Name: improvement of a closed chest porcine myocardial infarction model by standardization of tissue and blood sampling procedures
Uploaded: 2018-03-12T14:30:00
Description: Watch this Scientific Journal Video about Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures at JoVE.com

The authors wish to acknowledge Professor Christian Heinis for providing the FXIIa inhibitor and the respective control. We also gratefully acknowledge Olgica Beslac, Dr. Daniel Mettler and Kay Nettelbeck from the Experimental Surgery Unit, Department for Biomedical Research, University of Bern for technical support. Celine Guillod and Matthias Rausch from the Department for Diagnostic, Interventional and Pediatric Radiology, Bern University Hospital, Inselspital provided support with the X-ray equipment and techniques.This project was funded by the Swiss National Science Foundation, project no. 320030_156193.&#160;We also would like to thank Mr. Reto Haenni from communication and marketing, Bern University Hospital, Inselspital for video recording our experiment.

1. Animals:
All animals were treated according to the guidelines of the Swiss national laws. The study was approved by the local animal experimentation committee of the Canton of Bern (permission no. BE 25/16).
Use large white pigs of both sexes (~30 &#177;&#160;5 kg). Divide the animals blindly into two groups, one group receiving a bicyclic (80 kDa protease) inhibitor of FXIIa or treatment of choice and the other an inactive control.
2. Sur...

<ol>
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L., Granger, D. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathophysiology+of+ischaemia-reperfusion+injury.">Pathophysiology of ischaemia-reperfusion injury.</a> J Pathol. 190, 255-266 (2000).</li><li>P&#233;rez de Prado, 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=Closed-chest+experimental+porcine+model+of+acute+myocardial+infarction-reperfusion.">Closed-chest experimental porcine model of acute myocardial infarction-reperfusion.</a> J Pharmacol Toxicol Methods. 60, 301-306 (2009).</li><li>Lown, B., Levine, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+carotid+sinus.+Clinical+value+of+its+stimulation.">The carotid sinus. 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Myocardial I/R injury has a significant effect on the final infarct size which is directly translated into the patient&#39;s prognosis after acute myocardial infarction3. Understanding the pathophysiology of myocardial I/R injury is the first step to reduce or prevent it. Myocardial I/R injury is an acute condition that occurs directly after reperfusion of the occluded vessels. I/R injury leads to activation of the innate immune response and cellular damage occurs at the site of reperfusion and th...

Ischemic heart disease, in particular acute myocardial infarction (MI), is the main cause of death in developed countries 1. Today, the standard treatment of MI is percutaneous coronary intervention (PCI), the balloon catheter treatment. One of the critical factors that affects quality of life and prognosis of patients after PCI-treated acute MI is the infarction size. The reduction of the size can have a great impact on patient survival and prognosis 2. Myocardial ischemia/reperfusion (I/R) injury has a significant influence on the infarction size so one of the main aims in cardiovascular research is to prevent or reduce myocardial I/R injury 3. The exact mechanisms of I/R injury are still under investigation 4. Activation of the plasma cascades and endothelial cells are hallmarks of I/R injury 5. Activation of the coagulation system is clearly involved 6,7. Recently, the role of FXII, as an early upstream peptide involved in contact phase activation of the coagulation cascade, has been shown in a FXII knock out rat model of cerebral I/R injury 8. Validation of these results in a porcine model is an important step into clinical translation. Therefore, we are testing a novel bicyclic (80 kDa protease) FXIIa inhibitor in the context of myocardial I/R injury in a pilot study.
Animal models, which mimic the clinical situation of acute MI and PCI treatments, are essential to improve our understanding of the pathophysiology of myocardial I/R injury and to test novel treatment options. Pigs represent a good animal model for clinical myocardial I/R injury. This is not only because their hearts are very similar to human hearts with respect to anatomy and coronary circulation, but they also show similar pathophysiological responses to myocardial ischemia and reperfusion 9,10. Other models such as rats and mice do not fulfill these criteria and show considerable differences when compared to human hearts 11,12, whereas dogs for example, have many more collateral coronary vessels as compared with humans 13.
The porcine acute myocardial infarction model has been widely used in cardiovascular research to investigate ischemic heart disease including myocardial I/R injury 14,15,16,17. The latter is an inflammatory condition, because of which minimizing the inflammatory reaction related to sternotomy or thoracotomy used in open-chest surgery is essential. The closed chest model using a clinical C-arm angiography setting overcomes this problem. Furthermore, one of the most important points is that our protocol provides an accurate distinction between ischemic (area at risk, AAR) and non-ischemic areas of the left ventricle (area not at risk, ANR) so that the infarct size (necrotic ischemic tissue, NIT) can be accurately determined. Our aim for this paper is to clearly define a reproducible methodology of a porcine myocardial I/R injury model, in particular with respect to myocardial tissue sampling, which will allow for a more precise analysis of the molecular mechanisms of I/R injury and a clearer picture of the effects of novel drug treatments.

