Endogenous biosynthesis of docosahexaenoic acid(DHA)regulates fish oocyte maturation by promoting pregnenolone production

Omega-3 polyunsaturated fatty acids(n-3 PUFAs),particularly docosahexaenoic acid(22:6n-3,DHA),play crucial roles in the reproductive health of vertebrates,including humans.Nevertheless,the underlying mechanism related to this phenomenon remains largely unknown.In this study,we employed two zebrafish genetic models,i.e.,elovl2^(-/-)mutant as an endogenous DHAdeficient model and fat1(omega-3 desaturase encoding gene)transgenic zebrafish as an endogenous DHA-rich model,to investigate the effects of DHA on oocyte maturation and quality.Results show that the elovl2^(-/-)mutants had much lower fecundity and poorer oocyte quality than the wild-type controls,while the fat1 zebrafish had higher fecundity and better oocyte quality than wildtype controls.DHA deficiency in elovl2^(-/-)embryos led to defects in egg activation,poor microtubule stability,and reduced pregnenolone levels.Further study revealed that DHA promoted pregnenolone synthesis by enhancing transcription of cyp11a1,which encodes the cholesterol side-chain cleavage enzyme,thereby stabilizing microtubule assembly during oogenesis.In turn,the hypothalamic-pituitary-gonadal axis was enhanced by DHA.In conclusion,using two unique genetic models,our findings demonstrate that endogenously synthesized DHA promotes oocyte maturation and quality by promoting pregnenolone production via transcriptional regulation of cyp11a1.

Markers of Oocyte Quality to Enhance Human IVF Outcomes: A Bibliographic Review

The markers of oocyte quality have remained a major controversy in the field of embryology due to the subjectivity of the different methods of oocyte assessment. Various scholars use oocyte quality and oocyte competence interchangeably. Oocyte quality can be defined as the overall health of an oocyte whereas oocyte competence refers to the ability of an oocyte to be fertilized and develop into a healthy embryo. Diminished oocyte quality is believed to be a result of alterations in oocyte growth and maturation processes that stem from several pelvic and systemic factors before and after oocyte retrieval. In this review, we focus on the morphological and nonmorphological markers of oocyte quality. Strict restrictions that limit the number of oocytes fertilized in various countries have triggered researchers around the world to come up with the most appropriate and noninvasive markers that enhance oocyte selection and optimize IVF outcomes. PubMed, Google Scholar, and the Cochrane Library were used to search for peer-reviewed, original articles about oocyte quality markers. The review was written in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Morphological markers are commonly used, but they are subjective, and no single marker can be used exclusively to predict oocyte competence and subsequent embryonic development potential. Furthermore, transcriptomics of differentially expressed genes in cumulus cells and assessment of metabolomics and other contents of follicular fluid have shown greater precision. However, their specificity to the different quality determinants needs further research.

Effect of Insulin-Transferrin-Selenium on Goat Oocytes Maturation and Embryo Development

[Objective] The research aimed to enhance culture efficiencies of oocyte and embryo of goat in vitro and to explore serum-free culture system in vitro.[Method] At present,the conventional solutions of oocyte maturation and embryo development in vitro were always added into 1% ITS(Insulin-transferrin-selenium) or using 1% ITS to replace FBS in 2 kinds culture solutions for conducting in vitro cultures of goat oocyte and parthenogenetic embryo.The influences of ITS on their developments were detected.[Result] ITS in maturation liquid of oocytes could not increase oocytes maturation rate but significantly increased blastocyst rate (58.06% vs. 48.19%)of parthenogenetic embryo.If FBS in maturation liquid of oocytes was replaced by ITS, the maturation rate, cleavage rate and blastocyst rate were basically unchanged.Adding ITS into embryo medium could increase blastocyst rate (68.30% vs. 56.82%)of parthenogenetic embryo of goat.If FBS in embryo medium was replaced by ITS,the cleavage rate didn’t change basically,while the blastocyst rate in ITS was obviously lower than that in FBS group(42.33% vs.56.82%).[Conclusion] ITS could promote maturation of oocyte in vitro and early embryonic development, in addition,ITS could replace serum in maturation medium of oocyte as serum-free culture system for conducting relevant researches.

