Growth differentiation factor 9 (GDF9) is an oocyte-specific paracrine factor involved in bidirectional communication, which plays an important role in oocyte developmental competence. In spite of its vital role in reproduction, there is insufficient information about exact transcriptional control mechanism of GDF9. Hence, present study was undertaken with the aim to study the expression of basic helix-loop-helix (bHLH) transcription factors (TFs) such as the factor in the germline alpha (FIGLA), twist-related protein 1 (TWIST1) and upstream stimulating factor 1 and 2 (USF1 and USF2), and nuclear receptor (NR) superfamily TFs like germ cell nuclear factor (GCNF) and oestrogen receptor 2 (ESR2) under three different in vitro maturation (IVM) groups [follicle-stimulating hormone (FSH), insulin-like growth factor-1 (IGF1) and oestradiol)] along with all supplementation group as positive control, to understand their role in regulation of GDF9 expression. Buffalo cumulus–oocyte complexes were aspirated from abattoir-derived ovaries and matured in different IVM groups. Following maturation, TFs expression was studied at 8 h of maturation in all four different IVM groups and correlated with GDF9 expression. USF1 displayed positive whereas GCNF, TWIST1 and ESR2 revealed negative correlation with GDF9 expression. TWIST1 & ESR2 revealing negative correlation with GDF9 expression were found to be positively correlated amongst themselves also. GCNF & USF1 revealing highly significant correlation with GDF9 expression in an opposite manner were found to be negatively correlated. The present study concludes that the expression of GDF9 in buffalo oocytes remains under control through the involvement of NR and bHLH TFs.

Lipid accumulation occurs in cultured embryos and is associated with reduced cryotolerance. Here we report the use of a multiple pathway lipid modulator cocktail (l-carnitine, linoleic acid and forskolin) to improve cryosurvival. First, we stained oocytes and embryos with Oil Red to examine the time course of lipid accumulation during in vitro fertilization (IVF) and embryo culture. Then we evaluated the effects of the lipid modulators cocktail on lipid content, developmental rates and survival after vitrification. In our conditions, lipid accumulation was detected (P < 0.05) at the end of in vitro maturation (IVM) and after 4 days of embryo culture (D4-D5). In experiment 1, we used lipid modulator cocktail during IVM. Reduced (P < 0.05) lipid accumulation was detected in oocytes (Control: 49.9 ± 1.6, Lip. Mod. IVM: 45.0 ± 1.8) but no changes were present at blastocyst stage (Control: 62.4 ± 2.6, Lip. Mod. IVM: 66.8 ± 2.7). Treated oocytes presented decreased (P < 0.05) blastocyst rates and lower (P < 0.05) re-expansion after vitrification. In experiment 2, lipid modulators cocktail was used during embryo culture (from D4–D7 or D6–D7). Treatment had an effect on lipid metabolism, as lipid content was increased (P < 0.05) in D7 blastocysts in treated groups (Control: 52.7 ± 3.1a, D4: 65.9 ± 2.6b, D6: 78.1 ± 2.7b). However, no effect was present for cleavage, blastocyst and cryosurvival rates. No difference was detected in mean cell number comparing the three groups (Control: 78.9 ± 9.6, D4: 82.6 ± 16.5, D6: 68.3 ± 7.8), but apoptosis rate was increased (P < 0.05) in vitrified-warmed blastocysts from treated groups (Control: 14.77*, D4: 22.28, D6: 22.22). We concluded that the combined use of lipid modulators was efficient to promote changes in lipid content of oocytes and embryos in bovine, but those changes did not reflect positively on embryo development or cryosurvival.

