We would like to thank the Thoracic Surgery Foundation for Research and Education for their Financial Support of this project.

1. Preoperative Preparation and Anesthesia
<ol>
	<li>Be sure to observe sterile technique throughout the procedure.&#160;Lay out all instruments.</li>
	<li>Turn on the temperature control bed prior to anesthetic induction so that it may warm to the appropriate temperature (36.5 &#176;C).&#160; Power on the laser Doppler perfusion monitor so that it may boot during induction.</li>
	<li>Place the mouse in the induction chamber.
	<ol>
		<li>Carefully monitor the respiratory rate of the mouse during induction.</li>
		<li>As soon as the respiratory rate has visually slowed, remove the mouse from the induction chamber.</li>
		<li>Perform toe pinch to assess adequacy of anesthetic.</li>
	</ol>
	</li>
	<li>With the mouse properly anesthetized, place mouse in supine position.</li>
	<li>Insert face into nose cone and secure all extremities to the heating table.
	<ol>
		<li>Pay special attention to ensure that extremities are secured in anatomic position, with no deviation to one side.&#160;If the mouse is improperly positioned, it is difficult to avoid internal thoracic artery transection during sternotomy.</li>
	</ol>
	</li>
	<li>Using clippers or commercially available hair removal cream, remove hair from the midline thorax and left lower extremity ventral surface.
	<ol>
		<li>If using hair removal cream, avoid leaving cream in place for greater than 30 sec, as alkali burns can occur.</li>
	</ol>
	</li>
	<li>Titrate volatile anesthetic vaporizer concentration to maintain adequate anesthesia.
	<ol>
		<li>Expected vaporizer fractions are between 1-5% using isoflurane with high flow O2.</li>
		<li>Volatile anesthetic vaporizer concentration should be titrated to maintain anesthesia during surgical stimulation while maintaining spontaneous respirations.</li>
	</ol>
	</li>
</ol>
2. Rectal Probe Laser Doppler Placement
<ol>
	<li>Insert lubricated rectal probe into the mouse&#8217;s rectum.&#160;Secure in place to operating bed.</li>
	<li>Adjust the heating bed for a target rectal temperature of 36.5 &#176;C.</li>
	<li>Make small incision over femoral artery of mouse and dissect skin away from subcutaneous tissue.</li>
	<li>Insert laser Doppler probe over femoral artery.</li>
	<li>Adjust probe positions until the perfusion monitor registers greater than 800 perfusion units.
	<ol>
		<li>Firmly secure probe in place.&#160;Improperly secured probes can have falsely low perfusion measurements.</li>
	</ol>
	</li>
</ol>
3. Dissection of Aortic Arch/Subclavian Artery
<ol>
	<li>Make a 2 cm skin incision above the sternal notch and gently dissect skin away from subcutaneous tissue.</li>
	<li>Dissect the submandibular gland free.
	<ol>
		<li>If bleeding occurs, gentle pressure can be applied with a cotton swab.</li>
		<li>Divide the submandibular gland through midline in the avascular plane.</li>
	</ol>
	</li>
	<li>Gently lift sternum with forceps and using the scissors make 1 cm midline sternotomy through the midline of the sternum. Any deviation from midline can result in internal mammary artery hemorrhage which will be difficult to control.</li>
	<li>Place 5-0 retraction sutures on each side at the edge of the sternum and retract sternum laterally securing sutures to the operating bed. Avoid placing retraction sutures too laterally to prevent pneumothoraces. </li>
	<li>Using blunt dissection free strap muscles along trachea. The left strap muscle can be divided with scissors to improve exposure.</li>
	<li>Dissect free the thymus from surrounding tissue. Continue blunt dissection until the great vessels are visualized. Use extreme caution to prevent entrance into the pleural space.</li>
	<li>Place vascular clamps on aortic arch and left subclavian artery.</li>
	<li>Verify distal flow has appropriately disrupted. This will be seen as a &#62;90% reduction in perfusion units.
	<ol>
		<li>Continue occlusion for desired for 4-8 min.</li>
	</ol>
	</li>
	<li>Remove vascular clamp and verify hemostasis before closure of chest.</li>
</ol>
4. Closure of Sternotomy and Skin
<ol>
	<li>Remove the retraction suture on the left side of the mouse.</li>
	<li>Close the sternotomy with the right retraction suture.
	<ol>
		<li>A single sternal suture (using the previously placed retraction stitch) is adequate for sternal closure.&#160;Placing another stitch is unnecessary and increases risks of pneumothorax and hemorrhage.</li>
	</ol>
	</li>
	<li>Close skin with running 5-0 stitch.</li>
</ol>
5. Recovery and Postoperative Assessment
<ol>
	<li>Transfer the mouse to recovery cage. Cage should be placed on a heating pad to increase the ambient temperature of the recovery chamber and reduce heat loss to the environment.</li>
	<li>Closely monitor the mouse for signs respiratory distress or seizure activity. Administer analgesia per institution guidelines.&#160;Euthanize mice immediately if seizure or respiratory distress is observed.
	<ol>
		<li>CO2 chamber euthanasia is our preferred method.&#160;Cervical dislocation is another option if CO2 is not available.</li>
		<li>Complete recovery can be expected in 1-2 hr, depending on the length of volatile anesthetic and concentration used.</li>
	</ol>
	</li>
	<li>Return the mouse to normal cage. Place food and water place on the floor of the cage.</li>
	<li>Assess neurologic status at 12 hr&#160;intervals using Basso Mouse Scale for Locomotion8.</li>
</ol>

