An improved version of embolic model of brain ischemic injury in the rat

Modifying PTEN recruitment promotes neuron survival, regeneration, and functional recovery after CNS injury

Phosphatase and tensin homolog (PTEN) regulates apoptosis and axonal growth in the developing and adult central nervous system (CNS). Here, we show that human PTEN C-terminal PDZ interactions play a critical role in neuronal apoptosis and axon regeneration after traumatic CNS injury and stroke, highlighted by the findings that antagonizing the PDZ-motif interactions of PTEN has therapeutic applicability for these indications. Interestingly, the death-inducing function of PTEN following ischemic insult depends on a PDZ-domain interaction with MAGI-2 and MAST205, PDZ proteins that are known to recruit PTEN to the plasma membrane and stabilize its interaction with PIP3. Treatments with a human peptide that prevents PTEN association with MAGI-2 or MAST205 increased neuronal survival in multiple stroke models, in vitro. A pro-survival effect was also observed in models of retinal ischemia, optic nerve transection, and after middle cerebral artery occlusion (MCAO) in adult rats. The human PTEN peptide also improved axonal regeneration in the crushed optic nerve. Furthermore, human PTEN peptide therapy promoted functional improvement after MCAO or retinal ischemia induced via ophthalmic artery ligation. These findings show that the human peptide-based targeting of C-terminal PTEN PDZ interactions has therapeutic potential for insults of the CNS, including trauma and stroke.

Selective middle cerebral artery occlusion in the rabbit: Technique and characterization with pathologic findings and multimodal MRI

BACKGROUND

A reliable animal model of ischemic stroke is vital for pre-clinical evaluation of stroke therapies. We describe a reproducible middle cerebral artery (MCA) embolic occlusion in the French Lop rabbit characterized with multimodal MRI and histopathologic tissue analysis.

NEW METHOD

Fluoroscopic-guided microcatheter placement was performed in five consecutive subjects with angiographic confirmation of MCA occlusion with autologous clot. Multimodal MRI was obtained prior to occlusion and up to six hours post after which repeat angiography confirmed sustained occlusion. The brain was harvested for histopathologic examination.

RESULTS

Angiography confirmed successful MCA catheterization and durable (>6 h) MCA occlusion in all animals. There was increase of ADC volume over time and variable final core volume presumably related to individual variation in collateral flow. FLAIR hyperintensity indicative of cytotoxic edema and parenchymal contrast enhancement reflective of blood brain barrier disruption was observed over time. Tissue staining of the ischemic brain showed edema and structural alterations consistent with infarction.

COMPARISON WITH EXISTING METHODS

This study describes a technique of selective catheterization and embolic occlusion of the MCA in the rabbit with MRI characterization of evolution of ischemia in the model.

CONCLUSIONS

We demonstrate the feasibility of a rabbit model of embolic MCA occlusion with angiographic documentation. Serial MR imaging demonstrated changes comparable to those observed in human ischemic stroke, confirmed histopathologically.

Stem cell transplantation therapy for multifaceted therapeutic benefits after stroke

One of the exciting advances in modern medicine and life science is cell-based neurovascular regeneration of damaged brain tissues and repair of neuronal structures. The progress in stem cell biology and creation of adult induced pluripotent stem (iPS) cells has significantly improved basic and pre-clinical research in disease mechanisms and generated enthusiasm for potential applications in the treatment of central nervous system (CNS) diseases including stroke. Endogenous neural stem cells and cultured stem cells are capable of self-renewal and give rise to virtually all types of cells essential for the makeup of neuronal structures. Meanwhile, stem cells and neural progenitor cells are well-known for their potential for trophic support after transplantation into the ischemic brain. Thus, stem cell-based therapies provide an attractive future for protecting and repairing damaged brain tissues after injury and in various disease states. Moreover, basic research on naïve and differentiated stem cells including iPS cells has markedly improved our understanding of cellular and molecular mechanisms of neurological disorders, and provides a platform for the discovery of novel drug targets. The latest advances indicate that combinatorial approaches using cell based therapy with additional treatments such as protective reagents, preconditioning strategies and rehabilitation therapy can significantly improve therapeutic benefits. In this review, we will discuss the characteristics of cell therapy in different ischemic models and the application of stem cells and progenitor cells as regenerative medicine for the treatment of stroke.

Prospects of modeling poststroke epileptogenesis

This Review describes the current status of poststroke epilepsy (PSE) with an emphasis on poststroke epileptogenesis modeling for testing new therapeutic agents. Stroke is a leading cause of epilepsy in an aging population. Late-onset "epileptic" seizures have been reported in up to 30% cases after stroke. Nevertheless, the overall prevalence of PSE is 2-4%. Rodent models of stroke have contributed to our understanding of the relationship between seizures and the underlying ischemic damage to neurons. To understand whether acutely generated stroke events lead to a chronic phenotype more closely resembling PSE with recurrent seizures, a limited variety of approaches emerged in early 2000s. These limited methods of causing an occlusion in mice and rats show different infarct size and neurological deficits. The most often employed procedure for inducing focal ischemia is the middle cerebral artery occlusion. This mimics the pathophysiology seen in humans in terms of extent of damage to cortex and striatum. Photothrombosis and endothelin-1 models can similarly evoke episodes of ischemic stroke. These models are well suited to studying mechanisms and biomarkers of epileptogenesis or optimizing novel drug discoveries. However, modeling of PSE is tedious, is highly variable, and lacks validity; therefore, it is not widely implemented in epilepsy research. Moreover, the relevance of ischemic models to specific forms of human stroke remains unclear. Stroke modeling in young male rodents lacks clinical relevance to elderly populations and especially to women, likely as a result of sex differences. Nevertheless, because of the neuronal damage and epileptogenic insult that these models trigger, they are helpful tools in studying acquired epilepsy and prophylactic drug therapy. © 2016 Wiley Periodicals, Inc.

Is shorter transient middle cerebral artery occlusion (t-MCAO) duration better in stroke experiments on diabetic female Sprague Dawely rats?

AIM

To determine optimal duration of transient middle cerebral artery occlusion (t-MCAO) for a stroke model in female diabetic Sprague-Dawley (SD) rats.

METHODS

Streptozotocin-induced type-1 diabetic SD female rats (n = 25, 12 weeks old, five groups; n = 5 per group) were subjected to different duration of t-MCAO (20, 30, 45, 60 and 90 minutes) followed by reperfusion. A control group of rats without diabetes (n = 5) was subjected to 30 minutes of t-MCAO followed by reperfusion. Twenty-four hours after reperfusion, infarct volumes were evaluated by 2,3,5-triphenyltetrazolium chloride (TTC) staining.

