Name: inducing ischemia-reperfusion injury in the mouse ear skin for intravital multiphoton imaging of immune responses
Uploaded: 2016-12-22T15:00:00
Description: Watch this Scientific Journal Video about Inducing Ischemia-reperfusion Injury in the Mouse Ear Skin for Intravital Multiphoton Imaging of Immune Responses at JoVE.com

We thank Thomas Graf for providing us with the LysM-eGFP mice.

All experiments dealing with live animals were conducted in accordance to all relevant animal use and care guidelines and regulations.
1. Choice of Fluorescent Reporter Mice
<ol>
	<li>Use 6- to 12-week-old LysM-eGFP11 mice (no preference for either males or females). 
	Note: The use of various cell-specific fluorescent reporter mice enables the visualization of different immune cells in vivo. In this strain, circulating neutrophils (GFPhi cells), circulati...

<ol>
	<li>Black, 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=National+Pressure+Ulcer+Advisory+Panel's+updated+pressure+ulcer+staging+system.">National Pressure Ulcer Advisory Panel's updated pressure ulcer staging system.</a> Adv Skin Wound Care. 20, 269-274 (2007).</li><li>Kalogeris, T., Baines, C. P., Krenz, M., Korthuis, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+biology+of+ischemia/reperfusion+injury.">Cell biology of ischemia/reperfusion injury.</a> Int Rev Cell Mol Biol. 298, 229-317 (2012).</li><li>Huebener, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+HMGB1/RAGE+axis+triggers+neutrophil-mediated+injury+amplification+following+necrosis.">The HMGB1/RAGE axis triggers neutrophil-mediated injury amplification following necrosis.</a> J Clin Invest. 125, 539-550 (2015).</li><li>Wassermann, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chronic+pressure+ulcer+model+in+the+nude+mouse.">A chronic pressure ulcer model in the nude mouse.</a> Wound Repair Regen. 17, 480-484 (2009).</li><li>Stadler, I., Zhang, R. Y., Oskoui, P., Whittaker, M. S., Lanzafame, R. J. <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+simple,+noninvasive,+clinically+relevant+model+of+pressure+ulcers+in+the+mouse.">Development of a simple, noninvasive, clinically relevant model of pressure ulcers in the mouse.</a> J Invest Surg. 17, 221-227 (2004).</li><li>Tsuji, S., Ichioka, S., Sekiya, N., Nakatsuka, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+ischemia-reperfusion+injury+in+a+microcirculatory+model+of+pressure+ulcers.">Analysis of ischemia-reperfusion injury in a microcirculatory model of pressure ulcers.</a> Wound Repair Regen. 13, 209-215 (2005).</li><li>Ng, L. G., 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=Visualizing+the+neutrophil+response+to+sterile+tissue+injury+in+mouse+dermis+reveals+a+three-phase+cascade+of+events.">Visualizing the neutrophil response to sterile tissue injury in mouse dermis reveals a three-phase cascade of events.</a> J Invest Dermatol. 131, 2058-2068 (2011).</li><li>Li, J. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intravital+multiphoton+imaging+of+immune+responses+in+the+mouse+ear+skin.">Intravital multiphoton imaging of immune responses in the mouse ear skin.</a> Nat Protoc. 7, 221-234 (2012).</li><li>Tong, P. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+skin+immune+atlas:+three-dimensional+analysis+of+cutaneous+leukocyte+subsets+by+multiphoton+microscopy.">The skin immune atlas: three-dimensional analysis of cutaneous leukocyte subsets by multiphoton microscopy.</a> J Invest Dermatol. 135, 84-93 (2015).</li><li>Saito, Y., 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+loss+of+MCP-1+attenuates+cutaneous+ischemia-reperfusion+injury+in+a+mouse+model+of+pressure+ulcer.">The loss of MCP-1 attenuates cutaneous ischemia-reperfusion injury in a mouse model of pressure ulcer.</a> J Invest Dermatol. 128, 1838-1851 (2008).</li><li>Faust, N., Varas, F., Kelly, L. M., Heck, S., Graf, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insertion+of+enhanced+green+fluorescent+protein+into+the+lysozyme+gene+creates+mice+with+green+fluorescent+granulocytes+and+macrophages.">Insertion of enhanced green fluorescent protein into the lysozyme gene creates mice with green fluorescent granulocytes and macrophages.</a> Blood. 96, 719-726 (2000).</li><li>Roediger, B., Ng, L. G., Smith, A. L., Fazekasde de St Groth, B., Weninger, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+dendritic+cell+migration+within+the+skin.">Visualizing dendritic cell migration within the skin.</a> Histochem Cell Biol. 130, 1131-1146 (2008).</li><li>Kikushima, K., Kita, S., Higuchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+non-invasive+imaging+for+the+in+vivo+tracking+of+high-speed+vesicle+transport+in+mouse+neutrophils.">A non-invasive imaging for the in vivo tracking of high-speed vesicle transport in mouse neutrophils.</a> Sci Rep. 3, 1913 (2013).</li><li>Ng, L. G., 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=Migratory+dermal+dendritic+cells+act+as+rapid+sensors+of+protozoan+parasites.">Migratory dermal dendritic cells act as rapid sensors of protozoan parasites.</a> PLoS Pathog. 4, e1000222 (2008).</li><li>Soohoo, A. L., Bowersox, S. L., Puthenveedu, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+clathrin-mediated+endocytosis+of+G+protein-coupled+receptors+at+single-event+resolution+via+TIRF+microscopy.">Visualizing clathrin-mediated endocytosis of G protein-coupled receptors at single-event resolution via TIRF microscopy.</a> J Vis Exp. , e51805 (2014).</li><li>Beltman, J. B., Maree, A. F., de Boer, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysing+immune+cell+migration.">Analysing immune cell migration.</a> Nat Rev Immunol. 9, 789-798 (2009).</li></ol>

