Mitochondrial Activity and Morphology in Developing Porcine Oocytes and Pre-implantation Non-Cultured and Cultured Embryos

Aggressive sperm immobilization improves reproductive outcomes in patients with suboptimal semen parameters and previous ICSI fertilization failure

Intracytoplasmic sperm injection (ICSI) is the most effective procedure to resolve male infertility, enhancing overall fertilization and pregnancy outcomes. However, it is important to note that fertilization failure (FF) can still occur in a few cases after ICSI. This study aims to introduce a specialized technique of aggressive sperm immobilization for ICSI and evaluate its impact on reproductive outcomes in cases involving prior fertilization failure. All infertile couples with male partners having suboptimal semen samples and previous ICSI fertilization failure were evaluated using retrospective data from National Taiwan tertiary university hospital (NTUH) between January 2016 and February 2022. Fertilization failure in our study was defined as less than 30% fertilization rate (FR, the number of normally fertilized oocytes divided by the total number of injected mature oocytes). Data involving both standard (routine procedure) and aggressive sperm immobilization (SI) techniques during different ICSI cycles were included in this study. Standard and aggressive SI methods were performed by compressing the distal half tail of the spermatozoa ≦ 5 and 15 times prior to ICSI respectively. Generalized estimating equations analysis were applied to compare the clinical outcomes between two procedures. Overall, data from 23 infertile couples who had undergone 65 ICSI cycles (31 standard SI with low fertilization rate and 34 aggressive SI) were included in the study. The average FR in the ICSI cycles with standard SI and aggressive SI were 23.6 ± 23.1% and 49.5 ± 31.8 respectively (P = 0.0002). The majority of embryos were transferred at the day 3 stage, with an average number transferred of 2.6 ± 0.9 in the aggressive SI group and 1.9 ± 0.9 in the standard group. The number of embryos transferred per transfer cycle was higher in the aggressive SI (P = 0.015), whereas the number of good-quality embryos was similar between the two procedures (P = 0.44). There were one and seven live births from the standard SI cycles and aggressive SI cycles respectively. In conclusion, aggressive SI was associated with a significantly higher FR, resulting in more available embryos for transfer without compromising embryo quality. Therefore, this specialized technique improved pregnancy outcome among infertile couples with a previous ICSI-FF. It can be a safe, economic, and effective method to improve the assisted reproductive technologies outcomes for infertile patients affected by previous ICSI-FF.

KLF4 facilitates chromatin accessibility remodeling in porcine early embryos

Chromatin accessibility remodeling driven by pioneer factors is critical for the development of early embryos. Current studies have illustrated several pioneer factors as being important for agricultural animals, but what are the pioneer factors and how the pioneer factors remodel the chromatin accessibility in porcine early embryos is not clear. By employing low-input DNase-seq (liDNase-seq), we profiled the landscapes of chromatin accessibility in porcine early embryos and uncovered a unique chromatin accessibility reprogramming pattern during porcine preimplantation development. Our data revealed that KLF4 played critical roles in remodeling chromatin accessibility in porcine early embryos. Knocking down of KLF4 led to the reduction of chromatin accessibility in early embryos, whereas KLF4 overexpression promoted the chromatin openness in porcine blastocysts. Furthermore, KLF4 deficiency resulted in mitochondrial dysfunction and developmental failure of porcine embryos. In addition, we found that overexpression of KLF4 in blastocysts promoted lipid droplet accumulation, whereas knockdown of KLF4 disrupted this process. Taken together, our study revealed the chromatin accessibility dynamics and identified KLF4 as a key regulator in chromatin accessibility and cellular metabolism during porcine preimplantation embryo development.

The formins inhibitor SMIFH2 inhibits the cytoskeleton dynamics and mitochondrial function during goat oocyte maturation

The cytoskeleton plays a crucial role in facilitating the successful completion of the meiotic maturation of oocytes. Its influence extends to the process of oocyte nuclear maturation and the proper functioning of various organelles during cytoplasmic maturation. The formin family of proteins plays a crucial role in the molecular regulation of cytoskeletal assembly and organization; however, its role in goat oocytes are not fully understood. Our study examined the inhibition of formins activity, which revealed its crucial role in the maturation of goat oocytes. We observed that the inhibition of formins resulted in meiotic defects in goat oocytes, as evidenced by the hindered extrusion of polar bodies and the expansion of cumulus cells. Additionally, the oocytes exhibited altered actin dynamics and compromised spindle/chromosome structure upon formins inhibition. The results of the transcriptomic analysis highlighted a noteworthy alteration in the mRNA levels of genes implicated in mitochondrial functions and oxidative phosphorylation in formins inhibited oocytes. Validation experiments provided evidence that the meiotic defects observed in these oocytes were due to the excessive early apoptosis induced by reactive oxygen species (ROS). Our findings demonstrate that the involvement of formins in sustaining the cytoskeletal dynamics and mitochondrial function is crucial for the successful meiotic maturation of goat oocytes.

The Impact of Arp2/3 Complex Inhibition on Cytoskeleton Dynamics and Mitochondrial Function during Goat Oocyte Meiosis

F-actin is of critical importance in oocyte meiotic maturation. Actin assembly and its dynamics are mainly regulated by actin nucleation factors. The actin-related protein complex 2/3 (Arp2/3) is responsible for the organization of F-actin filaments. However, the role of Arp2/3 complex in goat oocytes has not been fully elucidated. Our findings demonstrate that Arp2/3 complex activity is necessary for the maturation of goat oocytes. The Arp2/3 complex-specific inhibitor CK666 impairs the maturation of goat oocytes and alters the genes associated with cumulus expansion, both of which suggest that normal meiosis is affected. Arp2, one of the subunits of the Arp2/3 complex, was found to be mainly accumulated at the oocyte cortex and to co-localize with F-actin during goat oocyte maturation in our results. Thus, we further investigated the cytoskeleton dynamics and found that Arp2/3 complex inhibition disrupts the F-actin assembly and spindle organization. Further analysis revealed that, in addition to direct effects on the cytoskeleton, Arp2/3 complex could also induce ROS accumulation and oxidative stress by disrupting mitochondrial distribution and function, ultimately increasing the rate of early apoptosis in goat oocytes. Our study provides evidence that the Arp2/3 complex is a key regulator of goat oocyte maturation through its regulation of the cytoskeleton dynamics and mitochondrial function.

