Clinical relevance of midline fluid percussion brain injury: Acute deficits, chronic morbidities and the utility of biomarkers.

BACKGROUND: After 30 years of characterisation and implementation, fluid percussion injury (FPI) is firmly recognised as one of the best-characterised reproducible and clinically relevant models of TBI, encompassing concussion through diffuse axonal injury (DAI). Depending on the specific injury parameters (e.g. injury site, mechanical force), FPI can model diffuse TBI with or without a focal component and may be designated as mild-to-severe according to the chosen mechanical forces and resulting acute neurological responses. Among FPI models, midline FPI may best represent clinical diffuse TBI, because of the acute behavioural deficits, the transition to late-onset behavioural morbidities and the absence of gross histopathology. REVIEW: The goal here was to review acute and chronic physiological and behavioural deficits and morbidities associated with diffuse TBI induced by midline FPI. In the absence of neurodegenerative sequelae associated with focal injury, there is a need for biomarkers in the diagnostic, prognostic, predictive and therapeutic approaches to evaluate outcomes from TBI. CONCLUSIONS: The current literature suggests that midline FPI offers a clinically-relevant, validated model of diffuse TBI to investigators wishing to evaluate novel therapeutic strategies in the treatment of TBI and the utility of biomarkers in the delivery of healthcare to patients with brain injury.

Assessment of metabolic brain damage and recovery following mild traumatic brain injury: a multicentre, proton magnetic resonance spectroscopic study in concussed patients.

Concussive head injury opens a temporary window of brain vulnerability due to the impairment of cellular energetic metabolism. As experimentally demonstrated, a second mild injury occurring during this period can lead to severe brain damage, a condition clinically described as the second impact syndrome. To corroborate the validity of proton magnetic resonance spectroscopy in monitoring cerebral metabolic changes following mild traumatic brain injury, apart from the magnetic field strength (1.5 or 3.0 T) and mode of acquisition, we undertook a multicentre prospective study in which a cohort of 40 athletes suffering from concussion and a group of 30 control healthy subjects were admitted. Athletes (aged 16-35 years) were recruited and examined at three different institutions between September 2007 and June 2009. They underwent assessment of brain metabolism at 3, 15, 22 and 30 days post-injury through proton magnetic resonance spectroscopy for the determination of N-acetylaspartate, creatine and choline-containing compounds. Values of these representative brain metabolites were compared with those observed in the group of non-injured controls. Comparison of spectroscopic data, obtained in controls using different field strength and/or mode of acquisition, did not show any difference in the brain metabolite ratios. Athletes with concussion exhibited the most significant alteration of metabolite ratios at Day 3 post-injury (N-acetylaspartate/creatine: -17.6%, N-acetylaspartate/choline: -21.4%; P < 0.001 with respect to controls). On average, metabolic disturbance gradually recovered, initially in a slow fashion and, following Day 15, more rapidly. At 30 days post-injury, all athletes showed complete recovery, having metabolite ratios returned to values detected in controls. Athletes self-declared symptom clearance between 3 and 15 days after concussion. Results indicate that N-acetylaspartate determination by proton magnetic resonance spectroscopy represents a non-invasive tool to accurately measure changes in cerebral energy metabolism occurring in mild traumatic brain injury. In particular, this metabolic evaluation may significantly improve, along with other clinical assessments, the management of athletes suffering from concussion. Further studies to verify the effects of a second concussive event occurring at different time points of the recovery curve of brain metabolism are needed.

Deletion of the p53 tumor suppressor gene improves neuromotor function but does not attenuate regional neuronal cell loss following experimental brain trauma in mice.

Deletion of the tumor suppressor gene p53 has been shown to improve the outcome in experimental models of focal cerebral ischemia and kainate-induced seizures. To evaluate the potential role of p53 in traumatic brain injury, genetically modified mice lacking a functional p53 gene (p53(-/-), n = 9) and their wild-type littermates (p53(+/+), n = 9) were anesthetized and subjected to controlled cortical impact (CCI) experimental brain trauma. After brain injury, neuromotor function was assessed by using composite neuroscore and rotarod tests. By 7 days posttrauma, p53(-/-) mice exhibited significantly improved neuromotor function, in the composite neuroscore (P = 0.002) as well as in two of three individual tests, when compared with brain-injured p53(+/+) animals. CCI resulted in the formation of a cortical cavity (mean volume = 6.1 mm(3)) 7 days postinjury in p53(+/+) as well as p53(-/-) mice. No difference in lesion volume was detected between the two genotypes (P = 0.95). Although significant cell loss was detected in the ipsilateral hippocampus and thalamus of brain-injured animals, no differences between p53(+/+) and p53(-/-) mice were detected. Although our results suggest that lack of the p53 gene results in augmented recovery of neuromotor function following experimental brain trauma, they do not support a role for p53 acting as a mediator of neuronal death in this context, underscoring the complexity of its role in the injured brain.

