Biomarkers Of Traumatic Brain Injury Research Articles

Serum apelin-13 and risk of death following severe traumatic brain injury

BackgroundApelin-13 can be expressed in brain tissue and exert neuroprotective effects. We attempted to determine whether serum apelin-13 is a prognostic biomarker for severe traumatic brain injury (sTBI). MethodsOf 126 sTBI patients and 126 healthy controls, serum apelin-13 concentrations were quantified using ELISA. The trauma severity was assessed by Glasgow coma scale scores and Rotterdam computerized tomography scores. The relationship between serum apelin-13 concentrations and posttraumatic 30-day mortality was assessed using multivariate analysis. ResultsSerum apelin-13 concentrations were significantly lower in patients than in controls. Serum apelin-13 concentrations of non-surviving and surviving patients within posttraumatic 30 days were strongly correlated with Glasgow coma scale scores and Rotterdam computerized tomography scores. Serum apelin-13 emerged as an independent predictor for 30-day mortality and overall survival. There was a significant discriminatory capability with respect to serum apelin-13 concentrations for the risk of 30-day death. Moreover, its prognostic predictive ability was similar to those of Glasgow coma scale scores and Rotterdam computerized tomography scores. ConclusionsDeclined serum apelin-13 concentrations, in substantial correlation with increasing severity, are independently associated with short-term mortality, hinting than serum apelin-13 might represent a useful prognostic biomarker for sTBI.

Assessment of Glial Fibrillary Acidic Protein Binding to the Surface of Leukocytes with Dark‐Field Imaging and Computational Analysis

AbstractThe glial fibrillary acidic protein (GFAP) is widely established as a traumatic brain injury (TBI) biomarker and can be used in early diagnosis. As essential primary human immune cells, leukocytes are recruited to injured cerebral sites during TBI response, where they can interact with and potentially bind to TBI biomarkers. To date, no studies have demonstrated ultra‐low GFAP binding enumeration on leukocytes. Herein, a dark‐field imaging technique coupled with computational analysis is introduced to quantify GFAP bound to peripheral blood mononuclear cells (PBMCs). Dark‐field microscopy (DFM) with a custom‐written image acquisition software is developed for rapid 3D PBMC imaging by utilizing specific antiGFAP monoclonal antibody functionalized gold nanoparticles (antiGFAP‐AuNPs) as contrast‐generating probes. Subsequently, the developed algorithm is utilized in processing thousands of acquired images for rapid visualization and enumeration of bound antiGFAP‐AuNP on each leukocyte. The proposed method is demonstrates the specific binding of GFAP to the surface of PBMCs on a healthy donor blood. Thereafter, subpopulations of PBMCs with antiGFAP‐AuNP binding are identified with the assistance of fluorescence imaging and DFM imaging, paving a new way to understanding the relationship between TBI and leukocyte classes. Hence, this study offers a rapid and ultra‐sensitive strategy for biomarker assessment following TBI.

Molecular and Diffusion Tensor Imaging Biomarkers of Traumatic Brain Injury: Principles for Investigation and Integration.

The last 20 years have seen the advent of new technologies that enhance the diagnosis and prognosis of traumatic brain injury (TBI). There is recognition that TBI affects the brain beyond initial injury, in some cases inciting a progressive neuropathology that leads to chronic impairments. Medical researchers are now searching for biomarkers to detect and monitor this condition. Perhaps the most promising developments are in the biomolecular and neuroimaging domains. Molecular assays can identify proteins indicative of neuronal injury and/or degeneration. Diffusion imaging now allows sensitive evaluations of the brain's cellular microstructure. As the pace of discovery accelerates, it is important to survey the research landscape and identify promising avenues of investigation. In this review, we discuss the potential of molecular and diffusion tensor imaging (DTI) biomarkers in TBI research. Integration of these technologies could advance models of disease prognosis, ultimately improving care. To date, however, few studies have explored relationships between molecular and DTI variables in patients with TBI. Here, we provide a short primer on each technology, review the latest research, and discuss how these biomarkers may be incorporated in future studies.

