Penetrating ballistic-like brain injury in the rat: differential time courses of hemorrhage, cell death, inflammation, and remote degeneration

Intravenous administration of anti-CD47 antibody augments hematoma clearance, mitigates acute neuropathology, and improves cognitive function in a rat model of penetrating traumatic brain injury

Traumatic brain injury (TBI)-induced intracerebral hematoma is a major driver of secondary injury pathology such as neuroinflammation, cerebral edema, neurotoxicity and blood brain barrier (BBB) dysfunction, which contribute to neuronal loss, motor deficits and cognitive impairment. Cluster of differentiation 47 (CD47) is an anti-phagocytic cell surface protein inhibiting hematoma clearance. This study was designed to evaluate the safety and efficacy of blockade of CD47 via intravenous administration of anti-CD47 antibodies in the presence of traumatic intracerebral hemorrhage (tICH). The PK profile of anti-CD47 antibody elicited that antibody concentration decayed over 7 days post-administration. Blood tests and necropsy analysis indicated no severe adverse events following treatment. Cerebral hemoglobin levels were significantly increased after injury, however, anti-CD47 antibody administration at 0.1 mg/kg resulted in a significant reduction in cerebral hemoglobin levels at 72 hours post-administration, indicating augmentation of hematoma clearance. Immunohistochemistry assessment of GFAP and IBA1 demonstrated a significant reduction of GFAP levels in the lesion core and peri-lesional area. Based on these analyses, the optimal dose was identified as 0.1 mg/kg. Lesion volume showed a reduction following treatment. Rotarod testing revealed significant motor deficits in all injured groups but no significant therapeutic benefits. Spatial learning performance revealed significant deficits in all injured groups which was significantly improved by the last testing day. Anti-CD47 antibody treated rats showed significantly improved attention deficits, but not retention scores. These results provide preliminary evidence that blockade of CD47 using intravenous administration of anit-CD47 antibodies may serve as a potential therapeutic for TBI with intracerebral hemorrhage. Keywords: Hematoma clearance, cognitive function, penetrating traumatic brain injury, intracerebral hematoma, anti-CD47 antibodies .

An overview of preclinical models of traumatic brain injury (TBI): relevance to pathophysiological mechanisms

Background

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, affecting millions annually worldwide. Although the majority of TBI patients return to premorbid baseline, a subset of patient can develop persistent and often debilitating neurocognitive and behavioral changes. The etiology of TBI within the clinical setting is inherently heterogenous, ranging from sport related injuries, fall related injuries and motor vehicle accidents in the civilian setting, to blast injuries in the military setting.

Objective

Animal models of TBI, offer the distinct advantage of controlling for injury modality, duration and severity. Furthermore, preclinical models of TBI have provided the necessary temporal opportunity to study the chronic neuropathological sequelae of TBI, including neurodegenerative sequelae such as tauopathy and neuroinflammation within the finite experimental timeline. Despite the high prevalence of TBI, there are currently no disease modifying regimen for TBI, and the current clinical treatments remain largely symptom based. The preclinical models have provided the necessary biological substrate to examine the disease modifying effect of various pharmacological agents and have imperative translational value.

Methods

The current review will include a comprehensive survey of well-established preclinical models, including classic preclinical models including weight drop, blast injury, fluid percussion injury, controlled cortical impact injury, as well as more novel injury models including closed-head impact model of engineered rotational acceleration (CHIMERA) models and closed-head projectile concussive impact model (PCI). In addition to rodent preclinical models, the review will include an overview of other species including large animal models and Drosophila.

Results

There are major neuropathological perturbations post TBI captured in various preclinical models, which include neuroinflammation, calcium dysregulation, tauopathy, mitochondrial dysfunction and oxidative stress, axonopathy, as well as glymphatic system disruption.

Conclusion

The preclinical models of TBI continue to offer valuable translational insight, as well as essential neurobiological basis to examine specific disease modifying therapeutic regimen.

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.

Weight-Drop Method for Inducing Closed Head Diffuse Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the foremost causes of disability and death globally. Prerequisites for successful therapy of disabilities associated with TBI involved improved knowledge of the neurobiology of TBI, measurement of quantitative changes in recovery dynamics brought about by therapy, and the translation of quantitative methodologies and techniques that were successful in tracking recovery in preclinical models to human TBI. Frequently used animal models of TBI in research and development include controlled cortical impact, fluid percussion injury, blast injury, penetrating blast brain injury, and weight-drop impact acceleration models. Preclinical models of TBI benefit from controlled injury settings and the best prospects for biometric quantification of injury and therapy-induced gradual recovery from disabilities. Impact acceleration closed head TBI paradigm causes diffuse TBI (DTBI) without substantial focal brain lesions in rats. DTBI is linked to a significant rate of death, morbidity, and long-term disability. DTBI is difficult to diagnose at the time of hospitalization with imaging techniques making it challenging to take prompt therapeutic action. The weight-drop method without craniotomy is an impact acceleration closed head DTBI model that is used to induce mild/moderate diffuse brain injuries in rodents. Additionally, we have characterized neuropathological and neurobehavioral outcomes of the weight-drop model without craniotomy for inducing closed head DTBI of graded severity with a range of mass of weights (50-450 gm). This chapter also discusses techniques and protocols for measuring numerous functional disabilities and pathological changes in the brain brought on by DTBI.

Recovery of neurosurgical high-frequency electroporation injury in the canine brain can be accelerated by 7,8-dihydroxyflavone

BACKGROUND

Although traumatic brain injury (TBI) occurs in a very short time, the biological consequence of a TBI, such as Alzheimer's disease, may last a lifetime. To date, effective interventions are not available to improve recovery from a TBI. Herein we aimed to ascertain whether recovery of neurosurgical high-frequency irreversible electroporation (HFIRE) injury in brain tissues can be accelerated by 7,8-dihydroxyflavone (7,8-DHF).

METHODS

The HFIRE injury was induced in the right parietal cortex of 8 adult healthy and neurologically intact male dogs. Two weeks before HFIRE injury, each dog was administered orally with or without 7,8-DHF (30 mg/kg) once daily for consecutive 2 weeks (n = 4 for each group). The values of blood-brain barrier (BBB) disruption, brain edema, and cerebral infarction volumes were measured. The concentrations of beta-amyloid, interleukin-1β, interleukin-6 and tumor necrosis factor-α in the cerebrospinal fluid were measured biochemically.

RESULTS

The BBB disruption, brain edema, infarction volumes, and maximal cross-section area caused by HFIRE injury in canine brain were significantly attenuated by 7,8-DHF therapy (P < 0.0001). Additionally, 7,8-DHF significantly reduced the HFIRE-induced cerebral overproduction of beta-amyloid and proinflammatory cytokines in the cerebrospinal fluid (P < 0.0001) in dogs with HFIRE.

CONCLUSIONS

Recovery of neurosurgical HFIRE injury in canine brain tissues can be accelerated by 7,8-DHT via ameliorating BBB disruption as well as cerebral overproduction of both beta-amyloid and proinflammatory cytokines.

Comprehensive evaluation of mitochondrial redox profile, calcium dynamics, membrane integrity and apoptosis markers in a preclinical model of severe penetrating traumatic brain injury

Traumatic Brain Injury (TBI) is caused by the external physical assaults damages the brain. It is a heterogeneous disorder that remains a leading cause of death and disability in the military and civilian population of the United States. Preclinical investigations of mitochondrial responses in TBI have ascertained that mitochondrial dysfunction is an acute indicator of cellular damage and plays a pivotal role in long-term injury progression through cellular excitotoxicity. The current study was designed to provide an in-depth evaluation of mitochondrial endpoints with respect to redox and calcium homeostasis, and cell death responses following penetrating TBI (PTBI). To evaluate these pathological cascades, anesthetized adult male rats (N = 6/group) were subjected to either 10% unilateral PTBI or Sham craniectomy. Animals were euthanized at 24 h post-PTBI, and purified mitochondrial fractions were isolated from the brain injury core and perilesional areas. Overall, increased reactive oxygen and nitrogen species (ROS/RNS) production, and elevated oxidative stress markers such as 4-hydroxynonenal (4-HNE), 3-nitrotyrosine (3-NT), and protein carbonyls (PC) were observed in the PTBI group compared to Sham. Mitochondrial antioxidants such as glutathione, peroxiredoxin (PRX-3), thioredoxin (TRX), nicotinamide adenine dinucleotide phosphate (NADPH), superoxide dismutase (SOD), and catalase (CAT) levels were significantly decreased after PTBI. Likewise, PTBI mitochondria displayed significant loss of Ca²⁺ homeostasis, early opening of mitochondrial permeability transition pore (mPTP), and increased mitochondrial swelling. Both, outer and inner mitochondrial membrane integrity markers, such as voltage-dependent anion channels (VDAC) and cytochrome c (Cyt C) expression were significantly decreased following PTBI. The apoptotic cell death was evidenced by significantly decreased B-cell lymphoma-2 (Bcl-2) and increased glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression after PTBI. Collectively, current results highlight the comprehensive picture of mitochondria-centric acute pathophysiological responses following PTBI, which may be utilized as novel prognostic indicators of disease progression and theragnostic indicators for evaluating neuroprotection therapeutics following TBI.

