In vivo oocytes grow and mature in ovarian follicles whereas oocytes are matured in vitro in plastic culture dishes with a hard surface. In vivo oocytes show a superior developmental ability to in vitro counterparts, indicating suboptimal environments of in vitro culture. This study aimed to evaluate the influence of an agarose matrix as a culture substrate during in vitro maturation (IVM) on the development of pig oocytes derived from small antral follicles (SAFs). Cumulusoocyte complexes (COCs) retrieved from SAFs were grown in a plastic culture dish without an agarose matrix and then cultured for maturation in a plastic dish coated without (control) or with a 1% or 2% (w/v) agarose hydrogel. Then, the effect of the soft agarose matrix on oocyte maturation and embryonic development was assessed by analyzing intra-oocyte contents of glutathione (GSH) and reactive oxygen species (ROS), expression of VEGFA, HIF1A , and PFKP genes, and blastocyst formation after parthenogenesis. IVM of pig COCs on a 1% (w/v) agarose matrix showed a significantly higher blastocyst formation, intra-oocyte GSH contents, and transcript abundance of VEGFA. Moreover, a significantly lower intra-oocyte ROS content was detected in oocytes matured on the 1% and 2% (w/v) agarose matrices than in control. Our results demonstrated that IVM of SAFs-derived pig oocytes on a soft agarose matrix enhanced developmental ability by improving the cytoplasmic maturation of oocytes through redox balancing and regulation of gene expression.

The aim of present study was to investigate regulatory mechanism of alpha-linolenic acid (ALA) during in vitro maturation (IVM) on nuclear and cytoplasmic maturation of porcine oocytes. Basically, immature cumulus-oocyte complexes (COCs) were incubated for 22 h in IVM-I to which hormone was added, and then further incubated for 22 h in IVM-II without hormone. As a result, relative cumulus expansion was increased at 22 h after IVM and it was enhanced by treatment of ALA compared with control group (p < 0.05). During IVM process within 22 h, cAMP level in oocytes was decreased at 6 h (p < 0.05) and it was recovered at 12 h in ALA-treated group, while oocytes in control group recovered cAMP level at 22 h. In cumulus cells, it was reduced in all time point (p < 0.05) and ALA did not affect. Treatment of ALA enhanced metaphase-I (MI) and MII population of oocytes compared with oocytes in control group at 22 and 44 h, respectively (p < 0.05). Intracellular GSH levels in ALA group was increased at 22 and 44 h after IVM (p < 0.05), whereas it was increased in control group at 44 h after IVM (p < 0.05). In particular, the GSH in ALA-treated oocytes during 22 h of IVM was higher than control group at 22 h (p < 0.05). Lipid amount in oocytes from ALA group was higher than control group (p < 0.05). Treatment of ALA did not influence to absorption of glucose from medium. Cleavage and blastocyst formation of ALA-treated oocytes were enhanced compared with control group (p < 0.05). These findings suggest that supplementation of ALA could improve oocyte maturation and development competence through increasing GSH synthesis, lipid storage, and regulation of cAMP accumulation during early 22 h of IVM, and these might be mediated by cumulus expansion.

Sestrin-2 (SESN2) as a stress-metabolic protein is known for its anti-oxidative effects as a downstream factor of PERK pathways in mammalian cells. However, the expression patterns of SESN2 in conjunction with the UPR signaling against to ER stress on porcine oocyte maturation in vitro, have not been reported. Therefore, we confirmed the expression pattern of SESN2 protein, for which to examine the relationship between PERK signaling and SESN2 in porcine oocyte during IVM. We investigated the SESN2 expression patterns using Western blot analysis in denuded oocytes (DOs), cumulus cells (CCs), and cumulus-oocyte complexes (COCs) at 22 and 44 h of IVM. As expected, the SESN2 protein level significantly increased (p < 0.01) in porcine COCs during 44 h of IVM. We investigated the meiotic maturation after applying ER stress inhibitor in various concentration (50, 100 and 200 μM) of tauroursodeoxycholic acid (TUDCA). We confirmed significant increase (p < 0.05) of meiotic maturation rate in TUDCA 200 μM treated COCs for 44 h of IVM. Finally, we confirmed the protein level of SESN2 and meiotic maturation via regulating ER-stress by only tunicamycin (Tm), only TUDCA, and Tm + TUDCA treatment in porcine COCs. As a result, treatment of the TUDCA following Tm pre-treatment reduced SESN2 protein level in porcine COCs. In addition, SESN2 protein level significantly reduced in only TUDCA treated porcine COCs. Our results suggest that the SESN2 expression is related to the stress mediator response to ER stress through the PERK signaling pathways in porcine oocyte maturation.

