The plastic monomer bisphenol A (BPA) is well known as a representative environmental hormones. Recent studies showed that the BPA exposure induced mitochondrial dysfunction and mitochondrial derived reactive oxygen species (mito-ROS). However, changes of antioxidant enzymes expression and ROS production from mitochondria according to the BPA exposure on in vitro maturation (IVM) of porcine oocytes have not been studied. We hypothesized that regulation of ROS production from mitochondria by BPA may play a critical role in meiotic maturation or expansion of cumulus cells in cumulus-oocyte complexes (COCs). To investigate the negative effects of BPA exposure on oocyte maturation, immature pig oocytes were matured in NCSU-23 medium supplemented with BPA (50, 75 and 100 μM) for 44 h. Expectedly, the rates of meiotic maturation and cumulus cell expansion of COCs in the BPA (75 μM) treated group was significantly lower than those of control group (p<0.01). Most of secretion factors expressions from COCs were significantly decreased (p<0.05) in the BPA treated COCs. Next, we investigated the intracellular ROS and mitochondrial specific superoxide production according to the BPA exposure using DCF-DA and mito-SOX staining, respectively. BPA exposure were showed that increasing of both intracellular ROS and mito-ROS, as well as mitochondrial related antioxidant enzymes (sod2, prdx3, prdx5) mRNA expression significantly increased (p<0.01) in COCs. And then, mitochondria membrane potential (MMP) dramatically reduced, and mitochondrial-derived apoptotic factors (bax, bcl-xl, caspase 3) mRNA expressions were increased (p<0.01) in BPA treated COCs. In additon, protein levels of mitochondrial-derived apoptosis genes (AIF, cleaved parp1 and caspase 3) were significantly increased (p<0.05) by BPA exposure. To confirm the reduction of BPA-induced mito-ROS, we used to the mitochondrial-targeted ROS scavenger, mito-TEMPO. Interestingly, addition of mito-TEMPO (0.1 μM) to the BPA pre-treated COCs recovered in meiotic maturation of porcine oocytes. These results demonstrated that BPA exposure was induced increasing of mitochondrial dysfunction, mito-ROS and mitochondrial-mediated apoptosis on pig oocyte maturation. Therefore, we suggest that controlling of mito-ROS plays a critical role in pig oocyte maturation in vitro. These findings will be helpful to solve causes of mitochondrial-related infertility.

Melatonin has an important role as anti-oxidative effect and reducing of endoplasmic reticulum(ER)-stress on oocyte maturation and embryo development. Under ER-stress condition, unfolding protein response (UPR) is a defence mechanism in mammalian cells. Recently, regulation of UPR signaling genes are involved in oocyte maturation, embryo development and female reproduction. However, there is no report on the role of melatonin for UPR signaling and ER-stress mediated apoptosis during pig oocyte maturation progression. Moreover, the changes of UPR genes expression according to the porcine oocyte maturation is not yet fully understood. Here, we investigated the changes of UPR signal (BIP/GRP78, ATF4, p90/p50ATF6, and XBP1) and ER-stress apoptotic factor CHOP genes expressions in porcine oocyte maturation by Western blot and RT-PCR analysis. During oocyte maturation, UPR marker and CHOP genes expressions were significantly increased in matured oocytes or cumulus-oocyte complexes (COCs). UPR markers expressions were significantly increased by ER-stress inducer, tunicamycin (Tm), treated (1, 5, 10 μg/ml) groups in a dose-dependent manner compared with control group. To confirm the reducing of ER-stress by melatonin (0.1 μM), we were compared to the effects of ER-stress inhibitor, TUDCA (200 μM), after pre-treated Tm (5 μg/ml) for 22 h maturation. Expressions of UPR markers and meiotic maturation were recovered by melatonin (0.1 μM) in COCs. And, we observed the role of Grp78/Bip as UPR signaling beginning marker using siRNA. In result, reduction of Grp78/Bip gene expression by siRNA was induced the inhibition of oocyte maturation (32.5±10.1 vs control; 77.8±5.3), and p50ATF6 protein level was significantly decreased (p<0.001) in cultured COCs for 44 h. In addition, these results were recovered through the addition of melatonin (0.1 μM) or TUDCA (200 μM) in maturation medium. These results demonstrated that the regulation of UPR signaling via Grp78/Bip gene induction plays a critical role in porcine oocyte maturation in vitro. Furthermore, this present study first confirmed a functional link between inhibition effect of ER-stress by melatonin and regulating of UPR signaling in porcine oocyte maturation. In conclusion, melatonin improves the oocyte maturation and cumulus cells expansion of COCs through the regulation of UPR signal pathway by BIP/GRP78 against the ER-stress during porcine oocyte maturation periods.

