Slaughterhouse-derived Cumulus Oocyte Complexes Research Articles

Effect of in Vitro Maturation Medium Supplementation with Chitosan Nanoparticles on The River Buffalo Cumulus-Oocyte Complexes

The present study aimed to investigate the possible effects of chitosan nanoparticles (CNPs) supplementation to the in vitro maturation medium on the expansion of cumulus cells, nuclear maturation, and relative gene expression of Superoxide dismutase-1 (SOD1), B-cell lymphoma-2 Apoptosis Regulator (BCL2), and BCL2 Associated X (BAX) in the River buffalo. Slaughterhouse-derived cumulus-oocyte complexes (COCs) became matured in vitro in the absence (control) or presence of CNPs (10, 25, and 50µg/mL). At the end of maturation, we assessed expansion rates and denuded COCs; then, some replicates were fixed and stained to determine nuclear maturation. Other replicates were vitrified until we acquired enough oocytes, thawed, and assessed gene expression. We concluded that 10µg/mL CNPs significantly increased cumulus cell expansion and nuclear maturation. Whereas 10 and 25µg/mL CNPs non-significantly increased SOD1 relative expression, BCL2/BAX ratio for 10µg/mL CNPs was significantly higher than in control, 25 and 50µg/mL CNPs groups.

Interleukin-6 supplementation improves post-transfer embryonic and fetal development of in vitro-produced bovine embryos

The use of in vitro produced embryos in dairy and beef cattle has increased in recent years, but compromised post-transfer pregnancy success prevents producers from capturing all the benefits this technology can provide. This study explored whether supplementing interleukin-6 (IL6) during in vitro embryo development influences post-transfer development of the embryo-proper, fetus and placenta during early gestation in cattle. Slaughterhouse-derived cumulus oocyte complexes underwent IVM (day −1) and IVF (day 0). On day 5 post-fertilization, embryos were treated with either 0 (CONT) or 100 ng/mL recombinant bovine IL6. No difference in blastocyst formation was detected on day 7.5 post-fertilization, but an increase (P < 0.05) in inner cell mass cell numbers and tendency for increased (P = 0.08) trophectoderm cell numbers were detected in IL6-treated blastocysts. A subset of the blastocysts was loaded individually into transfer straws, and embryo transfer (ET) was completed using estrous cycle stage-matched, nonlactating commercial beef and dairy cows. A subset of cows from each group underwent timed artificial insemination (TAI). Pregnancy rates were similar among all three treatment groups at day 28 and 70. No differences in crown-rump length (CRL), crown nose length (CNL), abdominal diameter (AD), or placental fluid volume (PFV) were detected between TAI and ET-IL6 groups. Reductions (P < 0.05) in CRL and AD were detected at day 56 and a tendency for a reduction (P = 0.08) in PFV was detected on day 35 when comparing the ET-CONT group with the TAI group. Reductions (P < 0.05) in CRL and PFV on day 28 and CNL and AD on day 56 as well as a tendency for a reduction (P = 0.08) in PFV on day 35 were detected when contrasting ET-CONT with ET-IL6. Circulating plasma pregnancy-associated glycoprotein concentrations were similar among all treatment groups. In summary, IL6 treatment to IVP embryos before ET produced pregnancies that more closely resembled TAI-generated pregnancies than pregnancies generated using conventionally cultured embryos. These findings failed to find any adverse effects of IL6 supplementation on early development of the embryo-proper and fetus or on placental activity. Rather, these observations suggest that IL6 treatment may normalize the developmental trajectory of the embryo-proper and fetus for in vitro produced embryos.

