A New Panel of Blood Biomarkers for the Diagnosis of Mild Traumatic Brain Injury/Concussion in Adults

Copeptin as a diagnostic and prognostic biomarker in pediatric diseases

Arginine vasopressin (AVP) plays a main role in maintaining the homeostasis of fluid balance and vascular tone and in regulating the endocrine stress response in response to osmotic, hemodynamic and stress stimuli. However, the difficulty in measuring AVP limits its clinical application. Copeptin, the C-terminal part of the AVP precursor, is released in an equimolar concentration mode with AVP from the pituitary but is more stable and simple to measure. Therefore, copeptin has emerged as a promising surrogate marker of AVP with excellent potential for the diagnosis, differentiation and prognosis of various diseases in recent decades. However, its application requires further validation, especially in the pediatric population. This review focuses on the clinical value of copeptin in different pediatric diseases and the prospects for its application as a potential biomarker.

Elevated cerebrospinal fluid galectin-3 and associated cytokines after severe traumatic brain injury in patients

This study aimed to investigate the galectin-3 and associated cytokines levels in the cerebrospinal fluid (CSF) of severe traumatic brain injury (sTBI) patients. Temporal CSF expression of galectin-3 and associated cytokines levels in sTBI patients within 1-week post-injury were studied using the multiplex bead array. STBI patient group was stratified using the Modified Rankin Score (mRS) into 3 groups: mRS 6 (died), mRS 5 (severely disabled) and mRS 1-4 (mild-to-moderately disabled) group. Analysis for bead array data using Kruskal-Wallis test with post hoc Dunn's multiple comparisons test, and temporal changes and correlation analysis using Spearman's correlation were carried out. At day 1 post-injury, CSF galectin-3 and interleukin-6 (IL-6), interleukin-10 (IL-10), cysteine-cysteine motif chemokine ligand-2 (CCL-2), and cysteine-cysteine motif chemokine ligand-20 (CCL-20), but not interleukin-1β (IL-1β) and tumor necrosis factor (TNF-α) levels were significantly elevated in mRS 5 group compared to non-TBI controls. Temporal correlation analysis at 1-7 days showed decreased IL-10 level in the mRS 6 group, decreased IL-10 and CCL-2 levels in mRS 5 group, and decreased IL-6, CCL-2, and CCL-20 levels in the mRS 1-4 group. Receiver operating characteristic curve analyses revealed a significant area under the curve for comparison between mRS 6 and mRS 5 groups for galectin-3 and IL-6. No significant differences in sex, age, Glasgow Coma Scale score, C-reactive protein levels and types of TBI-induced hemorrhages were observed between the groups. CSF galectin-3 and associated cytokines, especially IL-6, CCL-2 and CCL-20 levels were different within sub-groups of sTBI patients, suggesting their potential use in sTBI prognostics.

Inflammatory cytokines associated with mild traumatic brain injury and clinical outcomes: a systematic review and meta-analysis

Mild traumatic brain injuries (mTBIs) trigger a neuroinflammatory response, which leads to perturbations in the levels of inflammatory cytokines, resulting in a distinctive profile. A systematic review and meta-analysis were conducted to synthesize data related to levels of inflammatory cytokines in patients with mTBI. The electronic databases EMBASE, MEDLINE, and PUBMED were searched from January 2014 to December 12, 2021. A total of 5,138 articles were screened using a systematic approach based on the PRISMA and R-AMSTAR guidelines. Of these articles, 174 were selected for full-text review and 26 were included in the final analysis. The results of this study demonstrate that within 24 hours, patients with mTBI have significantly higher levels of Interleukin-6 (IL-6), Interleukin-1 Receptor Antagonist (IL-1RA), and Interferon-γ (IFN-γ) in blood, compared to healthy controls in majority of the included studies. Similarly one week following the injury, patients with mTBI have higher circulatory levels of Monocyte Chemoattractant Protein-1/C-C Motif Chemokine Ligand 2 (MCP-1/CCL2), compared to healthy controls in majority of the included studies. The results of the meta-analysis also confirmed these findings by demonstrating significantly elevated blood levels of IL-6, MCP-1/CCL2, and Interleukin-1 beta (IL-1β) in the mTBI population compared to healthy controls (p < 0.0001), particularly in the acute stages (<7 days). Furthermore, it was found that IL-6, Tumor Necrosis Factor-alpha (TNF-α), IL-1RA, IL-10, and MCP-1/CCL2 were associated with poor clinical outcomes following the mTBI. Finally, this research highlights the lack of consensus in the methodology of mTBI studies that measure inflammatory cytokines in the blood, and also provides direction for future mTBI research.

Potential Biomarkers of Impulsivity in Mild Traumatic Brain Injury: A Pilot Study

Very few studies have investigated cognition and impulsivity following mild traumatic brain injury (mTBI) in the general population. Furthermore, the neurobiological mechanisms underlying post-TBI neurobehavioral syndromes are complex and remain to be fully clarified. Herein, we took advantage of machine learning based-modeling to investigate potential biomarkers of mTBI-associated impulsivity. Twenty-one mTBI patients were assessed within one-month post-TBI and their data were compared to 19 healthy controls on measures of impulsivity (Barratt Impulsiveness Scale - BIS), executive functioning, episodic memory, self-report cognitive failures and blood biomarkers of inflammation, vascular and neuronal damage. mTBI patients were significantly more impulsive than controls in BIS total and subscales. Serum levels of sCD40L, Cathepsin D, IL-4, Neuropilin-1, IFN-α2, and Copeptin were associated with impulsivity in mTBI patients. Besides showing that mTBI are associated with impulsivity in non-military people, we unveiled different pathophysiological pathways potentially implicated in mTBI-related impulsivity.

Blood-Based Biomarkers of Repetitive, Subconcussive Blast Overpressure Exposure in the Training Environment: A Pilot Study

Because of their unknown long-term effects, repeated mild traumatic brain injuries (TBIs), including the low, subconcussive ones, represent a specific challenge to healthcare systems. It has been hypothesized that they can have a cumulative effect, and they may cause molecular changes that can lead to chronic degenerative processes. Military personnel are especially vulnerable to consequences of subconcussive TBIs because their training involves repeated exposures to mild explosive blasts. In this pilot study, we collected blood samples at baseline, 6 h, 24 h, 72 h, 2 weeks, and 3 months after heavy weapons training from students and instructors who were exposed to repeated subconcussive blasts. Samples were analyzed using the reverse and forward phase protein microarray platforms. We detected elevated serum levels of glial fibrillary acidic protein, ubiquitin C-terminal hydrolase L1 (UCH-L1), nicotinic alpha 7 subunit (CHRNA7), occludin (OCLN), claudin-5 (CLDN5), matrix metalloprotease 9 (MMP9), and intereukin-6 (IL-6). Importantly, serum levels of most of the tested protein biomarkers were the highest at 3 months after exposures. We also detected elevated autoantibody titers of proteins related to vascular and neuroglia-specific proteins at 3 months after exposures as compared to baseline levels. These findings suggest that repeated exposures to subconcussive blasts can induce molecular changes indicating not only neuron and glia damage, but also vascular changes and inflammation that are detectable for at least 3 months after exposures whereas elevated titers of autoantibodies against vascular and neuroglia-specific proteins can indicate an autoimmune process.

