Name: demonstration of the rat ischemic skin wound model
Uploaded: 2015-04-01T15:00:00
Description: Watch this Scientific Journal Video about Demonstration of the Rat Ischemic Skin Wound Model at JoVE.com

The authors would like to acknowledge funding support from the University of South Florida, Department of Surgery (Mack Wu, MD, PhD).

NOTE: Approval for all animal procedures presented below was obtained from the University of South Florida&#8217;s Animal Care Committee (IACUC) and abide by all requirements of the Animal Welfare Act and the Guide for Care and Use of Laboratory Animals.
1. Preparation of Silicone Sheets and Surgical Instruments
<ol>
	<li>Precut strips (10.5 cm x 3.0 cm) of non-reinforced 0.01 thickness, medical grade silicone sheeting and sterilize using an autoclave.</li>
	<li>Clean and sterilize suitable ...

<ol>
	<li>Ansell, D. M., Holden, K. A., Hardman, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+wound+repair:+Are+they+cutting+it.">Animal models of wound repair: Are they cutting it.</a> Experimental dermatology. 21 (8), 581-585 (2012).</li><li>Dorsett-Martin, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rat+models+of+skin+wound+healing:+a+review.">Rat models of skin wound healing: a review.</a> Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society. 12 (6), 591-599 (2003).</li><li>Davidson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+for+wound+repair.">Animal models for wound repair.</a> Arch Dermatol Res. 290 (S1-11), (1998).</li><li>Finn, G., Magnus, S. A., Tonny, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+for+use+in+wound+healing+research:+A+survey+focusing+on+in+vitro+and+in+vivo+adult+soft+tissue).">Models for use in wound healing research: A survey focusing on in vitro and in vivo adult soft tissue).</a> Wound Repair and Regeneration. 8, (2000).</li><li>Gould, L. J., Leong, M., Sonstein, J., Wilson, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+and+validation+of+an+ischemic+wound+model.">Optimization and validation of an ischemic wound model.</a> Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society. 13 (6), 576-582 (2004).</li><li>Loots, M. A., 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=Differences+in+cellular+infiltrate+and+extracellular+matrix+of+chronic+diabetic+and+venous+ulcers+versus+acute+wounds.">Differences in cellular infiltrate and extracellular matrix of chronic diabetic and venous ulcers versus acute wounds.</a> The Journal of investigative dermatology. 111 (5), 850-857 (1998).</li><li>Schwartz, D. A., Lindblad, W. J., Rees, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+collagen+metabolism+and+delayed+healing+in+a+novel+model+of+ischemic+wounds.">Altered collagen metabolism and delayed healing in a novel model of ischemic wounds.</a> Wound Repair Regen. 3 (2), 204-212 (1995).</li><li>Chen, C., 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=Molecular+and+mechanistic+validation+of+delayed+healing+rat+wounds+as+a+model+for+human+chronic+wounds.">Molecular and mechanistic validation of delayed healing rat wounds as a model for human chronic wounds.</a> Wound Repair and Regeneration. 7, (1999).</li><li>Zhang, Q., Chang, Q., Cox, R. A., Gong, X., Gould, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperbaric+oxygen+attenuates+apoptosis+and+decreases+inflammation+in+an+ischemic+wound+model.">Hyperbaric oxygen attenuates apoptosis and decreases inflammation in an ischemic wound model.</a> The Journal of investigative dermatology. 128 (8), 2102-2112 (2008).</li><li>Zhang, Q., Gould, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperbaric+oxygen+reduces+matrix+metalloproteinases+in+ischemic+wounds+through+a+redox-dependent+mechanism.">Hyperbaric oxygen reduces matrix metalloproteinases in ischemic wounds through a redox-dependent mechanism.</a> The Journal of investigative dermatology. 134 (1), 237-246 (2013).</li><li>Moor, A. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consequences+of+age+on+ischemic+wound+healing+in+rats:+altered+antioxidant+activity+and+delayed+wound+closure.">Consequences of age on ischemic wound healing in rats: altered antioxidant activity and delayed wound closure.</a> Age (Dordrecht, Netherlands). 36 (2), 733-748 (2014).</li><li>Roy, 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=Characterization+of+a+preclinical+model+of+chronic+ischemic+wound).">Characterization of a preclinical model of chronic ischemic wound).</a> Physiological genomics. 37 (3), 211-224 (2009).</li><li>Biswas, 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=Hypoxia+inducible+microRNA+210+attenuates+keratinocyte+proliferation+and+impairs+closure+in+a+murine+model+of+ischemic+wounds.">Hypoxia inducible microRNA 210 attenuates keratinocyte proliferation and impairs closure in a murine model of ischemic wounds.</a> Proceedings of the National Academy of Sciences of the United States of America. 107 (15), 6976-6981 (2010).</li><li>Winocour, S., Vorstenbosch, J., Trzeciak, A., Lessard, L., Philip, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CD109,+a+novel+TGF-beta+antagonist,+decreases+fibrotic+responses+in+a+hypoxic+wound+model.">CD109, a novel TGF-beta antagonist, decreases fibrotic responses in a hypoxic wound model.</a> Exp Dermatol. 23 (7), 475-479 (2014).</li></ol>

