Attribution 4.0 International (CC BY 4.0)2022-09-092022-09-092020-01-01Zhang, L. Y., Pan, J., Mamtilahun, M., Zhu, Y., Wang, L., Venkatesh, A., Shi, R., Tu, X., Jin, K., Wang, Y., Zhang, Z., & Yang, G. Y. (2020). Microglia exacerbate white matter injury via complement C3/C3aR pathway after hypoperfusion. Theranostics, 10(1), 74-90. https://doi.org/10.7150/thno.358411838-7640https://hdl.handle.net/20.500.12503/31704Microglial 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.http://creativecommons.org/licenses/by/4.0/chronic cerebral hypoperfusioncomplementinflammationmicrogliawhite matter injuryAnimalsBrain Injuries / metabolismBrain Injuries / pathologyBrain Ischemia / metabolismBrain Ischemia / pathologyComplement C3 / metabolismComplement Pathway, ClassicalInflammation / metabolismInflammation / pathologyMaleMiceMice, Inbred C57BLMice, KnockoutMicroglia / pathologyPerfusionRatsRats, Sprague-DawleyReceptors, G-Protein-Coupled / metabolismWhite Matter / metabolismWhite Matter / pathologyArticle© The author(s).101