Preclinical Models Of Traumatic Brain Injury Research Articles

Abstract P394: Pre-Existing Hypertension Intensifies Blood Brain Barrier Leakage But Not Astrogliosis Or Microgliosis After Traumatic Brain Injury In Mice

The extent of brain damage accompanying traumatic brain injury (TBI) depends on the type and severity of insult and is modulated by age, sex, and comorbidities. Nearly half of all US adults suffer from hypertension. Not surprisingly, hypertension is the most common premorbid condition in people aged 50 or above hospitalized with a TBI. Hypertension has been linked to cerebrovascular damage, neuroinflammation and cognitive decline. Neurogenic hypertension is elevated blood pressure initiated by the local renin angiotensin system within the brain; often times involved in resistant hypertension (high blood pressure poorly responsive to common antihypertensives). Despite an overlap in several aspects of brain pathology induced by hypertension and triggered by TBI, little is understood about the impact of premorbid hypertension on outcomes following TBI. We hypothesize that hypertension induces mild blood-brain barrier leakiness and neuroinflammation, priming the brain for greater cerebrovascular damage after TBI. To test this hypothesis, mice were rendered hypertensive via subcutaneous infusion of 1000 ng/kg/min angiotensin-II (Ang-II) two weeks prior to and one week following induction of a moderate severity controlled cortical impact or sham injury. Vascular damage and astrocyte and microglia activation were examined using histology and immunohistochemistry. Quantification was performed using HALO image analysis software. Compared to injured normotensive mice, injured hypertensive mice exhibited significantly more IgG extravasation in the cortex denoting a potentiation of blood-brain barrier damage. Despite robust injury-induced astrogliosis and microgliosis, neither GFAP nor Iba1 immunostaining was further increased by hypertension. Microbleeds were observed more in the cortex and corpus callosum but much less in the hippocampi or thalami after injury and were equivalent in hypertensive and normotensive injured mice. This study contributes to laying the groundwork of identifying and characterizing hypertension as a significant premorbid risk factor for poor outcome after TBI and provides a logical basis for incorporation of pre-existing hypertension in preclinical models of TBI, increasing their clinical relevance and predictive validity.

Visual Impairment in Pre-Clinical Models of Mild Traumatic Brain Injury.

Impairment in visual function is common after traumatic brain injury (TBI) in the clinical setting, a phenomenon that translates to pre-clinical animal models as well. In Morris et al. (2021), we reported histological changes following weight-drop-induced TBI in a rodent model including retinal ganglion cell (RGC) loss, decreased electroretinogram (ERG) evoked potential, optic nerve diameter reduction, induced inflammation and gliosis, and loss of myelin accompanied by markedly impaired visual acuity. In this review, we will describe several pre-clinical TBI models that result in injuries to the visual system, indicating that visual function may be impaired following brain injury induced by a number of different injury modalities. This underscores the importance of understanding the role of the visual system and the potential detrimental sequelae to this sensory modality post-TBI. Given that most commonly employed behavioral tests such as the Elevated Plus Maze and Morris Water Maze rely on an intact visual system, interpretation of functional deficits in diffuse models may be confounded by off- target effects on the visual system.

An overview of preclinical models of traumatic brain injury (TBI): relevance to pathophysiological mechanisms.

