Supplementation of maturation medium with CoQ10 enhances developmental competence of ovine oocytes through improvement of mitochondrial function

Clinical evidence of coenzyme Q10 pretreatment for women with diminished ovarian reserve undergoing IVF/ICSI: a systematic review and meta-analysis

BACKGROUND

To quantitatively evaluate the effect of coenzyme Q10 (CoQ10) pretreatment on outcomes of IVF or ICSI in women with diminished ovarian reserve (DOR) based on the existing randomized controlled trials (RCTs).

METHODS

Nine databases were comprehensively searched from database inception to November 01, 2023, to identify eligible RCTs. Reproductive outcomes of interest consisted of three primary outcomes and six secondary outcomes. The sensitivity analysis was adopted to verify the robustness of pooled results.

RESULTS

There were six RCTs in total, which collectively involved 1529 participants with DOR receiving infertility treatment with IVF/ICSI. The review of available evidence suggested that CoQ10 pretreatment was significantly correlated with elevated clinical pregnancy rate (OR = 1.84, 95%CI [1.33, 2.53], p = 0.0002), number of optimal embryos (OR = 0.59, 95%CI [0.21, 0.96], p = 0.002), number of oocytes retrieved (MD = 1.30, 95%CI [1.21, 1.40], p < 0.00001), and E2 levels on the day of hCG (SMD = 0.37, 95%CI [0.07, 0.66], p = 0.01), along with a reduction in cycle cancellation rate (OR = 0.60, 95%CI [0.44, 0.83], p = 0.002), miscarriage rate (OR = 0.38, 95%CI [0.15, 0.98], p = 0.05), total days of Gn applied (MD = -0.89, 95%CI [-1.37, -0.41], p = 0.0003), and total dose of Gn used (MD = -330.44, 95%CI [-373.93, -286.96], p < 0.00001). The sensitivity analysis indicated that our pooled results were robust.

CONCLUSIONS

These findings suggested that CoQ10 pretreatment is an effective intervention in improving IVF/ICSI outcomes for women with DOR. Still, this meta-analysis included relatively limited sample sizes with poor descriptions of their methodologies. Rigorously conducted trials are needed in the future.

Taurine, alpha lipoic acid and vitamin B6 ameliorate the reduced developmental competence of immature mouse oocytes exposed to methylglyoxal

Advanced glycation end products (AGEs) are the final products of the Maillard reaction, formed through the interaction of carbohydrates and proteins. Reactive dicarbonyl compounds such as methylglyoxal (MGO) serve as precursors for AGEs formation. Elevated levels of MGO/AGEs are observed in conditions like obesity, polycystic ovarian syndrome (PCOS), and diabetes, negatively impacting oocyte development. Previous studies have shown that hydrogen sulfide, a gasotransmitter with anti-AGEs effects, is produced in a process influenced by vitamin B6. R-α-lipoic acid (ALA) inhibits protein glycation and AGEs formation while stimulating glutathione (GSH) production. Taurine mitigates oxidative stress and acts as an anti-glycation compound, preventing in vitro glycation and AGEs accumulation. This study aimed to explore the ameliorative effects of a micronutrient support (Taurine, ALA and B6: TAB) on mouse oocytes challenged with MGO. Our results indicate that MGO reduces oocyte developmental competence, while TAB supplementation improves maturation, fertilization, and blastocyst formation rates. TAB also restores cell lineage allocation, redox balance and mitigates mitochondrial dysfunction in MGO-challenged oocytes. Furthermore, cumulus cells express key enzymes in the transsulfuration pathway, and TAB enhances their mRNA expression. However, TAB does not rescue MGO-induced damage in denuded oocytes, emphasizing the supportive role of cumulus cells. Overall, these findings suggest that TAB interventions may have significant implications for addressing reproductive dysfunctions associated with elevated MGO/AGEs levels. This study highlights the potential of TAB supplementation in preserving the developmental competence of COCs exposed to MGO stress, providing insights into mitigating the impact of dicarbonyl stress on oocyte quality and reproductive outcomes.

