Study supported by grant PID2020-113202RB-I00 funded by Ministerio de Ciencia e Innovaci&#243;n (MCIN)/Agencia Estatal de Investigaci&#243;n (AEI), Gobierno de Espa&#241;a/10.13039/501100011033 and &#34;European Regional Development Fund (ERDF). A way of making Europe&#34;. NCC and MAR had predoctoral fellowships (PRE2021-099481 and PRE2018-085737, respectively) funded by MCIN/AEI/ 10.13039/501100011033 and by &#34;European Social Fund (ESF) Investing in your future&#34;.&#160;We thank Francisca Ruiz-Ja&#233;n and Leonardo M&#225;rquez-Kisinousky for their technical support. We acknowledge the support of the MRI imaging facility of Institut d&#39;Investigacions Biom&#232;diques August Pi i Sunyer (IDIBAPS). The Centres de Recerca de Catalunya (CERCA) Program of Generalitat de Catalunya supports IDIBAPS.

Animal work was conducted following the Catalan and Spanish laws (Real Decreto 53/2013) and the European Directives, with approval of the ethical committee (Comit&#233; &#200;tic d&#39;Experimentaci&#243; Animal, CEEA) of the University of Barcelona, and the local regulatory bodies of the Generalitat de Catalunya. Studies are reported in compliance with the ARRIVE guidelines. This procedure is designed to be performed in adult mice, starting at 8 weeks of age, with no age limit. Examples of the surgical procedure developed in C57BL/6 mice of 10-12 weeks of age are provided here. Anatomical differences depending on mouse strain should be considered.
1. Animal preparation
<ol>
	<li>Before starting the surgical procedure, gather and sterilize all the required materials and tools. Set up the operating table with all the necessary surgical materials (listed in the Table of Materials).</li>
	<li>Anesthetize the animal using isoflurane inhalation in a mixture of oxygen and nitrous oxide (30%/70%).</li>
	<li>Administer buprenorphine (see Table of Materials) subcutaneously at a dosage of 0.05 mg/kg BW to provide analgesia and alleviate any pain and discomfort. 
	NOTE: Analgesia is mandatory, but different protocols are accepted. Pain and discomfort signs must also be controlled during the first days after MCAo (see step 4). Apply corrective solutions when necessary.</li>
	<li>Place the animal in an anesthesia induction box (see Table of Materials) with 5% isoflurane until it reaches a state of deep anesthesia (loss of reflex in paw puncture and ocular reflex).</li>
	<li>Position the mouse on the operating table and decrease the level of isoflurane to 1.5%, delivered by face mask. Apply vet ointment to avoid eye dryness during the procedure.</li>
	<li>Maintain body temperature at 37 &#177; 0.5 &#176;C controlled by a rectal probe connected to a heating pad (see Table of Materials).</li>
	<li>Shave the ventral part of the neck and the head (calvaria) with an electric razor. Carefully remove fur debris and disinfect the skin areas three times in circular movements with iodine-based disinfectant and 70% alcohol. 
	.</li>
</ol>
2. Cerebral blood flow (CBF) assessment with laser Doppler flowmetry (LDF)
<ol>
	<li>With scissors, make an incision on the skin of the head, in the direction of the sagittal suture, from the ears to the area between the eyes.</li>
	<li>Retract the skin and remove the periosteum on the right side of the skull.</li>
	<li>Find the coordinates (2.5 mm lateral from Bregma) and attach the Doppler holder (see Table of Materials) using cyanoacrylate. After the glue has dried, connect the Doppler probe and check for the correct signal readout.</li>
</ol>
3. Transient middle cerebral artery occlusion (tMCAo)
<ol>
	<li>Turn the mouse over to the supine position, and fix it to the surgical table with medical tape.</li>
	<li>Make a midline incision on the neck. Laterally pull back the skin and salivary glands using retractors (see Table of Materials) to expose the carotid territory.</li>
	<li>Identify the vascular anatomy of the common carotid artery (CCA), the ICA, and the ECA, as well as the different arteries derived from them (maxillary and lingual, superior thyroid, occipital, and pterygopalatine) (Figure 1A).</li>
	<li>Detach the main arteries from the adjacent connective tissue so that they can be handled. 
	NOTE: Take special care not to damage the nerves, especially the vagus nerve, which runs parallel to the CCA.</li>
	<li>Wrap a 6-0 silk suture (see Table of Materials) around the ECA at the maxillary/lingual bifurcation. Tightly secure a knot to permanently interrupt the circulation.</li>
