Smaller Infarct Volumes Research Articles

In vivo evaluation of urokinase-loaded hollow nanogels for sonothrombolysis on suture embolization-induced acute ischemic stroke rat model

The urokinase-type plasminogen activator (uPA) loaded hollow nanogels (nUK) were synthesized by a one-step reaction of glycol chitosan and aldehyde capped poly (ethylene oxide). The resultant formulation is sensitive to diagnostic ultrasound (US) of 2 MHz. Herein, we evaluated the in vivo sonothrombolysis performance of the nUK on acute ischemic stroke rat model which was established by suture embolization of middle cerebral artery (MCA). Via intravenous (i.v.) administration, the experimental data prove a controlled release of the therapeutic protein around the clots under ultrasound stimulation, leading to enhanced thrombolysis efficiency of the nUK, evidenced from smaller infarct volume and better clinical scores when compared to the i.v. dose of free uPA no matter with or without US intervention. Meanwhile, the preservation ability of the nanogels not only prolonged the circulation duration of the protein, but also resulted in the better blood-brain barrier protection of the nUK formulation, showing no increased risk on the hemorrhagic transformation than the controls. This work suggests that the nUK is a safe sonothrombolytic formulation for the treatment of acute ischemic stroke.

Degree of Vascular Encasement in Sphenoid Wing Meningiomas Predicts Postoperative Ischemic Complications.

Sphenoid wing meningiomas (SWMs) can encase arteries of the circle of Willis, increasing their susceptibility to intraoperative vascular injury and severe ischemic complications. To demonstrate the effect of circumferential vascular encasement in SWM on postoperative ischemia. A retrospective review of 75 patients surgically treated for SWM from 2009 to 2015 was undertaken to determine the degree of circumferential vascular encasement (0°-360°) as assessed by preoperative magnetic resonance imaging (MRI). A novel grading system describing "maximum" and "total" arterial encasement scores was created. Postoperative MRIs were reviewed for total ischemia volume measured on sequential diffusion-weighted images. Of the 75 patients, 89.3% had some degree of vascular involvement with a median maximum encasement score of 3.0 (2.0-3.0) in the internal carotid artery (ICA), M1, M2, and A1 segments; 76% of patients had some degree of ischemia with median infarct volume of 3.75 cm 3 (0.81-9.3 cm 3 ). Univariate analysis determined risk factors associated with larger infarction volume, which were encasement of the supraclinoid ICA ( P < .001), M1 segment ( P < .001), A1 segment ( P = .015), and diabetes ( P = .019). As the maximum encasement score increased from 1 to 5 in each of the significant arterial segments, so did mean and median infarction volume ( P < .001). Risk for devastating ischemic injury >62 cm 3 was found when the ICA, M1, and A1 vessels all had ≥360° involvement ( P = .001). Residual tumor was associated with smaller infarct volumes ( P = .022). As infarction volume increased, so did modified Rankin Score at discharge ( P = .025). Subtotal resection should be considered in SWM with significant vascular encasement of proximal arteries to limit postoperative ischemic complications.

Ischemic Cerebroprotection Conferred by Myeloid Lineage-Restricted or Global CD39 Transgene Expression.

Cerebral tissue damage after an ischemic event can be exacerbated by inflammation and thrombosis. Elevated extracellular ATP and ADP levels are associated with cellular injury, inflammation, and thrombosis. Ectonucleoside triphosphate diphosphohydrolase-1 (CD39), an enzyme expressed on the plasmalemma of leukocytes and endothelial cells, suppresses platelet activation and leukocyte infiltration by phosphohydrolyzing ATP/ADP. To investigate the effects of increased CD39 in an in vivo cerebral ischemia model, we developed a transgenic mouse expressing human CD39 (hCD39). A floxed-stop sequence was inserted between the promoter and the hCD39 transcriptional start site, generating a mouse in which the expression of hCD39 can be controlled tissue-specifically using Cre recombinase mice. We generated mice that express hCD39 globally or in myeloid-lineage cells only. Cerebral ischemia was induced by middle cerebral artery occlusion. Infarct volumes were quantified by MRI after 48 hours. Both global and transgenic hCD39- and myeloid lineage CD39-overexpressing mice (transgenic, n=9; myeloid lineage, n=6) demonstrated significantly smaller cerebral infarct volumes compared with wild-type mice. Leukocytes from ischemic and contralateral hemispheres were analyzed by flow cytometry. Although contralateral hemispheres had equal numbers of macrophages and neutrophils, ischemic hemispheres from transgenic mice had less infiltration (n=4). Transgenic mice showed less neurological deficit compared with wild-type mice (n=6). This is the first report of transgenic overexpression of CD39 in mice imparting a protective phenotype after stroke, with reduced leukocyte infiltration, smaller infarct volumes, and decreased neurological deficit. CD39 overexpression, either globally or in myeloid lineage cells, quenches postischemic leukosequestration and reduces stroke-induced neurological injury.