Significance
IR is one of the leading causes of skin pressure ulcers. The early stages (I and II) of pressure ulcers describe the condition of the human skin (as compared to the underlying subcutaneous tissues and muscles). However, an understanding of the immunological etiology is still lacking. Here, we present a simple and robust IR model on mouse ear skin in order to address this gap. We simulate ischemia by clamping the mouse ear between two magnets and subsequently study the downstream immu...

Ischemia-reperfusion injury (IRI) occurs when there is a transient hypoxia due to the obstruction of blood flow (ischemia) followed by a subsequent re-oxygenation of the tissues (reperfusion). In the skin, ischemia-reperfusion (IR) is thought to be one of the contributing factors to the pathophysiology of pressure ulcers, where prolonged bed rest predisposes long-term hospital patients to injury. In these patients, both the skin and the underlying muscles are constantly exposed to weight pressure exerted over areas of bony prominence, resulting in localized injuries that, if left untreated, may become necrotic1.
The damages involved in an IRI are twofold. During ischemia, the occlusion of blood vessels leads to a drastic drop of oxygen delivery to the tissues. This results in a decrease of ATP and pH, which inactivates ATPases involved in cellular metabolism. In turn, cellular calcium levels spike, and stressed or damaged cells undergo apoptosis or necrosis2. The release of intracellular contents or damage associated molecular patterns (DAMP), like HMGB1, contributes to the inflammatory response3. The second insult occurs during reperfusion. Although oxygen and pH levels are restored during reperfusion, this results in the generation of reactive oxygen species (ROS), which leads to the oxidation of intracellular lipids, DNA, and proteins. Consequently, pro-inflammatory mediators are activated, which sets off a secondary inflammatory response that involves the recruitment of immune cells to the inflammatory site2. While the cascade of biochemical events leading up to the inflammatory response has been well described, the spatial and temporal regulation of the immune cell activities are not well understood.
Here, we describe a robust IR model on mouse ear skin using simple magnet clamping. Coupled with multiphoton intravital imaging (MP-IVM), we established a model to study the in vivo inflammatory responses that occur after reperfusion takes place. The rationale behind the development and use of this technique is to try to understand how both interstitial and infiltrating cells respond to IR in real time.
Existing models of IR using the clamping technique on the skin flank are highly invasive, as they require the surgical implantation of steel plates in the skin flank, making them less-than-ideal for immunological studies4. A similar non-invasive clamping technique has been described in the mouse skin flank5,6. However, because of the incorporation of the intravital imaging component in this method, we instead chose the ear skin as the targeted IR site, as it circumvents movements due to breathing and offers stability during imaging7,8. Moreover, leukocyte subsets that span the interstitium are identical between the ear skin and the skin flank, although the numbers and proportions may vary slightly9. Thus, the ear skin represents an ideal imaging site.
In addition, most data retrieved from these IRI models are limited to macroscopic evaluations (grading of ulcers) and microscopic analyses of endpoint inflammatory indicators10. Using this model, real-time visualization of the cellular response of neutrophils after reperfusion in the skin of a fluorescent reporter mouse is enabled. A previously published intravital ear imaging model is utilized8 with additional modifications (Figures 1, 2).