	<li>Pass a second suture around the same artery, between the first knot and the CCA bifurcation, and keep this knot loose.</li>
	<li>Place a third thread around the CCA and tie a slip knot that can be easily untied. 
	NOTE: This can also be carried out with a vascular clip, but the thread allows more movement and flexibility. At this stage it is possible to observe a first decrease in CBF in the LDF signal.</li>
	<li>Place a vascular clip (see Table of Materials) interrupting blood circulation from the ICA.</li>
	<li>Make a small incision in the ECA, close to the area where the tight knot is located.</li>
	<li>Insert the monofilament until the thick coating has completely entered the arterial lumen.</li>
	<li>Tighten the second knot to hold the monofilament inside the artery and prevent the pressure exerted by the blood from pushing it out (Figure 1B).</li>
	<li>Remove the vascular clip from the ICA.</li>
	<li>Cut the ECA below the first knot and rotate the stump to orient it in the direction of the ICA (Figure 1C).</li>
	<li>Advance the monofilament via the ICA until the point where the MCA branches out. 
	NOTE: The occlusion is reflected in an abrupt blood flow drop in the LDF readout. We consider a successful occlusion when the drop in CBF is greater than 70% from the basal value. If CBF measurement systems are not available, the point of occlusion can be noted by the resistance to advance, which in adult mice is usually about 11 mm from the bifurcation of the CCA.
	<ol>
		<li>If anesthesia is continued during the occlusion period, monitor the mouse and keep it under constant observation for 45 min.</li>
		<li>In case the mouse is awakened during the occlusion period, suture the skin of the neck with several stitches. Without disconnecting the LDF probe, place the mouse in the temperature-controlled box, allowing recovery from anesthesia. 
		NOTE: It is common for the mouse to exhibit spontaneous circling behavior during this period, indicative of successful occlusion.</li>
		<li>After 40 min, anesthetize the mouse again following the same anesthesia and disinfection procedures as indicated in points 1.4, 1.5 and 1.7.&#160;Place it back on the surgical table, and remove the stitches from the neck.</li>
	</ol>
	</li>
	<li>After 45 min of occlusion, loosen the knot holding the monofilament in place. Pull slowly and gently on the filament and check that tissue recanalization occurs.</li>
	<li>Pull out the filament and tighten the knot to prevent blood loss.</li>
	<li>Untie the CCA knot. Ensure that there is no arterial wall damage.</li>
	<li>Remove the retractors and re-position the muscles, glands, and skin. Suture the skin (6-0) and apply disinfectant.</li>
	<li>Disconnect the Doppler probe, and detach the holder. Suture and disinfect the skin of the head.</li>
	<li>During the recovery period from anesthesia, leave the mouse in a cage provided with a heater to maintain the temperature. Keep it under constant observation until it is fully recovered from anesthesia. After recovery, the mouse can be returned to its cage. 
	&#8203;NOTE: Housing with social enrichment is highly recommended. However, never mix operated mice with non-operated mice in the same cage without any physical separation in order to prevent aggression.</li>
</ol>
4. Post-operative care
<ol>
	<li>Periodically supervise the animals following the procedures and regulations established according to the local regulations. Provide analgesic treatment on the appropriate schedule to minimize pain after the surgery. 
	NOTE: In the present study, the same analgesic was applied as at the beginning of the intervention (Buprenorphine 0.05mg/kg BW) at 6 h and 24 h after surgery.</li>
	<li>Perform euthanasia when the supervision parameters indicate so, following the institutionally approved protocols.</li>
	<li>Daily monitor the weight of the animals. Provide soft food to the animals during the first few days after surgery. In addition, hydrate them by subcutaneous injection of saline (200 &#181;L) immediately after surgery and periodically thereafter if it is observed that the mouse does not hydrate on its own. Arrange food and water in a way that is easily accessible to the animal.</li>
	<li>Once the in vivo study is completed, anesthetize the mice, euthanize them, and remove the brain tissue for further histopathological analysis (if needed).</li>
</ol>

