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Orbach G, Melendes EJ, Warren K, Qiu J, Meehan WP, Mannix R, Guilhaume-Correa F. Visual Impairment in Pre-Clinical Models of Mild Traumatic Brain Injury. J Neurotrauma 2024; 41:1842-1852. [PMID: 38497739 DOI: 10.1089/neu.2023.0574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2024] Open
Abstract
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.
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Affiliation(s)
- Gabriella Orbach
- Tufts University School of Medicine, Boston, Massachusetts, USA
- Division of Emergency Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Eva J Melendes
- Division of Emergency Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Kaitlyn Warren
- Division of Emergency Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Jianhua Qiu
- Division of Emergency Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
| | - William P Meehan
- Division of Sports Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
- The Micheli Center for Sports Injury Prevention, Waltham, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
| | - Rebekah Mannix
- Division of Emergency Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
| | - Fernanda Guilhaume-Correa
- Division of Emergency Medicine, Boston Children's Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
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2
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Katchur NJ, Notterman DA. Recent insights from non-mammalian models of brain injuries: an emerging literature. Front Neurol 2024; 15:1378620. [PMID: 38566857 PMCID: PMC10985199 DOI: 10.3389/fneur.2024.1378620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 02/26/2024] [Indexed: 04/04/2024] Open
Abstract
Traumatic brain injury (TBI) is a major global health concern and is increasingly recognized as a risk factor for neurodegenerative diseases including Alzheimer's disease (AD) and chronic traumatic encephalopathy (CTE). Repetitive TBIs (rTBIs), commonly observed in contact sports, military service, and intimate partner violence (IPV), pose a significant risk for long-term sequelae. To study the long-term consequences of TBI and rTBI, researchers have typically used mammalian models to recapitulate brain injury and neurodegenerative phenotypes. However, there are several limitations to these models, including: (1) lengthy observation periods, (2) high cost, (3) difficult genetic manipulations, and (4) ethical concerns regarding prolonged and repeated injury of a large number of mammals. Aquatic vertebrate model organisms, including Petromyzon marinus (sea lampreys), zebrafish (Danio rerio), and invertebrates, Caenorhabditis elegans (C. elegans), and Drosophila melanogaster (Drosophila), are emerging as valuable tools for investigating the mechanisms of rTBI and tauopathy. These non-mammalian models offer unique advantages, including genetic tractability, simpler nervous systems, cost-effectiveness, and quick discovery-based approaches and high-throughput screens for therapeutics, which facilitate the study of rTBI-induced neurodegeneration and tau-related pathology. Here, we explore the use of non-vertebrate and aquatic vertebrate models to study TBI and neurodegeneration. Drosophila, in particular, provides an opportunity to explore the longitudinal effects of mild rTBI and its impact on endogenous tau, thereby offering valuable insights into the complex interplay between rTBI, tauopathy, and neurodegeneration. These models provide a platform for mechanistic studies and therapeutic interventions, ultimately advancing our understanding of the long-term consequences associated with rTBI and potential avenues for intervention.
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Affiliation(s)
- Nicole J. Katchur
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States
- Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ, United States
| | - Daniel A. Notterman
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States
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3
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Wilson RJ, Bell MR, Giordano KR, Seyburn S, Kozlowski DA. Repeat subconcussion in the adult rat gives rise to behavioral deficits similar to a single concussion but different depending upon sex. Behav Brain Res 2023; 438:114206. [PMID: 36356721 DOI: 10.1016/j.bbr.2022.114206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 10/20/2022] [Accepted: 11/04/2022] [Indexed: 11/09/2022]
Abstract
Although concussions are a popular focus of neurotrauma research, subconcussions occur with higher frequency but are less well-studied. A subconcussion is an impact to the head that does not result in immediately diagnosable concussion but can result in later neurological consequences. Repeat subconcussions can produce behavioral impairments and neuropathology that is similar to or worse than those seen following a single concussion. The current study modified a previously established closed head injury model of concussion to create a subconcussion model and examines sex differences in behavioral responses to repeated subconcussion in the adult rat. Rats received a single concussion, single or repeat subconcussions, or no impact and behavior was monitored from 2 h through 31 days post-injury. A single concussion or repeat subconcussion resulted in deficits in locomotion, righting reflexes, and recognition memory. The degree of deficit induced by repeat subconcussions were either similar (righting reflexes) or greater/more persistent (locomotor deficits and recognition memory) than that of a concussion. Single subconcussion resulted in acute deficits that were mild and limited to righting reflexes and locomotion. Sex differences were observed in responses to repeat subconcussion: females showed greater deficits in righting reflexes, locomotion, and vestibular function, while males showed greater alterations in anxiety and depressive-like behavior. This study established a model of subconcussive impact where a single subconcussive impact resulted in minimal behavioral deficits but repeat subconcussions resulted in deficits similar to or worse than a single concussion. Our data also suggest sex differences in behavioral responses to both concussive and subconcussive impacts.