<table border="0" cellpadding="0" cellspacing="0" width="1506">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Mice strains</td>
			<td style="width:333px;"></td>
			<td style="width:125px;"></td>
			<td style="width:483px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Lysozyme-GFP C57BL/6</td>
			<td style="width:333px;">Thomas Graf, Center for Genomic Regulation</td>
			<td style="width:125px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">C57BL/6-C2J</td>
			<td style="width:333px;">Jackson Laboratories</td>
			<td style="width:125px;">000058</td>
			<td>To be crossed with Lysozyme-GFP to generate albino Lysozyme-GFP for skin imaging</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Name</td>
			<td style="width:333px;">Company</td>
			<td style="width:125px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Viaflex 0.9% (wt/vol) saline</td>
			<td>Baxter Healthcare</td>
			<td>F8B1323</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ketamine (100 mg ml&#8722;1 ketamine hydrochloride</td>
			<td>Parnell</td>
			<td></td>
			<td>Ketamine is a controlled drug and all relevant local regulations should be followed</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ilium Xylazil-20 (20 mg ml&#8722;1 xylazine hydrochloride)</td>
			<td>Troy Laboratories</td>
			<td></td>
			<td>Xylazil-20 is a controlled drug and all relevant local regulations should be followed.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Evans blue (10 mg ml&#8722;1 in PBS or saline)</td>
			<td>Sigma-Aldrich</td>
			<td>46160</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrapurified water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Name</td>
			<td style="width:333px;">Company</td>
			<td style="width:125px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Insulin syringe with needle</td>
			<td>BD</td>
			<td>328838</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Transfer pipettes</td>
			<td>Biologix Research Company</td>
			<td>30-0135</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3M paper masking tape</td>
			<td>3M</td>
			<td>2214</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Deckglaser microscope cover glass (22 mm &#215; 32 mm)</td>
			<td>Paul Marienfeld</td>
			<td>101112</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Curved splinter forceps</td>
			<td>Aesculap, B. Braun Melsungen</td>
			<td>BD312R</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Veet hair removal cream</td>
			<td>Reckitt Benckiser</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Medical cotton-tipped applicators</td>
			<td>Puritan Medical Products Company</td>
			<td>806-WC</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">C-fold towels</td>
			<td>Kimberly-Clark</td>
			<td>20311</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Kimwipes delicate task wipes</td>
			<td>Kimtech Science</td>
			<td>34155</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gold-plated, N42-grade neodymium magnets, 12mm in diameter and 2mm thick&#160;</td>
			<td>first4magnets</td>
			<td>F656S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plastic guide, 10cm by 1.5cm (polyvinyl chloride material)</td>
			<td></td>
			<td></td>
			<td>fold in half lengthwise, bind with masking tape and slot magnet in</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">High vacuum grease</td>
			<td>Dow Corning</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Name</td>
			<td style="width:333px;">Company</td>
			<td style="width:125px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TriM Scope II single-beam two-photon microscope</td>
			<td>LaVision BioTec</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tunable (680&#8211;1,080 nm) Coherent Chameleon Ultra II One Box Ti:sapphire laser (&#8805;3.3 W at 800 nm; pulse length of 140 fs, 80 MHz repetition rate)</td>
			<td>Coherent</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Water-dipping objectives (20&#215;, NA = 1.0)</td>
			<td>Olympus</td>
			<td>XLUMPLFLN20xW</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Name</td>
			<td style="width:333px;">Company</td>
			<td style="width:125px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Miscroscope filter and mirror sets (for imaging GFP, SHG, Evans Blue)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">495 long-pass</td>
			<td>Chroma</td>
			<td>T495LPXR</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">560 lomg-pass</td>
			<td>Chroma</td>
