We thank Hsia Ru-ching PhD, from the Electron Microscopy Core Facility of University of Maryland School of Medicine, for her technical support in processing the scanning electronic microscopy samples.

Ethics Statement: The protocols for animal handling were approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Maryland (protocol number 0416009) and conducted according to AAALAC-International standards.
1. Surgical Procedure
<ol>
	<li>Anesthetic Technique
	<ol>
		<li>Sterilize all instruments used in survival surgery with steam sterilization at 121 &#176;C for 30 min.</li>
		<li>Induce anesthesia via an induction tank with 100% O2 and 2.5% isoflurane delivered via precision vaporizer. Post-induction, discontinue the isoflurane and flush the chamber with O2. Maintain anesthesia with 1.5-2% isoflurane via face mask and 1 L/min O2 by inhalation.</li>
		<li>Attach both the induction chamber and the face mask to a charcoal scavenger for waste gas adsorption to protect personnel. Ensure an adequate anesthetic plane by demonstrating that there is no response to noxious stimuli (toe pinch).</li>
		<li>Create an operative field consisting of a surgical tray with isothermal pad to provide thermal support during surgery. An additional isothermal pad will provide thermal support to animals in their recovery cage.</li>
	</ol>
	</li>
	<li>Animal Preparation
	<ol>
		<li>Carry out the following investigation on 10-12 weeks old male C57BL/6 mice.</li>
		<li>Remove the hair on the ventral abdominal surface of the animal from the sternum to the inguinal region with a depilatory agent or an electrical clipper with a number 40 blade.
		<ol>
			<li>In case of depilatory agent, apply this compound to the surgical area for 2-3 min and then remove it with cotton. We use a commercially available compound of calcium hydroxide and sodium hydroxide.</li>
		</ol>
		</li>
		<li>Prep the area over the shoulder with 70% alcohol and subcutaneously inject carprofen (5 mg/kg) with a 25 gauge or smaller bore needle. This treatment will provide postoperative analgesia for the animal.</li>
		<li>Transfer the animal to the surgical field and position in dorsal recumbency.</li>
		<li>Prepare the surgical site by scrubbing 8-12% providone-iodine with a clean cotton applicator or cotton gauze. Then rinse the skin twice with 70% alcohol.</li>
		<li>Place ocular lubricant in both eyes to reduce the incidence of corneal desiccation. Cover the surgical site with a sterile drape.</li>
	</ol>
	</li>
	<li>Operative Technique
	<ol>
		<li>Make a median abdominal laparotomy incision approximately 2-2.5 cm in length with a scalpel beginning immediately caudal the xiphoid process and extending towards the pelvis.</li>
		<li>Mobilize the small bowel and duodenum and reflect laterally to the right. Roll up a strip of sterile cotton gauzed and soaked with sterile saline for injection to allow packing of the viscera to improve exposure.</li>
		<li>With the small intestine mobilized to the right side of the abdomen, expose the retroperitoneum and expose the abdominal aorta from the left renal vein to the aortic bifurcation (Figure 1).</li>
		<li>With a sterile cotton-tipped applicator, deliver 30 consecutive crushes, each five seconds in duration.</li>
		<li>Remove the packing and allow the viscera to return to their native position.</li>
		<li>Close fascia with a running 4-0 absorbable monofilament suture (polydioxanone). Skin is closed with a running 6-0 non-absorbable monofilament suture (nylon).</li>
	</ol>
	</li>
	<li>Recovery and Post-Procedure Care
	<ol>
		<li>After the procedure, place the animal in a recovery cage with clean bedding on an isothermal pad to continue thermal support until the animal is able to ambulate normally. Do not leave the animal unattended until it demonstrates the ability to maintain sternal recumbency.</li>
		<li>Monitor the animal every hour for the first 4 h after surgery. Once the animal is ambulating normally return it to the assigned husbandry room. The animal will not be housed in the company of another animal until it has fully recovered.</li>
		<li>Monitor the animal twice daily for the first 72 h after surgery and at least 3 times a week thereafter. Monitoring includes weighing the animal three times a week.</li>
		<li>Administer carpofen (5 mg/kg) subcutaneously twice daily for the first 72 h after surgery.</li>
	</ol>
	</li>
</ol>
2. Procurement of Tissue
<ol>
	<li>Method of Euthanasia
	<ol>
		<li>Euthanize the animals at predetermined time points.</li>
		<li>Induce anesthesia via an induction tank with 100% O2 and 2.5% isoflurane delivered via precision vaporizer.
		<ol>
			<li>To study the integrity of the endothelium, Administer Evans Blue dye to the animal. 
			NOTE: Evans Blue is a negatively charged azo dye with a high binding affinity for albumin and can only stain blood vessels in the absence of an intact endothelium6.</li>
			<li>For endothelial integrity studies, at the time of euthanasia, perfuse the animals with 5 mL of 0.3 % Evans Blue dye followed by 5 mL PBS at physiological pressure for 5 min. The animal is maintained in a surgical plane of anesthesia during the perfusion procedure.</li>
		</ol>
		</li>
		<li>After achieving a deep anesthetic plane, open the chest with a sternotomy. Make a laceration in the right atrium to allow drainage of blood from the animal and access the left ventricle is accessed with a 21 G needle and inject phosphate buffered saline (PBS) until the effluent from the right atrium is clear.</li>
