Fig. 8

Overview of the experimental results and interpretation. a Schematic overview of the dynamic regulation of microglia polarization: primary untreated microglia (yellow) can be polarized to an M1 phenotype (red) or M2 phenotype (green) in vitro. Prior to exposure to inflammatory mediators, primary microglia in vitro are close to the M2 phenotype regarding characteristic expression patterns. Switching between polarization states using distinct inflammatory mediators such as LPS or IL4 is possible, however much more effective when transforming M2 microglia towards the M1 phenotype (red arrow) than vice versa (green arrow). b Untreated microglia (yellow) are polarized towards an M1 phenotype (red) following exposure to LPS, or to an M2 phenotype (green) in the presence of IL4. Simultaneous exposure to LPS plus IL4 results in a hybrid phenotype (orange) expressing both M1- and M2-characteristic markers. While microglia of all polarization states have similar effects on NSCs (pink) in regard to proliferation and migration, they characteristically differ in their effects on NSCs differentiation potential