = 1.61; 95% CI: 1.07, 2.40). When models were stratified by race (White (86%)/Other race (14%)), associations remained positive for White women, yet inverse associations were observed for Other race women. An IQR increase in BDE47 was associated with a 46% decreased probability of clinical pregnancy (95% CI: 0.31, 0.95) for Other race women.

LIMITATIONS, REASONS FOR CAUTION

Despite the long half-lives of PBDEs and OH-BDEs, exposure misclassification is possible for women who underwent multiple treatment cycles over several months or years. It is also possible another medium, such as follicular fluid would be optimal to characterize exposure. We also tested associations for multiple congeners and metabolites with multiple outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

Detections of serum concentrations of PBDEs and OH-BDEs were highest in the early years of the study and suggests that the phase-out of these compounds has contributed to a decrease in exposure. The negative associations found for PBDEs and IVF outcomes among other race women suggests the potential for racial disparity. Potential racial disparities in PBDE exposure and exploration of alternative flame retardants with reproductive health outcomes should be the focus of future investigations.

STUDY FUNDING/COMPETING INTEREST(S)

Funding for this research was supported by the National Institutes of Environmental Health Sciences (NIEHS) [R01 ES009718, ES022955, ES000002 and 009718T32ES007069]. The authors have no conflicts of interest.

Cell-free mtDNA level and its biomarker potency for ART outcome are different in follicular fluid of PCOS and non-PCOS women

INTRODUCTION

Lack of reliable biomarkers for estimating the outcome is one of the current gaps in ART. In this study, we assessed whether cell-free mitochondrial DNA within the follicular fluid (FF cf-mtDNA) of PCOS patients has biomarker applicability or not. Furthermore, probable involved mechanisms in the FF cf-mtDNA pathway were evaluated.

METHODS

The level of FF cf-mtDNA was compared between 50 PCOS patients and 50 women without any certain reproductive disorder, and analyzed for correlations with ART outcome. The associations between levels of FF cf-mtDNA and TFAM, POLG, and RNase H1 genes expression in mural granulosa cells (MGCs), as well as IL-6, and TNFα in follicular fluid (FF) were assessed.

RESULTS

We identified that FF cf-mtDNA level was significantly lower in PCOS women and was accompanied by a reduction in the expression of mtDNA biogenesis genes in MGCs of the patients. Although a significant association between FF cf-mtDNA level and ART outcome was observed in the control group, no correlation could be proved in the PCOS group. Moreover, the expression level of TFAM was negatively associated, while amounts of IL-6 and TNFα were positively correlated with FF cf-mtDNA level in both groups.

CONCLUSION

PCOS patients present a lower FF cf-mtDNA level in comparison with non-PCOS women. FF cf-mtDNA has biomarker applicability for ART outcome in women without any certain reproductive disorder, but not for those with PCOS. It seems that mtDNA packaging dysfunction results in elevated FF cf-mtDNA, and subsequent effects are triggered by increasing the inflammatory cytokines.

Low Doses of Resveratrol Protect Human Granulosa Cells from Induced-Oxidative Stress

Resveratrol is a phytoalexin present in plant-derived foods, including grape’s skin, cocoa, and peanuts. Evidence suggests that it has beneficial effects on human health because of its antioxidant properties. However, there is limited knowledge about the part played by resveratrol in ovarian function. In this paper, the influence of resveratrol on granulosa cells (GC) was evaluated. In addition to being the main estradiol producers, GC are in direct contact with the oocyte, playing a fundamental role in its growth and development. The cell line COV434 and human granulosa cells (hGC), obtained from women undergoing assisted reproductive technology (ART), were used. GC were treated with resveratrol (0.001–20 μM) at different times (24–72 h). Low concentrations of this compound suggest a protective role, as they tend to reduce ROS/RNS formation after inducement of stress. On the contrary, high concentrations of resveratrol affect GC viability and steroidogenic function. As it may act as a direct modulator of GC oxidative balance, this work may help to clarify the impact of resveratrol on GC and the usefulness of this antioxidant as adjunct to infertility treatments.

