Experimental animal models of traumatic brain injury: medical and biomechanical mechanism

Insights from Rodent Models for Improving Bench-to-Bedside Translation in Traumatic Brain Injury

Road accidents, domestic falls, and persons associated with sports and military services exhibited the concussion or contusion type of traumatic brain injury (TBI) that resulted in chronic traumatic encephalopathy. In some instances, these complex neurological aberrations pose severe brain damage and devastating long-term neurological sequelae. Several preclinical (rat and mouse) TBI models simulate the clinical TBI endophenotypes. Moreover, many investigational neuroprotective candidates showed promising effects in these models; however, the therapeutic success of these screening candidates has been discouraging at various stages of clinical trials. Thus, a correct selection of screening model that recapitulates the clinical neurobiology and endophenotypes of concussion or contusion is essential. Herein, we summarize the advantages and caveats of different preclinical models adopted for TBI research. We suggest that an accurate selection of experimental TBI models may improve the translational viability of the investigational entity.

Contrecoup Traumatic Intracerebral Hemorrhage: A Geometric Study of the Impact Site and Association with Hemorrhagic Progression

Traumatic intracerebral hemorrhage (TICH) represents 13-48% of the lesions after a traumatic brain injury (TBI). The frequency of TICH-hemorrhagic progression (TICH-HP) is estimated to be approximately 38-63%. The relationship between the impact site and TICH location has been described in many autopsy-based series. This association, however, has not been consistently demonstrated since the introduction of computed tomography (CT) for studying TBI. This study aimed to determine the association between the impact site and TICH location in patients with moderate and severe TBI. We also analyzed the associations between the TICH location, the impact site, the production mechanism (coup or contrecoup), and hemorrhagic progression. We retrospectively analyzed the records of 408 patients after a moderate or severe TBI between January 2010 and November 2014. We identified 177 patients with a total of 369 TICHs. We found a statistically significant association between frontal TICHs and impact sites located on the anterior area of the head (OR 5.8, p < 0.001). The temporal TICH location was significantly associated with impact sites located on the posterior head area (OR 4.9, p < 0.001). Anterior and lateral TICHs were associated with impact sites located at less than 90 degrees (coup) (OR 1.64, p = 0.03) and more than 90 degrees (contrecoup), respectively. Factors independently associated with TICH-HP obtained through logistic regression included an initial volume of <1 cc, cisternal compression, falls, acute subdural hematoma, multiple TICHs, and contrecoup TICHs. We demonstrated a significant association between the TICH location and impact site. The contrecoup represents a risk factor independently associated with hemorrhagic progression.

Effect of Epidural Electrical Stimulation and Repetitive Transcranial Magnetic Stimulation in Rats With Diffuse Traumatic Brain Injury

OBJECTIVE

To evaluate the effects of epidural electrical stimulation (EES) and repetitive transcranial magnetic stimulation (rTMS) on motor recovery and brain activity in a rat model of diffuse traumatic brain injury (TBI) compared to the control group.

METHODS

Thirty rats weighing 270-285 g with diffuse TBI with 45 kg/cm(2) using a weight-drop model were assigned to one of three groups: the EES group (ES) (anodal electrical stimulation at 50 Hz), the rTMS group (MS) (magnetic stimulation at 10 Hz, 3-second stimulation with 6-second intervals, 4,000 total stimulations per day), and the sham-treated control group (sham) (no stimulation). They were pre-trained to perform a single-pellet reaching task (SPRT) and a rotarod test (RRT) for 14 days. Diffuse TBI was then induced and an electrode was implanted over the dominant motor cortex. The changes in SPRT success rate, RRT performance time rate and the expression of c-Fos after two weeks of EES or rTMS were tracked.

RESULTS

SPRT improved significantly from day 8 to day 12 in the ES group and from day 4 to day 14 in the MS group (p<0.05) compared to the sham group. RRT improved significantly from day 6 to day 11 in ES and from day 4 to day 9 in MS compared to the sham group. The ES and MS groups showed increased expression of c-Fos in the cerebral cortex compared to the sham group.

