Traumatic Brain Injury Animals Research Articles

Senolytic therapy is neuroprotective and improves functional outcome long-term after traumatic brain injury in mice.

Chronic neuroinflammation can exist for months to years following traumatic brain injury (TBI), although the underlying mechanisms remain poorly understood. In the current study, we used a controlled cortical impact mouse model of TBI to examine whether proinflammatory senescent cells are present in the brain long-term (months) after TBI and whether ablation of these cells via administration of senolytic drugs can improve long-term functional outcome after TBI. The results revealed that astrocytes and microglia in the cerebral cortex, hippocampus, corpus callosum and lateral posterior thalamus colocalized the senescent cell markers, p16Ink4a or p21Cip1/Waf1 at 5 weeks post injury (5wpi) and 4 months post injury (4mpi) in a controlled cortical impact (CCI) model. Intermittent administration of the senolytic drugs, dasatinib and quercetin (D + Q) beginning 1-month after TBI for 13 weeks significantly ablated p16Ink4a-positive- and p21Cip1/Waf1-positive-cells in the brain of TBI animals, and significantly reduced expression of the major senescence-associated secretory phenotype (SASP) pro-inflammatory factors, interleukin-1β and interleukin-6. Senolytic treatment also significantly attenuated neurodegeneration and enhanced neuron number at 18 weeks after TBI in the ipsilateral cortex, hippocampus, and lateral posterior thalamus. Behavioral testing at 18 weeks after TBI further revealed that senolytic therapy significantly rescued defects in spatial reference memory and recognition memory, as well as depression-like behavior in TBI mice. Taken as a whole, these findings indicate there is robust and widespread induction of senescent cells in the brain long-term after TBI, and that senolytic drug treatment begun 1-month after TBI can efficiently ablate the senescent cells, reduce expression of proinflammatory SASP factors, reduce neurodegeneration, and rescue defects in reference memory, recognition memory, and depressive behavior.

Models of traumatic brain injury-highlights and drawbacks.

Traumatic brain injury (TBI) is the leading cause for high morbidity and mortality rates in young adults, survivors may suffer from long-term physical, cognitive, and/or psychological disorders. Establishing better models of TBI would further our understanding of the pathophysiology of TBI and develop new potential treatments. A multitude of animal TBI models have been used to replicate the various aspects of human TBI. Although numerous experimental neuroprotective strategies were identified to be effective in animal models, a majority of strategies have failed in phase II or phase III clinical trials. This failure in clinical translation highlights the necessity of revisiting the current status of animal models of TBI and therapeutic strategies. In this review, we elucidate approaches for the generation of animal models and cell models of TBI and summarize their strengths and limitations with the aim of exploring clinically meaningful neuroprotective strategies.

Potential Biomarkers in Experimental Animal Models for Traumatic Brain Injury.

Traumatic brain injury (TBI) is a complex and multifaceted disorder that has become a significant public health concern worldwide due to its contribution to mortality and morbidity. This condition encompasses a spectrum of injuries, including axonal damage, contusions, edema, and hemorrhage. Unfortunately, specific effective therapeutic interventions to improve patient outcomes following TBI are currently lacking. Various experimental animal models have been developed to mimic TBI and evaluate potential therapeutic agents to address this issue. These models are designed to recapitulate different biomarkers and mechanisms involved in TBI. However, due to the heterogeneous nature of clinical TBI, no single experimental animal model can effectively mimic all aspects of human TBI. Accurate emulation of clinical TBI mechanisms is also tricky due to ethical considerations. Therefore, the continued study of TBI mechanisms and biomarkers, of the duration and severity of brain injury, treatment strategies, and animal model optimization is necessary. This review focuses on the pathophysiology of TBI, available experimental TBI animal models, and the range of biomarkers and detection methods for TBI. Overall, this review highlights the need for further research to improve patient outcomes and reduce the global burden of TBI.