Growth Differentiation Factor-9 Gene Expression of Mice Oocytes in Vitro and in Vivo

Mice preantral follicles were cultured in vitro for 12 days to achieve metaphase Ⅱ （M Ⅱ ） oocytes. Oocyte growth differentiation factor-9 （GDF-9） gene expression was measured during different growth stages to explore the relationship between oocyte maturation and GDF-9 gene expression. Preantral follicles of lO-day old mice were isolated from the ovaries and were cultured for 12 days. Oocytes from day 2 （D2）, D4, D6, D8, DIO, D12 cultured in vitro were named the in vitro group and oocytes of day 12 （D12）, D14, D16, D18, D20, D22 grown in vivo were named the in vivo group. Follicle survival, antrum formation and maturation rate were 89.5%, 51.8% and 56.6% respectively in follicles cultured in vitro. After RT-PCR and agarose gel electrophoresis, relative mRNA abundance of GDF-9 was measured in each group of oocytes. At day 8 - 12, the GDF-9 gene expression level of oocytes in vitro was significantly lower than that in vivo （P 〈 0.05）. We conclude that M Ⅱ oocytes can be obtained from in vitro culture of preantral follicles. The GDF- 9 gene expression of oocytes varies at different growth stages in vivo. The low expression of GDF-9 in oocytes cuhured in vitro may be the cause of their low developmental capacity.

Effects of in Vitro Maturation Time of Oocytes on Sheep Nuclear Transfer Efficiency

[Objective] The study aimed to provide references for the time of oocyte maturation in vitro and enucleation in the course of sheep nuclear transfer(NT).[Method] Compared the effects of different maturation time of oocytes on enucleation efficiency and reconstructed embryo development by means of blind enucleation and fluorescence microscopy.[Result] Treatment of IVM(in vitro maturation)19-21 h was significantly higher than IVM 16-18 h treatment in oocyte maturation rate(P<0.05)and was significantly higher than IVM 22-24 h treatment in enucleation rate(P<0.05).Three treatments had no significant difference in cleavage rate and blastocyst rate(P>0.05),but IVM 19-21 h treatment was significantly higher than the other 2 treatments in average cell number of blastocysts(P<0.05).[Conclusion] The appropriate in vitro maturation time of oocytes was 19-21 h for sheep nuclear transfer,which could significantly improve the quality of blastocysts according to the cell number per blastocyst(P<0.05).

Cloning of Rabbit Bone Morphogenetic Protein 15 and Its Expression During in vitro Maturation of Rabbit Oocytes

Partial cDNA sequence of rabbit BMP15 was cloned by RT-PCR from rabbit ovaries, showing a similarity of 83%-90% with the BMP15 nucleotide sequences in humans, mice, ovine, sheep, cows and pigs. The expression of BMP15 in rabbit cumulus-oocyte complexs during oocytes in vitro maturation （IVM） was measured by fluorescent quantitative RT-PCR method. BMP 15 was expressed at low levels in immature oocytes and increased to the highest level at 16h of IVM, which coincides with the time of cumulus cell expansion, then declined slowly under IVM cultivation. The expression pattern of BMP 15 suggested that it might be important in cumulus expansion in rabbits.

Embryonic stem cells generated by nuclear transfer of human somatic nuclei into rabbit oocytes

To solve the problem of immune incompatibility, nuclear transplantation has been envisaged as a means to produce cells or tissues for human autologous transplantation. Here we have derived embryonic stem cells by the transfer of human somatic nuclei into rabbit oocytes. The number of blastocysts that developed from the fused nuclear transfer was comparable among nuclear donors at ages of 5, 42, 52 and 60 years, and nuclear transfer (NT) embryonic stem cells (ntES cells) were subsequently derived from each of the four age groups. These results suggest that human somatic nuclei can form ntES cells independent of the age of the donor. The derived ntES cells are human based on karyotype, isogenicity, in situ hybridization, PCR and immunocytochemistry with probes that distinguish between the various species. The ntES cells maintain the capability of sustained growth in an undifferentiated state, and form embryoid bodies, which, on further induction, give rise to cell types such as neuron and muscle, as well as mixed cell populations that express markers representative of all three germ layers. Thus, ntES cells derived from human somatic cells by NT to rabbit eggs retain phenotypes similar to those of conventional human ES cells, including the ability to undergo multilineage cellular differentiation.

