Secondary Injury Mechanisms Research Articles

Animal models for the study of intracranial hematomas (Review).

Intracranial hematomas (ICH) are a frequent condition in neurosurgical and neurological practices, with several mechanisms of primary and secondary injury. Experimental research has been fundamental for the understanding of the pathophysiology implicated with ICH and the development of therapeutic interventions. To date, a variety of different animal approaches have been described that consider, for example, the ICH evolutive phase, molecular implications and hemodynamic changes. Therefore, choosing a test protocol should consider the scope of each particular study. The present review summarized investigational protocols in experimental research on the subject of ICH. With this subject, injection of autologous blood or bacterial collagenase, inflation of intracranial balloon and avulsion of cerebral vessels were the models identified. Rodents (mice) and swine were the most frequent species used. These different models allowed improvements on the understanding of intracranial hypertension establishment, neuroinflammation, immunology, brain hemodynamics and served to the development of therapeutic strategies.

Myostatin is a negative regulator of adult neurogenesis after spinal cord injury in zebrafish.

Intrinsic and extrinsic inhibition of neuronal regeneration obstruct spinal cord (SC) repair in mammals. In contrast, adult zebrafish achieve functional recovery after complete SC transection. While studies of innate SC regeneration have focused on axon regrowth as a primary repair mechanism, how local adult neurogenesis affects functional recovery is unknown. Here, we uncover dynamic expression of zebrafish myostatin b (mstnb) in a niche of dorsal SC progenitors after injury. mstnb mutants show impaired functional recovery, normal glial and axonal bridging across the lesion, and an increase in the profiles of newborn neurons. Molecularly, neuron differentiation genes are upregulated, while the neural stem cell maintenance gene fgf1b is downregulated in mstnb mutants. Finally, we show that human fibroblast growth factor 1 (FGF1) treatment rescues the molecular and cellular phenotypes of mstnb mutants. These studies uncover unanticipated neurogenic functions for mstnb and establish the importance of local adult neurogenesis for innate SC repair.

The Impact of Invasive Brain Oxygen Pressure Guided Therapy on the Outcome of Patients with Traumatic Brain Injury: A Systematic Review and Meta-Analysis.

Traumatic brain injury (TBI) is a major public health burden, causing death and disability worldwide. Intracranial hypertension and brain hypoxia are the main mechanisms of secondary brain injury. As such, management strategies guided by intracranial pressure (ICP) and brain oxygen (PbtO2) monitoring could improve the prognosis of these patients. Our objective was to summarize the current evidence regarding the impact of PbtO2-guided therapy on the outcome of patients with TBI. We performed a systematic search of PubMed, Scopus, and the Cochrane library databases, following the protocol registered in PROSPERO. Only studies comparing PbtO2/ICP-guided therapy with ICP-guided therapy were selected. Primary outcome was neurological outcome at 3 and 6months assessed by using the Glasgow Outcome Scale; secondary outcomes included hospital and long-term mortality, burden of intracranial hypertension, and brain tissue hypoxia. Out of 6254 retrieved studies, 15 studies (n = 37,245 patients, of who 2184 received PbtO2-guided therapy) were included in the final analysis. When compared with ICP-guided therapy, the use of combined PbO2/ICP-guided therapy was associated with a higher probability of favorable neurological outcome (odds ratio 2.21 [95% confidence interval 1.72-2.84]) and of hospital survival (odds ratio 1.15 [95% confidence interval 1.04-1.28]). The heterogeneity (I2) of the studies in each analysis was below 40%. However, the quality of evidence was overall low to moderate. In this meta-analysis, PbtO2-guided therapy was associated with reduced mortality and more favorable neurological outcome in patients with TBI. The low-quality evidence underlines the need for the results from ongoing phase III randomized trials.

