Penetrating Ballistic-like Brain Injury Research Articles

The Acute Effects of Hemorrhagic Shock on Cerebral Blood Flow, Brain Tissue Oxygen Tension, and Spreading Depolarization following Penetrating Ballistic-Like Brain Injury

Traumatic brain injury (TBI) often occurs in conjunction with additional trauma, resulting in secondary complications, such as hypotension as a result of blood loss. This study investigated the combined effects of penetrating ballistic-like brain injury (PBBI) and hemorrhagic shock (HS) on physiological parameters, including acute changes in regional cerebral blood flow (rCBF), brain tissue oxygen tension (P(bt)O₂), and cortical spreading depolarizations (CSDs). All recordings were initiated before injury (PBBI/HS/both) and maintained for 2.5 h. Results showed that PBBI alone and combined PBBI and HS produced a sustained impairment of ipsilateral rCBF that decreased by 70% from baseline (p<0.05). Significant and sustained reductions in P(bt)O₂ (50% baseline; p<0.05) were also observed in the injured hemisphere of the animals subjected to both PBBI and HS (PBBI+HS). In contrast, PBBI alone produced smaller, more transient reductions in P(bt)O₂ levels. The lower limit of cerebral autoregulation was significantly higher in the PBBI+HS group (p<0.05, compared to HS alone). Critically, combined injury resulted in twice the number of spontaneous CSDs as in PBBI alone (p<0.05). It also lowered the propagation speed of CSD and the threshold of CSD occurrence [induced CSD at higher mean arterial pressure (MAP)]. However, rCBF and P(bt)O₂ were not responsive to the depolarizations. Our data suggest that PBBI together with HS causes persistent impairment of CBF and brain tissue oxygen tension, increasing the probability of CSDs that likely contribute to secondary neuropathology and compromise neurological recovery.

Biomarkers Track Damage after Graded Injury Severity in a Rat Model of Penetrating Brain Injury

The goal of this project was to determine whether biochemical markers of brain damage can be used to diagnose and assess the severity of injury in a rat model of penetrating ballistic-like brain injury (PBBI). To determine the relationship between injury magnitude and biomarker levels, rats underwent three discrete PBBI severity levels defined by the magnitude of the ballistic component of the injury, calibrated to equal 5%, 10%, or 12.5% of total rat brain volume. Cortex, cerebrospinal fluid (CSF), and blood were collected at multiple time points. Levels of three biomarkers (αII-spectrin breakdown product [SBDP150], glial fibrillary acidic protein [GFAP], and ubiquitin C-terminal hydrolase-L1 [UCH-L1]), were measured using quantitative immunoblotting and/or enzyme-linked immunosorbent assays. In injured cortex, SBDP150 and GFAP levels were increased significantly over controls. Cortical SBDP150 was elevated at 1 day but not 7 days, and GFAP at 7 days but not 1 day. At their respective time points, mean levels of SBDP150 and GFAP biomarkers in the cortex rose stepwise as injury magnitude increased. In the CSF, increasing severity of PBBI was associated with increasing concentrations of both neuronal and glial biomarkers acutely at 1 day after injury, but no trends were observed at 7 days. In plasma, SBDP150 was elevated at 5 min after 10% PBBI and at 6 h after 12.5% PBBI. UCH-L1 levels in plasma were elevated acutely at 5 min post-injury reflecting injury severity and rapidly decreased within 2 h. Overall, our results support the conclusion that biomarkers are effective indicators of brain damage after PBBI and may also aid in the assessment of injury magnitude.

Mechanism of Action for NNZ-2566 Anti-inflammatory Effects Following PBBI Involves Upregulation of Immunomodulator ATF3