Mitotic spindle formation is regulated by centrosomes, composed of a centriole pair surrounded by pericentriolar materials(PCM) proteins. However, mammalian oocytes rely on acentriolar MTOCs for the function of meiotic spindle. The composition of acentriolar MTOCs and the molecular precesses that regulate the localization and accumulation in mammalian oocyte are not well understood. In this study, we analyzed the mechanisms of spindle microtubule nucleation and stability from MTOCs in mouse oocyte, and indentified Centrosomal protein192(CEP192) as a key regulator for acentriolar MTOC formation. CEP192 specifically colocalized with pericentrin (PCNT) during the oocyte maturaion. CEP192 proteins are localized throughout cytoplasm and around nucleus at GV stage, and then after BD stage, CEP192 proteins were further fragmented into smaller MTOCs around chromosomes. At metaphase, CEP192 proteins were concentrated in spindle pole. Knockdown of CEP192 using siRNAs resulted in metaphase I arrest. The arrested oocytes were characterized by reduced microtubule intensity and misalignment chromosome. Also at BD and ProMI stage, the oocytes reduced microtubule density and PCNT intensity. To confirm the mechanism of CEP192 regulation, we confirmed that PLK1 and AuroraA kinase were involved in CEP192 activation. The investigations for detailed molecular mechanisms of CEP192 and RanGTP for microtubule nucleation in oocytes are underway using various techniques including siRNA, mRNA, and positive or negative dominant injection and inhibitors.

Growth differentiation factor 8 (GDF8) is a member of the transforming growth factor-β that has been identified as a strong physiological regulator. The purpose of this study is to investigate the effects of GDF8 on porcine oocytes during in vitro maturation (IVM). We investigated a specific gene transcription levels in oocytes and cumulus cells (CC) after IVM, and protein kinase B (PKB) expression and activation levels in matured CCs by western blotting. Each concentration (0, 1, 10, and 100 ng/ml) of GDF8 was treated in maturation medium (TCM199) while process of IVM. Data were analyzed by ANOVA followed by Duncan using SPSS (Statistical Package for Social Science). Data are presented as the mean and differences were considered significant at P < 0.05. After 44 h of IVM, oocytes are mechanically denuded from CCs with 0.1% of hyaluronidase, and then the separated each group of oocytes and CCs were sampled. To assess the effect of GDF8 on specific gene transcription level changes as a dose response during IVM, the realtime PCR was performed. In CCs, all of GDF8 treatment groups showed significantly higher CREB transcription regulator cbp mRNA and the 1- and 10 ng/ml treatment groups observed significantly increased cumulus expansion related genes areg, cox-2, has2, ptx3 and tnfaip6 transcription levels after IVM. In matured oocytes, the maternal factors jmjd3 and zar1, transcriptional regulator foxo1 and sirt1, mitochondrial activity factor sirt3 and acadl, and anti-apoptosis gene bcl-2 mRNA transcription levels were significantly increased in 1- and10 ng/mL of GDF8 treatment groups compared with control. To determine effect of GDF8 treatment during IVM, translation regulator PKB protein expression and phosphorylation levels were analyzed in CCs by western blotting. The 10 ng/ml treatment group showed significantly increased phosphorylated PKB (1.4 times higher than control) protein levels (P < 0.05). In conclusion, treatment 10 ng/ml of GDF8 during IVM activates CREB related transcription and induced cumulus cells expansion via activation of PKB signaling in CCs. The transcriptional landscape changes in CCs result maternal factors accumulation and mitochondrial activation in oocytes during IVM.