Mitochondria as therapeutic targets in assisted reproduction

Mitochondria are essential organelles with specialized functions, which play crucial roles in energy production, calcium homeostasis, and programmed cell death. In oocytes, mitochondrial populations are inherited maternally and are vital for developmental competence. Dysfunction in mitochondrial quality control mechanisms can lead to reproductive failure. Due to their central role in oocyte and embryo development, mitochondria have been investigated as potential diagnostic and therapeutic targets in assisted reproduction. Pharmacological agents that target mitochondrial function and show promise in improving assisted reproduction outcomes include antioxidant coenzyme Q10 and mitoquinone, mammalian target of rapamycin signaling pathway inhibitor rapamycin, and nicotinamide mononucleotide. Mitochondrial replacement therapies (MRTs) offer solutions for infertility and mitochondrial disorders. Autologous germline mitochondrial energy transfer initially showed promise but failed to demonstrate significant benefits in clinical trials. Maternal spindle transfer (MST) and pronuclear transfer hold potential for preventing mitochondrial disease transmission and improving oocyte quality. Clinical trials of MST have shown promising outcomes, but larger studies are needed to confirm safety and efficacy. However, ethical and legislative challenges complicate the widespread implementation of MRTs.

In vitro maturation of oocytes in light of ovarian mitochondrial improvement: effectiveness and safety

In vitro maturation of oocytes (IVM) represents an assisted reproductive technique that involves the minimal or absence of ovarian stimulation and is beneficial to specific groups of patients. These may include women with polycystic ovarian syndrome and/or patients who need a fertility preservation option before undergoing gonadotoxic treatment. However, when IVM is applied in cases where it is not recommended, it can be considered as an add-on technique, as described by the ESHRE Guideline Group on Female Fertility Preservation. Interestingly, IVM has not been proven yet to be as effective as conventional IVF in the laboratory, in terms of clinical pregnancy and live birth rates, while concerns have been raised for its long-term safety. As a result, both safety and efficacy of IVM remain still questionable and additional data are needed to draw conclusions.

Advancements in Understanding and Enhancing Antioxidant-Mediated Sperm Cryopreservation in Small Ruminants: Challenges and Perspectives

Cryopreservation poses significant challenges to the preservation of sperm integrity and function, particularly in small ruminants where cryodamage is pronounced. This review explores the molecular mechanisms underlying sperm cryodamage and strategies for improving cryopreservation outcomes, with a focus on the role of antioxidants. Cryopreservation-induced alterations in proteins and RNA transcripts critical for sperm function, including motility, capacitation, fertilization, and embryo development, are discussed. Proteomic, transcriptomic, and epigenomic advancements have provided valuable insights into these mechanisms, offering potential biomarkers for predicting sperm freezability and enhancing cryopreservation strategies. Combining technologies such as mass spectrometry and flow cytometry allows for a comprehensive understanding of molecular and cellular changes induced by the freezing-thawing process. However, challenges remain in optimizing cryoprotectant formulations and antioxidant supplementation to improve post-thaw sperm fertility. Further research is needed to explore a wider range of novel cryoprotectants, antioxidants, and proteins for cryopreservation media, as well as to validate their efficacy in enhancing sperm viability and function. Additionally, investigations into the effects of cryopreservation on RNA transcripts and epigenetic factors in small ruminant species are warranted to advance our understanding of sperm preservation. Overall, this review highlights the importance of antioxidants in mitigating cryodamage and underscores the need for continued research to refine cryopreservation protocols and improve reproductive outcomes in small ruminants.

Mechanisms of mitochondrial dysfunction in ovarian aging and potential interventions

Mitochondria plays an essential role in regulating cellular metabolic homeostasis, proliferation/differentiation, and cell death. Mitochondrial dysfunction is implicated in many age-related pathologies. Evidence supports that the dysfunction of mitochondria and the decline of mitochondrial DNA copy number negatively affect ovarian aging. However, the mechanism of ovarian aging is still unclear. Treatment methods, including antioxidant applications, mitochondrial transplantation, emerging biomaterials, and advanced technologies, are being used to improve mitochondrial function and restore oocyte quality. This article reviews key evidence and research updates on mitochondrial damage in the pathogenesis of ovarian aging, emphasizing that mitochondrial damage may accelerate and lead to cellular senescence and ovarian aging, as well as exploring potential methods for using mitochondrial mechanisms to slow down aging and improve oocyte quality.

