This study was funded by NSFC 81570244, FoKo 23/2013, and SFB 1116/B01 and by the Cardiovascular Research Institute D&#252;sseldorf (CARID).

All experiments were approved by the local regulatory agency (LANUV of Nordrhein-Westfalen, Germany) and were performed according to the guidelines of animal use. Animals were fed with a standard chow diet and received tap water ad libitum. All equipment and chemicals necessary to each step of the experiment are available in the Table of Materials.
1. Preparation of the Latex Cap and Intraventricular Balloon
<ol>
	<li>Make an aluminum mold using a milling machine that matches the average size of the rat heart (bodyweight of 300-350 g). Polish the mold with superfine (10/0) emery paper. 
	NOTE: The detailed metrics of the mold are shown in Figure 1A.</li>
	<li>Vertically fix the neck of the aluminum mold to the milling machine to prepare the latex cap. 
	NOTE: The milling machine causes the mold to slowly rotate. Alternatively, an electric motor can be used.</li>
	<li>Pour 20 mL of liquid latex (commercially purchased, see the Table of Materials) into a 50 mL glass beaker.</li>
	<li>Lower the mold until the entire body of the mold is immersed in the latex solution.</li>
	<li>Slowly lift the mold (5 cm/min) while rotating.</li>
	<li>Keep rotating the mold for an additional 15 min, until the latex on the surface of the mold is solidified.</li>
	<li>Add about 1 g of talcum powder to the surface of the mold (already covered by a thin latex film) to prevent damage while detaching.</li>
	<li>Gently detach with fingers the already dried latex cap from the mold surface; the latex cap is now ready for use (Figure 1B).</li>
	<li>Connect the outlet of the latex cap to 15-cm silicon tubing (ID = 0.2 mm), used later for the collection of CT.</li>
	<li>Fill the ventricular latex balloon with water and firmly fix it onto an L-shaped metal cannula connected to a 1 mL, water-filled syringe (Figure 1C). 
	NOTE: This will be used to ensure the upright positioning of the heart (see below).</li>
	<li>Make sure that the balloon is airtight by performing several deflating/inflating tests with the attached 1 mL syringe.</li>
	<li>Connect the cannula, via a three-way stop, to a pressure transducer for the future measurement of intraventricular developed pressure (Figure 1C).</li>
</ol>
2. Preparation of Krebs-Henseleit Buffer (KHB) and the Langendorff Perfusion System
<ol>
	<li>Set up a Langendorff perfusion system by using either constant-flow (driven by a roller pump) or constant-pressure (generated by static pressure in a glass column) mode. 
	NOTE: Details of the Langendorff heart preparation have been described previously12.</li>
	<li>Prepare 2 L of a modified KHB (in mM: 116.02 NaCl, 4.63 KCl, 1.10 MgSO4&#183;7H2O, 1.21 K2HPO4, 2.52 CaCl2&#183;2H2O, 24.88 NaHCO3, 8.30 D-glucose, and 2.0 sodium pyruvate).
	<ol>
		<li>Weigh all chemicals but CaCl2 and dissolve them in 1.8 L of double-distilled water in a 2-L flask.</li>
		<li>Bubble the medium with carbogen (95% O2/5% CO2) for at least 5 min for equilibration (pH: 7.4) under magnetic stirring.</li>
		<li>Add 0.74 g of CaCl2.2H2O and bring up the total volume to 2 L with double-distilled water.</li>
		<li>Continue stirring and bubbling the medium with carbogen for an additional 5 min.</li>
		<li>Filter the KHB through a 0.2 &#181;m filter to eliminate small particles that may obstruct the microcirculation of the heart.</li>
	</ol>
	</li>
	<li>Preparation of the Langendorff perfusion system.
	<ol>
		<li>Place the filtered KHB into a pre-warmed water bath (38 &#176;C); keep bubbling with carbogen to generate a pressure of 100 cmH2O inside the KHB reservoir.</li>
		<li>Connect the reservoir to the glass column to establish 100 cmH2O hydrostatic pressure for the Langendorff perfusion with KHB; continue bubbling the KHB inside the column with carbogen.</li>
		<li>Adjust the temperature of the warming system so that the temperature at the aortic cannula outlet is 37 &#176;C.</li>
		<li>Ensure that the tubing system is bubble-free.</li>
		<li>Oxygenate the KHB with carbogen for an additional 5 min, until the PO2 in the KHB reaches 500-600 mmHg (measured by a blood-gas analyzer).</li>
	</ol>
	</li>
	<li>Set up the perfusion system to run either at a constant pressure of 100 cmH2O or at a constant flow of about 10-20 mL/min using manual switching. Alternatively, use an interchangeable STH pump controller to instantly switch to the perfusion mode.</li>
</ol>