α-solanine is toxic to human health by disturbing digestive and central nervous systems. However, little information has been focused on investigated with respect to α-solanine influence in mammal oocyte maturation and quality. In this study, we investigated the effects of α-solanine on oocyte maturation, quality and possible molecular mechanisms in a pig model. Porcine Cumulus-oocyte complexes (COCs) were treated with increasing concentration (0, 1, 10, 20, 50 μM) of α-solanine subjected to further in vitro maturation culture. The result showed that α-solanine significantly inhibited cumulus cells expansion and increased oocyte death rates when the concentration of α-solanine more than 10 μM. After cell cycle and cytoskeleton analysis, the results showed that α-solanine (10 μM) disturbed meiotic resumption, increased abnormal spindle formation and cortical granules (CGs) distribution rates when compared with the untreated group. α-solanine (10 μM) triggered autophagy by increasing the expression of autophagy-related genes (LC3, ATG7, LAMP2) and accumulation of LC3-specific puncta (an autophagy maker). TUNEL staining assay showed that α-solanine significantly increased apoptosis in porcine oocytes confirmed by up-regulated the levels of BAX and CAPS3 genes. Further study revealed that exposure α-solanine (10 μM) to porcine oocytes induced ROS generation, reduced mitochondrial membrane potential. In addition, our results suggested that α-solanine (10 μM) significantly increased the levels of H3K36me3 and H3K27me3 in porcine oocytes. Taken together, these data indicated that α-solanine toxic impaired oocyte maturation and quality by inhibited cumulus cells expansion, increased abnormal spindle and CGs distribution rates, triggered autophagy/apoptosis occur, accumulated ROS, decreased mitochondrial membrane potential, and changed epigenetic modifications.

Maturation-promoting factor (MPF) is well-known as cell cycle regulator during oocyte maturation and fertilization. MPF activity maintains high levels and arrest the cell cycle progression until fertilization. After fertilization, Anaphase-promoting complex/cyclosome (APC/C) mediated degradation of cyclin B causes decrease of MPF activity. One of the cytostatic factor (CSF), Emi2 inhibits APC/C activity by binding to APC/C-cdc20, therefore blocks the proteolysis of cyclin B. Degradation of Emi2 requires phosphorylation by Polo-like kinase 1 (Plk1). Thus recognition and phosphorylation of Emi2 by Plk1 are essential step for meiotic cell cycle resumption. In our previous research, we found that two phosphorylated threonine regions at amino acid position 152 and 176 in Emi2 are respectively contributed for recognition by polo-box domain of Plk1. Peptidomimetics 103-8 can block the interaction between Plk1-PBD and Emi2, and therefore meiotic maturation and meiosis resumption via parthenogenetic activation were impaired. However, major drawback of 103-8 was the limitation of penetration through the cell membrane. We synthesized the new peptidomimetics and checked bioavailability in mammalian oocyte by injection and media treatment. Medium treatment with peptidomimetics C-4, meiotic maturation has significantly decreased and meiotic resumption via parthenogenetic activation has perfectly impaired. For the next experiment, we are preparing X-ray crystallography to identify the binding modes between Plk1-PBD and peptidomimetics C-4.

