The authors gratefully acknowledge Dr. Matthew Kay for helpful experimental guidance, and Manelle Ramadan and Muhaymin Chowdhury for technical assistance. This work was supported by the National Institutes of Health (R01HL139472 to NGP, R01 HL139712 to NI), Children&#8217;s Research Institute, Children&#8217;s National Heart Institute and Sheikh Zayed Institute for Pediatric Surgical Innovation.

The authors have nothing to disclose.

Although cardiovascular research models range from cellular to in vivo preparations, there is an inherent trade-off between clinical relevance and experimental utility. On this spectrum, the isolated Langendorff-perfused heart remains a useful compromise for studying cardiac physiology48. The whole heart model represents a higher level of functional and structural integration than single cell or tissue monolayers, but also avoids the confounding complexities associated with in vivo models. A major advantage during dual optical mapping experiments is that the epicardial surface of the isolated heart can be observed, and fluorescence imaging of transmembrane potential and calcium handling can be used to monitor cardiac physiology34.
Rodent models are most commonly used for isolated heart preparations as opposed to larger animals, due in part to the associated cost of up-sizing all the elements involved (e.g., solution volume, perfusion circuit, quantity of dyes and mechanical uncouplers) along with greater instability and propensity for arrhythmias in larger animals10,36,49. One advantage to using pig hearts is that they closely resemble the human heart in structure, size and rate of contraction, therefore more accurately modeling hemodynamic parameters like coronary blood flow and cardiac output. Likewise, humans and pigs have similar calcium handling, electrocardiogram intervals37, and action potential morphology including the underlying channels that it represents12,50,51,52. This protocol describes in detail the steps for creating a reproducible large animal model to comprehensively characterize myocardial function. Simultaneous imaging of transmembrane voltage (RH237) and intracellular calcium (Rhod2), used in conjunction with established electrophysiological protocols, provides the opportunity to pinpoint mechanisms that are responsible for altered cardiac function. The described methodology can be used for preclinical safety testing, toxicological screening and the investigation of genetic or other disease pathologies. Moreover, the described methodology can be modified and adapted for use with other cardiac models (e.g., canine, human) depending on the specific research focus53,54,55.
There are a few critical modifications to keep in mind when transitioning from a smaller rodent model to a larger pig model for isolated, whole heart preparations. During preparation and setup, we recommend adding albumin to the perfusate to maintain oncotic pressure and reduce edema (plus antifoam, if needed)56,57,58,59. Moreover, perfusate containing albumin can also aid in metabolic studies that also require fatty acid-supplementation to the media60,61. Unlike rodent hearts, the larger pig heart does not need to be submerged in warm media due to its smaller surface to volume ratio and the increased volume of warmed media flowing through the coronary vessels which better maintains the temperature. As noted earlier, we placed temperature probes inside the right ventricle and on the epicardial surface of both the right and left ventricles, observing only slight temperature fluctuations of 1&#8722;2 &#176;C in all three locations throughout the study. Importantly, such faster flow rates can also increase the likelihood of bubbles and a potential embolism. To circumvent this problem, we recommend using a bubble trap with large bore tubing leading straight down to the aortic cannula. Similarly, we found it most useful to have two individuals working in tandem to cannulate the aorta on a larger (and heavier) heart; one person to hold the aorta open with sturdy hemostats and another to secure the aorta to the canula using umbilical tape. In the described methodology, we found that perfusion with cardioplegia and defibrillation were vital to cardiac recovery, which is contrary to rodent heart preparations. In our experience, only a few excised hearts resumed normal sinus-driven activity without cardioversion.
To improve optical imaging endpoints, a hanging heart preparation limited the effect of glare that can occur with a submerged heart. Moreover, the hanging heart also avoids any compression or compromise of the coronary vessels on the posterior aspect of the heart that can occur when laying the heart down horizontally for vertical imaging. We also found that loading fluorescent dyes after the bubble trap (close to the aortic cannula) greatly improved tissue staining and optical signals. Finally, to improve cardiac electrophysiology endpoints, the use of a larger coaxial stimulation electrode facilitated successful atrial pacing. Although we describe the use of electrocardiograms to identify capture and loss of capture for various EP parameters, intracardiac catheters or bipolar recording electrodes can also be used.
Our study was focused on developing a methodology for dual optical mapping and cardiac electrophysiological assessment in an isolated, intact porcine heart model. Due to similarities with the juvenile human heart, the porcine heart remains a popular model for studies focused on pediatric cardiology or congenital heart defects. Importantly, the described approach can be adapted to use with larger sized adult hearts and/or different species of interest. Indeed, other laboratories may find that the use of canine or human hearts (either donor or diseased) are more applicable for their specific research focus53,54,55. Another potential limitation to this study is the use of a mechanical uncoupler to reduce motion artifact during imaging. Blebbistatin has become the uncoupler of choice in cardiac imaging applications due to its minimal effects on ECG parameters, activation and refractory periods41,62,63. BDM is a less expensive choice, which can be particularly important in large animal studies that require greater volumes of perfusate and mechanical uncoupler, but it is known to have a greater impact on potassium and calcium currents that can alter action potential morphology64,65,66,67. If BDM is used, note that APD shortening increases the hearts vulnerability to shock-induced arrythmias68. Conversely, the main limitation to using blebbistatin is its photosensitivity and phototoxicity, although alternative formulations that have reduced these effects69,70,71. Finally, the described methodology utilizes a single camera system for dual optical mapping experimentation, but it is important to note that research studies focused on ventricular fibrillation and/or tracking of electrical waves across the epicardial surface would need to modify this approach to include three-dimensional panoramic imaging, as described by others15,19,72,73,74,75.

