Intimate Partner Violence-Related Brain Injury: Unmasking and Addressing the Gaps

Intimate partner violence (IPV) is a significant, global public health concern. Women, individuals with historically underrepresented identities, and disabilities are at high risk for IPV and tend to experience severe injuries. There has been growing concern about the risk of exposure to IPV-related head trauma, resulting in IPV-related brain injury (IPV-BI), and its health consequences. Past work suggests that a significant proportion of women exposed to IPV experience IPV-BI, likely representing a distinct phenotype compared with BI of other etiologies. An IPV-BI often co-occurs with psychological trauma and mental health complaints, leading to unique issues related to identifying, prognosticating, and managing IPV-BI outcomes. The goal of this review is to identify important gaps in research and clinical practice in IPV-BI and suggest potential solutions to address them. We summarize IPV research in five key priority areas: (1) unique considerations for IPV-BI study design; (2) understanding non-fatal strangulation as a form of BI; (3) identifying objective biomarkers of IPV-BI; (4) consideration of the chronicity, cumulative and late effects of IPV-BI; and (5) BI as a risk factor for IPV engagement. Our review concludes with a call to action to help investigators develop ecologically valid research studies addressing the identified clinical-research knowledge gaps and strategies to improve care in individuals exposed to IPV-BI. By reducing the current gaps and answering these calls to action, we will approach IPV-BI in a trauma-informed manner, ultimately improving outcomes and quality of life for those impacted by IPV-BI.

Treatment with the vascular endothelial growth factor-A antibody, bevacizumab, has sex-specific effects in a rat model of mild traumatic brain injury

Mild traumatic brain injury (mTBI) involves damage to the cerebrovascular system. Vascular endothelial growth factor-A (VEGF-A) is an important modulator of vascular health and VEGF-A promotes the brain's ability to recover after more severe forms of brain injury; however, the role of VEGF-A in mTBI remains poorly understood. Bevacizumab (BEV) is a monoclonal antibody that binds to VEGF-A and neutralises its actions. To better understand the role of VEGF-A in mTBI recovery, this study examined how BEV treatment affected outcomes in rats given a mTBI. Adult Sprague-Dawley rats were assigned to sham-injury + vehicle treatment (VEH), sham-injury + BEV treatment, mTBI + VEH treatment, mTBI + BEV treatment groups. Treatment was administered intracerebroventricularly via a cannula beginning at the time of injury and continuing until the end of the study. Rats underwent behavioral testing after injury and were euthanized on day 11. In both females and males, BEV had a negative impact on cognitive function. mTBI and BEV treatment increased the expression of inflammatory markers in females. In males, BEV treatment altered markers related to hypoxia and vascular health. These novel findings of sex-specific responses to BEV and mTBI provide important insights into the role of VEGF-A in mTBI.

ComBating inter-site differences in field strength: harmonizing preclinical traumatic brain injury MRI data

Integrating datasets from multiple sites and scanners can increase statistical power for neuroimaging studies but can also introduce significant inter-site confounds. We evaluated the effectiveness of ComBat, an empirical Bayes approach, to combine longitudinal preclinical MRI data acquired at 4.7 or 9.4 T at two different sites in Australia. Male Sprague Dawley rats underwent MRI on Days 2, 9, 28, and 150 following moderate/severe traumatic brain injury (TBI) or sham injury as part of Project 1 of the NIH/NINDS-funded Centre Without Walls EpiBioS4Rx project. Diffusion-weighted and multiple-gradient-echo images were acquired, and outcomes included QSM, FA, and ADC. Acute injury measures including apnea and self-righting reflex were consistent between sites. Mixed-effect analysis of ipsilateral and contralateral corpus callosum (CC) summary values revealed a significant effect of site on FA and ADC values, which was removed following ComBat harmonization. Bland-Altman plots for each metric showed reduced variability across sites following ComBat harmonization, including for QSM, despite appearing to be largely unaffected by inter-site differences and no effect of site observed. Following harmonization, the combined inter-site data revealed significant differences in the imaging metrics consistent with previously reported outcomes. TBI resulted in significantly reduced FA and increased susceptibility in the ipsilateral CC, and significantly reduced FA in the contralateral CC compared with sham-injured rats. Additionally, TBI rats also exhibited a reversal in ipsilateral CC ADC values over time with significantly reduced ADC at Day 9, followed by increased ADC 150 days after injury. Our findings demonstrate the need for harmonizing multi-site preclinical MRI data and show that this can be successfully achieved using ComBat while preserving phenotypical changes due to TBI.

Epilepsy phenotype and its reproducibility after lateral fluid percussion-induced traumatic brain injury in rats: Multicenter EpiBioS4Rx study project 1

OBJECTIVE

This study was undertaken to assess reproducibility of the epilepsy outcome and phenotype in a lateral fluid percussion model of posttraumatic epilepsy (PTE) across three study sites.

METHODS

A total of 525 adult male Sprague Dawley rats were randomized to lateral fluid percussion-induced brain injury (FPI) or sham operation. Of these, 264 were assigned to magnetic resonance imaging (MRI cohort, 43 sham, 221 traumatic brain injury [TBI]) and 261 to electrophysiological follow-up (EEG cohort, 41 sham, 220 TBI). A major effort was made to harmonize the rats, materials, equipment, procedures, and monitoring systems. On the 7th post-TBI month, rats were video-EEG monitored for epilepsy diagnosis.

RESULTS

A total of 245 rats were video-EEG phenotyped for epilepsy on the 7th postinjury month (121 in MRI cohort, 124 in EEG cohort). In the whole cohort (n = 245), the prevalence of PTE in rats with TBI was 22%, being 27% in the MRI and 18% in the EEG cohort (p > .05). Prevalence of PTE did not differ between the three study sites (p > .05). The average seizure frequency was .317 ± .725 seizures/day at University of Eastern Finland (UEF; Finland), .085 ± .067 at Monash University (Monash; Australia), and .299 ± .266 at University of California, Los Angeles (UCLA; USA; p < .01 as compared to Monash). The average seizure duration did not differ between UEF (104 ± 48 s), Monash (90 ± 33 s), and UCLA (105 ± 473 s; p > .05). Of the 219 seizures, 53% occurred as part of a seizure cluster (≥3 seizures/24 h; p >.05 between the study sites). Of the 209 seizures, 56% occurred during lights-on period and 44% during lights-off period (p > .05 between the study sites).

SIGNIFICANCE

The PTE phenotype induced by lateral FPI is reproducible in a multicenter design. Our study supports the feasibility of performing preclinical multicenter trials in PTE to increase statistical power and experimental rigor to produce clinically translatable data to combat epileptogenesis after TBI.

Investigating the Association Between Extended Participation in Collision Sports and Fluid Biomarkers Among Masters Athletes

Traumatic brain injuries (TBIs) and concussions are prevalent in collision sports, and there is evidence that levels of exposure to such sports may increase the risk of neurological abnormalities. Elevated levels of fluid-based biomarkers have been observed after concussions or among athletes with a history of participating in collision sports, and certain biomarkers exhibit sensitivity toward neurodegeneration. This study investigated a cohort of 28 male amateur athletes competing in "Masters" competitions for persons >35 years of age. The primary objective of this study was to compare the levels of blood and saliva biomarkers associated with brain injury, inflammation, aging, and neurodegeneration between athletes with an extensive history of collision sport participation (i.e., median = 27 years; interquartile range = 18-44, minimum = 8) and those with no history. Plasma proteins associated with neural damage and neurodegeneration were measured using Simoa® assays, and saliva was analyzed for markers associated with inflammation and telomere length using quantitative real-time polymerase chain reaction. There were no significant differences between collision and non-collision sport athletes for plasma levels of glial fibrillary acidic protein, neurofilament light, ubiquitin C-terminal hydrolase L1, tau, tau phosphorylated at threonine 181, and brain-derived neurotrophic factor. Moreover, salivary levels of genes associated with inflammation and telomere length were similar between groups. There were no significant differences between groups in symptom frequency or severity on the Sport Concussion Assessment Tool-5th Edition. Overall, these findings provide preliminary evidence that biomarkers associated with neural tissue damage, neurodegeneration, and inflammation may not exhibit significant alterations in asymptomatic amateur athletes with an extensive history of amateur collision sport participation.

Altered grey matter structural covariance in chronic moderate-severe traumatic brain injury

Traumatic brain injury (TBI) alters brain network connectivity. Structural covariance networks (SCNs) reflect morphological covariation between brain regions. SCNs may elucidate how altered brain network topology in TBI influences long-term outcomes. Here, we assessed whether SCN organisation is altered in individuals with chronic moderate-severe TBI (≥ 10 years post-injury) and associations with cognitive performance. This case-control study included fifty individuals with chronic moderate-severe TBI compared to 75 healthy controls recruited from an ongoing longitudinal head injury outcome study. SCNs were constructed using grey matter volume measurements from T1-weighted MRI images. Global and regional SCN organisation in relation to group membership and cognitive ability was examined using regression analyses. Globally, TBI participants had reduced small-worldness, longer characteristic path length, higher clustering, and higher modularity globally (p < 0.05). Regionally, TBI participants had greater betweenness centrality (p < 0.05) in frontal and central areas of the cortex. No significant associations were observed between global network measures and cognitive ability in participants with TBI (p > 0.05). Chronic moderate-severe TBI was associated with a shift towards a more segregated global network topology and altered organisation in frontal and central brain regions. There was no evidence that SCNs are associated with cognition.

A pre-existing Toxoplasma gondii infection exacerbates the pathophysiological response and extent of brain damage after traumatic brain injury in mice

Traumatic brain injury (TBI) is a key contributor to global morbidity that lacks effective treatments. Microbial infections are common in TBI patients, and their presence could modify the physiological response to TBI. It is estimated that one-third of the human population is incurably infected with the feline-borne parasite, Toxoplasma gondii, which can invade the central nervous system and result in chronic low-grade neuroinflammation, oxidative stress, and excitotoxicity-all of which are also important pathophysiological processes in TBI. Considering the large number of TBI patients that have a pre-existing T. gondii infection prior to injury, and the potential mechanistic synergies between the conditions, this study investigated how a pre-existing T. gondii infection modified TBI outcomes across acute, sub-acute and chronic recovery in male and female mice. Gene expression analysis of brain tissue found that neuroinflammation and immune cell markers were amplified in the combined T. gondii + TBI setting in both males and females as early as 2-h post-injury. Glutamatergic, neurotoxic, and oxidative stress markers were altered in a sex-specific manner in T. gondii + TBI mice. Structural MRI found that male, but not female, T. gondii + TBI mice had a significantly larger lesion size compared to their uninfected counterparts at 18-weeks post-injury. Similarly, diffusion MRI revealed that T. gondii + TBI mice had exacerbated white matter tract abnormalities, particularly in male mice. These novel findings indicate that a pre-existing T. gondii infection affects the pathophysiological aftermath of TBI in a sex-dependent manner, and may be an important modifier to consider in the care and prognostication of TBI patients.

