Denuded Oocytes Research Articles

Risk of Premature Chromatid Separation is Increased by Poor Cumulus Cell Layers and Inappropriate Culture Media forin vitroMaturation of Mouse Oocytes

Abstract: Recently, the quality of in vitro matured (IVM) oocytes has been improved by numerous studies using animal models. However, the implantation rates of IVM oocytes remain lower than those of in vitro fertilization (IVF). Chromosome abnormalities, which mainly occur during the first meiotic division, are often observed in IVM oocytes. To clarify how the properties of the cumulus cell layers relate to chromosome abnormalities of oocytes during IVM, we investigated the occurrence of aneuploidy and developmental competence using two different media in a mouse model. Maturation rates were significantly lower in denuded oocytes at oocyte collection in both types of maturation media as compared with those of oocytes mechanically denuded just after collection of cumulus-oocyte complex. Fertilization rates and blastocyst rates were lower in Waymouth's MB752/1 medium than in HTF medium. The occurrence of premature chromatid separation (PCS) remarkably increased in Waymouth's MB752/1 medium compared to HTF m...

In vitro culture of oocytes and granulosa cells collected from normal, obese, emaciated and metabolically stressed ewes

The present study was undertaken to investigate the oocyte morphology, its fertilizing capacity and granulosa cell functions in ewes (obese, normal, metabolic stressed and emaciated). Ewes (Ovis aries) of approximately 3 years of age (Bellary breed) from a local village were screened, chosen and categorized into a) normal b) obese but not metabolically stressed, c) Emaciated but not metabolically stressed d) Metabolically stressed based on body condition scoring and blood markers. Oocytes and granulosa cells were collected from ovaries of the ewes of all categories after slaughter and were classified into good (oocytes with more than three layers of cumulus cells and homogenous ooplasm), fair (oocytes one or two layers of cumulus cells and homogenous ooplasm) and poor (denuded oocytes or with dark ooplasm). The good and fair quality oocytes were in vitro matured and cultured with fresh semen present and the fertilization, cleavage and blastocyst development were observed. The granulosa cells were cultured for evaluation of metabolic activity by use of the MTT assay, and cell viability, cell number as well as estrogen and progesterone production were assessed. It was observed that the good and fair quality oocytes had greater metabolic activity when collected from normal and obese ewes compared with those from emaciated and metabolically stressed ewes. No significant difference was observed in oocyte quality and maturation amongst the oocytes collected from normal and obese ewes. The cleavage and blastocyst production rates were different for the various body condition classifications and when ranked were: normal>obese>metabolically stressed>emaciated. Lesser metabolic activity was observed in granulosa cells obtained from ovaries of emaciated ewes. However, no changes were observed in viability and cell number of granulosa cells obtained from ewes with the different body condition categories. Estrogen and progesterone production from cultured granulosa cells were not different in normal and obese ewes. Estrogen and progesterone secretions were less from granulosa cells recovered from metabolically stressed and emaciated ewes. The results suggested that oocyte morphology, fertilizing capacity and granulosa cell growth were dependent on body condition and feeding status of the animals.

Effects of the fish spawning inducer ovaprim on vasotocin receptor gene expression in brain and ovary of the catfish Heteropneustes fossilis with a note on differential transcript expression in ovarian follicles

Ovaprim (OVP), a commercial formulation of a salmon GnRH analogue and the dopamine receptor-2 blocker domperidone, is a successful spawning inducer for fish breeding. It induces a preovulatory surge in LH, which stimulates the synthesis of a maturation-inducing steroid (MIS, 17,20β-dihydroxy-4-pregnen-3-one) that initiates germinal vesicle breakdown (GVBD) and ovulation. Coincidently, the OVP treatment also stimulates vasotocin (VT) secretion in the brain and ovary of the catfish Heteropneustes fossilis that also stimulates the synthesis of the MIS. VT mediates its effect through V1- and V2-type receptors. In the present study in the catfish, we report that OVP stimulates the expression of VT receptor genes v1a1, v1a2 and v2a in the brain and ovary. A single intraperitoneal administration of OVP (0.5μL/g body weight) or incubation of post-vitellogenic ovarian follicles with 5μL/mL OVP, for 0, 4, 8, 12, 16, and 24h stimulated ovulation and GVBD, respectively, in a time-dependent manner. The OVP treatment in vivo stimulated brain VT receptor transcript levels 4h onwards. The peak expression was noticed at 12h (v1a1), 8 and 12h (v1a2), and 8, 12 and 16h (v2a), coinciding with FOM and ovulation. The VT receptor genes are expressed in the ovarian follicles compartmentally; both v1a1 and v1a2 are expressed in the isolated follicular layer (theca and granulosa) but absent in denuded oocytes. V2a is expressed in the denuded oocytes and not in the follicular layer. The OVP injection stimulated the v1a1 and v1a2 expression from 4h onwards in both intact follicle and isolated follicular layer, the peak expression was observed at 16h. The v2a expression was up-regulated in both intact follicles and denuded oocytes at 4h (denuded oocytes) or 8h (intact follicle) onwards with the peak expression at 12h and 16h (denuded oocytes) or at 16h (intact follicles). Under in vitro conditions, the OVP incubations elicited similar pattern of changes with the peak stimulation at 16h for all the genes. In conclusion, the VT receptor genes are differentially expressed in the ovarian follicles and OVP induced periovulatory stimulation of the VT receptor genes, coinciding with FOM and ovulation.