3. Isolation and Cannulation of the Heart
NOTE: Male Wistar rats with bodyweights of 300-350 g were used so that the sizes of hearts matched the pre-cast latex cap. Rats underwent either a ligation of the left arterial descending (LAD) for 50 min, followed by reperfusion or were sham operated. Details of the methodology for the induction of myocardial infarction (MI) were reported elsewhere13. The reversed-heart experiments in the infarct animals were performed 5 days after operation.
<ol>
	<li>Anesthetize rats using an isoflurane vaporizer (2% V/V) connected to an animal holding chamber (20 L).</li>
	<li>Transfer the rats to an operation table (not temperature controlled) after deep anesthesia is reached.</li>
	<li>Lift the skin and muscle just below the sternum using forceps and cut around the lower margin of the ribs with heavy scissors.</li>
	<li>Using fine scissors, make a small cut into the diaphragm, at the rib margin. Cut the ribs caudally to make a flap of the entire ventral chest wall.</li>
	<li>Gently grab the heart with the thumb and index and middle fingers and slowly lift it upwards so that the cardiac vessels become slightly stretched.</li>
	<li>Excise the heart until the aorta is fully exposed.</li>
	<li>Place the heart in a 100 mL beaker containing 50 mL of ice-cold KHB (4 &#176;C) and move it to the perfusion apparatus.</li>
	<li>Immediately mount the heart via the aorta onto a dripping cannula and securely tighten it with a suture (4-0). Avoid air bubbles entering the heart.</li>
	<li>Apply constant perfusion pressure (100 cmH2O). Alternatively, a full flow rate (starting with 20 mL/min) can be applied. 
	Note: The time from the opening of the thorax to the attachment of the heart to the perfusion cannula should take about 3 min in the hands of an experienced operator.</li>
</ol>
4. Reversed-heart Model
<ol>
	<li>Gently rotate the aortic cannula until the posterior wall of the heart is in en face view.</li>
	<li>Remove the connective tissue with scissors to expose the opening of the left atrium, making it ready for intraventricular cannulation.</li>
	<li>Insert the deflated latex balloon attached to a rigid catheter via the left atrium into the left ventricle.</li>
	<li>Inflate the balloon until it fills the entire ventricular cavity (the inflating volume is pre-marked on the syringe).</li>
	<li>Invert the heart until it is upside-down, supporting it by the intraventricular balloon catheter.</li>
	<li>As demonstrated in Figure 1C, mechanically stabilize the inverted heart in an upright position using the intraventricular balloon with a rigid metal catheter.</li>
	<li>Adjust the position of the heart to avoid excessive twisting of the aortic root.</li>
	<li>Adjust the diastolic pressure to 3-5 mmHg (measured by the intra-ventricular balloon; see Figure 1C).</li>
	<li>Observe the epicardial surface of the heart and ensure that small droplets form.</li>
	<li>Place the latex cap onto the surface of the heart by gently pushing it to cover the entire heart using the fingers.</li>
	<li>Make sure that the latex cap covers most of the ventricular surface.</li>
	<li>Remove the air bubbles, if any, inside the cap and the tubing by gently sucking with a 1-mL syringe.</li>
	<li>Adjust the distal opening of the CT-letting tubing to 10 cm below the horizontal level of the heart. 
	NOTE: This procedure ensures slight sucking by negative hydrostatic pressure.</li>
	<li>Collect drops of CT in a 1.5 mL collection tube placed in ice mixed 1:1 with NaCl. Collect about 0.15-1.5 mL of CT. 
	NOTE: The ice/NaCl mixture stabilizes the temperature in the collection tube to below zero (about -4 &#176;C). 
	NOTE: The sampling time depends on the experimental purpose. The flow rate of the CT is about 27 &#177; 20 &#181;L/ min in sham-operated animals (n = 3) and 100 &#177; 47 &#181;L/min for the coronary-ligated animals (n = 11).</li>
	<li>Weigh and snap-freeze CT samples in liquid nitrogen and store them at -80 &#176;C for later measurements.</li>
</ol>
5. Analysis of the CT
<ol>
	<li>Use the CT fluid for the analysis of metabolites, depending on the scientific question. 
	NOTE: The data shown in Figure 2 and Figure 3 were collected from a constant-pressure perfusion (100 cmH2O), and about 0.15-1.5 mL of CT fluid was collected within a period of 10 min. This time and volume were sufficient for the proteomic (minimum: 50 &#181;L; Figure 2)14 and HPLC (minimum: 20 &#181;L; Figure 3)15 analysis of various purines.</li>
</ol>

