FGF2, but not EGF, Induces multiciliated ependymal cells to dedifferentiate and adopt radial glial features in vitro

Abstract

Multiciliated ependymal cells form an epithelium lining most of the ventricular cavities of vertebrates brain. Although considered postmitotic and completely differentiated, ependymal cells maintain some phenotypic characteristics of neural stem cells. Thereby, under specific conditions they behave as neural stem cells, developing radial glia characteristics, and undergoing asymmetric division. Our group is searching for factors that promote dedifferentiation of ependymal cells in vitro. We developed a simple method to obtain pure cultures of non-adherent multiciliated ependymal cells from adult rats. These cultures were used to investigate the effect of FGF2 on the differentiation state and the aggregation of ependymal cells. Thus, FGF2 treated ependymal cells lose cilia and hence mobility, and after 7 days they aggregate to form irregular spheres (diameter ≥ 20-30 μm). Such changes were not observed when EFG was used instead of FGF2. To assess the specificity of FGF2 action on cell aggregation, the FGF receptor inhibitor PD166866 and an anti-FGF2 neutralizing antibody were used. In both conditions the aggregative effect of FGF2 was abolished. No cell proliferation was observed during sphere formation, at least in such experimental conditions. Spheres were analyzed by immunocytochemistry using radial glia markers. They were positive for GFAP, vimentin, BLBP and GLAST. These data suggest that FGF2 promotes the identity loss in multiciliated ependymal cells in vitro, which are transformed into cells with radial glia features.