Psychedelics for acquired brain injury: a review of molecular mechanisms and therapeutic potential

Acquired brain injury (ABI), such as traumatic brain injury and stroke, is a leading cause of disability worldwide, resulting in debilitating acute and chronic symptoms, as well as an increased risk of developing neurological and neurodegenerative disorders. These symptoms can stem from various neurophysiological insults, including neuroinflammation, oxidative stress, imbalances in neurotransmission, and impaired neuroplasticity. Despite advancements in medical technology and treatment interventions, managing ABI remains a significant challenge. Emerging evidence suggests that psychedelics may rapidly improve neurobehavioral outcomes in patients with various disorders that share physiological similarities with ABI. However, research specifically focussed on psychedelics for ABI is limited. This narrative literature review explores the neurochemical properties of psychedelics as a therapeutic intervention for ABI, with a focus on serotonin receptors, sigma-1 receptors, and neurotrophic signalling associated with neuroprotection, neuroplasticity, and neuroinflammation. The promotion of neuronal growth, cell survival, and anti-inflammatory properties exhibited by psychedelics strongly supports their potential benefit in managing ABI. Further research and translational efforts are required to elucidate their therapeutic mechanisms of action and to evaluate their effectiveness in treating the acute and chronic phases of ABI.

Tau Phosphorylation Patterns in the Rat Cerebral Cortex After Traumatic Brain Injury and Sodium Selenate Effects: An Epibios4rx Project 2 Study

Sodium selenate (SS) activates protein phosphatase 2 (PP2A) and reduces phosphorylated tau (pTAU) and late post-traumatic seizures after lateral fluid percussion injury (LFPI). In EpiBioS4Rx Project 2, a multi-center international study for post-traumatic targets, biomarkers, and treatments, we tested the target relevance and modification by SS of pTAU forms and PP2A and in the LFPI model, at two sites: Einstein and Melbourne. In Experiment 1, adult male rats were assigned to LFPI and sham (both sites) and naïve controls (Einstein). Motor function was monitored by neuroscores. Brains were studied with immunohistochemistry (IHC), Western blots (WBs), or PP2A activity assay, from 2 days to 8 weeks post-operatively. In Experiment 2, LFPI rats received SS for 7 days (SS0.33: 0.33 mg/kg/day; SS1: 1 mg/kg/day, subcutaneously) or vehicle (Veh) post-LFPI and pTAU, PR55 expression, or PP2A activity were studied at 2 days and 1 week (on treatment), or 2 weeks (1 week off treatment). Plasma selenium and SS levels were measured. In Experiment 1 IHC, LFPI rats had higher cortical pTAU-Ser202/Thr205-immunoreactivity (AT8-ir) and pTAU-Ser199/202-ir at 2 days, and pTAU-Thr231-ir (AT180-ir) at 2 days, 2 weeks, and 8 weeks, ipsilaterally to LFPI, than controls. LFPI-2d rats also had higher AT8/total-TAU5-ir in cortical extracts ipsilateral to the lesion (WB). PP2A (PR55-ir) showed time- and region-dependent changes in IHC, but not in WB. PP2A activity was lower in LFPI-1wk than in sham rats. In Experiment 2, SS did not affect neuroscores or cellular AT8-ir, AT180-ir, or PR55-ir in IHC. In WB, total cortical AT8/total-TAU-ir was lower in SS0.33 and SS1 LFPI rats than in Veh rats (2 days, 1 week); total cortical PR55-ir (WB) and PP2A activity were higher in SS1 than Veh rats (2 days). SS dose dependently increased plasma selenium and SS levels. Concordant across-sites data confirm time and pTAU form-specific cortical increases ipsilateral to LFPI. The discordant SS effects may either suggest SS-induced reduction in the numbers of cells with increased pTAU-ir, need for longer treatment, or the involvement of other mechanisms of action.

Successful harmonization in EpiBioS4Rx biomarker study on post-traumatic epilepsy paves the way towards powered preclinical multicenter studies

OBJECTIVE

Project 1 of the Preclinical Multicenter Epilepsy Bioinformatics Study for Antiepileptogenic Therapy (EpiBioS4Rx) consortium aims to identify preclinical biomarkers for antiepileptogenic therapies following traumatic brain injury (TBI). The international participating centers in Finland, Australia, and the United States have made a concerted effort to ensure protocol harmonization. Here, we evaluate the success of harmonization process by assessing the timing, coverage, and performance between the study sites.

METHOD

We collected data on animal housing conditions, lateral fluid-percussion injury model production, postoperative care, mortality, post-TBI physiological monitoring, timing of blood sampling and quality, MR imaging timing and protocols, and duration of video-electroencephalography (EEG) follow-up using common data elements. Learning effect in harmonization was assessed by comparing procedural accuracy between the early and late stages of the project.

RESULTS

The animal housing conditions were comparable between the study sites but the postoperative care procedures varied. Impact pressure, duration of apnea, righting reflex, and acute mortality differed between the study sites (p < 0.001). The severity of TBI on D2 post TBI assessed using the composite neuroscore test was similar between the sites, but recovery of acute somato-motor deficits varied (p < 0.001). A total of 99% of rats included in the final cohort in UEF, 100% in Monash, and 79% in UCLA had blood samples taken at all time points. The timing of sampling differed on day (D)2 (p < 0.05) but not D9 (p > 0.05). Plasma quality was poor in 4% of the samples in UEF, 1% in Monash and 14% in UCLA. More than 97% of the final cohort were MR imaged at all timepoints in all study sites. The timing of imaging did not differ on D2 and D9 (p > 0.05), but varied at D30, 5 months, and ex vivo timepoints (p < 0.001). The percentage of rats that completed the monthly high-density video-EEG follow-up and the duration of video-EEG recording on the 7th post-injury month used for seizure detection for diagnosis of post-traumatic epilepsy differed between the sites (p < 0.001), yet the prevalence of PTE (UEF 21%, Monash 22%, UCLA 23%) was comparable between the sites (p > 0.05). A decrease in acute mortality and increase in plasma quality across time reflected a learning effect in the TBI production and blood sampling protocols.

SIGNIFICANCE

Our study is the first demonstration of the feasibility of protocol harmonization for performing powered preclinical multi-center trials for biomarker and therapy discovery of post-traumatic epilepsy.

Reduced total number of enlarged perivascular spaces in post-traumatic epilepsy patients with unilateral lesions - a feasibility study

BACKGROUND

We investigated the value of automated enlarged perivascular spaces (ePVS) quantification to distinguish chronic traumatic brain injury (TBI) patients with post-traumatic epilepsy (PTE+) from chronic TBI patients without PTE (PTE-) in a feasibility study.

METHODS

Patients with and without PTE were recruited and underwent an MRI post-TBI. Multimodal auto identification of ePVS algorithm was applied to T1-weighted MRIs to segment ePVS. The total number of ePVS was calculated and corrected for white matter volume, and an asymmetry index (AI) derived.

RESULTS

PTE was diagnosed in 7 out of the 99 participants (male=69) after a median time of less than one year since injury (range 10-22). Brain lesions were observed in all 7 PTE+ cases (unilateral=4, 57%; bilateral=3, 43%) as compared to 40 PTE- cases (total 44%; unilateral=17, 42%; bilateral=23, 58%). There was a significant difference between PTE+ (M=1.21e-4, IQR [8.89e-5]) and PTE- cases (M=2.79e-4, IQR [6.25e-5]) in total corrected numbers of ePVS in patients with unilateral lesions (p=0.024). No differences in AI, trauma severity and lesion volume were seen between groups.

CONCLUSION

This study has shown that automated quantification of ePVS is feasible and provided initial evidence that individuals with PTE with unilateral lesions may have fewer ePVS compared to TBI patients without epilepsy. Further studies with larger sample sizes should be conducted to determine the value of ePVS quantification as a PTE-biomarker.

Utility of Acute and Subacute Blood Biomarkers to Assist Diagnosis in CT-Negative Isolated Mild Traumatic Brain Injury

BACKGROUND AND OBJECTIVES

Blood biomarkers glial fibrillary acidic protein (GFAP) and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) have recently been Food and Drug Administration approved as predictors of intracranial lesions on CT after mild traumatic brain injury (mTBI). However, most cases with mTBI are CT negative, and no biomarkers are approved to assist diagnosis in these individuals. In this study, we aimed to determine the optimal combination of blood biomarkers to assist mTBI diagnosis in otherwise healthy adults younger than 50 years presenting to an emergency department within 6 hours of injury. To further understand the utility of biomarkers, we assessed how biological sex, presence or absence of loss of consciousness and/or post-traumatic amnesia (LOC/PTA), and delayed presentation affected classification performance.

METHODS

Blood samples, symptom questionnaires, and cognitive tests were prospectively conducted for participants with mTBI recruited from The Alfred Hospital Level 1 Emergency & Trauma Center and uninjured controls. Follow-up testing was conducted at 7 days. Simoa quantified plasma GFAP, UCH-L1, tau, neurofilament light chain (NfL), interleukin (IL)-6, and IL-1β. Area under the receiver operating characteristic (AUC) analysis assessed classification accuracy for diagnosed mTBI, and logistic regression models identified optimal biomarker combinations.

RESULTS

Plasma IL-6 (AUC 0.91, 95% CI 0.86-0.96), GFAP (AUC 0.85, 95% CI 0.78-0.93), and UCH-L1 (AUC 0.79, 95% CI 0.70-0.88) best differentiated mTBI (n = 74) from controls (n = 44) acutely (<6 hours), with NfL (AUC 0.81, 95% CI 0.72-0.90) the only marker to have such utility subacutely (7 days). Biomarker performance was similar between sexes and for participants with and without LOC/PTA, with the exception at 7 days, where GFAP and IL-6 retained some utility in female participants (GFAP: AUC 0.71, 95% CI 0.55-0.88; IL-6: AUC 0.71, 95% CI 0.55-0.87) and in those with LOC/PTA (GFAP: AUC 0.73, 95% CI 0.59-0.86; IL-6: AUC 0.71, 95% CI 0.57-0.84). Acute IL-6 (R 2 = 0.50, 95% CI 0.34-0.64) outperformed GFAP and UCH-L1 combined (R 2 = 0.35, 95% CI 0.17-0.50), with the best acute model featuring GFAP and IL-6 (R 2 = 0.54, 95% CI 0.34-0.68).