What Happens in TBI? A Wide Talk on Animal Models and Future Perspective

Traumatic brain injury (TBI) is a global healthcare concern and a leading cause of death. The most common causes of TBI include road accidents, sports injuries, violence in warzones, and falls. TBI induces neuronal cell death independent of age, gender, and genetic background. TBI survivor patients often experience long-term behavioral changes like cognitive and emotional changes. TBI affects social activity, reducing the quality and duration of life. Over the last 40 years, several rodent models have been developed to mimic different clinical outcomes of human TBI for a better understanding of pathophysiology and to check the efficacy of drugs used for TBI. However, promising neuroprotective approaches that have been used preclinically have been found to be less beneficial in clinical trials. So, there is an urgent need to find a suitable animal model for establishing a new therapeutic intervention useful for TBI. In this review, we have demonstrated the etiology of TBI and post- TBI social life alteration, and also discussed various preclinical TBI models of rodents, zebrafish, and drosophila.

The benefits of exercise for outcome improvement following traumatic brain injury: Evidence, pitfalls and future perspectives

Traumatic brain injury (TBI), also known as a silent epidemic, is currently a substantial public health problem worldwide. Given the increased energy demands following brain injury, relevant guidelines tend to recommend absolute physical and cognitive rest for patients post-TBI. Nevertheless, recent evidence suggests that strict rest does not provide additional benefits to patients' recovery. By contrast, as a cost-effective non-pharmacological therapy, exercise has shown promise for enhancing functional outcomes after injury. This article summarizes the most recent evidence supporting the beneficial effects of exercise on TBI outcomes, focusing on the efficacy of exercise for cognitive recovery after injury and its potential mechanisms. Available evidence demonstrates the potential of exercise in improving cognitive impairment, mood disorders, and post-concussion syndrome following TBI. However, the clinical application for exercise rehabilitation in TBI remains challenging, particularly due to the inadequacy of the existing clinical evaluation system. Also, a better understanding of the underlying mechanisms whereby exercise promotes its most beneficial effects post-TBI will aid in the development of new clinical strategies to best benefit of these patients.

The Nanotheranostic Researcher’s Guide for Use of Animal Models of Traumatic Brain Injury

Traumatic brain injury (TBI) is currently the leading cause of injury-related morbidity and mortality worldwide, with an estimated global cost of USD 400 billion annually. Both clinical and preclinical behavioral outcomes associated with TBI are heterogeneous in nature and influenced by the mechanism and frequency of injury. Previous literature has investigated this relationship through the development of animal models and behavioral tasks. However, recent advancements in these methods may provide insight into the translation of therapeutics into a clinical setting. In this review, we characterize various animal models and behavioral tasks to provide guidelines for evaluating the therapeutic efficacy of treatment options in TBI. We provide a brief review into the systems utilized in TBI classification and provide comparisons to the animal models that have been developed. In addition, we discuss the role of behavioral tasks in evaluating outcomes associated with TBI. Our goal is to provide those in the nanotheranostic field a guide for selecting an adequate TBI animal model and behavioral task for assessment of outcomes to increase research in this field.

Penetrating Ballistic Brain Injury Produces Acute Alterations in Sleep and Circadian-Related Genes in the Rodent Cortex: A Preliminary Study

Traumatic brain injury (TBI) affects millions of Americans each year, with extremely high prevalence in the Veteran community, and sleep disturbance is one of the most commonly reported symptoms. Reduction in the quality and amount of sleep can negatively impact recovery and result in a wide range of behavioral and physiological symptoms, such as impaired cognition, mood and anxiety disorders, and cardiovascular effects. Thus, to improve long-term patient outcomes and develop novel treatments, it is essential to understand the molecular mechanisms involved in sleep disturbance following TBI. In this effort, we performed transcriptional profiling in an established rodent model of penetrating ballistic brain injury (PBBI) in conjunction with continuous sleep/wake EEG/EMG recording of the first 24 h after injury. Rats subjected to PBBI showed profound differences in sleep architecture. Injured animals spent significantly more time in slow wave sleep and less time in REM sleep compared to sham control animals. To identify PBBI-related transcriptional differences, we then performed transcriptome-wide gene expression profiling at 24 h post-injury, which identified a vast array of immune- related genes differentially expressed in the injured cortex as well as sleep-related genes. Further, transcriptional changes associated with total time spent in various sleep stages were identified. Such molecular changes may underlie the pathology and symptoms that emerge following TBI, including neurodegeneration, sleep disturbance, and mood disorders.

Prehospital Whole Blood Resuscitation Reduces Fluid Requirement While Maintaining Critical Physiology in a Model of Penetrating Traumatic Brain Injury and Hemorrhage: Implications on Resource-Limited Combat Casualty Care

ABSTRACT

Prehospital resuscitation using whole blood (WB) is the standard of care for hemorrhagic shock (HS) but there is no consensus recommendation for resuscitation in the presence of traumatic brain injury (TBI) due to a lack of sufficient evidence. In order to evaluate the optimal resuscitation strategies for TBI+HS, Sprague-Dawley rats were randomized into four groups based on resuscitation fluid and prehospital mean arterial pressure (MAP) threshold (n = 9-10/group): Lactated Ringer's (LR)-60 mm Hg (LR60), LR-70 mm Hg (LR70), WB-60 mm Hg (WB60), WB-70 mm Hg (WB70). All groups received a frontal penetrating ballistic-like brain injury followed by a 35-min period of HS. During the prehospital phase, rats received an initial bolus of resuscitation fluid (WB or LR) followed by LR as needed to maintain MAP above the designated threshold for 90 min. During the in-hospital phase, rats received definitive resuscitation with shed WB. Physiological parameters were recorded continuously and cerebral edema was measured at 3 and 24 h postinjury. The WB60 group demonstrated a significantly lower prehospital fluid requirement compared WB70, LR60, and LR70 (P < 0.05). Compared to the respective LR groups, both the WB60 and WB70 groups also demonstrated improved MAP, cerebral perfusion pressure, brain tissue oxygen tension, and cerebral edema. The edema benefits were observed at 3 h, but not 24 h postinjury, and were localized to the injury site. Together, these results provide evidence that prehospital WB resuscitation and lower MAP resuscitation thresholds can reduce the prehospital fluid requirement while still maintaining critical cerebral physiology in a model of HS and concomitant TBI.

Biological links between traumatic brain injury and Parkinson's disease

Parkinson's Disease (PD) is a progressive neurodegenerative disorder with no cure. Clinical presentation is characterized by postural instability, resting tremors, and gait problems that result from progressive loss of A9 dopaminergic neurons in the substantia nigra pars compacta. Traumatic brain injury (TBI) has been implicated as a risk factor for several neurodegenerative diseases, but the strongest evidence is linked to development of PD. Mild TBI (mTBI), is the most common and is defined by minimal, if any, loss of consciousness and the absence of significant observable damage to the brain tissue. mTBI is responsible for a 56% higher risk of developing PD in U.S. Veterans and the risk increases with severity of injury. While the mounting evidence from human studies suggests a link between TBI and PD, fundamental questions as to whether TBI nucleates PD pathology or accelerates PD pathology in vulnerable populations remains unanswered. Several promising lines of research point to inflammation, metabolic dysregulation, and protein accumulation as potential mechanisms through which TBI can initiate or accelerate PD. Amyloid precursor protein (APP), alpha synuclein (α-syn), hyper-phosphorylated Tau, and TAR DNA-binding protein 43 (TDP-43), are some of the most frequently reported proteins upregulated following a TBI and are also closely linked to PD. Recently, upregulation of Leucine Rich Repeat Kinase 2 (LRRK2), has been found in the brain of mice following a TBI. Subset of Rab proteins were identified as biological substrates of LRRK2, a protein also extensively linked to late onset PD. Inhibition of LRRK2 was found to be neuroprotective in PD and TBI models. The goal of this review is to survey current literature concerning the mechanistic overlap between TBI and PD with a particular focus on inflammation, metabolic dysregulation, and aforementioned proteins. This review will also cover the application of rodent TBI models to further our understanding of the relationship between TBI and PD.

