Translating biomarkers research to clinical care: applications and issues for rehabilomics

Navigating the Complexities of Traumatic Encephalopathy Syndrome (TES): Current State and Future Challenges

Chronic traumatic encephalopathy (CTE) is a unique neurodegenerative disease that is associated with repetitive head impacts (RHI) in both civilian and military settings. In 2014, the research criteria for the clinical manifestation of CTE, traumatic encephalopathy syndrome (TES), were proposed to improve the clinical identification and understanding of the complex neuropathological phenomena underlying CTE. This review provides a comprehensive overview of the current understanding of the neuropathological and clinical features of CTE, proposed biomarkers of traumatic brain injury (TBI) in both research and clinical settings, and a range of treatments based on previous preclinical and clinical research studies. Due to the heterogeneity of TBI, there is no universally agreed-upon serum, CSF, or neuroimaging marker for its diagnosis. However, as our understanding of this complex disease continues to evolve, it is likely that there will be more robust, early diagnostic methods and effective clinical treatments. This is especially important given the increasing evidence of a correlation between TBI and neurodegenerative conditions, such as Alzheimer's disease and CTE. As public awareness of these conditions grows, it is imperative to prioritize both basic and clinical research, as well as the implementation of necessary safe and preventative measures.

Pediatric Traumatic Brain Injury: Impact on the Developing Brain

Traumatic brain injury (TBI) is a serious public health concern impacting millions of children and adolescents each year. Experiencing a brain injury during key critical periods of brain development can affect the normal formation of brain networks that are responsible for a range of complex neurocognitive outcomes. In addition, there are multiple pre- and postinjury factors that influence the trajectory of recovery and outcomes. In this review, we will focus on the current state of the literature within pediatric TBI; systematically review the available research on developmental aspects of TBI in children, focusing on the pathophysiology of the injury and its impact on the developing brain; and highlight knowledge gaps for further exploration.

Blood-based traumatic brain injury biomarkers - Clinical utilities and regulatory pathways in the United States, Europe and Canada

INTRODUCTION

Traumatic brain injury (TBI) is a major global health issue, resulting in debilitating consequences to families, communities, and health-care systems. Prior research has found that biomarkers aid in the pathophysiological characterization and diagnosis of TBI. Significantly, the FDA has recently cleared both a bench-top assay and a rapid point-of-care assays of tandem biomarker (UCH-L1/GFAP)-based blood test to aid in the diagnosis mTBI patients. With the global necessity of TBI biomarkers research, several major consortium multicenter observational studies with biosample collection and biomarker analysis have been created in the USA, Europe, and Canada. As each geographical region regulates its data and findings, the International Initiative for Traumatic Brain Injury Research (InTBIR) was formed to facilitate data integration and dissemination across these consortia.

AREAS COVERED

This paper covers heavily investigated TBI biomarkers and emerging non-protein markers. Finally, we analyze the regulatory pathways for converting promising TBI biomarkers into approved in-vitro diagnostic tests in the United States, European Union, and Canada.

EXPERT OPINION

TBI biomarker research has significantly advanced in the last decade. The recent approval of an iSTAT point of care test to detect mild TBI has paved the way for future biomarker clearance and appropriate clinical use across the globe.

Erythropoietin Does Not Alter Serum Profiles of Neuronal and Axonal Biomarkers After Traumatic Brain Injury: Findings From the Australian EPO-TBI Clinical Trial

OBJECTIVE

To determine profiles of serum ubiquitin carboxy-terminal hydrolase L1 and phosphorylated neurofilament heavy-chain, examine whether erythropoietin administration reduce their concentrations, and whether biomarkers discriminate between erythropoietin and placebo treatment groups.

DESIGN

Single-center, prospective observational study.

SETTING

A sub-study of the erythropoietin-traumatic brain injury clinical trial, conducted at the Alfred Hospital, Melbourne, Australia.

PATIENTS

Forty-four patients with moderate-to-severe traumatic brain injury.

INTERVENTIONS

Epoetin alfa 40,000 IU or 1 mL sodium chloride 0.9 as subcutaneous injection within 24 hours of traumatic brain injury.

MEASUREMENTS AND MAIN RESULTS

Ubiquitin carboxy-terminal hydrolase L1, phosphorylated neurofilament heavy-chain, and erythropoietin concentrations were measured in serum by enzyme-linked immunosorbent assay from D0 (within 24 hr of injury, prior to erythropoietin/vehicle administration) to D5. Biomarker concentrations were compared between injury severities, diffuse versus focal traumatic brain injury and erythropoietin or placebo treatment groups. Ubiquitin carboxy-terminal hydrolase L1 peaked at 146.0 ng/mL on D0, significantly decreased to 84.30 ng/mL on D1, and declined thereafter. Phosphorylated neurofilament heavy-chain levels were lowest at D0 and peaked on D5 at 157.9 ng/mL. D0 ubiquitin carboxy-terminal hydrolase L1 concentrations were higher in diffuse traumatic brain injury. Peak phosphorylated neurofilament heavy-chain levels on D3 and D4 correlated with Glasgow Outcome Score-Extended, predicting poor outcome. Erythropoietin did not reduce concentrations of ubiquitin carboxy-terminal hydrolase L1 or phosphorylated neurofilament heavy-chain.

