Diverse Requirements for Microglial Survival, Specification, and Function Revealed by Defined-Medium Cultures

Neuron. 2017 May 17;94(4):759-773.e8. doi: 10.1016/j.neuron.2017.04.043.


Microglia, the resident macrophages of the CNS, engage in various CNS-specific functions that are critical for development and health. To better study microglia and the properties that distinguish them from other tissue macrophage populations, we have optimized serum-free culture conditions to permit robust survival of highly ramified adult microglia under defined-medium conditions. We find that astrocyte-derived factors prevent microglial death ex vivo and that this activity results from three primary components, CSF-1/IL-34, TGF-β2, and cholesterol. Using microglial cultures that have never been exposed to serum, we demonstrate a dramatic and lasting change in phagocytic capacity after serum exposure. Finally, we find that mature microglia rapidly lose signature gene expression after isolation, and that this loss can be reversed by engrafting cells back into an intact CNS environment. These data indicate that the specialized gene expression profile of mature microglia requires continuous instructive signaling from the intact CNS.

Keywords: CSF1R; TGF-β; astrocyte; cholesterol; inflammation; maturation; microglia; neurodegeneration; phagocytosis; transplant.

MeSH terms

  • Animals
  • Astrocytes / metabolism
  • Cell Culture Techniques
  • Cell Survival / drug effects*
  • Cholesterol / metabolism
  • Cholesterol / pharmacology*
  • Culture Media, Conditioned / metabolism
  • Humans
  • Interleukins / metabolism
  • Interleukins / pharmacology*
  • Macrophage Colony-Stimulating Factor / metabolism
  • Macrophage Colony-Stimulating Factor / pharmacology*
  • Mice
  • Microglia / cytology
  • Microglia / drug effects*
  • Microglia / immunology
  • Microglia / metabolism
  • Phagocytosis / drug effects*
  • Phagocytosis / immunology
  • Rats
  • Serum
  • Transcriptome
  • Transforming Growth Factor beta / metabolism
  • Transforming Growth Factor beta / pharmacology
  • Transforming Growth Factor beta2 / metabolism
  • Transforming Growth Factor beta2 / pharmacology*


  • Culture Media, Conditioned
  • Interleukins
  • TGFB2 protein, human
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta2
  • interleukin-34, mouse
  • Macrophage Colony-Stimulating Factor
  • Cholesterol