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Updated: Oct 1, 2026
Assessing Retinal Microglial Phagocytic Function In Vivo Using a Flow Cytometry-based Assay
Published on: October 18, 2016
Accelerated phagocytosis of amyloid-beta by mouse and human microglia overexpressing the macrophage
Olivera M Mitrasinovic1, Greer M Murphy
1Neuroscience Research Laboratories, Department of Psychiatry & Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305-5485, USA.
Abstract:
Microglia surrounding A beta plaques in Alzheimer's disease and in the APPV717F transgenic mouse model of Alzheimer's disease have enhanced immunoreactivity for the macrophage colony-stimulating factor receptor (M-CSFR), encoded by the proto-oncogene c-fms. Increased expression of M-CSFR on cultured microglia results in proliferation and release of pro-inflammatory cytokines and expression of inducible nitric-oxide synthase. We transfected mouse BV-2 and human SV-A3 microglia to overexpress M-CSFR and examined microglial phagocytosis of fluorescein-conjugated A beta. Flow cytometry and laser confocal microscopy showed accelerated phagocytosis of A beta in mouse and human microglia because of M-CSFR overexpression that was time- and concentration-dependent. In contrast, microglial uptake of 1-microm diameter polystyrene microspheres was not enhanced by M-CSFR overexpression. Microglial uptake of A beta was blocked by cytochalasin D, which inhibits phagocytosis. M-CSFR overexpression increased the mRNA for macrophage scavenger receptor A, and fucoidan blocking of macrophage scavenger receptors inhibited uptake of A beta. M-CSFR antibody blocking experiments demonstrated that increased A beta uptake depended on the interaction of the M-CSFR with its ligand. These results suggest that overexpression of M-CSFR in APPV717F mice may prime microglia for phagocytosis of A beta after immunization.
Insights
Overexpressing the macrophage colony-stimulating factor receptor (M-CSFR) in microglia accelerates amyloid-beta (A beta) plaque uptake. This finding suggests M-CSFR may prime microglia for clearing A beta in Alzheimer
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia, the brain's immune cells, play a crucial role in Alzheimer's disease (AD) pathogenesis.
- Enhanced expression of the macrophage colony-stimulating factor receptor (M-CSFR) is observed on microglia surrounding amyloid-beta (A beta) plaques in AD models.
- M-CSFR signaling influences microglial proliferation, inflammatory responses, and nitric oxide production.
Purpose of the Study:
- To investigate the role of M-CSFR overexpression in microglial phagocytosis of A beta.
- To determine if M-CSFR enhances the uptake of A beta specifically, not other particles.
- To elucidate the mechanisms by which M-CSFR influences A beta clearance.
Main Methods:
- Transfection of mouse BV-2 and human SV-A3 microglia to overexpress M-CSFR.
- Assessment of A beta phagocytosis using flow cytometry and laser confocal microscopy.
- Inhibition studies using cytochalasin D, fucoidan, and M-CSFR blocking antibodies.
Main Results:
- M-CSFR overexpression significantly accelerated the time- and concentration-dependent phagocytosis of A beta by both mouse and human microglia.
- M-CSFR overexpression did not enhance the uptake of polystyrene microspheres, indicating specificity for A beta.
- A beta uptake was dependent on M-CSFR-ligand interaction and involved macrophage scavenger receptor A.
- Phagocytosis of A beta was inhibited by cytochalasin D, confirming a phagocytic mechanism.
Conclusions:
- Overexpression of M-CSFR enhances microglial phagocytosis of A beta in a specific and receptor-dependent manner.
- The findings suggest that M-CSFR signaling pathways are critical for mediating A beta clearance by microglia.
- M-CSFR overexpression in APPV717F mice may prime microglia for enhanced A beta phagocytosis, potentially offering a therapeutic target for Alzheimer's disease.