Biofluid Biomarkers in Traumatic Brain Injury: A Systematic Scoping Review.

Emerging evidence suggests that biofluid-based biomarkers have diagnostic and prognostic potential in traumatic brain injuries (TBI). However, owing to the lack of a conceptual framework or comprehensive review, it is difficult to visualize the breadth of materials that might be available. We conducted a systematic scoping review to map and categorize the evidence regarding biofluid-based biochemical markers of TBI. A comprehensive search was undertaken in January 2019. Of 25,354 records identified through the literature search, 1036 original human studies were included. Five hundred forty biofluid biomarkers were extracted from included studies and classified into 19 distinct categories. Three categories of biomarkers including cytokines, coagulation tests, and nerve tissue proteins were investigated more than others and assessed in almost half of the studies (560, 515, and 502 from 1036 studies, respectively). S100 beta as the most common biomarker for TBI was tested in 21.2% of studies (220 articles). Cortisol was the only biomarker measured in blood, cerebrospinal fluid, urine, and saliva. The most common sampling time was at admission and within 24h of injury. The included studies focused mainly on biomarkers from blood and central nervous system sources, the adult population, and severe and blunt injuries. The most common outcome measures used in studies were changes in biomarker concentration level, Glasgow coma scale, Glasgow outcome scale, brain computed tomography scan, and mortality rate. Biofluid biomarkers could be clinically helpful in the diagnosis and prognosis of TBI. However, there was no single definitive biomarker with accurate characteristics. The present categorization would be a road map to investigate the biomarkers of the brain injury cascade separately and detect the most representative biomarker of each category. Also, this comprehensive categorization could provide a guiding framework to design combined panels of multiple biomarkers.

A “hot Spot”-Enhanced paper lateral flow assay for ultrasensitive detection of traumatic brain injury biomarker S-100β in blood plasma

Currently colorimetric paper lateral flow strips (PLFS) encounter two major limitations, that is, low sensitivity and severe interference from complex sample matrices such as blood. These shortcomings limit their application in detection of low-concentration analytes in complex samples. To solve these problems, a PLFS has been developed by utilizing surface-enhanced Raman scattering (SERS) for sensing signal transduction. In particular, a hierarchical three-dimensional nanostructure has been designed to create “hot spots”, which can significantly amplify the SERS sensing signal, leading to high sensitivity. As a result, this PLFS has demonstrated a limit of detection (LOD) of 5.0 pg mL−1 toward detection of S-100β, a traumatic brain injury (TBI) protein biomarker in blood plasma. The PLFS has been successfully used for rapid measurement of S-100β in clinical TBI patient samples taken in the emergency department. Availability of PLFS for blood testing would shift the paradigm of TBI patient management and clinical outcome in emergency departments. It is expected that this type of PLFS can be adapted for rapid detection of various human diseases due to its capability of measuring a low level of protein blood biomarkers in complex human fluids.

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).

Advances in traumatic brain injury research in 2020: A review article

Perhaps in no other area of neurosurgery, has a greater research been done as in traumatic brain injury (TBI). Despite this, TBI remains one of the biggest killers around the world and especially in India. Decompressive craniotomy still remains one of the mainstay paradigms in the management of TBI. The following article explores several new modalities of treatment, and these include the role of beta-blockers for TBI, updates on decompressive craniotomy, the results of DECRA and RESCUEicp trials, diagnostic and prognostic biomarkers in TBI, vascular dysfunction, neuroimaging, and role of neuroinflammation in TBI.

High-Sensitivity C-Reactive Protein is a Prognostic Biomarker of Six-Month Disability after Traumatic Brain Injury: Results from the TRACK-TBI Study.