133 Effect of cytokines on the quality bovine oocytes matured invitro

As has been shown previously, fibroblast growth factor 2 (FGF2), leukaemia inhibitory factor (LIF), and insulin-like growth factor 1 (IGF1) in combination play a positive role in maintaining the quality of mammalian oocytes maturing invitro. In the present work, we studied the effects of these cytokines in optimal concentrations when added in combination to IVM medium on the nuclear status and development competence of bovine oocytes. Slaughterhouse-derived cumulus–oocyte complexes (COC) (n=1107 COC) were cultured for 22h in either IVM medium [TCM-199 supplemented with 10% fetal calf serum (FCS), 0.2mM sodium pyruvate, 10μgmL−1 porcine FSH, and 10μgmL−1 ovine LH] (Control) or the same IVM medium supplemented with FGF2, LIF, and IGF1. The eight combinations of cytokines tested during maturation were (1) 20ngmL−1 LIF/10ngmL−1 IGF1/10ngmL−1 FGF2 (Group 1); (2) 20ngmL−1 LIF/10ngmL−1 IGF1/40ngmL−1 FGF2 (Group 2); (3) 20ngmL−1 LIF/20ngmL−1 IGF1/10ngmL−1 FGF2 (Group 3); (4) 20ngmL−1 LIF/20ngmL−1 IGF1/40ngmL−1 FGF2 (Group 4); (5) 5ngmL−1 LIF/10ngmL−1 IGF1/10ngmL−1 FGF2 (Group 5); (6) 5ngmL−1 LIF/10ngmL−1 IGF1/40ngmL−1 FGF2 (Group 6); (7) 5ngmL−1 LIF/20ngmL−1 IGF1/10ngmL−1 FGF2 (Group 7); and (8) 5ngmL−1 LIF/20ngmL− 1 IGF1/40ngmL−1 FGF2 (Group 8). After IVM, matured and denuded oocytes were activated by culturing in 5μM ionomycin solution for 5min followed by 4h in 2mM 4-dimethylaminopyridine (DMAP) and 10mgmL−1 cyclohexamide. Activated oocytes were cultured in CR1aa medium until Day 5 and then transferred to the same medium supplemented with 5% FCS and cultured until Day 7. All cultures were performed at 38.5°C and 5% CO2 in humidified air. At Days 2 and 7 after activation, the cleavage and blastocyst rates were determined. The data from 6 to 7 replicates (122–181 oocytes per treatment) were analysed by ANOVA. The rate of MII oocytes, assessed by the presence of the first polar body, did not differ between the groups and reached 67.1 to 84.5%. Cleavage rate was higher (84.5±2.9%, P&amp;lt;0.05) in Group 1 compared with Control (68.9±2.7%), Group 4 (67.1±4.9%) and Group 7 (66.6±2.0%), but not compared with Group 2 (76.5±4.8%), Group 3 (76.6±4.8%), Group 5 (78.2±3.1%), or Group 8 (79.9±3.1%). The percentage of blastocyst formation relative to the total number of MII oocytes in the control group was 19.6±2.4%. The culture of COC in Group 1 (20 ngmL−1 LIF/10ngmL−1 IGF1/10ngmL−1 FGF2) and Group 2 (20ngmL−1 LIF/10ngmL−1 IGF1/40ngmL−1 FGF2) caused the blastocyst yield to increase to 33.0±3.8 and 31.2±4.3%, respectively (P&amp;lt;0.05), whereas the culture COC in other cytokine-treated groups had no effect. In Groups 3 to 8, the blastocyst rates were 22.9±4.6, 19.2±3.0, 24.2±3.2, 27.8±1.7, 21.6±1.8, and 25.5±9.0%, respectively, and did not differ (except Group 4) compared with those of Group 1 and Group 2. In conclusion, LIF, FGF2, and IGF1 in optimal combinations can maintain competence for parthenogenetic development of bovine COC during their maturation invitro. This research was supported by RFBR (projects No. 18-29-07089) and the Ministry of Science and Higher Education of Russia.

187 Effect of cytokines during invitro maturation of bovine oocytes on the development potential of parthenogenetic embryos

