Rodent stroke induced by photochemical occlusion of proximal middle cerebral artery: evolution monitored with MR imaging and histopathology
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Published on: December 15, 2023
Feng Chen1, Yasuhiro Suzuki, Nobuo Nagai
1Department of Radiology, Faculty of Medicine, Catholic University of Leuven, Belgium.
Purpose:
To longitudinally investigate stroke in rats after photothrombotic occlusion of proximal middle cerebral artery (MCA) with magnetic resonance imaging (MRI) in correlation with histopathology.
Materials And 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).
Conclusion:
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.
Insights
Magnetic resonance imaging (MRI) effectively characterizes photothrombotic stroke evolution in rats. This model aids longitudinal studies of cerebral ischemia and potential anti-stroke therapies.
Area of Science:
- Neuroscience
- Radiology
- Pathology
Background:
- Stroke is a leading cause of death and disability worldwide.
- Animal models are crucial for understanding stroke pathophysiology and developing treatments.
- Photothrombotic stroke models offer a reproducible method to induce focal cerebral ischemia.
Purpose of the Study:
- To longitudinally investigate stroke progression in a rat model using MRI.
- To correlate MRI findings with histopathological outcomes.
- To validate MRI techniques for assessing blood-brain barrier integrity and lesion volume.
Main Methods:
- Forty-two rats underwent photothrombotic middle cerebral artery (MCA) occlusion.
- Serial MRI (T2WI, DWI, ADC, CE-T1WI) was performed at multiple time points (1h to 9 days).
- Histopathology (TTC staining) and blood-brain barrier (BBB) assessment (Evans blue) were used for correlation.
Main Results:
- Ischemic lesion volume peaked at 12h to 1 day, visualized by DWI, ADC, and T2WI.
- Apparent diffusion coefficient (ADC) changes indicated cytotoxic edema, vasogenic edema, and colliquative necrosis.
- Blood-brain barrier (BBB) leakage peaked at 6h and 3 days, with partial recovery at 24h.
- MRI-derived infarct volumes correlated well with TTC staining.
Conclusions:
- MRI can effectively characterize the temporal evolution of photothrombotic stroke in rats.
- This validated MRI approach supports longitudinal studies of cerebral ischemia.
- The findings facilitate research on novel anti-stroke agents using this animal model.