The tripeptide glycine-proline-glutamate analogue NNZ-2566 (Neuren Pharmaceuticals) demonstrates neuroprotective efficacy in models of traumatic brain injury. In penetrating ballistic-like brain injury (PBBI), it significantly decreases injury-induced upregulation of inflammatory cytokines including TNF-α, IFN-γ, and IL-6. However, the mechanism by which NNZ-2566 acts has yet to be determined. The activating transcription factor-3 (ATF3) is known to repress expression of these inflammatory cytokines and was increased at the mRNA and protein level 24-h post-PBBI. This study investigated whether 12 h of NNZ-2566 treatment following PBBI alters atf3 expression. PBBI alone significantly increased atf3 mRNA levels by 13-fold at 12 h and these levels were increased by an additional fourfold with NNZ-2566 treatment. To confirm that changes in mRNA translated to changes in protein expression, ATF3 expression levels were determined in vivo in microglia/macrophages, T cells, natural killer cells (NKCs), astrocytes, and neurons. PBBI alone significantly increased ATF3 in microglia/macrophages (820%), NKCs (58%), and astrocytes (51%), but decreased levels in T cells (48%). NNZ-2566 treatment further increased ATF3 protein expression in microglia/macrophages (102%), NKCs (308%), and astrocytes (13%), while reversing ATF3 decreases in T cells. Finally, PBBI increased ATF3 levels by 55% in neurons and NNZ-2566 treatment further increased these levels an additional 33%. Since increased ATF3 may be an innate protective mechanism to limit inflammation following injury, these results demonstrating that the anti-inflammatory and neuroprotective drug NNZ-2566 increase both mRNA and protein levels of ATF3 in multiple cell types provide a cellular mechanism for NNZ-2566 modulation of neuroinflammation following PBBI.

Similarities and Differences of Acute Nonconvulsive Seizures and Other Epileptic Activities following Penetrating and Ischemic Brain Injuries in Rats

The similarities and differences between acute nonconvulsive seizures (NCS) and other epileptic events, for example, periodic epileptiform discharges (PED) and intermittent rhythmic delta activities (IRDA), were characterized in rat models of penetrating and ischemic brain injuries. The NCS were spontaneously induced by either unilateral frontal penetrating ballistic-like brain injury (PBBI) or permanent middle cerebral artery occlusion (pMCAO), and were detected by continuous electroencephalogram (EEG) monitoring begun immediately after the injury and continued for 72 h or 24 h, respectively. Analysis of NCS profiles (incidence, frequency, duration, and time distribution) revealed a high NCS incidence in both injury models. The EEG waveform expressions of NCS and PED exhibited intrinsic variations that resembled human electrographic manifestations of post-traumatic and post-ischemic ictal and inter-ictal events, but these waveform variations were not distinguishable between the two types of brain injury. However, the NCS after pMCAO occurred more acutely and intensely (latency=0.6 h, frequency=25 episodes/rat) compared with the PBBI-induced NCS (latency=24 h, frequency=10 episodes/rat), such that the most salient features differentiating post-traumatic and post-ischemic NCS were the intensity and time distribution of the NCS profiles. After pMCAO, nearly 50% of the seizures occurred within the first 2 h of injury, whereas after PBBI, NCS occurred sporadically (0-5%/h) throughout the 72 h recording period. The PED were episodically associated with NCS. By contrast, the IRDA appeared to be independent of other epileptic events. This study provided comprehensive comparisons of post-traumatic and post-ischemic epileptic profiles. The identification of the similarities and differences across a broad spectrum of epileptic events may lead to differential strategies for post-traumatic and post-stroke seizure interventions.

Proteomic analysis and brain‐specific systems biology in a rodent model of penetrating ballistic‐like brain injury

Proteomics and systems biology have significantly contributed to biomarker discovery in the field of brain injury. This study utilized 2D-DIGE-PMF-MS as a preliminary screen to detect biomarkers in a rat model of penetrating ballistic-like brain injury (PBBI). Brain-specific systems biology analysis of brain tissue identified 386 proteins having a fold change of more than 2, of which 321 proteins were increased and 65 were decreased 24 h after PBBI compared to sham controls. The majority of upregulated proteins were cytoskeletal (10.5%), nucleic acid binding (9.3%), or kinases (8.9%). Most proteins were involved in protein metabolism (22.7%), signal transduction (20.4%), and development (9.6%). Pathway analysis indicated that these proteins were involved in neurite outgrowth and cell differentiation. Semiquantitative Western blotting of 6, 24, 48, and 72 h after PBBI indicated ubiquitin carboxyl-terminal hydrolase isozyme L1 (a proposed traumatic brain injury biomarker in human clinical trials), tyrosine hydroxylase, and syntaxin-6 were found to be consistently elevated in brain tissue and cerebral spinal fluid after PBBI compared to sham controls. Combining proteomics and brain-specific systems biology can define underlying mechanisms of traumatic brain injury and provide valuable information in biomarker discovery that, in turn, may lead to novel therapeutic targets.

