Cerebral stroke is a leading cause of death and disability worldwide1. The high mortality and morbidity of stroke result in immense public healthcare burden and serious socio-economic consequences. Although the rate of stroke incidence and mortality remain stable, the number of stroke patients and stroke-related deaths are increasing over decades2,3. Strokes can be categorized as ischemic or hemorrhagic. The majority of stroke cases are ischemic strokes caused by the occlusion of a main cerebral artery4. To date, tissue plasminogen activator (tPA) is the only FDA-approved drug for ischemic stroke, but its application is highly limited by the narrow therapeutic window, complications, and contraindications5,6,7. Thus, it is urgent to develop new treatment options with a wider therapeutic window to mitigate the effects of stroke.
Experimental animal models are useful tools to study the pathophysiology of ischemic stroke. In most human patients, ischemic stroke is caused by the blockage of the middle cerebral artery (MCA)8. Therefore, rodent models of middle cerebral artery occlusion (MCAO) have been developed to resemble human cerebral infarction. While there are several MCAO approaches that are used in small animal studies, the method most widely used is the intraluminal suture model, which involves inserting a nylon filament into the middle cerebral artery from either the external or internal carotid arteries, resulting in transient or permanent occlusion of the blood flow4,9. This model leads to a large volume of cerebral infarction and allows examination of cell death signaling in the infarcted brain tissue with immunofluorescent techniques.
The area surrounding the infarcted core, referred to as penumbra, is the target for potential stroke therapies10,11. Since blood flow in the penumbra is partially maintained, injured neurons and non-neuronal cells in this area may be salvaged by inhibiting the activation of cell death signaling. Targeting cell death pathways may be a promising strategy for neuroprotection after stroke12. Therefore, evaluating cell death signaling is crucial for experimental stroke research. Recently, cathepsin-B, a lysosomal protease, has been shown to play a role in mediating programmed cell death after stroke, and it has gained substantial attention in the neurological field13. Cathepsin-B represents a potential target for neuroprotection that merits further investigation.
This article demonstrates how to induce MCAO using the intraluminal suture approach in rats. We also show how to perform 2,3,5-triphenyltetrazalium chloride (TTC) staining to determine infarct size and detect apoptotic cells using Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining.