title: Dark microglia: Why are they dark?
abstract: Using transmission electron microscopy (TEM) we recently characterized a microglial phenotype that is induced by chronic stress, fractalkine receptor deficiency, aging, or Alzheimer disease pathology. These 'dark' microglia appear overly active compared with the normal microglia, reaching for synaptic clefts, and extensively engulfing pre-synaptic axon terminals and post-synaptic dendritic spines. From these findings we hypothesized that dark microglia could be specifically implicated in the pathological remodeling of neuronal circuits, which impairs learning, memory, and other essential cognitive functions. In the present addendum we further discuss about the possible causes of their dark appearance under TEM.
authors.affiliation: Axe Neurosciences, CRCHU de Québec , Québec City, QC, Canada.
authors.forename: Kanchan
authors.initials: K
authors.lastname: Bisht
authors.affiliation: Axe Neurosciences, CRCHU de Québec , Québec City, QC, Canada.
authors.forename: Kaushik
authors.initials: K
authors.lastname: Sharma
authors.affiliation: Department of Cellular & Molecular Medicine, Faculty of Medicine, The University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada; Neuroscience Program, The Ottawa Hospital Research Institute, Ottawa, ON, Canada.
authors.forename: Baptiste
authors.initials: B
authors.lastname: Lacoste
authors.affiliation: Axe Neurosciences, CRCHU de Québec , Québec City, QC, Canada.
authors.forename: Marie-Ève
authors.initials: MÈ
authors.lastname: Tremblay
keywords: Alzheimer disease; aging; dark microglia; electron microscopy; fractalkine receptor deficiency; microglia; oxidative stress; synapses