This work was supported by R01 NS067417 from the National Institute for Neurological Disorders and Stroke (MPB).

These studies were performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes Health. The protocol was approved by the Institutional Animal Care and Use Committee at Georgetown University. Mice were housed in a temperature controlled animal facility and were kept on a 12 h light/12 h dark cycle. Food and water were available ad libitum.
1. Preparation of the mTBI Apparatus
NOTE: The mTBI apparatus includes a data acquisition (DAQ) box to control impact parameters, a high-velocity pneumatic impactor to perform the impaction, and a moulded gel filled base to decelerate head after impact.
<ol>
	<li>Turn on compressed air and initialize the high-velocity pneumatic impactor to a pressure setting of 861.85 kPa.</li>
	<li>Calibrate the DAQ control system to following parameters- piston velocity of 2.35 m/s, surface dwell time of 31.5 ms.</li>
	<li>Place the molded gel-filled base (compressibility 64 kPa/mm) such that the midline is perpendicular with the trajectory of impactor tip.</li>
</ol>
2. mTBI Impaction
<ol>
	<li>Record the weights of all mice to be used.</li>
	<li>Anesthetize mice with 3% isoflurane in oxygen for 120 s in an induction chamber.</li>
	<li>Transfer mice to mTBI apparatus, continuing anesthesia via a pliable, non-fixed nose cone.</li>
	<li>Whilst in nose cone, position mouse head on the gel pad so that the flat surface of the skull is presented perpendicular to the impactor tip.</li>
	<li>Place tape over mouse head to create a flat surface and hold ears away from the impact site.</li>
	<li>Lower the polytetrafluoroethylene impactor tip to align with the sagittal midline in the center of the head. The impactor tip used is 10 mm in diameter and will cover the area of the scalp from just behind the eyes to the midline of the ears. Adjust the impactor so it is just touching the surface of the mouse head.</li>
	<li>Retract the impactor tip and manually dial down the required deflection depth (7.5 mm).</li>
	<li>Arm the DAQ control system and depress trigger button to impact mouse head, either a singular or repetitive impacts. Repetitive impacts are delivered in succession with no delay between each impact.</li>
	<li>Immediately after the final impact, remove mouse from anesthesia and the mTBI apparatus and place in supine position.</li>
	<li>Using a stopwatch measure the latency of the return of righting reflex (supine to prone), to determine loss of consciousness time, as well as time to ambulation (unimpeded walking).</li>
	<li>Monitor mouse and upon recovery to normal behaviour, return to its home cage.</li>
	<li>Sham mice receive identical handling and anesthesia, but receive no impact.</li>
</ol>

<ol>
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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnosis,+prognosis,+and+clinical+management+of+mild+traumatic+brain+injury.">Diagnosis, prognosis, and clinical management of mild traumatic brain injury.</a> Lancet Neurol. 14 (5), 506-517 (2015).</li><li>McCrory, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consensus+statement+on+concussion+in+sport:+the+4th+International+Conference+on+Concussion+in+Sport,+Zurich,+November+2012.">Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport, Zurich, November 2012.</a> J Athl Train. 48 (4), 554-575 (2012).</li><li>Talavage, T. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functionally-detected+cognitive+impairment+in+high+school+football+players+without+clinically-diagnosed+concussion.">Functionally-detected cognitive impairment in high school football players without clinically-diagnosed concussion.</a> J Neurotrauma. 31 (4), 327-338 (2014).</li><li>Angoa-Perez, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+sports-related+head+injury:+bridging+the+gap+between+pre-clinical+research+and+clinical+reality.">Animal models of sports-related head injury: bridging the gap between pre-clinical research and clinical reality.</a> J Neurochem. 129 (6), 916-931 (2014).</li><li>Creed, J. 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J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+mouse+model+of+human+repetitive+mild+traumatic+brain+injury.">A mouse model of human repetitive mild traumatic brain injury.</a> J Neurosci Methods. 203 (1), 41-49 (2012).</li><li>Prins, M. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repeat+traumatic+brain+injury+in+the+juvenile+rat+is+associated+with+increased+axonal+injury+and+cognitive+impairments.">Repeat traumatic brain injury in the juvenile rat is associated with increased axonal injury and cognitive impairments.</a> Dev Neurosci. 32 (5-6), 510-518 (2010).</li><li>Tang, Y. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+concussive-like+brain+injury+model+in+mice+(II):+selective+neuronal+loss+in+the+cortex+and+hippocampus.">A concussive-like brain injury model in mice (II): selective neuronal loss in the cortex and hippocampus.</a> J Neurotrauma. 14 (11), 863-873 (1997).</li><li>Winston, C. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendritic+Spine+Loss+and+Chronic+White+Matter+Inflammation+in+a+Mouse+Model+of+Highly+Repetitive+Head+Trauma.">Dendritic Spine Loss and Chronic White Matter Inflammation in a Mouse Model of Highly Repetitive Head Trauma.</a> Am J Pathol. 186 (3), 552-567 (2016).</li><li>Johnson, V. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+and+white+matter+degeneration+persist+for+years+after+a+single+traumatic+brain+injury.">Inflammation and white matter degeneration persist for years after a single traumatic brain injury.</a> Brain. 136, 28-42 (2013).</li><li>Barrio, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+characterization+of+chronic+traumatic+encephalopathy+using+[F-18]FDDNP+PET+brain+imaging.">In vivo characterization of chronic traumatic encephalopathy using [F-18]FDDNP PET brain imaging.</a> Proc Natl Acad Sci U S A. 112 (16), 2039-2047 (2015).</li></ol>

