The Controlled Cortical Impact Model of Experimental Brain Trauma: Overview, Research Applications, and Protocol

Neuroprotective effect of triptolide on neuronal inflammation in rats with mild brain injury

Concussions sustained while playing sports are a prominent cause of mild traumatic brain injury (mTBI), which is prevalent among teenagers. The early and intermediate stages of mild traumatic brain injury (mTBI) can be characterized by inflammation, neurodegeneration, and brain tissue edema, which can lead to permanent brain damage. The present study investigated the therapeutic effects of triptolide in mTBI and brain damage recovery. After building mTBI model in male rat, triptolide administrated daily for 1 week in the treated group. On day 3 and day 7 of administration, hippocampus tissues were collected to evaluate inflammation and autophagy in the brain. The expressions of inflammatory factors interleukin (IL)-1β and tumor necrosis factor-alpha in serum were downregulated, while IL-10 expression was upregulated when compared with the mTBI group on day 3 and day 7. The expression of IL-10 on day 7 was higher than on day 3. Quantitative polymerase chain reaction (qPCR) analysis of inflammatory-related factors (i.e., Il-1β and nuclear factor-κB (Nf-κb), and western blot as well as immunofluorescence staining of autophagy-related proteins (i.e., LC3B) and aquaporin (AQP 4) showed lower expression on day 3 and day 7 in the triptolide-treated group. Moreover, NeuN immunostaining, and hematoxylin and eosin (HE) staining for hippocampus region revealed that the triptolide-treated group showed a decrease in damaged cells. Our findings emphasize the effectiveness of triptolide therapy after mild traumatic brain injury via modulating autophagy, attenuating inflammation and reduces edema by decreasing AQP 4 expression.

Traumatic brain injury heterogeneity affects cell death and autophagy

Traumatic brain injury (TBI) mechanism and severity are heterogenous clinically, resulting in a multitude of physical, cognitive, and behavioral deficits. Impact variability influences the origin, spread, and classification of molecular dysfunction which limits strategies for comprehensive clinical intervention. Indeed, there are currently no clinically approved therapeutics for treating the secondary consequences associated with TBI. Thus, examining pathophysiological changes from heterogeneous impacts is imperative for improving clinical translation and evaluating the efficacy of potential therapeutic strategies. Here we utilized TBI models that varied in both injury mechanism and severity including severe traditional controlled cortical impact (CCI), modified mild CCI (MTBI), and multiple severities of closed-head diffuse TBI (DTBI), and assessed pathophysiological changes. Severe CCI induced cortical lesions and necrosis, while both MTBI and DTBI lacked lesions or significant necrotic damage. Autophagy was activated in the ipsilateral cortex following CCI, but acutely impaired in the ipsilateral hippocampus. Additionally, autophagy was activated in the cortex following DTBI, and autophagic impairment was observed in either the cortex or hippocampus following impact from each DTBI severity. Thus, we provide evidence that autophagy is a therapeutic target for both mild and severe TBI. However, dramatic increases in necrosis following CCI may negatively impact the clinical translatability of therapeutics designed to treat acute dysfunction in TBI. Overall, these results provide evidence that injury sequalae affiliated with TBI heterogeneity is linked through autophagy activation and/or impaired autophagic flux. Thus, therapeutic strategies designed to intervene in autophagy may alleviate pathophysiological consequences, in addition to the cognitive and behavioral deficits observed in TBI.

FMOD Alleviates Depression-Like Behaviors by Targeting the PI3K/AKT/mTOR Signaling After Traumatic Brain Injury

Depression frequently occurs following traumatic brain injury (TBI). However, the role of Fibromodulin (FMOD) in TBI-related depression is not yet clear. Previous studies have suggested FMOD as a potential key factor in TBI, yet its association with depression post-TBI and underlying mechanisms are not well understood. Serum levels of FMOD were measured in patients with traumatic brain injury using qPCR. The severity of depression was assessed using the self-depression scale (SDS). Neurological function, depressive state, and cognitive function in mice were assessed using the modified Neurological Severity Score (mNSS), forced swimming test (FST), tail suspension test (TST), Sucrose Preference Test (SPT), and morris water maze (MWM). The morphological features of mouse hippocampal synapses and neuronal dendritic spines were revealed through immunofluorescence, transmission electron microscopy, and Golgi-Cox staining. The protein expression levels of FMOD, MAP2, SYP, and PSD95, as well as the phosphorylation levels of the PI3K/AKT/mTOR signaling pathway, were detected through Western blotting. FMOD levels were decreased in TBI patients' serum. Overexpression of FMOD preserved neuronal function and alleviated depression-like behaviour, increased synaptic protein expression, and induced ultrastructural changes in hippocampal neurons. The increased phosphorylation of PI3K, AKT, and mTOR suggested the involvement of the PI3K/AKT/mTOR signaling pathway in FMOD's protective effects. FMOD exhibits potential as a therapeutic target for depression related to TBI, with its protective effects potentially mediated through the PI3K/AKT/mTOR signaling pathway.

Exploratory assessment of the effect of systemic administration of soluble glycoprotein 130 on cognitive performance and chemokine levels in a mouse model of experimental traumatic brain injury

Uncontrolled neuroinflammation mediates traumatic brain injury (TBI) pathology and impairs recovery. Interleukin-6 (IL-6), a pleiotropic inflammatory regulator, is associated with poor clinical TBI outcomes. IL-6 operates via classical-signaling through membrane-bound IL-6 receptor (IL-6R) and trans-signaling through soluble IL-6 receptor (s)IL-6R. IL-6 trans-signaling specifically contributes to neuropathology, making it a potential precision therapeutic TBI target. Soluble glycoprotein 130 (sgp130) prevents IL-6 trans-signaling, sparing classical signaling, thus is a possible treatment. Mice received either controlled cortical impact (CCI) (6.0 ± 0.2 m/s; 2 mm; 50-60ms) or sham procedures. Vehicle (VEH) or sgp130-Fc was subcutaneously administered to sham (VEH or 1 µg) and CCI (VEH, 0.25 µg or 1 µg) mice on days 1, 4, 7, 10 and 13 post-surgery to assess effects on cognition [Morris Water Maze (MWM)] and ipsilateral hemisphere IL-6 related biomarkers (day 21 post-surgery). CCI + sgp130-Fc groups (0.25 µg and 1 µg) were combined for analysis given similar behavior/biomarker outcomes. CCI + VEH mice had longer latencies and path lengths to the platform and increased peripheral zone time versus Sham + VEH and Sham + sgp130-Fc mice, suggesting injury-induced impairments in learning and anxiety. CCI + sgp130-Fc mice had shorter platform latencies and path lengths and had decreased peripheral zone time, indicating a therapeutic benefit of sgp130-Fc after injury on learning and anxiety. Interestingly, Sham + sgp130-Fc mice had shorter platform latencies, path lengths and peripheral zone times than Sham + VEH mice, suggesting a beneficial effect of sgp130-Fc, independent of injury. CCI + VEH mice had increased brain IL-6 and decreased sgp130 levels versus Sham + VEH and Sham + sgp130-Fc mice. There was no treatment effect on IL-6, sIL6-R or sgp130 in Sham + VEH versus Sham + sgp130-Fc mice. There was also no treatment effect on IL-6 in CCI + VEH versus CCI + sgp130-Fc mice. However, CCI + sgp130-Fc mice had increased sIL-6R and sgp130 versus CCI + VEH mice, demonstrating sgp130-Fc treatment effects on brain biomarkers. Inflammatory chemokines (MIP-1β, IP-10, MIG) were increased in CCI + VEH mice versus Sham + VEH and Sham + sgp130-Fc mice. However, CCI + sgp130-Fc mice had decreased chemokine levels versus CCI + VEH mice. IL-6 positively correlated, while sgp130 negatively correlated, with chemokine levels. Overall, we found that systemic sgp130-Fc treatment after CCI improved learning, decreased anxiety and reduced CCI-induced brain chemokines. Future studies will explore sex-specific dosing and treatment mechanisms for sgp130-Fc therapy.

CGRP as a potential mediator for the sexually dimorphic responses to traumatic brain injury

BACKGROUND

The outcomes of traumatic brain injury (TBI) exhibit variance contingent upon biological sex. Although female sex hormones exert neuroprotective effects, the administration of estrogen and progesterone has not yielded conclusive results. Hence, it is conceivable that additional mediators, distinct from female sex hormones, merit consideration due to their potential differential impact on TBI outcomes. Calcitonin gene-related peptide (CGRP) exhibits sexually dimorphic expression and demonstrates neuroprotective effects in acute brain injuries. In this study, we aimed to examine sex-based variations in TBI structural and functional outcomes with respect to CGRP expression.

METHODS

Male and female Sprague Dawley rats were exposed to controlled cortical impact to induce severe TBI, followed by interventions with and without CGRP inhibition. In the acute phase of TBI, the study centered on elucidating the influence of CGRP on oxidative stress, nuclear factor erythroid 2-related factor 2 (Nrf2) and endothelial nitric oxide synthase (eNOS) signaling in the peri-impact tissue. Subsequently, during the chronic phase of TBI, the investigation expanded to evaluate CGRP expression in relation to lesion volume, microvascular dysfunction, and white matter injury, as well as working and spatial memory, anxiety-like, and depression-like behaviors in subjects of both sexes.

RESULTS

Female rats exhibited elevated levels of CGRP in the peri-impact brain tissue during both baseline conditions and in the acute and chronic phases of TBI, in comparison to age-matched male counterparts. Enhanced CGRP levels in specific brain sub-regions among female rats correlated with superior structural and functional outcomes following TBI compared to their male counterparts. CGRP inhibition induced heightened oxidative stress and a reduction in the expression of Nrf2 and eNOS in both male and female rats, with the observed alteration being more pronounced in females than in males.

