Portions of this work were supported by a generous contribution by the Fondation Marcel et Rolande Gosselin and Fondation Mr Stefane Foumy. Nicolas Noiseux is scholar of the FRQ-S.
The authors wish to thanks Josh Zhuo Le Huang, Gabrielle Gascon, Sophia Ghiassi, and Catherine Scalabrini for their support in data collection.

All animal care and experimental protocols conformed to the Guide for the Care and Use of Laboratory Animals and were approved by the institutional animal care and use committee of the Centre Hospitalier de l&#8217;Universit&#233; de Montr&#233;al Research Center.
1. Preliminary Preparations
<ol>
	<li>Turn on the water bath to heat the cardioplegia delivery system (Figure 1A) and the Langendorff ex vivo perfusion system (Figure 1B). Set the water temperature to 38.5 &#176;C for a solution temperature of 37 &#176;C. Setup photographs can be seen in Supplementary Figure 1A,B.</li>
	<li>Prepare 1 L of cardioplegic solution. Add 1 mL of 2% lidocaine hydrochloride and 10 mL of 2 mM KCl (final concentration 20 mM) to 1 L of Plasma-Lyte A (140 mM Na, 5 mM K, 1.5 mM Mg, 98 mM Cl, 27 mM acetate, 23 mM gluconate). Correct pH to 7.4 using 6 N HCl. 
	CAUTION: This model is highly sensitive to pH. A wrong pH correction (outside the 7.3-7.4 physiological range) or pH unstable solutions may compromise the experiment or provide unreliable data.</li>
	<li>Prepare 4 L of Krebs solution (113 mM NaCl, 4.5 mM KCl, 1.6 mM NaH2PO4, 1.25 mM CaCl2, 1 mM MgCl2&#8729;6H2O, 5.5 mM D-Glucose, 25 mM NaHCO3). Substrate masses per 1 L of solution should be as follows: 6.1 g of NaCl, 0.3355 g of KCl, 0.2035 g of MgCl2&#8729;6H2O, 0.192 g of NaH2PO4, 0.1387 g of CaCl2, 0.99 g of D-Glucose, 2.1 g of NaHCO3, final volume of 1 L in ultrapure deionized water. Add the NaHCO3 last to avoid precipitation. Filter the solution using a 0.22 &#181;m filter and store overnight. Correct the pH to 7.4 when the solution is at 37 &#176;C and bubble with 5% CO2/95% O2.</li>
	<li>Fill the Langendorff circuit with Krebs solution and start the system pump. Make sure that no bubbles are left inside the tubing. Adjust the peristaltic pump speed to 80 rpm (equivalent to 1 L/min). Using the two way stop cock, adjust the flow to maintain a slow drip through the aortic cannula until the heart is attached (Figure 1B). Keep a sample of Krebs solution (15 mL) in a 50 mL conic tube on ice for heart transportation.</li>
	<li>Fill the cardioplegia delivery system with the cardioplegic solution. Once the bubbles are removed, switch the circuit to saline using a 3 way stop cock (Figure 1A). Adjust the drip rate. Saline must be slowly dripping from the tip of the catheter to assure that no cardioplegic solution is injected before the animal&#8217;s death.</li>
</ol>
2. Animal Preparation
<ol>
	<li>Using an inhalation chamber, induce anesthesia with 3% isoflurane. Once the animal is unresponsive, perform an intraperitoneal injection of ketamine (75 mg/kg) and xylazine (5 mg/kg) or similarly suitable anesthetic, following local regulations, to maintain anesthesia for the rest of the procedure. Ensure the depth of anesthesia by no reaction to toe pinch and palpebral reflex.</li>
	<li>Intubate the animal using a 14 G, 2-inch I.V. catheter. Start ventilation at 50 breaths per min, with airway pressure limited to 20 cmH2O.</li>
	<li>Place the animal on a heating pad set to &#8220;medium&#8221; and cover with an absorbent pad to maintain body temperature. Insert a rectal temperature probe and attach a transdermal pulse oximeter sensor to one of the feet. Maintain rectal temperature at 37 &#176;C throughout the procedure.</li>
	<li>Vascular access
	<ol>
		<li>Make a 3 to 4 cm midline skin incision in the neck using scissors. Using blunt tip curved scissors, blunt dissect the subcutaneous tissue and expose the right sternohyoid muscle. Using non traumatic forceps, move the muscle laterally until the right carotid artery (pulsating), jugular vein (non-pulsating) and the vagus nerve (white) are visually identified (Supplementary Figure 2A). Carefully separate the vagus nerve from the carotid artery using blunt tip curved scissors.</li>
		<li>Inject heparin (2,000 IU/kg) via the right jugular vein. Apply pressure to the injection site after needle retraction to avoid blood leakage.</li>
		<li>Using curved forceps, pass two 5-0 silk sutures around the carotid artery. Firmly attach a distal suture to occlude the carotid artery at the superior aspect of the exposed artery. Keep the proximal suture untied. Pulling of the proximal suture will be used for bleeding control in the next step (Supplementary Figure 2B). The distance between sutures should be approximately 2 cm.</li>
		<li>Using a stereomicroscope for better visualization, carefully make a 1 mm incision with microsurgery scissors over the anterior wall of the carotid artery. Insert a 22 G, 1-inch closed I.V. catheter towards the aortic arch. The catheter is connected to a 2 way stop cock, allowing for connection to a pressure transducer for constant monitoring, with the possibility of injecting saline or cardioplegia via the cardioplegia delivery system (Figure 1A).</li>
	</ol>
	</li>
</ol>
3. Initiation of Cardiac Donation After Circulatory Death (DCD) Protocol
NOTE: A complete protocol timeline can be seen in Figure 2.
<ol>
	<li>Re-asses the anesthetic depth by performing a toe pinch and evaluating palpebral reflex. If reaction is observed, perform an intraperitoneal injection of Ketamine (37.5 mg/Kg) and xylazine (2.5 mg/Kg). Re-evaluate after 5 minutes. If no response is observed continue the procedure. Tracheal clamp should only be performed in adequately anesthetized animals.</li>
	<li>Turn off the ventilator and extubate the animal. Using mosquito forceps, clamp the trachea. This moment is considered as the start of the agonal phase. Start counting the functional warm ischemic time (WIT) when the peak systolic blood pressure drops below 30 mmHg, or if asystole or ventricular fibrillation appears, whatever comes first (Figure 3). 