The authors have nothing to disclose.

In humans, mTBI is characterized by a functional impairment in the absence of structural injury. This can occur with, or without, a loss of consciousness1. Exposure to repeat concussions is currently thought to underlie the development and/or progression of neurodegenerative diseases such as CTE4. It is well documented that CTE is commonly found in boxers and football players and although exposure to repeat concussions (including those that do not result in a loss of consciousness) is known to be an essential element in developing CTE, we do not yet know why the mechanisms by which repeat concussion causes the distinct changes that occur in the brain.
A major hurdle to understanding these mechanisms is the difficulty in developing models that accurately recapitulate the key symptomologies observed in individuals that sustain an mTBI impact. This means the acute and chronic biological pathways underlying the concussive impacts are difficult to investigate and new treatments cannot be developed. In particular, existing animal models of repeat concussion are very severe, using only 2-3 repeat impacts that cause extensive neuronal cell loss, skull fracture and loss of brain tissue8,10,11,12. This extent of injury is not occurring after repeat concussion in humans, demonstrating the need for a new model of single and repetitive mild head impact.
Here we describe a novel model of mTBI, using a custom made diffuse injury device that has been specifically designed to transfer energy through the skull and brain and away from the mouse. Through both single impact and repetitive impact paradigms, the model allows for a means to begin investigating how concussion contributes neurological impairment later in life. The single hit paradigm recapitulates the hallmark characteristics of mild traumatic brain injury observed in humans, while the repetitive paradigm allows for the examination of how these seemingly mild injuries contribute to chronic and persistent degeneration over time. The device allows for repetitive mTBI head impacts without risk of skull fracture or structural brain damage.
As is the case with many techniques, certain aspects of this protocol are important to note for the generation of accurate, reliable results. During chamber induction and mTBI injury, it is essential to maintain a consistent level of anesthesia to each mouse. Due to the fact that righting and ambulation time is a key outcome measurement of this mTBI procedure, researchers should ensure that both mTBI injury and sham animals are exposed to comparable levels of anesthetic. Specifically, for the duration of the entire procedure, mice should only be under anesthesia for 3 min total (2 min in the induction chamber, 1 min with the mTBI nose cone device). This low level and duration of anesthesia is a major advantage over many other mTBI models, and yields consistent righting reflex response times (sham mice 20-40 s, mTBI mice 50-100 s). Additionally, when utilizing the repeat mTBI paradigm, it is important to maintain a record of mouse weights every day for the duration of the study. This is to ensure consistent monitoring for stress and general animal welfare throughout the entire time course of the mTBI procedures. This procedure does not result in mice becoming withdrawn or isolated. Normal grooming, eating and drinking should be observed within the first hour post procedure.
Post-injury there is no gross morphological pathology to the brain tissue resulting from either single or multiple impacts over a 1-week time course. Following a single mTBI, the only cellular response observed is a transient reduction in excitatory synapses; there is no inflammation, loss of grey or white matter, axonal injury or cell death. With 30 repeat mTBI (5 per day, over 6 days) there is chronic inflammation of the optic tract, at similar levels as previously quantitated1. Chronic white matter inflammation has been observed many years after a single mTBI14, and chronic inflammation can be detected in living athletes with a history of repeat mTBI15. The limitations of this model are that it cannot be used to study axonal injury outside of the optic tract or mechanisms of cell death, as these are absent in our model. Also based on our previously published data, this model does not induce changes in amyloid or tau pathology at 1-month post-mTBI in a mouse model of Alzheimer&#39;s disease13. We believe this lack of amyloid and tau pathology is related to the absence of axonal pathology in our model. Our model does provide a platform to investigate discrete changes in neuron networks, synaptic integrity and composition, and alterations in behavior following repeat concussive blows. Based on these outcomes, this novel model produces clinically relevant symptomology in a controlled, rigorous, and efficient manner. Further use of this model will allow for the investigation into the mechanisms that underlie the acute and chronic pathophysiology of mTBI and concussion.