Blood-Brain Barrier Disintegration in Growth-Restricted Fetuses with Brain Sparing Effect

The endothelial cells of the blood-brain barrier adhere closely, which is provided by tight junctions (TJs). The aim of the study was to assess the damage to the endothelial TJs in pregnancy, complicated by fetal growth restriction (FGR) and circulatory centralization (brain-sparing effect, BS). The serum concentrations of NR1 subunit of the N-methyl-D-aspartate receptor (NR1), nucleoside diphosphate kinase A (NME1), S100 calcium-binding protein B (S100B), occludin (OCLN), claudin-5 (CLN5), and zonula occludens protein – 1 (zo-1), and the placental expressions of OCLN, claudin-4 (CLN4), CLN5, and zo-1 were assessed with ELISA. The significantly higher serum NME1 concentrations and the serum CLN5/zo-1 index were observed in FGR pregnancy with BS, as compared to the FGR group without BS. The FGR newborns with BS were about 20 times more likely to develop an intraventricular hemorrhage (IVH) than the FGR infants without BS. The cerebroplacental ratio (CPR) allowed to predict the IVH in growth-restricted fetuses. The significantly lower placental CLN4 expression was observed in the FGR group with BS and who postnatally developed an IVH, as compared to the growth-restricted infants with BS without IVH signs. Pregnancy complicated by FGR and BS is associated with the destabilization of the fetal blood-brain barrier. The IVH in newborns is reflected in the inhibition of the placental CLN4 expression, which may be a useful marker in the prediction of an IVH among growth-restricted fetuses.

Traumatic Brain Injury (TBI) Detection: Past, Present, and Future

Traumatic brain injury (TBI) can produce temporary biochemical imbalance due to leaks through cell membranes or disruption of the axoplasmic flow due to the misalignment of intracellular neurofilaments. If untreated, TBI can lead to Alzheimer's, Parkinson's, or total disability. Mild TBI (mTBI) accounts for about about 90 percent of all TBI cases. The detection of TBI as soon as it happens is crucial for successful treatment management. Neuroimaging-based tests provide only a structural and functional mapping of the brain with poor temporal resolution. Such tests may not detect mTBI. On the other hand, the electroencephalogram (EEG) provides good spatial resolution and excellent temporal resolution of the brain activities beside its portability and low cost. The objective of this paper is to provide clinicians and scientists with a one-stop source of information to quickly learn about the different technologies used for TBI detection, their advantages and limitations. Our research led us to conclude that even though EEG-based TBI detection is potentially a powerful technology, it is currently not able to detect the presence of a mTBI with high confidence. The focus of the paper is to review existing approaches and provide the reason for the unsuccessful state of EEG-based detection of mTBI.

Galectin-3, a rising star in modulating microglia activation under conditions of neurodegeneration

The advent of high-throughput single-cell transcriptomic analysis of microglia has revealed different phenotypes that are inherently associated with disease conditions. A common feature of some of these activated phenotypes is the upregulation of galectin-3. Representative examples of these phenotypes include disease-associated microglia (DAM) and white-associated microglia (WAM), whose role(s) in neuroprotection/neurotoxicity is a matter of high interest in the microglia community. In this review, we summarise the main findings that demonstrate the ability of galectin-3 to interact with key pattern recognition receptors, including, among others, TLR4 and TREM2 and the importance of galectin-3 in the regulation of microglia activation. Finally, we discuss increasing evidence supporting the involvement of this lectin in the main neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, traumatic brain injury, and stroke.

Prognosis and Diagnostic Biomarkers of Mild Traumatic Brain Injury: Current Status and Future Prospects

Mild traumatic brain injury (mTBI) is the most prevalent type of TBI (80-90%). It is characterized by a loss consciousness for less than 30 minutes, post-traumatic amnesia for less than 24 hours, and Glasgow Coma Score of 13-15. Accurately diagnosing mTBIs can be a challenge because the majority of these injuries do not show noticeable or visible changes on neuroimaging studies. Appropriate determination of mTBI is tremendously important because it might lead in some cases to post-concussion syndrome, cognitive impairments including attention, memory, and speed of information processing problems. The scientists have studied different methods to improve mTBI diagnosis and enhanced approaches that would accurately determine the severity of the trauma. The present review focuses on discussing the role of biomarkers as potential key factors in diagnosing mTBI. The present review focuses on 1) protein based peripheral and CNS markers, 2) genetic biomarkers, 3) imaging biomarkers, 4) neurophysiological biomarkers, and 5) the studies and clinical trials in mTBI. Each section provides information and characteristics on different biomarkers for mTBI.

Sex Differences in Cerebral Blood Flow and Serum Inflammatory Cytokines and Their Relationships in Mild Traumatic Brain Injury

This study aimed to investigate sex differences in cerebral blood flow (CBF) and serum inflammatory cytokines, as well as their correlations in patients with acute-stage mild traumatic brain injury (mTBI). Forty-one patients with mTBI and 23 matched healthy controls underwent 3D-pseudo-continuous arterial spin labeling imaging on 3T magnetic resonance imaging. The patients underwent cognitive evaluations and measurement of a panel of ten serum cytokines: interleukin (IL)-1I, IL-4, IL-6, IL-8, IL-10, IL-12, C–C motif chemokine ligand 2, interferon-gamma, nerve growth factor-beta (β-NGF), and tumor necrosis factor-alpha (TNF-α). Spearman rank correlation analysis was performed to evaluate the relationship between inflammation levels and CBF. We found that both male and female patients showed increased IL-1L and IL-6 levels. Female patients also demonstrated overexpression of IL-8 and low expression of IL-4. As for CBF levels, three brain regions [the right superior frontal gyrus (SFG_R), left putamen, and right precuneus] increased in male patients while three brain regions [the right superior temporal gyrus (STG_R), left middle occipital gyrus, and right postcentral (PoCG_R)] decreased in female patients. Furthermore, the STG_R in female controls was positively correlated with β-NGF while the right PoCG_R in female patients was negatively correlated with IL-8. In addition, compared with male patients, female patients showed decreased CBF in the right pallidum, which was negatively correlated with IL-8. These findings revealed abnormal expression of serum inflammatory cytokines and CBF levels post-mTBI. Females may be more sensitive to inflammatory and CBF changes and thus more likely to get cognitive impairment. This may suggest the need to pay closer attention to the female mTBI group.

Aldolase C Profiling in Serum after Mild Traumatic Brain Injury: A Prospective Cohort Study

BACKGROUND

After a traumatic brain injury (TBI), in addition to clinical indices, the serum level of neurological biomarkers may provide valuable diagnostic and prognostic information. The present study aimed to investigate the aldolase C (ALDOC) profile in serum for early diagnosis of brain damage in patients with mild TBI (mTBI) presented to the Emergency Department (ED).

METHODS

A single-center prospective cohort study was carried out in 2018-2019 at Imam Khomeini Hospital affiliated with Mazandaran University of Medical Sciences, Sari, Iran. A total of 89 patients with mTBI were enrolled in the study. Blood samples were taken within three hours after head trauma to measure ALDOC serum levels. Brain CT scan was used as the gold standard. Statistical analysis was performed using the Kruskal Wallis, Mann-Whitney U, and Chi square tests. The receiver-operating characteristic (ROC) curve plot was used to determine the optimal cutoff point for ALDOC. The sensitivity and specificity of the determined cutoff point were calculated. P values less than 0.05 were considered statistically significant.

RESULTS

Of the 89 patients, the CT scan findings showed a positive TBI in 30 (33.7%) of the patients and in 59 (66.3%) a negative TBI. The median ALDOC serum level in the patients with positive CT scan findings (8.35 ng/mL [IQR: 1.65]) was significantly higher than those with negative CT scan findings (5.3 ng/mL [IQR: 6.9]) (P<0.001). The optimal cutoff point for ALDOC serum level was 6.95 ng/mL, and the area under the curve was 99.6% (P<0.001). The sensitivity and specificity of the determined cutoff point were 100% and 98%, respectively.

CONCLUSION

The ALDOC serum level in patients with mTBI significantly correlates with the pathologic findings of the brain CT scan. This biomarker, with 100% sensitivity, is a suitable tool to detect brain structural abnormalities in mTBI patients.

