Microglia in organotypic hippocampal slice culture and effects of hypoxia:Ultrastructure and lipocortin-1 immunoreactivity

Lipocortin-1 immunocytochemistry was used to study the various cell forms o f microglia that appear during organotypic hippocampal tissue culture, as w ell as in the in vitro toxic hypoxia model. Antibodies against lipocortin-l identified activated and phagocytic cells that were abundant in a slice af ter the plating of a culture: cells of the intermediate form at the later t ime points of culturing, resting ramified microglia beginning from the seve nth day of culturing, as well as activated and phagocytic cells that appear ed in the slice after experimental toxic hypoxia induced by potassium cyani de treatment. Lipocortin-l-positive microglia cell forms corresponded well to the description of the microglia in vivo, and the morphology of microgli a corresponded to the circumstances under which these cells were observed i n slice cultures. Electron microscopic studies have demonstrated, for the f irst time, that microglia in organotypic slice culture preserve morphologic al features typical of different microglial forms in vivo, as well as speci fic contacts and interactions with the other neural tissue elements. After experimental toxic hypoxia, rapid changes in microglial ultrastructure and localization were observed, reminiscent of in vivo models of ischaemia. In conclusion, observations of microglial morphology and behaviour allow us to suggest that microglia in the organotypic culture preserve their essent ial characteristic features and properties, thus providing an important mod el system for studying the structure and function of these cells. (C) 2000 IBRO. Published by Elsevier Science Ltd.