Cardiovascular disease is a leading cause of illness and death worldwide. As such, a primary research focus is to optimize methodologies that can be used to study normal cardiac physiology and underlying mechanisms that can contribute to morbidity and mortality in humans. Basic cardiovascular research has traditionally relied on small animal models, including rodents and rabbits1,2,3, due to the availability of genetically modified species4,5, lower-cost, smaller experimental footprint, and higher throughput. However, the use of a pig model has the potential to provide more clinically relevant data6. Indeed, previous studies have documented similarities in cardiac electrophysiology (EP) between humans and pigs, including similar ion currents7, action potential shape8, and responses to pharmacological testing9. Moreover, the porcine heart has contractile and relaxation kinetics that are more comparable to humans than either rodents or rabbits10. Compared to a canine model, the porcine coronary anatomy more closely resembles a human heart11,12 and is the model of choice for studies focused on heart development, pediatric cardiology and/or congenital heart defects13. Although there are differences between the pig and human heart8, these similarities make the porcine heart a valuable model for cardiovascular research14.
Retrograde perfusion of the heart has become a standard protocol for studying cardiac dynamics ex vivo15 since first established by Oskar Langendorff16. Accordingly, Langendorff-perfusion can be used to support an isolated, intact heart in the absence of autonomic influences. This model is a useful tool for directly comparing cardiac electrophysiology and contractility between healthy and non-healthy hearts. Since cardiac dynamics are both temporally and spatially complex, a slight alteration in one region can dramatically affect the entire heart&#8217;s ability to work as a syncytium17. Therefore, high spatiotemporal imaging of parameter sensitive dyes is a useful tool for monitoring cardiac function across the surface of the heart18,19. Indeed, simultaneous dual imaging of voltage and calcium-sensitive fluorescent probes allows for the assessment of electrical activity, calcium handling and excitation-contraction coupling at the tissue level20,21,22,23,24,25,26,27,28. Langendorff-perfusion and/or optical mapping techniques have previously been used to document the decline in cardiac performance due to aging or genetic mutations, and to assess the safety of pharmacological agents or environmental exposures29,30,31,32,33.
In the clinical setting, an invasive cardiac electrophysiology study is often used to investigate cardiac rhythm disturbances, identify pathologies, and pinpoint possible treatment options. Similarly, we describe an EP protocol that can be used to assess sinus node function, measure atrioventricular conduction, and identify the refractoriness of myocardial tissue. The described EP study can be performed in conjunction with optical mapping, or optocardiography34, to fully characterize cardiac physiology in isolated hearts. In the described protocol, high spatiotemporal resolution fluorescence imaging was performed with a combination of voltage (RH237) and calcium (Rhod-2AM) dyes in a dual emission setup. Additionally, cardiac electrophysiology parameters were monitored under both sinus rhythm and in response to programmed electrical stimulation.