Vessel Patency at 24 Hours and Its Relationship With Clinical Outcomes and Infarct Volume in REVASCAT Trial (Randomized Trial of Revascularization With Solitaire FR Device Versus Best Medical Therapy in the Treatment of Acute Stroke Due to Anterior Circulation Large Vessel Occlusion Presenting Within Eight Hours of Symptom Onset).

Higher rates of target vessel patency at 24 hours were noted in the thrombectomy group compared with control group in recent randomized trials. As a prespecified secondary end point, we aimed to assess 24-hour revascularization rates by treatment groups and occlusion site as they related to clinical outcome and 24-hour infarct volume in REVASCAT (Randomized Trial of Revascularization With Solitaire FR Device Versus Best Medical Therapy in the Treatment of Acute Stroke Due to Anterior Circulation Large Vessel Occlusion Presenting Within Eight Hours of Symptom Onset). Independent core laboratory adjudicated vessel status according to modified arterial occlusive lesion classification at 24 hours on computed tomographic/magnetic resonance (94.2%/5.8%) angiography and 24-hour infarct volume on computed tomography were studied (95/103 patients in the thrombectomy group versus 94/103 in the control group, respectively). Complete revascularization was defined as modified arterial occlusive lesion grade 3. Its effect on clinical outcome was analyzed by ordinal logistic regression. Complete revascularization was achieved in 70.5% of the solitaire group and in 22.3% of the control group (P<0.001). Significant differences in complete revascularization rates were found for terminus internal carotid artery, M1, and tandem occlusions (all P<0.001) but not for M2 occlusions. In the thrombectomy group, 2 out of 63 patients (3.1%) with modified Thrombolysis in Cerebral Infarction 2b/3 after thrombectomy showed arterial reocclusion (modified arterial occlusive lesion grade 0/1) at 24 hours. Complete revascularization was associated with improved outcome in both thrombectomy (adjusted odds ratio, 4.5; 95% confidence interval, 1.9-10.9) and control groups (adjusted odds ratio, 2.7; 95% confidence interval, 1.0-6.7). Revascularization (modified arterial occlusive lesion grade 2/3) was associated with smaller infarct volumes in either treatment arm. Complete revascularization at 24 hours is a powerful predictor of favorable clinical outcome, whereas revascularization of any type results in reduced infarct volume in both thrombectomy and control groups. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01692379.

Low-intensity (400 mW/cm2, 500 kHz) pulsed transcranial ultrasound preconditioning may mitigate focal cerebral ischemia in rats

BackgroundPreconditioning methods, which could increase tolerance of brain to subsequent ischemic injuries with a small dose of non-injury stimuli, have gained attention. Capitalizing on noninvasiveness and safety of ultrasound modality, the pulsed transcranial ultrasound stimulation (pTUS) approach may provide a novel treatment for patients with high risk of stroke. ObjectiveThis study's goal was to investigate whether the risk of stroke could be minimized or eliminated by prior exposure to low-intensity, pulsed transcranial ultrasound stimulation (pTUS). MethodsRats were randomly assigned to control (n = 12) and pTUS preconditioning (pTUS-PC) groups (n = 14). The animals in pTUS-PC group were exposed to transcranial ultrasound stimulation before the induction of photothrombotic stroke, whereas control animals were handled identically but without the ultrasound stimulation. Cerebral blood flow was monitored using laser speckle imaging in both groups during stroke induction, as well as 24 and 48 h after stroke, respectively. Also, infarct volumes and edema were measured at 48 h after stroke. ResultspTUS-PC rats had smaller ischemic areas during stroke induction, and 24 and 48 h after the stroke, and smaller infarct volume (1.770 ± 0.169%) than the controls (3.215 ± 0.401%) (p < 0.01). Moreover, the pTUS-PC group experienced lower volume of brain edema than the control group (pTUS-PC rats: 6.658 ± 1.183%; control rats: 12.48 ± 1.386%, p < 0.01). ConclusionThese results support the hypothesis that transcranial ultrasound stimulation applied before photothrombosis could provide neuroprotection by increasing the brain's tolerance to subsequently induced focal ischemic injury.

Role of Genetic Variation in Collateral Circulation in the Evolution of Acute Stroke: A Multimodal Magnetic Resonance Imaging Study.