<ol>
	<li>Conrad, M. F., Ye, J. Y., Chung, T. K., Davison, J. K., Cambria, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spinal+cord+complications+after+thoracic+aortic+surgery:+long-term+survival+and+functional+status+varies+with+deficit+severity.">Spinal cord complications after thoracic aortic surgery: long-term survival and functional status varies with deficit severity.</a> J. Vasc. Surg. 48, 47-53 (2008).</li><li>Okita, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fighting+spinal+cord+complication+during+surgery+for+thoracoabdominal+aortic+disease.">Fighting spinal cord complication during surgery for thoracoabdominal aortic disease.</a> Gen. Thorac. Cardiovasc. Surg. 59, 79-90 (2011).</li><li>Wong, D. 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=Delayed+spinal+cord+deficits+after+thoracoabdominal+aortic+aneurysm+repair.">Delayed spinal cord deficits after thoracoabdominal aortic aneurysm repair.</a> Ann. Thorac. Surg. 83, 1345-1355 (2007).</li><li>Taira, Y., Marsala, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+proximal+arterial+perfusion+pressure+on+function,+spinal+cord+blood+flow,+and+histopathologic+changes+after+increasing+intervals+of+aortic+occlusion+in+the+rat.">Effect of proximal arterial perfusion pressure on function, spinal cord blood flow, and histopathologic changes after increasing intervals of aortic occlusion in the rat.</a> Stroke. 27, 1850-1858 (1996).</li><li>Naslund, T. C., Hollier, L. H., Money, S. R., Facundus, E. C., Skenderis, B. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protecting+the+ischemic+spinal+cord+during+aortic+clamping.+The+influence+of+anesthetics+and+hypothermia.">Protecting the ischemic spinal cord during aortic clamping. The influence of anesthetics and hypothermia.</a> Ann. Surg. , 409-515 (1992).</li><li>Qayumi, A. K., Janusz, M. T., Lyster, D. M., Gillespie, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+model+for+investigation+of+spinal+cord+injury+caused+by+aortic+cross-clamping.">Animal model for investigation of spinal cord injury caused by aortic cross-clamping.</a> J. Invest. Surg. 10, 47-52 (1997).</li><li>Lang-Lazdunski, L., Matsushita, K., Hirt, L., Waeber, C., Vonsattel, J. P., Moskowitz, M. A., Dietrich, W. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spinal+Cord+Ischemia:+Development+of+a+model+in+the+mouse.">Spinal Cord Ischemia: Development of a model in the mouse.</a> Stroke. 31, 208-213 (2000).</li><li>Basso, D. M., Fisher, L. C., Anderson, A. J., Jakeman, L. B., McTigue, D. M., Popovich, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basso+Mouse+Scale+for+locomotion+detects+differences+in+recovery+after+spinal+cord+injury+in+five+common+mouse+strains.">Basso Mouse Scale for locomotion detects differences in recovery after spinal cord injury in five common mouse strains.</a> J. Neurotrauma. 23, 635-659 (2006).</li><li>Kwon, B. K., Tetzlaff, W., Grauer, J. N., Beiner, J., Vaccaro, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathophysiology+and+pharmacologic+treatment+of+acute+spinal+cord+injury.">Pathophysiology and pharmacologic treatment of acute spinal cord injury.</a> Spine. J. 4, 451-464 (2004).</li><li>Cheshire, W. P., Santos, C. C., Massey, E. W., Howard, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spinal+cord+infarction:+etiology+and+outcome.">Spinal cord infarction: etiology and outcome.</a> Neurology. 47, 321-330 (1996).</li><li>Kakinohana, 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=Delayed+paraplegia+after+spinal+cord+ischemic+injury+requires+caspase-3+activation+in+mice.">Delayed paraplegia after spinal cord ischemic injury requires caspase-3 activation in mice.</a> Stroke. 42 (8), 2302-2307 (2011).</li><li>Wang, Z., Yang, W., Britz, G. W., Lombard, F. W., Warner, D. S., Sheng, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+simplified+spinal+cord+ischemia+model+in+mice.">Development of a simplified spinal cord ischemia model in mice.</a> J. Neurosci. Methods. 189, 246-251 (2010).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=model+of+ischemic+spinal+cord+injury+with+delayed+paralysis+caused+by+aortic+cross-clamping.">model of ischemic spinal cord injury with delayed paralysis caused by aortic cross-clamping.</a> Anesthesiology. 113, 880-891 (2010).</li><li>Kang, 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=The+effects+of+systemic+hypothermia+on+a+murine+model+of+thoracic+aortic+ischemia+reperfusion.">The effects of systemic hypothermia on a murine model of thoracic aortic ischemia reperfusion.</a> J. Vasc. Surg. 52, 435-443 (2010).</li><li>Li, J., Benashski, S., McCullough, L. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Post-stroke+hypothermia+provides+neuroprotection+through+inhibition+of+AMP-activated+protein+kinase.">Post-stroke hypothermia provides neuroprotection through inhibition of AMP-activated protein kinase.</a> J. Neurotrauma. 28 (7), 1281-1288 (2011).</li></ol>

