Correlation of mechanical impact responses and biomarker levels: A new model for biomarker evaluation in TBI

Short-term behavioral and histological findings following a single concussive and repeated subconcussive brain injury in a rodent model

PRIMARY OBJECTIVE

It is unclear of the correlation between a mild traumatic brain injury (mTBI) and repeated subconcussive (RSC) impacts with respect to injury biomechanics. Thus, the present study was designed to determine the behavioral and histological differences between a single mTBI impact and RSC impacts with subdivided cumulative kinetic energies of the single mTBI impact.

RESEARCH DESIGN

Adult male Sprague-Dawley rats were randomly assigned to a single mTBI impact, RSC impact, sham, or repeated sham groups.

METHODS AND PROCEDURES

Following a weight drop injury, anxiety-like behavior and general locomotive activity and were assessed using the open field test, while motor coordination was evaluated using a rotarod unit. Neuronal loss, astrogliosis, and microgliosis were assessed using NeuN, GFAP and Iba-1 immunohistochemistry. All assessments were undertaken at 3- and 7-days post impact.

MAIN OUTCOMES AND RESULTS

No behavioral disturbances were observed in injury groups, however, both injury groups did lead to microgliosis following 3-days post-impact.

CONCLUSIONS

No pathophysiological differences were observed between a single mTBI impact and RSC impacts of the same energy input. Even though a cumulative injury threshold for RSC impacts was not determined, a threshold still may exist where no pathodynamic shift occurs.

Loss of Consciousness and Righting Reflex Following Traumatic Brain Injury: Predictors of Post-Injury Symptom Development (A Narrative Review)

Identifying predictors for individuals vulnerable to the adverse effects of traumatic brain injury (TBI) remains an ongoing research pursuit. This is especially important for patients with mild TBI (mTBI), whose condition is often overlooked. TBI severity in humans is determined by several criteria, including the duration of loss of consciousness (LOC): LOC < 30 min for mTBI and LOC > 30 min for moderate-to-severe TBI. However, in experimental TBI models, there is no standard guideline for assessing the severity of TBI. One commonly used metric is the loss of righting reflex (LRR), a rodent analogue of LOC. However, LRR is highly variable across studies and rodents, making strict numeric cutoffs difficult to define. Instead, LRR may best be used as predictor of symptom development and severity. This review summarizes the current knowledge on the associations between LOC and outcomes after mTBI in humans and between LRR and outcomes after experimental TBI in rodents. In clinical literature, LOC following mTBI is associated with various adverse outcome measures, such as cognitive and memory deficits; psychiatric disorders; physical symptoms; and brain abnormalities associated with the aforementioned impairments. In preclinical studies, longer LRR following TBI is associated with greater motor and sensorimotor impairments; cognitive and memory impairments; peripheral and neuropathology; and physiologic abnormalities. Because of the similarities in associations, LRR in experimental TBI models may serve as a useful proxy for LOC to contribute to the ongoing development of evidence-based personalized treatment strategies for patients sustaining head trauma. Analysis of highly symptomatic rodents may shed light on the biological underpinnings of symptom development after rodent TBI, which may translate to therapeutic targets for mTBI in humans.

Molecular evidence of the amelioration of toluene induced encephalopathy by human breast milk mesenchymal stem cells

Toluene was widely used volatile organic compound that accumulates in tissues with high lipid content. Stem cells have been proposed as an increasingly attractive approach for repair of damaged nervous system, we aimed to evaluate the ability of breast milk mesenchymal stem cells (MSc) to ameliorate toluene-induced encephalopathy. Sixty adult male albino rats were assigned to 3 groups, control, toluene, and toluene/breast milk-MSc. Neurological assessment was evaluated as well as serum levels of glial fibrillary acidic protein (GFAP), tumor necrosis factor-alpha (TNF-α), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), tissue dopamine and oxidative markers. Gene expression of peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ), nuclear factor-kappaB (NF-kB), and interleukin-6 (IL-6) were evaluated. Moreover, histological and immunohistochemical investigation were done. Results revealed that toluene caused cerebral injury, as evidenced by a significant increase in serum GFAP, TNF-α, malondialdehyde (MDA) and nitric oxide (NO), a significant decrease in serum NGF, tissue dopamine and oxidative markers, besides, a non-significant change in VEGF. Toluene also caused changes in normal cerebral structure and cellular degeneration, including a significant decrease in the total number of neurons and thickness of frontal cortex. Meninges showing signs of inflammation with inflammatory cell infiltration and exudation, a significant decrease in MBP immunoreactivity, and increase in the percent of high motility group box protein-1 (HMGB1) positive cells. PPAR- ɣ, NF-kB, and IL-6 gene expression were all considerably elevated by toluene. These changes were greatly improved by breast milk MSc. Therefore, we conclude that breast milk MSc can attenuate toluene-induced encephalopathy.