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, affecting millions annually worldwide. Although the majority of TBI patients return to premorbid baseline, a subset of patient can develop persistent and often debilitating neurocognitive and behavioral changes. The etiology of TBI within the clinical setting is inherently heterogenous, ranging from sport related injuries, fall related injuries and motor vehicle accidents in the civilian setting, to blast injuries in the military setting. Animal models of TBI, offer the distinct advantage of controlling for injury modality, duration and severity. Furthermore, preclinical models of TBI have provided the necessary temporal opportunity to study the chronic neuropathological sequelae of TBI, including neurodegenerative sequelae such as tauopathy and neuroinflammation within the finite experimental timeline. Despite the high prevalence of TBI, there are currently no disease modifying regimen for TBI, and the current clinical treatments remain largely symptom based. The preclinical models have provided the necessary biological substrate to examine the disease modifying effect of various pharmacological agents and have imperative translational value. The current review will include a comprehensive survey of well-established preclinical models, including classic preclinical models including weight drop, blast injury, fluid percussion injury, controlled cortical impact injury, as well as more novel injury models including closed-head impact model of engineered rotational acceleration (CHIMERA) models and closed-head projectile concussive impact model (PCI). In addition to rodent preclinical models, the review will include an overview of other species including large animal models and Drosophila. There are major neuropathological perturbations post TBI captured in various preclinical models, which include neuroinflammation, calcium dysregulation, tauopathy, mitochondrial dysfunction and oxidative stress, axonopathy, as well as glymphatic system disruption. The preclinical models of TBI continue to offer valuable translational insight, as well as essential neurobiological basis to examine specific disease modifying therapeutic regimen.

Deplete and repeat: microglial CSF1R inhibition and traumatic brain injury.

Traumatic brain injury (TBI) is a public health burden affecting millions of people. Sustained neuroinflammation after TBI is often associated with poor outcome. As a result, increased attention has been placed on the role of immune cells in post-injury recovery. Microglia are highly dynamic after TBI and play a key role in the post-injury neuroinflammatory response. Therefore, microglia represent a malleable post-injury target that could substantially influence long-term outcome after TBI. This review highlights the cell specific role of microglia in TBI pathophysiology. Microglia have been manipulated via genetic deletion, drug inhibition, and pharmacological depletion in various pre-clinical TBI models. Notably, colony stimulating factor 1 (CSF1) and its receptor (CSF1R) have gained much traction in recent years as a pharmacological target on microglia. CSF1R is a transmembrane tyrosine kinase receptor that is essential for microglia proliferation, differentiation, and survival. Small molecule inhibitors targeting CSF1R result in a swift and effective depletion of microglia in rodents. Moreover, discontinuation of the inhibitors is sufficient for microglia repopulation. Attention is placed on summarizing studies that incorporate CSF1R inhibition of microglia. Indeed, microglia depletion affects multiple aspects of TBI pathophysiology, including neuroinflammation, oxidative stress, and functional recovery with measurable influence on astrocytes, peripheral immune cells, and neurons. Taken together, the data highlight an important role for microglia in sustaining neuroinflammation and increasing risk of oxidative stress, which lends to neuronal damage and behavioral deficits chronically after TBI. Ultimately, the insights gained from CSF1R depletion of microglia are critical for understanding the temporospatial role that microglia develop in mediating TBI pathophysiology and recovery.

Pediatric Traumatic Brain Injury: Models, Therapeutics, and Outcomes.

Pediatric traumatic brain injury (TBI) is a significant healthcare issue, but potential treatments are absent despite robust investigation in several clinical trials. Factors attributed to clinical TBI, such as heterogeneity of injury and single-dose pharmacological treatments as well as timing of administration, may be reasons for the negative studies. Preclinical models of TBI can reduce some of the impediments by highlighting differences in injury depending on injury severity and location and by conducting dose response studies, thus providing better therapeutic targets and pharmacological profiles for clinical use. In this chapter, there were sufficient reports to make comparisons between the models in terms of pathophysiology, behavioral dysfunction, and the efficacy of therapeutic interventions. The models used to date include controlled cortical impact (CCI), weight drop, fluid percussion, and abusive head trauma. Several therapeutics were identified after CCI injury but none in the other models, which underscores the need for studies evaluating the therapies reported after CCI injury as well as novel potential approaches.

