What’s the Role of Microglia Cells in the Aged Brain?

Microglia cells are the primary immune cells of the central neuron system（CNS). They are the brain counterpart of macrophages and are known as the defender of the brain. Although they are neuroprotective in the young brain, microglia cells have also been found to react abnormally to stimuli in the aged brain and to become neurotoxic and destructive during neurodegeneration.


Aging-induced immune senescence with microglia senescence in the brain causes microglia to function abnormally and promote neurodegeneration. Microglia senescence includes morphological changes and alterations in immunophenotypic expression and inflammatory profile, usually caused by microinvironmental factors. The hypothesis of microglia senescence during aging give a novel perspective on their roles in aging-related neurodegeneration.


Many scientists believe that aberrant inflammatory responses play a role in the etiology of several neurodegenerative diseases, such as Parkinson's disease or Alzheimer's disease, in which aging is the most important risk factor. The CNS is relatively immune-privileged and major immune-cell antigens can be detected on microglia. Therefore, microglia cells have been considered to represent the brain's internal immune system. It is concluded that any changes in microglial activities during aging are key components in influencing the pathogenesis of neurodegeneration.


Microglia normally keep in a quiescent state, thus sometimes called resting microglia, with ramified morphology and weak expression of function-associated antigens. When triggered by appropriate stimulation, microglia rapidly become activated with deramified shape and enhanced antigen presentation. As an active sensor and monitor in the brain, microglia are neuroprotective. However, uncontrolled response of microglia may be dangerous to the survival of injured neurons or even cause damage to healthy neurons. In the normal aged monkey brain, microglial expression of MHC class II increases with age, and the phagocytic activity of microglia increases age-dependently. Immunohistochemical studies also reveal that microglial activation is age-related. Additionally, from activated microglia explanted from aged mice model, the increased pro-inflammatory cytokines and decreased anti-inflammatory cytokines have been demonstrated, which also suggests the abnormal immune state of microglia in the aged brain.


All of the facts suggests that the inflammatory state of microglia in the aged brain primes them to be over-responsive to small stimuli and so the activation of microglia in the aged brain loses control. However, it still remain uncertain what triggers the microglial activation in the healthy aged brain.
Creative Bioarray is the world’s largest primary cells supplier. The company offers 35 human cell systems with over 160 different cell types and also provide primary cells from over 13 types of other animals. We offer both rat microglia cells and human microglia cells for research use.

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