Interferon-gamma induces differentiation of ectoplacental cone cells to phenotypically distinct trophoblasts

Maturation of the murine ectoplacental cone results in the development of the placental tissue which essentially consists of two trophoblastic zones, the spongiotrophoblast and labyrinthine trophoblast. In this study we attempted to investigate the action of cytokines on ectoplacental cone cell differentiation to mature trophoblast cells. After determining the cellular composition of the ectoplacental cone cell suspensions based on the expression of cytokeratin, vimentin, Mac-1, class I and class II MHC antigens, the cells were exposed to the differentiation-inducing cytokines IL-3, GM-CSF, CSF-1 and IFN-gamma. From the four factors employed, only IFN-gamma increased the levels of cytokeratin-positive cells without inducing Mac-1 expression. IL-3 increased the percentages of cytokeratin as well as Mac-1- and vimentin-positive cells whereas GM-CSF and CSF-1 preferentially promoted an increase of the Mac-1 and vimentin markers. For further analysis, ectoplacental cone cells were negatively selected for Mac-1, class I and class II antigens to exclude non-trophoblastic contaminants and thereafter treated with the same cytokines. We show here that only IFN-gamma leads the sorted ectoplacental cone cells to a pure trophoblastic population composed of 100% cytokeratin-positive cells. The specificity of IFN-gamma on this differentiation pathway is strengthened by the fact that murine maternal serum on the day of EC formation contains high levels of this cytokine, suggesting that its natural presence supports - at least phenotypically - the in vivo differentiation of EC cells to trophoblasts.