RESULTS

Intra-ischaemic reductions of regional cerebral blood flow (rCBF) were similar in all groups (68-75% of baseline values). Reperfusion was significantly impaired in the 90-minute ischaemia group (56-62% vs 80-125% in other groups). Twenty minutes of t-MCAO induced a small infarct (3 ± 5% of ischaemic hemisphere). Thirty minutes of ischaemia produced a significantly larger infarct (46 ± 6%). In the 45 and 60 minute groups, ischaemia infarct was 52 ± 5% and 59 ± 3% of the ischaemic hemisphere, respectively. Ischaemia of 90' led to a massive stroke (89 ± 6% of ischaemic hemisphere encompassing the whole striatum (22 ± 3%) and almost the whole MCA irrigated cortex area (67 ± 6%)). Thirty minutes of t-MCAO did not produce stroke in the control group.

CONCLUSION

The diabetic rat stroke model should be different from the non-diabetic, because female type-1 diabetic SD rats are highly sensitive to brain ischaemia and it is necessary to significantly shorten the duration of t-MCAO, optimally to 30 minutes.

Kelussia odoratissima Mozaff attenuates thromboembolic brain injury, possibly due to its Z-ligustilide content

PRIMARY OBJECTIVE

Essential oil (EO) of Kelussia odoratissima Mozaff, whose main composition is Z-ligustilide, has been shown to have strong antioxidant and anti-inflammatory effects and potent neuroprotective properties.

RESEARCH DESIGN

This study examined whether or not the EO could ameliorate brain damage and behavioural dysfunction in a thromboembolic model of stroke in rats and compare its effects to that of the purified Z-ligustilide.

METHODS AND PROCEDURES

Stroke was induced in rats by middle cerebral artery occlusion using an autologous pre-formed clot. EO (10 mg kg(-1) and 45 mg kg(-1)) and Z-ligustilide (20 mg kg(-1)) were injected intraperitoneally 1 h prior to embolization. Behavioural scores, infarct size and brain oedema, as well as the level of tumour necrosis factor-alpha (TNF-α), malondialdehyde, glutathione, catalase and superoxide dismutase activity were determined in the ipsilateral cortex 24 hours following stroke induction.

MAIN OUTCOMES AND RESULTS

EO (45 mg kg(-1)), statistically similar to Z-ligustilide (20 mg kg(-1)), curtailed brain infarction and oedema, improved behavioural scores and prevented enhanced oxidative stress and TNF-α level in the ischaemic brain tissues.

CONCLUSIONS

The findings provide the first evidence of effectiveness of the extract in a thromboembolic model of stroke, whose action can be mediated, at least in part, by the antioxidative and anti-inflammatory mechanisms.

Targeting caspase-6 and caspase-8 to promote neuronal survival following ischemic stroke

Previous studies show that caspase-6 and caspase-8 are involved in neuronal apoptosis and regenerative failure after trauma of the adult central nervous system (CNS). In this study, we evaluated whether caspase-6 or -8 inhibitors can reduce cerebral or retinal injury after ischemia. Cerebral infarct volume, relative to appropriate controls, was significantly reduced in groups treated with caspase-6 or -8 inhibitors. Concomitantly, these treatments also reduced neurological deficits, reduced edema, increased cell proliferation, and increased neurofilament levels in the injured cerebrum. Caspase-6 and -8 inhibitors, or siRNAs, also increased retinal ganglion cell survival at 14 days after ischemic injury. Caspase-6 or -8 inhibition also decreased caspase-3, -6, and caspase-8 cleavage when assayed by western blot and reduced caspase-3 and -6 activities in colorimetric assays. We have shown that caspase-6 or caspase-8 inhibition decreases the neuropathological consequences of cerebral or retinal infarction, thereby emphasizing their importance in ischemic neuronal degeneration. As such, caspase-6 and -8 are potential targets for future therapies aimed at attenuating the devastating functional losses that result from retinal or cerebral stroke.

Modeling early-onset post-ischemic seizures in aging mice

Stroke is the leading cause of seizures and epilepsy in the aged population, with post-stroke seizures being a poor prognostic factor. The pathological processes underlying post-stroke seizures are not well understood and studies of these seizures in aging/aged animals remain scarce. Therefore, our primary objective was to model post-stroke seizures in aging mice (C57 black strain, 16-20 months-old), with a focus on early-onset, convulsive seizures that occur within 24-hours of brain ischemia. We utilized a middle cerebral artery occlusion model and examined seizure activity and brain injury using combined behavioral and electroencephalographic monitoring and histological assessments. Aging mice exhibited vigorous convulsive seizures within hours of the middle cerebral artery occlusion. These seizures manifested with jumping, rapid running, barrel-rolling and/or falling all in the absence of hippocampal-cortical electrographic discharges. Seizure development was closely associated with severe brain injury and acute mortality. Anticonvulsive treatments after seizure occurrence offered temporary seizure control but failed to improve animal survival. A separate cohort of adult mice (6-8 months-old) exhibited analogous early-onset convulsive seizures following the middle cerebral artery occlusion but had better survival outcomes following anticonvulsive treatment. Collectively, our data suggest that early-onset convulsive seizures are a result of severe brain ischemia in aging animals.

The macrosphere model-an embolic stroke model for studying the pathophysiology of focal cerebral ischemia in a translational approach

The main challenge of stroke research is to translate promising experimental findings from the bench to the bedside. Many suggestions have been made how to achieve this goal, identifying the need for appropriate experimental animal models as one key issue. We here discuss the macrosphere model of focal cerebral ischemia in the rat, which closely resembles the pathophysiology of human stroke both in its acute and chronic phase. Key pathophysiological processes such as brain edema, cortical spreading depolarizations (CSD), neuroinflammation, and stem cell-mediated regeneration are observed in this stroke model, following characteristic temporo-spatial patterns. Non-invasive in vivo imaging allows studying the macrosphere model from the very onset of ischemia up to late remodeling processes in an intraindividual and longitudinal fashion. Such a design of pre-clinical stroke studies provides the basis for a successful translation into the clinic.

Uncoupling Neogenin association with lipid rafts promotes neuronal survival and functional recovery after stroke

The dependence receptor Neogenin and its ligand, the repulsive guidance molecule a (RGMa), regulate apoptosis and axonal growth in the developing and the adult central nervous system (CNS). Here, we show that this pathway has also a critical role in neuronal death following stroke, and that providing RGMa to neurons blocks Neogenin-induced death. Interestingly, the Neogenin pro-death function following ischemic insult depends on Neogenin association with lipid rafts. Thus, a peptide that prevents Neogenin association with lipid rafts increased neuronal survival in several in vitro stroke models. In rats, a pro-survival effect was also observed in a model of ocular ischemia, as well as after middle cerebral artery occlusion (MCAO). Treatments that prevented Neogenin association with lipid rafts improved neuronal survival and the complexity of the neuronal network following occlusion of the middle artery. Toward the development of a treatment for stroke, we developed a human anti-RGMa antibody that also prevents Neogenin association with lipid rafts. We show that this antibody also protected CNS tissue from ischemic damage and that its application resulted in a significant functional improvement even when administrated 6 h after artery occlusion. Thus, our results draw attention to the role of Neogenin and lipid rafts as potential targets following stroke.