Role of cumulus cells during vitrification and fertilization of mature bovine oocytes: Effects on survival, fertilization, and blastocyst development

This study was designed to determine the role of cumulus cells during vitrification of bovine oocytes. Mature cumulus-oocyte complexes (COCs) with many layers of cumulus cells, corona radiata oocytes (CRs), with a few layers of cumulus cells, and denuded oocytes (DOs) without cumulus cells were vitrified in 15% ethylene glycol, 15% dimethyl sulfoxide, and 0.5-M sucrose. Oocytes that survived the vitrification process were fertilized. Denuded oocytes were fertilized with or without supplementation of intact COCs (DOsCOCs). First, survival and embryo development rates were studied. Higher survival rates were obtained for DOs and DOsCOCs (94% and 95%, respectively) compared with COCs (82.7%, P < 0.05). Corona radiata oocytes showed similar survival rates when compared with DOs. The cleavage and blastocyst rates of vitrified DOs were compromised because cumulus cells were not present during the fertilization (34% and 2.7%, respectively). However, the situation could be reverted when DOs were supplemented with intact COCs (DOsCOCs; 62.7% and 12.7%, respectively, P < 0.05). Vitrified CRs showed similar cleavage and blastocyst rate (49.3% and 7.7%, respectively) compared with COCs (54.8% and 4.9%, respectively). In the second experiment, the penetration rate was analyzed. Removing cumulus cells before fertilization reduced the fertilization of vitrified DOs compared with COCs (24.3% vs. 52.8%, P < 0.05). The supplementation of DOs with intact COCs (DOsCOCs) improved the fertilization rate though (49.6%, P < 0.05). No differences in the fertilization rate were found between CRs and COCs. In the third experiment, parthenogenetic activation was examined. Interestingly, the CRs group showed higher cleavage and blastocyst rates (76.8% and 29.6%, respectively) than the COCs (39.1% and 7.5%, respectively, P < 0.05). Furthermore, oocytes from vitrified CRs had the same odds to become a blastocyst as fresh oocytes (1.1 vs. 1.5, respectively). In conclusion, our data reported that cumulus cells reduce survival after the vitrification of mature bovine oocytes. Because cumulus cells are required for fertilization, the use of partially DOs (CRs) or the addition of intact COCs (DOsCOCs) during fertilization can result in higher survival and embryo development after vitrification.

The beneficial effects of cumulus cells and oocyte-cumulus cell gap junctions depends on oocyte maturation and fertilization methods in mice.

Cumulus cells are a group of closely associated granulosa cells that surround and nourish oocytes. Previous studies have shown that cumulus cells contribute to oocyte maturation and fertilization through gap junction communication. However, it is not known how this gap junction signaling affects in vivo versus in vitro maturation of oocytes, and their subsequent fertilization and embryonic development following insemination. Therefore, in our study, we performed mouse oocyte maturation and insemination using in vivo- or in vitro-matured oocyte-cumulus complexes (OCCs, which retain gap junctions between the cumulus cells and the oocytes), in vitro-matured, denuded oocytes co-cultured with cumulus cells (DCs, which lack gap junctions between the cumulus cells and the oocytes), and in vitro-matured, denuded oocytes without cumulus cells (DOs). Using these models, we were able to analyze the effects of gap junction signaling on oocyte maturation, fertilization, and early embryo development. We found that gap junctions were necessary for both in vivo and in vitro oocyte maturation. In addition, for oocytes matured in vivo, the presence of cumulus cells during insemination improved fertilization and blastocyst formation, and this improvement was strengthened by gap junctions. Moreover, for oocytes matured in vitro, the presence of cumulus cells during insemination improved fertilization, but not blastocyst formation, and this improvement was independent of gap junctions. Our results demonstrate, for the first time, that the beneficial effect of gap junction signaling from cumulus cells depends on oocyte maturation and fertilization methods.

Heat stress and antioxidant enzyme activity in bubaline (Bubalus bubalis) oocytes during in vitro maturation.

In vitro environments like heat stress usually increase the production of reactive oxygen species in bubaline oocytes which have been implicated as one of the major causes for reduced developmental competence. Oocytes during meiotic maturation are sensitive to oxidative stress, and heat stress accelerates cellular metabolism, resulting in the higher production of free radicals. Therefore, the aim of present work was to assess the impact of heat stress during meiotic maturation on bubaline cumulus-oocyte complexes (COC), denuded oocytes (DO), and cumulus cell mass in terms of their oxidative status. Accordingly, for control group, COC were matured at 38.5°C for complete 24h of meiotic maturation and heat stress of 40.5 and 41.5°C was applied to COC during the first 12h of maturation and then moved to 38.5°C for rest of the 12h. In another group, COC after maturation were denuded from the surrounding cumulus cells by manual pipetting. Results indicated that the production of reactive oxygen species (ROS), lipid peroxides, and nitric oxide (NO) was significantly (P < 0.05) higher in the oocytes subjected to heat stress (40.5 and 41.5°C) during meiotic maturation compared to the oocytes matured under standard in vitro culture conditions (38.5°C). Also, the antioxidant enzymatic activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase were significantly (P < 0.05) increased in all the treatment groups compared to the control group. Therefore, the present study clearly establishes that heat stress ensues oxidative stress in bubaline oocytes which triggers the induction of antioxidant enzymatic defense system for scavenging the ROS.

Effect of In Vitro Maturation Technique and Alpha Lipoic Acid Supplementation on Oocyte Maturation Rate: Focus on Oxidative Status of Oocytes.