C1-inhibitor attenuates neurobehavioral deficits and reduces contusion volume after controlled cortical impact brain injury in mice.

OBJECTIVE: The aim of the study was to evaluate the effects of C1-inhibitor (C1-INH), an endogenous inhibitor of complement and kinin systems, on neurobehavioral and histological outcome following controlled cortical impact brain injury. DESIGN: Experimental prospective randomized study in mice. SETTING: Experimental laboratory. SUBJECTS: Male C57Bl/6 mice (n = 81). INTERVENTIONS: Mice were subjected to controlled cortical impact brain injury followed by an intravenous bolus of either C1-INH (15 U either at 10 minutes or 1 hour postinjury) or saline (equal volume, 150 microl at 10 minutes postinjury). Sham-operated mice received identical surgery and saline injection without brain injury. Neurological motor function was evaluated weekly for 4 weeks using the Composite Neuroscore. Cognitive function was evaluated at 4 weeks postinjury using the Morris Water Maze. Histological outcome was performed by measuring the contusion volume at 1 week and 4 weeks postinjury. MEASUREMENTS AND MAIN RESULTS: Brain-injured mice receiving C1-INH at 10 minutes postinjury showed attenuated motor deficits, cognitive dysfunction and reduced contusion volume compared to brain-injured mice receiving saline. Mice receiving C1-INH at 1 hour postinjury showed reduced motor deficits compared to brain-injured mice receiving saline, but no significantly different cognitive and histological outcome. Immunohistochemical analysis showed that 20 minutes after infusion, C1-INH was localised on endothelial cells and in brain tissue surrounding brain capillaries of the injured hemisphere. CONCLUSION: Our results show that post-traumatic administration of C1-INH attenuates neuro-behavioral deficits and histological damage associated with traumatic brain injury.

Erythropoietin as a neuroprotective agent in traumatic brain injury Review.

BACKGROUND: In the United States, TBI remains a major cause of morbidity and mortality in children and young adults. A total of 1.5 million Americans experience head trauma every year, and the yearly economic cost of this exceeds $56 billion. The magnitude of this problem has generated a great deal of interest in elucidating the complex molecular mechanism underlying cell death and dysfunction after TBI and in the development of neuroprotective agents that will reduce morbidity and mortality. METHODS: A review of recent literature on EPO, TBI, and apoptosis is conducted with analysis of pathophysiologic mechanisms of TBI. In addition, animal experiments and clinical trials pertaining to mechanisms of cell death in TBI and EPO as a neuroprotective agent are reviewed. CONCLUSION: The literature and evidence for EPO as a potent inhibitor of apoptosis and promising therapeutic agent in a variety of neurological insults, including trauma, are mounting. With the recent interest in clinical trials of EPO in human stroke, it is both timely and prudent to consider the use of this pharmaceutical avenue in TBI in man.

TrkB gene transfer does not alter hippocampal neuronal loss and cognitive deficits following traumatic brain injury in mice.

PURPOSE: The ability of brain-derived neurotrophic factor (BDNF) to attenuate secondary damage and influence behavioral outcome after experimental traumatic brain injury (TBI) remains controversial. Because TBI can result in decreased expression of the trkB receptor, thereby preventing BDNF from exerting potential neuroprotective effects, the contribution of both BDNF and its receptor trkB to hippocampal neuronal loss and cognitive dysfunction were evaluated. METHODS: Full-length trkB was overexpressed in the left hippocampus of adult C57Bl/6 mice using recombinant adeno-associated virus serotype 2/5 (rAAV 2/5). EGFP (enhanced green fluorescent protein) expression was present at two weeks after AAV-EGFP injection and remained sustained up to four weeks after the injection. At 2 weeks following gene transduction, mice were subjected to parasagittal controlled cortical impact (CCI) brain injury, followed by either BDNF or PBS infusion into the hippocampus. RESULTS: No differences were observed in learning ability at two weeks post-injury or in motor function from 48 hours to two weeks among treatment groups. The number of surviving pyramidal neurons in the CA2-CA3 region of the hippocampus was also not different among treatment groups. CONCLUSIONS: These data suggest that neither overexpression of trkB, BNDF infusion or their combination affects neuronal survival or behavioral outcome following experimental TBI in mice.

