Measured Infarct Volume Research Articles

Editorial: the ischemic penumbra: still the target for stroke therapies?

Editorial: the ischemic penumbra: still the target for stroke therapies?

Safflor Protected Rat Cerebral Ischemia-reperfusion Injury Through Inhibiting the Expression of NF-kB and IL-1β

Objective: To observe the neutoprotective effect of the safflor on cerebral ischemia reperfusion injury in rat. Methods: Sixty-six rats were divided into six groups: the sham operation group, model group and four treat groups, with 11 rats in each group. Preconditioning with safflor (0.8, 1.6, 3.2 ml/kgd) and Nimodipine (2 ml/kgd) in treat groups respectively, and equal volume of saline in sham operation group and model group by peritoneal injection for 15 days before operation. To establish the focal cerebral ischemia model through right middle cerebral artery occlusion (MCAO) in ratsneurological function defected score and measurement of infarct volume was evaluated 24 hours later, and the level of Nuclear factor-kappa B (NF-κB) and Interleukin-1β (IL-1β) in peripheral zone of ischemia was detected by immunohistochemisty. Results: The neurological function defect score in treatment groups is lower, and the volume of infarcted tissue is reduced significantly as compared to the model group (P <0.05). The level of NF-κB and IL-1β protein in treatment groups is also significantly decreased contrast with the model group (P <0.05). Conclusion: Safflor possesses obvious neuroprotective effect on the cerebral ischemia reperfusion injury in rats, which may work in suppressing the activity of NF-κB and the expression of IL-1β protein. Keywords: Cerebral ischemia reperfusion injury, IL-1β, NF-κB, safflor.

Abstract 33: Vagus Nerve Stimulation for Acute Stroke Treatment: Role of Cholinergic Anti-Inflammatory Pathway

Introduction: Electrical stimulation of the cervical vagus nerve is neuroprotective after MCAO in rats; decrease in infarct volume ranges from ~40% (using surgically implanted electrodes) to ~30% (using clinically applicable non-invasive devices). The exact mechanism of vagus nerve stimulation (VNS)-induced neuroprotection is not known, but so far cerebral blood flow-related mechanism has been eliminated. VNS attenuates systemic inflammation via activation of alpha7 nicotinic acetylcholine receptors (α7 nAChR) on macrophages. We hypothesized that α7 nAChR -mediated anti-inflammatory effect plays a mechanistic role in VNS-induced neuroprotection after cerebral ischemia. Methods: Focal ischemia was induced by 2 hour transient MCAO in Wistar rats and verified by &gt;60% drop in baseline cerebral blood flow. Methyllycaconitine (MLA; 10 mg/kg, IP) was used to block α7 nAChRs. Animals were randomly assigned to one of four experimental groups: sham stimulation/vehicle, sham stimulation/MLA, VNS/vehicle, VNS/MLA (n=6 in each). VNS was initiated 30 minutes after MCAO and delivered for 1 hour via implanted electrodes, using previously published stimulation parameters. Animals were euthanized 24 hours later to measure infarct volume by TTC. In separate cohorts, immunohistochemistry was used to assess the changes in brain levels of α7 nAChR-related cytokines, TNF-α and high mobility group box protein 1 (HMGB1), in sham-stimulated and VNS groups. Results: Mean infarct volume in sham-stimulated and VNS groups were 43.83 ± 1.53% and 25.33 ± 3.39%, respectively (p&lt;0.05). MLA abolished the neuroprotective effect of VNS; after MLA treatment mean infarct volume in sham-stimulated and VNS groups were 45.24 ± 4.78% and 48.58 ± 2.78%, respectively (p=n.s.). MLA alone had no effect on ischemic outcome; there was no difference in infarct volume between MLA- treated and untreated sham-stimulated animals (p=n.s.). Ischemia-induced elevation in TNF-α and decrease in HMGB1 levels were completely reversed by VNS as early as 3 hours after ischemia. Conclusion: This study shows that anti-inflammatory mechanisms via nicotinic acetylcholine receptor-mediated signaling play a role in protective effect of VNS against ischemic tissue damage.