Actin nucleation factors, which promote the formation of new actin filaments, have emerged in the last decade as key regulatory factors controlling asymmetric division in mammalian oocytes. Actin nucleators such as formin-2, spire, and the ARP2/3 complex have been found to be important regulators of actin remodeling during oocyte maturation. We found that actin nucleation promoting factor called WASP homolog-associated protein with actin, membranes and microtubules (WHAMM) play crucial roles in mouse oocyte maturation by generation of ER-associated actin filaments during meiotic spindle migrations. We also investigate regulatory mechanism of actin nucleator spire and discovered the novel roles of Zinc in regulating spire localization and cytoplasmic actin mesh formation. Another class of actin-binding proteins including cofilin, tropomyosin, capping proteins and tropomodulin, are thought to control actin cytoskeleton dynamics at various steps of oocyte maturation. The heterodimeric actin-capping protein (CP) binds to the fast-growing (barbed) ends of actin filaments and plays essential roles in various actin-mediated cellular processes. When CP is knockdowned or inhibitory component was overexpressed, asymmetric divisions of oocytes have been compromised. It turns out that knockdown or inhibition of CP deplete cytoplasmic actin mesh level, which have been known to be essential for maintain cytoplasmic actin mesh. Another actin binding proteins, tropomodulin 3 (Tmod3), binds to the slow-growing end of actin filaments and knockdown or expression deletion mutant of Tmod3 also decrease actin mesh level in maturing oocyte and it severely ablated asymmetric division of oocyte. Finally, tropomyosin 3, actin filament binding proteins protect actin filament from depolymerization, is also important to maintain cortex integrity in maturing oocyte, therefore showed the importance maintenance of actin filaments during oocyte maturation. Taken together, our study on various actin nucleator and actin binding study showed the importance of actin dynamics in mammalian oocyte maturation and early embryonic developments.

CDK2 inhibition plays a central role in DNA damage–induced cell cycle arrest and DNA repair. However, whether CDK2 also influences early porcine embryo development is unknown. In this study, we examined whether CDK2 is involved in the regulation of oocyte meiosis and early embryonic development of porcine. We found that disrupting CDK2 activity with RNAi or an inhibitor did not affect meiotic resumption or MII arrest. However, CDK2 inhibitor-treated embryos showed delayed cleavage and ceased development before the blastocyst stage. Disrupting CDK2 activity is able to induce sustained DNA damage as demonstrated by the formation of distinct γH2AX foci in nuclei of day 3- and day 5-embryos. Inhibiting CDK2 triggers a DNA damage checkpoint by activating of the ATM-P53-P21 pathway. However, the mRNA expression of genes involved in non-homologous end-joining (NHEJ) or homologous recombination (HR) pathways for double strand break (DSB) repair reduced after administering CDK2 inhibitor to 5-day-old embryos. Furthermore, CDK2 inhibition caused apoptosis in day 7 blastocysts. Thus, our results indicate that an ATM-P53-P21 DNA damage checkpoint is intact in the absence of CDK2; however, CDK2 is important for proper repair of the damaged DNA by either directly or indirectly influencing DNA repair-related gene expression.

(-)-Epicatechin gallate (ECG) is a polyphenol compound of green tea exhibiting biological activities, such as antioxidant and anticancer effects. To examine the effect of ECG on porcine oocytes during in vitro maturation (IVM), oocytes were treated with 0-, 5-, 15-, and 25 μM ECG. After maturation, we investigated nuclear maturation, intracellular glutathione (GSH) and reactive oxygen species (ROS) levels and subsequent embryonic development after parthenogenetic activation (PA) and in vitro fertilization (IVF). After 42 hours of IVM, the 5 μM group exhibited significantly increased (p< 0.05) nuclear maturation (89.8%) compared with the control group (86.1%). However, the 25 μM group observed significantly decreased (p< 0.05) nuclear maturation (83.5%). In intracellular maturation assessment the 5-, 15-, and 25 μM groups had significantly increased (p< 0.05) GSH levels and decreased ROS levels compared with the controls. The 5- and 15 μM group showed significantly increased (p< 0.05) embryo formation rates and total cell number of blastocysts after PA (18% and 68.9, 15% and 85.1 vs. 12% and 59.5, respectively) compared with controls. Although the 25 μM group observed significantly lower blastocyst formation rates after PA (27.6% vs. 23.2%) than control group, the 5 μM group showed significantly increased blastocyst formation rates after PA (37.2% vs. 23.2%) compared to the control group. Furthermore, the 5 μM group measured significantly increased blastocyst formation rates (20.7% vs. 8.6%) and total cell number after IVF (88.3±1.5 vs. 58.0±3.6) compared to the control group. The treatment of 5 μM ECG during IVM affectively improved the porcine embryonic developmental competence by regulating intracellular oxidative stress during IVM.