Neuroprotective potential of intranasally delivered L-myc immortalized human neural stem cells in female rats after a controlled cortical impact injury

Efficacious stem cell-based therapies for traumatic brain injury (TBI) depend on successful delivery, migration, and engraftment of stem cells to induce neuroprotection. L-myc expressing human neural stem cells (LMNSC008) demonstrate an inherent tropism to injury sites after intranasal (IN) administration. We hypothesize that IN delivered LMNSC008 cells migrate to primary and secondary injury sites and modulate biomarkers associated with neuroprotection and tissue regeneration. To test this hypothesis, immunocompetent adult female rats received either controlled cortical impact injury or sham surgery. LMNSC008 cells or a vehicle were administered IN on postoperative days 7, 9, 11, 13, 15, and 17. The distribution and migration of eGFP-expressing LMNSC008 cells were quantified over 1 mm-thick optically cleared (CLARITY) coronal brain sections from TBI and SHAM controls. NSC migration was observed along white matter tracts projecting toward the hippocampus and regions of TBI. ELISA and Nanostring assays revealed a shift in tissue gene expression in LMNSC008 treated rats relative to controls. LMNSC008 treatment reduced expression of genes and pathways involved in inflammatory response, microglial function, and various cytokines and receptors. Our proof-of-concept studies, although preliminary, support the rationale of using intranasal delivery of LMNSC008 cells for functional studies in preclinical models of TBI and provide support for potential translatability in TBI patients.

Non-Invasive Vagus Nerve Stimulation Improves Brain Lesion Volume and Neurobehavioral Outcomes in a Rat Model of Traumatic Brain Injury.

Abstract Traumatic brain injury (TBI) continues to be a major cause of death and disability worldwide. This study assessed the effectiveness of non-invasive vagus nerve stimulation (nVNS) in reducing brain lesion volume and improving neurobehavioral performance in a rat model of TBI. Animals were randomized into three experimental groups: (1) TBI with sham stimulation treatment (Control), (2) TBI treated with five lower doses (2-min) nVNS, and (3) TBI treated with five higher doses (2 × 2-min) nVNS. We used the gammaCore nVNS device to deliver stimulations. Magnetic resonance imaging studies were performed 1 and 7 days post-injury to confirm lesion volume. We observed smaller brain lesion volume in the lower dose nVNS group compared with the control group on days 1 and 7. The lesion volume for the higher dose nVNS group was significantly smaller than either the lower dose nVNS or the control groups on days 1 and 7 post-injury. The apparent diffusion coefficient differences between the ipsilateral and contralateral hemispheres on day 1 were significantly smaller for the higher dose (2 × 2 min) nVNS group than for the control group. Voxel-based morphometry analysis revealed an increase in the ipsilateral cortical volume in the control group caused by tissue deformation and swelling. On day 1, these abnormal volume changes were 13% and 55% smaller in the lower dose and higher dose nVNS groups, respectively, compared with the control group. By day 7, nVNS dampened cortical volume loss by 35% and 89% in the lower dose and higher dose nVNS groups, respectively, compared with the control group. Rotarod, beam walking, and anxiety performances were significantly improved in the higher-dose nVNS group on day 1 compared with the control group. The anxiety indices were also improved on day 7 post-injury compared with the control and the lower-dose nVNS groups. In conclusion, the higher dose nVNS (five 2 × 2-min stimulations) reduced brain lesion volume to a level that further refined the role of nVNS therapy for the acute treatment of TBI. Should nVNS prove effective in additional pre-clinical TBI models and later in clinical settings, it would have an enormous impact on the clinical practice of TBI in both civilian and military settings, as it can easily be adopted into routine clinical practice.

Empowering Data Sharing and Analytics through the Open Data Commons for Traumatic Brain Injury Research.

Traumatic brain injury (TBI) is a major public health problem. Despite considerable research deciphering injury pathophysiology, precision therapies remain elusive. Here, we present large-scale data sharing and machine intelligence approaches to leverage TBI complexity. The Open Data Commons for TBI (ODC-TBI) is a community-centered repository emphasizing Findable, Accessible, Interoperable, and Reusable data sharing and publication with persistent identifiers. Importantly, the ODC-TBI implements data sharing of individual subject data, enabling pooling for high-sample-size, feature-rich data sets for machine learning analytics. We demonstrate pooled ODC-TBI data analyses, starting with descriptive analytics of subject-level data from 11 previously published articles (N = 1250 subjects) representing six distinct pre-clinical TBI models. Second, we perform unsupervised machine learning on multi-cohort data to identify persistent inflammatory patterns across different studies, improving experimental sensitivity for pro- versus anti-inflammation effects. As funders and journals increasingly mandate open data practices, ODC-TBI will create new scientific opportunities for researchers and facilitate multi-data-set, multi-dimensional analytics toward effective translation.