		<li>After perfusion with PBS, enter the abdomen through a midline incision.</li>
		<li>Once again, mobilize the small intestine to the right side of the abdomen exposing the infrarenal aorta, sharply dissect the aorta from adjacent tissues and excise it from the left renal vein to the aortic bifurcation.</li>
		<li>Store the excised aorta in a 4% paraformaldehyde solution until tissue processing occurs.
		<ol>
			<li>For endothelial integrity studies, open the aorta longitudinally and pin it to a wax sheet exposing the entirety of the luminal surface6. Carry out a qualitative assessment of endothelial integrity by the degree of staining with Evans Blue dye6.</li>
			<li>For other histologic assays, section the aorta transversely and embed it in optimal cutting temperature (OCT) compounds as dictated by the histological method to be used 7.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Carmeliet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+angiogenesis+and+arteriogenesis.">Mechanisms of angiogenesis and arteriogenesis.</a> Nat Med. 6 (4), 389-395 (2000).</li><li>Carmeliet, P., Moons, L., Collen, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+of+angiogenesis,+arterial+stenosis,+atherosclerosis+and+hemostasis.">Mouse models of angiogenesis, arterial stenosis, atherosclerosis and hemostasis.</a> Cardiovasc Res. 39 (1), 8-33 (1998).</li><li>Baker, A. B., 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=Heparanase+Alters+Arterial+Structure,+Mechanics,+and+Repair+Following+Endovascular+Stenting+in+Mice.">Heparanase Alters Arterial Structure, Mechanics, and Repair Following Endovascular Stenting in Mice.</a> Circ Res. 104 (3), 380-387 (2009).</li><li>Petrov, L., Laurila, H., Hayry, P., Vamvakopoulos, J. E. <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+aortic+angioplasty+for+genomic+studies+of+neointimal+hyperplasia.">A mouse model of aortic angioplasty for genomic studies of neointimal hyperplasia.</a> J Vasc Res. 42 (4), 292-300 (2005).</li><li>Li, 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=Vascular+smooth+muscle+cells+of+recipient+origin+mediate+intimal+expansion+after+aortic+allotransplantation+in+mice.">Vascular smooth muscle cells of recipient origin mediate intimal expansion after aortic allotransplantation in mice.</a> Am J Path. 158 (6), 1943-1947 (2001).</li><li>Radu, M., Chernoff, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+in+vivo+assay+to+test+blood+vessel+permeability.">An in vivo assay to test blood vessel permeability.</a> J Vis Exp. (73), e50062 (2013).</li><li>Turbett, G. R., Sellner, L. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+optimal+cutting+temperature+compound+can+inhibit+amplification+by+polymerase+chain+reaction.">The use of optimal cutting temperature compound can inhibit amplification by polymerase chain reaction.</a> Diagn Mol Pathol. 6 (5), 298-303 (1997).</li><li>Puchtler, H., Waldrop, F. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+mechanism+of+Verhoeff's+elastica+stain:+a+convenient+stain+for+myelin+sheaths.">On the mechanism of Verhoeff's elastica stain: a convenient stain for myelin sheaths.</a> Histochem. 62 (3), 233-247 (1979).</li><li>Salic, A., Mitchison, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chemical+method+for+fast+and+sensitive+detection+of+DNA+synthesis+in+vivo.">A chemical method for fast and sensitive detection of DNA synthesis in vivo.</a> Proc Natl Acad Sci U S A. 105 (7), 2415-2420 (2008).</li><li>Nelson, P. R., Yamamura, S., Mureebe, L., Itoh, H., Kent, K. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Smooth+muscle+cell+migration+and+proliferation+are+mediated+by+distinct+phases+of+activation+of+the+intracellular+messenger+mitogen-activated+protein+kinase.">Smooth muscle cell migration and proliferation are mediated by distinct phases of activation of the intracellular messenger mitogen-activated protein kinase.</a> J Vasc Surg. 27 (1), 117-125 (1998).</li><li>Rzucidlo, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Signaling+pathways+regulating+vascular+smooth+muscle+cell+differentiation.">Signaling pathways regulating vascular smooth muscle cell differentiation.</a> Vascular. 17, S15-S20 (2009).</li><li>Aoki, T., Sumii, T., Mori, T., Wang, X., Lo, E. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood-brain+barrier+disruption+and+matrix+metalloproteinase-9+expression+during+reperfusion+injury:+mechanical+versus+embolic+focal+ischemia+in+spontaneously+hypertensive+rats.">Blood-brain barrier disruption and matrix metalloproteinase-9 expression during reperfusion injury: mechanical versus embolic focal ischemia in spontaneously hypertensive rats.</a> Stroke. 33 (11), 2711-2717 (2002).</li><li>Yu, D., 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=MARCKS+Signaling+Differentially+Regulates+Vascular+Smooth+Muscle+and+Endothelial+Cell+Proliferation+through+a+KIS-,+p27kip1-+Dependent+Mechanism.">MARCKS Signaling Differentially Regulates Vascular Smooth Muscle and Endothelial Cell Proliferation through a KIS-, p27kip1- Dependent Mechanism.</a> PLoS One. 10 (11), e0141397 (2015).</li><li>Banai, S., 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=Rabbit+ear+model+of+injury-induced+arterial+smooth-muscle+cell-proliferation+-+kinetics,+reproducibility,+and+implications.">Rabbit ear model of injury-induced arterial smooth-muscle cell-proliferation - kinetics, reproducibility, and implications.</a> Circ Res. 69 (3), 748-756 (1991).</li></ol>