Among fatty acid families, the polyunsaturated fatty acids were demonstrated to be mediators in various reproductive processes as precursor of steroid hormone (via cholesterol) and prostaglandins (via arachidonic acid), and in the last decade, major research was focused on the effects of omega-6 and especially omega-3 fatty acid. Eicosapentaenoic acid, the longest members of omega-3 fatty acid family, can be produced by a series of desaturation and elongation reactions from shorter member such as α-Linolenic acid. However, very few studies have provided detailed descriptions of Eicosapentaenoic acid effects and mechanisms of action in mammalian oocytes. The purpose of this study was to evaluate the effect of Eicosapentaenoic acid supplementation on in vitro maturation and developmental potential of porcine oocytes. Various concentrations of Eicosapentaenoic acid was added into in vitro maturation medium, and we evaluated the degree of cumulus expansion, nuclear maturation rate, blastocysts quality, and levels of prostaglandin E2, 17β-estradiol, progesterone in the spent medium. High doses (100 mM) of Eicosapentaenoic acid supplementation significantly inhibited cumulus expansion and oocyte nuclear maturation, and prostaglandin E2 synthesis also significantly decreased compared with other groups (p < 0.05). Supplementation of 50 mM Eicosapentaenoic acid showed higher quality blastocysts in terms of high cell numbers and low apoptosis when compared with other groups (p < 0.05), and synthesis ratio of E2/P4 also significantly increased compared with control group (p < 0.05). However, Supplementation of 100 mM Eicosapentaenoic acid showed high apoptosis when compared with other groups (p < 0.05), and synthesis ratio of 17b-estradiol/progesterone also significantly decreased compared with control group (p < 0.05). Our results indicated that supplementation with appropriate levels of Eicosapentaenoic acid beneficially affects the change of hormone synthesis for controlling oocyte maturation, leading to improved embryo quality. However, high doses of Eicosapentaenoic acid treatment results in detrimental effects.

In this study, we investigated the possibility of using mouse embryonic stem cell conditioned medium (ESCM) and embryonic stem cell medium (ESM) for in vitro maturation in the efficient in vitro production of blastocysts from porcine follicular oocyte. Depending on the concentration of supplement of ESCM added to the NCSU-23 solution did not affect 2-cell development rates and blastocysts development. However, in particular, the survival rate (10 days of culture) of blastocyst was significantly higher than that of the control group as the additive concentration (30%) increased (p < 0.05). The survival rate of blastocysts showed a similar tendency even with addition of ESM (30%) alone. On the other hand, the duration of the addition of these additives during IVM (0-44 h) was that the IVM I period (0-22 h) were more effective than the IVM II period (22-44 h). Thus, the effect of these additives is probably due to the combination of the various physiologically active substances of ESCM or the appropriate amino acids and vitamins of ESM. In particular, these additives were more effective during the first half (IVM I) of in vitro maturation. In summary, optimization of ESCM or ESM supplementation may improve in vitro maturation of porcine oocyte and affect developmental competency. Therefore, if more efficient methods of adding ESCM or ESM to basal culture medium can be developed during in vitro maturation of porcine follicle oocytes, high quality blastocysts will be developed from low porcine follicular oocyte compared to other domestic animals.