Cerebral blood flow is associated with matrix metalloproteinase levels during the early symptomatic phase of concussion

Concussion is associated with disrupted cerebral blood flow (CBF), although there appears to be substantial inter-individual variability in CBF response. At present, the mechanisms of variable CBF response remain incompletely understood, but one potential contributor is matrix metalloproteinase (MMP) expression. In more severe forms of acquired brain injury, MMP up-regulation contributes to CBF impairments via increased blood-brain barrier permeability. A similar relationship is hypothesized for concussion, where recently concussed individuals with higher MMP levels have lower CBF. To test this hypothesis, 35 concussed athletes were assessed longitudinally at early symptomatic injury (median: 5 days post-injury) and at medical clearance (median: 24 days post-injury), along with 71 athletic controls. For all athletes, plasma MMPs were measured and arterial spin labelling was used to measure CBF. Consistent with our hypothesis, higher concentrations of MMP-2 and MMP-3 were correlated with lower global CBF. The correlations between MMPs and global CBF were also significantly diminished for concussed athletes at medical clearance and for athletic controls. These results indicate an inverse relationship between plasma MMP levels and CBF that is specific to the symptomatic phase of concussion. Analyses of regional CBF further showed that correlations with MMP levels exhibited some spatial specificity, with greatest effects in occipital, parietal and temporal lobes. These findings provide new insights into the mechanisms of post-concussion cerebrovascular dysfunction.

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.

A blood biomarker and clinical correlation cohort study protocol to diagnose sports-related concussion and monitor recovery in elite rugby

Introduction

In professional rugby, sports-related concussion (SRC) remains the most frequent time loss injury. Therefore, accurately diagnosing SRC and monitoring player recovery, through a multi-modal assessment process, is critical to SRC management. In this protocol study, we aim to assess SRC over multiple time points post-injury to determine the value of multi-modal assessments to monitor player recovery. This is of significance to minimise premature return-to-play and, ultimately, to reduce the long-term effects associated with SRC. The study will also establish the logistics of implementing such a study in a professional setting to monitor a player's SRC recovery.

Methods and analysis

All players from the participating professional rugby club within the Irish Rugby Football Union are invited to participate in the current study. Player assessment includes head injury assessment (HIA), neuropsychometric assessment (ImPACT), targeted biomarker analysis and untargeted biomarker analysis. Baseline HIA, ImPACT, and blood draws are performed prior to the start of playing season. During the baseline tests, player's complete consent forms and an SRC history questionnaire. Subsequently, any participant that enters the HIA process over the playing season due to a suspected SRC will be clinically assessed (HIA and ImPACT) and their blood will be drawn within 3 days of injury, 6 days post-injury, and 13 days post-injury.

Ethics and dissemination

Ethical approval was attained from the Science and Engineering Research Ethics Committee, University of Limerick (Approval Code: 2018_06_11_S&E). On completion of the study, further manuscripts will be published to present the results of the tests and their ability to measure player recovery from SRC.

Trial registration number

NCT04485494.

DNA methylation under the major depression pathway predicts pediatric quality of life four-month post-pediatric mild traumatic brain injury

BACKGROUND

Major depression has been recognized as the most commonly diagnosed psychiatric complication of mild traumatic brain injury (mTBI). Moreover, major depression is associated with poor outcomes following mTBI; however, the underlying biological mechanisms of this are largely unknown. Recently, genomic and epigenetic factors have been increasingly implicated in the recovery following TBI.

RESULTS

This study leveraged DNA methylation within the major depression pathway, along with demographic and behavior measures (features used in the clinical model) to predict post-concussive symptom burden and quality of life four-month post-injury in a cohort of 110 pediatric mTBI patients and 87 age-matched healthy controls. The results demonstrated that including DNA methylation markers in the major depression pathway improved the prediction accuracy for quality of life but not persistent post-concussive symptom burden. Specifically, the prediction accuracy (i.e., the correlation between the predicted value and observed value) of quality of life was improved from 0.59 (p = 1.20 × 10^-3) (clinical model) to 0.71 (p = 3.89 × 10^-5); the identified cytosine-phosphate-guanine sites were mainly in the open sea regions and the mapped genes were related to TBI in several molecular studies. Moreover, depression symptoms were a strong predictor (with large weights) for both post-concussive symptom burden and pediatric quality of life.

CONCLUSION

This study emphasized that both molecular and behavioral manifestations of depression symptoms played a prominent role in predicting the recovery process following pediatric mTBI, suggesting the urgent need to further study TBI-caused depression symptoms for better recovery outcome.

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.

The diagnosis and prognostic value of plasma copeptin in traumatic brain injury: a systematic review and meta-analysis

OBJECTIVE

The purpose of this meta-analysis was to assess the diagnosis and prognostic value of plasma copeptin levels after traumatic brain injury (TBI).

METHODS

The databases PubMed, Cochrane Library, OvidSP, Google Scholar, VIP, CNKI, and WFSD were systematically searched from the inception dates to May 9, 2020. The pooled analysis of relevant data was conducted by the RevMan 5.3 software. Subgroups analysis was performed to explore the impact of age, country, male ratio, follow-up time, and Glasgow coma score (GCS) on the pooled area under curve (AUC) values of assessment mortality.

RESULTS

A total of 17 studies involving 2654 participants were included in the current meta-analysis. The pooled results demonstrated that increased plasma copeptin levels were significantly associated with TBI [SMD, 2.44; 95%CI, 1.59 ~ 3.29; P < 0.00001] and also were significantly associated with mortality [SMD, 1.37; 95%CI, 1.16 ~ 1.58; P < 0.00001], and poor functional outcomes (PFO) [SMD, 1.44; 95%CI, 1.20 ~ 1.68; P < 0.00001] in patients with TBI. Furthermore, the copeptin had a significant value in diagnosing brain concussion [AUC, 0.90; 95%CI, 0.84 ~ 0.95; P < 0.00001] and predicting progressive hemorrhagic injury [AUC, 0.83; 95%CI, 0.80 ~ 0.87; P < 0.00001], acute traumatic coagulopathy [AUC, 0.84; 95%CI, 0.79 ~ 0.89; P < 0.00001], mortality [AUC, 0.89; 95%CI, 0.87 ~ 0.92; P < 0.00001], and PFO [AUC, 0.88; 95%CI, 0.84 ~ 0.92; P < 0.00001] in patients with TBI. The subgroup analysis findings suggested that the age, country, male ratio, follow-up time, and GCS were not obvious factors influencing the pooled AUC values of assessment mortality.

CONCLUSIONS

The authors indicate that the plasma copeptin is a potentially promising biomarker for TBI diagnosis and prognosis prediction.

Interleukin 10 and Heart Fatty Acid-Binding Protein as Early Outcome Predictors in Patients With Traumatic Brain Injury

Background: Patients with traumatic brain injury (TBI) exhibit a variable and unpredictable outcome. The proteins interleukin 10 (IL-10) and heart fatty acid-binding protein (H-FABP) have shown predictive values for the presence of intracranial lesions. Aim: To evaluate the individual and combined outcome prediction ability of IL-10 and H-FABP, and to compare them to the more studied proteins S100β, glial fibrillary acidic protein (GFAP), and neurofilament light (NF-L), both with and without clinical predictors. Methods: Blood samples from patients with acute TBI (all severities) were collected <24 h post trauma. The outcome was measured >6 months post injury using the Glasgow Outcome Scale Extended (GOSE) score, dichotomizing patients into: (i) those with favorable (GOSE≥5)/unfavorable outcome (GOSE ≤ 4) and complete (GOSE = 8)/incomplete (GOSE ≤ 7) recovery, and (ii) patients with mild TBI (mTBI) and patients with TBIs of all severities. Results: When sensitivity was set at 95-100%, the proteins' individual specificities remained low. H-FABP showed the best specificity (%) and sensitivity (100%) in predicting complete recovery in patients with mTBI. IL-10 had the best specificity (50%) and sensitivity (96%) in identifying patients with favorable outcome in patients with TBIs of all severities. When individual proteins were combined with clinical parameters, a model including H-FABP, NF-L, and ISS yielded a specificity of 56% and a sensitivity of 96% in predicting complete recovery in patients with mTBI. In predicting favorable outcome, a model consisting IL-10, age, and TBI severity reached a specificity of 80% and a sensitivity of 96% in patients with TBIs of all severities. Conclusion: Combining novel TBI biomarkers H-FABP and IL-10 with GFAP, NF-L and S100β and clinical parameters improves outcome prediction models in TBI.

