Journal Article

M-CSF increases proliferation and phagocytosis while modulating receptor and transcription factor expression in adult human microglia

Curtis, Maurice A, Gibbons, Hannah M, Mee, Edward W, Oldfield, Robyn L, Smith, Amy M, Faull, Richard L M, Dragunow, Mike, Bergin, Peter M

2013

Overview

Background Microglia are the primary immune cells of the brain whose phenotype largely depends on their surrounding micro-environment. Microglia respond to a multitude of soluble molecules produced by a variety of brain cells. Macrophage colony-stimulating factor (M-CSF) is a cytokine found in the brain whose receptor is expressed by microglia. Previous studies suggest a critical role for M-CSF in brain development and normal functioning as well as in several disease processes involving neuroinflammation. Methods Using biopsy tissue from patients with intractable temporal epilepsy and autopsy tissue, we cultured primary adult human microglia to investigate their response to M-CSF. Mixed glial cultures were treated with 25 ng/ml M-CSF for 96 hours. Proliferation and phagocytosis assays, and high through-put immunocytochemistry, microscopy and image analysis were performed to investigate microglial phenotype and function. Results We found that the phenotype of primary adult human microglia was markedly changed following exposure to M-CSF. A greater number of microglia were present in the M-CSF- treated cultures as the percentage of proliferating (BrdU and Ki67-positive) microglia was greatly increased. A number of changes in protein expression occurred following M-CSF treatment, including increased transcription factors PU.1 and C/EBPβ, increased DAP12 adaptor protein, increased M-CSF receptor (CSF-1R) and IGF-1 receptor, and reduced HLA-DP, DQ, DR antigen presentation protein. Furthermore, a distinct morphological change was observed with elongation of microglial processes. These changes in phenotype were accompanied by a functional increase in phagocytosis of Aβ 1-42 peptide. Conclusions We show here that the cytokine M-CSF dramatically influences the phenotype of adult human microglia. These results pave the way for future investigation of M-CSF-related targets for human therapeutic benefit.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V
• Subject: Adaptor Proteins, Signal Transducing - biosynthesis / Adaptor Proteins, Signal Transducing - genetics / Analysis / Antimetabolites / Autopsy / Biomedical and Life Sciences / Biomedicine / Biopsy / Brain / Brain research / Bromodeoxyuridine / CCAAT-Enhancer-Binding Protein-beta - biosynthesis / Cell culture / Cell Proliferation - drug effects / Cells, Cultured / Cytokines / Epilepsy / Experiments / Gene expression / Genotype & phenotype / Health aspects / HLA Antigens - biosynthesis / Humans / Image Processing, Computer-Assisted / Immunohistochemistry / Immunology / Insulin-like growth factors / Ki-67 Antigen - metabolism / Macrophage Activation - drug effects / Macrophage Colony-Stimulating Factor - pharmacology / Macrophages / Medical research / Membrane Proteins - biosynthesis / Membrane Proteins - genetics / Microglia - drug effects / Microglia - metabolism / Neurobiology / Neurology / Neurosciences / Pathogenesis / Phagocytosis - drug effects / Physiological aspects / Proteins / Proto-Oncogene Proteins - biosynthesis / Proto-Oncogene Proteins - genetics / Receptor, Macrophage Colony-Stimulating Factor - biosynthesis / Rodents / Studies / Trans-Activators - biosynthesis / Trans-Activators - genetics / Transcription Factors - biosynthesis