No studies have determined the effect of differences in pial collateral extent (number and diameter), independent of differences in environmental factors and unknown genetic factors, on severity of stroke. We examined ischemic tissue evolution during acute stroke, as measured by magnetic resonance imaging and histology, by comparing 2 congenic mouse strains with otherwise identical genetic backgrounds but with different alleles of the Determinant of collateral extent-1 (Dce1) genetic locus. We also optimized magnetic resonance perfusion and diffusion-deficit thresholds by using histological measures of ischemic tissue. Perfusion, diffusion, and T2-weighted magnetic resonance imaging were performed on collateral-poor (congenic-Bc) and collateral-rich (congenic-B6) mice at 1, 5, and 24 hours after permanent middle cerebral artery occlusion. Magnetic resonance imaging-derived penumbra and ischemic core volumes were confirmed by histology in a subset of mice at 5 and 24 hours after permanent middle cerebral artery occlusion. Although perfusion-deficit volumes were similar between strains 1 hour after permanent middle cerebral artery occlusion, diffusion-deficit volumes were 32% smaller in collateral-rich mice. At 5 hours, collateral-rich mice had markedly restored perfusion patterns showing reduced perfusion-deficit volumes, smaller infarct volumes, and smaller perfusion-diffusion mismatch volumes compared with the collateral-poor mice (P<0.05). At 24 hours, collateral-rich mice had 45% smaller T2-weighted lesion volumes (P<0.005) than collateral-poor mice, with no difference in perfusion-diffusion mismatch volumes because of penumbral death occurring 5 to 24 hours after permanent middle cerebral artery occlusion in collateral-poor mice. Variation in collateral extent significantly alters infarct volume expansion, transiently affects perfusion and diffusion magnetic resonance imaging signatures, and impacts salvage of ischemic penumbra after stroke onset.

Cerebral regions preserved by successful endovascular recanalization of acute M1 segment occlusions: a voxel based analysis.

To identify cerebral regions preserved by successful recanalization of the middle cerebral artery M1 segment and their association with early clinical outcome. 47 patients who underwent endovascular treatment for acute unilateral M1 segment occlusion were included. Successful recanalization was defined by a modified thrombolysis in cerebral infarction score of 2b/3. Final infarct volumes were segmented on follow-up MRI/CT, 2-7 days post-symptom onset. The differences in topography of infarct lesions associated with successful vs unsuccessful recanalization were assessed using voxel-based analysis. Favourable outcome was defined by a modified Rankin Scale score ≤2 at discharge, and disability/death by score >2. Successful recanalization of M1 segment occlusion was achieved in 26/47 (55%) patients, which was associated with higher rate of favourable outcome (54% vs 9%, p = 0.002) and smaller final infarct volumes (34.3 ± 43.7 vs 98.1 ± 47.7 ml, p < 0.001). In voxel-based analysis, patients with successful recanalization had a lower rate of infarction in precentral gyrus and posterior insular ribbon compared with those without recanalization. Favourable outcome was achieved in 16 (34%) patients, who were younger (62.2 ± 13.9 vs 70.9 ± 13.9, p = 0.048), had higher rate of successful recanalization (88% vs 39%, p = 0.002) and had smaller infarct volumes (25.2 ± 23.6 vs 82.2 ± 57.1 ml, p < 0.001) compared with those with disability/death. In voxel-based analysis, infarction of the insula, precentral gyrus, middle centrum semiovale and corona radiata were associated with disability/death. Successful endovascular recanalization of acute M1 segment occlusion tends to preserve posterior insular ribbon and precentral gyrus from infarction; and infarction of these regions was associated with higher rates of disability/death. Advances in knowledge: The knowledge of the topographic location of potentially salvageable cerebral tissue can provide additional information for treatment triage and selection of patients with acute stroke for endovascular treatment based on the "areas at risk" rather than the "volume at risk". Also, such knowledge can help with preferential recanalization, where the neurointerventionalist may choose to preferentially recanalize certain branches supplying salvageable and eloquent cerebral regions in favour of timely reperfusion treatment.

