Use of TTC staining for the evaluation of tissue injury in the early phases of reperfusion after focal cerebral ischemia in rats

Cerebroprotective effect of Eclipta alba against global model of cerebral ischemia induced oxidative stress in rats

Oxidative stress is believed to contribute to neuronal damage induced by cerebral ischemia/reperfusion (I/R) injury. The present study was undertaken to evaluate the possible cerebroprotective and antioxidant effect of hydroalcoholic extract of Eclipta alba against global cerebral ischemia in the rat. Adult Wistar albino rats were treated with extract of Eclipta alba (250 and 500mg/kg/day, p.o.) for 10 days. The global cerebral ischemia-reperfusion injury was induced by occluding bilateral common carotid arteries (BCCA) for 30min, followed by 4h reperfusion. Quercetin (20mg/kg, i.p.) was used for the reference compound. After that, animals were sacrificed by decapitation, brain was removed, various biochemical estimations, cerebral edema, assessment of cerebral infarct size, and histopathological examinations were carried out. BCCA caused significant depletion in superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), catalase (CAT), glutahione-S-transferase (GST), glutathione ruductase (GR) and significant increase in malondialdehyde (MDA) in brain. Pretreatment with hydroalcoholic extract of Eclipta alba significantly reversed the levels of biochemical parameters and significantly reduced the edema and cerebral infarct size as compared to the ischemic control group. Eclipta alba at higher dose markedly reduced ischemia-induced neuronal loss of the brain. Reduction of cerebral edema, an early symptom of ischemia, is one of the most important remedies for reducing subsequent chronic neural damage in stroke. The results of the study show that Eclipta alba pretreatment ameliorates cerebral ischemia/reperfusion injury and enhances the antioxidant defense against BCCA occlusion induced I/R in rats; so it exhibits cerebroprotective property. HPLC fingerprint of hydroalcoholic extract of Eclipta alba was performed for conforming the coumestan present in the plant extract.

Quercetin attenuates cell apoptosis in focal cerebral ischemia rat brain via activation of BDNF-TrkB-PI3K/Akt signaling pathway

Many studies have demonstrated that apoptosis play an important role in cerebral ischemic pathogenesis and may represent a target for treatment. Neuroprotective effect of quercetin has been shown in a variety of brain injury models including ischemia/reperfusion. It is not clear whether BDNF-TrkB-PI3K/Akt signaling pathway mediates the neuroprotection of quercetin, though there has been some reports on the quercetin increased brain-derived neurotrophic factor (BDNF) level in brain injury models. We therefore first examined the neurological function, infarct volume and cell apoptosis in quercetin treated middle cerebral artery occlusion (MCAO) rats. Then the protein expression of BDNF, cleaved caspase-3 and p-Akt were evaluated in either the absence or presence of PI3K inhibitor (LY294002) or tropomyosin receptor kinase B (TrkB) receptor antagonist (K252a) by immunohistochemistry staining and western blotting. Quercetin significantly improved neurological function, while it decreased the infarct volume and the number of TdT mediated dUTP nick end labeling positive cells in MCAO rats. The protein expression of BDNF, TrkB and p-Akt also increased in the quercetin treated rats. However, treatment with LY294002 or K252a reversed the quercetin-induced increase of BDNF and p-Akt proteins and decrease of cleaved caspase-3 protein in focal cerebral ischemia rats. These results demonstrate that quercetin can decrease cell apoptosis in the focal cerebral ischemia rat brain and the mechanism may be related to the activation of BDNF-TrkB-PI3K/Akt signaling pathway.

Well-defined cross-linked antioxidant nanozymes for treatment of ischemic brain injury

Development of well-defined nanomedicines is critical for their successful clinical translation. A simple synthesis and purification procedure is established for chemically cross-linked polyion complexes of Cu/Zn superoxide dismutase (SOD1) or catalase with a cationic block copolymer, methoxy-poly(ethylene glycol)-block-poly(L-lysine hydrochloride) (PEG-pLL₅₀). Such complexes, termed cross-linked nanozymes (cl-nanozymes) retain catalytic activity and have narrow size distribution. Moreover, their cytotoxicity is decreased compared to non-cross-linked complexes due to suppression of release of the free block copolymer. SOD1 cl-nanozymes exhibit prolonged ability to scavenge experimentally induced reactive oxygen species (ROS) in cultured brain microvessel endothelial cells and central neurons. In vivo they decrease ischemia/reperfusion-induced tissue injury and improve sensorimotor functions in a rat middle cerebral artery occlusion (MCAO) model after a single intravenous (i.v.) injection. Altogether, well-defined cl-nanozymes are promising modalities for attenuation of oxidative stress after brain injury.