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Affiliation(s)
- Rebecca J Wilson
- Department of Biological Sciences, DePaul University, 2325 N. Clifton, Chicago, IL, USA.
| | - Margaret R Bell
- Department of Biological Sciences, DePaul University, 2325 N. Clifton, Chicago, IL, USA; Department of Health Sciences, DePaul University, 1110 W. Belden, Chicago, IL, USA.
| | - Katherine R Giordano
- Department of Biological Sciences, DePaul University, 2325 N. Clifton, Chicago, IL, USA.
| | - Serena Seyburn
- Department of Biological Sciences, DePaul University, 2325 N. Clifton, Chicago, IL, USA.
| | - Dorothy A Kozlowski
- Department of Biological Sciences, DePaul University, 2325 N. Clifton, Chicago, IL, USA; Neuroscience Program, DePaul University, 2325 N. Clifton, Chicago, IL, USA.
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4
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White MR, VandeVord PJ. Regional variances depict a unique glial-specific inflammatory response following closed-head injury. Front Cell Neurosci 2023; 17:1076851. [PMID: 36909284 PMCID: PMC9996631 DOI: 10.3389/fncel.2023.1076851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 01/27/2023] [Indexed: 02/17/2023] Open
Abstract
Mild traumatic brain injuries (mTBI) constitute a significant health concern with clinical symptoms ranging from headaches to cognitive deficits. Despite the myriad of symptoms commonly reported following this injury, there is still a lack of knowledge on the various pathophysiological changes that occur. Preclinical studies are at the forefront of discovery delineating the changes that occur within this heterogeneous injury, with the emergence of translational models such as closed-head impact models allowing for further exploration of this injury mechanism. In the current study, male rats were subjected to a closed-head controlled cortical impact (cCCI), producing a concussion (mTBI). The pathological effects of this injury were then evaluated using immunoflourescence seven days following. The results exhibited a unique glial-specific inflammatory response, with both the ipsilateral and contralateral sides of the cortex and hippocampus showing pathological changes following impact. Overall these findings are consistent with glial changes reported following concussions and may contribute to subsequent symptoms.
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Affiliation(s)
- Michelle R White
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
| | - Pamela J VandeVord
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States.,Salem VA Medical Center, Salem, VA, United States
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5
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Clay AM, Carr R, Dubien J, To F. Short-term behavioral and histological changes in a rodent model of mild traumatic brain injury. BIOMEDICAL ENGINEERING ADVANCES 2022. [DOI: 10.1016/j.bea.2022.100061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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6
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Defining Experimental Variability in Actuator-Driven Closed Head Impact in Rats. Ann Biomed Eng 2022; 50:1187-1202. [PMID: 35994166 DOI: 10.1007/s10439-022-03012-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 07/04/2022] [Indexed: 11/01/2022]
Abstract
Traumatic brain injury (TBI) is a world-wide health challenge that lacks tools for diagnosis and treatment. There is a need for translational preclinical models to effectively design clinical tools, however, the diversity of models is a barrier to reproducible studies. Actuator-driven closed head impact (AD-CHI) models have translational advantages in replicating the pathophysiological and behavioral outcomes resulting from impact TBI. The main advantages of AD-CHI protocols include versatility of impact parameters such as impact angle, velocity, depth, and dwell time with the ability to interchange tip types, leading to consistent outcomes without the need for craniectomy. Sources of experimental variability within AD-CHI rat models are identified within this review with the aim of supporting further characterization to improve translational value. Primary areas of variability may be attributed to lack of standardization of head stabilization methods, reporting of tip properties, and performance of acute neurological assessments. AD-CHI models were also found to be more prevalently used among pediatric and repeated TBI paradigms. As this model continues to grow in use, establishing the relationships between impact parameters and associated injury outcomes will reduce experimental variability between research groups and encourage meaningful discussions as the community moves towards common data elements.