CONCLUSIONS

This study marks the inaugural identification of CGRP as a downstream mediator contributing to the sexually dimorphic response observed in TBI outcomes.

Lateral fluid percussion injury: A rat model of experimental traumatic brain injury

Traumatic brain injury (TBI) represents one of the leading causes of disability and death worldwide. The annual economic impact of TBI-including direct and indirect costs-is high, particularly impacting low- and middle-income countries. Despite extensive research, a comprehensive understanding of the primary and secondary TBI pathophysiology, followed by the development of promising therapeutic approaches, remains limited. These fundamental caveats in knowledge have motivated the development of various experimental models to explore the molecular mechanisms underpinning the pathogenesis of TBI. In this context, the Lateral Fluid Percussion Injury (LFPI) model produces a brain injury that mimics most of the neurological and systemic aspects observed in human TBI. Moreover, its high reproducibility makes the LFPI model one of the most widely used rodent-based TBI models. In this chapter, we provide a detailed surgical protocol of the LFPI model used to induce TBI in adult Wistar rats. We further highlight the neuroscore test as a valuable tool for the evaluation of TBI-induced sensorimotor consequences and their severity in rats. Lastly, we briefly summarize the current knowledge on the pathological aspects and functional outcomes observed in the LFPI-induced TBI model in rodents.

Deplete and repeat: microglial CSF1R inhibition and traumatic brain injury

Traumatic brain injury (TBI) is a public health burden affecting millions of people. Sustained neuroinflammation after TBI is often associated with poor outcome. As a result, increased attention has been placed on the role of immune cells in post-injury recovery. Microglia are highly dynamic after TBI and play a key role in the post-injury neuroinflammatory response. Therefore, microglia represent a malleable post-injury target that could substantially influence long-term outcome after TBI. This review highlights the cell specific role of microglia in TBI pathophysiology. Microglia have been manipulated via genetic deletion, drug inhibition, and pharmacological depletion in various pre-clinical TBI models. Notably, colony stimulating factor 1 (CSF1) and its receptor (CSF1R) have gained much traction in recent years as a pharmacological target on microglia. CSF1R is a transmembrane tyrosine kinase receptor that is essential for microglia proliferation, differentiation, and survival. Small molecule inhibitors targeting CSF1R result in a swift and effective depletion of microglia in rodents. Moreover, discontinuation of the inhibitors is sufficient for microglia repopulation. Attention is placed on summarizing studies that incorporate CSF1R inhibition of microglia. Indeed, microglia depletion affects multiple aspects of TBI pathophysiology, including neuroinflammation, oxidative stress, and functional recovery with measurable influence on astrocytes, peripheral immune cells, and neurons. Taken together, the data highlight an important role for microglia in sustaining neuroinflammation and increasing risk of oxidative stress, which lends to neuronal damage and behavioral deficits chronically after TBI. Ultimately, the insights gained from CSF1R depletion of microglia are critical for understanding the temporospatial role that microglia develop in mediating TBI pathophysiology and recovery.

Functional recovery following traumatic brain injury in rats is enhanced by oral supplementation with bovine thymus extract

Traumatic brain injury (TBI) is one of the leading causes of death worldwide. There are currently no effective treatments for TBI, and trauma survivors suffer from a variety of long-lasting health consequences. With nutritional support recently emerging as a vital step in improving TBI patients' outcomes, we sought to evaluate the potential therapeutic benefits of nutritional supplements derived from bovine thymus gland, which can deliver a variety of nutrients and bioactive molecules. In a rat model of controlled cortical impact (CCI), we determined that animals supplemented with a nuclear fraction of bovine thymus (TNF) display greatly improved performance on beam balance and spatial memory tests following CCI. Using RNA-Seq, we identified an array of signaling pathways that are modulated by TNF supplementation in rat hippocampus, including those involved in the process of autophagy. We further show that bovine thymus-derived extracts contain antigens found in neural tissues and that supplementation of rats with thymus extracts induces production of serum IgG antibodies against neuronal and glial antigens, which may explain the enhanced animal recovery following CCI through possible oral tolerance mechanism. Collectively, our data demonstrate, for the first time, the potency of a nutritional supplement containing nuclear fraction of bovine thymus in enhancing the functional recovery from TBI.

Altered N6-Methyladenosine Modification Patterns and Transcript Profiles Contributes to Cognitive Dysfunction in High-Fat Induced Diabetic Mice

N6-methyladenosine (m6A) constitutes the paramount post-transcriptional modification within eukaryotic mRNA. This modification is subjected to stimulus-dependent regulation within the central nervous system of mammals, being influenced by sensory experiences, learning processes, and injuries. The patterns of m6A methylation within the hippocampal region of diabetes cognitive impairment (DCI) has not been investigated. A DCI model was established by feeding a high-fat diet to C57BL/6J mice. m6A and RNA sequencing was conducted to profile the m6A-tagged transcripts in the hippocampus. Methylated RNA immunoprecipitation with next-generation sequencing and RNA sequencing analyses yielded differentially m6A-modified and expressed genes in the hippocampus of DCI mice, which were enriched in pathways involving synaptic transmission and axonal guidance. Mechanistic analyses revealed a remarkable change in m6A modification levels through alteration of the mRNA expression of m6A methyltransferases (METTL3 and METTL14) and demethylase (FTO) in the hippocampus of DCI mice. We identified a co-mediated specific RNA regulatory strategy that broadens the epigenetic regulatory mechanism of RNA-induced neurodegenerative disorders associated with metabolic and endocrine diseases.

Effects of Intrathecal Ketamine on Cerebrospinal Fluid Levels of Brain-Derived Neurotrophic Factor and Mechanical Allodynia in a Rat Model of Mild Traumatic Brain Injury

BACKGROUND Ketamine, a compelling candidate for neuropathic pain management, has attracted interest for its potential to elevate brain-derived neurotrophic factor (BDNF) levels. We aimed to assess the effects of intrathecally administered ketamine on the cerebrospinal fluid (CSF) levels of BDNF(c-BDNF) and allodynia in a rat model of traumatic brain injury (TBI). MATERIAL AND METHODS Forty-five rats were divided into 3 groups: sham operation (Group S), untreated TBI (Group T), and ketamine-treated TBI (Group K), with 15 rats in each group. Rats were anesthetized, and their skulls were secured in a stereotactic frame before undergoing craniotomy. A controlled cortical impact (CCI) was induced, followed by injection of ketamine (3.41 µg/g) into the CSF in Group K. In Group T, no drug was injected after CCI delivery. On postoperative days (POD) 1, 7, and 14, the 50% mechanical withdrawal threshold (50% MWT) and c-BDNF levels were assessed. RESULTS Groups T and K exhibited a significantly lower 50% MWT than Group S on POD 1(6.6 [5.7, 8.7] g, 10.0 [6.8, 11.6] g, and 18.7 [11.6, 18.7] g, respectively; P<0.001). The c-BDNF levels in Group K were significantly higher than those in Groups S and T on POD 1 (18.9 [16.1, 23.0] pg/ml, 7.3 [6.0, 8.8] pg/ml, and 11.0 [10.6, 12.3] pg/ml, respectively; P=0.006). CONCLUSIONS Intrathecal ketamine administration did not exhibit anti-allodynic effects following mild TBI. c-BDNF level is a promising potential indicator for predicting the expression of allodynia after mild TBI.

Acute brain injury increases pulmonary capillary permeability via sympathetic activation-mediated high fluid shear stress and destruction of the endothelial glycocalyx layer

Neurogenic pulmonary edema secondary to acute brain injury (ABI) is a common and fatal disease condition. However, the pathophysiology of brain-lung interactions is incompletely understood. This study aims to investigate whether sympathetic activation-mediated high fluid shear stress after ABI would damage pulmonary endothelial glycocalyx thus leading to increased pulmonary capillary permeability. The tricuspid annular plane systolic excursion (TAPSE) was detected in a rat model of controlled cortical impact (CCI) and CCI + transection of the cervical sympathetic trunk (TCST). Changes in pulmonary capillary permeability were assessed by analyzing the Evans blue, measuring the dry/wet weight ratio of the lungs and altering protein levels in the bronchoalveolar lavage fluid (BALF). The parallel-plate flow chamber system was used to simulate the fluid shear stress in vitro. Western blotting and immunofluorescence staining were used to determine the expression levels of hyaluronan-binding protein (CEMIP), syndecan-1 and tight junction proteins (TJPs, including claudin-5 and occludin). TCST could restrain cardiac overdrive and sympathetic activation in a rat model of CCI. Compared to the CCI group, the CCI + TCST group showed a reduction of CEMPI (which degrades hyaluronic acid), along with an increase of syndecan-1 and TJPs. CCI + TCST group presented decreasing pulmonary capillary permeability. In vitro, high shear stress (HSS) increased the expression of CEMIP and reduced syndecan-1 and TJPs, which was coordinated with the results in vivo. Our findings show that sympathetic activation-mediated high fluid shear stress after ABI would damage pulmonary endothelial glycocalyx thus leading to increased pulmonary capillary permeability.

Multiplexed Quantitative Proteomics Reveals Proteomic Alterations in Two Rodent Traumatic Brain Injury Models

In many cases of traumatic brain injury (TBI), conspicuous abnormalities, such as scalp wounds and intracranial hemorrhages, abate over time. However, many unnoticeable symptoms, including cognitive, emotional, and behavioral dysfunction, often last from several weeks to years after trauma, even for mild injuries. Moreover, the cause of such persistence of symptoms has not been examined extensively. Recent studies have implicated the dysregulation of the molecular system in the injured brain, necessitating an in-depth analysis of the proteome and signaling pathways that mediate the consequences of TBI. Thus, in this study, the brain proteomes of two TBI models were examined by quantitative proteomics during the recovery period to determine the molecular mechanisms of TBI. Our results show that the proteomes in both TBI models undergo distinct changes. A bioinformatics analysis demonstrated robust activation and inhibition of signaling pathways and core proteins that mediate biological processes after brain injury. These findings can help determine the molecular mechanisms that underlie the persistent effects of TBI and identify novel targets for drug interventions.

