94 MEIOSIS INHIBITION OF BOVINE OOCYTES: EFFECTS ON SURVIVAL AFTER VITRIFICATION BY OPEN PULLED-STRAW METHOD
C. Diez A , M. Carbajo C , L. Fernandez C , C.O. Hidalgo B , S. de la Varga C , A. Fernandez C , N. Facal A and E. Gomez AA Genetica y Reproducción, Serida Gijon, Spain. email: mcdiez@serida.org;
B Seleccion y Reproduccion, Serida Gijon, Spain;
C Facultad de Veterinaria, Leon, Spain.
Reproduction, Fertility and Development 16(2) 168-168 https://doi.org/10.1071/RDv16n1Ab94
Submitted: 1 August 2003 Accepted: 1 October 2003 Published: 2 January 2004
Abstract
Mammalian oocytes remain one of the most difficult cell types to successfully cryopreserve. The in vitro-maturation protocols (IVM) have a large impact on the oocyte maturation. Consequently, inhibition of meiosis has been used to improve developmental competence of oocytes without reducing blastocyst rates. Moreover, the meiotic stage influences the ability of oocytes to survive cryopreservation. This work analyzes the effect of the inhibition of meiosis (prematuration) on the freezability of the bovine oocyte. Cumulus-oocyte complexes (COCs) were recovered from slaughterhouse ovaries. Inmature oocytes (I) with compact cumulus and evenly granulated cytoplasm were selected. Prematuration (PM) was performed by incubating COCs for 22 h in TCM199 NaHCO3 and roscovitine 25 μM. IVM was accomplished in TCM199 NaHCO3, 10% FCS, FSH-LH and 17β-estradiol. Oocytes were subjected to 5 treatments prior the vitrification (see table). COCs were partially denuded from cumulus cells and vitrified/warmed using the OPS system (Vajta et al. 1998 Mol. Reprod. Dev. 51, 53–58). Warmed oocytes were fertilized (Day 0) and presumptive zygotes having a normal morphological appearance were cultured in SOFaa + 5% of FCS (Day 3); elements with degenerated appearance were discarded and recorded. Fresh oocytes submitted to IVM (c-M) or prematured and matured (c-PM + M) were fertilized and cultured as controls. Data were analyzed by ANOVA and Duncan’s multiple range test and expressed as LSM ± SE. Developmental data are referred to the zygotes cultured. Only oocytes vitrified after IVM reached the blastocyst stage, but at lower rates than fresh controls. However, no differences were found between treatments at any developmental stage. Oocytes vitrified both as prematured + matured and immature oocytes showed increased proportions (P < 0.01) of degenerated oocytes (37.3 ± 5.9 and 49.9 ± 5.9, respectively), as compared with oocytes matured before vitrification (17.6 ± 5.9). These results show that effects induced by incubation with roscovitine (Lonergan et al. 2003 Mol. Reprod. Dev. 64, 369–378) in combination with cryodamage compromise the oocyte developmental ability. Supported by CICYT, AGL2001-379.
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