N-Acetyl cysteine reduces the levels of reactive oxygen species and improves in vitro maturation of oocytes from medium-sized bovine antral follicles

This study aims to evaluate the effects of N-acetylcysteine (NAC) on bovine oocyte maturation, mitochondrial activity and transzonal projections (TZP), as well as on the levels of reactive oxygen species (ROS) and messenger RNA (mRNA) for catalase (CAT) superoxide dismutase (SOD), periredoxin-6 (Prdx6), glutathione peroxidase (GPx), growth and differentiation factor-9 (GDF9), histone H1Foo, cyclin B1 (CCNB1) and c-Mos. Bovine cumulus-oocyte complexes (COC) of medium-sized antral follicles (3.0-6.0 mm) were prematured in TCM-199 for 8 h at 38.5°C in 5% CO₂. After prematuration in the presence of forskolin and C-type natriuretic peptide, COCs were matured in TCM-199 alone or with 0.1, 0.5 or 2.5 mM NAC. Then, oocytes were classified according to the stage of chromatin. Furthermore, mitochondrial activity and intracellular levels of ROS and TZP were also evaluated. The levels of mRNAs for CAT, SOD, Prdx6, GPx, GDF9, H1Foo, CCNB1 and c-Mos were evaluated using real-time polymerase chain reaction (RT-PCR). The results showed that NAC significantly increased the percentages of oocytes with resumption of meiosis when compared with those oocytes matured in control medium. Oocytes had homogeneous mitochondrial distribution, and those cultured with 0.1 and 0.5 mM NAC had lower levels of ROS when compared with the control. In addition, 0.5 mM NAC reduced TZP and the levels of mRNA for CCNB1. In contrast, NAC did not influence the expression of CAT, GPx, Prdx6, SOD, GDF9, H1Foo, and c-Mos. In conclusion, 0.5 mM NAC reduced the levels of ROS, TZP and mRNA for CCNB1, and improved in vitro resumption of meiosis in oocytes from medium-sized bovine antral follicles.

Perfluorooctanoic acid (PFOA) exposure affects early embryonic development and offspring oocyte quality via inducing mitochondrial dysfunction

Perfluorooctanoic acid (PFOA) is a synthetic perfluorinated compound that is extensively used as an integral surfactant in commercial production. Owing to its hydrophilicity and persistence, PFOA can accumulate in living organisms and induce severe disease in animals and humans. It has been reported that PFOA exposure can affect ovarian function and induce reproductive toxicity; however, the effects and potential mechanism of PFOA exposure during gestation on early embryonic development and offspring remain unclear. This study found that PFOA exposure in vitro disrupted spindle assembly and chromosome alignment during the first cleavage of early mouse embryos, which impacted early embryonic cleavage and blastocyst formation. Moreover, PFOA exposure caused mitochondrial dysfunction and oxidative stress by inducing aberrant Ca²⁺ levels, liquid drops(LDs), and mitochondrial membrane potential in the 2-cell stage. Furthermore, we found that PFOA exposure resulted in DNA damage, autophagy, and apoptosis in 2-cell stage by inhibiting SOD2 function. Gestational exposure to PFOA significantly increased ovarian apoptosis and disrupted follicle development in F1 offspring. In addition, oocyte maturation competence was decreased in F1 offspring. Finally, single-cell transcriptome analysis revealed that PFOA-induced oocyte deterioration was caused by mitochondrial dysfunction and apoptosis in the F1 offspring. In summary, our results indicated that gestational exposure to PFOA had potential toxic effects on ovarian function and led to a higher incidence of meiotic defects in F1 female offspring.

Glyphosate exposure deteriorates oocyte meiotic maturation via induction of organelle dysfunctions in pigs

Background

Recently, defects in mammalian oocytes maturation induced by environmental pollution results in the decreasing animal reproduction. Animal exposed to glyphosate is largely unavoidable because glyphosate is one of the most widely used herbicide worldwide due to its high-efficiency and broad-spectrum effects, which causes glyphosate an environmental contaminant found in soil, water and food. During the last few years, the growing and wider use of glyphosate has raised great concerns about its effects of reproductive toxicity. In this study, using porcine models, we investigated effects of glyphosate on organelle functions during oocyte meiosis.

Results

The results showed glyphosate exposure disrupted porcine oocyte maturation. Expression levels of cumulus expansion-related genes were interfered, further indicating the meiotic defects. The damaging effects were mediated by destruction of mitochondrial distribution and functions, which induced ROS accumulation and oxidative stress, also indicated by the decreased mRNA expression of related antioxidant enzyme genes. We also found an interference of endoplasmic reticulum (ER) distribution, disturbance of Ca²⁺ homeostasis, as well as fluctuation of ER stress, showing with the reduced ER stress-related mRNA or protein expression, which could indicate the dysfunction of ER for protein processing and signal transduction in glyphosate-exposed oocytes. Moreover, glyphosate exposure induced the disruption of lysosome function for autophagy, showing with the decrease of LAMP2 expression and autophagy-related genes mRNA expression. Additionally, our data showed the distribution of Golgi apparatus and the functions of ribosome were disturbed after glyphosate exposure, which might affect protein synthesis and transport.

