Physiological and injury-induced microglial dynamics across the lifespan
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Microglia are brain’s resident immune cells known for their dynamic responses to tissue and vascular injury. Little is known about how microglial activity differs across the life-stages of early development, adulthood, and aging. Using two-photon live imaging, we show that microglia in the adult cerebral cortex exhibit highly ramified processes and relatively immobile somata under basal conditions. Their responses to injury occur over minutes and are highly coordinated neighboring microglia. In neonates, microglia are denser and more mobile but less morphologically complex. Their responses to focal laser-induced injuries of capillaries or parenchymal tissue are uncoordinated, delayed and persistent over days. In the aged brain, microglia somata remain immobile under basal conditions but their processes become less ramified. Their responses to focal injuries remain coordinated but are slower and less sensitive. These studies confirm that microglia undergo significant changes in their morphology, distribution, dynamics and response to injury across the lifespan.
HIGHLIGHTS
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Microglia undergo significant morphological and dynamic changes between life-stages.
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Neonatal microglia are highly dynamic, less morphologically complex and mount delayed responses to focal injury compared to adult microglia.
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Aged microglia are slightly less ramified and their responses to focal injury are slow and less sensitive than adult microglial.
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Maturation of microglial morphology in the developing cortex is disrupted by focal laser injury.