Equine maternal aging affects oocyte lipid content, metabolic function and developmental potential

Advanced maternal age is associated with a decline in fertility and oocyte quality. We used novel metabolic microsensors to assess effects of mare age on single oocyte and embryo metabolic function, which has not yet been similarly investigated in mammalian species. We hypothesized that equine maternal aging affects the metabolic function of oocytes and in vitro-produced early embryos, oocyte mitochondrial DNA (mtDNA) copy number, and relative abundance of metabolites involved in energy metabolism in oocytes and cumulus cells. Samples were collected from preovulatory follicles from young (≤14 years) and old (≥20 years) mares. Relative abundance of metabolites in metaphase II oocytes (MII) and their respective cumulus cells, detected by liquid and gas chromatography coupled to mass spectrometry, revealed that free fatty acids were less abundant in oocytes and more abundant in cumulus cells from old vs young mares. Quantification of aerobic and anaerobic metabolism, respectively measured as oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in a microchamber containing oxygen and pH microsensors, demonstrated reduced metabolic function and capacity in oocytes and day-2 embryos originating from oocytes of old when compared to young mares. In mature oocytes, mtDNA was quantified by real-time PCR and was not different between the age groups and not indicative of mitochondrial function. Significantly more sperm-injected oocytes from young than old mares resulted in blastocysts. Our results demonstrate a decline in oocyte and embryo metabolic activity that potentially contributes to the impaired developmental competence and fertility in aged females.

Shared aspects of mRNA expression associated with oocyte maturation failure in humans and rhesus monkeys indicating compromised oocyte quality

Oocyte maturation failure observed in assisted reproduction technology (ART) cycles can limit the number of quality oocytes obtained and present a pronounced barrier for some patients. The potential exists to use unmatured oocytes for ART through in vitro maturation. Understanding the molecular basis of oocyte maturation failure is pertinent to minimizing this loss of oocytes and considerations of whether such oocytes can be used safely for ART. We identified shared transcriptome abnormalities for rhesus monkey and human failed-to-mature (FTM) oocytes relative to healthy matured MII stage oocytes. We discovered that, although the number of shared affected genes was comparatively small, FTM oocytes in both species shared effects for several pathways and functions, including predicted activation of oxidative phosphorylation (OxPhos) with additional effects on mitochondrial function, lipid metabolism, transcription, nucleotide excision repair, endoplasmic reticulum stress, unfolded protein response, and cell viability. RICTOR emerged as a prominent upstream regulator with predicted inhibition across all analyses. Alterations in KDM5A, MTOR, MTORC1, INSR, CAB39L, and STK11 activities were implicated along with RICTOR in modulating mitochondrial activity and OxPhos. Defects in cell cycle progression were not a prominent feature of FTM oocytes. These results identify a common set of transcriptome abnormalities associated with oocyte maturation failure. While our results do not demonstrate causality, they indicate that fundamental aspects of cellular function are abnormal in FTM oocytes and raise significant concerns about the potential risks of using FTM oocytes for ART.

Mtor inhibition by INK128 extends functions of the ovary reconstituted from germline stem cells in aging and premature aging mice

Stem cell transplantation has been generally considered as promising therapeutics in preserving or recovering functions of lost, damaged, or aging tissues. Transplantation of primordial germ cells (PGCs) or oogonia stem cells (OSCs) can reconstitute ovarian functions that yet sustain for only short period of time, limiting potential application of stem cells in preservation of fertility and endocrine function. Here, we show that mTOR inhibition by INK128 extends the follicular and endocrine functions of the reconstituted ovaries in aging and premature aging mice following transplantation of PGCs/OSCs. Follicular development and endocrine functions of the reconstituted ovaries by transplanting PGCs into kidney capsule of the recipient mice were maintained by INK128 treatment for more than 12 weeks, in contrast to the controls for only about 4 weeks without receiving the mTOR inhibitors. Comparatively, rapamycin also can prolong the ovarian functions but for limited time. Furthermore, our data reveal that INK128 promotes mitochondrial function in addition to its known function in suppression of immune response and inflammation. Taken together, germline stem cell transplantation in combination with mTOR inhibition by INK128 improves and extends the reconstituted ovarian and endocrine functions in reproductive aging and premature aging mice.