Abstract 168: Intra-arterial Stem Cell Treatment Reduces Ischemic Brain Injury In Reproductively Senescent Female Rats

Background: Cell therapy is emerging as a promising treatment for stroke. We recently we demonstrated the efficacy of intra-arterial delivery of MSCs (IA MSCs) at 24h after a reversible middle cerebral artery occlusion (MCAo). Our study also identified a maximum tolerated dose of MSCs that could be delivered IA without compromising middle cerebral artery flow. The IA approach avoids first-pass trapping of MSCs in the lungs and liver as seen with intravenous delivery. Intra-arterial treatment is also minimally invasive and widely available in clinical practice and thus appealing for clinical translation. Since majority of ischemic strokes in women occur after onset of menopause it is crucial that we test the efficacy of IA MSCs in reproductively senescent females consistent with STAIR recommendations. We aimed to validate the efficacy of IA MSCs in reproductively senescent female rats. Methods: Retired breeder female (9-11 months; 280-350 g) Sprague-Dawley rats showing estrous acyclicity were exposed to MCAo (90 min). A day later, rats were treated with IA MSCs (1x10^5 cells) or phosphate-buffered saline (PBS). MSCs or PBS treated rats were sacrificed at 28-30 days for infarct volume measurement using histology. To test motor function, the rotarod test was performed. Rats were trained for 3 consecutive days for the rotarod test before undergoing the MCAo procedure. The mean duration (in seconds) on the device was recorded from 3 rotarod measurements 1 day before surgery. The rats were tested at 1, 7, 15 and 28-30 days after MCAo. Results: We observed significantly lower mean infarct volume in the MSC-treated group (12 ± 3 mm3; n=6) compared to the PBS-treated group (29 ± 7 mm3; Mean ± SEM; n=4, p&lt;0.05). Treatment at 1 day after MCAO with MSCs significantly improved functional recovery, as evidenced by improved rotarod test results and neurological scores at 7, 15 and 30 days (P&lt;0.05) compared with the PBS-treated group. Conclusions: Intra-arterial stem cell treatment reduces ischemic brain injury and improves functional outcomes in reproductively senescent female rats. Validating the efficacy of IA MSC treatment using a reproductively senescent animal stroke model suggests high potential for future clinical translation in a population at high risk for stroke.

Platelet rich clots are resistant to lysis by thrombolytic therapy in a rat model of embolic stroke.

BackgroundEarly recanalization of occluded vessels in stroke is closely associated with improved clinical outcome. Microbubble-enhanced sonothrombolysis is a promising therapy to improve recanalization rates and reduce the time to recanalization. Testing any thrombolytic therapy requires a model of thromboembolic stroke, but to date these models have been highly variable with regards to clot stability. Here, we developed a model of thromboembolic stroke in rats with site-specific delivery of platelet-rich clots (PRC) to the main stem of the middle cerebral artery (MCA). This model was used in a subsequent study to test microbubble-enhanced sonothrombolysis.MethodsIn Study 1 we investigated spontaneous recanalization rates of PRC in vivo over 4 hours and measured infarct volumes at 24 hours. In Study 2 we investigated tPA-mediated thrombolysis and microbubble-enhanced sonothrombolysis in this model.ResultsStudy 1 demonstrated stable occlusion out to 4 hours in 5 of 7 rats. Two rats spontaneously recanalized at 40 and 70 minutes post-embolism. Infarct volumes were not significantly different in recanalized rats, 43.93 ± 15.44% of the ischemic hemisphere, compared to 48.93 ± 3.9% in non-recanalized animals (p = 0.7). In Study 2, recanalization was not observed in any of the groups post-treatment.ConclusionsSite specific delivery of platelet rich clots to the MCA origin resulted in high rates of MCA occlusion, low rates of spontaneous clot lysis and large infarction. These platelet rich clots were highly resistant to tPA with or without microbubble-enhanced sonothrombolysis. This resistance of platelet rich clots to enhanced thrombolysis may explain recanalization failures clinically and should be an impetus to better clot-type identification and alternative recanalization methods.Electronic supplementary materialThe online version of this article (doi:10.1186/s13231-014-0014-y) contains supplementary material, which is available to authorized users.

Mitochondrial Dihydrolipoamide Dehydrogenase is Upregulated in Response to Intermittent Hypoxic Preconditioning.

