Characterization of the dynamic nature of microglial cells.

Dynamic properties of ramified microglia were investigated in tissue cultures of rat brain cells. Microglia were identified in viable cultures based on previously determined aspects of their morphology and location, and this identification was confirmed through immunohistochemical staining for type-three complement receptors. When living microglial cells were monitored using time-lapse video recording, an extremely dynamic nature was revealed. These cells exhibited morphological alteration, surface and cytoplasmic activity, and migration. All of these properties were both constant and rapid, with individual cells being capable of assuming a completely different overall morphology within a period as short as 5-10 min. These dynamic properties were consistently observed in microglia and appeared specific to this cell type. Thus, ramified microglia appear to possess a unique and highly dynamic nature, and this feature is proposed as a potential marker for these cells. Additionally, the significance of microglial cellular dynamics in the functional role of this cell population in vivo is considered.