The authors declare&#160;no competing financial interests.

Paraplegia secondary to spinal cord ischemia&#160;reperfusion is the result of a complex of poorly understood pathologies9. While this is most commonly seen after thoracoabdominal aortic surgery, a variety of other insults such as&#160; aortic dissections, trauma, embolic phenomena, vasculitis, and systemic hypotension10 can result in paraplegia.&#160;To gain further understanding of this injury and provide future targets to eliminate this injury, animal models have become a necessity.
Patients afflicted with this complication exhibit either an immediate or delayed paralysis. This model and others adequately parallel11 the bimodal distribution of paralysis seen clinically. While moderate ischemia (4 min) produced a delayed paralysis, prolonged ischemia (8 min) resulted in an immediate and permanent paralysis.
The presented model has advantages compared to those requiring a lateral thoracotomy12,13. The median sternotomy exposure leaves the pleural cavity intact and eliminates the need for tracheal intubations or reestablishing negative pressure in the pleural space.&#160;Clinically, the sternotomy is associated with much less postoperative pain in than the lateral thoracotomy and might reduce postoperative analgesic requirements.
This model is not without limitations. As with other models, murine surgery has a learning curve and good surgical technique is imperative. Mice can quickly succumb if dissection is not done with care. The most common causes of intraoperative mortality are hemorrhage or pneumothorax. To avoid potentially fatal hemorrhage the sternotomy must be made midline. If the sternotomy is made too laterally a transaction of internal mammary arteries and subsequent hemorrhage may occur. Additionally, rough dissection of descending aorta and subclavian artery can result in hemorrhage the will be difficult or impossible to control.&#160;Pneumothoraces are another potentially fatal complication.&#160;These typically occur during the placement of retraction sutures or dissection of the aorta. If retraction sutures are place too laterally or the aortic arch is not dissected with care a pneumothorax can occur and are universally fatal.
Further steps need to be employed to ensure reproducibility. Normothermia is critical. During surgery mice are kept as close to 36.5 &#176;C as possible.&#160;Even mild hypothermia has been shown in to have significant neuroprotective effects in spinal cord and stroke models14,15. Furthermore, laser Doppler measurements should be closely monitored and mice with only 90% reduction in distal flow should be included for comparison. Incomplete occlusion of the aorta or subclavian arteries can results in higher distal flows and results that are highly variable.
In conclusion, the murine model of lower extremity paralysis presented can be easily adopted, yielding highly reproducible results. Applications of this model can provided the investigator with a means to study the immediate and delayed paralysis. Moreover, adoption of this model might prove beneficial in combating this devastating complication.