			<td>T560LPXR</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">475/42 band-pass</td>
			<td>Semrock</td>
			<td>FF01-475/42-25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">525/50 band-pass</td>
			<td>Chroma</td>
			<td>ET525/50m</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">655/40 band-pass</td>
			<td>Chroma</td>
			<td>NC028647</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Name</td>
			<td style="width:333px;">Company</td>
			<td style="width:125px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Skin-imaging stage platform (refer to diagram for assembly)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">A metal base plate (126 mm &#215; 126 mm &#215; 1 mm)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;">A brass platform for the ear (79 mm &#215; 19 mm; 1 mm thickness at side, 0.5 mm thickness in the middle; Fig. 1) with slit (1.7 mm &#215; 1 mm; 1.5 mm away from long edge)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Two plastic blocks (10 mm in height)&#8212;for heat insulation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Curved holder, for positioning the control thermistor on the ear platform</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Interface cable CC-28 with DIN connector and thermistors, one for the temperature control and the other for the temperature monitor</td>
			<td>(Warner Instruments (Harvard Apparatus)</td>
			<td>640106</td>
			<td>connect the interface cable to both resistive heater blocks set at 35&#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Resistive heater blocks RH-2</td>
			<td>(Warner Instruments (Harvard Apparatus)</td>
			<td>640274</td>
			<td>Resistive heater blocks can heat the brass ear platform up to over 100 &#176;C within minutes. Ensure that the control thermistor has been properly secured in the holder in order to avoid overheating.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Temperature controller TC-344B for the ear platform</td>
			<td>(Warner Instruments (Harvard Apparatus)</td>
			<td>640101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Temperature controller TR-200 for mouse heating pad</td>
			<td>Fine Science Tools</td>
			<td>21052-00</td>
			<td>Unit is no longer for sale. Ask manufacturer for alternatives</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Power supply for TR-200</td>
			<td>Fine Science Tools</td>
			<td>21051-00</td>
			<td>Unit is no longer for sale. Ask manufacturer for alternatives</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heating pad</td>
			<td>Fine Science Tools</td>
			<td>21060-00</td>
			<td>Unit is no longer for sale. Ask manufacturer for alternatives.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Animal rectal probe&#160;</td>
			<td>Fine Science Tools</td>
			<td>21060-01</td>
			<td>Unit is no longer for sale. Ask manufacturer for alternatives. After connecting the rectal probe and heating pad to the temperature controller TR-200, set the temperature to 37 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Name</td>
			<td style="width:333px;">Company</td>
			<td style="width:125px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Coverslip holder</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2 plastic rods, 1 cm in diameter, 10 cm in length</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1 plastic adaptor with holes drilled to accommodate rods (refer to diagram)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3 plastic tightening screws for keeping plastic rods in place</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td colspan="2" height="21" style="height:21px;">1 metal plate, 6 cm x 2.5 cm, with a 2 cm square cut at 1 end, 2 mm edge away from short edge</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1 pair of nut and bolt for attaching metal plate to plastic rod</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td colspan="3" height="21" style="height:21px;">1 acrylic base (4 cm x 5 cm x 1.5 cm) with magnet to hold coverslip holder on skin-imaging stage platform. 1 rod is permanently fixed onto base.</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:565px;">Name</td>
			<td style="width:333px;">Company</td>
			<td style="width:125px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Imaging analysis software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Imaris v8.1.2</td>
			<td>Bitplane</td>
			<td></td>
			<td></td>
		</tr>
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</table>