Systemic inflammation impacts outcome after traumatic brain injury (TBI), but most TBI biomarker studies have focused on brain-specific proteins. C-reactive protein (CRP) is a widely used biomarker of inflammation with potential as a prognostic biomarker after TBI. The Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study prospectively enrolled TBI patients within 24 h of injury, as well as orthopedic injury and uninjured controls; biospecimens were collected at enrollment. A subset of hospitalized participants had blood collected on day 3, day 5, and 2 weeks. High-sensitivity CRP (hsCRP) and glial fibrillary acidic protein (GFAP) were measured. Receiver operating characteristic analysis was used to evaluate the prognostic ability of hsCRP for 6-month outcome, using the Glasgow Outcome Scale-Extended (GOSE). We included 1206 TBI subjects, 122 orthopedic trauma controls (OTCs), and 209 healthy controls (HCs). Longitudinal biomarker sampling was performed in 254 hospitalized TBI subjects and 19 OTCs. hsCRP rose between days 1 and 5 for TBI and OTC subjects, and fell by 2 weeks, but remained elevated compared with HCs (p < 0.001). Longitudinally, hsCRP was significantly higher in the first 2 weeks for subjects with death/severe disability (GOSE <5) compared with those with moderate disability/good recovery (GOSE ≥5); AUC was highest at 2 weeks (AUC = 0.892). Combining hsCRP and GFAP at 2 weeks produced AUC = 0.939 for prediction of disability. Serum hsCRP measured within 2 weeks of TBI is a prognostic biomarker for disability 6 months later. hsCRP may have utility as a biomarker of target engagement for anti-inflammatory therapies.

Development of an Electrochemical Biosensor of Ubiquitin C-Terminal Hydrolase L1 (UCH-L1) for the Assessment of Traumatic Brain Injury (TBI)