Extract of Antrodia camphorata exerts neuroprotection against embolic stroke in rats without causing the risk of hemorrhagic incidence

In this study, the neuroprotective effect of an extract of Antrodia camphorata (A. camphorata), a fungus commonly used in Chinese folk medicine for treatment of viral hepatitis and cancer, alone or in combination with aspirin was investigated in a rat embolic stroke model. An ischemic stroke was induced in rats by a selective occlusion of the middle cerebral artery (MCA) with whole blood clots and then orally treated with A. camphorata (0.25 and 0.75 g/kg/day) alone and combined with aspirin (5 mg/kg/day). Sixty days later, the brains were removed, sectioned, and stained with triphenyltetrazolium chloride and analysed by a commercial image processing software program. Brain infarct volume, neurobehavioral score, cerebral blood perfusion, and subarachnoid and intracerebral hemorrhage incidence were perceived. In addition, potential bleeding side effect of the combinative therapy was assessed by measuring hemoglobin (Hb) content during intracerebral hemorrhage and gastric bleeding, prothrombin time (PT), and occlusion time (OT) after oral administration. Posttreatment with high dose A. camphorata significantly reduced infarct volume and improved neurobehavioral score (P < 0.05). Since A. camphorata alone or with aspirin did not alter the Hb level, this treatment is safe and does not cause hemorrhagic incident. Remarkably, the combination of A. camphorata and aspirin did not show a significant effect on the bleeding time, PT and OT increase suggesting that A. camphorata may have the neuroprotective effect without the prolongation of bleeding time or coagulation time. From these observations, we suggest that combinative therapy of A. camphorata and aspirin might offer enhanced neuroprotective efficacies without increasing side effects.

Complexity in differentiating the expression of truncated or matured forms of MMP-2 and MMP-9 through zymography in rat brain tissues after acute ischaemic stroke

Matrix metalloproteinases (MMPs) play an important role in the pathogenesis of ischaemic stroke. In particular, the mature forms of MMPs 2 and 9 have similar sizes and share gelatine as a common substrate. Both MMPs are upregulated in ischaemic stroke and play detrimental roles during stroke pathogenesis. Throughout this study, we demonstrated that pro-MMP-2 and pro-MMP-9 from ischaemic rat brain tissue homogenate is detected either through immunoblotting or zymography because of the remarkable size difference between these enzymes (72 versus 95 kDa, respectively). However, the mature MMP-2 and MMP-9 cannot be discriminated through zymography because of the almost identical sizes of these forms (66 and 67 kDa, respectively). The use of gelatine zymography on ischaemic rat brain tissue homogenate revealed a 65-kDa MMP band, corresponding to the heterogeneous band of mature MMP-2 and/or MMP-9. Furthermore, we also detected mature MMPs of 65 kDa generated from both recombinant human MMP-2 and MMP-9. Using a pull down assay in rat brain tissue homogenate with gelatine-agarose beads, we showed increased activities for both the pro and mature forms of MMP-2 and MMP-9. However, we could not determine the origin of the respective mature MMPs from the heterogeneous band. Thus, in this study, we demonstrated that the identification and quantification of mature MMP-2 and MMP-9 could not be achieved using zymography alone. Therefore, the development of a reliable technique to identify and measure the respective MMPs is needed to test new stroke therapies targeting MMP-2 and MMP-9.

High-density lipoprotein-based therapy reduces the hemorrhagic complications associated with tissue plasminogen activator treatment in experimental stroke

BACKGROUND AND PURPOSE

We have previously reported that intravenous injection of high-density lipoproteins (HDLs) was neuroprotective in an embolic stroke model. We hypothesized that HDL vasculoprotective actions on the blood-brain barrier (BBB) may decrease hemorrhagic transformation-associated with tissue plasminogen activator (tPA) administration in acute stroke.

METHODS

We used tPA alone or in combination with HDLs in vivo in 2 models of focal middle cerebral artery occlusion (MCAO) (embolic and 4-hour monofilament MCAO) and in vitro in a model of BBB. Sprague-Dawley rats were submitted to MCAO, n=12 per group. The rats were then randomly injected with tPA (10 mg/kg) or saline with or without human plasma purified-HDL (10 mg/kg). The therapeutic effects of HDL and BBB integrity were assessed blindly 24 hours later. The integrity of the BBB was also tested using an in vitro model of human cerebral endothelial cells under oxygen-glucose deprivation.

RESULTS

tPA-treated groups had significantly higher mortality and rate of hemorrhagic transformation at 24 hours in both MCAO models. Cotreatment with HDL significantly reduced stroke-induced mortality versus tPA alone (by 42% in filament MCAO, P=0.009; by 73% in embolic MCAO, P=0.05) and tPA-induced intracerebral parenchymal hematoma (by 92% in filament MCAO, by 100% in embolic MCAO; P<0.0001). This was consistent with an improved BBB integrity. In vitro, HDLs decreased oxygen-glucose deprivation-induced BBB permeability (P<0.05) and vascular endothelial cadherin disorganization.

CONCLUSIONS

HDL injection decreased tPA-induced hemorrhagic transformation in rat models of MCAO. Both in vivo and in vitro results support the vasculoprotective action of HDLs on BBB under ischemic conditions.

Hyperthermia worsens ischaemic brain injury through destruction of microvessels in an embolic model in rats

PURPOSE

Basal lamina is a major part of the microvascular wall and plays a critical role in the integrity of microvasculature. The aim of this study is to determine whether hyperthermia worsens the destruction of microvascular integrity in the ischaemic injured brain.

MATERIALS AND METHODS

Focal cerebral ischaemia was induced by embolising a pre-formed clot into the middle cerebral artery (MCA). Rats received either normothermic or hyperthermic treatment. Neurological score and infarct size were evaluated at 24 h after the MCA occlusion. Microvascular collagen type IV and laminin were measured with fluorescence microscopy. The activities of matrix metalloproteinases (MMP-2 and MMP-9) and plasminogen activators (tPA and uPA) were determined by zymography.