<table>
	<tbody>
		<tr>
			<td>ABL 90 Flex, blood gas analyser</td>
			<td>Radiometer</td>
			<td>-</td>
			<td>Blood gas analysis (BGA)</td>
		</tr>
		<tr>
			<td>ACT Plus</td>
			<td>Medtronic</td>
			<td>-</td>
			<td>Activated clotting time</td>
		</tr>
		<tr>
			<td>Atropin</td>
			<td>Sintetica</td>
			<td>-</td>
			<td>Atropinum Sulfas, 0,5mg/ml</td>
		</tr>
		<tr>
			<td>Balance (20-500 Kg)</td>
			<td>NAGATA Scale, Tiwan</td>
			<td>HTB/HTR</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Balance (21-4200 g)</td>
			<td>Mettler toledo, Switzerland</td>
			<td>MS4002SDR</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Blood collection tubes: EDTA, citrate and serum</td>
			<td>S-Monovette, Nuembrecht, Germany</td>
			<td>05.1167.001, 
			05.1071.001 
			and 
			05.1557.001 respectively</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>BV Pulsera mobile C-arm</td>
			<td>Philips</td>
			<td>-</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Labcare, UK</td>
			<td>ALC PK120R</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Defibrillator Lifepak 12</td>
			<td>Medtronic</td>
			<td>-</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Dextran from Leuconostoc mesenteroides</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>D3759</td>
			<td>Average M.wt 48000-90000</td>
		</tr>
		<tr>
			<td>Digital single lens reflex camera</td>
			<td>Sony, Thailand</td>
			<td>DSLR-A500/A550</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Dissecting forceps</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>EMPIRA RX PCI dilatation catheter</td>
			<td>Cordis, Johnson&#38;Johnson, USA</td>
			<td>85R15300S</td>
			<td>Diameter 3 mm, length 15 mm, Alternative products can be used</td>
		</tr>
		<tr>
			<td>EMPIRA RX PCI dilatation catheter</td>
			<td>Cordis, Johnson&#38;Johnson, USA</td>
			<td>85R15350S</td>
			<td>Diameter 3.5 mm, length 15 mm, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Evans Blue</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>E2129</td>
			<td>Toxic</td>
		</tr>
		<tr>
			<td>Fabius GS premium respirator</td>
			<td>Dr&#228;ger, L&#252;beck, Germany</td>
			<td>-</td>
			<td>Anesthesia work station, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Fentanyl</td>
			<td>Inselspital ISPI</td>
			<td>-</td>
			<td>Fentanyl 2500mcg/50ml</td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Pathology Institute, Bern University</td>
			<td>SI148701</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>FXIIa inhibitor</td>
			<td>Provided by Prof. Christian Heinis&#39; laboratory in EPFL</td>
			<td></td>
			<td>Novel bicyclic peptide</td>
		</tr>
		<tr>
			<td>Galeo, coronary guidewire</td>
			<td>Biotronik, Germany</td>
			<td>125497</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Guidance catheter</td>
			<td>Boston Scientific, Florida, USA</td>
			<td>34356-06</td>
			<td>6F (100 cm, EB3.75). Alternative products can be used</td>
		</tr>
		<tr>
			<td>Heparin Sodium</td>
			<td>Drossapharm, Basel, Switzerland</td>
			<td>-</td>
			<td>Liquemin, 25000 U.I./5 ml</td>
		</tr>
		<tr>
			<td>High end electrosurgery</td>
			<td>BOWA, Germany</td>
			<td>ARC 400</td>
			<td>Electrical source for blood suction. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Hydro-Guardmini breathing filter</td>
			<td>Intersurgical, Lithuania</td>
			<td>1745000</td>
			<td>Filters</td>
		</tr>
		<tr>
			<td>Image J</td>
			<td>National Institute of Health, USA</td>
			<td>1.47v</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Inflation device, Atrion QL2530</td>
			<td>Atrion medical product, Alabama, USA</td>
			<td>96402</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>IntelliVue MP 70</td>
			<td>Philips, Boeblingen, Germany</td>
			<td>-</td>