This work was funded by the Department of Veterans Affairs Career Development Award (1IK2BX001553-01) (TSM) and the Vascular Cures E. J. Wylie Scholarship (TSM).

We have characterized the effects of a murine aortic injury model that results in medial hyperplasia and endothelial barrier dysfunction. Partial EC detachment along the aorta intima accompanied the loss of cell-cell contact and enhancement of cell protrusions. Correspondingly, endothelial barrier function was significantly impaired, which stimulated the mitogen-sensitive signaling pathways, leading to proliferation of VSMCs and thickening of the vessel wall. The strengths of this model is that it is technically easier t...

Restenosis following cardiovascular procedures (bypass surgery, angioplasty, or stenting) is a significant problem reducing the durability of these procedures. All revascularization procedures are plagued by restenosis. Present strategies to prevent restenosis (drug-eluting stents and drug-coated balloons) inhibit both vascular smooth muscle cell (VSMC) and endothelial cell proliferation (EC). Consequently, these interventions prevent VSMC mediated restenosis, but also prevent the regeneration of the endothelium. Without an intact endothelium, patients are required to be on potent antiplatelet agents to decrease the risk of in situ thrombosis at the risk of bleeding complications. An ideal therapy would inhibit VSMC proliferation while promoting regeneration of the endothelium. Thus, there is a need to simultaneously study VSMC proliferation and endothelial barrier function in vivo.
Presently, there are several mouse models of restenosis 1. These models include carotid ligation and femoral artery wire injury 2. Aortic models include stent placement 3, balloon injury 4, and aortic allograft 5. All of the present models are limited. Carotid ligation generates a flow-mediated neointimal lesion and does not have endothelial injury. Additionally, both carotid and femoral arteries have many fold fewer cell layers than human vessels, limiting their translational value. The mouse aorta which is approximately 1.3 mm in diameter, is the only vessel that approximates a clinically relevant (coronary) human artery (3).
Despite the translational potential of murine aortic models of disease, current models have limitations. These models require advanced microsurgical skills and specialized equipment such as angioplasty balloons and stents. Herein, we present a novel, reproducible technique to simultaneously induce VSMC proliferation and disrupt endothelial barrier function.