The objective of this study was to establish an in vitro culture system for ovarian preantral follicles of B6D2F1. First, we optimized the in vitro preantral-follicle culture by culture duration, follicle stimulating hormone (FSH) type, and activin A concentration. Duration of in vitro culture for 9, 11, and 13 days was sufficient for the normal development of preantral follicles to antral follicles. Formation of cumulus cell–oocyte complex (COC) was induced by treatment with human chorionic gonadotropin (hCG; 2.5 IU/mL) and epidermal growth factor (EGF; 5 ng/mL). In addition, metaphase II (MII) oocytes formed during this in vitro culture of preantral follicles. In vitro preantral-follicle culture for 9 days showed higher rates of growth and maturation, thus yielding a greater number of antral follicles, and there were significant differences (p < 0.05) in the number of MII oocytes (that formed from these preantral follicles via differentiation) between the 9-day culture and 11-day or 13-day culture. The follicles cultured for 9 days contained a tightly packed well-defined COC, whereas in follicles cultured for 11 days, the COC was not well defined (spreading was observed in the culture dish); the follicles cultured for 13 days disintegrated and released the oocyte. Second, we compared the growth of the preantral follicles in vitro in the presence of various FSH types. There were no significant differences in the growth and maturation rates and in differentiation into MII oocytes during in vitro culture between preantral follicles supplemented with FSH from Merck and those supplemented with FSH from Sigma. To increase the efficiency of MII oocyte formation, the preantral follicles were cultured at different activin A concentrations (0 to 200 ng/mL). The control follicles, which were not treated with activin A, showed the highest rate of differentiation into antral follicles and into MII oocytes among all the groups (0 to 200 ng/mL). Therefore, activin A (50 to 200 ng/mL) had a negative effect on oocyte maturation. Thus, in this study, we propose an in vitro system of preantral-follicle culture that can serve as a therapeutic strategy for fertility preservation of human oocytes for assisted reproductive medicine, for conservation of endangered species, and for creation of superior breeds.

The aim of this study was to investigate effects of hyaluronidase during IVM on oocyte maturation, oxidative stress status, expression of cumulus expansion-related (PTX, pentraxin; GJA1, gap junction protein alpha 1; PTGS2, prostaglandin-endoperoxide synthase 2) and fatty acid metabolism-related (FADS1, delta-6 desaturase; FADS2, delta-5 desaturase; PPARα, peroxisome proliferator-activated receptor-alpha) mRNA, and embryonic development of porcine oocytes. The cumulus-oocyte complexes (COCs) were incubated with 0.1 mg/mL hyaluronidase for 44 h. Cumulus expansion was measured at 22 h after maturation. At 44 h after maturation, nuclear maturation, intracellular glutathione (GSH) and reactive oxygen species (ROS) levels were measured. Gene expression in cumulus cells was analyzed using real time PCR. The cleavage rate and blastocyst formation were evaluated at Day 2 and 7 after insemination. In results, expansion of cumulus cells was suppressed by treatment of hyaluronidase at 22 h after maturation. Intracellular GSH level was reduced by hyaluronidase treatment (p < 0.05). On the other hand, hyaluronidase increased ROS levels in oocytes (p < 0.05). Only PTGS2 mRNA was enhanced in COCs by hyaluronidase (p < 0.05). Population of oocytes reached at metaphase II stage was higher in control group than hyaluronidase treated group (p < 0.05). Both of cleavage rate and blastocyst formation were higher in control group than hyaluronidase group (p < 0.05). Our present results showed that developmental competence of porcine oocytes could be reduce by hyaluronidase via inducing oxidative stress during maturation process and it might be associated with prostaglandin synthesis. Therefore, we suggest that suppression of cumulus expansion of COCs could induce oxidative stress and decrease nuclear maturation via reduction of GSH synthesis and it caused to decrease developmental competence of mammalian oocytes.

Omega-3 α-linolenic acid and omega-6 linoleic acid are essential fatty acids for health maintenance of human and animals because they are not synthesized in vivo. The purpose of this study was to evaluate the effect of α-linolenic acid and linoleic acid supplementation on in vitro maturation and developmental potential of porcine oocytes. Various concentrations of α-linolenic acid and linoleic acid were added into in vitro maturation medium, and we evaluated the degree of cumulus expansion, oocyte nuclear-maturation rate, blastocyst rate, blastocyst quality, and levels of prostaglandin E2, 17b-estradiol, and progesterone in the spent medium. High doses (100 μM) of α-linolenic acid and linoleic acid supplementation significantly inhibited cumulus expansion and oocyte nuclear maturation, and prostaglandin E2 synthesis also significantly decreased compared with other groups (p < 0.05). Supplementation of 50 μM α-linolenic acid and 10 μM linoleic acid showed higher quality blastocysts in terms of high cell numbers and low apoptosis when compared with other groups (p < 0.05), and synthesis ratio of 17b-estradiol / progesterone also significantly increased compared with control group (3.59 ± 0.22 vs. 2.97 ± 0.22, 3.4 ± 0.28 vs. 2.81 ± 0.19, respectively; p < 0.05). Our results indicated that supplementation with appropriate levels of α-linolenic acid and linoleic acid beneficially affects the change of hormone synthesis (in particular, an appropriate increase in the 17b-estradiol / progesterone synthesis ratio) for controlling oocyte maturation, leading to improved embryo quality. However, high doses of α-linolenic acid and linoleic acid treatment results in detrimental effects.

