Where are we in the modelling of traumatic brain injury? Models complicated by secondary brain insults

Fluid-Based Protein Biomarkers in Traumatic Brain Injury: The View from the Bedside

There has been an explosion of research into biofluid (blood, cerebrospinal fluid, CSF)-based protein biomarkers in traumatic brain injury (TBI) over the past decade. The availability of very large datasets, such as CENTRE-TBI and TRACK-TBI, allows for correlation of blood- and CSF-based molecular (protein), radiological (structural) and clinical (physiological) marker data to adverse clinical outcomes. The quality of a given biomarker has often been framed in relation to the predictive power on the outcome quantified from the area under the Receiver Operating Characteristic (ROC) curve. However, this does not in itself provide clinical utility but reflects a statistical association in any given population between one or more variables and clinical outcome. It is not currently established how to incorporate and integrate biofluid-based biomarker data into patient management because there is no standardized role for such data in clinical decision making. We review the current status of biomarker research and discuss how we can integrate existing markers into current clinical practice and what additional biomarkers do we need to improve diagnoses and to guide therapy and to assess treatment efficacy. Furthermore, we argue for employing machine learning (ML) capabilities to integrate the protein biomarker data with other established, routinely used clinical diagnostic tools, to provide the clinician with actionable information to guide medical intervention.

Silencing of TRIM44 Inhibits Inflammation and Alleviates Traumatic Brain Injury in Rats by Downregulating TLR4-NF-κB Signaling

BACKGROUND

Neuroinflammation subsequent to traumatic brain injury (TBI) is important for the recovery of patients and is associated with neurodegenerative changes post-TBI. The tripartite motif containing 44 (TRIM44) protein is an E3 ligase involved in the regulation of immune function with no previously known link to TBI. This study explores the connection between TRIM44 and TBI.

METHODS

After induction of TBI in rats by control cortex injury, TRIM44 expressions were determined with quantitative real-time reverse transcription polymerase chain reaction and Western blot, and Toll-like receptor 4 (TLR4)-NF-κB signaling was examined by the expression of TLR4, p65 phosphorylation, and the specific NF-κB transcription activity. The effects of TRIM44 knockdown on inflammation, neurological function, and TLR4-NF-κB signaling in TBI rats were revealed by the detection of proinflammatory cytokines and TLR4-NF-κB signaling molecules, modified neurological severity score, brain water content, and Evans blue permeability.

RESULTS

We found that TRIM44 expression was significantly increased following TBI induction along with TLR4-NF-κB activation. Silencing of TRIM44 suppressed proinflammatory cytokine production, improved neurological outcomes, alleviated brain edema, and inhibited TLR4-NF-κB signaling in TBI rats.

CONCLUSION

Our findings suggest that suppressing TRIM44 or modulation of relevant pathways may be a therapeutic strategy for TBI.

Continuous remote ischemic conditioning attenuates cognitive and motor deficits from moderate traumatic brain injury

BACKGROUND

While studies show that single-dose remote ischemic conditioning (RIC) improves outcomes, the effect of continuous (daily) RIC is unknown. Thus, we aimed to investigate the role of continuous RIC on cognitive and motor function following traumatic brain injury (TBI).

METHODS

We subjected 24 male C57BL mice to a cortical-controlled TBI. Two hours after TBI, the animals were randomly allocated to the RIC group (n = 12) or the sham group (n = 12). Remote ischemic conditioning was induced by noninvasive external compression of the hind limb using an occlusive band (six 4-minute cycles/24 hours) for six consecutive days. Before TBI, a baseline rotarod test and novel object recognition were performed. Post-TBI rotarod and novel object recognition tests were performed on Days 1 to 5, 7, 14, and 21. After the animals were sacrificed on Day 21, brain sections were analyzed using hematoxylin and eosin and glial fibrillary acidic protein staining to evaluate the hippocampal CA1 area for neuronal injury.

RESULTS

Both the RIC and sham groups had lower latency to fall compared with the baseline post-TBI. The RIC animals had a higher latency to fall compared with the sham animals at all time points, statistically significant after Day 3, until Day 21 post-TBI. Both the RIC and sham groups had lower recognition index compared with the baseline post-TBI. The RIC animals had a significantly higher recognition index than the sham animals after Day 1, until Day 21 post-TBI. Hematoxylin and eosin and glial fibrillary acidic protein staining of the brain samples of the sham group revealed that more neurons in the hippocampal CA1 area appeared shrunken with eosinophilic cytoplasm and pyknotic nuclei compared with the brain samples of the RIC group.