	NOTE: Damage extent should be proportional to WIT. Experiments are needed to optimize WIT time according to anesthetic used, animal strain, sex and weight chosen. In control animals, immediately after carotid vascular access is secured, cardioplegia is injected and the heart is procured as described in the next step (Figure 2). The start of perfusion with cardioplegia is considered as the end of WIT.</li>
	<li>At the end of WIT, perform a medial sternotomy. Keep the thorax open by using an Alm retractor. Using scissors, open the inferior vena cava and both atria to avoid myocardial distension or cardioplegia recirculation (Supplementary figure 3). Clamp the aorta above the diaphragm. Through the previously catheterized carotid artery, infuse the cardioplegic solution at a constant pressure of 60 mmHg for 5 min using the cardioplegia delivery system. Infusion pressure can be modified by altering the height of the water column.</li>
	<li>At the end of cardioplegic infusion, dissect the ascending proximal aorta from the pulmonary artery using curved forceps (Supplementary Figure 4A). Cut the aorta distal to the left subclavian artery. Ensure an aortic length of at least 0.5 cm for cannulation for the Langendorff apparatus.</li>
	<li>Holding the heart from the aorta, complete the cardiectomy by separating the heart from the pulmonary veins and other thoracic structures (Supplementary Figure 4B). Rapidly, submerge the heart in to ice-cold Krebs solution for rapid transportation to the ex vivo system. Keep the dissection and transport times as short as possible (5 min).</li>
</ol>
4. Ex Vivo Heart Perfusion System (EVHP) and Cardiac Functional Assessment
<ol>
	<li>Open the aortic lumen using forceps. Deair the aorta by filling the lumen with the dripping Krebs solution to avoid forcing bubbles in to the coronary vessels. Lower the cannula into the aorta, taking care not to pass the aortic root or damage the aortic valve leaflets. Fix the setup with a small clamp.</li>
	<li>Using the 2 way stopcock, increase the flow to search for possible leaks in the aorta. If none are detected, tightly fix the aorta to the cannula using a 2-0 silk suture. Fully open the flow to the cannula. Maintain aortic pressure at a physiological pressure of 60-70 mmHg (adjusted by changing the height of the system). At this moment the initial reperfusion and stabilization time is initiated. Aortic pressure can be modified according to the investigator&#8217;s experimental plan.</li>
	<li>Rotate the heart so the base of the heart (atria) is facing the pressure sensor. Widen the left ventricular atrial opening by dissecting the pulmonary veins. Insert the latex balloon connected to a pressure sensor. Make sure that the balloon is fully positioned inside the ventricle by visual inspection. Slowly fill the balloon with saline until end diastolic pressure (EDP) is set to 15 mmHg. Adjust as needed to keep EDP constant (pre-determined physiological EDP). The EDP can be adjusted according to the experimental objectives of each investigator.</li>
	<li>Insert the pacing electrode in the anterior face of the heart (right ventricular outflow tract). Avoid puncturing the coronary vessels. Once spontaneous beating is observed, initiate pacing at 300 beats per min. Required voltage may vary between experiments and rat strains.</li>
	<li>After 10 min of stabilization, initiate continuous intraventricular pressure measurement recording. This moment is considered the beginning of the reconditioning and assessment phase (time 0) that will last for 1 h (Figure 2). Reconditioning may be prolonged, but a time-dependent decrease in contractility is expected in all hearts.</li>
	<li>At the start of reconditioning, collect cardiac effluent dropping from the cardiac veins for 5 min for baseline coronary flow assessment and biochemical analyses. For troponin T repeat every 15 min (times 0, 15, 30, 45 and 60 min). For other analyses individualization of collection times is needed (Figure 2).</li>
</ol>
5. End of Experience
<ol>
	<li>Remove the heart from the Langendorff apparatus.</li>
	<li>Using a straight high carbon steel blade (microtome blade or similar), remove the base of the heart (including aorta and pulmonary artery).</li>
	<li>With the right ventricle facing down, cut transverse ventricular slides of 1-2 mm thickness. In one representative section (normally the third) excise the right ventricle and snap freeze the left ventricle. This sample can be used for biochemical analyses.</li>
	<li>Submerge the remaining sections in to freshly prepared 5% 2,3,5-triphenyl-tetrazolium chloride in commercial phosphate buffer saline pH 7.4 for 10 min at 37 &#176;C. Viable tissues are colored red brick.</li>
	<li>Wash twice with phosphate buffer saline pH 7.4 and fix with 10% formalin at 4 &#176;C overnight. Wash twice with phosphate buffered saline pH 7.4 and keep each slice submerged.</li>
	<li>Withdraw excess liquid and weight each slide. Take digital color images of both sides. Use planimetric analyses to calculate percent infarct size and correct for slice and total ventricular weight. Coloration fades with time. Photos must be taken as soon as possible.</li>
</ol>
6. Data analyses
<ol>
	<li>Save all pressure data in a new file per animal.</li>
	<li>For pressure analyses, select at least 200 pressure cycles per time points. Analyses can be performed off-line (after completion of the experiment) using dedicated software (i.e., LabChart). Common cardiovascular parameters available include: Maximal generated pressure, end diastolic pressure, +dP/dt (steepest slope during the upstroke of the pressure curve, an indicator of ventricular contractile ability), -dP/dt (steepest slope during the downstroke of the pressure curve, an indicator of ventricular relaxation capacity) among others. 
	NOTE: For troponin analyses, an increase in troponin release at reperfusion is expected. After 1 h of reperfusion in the EVHP system, troponin levels may decrease to baseline, stressing the need for careful timing in the collection and handling of these samples.</li>
</ol>