Therapeutic potential of in vitro maturation (IVM) in infertility is growing with great promise. Although significant progress is obtained in recent years, existing IVM protocols are far from favorable results. The first aim of this study was to investigate whether two step IVM manner change reactive oxygen species (ROS) and total anti- oxidant capacity (TAC) levels. The second aim was to find the effect of alpha lipoic acid (ALA) supplementation on oocyte maturation rate and on ROS/TAC levels during IVM. In this experimental study, mouse germinal vesicle (GV) oocytes divided into cumulus denuded oocytes (DOs) and cumulus oocyte complexes (COCs) groups. GVs were matured in vitro in the presence or absence of ALA only for 18 hours (control) or with pre-culture of forskolin plus cilostamide for an additional 18 hours. Matured oocytes obtained following 18 and 36 hours based on experimental design. In parallel, the ROS and TAC levels were measured at different time (0, 18 and 36 hours) by 2',7'-dichlorodihydrofluorescein (DCFH) probe and ferric reducing/antioxidant power (FRAP) assay, respectively. Maturation rate of COCs was significantly higher than DOs in control group (P<0.05), while there was no significant difference between COCs and DOs when were pre-cultured with forskolin plus cilostamide. ROS and TAC levels was increased and decreased respectively in DOs after 18 hours while in COCs did not change at 18 hours and showed a significant increase and decrease respectively at 36 hours (P<0.05). ROS and TAC levels in the presence of ALA were significantly decreased and increased respectively after 36 hours (P<0.05) whereas, maturation rates of COCs and DOs were similar to their corresponding control groups. ALA decreased ROS and increased TAC but could not affect maturation rate of both COCs and DOs in one or two step IVM manner.

201 ROLE OF THE NITRIC OXIDE SYSTEM IN EFFECTS OF PROLACTIN AND GROWTH HORMONE ON METAPHASE-II CHROMOSOMES IN BOVINE OOCYTES AGING IN VITRO

Aging of mammalian oocytes is the time-dependent process of cytological and molecular transformations leading to a decline in the ovum quality and developmental capacity. We have previously shown that 2 related pituitary hormones, prolactin (PRL) and growth hormone (GH), may decelerate abnormal changes in the morphology of metaphase II (MII) chromosomes in bovine cumulus-enclosed oocytes (CEO) aging in vitro. The goal of the present research was to examine the involvement of different isoforms of nitric oxide synthase (NOS) in the actions of PRL and GH on MII chromosomes in aging bovine oocytes. Bovine CEO were matured for 20 h in TCM 199 containing 10% FCS, 10 μg mL–1 porcine FSH, and 10 μg mL–1 ovine LH. After IVM, CEO or denuded oocytes (DO) were cultured for 24 h in the aging medium of TCM 199 supplemented with 10% FCS (control). In experimental groups, the medium contained either 50 ng mL–1 bovine PRL or 10 ng mL–1 bovine GH and/or NOS inhibitors. The following inhibitors were applied: (1) N-propyl-l-arginine (NPLA; an inhibitor of neuronal NOS (nNOS), 5 μM) and (2) L-NAME (an effective inhibitor of both endothelial NOS (eNOS) and nNOS, 20 μM). Destructive changes of MII chromosomes in oocytes were assessed by the following morphological signs: decondensation, partial adherence, chromosome clumping into a single mass, and fragmentation. The total activity of NOS in oocytes was determined by NADPH-diaphorase staining. The data from 4–5 replicates were analysed by ANOVA. During CEO aging in the control medium, the rate of MII oocytes with destructive changes of chromosomes rose from 16.8 ± 2.1% to 58.5 ± 1.4% (P &lt; 0.001), whereas both PRL and GH reduced this rate up to 42.0 ± 1.3% and 46.5 ± 1.6%, respectively (P &lt; 0.001). The nNOS inhibitor NPLA abolished (P &lt; 0.001) the inhibitory effect of PRL on abnormal modifications of chromosomes in CEO but did not affect the frequency of these modifications in the control or GH-treated groups. In the absence of the hormones, L-NAME (the eNOS+nNOS inhibitor) decreased the rate of aging CEOs with chromosome abnormalities from 58.5 ± 1.4% to 41.2 ± 2.5% (P &lt; 0.001), acting unidirectionally with PRL and GH. Meanwhile, L-NAME enhanced (P &lt; 0.05) the suppressing effect of PRL on destructive changes of MII chromosomes but did not influence the similar effect of GH. At the same time the chromosome morphology in senescent DOs was unaffected by the hormones or NOS inhibitors. Furthermore, the total activity of NOS in oocytes separated of cumulus after 24 h of aging was similar in the control and experimental groups. Thus, the inhibitory effect of GH on abnormal modifications of MII chromosomes in aging bovine oocytes may be related to a reduction of the eNOS activity in cumulus cells, whereas the respective effect of PRL is likely to be achieved by both inactivation of eNOS and activation of nNOS. This research was supported by RFBR (No. 13–04–01888).

66 CUMULUS-OOCYTE-COMPLEX SECRETIONS FROM THE FIRST 8 HOURS OF IN VITRO MATURATION AFFECT OOCYTE DEVELOPMENTAL COMPETENCE