DISCUSSION

These findings indicate that adding IL-6 to a panel of brain-specific proteins such as GFAP and UCH-L1 might assist in the acute diagnosis of mTBI in adults younger than 50 years. Multiple markers had high classification accuracy in participants without LOC/PTA. When compared with the best-performing acute markers, subacute measures of plasma NfL resulted in minimal reduction in classification accuracy. Future studies will investigate the optimal time frame over which plasma IL-6 might assist diagnostic decisions and how extracranial trauma affects utility.

Phase II randomised placebo-controlled trial of sodium selenate as a disease-modifying treatment in chronic drug-resistant temporal lobe epilepsy: the SeLECT study protocol

INTRODUCTION

Epilepsy is one of the most common neurological conditions worldwide. Despite many antiseizure medications (ASMs) being available, up to one-third of patients do not achieve seizure control. Preclinical studies have shown treatment with sodium selenate to have a disease-modifying effect in a rat model of chronic temporal lobe epilepsy (TLE).

AIM

This randomised placebo-controlled trial aims to evaluate the antiseizure and disease-modifying effects of sodium selenate in people with drug-resistant TLE.

METHODS

This will be a randomised placebo-controlled trial of sodium selenate. One hundred and twenty-four adults with drug-resistant TLE and ≥4 countable seizures/month will be recruited. Outcomes of interest will be measured at baseline, week 26 and week 52 and include an 8-week seizure diary, 24-hour electroencephalogram and cognitive, neuropsychiatric and quality of life measures. Participants will then be randomised to receive a sustained release formulation of sodium selenate (initially 10 mg three times a day, increasing to 15 mg three times a day at week 4 if tolerated) or a matching placebo for 26 weeks.

OUTCOMES

The primary outcome will be a consumer codesigned epilepsy-Desirability of Outcome Rank (DOOR), combining change in seizure frequency, adverse events, quality of life and ASM burden measures into a single outcome measure, compared between treatment arms over the whole 52-week period. Secondary outcomes will compare baseline measures to week 26 (antiseizure) and week 52 (disease modification). Exploratory measures will include biomarkers of treatment response.

ETHICS AND DISSEMINATION

The study has been approved by the lead site, Alfred Hospital Ethics Committee (594/20). Each participant will provide written informed consent prior to any trial procedures. The results of the study will be presented at national and international conferences, published in peer-reviewed journals and disseminated through consumer organisations.

CONCLUSION

This study will be the first disease-modification randomised controlled trial in patients with drug-resistant TLE.

TRIAL REGISTRATION NUMBER

ANZCTR; ACTRN12623000446662.

E2730, an uncompetitive γ-aminobutyric acid transporter-1 inhibitor, suppresses epileptic seizures in a rat model of chronic mesial temporal lobe epilepsy

OBJECTIVE

More than one third of mesial temporal lobe epilepsy (MTLE) patients are resistant to current antiseizure medications (ASMs), and half experience mild-to-moderate adverse effects of ASMs. There is therefore a strong need to develop and test novel ASMs. The objective of this work is to evaluate the pharmacokinetics and neurological toxicity of E2730, a novel uncompetitive inhibitor of γ-aminobutyric acid transporter-1, and to test its seizure suppression effects in a rat model of chronic MTLE.

METHODS

We first examined plasma levels and adverse neurological effects of E2730 in healthy Wistar rats. Adult male rats were implanted with osmotic pumps delivering either 10, 20, or 100 mg/kg/day of E2730 subcutaneously for 1 week. Blood sampling and behavioral assessments were performed at several timepoints. We next examined whether E2730 suppressed seizures in rats with chronic MTLE. These rats were exposed to kainic acid-induced status epilepticus, and 9 weeks later, when chronic epilepsy was established, were assigned to receive one of the three doses of E2730 or vehicle for 1 week in a randomized crossover design. Continuous video-electroencephalographic monitoring was acquired during the treatment period to evaluate epileptic seizures.

RESULTS

Plasma levels following continuous infusion of E2730 showed a clear dose-related increase in concentration. The drug was well tolerated at all doses, and any sedation or neuromotor impairment was mild and transient, resolving within 48 h of treatment initiation. Remarkably, E2730 treatment in chronically epileptic rats led to seizure suppression in a dose-dependent manner, with 65% of rats becoming seizure-free at the highest dose tested. Mean seizure class did not differ between the treatment groups.

SIGNIFICANCE

This study shows that continuous subcutaneous infusion of E2730 over 7 days results in a marked, dose-dependent suppression of spontaneous recurrent seizures, with minimal adverse neurological effects, in a rat model of chronic MTLE. E2730 shows strong promise as an effective new ASM to be translated into clinical trials.

MicroRNA biomarkers for diagnosis of mild traumatic brain injury and prediction of persistent symptoms: A prospective cohort study

The diagnosis of mild traumatic brain injury (mTBI) and early identification of patients who have persistent symptoms remains challenging. Symptoms are variably reported, and tests for cognitive impairment require specific expertise. The aim of this study was to assess the ability of plasma micro-ribonucleic acid (miRNA) biomarkers to distinguish between patients with mTBI and healthy controls. A secondary aim was to assess whether miRNA biomarker levels on the day of injury could predict persistent symptoms on day 7. Injured patients presented to an adult, tertiary referral hospital emergency department and were diagnosed with isolated mTBI (n = 75). Venous blood samples were collected within 6 h of injury. Symptom severity was assessed using the Rivermead Post-Concussion Symptom Questionnaire (RPQ) on the day of injury and at 7 days post-injury. The comparator group (n = 44) were healthy controls without any injury, who had bloods sampled and symptom severity assessed at the same time-point. Patients after mTBI reported higher symptom severity and had worse cognitive performance than the control group. Plasma miR423-3p levels were significantly higher among mTBI patients acutely post-injury compared to healthy controls and provided moderate discriminative ability (AUROC 0.67; 95 %CI: 0.57-0.77). None of the assessed miRNA biomarkers predicted persistent symptoms at 7 days. Plasma miR423-3p levels measured within 6 h of injury can discriminate for mTBI compared to healthy controls, with potential utility for screening after head injury or as an adjunct to the diagnosis of mTBI. Acute plasma miRNA levels did not predict patients who reported persistent symptoms at 7 days.

Image data harmonization tools for the analysis of post-traumatic epilepsy development in preclinical multisite MRI studies

Preclinical MRI studies have been utilized for the discovery of biomarkers that predict post-traumatic epilepsy (PTE). However, these single site studies often lack statistical power due to limited and homogeneous datasets. Therefore, multisite studies, such as the Epilepsy Bioinformatics Study for Antiepileptogenic Therapy (EpiBioS4Rx), are developed to create large, heterogeneous datasets that can lead to more statistically significant results. EpiBioS4Rx collects preclinical data internationally across sites, including the United States, Finland, and Australia. However, in doing so, there are robust normalization and harmonization processes that are required to obtain statistically significant and generalizable results. This work describes the tools and procedures used to harmonize multisite, multimodal preclinical imaging data acquired by EpiBioS4Rx. There were four main harmonization processes that were utilized, including file format harmonization, naming convention harmonization, image coordinate system harmonization, and diffusion tensor imaging (DTI) metrics harmonization. By using Python tools and bash scripts, the file formats, file names, and image coordinate systems are harmonized across all the sites. To harmonize DTI metrics, values are estimated for each voxel in an image to generate a histogram representing the whole image. Then, the Quantitative Imaging Toolkit (QIT) modules are utilized to scale the mode to a value of one and depict the subsequent harmonized histogram. The standardization of file formats, naming conventions, coordinate systems, and DTI metrics are qualitatively assessed. The histograms of the DTI metrics were generated for all the individual rodents per site. For inter-site analysis, an average of the individual scans was calculated to create a histogram that represents each site. In order to ensure the analysis can be run at the level of individual animals, the sham and TBI cohort were analyzed separately, which depicted the same harmonization factor. The results demonstrate that these processes qualitatively standardize the file formats, naming conventions, coordinate systems, and DTI metrics of the data. This assists in the ability to share data across the study, as well as disseminate tools that can help other researchers to strengthen the statistical power of their studies and analyze data more cohesively.

Persistent Changes in Mechanical Nociception in Rats With Traumatic Brain Injury Involving Polytrauma

Traumatic brain injury (TBI) survivors often experience debilitating consequences. Due to the high impact nature of TBI, patients often experience concomitant peripheral injuries (ie, polytrauma). A common, yet often overlooked, comorbidity of TBI is chronic pain. Therefore, this study investigated how common concomitant peripheral injuries (ie, femoral fracture and muscle crush) can affect long-term behavioral and structural TBI outcomes with a particular focus on nociception. Rats were randomly assigned to 1 of 4 groups: polytrauma (POLY; ie, fracture + muscle crush + TBI), peripheral injury (PERI; ie, fracture + muscle crush + sham TBI), TBI (ie, sham fracture + sham muscle crush + TBI), and sham-injured (SHAM; ie, sham fracture + sham muscle crush + sham TBI). Rats underwent behavioral testing at 3-, 6-, and 11-weeks postinjury, and were then euthanized for postmortem magnetic resonance imaging (MRI). POLY rats had a persisting increase in pain sensitivity compared to all groups on the von Frey test. MRI revealed that POLY rats also had abnormalities in the cortical and subcortical brain structures involved in nociceptive processing. These findings have important implications and provide a foundation for future studies to determine the underlying mechanisms and potential treatment strategies for chronic pain in TBI survivors. PERSPECTIVE: Rats with TBI and concomitant peripheral trauma displayed chronic nociceptive pain and MRI images also revealed damaged brain structures/pathways that are involved in chronic pain development. This study highlights the importance of polytrauma and the affected brain regions for developing chronic pain.

Associations of Enlarged Perivascular Spaces With Brain Lesions, Brain Age, and Clinical Outcomes in Chronic Traumatic Brain Injury

BACKGROUND AND OBJECTIVES

Enlarged perivascular spaces (ePVS) have been identified as a key signature of glymphatic system dysfunction in neurologic conditions. The incidence and clinical implications of ePVS after traumatic brain injury (TBI) are not yet understood. We investigated whether individuals with chronic moderate-to-severe TBI had an increased burden of ePVS and whether ePVS burden is modulated by the presence of focal lesions, older brain age, and poorer sleep quality. We examined whether an increased burden of ePVS was associated with poorer cognitive and emotional outcomes.