RESULTS

Treatment with hyperthermia significantly increased infarct volume (p<0.01), cortex swelling (p<0.01), striatum swelling (p<0.05) and neurologic score (p<0.01) at 24 h after the MCA occlusion. Compared to the normothermic groups, hyperthermia significantly worsened the losses of microvascular basal lamina structure proteins, collagen type IV and laminin, at 6 h (p<0.001) and 24 h (p<0.01) after MCA occlusion. Hyperthermia increased the MMP-9 activity at 6 and 24 h after MCA occlusion compared with normothermia (p<0.05), whereas increased the MMP-2 activity at 6 h only (p<0.05). Hyperthermia also elevated uPA activity significantly at 6 and 24 h after MCA occlusion compared to normothermia (p<0.05).

CONCLUSIONS

These results demonstrate that hyperthermia exacerbates the destruction of microvascular integrity possibly by increasing the activities of MMP-2, MMP-9 and uPA in the ischaemic cerebral tissues.

Screen-imaging guidance using a modified portable video macroscope for middle cerebral artery occlusion

The use of operating microscopes is limited by the focal length. Surgeons using these instruments cannot simultaneously view and access the surgical field and must choose one or the other. The longer focal length (more than 1 000 mm) of an operating telescope permits a position away from the operating field, above the surgeon and out of the field of view. This gives the telescope an advantage over an operating microscope. We developed a telescopic system using screen-imaging guidance and a modified portable video macroscope constructed from a Computar MLH-10 × macro lens, a DFK-21AU04 USB CCD Camera and a Dell laptop computer as monitor screen. This system was used to establish a middle cerebral artery occlusion model in rats. Results showed that magnification of the modified portable video macroscope was appropriate (5–20 ×) even though the Computar MLH-10 × macro lens was placed 800 mm away from the operating field rather than at the specified working distance of 152.4 mm with a zoom of 1–40 ×. The screen-imaging telescopic technique was clear, life-like, stereoscopic and matched the actual operation. Screen-imaging guidance led to an accurate, smooth, minimally invasive and comparatively easy surgical procedure. Success rate of the model establishment evaluated by neurological function using the modified neurological score system was 74.07%. There was no significant difference in model establishment time, sensorimotor deficit and infarct volume percentage. Our findings indicate that the telescopic lens is effective in the screen surgical operation mode referred to as “long distance observation and short distance operation” and that screen-imaging guidance using an modified portable video macroscope can be utilized for the establishment of a middle cerebral artery occlusion model and micro-neurosurgery.

Direct Thrombus Imaging as a Means to Control the Variability of Mouse Embolic Infarct Models

Background and Purpose—

High experimental variability in mouse embolic stroke models could mask the effects of experimental treatments. We hypothesized that imaging thrombus directly would allow this variability to be controlled.

Methods—

We optically labeled thrombi with a near-infrared fluorescent (NIRF) probe C15 that is covalently linked to fibrin by factor-XIIIa. Labeled thrombus was injected into the left distal internal carotid artery (ICA) of C57/BL6 mice (n=47), near its bifurcation, and laser-Doppler cerebral-blood-flow (CBF) was assessed for 30 minutes. NIRF thrombus imaging was done ex vivo at 24 hours.

Results—

CBF variably decreased to 43.9±17.3% at 5 minutes (rCBF; 11.2∼80.4%). NIRF thrombus imaging at 24 hours showed variability in distribution (ICA bifurcation, adjacent and/or remote areas) and burden (2279±1270 pixels; 0∼5940 pixels). Final infarct size was also variable (21.0±10.3%; 4.7∼60.3% of the bihemispheric volume). Despite this heterogeneity, a strong thrombus-infarct correlation was maintained. The left hemispheric target infarct size (% of the hemisphere) correlated with thrombus burden, as a stronger predictor of infarct volume ( P <0.001, r=0.50) than rCBF ( P =0.02, r=−0.34). The infarct size was best predicted by a combination of thrombus imaging and CBF: left-hemispheric big-thrombi (>1865 pixels)/low-rCBF (≤42%) had an infarct volume of 56.9±10.4% (n=12), big-thrombi/high-rCBF had 45.9±23.5% (n=11), small-thrombi/low-rCBF 35.7±17.3% (n=11) and small-thrombi/ high-rCBF 27.3±16.4% (n=12).

Conclusions—

This is the first study to demonstrate that the highly heterogeneous nature of the mouse embolic stroke model can be characterized and managed by using near-infrared fluorescent thrombus imaging combined with CBF monitoring to stratify animals into useful subgroups.

Sigma-1 receptor ligand PRE-084 reduced infarct volume, neurological deficits, pro-inflammatory cytokines and enhanced anti-inflammatory cytokines after embolic stroke in rats

Sigma receptor agonists have been found to provide potent neuroprotection in rats and mice. This neuroprotection is thought to be mediated through anti-excitotoxic mechanisms. Neuroprotective and immune modulatory effects of sigma ligands have not been investigated in embolic stroke. In the present study, rats were subjected to embolic stroke or sham stroke and were treated with the sigma-1 receptor agonist PRE-084 (5mg/kg i.p.) or saline vehicle 3 and 24h after stroke. Infarct volume and behavioural tests were conducted, and cytokine levels (ILs-1α and β, IL-2, IL-4, IL-6, IL-10, GM-CSF and TNF-α) were determined in ischemic and non-ischemic cortices. Axonal damage was determined using the pNF-H ELISA assay. Treatment with PRE-084 afforded neuroprotection following embolic stroke as evidenced by significantly reduced infarct volume and improved behavioural outcome. Remarkably, treatment with PRE-084 reduced levels of pro-inflammatory cytokines and enhanced anti-inflammatory cytokines. Levels of pNF-H were lower in rats treated with PRE-084 suggesting reduced axonal damage but this finding did not reach statistical significance. The findings of the present study suggest that part of the neuroprotective effects of sigma-1 receptor agonists may be mediated through a dual effect on cytokine release following stroke.

Morphological and neuro-behavioral parallels in the rat model of stroke

Middle cerebral artery occlusion (MCAO) is widely used as a rat model of focal brain ischemia. Evaluation of brain damage often includes the morphological analysis of the injury area, MRI, and various scales which depend on functional tests, commonly known as neurological severity score (NSS). We determined the optimal number of NSS tests and assessed their capacity for non-invasive evaluation of brain ischemic injury in the rat MCAO model. 275 male Sprague-Dawley rats were randomly divided into five groups, given either permanent (p) MCAO or transient (t) MCAO using an uncoated 4-0 monofilament catheter or a silicone-coated monofilament. The rats' neurological status was examined before and at 1 and 24h following MCAO. The size of brain injury was then measured histologically and the extent of right cerebral hemisphere edema was calculated. We established a correlation between these tests and morphological data for brain injury. Adjusted R(2) of the prediction of total histology score was 0.7. The Hosmer-Lemeshow p-value of this model was 0.812 for total brain histology. For the brain edema the adjusted R(2) of the prediction model was 0.48. The Hosmer-Lemeshow p-value of this model was 0.558 for brain edema. Our methods of estimating infarct size produces reliable and well correlated results at 24h and demonstrates to be an easy and quick way to assess infarct size soon after ischemic injury has occurred. The described method for neurological assessment could ultimately aid in assessing various treatment modalities in the early hours following stroke.