This study examined the effects of zinc chloride (ZnCl2) and sodium selenite (Na2SeO3) supplementation in maturation medium on in vitro maturation (IVM) rate, oxidative biomarkers and gene expression in buffalo oocytes. Ovaries from a slaughterhouse were aspirated and good quality cumulus–oocyte complexes (COCs) with at least four layers of compact cumulus cells and evenly granulated dark ooplasm were selected. COCs were randomly allocated during IVM (22 h) to one of four treatment groups: (1) control maturation medium (basic medium), or basic medium supplemented with (2) ZnCl2 (1.5 µg/ml), (3) Na2SeO3 (5 µg/l), or (4) ZnCl2 + Na2SeO3 (1.5 µg/ml + 5 µg/l, respectively). Oocytes were denuded after 22 h of IVM in the first four replicates. Specimens were fixed and stained to evaluate the stage of nuclear maturation. The spent medium was collected for biochemical assays of total antioxidant capacity (TAC), malondialdehyde (MDA) and hydrogen peroxide concentrations. A second four replicates were used for COCs for RNA extraction. The expression levels of antioxidant (SOD1, GPX4, CAT and PRDX1), antiapoptotic (BCL2 and BCL-XL) and proapoptotic (BAX and BID) genes were measured. Supplementation with ZnCl2 and Na2SeO3 during IVM increased the ratio of oocytes reaching metaphase II at 22 h, increased TAC and decreased MDA and H2O2 concentrations in the maturation medium (P < 0.05). Moreover, beneficial effects were associated with complementary changes in expression patterns of antioxidative, antiapoptotic and proapoptotic genes, suggesting lower oxidative stress and apoptosis. Supplementation medium with zinc chloride and sodium selenite improves the maturation rate, reduces oxidative stress and increases expression levels of antioxidative and antiapoptotic genes.

The aim of this study was to investigate the effect of cyanocobalamin supplementation on in vitro maturation (IVM), in vitro fertilization (IVF), and subsequent embryonic development competence to the blastocyst stage, and in vitro development of mouse 2-cell embryos. Cumulus cells were prepared from mouse cumulus–oocyte complexes (COCs) and incubated for 24 h in an in vitro culture (IVC) medium that contained different concentrations of cyanocobalamin (100, 200, 300 or 500 pM). We collected 2-cell embryos from superovulated NMRI mice and cultured them in the same concentrations of cyanocobalamin (100, 200, 300 or 500 pM). After 42 h of IVM, we observed significantly increased oocyte maturation in the 200 pM cyanocobalamin-treated group compared with the control group (P < 0.0001). Mature oocytes cultured in 200 pM cyanocobalamin were fertilized and cultured in IVC medium with cyanocobalamin (100, 200, 300 or 500 pM) during early embryogenesis. The matured oocytes that were cultured in 200 pM cyanocobalamin had significantly higher 2-cell development rates compared with the control oocytes (P < 0.01). Embryos obtained from in vitro mature oocytes and in vivo fertilized oocytes that were cultured in 200 pM cyanocobalamin had significantly greater frequencies of development to the blastocyst stage and a significant reduction in 2-cell blocked and degenerated embryos compared with the control embryos (P < 0.0001). Embryos derived from oocytes fertilized in vivo with 200 pM cyanocobalamin had a higher percentage of blastocyst embryos compared with those derived from matured oocytes cultured in vitro (P < 0.0001). These finding demonstrated that the effects of cyanocobalamin on oocyte maturation, fertilization, and embryo development in mice depend on the concentration used in IVC medium.

The aim of the present study was to investigate the effects of porcine follicular fluid (pFF) from large-sized (LFF; >8 mm in diameter) and medium-sized (MFF; 3–6 mm in diameter) follicles on the maturation and developmental competence of porcine oocytes. Cumulus–oocyte complexes (COCs) were collected from follicles 3–6 mm in diameter. The collected COCs were incubated for 22 h with LFF or MFF (in vitro maturation (IVM)-I stage) and were incubated subsequently for 22 h with LFF or MFF (IVM-II stage). Cumulus expansion was confirmed after the IVM-I stage and nuclear maturation was evaluated after the IVM-II stage. Intracellular glutathione (GSH) and reactive oxygen species (ROS) levels were measured and embryonic development was evaluated. Relative cumulus expansion and GSH levels were higher in the LFF group compared with in the MFF group after the IVM-I stage (P < 0.05). After the IVM-II stage, the numbers of oocytes in metaphase-II were increased in the LFF group and GSH content was higher in all of the LFF treatment groups compared with in the MFF treatment groups during both IVM stages (P < 0.05). ROS levels were reduced by LFF treatment regardless of IVM stage (P < 0.05). Blastocyst formation and the total numbers of cells in blastocysts were increased in all LFF treatment groups compared with the control group (P < 0.05). These results suggested that pFF from large follicles at the IVM stage could improve nucleic and cytoplasmic maturation status and further embryonic development through reducing ROS levels and enhancing responsiveness to gonadotropins.