Traumatic brain injury extending to the striatum alters autonomic thermoregulation and hypothalamic monoamines in recovering rats

The brain cortex is the structure that is typically injured in traumatic brain injury (TBI) and is anatomically connected with other brain regions, including the striatum and hypothalamus, which are associated in part with motor function and the regulation of body temperature, respectively. We investigated whether a TBI extending to the striatum could affect peripheral and core temperatures as an indicator of autonomic thermoregulatory function. Moreover, it is unknown whether thermal modulation is accompanied by hypothalamic and cortical monoamine changes in rats with motor function recovery. The animals were allocated into three groups: the sham group (sham), a TBI group with a cortical contusion alone (TBI alone), and a TBI group with an injury extending to the dorsal striatum (TBI + striatal injury). Body temperature and motor deficits were evaluated for 20 days post-injury. On the 3rd and 20th days, rats were euthanized to measure the serotonin (5-HT), noradrenaline (NA), and dopamine (DA) levels using high-performance liquid chromatography (HPLC). We observed that TBI with an injury extending to the dorsal striatum increased core and peripheral temperatures. These changes were accompanied by a sustained motor deficit lasting for 14 days. Furthermore, there were notable increases in NA and 5-HT levels in the brain cortex and hypothalamus both 3 and 20 days after injury. In contrast, rats with TBI alone showed no changes in peripheral temperatures and achieved motor function recovery by the 7th day post-injury. In conclusion, our results suggest that TBI with an injury extending to the dorsal striatum elevates both core and peripheral temperatures, causing a delay in functional recovery and increasing hypothalamic monoamine levels. The aftereffects can be attributed to the injury site and changes to the autonomic thermoregulatory functions.

Activation of CB2R by synthetic CB2R agonist, PM289, improves brain endothelial barrier properties, decreases inflammatory response and enhances endothelial repair

The Cannabinoid 2 Receptor (CB2R) has been found to provide immunological modulation in different cell types. More recently, detection of CB2R in the cerebral endothelium suggests a possible role in the resolution of inflammation at the level of the blood-brain-barrier (BBB). Here, the notion that CB2R upregulation in brain endothelial cells could be exploited to promote vascular protection and BBB integrity was evaluated. Targeting and activation of CB2R was accomplished by a novel and highly specific chromenopyrazole based CB2R agonist, PM289. This study demonstrates that CB2R upregulation is induced as early as 8 h in the cortical vasculature in an experimental mouse model of TBI. Unlike CB2R, CB1R was marginally detected and not significantly induced. In the human brain endothelial cell line, hCMEC/D3 cells, similar induction of CB2R was observed upon stimulation with TNFα. Analysis of transendothelial electrical resistance shows that PM289 markedly prevented the barrier-leakiness induced by TNFα. The BBB is also responsible for maintaining an immunological barrier. The five-fold increase in ICAM1 expression in stimulated endothelial cells was significantly diminished due to CB2R activation. Utilizing wounding assays, results showed that wound repair could be accomplished in nearly half the time when the novel CB2R agonist is present compared to the untreated control. Lastly, mechanistically, the effects of CB2R may be explained by the observed inhibition of the p65 NFκB subunit. Overall, these studies support the notion that targeting and activating CB2R in the brain vasculature could aid in BBB and vascular protection in the context of neuroinflammation.

Curcumin ameliorates traumatic brain injury via C1ql3-mediated microglia M2 polarization

PURPOSE

Curcumin can regulate the polarization of microglia and alleviate traumatic brain injury (TBI). However, its detailed action mechanism on downregulating Complement 1q-like-3 protein (C1ql3) in TBI is less reported. The purpose of this study is to explore the role and mechanism of curcumin-regulated C1ql3 in TBI.

METHOD

GSE23639 dataset was used to acquire gene data for microglia. C57BL/6 J wild-type (WT) mice were subjected to establish a controlled cortical impact model of TBI. The effects of curcumin (200 mg/kg) on the brain injury, inflammatory cytokine levels, microglia polarization, and C1ql3 protein expression in mice and BV-2 cells were detected by H&E staining, qRT-PCR, immunofluorescence, and Western blot, respectively. The effects of curcumin (5, 10, 20 μmol/L) and lipopolysaccharides (LPS, 1 µg/mL) on the viability of BV-2 cells were determined by MTT assay. After the transfection of C1ql3 overexpression plasmid, C1ql3 expression, IL-1β and IL-6 levels, and the number of CD16+/32+ and CD206+ cells were determined by qRT-PCR, ELISA and flow cytometry, respectively.

RESULT

C1ql3 expression was down-regulated in microglia after the curcumin treatment. Curcumin treatment could alleviate the TBI-induced brain injury in mice, reduce IL-1β and IL-6 levels, promote M2 polarization of microglia, and decrease C1ql3 protein expression. For BV-2 cells, curcumin treatment had no significant toxic effect on cell viability, but reversed the effect of LPS on cells, while C1ql3 overexpression counteracted the effect of curcumin.

CONCLUSION

Curcumin induces M2 microglia polarization through down-regulating C1ql3 expression, which may become a new treatment method for TBI.

AVAILABILITY OF DATA AND MATERIALS

The analyzed data sets generated during the study are available from the corresponding author on reasonable request.

Non-Invasive Vagus Nerve Stimulation Improves Brain Lesion Volume and Neurobehavioral Outcomes in a Rat Model of Traumatic Brain Injury

Abstract Traumatic brain injury (TBI) continues to be a major cause of death and disability worldwide. This study assessed the effectiveness of non-invasive vagus nerve stimulation (nVNS) in reducing brain lesion volume and improving neurobehavioral performance in a rat model of TBI. Animals were randomized into three experimental groups: (1) TBI with sham stimulation treatment (Control), (2) TBI treated with five lower doses (2-min) nVNS, and (3) TBI treated with five higher doses (2 × 2-min) nVNS. We used the gammaCore nVNS device to deliver stimulations. Magnetic resonance imaging studies were performed 1 and 7 days post-injury to confirm lesion volume. We observed smaller brain lesion volume in the lower dose nVNS group compared with the control group on days 1 and 7. The lesion volume for the higher dose nVNS group was significantly smaller than either the lower dose nVNS or the control groups on days 1 and 7 post-injury. The apparent diffusion coefficient differences between the ipsilateral and contralateral hemispheres on day 1 were significantly smaller for the higher dose (2 × 2 min) nVNS group than for the control group. Voxel-based morphometry analysis revealed an increase in the ipsilateral cortical volume in the control group caused by tissue deformation and swelling. On day 1, these abnormal volume changes were 13% and 55% smaller in the lower dose and higher dose nVNS groups, respectively, compared with the control group. By day 7, nVNS dampened cortical volume loss by 35% and 89% in the lower dose and higher dose nVNS groups, respectively, compared with the control group. Rotarod, beam walking, and anxiety performances were significantly improved in the higher-dose nVNS group on day 1 compared with the control group. The anxiety indices were also improved on day 7 post-injury compared with the control and the lower-dose nVNS groups. In conclusion, the higher dose nVNS (five 2 × 2-min stimulations) reduced brain lesion volume to a level that further refined the role of nVNS therapy for the acute treatment of TBI. Should nVNS prove effective in additional pre-clinical TBI models and later in clinical settings, it would have an enormous impact on the clinical practice of TBI in both civilian and military settings, as it can easily be adopted into routine clinical practice.

Transplantation of glutamatergic neuronal precursor cells in the paraventricular thalamus and claustrum facilitates awakening with recovery of consciousness

BACKGROUND

Stem cells offer a promising therapeutic strategy for patients with disorders of consciousness (DOC) after severe traumatic brain injury (TBI), but the optimal transplantation sites and cells are not clear. Although the paraventricular thalamus (PVT) and claustrum (CLA) are associated with consciousness and are candidate transplantation targets, few studies have been designed to investigate this possibility.

METHODS

Controlled cortical injury (CCI) was performed to establish a mouse model of DOC. CCI-DOC paradigm was established to investigate the role of excitatory neurons of PVT and CLA in disorders of consciousness. The role of excitatory neuron transplantation in promoting arousal and recovery of consciousness was determined by optogenetics, chemogenetics, electrophysiology, Western blot, RT-PCR, double immunofluorescence labeling, and neurobehavioral experiments.

RESULTS

After CCI-DOC, neuronal apoptosis was found to be concentrated in the PVT and CLA. Prolonged awaking latency and cognitive decline were also seen after destruction of the PVT and CLA, suggesting that the PVT and CLA may be key nuclei in DOC. Awaking latency and cognitive performance could be altered by inhibiting or activating excitatory neurons, implying that excitatory neurons may play an important role in DOC. Furthermore, we found that the PVT and CLA function differently, with the PVT mainly involved in arousal maintenance while the CLA plays a role mainly in the generation of conscious content. Finally, we found that by transplanting excitatory neuron precursor cells in the PVT and CLA, respectively, we could facilitate awakening with recovery of consciousness, which was mainly manifested by shortened awaking latency, reduced duration of loss of consciousness (LOC), enhanced cognitive ability, enhanced memory, and improved limb sensation.

CONCLUSION

In this study, we found that the deterioration in the level and content of consciousness after TBI was associated with a large reduction in glutamatergic neurons within the PVT and CLA. Transplantation of glutamatergic neuronal precursor cells could play a beneficial role in promoting arousal and recovery of consciousness. Thus, these findings have the potential to provide a favorable basis for promoting awakening and recovery in patients with DOC.