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

<ol><li>Siddiqi, A. Z., Wadhwa, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Treatment+of+acute+stroke%3A+current+practices+and+future+horizons%5BTitle%5D)+AND+%22Cardiovascular+Revascularization+Medicine%22%5BJournal%5D)">Treatment of acute stroke: current practices and future horizons.</a> Cardiovascular Revascularization Medicine. 49, 56-65 (2023).</li>
<li>Tamura, A., Graham, D. I., McCulloch, J., Teasdale, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Focal+cerebral+ischemia+in+the+rat%3A+1.+Description+of+technique+and+early+neuropathological+consequences+following+middle+cerebral+artery+occlusion%5BTitle%5D)+AND+%22Journal+of+Cerebral+Blood+Flow+%26+Metabolism%22%5BJournal%5D)">Focal cerebral ischemia in the rat: 1. Description of technique and early neuropathological consequences following middle cerebral artery occlusion.</a> Journal of Cerebral Blood Flow & Metabolism. 1, 53-60 (1981).</li>
<li>Koizumi, J., Nakazawa, T., Ooneda, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Experimental+studies+of+ischemic+brain+edema.+A+new+experimental+model+of+cerebral+embolism+in+rats+in+which+recirculation+can+be+introduced+in+the+ischemic+area%5BTitle%5D)+AND+%22Japanese+Journal+of+Stroke%22%5BJournal%5D)">Experimental studies of ischemic brain edema. A new experimental model of cerebral embolism in rats in which recirculation can be introduced in the ischemic area.</a> Japanese Journal of Stroke. 8, 1-8 (1986).</li>
<li>Longa, E. Z., Weinstein, P. R., Carlson, R., Cummins, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Reversible+middle+cerebral+artery+occlusion+without+craniectomy+in+rats%5BTitle%5D)+AND+%22Stroke%22%5BJournal%5D)">Reversible middle cerebral artery occlusion without craniectomy in rats.</a> Stroke. 20 (1), 84-91 (1989).</li>
<li>Hossmann, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cerebral+ischemia%3A+Models%2C+methods%2C+and+outcomes%5BTitle%5D)+AND+%22Neuropharmacology%22%5BJournal%5D)">Cerebral ischemia: Models, methods, and outcomes.</a> Neuropharmacology. 55, 257-270 (2008).</li>
<li>Seto, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Induction+of+ischemic+stroke+in+awake+freely+moving+mice+reveals+that+isoflurane+anesthesia+can+mask+the+benefits+of+a+neuroprotection+therapy%5BTitle%5D)+AND+%22Frontiers+in+Neuroenergetics%22%5BJournal%5D)">Induction of ischemic stroke in awake freely moving mice reveals that isoflurane anesthesia can mask the benefits of a neuroprotection therapy.</a> Frontiers in Neuroenergetics. 6, 1(2014).</li>
<li>Díaz-Marugan, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Poststroke+lung+infection+by+opportunistic+commensal+bacteria+is+not+mediated+by+their+expansion+in+the+gut+microbiota%5BTitle%5D)+AND+%22Stroke%22%5BJournal%5D)">Poststroke lung infection by opportunistic commensal bacteria is not mediated by their expansion in the gut microbiota.</a> Stroke. 54 (7), 1875-1887 (2023).</li>
<li>Xie, L., Kang, H., Nedergaard, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+novel+model+of+transient+occlusion+of+the+middle+cerebral+artery+in+awake+mice%5BTitle%5D)+AND+%22Journal+of+Natural+Sciences%22%5BJournal%5D)">A novel model of transient occlusion of the middle cerebral artery in awake mice.</a> Journal of Natural Sciences. 2 (2), e176(2016).</li>
<li>Arbaizar-Rovirosa, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Aged+lipid-laden+microglia+display+impaired+responses+to+stroke%5BTitle%5D)+AND+%22EMBO+Molecular+Medicine%22%5BJournal%5D)">Aged lipid-laden microglia display impaired responses to stroke.</a> EMBO Molecular Medicine. 15 (2), e17175(2023).</li>