Translationally Relevant Magnetic Resonance Imaging Markers in a Ferret Model of Closed Head Injury.

Pre-clinical models of traumatic brain injury (TBI) have been the primary experimental tool for understanding the potential mechanisms and cellular alterations that follow brain injury, but the human relevance and translational value of these models are often called into question. Efforts to better recapitulate injury biomechanics and the use of non-rodent species with neuroanatomical similarities to humans may address these concerns and promise to advance experimental studies toward clinical impact. In addition to improving translational aspects of animal models, it is also advantageous to establish pre-clinical outcomes that can be directly compared with the same outcomes in humans. Non-invasive imaging and particularly MRI is promising for this purpose given that MRI is a primary tool for clinical diagnosis and at the same time increasingly available at the pre-clinical level. The objective of this study was to identify which commonly used radiologic markers of TBI outcomes can be found also in a translationally relevant pre-clinical model of TBI. The ferret was selected as a human relevant species for this study with folded cortical geometry and relatively high white matter content and the closed head injury model of engineered rotation and acceleration (CHIMERA) TBI model was selected for biomechanical similarities to human injury. A comprehensive battery of MRI protocols based on common data elements (CDEs) for human TBI was collected longitudinally for the identification of MRI markers and voxelwise analysis of T2, contrast enhancement and diffusion tensor MRI values. The most prominent MRI findings were consistent with focal hemorrhage and edema in the brain stem region following high severity injury as well as vascular and meningeal injury evident by contrast enhancement. While conventional MRI outcomes were not highly conspicuous in less severe cases, quantitative voxelwise analysis indicated diffusivity and anisotropy alterations in the acute and chronic periods after TBI. The main conclusions of this study support the translational relevance of closed head TBI models in intermediate species and identify brain stem and meningeal vulnerability. Additionally, the MRI findings highlight a subset of CDEs with promise to bridge pre-clinical studies with human TBI outcomes.

Systematic review and meta-analysis of preclinical studies testing mesenchymal stromal cells for traumatic brain injury

Mesenchymal stromal cells (MSCs) are widely used in preclinical models of traumatic brain injury (TBI). Results are promising in terms of neurological improvement but are hampered by wide variability in treatment responses. We made a systematic review and meta-analysis: (1) to assess the quality of evidence for MSC treatment in TBI rodent models; (2) to determine the effect size of MSCs on sensorimotor function, cognitive function, and anatomical damage; (3) to identify MSC-related and protocol-related variables associated with greater efficacy; (4) to understand whether MSC manipulations boost therapeutic efficacy. The meta-analysis included 80 studies. After TBI, MSCs improved sensorimotor and cognitive deficits and reduced anatomical damage. Stratified meta-analysis on sensorimotor outcome showed similar efficacy for different MSC sources and for syngeneic or xenogenic transplants. Efficacy was greater when MSCs were delivered in the first-week post-injury, and when implanted directly into the lesion cavity. The greatest effect size was for cells embedded in matrices or for MSC-derivatives. MSC therapy is effective in preclinical TBI models, improving sensorimotor, cognitive, and anatomical outcomes, with large effect sizes. These findings support clinical studies in TBI.

Cell-Based Therapies for Traumatic Brain Injury: Therapeutic Treatments and Clinical Trials.