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Foecking EM, Segismundo AB, Lotesto KM, Westfall EJ, Bolduan AJ, Peter TK, Wallace DG, Kozlowski DA, Stubbs EB, Marzo SJ, Byram SC. Testosterone treatment restores vestibular function by enhancing neuronal survival in an experimental closed-head repetitive mild traumatic brain injury model. Behav Brain Res 2022; 433:113998. [PMID: 35809692 DOI: 10.1016/j.bbr.2022.113998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 06/22/2022] [Accepted: 07/05/2022] [Indexed: 11/28/2022]
Abstract
Repetitive mild traumatic brain injury (rmTBI) results in a myriad of symptoms, including vestibular impairment. The mechanisms underlying vestibular dysfunction in rmTBI patients remain poorly understood. Concomitantly, acute hypogonadism occurs following TBI and can persist chronically in many patients. Using a repetitive mild closed-head animal model of TBI, the role of testosterone on vestibular function was tested. Male Long Evans Hooded rats were randomly divided into sham or rmTBI groups. Significant vestibular deficits were observed both acutely and chronically in the rmTBI groups. Systemic testosterone was administered after the development of chronic vestibular dysfunction. rmTBI animals given testosterone showed improved vestibular function that was sustained for 175 days post-rmTBI. Significant vestibular neuronal cell loss was, however, observed in the rmTBI animals compared to Sham animals at 175 days post-rmTBI and testosterone treatment significantly improved vestibular neuronal survival. Taken together, these data demonstrate a critical restorative role of testosterone in vestibular function following rmTBI. This study has important clinical implications because it identifies testosterone treatment as a viable therapeutic strategy for the long-term recovery of vestibular function following TBI.
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Affiliation(s)
- Eileen M Foecking
- Loyola University Chicago, Department of Otolaryngology, Burn Shock Trauma Research Institute, Loyola University Chicago, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America; Burn Shock Trauma Research Institute, Loyola University Chicago, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America; Edward Hines Jr. VA Hospital Research Service, Hines, IL 60141, the United States of America.
| | - Arthur B Segismundo
- Loyola University of Chicago, Biomedical Graduate School, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America.
| | - Krista M Lotesto
- Burn Shock Trauma Research Institute, Loyola University Chicago, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America.
| | - Edward J Westfall
- Loyola University Medical Center, Department of Otolaryngology, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America.
| | - Alyssa J Bolduan
- Loyola University Medical Center, Department of Otolaryngology, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America.
| | - Tony K Peter
- Loyola University Medical Center, Department of Otolaryngology, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America.
| | - Douglas G Wallace
- Northern Illinois University, Department of Psychology, 1425 Lincoln Hwy, DeKalb, IL 60115, the United States of America.
| | - Dorothy A Kozlowski
- DePaul University, Department of Biological Sciences and Neuroscience Program, 2325 N., Chicago, IL 60604, the United States of America.
| | - Evan B Stubbs
- Edward Hines Jr. VA Research Service, Hines, IL 60141, the United States of America; Loyola University Medical Center, Department of Otolaryngology, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America.
| | - Sam J Marzo
- Loyola University Medical Center, Department of Otolaryngology, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America.
| | - Susanna C Byram
- Loyola University Medical Center, Department of Anesthesiology and Perioperative Medicine, 2160 South 1st Avenue, Maywood, IL 60153, the United States of America; Edward Hines Jr. VA Hospital Research Service, Hines, IL 60141, the United States of America.
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8
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Mountney A, Blaze J, Wang Z, Umali M, Flerlage WJ, Dougherty J, Ge Y, Shear D, Haghighi F. Penetrating Ballistic Brain Injury Produces Acute Alterations in Sleep and Circadian-Related Genes in the Rodent Cortex: A Preliminary Study. Front Neurol 2021; 12:745330. [PMID: 34777213 PMCID: PMC8580116 DOI: 10.3389/fneur.2021.745330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 09/22/2021] [Indexed: 11/23/2022] Open
Abstract
Traumatic brain injury (TBI) affects millions of Americans each year, with extremely high prevalence in the Veteran community, and sleep disturbance is one of the most commonly reported symptoms. Reduction in the quality and amount of sleep can negatively impact recovery and result in a wide range of behavioral and physiological symptoms, such as impaired cognition, mood and anxiety disorders, and cardiovascular effects. Thus, to improve long-term patient outcomes and develop novel treatments, it is essential to understand the molecular mechanisms involved in sleep disturbance following TBI. In this effort, we performed transcriptional profiling in an established rodent model of penetrating ballistic brain injury (PBBI) in conjunction with continuous sleep/wake EEG/EMG recording of the first 24 h after injury. Rats subjected to PBBI showed profound differences in sleep architecture. Injured animals spent significantly more time in slow wave sleep and less time in REM sleep compared to sham control animals. To identify PBBI-related transcriptional differences, we then performed transcriptome-wide gene expression profiling at 24 h post-injury, which identified a vast array of immune- related genes differentially expressed in the injured cortex as well as sleep-related genes. Further, transcriptional changes associated with total time spent in various sleep stages were identified. Such molecular changes may underlie the pathology and symptoms that emerge following TBI, including neurodegeneration, sleep disturbance, and mood disorders.
