This work was supported in part by the National Institutes of Health under award numbers R01NS120882, RF1NS119165, and R01NS103785 and the Department of Defense award number AZ190017. The content is solely the responsibility of the authors and does not represent the official views of the National Institutes of Health or the Department of Defense.

The experiments performed were approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Kentucky, and both the ARRIVE and the Guide for the Care and Use of Laboratory Animals guidelines were followed during the study.
1. Surgical setup
NOTE: Mice are housed in groups of 4-5/cage, humidity in the housing room is maintained at 43%-47%, and the temperature is maintained at 22-23 &#730;C. Mice are given ad libitum ...

<ol>
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The authors have nothing to disclose.

Several steps are involved in recreating a consistent injury model using the described model. First, it is critical to correctly secure the animal into the stereotaxic frame. The animal's head should not be able to move laterally, and the skull should be completely flat with bregma and lambda reading the same coordinates. Correctly placing the ear bars is the most difficult aspect of this surgery, and this can only be learned with practice. If the skull is not level, the head should be adjusted before inducing CHI. Failu...

Traumatic brain injury (TBI) is caused by an external force on the brain, often associated with falls, sports injuries, physical violence, or road accidents. In 2014, the Centers for Disease Control and Prevention determined that 2.53 million Americans visited the emergency department to seek medical help for TBI-related accidents1. Since mild TBI (mTBI) represents the majority of TBI cases, over the past several decades, multiple models of mTBI have been adopted, which include weight drop, piston-driven closed head injury and controlled cortical impact, rotational injury, mild fluid percussion injury, and blast injury models2,3. The heterogeneity of the mTBI models is useful to address the different features associated with mTBI seen in people and to help evaluate the cellular and molecular mechanisms associated with brain injury.
Of the commonly used models of closed head injury, one of the first and most widely used models is the weight drop method, where an object is dropped from a specific height onto the animal&#39;s head (anesthetized or awake)2,4. In the weight drop method, the injury&#39;s severity depends on several parameters, including craniotomy performed or not, head fixed or free, and the distance and weight of the falling object2,4. One disadvantage of this model is the high variability in the severity of the injury and the high mortality rate associated with respiratory depression5,6. A common alternative is to deliver the impact using a pneumatic or electromagnetic device, which can be done directly on the exposed dura (controlled cortical impact: CCI) or closed skull (closed head injury: CHI). One of the strengths of the piston-driven injury is its high reproducibility and low mortality. However, CCI requires craniotomy7,8, and a craniotomy itself induces inflammation9. Instead, in the CHI model, there is no need for craniotomy. As already stated, each model has limitations. One of the limitations of the CHI model described in this paper is that the surgery is performed using a stereotaxic frame, and the head of the animal is immobilized. While the full head immobilization assures reproducibility, it does not account for movement after the impact that could contribute to the injury associated with a mTBI.
This protocol describes a basic method to perform a CHI impact with a commercially available electromagnetic impactor device10 in a mouse. This protocol details the exact parameters involved to achieve a highly reproducible injury. In particular, the investigator has precise control over the parameters (depth of injury, dwell time, and velocity of impact) to precisely define the injury severity. As described, this CHI model produces an injury that results in bilateral pathology, both diffuse and microscopic (i.e., chronic activation of glia, axonal and vascular damage), and behavioral phenotypes11,12,13,14,15. In addition, the described model is considered mild as it does not induce structural brain lesions based on MRI or gross lesions on pathology even 1 year after the injury16,17.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>9 mm Autoclip Applier</td>
			<td>Braintree scientific</td>
			<td>ACS- APL</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>9 mm Autoclip Remover</td>
			<td>Braintree scientific</td>
			<td>ACS- RMV</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>9 mm Autoclip, Case of 1,000 clips</td>
			<td>Braintree scientific</td>
			<td>ACS- CS</td>
			<td>Surgery (Staples)</td>
		</tr>
		<tr>
			<td>Aperio ImageScope software&#160;</td>
			<td>Leica BioSystems</td>
			<td>NA&#160;</td>
			<td>IHC</td>
		</tr>
		<tr>
			<td>BladeFLASK Blade Remover</td>
			<td>Fisher Scientific</td>
			<td>22-444-275</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Cotton tip applicator</td>
			<td>VWR</td>
			<td>89031-270</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Digitial mouse stereotaxic frame</td>
			<td>Stoelting</td>
			<td>51730D</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Dumont #7 Forceps</td>
			<td>Roboz</td>
			<td>RS-5047</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Ear bars</td>
			<td>Stoelting</td>
			<td>51649</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>EthoVision XT 11.0&#160;</td>
			<td>Noldus Information Technology</td>
			<td>NA</td>
			<td>RAWM&#160;</td>
		</tr>
		<tr>
			<td>Fiber-Lite</td>
			<td>Dolan-Jeffer Industries</td>
			<td>UN16103-DG</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Fisherbrand Bulb for Small Pipets</td>
			<td>Fisher Scientific</td>
			<td>03-448-21</td>
			<td>Head support apparatus</td>
		</tr>
		<tr>
			<td>Gemini Avoidance System</td>
			<td>San Diego Instruments</td>
			<td>NA</td>
			<td>Active avoidance</td>
		</tr>
		<tr>
			<td>Heating Pad</td>
			<td>Sunbeam&#160;</td>
			<td>732500000U</td>
			<td>Surgery prep</td>
		</tr>
		<tr>
			<td>HRP conjugated goat anti-rabbit IgG&#160;</td>
			<td>Jackson Immuno Research laboratories</td>
			<td>111-065-144&#160;</td>
			<td>IHC</td>
		</tr>
		<tr>
			<td>Induction chamber</td>
			<td>Kent Scientific</td>
			<td>VetFlo-0530XS</td>
			<td>Surgery prep</td>
		</tr>
		<tr>
			<td>Isoflurane, USP</td>
			<td>Covetrus</td>
			<td>NDC: 11695-6777-2</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Mouse gas anesthesia head holder</td>
			<td>Stoelting</td>
			<td>51609M</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Neuropactor Stereotaxic Impactor</td>
			<td>Neuroscience Tools</td>
			<td>n/a</td>
			<td>Surgery: Formally distributed by Lecia as impact one</td>
		</tr>
		<tr>
			<td>NexGen Mouse 500</td>
			<td>Allentown&#160;</td>
			<td>n/a</td>
			<td>Post-surgery, holding cage</td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>Bemis</td>
			<td>PM992</td>
			<td>Head support apparatus</td>
		</tr>
		<tr>
			<td>Peanut - Professional Hair Clipper</td>
			<td>Whal</td>
			<td>8655-200&#160;</td>
			<td>Surgery prep</td>
		</tr>
		<tr>
			<td>Povidone-Iodine Solution USP, 10% (w/v), 1% (w/v) available Iodine, for laboratory</td>
			<td>Ricca</td>
			<td>3955-16</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Puralube Vet Oinment,petrolatum ophthalmic ointment, Sterile ocular lubricant</td>
			<td>Dechra</td>
			<td>17033-211-38</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Rabbit anti-GFAP&#160;</td>
			<td>Dako</td>
			<td>Z0334</td>
			<td>IHC</td>
		</tr>
		<tr>
			<td>Rabbit anti-IBA1&#160;</td>
			<td>Wako</td>
			<td>019-19741</td>
			<td>IHC</td>
		</tr>
		<tr>
			<td>8-arm Radial Arm Water Maze</td>
			<td>MazeEngineers</td>
			<td>n/a</td>
			<td>RAWM&#160;</td>
		</tr>
		<tr>
			<td>Scale</td>
			<td>OHAUS CS series</td>
			<td>BAL-101</td>
			<td>Surgery prep</td>
		</tr>
		<tr>
			<td>Scalpel Handle #7 Solid 6.25&#34;&#160;</td>
			<td>Roboz</td>
			<td>RS-9847</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Sterile Alcohol Prep Pads (isopropyl alcohol 70% v/v)</td>
			<td>Fisher Brand</td>
			<td>22-363-750</td>
			<td>Surgery prep</td>
		</tr>
		<tr>
			<td>SumnoSuite low-flow anesthesia system</td>
			<td>Kent Scientific</td>
			<td>SS-01</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>10 mL syringe Luer-Lok Tip</td>
			<td>BD Bard-Parker</td>
			<td>302995</td>
			<td>Head support apparatus</td>
		</tr>
		<tr>
			<td>Timers</td>
			<td>Fisher Scientific</td>
			<td>6KED8</td>
			<td>Surgery</td>
		</tr>
		<tr>
			<td>Topical anesthetic cream</td>
			<td>L.M.X 4</td>
			<td>NDC 0496-0882-15</td>
			<td>Surgery prep</td>
		</tr>
		<tr>
			<td>Triple antibiotic ointment</td>
			<td>Major</td>
			<td>NDC 0904-0734-31</td>
			<td>Post-surgery</td>
		</tr>
		<tr>
			<td>Tubing</td>
			<td>MasterFlex</td>
			<td>96410-16</td>
			<td>Head support apparatus</td>
		</tr>
		<tr>
			<td>Vaporizer Single Channel Anesthesia System</td>
			<td>Kent Scientific</td>
			<td>VetFlo-1210S</td>
			<td>Surgery prep</td>
		</tr>
	</tbody>
</table>