Longitudinal assessment of gait abnormalities following penetrating ballistic-like brain injury in rats

Traumatic brain injury (TBI) results in enduring motor and cognitive dysfunction. Although gait disturbances have been documented among TBI patients, few studies have profiled gait abnormalities in animal models of TBI. We sought to obtain a comprehensive longitudinal analysis of gait function following severe penetrating ballistic-like brain injury (PBBI) in rats. Rats were subjected to either unilateral frontal PBBI, probe insertion alone, or sham surgery. Sensorimotor performance was assessed using the CatWalk automated gait analysis system. Baseline measurements were taken 3 days prior to injury and detailed analysis of gait was performed at 1, 3, 7, 14, and 28 days post-injury. Both PBBI and probe-inserted rats displayed altered static and dynamic gait parameters that were primarily evident during the early (<7 days) post-injury phase and were resolved by 1 month post-injury. PBBI produced more severe deficits compared to probe-alone which were reflected in the number, magnitude, and resolution time of abnormal gait parameters. While altered parameters were detected in all four paws, they were more apparent on the contralateral side. Gait parameters including paw pressure, print area, swing speed, and stride length were significantly decreased whereas stance, swing, and step cycle duration were increased compared to sham. Overall, altered gait patterns detected using the CatWalk system in the PBBI model were injury-severity dependent, resolved at later time points, and appeared similar to those reported in severe TBI patients. These results indicate that the CatWalk may be most useful for neuroprotection studies that focus on the acute/subacute recovery period after TBI.

Long-term administration of amnion-derived cellular cytokine suspension promotes functional recovery in a model of penetrating ballistic-like brain injury

Previous work has shown that human amnion-derived progenitor (AMP) cell therapy is neuroprotective in a penetrating ballistic-like brain injury (PBBI) model. However, the neuroprotective capacity of AMP cells seemed to be mediated by the sustained secretion of AMP cell-derived neurotrophic factors, which are abundant in the amnion-derived cellular cytokine suspension (ACCS). To test this theory, the current study assessed the neuroprotective efficacy of long-term ACCS delivery in the PBBI model. Experiment 1 assessed the bioactive stability and neuroprotective capacity of ACCS in an in vitro model of neurodegeneration. Experiment 2 evaluated the therapeutic effects of ACCS delivery initiated 15 minutes after PBBI and continued for 2 weeks after injury. Experiment 3 was designed to identify the therapeutic window for long-term ACCS delivery in the PBBI model. Outcome metrics included neurobehavioral assessments and neuropathologic measures of neuroinflammation and axonal/neuronal degeneration. Experiment 1 demonstrated that ACCS is thermally stable for 1 week at 37°C and that ACCS treatment protected neurite against staurosporine toxicity. Experiment 2 identified the optimal infusion rate of ACCS (1 μL/h) and demonstrated that long-term infusion of ACCS was capable of promoting significant protection against PBBI-induced neuropathology and motor abnormalities, but was not sufficient for reducing cognitive deficits. Finally, the results of Experiment 3 showed that ACCS is effective in promoting significant neuroprotection even when onset of treatment is delayed out to 24 hours (but not 48 hours) after PBBI. Collectively, our results support the hypothesis that the neuroprotective effects of AMP cells are mediated through a sustained delivery of ACCS, which implicates ACCS as a promising neuroprotection agent for clinical study.

Changes in Apoptotic Mechanisms Following Penetrating Ballistic-Like Brain Injury

We investigated apoptotic pathways in a model of severe traumatic brain injury, penetrating ballistic-like brain injury (PBBI). TUNEL staining identified increasing apoptosis within 24 h. From targeted arrays, 11 genes were identified for temporal mRNA evaluation. In addition, mRNA levels and enzyme activity for caspases 3, 8, and 9 were examined. In the death receptor-mediated apoptosis pathway, the relative quantities (RQs) of mRNA for tnfr1, fas, and tnf were upregulated while trail mRNA was downregulated. In the anti-apoptotic TNF-R2 pathway, tnfr2 and flip were upregulated while xiap was downregulated. These findings indicate that increases in tnf levels following injury are not only pro-apoptotic but may also signal competing anti-apoptotic mechanisms. For the mitochondria-mediated apoptosis pathway, RQs of anti-apoptotic factors bcl2a1d and birc3 were upregulated while both bcl2 and bax were downregulated. RQs for casp 3 and casp 8 increased while casp9 decreased. Enzymatic activity increased for caspases 3, 8, and 9. While multiple mechanisms promoting and inhibiting apoptosis are at play during the first week after a PBBI, the cumulative result remains increased apoptosis. The ability to understand and dissect these events will assist in the development and evaluation of treatments targeting apoptosis following severe brain injury.