This study aimed to evaluate the relationship between antral follicular count (AFC) and ovarian volume (OV), preantral follicular population and survival, meiotic progression and ultrastructure of cumulus–oocyte complexes (COCs) after in vitro maturation. In experiment 1, the relationship between AFC and preantral follicle population and survival was evaluated by classical histology. In experiment 2, the relationship among AFC, OV, ability of oocytes to resume meiosis and ultrastructure of in vitro matured bovine COCs was studied. A positive correlation (P < 0.05) between AFC and the numbers of healthy primordial, degenerate and total follicles was observed, as well as with healthy secondary follicles and total follicles. The numbers of grades I and II oocytes in ovaries of high AFC class were higher compared with those with intermediate or lower AFC. After in vitro maturation, COCs from ovaries of high AFC had a higher percentage of oocytes in metaphase II compared with those of intermediate and low AFC (P < 0.0001). Ovaries of intermediate AFC had a higher percentage of oocytes in metaphase II compared with ovaries with low AFC (P < 0.0001). The proportion of oocytes in metaphase I, telophase I and anaphase I in COCs from ovaries of intermediate AFC (26.04%) was higher (P < 0.05) compared with that seen in COCs of ovaries with high (8.55%) and low (14.15%) AFC. No differences in the ultrastructure of oocytes were seen. In conclusion, after in vitro maturation, cow ovaries with high AFC have higher numbers of oocytes that reach in metaphase II (MII), but they also have higher numbers of degenerated primordial and primary follicles.

Experiments were conducted to study in vitro maturation of prepubertal goat oocytes and their developmental potential after chemical activation. In Experiment 1, cumulus–oocytes complexes collected from the ovaries of prepubertal goats slaughtered at a local abattoir were matured in vitro in TCM-199-based medium supplemented with 10 µg/ml luteinizing hormone (LH) (treatment 1) or 10 µg/ml LH + 0.1 mM l-cysteine (treatment 2). In Experiment 2, mature oocytes were activated with either 5 µM ionomycin or 7% ethanol. After 18 h, some oocytes were randomly fixed and stained to evaluate their chromatin status, while others were cultured in embryo culture medium to study their further development. In Experiment 3, oocytes activated with 5 µM ionomycin were cultured for 7 days in one of the four different culture media [Charles Rosenkrans medium (CR-1), TCM-199, potassium simplex optimization medium (KSOM) and synthetic oviductal fluid (SOF)] to study their developmental potential. The maturation rate in control, treatment 1, and treatment 2 media did not differ from each other (P > 0.05). However, the lowest degeneration of oocytes was observed in treatment 3 (P < 0.05) when compared with the other two groups. The proportion of activated oocytes was higher, while non-activated oocytes were lower in ionomycin group when compared with the group activated with ethanol (P < 0.05). The proportions of oocytes cleaved were 65.7, 56.8, 61.0 and 54.4% in CR-1, TCM-199, KSOM and SOF medium, respectively, with no significant difference. However, further development of cleaved oocytes was better in KSOM followed by SOF.

The aims of the present study were to: (i) evaluate the ultrastructural differences in the zona pellucida (ZP) surface between immature and mature bovine oocytes, and (ii) describe a new objective technique to measure the pores in the outer ZP. Intact cumulus–oocyte complexes (COCs) obtained from a local abattoir were immediately fixed (immature group) or submitted to in vitro maturation (IVM) at 38.5 °C for 24 h in a humidified atmosphere of 5% CO2 in air (mature group). Oocytes from both groups were morphologically evaluated via Scanning Electron Microscopy (SEM) and the images were processed in the Fiji/ImageJ software using a new objective methodology through the Trainable Weka Segmentation plugin. The average number of pores in ZP was greater (p < 0.05) in the mature group than the immature group. However, the size and circularity of pores in ZP did not differ (p > 0.05) between groups. In conclusion, it has been shown that the number of pores highlighted the main ultrastructural change in the morphology of the ZP surface of bovine oocytes during the IVM process. We have described an objective method that can be used to evaluate ultrastructural modifications of the ZP surface during oocyte maturation and early embryo development.