P.121 Memantine inhibits cortical spreading depolarization and improves neurovascular function following traumatic brain injury: results of a randomized pre-clinical trial

Background: Cortical spreading depolarization (CSD) is associated with poor outcomes following traumatic brain injury (TBI). Here we aimed to: (1) determine the effect of NMDA-receptor antagonism on CSDs in healthy and TBI animals in vivo; and (2) conduct a randomized pre-clinical trial (RCT) of memantine for prevention neurological decline following repetitive mild TBI (rmTBI). Methods: Rodents received either one moderate (n = 23) or four daily mild (rmTBI; n = 30) head impacts (weight drop). Sham animals received brief anesthetic without TBI (n = 40). 93 animals underwent cranial window surgery with electrocorticographic (ECoG) monitoring and electrically triggered CSDs. Ketamine (100uM topical or 25 mg/kg IP) and memantine (10 mg/kg IP) were tested in vivo. An RCT was conducted (N=31) using memantine (10 mg/kg) or saline (2.5 cc/kg) for rmTBI with daily neurobehavioural testing. Results: In TBI animals, ketamine or memantine inhibited CSDs in 44-88%, and 50-67% of cases, respectively. Near-DC/AC-ECoG amplitude was reduced by 44-75% and 52-67%, and duration by 39-87% and 61-78%, respectively. RCT animals that received memantine had higher mean neurological scores (9.27 (SD 3.08) vs. 5.56 (SD 3.05), p< 0.001) vs. saline. Conclusions: Memantine suppressed CSDs following TBI, in vivo. In a pre-clinical RCT of rmTBI, memantine prevented neurological decline.

Dietary (Poly)phenols in Traumatic Brain Injury.

Traumatic brain injury (TBI) remains one of the leading causes of death and disability in young adults worldwide. Despite growing evidence and advances in our knowledge regarding the multifaceted pathophysiology of TBI, the underlying mechanisms, though, are still to be fully elucidated. Whereas initial brain insult involves acute and irreversible primary damage to the brain, the processes of subsequent secondary brain injury progress gradually over months to years, providing a window of opportunity for therapeutic interventions. To date, extensive research has been focused on the identification of druggable targets involved in these processes. Despite several decades of successful pre-clinical studies and very promising results, when transferred to clinics, these drugs showed, at best, modest beneficial effects, but more often, an absence of effects or even very harsh side effects in TBI patients. This reality has highlighted the need for novel approaches that will be able to respond to the complexity of the TBI and tackle TBI pathological processes on multiple levels. Recent evidence strongly indicates that nutritional interventions may provide a unique opportunity to enhance the repair processes after TBI. Dietary (poly)phenols, a big class of compounds abundantly found in fruits and vegetables, have emerged in the past few years as promising agents to be used in TBI settings due to their proven pleiotropic effects. Here, we give an overview of the pathophysiology of TBI and the underlying molecular mechanisms, followed by a state-of-the-art summary of the studies that have evaluated the efficacy of (poly)phenols administration to decrease TBI-associated damage in various animal TBI models and in a limited number of clinical trials. The current limitations on our knowledge concerning (poly)phenol effects in TBI in the pre-clinical studies are also discussed.

Mesenchymal stem cell-derived extracellular vesicles therapy in traumatic central nervous system diseases: a systematic review and meta-analysis.