Abstract WP213: Comparison of Clinical and Imaging Characteristic of Cryptogenic Stroke to Known Ischemic Subtypes

Introduction: Cryptogenic stroke is defined as not attributable to an identified source despite standard evaluation. The absence of small vessel or large artery disease in such evaluation suggests that cryptogenic stroke may be largely cardioembolic. We hypothesized that cryptogenic stroke would be similar to cardioembolic stroke in clinical and imaging characteristics. Methods: The Greater Cincinnati/Northern Kentucky Stroke Study (GCNKSS) is a population-based study that tracks the regional incidence of stroke. A convenient subsample from the 2010 GCNKSS ischemic stroke cohort (N= 368) was selected for detailed neuroimaging analysis. The study physician subtyped cases based on clinical, radiographic and laboratory findings (carotid ultrasound, echocardiography, vascular imaging). Subtypes included cryptogenic, cardioembolic, large-vessel, small-vessel, undetermined, and other. Three radiologists performed imaging analysis including number of acute infarcts, location and white matter hyperintensity (WMH). Infarct volume was segmented using manual tracing. Results: Of 368 ischemic stroke cases with imaging data, subtypes were 26.4% cryptogenic, 16.3% large vessel, 15.5% small vessel, 24.7% cardioembolic, 5.4% undetermined, and 11.7% other. Compared to cardioembolic, cryptogenic stroke patients were younger, had less hypertension, higher alcohol use, smaller infarct volume and differed in location of stroke. Cryptogenic stroke had more clinical and radiological features in common with large and small-vessel stroke (Table). Undetermined and other had no significant differences to cryptogenic. Conclusion: Contrary to our hypothesis, cryptogenic stroke was different from cardioembolic stroke and appeared more similar to large vessel stroke in clinical and radiological characteristics. Further testing on a larger sample size to evaluate the impact of cardiac event monitoring on subtype distribution is needed.

Abstract TP100: Pharmacological Inhibition of ACC1 Restrains Peripheral T Cell Activation and Protects Against Cerebral Ischemic Stroke

Background and purpose: T cell activation, which is detrimental to the ischemic brain, requires metabolic reprogramming to meet the increased fuel demanding. ACC1 is an enzyme catalyzing the carboxylation of acetyl-CoA to malonyl CoA, a key substrate in the glycolytic-lipogenic pathway, which is extremely critical for T cell differentiation and phenotype polarization. We tested the hypothesis that pharmacologically inhibiting the enzyme ACC1 early after stroke may restrain T cell activation and protect against cerebral ischemic injury. Methods: Cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 60 minutes in C57/B6 mice. Soraphen A, the specific pharmacological inhibitor of ACC1 was administered at 1 hour after reperfusion at the dose of 1mg/kg, 5mg/kg, 10mg/kg and 50mg/kg intraperitoneally. Infarct volume was assess at 3 days after surgery by staining with 2,3,5-triphenyltetrazolium chloride. Behavior assessments, such as body proprioception, climbing, forelimb walking, lateral turning, foot fault and adhesive removal were examined at 3, 5, 7, 14, 21 and 28 days after stroke. T cell infiltration into the ischemic brain was examined by immunofluorescent staining. Results: Mice treated with 5mg/kg or 10mg/kg soraphen A exhibited significantly smaller infarct volume at 3 days after stroke. 5mg/kg was chosen as the dose for further experiments. Soraphen A treatment improved the overall neurological assessment and enhanced the performance of mice in adhesive removal test and grid walking test. Soraphen A treatment significantly attenuated the CD3+ T cell and Gr-1+ neutrophil infiltration in the ischemic mice brain at 3 days after surgery. Conclusion: Pharmacological inhibition of T cell activation by soraphen A is protective against cerebral ischemic injury and may represent a novel strategy for stroke therapy.

Abstract 45: IRF5/IRF4 Regulatory Axis Mediated Microglial M1/M2 Polarization After Ischemic Stroke