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Affiliation(s)
- Andrea Mountney
- Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Jennifer Blaze
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Zhaoyu Wang
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Michelle Umali
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | | | - Jacqueline Dougherty
- Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Yongchao Ge
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Deborah Shear
- Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Fatemeh Haghighi
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States
- Research and Development Service, James J. Peters Veterans Affairs Medical Center, Bronx, NY, United States
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9
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McCunn P, Xu X, Moszczynski A, Li A, Brown A, Bartha R. Neurite orientation dispersion and density imaging in a rodent model of acute mild traumatic brain injury. J Neuroimaging 2021; 31:879-892. [PMID: 34473386 DOI: 10.1111/jon.12917] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/24/2021] [Accepted: 07/27/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Identification of changesin brain microstructure following mild traumatic brain injury (mTBI) could be instrumental in understanding the underlying pathophysiology. The purpose of this study was to apply neurite orientation dispersion and density imaging (NODDI) to a rodent model of mTBI to determine whether microstructural changes could be detected immediately following injury. METHODS Fifteen adult male Wistar rats were scanned on a Bruker 9.4 Tesla small animal MRI using a multi-shell acquisition (30 b = 1000 s/mm2 and 60 b = 2000 s/mm2 ). Nine animals experienced a single closed head controlled cortical impact followed by NODDI from 1 to 4 h post injury. Region of interest analysis focused on the corpus callosum and hippocampus. A mixed analysis of variance (ANOVA) was used to determine statistically significant interactions in neurite density index (NDI), orientation dispersion index (ODI), fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity. Follow up repeated-measures ANOVAs were used to determine individual changes over time. RESULTS NDI showed a significant increase in the hippocampus and corpus callosum following injury, while ODI showed increases in the corpus callosum. No significant changes were observed in the sham control animals. No changes were found in FA, MD, AD, or RD. Histological analysis revealed increased glial fibrillary acidic protein staining relative to controls in both the hippocampus and corpus callosum, with evidence of activated astrocytes in these regions. CONCLUSIONS Changes in NODDI metrics were detected as early as 1 h following mTBI. No changes were detected with conventional diffusion tensor imaging (DTI) metrics, suggesting that NODDI provides greater sensitivity to microstructural changes than conventional DTI.
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Affiliation(s)
- Patrick McCunn
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - Xiaoyun Xu
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
| | | | - Alex Li
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.,Departments of Psychiatry and Medical Imaging, University of Western Ontario, London, Ontario, Canada
| | - Arthur Brown
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.,Department of Neuroscience, University of Western Ontario, London, Ontario, Canada
| | - Robert Bartha
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.,Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
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10
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McDaid J, Briggs CA, Barrington NM, Peterson DA, Kozlowski DA, Stutzmann GE. Sustained Hippocampal Synaptic Pathophysiology Following Single and Repeated Closed-Head Concussive Impacts. Front Cell Neurosci 2021; 15:652721. [PMID: 33867941 PMCID: PMC8044326 DOI: 10.3389/fncel.2021.652721] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/11/2021] [Indexed: 11/24/2022] Open
Abstract
Traumatic brain injury (TBI), and related diseases such as chronic traumatic encephalopathy (CTE) and Alzheimer's (AD), are of increasing concern in part due to enhanced awareness of their long-term neurological effects on memory and behavior. Repeated concussions, vs. single concussions, have been shown to result in worsened and sustained symptoms including impaired cognition and histopathology. To assess and compare the persistent effects of single or repeated concussive impacts on mediators of memory encoding such as synaptic transmission, plasticity, and cellular Ca2+ signaling, a closed-head controlled cortical impact (CCI) approach was used which closely replicates the mode of injury in clinical cases. Adult male rats received a sham procedure, a single impact, or three successive impacts at 48-hour intervals. After 30 days, hippocampal slices were prepared for electrophysiological recordings and 2-photon Ca2+ imaging, or fixed and immunostained for pathogenic phospho-tau species. In both concussion groups, hippocampal circuits showed hyper-excitable synaptic responsivity upon Schaffer collateral stimulation compared to sham animals, indicating sustained defects in hippocampal circuitry. This was not accompanied by sustained LTP deficits, but resting Ca2+ levels and voltage-gated Ca2+ signals were elevated in both concussion groups, while ryanodine receptor-evoked Ca2+ responses decreased with repeat concussions. Furthermore, pathogenic phospho-tau staining was progressively elevated in both concussion groups, with spreading beyond the hemisphere of injury, consistent with CTE. Thus, single and repeated concussions lead to a persistent upregulation of excitatory hippocampal synapses, possibly through changes in postsynaptic Ca2+ signaling/regulation, which may contribute to histopathology and detrimental long-term cognitive symptoms.