Traumatic Brain Injury (TBI) is defined as a head injury sustained from an external physical force, resulting in the disruption of normal brain function. It represents a significant socio-economic and public health burden, with the Center for Disease Control and Prevention 2015 Report to Congress estimating that 2.5 million Americans sustain a TBI every year. This impacts not only the patient&#39;s quality of life, but also places an extremely high economic cost on the community, currently estimated at $76.5 billion annually. The amount of actual brain damage conveyed and the acute phase symptomologies is what defines mild, moderate and severe TBI.
Mild Traumatic Brain Injury (mTBI), also referred to as concussion, accounts for over 70% of TBIs reported each year1. It is most common among athletes who participate in high-risk contact sports including boxing and football2. Unlike moderate or severe forms of TBI, the immediate damage and symptoms associated with mTBI are sometimes not as pronounced3. By contrast, the long-term effects of mTBI can be just as debilitating as those seen in the moderate and severe forms. Those who suffer from repetitive mTBI have been shown to develop chronic traumatic encephalopathy (CTE), as well as other cognitive and degenerative illnesses4. Therefore, it is important to gain a greater understanding of the mechanisms that contribute to the short-term symptoms and overall long-term damage that arises following mTBI.
In humans, the definition of concussion as defined by the Fourth International Conference on Concussion in Sport (Zurich 2012)5 states that the level of injury for sports concussion is mild, does not cause gross pathological changes, but does cause short-term neurological deficits that are spontaneously resolved. Indeed, a recent study investigated the effect of mTBI on cognitive impairment in high school football players, using head impact telemetry systems. This study showed the amount of times players sustained helmet impacts &#62;20 g in a single season ranged from a low of 226 (average, 4.7 per session) to a high of 1855 (average, 38.6 per session)6. Most of these impacts did not result in the clinical diagnosis of a concussion; but evidence of functional changes in brain function could be observed using fMRI6. The brain changes that cause these functional changes are unknown, and therefore there is a pressing need to have a reliable and reproducible model to facilitate research into the effects of concussive and subconcussive mTBI.
Despite previous attempts to model mTBI in mice and rats7, many report adverse effects. In particular, most rodent models are limited in their repetitive nature using fewer than five mTBIs impacts, as well as having adverse pathological events including intracerebral bleeding, skull fractures, severe axonal injury, neuronal cell death, and increased mortality8,9,10,11,12. Herein, we describe a mouse model of mTBI that is closer to the true definition of concussion in humans. This model recapitulates many of the symptoms observed in human mTBI, such as the mechanical force that results in the transient loss of consciousness with no overt gross brain pathology. Furthermore, it is advantageous in the fact that it can be utilised for both single impact and repetitive impact paradigms over long time periods as reported previously13.

<table><tbody><tr><td>Powerlab 8SP data acquisition (DAQ) control box&amp;nbsp;</td><td>(AD instruments)</td><td></td><td></td></tr><tr><td>VIP 3000 calibrated vaporizer</td><td>Matrx</td><td></td><td></td></tr><tr><td>Isoflurane</td><td>Henry Schein Animal Health</td><td>29405</td><td></td></tr><tr><td>Oxygen</td><td></td><td></td><td>Commercially available</td></tr><tr><td>Compressed Air</td><td></td><td></td><td>Commercially available</td></tr><tr><td>Masking Tape</td><td></td><td></td><td>Commercially available</td></tr><tr><td>Stop Watch</td><td>Fisher Scientific</td><td>02-261-840</td><td></td></tr><tr><td>C57 Bl/6 Mice</td><td>Jackson Laboratories</td><td></td><td></td></tr><tr><td>Digital Scale and weigh container</td><td>Fisher Scientific</td><td>20031</td><td></td></tr><tr><td>anti-Iba1 antibody</td><td>Wako</td><td>019-19741</td><td></td></tr><tr><td>HRP labelled secondary&amp;nbsp;</td><td>Jackson Immunoresearch</td><td>111-035-003</td><td></td></tr></tbody></table>