<ol>
	<li>Henkel, D. M., Redfield, M. M., Weston, S. A., Gerber, Y., Roger, V. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Death+in+heart+failure:+a+community+perspective.">Death in heart failure: a community perspective.</a> Circ Heart Fail. 1 (2), 91-97 (2008).</li><li>Limana, F., 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=Myocardial+infarction+induces+embryonic+reprogramming+of+epicardial+c-kit(+)+cells:+role+of+the+pericardial+fluid.">Myocardial infarction induces embryonic reprogramming of epicardial c-kit(+) cells: role of the pericardial fluid.</a> J Mol Cell Cardiol. 48 (4), 609-618 (2010).</li><li>Brunner, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+tissue+endothelin-1+levels+under+basal,+stimulated,+and+ischemic+conditions.">Cardiac tissue endothelin-1 levels under basal, stimulated, and ischemic conditions.</a> J Cardiovasc Pharmacol. 26, S44-S46 (1995).</li><li>de Lannoy, L. M., 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=Renin-angiotensin+system+components+in+the+interstitial+fluid+of+the+isolated+perfused+rat+heart.+Local+production+of+angiotensin+I.">Renin-angiotensin system components in the interstitial fluid of the isolated perfused rat heart. Local production of angiotensin I.</a> Hypertension. 29 (6), 1240-1251 (1997).</li><li>Strupp, M., Kammermeier, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interstitial+Lactate+And+Glucose-Concentrations+Of+the+Isolated-Perfused+Rat-Heart+before,+during+And+after+Anoxia.">Interstitial Lactate And Glucose-Concentrations Of the Isolated-Perfused Rat-Heart before, during And after Anoxia.</a> Pflugers Arch. 423 (3-4), 232-237 (1993).</li><li>Wienen, W., Jungling, E., Kammermeier, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzyme-Release+into+the+Interstitial+Space+of+the+Isolated+Rat-Heart+Induced+by+Changes+in+Contractile+Performance.">Enzyme-Release into the Interstitial Space of the Isolated Rat-Heart Induced by Changes in Contractile Performance.</a> Cardiovasc Res. 28 (8), 1292-1298 (1994).</li><li>De Deckere, E. A., Ten Hoor, ., P, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modified+Langendorff+technique+for+metabolic+investigations.">A modified Langendorff technique for metabolic investigations.</a> Pflugers Arch. 370 (1), 103-105 (1977).</li><li>Tschubar, F., Rose, H., Kammermeier, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fatty+acid+transfer+across+the+myocardial+capillary+wall.">Fatty acid transfer across the myocardial capillary wall.</a> J Mol Cell Cardiol. 25 (4), 355-366 (1993).</li><li>Wienen, W., Kammermeier, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intra-+and+extracellular+markers+in+interstitial+transudate+of+perfused+rat+hearts.">Intra- and extracellular markers in interstitial transudate of perfused rat hearts.</a> Am J Physiol. 254 (4 Pt 2), H785-H794 (1988).</li><li>Sasse, A., Ding, Z. P., Wallich, M., Godecke, A., Schrader, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+transfer+of+adenovirus+is+augmented+by+nitric+oxide+in+the+rat+heart.">Vascular transfer of adenovirus is augmented by nitric oxide in the rat heart.</a> Am J Physiol Heart Circ Physiol. 287 (3), H1362-H1368 (2004).</li><li>Gnecchi, M., Zhang, Z., Ni, A., Dzau, V. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paracrine+mechanisms+in+adult+stem+cell+signaling+and+therapy.">Paracrine mechanisms in adult stem cell signaling and therapy.</a> Circ Res. 103 (11), 1204-1219 (2008).</li><li>Herr, D. J., Aune, S. E., Menick, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+and+Assessment+of+Ischemia-reperfusion+Injury+in+Langendorff-perfused+Rat+Hearts.">Induction and Assessment of Ischemia-reperfusion Injury in Langendorff-perfused Rat Hearts.</a> J Vis Exp. (101), e52908 (2015).</li><li>Ding, Z., 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=Epicardium-Derived+Cells+Formed+After+Myocardial+Injury+Display+Phagocytic+Activity+Permitting+In+Vivo+Labeling+and+Tracking.">Epicardium-Derived Cells Formed After Myocardial Injury Display Phagocytic Activity Permitting In Vivo Labeling and Tracking.</a> Stem Cells Transl Med. 5 (5), 639-650 (2016).</li><li>Hartwig, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Secretome+profiling+of+primary+human+skeletal+muscle+cells.">Secretome profiling of primary human skeletal muscle cells.</a> Biochim Biophys Acta. 1844 (5), 1011-1017 (2014).</li><li>Smolenski, R. T., Lachno, D. R., Ledingham, S. J. M., Yacoub, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+sixteen+nucleotides,+nucleosides+and+bases+using+high-performance+liquid+chromatography+and+its+application+to+the+study+of+purine+metabolism+in+hearts+for+transplantation.">Determination of sixteen nucleotides, nucleosides and bases using high-performance liquid chromatography and its application to the study of purine metabolism in hearts for transplantation.</a> J Chromatogr. 527 (2), 414-420 (1990).</li><li>Decking, U. K., Juengling, E., Kammermeier, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interstitial+transudate+concentration+of+adenosine+and+inosine+in+rat+and+guinea+pig+hearts.">Interstitial transudate concentration of adenosine and inosine in rat and guinea pig hearts.</a> Am J Physiol. 254 (6 Pt 2), H1125-H1132 (1988).</li><li>Heller, L. J., Mohrman, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimates+of+interstitial+adenosine+from+surface+exudates+of+isolated+rat+hearts.">Estimates of interstitial adenosine from surface exudates of isolated rat hearts.</a> J Mol Cell Cardiol. 20 (6), 509-523 (1988).</li></ol>