194. Expansile duraplasty improves motor outcomes after acute traumatic spinal cord injury

<h3>BACKGROUND CONTEXT</h3> Traumatic spinal cord injury (SCI) can lead to debilitating motor weakness with long term impacts on quality of life. Following the initial trauma, secondary injury mechanisms, including edema, ischemia and inflammation can lead to considerable extension of the injury, providing a window of opportunity for interventions to preserve function. Early surgical decompression and optimization of spinal cord perfusion have emerged as potential targets. Expansile duraplasty could provide benefit by extending surgical decompression to the intrathecal space and increasing spinal cord perfusion; however, there remains a paucity of data on whether this provides a measurable benefit. <h3>PURPOSE</h3> Assess whether expansile duraplasty is associated with greater motor recovery in patients with acute traumatic SCI compared with bony decompression alone. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of medical records. <h3>PATIENT SAMPLE</h3> Patients who underwent surgical spinal decompression and stabilization for traumatic spinal cord injury from February 2017 to June 2021 at an academic, Level 1 trauma center. Patients were excluded from analysis if they did not attend inpatient rehabilitation after their acute hospital stay. <h3>OUTCOME MEASURES</h3> Change in American Spinal Injury Association (ASIA) motor scores between preoperative evaluation, acute hospital discharge, and discharge from inpatient rehabilitation. <h3>METHODS</h3> Patients were divided between those who had expansile duraplasty performed at the time of surgical stabilizationand those who did not. Data collected included patient demographics, injury type, surgery performed, and ASIA motor scores (International Standards for Neurological Classification of SCI, range 0-100) preoperatively and at the time of hospital and inpatient rehabilitation discharge. <h3>RESULTS</h3> A total of 101 patients were included: 12 treated with expansile duraplasty and 89 treated without duraplasty. Patients were 76% male with a mean age of 50.9 years. The mean preoperative motor score for all patients was 48.7+/-29.3 (mean +/- std.dev.), 50.5+/-19.7 for the control group and 35.7+/-23.0 for the expansile duraplasty group (p=0.06). From preoperative exam to hospital discharge, the mean improvement in motor score for the control group was 3.7+/-11.3, compared to 9.3+/-11.4 in the expansile duraplasty group (p=0.12). Mean change in motor score from preoperative exam to rehabilitation discharge was 10.9+/-13.4 for controls and 19.9+/-11.0 for expansile duraplasty patients (p=0.02). <h3>CONCLUSIONS</h3> In this contemporaneous, single-center, retrospective study, SCI patients undergoing expansile duraplasty had significantly greater improvement in ASIA motor scores at rehabilitation discharge compared to non-duraplasty controls. These data present an independent and the first US validation of preliminary data from international centers in favor of expansile duraplasty. Further prospective studies are warranted to assess whether this adjunctive surgical technique is efficacious in treating acute traumatic SCI. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

28. International perspectives on the current practice of acute spinal cord injury management: results of a global survey

28. International perspectives on the current practice of acute spinal cord injury management: results of a global survey

Utilizing novel TBI-on-a-chip device to link physical impacts to neurodegeneration and decipher primary and secondary injury mechanisms

While clinical observations have confirmed a link between the development of neurodegenerative diseases and traumatic brain injuries (TBI), there are currently no treatments available and the underlying mechanisms remain elusive. In response, we have developed an in vitro pendulum trauma model capable of imparting rapid acceleration injuries to neuronal networks grown on microelectrode arrays within a clinically relevant range of g forces, with real-time electrophysiological and morphological monitoring. By coupling a primary physical insult with the quantification of post-impact levels of known biochemical pathological markers, we demonstrate the capability of our system to delineate and investigate the primary and secondary injury mechanisms leading to post-impact neurodegeneration. Specifically, impact experiments reveal significant, force-dependent increases in the pro-inflammatory, oxidative stress marker acrolein at 24 h post-impact. The elevation of acrolein was augmented by escalating g force exposures (30–200 g), increasing the number of rapidly repeated impacts (4–6 s interval, 3, 5 and 10×), and by exposing impacted cells to 40 mM ethanol, a known comorbidity of TBI. The elevated levels of acrolein following multiple impacts could be reduced by increasing time-intervals between repeated hits. In addition, we show that conditioned media from maximally-impacted cultures can cause cellular acrolein elevation when introduced to non-impact, control networks, further solidifying acrolein’s role as a diffusive-factor in post-TBI secondary injuries. Finally, morphological data reveals post-impact acrolein generation to be primarily confined to soma, with some emergence in cellular processes. In conclusion, this novel technology provides accurate, physical insults with a unique level of structural and temporal resolution, facilitating the investigation of post-TBI neurodegeneration.