Penetrating Traumatic Brain Injury Triggers Dysregulation of Cathepsin B Protein Levels Independent of Cysteine Protease Activity in Brain and Cerebral Spinal Fluid

Cathepsin B (CatB), a lysosomal cysteine protease, is important to brain function and may have dual utility as a peripheral biomarker of moderate-severe traumatic brain injury (TBI). The present study determined levels of pro- and mature (mat) CatB protein as well as cysteine protease activity within the frontal cortex (FC; proximal injury site), hippocampus (HC; distal injury site), and cerebral spinal fluid (CSF) collected 1-7 days after craniotomy and penetrating ballistic-like brain injury (PBBI) in rats. Values were compared with naïve controls. Further, the utility of CatB protein as a translational biomarker was determined in CSF derived from patients with severe TBI. Craniotomy increased matCatB levels in the FC and HC, and led to elevation of HC activity at day 7. PBBI caused an even greater elevation in matCatB within the FC and HC within 3-7 days. After PBBI, cysteine protease activity peaked at 3 days in the FC and was elevated at 1 day and 7 days, but not 3 days, in the HC. In rat CSF, proCatB, matCatB, and cysteine protease activity peaked at 3 days after craniotomy and PBBI. Addition of CA-074, a CatB-specific inhibitor, confirmed that protease activity was due to active matCatB in rat brain tissues and CSF at all time-points. In patients, CatB protein was detectable from 6 h through 10 days after TBI. Notably, CatB levels were significantly higher in CSF collected within 3 days after TBI compared with non-TBI controls. Collectively, this work indicates that CatB and its cysteine protease activity may serve as collective molecular signatures of TBI progression that differentially vary within both proximal and distal brain regions. CatB and its protease activity may have utility as a surrogate, translational biomarker of acute-subacute TBI.

The Effects of Balloon Occlusion of the Aorta on Cerebral Blood Flow, Intracranial Pressure, and Brain Tissue Oxygen Tension in a Rodent Model of Penetrating Ballistic-Like Brain Injury

Trauma is among the leading causes of death in the United States. Technological advancements have led to the development of resuscitative endovascular balloon occlusion of the aorta (REBOA) which offers a pre-hospital option to non-compressible hemorrhage control. Due to the prevalence of concomitant traumatic brain injury (TBI), an understanding of the effects of REBOA on cerebral physiology is critical. To further this understanding, we employed a rat model of penetrating ballistic-like brain injury (PBBI). PBBI produced an injury pattern within the right frontal cortex and striatum that replicates the pathology from a penetrating ballistic round. Aortic occlusion was initiated 30 min post-PBBI and maintained continuously (cAO) or intermittently (iAO) for 30 min. Continuous measurements of mean arterial pressure (MAP), intracranial pressure (ICP), cerebral blood flow (CBF), and brain tissue oxygen tension (PbtO₂) were recorded during, and for 60 min following occlusion. PBBI increased ICP and decreased CBF and PbtO₂. The arterial balloon catheter effectively occluded the descending aorta which augmented MAP in the carotid artery. Despite this, CBF levels were not changed by aortic occlusion. iAO caused sustained adverse effects to ICP and PbtO₂ while cAO demonstrated no adverse effects on either. Temporary increases in PbtO₂ were observed during occlusion, along with restoration of sham levels of ICP for the remainder of the recordings. These results suggest that iAO may lead to prolonged cerebral hypertension following PBBI. Following cAO, ICP, and PbtO₂ levels were temporarily improved. This information warrants further investigation using TBI-polytrauma model and provides foundational knowledge surrounding the non-hemorrhage applications of REBOA including neurogenic shock and stroke.

Brain tissue saving effects by single-dose intralesional administration of Neuroprotectin D1 on experimental focal penetrating brain injury in rats

Traumatic brain injury (TBI) is followed by a secondary inflammation in the brain. Neuroprotectin D1 (NPD1) is synthesized from docosahexaenoic acid (DHA) and has anti-inflammatory and antiapoptotic effects in experimental models of neurodegenerative disease and brain ischemia-reperfusion. It is not known whether intralesional administration of NPD1 ameliorates inflammation and cell death after severe TBI. We therefore investigated the effects of NPD1 following a severe form of focal penetrating TBI. A total of 30 male Sprague-Dawley rats weighing between 350 and 450 g were exposed to focal penetrating TBI or sham surgery. The rats were randomized to NPD1 treatment (50 ng intralesionally, immediately following TBI) or no treatment. The rats were sacrificed at 24 or 72 h. All subgroups consisted of 5 rats. Brains were removed, fresh frozen, cut in 14-µm coronal sections and subjected to Fluoro-Jade, TUNEL, MnSOD, 3-NT, COX-2, Ox-42 and NF-κB immuno-staining and lesion size analyses. NPD1 decreased the lesion area at 72 h compared to no treatment with a mean change 42% (NPD1 14.1 mm²; no treatment 24.5 mm²) (p < 0.01). No difference was detected in markers for neuronal degeneration, apoptosis, anti-inflammatory or antioxidative enzymes, or immune cells. In conclusion, single-dose intralesional administration of NPD1 had brain tissue sparing effects after focal penetrating TBI, which may be beneficial in preventing brain tissue damage, making NPD1 a potential candidate for further clinical applications. Exact mechanisms of action could not be determined and it is possible that continuous or multiple administration regimens may increase efficacy in sequential preclinical studies.

Differential Effects of Caffeine on Motor and Cognitive Outcomes of Penetrating Ballistic-Like Brain Injury

This study assessed the effect of caffeine on neurobehavioral recovery in the WRAIR penetrating ballistic-like brain injury (PBBI) model. Unilateral frontal PBBI was produced in the right hemisphere of anesthetized rats at moderate (7%-PBBI) or severe (10%-PBBI) injury levels. Animals were randomly assigned to pretreatment groups: acute caffeine (25 mg/kg CAF gavage, 1 h prior to PBBI), or chronic caffeine (0.25 g/L CAF drinking water, 30 days prior to PBBI). Motor function was evaluated on the rotarod at fixed-speed increments of 10, 15, and 20 RPM. Cognitive performance was evaluated on the Morris water maze. Acute caffeine showed no significant treatment effect on motor or cognitive outcome. Acute caffeine exposure prior to 10%-PBBI resulted in a significantly higher thigmotaxic response compared to vehicle-PBBI groups, which may indicate caffeine exacerbates post-injury anxiety/attention decrements. Results of the chronic caffeine study revealed a significant improvement in motor outcome at 7 and 10 days post-injury in the 7%-PBBI group. However, chronic caffeine exposure significantly increased the latency to locate the platform in the Morris water maze task at all injury levels. Results indicate that chronic caffeine consumption prior to a penetrating TBI may provide moderate beneficial effects to motor recovery, but may worsen the neurocognitive outcome.

The role of microglial inflammasome activation in pyroptotic cell death following penetrating traumatic brain injury

BACKGROUND

Traumatic brain injury remains a significant cause of death and disability in the USA. Currently, there are no effective therapies to mitigate disability except for surgical interventions necessitating a need for continued research into uncovering novel therapeutic targets. In a recent study, we used a rodent model of penetrating traumatic brain injury known as penetrating ballistic-like brain injury (PBBI) to examine the role of innate immunity in post-traumatic secondary injury mechanisms. We previously reported that the inflammasome, a multiprotein complex composed of apoptosis-associated speck-like protein containing card and caspase-1, plays a role in secondary cell death mechanisms after PBBI, including inflammatory cell death (pyroptosis).

METHODS

In the current study, we used flow cytometry analysis to evaluate activated microglia and CD11b-positive leukocytes after PBBI and assessed inflammasome activation and pyroptosis of specific cellular populations. Sprague-Dawley male rats underwent PBBI or sham-operated procedures and ipsilateral cortical regions processed for flow cytometry and cellular analysis. Flow cytometry results were compared using one-way ANOVA followed by Tukey's multiple comparisons.

RESULTS

At 48 h following PBBI, there was an increase in activated microglia and infiltrating leukocytes compared to sham controls that were associated with increased caspase-1 activity. Using a florescent probe to identify caspase-1 activity and a fluorescent assay to determine cell viability, evidence for pyroptosis in CD11b+ cells was also determined. Finally, while post-traumatic treatment with an anti-ASC antibody had no effect on the number of activated microglia and infiltrating leukocytes, antibody treatment decreased caspase-1 activity in both resident microglia and infiltrating leukocytes and reduced pyroptotic CD11b+ cell death.