a mouse model of single and repetitive mild traumatic brain injury

Mild Traumatic Brain Injury (mTBI) can result in the acute loss of brain function, including a period of confusion, a loss of consciousness (LOC), focal neurological deficits and even amnesia. Athletes participating in contact sports are at high risk of exposure to large number of mTBIs. In terms of the level of injury in a sporting athlete, a mTBI is defined as a mild injury that does not cause gross pathological changes, but does cause short-term neurological deficits that are spontaneously resolved. Despite previous attempts to model mTBI in mice and rats, many have reported gross adverse effects including skull fractures, intracerebral bleeding, axonal injury and neuronal cell death. Herein, we describe our highly reproducible animal model of mTBI that reproduces clinically relevant symptoms. This model uses a custom made pneumatic impactor device to deliver a closed-head trauma. This impact is made under precise velocity and deformation parameters, creating a reliable and reproducible model to examine the mechanisms that contribute to effects of single or repetitive concussive mTBI.

The use of this novel mTBI device allows for single and repetitive mild head injuries without risk of skull fracture or structural brain damage. The model uses a custom made pneumatic Teflon impactor device to deliver a closed head mechanical energy impact. The impact is made under precise velocity and deformation parameters, creating a reliable and reproducible model to examine the mechanisms that contribute to effects of single or repetitive concussive mTBI (Figure 1).
The presence or absence of LOC is a useful tool in grading concussion severity in animal models. The return of the righting reflex time is an acute neurological evaluation of injury severity that we used to quantify the LOC after a single and repeat mTBIs (7.5 mm depth, Figure 2). During the procedure mice receive a total of 3 min of isoflurane in oxygen, and thus all mice including shams have a LOC period after anaesthesia withdrawal. Single mTBI results in significantly increased LOC compared to sham mice (36.4 &#177; 1.6 s v 64.2 &#177; 7.7 s, n = 5, **p &#60;0.01, Figure 2A). This also correlated with increased ambulation times following a single mTBI (52.0 &#177; 4.5 s v 140.0 &#177; 21.1 s, n = 5, **p &#60;0.01, Figure 2B). In repeat injury paradigms (a total of 30 impacts, 5 impacts per day for 6 days), there was significantly elevated LOC and ambulation times on all testing days (repeated measures two-way analysis of variance injury effect F1,14= 22.92, p &#60;0.0003). During the entire study, the average LOC over the 6 days was Sham: 35.5 &#177; 1.4 s v mTBI: 64.9 &#177; 1.7 s, n = 8, p &#60;0.01, Figure 2C, and average ambulation times Sham: 64.3 &#177; 3.3 s v mTBI: 160.8 &#177; 5.3 s, n = 8, p &#60;0.01, Figure 2D. Iba1 staining for microglia/macrophages revealed no change between sham and single mTBI mice, but extensive Iba1 immunoreactivity in the optic tract in repeat mTBI mice (Figure 3). Repeat mTBI mice showed no evidence of grey matter inflammation in the cortex (Figure 3) or other brain areas.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/55713/55713fig1.jpg" /> 
Figure 1: Illustrative Representation of the Mouse Model of mTBI. (A) The setup of all materials required to perform mTBI. (B) Mouse placed in isoflurane induction chamber for 2 min. (C) On the mTBI apparatus, mouse placed in a non-fixed nose cone to continue anesthesia. (D) Gently tape mouse head to create a flat surface and hold ears back. Impactor tip lowered to just touch the surface of the head. (E) Impactor tip retracted and required deflection depth is lowered using the dial (inset). mTBI performed by depressing trigger button. (F) Loss of consciousness measured by the time taken for the return of righting reflex (supine to prone). <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/55713/55713fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/55713/55713fig2.jpg" /> 
Figure 2: Single and Repeat mTBIs Increases Transient Loss of Consciousness and Return to Ambulation Times. Mice that receive a single mTBI have significantly increased (A) loss of consciousness (LOC) and (B) ambulation times compared to sham control mice (n = 5 per group, **p &#60;0.01). (C-D) Repetitive mTBI (5 impacts per day for 6 days) significantly increases daily LOC and ambulation times compared to sham mice (n = 8 per group, *p &#60;0.05, **p &#60;0.01, ***p &#60;0.001). Data expressed as mean &#177; S.E.M, analyzed by Two-way repeated measures ANOVA with a Bonferroni post-hoc test. <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/55713/55713fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/55713/55713fig3.jpg" /> 
Figure 3: Repeat mTBI Induces Microglia/Macrophages Activation in the Optic Tract. (A) Iba1 staining in sham mice reveals quiescent microglia/macrophages in the cortex (a1 - a3) and limited staining in the optic tract (a4-a6). (B) Mice that receive a single mTBI (7.5 mm) have similar Iba1 staining profiles as sham mice in both the cortex (b1-b3) and optic tract (b4-b6), 24 h post-impact. (C) Repeat mTBI mice (5 impacts per day for 6 consecutive days) display a strong inflammatory response in the optic tract (c4-c6) but not in the cortex (c1-c3), 24 h after the last impact (Day 7). Enlarged images demonstrating the morphology of Iba-1 positive microglia/macrophages in the cortex (a3, b3, c3) and optic tract (a6, b6, c6) of sham, single and repetitive mTBI mice, respectively. Scale bars = 200 &#181;m (A, B, C); 50 &#181;m (a1-a5, b1-b5, c1-c5); 20 &#181;m (a3, a6, b3, b6, c3, c6, magnified panels). Images representative of n = 6 per group. Cortex (cx), optic tract (opt), mild traumatic brain injury (mTBI). <a href="https://cloudflare-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/55713/55713fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about A Mouse Model of Single and Repetitive Mild Traumatic Brain Injury at JoVE.com