CONCLUSION

ES or MS in a rat model of diffuse TBI can be used to enhance motor recovery and brain activity.

Alpha lipoic acid inhibits neural apoptosis via a mitochondrial pathway in rats following traumatic brain injury

Alpha lipoic acid (ALA) is a powerful antioxidant that has proven protective effects against brain damage following a traumatic brain injury (TBI) in rats. However, the molecular mechanisms underlying these effects are not well understood. This study investigated the effect of ALA on neural apoptosis and the potential mechanism of these effects in the weight-drop model of TBI in male Sprague-Dawley rats that were treated with ALA (20 or 100 mg/kg) or vehicle via intragastric administration 30 min after TBI. Brain samples were collected 48 h later for analysis. ALA treatment resulted in a downregulation of caspase-3 expression, reduced the number of positive cells in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and improved neuronal survival. Furthermore, the level of malondialdehyde and glutathione peroxidase activity were restored, while Bcl-2-associated X protein translocation to mitochondria and cytochrome c release into the cytosol were reduced by ALA treatment. These results demonstrate that ALA improves neurological outcome in rats by protecting neural cell against apoptosis via a mechanism that involves the mitochondria following TBI.

Animal models of sports-related head injury: bridging the gap between pre-clinical research and clinical reality

Sports-related head impact and injury has become a very highly contentious public health and medico-legal issue. Near-daily news accounts describe the travails of concussed athletes as they struggle with depression, sleep disorders, mood swings, and cognitive problems. Some of these individuals have developed chronic traumatic encephalopathy, a progressive and debilitating neurodegenerative disorder. Animal models have always been an integral part of the study of traumatic brain injury in humans but, historically, they have concentrated on acute, severe brain injuries. This review will describe a small number of new and emerging animal models of sports-related head injury that have the potential to increase our understanding of how multiple mild head impacts, starting in adolescence, can have serious psychiatric, cognitive and histopathological outcomes much later in life. Sports-related head injury (SRHI) has emerged as a significant public health issue as athletes can develop psychiatric and neurodegenerative disorders later in life. Animal models have always been an integral part of the study of human TBI but few existing methods are valid for studying SRHI. In this review, we propose criteria for effective animal models of SRHI. Movement of the head upon impact is judged to be of primary importance in leading to concussion and persistent CNS dysfunction.

Perspectives on molecular biomarkers of oxidative stress and antioxidant strategies in traumatic brain injury

Traumatic brain injury (TBI) is frequently associated with abnormal blood-brain barrier function, resulting in the release of factors that can be used as molecular biomarkers of TBI, among them GFAP, UCH-L1, S100B, and NSE. Although many experimental studies have been conducted, clinical consolidation of these biomarkers is still needed to increase the predictive power and reduce the poor outcome of TBI. Interestingly, several of these TBI biomarkers are oxidatively modified to carbonyl groups, indicating that markers of oxidative stress could be of predictive value for the selection of therapeutic strategies. Some drugs such as corticosteroids and progesterone have already been investigated in TBI neuroprotection but failed to demonstrate clinical applicability in advanced phases of the studies. Dietary antioxidants, such as curcumin, resveratrol, and sulforaphane, have been shown to attenuate TBI-induced damage in preclinical studies. These dietary antioxidants can increase antioxidant defenses via transcriptional activation of NRF2 and are also known as carbonyl scavengers, two potential mechanisms for neuroprotection. This paper reviews the relevance of redox biology in TBI, highlighting perspectives for future studies.