Galectin-3: Roles in Neurodevelopment, Neuroinflammation, and Behavior

There is a plethora of evidence to suggest that Galectin-3 plays an important role in normal functions of mammalian cells, as well as in different pathogenic conditions. This review highlights recent data published by researchers, including our own team, on roles of Galectin-3 in the nervous system. Here, we discuss the roles of Galectin-3 in brain development, its roles in glial cells, as well as the interactions of glial cells with other neural and invading cells in pathological conditions. Galectin-3 plays an important role in the pathogenesis of neuroinflammatory and neurodegenerative disorders, such as multiple sclerosis, Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. On the other hand, there is also evidence of the protective role of Galectin-3 due to its anti-apoptotic effect in target cells. Interestingly, genetic deletion of Galectin-3 affects behavioral patterns in maturing and adult mice. The results reviewed in this paper and recent development of highly specific inhibitors suggests that Galectin-3 may be an important therapeutic target in pathological conditions including the disorders of the central nervous system.

Exploring blood-brain barrier hyperpermeability and potential biomarkers in traumatic brain injury

Blood-brain barrier breakdown and associated vascular hyperpermeability leads to vasogenic edema in traumatic brain injury (TBI). Tight junctions maintain blood-brain barrier integrity; their disruption in TBI holds significant promise for diagnosis and treatment. A controlled cortical impactor was used for TBI in mouse studies. Blood was collected 1 h after injury and sent for antibody microarray analysis. Twenty human subjects with radiographic evidence of TBI were enrolled and blood collected within 48 h of admission. Control subjects were individuals with nontrauma diagnoses. The subjects were matched by age and gender. Enzyme-linked immunosorbent assays were performed on each TBI and control sample for tight junction-associated proteins (TJPs), inflammatory markers, and S100β. Plasma was used to conduct in vitro monolayer permeability studies with human brain endothelial cells. S100β and the TJP occludin were significantly elevated in TBI plasma in both the murine and human studies. Monolayer permeability studies showed increased hyperpermeability in TBI groups. Plasma from TBI subjects increases microvascular hyperpermeability in vitro. TJPs in the blood may be a potential biomarker for TBI.

Defining New Research Questions and Protocols in the Field of Traumatic Brain Injury through Public Engagement: Preliminary Results and Review of the Literature

Traumatic brain injury (TBI) is the most common cause of death and disability in the age group below 40 years. The financial cost of loss of earnings and medical care presents a massive burden to family, society, social care, and healthcare, the cost of which is estimated at £1 billion per annum (about brain injury (online)). At present, we still lack a full understanding on the pathophysiology of TBI, and biomarkers represent the next frontier of breakthrough discoveries. Unfortunately, many tenets limit their widespread adoption. Brain tissue sampling is the mainstay of diagnosis in neuro-oncology; following on this path, we hypothesise that information gleaned from neural tissue samples obtained in TBI patients upon hospital admission may correlate with outcome data in TBI patients, enabling an early, accurate, and more comprehensive pathological classification, with the intent of guiding treatment and future research. We proposed various methods of tissue sampling at opportunistic times: two methods rely on a dedicated sample being taken; the remainder relies on tissue that would otherwise be discarded. To gauge acceptance of this, and as per the guidelines set out by the National Research Ethics Service, we conducted a survey of TBI and non-TBI patients admitted to our Trauma ward and their families. 100 responses were collected between December 2017 and July 2018, incorporating two redesigns in response to patient feedback. 75.0% of respondents said that they would consent to a brain biopsy performed at the time of insertion of an intracranial pressure (ICP) bolt. 7.0% replied negatively and 18.0% did not know. 70.0% would consent to insertion of a jugular bulb catheter to obtain paired intracranial venous samples and peripheral samples for analysis of biomarkers. Over 94.0% would consent to neural tissue from ICP probes, external ventricular drains (EVD), and lumbar drains (LD) to be salvaged, and 95.0% would consent to intraoperative samples for further analysis.

Metabolomics and Biomarker Discovery in Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the leading causes of disability and mortality worldwide. The TBI pathogenesis can induce broad pathophysiological consequences and clinical outcomes attributed to the complexity of the brain. Thus, the diagnosis and prognosis are important issues for the management of mild, moderate, and severe forms of TBI. Metabolomics of readily accessible biofluids is a promising tool for establishing more useful and reliable biomarkers of TBI than using clinical findings alone. Metabolites are an integral part of all biochemical and pathophysiological pathways. Metabolomic processes respond to the internal and external stimuli resulting in an alteration of metabolite concentrations. Current high-throughput and highly sensitive analytical tools are capable of detecting and quantifying small concentrations of metabolites, allowing one to measure metabolite alterations after a pathological event when compared to a normal state or a different pathological process. Further, these metabolic biomarkers could be used for the assessment of injury severity, discovery of mechanisms of injury, and defining structural damage in the brain in TBI. Metabolic biomarkers can also be used for the prediction of outcome, monitoring treatment response, in the assessment of or prognosis of post-injury recovery, and potentially in the use of neuroplasticity procedures. Metabolomics can also enhance our understanding of the pathophysiological mechanisms of TBI, both in primary and secondary injury. Thus, this review presents the promising application of metabolomics for the assessment of TBI as a stand-alone platform or in association with proteomics in the clinical setting.

Multi-Dimensional Mapping of Brain-Derived Extracellular Vesicle MicroRNA Biomarker for Traumatic Brain Injury Diagnostics

The diagnosis and prognosis of traumatic brain injury (TBI) is complicated by variability in the type and severity of injuries and the multiple endophenotypes that describe each patient's response and recovery to the injury. It has been challenging to capture the multiple dimensions that describe an injury and its recovery to provide clinically useful information. To address this challenge, we have performed an open-ended search for panels of microRNA (miRNA) biomarkers, packaged inside of brain-derived extracellular vesicles (EVs), that can be combined algorithmically to accurately classify various states of injury. We mapped GluR2+ EV miRNA across a variety of injury types, injury intensities, history of injuries, and time elapsed after injury, and sham controls in a pre-clinical murine model (n = 116), as well as in clinical samples (n = 36). We combined next-generation sequencing with a technology recently developed by our lab, Track Etched Magnetic Nanopore (TENPO) sorting, to enrich for GluR2+ EVs and profile their miRNA. By mapping and comparing brain-derived EV miRNA between various injuries, we have identified signaling pathways in the packaged miRNA that connect these biomarkers to underlying mechanisms of TBI. Many of these pathways are shared between the pre-clinical model and the clinical samples, and present distinct signatures across different injury models and times elapsed after injury. Using this map of EV miRNA, we applied machine learning to define a panel of biomarkers to successfully classify specific states of injury, paving the way for a prognostic blood test for TBI. We generated a panel of eight miRNAs (miR-150-5p, miR-669c-5p, miR-488-3p, miR-22-5p, miR-9-5p, miR-6236, miR-219a.2-3p, miR-351-3p) for injured mice versus sham mice and four miRNAs (miR-203b-5p, miR-203a-3p, miR-206, miR-185-5p) for TBI patients versus healthy controls.

