Rodent stroke induced by photochemical occlusion of proximal middle cerebral artery: evolution monitored with MR imaging and histopathology.
OBJECTIVE
To longitudinally investigate stroke in rats after photothrombotic occlusion of proximal middle cerebral artery (MCA) with magnetic resonance imaging (MRI) in correlation with histopathology.


METHODS
Forty-two rats were subjected to photochemical MCA occlusion and MRI at 1.5T, and sacrificed in seven groups (n=6 each) at the following time points: 1, 3, 6 and 12h, and at day 1, 3 and 9. T2-weighted (T2WI) and diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) map was performed in all rats. Contrast-enhanced T1-weighted imaging (CE-T1WI) was compared to intravital staining with Evans blue in one group for assessing blood-brain barrier (BBB) integrity. The brain was stained histochemically with triphenyl tetrazolium chloride (TTC) and processed for pathological assessment. The evolutional changes of relative lesion volume, signal intensity (SI), and the BBB integrity on MRI with corresponding histopathology were evaluated.


RESULTS
The ischemic lesion volume reached a maximum around 12h to day 1 as visualized successively by DWI, ADC map and T2WI, implicating the evolving pathology from cytotoxic edema through vasogenic edema to tissue death. The ADC of brain infarction underwent a significant reversion after 12h, reflecting the colliquative necrosis. On CE-T1WI, BBB leakage peaked at 6h and at day 3 with a transitional partial recovery around 24h. The infarct volume on T2WI, DWI and ADC map matched well with that on TTC staining at 12h and at day 1 (p>0.05).


CONCLUSIONS
The evolution of the present photothrombotic stroke model in rats could be characterized by MRI. The obtained information may help longitudinal studies of cerebral ischemia and anti-stroke agents using the same model.
Chen
Feng
F
Department of Radiology, Faculty of Medicine, Catholic University of Leuven, Belgium.
Suzuki
Yasuhiro
Y
Nagai
Nobuo
N
Jin
Lixin
L
Yu
Jie
J
Wang
Huaijun
H
Marchal
Guy
G
Ni
Yicheng
Y
D000818:Animals; D001812:Blood-Brain Barrier / Q000473:pathology; D001921:Brain / Q000098:blood supply / Q000473:pathology; D001929:Brain Edema / Q000175:diagnosis / Q000209:etiology / Q000473:pathology; D002545:Brain Ischemia / Q000150:complications / Q000473:pathology*; D004396:Coloring Agents; D003287:Contrast Media / Q000008:administration & dosage; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D004195:Disease Models, Animal; D018450:Disease Progression; D005070:Evans Blue; D019786:Gadolinium DTPA; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D020768:Middle Cerebral Artery / Q000473:pathology*; D010777:Photochemistry / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D020521:Stroke / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology*; D013778:Tetrazolium Salts; D013997:Time Factors
D004396:Coloring Agents; D003287:Contrast Media; D013778:Tetrazolium Salts; D005070:Evans Blue; C009591:triphenyltetrazolium; C064925:gadodiamide; D019786:Gadolinium DTPA