Brain oxygen tension monitoring following penetrating ballistic-like brain injury in rats

While brain oxygen tension (PbtO2) monitoring is an important parameter for evaluating injury severity and therapeutic efficiency in severe traumatic brain injury (TBI) patients, many factors affect the monitoring. The goal of this study was to identify the effects of FiO2 (fraction of inspired oxygen) on PbtO2 in uninjured anesthetized rats and measure the changes in PbtO2 following penetrating ballistic-like brain injury (PBBI). Continuous PbtO2 monitoring in uninjured anesthetized rats showed that PbtO2 response was positively correlated with FiO2 (0.21–0.35) but PbtO2 remained stable when FiO2 was maintained at ∼0.26. Importantly, although increasing FiO2 from 0.21 to 0.35 improved PaO2, it concomitantly reduced pH levels and elevated PaCO2 values out of the normal range. However, when the FiO2 was maintained between 0.26 and 0.30, the pH and PaO2 levels remained within the normal or clinically acceptable range. In PBBI rats, PbtO2 was significantly reduced by ∼40% (16.9±1.2mmHg) in the peri-lesional region immediately following unilateral, frontal 10% PBBI compared to sham rats (28.6±1.7mmHg; mean±SEM, p<0.05) and the PBBI-induced reductions in PbtO2 were sustained for at least 150min post-PBBI. Collectively, these results demonstrate that FiO2 affects PbtO2 and that PBBI produces acute and sustained hypoxia in the peri-lesional region of the brain injury. This study provides important information for the management of PbtO2 monitoring in this brain injury model and may offer insight for therapeutic strategies targeted to improve the hypoxia/ischemia state in the penetrating-type brain injury.

Severity Profile of Penetrating Ballistic-Like Brain Injury on Neurofunctional Outcome, Blood–Brain Barrier Permeability, and Brain Edema Formation

This study evaluated the injury severity profile of unilateral, frontal penetrating ballistic-like brain injury (PBBI) on neurofunctional outcome, blood-brain barrier (BBB) permeability, and brain edema formation. The degree of injury severity was determined by the delivery of a water-pressure pulse designed to produce a temporary cavity by rapid (<40 ms) expansion of the probe's elastic balloon calibrated to equal 5%, 10%, 12.5%, or 15% of total rat brain volume (control groups consisted of sham surgery or insertion of the probe only). Neurofunctional assessments revealed motor and cognitive deficits related to the degree of injury severity, with the most clear-cut profile of PBBI injury severity depicted by the Morris water maze (MWM) results. A biphasic pattern of BBB leakage was detected in the injured hemisphere at all injury severity levels at 4 h post-injury, and again at 48-72 h post-injury, which remained evident out to 7 days post-PBBI in the 10% and 12.5% PBBI groups. Likewise, significant brain edema was detected in the injured hemisphere by 4 h post-injury and remained elevated out to 7 days post-injury in the 10% and 12.5% PBBI groups. However, following 5% PBBI, significant levels of edema were only detected from 24 h to 48h post-injury. These results identify an injury severity profile of BBB permeability, brain edema, and neurofunctional impairment that provides sensitive and clinically relevant outcome metrics for studying potential therapeutics.

Selective Brain Cooling in Rats Ameliorates Intracerebral Hemorrhage and Edema Caused by Penetrating Brain Injury: Possible Involvement of Heme Oxygenase-1 Expression

Brain edema formation associated with trauma-induced intracerebral hemorrhage (ICH) is a clinical complication with high mortality. Studies have shown that heme oxygenase-1 (HO-1) plays an important role in ICH-induced brain edema. In order to understand the role of HO-1 in the protective effect of selective brain cooling (SBC), we investigated the time course of HO-1 changes following penetrating ballistic-like brain injury (PBBI) in rats. Samples were collected from injured and control animals at 6, 24, 48, and 72 h, and 7 days post-injury to evaluate HO-1 expression, heme concentration, brain water content, and immunohistochemistry (IHC). Following a 10% frontal PBBI, HO-1 mRNA and protein was increased at all time points studied, reaching maximum expression levels at 24-48 h post-injury. An increase in the heme concentration and the development of brain edema coincided with the upregulation of HO-1 mRNA and protein during the 7-day post-injury period. SBC significantly decreased PBBI-induced heme concentration, attenuated HO-1 upregulation, and concomitantly reduced brain water content. These results suggest that the neuroprotective effects of SBC may be partially mediated by reducing the heme accumulation, which reduced injury-mediated upregulation of HO-1, and in turn ameliorated edema formation. Collectively, these results suggest a potential value of HO-1 as a diagnostic and/or therapeutic biomarker in hemorrhagic brain injury.