Allopregnanolone protects against dopamine-induced striatal damage after in vitro ischaemia via interaction at GABA A receptors

Sex steroid hormones, such as progesterone, have been shown to display neuroprotective properties after various models of central nervous system injury, including cerebral ischaemia, although the mechanism(s) of action remain largely undetermined. Allopregnanolone, an active progesterone metabolite, may explain some of the protective actions of progesterone. We utilised an in vitro model of ischaemia to evaluate the neuroprotective potential of allopregnanolone and examine its interaction at the GABA(A) receptor, which is hypothesised to be its main neuroprotective mechanism. In adult male mouse coronal caudate slices exposed to oxygen glucose deprivation (OGD), we measured aspects of OGD-induced dopamine release, which is neurotoxic during ischaemia, using fast cyclic voltammetry and also assessed tissue viability. The GABA(A) agonist, muscimol, displayed a neuroprotective profile in terms of delaying the OGD-evoked dopamine efflux (P < 0.05) and reducing the amount of dopamine released after OGD (P < 0.05). Allopregnanolone, at a concentration of 10(-6)  m, also displayed a neuroprotective profile because it significantly reduced the amount of dopamine efflux (P < 0.05) and reduced the loss of viable tissue after OGD compared to slices exposed to vehicle during OGD (P < 0.05). However, the effect of 10(-6)  m allopregnanolone on dopamine efflux was prevented in the presence of bicuculline, a competitive GABA(A) receptor antagonist. These results describe the use of an in vitro model of ischaemia with respect to determining that allopregnanolone is neuroprotective during the acute phase of ischaemia, and also demonstrate that such actions are dependent, at least in part, upon interaction at the GABA(A) receptor.

Pre-ischemic treadmill training for prevention of ischemic brain injury via regulation of glutamate and its transporter GLT-1

Pre-ischemic treadmill training exerts cerebral protection in the prevention of cerebral ischemia by alleviating neurotoxicity induced by excessive glutamate release following ischemic stroke. However, the underlying mechanism of this process remains unclear. Cerebral ischemia-reperfusion injury was observed in a rat model after 2 weeks of pre-ischemic treadmill training. Cerebrospinal fluid was collected using the microdialysis sampling method, and the concentration of glutamate was determined every 40 min from the beginning of ischemia to 4 h after reperfusion with high-performance liquid chromatography (HPLC)-fluorescence detection. At 3, 12, 24, and 48 h after ischemia, the expression of the glutamate transporter-1 (GLT-1) protein in brain tissues was determined by Western blot respectively. The effect of pre-ischemic treadmill training on glutamate concentration and GLT-1 expression after cerebral ischemia in rats along with changes in neurobehavioral score and cerebral infarct volume after 24 h ischemia yields critical information necessary to understand the protection mechanism exhibited by pre-ischemic treadmill training. The results demonstrated that pre-ischemic treadmill training up-regulates GLT-1 expression, decreases extracellular glutamate concentration, reduces cerebral infarct volume, and improves neurobehavioral score. Pre-ischemic treadmill training is likely to induce neuroprotection after cerebral ischemia by regulating GLT-1 expression, which results in re-uptake of excessive glutamate.

Visualizing cell death in experimental focal cerebral ischemia: promises, problems, and perspectives

One of the hallmarks of stroke pathophysiology is the widespread death of many different types of brain cells. As our understanding of the complex disease that is stroke has grown, it is now generally accepted that various different mechanisms can result in cell damage and eventual death. A plethora of techniques is available to identify various pathological features of cell death in stroke; each has its own drawbacks and pitfalls, and most are unable to distinguish between different types of cell death, which partially explains the widespread misuse of many terms. The purpose of this review is to summarize the standard histopathological and immunohistochemical techniques used to identify various pathological features of stroke. We then discuss how these methods should be properly interpreted on the basis of what they are showing, as well as advantages and disadvantages that require consideration. As there is much interest in the visualization of stroke using noninvasive imaging strategies, we also specifically discuss how these techniques can be interpreted within the context of cell death.

MALDI mass spectrometric imaging of cardiac tissue following myocardial infarction in a rat coronary artery ligation model

Although acute myocardial infarction (MI) is consistently among the top causes of death in the United States, the spatial distribution of lipids and metabolites following MI remains to be elucidated. This work presents the investigation of an in vivo rat model of MI using mass spectrometric imaging (MSI) and multivariate data analysis. MSI was conducted on cardiac tissue following a 24-h left anterior descending coronary artery ligation to analyze multiple compound classes. First, the spatial distribution of a small metabolite, creatine, was used to identify areas of infarcted myocardium. Second, multivariate data analysis and tandem mass spectrometry were used to identify phospholipid (PL) markers of MI. A number of lysophospholipids demonstrated increased ion signal in areas of infarction. In contrast, select intact PLs demonstrated decreased ion signal in the area of infarction. The complementary nature of these two lipid classes suggests increased activity of phospholipase A(2), an enzyme that has been implicated in coronary heart disease and inflammation.

Neuronal damage in hippocampal subregions induced by various durations of transient cerebral ischemia in gerbils using Fluoro-Jade B histofluorescence

Although there are many studies on ischemic brain damage in the gerbil, which is a good model of transient cerebral ischemia, studies on neuronal damage according to the duration of ischemia-reperfusion (I-R) time are limited. We carried out neuronal damage in the gerbil hippocampus after various durations of I-R (5, 10, 15 and 20 min) using Fluoro-Jade B (F-J B, a maker for neuronal degeneration) histofluorescence as well as cresyl violet (CV) staining. The changes of CV positive ((+)) neurons were well detected in the hippocampal CA1 region, not in the other regions. F-J B histofluorescence staining showed apparent neuronal damage in all the hippocampal subregions. In the CA1, most of the pyramidal neurons of the stratum pyramidale (SP) were stained with F-J B (about 100/mm(2) in a section), and F-J B(+) neurons in the other ischemia-groups were not changed. In the CA2, a few F-J B(+) neurons were detected in the SP of the 5 min ischemia-group, and F-J B(+) neurons were gradually increased with the longer time of ischemia: in the 20 min ischemia-group, the mean number of F-J B(+) neurons was about 85/mm(2) in a section. In the CA3, some F-J B(+) neurons were observed only in the SP of the 20 min ischemia-group. In the dentate gyrus, some F-J B positive neurons were detected only in the polymorphic layer (PL) of the 5 min ischemia-group, and the number of F-J B(+) neurons were gradually increased with the longer ischemic time. Our findings indicate that F-J B histofluorescence showed a very high quality of neuronal damage in all the hippocampal subregions.