Scriptaid, a novel histone deacetylase inhibitor, protects against traumatic brain injury via modulation of PTEN and AKT pathway : scriptaid protects against TBI via AKT

Traumatic brain injury (TBI) is a leading cause of motor and cognitive deficits in young adults for which there is no effective therapy. The present study characterizes the protective effect of a new histone deacetylase inhibitor, Scriptaid (Sigma-Aldrich Corporation, St. Louis, MO), against injury from controlled cortical impact (CCI). Scriptaid elicited a dose-dependent decrease in lesion size at 1.5 to 5.5 mg/kg and a concomitant attenuation in motor and cognitive deficits when delivered 30 minutes postinjury in a model of moderate TBI. Comparable protection was achieved even when treatment was delayed to 12 h postinjury. Furthermore, the protection of motor and cognitive functions was long lasting, as similar improvements were detected 35 days postinjury. The efficacy of Scriptaid (Sigma-Aldrich Corporation) was manifested as an increase in surviving neurons, as well as the number/length of their processes within the CA3 region of the hippocampus and the pericontusional cortex. Consistent with other histone deacetylase inhibitors, Scriptaid treatment prevented the decrease in phospho-AKT (p-AKT) and phosphorylated phosphatase and tensin homolog deleted on chromosome 10 (p-PTEN) induced by TBI in cortical and CA3 hippocampal neurons. Notably, the p-AKT inhibitor LY294002 attenuated the impact of Scriptaid, providing mechanistic evidence that Scriptaid functions partly by modulating the prosurvival AKT signaling pathway. As Scriptaid offers long-lasting neuronal and behavioral protection, even when delivered 12 h after controlled cortical impact, it is an excellent new candidate for the effective clinical treatment of TBI.

The effect of electric cortical stimulation after focal traumatic brain injury in rats

Objective

To evaluate the effects of electric cortical stimulation in the experimentally induced focal traumatic brain injury (TBI) rat model on motor recovery and plasticity of the injured brain.

Method

Twenty male Sprague-Dawley rats were pre-trained on a single pellet reaching task (SPRT) and on a Rotarod task (RRT) for 14 days. Then, the TBI model was induced by a weight drop device (40 g in weight, 25 cm in height) on the dominant motor cortex, and the electrode was implanted over the perilesional cortical surface. All rats were divided into two groups as follows: Electrical stimulation (ES) group with anodal continuous stimulation (50 Hz and 194 µs duration) or Sham-operated control (SOC) group with no electrical stimulation. The rats were trained SPRT and RRT for 14 days for rehabilitation and measured Garcia's neurologic examination. Histopathological and immunostaining evaluations were performed after the experiment.

Results

There were no differences in the slice number in the histological analysis. Garcia's neurologic scores & SPRT were significantly increased in the ES group (p<0.05), yet, there was no difference in RRT in both groups. The ES group showed more expression of c-Fos around the brain injured area than the SOC group.

Conclusion

Electric cortical stimulation with rehabilitation is considered to be one of the trial methods for motor recovery in TBI. However, more studies should be conducted for the TBI model in order to establish better stimulation methods.

Closed head injury in rats: histopathological aspects in an experimental weight drop model

PURPOSE

To study histopathological findings due to a model of closed head injury by weight loss in rats.

METHODS

A platform was used to induce closed cranial lesion controlled by weight loss with a known and predefined energy. 25 male Wistar rats (Rattus novergicus albinus) were divided in five equal groups which received different cranial impact energy levels: G1, G2, G3 and G4 with 0.234J, 0.5J, 0.762J and 1J respectively and G5 (Sham). Under the effect of analgesia, the brain of each group was collected and prepared for histopathological analysis by conventional optic microscopy.

RESULTS

It was observed greater number of injured neurons in animals of group 4, however neuronal death also could be noticed in animals of group 5. Intraparenchymal hemorrhages were more frequent in animals of group 4 and the cytotoxic brain swelling and vascular congestion were more intense in this group

CONCLUSION

The histopathological analysis of these findings allowed to observe typical cranial trauma alterations and these keep close relation with impact energy.