METHODS

Using a cross-sectional design, participants with a single moderate-to-severe chronic TBI (sustained ≥10 years ago) were recruited from an inpatient rehabilitation program. Control participants were recruited from the community. Participants underwent 3T brain MRI, neuropsychological assessment, and clinical evaluations. ePVS burden in white matter was quantified using automated segmentation. The relationship between the number of ePVS, group membership, focal lesions, brain age, current sleep quality, and outcome was modeled using negative binomial and linear regressions.

RESULTS

This study included 100 participants with TBI (70% male; mean age = 56.8 years) and 75 control participants (54.3% male; mean age = 59.8 years). The TBI group had a significantly greater burden of ePVS (prevalence ratio rate [PRR] = 1.29, p = 0.013, 95% CI 1.05-1.57). The presence of bilateral lesions was associated with greater ePVS burden (PRR = 1.41, p = 0.021, 95% CI 1.05-1.90). There was no association between ePVS burden, sleep quality (PRR = 1.01, p = 0.491, 95% CI 0.98-1.048), and sleep duration (PRR = 1.03, p = 0.556, 95% CI 0.92-1.16). ePVS was associated with verbal memory (β = -0.42, p = 0.006, 95% CI -0.72 to -0.12), but not with other cognitive domains. The burden of ePVS was not associated with emotional distress (β = -0.70, p = 0.461, 95% CI -2.57 to 1.17) or brain age (PRR = 1.00, p = 0.665, 95% CI 0.99-1.02).

DISCUSSION

TBI is associated with a greater burden of ePVS, especially when there have been bilateral brain lesions. ePVS was associated with reduced verbal memory performance. ePVS may indicate ongoing impairments in glymphatic system function in the chronic postinjury period.

Acute effects of single and repeated mild traumatic brain injury on levels of neurometabolites, lipids, and mitochondrial function in male rats

Introduction

Mild traumatic brain injuries (mTBIs) are the most common form of acquired brain injury. Symptoms of mTBI are thought to be associated with a neuropathological cascade, potentially involving the dysregulation of neurometabolites, lipids, and mitochondrial bioenergetics. Such alterations may play a role in the period of enhanced vulnerability that occurs after mTBI, such that a second mTBI will exacerbate neuropathology. However, it is unclear whether mTBI-induced alterations in neurometabolites and lipids that are involved in energy metabolism and other important cellular functions are exacerbated by repeat mTBI, and if such alterations are associated with mitochondrial dysfunction.

Methods

In this experiment, using a well-established awake-closed head injury (ACHI) paradigm to model mTBI, male rats were subjected to a single injury, or five injuries delivered 1 day apart, and injuries were confirmed with a beam-walk task and a video observation protocol. Abundance of several neurometabolites was evaluated 24 h post-final injury in the ipsilateral and contralateral hippocampus using in vivo proton magnetic resonance spectroscopy (1H-MRS), and mitochondrial bioenergetics were evaluated 30 h post-final injury, or at 24 h in place of 1H-MRS, in the rostral half of the ipsilateral hippocampus. Lipidomic evaluations were conducted in the ipsilateral hippocampus and cortex.

Results

We found that behavioral deficits in the beam task persisted 1- and 4 h after the final injury in rats that received repetitive mTBIs, and this was paralleled by an increase and decrease in hippocampal glutamine and glucose, respectively, whereas a single mTBI had no effect on sensorimotor and metabolic measurements. No group differences were observed in lipid levels and mitochondrial bioenergetics in the hippocampus, although some lipids were altered in the cortex after repeated mTBI.

Discussion

The decrease in performance in sensorimotor tests and the presence of more neurometabolic and lipidomic abnormalities, after repeated but not singular mTBI, indicates that multiple concussions in short succession can have cumulative effects. Further preclinical research efforts are required to understand the underlying mechanisms that drive these alterations to establish biomarkers and inform treatment strategies to improve patient outcomes.

Early preclinical plasma protein biomarkers of brain trauma are influenced by early seizures and levetiracetam

OBJECTIVE

We used the lateral fluid percussion injury (LFPI) model of moderate-to-severe traumatic brain injury (TBI) to identify early plasma biomarkers predicting injury, early post-traumatic seizures or neuromotor functional recovery (neuroscores), considering the effect of levetiracetam, which is commonly given after severe TBI.

METHODS

Adult male Sprague-Dawley rats underwent left parietal LFPI, received levetiracetam (200 mg/kg bolus, 200 mg/kg/day subcutaneously for 7 days [7d]) or vehicle post-LFPI, and were continuously video-EEG recorded (n = 14/group). Sham (craniotomy only, n = 6), and naïve controls (n = 10) were also used. Neuroscores and plasma collection were done at 2d or 7d post-LFPI or equivalent timepoints in sham/naïve. Plasma protein biomarker levels were determined by reverse phase protein microarray and classified according to injury severity (LFPI vs. sham/control), levetiracetam treatment, early seizures, and 2d-to-7d neuroscore recovery, using machine learning.

RESULTS

Low 2d plasma levels of Thr231 -phosphorylated tau protein (pTAU-Thr231 ) and S100B combined (ROC AUC = 0.7790) predicted prior craniotomy surgery (diagnostic biomarker). Levetiracetam-treated LFPI rats were differentiated from vehicle treated by the 2d-HMGB1, 2d-pTAU-Thr231 , and 2d-UCHL1 plasma levels combined (ROC AUC = 0.9394) (pharmacodynamic biomarker). Levetiracetam prevented the seizure effects on two biomarkers that predicted early seizures only among vehicle-treated LFPI rats: pTAU-Thr231 (ROC AUC = 1) and UCHL1 (ROC AUC = 0.8333) (prognostic biomarker of early seizures among vehicle-treated LFPI rats). Levetiracetam-resistant early seizures were predicted by high 2d-IFNγ plasma levels (ROC AUC = 0.8750) (response biomarker). 2d-to-7d neuroscore recovery was best predicted by higher 2d-S100B, lower 2d-HMGB1, and 2d-to-7d increase in HMGB1 or decrease in TNF (P < 0.05) (prognostic biomarkers).

SIGNIFICANCE

Antiseizure medications and early seizures need to be considered in the interpretation of early post-traumatic biomarkers.

Stress and traumatic brain injury: An inherent bi-directional relationship with temporal and synergistic complexities

Traumatic brain injury (TBI) and stress are prevalent worldwide and can both result in life-altering health problems. While stress often occurs in the absence of TBI, TBI inherently involves some element of stress. Furthermore, because there is pathophysiological overlap between stress and TBI, it is likely that stress influences TBI outcomes. However, there are temporal complexities in this relationship (e.g., when the stress occurs) that have been understudied despite their potential importance. This paper begins by introducing TBI and stress and highlighting some of their possible synergistic mechanisms including inflammation, excitotoxicity, oxidative stress, hypothalamic-pituitary-adrenal axis dysregulation, and autonomic nervous system dysfunction. We next describe different temporal scenarios involving TBI and stress and review the available literature on this topic. In doing so we find initial evidence that in some contexts stress is a highly influential factor in TBI pathophysiology and recovery, and vice versa. We also identify important knowledge gaps and suggest future research avenues that will increase our understanding of this inherent bidirectional relationship and could one day result in improved patient care.

Critical Windows: Exploring the Association Between Perinatal Trauma, Epigenetics, and Chronic Pain

Chronic pain is highly prevalent and burdensome, affecting millions of people worldwide. Although it emerges at any point in life, it often manifests in adolescence. Given that adolescence is a unique developmental period, additional strains associated with persistent and often idiopathic pain lead to significant long-term consequences. While there is no singular cause for the chronification of pain, epigenetic modifications that lead to neural reorganization may underpin central sensitization and subsequent manifestation of pain hypersensitivity. Epigenetic processes are particularly active during the prenatal and early postnatal years. We demonstrate how exposure to various traumas, such as intimate partner violence while in utero or adverse childhood experiences, can significantly influence epigenetic regulation within the brain and in turn modify pain-related processes. We provide compelling evidence that the burden of chronic pain is likely initiated early in life, often being transmitted from mother to offspring. We also highlight two promising prophylactic strategies, oxytocin administration and probiotic use, that have the potential to attenuate the epigenetic consequences of early adversity. Overall, we advance understanding of the causal relationship between trauma and adolescent chronic pain by highlighting epigenetic mechanisms that underlie this transmission of risk, ultimately informing how to prevent this rising epidemic.

BDNF: New Views of an Old Player in Traumatic Brain Injury

Traumatic brain injury is a common health problem affecting millions of people each year. BDNF has been investigated in the context of traumatic brain injury due to its crucial role in maintaining brain homeostasis. Val66Met is a functional single-nucleotide polymorphism that results in a valine-to-methionine amino acid substitution at codon 66 in the BDNF prodomain, which ultimately reduces secretion of BDNF. Here, we review experimental animal models as well as clinical studies investigating the role of the Val66Met single-nucleotide polymorphism in traumatic brain injury outcomes, including cognitive function, motor function, neuropsychiatric symptoms, and nociception. We also review studies investigating the role of BDNF on traumatic brain injury pathophysiology as well as circulating BDNF as a biomarker of traumatic brain injury.

Disease-modifying effects of sodium selenate in a model of drug-resistant, temporal lobe epilepsy

There are no pharmacological disease-modifying treatments with an enduring effect to mitigate the seizures and comorbidities of established chronic temporal lobe epilepsy (TLE). This study aimed to evaluate for disease modifying effects of sodium selenate treatment in the chronically epileptic rat post-status epilepticus (SE) model of drug-resistant TLE. Wistar rats underwent kainic acid-induced SE or sham. Ten-weeks post-SE, animals received sodium selenate, levetiracetam, or vehicle subcutaneousinfusion continuously for 4 weeks. To evaluate the effects of the treatments, one week of continuous video-EEG was acquired before, during, and 4, 8 weeks post-treatment, followed by behavioral tests. Targeted and untargeted proteomics and metabolomics were performed on post-mortem brain tissue to identify potential pathways associated with modified disease outcomes. Telomere length was investigated as a novel surrogate marker of epilepsy disease severity in our current study. The results showed that sodium selenate treatment was associated with mitigation of measures of disease severity at 8 weeks post-treatment cessation; reducing the number of spontaneous seizures (p< 0.05), cognitive dysfunction (p< 0.05), and sensorimotor deficits (p< 0.01). Moreover, selenate treatment was associated with increased protein phosphatase 2A (PP2A) expression, reduced hyperphosphorylated tau, and reversed telomere length shortening (p< 0.05). Network medicine integration of multi-omics/pre-clinical outcomes identified protein-metabolite modules positively correlated with TLE. Our results provide evidence that treatment with sodium selenate results in a sustained disease-modifying effect in chronically epileptic rats in the post-KA SE model of TLE, including improved comorbid learning and memory deficits.