Mammalian oocytes are surrounded by cumulus cells, forming a structure known as the cumulus-oocyte complex (COC). Cumulus cells play important protective functions during oocyte maturation, for example, protecting the oocyte against reactive oxygen species. However, it is not yet fully understood how the cumulus complex modulates the developmental competence of the enclosed oocyte. It was investigated whether direct contact between an oocyte and its cumulus cells is essential throughout the maturation process. To this end, bovine oocytes aspirated from ovarian follicles were matured in vitro. Eight hours after the onset of maturation the cumulus cells were removed, and the oocytes either placed back in the original medium or cultured further in fresh maturation medium. In all experiments, COCs/oocytes were matured for 23 h in M199 supplemented with 0.05 IU FSH and penicillin/streptomycin. All experiments were performed in triplicate, with 35 to 45 COCs per group. Student’s t-test was used for a paired comparison. Denudation after 8 h and return to the same maturation medium had no effect on the cleavage rate (93%) compared with culture without denudation (90.7%). Only if the oocytes were transferred to fresh medium did the cleavage rate decrease slightly (75.4%; P = 0.038). By contrast, blastocyst formation was reduced nearly four times if COCs were denuded before being returned to the medium, compared with controls (14% v. 50.8%; P &lt; 0.001). If the oocytes were transferred to fresh medium after denudation, very few blastocysts resulted (0.9%; P &lt; 0.001). In a second study, oocytes denuded immediately after removal from the follicle were matured in the absence or presence of cumulus cells in a Corning® Transwell® system. Culturing denuded oocytes in the presence of cumulus cells resulted in similar cleavage rates (83.5%) to control conditions (84.8%). However, blastocyst formation was markedly lower (4.3%) than for controls (29.6%; P = 0.003). We conclude that COCs secrete substances during the first 8 h of maturation that are beneficial for oocyte acquisition of developmental competence. Moreover, intimate contact between the cumulus cells and oocyte is essential. This work was supported by EU FP7 EpiHealthNet, PITN-GA-2012–317146.

Cumulus Cells Block Oocyte Meiotic Resumption via Gap Junctions in Cumulus Oocyte Complexes Subjected to DNA Double-Strand Breaks.

During mammalian oocyte growth, genomic DNA may accumulate DNA double-strand breaks (DSBs) induced by factors such as reactive oxygen species. Recent evidence demonstrated that slight DSBs do not activate DNA damage checkpoint proteins in denuded oocytes. These oocytes, even with DNA DSBs, can resume meiosis and progress to metaphase of meiosis II. Meiotic resumption in oocytes is also controlled by the surrounding cumulus cells; accordingly, we analyzed whether cumulus-cell enclosed oocytes (CEOs) with DNA damage are able to resume meiosis. Compared with DNA-damaged denuded oocytes, we found that meiotic resumption rates of CEOs significantly decreased. To assess the mechanism by which cumulus cells block meiotic resumption in CEOs with DNA DSBs, we treated the cumulus oocyte complex with the gap junction inhibitor carbenoxolone and found that carbenoxolone can rescue the block in CEO meiosis induced by DNA DSBs. Since cumulus cell-synthesized cAMPs can pass through the gap junctions between oocyte and cumulus cell to block oocyte meiosis, we measured the expression levels of adenylate cyclase 1 (Adcy1) in cumulus cells, and G-protein coupled receptor 3 (Gpr3) and phosphodiesterase 3A (Pde3a) in oocytes, and found that the mRNA expression level of Adcy1 increased significantly in DNA-damaged cumulus cells. In conclusion, our results indicate that DNA DSBs promote cAMP synthesis in cumulus cells, and cumulus cAMPs can inhibit meiotic resumption of CEOs through gap junctions.

LITTER SIZE, OVARIAN CHARACTERISTICS, AND OOCYTE IN VITRO MATURATION AND FERTILIZATION OF RABBITS ADMINISTRATED WITH COENZYME Q10 AND L-CARNITINE

The objective of this study was to evaluate the effect of coenzyme Q10 (CoQ10) and L-carnitine (LC) administration on litter size, ovarian characteristics and in vitro production of rabbit embryos. This study was carried out at the International Livestock Management Training Center (ILMTC), belonging to the Animal Production Research Institute, Agricultural Research Center, Ministry of Agriculture. Total of 36 mature NZW rabbit does (5-6 months of age, 3-3.5 kg LBW as well as 6 NZW bucks (7.5-8 months of age and 3.5-4.0 kg LBW) were used in this study. Does were divided into 3 similar groups, (n=12). The 1 group was control (G1), while does in the 2 and 3 groups were given daily oral dose of 10 mg CoQ10/kg LBW (G2) and 40 mg LC/kg LBW (G3) for 21 days prior to natural mating, respectively. Five does from each group were slaughtered post-mating as oocyte donors for studying the effect of treatments on ovarian characteristics and in vitro maturation and fertilization of oocytes. Immediately after slaughtering, ovaries were removed and oocytes were collected by slicing technique and evaluated, then only compact-cumulus oocytes (COCs) were matured and fertilized in vitro. For the rest number of does in each group (n=7), pregnancy was handy diagnosed by palpation 10-12 days post-mating. Also, litter size and weight at birth up to weaning were recorded. The obtained results showed that, ovarian weight and number of follicles increased (P<0.05) in G2 and G3. Number of bleeding follicles and recovered oocytes increased (P<0.05) only in G2 as compared to G1, however, oocyte recovery rate was not affected by treatment. Frequency distribution of compact and partial denuded oocytes was higher (P<0.05), while that of expanded and denuded oocytes was lower in G2 and G3 as compared to G1. Percentage of oocytes with full expansion (maturation rate) was 80.3 and 79.3% vs. 73.8% and fertilization rate was 67.4 and 66.7% vs. 64.5% in G2 and G3 vs. G ((P≥0.05). Percentage of embryos at morula stage was higher (P<0.05) in G2 and G3 than in G1 (30.3 and 3.1% vs. 20%), respectively. Percentage of embryos at blastocyst stage was 21.2 and 21.4% vs. 15% in G2 and G3 vs. G1, respectively. Litter size of rabbit does was higher (P<0.05) in G2 and G3 than in G1 at birth (7.29 and 6.71 vs. 5.43/doe), at 21 days of age (6.71 and 5.86 vs. 4.43/doe) and at weaning (6.43 and 5.43 vs. 4.14/doe). Mortality rate of kits at birth or weaning was not affected by treatment. Average kit weight at birth was higher (P<0.05) in G2 and G1. However, average kit weight at weaning, average litter weight from birth up to weaning and average litter daily gain from birth up to weaning were higher (P<0.05) in G2 and G3 than in G1.In conclusion, treatment of rabbit does 21 days prior to insemination with CoQ10 at a level of 10 mg/kg LBW or L-carnitine at level 40 mg/kg LBW as daily oral dose is recommended to improve in vitro embryo production and also to increase litter characteristics (size and weight from birth up to weaning) of New Zealand White rabbit does.

