There have been many advances in the procedures for culturing the preimplantation embryo in recent years. In this study we analysed potential interactions between several of the major factors thought to determine successful embryo development. The effects of culture media composition (modHTF, KSOM v sIVF), O₂ tension (5% v 20%), embryo culture density (individual v groups of 10), media supplements and embryotrophin (mixed amino acids, the embryotropin Paf, IGF1), and the genetic background of embryos (inbred C57BL6/j (B6) v hybrid B6CBF1) on the development of embryos in vitro were assessed.

Culture from either the zygote or 2-cell stage caused a slower rate of accumulation of cells within embryos than when development occurred within the reproductive tract, and this was more pronounced for zygotes. This retardation occurred irrespective of media composition. Growth was faster in 5% than 20% O₂ and there was a beneficial effect of supplementation with amino acids, particularly at low oxygen tension. There was also a beneficial effect of communal culture, irrespective of media used. Supplementation with Paf enhanced development during individual culture, even when media was supplemented with amino acids and at low O₂. Culture of hybrid zygotes in the improved conditions (KSOM with amino acids, BSA and Paf in 5% O₂) resulted in a similar developmental rate as embryos in vivo. B6 zygotes accumulated fewer cells, with fewer cells in the inner cell mass than hybrids and showed a smaller beneficial response to 5% O₂ than hybrids. 5% O₂ did reduce the proportion of cells with nuclear damage. IGF1 (1 ng/mL) improved the developmental rate in 5% O₂, and supplement of IGF1 into above improved media further elevated the developmental rate of B6 embryo by ~8%. However, they still showed some growth deficiency compared to in vivo.

The results show interactions between a range of culture conditions and media design result in a marked improvements in embryo development. In hybrid strain embryos, the growth rates and allocation of cells to the ICM was equivalent to their development in the reproductive tract, but inbred (B6) starin embryos still displayed some reduced developmental rate.