<li>Orsini, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Targeting+mannose-binding+lectin+confers+long-lasting+protection+with+a+surprisingly+wide+therapeutic+window+in+cerebral+ischemia%5BTitle%5D)+AND+%22Circulation%22%5BJournal%5D)">Targeting mannose-binding lectin confers long-lasting protection with a surprisingly wide therapeutic window in cerebral ischemia.</a> Circulation. 126 (12), 1484-1494 (2012).</li>
<li>Majid, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Differences+in+vulnerability+to+permanent+focal+cerebral+ischemia+among+3+common+mouse+strains%5BTitle%5D)+AND+%22Stroke%22%5BJournal%5D)">Differences in vulnerability to permanent focal cerebral ischemia among 3 common mouse strains.</a> Stroke. 31, 2707-2714 (2000).</li>
<li>Rogers, D. C., Campbell, C. A., Stretton, J. L., Mackay, K. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Correlation+between+motor+impairment+and+infarct+volume+after+permanent+and+transient+middle+cerebral+artery+occlusion+in+the+rat%5BTitle%5D)+AND+%22Stroke%22%5BJournal%5D)">Correlation between motor impairment and infarct volume after permanent and transient middle cerebral artery occlusion in the rat.</a> Stroke. 28, 2060-2065 (1997).</li>
<li>Hedna, V. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Validity+of+Laser+Doppler+flowmetry+in+predicting+outcome+in+murine+intraluminal+middle+cerebral+artery+occlusion+stroke%5BTitle%5D)+AND+%22Journal+of+Vascular+and+Interventional+Neurology%22%5BJournal%5D)">Validity of Laser Doppler flowmetry in predicting outcome in murine intraluminal middle cerebral artery occlusion stroke.</a> Journal of Vascular and Interventional Neurology. 8 (3), 74-82 (2015).</li>
<li>Yin, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Laser+speckle+contrast+imaging+for+blood+flow+monitoring+in+predicting+outcomes+after+cerebral+ischemia-reperfusion+injury+in+mice%5BTitle%5D)+AND+%22BMC+Neuroscience%22%5BJournal%5D)">Laser speckle contrast imaging for blood flow monitoring in predicting outcomes after cerebral ischemia-reperfusion injury in mice.</a> BMC Neuroscience. 23, 80(2022).</li>
<li>Thakkar, P. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Therapeutic+relevance+of+elevated+blood+pressure+after+ischemic+stroke+in+the+hypertensive+rats%5BTitle%5D)+AND+%22Hypertension%22%5BJournal%5D)">Therapeutic relevance of elevated blood pressure after ischemic stroke in the hypertensive rats.</a> Hypertension. 75 (3), 740-747 (2020).</li>
<li>Yu, X., Feng, Y., Liu, R., Chen, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hypothermia+protects+mice+against+ischemic+stroke+by+modulating+macrophage+polarization+through+upregulation+of+interferon+regulatory+factor-4%5BTitle%5D)+AND+%22Journal+of+Inflammation+Research%22%5BJournal%5D)">Hypothermia protects mice against ischemic stroke by modulating macrophage polarization through upregulation of interferon regulatory factor-4.</a> Journal of Inflammation Research. 14, 1271-1281 (2021).</li>
<li>Denorme, F., Portier, I., Kosaka, Y., Campbell, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hyperglycemia+exacerbates+ischemic+stroke+outcome+independent+of+platelet+glucose+uptake%5BTitle%5D)+AND+%22Journal+of+Thrombosis+and+Haemostasis%22%5BJournal%5D)">Hyperglycemia exacerbates ischemic stroke outcome independent of platelet glucose uptake.</a> Journal of Thrombosis and Haemostasis. 19, 536-546 (2021).</li>
</ol>