The novel antiepileptic agent RWJ-333369-A, but not its analog RWJ-333369, reduces regional cerebral edema without affecting neurobehavioral outcome or cell death following experimental traumatic brain injury.

PURPOSE: To evaluate the therapeutic efficacy of two antiepileptic compounds, RWJ-333369 and RWJ-333369-A in a well-established experimental model of lateral fluid percussion (FP) traumatic brain injury (TBI) in the rat. METHODS: Anethestized Male Sprague-Dawley rats (n=227) were subjected to lateral FP brain injury or sham-injury. Animals were randomized to receive treatment with RWJ-333369 (60 mg/kg, p.o.) or its analog RWJ-333369-A (60 mg/kg, p.o.), or vehicle (equal volume) at 15 minutes, 4, 8, and 24 hours post-injury. In Study I, animals were assessed at 48 hours for acute motor and cognitive function and then sacrificed to evaluate regional cerebral edema. In Study II, animals were evaluated post-injury for motor function at 48 hours and weekly thereafter from 1 to 4 weeks. Post-traumatic learning ability was assessed 4 weeks post-injury, followed by evaluation of hemispheric tissue loss. RESULTS: In Study I, no improvement in acute memory or motor function was observed following administration of either RWJ-333369 or RWJ-333369-A in brain-injured animals compared to vehicle-treated, brain-injured animals. However, brain-injured animals receiving treatment with RWJ-333369-A had a significant reduction in post-traumatic cerebral edema in both injured and contralateral hippocampus compared to brain-injured, vehicle-treated controls (p<0.05). In Study II, treatment with either compound did not result in any improvement of neuromotor function, learning ability or change in lesion volume following brain injury. CONCLUSION: These results indicate that the novel antiepileptic compound RWJ-333369-A reduces post-traumatic hippocampal edema without affecting neurobehavioral or histological outcome. It remains unclear whether this small effect on hippocampal edema ie related to the ability of this compound to attenuate seizure activity.

Cognitive outcome following brain injury and treatment with an inhibitor of Nogo-A in association with an attenuated downregulation of hippocampal growth-associated protein-43 expression.

OBJECT: Central nervous system axons regenerate poorly after traumatic brain injury (TBI), partly due to inhibitors such as the protein Nogo-A present in myelin. The authors evaluated the efficacy of anti-Nogo-A monoclonal antibody (mAb) 7B12 administration on the neurobehavioral and cognitive outcome of rats following lateral fluid-percussion brain injury, characterized the penetration of the 7B12 or control antibodies into target brain regions, and evaluated the effects of Nogo-A inhibition on hemispheric tissue loss and sprouting of uninjured motor tracts in the cervical cord. To elucidate a potential molecular response to Nogo-A inhibition, we evaluated the effects of 7B12 on hippocampal GAP-43 expression. METHODS: Beginning 24 hours after lateral fluid-percussion brain injury or sham injury in rats, the mAb 7B12 or control antibody was infused intracerebroventricularly over 14 days, and behavior was assessed over 4 weeks. RESULTS: Immunoreactivity for 7B12 or immunoglobulin G was detected in widespread brain regions at 1 and 3 weeks postinjury. The brain-injured animals treated with 7B12 showed improvement in cognitive function (p < 0.05) at 4 weeks but no improvement in neurological motor function from 1 to 4 weeks postinjury compared with brain-injured, vehicle-treated controls. The enhanced cognitive function following inhibition of Nogo-A was correlated with an attenuated postinjury downregulation of hippocampal GAP-43 expression (p < 0.05). CONCLUSIONS: Increased GAP-43 expression may be a novel molecular mechanism of the enhanced cognitive recovery mediated by Nogo-A inhibition after TBI in rats.