Fibronectin 1 supports oocyte in vitro maturation in pigs

Oocyte in vitro maturation (IVM) based on the follicular fluid (FF) environment can exploit untapped resources, however, what FF factors regulate oocyte maturation remains unclear. This work demonstrated that serum and FF significantly promoted oocyte polar body extrusion (PBE) and subsequent embryo development, and FF was especially effective. Fibronectin 1 (FN1) was predicted as one potential candidate to regulate oocyte maturation by proteomics. FN1 transcription obviously decreased, and the protein expression significantly increased and migrated to plasma membrane or even outside during oocyte IVM. Treatment with 10 ng/mL FN1 significantly improved oocyte PBE rate. FN1 significantly upregulated the percentage of regular spindle morphology, downregulated the γ-H2AX level, decreased the levels of ROS and apoptosis, and increased GSH and mitochondrion contents by ameliorating the expression of corresponding genes. Moreover, FN1 significantly increased the p-PI3K level to enhance the activation of PI3K signaling pathway. In conclusion, this study discovers and confirms that FN1 is one factor in FF that significantly enhances oocyte maturation, and the underlying mechanism is that FN1 ameliorates oocyte nuclear and cytoplasmic maturation by promoting the activation of PI3K signaling pathway.

The role of CoQ10 in embryonic development

Coenzyme Q10 (CoQ10) is a natural component widely present in the inner membrane of mitochondria. CoQ10 functions as a key cofactor for adenosine triphosphate (ATP) production and exhibits antioxidant properties in vivo. Mitochondria, as the energy supply center of cells, play a crucial role in germ cell maturation and embryonic development, a complicated process of cell division and cellular differentiation that transforms from a single cell (zygote) to a multicellular organism (fetus). Here, we discuss the effects of CoQ10 on oocyte maturation and the important role of CoQ10 in the growth of various organs during different stages of fetal development. These allowed us to gain a deeper understanding of the pathophysiology of embryonic development and the potential role of CoQ10 in improving fertility quality. They also provide a reference for further developing its application in clinical treatments.

The effect of Coenzyme Q10 on mitochondrial biogenesis in mouse ovarian follicles during in vitro culture

The aim of this research was to investigate the effect of Coenzyme Q10 (CoQ10) on the expression of the Transcription Factor A Mitochondrial (Tfam) gene and mtDNA copy number in preantral follicles (PFs) of mice during in vitro culture. To conduct this experimental study, PFs were isolated from 14-day-old National Medical Research Institute mice and cultured in the presence of 50 µm CoQ10 for 12 days. On the 12th day, human chorionic gonadotropin was added to stimulate ovulation. The fundamental parameters, including preantral follicle developmental rate and oocyte maturation, were evaluated. Additionally, the Tfam gene expression and mtDNA copy number of granulosa cells and oocytes were assessed using the real-time polymerase chain reaction. The results revealed that CoQ10 significantly increased the diameter of PFs, survival rate, antrum formation, and metaphase II (MII) oocytes (P < 0.05). Moreover, in the CoQ10-treated groups, the Tfam gene expression in granulosa cells and oocytes increased considerably compared with the control group. The mtDNA copy number of granulosa cells and oocytes cultured in the presence of CoQ10 was substantially higher compared with the control groups (P < 0.05). The addition of CoQ10 to the culture medium enhances the developmental competence of PFs during in vitro culture by upregulating Tfam gene expression and increasing mtDNA copy number in oocyte and granulosa cells.

Spatiotemporal Distribution and Function of Mitochondria in Oocytes

Mitochondria are energy provider organelles in eukaryotic cells that contain their own specific genome. This review addresses structural and functional properties of mitochondria, focusing on recent discoveries about the changes in quality and number of mitochondria per cell during oocyte development. We highlight how oocyte mitochondria exhibit stage-specific morphology and characteristics at different stages of development, in sharp contrast to the elongated mitochondria present in somatic cells. We then evaluate the latest transcriptomic data to elucidate the complex functions of mitochondria during oocyte maturation and the impact of mitochondria on oocyte development. Finally, we describe the methodological progress of mitochondrial replacement therapy to rescue oocytes with developmental disorders or mitochondrial diseases, hoping to provide a guiding reference to future clinical applications.