The authors declare no conflicts of interest.

The intraluminal tMCAo procedure is the most commonly used model of focal brain ischemia with reperfusion in basic research. Currently, mice are the preferred animal model due to the availability of genetically modified strains. However, it&#39;s essential to acknowledge that genetically modified mice and their genetic backgrounds can impact brain vascularization. The presence of collateral circulation and anastomoses between different arterial territories can significantly influence the outcomes of experimental procedur...

Stroke is a devastating disease that affects approximately 15 million people worldwide annually, according to the WHO. Around one-third of patients succumb to the condition, while another third experience permanent disability. Stroke is a complex pathology involving various cell types, such as neural and peripheral immune cells, vasculature, and systemic responses1. The intricate network of reactions triggered by stroke at the systems level cannot be currently replicated using in vitro models. Thus, experimental animal models are essential to delve into the disease&#39;s mechanisms and to develop and test new therapies. Currently, early tissue reperfusion is the only approved intervention, either through thrombolysis with tissue-type plasminogen activator (tPA) or endovascular thrombectomy1.
Occlusions of the middle cerebral artery (MCA) are frequent in stroke patients. Consequently, rodent models of transient MCA occlusion (tMCAo) were initially developed in rats2,3,4. Nowadays, genetically modified mice are the most commonly used animals in experimental stroke models. In this study, we describe a minimally invasive model of intraluminal tMCAo in mice. The approach is performed via the carotid artery at the neck level, without craniectomy.
The duration of the occlusion period is a critical factor that determines the extent of the ischemic lesion. Even short occlusions of 10 min can cause selective neuronal death without an apparent infarction, while longer occlusions, typically lasting 30 to 60 min, result in some degree of cerebral infarction. Unlike the proximal and distal branches of the MCA that supply the cortex and have collaterals, the lenticulo-striatal arteries providing blood to the striatum lack collaterals5. As a consequence, there is a greater reduction of blood flow in the striatum than in the cortex after tMCAo. Thus, occlusions of 30 min or less generally affect the striatum but not the cortex, whereas longer occlusions, from 45 min onwards, often generate an ischemic lesion in the entire MCA territory, including the striatum and dorsolateral cortex.
To ensure the well-being of the mice, we administer analgesics prior to the procedure and use anesthesia during surgery. Nevertheless, anesthesia can potentially introduce artificial alterations in the physiology of the mouse and affect some outcome measures6. The surgical intervention, when performed by experienced personnel, usually lasts about 15 min for inducing MCAo. Subsequently, the total time under anesthesia depends on the occlusion period. For experiments where minimizing anesthesia is crucial, an alternative step in the procedure involves discontinuing anesthesia during the occlusion period and limiting it only to the surgical steps for inserting and withdrawing the filament occluding the MCA. This approach reduces the duration of anesthesia and minimizes its potential artifactual effects on the experimental model7,8. Therefore, the method of inducing transient focal ischemia is presented by intraluminal occlusion of the MCA with two variants: with the mouse anesthetized during the entire occlusion period or with the mouse awake during this period. In either case, a sham surgery should be performed in parallel with the intervention carried out on the ischemic mice. Additionally, data on outcome assessment is provided as measured by behavioral tests and MRI at various time points after reperfusion. Finally, the main factors to consider when implementing the experimental procedure are discussed.

<table><tbody><tr><td>6/0 suture&amp;nbsp;</td><td>Arago</td><td></td><td>Vascular ligatures</td></tr><tr><td>6/0 suture with curved needle</td><td>Arago</td><td></td><td>Skin sutures</td></tr><tr><td>9 mg/mL Saline</td><td>Fresenius Kabi</td><td>CN616003 EC</td><td>For hydration</td></tr><tr><td>Anaesthesia system</td><td>SurgiVet</td><td></td><td></td></tr><tr><td>Blunt retractors, 1 mm wide</td><td>Fine Science Tools</td><td>18200-09</td><td></td></tr><tr><td>Buprenorfine</td><td>Buprex</td><td></td><td>For pain relief</td></tr><tr><td>Clamp applying forceps</td><td>Fine Science Tools</td><td>S&amp;amp;T CAF4</td><td></td></tr><tr><td>Dumont mini forceps</td><td>Fine Science Tools</td><td>M3S 11200-10</td><td></td></tr><tr><td>Forceps</td><td>Fine Science Tools</td><td>91106-12</td><td></td></tr><tr><td>Glue</td><td>Loctite</td><td></td><td>To stick LDF probe to the skull</td></tr><tr><td>Grip Strength Meter</td><td>IITC Life Science Inc.</td><td>#2200</td><td></td></tr><tr><td>Isoflurane</td><td>B-Braun</td><td>CN571105.8</td><td></td></tr><tr><td>LDF Perimed</td><td>Perimed</td><td>Periflux System 5000</td><td></td></tr><tr><td>LDF Probe Holders</td><td>Perimed</td><td>PH 07-4</td><td></td></tr><tr><td>Medical tape</td><td></td><td></td><td></td></tr><tr><td>MRI magnet</td><td>Bruker BioSpin, Ettlingen, Germany</td><td></td><td>BioSpec 70/30 horizontal animal scanner&amp;nbsp;</td></tr><tr><td>Needle Holder with Suture Cutter</td><td>Fine Science Tools</td><td>12002-14</td><td></td></tr><tr><td>Nylon filament</td><td>Doccol</td><td>701912PK5Re</td><td></td></tr><tr><td>Recovery cage with heating pad</td><td></td><td></td><td></td></tr><tr><td>Sirgical scissors</td><td>Fine Science Tools</td><td>91401-12</td><td></td></tr><tr><td>Small vessel cauterizer kit</td><td>Fine Science Tools</td><td>18000-00</td><td></td></tr><tr><td>Stereomicroscope and cold light</td><td>Leica</td><td>M60</td><td></td></tr><tr><td>Suture tying forceps</td><td>Fine Science Tools</td><td>18025-10</td><td></td></tr><tr><td>Thermostat, rectal probe and mouse pad</td><td>Letica Science Instruments</td><td>LE 13206</td><td></td></tr><tr><td>Vannas spring scissors (4mm cutting edge)</td><td>Fine Science Tools</td><td>15019-10</td><td></td></tr><tr><td>Vascular clamps</td><td>Fine Science Tools</td><td>00396-01</td><td></td></tr></tbody></table>

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.