Optimizing Yanbian Cow Oocytes Mature in vitro and Cleavage System after Nuclear Transfer Based on Uniform Design

[Objective] The aim was to optimize Yanbian cow oocytes mature in vitro and cleavage system after nuclear transfer based on uniform design. [Method] Oocytes were recovered by aspiration method, and oocytes were matured in vitro （IVM） with different conditions, and then carried out nucleus transfer, fusion, activation and in vitro culture （IVC） of embryo. Effects of ovary storage temperature, maturation time and follicular diameter size on in vitro maturation and cleavage rates of cow oocytes were compared. [ Result] The best conditions of IVM of Yanbian cow oocytes was that： the oocytes of 8 mm diameter were matured in vitro for 24 hours when the ovaries were stored at 26℃ or 31 ℃. The best cleave conditions after nucleus transfer of oocytes was that： the oocytes of 6 mm or 8 mm diameter were cultured in vitro for 24 hours when the ovaries were stored at 26℃. [ Conclusion] The result has some reference to Yanbian cow and other cow breeding and population expanding propagation.

Manufacturing of SEM and TEM Samples for Oocyte

[ Objective] The research aimed to explore the manufacturing methods of scanning electron microscope （SEM） and transmission electron microscopy （TEM） for oocyte and provide technical support for related research. [ Method] Based on GV-and MII-stage oocytes, samples of SEM and TEM were prepared respectively, then ultrastructure changes were observed. [ Result] The results showed that the method needed few samples, keep intact cell morphology and can see clear ultrastructure. [Conclusion] The method is suitable for ultrastructural observation of oocyte.

Improvement of in vitro Cytoplasmic Maturation of Denuded Porcine Oocytes by Coculture with Follicular Mural Granulosa Cells

[Objective] This study aimed to improve the in vitro maturation quality of denuded porcine oocytes and provide scientific basis for establishing a stable and efficient denuded oocyte culture system. [Method] The first polar body extrusion rate, oocyte glutathione （GSH） content, positive rate of brilliant cresyl blue （BCB） staining and development potential of activated oocytes or fertilized oocytes were employed as main indicators to investigate the effects of follicular mural granulosa cell （MGC） coculture on cytoplasmic maturation of cumulus cell-removal oocytes （Denuded Oocyte, DO）. [Result] According to in vitro maturation results, compared with DO group, the first polar body extrusion rate of porcine oocytes in DO＋MGC group was not significantly different, but the nuclear maturation process was improved and was more similar to that in COC （cumulus-oocyte complex） group. Detection of GSH content in mature oocytes showed that there was no significant difference between DO＋ MGC group （optical density of 1 053.67） and COC group （optical density of 1 426.00） or between DO＋MGC group and COC＋GC group （optical density of 1 541.00）, however, GSH content in mature oocytes of DO group （optical density of 724.67） was significantly lower than that of COC group and COC＋GC group （P0.05）. Detection of glucose-6-phosphate dehydrogenase （G6PDH） activity showed that there was no significant difference in BCB positive oocyte rate between DO ＋MGC group （88.26% ） and COC group （92.75%） or between DO＋MGC group and DO group （82.86% ）, however, BCB positive oocyte rate of DO group was significantly lower than that of COC group （P0.05）. Furthermore, the cleavage rate and blastocyst rate of activated mature oocytes derived from DO ＋MGC group （94.98% and 43.67% , respectively） were significantly higher than those from DO group （52.54% and 8.97%, respectively） （P0.05）, and were not significantly different compared with those from COC group （97.11% and 38.30%, respectively）. In addition, the cleavage rate of fertilized oocytes derived from DO＋MGC group （72.65%） showed no significant difference compared with that from DO group （63.59%）, but the blastocyst rate of DO＋MGC group was significantly higher than that of DO group （9.88%） （P0.05）. [Conclusion] MGC coculture can significantly improve the in vitro cytoplasmic maturation quality of denuded porcine oocytes, thereby enhancing the subsequent developmental potential.

Application of PDE3 and Brilliant Cresyl Blue in In-vitro Culture of Sheep Oocyte

[Objective] The aim of this study was to increase the viability of sheep oocytes in vitro by using phosphodiesterase type 3（PDE 3） inhibitor milrinone combined with brilliant cresyl blue（BCB） staining.[Method] The differences between BCB tested and morphologically selected oocytes,as well as the effect of them on embryo development were compared;and then suitable inhibitive time of milrinone to sheep oocytes in vitro was studied and used in BCB-oocytes for in vitro embryo production（IVEP）.[Result] The BCB＋ oocytes percentage in A-and B-level sheep oocytes was 64.42%,which was extremely significantly higher than that in C-level（17.0%）.The maturing rate,cleavage rate and blastocyst rate of BCB＋ oocytes（86.16%,85.29% and 34.40%） of was significantly higher than those of BCB-oocytes（50.94%,36.19% and 6.73%）.The best time for PDE 3 inhibitor delaying the sheep oocyte mature in vitro was 6 h.In addition,the rate of embryo development in vitro could be significantly increased by inhibiting the BCB-oocytes for 6 h with Milrinone.[Conclusion] The study will provide reference for improving the efficiency of sheep oocytes culture in vitro.