Conclusions

Collectively, our study showed that exposed to glyphosate could affect animal reproduction by compromising the quality of oocytes through its wide toxic effects on organelle functions.

The Molecular Quality and Mitochondrial Activity of Porcine Cumulus-Oocyte Complexes Are Affected by Their Exposure to Three Endocrine-Active Compounds under 3D In Vitro Maturation Conditions

Thus far, the potential short- and long-term detrimental effects of a variety of environmental chemicals designated as endocrine-active compounds (EACs) have been found to interfere with histo- and anatomo-physiological functions of the reproductive system in humans and wildlife species. For those reasons, this study sought to examine whether selected EACs, which encompass the fungicide vinclozolin (Vnz), the androgenic anabolic steroid nandrolone (Ndn) and the immunosuppressant cyclosporin A (CsA), affect the developmental competence and molecular quality (MQ) of porcine cumulus–oocyte complexes (COCs) subjected to in vitro maturation (IVM) under 3D culture conditions. The COCs underwent 3D-IVM in the presence of Vnz, Ndn or CsA for 48 h. To explore whether the selected EACs induce internucleosomal DNA fragmentation in cumulus cells (CCs), TUNEL-assisted detection of late apoptotic cells was performed. Additionally, for the detailed evaluation of pro- and antiapoptotic pathways in COCs, apoptosis proteome profiler arrays were used. To determine changes in intracellular metabolism in COCs, comprehensive assessments of mitochondrial ultrastructure and activity were carried out. Moreover, the relative abundances (RAs) of mRNAs transcribed from genes that are involved in scavenging reactive oxygen species (ROS), such as SIRT3 and FOXO3, and intramitochondrial bioenergetic balance, such as ATP synthase subunit (ATP5A1), were ascertained. Finally, to investigate the extent of progression of oocyte maturation, the intraooplasmic levels of cAMP and the RAs of mRNA transcripts encoding regulatory and biocatalytic subunits of a heterodimeric meiosis-promoting factor, termed cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDC2), were also estimated. The obtained results provide, for the first time, strong evidence that both Vnz and Ndn decrease the developmental competence of oocytes and stimulate apoptosis processes in CCs. The present study is also the first to highlight that Vnz accelerates the maturation process in immature oocytes due to both increased ROS production and the augmented RA of the CCNB1 gene. Furthermore, Vnz was proven to trigger proapoptotic events in CCs by prompting the activity of the FOXO3 transcription factor, which regulates the mitochondrial apoptosis pathway. In turn, Ndn was shown to inhibit oocyte maturation by inducing molecular events that ultimately lead to an increase in the intraooplasmic cAMP concentration. However, due to the simultaneous enhancement of the expression of TNF-β and HSP27 proteins in CCs, Ndn might be responsible for the onset of their neoplastic transformation. Finally, our current investigation is the first to clearly demonstrate that although CsA did not interfere with the nuclear and cytoplasmic maturation of oocytes, by inducing mitophagy in CCs, it disrupted oocyte metabolism, consequently attenuating the parameters related to the MQ of COCs. Summing up, Vnz, Ndn and CsA reduced not only the processes of growth and IVM but also the MQ of porcine COCs, which might make them unsuitable for assisted reproductive technologies (ARTs) such as in vitro fertilization by either gamete co-incubation or intracytoplasmic sperm injection (ICSI) and cloning by somatic cell nuclear transfer (SCNT).

Mitochondria Lead the Way: Mitochondrial Dynamics and Function in Cellular Movements in Development and Disease

The dynamics, distribution and activity of subcellular organelles are integral to regulating cell shape changes during various physiological processes such as epithelial cell formation, cell migration and morphogenesis. Mitochondria are famously known as the powerhouse of the cell and play an important role in buffering calcium, releasing reactive oxygen species and key metabolites for various activities in a eukaryotic cell. Mitochondrial dynamics and morphology changes regulate these functions and their regulation is, in turn, crucial for various morphogenetic processes. In this review, we evaluate recent literature which highlights the role of mitochondrial morphology and activity during cell shape changes in epithelial cell formation, cell division, cell migration and tissue morphogenesis during organism development and in disease. In general, we find that mitochondrial shape is regulated for their distribution or translocation to the sites of active cell shape dynamics or morphogenesis. Often, key metabolites released locally and molecules buffered by mitochondria play crucial roles in regulating signaling pathways that motivate changes in cell shape, mitochondrial shape and mitochondrial activity. We conclude that mechanistic analysis of interactions between mitochondrial morphology, activity, signaling pathways and cell shape changes across the various cell and animal-based model systems holds the key to deciphering the common principles for this interaction.

Nivalenol affects spindle formation and organelle functions during mouse oocyte maturation

Oocyte maturation is essential for fertilization and early embryo development, and proper organelle functions guarantee this process to maintain high-quality oocytes. The type B trichothecene nivalenol (NIV) is a mycotoxin produced by Fusarium oxysporum and is commonly found in contaminated food. NIV intake affect growth, the immune system, and the female reproductive system. Here, we investigated NIV toxicity on mouse oocyte quality. Transcriptome analysis results showed that NIV exposure altered the expression of multiple genes involved in spindle formation and organelle function in mouse oocytes, indicating its toxicity on mouse oocyte maturation. Further analysis indicated that NIV exposure disrupted spindle structure and chromosome alignment, possibly through tubulin acetylation. NIV exposure induced aberrant mitochondria distribution and reduced mitochondria number, mitochondria membrane potential (MMP), and ATP levels. In addition, NIV caused the abnormal distribution of the Golgi apparatus and altered the expression of the vesicle trafficking protein Rab11. ER distribution was also disturbed under NIV exposure, indicating the effects of NIV on protein modification and transport in oocytes. Thus, our results demonstrated that NIV exposure affected spindle structure and organelles function in mouse oocytes.