Intermittent hypoxia preconditioning (IHP) has been shown to protect neurons against ischemic stroke injury. Studying how proteins respond to IHP may identify targets that can help fight stroke. The objective of the present study was to investigate whether mitochondrial dihydrolipoamide dehydrogenase (DLDH) would respond to IHP and if so, whether such a response could be linked to neuroprotection in ischemic stroke injury. To do this, we subjected male rats to IHP for 20 days and measured the content and activity of DLDH as well as the three α-keto acid dehydrogenase complexes that contain DLDH. We also measured mitochondrial electron transport chain enzyme activities. Results show that DLDH content was indeed upregulated by IHP and this upregulation did not alter the activities of the three α-keto acid dehydrogenase complexes. Results also show that the activities of the five mitochondrial complexes (I-V) were not altered either by IHP. To investigate whether IHP-induced DLDH upregulation is linked to neuroprotection against ischemic stroke injury, we subjected both DLDH deficient mouse and DLDH transgenic mouse to stroke surgery followed by measurement of brain infarction volume. Results indicate that while mouse deficient in DLDH had exacerbated brain injury after stroke, mouse overexpressing human DLDH also showed increased brain injury after stroke. Therefore, the physiological significance of IHP-induced DLDH upregulation remains to be further investigated.

Limited Reliability of Computed Tomographic Perfusion Acute Infarct Volume Measurements Compared With Diffusion-Weighted Imaging in Anterior Circulation Stroke

Diffusion-weighted imaging (DWI) can reliably identify critically ischemic tissue shortly after stroke onset. We tested whether thresholded computed tomographic cerebral blood flow (CT-CBF) and CT-cerebral blood volume (CT-CBV) maps are sufficiently accurate to substitute for DWI for estimating the critically ischemic tissue volume. Ischemic volumes of 55 patients with acute anterior circulation stroke were assessed on DWI by visual segmentation and on CT-CBF and CT-CBV with segmentation using 15% and 30% thresholds, respectively. The contrast:noise ratios of ischemic regions on the DWI and CT perfusion (CTP) images were measured. Correlation and Bland-Altman analyses were used to assess the reliability of CTP. Mean contrast:noise ratios for DWI, CT-CBF, and CT-CBV were 4.3, 0.9, and 0.4, respectively. CTP and DWI lesion volumes were highly correlated (R(2)=0.87 for CT-CBF; R(2)=0.83 for CT-CBV; P<0.001). Bland-Altman analyses revealed little systemic bias (-2.6 mL) but high measurement variability (95% confidence interval, ±56.7 mL) between mean CT-CBF and DWI lesion volumes, and systemic bias (-26 mL) and high measurement variability (95% confidence interval, ±64.0 mL) between mean CT-CBV and DWI lesion volumes. A simulated treatment study demonstrated that using CTP-CBF instead of DWI for detecting a statistically significant effect would require at least twice as many patients. The poor contrast:noise ratios of CT-CBV and CT-CBF compared with those of DWI result in large measurement error, making it problematic to substitute CTP for DWI in selecting individual acute stroke patients for treatment. CTP could be used for treatment studies of patient groups, but the number of patients needed to identify a significant effect is much higher than the number needed if DWI is used.

Computer-assisted volumetric measurement of core infarct volume in pediatric patients: feasibility for clinical use and development of quantitative metrics for outcome prediction.

Infarct volume may predict clinical outcome in acute stroke, but manual segmentation techniques limit its routine use. We hypothesized that computer-assisted volumetric analysis to quantify acute infarct volume will show no difference compared with manual segmentation but will show increased speed of performance and will correlate with outcome. Patients with acute stroke younger than 18 years were included. Infarct volume on diffusion-weighted imaging was quantified by using computer-assisted volumetric and manual techniques. The Pediatric Stroke Outcome Measure scored clinical outcome. Computer-assisted volumetric and manual techniques were compared with correlation coefficients. Linear regression analysis compared Pediatric Stroke Outcome Measure with core infarct volume and percentage volume of brain infarction. Twenty-three patients were analyzed (mean age, 4.6 years). Mean infarct volume from computer-assisted volumetric and manual approaches was 65.6 and 63.7 mL, respectively (P = .56). Concordance correlation between methods was 0.980, and between users, 0.968. The mean times for segmentation between computer-assisted volumetric and manual techniques were <1 minute and 7.3 minutes (P < .001). The mean infarct volumes for good and poor outcome groups were 7.4 and 75.7 mL (P < .007). The mean percentages of infarcted brain parenchyma for good and poor outcome groups were 0.6% and 10.4% (P < .006). Volumes of 32 mL and 3% for infarcted brain were associated with poor outcome in all patients. Computer-assisted volumetric quantification of infarct volume is reproducible, is significantly faster than manual techniques, and may have important applications for future clinical workflow. Core infarct volumes and infarct percentage correlated with outcome severity.