Exploring the impact of heat stress on oocyte maturation and embryo development in dairy cattle using a culture medium supplemented with vitamins E, C, and coenzyme Q10

Heat stress is a significant factor affecting the fertility of dairy cattle due to the generation of free radicals. In assisted reproductive techniques, the inclusion of protective antioxidants becomes crucial to mitigate potential cellular damage. This study aimed to explore the impact of supplementing vitamins E, C, and coenzyme Q10 into the oocyte culture medium, with the goal of ameliorating the adverse effects of heat stress on oocyte maturation and embryo development in dairy cattle. A group of fifty Holstein dairy cows were synchronized, and their oocytes were harvested using the ovum pick-up method. High-quality oocytes were subjected to in vitro maturation (IVM) and in vitro fertilization (IVF) procedures, utilizing a culture medium containing, no supplements (Group 1), 100 μM of vitamins E (Group 2) and C (Group 3), along with 50 μM of coenzyme Q10 (Group 4). The ensuing zygotes were cultured, and the ensuing embryos were evaluated for blastocyst formation by the seventh day. An analysis of the blastocysts' inner cell mass (ICM) and trophectoderm (TE) cells was also conducted. The findings revealed that the group receiving supplementation of vitamin E and coenzyme Q10 exhibited significantly higher maturation and cleavage rates in comparison to both the control and the vitamin C groups. Furthermore, the count of ICM, TE, and blastocyst cells was notably elevated in the vitamin E supplemented group when compared to the control group. In summary, the effectiveness of vitamin E in enhancing IVM, IVF, and embryo development under conditions of heat stress surpassed that of vitamin C and coenzyme Q10.

Mito-Q supplementation of in vitro maturation or in vitro culture medium improves maturation of buffalo oocytes and developmental competence of cloned embryos by reducing ROS production

Mito-Q is a well-known mitochondria-specific superoxide scavenger. To our knowledge, the effect of Mito-Q on buffalo oocyte maturation and developmental competency of cloned embryos has not been examined. To investigate the effects of Mito-Q on the in vitro maturation (IVM) of buffalo oocytes and the developmental competence of cloned embryos, different concentration of Mito-Q were supplemented with IVM (0, 0.1, 0.5, 1, 2 μM) and in vitro culture (IVC) medium (0, 0.1 μM). Supplementation of IVM medium with 0.1 μM Mito-Q significantly (P ≤ 0.05) increased the cumulus expansion, nuclear maturation, mitochondrial membrane potential (MMP) and antioxidants genes (GPX1 and SOD2) expression and effectively reduced ROS production leading to a significant improvement in the maturation rate of buffalo oocytes. Further, the supplementation of 0.1 μM Mito-Q in IVC medium promotes the cleavage and blastocyst rate significantly over the control. Mito-Q supplementation improves (P ≤ 0.05) MMP, antioxidant gene (GPX1) expression and reduced the ROS level and apoptosis related genes (caspase 9) expression in cloned blastocysts. In conclusion, the present study demonstrated that the supplementation of 0.1 μM Mito-Q in IVM and IVC media exerts a protective role against oxidative stress by reducing ROS production and improving MMP, fostering improved maturation of buffalo oocytes and enhanced developmental competence of cloned embryos. These findings contribute valuable insights into the optimization of assisted reproductive technologies protocols for buffalo breeding and potentially offer novel strategies to enhance reproductive outcomes in livestock species.

Coenzyme Q10 Stimulate Reproductive Vatality

Female infertility and pregnancy maintenance are associate with various factors, including quantity and quality of oocytes, genital inflammation, endometriosis, and other diseases. Women are even diagnosed as unexplained infertility or unexplained recurrent spontaneous abortion when failed to achieve pregnancy with current treatment, which are urgent clinical issues need to be addressed. Coenzyme Q10 (CoQ10) is a lipid-soluble electron carrier in the mitochondrial electron transport chain. It is not only essential for the mitochondria to produce energy, but also function as an antioxidant to maintain redox homeostasis in the body. Recently, the capacity of CoQ10 to reduce oxidative stress (OS), enhance mitochondrial activity, regulate gene expression and inhibit inflammatory responses, has been discovered as a novel adjuvant in male reproductive performance enhancing in both animal and human studies. Furthermore, CoQ10 is also proved to regulate immune balance, antioxidant, promote glucose and lipid metabolism. These properties will bring highlight for ovarian dysfunction reversing, ovulation ameliorating, oocyte maturation/fertilization promoting, and embryonic development optimizing. In this review, we systematically discuss the pleiotropic effects of CoQ10 in female reproductive disorders to investigate the mechanism and therapeutic potential to provide a reference in subsequent studies.