Grape Seed Proanthocyanidin Ameliorates FB1-Induced Meiotic Defects in Porcine Oocytes

Fumonisin B₁ (FB₁), as the most prevalent and toxic fumonisin, poses a health threat to humans and animals. The cytotoxicity of FB₁ is closely related to oxidative stress and apoptosis. The purpose of this study is to explore whether Grape seed proanthocyanidin (GSP), a natural antioxidant, could alleviate the meiotic maturation defects of oocytes caused by FB₁ exposure. Porcine cumulus oocyte complexes (COCs) were treated with 30 μM FB₁ alone or cotreated with 100, 200 and 300 μM GSP during in vitro maturation for 44 h. The results show that 200 μM GSP cotreatment observably ameliorated the toxic effects of FB₁ exposure, showing to be promoting first polar body extrusion and improving the subsequent cleavage rate and blastocyst development rate. Moreover, 200 μM GSP cotreatment restored cell cycle progression, reduced the proportion of aberrant spindles, improved actin distribution and protected mitochondrial function in FB₁-exposed oocytes. Furthermore, reactive oxygen species (ROS) generation was significantly decreased and the mRNA levels of CAT, SOD2 and GSH-PX were obviously increased in the 200 μM GSP cotreatment group. Notably, the incidence of early apoptosis and autophagy level were also significantly decreased after GSP cotreatment and the mRNA expression levels of BAX, CASPASE3, LC3 and ATG5 were markedly decreased, whereas BCL2 and mTOR were observably increased in the oocytes after GSP cotreatment. Together, these results indicate that GSP could exert significant preventive effects on FB₁-induced oocyte defects by ameliorating oxidative stress through repairing mitochondrial dysfunction.

Fumonisin B1 exposure deteriorates oocyte quality by inducing organelle dysfunction and DNA damage in mice

Oocyte quality is critical for fertilization and early embryo development. Fumonisin B1 (FB1) is a Fusarium mycotoxin and it is commonly found in contaminated food and feedstuff, posing a potential health hazard to both animals and human. FB1 is reported to have hepatotoxicity, neurotoxicity, nephrotoxicity, immunotoxicity and embryotoxicity. However, the effects of FB1 on mouse oocyte quality are still unknown. Here, we explored the toxic effects and potential mechanisms of FB1 on oocyte maturation quality in mice. FB1 exposure inhibited the first polar body extrusion at concentrations of 30 μM and 50 μM, which further induced oocyte meiotic arrest. Besides, disrupted spindle structure was found in oocytes after FB1 exposure. Our results also showed that FB1 exposure impaired mitochondria dysfunction, which further induced oxidative stress and early apoptosis. In addition, we reported that FB1 exposure induced the accumulation of lysosome and occurrence of autophagy. Aberrant ER distribution and ER stress were also found in FB1-exposed oocytes. Moreover, DNA damage was also observed. These results together suggested that FB1 exposure affected oocyte quality by destroying spindle structure, leading to mitochondria, lysosome and ER dysfunction, which further induced oxidative stress, apoptosis, autophagy and DNA damage in mouse oocytes.

Lycopene Improves In Vitro Development of Porcine Embryos by Reducing Oxidative Stress and Apoptosis

In vitro culture (IVC) for porcine embryo development is inferior compared to in vivo development because oxidative stress can be induced by the production of excessive reactive oxygen species (ROS) under high oxygen tension in the in vitro environment. To overcome this problem, we investigated the effect of lycopene, an antioxidant carotenoid, on developmental competence and the mechanisms involved in mitochondria-dependent apoptosis pathways in porcine embryos. In vitro fertilized (IVF) embryos were cultured in IVC medium supplemented with 0, 0.02, 0.05, 0.1, or 0.2 μM lycopene. The results indicate that 0.1 μM lycopene significantly increased the rate of blastocyst formation and the total cell numbers, including trophectoderm cell numbers, on Day In terms of mitochondria-dependent apoptosis, IVF embryos treated with 0.1 μM lycopene exhibited significantly decreased levels of ROS, increased mitochondrial membrane potential, and decreased expression of cytochrome c on Days 2 and Furthermore, 0.1 μM lycopene significantly decreased the number and percentage of caspase 3-positive and apoptotic cells in Day-6 blastocysts. In addition, Day-2 embryos and Day-6 blastocysts treated with 0.1 μM lycopene showed significantly reduced mRNA expression related to antioxidant enzymes (SOD1, SOD2, CATALASE) and apoptosis (BAX/BCL2L1 ratio). These results indicate that lycopene supplementation during the entire period of IVC enhanced embryonic development in pigs by regulating oxidative stress and mitochondria-dependent apoptosis.

Fumonisin B1 exposure adversely affects porcine oocyte maturation in vitro by inducing mitochondrial dysfunction and oxidative stress

