Investigation of LIF and EGF signal transduction in preimplantation stage murine embryo development

Introduction：Leukemia inhibitory factor (LIF) is an essential factor for embryonic development and establishment of pregnancy. We have reported changes in gene expressionin murine preimplantation stage blastocyst after LIF-deficiency in zygotic stage by in vitro gene chip analysis. In addition, because of LIF deficiency, elevated epidermal growth factor (EGF) increased the blastocyst rate. The aim of this study is to explore the effects of LIF and EGF on signal transduction pathways at preimplantation stage murine embryos.

Methods：B6CBF1 murine zygotes were collected, various inhibitors or 50 ug LIF or EGF were supplemented in the embryo culture. Three known LIF and EGF signal transduction pathways were chosen for analysis. Phosphorylation of MEK1 (Ser221), MEK1 (A221), STAT3 protein (Ser727), STAT3 protein (Ab727), protein (Thr308) and Akt (Ab308) in preimplantation stage embryos was analyzed via immunohistochemistry.

Results：Our results revealed co-existence of EGF and LIF pathway in preimplantation stage murine embryos. Embryo development rates were decreased by pathway inhibitors at various concentrations. However, for the embryos developed into blastocyst stage, no significant difference in the embryo size was found when compared to the control group. The degenerated embryo caused by the addition of excess inhibitor were positive for apoptotic assay.

CONCLUSION：We found that LIF and EGF may share STAT3 pathway in in vitro cultured embryos. Understanding the mechanism of LIF and EGF in embryonic development facilitate the application of embryonic development in reproductive medicine.