Granulocyte macrophage colony stimulating factor stimulates in vitro proliferation of astrocytes derived from simian mature brains

In the brain, granulocyte-macrophage colony stimulating factor (GM-CSF) may be released by infiltrated cells of the immune system including T and B lymphocytes and mononuclear phagocytes, but also by nervous system resident cells such as microglia and astrocytes. Astrocyte-secreted GM-CSF may play an important role in enhancing the local inflammatory response to central nervous system (CNS) injury and in recruting microglia and activated macrophages. In this study, we demonstrated that GM-CSF, as TNF alpha and IL 6, stimulates in vitro proliferation of simian astrocytes in primary cultures. Results were confirmed by blocking experiments performed with a specific neutralizing mAb directed against GM-CSF. Furthermore, we demonstrated that GM-CSF mediates its effect on these cells through the alpha subunit of the GM-CSF receptor which is constitutively expressed at the membrane of the cultured simian astrocytes as assessed by immunofluorescence. GM-CSF effects on astrocytes could be involved in astrocytosis, a hallmark of various neurological injuries and in inflammatory processes in an autocrine manner.