Wound healing in rats has often been the subject of debate due to their ability to heal infected wounds and high rate of interanimal variability5. One of the original goals of the model during its development was to decrease this variation. Modifications to the width of the flap, reducing the number of wounds with specific placement (centered on the flap with consistent cranio-caudal location) and introduction of a silicone sheet has accomplished this goal. Wound healing by contraction has also been reduced an...

Effective drug development and other wound healing therapeutics require appropriate in vivo models, despite known problems in translating findings in animal models to human therapies1. What follows is a description of a detailed protocol for the use of a rat model of ischemic skin wound healing to investigate mechanisms that further the understanding of pathological wound healing. The rat species, often employed due to its wide availability, size and docile nature is used for wound healing studies as it is large enough to provide a suitable skin area for incisional and excisional wounding, imaging and tissue collection2. However it should be taken into careful consideration that the skin of a rat and a human are different anatomically, with rats being referred to as loose-skinned animals. This distinct characteristic allows for wound contraction, rather than epithelialization to contribute significantly to the closing of rat skin wounds2. Additionally, the presence of a subcutaneous panniculus carnosus muscle in rats, contributes to healing by both contraction and collagen formation3,4. These very important anatomical distinctions were considered in the development of the rat ischemic skin wound model and specific modifications were implemented to decrease wound contraction and reduce the influence of the panniculus carnosus muscle5.
In diabetic foot ulcers, venous leg ulcers, and pressure ulcers, healing is delayed and these wounds are considered chronic. The wounds are characterized by excessive inflammation, which prevents the wound from progressing to the next phases of wound repair6. One of the main factors in the development of a chronic wound is localized tissue ischemia (reduced blood flow)5 contributing to the inability to clear inflammation. At the time during which this model was being developed and validated (in 2003-4), there were no standardized animal models that could provide enough tissue to test induction of angiogenesis in the wound bed, a key stage during normal wound healing and the motivation for developing this model5. That said, the model presented here is a modification of the ischemic wound model originally described by Schwartz et al.7 and subsequently used in modified form by Chen et al.8
In the modified ischemic wound model, changes have been made to circumvent the above mentioned anatomical characteristics of the rat that lead to healing by contraction rather than epithelialization: (1) Two full-thickness excisional wounds are created within a bipedicled dorsal skin flap and the panniculus carnosus muscle is removed from the wound bed by dissecting just above the muscle fascia. (2) The flap itself has more narrow dimensions, ensuring that blood supply is random and the wounds located at the midpoint of the flap are ischemic. (3) A silicone sheet is inserted beneath the flap, preventing readherence and reperfusion of the flap from underlying tissue. Wound contraction is limited (not eliminated) by anchoring or suturing the flap to the silicone sheet5.
The model has recently been used in studies ranging from hyperbaric oxygen effects on ischemic wound healing9,10 to ischemic wound healing in young versus aged rats11 and has proven to be a reliable model of prolonged tissue ischemia. The dimensions of the bipedicled flap have also been adapted to different rat strains, including Sprague Dawley (11 cm long by 2 cm wide) and F344 rats (10.5 cm long by 3.0-3.5 cm wide) and other species, including swine12 and mice13,14 . This video utilizes the F344 inbred rat strain in the demonstration of the ischemic skin wound model.
Approval for all animal procedures presented below was obtained from the University of South Florida&#8217;s Animal Care Committee (IACUC) and abide by all requirements of the Animal Welfare Act and the Guide for Care and Use of Laboratory Animals.

