We thank all our collaboration partners of the ImmunoStroke Consortia (FOR 2879, From immune cells to stroke recovery) for suggestions and discussions. This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany&#39;s Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy - ID 390857198) and under the grants LI-2534/6-1, LI-2534/7-1 and LL-112/1-1.

The experiments reported in this video were conducted following the national guidelines for the use of experimental animals, and the protocols were approved by the German governmental committees (Regierung von Oberbayern, Munich, Germany). Ten-week-old male C57Bl/6J mice were used and housed under controlled temperature (22 &#177; 2 &#176;C), with a 12 h light-dark cycle period and access to pelleted food and water ad libitum.
1. Preparation of the material and instruments
<ol>
	<li>Connect the heat blanket to maintain the temperature of the operation area and the mouse body temperature during anesthesia at 37 &#176;C.</li>
	<li>Autoclave scissors and forceps, prepare 70% ethanol solution and keep available dexpanthenol eye ointment, several pieces of cotton, and 5-0 coated braided polyester suture ready for use. Prepare a 1 mL syringe with 0.9% saline solution (without needle) to keep the animal&#39;s incision site hydrated. Prepare the anesthesia gas (100% O2 + isoflurane).</li>
	<li>Prepare a holder for the laser Doppler probe by cutting the tip of a 10 &#181;L pipet tip (3-5 mm length). 
	NOTE: All instruments are sterilized using a hot bead sterilizer. Surfaces are also disinfected before and after surgery with a microbial disinfectant spray. Prior to surgery, the areas surrounding the head and chest of mice are disinfected with a wound disinfection spray.</li>
</ol>
2. Preparation of the laser Doppler
<ol>
	<li>Inject analgesia to the mouse 30 min before the surgery (4 mg/kg Carprofen and 0,1 mg/kg Buprenorphine, intraperitoneally).</li>
	<li>Anesthetize the mouse by placing it in the induction chamber with an isoflurane flow rate of 4% until the cessation of spontaneous body movement and vibrissae.</li>
	<li>Place the mouse in a prone position in the operation area with its nose in the anesthesia mask. Maintain isoflurane concentration at 4% for another minute, then reduce it and keep it at 2%.</li>
	<li>Set the associated feedback-controlled heating pad for maintaining the mouse body temperature at 37 &#176;C, and gently insert the rectal probe to monitor the temperature throughout the surgical procedures.</li>
	<li>Apply dexpanthenol eye ointment on both eyes.</li>
	<li>Disinfect the skin and hair surrounding the left eye and ear with 70% ethanol.</li>
	<li>Cut the scalp between the left ear and the eye (1 cm long) to expose the skull bone.</li>
	<li>Cut and retire the temporal muscle to visualize the MCA beneath the skull.</li>
	<li>Fix with glue the outer part of the tip holding the laser Doppler probe/fiber on top of the left MCA with glue. Then, glue the skin to close the wound around the tip holder. Apply 2-3 drops of hardener glue to speed up the process. Make sure that the laser Doppler fiber is not glued and can be easily removed from the tip holder at any time.</li>
</ol>
3. Transient MCAo model (occlusion)
<ol>
	<li>Turn the mouse into the supine position. Put the snout into the anesthesia cone and fix the paws with tape.</li>
	<li>Disinfect the skin and hair surrounding the chest and make a 2-cm-long midline incision in the neck.</li>
	<li>Use forceps to pull the skin and the&#160;submandibular glands apart. Use retractors to hold the sternomastoid muscle,&#160;expose the surgical field and find the left common carotid artery (CCA). Dissect the CCA free from connective tissue and surrounding nerves (without harming the vagal nerve) and perform a transient ligation before the bifurcation.</li>
	<li>Dissect the external carotid artery (ECA) and tie a permanent knot at the most distal visible part. Place another suture under the ECA, close to the bifurcation, and prepare a loose knot to be used later.</li>
	<li>Dissect the internal carotid artery (ICA) and place a microvascular clip on it, 5 mm over the bifurcation. Make sure not to damage the vagal nerve.</li>
	<li>Cut a small hole into the ECA between the tight and the loose ligations; be careful not to cut the entire ECA.</li>
	<li>Introduce the filament and advance it towards the CCA. Tighten the loose ligation in the ECA around the lumen to shortly&#160;secure the filament in that position and avoid bleeding when removing the microvascular clip.</li>
	<li>Remove the microvascular clip and insert the filament through the ICA until the origin of the MCA is reached by detecting a sharp reduction (&#62;80%) in the cerebral blood flow as measured by the laser Doppler. Fix the filament in this position by further tightening the knot around the ECA. 
	NOTE: When the filament goes toward the appropriate direction, it advances smoothly, and no resistance should be observed.</li>
	<li>Record laser Doppler values before and after filament insertion.</li>
	<li>Remove the retractor and relocate the sternomastoid muscle and the submandibular glands before suturing the wound. Remove the laser Doppler probe, and place the animal in a recovery chamber at 37 &#176;C for 1 h (until filament removal).</li>
</ol>
4. Transient MCAo model (Reperfusion)
<ol>
	<li>Anesthetize the mouse by placing it in the induction chamber with an isoflurane flow rate of 4% until the cessation of spontaneous body movement and vibrissae.</li>
	<li>Apply dexpanthenol eye ointment on both eyes.</li>
	<li>Place the mouse in a prone position in the operation area with its snout in the anesthesia mask. Maintain isoflurane concentration at 4% for another minute, then reduce it and keep it at 2%. Fix the animal&#180;s paws with tape.</li>
	<li>Insert the laser Doppler probe into the probe holder.</li>
	<li>Remove the wound suture, use forceps to pull the skin and the submandibular glands apart. Use retractors to gently pull the sternomastoid muscle and expose the surgical field.</li>