<table border="0" cellpadding="0" cellspacing="0" width="920">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Ocular lubricant</td>
			<td style="width:160px;">Dechra</td>
			<td style="width:163px;">17033-211-38</td>
			<td style="width:247px;">Pharmaceutical agents</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Isoflurane</td>
			<td>VetOne</td>
			<td>502017</td>
			<td>Pharmaceutical agents</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Carprofen</td>
			<td>Zoetis</td>
			<td>26357</td>
			<td>Pharmaceutical agents</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Precision vaporizer</td>
			<td>Summit Medical</td>
			<td>10675</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Charcoal scavenger</td>
			<td>Bickford Inc.</td>
			<td>80120</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Isothermal pad</td>
			<td>Harvard Apparatus</td>
			<td>50-7053-R</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Sterile cotton-tipped applicator</td>
			<td>Fisher Scientific</td>
			<td>23-400-124</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">4-0 absorbable monofilament suture&#160;</td>
			<td>Ethicon, Inc</td>
			<td>J310</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">5-0 non-absorbable monofilament suture</td>
			<td>Ethicon,Inc</td>
			<td>1666</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">21-gauge x 1 inch needle</td>
			<td>BD Biosciences</td>
			<td>305165</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">25-gauge x 1 inch&#160; needle</td>
			<td>BD Biosciences</td>
			<td>305125</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dry sterilizer</td>
			<td>Cellpoint&#160;</td>
			<td>7770</td>
			<td>Surgical supplies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fine scissors</td>
			<td>Fine Science Tools</td>
			<td>14058-09</td>
			<td>Surgical instruments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Adson forceps</td>
			<td>Fine Science Tools</td>
			<td>11006-12</td>
			<td>Surgical instruments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Dumont #5 fine forceps</td>
			<td>Fine Science Tools</td>
			<td>11254-20</td>
			<td>Surgical instruments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Vannas Spring Scissors 3mm cutting edge</td>
			<td>Fine Science Tools</td>
			<td>15000-00</td>
			<td>Surgical instruments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Needle driver</td>
			<td>Fine Science Tools</td>
			<td>91201-13</td>
			<td>Surgical instruments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Scalpel handle #4</td>
			<td>Fine Science Tools</td>
			<td>10004-13</td>
			<td>Surgical instruments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Scalpel blades #10</td>
			<td>Fine Science Tools</td>
			<td>10010-00</td>
			<td>Surgical instruments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PBS&#160;</td>
			<td>Lonza</td>
			<td>17-516F</td>
			<td>Reagents for tissue processing</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Evans Blue</td>
			<td>Sigma-Aldrich</td>
			<td>E2129</td>
			<td>Reagents for tissue processing</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>P6148</td>
			<td>Reagents for tissue processing</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Modeling wax</td>
			<td>Bego</td>
			<td>40001</td>
			<td>Reagents for tissue processing</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">OCT compound</td>
			<td>Tissue-Tek Sakura</td>
			<td>4583</td>
			<td>Reagents for tissue processing</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Mayer&#39;s hematoxylin solution</td>
			<td>Sigma-Aldrich</td>
			<td>MHS16</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Eosin Y solution alcoholic&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>HT110316</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Elastin stain kit</td>
			<td>Sigma-Aldrich</td>
			<td style="width:163px;">HT25A</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Click-it Edu Alexa-488 Imaging Kit</td>
			<td>Invitrogen</td>
			<td>C10337</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Anti-Erk1/2 antibody</td>
			<td>Cell Signaling Technology</td>
			<td>4695</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Anti-phospho-Erk1/2 antibody</td>
			<td>Cell Signaling Technology</td>
			<td>4370</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Anti-p27kip1 antibody</td>
			<td>Cell Signaling Technology</td>
			<td>3698</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:351px;">Trichloroacetic acid</td>
			<td>Sigma-Aldrich</td>
			<td>T9159</td>
			<td>Reagents for immunohistological analysis</td>
		</tr>
	</tbody>
</table>

murine aortic crush injury: an efficient in vivo model of smooth muscle cell proliferation and endothelial function

Arterial reconstruction, whether angioplasty or bypass surgery, involves iatrogenic trauma causing endothelial disruption and vascular smooth muscle cell (VSMC) proliferation. Common murine models study small vessels such as the carotid and femoral arteries. Herein we describe an in vivo system in which both VSMC proliferation and endothelial barrier function can be simultaneously assessed in a large vessel. We studied the infrarenal aortic response to injury in C57BL/6 mice. The aorta was injured from the left renal vein to the aortic bifurcation by 30 transmural crushes of 5-seconds duration with a cotton-tipped applicator. Morphological changes were assessed with conventional histology. Aorta wall thickness was measured from the luminal surface to the adventitia. EdU integration and counter staining with DAPI and alpha-actin was used to demonstrate VSMC proliferation. Activation of ERK1/2, a known moderator of intimal hyperplasia formation, was determined by Western Blot analysis. The effect of inflammation was determined by immunohistochemistry for B-cells, T-cells, and macrophages. En face sections of endothelium were visualized with scanning electron microscopy (SEM). Endothelial barrier function was determined with Evans Blue staining. Transmural injury resulted in aortic wall thickening. This injury induced VSMC proliferation, most prominently at 3 days after injury, and early activation of ERK1/2 and decreased p27kip1 expression. Injury did not result in increased B-cells, T-cells, or macrophages infiltration in the vessel wall. Injury caused partial endothelial cell denudation and loss of cell-cell contact. Injury resulted in a significant loss of endothelial barrier function, which returned to baseline after seven days. The murine transmural blunt aortic injury model provides an efficient system to simultaneously study both VSMC proliferation and endothelial barrier function in a large vessel.

Transverse sections aorta embedded in OCT were sectioned, and stained with hematoxylin and eosin then counter stained with Verhoeff-Van Gieson (VVG) stain to identify the internal and external elastic lamina 7. Crush injury induced aortic wall thickening compared to the aortas of animals treated with a sham procedure (laparotomy and small bowel mobilization alone). Wall thickness, as assessed by the distance from adventitia to the lumen, was greatest three days aft...