Preconditioning with a novel metallopharmaceutical NO donor in anesthetized rats subjected to brain ischemia/reperfusion

Rut-bpy is a novel nitrosyl-ruthenium complex releasing NO into the vascular system. We evaluated the effect of Rut-bpy (100 mg/kg) on a rat model of brain stroke. Forty rats were assigned to four groups (Saline solution [SS], Rut-bpy, SS+ischemia-reperfusion [SS+I/R] and Rut-bpy+ischemia-reperfusion [Rut-bpy+I/R]) with their mean arterial pressure (MAP) continuously monitored. The groups were submitted (SS+I/R and Rut-bpy+I/R) or not (SS and Rut-bpy) to incomplete global brain ischemia by occlusion of the common bilateral carotid arteries during 30 min followed by reperfusion for further 60 min. Thirty minutes before ischemia, rats were treated pairwise by intraperitoneal injection of saline solution or Rut-bpy. At the end of experiments, brain was removed for triphenyltetrazolium chloride staining in order to quantify the total ischemic area. In a subset of rats, hippocampus was obtained for histopathology scoring, nitrate and nitrite measurements, immunostaining and western blotting of the nuclear factor- κB (NF-κB). Rut-bpy pre-treatment decreased MAP variations during the transition from brain ischemia to reperfusion and decreased the fractional injury area. Rut-bpy pre-treatment reduced NF-κB hippocampal immunostaining and protein expression with improved histopathology scoring as compared to the untreated operated control. In conclusion, Rut-bpy improved the total brain infarction area and hippocampal neuronal viability in part by inhibiting NF-κB signaling and helped to stabilize the blood pressure during the transition from ischemia to reperfusion.

Role of activating transcription factor 3 in ischemic penumbra region following transient middle cerebral artery occlusion and reperfusion injury

The activating transcription factor 3 (ATF3) is expressed by various types of cellular insults. It has been suggested to serve diverse functions in both cellular survival and death signal cascades, but the exact role of ATF3 in brain ischemia is little known so far. Thus, the authors examined the expression pattern of ATF3 following middle cerebral artery occlusion (MCAO) and reperfusion injury. At 1-2 days after MCAO and reperfusion injury, numerous number of ATF3-immunoreacitive (-ir) nuclei was observed in the ipsilateral peri-infarct cortex, but declined rapidly at 3 days. Almost all ATF3-ir nuclei were co-localized with NeuN-ir neurons. Neither GFAP- nor OX42-ir neuroglia were co-localized with ATF3. Double labeling of Fluoro-Jade B with ATF3 showed that ATF3-ir nuclei mismatched with Fluoro-Jade B-ir neurons. To further examine the role of ATF3 in ischemic peri-infarct regions, double immunofluorescent labeling of ATF3/caspase 3, ATF3/Bcl-xl, and ATF3/HSP27 was conducted. Semiquantitive estimation showed that about 15% of ATF3-ir neurons also expressed caspase 3. However, about only 0.4% and 2.6% of ATF3-ir neurons were double-stained with Bcl-xl and Hsp27, respectively. Consequently, it would be suggested that ATF3 seem to play an important role in caspase-dependent neuronal apoptotic signal transduction pathways caused by focal cerebral ischemia and reperfusion injury.

Gonadal steroids prevent cell damage and stimulate behavioral recovery after transient middle cerebral artery occlusion in male and female rats

17β-estradiol (E) and progesterone (P) are neuroprotective factors in the brain preventing neuronal death under different injury paradigms. Our previous work demonstrates that both steroids compensate neuronal damage and activate distinct neuroprotective strategies such as improving local energy metabolism and abating pro-inflammatory responses. The current study explored steroid hormone-mediated protection from brain damage and restoration of behavioral function after 1h transient middle cerebral artery occlusion (tMCAO). Male and ovariectomized female rats were studied 24h after stroke. Both steroid hormones reduced the cortical infarct area in males and females to a similar extent. A maximum effect of ~60-70% reduction of the infarct size was evident after P and a combined treatment with both hormones. No infarct protection was seen in the basal ganglia. Testing of motor and sensory behavioral revealed an equal high degree of functional recovery in all three hormone groups. Gene expression studies in the delineated penumbra revealed that estrogen receptor (ER) alpha and beta are locally up-regulated. tMCAO-mediated induction of the pro-inflammatory chemokines CCL2, CCL5 and interleukin 6 was attenuated by E and P, whereas the expression of vascular endothelial growth factor (VEGF) was fortified. Local expression of microglia/macrophage/lymphocyte markers, i.e. Iba1, CD68 and CD3, were significantly reduced in the penumbra after hormone treatment suggesting attenuation of microglia and lymphocyte attraction. These results demonstrate the neuroprotective potency of a combined treatment with E and P under ischemic conditions in both sexes and point at the regulation of chemokine-microglia/lymphocyte interactions as a supposable mechanism implicated in cell protection.

