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 of microglia that appear during organotypic hippocampal tissue culture, as well as in the in vitro toxic hypoxia model. Antibodies against lipocortin-1 identified activated and phagocytic cells that were abundant in a slice after the plating of a culture: cells of the intermediate form at the later time-points of culturing, resting ramified microglia beginning from the seventh day of culturing, as well as activated and phagocytic cells that appeared in the slice after experimental toxic hypoxia induced by potassium cyanide treatment. Lipocortin-1-positive microglia cell forms corresponded well to the description of the microglia in vivo, and the morphology of microglia corresponded to the circumstances under which these cells were observed in slice cultures. Electron microscopic studies have demonstrated, for the first time, that microglia in organotypic slice culture preserve morphological features typical of different microglial forms in vivo, as well as specific 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 essential characteristic features and properties, thus providing an important model system for studying the structure and function of these cells.