Although there are challenges in treating traumatic central nervous system diseases, mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have recently proven to be a promising non-cellular therapy. We comprehensively evaluated the efficacy of mesenchymal stem cell-derived extracellular vesicles in traumatic central nervous system diseases in this meta-analysis based on preclinical studies. Our meta-analysis was registered at PROSPERO (CRD42022327904, May 24, 2022). To fully retrieve the most relevant articles, the following databases were thoroughly searched: PubMed, Web of Science, The Cochrane Library, and Ovid-Embase (up to April 1, 2022). The included studies were preclinical studies of mesenchymal stem cell-derived extracellular vesicles for traumatic central nervous system diseases. The Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE)'s risk of bias tool was used to examine the risk of publication bias in animal studies. After screening 2347 studies, 60 studies were included in this study. A meta-analysis was conducted for spinal cord injury (n = 52) and traumatic brain injury (n = 8). The results indicated that mesenchymal stem cell-derived extracellular vesicles treatment prominently promoted motor function recovery in spinal cord injury animals, including rat Basso, Beattie and Bresnahan locomotor rating scale scores (standardized mean difference [SMD]: 2.36, 95% confidence interval [CI]: 1.96-2.76, P < 0.01, I2 = 71%) and mouse Basso Mouse Scale scores (SMD = 2.31, 95% CI: 1.57-3.04, P = 0.01, I2 = 60%) compared with controls. Further, mesenchymal stem cell-derived extracellular vesicles treatment significantly promoted neurological recovery in traumatic brain injury animals, including the modified Neurological Severity Score (SMD = -4.48, 95% CI: -6.12 to -2.84, P < 0.01, I2 = 79%) and Foot Fault Test (SMD = -3.26, 95% CI: -4.09 to -2.42, P = 0.28, I2 = 21%) compared with controls. Subgroup analyses showed that characteristics may be related to the therapeutic effect of mesenchymal stem cell-derived extracellular vesicles. For Basso, Beattie and Bresnahan locomotor rating scale scores, the efficacy of allogeneic mesenchymal stem cell-derived extracellular vesicles was higher than that of xenogeneic mesenchymal stem cell-derived extracellular vesicles (allogeneic: SMD = 2.54, 95% CI: 2.05-3.02, P = 0.0116, I2 = 65.5%; xenogeneic: SMD: 1.78, 95%CI: 1.1-2.45, P = 0.0116, I2 = 74.6%). Mesenchymal stem cell-derived extracellular vesicles separated by ultrafiltration centrifugation combined with density gradient ultracentrifugation (SMD = 3.58, 95% CI: 2.62-4.53, P < 0.0001, I2 = 31%) may be more effective than other EV isolation methods. For mouse Basso Mouse Scale scores, placenta-derived mesenchymal stem cell-derived extracellular vesicles worked better than bone mesenchymal stem cell-derived extracellular vesicles (placenta: SMD = 5.25, 95% CI: 2.45-8.06, P = 0.0421, I2 = 0%; bone marrow: SMD = 1.82, 95% CI: 1.23-2.41, P = 0.0421, I2 = 0%). For modified Neurological Severity Score, bone marrow-derived MSC-EVs worked better than adipose-derived MSC-EVs (bone marrow: SMD = -4.86, 95% CI: -6.66 to -3.06, P = 0.0306, I2 = 81%; adipose: SMD = -2.37, 95% CI: -3.73 to -1.01, P = 0.0306, I2 = 0%). Intravenous administration (SMD = -5.47, 95% CI: -6.98 to -3.97, P = 0.0002, I2 = 53.3%) and dose of administration equal to 100 μg (SMD = -5.47, 95% CI: -6.98 to -3.97, P < 0.0001, I2 = 53.3%) showed better results than other administration routes and doses. The heterogeneity of studies was small, and sensitivity analysis also indicated stable results. Last, the methodological quality of all trials was mostly satisfactory. In conclusion, in the treatment of traumatic central nervous system diseases, mesenchymal stem cell-derived extracellular vesicles may play a crucial role in promoting motor function recovery.

Genetic predisposition to Alzheimer's disease alters inflammasome activity after traumatic brain injury

Traumatic Brain Injury (TBI) is a major cause of death and disability in the US and a recognized risk factor for the development of Alzheimer's disease (AD). The relationship between these conditions is not completely understood, but the conditions may share additive or synergistic pathological hallmarks that may serve as novel therapeutic targets. Heightened inflammasome signaling plays a critical role in the pathogenesis of central nervous system injury (CNS) and the release of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) speck from neurons and activated microglia contribute significantly to TBI and AD pathology. This study investigated whether inflammasome signaling after TBI was augmented in AD and whether this signaling pathway impacted biochemical and neuropathological outcomes and overall cognitive function. Five-month-old, 3xTg mice and respective wild type controls were randomized and underwent moderate controlled cortical impact (CCI) injury or served as sham/uninjured controls. Animals were sacrificed at 1 hour, 1 day, or 1 week after TBI to assess acute pathology or at 12 weeks after assessing cognitive function. The ipsilateral cerebral cortex was processed for inflammasome protein expression by immunoblotting. Mice were evaluated for behavior by open field (3 days), novel object recognition (2 weeks), and Morris water maze (6 weeks) testing after TBI. There was a statistically significant increase in the expression of inflammasome signaling proteins Caspase-1, Caspase-8, ASC, and interleukin (IL)-1β after TBI in both wild type and 3xTg animals. At 1-day post injury, significant increases in ASC and IL-1β protein expression were measured in AD TBI mice compared to WT TBI. Behavioral testing showed that injured AD mice had altered cognitive function when compared to injured WT mice. Elevated Aβ was seen in the ipsilateral cortex and hippocampus of sham and injured AD when compared to respective groups at 12 weeks post injury. Moreover, treatment of injured AD mice with IC100, an anti-ASC monoclonal antibody, inhibited the inflammasome, as evidenced by IL-1β reduction in the injured cortex at 1-week post injury. These findings show that the inflammasome response is heightened in mice genetically predisposed to AD and suggests that AD may exacerbate TBI pathology. Thus, dampening inflammasome signaling may offer a novel approach for the treatment of AD and TBI.