The authors declare that they have no competing financial interests.

The reversed-heart model is based on the well-established Langendorff heart perfusion technique12 and is performed by simply inverting the heart into an upside-down position and holding this position using a rigid intra-ventricular balloon catheter. In such a way, cardiac interstitial transudate can be physically separated from coronary venous effluent perfusate, dripping by gravity from the base of the heart9. The CT can be continuously collected by means of a thin and fle...

Heart failure (HF) is the leading cause of death in humans worldwide1. HF often occurs because of myocarditis, ischemic insults to the myocardium, and left ventricular remodeling, leading to the progressive deterioration of cardiac contractile function and patients&#39; quality of life. Although advances in cardiology and cardiac surgery have remarkably lowered HF mortality, they merely serve as transient &#34;delayers&#34; of an inevitably progressive disease process that carries signi&#64257;cant morbidity. Therefore, the current lack of effective treatment underscores the need to identify novel molecular targets that can prevent or even reverse HF. This includes changes in the extracellular matrix, uncontrolled cardiac immune response, and interactions between cardiac and non-cardiac cells2.
It is important to recognize that the microenvironment that cardiac cells are exposed to directly shapes the immune and regenerative response of the injured heart. In the isolated, saline-perfused heart, CT is generated on the heart surface in the form of small droplets that are derived from the interstitial fluid space (i.e., microenvironment), both under physiological and pathophysiological conditions3,4,5. Therefore, analysis of the CT (i.e., interstitial fluid) may help to identify factors that regulate cardiac metabolism and contractile function6 or influence immune cell functions after migration into the injured heart. Potentially, this may lead to the development of novel therapeutic strategies for the treatment of HF.
The collection of CT from murine hearts is technically challenging. In regular Langendorff-perfused hearts, the exclusive collection of CT is difficult because the mixture of the CT with coronary venous effluent perfusate unpredictably dilutes any concentration of metabolites/enzymes released from the interstitial space. One possible strategy to overcome this limitation is to exclude the venous effluent by cannulating the pulmonary and simultaneously ligating the pulmonary vein7. However, this method faces difficulties associated with the cannulation and ligation of the pulmonary artery and vein, causing potential leakage of venous effluent into the cardiac transudate. The concept of using a reverse heart model was first introduced by the group of Kammermeier, who inverted the isolated, perfused heart into an upside-down position and placed a thin latex cap on the epicardial surface to continuously sample CT without the contamination of venous effluent8,9. Using this procedure, CT was shown to provide a very sensitive measure of the metabolites released from the heart9, the capillary transfer of fatty acids8, and viral particles10.
More recently, paracrine factors that may regulate the local immune response and augment cardiac angiogenesis11 have been implicated in the beneficial effects of stem cell-based therapy for heart disease. The analysis of CT in the reversed heart may help to chemically identify these individual paracrine factors. In addition, CT may help to identify the factors involved in the in vivo activation of immune cells in the heart.
The detailed description of CT collection from the heart surface, provided here, is experimentally useful for researchers studying the interplay of immune cells, fibroblasts, endothelial cells, and cardiomyocytes in relation to overall cardiac function. As mentioned above, the interstitial fluid carries the information for cell-to-cell communication within the heart, which can conveniently be assessed by the collection of CT. The detailed technical description, including a video protocol of how to collect CT from the reversed heart, should facilitate the future application of this unique technique.