A Mouse Model of Single and Repetitive Mild Traumatic Brain Injury

Athletes absorb several hundred mild traumatic brain injuries (mTBI)/concussions every year; however, the consequence of these on the brain is poorly understood. Therefore, an animal model of single and repetitive mTBI that consistently replicates clinically relevant symptoms provides the means to advance the study of mTBI and concussion.

Mild Traumatic Brain Injury (mTBI) can result in the acute loss of brain function, including a period of confusion, a loss of consciousness (LOC), focal ...

a-mouse-model-of-single-and-repetitive-mild-traumatic-brain-injury

Universidad San Sebastian

Research

JoVE Journal

Medicine

11.0K Views.  Georgetown University Medical Center. Athletes absorb several hundred mild traumatic brain injuries (mTBI)/concussions every year; however, the consequence of these on the brain is poorly understood. Therefore, an animal model of single and repetitive mTBI that consistently replicates clinically relevant symptoms provides the means to advance the study of mTBI and concussion.

Video: A Mouse Model of Single and Repetitive Mild Traumatic Brain Injury

Inducing Post-Traumatic Epilepsy in a Mouse Model of Repetitive Diffuse Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of acquired epilepsy. TBI can result in a focal or diffuse brain injury. Focal injury is a result of direct mechanical forces, sometimes penetrating through the cranium, creating a direct lesion in the brain tissue. These are visible during brain imaging as areas with contusion, laceration, and hemorrhage. Focal lesions induce neuronal death and glial scar formation and are present in 20%&minus;25% of all people who incur a TBI. However, in the majority of TBI cases, injury is caused by acceleration-deceleration forces and subsequent tissue shearing, resulting in nonfocal, diffuse damage. A subpopulation of TBI patients continues to develop post-traumatic epilepsy (PTE) after a latency period of months or years. Currently, it is impossible to predict which patients will develop PTE, and seizures in PTE patients are challenging to control, necessitating further research. Until recently, the field was limited to only two animal/rodent models with validated spontaneous post-traumatic seizures, both presenting with large focal lesions with massive tissue loss in the cortex and sometimes subcortical structures. In contrast to these approaches, it was determined that diffuse TBI induced using a modified weight drop model is sufficient to initiate development of spontaneous convulsive and non-convulsive seizures, even in the absence of focal lesions or tissue loss. Similar to human patients with acquired post-traumatic epilepsy, this model presents with a latency period after injury before seizure onset. In this protocol, the community will be provided with a new model of post-traumatic epilepsy, detailing how to induce diffuse non-lesional TBI followed by continuous long-term video-electroencephalographic animal monitoring over the course of several months. This protocol will detail animal handling, the weight drop procedure, the electrode placement for two acquisition systems, and the frequent challenges encountered during each of the steps of surgery, postoperative monitoring, and data acquisition.