Spatial and temporal dynamics of HDACs class IIa following mild traumatic brain injury in adult rats

The fundamental role of epigenetic regulatory mechanisms involved in neuroplasticity and adaptive responses to traumatic brain injury (TBI) is gaining increased recognition. TBI-induced neurodegeneration is associated with several changes in the expression-activity of various epigenetic regulatory enzymes, including histone deacetylases (HDACs). In this study, PET/CT with 6-([¹⁸F]trifluoroacetamido)-1- hexanoicanilide ([¹⁸F]TFAHA) to image spatial and temporal dynamics of HDACs class IIa expression-activity in brains of adult rats subjected to a weight drop model of diffuse, non-penetrating, mild traumatic brain injury (mTBI). The mTBI model was validated by histopathological and immunohistochemical analyses of brain tissue sections for localization and magnitude of expression of heat-shock protein-70 kDa (HSP70), amyloid precursor protein (APP), cannabinoid receptor-2 (CB2), ionized calcium-binding adapter protein-1 (IBA1), histone deacetylase-4 and -5 (HDAC4 and HDAC5). In comparison to baseline, the expression-activities of HDAC4 and HDAC5 were downregulated in the hippocampus, nucleus accumbens, peri-3rd ventricular part of the thalamus, and substantia nigra at 1-3 days post mTBI, and remained low at 7-8 days post mTBI. Reduced levels of HDAC4 and HDAC5 expression observed in neurons of these brain regions post mTBI were associated with the reduced nuclear and neuropil levels of HDAC4 and HDAC5 with the shift to perinuclear localization of these enzymes. These results support the rationale for the development of therapeutic strategies to upregulate expression-activity of HDACs class IIa post-TBI. PET/CT (MRI) with [¹⁸F]TFAHA can facilitate the development and clinical translation of unique therapeutic approaches to upregulate the expression and activity of HDACs class IIa enzymes in the brain after TBI.

A Kinetic Model for Blood Biomarker Levels After Mild Traumatic Brain Injury

Traumatic brain injury (TBI) imposes a significant economic and social burden. The diagnosis and prognosis of mild TBI, also called concussion, is challenging. Concussions are common among contact sport athletes. After a blow to the head, it is often difficult to determine who has had a concussion, who should be withheld from play, if a concussed athlete is ready to return to the field, and which concussed athlete will develop a post-concussion syndrome. Biomarkers can be detected in the cerebrospinal fluid and blood after traumatic brain injury and their levels may have prognostic value. Despite significant investigation, questions remain as to the trajectories of blood biomarker levels over time after mild TBI. Modeling the kinetic behavior of these biomarkers could be informative. We propose a one-compartment kinetic model for S100B, UCH-L1, NF-L, GFAP, and tau biomarker levels after mild TBI based on accepted pharmacokinetic models for oral drug absorption. We approximated model parameters using previously published studies. Since parameter estimates were approximate, we did uncertainty and sensitivity analyses. Using estimated kinetic parameters for each biomarker, we applied the model to an available post-concussion biomarker dataset of UCH-L1, GFAP, tau, and NF-L biomarkers levels. We have demonstrated the feasibility of modeling blood biomarker levels after mild TBI with a one compartment kinetic model. More work is needed to better establish model parameters and to understand the implications of the model for diagnostic use of these blood biomarkers for mild TBI.

Myelin basic protein and neurofilament H in postmortem cerebrospinal fluid as surrogate markers of fatal traumatic brain injury

The aim of this study was to investigate if the biomarkers myelin basic protein (MBP) and neurofilament-H (NF-H) yielded informative value in forensic diagnostics when examining cadaveric cerebrospinal fluid (CSF) biochemically via an enzyme-linked immunosorbent assay (ELISA) and comparing the corresponding brain tissue in fatal traumatic brain injury (TBI) autopsy cases by immunocytochemistry versus immunohistochemistry. In 21 trauma and 19 control cases, CSF was collected semi-sterile after suboccipital puncture and brain specimens after preparation. The CSF MBP (p = 0.006) and NF-H (p = 0.0002) levels after TBI were significantly higher than those in cardiovascular controls. Immunohistochemical staining against MBP and against NF-H was performed on cortical and subcortical samples from also biochemically investigated cases (5 TBI cases/5 controls). Compared to the controls, the TBI cases showed a visually reduced staining reaction against MBP or repeatedly ruptured neurofilaments against NF-H. Immunocytochemical tests showed MBP-positive phagocytizing macrophages in CSF with a survival time of > 24 h. In addition, numerous TMEM119-positive microglia could be detected with different degrees of staining intensity in the CSF of trauma cases. As a result, we were able to document that elevated levels of MBP and NF-H in the CSF should be considered as useful neuroinjury biomarkers of traumatic brain injury.