	<li>Loosen the ECA suture that tightens the filament, and gently pull the filament. Avoid damaging the silicone-rubber coating of the filament during the removal.</li>
	<li>Tightly tie the ECA suture.</li>
	<li>Confirm the increase in the cerebral blood flow in the laser Doppler device (&#62;80% of the initial value before reperfusion).</li>
	<li>Record laser Doppler values before and after filament removal.</li>
	<li>Open the transient ligation before the bifurcation from the CCA.</li>
	<li>Remove the retractor, and relocate the sternomastoid muscle and the submandibular glands before suturing the wound. Place the animal in a recovery chamber at 37 &#176;C for 1 h to recover from anesthesia.</li>
	<li>After recovery, return the mice to their cages in a temperature-controlled room.</li>
	<li>Take care of the animals by adding wet food pellets and hydrogel in small Petri dishes on the cage floor until day 3 after the surgery.</li>
	<li>Inject analgesia every 12 h for 3 d after surgery (4 mg/kg Carprofen and 0.1 mg/kg Buprenorphine).</li>
</ol>
5. Sham operation
<ol>
	<li>Perform all procedures as described above, including the ligation of the arteries and the introduction of the filament (steps 1-3.7).</li>
	<li>Remove the filament immediately after its insertion. Then, place the animal in the recovery chamber for 1 h.</li>
	<li>Place the animal in the operation area again, and remove the transient ligation of the CCA to ensure complete cerebral blood flow restoration.</li>
	<li>Suture the wound, and place the animal in a recovery chamber at 37 &#176;C for 1 h to recover from anesthesia. After recovery, return the mice to their cages in a temperature-controlled room.</li>
	<li>Take care of the animals by adding wet food pellets and hydrogel in small Petri dishes on the cage floor until day 3 after surgery.</li>
	<li>Inject analgesia every 12 h for 3 d after surgery (4 mg/kg Carprofen and 0.1 mg/kg Buprenorphine).</li>
</ol>
6. Neuroscore
<ol>
	<li>Perform the Neuroscore always at the same time of the day, and use surgical clothes to maintain a &#34;neutral smell&#34; between individual surgeons.</li>
	<li>Let the mice rest for 30 min in the room with an &#34;open&#34; cage before the test.</li>
	<li>Observe each item in Table 1 and Table 2 for 30 s.</li>
</ol>
7. Intracardiac perfusion
<ol>
	<li>Prepare a 20 mL syringe containing phosphate-buffered saline (PBS)-heparin (2 U/mL) and place it 1 m above the bench to facilitate gravity-driven perfusion. (OPTIONAL: Perform intracardiac perfusion with 4% paraformaldehyde (PFA) using a 20 mL syringe containing 4% PFA in PBS, pH 7.4).</li>
	<li>Inject intrperitoneally 100 &#181;L of ketamine and xylazine (120 and 16&#160; mg/kg body weight, respectively). Wait 5 min and confirm the cessation of spontaneous body movement and vibrissae.</li>
	<li>Fix the animal in a supine position, and disinfect the abdominal body surface with 70% ethanol.</li>
	<li>Make a 3-cm-long incision into the abdomen; cut the diaphragm, the ribs, and sternum to visualize the heart completely.</li>
	<li>Make a small incision in the right atrium, and insert the perfusion cannula into the left ventricle.</li>
	<li>Perfuse with 20 mL of PBS-heparin.</li>
	<li>After perfusion, decapitate the animal and remove the brain.</li>
	<li>Freeze the brain on powdered dry ice and store at -80 &#176;C until further use.</li>
</ol>
8. Infarct volumetry
<ol>
	<li>For cryosectioning, use a cryostat to cut the brains into 20-&#181;m-thick sections every 400 &#181;m. Place the sections on slides, and store the slides at &#8722;80 &#176;C until use.</li>
	<li>Cresyl violet (CV) staining
	<ol>
		<li>Prepare the staining solution by stirring and heating (60 &#176;C) 0.5 g of CV acetate in 500 mL of H2O until the crystals are dissolved. After the solution has cooled, store it in a dark bottle. Reheat to 60 &#176;C and filter before every use.</li>
		<li>Let the slides dry at room temperature for 30 min. Immerse them in 95% ethanol for 15 min, in 70% ethanol for 1 min, and then in 50% ethanol for 1 min.</li>
		<li>Immerse the slides in distilled water for 2 min; refresh the distilled water and place the slides in the water for 1 min. Afterward, immerse the slides in the pre-heated staining solution for 10 min at 60 &#176;C. Wash the slides twice in distilled water for 1 min.</li>
		<li>Immerse the slides in 95% ethanol for 2 min. Place them in 100% ethanol for 5 min; refresh the 100% ethanol and place the slides again in the ethanol for 2 min. Afterward, cover the slides with a mounting medium.</li>
		<li>Analysis (Figure 4C)
		<ol>
			<li>Scan the slides and analyze the indirect infarct volume by the Swanson method12 to correct for edema by using the following&#160;equation: 
			(Ischemic area) = (ischemic region)-((ipsilateral hemisphere)-(contralateral hemisphere))</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ischemic+stroke:+experimental+models+and+reality.">Ischemic stroke: experimental models and reality.</a> Acta Neuropathologica. 133 (2), 245-261 (2017).</li><li>Jones, B. J., Roberts, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rotarod+suitable+for+quantitative+measurements+of+motor+incoordination+in+naive+mice.">A rotarod suitable for quantitative measurements of motor incoordination in naive mice.</a> Naunyn-Schmiedebergs Archiv f&#252;r Experimentelle Pathologie und Pharmakologie. 259 (2), 211 (1968).</li><li>Bouet, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+adhesive+removal+test:+a+sensitive+method+to+assess+sensorimotor+deficits+in+mice.">The adhesive removal test: a sensitive method to assess sensorimotor deficits in mice.</a> Nature Protocols. 4 (10), 1560-1564 (2009).</li><li>Zhang, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+test+for+detecting+long-term+sensorimotor+dysfunction+in+the+mouse+after+focal+cerebral+ischemia.">A test for detecting long-term sensorimotor dysfunction in the mouse after focal cerebral ischemia.</a> Journal of Neuroscience Methods. 117 (2), 207-214 (2002).</li><li>Schallert, T., Fleming, S. M., Leasure, J. L., Tillerson, J. L., Bland, S. 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The authors have no competing interests to disclose.

