Granulocyte-macrophage colony-stimulating factor promotes human blastocyst development in vitro

The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) is synthesized in the female reproductive tract and has been implicated in the growth and development of the preimplantation embryo in rodent and livestock species. To examine the effect of GM-CSF on human embryo development in vitro, surplus frozen 2-4-cell embryos were cultured in media supplemented with 2 ngl mi recombinant human GM-CSF. The addition of cytokine increased the proportion of embryos that developed to the blastocyst stage from 30 to 76%, The developmental competence of these blastocysts, as assessed by hatching and attachment to extracellular matrix-coated culture dishes, was also improved by GM-CSF, The period in culture required for 50% of the total number of blastocysts to form was reduced by 14 h, and blastocysts grown in GM-CSF: were found to contain similar to 35% more cells, due primarily to an increase in the size of the inner cell mass. The beneficial effect of GM-CSF was exerted in each of two sequential media systems (IVF-50/S2 and G1.2/G2.2) and was independent of the formulation of recombinant cytokine that was used. These data indicate that GM-CSF may have a physiological role in promoting the development of the: human embryo as it traverses the reproductive tract in vivo, and suggest that addition of this cytokine to embryo culture media may improve the yield of implantation-competent blastocysts in human in-vitro fertilization programmes.