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Affiliation(s)
- John McDaid
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Clark A. Briggs
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Nikki M. Barrington
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
- Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Daniel A. Peterson
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
- Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
- Center for Stem Cell and Regenerative Medicine, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Dorothy A. Kozlowski
- Department of Biological Sciences and Neuroscience Program, DePaul University, Chicago, IL, United States
| | - Grace E. Stutzmann
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
- Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
- Center for Stem Cell and Regenerative Medicine, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
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11
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Maigler KC, Buhr TJ, Park CS, Miller SA, Kozlowski DA, Marr RA. Assessment of the Effects of Altered Amyloid-Beta Clearance on Behavior following Repeat Closed-Head Brain Injury in Amyloid-Beta Precursor Protein Humanized Mice. J Neurotrauma 2021; 38:665-676. [PMID: 33176547 DOI: 10.1089/neu.2020.6989] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Traumatic brain injury (TBI) increases the risk for dementias including Alzheimer's disease (AD) and chronic traumatic encephalopathy. Further, both human and animal model data indicate that amyloid-beta (Aβ) peptide accumulation and its production machinery are upregulated by TBI. Considering the clear link between chronic Aβ elevation and AD as well as tau pathology, the role(s) of Aβ in TBI is of high importance. Endopeptidases, including the neprilysin (NEP)-like enzymes, are key mediators of Aβ clearance and may affect susceptibility to pathology post-TBI. Here, we use a "humanized" mouse model of Aβ production, which expresses normal human amyloid-beta precursor protein (APP) under its natural transcriptional regulation and exposed them to a more clinically relevant repeated closed-head TBI paradigm. These transgenic mice also were crossed with mice deficient for the Aβ degrading enzymes NEP or NEP2 to assess models of reduced cerebral Aβ clearance in our TBI model. Our results show that the presence of the human form of Aβ did not exacerbate motor (Rotarod) and spatial learning/memory deficits (Morris water maze) post-injuries, while potentially reduced anxiety (Open Field) was observed. NEP and NEP2 deficiency also did not exacerbate these deficits post-injuries and was associated with protection from motor (NEP and NEP2) and spatial learning/memory deficits (NEP only). These data suggest that normally regulated expression of wild-type human APP/Aβ does not contribute to deficits acutely after TBI and may be protective at this stage of injury.