Currently, rescue in vitro maturation (IVM) is not a routine method in assisted reproductive treatment (ART) programmes but is a promising procedure for ART to improve IVM. The aim of this study was to compare embryo morphokinetics of germinal vesicles (GV) with metaphase II (MII) oocytes from controlled ovarian hyperstimulation (COH) cycles by time-lapse photography monitoring (TLM). Morphokinetics of the same number of embryos derived from the in vivo (group I) and rescue of in vitro matured oocytes (group II) from 310 patients were analyzed and compared retrospectively. The time to form second PB extrusion (tPB2), time of pronuclei appearance (tPNa), time of pronuclei fading (tPNf) and time of two to eight discrete cells (t2–t8) were assessed. Abnormal cleavage patterns such as uneven blastomeres at the two-cell stage, cell fusion (Fu), trichotomous mitoses (TM), and the rates of embryo arrest were assessed. These data showed that tPB2, tPNa, tPNf, t2, t3 and t4 stages took place later in group II compared with group I (P<0.001, P=0.017, P<0.001, P<0.001, P<0.001, P<0.001, respectively). The rates of uneven blastomeres, Fu, TM, and embryo arrest were increased significantly in group II compared with group I (P=0.001, P<0.001, P=0.003, P<0.001, respectively). Based on the exact annotation of timing parameters and cleavage patterns, the present data agreed with the concept that rescue IVM of oocytes negatively influences embryo morphokinetics. Therefore, cautious use of embryos derived from rescue IVM of GV oocytes should be made.

The high miscarriage rates that result following transfer of embryos derived from in vitro maturation (IVM) of oocytes necessitate improvements in the processes involved. This study aimed to improve the quality of in vitro matured oocytes using granulosa cell conditioned medium (GCCM) as the culture medium. In this work, germinal vesicle (GV)-stage oocytes from NMRI mice were collected and cultured using three types of culture medium: Base medium (BM) (control), 50% granulosa cell conditioned medium (GCCM50) and 100% GCCM (GCCM100). After IVM, the mitochondria activity potential and viability of metaphase II (MII) oocytes were evaluated by JC-1 and trypan blue staining, respectively. Maturational gene expression levels of CyclinB1, Cdk1 and Gdf9 in the control, GCCM50 and GCCM100 samples were analyzed using real-time polymerase chain reaction (PCR). The viability rate of in vitro matured oocytes was highest in the GCCM50 group. JC-1 staining showed that GCCM50 enhances mitochondrial activity more than the other groups (P < 0.05). Gene expression levels of Cdk1 and Gdf9 were higher in the group with GCCM50 treatment, than in the control and GCCM100 groups (P < 0.05), while the expression level of CyclinB1 did not differ among the groups. The results indicated that a 50% concentration of GCCM in combination with BM components enhanced MII and viability rates and mitochondria activity of mouse immature oocytes.

