CCR3 Expression in Relation to Delayed Microbleeds in a Rat Model of Large Vessel Occlusion

Thirty percent of ischemic stroke patients develop vascular cognitive impairment and dementia (VCID) within 1 year of stroke onset. The expression of C-C motif chemokine receptor 3 (CCR3) is associated with endothelial dysfunction and memory impairment. CCR3 has been reported to increase after experimental stroke and in human stroke patients. Using an in vivo model of stroke, our study aims to link CCR3 expression with endothelial dysfunction in this rodent stroke model.

5-hour transient Middle Cerebral Artery Occlusion (5t-MCAO) or sham surgery was performed on rats and tissue collected at 3- and 30-days post-stroke. We measured the change in expression of CCR3 and its ligands in the venous blood before and after occlusion in the rat model.Immunohistochemistry was performed on consecutive coronal brain sections using Prussian blue to visualize microbleeds and DAB to visualize CCR3. Images were quantified using HALO.

Using linear regression, we found that increased expression of CCR3 and its ligands after stroke were positively correlated with infarct volume. CCR3 expression was significantly increased in the ipsilateral hemisphere at 30 days post 5t-MCAO. Prussian blue staining was significantly increased in ipsilateral sections at 30 days post-stroke. Immunostaining for CCR3 was primarily detected in endothelium in areas of Prussian blue staining.

Our results demonstrate that CCR3 expression is associated with the presence of microbleeds at 30 days but not 3 days post-stroke in the ipsilateral hemisphere, and further supports the link between CCR3 and the endothelial dysfunction that is associated with VCID. CCR3 and its inflammatory pathway is a potential target for reducing endothelial dysfunction after ischemic stroke that may lead to VCID.