Fumonisin B₁ (FB₁), as the most toxic fumonisin, is a common Fusarium mycotoxin contaminant of feed stuff and food, posing a potential health hazard to animals and humans. FB₁ has been reported to cause hepatotoxicity, neurotoxicity, nephrotoxicity, immunotoxicity and embryotoxicity; however, little information is available on whether FB₁ has toxic effects on mammalian oocytes. Herein, we adopted porcine oocytes as models to explore the effects and potential mechanisms of FB₁ on mammalian oocytes during in vitro maturation. Porcine cumulus oocyte complexes (COCs) were exposed to 0, 20, 30 and 40 μM FB₁ for 44 h during in vitro maturation, and the results reported that first polar body (PB1) extrusion was significantly inhibited when the FB₁ concentration reached 30 (P < 0.01) or 40 μM (P < 0.001). Further cell cycle analysis revealed that meiotic progression was disrupted, with a larger proportion of the 30 μM FB₁-treated oocytes being arrested at the germinal vesicle breakdown (GVBD) stage (P < 0.01). After being treated with 30 μM FB₁ for 28 h, the percentage of oocytes with aberrant spindle assembly was observably increased (P < 0.01), and the distribution of actin filaments on the plasma membrane was significantly reduced (P < 0.05). Furthermore, an observably higher rate of abnormal mitochondrial distribution (P < 0.05) and significantly decreased mitochondrial membrane potential (MMP) (P < 0.05) were observed in FB₁-exposed oocytes. In addition, ROS generation in FB₁-treated oocytes was rapidly increased (P < 0.05), while the transcriptional levels of antioxidant-related genes (CAT, SOD2 and GSH-Px) were sharply decreased compared with those in the control group. Additionally, the incidence of early apoptosis in FB₁-treated oocytes was also significantly increased (P < 0.05), suggesting that FB₁ exposure induced oxidative stress and further triggered apoptosis in porcine oocytes. Thus, these results suggested that FB₁ adversely affected oocyte maturation by disturbing cell cycle progression, destroying cytoskeletal dynamics and damaging mitochondrial function, which eventually induced oxidative stress and apoptosis in porcine oocytes.

Embryo aggregation regulates in vitro stress conditions to promote developmental competence in pigs

Embryo aggregation is a useful method to produce blastocysts with high developmental competence to generate more offspring in various mammals, but the underlying mechanism(s) regarding the beneficial effects are largely unknown. In this study, we investigated the effects of embryo aggregation using 4-cell stage embryos in in vitro developmental competence and the relationship of stress conditions in porcine early embryogenesis. We conducted aggregation using the well of the well system and confirmed that aggregation using two or three embryos was useful for obtaining blastocysts. Aggregated embryos significantly improved developmental competence, including blastocyst formation rate, blastomere number, ICM/TE ratio, and cellular survival rate, compared to non-aggregated embryos. Investigation into the relationship between embryo aggregation and stress conditions revealed that mitochondrial function increased, and oxidative and endoplasmic reticulum (ER)-stress decreased compared to 1X (non-aggregated embryos) blastocysts. In addition, 3X (three-embryo aggregated) blastocysts increased the expression of pluripotency, anti-apoptosis, and implantation related genes, and decreased expression of pro-apoptosis related genes. Therefore, these findings indicate that embryo aggregation regulates in vitro stress conditions to increase developmental competence and contributes to the in vitro production of high-quality embryos and the large-scale production of transgenic and chimeric pigs.

Effect of high hydrostatic pressure on mitochondrial activity, reactive oxygen species level and developmental competence of cultured pig embryos

High hydrostatic pressure (HHP) has been previously used to increase mammalian oocyte and embryo tolerance on subsequent stresses related with different assisted reproductive technologies. Nevertheless, the mechanisms for HHP-induced stress responses in early embryos have not been yet well understood. Previous studies focused mainly on HHP-modified gene expression while possible changes in cellular functions, including modification of energy metabolism and oxidative stress were neglected. Therefore, we aimed to analyze the effect of HHP treatment on the efficiency of subsequent in vitro pig embryos culture in NCSU-23 medium, on mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) level during their pre-implantation development. Porcine embryos were exposed to the hydrostatic pressure of 20 MPa and their quick response to such stress was analyzed 1 h later. In comparison with control embryos, we detected lower ΔΨm by ∼13% only in expanded blastocysts as well as decreased ROS level by ∼30% and ∼42% at the morula and expanded blastocyst stages, respectively. After HHP-treatment at transcriptionally inactive zygote stage and subsequent embryo culture, long-time responses were found: (1) at expanded blastocyst stage manifesting by ΔΨm decrease by ∼16%, (2) at the morula and expanded blastocyst stages in the form of ROS level reduction by ∼38% and ∼33% respectively. Following HHP stress applied at the transcriptionally active morula stage the long-time response in the expanded blastocysts as a decrease of ΔΨm by ∼19% and ROS level by ∼37% was observed. The percentage of obtained expanded blastocysts was higher after culture of HHP-treated zygotes in comparison to the control. Moreover, expanded blastocysts developed in vitro from both HHP-treated zygotes or morulae, exhibited higher total number of cells per blastocyst, higher number of cells in the inner cell mass as well as lower number of TUNEL-positive nuclei per blastocyst and lower TUNEL index, when compared to untreated embryos. Therefore, the HHP stress applied at the zygote stage, enhances developmental potential and quality of in vitro obtained porcine blastocysts due to the both decreased ΔΨm and ROS level. Our findings may contribute to better understanding of the mechanism of HHP-mediated modifications of energy metabolism and oxidative stress during in vitro development of pig embryos.

Protective Effects of Melatonin Against Zearalenone Toxicity on Porcine Embryos in vitro

Zearalenone (ZEA) is an estrogenic mycotoxin produced by Fusarium fungi commonly found in corn, wheat, and other cereals which can infect food and feed commodities, and ZEA mainly has reproductive toxicity which causes widely reproductive disorders in pigs and other animals. However, the toxicity and the functional ways of ZEA on early embryo development is still unclear. In present study we showed that exposure to ZEA (10 μM) significantly decreased the 2-cell and blastocyst developmental rate in porcine early embryos in vitro. ZEA treatment resulted in the occurrence of oxidative stress, showing with increased reactive oxygen species (ROS) level, following with aberrant mitochondrial distribution. Moreover, we found positive signals of γH2A.X in the ZEA-treated embryos, indicating that ZEA induced DNA damage, and the increased autophagy confirmed this. These results suggested that ZEA induced oxidative stress, which further caused mitochondria dysfunction and DNA damage on early embryonic development. We next investigated the effects of melatonin on the ZEA-treated embryo development, and we found that melatonin supplementation could significantly ameliorate ZEA-induced oxidative stress, aberrant mitochondria distribution and DNA damage. In all, our results showed that ZEA was toxic for porcine embryos cultured in vitro and melatonin supplementation could protect their development from the effects of ZEA.