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The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article.

The protocol presented here introduces a simple, convenient and versatile model of cardiac DCD, offering the opportunity to assess cardiac functional recovery, tissue damage and the use of post-conditioning cardioprotective agents to improve recovery of donor hearts otherwise discarded for transplantation. Ex vivo heart perfusion systems (EVHP) systems have been optimized to provide a platform for evaluating cardiac function and offer a unique opportunity to deliver and test modified solutions supplemented with post-cond...

Solid organ transplantation in general and cardiac transplantation, in particular, are on the rise worldwide1,2. The standard method of organ procurement is donation after brain death (DBD). Given the strict inclusion criteria of DBD, less than 40% of the offered hearts are accepted3, thereby limiting the offer in face of increasing demand and extending the organ waiting list. To address this issue, the use of organs donated after circulatory death (DCD) is considered a potential solution4.
In DCD donors, however, an agonal phase following withdrawal of care and a period of unprotected warm ischemia before resuscitation are inevitable5. The potential organ injury after circulatory death can lead to organ dysfunction, explaining the reluctance to routinely adopt DCD heart transplantations. It is reported that only 4 centers use DCD hearts clinically, with stringent criteria that includes very short warm ischemia times and young donors without chronic pathologies6,7. For ethical and legal reasons, limited or no cardioprotective interventions can be applied in donors prior to circulatory death5,8,9. Thus, any mitigation to alleviate the ischemia-reperfusion (IR) injury is limited to cardioprotective therapies initiated during early reperfusion with cardioplegic solutions, and do not allow for proper functional assessment. Ex vivo heart perfusion (EVHP) and reconditioning of the DCD heart using dedicated platforms has been proposed as an alternative solution and studied by various scholars10,11,12,13. EVHP offers a unique opportunity to deliver post-conditioning agents to DCD hearts to improve functional recovery. However, for efficient clinical translation, many technical and practical issues remain to be addressed, and this is further compounded by a lack of consensus on a range of perfusion and functional criteria to determine transplantability6,8.
Herein we report the development of a reproducible pre-clinical small animal DCD protocol combined with an ex vivo heart perfusion system that can be used to investigate organ post-conditioning initiated at the time of procurement, during initial reperfusion, and/or throughout EVHP.

