Abstract #180

# 180
P. C. Dall’Acqua*1,2, B. C. S. Leao1,3, N. A. S. Rocha-Frigoni1,3, G. B. Nunes1,2, M. Ambrogi1, M. I. A. Silva1,3, L. T. Rodrigues1,3, G. Z. Mingoti1,2, 1Laboratory of Physiology of Reproduction, School of Veterinary Medicine, University of Sao Paulo State (UNESP), Araçatuba, SP, Brazil;, 2School of Agrarian and Veterinarian Sciences, Department of Animal Reproduction, University of Sao Paulo State (UNESP), Jaboticabal, SP, Brazil;, 3School of Veterinary Medicine, UniSalesiano, Catholic University Center Salesiano Auxilium, Araçatuba, SP, Brazil.

The aim of this study was to assess the blockade and the reversal of meiosis block in bovine oocytes treated with a cyclin-dependent kinase inhibitor (butyrolactone-I; BL) combined or not with a selective inhibitor of epidermal growth factor receptor protein (tyrphostin AG 1478; AG) in a prematuration (PM) culture during oocyte transport. Cumulus-oocyte complexes (n = 4107) were transported in PM medium (TCM-199 with bicarbonate and 0.3% BSA) supplemented with one of the following inhibitors: 50 µm BL; 100 µm BL; 1 µm AG; 50 µm BL + 1 µm AG; or 100 µm BL + 1µm AG. Cumulus-oocyte complexes were transported in well-sealed polystyrene tubes (30 oocytes/tube) containing 200 μL of PM medium covered with mineral oil and gassed with 5% O2, 5% CO2, and 90% N2. The tubes were packed in a portable incubator (Thawing Unit MT 35/42, Minitub, Tiefenbach, Germany) at 38.5°C for 22 h. Afterward, treated oocytes were removed from meiotic inhibitors, transferred to in vitro maturation (IVM) medium (TCM-199 with bicarbonate, 0.5 mg/mL of FSH, 100 IU/mL of hCG, and 10% FCS), and cultured in a bench-top incubator (Thermo Fisher Scientific, Waltham, MA, USA) under 38.5°C and 5% CO2 in air for 20, 22, 24, or 26 h. The control groups were IVM for 20, 22, 24, or 26 h in IVM medium in the bench-top incubator at 38.5°C and 5% CO2 in air (Control; C) or in the portable incubator under the same conditions used for the treated groups (Transport Control; TC). For meiosis evaluation, oocytes were stained with 1% Hoescht immediately after follicle removal (0 h), at 6 and 22 h of PM, and after 20, 22, 24, and 26 h of IVM, and were classified as immature (germinal vesicle; GV) or mature (metaphase II; MII); intermediate phases of meiosis (GV breakdown, metaphase I, anaphase I, or telophase I) were not demonstrated in this study. Data were analysed by ANOVA followed by Tukey’s test (P < 0.05) and are presented as mean ± standard error of the mean. The GV rates after 6 h of transport did not differ (P > 0.05) between 0-h oocytes (88.6 ± 2.3%) and the treated groups (70.3 ± 1.9% to 79.3 ± 2.2%); although GV rates of C (49.5 ± 2.4%) and TC (49.5 ± 2.4%) groups differed (P < 0.05) from 0-h oocytes, they did not differ from treated oocytes with the exception of the 1 µm AG group (79.3 ± 2.2%), which differed from TC (P < 0.05). After 22 h of transport, the GV rates of treated oocytes (50.3 ± 5.5 to 70.3 ± 6.6%) did not differ (P > 0.05) from 0-h oocytes (88.6 ± 2.3%) and were higher (P < 0.05) than C (4.6 ± 2.8%) and TC (8.3 ± 4.5%) that had the highest MII rates (68.4 ± 5.3 and 75.5 ± 2.0%, respectively, for C and TC) compared with the other groups (0 to 13.2 ± 10.2%). After meiotic inhibitors removal and IVM, meiosis block was fully reversed and there were no differences (P > 0.05) in the rates of MII between treated oocytes and C and TC groups after 20 (56.6%, averaged), 22 (57.7%, averaged), 24 (66.2%, averaged), or 26 h of IVM (57.0%, averaged). In conclusion, the meiotic inhibitors were effective in maintaining the majority of treated oocytes in GV stage after 22 h of transport and the inhibitory effect was fully reverted after its removal.