Differential impacts of gonadotrophins, IVF and embryo culture on mouse blastocyst development

RESEARCH QUESTION

Conception via assisted reproductive technology (ART) increases the risk of type 2 diabetes and cardiovascular disease in adulthood. Underlying differences between ART-conceived and in-vivo-conceived embryos that contribute to this increased risk are, however, not known.

DESIGN

This study examined the developmental characteristics of mouse blastocysts derived from ART- compared with in-vivo-conceived embryos. To determine the effect of ovarian stimulation versus IVF versus in-vitro embryo culture on phenotype, six distinct groups of blastocysts were generated. Female mice were naturally cycling or treated with high or mild doses of gonadotrophin, followed by natural mating or IVF under clinical conditions. Embryo morphokinetics were assessed by continuous time-lapse monitoring. Cell lineage allocation to the inner cell mass (Oct4+) or trophectoderm (Cdx2+) was determined by immunohistochemistry, and mitochondrial DNA (mtDNA) copy number was measured by quantitative PCR.

RESULTS

Ovarian stimulation increased embryo number but reduced the percentage of blastocysts. Morphokinetic analysis showed that gonadotrophin treatment led to advanced development (P < 0.05) due to earlier post-pronuclear breakdown. The blastocyst rate was reduced in IVF embryos compared with those fertilized in vivo before culture (P < 0.001). Morphokinetics showed that embryo development was slower in all the IVF groups (P < <0.05), due to a delay from the 3-cell stage. A reduced total and trophectoderm cell number was observed in all groups of cultured blastocysts compared with naturally conceived blastocysts (P < 0.01). Gonadotrophin treatment did not affect the blastocyst mtDNA copy number; however, IVF embryos exhibited reduced mtDNA copy number compared with naturally conceived embryos.

CONCLUSION

Ovarian stimulation, IVF and in-vitro culture differentially impair blastocyst developmental kinetics, differentiation and mtDNA copy number.

Improved quality of porcine embryos cultured with hyaluronan due to the modification of the mitochondrial membrane potential and reactive oxygen species level

Although considerable progress has been made in pig embryo culture systems, the developmental competence and quality of the produced embryos are still lower than their in vivo-derived counterparts. Because hyaluronan (HA) regulates various cellular processes and possesses antioxidant properties, this glycosaminoglycan seems to be a promising supplement in culture media. However, until now, its beneficial influence on in vitro pig embryo development has been debatable. Hence, we aimed to investigate the effect of 0.25 mg/mL, 0.5 mg/mL and 1 mg/mL concentrations of HA on the developmental potential and quality of cultured porcine embryos. We found that 1 mg/mL HA supplementation significantly increased the obtained percentages of cleaved embryos to ∼95%, morulae to ∼87% and blastocysts to ∼77%. At 0.5 mg/mL and 1 mg/mL HA concentrations, we observed a significantly improved blastocyst quality, expressed as the total number of cells per blastocyst, number of cells in the inner cell mass, number of TUNEL-positive nuclei per blastocyst, the TUNEL index and the blastocyst diameter. Because the inner mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) level are important for proper embryo development, for the first time, we measured these two parameters in cultured embryos at various HA concentrations and during their development up to the expanded blastocyst stage. For blastocysts cultured with 1 mg/mL HA, the ΔΨm and ROS level were ∼1.6 and 2.7 times lower, respectively, than those of the control blastocysts. Both ΔΨm and the ROS level were increased in parallel during in vitro embryo development with and without HA, but this increase was less pronounced in the presence of HA. Hence, our quantitative data unequivocally show that supplementation of NCSU-23 culture medium with 1 mg/mL HA improves the developmental potential and quality of pig embryos. This effect results from a significant decrease in the ROS level induced by the HA-dependent ΔΨm reduction.

Exposure to cadmium during in vitro maturation at environmental nanomolar levels impairs oocyte fertilization through oxidative damage: A large animal model study

Cadmium is a highly toxic heavy metal with negative effects on oocyte fertilization. The aim of this study was to analyse whether cadmium-induced impairment of fertilization is caused by mitochondria dysfunction and oxidative stress in the cumulus-oocyte complex (COC). Preliminarily, 19 trace element levels were measured in ovaries from juvenile and adult ewes and age-related cadmium ovarian bioaccumulation at nanomolar concentrations was found. COCs from juvenile and adult ewes, exposed during in vitro maturation to 1nM or 100nM CdCl₂, and subjected to in vitro fertilization showed significantly lower fertilization rates in exposed COCs compared with controls. In vitro matured exposed and control COCs underwent confocal microscopy analysis of mitochondria activity and reactive oxygen species (ROS) levels and lipid peroxidation (LPO) assay at cumulus cell and oocyte level. In both age groups, cadmium at nanomolar concentrations induced cumulus-oocyte mitochondria over-activity and oxidative damage which were related to impaired oocyte fertilization.

Supplementation with nanomolar concentrations of verbascoside during in vitro maturation improves embryo development by protecting the oocyte against oxidative stress: a large animal model study

The effects of verbascoside (VB), added at nanomolar concentrations during in vitro maturation (IVM) of juvenile sheep oocytes, on in vitro embryo development and its mechanisms of action at the oocyte level were analyzed. Developmental rates, after IVM in the presence/absence of VB (1nM for 24h; 1nM for 2h; 10nM for 2h), were evaluated. The bioenergetic/oxidative status of oocytes matured after IVM in the presence/absence of 1nM VB for 24h was assessed by confocal analysis of mitochondria and reactive oxygen species (ROS), lipid peroxidation (LPO) assay, and quantitative PCR of bioenergy/redox-related genes. The addition of 1nM VB during 24h IVM significantly increased blastocyst formation and quality. Verbascoside reduced oocyte ROS and LPO and increased mitochondria/ROS colocalization while keeping mitochondria activity and gene expression unchanged. In conclusion, supplementation with nanomolar concentrations of VB during IVM, in the juvenile sheep model, promotes embryo development by protecting the oocyte against oxidative stress.

