Energy substrate requirements for in-vitro development of hamster 1- and 2-cell embryos to the blastocyst stage

Energy substrate requirements (pyruvate, lactate and amino acids) were determined for in-vitro development of hamster 1- and 2-cell embryos to blastocysts, using a chemically defined, protein free medium (hamster embryo culture medium, HECM). One-cell embryos were very sensitive to energy substrate type and concentration. Pyruvate alone could not support development of 1-cell embryos to greater than 4-cells, whereas lactate as sole energy substrate supported 14% development into morulae/blastocysts. Pyruvate, with lactate and 20 amino acids, inhibited 1-cell embryo development into blastocysts relative to lactate and 20 amino acids. The highest development of 1-cell embryos to blastocysts (up to 27%) occurred with reduced lactate concentration (less than 10 mM) and either 20 amino acids or 0.2 mM glutamine. Hamster 2-cell embryos were much less sensitive to energy substrates, requiring only lactate for development to blastocysts (53%). Lactate with 20 amino acids supported 70-75% of 2-cell embryos to blastocysts. Glutamine as sole energy and nitrogen source supported development to morulae and blastocysts of some 2-cell, but not 1-cell, embryos. Pyruvate did not enhance development of 2-cell embryos. We conclude that (i) altering the types and concentrations of available energy substrates drastically changes the developmental responses of 1-cell hamster embryos in vitro and (ii) energy substrate requirements for hamster embryo development in vitro are markedly different from those of mouse embryos, the standard model for studies on preimplantation development. This is the first report of successful in-vitro culture of hamster 1-cell embryos to the blastocyst stage.