Traumatic brain injury: clinical and pathological parameters in an experimental weightdrop model

PURPOSE

To investigate the function of an experimental cranium trauma model in rats.

METHODS

The equipment, already described in the literature and under discreet adaptations, is composed by a platform that produces closed head impact controlled by weight drop with pre-defined and known energy. 25 Wistar male rats (Rattus norvegicus albinus) were divided into five equal groups that received different quantities of cranial impact energy: G1, G2, G3 and G4 with 0,234J, 0,5J, 0,762J and 1J respectively and G5 (Sham). Under intense analgesia, each group was evaluated clinically in a sequence of intervals and had their encephalon removed for pathologic analysis.

RESULTS

Important clinical alterations (convulsions, bradycardia, bradypnea and abnormal postures) and focal pathologic (hematomas and hemorrhages) kept proportion with the intensity of the impact. No fracture was observed and the group 4 had 80% mortality rate.

CONCLUSION

The experimental cranium trauma animal model by weight drop is an alternative of low cost and easy reproduction that allows evaluating clinical and pathological alterations in accordance with studies in experimental surgery aims for new traumatic brain injury approach in rats.

Neuroprotective effects of osthole pretreatment against traumatic brain injury in rats

Osthole, a coumarin compound isolated from the plant-derived herb Cnidium monnieri, has been the subject of considerable interest because of its broad spectrum of pharmacological properties. The aim of this study was to investigate the potential protective effects of osthole in adult rats in the setting of traumatic brain injury (TBI). We employed Feeney's weight-drop model to ascertain whether intraperitoneal administration of osthole (10mg/kg, 20mg/kg and 40 mg/kg) 30 min before TBI could reduce the severity of neurological deficits, cerebral edema, and hippocampal neuron loss. The levels of malondialdehyde (MDA) and glutathione (GSH), the activity of superoxide dismutase (SOD), the expressions of Bcl-2, Bax, and active caspase-3, and the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive apoptotic cells were also measured to characterize the antioxidative and antiapoptotic properties. A significant reduction of neurological deficits, cerebral edema and hippocampal neuron loss was observed in the osthole pretreatment groups (20mg/kg and 40 mg/kg, but not 10mg/kg) by 24h after TBI compared with the TBI group. Furthermore, pretreatment with osthole (40 mg/kg) significantly increased the activity of SOD, the level of GSH, and the ratio of Bcl-2/Bax, and also reduced the level of MDA, the expression of active caspase-3, and the number of apoptotic cells at 24h after TBI. In summary, these results suggested that osthole had a neuroprotective effect against TBI, and the protection may be associated with its antioxidative and antiapoptotic functions.

Early microstructural and metabolic changes following controlled cortical impact injury in rat: a magnetic resonance imaging and spectroscopy study

Understanding tissue alterations at an early stage following traumatic brain injury (TBI) is critical for injury management and limiting severe consequences from secondary injury. We investigated the early microstructural and metabolic profiles using in vivo diffusion tensor imaging (DTI) and proton magnetic resonance spectroscopy ((1)H MRS) at 2 and 4 h following a controlled cortical impact injury in the rat brain using a 7.0 Tesla animal MRI system and compared profiles to baseline. Significant decrease in mean diffusivity (MD) and increased fractional anisotropy (FA) was found near the impact site (hippocampus and bilateral thalamus; p<0.05) immediately following TBI, suggesting cytotoxic edema. Although the DTI parameters largely normalized on the contralateral side by 4 h, a large inter-individual variation was observed with a trend towards recovery of MD and FA in the ipsilateral hippocampus and a sustained elevation of FA in the ipsilateral thalamus (p<0.05). Significant reduction in metabolite to total creatine ratios of N-acetylaspartate (NAA, p=0.0002), glutamate (p=0.0006), myo-inositol (Ins, p=0.04), phosphocholine and glycerophosphocholine (PCh+GPC, p=0.03), and taurine (Tau, p=0.009) were observed ipsilateral to the injury as early as 2 h, while glutamine concentration increased marginally (p=0.07). These metabolic alterations remained sustained over 4 h after TBI. Significant reductions of Ins (p=0.024) and Tau (p=0.013) and marginal reduction of NAA (p=0.06) were also observed on the contralateral side at 4 h after TBI. Overall our findings suggest significant microstructural and metabolic alterations as early as 2 h following injury. The tendency towards normalization at 4 h from the DTI data and no further metabolic changes at 4 h from MRS suggest an optimal temporal window of about 3 h for interventions that might limit secondary damage to the brain. Results indicate that early assessment of TBI patients using DTI and MRS may provide valuable information on the available treatment window to limit secondary brain damage.