<table>
	<tbody>
		<tr>
			<td>(-)-Blebbistatin</td>
			<td>Sigma-Aldrich</td>
			<td>B0560-5MG</td>
			<td>Mechanical Uncoupler</td>
		</tr>
		<tr>
			<td>2,3-Butanedione monoxime (BDM)</td>
			<td>Sigma-Aldrich</td>
			<td>B0753-100G</td>
			<td>Mechanical Uncoupler</td>
		</tr>
		<tr>
			<td>Albumin</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>A9418</td>
			<td></td>
		</tr>
		<tr>
			<td>Analog signal interface</td>
			<td>emka Technologies</td>
			<td>itf16USB</td>
			<td></td>
		</tr>
		<tr>
			<td>Antifoam</td>
			<td>Sigma-Aldrich</td>
			<td>A5758-250ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Antifoam Y-30 Emulsion</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>A5758</td>
			<td></td>
		</tr>
		<tr>
			<td>Aortic cannula, 5/16&#8221;</td>
			<td>Cole-Parmer</td>
			<td>45509-60</td>
			<td></td>
		</tr>
		<tr>
			<td>Bubble trap</td>
			<td>Sigma-Aldrich</td>
			<td>CLS430641U-100EA</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Fisher Scientific, Fair Lawn, NJ</td>
			<td>C77-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Camera, sCMOS</td>
			<td>Andor Technology</td>
			<td>Zyla 4.2 PLUS</td>
			<td></td>
		</tr>
		<tr>
			<td>Coaxial stimulation electrode (atria)</td>
			<td>Harvard Apparatus</td>
			<td>73-0219</td>
			<td></td>
		</tr>
		<tr>
			<td>Defibrillator</td>
			<td>Zoll</td>
			<td>M Series</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichroic mirror</td>
			<td>Chroma Technology</td>
			<td>T660lpxrxt-UF2</td>
			<td></td>
		</tr>
		<tr>
			<td>Differential amplifier</td>
			<td>Warner Instruments</td>
			<td>DP-304A</td>
			<td></td>
		</tr>
		<tr>
			<td>Emission filter, calcium</td>
			<td>Chroma Technology</td>
			<td>ET585/40m</td>
			<td></td>
		</tr>
		<tr>
			<td>Emission filter, voltage</td>
			<td>Chroma Technology</td>
			<td>ET710lp</td>
			<td></td>
		</tr>
		<tr>
			<td>EP stimulator (Bloom)</td>
			<td>Fisher Medical</td>
			<td>DTU-215B</td>
			<td></td>
		</tr>
		<tr>
			<td>Excitation filter</td>
			<td>Chroma Technology</td>
			<td>CT510/60bp</td>
			<td></td>
		</tr>
		<tr>
			<td>Excitation lights</td>
			<td>Thorlabs</td>
			<td>SOLIS-525C</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter</td>
			<td>McMaster-Carr</td>
			<td>8147K52</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter cartridge, polypropylene</td>
			<td>Pentair</td>
			<td>PD-5-934</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter housing</td>
			<td>McMaster-Carr</td>
			<td>9979T21</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow transducer</td>
			<td>Transonic</td>
			<td>ME6PXN</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>158968</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating coil</td>
			<td>Radnoti</td>
			<td>158821</td>
			<td></td>
		</tr>
		<tr>
			<td>Hemofilter</td>
			<td>Hemocor</td>
			<td>HPH 400</td>
			<td></td>
		</tr>
		<tr>
			<td>Hemostatic Forceps</td>
			<td>World Precision Instruments</td>
			<td>501326</td>
			<td></td>
		</tr>
		<tr>
			<td>Image Splitter</td>
			<td>Cairn Research</td>
			<td>OptoSplit II</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>P3911</td>
			<td></td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Fisher Scientific, Fair Lawn, NJ</td>
			<td>423-316</td>
			<td></td>
		</tr>
		<tr>
			<td>Large-bore tubing, I.D. 3/8&#8221;</td>
			<td>Fisher Scientific</td>
			<td>14-169-7H</td>
			<td></td>
		</tr>
		<tr>
			<td>Lens 50 mm, 0.95 f-stop</td>
			<td>Navitar</td>
			<td>DO-5095</td>
			<td></td>
		</tr>
		<tr>
			<td>Metamorph</td>
			<td>Molecular Devices</td>
			<td></td>
			<td>Image Alignment</td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>M-7506</td>
			<td></td>
		</tr>
		<tr>
			<td>Mucasol detergent</td>
			<td>Sigma-Aldrich</td>
			<td>Z637181-2L</td>
			<td></td>
		</tr>
		<tr>
			<td>Na Pyruvate</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>P2256</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>S-3014</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Fisher Scientific, Fair Lawn, NJ</td>
			<td>S-233</td>
			<td></td>
		</tr>
		<tr>
			<td>Needle Electrodes 29 gauge, 2 mm</td>
			<td>AD Instruments Inc.</td>
			<td>MLA1204</td>
			<td></td>
		</tr>
		<tr>
			<td>Noise eliminator</td>
			<td>Quest Scientific</td>
			<td>Humbug</td>
			<td></td>
		</tr>
		<tr>
			<td>Perfusion pump</td>
			<td>PolyStan</td>
			<td>A/S 1481</td>