Ccr2 Gene Ablation Does Not Influence Seizure Susceptibility, Tissue Damage, or Cellular Inflammation after Murine Pediatric Traumatic Brain Injury

Pediatric traumatic brain injury (TBI) is a major public health issue, and a risk factor for the development of post-traumatic epilepsy that may profoundly impact the quality of life for survivors. As the majority of neurotrauma research is focused on injury to the adult brain, our understanding of the developing brain's response to TBI remains incomplete. Neuroinflammation is an influential pathophysiological mechanism in TBI, and is thought to increase neuronal hyperexcitability, rendering the brain more susceptible to the onset of seizures and/or epileptogenesis. We here hypothesized that peripheral blood-derived macrophages, recruited into the injured brain via C-C motif ligand 2 (CCL2) chemokine/C-C chemokine receptor type 2 (CCR2) signaling, contributes to neuroinflammation and thus seizure susceptibility after experimental pediatric TBI. Using Ccr2 gene-deficient mice in the controlled cortical impact (CCI) model of TBI, in 3-week-old male mice we found that TBI led to an increase in susceptibility to pentylenetetrazol (PTZ)-evoked seizures, associated with considerable cortical tissue loss, a robust cellular neuroinflammatory response, and oxidative stress. Intriguingly, although Ccr2-deficiency increased CCL2 levels in serum, it did not exacerbate seizure susceptibility or the neuroinflammatory cellular response after pediatric TBI. Similarly, acute post-injury treatment with a CCR2 antagonist did not influence seizure susceptibility or the extent of tissue damage in wild-type (WT) mice. Together, our findings suggest that CCR2 is not a crucial driver of epileptogenesis or neuroinflammation after TBI in the developing brain. We propose that age may be an important factor differentiating our findings from previous studies in which targeting CCL2/CCR2 has been reported to be anti-inflammatory, neuroprotective or anti-seizure.

Initial Severity of Injury Has Little Effect on the Temporal Profile of Long-Term Deficits in Locomotion, Anxiety, and Cognitive Function After Diffuse Traumatic Brain Injury

Traumatic brain injury (TBI) is associated with persistent impairments in multiple domains, including cognitive and neuropsychiatric function. Previous literature has suggested that the risk of such impairments may differ as a function of the initial severity of injury, with moderate-severe TBI (msTBI) associated with more severe cognitive dysfunction and mild TBI (mTBI) associated with a higher risk of developing an anxiety disorder. Despite this, relatively few pre-clinical studies have investigated the time course of behavioral change after different severities of injury. The current study compared the temporal profile of functional deficits incorporating locomotion, cognition, and anxiety up to 12 months post-injury after an mTBI, repeated mild TBI (rmTBI), and single msTBI in an experimental model of diffuse TBI. Injury appeared to alter the effect of aging on locomotor activity, with both msTBI and rmTBI rats showing a decrease in locomotion at 12 months relative to their earlier performance on the task, an effect not observed in shams or after a single mTBI. Further, mTBI seemed to be associated with decreased anxiety over time, as measured by increased time spent in the open arm of the elevated plus maze from 3 to 12 months post-injury. No significant findings were observed on spatial memory or volumetric magnetic resonance imaging. Future studies will need to use a more comprehensive behavioral battery, capable of capturing subtle alterations in function, and longer time points, following rats into old age, in order to more fully assess the evolution of persistent behavioral deficits in key domains after different severities of TBI, as well as their accompanying neuroimaging changes. Given the prevalence and significance of such deficits post-TBI for a person's quality of life, as well as the elevated risk of neurodegenerative disease post-injury, such investigations may play a critical role in identifying optimal windows of therapeutic intervention post-injury.

Pre-existing Toxoplasma gondii infection increases susceptibility to pentylenetetrazol-induced seizures independent of traumatic brain injury in mice

Introduction

Post-traumatic epilepsy (PTE) is a debilitating chronic outcome of traumatic brain injury (TBI), and neuroinflammation is implicated in increased seizure susceptibility and epileptogenesis. However, how common clinical factors, such as infection, may modify neuroinflammation and PTE development has been understudied. The neurotropic parasite, Toxoplasma gondii (T. gondii) incurably infects one-third of the world's population. Thus, many TBI patients have a pre-existing T. gondii infection at the time of injury. T. gondii infection results in chronic low-grade inflammation and altered signaling pathways within the brain, and preliminary clinical evidence suggest that it may be a risk factor for epilepsy. Despite this, no studies have considered how a pre-existing T. gondii infection may alter the development of PTE.

Methods

This study aimed to provide insight into this knowledge gap by assessing how a pre-existing T. gondii infection alters susceptibility to, and severity of, pentylenetetrazol (PTZ)-induced seizures (i.e., a surrogate marker of epileptogenesis/PTE) at a chronic stage of TBI recovery. We hypothesized that T. gondii will increase the likelihood and severity of seizures following PTZ administration, and that this would occur in the presence of intensified neuroinflammation. To test this, 6-week old male and female C57BL/6 Jax mice were intraperitoneally injected with 50,000 T. gondii tachyzoites or with the PBS vehicle only. At 12-weeks old, mice either received a severe TBI via controlled cortical impact or sham injury. At 18-weeks post-injury, mice were administered 40 mg/kg PTZ and video-recorded for evaluation of seizure susceptibility. Fresh cortical tissue was then collected for gene expression analyses.

Results

Although no synergistic effects were evident between infection and TBI, chronic T. gondii infection alone had robust effects on the PTZ-seizure response and gene expression of markers related to inflammatory, oxidative stress, and glutamatergic pathways. In addition to this, females were more susceptible to PTZ-induced seizures than males. While TBI did not impact PTZ responses, injury effects were evident at the molecular level.

Discussion

Our data suggests that a pre-existing T. gondii infection is an important modifier of seizure susceptibility independent of brain injury, and considerable attention should be directed toward delineating the mechanisms underlying this pro-epileptogenic factor.

Clinical and Blood Biomarker Trajectories after Concussion: New Insights from a Longitudinal Pilot Study of Professional Flat-Track Jockeys

There is a recognized need for objective tools for detecting and tracking clinical and neuropathological recovery after sports-related concussion (SRC). Although computerized neurocognitive testing has been shown to be sensitive to cognitive deficits after SRC, and some blood biomarkers have shown promise as indicators of axonal and glial damage, the potential utility of these measures in isolation and combination for assisting SRC diagnosis and tracking recovery is not well understood. To provide new insights, we conducted a prospective study of 64 male and female professional flat-track jockeys (49 non-SRC, 15 SRC), with each jockey undergoing symptom evaluation, cognitive testing using the CogSport battery, and serum biomarker quantification of glial fibrillary acidic protein (GFAP), tau, and neurofilament light (NfL) using a Simoa HD-X Analyzer. Measures were performed at baseline (i.e., pre-injury), and 2 and 7 days and 1 and 12 months after SRC. Symptoms were most pronounced at 2 days and had largely resolved by either 7 days or 1 month. CogSport testing at 2 days revealed cognitive impairments relative to both non-concussed peers and their own pre-injury baselines, with SRC classification utility found at 2 days, and to a slightly lesser extent, at 7 days. Relatively prolonged changes in serum NfL were observed, with elevated levels and classification utility persisting beyond the resolution of SRC symptoms and cognitive deficits. Finally, SRC classification performance throughout the 1st month after SRC was optimized through the combination of cognitive testing and serum biomarkers. Considered together, these findings provide further evidence for a role of computerized cognitive testing and fluid biomarkers of neuropathology as objective measures to assist in the identification of SRC and the monitoring of clinical and neuropathological recovery.

Temporal proteomics of human cerebrospinal fluid after severe traumatic brain injury

The pathophysiology of traumatic brain injury (TBI) requires further characterization to fully elucidate changes in molecular pathways. Cerebrospinal fluid (CSF) provides a rich repository of brain-associated proteins. In this retrospective observational study, we implemented high-resolution mass spectrometry to evaluate changes to the CSF proteome after severe TBI. 91 CSF samples were analyzed with mass spectrometry, collected from 16 patients with severe TBI (mean 32 yrs; 81% male) on day 0, 1, 2, 4, 7 and/or 10 post-injury (8-16 samples/timepoint) and compared to CSF obtained from 11 non-injured controls. We quantified 1152 proteins with mass spectrometry, of which approximately 80% were associated with CSF. 1083 proteins were differentially regulated after TBI compared to control samples. The most highly-upregulated proteins at each timepoint included neutrophil elastase, myeloperoxidase, cathepsin G, matrix metalloproteinase-8, and S100 calcium-binding proteins A8, A9 and A12-all proteins involved in neutrophil activation, recruitment, and degranulation. Pathway enrichment analysis confirmed the robust upregulation of proteins associated with innate immune responses. Conversely, downregulated pathways included those involved in nervous system development, and several proteins not previously identified after TBI such as testican-1 and latrophilin-1. We also identified 7 proteins (GM2A, Calsyntenin 1, FAT2, GANAB, Lumican, NPTX1, SFRP2) positively associated with an unfavorable outcome at 6 months post-injury. Together, these findings highlight the robust innate immune response that occurs after severe TBI, supporting future studies to target neutrophil-related processes. In addition, the novel proteins we identified to be differentially regulated by severe TBI warrant further investigation as potential biomarkers of brain damage or therapeutic targets.