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Affiliation(s)
- Kathleen C Maigler
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Trevor J Buhr
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Christopher S Park
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Steven A Miller
- Department of Psychology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Dorothy A Kozlowski
- Department of Biological Sciences and Neuroscience Program, DePaul University, Chicago, Illinois, USA
| | - Robert A Marr
- Center for Neurodegenerative Disease and Therapeutics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
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12
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Shultz SR, McDonald SJ, Corrigan F, Semple BD, Salberg S, Zamani A, Jones NC, Mychasiuk R. Clinical Relevance of Behavior Testing in Animal Models of Traumatic Brain Injury. J Neurotrauma 2020; 37:2381-2400. [DOI: 10.1089/neu.2018.6149] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Sandy R. Shultz
- Department of Neuroscience, Monash University, Melbourne, Victoria, Australia
- Department of Medicine, The University of Melbourne, Parkville, Victoria, Australia
| | - Stuart J. McDonald
- Department of Neuroscience, Monash University, Melbourne, Victoria, Australia
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Melbourne, Victoria, Australia
| | - Frances Corrigan
- Department of Anatomy, University of South Australia, Adelaide, South Australia, Australia
| | - Bridgette D. Semple
- Department of Neuroscience, Monash University, Melbourne, Victoria, Australia
- Department of Medicine, The University of Melbourne, Parkville, Victoria, Australia
| | - Sabrina Salberg
- Department of Neuroscience, Monash University, Melbourne, Victoria, Australia
| | - Akram Zamani
- Department of Neuroscience, Monash University, Melbourne, Victoria, Australia
| | - Nigel C. Jones
- Department of Neuroscience, Monash University, Melbourne, Victoria, Australia
- Department of Medicine, The University of Melbourne, Parkville, Victoria, Australia
| | - Richelle Mychasiuk
- Department of Neuroscience, Monash University, Melbourne, Victoria, Australia
- Department of Psychology, University of Calgary, Calgary, Alberta, Canada
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13
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Faroqi AH, Lim MJ, Kee EC, Lee JH, Burgess JD, Chen R, Di Virgilio F, Delenclos M, McLean PJ. In Vivo Detection of Extracellular Adenosine Triphosphate in a Mouse Model of Traumatic Brain Injury. J Neurotrauma 2020; 38:655-664. [PMID: 32935624 PMCID: PMC7898407 DOI: 10.1089/neu.2020.7226] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Traumatic brain injury (TBI) is traditionally characterized by primary and secondary injury phases, both contributing to pathological and morphological changes. The mechanisms of damage and chronic consequences of TBI remain to be fully elucidated, but synaptic homeostasis disturbances and impaired energy metabolism are proposed to be a major contributor. It has been proposed that an increase of extracellular (eATP) adenosine triphosphate (ATP) in the area immediately surrounding impact may play a pivotal role in this sequence of events. After tissue injury, rupture of cell membranes allows release of intracellular ATP into the extracellular space, triggering a cascade of toxic events and inflammation. ATP is a ubiquitous messenger; however, simple and reliable techniques to measure its concentration have proven elusive. Here, we integrate a sensitive bioluminescent eATP sensor known as pmeLUC, with a controlled cortical impact mouse model to monitor eATP changes in a living animal after injury. Using the pmeLUC probe, a rapid increase of eATP is observed proximal to the point of impact within minutes of the injury. This event is significantly attenuated when animals are pretreated with an ATP hydrolyzing agent (apyrase) before surgery, confirming the contribution of eATP. This new eATP reporter could be useful for understanding the role of eATP in the pathogenesis in TBI and may identify a window of opportunity for therapeutic intervention.
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Affiliation(s)
- Ayman H Faroqi
- Department of Neuroscience, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA.,Neuroscience PhD Program, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA
| | - Melina J Lim
- Department of Neuroscience, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA
| | - Emma C Kee
- Department of Neuroscience, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA
| | - Jannifer H Lee
- Department of Neuroscience, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA.,Neuroscience PhD Program, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA
| | - Jeremy D Burgess
- Department of Neuroscience, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA.,Neuroscience PhD Program, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA
| | - Ridong Chen
- APT Therapeutics, Inc., St. Louis, Missouri, USA
| | - Francesco Di Virgilio
- Department of Morphology Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Marion Delenclos
- Department of Neuroscience, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA
| | - Pamela J McLean
- Department of Neuroscience, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA.,Neuroscience PhD Program, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic College of Medicine, Mayo Clinic, Jacksonville, Florida, USA
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14
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McNamara EH, Grillakis AA, Tucker LB, McCabe JT. The closed-head impact model of engineered rotational acceleration (CHIMERA) as an application for traumatic brain injury pre-clinical research: A status report. Exp Neurol 2020; 333:113409. [PMID: 32692987 DOI: 10.1016/j.expneurol.2020.113409] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 06/18/2020] [Accepted: 07/14/2020] [Indexed: 02/06/2023]
Abstract
Closed-head traumatic brain injury (TBI) is a worldwide concern with increasing prevalence and cost to society. Rotational acceleration is a primary mechanism in TBI that results from tissue strains that give rise to diffuse axonal injury. The Closed-Head Impact Model of Engineered Rotational Acceleration (CHIMERA) was recently introduced as a method for the study of impact acceleration effects in pre-clinical TBI research. This review provides a survey of the published literature implementing the CHIMERA device and describes pathological, imaging, neurophysiological, and behavioral findings. Findings show CHIMERA inflicts damage in white matter tracts as a key area of injury. Behaviorally, repeated studies have shown motor deficits and more chronic cognitive effects after CHIMERA injury. Good progress with model application has been accomplished by investigators attending to what is required for model validation. However, the majority of CHIMERA studies only utilize adult male mice. To further establish this model, more work with female animals and various age groups need to be performed, as well as studies to further establish and standardize methodologies for validation of the models for clinical relevance. Common data elements to standardize the reporting methodology for the CHIMERA literature are suggested.