<table border="0" cellpadding="0" cellspacing="0" width="815">
	<tbody>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Latex Solution</td>
			<td style="width:129px;">ProChemie</td>
			<td style="width:184px;">Z-Latex LA-TZ</td>
			<td style="width:201px;">&#160;http://kautschukgesellschaft.de/%E2%80%A8z-latexla-tz%E2%80%A8</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Aluminum Mold</td>
			<td style="width:129px;">Home made</td>
			<td style="width:184px;">-</td>
			<td>Reverse heart model</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Universal Ovens</td>
			<td style="width:129px;">Memmert</td>
			<td style="width:184px;">UNB 400</td>
			<td>Reverse heart model</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Latex Balloon</td>
			<td style="width:129px;">Hugo Sachs</td>
			<td style="width:184px;">Size 4</td>
			<td>Reverse heart model</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Milling Machine</td>
			<td style="width:129px;">Proxxon</td>
			<td style="width:184px;">MF70</td>
			<td>Reverse heart model</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Sodium Chloride</td>
			<td style="width:129px;">Sigma</td>
			<td style="width:184px;">SZBD0810V</td>
			<td>Chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Sodium Hydrogen Carbonate</td>
			<td style="width:129px;">Roth</td>
			<td style="width:184px;">68852</td>
			<td>Chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Potassium Chloride</td>
			<td style="width:129px;">Merck</td>
			<td style="width:184px;">49361</td>
			<td>Chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Magnesium Sulphate Heptahydrate</td>
			<td style="width:129px;">Merck</td>
			<td style="width:184px;">58861</td>
			<td>Chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Potassium Dihydrogen Phosphate</td>
			<td style="width:129px;">Merck</td>
			<td style="width:184px;">48731</td>
			<td>Chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">D(+)-Glucose Anhydrous</td>
			<td style="width:129px;">Merck</td>
			<td style="width:184px;">83371</td>
			<td>Chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Calcium Chloride Dihydrate</td>
			<td style="width:129px;">Fluka</td>
			<td style="width:184px;">21097</td>
			<td>Chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Balance</td>
			<td style="width:129px;">VWR</td>
			<td>SE 1202&#160;</td>
			<td>Weighing chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Double Distilled Water</td>
			<td style="width:129px;">Millpore</td>
			<td style="width:184px;">-</td>
			<td>Disolving chemicals</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Medical Pressure Transducer</td>
			<td style="width:129px;">Gold</td>
			<td style="width:184px;">-</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Medical Flow Probe</td>
			<td style="width:129px;">Transonic</td>
			<td style="width:184px;">3PXN</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Heating Circulating Bath</td>
			<td style="width:129px;">Haake&#160;</td>
			<td style="width:184px;">B3 ; DC1</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Laboratory and Vaccum Tubing</td>
			<td style="width:129px;">Tygon</td>
			<td style="width:184px;">R-3603</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Animal Research Flowmeters</td>
			<td style="width:129px;">Transonic</td>
			<td style="width:184px;">T206</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">PowerLab Data Acquisition Device</td>
			<td style="width:129px;">AD Instruments</td>
			<td style="width:184px;">Chart 7.1</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">LabChart Data Acquisition Software</td>
			<td style="width:129px;">AD Instruments</td>
			<td style="width:184px;">Chart 7.1</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Peristaltic Pump</td>
			<td style="width:129px;">Glison</td>
			<td style="width:184px;">MINIPULS 3</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Glass Water Column</td>
			<td style="width:129px;">home made</td>
			<td style="width:184px;">-</td>
			<td>Langendorff apparatus</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Water Bath Protective Agent</td>
			<td style="width:129px;">VWR</td>
			<td style="width:184px;">462-7000</td>
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			<td height="53" style="height:53px;width:301px;">Sterile Disposable&#160; Filters (0.2&#181;m)</td>
			<td style="width:129px;">Thermo Scientific</td>
			<td style="width:184px;">595-4520</td>
			<td>Langendorff apparatus</td>
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			<td height="32" style="height:32px;width:301px;">Blood gas analyzers</td>
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			<td style="width:184px;">ABL90 FLEX PLUS</td>
			<td>Gas analyzer</td>
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		<tr height="32">
			<td height="32" style="height:32px;width:301px;">70% ethanol</td>
			<td style="width:129px;">VWR</td>
			<td style="width:184px;">UN1170</td>
			<td>Cleaning&#160; tubings</td>
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		<tr height="32">
			<td height="32" style="height:32px;width:301px;">100% ethanol</td>
			<td style="width:129px;">Merck</td>
			<td style="width:184px;">64-17-5</td>
			<td>Cleaning tubings</td>
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		<tr height="32">
			<td height="32" style="height:32px;">Wistar Rats</td>
			<td style="width:129px;">Janvier</td>
			<td style="width:184px;">-</td>
			<td>Animals</td>
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		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Stainless Scissors</td>
			<td style="width:129px;">AESCULAP</td>
			<td style="width:184px;">BC702R</td>
			<td>Surgical Instruments</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Stainless Scissors</td>
			<td style="width:129px;">AESCULAP</td>
			<td style="width:184px;">BC257R</td>
			<td>Surgical Instruments</td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:301px;">Big Forceps&#160;</td>
			<td style="width:129px;">AESCULAP</td>
			<td style="width:184px;">-</td>
			<td>Surgical Instruments</td>
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		<tr height="32">
			<td height="32" style="height:32px;width:301px;">8m/m Stainless Forceps</td>
			<td style="width:129px;">F.S.T</td>
			<td style="width:184px;">11052-10</td>
			<td>Surgical Instruments</td>
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		<tr height="32">
			<td height="32" style="height:32px;width:301px;">superfine (10/0) emery paper</td>
			<td style="width:129px;">3M</td>
			<td style="width:184px;">051111-11694</td>
			<td>Reverse heart model</td>
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the inverted heart model for interstitial transudate collection from the isolated rat heart

The present protocol describes a unique approach that enables the collection of cardiac transudate (CT) from the isolated, saline-perfused rat heart. After isolation and retrograde perfusion of the heart according to the Langendorff technique, the heart is inverted into an upside-down position and is mechanically stabilized by a balloon catheter inserted into the left ventricle. Then, a thin latex cap &#8211; previously cast to match the average size of the rat heart &#8211; is placed over the epicardial surface. The outlet of the latex cap is connected to silicon tubing, with the distal opening 10 cm below the base level of the heart, creating slight suction. CT continuously produced on the epicardial surface is collected in ice-cooled vials for further analysis. The rate of CT formation ranged from 17 to 147 &#181;L/min (n = 14) in control and infarcted hearts, which represents 0.1-1% of the coronary venous effluent perfusate. Proteomic analysis and high performance liquid chromatography (HPLC) revealed that the collected CT contains a wide spectrum of proteins and purinergic metabolites.