Opening the black box of traumatic brain injury: a holistic approach combining human 3D neural tissue and an in vitro traumatic brain injury induction device

Traumatic brain injury (TBI) is caused by a wide range of physical events and can induce an even larger spectrum of short- to long-term pathophysiologies. Neuroscientists have relied on animal models to understand the relationship between mechanical damages and functional alterations of neural cells. These in vivo and animal-based in vitro models represent important approaches to mimic traumas on whole brains or organized brain structures but are not fully representative of pathologies occurring after traumas on human brain parenchyma. To overcome these limitations and to establish a more accurate and comprehensive model of human TBI, we engineered an in vitro platform to induce injuries via the controlled projection of a small drop of liquid onto a 3D neural tissue engineered from human iPS cells. With this platform, biological mechanisms involved in neural cellular injury are recorded through electrophysiology measurements, quantification of biomarkers released, and two imaging methods [confocal laser scanning microscope (CLSM) and optical projection tomography (OPT)]. The results showed drastic changes in tissue electrophysiological activities and significant releases of glial and neuronal biomarkers. Tissue imaging allowed us to reconstruct the injured area spatially in 3D after staining it with specific nuclear dyes and to determine TBI resulting in cell death. In future experiments, we seek to monitor the effects of TBI-induced injuries over a prolonged time and at a higher temporal resolution to better understand the subtleties of the biomarker release kinetics and the cell recovery phases.

Chronic motor performance following different traumatic brain injury severity-A systematic review

Introduction

Traumatic brain injury (TBI) is now known to be a chronic disease, causing ongoing neurodegeneration and linked to increased risk of neurodegenerative motor diseases, such as Parkinson's disease and amyotrophic lateral sclerosis. While the presentation of motor deficits acutely following traumatic brain injury is well-documented, however, less is known about how these evolve in the long-term post-injury, or how the initial severity of injury affects these outcomes. The purpose of this review, therefore, was to examine objective assessment of chronic motor impairment across the spectrum of TBI in both preclinical and clinical models.

Methods

PubMed, Embase, Scopus, and PsycINFO databases were searched with a search strategy containing key search terms for TBI and motor function. Original research articles reporting chronic motor outcomes with a clearly defined TBI severity (mild, repeated mild, moderate, moderate-severe, and severe) in an adult population were included.

Results

A total of 97 studies met the inclusion criteria, incorporating 62 preclinical and 35 clinical studies. Motor domains examined included neuroscore, gait, fine-motor, balance, and locomotion for preclinical studies and neuroscore, fine-motor, posture, and gait for clinical studies. There was little consensus among the articles presented, with extensive differences both in assessment methodology of the tests and parameters reported. In general, an effect of severity was seen, with more severe injury leading to persistent motor deficits, although subtle fine motor deficits were also seen clinically following repeated injury. Only six clinical studies investigated motor outcomes beyond 10 years post-injury and two preclinical studies to 18-24 months post-injury, and, as such, the interaction between a previous TBI and aging on motor performance is yet to be comprehensively examined.

Conclusion

Further research is required to establish standardized motor assessment procedures to fully characterize chronic motor impairment across the spectrum of TBI with comprehensive outcomes and consistent protocols. Longitudinal studies investigating the same cohort over time are also a key for understanding the interaction between TBI and aging. This is particularly critical, given the risk of neurodegenerative motor disease development following TBI.

Increased Risk of Aging-Related Neurodegenerative Disease after Traumatic Brain Injury

Traumatic brain injury (TBI) survivors frequently suffer from chronically progressive complications, including significantly increased risk of developing aging-related neurodegenerative disease. As advances in neurocritical care increase the number of TBI survivors, the impact and awareness of this problem are growing. The mechanisms by which TBI increases the risk of developing aging-related neurodegenerative disease, however, are not completely understood. As a result, there are no protective treatments for patients. Here, we review the current literature surrounding the epidemiology and potential mechanistic relationships between brain injury and aging-related neurodegenerative disease. In addition to increasing the risk for developing all forms of dementia, the most prominent aging-related neurodegenerative conditions that are accelerated by TBI are amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Parkinson's disease (PD), and Alzheimer's disease (AD), with ALS and FTD being the least well-established. Mechanistic links between TBI and all forms of dementia that are reviewed include oxidative stress, dysregulated proteostasis, and neuroinflammation. Disease-specific mechanistic links with TBI that are reviewed include TAR DNA binding protein 43 and motor cortex lesions in ALS and FTD; alpha-synuclein, dopaminergic cell death, and synergistic toxin exposure in PD; and brain insulin resistance, amyloid beta pathology, and tau pathology in AD. While compelling mechanistic links have been identified, significantly expanded investigation in the field is needed to develop therapies to protect TBI survivors from the increased risk of aging-related neurodegenerative disease.

Neurobiochemical, Peptidomic, and Bioinformatic Approaches to Characterize Tauopathy Peptidome Biomarker Candidates in Experimental Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a multidimensional damage, and currently, no FDA-approved medicine is available. Multiple pathways in the cell are triggered through a head injury (e.g., calpain and caspase activation), which truncate tau and generate variable fragment sizes (MW 400-45,000 K). In this study, we used an open-head TBI mouse model generated by controlled cortical impact (CCI) and collected ipsilateral (IC) and contralateral (CC) mice htau brain cortices at one (D1) three (D3), and seven (D7) days post-injury. We implemented immunological (antibody-based detection) and peptidomic approaches (nano-reversed-phase liquid chromatography/tandem mass spectrometry) to investigate proteolytic tau peptidome (low molecular weight (LMW) < 10 K)) and pathological phosphorylation sites (high-molecular-weight (HMW); > 10 K) derived from CCI-TBI animal models. Our immunoblotting analysis verified tau hyperphosphorylation, HMW, and HMW breakdown products (HMW-BDP) formation of tau (e.g., pSer₂₀₂, pThr₁₈₁, pThr₂₃₁, pSer₃₉₆, and pSer₄₀₄), following CCI-TBI. Peptidomic data revealed unique sequences of injury-dependent proteolytic peptides generated from human tau protein. Among the N-terminal tau peptides, EIPEGTTAEEAGIGDTPSLEDEAAGHVTQA (a.a. 96-125) and AQPHTEIPEGTTAEEAGIGDTPSLEDEAAGHVTQARM (a.a. 91-127). Examples of tau C-terminal peptides identified include NVSSTGSIDMVDSPQLATLADEVSASLAKQGL (a.a. 410-441) and QLATLADEVSASLAKQGL (a.a. 424-441). Our peptidomic bioinformatic tools showed the association of proteases, such as CAPN1, CAPN2, and CTSL; CASP1, MMP7, and MMP9; and ELANE, GZMA, and MEP1A, in CCI-TBI tau peptidome. In clinical trials for novel TBI treatments, it might be useful to monitor a subset of tau peptidome as targets for biomarker utility and use them for a "theranostic" approach.

Real-time imaging of traumatic brain injury using magnetic induction tomography

Objective. Early diagnosis of traumatic brain injury (TBI) is crucial for its prognosis; however, traditional computed tomography diagnostic methods rely on large medical devices with an associated lag time to receive results. Therefore, an imaging modality is needed that provides real-time monitoring, can easily be carried out to assess the extent of TBI damage, and thus guides treatment.Approach. In the present study, an improved magnetic induction tomography (MIT) data acquisition system was used to monitor TBI in an animal model and distinguish the injury level. A pneumatically controlled cortical impactor was used to strike the parietal lobe of anesthetized rabbits two or three times under the same parameter mode to establish two different rabbit models of TBI. The MIT data acquisition system was used to record data and continuously monitor the brain for one hour without intervention.Main results. A target with increased conductivity was clearly observed in the reconstructed image. The position was relatively fixed and accurate, and the average positioning error of the image was 0.013 72 m. The normalized mean reconstruction value of all images increased with time. The slope of the regression line of the normalized mean reconstruction value differed significantly between the two models (p< 0.0001).Significance. This indicates that in the animal model, the unique features of MIT may facilitate the early monitoring of TBI and distinguish different degrees of injuries, thereby reducing the risk and mortality of associated complications.

Paired associates learning is disrupted after unilateral parietal lobe controlled cortical impact in rats: A trial-by-trial behavioral analysis

Approximately 60-70 million people suffer from traumatic brain injury (TBI) each year. Animal models continue to be paramount in understanding mechanisms of cellular dysfunction and testing new treatments for TBI. Enhancing the translational potential of novel interventions therefore necessitates testing pre-clinical intervention strategies with clinically relevant cognitive assays. This study used a unilateral parietal lobe controlled cortical impact (CCI) model of TBI and tested rats on a touchscreen-based Paired Associates Learning (PAL) task, which is part of the Cambridge Neuropsychological Test Automated Battery. In humans, the PAL task has been used to assess cognitive deficits in the ability to form stimulus-location associations in a multitude of disease states, including TBI. Although the use of PAL in animal models could be important for understanding the clinical severity of cognitive impairment post-injury and throughout intervention, to date, the extent to which a rat model of TBI produces deficits in PAL task performance has not yet been reported. This study details the behavioral consequences of the CCI injury model with a Trial-by-Trial analysis of PAL performance that enables behavioral strategy use to be inferred. Following behavior, the extent of the injury was quantified with histology and staining for the presence of glial fibrillary acid protein and ionized calcium-binding adapter molecule 1. Rats that received unilateral CCI were impaired on the PAL task and showed more aberrant response-driven behavior. The magnitude of PAL impairment was also correlated with Iba1 staining in the thalamus. These observations suggest that PAL could be useful for pre-clinical assessments of novel interventions for treating TBI.

