Insulin-Like Growth Factor-I Improves Development of 8-Cell Rat Embryos In Vitro and Subsequent Development In Vivo

The present study examined the role for insulin-like growth factor-I (IGF-I) in preimplantation development in rats. The 8-cell stage rat embryos were cultured with 0 (control), 0.02, 0.2, or 2.0 nM human recombinant (hr) IGF-I for 36 h. Morphological development of embryos to the blastocyst stage was stimulated by hrIGF-I at all examined concentrations. Human recombinant IGF-I at ≥ 0.2 nM increased the number of live cells in the inner cell mass (ICM), the embryonic lineage, of resulting blastocysts by increasing total cell number and decreasing the rate of dead cells in the ICM. Levels of protein synthesis by blastocysts cultured with ≥ 0.2 nM hrIGF-I increased to the same levels as that of in vivo grown counterparts. When blastocysts were transferred to a receptive uterus, the rates of implantation and fetal development to day 18 of pregnancy in the 0.2 and 2.0 nM hrIGF-I groups were greater than those of the control group. In conclusion, hrIGF-I at ≥ 0.2 nM may promote development of 8-cell rat embryos to blastocysts that are fully-potent to postimplantational development.