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      Animal models of ischemic stroke and their application in clinical research

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          Abstract

          This review outlines the most frequently used rodent stroke models and discusses their strengths and shortcomings. Mimicking all aspects of human stroke in one animal model is not feasible because ischemic stroke in humans is a heterogeneous disorder with a complex pathophysiology. The transient or permanent middle cerebral artery occlusion (MCAo) model is one of the models that most closely simulate human ischemic stroke. Furthermore, this model is characterized by reliable and well-reproducible infarcts. Therefore, the MCAo model has been involved in the majority of studies that address pathophysiological processes or neuroprotective agents. Another model uses thromboembolic clots and thus is more convenient for investigating thrombolytic agents and pathophysiological processes after thrombolysis. However, for many reasons, preclinical stroke research has a low translational success rate. One factor might be the choice of stroke model. Whereas the therapeutic responsiveness of permanent focal stroke in humans declines significantly within 3 hours after stroke onset, the therapeutic window in animal models with prompt reperfusion is up to 12 hours, resulting in a much longer action time of the investigated agent. Another major problem of animal stroke models is that studies are mostly conducted in young animals without any comorbidity. These models differ from human stroke, which particularly affects elderly people who have various cerebrovascular risk factors. Choosing the most appropriate stroke model and optimizing the study design of preclinical trials might increase the translational potential of animal stroke models.

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          Most cited references 88

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          Induction of reproducible brain infarction by photochemically initiated thrombosis.

          We have used a photochemical reaction in vivo to induce reproducible thrombosis leading to cerebral infarction in rats. After the intravenous injection of rose bengal, a potent photosensitizing dye, an ischemic lesion was formed by irradiating the left parietal convexity of the exposed skull for 20 minutes with green light (560 nm) from a filtered xenon arc lamp. Animals were allowed to survive from 30 minutes to 15 days after irradiation. Early microscopic alterations within the irradiated zone included the formation of thrombotic plugs and adjacent red blood cell stasis within pial and parenchymal vessels. Scanning electron microscopy revealed frequent platelet aggregates adhering to the vascular endothelium, often resulting in vascular occlusion. Carbon-black brain perfusion demonstrated that occlusion of vascular channels progressed after irradiation and was complete within 4 hours. Histopathological examination at 1, 5, and 15 days revealed that the associated infarct evolved reproducibly through several characteristic stages, including a phase of massive macrophage infiltration. Although cerebral infarction in this model is initiated by thrombosis of small blood vessels, the fact that the main pathological features of stroke are consistently reproduced should permit its use in assessing treatment regimens. Further, the capability of producing infarction in preselected cortical regions may facilitate the study of behavioral, functional, and structural consequences of acute and chronic stroke.
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            Timeliness of tissue-type plasminogen activator therapy in acute ischemic stroke: patient characteristics, hospital factors, and outcomes associated with door-to-needle times within 60 minutes.

            The benefits of intravenous tissue-type plasminogen activator (tPA) in acute ischemic stroke are time dependent, and guidelines recommend an arrival to treatment initiation (door-to-needle) time of ≤60 minutes. Data from acute ischemic stroke patients treated with tPA within 3 hours of symptom onset in 1082 hospitals participating in the Get With the Guidelines-Stroke Program from April 1, 2003, to September 30, 2009 were studied to determine frequency, patient and hospital characteristics, and temporal trends in patients treated with door-to-needle times ≤60 minutes. Among 25 504 ischemic stroke patients treated with tPA, door-to-needle time was ≤60 minutes in only 6790 (26.6%). Patient factors most strongly associated with door-to-needle time ≤60 minutes were younger age, male gender, white race, or no prior stroke. Hospital factors associated with ≤60 minute door-to-needle time included greater annual volumes of tPA-treated stroke patients. The proportion of patients with door-to-needle times ≤60 minutes varied widely by hospital (0% to 79.2%) and increased from 19.5% in 2003 to 29.1% in 2009 (P 60 minutes. Fewer than one-third of patients treated with intravenous tPA had door-to-needle times ≤60 minutes, with only modest improvement over the past 6.5 years. These findings support the need for a targeted initiative to improve the timeliness of reperfusion in acute ischemic stroke.
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              Quantitative evaluation of blood-brain barrier permeability following middle cerebral artery occlusion in rats.

              A sensitive quantitative fluorescence method was used to explore the time course and regional pattern of blood-brain barrier (BBB) opening after transient middle cerebral artery occlusion (MCAo). Male Sprague-Dawley rats were anesthetized with halothane and subjected to 2 h of temporary MCAo by retrograde insertion of an intraluminal nylon suture, coated with poly-L-lysine, through the external carotid artery into the internal carotid artery and MCA. Damage to the BBB was judged by extravasation of Evans Blue (EB) dye, which was administered either 2, 3, 24 or 48 h after onset of MCAo. Fluorometric quantitation of EB was performed 1 or 2 h later in six brain regions. Cerebral infarction volumes were quantitated from histopathological material at 72 h. EB extravasation first became grossly visible in the ipsilateral caudoputamen and neocortex following 3 h of MCAo, was grossly unapparent at 24-26 h, and was maximal at 48-50 h. Fluorescence quantitation confirmed that BBB opening was absent at 2-3 h but present at all later times. In the hemisphere ipsilateral to MCAo, a 179% mean increase in extravasation of EB (compared to sham rats) was measured at 4 h, 407% at 5 h, 311% at 26 h and 264% at 50 h. (in each case, P < 0.05 vs. sham). The volume of infarcted tissue at 72 h in this model was 163.6 +/- 7.7 mm3. Our results indicate that an initial, acute disruption of the BBB occurs between 3 and 5 h following MCAo, and that a later, more widespread increase in regional BBB permeability is present at 48 h. Regional measurement of Evans Blue extravasation offers a precise means of quantitating BBB disruption in focal cerebral ischemia; this method will be of considerable utility in assessing the BBB-protective properties of pharmacological agents.
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                Author and article information

                Journal
                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                Drug Design, Development and Therapy
                Dove Medical Press
                1177-8881
                2015
                02 July 2015
                : 9
                : 3445-3454
                Affiliations
                Department of Neurology, University Clinic Wuerzburg, Wuerzburg, Germany
                Author notes
                Correspondence: Christoph Kleinschnitz, Department of Neurology, University Clinic Wuerzburg, Josef-Schneider Strasse 11, 97080 Wuerzburg, Germany, Tel +49 931 2012 3756, Fax +49 931 2012 3488, Email christoph.kleinschnitz@ 123456uni-wuerzburg.de
                Article
                dddt-9-3445
                10.2147/DDDT.S56071
                4494187
                © 2015 Fluri et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

                The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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