CSF-1 AND MOUSE PREIMPLANTATION DEVELOPMENT IN-VITRO

The effects of macrophage colony stimulating factor on the development of the zygote to the blastocyst stage of an outbred strain of mouse h ave been studied in KSOM, an improved medium that supports a high rate of in vitro development. Macrophage colony stimulating factor acceler ates the formation of the blastocyst cavity by day 4 (96 hours post-hC G). It also increases overall embryonic cell number through a differen tial increase in the number of trophoblast cells, with no significant effect on the number of inner cell mass cells. By day 5 of culture (12 0 hours post-hCG), colony stimulating factor-treated embryos have abou t 20 more trophoblast cells than control embryos, an increase of about 30 percent of the total number of cells in a control blastocyst. The maximum response of embryos was obtained at a concentration around 540 U ml(-1) colony stimulating factor (drop 918 Stanley units ml(-1)), a nd the cytokine can produce the same effects even if it is present in the medium for only part of the culture period. This in vitro stimulat ion of preimplantation development with macrophage colony stimulating factor is compatible with continued normal fetal development in vivo.