Postischemic Neuroprotection of Aminoethoxydiphenyl Borate Associates Shortening of Peri-Infarct Depolarizations.

Brain stroke is a highly prevalent pathology and a main cause of disability among older adults. If not promptly treated with recanalization therapies, primary and secondary mechanisms of injury contribute to an increase in the lesion, enhancing neurological deficits. Targeting excitotoxicity and oxidative stress are very promising approaches, but only a few compounds have reached the clinic with relatively good positive outcomes. The exploration of novel targets might overcome the lack of clinical translation of previous efficient preclinical neuroprotective treatments. In this study, we examined the neuroprotective properties of 2-aminoethoxydiphenyl borate (2-APB), a molecule that interferes with intracellular calcium dynamics by the antagonization of several channels and receptors. In a permanent model of cerebral ischemia, we showed that 2-APB reduces the extent of the damage and preserves the functionality of the cortical territory, as evaluated by somatosensory evoked potentials (SSEPs). While in this permanent ischemia model, the neuroprotective effect exerted by the antioxidant scavenger cholesteronitrone F2 was associated with a reduction in reactive oxygen species (ROS) and better neuronal survival in the penumbra, 2-APB did not modify the inflammatory response or decrease the content of ROS and was mostly associated with a shortening of peri-infarct depolarizations, which translated into better cerebral blood perfusion in the penumbra. Our study highlights the potential of 2-APB to target spreading depolarization events and their associated inverse hemodynamic changes, which mainly contribute to extension of the area of lesion in cerebrovascular pathologies.

The Role of Neuroinflammatory Mediators in the Pathogenesis of Traumatic Brain Injury: A Narrative Review.

Traumatic brain injury (TBI) is a debilitating acquired neurological disorder that afflicts nearly 74 million people worldwide annually. TBI has been classified as more than just a single insult because of its associated risk toward various long-term neurological and neurodegenerative disorders. This risk may be triggered by a series of postinjury secondary molecular and cellular pathology, which may be dependent on the severity of the TBI. Among the secondary injury mechanisms, neuroinflammation may be the most crucial as it may exacerbate brain damage and lead to fatal consequences when prolonged. This Review aimed to elucidate the influence of neuroinflammatory mediators on the TBI functional and pathological outcomes, particularly focusing on inflammatory cytokines which were associated with neuronal dysfunctions in the acute and chronic stages of TBI. These cytokines include interleukins (IL) such as IL-1(beta)β, IL-4, IL-6, IL8, IL-10, IL-18, IL-33 and tumor necrosis factor alpha (TNF-α), which have been extensively studied. Apart from these, IL-2, interferon gamma (IFN-γ), and transforming growth factor-beta (TGF-β) may also play a significant role in the pathogenesis of TBI. These neuroinflammatory mediators may trigger a series of pathological events such as cell death, microglial suppression, and increased catecholaminergic activity. Interestingly, in the acute phase of TBI, most of these mediators may also play a neuroprotective role by displaying anti-inflammatory properties, which may convert to a pro-inflammatory action in the chronic stages post TBI. Early identification and treatment of these mediators may help the development of more effective treatment options for TBI.

Females Exhibit Better Cerebral Pressure Autoregulation, Less Mitochondrial Dysfunction, and Reduced Excitotoxicity after Severe Traumatic Brain Injury.