This study examined the effects of meiosis inhibition during bovine oocyte transportation on developmental competence and quality of produced embryos. The transportation medium was supplemented with: 100 μM butyrolactone I (BL), 500 μM IBMX + 100 μM forskolin (mSPOM), 100 μM milrinone (MR) or follicular fluid (bFF), and was carried out in a portable incubator for 6 h. Next, oocytes were in vitro matured (IVM) for 18 h, without the meiotic inhibitors, with the exception of mSPOM group, in which was added 20 μM cilostamide. The three control groups were IVM with 10% fetal calf serum (FCS) (Control Lab FCS) or 0.6% bovine serum albumin (BSA) (Control Lab BSA) in a CO2 in air incubator or in the portable incubator with 0.6% BSA (Control Transp BSA). Higher cleavage rates (P < 0.05) were obtained in the Control Lab FCS group (84.5 ± 5.3%) compared with the other groups (59.6 ± 3.4% to 70.9 ± 2.3%). Embryonic development was higher (P < 0.05) in the Control Lab FCS group (39.8 ± 4.7%) than in the Control Transp BSA (22.7 ± 3.4%) and MR (21.6 ± 2.3%) groups. However, they were similar (P > 0.05) to the other groups (23.6 ± 3.3% to 28.8 ± 2.7%). The total number of blastomeres was higher (P < 0.05) in the Control Lab FCS group (85.2 ± 5.6) than in Control Lab BSA (53.6 ± 2.9), Control Transp BSA (55.5 ± 4.4), BL (58.2 ± 3.0), mSPOM (57.9 ± 4.9) and MR (59.2 ± 3.9), but all these treatments did not differ (P > 0.05) from bFF (67.7 ± 4.2). No differences (P > 0.05) were found in apoptosis by the activity of caspases (139.0 ± 3.2 to 152.4 ± 6.5, expressed in fluorescence intensity) as well as the percentage of TUNEL-positive cells (12.3 ± 2.0% to 15.7 ± 1.7%). In conclusion, the transportation of oocytes over 6 h with BL, mSPOM or bFF enabled the acquisition of developmental competence at similar rates to the Control Lab FCS group.

Allicin (AL) regulates the cellular redox, proliferation, viability, and cell cycle of different cells against extracellular-derived stress. This study investigated the effects of allicin treatment on porcine oocyte maturation and developmental competence. Porcine oocytes were cultured in medium supplemented with 0 (control), 0.01, 0.1, 1, 10 or 100 μM AL, respectively, during in vitro maturation (IVM). The rate of polar body emission was higher in the 0.1 AL-treated group (74.5% ± 2.3%) than in the control (68.0% ± 2.6%) (P < 0.1). After parthenogenetic activation, the rates of cleavage and blastocyst formation were significantly higher in the 0.1 AL-treated group than in the control (P < 0.05). The reactive oxygen species level at metaphase II did not significantly differ among all groups. In matured oocytes, the expression of both BAK and CASP3, and BIRC5 was significantly lower and higher, respectively, in the 0.1 AL-treated group than in the control. Similarly, the expression of BMP15 and CCNB1, and the activity of phospho-p44/42 mitogen-activated protein kinase (MAPK), significantly increased. These results indicate that supplementation of oocyte maturation medium with allicin during IVM improves the maturation of oocytes and the subsequent developmental competence of porcine oocytes.

Mammalian oocyte maturation is achieved when oocytes reach metaphase II (MII) stage, and accumulate mRNA and proteins in the cytoplasm following fertilization. It has been shown that oocytes investigated before and after in vitro maturation (IVM) differ significantly in transcriptomic and proteomic profiles. Additionally, folliculogenesis and oogenesis is accompanied by morphogenetic changes, which significantly influence further zygote formation and embryo growth. This study aimed to determine new transcriptomic markers of porcine oocyte morphogenesis that are associated with cell maturation competence. An Affymetrix microarray assay was performed on an RNA template isolated from porcine oocytes before (n = 150) and after (n = 150) IVM. The brilliant cresyl blue (BCB) staining test was used for identification of cells with the highest developmental capacity. DAVID (Database for Annotation, Visualization, and Integrated Discovery) software was used for the extraction of the genes belonging to a cell morphogenesis Gene Ontology group. The control group consisted of freshly isolated oocytes. In total, 12,000 different transcripts were analysed, from which 379 genes were downregulated and 40 were upregulated in oocytes following IVM. We found five genes, SOX9, MAP1B, DAB2, FN1, and CXCL12, that were significantly upregulated in oocytes after IVM (in vitro group) compared with oocytes analysed before IVM (in vivo group). In conclusion, we found new transcriptomic markers of oocyte morphogenesis, which may be also recognized as significant mediators of cellular maturation capacity in pigs. Genes SOX9, MAP1B, DAB2, FN1, and CXCL12 may be involved in the regulation of the MII stage oocyte formation and several other processes that are crucial for porcine reproductive competence.