Phosphorylation enhances recombinant HSP27 neuroprotection against focal cerebral ischemia in mice

Heat shock protein 27 (HSP27) exerts cytoprotection against many cellular insults including cerebral ischemia. We previously indicated that intravenous injection of HSP27 purified from human lymphocytes (hHSP27) significantly reduced infarct volume following cerebral ischemia–reperfusion injury, while recombinant HSP27 (rHSP27) was less effective. Phosphorylation is important for HSP27 function, and hHSP27 was more highly phosphorylated than rHSP27. We hypothesized that MAPKAP kinase 2 in vitro-phosphorylated rHSP27 (prHSP27) might increase its brain protection. Mice underwent transient 1-h middle cerebral artery occlusion (MCAO), and then received tail-vein injections of one of the following 1h after reperfusion: hHSP27 as positive control, rHSP27, prHSP27, or bovine serum albumin (BSA) as control. We measured infarct volume, neurological deficits, neurological severity, physiological parameters, cell-death, oxidative stress, and inflammatory response. Compared with BSA controls (30.7±3.1mm3, n=5), infarct volume was reduced by 67% in the hHSP27 positive-control group (10.1±4.6mm3, P<0.001, n=5), 17% following rHSP27 (25.4±3.6mm3, P<0.05, n=5), and 46% following prHSP27 (16.5±4.0mm3, P<0.001, n=9). Compared to the rHSP27 and BSA-treated groups, prHSP27 also reduced functional deficits, and significantly suppressed apoptosis, oxidative stress, and inflammatory responses. Here, we showed the superior neuroprotective effects of phosphorylated HSP27 by administering prHSP27. prHSP27 may be a useful therapeutic agent to protect against acute cerebral ischemic stroke.

Vigorous Exercise Training Improves Reactivity of Cerebral Arterioles and Reduces Brain Injury Following Transient Focal Ischemia

Our objective was to examine whether vigorous exercise training (VExT) could influence nitric oxide synthase (NOS)-dependent vasodilation and transient focal ischemia-induced brain injury. Rats were divided into sedentary (SED) or VExT groups. Exercise was carried out 5 days/week for a period of 8-10 weeks. First, we measured responses of pial arterioles to an eNOS-dependent (ADP), an nNOS-dependent (NMDA) and a NOS-independent (nitroglycerin) agonist in SED and VExT rats. Second, we measured infarct volume in SED and VExT rats following middle cerebral artery occlusion (MCAO). Third, we measured superoxide levels in brain tissue of SED and VExT rats under basal and stimulated conditions. We found that eNOS- and nNOS-dependent, but not NOS-independent vasodilation, was increased in VExT compared to SED rats, and this could be inhibited with L-NMMA in both groups. In addition, we found that VExT reduced infarct volume following MCAO when compared to SED rats. Further, superoxide levels were similar in brain tissue from SED and VExT rats under basal and stimulated conditions. We suggest that VExT potentiates NOS-dependent vascular reactivity and reduces infarct volume following MCAO via a mechanism that appears to be independent of oxidative stress, but presumably related to an increase in the contribution of nitric oxide.

Posttreatment Variables Improve Outcome Prediction after Intra-Arterial Therapy for Acute Ischemic Stroke