Glucocorticoid metabolism in the bovine cumulus-oocyte complex matured in vitro.

Glucocorticoid action in target organs is regulated by relative activities of 11β-HSD type 1 (HSD11B1) that mainly converts cortisone to active cortisol and type 2 (HSD11B2) that inactivates cortisol to cortisone. HSD11Bs have been shown to be expressed in the ovary of various species. However, little is known about the expression and activity of HSD11Bs in the bovine cumulus-oocyte complex (COC). In the present study, we investigated the expression and activities of HSD11Bs in in vitro-matured (IVM) bovine COCs. Bovine COCs were matured in M199 supplemented with or without FSH and FCS. The expression of HSD11B1 and HSD11B2 was measured by using quantitative RT-PCR in denuded oocytes (DO) and cumulus cells (CC). Reductive and oxidative activities of HSD11Bs were determined by radiometric conversion assay using labeled cortisol, cortisone or dexamethasone in intact COCs, DO or CC in the presence or absence of 11-keto-progesterone (11kP), a selective inhibitor of HSD11B2. The presence of HSD11Bs in the oocyte was examined by immunofluorescence microscopy. Oocytes exclusively expressed HSD11B2 and its expression and activity were largely unchanged during IVM. CC, on the other hand, exclusively expressed HSD11B1 and its expression and activity were upregulated as IVM progressed. As a result, the net glucocorticoid metabolism shifted from inactivation to activation towards the end of IVM. These results indicate that the bovine COC is capable of modulating local glucocorticoid concentration and, by doing so, may create an environment that is favorable to ovulating oocyte for maturation, fertilization and subsequent development.

Gene Expression of Monocarboxylate Transporters and Oocyte-secreted Factors inBovine Cumulus-oocyte Complexes Selected by Brilliant Cresyl Blue.

Oocyte selection based on the brilliant cresyl blue (BCB) staining test has been successfully used to differentiate between competent and incompetent bovine oocytes. Here, the expression of genes involved in transport of monocarboxylates (Mct1-4) and oogenesis specific genes (Bmp15, Gdf9 and Has2) in BCB+ and BCB- selected immature and mature bovine cumulus-oocyte complexes (COC) was evaluated. In order to find specific molecular markers to characterize successful oocyte maturation, our study was also aimed at identifying the expression of Mcts and oogenesis specific genes in denuded oocytes and cumulus cells. Immature COCs morphological appropriate were (i) stained with 26mm BCB for 90min before IVM, (ii) exposed to same incubation conditions as stained COCs, but without BCB (holding group) or (iii) transferred into a maturation medium immediately after morphological selection (control group). mRNA expression was investigated by RT-PCR in COCs before and after IVM. No relationship was observed in the relative expression of Has2, Gdf9, Bmp15 or Mct1, 2 and 4 transcripts between BCB+ and BCB- COCs. Transcripts analysis showed that Gdf9 and Bmp15 in BCB+, BCB- and holding groups were up-regulated (p<0.05) before IVM, while Has2 was up-regulated (p<0.01) after IVM in the control group. Other genes remained stable during maturation (Mct1, 2 and 4). Our results showed, for the first time, Mct1, 2 and 4 expression in bovine COCs. Mct1 and Mct4 transcripts were present in denuded oocytes and cumulus cell, while Mct2 was detected only in cumulus cells. These differences between the three isoforms in localization suggest unique roles for each in monocarboxylate transport during maturation.

Influence of co-culture with denuded oocytes during in vitro maturation on fertilization and developmental competence of cumulus-enclosed porcine oocytes in a defined system.

Co-culture of cumulus-oocyte complexes (COCs) with denuded oocytes (DOs) during in vitro maturation (IVM) was reported to improve the developmental competence of oocytes via oocyte-secreted factors in cattle. The aim of the present study was to investigate if addition of DOs during IVM can improve in vitro fertilization (IVF) and in vitro culture (IVC) results for oocytes in a defined in vitro production system in pigs. The maturation medium was porcine oocyte medium supplemented with gonadotropins, dbcAMP and β-mercaptoethanol. Cumulus-oocyte complexes were matured without DOs or with DOs in different ratios (9 COC, 9 COC+16 DO and 9 COC+36 DO). Consequently; oocytes were subjected to IVF as intact COCs or after denudation to examine if DO addition during IVM would affect cumulus or oocyte properties. After fertilization, penetration and normal fertilization rates of zygotes were not different between all tested groups irrespective of denudation before IVF. When zygotes were cultured for 6 days, no difference could be observed between all treatment groups in cleavage rate, blastocyst rate and cell number per blastocyst. In conclusion, irrespective of the ratio, co-culture with DOs during IVM did not improve fertilization parameters and embryo development of cumulus-enclosed porcine oocytes in a defined system.

