Glycine ameliorates mitochondrial dysfunction caused by ABT-199 in porcine oocytes

Mitochondria play an important role in controlling oocyte developmental competence. Our previous studies showed that glycine (Gly) can regulate mitochondrial function and improve oocyte maturation in vitro. However, the mechanisms by which Gly affects mitochondrial function during oocyte maturation in vitro have not been fully investigated. In this study, we induced a mitochondrial damage model in oocytes with the Bcl-2-specific antagonist ABT-199. We investigated whether Gly could reverse the mitochondrial dysfunction caused by ABT-199 exposure and whether it is related to calcium regulation. Our results showed that ABT-199 inhibited cumulus expansion, decreased the oocyte maturation rate and the intracellular glutathione (GSH) level, caused mitochondrial dysfunction, which was confirmed by decreased mitochondrial membrane potential (ΔΨm) and the expression of mitochondrial function-related genes PGC-1α, and increased reactiveoxygenspecies (ROS) levelsand the expression of apoptosis-associated genes Bax, Caspase-3, and Cyto C.More importantly, ABT-199-treated oocytes showed an increase in the intracellular free calcium concentration ([Ca²⁺]i) and had impaired cortical type 1 inositol 1,4,5-trisphosphate receptors (IP₃R1) distribution. Nevertheless, treatment with Gly significantly ameliorated mitochondrial dysfunction, oxidative stress, and apoptosis, and Gly also regulated [Ca²⁺]i levels and IP₃R1 cellular distribution, which further protects oocyte maturation in ABT-199-induced porcine oocytes.Taken together, our results indicate that Gly has a protective action against ABT-199-induced mitochondrial dysfunction in porcine oocytes.     

Resveratrol Improves the Mitochondrial Function and Fertilization Outcome of Bovine Oocytes

The aim of the present study was to address the effect of resveratrol-mediated upregulation of sirtuin 1 (SIRT1) during oocyte maturation on mitochondrial function, the developmental ability of oocytes and on mechanisms responsible for blockage of polyspermic fertilization. Oocytes collected from slaughterhouse-derived ovaries were cultured in TCM-199 medium supplemented with 10% FCS and 0 or 20 µM resveratrol (Res). We examined the effect of Res on SIRT1 expression in in vitro-matured oocytes (Exp 1); fertilization and developmental ability (Exp 2); mitochondrial DNA copy number (Mt number), ATP content and mitochondrial membrane potential in matured oocytes (Exp 3); and the time required for proteinase to dissolve the zona pellucida following in vitro fertilization (as a marker of zona pellucida hardening), as well as on the distribution of cortical granules before and after fertilization (Exp 4). In Exp 1, the 20 µM Res treatment upregulated protein expression of SIRT1 in oocytes. In Exp 2, Res treatment improved the ratio of normal fertilization and the total cell number of blastocysts. In Exp 3, Res treatment significantly increased the ATP content in matured oocytes. Additionally, Res increased the overall Mt number and mitochondrial membrane potential, but the effect was donor-dependent. In Exp 4, Res-induced zona hardening improved the distribution and exocytosis of cortical granules after in vitro fertilization. In conclusion, Res improved the quality of oocytes by improving mitochondrial quantity and quality. In addition, Res added to the maturation medium enhanced SIRT1 protein expression in oocytes and improved fertilization via reinforcement of the mechanisms responsible for blockage of polyspermic fertilization.     

Resveratrol-induced mitochondrial synthesis and autophagy in oocytes derived from early antral follicles of aged cows

Mitochondrial numbers increase during oocyte growth. In this study, we collected oocytes and granulosa cell complexes (OGCs) from early antral follicles (EAFs) of aged cows (> 120 months of age) and examined the effects of resveratrol on mitochondrial generation, degradation, and quality in oocytes grown in vitro. We also examined the effects of resveratrol on gene expression of the granulosa cells. Resveratrol (20 µM) enhanced the expression of SIRT1 and induced autophagy in both granulosa cells and oocytes derived from aged cows. Culturing the OGCs with resveratrol increased mitochondrial DNA copy numbers in oocytes grown in vitro. Furthermore, resveratrol increased the ATP content in oocytes and improved the developmental ability of the oocytes to the blastocyst stage. Gene expression profiles in granulosa cells, as evaluated by next-generation sequencing technology, revealed that resveratrol enhanced the expression of EIF2-related genes but downregulated the expression of mammalian target of rapamycin (mTOR)-, inflammation-, and cholesterol homeostasis-related genes in granulosa cells. In conclusion, resveratrol affected both oocytes and granulosa cells derived from aged cows and improved the quality of oocytes grown in vitro through upregulation of mitochondrial biogenesis and degradation in growing oocytes and conditioning of granulosa cells.     