Glial Fibrillary Acidic Protein (GFAP) Outperforms S100 Calcium-Binding Protein B (S100B) and Ubiquitin C-Terminal Hydrolase L1 (UCH-L1) as Predictor for Positive Computed Tomography of the Head in Trauma Subjects

OBJECTIVE

Traumatic brain injuries (TBIs) are largely underdiagnosed and may have persistent refractory consequences. Current assessments for acute TBI are limited to physical examination and imaging. Biomarkers such as glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase L1 (UCH-L1), and S100 calcium-binding protein B (S100B) have shown predictive value as indicators of TBI and potential screening tools.

METHODS

In total, 37 controls and 118 unique trauma subjects who received a clinically ordered head computed tomography (CT) in the emergency department of a level 1 trauma center were evaluated. Blood samples collected at 0-8 hours (initial) and 12-32 hours (delayed) postinjury were analyzed for GFAP, UCH-L1, and S100B concentrations. These were then compared in CT-negative and CT-positive subjects.

RESULTS

Median GFAP, UCH-L1, and S100B concentrations were greater in CT-positive subjects at both timepoints compared with CT-negative subjects. In addition, median UCH-L1 and S100B concentrations were lower at the delayed timepoint, whereas median GFAP concentrations were increased. As predictors of a positive CT of the head, GFAP outperformed UCH-L1 and S100B at both timepoints (initial: 0.89 sensitivity, 0.62 specificity; delayed: 0.94 sensitivity, 0.67 specificity). GFAP alone also outperformed all possible combinations of biomarkers.

CONCLUSIONS

GFAP, UCH-L1, and S100B demonstrated utility for rapid prediction of a CT-positive TBI within 0-8 hours of injury. GFAP exhibited the greatest predictive power at 12-32 hours. Furthermore, these results suggest that GFAP alone has greater utility for predicting a positive CT of the head than UCH-L1, S100B, or any combination of the 3.

Blood and cerebrospinal fluid biomarkers

Sports-related traumatic brain injuries (TBIs) range in severity from severe to subconcussive. Although technologies exist for clinical diagnosis of more severe injuries, methods for diagnosis of milder forms of brain injury are limited. Developing objective measures to indicate pathogenic processes after a suspected mild TBI is challenging for multiple reasons. The field of biomarker discovery for diagnosing TBI continues to expand, with newly identified candidate biomarkers being reported regularly. Brain-specific biomarkers include proteins derived from neurons and glia, and are often measured to assess neural injury and repair, and to predict outcomes. Ideally, changes in biomarker levels should indicate pathologic events and answer critical questions for accurate diagnosis and prognosis. For example, does the presence or a change in the biomarker level suggest greater vulnerability for sustaining a second concussion or show that the window of increased vulnerability has passed? Likewise, do changes in biomarker levels predict postconcussion syndrome or recovery/repair? Although there are numerous promising candidates for fluid biomarkers that may diagnose mild TBI or concussion, none has reached the clinic to date. In this chapter, we will define biomarkers, discuss the importance of understanding their normal and pathologic functions, and outline some considerations for interpreting detection assay results in TBI. We will then review five proposed blood and cerebrospinal fluid biomarkers (tau, neurofilament, ubiquitin carboxyl-terminal hydrolase L1, S100β, and glial fibrillary acidic protein) used currently to address TBI. Lastly, we will discuss a future trajectory for developing new, clinically useful fluid biomarkers.

Persistently high circulating tissue inhibitor of matrix metalloproteinase-1 levels in non-survivor brain trauma injury patients

PURPOSE

Previously, higher circulating levels of matrix metalloproteinase (MMP)-9 and tissue inhibitor matrix metalloproteinases (TIMP)-1 were reported in the first hours after TBI in blood samples from patients with poor prognosis. Thus, the objectives of this study were to determine whether MMP-9 and TIMP-1 levels during the first week of a severe TBI could be used as biomarker predictive of mortality.

METHODS

We included patients with severe TBI (defined as Glasgow Coma Scale lower than 9), and with Injury Severity Score in non-cranial aspects lower than 9. We determined serum concentrations of MMP-9 and TIMP-1 at days 1, 4 and 8 of TBI.

RESULTS

TIMP-1 concentrations at days 1 (p < .001), 4 (p = .001), and 8 (p = .01) of TBI were higher in non-surviving (n = 34) than in surviving (n = 90) patients. ROC curve analyses showed an area under curve of TIMP-1 concentrations at days 1, 4, and 8 of TBI to predict 30-day mortality of 78% (p < .001), 76% (p < .001) and 71% (p = .02) respectively.

CONCLUSIONS

The most relevant new findings of our study were that TIMP-1 levels during the first week of a severe TBI were higher in non-surviving than in surviving patients and that could be used as biomarker predictive of mortality.

Concussions in Sports

Although concussions are common, they are complex, variable, and not entirely understood in terms of pathophysiology and treatment. The incidence of concussion is expected to continue to rise with the increased participation of youth in sports and improved awareness. The role of orthopedic surgeons in concussion management is murky. However, the existing literature does provide a foundation from which orthopedic surgeons who are exposed to concussed patients can function. [Orthopedics. 2019; 42(1):12-21.].

Testing a Multivariate Proteomic Panel for Traumatic Brain Injury Biomarker Discovery: A TRACK-TBI Pilot Study

The complex and heterogeneous nature of traumatic brain injury (TBI) has rendered the identification of diagnostic and prognostic biomarkers elusive. A single acute biomarker may not be sufficient to categorize injury severity and/or predict outcome. Using multivariate dimension reduction analyses, we tested the sensitivity and specificity of a multi-analyte panel of proteins as an ensemble biomarker for TBI. Serum was collected within 24 h of injury in a cohort of 130 patients enrolled in the multi-center prospective Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot (TRACK-TBI Pilot) study and run on an array that measured 72 proteins. Using unsupervised principal components analysis, we first identified the subset of protein changes accounting for the most variance across patients. This yielded a group of 21 proteins that reflected an inverse relationship between inflammatory cytokines and regulators of anti-inflammation, and generated an individual inflammatory profile score for each patient. We then tested the association between these scores and computed tomography (CT) findings at hospital admission, as well as their prognostic association with functional recovery at 3 and 6 months (Glasgow Outcome Scale-Extended), and cognitive recovery at 6 months (California Verbal Learning Test, Second Edition) after injury. Inflammatory signatures were significantly increased in patients with positive CT findings, as well as in those who showed poor or incomplete recovery. Inflammation biomarker scores also showed significant sensitivity and specificity as a discriminator of these outcome measures (all areas under the curve [AUCs] >0.62). This proof of concept for the feasibility of multivariate biomarker identification demonstrates the prognostic validity of using a proteomic panel as a potential biomarker for TBI.

Changes in Transcranial Sonographic Measurement of the Optic Nerve Sheath Diameter in Non-concussed Collegiate Soccer Players Across a Single Season

Introduction

Bedside ultrasound measurement of the optic nerve sheath diameter (ONSD) is emerging as a non-invasive technique to evaluate and predict raised intracranial pressure (ICP) in both children and adults. The prognostic value of increased ONSD on brain computed tomography (CT) scan has previously been correlated with increased intensive care unit (ICU) mortality in patients with severe traumatic brain injury (TBI). Previous studies have also evaluated the association between high-contact sports, such as soccer, and TBI; however, the related changes in ONSD are still unknown. The aim of this study was to evaluate for the natural evolution of changes in ONSD in athletes who participate in high-contact sports.