Porcine embryo production following in vitro fertilization and intracytoplasmic sperm injection from vitrified immature oocytes matured with a granulosa cell co-culture system

This study was designed to evaluate the capacity of vitrified–warmed porcine immature oocytes to mature and to be fertilized using in vitro fertilization or intracytoplasmic sperm injection, and to determine the subsequent embryo development. Immature oocytes were vitrified using ethylene glycol and dimethylsulphoxide as cryoprotectants and the Cryolock method. After warming oocytes were cultured 44h for maturation. Oocytes were randomly distributed in three treatment groups and subjected to in vitro fertilization (Experiment 1) or intracytoplasmic sperm injection (Experiment 2) procedures. The results indicate that the embryo development was higher in denuded oocytes co-cultured with granulosa cells (NkO-CC group) fertilized by in vitro fertilization or intracytoplasmic sperm injection compared to cumulus-cell oocyte complexes (COCs group), showing no significant differences with control. Vitrified denuded oocytes matured with a co-culture system NkO-CC group, displayed higher cleavage rate and blastocyst production than vitrified COCs group. Blastocysts were successfully obtained after IVF and ICSI procedures; however, the development to the blastocyst stage was better after IVF. These results show that the vitrification–warming media, the employment of a granulosa cell co-culture system and the Cryolock method during vitrification, increased the nuclear and cytoplasmic maturation of vitrified porcine immature oocytes. Further experiments are required to enhance porcine embryo production after vitrification.

296 IMPACT OF CO-CULTURING CUMULUS-ENCLOSED PORCINE OOCYTES WITH DENUDED OOCYTES DURING IN VITRO MATURATION IN A DEFINED MEDIUM ON CUMULUS EXPANSION AND OOCYTE MATURATION

Recent research has revealed that oocyte-secreted factors (OSF) affect cumulus expansion and play important roles during maturation and embryo development of mammalian oocytes. The use of denuded oocytes (DO) as supplements during in vitro maturation (IVM) in a nondefined medium improved developmental competence of cumulus-enclosed porcine oocytes (COC; Gomez et al. 2012 Zygote 20, 135–145). We investigated the effect of DO on cumulus expansion and nuclear maturation of COC in pigs during IVM using a defined medium. If the DO exert a positive influence on IVM, the defined medium can then be analysed for the presence of OSF. Immature COC were collected in the slaughterhouse from prepubertal gilts. To obtain DO, some COC were completely denuded by pipetting through a narrow-bore glass pipette. The COC used as a source for DO fulfilled the same morphological criteria as the COC used for IVM. The IVM medium was porcine oocyte medium (POM; Yoshioka et al. 2008 J. Reprod. Dev. 54, 208–213) with hormone supplementations applied only during the first 20 h of the IVM period. The COC were fixed to the bottom of 35-mm plastic Petri dishes in 3 × 3 grids by Cell-Tak (BD Bioscience, Bedford, MA, USA) in 100-µL droplets POM covered by paraffin oil. Culture droplets (each including 1 COC grid) were supplemented with (DO+ group, n = 179) or without 16 DO (DO– group, n = 143). After 20 h of IVM, the medium was replaced with a preincubated hormone-free POM and oocytes were cultured for an additional 28 h. At 0, 20, and 48 h of IVM, images of each grid were taken at the same magnification. The size of each COC was measured as a 2-dimensional area in pixels by analysing images with ImageJ software. Relative cumulus expansion was calculated at 20 and 48 h of IVM on the basis of the initial COC size at 0 h, which was assigned as 1. At 48 h of IVM, the COC were denuded and examined for oocyte maturation by orcein staining. The experiment was replicated 5 times. Cumulus expansion ratios at 20 and 48 h of IVM were compared between the DO+ and DO– groups by ANOVA. Maturation rates were compared between the DO+ and DO– groups by binary logistic regression. No difference in cumulus expansion between DO– and DO+ could be observed at 20 h (1.83 ± 0.04 and 1.75 ± 0.03, respectively) and 48 h (1.41 ± 0.03 and 1.47 ± 0.02, respectively) of IVM. Nuclear maturation rates of COC in DO– and DO+ groups did not differ significantly (39.0 ± 5.4 and 32.9 ± 8.8%, respectively). In conclusion, addition of DO to the defined IVM medium did not affect the cumulus expansion and oocyte maturation of follicular porcine COC. Further research is needed to assess the effects of DO during IVM on subsequent fertilization. If DO prove to be beneficial for fertilization, the nature of the OSF will be investigated.This study was supported by FCWO of UGent and by FWO-Flanders (grant number FWO11/ASP/276).

230 ROLE OF PITUITARY HORMONES AND CUMULUS CELLS IN MODULATING THE DEVELOPMENTAL CAPACITY OF AGING BOVINE OOCYTES

The competence for embryonic development acquired during the oocyte maturation attenuates during the subsequent oocyte aging both in vivo and in vitro. Thus, the successful control of the female fertility requires information regarding factors responsible for the oocyte protection from early aging. The aim of the present research was to study the pattern and pathways of actions of two closely related pituitary hormones, prolactin (PRL), and growth hormone (GH), on the developmental potential of bovine oocytes during their aging in vitro. Therefore, we analysed (1) effects of PRL and GH during the prolonged culture of bovine oocytes on their subsequent development up to the blastocyst stage and (2) the role of cumulus cells (CC) and tyrosine kinases, the well-known mediators of PRL and GH signalling, in these effects. Bovine cumulus-enclosed oocytes (CEO) were cultured for 22 h in the following maturation medium: TCM 199 containing 10% fetal calf serum (FCS), 10 μg mL–1 of porcine FSH, and 10 μg mL–1 of ovine LH. After IVM, CEO or denuded oocytes (DO) were transferred to the aging medium consisting of TCM 199 supplemented with 10% FCS and cultured for 10 h in the absence (Control) or presence of 50 ng mL–1 bovine PRL or 10 ng mL–1 recombinant bovine GH and/or 10 μg mL–1 genistein (a non-selective inhibitor of tyrosine kinases). Genistein was not applied in the case of aging DO, since their developmental potential was not affected by both hormones. Following the prolonged culture, oocytes underwent IVF and IVC. Embryos were cultured in CR1aa medium until Day 5 post-insemination and then transferred to the same medium supplemented with 5% FCS and cultured up to Day 8. The embryo development was evaluated at Days 2 and 8 for cleavage and blastocyst formation. The data from 5 to 6 replicates using 135–184 oocytes per treatment were analysed by ANOVA. Aging of oocytes in the control medium had no effect on the cleavage rate, but caused the blastocyst yield to decline (P &lt; 0.001) from 31.1 ± 2.3% (CEO fertilized immediately after maturation) to 10.5 ± 2.4% (aged CEO) and 7.9 ± 1.9% (aged DO). Cleavage rates of aging CEO and DO were unaffected by both PRL and GH. In the case of CEO, the addition of PRL (but not GH) to the aging medium raised the blastocyst yield from 8.2 ± 0.9% to 15.2 ± 2.1% (P &lt; 0.05), whereas the removal of CC abolished this effect, reducing the yield up to 9.1 ± 2.7% (P &lt; 0.05). At the same time, genistein did not influence the blastocyst yield in the PRL-treated group. The findings demonstrate that PRL can inhibit the attenuation of the developmental competence of bovine oocytes aging in vitro, with this effect being achieved via cumulus cells. Tyrosine kinases are unlikely to mediate the beneficial action of PRL on the CEO capacity for embryonic development. Meanwhile, closely related GH does not affect the developmental competence of aging bovine oocytes.This research was supported by RFBR (project No. 13-04-01888).