The reversed-heart model enables the collection of cardiac interstitial transudate in an isolated, retro-perfused rat heart (Figure 1A-C). When perfused at a constant pressure of 100 cmH2O, the rate of interstitial fluid formation ranged between 17 and 147 &#181;L/min, amounting to 0.1-1% of the coronary venous effluent in the isolated heart.
The protein content of the CT...

Watch this Scientific Journal Video about The Inverted Heart Model for Interstitial Transudate Collection from the Isolated Rat Heart at JoVE.com

The Inverted Heart Model for Interstitial Transudate Collection from the Isolated Rat Heart

This protocol describes a method to collect cardiac interstitial fluid from the isolated, perfused rat heart. To physically separate interstitial transudate from coronary venous effluent perfusate, the Langendorff perfused heart is inverted, and the transudate (interstitial fluid) formed on the cardiac surface is collected using a soft latex cap.

The present protocol describes a unique approach that enables the collection of cardiac transudate (CT) from the isolated, saline-perfused rat heart. ...

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8.3K Views.  Second Military Medical University. This protocol describes a method to collect cardiac interstitial fluid from the isolated, perfused rat heart. To physically separate interstitial transudate from coronary venous effluent perfusate, the Langendorff perfused heart is inverted, and the transudate (interstitial fluid) formed on the cardiac surface is collected using a soft latex cap. 

Video: The Inverted Heart Model for Interstitial Transudate Collection from the Isolated Rat Heart

Orthotopic Aortic Transplantation: A Rat Model to Study the Development of Chronic Vasculopathy

Research models of chronic rejection are essential to investigate pathobiological and pathophysiological processes during the development of transplant vasculopathy (TVP).
The commonly used animal model for cardiovascular chronic rejection studies is the heterotopic heart transplant model performed in laboratory rodents. This model is used widely in experiments since Ono and Lindsey (3) published their technique. To analyze the findings in the blood vessels, the heart has to be sectioned and all vessels have to be measured.
Another method to investigate chronic rejection in cardiovascular questionings is the aortic transplant model (1, 2). In the orthotopic aortic transplant model, the aorta can easily be histologically evaluated (2). The PVG-to-ACI model is especially useful for CAV studies, since acute vascular rejection is not a major confounding factor and Cyclosporin A (CsA) treatment does not prevent the development of CAV, similar to what we find in the clinical setting (4). A7-day period of CsA is required in this model to prevent acute rejection and to achieve long-term survival with the development of TVP.
This model can also be used to investigate acute cellular rejection and media necrosis in xenogeneic models (5).

This video demonstrates the orthotopic aortic transplant model as a simple model to study the development of transplant vasculopathy (TVP) in rats.

Research models of chronic rejection are essential to investigate pathobiological and pathophysiological processes during the development of transplant ...

Magnetic Resonance Derived Myocardial Strain Assessment Using Feature Tracking

Purpose: An accurate and practical method to measure parameters like strain in myocardial tissue is of great clinical value, since it has been shown, that strain is a more sensitive and earlier marker for contractile dysfunction than the frequently used parameter EF. Current technologies for CMR are time consuming and difficult to implement in clinical practice. Feature tracking is a technology that can lead to more automization and robustness of quantitative analysis of medical images with less time consumption than comparable methods.
Methods: An automatic or manual input in a single phase serves as an initialization from which the system starts to track the displacement of individual patterns representing anatomical structures over time. The specialty of this method is that the images do not need to be manipulated in any way beforehand like e.g. tagging of CMR images.
Results: The method is very well suited for tracking muscular tissue and with this allowing quantitative elaboration of myocardium and also blood flow.
Conclusions: This new method offers a robust and time saving procedure to quantify myocardial tissue and blood with displacement, velocity and deformation parameters on regular sequences of CMR imaging. It therefore can be implemented in clinical practice.

An accurate and practical method to measure parameters like strain in myocardial tissue is of great clinical value, since it has been shown, that strain is a more sensitive and earlier marker for contractile dysfunction than the frequently used parameter EF.

Purpose: An accurate and practical method to measure parameters like strain in myocardial tissue is of great clinical value, since it has been shown, that ...

A Murine Model of Myocardial Ischemia-reperfusion Injury through Ligation of the Left Anterior Descending Artery

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms at work during MI and developing effective therapeutic approaches requires methodology to reproducibly simulate the clinical incidence and reflect the pathophysiological changes associated with MI. Here, we describe a surgical method to induce MI in mouse models that can be used for short-term ischemia-reperfusion (I/R) injury as well as permanent ligation. The major advantage of this method is to facilitate location of the left anterior descending artery (LAD) to allow for accurate ligation of this artery to induce ischemia in the left ventricle of the mouse heart. Accurate positioning of the ligature on the LAD increases reproducibility of infarct size and thus produces more reliable results. Greater precision in placement of the ligature will improve the standard surgical approaches to simulate MI in mice, thus reducing the number of experimental animals necessary for statistically relevant studies and improving our understanding of the mechanisms producing cardiac dysfunction following MI. This mouse model of MI is also useful for the preclinical testing of treatments targeting myocardial damage following MI.