Intravascularly infused extracellular matrix as a biomaterial for targeting and treating inflamed tissues

Decellularized extracellular matrix in the form of patches and locally injected hydrogels has long been used as therapies in animal models of disease. Here we report the safety and feasibility of an intravascularly infused extracellular matrix as a biomaterial for the repair of tissue in animal models of acute myocardial infarction, traumatic brain injury and pulmonary arterial hypertension. The biomaterial consists of decellularized, enzymatically digested and fractionated ventricular myocardium, localizes to injured tissues by binding to leaky microvasculature, and is largely degraded in about 3 d. In rats and pigs with induced acute myocardial infarction followed by intracoronary infusion of the biomaterial, we observed substantially reduced left ventricular volumes and improved wall-motion scores, as well as differential expression of genes associated with tissue repair and inflammation. Delivering pro-healing extracellular matrix by intravascular infusion post injury may provide translational advantages for the healing of inflamed tissues 'from the inside out'.

N6-methyladenosine RNA is modified in the rat hippocampus following traumatic brain injury with hypothermia treatment

Recent studies have suggested a role for N6-methyladenosine (m6A) modification in neurological diseases. Hypothermia, a commonly used treatment for traumatic brain injury, plays a neuroprotective role by altering m6A modifications. In this study, methylated RNA immunoprecipitation sequencing (MeRIP-Seq) was applied to conduct a genome-wide analysis of RNA m6A methylation in the rat hippocampus of Sham and traumatic brain injury (TBI) groups. In addition, we identified the expression of mRNA in the rat hippocampus after TBI with hypothermia treatment. Compared with the Sham group, the sequencing results of the TBI group showed that 951 different m6A peaks and 1226 differentially expressed mRNAs were found. We performed cross-linking analysis of the data of the two groups. The result showed that 92 hyper-methylated genes were upregulated, 13 hyper-methylated genes were downregulated, 25 hypo-methylated genes were upregulated, and 10 hypo-methylated genes were downregulated. Moreover, a total of 758 differential peaks were identified between TBI and hypothermia treatment groups. Among these differential peaks, 173 peaks were altered by TBI and reversed by hypothermia treatment, including Plat, Pdcd5, Rnd3, Sirt1, Plaur, Runx1, Ccr1, Marveld1, Lmnb2, and Chd7. We found that hypothermia treatment transformed some aspects of the TBI-induced m6A methylation landscape of the rat hippocampus.

Sex-Specific Alterations in Inflammatory MicroRNAs in Mouse Brain and Bone Marrow CD11b+ Cells Following Traumatic Brain Injury

Sex is a key biological variable in traumatic brain injury (TBI) and plays a significant role in neuroinflammatory responses. However, the molecular mechanisms contributing to this sexually dimorphic neuroinflammatory response remain elusive. Here we describe a significant and previously unreported tissue enrichment and sex-specific alteration of a set of inflammatory microRNAs (miRNAs) in CD11b+ cells of brain and bone marrow isolated from naïve mice as well as mice subjected to TBI. Our data from naïve mice demonstrated that expression levels of miR-146a-5p and miR-150-5p were relatively higher in brain CD11b+ cells, and that miR-155-5p and miR-223-3p were highly enriched in bone marrow CD11b+ cells. Furthermore, while miR-150-5p and miR-155-5p levels were higher in male brain CD11b+ cells, no significant sexual difference was observed for miR-146a-5p and miR-223-3p. However, TBI resulted in sex-specific differential responses of these miRNAs in brain CD11b+ cells. Specifically, miR-223-3p levels in brain CD11b+ cells were markedly elevated in both sexes in response to TBI at 3 and 24 h, with levels in females being significantly higher than males at 24 h. We then focused on analyzing several miR-223-3p targets and inflammation-related marker genes following injury. Corresponding to the greater elevation of miR-223-3p in females, the miR-223-3p targets, TRAF6 and FBXW7 were significantly reduced in females compared to males. Interestingly, anti-inflammatory genes ARG1 and IL4 were higher in females after TBI than in males. These observations suggest miR-223-3p and other inflammatory responsive miRNAs may play a key role in sex-specific neuroinflammatory response following TBI.

Beneficial Effects of Hyaluronan-Based Hydrogel Implantation after Cortical Traumatic Injury

Traumatic brain injury (TBI) causes cell death mainly in the cerebral cortex. We have previously reported that transplantation of embryonic cortical neurons immediately after cortical injury allows the anatomical reconstruction of injured pathways and that a delay between cortical injury and cell transplantation can partially improve transplantation efficiency. Biomaterials supporting repair processes in combination with cell transplantation are in development. Hyaluronic acid (HA) hydrogel has attracted increasing interest in the field of tissue engineering due to its attractive biological properties. However, before combining the cell with the HA hydrogel for transplantation, it is important to know the effects of the implanted hydrogel alone. Here, we investigated the therapeutic effect of HA on host tissue after a cortical trauma. For this, we implanted HA hydrogel into the lesioned motor cortex of adult mice immediately or one week after a lesion. Our results show the vascularization of the implanted hydrogel. At one month after HA implantation, we observed a reduction in the glial scar around the lesion and the presence of the newly generated oligodendrocytes, immature and mature neurons within the hydrogel. Implanted hydrogel provides favorable environments for the survival and maturation of the newly generated neurons. Collectively, these results suggest a beneficial effect of biomaterial after a cortical traumatic injury.

Defining Experimental Variability in Actuator-Driven Closed Head Impact in Rats

Traumatic brain injury (TBI) is a world-wide health challenge that lacks tools for diagnosis and treatment. There is a need for translational preclinical models to effectively design clinical tools, however, the diversity of models is a barrier to reproducible studies. Actuator-driven closed head impact (AD-CHI) models have translational advantages in replicating the pathophysiological and behavioral outcomes resulting from impact TBI. The main advantages of AD-CHI protocols include versatility of impact parameters such as impact angle, velocity, depth, and dwell time with the ability to interchange tip types, leading to consistent outcomes without the need for craniectomy. Sources of experimental variability within AD-CHI rat models are identified within this review with the aim of supporting further characterization to improve translational value. Primary areas of variability may be attributed to lack of standardization of head stabilization methods, reporting of tip properties, and performance of acute neurological assessments. AD-CHI models were also found to be more prevalently used among pediatric and repeated TBI paradigms. As this model continues to grow in use, establishing the relationships between impact parameters and associated injury outcomes will reduce experimental variability between research groups and encourage meaningful discussions as the community moves towards common data elements.

Metabolism of Exogenous [2,4-13C]β-Hydroxybutyrate following Traumatic Brain Injury in 21-22-Day-Old Rats: An Ex Vivo NMR Study

Traumatic brain injury (TBI) is leading cause of morbidity in young children. Acute dysregulation of oxidative glucose metabolism within the first hours after injury is a hallmark of TBI. The developing brain relies on ketones as well as glucose for energy. Thus, the aim of this study was to determine the metabolism of ketones early after TBI injury in the developing brain. Following the controlled cortical impact injury model of TBI, 21-22-day-old rats were infused with [2,4-¹³C]β-hydroxybutyrate during the acute (4 h) period after injury. Using ex vivo ¹³C-NMR spectroscopy, we determined that ¹³C-β-hydroxybutyrate (¹³C-BHB) metabolism was increased in both the ipsilateral and contralateral sides of the brain after TBI. Incorporation of the label was significantly higher in glutamate than glutamine, indicating that ¹³C-BHB metabolism was higher in neurons than astrocytes in both sham and injured brains. Our results show that (i) ketone metabolism was significantly higher in both the ipsilateral and contralateral sides of the injured brain after TBI; (ii) ketones were extensively metabolized by both astrocytes and neurons, albeit higher in neurons; (iii) the pyruvate recycling pathway determined by incorporation of the label from the metabolism of ¹³C-BHB into lactate was upregulated in the immature brain after TBI.

A cannabidiol aminoquinone derivative activates the PP2A/B55α/HIF pathway and shows protective effects in a murine model of traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is characterized by a primary mechanical injury and a secondary injury associated with neuroinflammation, blood-brain barrier (BBB) disruption and neurodegeneration. We have developed a novel cannabidiol aminoquinone derivative, VCE-004.8, which is a dual PPARγ/CB₂ agonist that also activates the hypoxia inducible factor (HIF) pathway. VCE-004.8 shows potent antifibrotic, anti-inflammatory and neuroprotective activities and it is now in Phase II clinical trials for systemic sclerosis and multiple sclerosis. Herein, we investigated the mechanism of action of VCE-004.8 in the HIF pathway and explored its efficacy in a preclinical model of TBI.

METHODS

Using a phosphoproteomic approach, we investigated the effects of VCE-004.8 on prolyl hydroxylase domain-containing protein 2 (PHD2) posttranslational modifications. The potential role of PP2A/B55α in HIF activation was analyzed using siRNA for B55α. To evaluate the angiogenic response to the treatment with VCE-004.8 we performed a Matrigel plug in vivo assay. Transendothelial electrical resistance (TEER) as well as vascular cell adhesion molecule 1 (VCAM), and zonula occludens 1 (ZO-1) tight junction protein expression were studied in brain microvascular endothelial cells. The efficacy of VCE-004.8 in vivo was evaluated in a controlled cortical impact (CCI) murine model of TBI.

RESULTS

Herein we provide evidence that VCE-004.8 inhibits PHD2 Ser125 phosphorylation and activates HIF through a PP2A/B55α pathway. VCE-004.8 induces angiogenesis in vivo increasing the formation of functional vessel (CD31/α-SMA) and prevents in vitro blood-brain barrier (BBB) disruption ameliorating the loss of ZO-1 expression under proinflammatory conditions. In CCI model VCE-004.8 treatment ameliorates early motor deficits after TBI and attenuates cerebral edema preserving BBB integrity. Histopathological analysis revealed that VCE-004.8 treatment induces neovascularization in pericontusional area and prevented immune cell infiltration to the brain parenchyma. In addition, VCE-004.8 attenuates neuroinflammation and reduces neuronal death and apoptosis in the damaged area.