Effects of the addition of insulin-transferrin-selenium (ITS) and/or metformin to the in vitro maturation of porcine oocytes on cytoplasmic maturation and embryo development

CONTEXT

One of the main problems of porcine in vitro maturation (IVM) is incomplete cytoplasmatic maturation. Nuclear and cytoplasmic maturation will determine the future success of fertilisation and embryo development. Insulin-transferrin-selenium (ITS) has insulin-like and antioxidant effects, and metformin (M) is an insulin-sensitiser and antioxidant drug.

AIMS

To assess the effects of adding ITS and/or M in porcine IVM media on cytoplasmic maturation and early embryo development.

METHODS

Cumulus -oocyte complexes (COC) were IVM with M (10-4 M), ITS (0.1% v/v), M+ITS or no adding (Control).

KEY RESULTS

ITS increased glucose consumption compared to Control and M (P <0.01), and M+ITS did not differ from ITS or Control. Redox balance: M, ITS and M+ITS increased glutathione (P <0.01) and decreased lipid peroxidation (P <0.005). The viability of cumulus cells by flow cytometry increased with M (P <0.005) and decreased with ITS (P <0.001); M+ITS did not differ from Control. After IVF, M increased penetration and decreased male pronucleus (P <0.05). Embryo development: cleavage increased with M (P <0.05), and blastocysts increased with ITS and M+ITS (P <0.05). The number of blastocyst cells increased with ITS (P <0.05).

CONCLUSIONS

Adding ITS and M+ITS to porcine IVM media benefits embryo development to blastocysts, but ITS alone has better effects than M+ITS.

IMPLICATIONS

ITS is an excellent tool to improve IVM and embryo development after IVF in pigs.

Beneficial antioxidant effects of Coenzyme Q10 on reproduction

This chapter focuses on preclinical and clinical studies conducted in recent years that contribute to increasing knowledge on the role of Coenzyme Q10 in female reproductive health. General aspects of CoQ10, such as its role as an antioxidant and in mitochondrial bioenergetics are considered. The age-dependent decline in human female reproductive potential is associated with cellular mitochondrial dysfunction and oxidative stress, and in some cases accompanied by a decrease in CoQ10 levels. Herein, we discuss experimental and clinical evidence on CoQ10 protective effects on reproductive health. We also address the potential of supplementation with this coenzyme to rescue reprotoxicity induced by exposure to environmental xenobiotics. This review not only contributes to our general understanding of the effects of aging on female reproduction but also provides new insights into strategies promoting reproductive health. The use of CoQ10 supplementation can improve reproductive performance through the scavenging of reactive oxygen species and free radicals. This strategy can constitute a low-risk and low-cost strategy to attenuate the impact on fertility related to aging and exposure to environmental chemicals.

In Vitro Maturation of Oocytes Retrieved from Ovarian Tissue: Outcomes from Current Approaches and Future Perspectives

In vitro maturation (IVM) of transvaginally aspirated immature oocytes is an effective and safe assisted reproductive treatment for predicted or high responder patients. Currently, immature oocytes are also being collected from the contralateral ovary during laparoscopy/laparotomy and even ex vivo from the excised ovary or the spent media during ovarian tissue preparation prior to ovarian cortex cryopreservation. The first live births from in vitro-matured ovarian tissue oocytes (OTO-IVM) were reported after monophasic OTO-IVM, showing the ability to achieve mature OTO-IVM oocytes. However, fertilisations rates and further embryological developmental capacity appeared impaired. The introduction of a biphasic IVM, also called capacitation (CAPA)-IVM, has been a significant improvement of the oocytes maturation protocol. However, evidence on OTO-IVM is still scarce and validation of the first results is of utmost importance to confirm reproducibility, including the follow-up of OTO-IVM children. Differences between IVM and OTO-IVM should be well understood to provide realistic expectations to patients.

The Role of Mitochondria in Oocyte Maturation

With the nucleus as an exception, mitochondria are the only animal cell organelles containing their own genetic information, called mitochondrial DNA (mtDNA). During oocyte maturation, the mtDNA copy number dramatically increases and the distribution of mitochondria changes significantly. As oocyte maturation requires a large amount of ATP for continuous transcription and translation, the availability of the right number of functional mitochondria is crucial. There is a correlation between the quality of oocytes and both the amount of mtDNA and the amount of ATP. Suboptimal conditions of in vitro maturation (IVM) might lead to changes in the mitochondrial morphology as well as alternations in the expression of genes encoding proteins associated with mitochondrial function. Dysfunctional mitochondria have a lower ability to counteract reactive oxygen species (ROS) production which leads to oxidative stress. The mitochondrial function might be improved with the application of antioxidants and significant expectations are laid on the development of new IVM systems supplemented with mitochondria-targeted reagents. Different types of antioxidants have been tested already on animal models and human rescue IVM oocytes, showing promising results. This review focuses on the recent observations on oocytes’ intracellular mitochondrial distribution and on mitochondrial genomes during their maturation, both in vivo and in vitro. Recent mitochondrial supplementation studies, aiming to improve oocyte developmental potential, are summarized.