Intermittent fasting ameliorates neuronal ferroptosis and cognitive impairment in mice after traumatic brain injury

Ferroptosis, a newly characterized form of programmed cell death that results from lipid peroxidation and mitochondrial dysfunction, has been demonstrated to be involved in the pathogenesis of traumatic brain injury (TBI). Scientific evidence has shown that intermittent fasting (IF) reduces both the lipid peroxidation and the mitochondrial dysfunction, raising the question of whether IF affects the ferroptosis induced by TBI. Here, based on an established TBI animal model, we examine the effects of IF on the activation of ferroptosis pathway as well as related outcomes. We uncovered that a 1-mo IF elevated the protective Gpx4 and Hspb1 expression, and partly abolished the increase of Nfe2l2, Slc7a11, Alox8, Steap3, and Nox2 in the cortex, which were induced by TBI. Furthermore, the characteristic cellular damage induced by ferroptosis was alleviated by IF, as revealed by Perls’ Prussian blue staining, Nissl staining, and transmission electron microscope examination. Consistently, we examined the outcomes of mice subjected to TBI and found an improved cognitive function of the IF mice. In sum, our study demonstrated, to our knowledge for the first time, that a 1-mo IF regimen partly ameliorates ferroptosis in the cortex of mice subjected to TBI, which potentially contributes to a lessening of cognitive impairment.

Hypothermia impairs glymphatic drainage in traumatic brain injury as assessed by dynamic contrast-enhanced MRI with intrathecal contrast.

The impact of hypothermia on the impaired drainage function of the glymphatic system in traumatic brain injury (TBI) is not understood. Male Sprague-Dawley rats undergoing controlled cortical impact injury (CCI) were subjected to hypothermia or normothermia treatment. The rats undergoing sham surgery without CCI were used as the control. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with intrathecal administration of low- and high-molecular-weight contrast agents (Gd-DTPA and hyaluronic acid conjugated Gd-DTPA) was performed after TBI and head temperature management. The semiquantitative kinetic parameters characterizing the contrast infusion and cleanout in the brain, including influx rate, efflux rate, and clearance duration, were calculated from the average time-intensity curves. The qualitative and semiquantitative results of DCE-MRI obtained from all examined perivascular spaces and most brain tissue regions showed a significantly increased influx rate and efflux rate and decreased clearance duration among all TBI animals, demonstrating a significant impairment of glymphatic drainage function. This glymphatic drainage dysfunction was exacerbated when additional hypothermia was applied. The early glymphatic drainage reduction induced by TBI and aggravated by hypothermia was linearly related to the late increased deposition of p-tau and beta-amyloid revealed by histopathologic and biochemical analysis and cognitive impairment assessed by the Barnes maze and novel object recognition test. The glymphatic system dysfunction induced by hypothermia may be an indirect alternative pathophysiological factor indicating injury to the brain after TBI. Longitudinal studies and targeted glymphatic dysfunction management are recommended to explore the potential effect of hypothermia in TBI.

Curcumin Alleviates Oxidative Stress, Neuroinflammation, and Promotes Behavioral Recovery After Traumatic Brain Injury.