Background: There are multiple clinical and radiographic factors that influence outcomes after endovascular reperfusion therapy (ERT) in acute ischemic stroke (AIS). We sought to derive and validate an outcome prediction score for AIS patients undergoing ERT based on readily available pretreatment and posttreatment factors. Methods: The derivation cohort included 511 patients with anterior circulation AIS treated with ERT at 10 centers between September 2009 and July 2011. The prospective validation cohort included 223 patients with anterior circulation AIS treated in the North American Solitaire Acute Stroke registry. Multivariable logistic regression identified predictors of good outcome (modified Rankin score ≤2 at 3 months) in the derivation cohort; model β coefficients were used to assign points and calculate a risk score. Discrimination was tested using C statistics with 95% confidence intervals (CIs) in the derivation and validation cohorts. Calibration was assessed using the Hosmer-Lemeshow test and plots of observed to expected outcomes. We assessed the net reclassification improvement for the derived score compared to the Totaled Health Risks in Vascular Events (THRIVE) score. Subgroup analysis in patients with pretreatment Alberta Stroke Program Early CT Score (ASPECTS) and posttreatment final infarct volume measurements was also performed to identify whether these radiographic predictors improved the model compared to simpler models. Results: Good outcome was noted in 186 (36.4%) and 100 patients (44.8%) in the derivation and validation cohorts, respectively. Combining readily available pretreatment and posttreatment variables, we created a score (acronym: SNARL) based on the following parameters: symptomatic hemorrhage [2 points: none, hemorrhagic infarction (HI)1-2 or parenchymal hematoma (PH) type 1; 0 points: PH2], baseline National Institutes of Health Stroke Scale score (3 points: 0-10; 1 point: 11-20; 0 points: >20), age (2 points: <60 years; 1 point: 60-79 years; 0 points: >79 years), reperfusion (3 points: Thrombolysis In Cerebral Ischemia score 2b or 3) and location of clot (1 point: M2; 0 points: M1 or internal carotid artery). The SNARL score demonstrated good discrimination in the derivation (C statistic 0.79, 95% CI 0.75-0.83) and validation cohorts (C statistic 0.74, 95% CI 0.68-0.81) and was superior to the THRIVE score (derivation cohort: C statistic 0.65, 95% CI 0.60-0.70; validation cohort: C-statistic 0.59, 95% CI 0.52-0.67; p < 0.01 in both cohorts) but was inferior to a score that included age, ASPECTS, reperfusion status and final infarct volume (C statistic 0.86, 95% CI 0.82-0.91; p = 0.04). Compared with the THRIVE score, the SNARL score resulted in a net reclassification improvement of 34.8%. Conclusions: Among AIS patients treated with ERT, pretreatment scores such as the THRIVE score provide only fair prognostic information. Inclusion of posttreatment variables such as reperfusion and symptomatic hemorrhage greatly influences outcome and results in improved outcome prediction.

Calycosin-7-O-β-d-glucoside regulates nitric oxide /caveolin-1/matrix metalloproteinases pathway and protects blood–brain barrier integrity in experimental cerebral ischemia–reperfusion injury

Ethnopharmacology relevanceAstragali Radix (AR) has been used for thousands years to treat ischemic stroke. Calycosin and its glycoside form calycosin-7-O-β-d-glucoside (CG) are two representative isoflavones in Astragali Radix. However, its neurological effects and related molecular mechanisms are largely unknown. The present study aims to evaluate the neuroprotective effects of CG on blood–brain barrier (BBB) integrity of ischemic brain tissue and explore the relevant signaling mechanisms. Material and methodMale adult Sprague-Daweley rats were subjected to 2h of middle cerebral artery occlusion (MCAO) plus 24h or 14 days of reperfusion. CG (26.8 mg/kg) was intraperitoneally administered into the rats at 15min before onset of ischemia. The neuroprotective effects of CG were evaluated by measuring infarct volume, histological damage and BBB permeability. Furthermore, the effects of CG on scavenging nitric oxide (NO), and modulating matrix metalloproteinases (MMPs) and caveolin-1 (cav-1) were investigated with in vitro cultured brain microvascular endothelial cells treated with NO donor or oxygen–glucose deprivation (OGD) and/or in vivo rat model of MCAO cerebral ischemia–reperfusion injury. ResultsCG treatment significantly reduced infarct volume, histological damage and BBB permeability in the in vivo MCAO ischemia–reperfusion rat model. CG treatment remarkably inhibited the expression and activities of MMPs, and secured the expression of cav-1 and tight junction proteins in the microvessels isolated from ischemic rat cortex. Furthermore, CG was revealed to scavenge NO, inhibit the activities of MMP-2 and MMP-9, and attenuate cell death in the in vitro cultured brain microvascular endothelial cells under OGD condition. ConclusionCG could protect BBB integrity in experimental cerebral ischemia–reperfusion injury via regulating NO/cav-1/MMPs pathway.

Anti-neutrophil antibody enhances the neuroprotective effects of G-CSF by decreasing number of neutrophils in hypoxic ischemic neonatal rat model