Blood-Based Brain and Global Biomarker Changes after Combined Hypoxemia and Hemorrhagic Shock in a Rat Model of Penetrating Ballistic-Like Brain Injury

Penetrating traumatic brain injury (pTBI) often occurs with systemic insults such as hemorrhagic shock (HS) and hypoxemic (HX). This study examines rat models of penetrating ballistic-like brain injury (PBBI) and HX+HS to assess whether the blood levels of brain and systemic response biomarkers phosphorylated neurofilament-heavy protein (pNF-H), neurofilament-light protein (NF-L), αII-spectrin, heat shock protein (HSP70), and high mobility group box 1 protein (HMGB1) can distinguish pTBI from systemic insults and guide in pTBI diagnosis, prognosis, and monitoring. Thirty rats were randomly assigned to sham, PBBI, HS+HX, and PBBI+HS+HX groups. PBBI and sham groups underwent craniotomy with and without probe insertion and balloon expansion, respectively. HX and HS was then simulated by blood withdrawal and fraction of inspired oxygen (FIO₂) reduction. Biomarker serum concentrations were determined at one (D1) and two (D2) days post-injury with enzyme-linked immunosorbent assay (ELISA) methods. Axonal injury-linked biomarkers pNF-H and NF-L serum levels in PBBI groups were higher than those in sham and HX+HS groups at D1 and D2 post-injury. The same was true for PBBI+HX+HS compared with sham (D2 only for pNF-H) and HX+HS groups. However, pNF-H and NF-L levels in PBBI+HX+HS groups were not different than their PBBI counterparts. At D1, αII-spectrin levels in the HX+HS and PBBI+HS+HX groups were higher than the sham groups. αII-spectrin levels in the HX+HS group were higher than the PBBI group. This suggests HX+HS as the common insult driving αII-spectrin elevations. In conclusion, pNF-H and NF-L may serve as specific serum biomarkers of pTBI in the presence or absence of systemic insults. αII-spectrin may be a sensitive acute biomarker in detecting systemic insults occurring alone or with pTBI.

Investigate the Variations of the Head and Brain Response in a Rodent Head Impact Acceleration Model by Finite Element Modeling

Diffuse axonal injury (DAI) is a severe form of traumatic brain injury and often induced by blunt trauma. The closed head impact acceleration (IA) model is the most widely used rodent DAI model. However, this model results in large variations of injury severity. Recently, the impact device/system was modified to improve the consistency of the impact energy, but variations of the head kinematics and subsequent brain injuries were still observed. This study was aimed to utilize a Finite Element (FE) model of a rat head/body and simulation to investigate the potential biomechanical factors influencing the impact energy transfer to the head. A detailed FE rat head model containing detailed skull and brain anatomy was developed based on the MRI, microCT and atlas data. The model consists of over 722,000 elements, of which 310,000 are in the brain. The white matter structures consisting of highly aligned axonal fibers were simulated with transversely isotropic material. The rat body was modeled to provide a realistic boundary at the spine-medulla junction. Rodent experiments including dynamic cortical deformation, brain-skull displacement, and IA kinematics were simulated to validate the FE model. The model was then applied to simulate the rat IA experiments. Parametric studies were conducted to investigate the effect of the helmet inclination angles (0°-5°) and skull stiffness (varied 20%) on the resulting head kinematics and maximum principal strain in the brain. The inclination angle of the helmet at 5° could vary head linear acceleration by 8-31%. The change in head rotational velocity was inversely related to the change in linear acceleration. Varying skull stiffness resulted in changes in head linear acceleration by 3% but with no effect on rotational velocity. The brain strain in the corpus callosum was only affected by head rotation while the strain in the brainstem was influenced by the combined head kinematics, local skull deformation, and head-neck position. Validated FE models of rat impact head injury can assist in exploring various biomechanical factors influencing the head impact response and internal brain response. Identification of these variables may help explain the variability of injury severity observed among experiments and across different labs.