The purpose of this study was to investigate the possible molecular pathways through which ghrelin accelerates in vitro oocyte maturation. Bovine cumulus–oocyte complexes (COCs), after 18 or 24 h maturation in the absence or the presence of 800 pg ml–1 of acylated ghrelin were either assessed for nuclear maturation or underwent in vitro fertilization in standard media and putative zygotes were cultured in vitro for 8 days. In a subset of COCs the levels of phosphorylated Akt1 and ERK1/2 (MAPK1/3) were assessed at the 0th, 6th, 10th, 18th and 24th hours of in vitro maturation (IVM). At 18 and 24 h no difference existed in the proportion of matured oocytes in the ghrelin-treated group, while in the control group more (P < 0.05) matured oocyte were found at 24 h. Oocyte maturation for 24 h in the presence of ghrelin resulted in substantially reduced (P < 0.05) blastocyst yield(16.3%) in comparison with that obtained after 18 h (30.0%) or to both control groups (29.3% and 26.9%, for 18 and 24 h in maturation, respectively). Ghrelin-treated oocytes expressed lower Akt1 phosphorylation rate at the 10th hour of IVM, and higher ERK1/2 at the 6th and 10th hours of IVM compared with controls. In cumulus cells, at the 18th and 24th hours of IVM Akt1 phosphorylation rate was higher in ghrelin-treated oocytes. Our results imply that ghrelin acts in a different time-dependent manner on bovine oocytes and cumulus cells modulating Akt1 and ERK1/2 phosphorylation, which brings about acceleration of the oocyte maturation process.

The developmental potential of in vitro matured porcine oocytes is still lower than that of oocytes matured and fertilized in vivo. Major problems that account for the lower efficiency of in vitro production include the improper nuclear and cytoplasmic maturation of oocytes. With the aim of improving this issue, the single and combined effects of epidermal growth factor (EGF) and glial cell line-derived neurotrophic factor (GDNF) on oocyte developmental competence were investigated. Porcine cumulus–oocyte cell complexes (COCs) were matured in serum-free medium supplemented with EGF (0, 10 or 50 ng/ml) and/or GDNF (0, 10 or 50 ng/ml) for 44 h, and subsequently subjected to fertilization and cultured for 7 days in vitro. The in vitro-formed blastocysts derived from selected growth factor groups (i.e. EGF = 50 ng/ml; GDNF = 50 ng/ml; EGF = 50 ng/ml + GDNF = 50 ng/ml) were also used for mRNA expression analysis, or were subjected to Hoechst staining. The results showed that the addition of EGF and/or GDNF during oocyte maturation dose dependently enhanced oocyte developmental competence. Compared with the embryos obtained from control or single growth factor-treated oocytes, treatment with the combination of EGF and GDNF was shown to significantly improve oocyte competence in terms of blastocyst formation, blastocyst cell number and blastocyst hatching rate (P < 0.05), and also simultaneously induced the expression of BCL-xL and TERT and suppressed the expression of caspase-3 in resulting blastocysts (P < 0.05). These results suggest that both GDNF and EGF may play an important role in the regulation of porcine in vitro oocyte maturation and the combination of these growth factors could promote oocyte competency and blastocyst quality.