Energy Status Characteristics of Porcine Oocytes During In Vitro Maturation is Influenced by Their Meiotic Competence

The characteristics of energy status in porcine oocytes as related to their meiotic competence and in vitro maturation were studied. Cycling pubertal gilts in the early luteal to early follicular phases of the ovarian cycle were used as oocyte donors. The oocytes recovered from medium (MF) or small follicles (SF) were considered meiotically more or less competent, respectively. A half of oocytes from each category was matured by the standard protocol. The oocytes were examined before or after maturation by confocal microscopy, a bioluminescent cell assay and Western blotting. Four experiments, each in triplicate, were performed to assess both SF and MF oocytes in terms of metabolic units formed by mitochondria and lipids, ATP and lipid consumption and lipid droplets with adipose differentiation‐related protein (ADRP) expression. The proportion of oocytes with metabolic units, the mean ATP content and the number of lipid droplets per oocyte, and the relative number of lipid droplets with ADRP expression were significantly higher in the MF compared to SF oocytes before maturation. On the other hand, after maturation, there was an increase in the proportion of oocytes with metabolic units and the relative number of lipid droplets with ADRP expression in the SF compared to MF oocytes. In conclusion, specific differences in energy characteristics between porcine oocytes with different meiotic competence were found. Meiotically more competent oocytes are more advanced in terms of energy reserves before maturation, while meiotically less competent oocytes are more active in replenishing energy stores during maturation.     

Aging-related Changes in In Vitro-matured Bovine Oocytes: Oxidative Stress,Mitochondrial Activity and ATP Content After Nuclear Maturation

The objective of this research was to clarify the aging-related changes in in vitro-matured bovine oocytes. Firstly, we examined the fertilization and embryonic development of bovine oocytes after 22 and 30–34 h of in vitro maturation (IVM). The oocytes after 30–34 h of IVM (penetrated by sperm at around 40 h after starting IVM) showed a lower developmental rate to blastocysts (P<0.01), although normal fertilization rates were similar regardless of IVM duration. In the next experiment, reactive oxygen species (ROS), mitochondrial activity and ATP content in oocytes after 20, 30 and 40 h of IVM were examined. The lowest level of ROS was found in the group subjected to 30 h of IVM. The mitochondrial activity and ATP content in the group subjected to 40 h of IVM were higher than in the group subjected to 20 h of IVM (P<0.01), and those in the group subjected to 30 h of IVM showed intermediate values. Thereafter, the mitochondrial activities at 3 days after in vitro fertilization in embryos derived from the oocytes subjected to 22 and 34 h of IVM were evaluated. In the group subjected to 34 h of IVM, high-polarized mitochondria were frequently observed at the periphery of blastomeres. The present results suggest that high mitochondrial activity observed in oocytes after prolonged IVM culture and localization of high-polarized mitochondria at the periphery of blastomeres during early embryonic development may be associated with the low developmental competence in aged bovine oocytes.     

Inhibition of cathepsin B activity reduces apoptosis by preventing cytochrome c release from mitochondria in porcine parthenotes

Cathepsin B, a lysosomal cysteine protease of the papain family, has recently been implicated in the quality and developmental competence of bovine preimplantation embryos. In this study, to determine whether inhibition of cathepsin B activity can improve porcine oocyte maturation and early embryo developmental competence, we supplemented in vitro maturation or embryo culture media with E-64, a cathepsin B inhibitor. Cathepsin B activity was high in poor quality germinal vesicle stage oocytes, but no differences in mRNA expression or protein localization were observed between good and poor quality oocytes, which were categorized based on morphology. Following treatment with 1 μM E-64, cathepsin B activity sharply decreased in 4-cell and blastocyst stage embryos. E-64 had no effect on cell number but significantly (P < 0.05) increased blastocyst formation and decreased the number of apoptotic cells in blastocysts. It also significantly (P < 0.05) enhanced mitochondrial membrane potential in blastocysts, reducing the release of cytochrome c and resulting in decreased expression of Caspase-3 and Caspase-9. In conclusion, inhibition of cathepsin B activity in porcine parthenotes using 1 μM E-64 resulted in attenuation of apoptosis via a reduction in the release of cytochrome c from mitochondria.     