CONCLUSIONS

These results provide evidence for inflammasome activation in microglia and infiltrating leukocytes after penetrating traumatic brain injury and a role for pyroptotic cell death in the pathophysiology. In addition to inhibiting neuronal cell death, therapeutic treatments targeting inflammasome activation may also provide beneficial effects by reducing the potentially detrimental consequences of activated microglia and infiltrating CD11b+ leukocytes following penetrating traumatic brain injury.

Microglial Inflammasome Activation in Penetrating Ballistic-Like Brain Injury

Penetrating traumatic brain injury (PTBI) is a significant cause of death and disability in the United States. Inflammasomes are one of the key regulators of the interleukin (IL)-1β mediated inflammatory responses after traumatic brain injury. However, the contribution of inflammasome signaling after PTBI has not been determined. In this study, adult male Sprague-Dawley rats were subjected to sham procedures or penetrating ballistic-like brain injury (PBBI) and sacrificed at various time-points. Tissues were assessed by immunoblot analysis for expression of IL-1β, IL-18, and components of the inflammasome: apoptosis-associated speck-like protein containing a caspase-activation and recruitment domain (ASC), caspase-1, X-linked inhibitor of apoptosis protein (XIAP), nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3), and gasdermin-D (GSDMD). Specific cell types expressing inflammasome proteins also were evaluated immunohistochemically and assessed quantitatively. After PBBI, expression of IL-1β, IL-18, caspase-1, ASC, XIAP, and NLRP3 peaked around 48 h. Brain protein lysates from PTBI animals showed pyroptosome formation evidenced by ASC laddering, and also contained increased expression of GSDMD at 48 h after injury. ASC-positive immunoreactive neurons within the perilesional cortex were observed at 24 h. At 48 h, ASC expression was concentrated in morphologically activated cortical microglia. This expression of ASC in activated microglia persisted until 12 weeks following PBBI. This is the first report of inflammasome activation after PBBI. Our results demonstrate cell-specific patterns of inflammasome activation and pyroptosis predominantly in microglia, suggesting a sustained pro-inflammatory state following PBBI, thus offering a therapeutic target for this type of brain injury.

Cerebrospinal Fluid Biomarkers Are Associated With Glial Fibrillary Acidic Protein and αII-spectrin Breakdown Products in Brain Tissues Following Penetrating Ballistic-Like Brain Injury in Rats

Treatments to improve outcomes following severe traumatic brain injury (TBI) are limited but may benefit from understanding subacute-chronic brain protein profiles and identifying biomarkers suitable for use in this time. Acute alterations in the well-known TBI biomarkers glial fibrillary acidic protein (GFAP), αII-spectrin, and their breakdown products (BDPs) have been well established, but little is known about the subacute-chronic post-injury profiles of these biomarkers. Thus, the current study was designed to determine the extended profile of these TBI-specific biomarkers both in brain tissue and cerebral spinal fluid (CSF). Protein abundance was evaluated in brain tissue samples taken from regions of interest and in CSF at 24 h, 3 days, 7 days, 1 month, and 3 months following severe TBI in rats. Results showed increased full length GFAP (GFAP-FL) and GFAP-BDPs starting at 24 h that remained significantly elevated in most brain regions out to 3 months post-injury. However, in CSF, neither GFAP-FL nor GFAP-BDPs were elevated as a consequence of injury. Regional-specific reduction in αII-spectrin was evident in brain tissue samples from 24 h through 3 months. In contrast, SBDP-145/150 was robustly elevated in most brain regions and in CSF from 24 h through 7 days. Correlation analyses revealed numerous significant relationships between proteins in CSF and brain tissue or neurological deficits. This work indicates that TBI results in chronic changes in brain protein levels of well-known TBI biomarkers GFAP, αII-spectrin, and their BDPs and that SBDP-145/150 may have utility as an acute-chronic biomarker.

The Inflammatory Continuum of Traumatic Brain Injury and Alzheimer's Disease

The post-injury inflammatory response is a key mediator in long-term recovery from traumatic brain injury (TBI). Moreover, the immune response to TBI, mediated by microglia and macrophages, is influenced by existing brain pathology and by secondary immune challenges. For example, recent evidence shows that the presence of beta-amyloid and phosphorylated tau protein, two hallmark features of AD that increase during normal aging, substantially alter the macrophage response to TBI. Additional data demonstrate that post-injury microglia are “primed” and become hyper-reactive following a subsequent acute immune challenge thereby worsening recovery. These alterations may increase the incidence of neuropsychiatric complications after TBI and may also increase the frequency of neurodegenerative pathology. Therefore, the purpose of this review is to summarize experimental studies examining the relationship between TBI and development of AD-like pathology with an emphasis on the acute and chronic microglial and macrophage response following injury. Furthermore, studies will be highlighted that examine the degree to which beta-amyloid and tau accumulation as well as pre- and post-injury immune stressors influence outcome after TBI. Collectively, the studies described in this review suggest that the brain’s immune response to injury is a key mediator in recovery, and if compromised by previous, coincident, or subsequent immune stressors, post-injury pathology and behavioral recovery will be altered.

Traumatic brain injury: classification, models, and markers

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. Due to its high incidence rate and often long-term sequelae, TBI contributes significantly to increasing costs of health care expenditures annually. Unfortunately, advances in the field have been stifled by patient and injury heterogeneity that pose a major challenge in TBI prevention, diagnosis, and treatment. In this review, we briefly discuss the causes of TBI, followed by its prevalence, classification, and pathophysiology. The current imaging detection methods and animal models used to study brain injury are examined. We discuss the potential use of molecular markers in detecting and monitoring the progression of TBI, with particular emphasis on microRNAs as a novel class of molecular modulators of injury and its repair in the neural tissue.

Epileptogenesis following experimentally induced traumatic brain injury - a systematic review

Traumatic brain injury (TBI) is a complex neurotrauma in civilian life and the battlefield with a broad spectrum of symptoms, long-term neuropsychological disability, as well as mortality worldwide. Posttraumatic epilepsy (PTE) is a common outcome of TBI with unknown mechanisms, followed by posttraumatic epileptogenesis. There are numerous rodent models of TBI available with varying pathomechanisms of head injury similar to human TBI, but there is no evidence for an adequate TBI model that can properly mimic all aspects of clinical TBI and the first successive spontaneous focal seizures follow a single episode of neurotrauma with respect to epileptogenesis. This review aims to provide current information regarding the various experimental animal models of TBI relevant to clinical TBI. Mossy fiber sprouting, loss of dentate hilar neurons along with recurrent seizures, and epileptic discharge similar to human PTE have been studied in fluid percussion injury, weight-drop injury, and cortical impact models, but further refinement of animal models and functional test is warranted to better understand the underlying pathophysiology of posttraumatic epileptogenesis. A multifaceted research approach in TBI model may lead to exploration of the potential treatment measures, which are a major challenge to the research community and drug developers. With respect to clinical setting, proper patient data collection, improved clinical trials with advancement in drug delivery strategies, blood-brain barrier permeability, and proper monitoring of level and effects of target drug are also important.

Cranial trauma in handgun executions: Experimental data using polyurethane proxies

Gun violence is a global phenomenon with regional variation in frequency and severity. Handguns are often used in violent deaths such as suicides and homicides. Hence, ballistic trauma is a critical subject of forensic investigations. Trauma patterns are fundamental evidence for the reconstruction of the incident and for the determination of the manner of death. This study investigated the differences in trauma patterns with a series of experiments using six different calibers (.22 LR, .38 Special, .380 ACP, 9×19mm, .40 S&W, and .45 ACP) and four different bullet types. Synbone^® spheres (polyurethane bone proxies) were used for close range 30cm simulated executions. The polyurethane spheres constitute an excellent proxy for human crania at the macroscopic level as suggested by other studies. The results showed that the radius of the entrance wound is positively correlated (Pearson's correlation coefficient R=0.846, p<0.05) with the caliber dimension. As muzzle velocity increased, endocranial beveling increased. Bullet weight, conversely, does not seem to have an effect on the size of the endocranial beveling present in Synbone^® spheres. The ballistic experiments exhibited similarities in entrance wound morphology; radial and concentric fracture patterns, hydraulic burst effect, circumferential delamination, and endocranial beveling with that of documented forensic cases with corresponding caliber shot. Synbone spheres seem appropriate for ballistic simulations of cranial injuries; yet, more research is needed to verify these observations.

Alterations in brain-derived neurotrophic factor and insulin-like growth factor-1 protein levels after penetrating ballistic-like brain injury in rats

BACKGROUND

Brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1) are essential for neuroplasticity and neuronal survival. Despite the importance of these endogenous factors in mediating posttraumatic recovery, little is known about their response after penetrating type traumatic brain injury. The objective of this study was to quantify the expression levels BDNF and IGF-1, two well-known neuroplasticity mediators, after penetrating ballistic-like brain injury (PBBI).