Introduction: Microglia have a prominent role in initiating, sustaining and resolving post-stroke inflammation. The pathology of stroke largely depends on the spectrum of microglial activation with the classically (M1; pro-inflammatory) and/or alternatively activated (M2; anti-inflammatory) phenotype. It has been reported that interferon regulatory factor 5 (IRF5) and IRF4 regulate the M1 and M2 phenotype of macrophages respectively in systemic inflammation; however, it is unknown if microglial activation is regulated by the same mechanism after stroke. We hypothesize that IRF5/IRF4 directs M1/M2 microglial polarization respectively after stroke and the balance of the IRF5/IRF4 regulatory axis influences stroke outcomes. Methods: C57BL6 mice (8-12 weeks) were subjected to a 90-minute middle cerebral artery occlusion (MCAO). Stroke outcomes were evaluated at 12h, 3d, 10d of MCAO. Protein and mRNA levels of IRF4/5 at each time point were examined by IHC, Western blot and RT-PCR. Microglial phenotypes were evaluated by flow cytometry (FC) and determined by the ratio of MHC-II + (M1) or CD206 + (M2) microglia number over the total microglia. IRF4/IRF5 conditional knockout (CKO) mice will also be utilized to examine the effect of gene deletion on stroke outcomes. Results: IRF4 protein level increased at 10d in the ipsilateral brain lysates, but IRF5 level decreased at day 10 compared to that of 3d. M2 microglia number was higher at 10d vs. 3d by FC analysis; while M1 microglia ratio was lower at 10d vs. 3d. The Iba1 + IRF4 + (M2) and Iba1 + IRF5 + (M1) cell number by IHC showed the same pattern as that in FC data. In addition, IRF4 mRNA in FC-sorted microglia was up-regulated at 3d of stroke and peaked at 10d, but IRF5 mRNA significantly increased at 3d vs. sham and declined to baseline at 10d. IRF5-CKO mice had significantly smaller infarct volume and improved behavior deficits than IRF5 flox/flox mice while IRF4-CKO mice had worse outcomes than that of IRF4 flox/flox mice. Conclusion: IRF5-mediated pro-inflammatory phenotype (M1) is predominate in the acute stage of stroke that switches to IRF4-mediated anti-inflammatory phenotype (M2) in the chronic stage. IRF5/IRF4 regulatory axis regulates the microglial M1/M2 activation and impacts stroke outcomes.

Isoquercetin activates the ERK1/2-Nrf2 pathway and protects against cerebral ischemia-reperfusion injury in vivo and in vitro.

Isoquercetin has exhibited a wide range of therapeutic properties, including antioxidant, anti-inflammatory and anti-allergic activities. The aim of the present study was to investigate the effect of isoquercetin on rats with 2 h middle cerebral artery occlusion (MCAO) and evaluate the neuroprotective effect of isoquercetin on a primary culture of rat hippocampal neuronal cells subjected to oxygen-glucose deprivation followed by reoxygenation (OGD/R). In vivo, the rats treated with isoquercetin exhibited a lower degree of neurological dysfunction and smaller infarct volume than the vehicle-treated rats. In vitro, it was found that isoquercetin prevented the OGD/R-induced increase in apoptosis, lactate dehydrogenase release and reduction in cell viability. Additionally, isoquercetin induced the upregulation of nuclear factor erythroid 2-related factor 2 gene and protein expression, and increased extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation. This indicates that the ERK1/2 pathway may contribute to the neuroprotective effect of isoquercetin against OGD/R-induced oxidative damage in rat hippocampal neurons. These findings suggest the potential importance of isoquercetin in the treatment of ischemia/reperfusion-related brain injury and associated diseases.

Sex Differences in the Cerebral Collateral Circulation.

Premenopausal women and intact female rodents sustain smaller cerebral infarctions than males. Several sex-dependent differences have been identified as potential contributors, but many questions remain unanswered. Mice exhibit wide variation in native collateral number and diameter (collateral extent) that is dependent on differences in genetic background, aging, and other comorbidities and that contributes to their also-wide differences in infarct volume. Likewise, variation in infarct volume correlates with differences in collateral-dependent blood flow in patients with acute ischemic stroke. We examined whether extent of pial collateral arterioles and posterior communicating collateral arteries (PComAs) differ depending on sex in young, aged, obese, hypertensive, and genetically different mice. We combined new data with meta-analysis of our previously published data. Females of C57BL/6J (B6) and BALB/cByJ (BC) strains sustained smaller infarctions than males after permanent MCA occlusion. This protection was unchanged in BC mice after introgression of the B6 allele of Dce1, the major genetic determinant of variation in pial collaterals among mouse strains. Consistent with this, collateral extent in these and other strains did not differ with sex. Extent of PComAs and primary cerebral arteries also did not vary with sex. No dimorphism was evident for loss of pial collateral number and/or diameter (collateral rarefaction) caused by aging, obesity, and hypertension, nor for collateral remodeling after pMCAO. However, rarefaction was greater in females with long-standing hypertension. We conclude that smaller infarct volume in female mice is not due to greater collateral extent, greater remodeling, or less rarefaction caused by aging, obesity, or hypertension.