inducing ischemia-reperfusion injury in the mouse ear skin for intravital multiphoton imaging of immune responses

Ischemia-reperfusion injury (IRI) occurs when there is transient hypoxia due to the obstruction of blood flow (ischemia) followed by a subsequent re-oxygenation of the tissues (reperfusion). In the skin, ischemia-reperfusion (IR) is the main contributing factor to the pathophysiology of pressure ulcers. While the cascade of events leading up to the inflammatory response has been well studied, the spatial and temporal responses of the different subsets of immune cells to an IR injury are not well understood. Existing models of IR using the clamping technique on the skin flank are highly invasive and unsuitable for studying immune responses to injury, while similar non-invasive magnet clamping studies in the skin flank are less-than-ideal for intravital imaging studies. In this protocol, we describe a robust model of non-invasive IR developed on mouse ear skin, where we aim to visualize in real-time the cellular response of immune cells after reperfusion via multiphoton intravital imaging (MP-IVM).

This protocol uses a custom-built ear skin imaging platform, as shown in Figure 1. Several features of this platform are specifically designed to facilitate imaging while maintaining physiological settings. Placing the ear on the heated brass platform not only maintains the ear at a physiological temperature of 35 &#176;C, but it also isolates the ear from inevitable movements due to breathing. The addition of a metal clip on the brass platform creates a gap to prevent th...

Watch this Scientific Journal Video about Inducing Ischemia-reperfusion Injury in the Mouse Ear Skin for Intravital Multiphoton Imaging of Immune Responses at JoVE.com

Inducing Ischemia-reperfusion Injury in the Mouse Ear Skin for Intravital Multiphoton Imaging of Immune Responses

This protocol describes the induction of an ischemia-reperfusion (IR) model on mouse ear skin using magnet clamping. Using a custom-built intravital imaging model, we study in vivo inflammatory responses post-reperfusion. The rationale behind the development of this technique is to extend the understanding of how leukocytes respond to skin IR injury.

Ischemia-reperfusion injury (IRI) occurs when there is transient hypoxia due to the obstruction of blood flow (ischemia) followed by a subsequent ...

The overall goal of this experiment is to understand how immune cells respond to ischemia reperfusion through intravital multiphoton imaging of the mouse ear skin. This method can help to address some of the very important questions in the field of Immunology and Dermatology to understand the dynamic behavior of immune cell. The main advantage of this technique is that it provide a robust imaging model for studying cellular activities in the skin under inflamed or a resting state.Though this method may provide insight into ischemic reperfusion injuries, this can also be applied to other systems such as hypersensitivity reactions as well as infections. To begin this procedure, place the mouse on a heating pad to maintain its body temperature at 37 degrees Celsius throughout the preparation procedure. Confirm the depth of anesthesia by the absence of toe pinch reflex.Next, apply ophthalmic lubricant on the animal's eyes to prevent dryness while under anesthesia. Afterward, carefully apply depilatory cream to the upper two thirds of the dorsal ear and wait for two to three minutes. Then, remove the cream using wet cotton tip applicators in a thorough but gentle manner.Now, induce ischemia in the mouse ear skin using the neodymium magnets. To do so, first slot the magnets into their individual plastic guides. Position one magnet such that only the edge will contact with a second ventral magnet, which should be placed below the ventral side of the ear with the ear laying flat on the magnet.Once ready, carefully let the magnets come together. After 1.5 hours of ischemia, remove the magnets by twisting them away from each other using the plastic guides, allowing reperfusion to take place. Immediately after magnet removal, administer Evans Blue or another blood vessel labeling agent of choice intravenously.In this step, cut two pieces of masking tape. Allow the adhesive sides to stick together whilst leaving about one millimeter of adhesive along its width. Then, cut the masking tape in two to accommodate its placement within the slit on the ear platform.Insert this masking tape about halfway through the slit such that the adhesive side faces up. After that, position the mouse on the heating pad such that the ear to be imaged is next to the masking tape strip. By using two PBS moistened cotton tip applicators, gently press the ear against the adhesive strip.Using the strip as a guide, bring the mouse ear through the slit while simultaneously adjusting the mouse closer towards the stage. As the ear skin is very fragile, this step must be done very carefully to avoid any preparation-induced injuries. To remove the sticky tape, first add a drop of PBS to reduce the adhesiveness of the tape.Then, separate the mouse ear from the masking tape as gently as possible using a fine paint brush. Flatten the ear against the ear platform by gently rolling a moist cotton tip applicator over the ear. Subsequently, put a drop of PBS underneath the coverslip and gently place it over the ear.Afterward, insert the rectal temperature probe and connect the wires to the heating system according to manufacturer's instructions. To acquire images, place the animal under the multiphoton microscope. Start with an imaging region that is in close proximity to the edge of the ischemia characterized by massive Evans Blue leakage.The schematic diagram here shows the positioning of the magnets. These two photos show a pre-ischemic and a post-ischemic ear after magnet clamping. In this schematic of the ear indicates the region imaged with respect to where the magnet had been placed.This time lapse sequence of maximum projection, shows the neutrophil infiltration in response to reperfusion in LysM-eGFPM albino mouse ear skin after 1.5 hours of ischemia. At earlier time points, the lack of Evans Blue signal indicates temporary vessel occlusion after ischemia. Once mastered, preparations for the ischemic reperfused ear for imaging can be done in less than 30 minutes if it is performed properly.While performing this procedure, it is important to constantly check the depth of anesthesia and the temperature of the mouse. Following this procedure, other method like whole mouse staining of the mouse ear skin can be performed to have a global view of the cellular localizations. After the developments of this protocol, it paved the way for researcher in the field of Immunology and Dermatology to explore innate immunity in the mouse ear skin.After watching these videos, you should have a good understanding of how to establish a mouse ear skin imaging model to study ischemic reperfusion injury. Don't forget that working with multiphoto microscope can be hazardous. And precautions such as laser safety training should be undertaken.