Effects of reaggregated granulosa cells and oocytes derived from early antral follicles on the properties of oocytes grown in vitro

In this study, we examined the effects of reconstructed oocyte–granulosa cell complexes (OGCs) on the development of porcine oocytes derived from early antral follicles (EAFs; 0.5–0.7 mm in diameter). When denuded oocytes were cocultured with granulosa cells derived from other EAFs, the oocytes and granulosa cells aggregated to form OGCs after 2 days of culture. After 14 days of culture, we compared cell number, oocyte diameter, and oocyte chromatin configuration in unmanipulated (natural) OGCs, reconstructed OGCs, and OGCs collected from antral follicles (AFs, 3.0–6.0 mm in diameter). The diameters of oocytes from reconstructed OGCs grown in vitro were not different from those of oocytes from natural OGCs, although they were significantly smaller than those of oocytes from antral follicle (AF) OGCs. Oocyte chromatin configuration did not differ among the 3 OGC groups, but the oocyte nuclear maturation rate was lower in the reconstructed OGCs and higher in the AF OGCs. However, when the in vitro culture period for the reconstructed OGCs was extended by 2 days, the nuclear maturation rate of oocytes from reconstructed OGCs was similar to that of oocytes from natural OGCs. In addition, blastocysts were successfully obtained from oocytes from reconstructed OGCs. In conclusion, we established an innovative culture method that allows oocytes and granulosa cells from EAFs to reaggregate as reconstructed OGCs, which yield oocytes with the ability to develop to the blastocyst stage.     

Mitochondrial and DNA damage in bovine somatic cell nuclear transfer embryos

The generation of reactive oxygen species (ROS) and subsequent mitochondrial and DNA damage in bovine somatic cell nuclear transfer (SCNT) embryos were examined. Bovine enucleated oocytes were electrofused with donor cells and then activated by a combination of Ca-ionophore and 6-dimethylaminopurine culture. The H₂O₂ and ˙OH radical levels, mitochondrial morphology and membrane potential (ΔΨ), and DNA fragmentation of SCNT and in vitro fertilized (IVF) embryos at the zygote stage were analyzed. The H₂O₂ (35.6 ± 1.1 pixels/embryo) and ˙OH radical levels (44.6 ± 1.2 pixels/embryo) of SCNT embryos were significantly higher than those of IVF embryos (19.2 ± 1.5 and 23.8 ± 1.8 pixels/embryo, respectively, p < 0.05). The mitochondria morphology of SCNT embryos was diffused within the cytoplasm. The ΔΨ of SCNT embryos was significantly lower (p < 0.05) than that of IVF embryos (0.95 ± 0.04 vs. 1.21 ± 0.06, red/green). Moreover, the comet tail length of SCNT embryos was longer than that of IVF embryos (515.5 ± 26.4 µm vs. 425.6 ± 25.0 µm, p < 0.05). These results indicate that mitochondrial and DNA damage increased in bovine SCNT embryos, which may have been induced by increased ROS levels.     

Effects of oocyte-derived growth factors on the growth of porcine oocytes and oocyte–cumulus cell complexes in vitro

During oocyte growth and follicle development, oocytes closely communicate with cumulus cells. We examined the effects of oocyte-derived growth factors, growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), on the growth and acquisition of meiotic competence of porcine oocytes collected from early antral follicles (1.2–1.5 mm). First, we confirmed that GDF9 and BMP15 mRNAs were expressed almost exclusively in the oocytes. Oocyte–cumulus cell complexes (OCCs) collected from early antral follicles were cultured in growth medium supplemented with 0–100 ng/ml of GDF9 or BMP15 for 5 days. GDF9 dose-dependently increased the OCC diameter, while BMP15 did not. GDF9 and BMP15 had no significant effects on oocyte growth (P > 0.05). When OCCs that had been cultured with 50 and 100 ng/ml BMP15 were subjected to a subsequent maturation culture, they expanded fully by gonadotropic stimulation and 49% and 61% of oocytes matured to metaphase II (MII), respectively. In contrast, GDF9 did not promote cumulus expansion, and < 10% of oocytes matured to MII. Based on the difference in cumulus expansion, we compared the expression of luteinizing hormone/choriogonadotropin receptor (LHCGR) and follicle stimulating hormone receptor (FSHR) mRNAs in cumulus cells. The level of LHCGR mRNA was increased in cumulus cells of the BMP15 group, although there were no significant differences in FSHR mRNA levels among the groups. These results suggest that GDF9 promotes the growth of OCCs and that BMP15 promotes LHCGR mRNA expression in cumulus cells during oocyte growth culture, which may contribute to cumulus expansion and oocyte maturation.     