Watch this Scientific Journal Video about Murine Aortic Crush Injury: An Efficient In Vivo Model of Smooth Muscle Cell Proliferation and Endothelial Function at JoVE.com

Murine Aortic Crush Injury: An Efficient In Vivo Model of Smooth Muscle Cell Proliferation and Endothelial Function

Restenosis following cardiovascular procedures (bypass surgery, angioplasty, or stenting) is a significant problem reducing the durability of these procedures. An ideal therapy would inhibit smooth muscle cell (VSMC) proliferation while promoting regeneration of the endothelium. We describe a model for simultaneous assessment of VSMC proliferation and endothelial function in vivo.

Murine Aortic Crush Injury: An Efficient In Vivo Model of Smooth Muscle Cell Proliferation and Endothelial Function

Arterial reconstruction, whether angioplasty or bypass surgery, involves iatrogenic trauma causing endothelial disruption and vascular smooth muscle cell ...

murine-aortic-crush-injury-an-efficient-vivo-model-smooth-muscle-cell

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8.3K Views.  Baltimore Veterans Affairs Medical Center. Restenosis following cardiovascular procedures (bypass surgery, angioplasty, or stenting) is a significant problem reducing the durability of these procedures. An ideal therapy would inhibit smooth muscle cell (VSMC) proliferation while promoting regeneration of the endothelium. We describe a model for simultaneous assessment of VSMC proliferation and endothelial function in vivo.

Video: Murine Aortic Crush Injury: An Efficient In Vivo Model of Smooth Muscle Cell Proliferation and Endothelial Function

Focal Ca2+ Transient Detection in Smooth Muscle

Ca2+ imaging of smooth muscle provides insight into cellular mechanisms that may not result in changes of membrane potential, such as the release of Ca2+ from internal stores, and allows multiple cells to be monitored simultaneously to assess, for example, coupling in syncytial tissue. Subcellular Ca2+ transients are common in smooth muscle, yet are difficult to measure accurately because of the problems caused by their stochastic occurrence, over an often wide field of view, in an organ that it prone to contract. To overcome this problem, we've developed a series of imaging protocols and analysis routines to acquire and then analyse, in an automated fashion, the frequency, location and amplitude of such events. While this approach may be applied in other contexts, our own work involves the detection of local purinergic Ca2+ transients for locating transmitter release with submicron resolution. 
ATP is released as a cotransmitter from autonomic nerves, where it binds to P2X1 receptors on the smooth muscle of the detrusor and vas deferens. Ca2+ enters the smooth muscle, resulting in purinergic neuroeffector Ca2+ transients (NCTs). The focal Ca2+ transients allow the optical monitoring of neurotransmitter release in a manner that has many advantages over electrophysiology. Apart from the greatly improved spatial resolution, optical recording has the additional advantage of allowing the recording of transmitter release from many distinguishable sites simultaneously. Furthermore, the optical plane of focus is easier to maintain or correct during long recording series than is the repositioning of an intracellular sharp microelectrode. 
In summary, a method for imaging of Ca2+ fluorescence is outlined which details the preparation of tissue, and the acquisition and analysis of data. We outline the use of several scripts for the analysis of such Ca2+ transients.

Focal Ca2+ Transient Detection in Smooth Muscle

Details methods for high-resolution Ca2+ imaging of smooth muscle within isolated organs, including: preparation of the tissue, image acquisition and data analysis.

Ca2+ imaging of smooth muscle provides insight into cellular mechanisms that may not result in changes of membrane potential, such as the release of Ca2+ ...

Exploring Arterial Smooth Muscle Kv7 Potassium Channel Function using Patch Clamp Electrophysiology and Pressure Myography

Contraction or relaxation of smooth muscle cells within the walls of resistance arteries determines the artery diameter and thereby controls flow of blood through the vessel and contributes to systemic blood pressure. The contraction process is regulated primarily by cytosolic calcium concentration ([Ca2+]cyt), which is in turn controlled by a variety of ion transporters and channels. Ion channels are common intermediates in signal transduction pathways activated by vasoactive hormones to effect vasoconstriction or vasodilation. And ion channels are often targeted by therapeutic agents either intentionally (e.g. calcium channel blockers used to induce vasodilation and lower blood pressure) or unintentionally (e.g. to induce unwanted cardiovascular side effects).
Kv7 (KCNQ) voltage-activated potassium channels have recently been implicated as important physiological and therapeutic targets for regulation of smooth muscle contraction. To elucidate the specific roles of Kv7 channels in both physiological signal transduction and in the actions of therapeutic agents, we need to study how their activity is modulated at the cellular level as well as evaluate their contribution in the context of the intact artery.
The rat mesenteric arteries provide a useful model system. The arteries can be easily dissected, cleaned of connective tissue, and used to prepare isolated arterial myocytes for patch clamp electrophysiology, or cannulated and pressurized for measurements of vasoconstrictor/vasodilator responses under relatively physiological conditions. Here we describe the methods used for both types of measurements and provide some examples of how the experimental design can be integrated to provide a clearer understanding of the roles of these ion channels in the regulation of vascular tone.