INTRODUCTION Traumatic brain injury (TBI) is defined as a neurotrauma caused by a mechanical force applied to a head. An appropriate clinical therapy after TBI is crucial, or patients may suffer lasting effects in physical and mental abilities [1]. To find TBI, cranial computer tomography (CT) is commonly used, however, CT sometimes fails to find mild TBI (mTBI) even it accounts for majority of all cases of TBI. Recently, a blood-based biomarker, ubiquitin C-terminal hydrolase L1 (UCH-L1) has been regarded a promising marker for mTBI, as it becomes present in serum soon after TBI [2,3]. Actually, it was reported the elevated serum UCH-L1 level was observed with the soldiers exposed to low-level blast [4] and the athletes after sub-concussive dead hits [5]. Enzyme-linked immuno sorbent assay (ELISA) is currently used to detect the biomarker, however, since the ELISA is time-consuming procedure and requires specific laboratory equipment, development of a hand-held device to be used on-site in the field is expected. In this study, we propose and report a novel principle for a rapid, one-step electrochemical detection system for UCH-L1 to be dedicated for mTBI diagnosis. METHOD To detect UCH-L1, we chose an electrochemical method in terms of a rapid response time, miniaturization, and simple instrumentation. We employed a competitive assay combined with square wave voltammetry (SWV) on anti-UCH-L1 antibody immobilized electrode. In this system, a redox probe (phenazine ethosulfate: PES) modified UCH-L1 and the target biomarker is going to competitively bind to the antibody on the electrode, resulting electrochemical signal depend on the concentration of UCH-L1 in a sample. To construct the system, PES modified UCH-L1 was prepared using amine-reactive PES. This molecule has N-hydroxysuccinimide linked to PES, therefore, upon mixing amine-reactive PES with UCH-L1, it will react with amine group of lysine residue and make a covalent bond. After the modification, enzyme-linked immuno sorbent assay (ELISA) was performed to investigate the binding affinity of anti-UCH-L1 antibody against UCHH-L1 and PES modified UCH-L1. To detect UCH-L1, we added UCH-L1 together with PES-modified UCH-L1 on the antibody immobilized gold electrode, and performed SWV at a potential range of -0.5 to 0.1 V with different frequencies of square wave. RESUTLS The result of ELISA showed that the antibody had almost same affinity against non-labeled UCH-L1 and PES-modified UCH-L1. Therefore, the modification of PES did not affect the recognition of antibody. When we incubated the electrode with different concentration of PES-modified UCH-L1, a square wave voltammetry signal was increased in a concentration dependent manner, indicating the PES modified on the UCH-L1 was electrochemically active, and the amount of PES-modified UCH-L1 was detected by SWV when it was captured by anti-UCH-L1 antibody on the electrode. In the competitive assay, the incubation of intact UCH-L1 together with PES-modified UCH-L1 resulted in the SWV signal change depend on the UCH-L1 concentration. With this detection principle, we could detect UCH-L1 within 10 minutes without any washing procedure, which is ideal for the on-site detection of mTBI. CONCLUSION In this study, we developed a rapid electrochemical detection system of TBI biomarker, UCH-L1, based on the competitive of redox probe-modified UCH-L1 with the target. Using this detection system, we were able to observe SWV signal change within 10 minutes upon addition of UCH-L1. This study shows the proof-of-concept of this rapid competitive assay, and we hope it would help future development of TBI detection device. REFERENCES [1] S. W. Hoffman and C. Harrison, Clin. Neuropsychol., 23(8), 1400–1415 (2009).[2] R. Diaz-Arrastia, K. K. W. Wang, L. Papa, M.D. Sorani, J. K. Yue, A. M. Puccio, P. J. McMahon, T. Inoue, E. L. Yuh, H. F. Lingsma, A. I. R. Maas, A. B. Valadka, D. O. Okonkwo, G. T. Manley, TRACK-TBI Investigators, J. Neurotrauma, 31(1), 19–25 (2013).[3] L. Papa, G. M. Brophy, R. D. Welch, L. M. Lewis, C. F. Braga, C. N. Tan, N. J. Ameli, M. A. Lopez, C. A. Haeussler, D. I. M. Giordano, S. Silvestri, P. Giordano, K. D. Weber, C. Hill-Pryor, D. C. Hack, JAMA Neurol., 73(5), 551–560 (2016).[4] C. M. Tate, K. K. W. Wang, S. Eonta, Y. Zhang, W. Carr, F. C. Tortella, R. L. Hayes, G. H. Kamimori, J. Neurotrauma, 30(19), 1620–1630 (2013).[5] V. Puvenna, C. Brennan, G. Shaw, C. Yang, N. Marchi, J. J. Bazarian, K. Merchant-Borna, D. Janigro, PLoS ONE, 9(5), e96296–9 (2015).

Traumatic Optic Nerve Injury Elevates Plasma Biomarkers of Traumatic Brain Injury in a Porcine Model.

A diagnosis of traumatic brain injury (TBI) is typically based on patient medical history, a clinical examination, and imaging tests. Elevated plasma levels of glial fibrillary acidic protein (GFAP), ubiquitin c-terminal hydrolase L1 (UCH-L1), and neurofilament light chain (NFL) have been observed in numerous studies of TBI patients. It is reasonable to view traumatic optic neuropathy (TON) as a focal form of TBI. The purpose of this study was to assess if circulating GFAP, UCH-L1, and NFL are also elevated in a porcine model of TON. Serum levels of GFAP, UCH-L1, and NFL were measured immediately before optic nerve crush and 1 h post-injury in 10 Yucatan minipigs. Severity of optic nerve crush was confirmed by visual inspection of the optic nerve at time of injury, loss of visual function as measured by flash visual evoked potential (fVEP) at 7 and 14 days, and histological analysis of axonal transport of cholera toxin-β (CT-β) within the optic nerve. Post-crush concentrations of GFAP, UCH-L1, and NFL were all significantly elevated compared with pre-crush concentrations (p < 0.01, p = 0.01, and p < 0.01, respectively). The largest increase was observed for GFAP with the post-injury median concentration increasing nearly sevenfold. The use of these TBI biomarkers for diagnosing and managing TON may be helpful for non-ophthalmologists in particular in diagnosing this condition. In addition, the potential utility of these biomarkers for diagnosing other optic nerve and/or retinal pathologies should be evaluated.

