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Disease Models | Stroke Model: the MCAO Animal Model of Cerebral Ischemia

Introduction:

Cerebral stroke, also known as “stroke,” encompasses both ischemic and hemorrhagic strokes. Ischemic stroke is more common than hemorrhagic stroke, accounting for 60% to 70% of all cerebrovascular events.

Stroke is characterized by high incidence, high disability rates, high recurrence rates, and high mortality. Owing to the longstanding lack of effective therapeutic strategies, animal models have become indispensable tools for elucidating its pathogenic mechanisms and for developing efficacious treatments.

 

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Stroke refers to a group of conditions in which brain tissue is damaged due to impaired blood flow to the brain caused by vascular occlusion. Based on this underlying mechanism, numerous methods and types of cerebral ischemia models have been developed, which can be broadly classified as follows:

 

The middle cerebral artery (MCA) is a common site of stroke; accordingly, the MCA occlusion (MCAO) animal model is an internationally recognized standard for focal cerebral ischemia, with pathogenic mechanisms that closely resemble those of human cerebral ischemic conditions.

 

Main construction method: Craniotomy‑based mechanical occlusion, photochemical methods, filament‑thread embolization, and embolization techniques. Among these, the filament‑thread method has become the most widely used approach for establishing the model in recent years.

 

MCAO model: the filament occlusion method in rats

Selection of animals and tools: SD rats, male, weighing 250–300 g; wire length 17 mm or 18 mm, wire diameter 0.28 mm.

Construction method: After anesthetizing the animal, it is placed in a supine position and immobilized. A 4-0 nylon suture is inserted through the external carotid artery (ECA) into the internal carotid artery (ICA), then advanced across the middle cerebral artery (MCA) to occlude its proximal segment, thereby inducing localized cerebral ischemia. Following 1–3 hours, the nylon suture can be slowly withdrawn to allow reperfusion.

Schematic diagram of the suture pathway in the MCAO model

 

Precautions:

(1) Routine skin preparation is required for rats, and continuous warming must be maintained throughout the entire surgical procedure.

(2) Anesthetics shall be prepared immediately before use;

(3) Fixation of rat incisors;

(4) The suture should not be too stiff; otherwise, it may easily puncture the subarachnoid vessels.

(5) Postoperative care of the animal must be provided.

 

Regarding fasting: Many animal studies require animals to be fasted the day before the experiment; however, after reviewing the literature, the author believes that this protocol can be flexibly adjusted according to the study’s specific objectives.

When rat blood glucose levels are either elevated or reduced, the extent of brain injury increases, the infarct size expands, cerebral edema worsens, and the incidence of post‑infarct hemorrhage rises; therefore, it is necessary to monitor the rats’ glycemic status. If required, fasting may be implemented 12–24 hours prior to the experiment.

 

However, rodents have a relatively high metabolic rate; fasting for more than 6 hours can lead to weight loss and hepatic glycogen depletion, thereby compromising the animals’ physiological status and surgical tolerance, as well as the neuroprotective effects of candidate drugs.

Model features: It requires no craniotomy, causes minimal injury to the animal, achieves a highly satisfactory MCA occlusion, boasts a high success rate and good reproducibility, and is considered the only focal cerebral ischemia model in which reperfusion flow can be directly observed. However, the surgical procedure demands considerable experience and technical skill.

Neurological and Behavioral Assessment Methods ： Assessment should be performed 24 hours after the onset of ischemia in animals, with two primary methods: the Longa scale and the Bederson scale.

0 points: No symptoms of nerve injury

1 point: Unable to fully extend the contralateral forepaw.

2 points: Turns in a circle toward the opposite side

3 points: Falls toward the contralateral side

4 points: Unable to walk independently; loss of consciousness.

After model establishment, the mice’s behavioral performance can be viewed by clicking the link to access the video: MCAO cerebral ischemia model mice (model establishment outcomes)

 

Pathological examination: TTC staining of brain tissue, with pathological morphological description.

 

 

 

At the Aniphe BioLabLaboratory, a variety of cerebral ischemia animal models have been established— including global cerebral ischemia, focal cerebral ischemia, permanent occlusion, and reperfusion—based on the site and severity of ischemia as well as the status of blood flow recovery. These models are used to evaluate the preventive or therapeutic efficacy of drugs through either prophylactic or therapeutic administration.

Aniphe BioLab offers comprehensive project solutions, backed by real-world data and tangible results. Feel free to contact us for more information!

 

 

Reference:

【1】Ma R, Xie Q, Li Y, et al. Animal models of cerebral ischemia: A review[J]. Biomedicine & Pharmacotherapy, 131.

[2] Methodology for the Replication of Animal Models of Human Diseases / Edited by Zhou Guangxing et al. — Shanghai: Shanghai Scientific & Technological Literature Publishing House, Jan. 2008.

[3] Derek Barthels, Hiranmoy Das. (2020). Current advances in ischemic stroke research and therapies. Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease[N], Volume 1866, Issue 4, 1 April 2020, 165260.

[4] Hu Zhibin, Huang Ying, Ding Yuqiang (2021). Advances in the Preparation and Evaluation of Animal Models of Cerebral Ischemia, Laboratory Animals and Comparative Medicine [J], 2021, 41(4), ISSN: 1674-5817.

 

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Editor  |  Lemon

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