Methods

In this prospective observational study, volunteers from a collegiate women’s soccer team underwent the measurement of ONSD with transcranial Doppler (TCD). ONSDs were measured during the initial visit during the pre-season period and again at the three-month follow-up. A single experienced neuro-sonographer performed all measurements to eliminate any operator bias.

Results

Twenty-four female college soccer players between the ages of 18 and 23 were included in this analysis. Mean ONSD during the initial pre-season clinic visit and the three-month follow-up were 4.14±0.6 mm and 5.02±0.72 mm, respectively (P < 0.0001). A two-tailed t-test analysis was performed, which resulted in a t-value of 4.76 and P < 0.00001. The average ONSD measured during the post-season follow-up showed a 21.3% increase compared to the baseline.

Conclusion

The evaluation of high-contact sports athletes is limited due to the lack of objective radiologic and diagnostic tools. Moreover, in an athlete suffering a concussion, return-to-play decisions are heavily dependent on the symptoms reported by the athletes. In our analysis of collegiate women’s soccer players, active participation in soccer competitions and practice may be associated with an increase in ONSD, independent of concussions. Further studies are underway to evaluate the clinical significance of these findings as well as possible correlations between concussions and changes in ONSD.

Sport related concussion - Potential for biomarkers to improve acute management

Sport-related concussion is a common form of mild traumatic brain injury that is now recognised as a serious health issue. Growing evidence suggests concussion may result in long-term and severe neurological disabilities. Recent research into the diagnosis and management of concussion may provide new approaches to concussion management that limit the potential long-term adverse effects of concussion. This paper summarises the problem of sport-related concussion and reviews key factors (sex, age, genetics) that may modify concussion outcomes. Current sport-related concussion tools are described. Analysis of emerging methods of acute concussion diagnosis using objective fluid and neuroimaging biomarkers is provided. These new concussion biomarkers have the potential to change management of sport-related concussion.

Combining H-FABP and GFAP increases the capacity to differentiate between CT-positive and CT-negative patients with mild traumatic brain injury

Mild traumatic brain injury (mTBI) patients may have trauma-induced brain lesions detectable using CT scans. However, most patients will be CT-negative. There is thus a need for an additional tool to detect patients at risk. Single blood biomarkers, such as S100B and GFAP, have been widely studied in mTBI patients, but to date, none seems to perform well enough. In many different diseases, combining several biomarkers into panels has become increasingly interesting for diagnoses and to enhance classification performance. The present study evaluated 13 proteins individually-H-FABP, MMP-1, MMP-3, MMP-9, VCAM, ICAM, SAA, CRP, GSTP, NKDA, PRDX1, DJ-1 and IL-10-for their capacity to differentiate between patients with and without a brain lesion according to CT results. The best performing proteins were then compared and combined with the S100B and GFAP proteins into a CT-scan triage panel. Patients diagnosed with mTBI, with a Glasgow Coma Scale score of 15 and one additional clinical symptom were enrolled at three different European sites. A blood sample was collected at hospital admission, and a CT scan was performed. Patients were divided into two two-centre cohorts and further dichotomised into CT-positive and CT-negative groups for statistical analysis. Single markers and panels were evaluated using Cohort 1. Four proteins-H-FABP, IL-10, S100B and GFAP-showed significantly higher levels in CT-positive patients. The best-performing biomarker was H-FABP, with a specificity of 32% (95% CI 23-40) and sensitivity reaching 100%. The best-performing two-marker panel for Cohort 1, subsequently validated in Cohort 2, was a combination of H-FABP and GFAP, enhancing specificity to 46% (95% CI 36-55). When adding IL-10 to this panel, specificity reached 52% (95% CI 43-61) with 100% sensitivity. These results showed that proteins combined into panels could be used to efficiently classify CT-positive and CT-negative mTBI patients.

Extracellular vesicles: mediators and biomarkers of pathology along CNS barriers

Extracellular vesicles (EVs) are heterogeneous, nano-sized vesicles that are shed into the blood and other body fluids, which disperse a variety of bioactive molecules (e.g., protein, mRNA, miRNA, DNA and lipids) to cellular targets over long and short distances. EVs are thought to be produced by nearly every cell type, however this review will focus specifically on EVs that originate from cells at the interface of CNS barriers. Highlighted topics include, EV biogenesis, the production of EVs in response to neuroinflammation, role in intercellular communication and their utility as a therapeutic platform. In this review, novel concepts regarding the use of EVs as biomarkers for BBB status and as facilitators for immune neuroinvasion are also discussed. Future directions and prospective are covered along with important unanswered questions in the field of CNS endothelial EV biology.

Current and Future Applications of Biomedical Engineering for Proteomic Profiling: Predictive Biomarkers in Neuro-Traumatology

This systematic review aims to summarize the impact of nanotechnology and biomedical engineering in defining clinically meaningful predictive biomarkers in patients with traumatic brain injury (TBI), a critical worldwide health problem with an estimated 10 billion people affected annually worldwide. Data were collected through a review of the existing English literature performed on Scopus, MEDLINE, MEDLINE in Process, EMBASE, and/or Cochrane Central Register of Controlled Trials. Only experimental articles revolving around the management of TBI, in which the role of new devices based on innovative discoveries coming from the field of nanotechnology and biomedical engineering were highlighted, have been included and analyzed in this study. Based on theresults gathered from this research on innovative methods for genomics, epigenomics, and proteomics, their future application in this field seems promising. Despite the outstanding technical challenges of identifying reliable biosignatures for TBI and the mixed nature of studies herein described (single cells proteomics, biofilms, sensors, etc.), the clinical implementation of those discoveries will allow us to gain confidence in the use of advanced neuromonitoring modalities with a potential dramatic improvement in the management of those patients.

Plasma Glial Fibrillary Acidic Protein, Copeptin, and Matrix Metalloproteinase-9 Concentrations among West African Stroke Subjects Compared with Stroke-Free Controls

BACKGROUND

Measurement of plasma molecular markers among stroke patients has been proposed as an avenue for improving the accuracy of stroke diagnosis. There is paucity of data on the potential role of these markers in resource-limited settings, where the burden of stroke is greatest.

OBJECTIVE

To assess the potential diagnostic and prognostic performance of 3 proposed biomarkers for stroke in a resource-constrained setting.

METHODS

Consecutive stroke subjects presenting at a tertiary medical center in Kumasi, Ghana, with radiologically confirmed diagnosis and etiologic subtype information available were recruited along with age- and gender-matched controls in a 2:1 ratio. Plasma concentrations of glial fibrillary acidic protein (GFAP), copeptin, and matrix metalloproteinase-9 (MMP-9) among stroke patients and stroke-free controls were measured in duplicates using enzyme linked immunoassays. Diagnostic and prognostic correlates were assessed using area-under-the-curve (AUC) measures of receiver operator curves and logistic regression analysis, respectively.

RESULTS

There were 156 stroke subjects with a mean age of 61.3 years of which 47.4% were females and 74 age- and gender-matched stroke-free controls. Median (interquartile range) time from symptom onset to hospital presentation for care was 7 days (5-11). Diagnostic accuracy of a single measurement of the 3 biomarkers for stroke using AUC (95% confidence interval) plots were as follows: .84 (.77-0.91), P < .0001, for GFAP; .85 (.79-0.92), P < .0001, for copeptin; and .65 (.56-0.73), P = .0003, for MMP-9. None of the biomarkers was associated with stroke severity or mortality.

CONCLUSION

Plasma concentrations of GFAP and copeptin demonstrated stronger associations with stroke occurrence in this West African cohort compared with controls.