This study investigated the use of bovine serum albumin (BSA) as alternatives to fetal bovine serum (FBS) in in vitro maturation medium. The oocyte maturation, cumulus cell-oocyte gap junctional communication, and development of bovine embryos were determined by assessing their cell number, lipid content, mitochondrial activity, gene expression and cryo-tolerance. Oocytes were cultured in TCM-199 supplemented with 1 μg/ml estradiol-17ß, 10 μg/ml FSH, 10 ng/ml EGF, 0.6 mM cysteine, 0.2 mM sodium pyruvate and either 8% BSA (BSA group), 10% FBS (FBS group), or neither BSA nor FBS (TCM group), and followed by in vitro fertilization and the zygotes were cultured in SOF-BE1 medium. The differences in embryo development between experimental groups were analyzed by one-way ANOVA. We have shown that the percentages of embryos that underwent cleavage and formed a blastocyst were non significantly different among all experimental groups (37.4 ± 1.5% for FBS group vs. 31.1 ± 3.9% for BSA group and 34.5 ± 1.6% for TCM group, six replicates were performed). Furthermore, there was no significant difference between the percentage of MII oocyte between FBS (71.8 ± 1.9%) and BSA groups (69.3 ± 2.3%). However, culture of oocytes with FBS increased (P < 0.05) the cumulus cell expansion as well as expression of gape junction proteins, CX37 and CX43, at both transcriptional and translation levels. We also found that FBS significantly increased total cell number and decreased the apoptotic index in day-8 blastocyst comparing to BSA group. The beneficial effects of BSA on embryos were associated with significantly reduced intracellular lipid content and increased mitochondrial activity in both oocytes and blastocyst. Taken together, these data suggest that supplementation of maturation medium with BSA, as alternatives to FBS, can be used as defined medium that support consistently the development of IVP bovine embryos.

When sperm penetrates into the ovum, hyaluronidase plays a role of hydrolyzing the hyaluronic acid present in the membrane surrounding the oocytes. The zona pelucida of the ovum is hydrolysed to facilitate sperm entry. Therefore, the aim of this study was to investigate the effects of hyaluronidase during the in vitro maturation in porcine oocytes. The cumulus-oocyte complexes (COCs) were cultured during in vitro maturation (IVM) medium containing 0 and 0.1mg/ml hyaluronidase for 44 h. Representative images of oocytes were captured after cultured for 0 h and 22 h by using a microscope. The area was quantified using a image J software. After 44 h of IVM, nuclear maturation stage was assessed by the aceto-orcein method. In results, cumulus cells expansion was no significant difference between control and hyaluronidase treatment groups in 0 h. However, after 22 h of IVM, in 0.1mg/ml hyaluronidase group, cumulus cells diffusion was significantly reduced than control group (p<0.05). After 22 h matured COCs, the cumulus cells were normally expanded in the control group, but there was a significantly lower 0.1mg/ml hyaluronidase group than control group (p<0.05). The nuclear maturation rate was treated with 0.1mg/ml hyaluronidase, it was significantly decrease than control group (p<0.05). In conclusion, our study indicated that hyaluronidase exposure could reduce nuclear maturation in vitro by reducing the expansion of cumulus cells. According to the results, we conjectured that hyaluronidase treatment disrupted the oocyte maturation by hydrolyzing the hyaluronic acid around the oocytes and it reduces the activity of the intercellular gap junction because it weakens cumulus cell bonds and interferes with communication. However, additional studies on hyaluronidase are needed. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Education) (2016R1D1A1B03931746).