CONCLUSIONS

Serum ubiquitin carboxy-terminal hydrolase L1 and phosphorylated neurofilament heavy-chain increase after traumatic brain injury reflecting early neuronal and progressive axonal injury. Consistent with lack of improved outcome in traumatic brain injury patients treated with erythropoietin, biomarker concentrations and profiles were not affected by erythropoietin. Pharmacokinetics of erythropoietin suggest that the dose given was possibly too low to exert neuroprotection.

Cerebral Expression of Glial Fibrillary Acidic Protein, Ubiquitin Carboxy-Terminal Hydrolase-L1, and Matrix Metalloproteinase 9 After Traumatic Brain Injury and Secondary Brain Insults in Rats

Glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1), and matrix metalloproteinase 9 (MMP-9) are potential biomarkers of traumatic brain injury (TBI) but also of secondary insults to the brain. The aim of this study was to describe the cerebral distribution of GFAP, UCH-L1, and MMP-9 in a rat model of diffuse TBI associated with standardized hypoxia-hypotension (HH). Adult male Sprague-Dawley rats were allocated to Sham (n = 10), TBI (n = 10), HH (n = 10), and TBI+HH (n = 10) groups. After 4 hours, brains were rapidly removed and immunostaining of GFAP, UCH-L1, and MMP-9 was performed. Areas of interest that have been described as particularly sensitive to hypoxic insults were analyzed. For GFAP, in the neocortex, immunostaining revealed a significant decrease in strong staining for HH and TBI+HH groups compared with TBI group (P < .0001). For UCH-L1, the total immunostaining (6 regions of interest) reported a significant increase in strong staining (P < .0001) and decrease in weak staining (P < .0001) for the HH and TBI+HH groups compared with the Sham and TBI groups. For MMP-9, for the HH and TBI+HH groups, a significant increase in moderate (P < .0001) and weak staining (P < .0001) and a decrease in negative staining (P < .0001) compared with the Sham and TBI groups were observed. UCH-L1 and MMP-9 immunostainings increased after HH alone or HH combined with TBI compared with TBI alone. GFAP immunostaining decreased particularly in the neocortex after HH alone or HH combined with TBI compared with TBI alone. These three biomarkers could therefore be considered as potential biomarkers of HH insults independently of TBI.

TBI Rehabilomics Research: Conceptualizing a humoral triad for designing effective rehabilitation interventions

Most areas of medicine use biomarkers in some capacity to aid in understanding how personal biology informs clinical care. This article draws upon the Rehabilomics research model as a translational framework for programs of precision rehabilitation and intervention research focused on linking personal biology to treatment response using biopsychosocial constructs that broadly represent function and that can be applied to many clinical populations with disability. The summary applies the Rehabilomics research framework to the population with traumatic brain injury (TBI) and emphasizes a broad vision for biomarker inclusion, beyond typical brain-derived biomarkers, to capture and/or reflect important neurological and non-neurological pathology associated with TBI as a chronic condition. Humoral signaling molecules are explored as important signaling and regulatory drivers of these chronic conditions and their impact on function. Importantly, secondary injury cascades involved in the humoral triad are influenced by the systemic response to TBI and the development of non-neurological organ dysfunction (NNOD). Biomarkers have been successfully leveraged in other medical fields to inform pre-randomization patient selection for clinical trials, however, this practice largely has not been utilized in TBI research. As such, the applicability of the Rehabilomics research model to contemporary clinical trials and comparative effectiveness research designs for neurological and rehabilitation populations is emphasized. Potential points of intervention to modify inflammation, hormonal, or neurotrophic support through rehabilitation interventions are discussed. This article is part of the Special Issue entitled "Novel Treatments for 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.

Chapter 6 state of the science of pediatric traumatic brain injury: biomarkers and gene association studies

OBJECTIVES

Our objective is to review the most widely used biomarkers and gene studies reported in pediatric traumatic brain injury (TBI) literature, to describe their findings, and to discuss the discoveries and gaps that advance the understanding of brain injury and its associated outcomes. Ultimately, we aim to inform the science for future research priorities.

DATA SOURCES

We searched PubMed, MEDLINE, CINAHL, and the Cochrane Database of Systematic Reviews for published English language studies conducted in the last 10 years to identify reviews and completed studies of biomarkers and gene associations in pediatric TBI. Of the 131 biomarker articles, only 16 were specific to pediatric TBI patients, whereas of the gene association studies in children with TBI, only four were included in this review.

CONCLUSION

Biomarker and gene attributes are grossly understudied in pediatric TBI in comparison to adults. Although recent advances recognize the importance of biomarkers in the study of brain injury, the limited number of studies and genomic associations in the injured brain has shown the need for common data elements, larger sample sizes, heterogeneity, and common collection methods that allow for greater understanding of the injured pediatric brain. By building on to the consortium of interprofessional scientists, continued research priorities would lead to improved outcome prediction and treatment strategies for children who experience a TBI.