The present protocol describes an experimental stroke model based on the consensus agreement of a German multicenter research consortium (&#8220;ImmunoStroke&#8221;) to establish a standardized transient MCAo model. The transient MCAo model established by introducing a silicon-coated filament through the ECA to the origin of the MCA is one of the most widely used stroke models to achieve arterial reperfusion after a delimitated occlusion period. Therefore, this procedure can be considered a translationally relevant strok...

Stroke is one of the most common causes of death and disability worldwide. Although there are mainly two distinct forms of stroke, ischemic and hemorrhagic, 80&#8211;85% of all stroke cases are ischemic1. Currently, only two treatments are available for patients with ischemic stroke: pharmacological treatment with recombinant tissue plasminogen activator (rtPA) or mechanical thrombectomy. However, due to the narrow therapeutic time window and multiple exclusion criteria, only a select number of patients can benefit from these specific treatment options. Over the last two decades, preclinical and translational stroke research has focused on the study of neuroprotective approaches. However, all compounds that reached clinical trials have so far shown no improvements for the patient2.&#160;
Since in vitro models cannot accurately reproduce all brain interactions and pathophysiological mechanisms of stroke, animal models are crucial for preclinical stroke research. However, mimicking all aspects of human ischemic stroke in a single animal model is not feasible, as ischemic stroke is a highly complex and heterogeneous disease. For this reason, different ischemic stroke models have been developed over time in different species. Photothrombosis of cerebral arterioles or permanent distal occlusion of the middle cerebral artery (MCA) are commonly used models that induce small and locally defined lesions in the neocortex3,4. Besides those, the most commonly used stroke model is probably the so-called &#8220;filament model,&#8221; in which a transient occlusion of MCA is achieved. This model consists of a transient introduction of a suture filament to the origin of the MCA, leading to an abrupt reduction of the cerebral blood flow and the subsequent large infarction of subcortical and cortical brain regions5. Although most stroke models mimic MCA occlusions 6, the &#34;filament model&#34; allows precise delimitation of the ischemic time. Reperfusion by filament removal mimics the human clinical scenario of cerebral blood flow restoration after spontaneous or therapeutic (rtPA or mechanical thrombectomy) clot lysis. To date, different modifications of this &#8220;filament model&#8221; have been described. In the most common approach, first described by Longa et al. in 19895, a silicon-coated filament is introduced via the common carotid artery (CCA) to the origin of the MCA7. Although it is a widely used approach, this model does not allow complete restoration of the blood flow during reperfusion, as the CCA is permanently ligated after removal of the filament.
Over the past decade, an increasing number of research groups have been interested in modeling stroke in mice using this &#8220;filament model.&#8221; However, the considerable variability of this model and the lack of standardization of the procedures are some of the reasons for the high variability and poor reproducibility of the experimental results and scientific findings reported so far2,8. A potential cause of the current &#8220;replication crisis,&#8221; referring to the low reproducibility among research laboratories, is the non-comparable stroke infarct volumes between research groups using the same experimental methodology9. In fact, after conducting the first preclinical randomized controlled multicenter trial study10, we were able to confirm that the lack of sufficient standardization of this experimental stroke model and the subsequent outcome parameters were the main reasons for the failure of reproducibility in preclinical studies between independent laboratories11. These drastic differences in the resulting infarct sizes, despite using the same stroke model, justifiably pose not only a threat to confirmatory research, but also for scientific collaborations due to the lack of robust and reproducible models.