ObjectivesNeonatal hypoxia ischemia (HI) is an injury that can lead to neurological impairments such as behavioral and learning disabilities. Granulocyte-colony stimulating factor (G-CSF) has been demonstrated to be neuroprotective in ischemic stroke however it has also been shown to induce neutrophilia, ultimately exacerbating neuronal injury. Our hypothesis is that coadministration of anti-neutrophil antibody (Ab) with G-CSF will decrease blood neutrophil counts thereby reducing infarct volume and improving neurological function post HI brain injury. MethodsRat pups were subjected to unilateral carotid artery ligation followed by 2.5h of hypoxia. Animals were randomly assigned to five groups: Sham (n=15), vehicle (HI, n=15), HI with G-CSF treatment (n=15), HI with G-CSF+Ab treatment (n=15), and HI with Ab treatment (n=15). Ab (325μg/kg) was administered intraperitoneally while G-CSF (50μg/kg) was administered subcutaneously 1h post HI followed by daily injections for 3 consecutive days. Animals were euthanized at 96h post HI for blood neutrophil counts and brain infarct volume measurements as well as at 5weeks for neurological function testing and brain weight measurements. Lung and spleen weights at both time points were further analyzed. ResultsThe G-CSF treatment group showed tendencies to reduce infarct volume and improve neurological function while significantly increasing neutrophil counts. On the other hand, the G-CSF+Ab group significantly reduced infarct volume, improved neurological function and decreased neutrophil counts. The Ab alone group showed reversal of the neuroprotective effects of the G-CSF+Ab group. No significant differences were found in peripheral organ weights between groups. ConclusionOur data suggest that coadministration of G-CSF with Ab not only prevented brain atrophy but also significantly improved neurological function by decreasing blood neutrophil counts. Hence the neuroprotective effects of G-CSF may be further enhanced if neutrophilia is avoided.

Automatic detection and quantification of acute cerebral infarct by fuzzy clustering and histographic characterization on diffusion weighted MR imaging and apparent diffusion coefficient map.

Determination of the volumes of acute cerebral infarct in the magnetic resonance imaging harbors prognostic values. However, semiautomatic method of segmentation is time-consuming and with high interrater variability. Using diffusion weighted imaging and apparent diffusion coefficient map from patients with acute infarction in 10 days, we aimed to develop a fully automatic algorithm to measure infarct volume. It includes an unsupervised classification with fuzzy C-means clustering determination of the histographic distribution, defining self-adjusted intensity thresholds. The proposed method attained high agreement with the semiautomatic method, with similarity index 89.9 ± 6.5%, in detecting cerebral infarct lesions from 22 acute stroke patients. We demonstrated the accuracy of the proposed computer-assisted prompt segmentation method, which appeared promising to replace the laborious, time-consuming, and operator-dependent semiautomatic segmentation.

Contrast-free T1 mapping at 3T can characterize chronic myocardial infarctions with high diagnostic accuracy

Background Characterizing myocardial infarctions (MIs) on the basis of LGE CMR requires gadolinium infusion, which poses limitations in certain patient populations and imaging workflow. We hypothesized that T1 differences between MI and remote territories at 3T would enable reliable characterization of chronic MI. Methods Canines (n = 29) underwent CMR at 7 days (acute) and 4 months (chronic) following reperfused MIs at 3T (n = 19) and 1.5T (n = 10). Contrast-free T1 maps (MOLLI; 8 TIs with 2 inversion blocks of 3+5 images; minimum TI = 110 ms; ΔTI = 80 ms; TR/TE = 2.2/1.1 ms) and LGE images (IR-prepared FLASH; TI optimized to null remote myocardium; TR/TE = 3.5/1.75 ms) were acquired. MI location, size and transmurality were determined using Mean+5SD criterion relative to remote myocardium. T2 maps (T2-prepared SSFP; T2 preparation times = 0, 24 and 55 ms; TR/TE = 2.8/1.4 ms) were acquired to compare acute and chronic MIs. Commonly used imaging parameters were slice thickness = 6 mm and spatial resolution = 1.3 × 1.3 mm 2. Histological validation was sought to confirm the presence of replacement fibrosis within the chronic infarct zones. Results Contrast-free T1 maps and LGE images of a representative mid-ventricular slice, along with AHA 17-segment bulls-eye plots depicting the MI size and transmurality acquired from a canine scanned imaged 4 months post-MI at 3T are shown in Figure 1. Bland-Altman plots, linear regression plots and receiver-operating characteristic curve comparing T1 maps and LGE images for measuring infarct volume (IV, %LV) and transmurality (IT) in the chronic phase at 3T are also shown. At 3T, T1 maps and LGE images were not different for measuring IV (5.6 ± 3.7% vs. 5.5 ± 3.7%; p = 0.61) and IT (44 ± 15% vs. 46 ± 15%; p = 0.81) in the chronic phase, but were significantly different in the acute phase (IS: 13.3 ± 8.4% vs. 11.6 ± 6.8%, p = 0.007 and IT: 64 ± 19% vs. 56 ± 17%, p = 0.007). At 1.5T, IV and IT were significantly underestimated by T1 maps relative to LGE images during acute (IS: 9.4 ± 5.6% vs. 15.5 ± 9.4%, p < 0.001 and IT: 59 ± 5% vs. 76 ± 6%, p < 0.001) and chronic phases (IS: 2.1 ± 1.2% vs. 4.8 ± 1.8%, p < 0.001 and IT: 47 ± 7% vs. 66 ± 9%, p < 0.001). At 3T and 1.5T, T1 values of the MI remained elevated in both acute (3T: p < 0.001; 1.5T: p < 0.001) and chronic phases (3T: p < 0.001; 1.5T: p = 0.037) compared to remote myocardium (Table 1). At both 3T and 1.5T, relative to the remote myocardium, T2 values of the MI were elevated in the acute phase (p < 0.001 for both cases), but were not different in the chronic phase (3T: p = 0.19, 1.5T: p = 0.55). Ex-vivo TTC and Elastinmodified Masson’s Trichrome (EMT) stainings (Figure 1) confirmed extensive replacement fibrosis within the MI territories at 4 months post MI. Sensitivity and specificity of contrast-free T1 maps at 3T for detecting chronic MIs were 95% and 97%, respectively. Conclusions Contrast-free T1 maps at 3T can determine the location, size and transmurality of chronic MIs with high diagnostic accuracy.