Generally, in vivo, primary oocytes are grown and matured into secondary oocytes in the ovarian follicles. Quality of the oocytes matured in vivo is higher than that of oocytes matured in vitro, indicating the importance of materializing the microenvironment of ovarian follicles for production of high quality oocyte. Therefore, we tried to mimic the stiffness of ovarian follicles using an agarose as a biocompatible natural polymer. Unfortunately, to date, there are no many reports on whether the quality of porcine oocytes can be increased effectively under the soft matrix. Accordingly, we tried to evaluate the effects of IVM using different mechanical properties of agarose substrate on developmental competence of porcine oocytes. Agarose substrate was constructed and cumulus-oocyte-complexes (COCs) retrieved from porcine medium antral follicles were matured on non-coated (control) culture dish or dishes coated with 1% and 2% (w/v) agarose substrate. Then, cumulus expansion, embryonic development after parthenogenetic activation, and gene expression level were analyzed and compared. As the results, significant increase in blastocyst formation and cumulus expansion were detected in COCs matured on 1% (w/v) agarose substrate compared with control. Moreover, oocytes of COCs matured on 1% (w/v) agarose substrate showed significantly higher BMP15 expression level compared with control. Pro-apoptotic gene BAX expression was significantly increased in oocytes of COCs matured on 2% (w/v) agarose substrate compared with control. In the glycolytic enzyme phosphofructokinase (PFKP) gene expression, cumulus cells of COCs matured on agarose substrate showed significantly higher PFKP expression than control while they showed significantly lower BAX expression than control. These results demonstrated that quality of porcine oocytes could be increased efficiently by the IVM of immature oocytes on the soft culture matrix using agarose.

Alpha-linolenic acid (ALA; n-3 18:3), a one of omega-3 fatty acid, is mainly contained in chloroplast of plant and ALA is an essential fatty acid, not synthesized in mammalian body, it must be supplied from foods. Polyspermy is especially high on in vitro fertilization (IVF) in pigs, which is a major obstacle to in vitro embryo production systems. In our previous study, when ALA was supplemented during in vitro maturation (IVM), the methaphase-II rate and gluthathione level was increased. The objective of this study was to evaluate the effects of alpha-linolenic acid (ALA) supplementation during IVM and subsequent of IVF in pigs. The cumulus-oocyte complexes (COCs) were submitted to IVM medium containing 0, 25, 50, and 100 μM ALA for 44 h. After 44 h of IVM, denuded oocytes were co-cultured with spermatozoa during 18 h. After 18 h of in vitro fertilization, oocyte were using aceto-orcein method, to evaluated penetration rate, monospermy (number of monospermy oocytes/total oocytes), and the IVF efficiency (number of monospermy/total penetrated oocytes). In results, 25 and 50 μM ALA groups were significantly increased on penetration rate compared with 100 μM ALA group (p<0.05). Similarly, monospermy rate were significantly increased 25 and 50 μM ALA groups than control group (p<0.05). IVF efficiency was no significant difference between control and ALA treatment groups. Our findings suggested that treatment of ALA supplementation during in vitro maturation (IVM) and subsequent of in vitro fertilization in pigs, ALA can increase IVF efficiency by effectively blocking polyspermy and increasing monospermy some mechanism in porcine oocytes. However, the study of mechanism by which ALA blocks polyspermy are needed, and this study suggests that ALA has a positive effect on in vitro production of porcine oocytes by decreasing polyspermy. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Education) (2016R1D1A1B03931746).

ompared the expression of MMPs in these oocytes and cumulus cell throughout oocytes maturated. In an attempt to investigate the effect of MMP activation and inhibitors in total protein of cumulus cell and, oocytes during oocytes maturation, we examined and monitored the localization and expression of MMPs (MMP-2 and MMP-9), TIMPs (TIMP-2 and TIMP-3), as well as their expression profiles (Real-time PCR, Gelatin Zymography and ELISA). Our results that the bovine oocytes MMP-2 and MMP-9 level was significantly associated with the rate of maturity of oocytes (P<0.05). In cumulus cell, MMP-2 was highly expressed in all stages of the oocyte’s maturation. The final oocytes maturation exhibited strong gelatinase activity. There was no significant correlation between cumulus cell MMP-9 and the maturation rate of oocytes. However, for the oocyte cytoplasm MMP-9 expression was significant correlation to the maturation oocytes. There was no significant correlation between cumulonimbus cells MMP-9 and oocyte maturation rates; however, for oocyte cytoplasm, MMP-9 expression was significantly correlated with mature oocyte. However, the TIMP-1 and TIMP-2 protein expression patterns are not correlated with the maturation rate of the oocyte. Our results suggest that MMP different expression pattern may regulate the morphological remodeling of oocyte's in the cumulus cell. Further, the MMP-2 expression has a strong relation with a higher maturation rate of the oocyte.