MiRNAs as Potential Biomarkers for Traumatic Brain Injury: Pathway From Diagnosis to Neurorehabilitation.

Biomarkers that can advance precision neurorehabilitation of the traumatic brain injury (TBI) are needed. MicroRNAs (miRNAs) have biological properties that could make them well suited for playing key roles in differential diagnoses and prognoses and informing likelihood of responsiveness to specific treatments. To review the evidence of miRNA alterations after TBI and evaluate the state of science relative to potential neurorehabilitation applications of TBI-specific miRNAs. This scoping review includes 57 animal and human studies evaluating miRNAs after TBI. PubMed, Scopus, and Google Scholar search engines were used. Gold standard analytic steps for miRNA biomarker assessment are presented. Published studies evaluating the evidence for miRNAs as potential biomarkers for TBI diagnosis, severity, natural recovery, and treatment-induced outcomes were reviewed including statistical evaluation. Growing evidence for specific miRNAs, including miR21, as TBI biomarkers is presented. There is evidence of differential miRNA expression in TBI in both human and animal models; however, gaps need to be filled in terms of replication using rigorous, standardized methods to isolate a consistent set of miRNA changes. Longitudinal studies in TBI are needed to understand how miRNAs could be implemented as biomarkers in clinical practice.

Traumatic Brain Injury and Neuroinflammation: Review of the Main Biomarkers

Traumatic brain injury is one of the main causes of both acute and long-term morbidity that concern that affects individuals in all demographics. The processes that occur during traumatic brain injury and neuroinflammation cannot be fully explained in most clinical and preclinical researches. Neuroinflammation is a very complex interaction between the cells of the innate and adaptive immune systems. The development of reactions of the innate immune system occurs under the influence of various signals that are released from damaged cells and tissues. This leads to the activation of neutrophils, microglia and astrocytes, the release of complement, as well as the release of histamine by mast cells. Subsequently, activation of an adaptive immune response leads to the development of later effects of neuroinflammation. The topic of biomarkers in traumatic brain injury is extensive and rapidly developing. We presented an overview of the most common and well-studied biomarkers in the literature regarding head injury in humans and their role in predicting the outcome in traumatic brain injury. Among the presented biomarkers, the most specific for traumatic brain injury are interleukins-6, -8, -10 and matrix metalloproteinases. We can use interleukin-6 to predict the outcome and risk of complications of traumatic brain injury. The concentration of interleukin-8 shows the relationship of the biomarker with mortality. We can use interleukin-10 to confirm the results of computed tomography in traumatic brain injury. Matrix metalloproteinases present the degree of violation of the blood-brain barrier and brain dysfunction. Other indicators need a more complete study to clarify their role in this pathology. Of course, for a more reliable conclusion about the patient›s condition, it is preferable to use the data of several biomarkers at the same time.

Biomarkers for traumatic brain injury: a short review.

Cellular response to TBI is a mixture of excitotoxicity, neuroinflammation, and cell death. Biomarkers that can track these lesions and inflammatory processes are being explored for their potential to provide objective measures in the evaluation of TBI, from prehospital care to rehabilitation. By understanding the pathways involved, we could be able to improve diagnostic accuracy, guide management, and prevent long-term disability. We listed some of the recent advances in this translational, intriguing, fast-growing field. Although the knowledge gaps are still significant, some markers are showing promising results and could be helping patients in the near future.

Recent Advances in Blood-Based Biomarkers of Remote Combat-Related Traumatic Brain Injury.