Traumatic brain injury (TBI) represents physical damage to the brain tissue that induces transitory or permanent neurological disabilities. TBI contributes to 50% of all trauma deaths, with many enduring long-term consequences and significant medical and rehabilitation costs. There is currently no therapy to reverse the effects associated with TBI. An increasing amount of research has been undertaken regarding the use of different stem cells (SCs) to treat the consequences of brain damage. Neural stem cells (NSCs) (adult and embryonic) and mesenchymal stromal cells (MSCs) have shown efficacy in pre-clinical models of TBI and in their introduction to clinical research. The purpose of this review is to provide an overview of TBI and the state of clinical trials aimed at evaluating the use of stem cell-based therapies in TBI. The primary aim of these studies is to investigate the safety and efficacy of the use of SCs to treat this disease. Although an increasing number of studies are being carried out, few results are currently available. In addition, we present our research regarding the use of cell therapy in TBI. There is still a significant lack of understanding regarding the cell therapy mechanisms for the treatment of TBI. Thus, future studies are needed to evaluate the feasibility of the transplantation of SCs in TBI.

Neuropharmacology in traumatic brain injury: from preclinical to clinical neuroprotection?

Traumatic brain injury (TBI) constitutes a major health problem worldwide and is a leading cause of death and disability in individuals, contributing to devastating socioeconomic consequences. Despite numerous promising pharmacological strategies reported as neuroprotective in preclinical studies, the translation to clinical trials always failed, albeit the great diversity of therapeutic targets evaluated. In this review, first, we described epidemiologic features, causes, and primary and secondary injuries of TBI. Second, we outlined the current literature on animal models of TBI, and we described their goals, their advantages and disadvantages according to the species used, the type of injury induced, and their clinical relevance. Third, we defined the concept of neuroprotection and discussed its evolution. We also identified the reasons that might explain the failure of clinical translation. Then, we reviewed post‐TBI neuroprotective treatments with a focus on the following pleiotropic drugs, considered “low hanging fruit” with high probability of success: glitazones, glibenclamide, statins, erythropoietin, and progesterone, that were largely tested and demonstrated efficient in preclinical models of TBI. Finally, our review stresses the need to establish a close cooperation between basic researchers and clinicians to ensure the best clinical translation for neuroprotective strategies for TBI.

A Role for Nanoparticles in Treating Traumatic Brain Injury.

Traumatic brain injury (TBI) is one of the main causes of disability in children and young adults, as well as a significant concern for elderly individuals. Depending on the severity, TBI can have a long-term impact on the quality of life for survivors of all ages. The primary brain injury can result in severe disability or fatality, and secondary brain damage can increase the complexities in cellular, inflammatory, neurochemical, and metabolic changes in the brain, which can last decades post-injury. Thus, survival from a TBI is often accompanied by lifelong disabilities. Despite the significant morbidity, mortality, and economic loss, there are still no effective treatment options demonstrating an improved outcome in a large multi-center Phase III trial, which can be partially attributed to poor target engagement of delivered therapeutics. Thus, there is a significant unmet need to develop more effective delivery strategies to overcome the biological barriers that would otherwise inhibit transport of materials into the brain to prevent the secondary long-term damage associated with TBI. The complex pathology of TBI involving the blood-brain barrier (BBB) has limited the development of effective therapeutics and diagnostics. Therefore, it is of great importance to develop novel strategies to target the BBB. The leaky BBB caused by a TBI may provide opportunities for therapeutic delivery via nanoparticles (NP). The focus of this review is to provide a survey of NP-based strategies employed in preclinical models of TBI and to provide insights for improved NP based diagnostic or treatment approaches. Both passive and active delivery of various NPs for TBI are discussed. Finally, potential therapeutic targets where improved NP-mediated delivery could increase target engagement are identified with the overall goal of providing insight into open opportunities for NP researchers to begin research in TBI.

The Importance of Inter-Species Variation in Traumatic Brain Injury-Induced Alterations of Microglial-Axonal Interactions.