METHODS

Rats were randomly assigned to receive unilateral sham or PBBI injuries. Using enzyme-linked immunosorbent assay and immunohistochemistry, we performed a comprehensive evaluation of BDNF and IGF-1 expression at acute (1 hour, 6 hours, 1 day) and subacute (2, 3, 7, and 14 days) timepoints after injury.

RESULTS

BDNF and IGF-1 expression was transiently upregulated in both cortex and hippocampus after PBBI. Although BDNF levels increased at acute timepoints, IGF-1 expression peaked at 3 days in cortical homogenates. Although there was loss of staining in cells bordering the cavity, increased BDNF and IGF-1 immunoreactivity was observed in scattered neurons away from the contusion site. Glial upregulation of both growth factors was observed at early timepoints in the hippocampus.

CONCLUSION

Our findings demonstrate that PBBI results in a brief upregulation of BDNF and IGF-1 during early posttraumatic period, providing critical information for interventions aiming to enhance neuronal survival and brain plasticity.

Epilepsy in hemiplegic migraine: Genetic mutations and clinical implications

Objective

We performed a systematic review on the comorbidities of familial/sporadic hemiplegic migraine (F/SHM) with seizure/epilepsy in patients with CACNA1A, ATP1A2 or SCN1A mutations, to identify the genotypes associated and investigate for the presence of mutational hot spots.

Methods

We performed a search in MEDLINE and in the Human Gene Mutation and Leiden Open Variation Databases for mutations in the CACNA1A, ATP1A2 and SCN1A genes. After having examined the clinical characteristics of the patients, we selected those having HM and seizures, febrile seizures or epilepsy. For each gene, we determined both the frequency and the positions at protein levels of these mutations, as well as the penetrance of epilepsy within families.

Results

Concerning F/SHM-Epilepsy1 (F/SHME1) and F/SHME2 endophenotypes, we observed a prevalent involvement of the transmembrane domains, and a strong correlation in F/SHME1 when the positively charged amino acids were involved. The penetrance of epilepsy within the families was highest for patients carrying mutation in the CACNA1A gene (60%), and lower in those having SCN1A (33.3%) and ATP1A2 (30.9%) mutations.

Conclusion

Among the HM cases with seizure/epilepsy, we observed mutational hot spots in the transmembrane domains of CACNA1A and ATP1A2 proteins. These findings could lead to a better understanding of the pathological mechanisms underlying migraine and epilepsy, therein guaranteeing the most appropriate therapeutic approach.

Effects of estrogen receptor modulators on cytoskeletal proteins in the central nervous system

Estrogen receptor modulators are compounds of interest because of their estrogenic agonistic/antagonistic effects and tissue specificity. These compounds have many clinical applications, particularly for breast cancer treatment and osteoporosis in postmenopausal women, as well as for the treatment of climacteric symptoms. Similar to estrogens, neuroprotective effects of estrogen receptor modulators have been described in different models. However, the mechanisms of action of these compounds in the central nervous system have not been fully described. We conducted a systematic search to investigate the effects of estrogen receptor modulators in the central nervous system, focusing on the modulation of cytoskeletal proteins. We found that raloxifene, tamoxifen, and tibolone modulate some cytoskeletal proteins such as tau, microtuble-associated protein 1 (MAP1), MAP2, neurofilament 38 (NF38) by different mechanisms of action and at different levels: neuronal microfilaments, intermediate filaments, and microtubule-associated proteins. Finally, we emphasize the importance of the study of these compounds in the treatment of neurodegenerative diseases since they present the benefits of estrogens without their side effects.

Insight into Pre-Clinical Models of Traumatic Brain Injury Using Circulating Brain Damage Biomarkers: Operation Brain Trauma Therapy

Operation Brain Trauma Therapy (OBTT) is a multicenter pre-clinical drug screening consortium testing promising therapies for traumatic brain injury (TBI) in three well-established models of TBI in rats--namely, parasagittal fluid percussion injury (FPI), controlled cortical impact (CCI), and penetrating ballistic-like brain injury (PBBI). This article presents unique characterization of these models using histological and behavioral outcomes and novel candidate biomarkers from the first three treatment trials of OBTT. Adult rats underwent CCI, FPI, or PBBI and were treated with vehicle (VEH). Shams underwent all manipulations except trauma. The glial marker glial fibrillary acidic protein (GFAP) and the neuronal marker ubiquitin C-terminal hydrolase (UCH-L1) were measured by enzyme-linked immunosorbent assay in blood at 4 and 24 h, and their delta 24-4 h was calculated for each marker. Comparing sham groups across experiments, no differences were found in the same model. Similarly, comparing TBI + VEH groups across experiments, no differences were found in the same model. GFAP was acutely increased in injured rats in each model, with significant differences in levels and temporal patterns mirrored by significant differences in delta 24-4 h GFAP levels and neuropathological and behavioral outcomes. Circulating GFAP levels at 4 and 24 h were powerful predictors of 21 day contusion volume and tissue loss. UCH-L1 showed similar tendencies, albeit with less robust differences between sham and injury groups. Significant differences were also found comparing shams across the models. Our findings (1) demonstrate that TBI models display specific biomarker profiles, functional deficits, and pathological consequence; (2) support the concept that there are different cellular, molecular, and pathophysiological responses to TBI in each model; and (3) advance our understanding of TBI, providing opportunities for a successful translation and holding promise for theranostic applications. Based on our findings, additional studies in pre-clinical models should pursue assessment of GFAP as a surrogate histological and/or theranostic end-point.

Nicotinamide Treatment in Traumatic Brain Injury: Operation Brain Trauma Therapy

Nicotinamide (vitamin B3) was the first drug selected for cross-model testing by the Operation Brain Trauma Therapy (OBTT) consortium based on a compelling record of positive results in pre-clinical models of traumatic brain injury (TBI). Adult male Sprague-Dawley rats were exposed to either moderate fluid percussion injury (FPI), controlled cortical impact injury (CCI), or penetrating ballistic-like brain injury (PBBI). Nicotinamide (50 or 500 mg/kg) was delivered intravenously at 15 min and 24 h after injury with subsequent behavioral, biomarker, and histopathological outcome assessments. There was an intermediate effect on balance beam performance with the high (500 mg/kg) dose in the CCI model, but no significant therapeutic benefit was detected on any other motor task across the OBTT TBI models. There was an intermediate benefit on working memory with the high dose in the FPI model. A negative effect of the low (50 mg/kg) dose, however, was observed on cognitive outcome in the CCI model, and no cognitive improvement was observed in the PBBI model. Lesion volume analysis showed no treatment effects after either FPI or PBBI, but the high dose of nicotinamide resulted in significant tissue sparing in the CCI model. Biomarker assessments included measurements of glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl-terminal hydrolase-1 (UCH-L1) in blood at 4 or 24 h after injury. Negative effects (both doses) were detected on biomarker levels of GFAP after FPI and on biomarker levels of UCH-L1 after PBBI. The high dose of nicotinamide, however, reduced GFAP levels after both PBBI and CCI. Overall, our results showed a surprising lack of benefit from the low dose nicotinamide. In contrast, and partly in keeping with the literature, some benefit was achieved with the high dose. The marginal benefits achieved with nicotinamide, however, which appeared sporadically across the TBI models, has reduced enthusiasm for further investigation by the OBTT Consortium.

Neuroprotective levels of IGF-1 exacerbate epileptogenesis after brain injury

Exogenous Insulin-Like Growth Factor-1 (IGF-1) is neuroprotective in animal models of brain injury, and has been considered as a potential therapeutic. Akt-mTOR and MAPK are downstream targets of IGF-1 signaling that are activated after brain injury. However, both brain injury and mTOR are linked to epilepsy, raising the possibility that IGF-1 may be epileptogenic. Here, we considered the role of IGF-1 in development of epilepsy after brain injury, using the organotypic hippocampal culture model of post-traumatic epileptogenesis. We found that IGF-1 was neuroprotective within a few days of injury but that long-term IGF-1 treatment was pro-epileptic. Pro-epileptic effects of IGF-1 were mediated by Akt-mTOR signaling. We also found that IGF-1 - mediated increase in epileptic activity led to neurotoxicity. The dualistic nature of effects of IGF-1 treatment demonstrates that anabolic enhancement through IGF-1 activation of mTOR cascade can be beneficial or harmful depending on the stage of the disease. Our findings suggest that epilepsy risk may need to be considered in the design of neuroprotective treatments for brain injury.