MicroRNAs: The New Challenge for Traumatic Brain Injury Diagnosis

The acronym TBI refers to traumatic brain injury, an alteration of brain function, or an evidence of brain pathology, that is caused by an external force. TBI is estimated to become the third leading cause of permanent disability and mortality worldwide. TBI-related injuries can be classified in many ways, according to the degree of severity or the pathophysiology of brain injury (primary and secondary damage). Numerous cellular pathways act in secondary brain damage: excitotoxicity (mediated by excitatory neurotransmitters), free radical generation (due to mitochondrial impairment), neuroinflammatory response (due to central nervous system and immunoactivation) and apoptosis. In this scenario, microRNAs are implicated in the regulation of almost all genes at the post-transcriptional level. Several microRNAs have been demonstrated to be specifically expressed in particular cerebral areas; moreover, physiological changes in microRNA expression during normal cerebral development upon the establishment of neural networks have been characterized. More importantly, microRNAs show profound alteration in expression in response to brain pathological states, both traumatic or not. This review summarizes the most important molecular networks involved in TBI and examines the most recent and important findings on TBI-related microRNAs, both in animal and clinical studies. The importance of microRNA research holds promise to find biomarkers able to unearth primary and secondary molecular patterns altered upon TBI, to ultimately identify key points of regulation, as a valuable support in forensic pathology and potential therapeutic targets for clinical treatment.

Anti-CD52 antibody treatment depletes B cell aggregates in the central nervous system in a mouse model of multiple sclerosis

Background

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) for which several new treatment options were recently introduced. Among them is the monoclonal anti-CD52 antibody alemtuzumab that depletes mainly B cells and T cells in the immune periphery. Considering the ongoing controversy about the involvement of B cells and in particular the formation of B cell aggregates in the brains of progressive MS patients, an in-depth understanding of the effects of anti-CD52 antibody treatment on the B cell compartment in the CNS itself is desirable.

Methods

We used myelin basic protein (MBP)-proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE) in C57BL/6 (B6) mice as B cell-dependent model of MS. Mice were treated intraperitoneally either at the peak of EAE or at 60 days after onset with 200 μg murine anti-CD52 vs. IgG2a isotype control antibody for five consecutive days. Disease was subsequently monitored for 10 days. The antigen-specific B cell/antibody response was measured by ELISPOT and ELISA. Effects on CNS infiltration and B cell aggregation were determined by immunohistochemistry. Neurodegeneration was evaluated by Luxol Fast Blue, SMI-32, and Olig2/APC staining as well as by electron microscopy and phosphorylated heavy neurofilament serum ELISA.

Results

Treatment with anti-CD52 antibody attenuated EAE only when administered at the peak of disease. While there was no effect on the production of MP4-specific IgG, the treatment almost completely depleted CNS infiltrates and B cell aggregates even when given as late as 60 days after onset. On the ultrastructural level, we observed significantly less axonal damage in the spinal cord and cerebellum in chronic EAE after anti-CD52 treatment.

Conclusion

Anti-CD52 treatment abrogated B cell infiltration and disrupted existing B cell aggregates in the CNS.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1263-9) contains supplementary material, which is available to authorized users.

Profiling biomarkers of traumatic axonal injury: From mouse to man

Traumatic brain injury (TBI) poses a major public health problem on a global scale. Its burden results from high mortality and significant morbidity in survivors. This stems, in part, from an ongoing inadequacy in diagnostic and prognostic indicators despite significant technological advances. Traumatic axonal injury (TAI) is a key driver of the ongoing pathological process following TBI, causing chronic neurological deficits and disability. The science underpinning biomarkers of TAI has been a subject of many reviews in recent literature. However, in this review we provide a comprehensive account of biomarkers from animal models to clinical studies, bridging the gap between experimental science and clinical medicine. We have discussed pathogenesis, temporal kinetics, relationships to neuro-imaging, and, most importantly, clinical applicability in order to provide a holistic perspective of how this could improve TBI diagnosis and predict clinical outcome in a real-life setting. We conclude that early and reliable identification of axonal injury post-TBI with the help of body fluid biomarkers could enhance current care of TBI patients by (i) increasing speed and accuracy of diagnosis, (ii) providing invaluable prognostic information, (iii) allow efficient allocation of rehabilitation services, and (iv) provide potential therapeutic targets. The optimal model for assessing TAI is likely to involve multiple components, including several blood biomarkers and neuro-imaging modalities, at different time points.