In vitro Maturation of Tan Sheep Oocytes

[Objective] This study aimed to investigate the appropriate concentrations of follicle-stimulating hormone（FSH）, luteotropic hormone（LH） and estrodiol（E2） during in vitro maturation of Tan sheep oocytes. [Method] Tan sheep oocytes were divided into five groups for in vitro maturation culture： control group, FSH group（10,50, 100, 200 and 300 μg/ml FSH, respectively）, LH group（5, 10, 20, 50 and 100μg/ml LH, respectively）, E2group（5, 10, 25, 50 and 100 μg/ml E2, respectively）, and FSH ＋ LH group（100 μg/ml FSH ＋ 20 μg/ml LH）. The releasing rate of first polar bodies was analyzed. [Result] The maturation rate of Tan sheep oocytes in 100 μg/ml FSH ＋ 20 μg/ml LH group reached the highest（64.64%）, which was significantly higher than that in other four groups（P〈0.05）; among different FSH concentrations,100 μg/ml FSH was superior to other four concentrations and the control group, exhibiting significant differences（P〈0.05）; among different LH concentrations, 20 μg/ml LH was superior to other four concentrations and the control group, exhibiting significant differences（P〈0.05）; among different E2 concentrations, 50 μg/ml E2 was superior to other four concentrations and the control group, exhibiting significant differences（P〈0.05）. [Conclusion] Under the experimental conditions, 100 μg/ml FSH ＋20 μg/ml LH was the most appropriate hormone combination for in vitro maturation of Tan sheep oocytes.

Comparative Study on Activation and Fertilization of Mouse Oocytes at Different Ages

Comparisons of activation rates and fertilization rates were made among oocytes at different ages. Results showed that oocytes at different ages had different activation and fertilization rates when stimulated by sperm or ethanol. Oocytes at 15～24 h after the injection of hCG were readily activated by 8% ethanol. The activation rate of oocytes increased with the age of oocytes, up to the highest average of 81.6%, but decreased after 20 h posthCG. Oocytes at 20 h posthCG exhibited the highest immediate cleavage rate(48.0%) after being stimulated by ethanol. On the other hand, 13～15 h oocytes exhibited higher fertilization rates, and the older oocytes were more difficult to be fertilized by sperm in vitro. These suggest that oocytes can be activated in different ways; the mechanism of fertilization might be different from that of activation; and in vitro fertilization is more dependent on oocyte age.

Presence and integration of HBV DNA in mouse oocytes

AIM: Hepatitis B is a worldwide public health problem. To explore the feasibility of hepatitis B virus (HBV) vertical transmission via oocytes, the presence and integration of HBV DNA in mouse oocytes were studied. METHODS: Genomic DNA was isolated and metaphases were prepared, respectively from mouse oocytes cocultured with pBR322-HBV DNA plasmids. PCR, Southern blot, dot hybridization and fluorescence in situ hybridization (FISH) were performed to explore the existence and integration of HBV DNA in oocytes.RESULTS: PCR detected positive bands in the tested samples, and then Southern blot revealed clear hybridization signals in PCR products. Final washing solutions were collected for dot hybridization and no signal for HBV DNA was observed, which excluded the possibility that contamination of washing solutions gave rise to positive results of PCR and Southern blot. FISH demonstrated that 36 of 1 000 metaphases presented positive signals. CONCLUSION: HBV DNA sequences are able to pass through the zona and oolemma to enter into oocytes and tointegrate into their chromosomes. HBV DNA sequences might be brought into embryo via oocytes as vectors when they are fertilized with normal spermatozoa.