<table>
	<tbody>
		<tr>
			<td>0,9% Sodium Chloride. 1L bag</td>
			<td>Baxter</td>
			<td></td>
			<td>Electrolyte solution for flushing in the modified Langendorff system.</td>
		</tr>
		<tr>
			<td>14G 2&#34; I.V catheter</td>
			<td>Jelco</td>
			<td>4098</td>
			<td>To act as endotracheal tube.</td>
		</tr>
		<tr>
			<td>2,3,5-Triphenyltetrazolium chloride</td>
			<td>Milipore-Sigma</td>
			<td>T8877</td>
			<td>Vital coloration</td>
		</tr>
		<tr>
			<td>22G 1&#34; I.V catheter</td>
			<td>BD</td>
			<td>383532</td>
			<td>I.V catheter with extension tube that facilitates manipulation for carotid catheterization</td>
		</tr>
		<tr>
			<td>Adson Dressing Fcp, 4 3/4&#34;, Serr</td>
			<td>Skalar</td>
			<td>50-3147</td>
			<td>Additional forceps for tissue manipulation</td>
		</tr>
		<tr>
			<td>Alm Self-retaining retractor 4x4 Teeth Blunt 2-3/4&#34;</td>
			<td>Skalar</td>
			<td>22-9027</td>
			<td>Tissue retractor used to maintain the chest open.</td>
		</tr>
		<tr>
			<td>Bridge amp</td>
			<td>ADinstruments</td>
			<td>FE221</td>
			<td>Bridge amp for intracarotid blood pressure measurement</td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>Milipore-Sigma</td>
			<td>C1016</td>
			<td>CaCl2 anhydrous, granular, &#8804;7.0 mm, &#8805;93.0% Part of the Krebs solution</td>
		</tr>
		<tr>
			<td>D-(+)-Glucose</td>
			<td>Milipore-Sigma</td>
			<td>G8270</td>
			<td>D-Glucose &#8805;99.5% Part of the Krebs solution</td>
		</tr>
		<tr>
			<td>DIN(8) to Disposable BP Transducer</td>
			<td>ADinstruments</td>
			<td>MLAC06</td>
			<td>Adapter cable for link between bridge amp and pressure transducer</td>
		</tr>
		<tr>
			<td>Disposable BP Transducer (stopcock)</td>
			<td>ADinstruments</td>
			<td>MLT0670</td>
			<td>Pressure transducer for intracarotid blood pressure measurement</td>
		</tr>
		<tr>
			<td>dPBS</td>
			<td>Gibco</td>
			<td>14190-144</td>
			<td>Electrolyte solution without calcium or magnesium.</td>
		</tr>
		<tr>
			<td>Eye Dressing Fcp, Str, Serr, 4&#34;</td>
			<td>Skalar</td>
			<td>66-2740</td>
			<td>Additional forceps for tissue manipulation</td>
		</tr>
		<tr>
			<td>Formalin solution, neutral buffered, 10%</td>
			<td>Milipore-Sigma</td>
			<td>HT501128</td>
			<td>Fixative solution</td>
		</tr>
		<tr>
			<td>Heating Pad</td>
			<td>Sunbean</td>
			<td>756-CN</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin sodium 1000 UI/mL</td>
			<td>Sandoz</td>
			<td></td>
			<td>For systemic anticoagulation</td>
		</tr>
		<tr>
			<td>Hydrochloric Acid 36,5 to 38,0%</td>
			<td>Fisher scientific</td>
			<td>A144-500</td>
			<td>Diluted 1:1 for pH correction</td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>Bimeda</td>
			<td></td>
			<td>Anesthetic. 100 mg/ml</td>
		</tr>
		<tr>
			<td>LabChart</td>
			<td>ADinstruments</td>
			<td></td>
			<td>Control software for the Powerlab polygraph, allowing off-line analyses. Version 7, with blood pressure and PV loop modules enabled</td>
		</tr>
		<tr>
			<td>Left ventricle pressure balloon</td>
			<td>Radnoti</td>
			<td>170404</td>
			<td>In latex. Size 4.</td>
		</tr>
		<tr>
			<td>Lidocaine HCl 2% solution</td>
			<td>AstraZeneca</td>
			<td></td>
			<td>Antiarrhythmic for the cardioplegic solution</td>
		</tr>
		<tr>
			<td>Magnesium Chloride ACS</td>
			<td>ACP Chemicals</td>
			<td>M-0460</td>
			<td>MgCl2+6H2O &#8805;99.0% Part of the Krebs solution</td>
		</tr>
		<tr>
			<td>Micro pressure sensor</td>