Alpha lipoic acid (ALA) is a biological membranes compound. As the antioxidant, it decreases the oxidized forms of other antioxidant substances such as vitamin C, vitamin E, and glutathione (GSH). To examine the effect of ALA on the in vitro maturation (IVM) of porcine oocytes, we investigated intracellular GSH and reactive oxygen species (ROS) levels, and subsequent embryonic development after parthenogenetic activation (PA). Intracellular GSH levels in oocytes treated with 50uM ALA increased significantly (P < 0.05) and exhibited a significant (P < 0.05) decrease in intracellular ROS levels compared with the control group. Oocytes matured with 50 uM of ALA during IVM displayed significantly higher cleavage rates (67.8% vs. 83.4%, respectively), and higher blastocyst formation rates and total cell number of blastocysts after PA (31.6%, 58.49 vs. 46.8%, 68.58, respectively) than the control group. In conclusion, these results suggest that treatment with ALA during IVM improves the cytoplasmic maturation of porcine oocytes by increasing the intracellular GSH levels, thereby decreasing the intracellular ROS levels and subsequent embryonic developmental potential of PA.

Ferulic Acid (FA) is a metabolite of phenylalanine and tyrosine, a phenolic compound commonly found in fruits and vegetables. Several studies have shown that FA has various functions such as antioxidant effect, prevention of cell damage from irradiation, protection from cell damage caused by oxygen deficiency, anti-inflammatory action, anti-aging action, liver protective effect and anti-cancer action. In this study, we investigated the maturation rate, intracellular glutathione (GSH) and reactive oxygen species (ROS) of porcine oocytes by adding FA to the in vitro maturation (IVM) medium and examined subsequent embryonic developmental competence at 5% oxygen through parthenogenesis. There is no significant difference between the control group (0μM) and treatment groups (5μM, 10μM, 20μM) on maturation rates. Intracellular GSH levels in oocyte treated with 5μM of FA significantly increased (P < 0.05), and 20μM of FA revealed significant decrease (P < 0.05) in intracellular ROS levels compared with the control group. Oocytes treated with FA exhibited significantly higher cleavage rates (79.01% vs 89.19%, 92.20%, 90.89%, respectively) than the control group. Oocytes treated with 10μM showed significantly higher blastocyst formation rates (28.3% vs 40.3%, respectively) after PA than the control group. Total cell numbers in blastocyst of 10μM FA displayed significantly higher (39.4 vs 51.9, respectively) than the control group. In conclusion, these results suggested that treatment with FA during IVM improved the developmental potential of porcine embryos by increasing intracellular GSH synthesis and reducing ROS levels. Also, there was an improvement of cleavage rate, blastocyst formation and total cell numbers in blastocysts. It might be associated with Keap1-Nrf2 pathway as an antioxidant regulate pathway that plays a crucial role in determining the sensitivity of cells to oxidative damages by regulating the basal and inducible expression of enzymes which is related to detoxification and anti-oxidative effects, stress response enzymes and/or proteins and ABC transporters.