Applying fluid biomarkers to Alzheimer's disease

Alzheimer's disease (AD) is a common neurodegenerative disease that starts with a clinically silent phase of a decade or more during which brain pathologies accumulate predominantly in the medial temporal lobe but also elsewhere in the brain. Network dysfunction and clinical symptoms typically appear when senile plaque (amyloid-β) and neurofibrillary tangle (tau) pathologies meet in the brain parenchyma, producing synapse and neuronal loss. For plaque and tangle pathologies, reliable fluid biomarkers have been developed. These require sampling of cerebrospinal fluid. Reliable blood tests for plaque and tangle pathologies are currently lacking, but blood tests for general neurodegeneration have recently been developed. In AD, plaques and tangles often coexist with other pathologies, including Lewy bodies, and to what extent these contribute to symptoms is currently unknown. There are also important differential diagnoses that may be possible to distinguish from AD with the aid of biomarkers. The scope of this review is fluid biomarkers for AD and related pathologies. The purpose is to provide the reader with an updated account of currently available fluid biomarkers for AD and clinically relevant differential diagnoses.

Intranasal Administration of the Antisecretory Peptide AF-16 Reduces Edema and Improves Cognitive Function Following Diffuse Traumatic Brain Injury in the Rat

A synthetic peptide with antisecretory activity, antisecretory factor (AF)-16, improves injury-related deficits in water and ion transport and decreases intracranial pressure after experimental cold lesion injury and encephalitis although its role in traumatic brain injury (TBI) is unknown. AF-16 or an inactive reference peptide was administrated intranasally 30 min following midline fluid percussion injury (mFPI; n = 52), a model of diffuse mild-moderate TBI in rats. Sham-injured (n = 14) or naïve (n = 24) animals were used as controls. The rats survived for either 48 h or 15 days post-injury. At 48 h, the animals were tested in the Morris water maze (MWM) for memory function and their brains analyzed for cerebral edema. Here, mFPI-induced brain edema compared to sham or naïve controls that was significantly reduced by AF-16 treatment (p < 0.05) although MWM performance was not altered. In the 15-day survival groups, the MWM learning and memory abilities as well as histological changes were analyzed. AF-16-treated brain-injured animals shortened both MWM latency and swim path in the learning trials (p < 0.05) and improved probe trial performance compared to brain-injured controls treated with the inactive reference peptide. A modest decrease by AF-16 on TBI-induced changes in hippocampal glial acidic fibrillary protein (GFAP) staining (p = 0.11) was observed. AF-16 treatment did not alter any other immunohistochemical analyses (degenerating neurons, beta-amyloid precursor protein (β-APP), and Olig2). In conclusion, intranasal AF-16-attenuated brain edema and enhanced visuospatial learning and memory following diffuse TBI in the rat. Intranasal administration early post-injury of a promising neuroprotective substance offers a novel treatment approach for TBI.

Galectin-3 released in response to traumatic brain injury acts as an alarmin orchestrating brain immune response and promoting neurodegeneration

Traumatic brain injury (TBI) is currently a major cause of morbidity and poor quality of life in Western society, with an estimate of 2.5 million people affected per year in Europe, indicating the need for advances in TBI treatment. Within the first 24 h after TBI, several inflammatory response factors become upregulated, including the lectin galectin-3. In this study, using a controlled cortical impact (CCI) model of head injury, we show a large increase in the expression of galectin-3 in microglia and also an increase in the released form of galectin-3 in the cerebrospinal fluid (CSF) 24 h after head injury. We report that galectin-3 can bind to TLR-4, and that administration of a neutralizing antibody against galectin-3 decreases the expression of IL-1β, IL-6, TNFα and NOS2 and promotes neuroprotection in the cortical and hippocampal cell populations after head injury. Long-term analysis demonstrated a significant neuroprotection in the cortical region in the galectin-3 knockout animals in response to TBI. These results suggest that following head trauma, released galectin-3 may act as an alarmin, binding, among other proteins, to TLR-4 and promoting inflammation and neuronal loss. Taking all together, galectin-3 emerges as a clinically relevant target for TBI therapy.

Biofluid Proteomics and Biomarkers in Traumatic Brain Injury

Traumatic brain injury (TBI) is an injury to the brain caused by an external mechanical force, affecting millions of people worldwide. The disease course and prognosis are often unpredictable, and it can be challenging to determine an early diagnosis in case of mild injury as well as to accurately phenotype the injury. There is currently no cure for TBI-drugs having failed repeatedly in clinical trials-but an intense effort has been put to identify effective neuroprotective treatment. The detection of novel biomarkers, to understand more of the disease mechanism, facilitates early diagnosis, predicts disease progression, and develops molecularly targeted therapies that would be of high clinical interest. Over the last decade, there has been an increasing effort and initiative toward finding TBI-specific biomarker candidates. One promising strategy has been to use state-of-the-art neuroproteomics approaches to assess clinical biofluids and compare the cerebrospinal fluid (CSF) and blood proteome between TBI and control patients or between different subgroups of TBI. In this chapter, we summarize and discuss the status of biofluid proteomics in TBI, with a particular focus on the latest findings.

The Involvement of Pial Microvessels in Leukocyte Invasion after Mild Traumatic Brain Injury

The pathophysiological mechanisms underlying mild traumatic brain injury (mTBI) are not well understood, but likely involve neuroinflammation. Here the controlled cortical impact model of mTBI in rats was used to test this hypothesis. Mild TBI caused a rapid (within 6 h post-mTBI) upregulation of synthesis of TNF-α and IL-1β in the cerebral cortex and hippocampus, followed by an increase in production of neutrophil (CXCL1-3) and monocyte (CCL2) chemoattractants. While astrocytes were not a significant source of CXC chemokines, they highly expressed CCL2. An increase in production of CXC chemokines coincided with the influx of neutrophils into the injured brain. At 6 h post-mTBI, we observed a robust influx of CCL2-expressing neutrophils across pial microvessels into the subarachnoid space (SAS) near the injury site. Mild TBI was not accompanied by any significant influx of neutrophils into the brain parenchyma until 24 h after injury. This was associated with an early induction of expression of intercellular adhesion molecule 1 on the endothelium of the ipsilateral pial, but not intraparenchymal, microvessels. At 6 h post-mTBI, we also observed a robust influx of neutrophils into the ipsilateral cistern of velum interpositum (CVI), a slit-shaped cerebrospinal fluid space located above the 3rd ventricle with highly vascularized pia mater. From SAS and CVI, neutrophils appeared to move along the perivascular spaces to enter the brain parenchyma. The monocyte influx was not observed until 24 h post-mTBI, and these inflammatory cells predominantly entered the ipsilateral SAS and CVI, with a limited invasion of brain parenchyma. These observations indicate that the endothelium of pial microvessels responds to injury differently than that of intraparenchymal microvessels, which may be associated with the lack of astrocytic ensheathment of cerebrovascular endothelium in pial microvessels. These findings also suggest that neuroinflammation represents the potential therapeutic target in mTBI.

Appearance of claudin-5+ leukocytes in the central nervous system during neuroinflammation: a novel role for endothelial-derived extracellular vesicles

BACKGROUND

The mechanism of leukocyte transendothelial migration (TEM) across the highly restrictive blood-brain barrier (BBB) remains enigmatic, with paracellular TEM thought to require leukocytes to somehow navigate the obstructive endothelial tight junctions (TJs). Transient interactions between TJ proteins on the respective leukocyte and endothelial surfaces have been proposed as one mechanism for TEM. Given the expanding role of extracellular vesicles (EVs) in intercellular communication, we investigated whether EVs derived from brain microvascular endothelial cells (BMEC) of the BBB may play a role in transferring a major TJ protein, claudin-5 (CLN-5), to leukocytes as a possible basis for such a mechanism during neuroinflammation.