We introduce a surgical method to induce experimental ischemia/reperfusion (I/R) injury to simulate myocardial infarction (MI) in mouse models that allows for more clarity in positioning of the ligation on the left anterior descending artery (LAD) to increase the reproducibility of MI experiments in mice.

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms ...

Implantation of Total Artificial Heart in Congenital Heart Disease

In patients with end-stage heart failure (HF), a total artificial heart (TAH) may be implanted as a bridge to cardiac transplant. However, in congenital heart disease (CHD), the malformed heart presents a challenge to TAH implantation. 
In the case presented here, a 17 year-old patient with congenital transposition of the great arteries (CCTGA) experienced progressively worsening HF due to his congenital condition. He was hospitalized multiple times and received an implantable cardioverter defibrillator (ICD). However, his condition soon deteriorated to end-stage HF with multisystem organ failure. 
Due to the patient's grave clinical condition and the presence of complex cardiac lesions, the decision was made to proceed with a TAH. The abnormal arrangement of the patient's ventricles and great arteries required modifications to the TAH during implantation.
With the TAH in place, the patient was able to return home and regain strength and physical well-being while awaiting a donor heart. He was successfully bridged to heart transplantation 5 months after receiving the device. This report highlights the TAH is feasible even in patients with structurally abnormal hearts, with technical modification.

This is a case report of a patient with congenitally corrected transposition of the great arteries (CCTGA) who received a total artificial heart (TAH) as a bridge to heart transplant. The TAH was successfully implanted with modifications to accommodate the patient's congenitally malformed heart.

In patients with end-stage heart failure (HF), a total artificial heart (TAH) may be implanted as a bridge to cardiac transplant. However, in congenital ...

An Isolated Working Heart System for Large Animal Models

Since its introduction in the late 19th century, the Langendorff isolated heart perfusion apparatus, and the subsequent development of the working heart model, have been invaluable tools for studying cardiovascular function and disease1-15. Although the Langendorff heart preparation can be used for any mammalian heart, most studies involving this apparatus use small animal models (e.g., mouse, rat, and rabbit) due to the increased complexity of systems for larger mammals1,3,11. One major difficulty is ensuring a constant coronary perfusion pressure over a range of different heart sizes &#8211; a key component of any experiment utilizing this device1,11. By replacing the classic hydrostatic afterload column with a centrifugal pump, the Langendorff working heart apparatus described below allows for easy adjustment and tight regulation of perfusion pressures, meaning the same set-up can be used for various species or heart sizes. Furthermore, this configuration can also seamlessly switch between constant pressure or constant flow during reperfusion, depending on the user&#8217;s preferences. The open nature of this setup, despite making temperature regulation more difficult than other designs, allows for easy collection of effluent and ventricular pressure-volume data.

Most studies involving the Langendorff apparatus use small animal models due to the increased complexity of systems for larger mammals. We describe a Langendorff system for large animal models that allows for use across a range of species, including humans, and relatively easy data acquisition.

Since its introduction in the late 19th century, the Langendorff isolated heart perfusion apparatus, and the subsequent development of the working heart ...

Method of Isolated Ex Vivo Lung Perfusion in a Rat Model: Lessons Learned from Developing a Rat EVLP Program

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. As this technology expands and improves, the ability to potentially evaluate and improve the quality of substandard lungs prior to transplant is a critical need. In order to more rigorously evaluate these approaches, a reproducible animal model needs to be established that would allow for testing of improved techniques and management of the donated lungs as well as to the lung-transplant recipient. In addition, an EVLP animal model of associated pathologies, e.g., ventilation induced lung injury (VILI), would provide a novel method to evaluate treatments for these pathologies. Here, we describe the development of a rat EVLP lung program and refinements to this method that allow for a reproducible model for future expansion. We also describe the application of this EVLP system to model VILI in rat lungs. The goal is to provide the research community with key information and &#8220;pearls of wisdom&#8221;/techniques that arose from trial and error and are critical to establishing an EVLP system that is robust and reproducible.

Method of Isolated Ex Vivo Lung Perfusion in a Rat Model: Lessons Learned from Developing a Rat EVLP Program

Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. Here, we describe the development of a rat EVLP program and refinements that allow for a reproducible model for future expansion.

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed ...