The efficiency of assisted reproductive technologies is critically dependent on the quality of the oocytes used to produce the embryos. The aim of the present research was to study dose-dependent effects of three cytokines: fibroblast growth factor 2 (FGF2), leukemia inhibitory factor (LIF), and insulin-like growth factor 1 (IGF1) individually on IVM in bovine oocytes and their consecutive development to blastocysts after artificial activation. Slaughterhouse-derived cumulus-oocyte complexes (COC) (n=2052 COC) were cultured for 22h in either standard maturation medium [TCM-199 supplemented with 10% fetal calf serum (FCS), 0.2mM sodium pyruvate, 10μgmL−1porcine FSH, and 10μgmL−1 ovine LH; control] or maturation medium supplemented with different concentrations (5-160ngmL−1) of FGF2, LIF, and IGF1. After IVM, matured oocytes were activated by culturing in 5μM ionomycin solution for 5min followed by 4h in 2mM 4-dimethylaminopyridine (DMAP) and 10mgmL−1 cyclohexamide. Activated oocytes were cultured in CR1aa medium until Day 5 and then transferred to the same medium supplemented with 5% FCS and cultured until Day 7. All cultures were performed at 38.5°C and 5% CO2 in humidified air. At Days 2 and 7 after activation, cleavage and blastocyst rates were determined. In addition, obtained blastocysts were fixed with 4% paraformaldehyde, and the total cell number was determined by 4′,6-diamidino-2-phenylindole (DAPI) staining. The data from 4 to 6 replicates (77-140 oocytes per treatment) were analysed by ANOVA. After 22h of culture, the rate of MII oocytes, assessed by the presence of the first polar body, did not differ between the groups and ranged from 74.4 to 90.7%. No statistical differences were found in the cleavage rate between oocytes matured in cytokine-treated groups compared with the control. Cleavage rates for the LIF experimental groups was 63.5 to 77.2%, for the IGF1 experimental groups was 68.1 to 80.7%, and for the FGF experimental groups 63.7 to 77.0%. Optimal concentrations of LIF (5 and 20ngmL−1), and FGF2 (20 and 40ngmL−1) increased (P&amp;lt;0.05) the blastocyst rate from 21.7±1.5 (control for LIF-treated groups) to 32.7±7.1 and 27.1±3.4 and from 19.6±1.8% (control for FGF-treated groups) to 29.8±1.9 and 31.1±2.1%, respectively. Furthermore, the addition of FGF2 in IVM medium (except at 5ngmL−1) led to an increase in the total cell number in embryos that developed to the blastocyst stage, whereas LIF did not have this effect. The maturation of COC in the presence of IGF1 had no effect on the yield of parthenogenetic blastocysts or on the total cell number in blastocysts compared with the control medium. However, the blastocyst rate was lower in groups with IGF1 at 40 to 80ngmL−1 compared with those with IGF1 at 5 to 20ngmL−1 (P&amp;lt;0.05). Thus, both LIF and FGF2 (each individually) (but not IGF1) are able to maintain competence for parthenogenetic development of bovine COC during their maturation invitro, and FGF2 additionally can improve parthenogenetic blastocyst quality. This research was supported by RFBR (Project no. 18-29-07089).

131 Fatty acid binding protein inhibition as a strategy to reduce the lipid content of in vitro-produced bovine embryos

Lipid accumulation decreases cryopreservation survival of in vitro-produced embryos, reducing pregnancy rate after embryo transfer. Fatty acid binding protein 3 (FABP3) plays a role in lipid transport from cumulus cells to the oocyte during maturation. Blocking this transport could reduce lipid content in the oocyte and embryo and increase cryopreservation survival. This preliminary study aimed to test the effect of α-truxillic acid (FABP-I), a chemical molecule that inhibits FABP3/5 action by receptor competition, on lipid content of matured oocytes and blastocysts after culture. Slaughterhouse-derived cumulus-oocyte complexes were matured with 0 (control), 10, 50, 100 and 500nM FABP-I for 22h. In Experiment 1, 346 oocytes in 3 replicates were fixed following maturation and stained with 1μg mL−1 Nile Red to evaluate total lipid content; maturation was assessed by nuclear staining with 10μg mL−1 Hoechst 33342[ACD1]. In Experiment 2, 876 cumulus-oocyte complexes in 5 replicates were matured for 22h under the same concentrations of FABP-I, then fertilized for 18h and cultured for 7 days. Cleavage and blastocyst development were evaluated on Day 2 and 7, respectively. Blastocysts were fixed at Day 7 and stained with Nile Red. Fluorescence intensity was measured in arbitrary units using ImageJ (NIH), and data was analysed using GLM procedure of SAS (SAS Institute Inc., Cary, NC, USA). In Experiment 1, maturation rate did not differ among treatments (70.2±8.7; P=0.7). There were significant effects of treatment, replicate and interaction of treatment by replicate on fluorescence intensity. Compared with control (23.6±0.6), intensity was lowest in oocytes matured with 500nM FABP-I (21.2±0.6; P&amp;lt;0.01) and highest in the 10nM group (26.5±0.6; P&amp;lt;0.01). Staining intensity tended to decrease in the 100nM group (22.1±0.6; P=0.09) and was not different in the 50nM group (24.0±0.7; P=0.6). In Experiment 2, cleavage rate (75.8±2.9; P=0.3) did not differ and blastocyst development tended to be different among treatments (P=0.06). Compared with the control (33.3±4.8), the 500nM group had lower development (17.0±4.8; P&amp;lt;0.03); 10 and 50nM groups had numerically lower (24.7 and 24.0±4.8) and the 100nM group had the highest development rate (37.3±4.8), although either was significant. Treatment tended to affect fluorescence intensity of blastocysts (P=0.07; n=209), and there were significant effects of replicate and interaction between replicate and treatment. Compared with the control (11.7±1.3), fluorescence intensity was lower in the 50nM group (6.8±1.3; P&amp;lt;0.01), whereas 10nM had a tendency for lower intensity (8.3±1.2; P=0.06). Groups 100 and 500nM were not significantly different from controls (9.4±0.9 and 10.7±1.5, respectively). In conclusion, addition of FABP-I up to 500nM did not affect maturation or embryo cleavage but altered blastocyst development. Exposure to 50nM reduced staining intensity in blastocysts without significant decrease in development, whereas 100nM resulted in numerically lower oocyte staining intensity and higher blastocyst development. Future experiments will evaluate cryopreservation survival of embryos treated with FABP-I, and embryo transfer.

