Microglia are important immune system cells in the brain that can destroy target cells. They are important for proper brain development and associated with neuropsychiatric or neurological disorders in humans.
A team of researchers set out to address this question: what controls microglia maturation and function under normal conditions? They found that host microbiota contributed substantially to microglia homeostasis. Germ-free mice had ‘global defects’ in their microglia, with altered cell proportions and impairments in their innate immune responses. In these mice, other central nervous system cell populations appeared to be unaltered. Mice with a limited microbiota complexity also had defective microglia. Adding back a complex microbiota partially restored microglia features.
Mice that were deficient in the short-chain fatty acid (SCFA) receptor FFAR2 were similar to the mice under germ-free conditions, suggesting that SCFAs produced by the microbiota have a key role in regulating microglia homeostasis.
Erny D, et al. (2015) Host microbiota constantly control maturation and function of microglia in the CNS. Nature Neuroscience doi:10.1038/nn.4030