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			<td height="21" style="height:21px;width:216px;">Name of Reagent/ Equipment</td>
			<td style="width:103px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:216px;">Sil-Tec medical grade sheeting</td>
			<td style="width:103px;">Technical Products Inc.</td>
			<td style="width:119px;">500-3</td>
			<td>nonreinforced, 0.01 inches in thickness</td>
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			<td height="61" style="height:61px;width:216px;">Mini Iris scissors, 8cm, curved, SS</td>
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			<td height="21" style="height:21px;width:216px;">Ethilon Nylon Sutures</td>
			<td style="width:103px;">Ethicon</td>
			<td style="width:119px;">1964G</td>
			<td>black, size 4.0, PC-3 16mm needles (3/8 circle)</td>
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			<td height="41" style="height:41px;width:216px;">Laser Doppler Imager</td>
			<td style="width:103px;">Moor Instruments</td>
			<td style="width:119px;">moorLDI2-IR</td>
			<td>Standard blood flow imager: http://us.moor.co.uk/product/moorldi2-laser-doppler-imager/8</td>
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			<td height="21" style="height:21px;width:216px;">ImageJ</td>
			<td style="width:103px;">NIH</td>
			<td style="width:119px;">free download</td>
			<td>http://rsb.info.nih.gov/ij/</td>
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			<td height="21" style="height:21px;width:216px;">Mastisol</td>
			<td style="width:103px;">Henry Schein</td>
			<td style="width:119px;">Cat # 7289210</td>
			<td>Fisher Scientific NC9774929</td>
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			<td height="41" style="height:41px;width:216px;">Tegaderm</td>
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</table>

demonstration of the rat ischemic skin wound model

The propensity for chronic wounds in humans increases with ageing, disease conditions such as diabetes and impaired cardiovascular function, and unrelieved pressure due to immobility. Animal models have been developed that attempt to mimic these conditions for the purpose of furthering our understanding of the complexity of chronic wounds. The model described herein is a rat ischemic skin flap model that permits a prolonged reduction of blood flow resulting in wounds that become ischemic and resemble a chronic wound phenotype (reduced vascularization, increased inflammation and delayed wound closure). It consists of a bipedicled dorsal flap with 2 ischemic wounds placed centrally and 2 non-ischemic wounds lateral to the flap as controls. A novel addition to this ischemic skin flap model is the placement of a silicone sheet beneath the flap that functions as a barrier and a splint to prevent revascularization and reduce contraction as the wounds heal. Despite the debate of using rats for wound healing studies due to their quite distinct anatomic and physiologic differences compared to humans (i.e., the presence of a panniculus carnosus muscle, short life-span, increased number of hair follicles, and their ability to heal infected wounds) the modifications employed in this model make it a valuable alternative to previously developed ischemic skin flap models.

The rat ischemic wound healing model protocol should take approximately 20 min&#160;per animal if performed efficiently. Prior to application of a dressing the model should appear as represented in Figure 1G. It will be important to verify that the bipedicled flap and wounds therein are ischemic. Subcutaneous oxygen tension (PscO2) at the level of the wounds has been measured during validation of this model5 by placing a polarographic electrode in the subcutaneous tissue between the...

Watch this Scientific Journal Video about Demonstration of the Rat Ischemic Skin Wound Model at JoVE.com

Demonstration of the Rat Ischemic Skin Wound Model

The rat, due to its size, availability, and rather docile behavior, has been utilized as a research model for many years. The goal of this protocol is to utilize the rat as an ischemic skin wound healing model to provide valuable insight into the pathophysiology of chronic wounds.

The propensity for chronic wounds in humans increases with ageing, disease conditions such as diabetes and impaired cardiovascular function, and ...

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