IL-17A promotes microglial activation and neuroinflammation in mouse models of intracerebral haemorrhage

Microglial activation is an important contributor to neuroinflammation in intracerebral haemorrhage (ICH). IL-17A has been demonstrated to be involved in neuroinflammatory diseases such as multiple sclerosis. However, the exact mechanism of IL-17A mediated microglial activation in ICH has not been well identified. The purpose of this experiment is to investigate the role of IL-17A in ICH induced microglial activation and neuroinflammation. ICH mice were made by injection of autologous blood model. IL-17A expression and inflammatory factors in perihematomal region, and neurological function of mice were examined after ICH. In addition, IL-17A-neutralizing antibody was utilized to potentially prevent microglial activation and neuroinflammation in ICH mice. The expression of IL-17A, inflammatory factors and microglial activation in perihematomal region were significantly increased, and neurological function of mice was impaired after ICH. In addition, IL-17A Ab prevented ICH-induced cytokine expression, including TNF-α, IL-1β and IL-6, and downstream signaling molecules, including MyD88, TRIF, IκBα, and NF-κBp65 expression, and attenuated microglial activation. IL-17A Ab significantly reduced brain water content and improved neurological function of ICH mice. In conclusion, our results demonstrated that IL-17A was involved in ICH-induced microglial activation and neuroinflammation. IL-17A Ab might also provide a promising therapeutic strategy in ICH.

Cognitive Evaluation Using Morris Water Maze in Neurotrauma

The Morris water maze (MWM) task is one of the most widely used and versatile tools in behavioral neuroscience for evaluating spatial learning and memory. With regard to detecting cognitive deficits following central nervous system (CNS) injuries, MWM has been commonly utilized in various animal models of neurotrauma, such as fluid percussion injury (FPI), cortical controlled impact (CCI) injury, weight-drop impact injury, and penetrating ballistic-like brain injury (PBBI). More importantly, it serves as a therapeutic index for assessing the efficacy of treatment interventions on cognitive performance following neurotrauma. Thus, it is critical to design an MWM testing paradigm that is sensitive yet discriminating for the purpose of evaluating potential therapeutic interventions. In this chapter, we discuss how multiple test manipulations, including the size of platform, numbers of trials per day, the frequency of retesting intervals, and the texture of platform surface, impact MWM's ability to detect cognitive deficits using a rat model of PBBI.

Clinical Traumatic Brain Injury in the Preclinical Setting

Traumatic brain injury (TBI) is the leading cause of death and disability for people under 45 years of age. Clinical TBI is often the result of disparate forces resulting in heterogeneous injuries. Preclinical modeling of TBI is a vital tool for studying the complex cascade of metabolic, cellular, and molecular post-TBI events collectively termed secondary injury. Preclinical models also provide an important platform for studying therapeutic interventions. However, modeling TBI in the preclinical setting is challenging, and most models replicate only certain aspects of clinical TBI. This chapter details the most widely used models of preclinical TBI, including the controlled cortical impact, fluid percussion, blast, and closed head models. Each of these models replicates particular critical aspects of clinical TBI. Prior to selecting a preclinical TBI model, it is important to address what aspect of human TBI is being sought to evaluate.

Approach to Modeling, Therapy Evaluation, Drug Selection, and Biomarker Assessments for a Multicenter Pre-Clinical Drug Screening Consortium for Acute Therapies in Severe Traumatic Brain Injury: Operation Brain Trauma Therapy

Traumatic brain injury (TBI) was the signature injury in both the Iraq and Afghan wars and the magnitude of its importance in the civilian setting is finally being recognized. Given the scope of the problem, new therapies are needed across the continuum of care. Few therapies have been shown to be successful. In severe TBI, current guidelines-based acute therapies are focused on the reduction of intracranial hypertension and optimization of cerebral perfusion. One factor considered important to the failure of drug development and translation in TBI relates to the recognition that TBI is extremely heterogeneous and presents with multiple phenotypes even within the category of severe injury. To address this possibility and attempt to bring the most promising therapies to clinical trials, we developed Operation Brain Trauma Therapy (OBTT), a multicenter, pre-clinical drug screening consortium for acute therapies in severe TBI. OBTT was developed to include a spectrum of established TBI models at experienced centers and assess the effect of promising therapies on both conventional outcomes and serum biomarker levels. In this review, we outline the approach to TBI modeling, evaluation of therapies, drug selection, and biomarker assessments for OBTT, and provide a framework for reports in this issue on the first five therapies evaluated by the consortium.

Chronic Histopathological and Behavioral Outcomes of Experimental Traumatic Brain Injury in Adult Male Animals

The purpose of this review is to survey the use of experimental animal models for studying the chronic histopathological and behavioral consequences of traumatic brain injury (TBI). The strategies employed to study the long-term consequences of TBI are described, along with a summary of the evidence available to date from common experimental TBI models: fluid percussion injury; controlled cortical impact; blast TBI; and closed-head injury. For each model, evidence is organized according to outcome. Histopathological outcomes included are gross changes in morphology/histology, ventricular enlargement, gray/white matter shrinkage, axonal injury, cerebrovascular histopathology, inflammation, and neurogenesis. Behavioral outcomes included are overall neurological function, motor function, cognitive function, frontal lobe function, and stress-related outcomes. A brief discussion is provided comparing the most common experimental models of TBI and highlighting the utility of each model in understanding specific aspects of TBI pathology. The majority of experimental TBI studies collect data in the acute postinjury period, but few continue into the chronic period. Available evidence from long-term studies suggests that many of the experimental TBI models can lead to progressive changes in histopathology and behavior. The studies described in this review contribute to our understanding of chronic TBI pathology.

Pre-Clinical Traumatic Brain Injury Common Data Elements: Toward a Common Language Across Laboratories

Traumatic brain injury (TBI) is a major public health issue exacting a substantial personal and economic burden globally. With the advent of "big data" approaches to understanding complex systems, there is the potential to greatly accelerate knowledge about mechanisms of injury and how to detect and modify them to improve patient outcomes. High quality, well-defined data are critical to the success of bioinformatics platforms, and a data dictionary of "common data elements" (CDEs), as well as "unique data elements" has been created for clinical TBI research. There is no data dictionary, however, for preclinical TBI research despite similar opportunities to accelerate knowledge. To address this gap, a committee of experts was tasked with creating a defined set of data elements to further collaboration across laboratories and enable the merging of data for meta-analysis. The CDEs were subdivided into a Core module for data elements relevant to most, if not all, studies, and Injury-Model-Specific modules for non-generalizable data elements. The purpose of this article is to provide both an overview of TBI models and the CDEs pertinent to these models to facilitate a common language for preclinical TBI research.

Dual Therapeutic Effects of C-10068, a Dextromethorphan Derivative, Against Post-Traumatic Nonconvulsive Seizures and Neuroinflammation in a Rat Model of Penetrating Ballistic-Like Brain Injury

Post-traumatic seizures can exacerbate injurious outcomes of severe brain trauma, yet effective treatments are limited owing to the complexity of the pathology underlying the concomitant occurrence of both events. In this study, we tested C-10068, a novel deuterium-containing analog of (+)-N-methyl-3-ethoxymorphinan, in a rat model of penetrating ballistic-like brain injury (PBBI) and evaluated the effects of C-10068 on PBBI-induced nonconvulsive seizures (NCS), acute neuroinflammation, and neurofunctional outcomes. NCS were detected by electroencephalographic monitoring. Neuroinflammation was evaluated by immunohistochemical markers, for example, glial fibrillary acidic protein and major histocompatibility complex class I, for activation of astrocytes and microglia, respectively. Neurofunction was tested using rotarod and Morris water maze tasks. Three infusion doses of C-10068 (1.0, 2.5, and 5.0 mg/kg/h × 72 h) were tested in the antiseizure study. Neuroinflammation and neurofunction were evaluated in animals treated with 5.0 mg/kg/h × 72 h C-10068. Compared to vehicle treatment, C-10068 dose dependently reduced PBBI-induced NCS incidence (40-50%), frequency (20-70%), and duration (30-82%). The most effective antiseizure dose of C-10068 (5.0 mg/kg/h × 72 h) also significantly attenuated hippocampal astrocyte activation and perilesional microglial reactivity post-PBBI. Within C-10068-treated animals, a positive correlation was observed in reduction in NCS frequency and reduction in hippocampal astrocyte activation. Further, C-10068 treatment significantly attenuated astrocyte activation in seizure-free animals. However, C-10068 failed to improve PBBI-induced motor and cognitive functions with the dosing regimen used in this study. Overall, the results indicating that C-10068 exerts both potent antiseizure and antiinflammatory effects are promising and warrant further investigation.