In light of these challenges, we aimed to develop and describe in detail the procedure for a standardized transient MCAo model as used for the collaborative research efforts within the &#8220;ImmunoStroke&#8221; research consortium (https://immunostroke.de/). This consortium aims to understand the brain-immune interactions underlying the mechanistic principles of stroke recovery. In addition, histological and related functional methods for stroke outcome analysis are presented. All methods are based on established standard operating procedures used in all research laboratories of the ImmunoStroke consortium.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>45&#176; ramp</td>
			<td>H&#38;S Kunststofftechnik</td>
			<td></td>
			<td>height: 18 cm</td>
		</tr>
		<tr>
			<td>5/0 threat</td>
			<td>Pearsalls</td>
			<td>10C103000</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL Syringe</td>
			<td>Braun</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic Acid</td>
			<td>Sigma Life Science</td>
			<td>695092</td>
			<td></td>
		</tr>
		<tr>
			<td>Anesthesia system for isoflurane</td>
			<td>Drager</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bepanthen pomade</td>
			<td>Bayer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>C57Bl/6J mice</td>
			<td>Charles River</td>
			<td>000664</td>
			<td></td>
		</tr>
		<tr>
			<td>Clamp</td>
			<td>FST</td>
			<td>12500-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Clip</td>
			<td>FST</td>
			<td>18055-04</td>
			<td></td>
		</tr>
		<tr>
			<td>Clip holder</td>
			<td>FST</td>
			<td>18057-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Cotons</td>
			<td>NOBA Verbondmitel Danz</td>
			<td>974116</td>
			<td></td>
		</tr>
		<tr>
			<td>Cresyl violet</td>
			<td>Sigma Life Science</td>
			<td>C5042-10G</td>
			<td></td>
		</tr>
		<tr>
			<td>Cryostat</td>
			<td>Thermo Scientific CryoStarNX70</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol 70%</td>
			<td>CLN Chemikalien Laborbedorf</td>
			<td>521005</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol 96%</td>
			<td>CLN Chemikalien Laborbedorf</td>
			<td>522078</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol 99%</td>
			<td>CLN Chemikalien Laborbedorf</td>
			<td>ETO-5000-99-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Filaments</td>
			<td>Doccol</td>
			<td>602112PK5Re</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine 45 angled forceps</td>
			<td>FST</td>
			<td>11251-35</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine forceps</td>
			<td>FST</td>
			<td>11252-23</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine Scissors</td>
			<td>FST</td>
			<td>14094-11</td>
			<td></td>
		</tr>
		<tr>
			<td>Glue</td>
			<td>Orechseln</td>
			<td>BSI-112</td>
			<td></td>
		</tr>
		<tr>
			<td>Hardener Glue</td>
			<td>Drechseln &#38; Mehr</td>
			<td>BSI-151</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating blanket</td>
			<td>FHC DC Temperature Controller</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Abbot</td>
			<td>B506</td>
			<td></td>
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		<tr>
			<td>Isopentane</td>
			<td>Fluka</td>
			<td>59070</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>Inresa Arzneimittel GmbH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Doppler</td>
			<td>Perimed</td>
			<td>PF 5010 LDPM, Periflux System 5000</td>
			<td></td>
		</tr>
		<tr>
			<td>Laser Doppler probe</td>
			<td>Perimed</td>
			<td>91-00123</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline pH: 7.4</td>
			<td>Apotheke Innestadt Uni Munchen</td>
			<td>P32799</td>
			<td></td>
		</tr>
		<tr>
			<td>Recovery chamber</td>
			<td>Mediheat</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Roti-Histokit mounting medium</td>
			<td>Roth</td>
			<td>6638.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Saline solution</td>
			<td>Braun</td>
			<td>131321</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel</td>
			<td>Feather</td>
			<td>02.001.30.011</td>
			<td></td>
		</tr>
		<tr>
			<td>Silicon-coated filaments</td>
			<td>Doccol</td>
			<td>602112PK5Re</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicropscope</td>
			<td>Leica</td>
			<td>M80</td>
			<td></td>
		</tr>
		<tr>
			<td>Superfrost Plus Slides</td>
			<td>Thermo Scientific</td>
			<td>J1800AMNZ</td>
			<td></td>
		</tr>
		<tr>
			<td>Vannas Spring Scissors</td>
			<td>FST</td>
			<td>15000-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylacine</td>
			<td>Albrecht</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