Toxicity of beauvericin on porcine oocyte maturation and preimplantation embryo development

Beauvericin (BEA) is one of many toxins produced by Fusarium species that contaminate feed materials. The aim of this study was to assess its effects on porcine oocyte maturation and preimplantation embryo development. Cumulus-oocyte-complexes and developing embryos were exposed to BEA and cultured until the blastocyst stage. Cumulus cells, oocytes and embryos were examined for viability, progesterone synthesis, multidrug resistance protein (MDR1), ATP content and gene expression related to MDR1 function, oxidative phosphorylation, steroidogenesis and apoptosis. BEA was toxic in embryos, oocytes and cumulus cells at concentrations exceeding 0.5μM, and embryos were most vulnerable after the four-cell stage. Since BEA exerted different effects in embryos, oocytes and cumulus cells, the toxic mechanism is suggested to involve different pathways. Currently there are no consistent data on adverse effects of BEA in pig farms.

Effect of acteoside on the re-localization and abnormal morphology of mitochondria in porcine oocytes during in vitro maturation

PURPOSE

The aim of this study is to investigate the effect of acteoside, an antioxidant, on in vitro maturation (IVM) of oocytes to improve early parthenogenetic embryonic developmental competence.

METHODS

Porcine immature oocytes (total 770) were cultured in IVM medium with acteoside at various concentrations, 0 (control), 10, 30, and 50 μM. Each group was assessed for maturation and subsequent development rates, reactive oxygen species (ROS) level (15 oocytes per group and four independent experiments performed), ultrastructure observation (15 oocytes per group), mitochondrial activity (30 oocytes per groups and three independent experiments performed), and expression patterns of apoptosis-related genes (100 expended parthenogenetic embryos per group and three independent experiment performed). Main outcome measures were the rates of IVM, blastocyst formation, ROS, mitochondria, and expression of apoptosis-related genes in oocytes treated with acteoside.

RESULT(S)

Addition of acteoside during IVM did not change the maturation efficiency of oocytes but improved the rate of blastocyst formation with significantly decreased ROS level. Moreover, in acteoside-treated oocytes, cytoplasmic maturation was improved with morphologically uniform distribution of mitochondria and lipid droplets in cytoplasm. Acteoside supplementation also increased the mRNA expression levels of antiapoptotic genes and reduced those of pro-apoptotic genes.

CONCLUSION(S)

Acteoside supplementation in IVM medium improves the oocyte quality and subsequent development of pre-implantation embryos that would eventually contribute to produce embryos with high embryonic development competence.

Mitochondrial activity during pre-maturational culture in in vitro-grown bovine oocytes is related to maturational and developmental competences

The objective of this study was to investigate the dynamics of mitochondrial activity in in vitro-grown (IVG) bovine oocytes during pre-maturational culture (pre-IVM) and its relationship to their developmental competence upon being subjected to different pre-IVM durations. After 12-day IVG culture, oocytes were cultured for 0, 10 or 20 h with 3-isobutyl-1-methylxanthine (IBMX) as pre-IVM. Mitochondrial activity in IVG oocytes after 10 h pre-IVM was the highest among all the pre-IVM durations (P < 0.05). In addition, cleavage (79.4%) and blastocyst rates (38.9%) of embryos derived from IVG oocytes with 10 h pre-IVM were higher than those with 20 h pre-IVM (63.0 and 25.8%, respectively; P < 0.05) and similar to those of in vivo-grown oocytes (82.7 and 36.7%, respectively). To confirm the developmental ability of IVG oocytes with 10 h pre-IVM beyond the blastocyst stage in vivo, embryo transfer was attempted. Transferred embryos developed to the elongated embryonic stage (63.6%, 7/11) in the recipient uterus at Day 16 of oestrus, and a male calf was delivered (50%, 1/2). In conclusion, it was indicated that the mitochondrial activity of bovine IVG oocytes peaked at 10 h pre-IVM and was closely correlated with the nuclear maturation and developmental competences of IVG oocytes.

How to Quantify Penile Corpus Cavernosum Structures with Histomorphometry: Comparison of Two Methods

The use of morphometrical tools in biomedical research permits the accurate comparison of specimens subjected to different conditions, and the surface density of structures is commonly used for this purpose. The traditional point-counting method is reliable but time-consuming, with computer-aided methods being proposed as an alternative. The aim of this study was to compare the surface density data of penile corpus cavernosum trabecular smooth muscle in different groups of rats, measured by two observers using the point-counting or color-based segmentation method. Ten normotensive and 10 hypertensive male rats were used in this study. Rat penises were processed to obtain smooth muscle immunostained histological slices and photomicrographs captured for analysis. The smooth muscle surface density was measured in both groups by two different observers by the point-counting method and by the color-based segmentation method. Hypertensive rats showed an increase in smooth muscle surface density by the two methods, and no difference was found between the results of the two observers. However, surface density values were higher by the point-counting method. The use of either method did not influence the final interpretation of the results, and both proved to have adequate reproducibility. However, as differences were found between the two methods, results obtained by either method should not be compared.