			<td>Monitor (ECG, heart rate, blood presure and body temperature). Alternative products can be used</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sintetica SA</td>
			<td>-</td>
			<td>Potassium chloride 15%</td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>Vetoquinol</td>
			<td>-</td>
			<td>Narketan, 1ml/100mg</td>
		</tr>
		<tr>
			<td>LR-ACT</td>
			<td>Medtronic</td>
			<td>402-01</td>
			<td>ACT special syringes</td>
		</tr>
		<tr>
			<td>Midazolam</td>
			<td>Roche</td>
			<td>-</td>
			<td>Dormicum, 5mg/ml</td>
		</tr>
		<tr>
			<td>Monopolar scalpel</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Needle holder</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>High resolution camera, PathStand Macro Imaging Stand for Grossing</td>
			<td>Spotimaging, USA</td>
			<td></td>
			<td>1080 p HD resolution. Alternative products can be used</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>In-house preparation</td>
			<td>-</td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Peripheral venous cannula, 18 G</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>PowerLab 4/35 data acquisition system</td>
			<td>Adinstruments, Spechbach, Germany</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotamax120T</td>
			<td>Heidolph, Germany</td>
			<td>544-41200-00</td>
			<td>Shaker. Alternative can be used</td>
		</tr>
		<tr>
			<td>R&#252;schelit-Super Safety Clear Tube</td>
			<td>Teleflex, Dublin, Irland</td>
			<td>112480</td>
			<td>Air way tubing, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Safe Pico Aspirator Syringes</td>
			<td>Radiometer</td>
			<td>956-622</td>
			<td>BGA special syringes</td>
		</tr>
		<tr>
			<td>Saline</td>
			<td>Sintetica Bioren</td>
			<td>-</td>
			<td>NaCl 0,9%. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Sevorane 1.5%</td>
			<td>AbbVie AG</td>
			<td>-</td>
			<td>Sevorane 250ml 100%</td>
		</tr>
		<tr>
			<td>Sheath</td>
			<td>Cordis, Johnson&#38;Johnson, USA</td>
			<td>504-607 A</td>
			<td>AVANTI + / 7 F, Alternative products can be used</td>
		</tr>
		<tr>
			<td>Space infusion pump</td>
			<td>B.Braun Medical AG, Germany</td>
			<td>-</td>
			<td>For infusion of fentanyl. Alternative products can be used</td>
		</tr>
		<tr>
			<td>SPR-350 (Millar catheter)</td>
			<td>Adinstruments, Texas, USA</td>
			<td>840-8166</td>
			<td>MIKRO-TIP, 5F, 120 cm</td>
		</tr>
		<tr>
			<td>Sternotomy saw</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Sutures</td>
			<td>ETHICON, Johnson&#38;Johnson, USA</td>
			<td>Y3110H</td>
			<td>Monocryl 3-0 SH-1 Plus. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Syringes (20, 10 and 5 mL)</td>
			<td>CODAN,Baar, Switzerland</td>
			<td>62.7602, 
			62.6616, 
			62.5607 
			respectively</td>
			<td>Used to inject anesthetic materials intramuscularly or directly into the central venous line. Also to inject heparin or FXIIa or the respective control. Alternative products can be used</td>
		</tr>
		<tr>
			<td>Thorax spreader</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Tissue-tek</td>
			<td>SAKURA, Netherlands</td>
			<td>4583</td>
			<td>O.C.T. compound</td>
		</tr>
		<tr>
			<td>Vascular forceps</td>
			<td></td>
			<td></td>
			<td>Alternative products can be used</td>
		</tr>
		<tr>
			<td>Xenetix 300 contrast media</td>
			<td>Guerbet, Z&#252;rich, Switzerland</td>
			<td>-</td>
			<td>Lobitridol, 300 mg iodide/ml</td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>Vetoquinol</td>
			<td>-</td>
			<td>Xylapan, 20mg/1 mL</td>
		</tr>
		<tr>
			<td>2,3,5-Triphenyltetrazolium choride</td>
			<td>Sigma-Aldrich, Austria</td>
			<td>T8877</td>
			<td></td>
		</tr>
		<tr>
			<td>500 &#956;L tubes (eppendorf)</td>
			<td>Trefflab, Switzerland</td>
			<td>96.08185.9.03</td>
			<td>Alternative products can be used</td>
		</tr>
	</tbody>
</table>