Aminoguanidine administration ameliorates hippocampal damage after middle cerebral artery occlusion in rat

The effects of a selective inducible nitric oxide synthase inhibitor aminoguanidine (AG) on neuronal cells survival in hippocampal CA1 region after middle cerebral artery occlusion (MCAO) were examined. Transient focal cerebral ischemia was induced in rats by 60 or 90 min of MCAO, followed by 7 days of reperfusion. AG treatment (150 mg/kg i.p.) significantly reduced total infarct volumes: by 70% after 90 min MCAO and by 95% after 60 min MCAO, compared with saline-treated ischemic group. The number of degenerating neurons in hippocampal CA1 region was also markedly lower in aminoguanidine-treated ischemic groups compared to ischemic groups without AG-treatment. The number of iNOS-positive cells significantly increased in the hippocampal CA1 region of ischemic animals, whereas it was reduced in AG-treated rats. Our findings demonstrate that aminoguanidine decreases ischemic brain damage and improves neurological recovery after transient focal ischemia induced by MCAO.

Changes in Host Blood Factors and Brain Glia Accompanying the Functional Recovery after Systemic Administration of Bone Marrow Stem Cells in Ischemic Stroke Rats

In this study, we examined the effects of systemic administration of rat or human bone marrow stromal stem cells (MSC) at early and later times following middle cerebral artery occlusion (MCAO) on blood cytokines/growth factors, brain glia, and motor behavior in rats. Rats were tail vein injected with rat (r) and human (h) MSCs at 1 or 7 days post-MCAO. In some rats ( N = 4) MSCs isolated from transgenic GFP rats were used to track the migration of cells peripherally and centrally at 2.5 and 28 days. Motor behavior was assessed using the modified Neurological Severity Score/climbing test at various time points before and after MCAO and transplantation. Prior to sacrifice at 1, 7, or 28 days post-MCAO, blood serum was collected for cytokine array analysis. Brains were analyzed for markers of activated microglia (CD11) and reactive astrocytes (GFAP). Administration of either allogeneic (rMSCs) or xenogeneic (hMSCs) stem cells produced a significant recovery of motor behavior after MCAO, with cells delivered at 1 day having greater effect than those at 7 days. Correlated with recovery was an amplification in activated microglia, reactive astrocytes, and new blood vessels in the infarct region, resulting in greater preservation in brain integrity. Concomitantly, expression of blood cytokines/chemokines (IL-13, MMP2, MIP) and growth factors/receptors (VEGF, neuropilin, EPOR, TROY, NGFR, RAGE) were modified following MSC administration. Because only rare GFP-labeled MSCs were observed in the brain, these effects did not depend on the central incorporation of stem cells. The early systemic administration of allogeneic or xenogeneic MSCs soon after experimental stroke produces a structural/functional recovery in the brain which is correlated with an increase in activated brain glia and changes in circulating cytokines and growth factors. Stem cells therefore induce an important neuroprotective and/or regenerative response in the host organism.

Visualization of the ischemic core on native human brain slices by potassium staining method

The potassium staining method is based on the formation of potassium cobaltnitrite crystals after the treatment by sodium cobaltnitrite of brain tissue. The degree of staining correlates with the distinct potassium content of infracted and non-infarcted brain areas. The aim of the present study was to prove that potassium staining technique is a reliable method for localization of ischemic core on native whole hemisphere cryosections of stroke patients. Furthermore, potassium stained sections have been compared with appropriate postmortem MRI images of respective brains. Brains of stroke patients were removed within 24h after death and postmortem MRI scanning was performed. Horizontal cryosections of frozen brains were taken and potassium staining was performed. Using the stained whole hemisphere sections as "map" tissue sampling has been made in order to determine water and potassium content. Potassium content of infarcted samples was significantly decreased in comparison with intact regions (0.7346+/-0.2142 mg/L and 1.928+/-0.447 mg/L, respectively, p<0.01) (mean values+/-SD). Water content of affected areas (expressed in percents) has been found to be above non-infarcted regions (81.657%+/-4.07 and 72.96%+/-6.37, respectively, p<0.01). According to our results the potassium staining method of human whole hemisphere brain sections reliably differentiates focal ischemic areas from intact brain regions. In conclusion, the postmortem examination of ischemic brain could be started with making the potassium map of infarcted whole hemisphere cryosections providing guidance for targeted tissue sampling and base of comparison for further examinations.

Oxygen-sensitive outcomes and gene expression in acute ischemic stroke

Acute ischemic stroke (AIS) results in focal deprivation of blood-borne factors, one of them being oxygen. The purpose of this study was two-fold: (1) to identify therapeutic conditions for supplemental oxygen in AIS and (2) to use transcriptome-wide screening toward uncovering oxygen-sensitive mechanisms. Transient MCAO in rodents was used to delineate the therapeutic potential of normobaric (NBO, 100% O(2), 1ATA) and hyperbaric oxygen (HBO, 100% O(2), 2ATA) during ischemia (iNBO, iHBO) and after reperfusion (rNBO, rHBO). Stroke lesion was quantified using 4.7 T MRI at 48 h. Supplemental oxygen during AIS significantly attenuated percent stroke hemisphere lesion volume as compared with that in room air (RA) controls, whereas identical treatment immediately after reperfusion exacerbated lesion volume (RA=22.4+/-1.8, iNBO=9.9+/-3.6, iHBO=6.6+/-4.8, rNBO=29.8+/-3.6, rHBO=35.4+/-7.6). iNBO and iHBO corrected penumbra tissue pO(2) during AIS as measured by EPR oxymetry. Unbiased query of oxygen-sensitive transcriptome in stroke-affected tissue identified 5,769 differentially expressed genes. Candidate genes were verified by real-time PCR using neurons laser-captured from the stroke-affected somatosensory cortex. Directed microarray analysis showed that supplemental oxygen limited leukocyte accumulation to the infarct site by attenuation of stroke-inducible proinflammatory chemokine response. The findings provide key information relevant to understanding oxygen-dependent molecular mechanisms in the AIS-affected brain.