61 Expression Profiles and Functional Roles of H3.3 and HIRA in Bovine Early Embryos

Early embryo death is one major reason for poor reproductive efficiency in dairy cows. In particular, ~20 to 50% of high-producing cows are subject to pregnancy loss during the first week of gestation, indicating the importance of embryonic development from fertilization to the blastocyst stage. To highlight this importance, multiple critical molecular and developmental events, including zygote reprogramming, maternal RNA decay, and embryonic genome activation, occur during bovine pre-implantation development. However, the molecular mechanisms of these events have yet to be defined. H3.3 is a histone H3 variant that encoded by 2 genes, namely, H3F3A and H3F3B. It is generally believed that H3.3 is closely related to active transcribed genes. Of interest, H3.3 required for establishing proper chromatin structure during mouse oogenesis. Immediately following fertilization, H3.3 is incorporated to parental chromatins and essential for blastocyst formation in mice. HIRA is a chaperone for H3.3 deposition and indispensable for zygote development. Previously, our results showed that H3.3 is needed for bovine early embryonic development. Herein, experiments were designed to determine the mechanisms of functional requirement of H3.3 in bovine early embryos. Slaughterhouse-derived cumulus–oocyte complexes (COC) were matured in vitro and IVF was performed. To knock down genes of interest, small interfering (si)RNAs were delivered into zygotes via microinjection. The qPCR results showed that H3F3A mRNA level is stable, whereas H3F3B and HIRA mRNA are dynamic during early embryonic development (4 replicates). The mRNA abundance of H3F3B is significantly higher than that of H3F3A (4 replicates; P &lt; 0.05), which is also found in mouse and human. Immunostaining results revealed a stage-specific pattern for the localization of H3.3 in bovine early embryos, and the H3.3 signal was not different between paternal and maternal pronuclei in zygotes, which was different from the pattern in mice. The siRNA-mediated silencing of H3.3 dramatically reduces the expression of CTGF (a putative trophectoderm marker) in bovine blastocysts (3 replicates; P &lt; 0.05). Furthermore, we found that the signal intensity of dimethylation of histone H3 lysine 36 (H3K36me2) and linker histone H1 decreases in H3.3-ablated embryos, which is similar to CHD1 knockdown (3 replicates; P &lt; 0.05). However, no difference was found for the intensity of trimethylation of histone H3 lysine 4, dimethylation of histone H3 lysine 9 (H3K9me2) and splicing factor 3 B1 (SF3B1). We also found that HIRA deletion does not affect bovine early embryonic development. Taken together, the results described herein suggest that H3.3 is required for proper epigenetic modifications and H1 deposition during bovine early embryonic development. This project was supported by National Natural Science Foundation of China grant (No. 31672416) and the Fundamental Research Funds for the Central Universities.