improvement of a closed chest porcine myocardial infarction model by standardization of tissue and blood sampling procedures

Myocardial ischemia reperfusion (I/R) injury contributes to almost half of the necrotic area after myocardial infarction. To date there is no approved drug to prevent or reduce myocardial I/R injury. The study and understanding of the pathophysiological mechanisms of myocardial I/R injury is essential to develop successful treatments. Large animal experiments are an important step in translational methods. The porcine model of acute myocardial infarction has been established and described by ourselves and others. We aimed to further improve the value of the model by focusing in detail on the sampling techniques for use in future experiments. Furthermore, we emphasize small but important steps that can affect the quality of the final results. To mimic the clinical situation of myocardial I/R injury, a percutaneous coronary intervention (PCI) catheter was inserted into the left anterior descending coronary artery (LAD) of an anesthetized pig. &#176;&#176;&#176;This model mimics acute myocardial infarction and PCI treatment in humans with the possibility of accurately determining the area at risk as well as the necrotic- and viable ischemic tissue. Here the model was used to investigate the effect of a bicyclic peptide inhibitor of FXIIa. The model can also be modified to allow longer reperfusion times to study later effects of myocardial infarction.

One animal died prematurely before administration of FXIIa inhibitor or control peptide due to a technical error (sudden drop of blood pressure during ischemia time, before addition of test substance). One animal was excluded from the FXIIa inhibitor group because no ischemia/reperfusion injury was observed due to abnormal anatomy of the left anterior descending artery (LAD). A large part of the left ventricle, including the apex, was perfused by the circumflex artery in this animal. The ...

Watch this Scientific Journal Video about Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures at JoVE.com

Improvement of a Closed Chest Porcine Myocardial Infarction Model by Standardization of Tissue and Blood Sampling Procedures

Here we demonstrate a protocol to standardize sampling procedures of an established porcine model of acute myocardial infarction in order to increase its translational value in the understanding of the pathophysiology of myocardial ischemia/reperfusion injury and to test novel drug candidates.

Myocardial ischemia reperfusion (I/R) injury contributes to almost half of the necrotic area after myocardial infarction. To date there is no approved ...