Interactions between microglia and neuronal components are important for normal CNS function. They are also associated with neuroinflammation and many pathological processes and several studies have explored these interactions in terms of phagocytic engulfment. Much progress has also been made in understanding the consequences of chronic neuroinflammatory changes following trauma. However, little is known about acute alterations to these physical non-phagocytic microglial-neuronal interactions following traumatic brain injury (TBI), and particularly to what degree these post-injury interactions may be influenced by the animal species utilized in pre-clinical models of TBI. To investigate these problems, we evaluated the physical interactions between microglia and injured axons acutely (6 h and 1 day) following central fluid percussion injury (cFPI) in both rats and micro pigs. The physical interactions between Iba-1+ microglia and either normal MBP+ myelinated fibers or APP+ injured axonal swellings in the thalamus were assessed following injury or sham via quantitative image analysis of 3D confocal micrographs. The results indicated that the physical interactions between microglia and injured axonal swellings decreased by nearly half in rats 6 h following cFPI but was consistent with sham control at 1 day post-cFPI. This reduction was also observed in non-injured intact fibers at both timepoints following TBI in the rat. Microglial process interactions with injured axons in the micro pig, however, increased nearly 2-fold compared to interactions with intact axonal segments 1 day post-cFPI. This study shows that the species utilized for in vivo pre-clinical studies influences the manner in which microglial-axonal interactions change following TBI. These species differences can be leveraged to further our understanding of the mechanisms involved in microglial process convergence and how these neuro-immune interactions alter the progression of axonal injury following TBI.

Delayed Hypoxemia after Traumatic Brain Injury Exacerbates Long-Term Behavioral Deficits.

Hypoxemia during initial stabilization of patients with severe traumatic brain injury (TBI) has been associated with poorer outcomes. However, the effects of delayed hypoxemia occurring during intensive care post-TBI on outcome is unclear. Pre-clinical models of TBI have rarely shown cognitive or behavioral deficits beyond 6 weeks post-injury and commonly have not included modeling of secondary insults. We have previously developed a murine model of TBI followed by delayed hypoxemia to model the secondary insult of hypoxemia and brain hypoxia occurring in the intensive care setting. Understanding long-term effects of delayed hypoxemia post-TBI in our murine model is critical for future testing of candidate therapeutics targeting secondary brain hypoxia. For this study, forty 5-week-old male mice were randomized to controlled cortical impact (CCI; N = 24) or sham surgery (N = 16). One day later, awake animals were randomized to 60 min of hypoxemia or normoxemia. Six months after initial injury, animals underwent behavior testing (Morris water maze, social interaction, and tail suspension) before euthanasia for immunohistochemistry (IHC) assessments. At 6 months post-injury, mice experiencing CCI and hypoxemia (CCI+H) had longer swim distances to the hidden platform (51 cm) compared to CCI alone (26 cm) or sham animals (22 cm). During social interaction assessments, CCI + H mice spent less time interacting with novel stimulus mice (79 sec) than CCI alone (101 sec) or sham animals (139 sec). CCI + H had larger lesion volumes compared to CCI alone (14.0% vs. 9.9%; p < 0.003). Glial fibrillary acidic protein IHC at 6 months post-injury demonstrated increased astrogliosis in the ipsilateral white matter of CCI + H compared to CCI alone. To summarize, this clinically relevant model of delayed hypoxia post-TBI resulted in long-term behavioral deficits and evidence of exacerbated structural injury.

Controlled Cortical Impact in the Rat.

Traumatic brain injury (TBI) is a major cause of death and disability world-wide. Following initial injury, TBI patients can face long-term disability in the form of cognitive, physical, and psychological deficits, depending on the severity and location of injury. This results in an economic burden in the United States estimated to be $60 billion due to health-care costs and loss of productivity. TBI is a significant area of active research interest for both military and civilian medicine. Numerous pre-clinical animal models of TBI are used to characterize the anatomical and physiological pathways involved and to evaluate therapeutic interventions. Due to its flexibility and scalability, controlled cortical impact (CCI) is one of the most commonly used preclinical TBI models. This unit provides a basic CCI protocol performed in the rat. © 2017 by John Wiley & Sons, Inc.

Role of Interleukin-10 in Acute Brain Injuries.

