Influences of Activated Microglia/Brain Macrophages on Spinal Cord Injury and Regeneration
Damage to the central nervous system (CNS) systematically elicits the activation of both astrocytes and microglia, often termed reactive gliosis. This article is focused on the principal features that characterize cellular events associated with the activation of microglia after spinal cord injury (SCI) that govern the regenerative success or failure of injured neurons. In addition to discussing the role of microglia as immunocompetent cells of the CNS, it addresses the influences of activated microglia/brain macrophages on astrogliosis. The controversial issue of whether reactive microgliosis is a beneficial or harmful process with respect to neuroprotection is addressed, and a resolution of this dilemma is offered by suggesting different interpretations of the term “activated microglia” depending on its usage during experimentation in vivo or in vitro. Importantly, it provides a critical discussion regarding the distinction and relation between microglia-derived brain macrophages and infiltrating peripheral macrophages, and their conflicting roles in creating a pro-regenerative environment. To this end, evidence is reviewed that suggests that microglia-derived brain macrophages are capable of overriding many of the inhibitory obstacles to regeneration following SCI through their production of growth factors and cytokines, as well as their deposition or modulation of the extacellular matrix in the injured environment.
KeywordsMigration Superoxide Retina Neurol NMDA
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