The aim of the study was to investigate sex-related differences in intracranial pressure (ICP) dynamics, cerebral pressure autoregulation (PRx55-15), cerebral energy metabolism, and clinical outcome after severe traumatic brain injury (TBI). One-hundred sixty-nine adult patients with TBI, treated at the Neurointensive Care (NIC) Unit at Uppsala University Hospital between 2008 and 2020 with ICP and cerebral microdialysis (MD) monitoring were included. Of the 169 patients with TBI, 131 (78%) were male and 38 (22%) female. Male patients were more often injured by motor vehicle accidents and less often by bicycle accidents (p < 0.05). There were otherwise no differences in age, neurological status at admission, and types of intracranial hemorrhages between the sexes. The percent of monitoring time with ICP above 20 mm Hg and cerebral perfusion pressure (CPP) below 60 mm Hg were similar for both sexes. Males exhibited more disturbed cerebral pressure autoregulation (PRx55-15 [mean ± standard deviation (SD)]; 0.28 ± 0.18 vs. 0.17 ± 0.23, p < 0.05) on day 1, worse cerebral energy metabolism (MD-lactate-/pyruvate-ratio [median (interquartile range)]; 25 [19-31] vs. 20 [17-25], p < 0.01) and mitochondrial dysfunction (higher burden of MD-lactate-/pyruvate-ratio >25 and MD-pyruvate >120 μM [median (interquartile range)]; 13 [0-58] % vs. 3 [0-17] %, p < 0.05) on days 2 to 5, increased excitotoxicity (MD-glutamate median [interquartile range]; 9 [4-32] μM vs. 5 [3-10] μM, p < 0.05) on days 2 to 5, and higher biomarker levels of cellular injury (MD-glycerol median [interquartile range]; 103 [66-193] μM vs. 68 [49-106] μM, p < 0.01) most pronounced on days 6 to 10. There was no difference in mortality or the degree of favorable outcome between the sexes. Altogether, females exhibited more favorable cerebral physiology post-TBI, particularly better mitochondrial function and reduced excitotoxicity, but this did not translate into better clinical outcome compared with males. Future studies are needed to further explore potential sex differences in secondary injury mechanisms in TBI.

Leveraging Continuous Vital Sign Measurements for Real-Time Assessment of Autonomic Nervous System Dysfunction After Brain Injury: A Narrative Review of Current and Future Applications.

Subtle and profound changes in autonomic nervous system (ANS) function affecting sympathetic and parasympathetic homeostasis occur as a result of critical illness. Changes in ANS function are particularly salient in neurocritical illness, when direct structural and functional perturbations to autonomic network pathways occur and may herald impending clinical deterioration or intervenable evolving mechanisms of secondary injury. Sympathetic and parasympathetic balance can be measured quantitatively at the bedside using multiple methods, most readily by extracting data from electrocardiographic or photoplethysmography waveforms. Work from our group and others has demonstrated that data-analytic techniques can identify quantitative physiologic changes that precede clinical detection of meaningful events, and therefore may provide an important window for time-sensitive therapies. Here, we review data-analytic approaches to measuring ANS dysfunction from routine bedside physiologic data streams and integrating this data into multimodal machine learning-based model development to better understand phenotypical expression of pathophysiologic mechanisms and perhaps even serve as early detection signals. Attention will be given to examples from our work in acute traumatic brain injury on detection and monitoring of paroxysmal sympathetic hyperactivity and prediction of neurologic deterioration, and in large hemispheric infarction on prediction of malignant cerebral edema. We also discuss future clinical applications and data-analytic challenges and future directions.