298 CYCLIC AMP AND CYCLIC GMP CONTENTS IN PORCINE OOCYTE&ndash;CUMULUS COMPLEXES, DENUDED OOCYTES, AND CUMULUS CELLS DERIVED FROM SMALL AND MIDDLE FOLLICLES DURING IN VITRO MATURATION

Drastic changes in intracellular cAMP and cGMP levels play a critical role in the regulation of meiotic resumption. The objective of this study was to compare cAMP and cGMP contents in cumulus-oocyte complexes (COC), denuded oocytes (DO), and cumulus cell masses (CC) derived from small (SF) and middle follicles (MF) during in vitro maturation (IVM). The COC were aspirated from SF (1–3 mm in diameter) or MF (3–6 mm in diameter) of prepubertal gilt ovaries. The COC were cultured in modified porcine oocyte medium (mPOM) with eCG, hCG, and dibutyryl cAMP for 20 h and then in fresh mPOM without those supplements for 4 h in an atmosphere of 5% CO2 in air at 39°C. At 0, 10, 20, and 24 h of IVM, COC, DO, and CC were collected. The DO were prepared by removal of cumulus cells and zona pellucida. The CC were prepared by puncturing ooplasm by using 18-gauge needle. Intracellular contents of cAMP and cGMP were determined by direct enzyme immunoassay kits. Statistical analyses of 3 to 7 replicated data were performed by ANOVA. There were no significant differences in contents of cAMP and cGMP between DO from SF and MF in all observation points (P &gt; 0.05). Cyclic AMP contents in COC and CC derived from MF were higher than those from SF at 20 h of IVM (MF 33.0 ± 0.5 fmol/COC v. SF 28.4 ± 1.0 fmol/COC, MF 20.9 ± 0.9 fmol/CC v. SF 14.6 ± 0.8 fmol/CC; P &lt; 0.05), whereas there were no significant differences between origins of those (SF v. MF, P &gt; 0.05) at 0, 10, and 24 h of IVM. Furthermore, although cAMP content in CC from MF was not significantly different between 10 and 20 h of IVM (25.4 ± 1.7 and 20.9 ± 0.9 fmol/CC, respectively; P &gt; 0.05), the content in CC from SF significantly decreased between 10 and 20 h (23.1 ± 1.2 , and 14.6 ± 0.8 fmol/CC, respectively; P &lt; 0.05). At 0 and 10 h of IVM, cGMP contents in COC and CC from MF were significantly higher than those from SF (0 h: 81.8 ± 4.5 fmol/COC from MF v. 41.7 ± 10.6 fmol/COC from SF and 82.7 ± 7.5 fmol/CC from MF v. 10.7 ± 2.7 fmol/CC from SF; 10 h: 64.8 ± 8.4 fmol/COC from MF v. 24.8 ± 8.2 fmol/COC from SF, 49.3 ± 14.9 fmol/CC from MF v. 13.5 ± 4.8 fmol/CC from SF; P &lt; 0.05). However, there were no significant differences in cGMP contents in COC and CC between the origins (MF v. SF) at 20 and 24 h of IVM (P &gt; 0.05). From these results, we conclude that cAMP and cGMP contents in cumulus cells are significantly differences between the origins (MF v. SF) during IVM.

284 INTRACELLULAR PATHWAYS MEDIATING DIRECT EFFECTS OF PROLACTIN AND GROWTH HORMONE ON BOVINE METAPHASE-II OOCYTES AGING IN VITRO

