This study characterizes a new model of thromboembolic stroke of the middle cerebral artery in C57 black/6J mice, thus offering an opportunity to use the model for studying ischemic stroke in transgenic mice. Thromboembolic stroke was induced by local injection of either 1.5 or 3.0 UI of thrombin directly into the right MCA of C57 black/6J mice. Cerebral blood flow (CBF) velocity was measured continuously by laser Doppler flowmetry, which allowed documentation of both MCA occlusion and of spontaneous recanalization. After 24 h, all animals were euthanized. Cryosections were cut at 400-μm intervals and silver stained with the high-contrast method for volumetric assessment of infarct size. Interleukin (IL)-6, tumor necrosis factor-alpha (TNF-α), caspase-3 and hsp 70 protein levels were investigated by immunofluorescence. Thrombin injection resulted in clot formation in all animals. Cortical infarction occurred in 63 % of the mice while 37 % had a spontaneous MCA recanalization during the first 20 min following thrombin injection. In cases of successful MCA occlusion with consequent infarction, the clot was stable up to 2 h after formation. Subsequently, 20 % recanalized spontaneously. Infarctions were restricted to the cortex with a mean lesion volume of 36 ± 5 for 1.5 UI and 56 ± 8 for 3.0 UI thrombin. Protein levels of IL-6, TNF-α, caspase-3, and hsp 70 were significantly increased after MCAO. The results demonstrate that the mouse thromboembolic stroke model produces cortical infarctions of consistent size in C57 black/6J mice, which is dependent upon the amount of thrombin used for clot formation. Spontaneous MCA recanalization occurs after 2 h of ischemia in 20 % of mice. Thus, the thromboembolic model is an applicable stroke model for C57 black/6J mice, which mimics many of the features of human stroke, including spontaneous recanalization. However, strain differences between Swiss and C57 black/6J mice must be taken into account when using the model.

Background and Purpose-Intracerebral hemorrhage (ICH) is the most adverse event of thrombolysis in ischemic stroke.Cerebral amyloid angiopathy increases the risk for spontaneous lobar ICH. Although thrombolysis may be performed in cerebral amyloid angiopathy-affected patients, there is still little knowledge available on the risk for secondary ICH. Methods-We investigated the effect of recombinant tissue-type plasminogen activator on experimental ischemic stroke in APP23 transgenic mice (n=18) and wild-type littermates (n=15). Focal ischemic stroke was induced in 26-month-old mice by temporal middle cerebral artery occlusion (filament model), followed by treatment with 10 mg/kg recombinant tissue-type plasminogen activator. Twenty-four hours later, a functional score was assessed and the mice were euthanized for histological analysis. ICH was classified as grades 1 to 3 depending on severity. Results-The groups did not differ regarding mortality (P=0.67) and functional deficit (P=0.18). Compared with wild-type mice, the APP23 genotype was associated with a higher appearance for ICH in the infarct area (P=0.05). ICH severity grades 2 and 3 correlated significantly with infarct size (P=0.004 and 0.008, respectively). Conclusions-The APP23 genotype was not associated with increased mortality or worse functional outcome. Our results suggest an increased risk for ICH in the cerebral amyloid angiopathy-affected brain; however, no ICH was observed outside the ischemic area. (Stroke. 2014;45:2411-2416.)