A new embolus injection method to evaluate intracerebral hemorrhage in New Zealand white rabbits

The rabbit large clot embolic stroke model has been used for over 23 years to study methods to manipulate hemorrhage and to test drugs and devices for safety, because the rabbit model is particularly sensitive to embolism-induced hemorrhage. This study refined the original embolization procedure using an automated, pump-assisted injection method to introduce large blood clots or macroscopic emboli into the middle cerebral artery (MCA) via an indwelling carotid artery catheter. The study shows that rapid injection of blood clots (3 ml/30s) produced a model where there is a high hemorrhage incidence rate (79%) and a high stroke success rate (63%), compared to a low stroke success rate (19%) with no hemorrhages when clots were injected at a slow rate (3 ml/90 s). The rapid injection method, which produces a high hemorrhage rate, is particularly useful to study neuroprotective agents to attenuate embolism-induced hemorrhage. In addition, we show that manual injection of blood clots, which produces a lower baseline hemorrhage rate (41%) with a similar stroke success rate (65%), may allow investigators to study pharmacological agents to either up or down-regulate hemorrhage incidence. Lastly, we show that in the rabbit embolic stroke model, hemorrhages are adjacent to areas of 2,3,5-triphenyltetrazolium (TTC)-negative tissue, normally associated with infarcted or ischemic tissue. Thus, there is clear separation of ischemia and hemorrhage in the model, suggesting that therapeutics that are neuroprotective may also be useful to limit the evolution of ischemic damage associated with a hemorrhage, if not attenuate hemorrhage itself.

The preparation and biological characterization of a new HL91-derivative for hypoxic imaging on stroke mice

AIM

(99m)Tc-HL91 (Prognox, GE-Healthcare) was the first nonnitro-aryl-based radiotracer for evaluating hypoxic fraction in neoplasm, stroke and myocardium infarction regions. However, the high hydrophilicity of (99m)Tc-HL91 might hamper its penetration into cells. In this study, we prepared a new ligand 4,4,11,11-tetramethyl- 5,10-diazatetradecane- 3,12-dionedioxime (HL91-ET) with higher lipophilicity but structurally similar compared with that of HL91. The chemical and biological characterizations of (99m)Tc-HL91-ET as a scintigraphic probe for hypoxia were performed with a stroke-bearing mouse model.

MATERIALS AND METHODS

HL91-ET was synthesized and formulated with stannous chloride and buffer to afford kits. After mixing with (99m)Tc-pertechnetate, (99m)Tc-HL91-ET can be prepared in high yield and high radiochemical purity (both >96%). The partition coefficient of (99m)Tc-HL91-ET was determined in n-octanol/PBS system. Cellular uptake assays under normoxic and hypoxic conditions were performed in an oxygen-controlled CO(2) incubator. Brain stroke in the mouse model was induced by the electrocautery of the middle cerebral artery. After intravenous injection of (99m)Tc-HL91-ET into the Balb/c mouse suffering brain stroke, small-animal SPECT images were acquired at designated time points and autoradiography of the brain slides was conducted. Parallel studies of (99m)Tc-HL91 were also conducted at the same conditions for comparison.

RESULTS

The higher partition coefficient of (99m)Tc-HL91-ET (0.294+/-0.007) indicated higher lipophlicity compared with that of (99m)Tc-HL91 (0.089+/-0.005). The (99m)Tc-HL91-ET preparation was stable at ambient temperature for 24h. Cellular uptake assay showed that (99m)Tc-HL91-ET was less selectively retained in hypoxic cells than (99m)Tc-HL91. The target-to-normal brain ratios derived from the autoradiograms of the brains of stroke mice were 1.31+/-0.02 and 17.47+/-0.10 (n=3), respectively, at 2h post injection of (99m)Tc-HL91-ET and (99m)Tc-HL91.

CONCLUSIONS

This study revealed that (99m)Tc-HL91-ET, though with higher lipophilicity than (99m)Tc-HL91, did not suggest better specific accumulation in hypoxic cells or tissues than (99m)Tc-HL91. The uptake mechanism of (99m)Tc-HL91 was at least not solely by passive diffusion. Lipophilicity should not be the major consideration in designing HL91-derivatives for hypoxia imaging.

TTC staining of damaged brain areas after MCA occlusion in the rat does not constrict quantitative gene and protein analyses

In models of ischemic stroke, TTC (2,3,5-triphenyltetrazolium chloride) staining is commonly applied for the fast and reliable visualization of hypoxic brain tissue and for defining the size of cerebral infarction and penumbra. Deciphering molecular processes of pathogenesis within the penumbra is of particular interest for the development of therapeutic strategies. The aim of this study was to assess whether TTC-stained tissues can easily and in a reliable quantitative manner be processed for further molecular and biochemical analyses. We applied phenol-based RNA isolation, protein lysis by conventional RIPA buffer, and combined RNA/protein isolation with NucleoSpinRNA/Protein-Kit. Gene and protein expression analyses were performed by RT-rtPCR and Western-blotting. Middle cerebral arteria occlusion (MCAO) in rats was performed following a standardized experimental procedure. After MCAO, TTC staining revealed massive cell death in cortical and sub-cortical areas. TTC processing did not affect the quality of tissue RNA and protein. The expression of housekeeping and regulatory genes and proteins revealed no difference between control and TTC-stained groups. The expression of known stroke-regulated genes such as TNFalpha and IL1beta revealed similar induction profiles after TTC staining as described in the literature. TTC staining allows the precise delineation of lesioned and primarily non-lesioned brain areas for subsequent dissection of selected tissue pieces for molecular analysis. Our study demonstrates that TTC-stained tissues in stroke animal models can be used for quantitative gene and protein expression analyses without constriction. Pathomechanisms of ongoing tissue damage within the penumbra region can now be investigated in detail.