Thalamic nuclei after human blunt head injury.

Paraffin-embedded blocks from the thalamus of 9 control patients, 9 moderately disabled, 12 severely disabled, and 10 vegetative head-injured patients assessed using the Glasgow Outcome Scale and identified from the Department of Neuropathology archive. Neurons, astrocytes, macrophages, and activated microglia were differentiated by Luxol fast blue/cresyl violet, GFAP, CD68, and CR3/43 staining and stereological techniques used to estimate cell number in a 28-microm-thick coronal section. Counts were made in subnuclei of the mediodorsal, lateral posterior, and ventral posterior nuclei, the intralaminar nuclei, and the related internal lamina. Neuronal loss occurred from mediodorsal parvocellularis, rostral center medial, central lateral and paracentral nuclei in moderately disabled patients; and from mediodorsal magnocellularis, caudal center medial, rhomboid, and parafascicular nuclei in severely disabled patients; and all of the above and the centre median nucleus in vegetative patients. Neuronal loss occurred primarily from cognitive and executive function nuclei, a lesser loss from somatosensory nuclei and the least loss from limbic motor nuclei. There was an increase in the number of reactive astrocytes, activated microglia, and macrophages with increasing severity of injury. The study provides novel quantitative evidence for differential neuronal loss, with survival after human head injury, from thalamic nuclei associated with different aspects of cortical activation.

Evaluation of pharmacological treatment strategies in traumatic brain injury.

Traumatic brain injury (TBI) is a devastating disease, predominately affecting young people. Although the prognosis for TBI victims has improved in recent years, many survivors of TBI suffer from emotional, cognitive and motor disturbances and a decreased quality of life. In recent years, there has been a rapid increase in the number of pharmacological targets evaluated in clinically-relevant experimental TBI models, showing improved cognitive and motor outcome and decreased loss of brain tissue. Despite the completion of several recent clinical trials using compounds showing neuroprotection in preclinical studies, pharmaceutical treatment strategies with proven clinical benefit are still lacking. This paper reviews the preclinical pharmacological treatment studies evaluated to date in experimental models of TBI. Although human TBI is a complex and multifaceted disease, these studies provide encouraging translational data suggesting that pharmacological compounds, delivered in a clinically-relevant time window, may improve the outcome of TBI patients.

Animal models of post-traumatic epilepsy.

Epilepsy is a major unfavorable long-term consequence of traumatic brain injury (TBI). Moreover, TBI is one of the most important predisposing factors for the development of epilepsy, particularly in young adults. Understanding the molecular and cellular cascades that lead to the development of post-traumatic epilepsy (PTE) is key for preventing its development or modifying the disease process in such a way that epilepsy, if it develops, is milder and easier-to-treat. Tissue from TBI patients undergoing epileptogenesis is not available for such studies, which underscores the importance of developing clinically relevant animal models of PTE. The goal of this review is to (1) provide a description of PTE in humans, which is critical for the development of clinically relevant models of PTE, (2) review the characteristics of currently available PTE models, and (3) provide suggestions for the development of future models of PTE based on our current understanding of the mechanisms of TBI and epilepsy. The development of clinically relevant models of PTE is critical to advance our understanding of the mechanisms of post-traumatic epileptogenesis and epilepsy, as well as for producing breakthroughs in the development and testing of novel antiepileptogenic treatments.

Early, transient increase in complexin I and complexin II in the cerebral cortex following traumatic brain injury is attenuated by N-acetylcysteine.

