Improved pronuclear mouse embryo development over an extended pH range in Ham's F-10 medium without protein

Pronuclear mouse embryos were cultured at four different pHs (7.17, 7.27, 7.37, and 7.50) in Ham's F-10 medium (Gibco, Grand Island, NY) alone and in Ham's F-10 medium supplemented with 10% human cord serum (v/v) to assess the effects of pH and serum on preimplantation embryo development. Media used in these experiments was stored both without (old protocol) or with triple gas equilibration (new protocol). Development was assessed by the percent of embryos developing to the 2-cell stage and on to the morula and blastocyst stages. Triple gas equilibration prior to media storage improved development to the morula and blastocyst stages. Development to the 2-cell and morula stages was not adversely affected by the presence of serum, but development to the blastocyst stage was significantly higher in Ham's F-10 medium without serum at all pHs tested. In conditions without serum, percent development at all stages examined was similar over the pH range of 7.17 to 7.37, with a significant decrease in development to the morula and blastocyst stage at pH 7.50. Embryos cultured in the presence of serum demonstrated a greater decrease in the percent development to blastocyst at both the low, 7.17 and 7.27, and high, 7.50, pHs, with an apparent pH optimum at 7.37. In summary, the complex media Ham's F-10 medium supports mouse embryo development without the need for serum. Serum inhibits pronuclear embryo development to the blastocyst stage. Mouse embryo culture in the absence of serum can tolerate a pH as low as 7.17 (8.4% CO2) without any detrimental effects.