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Affiliation(s)
- Eileen H McNamara
- Neuroscience Graduate Program, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA; Department of Anatomy, Physiology & Genetics, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA
| | - Antigone A Grillakis
- Neuroscience Graduate Program, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA; Department of Anatomy, Physiology & Genetics, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA
| | - Laura B Tucker
- Department of Anatomy, Physiology & Genetics, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA; Pre-Clinical Studies Core, Center for Neuroscience and Regenerative Medicine, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA
| | - Joseph T McCabe
- Neuroscience Graduate Program, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA; Department of Anatomy, Physiology & Genetics, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA; Pre-Clinical Studies Core, Center for Neuroscience and Regenerative Medicine, F.E. Hébert School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20817-4799, USA.
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15
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Sempere L, Rodríguez-Rodríguez A, Boyero L, Egea-Guerrero J. Principales modelos experimentales de traumatismo craneoencefálico: de la preclínica a los modelos in vitro. Med Intensiva 2019; 43:362-372. [DOI: 10.1016/j.medin.2018.04.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 04/23/2018] [Accepted: 04/26/2018] [Indexed: 02/08/2023]
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16
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Pham L, Shultz SR, Kim HA, Brady RD, Wortman RC, Genders SG, Hale MW, O'Shea RD, Djouma E, van den Buuse M, Church JE, Christie BR, Drummond GR, Sobey CG, McDonald SJ. Mild Closed-Head Injury in Conscious Rats Causes Transient Neurobehavioral and Glial Disturbances: A Novel Experimental Model of Concussion. J Neurotrauma 2019; 36:2260-2271. [DOI: 10.1089/neu.2018.6169] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Louise Pham
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Sandy R. Shultz
- Department Neuroscience, Monash University, Melbourne, Australia
- Department of Medicine, University of Melbourne, Melbourne, Australia
| | - Hyun Ah Kim
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Rhys D. Brady
- Department Neuroscience, Monash University, Melbourne, Australia
- Department of Medicine, University of Melbourne, Melbourne, Australia
| | - Ryan C. Wortman
- Department Neuroscience, Monash University, Melbourne, Australia
| | - Shannyn G. Genders
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Matthew W. Hale
- Department of Psychology and Counseling, La Trobe University, Bundoora, Australia
| | - Ross D. O'Shea
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Elvan Djouma
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Maarten van den Buuse
- Department of Psychology and Counseling, La Trobe University, Bundoora, Australia
- Department of Pharmacology, University of Melbourne, Melbourne, Australia
- The College of Public Health, Medical, and Veterinary Sciences, James Cook University, Queensland, Australia
| | - Jarrod E. Church
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Brian R. Christie
- Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada
| | - Grant R. Drummond
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Christopher G. Sobey
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
| | - Stuart J. McDonald
- Department of Physiology, Anatomy, and Microbiology, La Trobe University, Bundoora, Australia
- Department Neuroscience, Monash University, Melbourne, Australia
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17
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Bolton-Hall AN, Hubbard WB, Saatman KE. Experimental Designs for Repeated Mild Traumatic Brain Injury: Challenges and Considerations. J Neurotrauma 2019; 36:1203-1221. [PMID: 30351225 PMCID: PMC6479246 DOI: 10.1089/neu.2018.6096] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Mild traumatic brain injury (mild TBI) is a growing public concern, as evidence mounts that even brain injuries classified as "mild" can result in persistent neurological dysfunction. Multiple brain injuries heighten the likelihood of worsened or more prolonged symptomatology and may trigger long-term neurodegeneration. Animal models provide a logical platform to identify key parameters, such as loading forces, duration between injuries, and number of injuries, which contribute to additive or synergistic damage after repeated mild TBI. Despite the tremendous increase in research productivity in the field of repeated mild TBI, relatively few studies have been designed in such a way as to provide experimental-based insights into the dependence of cellular and functional outcomes on the prescribed parameters of mild TBI. In this review, we summarize how standard models of TBI have been adapted to produce mild TBI and highlight commonly observed aspects of neuropathology replicated in rodent models of mild TBI. The complexity of designing studies of repeated TBI is discussed, including challenges of incorporating appropriate control groups, informative experimental design, and relevant outcome measures. We then feature studies that provide a well-controlled, within-study design varying either the number of injuries or the interinjury interval. Harnessing the power of experimental models of TBI to elucidate which injury parameters are critical contributors to acute and chronic damage after repeated injury can further efforts at prevention and provide improved models for testing mechanisms and therapeutic interventions.