Alteration of excitatory neurotransmission is a key feature of traumatic brain injury (TBI) in which extracellular glutamate levels rise. Although increased synaptic release of glutamate occurs at the injury site, the precise mechanism is unclear. Complexin I and complexin II constitute a family of cytosolic proteins involved in the regulation of neurotransmitter release, competing with the chaperone protein alpha-SNAP (soluble N-ethylmaleimide-sensitive factor-attachment protein) for binding to the synaptic vesicle protein synaptobrevin as well as the synaptic membrane proteins SNAP-25 and syntaxin, which together form the SNAP receptor (SNARE) complex. Complexin I is predominantly a marker of axosomatic (inhibitory) synapses, whereas complexin II mainly labels axodendritic and axospinous synapses, the majority of which are excitatory. In order to examine the role of these proteins in TBI, we have studied levels of both complexins in the injured hemisphere by immunoblotting over a time period ranging from 6 h to 7 days following lateral fluid-percussion brain injury in the rat. Transient increases in the levels of complexin I and complexin II proteins were detected in the injured cerebral cortex 6 h following TBI. This increase was followed by a decrease of complexin I in the injured cortex and hippocampus, and a decrease in both complexins in the injured thalamus region at day 3 and day 7 post-injury. The early, transient increase in the injured cortex was completely blocked by N-acetylcysteine (NAC) administered 5 min following trauma, suggesting an involvement of oxidative stress. Neuronal loss was also reduced in the injured hemisphere with post-TBI NAC treatment. Our findings suggest a dysregulation of both inhibitory and excitatory neurotransmission following traumatic injury that is responsive to antioxidant treatment. These alterations in complexin levels may also play an important role in neuronal cell loss following TBI, and thus contribute to the pathophysiology of cerebral damage following brain injury.

Impaired fibrinolysis and traumatic brain injury in mice.

Traumatic brain injury (TBI) has been associated with intravascular coagulation, which may be a result of thromboplastin released following brain injury. Clots thus formed are lysed by plasmin, which is activated by tissue-type and urokinase-type plasminogen activators (uPA). To evaluate the association between traumatic intravascular coagulation and post-traumatic outcome, uPA knockout (uPA-/-) transgenic mice (n=12) or wild-type littermates (WT; n=12) were anesthetized and subjected to controlled cortical impact (CCI) brain injury. A second group of uPA-/- (n=12) and WT mice (n=12) were subjected to sham injury. Motor function was assessed over 2 weeks using the composite neuroscore test and cognition (learning) was assessed with the Morris Water Maze (MWM) at 2 weeks post-injury, whereupon the animals were sacrificed for cortical lesion volume analysis. Motor function was significantly worse in the brain-injured uPA-/- mice when compared to brain-injured WT mice at 48 h (p<0.05) and one week post-injury (p<0.05). These differences resolved by 2 weeks post-injury. There was no significant difference in post-injury cognitive function between uPA-/- mice and WT mice. However, at 2 weeks post-injury, the brain-injured uPA-/- had a significantly larger volume of cortical tissue loss than their WT counterparts (p<0.05). These results demonstrate that the absence of uPA in mice aggravates acute motor deficit and exacerbates cortical tissue loss following CCI brain injury, and suggests a neuroprotective role of the fibrinolytic process following TBI.

Cognitive evaluation of traumatically brain-injured rats using serial testing in the Morris water maze.

PURPOSE: As deficits in memory and cognition are commonly observed in survivors of traumatic brain injury (TBI), causing reduced quality of life for the patient, a major goal in experimental TBI research is to identify and evaluate cognitive dysfunction. The present study assessed the applicability of the serial Morris water maze (MWM) test to determine cognitive function following experimental TBI in the same group of rats which is particularly important for long-term studies and increasingly valuable for the evaluation of novel treatment strategies. METHODS: Male Sprague-Dawley rats (n = 27) were anesthetized and subjected to either sham injury (n = 9) or lateral fluid percussion (FP) brain injury of moderate severity (n = 18). At 4 weeks post-injury, animals were trained in a water maze over 3 days (acquisition/learning phase) to find a submerged platform. At 8 weeks post-injury the hidden platform was then moved to the opposite quadrant, and animals were trained to find the new position of the platform over 3 days. Forty-eight hours later, animals were tested for memory retention in a probe trial in which the platform was not present. RESULTS: Brain-injured animals had significant learning impairment (p < 0.0001), shifted-learning impairment (p < 0.001) and memory retention deficits (p < 0.01) in comparison to their sham-injured counterparts over the 8 week testing period. Swim speed and distance were not significantly altered by brain injury at any time point. CONCLUSION: The validation of this testing paradigm using a clinically relevant experimental brain injury model is an important addition to behavioral outcome testing.

Single neurons as experimental systems in molecular biology.

