320EFFECT OF CYSTEAMINE DURING IN VITRO MATURATION ON FURTHER EMBRYONIC DEVELOPMENT AND POSTTHAW SURVIVAL OF IVP BOVINE EMBRYOS

Abstract

The uptake of cysteamine by immature oocytes may facilitate the synthesis of glutathione (GSH) during in vitro maturation, as reported by Matos et al. (1995 Mol. Reprod. Dev. 42 432–436). GSH plays an important protective role in relation to reactive oxygen species generated by normal oxidative metabolism. This study investigated the effects of the presence of cysteamine during in vitro maturation on subsequent in vitro embryonic development and postthaw in vitro survival. Immature Cumulus-Oocyte-Complexes (COCs) were recovered from ovaries 6 to 8h after slaughter. COCs were matured in vitro for 22 to 24h in TCM199/FCS/LH/FSH supplemented either with or without cysteamine (0.1mM), Subsequently, matured oocytes were fertilized with frozen-thawed Percoll-separated semen and further cultured for seven days in SOFaaBSA. Morulae grade 1 (IETS) and blastocysts grades 1 and 2 (IETS) were frozen on Day 7 in 10% Glycerol using a conventional slow freezing procedure (Wagtendonk-de Leeuw et al. 1995 Cryobiology;; 32 157–167). In vitro survival was measured by rates of blastocyst formation and reexpansion at 24h and hatching/ed blastocysts at 72h in SOFaaBSA supplemented with 5% FCS. Results were analyzed by Chi-square analyses. The presence of cysteamine during in vitro maturation significantly affected the embryo production rate (19.4% and 24.0% for control and cysteamine at Day 7, respectively). The higher number of embryos at Day 7 was totally due to an increased number of blastocysts (Table 1); however, the distribution of embryos among the different quality grades was not affected. Addition of cysteamine did not affect the post thaw survival of the frozen/thawed embryos (85% v. 91% reexpansion and 33% v. 34% hatching/ed for control v. cysteamine, respectively). These results show that the presence of cysteamine during in vitro maturation, does affect further in vitro embryonic development, resulting in a higher embryo production rate. Embryo quality, expressed in morphological grades and postthaw survival rates, were not affected. A field trial will be conducted in order to confirm these results with ovum pick up-derived oocytes. Table 1 Effect of cysteamine during in vitro maturation on subsequent in vitro embryonic development of IVP bovine embryos (number of replicates: 5)