title: Glioma-associated microglia and macrophages/monocytes display distinct electrophysiological properties and do not communicate via gap junctions.
abstract: Both brain-resident microglia and peripheral macrophages/monocytes infiltrate into glioma and promote glioma growth. In the present study we analyzed coupling and membrane currents in glioma-associated microglia and macrophages/monocytes and compared this to control and stab wound-associated microglia. Using the Cx3cr1(GFP/wt)Ccr2(RFP/wt) knock-in mouse line, we distinguished membrane currents of glioma-associated microglia and macrophages/monocytes in acute brain slices prepared 14-16 days after inoculation of GL261 glioma cells. The current profile of microglia showed inward rectifying currents reminiscent of an intermediate activation state when compared to other disease models or cell culture. Macrophages/monocytes showed a higher specific outward conductance and a significantly lower capacitance indicative of a smaller membrane area than microglia. As controls, we also recorded currents from control microglia and stab wound-associated microglia. Since there are reports of microglial coupling in vitro, we injected biocytin into these cells and analyzed for cell coupling after fixing the slices and processed for biocytin labeling with Cy3-conjugated-Streptavidin. Neither control microglia nor glioma-associated microglia and macrophages/monocytes nor stab wound-associated microglia showed any sign of coupling. Moreover, performing qRT-PCR revealed that no connexin43 was detectable on isolated and sorted glioma-associated microglia and macrophages/monocytes, indicating that these cells are not part of a coupled network.
authors.affiliation: Max Delbrueck Center for Molecular Medicine, Robert Roessle Str. 10, 13125 Berlin, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Richter
authors.affiliation: Max Delbrueck Center for Molecular Medicine, Robert Roessle Str. 10, 13125 Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wendt
authors.affiliation: Max Delbrueck Center for Molecular Medicine, Robert Roessle Str. 10, 13125 Berlin, Germany.
authors.forename: Petya B
authors.initials: PB
authors.lastname: Georgieva
authors.affiliation: Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Dolores
authors.initials: D
authors.lastname: Hambardzumyan
authors.affiliation: Max Delbrueck Center for Molecular Medicine, Robert Roessle Str. 10, 13125 Berlin, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Nolte
authors.affiliation: Max Delbrueck Center for Molecular Medicine, Robert Roessle Str. 10, 13125 Berlin, Germany. Electronic address: kettenmann@mdc-berlin.de.
authors.forename: Helmut
authors.initials: H
authors.lastname: Kettenmann
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D018031:Connexin 43 / Q000378:metabolism; D017629:Gap Junctions / Q000502:physiology*; D005910:Glioma / Q000473:pathology*; D008264:Macrophages / Q000502:physiology*; D008564:Membrane Potentials; D051379:Mice; D017628:Microglia / Q000502:physiology*; D009000:Monocytes / Q000502:physiology*; D009368:Neoplasm Transplantation; D018408:Patch-Clamp Techniques
chemical_list: D018031:Connexin 43
keywords: Electrophysiology; Gap junctions; Glioma; Glioma-associated macrophages/monocytes; Glioma-associated microglia