A mouse model of human repetitive mild traumatic brain injury

A novel method for the study of repetitive mild traumatic brain injury (rmTBI) that models the most common form of head injury in humans is presented. Existing animal models of TBI impart focal, severe damage unlike that seen in repeated and mild concussive injuries, and few are configured for repetitive application. Our model is a modification of the Marmarou weight drop method and allows repeated head impacts to lightly anesthetized mice. A key facet of this method is the delivery of an impact to the cranium of an unrestrained subject allowing rapid acceleration of the free-moving head and torso, an essential characteristic known to be important for concussive injury in humans, and a factor that is missing from existing animal models of TBI. Our method does not require scalp incision, emplacement of protective skull helmets or surgery and the procedure can be completed in 1-2 min. Mice spontaneously recover the righting reflex and show no evidence of seizures, paralysis or impaired behavior. Skull fractures and intracranial bleeding are very rare. Minor deficits in motor coordination and locomotor hyperactivity recover over time. Histological analyses reveal mild astrocytic reactivity (increased expression of GFAP) and increased phospho-tau but a lack of blood-brain-barrier disruption, edema and microglial activation. This new animal model is simple and cost-effective and will facilitate characterization of the neurobiological and behavioral consequences of rmTBI. It is also ideal for high throughput screening of potential new therapies for mild concussive injuries as experienced by athletes and military personnel.

Neuroprotective effects of hyperbaric oxygen treatment on traumatic brain injury in the rat

This study was designed to evaluate the potential benefits of hyperbaric oxygen (HBO) in the treatment of traumatic brain injury (TBI). The right cerebral cortex of rats was injured by the impact of a 20-g object dropped from a predetermined height. The rats received HBO treatment at 3 ATA for 60 min after TBI. Neurological behavior score, brain water content, neuronal loss in the hippocampus, and cell apoptosis in brain tissue surrounding the primary injury site were examined to determine brain damage severity. Three and six hours after TBI, HBO-treated rats displayed a significant reduction in brain damage. However, by 12 h after TBI, the efficacy of HBO treatment was considerably attenuated. Furthermore, at 24, 48, and 72 h after TBI, the HBO treatment did not show any notable effects. In contrast, multiple HBO treatments (three or five times in all), even when started 48 h after TBI, remarkably reduced neurology deficit scores and the loss of neuronal numbers in the hippocampus. Although multiple treatments started at 48 h significantly improved neurological behaviors and reduced brain injury, the overall beneficial effects were substantially weaker than those seen after a single treatment at 6 h. These results suggest that: (1) HBO treatment could alleviate brain damage after TBI; (2) a single treatment with HBO has a time limitation of 12 h post-TBI; and (3) multiple HBO treatments have the possibility to extend the post-TBI delivery time window. Therefore, our results clearly suggest the validity of HBO therapy for the treatment of TBI.