Traumatic brain injury (TBI) is highly prevalent among service members and Veterans (SMVs) and associated with changes in blood-based biomarkers. This manuscript reviews candidate biomarkers months/years following military-associated TBI. Several blood-based biomarkers have been investigated for diagnostic or prognostic use to inform care years after military-associated TBI. The most promising include increased levels of plasma/serum and exosomal proteins reflecting neuronal, axonal and/or vascular injury, and inflammation, as well as altered microRNA expression and auto-antibodies of central nervous system markers. Diagnostic and prognostic biomarkers of remote TBI outcomes remain in the discovery phase. Current evidence does not yet support single or combination biomarkers for clinical diagnostic use remotely after injury, but there are promising candidates that require validation in larger, longitudinal studies. The use of prognostic biomarkers of future neurodegeneration, however, holds much promise and could improve treatments and/or preventive measures for serious TBI outcomes.

Protein in Blood Offers Clues About TBI Severity

Protein in Blood Offers Clues About TBI Severity

Time-dependent cytokine and chemokine changes in mouse cerebral cortex following a mild traumatic brain injury

Traumatic brain injury (TBI) is a serious global health problem, many individuals live with TBI-related neurological dysfunction. A lack of biomarkers of TBI has impeded medication development. To identify new potential biomarkers, we time-dependently evaluated mouse brain tissue and neuronally derived plasma extracellular vesicle proteins in a mild model of TBI with parallels to concussive head injury. Mice (CD-1, 30-40 g) received a sham procedure or 30 g weight-drop and were euthanized 8, 24, 48, 72, 96 hr, 7, 14 and 30 days later. We quantified ipsilateral cortical proteins, many of which differed from sham by 8 hours post-mTBI, particularly GAS-1 and VEGF-B were increased while CXCL16 reduced, 23 proteins changed in 4 or more of the time points. Gene ontology pathways mapped from altered proteins over time related to pathological and physiological processes. Validation of proteins identified in this study may provide utility as treatment response biomarkers.

Proteomic analysis identifies plasma correlates of remote ischemic conditioning in the context of experimental traumatic brain injury

Remote ischemic conditioning (RIC), transient restriction and recirculation of blood flow to a limb after traumatic brain injury (TBI), can modify levels of pathology-associated circulating protein. This study sought to identify TBI-induced molecular alterations in plasma and whether RIC would modulate protein and metabolite levels at 24 h after diffuse TBI. Adult male C57BL/6 mice received diffuse TBI by midline fluid percussion or were sham-injured. Mice were assigned to treatment groups 1 h after recovery of righting reflex: sham, TBI, sham RIC, TBI RIC. Nine plasma metabolites were significantly lower post-TBI (six amino acids, two acylcarnitines, one carnosine). RIC intervention returned metabolites to sham levels. Using proteomics analysis, twenty-four putative protein markers for TBI and RIC were identified. After application of Benjamini–Hochberg correction, actin, alpha 1, skeletal muscle (ACTA1) was found to be significantly increased in TBI compared to both sham groups and TBI RIC. Thus, identified metabolites and proteins provide potential biomarkers for TBI and therapeutic RIC in order to monitor disease progression and therapeutic efficacy.

Reliability of serum S100B measurement following mild traumatic brain injury: a comparison of assay measurements from two laboratories

ABSTRACT Objective There is enormous research and clinical interest in blood-based biomarkers of mild traumatic brain injury (MTBI) sustained in sports, daily life, or military service. We examined the reliability of a commercially available assay for S100B used on the same samples by two different laboratories separated by 2 years in time. Methods and Procedures A cohort of 163 adult patients (head CT-scanned, n = 110) with mild head injury were enrolled from the emergency department (ED). All had Glasgow Coma Scale scores of 14 or 15 in the ED (94.4% = 15). The mean time between injury and venous blood sampling was 2.9 h (SD = 1.4; Range = 0.5–6.0 h). Serum S100B was measured at two independent centers using the same high throughput clinical assay (Elecsys S100B®; Roche Diagnostics). Results The Spearman correlation between the two assays in the total sample (N = 163) was r = 0.93. A Wilcoxson Signed Ranks test indicated that the median scores for the values differed (Z = 2,082, p < .001, Cohen’s d = 0.151, small effect size). The values obtained from the two laboratories were very similar for identifying traumatic intracranial abnormalities (sensitivity = 80.1% versus 85.7%). Conclusions The serum S100B results measured using the same assay in different laboratories yielded highly correlated and clinically similar, but clearly not identical, results.

