Resting Microglial Cells Are Highly Dynamic Surveillants of Brain Parenchyma in Vivo

TLDR

Microglial cells are the brain’s immune cells, implicated in injury and disease, yet their function in the healthy brain remains poorly understood. In vivo two‑photon imaging shows resting microglia are highly motile, continuously surveying the parenchyma, and rapidly activate to shield sites of blood‑brain barrier disruption.

Abstract

Microglial cells represent the immune system of the mammalian brain and therefore are critically involved in various injuries and diseases. Little is known about their role in the healthy brain and their immediate reaction to brain damage. By using in vivo two-photon imaging in neocortex, we found that microglial cells are highly active in their presumed resting state, continually surveying their microenvironment with extremely motile processes and protrusions. Furthermore, blood-brain barrier disruption provoked immediate and focal activation of microglia, switching their behavior from patroling to shielding of the injured site. Microglia thus are busy and vigilant housekeepers in the adult brain.