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Updated: Aug 14, 2026
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
Macrophage/microglia activation factor expression is restricted to lesion-associated microglial cells after brain
Anna Lünemann1, Oliver Ullrich, Antje Diestel
1Center for Anatomy, Institute of Cell Biology and Neurobiology, Center for Anatomy, Charité Universitätsmedizin Berlin, Humboldt University, 10098 Berlin, Germany.
Abstract:
After traumatic brain lesion, microglial cells are rapidly activated, migrate toward the sites of injury, and cause secondary damage that accounts for most of the loss of brain function. In the present study, we have characterized a new macrophage/microglia activation factor (MAF). Using the monocytic cell line U937, we were able to demonstrate that MAF is upregulated after TPA-induced differentiation into macrophages. We have generated a specific antibody against MAF. In BV-2 microglial cells, MAF is partially co-localized with IB4, a classical microglial marker. In addition, we have analyzed the in vivo expression patterns of MAF after entorhinal cortex lesion. We were able to show a substantial upregulation of MAF on selected CD11b(+) and IB4(+) macrophages/microglial cells in the deafferented hippocampus and in the perilesional region, while no MAF expression was detectable on the contralateral side. Confocal microscopy revealed a lysosome-like expression pattern in BV-2 cells, as well as in ECL-associated macrophages/microglial cells in vivo. Furthermore, we were able to demonstrate that U937 cells with downregulated MAF converted slower and to a significantly reduced extent to the macrophageal phenotype after TPA treatment. In addition, MAF downregulation in BV-2 microglial cells substantially reduced the phagocytotic uptake of dextran beads. Our data indicate that MAF is expressed in selected macrophages/microglial cells around the lesion and in the degenerating hippocampus after ECL. Furthermore, MAF expression in monocytic cells seems to play a functional role in the differentiation to a phagocytosing phenotype and may be, at least partially, required for phagocytotic activity, specifically in lesioned tissue after brain trauma.
Insights
A newly identified macrophage/microglia activation factor (MAF) is upregulated in brain injury. MAF plays a key role in macrophage differentiation and phagocytosis, crucial for healing after traumatic brain lesions.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglial cells rapidly activate after traumatic brain injury, contributing to secondary damage and brain function loss.
- Understanding the molecular mechanisms of microglial activation is crucial for developing therapeutic strategies.
Purpose of the Study:
- To characterize a novel macrophage/microglia activation factor (MAF).
- To investigate the role of MAF in microglial differentiation and phagocytosis following brain injury.
Main Methods:
- Utilized the monocytic cell line U937 and BV-2 microglial cells.
- Generated a specific antibody against MAF for expression analysis.
- Analyzed MAF expression in vivo after entorhinal cortex (ECL) lesion using confocal microscopy.
- Assessed the functional role of MAF in cell differentiation and phagocytosis via gene downregulation.
Main Results:
- MAF is upregulated in U937 cells differentiated into macrophages and in microglial cells post-ECL.
- MAF expression is localized in macrophages/microglial cells in the injured hippocampus and perilesional regions.
- Downregulation of MAF impaired U937 cell differentiation and reduced phagocytosis in BV-2 cells.
Conclusions:
- MAF is expressed in activated macrophages/microglial cells in response to brain lesions.
- MAF is essential for the differentiation of monocytic cells into a phagocytic phenotype.
- MAF may be critical for phagocytic activity in lesioned brain tissue after trauma.
