Effect of granulocyte–macrophage colony stimulating factor on growth, resistance to freezing and thawing and re-expansion of murine blastocysts

Two-cell murine embryos were cultured for 72 h in the presence or absence of granulocyte-macrophage colony stimulating factor (GM-CSF), frozen for 60 days and, after thawing, cultured for an additional 24 h in the presence or absence of GM-CSF. During the initial 72 h period, GM-CSF did not influence the percentage of embryos reaching the expanded blastocyst stage, but there was a significant increase (P < 0.05) in the number of cells in the embryos grown with GM-CSF. Survival after thawing was not affected by previous exposure to GM-CSF, but re-expansion of the blastocoele was diminished in that group. Exposure to GM-CSF during the post-thaw period greatly enhanced re-expansion of the blastocoele. The presence of human serum albumin in the culture media is thought to have masked the beneficial effect of GM-CSF upon embryos.