CONCLUSIONS

This study provides new insight about the mechanism of action of VCE-004.8 regulating the PP2A/B55α/PHD2/HIF pathway. Furthermore, we show the potential efficacy for TBI treatment by preventing BBB disruption, enhancing angiogenesis, and ameliorating neuroinflammation and neurodegeneration after brain injury.

Bioinformatics Analysis of miRNAs and mRNAs Network-Xuefu Zhuyu Decoction Exerts Neuroprotection of Traumatic Brain Injury Mice in the Subacute Phase

Xuefu Zhuyu decoction (XFZYD) is used to treat traumatic brain injury (TBI). XFZYD-based therapies have achieved good clinical outcomes in TBI. However, the underlying mechanisms of XFZYD in TBI remedy remains unclear. The study aimed to identify critical miRNAs and putative mechanisms associated with XFYZD through comprehensive bioinformatics analysis. We established a controlled cortical impact (CCI) mice model and treated the mice with XFZYD. The high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) confirmed the quality of XFZYD. The modified neurological severity score (mNSS) and Morris water maze (MWM) tests indicated that XFZYD improved the neurological deficit (p < 0.05) and cognitive function (p < 0.01). Histological analysis validated the establishment of the CCI model and the treatment effect of XFZYD. HE staining displayed that the pathological degree in the XFZYD-treated group was prominently reduced. The transcriptomic data was generated using microRNA sequencing (miRNA-seq) of the hippocampus. According to cluster analysis, the TBI group clustered together was distinct from the XFZYD group. Sixteen differentially expressed (5 upregulated; 11 downregulated) miRNAs were detected between TBI and XFZYD. The reliability of the sequencing data was confirmed by qRT-PCR. Three miRNAs (mmu-miR-142a-5p, mmu-miR-183-5p, mmu-miR-96-5p) were distinctively expressed in the XFZYD compared with the TBI and consisted of the sequencing results. Bioinformatics analysis suggested that the MAPK signaling pathway contributes to TBI pathophysiology and XFZYD treatment. Subsequently, the functions of miR-96-5p, miR-183-5p, and miR-142a-5p were validated in vitro. TBI significantly induces the down-expression of miR-96-5p, and up-expression of inflammatory cytokines, which were all inhibited by miR-96-5p mimics. The present research provides an adequate fundament for further knowing the pathologic and prognostic process of TBI and supplies deep insights into the therapeutic effects of XFZYD.

Characterizing Brain Perfusion in a Swine Model of Raised Intracranial Pressure

INTRODUCTION

Perfusion of the brain is critical, but this can be compromised due to focal space occupying lesions (SOL). SOLs can raise intracranial pressure (ICP), resulting in reduced cerebral blood flow (CBF). Most gyrencephalic models of brain injury focus on parenchymal injury, with few models of acutely elevated ICP. We hypothesized that we could employ a SOL technique to develop a titratable ICP model and sought to quantitate the resulting decrease in brain perfusion.

METHODS

Six swine were anesthetized and instrumented. A Fogarty balloon catheter was inserted intracranially. Blood CO₂ partial pressure was maintained between 35 and 45 mmHg. The Fogarty balloon was infused with normal saline at 1 mL/min to ICP targets of 10, 20, 30, and 40 mmHg. CBF (mL/100 g/min) were assessed at each ICP level using computed tomography perfusion (CTP). Data are presented as the mean ± standard deviation with all pressures measured in mmHg. CBF values were compared between baseline and each ICP level using analysis of variance.

RESULTS

Baseline ICP was 5 ± 2 and systolic blood pressure was 106 ± 7. Balloon volumes (mL) required to achieve each incremental ICP level were 2.4 ± 0.5, 4.9 ± 1.7, 7.6 ± 1.6, and 9.9 ± 1.7. CBF decreased with each raised ICP level, with CBF being significantly less than baseline at ICP values of 30 (56.1 ± 34.7 versus 20.6 ± 11.0, P < 0.05) and 40 (56.1 ± 34.7 versus 6.5 ± 10.6, P < 0.05).

CONCLUSIONS

An intracranial balloon catheter can be used to increase ICP, delivering a proportionate reduction in CBF. This model can be used in the future studies to examine adjuncts that manipulate intracranial pressure and their effect on brain perfusion.

The effect of clopidogrel and aspirin on the severity of traumatic brain injury in a rat model

Traumatic Brain Injury (TBI) is one of the leading causes of death and disability worldwide. Aspirin (ASA) and clopidogrel (CLOP) are antiplatelet agents that inhibit platelet aggregation. They are implicated in worsening the intracerebral haemorrhage (ICH) risk post-TBI. However, antiplatelet drugs may also exert a neuroprotective effect post-injury. We determined the impact of aspirin and clopidogrel treatment, alone or in combination, on ICH and brain damage in an experimental rat TBI model. We assessed changes in platelet aggregation and measured serum thromboxane by enzyme immune assay. We also explored a panel of brain damage and apoptosis biomarkers by immunoblotting. Rats were treated with aspirin and/or clopidogrel for 48 h prior to TBI and sacrificed 48 h post-injury. In rats treated with antiplatelet agents prior to TBI, platelet aggregation was completely inhibited, and serum thromboxane was significantly decreased, compared to the TBI group without treatment. TBI increases UCHL-1 and GFAP, but decreases hexokinase expression compared to the non-injured controls. All groups treated with antiplatelet drugs prior to TBI had decreased UCH-L1 and GFAP serum levels compared to the TBI untreated group. Furthermore, the ASA and CLOP single treatments increased the hexokinase serum levels. We confirmed that αII-spectrin cleavage increased post-TBI, with the highest cleavage detected in CLOP-treated rats. Aspirin and/or clopidogrel treatment prior to TBI is a double-edged sword that exerts a dual effect post-injury. On one hand, ASA and CLOP single treatments increase the post-TBI ICH risk, with a further detrimental effect from the ASA + CLOP treatment. On the other hand, ASA and/or CLOP treatments are neuroprotective and result in a favourable profile of TBI injury markers. The ICH risk and the neuroprotection benefits from antiplatelet therapy should be weighed against each other to ameliorate the management of TBI patients.

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

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

A Machine Learning Approach to Investigate the Uncertainty of Tissue-Level Injury Metrics for Cerebral Contusion

Controlled cortical impact (CCI) on porcine brain is often utilized to investigate the pathophysiology and functional outcome of focal traumatic brain injury (TBI), such as cerebral contusion (CC). Using a finite element (FE) model of the porcine brain, the localized brain strain and strain rate resulting from CCI can be computed and compared to the experimentally assessed cortical lesion. This way, tissue-level injury metrics and corresponding thresholds specific for CC can be established. However, the variability and uncertainty associated with the CCI experimental parameters contribute to the uncertainty of the provoked cortical lesion and, in turn, of the predicted injury metrics. Uncertainty quantification via probabilistic methods (Monte Carlo simulation, MCS) requires a large number of FE simulations, which results in a time-consuming process. Following the recent success of machine learning (ML) in TBI biomechanical modeling, we developed an artificial neural network as surrogate of the FE porcine brain model to predict the brain strain and the strain rate in a computationally efficient way. We assessed the effect of several experimental and modeling parameters on four FE-derived CC injury metrics (maximum principal strain, maximum principal strain rate, product of maximum principal strain and strain rate, and maximum shear strain). Next, we compared the in silico brain mechanical response with cortical damage data from in vivo CCI experiments on pig brains to evaluate the predictive performance of the CC injury metrics. Our ML surrogate was capable of rapidly predicting the outcome of the FE porcine brain undergoing CCI. The now computationally efficient MCS showed that depth and velocity of indentation were the most influential parameters for the strain and the strain rate-based injury metrics, respectively. The sensitivity analysis and comparison with the cortical damage experimental data indicate a better performance of maximum principal strain and maximum shear strain as tissue-level injury metrics for CC. These results provide guidelines to optimize the design of CCI tests and bring new insights to the understanding of the mechanical response of brain tissue to focal traumatic brain injury. Our findings also highlight the potential of using ML for computationally efficient TBI biomechanics investigations.

Neuroprotective Roles of the Adenosine A3 Receptor Agonist AST-004 in Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) remains one of the greatest public health concerns with increasing morbidity and mortality rates worldwide. Our group reported that stimulation of astrocyte mitochondrial metabolism by P2Y1 receptor agonists significantly reduced cerebral edema and reactive gliosis in a TBI model. Subsequent data on the pharmacokinetics (PK) and rapid metabolism of these compounds suggested that neuroprotection was likely mediated by a metabolite, AST-004, which binding data indicated was an adenosine A3 receptor (A3R) agonist. The neuroprotective efficacy of AST-004 was tested in a control closed cortical injury (CCCI) model of TBI in mice. Twenty-four (24) hours post-injury, mice subjected to CCCI and treated with AST-004 (0.22 mg/kg, injected 30 min post-trauma) exhibited significantly less secondary brain injury. These effects were quantified with less cell death (PSVue794 fluorescence) and loss of blood brain barrier breakdown (Evans blue extravasation assay), compared to vehicle-treated TBI mice. TBI-treated mice also exhibited significantly reduced neuroinflammatory markers, glial-fibrillary acidic protein (GFAP, astrogliosis) and ionized Ca2+-binding adaptor molecule 1 (Iba1, microgliosis), both at the mRNA (qRT-PCR) and protein (Western blot and immunofluorescence) levels, respectively. Four (4) weeks post-injury, both male and female TBI mice presented a significant reduction in freezing behavior during contextual fear conditioning (after foot shock). AST-004 treatment prevented this TBI-induced impairment in male mice, but did not significantly affect impairment in female mice. Impairment of spatial memory, assessed 24 and 48 h after the initial fear conditioning, was also reduced in AST-004-treated TBI-male mice. Female TBI mice did not exhibit memory impairment 24 and 48 h after contextual fear conditioning and similarly, AST-004-treated female TBI mice were comparable to sham mice. Finally, AST-004 treatments were found to increase in vivo ATP production in astrocytes (GFAP-targeted luciferase activity), consistent with the proposed mechanism of action. These data reveal AST-004 as a novel A3R agonist that increases astrocyte energy production and enhances their neuroprotective efficacy after brain injury.