Interleukin-10 (IL-10) is an important anti-inflammatory cytokine expressed in response to brain injury, where it facilitates the resolution of inflammatory cascades, which if prolonged causes secondary brain damage. Here, we comprehensively review the current knowledge regarding the role of IL-10 in modulating outcomes following acute brain injury, including traumatic brain injury (TBI) and the various stroke subtypes. The vascular endothelium is closely tied to the pathophysiology of these neurological disorders and research has demonstrated clear vascular endothelial protective properties for IL-10. In vitro and in vivo models of ischemic stroke have convincingly directly and indirectly shown IL-10-mediated neuroprotection; although clinically, the role of IL-10 in predicting risk and outcomes is less clear. Comparatively, conclusive studies investigating the contribution of IL-10 in subarachnoid hemorrhage are lacking. Weak indirect evidence supporting the protective role of IL-10 in preclinical models of intracerebral hemorrhage exists; however, in the limited number of clinical studies, higher IL-10 levels seen post-ictus have been associated with worse outcomes. Similarly, preclinical TBI models have suggested a neuroprotective role for IL-10; although, controversy exists among the several clinical studies. In summary, while IL-10 is consistently elevated following acute brain injury, the effect of IL-10 appears to be pathology dependent, and preclinical and clinical studies often paradoxically yield opposite results. The pronounced and potent effects of IL-10 in the resolution of inflammation and inconsistency in the literature regarding the contribution of IL-10 in the setting of acute brain injury warrant further rigorously controlled and targeted investigation.

Accumulation of nanoparticles after acute traumatic brain injury is particle size dependent

Event Abstract Back to Event Accumulation of nanoparticles after acute traumatic brain injury is particle size dependent Vimala Bharadwaj1, Jonathan Lifshitz2, 3, David P. Adelson2, Vikram D. Kodibagkar1 and Sarah E. Stabenfeldt1 1 Arizona State University, School of Biological and Health Systems Engineering, United States 2 Barrow Neurological Institute at Phoenix Children's Hospital, Translational Neurotrauma Research Program, United States 3 College of Medicine-Phoenix, University of Arizona, United States Introduction: Traumatic brain injury (TBI) is a major cause of death and permanent neurological disability, an estimated of 1.7 million TBI occur annually and account for over 50,000 deaths in the U.S. TBI is initiated by a mechanical insult that leads to a host of cellular and molecular alterations, including transient blood-brain-barrier (BBB) breakdown. Nanoparticles (NP) have played an important role as diagnostic and therapeutic (theranostic) agents in various diseases, but, limited permeability across BBB is a major obstacle for NP-based approaches for neural disease/injury. Previous studies with pre-clinical TBI models demonstrated permeability of large molecules such as Evans blue[1] or horseradish peroxidase[2] (~5nm) post-injury. There is a critical gap in understanding the behavior of theranostic sized (>10nm) NP delivery after TBI. Therefore, the objective of this study was to investigate the effect of NP’s size on extravasation after TBI. Materials and Methods: Specifically, carboxylated polystyrene NPs of 20, 40, 100, and 500nm with unique fluorescent spectra were pegylated to both increase circulation time and neutralize the surface charge of the nanoparticles. Pegylated-NP cocktail were intravenously injected in mice (n=4 retro-orbital injection) immediately, 2h, 12h and 23h post-injury (controlled cortical impact) and allowed to circulate for 1h prior to sacrifice and perfusion. The brains were frozen, sectioned, and imaged (8 sections per animal, four animals per cohort) using confocal microscopy. Images were analyzed using ImageJ and the total number of positive pixels was quantified for each NP over the time course. Results and Discussion: Pegylation of NPs led to modest increases in hydrodynamic diameter (~5-7nm above baseline diameter) and reduced zeta-potential (range: -9mV to -29mV). Histological analysis demonstrated the presence of pegylated-NPs exclusively within the injury penumbra, indicating BBB breakdown and accumulation post injury. Results showed maximum accumulation occurred at 1h post injury for all the NPs compared to their respective contralateral region. The accumulation of each NP was reduced over the time course from 1h to 24h, compared to the contralateral region. Accumulation of 40nm particles was highest compared to 20nm, 100nm and 500nm at each time point. NPs accumulate at the injury site due to leaky vasculature, leading to enhanced permeability and retention effect. Conclusion: We have demonstrated the potential for NP accumulation up to 24h post injury, with 40nm particles having highest accumulation. Thus, the short-lived BBB permeability post-injury can be effectively utilized to deliver NP-based theranostics for TBI. Further characterization of NP accumulation using injury models such as fluid-percussion, will provide insights as to the full utility of NP-based theranostics agents for TBI. Flinn Founda5on (SES, VDK, JL, PDA); NIH (1DP2HD084067)