Changes in Apoptotic Mechanisms Following Penetrating Ballistic‐like Brain Injury

Following penetrating ballistic‐like brain injury (PBBI), we examined 84 genes known to be involved in apoptosis. Enzyme activity for Caspases 3, 8, and 9 was also examined. PCR arrays (n=2) were done using pooled RNA from sham or PBBI rats collected 4 h post‐injury. In death receptor mediated apoptosis the mean relative quantity (RQ) of RNA for tnf increased &gt; 5 fold but did not reach significance (p=0.13). In contrast, RQs for fas and trail were significantly decreased (p&lt;0.05). There were no significant changes in RQs for casp8 or casp3; however, significant increases in enzymatic activity were measured for both (p&lt;0.001). In the anti‐apoptotic TNF‐R2 pathway we found significant increases in RQs for tnfr2 and flip (p&lt;0.001), indicating that TNF may mediate both pro‐ and anti‐apoptotic pathways following this brain injury. For mitochondria mediated apoptosis RQ increased &gt; 3 fold for the anti‐apoptotic gene birc 3 but did not reach significance (p=0.11). There were no changes in RQs for p53 or bcl2, but a significant decrease in bax RQ was measured (p&lt;0.05), possibly due to compensatory mechanisms following changes in either quantity of Bax protein or translocation of Bax to mitochondria. There was no change in RQ for casp9, but enzymatic activity was significantly increased post‐PBBI (p&lt;0.001). These data indicate that within 4 hours of a PBBI injury multiple mechanisms promoting and inhibiting apoptosis are at play.

Injury Severity Profile of Penetrating Ballistic-Like Brain Injury in Rats on Neurofunctional Outcome, Blood-Brain Barrier Permeability, and Brain Edema Formation

This study evaluated the injury severity profile of penetrating ballistic-like brain injury (PBBI) on neurofunctional outcome, blood-brain barrier (BBB) permeability, and brain edema formation. Ane...

Neuroprotection of Selective Brain Cooling After Penetrating Ballistic-like Brain Injury in Rats

Induced hypothermia has been reported to provide neuroprotection against traumatic brain injury. We recently developed a novel method of selective brain cooling (SBC) and demonstrated its safety and neuroprotection efficacy in a rat model of ischemic brain injury. The primary focus of the current study was to evaluate the potential neuroprotective efficacy of SBC in a rat model of penetrating ballistic-like brain injury (PBBI) with a particular focus on the acute cerebral pathophysiology, neurofunction, and cognition. SBC (34°C) was induced immediately after PBBI, and maintained for 2 hours, followed by a spontaneous re-warming. Intracranial pressure (ICP) and regional cerebral blood flow were monitored continuously for 3 hours, and the ICP was measured again at 24 hours postinjury. Brain swelling, blood-brain barrier permeability, intracerebral hemorrhage, lesion size, and neurological status were assessed at 24 hours postinjury. Cognitive abilities were evaluated in a Morris water maze task at 12-16 days postinjury. Results showed that SBC significantly attenuated PBBI-induced elevation of ICP (PBBI = 33.2 ± 10.4; PBBI + SBC = 18.8 ± 6.7 mmHg) and reduced brain swelling, blood-brain barrier leakage, intracerebral hemorrhage, and lesion volume by 40%-45% for each matrix, and significantly improved neurologic function. However, these acute neuroprotective benefits of SBC did not translate into improved cognitive performance in the Morris water maze task. These results indicate that 34°C SBC is effective in protecting against acute brain damage and related neurological dysfunction. Further studies are required to establish the optimal treatment conditions (i.e., duration of cooling and/or combined therapeutic approaches) needed to achieve significant neurocognitive benefits.

