Genome transfer technique for bovine embryo production using the metaphase plate and polar body

Despite many studies in humans and mice using genome transfer (GT), there are few reports using this technique in oocytes of wild or domestic animals. Therefore, we aimed to establish a GT technique in bovine oocytes using the metaphase plate (MP) and polar body (PB) as the sources of genetic material. In the first experiment, GT was established using MP (GT-MP), and a sperm concentration of 1 × 106 or 0.5 × 106 spermatozoa/ml gave similar fertilization rates. The cleavage rate (50%) and blastocyst rate (13.6%) in the GT-MP group was lower than that of the in vitro production control group (80.2% and 32.6%, respectively). The second experiment evaluated the same parameters using PB instead of MP; the GT-PB group had lower fertilization (82.3% vs. 96.2%) and blastocyst (7.7% vs. 36.8%) rates than the control group. No differences in the amount of mitochondrial DNA (mtDNA) were observed between groups. Finally, GT-MP was performed using vitrified oocytes (GT-MPV) as a source of genetic material. The cleavage rate of the GT-MPV group (68.4%) was similar to that of the vitrified oocytes (VIT) control group (70.0%) and to that of the control IVP group (81.25%, P < 0.05). The blastocyst rate of GT-MPV (15.7) did not differ neither from the VIT control group (5.0%) nor from the IVP control group (35.7%). The results suggested that the structures reconstructed by the GT-MPV and GT-PB technique develop in embryos even if vitrified oocytes are used.

Maturation system affects lipid accumulation in bovine oocytes

This study evaluated the effects of three maturation systems, namely invitro (MatV) and invivo (MatS) systems, as well as intrafollicular transfer of immature oocytes (IFIOT; MatT), on the accumulation of lipid droplets in bovine oocytes. Lipids were evaluated using confocal microscopy and transmission electron microscopy. The expression of genes related to lipid metabolism, namely acyl-CoA synthetase short chain family member 2 (ACSS2), ELOVL fatty acid elongase 1 (ELOVL1) and fatty acid binding protein 3 (FABP3), was quantified by quantitative polymerase chain reaction. The mean (±s.d.) area occupied by lipids in immature oocytes (13±2%) was similar to those matured invivo (MatS, 16±2%; MatT, 12±2%). However, there was a significant increase in lipids in oocytes in the MatV group (24±2%) compared with all other groups (P<0.001). In the ultrastructural evaluations, MatV oocytes also showed the highest lipid content. The expression of ELOVL1 and FABP3 was similar in the MatS and IFIOT groups. However, transcript levels of ACSS2 were lower in IFIOT than MatV oocytes. These results indicate, for the first time, that oocytes matured by IFIOT are similar to those matured invivo with regard to lipid accumulation, which indicates better quality than those matured invitro.

35 Ethanolic extracts of Cerrado plants in cryotolerance of invitro-produced bovine embryos

Invitro embryo culture induces excessive production of reactive oxygen species (ROS) that impair the quality of produced blastocysts, making them less cryotolerant. Supplementation of culture media with antioxidants would be an alternative to minimise these effects. The present study evaluated the effect of ethanolic extracts obtained from Brazilian Cerrado plants on the cryotolerance of invitro-produced embryos. Bovine ovaries from a slaughterhouse were used to obtain grade I and II oocytes, which were submitted to maturation, fertilization (Day 0), and invitro culture. After fertilization, zygotes were distributed into five groups: one fresh control group (GCont), cultured in high O2 tension (~21%), and four groups cryopreserved at Day 7: a control group subject to high O2 tension without extract supplementation (GDT); a group (G5%) cultured in low O2 tension (5%) without extract supplementation, and two groups cultured under high O2 tension, one supplemented with 0.01mgmL−1 of the ethanolic cagaita extract (Eugenia dysenterica; GCag) and another with 0.01mgmL−1 of murici extract (Byrsonima crassifolia; GMur). Only the expanded blastocysts (EB) of each group were submitted to the direct-transfer cryopreservation system, with slow freezing with ethylene glycol (Sanches et al. 2016 Theriogenology 85, 1147-1151). A total of 163 thawed embryos were evaluated 12, 24, and 36h post-thawing for re-expansion, hatching, and embryonic degeneration rate. In addition, after 12h of post-thaw culture, only the EB embryos were subjected to ROS measurement, quantified in confocal microscopy using 2′,7′-dichlorodihydrofluorescein diacetate, and the rate of apoptosis was obtained by the terminal deoxynucleotidyl transferase dUTP nick end labelling method. Data were analysed by analysis of variance, and the means were compared by TUKEY. A total of 133 EB were used (GCont: 20; GDT: 22; GCag: 35; GMur: 36; G5%: 20). Results are expressed as means±standard deviation. No differences were observed on re-expansion among treatments and time of culture. However, 24h post-thaw, hatching and degeneration rates differed between groups. The group GCont had a higher (P&lt;0.05) hatching rate (47.5±10.3) than the GDT (14.4±6.7) and G5% (10.5±5.8) groups but was similar (P&gt;0.05) to groups supplemented with extracts GCag (22.2±17.1) and GMur (17.5±17.5). Degeneration rate was higher (P&lt;0.05) at 12h for the direct-transfer group (30.2±11.3) and similar among the others (GCont: 0; GCag: 16.8±12; GMur: 10.8±10.8; G5%: 11±11). Nevertheless, GCag had lower embryonic degeneration rates (20±16.7) than the others cryopreserved groups 24h after thawing (GDT: 37.7±5.5; GMur: 38.9±8.2; G5%: 41.3±14.4). Although ROS levels were similar among all groups (P&gt;0.05), apoptosis rate was higher (P&lt;0.05) in the GDT group (23.4±1.9) than in the GCont groups (10.6±1.3): GCag (10.8±1.1), GMur (10.1±1.1), and G5% (7.8±1.2). Therefore, supplementation of ethanolic extracts (0.01mgmL−1) of cagaita and murici improved the embryo quality by reducing the degeneration and apoptosis rates of cryopreserved embryos when compared with the group without supplementation (GDT). Such extracts may be an alternative to increase the cryotolerance of invitro-produced bovine embryos.