Serum neurofilament light as a biomarker of vulnerability to a second mild traumatic brain injury

A second mild traumatic brain injury (mTBI) sustained prior to neuropathological recovery can lead to exacerbated effects. Without objective indicators of this neuropathology, individuals may return to activities at risk of mTBI when their brain is still vulnerable. With axonal injury recognized as a neuropathological hallmark of mTBI, we hypothesized that serum levels of neurofilament light (NfL), a highly sensitive biomarker of axonal injury, may be predictive of vulnerability to worse outcomes in the event of a second mTBI. Given this hypothesis is difficult to test clinically, we used a two-hit model of mTBI in rats and staggered inter-injury intervals by 1-, 3-, 7-, or 14-days. Repeat-mTBI rats were dichotomized into NfL^high (NfL>median at the time of re-injury) and NfL^low (NfL<median) groups, with behavior and NfL levels analyzed throughout the 28-days, followed by ex vivo diffusion tensor imaging. NfL levels at the time of the second mTBI were found to be predictive of vulnerability to re-injury, with NfL^high rats displaying more neurological signs and a greater potentiation of NfL levels after the second mTBI. Importantly, this potentiation phenomenon remained even when limiting analyses to rats with longer inter-injury intervals, providing evidence that vulnerability to re-injury may not be exclusively dependent on inter-injury interval. Finally, NfL levels correlated with, and were predictive of, the severity of neurological signs following the second mTBI. These findings provide evidence that measurement of NfL during mTBI recovery may be reflective of the vulnerability to a second mTBI, and as such may have utility to assist return to sport, duty and work decisions.

Monitoring the acute and subacute recovery of cognitive ocular motor changes after a sports-related concussion

Identifying when recovery from a sports-related concussion (SRC) has occurred remains a challenge in clinical practice. This study investigated the utility of ocular motor (OM) assessment to monitor recovery post-SRC between sexes and compared to common clinical measures. From 139 preseason baseline assessments (i.e. before they sustained an SRC), 18 (12 males, 6 females) consequent SRCs were sustained and the longitudinal follow-ups were collected at 2, 6, and 13 days post-SRC. Participants completed visually guided, antisaccade (AS), and memory-guided saccade tasks requiring a saccade toward, away from, and to a remembered target, respectively. Changes in latency (processing speed), visual–spatial accuracy, and errors were measured. Clinical measures included The Sports Concussion Assessment Tool, King-Devick test, Stroop task, and Digit span. AS latency was significantly longer at 2 days and returned to baseline by 13-days post-SRC in females only (P &lt; 0.001). Symptom numbers recovered from 2 to 6 days and 13 days (P &lt; 0.05). Persistently poorer AS visual–spatial accuracy was identified at 2, 6 and 13 days post-SRC (P &lt; 0.05) in both males and females but with differing trajectories. Clinical measures demonstrated consistent improvement reminiscent of practice effects. OM saccade assessment may have improved utility in tracking recovery compared to conventional measures and between sexes.

Treatment with vascular endothelial growth factor-A worsens cognitive recovery in a rat model of mild traumatic brain injury

Mild traumatic brain injury (mTBI) is a common and unmet clinical issue, with limited treatments available to improve recovery. The cerebrovascular system is vital to provide oxygen and nutrition to the brain, and a growing body of research indicates that cerebrovascular injury contributes to mTBI symptomatology. Vascular endothelial growth factor-A (VEGF-A) is a potent promoter of angiogenesis and an important modulator of vascular health. While indirect evidence suggests that increased bioavailability of VEGF-A may be beneficial after mTBI, the direct therapeutic effects of VEGF-A in this context remains unknown. This study therefore aimed to determine whether intracerebroventricular administration of recombinant VEGF-A could improve recovery from mTBI in a rat model. Male and female Sprague-Dawley rats were assigned to four groups: sham + vehicle (VEH), sham + VEGF-A, mTBI + VEH, mTBI + VEGF-A. The mTBI was induced using the lateral impact model, and treatment began at the time of the injury and continued until the end of the study. Rats underwent behavioral testing between days 1 and 10 post-injury, and were euthanized on day 11 for post-mortem analysis. In males, the mTBI + VEGF-A group had significantly worse cognitive recovery in the water maze than all other groups. In females, the VEGF treatment worsened cognitive performance in the water maze regardless of mTBI or sham injury. Analysis of hippocampal tissue found that these cognitive deficits occurred in the presence of gene expression changes related to neuroinflammation and hypoxia in both male and female rats. These findings indicate that the VEGF-A treatment paradigm tested in this study failed to improve mTBI outcomes in either male or female rats.

Decrease in Plasma miR-27a and miR-221 After Concussion in Australian Football Players

Introduction:

Sports-related concussion (SRC) is a common form of brain injury that lacks reliable methods to guide clinical decisions. MicroRNAs (miRNAs) can influence biological processes involved in SRC, and measurement of miRNAs in biological fluids may provide objective diagnostic and return to play/recovery biomarkers. Therefore, this prospective study investigated the temporal profile of circulating miRNA levels in concussed male and female athletes.

Methods:

Pre-season baseline blood samples were collected from amateur Australian rules football players (82 males, 45 females). Of these, 20 males and 8 females sustained an SRC during the subsequent season and underwent blood sampling at 2-, 6- and 13-days post-injury. A miRNA discovery Open Array was conducted on plasma to assess the expression of 754 known/validated miRNAs. miRNA target identified were further investigated with quantitative real-time PCR (qRT-PCR) in a validation study. Data pertaining to SRC symptoms, demographics, sporting history, education history and concussion history were also collected.

Results:

Discovery analysis identified 18 candidate miRNA. The consequent validation study found that plasma miR-221-3p levels were decreased at 6d and 13d, and that miR-27a-3p levels were decreased at 6d, when compared to baseline. Moreover, miR-27a and miR-221-3p levels were inversely correlated with SRC symptom severity.

Conclusion:

Circulating levels of miR-27a-3p and miR-221-3p were decreased in the sub-acute stages after SRC, and were inversely correlated with SRC symptom severity. Although further studies are required, these analyses have identified miRNA biomarker candidates of SRC severity and recovery that may one day assist in its clinical management.

Serum protein biomarkers of inflammation, oxidative stress, and cerebrovascular and glial injury in concussed Australian football players

Clinical decisions related to sports-related concussion (SRC) are challenging due to the heterogenous nature of SRC symptoms coupled with the current reliance on subjective self-reported symptom measures. Sensitive and objective methods that can diagnose SRC and determine recovery would aid clinical management, and there is evidence that SRC induces changes in circulating protein biomarkers indicative of neuroaxonal injury. However, potential blood biomarkers related to other pathobiological responses linked to SRC are still poorly understood. Therefore, here we analyzed blood samples from concussed (male = 30; female = 9) and non-concussed (male = 74; female = 27) amateur Australian rules football players collected during the pre-season (i.e., baseline), and at 2-, 6-, and 13-days post-SRC to determine time dependent changes in serum levels of biomarkers related to glial (i.e., brain lipid-binding protein, BLBP; phosphoprotein enriched in astrocytes 15) and cerebrovascular injury (i.e., von Willebrand factor, claudin-5), inflammation (i.e., fibrinogen, high mobility group box protein 1), and oxidative stress (i.e., 4-hydroxynoneal). In females, BLBP levels were significantly decreased at 2-days post-SRC compared to their pre-season baseline; however, area under the receiver operating characteristic curve (AUROC) analysis found that BLBP was unable to distinguish between SRC and controls. In males, AUROC analysis revealed a statistically significant change at 2-days post-SRC in the serum levels of 4-hydroxynoneal, however the associated AUROC value (0.6373) indicated little clinical utility for this biomarker in distinguishing SRC from controls. There were no other statistically significant findings. These results indicate that the serum biomarkers tested in this study hold little clinical value in the management of SRC at 2-, 6-, and 13-days post-injury.

Pediatric traumatic brain injury and a subsequent transient immune challenge independently influenced chronic outcomes in male mice

Traumatic brain injury (TBI) is a major contributor to death and disability worldwide. Children are at particularly high risk of both sustaining a TBI and experiencing serious long-term consequences, such as cognitive deficits, mental health problems and post-traumatic epilepsy. Severe TBI patients are highly susceptible to nosocomial infections, which are mostly acquired within the first week of hospitalization post-TBI. Yet the potential chronic impact of such acute infections following pediatric TBI remains unclear. In this study, we hypothesized that a peripheral immune challenge, such as lipopolysaccharide (LPS)-mimicking a hospital-acquired infection-would worsen inflammatory, neurobehavioral, and seizure outcomes after experimental pediatric TBI. To test this, three-week old male C57Bl/6J mice received a moderate controlled cortical impact or sham surgery, followed by 1 mg/kg i.p. LPS (or 0.9% saline vehicle) at 4 days TBI. Mice were randomized to four groups; sham-saline, sham-LPS, TBI-saline or TBI-LPS (n = 15/group). Reduced general activity and increased anxiety-like behavior were observed within 24 h in LPS-treated mice, indicating a transient sickness response. LPS-treated mice also exhibited a reduction in body weights, which persisted chronically. From 2 months post-injury, mice underwent a battery of tests for sensorimotor, cognitive, and psychosocial behaviors. TBI resulted in hyperactivity and spatial memory deficits, independent of LPS; whereas LPS resulted in subtle deficits in spatial memory retention. At 5 months post-injury, video-electroencephalographic recordings were obtained to evaluate both spontaneous seizure activity as well as the evoked seizure response to pentylenetetrazol (PTZ). TBI increased susceptibility to PTZ-evoked seizures; whereas LPS appeared to increase the incidence of spontaneous seizures. Post-mortem analyses found that TBI, but not LPS, resulted in robust glial reactivity and loss of cortical volume. A TBI × LPS interaction in hippocampal volume suggested that TBI-LPS mice had a subtle increase in ipsilateral hippocampus tissue loss; however, this was not reflected in neuronal cell counts. Both TBI and LPS independently had modest effects on chronic hippocampal gene expression. Together, contrary to our hypothesis, we observed minimal synergy between TBI and LPS. Instead, pediatric TBI and a subsequent transient immune challenge independently influenced chronic outcomes. These findings have implications for future preclinical modeling as well as acute post-injury patient management.

Micro-RNA levels and symptom profile after mild traumatic brain injury: A longitudinal cohort study

Micro riboneucleic acids (miRNAs) may be transcribed after brain injury and be detectable in plasma. This study aimed to assess the discriminative ability of seven miRNAs in plasma to differentiate between patients with mild traumatic brain injury (mTBI) and healthy controls. Changes in miRNA levels over 28 days were compared to changes in self-reported symptom profile. This was a prospective cohort study with longitudinal measurements of miRNA levels and symptom self-report. The Rivermead Post-Concussion Symptom Questionnaire (RPQ) was used to determine symptom severity. Mean normalised expression ratios (NER) of miRNAs at day 0 between mTBI and healthy controls were compared. An analysis of response profiles compared the response over time of miRNA species with RPQ symptom severity. miRNA levels of subjects who were defined to have "recovered" on Day 7 and 28 were compared to "non-recovered" subjects. There were 28 mTBI patients and 30 healthy controls included for analysis. Symptom severity was significantly higher on the day of injury among mTBI subjects (p < 0.001), and miRNA 32-5p levels were also higher (p = 0.009). Change of miRNA levels were similar to RPQ change at Day 7, but significantly different at Day 28. Differences were observed among miRNA levels of recovered subjects. This study demonstrated differences in miRNA levels among mTBI subjects compared to healthy controls and different miRNA levels among those who had recovered compared to those reporting symptoms. The change in profiles of miRNAs was different to symptom severity, suggesting that the two measures reflect different aspects of brain injury and recovery.

