Granulocyte macrophage-colony stimulating factor activates microglia in rat cortex organotypic brain slices.

Cytokines play an important role in the regulation of proliferation and migration in the central nervous system. The aim of this study was to determine if granulocyte macrophage-colony stimulating factor (GM-CSF) activates cells in the cortex of organotypic brain slice cultures. Our data show that murine GM-CSF markedly stimulated the proliferation and migration of small round microglia from a cortex slice. These round cells were strongly positive for integrin CD11b (OX-42), isolectin B4-lectin-binding, the monocytic marker ED1 and partly expressed major histocompatibility complex (MHC) class II antigen (OX-6). Only some differentiated microglia were visible which expressed the integrin CD11c and MHCII. GM-CSF enhanced the proliferation as analyzed by bromodeoxyuridine incorporation. The number of migrated cells decreased during culturing and enhanced terminal dUTP nick-end labelling positive nuclei were found. Taken together, our data conclude that GM-CSF is an important cytokine, which regulates the proliferation and migration of cortical microglia.