			<td>Radnoti</td>
			<td>159905</td>
			<td>Micro pressure sensor and amplifier connected to the intraventricular balloon</td>
		</tr>
		<tr>
			<td>Pacemaker</td>
			<td>Biotronik</td>
			<td>Reliaty</td>
			<td>Set to generate a pulse each 200 ms for a heart rate of 300 bpm.</td>
		</tr>
		<tr>
			<td>pH bench top meter</td>
			<td>Fisher scientific</td>
			<td>AE150</td>
			<td></td>
		</tr>
		<tr>
			<td>Physiological monitor</td>
			<td>Kent Scientific</td>
			<td>Physiosuite</td>
			<td>For continuous monitoring of rodent temperature and saturation during the procedure</td>
		</tr>
		<tr>
			<td>Plasma-Lyte A</td>
			<td>Baxter</td>
			<td></td>
			<td>Electrolyte solution used as base to prepare cardioplegia</td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Milipore-Sigma</td>
			<td>P4504</td>
			<td>KCl &#8805;99.0% Part of the Krebs solution</td>
		</tr>
		<tr>
			<td>Potassium Chloride 2 meq/ml</td>
			<td>Hospira</td>
			<td></td>
			<td>Part of the cardioplegic solution</td>
		</tr>
		<tr>
			<td>PowerLab 8/30 Polygraph</td>
			<td>ADinstruments</td>
			<td></td>
			<td>Electronic polygraph</td>
		</tr>
		<tr>
			<td>Silk 2-0</td>
			<td>Ethicon</td>
			<td>A305H</td>
			<td>Suture material for Langendorff apparatus</td>
		</tr>
		<tr>
			<td>Silk 5-0</td>
			<td>Ethicon</td>
			<td>A302H</td>
			<td>Suture material for carotid</td>
		</tr>
		<tr>
			<td>Small animal anesthesia workstation</td>
			<td>Hallowell EMC</td>
			<td>000A2770</td>
			<td>Small animal ventilator</td>
		</tr>
		<tr>
			<td>Sodium bicarbonate</td>
			<td>Milipore-Sigma</td>
			<td>S5761</td>
			<td>NaHCO3 &#8805;99,5% Part of the Krebs solution</td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Milipore-Sigma</td>
			<td>S7653</td>
			<td>NaCl &#8805;99.5% Part of the Krebs solution</td>
		</tr>
		<tr>
			<td>Sodium Hydroxide pellets</td>
			<td>ACP chemicals</td>
			<td>S3700</td>
			<td>Diluted to 5N (10 g in 50 ml) for pH correction</td>
		</tr>
		<tr>
			<td>Sodium phosphate monobasic</td>
			<td>Milipore-Sigma</td>
			<td>S0751</td>
			<td>NaH2PO4 &#8805;99.0% Part of the Krebs solution</td>
		</tr>
		<tr>
			<td>Stevens Tenotomy Sciss, Str, Delicate, SH/SH, 4 1/2&#34;</td>
			<td>Skalar</td>
			<td>22-1240</td>
			<td>Small scisors for atria and cava vein opening</td>
		</tr>
		<tr>
			<td>Tissue slicer blades</td>
			<td>Thomas scientific</td>
			<td>6727C18</td>
			<td>Straight carbon steel blades for tissue slicing at the end of the protocol</td>
		</tr>
		<tr>
			<td>Tuberculin safety syringe with needle 25G 5/8&#34;</td>
			<td>CardinalHealth</td>
			<td>8881511235</td>
			<td>For heparin injection</td>
		</tr>
		<tr>
			<td>Veterinary General Surgery Set</td>
			<td>Skalar</td>
			<td>98-1275</td>
			<td>Surgery instruments including disection scisors and mosquito clamps</td>
		</tr>
		<tr>
			<td>Veterinary Micro Set</td>
			<td>Skalar</td>
			<td>98-1311</td>
			<td>Surgery instruments with microscisors used for carotid artery opening</td>
		</tr>
		<tr>
			<td>Working Heart Rat/Guinea Pig/Rabbit system</td>
			<td>Radnoti</td>
			<td>120101BEZ</td>
			<td>Modular working heart system modified for the needs of the protocol. Includes all the necesary tubbing, water jacketed reservoirs and valves, including 2 and 3 way stop cock</td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>Bayer</td>
			<td></td>
			<td>Sedative. 20 mg/ml</td>
		</tr>
	</tbody>
</table>