This systematic protocol describes a new animal model of post-traumatic epilepsy after repetitive mild traumatic brain injury. The first part details steps for traumatic brain injury induction using a modified weight drop model. The second part provides instructions on the surgical approach for single- and multi-channel electroencephalographic data acquisition systems.

Traumatic brain injury (TBI) is a leading cause of acquired epilepsy. TBI can result in a focal or diffuse brain injury. Focal injury is a result of ...

Behavior

A Novel Model of Mild Traumatic Brain Injury for Juvenile Rats

Despite growing evidence that childhood represents a major risk period for mild traumatic brain injury (mTBI) from sports-related concussions, motor vehicle accidents, and falls, a reliable animal model of mTBI had previously not been developed for this important aspect of development. The modified weight-drop technique employs a glancing impact to the head of a freely moving rodent transmitting acceleration, deceleration, and rotational forces upon the brain. When applied to juvenile rats, this modified weight-drop technique induced clinically relevant behavioural outcomes that were representative of post-concussion symptomology. The technique is a rapidly applied procedure with an extremely low mortality rate, rendering it ideal for high-throughput studies of therapeutics. In addition, because the procedure involves a mild injury to a closed head, it can easily be used for studies of repetitive brain injury. Owing to the simplistic nature of this technique, and the clinically relevant biomechanics of the injury pathophysiology, the modified weight-drop technique provides researchers with a reliable model of mTBI that can be used in a wide variety of behavioural, molecular, and genetic studies.

The modified weight-drop technique is an easy, cost-effective procedure used for the induction of mild traumatic brain injury in juvenile rats. This novel technique produces clinically relevant symptomology that will advance the study of mild traumatic brain injury (mTBI) and concussion.

Despite growing evidence that childhood represents a major risk period for mild traumatic brain injury (mTBI) from sports-related concussions, motor ...

A Repetitive Concussive Head Injury Model in Mice

Despite the concussion/ mild traumatic brain injury (mTBI) being the most frequent occurrence of traumatic brain injury, there is still a lack of knowledge on the injury and its effects. To develop a better understanding of concussions, animals are often used because they provide a controlled, rigorous, and efficient model. Studies have adapted traditional animal models to perform mTBI to stimulate mild injury severity by changing the injury parameters. These models have been used because they can produce morphologically similar brain injuries to the clinical condition and provide a spectrum of injury severities. However, they are limited in their ability to present the identical features of injuries in patients. Using a traditional impact system, a repetitive concussive injury (rCHI) model can induce mild to moderate human-like concussion. The injury degree can be determined by measuring the period of loss of consciousness (LOC) with a sign of a transient termination of breathing. The rCHI model is beneficial to use for its accuracy and simplicity in determining mTBI effects and potential treatments.

Concussion presents the most common type of traumatic brain injury. Therefore, a repetitive concussive animal model, which replicates the important features of an injury in patients, may provide a means to study concussion in a rigorous, controlled, and efficient manner.

Despite the concussion/ mild traumatic brain injury (mTBI) being the most frequent occurrence of traumatic brain injury, there is still a lack of ...

Murine Model of Controlled Cortical Impact for the Induction of Traumatic Brain Injury

The Centers for Disease Control and Injury Prevention estimate that almost 2 million people sustain a traumatic brain injury (TBI) every year in the United States. In fact, TBI is a contributing factor to over a third of all injury-related mortality. Nonetheless, the cellular and molecular mechanisms underlying the pathophysiology of TBI are poorly understood. Thus, preclinical models of TBI capable of replicating the injury mechanisms pertinent to TBI in human patients are a critical research need. The controlled cortical impact (CCI) model of TBI utilizes a mechanical device to directly impact the exposed cortex. While no model can full recapitulate the disparate injury patterns and heterogeneous nature of TBI in human patients, CCI is capable of inducing a wide range of clinically applicable TBI. Furthermore, CCI is easily standardized allowing investigators to compare results across experiments as well as across investigative groups. The following protocol is a detailed description of applying a severe CCI with a commercially available impacting device in a murine model of TBI.

Here we describe a protocol for the induction of murine traumatic brain injury via an open-head controlled cortical impact.

The Centers for Disease Control and Injury Prevention estimate that almost 2 million people sustain a traumatic brain injury (TBI) every year in the ...