147 THE DEVELOPMENTAL CHARACTERISTICS OF IN VITRO-PRODUCED CATTLE-WISENT (BOS TAURUS-BISON BONASUS) HYBRID EMBRYOS

Interspecies hybrids are important resources for research and agriculture. Therefore, the aim of this study was to evaluate development, quality, and viability of embryos produced in vitro using cattle (Bos taurus) oocytes and European bison (Bison bonasus) epididymal sperm. The epididymes were obtained following a forced slaughter of one bull aged 7 years. The sperm was collected by scraping the inner surface of the epididymes, diluted with the cryopreservation medium, and equilibrated for 4 h at 4°C. Thereafter, sperm aliquots (0.2 mL) were frozen in liquid nitrogen vapor for 5 min and then plunged into liquid nitrogen for storage. Prior to fertilization, frozen semen was thawed in pre-warmed medium for 1 min at 37°C and prepared by the swim-up method. The frozen-thawed ejaculated sperm from the Russian Black Pied bulls was used as a positive control. Slaughterhouse-derived cumulus-oocyte complexes were matured for 24 h in TCM-199 supplemented with 10% FCS, 0.2 mM sodium pyruvate, 10 μg mL−1 porcine FSH, and 10 μg mL−1 ovine LH. Matured oocytes (35–40 oocytes per group) were co-incubated for 18 h with homologous (n = 266 oocytes) or heterologous (n = 292 oocytes) sperm (spermatozoa/mL) in 500 µL of TALP containing 10 μg mL−1 heparin, 20 μM penicillamine, 10 μM hypotaurine, 1 μM epinephrine, and 0.1% minimal essential medium nonessential amino acids. After IVF, the oocytes were cultured in CR1aa medium (Rosenkrans 1994 J. Anim. Sci. 72, 434–437) to the blastocyst stage. All the cultures were performed at 38.5°C and 5% CO2 in humidified air. At Days 2 and 7 after insemination, the cleavage and blastocyst rates were determined. In addition, a part of obtained blastocysts was fixed with 4% paraformaldehyde, and the total cell number and apoptotic cell ratio were determined by 4’,6-diamidino-2-phenylindole and TUNEL staining. The remaining blastocysts were cultured up to Day 10, and the hatching rates were assessed. The data (3–5 replicates) were analysed by ANOVA. The cleavage rates did not differ among both male species (72.4 and 77.1%). Furthermore, no significant effects of interspecies fertilization on the blastocyst rate or total cell number per blastocyst were found (27.4 ± 1.6% and 77.0 ± 5.7 for cattle embryos and 26.2 ± 1.9% and 83.1 ± 8.9 for cattle-wisent hybrid embryos). On the other hand, the significant differences between homologous and heterologous fertilization were detected in the rate of hatched blastocysts (60.3 ± 5.1 v. 38 ± 2.9, P &lt; 0.05) and apoptotic cell ratio 7.3 ± 0.8 v. 11.6 ± 1.04, P &lt; 0.05). Our findings demonstrate that hybrid embryos produced by IVF of bovine oocytes with the epididymal sperm of European bison can be developed up to advanced blastocyst stages. However, the hybrid embryos have a lower quality and viability than cattle embryos. Research was supported by the Program of Presidium of the Russian Academy of Science, project no. IV.13.3.

