EFFECTS OF GM-CSF AND ORDINARY SUPPLEMENTS ON THE RAMIFICATION OF MICROGLIA IN CULTURE - A MORPHOMETRICAL STUDY

Microglia transform from ameboid to ramified cells during development and display an ameboid appearance again under certain pathological con ditions. Some cytokines produced by astrocytes may be responsible for the microglial transformation. In the present study, we compared the e ffects of cytokines, granulocyte/macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), and interleuki n-3 (IL-3) on the morphology of rat cultured microglia. For quantitati ve evaluation, we employed ''transformation index'' as calculated by ( perimeter of cell)(2)/4 pi (cell area). GM-CSF facilitated the ramific ation of cultured rat microglia, which was effectively induced in a se rum-free medium. However, M-CSF and IL-3 did not induce the ramificati on. A certain serum adhesion protein (possibly vitronectin) as well as other high molecular weight substances in fetal calf serum inhibited the GM-CSF-induced microglial ramification. Among ordinary supplements for a chemically defined medium, progesterone, insulin, and a high co ncentration of glucose suppressed the ramification. These findings sug gest that GM-CSF may be involved in microglial ramification and that m any kinds of supplements that are added to culture media profoundly af fect the morphology of microglial cells. (C) 1996 Wiley-Liss, Inc.