Murine Isolated Heart Model of Myocardial Stunning Associated with Cardioplegic Arrest

The following protocol is of use to evaluate impaired cardiac function or myocardial stunning following moderate ischemic insults. The technique is useful for modeling ischemic injury associated with numerous clinically relevant phenomenon including cardiac surgery with cardioplegic arrest and cardiopulmonary bypass, off-pump CABG, transplant, angina, brief ischemia, etc. The protocol presents a general method to model hypothermic hyperkalemic cardioplegic arrest and reperfusion in rodent hearts focusing on measurement of myocardial contractile function. In brief, a mouse heart is perfused in langendorff mode, instrumented with an intraventricular balloon, and baseline cardiac functional parameters are recorded. Following stabilization, the heart is then subject to brief infusion of a cardioprotective hypothermic cardioplegia solution to initiate diastolic arrest. Cardioplegia is delivered intermittently over 2 hr. The heart is then reperfused and warmed to normothermic temperatures and recovery of myocardial function is monitored. Use of this protocol results in reliable depressed cardiac contractile function free from gross myocardial tissue damage in rodents.

The goal of this protocol to assess myocardial stunning following ischemic cardioplegic arrest in rodents.

The following protocol is of use to evaluate impaired cardiac function or myocardial stunning following moderate ischemic insults. The technique is useful ...

Repeated Blood Collection from Tail Vein of Non-Anesthetized Rats with a Vacuum Blood Collection System

Blood can be collected from rats in a number of sampling locations. For instance, the tail vein is a superior location for blood sampling. However, the tail vein is thin so that it is sometimes hard to puncture. In addition, the tail vein has low blood flow and requires a long sampling time to get sufficient blood. The present report describes a simple blood sampling method, the vacuum blood collection method, which is usually used to obtain blood samples from patients, here used for non-anesthetized rats. The 22 G butterfly needle tip was inserted into one of the lateral tail veins approximately 2-3 cm from the tip of the tail at an angle of approximately 20&#176;, and blood was collected in the vacuum collection tube by inserting the rubber end of the butterfly needle into the vacuum blood collection tube. The present experimental results show that the success rate was 95% in the experimental group and 90% in the beginner group. The success rate and puncture times were similar between two groups. The sampling duration was significantly shorter in the experimental group compared to beginner group. In conclusion, this vacuum blood collection method for sequential blood sampling from the tail vein of non- anesthetized rats is feasible and easy-to-learn, which might serve as a reliable alternative to other conventionally used blood sampling techniques for rats.

Here, we describe a simple tail vein blood sampling method in non-anesthetized rats using a vacuum extraction tube system. This method reduces the risk of direct exposure to blood and simplifies taking multiple samples from a single venipuncture.

Blood can be collected from rats in a number of sampling locations. For instance, the tail vein is a superior location for blood sampling. However, the ...

A Cryoinjury Model to Study Myocardial Infarction in the Mouse

The use of animal models is essential for developing new therapeutic strategies for acute coronary syndrome and its complications. In this article, we demonstrate a murine cryoinjury infarct model that generates precise infarct sizes with high reproducibility and replicability. In brief, after intubation and sternotomy of the animal, the heart is lifted from the thorax. The probe of a handheld liquid nitrogen delivery system is applied onto the myocardial wall to induce cryoinjury. Impaired ventricular function and electrical conduction can be monitored with echocardiography or optical mapping. Transmural myocardial remodeling of the infarcted area is characterized by collagen deposition and loss of cardiomyocytes. Compared to other models (e.g., LAD-ligation), this model utilizes a handheld liquid nitrogen delivery system to generate more uniform infarct sizes.

This article demonstrates a model to study cardiac remodeling after myocardial cryoinjury in mice.

The use of animal models is essential for developing new therapeutic strategies for acute coronary syndrome and its complications. In this article, we ...

An Image Guided Transapical Mitral Valve Leaflet Puncture Model of Controlled Volume Overload from Mitral Regurgitation in the Rat

Mitral regurgitation (MR) is a widely prevalent heart valve lesion, which causes cardiac remodeling and leads to congestive heart failure. Though the risks of uncorrected MR and its poor prognosis are known, the longitudinal changes in cardiac function, structure and remodeling are incompletely understood. This knowledge gap has limited our understanding of the optimal timing for MR correction, and the benefit that early versus late MR correction may have on the left ventricle. To investigate the molecular mechanisms that underlie left ventricular remodeling in the setting of MR, animal models are necessary. Traditionally, the aorto-caval fistula model has been used to induce volume overload, which differs from clinically relevant lesions such as MR. MR represents a low-pressure volume overload hemodynamic stressor, which requires animal models that mimic this condition. Herein, we describe a rodent model of severe MR in which the anterior leaflet of the rat mitral valve is perforated with a 23G needle, in a beating heart, with echocardiographic image guidance. The severity of MR is assessed and confirmed with echocardiography, and the reproducibility of the model is reported.&#160;&#160;

A rodent model of left heart volume overload from mitral regurgitation is reported. Mitral regurgitation of controlled severity is induced by advancing a needle of defined dimensions into the anterior leaflet of the mitral valve, in a beating heart, with ultrasound guidance.&#160;

Mitral regurgitation (MR) is a widely prevalent heart valve lesion, which causes cardiac remodeling and leads to congestive heart failure. Though the ...