Effects of melatonin on oocyte developmental competence and the role of melatonin receptor 1 in juvenile goats

Melatonin enhances in vitro embryo development in several species by improving the oocyte developmental competence during in vitro maturation (IVM). Melatonin has a wide range of actions, from scavenging reactive oxygen species (ROS) to regulating gene expression, and it can also act by way of melatonin receptors. The aim of this study was to determine the mechanism of action of melatonin during the IVM of juvenile goat oocytes and the role of the membrane receptors. Melatonin receptor 1 was immunolocalized in cumulus cells and oocytes before and after 24 hr of IVM. The effect of melatonin on oocyte developmental competence was tested in three experimental IVM groups: (a) control, (b) 10^?7 M melatonin, and (c) 10^?7 M melatonin +10^?7 M luzindole (an inhibitor of both melatonin receptors). After IVM oocytes were assessed for ROS levels, mitochondrial activity, adenosine 5′‐triphosphate (ATP) concentration and relative gene expression (ACTB, SLC1A1, SOD1, GPx1, BAX, DNMT1, GCLC and GDF9). IVM‐oocytes were in vitro fertilized and cultured under conventional conditions. Blastocyst rate and quality (differential cell count) were assessed at 8 days post‐fertilization. Melatonin decreased ROS levels, increased mitochondrial activity and ATP content and increased blastocyst quality compared to control group (55.8 vs. 30.4 inner cell mass ICM, p < 0.05). There was no effect on the relative gene expression due to treatment with melatonin. In conclusion, we have showed that melatonin improves oocyte developmental competence in juvenile goats by reducing ROS levels and improving mitochondrial activity.     

In vitro maturation using αMEM with reduced NaCl enhances maturation and developmental competence of pig oocytes after somatic cell nuclear transfer

BackgroundCompared to medium containing 108 mM sodium chloride (NaCl), in vitro maturation (IVM) using a simple medium with reduced (61.6 mM) NaCl increases the cytoplasmic maturation and embryonic development of pig oocytes.ObjectivesThis study determines the effect of a complex medium containing reduced NaCl on the IVM and embryonic development of pig oocytes.MethodsPig oocytes were matured in Minimum Essential Medium Eagle-alpha modification (αMEM) supplemented with 61.6 (61αMEM) or 108 (108αMEM) mM NaCl, and containing polyvinyl alcohol (PVA) (αMEMP) or pig follicular fluid (PFF) (αMEMF). Medium-199 (M199) served as the control for conventional IVM. Cumulus cell expansion, nuclear maturation, intra-oocyte glutathione (GSH) contents, size of perivitelline space (PVS), and embryonic development after parthenogenesis (PA) and somatic cell nuclear transfer (SCNT) were evaluated after IVM.ResultsRegardless of PVA or PFF supplementation, oocytes matured in 61αMEM showed increased intra-oocyte GSH contents and width of PVS (p < 0.05), as well as increased blastocyst formation (p < 0.05) after PA and SCNT, as compared to oocytes matured in 108αMEMP and M199. Under conditions of PFF-enriched αMEM, SCNT oocytes matured in 61αMEMF showed higher blastocyst formation (p < 0.05), compared to maturation in 108αMEMF and M199, whereas PA cultured oocytes showed no significant difference.ConclusionsIVM in αMEM supplemented with reduced NaCl (61.6 mM) enhances the embryonic developmental competence subsequent to PA and SCNT, which attributes toward improved oocyte maturation.     