162 EFFECTS OF PROLACTIN AND DITHIOTHREITOL ON THE QUALITY AND DEVELOPMENTAL CAPACITY OF IN VITRO MATURED BOVINE OOCYTES

In vitro maturation (IVM) and IVF of domestic animal oocytes is widely used for commercial and research purposes. The oocyte quality and capacity for further development acquired during in vitro maturation and reduced during the subsequent aging are the main limitative factors affecting the embryo production (Miao et al. 2009 Hum. Reprod. Update 15, 573–585). Our objective was to evaluate effects of prolactin (PRL) and dithiothreitol (DTT) on apoptosis and the embryo development of bovine oocytes matured in vitro using 2 different systems. A total of 1437 slaughterhouse-derived cumulus-oocyte complexes (COC) were matured for 24 h in TCM-199 supplemented with 10% FCS, 0.2 mM sodium pyruvate, 10 μg mL–1 porcine FSH, and 5 μg mL–1 ovine LH. In system 1, 251 COC from a total of IVM oocytes were transferred to the aging medium (TCM-199 supplemented with 10% FCS) and cultured for 24 h in the absence (control) and the presence of either PRL (20 and 50 ng mL–1) or DTT (2.5, 5, and 10 μM). At the end of culture, oocyte apoptosis was detected using the TUNEL method. In system 2, another part of IVM oocytes (1186 COC) was co-incubated for 18 h with sperm in Fert-TALP medium modified by addition of 10 μg mL–1 heparin, PHE (20 μM penicillamine, 10 μM hypotaurine, 1 μM epinephrine), and 0.1% modified Eagle’s medium (MEM) nonessential amino acids. In this case, PRL and DTT (at the above listed concentrations) were added directly to the fertilization medium. After IVF, oocytes were cultured in CR1aa medium for assessment of the cleavage and blastocyst rates on Days 2 and 8, respectively. The nuclear status of blastocysts was evaluated by the cytogenetic method. The data from 3–7 replicates were analysed by ANOVA. Culture of matured COC in the aging medium (system 1) increased the rate of apoptotic oocytes from 8.1 ± 4.7% (0 h) to 48.6 ± 5.8% (24 h) (P &lt; 0.01). This rate was reduced (P &lt; 0.05) up to 22.5 ± 3.1% and 17.8 ± 5.1% in the presence of PRL (20 and 50 ng mL–1) and up to 15.0 ± 6.9% and 19.5 ± 3.7% in the presence of DTT (2.5 and 5 μM). The direct addition of PRL at a concentration of 20 ng mL–1 to the IVF medium raised the blastocyst rate from 21.6 ± 2.2% to 29.8 ± 2.4% (P &lt; 0.05) but did not affect the cleavage rate (72.1 ± 2.2% v. 74.3 ± 2.1%). By contrast, 50 ng mL–1 PRL did not increase the yield of blastocysts and decreased the cleavage rate (from 74.3 ± 2.1% to 62.9 ± 2.4%, P &lt; 0.05). When added to the IVF medium, DTT raised the blastocyst rate only at a concentration of 2.5 μM (P &lt; 0.05). No effects of PRL and DTT on the number of cells in embryos at the blastocyst stage were found. Our findings indicated that PRL and DTT supplements during in vitro fertilization of bovine oocytes may improve their capacity for the subsequent embryo development. This effect was probably due to the inhibitory influence of PRL and DTT on apoptosis of matured oocytes. The study was supported by the Federal Agency for Scientific Organizations and RFBR (project No. 14–48–03681).

81 EFFECT OF IN VITRO CULTURE SYSTEM MODIFICATION USING CR1aa MEDIUM ON EMBRYO DEVELOPMENT AND PREGNANCY RATE IN CATTLE

The culture of in vitro matured and fertilized oocytes is a critical step of in vitro production of bovine embryos. Generally, oocytes are co-incubated with sperm in TALP medium containing different additions and then zygotes are transferred to a medium with another composition. At the same time the effect of the medium alteration on the development of early embryos is unknown. Continual adjustment of fertilized oocytes to the changing culture environment may result in a reduction of their developmental potential. The aim of the present study was to compare effects of two different culture systems on the embryo development and subsequent pregnancy rate in cattle. Slaughterhouse-derived cumulus–oocyte complexes were matured for 24 h in TCM-199 supplemented with 10% FCS, 0.2 mM sodium pyruvate, 10 μg mL–1 porcine FSH, and 5 μg mL–1 ovine LH. Frozen/thawed sperm from different Russian Black Pied bulls were prepared in Sperm-TALP medium by swim-up procedure. In vitro matured oocytes were co-incubated for 18 h with prepared sperm in the modified Fert-TALP medium containing 10 μg mL–1 heparin, PHE (20 μM penicillamine, 10 μM hypotaurine, 1 μM epinephrine), and 0.1% MEM nonessential amino acids. The embryo culture was carried out using 2 systems. A total of 340 presumptive zygotes were incubated in CR1aa medium (Rosenkrans et al. 1994 J. Anim. Sci. 72, 434–437) up to Day 5 post-insemination (System 1) and a total of 442 presumptive zygotes were incubated for 24 h in a fresh Fert-TALP medium without PHE and heparin and then cleaved embryos were transferred to CR1aa medium and incubated until Day 5 post-insemination (System 2). Thereupon, the embryos were transferred to a fresh CR1aa medium supplemented with 5% FCS and cultured for 3 or 5 days. The embryo development was evaluated at Days 2, 8, and 10 for cleavage and blastocyst formation and hatching rates, respectively. A portion of blastocysts (of Grade 1 according to IETS classification) obtained at Day 8 were immediately transferred to recipients or were frozen in 1.5 M ethylene glycol and stored in liquid nitrogen until transplantation. The embryo development data (from 6–8 replicates) were analysed by ANOVA and the embryo transplantation data were analysed using the chi-squared test. The cleavage rates did not differ among Systems 1 and 2 and were 63.6–65.7%. On the other hand, the significant differences between culture Systems 1 and 2 were detected in rates of blastocysts (21.9 ± 1.4 v. 28.8 ± 2.8; P &lt; 0.05) and hatched blastocysts (7.2 ± 1.2 v. 12.3 ± 1.6; P &lt; 0.05). The pregnancy rate for frozen embryos was also higher (but not significantly) in System 2 than in System 1 [26.3% (9/34) v. 16.7% (2/12)], whereas for fresh embryos the similar values of the pregnancy rate were observed [on average 42.9% (6/14)]. Thus the additional 24-h culture of zygotes in Fert-TALP medium favourably affects bovine embryo development in vitro.