			<td></td>
		</tr>
		<tr>
			<td>Pressure transducer</td>
			<td>World Precision Instruments</td>
			<td>BLPR2</td>
			<td></td>
		</tr>
		<tr>
			<td>Reservoir, 2 liter</td>
			<td>Cole-Parmer</td>
			<td>UX-34541-07</td>
			<td></td>
		</tr>
		<tr>
			<td>RH237</td>
			<td>AAT Bioquest Inc.</td>
			<td>21480</td>
			<td></td>
		</tr>
		<tr>
			<td>Rhod2-AM</td>
			<td>AAT Bioquest Inc.</td>
			<td>21062</td>
			<td></td>
		</tr>
		<tr>
			<td>Stimulation electrode (ventricle)</td>
			<td>Harvard Apparatus</td>
			<td>73-0160</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical Suture</td>
			<td>McKesson Medical-Surgical</td>
			<td>890186</td>
			<td></td>
		</tr>
		<tr>
			<td>Transducer amplifier</td>
			<td>World Precision Instruments</td>
			<td>TBM4M</td>
			<td></td>
		</tr>
		<tr>
			<td>Tubing flow console</td>
			<td>Transonic</td>
			<td>TS410</td>
			<td></td>
		</tr>
		<tr>
			<td>Umbilical tape</td>
			<td>Jorvet</td>
			<td>J0025UA</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath/circulator</td>
			<td>VWR</td>
			<td>89400-970</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical Tools</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bandage shears</td>
			<td>Harvard Apparatus</td>
			<td>72-8448</td>
			<td>Lister Bandage Scissors, Angled, Blunt/Blunt, 42.0mm blade length, 17.0 cm</td>
		</tr>
		<tr>
			<td>Electrocautery</td>
			<td>Dalwha Corp. Ltd.</td>
			<td>BA2ALD001</td>
			<td>Model: 200 Basic</td>
		</tr>
		<tr>
			<td>Hemostat</td>
			<td>Roboz</td>
			<td>RS-7476</td>
			<td>St Vincent Tube Occluding Forceps</td>
		</tr>
		<tr>
			<td>Hemostatic forceps</td>
			<td>Harvard Apparatus</td>
			<td>72-8960</td>
			<td>Hartmann Hemostatic Forceps, Curved, Serrated 2.2 mm tip width, 9.5 cm</td>
		</tr>
		<tr>
			<td>Hemostats</td>
			<td>Harvard Apparatus</td>
			<td>72-8985</td>
			<td>Halstead-Mosquito Hemostatic Forceps Curved, Serrated, 2mm tip 14cm</td>
		</tr>
		<tr>
			<td>Mayo scissors</td>
			<td>WPI</td>
			<td>501749</td>
			<td>14.5 cm, Straight</td>
		</tr>
		<tr>
			<td>Metzenbaum scissors</td>
			<td>WPI</td>
			<td>501747</td>
			<td>11.5 cm, Straight</td>
		</tr>
		<tr>
			<td>Mosquito forceps</td>
			<td>Harvard Apparatus</td>
			<td>72-8980</td>
			<td>Halstead-Mosquito Hemostatic Forceps Straight, Smooth, 2mm tip width 12cm</td>
		</tr>
		<tr>
			<td>Needle holder</td>
			<td>Harvard Apparatus</td>
			<td>72-8828</td>
			<td>Webster Needle Holders, Straight, Smooth,13.0 cm overall length</td>
		</tr>
		<tr>
			<td>Pediatric cross clamp</td>
			<td>Roboz</td>
			<td>RS-7660</td>
			<td>Cooley-Derra Clamp 6.25&#34; 5mm Calibrations</td>
		</tr>
		<tr>
			<td>Right angle forceps</td>
			<td>WPI</td>
			<td>501240</td>
			<td>Baby Mixter Hemostatic Forceps, 14cm, Right Angle</td>
		</tr>
		<tr>
			<td>Scalpel</td>
			<td>Ted Pella</td>
			<td>549-4</td>
			<td>Scalpel Handle No. 4, 13.7cm Stainless Steel and 10 No. 22 Blades</td>
		</tr>
		<tr>
			<td>scissors</td>
			<td>Harvard Apparatus</td>
			<td>72-8380</td>
			<td>Operating Scissors, Straight, Blunt/Blunt, 42mm blade,12cm</td>
		</tr>
		<tr>
			<td>Straight Serrated forceps</td>
			<td>WPI</td>
			<td>500363</td>
			<td>Dressing Forceps 15.5cm</td>
		</tr>
		<tr>
			<td>Towel clamp</td>
			<td>WPI</td>
			<td>501700</td>
			<td>Backhaus Towel Clamp, 13cm, Curved, Locking handle, SS</td>
		</tr>
		<tr>
			<td>Weitlaner retractor</td>
			<td>WPI</td>
			<td>501314</td>
			<td>Weitlaner Retractor, Self-Retaining, 10.2cm, 2x3 Sharp Prongs</td>
		</tr>
		<tr>
			<td>Disposables</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3-0 prolene suture</td>
			<td>Various vendors</td>
			<td>Various vendors</td>
			<td></td>
		</tr>
		<tr>
			<td>Vessel loop</td>
			<td>Aspen surgical</td>
			<td>011001PBX</td>
			<td>Sterion&#174; Vessel Loop, 0.8 x 406mm</td>
		</tr>
		<tr>
			<td>Cardioplegia (Plegisol)</td>
			<td>Pfizer</td>
			<td>00409-7969-05</td>
			<td>Plegisol; St Thomas crystalloid cardioplegia solution 20ml/kg</td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td>Various vendors</td>
			<td>Various vendors</td>
			<td>300 U/kg</td>
		</tr>
		<tr>
			<td>Syringe and Needle</td>
			<td>Various vendors</td>
			<td>Various vendors</td>
			<td>60mL &#38; 18G respectively</td>
		</tr>
		<tr>
			<td>Umbilical tape</td>
			<td>Ethicon</td>
			<td>U12T</td>
			<td></td>
		</tr>
	</tbody>
</table>