Clinical-pathological study on β-APP, IL-1β, GFAP, NFL, Spectrin II, 8OHdG, TUNEL, miR-21, miR-16, miR-92 expressions to verify DAI-diagnosis, grade and prognosis

Traumatic brain injury (TBI) is one of the most important death and disability cause, involving substantial costs, also in economic terms, when considering the young age of the involved subject. Aim of this paper is to report a series of patients treated at our institutions, to verify neurological results at six months or survival; in fatal cases we searched for βAPP, GFAP, IL-1β, NFL, Spectrin II, TUNEL and miR-21, miR-16, and miR-92 expressions in brain samples, to verify DAI diagnosis and grade as strong predictor of survival and inflammatory response. Concentrations of 8OHdG as measurement of oxidative stress was performed. Immunoreaction of β-APP, IL-1β, GFAP, NFL, Spectrin II and 8OHdG were significantly increased in the TBI group with respect to control group subjects. Cell apoptosis, measured by TUNEL assay, were significantly higher in the study group than control cases. Results indicated that miR-21, miR-92 and miR-16 have a high predictive power in discriminating trauma brain cases from controls and could represent promising biomarkers as strong predictor of survival, and for the diagnosis of postmortem traumatic brain injury.

An update on diagnostic and prognostic biomarkers for traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major worldwide neurological disorder of epidemic proportions. To date, there are still no FDA-approved therapies to treat any forms of TBI. Encouragingly, there are emerging data showing that biofluid-based TBI biomarker tests have the potential to diagnose the presence of TBI of different severities including concussion, and to predict outcome. Areas covered: The authors provide an update on the current knowledge of TBI biomarkers, including protein biomarkers for neuronal cell body injury (UCH-L1, NSE), astroglial injury (GFAP, S100B), neuronal cell death (αII-spectrin breakdown products), axonal injury (NF proteins), white matter injury (MBP), post-injury neurodegeneration (total Tau and phospho-Tau), post-injury autoimmune response (brain antigen-targeting autoantibodies), and other emerging non-protein biomarkers. The authors discuss biomarker evidence in TBI diagnosis, outcome prognosis and possible identification of post-TBI neurodegernative diseases (e.g. chronic traumatic encephalopathy and Alzheimer's disease), and as theranostic tools in pre-clinical and clinical settings. Expert commentary: A spectrum of biomarkers is now at or near the stage of formal clinical validation of their diagnostic and prognostic utilities in the management of TBI of varied severities including concussions. TBI biomarkers could serve as a theranostic tool in facilitating drug development and treatment monitoring.

Dosing, collection, and quality control issues in cerebrospinal fluid research using animal models

Cerebrospinal fluid (CSF) is a complex fluid filling the ventricular system and surrounding the brain and spinal cord. Although the bulk of CSF is created by the choroid plexus, a significant fraction derives from the interstitial fluid in the brain and spinal cord parenchyma. For this reason, CSF can often be used as a source of pharmacodynamic and prognostic biomarkers to reflect biochemical changes occurring within the brain. For instance, CSF biomarkers can be used to diagnose and track progression of disease as well as understand pharmacokinetic and pharmacodynamic relationships in clinical trials. To facilitate the use of these biomarkers in humans, studies in preclinical species are often valuable. This review summarizes methods for preclinical CSF collection for biomarkers from mice, rats, and nonhuman primates. In addition, dosing directly into CSF is increasingly being used to improve drug levels in the brain. Therefore, this review also summarizes the state of the art in CSF dosing in these preclinical species.

Multicenter immunoassay validation of cerebrospinal fluid neurofilament light: a biomarker for neurodegeneration

AIM

Neurofilament light (NfL) chain, a putative cerebrospinal fluid biomarker, can support neurodegenerative disease diagnosis and indicate disease severity and prognosis. Universal validation protocols when used to measure biomarkers can reduce pre and analytical laboratory variation, thus increasing end-user confidence in the consistency of validation data across sites.

METHODOLOGY

Here, a commercially available NfL ELISA (UmanDiagnostics, Umeå, Sweden) was validated in a multicentered setting using comprehensive newly developed standard operating procedures.

RESULTS

The data showed good assay sensitivity and intra and interassay precision. Interlaboratory precision was, however, suboptimal.

CONCLUSION

The UmanDiagnostics assay is suitable for the quantification of NfL in human cerebrospinal fluid. However, sources of interlaboratory variation in the data require further investigation.