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.

This stereotaxic electromagnetic impactor device is versatile. It is used for both an open skull controlled cortical impact (CCI) or a closed head injury (CHI) surgery. Furthermore, the injury severity can be modulated by changing the injury parameters such as impact velocity, dwell time, impact depth, impactor tip, and injury target. Herein is described a CHI surgery using a 5.0 mm steel tip impactor. This injury is considered mild because there are no structural brain lesions. The mortality rate in adult mice is less t...

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

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 ...

Most traumatic brain injuries are mild, or more commonly known as a concussion.The CHI procedure models pathologists that can occur following a mild TBI in people.The CHI protocol is highly reproducible with low variability, and only requires a single closed head impact, making the model accessible to new users.In addition to understanding how the brain changes after a mild TBI, the CHI model can be used to test therapies to speed recovery.One of the challenging steps in performing the CHI surgery is securing the animal into the stereotaxic frame.In particular, the most difficult part is placing the ear bars.This can only be learned with practice.Use a designated surgical area, such as a hood or dedicated surgical room to perform surgery.Ensure that the surgical area includes a heating pad, a stereotaxic frame equipped with an electromagnetic impactor, and an anesthesia mask designed to administer isoflurane gas.For impactor setup, select the five-millimeter probe tip.Screw the probe tip to the piston at the bottom center of the actuator, and gently tighten the probe without applying excessive force.Re-tighten the tip between impacts.Next, set up the impact velocity by rotating the large knob on the left side of the control box until an impact velocity of 5.0

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Research

JoVE Journal

Neuroscience

1.9K ビュー.  University of Kentucky. Most traumatic brain injuries are mild, or more commonly known as a concussion.The CHI procedure models pathologists that can occur following a mild TBI in people.The CHI protocol is highly reproducible with low variability, and only requires a single closed head impact, making the model accessible to new users.In addition to understanding how the brain changes after a mild TBI, the CHI model can be used to test therapies to speed recovery.One of the challenging steps in performing the CHI su...