Serum Neurofilament Light as a Biomarker of Traumatic Brain Injury in the Presence of Concomitant Peripheral Injury

Introduction:

Serum neurofilament light (NfL) is an emerging biomarker of traumatic brain injury (TBI). However, the effect of peripheral injuries such as long bone fracture and skeletal muscle injury on serum NfL levels is unknown. Therefore, the aim of this study was to determine whether serum NfL levels can be used as a biomarker of TBI in the presence of concomitant peripheral injuries.

Methods:

Rats were randomly assigned to one of four injury groups: polytrauma (muscle crush + fracture + TBI; n = 11); peripheral injuries (muscle crush + fracture + sham-TBI; n = 12); TBI-only (sham-muscle crush + sham-fracture + TBI; n = 13); and triple-sham (n = 7). At 2-days post-injury, serum levels of NfL were quantified using a Simoa HD-X Analyzer.

Results:

Compared to triple-sham rats, serum NfL concentrations were higher in rats with peripheral injuries-only, TBI-only, and polytrauma. When compared to peripheral injury-only rats, serum NfL levels were higher in TBI-only and polytrauma rats. No differences were found between TBI-only and polytrauma rats.

Conclusion:

Serum NfL levels did not differ between TBI-only and polytrauma rats, indicating that significant peripheral injuries did not affect the sensitivity and specificity of serum NfL as a biomarker of moderate TBI. However, the finding of elevated serum NfL levels in rats with peripheral injuries in the absence of a TBI suggests that the presence of such injuries may limit the utility of NfL as a biomarker of less severe TBI (eg, concussion).

Cognitive ocular motor deficits and white matter damage chronically after sports-related concussion

A history of concussion has been linked to long-term cognitive deficits; however, the neural underpinnings of these abnormalities are poorly understood. This study recruited 26 asymptomatic male Australian footballers with a remote history of concussion (i.e. at least six months since last concussion), and 23 non-collision sport athlete controls with no history of concussion. Participants completed three ocular motor tasks (prosaccade, antisaccade and a cognitively complex switch task) to assess processing speed, inhibitory control and cognitive flexibility, respectively. Diffusion tensor imaging data were acquired using a 3 T MRI scanner, and analysed using tract-based spatial statistics, to investigate white matter abnormalities and how they relate to ocular motor performance. Australian footballers had significantly slower adjusted antisaccade latencies compared to controls (P = 0.035). A significant switch cost (i.e. switch trial error > repeat trial error) was also found on the switch task, with Australian footballers performing increased magnitude of errors on prosaccade switch trials relative to prosaccade repeat trials (P = 0.023). Diffusion tensor imaging analysis found decreased fractional anisotropy, a marker of white matter damage, in major white matter tracts (i.e. corpus callosum, corticospinal tract) in Australian footballers relative to controls. Notably, a larger prosaccade switch cost was significantly related to reduced fractional anisotropy in anterior white matter regions found to connect to the prefrontal cortex (i.e. a key cortical ocular motor centre involved in executive functioning and task switching). Taken together, Australian footballers with a history of concussion have ocular motor deficits indicative of poorer cognitive processing speed and cognitive flexibility, which are related to reduce white matter integrity in regions projecting to important cognitive ocular motor structures. These findings provide novel insights into the neural mechanisms that may underly chronic cognitive impairments in individuals with a history of concussion.

The Known Unknowns: An Overview of the State of Blood-Based Protein Biomarkers of Mild Traumatic Brain Injury

Blood-based protein biomarkers have revolutionized several fields of medicine by enabling molecular level diagnosis, as well as monitoring disease progression and treatment efficacy. Traumatic brain injury (TBI) so far has benefitted only moderately from using protein biomarkers to improve injury outcome. Because of its complexity and dynamic nature, TBI, especially its most prevalent mild form (mild TBI; mTBI), presents unique challenges toward protein biomarker discovery and validation given that blood is frequently obtained and processed outside of the clinical laboratory (e.g., athletic fields, battlefield) under variable conditions. As it stands, the field of mTBI blood biomarkers faces a number of outstanding questions. Do elevated blood levels of currently used biomarkers-ubiquitin carboxy-terminal hydrolase L1, glial fibrillary acidic protein, neurofilament light chain, and tau/p-tau-truly mirror the extent of parenchymal damage? Do these different proteins represent distinct injury mechanisms? Is the blood-brain barrier a "brick wall"? What is the relationship between intra- versus extracranial values? Does prolonged elevation of blood levels reflect de novo release or extended protein half-lives? Does biological sex affect the pathobiological responses after mTBI and thus blood levels of protein biomarkers? At the practical level, it is unknown how pre-analytical variables-sample collection, preparation, handling, and stability-affect the quality and reliability of biomarker data. The ever-increasing sensitivity of assay systems and lack of quality control of samples, combined with the almost complete reliance on antibody-based assay platforms, represent important unsolved issues given that false-negative results can lead to false clinical decision making and adverse outcomes. This article serves as a commentary on the state of mTBI biomarkers and the landscape of significant challenges. We highlight and discusses several biological and methodological "known unknowns" and close with some practical recommendations.

The biological significance and clinical utility of emerging blood biomarkers for traumatic brain injury

HUIBREGTSE, M.E, Bazarian, J.J., Shultz, S.R., and Kawata K. The biological significance and clinical utility of emerging blood biomarkers for traumatic brain injury. NEUROSCI BIOBEHAV REV XX (130) 433-447, 2021.- Blood biomarkers can serve as objective measures to gauge traumatic brain injury (TBI) severity, identify patients at risk for adverse outcomes, and predict recovery duration, yet the clinical use of blood biomarkers for TBI is limited to a select few and only to rule out the need for CT scanning. The biomarkers often examined in neurotrauma research are proteomic markers, which can reflect a range of pathological processes such as cellular damage, astrogliosis, or neuroinflammation. However, proteomic blood biomarkers are vulnerable to degradation, resulting in short half-lives. Emerging biomarkers for TBI may reflect the complex genetic and neurometabolic alterations that occur following TBI that are not captured by proteomics, are less vulnerable to degradation, and are comprised of microRNA, extracellular vesicles, and neurometabolites. Therefore, this review aims to summarize our understanding of how biomarkers for brain injury escape the brain parenchymal space and appear in the bloodstream, update recent research findings in several proteomic biomarkers, and characterize biological significance and examine clinical utility of microRNA, extracellular vesicles, and neurometabolites.

Beyond the Brain: Peripheral Interactions after Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death and disability, and there are currently no pharmacological treatments known to improve patient outcomes. Unquestionably, contributing toward a lack of effective treatments is the highly complex and heterogenous nature of TBI. In this review, we highlight the recent surge of research that has demonstrated various central interactions with the periphery as a potential major contributor toward this heterogeneity and, in particular, the breadth of research from Australia. We describe the growing evidence of how extracranial factors, such as polytrauma and infection, can significantly alter TBI neuropathology. In addition, we highlight how dysregulation of the autonomic nervous system and the systemic inflammatory response induced by TBI can have profound pathophysiological effects on peripheral organs, such as the heart, lung, gastrointestinal tract, liver, kidney, spleen, and bone. Collectively, this review firmly establishes TBI as a systemic condition. Further, the central and peripheral interactions that can occur after TBI must be further explored and accounted for in the ongoing search for effective treatments.

The Neurological Consequences of Engaging in Australian Collision Sports

Collision sports are an integral part of Australian culture. The most common collision sports in Australia are Australian rules football, rugby union, and rugby league. Each of these sports often results in participants sustaining mild brain traumas, such as concussive and subconcussive injuries. However, the majority of previous studies and reviews pertaining to the neurological implications of sustaining mild brain traumas, while engaging in collision sports, have focused on those popular in North America and Europe. As part of this 2020 International Neurotrauma Symposium special issue, which highlights Australian neurotrauma research, this article will therefore review the burden of mild brain traumas in Australian collision sports athletes. Specifically, this review will first provide an overview of the consequences of mild brain trauma in Australian collision sports, followed by a summary of the previous studies that have investigated neurocognition, ocular motor function, neuroimaging, and fluid biomarkers, as well as neuropathological outcomes in Australian collision sports athletes. A review of the literature indicates that although Australians have contributed to the field, several knowledge gaps and limitations currently exist. These include important questions related to sex differences, the identification and implementation of blood and imaging biomarkers, the need for consistent study designs and common data elements, as well as more multi-modal studies. We conclude that although Australia has had an active history of investigating the neurological impact of collision sports participation, further research is clearly needed to better understand these consequences in Australian athletes and how they can be mitigated.

Activation of the Protein Kinase R-Like Endoplasmic Reticulum Kinase (PERK) Pathway of the Unfolded Protein Response after Experimental Traumatic Brain Injury and Treatment with a PERK Inhibitor

Neurodegeneration after traumatic brain injury (TBI) is increasingly recognized as a key factor contributing to poor chronic outcomes. Activation (i.e., phosphorylation) of the protein kinase R-like endoplasmic reticulum kinase (PERK) pathway has been implicated in neurodegenerative conditions with pathological similarities to TBI and may be a potential target to improve TBI outcomes. Here, we aimed to determine whether a moderate TBI would induce activation of the PERK pathway and whether treatment with the PERK inhibitor, GSK2606414, would improve TBI recovery. Male mice were administered a lateral fluid percussion injury (FPI) or sham injury and were euthanized at either 2 h, 24 h, or 1 week post-injury (n = 5 per injury group and time point) to assess changes in the PERK pathway. In the injured cortex, there was increased phosphorylated-PERK at 2 h post-FPI and increased phosphorylation of eukaryotic translation initiation factor α at 24 h post-FPI. We next examined the effect of acute treatment with GSK2606414 on pathological and behavioral outcomes at 4 weeks post-injury. Thus, there were a total of four groups: sham + VEH (n = 9); sham + GSK4606414 (n = 10); FPI + VEH (n = 9); and FPI + GSK2606414 (n = 9). GSK2606414 (50 mg/kg) or vehicle treatment was delivered by oral gavage beginning at 30 min post-injury, followed by two further treatments at 12-h increments. There were no significant effects of GSK2606414 on any of the outcomes assessed, which could be attributable to several reasons. For example, activation of PERK may not be a significant contributor to the neurological consequences 4 weeks post-FPI in mice. Further research is required to elucidate the role of the PERK pathway in TBI and whether interventions that target this pathway are beneficial.