Neuroinflammation and oxidative stress after traumatic brain injury (TBI) can further lead to neuronal apoptosis, which plays a crucial role in the process of neuron death. Curcumin, which is derived from the rhizome of the Curcuma longa plant, has multiple pharmacological effects. The objective of this study was to investigate whether curcumin treatment has neuroprotective effects after TBI, and to elucidate the underlying mechanism. A total of 124 mice were randomly divided into 4 groups: Sham group, TBI group, TBI+Vehicle group, and TBI+Curcumin group. The TBI mice model used in this study was constructed with TBI device induced by compressed gas, and 50 mg/kg curcumin was injected intraperitoneally 15 minutes after TBI. Then, the blood-brain barrier permeability, cerebral edema, oxidative stress, inflammation, apoptosis-related protein, and behavioral tests of neurological function were utilized to evaluate the protective effect of curcumin after TBI. Curcumin treatment markedly alleviated post-trauma cerebral edema and blood-brain barrier integrity, and suppressed neuronal apoptosis, reduced mitochondrial injury and the expression of apoptosis-related proteins. Moreover, curcumin also attenuates TBI-induced inflammatory response and oxidative stress in brain tissue and improves cognitive dysfunction after TBI. These data provide substantial evidence that curcumin has neuroprotective effects in animal TBI models, possibly through the inhibition of inflammatory response and oxidative stress.

Establishment and Application of a Novel In Vitro Model of Microglial Activation in Traumatic Brain Injury.

Mechanical impact-induced primary injury after traumatic brain injury (TBI) leads to acute microglial pro-inflammatory activation and consequently mediates neurodegeneration, which is a major secondary brain injury mechanism. However, the detailed pathologic cascades have not been fully elucidated, partially because of the pathologic complexity in animal TBI models. Although there are several in vitro TBI models, none of them closely mimic post-TBI microglial activation. In the present study, we aimed to establish an in vitro TBI model, specifically reconstituting the pro-inflammatory activation and associated neurodegeneration following TBI. We proposed three sets of experiments. First, we established a needle scratch injured neuron-induced microglial activation and neurodegeneration in vitro model of TBI. Second, we compared microglial pro-inflammatory cytokines profiles between the in vitro TBI model and TBI in male mice. Additionally, we validated the role of injured neurons-derived damage-associated molecular patterns in amplifying microglial pro-inflammatory pathways using the in vitro TBI model. Third, we applied the in vitro model for the first time to characterize the cellular metabolic profile of needle scratch injured-neuron-activated microglia, and define the role of metabolic reprogramming in mediating pro-inflammatory microglial activation and mediated neurodegeneration. Our results showed that we successfully established a novel in vitro TBI model, which closely mimics primary neuronal injury-triggered microglial pro-inflammatory activation and mediated neurodegeneration after TBI. This in vitro model provides an advanced and highly translational platform for dissecting interactions in the pathologic processes of neuronal injury-microglial activation-neuronal degeneration cascade, and elucidating the detailed underlying cellular and molecular insights after TBI.SIGNIFICANCE STATEMENT Microglial activation is a key component of acute neuroinflammation that leads to neurodegeneration and long-term neurologic outcome deficits after TBI. However, it is not feasible to truly dissect primary neuronal injury-induced microglia activation, and consequently mediated neurodegeneration in vivo Furthermore, there is currently lacking of in vitro TBI models closely mimicking the TBI primary injury-mediated microglial activation. In this study, we successfully established and validated a novel in vitro TBI model of microglial activation, and for the first time, characterized the cellular metabolic profile of microglia in this model. This novel microglial activation in vitro TBI model will help in elucidating microglial inflammatory activation and consequently associated neurodegeneration after TBI.

Dexamethasone-Loaded Hydrogels Improve Motor and Cognitive Functions in a Rat Mild Traumatic Brain Injury Model.