The cellular and the inter-connective complexity of the central nervous system (CNS) necessitate's analysis of functioning at both the system and single cell levels. Systems neuroscience has developed procedures that facilitate the analysis of multicellular systems including multielectrode arrays, dye tracings and lesioning assays, and at the single cell level there have been significant strides in assessing the physiology and morphology of individual cells. Until recently little progress had been made in understanding the molecular biology of single neuronal cells. This review will highlight the development of PCR and aRNA procedures for analysis of mRNA abundances in single cells. Also, other procedures for the analysis of protein abundances as well as the association of RNA with proteins will also be summarized. These procedures promise to provide experimental insights that will help unravel the functional mechanisms regulating the cellular components of the CNS.

Repetitive mild brain trauma accelerates Abeta deposition, lipid peroxidation, and cognitive impairment in a transgenic mouse model of Alzheimer amyloidosis.

Traumatic brain injury (TBI) increases susceptibility to Alzheimer's disease (AD), but it is not known how TBI contributes to the onset or progression of this common late life dementia. To address this question, we studied neuropathological and behavioral consequences of single versus repetitive mild TBI (mTBI) in transgenic (Tg) mice (Tg2576) that express mutant human Abeta precursor protein, and we demonstrate elevated brain Abeta levels and increased Abeta deposition. Nine-month-old Tg2576 and wild-type mice were subjected to single (n = 15) or repetitive (n = 39) mTBI or sham treatment (n = 37). At 2 d and 9 and 16 weeks after treatment, we assessed brain Abeta deposits and levels in addition to brain and urine isoprostanes generated by lipid peroxidation in these mice. A subset of mice also was studied behaviorally at 16 weeks after injury. Repetitive but not single mTBI increased Abeta deposition as well as levels of Abeta and isoprostanes only in Tg mice, and repetitive mTBI alone induced cognitive impairments but no motor deficits in these mice. This is the first experimental evidence linking TBI to mechanisms of AD by showing that repetitive TBI accelerates brain Abeta accumulation and oxidative stress, which we suggest could work synergistically to promote the onset or drive the progression of AD. Additional insights into the role of TBI in mechanisms of AD pathobiology could lead to strategies for reducing the risk of AD associated with previous episodes of brain trauma and for preventing progressive brain amyloidosis in AD patients.

Apolipoprotein E4 influences amyloid deposition but not cell loss after traumatic brain injury in a mouse model of Alzheimer's disease.

The epsilon4 allele of apolipoprotein E (APOE) and traumatic brain injury (TBI) are both risk factors for the development of Alzheimer's disease (AD). These factors may act synergistically, in that APOE4+ individuals are more likely to develop dementia after TBI. Because the mechanism underlying these effects is unclear, we questioned whether APOE4 and TBI interact either through effects on amyloid-beta (Abeta) or by enhancing cell death/tissue injury. We assessed the effects of TBI in PDAPP mice (transgenic mice that develop AD-like pathology) expressing human APOE3 (PDAPP:E3), human APOE4 (PDAPP:E4), or no APOE (PDAPP:E-/-). Mice were subjected to a unilateral cortical impact injury at 9-10 months of age and allowed to survive for 3 months. Abeta load, hippocampal/cortical volumes, and hippocampal CA3 cell loss were quantified using stereological methods. All of the groups contained mice with Abeta-immunoreactive deposits (56% PDAPP:E4, 20% PDAPP:E3, 75% PDAPP:E-/-), but thioflavine-S-positive Abeta (amyloid) was present only in the molecular layer of the dentate gyrus in the PDAPP:E4 mice (44%). In contrast, our previous studies showed that in the absence of TBI, PDAPP:E3 and PDAPP:E4 mice have little to no Abeta deposition at this age. After TBI, all of the Abeta deposits present in PDAPP:E3 and PDAPP:E-/- mice were diffuse plaques. In contrast to the effect of APOE4 on amyloid, PDAPP:E3, PDAPP:E4, and PDAPP:E-/- mice did not differ in the amount of brain tissue or cell loss. These data support the hypothesis that APOE4 influences the neurodegenerative cascade after TBI via an effect on Abeta.

Neuron-specific mRNA complexity responses during hippocampal apoptosis after traumatic brain injury.