Electrocortical Pathology in a Rat Model of Penetrating Ballistic-Like Brain Injury

Traumatic brain injury (TBI) causes severe disruption of cerebral electrical activity and electroencephalography (EEG) is emerging as a standard tool to monitor TBI patients in the acute period of risk for secondary injuries. However, animal studies of EEG pathology in the context of TBI are surprisingly sparse, largely because of the lack of real-time continuous EEG (cEEG) monitoring in animal TBI models. Here, we performed long-term EEG monitoring to study nonconvulsive seizures (NCS), periodic epileptiform discharges (PED), and EEG power spectra following three injury severity levels in a rat model of penetrating ballistic-like brain injury (PBBI). EEG signals were recorded continuously from bilateral hemispheres of freely behaving rats for 72 h and for 2 h on days 7 and 14 after the injury. We report that the incidence of NCS and PED positively correlated with the injury severity, where 13%, 39%, and 59% of the animals exhibited NCS, and 0%, 30%, and 65% of the animals exhibited PED following 5%, 10% and 12.5% PBBI, respectively. Similar correlations existed for the number of NCS and PED events and their duration. NCS and PED occurred either independently or in tandem. Longer NCS durations were associated with larger lesion volumes. Significant EEG slowing evidenced by the EEG power shift toward the δ frequency band (0.5-4 Hz) occurred within 2 h after PBBI, which resolved over time but persisted longer after greater injury severity. In contrast, decreases in higher frequency power (i.e., 30-35 Hz) remained depressed throughout 14 days. This is the first long-term cEEG study of the acute injury phase in a rat model of severe TBI, demonstrating common occurrences of clinically observed electrocortical pathology, such as NCS, PED, and cortical slowing. These EEG pathologies may serve as critical care biomarkers of brain injury, and offer clinically relevant metrics for studying acute therapeutic interventions.

Synergism of human amnion-derived multipotent progenitor (AMP) cells and a collagen scaffold in promoting brain wound recovery: Pre-clinical studies in an experimental model of penetrating ballistic-like brain injury

One of the histopathological consequences of a penetrating ballistic brain injury is the formation of a permanent cavity. In a previous study using the penetrating ballistic-like brain injury (PBBI) model, engrafted human amnion-derived multipotent progenitor (AMP) cells failed to survive when injected directly in the injury tract, suggesting that the cell survival requires a supportive matrix. In this study, we seated AMP cells in a collagen-based scaffold, injected into the injury core, and investigated cell survival and neuroprotection following PBBI. AMP cells suspended in AMP cell conditioned medium (ACCS) or in a liquefied collagen matrix were injected immediately after a PBBI along the penetrating injury tract. Injured control rats received only liquefied collagen matrix. All animals were allowed to survive two weeks. Consistent with our previous results, AMP cells suspended in ACCS failed to survive; likewise, no collagen was identified at the injury site when injected alone. In contrast, both AMP cells and the collagen were preserved in the injury cavity when injected together. In addition, AMP cells/collagen treatment preserved some apparent brain tissue in the injury cavity, and there was measurable infiltration of endogenous neural progenitor cells and astrocytes into the preserved brain tissue. AMP cells were also found to have migrated into the subventricular zone and the corpus callosum. Moreover, the AMP cell/collagen treatment significantly attenuated the PBBI-induced axonal degeneration in the corpus callosum and ipsilateral thalamus and improved motor impairment on rotarod performance. Overall, collagen-based scaffold provided a supportive matrix for AMP cell survival, migration, and neuroprotection.

Longitudinal Characterization of Motor and Cognitive Deficits in a Model of Penetrating Ballistic-Like Brain Injury

Traumatic brain injury (TBI) produces a wide range of motor and cognitive changes. While some neurological symptoms may respond to therapeutic intervention during the initial recovery period, others may persist for many years after the initial insult, and often have a devastating impact on quality of life for the TBI victim. The aim of the current study was to develop neurobehavioral testing parameters designed to provide a longitudinal assessment of neurofunctional deficits in a rodent model of penetrating ballistic-like brain injury (PBBI). We report here a series of experiments in which unilateral frontal PBBI was induced in rats, and motor/cognitive abilities were assessed using a battery of tests ranging from 30 min to 10 weeks post-injury. The results showed that PBBI produced consistent and significant (1) neurological deficits (neuroscore examination: 30 min to 10 weeks post-PBBI), (2) sensorimotor dysfunction in the contralateral forelimb (forelimb asymmetry task: 7 and 21 days), (3) motor dysfunction (balance beam task: 3-7 days; and fixed-speed rotarod task: 3-28 days), and (4) spatial learning deficits in the Morris water maze (MWM) task out to 10 weeks post-injury. Overall, the results of this study demonstrate that PBBI produces enduring motor and cognitive deficits, and identifies the optimal task and testing parameters for facilitating longitudinal screening of promising therapeutic interventions in this brain injury model.