Bisphenol AF (BPAF), a homolog of bisphenol A (BPA), is a widely used environmental chemical that has adverse effects on reproduction. The aim of this study was to analyse the effects of BPA and BPAF exposure on oocyte maturation in vitro. Oocytes were cultured in the presence of BPA or BPAF (2, 20, 50 or 100 μg/ml) for 18 h. At concentrations of 50 and 100 μg/ml, BPA and BPAF inhibited oocyte maturation, with BPAF treatment causing a sharp decrease in the number of oocytes reaching maturity. Oocytes were exposed to BPA or BPAF at 2 μg/ml and cultured for different durations (6, 9, 12, 15 or 18 h). Both BPAF and BPA caused a cell cycle delay under these conditions. Oocytes cultured in the presence of BPA or BPAF (50 μg/ml) for 21 h were tested for the localization of α-tubulin and MAD2 using immunofluorescence. High concentrations of BPAF induced cell cycle arrest through the activation of the spindle assembly checkpoint. After 12 h of culture in BPAF (50 μg/ml), oocytes were transferred to control medium for 9 h. Only 63.3% oocytes treated in this manner progressed to metaphase II (MII). Oocytes exposed to high doses of BPA experienced a cell cycle delay, but managed to progress to MII when the culture period was prolonged. In addition, MAD2 was localized in the cytoplasm of these oocytes. In conclusion, both BPAF and BPA exposure affected oocyte maturation, however BPAF and BPA have differential effects on SAC activity.

We measured the ATP concentrations in the porcine follicular fluid derived from three sizes of follicles (small: <3 mm, medium: 3–6 mm, large: >6 mm in diameter). Then, the effects of pre-treatment (100 μM each for 30 min before maturation) with antagonists for extracellular ATP receptor P2X or P2Y on the nuclear maturation rate of cumulus-cell-enclosed (COs) or -denuded oocytes (DOs) up to the preovulatory stage in the presence or absence of 20 nM ATP (a similar concentration to that of medium-sized follicle fluid) were investigated. The antagonists used were pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS) or reactive blue 2 (RB2), for extracellular ATP receptor P2X and P2Y, respectively. In addition, the embryonic development rates of COs pre-treated with RB2 were also evaluated. It was found that when the follicular sizes increased, the ATP concentrations significantly decreased (P < 0.05). No differences were observed in the nuclear maturation rates among all COs, regardless of pre-treatment with (+) or without (–) PPADS and in the presence (+) or absence (–) of ATP during maturation. In contrast, the nuclear maturation rate of the COs, but not DOs, in the ATP(–) RB2(+) group was significantly lower (P < 0.05) than that of the ATP(–) RB2(–) and ATP(+)RB2(–) groups. The pronuclear formation and blastocyst formation rates by parthenogenetic activation in the ATP(–) RB2(+) and ATP(+) RB2(+) groups were significantly lower (P < 0.05) than those in the ATP(–) RB2(–) group. In conclusion, it is suggested that the nuclear maturation of porcine oocytes may be influenced by the ATP receptor P2Y present in the cumulus cells.

The aim of this study was to evaluate the dose–response effect of insulin, plus follicle-simulating hormone (FSH) at a fixed concentration, in a serum-free defined culture medium (DCM) on the in vitro maturation of bovine cumulus–oocyte complexes (COCs). For oocyte nuclear maturation, the expression levels of GDF9, GLUT1, PRDX1 and HSP70.1 transcripts related to oocyte and embryo developmental competence were analysed. For in vitro maturation (IVM), cumulus–oocyte complexes from slaughterhouse ovaries were distributed into four groups based on insulin concentration added to serum-free DCM, which was composed of alpha minimum essential medium (α-MEM), as basal medium: (1) DCM control: 0 ng/ml; (2) DCM1: 1 ng/ml; (3) DCM10: 10 ng/ml; and (4) DCM100: 100 ng/ml. After IVM, the nuclear status of a sample of oocytes was analysed and the other oocytes were submitted for in vitro fertilization (IVF) and in vitro culture (IVC). Different concentrations of insulin did not affect significantly the nuclear maturation and cleavage rate (72 h post-insemination) across all groups. Blastocyst rate (192 h post-insemination) did not differ in DCM control (24.3%), DCM1 (27.0%) and DCM10 (26.3%) groups, but the DCM100 (36.1%) group showed a greater blastocyst rate (P < 0.05) than the DCM control. Insulin concentrations of 1, 10, or 100 ng/ml decreased the relative levels of GDF9 and HSP70-1 transcripts in oocytes at the end of IVM (P < 0.05). The transcripts levels of PRDX1 decreased (P < 0.05) only when 10 or 100 ng/ml insulin was added to the DCM medium. No difference in levels of GLUT1 transcripts (P > 0.05) was observed at the different insulin concentrations. The results indicated that insulin added to DCM influenced levels of transcripts related to cellular stress (HSP70-1 and PRDX1) and oocyte competence (GDF9) in bovine oocytes and at higher concentrations enhanced blastocyst production.