In vitro rescue immature oocytes - a literature review

Immature oocytes retrieved from in vitro fertilization (IVF) and clinical in vitro maturation (IVM) is a common problem, especially in patients with advanced age, poor ovarian response (POR), or polycystic ovary syndrome (PCOS). Considering there is no common name to describe this group of oocytes, we suggest naming all of immature oocytes retrieved from IVF and clinical IVM cycles as 'Medical Unusable Oocytes' (MUO) as none of them will be used for subsequent treatment and will eventually be discarded. Scientists attempt to improve the clinical utilization rate of MUO instead of discarding them. Rescue IVM and mitochondria supplementation may be available approaches to mature MUO. We propose a specific definition of rescue IVM, namely the cultivation and maturation of immature oocytes in vitro collected from IVF cycles with human chorionic gonadotropin (hCG) trigger. Rescue IVM is usually mixed up with clinical IVM. Clarification of the differences between rescue IVM and clinical IVM is necessary. This manuscript aims to clarify the rather confusing IVM procedures and review existing methods of improving rescue IVM, currently available information on the success rate, and explore the future possibility of rescue IVM serving as a promising tool in reproductive medicine.

Embryo and Its Mitochondria

The mitochondria, present in almost all eukaryotic cells, produce energy but also contribute to many other essential cellular functions. One of the unique characteristics of the mitochondria is that they have their own genome, which is only maternally transmitted via highly specific mechanisms that occur during gametogenesis and embryogenesis. The mature oocyte has the highest mitochondrial DNA copy number of any cell. This high mitochondrial mass is directly correlated to the capacity of the oocyte to support the early stages of embryo development in many species. Indeed, the subtle energetic and metabolic modifications that are necessary for each of the key steps of early embryonic development rely heavily on the oocyte’s mitochondrial load and activity. For example, epigenetic reprogramming depends on the metabolic cofactors produced by the mitochondrial metabolism, and the reactive oxygen species derived from the mitochondrial respiratory chain are essential for the regulation of cell signaling in the embryo. All these elements have also led scientists to consider the mitochondria as a potential biomarker of oocyte competence and embryo viability, as well as a key target for future potential therapies. However, more studies are needed to confirm these findings. This review article summarizes the past two decades of research that have led to the current understanding of mitochondrial functions in reproduction

The Impact of Unbalanced Maternal Nutritional Intakes on Oocyte Mitochondrial Activity: Implications for Reproductive Function

Accumulating evidence on the effect of nutrition on reproduction is emerging from both animal and human studies. A healthy dietary pattern and nutrient supplementation, especially during the peri-conceptional period, might be helpful to achieve a live birth, although the mechanisms implicated are not fully understood. The endocrine system and the ooplasmic organelles apparatus, in particular the mitochondria, are clearly key elements during oogenesis and subsequent embryo development, and their proper functioning is associated with nutrition, even beyond maternal aging. Several studies in animal models have reported various adverse effects on mitochondria caused by unbalanced dietary intakes such as high fat diet, high fat high sugar diet, and low protein diet. The alterations produced might include mitochondrial intracellular distribution, content, structure, biogenesis, and functioning. This review summarizes the key role of mitochondria in female reproduction and the effects of different dietary macronutrient compositions on oocyte mitochondrial activity with their possible short-, medium-, and long-term effects.