There are different approaches to evaluate the outcome of the tMCAo procedure. In vivo neuroimaging methods (MRI) and behavioral testing are utilized here.
Mice develop ischemic lesions in the brain, mainly affecting the territory supplied by the MCA ipsilateral to the occlusion, such as the striatum and dorsolateral cortex. Several methods exist to determine the extent of the lesion, including 2,3,5-triphenyltetrazolium chloride (TTC) tissue staining, histological staining (hematoxyl...

Watch this Scientific Journal Video about Assessing Ischemic Stroke Damage Through Middle Cerebral Artery Occlusion Model at JoVE.com

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.

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 ...

transient-middle-cerebral-artery-occlusion-model-of-stroke

Research

JoVE Journal

Neuroscience

1.8K Views.  Spanish National Research Council (CSIC). 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.

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

Mouse Model of Middle Cerebral Artery Occlusion

Stroke is the most common fatal neurological disease in the United States 1. The majority of strokes (88%) result from blockage of blood vessels in the brain (ischemic stroke) 2. Since most ischemic strokes (~80%) occur in the territory of middle cerebral artery (MCA) 3, many animal stroke models that have been developed have focused on this artery. The intraluminal monofilament model of middle cerebral artery occlusion (MCAO) involves the insertion of a surgical filament into the external carotid artery and threading it forward into the internal carotid artery (ICA) until the tip occludes the origin of the MCA, resulting in a cessation of blood flow and subsequent brain infarction in the MCA territory 4. The technique can be used to model permanent or transient occlusion 5. If the suture is removed after a certain interval (30 min, 1 h, or 2 h), reperfusion is achieved (transient MCAO); if the filament is left in place (24 h) the procedure is suitable as a model of permanent MCAO. This technique does not require craniectomy, a neurosurgical procedure to remove a portion of skull, which may affect intracranial pressure and temperature 6. It has become the most frequently used method to mimic permanent and transient focal cerebral ischemia in rats and mice 7,8. To evaluate the extent of cerebral infarction, we stain brain slices with 2,3,5-triphenyltetrazolium chloride (TTC) to identify ischemic brain tissue 9. In this video, we demonstrate the MCAO method and the determination of infarct size by TTC staining.

We demonstrate in the video a method for producing a middle cerebral artery occlusion in adult mice using an intraluminal monofilament. We also show how to evaluate the extent of cerebral infarction by 2,3,5-triphenyltetrazolium chloride (TTC) staining.

Stroke is the most common fatal neurological disease in the United States 1. The majority of strokes (88%) result from blockage of blood vessels in the ...

Medicine

Permanent Cerebral Vessel Occlusion via Double Ligature and Transection

Stroke is a leading cause of death, disability, and socioeconomic loss worldwide. The majority of all strokes result from an interruption in blood flow (ischemia) 1. Middle cerebral artery (MCA) delivers a great majority of blood to the lateral surface of the cortex 2, is the most common site of human stroke 3, and ischemia within its territory can result in extensive dysfunction or death 1,4,5. Survivors of ischemic stroke often suffer loss or disruption of motor capabilities, sensory deficits, and infarct. In an effort to capture these key characteristics of stroke, and thereby develop effective treatment, a great deal of emphasis is placed upon animal models of ischemia in MCA.
Here we present a method of permanently occluding a cortical surface blood vessel. We will present this method using an example of a relevant vessel occlusion that models the most common type, location, and outcome of human stroke, permanent middle cerebral artery occlusion (pMCAO). In this model, we surgically expose MCA in the adult rat and subsequently occlude via double ligature and transection of the vessel. This pMCAO blocks the proximal cortical branch of MCA, causing ischemia in all of MCA cortical territory, a large portion of the cortex. This method of occlusion can also be used to occlude more distal portions of cortical vessels in order to achieve more focal ischemia targeting a smaller region of cortex. The primary disadvantages of pMCAO are that the surgical procedure is somewhat invasive as a small craniotomy is required to access MCA, though this results in minimal tissue damage. The primary advantages of this model, however, are: the site of occlusion is well defined, the degree of blood flow reduction is consistent, functional and neurological impairment occurs rapidly, infarct size is consistent, and the high rate of survival allows for long-term chronic assessment.