Intracranial Pressure following Penetrating Ballistic-Like Brain Injury in Rats

Penetrating ballistic brain injury involves a leading shockwave producing a temporary cavity causing substantial secondary injury. In response to the prevalence of this type of brain trauma in the military, a rat model of penetrating ballistic-like brain injury (PBBI) was established. This study focuses on cerebral physiological responses resulting from a PBBI, specifically the immediate and delayed changes in intracranial pressure (ICP) and cerebral perfusion pressure (CPP). ICP/CPP was measured continuously in rats subjected to PBBI, probe insertion alone, or sham injury. Immediately following the PBBI, a transient (<0.1 sec) and dramatic elevation of ICP reaching 280.0 ± 86.0 mm Hg occurred, accompanied by a profound decrease in CPP to -180.2 ± 90.1 mm Hg. This emergent ICP/CPP response resolved spontaneously within seconds, but was followed by a slowly-developing and sustained secondary phase, which peaked at 24 h post-injury, reaching 37.2 ± 10.4 mm Hg, and remained elevated until 72 h post-injury. The measured decrease in CPP reached 85.3 ± 17.2 mm Hg at 3 h post-injury. By comparison, probe insertion alone did not produce the immediate ICP crisis (28.6 ± 9.1 mm Hg), and only a mild and sustained increase in ICP (13.5 ± 2.1 mm Hg) was observed in the following 3 h post-injury. Injury severity, as measured by lesion volume, brain swelling, and neurological deficits at 1, 3, and 7 days post-injury, also reflected the distinctive differences between the dynamics of the PBBI versus controls. These results not only reinforced the severe nature of this model in mimicking the ballistic effect of PBBI, but also established cerebral pathophysiological targets for neuroprotective therapies.

A comparison of two cognitive test paradigms in a penetrating brain injury model

A rat model of penetrating ballistic-like brain injury (PBBI) was recently established to study military-relevant severe traumatic brain injury (TBI). The purpose of this study was to conduct a side-by-side evaluation of two well-established cognitive testing paradigms: the novel object recognition (NOR) task and the Morris water maze (MWM) task. Accordingly, male Sprague–Dawley rats were subjected to PBBI and their cognitive abilities were assessed at 7 and 21 days post-PBBI. Although PBBI animals had more difficulty completing both tasks compared to sham animals, their performance on the NOR task was confounded by a high degree of within-group variability that was likely due to attention deficits produced by the injury. In contrast, PBBI produced consistent, significant spatial learning deficits in the MWM task. Overall, these results suggest that the MWM task provides a more appropriate cognitive test for the PBBI model that would be useful for testing promising neuroprotective therapeutics.

Human Amnion-Derived Multipotent Progenitor Cell Treatment Alleviates Traumatic Brain Injury-Induced Axonal Degeneration

To identify a viable cell source with potential neuroprotective effects, we studied amnion-derived multipotent progenitor (AMP) cells in a rat model of penetrating ballistic-like brain injury (PBBI). AMP cells were labeled with fluorescent dye PKH26 and injected in rats immediately following right hemispheric PBBI or sham PBBI surgery by ipsilateral i.c.v. administration. At 2 weeks post-injury, severe necrosis developed along the PBBI tract and axonal degeneration was prominent along the corpus callosum (cc) and in the ipsilateral thalamus. Injected AMP cells first entered the subventricular zone (SVZ) in both sham and PBBI rats. Further AMP cell migration along the cc only occurred in PBBI animals. No significant difference in injury volume was observed across all treatment groups. In contrast, treatment with AMP cells significantly attenuated axonal degeneration in both the thalamus and the cc. Interestingly, PKH26-labeled AMP cells were detected only in the SVZ and the cc (in parallel with the axonal degeneration), but not in the thalamus. None of the labeled AMP cells appeared to express neural differentiation, as evidenced by the lack of double labeling with nestin, S-100, GFAP, and MAP-2 immunostaining. In conclusion, AMP cell migration was specifically induced by PBBI and requires SVZ homing, yet the neuroprotective effect of intracerebral ventrical treatment using AMP cells was not limited to the area where the cells were present. This suggests that the attenuation of the secondary brain injury following PBBI was likely to be mediated by mechanisms other than cell replacement, possibly through delivery or sustained secretion of neurotrophic factors.