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Updated: Dec 31, 2025
Characterization and Isolation of Mouse Primary Microglia by Density Gradient Centrifugation
Published on: February 16, 2018
Microglia exacerbate white matter injury via complement C3/C3aR pathway after hypoperfusion
Lin-Yuan Zhang1, Jiaji Pan1, Muyassar Mamtilahun1
1Department of Neurology, Ruijin Hospital School of Medicine, and Med-X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
Abstract:
Microglial activation participates in white matter injury after cerebral hypoperfusion. However, the underlying mechanism is unclear. Here, we explore whether activated microglia aggravate white matter injury via complement C3-C3aR pathway after chronic cerebral hypoperfusion. Methods: Adult male Sprague-Dawley rats (n = 80) underwent bilateral common carotid artery occlusion for 7, 14, and 28 days. Cerebral vessel density and blood flow were examined by synchrotron radiation angiography and three-dimensional arterial spin labeling. Neurobehavioral assessments, CLARITY imaging, and immunohistochemistry were performed to evaluate activation of microglia and C3-C3aR pathway. Furthermore, C3aR knockout mice were used to establish the causal relationship of C3-C3aR signaling on microglia activation and white matter injury after hypoperfusion. Results: Cerebral vessel density and blood flow were reduced after hypoperfusion (p<0.05). Spatial learning and memory deficits and white matter injury were shown (p<0.05). These impairments were correlated with aberrant microglia activation and an increase in the number of reactive microglia adhering to and phagocytosed myelin in the hypoperfusion group (p<0.05), which were accompanied by the up-regulation of complement C3 and its receptors C3aR (p<0.05). Genetic deletion of C3ar1 significantly inhibited aberrant microglial activation and reversed white matter injury after hypoperfusion (p<0.05). Furthermore, the C3aR antagonist SB290157 decreased the number of microglia adhering to myelin (p<0.05), attenuated white matter injury and cognitive deficits in chronic hypoperfusion rats (p<0.05). Conclusions: Our results demonstrated that aberrant activated microglia aggravate white matter injury via C3-C3aR pathway during chronic hypoperfusion. These findings indicate C3aR plays a critical role in mediating neuroinflammation and white matter injury through aberrant microglia activation, which provides a novel therapeutic target for the small vessel disease and vascular dementia.
Insights
Activated microglia worsen white matter injury through the complement C3-C3aR pathway in chronic cerebral hypoperfusion. Blocking C3aR signaling reduces neuroinflammation and cognitive deficits, offering a potential therapeutic target.
Area of Science:
- Neuroscience
- Immunology
- Vascular Biology
Background:
- Microglial activation is implicated in white matter injury following cerebral hypoperfusion.
- The precise mechanisms driving this microglial involvement remain incompletely understood.
- Chronic cerebral hypoperfusion can lead to significant neurological deficits and white matter damage.
Purpose of the Study:
- To investigate if activated microglia exacerbate white matter injury via the complement C3-C3aR pathway in chronic cerebral hypoperfusion.
- To elucidate the role of the C3-C3aR signaling cascade in microglial activation and subsequent white matter damage.
- To assess the therapeutic potential of targeting the C3aR pathway for neuroprotection.
Main Methods:
- Adult rats underwent chronic cerebral hypoperfusion via bilateral common carotid artery occlusion.
- Cerebral blood flow, vessel density, neurobehavioral functions, and white matter integrity were assessed.
- Microglial activation, complement C3, and C3aR expression were evaluated using immunohistochemistry and genetic knockout models (C3aR knockout mice) and pharmacological inhibition (C3aR antagonist SB290157).
Main Results:
- Chronic hypoperfusion reduced cerebral blood flow and vessel density, leading to cognitive deficits and white matter injury.
- Aberrant microglial activation, characterized by myelin phagocytosis, correlated with increased C3 and C3aR expression.
- Genetic deletion of C3aR and pharmacological blockade significantly attenuated microglial activation, white matter injury, and cognitive impairments.
Conclusions:
- Activated microglia exacerbate white matter injury through the C3-C3aR pathway during chronic cerebral hypoperfusion.
- The C3aR pathway is critical in mediating neuroinflammation and white matter damage driven by aberrant microglial activation.
- Targeting C3aR presents a novel therapeutic strategy for small vessel disease and vascular dementia.