Plasma extracellular vesicles as a source of biomarkers in traumatic brain injury.

The objective of this study was to isolate extracellular vesicles (EVs) from plasma in a cohort of patients with traumatic brain injury (TBI) and analyze their contents for novel biomarkers that could prove useful for rapid diagnosis and classification of brain injury during initial evaluation. Plasma EVs were isolated by serial ultracentrifugation from patients with TBI (n = 15) and healthy controls (n = 5). Samples were obtained from the TRACK-TBI biorepository (2010-present). Size and concentration were determined by nanoparticle tracking. Glial fibrillary acidic protein (GFAP) concentration was determined in EV protein. EV RNA was isolated and deep sequencing of short noncoding RNA was performed. Plasma EVs are physically similar but contained approximately 10 times more GFAP in TBI patients with altered consciousness than patients and controls with normal consciousness. Eleven highly differentially expressed microRNAs (miRNAs) were identified between these groups. Genes targeted by these miRNAs are highly associated with biologically relevant cellular pathways, including organismal injury, cellular development, and organismal development. Multiple additional coding and noncoding RNA species with potential biomarker utility were identified. Isolating plasma EVs in patients with TBI is feasible. Increased GFAP concentration-a validated plasma TBI marker-in EVs from TBI patients with altered consciousness, along with differential expression of multiple miRNAs targeting TBI-relevant pathways, suggests that EVs may be a useful source of TBI biomarkers. Additional evaluation in larger patient cohorts is indicated.

Extracellular Vesicle Proteins and MicroRNAs as Biomarkers for Traumatic Brain Injury.

Traumatic brain injury (TBI) is a heterogeneous condition, associated with diverse etiologies, clinical presentations and degrees of severity, and may result in chronic neurobehavioral sequelae. The field of TBI biomarkers is rapidly evolving to address the many facets of TBI pathology and improve its clinical management. Recent years have witnessed a marked increase in the number of publications and interest in the role of extracellular vesicles (EVs), which include exosomes, cell signaling, immune responses, and as biomarkers in a number of pathologies. Exosomes have a well-defined lipid bilayer with surface markers that reflect the cell of origin and an aqueous core that contains a variety of biological material including proteins (e.g., cytokines and growth factors) and nucleic acids (e.g., microRNAs). The presence of proteins associated with neurodegenerative changes such as amyloid-β, α-synuclein and phosphorylated tau in exosomes suggests a role in the initiation and propagation of neurological diseases. However, mechanisms of cell communication involving exosomes in the brain and their role in TBI pathology are poorly understood. Exosomes are promising TBI biomarkers as they can cross the blood-brain barrier and can be isolated from peripheral fluids, including serum, saliva, sweat, and urine. Exosomal content is protected from enzymatic degradation by exosome membranes and reflects the internal environment of their cell of origin, offering insights into tissue-specific pathological processes. Challenges in the clinical use of exosomal cargo as biomarkers include difficulty in isolating pure exosomes, variable yields of the isolation processes, quantification of vesicles, and lack of specificity of exosomal markers. Moreover, there is no consensus regarding nomenclature and characteristics of EV subtypes. In this review, we discuss current technical limitations and challenges of using exosomes and other EVs as blood-based biomarkers, highlighting their potential as diagnostic and prognostic tools in TBI.