The effect of extracorporeal shock wave therapy in acute traumatic spinal cord injury on motor and sensory function within 6\u2009months post-injury: a study protocol for a two-arm three-stage adaptive, prospective, multi-center, randomized, blinded, placebo-controlled clinical trial

BackgroundThe pathological mechanism in acute spinal cord injury (SCI) is dual sequential: the primary mechanical lesion and the secondary injury due to a cascade of biochemical and pathological changes initiated by the primary lesion. Therapeutic approaches have focused on modulating the mechanisms of secondary injury. Despite extensive efforts in the treatment of SCI, there is yet no causal, curative treatment approach available.Extracorporeal shock wave therapy (ESWT) has been successfully implemented in clinical use. Biological responses to therapeutic shock waves include altered metabolic activity of various cell types due to direct and indirect mechanotransduction leading to improved migration, proliferation, chemotaxis, modulation of the inflammatory response, angiogenesis, and neovascularization, thus inducing rather a regeneration than repair.The aim of this clinical study is to investigate the effect of ESWT in humans within the first 48 h after an acute traumatic SCI, with the objective to intervene in the secondary injury phase in order to reduce the extent of neuronal loss.MethodsThis two-arm three-stage adaptive, prospective, multi-center, randomized, blinded, placebo-controlled study has been initiated in July 2020, and a total of 82 patients with acute traumatic SCI will be recruited for the first stage in 15 participating hospitals as part of a two-armed three-stage adaptive trial design. The focused ESWT (energy flux density: 0.1–0.19 mJ/mm2, frequency: 2–5 Hz) is applied once at the level of the lesion, five segments above/below, and on the plantar surface of both feet within the first 48 h after trauma.The degree of improvement in motor and sensory function after 6 months post-injury is the primary endpoint of the study. Secondary endpoints include routine blood chemistry parameters, the degree of spasticity, the ability to walk, urological function, quality of life, and the independence in everyday life.DiscussionThe application of ESWT activates the nervous tissue regeneration involving a multitude of various biochemical and cellular events and leads to a decreased neuronal loss. ESWT might contribute to an improvement in the treatment of acute traumatic SCI in future clinical use.Trial registrationClinicalTrials.govNCT04474106

Localization of Multi-Lamellar Vesicle Nanoparticles to Injured Brain Tissue in a Controlled Cortical Impact Injury Model of Traumatic Brain Injury in Rodents.

Severe traumatic brain injury (TBI), such as that suffered by patients with cerebral contusion, is a major cause of death and disability in young persons. Effective therapeutics to treat or mitigate the effects of severe TBI are lacking, in part because drug delivery to the injured brain remains a challenge. Promising therapeutics targeting secondary injury mechanisms may have poor pharmacokinetics/pharmacodynamics, unwanted side effects, or high hydrophobicity. To address these challenges, we have developed a multi-lamellar vesicle nanoparticle (MLV-NP) formulation with a narrow size distribution (243 nm in diameter, 0.09 polydispersity index) and the capability of encapsulating hydrophobic small molecule drugs for delivery to the injured brain. To demonstrate the utility of these particles, we produced dual-fluorescent labeled nanoparticles containing the organic dyes, coumarin 153 and rhodamine B, that were delivered intravenously to Sprague-Dawley rats and C57Bl6/J mice at 1, 1 and 4, 24, or 48 h after controlled cortical impact injury. Distribution of particles was measured at 5, 25, 48, or 49 h post-injury by fluorescence microscopy of coronal brain sections. In all cases of MLV administration, a 1.2- to 1.9-fold enhancement of ipsilateral fluorescence signal was observed compared to the contralateral cortex. Enhanced fluorescence was also observed in the injured hippocampal tissue in these animals. MLV-NPs administered at 1 h were observed intracellularly in the injured hemisphere at 48 h, suggesting the possibility of concentrated drug delivery to injured cells. These results suggest that MLV-NP delivery of therapeutic agents may be a viable strategy for treating cerebral contusion TBI.

Stereotactic Vacuum-Assisted Minimally Invasive Aspiration of Hemorrhagic Stroke.