Sleep deprivation attenuates experimental stroke severity in rats

Indirect epidemiological and experimental evidence suggest that the severity of injury during stroke is influenced by prior sleep history. The aim of our study was to test the effect of acute sleep deprivation on early outcome following experimental stroke. Young male Sprague-Dawley rats (n=20) were subjected to focal cerebral ischemia by reversible right middle cerebral artery occlusion (MCAO) for 90 min. In 10 rats, MCAO was performed just after 6-h of total sleep deprivation (TSD) by "gentle handling", whereas the other rats served as controls. Neurological function during the first week after stroke was monitored using a battery of behavioral tests investigating the asymmetry of sensorimotor deficit (tape removal test and cylinder test), bilateral sensorimotor coordination (rotor-rod and Inclined plane) and memory (T-maze and radial maze). Following MCAO, control rats had impaired behavioral performance in all tests. The largest impairment was noted in the tape test where the tape removal time from the left forelimb (contralateral to MCAO) was increased by approximately 10 fold (p<0.01). In contrast, rats subjected to TSD had complete recovery of sensorimotor performance consistent with a 2.5 fold smaller infarct volume and reduced morphological signs of neuronal injury at day 7 after MCAO. Our data suggest that brief TSD induces a neuroprotective response that limits the severity of a subsequent stroke, similar to rapid ischemic preconditioning.

Scalp Acupuncture Effects of Stroke Studied with Magnetic Resonance Imaging: Different Actions in the Two Stroke Model Rats

Background

Scalp acupuncture (SA) therapy on strokes has been empirically established and widely used in clinics in China. The evidence from clinical studies suggests that SA produces significant benefits for some patients with stroke.

Methods

The effect of scalp acupuncture was studied using MRI for two different stroke models: spontaneously hypertensive stroke-prone (SHR-SP) rats and rats with transiently induced focal cerebral ischaemia by middle cerebral artery occlusion for 2 h (MCAO rats).

Results

Stroke onset in SHR-SP rats was characterised by a development of vasogenic oedema without any appearance of cytotoxic oedema. Scalp acupuncture reduced rapidly neurological dysfunction in SHR-SP rats and reduced the volume of the vasogenic oedema during the same period. In contrast, in MCAO rats, focal cerebral ischaemia caused an immediate development of cytotoxic oedema without any appearance of vasogenic oedema. Vasogenic oedema developed after reperfusion. Scalp acupuncture had no significant effects on the cytotoxic oedema, vasogenic oedema or neurological dysfunction of the MCAO rats within the time span examined.

Conclusion

Scalp acupuncture had a rapid and strong effect on neurological dysfunction only in the hypertensive stroke-model by reducing the vasogenic oedema. Our results suggest that, if there are similar underlying mechanisms in human strokes, scalp acupuncture may be more beneficial for patients with strokes of hypertension-caused vasogenic origin than ischaemic origin.

A simple and efficient method for generating Nurr1-positive neuronal stem cells from human wisdom teeth (tNSC) and the potential of tNSC for stroke therapy

BACKGROUND AIMS

We have isolated human neuronal stem cells from exfoliated third molars (wisdom teeth) using a simple and efficient method. The cultured neuronal stem cells (designated tNSC) expressed embryonic and adult stem cell markers, markers for chemotatic factor and its corresponding ligand, as well as neuron proteins. The tNSC expressed genes of Nurr1, NF-M and nestin. They were used to treat middle cerebral artery occlusion (MCAO) surgery-inflicted Sprague-Dawley (SD) rats to assess their therapeutic potential for stroke therapy.

METHODS

For each tNSC cell line, a normal human impacted wisdom tooth was collected from a donor with consent. The tooth was cleaned thoroughly with normal saline. The molar was vigorously shaken or vortexed for 30 min in a 50-mL conical tube with 15-20mL normal saline. The mixture of dental pulp was collected by centrifugation and cultured in a 25-cm(2) tissue culture flask with 4-5mL Medium 199 supplemented with 5-10% fetal calf serum. The tNSC harvested from tissue culture, at a concentration of 1-2x10(5), were suspended in 3 microL saline solution and injected into the right dorsolateral striatum of experimental animals inflicted with MCAO.

RESULTS

Behavioral measurements of the tNSC-treated SD rats showed a significant recovery from neurologic dysfunction after MCAO treatment. In contrast, a sham group of SD rats failed to recover from the surgery. Immunohistochemistry analysis of brain sections of the tNSC-treated SD rats showed survival of the transplanted cells.

CONCLUSIONS

These results suggest that adult neuronal stem cells may be procured from third molars, and tNSC thus cultivated have potential for treatment of stroke-inflicted rats.