Effect of Maternal Age on the Ratio of Cleavage and Mitochondrial DNA Copy Number in Early Developmental Stage Bovine Embryos

Age-associated deterioration in both the quality and quantity of mitochondria occurs in older women. The main aim of this study was to examine the effect of age on mitochondrial DNA copy number (mtDNA number) in early developmental stage bovine embryos as well as the dynamics of mtDNA number during early embryo development. Real-time PCR was used to determine mtDNA number. In vitro-produced embryos 48 h after insemination derived from Japanese black cows, ranging in age from 25 to 209 months were categorized based on their cleavage status. There was an overall negative relationship between the age of the cow and cleavage status, to the extent that the ratio of embryos cleaved over the 4-cell stage was greater in younger cows. The mtDNA number did not differ among the cleaved status of embryos. In the next experiment, oocytes collected from each donor cow were divided into 2 groups containing 10 oocytes each, in order to compare the mtDNA number of mature oocytes and early developmental stage embryos within individuals. Upon comparing the mtDNA number between oocytes at the M2 stage and early developmental stage 48 h post insemination, mtDNA number was found to decrease in most cows, but was found to increase in some cows. In conclusion, age affects the cleaving ability of oocytes, and very old cows (> 180 months) tend to have lower mtDNA numbers in their oocytes. The change in mtDNA number during early development varied among individual cows, although overall, it showed a tendency to decrease.     

Mitochondrial Patterns in Bovine Oocytes with Different Meiotic Competence Related to Their in vitro Maturation

This study was designed to specify chromatin and mitochondrial patterns in bovine oocytes with different meiotic competence in relation to maturation progress, resumption of meiosis, MII onset and completion of maturation. Oocytes with greater or lesser meiotic competence, recovered separately from medium (MF) and small follicles (SF), were categorized according to morphology. Four oocyte categories, healthy and light‐atretic MF and healthy and light‐atretic SF oocytes were matured and collected at 0, 3, 7, 16 and 24 h of maturation. Specific differences in terms of chromatin and mitochondrial patterns were found among the maturing oocyte categories. Resumption of meiosis was accelerated in light‐atretic oocytes, as compared with healthy oocytes, regardless of their meiotic competence. More competent oocytes activated mitochondria twice during maturation, before resumption of meiosis and before completion of maturation, while less competent oocytes did it only once, before completion of maturation. Changes in mitochondrial activity differed in light‐atretic compared with healthy in both more and less competent oocytes. Healthy meiotically more competent oocytes formed clusters and produced ATP for the whole time of maturation until its completion, while light‐atretic more competent oocytes and healthy less competent oocytes reduced these activities earlier, at MII onset. Contrary to these oocyte categories, light‐atretic less competent oocytes increased cluster formation significantly before resumption of meiosis. It can be concluded that bovine oocytes with different meiotic competence and health differed in the kinetics of mitochondrial patterns during maturation.     

Overfeeding and underfeeding have detrimental effects on oocyte quality measured by in vitro fertilization and early embryonic development in sheep

To determine effects of maternal diet on in vitro fertilization (IVF) and early embryonic development, ewes (n = 48) were divided into control, overfed (ad libitum feeding), and underfed (60% of control) nutritional planes for 8 wk before oocyte collection. Follicular development was induced by twice-daily injections of FSH on days 13 and 14 of the estrous cycle, and ovaries and blood samples were collected on day 15 of the estrous cycle. During the 8-wk experiment, for control ewes BW and BCS did not change, but for overfed ewes mean (± SEM) BW and BCS increased (11.8 ± 1.1 kg and 2.0 ± 0.1, respectively) and for underfed ewes decreased (14.2 ± 0.9 kg and 0.7 ± 0.1, respectively). The number of follicles was determined; oocytes were collected and subjected to in vitro maturation and fertilization. After IVF, developing embryos were evaluated throughout the 8-d culture period. The proportion of cleaved oocytes after IVF and developing morula and blastocyst were less (P < 0.0001) in overfed and underfed ewes than in control ewes. However, number of visible follicles, total number of oocytes, number of healthy oocytes, and percentage of healthy oocytes were similar for control, overfed, and underfed ewes. Serum insulin concentration was greater (P < 0.05) in overfed ewes than in underfed ewes, estradiol 17-β (E₂) concentration was greater (P < 0.05) in underfed ewes than in overfed ewes, but triiodothyronine (T₃) and thyroxine (T₄) concentrations were similar in all treatment groups. These data show that inadequate feeding has a negative effect on oocyte quality which results in lower oocyte cleavage after IVF and morula and blastocyst formation; overfeeding increased serum insulin and underfeeding increased serum E₂ but not T₃ or T₄. These data emphasize the importance of diet for reproductive and metabolic functions. Furthermore, the mechanisms through which enhanced or decreased energy in diet affect oocyte quality and serum insulin and E₂ concentrations remain to be elucidated.     