Alpha-linolenic acid (ALA) is one of n-3 polyunsaturated fatty acids and found mainly in the chloroplasts. Many studies have been reported that intracellular reactive oxygen species (ROS) in mammalian oocytes were reduced by supplementation of ALA in in vitro maturation (IVM) medium. Based on these reports, we expected that ALA acts as an antioxidant during IVM of porcine oocytes. Therefore, the objective of this study was to investigate the antioxidant effect of ALA supplementation during IVM in porcine oocytes. The cumulus-oocyte complexes (COCs) were incubated in IVM medium containing 200 μM H2O2 or H2O2 with 50 μM ALA for 44 h. Nuclear maturation stage of oocytes was evaluated using aceto-orcein method. For measurement of oxidative stress state, intracellular ROS and glutathione (GSH) levels were measured using carboxy-DCFDA and cell tracker red, respectively. In results, oocytes in metaphase-II (MII) stage development was significantly reduced in H2O2 group compared to non-treated control group (61.84±1.42% and 80.00%, respectively; p<0.05) and it was slightly recovered by treatment of ALA (69.76±1.67%; p<0.05). The intracellular GSH levels was decreased in H2O2 groups compared with control groups, but it was enhanced by ALA treatment (p<0.05). On the contrary, H2O2 treatment increased intracellular ROS level in oocytes and H2O2-induced ROS was decreased by treatment of ALA (p<0.05). Our findings suggested that ALA treatment under oxidative stress condition improve oocyte maturation via elevated GSH and reduced ROS levels in oocytes. Therefore, these results suggest that ALA have an antioxidative ability and it could be used as antioxidant in in vitro production system of porcine embryo.

In most mammals, metaphase II (MII) oocytes having high maturation promoting factor (MPF) activity have been considered as good oocytes and then used for assisted reproductive technologies including somatic cell nuclear transfer (SCNT). Caffeine increases MPF activity in mammalian oocytes by inhibiting p34cdc2 phosphorylation. The objective of this study was to investigate the effects of caffeine treatment during in Vitro maturation (IVM) on oocyte maturation and embryonic development after SCNT in pigs. To this end, morphologically good (MGCOCs) and poor oocytes (MPCOCs) based on the thickness of cumulus cell layer were untreated or treated with 2.5 mM caffeine during 22-42, 34-42, or 38-42 h of IVM according to the experimental design. Caffeine treatment for 20 h during 22-42 h of IVM significantly inhibited nuclear maturation compared to no treatment. Blastocyst formation of SCNT embryos was not influenced by the caffeine treatment during 38-42 h of IVM in MGCOCs (41.1-42.1%) but was significantly improved in MPCOCs compared to no treatment (43.4 vs. 30.1%, P<0.05). No significant effects of caffeine treatment was observed in embryo cleavage (78.7-88.0%) and mean cell number in blastocyst (38.7-43.5 cells). The MPF activity of MII oocytes in terms of p34cdc2 kinase activity was not influenced by the caffeine treatment in MGCOCs (160.4 vs. 194.3 pg/ml) but significantly increased in MPCOCs (133.9 vs. 204.8 pg/ml). Our results demonstrate that caffeine treatment during 38-42 h of IVM improves developmental competence of SCNT embryos derived from MPCOCs by influencing cytoplasmic maturation including increased MPF activity in IVM oocytes in pigs.

In vitro maturation (IVM) systems have become indispensable for the production of large numbers of competent oocytes in domestic species. The quality of in vitro matured oocyte is one of the important factors determining the success of assisted reproductive technologies (ARTs) including intracytoplasmic sperm injection (ICSI), in vitro fertilization (IVF), and somatic cell nuclear transfer (SCNT) in human and livestock. Incomplete cytoplasmic maturation of oocytes can lead not only to a failure of fertilization but also to a developmental arrest after ARTs. Thus, establishment of a stable IVM system to produce a large number of high quality oocytes, especially in domestic animals, is essential for improvement of ARTs efficiency by producing high quality embryos. The morphological characteristics are commonly used to predict the developmental potential of oocytes and embryos. Usually, normal oocytes shrink when exposed to a hypertonic medium, and recover their morphology when returned to an isotonic medium. During this process, oocytes show various morphologic changes, such as shrinkage in spherical (SSP) or irregular shapes (SIR). In the first study, we investigated whether the shrinkage pattern of oocytes that was observed after hyperosmotic treatment could be used as a morphologic characteristic to predict the quality of IVM oocytes in pigs. We found that SSP oocytes showed improved developmental competence after PA and SCNT. This improved embryonic development was most likely because of the more advanced nuclear and cytoplasmic maturation in SSP oocytes compared with SIR oocytes. Pig oocytes shows a wide variation in the size of perivitelline space (PVS) after IVM. Based on this finding, we examined in the second study whether or not there was any correlation between the PVS size of IVM oocytes and their developmental competence after PA and SCNT. Our results demonstrated that in vitro developmental competence to the blastocyst stage positively correlated with the size of the PVS of oocytes after IVM. In addition, we observed that mature oocytes with a larger PVS showed higher levels of intracellular GSH content and transcription factor expression. Furthermore, enlargement of the PVS by culturing in reduced NaCl medium improves the embryonic development after PA and SCNT. In the third study, we investigated the effects of a hypotonic medium with reduced NaCl (61.6 mM) compared with an isotonic medium (108.0 mM NaCl) on oocyte maturation and embryonic development after PA and SCNT. In addition, we attempted to optimize our IVM system using a hypotonic maturation medium by examining the effects of hypotonic medium during various stages of IVM on oocyte maturation and subsequent embryonic development. Our results demonstrated that maturation of pig oocytes in hypotonic medium with reduced NaCl during the last 11 hr of IVM increased the developmental competence of oocytes after PA and SCNT. These beneficial effects was also shown in a commercial medium (a minimum essential medium; aMEM) in which the NaCl concentration was reduced to 61.6 mM. In addition, IVM of oocytes in medium with reduced NaCl increases the proportion of SSP oocytes in pigs. In summary, our results demonstrate that IVM of pig oocytes in a hypotonic medium with low-NaCl is better able to support embryonic development after PA and SCNT, most likely by improving the cytoplasmic maturation via increased intraoocyte GSH content and widened PVS. Based on these results, the newly developed IVM system using a hypotonic medium with reduced NaCl can produce high quality oocytes and be considered a new strategy for improving ARTs efficiency in pigs.