Permanent Cerebral Vessel Occlusion via Double Ligature and Transection

We describe a highly reproducible method for the permanent occlusion of a rodent major cerebral blood vessel. This technique can be accomplished with very little peripheral damage, minimal blood loss, a high rate of long-term survival, and consistent infarct volume commensurate with the human clinical population.

Stroke is a leading cause of death, disability, and socioeconomic loss worldwide. The majority of all strokes result from an interruption in blood flow ...

Modeling Stroke in Mice: Permanent Coagulation of the Distal Middle Cerebral Artery

Stroke is the third most common cause of death and a main cause of acquired adult disability in developed countries. Only very limited therapeutical options are available for a small proportion of stroke patients in the acute phase. Current research is intensively searching for novel therapeutic strategies and is increasingly focusing on the sub-acute and chronic phase after stroke because more patients might be eligible for therapeutic interventions in a prolonged time window. These delayed mechanisms include important pathophysiological pathways such as post-stroke inflammation, angiogenesis, neuronal plasticity and regeneration. In order to analyze these mechanisms and to subsequently evaluate novel drug targets, experimental stroke models with clinical relevance, low mortality and high reproducibility are sought after. Moreover, mice are the smallest mammals in which a focal stroke lesion can be induced and for which a broad spectrum of transgenic models are available. Therefore, we describe here the mouse model of transcranial, permanent coagulation of the middle cerebral artery via electrocoagulation distal of the lenticulostriatal arteries, the so-called &#8220;coagulation model&#8221;. The resulting infarct in this model is located mainly in the cortex; the relative infarct volume in relation to brain size corresponds to the majority of human strokes. Moreover, the model fulfills the above-mentioned criteria of reproducibility and low mortality. In this video we demonstrate the surgical methods of stroke induction in the &#8220;coagulation model&#8221; and report histological and functional analysis tools.

Various murine models of middle cerebral artery occlusion (MCAO) are widely used in experimental brain research. Here, we demonstrate the model of transcranial permanent distal MCAO which produces consistent cortical infarction of a size corresponding to damage imposed by the majority of human ischemic strokes.

Stroke is the third most common cause of death and a main cause of acquired adult disability in developed countries. Only very limited therapeutical ...

A Thrombotic Stroke Model Based On Transient Cerebral Hypoxia-ischemia

Stroke research has endured many setbacks in translating neuroprotective therapies into clinical practice. In contrast, the real-world therapy (tPA thrombolysis) rarely produces benefits in mechanical occlusion-based experimental models, which dominate preclinical stroke research. This split between the bench and bedside suggests the need to employ tPA-responsive models in preclinical stroke research. To this end, a simple and tPA-reactive thrombotic stroke model is invented and described here. This model consists of transient occlusion of the unilateral common carotid artery and delivery of 7.5% oxygen through a face mask in adult mice for 30 min, while maintaining the animal rectal temperature at 37.5 &#177; 0.5 &#176;C. Although reversible ligation of the unilateral carotid artery or hypoxia each suppressed cerebral blood flow only transiently, the combination of both insults caused lasting reperfusion deficits, fibrin and platelet deposition, and large infarct in the middle cerebral artery-supplied territory. Importantly, tail-vein injection of recombinant tPA at 0.5, 1, or 4 hr post-tHI (10 mg/kg) provided time-dependent reduction of the mortality rate and infarct size. This new stroke model is simple and can be standardized across laboratories to compare experimental results. Further, it induces thrombosis without craniectomy or introducing pre-formed emboli. Given these unique merits, the tHI model is a useful addition to the repertoire of preclinical stroke research.

Thromboembolic stroke models are vital tools for optimizing the recanalization therapy. Here we report a murine thrombotic stroke model based on transient cerebral hypoxic-ischemic (tHI) insult, which triggers thrombosis and infarction, and responds favorably to tissue plasminogen activator (tPA)-mediated fibrinolysis in a therapeutic window similar to those in stroke patients.

Stroke research has endured many setbacks in translating neuroprotective therapies into clinical practice. In contrast, the real-world therapy (tPA ...