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Research

JoVE Journal

Medicine

Normothermic Cardiac Arrest and Cardiopulmonary Resuscitation: A Mouse Model of Ischemia-Reperfusion Injury

Acute Kidney Injury (AKI) is a common, highly lethal, complication of critical illness which has a high mortality1-4 and which is most 
frequently caused by whole-body hypoperfusion.5,6 Successful reproduction of whole-body hypoperfusion in rodent models has been fraught with 
difficulty.7-9,9,10 Models which employ focal ischemia have repeatedly demonstrated results which do not translate to the clinical setting, and larger 
animal models which allow for whole body hypoperfusion lack access to the full toolset of genetic manipulation possible in the mouse.11,12 However, in recent 
years a mouse model of cardiac arrest and cardiopulmonary resuscitation has emerged which can be adapted to model AKI.13 This model reliably reproduces 
physiologic, functional, anatomic, and histologic outcomes seen in clinical AKI, is rapidly repeatable, and offers all of the significant advantages of a murine surgical 
model, including access to genetic manipulative techniques, low cost relative to large animals, and ease of use. Our group has developed extensive experience 
with use of this model to assess a number of organ-specific outcomes in AKI.14,15

A powerful model for perioperative and critical care related acute kidney injury is presented. Using whole body hypoperfusion induced by cardiac arrest it is possible to nearly replicate the histologic and functional changes of clinical AKI.

Acute Kidney Injury (AKI) is a common, highly lethal, complication of critical illness which has a high mortality1-4 and which is most 
frequently caused ...

Real-time Digital Imaging of Leukocyte-endothelial Interaction in Ischemia-reperfusion Injury (IRI) of the Rat Cremaster Muscle

Ischemia-reperfusion injury (IRI) has been implicated in a large array of pathological conditions such as cerebral stroke, myocardial infarction, intestinal ischemia as well as following transplant and cardiovascular surgery.1 Reperfusion of previously ischemic tissue, while essential for the prevention of irreversible tissue injury, elicits excessive inflammation of the affected tissue. Adjacent to the production of reactive oxygen species, activation of the complement system and increased microvascular permeability, the activation of leukocytes is one of the principle actors in the pathological cascade of inflammatory tissue damage during reperfusion.2, 3 Leukocyte activation is a multistep process consisting of rolling, firm adhesion and transmigration and is mediated by a complex interaction between adhesion molecules in response to chemoattractants such as complement factors, chemokines, or platelet-activating factor.4
While leukocyte rolling in postcapillary venules is predominantly mediated by the interaction of selectins5 with their counter ligands, firm adhesion of leukocytes to the endothelium is selectin-controlled via binding to intercellular adhesion molecules (ICAM) and vascular cellular adhesion molecules (VCAM).6, 7 
Gold standard for the in vivo observation of leukocyte-endothelial interaction is the technique of intravital microscopy, first described in 1968.8
Though various models of IRI (ischemia-reperfusion injury) have been described for various organs, 9-12 only few are suitable for direct visualization of leukocyte recruitment in the microvascular bed on a high level of image quality.8 
We here promote the digital intravital epifluorescence microscopy of the postcapillary venule in the cremasteric microcirculation of the rat 13 as a convenient method to qualitatively and quantitatively analyze leukocyte recruitment for IRI-research in striated muscle tissue and provide a detailed manual for accomplishing the technique. We further illustrate common pitfalls and provide useful tips which should enable the reader to truly appreciate, and safely perform the method.
In a step by step protocol we depict how to get started with respiration controlled anesthesia under sufficient monitoring to keep the animal firmly anesthetized for longer periods of time. We then describe the cremasteric preparation as a thin flat sheet for outstanding optical resolution and provide a protocol for leukocyte imaging in IRI that has been well established in our laboratories.