Lower extremity paralysis continues to complicate thoracoabdominal interventions. The injury, known as spinal cord ischemia-reperfusion injury (SCIR), results in paralysis in up to 20% of high risk patients1. Surgical adjuncts such as left heart bypass, lumbar cerbrospinal fluid drains,&#160;hypothermic circulatory arrest and intercostal artery reimplantation have reduced the incidence of this complication2; however, far too many patients continue to be affected.
Clinically, spinal cord ischemia and reperfusion injury is seen as either immediate or delayed paralysis following intervention3.&#160;However, our understanding of this injury has been stifled by a lack of mechanistic detail.&#160;As a result, few options are available to attenuate the injury once it has occurred.
We have thus enlisted a small animal, murine, model of spinal cord ischemia, and reperfusion injury to better characterize its pathogenesis.&#160;The majority of studies to date have used larger animal models to characterize this injury, namely rat4, rabbit5, and pig6 models.&#160; However, these are limited by their cost, complexity, variable reproducibility, and, most importantly, lack of available techniques for genetic manipulation.&#160;&#160;The most reliable of these published animal models involves infrarenal cross&#160;clamping of the abdominal aorta in rabbits.&#160;However, human anterior spinal neurons most often derive their vascular supply from more proximal branches7.&#160;Variable vascular anatomy of the spinal cord in these models adds to difficulty in transitioning their results into clinical use.
This manuscript presents a model for immediate or delayed paraplegia following thoracic aortic occlusion that is clinically relevant and easy to employ. Exposure of the aortic arch via mini&#160;sternotomy is less invasive and can elicit highly reproducible results with minimal morbidity and mortality. While this model in not without challenges and technical nuances, these can be overcome with careful dissection and tissue handling to produce a model of hind&#160;limb paralysis that can be easily implemented.

<table border="0" cellpadding="0" cellspacing="0" width="749">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">VMS Anesthesia Machine</td>
			<td style="width:247px;">MDS Matrx</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Isoflurane</td>
			<td style="width:247px;">Vet One</td>
			<td style="width:119px;">13985-528-60</td>
			<td>2.0% through nose cone&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Induction Chamber</td>
			<td style="width:247px;">Vet Equip</td>
			<td>941444</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Heating Bed</td>
			<td style="width:247px;">Vestavia Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laser Doppler Monitor</td>
			<td style="width:247px;">Moor Instruments</td>
			<td style="width:119px;">VMS-LDF1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">5-0 Suture, Polyester</td>
			<td style="width:247px;">Surgidac</td>
			<td style="width:119px;">VD-551</td>
			<td>Taper Needel</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">Microdissecting Clips</td>
			<td style="width:247px;">Biomedical Research Insturments</td>
			<td style="width:119px;">14-1030, 14-1060</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">Surgical Instruments</td>
			<td style="width:247px;">Fine Surgical Instruments</td>
			<td style="width:119px;"></td>
			<td>Forceps, needle holder</td>
		</tr>
	</tbody>
</table>

reproducable paraplegia by thoracic aortic occlusion in a murine model of spinal cord ischemia-reperfusion

Background 
Lower extremity paralysis continues to complicate aortic interventions. The lack of understanding of the underlying pathology has hindered advancements to decrease the occurrence this injury.&#160;The current model demonstrates reproducible lower&#160;extremity paralysis following thoracic aortic occlusion.
Methods 
Adult male C57BL6 mice were anesthetized with isoflurane. Through a cervicosternal incision the aorta was exposed. The descending thoracic aorta and left subclavian arteries were identified without entrance into pleural space. Skeletonization of these arteries was followed by immediate closure (Sham) or occlusion for 4 min (moderate ischemia) or 8 min (prolonged ischemia). The sternotomy and skin were closed and the mouse was transferred to warming bed for recovery.&#160; Following recovery, functional analysis was obtained at 12 hr intervals until 48 hr.
Results 
Mice that underwent sham surgery showed no observable hind&#160;limb deficit. Mice subjected to moderate ischemia for 4 min had minimal functional deficit at 12 hr followed by progression to complete paralysis at 48 hr. Mice subjected to prolonged ischemia had an immediate paralysis with no observable hind-limb movement at any point in the postoperative period. There was no observed intraoperative or post&#160;operative mortality.
Conclusion 
Reproducible lower extremity paralysis whether immediate or delayed can be achieved in a murine model. Additionally, by using a median sternotomy and careful dissection, high survival rates, and reproducibility can be achieved.