200 Maturation method affects lipid accumulation in bovine oocytes

Invitro maturation is a key step in invitro embryo production, since its success will depend on the availability of good quality oocytes. Previous studies have shown that it is during this stage that the greatest accumulation of lipid droplets occurs, which is reflected in the amount of lipid present in embryos produced invitro. However, this is not observed when maturation is performed invivo. Therefore, we hypothesised that lipid accumulation would be avoided if oocyte maturation were carried out in ovarian follicles following intrafollicular transfer of immature oocytes (IFIOT). We compared lipid accumulation in oocytes matured invitro, invivo, and by IFIOT. A total of 90 Nellore heifers were distributed in 3 experimental groups: donors of immature oocytes (D-IMA), ovulators of IFIOT oocytes (D-OV), and superstimulated donors of invivo-matured oocytes (D-FSH). All animals rotated through all groups during the experiment. To obtain immature oocytes, the D-IMA were submitted to ovum pickup (OPU), in which aspiration medium was supplemented with 500μM 3-isobutyl-1-methylxanthine (IBMX), and, after selection, part of the oocytes were cultured invitro for 22h (MatF) and part were used for IFIOT (MatT). To perform MatT, the D-OV had their ovulation synchronized by a progesterone and benzoate oestradiol protocol, in which 30h after the implant removal, the IFIOT was performed on the dominant follicle. The D-FSH oocytes were stimulated with 80mg of FSH (Folltropin; Vetoquinol) over 4 days, every 12h, in decreasing doses. At the same time that the immature oocytes were placed in MatF and IFIOT, ovulation was induced with the gonadotrophin releasing hormone (GnRH) analogue (50µg of lecirelin) in D-OV and D-FSH groups. After 22h, matured oocytes were either removed from culture (MatF) or recovered from follicles by OPU (MatT and MatS). From the recovered oocytes of all groups, only those with a polar body were used for lipid droplet evaluation. To quantify lipid accumulation, denuded oocytes were fixed and stained with boron-dipyrromethene (Bodipy) 493/503 (20 µgmL−1) and evaluated by confocal microscopy. Captured images were evaluated in the ImageJ program (National Institutes of Health), and lipid content was determined by calculating the ratio of the area of the lipid droplets to total oocyte area. Data were analysed by ANOVA with statistical significance set at P&lt;0.05. A total of 95 oocytes were evaluated: 25 immature (CT), 24 invitro (MatF), 30 invivo (MatS), and 16 invivo (MatT). The mean area containing lipid droplets in immature oocytes (14%±0.9) was similar (P&gt;0.05) to that observed in both invivo maturation systems (MatS=17.26%±0.8 and MatT=14.11%±0.9). However, in the MatF oocytes, lipid content (24.34%±1) increased during maturation and was higher than in the other groups (P&lt;0.05). We showed for the first time that oocytes matured by IFIOT are similar to those invivo matured with regard to lipid content, which may imply their superior quality over those matured invitro. This new maturation method opens new possibilities for biotechnologies that need to use mature oocytes, such invitro embryo production, oocyte and embryo cryopreservation, cloning, and transgenesis. This study was supported by FAP-DF and Capes.