Influence of bovine serum albumin and fetal bovine serum supplementation during in vitro maturation on lipid and mitochondrial behaviour in oocytes and lipid accumulation in bovine embryos

Proper oocyte maturation is crucial for subsequent embryo development; however, oocyte mitochondrial and lipid-droplet behaviour are still poorly understood. Although excessive lipid accumulation during in vitro production (IVP) of bovine embryos has been linked with impaired cryotolerance, lipid oxidation is essential for adequate energy supply. Fetal bovine serum (FBS) and bovine serum albumin (BSA) are supplements used during IVP, containing high and low lipid content, respectively. This study aimed to understand how these supplements influence oocyte mitochondrial and lipid behaviour during in vitro maturation (IVM) in comparison to in vivo maturation, as well as their influence on development rates and embryo lipid accumulation during IVP. We demonstrate that only in vivo-matured oocytes maintained correlation between lipid content and active mitochondria. IVM media containing FBS increased total lipid content 18-fold and resulted in higher lipid accumulation in oocytes when compared with media with BSA. IVM using a lower FBS concentration combined with BSA resulted in satisfactory maturation and embryo development and also reduced lipid accumulation in blastocysts. In conclusion, IVM causes changes in mitochondrial and lipid dynamics, which may have negative effects on oocyte development rates and embryo lipid accumulation. Moreover, decreasing FBS concentrations during IVM may reduce embryo lipid accumulation without affecting production rates.

Differential expression of selected candidate genes in bovine embryos produced in vitro and cultured with chemicals modulating lipid metabolism

Lipid accumulated in embryos produced in vitro has been linked to reductions in both quality and postcryopreservation viability. Therefore, the objective of the present study was to investigate the influence of lipid-reducing chemicals on embryo development, quality, and postcryopreservation viability, in addition to expression profiles of selected lipid metabolism-regulating genes. Bovine cumulus-oocyte complexes were matured and fertilized in vitro; eight-cell stage embryos were cultured in IVC medium supplemented with phenazine ethosulfate (PES), L-carnitine (LC), PES + LC, or no supplementation (control). Culturing embryos in medium with LC increased (P < 0.05) blastocyst rate (38.8%) compared with the other groups (control = 28.1%, PES = 27.1%, PES + LC = 26.3%). Embryos cultured with supplements had greater total cell number and fewer apoptotic cells than the control. Cytoplasmic lipid content was reduced, whereas mitochondria density was increased in embryos treated with culture supplements; this was linked to altered expression profiles of selected genes regulating lipid metabolism. For example, transcript abundance of transmembrane lipid gene (SGPP1) was greater in LC- and PES-treated embryos, and they had increased postcryopreservation hatching ability (indicative of embryo cryotolerance). In conclusion, the two lipid metabolism regulators added to the culture media had improved embryo quality and cryotolerance, but embryo development rate and downstream lipid metabolism-regulating genes were more influenced with LC supplementation.

Cell cycle-dependent dynamics of cytoskeleton involving mitochondrial redistribution in hamster embryos

Mitochondria-cytoskeleton interactions were studied in the hamster embryos during interphase and M phase of the cell cycle. Two-cell embryos were cultured for 1 h with nocodazole, cytochalasin D or in a combination of both inhibitors and then centrifuged at 10,000 × g for 2 min. The control embryos were only centrifuged with no inhibitor treatment. Centrifuged embryos were fluorescently stained to examine the distribution of active mitochondria and nuclear configuration. In the control 2-cell embryos, most mitochondria were accumulated at the perinuclear region with some at the cell cortex. Neither each inhibitor nor centrifugation did affect the distribution of mitochondria in interphase blastomeres. However, mitochondria were spun down towards the centrifugal pole in 71% (n = 41) of the interphase blastomeres treated with centrifugation following a combination of nocodazole plus cytochalasin D, suggesting that both microtubules and microfilaments may involve in mitochondrial redistribution during interphase of the cell cycle. In contrast, when M-phase blastomeres were treated with all drug treatments applied, including cytochalasin D, mitochondria had been usually dislocated in a unipolar cluster, suggesting that microfilaments, not microtubules, may involve in the mitochondrial redistribution during M phase of the cell cycle. The data indicate that microfilaments function in mitochondrial redistribution regardless of the stages of the cell cycle and that microtubules may strongly associate with mitochondria during the interphase but dissociate from them during the M phase.

Characteristics of bovine oocytes with different meiotic competence in terms of their mitochondrial status and expression of nuclear-encoded factors

The present study was designed to characterize bovine oocytes with different meiotic competence and atresia levels in terms of their mitochondrial status. Oocyte subpopulations were recovered either from medium (MF) or small (SF) follicles and categorized as healthy, light-atretic and mid-atretic according to oocyte morphology. Mitochondrial activity, morphology and distribution, adenosine triphosphate (ATP) content and expression of mitochondrial transcription factor A (TFAM) and nuclear respiratory factor 1 (NRF1) were assessed before (GV) and after (MII) maturation. The data were related to follicular size regardless of or with regard to oocyte atresia. Regardless of atresia, the MF subpopulation showed a significantly higher mitochondrial activity and frequency of oocytes with granulated mitochondria at GV and clustered mitochondria at MII than the SF subpopulation. With regard to atresia, mitochondrial activity decreased from healthy to mid-atretic oocytes in both MF and SF subpopulations at GV, but in the SF subpopulation at MII, the mitochondrial activity and frequency of oocytes with clustered mitochondria were significantly higher in light-atretic than in healthy oocytes. The light-atretic oocytes also produced more ATP than healthy ones in both SF and MF subpopulations. However, a significantly higher relative abundance of mRNA TFAM was found in SF than MF subpopulations at GV, and this difference remained in mid-atretic oocytes at MII. It can be concluded that meiotic competence and atresia level influence mitochondrial status of immature bovine oocytes. After maturation, healthy oocytes from medium follicles and light-atretic oocytes from small follicles were more developed in terms of mitochondrial status than the other oocytes.