The role of the blood transcriptome in innate inflammation and stroke

Cerebrovascular disease is a major cause of death and disability, with a poorer outcome in patients having select risk factors including diabetes and hypertension. Risk factors and the state of cerebral ischemia-reperfusion associated with cerebrovascular occlusion are known to cause inflammatory changes. These events and the inflammatory state are reflected by transcript changes in various components of the blood and can be specifically measured. By defining these changes, new insight into cerebrovascular disease and its therapeutics is being achieved.

Different strokes for different folks: the rich diversity of animal models of focal cerebral ischemia

No single animal model is able to encompass all of the variables known to affect human ischemic stroke. This review highlights the major strengths and weaknesses of the most commonly used animal models of acute ischemic stroke in the context of matching model and experimental aim. Particular emphasis is placed on the relationships between outcome and underlying vascular variability, physiologic control, and use of models of comorbidity. The aim is to provide, for novice and expert alike, an overview of the key controllable determinants of experimental stroke outcome to help ensure the most effective application of animal models to translational research.

Protective effect of high-density lipoprotein-based therapy in a model of embolic stroke

BACKGROUND AND PURPOSE

High-density lipoprotein (HDL) levels are inversely associated with stroke incidence, suggesting a protective effect. Using a rat model, we tested the hypothesis that HDL exerts direct vasculo-/neuroprotective effects when administered during the acute phase of embolic stroke.

METHODS

After embolic occlusion, Sprague-Dawley rats were randomly treated intravenously with purified HDL versus saline immediately (2, 10 mg/kg) or 3 or 5 hours (10 mg/kg) after stroke. The effects of HDL were assessed blindly 24 hours later by evaluating neurological deficit score and measuring the infarct volume and blood-brain barrier breakdown. Protease activities and neutrophil infiltration were also evaluated.

RESULTS

HDL injection immediately after stroke (10 mg/kg) reduced by 68% the mortality at 24 hours (P=0.015). HDL administration immediately or at 3 or 5 hours after stroke also reduced cerebral infarct volume by 74%, 68%, and 70.7%, respectively (P=0.0003, P=0.011, and P=0.019; n=17 per group). The neurological deficit at 24 hours in the HDL-treated group was decreased versus the saline-treated group (P=0.015). Ischemia-induced blood-brain barrier breakdown was significantly reduced in HDL-treated rats versus controls (P=0.0045). Neuroprotective effects of HDL were associated with decreased neutrophil recruitment in the infarct area (P=0.0027) accompanied by reduced matrix metalloproteinase gelatinase activity. Immunostaining showed that HDL was associated with endothelial and glial cells, and also that intercellular adhesion molecule-1 expression was decreased in vessels within the infarct area.

CONCLUSIONS

Administration of HDL is neuroprotective when performed up to 5 hours after experimental stroke. This effect may be attributed to the ability of HDL to protect the blood-brain barrier and limit neutrophil recruitment.

Technique for collection of cerebrospinal fluid from the cisterna magna in rat

Cerebrospinal fluid (CSF) is in direct contact with the extracellular space in the central nervous system (CNS), and biological changes in the brain can be reflected in CSF. In the present article, a procedure for collection of CSF in rats is described. The technique quickly and reliably yields large quantities of CSF (50-150 microl) in rats. More importantly, blood contamination of the CSF is avoided. Furthermore, detections of ATP and interleukin (IL)-1 beta in the CSF have been carried out. ATP concentration in the CSF samples was between 8.3 and 15.8 nM, with an average of 10.5+/-0.83 nM (mean+/-SEM). The concentrations of IL-1beta were below the detection limit in the CSF in the laminectomy control rats, but it increased to 0.26+/-0.07 ng/ml at 1h after spinal cord injury. This technique offers an alternative method to surgical cannulation for the collection of CSF in rats.

Rodent models of focal cerebral ischemia: procedural pitfalls and translational problems

Rodent models of focal cerebral ischemia are essential tools in experimental stroke research. They have added tremendously to our understanding of injury mechanisms in stroke and have helped to identify potential therapeutic targets. A plethora of substances, however, in particular an overwhelming number of putative neuroprotective agents, have been shown to be effective in preclinical stroke research, but have failed in clinical trials. A lot of factors may have contributed to this failure of translation from bench to bedside. Often, deficits in the quality of experimental stroke research seem to be involved. In this article, we review the commonest rodent models of focal cerebral ischemia - middle cerebral artery occlusion, photothrombosis, and embolic stroke models - with their respective advantages and problems, and we address the issue of quality in preclinical stroke modeling as well as potential reasons for translational failure.

Partial intra-aortic occlusion improves perfusion deficits and infarct size following focal cerebral ischemia

Reperfusion with intravenous tissue plasminogen activator (tPA) has been the goal of therapy for acute ischemic stroke; however, tPA is contraindicated in many patients, has low recanalization rates in major occlusions, and carries a substantial risk of symptomatic intracerebral hemorrhage. In the present study, we hypothesized that partial intra-aortic occlusion of the abdominal aorta would increase salvage of ischemic penumbra and reduce infarct volume after focal embolic stroke in rats. We examined the effects of aortic occlusion on infarct volume, expression and activation of matrix metalloprotease-9, and hemorrhagic transformation with or without treatment with tPA. We then examined the effects of aortic occlusion on perfusion deficits following embolic occlusion. Results showed that partial aortic occlusion significantly reduces brain infarction volume with or without treatment with tPA after focal ischemia, but does not increase risk for hemorrhagic transformation or matrix metalloprotease-9 expression and activation. Partial intra-aortic occlusion also reduces perfusion deficits after focal cerebral ischemia as compared to control. The present study shows that partial intra-aortic occlusion significantly decreases infarction volume and perfusion deficits following ischemic injury in an embolic model of cerebral ischemia. Moreover, combination treatment with tPA and partial intra-aortic occlusion further reduces infarction volume without any increase in hemorrhagic transformation.