Mice underwent sham surgery (n=3) or aortic occlusion for 4 (n=3) to 8 min (n=3). Postoperatively mice were graded by the Basso Mouse Score (Figure 1).&#160;Mice that underwent sham surgery had no observable functional deficits at any point postoperatively. Mice subjected to moderate ischemia (4 min) had near normal hind-limb function at 12 hr with progressive functional decline to complete paralysis by 48 hr. Mice in prolonged ischemia group (8min) had complete paralysis following surgery without any recoverable function (Figure 2).
<img alt="Figure 1" fo:content-width="5in" fo:src="/files/ftp_upload/50910/50910fig1highres.jpg" src="/files/ftp_upload/50910/50910fig1.jpg" /> 
Figure 1. Basso Score for Hind Limb Motor Function8.&#160; Scoring system for hind limb neurologic dysfunction graded from 0 (no function) to 9 (normal function). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/50910/50910fig1highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 2" fo:content-width="5in" fo:src="/files/ftp_upload/50910/50910fig2highres.jpg" src="/files/ftp_upload/50910/50910fig2.jpg" /> 
Figure 2. Postoperative Hind-Limb Function. The severity of neurologic deficit was graded using the Basso Mouse Scale at 12 hr intervals postoperatively until 48 hr. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/50910/50910fig2highres.jpg" target="_blank">Click here to view larger image.</a>

Watch this Scientific Journal Video about Reproducable Paraplegia by Thoracic Aortic Occlusion in a Murine Model of Spinal Cord Ischemia-reperfusion at JoVE.com

Reproducable Paraplegia by Thoracic Aortic Occlusion in a Murine Model of Spinal Cord Ischemia-reperfusion

The lack of mechanistic understanding of spinal cord ischemia-reperfusion injury has hindered further adjuncts to prevent paraplegia following high risk aortic operations. Thus, the development of animal models is imperative. This manuscript demonstrates reproducible lower extremity paralysis following thoracic aortic occlusion in a murine model.

Background
Lower extremity paralysis continues to complicate aortic interventions. The lack of understanding of the underlying pathology has hindered ...

reproducable-paraplegia-thoracic-aortic-occlusion-murine-model-spinal

Nanyang Technological University

Research

JoVE Journal

Medicine

12.0K Views.  University of Colorado. The lack of mechanistic understanding of spinal cord ischemia-reperfusion injury has hindered further adjuncts to prevent paraplegia following high risk aortic operations. Thus, the development of animal models is imperative. This manuscript demonstrates reproducible lower extremity paralysis following thoracic aortic occlusion in a murine model. 

Video: Reproducable Paraplegia by Thoracic Aortic Occlusion in a Murine Model of Spinal Cord Ischemia-reperfusion

Acute and Chronic Tactile Sensory Testing after Spinal Cord Injury in Rats

Spinal cord injury (SCI) impairs sensory systems causing allodynia1-8. To identify cellular and molecular causes of allodynia, sensitive and valid sensory testing in rat SCI models is needed. However, until recently, no single testing approach had been validated for SCI so that standardized methods have not been implemented across labs. Additionally, available testing methods could not be implemented acutely or when severe motor impairments existed, preventing studies of the development of SCI-induced allodynia3. Here we present two validated sensory testing methods using von Frey Hair (VFH) monofilaments which quantify changes in tactile sensory thresholds after SCI4-5. One test is the well-established Up-Down test which demonstrates high sensitivity and specificity across different SCI severities when tested chronically5. The other test is a newly-developed dorsal VFH test that can be applied acutely after SCI when allodynia develops, prior to motor recovery4-5. Each VFH monofilament applies a calibrated force when touched to the skin of the hind paw until it bends. In the up-down method, alternating VFHs of higher or lower forces are used on the plantar L5 dermatome to delineate flexor withdrawal thresholds. Successively higher forces are applied until withdrawal occurs then lower force VFHs are used until withdrawal ceases. The tactile threshold reflects the force required to elicit withdrawal in 50% of the stimuli. For the new test, each VFH is applied to the dorsal L5 dermatome of the paw while the rat is supported by the examiner. The VFH stimulation occurs in ascending order of force until at least 2 of 3 applications at a given force produces paw withdrawal. Tactile sensory threshold is the lowest force to elicit withdrawal 66% of the time. Acclimation, testing and scoring procedures are described. Aberrant trials that require a retest and typical trials are defined. Animal use was approved by Ohio State University Animal Care and Use Committee.

We describe two tactile sensory testing methods for acute or chronic periods of spinal cord injury in rats. These validated procedures can detect the development and maintenance of allodynia-like sensations.

