IschemiaPhotochemically induced cerebral ischemia in a mouse model
Introduction
Stroke is one of the leading causes of death and the most common cause of adult disability. Stroke often causes devastating and irreversible loss of function. There is a wide range of sensory, motor, and cognitive deficits including tremor, lack of coordination, and partial paralysis [6]. There is no specific treatment for improving functional recovery after stroke. A large number of neuroprotective drugs have failed to demonstrate efficacy in clinical trials [20].
Development of effective stroke therapy requires use of animal models that can simulate human pathology in a reproducible and physiologically relevant manner. Currently, the intraluminal suture model of MCAO has been widely used to induce ischemic brain lesions. As the MCA is occluded via a cervical carotid approach, this obviates the requirement for a craniectomy and the associated problems with opening the skull [4], [7], [14]. However, the lesions caused by the MCAO tend to be variable in size; in addition, animals have been excluded from analysis by arbitrary criteria such as unexpected behavior in most series [1], [16]. The collateral blood supply in the mouse brain is variable depending on the mouse strain; this results in variability of clinical outcome and stroke size [6]. The C57BL/6 strain, frequently used for genetic studies, is particularly unsuitable for MCAO [3]. The development of reliable and reproducible animal models for cerebral ischemia is needed for the systematic study of the pathophysiology and treatment of stroke. In this study, we adapted the rat photothrombosis model for use in mice by modifying the application route of the dye and illumination and stereotactic parameters.
Section snippets
Photothrombotic cortical lesion
All surgical procedures and postoperative care were performed in accordance with guidelines of the Chonnam National University Animal Care and Use Committee. A total of 25 male C57BL/6 mice (8-10 weeks old) weighing 20 to 25 g were maintained on a 12-hour light/dark cycle. The mice were fasted overnight before the day of the experiment but were allowed free access to tap water.
Focal cortical ischemia was induced by photothrombosis of the cortical microvessels. Each mouse was anesthetized with
Results
In this experiment, rose bengal dye was injected systemically and then the cortex was illuminated, at the left sensorimotor cortex, in a mouse stroke model to produce a discrete photothrombotic lesion based on light absorption by the dye. Histologic examination of the brain after 24 hours showed a consistent pattern of ischemic brain damage. At 24 hours after induction of ischemia, the infarct was demarcated from the surrounding vital tissue after incubation with TTC. The lesion was located in
Discussion
Cerebral ischemia in mice has been introduced by transient and permanent occlusion of the MCA with intraluminal filament [7], [11]. However, the procedure requires sophisticated microsurgical skills because of the proximity to the vagus nerve and the tiny anatomy of the carotid system in mice. The size of the cerebral infarct is highly dependent on the vascular anatomy of the MCA and collateral vessels, which differs considerably among mouse strains [12]. Furthermore, the size of the infarction
Conclusion
Our results demonstrate that photothrombotic occlusion of cerebral microvessels in mice is a minimally invasive and simple model for study of focal cortical ischemia. The cortical lesion produced is consistent and the lesion has a precise location and size. Therefore, this model offers a reliable method for the study of the functional aspects of lesion-associated cerebral ischemia and for evaluation of potential neuroprotective and therapeutic agents in human stroke.
Acknowledgment
This work was supported by Research Institute of Medical Sciences of Chonnam National University.
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Stroke
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