optocardiography and electrophysiology studies of ex vivo langendorff-perfused hearts

Small animal models are most commonly used in cardiovascular research due to the availability of genetically modified species and lower cost compared to larger animals. Yet, larger mammals are better suited for translational research questions related to normal cardiac physiology, pathophysiology, and preclinical testing of therapeutic agents. To overcome the technical barriers associated with employing a larger animal model in cardiac research, we describe an approach to measure physiological parameters in an isolated, Langendorff-perfused piglet heart. This approach combines two powerful experimental tools to evaluate the state of the heart: electrophysiology (EP) study and simultaneous optical mapping of transmembrane voltage and intracellular calcium using parameter sensitive dyes (RH237, Rhod2-AM). The described methodologies are well suited for translational studies investigating the cardiac conduction system, alterations in action potential morphology, calcium handling, excitation-contraction coupling and the incidence of cardiac alternans or arrhythmias.

Figure 1A shows a diagram of the isolated heart perfusion system, which includes the tubing circuit, pump, filter, oxygenator, reservoirs and heating elements. Placement of the ECG (lead II configuration) and pacing electrodes is shown in Figure 1B, and the imaging setup is depicted in Figure 1C. A schematic of the optical components and light paths are shown in Figure 1D.
Experimental studies were performed on intact, whole hearts isolated from juvenile Yorkshire pigs (14&#8722;42 days, n = 18) that ranged in size from 2.5&#8722;10.5 kg body weight and 18&#8722;137 g heart weight (Figure 2A). After transferring the isolated heart to a Langendorff system (37 &#176;C), the heart rate stabilized to 70 &#177; 4.5 bpm (mean &#177; SEM) within ~10 min of defibrillation and remained constant throughout the duration of study (Figure 2B). An average flow rate of 184 &#177; 17 mL/min (mean &#177; SEM) was measured, which slowed to 70 &#177; 7.5 mL/min after perfusing with warmed media containing a mechanical uncoupler (Figure 2C).
Lead II ECGs were recorded throughout the duration of the study during sinus rhythm (Figure 3A) or in response to external pacing (Figure 3B-E) to quantify electrophysiological parameters. For EP assessment, dynamic pacing (S1&#8722;S1) was applied to the right atrium to pinpoint the WBCL and SNRT (recovery time after S1&#8722;S1 commences, Figure 3C), wherein WBCL was denoted as the shortest PCL that initiated atrial to ventricular conduction. An S1&#8722;S2 pacing protocol was implemented using a bipolar stimulus electrode on the left ventricle in order to identify the shortest coupling interval that initiated ventricular depolarization, thereby pinpointing VERP (Figure 3D). Alternatively, an S1&#8722;S2 atrial pacing protocol is applied to pinpoint AVNERP (S1&#8722;S2), as shown in Figure 3E. Representative examples of pig heart electrophysiology parameters align closely with those previously published37.
Optical mapping experiments were performed during sinus rhythm, spontaneous ventricular fibrillation (Figure 4), or during dynamic pacing (S1&#8722;S1) of the left ventricle (LV) to generate electrical and calcium restitution curves depicted in Figure 5. Representative images of a dye-loaded piglet heart are shown in Figure 4 with corresponding optical action potentials (Vm) and calcium (Ca) transients collected from two regions of interest on the epicardial surface (right ventricle [RV] = blue, LV = red). Unprocessed signals are displayed during sinus rhythm and during ventricular fibrillation. As previously mentioned, dynamic epicardial pacing (S1&#8722;S1) was also used during optical mapping experiments to normalize any slight difference in the intrinsic heart rate (Figure 5A-E). Raw signals are displayed (RV = blue, LV = red), which were used to depict the action potential &#8212; calcium transient coupling time (Figure 5C), activation and duration time (Figure 5D), electrical and calcium restitution (Figure 5E). For thick myocardial preparations, spatial filtering with kernel size ~3 mm x 3 mm is appropriate for epicardial action potential or calcium transient analysis19,47. Accordingly, high spatial resolution images (in the described setup 1240 x 1024 total, or 620 x 512 per channel, 6.5 &#181;m pixel size) are often spatially binned during or post-acquisition (Figure 5C). Image processing can be performed to generate activation and repolarization maps using custom algorithms23,33,43,45 (Figure 3D), with the activation time of each pixel on the heart was defined as the maximum derivative of the action potential or calcium transient upstroke.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/60472/60472fig01.jpg" /> 
Figure 1: Experimental setup.&#160;(A) Diagram of the isolated heart perfusion system; arrows denote the direction of flow. (B) A cannulated heart is shown with electrode placement. RA = right atria, RV = right ventricle, LV = left ventricle, ECG = lead II electrocardiogram. (C) The imaging platform in close proximity to the heart tissue. (D) Emission of each complementary probe (voltage, calcium) is separated by wavelength using an image splitting device with appropriate emission filters and dichroic mirror. <a href="https://www.jove.com/files/ftp_upload/60472/60472fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/60472/60472fig02.jpg" /> 
Figure 2: Heart weight, rate and flow measurements.&#160;(A) Heart weight to body weight ratio for each piglet used in the study (n = 18). (B) Heart rate measured ~10 min after defibrillation and again at the end of study (approximately 1 h). (C) Coronary flow drops precipitously after perfusion with a mechanical uncoupler (+BDM) due to reduced oxygen demand. Scale bars represent mean &#177; SEM. <a href="https://www.jove.com/files/ftp_upload/60472/60472fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/60472/60472fig03.jpg" /> 
Figure 3: Representative examples of lead II electrocardiogram recordings collected during sinus rhythm or in response to external pacing.&#160;(A) Normal sinus rhythm. (B) Example of epicardial pacing at cycle length of 400 ms (S1&#8722;S1), which was used for imaging experiments. (C) Top: Atrial pacing to identify WBCL; successful capture is observed at S1 = 250 ms wherein atrial to ventricular conduction is observed. Note that atrial pacing can be used to determine SNRT (time to sinus node discharge, after commencing external pacing). Bottom: As the S1 cycle length is decreased to 205 ms, the conduction to the ventricle fails. (D) Top: Epicardial pacing (S1&#8722;S2) to identify VERP; successful capture is observed at S1 = 450 ms, S2 = 300 ms. Bottom: As the S2 cycle length is decreased to 250 ms, the ventricular tissue fails to capture. (E) Atrial pacing (S1&#8722;S2) to identify AVNERP. Top: Successful capture is observed at S1 = 450 ms, S2 = 200 ms. Bottom: As the S2 cycle length is decreased to 199 ms, conduction to the ventricle fails. Blue arrows denote pacing spikes, red arrows denote capture (&#8216;C&#8217;) or no capture (&#8216;NC&#8217;). S1&#8722;S1 = dynamic pacing, S1&#8722;S2 = extrastimulus pacing. <a href="https://www.jove.com/files/ftp_upload/60472/60472fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/60472/60472fig04.jpg" /> 
Figure 4: Optical data during sinus rhythm and ventricular fibrillation.&#160;Left: Representative images of a dye-loaded pig heart (Vm = voltage, RH237; Ca = calcium, Rhod2), anterior view. Spatially filtered transmembrane voltage and intracellular calcium fluorescent signals from a pig heart during sinus rhythm (Center). Voltage and calcium signals during ventricular fibrillation (Right). Signal region sizes (15 x 15 pixels = 2.4 x 2.4 mm2, 30 x 30 = 4.8 x 4.8 mm2 kernel size) represented as red and blue squares. Units = &#916;F/F. <a href="https://www.jove.com/files/ftp_upload/60472/60472fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/60472/60472fig05.jpg" /> 
Figure 5: Optical data from Langendorff-perfused pig hearts.&#160;Unprocessed, spatially filtered (A) transmembrane voltage and (B) intracellular calcium fluorescence signals from the right and left ventricles during electrical pacing at the apex. Unfiltered, spatially averaged signals depict optical action potentials and calcium transients from regions of interest (signal units are &#916;F/F). (C) An overlay of normalized transients illustrates action potential-calcium transient coupling time (low-pass filtered at 75 Hz). (D) Processing signals across the epicardial surface to generate isochronal maps of temporal parameters, including activation time (tact) and 80% repolarization time. (E) Electrical and calcium transient restitution curves generated at multiple frequencies (left) with statistical analysis (right) to illustrate longer repolarization time at slower pacing cycle lengths. Scale bars = mean &#177; SEM. <a href="https://www.jove.com/files/ftp_upload/60472/60472fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Chemical</td>
			<td>Formula</td>
			<td>Molecular weight</td>
			<td>g/L</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>NaCl</td>
			<td>58.44</td>
			<td>5.26</td>
		</tr>
		<tr>
			<td>Sodium gluconate</td>
			<td>C6H11NaO7</td>
			<td>218.14</td>
			<td>5.02</td>
		</tr>
		<tr>
			<td>Sodium acetate trihydrate</td>
			<td>C2H3NaO2&#8226;3H2O</td>
			<td>136.08</td>
			<td>3.68</td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>KCl</td>
			<td>74.55</td>
			<td>0.63</td>
		</tr>
		<tr>
			<td>Magnesium chloride (anhydrous)</td>
			<td>MgCl2</td>
			<td>95.21</td>
			<td>0.1405</td>
		</tr>
		<tr>
			<td>8.4% Sodium bicarbonate</td>
			<td>NaHCO3</td>
			<td>84.01</td>
			<td>13</td>
		</tr>
		<tr>
			<td>Mannitol</td>
			<td>C6H14O6</td>
			<td>182.17</td>
			<td>16.3</td>
		</tr>
		<tr>
			<td>Magnesium sulfate</td>
			<td>MgSO4</td>
			<td>120.37</td>
			<td>4</td>
		</tr>
		<tr>
			<td>pH</td>
			<td>7.4</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Osmolarity (mOsmol/L)</td>
			<td>294</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>
Table 1: Modified del Nido&#8217;s cardioplegia recipe.