Coenzyme Q10 ameliorates the quality of mouse oocytes during in vitro culture

Oxidative stress causes several diseases and dysfunctions in cells, including oocytes. Clearly, oxidative stress influences oocyte quality during in vitro maturation and fertilization. Here we tested the ability of coenzyme Q10 (CoQ10) to reduce reactive oxygen species (ROS) and improve mouse oocyte quality during in vitro culture. Treatment with 50 μM CoQ10 efficiently reduced ROS levels in oocytes cultured in vitro. The fertilizable form of an oocyte usually contains a cortical granule-free domain (CGFD). CoQ10 enhanced the ratio of CGFD-oocytes from 35% to 45%. However, the hardening of the zona pellucida in oocytes was not affected by CoQ10 treatment. The in vitro maturation capacity of oocytes, which was determined by the first polar body extrusion, was enhanced from 48.9% to 75.7% by the addition of CoQ10 to the culture medium. During the parthenogenesis process, the number of two-cell embryos was increased by CoQ10 from 43.5% to 67.3%. Additionally, treatment with CoQ10 increased the expression of Bcl2 and Sirt1 in cumulus cells. These results suggested that CoQ10 had a positive effect on ROS reduction, maturation rate and two-cell embryo formation in mouse oocyte culture.

The Effect of Sodium Selenite on Expression of Mitochondrial Transcription Factor A during In Vitro Maturation of Mouse Oocyte

BACKGROUND

The aim of the present study was to investigate the effect of Sodium Selenite (SS) supplemented media on oocyte maturation, expression of mitochondrial transcription factor A (TFAM) and embryo quality.

METHODS

Mouse Germinal Vesicle (GV) oocytes were collected after administration of Pregnant Mare Serum Gonadotropin (PMSG); in experimental group 1, oocytes were cultured and then subjected for in vitro maturation in the absence of SS, and in experimental group 2, they were matured in vitro in the presence of 10 ng/ml of SS up to 16 hr. The control group included MII oocytes obtained from the fallopian tubes after ovarian stimulation with PMSG, followed by human chorionic gonadotropin. Then, the expression of TFAM in MII oocytes in all three groups was investigated using real-time RT-PCR. The fertilization and embryo developmental rates were assessed, and finally the quality of the blastocysts was evaluated using propidium iodide staining.

RESULTS

The oocyte maturation rate to MII stage in SS treated group was significantly higher than non-treated oocytes (75.65 vs. 68.17%, p<0.05). Also, the rates of fertilization, embryo development to blastocyst stage as well as the cell number of blastocyst in SS supplemented group were higher than other experimental group (p<0.05). There was a significant decrease in TFAM gene expression in both in vitro groups compared to the group with in vivo obtained oocytes (p<0.05). Moreover, there was a significant increase in TFAM gene expression in oocytes that matured in the presence of SS compared to that of the group without SS (p<0.05).

CONCLUSION

Supplementation of oocyte maturation culture media with SS improved the development rate of oocytes and embryo and also enhanced TFAM expression in MII oocytes which can affect the mitochondrial biogenesis of oocytes.

Mitochondria: emerging therapeutic strategies for oocyte rescue

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

Treatment of cattle oocytes with C-type natriuretic peptide before in vitro maturation enhances oocyte mitochondrial function