101 Effects of Active Immunization Against GnRH in Oocyte Donors with Cystic Ovarian Disease

Cows intensively used as oocyte donors for in vitro embryo production (IVEP) are usually kept nonpregnant for prolonged intervals, exposed to successive hormonal treatments, and frequently become overweight. These are all risk factors for the development of endocrine unbalance and, consequently, cystic ovarian disease (COD). The aim of this study was to evaluate the effect of active immunization against gonadotropin-releasing hormone (GnRH) on (1) ovarian follicular population, and (2) development potential of oocytes used for IVEP. Nelore (Bos indicus) cows (n = 14), previously diagnosed with chronic COD (Faria et al. 2017 Anim. Reprod., in press), weighing 620.0 ± 12.8 kg and with body condition score of 4.1 ± 0.2, were assigned to control (n = 6) or treatment (n = 8) group. Cows in the treatment group received 2 SC injections of 1.0 mL of anti-GnRH vaccine (Bopriva, Zoetis, Brazil), 28 days apart (weeks 0 and 4), whereas cows in the control group received placebo on the same schedule. Transrectal ultrasonography was performed weekly from week 0 to evaluate the number and distribution of follicles among size classes, endometrial thickness, and clinical presence of mucometra. Immunization was considered effective (E-IM) when no follicles ≥5.0 mm were observed on the ovaries during a given examination. Cows having E-IM were then used as oocyte donors for IVEP. Cumulus-oocyte complexes (COC) were collected in 5 consecutive ovum pick-up weekly sessions. As a control for IVEP, oocytes from a slaughterhouse were used, with similar procedures performed on the same days and using the same semen batch. The MIXED procedure of SAS (SAS Institute Inc., Cary, NC, USA) with repeated-measures statement was used to evaluate the effects of treatment, time, and interactions on ovarian endpoints; and the GLM procedure was used to analyse embryo production data. Results are shown as mean ± SEM. There were time and time × treatment effects on ovarian parameters. Treated cows had a decrease (P < 0.05) in the average diameter of the largest follicle and in the number of follicles ≥8 mm, and an increase (P < 0.05) in follicular population after week 6. Nonetheless, individual response to treatment was variable: only 50% of the cows (4 of 8) were E-IM at week 8, whereas 25% (2 of 8) still had COD (largest follicle ≥18.0 mm) at this timepoint. Overall, a negative correlation was detected between follicular population and the diameter of the largest follicle (r = –0.60, P < 0.0001) or the number of follicles ≥8 mm (r = –0.47, P < 0.0001). There was no effect (P > 0.05) of treatment on endometrial thickness or mucometra score. Cows with E-IM produced 22.2 ± 3.6 total and 12.9 ± 2.3 viable COC. Cleavage rate did not differ between E-IM and control (slaughterhouse) oocytes (70.8 ± 7.0 v. 75.1 ± 3.0%, respectively; P > 0.05); however, blastocyst rate was greater in the E-IM group compared with controls (39.7 ± 5.5 v. 20.5 ± 4.7%, respectively; P < 0.02). In summary, our results suggest that active immunization against GnRH leads to variable results in the distribution of the follicular population in cows with COD, but it does not negatively affect IVEP efficiency. This research was supported by Zoetis, CNPq, and CAPES.

Buffalo (Bubalus bubalis) pre-antral follicle population and ultrastructural characterization of antral follicle oocyte

The main objectives of the present study were to determine the ultrastructural modifications occurring in the oocyte during late folliculogenesis and to estimate pre-antral follicle population in buffalo. Half the collected ovaries were fixed and prepared for optic microscopy; the antral follicles from the other ovaries were measured and individually punctured. The cumulus-oocyte complexes (COCs) were processed for transmission electron microscopy. The number of pre-antral follicles in buffalo ovaries was estimated at 19 819 structures. Cumulus-oocyte complexes derived from 1-mm antral follicle had an eccentrical nucleus and compact corona radiata, ooplasm vilosities were fully embedded in zona pellucida (ZP) and a well-defined junction could be observed. Mitochondria were predominantly round and well distributed in ooplasm, as were small lipid vacuoles. In COCs derived from 2-mm antral follicles, the initial formation of perivitelline space was observed. The nucleus was peripherally located and the number of pleomorphic mitochondria increased. Cortical granules were clustered at oocyte periphery and lipid vacuoles increased in number and size. In COCs derived from 6-mm antral follicles, the organelles were located mainly in the perinuclear region. Golgi complexes and smooth endoplasmic reticulum (SER) were more developed. Mitochondria migrated to the cortical region and lipid vacuoles migrated to the medullar region. In COCs derived from 10-mm antral follicles, the lipid vacuoles coalesced and occupied the medullar region of the oocyte, together with a well-developed SER. Mitochondria were pleomorphic and located at the oocyte periphery. In conclusion, the morphological differences described in this paper could be responsible for some functional differences observed in in vitro embryo production and follicular dynamics for buffalo, when compared with cattle.