Watch this Scientific Journal Video about Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts at JoVE.com

Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts

The objective of this study was to establish a method for investigating cardiac dynamics using a translational animal model. The described experimental approach incorporates dual-emission optocardiography in conjunction with an electrophysiological study to assess electrical activity in an isolated, intact porcine heart model.

Small animal models are most commonly used in cardiovascular research due to the availability of genetically modified species and lower cost compared to ...

optocardiography-electrophysiology-studies-ex-vivo-langendorff

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12.8K Views.  Children's National Hospital. The objective of this study was to establish a method for investigating cardiac dynamics using a translational animal model. The described experimental approach incorporates dual-emission optocardiography in conjunction with an electrophysiological study to assess electrical activity in an isolated, intact porcine heart model.

Video: Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts

Ex Vivo Culture of Patient Tissue &amp; Examination of Gene Delivery

This video describes the use of patient tissue as an ex vivo model for the study of gene delivery. Fresh patient tissue obtained at the time of surgery is sliced and maintained in culture. The ex vivo model system allows for the physical delivery of genes into intact patient tissue and gene expression is analysed by bioluminescence imaging using the IVIS detection system. The bioluminescent detection system demonstrates rapid and accurate quantification of gene expression within individual slices without the need for tissue sacrifice. This slice tissue culture system may be used in a variety of tissue types including normal and malignant tissue and allows us to study the effects of the heterogeneous nature of intact tissue and the high degree of variability between individual patients. This model system could be used in certain situations as an alternative to animal models and as a complementary preclinical mode prior to entering clinical trial.

Ex Vivo Culture of Patient Tissue &amp; Examination of Gene Delivery

This article describes the culture of patient tissue slices for gene delivery studies and subsequent analysis of gene expression using IVIS bioluminescence imaging.

This video describes the use of patient tissue as an ex vivo model for the study of gene delivery.  Fresh patient tissue obtained at the time of surgery ...

Ex Vivo Infection of Live Tissue with Oncolytic Viruses

Oncolytic Viruses (OVs) are novel therapeutics that selectively replicate in and kill tumor cells1. Several clinical trials evaluating the effectiveness of a variety of oncolytic platforms including HSV, Reovirus, and Vaccinia OVs as treatment for cancer are currently underway2-5. One key characteristic of oncolytic viruses is that they can be genetically modified to express reporter transgenes which makes it possible to visualize the infection of tissues by microscopy or bio-luminescence imaging6,7. This offers a unique advantage since it is possible to infect tissues from patients ex vivo prior to therapy in order to ascertain the likelihood of successful oncolytic virotherapy8. To this end, it is critical to appropriately sample tissue to compensate for tissue heterogeneity and assess tissue viability, particularly prior to infection9. It is also important to follow viral replication using reporter transgenes if expressed by the oncolytic platform as well as by direct titration of tissues following homogenization in order to discriminate between abortive and productive infection. The object of this protocol is to address these issues and herein describes 1. The sampling and preparation of tumor tissue for cell culture 2. The assessment of tissue viability using the metabolic dye alamar blue 3. Ex vivo infection of cultured tissues with vaccinia virus expressing either GFP or firefly luciferase 4. Detection of transgene expression by fluorescence microscopy or using an In Vivo Imaging System (IVIS) 5. Quantification of virus by plaque assay. This comprehensive method presents several advantages including ease of tissue processing, compensation for tissue heterogeneity, control of tissue viability, and discrimination between abortive infection and bone fide viral replication.

Ex Vivo Infection of Live Tissue with Oncolytic Viruses

Oncolytic viruses are promising for cancer therapeutics. The ability to ascertain the infectability of live tissue specimens obtained from patients prior to treatment is a unique advantage of this therapeutic approach. This protocol describes how to process tissues for ex vivo infection with oncolytic virus and subsequent viral quantification.

Oncolytic Viruses (OVs) are novel therapeutics that selectively replicate in and kill tumor cells1. Several clinical trials evaluating the effectiveness ...

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal hyperplasia (IH) that eventually leads to vessel occlusion and graft failure. Mechanical forces, particularly low shear stress and high wall tension, are thought to initiate and to sustain these cellular and molecular changes, but their exact contribution remains to be unraveled. To selectively evaluate the role of pressure and shear stress on the biology of IH, an ex&#160;vivo perfusion system (EVPS) was created to perfuse segments of human saphenous veins under arterial regimen (high shear stress and high pressure). Further technical innovations allowed the simultaneous perfusion of two segments from the same vein, one reinforced with an external mesh. Veins were harvested using a no-touch technique and immediately transferred to the laboratory for assembly in the EVPS. One segment of the freshly isolated vein was not perfused (control, day 0). The two others segments were perfused for up to 7 days, one being completely sheltered with a 4 mm (diameter) external mesh. The pressure, flow velocity, and pulse rate were continuously monitored and adjusted to mimic the hemodynamic conditions prevailing in the femoral artery. Upon completion of the perfusion, veins were dismounted and used for histological and molecular analysis. Under ex&#160;vivo conditions, high pressure perfusion (arterial, mean = 100 mm Hg) is sufficient to generate IH and remodeling of human veins. These alterations are reduced in the presence of an external polyester mesh.

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

The mechanisms leading to the development of intimal hyperplasia (IH) and vein graft failure are still poorly understood. This study describes an ex&#160;vivo system to perfuse human veins under controlled flow and pressure. Furthermore the efficiency of external mesh reinforcement to limit the development of IH was evaluated.

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal ...