Intracerebral hemorrhage (ICH), accounting for 9-27% of all strokes, carries substantial rates of morbidity and mortality that have not shown much improvement in the past decades. The poor outcomes of ICH can be attributed to the primary and secondary brain injuries caused by mass effects and inflammatory mechanisms, respectively. Early ICH evacuation is a critical component of treatment, as it mitigates the effect of both the primary and secondary mechanisms of brain injury and is associated with significant improvement in patient outcomes. However, no standardized evacuation technique exists. This technical report introduces a novel stereotactic vacuum-assisted minimally invasive (MIS) aspiration of a hemorrhagic stroke with its effectiveness evidenced by excellent patient recovery.

Activation of P2X4 receptor exacerbates acute brain injury after intracerebral hemorrhage.

IntroductionIntracerebral hemorrhage (ICH) accounts for 10%–15% of all strokes and culminates in high mortality and disability. After ICH, brain injury is initiated by the mass effect of hematoma, followed by secondary cytotoxic injury from dying brain cells, hematoma disintegration, and cascading brain immune response. However, the molecular mechanism of secondary cytotoxic brain injury in ICH is not completely understood. The sensitive purinergic receptor, P2X4 receptor (P2X4R), was known to recognize extracellular free ATP released by dying cells during tissue injury.AimsIn this study, we aim to understand the role of P2X4R in acute brain injury triggered by ICH.ResultsIn this study, we found that the sensitive purinergic receptor, P2X4R, was upregulated in the brain of patients with ICH as well as in a mouse model of ICH induced by collagenase injection. P2X4R blockage with the specific inhibitor 5‐BDBD attenuated brain injury in ICH mice by significantly reducing brain edema, blood–brain barrier leakage, neural death, and ultimately acute neurodeficits. Further study indicated that the protective effect of P2X4R inhibition is related to decreased pro‐inflammatory activity of microglia and recruitment of peripheral immune cells into the hemorrhagic brain.ConclusionsThese results suggest that the P2X4 receptor is activated by ICH stimuli which worsen brain injury following ICH.

Practical Considerations for Continuous Time-Domain Cerebrovascular Reactivity Indices in Traumatic Brain Injury: Do Scaling Errors in Parent Signals Matter?

Literature pertaining to traumatic brain injury care involves the mediation and control of secondary brain injury mechanisms, chief among these is cerebral autoregulation. Cerebral autoregulation is frequently assessed through surrogate measures of cerebrovascular reactivity. An important aspect to acknowledge when calculating cerebrovascular reactivity indices is the linearity within two-parent bio-signals or variables. We highlighted the concept of linearity in raw parent bio-signals used for the calculation of the cerebrovascular reactivity index and what potential implications linearity carries for index derivation. Key of which is that the initial differencing or location of the pressure probes does not influence linear methods of cerebral reactivity calculations so long as the slow-wave vasogenic changes are being recorded.

Paroxysmal sympathetic hyperactivity following acute diffuse brain swelling due to traumatic brain injury: a case report with good clinical outcome

BackgroundParoxysmal sympathetic hyperactivity (PSH) may occur after acquired brain injury. The clinical presentation of PSH results from increased sympathetic overdrive, including transient paroxysms of tachycardia, hypertension, hyperventilation, hyperthermia, dystonic posturing, and excessive sweating. The exact pathophysiology of PSH, however, remains unclear, and no definitive treatment is available. Herein, the authors report a case of PSH in a male patient who experienced acute brain swelling after acquired head injury, for which a good clinical outcome was achieved due to multimodal treatment. The ensuing discussion also addresses the pathophysiology of PSH.Case presentationAn 18-year-old man was transported to the authors’ hospital after experiencing a traumatic brain injury. On admission, computed tomography revealed cerebral herniation due to diffuse brain edema in the left parietal lobe. Emergency decompressive craniotomy and internal decompression were performed. After surgery, anti-edema therapy (glycerol and mannitol) was continued. Ten days postoperatively, PSH was diagnosed in accordance with the PSH assessment score (20 points). Vecuronium, fentanyl, morphine, propofol, dexmedetomidine, and a calcium channel blocker were administered; however, the drug effect was insufficient. Thirty-two days postsurgery, the patient gradually recovered from the adrenergic symptoms of PSH, and head computed tomography performed 32 days after surgery revealed improvement in diffuse brain edema. Ultimately, the patient fully recovered and lived independently at home.ConclusionsConsidering the pathophysiology of PSH, cerebral contusion, acute brain swelling, and secondary mechanisms of brain injury may trigger sympathetic nerve-enhancing regions and cause hyperexcitation of the sympathetic nervous system, resulting in PSH. The outcome of the present case demonstrates that PSH can be reversed if it is identified early and before it becomes irreversible, that is, post the development of hypoxic encephalopathy or widespread brain damage. Appropriate management, including decompression craniotomy for brain swelling and multidisciplinary treatment, leads to good clinical outcomes.

