A subpopulation of bone marrow‐derived macrophage‐like cells shares a unique ion channel pattern with microglia

Abstract

Rat microglia share a number of antigenic, functional, and morphological similarities with macrophages from other tissues, but are characterized by a distinctly different pattern of ion channels in the cellular membrane (Kettenmann et al., J Neurosci Res 26:278-287, 1990). Macrophages typically express outward and inward K+ currents. In contrast, microglia lack outward currents and only show inwardly rectifying K+ currents, regardless of the isolation or cultivation method employed for microglia. In this study we demonstrate that a subpopulation of bone marrow-derived macrophage-like cells possesses inward rectifier K+ currents, but no outward currents and thus with regard to the electrophysiological characteristics closely resembles microglia. A second population of bone marrow-derived macrophage-like cells shows the usual channel pattern described for other body macrophages. Our results strengthen the hypothesis that in the bone marrow distinct pools of precursor cells exist, possibly reflecting an early differential lineage determination for body and brain macrophages, i.e., microglia.

Characterization of the Microglial Response to Cerebral Ischemia in the Stroke-Prone Spontaneously Hypertensive Rat

“…High extracellular potassium levels, as found in ischemic tissue, potentiate glutamate release from microglia that are particularly sensitive to changes in potassium levels because of their lack of a substantial potassium outward current. 26 A recent study has suggested that microglia are capable of contributing to the development of the ischemic infarct at time points similar to those in the present study. 27 However, the conclusion was based on the expression of interleukin-1␤ and Bax in microglia within the zone of injury rather than from the results of an intervention strategy.…”

Prostaglandin E2 and 4‐Aminopyridine Prevent the Lipopolysaccharide‐Induced Outwardly Rectifying Potassium Current and Interleukin‐1β Production in Cultured Rat Microglia

“…Following LPS stimulation, microglia are transformed into a reactive state that is characterized electrophysiologically by the expression of the K+ OR (Niirenberg et al, 1992), which is lacking in most nonstimulated microglia (Kettenmann et al, 1990;Banati et al, 1991). The presence of this K+ OR is a robust indicator of the functional state of the cell (Fischer et al, 1995).…”

The origin and differentiation of microglial cells during development

“…Giulian et al (1995) found that mononuclear phagocytes isolated from the brain of newborn rats gave rise to cells with particular morphological features which did not appear in cultured mononuclear phagocytes from non-nervous sources; these authors concluded that microglial precursors are a unique class of cell di erent from precursors of other types of mononuclear phagocytes. In this connection, it was found that a subpopulation of bone marrow-derived cells showed the same ion channel pattern as microglial cells, suggesting that the bone marrow contains precursors that are committed to produce microglia and that they are di erent from the precursors which produce macrophages for other body regions (Banati et al, 1991).…”