In Vitro culture of bovine early embryos using chemically defined media.

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To establish a reliable bovine embryo culture system without co-culture of somatic cells, bovine one-cell embryos derived from in vitro fertilization were cultured in chemically defined media after removal of cumulus cells, and factors affecting embryonic development were investigated. Modified synthetic oviductal fluid medium containing polyvinyl alcohol instead of BSA (mSOF) was used as a basal medium. Results from the present study are summarized as follows.(1) Supplementation of 20 amino acids contained in basal medium Eagle's (BME) and minimum essential medium (MEM) improved development to the blastocyst stage dramatically. In addition to these 20 amino acids, supplementation of taurine and/or increasing the dose of glycine further improved the embryonic development in vitro.(2) In the presence of amino acids and/or glucose, supplementation of insulin or insulin-like growth factor-I (IGF-I) enhanced early embryonic development with an increase in the cell numbers in blastocysts.(3) Oxygen concentration in the gas atmosphere was one of the most critical factors which affect embryonic development invitro. Under a gas atmosphere of 5% oxygen, embryonic development in mSOF supplemented with amino acids and insulin without somatic cells was superior to that of co-culture with bovine oviductal epitherial cells in TCM-199+FCS.(4) Quality of water for preparing culture media also affected the embryonic development in vitro. The embryonic development in a chemically defined medium prepared with Milli-Q water was superior to those for distillled water and ion-exchanged water.The present study clearly demonstrates that bovine one-cell embryos can be successfully cultured up to the blastocyst stage under a gas atmosphere of 5% oxygen using a chemically defined medium prepared with pure water and supplemented with amino acids and insulin or IGF-I.