modeling stroke in mice: transient middle cerebral artery occlusion via the external carotid artery

Stroke is the third most common cause of mortality and the leading cause of acquired adult disability in developed countries. To date, therapeutic options are limited to a small proportion of stroke patients within the first hours after stroke. Novel therapeutic strategies are being extensively investigated, especially to prolong the therapeutic time window. These current investigations include the study of important pathophysiological pathways after stroke, such as post-stroke inflammation, angiogenesis, neuronal plasticity, and regeneration. Over the last decade, there has been increasing concern about the poor reproducibility of experimental results and scientific findings among independent research groups. To overcome the so-called &#8220;replication crisis&#8221;, detailed standardized models for all procedures are urgently needed. As an effort within the &#8220;ImmunoStroke&#8221; research consortium (https://immunostroke.de/), a standardized mouse model of transient middle cerebral artery occlusion (MCAo) is proposed. This model allows the complete restoration of the blood flow upon removal of the filament, simulating the therapeutic or spontaneous clot lysis that occurs in a large proportion of human strokes. The surgical procedure of this &#8220;filament&#8221; stroke model and tools for its functional analysis are demonstrated in the accompanying video.

The model described here is a modification of the commonly used &#34;filament&#34; stroke model, which consists of introducing a silicon-coated filament through the ECA to transiently block the origin of the MCA (Figure 1). After removing the filament, only the blood flow in the ECA is permanently ceased, allowing complete recanalization of the CCA and ICA. This allows an adequate reperfusion of the brain (Figure 2), similar to the situation observed after succe...

Watch this Scientific Journal Video about Modeling Stroke in Mice: Transient Middle Cerebral Artery Occlusion via the External Carotid Artery at JoVE.com

Modeling Stroke in Mice: Transient Middle Cerebral Artery Occlusion via the External Carotid Artery

Different models of middle cerebral artery occlusion (MCAo) are used in experimental stroke research. Here, an experimental stroke model of transient MCAo via the external carotid artery (ECA) is described, which aims to mimic human stroke, in which the cerebrovascular thrombus is removed due to spontaneous clot lysis or therapy.