White and Gray Matter Abnormalities in Australian Footballers With a History of Sports-Related Concussion: An MRI Study

Sports-related concussion (SRC) is a form of mild traumatic brain injury that has been linked to long-term neurological abnormalities. Australian rules football is a collision sport with wide national participation and is growing in popularity worldwide. However, the chronic neurological consequences of SRC in Australian footballers remain poorly understood. This study investigated the presence of brain abnormalities in Australian footballers with a history of sports-related concussion (HoC) using multimodal MRI. Male Australian footballers with HoC (n = 26), as well as noncollision sport athletes with no HoC (n = 27), were recruited to the study. None of the footballers had sustained a concussion in the preceding 6 months, and all players were asymptomatic. Data were acquired using a 3T MRI scanner. White matter integrity was assessed using diffusion tensor imaging. Cortical thickness, subcortical volumes, and cavum septum pellucidum (CSP) were analyzed using structural MRI. Australian footballers had evidence of widespread microstructural white matter damage and cortical thinning. No significant differences were found regarding subcortical volumes or CSP. These novel findings provide evidence of persisting white and gray matter abnormalities in Australian footballers with HoC, and raise concerns related to the long-term neurological health of these athletes.

Targeting the Cerebrovascular System: Next-Generation Biomarkers and Treatment for Mild Traumatic Brain Injury

The diagnosis, prognosis, and treatment of mild traumatic brain injuries (mTBIs), such as concussions, are significant unmet medical issues. The kinetic forces that occur in mTBI adversely affect the cerebral vasculature, making cerebrovascular injury (CVI) a pathophysiological hallmark of mTBI. Given the importance of a healthy cerebrovascular system in overall brain function, CVI is likely to contribute to neurological dysfunction after mTBI. As such, CVI and related pathomechanisms may provide objective biomarkers and therapeutic targets to improve the clinical management and outcomes of mTBI. Despite this potential, until recently, few studies have focused on the cerebral vasculature in this context. This article will begin by providing a brief overview of the cerebrovascular system followed by a review of the literature regarding how mTBI can affect the integrity and function of the cerebrovascular system, and how this may ultimately contribute to neurological dysfunction and neurodegenerative conditions. We then discuss promising avenues of research related to mTBI biomarkers and interventions that target CVI, and conclude that a clinical approach that takes CVI into account could result in substantial improvements in the care and outcomes of patients with mTBI.

Diffusion Imaging Reveals Sex Differences in the White Matter Following Sports-Related Concussion

Sports-related concussion (SRC) is a serious health concern. However, the temporal profile of neuropathophysiological changes after SRC and how these relate to biological sex are still poorly understood. This preliminary study investigated whether diffusion-weighted magnetic resonance imaging (dMRI) was sensitive to neuropathophysiological changes following SRC; whether these changes were sex-specific; and whether they persisted beyond the resolution of self-reported symptoms. Recently concussed athletes (n = 14), and age- and education-matched nonconcussed control athletes (n = 16), underwent MRI 24-48-h postinjury and again at 2-week postinjury (i.e., when cleared to return-to-play). Male athletes reported more symptoms and greater symptom severity compared with females. dMRI revealed white matter differences between athletes with SRC and their nonconcussed counterparts at 48-h postinjury. These differences were still present at 2-week postinjury, despite SRC athletes being cleared to return to play and may indicate increased cerebral vulnerability beyond the resolution of subjective symptoms. Furthermore, we identified sex-specific differences, with male SRC athletes having significantly greater white matter disruption compared with female SRC athletes. These results have important implications for the management of concussion, including guiding return-to-play decisions, and further improve our understanding regarding the role of sex in SRC outcomes.

A systemic immune challenge to model hospital-acquired infections independently regulates immune responses after pediatric traumatic brain injury

Background

Traumatic brain injury (TBI) is a major cause of disability in young children, yet the factors contributing to poor outcomes in this population are not well understood. TBI patients are highly susceptible to nosocomial infections, which are mostly acquired within the first week of hospitalization, and such infections may modify TBI pathobiology and recovery. In this study, we hypothesized that a peripheral immune challenge such as lipopolysaccharide (LPS)—mimicking a hospital-acquired infection—would worsen outcomes after experimental pediatric TBI, by perpetuating the inflammatory immune response.

Methods

Three-week-old male mice received either a moderate controlled cortical impact or sham surgery, followed by a single LPS dose (1 mg/kg i.p.) or vehicle (0.9% saline) at 4 days post-surgery, then analysis at 5 or 8 days post-injury (i.e., 1 or 4 days post-LPS).

Results

LPS-treated mice exhibited a time-dependent reduction in general activity and social investigation, and increased anxiety, alongside substantial body weight loss, indicating transient sickness behaviors. Spleen-to-body weight ratios were also increased in LPS-treated mice, indicative of persistent activation of adaptive immunity at 4 days post-LPS. TBI + LPS mice showed an impaired trajectory of weight gain post-LPS, reflecting a synergistic effect of TBI and the LPS-induced immune challenge. Flow cytometry analysis demonstrated innate immune cell activation in blood, brain, and spleen post-LPS; however, this was not potentiated by TBI. Cytokine protein levels in serum, and gene expression levels in the brain, were altered in response to LPS but not TBI across the time course. Immunofluorescence analysis of brain sections revealed increased glia reactivity due to injury, but no additive effect of LPS was observed.

Conclusions

Together, we found that a transient, infection-like systemic challenge had widespread effects on the brain and immune system, but these were not synergistic with prior TBI in pediatric mice. These findings provide novel insight into the potential influence of a secondary immune challenge to the injured pediatric brain, with future studies needed to elucidate the chronic effects of this two-hit insult.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02114-1.

Temporal profile and utility of serum neurofilament light in a rat model of mild traumatic brain injury

There is a widely recognized need for blood biomarkers to assist clinical decisions surrounding mild traumatic brain injury (mTBI). Serum neurofilament light (NfL), an indicator of neuroaxonal damage, is one such candidate, with early mTBI clinical investigations demonstrating significant promise. To facilitate the translation of pre-clinical mTBI findings, clinically relevant outcomes should be integrated into animal studies wherever possible. Despite this, the temporal profile and potential utility of NfL as a blood biomarker in pre-clinical mTBI is poorly understood. Here, we quantified serum NfL at 2-h, 1-, 3-, 7- and 14-days following mTBI in rats and compared these to pre-injury levels. We also investigated cumulative effects of repeat-mTBI by delivering 0, 1 or 5 mTBIs separated by 24 h. Sensorimotor performance was evaluated with the beam task at 1- and 4-h after mTBI, and serum was collected 1-day after the final procedure. We found that serum NfL levels were substantially elevated at all acute and sub-acute time-points after a single-mTBI, peaked at 1-day, and remained elevated 14-days post-injury. An mTBI dose-dependent effect on serum NfL levels was also observed, with substantially higher NfL levels found at 1-day post repeat-mTBI when compared to single-mTBI and sham-injured rats. Furthermore, NfL levels were found to be greatest in rats with the highest degree of sensorimotor impairment. In conclusion, these findings have described the temporal profile of serum NfL elevations following a single-mTBI in rats, and indicate a profile with some similarities and differences to that seen in the clinical condition. Moreover, we found that serum NfL levels were potentiated by repeat-mTBI, and that this biomarker may have utility as an indicator of injury severity. As such, future pre-clinical TBI studies may benefit from incorporating measures of serum NfL as an objective injury outcome.

Elevated Serum Interleukin-1β Levels in Male, but not Female, Collision Sport Athletes with a Concussion History

It is increasingly reported that a history of concussion may be associated with chronic deleterious consequences. While the pathophysiology that contributes to these consequences is not well understood, neuroinflammation is postulated to be critical. Activation of multi-protein complexes termed inflammasomes, a key component of this inflammatory response, has been reported in more severe TBIs; however, it has not been investigated in milder TBIs, such as concussion. This study investigated serum levels of interleukin (IL)-1β and IL-18 (key proteins activated downstream of these inflammasomes) at acute, sub-acute, and chronic time-points post-concussion. We recruited 105 Australian footballers (65 male, 40 female) during the pre-season, then prospectively followed these players for the occurrence of concussion during the season. At baseline, 58 footballers reported a previous concussion history, and 47 reported no previous concussion history. Additionally, 25 players sustained a mid-season concussion and were sampled at 2, 6, and 13 days post-concussion. Serum levels of IL-1β and IL-18 were quantified using highly sensitive Simoa HD-X Analyzer assays. At baseline, IL-1β levels were higher in male, but not female, footballers with a previous concussion history compared with footballers with no concussion history. There was also a positive correlation between years of collision sport participation and IL-18 levels in males. No evidence was found in males or females to indicate that IL-1β or IL-18 levels differed at 2, 6, or 13 days post-concussion. These findings provide novel insights into potential sex-specific physiological consequences of concussion, and suggest that neuroinflammation may be persistent chronically following concussion in male athletes.

Pain in the Developing Brain: Early Life Factors Alter Nociception and Neurobiological Function in Adolescent Rats

Although adverse early experiences prime individuals to be at increased risk for chronic pain, little research has examined the trauma–pain relationship in early life or the underlying mechanisms that drive pathology over time. Given that early experiences can potentiate the nociceptive response, this study aimed to examine the effects of a high-fat, high-sugar (HFHS) diet and early life stress (maternal separation [MS]) on pain outcomes in male and female adolescent rats. Half of the rats also underwent a plantar-incision surgery to investigate how the pain system responded to a mildly painful stimuli in adolescence. Compared with controls, animals that were on the HFHS diet, experienced MS, or had exposure to both, exhibited increased anxiety-like behavior and altered thermal and mechanical nociception at baseline and following the surgery. Advanced magnetic resonance imaging demonstrated that the HFHS diet and MS altered the maturation of the brain, leading to changes in brain volume and diffusivity within the anterior cingulate, amygdala, corpus callosum, nucleus accumbens, and thalamus, while also modifying the integrity of the corticospinal tracts. The effects of MS and HFHS diet were often cumulative, producing exacerbated pain sensitivity and increased neurobiological change. As early experiences are modifiable, understanding their role in pain may provide targets for early intervention/prevention.