Real-time Digital Imaging of Leukocyte-endothelial Interaction in Ischemia-reperfusion Injury IRI of the Rat Cremaster Muscle

Digital intravital epifluorescence microscopy of postcapillary venules in the cremasteric microcirculation is a convenient method to gain insights into leukocyte-endothelial interaction in vivo in ischemia-reperfusion injury (IRI) of striated muscle tissue. We here provide a detailed protocol to safely perform the technique and discuss its applications and limitations.

Ischemia-reperfusion injury (IRI) has been implicated in a large array of pathological conditions such as cerebral stroke, myocardial infarction, ...

Ischemia-reperfusion Model of Acute Kidney Injury and Post Injury Fibrosis in Mice

Ischemia-reperfusion induced acute kidney injury (IR-AKI) is widely used as a model of AKI in mice, but results are often quite variable with high, often unreported mortality rates that may confound analyses. Bilateral renal pedicle clamping is commonly used to induce IR-AKI, but differences between effective clamp pressures and/or renal responses to ischemia between kidneys often lead to more variable results. In addition, shorter clamp times are known to induce more variable tubular injury, and while mice undergoing bilateral injury with longer clamp times develop more consistent tubular injury, they often die within the first 3 days after injury due to severe renal insufficiency. To improve post-injury survival and obtain more consistent and predictable results, we have developed two models of unilateral ischemia-reperfusion injury followed by contralateral nephrectomy. Both surgeries are performed using a dorsal approach, reducing surgical stress resulting from ventral laparotomy, commonly used for mouse IR-AKI surgeries. For induction of moderate injury BALB/c mice undergo unilateral clamping of the renal pedicle for 26 min and also undergo simultaneous contralateral nephrectomy. Using this approach, 50-60% of mice develop moderate AKI 24 hr after injury but 90-100% of mice survive. To induce more severe AKI, BALB/c mice undergo renal pedicle clamping for 30 min followed by contralateral nephrectomy 8 days after injury. This allows functional assessment of renal recovery after injury with 90-100% survival. Early post-injury tubular damage as well as post injury fibrosis are highly consistent using this model.

We describe models of moderate and severe ischemia-reperfusion-induced kidney injury in which the mice undergo unilateral renal pedicle clamping followed by simultaneous or delayed contralateral nephrectomy, respectively. These models consistently give rise to renal dysfunction and post-injury fibrosis, but injury severity and survival are dependent on mouse background, age and surgical equipment.

Ischemia-reperfusion induced acute kidney injury (IR-AKI) is widely used as a model of AKI in mice, but results are often quite variable with high, often ...

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, ...

A Mouse Model of Retinal Ischemia-Reperfusion Injury Through Elevation of Intraocular Pressure

Retinal ischemia-reperfusion (I/R) is a pathophysiological process contributing to cellular damage in multiple ocular conditions, including glaucoma, diabetic retinopathy, and retinal vascular occlusions. Rodent models of I/R injury are providing significant insights into mechanisms and treatment strategies for human I/R injury, especially with regard to neurodegenerative damage in the retinal neurovascular unit. Presented here is a protocol for inducing retinal I/R injury in mice through elevation of intraocular pressure (IOP). In this protocol, the ocular anterior chamber is cannulated with a needle, through which flows the drip of an elevated saline reservoir. Using this drip to raise IOP above systolic arterial blood pressure, a practitioner temporarily halts inner retinal blood flow (ischemia). When circulation is reinstated (reperfusion) by removal of the cannula, severe cellular damage ensues, resulting ultimately in retinal neurodegeneration. Recent studies demonstrate inflammation, vascular permeability, and capillary degeneration as additional elements of this model. Compared to alternative retinal I/R methodologies, such as retinal arterial ligation, retinal I/R injury by elevated IOP offers advantages in its&#160;anatomical specificity, experimental tractability, and technical accessibility, presenting itself as a valuable tool for examining neuronal pathogenesis and therapy in the retinal neurovascular unit.

This article describes a procedure for inducing retinal ischemia-reperfusion injury by elevated intraocular pressure in mice. Retinal ischemia-reperfusion injury by elevated intraocular pressure serves to model human pathologies characterized by compromised oxygen and nutrient delivery in the retina, enabling researchers to examine potential cellular mechanisms and treatments for human diseases of the retinal neurovascular unit.

Retinal ischemia-reperfusion (I/R) is a pathophysiological process contributing to cellular damage in multiple ocular conditions, including glaucoma, ...