Ganglioside GD1a is specifically formed by the addition of sialic acid to ganglioside GM1a by ST3 β- galactoside α -2,3-sialyltransferase 2 (ST3GAL2). Above all, GD1a are known to be related with the functional regulation of several growth factor receptors, including activation and dimerization of epidermal growth factor receptor (EGFR) in tumor cells. The activity of EGF and EGFR is known to be a very important factor for meiotic and cytoplasmic maturation during in vitro maturation (IVM) of mammalian oocytes. However, the role of gangliosides GD1a for EGFR-related signaling pathways in porcine oocyte is not yet clearly understood. Here, we investigated that the effect of ST3GAL2 as synthesizing enzyme GD1a for EGFR activation and phosphorylation during meiotic maturation. To investigate the expression of ST3GAL2 according to the EGF treatment (0, 10 and 50 ng/ml), we observed the patterns of ST3GAL2 genes expression by immunofluorescence staining in denuded oocyte (DO) and cumulus cell-oocyte-complex (COC) during IVM process (22 and 44 h), respectively. Expression levels of ST3GAL2 significantly decreased (p<0.01) in an EGF concentration (10 and 50 ng/ml) dependent manner. And fluorescence expression of ST3GAL2 increased (p<0.01) in the matured COCs for 44 h. Under high EGF concentration (50 ng/ml), ST3GAL2 protein levels was decreased (p<0.01), and their shown opposite expression pattern of phosphorylation-EGFR in COCs of 44 h. Phosphorylation of EGFR significantly increased (p<0.01) in matured COCs treated with GD1a for 44 h. In addition, ST3GAL2 protein levels significantly decreased (p<0.01) in GD1a (10 μM) treated COCs without reference to EGF pre-treatment. These results suggest that treatment of exogenous ganglioside GD1a may play an important role such as EGF in EGFR-related activation and phosphorylation in porcine oocyte maturation of in vitro.

The oocyte undergoes various events during In vitro maturation (IVM) and subsequence development. One of the events is production of reactive oxygen species (ROS) that is a normal process of cell metabolism. But imbalances between ROS production and antioxidant systems induce oxidative stress that negatively affect to mammalian reproductive process. In vitro environments, In vitro matured oocytes have many problems, such as excessive production of ROS and imperfect cytoplasmic maturation. Therefore, In vitro matured oocytes still have lower maturation rates and developmental competence than in vivo matured oocytes. In order to improve the IVM and In vitro culture (IVC) system, antioxidants, vitamins were added to the IVM, IVC medium. Antioxidant supplementation was effective in controlling the production of ROS and it continues to be explored as a potential strategy to overcome mammalian reproductive disorders. Based on these studies, we expect that the use of antioxidants in porcine oocytes could improved maturation and development rates.