Spinal cord injury (SCI) impairs sensory systems causing allodynia1-8. To identify cellular and molecular causes of allodynia, sensitive and valid sensory ...

A Murine Model of Cervical Spinal Cord Injury to Study Post-lesional Respiratory Neuroplasticity

A cervical spinal cord injury induces permanent paralysis, and often leads to respiratory distress. To date, no efficient therapeutics have been developed to improve/ameliorate the respiratory failure following high cervical spinal cord injury (SCI). Here we propose a murine pre-clinical model of high SCI at the cervical 2 (C2) metameric level to study diverse post-lesional respiratory neuroplasticity. The technique consists of a surgical partial injury at the C2 level, which will induce a hemiparalysis of the diaphragm due to a deafferentation of the phrenic motoneurons from the respiratory centers located in the brainstem. The contralateral side of the injury remains intact and allows the animal recovery. Unlike other SCIs which affect the locomotor function (at the thoracic and lumbar level), the respiratory function does not require animal motivation and the quantification of the deficit/recovery can be easily performed (diaphragm and phrenic nerve recordings, whole body ventilation). This pre-clinical C2 SCI model is a powerful, useful, and reliable pre-clinical model to study various respiratory and non-respiratory neuroplasticity events at different levels (molecular to physiology) and to test diverse putative therapeutic strategies which might improve the respiration in SCI patients.

Respiratory failure is the leading cause of death following a cervical spinal cord injury. Having a reproducible, quantifiable, and reliable pre-clinical animal model of respiratory failure induced by a partial cervical injury will help to understand the subsequent respiratory and non-respiratory neuroplasticity and allow testing putative repair strategies.

A cervical spinal cord injury induces permanent paralysis, and often leads to respiratory distress. To date, no efficient therapeutics have been developed ...

A Murine Model of Myocardial Ischemia-reperfusion Injury through Ligation of the Left Anterior Descending Artery

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms at work during MI and developing effective therapeutic approaches requires methodology to reproducibly simulate the clinical incidence and reflect the pathophysiological changes associated with MI. Here, we describe a surgical method to induce MI in mouse models that can be used for short-term ischemia-reperfusion (I/R) injury as well as permanent ligation. The major advantage of this method is to facilitate location of the left anterior descending artery (LAD) to allow for accurate ligation of this artery to induce ischemia in the left ventricle of the mouse heart. Accurate positioning of the ligature on the LAD increases reproducibility of infarct size and thus produces more reliable results. Greater precision in placement of the ligature will improve the standard surgical approaches to simulate MI in mice, thus reducing the number of experimental animals necessary for statistically relevant studies and improving our understanding of the mechanisms producing cardiac dysfunction following MI. This mouse model of MI is also useful for the preclinical testing of treatments targeting myocardial damage following MI.

We introduce a surgical method to induce experimental ischemia/reperfusion (I/R) injury to simulate myocardial infarction (MI) in mouse models that allows for more clarity in positioning of the ligation on the left anterior descending artery (LAD) to increase the reproducibility of MI experiments in mice.

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms ...

Controlled Cortical Impact Model for Traumatic Brain Injury

Every year over a million Americans suffer a traumatic brain injury (TBI). Combined with the incidence of TBIs worldwide, the physical, emotional, social, and economical effects are staggering. Therefore, further research into the effects of TBI and effective treatments is necessary. The controlled cortical impact (CCI) model induces traumatic brain injuries ranging from mild to severe. This method uses a rigid impactor to deliver mechanical energy to an intact dura exposed following a craniectomy. Impact is made under precise parameters at a set velocity to achieve a pre-determined deformation depth. Although other TBI models, such as weight drop and fluid percussion, exist, CCI is more accurate, easier to control, and most importantly, produces traumatic brain injuries similar to those seen in humans. However, no TBI model is currently able to reproduce pathological changes identical to those seen in human patients. The CCI model allows investigation into the short-term and long-term effects of TBI, such as neuronal death, memory deficits, and cerebral edema, as well as potential therapeutic treatments for TBI.

Traumatic brain injuries (TBIs) remain a serious health problem. Using the controlled cortical impact surgery model, research on the effects of TBI and possible treatment methods may be performed.

Every year over a million Americans suffer a traumatic brain injury (TBI).  Combined with the incidence of TBIs worldwide, the physical, emotional, ...