Neuroscience

Electromagnetic Controlled Closed-Head Model of Mild Traumatic Brain Injury in Mice

Highly reproducible animal models of traumatic brain injury (TBI), with well-defined pathologies, are needed for testing therapeutic interventions and understanding the mechanisms of how a TBI alters brain function. The availability of multiple animal models of TBI is necessary to model the different aspects and severities of TBI seen in people. This manuscript describes the use of a midline closed head injury (CHI) to develop a mouse model of mild TBI. The model is considered mild because it does not produce structural brain lesions based on neuroimaging or gross neuronal loss. However, a single impact creates enough pathology that cognitive impairment is measurable at least 1 month after injury. A step-by-step protocol to induce a CHI in mice using a stereotaxically guided electromagnetic impactor is defined in the paper. The benefits of the mild midline CHI model include the reproducibility of the injury-induced changes with low mortality. The model has been temporally characterized up to 1 year after the injury for neuroimaging, neurochemical, neuropathological, and behavioral changes. The model is complementary to open skull models of controlled cortical impact using the same impactor device. Thus, labs can model both mild diffuse TBI and focal moderate-to-severe TBI with the same impactor.

The protocol describes mild traumatic brain injury in a mouse model. In particular, a step-by-step protocol to induce a mild midline closed head injury and the characterization of the animal model is fully explained.

Highly reproducible animal models of traumatic brain injury (TBI), with well-defined pathologies, are needed for testing therapeutic interventions and ...

Validating Injury Response and Behavioral Assessments in an mTBI Rat Model

Rat Model of Closed-Head Mild Traumatic Injury and its Validation

Animal models are crucial for advancing our understanding of mild traumatic brain injury (mTBI) and guiding clinical research. To achieve meaningful insights, developing a stable and reproducible animal model is essential. In this study, we report a detailed description of a closed-head mTBI model and a representative validation method using Sprague-Dawley rats to verify the modeling effect. The model involves dropping a 550 g mass weight from a height of 100 cm directly onto the head of a rat on a destructible surface, followed by a 180-degree turn. To assess the injury, rats underwent a series of neurobehavioral assessments 10 min post-injury, including time of loss of consciousness, first seeking-behavior time, escape ability, and beam balance ability test. During the acute and subacute stages following the injury, behavioral tests were conducted to assess motor coordination ability (Beam task), anxiety (Open Field test), and learning and memory abilities (Morris Water Maze test). The closed-head mTBI model produced a consistent injury response with minimal mortality and replicated real-life situations. The validation method effectively verified the model development and ensured the stability and consistency of the model.

Author Spotlight: Advancing Traumatic Brain Injury Research - A Closed-Head Model for Accurate Replication and Rapid Assessment 

Here, we present a closed-head mild traumatic brain injury (mTBI) rat model and its validation exhibiting remarkable similarity to human mTBI concerning behavioral manifestations during the acute and subacute stages.

Animal models are crucial for advancing our understanding of mild traumatic brain injury (mTBI) and guiding clinical research. To achieve meaningful ...

rmTBI Induction in Mice via a Closed-Head Injury Method

Modified Mouse Model of Repetitive Mild Traumatic Brain Injury Incorporating Thinned-Skull Window and Fluid Percussion

Mild traumatic brain injury is a clinically highly heterogeneous neurological disorder. Highly reproducible traumatic brain injury (TBI) animal models with well-defined pathologies are urgently needed for studying the mechanisms of neuropathology after mild TBI and testing therapeutics. Replicating the entire sequelae of TBI in animal models has proven to be a challenge. Therefore, the availability of multiple animal models of TBI is necessary to account for the diverse aspects and severities seen in TBI patients. CHI is one of the most common methods for fabricating rodent models of rmTBI. However, this method is susceptible to many factors, including the impact method used, the thickness and shape of the skull bone, animal apnea, and the type of head support and immobilization utilized. The aim of this protocol is to demonstrate a combination of the thinned-skull window and fluid percussion injury (FPI) methods to produce a precise mouse model of CHI-associated rmTBI. The primary objective of this protocol is to minimize factors that could impact the accuracy and consistency of CHI and FPI modeling, including skull bone thickness, shape, and head support. By utilizing a thinned-skull window method, potential inflammation due to craniotomy and FPI is minimized, resulting in an improved mouse model that replicates the clinical features observed in patients with mild TBI. Results from behavior and histological analysis using hematoxylin and eosin (HE) staining suggest that rmTBI can lead to a cumulative injury that produces changes in both behavior and gross morphology of the brain. Overall, the modified CHI-associated rmTBI presents a useful tool for researchers to explore the underlying mechanisms that contribute to focal and diffuse pathophysiological changes in rmTBI.