Qualitative and Quantitative Ovarian and Peripheral Blood Mitochondrial DNA (mtDNA) Alterations: Mechanisms and Implications for Female Fertility

The reduction of female fertility over time is considered as a natural consequence of ovarian aging. The exact mechanism underlying this process is not fully elucidated. However, it is becoming increasingly evident that qualitative and quantitative mitochondrial genome alterations might play a relevant role. The former include mitochondrial DNA (mtDNA) damage caused by oxidative stress, the accumulation of acquired mtDNA mutations, the effects of inherited mtDNA mutations, and alterations in the mitochondrial stress response mechanism. The latter refer to alterations in the oocytes, granuolosa cells, and embryonic cells mtDNA content. The present review aims to investigate the evidence about: (1) the effect of qualitative and quantitative mtDNA alterations on female fertility, paying particular attention to those with a pathophysiology characterized by a relevant role of oxidative stress; (2) the use of oocytes, granulosa cells (GCs), embryonic cells, and peripheral blood cells mtDNA copy number as a female fertility surrogate biomarker; (3) experimental therapies tested to try to subvert the ovarian aging process with particular reference to antioxidant treatments.

Mitochondrial Dysfunction in Obesity and Reproduction

Mounting evidence suggests a role for mitochondrial dysfunction in the pathogenesis of many diseases, including type 2 diabetes, aging, and ovarian failure. Because of the central role of mitochondria in energy production, heme biosynthesis, calcium buffering, steroidogenesis, and apoptosis signaling within cells, understanding the molecular mechanisms behind mitochondrial dysregulation and its potential implications in disease is critical. This review will take a journey through the past and summarize what is known about mitochondrial dysfunction in various disorders, focusing on metabolic alterations and reproductive abnormalities. Evidence is presented from studies in different human populations, and rodents with genetic manipulations of pathways known to affect mitochondrial function.

Systemic Regulation of Host Energy and Oogenesis by Microbiome-Derived Mitochondrial Coenzymes

Gut microbiota have been shown to promote oogenesis and fecundity, but the mechanistic basis of remote influence on oogenesis remained unknown. Here, we report a systemic mechanism of influence mediated by bacterial-derived supply of mitochondrial coenzymes. Removal of microbiota decreased mitochondrial activity and ATP levels in the whole-body and ovary, resulting in repressed oogenesis. Similar repression was caused by RNA-based knockdown of mitochondrial function in ovarian follicle cells. Reduced mitochondrial function in germ-free (GF) females was reversed by bacterial recolonization or supplementation of riboflavin, a precursor of FAD and FMN. Metabolomics analysis of GF females revealed a decrease in oxidative phosphorylation and FAD levels and an increase in metabolites that are degraded by FAD-dependent enzymes (e.g., amino and fatty acids). Riboflavin supplementation opposed this effect, elevating mitochondrial function, ATP, and oogenesis. These findings uncover a bacterial-mitochondrial axis of influence, linking gut bacteria with systemic regulation of host energy and reproduction.

Clinical translation of mitochondrial replacement therapy in Canada: a qualitative study of stakeholders’ attitudes

Mitochondrial replacement therapy (MRT) in Canada is considered a criminal offense according to article 5(1)(f) of the Assisted Human Reproduction Act (AHRA) (2004). The Act prohibits any practice that modifies the genome of “a human being or in vitro embryo such that the alteration is capable of being transmitted to descendants.” We carried out 32 semi-structured interviews with clinicians, researchers, patient groups, egg donors, and members of the public to explore their attitudes toward the clinical implementation of MRT in Canada. Our interview guide was informed by the socio-ethical, legal, and scientific literature of MRT. We used a thematic analysis to identify and analyze emerging themes and sub-themes. Our findings were divided into five broad themes: ( i) an outdated criminal ban, ( ii) motives for using MRT, ( iii) terminology, ( iv) practical and theoretical risks and benefits, and ( v) the feasibility of clinical translation in Canada. Although the public and stakeholders’ views on the feasibility of foreseeable translation of MRT in Canadian clinics varied, there was consensus on conducting an overdue review of the current AHRA ban on MRT.

