225 TERATOMA FORMATION BY BOVINE EMBRYOS

Abstract

Teratoma formation is commonly used as a model for examining the in vivo differentiation potential of embryonic stem cells. We wanted to investigate the teratoma-forming ability of bovine ES cells; however, there are no reports of teratoma-forming ability of bovine pluripotent cells including pre-implantation embryos. In vivo-produced bovine embryos at stages earlier than Day 14 failed to develop teratomas when transplanted into one of the kidneys of immuno-deficient mice (Anderson et al. 1996 Anim. Reprod. Sci. 45, 231–240), and this prompted questions about the ability of bovine embryos to form teratomas. Bovine oocytes were cultured for 20 to 22 h after aspiration at 39°C (5% CO₂/95% air) in TCM-199-bicarbonate medium supplemented with GlutaMax6^" (Invitrogen Australia Pty Ltd., Mount Waverley, Victoria, Australia), penicillin/streptomycin, β-mercaptoethanol, 17β-estradiol, fetal calf serum, LH, follicle stimulating hormone, basic fibroblast growth factor, epidermal growth factor, glycine, and l-cysteine. Oocytes were fertilized with IVF media (Cook Australia, Brisbane, Queensland, Australia) and kept for 7 days at 39°C in 5% CO₂/95% air to generate blastocysts. The zona pellucida of Day 7 blastocysts was enzymatically removed, and one or two zona-free embryos were injected into each testis of 5-week-old immunodeficient (SCID) mice (CB-17/ICR-Prkdc^scid strain; Walter and Eliza Hall Institute, Melbourne, Australia). Eight weeks post-injection, teratomas partially expelled from testes were identified. Histological analysis has confirmed the derivatives of all 3 germ layers in teratomas. In conclusion, we report that Day 7 in vitro-produced embryos can form teratomas when injected into testes of SCID mice.