Effect of enriched environment on angiogenesis and neurological functions in rats with focal cerebral ischemia

The purpose of this study was to investigate the effect of enriched environment (EE) on cerebral angiogenesis after ischemia-reperfusion injury. Middle cerebral artery occlusion (MCAO) followed by reperfusion was performed in rats to set up an animal model of ischemia-reperfusion injury. In a set of behavioral tests, we demonstrated that the animals in the IEE (ischemia + enriched environment) group exhibited significantly improved neurological functions compared to those in the standard housing condition group. In consistent with the functional tests, smaller infarction volumes were observed in the animals of IEE group. Laser scanning confocal microscopy and 3D quantitative analysis of cerebral microvessels revealed that EE treatment increased the total vessel surface area and number of branch point in the ischemic boundary zone. IgG extraction assay showed that the blood brain barrier (BBB) leakage in the ischemic brain was attenuated after EE treatment. EE treatment also enhanced endothelial cells (ECs) proliferation and increased the expression levels of VEGF and its receptor Flk-1 after ischemia-reperfusion injury. Analyses of Spearman's correlation coefficients indicated a correlation of mNSS scores with enhanced cerebral angiogenesis. Together, the results suggest that EE treatment-induced cerebral angiogenesis may contribute to the improved neurological outcome of stroke animals after ischemia-reperfusion injury.

Susceptibility-diffusion mismatch in middle cerebral artery territory acute ischemic stroke: clinical and imaging implications.

Background Recent studies have suggested a correlation between susceptibility-diffusion mismatch and perfusion-diffusion mismatch in acute ischemic stroke patients. Purpose To determine the clinical and imaging associations of susceptibility-diffusion mismatch in patients with acute ischemic stroke in the middle cerebral artery (MCA) territory. Material and Methods Consecutive patients with MCA territory acute ischemic stroke, who had magnetic resonance imaging (MRI) performed with susceptibility-weighted imaging (SWI) and diffusion-weighted imaging (DWI) within 24 h of symptom onset or time last-seen-well, were included. Two neuroradiologists reviewed SWI scans for SWI-DWI mismatch defined by regionally increased vessel number or diameter on SWI extending beyond the DWI hyperintensity territory in the affected hemisphere. The stroke severity at admission was evaluated using the National Institutes of Health Stroke Scale (NIHSS) score. Poor clinical outcome was defined by a 3-month modified Rankin Scale (mRS) score >2. Results The SWI-DWI mismatch was identified in 44 (29.3%) of 150 patients included in this study. Patients with SWI-DWI mismatch had smaller admission infarct volumes (31.2 ± 44.7 versus 55.9 ± 117.7 mL, P = 0.045) and were younger (60.4 ± 18.9 versus 67.1 ± 15.5, P = 0.026). After correction for age, admission NIHSS score, and infarct volume, the SWI-DWI mismatch was associated with a 22.6% lower rate of poor clinical outcome using propensity score matching ( P = 0.032). In our cohort, thrombolytic therapy showed no significant effect on outcome. Conclusion The presence of SWI-DWI mismatch in acute MCA territory ischemic infarct is associated with smaller infarct volume. Moreover, SWI-DWI mismatch was associated with better outcome after correction for infarct size, severity of admission symptoms, and age.

Reported Prestroke Physical Activity Is Associated with Vascular Endothelial Growth Factor Expression and Good Outcomes after Stroke

Physical activity (PhA) prior to stroke has been associated with good outcomes after the ischemic insult, but there is scarce data on the involved molecular mechanisms. We studied consecutive acute ischemic stroke patients admitted to a single tertiary stroke center. Prestroke PhA was evaluated with the International Physical Activity Questionnaire (metabolic equivalent of minutes/week). We studied several circulating angiogenic and neurogenic factors at different time points: vascular endothelial growth factor (VEGF), granulocyte colony-stimulating factor (G-CSF), and brain-derived neurotrophic factor (BDNF) at admission, day 7, and at 3 months. We considered good functional outcome at 3 months (modified Rankin scale ≤ 2) as primary end point, and final infarct volume as secondary outcome. We studied 83 patients with at least 2 time point serum determinations (mean age 69.6 years, median National Institutes of Health Stroke Scale 17 at admission). Patients more physically active before stroke had a significantly higher increment of serum VEGF on the seventh day when compared to less active patients. This increment was an independent predictor of good functional outcome at 3 months and was associated with smaller infarct volume in multivariate analyses adjusted for relevant covariates. We did not find independent associations of G-CSF or BDNF levels neither with level of prestroke PhA nor with stroke outcomes. Although there are probably more molecular mechanisms by which PhA exerts its beneficial effects in stroke outcomes, our observation regarding the potential role of VEGF is plausible and in line with previous experimental studies. Further research in this field is needed.