Stroke is the third most common cause of mortality and the leading cause of acquired adult disability in developed countries. To date, therapeutic options ...

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Research

JoVE Journal

Neuroscience

6.8K Views.  LMU Munich. Different models of middle cerebral artery occlusion (MCAo) are used in experimental stroke research. Here, an experimental stroke model of transient MCAo via the external carotid artery (ECA) is described, which aims to mimic human stroke, in which the cerebrovascular thrombus is removed due to spontaneous clot lysis or therapy.

Video: Modeling Stroke in Mice: Transient Middle Cerebral Artery Occlusion via the External Carotid Artery

Focal Cerebral Ischemia Model by Endovascular Suture Occlusion of the Middle Cerebral Artery in the Rat

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable clinical state; in the development of animal models of focal ischemia, however, achieving reproducibility of experimentally induced infarct volume is essential. The rat is a widely used animal model for stroke due to its relatively low animal husbandry costs and to the similarity of its cranial circulation to that of humans2,3. In humans, the middle cerebral artery (MCA) is most commonly affected in stroke syndromes and multiple methods of MCA occlusion (MCAO) have been described to mimic this clinical syndrome in animal models. Because recanalization commonly occurs following an acute stroke in the human, reperfusion after a period of occlusion has been included in many of these models. In this video, we demonstrate the transient endovascular suture MCAO model in the spontaneously hypertensive rat (SHR). A filament with a silicon tip coating is placed intraluminally at the MCA origin for 60 minutes, followed by reperfusion. Note that the optimal occlusion period may vary in other rat strains, such as Wistar or Sprague-Dawley. Several behavioral indicators of stroke in the rat are shown. Focal ischemia is confirmed using T2-weighted magnetic resonance images and by staining brain sections with 2,3,5-triphenyltetrazolium chloride (TTC) 24 hours after MCAO.

Surgical induction of ischemic brain damage in the rat is a widely used model for stroke research. Here we demonstrate the induction of focal cerebral ischemia by occlusion of the middle cerebral artery. Visualization of the resulting infarct by histological staining and magnetic resonance imaging is also shown.

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable ...

Lateral Chronic Cranial Window Preparation Enables In Vivo Observation Following Distal Middle Cerebral Artery Occlusion in Mice

Focal cerebral ischemia (i.e., ischemic stroke) may cause major brain injury, leading to a severe loss of neuronal function and consequently to a host of motor and cognitive disabilities. Its high prevalence poses a serious health burden, as stroke is among the principal causes of long-term disability and death worldwide1. Recovery of neuronal function is, in most cases, only partial. So far, treatment options are very limited, in particular due to the narrow time window for thrombolysis2,3. Determining methods to accelerate recovery from stroke remains a prime medical goal; however, this has been hampered by insufficient mechanistic insights into the recovery process. Experimental stroke researchers frequently employ rodent models of focal cerebral ischemia. Beyond the acute phase, stroke research is increasingly focused on the sub-acute and chronic phase following cerebral ischemia. Most stroke researchers apply permanent or transient occlusion of the MCA in mice or rats. In patients, occlusions of the MCA are among the most frequent causes of ischemic stroke4. Besides proximal occlusion of the MCA using the filament model, surgical occlusion of the distal MCA is probably the most frequently used model in experimental stroke research5. Occlusion of a distal (to the branching of the lenticulo-striate arteries) MCA branch typically spares the striatum and primarily affects the neocortex. Vessel occlusion can be permanent or transient. High reproducibility of lesion volume and very low mortality rates with respect to the long-term outcome are the main advantages of this model. Here, we demonstrate how to perform a chronic cranial window (CW) preparation lateral to the sagittal sinus, and afterwards how to surgically induce a distal stroke underneath the window using a craniotomy approach. This approach can be applied for sequential imaging of acute and chronic changes following ischemia via epi-illuminating, confocal laser scanning, and two-photon intravital microscopy.

Lateral Chronic Cranial Window Preparation Enables In Vivo Observation Following Distal Middle Cerebral Artery Occlusion in Mice

Surgical occlusion of a distal middle cerebral artery branch (MCAo) is a frequently used model in experimental stroke research. This manuscript describes the basic technique of permanent MCAo, combined with the insertion of a lateral cranial window, which offers the opportunity for longitudinal intravital microscopy in mice.

Focal cerebral ischemia (i.e., ischemic stroke) may cause major brain injury, leading to a severe loss of neuronal function and consequently to a host of ...