Selection of oocytes for in vitro maturation by brilliant cresyl blue staining： a study using the mouse model

Selecting oocytes that are most likely to develop is crucial for in vitro fertilization and animal cloning. Brilliant cresyl blue （BCB） staining has been used for oocyte selection in large animals, but its wider utility needs further evaluation. Mouse oocytes were divided into those stained （BCB＋） and those unstained （BCB-） according to their ooplasm BCB coloration. Chromatin configurations, cumulus cell apoptosis, cytoplasmic maturity and developmental competence were compared between the BCB＋ and BCB- oocytes. The effects of oocyte diameter, sexual maturity and gonadotropin stimulation on the competence of BCB＋ oocytes were also analyzed. In the large- and medium-size groups, BCB＋ oocytes were larger and showed more surrounded nucleoli （SN） chromatin configurations and higher frequencies of early atresia, and they also gained better cytoplasmic maturity （determined as the intracellular GSH level and pattern of mitochondrial distribution） and higher developmental potential after in vitro maturation （IVM） than the BCB-oocytes. Adult mice produced more BCB＋ oocytes with higher competence than the prepubertal mice when not primed with PMSG. PMSG priming increased both proportion and developmental potency of BCB＋ oocytes. The BCB＋ oocytes in the large-size group showed more SN chromatin configurations, better cytoplasmic maturity and higher developmental potential than their counterparts in the medium-size group. It is concluded that BCB staining can be used as an efficient method for oocyte selection, but that the competence of the BCB＋ oocytes may vary with oocyte diameter, animal sexual maturity and gonadotropin stimulation. Taken together, the series of criteria described here would allow for better choices in selecting oocytes for better development.

Effects of MEK inhibitor U0126 on meiotic progression in mouse oocytes: microtuble organization, asymmetric division and metaphase Ⅱ arrest

In this study we used U0126, a potent and specific inhibitor of MEK, to study the roles of MEK/ERK/p90rsk signaling pathway in the meiotic cell cycle of mouse oocytes. The phosphorylation of MAP kinase and p90rsk in the oocytes treated with 1.5 μMU0126 was the same as that in oocytes cultured in drug-free medium. With 1.5 μM U0126 treatment, the spindles appeared normal as they formed in oocytes, but failed to maintain its structure.Instead, the spindle lost one pole or elongated extraordinarily. After further culture, some oocytes extruded gigantic polar bodies (＞30 μm) that later divided into two small ones. Some oocytes underwent symmetric division and produced two equal-size daughter cells in which normal spindles formed. In oocytes with different division patterns,MAP kinase was normally phosphorylated. When the concentration of U0126 was increased to 15 mM, the phosphorylation of both MAPK and p90rsk were inhibited, while symmetric division was decreased. When incubating in medium containing 15 μM U0126 for 14 h, oocytes were activated, but part of them failed to emit polar bodies. MII oocytes were also activated by 15 μM U0126, at the same time the dephosphorylation of MAP kinase and p90rsk was observed. Our results indicate that 1) MEK plays important but not indispensable roles in microtubule organization;2) MEK keeps normal meiotic spindle morphology, targets peripheral spindle positioning and regulates asymmetric division by activating some unknown substrates other than MAP kinase/p90rsk; and 3) activation of MEK/ERK/p90rsk cascade maintains MII arrest in mouse oocytes.

A novel ubiquitin carboxyl terminal hydrolase is involved in toad oocyte maturation

p28, a 28kD protein from toad (Bufo bufo gargarizans) oocytes, was identified by using p13sucl-agarose affinity chromatography. Sequence homology analysis of the full-length cDNA of p28 (Gene Bank accession number: AF 314091) indicated that it encodes a protein containing 224 amino-acids with about 55% identities and more than 70% positives to human, rat or mouse UCH-L1, and contains homological functional domains of UCH family. Anti-p28 monoclonal antibody, on injecting into the oocytes, could inhibit the progesterone-induced resumption of meiotic division in a dose-dependent manner. The recombinant protein p28 showed similar SDS/PAGE behaviors to the native one, and promoted ubiquitin ethyl ester hydrolysis, a classical catalytic reaction for ubiquitin carboxyl terminal hydrolases (UCHs). The results in this paper reveal that a novel protein, p28, exists in the toad oocytes, is a UCH L1 homolog, was engaged in the process of progesterone-induced oocyte maturation possibly through an involvement in protein turnover and degradation.