Measurements of Kv7 (KCNQ) potassium channel activity in isolated arterial myocytes (using patch clamp electrophysiological techniques) in parallel with measurements of constrictor/dilator responses (using pressure myography) can reveal important information about the roles of Kv7 channels in vascular smooth muscle physiology and pharmacology.

Contraction  or relaxation of smooth muscle cells within the walls of resistance arteries  determines the artery diameter and thereby controls flow of ...

Evaluation of Muscle Function of the Extensor Digitorum Longus Muscle Ex vivo and Tibialis Anterior Muscle In situ in Mice

Body movements are mainly provided by mechanical function of skeletal muscle. Skeletal muscle is composed of numerous bundles of myofibers that are sheathed by intramuscular connective tissues. Each myofiber contains many myofibrils that run longitudinally along the length of the myofiber. Myofibrils are the contractile apparatus of muscle and they are composed of repeated contractile units known as sarcomeres. A sarcomere unit contains actin and myosin filaments that are spaced by the Z discs and titin protein. Mechanical function of skeletal muscle is defined by the contractile and passive properties of muscle. The contractile properties are used to characterize the amount of force generated during muscle contraction, time of force generation and time of muscle relaxation. Any factor that affects muscle contraction (such as interaction between actin and myosin filaments, homeostasis of calcium, ATP/ADP ratio, etc.) influences the contractile properties. The passive properties refer to the elastic and viscous properties (stiffness and viscosity) of the muscle in the absence of contraction. These properties are determined by the extracellular and the intracellular structural components (such as titin) and connective tissues (mainly collagen) 1-2. The contractile and passive properties are two inseparable aspects of muscle function. For example, elbow flexion is accomplished by contraction of muscles in the anterior compartment of the upper arm and passive stretch of muscles in the posterior compartment of the upper arm. To truly understand muscle function, both contractile and passive properties should be studied.
The contractile and/or passive mechanical properties of muscle are often compromised in muscle diseases. A good example is Duchenne muscular dystrophy (DMD), a severe muscle wasting disease caused by dystrophin deficiency 3. Dystrophin is a cytoskeletal protein that stabilizes the muscle cell membrane (sarcolemma) during muscle contraction 4. In the absence of dystrophin, the sarcolemma is damaged by the shearing force generated during force transmission. This membrane tearing initiates a chain reaction which leads to muscle cell death and loss of contractile machinery. As a consequence, muscle force is reduced and dead myofibers are replaced by fibrotic tissues 5. This later change increases muscle stiffness 6. Accurate measurement of these changes provides important guide to evaluate disease progression and to determine therapeutic efficacy of novel gene/cell/pharmacological interventions. Here, we present two methods to evaluate both contractile and passive mechanical properties of the extensor digitorum longus (EDL) muscle and the contractile properties of the tibialis anterior (TA) muscle.

Evaluation of Muscle Function of the Extensor Digitorum Longus Muscle Ex vivo and Tibialis Anterior Muscle In situ in Mice

Changes in limb muscle contractile and passive mechanical properties are important biomarkers for muscle diseases. This manuscript describes physiological assays to measure these properties in the murine extensor digitorum longus and tibialis anterior muscles.

Body  movements are mainly provided by mechanical function of skeletal muscle. Skeletal  muscle is composed of numerous bundles of myofibers that are ...

Measurement of Smooth Muscle Function in the Isolated Tissue Bath-applications to Pharmacology Research

Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues. While this technique has been implemented for over 100 years, the versatility, simplicity and reproducibility of this assay helps it to remain an indispensable tool for pharmacologists and physiologists alike. Tissue bath systems are available in a wide array of shapes and sizes, allowing a scientist to evaluate samples as small as murine mesenteric arteries and as large as porcine ileum &#8211; if not larger. Central to the isolated tissue bath assay is the ability to measure concentration-dependent changes to isometric contraction, and how the efficacy and potency of contractile agonists can be manipulated by increasing concentrations of antagonists or inhibitors. Even though the general principles remain relatively similar, recent technological advances allow even more versatility to the tissue bath assay by incorporating computer-based data recording and analysis software. This video will demonstrate the function of the isolated tissue bath to measure the isometric contraction of an isolated smooth muscle (in this case rat thoracic aorta rings), and share the types of knowledge that can be created with this technique. Included are detailed descriptions of aortic tissue dissection and preparation, placement of aortic rings in the tissue bath and proper tissue equilibration prior to experimentation, tests of tissue viability, experimental design and implementation, and data quantitation. Aorta will be connected to isometric force transducers, the data from which will be captured using a commercially available analog-to-digital converter and bridge amplifier specifically designed for use in these experiments. The accompanying software to this system will be used to visualize the experiment and analyze captured data.