The present study was conducted to evaluate the effects in vitro on oocyte mitochondrial function of C-type natriuretic peptide (CNP) when treatments were imposed before in vitro maturation (IVM). Immature oocytes were either directly matured in vitro for 24 h (Control, no pre-IVM), or cultured in basic medium not supplemented or supplemented with CNP (100 nM) (Control pre-IVM and CNP pre-IVM, respectively) for 6 h, followed by IVM for 24 h. The results indicated treatment with CNP before IVM affected patterns of distribution of mitochondria, increased the mitochondrial content, membrane potential, and decreased the ROS content in cattle oocytes before and after IVM. Furthermore, treatment of immature cattle oocytes with CNP before IVM induced marked increases in the relative abundance of mRNA transcripts and proteins related to mitochondria development and antioxidative defense mechanisms. Treatment with CNP before oocyte IVM also resulted in an enhanced relative abundance of sirtuin-1 (SIRT1) mRNA transcript in cattle oocytes. Taken together, these results provide evidence that treatment of cattle oocytes with CNP before IVM improved mitochondrial function and antioxidant defense mechanisms in cattle oocytes. Findings in the present study provide insights into the potential mechanisms by which CNP has positive effects on oocyte cytoplasmic organelles, specifically mitochondria.

CoQ10 improves meiotic maturation of pig oocytes through enhancing mitochondrial function and suppressing oxidative stress

Coenzyme Q10 (CoQ10) is essential to many fundamental biological processes. However, the effect of CoQ10 on meiotic maturation of pig oocytes still remains elusive. In the present study we aimed to understand the effects of CoQ10 on porcine oocyte maturation, by supplementing different concentrations of CoQ10 (25, 50 and 100 μM) into the maturation medium. We showed that CoQ10 at 50 μM had better capacity to promote the nuclear maturation of pig oocytes derived from both small and large antral follicles. Though the cleavage and blastocyst rates of parthenotes stayed stable, 50 μM CoQ10 treatment could accelerate the development of parthenotes to blastocyst stage, and increase the average cell number of blastocyst. For cumulus-oocyte complexes from large antral follicles categorized by the brilliant cresyl blue (BCB) test, 50 μM CoQ10 treatment could specifically promote the nuclear maturation of poor-quality oocytes in the BCB-negative group. Mitochondrial function of oocytes treated by 50 μM CoQ10 could be boosted, through increasing the levels of mitochondrial membrane potential, ATP production and CoQ6, and changing the pattern of mitochondrial distribution as well. Moreover, 50 μM CoQ10 treatment suppressed the level of reactive oxygen species and reduced the percentage of oocytes with early apoptosis signal. Taken together, CoQ10 could improve the meiotic maturation of pig oocytes, especially for poor-quality oocytes, mainly through enhancing mitochondrial function and suppressing oxidative stress to reduce apoptosis.

Single cell RNA-seq reveals molecular pathways altered by 7, 12-dimethylbenz[a]anthracene treatment on pig oocytes

Oocytes of better quality and developmental competence are highly demanded, which is affected by many intrinsic and external factors, including environmental pollutants. We have previously demonstrated that 7, 12-dimethylbenz [a]anthracene (DMBA) reduces the developmental competence of porcine oocytes, by desynchronizing nuclear and ooplasmic maturation. However, the underlying molecular mechanism remains obscure. Here we performed single cell RNA-seq to study the transcriptome changes in DMBA-treated porcine MII oocytes, and identified 19 protein-coding genes and 156 novel long non-coding RNAs (lncRNAs) with abundance to be significantly different (P < 0.05), which enriched in signaling pathways such as glycosphingolipid biosynthesis, nicotine addiction, basal transcription factors and nucleotide excision repair. RT-qPCR on oocyte pools confirmed ornithine aminotransferase (Oat) and serine/arginine-rich splicing factor 4 (Srsf4) to be significantly up- and down-regulated, respectively (P < 0.05). Treating porcine COCs with MAPK and PLC pathway inhibitors suppressed DMBA's effects on increasing PB1 extrusion rate. In addition, DMBA co-incubation with 250 μM vitamin C derivative (l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate, AA2P) and 100 μM co-enzyme Q10 (CoQ10) could significantly reduce the DMBA-induced high ROS level, and partially alleviate the DMBA-induced high PB1 rate, whereas the cleavage and blastocyst rates of parthenotes derived from treated mature oocytes remained to be low. Collectively, our findings indicate that single cell RNA-seq can help reveal the dynamics of molecular signaling pathways for porcine oocytes treated by DMBA, and supplement of anti-oxidative reagents could not sufficiently rescue DMBA-induced defects of porcine 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.