A Radio-telemetric System to Monitor Cardiovascular Function in Rats with Spinal Cord Transection and Embryonic Neural Stem Cell Grafts

High thoracic or cervical spinal cord injury (SCI) can lead to cardiovascular dysfunction. To monitor cardiovascular parameters, we implanted a catheter connected to a radio transmitter into the femoral artery of rats that underwent a T4 spinal cord transection with or without grafting of embryonic brainstem-derived neural stem cells expressing green fluorescent protein. Compared to other methods such as cannula insertion or tail-cuff, telemetry is advantageous to continuously monitor blood pressure and heart rate in freely moving animals. It is also capable of long term multiple data acquisitions. In spinal cord injured rats, basal cardiovascular data under unrestrained condition and autonomic dysreflexia in response to colorectal distension were successfully recorded. In addition, cardiovascular parameters before and after SCI can be compared in the same rat if a transmitter is implanted before a spinal cord transection. One limitation of the described telemetry procedure is that implantation in the femoral artery may influence the blood supply to the ipsilateral hindlimb.

We present a protocol for using a radio-telemetric system to record cardiovascular parameters in T4 spinal cord transected rats eight weeks after embryonic brainstem neural stem cell grafting into the lesion site. Telemetry is an advanced technique to accurately evaluate cardiovascular function in conscious freely moving spinal cord injured rats.

High thoracic or cervical spinal cord injury (SCI) can lead to cardiovascular dysfunction. To monitor cardiovascular parameters, we implanted a catheter ...

Murine Model of Intestinal Ischemia-reperfusion Injury

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, hypotension, necrotizing enterocolitis, bowel transplantation, trauma and chronic inflammation. Intestinal ischemia-reperfusion (IR) injury is a consequence of acute mesenteric ischemia, caused by inadequate blood flow through the mesenteric vessels, resulting in intestinal damage. Reperfusion following ischemia can further exacerbate damage of the intestine. The mechanisms of IR injury are complex and poorly understood. Therefore, experimental small animal models are critical for understanding the pathophysiology of IR injury and the development of novel therapies.
Here we describe a mouse model of acute intestinal IR injury that provides reproducible injury of the small intestine without mortality. This is achieved by inducing ischemia in the region of the distal ileum by temporally occluding the peripheral and terminal collateral branches of the superior mesenteric artery for 60 min using microvascular clips. Reperfusion for 1 hr, or 2 hr after injury results in reproducible injury of the intestine examined by histological analysis. Proper position of the microvascular clips is critical for the procedure. Therefore the video clip provides a detailed visual step-by-step description of this technique. This model of intestinal IR injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Here we describe the detailed procedure of intestinal ischemia-reperfusion in mice which results in reproducible injury without mortality to encourage the standardization of this technique across the field. This model of intestinal ischemia-reperfusion injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, ...

Reproducible Motor Deficit Following Aortic Occlusion in a Rat Model Of Spinal Cord Ischemia

Spinal cord ischemia is a fatal complication following thoracoabdominal aortic aneurysm surgery. Researchers can investigate the strategies for preventing and treating this complication using experimental models of spinal cord ischemia. The model described here demonstrates varying degrees of paraplegia that relate to the length of occlusion following thoracic aortic occlusion in a rat spinal cord ischemia model.
A 2-Fr. balloon-tipped catheter was advanced through the femoral artery into the descending thoracic aorta until the catheter tip was placed at the left subclavian artery in anesthetized male Sprague-Dawley rats. Spinal cord ischemia was induced by inflating the catheter balloon. After a set period of occlusion (9, 10, or 11 min), the balloon was deflated. Neurologic assessment was performed using the motor deficit index at 24 h after surgery, and the spinal cord was harvested for histopathological examination.
Rats that underwent 9 min of aortic occlusion showed mild and reversible motor impairment in the hind limb. Rats subjected to 10 min of aortic occlusion presented with moderate but reversible motor impairment. Rats subjected to 11 min of aortic occlusion displayed complete and persistent paralysis. The motor neurons in the spinal cord sections were more preserved in rats subjected to shorter duration of aortic occlusion.
Researchers can achieve a reproducible hind limb motor deficit following thoracic aortic occlusion using this spinal cord ischemia model.

This study demonstrates the technique to make a minimally invasive and easily reproducible model of spinal cord ischemia in rats. Various degrees of hind limb motor deficit can be produced by controlling the aortic occlusion time.

Spinal cord ischemia is a fatal complication following thoracoabdominal aortic aneurysm surgery. Researchers can investigate the strategies for preventing ...