Continuous oral administration of atorvastatin ameliorates brain damage after transient focal ischemia in rats

AimsPre-treatment with statins is known to ameliorate ischemic brain damage after experimental stroke, and is independent of cholesterol levels. We undertook pre- vs post-ischemic treatment with atorvastatin after focal cerebral ischemia in rats. Main methodsMale Sprague–Dawley rats underwent transient 90-min middle cerebral artery occlusion (MCAO). Atorvastatin (20mg/kg/day) or vehicle was administered orally. Rats were divided into vehicle-treated, atorvastatin pre-treatment, atorvastatin post-treatment, and atorvastatin continuous-treatment groups. In the pre-treatment, rats were given atorvastatin or vehicle for 7days before MCAO. In the post-treatment, rats received atorvastatin or vehicle for 7days after MCAO. Measurement of infarct volume, as well as neurological and immunohistochemical assessments, were done 24h and 7days after reperfusion. Key findingsEach atorvastatin-treated group demonstrated significant reductions in infarct and edema volumes compared with the vehicle-treated group 24h after reperfusion. Seven days after reperfusion, infarct volumes in the post-treatment group and continuous-treatment group (but not the pre-treatment group) were significantly smaller than in the vehicle-treated group. Only the continuous-treatment group had significantly improved neurological scores 7days after reperfusion compared with the vehicle group. Post-treatment and continuous-treatment groups had significantly decreased lipid peroxidation, oxidative DNA damage, microglial activation, expression of tumor necrosis factor-alpha, and neuronal damage in the cortical ischemic boundary area after 7days of reperfusion. SignificanceThese results suggest that continuous oral administration (avoiding withdrawal) with statins after stroke may reduce the extent of post-ischemic brain damage and improve neurological outcome by inhibiting oxidative stress and inflammatory responses.

Endothelial Nitric Oxide Synthase Regulates White Matter Changes via the BDNF/TrkB Pathway after Stroke in Mice

Stroke induced white matter (WM) damage is associated with neurological functional deficits, but the underlying mechanisms are not well understood. In this study, we investigate whether endothelial nitric oxide synthase (eNOS) affects WM-damage post-stroke. Adult male wild-type (WT) and eNOS knockout (eNOS-/-) mice were subjected to middle cerebral artery occlusion. Functional evaluation, infarct volume measurement, immunostaining and primary cortical cell culture were performed. To obtain insight into the mechanisms underlying the effects of eNOS-/- on WM-damage, measurement of eNOS, brain-derived neurotrophic factor (BDNF) and its receptor TrkB in vivo and in vitro were also performed. No significant differences were detected in the infarction volume, myelin density in the ipsilateral striatal WM-bundles and myelin-based protein expression in the cerebral ischemic border between WT and eNOS-/- mice. However, eNOS-/- mice showed significantly: 1) decreased functional outcome, concurrent with decreases of total axon density and phosphorylated high-molecular weight neurofilament density in the ipsilateral striatal WM-bundles. Correlation analysis showed that axon density is significantly positive correlated with neurological functional outcome; 2) decreased numbers of oligodendrocytes / oligodendrocyte progenitor cells in the ipsilateral striatum; 3) decreased synaptophysin, BDNF and TrkB expression in the ischemic border compared with WT mice after stroke (n = 12/group, p<0.05). Primary cortical cell culture confirmed that the decrease of neuronal neurite outgrowth in the neurons derived from eNOS-/- mice is mediated by the reduction of BDNF/TrkB (n = 6/group, p<0.05). Our data show that eNOS plays a critical role in WM-damage after stroke, and eNOS-/--induced decreases in the BDNF/TrkB pathway may contribute to increased WM-damage, and thereby decrease functional outcome.