Long noncoding RNA 2193 regulates meiosis through global epigenetic modification and cytoskeleton organization in pig oocytes

Long noncoding RNAs (lncRNAs) regulate a variety of physiological and pathological processes. However, the biological function of lncRNAs in mammalian germ cells remains largely unexplored. Here we identified one novel lncRNA (lncRNA2193) from single-cell RNA sequencing performed on porcine oocytes and investigated its function in oocyte meiosis. During in vitro maturation (IVM), from germinal vesicle (GV, 0 hr), GV breakdown (GVBD, 24 hr), to metaphase II stage (MII, 44 hr), the transcriptional abundance of lncRNA2193 remained stable and high. LncRNA2193 interference by small interfering RNA microinjection into porcine GV oocytes could significantly inhibit rates of GVBD and the first polar body extrusion, but enhance the rates of oocytes with a nuclear abnormality. Moreover, lncRNA2193 knockdown disturbed cytoskeletal organization (F-actin and spindle), and decreased DNA 5-methylcytosine (5mC) and histone trimethylation (H3K4me3, H3K9me3, H3K27me3, and H3K36me3) levels. The lncRNA2193 downregulation induced a decrease of 5mC level could be partially due to the reduction of DNA methyltransferase 3A and 3B, and the elevation of 5mC-hydroxylase ten-11 translocation 2 (TET2). After parthenogenetic activation of MII oocytes, parthenotes exhibited higher fragmentation but lower cleavage rates in the lncRNA2193 downregulated group. However, lncRNA2193 interference performed on mature MII oocytes and parthenotes at 1-cell stage did not affect the cleavage and blasctocyst rates of pathenotes. Taken together, lncRNA2193 plays an important role in porcine oocyte maturation, providing more insights for relevant investigations on mammalian germ cells.

Source and Follicular Fluid Treatment During the In Vitro Maturation of Recipient Oocytes Affects the Development of Cloned Pig Embryo

Pig cloning technique is valuable in agriculture, biomedicine, and life sciences. However, the full-term developmental efficiency of cloned pig embryos is only about 1%, which limits pig cloning application. The quality of recipient oocytes greatly affects the developmental competence of cloned pig embryos. Thus, this study investigated the effects of a recipient oocyte source (in vivo matured [IVVM] oocytes vs. slaughter house-derived in vitro matured [IVTM] oocytes), and follicular liquid treatment (slaughter house-derived immature follicle-derived fluid [IFF] vs. in vivo-matured follicle-derived fluid [MFF]) during the in vitro maturation (IVM) of oocytes on the development of the cloned pig embryos. Our results showed that using IVVM oocytes to replace IVTM oocytes as recipient oocytes, and using 10% MFF IVM medium to replace 10% IFF IVM medium could enhance the development of the cloned pig embryos. IFF and MFF contained different levels of oocyte quality-related proteins, resulting in different oocyte quality-related gene expression levels and reactive oxygen species levels between the 10% MFF medium-cultured oocytes and 10% IFF medium-cultured oocytes. This study provided useful information for enhancing the pig cloning efficiency by improving the quality of recipient oocytes.

Ubiquinol-10 delays postovulatory oocyte aging by improving mitochondrial renewal in pigs

Ubiquinol-10, the reduced form of coenzyme Q10, protects mammalian cells from oxidative damage and enhances mitochondrial activity. However, the protective effect of ubiquinol-10 on mammalian oocytes is not well understood. In this study, we investigated the effect of ubiquinol-10 on porcine oocytes during postovulatory aging. Metaphase II oocytes were selected as fresh oocytes and further cultured for 48 h with different concentrations of ubiquinol-10 (0–400 μM) in vitro as a postovulatory aging model. After choosing the optimal concentration of ubiquinol-10 (100 μM) that maintained oocyte morphology and developmental competence during the progression of aging, the oocytes were randomly divided into five groups: fresh, control-24 h, ubiquinol-24 h, control-48 h, and ubiquinol-48 h. The results revealed that ubiquinol-10 significantly prevented aging-induced oxidative stress, GSH reduction, cytoskeleton impairment, apoptosis, and autophagy. Mitochondrial biogenesis (SIRT1 and PGC-1α) and mitophagy (PINK1 and PARKIN)-related proteins were decreased during aging. Addition of ubiquinol-10 prevented the aging-induced reduction of these proteins. Consequently, although mitochondrial content was decreased, the number of active mitochondria and ATP level were significantly increased upon treatment with ubiquinol-10. Thus, ubiquinol-10 has beneficial effects on porcine postovulatory aging oocytes owing to its antioxidant properties and ability to promote mitochondrial renewal.