IMPLICATIONS FOR NURSING RESEARCH

Understanding recent advances in biomarker and genomic studies in pediatric TBI is important because these advances may guide future research, collaborations, and interventions. It is also important to ensure that nursing is a part of this evolving science to promote improved outcomes in children with TBIs.

Serum D-dimer concentrations are increased after pediatric traumatic brain injury

OBJECTIVE

To determine whether D-dimer would be increased in children with traumatic brain injury (TBI), specifically mild abusive head trauma.

STUDY DESIGN

D-dimer was measured using multiplex bead technology in 195 children <4 years old (n = 93 controls without TBI, n = 102 cases with TBI) using previously collected serum. D-dimer was then measured prospectively in a clinical setting in 44 children (n = 24 controls, n = 20 cases). Receiver operator curves were generated for prospective data.

RESULTS

In both the retrospective and prospective cohorts, median (25th-75th percentile) D-dimer was significantly higher in cases vs controls. A receiver operator curve demonstrated an area under the curve of 0.91 (95% CI 0.83-0.99) in the prospective cohort. At a cut-off of 0.59 μg/L, the sensitivity and specificity for identification of a case was 90% and 75%, respectively.

CONCLUSIONS

Our data suggest that serum D-dimer may be able to be used to identify which young children at risk for abusive head trauma might benefit from a head computed tomography or other additional evaluation. Additional data are needed to better identify the clinical scenarios that may result in false positive or false negative D-dimer concentrations.

A Rehabilomics framework for personalized and translational rehabilitation research and care for individuals with disabilities: Perspectives and considerations for spinal cord injury

Despite many people having similar clinical presentation, demographic factors, and clinical care, outcome can differ for those sustaining significant injury such as spinal cord injury (SCI) and traumatic brain injury (TBI). In addition to traditional demographic, social, and clinical factors, variability also may be attributable to innate (including genetic, transcriptomic proteomic, epigenetic) biological variation that individuals bring to recovery and their unique response to their care and environment. Technologies collectively called "-omics" enable simultaneous measurement of an enormous number of biomolecules that can capture many potential biological contributors to heterogeneity of injury/disease course and outcome. Due to the nature of injury and complex disease, and its associations with impairment, disability, and recovery, rehabilitation does not lend itself to a singular "protocolized" plan of therapy. Yet, by nature and by necessity, rehabilitation medicine operates as a functional model of "Personalized Care". Thus, the challenge for successful programs of translational rehabilitation care and research is to identify viable approaches to examine broad populations, with varied impairments and functional limitations, and to identify effective treatment responses that incorporate personalized protocols to optimize functional recovery. The Rehabilomics framework is a translational model that provides an "-omics" overlay to the scientific study of rehabilitation processes and multidimensional outcomes. Rehabilomics research provides novel opportunities to evaluate the neurobiology of complex injury or chronic disease and can be used to examine methods and treatments for person-centered care among populations with disabilities. Exemplars for application in SCI and other neurorehabilitation populations are discussed.

Post-traumatic hypoxia is associated with prolonged cerebral cytokine production, higher serum biomarker levels, and poor outcome in patients with severe traumatic brain injury

Secondary hypoxia is a known contributor to adverse outcomes in patients with traumatic brain injury (TBI). Based on the evidence that hypoxia and TBI in isolation induce neuroinflammation, we investigated whether TBI combined with hypoxia enhances cerebral cytokine production. We also explored whether increased concentrations of injury biomarkers discriminate between hypoxic (Hx) and normoxic (Nx) patients, correlate to worse outcome, and depend on blood-brain barrier (BBB) dysfunction. Forty-two TBI patients with Glasgow Coma Scale ≤8 were recruited. Cerebrospinal fluid (CSF) and serum were collected over 6 days. Patients were divided into Hx (n=22) and Nx (n=20) groups. Eight cytokines were measured in the CSF; albumin, S100, myelin basic protein (MBP) and neuronal specific enolase (NSE) were quantified in serum. CSF/serum albumin quotient was calculated for BBB function. Glasgow Outcome Scale Extended (GOSE) was assessed at 6 months post-TBI. Production of granulocye macrophage-colony stimulating factor (GM-CSF) was higher, and profiles of GM-CSF, interferon (IFN)-γ and, to a lesser extent, tumor necrosis factor (TNF), were prolonged in the CSF of Hx but not Nx patients at 4-5 days post-TBI. Interleukin (IL)-2, IL-4, IL-6, and IL-10 increased similarly in both Hx and Nx groups. S100, MBP, and NSE were significantly higher in Hx patients with unfavorable outcome. Among these three biomarkers, S100 showed the strongest correlations to GOSE after TBI-Hx. Elevated CSF/serum albumin quotients lasted for 5 days post-TBI and displayed similar profiles in Hx and Nx patients. We demonstrate for the first time that post-TBI hypoxia is associated with prolonged neuroinflammation, amplified extravasation of biomarkers, and poor outcome. S100 and MBP could be implemented to track the occurrence of post-TBI hypoxia, and prompt adequate treatment.