pre-clinical model of cardiac donation after circulatory death

Cardiac transplantation demand is on the rise; nevertheless, organ availability is limited due to a paucity of suitable donors. Organ donation after circulatory death (DCD) is a solution to address this limited availability, but due to a period of prolonged warm ischemia and the risk of tissue injury, its routine use in cardiac transplantation is seldom seen. In this manuscript we provide a detailed protocol closely mimicking current clinical practices in the context of DCD with continuous monitoring of heart function, allowing for the evaluation of novel cardioprotective strategies and interventions to decrease ischemia-reperfusion injury.
In this model, the DCD protocol is initiated in anesthetized Lewis rats by stopping ventilation to induce circulatory death. When systolic blood pressure drops below 30 mmHg, the warm ischemic time is initiated. After a pre-set warm ischemic period, hearts are flushed with a normothermic cardioplegic solution, procured, and mounted onto a Langendorff ex vivo heart perfusion system. Following 10 min of initial reperfusion and stabilization, cardiac reconditioning is continuously evaluated for 60 min using intraventricular pressure monitoring. A heart injury is assessed by measuring cardiac troponin T and the infarct size is quantified by histological staining. The warm ischemic time can be modulated and tailored to develop the desired amount of structural and functional damage. This simple protocol allows for the evaluation of different cardioprotective conditioning strategies introduced at the moment of cardioplegia, initial reperfusion and/or during ex vivo perfusion. Findings obtained from this protocol can be reproduced in large models, facilitating clinical translation.

Following extubation, blood pressure rapidly drops in a predictable pattern (Figure 3). Expected time to death is less than 5 min.
Figure 4 shows an average pressure/time curve at the start of reconditioning following 0, 10 and 15 min of WIT. Contractile function will improve over time. The use of short periods of WIT will allow for contractility to return to normal, and morphological damage will not be detectable (<strong class="xfig...

Watch this Scientific Journal Video about Pre-clinical Model of Cardiac Donation after Circulatory Death at JoVE.com

Pre-clinical Model of Cardiac Donation after Circulatory Death

This protocol shows a simple and flexible approach for the evaluation of new conditioning agents or strategies to increase the feasibility of cardiac donation after circulatory death.

Cardiac transplantation demand is on the rise; nevertheless, organ availability is limited due to a paucity of suitable donors. Organ donation after ...

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Medicine

7.8K Views.  Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM). This protocol shows a simple and flexible approach for the evaluation of new conditioning agents or strategies to increase the feasibility of cardiac donation after circulatory death.

Video: Pre-clinical Model of Cardiac Donation after Circulatory Death

The Use of Pharmacological-challenge fMRI in Pre-clinical Research: Application to the 5-HT System

Pharmacological MRI (phMRI) is a new and promising method to study the effects of substances on brain function that can ultimately be used to unravel underlying neurobiological mechanisms behind drug action and neurotransmitter-related disorders, such as depression and ADHD. Like most of the imaging methods (PET, SPECT, CT) it represents a progress in the investigation of brain disorders and the related function of neurotransmitter pathways in a non-invasive way with respect of the overall neuronal connectivity. Moreover it also provides the ideal tool for translation to clinical investigations. MRI, while still behind in molecular imaging strategies compared to PET and SPECT, has the great advantage to have a high spatial resolution and no need for the injection of a contrast-agent or radio-labeled molecules, thereby avoiding the repetitive exposure to ionizing radiations. Functional MRI (fMRI) is extensively used in research and clinical setting, where it is generally combined with a psycho-motor task. phMRI is an adaptation of fMRI enabling the investigation of a specific neurotransmitter system, such as serotonin (5-HT), under physiological or pathological conditions following activation via administration of a specific challenging drug.
The aim of the method described here is to assess brain 5-HT function in free-breathing animals. By challenging the 5-HT system while simultaneously acquiring functional MR images over time, the response of the brain to this challenge can be visualized. Several studies in animals have already demonstrated that drug-induced increases in extracellular levels of e.g. 5-HT (releasing agents, selective re-uptake blockers, etc) evoke region-specific changes in blood oxygenation level dependent (BOLD) MRI signals (signal due to a change of the oxygenated/deoxygenated hemoglobin levels occurring during brain activation through an increase of the blood supply to supply the oxygen and glucose to the demanding neurons) providing an index of neurotransmitter function. It has also been shown that these effects can be reversed by treatments that decrease 5-HT availability16,13,18,7. In adult rats, BOLD signal changes following acute SSRI administration have been described in several 5-HT related brain regions, i.e. cortical areas, hippocampus, hypothalamus and thalamus9,16,15. Stimulation of the 5-HT system and its response to this challenge can be thus used as a measure of its function in both animals and humans2,11.

The goal of this technique is to assess serotonin (5-HT) neurotransmitter function in the live and free-breathing animal with pharmacological magnetic resonance imaging (phMRI) and an intravenous challenge with a selective serotonin reuptake inhibitor (SSRI), fluoxetine.

Pharmacological MRI (phMRI) is a new and promising method to study the effects of substances on brain function that can ultimately be used to unravel ...

