mouse brain histology to study the pathological mechanisms of ischemic stroke induced by distal middle artery occlusion

Occlusion of Distal Middle Artery to Develop an Ischemic Stroke Mouse Model

Stroke is a common acute cerebrovascular disease characterized by high incidences of disability and fatality1. Of all stroke cases, nearly 80% belong to ischemic stroke2. Up to now, intravenous thrombolysis remains one of a limited number of productive approaches for the treatment of acute ischemic stroke. However, the effectiveness of thrombolytic treatment is restricted by the narrow effective time window and the occurrence of hemorrhagic transformation3. In the long-term rehabilitation phase following an ischemic stroke, a considerable number of patients are likely to experience durable neurological dysfunctions4. Further investigation is urgently required to unravel the underlying pathophysiological mechanisms of ischemic stroke, as well as to facilitate the development of novel therapeutic strategies targeting ischemic stroke. The establishment of a dependable and replicable model of ischemic stroke is crucial for basic research as well as subsequent translational research in the field of ischemic stroke.
In 1981, Tamura et al. developed a focal cerebral ischemia model by employing transcranial electrocoagulation at the proximal site of the middle cerebral artery (MCA)5. Since then, numerous researchers have utilized various methodologies such as ligation, compression, or clipping to induce distal MCA occlusion (dMCAO) for establishing transient or permanent ischemic stroke models6,7,8. Compared to the filament model, the dMCAO model exhibits notable advantages such as smaller infarct size and higher survival rate, rendering it more suitable for investigating long-term functional recovery subsequent to ischemic stroke9. In addition, the dMCAO model demonstrates a higher survival rate in aged rodents compared to the filament model, making it an advantageous tool for investigating ischemic stroke in elderly and comorbid animal models10. The photothrombotic (PT) stroke model has been demonstrated to possess the characteristics of less surgical invasiveness and a significantly low mortality rate. However, the PT model exhibits a greater degree of cellular necrosis and tissue edema compared to the dMCAO model, leading to the absence of collateral circulation11. Furthermore, it is noteworthy that the ischemic lesions observed in the PT model predominantly arise from microvascular occlusion, which differs substantially from the cerebral ischemia induced by large vessel embolism in the dMCAO model12.
In this paper, we present the methodology for inducing the murine dMCAO model by coagulating the distal MCA via small bone window craniotomy. Additionally, we conducted histological examinations and behavioral evaluations to comprehensively characterize the ischemic insults and stroke outcomes in this experimental model. We aim to acquaint researchers with this model and facilitate further investigations into the pathologic mechanisms of ischemic stroke.

Author Spotlight: Establishing a Reliable Distal MCA Occlusion Model in Mice for Stroke Research

Induction of Acute Ischemic Stroke in Mice Using the Distal Middle Artery Occlusion Technique

In the present research, we aim to provide a comprehensive and detailed protocol for establish middle cerebral artery occlusion model in C57BL/6J mice using transcranial electrocoagulation and we evaluated the subsequent neurological behavior and histopathological features. The middle cerebral artery or MCA is recognized as the primary site of ischemic stroke in humans. The MCA occlusion methods, including technique, photochemical introduction, and occlusion have been extensively employed to induce focal cerebral ischemia in rodents.Compared to other ischemia stroke models, this model has the advantage of less surgical invasiveness, smaller infarct size, and higher survival rate, rendering it more suitable for investigation the long-term functional recovery after ischemic stroke. Overall, the current approach effectively generates a reliable experimental ischemic stroke model that exhibits high survivability and excellent repeatability. Consequently, this methodology serves as an invaluable tool for both foundation and translational research in the field of stroke.In the future, we will employ behavior paradigms such as novel object recognition and water maze to investigate the dynamic alterations in long-term learning and memory capabilities among distal MCA-occluded mice. This will enable us to ascertain the viability of utilizing them as animal model for cognition-impairment studies post-stroke.

Mouse Brain Histology to Study the Pathological Mechanisms of Ischemic Stroke Induced by Distal Middle Artery Occlusion

To begin, obtain the dissected brain of the euthanized distal MCAO mouse model after behavioral testing, and place it in a minus 20 degrees Celsius freezer for 20 minutes. Then position the brain into a one-millimeter brain matrix. And using microtone blades, slice the brain into two-millimeter-thick coronary sections.Transfer the brain sections to a 24-well culture plate and add 2%TTC to cover the brain tissue. Incubate the plate at 37 degrees Celsius for 30 minutes. Then carefully fix the brain section in 4%Paraldehyde solution for 15 minutes.Using a scanister, perform optical scanning of the brain sections. The histological analysis of the brain revealed the disordered arrangement of neuron cells and a significant reduction in the density of NeuN positive cells in the peri-infarct area of the distal MCA occluded mice.

Research

JoVE Journal

Neuroscience

Ischemic stroke remains the predominant cause of mortality and functional impairment among the adult populations globally. Only a minority of ischemic ...