Gangliosides exist in glycosphingolipid-enriched domains on the cell membrane and regulate various functions such as adhesion, differentiation, and receptor signaling. Ganglioside GM3 by ST3GAL5 enzyme provides an essential function in the biosynthesis of more complex ganglio-series gangliosides. However, the role of gangliosides GM3 in porcine oocytes during in vitro maturation and early embryo development stage has not yet understood clear. Therefore, we examined ganglioside GM3 expression patterns under apoptosis stress during maturation and preimplantation development of porcine oocytes and embryos. First, porcine oocytes cultured in the NCSU-23 medium for 44 h after H2O2 treated groups (0.01, 0.1, 1 mM). After completion of meiotic maturation, the proportion MII (44 h) was significantly different among control and the H2O2 treated groups (76.8±0.3 vs 69.1±0.4; 0.01 mM, 55.7±1.0; 0.1 mM, 38.2±1.6%; 1 mM, P<0.05). The expressions of ST3GAL5 in H2O2 treated groups were gradually decreased compared with control group. Next, changes of ST3GAL5 expression patterns were detected by using immunofluorescene (IF) staining during preimplantation development until blastocyst. As a result, we confirmed that the expressions of ST3GAL5 in cleaving embryos were gradually decreased (P<0.05) according to the early embryo development progress. Based on these results, we suggest that the ganglioside GM3 was used to the marker as pro-apoptotic factor in porcine oocyte of maturation and early embryo production in vitro, respectively. Furthermore, our findings will be helpful for better understanding the basic mechanism of gangliosides GM3 regulating in oocyte maturation and early embryonic development of porcine in vitro.

The oocyte undergoes various events during maturation and requires many substances for the maturation process. Various intracellular organelles are also involved in maturation of the oocyte. During the process glucose is essential for nuclear and cytoplasmic maturation, and adenosine triphosphate is needed for reorganization of the organelles and cytoskeleton. If mitochondrial function is lost, several developmental defects in meiotic chromosome segregation and maturation cause fertilization failure. The endoplasmic reticulum, a store for Ca2+, releases Ca2+ into the cytoplasm in response to various cellular signaling molecules. This event stimulates secretion of hormones, growth factors and antioxidants in oocyte during maturation. Also, oocyte nuclear maturation is stimulated by growth factors such as epidermal growth factor. This review summarizes roles of organelles with focus on the Golgi apparatus during maturation in oocyte.

The present study assessed the effect of FSH and LH on oocyte meiotic, cytoplasmic maturation and on the expression level and polyadenylation status of several maternal genes. Cumulus-oocyte complexes were cultured in the presence of FSH, LH, or the combination of FSH and LH. Significant cumulus expansion and nuclear maturation was observed upon exposure to FSH alone and to the combination of FSH and LH. The combination of FSH and LH during entire IVM increased the mRNA level of four maternal genes, C-mos, Cyclin B1, Gdf9 and Bmp15, at 28 h. Supplemented with FSH or LH significantly enhanced the polyadenylation of Gdf9 and Bmp15; and altered the expression level of Gdf9 and Bmp15. Following parthenogenesis, the exposure of oocytes to combination of FSH and LH during IVM significantly increased cleavage rate, blastocyst formation rate and total cell number, and decreased apoptosis. In addition, FSH and LH down-regulated the autophagy gene Atg6 and upregulated the apoptosis gene Bcl-xL at the mRNA level in blastocysts. These data suggest that the FSH and LH enhance meiotic and cytoplasmic maturation, possibly through the regulation of maternal gene expression and polyadenylation. Overall, we show here that FSH and LH inhibit apoptosis and autophagy and improve parthenogenetic embryo competence and development.