Moderate Intensity Treadmill Exercise Increases Survival of Newborn Hippocampal Neurons and Improves Neurobehavioral Outcomes after Traumatic Brain Injury

Physician-prescribed rest after traumatic brain injury (TBI) is both commonplace and an increasingly scrutinized approach to TBI treatment. Although this practice remains a standard of patient care for TBI, research of patient outcomes reveals little to no benefit of prescribed rest after TBI, and in some cases prolonged rest has been shown to interfere with patient well-being. In direct contrast to the clinical advice regarding physical activity after TBI, animal models of brain injury consistently indicate that exercise is neuroprotective and promotes recovery. Here, we assessed the effect of low and moderate intensity treadmill exercise on functional outcome and hippocampal neural proliferation after brain injury. Using the controlled cortical impact (CCI) mouse model of TBI, we show that 10 days of moderate intensity treadmill exercise initiated after CCI reduces anxiety-like behavior, improves hippocampus-dependent spatial memory, and promotes hippocampal proliferation and newborn neuronal survival. Pathophysiological measures including lesion volume and axon degeneration were not altered by exercise. Taken together, these data reveal that carefully titrated physical activity may be a safe and effective approach to promoting recovery after brain injury.

From biomechanics to pathology: predicting axonal injury from patterns of strain after traumatic brain injury

The relationship between biomechanical forces and neuropathology is key to understanding traumatic brain injury. White matter tracts are damaged by high shear forces during impact, resulting in axonal injury, a key determinant of long-term clinical outcomes. However, the relationship between biomechanical forces and patterns of white matter injuries, associated with persistent diffusion MRI abnormalities, is poorly understood. This limits the ability to predict the severity of head injuries and the design of appropriate protection. Our previously developed human finite element model of head injury predicted the location of post-traumatic neurodegeneration. A similar rat model now allows us to experimentally test whether strain patterns calculated by the model predicts in vivo MRI and histology changes. Using a controlled cortical impact, mild and moderate injuries (1 and 2 mm) were performed. Focal and axonal injuries were quantified with volumetric and diffusion 9.4 T MRI at 2 weeks post injury. Detailed analysis of the corpus callosum was conducted using multi-shell diffusion MRI and histopathology. Microglia and astrocyte density, including process parameters, along with white matter structural integrity and neurofilament expression were determined by quantitative immunohistochemistry. Linear mixed effects regression analyses for strain and strain rate with the employed outcome measures were used to ascertain how well immediate biomechanics could explain MRI and histology changes. The spatial pattern of mechanical strain and strain rate in the injured cortex shows good agreement with the probability maps of focal lesions derived from volumetric MRI. Diffusion metrics showed abnormalities in the corpus callosum, indicating white matter changes in the segments subjected to high strain, as predicted by the model. The same segments also exhibited a severity-dependent increase in glia cell density, white matter thinning and reduced neurofilament expression. Linear mixed effects regression analyses showed that mechanical strain and strain rate were significant predictors of in vivo MRI and histology changes. Specifically, strain and strain rate respectively explained 33% and 28% of the reduction in fractional anisotropy, 51% and 29% of the change in neurofilament expression and 51% and 30% of microglia density changes. The work provides evidence that strain and strain rate in the first milliseconds after injury are important factors in determining patterns of glial and axonal injury and serve as experimental validators of our computational model of traumatic brain injury. Our results provide support for the use of this model in understanding the relationship of biomechanics and neuropathology and can guide the development of head protection systems, such as airbags and helmets.

Biologic Effect of Hydrogen Sulfide and Its Role in Traumatic Brain Injury

Ever since endogenous hydrogen sulfide (H₂S) was found in mammals in 1989, accumulated evidence has demonstrated that H₂S functions as a novel neurological gasotransmitter in brain tissues and may play a key role in traumatic brain injury. It has been proved that H₂S has an antioxidant, anti-inflammatory, and antiapoptosis function in the neuron system and functions as a neuroprotective factor against secondary brain injury. In addition, H₂S has other biologic effects such as regulating the intracellular concentration of Ca²⁺, facilitating hippocampal long-term potentiation (LTP), and activating ATP-sensitive K channels. Due to the toxic nature of H₂S when exceeding the physiological dose in the human body, only a small amount of H₂S-related therapies was applied to clinical treatment. Therefore, it has huge therapeutic potential and has great hope for recovering patients with traumatic brain injury.

Inhibition of extracellular vesicle pathway using neutral sphingomyelinase inhibitors as a neuroprotective treatment for brain injury

Traumatic brain injury is a sudden trauma or blow on the head, and severe traumatic brain injury is a major cause of death and disability worldwide. The acute and chronic consequences following traumatic brain injury can lead to progressive secondary neurodegenerative changes and cognitive dysfunction. To date, there is no effective pharmaceutical products for the treatment to reduce secondary damage after brain injury. The discovery of extracellular vesicles has attracted considerable scientific attention due to their role in cell-to-cell communication. Extracellular vesicles have shown their potential to carry not only biological molecules but also as a drug delivery vehicle. As a carrier of molecular information, extracellular vesicles have been involved in physiological functions as well as in the modulation of immune responses. Here, we aim to provide new insights into the contrasting role of extracellular vesicles in the propagation of inflammatory responses after brain injury. As a carrier of pro-inflammatory molecules, their role as functional mediators in the pathophysiology of brain injury is discussed, addressing the inhibition of the extracellular vesicle pathway as an anti-inflammatory or neuroprotective approach to improve the outcome of both acute and chronic inflammation following brain injury. Here, we summarize therapeutic strategies to diminish the risk the neurodegeneration post brain injury and propose that neutral sphingomyelinase inhibitors could be used as potentially useful therapeutic agents for the treatment of brain injury associated neuroinflammation.

Initiators of Classical and Lectin Complement Pathways Are Differently Engaged after Traumatic Brain Injury-Time-Dependent Changes in the Cortex, Striatum, Thalamus and Hippocampus in a Mouse Model

The complement system is involved in promoting secondary injury after traumatic brain injury (TBI), but the roles of the classical and lectin pathways leading to complement activation need to be clarified. To this end, we aimed to determine the ability of the brain to activate the synthesis of classical and lectin pathway initiators in response to TBI and to examine their expression in primary microglial cell cultures. We have modeled TBI in mice by controlled cortical impact (CCI), a clinically relevant experimental model. Using Real-time quantitative polymerase chain reaction (RT-qPCR) we analyzed the expression of initiators of classical the complement component 1q, 1r and 1s (C1q, C1r, and C1s) and lectin (mannose binding lectin A, mannose binding lectin C, collectin 11, ficolin A, and ficolin B) complement pathways and other cellular markers in four brain areas (cortex, striatum, thalamus and hippocampus) of mice exposed to CCI from 24 h and up to 5 weeks. In all murine ipsilateral brain structures assessed, we detected long-lasting, time- and area-dependent significant increases in the mRNA levels of all classical (C1q, C1s, C1r) and some lectin (collectin 11, ficolin A, ficolin B) initiator molecules after TBI. In parallel, we observed significantly enhanced expression of cellular markers for neutrophils (Cd177), T cells (Cd8), astrocytes (glial fibrillary acidic protein—GFAP), microglia/macrophages (allograft inflammatory factor 1—IBA-1), and microglia (transmembrane protein 119—TMEM119); moreover, we detected astrocytes (GFAP) and microglia/macrophages (IBA-1) protein level strong upregulation in all analyzed brain areas. Further, the results obtained in primary microglial cell cultures suggested that these cells may be largely responsible for the biosynthesis of classical pathway initiators. However, microglia are unlikely to be responsible for the production of the lectin pathway initiators. Immunofluorescence analysis confirmed that at the site of brain injury, the C1q is localized in microglia/macrophages and neurons but not in astroglial cells. In sum, the brain strongly reacts to TBI by activating the local synthesis of classical and lectin complement pathway activators. Thus, the brain responds to TBI with a strong, widespread and persistent upregulation of complement components, the targeting of which may provide protection in TBI.

A machine learning approach for magnetic resonance image-based mouse brain modeling and fast computation in controlled cortical impact

Computational modeling of the brain is crucial for the study of traumatic brain injury. An anatomically accurate model with refined details could provide the most accurate computational results. However, computational models with fine mesh details could take prolonged computation time that impedes the clinical translation of the models. Therefore, a way to construct a model with low computational cost while maintaining a computational accuracy comparable with that of the high-fidelity model is desired. In this study, we constructed magnetic resonance (MR) image-based finite element (FE) models of a mouse brain for simulations of controlled cortical impact. The anatomical details were kept by mapping each image voxel to a corresponding FE mesh element. We constructed a super-resolution neural network that could produce computational results of a refined FE model with a mesh size of 70 μm from a coarse FE model with a mesh size of 280 μm. The peak signal-to-noise ratio of the reconstructed results was 33.26 dB, while the computational speed was increased by 50-fold. This proof-of-concept study showed that using machine learning techniques, MR image-based computational modeling could be applied and evaluated in a timely fashion. This paved ways for fast FE modeling and computation based on MR images. Results also support the potential clinical applications of MR image-based computational modeling of the human brain in a variety of scenarios such as brain impact and intervention.Graphical abstract MR image-based FE models with different mesh sizes were generated for CCI. The training and testing data sets were computed with 5 different impact locations and 3 different impact velocities. High-resolution strain maps were estimated using a SR neural network with greatly reduced computational cost.