Effect of Mouse Oocyte Vitrification on Mitochondrial Membrane Potential and Distribution

The effects of mouse oocyte vitrification on mitochondrial membrane potential and distribution were explored in this study. The collected mouse oocytes were randomly divided into vitrification and control groups. Ethylene glycol（EG） and dimethylsulphoxide（DMSO） were used as cryoprotectants in the vitrification group. The mitochondrial function and distribution in the oocytes were examined by using the fluorescent probes, JC-1 and Mito Tracker green. The results showed that the ratio of red to green fluorescence in mouse oocytes was significantly decreased after thawing in the vitrification group as compared with the control group（1.28 vs. 1.70, P0.05）. The percentage of polarized distribution of the mitochondria in oocytes was conspicuously reduced in the vitrification group when compared with the control group（31% vs. 63%, P0.05）. It was suggested that vitrification significantly affects the mitochondrial function and distribution in oocytes and reduces the potential of oocyte fertilization and embryo development.

Lipid transport to avian oocytes and to the developing embryo

Studies of receptor-mediated lipoprotein metabolic pathways in avian species have revealed that physiological intricacies of specific cell types are highly analogous to those in mammals. A prime example for the power of com- parative studies across different animal kingdoms, elucidated in the chicken, is that the expression of different lipo- protein receptors in somatic cells and oocytes are the key to oocyte growth. In avian species, yolk precursor transport from the hen＇s liver to rapidly growing oocytes and the subsequent transfer of yolk nutrients via the yolk sac to the developing embryo are highly efficient processes. Oocytes grow from a diameter of 5 mm to 2.5-3 cm in only 7 days, and the yolk sac transfers nutrients from the yolk stored in the mature oocyte to the embryo within just 2 weeks. The underlying key transport mechanism is receptor-mediated endocytosis of macromolecules, i.e., of hepatically synthesized yolk precursors for oocyte growth, and of mature yolk components for embryo nutrition, respectively. Recently, the receptors involved, as well as the role of lipoprotein synthesis in the yolk sac have been identified. As outlined here, lipoprotein degradation/resynthesis cycles and the expression of lipoprotein receptors are not only coordinated with the establishment of the tbllicular architecture embedding the oocyte, but also with the generation of the yolk sac vasculature essential for nutrient transfer to the embryo.

Isorhamnetin protects porcine oocytes from zearalenone-induced reproductive toxicity through the PI3K/Akt signaling pathway

Background Zearalenone(ZEA)widely exists in moldy grains,which seriously destroys the fertility of females.Isorhamnetin,a natural flavonoid,has extensive of pharmacological activities.However,the beneficial effect and the underlying molecular mechanism of isorhamnetin involvement in ZEA-induced porcine oocyte damage have not been investigated.Methods Oocytes were treated with different concentrations of ZEA(3,5,8 and 10μmol/L)and isorhamnetin(5,10,20 and 30μmol/L)for 44 h at 39℃.ZEA(5μmol/L)and isorhamnetin(10μmol/L)were selected for subsequent studies.Polar body exclusion rate,apoptosis rate and apoptosis related proteins,ROS levels and SOD2 protein,mitochondrial membrane potential and distribution,endoplasmic reticulum distribution and proteins expression,and PI3K,Akt and p-Akt proteins expression of oocytes were detected.In addition,the effect of PI3K antagonist(LY294002)on oocyte nuclear maturation and apoptosis were used to determine the involvement of PI3K/Akt signaling pathway.Results Our findings showed that ZEA exposure damaged oocytes and isorhamnetin therapy restored the developmental capability of porcine oocytes.Isorhamnetin promoted polar body extrusion rate to rescue ZEA-induced meiotic arrest in porcine oocytes.Isorhamnetin alleviated ZEA-induced oxidative stress by stimulating SOD2 protein expression and inhibiting ROS production.Moreover,isorhamnetin enhanced normal mitochondrial distribution and mitochondrial membrane potential to prevent mitochondrial dysfunction induced by ZEA.Changing the expression of endoplasmic reticulum stress-related marker proteins(CHOP,GRP78)and the distribution rate of normal endoplasmic reticulum showed that isorhamnetin relieved ZEA-caused endoplasmic reticulum stress.Mechanistically,isorhamnetin decreased Bax/Bcl-2 protein expression and inhibited ZEA-induced apoptosis through PI3K/Akt signaling pathway.Conclusions Collectively,these results suggest that isorhamnetin protects oocytes from ZEA-caused damage through PI3K/Akt signaling pathway,which enhances meiotic maturation and mitochondrial function,and inhibits early apoptosis,oxidative stress and endoplasmic reticulum stress in porcine oocytes.Our study provides a new strategy for solving the reproductive toxicity induced by ZEA and treating woman infertility.