The overall goal of this porcine closed chest myocardial infarction model is to investigate myocardial ischemia reperfusion injury. This method can help to answer key questions in cardiovascular research such as investigating the pathophysiology of ischemia reperfusion injury in the context of acute myocardial infarction. The main advantage of this technique is that it allows an accurate determination of the infarct size and precise sampling technique for further analysis.Prepare the pig for the surgery and administer anesthetics as described in the text protocol. Start the dissection by freeing the carotid arteries on both sides. Cannulate them with 7-French sheaths.Next, cannulate the left jugular vein with a 7-French sheath for venous blood sampling. Then use standard blood collection tubes to withdraw baseline blood samples from the venous line. Collect five and 2.9 milliliters of blood into citrated and EDTA plasma collecting tubes respectively and immediately centrifuge at 2, 000 g for 15 minutes at four degrees Celsius.Next, collect 2.9 milliliters of blood into a serum tube and allow it to coagulate for 30 minutes at room temperature, then centrifuge it at 2, 000 g for 15 minutes at four degrees Celsius. Next, use fluoroscopic guidance to insert a pressure catheter via the previously placed sheath into the left carotid artery. Advance it into the left ventricle and then connect it to an acquisition system to record left ventricular pressure.Set up the acquisition system to continuously calculate and record the heart rate, the developed pressure, the contractility of the left ventricle, and the relaxation of the left ventricle during the entire experiment. Next, insert a guiding catheter via the previously placed sheath into the right carotid artery. Using x-ray guidance, advance the catheter into the left coronary artery and then to the LAD or Left Anterior Descending coronary artery.Once in position, inject contrast medium into the guiding catheter from a 20 milliliter syringe to perform a baseline coronary angiography. Next, assembly the PCI catheter and the appropriately sized coronary guide wire, then connect the PCI catheter to the inflation device prefilled with contrast medium. Insert the assembled system into the lumen of the guiding catheter and advance the guide wire into the LAD until it reaches beyond the first diagonal branch of the LAD.Next, use fluoroscopic guidance to advance the PCI catheter until it reaches about the middle of the LAD. Choose the LAD blocking site as described in the text protocol. Now remove the guide wire and increase the pressure in the inflation device to seven to 10 bar to inflate the balloon of the PCI catheter and induce myocardial ischemia.Keep the balloon inflated for one hour. Just after starting the ischemia, record five to 10 seconds of video while injecting contrast medium to have an angiogram of the balloon of the PCI catheter. Repeat this after 10 minutes to verify the occlusion of the LAD.From 15 to 40 minutes into the ischemia, gradually increase the fraction of inspired oxygen from 50 to 60%Always be quick to treat cardiac arrhythmias which typically occur between 20 and 40 minutes after coronary occlusion. An effective treatment to reestablish a regular heartbeat is to gently massage the neck on both sides just below the cheek. Start this treatment when extra systoles occur more than three times per minute, then inject the test substance intravenously through the central venous line and flush the line with 20 milliliters of saline.Next, perform another angiogram to confirm that the LAD is still occluded, then deflate the balloon of the PCI catheter and remove it from the guiding catheter. Immediately after removing the catheter, confirm the perfusion of the LAD distal to the occlusion using another angiogram. Take another angiogram after 10 minutes and whenever signs of myocardial ischemia are visible by ECG for more than five minutes.The ischemic myocardium is now allowed to reperfuse for two hours. Take plasma and serum samples at 10, 30, 60, and 115 minutes into the reperfusion. Also monitor blood gas analysis at 60 and 115 minutes into the reperfusion.After two hours of reperfusion, perform another angiogram, then reocclude the LAD. Reinsert the PCI catheter together with the guide wire to exactly the same position as used for the ischemia. Inflate the PCI catheter and confirm LAD occlusion by angiogram.Now remove the pressure catheter from the left ventricle and stop the recording. Finally, inject 100 milliliters of 2%Evans Blue in PBS into the central venous line and proceed with euthanizing the animal. After excising the heart, rinse it out with room temperature saline and weigh it.Within 30 to 40 minutes, cut the heart into slices starting about three to five millimeters from the apex and moving toward the chordae tendineae of the mitral valve. Cut perpendicular to the long axis using a sharp knife. Next, cut away the right ventricle and weigh the left ventricle slices to obtain its total weight.Then use a scalpel to dissect the slices to separate the Evans Blue negative tissue, which is ischemic, from the non-ischemic tissue which is Evans Blue positive. First, analyze the Evans Blue negative sections. They are the areas at risk.Weigh them all and put them all into a plastic container, then submerge them in 100 to 150 milliliters of freshly made TTC solution and incubate them for 20 minutes. During the incubation time, take samples from the most distal part of the injury. Embed them in OCT compound and store them at minus 80 degrees Celsius for further analysis.Transfer the remaining tissue into a 4%formaldehyde solution and store it at room temperature for future analysis. Now remove the pieces of the areas at risk from the TTC solution. The red-stained tissue is viable ischemic tissue and the non-stained tissue is necrotic ischemic tissue.Cut two small blocks of similar mass from both tissue types and embed them into OCT compound, then store at minus 80 degrees Celsius for further analysis. Store the remaining tissue in 4%formaldehyde at room temperature for 24 hours. The tissue is then stained and the Areas AT Risk or AAR were compared with the areas Not At Risk or ANR.The AAR expressed as a percentage of the LV showed no statistically significant differences between the FXIIa treated group and the control group. The infarct size also showed no differences between the groups. These data suggest that FXIIa inhibitor alone at the concentration used and duration of application could not protect the heart from myocardial IR injury.The cardiac muscle damage marker troponin-I was monitored in the blood. There was almost no change after one hour of ischemia, but after reperfusion, troponin-I levels steadily increased. After watching this video, you should have a good understanding of how to calculate accurately the infarct size and perform correct sampling.Once mastered, this technique can be done in six hours if it is performed properly. While attempting this procedure, it's important to remember to have a similar ischemic area at risk, inject Evans Blue intravenously, use freshly prepared TTC, and accurately calculate the NIT. Following this procedure, other methods like changing the ischemia and the reperfusion time can be performed in order to answer additional questions like the long-term effect of the treatment used to reduce reperfusion injury.

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