METHODS

High-resolution 3D confocal imaging was used to highlight CLN-5 immunoreactivity in the central nervous system (CNS) and on leukocytes of mice with the neuroinflammatory condition experimental autoimmune encephalomyelitis (EAE). Both Western blotting of circulating leukocytes from wild-type mice and fluorescence imaging of leukocyte-associated eGFP-CLN-5 in the blood and CNS of endothelial-targeted, Tie-2-eGFP-CLN-5 transgenic mice were used to confirm the presence of CLN-5 protein on these cells. EVs were isolated from TNF-α-stimulated BMEC cultures and blood plasma of Tie-2-eGFP-CLN-5 mice with EAE and evaluated for CLN-5 protein by Western blotting and fluorescence-activated cell sorting (FACS), respectively. Confocal imaging and FACS were used to detect binding of endothelial-derived EVs from these two sources to leukocytes in vitro. Serial electron microscopy (serial EM) and 3D contour-based surface reconstruction were employed to view EV-like structures at the leukocyte:BBB interface in situ in inflamed CNS microvessels.

RESULTS

A subpopulation of leukocytes immunoreactive for CLN-5 on their surface was seen to infiltrate the CNS of mice with EAE and reside in close apposition to inflamed vessels. Confocal imaging of immunostained samples and Western blotting established the presence of CLN-5+ leukocytes in blood as well, implying these cells are present prior to TEM. Moreover, imaging of inflamed CNS vessels and the associated perivascular cell infiltrates from Tie-2-eGFP-CLN-5 mice with EAE revealed leukocytes bearing the eGFP label, further supporting the hypothesis CLN-5 is transferred from endothelial cells to circulating leukocytes in vivo. Western blotting of BMEC-derived EVs, corresponding in size to both exosomes and microvesicles, and FACS analysis of plasma-derived EVs from Tie-2-eGFP-CLN-5 mice with EAE validated expression of CLN-5 by EVs of endothelial origin. Confocal imaging and FACS further revealed both PKH-67-labeled EVs from cultured BMECs and eGFP-CLN-5+ EVs from plasma of Tie-2-eGFP-CLN-5 mice with EAE can bind to leukocytes. Lastly, serial EM and 3D contour-based surface reconstruction revealed a close association of EV-like structures between the marginating leukocytes and BMECs in situ during EAE.

CONCLUSIONS

During neuroinflammation, CLN-5+ leukocytes appear in the CNS, and both CLN-5+ leukocytes and CLN-5+ EVs are detected in the blood. As endothelial cells transfer CLN-5+ to leukocytes in vivo, and EVs released from BMEC bind to leukocytes in vitro, EVs may serve as the vehicles to transfer CLN-5 protein at sites of leukocyte:endothelial contact along the BBB. This action may be a prelude to facilitate TEM through the formation of temporary TJ protein bridges between these two cell types.

Dynamic Profiling: Modeling the Dynamics of Inflammation and Predicting Outcomes in Traumatic Brain Injury Patients

Inflammation induced by traumatic brain injury (TBI) is complex, individual-specific, and associated with morbidity and mortality. We sought to develop dynamic, data-driven, predictive computational models of TBI-induced inflammation based on cerebrospinal fluid (CSF) biomarkers. Thirteen inflammatory mediators were determined in serial CSF samples from 27 severe TBI patients. The Glasgow Coma Scale (GCS) score quantifies the initial severity of the neurological status of the patient on a numerical scale from 3 to 15. The 6-month Glasgow Outcome Scale (GOS) score, the outcome variable, was taken as the variable to express and predict as a function of the other input variables. Data on each subject consisting of ten clinical (one-dimensional) variables, such as age, gender, and presence of infection, along with inflammatory biomarker time series were used to generate both multinomial logistic as well as probit models that predict low (poor outcome) or high (favorable outcome) levels of the GOS score. To determine if CSF inflammation biomarkers could predict TBI outcome, a logistic model for low (≤3; poor neurological outcome) or high levels (≥4; favorable neurological outcome) of the GOS score involving a full effect of the pro-inflammatory cytokine tumor necrosis factor-α and both linear and quadratic effects of the anti-inflammatory cytokine interleukin-10 was obtained. To better stratify patients as their pathology progresses over time, a technique called “Dynamic Profiling” was developed in which patients were clustered, using the spectral Laplacian and Hartigan’s k-means method, into disjoint groups at different stages. Initial clustering was based on GCS score; subsequent clustering was performed based on clinical and demographic information and then further, sequential clustering based on the levels of individual inflammatory mediators over time. These clusters assess the risk of mortality of a new patient after each inflammatory mediator reading, based on the existing information in the previous data in the cluster to which the new patient belongs at the time, in essence acting as a “virtual clinician.” Using the Dynamic Profiling method, we show examples that suggest that severe TBI patient neurological outcomes could be predicted as a function of time post-TBI using CSF inflammatory mediators.

Prognostic value of plasma galectin-3 levels after aneurysmal subarachnoid hemorrhage

BACKGROUND

Inflammatory responses are correlated with secondary brain injury after aneurysmal subarachnoid hemorrhage (aSAH). Galectin-3 (Gal-3) is a novel biomarker reflecting inflammation status, and its elevated circulating levels are associated with poor prognosis of some inflammatory diseases. The aim of this study was to evaluate the relationship between Gal-3 plasma levels and prognosis in a group of aSAH patients.

MATERIALS AND METHODS

We assessed plasma Gal-3 levels in 120 patients and 120 healthy individuals. 6-month clinical outcomes included mortality and unfavorable outcome (Glasgow Outcome Scale score of 1-3). Associations of plasma Gal-3 levels with clinical outcomes were investigated using multivariate analysis.

RESULTS

Patients showed significantly higher Gal-3 levels as compared to controls. Circulating Gal-3 was significantly and independently associated with 6-month clinical outcomes in the logistic regression analysis. Moreover, we observed a significant correlation between circulating Gal-3 and World Federation of Neurological Surgeons scores and modified Fisher scores. Furthermore, Gal-3 possessed high area under receiver operating characteristic curve for prognostic assessment.

CONCLUSION

Our findings indicate the associations between Gal-3 levels and the severity and poor prognosis following aSAH. This suggests the possible role of Gal-3 in the prognostic prediction after aSAH.

The potential for animal models to provide insight into mild traumatic brain injury: Translational challenges and strategies

Mild traumatic brain injury (mTBI) is a common health problem. There is tremendous variability and heterogeneity in human mTBI, including mechanisms of injury, biomechanical forces, injury severity, spatial and temporal pathophysiology, genetic factors, pre-injury vulnerability and resilience factors, and clinical outcomes. Animal models greatly reduce this variability and heterogeneity, and provide a means to study mTBI in a rigorous, controlled, and efficient manner. Rodent models, in particular, are time- and cost-efficient, and they allow researchers to measure morphological, cellular, molecular, and behavioral variables in a single study. However, inter-species differences in anatomy, morphology, metabolism, neurobiology, and lifespan create translational challenges. Although the term "mild" TBI is used often in the pre-clinical literature, clearly defined criteria for mild, moderate, and severe TBI in animal models have not been agreed upon. In this review, we introduce current issues facing the mTBI field, summarize the available research methodologies and previous studies in mTBI animal models, and discuss how a translational research approach may be useful in advancing our understanding and management of mTBI.

Priming the inflammatory pump of the CNS after traumatic brain injury

Traumatic brain injury (TBI) can lead to secondary neuropsychiatric problems that develop and persist years after injury. Mounting evidence indicates that neuroinflammatory processes progress after the initial head injury and worsen with time. Microglia contribute to this inflammation by maintaining a primed profile long after the acute effects of the injury have dissipated. This may set the stage for glial dysfunction and hyperactivity to challenges including subsequent head injury, stress, or induction of a peripheral immune response. This review discusses the evidence that microglia become primed following TBI and how this corresponds with vulnerability to a 'second hit' and subsequent neuropsychiatric and neurodegenerative complications.