CONCLUSION

Postinjury continuous RIC resulted in improved cognitive functions and motor coordination in a mouse model of moderate TBI. Further studies are required to determine optimum dosage and frequency of this novel therapy to maximize its beneficial effects following TBI.

Large animal models of traumatic brain injury

Purpose/Aim: Animal models of traumatic brain injury (TBI) provide powerful tools to study TBI in a controlled, rigorous and cost-efficient manner. The mostly used animals in TBI studies so far are rodents. However, compared with rodents, large animals (e.g. swine, rabbit, sheep, ferret, etc.) show great advantages in modeling TBI due to the similarity of their brains to human brain. The aim of our review was to summarize the development and progress of common large animal TBI models in past 30 years.

MATERIALS AND METHODS

Mixed published articles and books associated with large animal models of TBI were researched and summarized.

RESULTS

We majorly sumed up current common large animal models of TBI, including discussion on the available research methodologies in previous studies, several potential therapies in large animal trials of TBI as well as advantages and disadvantages of these models.

CONCLUSIONS

Large animal models of TBI play crucial role in determining the underlying mechanisms and screening putative therapeutic targets of TBI.

Age and Diet Affect Genetically Separable Secondary Injuries that Cause Acute Mortality Following Traumatic Brain Injury in Drosophila

Outcomes of traumatic brain injury (TBI) vary because of differences in primary and secondary injuries. Primary injuries occur at the time of a traumatic event, whereas secondary injuries occur later as a result of cellular and molecular events activated in the brain and other tissues by primary injuries. We used a Drosophila melanogaster TBI model to investigate secondary injuries that cause acute mortality. By analyzing mortality percentage within 24 hr of primary injuries, we previously found that age at the time of primary injuries and diet afterward affect the severity of secondary injuries. Here, we show that secondary injuries peaked in activity 1–8 hr after primary injuries. Additionally, we demonstrate that age and diet activated distinct secondary injuries in a genotype-specific manner, and that concurrent activation of age- and diet-regulated secondary injuries synergistically increased mortality. To identify genes involved in secondary injuries that cause mortality, we compared genome-wide mRNA expression profiles of uninjured and injured flies under age and diet conditions that had different mortalities. During the peak period of secondary injuries, innate immune response genes were the predominant class of genes that changed expression. Furthermore, age and diet affected the magnitude of the change in expression of some innate immune response genes, suggesting roles for these genes in inhibiting secondary injuries that cause mortality. Our results indicate that the complexity of TBI outcomes is due in part to distinct, genetically controlled, age- and diet-regulated mechanisms that promote secondary injuries and that involve a subset of innate immune response genes.

Epidemiology and aetiology of traumatic cardiac arrest in England and Wales - A retrospective database analysis

BACKGROUND

Historically, reported survival from traumatic cardiac arrest (TCA) was extremely low. More recent publications have recorded survival to discharge of up to 8%. This improvement is likely to be multi-factorial; however, there are currently no published data describing the epidemiology or aetiology of TCA in England and Wales to guide future practice improvement.

METHODS

Population-based analysis of 2009-2015 Trauma Audit and Research Network (TARN) data. The primary aim was to describe the 30-day survival following TCA. Patients of all ages with traumatic cardiac arrest pre-hospital or in the emergency department (ED) were included. Data are described as number (%), and median [interquartile range]. Two-group analysis with Chi-squared test was performed.

RESULTS

During the study period 227,944 patients were included in the TARN database. Seven hundred and five (0.3%) suffered TCA: 74.3% were male, aged 44.3 [25.2-83.2] years, ISS 29 [21-75], and 601 (85.2%) had blunt injuries. 612 (86.8%) had a severe traumatic brain injury and or severe haemorrhage. Overall 30-day survival was 7.5% (95%CI 5.6-9.5) - 'pre-hospital only' TCA 11.5%, 'ED only' TCA 3.9%, p<0.02. No patients who were in TCA both pre-hospital and in the ED survived.

CONCLUSION

This study has shown that short-term survival from TCA in this large civilian registry is 7.5%. Early and aggressive management of patients with TCA, using protocols that target the reversible causes of TCA, should be initiated. Further work to establish novel ways to manage patients with reversible causes of TCA is indicated. Resuscitation in this patient group is not futile.