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 ...

A Pre-clinical Rat Model for the Study of Ischemia-reperfusion Injury in Reconstructive Microsurgery

Ischemia-reperfusion injury is the main cause of flap failure in reconstructive microsurgery. The rat is the preferred preclinical animal model in many areas of biomedical research due to its cost-effectiveness and its translation to humans. This protocol describes a method to create a preclinical free skin flap model in rats with ischemia-reperfusion injury. The described 3 cm x 6 cm rat free skin flap model is easily obtained after the placement of several vascular ligatures and the section of the vascular pedicle. Then, 8 h after the ischemic insult and completion of the microsurgical anastomosis, the free skin flap develops the tissue damage. These ischemia-reperfusion injury-related damages can be studied in this model, making it a suitable model for evaluating therapeutic agents to address this pathophysiological process. Furthermore, two main monitoring techniques are described in the protocol for the assessment of this animal model: transit-time ultrasound technology and laser speckle contrast analysis.

Here, we describe a pre-clinical animal model for studying the pathophysiology of ischemia-reperfusion injury in reconstructive microsurgery. This free skin flap model based on the superficial caudal epigastric vessels in the rat may also allow for the evaluation of different therapies and compounds to counteract ischemia-reperfusion injury-related damage.

Ischemia-reperfusion injury is the main cause of flap failure in reconstructive microsurgery. The rat is the preferred preclinical animal model in many ...

Delayed Intramyocardial Delivery of Stem Cells after Ischemia Reperfusion Injury in a Murine Model

There is significant interest in the use of stem cells (SCs) for the recovery of cardiac function in individuals with myocardial injuries. Most commonly, cardiac stem cell therapy is studied by delivering SCs concurrently with the induction of myocardial injury. However, this approach presents two significant limitations: the early hostile pro-inflammatory ischemic environment may affect the survival of transplanted SCs, and it does not represent the subacute infarction scenario where SCs will likely be used. Here we describe a two-part series of surgical procedures for the induction of ischemia-reperfusion injury and delivery of mesenchymal stem cells (MSCs). This method of stem cell administration may allow for the longer viability and retention around damaged tissue by circumventing the initial immune response. A model of ischemia reperfusion injury was induced in mice accompanied by the delivery of mesenchymal stem cells (3.0 x 105), stably expressing the reporter gene firefly luciferase under the constitutively expressed CMV promoter, intramyocardially 7 days later. The animals were imaged via ultrasound and bioluminescent imaging for confirmation of injury and injection of cells, respectively. Importantly, there was no added complication rate when performing this two-procedure approach for SC delivery. This method of stem cell administration, collectively with the utilization of state-of-the-art reporter genes, may allow for the in vivo study of viability and retention of transplanted SCs in a situation of chronic ischemia commonly seen clinically, while also circumventing the initial pro-inflammatory response. In summary, we established a protocol for the delayed delivery of stem cells into the myocardium, which can be used as a potential new approach in promoting regeneration of the damaged tissue.

Stems cells are continuously investigated as potential treatments for individuals with myocardial damage, however, their decreased viability and retention within injured tissue can impact their long-term efficacy. In this manuscript we describe an alternative method for stem cell delivery in a murine model of ischemia reperfusion injury.

There is significant interest in the use of stem cells (SCs) for the recovery of cardiac function in individuals with myocardial injuries. Most commonly, ...

Organ Ischemia-Reperfusion Injury by Simulating Hemodynamic Changes in Rat Liver Transplant Model

Orthotopic liver transplantation (OLT) in rats is a tried and proven animal model used for preoperative, intraoperative, and postoperative studies, including ischemia-reperfusion injury (IRI) of extrahepatic organs. This model requires numerous experiments and devices. The duration of anhepatic phase is closely related to the time to develop IRI after transplantation. In this experiment, we used hemodynamic changes to induce extrahepatic organ damage in rats and determined the maximum tolerance time. The time until the most severe organ injury varied for different organs. This method can easily be replicated and can also be used to study IRI of the extrahepatic organs after liver transplantation.

This paper provides a detailed description of how to build an animal model of the anhepatic phase (liver ischemia) in rats to facilitate basic research into ischemia-reperfusion injury after liver transplantation.

Orthotopic liver transplantation (OLT) in rats is a tried and proven animal model used for preoperative, intraoperative, and postoperative studies, ...