Surgical Approach for Middle Cerebral Artery Occlusion and Reperfusion Induced Stroke in Mice

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ischemic in origin and occur in the territory of the middle cerebral artery (MCA). Currently the only Food and Drug Administration (FDA) approved drug for the treatment of this devastating disease is tissue plasminogen activator (tPA). However, tPA has a small therapeutic window for administration (3 - 6 hr), and is only effective in 4% of the patients who actually receive it. Current research focuses on understanding the pathophysiology of stroke in order to find potential therapeutic targets. Thus, reliable models are crucial, and the MCA occlusion (MCAo) model (also termed the intraluminal filament or suture model) is deemed to be the most clinically relevant surgical model of ischemic stroke, and is fairly non-invasive and easily reproducible. Typically the MCAo model is used with rodents, especially with mice due to all the genetic variations available for this species. Here we describe (and present in the video) how to successfully perform the MCAo model (with reperfusion) in mice to generate reliable and reproducible data.

In order to understand the pathophysiology of stroke, it is important to use reliable models. This paper will describe one of the most frequently used stroke models in mice, termed the middle cerebral artery occlusion (MCAo) model (also termed the intraluminal filament or suture model) with reperfusion.

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ...

Transient Middle Cerebral Artery Occlusion Model of Neonatal Stroke in P10 Rats

A number of animal models have been used to study hypoxic-ischemic injury, traumatic injury, global hypoxia, or permanent ischemia in both the immature and mature brain. Stroke occurs commonly in the perinatal period in humans, and transient ischemia-reperfusion is the most common form of stroke in neonates. The reperfusion phase is a critical component of injury progression, which occurs over a period of days to weeks, and of the endogenous response to injury. This postnatal day 10 (p10) rat model of transient middle cerebral artery occlusion (tMCAO) creates a unilateral, non-hemorrhagic focal ischemia-reperfusion injury that can be utilized to study the mechanisms of focal injury and repair in the full-term-equivalent brain. The injury pattern that is produced by tMCAO is consistent and highly reproducible and can be confirmed with MRI or histological analyses. The severity of injury can be manipulated through changes in occlusion time and other methods that will be discussed.

Neonatal stroke is a significant cause of early brain injury requiring a translational model with consistent focal injury patterns and high reproducibility in order to enable study. This study describes the detailed surgical procedure for creating a non-hemorrhagic, unilateral focal ischemia-reperfusion injury in full-term-equivalent rodents.

A number of animal models have been used to study hypoxic-ischemic injury, traumatic injury, global hypoxia, or permanent ischemia in both the immature ...

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.

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 ...

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. ...

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 ...

Middle Cerebral Artery Occlusion in Rats with Preserved Vascular Anatomy

A Rat Model of Middle Cerebral Artery Occlusion/Reperfusion Without Damaging the Anatomical Structure of Cerebral Vessels

Ischemic stroke stands as the primary cause of long-term disability and mortality among adults worldwide. Animal models of ischemic stroke have significantly contributed to our understanding of its pathological mechanisms and the development of potential treatments. Presently, there are two common methods involving filament (endovascular suture) techniques to induce animal models of cerebral ischemia. However, these methods have inherent limitations, such as reduced blood perfusion to the brain, damage to the external carotid artery system, impaired food and/or water intake, and sensory dysfunction of the face. This article introduces a new method for inducing a rat ischemic stroke model without compromising the cerebral vascular anatomy. In this study, the common carotid artery (CCA) of Sprague-Dawley rats was exposed, and an incision was made. A filament was then inserted through the incision into the internal carotid artery to occlude the middle cerebral artery. After 1.5 h of induced ischemia, the occluding filament was fully removed from both the internal carotid artery and the CCA. The incision in the CCA was subsequently sutured using 11-0 microsurgical sutures under a microscope (magnification 4x). Through the utilization of microsurgical techniques to repair the CCA, this study successfully developed a unique method to induce an ischemic stroke model in rats while preserving the anatomical integrity of cerebral blood vessels.

The current protocol describes a rat model of middle cerebral artery occlusion/reperfusion that preserves the anatomical structure of cerebral vessels without causing damage.

Transient Middle Cerebral Artery Occlusion Model of Stroke

Summary

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Mouse Model of Middle Cerebral Artery Occlusion

Permanent Cerebral Vessel Occlusion via Double Ligature and Transection

Modeling Stroke in Mice: Permanent Coagulation of the Distal Middle Cerebral Artery

A Thrombotic Stroke Model Based On Transient Cerebral Hypoxia-ischemia

Surgical Approach for Middle Cerebral Artery Occlusion and Reperfusion Induced Stroke in Mice

Transient Middle Cerebral Artery Occlusion Model of Neonatal Stroke in P10 Rats

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

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

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

A Rat Model of Middle Cerebral Artery Occlusion/Reperfusion Without Damaging the Anatomical Structure of Cerebral Vessels