Abstract TP253: Early Intense Rehabilitation Does Not Reduce Impairment After Intra-striatal Hemorrhagic Stroke In Rats

Intracerebral hemorrhage (ICH) causes rapid mechanical damage and initiates secondary injury mechanisms, such as from toxic by-products of blood degradation, that cause extended cell death. Experimentally, several rehabilitative treatments (rehab) can mitigate late cell death, and one recent study suggests it is by accelerating hematoma clearance, thereby minimizing neurotoxicity. Here, we assessed whether early, intense, enriched rehab (ER) enhances functional benefit and reduces ICH injury. Methods: In experiment 1, rats (n=56) were randomly assigned to groups following collagenase-induced striatal ICH: ER-Dark, ER-Light, CONTROL-Dark, or CONTROL-Light. ER rats completed four reach training sessions and six hours of environmental enrichment daily for 10d (d5-14 after ICH), in either the dark or light phase of their housing cycle. Rats were euthanized on d14 and hematoma volume was assessed. In experiment 2 (n=72), rats were randomized to: ER-10, ER-20, or CONTROL. Using the same ER protocol, rats in ER-10 and ER-20 completed 10d (d5-14) or 20d (d5-14 and 19-28) of ER during the dark phase of their housing cycle. Rats were euthanized on d60, and brains were fixed for histological processing. In both experiments, rats completed behavioural assessments prior to ICH, pre-treatment (d4 post-ICH) and post treatment (experiment 1, d13-14; experiment 2, d16-17 and d30-31). Results: In experiment 1 there was no significant difference in reaching intensity between ER completed in light vs. dark (p=0.3318), and both groups reached extensively (3912±947 reaches). ER resulted in slightly better reaching success between d4 and d14 (p=0.0272) but did not significantly alter residual hematoma volume (p=0.9653). In experiment 2, ER duration did not significantly impact reaching success between d4 and d31 (p=0.0587) or reduce lesion size (p=0.6401). Conclusion: While similar rehab methods have been beneficial in other work, these findings suggest that slight variations in protocols (rehab initiation, intensity, time in enrichment) have a large impact on treatment efficacy. Additionally, these results underscore the importance of studying rehabilitation after ICH, as the use of comparable treatments appear to be far more efficacious for ischemic injury.

Tracking Antioxidant Status in Spinal Cord Injured Rodents: A Voltammetric Method Suited for Clinical Translation