One hour reperfusion is enough to assess function and infarct size with TTC staining in Langendorff rat model

BACKGROUND

There is not general agreement concerning the optimal time of reperfusion necessary to assess myocardial function and necrosis on isolated perfused heart model. Nevertheless, the study of cardioprotection (especially, pre- and postconditioning) requires a reliable and standardized assessment of myocardial necrosis.

OBJECTIVE

The objective of this study was thus to evaluate whether 1 h of reperfusion was sufficient to assess rat heart viability on Langendorff preparation. Isolated rat hearts (n = 30) underwent 40 min of global normothermic ischemia followed by 60 or 120 min Langendorff reperfusion. In each group, hearts were also randomly assigned into the 2 following sub-groups: postconditioning (PostC, consisting in 2 episodes of 30 s ischemia and 30 s reperfusion at the onset of reperfusion), and control (no intervention). Coronary flow, heart rate, dP/dt and rate-pressure-product were measured. Myocardial necrosis was assessed by TTC staining and LDH, CK release analysis.

RESULTS

Our results indicated that heart function tended to slightly decrease between 60 min and 120 min reperfusion. Infarct size was identical at 60 min and 120 min reperfusion, averaging 33-34% of total LV area in controls versus 17% in PostC (p < 0.001 between control and PostC groups). Similarly, the maximum of enzymatic releases (CK and LDH) measured in coronary effluents was at 60 min of reperfusion, followed by a progressive decrease at 90 min and 120 min. As expected, postconditioning limited enzymatic releases whatever the studied time of reperfusion.

CONCLUSION

In conclusion, we showed that prolonged reperfusion beyond 60 min was not useful for function assessment and did not change infarct size measurement, on Langendorff rat model of ischemia-reperfusion.

MAP2 immunostaining in thick sections for early ischemic stroke infarct volume in non-human primate brain

The delineation of early infarction in large gyrencephalic brain cannot be accomplished with triphenyl-tetrazolium chloride (TTC) due to its limitations in the early phase, nor can it be identified with microtubule-associated protein 2 (MAP2) immunohistochemistry, due to the fragility of large thin sections. We hypothesize that MAP2 immunostaining of thick brain sections can accurately identify early ischemia in the entire monkey brain. Using ischemic brains of one rat and three monkeys, a thick-section MAP2 immunostaining protocol was developed to outline the infarct region over the entire non-human primate brain. Comparison of adjacent thick and thin sections in a rat brain indicated complete correspondence between ischemic regions (100.4mm(3)+/-1.2%, n=7, p=0.44). Thick sections in monkey brain possessed the increased structural stability necessary for the extensive MAP2 immunostaining procedure permitting quantification of the ischemic region as a percent of total monkey brain, giving infarct volumes of 11.4, 16.3, and 19.0% of total brain. Stacked 2D images of the intact thick brain tissue sections provided a 3D representation for comparison to MRI images. The infarct volume of 16.1cm(3) from the MAP2 sections registered with MRI images agreed well with the volume calculated directly from the stained sections of 16.6 cm(3). Thick brain tissue section MAP2 immunostaining provides a new method for determining infarct volume over the entire brain at early time points in a non-human primate model of ischemic stroke.

TTC, fluoro-Jade B and NeuN staining confirm evolving phases of infarction induced by middle cerebral artery occlusion

Considerable debate exists in the literature on how best to measure infarct damage and at what point after middle cerebral artery occlusion (MCAO) infarct is histologically complete. As many researchers are focusing on more chronic endpoints in neuroprotection studies it is important to evaluate histological damage at later time points to ensure that standard methods of tissue injury measurement are accurate. To compare tissue viability at both acute and sub-acute time points, we used 2,3,5-triphenyltetrazolium chloride (TTC), Fluoro-Jade B, and NeuN staining to examine the evolving phases of infarction induced by a 90-min MCAO in mice. Stroke outcomes were examined at 1.5h, 6h, 12h, 24h, 3d, and 7d after MCAO. There was a time-dependent increase in infarct volume from 1.5h to 24h in the cortex, followed by a plateau from 24h to 7d after stroke. Striatal infarcts were complete by 12h. Fluoro-Jade B staining peaked at 24h and was minimal by 7d. Our results indicated that histological damage as measured by TTC and Fluoro-Jade B reaches its peak by 24h after stroke in a reperfusion model of MCAO in mice. TTC staining can be accurately performed as late as 7d after stroke. Neurological deficits do not correlate with the structural lesion but rather transient impairment of function. As the infarct is complete by 24h and even earlier in the striatum, even the most efficacious neuroprotective therapies are unlikely to show any efficacy if given after this point.

Ischemic stroke in mice and rats

Ischemic stroke occurs most often in the territory of the middle cerebral artery (MCA) in humans. Since its description in rats more than two decades ago, the minimally invasive intraluminal suture occlusion of MCA is an increasingly used model of stroke in both rats and mice due to its ease of inducing ischemia and achieving reperfusion under well-controlled conditions. This method can be used under the guidance of laser-Doppler flowmetry to ascertain the magnitude of occlusion or reperfusion and to decrease the rate of subarachnoid hemorrhage. Ninety minutes of transient ischemia in the territory of MCA results in substantial and reproducible ischemic lesions in both the striatum and the cortex, with characteristics of lesion core and penumbra. Thus, this model is applicable to neuroprotective drug studies, including ischemic brain lesion evaluation (either in vivo with magnetic resonance imaging or post-mortem with brain tissue staining) and neurological status (motor deficits simply assessed by a six-point neurological score scale) as outcome parameters.