This protocol describes the measurement of isometric contraction in an isolated smooth muscle preparation, using an isolated tissue bath system and computer-based data acquisition.

Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues.  ...

Two-photon Imaging of Intracellular Ca2+ Handling and Nitric Oxide Production in Endothelial and Smooth Muscle Cells of an Isolated Rat Aorta

Calcium is a very important regulator of many physiological processes in vascular tissues. Most endothelial and smooth muscle functions highly depend on changes in intracellular calcium ([Ca2+]i) and nitric oxide (NO). In order to understand how [Ca2+]i, NO and downstream molecules are handled by a blood vessel in response to vasoconstrictors and vasodilators, we developed a novel technique that applies calcium-labeling (or NO-labeling) dyes with two photon microscopy to measure calcium handling (or NO production) in isolated blood vessels. Described here is a detailed step-by-step procedure that demonstrates how to isolate an aorta from a rat, label calcium or NO within the endothelial or smooth muscle cells, and image calcium transients (or NO production) using a two photon microscope following physiological or pharmacological stimuli. The benefits of using the method are multi-fold: 1) it is possible to simultaneously measure calcium transients in both endothelial cells and smooth muscle cells in response to different stimuli; 2) it allows one to image endothelial cells and smooth muscle cells in their native setting; 3) this method is very sensitive to intracellular calcium or NO changes and generates high resolution images for precise measurements; and 4) described approach can be applied to the measurement of other molecules, such as reactive oxygen species. In summary, application of two photon laser emission microscopy to monitor calcium transients and NO production in the endothelial and smooth muscle cells of an isolated blood vessel has provided high quality quantitative data and promoted our understanding of the mechanisms regulating vascular function.

Two-photon Imaging of Intracellular Ca2+ Handling and Nitric Oxide Production in Endothelial and Smooth Muscle Cells of an Isolated Rat Aorta

Vascular cell functiondepends on activity of intracellular messengers. Described here is an ex vivo two photon imaging method that allows the measurement of intracellular calcium and nitric oxide levels in response to physiological and pharmacological stimuli in individual endothelial and smooth muscle cells of an isolated aorta.

Calcium is a very important regulator of many physiological processes in vascular tissues. Most endothelial and smooth muscle functions highly depend on ...

Isolation and Primary Culture of Mouse Aortic Endothelial Cells

The vascular endothelium is essential to normal vascular homeostasis. Its dysfunction participates in various cardiovascular disorders. The mouse is an important model for cardiovascular disease research. This study demonstrates a simple method to isolate and culture endothelial cells from the mouse aorta without any special equipment. To isolate endothelial cells, the thoracic aorta is quickly removed from the mouse body, and the attached adipose tissue and connective tissue are removed from the aorta. The aorta is cut into 1 mm rings. Each aortic ring is opened and seeded onto a growth factor reduced matrix with the endothelium facing down. The segments are cultured in endothelial cell growth medium for about 4 days. The endothelial sprouting starts as early as day 2. The segments are then removed and the cells are cultured continually until they reach confluence. The endothelial cells are harvested using neutral proteinase and cultured in endothelial cell growth medium for another two passages before being used for experiments. Immunofluorescence staining indicated that after the second passage the majority of cells were double positive for Dil-ac-LDL uptake, Lectin binding, and CD31 staining, the typical characteristics of endothelial cells. It is suggested that cells at the second to third passages are suitable for in vitro and in vivo experiments to study the endothelial biology. Our protocol provides an effective means of identifying specific cellular and molecular mechanisms in endothelial cell physiopathology.

The vascular endothelial cells play a significant role in many important cardiovascular disorders. This article describes a simple method to isolate and expand endothelial cells from the mouse aorta without using any special equipment. Our protocol provides an effective means of identifying mechanisms in endothelial cell physiopathology.

The vascular endothelium is essential to normal vascular homeostasis. Its dysfunction participates in various cardiovascular disorders. The mouse is an ...

Isolation of Murine Coronary Vascular Smooth Muscle Cells

While the isolation and culture of vascular smooth muscle cells (VSMCs) from large vessels is well established, we sought to isolate and culture VSMCs from the coronary circulation. Hearts with intact aortic arches were removed and perfused via retrograde Langendorff with digestion solution containing 300 Units/ml of collagenase type II, 0.1 mg/ml soybean trypsin inhibitor and 1 M CaCl2. The perfusates were collected at 15 min intervals for 90 min, pelleted by centrifugation, resuspended in plating media, and plated on tissue culture dishes. VSMCs were characterized by presence of SM22&#945;, &#945;-SMA, and vimentin. One of the main advantages of using this technique is the ability to isolate VSMCs from the coronary circulation of mice. Although the small number of cells obtained can limit some of the applications for which the cells can be utilized, isolated coronary VSMCs can be used in a variety of well-established cell culture techniques and assays. Studies investigating VSMCs from genetically modified mice can provide further information about structure-function and signaling processes associated with vascular pathologies.