Functional recovery following traumatic brain injury (TBI) is limited due to progressive neuronal damage resulting from secondary injury-associated neuroinflammation. Steroidal anti-inflammatory drugs, such as dexamethasone (DX), can reduce neuroinflammation by activated microglia and infiltrated macrophages. In our previous work, we developed hydrolytically degradable poly(ethylene) glycol-bis-(acryloyloxy acetate) (PEG-bis-AA) hydrogels with dexamethasone (DX)-conjugated hyaluronic acid (HA-DXM) and demonstrated that dexamethasone-loaded hydrogels (PEG-bis-AA/HA-DXM) can reduce neuroinflammation, apoptosis, and lesion volume and improve neuronal cell survival and motor function recovery at seven days post-injury (DPI) in a rat mild-TBI model. In this study, we investigate the effects of the local application of PEG-bis-AA/HA-DXM hydrogels on motor function recovery at 7 DPI and cognitive functional recovery as well as secondary injury at 14 DPI in a rat mild-CCI TBI model. We observed that PEG-bis-AA/HA-DXM-treated animals exhibit significantly improved motor functions by the rotarod test and cognitive functions by the Morris water maze test compared to untreated TBI animals. We also observed that PEG-bis-AA/HA-DXM hydrogels reduce the inflammatory response, apoptosis, and lesion volume compared to untreated animals at 14 DPI. Therefore, PEG-bis-AA/HA-DXM hydrogels can be promising a therapeutic intervention for TBI treatment.

A Mouse Model of Neurodegeneration Induced by Blade Penetrating Stab Wound to the Hippocampus.

Simple SummaryTo date, various animal models of traumatic brain injury (TBI) have been developed to investigate the cellular and molecular networks underlying the pathogenesis of neurodegeneration, and to examine the safeness and therapeutic efficacy of drugs. However, the commonly used animal TBI models usually have the weaknesses of low reproducibility and high mortality rates. In the present study, we created a mouse model of cognitive deficits induced by a blade penetrating stab wound to the hippocampus (HBSI). This model will contribute a better understanding of neurodegeneration and accelerate the translation of preclinical research to clinical applications.Traumatic brain injury (TBI) is closely associated with the later development of neurodegenerative and psychiatric diseases which are still incurable. Although various animal TBI models have been generated, they usually have weaknesses in standardization, survivability and/or reproducibility. In the present study, we investigated whether applying a blade penetrating stab wound to the hippocampus would create an animal model of cognitive deficits. Open-field, Morris water maze and Barnes maze tests were used to evaluate the animal behaviors. The immunofluorescence staining of NeuN, GFAP, IBA1, and TUNEL was conducted to analyze the changes in neurons, astrocytes, and microglia, as well as cell death. Mice with a hippocampal blade stab injury (HBSI) displayed the activation of microglia and astrocytes, inflammation, neuronal apoptosis, and deficits in spatial learning and memory. These findings suggest that HBSI is an easy approach to generate a reliable in vivo model of TBI to capture hemorrhage, neuroinflammation, reactive gliosis, and neural death, as well as cognitive deficits observed in human patients.

Ultrasmall polymer-coated cerium oxide nanoparticles as a traumatic brain injury therapy

No medication has been approved for secondary injuries after traumatic brain injury (TBI). While free radicals are considered a major mediator of secondary injury, conventional antioxidants only have modest clinical efficacy. Here, we synthesized CX201 consisting of core cerium oxide nanoparticles coated with 6-aminocaproic acid and polyvinylpyrrolidone in aqueous phase. CX201 with 3.49 ± 1.11 nm of core and 6.49 ± 0.56 nm of hydrodynamic diameter showed multi-enzymatic antioxidant function. Owing to its excellent physiological stability and cell viability, CX201 had a neuroprotective effect in vitro. In a TBI animal model, an investigator-blinded randomized experiment showed a single intravenously injected CX201 significantly improved functional recovery compared to the control. CX201 reduced lipid peroxidation and inflammatory cell recruitment at the damaged brain. These suggest ultrasmall CX201 can efficiently reduce secondary brain injuries after TBI. Given the absence of current therapies, CX201 may be proposed as a novel therapeutic strategy for TBI.

GABAergic circuits of the basolateral amygdala and generation of anxiety after traumatic brain injury.