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Affiliation(s)
- Amanda N. Bolton-Hall
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Neurosurgery, Wayne State University School of Medicine, Detroit, Michigan
| | - W. Brad Hubbard
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Kathryn E. Saatman
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
- Department of Neurosurgery, University of Kentucky College of Medicine, Lexington, Kentucky
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18
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Vest V, Bernardo-Colón A, Watkins D, Kim B, Rex TS. Rapid Repeat Exposure to Subthreshold Trauma Causes Synergistic Axonal Damage and Functional Deficits in the Visual Pathway in a Mouse Model. J Neurotrauma 2019; 36:1646-1654. [PMID: 30451083 DOI: 10.1089/neu.2018.6046] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We examined the effect of repeat exposure to a non-damaging insult on central nervous system axons using the optic projection as a model. The optic projection is attractive because its axons are spatially separated from the cell bodies, it is easily accessible, it is composed of long axons, and its function can be measured. We performed closed-system ocular neurotrauma in C57Bl/6 mice using bursts of 15 or 26-psi (pounds per square inch) overpressure air that caused no gross damage. We quantified the visual evoked potential (VEP) and total and degenerative axons in the optic nerve. Repeat exposure to a 15-psi air blast caused more axon damage and vision loss than a single exposure to a 26-psi air blast. However, an increased VEP latency was detected in both groups. Exposure to three 15-psi air blasts separated by 0.5 sec caused 15% axon degeneration at 2 weeks. In contrast, no axon degeneration above sham levels was detected when the interinjury interval was increased to 10 min. Exposure to 15-psi air blasts once a day for 6 consecutive days caused 3% axon degeneration. Therefore, repeat mild trauma within an interinjury interval of 1 min or less causes synergistic axon damage, whereas mild trauma repeated at a longer interinjury interval causes additive, cumulative damage. The synergistic damage may underlie the high incidence of traumatic brain injury and traumatic optic neuropathy in blast-injured service members given that explosive blasts are multiple injury events that occur in a very short time span. This study also supports the use of the VEP as a biomarker for traumatic optic neuropathy.
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Affiliation(s)
- Victoria Vest
- 1 Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee
| | | | - Dexter Watkins
- 3 Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee
| | - Bohan Kim
- 2 Department of Ophthalmology & Visual Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Tonia S Rex
- 1 Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee.,2 Department of Ophthalmology & Visual Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee
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19
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Osier N, Dixon CE. Mini Review of Controlled Cortical Impact: A Well-Suited Device for Concussion Research. Brain Sci 2017; 7:E88. [PMID: 28726717 PMCID: PMC5532601 DOI: 10.3390/brainsci7070088] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 07/12/2017] [Accepted: 07/18/2017] [Indexed: 01/25/2023] Open
Abstract
Mild traumatic brain injury (mTBI) is increasingly recognized as a significant public health problem which warrants additional research. Part of the effort to understand mTBI and concussion includes modeling in animals. Controlled cortical impact (CCI) is a commonly employed and well-characterized model of experimental TBI that has been utilized for three decades. Today, several commercially available pneumatic- and electromagnetic-CCI devices exist as do a variety of standard and custom injury induction tips. One of CCI's strengths is that it can be scaled to a number of common laboratory animals. Similarly, the CCI model can be used to produce graded TBI ranging from mild to severe. At the mild end of the injury spectrum, CCI has been applied in many ways, including to study open and closed head mTBI, repeated injuries, and the long-term deficits associated with mTBI and concussion. The purpose of this mini-review is to introduce the CCI model, discuss ways the model can be applied to study mTBI and concussion, and compare CCI to alternative pre-clinical TBI models.
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Affiliation(s)
- Nicole Osier
- School of Nursing, Holistic Adult Health Division, University of Texas at Austin, Austin, TX 78701, USA.
- Dell Medical School, Department of Neurology, University of Texas at Austin, Austin, TX 78701, USA.
| | - C Edward Dixon
- Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA 15224, USA.
- Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15260, USA.
- VA Pittsburgh Healthcare System, Pittsburgh, PA 15240, USA.
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