RODENT STROKE MODEL GUIDELINES FOR PRECLINICAL STROKE TRIALS (1ST EDITION)

Translational stroke research is a challenging task that needs long term team work of the stroke research community. Highly reproducible stroke models with excellent outcome consistence are essential for obtaining useful data from preclinical stroke trials as well as for improving inter-lab comparability. However, our review of literature shows that the infarct variation coefficient of commonly performed stroke models ranges from 5% to 200%. An overall improvement of the commonly used stroke models will further improve the quality for experimental stroke research as well as inter-lab comparability. Many factors play a significant role in causing outcome variation; however, they have not yet been adequately addressed in the Stroke Therapy Academic Industry Roundtable (STAIR) recommendations and the Good Laboratory Practice (GLP). These critical factors include selection of anesthetics, maintenance of animal physiological environment, stroke outcome observation, and model specific factors that affect success rate and variation. The authors have reviewed these major factors that have been reported to influence stroke model outcome, herewith, provide the first edition of stroke model guidelines so to initiate active discussion on this topic. We hope to reach a general agreement among stroke researchers in the near future with its successive updated versions.

Evidence for the efficacy of NXY-059 in experimental focal cerebral ischaemia is confounded by study quality

BACKGROUND AND PURPOSE

The neutral results of the SAINT II trial have again highlighted difficulties translating neuroprotective efficacy from bench to bedside. Animal studies are susceptible to study quality biases, which may lead to overstatement of efficacy. We report the impact of study quality on published estimates of the efficacy of NXY-059 in animal models of stroke.

METHODS

We conducted a systematic review and stratified meta-analysis of published studies describing the efficacy of NXY-059 in experimental focal cerebral ischemia.

RESULTS

Overall, NXY-059 improved infarct volume by 43.3% (95% CI, 34.7 to 52.8). Only 2 of 9 publications reported randomization, concealment of treatment allocation, and blinded outcome assessment. Studies not reporting these quality items gave substantially higher estimates of efficacy than did higher-quality studies.

CONCLUSIONS

The reported efficacy of NXY-059 in animal models of stroke is confounded by low study quality. The failure of SAINT II highlights the need for substantial improvements in the design, conduct, and reporting of animal studies; journals can play an important role in this by adopting standards for animal studies similar to those agreed over 10 years ago for clinical trials.

Characterization of the structural and functional changes in the myocardium following focal ischemia-reperfusion injury

High-resolution (11.7 T) cardiac magnetic resonance imaging (MRI) and histological approaches have been employed in tandem to characterize the secondary damage suffered by the murine myocardium following the initial insult caused by ischemia-reperfusion (I/R). I/R-induced changes in the myocardium were examined in five separate groups at the following time points after I/R: 1 h, day 1, day 3, day 7, and day 14. The infarct volume increased from 1 h to day 1 post-I/R. Over time, the loss of myocardial function was observed to be associated with increased infarct volume and worsened regional wall motion. In the infarct region, I/R caused a decrease in end-systolic thickness coupled with small changes in end-diastolic thickness, leading to massive wall thickening abnormalities. In addition, compromised wall thickening was also observed in left ventricular regions adjacent to the infarct region. A tight correlation (r2 = 0.85) between measured MRI and triphenyltetrazolium chloride (TTC) infarct volumes was noted. Our observation that until day 3 post-I/R the infarct size as measured by TTC staining and MRI was much larger than that of the myocyte-silent regions in trichrome- or hematoxylin-eosin-stained sections is consistent with the literature and leads to the conclusion that at such an early phase, the infarct site contains structurally intact myocytes that are functionally compromised. Over time, such affected myocytes were noted to structurally disappear, resulting in consistent infarct sizes obtained from MRI and TTC as well as trichrome and hematoxylin-eosin analyses on day 7 following I/R. Myocardial remodeling following I/R includes secondary myocyte death followed by the loss of cardiac function over time.

Neuroprotection in mice by NGP1-01 after transient focal brain ischemia

The effect of the polycyclic cage amine NGP1-01, a dual action antagonist at both L-type calcium channels and NMDA receptors, was measured after transient (1 h) focal cerebral ischemia in the mouse middle cerebral artery occlusion (MCAO) model. Mice were left untreated, or received NGP1-01 (20 mg/kg per dose intraperitoneally), memantine (20 mg/kg per dose intraperitoneally), or vehicle (DMSO) at 15 min, 24 h and 48 h after reperfusion. Sensorimotor function was tested daily for two weeks using the "corner test", a proven paradigm for the assessment of functional integrity in rodents. NGP1-01 significantly reduced sensorimotor deficits over the 2-week period (p<0.001, ANOVA). Although memantine was less effective than NGP1-01 (p<0.05), it still significantly attenuated sensorimotor deficits in the animals. In a separate study, brain damage 3 days after stroke was determined histologically in mice receiving no treatment, DMSO, or NGP1-01 (dosages and dosage schedule same as above). Serial brain sections were stained for nonviable neurons with Fluoro-Jade B and the volume of damaged tissue was estimated. NGP1-01 treated mice had a significantly lower volume of brain damage (13+/-7 mm(3), p<0.01) than both control groups (no treatment: 47+/-4 mm(3), DMSO: 50+/-10 mm(3)). In conclusion, at weight-equivalent doses, NGP1-01 was at least as neuroprotective as the established NMDA receptor antagonist memantine. It may be a promising lead structure for the development of novel multiple-action drugs in treating ischemic stroke and other neurodegenerative diseases with an excitotoxic component.