Rosiglitazone alone or in combination with tissue plasminogen activator improves ischemic brain injury in an embolic model in rats

In this study, we examined whether rosiglitazone, a peroxisome proliferator-activated receptor gamma (PPARgamma) agonist, is neuroprotective in focal ischemic brain injury, and whether rosiglitazone can enhance the protective action of tissue plasminogen activator (tPA), an agent used clinically for thrombolytic therapy. Rats were subjected to ischemic brain injury by embolizing preformed clots into the middle cerebral artery (MCA). Treatment with rosiglitazone reduced infarction and improved functional recovery; it also enhanced the neuroprotective action of tPA and lengthened the time window for initiating tPA treatment. Occlusion of MCA resulted in a loss of collagen type IV, a major structural protein of the microvascular basal lamina, and tPA treatment worsened this loss. Rosiglitazone treatment prevented the reduction of collagen type IV in the ischemic injured brain by inhibiting the activation of matrix metallopeptidase-9 (MMP-9). In addition, rosiglitazone treatment reduced inflammatory reactions in the ischemic injured brain. Rosiglitazone either alone or in combination with tPA is an effective agent in the reduction of ischemic brain injury. The reduction of microvascular damage and inflammation contributes to the beneficial actions of rosiglitazone.

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.

Protective effect of delayed treatment with low-dose glibenclamide in three models of ischemic stroke

BACKGROUND AND PURPOSE

Ischemia/hypoxia induces de novo expression of the sulfonylurea receptor 1-regulated NC(Ca-ATP) channel. In rodent models of ischemic stroke, early postevent administration of the sulfonylurea, glibenclamide, is highly effective in reducing edema, mortality, and lesion volume, and in patients with diabetes presenting with ischemic stroke, pre-event plus postevent use of sulfonylureas is associated with better neurological outcome. However, the therapeutic window for treatment with glibenclamide has not been studied.

METHODS

We examined the effect of low-dose (nonhypoglycemogenic) glibenclamide in 3 rat models of ischemic stroke, all involving proximal middle cerebral artery occlusion (MCAo): a thromboembolic model, a permanent suture occlusion model, and a temporary suture occlusion model with reperfusion (105 minutes occlusion, 2-day reperfusion). Treatment was started at various times up to 6 hours post-MCAo. Lesion volumes were measured 48 hours post-MCAo using 2,3,5-triphenyltetrazolium chloride.

RESULTS

Glibenclamide reduced total lesion volume by 53% in the thromboembolic MCAo model at 6 hours, reduced corrected cortical lesion volume by 51% in the permanent MCAo model at 4 hours, and reduced corrected cortical lesion volume by 41% in the temporary MCAo model at 5.75 hours (P<0.05 for all 3). Analysis of pooled data from the permanent MCAo and temporary MCAo series indicated a sigmoidal relationship between hemispheric swelling and corrected cortical lesion volume with the half-maximum cortical lesion volume being observed with 10% hemispheric swelling.

CONCLUSIONS

Low-dose glibenclamide has a strong beneficial effect on lesion volume and has a highly favorable therapeutic window in several models of ischemic stroke.

Delayed matrix metalloproteinase inhibition reduces intracerebral hemorrhage after embolic stroke in rats

Hemorrhagic transformation (HT) and brain edema are life-threatening complications of recombinant tissue plasminogen activator (rt-PA)-induced reperfusion after ischemic stroke. The risk of HT limits the therapeutic window for reperfusion to 3 h after stroke onset. Pre-treatment with matrix metalloproteinase (MMP) inhibitors reduces HT and cerebral edema in experimental stroke. However, whether a delayed therapeutic intervention would be beneficial is unknown. In this study, 215 male Sprague-Dawley rats were subjected to embolic stroke and 75 rats were included in the final analysis. The animals were treated with the MMP inhibitor p-aminobenzoyl-gly-pro-D-leu-D-ala-hydroxamate before or after 3 or 6 h of ischemia. Animals were monitored for reperfusion and received rt-PA 6 h after ischemia onset. The results at 24 h showed that MMP inhibition 3 h after ischemia significantly decreased the degree of brain edema (17% of hemispheric enlargement in the treated group versus 24% in controls, P=0.018), reduced the risk (OR=0.163; 95% CI: 0.029 to 0.953) and gravity (0.09 versus 0.19 mg of parenchymal hemoglobin, P=0.02) of intracerebral hemorrhage, and improved neurological outcome (20% of the treated animals had a slight deficit; all of the controls had a bad outcome, P<0.05). Delaying MMP inhibition to 6 h after ischemia restricted the beneficial role of the treatment to a reduction in the risk of parenchymal hemorrhage (OR=0.242; 95% CI: 0.060 to 0.989). Our results confirm the involvement of MMPs in HT and support the possibility of extending the therapeutic window for thrombolysis in stroke by administering a broad-spectrum MMP inhibitor after the onset of ischemia.

Combination therapy of rosiglitazone, a peroxisome proliferator-activated receptor-gamma ligand, and NMDA receptor antagonist (MK-801) on experimental embolic stroke in rats

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists have been found to have potent anti-inflammatory actions and suggested as potential therapies for brain ischaemia. Glutamate is the most common excitatory neurotransmitter in the central nervous system and is released excessively during ischaemia. Stroke therapy will require combinations of drug classes, because no single drug class has yet been proven efficacious in human beings. The present study was conducted to assess whether N-methyl-d-aspartate (NMDA) receptor antagonist (MK-801) treatment can improve recovery from ischaemic brain injury and whether rosiglitazone, a PPAR-gamma ligand, can increase its neuroprotective effect in an embolic model of stroke. Stroke was induced in rats by embolizing a preformed clot into the middle cerebral artery. Rosiglitazone (0.1 mg/kg, intraperitoneally) and MK-801 (0.1 mg/kg, intravenously) were injected immediately after embolization. Forty-eight hours later, the brains were removed, sectioned and stained with triphenyltetrazolum chloride and analysed by a commercial image processing software programme. Rosiglitazone and MK-801 alone or in combination decreased infarct volume by 49.16%, 50.26% and 81.32%, respectively (P < 0.001). Moreover, the combination therapy significantly decreased the infarct volume when compared to any drug used alone (P < 0.05). MK-801 reduced the brain oedema by 68% compared to the control group (P < 0.05), but rosiglitazone or combination did not show any significant effect. The drugs alone or in combination also demonstrated improved neurological function, but combination therapy was more effective on neurological deficits improving. Our data show that the combination of MK-801 and rosiglitazone is more neuroprotective in thromboembolic stroke than given alone; this effect perhaps represents a possible additive effect in the brain infarction.