The acute inflammatory response in trauma / hemorrhage and traumatic brain injury: current state and emerging prospects

Traumatic injury/hemorrhagic shock (T/HS) elicits an acute inflammatory response that may result in death. Inflammation describes a coordinated series of molecular, cellular, tissue, organ, and systemic responses that drive the pathology of various diseases including T/HS and traumatic brain injury (TBI). Inflammation is a finely tuned, dynamic, highly-regulated process that is not inherently detrimental, but rather required for immune surveillance, optimal post-injury tissue repair, and regeneration. The inflammatory response is driven by cytokines and chemokines and is partially propagated by damaged tissue-derived products (Damage-associated Molecular Patterns; DAMP's). DAMPs perpetuate inflammation through the release of pro-inflammatory cytokines, but may also inhibit anti-inflammatory cytokines. Various animal models of T/HS in mice, rats, pigs, dogs, and non-human primates have been utilized in an attempt to move from bench to bedside. Novel approaches, including those from the field of systems biology, may yield therapeutic breakthroughs in T/HS and TBI in the near future.

The expression of NF-E2-related factor 2 in the rat brain after traumatic brain injury

BACKGROUND

Secondary brain damage plays a critical role in the outcome of patients with traumatic brain injury (TBI). The mechanisms underlying secondary brain damage are complex. A target that can interrupt multiple mechanisms underlying secondary brain damage may represent a promising new therapeutic approach for TBI. NF-E2-related factor 2 (Nrf2) is the key regulator in reducing oxidative stress, inflammatory damage, and the accumulation of toxic metabolites, which are all involved in secondary brain damage after TBI. Therefore, Nrf2 might represent a new direction for the treatment of TBI. However, the expression pattern of Nrf2 after TBI has not yet been studied.

METHODS

This study involved the detection of Nrf2 mRNA levels by reverse-transcriptase polymerase chain reaction, and its nuclear protein levels by Western blot from 3 hour to 72 hour after TBI. Nrf2 distribution in the brain after TBI was also investigated by immunohistochemistry.

RESULTS

After TBI, the nuclear Nrf2 protein level is significantly increased, whereas its mRNA level remains unchanged. Increased Nrf2 immunostaining was detected not only in the vulnerable regions but also in the brain barrier system.

CONCLUSION

Nrf2 might play a protective role in the brain after TBI, possibly by reducing oxidative stress and brain edema.

Quantitative detection of the expression of mitochondrial cytochrome c oxidase subunits mRNA in the cerebral cortex after experimental traumatic brain injury

Secondary brain damage plays a critical role in the outcome of patients with traumatic brain injury (TBI). The multiple mechanisms underlying secondary brain damage, including posttraumatic cerebral ischemia, glutamate excitotoxicity, oxidative stress, calcium overload and inflammation, are associated with increased mortality and morbidity after head injury. TBI is documented to have detrimental effects on mitochondria, such as alterations in glucose utilization and the depression of mitochondrial oxidative phosphorylation. Studies on mitochondrial metabolism have provided evidence for dysfunction of the cytochrome oxidase complex of the electron transport chain (complex IV) after TBI. A growing body of evidence indicates that cytochrome c oxidase is vital for mitochondrial oxidative phosphorylation. Therefore, this study aimed to detect the expression of cytochrome c oxidase (CO) mRNA in a rat weight-dropping trauma model and to clarify the differences between injured cortex (IC) and contralateral cortex (CC) after TBI. A total of forty-four rats were randomly assigned to 7 groups: control groups (n=4), sham-operated group (n=20), 6 h, 1 d, 3 d, 5 d and 7 d postinjury groups (n=4 for each group). The group consisted of sham-operated animals underwent parietal craniotomy without TBI. The rats in postinjury groups were subjected to TBI. The rats of control group were executed immediately without TBI or craniotomy after anesthesia. The brain-injured and sham-operated animals were killed on 6 h, 1 d, 3 d, 5 d and 7 d, respectively. Tissue sections from IC and CC were obtained and the expression of cytochrome c oxidase I, II, and III (CO I, II, III) mRNA, three mitochondrial encoded subunits of complex IV, were assessed by Real-time quantitative PCR. A reduction of CO I, II, and III mRNA expression was detected from IC and reduced to the lowest on 3 d. By contrast, the mRNA expression from CC suggested a slight elevation. The differences may indicate the degree of metabolic and physiologic dysfunction. Our results will better define the roles of gene expression and metabolic function in long-term prognosis and outcome after TBI. With a considerable understanding of post-injury mitochondrial dysfunction, therapeutic interventions targeted to the mitochondria may prevent secondary brain damage that leads to long-term cell death and neurobehavioral disability.