Pre-clinical Evaluation of Tyrosine Kinase Inhibitors for Treatment of Acute Leukemia

Receptor tyrosine kinases have been implicated in the development and progression of many cancers, including both leukemia and solid tumors, and are attractive druggable therapeutic targets. Here we describe an efficient four-step strategy for pre-clinical evaluation of tyrosine kinase inhibitors (TKIs) in the treatment of acute leukemia. Initially, western blot analysis is used to confirm target inhibition in cultured leukemia cells. Functional activity is then evaluated using clonogenic assays in methylcellulose or soft agar cultures. Experimental compounds that demonstrate activity in cell culture assays are evaluated in vivo using NOD-SCID-gamma (NSG) mice transplanted orthotopically with human leukemia cell lines. Initial in vivo pharmacodynamic studies evaluate target inhibition in leukemic blasts isolated from the bone marrow. This approach is used to determine the dose and schedule of administration required for effective target inhibition. Subsequent studies evaluate the efficacy of the TKIs in vivo using luciferase expressing leukemia cells, thereby allowing for non-invasive bioluminescent monitoring of leukemia burden and assessment of therapeutic response using an in vivo bioluminescence imaging system. This strategy has been effective for evaluation of TKIs in vitro and in vivo and can be applied for identification of molecularly-targeted agents with therapeutic potential or for direct comparison and prioritization of multiple compounds.

Receptor tyrosine kinases are ectopically expressed in many cancers and have been identified as therapeutic targets in acute leukemia. This manuscript describes an efficient strategy for pre-clinical evaluation of tyrosine kinase inhibitors for the treatment of acute leukemia.

Receptor tyrosine kinases have been implicated in the development and progression of many cancers, including both leukemia and solid tumors, and are ...

Handling of the Cotton Rat in Studies for the Pre-clinical Evaluation of Oncolytic Viruses

Oncolytic viruses are a novel anticancer therapy with the ability to target tumor cells, while leaving healthy cells intact. For this strategy to be successful, recent studies have shown that involvement of the host immune system is essential. Therefore, oncolytic virotherapy should be evaluated within the context of an immunocompetent model. Furthermore, the study of antitumor therapies in tolerized animal models may better recapitulate results seen in clinical trials. Cotton rats, commonly used to study respiratory viruses, are an attractive model to study oncolytic virotherapy as syngeneic models of mammary carcinoma and osteosarcoma are well established. However, there is a lack of published information on the proper handling procedure for these highly excitable rodents. The handling and capture approach outlined minimizes animal stress to facilitate experimentation. This technique hinges upon the ability of the researcher to keep calm during handling and perform procedures in a timely fashion. Finally, we describe how to prepare cotton rat mammary tumor cells for consistent subcutaneous tumor formation, and how to perform intratumoral and intraperitoneal injections. These methods can be applied to a wide range of studies furthering the development of the cotton rat as a relevant pre-clinical model to study antitumor therapy.

Cotton rats are extremely excitable and have a strong flight-or-fight response. A handling method optimized to reduce the stress of the animals is described which will make cotton rats more accessible as a preclinical model.

Oncolytic viruses are a novel anticancer therapy with the ability to target tumor cells, while leaving healthy cells intact.  For this strategy to be ...

Pre-clinical Orthotopic Murine Model of Human Prostate Cancer

To study the multifaceted biology of prostate cancer, pre-clinical in vivo models offer a range of options to uncover critical biological information about this disease. The human orthotopic prostate cancer xenograft mouse model provides a useful alternative approach for understanding the specific interactions between genetically and molecularly altered tumor cells, their organ microenvironment, and for evaluation of efficacy of therapeutic regimens. This is a well characterized model designed to study the molecular events of primary tumor development and it recapitulates the early events in the metastatic cascade prior to embolism and entry of tumor cells into the circulation. Thus it allows elucidation of molecular mechanisms underlying the initial phase of metastatic disease. In addition, this model can annotate drug targets of clinical relevance and is a valuable tool to study prostate cancer progression. In this manuscript we describe a detailed procedure to establish a human orthotopic prostate cancer xenograft mouse model.

Prostate cancer is the second most common cause of cancer-related deaths in the United States. An orthotopic cancer model provides a useful approach to understand the biology of prostate cancer and to evaluate the efficacy of therapeutic regimens. This protocol describes detailed steps necessary to establish an orthotopic prostate cancer mouse model.

To study the multifaceted biology of prostate cancer, pre-clinical in vivo models offer a range of options to uncover critical biological information ...

Use of a Low-flow Digital Anesthesia System for Mice and Rats

A traditional vaporizer depends on flowing gas and atmospheric pressure for passive anesthetic vaporization. Newly developed direct injection vaporizers utilize a syringe pump to directly administer volatile anesthetics into a gas stream. Unlike a traditional vaporizer, it can be used at very low flow rates, making it ideal for use on mice and rats. 
The equipment's capability to use low flow rates could result in a substantial cost savings due to the reduced need for anesthetic agents, compressed gas, and charcoal scavenging filters1. A lower flow rate means less waste of anesthetic gas and likely reduces the risk of anesthetic exposure to laboratory personnel. Thus, the high levels of precision and safety associated with direct injection vaporizers, along with a reduced need for anesthetic agents, compressed gas, and charcoal filters are beneficial for research requiring small animal anesthesia. 
The goal of this protocol is to demonstrate the use of a syringe-driven direct injection vaporizer as part of a digital, low-flow anesthesia system. The direct injection vaporizer is capable of accurately delivering anesthesia at very low flow rates compared to a traditional vaporizer, making it a promising alternative for controlled gas anesthetic delivery to rodents.