A Model for Encephalomyosynangiosis Treatment after Middle Cerebral Artery Occlusion-Induced Stroke in Mice

There is no effective treatment available for most patients suffering with ischemic stroke, making development of novel therapeutics imperative. The brain's ability to self-heal after ischemic stroke is limited by inadequate blood supply in the impacted area. Encephalomyosynangiosis (EMS) is a neurosurgical procedure that achieves angiogenesis in patients with moyamoya disease. It involves craniotomy with placement of a vascular temporalis muscle graft on the ischemic brain surface. EMS has never been studied in the setting of acute ischemic stroke in mice. The hypothesis driving this study is that EMS enhances cerebral angiogenesis at the cortical surface surrounding the muscle graft. The protocol shown here describes the procedure and provides initial data supporting the feasibility and efficacy of the EMS approach. In this protocol, after 60 min of transient middle cerebral artery occlusion (MCAo), mice were randomized to either MCAo or MCAo + EMS treatment. The EMS was performed 3-4 h after occlusion. The mice were sacrificed 7 or 21 days after MCAo or MCAo + EMS treatment. Temporalis graft viability was measured using nicotinamide adenine dinucleotide reduced-tetrazolium reductase assay. A mouse angiogenesis array quantified angiogenic and neuromodulating protein expression. Immunohistochemistry was used to visualize graft bonding with brain cortex and change in vessel density. The preliminary data here suggest that grafted muscle remained viable 21 days after EMS. Immunostaining showed successful graft implantation and increase in vessel density near the muscle graft, indicating increased angiogenesis. Data show that EMS increases fibroblast growth factor (FGF) and decreases osteopontin levels after stroke. Additionally, EMS after stroke did not increase mortality suggesting that protocol is safe and reliable. This novel procedure is effective and well-tolerated and has the potential to provide information of novel interventions for enhanced angiogenesis after acute ischemic stroke.

The protocol aims to provide methods for encephalomyosynangiosis-grafting of a vascular temporalis muscle flap on the pial surface of ischemic brain tissue-for the treatment of non-moyamoya acute ischemic stroke. The approach's efficacy in increasing angiogenesis is evaluated using a transient middle cerebral artery occlusion model in mice.

There is no effective treatment available for most patients suffering with ischemic stroke, making development of novel therapeutics imperative. The ...

Establishing a Transcranial Middle Cerebral Artery Occlusion Mice Model

A Modified Transcranial Middle Cerebral Artery Occlusion Model to Study Stroke Outcomes in Aged Mice

In experimental stroke research, middle cerebral artery occlusion (MCAO) with an intraluminal filament is widely used to model ischemic stroke in mice. The filament MCAO model typically exhibits a massive cerebral infarction in C57Bl/6 mice that sometimes includes brain tissue in the territory supplied by the posterior cerebral artery, which is largely due to a high incidence of posterior communicating artery atresia. This phenomenon is considered a major contributor to the high mortality rate observed in C57Bl/6 mice during long-term stroke recovery after filament MCAO. Thus, many chronic stroke studies exploit distal MCAO models. However, these models usually produce infarction only in the cortex area, and consequently, the assessment of post-stroke neurologic deficits could be a challenge. This study has established a modified transcranial MCAO model in which the MCA at the trunk is partially occluded either permanently or transiently via a small cranial window. Since the occlusion location is relatively proximal to the origin of the MCA, this model generates brain damage in both the cortex and striatum. Extensive characterization of this model has demonstrated an excellent long-term survival rate, even in aged mice, as well as readily detectable neurologic deficits. Therefore, the MCAO mouse model described here represents a valuable tool for experimental stroke research.

Author Spotlight: Innovative Techniques and Future Directions in Stroke Research 

This protocol demonstrates a unique mouse stroke model with a medium-sized infarct and an excellent survival rate. This model allows preclinical stroke researchers to extend the ischemia duration, use aged mice, and assess long-term functional outcomes.

In experimental stroke research, middle cerebral artery occlusion (MCAO) with an intraluminal filament is widely used to model ischemic stroke in mice. ...