Two-vessel Occlusion Mouse Model of Cerebral Ischemia-reperfusion

In this study, a middle cerebral artery (MCA) occlusion mouse model is employed to study cerebral ischemia-reperfusion. A reproducible and reliable mouse model is useful for investigating the pathophysiology of cerebral ischemia-reperfusion and determining potential therapeutic strategies for patients with stroke. Variations in the anatomy of the circle of Willis of C57BL/6 mice affects their infarct volume after cerebral-ischemia-induced injury. Studies have indicated that distal MCA occlusion (MCAO) can overcome this problem and result in a stable infarct size. In this study, we establish a two-vessel occlusion mouse model of cerebral ischemia-reperfusion through the interruption of the blood flow to the right MCA. We distally ligate the right MCA and right common carotid artery (CCA) and restore blood flow after a certain period of ischemia. This ischemia-reperfusion injury induces an infarct of stable size and a behavioral deficit. Peripheral immune cells infiltrate the ischemic brain within the 24 h infiltration period. Additionally, the neuronal loss in the cortical area is less for a longer reperfusion duration. Therefore, this two-vessel occlusion model is suitable for investigating the immune response and neuronal recovery during the reperfusion period after cerebral ischemia.

A mouse model of cerebral ischemia-reperfusion is established to investigate the pathophysiology of stroke. We distally ligate the right middle cerebral artery and right common carotid artery and restore blood flow after 10 or 40 min of ischemia.

In this study, a middle cerebral artery (MCA) occlusion mouse model is employed to study cerebral ischemia-reperfusion. A reproducible and reliable mouse ...

Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via recanalization of the coronary artery is the most effective strategy for reducing the size of ischemic myocardium. The coronary microvasculature cannot be visualized and imaged&#160;in vivo, but there are several invasive and noninvasive techniques that can be used to assess parameters which depend directly on coronary microvascular function. The endothelial function after ischemia reperfusion can be assessed also at the level of the coronary circulation via the coronary flow reserve (CFR).&#160;In this study, peak velocity of left anterior descending (LAD) coronary arteries was measured in rats in vivo via Transthoracic Doppler Echocardiography during resting and stress challenge (induced by Dobutamine). A normal heart can increase its coronary blood flow up to four times above the resting values during stress induction. Following ischemia reperfusion, we found a significantly diminished CFR, which can be used as a marker of coronary microvascular dysfunction. CFR has opened a window on the importance of microvascular dysfunction and has been shown to predict cardiovascular risk independent of whether the severe obstructive disease is present.

Coronary flow reserve (CFR), is defined as the ratio of maximal coronary blood flow to the resting coronary blood flow. We present a protocol for evaluating CFR in rats via ultrasound, which offers the opportunity to predict cardiovascular risk factors in the absence of obstructive coronary disease.

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via ...

Murine Surgical Model of Topical Elastase Induced Descending Thoracic Aortic Aneurysm

According to the Center for Disease Control, aortic aneurysms (AAs) were considered a leading cause of death in all races and both sexes from 1999-2016. An aneurysm forms as a result of progressive weakening and eventual dilation of the aorta, which can rupture or tear once it reaches a critical diameter. Aneurysms of the descending aorta in the chest, called descending thoracic aortic aneurysms (dTAA), make up a large proportion of aneurysm cases in the United States. Uncontained dTAA rupture is almost universally lethal, and elective repair has a high rate of morbidity and mortality. The purpose of our model is to study dTAA specifically, to elucidate the pathophysiology of dTAA and to search for molecular targets to halt the growth or reduce the size of dTAA. By having a murine model to study thoracic pathology precisely, targeted therapies can be developed to specifically test dTAA. The method is based on the placement of porcine pancreatic elastase (PPE) directly on the outer murine aortic wall after surgical exposure. This creates a destructive and inflammatory reaction, which weakens the aortic wall and allows for aneurysm formation over weeks to months. Though murine models possess limitations, our dTAA model produces robust aneurysms of predictable size. Furthermore, this model can be used to test genetic and pharmaceutical targets which may arrest dTAA growth or prevent rupture. In human patients, interventions such as these could help avoid aneurysm rupture, and difficult surgical intervention.

We describe a surgical protocol to consistently induce robust descending thoracic aortic aneurysms in mice. The procedure involves left thoracotomy, thoracic aorta exposure, and placement of a sponge soaked in porcine pancreatic elastase on the aortic wall.

According to the Center for Disease Control, aortic aneurysms (AAs) were considered a leading cause of death in all races and both sexes from 1999-2016. ...