This study was designed to determine the effect of melatonin on the in vitro maturation (IVM) and developmental potential of bovine oocytes denuded of the cumulus oophorus (DOs). DOs were cultured alone (DOs) or with 10−9 M melatonin (DOs + MT), cumulus–oocyte complexes (COCs) were cultured without melatonin as the control. After IVM, meiosis II (MII) rates of DOs, and reactive oxygen species (ROS) levels, apoptotic rates and parthenogenetic blastocyst rates of MII oocytes were determined. The relative expression of ATP synthase F0 Subunit 6 and 8 (ATP6 and ATP8), bone morphogenetic protein 15 (BMP-15) and growth differentiation factor 9 (GDF-9) mRNA in MII oocytes and IFN-tau (IFN-τ), Na+/K+-ATPase, catenin-beta like 1 (CTNNBL1) and AQP3 mRNA in parthenogenetic blastocysts were quantified using real-time polymerase chain reaction (PCR). The results showed that: (1) melatonin significantly increased the MII rate of DOs (65.67 ± 3.59 % vs. 82.29 ± 3.92%; P < 0.05), decreased the ROS level (4.83 ± 0.42 counts per second (c.p.s) vs. 3.78 ± 0.29 c.p.s; P < 0.05) and apoptotic rate (36.99 ± 3.62 % vs. 21.88 ± 2.08 %; P < 0.05) and moderated the reduction of relative mRNA levels of ATP6, ATP8, BMP-15 and GDF-9 caused by oocyte denudation; (2) melatonin significantly increased the developmental rate (24.17 ± 3.54 % vs. 35.26 ± 4.87%; P < 0.05), and expression levels of IFN-τ, Na+/K+-ATPase, CTNNBL1 and AQP3 mRNA of blastocyst. These results indicated that melatonin significantly improved the IVM quality of DOs, leading to an increased parthenogenetic blastocyst formation rate and quality.

Cyclic adenosine monophosphate (cAMP) modulators have been used to avoid spontaneous oocyte maturation and concomitantly improve oocyte developmental competence. The current work evaluated the effects of the addition of cAMP modulators forskolin, 3-isobutyl-1-methylxanthine (IBMX) and cilostamide during in vitro maturation on the quality and yields of blastocysts. The following experimental groups were evaluated: (i) slicing or (ii) aspiration and maturation in tissue culture medium (TCM)199 for 24 h (TCM24slicing and TCM24aspiration, respectively), (iii) aspiration and maturation in the presence of cAMP modulators for 30 h (cAMP30aspiration) and in vivo-produced blastocysts. In vitro-matured oocytes were fertilized and presumptive zygotes were cultured in vitro to assess embryo development. Cleavage, blastocyst formation, blastocyst cell number, mRNA abundance of selected genes and global methylation profiles were evaluated. Blastocyst rate/zygotes for the TCM24aspiration protocol was improved (32.2 ± 2.1%) compared with TCM24slicing and cAMP30aspiration (23.4 ± 1.2% and 23.3 ± 2.0%, respectively, P<0.05). No statistical differences were found for blastocyst cell numbers. The mRNA expression for the EGR1 gene was down-regulated eight-fold in blastocysts that had been produced in vitro compared with their in vivo counterparts. Gene expression profiles for IGF2R, SLC2A8, COX2, DNMT3B and PCK2 did not differ among experimental groups. Bovine testis satellite I and Bos taurus alpha satellite methylation profiles from cAMP30aspiration protocol-derived blastocysts were similar to patterns that were observed in their in vivo equivalents (P > 0.05), while those from the other groups were significantly elevated. It is concluded that retrieval, collection systems and addition of cAMP modulators can affect oocyte developmental competence, which is reflected not only in blastocyst rates but also in global DNA methylation and gene expression patterns.