Mitochondria in Ovarian Aging and Reproductive Longevity

Mitochondrial dysfunction is one of the hallmarks of aging. Consistently mitochondrial DNA (mtDNA) copy number and function decline with age in various tissues. There is increasing evidence to support that mitochondrial dysfunction drives ovarian aging. A decreased mtDNA copy number is also reported during ovarian aging. However, the mitochondrial mechanisms contributing to ovarian aging and infertility are not fully understood. Additionally, investigations into mitochondrial therapies to rejuvenate oocyte quality, select viable embryos and improve mitochondrial function may help enhance fertility or extend reproductive longevity in the future. These therapies include the use of mitochondrial replacement techniques, quantification of mtDNA copy number, and various pharmacologic and lifestyle measures. This review aims to describe the key evidence and current knowledge of the role of mitochondria in ovarian aging and identify the emerging potential options for therapy to extend reproductive longevity and improve fertility.

Carnosic acid improves porcine early embryonic development by inhibiting the accumulation of reactive oxygen species

Carnosic acid (CA), a natural catechol rosin diterpene, is used as an additive in animal feeds and human foods. However, the effects of CA on mammalian reproductive processes, especially early embryonic development, are unclear. In this study, we added CA to parthenogenetically activated porcine embryos in an in vitro culture medium to explore the influence of CA on apoptosis, proliferation, blastocyst formation, reactive oxygen species (ROS) levels, glutathione (GSH) levels, mitochondrial membrane potential, and embryonic development-related gene expression. The results showed that supplementation with 10 μM CA during in vitro culture significantly improved the cleavage rates, blastocyst formation rates, hatching rates, and total numbers of cells of parthenogenetically activated porcine embryos compared with no supplementation. More importantly, supplementation with CA also improved GSH levels and mitochondrial membrane potential, reduced natural ROS levels in blastomeres, upregulated Nanog, Sox2, Gata4, Cox2, Itga5, and Rictor expression, and downregulated Birc5 and Caspase3 expression. These results suggest that CA can improve early porcine embryonic development by regulating oxidative stress. This study elucidates the effects of CA on early embryonic development and their potential mechanisms, and provides new applications for improving the quality of in vitro-developed embryos.

Early Life Oxidative Stress and Long-Lasting Cardiovascular Effects on Offspring Conceived by Assisted Reproductive Technologies: A Review

Assisted reproductive technology (ART) has rapidly developed and is now widely practised worldwide. Both the characteristics of ART (handling gametes/embryos in vitro) and the infertility backgrounds of ART parents (such as infertility diseases and unfavourable lifestyles or diets) could cause increased oxidative stress (OS) that may exert adverse influences on gametogenesis, fertilisation, and foetation, even causing a long-lasting influence on the offspring. For these reasons, the safety of ART needs to be closely examined. In this review, from an ART safety standpoint, the origins of OS are reviewed, and the long-lasting cardiovascular effects and potential mechanisms of OS on the offspring are discussed.

Bisphenol A-induced mechanistic impairment of decidualization

Decidualization is a crucial precedent to embryo implantation, as its impairment is a major contributor to female infertility and pregnancy complications. Unraveling the molecular mechanisms involved in the impairment of decidualization has been a subject of interest in the field of reproductive medicine. Evidence from several experimental settings show that exposure to bisphenol A (BPA), an endocrine-disrupting chemical, affects the expression of several molecules that are involved in decidualization. Both low and high doses of BPA impair decidualization through the dysregulation of estrogen (ER) and progesterone (PR) receptors. Exposure to low doses of BPA leads to decreased levels and activities of several antioxidant enzymes, increased activity of endothelial nitric oxide synthase (eNOS), and increased production of nitric oxide (NO) via the upregulation of ER and PR. Consequently, oxidative stress is induced and decidualization becomes impaired. On the other hand, exposure to high doses of BPA downregulates ER and PR and impairs decidualization through two distinct pathways. One is through the upregulation of early growth response-1 (EGR1) via increased phosphorylation of extracellular signal-regulated protein kinases 1 and 2; and the other is through a reduced serum glucocorticoid-induced kinase-1 (SGK1)-mediated downregulation of epithelial sodium channel-α and the induction of oxidative stress. Thus, regardless of the dose, BPA can impair decidualization to trigger infertility and pregnancy complications. This warrants the need to adopt lifestyles that will decrease the tendency of getting exposed to BPA.