Assessment of Long-Term Effects of Sports-Related Concussions: Biological Mechanisms and Exosomal Biomarkers

Concussion or mild traumatic brain injury (mTBI) in athletes can cause persistent symptoms, known as post-concussion syndrome (PCS), and repeated injuries may increase the long-term risk for an athlete to develop neurodegenerative diseases such as chronic traumatic encephalopathy (CTE), and Alzheimer's disease (AD). The Center for Disease Control estimates that up to 3.8 million sport-related mTBI are reported each year in the United States. Despite the magnitude of the phenomenon, there is a current lack of comprehensive prognostic indicators and research has shown that available monitoring tools are moderately sensitive to short-term concussion effects but less sensitive to long-term consequences. The overall aim of this review is to discuss novel, quantitative, and objective measurements that can predict long-term outcomes following repeated sports-related mTBIs. The specific objectives were (1) to provide an overview of the current clinical and biomechanical tools available to health practitioners to ensure recovery after mTBIs, (2) to synthesize potential biological mechanisms in animal models underlying the long-term adverse consequences of mTBIs, (3) to discuss the possible link between repeated mTBI and neurodegenerative diseases, and (4) to discuss the current knowledge about fluid biomarkers for mTBIs with a focus on novel exosomal biomarkers. The conclusions from this review are that current post-concussion clinical tests are not sufficiently sensitive to injury and do not accurately quantify post-concussion alterations associated with repeated mTBIs. In the current review, it is proposed that current practices should be amended to include a repeated symptom inventory, a cognitive assessment of executive function and impulse control, an instrumented assessment of balance, vestibulo-ocular assessments, and an improved panel of blood or exosome biomarkers.

Reduced Reelin Expression in the Hippocampus after Traumatic Brain Injury

Traumatic brain injury (TBI) is a relatively common occurrence following accidents or violence, and often results in long-term cognitive or motor disability. Despite the high health cost associated with this type of injury, presently there are no effective treatments for many neurological symptoms resulting from TBI. This is due in part to our limited understanding of the mechanisms underlying brain dysfunction after injury. In this study, we used the mouse controlled cortical impact (CCI) model to investigate the effects of TBI, and focused on Reelin, an extracellular protein that critically regulates brain development and modulates synaptic activity in the adult brain. We found that Reelin expression decreases in forebrain regions after TBI, and that the number of Reelin-expressing cells decrease specifically in the hippocampus, an area of the brain that plays an important role in learning and memory. We also conducted in vitro experiments using mouse neuronal cultures and discovered that Reelin protects hippocampal neuronal cells from glutamate-induced neurotoxicity, a well-known secondary effect of TBI. Together our findings suggest that the loss of Reelin expression may contribute to neuronal death in the hippocampus after TBI, and raise the possibility that increasing Reelin levels or signaling activity may promote functional recovery.

Current ex Vivo and in Vitro Approaches to Uncovering Mechanisms of Neurological Dysfunction after Traumatic Brain Injury

Traumatic brain injury often leads to progressive alterations at the molecular to circuit levels resulting in epilepsy and memory impairments. Ex vivo and in vitro models have provided a powerful platform for investigating the multimodal alteration after trauma. Recent ex vivo analyses using voltage sensitive dye imaging, optogenetics, and glutamate uncaging have revealed circuit abnormalities following in vivo brain injury. In vitro injury models have enabled examination of early and progressive changes in activity while development of three-dimensional organoids derived from human induced pluripotent stem cells have opened novel avenues for injury research. Here, we highlight recent advances in ex vivo and in vitro systems, focusing on their potential for advancing mechanistic understandings, possible limitations, and implications for therapeutics.

Combined Diffusion Tensor Imaging and Quantitative Susceptibility Mapping Discern Discrete Facets of White Matter Pathology Post-injury in the Rodent Brain

Early loss of white matter microstructure integrity is a significant cause of long-term neurological disorders following traumatic brain injury (TBI). White matter abnormalities typically involve axonal loss and demyelination. In-vivo imaging tools to detect and differentiate such microstructural changes are not well-explored. This work utilizes the conjoint potential offered by advanced magnetic resonance imaging techniques, including quantitative susceptibility mapping (QSM) and diffusion tensor imaging (DTI), to discern the underlying white matter pathology at specific time points (5 h, 1, 3, 7, 14, and 30 days) post-injury in the controlled cortical impact mouse model. A total of 42 animals were randomized into six TBI groups (n = 6 per group) and one sham group (n = 6). Histopathology was performed to validate in-vivo findings by performing myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP) immunostaining for the assessment of changes to myelin and astrocytes. After 5 h of injury radial diffusivity (RD) was increased in white matter without a significant change in axial diffusivity (AxD) and susceptibility values. After 1 day post-injury RD was decreased. AxD and susceptibility changes were seen after 3 days post-injury. Susceptibility increases in white matter were observed in both ipsilateral and contralateral regions and persisted for 30 days. In histology, an increase in GFAP immunoreactivity was observed after 3 days post-injury and remained high for 30 days in both ipsilateral and contralateral white matter regions. A loss in MBP signal was noted after 3 days post-injury that continued up to 30 days. In conclusion, these results demonstrate the complementary ability of DTI and QSM in discerning the micro-pathological processes triggered following TBI. While DTI revealed acute and focal white matter changes, QSM mirrored the temporal demyelination in the white matter tracts and diffuse regions at the chronic state.

Epitranscriptomic profiling of N6-methyladenosine-related RNA methylation in rat cerebral cortex following traumatic brain injury

Background

N6-methyladenosine (m6A) is the most prevalent post-transcriptional modification of eukaryotic mRNA. It has been reported that there is a stimulus-dependent regulation of m6A in the mammalian central nervous system in response to sensory experience, learning, and injury. The mRNA m6A methylation pattern in rat cortex after traumatic brain injury (TBI) has not been investigated.

Results

In this study, we conducted a genome-wide profiling of mRNA m6A methylation in rat cortex via methylated RNA immunoprecipitation sequencing (MeRIP-Seq). After TBI, the expressions of METTL14 and FTO were significantly down-regulated in rat cerebral cortex. Using MeRIP-Seq, we identified a total of 2165 significantly changed peaks, of which 1062 were significantly up-regulated and 1103 peaks were significantly down-regulated. These m6A peaks were located across 1850 genes. The analysis of both m6A peaks and mRNA expression revealed that there were 175 mRNA significantly altered methylation and expression levels after TBI. Moreover, it was found that functional FTO is necessary to repair neurological damage caused by TBI but has no effect on the spatial learning and memory abilities of TBI rats by using FTO inhibitor FB23–2.

Conclusion

This study explored the m6A methylation pattern of mRNA after TBI in rat cortex and identified FTO as possible intervention targets in the epigenetic modification of TBI.

Differences in pathological changes between two rat models of severe traumatic brain injury

The rat high-impact free weight drop model mimics the diffuse axonal injury caused by severe traumatic brain injury in humans, while severe controlled cortical impact can produce a severe traumatic brain injury model using precise strike parameters. In this study, we compare the pathological mechanisms and pathological changes between two rat severe brain injury models to identify the similarities and differences. The severe controlled cortical impact model was produced by an electronic controlled cortical impact device, while the severe free weight drop model was produced by dropping a 500 g free weight from a height of 1.8 m through a plastic tube. Body temperature and mortality were recorded, and neurological deficits were assessed with the modified neurological severity score. Brain edema and blood-brain barrier damage were evaluated by assessing brain water content and Evans blue extravasation. In addition, a cytokine array kit was used to detect inflammatory cytokines. Neuronal apoptosis in the brain and brainstem was quantified by immunofluorescence staining. Both the severe controlled cortical impact and severe free weight drop models exhibited significant neurological impairments and body temperature fluctuations. More severe motor dysfunction was observed in the severe controlled cortical impact model, while more severe cognitive dysfunction was observed in the severe free weight drop model. Brain edema, inflammatory cytokine changes and cortical neuronal apoptosis were more substantial and blood-brain barrier damage was more focal in the severe controlled cortical impact group compared with the severe free weight drop group. The severe free weight drop model presented with more significant apoptosis in the brainstem and diffused blood-brain barrier damage, with higher mortality and lower repeatability compared with the severe controlled cortical impact group. Severe brainstem damage was not found in the severe controlled cortical impact model. These results indicate that the severe controlled cortical impact model is relatively more stable, more reproducible, and shows obvious cerebral pathological changes at an earlier stage. Therefore, the severe controlled cortical impact model is likely more suitable for studies on severe focal traumatic brain injury, while the severe free weight drop model may be more apt for studies on diffuse axonal injury. All experimental procedures were approved by the Ethics Committee of Animal Experiments of Tianjin Medical University, China (approval No. IRB2012-028-02) in February 2012.

Improving Understanding and Outcomes of Traumatic Brain Injury Using Bidirectional Translational Research

Recent clinical trials in traumatic brain injury (TBI) have failed to demonstrate therapeutic effects even when there appears to be good evidence for efficacy in one or more appropriate pre-clinical models. While existing animal models mimic the injury, difficulties in translating promising therapeutics are exacerbated by the lack of alignment of discrete measures of the underlying injury pathology between the animal models and human subjects. To address this mismatch, we have incorporated reverse translation of bedside experience to inform pre-clinical studies in a large animal (pig) model of TBI that mirror practical clinical assessments. Cerebral autoregulation is impaired after TBI, contributing to poor outcome. Cerebral perfusion pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. Vasoactive agents clinically used to elevate MAP to increase CPP after TBI, such as phenylephrine (Phe), dopamine (DA), norepinephrine (NE), and epinephrine (EPI), however, have not been compared sufficiently regarding effect on CPP, autoregulation, and survival after TBI, and clinically, current vasoactive agent use is variable. The cerebral effects of these clinically commonly used vasoactive agents are not known. This review will emphasize pediatric work and will describe bidirectional translational studies using a more human-like animal model of TBI to identify better therapeutic strategies to improve outcome post-injury. These studies in addition investigated the mechanism(s) involved in improvement of outcome in the setting of TBI.