Induction and Assessment of Ischemia-reperfusion Injury in Langendorff-perfused Rat Hearts

The biochemical events surrounding ischemia reperfusion injury in the acute setting are of great importance to furthering novel treatment options for myocardial infarction and cardiac complications of thoracic surgery. The ability of certain drugs to precondition the myocardium against ischemia reperfusion injury has led to multiple clinical trials, with little success. The isolated heart model allows acute observation of the functional effects of ischemia reperfusion injury in real time, including the effects of various pharmacological interventions administered at any time-point before or within the ischemia-reperfusion injury window. Since brief periods of ischemia can precondition the heart against ischemic injury, in situ aortic cannulation is performed to allow for functional assessment of non-preconditioned myocardium. A saline filled balloon is placed into the left ventricle to allow for real-time measurement of pressure generation. Ischemic injury is simulated by the cessation of perfusion buffer flow, followed by reperfusion. The duration of both ischemia and reperfusion can be modulated to examine biochemical events at any given time-point. Although the Langendorff isolated heart model does not allow for the consideration of systemic events affecting ischemia and reperfusion, it is an excellent model for the examination of acute functional and biochemical events within the window of ischemia reperfusion injury as well as the effect of pharmacological intervention on cardiac pre- and postconditioning. The goal of this protocol is to demonstrate how to perform in situ aortic cannulation and heart excision followed by ischemia/reperfusion injury in the Langendorff model.

The isolated rat heart is an enduring model for ischemia reperfusion injury. Here, we describe the process of harvesting the beating heart from a rat via in situ aortic cannulation, Langendorff perfusion of the heart, simulated ischemia-reperfusion injury, and infarct staining to confirm the extent of ischemic insult.

The biochemical events surrounding ischemia reperfusion injury in the acute setting are of great importance to furthering novel treatment options for ...

Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment

Metastasis is a major cause for cancer-related morbidity and mortality. Metastasis is a multistep process and due to its complexity, the exact cellular and molecular processes that govern metastatic dissemination and growth are still elusive. Live imaging allows visualization of the dynamic and spatial interactions of cells and their microenvironment. Solid tumors commonly metastasize to the lungs. However, the anatomical location of the lungs poses a challenge to intravital imaging. This protocol provides a relatively simple and quick method for ex vivo live imaging of the dynamic interactions between tumor cells and their surrounding stroma within lung metastasis. Using this method, the motility of cancer cells as well as interactions between cancer cells and stromal cells in their microenvironment can be visualized in real time for several hours. By using transgenic fluorescent reporter mice, a fluorescent cell line, injectable fluorescently labeled molecules and/or antibodies, multiple components of the lung microenvironment can be visualized, such as blood vessels and immune cells. To image the different cell types, a spinning disk confocal microscope that allows long-term continuous imaging with rapid, four-color image acquisition has been used. Time-lapse movies compiled from images collected over multiple positions and focal planes show interactions between live metastatic and immune cells for at least 4 hr. This technique can be further used to test chemotherapy or targeted therapy. Moreover, this method could be adapted for the study of other lung-related pathologies that may affect the lung microenvironment.

Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment

We describe a relatively simple method for ex vivo live imaging of the tumor cell-stroma interactions within lung metastasis, utilizing fluorescent reporters in mice. Using spinning-disk confocal microscopy, this technique enables visualization of live cells for at least 4 hr and could be adapted to study other inflammatory lung conditions.

Metastasis is a major cause for cancer-related morbidity and mortality. Metastasis is a multistep process and due to its complexity, the exact cellular ...

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, normothermic ex vivo liver perfusion (NEVLP) has been introduced as a method to evaluate and modify organ function. NEVLP has many advantages in comparison to hypothermic and subnormothermic perfusion including reduced preservation injury, restoration of normal organ function under physiologic conditions, assessment of organ performance, and as a platform for organ repair, remodeling, and modification. Both murine and porcine NEVLP models have been described. We demonstrate a rat model of NEVLP and use this model to show one of its important applications &#8212; the use of a therapeutic molecule added to liver perfusate. Catalase is an endogenous reactive oxygen species (ROS) scavenger and has been demonstrated to decrease ischemia-reperfusion in the eye, brain, and lung. Pegylation has been shown to target catalase to the endothelium. Here, we added pegylated-catalase (PEG-CAT) to the base perfusate and demonstrated its ability to mitigate liver preservation injury. An advantage of our rodent NEVLP model is that it is inexpensive in comparison to larger animal models. A limitation of this study is that it does not currently include post-perfusion liver transplantation. Therefore, prediction of the function of the organ post-transplantation cannot be made with certainty. However, the rat liver transplant model is well established and certainly could be used in conjunction with this model. In conclusion, we have demonstrated an inexpensive, simple, easily replicable NEVLP model using rats. Applications of this model can include testing novel perfusates and perfusate additives, testing software designed for organ evaluation, and experiments designed to repair organs.

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant liver donor shortage, and criteria for liver donors have been expanded. Normothermic ex vivo liver perfusion (NEVLP) has been developed to evaluate and modify organ function. This study demonstrates a rat model of NEVLP and tests the ability of pegylated-catalase, to mitigate liver preservation injury.

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, ...

Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System

Since its invention in the late 19th century, the Langendorff ex vivo heart perfusion system continues to be a relevant tool for studying a broad spectrum of physiological, biochemical, morphological, and pharmacological parameters in centrally denervated hearts. Here, we describe a setup for the modulation of the intracardiac autonomic nervous system and the assessment of its influence on basic electrophysiology, arrhythmogenesis, and cyclic adenosine monophosphate (cAMP) dynamics. The intracardiac autonomic nervous system is modulated by the mechanical dissection of atrial fat pads-in which murine ganglia are located mainly&#8212;or by the usage of global as well as targeted pharmacological interventions. An octapolar electrophysiological catheter is introduced into the right atrium and the right ventricle, and epicardial-placed multi-electrode arrays (MEA) for high-resolution mapping are used to determine cardiac electrophysiology and arrhythmogenesis. F&#246;rster resonance energy transfer (FRET) imaging is performed for the real-time monitoring of cAMP levels in different cardiac regions. Neuromorphology is studied by means of antibody-based staining of whole hearts using neuronal markers to guide the identification and modulation of specific targets of the intracardiac autonomic nervous system in the performed studies. The ex vivo Langendorff setup allows for a high number of reproducible experiments in a short time. Nevertheless, the partly open nature of the setup (e.g., during MEA measurements) makes constant temperature control difficult and should be kept to a minimum. This described method makes it possible to analyze and modulate the intracardiac autonomic nervous system in decentralized hearts.

Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System

Here, we present a protocol for the modulation of the intracardiac autonomic nervous system and the assessment of its influence on basic electrophysiology, arrhythmogenesis, and cAMP dynamics using an ex vivo Langendorff setup.

Since its invention in the late 19th century, the Langendorff ex vivo heart perfusion system continues to be a relevant tool for studying a broad spectrum ...

Ex Vivo Corneal Organ Culture Model for Wound Healing Studies

The cornea has been used extensively as a model system to study wound healing. The ability to generate and utilize primary mammalian cells in two dimensional (2D) and three dimensional (3D) culture has generated a wealth of information not only about corneal biology but also about wound healing, myofibroblast biology, and scarring in general. The goal of the protocol is an assay system for quantifying myofibroblast development, which characterizes scarring. We demonstrate a corneal organ culture ex vivo model using pig eyes. In this anterior keratectomy wound, corneas still in the globe are wounded with a circular blade called a trephine. A plug of approximately 1/3 of the anterior cornea is removed including the epithelium, the basement membrane, and the anterior part of the stroma. After wounding, corneas are cut from the globe, mounted on a collagen/agar base, and cultured for two weeks in supplemented-serum free medium with stabilized vitamin C to augment cell proliferation and extracellular matrix secretion by resident fibroblasts. Activation of myofibroblasts in the anterior stroma is evident in the healed cornea. This model can be used to assay wound closure, the development of myofibroblasts and fibrotic markers, and for toxicology studies. In addition, the effects of small molecule inhibitors as well as lipid-mediated siRNA transfection for gene knockdown can be tested in this system.

A protocol for an ex vivo corneal organ culture model useful for wound healing studies is described. This model system can be used to assess the effects of agents to promote regenerative healing or drug toxicity in an organized 3D multicellular environment.

The cornea has been used extensively as a model system to study wound healing. The ability to generate and utilize primary mammalian cells in two ...

Murine Precision-Cut Liver Slices as an Ex Vivo Model of Liver Biology

Understanding the mechanisms of liver injury, hepatic fibrosis, and cirrhosis that underlie chronic liver diseases (i.e., viral hepatitis, non-alcoholic fatty liver disease, metabolic liver disease, and liver cancer) requires experimental manipulation of animal models and in vitro cell cultures. Both techniques have limitations, such as the requirement of large numbers of animals for in vivo manipulation. However, in vitro cell cultures do not reproduce the structure and function of the multicellular hepatic environment. The use of precision-cut liver slices is a technique in which uniform slices of viable mouse liver are maintained in laboratory tissue culture for experimental manipulation. This technique occupies an experimental niche that exists between animal studies and in vitro cell culture methods. The presented protocol describes a straightforward and reliable method to isolate and culture precision-cut liver slices from mice. As an application of this technique, ex vivo liver slices are treated with bile acids to simulate cholestatic liver injury and ultimately assess the mechanisms of hepatic fibrogenesis.

This protocol provides a simple and reliable method for the production of viable precision-cut liver slices from mice. The ex vivo tissue samples can be maintained under laboratory tissue culture conditions for multiple days, providing a flexible model to examine liver pathobiology.

Understanding the mechanisms of liver injury, hepatic fibrosis, and cirrhosis that underlie chronic liver diseases (i.e., viral hepatitis, non-alcoholic ...

Precision Cut Lung Slices as an Efficient Tool for Ex vivo Pulmonary Vessel Structure and Contractility Studies

The visualization of murine lung tissue provides valuable structural and cellular information regarding the underlying airway and vasculature. However, the preservation of pulmonary vessels that truly represents physiological conditions still presents challenges. In addition, the delicate configuration of murine lungs result in technical challenges preparing samples for high-quality images that preserve both cellular composition and architecture. Similarly, cellular contractility assays can be performed to study the potential of cells to respond to vasoconstrictors in vitro, but these assays do not reproduce the complex environment of the intact lung. In contrast to these technical issues, the precision-cut lung slice (PCLS) method can be applied as an efficient alternative to visualize lung tissue in three dimensions without regional bias and serve as a live surrogate contractility model for up to 10 days. Tissue prepared using PCLS has preserved structure and spatial orientation, making it ideal to study disease processes ex vivo. The location of endogenous tdTomato-labeled cells in PCLS harvested from an inducible tdTomato reporter murine model can be successfully visualized by confocal microscopy. After exposure to vasoconstrictors, PCLS demonstrates the preservation of both vessel contractility and lung structure, which can be captured by a time-lapse module. In combination with the other procedures, such as western blot and RNA analysis, PCLS can contribute to the comprehensive understanding of signaling cascades that underlie a wide variety of disorders and lead to a better understanding of the pathophysiology in pulmonary vascular diseases.

Precision Cut Lung Slices as an Efficient Tool for Ex vivo Pulmonary Vessel Structure and Contractility Studies

Presented here is a protocol for preserving the vascular contractility of PCLS murine lung tissue, resulting in a sophisticated three-dimensional image of the pulmonary vasculature and airway, which can be preserved for up to 10 days that is susceptible to numerous procedures.

The visualization of murine lung tissue provides valuable structural and cellular information regarding the underlying airway and vasculature. However, ...