Mir363-3p improves ischemic stroke outcomes in female but not male rats

With age, stroke prevalence is higher, and stroke outcome, worse, in women. Thus there is an urgent need to identify stroke neuroprotectants for this population. Using a preclinical stroke model, our studies focused on microRNAs (miRNAs), a class of translational repressors, as neuroprotectants. Analysis of circulating miRNA in the acute phase of stroke indicated potential neuroprotective capacity for miR363. Specifically, mir363 is elevated in serum of adult female rats that typically have small infarct volumes, but is deficient in age-matched males or middle-aged males and females, groups that have greater stroke-associated impairment. To directly test the effect of mir363 on stroke outcomes, first, adult females were treated with antagomirs to mir363 post stroke and next, middle-aged females were treated with mimic to mir363-3p post stroke. Antagomir treatment to adult females significantly increased infarct volume and impaired sensory motor performance. Reciprocally, mir363 mimic to middle-aged females reduced infarct volume, preserved forebrain microvessels and improved sensory motor performance. In the early acute stroke phase, mir363-3p mimic reduced the expression and functional activity of caspase-3, a critical component of the apoptotic cell cascade. In contrast, mir363-3p mimic treatment had no effect on stroke outcomes or caspase regulation in young males. Collectively, these studies show that mir363 is neuroprotective for stroke in females and implicates caspase-3 as a sex-specific miRNA-sensitive node for recovery from ischemic stroke.

Repeated Intravenous Thrombolysis for Early Recurrent Stroke

Intravenous thrombolysis (IVT) within 4.5 hours from symptom onset improves functional outcome in patients with acute ischemic stroke. Its use in patients with previous stroke within the preceding 3 months is contraindicated because of the assumed higher risk of intracranial hemorrhage. In addition, tissue-type plasminogen activator may itself promote neurotoxicity and blood-brain barrier disruption. However, safety and effectiveness of repeated IVT is essentially unknown in patients with early (<3 months) recurrent stroke (ERS), because they were excluded from thrombolysis trials. This article reports the largest case series of repeated IVT in ERS. We reviewed databases of prospectively collected patient data of 8 European stroke centers for the presence of patients with ERS, who received IVT for both the index stroke and ERS. Demographics, clinical and radiological data, bleeding complications, and functional outcome were analyzed. We identified 19 subjects with repeated IVT in ERS. Mean age was 68±12 years, and 37% of them were female. Median interthrombolysis interval was 30 days (interquartile range, 13-50). Functional independence (modified Rankin scale score ≤2) was achieved in 79% of patients after the first and in 47.4% after repeated IV tissue-type plasminogen activator, respectively. There was no symptomatic intracranial hemorrhage. Median final infarct volume after the first IVT was 1.5 cm(3) (interquartile range, 0.5-3.1). Patients with small infarct volumes and robust clinical improvement might be considered for repeated IVT within 3 months. Studies following strict protocols and larger registries incorporating these patients might serve to identify selection criteria for the safe use of repeated IVT in ERS.

Hyperintense Acute Reperfusion Marker on FLAIR in Posterior Circulation Infarction.

PurposeIn the present study, we aimed to investigate the frequency of blood brain barrier injury in posterior circulation infarction as demonstrated by the hyperintense acute reperfusion marker (HARM) on fluid attenuated inversion recovery images (FLAIR).MethodsFrom a MRI report database we identified patients with posterior circulation infarction who underwent MRI, including perfusion-weighted images (PWI), within 12 hours after onset and follow-up MRI within 24 hours and analyzed diffusion-weighted images (DWI), PWI, FLAIR, and MR angiography (MRA). On FLAIR images, the presence of HARM was noted by using pre-specified criteria (focal enhancement in the subarachnoid space and/or the ventricles).ResultsOverall 16 patients (median age of patients 68.5 (IQR 55.5–82.75) years) with posterior circulation infarction were included. Of these, 13 (81.3%) demonstrated PCA occlusion, and 3 (18.7%) patients BA occlusion on MRA. Initial DWI demonstrated ischemic lesions in the thalamus (68.8%), splenium (18.8%), hippocampus (75%), occipital lobe (81.3%), mesencephalon (18.8%), pons (18.8%), and cerebellum (50%). On follow-up MRA recanalization was noted in 10 (62.5%) patients. On follow-up FLAIR images, HARM was observed in 8 (50%) patients. In all of these, HARM was detected remote from the acute ischemic lesion. HARM was more frequently observed in patients with vessel recanalization (p = 0.04), minor infarction growth (p = 0.01), and smaller ischemic lesions on follow-up DWI (p = 0.05).ConclusionsHARM is a frequent finding in posterior circulation infarction and associated with vessel recanalization, minor infarction growth as well as smaller infarction volumes in the course. Neuroradiologists should be cognizant of the fact that HARM may be present on short interval follow-up FLAIR images in patients with acute ischemic infarction who initially underwent MRI and received intravenous gadolinium-based contrast agents.