Spinal cord injury (SCI) triggers a signalling cascade that produces oxidative stress and damages the spinal cord. Voltammetry is a clinically accessible technique to detect, monitor, and guide correction of this potentially reversible secondary injury mechanism. Voltammetry is well suited for clinical translation because the method is inexpensive, simple, rapid, and portable. Voltammetry relies on the measurement of anodic current from a reagent-free, electrochemical reaction on the surface of a small electrode. The present study tested the use of new disposable carbon nanotube based screen printed electrodes (CNT-SPE) for the voltammetric measurement of antioxidant current (AC). Spinal cord, cerebrospinal fluid, and plasma were obtained from Sprague-Dawley rats after SCI. Locomotor function after SCI was assessed by using the Basso, Beattie, Bresnahan (BBB) score. The more severe SCI caused a decline in spinal cord AC419 at 10 minutes (P < 0.05), 4 hours (P < 0.0001), and 1 day (P < 0.01) after injury compared with sham controls. It also caused a decline in plasma AC375 at 1 (P < 0.001) and 3 days (P < 0.05) after injury compared with their pre-injury baseline. Spinal cord AC419 correlated with plasma AC375 (r = 0.49, P < 0.01) and BBB score (r = 0.66, P < 0.0001) at 1 day after SCI. AC measured by CNT-SPE demonstrated a time- and severity-dependent decline after SCI. Plasma AC could serve as a surrogate marker for spinal cord AC.

Transfer RNA-Derived Fragments and isomiRs Are Novel Components of Chronic TBI-Induced Neuropathology

Neuroinflammation is a secondary injury mechanism that evolves in the brain for months after traumatic brain injury (TBI). We hypothesized that an altered small non-coding RNA (sncRNA) signature plays a key role in modulating post-TBI secondary injury and neuroinflammation. At 3threemonths post-TBI, messenger RNA sequencing (seq) and small RNAseq were performed on samples from the ipsilateral thalamus and perilesional cortex of selected rats with a chronic inflammatory endophenotype, and sham-operated controls. The small RNAseq identified dysregulation of 2 and 19 miRNAs in the thalamus and cortex, respectively. The two candidates from the thalamus and the top ten from the cortex were selected for validation. In the thalamus, miR-146a-5p and miR-155-5p levels were upregulated, and in the cortex, miR-375-3p and miR-211-5p levels were upregulated. Analysis of isomiRs of differentially expressed miRNAs identified 3′ nucleotide additions that were increased after TBI. Surprisingly, we found fragments originating from 16 and 13 tRNAs in the thalamus and cortex, respectively. We further analyzed two upregulated fragments, 3′tRF-IleAAT and 3′tRF-LysTTT. Increased expression of the full miR-146a profile, and 3′tRF-IleAAT and 3′tRF-LysTTT was associated with a worse behavioral outcome in animals with chronic neuroinflammation. Our results highlight the importance of understanding the regulatory roles of as-yet unknown sncRNAs for developing better strategies to treat TBI and neuroinflammation.

Microstructural Tissue Changes in a Rat Model of Mild Traumatic Brain Injury.

Our study investigates the potential of diffusion MRI (dMRI), including diffusion tensor imaging (DTI), fixel-based analysis (FBA) and neurite orientation dispersion and density imaging (NODDI), to detect microstructural tissue abnormalities in rats after mild traumatic brain injury (mTBI). The brains of sham-operated and mTBI rats 35 days after lateral fluid percussion injury were imaged ex vivo in a 11.7-T scanner. Voxel-based analyses of DTI-, fixel- and NODDI-based metrics detected extensive tissue changes in directly affected brain areas close to the primary injury, and more importantly, also in distal areas connected to primary injury and indirectly affected by the secondary injury mechanisms. Histology revealed ongoing axonal abnormalities and inflammation, 35 days after the injury, in the brain areas highlighted in the group analyses. Fractional anisotropy (FA), fiber density (FD) and fiber density and fiber bundle cross-section (FDC) showed similar pattern of significant areas throughout the brain; however, FA showed more significant voxels in gray matter areas, while FD and FDC in white matter areas, and orientation dispersion index (ODI) in areas most damage based on histology. Region-of-interest (ROI)-based analyses on dMRI maps and histology in selected brain regions revealed that the changes in MRI parameters could be attributed to both alterations in myelinated fiber bundles and increased cellularity. This study demonstrates that the combination of dMRI methods can provide a more complete insight into the microstructural alterations in white and gray matter after mTBI, which may aid diagnosis and prognosis following a mild brain injury.