表儿茶素对小鼠卵母细胞mtDNA拷贝数和胚胎体外发育能力的影响

本研究旨在探究表儿茶素(epicatechin,EC)对小鼠体外成熟培养卵母细胞线粒体DNA(mtDNA)拷贝数及其随后孤雌激活胚胎发育能力的影响。小鼠卵丘-卵母细胞复合体(COCs)在添加不同浓度EC(0、5、10、15、20μmol/L)的成熟液中体外成熟培养16h后,采用实时荧光定量PCR的方法检测卵母细胞mtDNA拷贝数;同时,通过对卵母细胞进行孤雌激活处理,探讨其后续胚胎的体外发育能力。实时荧光定量PCR分析结果显示,添加EC各处理组的卵母细胞mtDNA拷贝数均有所增加,其中,10、15μmol/L组的mtDNA拷贝数均显著高于0μmol/L对照组(P0.05);但10μmol/L组mtDNA拷贝数更接近自然排卵周期合子的mtDNA含量(P0.05)。体外培养观察结果发现,成熟液中添加10μmol/L EC能提高卵母细胞第一极体排出率,与对照组相比差异不显著(P0.05),但能显著提高卵母细胞孤雌激活后胚胎的囊胚发育率(P0.05)。综上表明,小鼠卵母细胞体外成熟液中添加10μmol/L EC可提高卵母细胞的mtDNA拷贝数,有利于促进卵母细胞后续的发育能力。     

Androgens promote the acquisition of maturation competence in bovine oocytes

Recent studies in mice suggest that androgens are important for normal follicle development. However, there have been few reports concerning the action of androgens in the growth of oocytes from large animals. The purpose of this study was to determine the roles of androgens in bovine oocyte growth in vitro. Oocyte-granulosa cell complexes (OGCs) collected from 0.4−0.7 mm early antral follicles were cultured for 14 days with 17β-estradiol (E₂) and a non-aromatizable androgen, dihydrotestosterone (DHT). We also examined the ability of an androgen receptor (AR) inhibitor, hydroxyflutamide, to antagonize the effect of androgens on the oocytes. During growth culture, the OGC structures collapsed in the medium with DHT alone, while in the presence of E₂, the OGC structures were maintained. In the medium with both androgens and E₂, the mean diameter of oocytes was increased from 95 μm to around 120 μm, larger than those grown with E₂ alone (115 μm). Also in the maturation culture, oocytes grown with androgens (A₄ or DHT) and E₂ showed higher percentages of metaphase II oocytes (63% or 69%, respectively) than those grown with E₂ alone (32%). Moreover, these maturation rates were decreased by hydroxyflutamide in a dose-dependent manner. Immunostaining showed that ARs were expressed in oocytes and granulosa cells in early antral follicles, and the nuclei of granulosa cells showed intense AR expression. In conclusion, although E₂ supports the OGC structure, additional androgens promote oocyte growth and their acquisition of meiotic competence via AR during in vitro growth culture.     

Effects of electromagnetic waves on oocyte maturation and embryonic development in pigs

Our living environment has been full of electromagnetic radiation (EMR) due to the prevailing electronic devices and equipment. Intermediate frequency electromagnetic field (IF-EMF) or waves constitute a significant part of EMR; therefore, an increasing number of household electrical appliances have become a source of IF-EMF, and concerns about IF-EMF on health are gaining more attention. However, little information is available about its impact on female reproductive traits, such as germ cell viability and early embryonic development, particularly at the cellular and molecular levels. In this study, we used porcine oocytes as a model system to explore the effect of IF-EMF at various intensities on the in vitro maturation (IVM) of oocytes and their subsequent embryonic development. Our results showed that no difference in oocyte maturation rates was detected among groups, but the cleavage and blastocyst rates of parthenotes derived from EMF-treated oocytes decreased with the weaker IF-EMF intensity (25 and 50 Gauss) groups compared to the control group (P < 0.05). For cytoplasmic maturation, the weaker IF-EMF intensity groups also showed a peripheral pattern of mitochondrial distribution resembling that of immature oocytes and increased autophagy activity. No obvious differences in cytoskeletal distribution and total cell numbers of blastocysts were investigated in the four IF-EMF treatments compared to those in the control group. Although the underlying mechanism associated with EMF effects on oocytes and embryos is still elusive, we have demonstrated that low intensity IF-EMF exerts harmful effects on porcine oocytes during the maturation stage, carrying over such effects to their subsequent embryonic development.