ROSIGLITAZONE, A PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-? LIGAND, REDUCES INFARCTION VOLUME AND NEUROLOGICAL DEFICITS IN AN EMBOLIC MODEL OF STROKE

1. Stroke is accompanied by a robust inflammatory response, glutamate-mediated excitotoxicity, release of reactive oxygen species and apoptosis. Thiazolidinediones, which target the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-g, have been reported recently to exhibit potent anti-inflammatory and anti-oxidant actions and inhibit both neural excitotoxicity and apoptosis. 2. The present study was conducted to determine whether rosiglitazone, a potent thiazolidinedione for PPAR-g, would show efficacy against the cerebral infarction and neurological dysfunctions induced by embolic middle cerebral artery (MCA) occlusion in the rat. 3. Focal ischaemic injury was induced by embolizing a preformed clot into the MCA. Rosiglitazone was dissolved in dimethyl sulphoxide and injected i.p. 1 h before MCA occlusion at doses of 0.33, 0.1, 0.3 or 1 mg/kg. In addition, 1 mg/kg rosiglitazone was used immediately or 4 h after embolization. Forty-eight hours after MCA occlusion, brains were removed, sectioned and stained with a 2% solution of 2,3,5-triphenyltetrazolum chloride and analysed using a commercial image-processing software program. 4. When rosiglitazone was administered 1 h before embolization, it significantly reduced infarct volume by 48.2, 68.4% and 70.3% at doses of 0.1, 0.3 and 1 mg/kg, respectively (P < 0.001). Administration of rosiglitazone (1 mg/kg) immediately or 4 h after stroke also reduced infarct volume by 67 and 50.8%, respectively (P < 0.001). Rosiglitazone-treated rats also demonstrated improved neurological functions. However, there were no statistically significant differences between control and treated groups in terms of brain oedema at 48 h after ischaemic injury. 5. The findings of the present study may support the idea of a potential benefit of thiazolidinediones in the management of ischaemic stroke.

Selective, reversible occlusion of the middle cerebral artery in rats by an intraluminal approach

These studies optimized design and application of an intraluminal filament method to achieve selective middle cerebral artery (MCA) occlusion in rats. Silicone plugs of 300 microm diameter and 700-800 microm length were molded onto 6-0 suture. These were introduced into Wistar rats previously fitted with telemetric probes, using established placement procedures, with and without heparinization. Temperature and activity were monitored for 3 days, after which lesion volumes were assessed by triphenyltetrazolium chloride staining. Optimized filaments entered the MCA in 85% of Wistar rats, failures being attributable to anatomical variation at its origin from the internal carotid artery. Infarcts restricted to the MCA territory were apparent after 90 min occlusion, and maximal after 3 h occlusion. Intraischemic hyperthermia was noted in a third of occlusions performed without heparin, but never with anticoagulant treatment. Permanent occlusions were also evaluated in Fisher, Lewis, Long-Evans, Spontaneously Hypertensive and Sprague-Dawley rats, and Wistar rats from a second supplier, and compared with data for surgical MCA occlusions. Success rates varied among strains, but infarct volumes correlated with those obtained after surgical occlusions in respective populations. These studies demonstrate the feasibility and limitations of reversible and selective intraluminal filament occlusion of the MCA in rats.

Epileptogenesis after experimental focal cerebral ischemia

Cerebrovascular diseases are one of the most common causes of epilepsy in adults, and the incidence of stroke-induced epileptogenesis is increasing as the population ages. The mechanisms that lead to stroke-induced epileptogenesis in a subpopulation of patients, however, are still poorly understood. Recent advances in inducing epileptogenesis in rodent focal ischemia models have provided tools that can be used to identify the risk factors and neurobiologic changes leading to development of epilepsy after stroke. Here we summarize data from models in which epileptogenesis has been studied after focal ischemia; photothrombosis, middle cerebral artery (MCA) occlusion with filament, and endothelin-1-induced MCA occlusion. Analysis of the data indicates that neurobiologic changes occurring during stroke-induced epileptogenesis share some similarities to those induced by status epilepticus or traumatic brain injury.

Role of MC-1 alone and in combination with tissue plasminogen activator in focal ischemic brain injury in rats

OBJECT

Pyridoxal-5-phosphate (PLP), the biologically active form of pyridoxine, can rescue neurons from death in vitro and in vivo. In the present project, the authors have studied whether MC-1, an analog of PLP, alone or in combination with the thrombolytic agent tissue plasminogen activator (tPA), can protect the brains of rats injured by ischemia.

METHODS

Ischemic brain injury was induced in rats by injecting a preformed blood clot in the middle cerebral artery (MCA). Neurological deficits and infarct volumes caused by the embolus were measured to evaluate the effects of MC-1 on the ischemic injury. Systemic blood pressure and local brain blood flow were also monitored. Administration of different doses of MC-1 1 hour after embolization significantly reduced the infarct volume and improved functional recovery. Injection of MC-1 (40 mg/kg) at 3 or 6 hours after embolization also reduced the volume of the infarct significantly and improved functional recovery. Combined treatment with MC-1 and tPA was also neuroprotective, although it was not superior to treatment involving either MC-1 or tPA alone. Treatment with MC-1 did not result in significant changes in either systemic blood pressure or local blood flow in the ischemic brain.

CONCLUSIONS

These data support the hypothesis that in the focal embolic stroke model in rats MC-1 is a neuroprotective agent. The neuroprotection this compound provides still exists when MC-1 administration is delayed up to 6 hours after ischemic injury.

Simvastatin reduced ischemic brain injury and perfusion deficits in an embolic model of stroke

Simvastatin is cholesterol lowering agent and also a modulator of cytokine in the nervous system. The functional significance and neuroprotectiove mechanism of simvastatins in ischemic brain injury is controversial. The purpose of study is to evaluate the effect of simvastatin on ischemic brain injury and to investigate the perfusion capability of brain microvessels in the ischemic injury. This study included two series of experiments. In the first series, we studied if simvastatin is neuroprotective in an embolic model of stroke. The treatments began 2 weeks before middle cerebral artery (MCA) occlusion. Infarct volume was measured at 48 h post stroke. Neurological deficits were assessed at 2 h, 24 h and 48 h post stroke. Results showed that infarct volume in rats which received saline and simvastatin was 32.5 +/- 9.3% (mean +/- SD) and 18.7 +/- 6.5%, respectively. The infarct volume in the simvastatin group was significantly smaller than in the controls (P < 0.002). Treatment with simvastatin also improved neurological deficits and reduced brain edema significantly (P < 0.05). In the second series, we studied if simvastatin can improve microvascular reperfusions after ischemia. Perfusion deficits were detected at 8 h post stroke using Evens blue dye. Neurological deficits were assessed at 2 h and 8 h post stroke. Results showed that perfusion deficit in saline and simvastatin-treated groups were 58.7 +/- 8.7% and 23.4 +/- 7.5%, respectively. The perfusion deficit in simvastatin-treated group was decreased 61% (P < 0.01). These studies thus suggest that simvastatin is a protective agent in ischemic brain injury and this protective effect may be partially due to its action in the improvement of microvascular reperfusion.

Hyperthermia Masks the Neuroprotective Effects of Tissue Plaminogen Activator

BACKGROUND AND PURPOSE

Previously, we have shown that hyperthermia significantly increased neuronal damage after ischemic injury in a focal embolic model of stroke in rats. In the present study, we examined the effects of hyperthermia on the efficacy of thrombolytic therapy in this stroke model.