Traumatic brain injury (TBI) has reached epidemic proportions around the world and is a major public health concern in the United States. Approximately 2.8 million individuals sustain a traumatic brain injury and are treated in an Emergency Department yearly in the U.S., and about 50,000 of them die. Persistent symptoms develop in 10-15% of the cases including neuropsychiatric disorders. Anxiety is the second most common neuropsychiatric disorder that develops in those with persistent neuropsychiatric symptoms after TBI. Abnormalities or atrophy in the temporal lobe has been shown in the overwhelming number of TBI cases. The basolateral amygdala (BLA), a temporal lobe structure that consolidates, stores and generates fear and anxiety-based behavioral outputs, is a critical brain region in the anxiety circuitry. In this review, we sought to capture studies that characterized the relationship between human post-traumatic anxiety and structural/functional alterations in the amygdala. We compared the human findings with results obtained with a reproducible mild TBI animal model that demonstrated a direct relationship between the alterations in the BLA and an anxiety-like phenotype. From this analysis, both preliminary insights, and gaps in knowledge, have emerged which may open new directions for the development of rational and more efficacious treatments.

Abstracts from The 39th Annual Symposium of the National Neurotrauma Society, including the AANS/CNS Joint Section on Neurotrauma and Critical Care

Abstracts from The 39^th Annual Symposium of the National Neurotrauma Society, including the AANS/CNS Joint Section on Neurotrauma and Critical Care

Fecal Microbiota Transfer Attenuates Gut Dysbiosis and Functional Deficits After Traumatic Brain Injury.

Traumatic brain injury (TBI) is an underrecognized public health threat. Survivors of TBI often suffer long-term neurocognitive deficits leading to the progressive onset of neurodegenerative disease. Recent data suggests that the gut-brain axis is complicit in this process. However, no study has specifically addressed whether fecal microbiota transfer (FMT) attenuates neurologic deficits after TBI. We hypothesized that fecal microbiota transfer would attenuate neurocognitive, anatomic, and pathologic deficits after TBI. C57Bl/6 mice were subjected to severe TBI (n = 20) or sham-injury (n = 20) via an open-head controlled cortical impact. Post-injury, this cohort of mice underwent weekly oral gavage with a slurry of healthy mouse stool or vehicle alone beginning 1 h post-TBI followed by behavioral testing and neuropathologic analysis. 16S ribosomal RNA sequencing of fecal samples was performed to characterize gut microbial community structure pre- and post-injury. Zero maze and open field testing were used to evaluate post-traumatic anxiety, exploratory behavior, and generalized activity. 3D, contrast enhanced, magnetic resonance imaging was used to determine differences in cortical volume loss and white matter connectivity. Prior to euthanasia, brains were harvested for neuropathologic analysis. Fecal microbiome analysis revealed a large variance between TBI, and sham animals treated with vehicle, while FMT treated TBI mice had restoration of gut dysbiosis back to levels of control mice. Neurocognitive testing demonstrated a rescue of normal anxiety-like and exploratory behavior in TBI mice treated with FMT. FMT treated TBI mice spent a greater percentage of time (22%, P = 0.0001) in the center regions of the Open Field as compared to vehicle treated TBI mice (13%). Vehicle-treated TBI animals also spent less time (19%) in the open areas of zero maze than FMT treated TBI mice (30%, P = 0.0001). Comparing in TBI mice treated with FMT, MRI demonstrated a marked attenuation in ventriculomegaly (P < 0.002) and a significant change in fractional anisotropy (i.e., loss of white matter connectivity) (P < 0.0001). Histologic analysis of brain sections revealed a FMT- injury dependent interaction in the microglia/macrophage-specific ionized calcium-binding protein, Iba1 (P = 0.002). These data suggest that restoring a pre-injury gut microbial community structure may be a promising therapeutic intervention after TBI.

Dietary influences on closed‐head traumatic brain injury in a pediatric rodent model