Cysteamine supplementation during in vitro maturation of slaughterhouse- and opu-derived bovine oocytes improves embryonic development without affecting cryotolerance, pregnancy rate, and calf characteristics

Optimization of ovum pick up (OPU) followed by in vitro embryo production (IVP) is strongly driven by the needs of both beef and dairy cattle breeders to enhance genetic improvement. The rapidly growing use of genomic selection in cattle has increased the interest in using OPU-IVP technology to increase the number of embryos and offspring per donor, thus allowing enhanced selection intensity for the next generation. The aim of this study was to optimize embryo production through supplementation of cysteamine during in vitro maturation (IVM) and in vitro culture (IVC) of both slaughterhouse- and OPU-derived oocytes. The effects on embryo production and on embryo cryotolerance, post-transfer embryo survival, and calf characteristics, including gestation length, birth weight, perinatal mortality, and sex ratio were studied. In study 1, immature slaughterhouse-derived cumulus-oocyte complexes (COCs) were matured in IVM medium supplemented with or without 0.1 mM cysteamine, fertilized and cultured for 7 days in 0.5 ml SOFaaBSA. In study 2, cysteamine was present during both IVM (0.1 mM) and IVC (0.01, 0.05, 0.1 mM) from Days 1 to 4. In study 3, OPU-derived COCs were matured in medium supplemented with or without 0.1 mM cysteamine in a 2 × 2 factorial design (OPU week and cysteamine treatment). Embryos were evaluated for stage and grade on Day 7 and, depending on the number of transferable embryos and recipients available, the embryos were transferred either fresh or frozen-thawed at a later date. The presence of cysteamine during IVM significantly increased the embryo production rate with slaughterhouse-derived COCs (24.0% vs. 19.4%). The higher number of embryos at Day 7 was due to an increased number of blastocysts, whereas the distribution of embryos among different quality grades and cryotolerance was not affected. Embryo production rate was negatively affected when cysteamine was present during both the processes of IVM and IVC during Days 1 to 4 of culture (13.2%–19.3% vs. 26.4%). The presence of cysteamine during IVM of OPU-derived COCs also significantly increased the embryo production rate (34.4% vs. 23.4%). The higher number of embryos was again totally due to an increased number of blastocysts, whereas cryotolerance was not affected. The relative increase in embryo production rate was higher with OPU-derived oocytes compared with slaughterhouse-derived COCs (47% vs. 24%). This improvement resulted in a mean of 1.73 transferable embryos per OPU session compared with 1.06 in the absence of cysteamine. The presence of cysteamine did not affect pregnancy rate, gestation length, birth weight, perinatal mortality, and sex of calves born from either fresh or frozen-thawed embryos. This study reported that cysteamine supplementation during IVM greatly improved the efficiency and affectivity of an OPU-IVP program.

193 INSULIN-LIKE GROWTH FACTOR-1 EXERTS A THERMOPROTECTIVE ROLE ON MITOCHONDRIAL FUNCTION OF BOVINE OOCYTES EXPOSED TO HEAT SHOCK