Glucose and oxygen metabolism after penetrating ballistic-like brain injury

Traumatic brain injury (TBI) is a major cause of death and disability in all age groups. Among TBI, penetrating traumatic brain injuries (PTBI) have the worst prognosis and represent the leading cause of TBI-related morbidity and death. However, there are no specific drugs/interventions due to unclear pathophysiology. To gain insights we looked at cerebral metabolism in a PTBI rat model: penetrating ballistic-like brain injury (PBBI). Early after injury, regional cerebral oxygen tension and consumption significantly decreased in the ipsilateral cortex in the PBBI group compared with the control group. At the same time point, glucose uptake was significantly reduced globally in the PBBI group compared with the control group. Examination of Fluorojade B-stained brain sections at 24 hours after PBBI revealed an incomplete overlap of metabolic impairment and neurodegeneration. As expected, the injury core had the most severe metabolic impairment and highest neurodegeneration. However, in the peri-lesional area, despite similar metabolic impairment, there was lesser neurodegeneration. Given our findings, the data suggest the presence of two distinct zones of primary injury, of which only one recovers. We anticipate the peri-lesional area encompassing the PBBI ischemic penumbra, could be salvaged by acute therapies.

Electrophysiologic recordings in traumatic brain injury

Following a traumatic brain injury (TBI), the brain undergoes numerous electrophysiologic changes. The most common techniques used to evaluate these changes include electroencepalography (EEG) and evoked potentials. In animals, EEGs immediately following TBI can show either diffuse slowing or voltage attenuation, or high voltage spiking. Following a TBI, many animals display evidence of hippocampal excitability and a reduced seizure threshold. Some mice subjected to severe TBI via a fluid percussion injury will eventually develop seizures, which provides a useful potential model for studying the neurophysiology of epileptogenesis. In humans, the EEG changes associated with mild TBI are relatively subtle and may be challenging to distinguish from EEG changes seen in other conditions. Quantitative EEG (QEEG) may enhance the ability to detect post-traumatic electrophysiologic changes following a mild TBI. Some types of evoked potential (EP) and event related potential (ERP) can also be used to detect post-traumatic changes following a mild TBI. Continuous EEG monitoring (cEEG) following moderate and severe TBI is useful in detecting the presence of seizures and status epilepticus acutely following an injury, although some seizures may only be detectable using intracranial monitoring. CEEG can also be helpful for assessing prognosis after moderate or severe TBI. EPs, particularly somatosensory evoked potentials, can also be useful in assessing prognosis following severe TBI. The role for newer technologies such as magnetoencephalography and bispectral analysis (BIS) in the evaluation of patients with TBI remains unclear.

Cellular and molecular mechanisms of injury and spontaneous recovery

Until recently, most have assumed that traumatic brain injury (TBI) was singularly associated with the overt destruction of brain tissue resulting in subsequent morbidity or death. More recently, experimental and clinical studies have shown that the pathobiology of TBI is more complex, involving a host of cellular and subcellular changes that impact on neuronal function and viability while also affecting vascular reactivity and the activation of multiple biological response pathways. Here we review the brain's response to injury, examining both focal and diffuse changes and their implications for post-traumatic brain dysfunction and recovery. TBI-induced neuronal dysfunction and death as well as the diffuse involvement of multiple fiber projections are discussed together with considerations of how local axonal membrane changes or channelopathy translate into local ionic dysregulation and axonal disconnection. Concomitant changes in the cerebral microcirculation are also discussed and their relationship with the parallel changes in the brain's metabolism is considered. These cellular and subcellular events occurring within neurons and their blood supply are correlated with multiple biological response modifiers evoked by generalized post-traumatic inflammation and the parallel activation of oxidative stress processes. The chapter closes with considerations of recovery following focal or diffuse injury. Evidence for dynamic brain reorganization/repair is presented, with considerations of traumatically induced circuit disruption and their progression to either adaptive or in some cases, maladaptive reorganization.

A model of posttraumatic epilepsy after penetrating brain injuries: effect of lesion size and metal fragments

OBJECTIVE

Penetrating brain injury (PBI) has the highest risk for inducing posttraumatic epilepsy, and those PBIs with retained foreign materials such as bullet fragments carry the greatest risk. This study examines the potential contribution of copper, a major component of bullets, to the development of epilepsy following PBI.

METHODS

Anesthetized adult male rats received a penetrating injury from the dorsal cortex to the ventral hippocampus from a high speed small bit drill. In one group of animals, copper wire was inserted into the lesion. Control animals had only the lesion or the lesion plus stainless steel wire (biologically inert foreign body). From 6 to up to 11 months following the injury the rats were monitored intermittently for the development of epilepsy with video-electroencephalography (EEG). A separate set of animals was examined for possible acute seizures in the week following the injury.

RESULTS

Twenty-two of the 23 animals with copper wire developed chronic epilepsy, compared to three of the 20 control rats (lesion and lesion with stainless steel). Copper was associated with more extensive injury. The control rats with epilepsy had larger lesions. In the acute injury group, there was no difference in the incidence of seizures (83% lesion plus stainless steel, 70% lesion plus copper).

SIGNIFICANCE

Copper increases the risk for epilepsy and may increase damage over time, but there were no differences between the groups in the incidence of acute postinjury seizures. Lesion size may contribute to epilepsy development in lesion-only animals. Copper may be an independent risk factor for the development of epilepsy and possible secondary injury, but lesion size also contributes to the development of epilepsy. The consequences of prolonged exposure of the brain to copper observed in these animals may have clinical implications that require further evaluation.

A systems biology strategy to identify molecular mechanisms of action and protein indicators of traumatic brain injury

The multifactorial nature of traumatic brain injury (TBI), especially the complex secondary tissue injury involving intertwined networks of molecular pathways that mediate cellular behavior, has confounded attempts to elucidate the pathology underlying the progression of TBI. Here, systems biology strategies are exploited to identify novel molecular mechanisms and protein indicators of brain injury. To this end, we performed a meta-analysis of four distinct high-throughput gene expression studies involving different animal models of TBI. By using canonical pathways and a large human protein-interaction network as a scaffold, we separately overlaid the gene expression data from each study to identify molecular signatures that were conserved across the different studies. At 24 hr after injury, the significantly activated molecular signatures were nonspecific to TBI, whereas the significantly suppressed molecular signatures were specific to the nervous system. In particular, we identified a suppressed subnetwork consisting of 58 highly interacting, coregulated proteins associated with synaptic function. We selected three proteins from this subnetwork, postsynaptic density protein 95, nitric oxide synthase 1, and disrupted in schizophrenia 1, and hypothesized that their abundance would be significantly reduced after TBI. In a penetrating ballistic-like brain injury rat model of severe TBI, Western blot analysis confirmed our hypothesis. In addition, our analysis recovered 12 previously identified protein biomarkers of TBI. The results suggest that systems biology may provide an efficient, high-yield approach to generate testable hypotheses that can be experimentally validated to identify novel mechanisms of action and molecular indicators of TBI.

Correlations between blood-brain barrier disruption and neuroinflammation in an experimental model of penetrating ballistic-like brain injury

Abstract Blood-brain barrier (BBB) disruption is a pathological hallmark of severe traumatic brain injury (TBI) and is associated with neuroinflammatory events contributing to brain edema and cell death. The goal of this study was to elucidate the profile of BBB disruption after penetrating ballistic-like brain injury (PBBI) in conjunction with changes in neuroinflammatory markers. Brain uptake of biotin-dextran amine (BDA; 3 kDa) and horseradish peroxidase (HRP; 44 kDa) was evaluated in rats at 4 h, 24 h, 48 h, 72 h, and 7 days post-PBBI and compared with the histopathologic and molecular profiles for inflammatory markers. BDA and HRP both displayed a uniphasic profile of extravasation, greatest at 24 h post-injury and which remained evident out to 48 h for HRP and 7 days for BDA. This profile was most closely associated with markers for adhesion (mRNA for intercellular adhesion molecule-1) and infiltration of peripheral granulocytes (mRNA for matrix metalloproteinase-9 [MMP-9] and myeloperoxidase staining). Improvement of BBB dysfunction coincided with increased expression of markers implicated in tissue remodeling and repair. The results of this study reveal a uniphasic and gradient opening of the BBB after PBBI and suggest MMP-9 and resident inflammatory cell activation as candidates for future neurotherapeutic intervention after PBBI.