Antibodies to serotonin attenuate closed head injury induced blood brain barrier disruption and brain pathology

Closed head injury (CHI) often results in profound brain swelling and instant death of the victims due to compression of the vital centers. However, the neurochemical basis of edema formation in CHI is still obscure. Previous studies from our laboratory show that blockade of serotonin synthesis prior to CHI in a rat model attenuates brain edema, indicating a prominent role for serotonin in head injury. Thus, neutralization of endogenous serotonin activity and/or blocking of its receptors will induce neuroprotection in CHI. Since serotonin has more than 14 receptors and selective serotonin antagonists are still not available, we used serotonin antiserum to neutralize its in vivo effects before or after CHI in a rat model. CHI was produced by an impact of 0.224 N on the right parietal skull bone under Equithesin anesthesia by dropping a weight of 114.6 g from a height of 20 cm through a guide tube. This concussive brain injury resulted in blood-brain barrier (BBB) disruption, brain edema formation, and volume swelling at 5 h that were most pronounced in the contralateral cerebral hemisphere. The plasma and brain serotonin levels were increased several-fold at this time. Intracerebroventricular administration of serotonin antiserum (1:20, monoclonal) into the left lateral cerebral ventricle (30 microL in PBS) 30 min before or 30 min (but not 60 min) after CHI significantly attenuated BBB disruption, brain edema formation, volume swelling, and brain pathology. The plasma and brain serotonin levels continued to remain high. These observations are the first to suggest that antiserum to serotonin when administered into the CSF during the early phase of CHI are capable of inducing neuroprotection.

Activation of Nrf2-ARE pathway in brain after traumatic brain injury

Secondary brain injury plays a pivotal role in the outcome of patients suffering from traumatic brain injury (TBI). The mechanisms underlying secondary brain injury are complex and interrelated. Previous studies focused on one of these mechanisms have been proved to be ineffective in clinical practice. Therefore, a target, which can interrupt multi-mechanisms underlying TBI, is desirable. Nrf2-ARE pathway has been proved to be the key regulator in reducing oxidative stress, inflammatory damage and accumulation of toxic metabolites, which are all involved in TBI. However, whether Nrf2-ARE pathway is activated after TBI has not been studied. In the present study, the nuclear Nrf2 protein level was detected by Western blot, and the mRNA levels of heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase-1 (NQO1), two Nrf2-regulated gene products, were determined using reverse-transcriptase polymerase chain reaction (RT-PCR) 24h after TBI. Furthermore, we also localized the expression of Nrf2 and HO-1 using immunohistochemical study. After TBI, the nuclear Nrf2 protein level was significantly increased, and the mRNA levels of both HO-1 and NQO1 were also up regulated. Moreover, both Nrf2 and HO-1 were localized in the same types of cells. According to these results, it could be postulated that Nrf2-ARE pathway was activated in brain after TBI.

CNS injury research; reviewing the last decade: methodological errors and a proposal for a new strategy