A Model of Transient Cerebral Ischemia by Occlusion of Middle Cerebral Artery

Transient Middle Cerebral Artery Occlusion Model of Stroke

Stroke stands as a major cause of death or chronic disability globally. Nevertheless, existing optimal treatments are limited to reperfusion therapies during the acute phase of ischemic stroke. To gain insights into stroke physiopathology and develop innovative therapeutic approaches, in vivo rodent models of stroke play a fundamental role. The availability of genetically modified animals has particularly propelled the use of mice as experimental stroke models.
In stroke patients, occlusion of the middle cerebral artery (MCA) is a common occurrence. Consequently, the most prevalent experimental model involves intraluminal occlusion of the MCA, a minimally invasive technique that doesn't require craniectomy. This procedure involves inserting a monofilament through the external carotid artery (ECA) and advancing it through the internal carotid artery (ICA) until it reaches the branching point of the MCA. After a 45 min arterial occlusion, the monofilament is removed to allow reperfusion. Throughout the process, cerebral blood flow is monitored to confirm the reduction during occlusion and subsequent recovery upon reperfusion. Neurological and tissue outcomes are evaluated using behavioral tests and magnetic resonance imaging (MRI) studies.

Author Spotlight: Assessing Ischemic Stroke Damage Through Middle Cerebral Artery Occlusion Model 

This protocol describes the model of transient focal cerebral ischemia in mice through intraluminal occlusion of the middle cerebral artery. Additionally, examples of outcome assessment are shown using magnetic resonance imaging and behavioral tests.

Stroke stands as a major cause of death or chronic disability globally. Nevertheless, existing optimal treatments are limited to reperfusion therapies ...

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

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

Ischemic stroke remains the predominant cause of mortality and functional impairment among the adult populations globally. Only a minority of ischemic stroke patients are eligible to receive intravascular thrombolysis or mechanical thrombectomy therapy within the optimal time window. Among those stroke survivors, around two-thirds suffer neurological dysfunctions over an extended period. Establishing a stable and repeatable experimental ischemic stroke model is extremely significant for further investigating the pathophysiological mechanisms and developing effective therapeutic strategies for ischemic stroke. The middle cerebral artery (MCA) represents the predominant location of ischemic stroke in humans, with the MCA occlusion serving as the frequently employed model of focal cerebral ischemia. In this protocol, we describe the methodology of establishing the distal MCA occlusion (dMCAO) model through transcranial electrocoagulation in C57BL/6 mice. Since the occlusion site is located at the cortical branch of MCA, this model generates a moderate infarcted lesion restricted to the cortex. Neurological behavioral and histopathological characterization have demonstrated visible motor dysfunction, neuron degeneration, and pronounced activation of microglia and astrocytes in this model. Thus, this dMCAO mouse model provides a valuable tool for investigating the ischemiastroke and worth of popularization.

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

Here, we present a protocol to establish a distal middle cerebral artery occlusion (dMCAO) model through transcranial electrocoagulation in C57BL/6J mice and evaluate the subsequent neurological behavior and histopathological features.

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

Surgical Procedure for Transient Middle Cerebral Artery Occlusion

Distal Middle Artery Occlusion Procedure to Induce Ischemic Stroke in Mice

Neurological Behavioral Tests in Distal Middle Artery Occluded Mice to Study Ischemic Stroke Outcomes

Optimization of the Longa Middle Cerebral Artery Occlusion Method for Complete Reperfusion

The middle cerebral artery occlusion model serves as the primary animal model for studying ischemic stroke. Despite being used in research for over three decades, its standardization remains inadequate. Predominantly conducted on rats and mice, the procedure poses challenges due to mice's smaller and more fragile nature. Unlike the Koizumi common carotid artery method, the Longa external carotid artery is the sole intraluminal filament stroke model ensuring complete reperfusion post-ischemia. This aspect holds critical significance for studies investigating reperfusion phenomena. The surgical modifications demonstrated in this article ensure continuous blood flow from the common carotid artery throughout the ischemic phase and after the reperfusion onset. The goal of these modifications is to selectively occlude the middle cerebral artery by keeping the perfusion uninterrupted in branches proximal to the middle cerebral artery during the ischemia period. Furthermore, the onset of reperfusion is sudden and can be precisely controlled, thereby modeling endovascular thrombectomy in human medicine more accurately. Our aim in presenting this comprehensive video article is to ease the training of new surgeons and promote the standardization of surgical procedures within the scientific community.

This protocol presents a step-by-step guide for researchers to perform the middle cerebral artery occlusion procedure on mice using the modified Longa external carotid artery method. Modifications presented in this article aim to increase the accuracy of middle cerebral artery occlusion and ensure complete reperfusion.

The middle cerebral artery occlusion model serves as the primary animal model for studying ischemic stroke. Despite being used in research for over three ...