Deficient eNOS Phosphorylation Is a Mechanism for Diabetic Vascular Dysfunction Contributing to Increased Stroke Size

Phosphorylation of eNOS, an important post-translational modulator of its enzymatic activity, is reduced in diabetes mellitus. We hypothesized that modulation of eNOS phosphorylation could overcome diabetic vascular dysfunction and improves the outcome to stroke. We used the db/db mouse model of type 2 diabetes mellitus. We mated db/db mice with eNOS knock-in mice that carry single amino acid mutations at the S1176 phosphorylation site; the phosphomimetic SD mutation (serine replaced by aspartate) shows increased eNOS enzymatic activity, whereas the unphosphorylatable SA mutation (serine replaced by alanine) shows decreased eNOS activity. We characterized the vascular anatomy, baseline physiological parameters, and vascular reactivity. We used the middle cerebral artery occlusion model of stroke and measured infarct volume and neurological deficits. db/db mice showed diminished eNOS phosphorylation at S1176. eNOS SD and SA mutations do not change the vascular anatomy at the Circle of Willis, brain capillary density, heart rate, or arterial blood gases of db/db mice. The eNOS SD mutation, but not the SA mutation, lowers blood pressure and improves vascular reactivity to acetylcholine in db/db mice. The eNOS SD mutation reduces stroke size and neurological deficit after middle cerebral artery occlusion. Diminished eNOS phosphorylation is a mechanism of vascular dysfunction in db/db mice. We show here that modulation of the eNOS S1176 phosphorylation site in db/db mice is associated with improved vascular reactivity and improved outcome to stroke after middle cerebral artery occlusion.

Effect of focal mild hypothermia on expression of MMP-9, TIMP-1, Tau-1 and β-APP in rats with cerebral ischaemia/reperfusion injury

Primary objective: Following stroke, hypothermia is reported to reduce both cellular and extracellular damage. This study aimed to examine the effects of focal mild hypothermia on proteins associated with both extracellular (matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of MMP-9 (TIMP-1)) and cellular damage (Tau-1 and β-amyloid precursor protein (β-APP)) to characterize the protective effects of hypothermia.Methods and procedures: Male Wistar rats received ischaemic damage using a transient, focal ischaemia/reperfusion model. Afterwards, one group (HT) received 6 hours of focal mild hypothermia (33 °C) applied to the head, while another remained at normal temperature (NT). The brains were collected at 6, 12, 24, 48 and 72 hours after hypothermia to measure infarct volume ratio and to detect cells immunopositive for MMP-9, TIMP-1, Tau-1 and β-APP, while neurological deficits were examined separately after 2 weeks.Main outcomes and results: Focal mild hypothermia had no effect on infarct volume ratio but expression of MMP-9, TIMP-1 Tau-1 and β-APP was decreased. Furthermore, neurological function in the HT group was better than in the NT group.Conclusions: Focal mild hypothermia has protective effects on cerebral ischaemia-reperfusion injury characterized by decreased expression of MMP-9, TIMP-1, Tau-1 and β-APP, along with improvement of neurological function despite no changes in infarct volume.

The Utility of Infarct Volume Measurement in Pediatric Ischemic Stroke

This study aims to determine if stroke volume as measured on diffusion-weighted imaging is associated with neurologic outcome in children with acute arterial ischemic stroke. A cohort of patients presenting to a tertiary care children's hospital with acute ischemic stroke were studied. The relationship between stroke volume, clinical characteristics, and neurologic outcome utilizing the Glasgow Outcome Scale were analyzed. In children with poor outcome, the median volume of infarction on diffusion-weighted imaging was larger when compared with children who had a good outcome. Children with stroke volume >10% of total brain volume were more likely than patients with stroke volume <5% total brain volume to have a poor outcome. Seizures were associated with a 10.5-fold increase in the risk of a poor outcome. Stroke volume, in conjunction with clinical characteristics, can assist practitioners in identifying a subset of patients with acute ischemic stroke who might benefit from aggressive medical and/or surgical management.