METHODS

In part A, efficacy of tissue plaminogen activator (tPA) treatment was examined in normothermic and hyperthermic rats after embolization of preformed clots into middle cerebral artery (MCA). In part B, brain perfusion deficits were assessed in rats after MCA occlusion. In part C, blood-brain barrier (BBB) permeability was examined in rats after MCA occlusion. In part D, we examined the influence of hyperthermia on fibrinolytic activity of tPA in vitro.

RESULTS

Results showed that treatment with tPA significantly reduced infarct volume in normothermic and 38 degrees C hyperthermic rats. When compared with normothermic rats, perfusion deficits in hyperthermic rats were significantly increased at both 3 hours and 6 hours after ischemic injury. Compared with normothermic sham-operated rats, Evans blue dye extravasation was increased in the injured rats with 39 degrees C hyperthermia. In vitro study showed that hyperthermia increased the fibrinolytic activity of tPA.

CONCLUSIONS

The present study shows that hyperthermia masks the neuroprotective effects of tPA treatment after ischemic injury and that this may be caused by increased BBB permeability, increased edema, and early progression of ischemic penumbral region to irreversibly damaged tissue as shown by progressively increasing perfusion deficits in hyperthermic rats.

NXY-059: a neuroprotective agent in acute stroke

Free radicals play an important role in secondary processes in ischaemic brain injury. Disodium 4-[(tert-butylimino) methyl] benzene-1,3-disulphonate N-oxide (NXY-059) is a nitrone-based free radical trapping agent. Findings from animal stroke models showed that NXY-059 is a potent neuroprotective agent that has a large window of therapeutic opportunity and long-lasting effects. Therefore, NXY-059 may be used as a monotherapy agent for treatment of acute stroke. NXY-059 may also be used as an adjunct agent to thrombolytic therapy, as it can reduce tissue plasminogen activator-induced haemorrhage in ischaemic stroke.

Pyridoxine as a template for the design of antiplatelet agents

The B(6) vitamers have been shown to display beneficial therapeutic effects in cardiovascular related disorders. The design of novel antiplatelet agents using pyridoxine as a template has led to the discovery of a class of novel cardio- and cerebro-protective agents. The present study describes the synthesis of several of these derivatives along with the antiplatelet and antiischemic activity of derivative 16.

Genetic and Cellular Therapies for Cerebral Infarction

Neurosurgeons, working as surgical scientists, can have a prominent role in developing and implementing genetic and cellular therapies for cerebral ischemia. The rapid emergence of both genetic and cellular therapies for neural regeneration warrants a careful analysis before implementation of human studies to understand the pitfalls and promises of this strategy. In this article, we review the topic of genetic and cellular therapy for stroke to provide a foundation for practicing neurosurgeons and clinical scientists who may become involved in this type of work. In Part 1, we review preclinical approaches with gene transfer, such as 1) improved energy delivery, 2) reduction of intracellular calcium availability, 3) abrogation of effects of reactive oxygen species, 4) reduction of proinflammatory cytokine signaling, 5) inhibition of apoptosis mediators, and 6) restorative gene therapy, that are paving the way to develop new strategies to treat cerebral infarction. In Part 2, we discuss the results of studies that address the possibility of using cellular therapies for stroke in animal models and in human trials by reviewing 1) the basics of stem cell biology, 2) exogenous and 3) and endogenous cell sources for therapy, and 4) clinical considerations in cell therapy applications. These emerging technologies based on the advancements made in recent years in the fields of genetics, therapeutic cloning, neuroscience, stem cell biology, and gene therapy provide significant potential for new therapies for stroke.

Middle cerebral artery occlusion during MR-imaging: investigation of the hyperacute phase of stroke using a new in-bore occlusion model in rats

Magnetic resonance imaging (MRI) provides insights into the dynamics of focal cerebral ischemia. Usually, experimental stroke is induced outside the magnet bore, preventing investigators from acquiring pre-ischemic images for later pixel-by-pixel comparisons and from studying the earliest changes in the hyperacute phase of ischemia. Herein, we introduce a new and easy to apply in-bore occlusion protocol based on the intraarterial embolization of ceramic macrospheres. PE-50 tubing, filled with saline and six macrospheres (0.315-0.355 mm in diameter), was placed into the internal carotid artery (ICA) of anesthetized Sprague-Dawley rats. The animals were transferred into an MRI scanner (7.0 T) and baseline diffusion-weighted imaging (DWI) and T2-imaging was performed. Then the macrospheres were injected into the internal artery to occlude the MCA. Post-ischemic DWI and T2-imaging was started immediately thereafter. The apparent diffusion coefficient (ADC) (a marker for cytotoxic brain edema) and T2-relaxation time (a marker for vasogenic brain edema) were determined in the ischemic lesions and compared to the unaffected hemisphere. ADC significantly declined within the first 5-10 min after stroke onset. T2-relaxation time increased as early as at the first T2-imaging time-point (20-35 min after embolization). After 150 min of ischemia, the lesions covered 18.0 +/- 7.4% of the hemispheres. The model failed in one out of nine animals (11%). This model allows MR-imaging from the initial minutes after permanent middle cerebral artery (MCA) occlusion. It does not permit reperfusion. This technique might provide information about the pathophysiological processes in the hyperacute phase of stroke.

Effect of zinc in ischemic brain injury in an embolic model of stroke in rats

Zinc is prevalent in the mammalian central nervous system and its role in ischemic brain injury is still controversial. In the present study, the effect of zinc in ischemic brain injury was examined in an embolic model of stroke in rats. Furthermore, the effect of zinc in combination with bicuculline, a GABAa antagonist, was also examined in the ischemic injury. Treatment with zinc or zinc plus bicuculline increased infarct volume significantly and also worsened neurological deficits. Moreover, treatment with zinc plus bicuculline also enhanced ischemic brain edema. These results thus support the hypothesis that administration of zinc i.p. worsens the outcome of ischemic brain injury in the embolic model of stroke in rats.

Effects of hyperthermia on infarct volume in focal embolic model of cerebral ischemia in rats

Hyperthermia worsens outcome of stroke in patients and also in animal models. In the present study, we tested the effects of hyperthermia in a focal embolic model of cerebral ischemia in rats. Focal ischemic injury was induced by embolizing a preformed clot into the middle cerebral artery. Hyperthermia significantly increased the brain infarct volume as compared to the normothermic controls measured at 48 h following the ischemic insult. Neurological deficits were also significantly elevated in the animals undergoing hyperthermic treatment. In addition, hyperthermia also significantly increased mortality. Our data thus show that hyperthermia exacerbates neuronal injury in the focal embolic model of cerebral ischemia in rats.