02982naa a2200157 a 450000100080000000500110000800800410001910000110006024500780007126000090014952024660015865300080262465300240263265300180265677301500267410811642011-10-10       2011    bl uuuu     u00u1 u    #d1 aEpagri  aIn vitro maturation of oocytes vitrified immature in diferent conditions.  c2011  aVitrification of immature oocytes is an important tool for use in both the IVF and cloning, though the efficiency of this technique is still low, limiting its application in commercial scale. For application in nuclear transfer, besides of survival of oocytes, vitrification of a large number of structures is required. The vitrified oocytes undergo various morphological and molecular changes during cooling and warming, which may potentially require another maturation conditions than those for non-cryopreserved oocytes. Thus, this study aimed to compare survival rates after in vitro maturation and embryo development of vitrified oocytes and matured under different conditions. Bovine oocytes were obtained from bovine ovaries and vitrified in groups of 15 COCs, loaded in a 5-??L vitrification solution microdrop in beveled-cut straws (Forell et al. Rep. Fert. Dev, 2009, 21 (1) 115). After warming all recovered COCs were submitted to IVM for 24 h at 38.8??C with 5% CO2 in air. Groups of 40 COCs allocated in 400 uL of medium, were subjected to three treatments: 1) ESS M199 +10% +0.5 ug/mL FSH +5 ug/mL LH (standard laboratory system) 2) M199 +10 % ESS + FSH + LH +10 ng/mL EGF, or 3) M199 +10% FCS +10 ng/mL EGF. After IVM, cumulus cells were mechanically removed and the surviving oocytes were parthenogenetically activated (5 min in ionomycin, and 4 h in 6DMAP) and in vitro cultured in SOFaaci with atmosphere of 5% CO2 +5% O2 in N2, for 7 days. Oocytes non-vitrified (control) were also subjected to the same treatments. The results were analyzed by chi-square test with significance level of 5%. The survival rate after the denudation did not differ between experimental groups, 44% (266/315), 49% (157/321) and 52% (165/320) respectively for groups 1, 2 and 3. There was no difference in cleavage rates of groups 1 - 36% (48/133), 2 - 45% (59/132) and 3 - 39% (65/165). The blastocyst rates were 3.8%, 3.8% and 9.7% respectively for groups 1 (n = 133), 2 (n = 132) and 3 (n = 165) and the rates of group 3 was higher (p &lt0.05) than others. In fresh control groups was not statistically significant difference between the experimental groups in the cleavage rate (83%, 84% and 76%) or blastocyst rate (43%, 42% and 48%) for groups 1 (n = 121 ), 2 (n = 125) and 3 (n = 121) respectively. Thus, among the tested systems, the maturation medium composed of FCS and EGF improves blastocyst rates for vitrified immature oocytes. Funded by PNPD/CAPES.  aEGF  aIn vitro maturation  aVitrification  tIn: REUNI??O ANUAL DA SOCIEDADE BRASILEIRA DE TECNOLOGIA DE EMBRI??ES, 25., 2011, Cumbuco, CE. [Abstracts...]. Porto Alegre: UFRGS, 2011. p. 463.