Author Spotlight: Optimizing Rodent Models for Investigating the Mechanisms and Rehabilitation in Repeated Mild Traumatic Brain Injury

This protocol presents a modified mouse model of repetitive mild traumatic brain injury (rmTBI) induced via a closed-head injury (CHI) method. The approach features a thinned-skull window and fluid percussion to reduce the inflammation commonly caused by meninges exposure, along with improved reproducibility and accuracy in modeling rmTBI in rodents.

Mild traumatic brain injury is a clinically highly heterogeneous neurological disorder. Highly reproducible traumatic brain injury (TBI) animal models ...

Development of an Uncomplicated Mild Traumatic Brain Injury Model Modified by Weight-Drop Method and Evidenced by Magnetic Resonance Imaging

Mild traumatic brain injury (mTBI), known as concussion, accounts for more than 85% of brain injuries globally. Specifically, uncomplicated mTBI showing negative findings in routine clinical imaging in the acute phase hinders early and appropriate care in these patients. It has been acknowledged that different impact parameters may affect and even accelerate the progress of subsequent neuropsychological symptoms following mTBI. However, the association of impact parameters during concussion to the outcome has not been extensively examined. In the current study, an animal model with closed-head injury (CHI) modified from the weight-drop injury paradigm was described and demonstrated in detail. Adult male Sprague-Dawley rats (n = 20) were randomly assigned to CHI groups with different impact parameters (n = 4 per group). Longitudinal MR imaging studies, including T2-weighted imaging and diffusion tensor imaging, and sequential behavioral assessments, such as modified neurological severity score (mNSS) and the beam walk test, were conducted over a 50-day study period. Immunohistochemical staining for astrogliosis was performed on day 50 post-injury. Worse behavioral performance was observed in animals following repetitive CHI compared to the single injury and sham group. By using longitudinal magnetic resonance imaging (MRI), no significant brain contusion was observed at 24 h post-injury. Nevertheless, cortical atrophy and alteration of cortical fractional anisotropy (FA) were demonstrated on day 50 post-injury, suggesting the successful replication of clinical uncomplicated mTBI. Most importantly, changes in neurobehavioral outcomes and image features observed after mTBI were dependent on impact number, inter-injury intervals, and the selected impact site in the animals. This in vivo mTBI model combined with preclinical MRI provides a means to explore brain injury on a whole-brain scale. It also allows the investigation of imaging biomarkers sensitive to mTBI across varying impact parameters and severity levels.

Here, we present a protocol to establish a closed-head injury animal model replicating the neuroimage outcome of uncomplicated mild traumatic brain injury with the preserved brain structure in the acute phase and long-term brain atrophy. Longitudinal magnetic resonance imaging is the primary method used for evidence.

Mild traumatic brain injury (mTBI), known as concussion, accounts for more than 85% of brain injuries globally. Specifically, uncomplicated mTBI showing ...

Generating a Mouse Model of Traumatic Brain Injury Using an Impactor Device

Source: Schwulst, S. J. et al. <a href="https://app-jove-com.bdigitaluss.remotexs.co/v/60027">Murine Model of Controlled Cortical Impact for the Induction of Traumatic Brain Injury.</a> J. Vis. Exp. (2019)
This video demonstrates the procedure for inducing traumatic brain injury (TBI) in a mouse model. An anesthetized mouse with an exposed skull is taken to create an opening in the skull, and then a controlled cortical injury is induced using an impact device. The injury damages the brain tissue, causing impaired cognitive function and motor coordination.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. Induce ...

JoVE Encyclopedia of Experiments

Neuropathology

Trauma

Modeling Repetitive Concussive Head Injuries in a Mouse Model

<a href='https://app-jove-com.bdigitaluss.remotexs.co/v/54530/a-repetitive-concussive-head-injury-model-in-mice'>Source: Yang, Z., et.al.&#160;A Repetitive Concussive Head Injury Model in Mice. J. Vis. Exp. (2016).</a>This video demonstrates the induction of repetitive concussive head injuries in a mouse using an electromagnetic impact device. The procedure involves positioning the impact tip between the interfrontal and lambdoid sutures on the skull of an anesthetized mouse and using a probe tip to precisely set the impact depth. The impact is delivered at a controlled velocity and depth to simulate mild traumatic brain injuries, followed by a recovery period, with the injuries repeated at specified intervals.

Source: Yang, Z., et.al.&#160;A Repetitive Concussive Head Injury Model in Mice. J. Vis. Exp. (2016).This video demonstrates the induction of repetitive ...