The objective of this study was to examine the effect of in vitro maturation (IVM) medium, cytochalasin B (CB) treatment during intracytoplasmic sperm injection (ICSI), and electric activation on in vitro development ICSI-derived embryos in pigs. Immature pig oocytes were matured in vitro in medium 199 (M199) or porcine zygote medium (PZM)-3 that were supplemented with porcine follicular fluid, cysteine, pyruvate, EGF, insulin, and hormones for the first 22 h and then further cultured in hormone-free medium for an additional 21～22 h. ICSI embryos were produced by injecting single sperm directly into the cytoplasm of IVM oocytes. The oocytes matured in PZM-3 with 61.6 mM NaCl (low-NaCl PZM-3) tended to decrease (0.05<P<0.1) nuclear maturation when compared with oocytes matured in M199 (76.9% vs. 83.8%) but no significant differences were found in embryo cleavage, blastocyst formation, and mean number of cells in blastocyst (73.8% vs. 74.6%, 11.1% vs. 12.1%, and 28.4 cells vs. 30.1 cells, respectively). The oocyte degeneration was not reduced by CB treatment during ICSI (11.9%) when compared with no treatment control (11.3%) while the treatment showed detrimental effects (P<0.05) on embryonic cleavage (40.0%) and blastocyst formation (1.8%) rates when compared with control (60.0% and 11.5%, respectively). For activation of ICSI oocytes, additional electric stimulus has no positive or negative effect on in vitro development of preimplantation stage ICSI porcine embryos. Our results demonstrate that CB treatment during ICSI inhibits embryonic development of ICSI oocytes and additional electric activation after ICSI has no effect in improving ICSI embryonic development in pigs. Further studies are needed to improve ICSI efficiency by investigating factors influencing embryonic development after ICSI in pigs.

Biotechnologies for cloning animals and in vitro embryo production have the potential to produce biomedical models for various researches. Especially, pigs are a suitable model for xenotransplantation, transgenic production and various areas of reproductive research due to its physiological similarities to human. However, utilization of in vitro-produced embryos for transfer remains limited. Despite improvement over past few decades, obstacles associated with the production of good quality embryos in vitro still exist which limit the efficiency of cloning. One of major problems includes improper in vitro maturation (IVM) and culture (IVC). Oxidative stress caused from in vitro culture conditions contributes to inadequate IVM and IVC which leads to poor developmental competence of oocytes, failure of fertilization and embryo development. To reduce the oxidative stress, various antioxidants have been used to IVM and IVC system. However, limited information is available on the effects of resveratrol on livestock reproductions. Resveratrol is a polyphenolic natural product and well known as an antioxidant in foods and beverages (e.g. in grapes and red wine). Resveratrol is known to be cardioprotective, anticarcinogenic, anti-inflammatory, antioxidant and antiapoptotic. This paper will review the effects of resveratrol on in vitro maturation of oocytes and embryo development.

It is well established that mammalian cumulus cell (CC) expansion requires BMP15 (bone morphogenetic protein bone morphogenetic protein 15) and GDF9 (growth differentiation factor 9). However, the mechanisms of the factors in CC expansion are largely unclear. This study was conducted to examine the two paracrine factors and their receptor SMAD intracellular signaling mechanism of mediating porcine CC expansion and oocyte maturation, and to compare COCs (Cumulus–oocyte complexes) maturation to DOs (Denuded oocytes). COCs and DOs were in vitro matured in medium with FSH, LH and TGFB superfamily antagonists. Our results showed that the expansion of COCs was unaffected by addition of GDF9 and BMP15 recombinant protein, but cumulus cell proliferation and DOs maturation rate were enhanced. The mRNA expressions of SMAD receptor confirmed that oocytes secreted factors that activate SMAD3,4 and SMAD1 in granulosa cells and oocytes, but unaffected SMAD2. Treatment of COCs with a SMAD2/3 phosphorylation inhibitor (SB431542) inhibited CC expansion and expression of TNFAIP6. SB431542 also was revealed to inhibit DOs maturation. The activation of CC SMAD signaling by oocytes, and the requirement of SMAD2/3 signaling for expansion and oocyte maturation were studied in pig. Nonetheless, porcine oocyte maturation without SMAD2/3 signaling is likely to be needed for optimal matrix formation, but also BMP15 and GDF9 is likely to be needed in oocyte.