Abstract TP429: Early Oral Anticoagulation After Acute Ischemic Stroke in Patients With Atrial Fibrillation

Introduction: Uncertainty exists as to the optimum interval for initiation of oral anticoagulation (OAC) after an acute ischemic stroke (AIS) in patients with atrial fibrillation (AF). Randomized clinical trials of novel oral anticoagulants excluded patients with AIS within 7-14 days. We sought to identify patients at low risk for early initiation of OAC after AIS. Hypothesis: The benefit of starting OAC within 2 days to prevent recurrent AIS outweighs the risk of hemorrhagic transformation (HT) in select patients. Methods: Following IRB approval, we completed a retrospective review of patients from the Cleveland Clinic from 2012-2014 with AIS, AF, and at least 1 follow up visit. In addition to demographic and medical history, acute infarct volume on imaging, presence of HT on imaging prior to OAC, timing and type of oral anticoagulation, and ischemic and hemorrhagic complications were noted. Early OAC was defined as starting within 48 hours after stroke onset, and late OAC was thereafter. The two groups were compared using Fisher’s exact test for categorical and Wilcoxon Rank Sum for numeric variables. Results: One hundred patients (median age 76, interquartile range 66-84) met our study criteria. Thirty-one patients were started on OAC within 2 days vs 53 patients after 2 days (median 1 days vs median 11 days). Compared to patients started on OAC after 2 days, those who initiated OAC within 2 days had significantly lower infarct volume (median 3.35 ml vs median 9.8 ml; p&lt;0.0001), initial NIHSS (median 3 vs median 7; p &lt;0.0001), and fewer people with blood on brain imaging (3% vs 26%; p= 0.0074). Age, prior stroke, and choice of OAC were not significantly associated with timing of OAC. No patients had recurrent AIS or symptomatic HT at median follow-up observation of 37 days. One patient had a non-CNS major hemorrhage after starting OAC. Sixteen patients were not started on OAC for a variety of reasons. Conclusions: Our results suggest the safety of early initiation of OAC with 2 days in an appropriately selected population of patients with AIS, who have small infarct volumes, mild stroke severity, and lack of HT.

Abstract 142: Extended Therapeutic Window of a Novel Peptide Inhibitor of TRPM2 Channels Following Focal Cerebral Ischemia

Introduction: Recent data demonstrates that inhibition of TRPM2 channels protect the brain against ischemia, specifically in males. A major hindrance to our research has been the lack of specific TRPM2 inhibitors. The current study characterized the specificity and neuroprotective efficacy of a novel TRPM2 inhibitor developed in our laboratory. Methods: Fluorescent calcium imaging was used to determine inhibitor efficacy of the TRPM2 peptide inhibitor (tat-M2NX) in HEK293 cells stably expressing hTRPM2. tat-peptides were detected by immunohistochemistry using an anti-tat antibody. Adult (2-3 mo) and aged (18-20 mo) were subjected to 60 min middle cerebral artery occlusion (MCAo) and injected iv with tat-M2NX (20 mg/kg), control tat-SCR (20 mg/kg) or clotrimazole (CTZ) (30 mg/kg) either 20min prior or 3hr after reperfusion. Infarct size was assessed using TTC staining. Results: Successful TRPM2 inhibition in HEK293 cells was observed by decreased Ca2+ influx following H2O2 exposure. Male mice pre-treated with tat-M2NX had smaller infarct volume compared to tat-SCR; 29.2±4.6% (n=8) vs. 43.4±3.2% (n=8; p&lt;0.01), respectively. No effect of tat-M2NX was observed in female mice. Immunostaining demonstrates tat-M2NX accumulation in striatal and cortical neurons 4-6 hours of IV injection. Importantly, male TRPM2-/- mice were not further protected by tat-M2NX, demonstrating selectivity of our new inhibitor. Administration of tat-M2NX at a delayed time point (3hr) provided significant protection to males when analyzed at 24 hr (28.33 ± 5.1% (n=7) vs. 46.45 ± 3.0% (n=6; p&lt;0.01) or 4 days after MCAo (23.84 ± 4.416, (n=8) vs. 41.41 ± 2.831; (n=8; p&lt;0.01). In contrast, delayed administration of CTZ failed to reduce infarct volume. Finally, we observed that tat-M2NX reduced ischemic injury in aged male mice. Conclusions: These data demonstrate the development of a new peptide inhibitor of TRPM2 channels that provides protection from ischemic stroke in young adult and aged male animals with a relatively wide therapeutic window. Furthermore, we took advantage of TRPM2-/- mice to confirm specificity of tat-M2NX protection.