Blood biomarkers indicate mild neuroaxonal injury and increased amyloid β production after transient hypoxia during breath-hold diving

OBJECTIVE

To determine whether transient hypoxia during breath-hold diving causes neuronal damage or dysfunction or alters amyloid metabolism as measured by certain blood biomarkers.

DESIGN

Sixteen divers competing in the national Swedish championship in breath-hold diving and five age-matched healthy control subjects were included. Blood samples were collected at baseline and over a course of 3 days where the divers competed in static apnea (STA), dynamic apnea without fins (DYN1) and dynamic apnea with fins (DYN2).

MAIN OUTCOMES

Biomarkers reflecting brain injury and amyloid metabolism were analysed in serum (S-100β, NFL) and plasma (T-tau, Aβ42) using immunochemical methods.

RESULTS

Compared to divers' baseline, Aβ42 increased after the first event of static apnea (p = 0.0006). T-tau increased (p = 0.001) in STA vs baseline and decreased after one of the dynamic events, DYN2 (p = 0.03). Further, T-tau correlated with the length of the apneic time during STA (ρ = 0.7226, p = 0.004) and during DYN1 (ρ = 0.66, p = 0.01).

CONCLUSION

The findings suggest that transient hypoxia may acutely increase the levels of Aβ42 and T-tau in plasma of healthy adults, further supporting that general hypoxia may cause mild neuronal dysfunction or damage and stimulate Aβ production.

Challenging the Paradigms of Experimental TBI Models: From Preclinical to Clinical Practice

Despite prodigious advances in TBI neurobiology research and a broad arsenal of animal models mimicking different aspects of human brain injury, this field has repeatedly experienced collective failures to translate from animals to humans, particularly in the area of therapeutics. This lack of success stems from variability and inconsistent standardization across models and laboratories, as well as insufficient objective and quantifiable diagnostic measures (biomarkers, high-resolution imaging), understanding of the vast clinical heterogeneity, and clinically centered conception of the TBI animal models. Significant progress has been made by establishing well-defined standards for reporting animal studies with "preclinical common data elements" (CDE), and for the reliability and reproducibility in preclinical TBI therapeutic research with the Operation Brain Trauma Therapy (OBTT) consortium. However, to break the chain of failures and achieve a therapeutic breakthrough in TBI will probably require the use of higher species models, specific mechanism-based injury models by which to theranostically targeted treatment portfolios are tested, more creative concepts of therapy intervention including combination therapy and regeneration neurobiology strategies, and the adoption of dosing regimens based upon pharmacokinetic-pharmacodynamic (PK-PD) studies and guided by the injury severity and TBI recovery process.

Characterization of pressure distribution in penetrating traumatic brain injuries

Severe impacts to the head commonly lead to localized brain damage. Such impacts may also give rise to temporary pressure changes that produce secondary injuries in brain volumes distal to the impact site. Monitoring pressure changes in a clinical setting is difficult; detailed studies into the effect of pressure changes in the brain call for the development and use of animal models. The aim of this study is to characterize the pressure distribution in an animal model of penetrating traumatic brain injuries (pTBI). This data may be used to validate mathematical models of the animal model and to facilitate correlation studies between pressure changes and pathology. Pressure changes were measured in rat brains while subjected to pTBI for a variety of different probe velocities and shapes; pointy, blunt, and flat. Experiments on ballistic gel samples were carried out to study the formation of any temporary cavities. In addition, pressure recordings from the gel experiments were compared to values recorded in the animal experiments. The pTBI generated short lasting pressure changes in the brain tissue; the pressure in the contralateral ventricle (CLV) increased to 8 bar followed by a drop to 0.4 bar when applying flat probes. The pressure changes in the periphery of the probe, in the Cisterna Magna, and the spinal canal, were significantly less than those recorded in the CLV or the vicinity of the skull base. High-speed videos of the gel samples revealed the formation of spherically shaped cavities when flat and spherical probes were applied. Pressure changes in the gel were similar to those recorded in the animals, although amplitudes were lower in the gel samples. We concluded cavity expansion rate rather than cavity size correlated with pressure changes in the gel or brain secondary to probe impact. The new data can serve as validation data for finite element models of the trauma model and the animal and to correlate physical measurements with secondary injuries.