A Combination Therapy of Nicotinamide and Progesterone Improves Functional Recovery following Traumatic Brain Injury.

Neuroprotection, recovery of function, and gene expression were evaluated in an animal model of traumatic brain injury (TBI) after a combination treatment of nicotinamide (NAM) and progesterone (Prog). Animals received a cortical contusion injury over the sensorimotor cortex, and were treated with either Vehicle, NAM, Prog, or a NAM/Prog combination for 72 h and compared with a craniotomy only (Sham) group. Animals were assessed in a battery of behavioral, sensory, and both fine and gross motor tasks, and given histological assessments at 24 h post-injury to determine lesion cavity size, degenerating neurons, and reactive astrocytes. Microarray-based transcriptional profiling was used to determine treatment-specific changes on gene expression. Our results confirm the beneficial effects of treatment with either NAM or Prog, demonstrating significant improvements in recovery of function and a reduction in lesion cavitation, degenerating neurons, and reactive astrocytes 24 h post-injury. The combination treatment of NAM and Prog led to a significant improvement in both neuroprotection at 24 h post-injury and recovery of function in sensorimotor related tasks when compared with individual treatments. The NAM/Prog-treated group was the only treatment group to show a significant reduction of cortical loss 24 h post-injury. The combination appears to affect inflammatory and immune processes, reducing expression of a significant number of genes in both pathways. Further preclinical trials using NAM and Prog as a combination treatment should be conducted to identify the window of opportunity, determine the optimal duration of treatment, and evaluate the combination in other pre-clinical models of TBI.

Pre and post-injury environmental enrichment effects functional recovery following medial frontal cortical contusion injury in rats

The rodent has been the preferred research model for evaluating the mechanisms related to, and potential treatments for, traumatic brain injury (TBI). Many therapies previously determined to be effective in pre-clinical investigations have failed to show the same effectiveness in clinical trials. The environment a rodent is housed in plays an important role in brain and behavioral development. Housing rodents in non-enriched environments significantly alters the development of the rodent brain and its behavioral profile, negatively impacting the ecological validity of the rodent model. This investigation employed 113 male Long-Evans rats assigned to either an enriched environment (EE) or standard environment (SE) from post-natal day 25. At four months of age, rats received either a controlled cortical impact (CCI) to the medial frontal cortex (mFC) or sham injury. Rats assigned to EE or SE pre-injury were re-assigned to remain in, or switch to, EE or SE post-injury. The open-field test (OFT), vermicelli handling test (VHT) Morris water maze (MWM), and rotor-rod (RR), were used to evaluate the animals response to TBI. The data from the current investigation indicates that the performance of TBI rats assigned to pre-injury EE was improved on the MWM compared to the TBI rats assigned to pre-injury SE. However, those that were reared in the EE performed better on the MWM if placed into a SE post-injury as compared to those placed into the EE after insult. The TBI and sham groups that were raised, and remained, in the SE performed worse than any of the EE groups on the RR. TBI rats that were placed in the EE had larger cortices and more cells in the hippocampus than the TBI rats housed in the SE. These data strongly suggest that the pre-injury housing environment should be considered as investigators refine pre-clinical models of TBI.