EMBRYO DEVELOPMENT OF EQUINE OOCYTES MATURED IN VITRO IN THE PRESENCE OF CYSTEINE AND FERTILIZED BY ICSI

• C. HERRERA, P. CONDE, M. REVORA, M. SANSINENA, C.J. QUINTANS, M.G. CHAVEZ, M.R. PINTO, M.H. MIRAGAYA, A. AGÜERO AND R.S. PASQUALINI

Rio de Janeiro, Brazil

Simposio; Proceedings of the 6th International Symposium on Equine Embryo Transfer; 2004

Havemeyer Foundation

Oxidative stress, via the reactive oxygen species (ROS), is one of the main processes affecting proper in vitro mammalian embryo development. In most cells, the damaging effects of ROS can be attenuated by means of efficient antioxidant systems that scavenge the active oxygen species. Equine oocytes and embryos carry large amounts of lipid droplets in their cytoplasm. This lipid content not only gives them their characteristic dark cytoplasm appearance, but might also raise their susceptibility to oxidative stress. Glutathione (GSH) is the major non-protein sulphydryl compound in mammalian cells and participates in the protection of the cell from oxidative damage. GSH is synthesised during oocyte development and maturation (Perreault et al. 1988) and accumulates to form a pool which will participate at different stages of post-fertilisation and embryo development. After fertilisation, GSH is involved in sperm decondensation, oocyte activation and in the transformation of the sperm head into the male pronucleus (Perreault et al. 1984; Calvin et al. 1986; Perreault 1990; Yoshida et al. 1992; Yosida et al. 1993). Moreover, it has been demonstrated the addition of cysteamine to in vitro maturation (IVM) medium of bovine (de Matos and Furnus 2000), bubaline (Gasparrini et al. 2003) and ovine (de Matos et al. 2002) oocytes induces GSH de novo synthesis improving further embryo development in vitro. Although recent progress has been achieved on the in vitro culture of equine embryos (Choi et al. 2004), the results obtained with this species are still low. Therefore, the aim of this study was to investigate the effect of cysteamine during IVM of equine oocytes and its effect on in vitro embryo development after fertilisation by Intracytoplasmic Sperm Injection