Traumatic brain injury (TBI) is one of the most common causes of emergency room visits in children, and it is a leading cause of death in juveniles in the United States. Similarly, a high proportion of this population consumes diets high in saturated fats, and millions of children are overweight or obese. Therefore, the goal of the present study was to assess the relationship between diet and TBI outcomes in juvenile rats. In the current study, groups of juvenile male Long Evans rats were provided with a combination of a high fat diet (HFD) and a solution of 10% high‐fructose corn syrup or a standard chow diet. The animals were trained on the Morris water maze (MWM) for two consecutive days to test spatial learning. Rats were then subjected to either mild TBI via the Closed‐Head Injury Model of Engineered Rotational Acceleration (CHIMERA) or sham procedures. Immediately after TBI, the animals’ righting reflexes were tested. Animals were retested in the MWM either three hours or four days post‐injury. The animals were euthanized either four days or seven days post‐injury, and brain samples and blood plasma were collected for QRT‐PCR, immunohistochemistry, and triglyceride assays. Acute HFD intake did not alter the body weight of the weanling rats, but the HFD significantly elevated triglyceride levels by two weeks. Latency to the platform during the MWM training period was not affected by diet. Nor were there any differences in post‐injury time to righting and walking by diet group. However, the TBI rats’ time to righting and walking was significantly reduced compared to the sham rats, p &lt; 0.05. The latency and distance traveled to the platform in the MWM were significantly increased by TBI three hours post‐injury. Alternately, these changes were abolished four days post‐injury. QRT‐PCR revealed that CREB1 and IL1β were increased in the hippocampus. On the other hand, IL6 was increased in the prefrontal cortex as a function of injury. CREB1, IL1β, and IL6 gene expression were significantly elevated by TBI, while CLDN5, IL6, and IL1R1 were increased in the hippocampus due to diet. Immunohistochemistry revealed an increased immunoreactivity of IBA‐1 in the cortex and corpus callosum in the TBI animals, regardless of diet. The results from this study offer evidence that both HFD and TBI influence behavior and biochemical markers in juvenile rats using the novel CHIMERA device.

Transcriptional Profiling in a Novel Swine Model of Traumatic Brain Injury.

Transcriptomic investigations of traumatic brain injury (TBI) can give us deep insights into the pathological and compensatory processes post-injury. Thus far, transcriptomic studies in TBI have mostly used microarrays and have focused on rodent models. However, a large animal model of TBI bears a much stronger resemblance to human TBI with regard to the anatomical details, mechanics of injury, genetics, and, possibly, molecular response. Because of the advantages of a large animal TBI model, we investigated the gene expression changes between injured and uninjured sides of pig cerebral cortex after TBI. Given acute inflammation that follows after TBI and the important role that immune response plays in neuroplasticity and recovery, we hypothesized that transcriptional changes involving immune function will be upregulated. Eight female 4-week-old piglets were injured on the right hemisphere with controlled cortical impact (CCI). At 24 h after TBI, pericontusional cortex tissues from the injured side and contralateral cortical tissues were collected. After RNA extraction, library preparation and sequencing as well as gene expression changes between the ipsi- and contralateral sides were compared. There were 6642 genes that were differentially expressed between the ipsi- and contralateral sides, and 1993 genes among them had at least 3-fold differences. Differentially expressed genes were enriched for biological processes related to immune system activation, regulation of immune response, and leukocyte activation. Many of the differentially expressed genes, such as CD4, CD86, IL1A, IL23R, and IL1R1, were major regulators of immune function. This study demonstrated some of the major transcriptional changes between the pericontusional and contralateral tissue at an acute time point after TBI in pigs.

GACSON software for automated segmentation and morphology analyses of myelinated axons in 3D electron microscopy

Background and ObjectiveAdvances in electron microscopy (EM) now allow three-dimensional (3D) imaging of hundreds of micrometers of tissue with nanometer-scale resolution, providing new opportunities to study the ultrastructure of the brain. In this work, we introduce a freely available Matlab-based gACSON software for visualization, segmentation, assessment, and morphology analysis of myelinated axons in 3D-EM volumes of brain tissue samples. MethodsThe software is equipped with a graphical user interface (GUI). It automatically segments the intra-axonal space of myelinated axons and their corresponding myelin sheaths and allows manual segmentation, proofreading, and interactive correction of the segmented components. gACSON analyzes the morphology of myelinated axons, such as axonal diameter, axonal eccentricity, myelin thickness, or g-ratio. ResultsWe illustrate the use of the software by segmenting and analyzing myelinated axons in six 3D-EM volumes of rat somatosensory cortex after sham surgery or traumatic brain injury (TBI). Our results suggest that the equivalent diameter of myelinated axons in somatosensory cortex was decreased in TBI animals five months after the injury. ConclusionOur results indicate that gACSON is a valuable tool for visualization, segmentation, assessment, and morphology analysis of myelinated axons in 3D-EM volumes. It is freely available at https://github.com/AndreaBehan/g-ACSON under the MIT license.