During the last decades the field of Traumatic Brain Injury (TBI) has been characterized by a paucity of new treatments. This is in contrast to the amount of pre-clinical experimental work and the number of clinical trials done. This paper aims to contribute to the ongoing debate on the reasons that have led to this phenomenon. A reasonable suggestion could be the presence of methodological limitations when comparing and integrating experimental results. The first methodological drawback, which is shortly discussed, is the insistence (during the last decades) on the concept of "similarity to the human pathology" as the main criterion to evaluate results, and the constant effort to create a "super model" that would fully replicate human TBI cases. The second methodological limitation examined is the lack of a common way to present and analyze data. It is proposed that the basic neuro-histo-pathology of each injury model should serve as the ground on which hypotheses should be built, as it could constitute the common basis for comparisons between different experimental settings. In this context, 95 papers reporting experimental results from various models of animal CNS injury were reviewed in order to examine the extent to which results were presented and analyzed using a common basis. No such common basis was observed; moreover, the review revealed a remarkable lack of histopathological examination of the animals, especially when biochemical and/or behavioral endpoints were assessed. It is argued that this practice deprives data of an objective common basis. Conclusively, a new theoretical way of organizing experimental work in the field of TBI is briefly presented.

Technical pitfalls in a porcine brain retraction model

We describe technical pitfalls of a porcine brain injury model for identifying primary and secondary pathological sequelae following brain retraction by brain spatula. In 16 anaesthetised male pigs, the right frontal brain was retracted in the interhemispheric fissure by a brain spatulum with varying pressures applied by the gravitational force of weights from 10 to 70 g for a duration of 30 min. The retracted brain tissue was monitored for changes in intracranial pressure and perfusion of the cortex using a Laser Doppler Perfusion Imager (MoorLDI). To evaluate the extent of oedema and cortical contusions, MRI was performed 30 min and 72 h after brain retraction. Following the MR scan, the retracted brain areas were histopathologically assessed using H&E and Fluoro-Jade B staining for neuronal damage. Sinus occlusion occurred in four animals, resulting in bilateral cortical contusions and extensive brain oedema. Retracting the brain with weights of 70 g (n = 4) caused extensive oedema on FLAIR images that correlated clinically with a hemiparesis in three animals. Morphologically, an increased number of Fluoro-Jade B-positive neurons were found. A sequential decrease in weights prevented functional deficits in animals. A retraction pressure applied by 10-g weights (n = 7) caused a mean rise in intracranial pressure to 4.0 +/- 3.1 mm Hg, and a decrement in mean cortical perfusion from 740.8 +/- 41.5 to 693.8 +/- 72.4 PU/cm2 (P < 0.24). A meticulous dissection of the interhemispheric fissure and a reduction of weights to 10 g were found to be mandatory to study the cortical impact caused by brain spatula reproducibly.

Traumatic brain injury

Animal models have played a critical role in elucidating the complex pathogenesis of traumatic brain injury, the major cause of death and disability in young adults in Western countries. This review discusses how different types of animal models are useful for the study of neuropathologic processes in traumatic, blunt, nonmissile head injury.

Cortical devascularization: quantitative diffusion weighted magnetic resonance imaging and histological findings

This study investigates the development of a small focal cortical lesion produced in a model of brain injury. Two approaches were chosen: diffusion weighted magnetic resonance imaging (DWI) and histology. DW images were collected before devascularization and at 0.5, 1, 2, 3, 5, 7 and 14 days after treatment. Apparent diffusion coefficient (ADC) maps were calculated from the DW images to quantify lesion development. As a second measure of injury, tissue morphology was analyzed using cresyl violet histochemistry. A significant reduction in ADC values within the cortex below the injury site by 0.5 days after surgery was observed. Between 5 and 14 days the ADC values recovered to control levels. ADC changes were also observed in the contralateral cortex at 0.5, 1 and 5 days. The decrease in ADC observed at the early time points suggested cytotoxic edema, whereas the recovery to control levels at later time points suggested infarct formation. This model of brain injury resulted in progressive but relatively slow formation of a pan-necrotic infarct within 14 days. In particular, substantial amounts of cell death were not observed until 2 days after surgery. Overall, the quantitative and histological measures of this lesion are consistent with those observed for an ischemic type of injury, however, the time course of these lesions' development are consistent with other models of traumatic brain injury. Our data demonstrates that DWI is a highly sensitive metric for ischemic-type damage that results from brain injury.