The objective of the present study was to investigate the effects of different concentrations of sorbitol supplementation for in vitro maturation medium and in vitro culture medium, on porcine cumulus oocyte complexe(COC) maturation and subsequent developmental capacity after parthenogenetic activation. Porcine COC were cultured for 44 h(0～ 22 h termed MI stage and 22～44 h termed MII stage) in TCM199 without(— ) or with(+) sorbitol (20 μM, 100 μM, 200 μM), and the resultant metaphase II oocytes cultured in PZM-3 for 7 days following activation. Our results showed that supplementation with appropriate concentrations of sorbitol (20 μM) during full term maturation culture(MI+/MII+) significantly(p<0.05) improved blastocyst formation rates and total cell number. When the concentration of sorbitol were increased to 100 μM and 200 μM during maturation culture, the maturation rate of COC were significantly reduced compared with 20 μΜ or control groups. Also blastocyst formation rates significantly(p<0.05) reduced with increasing concentration of sorbitol(200 μM). Supplementation with sorbitol(20 μM, 50 μM, 100 μM) into PZM-3 for in vitro culture significantly(p<0.05) inhibited blastocyst formation compared with control group. However, the blastocyst formation rates start to rise again when 50 μ M sorbitol was used for the first 48 hours and then cultured in PZM-3 without sorbitol. There was no significant difference in cell number between control and sorbitol treated groups. When the activated oocytes were cultured in PZM-3 for 48h and then cultured in PZM-3 with sorbitol, interestingly, the blastocyst formation rate was similar to that of PZM-3 with sorbitol for in vitro culture and significantly lower than control group. These results suggest that addition of low concentrations of sorbitol(20 μM) during oocyte maturation is beneficial for subsequent blastocyst development and improved embryo quality. However, treatment with sorbitol supplementation during in vitro culture medium is negative effect to blastocyst formation.

In all the studies of mammalian species, chromatin in the germinal vesicle (GV) is initially decondensed with the nucleolus not surrounded by heterochromatin (the NSN configurations). During oocyte growth, the GV chromatin condenses into perinucleolar rings (the SN configurations) or other corresponding configurations with or without the perinucleolar rings, depending on species. During oocyte maturation, the GV chromatin is synchronized in a less condensed state before germinal vesicle breakdown (GVBD) in species that has been minutely studied. As not all the species show the SN configuration and gene transcription always stops at the late stage of oocyte growth, it is suggested that a thorough condensation of GV chromatin is essential for transcriptional repression. Because the GV chromatin status is highly correlated with oocyte competence, oocytes must end the NSN configuration before they gain the full meiotic competence and they must take on the SN or corresponding configurations to stop gene transcription before they acquire the competence for early embryonic development. In this study, we firstly investigated whether the follicle size could determine chromatin configuration in porcine oocyte. For this experiment, follicles was divided into three groups (<1 mm follicle, 1～3 mm follicle and 3～6 follicle). Using DAPI staining, the GV nucleolus and chromatin of porcine oocytes was classified into SN, SN-NSN and NSN configurations. MⅠ and M Ⅱ of three groups's Mature oocytes by staining was confirmed the configuration of chromatin. The maturation rate and parthenogenetic development potential were significant different between the SN and NSN configurations oocytes. These results indicated that chromatin changes in GV oocytes affect the development potential of porcine embryos.