Maturation of mammalian oocytes coincides with various aging processes, which negatively affect the oocyte quality. Cellular and molecular changes in matured oocytes aging in vivo and in vitro are very similar, suggesting similarities in the underlying mechanisms. The goal of the present research was to study direct effects of prolactin (PRL) and growth hormone (GH) on bovine metaphase-II (M-II) oocytes aging in vitro and intracellular pathways mediating these effects. Cumulus-enclosed oocytes were matured for 20 h in TCM 199 containing 10% fetal calf serum (FCS), 10 µg mL–1 of porcine FSH, and 10 µg mL–1 of ovine LH. After IVM, oocytes were set free from cumulus and denuded oocytes (DO) were cultured for 44 h in the aging medium consisting of TCM 199 supplemented with 10% FCS in the absence of PRL and GH (Control), then in the presence of either 50 ng mL–1 of bovine PRL or 10 ng mL–1 of bovine GH or protein kinase inhibitors. The following inhibitors were added: (1) PP2 (an inhibitor of Src-family tyrosine kinases, 20 µM), (2) U0126 (a MEK inhibitor, 20 µM), and (3) triciribine (an inhibitor of Akt kinase, 50 µM). At the end of culture, the state of the nuclear material of oocytes and embryos was evaluated by the method of Tarkowski. The number of oocytes undergone spontaneous parthenogenetic activation was determined by summarising the numbers of embryos cleaved and oocytes reached anaphase-II to pronucleus stages. The data from 4 replicates were analysed by ANOVA. During aging in the control medium, the rate of M-II oocytes with destructive changes of chromosomes (decondensation, clumping, fragmentation) increased from 20.3 ± 1.7 to 65.1 ± 3.5% (P &lt; 0.001) and was unaffected by PRL and GH. At the same time, the frequency of oocyte parthenogenetic activation (18.7 ± 4.9%) was reduced (P &lt; 0.001) by both PRL and GH (up to 6.0 ± 2.9 and 5.9 ± 2.4%, respectively). The inhibitor of Src-family tyrosine kinases PP2 eliminated (at least P &lt; 0.05) the supporting effects of PRL and GH on the meiotic arrest at M-II. The MEK inhibitor U0126 also abolished the effect of PRL (but not that of GH), increasing the frequency of the oocyte activation from 5.9 ± 2.3 to 21.6 ± 1.9% (P &lt; 0.01). Concurrently, both inhibitors did not affect the meiotic arrest in the control group. The inhibitor of Akt kinase triciribine did not influence the frequency of the oocyte activation in the PRL- and GH-treated groups. Meanwhile, triciribine decreased the rate of M-II oocytes with chromosome abnormalities in the control medium (from 71.2 ± 1.7 to 47.0 ± 2.7%; P &lt; 0.001). When added to the aging medium, PRL enhanced the triciribine effect, while GH suppressed it (P &lt; 0.01). Thus, PRL and GH can directly support the meiotic arrest at M-II in aging oocytes by activating MAP kinases or Src-family tyrosine kinases. Besides, GH may enhance the chromosome destruction in DOs through activation of Akt kinase.The research was supported by RFBR (No. 13-04-01888).

312 EFFECTS OF TRANSFORMING GROWTH FACTOR ALPHA AND INSULIN-LIKE GROWTH FACTOR 1 SUPPLEMENTATION ON IN VITRO MATURATION OF CANINE OOCYTES

Although in vitro maturation (IVM) of oocytes has been successfully established for many species, the efficiency of IVM in canine oocytes is still very low. As growth factors have been shown to promote oocyte maturation in some species, we investigated whether use of transforming growth factor α (TGF-a) and insulin-like growth factor 1 (IGF-1) might overcome the difficulties of achieving meiotic maturation in cultured canine cumulus-oocyte complexes (COC). Ovaries were obtained from bitches at 6 months to 7 years of age by ovariohysterectomy and were sliced repeatedly to release COC. In the first experiment, the COC were cultured at 38.8°C for 48 h in 5% CO2 in air in medium 199 supplemented with either TGF-a (0, 1, 10, or 100 ng mL–1) or IGF-1 (0, 0.5, 5, 10, or 50 µg mL–1). In the second experiment, the synergistic effect of TGF-a and IGF-1 was investigated by culturing COC in medium 199 supplemented with both TGF-a (0, 1, 10, or 100 ng mL–1) and IGF-1 (0, 0.5, 5, 10, or 50 µg mL–1). At the end of the culture period, the oocytes were denuded of cumulus cells by pipetting with a fine bore glass pipette; the denuded oocytes were then fixed in Carnoy's solution and stained with Hoechst 33342. The nuclear configuration and chromatin morphology of the oocytes were evaluated under confocal laser scanning microscopy. The cells were assigned to 1 of the following meiotic stages: germinal vesicle (GV), germinal vesicle breakdown (GVBD), metaphase I (MI), or metaphase II (MII). Data were analysed by ANOVA with Fisher's PLSD test. In experiment 1, no significant difference were observed in the rates of cells maturing to the MI and MII stages, but that in the 10 ng mL–1 of TGF-a group (56.3%) were larger than in the other treatment groups (38.8–51.0%). The frequencies of MII stage cells in the 5, 10, and 50 µg mL–1 of IGF-1 treatment groups (9.8, 13.3, and 12.2%, respectively) were significantly higher than in the 0.5 µg mL–1 of IGF-1 group and the control group (5.3 and 2.2%, respectively). In experiment 2, the frequency of MI and MII cells in the control, 1 ng mL–1 of TGF-a plus 0.5 µg mL–1 of IGF-1, 10 ng mL–1 of TGF-a plus 5 µg mL–1 of IGF-1, 10 ng mL–1 of TGF-a plus 10 µg mL–1 of IGF-1, and 100 ng mL–1 of TGF-a plus 50 µg mL–1 of IGF-1 group were 44.1, 36.1, 63.5, 70.8, and 50.8%, respectively. The frequency of MII cells in the control group and the same treatment groups were 2.8, 7.2, 10.4, 15.3, and 10.8%, respectively. Both frequencies in the 10 ng mL–1 of TGF-a plus 10 µg mL–1 of IGF-1 group were significantly higher than in the control group. The TGF-a may act in a paracrine fashion on the surrounding granulosa cells, and IGF-1 may play multiple roles in cellular metabolism, proliferation, growth, and differentiation in canine oocyte maturation, as has been reported for many other species. In conclusion, these results demonstrate that a synergistic effect between TGF-a and IGF-1 produces an increased rate of in vitro maturation to the MI and MII stages in canine oocytes.