In an effort to understand the complexity of genomic responses within selectively vulnerable regions after experimental brain injury, we examined whether single apoptotic neurons from both the CA3 and dentate differed from those in an uninjured brain. The mRNA from individual active caspase 3(+)/terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling [TUNEL(-)] and active caspase 3(+)/TUNEL(+) pyramidal and granule neurons in brain-injured mice were amplified and compared with those from nonlabeled neurons in uninjured brains. Gene analysis revealed that overall expression of mRNAs increased with activation of caspase 3 and decreased to below uninjured levels with TUNEL reactivity. Cell type specificity of the apoptotic response was observed with both regionally distinct expression of mRNAs and differences in those mRNAs that were maximally regulated. Immunohistochemical analysis for two of the most highly differentially expressed genes (prion and Sos2) demonstrated a correlation between the observed differential gene expression after traumatic brain injury and corresponding protein translation.

Development of posttraumatic hyperthermia after traumatic brain injury in rats is associated with increased periventricular inflammation.

Posttraumatic hyperthermia (PTH) is a noninfectious elevation in body temperature that negatively influences outcome after traumatic brain injury (TBI). We sought to (1) characterize a clinically relevant model and (2) investigate potential cellular mechanisms of PTH. In study I, body temperature patterns were analyzed for 1 week in male rats after severe lateral fluid percussion (FP) brain injury (n=75) or sham injury (n=17). After injury, 27% of surviving animals experienced PTH, while 69% experienced acute hypothermia with a slow return to baseline. A profound blunting or loss of circadian rhythmicity (CR) that persisted up to 5 days after injury was experienced by 75% of brain-injured animals. At 2 and 7 days after injury, patterns of cell loss and inflammation were assessed in selected brain thermoregulatory and circadian centers. Significant cell loss was not observed, but PTH was associated with inflammatory changes in the hypothalamic paraventricular nucleus (PVN) by one week after injury. In brain-injured animals with altered CR, reactive astrocytes were bilaterally localized in the suprachiasmatic nucleus (SCN) and the PVN. Occasional IL-1beta+/ED-1+ macrophages/microglia were observed in the PVN and SCN exclusively in brain-injured animals developing PTH. In animals with PTH there was a significant positive correlation (r=0.788, P<0.01) between the degree of postinjury hyperthermia and the total number of cells positive for inflammatory markers within selected thermoregulatory and circadian nuclei. In study II, a separate group of animals underwent the same injury and temperature monitoring paradigm as in study I, but had additional physiologic data obtained, including vital signs, arterial blood gases, white blood cell counts, and C-reactive protein levels. All parameters remained within normal ranges after injury. These data suggest that PTH and the alteration in CR of temperature may be due, in part, to acute reactive astrocytosis and inflammation in hypothalamic centers responsible for both thermoregulation and CR.

Characterization of a new rat model of experimental combined neurotrauma.

Traumatic brain injury (TBI) is present in two-thirds of patients with multiple injuries and in one-third combined with injuries of the extremities. Studies on interactive effects between central and peripheral injuries are scarce due to the absence of clinically relevant models. To meet the demand for "more-hit" models, an experimental model of combined neurotrauma (CNT) incorporating a standardized TBI via lateral fluid percussion (LFP) together with a peripheral bone fracture, i.e., tibia fracture, is introduced. Sprague-Dawley rats were randomized to four experimental groups: controls (n = 10), animals with TBI (n = 30), animals with tibia fracture (n = 30), and animals with CNT (n = 30). Morphological aspects of brain and bone injury were analyzed via standard histopathological procedures and x-ray. Trauma-induced neuromotor dysfunction was assessed using a standardized neuroscore. For interactive effects between injuries, we studied the extent and temporal pattern of circulating interleukin 6 (IL-6) levels via immunoassay and callus formation at fracture sites by means of microradiography. LFP produced an ipsilateral lesion with cortical contusion, hemorrhage, mass shift, and neuronal cell loss (adjacent cortex and hippocampus CA-2/-3), along with contralateral neuromotor dysfunction. X-rays confirmed complete fractures in the middle of the bone shaft. The type of injury (P < 0.001) and time (P = 0.022) were significantly associated with increased IL-6 levels. CNT produced the highest IL-6 plasma levels with a maximum peak at 6 h after trauma (P < 0.001). Similarly, callus formation at fracture sites in CNT was significantly increased versus fracture only (P < 0,01). The CNT model mimics a variety of clinically relevant features known from human multiple injury, including TBI, and offers novel approaches for investigation of interactive mechanisms and therapeutic approaches.