Here, we present a protocol to more safely and efficiently administer anesthetic gas to mice using a digital, low flow anesthesia system utilizing a syringe-driven direct injection vaporizer.

A traditional vaporizer depends on flowing gas and atmospheric pressure for passive anesthetic vaporization. Newly developed direct injection vaporizers ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Implantation of hiPSC-derived Cardiac-muscle Patches after Myocardial Injury in a Guinea Pig Model

Due to the limited regeneration capacity of the heart in adult mammals, myocardial infarction results in an irreversible loss of cardiomyocytes. This loss of relevant amounts of heart muscle mass can lead to the heart failure. Besides heart transplantation, there is no curative treatment option for the end-stage heart failure. In times of organ donor shortage, organ independent treatment modalities are needed. Left-ventricular assist devices are a promising therapy option, however, especially as destination therapy, limited by its side-effects like stroke, infections and bleedings. In recent years, several cardiac repair strategies including stem cell injection, cardiac progenitors or myocardial tissue engineering have been investigated. Recent improvements in cell biology allow for the differentiation of large amounts of cardiomyocytes derived from human induced pluripotent stem cells (iPSC). One of the cardiac repair strategies currently under evaluation is to transplant artificial heart tissue. Engineered heart tissue (EHT) is a three-dimensional in vitro created cardiomyocyte network, with functional properties of native heart tissue. We have created EHT-patches from hiPSC derived cardiomyocytes. Here we present a protocol for the induction of left ventricular myocardial cryoinjury in a guinea pig, followed by implantation of hiPSC derived EHT on the left ventricular wall.

Here we present a protocol for the induction of left ventricular cryoinjury followed by the implantation of a cardiac muscle patch, derived from human iPS-cell cardiomyocytes in a guinea pig model.

Due to the limited regeneration capacity of the heart in adult mammals, myocardial infarction results in an irreversible loss of cardiomyocytes. This loss ...

A Pre-Clinical Porcine Model of Orthotopic Heart Transplantation

Fifty-years following the first successful report, cardiac transplantation remains the gold-standard treatment for eligible patients with advanced heart failure. Multiple small-animal models of heart transplantation have been used to study the acute and long-term effects of novel therapies. However, few are tested and demonstrated success in clinical trials. It is of critical importance to evaluate new therapies in a clinically relevant large-animal model for efficient and reliable translation of basic studies&#39;&#160;findings. Here, we describe a pre-clinical large-animal (porcine) model of orthotopic heart transplantation that has been firmly established and previously used to investigate novel cardioprotective strategies. This procedure focuses on acute ischemia-reperfusion injury and is a reliable method to investigate novel interventions which have been tested and validated in smaller experimental models, such as the murine model. We demonstrate its usefulness in assessing cardiac performance during the early post-transplantation period and other potential possibilities enabled by the model.

Here, we describe a pre-clinical large-animal (porcine) model of orthotopic heart transplantation that has been firmly established and utilized to investigate novel cardioprotective strategies.

Fifty-years following the first successful report, cardiac transplantation remains the gold-standard treatment for eligible patients with advanced heart ...

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 ...

Use of an Integrated Low-Flow Anesthetic Vaporizer, Ventilator, and Physiological Monitoring System for Rodents

Low-flow digital vaporizers commonly utilize a syringe pump to directly administer volatile anesthetics into a stream of carrier gas. Per animal welfare recommendations, animals are warmed and monitored during procedures requiring anesthesia. Common anesthesia and physiological monitoring equipment include gas tanks, anesthetic vaporizers and stands, warming controllers and pads, mechanical ventilators, and pulse oximeters. A computer is also necessary for data collection and to run equipment software. In smaller spaces or when performing field work, it can be challenging to configure all this equipment in limited space.
The goal of this protocol is to demonstrate best practices for use of a low-flow digital vaporizer using both compressed oxygen and room air, along with an integrated mechanical ventilator, pulse oximeter, and far infrared warming as an all-inclusive anesthesia and physiological monitoring suite ideal for rodents.

Here, we present a protocol to safely and effectively administer anesthetic gas to mice using a digital, low flow anesthesia system with integrated ventilator and physiological monitoring modules.

Low-flow digital vaporizers commonly utilize a syringe pump to directly administer volatile anesthetics into a stream of carrier gas. Per animal welfare ...