A novel mouse model of penetrating brain injury

Penetrating traumatic brain injury (pTBI) has been difficult to model in small laboratory animals, such as rats or mice. Previously, we have established a non-fatal, rat model for pTBI using a modified air-rifle that accelerates a pellet, which hits a small probe that then penetrates the experimental animal’s brain. Knockout and transgenic strains of mice offer attractive tools to study biological reactions induced by TBI. Hence, in the present study, we adapted and modified our model to be used with mice. The technical characterization of the impact device included depth and speed of impact, as well as dimensions of the temporary cavity formed in a brain surrogate material after impact. Biologically, we have focused on three distinct levels of severity (mild, moderate, and severe), and characterized the acute phase response to injury in terms of tissue destruction, neural degeneration, and gliosis. Functional outcome was assessed by measuring bodyweight and motor performance on rotarod. The results showed that this model is capable of reproducing major morphological and neurological changes of pTBI; as such, we recommend its utilization in research studies aiming to unravel the biological events underlying injury and regeneration after pTBI.

Temporal alterations in aquaporin and transcription factor HIF1α expression following penetrating ballistic-like brain injury (PBBI)

OBJECTIVES

Brain edema is a primary factor in the morbidity and mortality of traumatic brain injury (TBI). The various isoforms of aquaporin 4 (AQP4) and aquaporin 9 (AQP9) are important factors influencing edema following TBI. Others have reported that these AQPs are regulated by the transcription factor hypoxia inducible factor (HIF) 1α. Therefore, we examined the temporal alterations in the multiple isoforms of AQP4 and AQP9, and its possible upstream regulation by HIF1α, and evaluated whether different severities of penetrating injury influence these mechanisms.

METHODS

In the penetrating ballistic-like brain injury (PBBI) model, a temporary cavity and resultant injury was formed by the rapid inflation/deflation (i.e. <40ms) of an elastic balloon attached to the end of the custom probe, injuring 10% of total rat brain volume. Tissue from the ipsilateral core and perilesional injury zones was collected. Total RNA was isolated at 4, 12, and 24h, 3 and 7days post-injury (sham and PBBI, n=6 per group). cDNA was synthesized using oligodT primers. Quantitative real time PCR was performed using Taqman expression assays for aqp4 (recognizing all isoforms), aqp9, and hif1α. Using separate animals, tissue lysate was collected at 4 and 24h, 3 and 7days post-injury and analyzed by immunoblot for protein expression of multiple isoforms of AQP4, the single known isoform of AQP9 and for expression of transcription factor HIF1α (sham, probe only control, and PBBI, n=8-10 per group).

RESULTS

Global aqp4 mRNA was decreased at 24h (p<0.01) with PBBI. Three of the four known protein isoforms of AQP4 were detected, M1 (34kDa), M23 (32kDa) and isoform 3 (30kDa). AQP4 M1 decreased at 3 and 7days post-injury (p<0.001; p<0.01). AQP4 M23 levels were highly variable with no significant changes. AQP4 isoform 3 levels were decreased 3days post-PBBI (p<0.05). From 4, 12, and 24h aqp9 mRNA levels were decreased with injury (p<0.01, p<0.05, p<0.01) while AQP9 levels were decreased at 3 and 7days after PBBI (p<0.001, p<0.01). At 12 and 24h post-PBBI hif1α mRNA levels increased (p<0.05, p<0.01) but at 3 and 7days mRNA levels decreased (p<0.05, p<0.01). From 24h and 3 and 7days HIF1α protein levels were decreased (p<0.0001, p<0.0001, p<0.0001). In comparison to probe control, PBBI led to greater decreases in protein for AQP4 M1 (trend), AQP4 isoform 3 (trend), AQP9 (p<0.05) and HIF1α (p<0.05).

CONCLUSION

PBBI is characterized by a loss of AQP4 M1, AQP4 isoform 3 and AQP9 at delayed time-points. The severity of the injury (PBBI versus probe control) increased these effects. Therefore, AQP9 and the AQP4 M1 isoform may be regulated by HIF1α, but not AQP4 isoform 3. This delayed loss of aquaporins may markedly reduce the ability of the brain to efflux water, contributing to the protracted edema that is a characteristic following severe penetrating TBI. Factors contributing to edema differ with different types and severities of TBI. For example, cellular based edema is more prominent in diffuse non-penetrating TBI whereas vasogenic edema is more prevalent with TBI involving hemorrhage. Molecular regulation leading to edema will likely also differ, such that treatments which have been suggested for non-hemorrhagic moderate TBI, such as the suppression of aquaporins, may be detrimental in more severe forms of TBI.

Human traumatic brain injury induces autoantibody response against glial fibrillary acidic protein and its breakdown products

The role of systemic autoimmunity in human traumatic brain injury (TBI) and other forms of brain injuries is recognized but not well understood. In this study, a systematic investigation was performed to identify serum autoantibody responses to brain-specific proteins after TBI in humans. TBI autoantibodies showed predominant immunoreactivity against a cluster of bands from 38-50 kDa on human brain immunoblots, which were identified as GFAP and GFAP breakdown products. GFAP autoantibody levels increased by 7 days after injury, and were of the IgG subtype predominantly. Results from in vitro tests and rat TBI experiments also indicated that calpain was responsible for removing the amino and carboxyl termini of GFAP to yield a 38 kDa fragment. Additionally, TBI autoantibody staining co-localized with GFAP in injured rat brain and in primary rat astrocytes. These results suggest that GFAP breakdown products persist within degenerating astrocytes in the brain. Anti-GFAP autoantibody also can enter living astroglia cells in culture and its presence appears to compromise glial cell health. TBI patients showed an average 3.77 fold increase in anti-GFAP autoantibody levels from early (0-1 days) to late (7-10 days) times post injury. Changes in autoantibody levels were negatively correlated with outcome as measured by GOS-E score at 6 months, suggesting that TBI patients with greater anti-GFAP immune-responses had worse outcomes. Due to the long lasting nature of IgG, a test to detect anti-GFAP autoantibodies is likely to prolong the temporal window for assessment of brain damage in human patients.

Functional assessment of long-term deficits in rodent models of traumatic brain injury

Traumatic brain injury (TBI) ranks as the leading cause of mortality and disability in the young population worldwide. The annual US incidence of TBI in the general population is estimated at 1.7 million per year, with an estimated financial burden in excess of US$75 billion a year in the USA alone. Despite the prevalence and cost of TBI to individuals and society, no treatments have passed clinical trial to clinical implementation. The rapid expansion of stem cell research and technology offers an alternative to traditional pharmacological approaches targeting acute neuroprotection. However, preclinical testing of these approaches depends on the selection and characterization of appropriate animal models. In this article we consider the underlying pathophysiology for the focal and diffuse TBI subtypes, discuss the existing preclinical TBI models and functional outcome tasks used for assessment of injury and recovery, identify criteria particular to preclinical animal models of TBI in which stem cell therapies can be tested for safety and efficacy, and review these criteria in the context of the existing TBI literature. We suggest that 2 months post-TBI is the minimum period needed to evaluate human cell transplant efficacy and safety. Comprehensive review of the published TBI literature revealed that only 32% of rodent TBI papers evaluated functional outcome ≥1 month post-TBI, and only 10% evaluated functional outcomes ≥2 months post-TBI. Not all published papers that evaluated functional deficits at a minimum of 2 months post-TBI reported deficits; hence, only 8.6% of overall TBI papers captured in this review demonstrated functional deficits at 2 months or more postinjury. A 2-month survival and assessment period would allow sufficient time for differentiation and integration of human neural stem cells with the host. Critically, while trophic effects might be observed at earlier time points, it will also be important to demonstrate the sustainability of such an effect, supporting the importance of an extended period of in vivo observation. Furthermore, regulatory bodies will likely require at least 6 months survival post-transplantation for assessment of toxicology/safety, particularly in the context of assessing cell abnormalities.

Traumatic brain injury using mouse models

The use of mouse models in traumatic brain injury (TBI) has several advantages compared to other animal models including low cost of breeding, easy maintenance, and innovative technology to create genetically modified strains. Studies using knockout and transgenic mice demonstrating functional gain or loss of molecules provide insight into basic mechanisms of TBI. Mouse models provide powerful tools to screen for putative therapeutic targets in TBI. This article reviews currently available mouse models that replicate several clinical features of TBI such as closed head injuries (CHI), penetrating head injuries, and a combination of both. CHI may be caused by direct trauma creating cerebral concussion or contusion. Sudden acceleration-deceleration injuries of the head without direct trauma may also cause intracranial injury by the transmission of shock waves to the brain. Recapitulation of temporary cavities that are induced by high-velocity penetrating objects in the mouse brain are difficult to produce, but slow brain penetration injuries in mice are reviewed. Synergistic damaging effects on the brain following systemic complications are also described. Advantages and disadvantages of CHI mouse models induced by weight drop, fluid percussion, and controlled cortical impact injuries are compared. Differences in the anatomy, biomechanics, and behavioral evaluations between mice and humans are discussed. Although the use of mouse models for TBI research is promising, further development of these techniques is warranted.