The purpose of this protocol is to demonstrate the isolation and culture techniques of murine primary vascular smooth muscle cells (VSMCs) from the coronary circulation. Once VSMCs have been isolated, they can be used for many standard culture techniques.

While the isolation and culture of vascular smooth muscle cells (VSMCs) from large vessels is well established, we sought to isolate and culture VSMCs ...

Measuring Proliferation of Vascular Smooth Muscle Cells Using Click Chemistry

The ability of a cell to proliferate is integral to the normal function of most cells, and dysregulation of proliferation is at the heart of many disease processes. For these reasons, measuring proliferation is a common tool used to assess cell function. Cell proliferation can be measured simply by counting; however, this is an indirect means of measuring proliferation. One common means of directly detecting cells preparing to divide is by incorporation of labeled nucleoside analogs. These include the radioactive nucleoside analog 3H-thymidine plus non-radioactive nucleoside analogs such as 5-bromo-2&#8217; deoxyuridine (BrdU) and 5-ethynyl-2&#8242;-deoxyuridine (EdU). Incorporation of EdU is detected by click chemistry, which has several advantages when compared to BrdU. In this report, we provide a protocol for measuring proliferation by the incorporation of EdU. This protocol includes options for various readouts, along with the advantages and disadvantages of each. We also discuss places where the protocol can be optimized or altered to meet the specific needs of the experiment planned. Finally, we touch on the ways that this basic protocol can be modified for measuring other cell metabolites.

Proliferation is a critical part of cellular function, and a common readout used to assess potential toxicity of new drugs. Measuring proliferation is, therefore, a frequently used assay in cell biology. Here we present a simple, versatile method of measuring proliferation that can be used in adherent and non-adherent cells.

The ability of a cell to proliferate is integral to the normal function of most cells, and dysregulation of proliferation is at the heart of many disease ...

In vivo Measurement of Knee Extensor Muscle Function in Mice

Skeletal muscle plasticity in response to countless conditions and stimuli mediates concurrent functional adaptation, both negative and positive. In the clinic and the research laboratory, maximal muscular strength is widely measured longitudinally in humans, with knee extensor musculature the most reported functional outcome. Pathology of the knee extensor muscle complex is well documented in aging, orthopedic injury, disease, and disuse; knee extensor strength is closely related to functional capacity and injury risk, underscoring the importance of reliable measurement of knee extensor strength. Repeatable, in vivo assessment of knee extensor strength in pre-clinical rodent studies offers valuable functional endpoints for studies exploring osteoarthritis or knee injury. We report an in vivo and non-invasive protocol to repeatedly measure isometric peak tetanic torque of the knee extensors in mice across time. We demonstrate consistency using this novel method to measure knee extensor strength with repeated assessment in multiple mice producing similar results.

Quantification of knee extensor maximal strength is imperative to understand functional adaptations to aging, disease, injury, and rehabilitation. We present a novel method to repeatedly measure in vivo knee extension isometric peak tetanic torque.

Skeletal muscle plasticity in response to countless conditions and stimuli mediates concurrent functional adaptation, both negative and positive. In the ...

Isolation of Primary Patient-specific Aortic Smooth Muscle Cells and Semiquantitative Real-time Contraction Measurements In Vitro

Smooth muscle cells (SMCs) are the predominant cell type in the aortic media. Their contractile machinery is important for the transmission of force in the aorta and regulates vasoconstriction and vasodilation. Mutations in genes encoding for the SMC contractile apparatus proteins are associated with aortic diseases, such as thoracic aortic aneurysms. Measuring SMC contraction in vitro is challenging, especially in a high-throughput manner, which is essential for screening patient material. Currently available methods are not suitable for this purpose. This paper presents a novel method based on electric cell-substrate impedance sensing (ECIS). First, an explant protocol is described to isolate patient-specific human primary SMCs from aortic biopsies and patient-specific human primary dermal fibroblasts for the study of aortic aneurysms. Next, a detailed description of a new contraction method is given to measure the contractile response of these cells, including the subsequent analysis and suggestion for comparing different groups. This method can be used to study the contraction of adherent cells in the context of translational (cardiovascular) studies and patient and drug screening studies.

Isolation of Primary Patient-specific Aortic Smooth Muscle Cells and Semiquantitative Real-time Contraction Measurements In Vitro

This paper describes an explant culture-based method for the isolation and culturing of primary, patient-specific human aortic smooth muscle cells and dermal fibroblasts. Furthermore, a novel method is presented for measuring cell contraction and subsequent analysis, which can be used to study patient-specific differences in these cells.

Smooth muscle cells (SMCs) are the predominant cell type in the aortic media. Their contractile machinery is important for the transmission of force in ...