The series of events associated with oocyte maturation are susceptible to disruption by elevated temperature. These events are regulated by a variety of growth factors, such as insulin-like growth factor-1 (IGF-1). Exposure of bovine oocytes to heat shock compromises oocyte competence and triggers apoptosis. It has been shown that cellular stresses often alter mitochondrial function and activate the mitochondrial apoptotic cascade. Therefore, the objective of this study was to determine the effect of heat shock on bovine oocyte mitochondrial activity and the role of IGF-1 in this context. Slaughterhouse derived cumulus–oocyte complexes (COC) were subjected to control (38.5°C for 22 h) and heat shock (41°C for 14 h, followed by 38.5°C for 8 h) treatments in the presence of 0 or 100 ng mL–1 of IGF-1 during in vitro maturation (IVM). After 22 h, IVM COC were mechanically denuded and subjected to MitoTracker Red CMX-Ros assay (Invitrogen M-7512) to localize and quantify active mitochondria. Denuded oocytes were incubated in TCM-199-HEPES containing 10 μg mL–1 of polyvinyl alcohol and 50 nM MitoTracker at 37°C for 15 min. Oocytes were evaluated under fluorescence microscope and digital images were obtained and stored as TIFF files. Mitochondrial activity from each oocyte was quantified using the software Image J 1.43. This experiment was replicated 6 times using 97 to 204 COC/treatment. Data were analyzed by least-squares analysis of variance using the general linear model procedure of SAS. In the absence of IGF-1, heat shock reduced (P &lt; 0.001) mitochondrial activity from 64.31 ± 1.91 to 56.74 ± 1.26 arbitrary units for control and heat shock groups, respectively. Addition of IGF-1 to maturation medium did not affect mitochondrial activity in the control group (66.25 ± 1.56). However, IGF-1 improved (temperature × IGF-1; P &lt; 0.001) mitochondrial activity of bovine oocytes subjected to heat shock (70.32 ± 1.32). In conclusion, heat shock reduced bovine oocyte mitochondrial activity, suggesting activation of mitochondrial apoptotic cascade. Moreover, IGF-1 exerted a thermoprotective role, reducing the mitochondrial damage caused by elevated temperature.

87 VITRIFICATION OF BOVINE OOCYTES TREATED WITH CHOLESTEROL-LOADED METHYL-β-CYCLODEXTRIN

Addition of cholesterol-loaded cyclodextrin (CLC) can increase sperm cryosurvival (Purdy et al. 2000 Cryobiology 48, 36–45). The purpose of this study was to determine if cryosurvival of vitrified oocytes could be improved by incubation with CLC prior to vitrification. Slaughterhouse-derived cumulus oocyte complexes were matured in a chemically defined medium with fatty acid-free BSA and hormones for 21 h followed by partial cumulus removal with 100 U/mL hyaluronidase and gentle pipetting. For an additional hour, oocytes were placed into maturation medium supplemented with 0.5% PVA instead of BSA with or without 2.5 mg/mL CLC. At 22 h after the start of maturation, oocytes were transferred to handling media containing 20% FCS or 0.5% PVA in TCM-199 + HEPES (HTCM-199). Oocytes with approximately 3 layers of cumulus were vitrified in two steps. First, they were exposed to VS1 (10% ethylene glycol (EG), 10% DMSO, 6% PVP, or 20% FCS, in HTCM-199) for 30 s, then exposed to VS2 (20% EG, 20% DMSO, 6% PVP, or 20% FCS, 0.48 M galactose in HTCM-199) for 25 s, loaded into cryoloops in groups of five, and plunged into liquid nitrogen. Rapidly warmed oocytes were moved stepwise through 0.5, 0.25, 0.125, and 0 M galactose in HTCM-199 + 20% FCS, 3 min each. All procedures were conducted at 39°C. Warmed oocytes were placed in maturation medium for an additional hour, fertilized with semen from 3 bulls, 3 replicates each, and cultured according to standard procedures (Zhang et al. 2003 Theriogenology 60, 1657–1663). For each replicate, 30 oocytes were assigned to the following treatments: A: chemically-defined media with PVA for the last hour of maturation, handling and vitrification; B: same as A except CLC treatment, for 1 h before vitrification; C: chemically defined media for maturation, but with 20% FCS for HM, VS1 and VS2. Data were analyzed by ANOVA. CLC treatment resulted in higher cleavage rates and 8- to 16-cell embryo production, but not higher blastocyst (bl) production (Table 1). Non-vitrified oocytes developed better than vitrified ones (means: cleavage, 76%; 8- to 16-cell, 64%; bl D8, 21%; bl D9, 24%). Further studies with vitrification of cholesterol-loaded cyclodextrin-treated oocytes and chemically defined media are warranted. Table 1. Development of vitrified oocytes (LS means ± SE)