Name: slicing and culturing pig hearts under physiological conditions
Uploaded: 2020-03-20T14:00:00
Description: Watch this Scientific Journal Video about Slicing and Culturing Pig Hearts under Physiological Conditions at JoVE.com

TMAM is supported by NIH grant P30GM127607 and American Heart Association grant 16SDG29950012. RB is supported by P01HL78825 and UM1HL113530.

All animal procedures were in accordance with the institutional guidelines of the University of Louisville and approved by the Institutional Animal Care and Use Committee.
1. Preparation for Slicing (One Day Before Slicing)
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	<li>Preparation of the vibrating microtome
	<ol>
		<li>Place the ceramic blade into its holder by following these steps: after carefully unwrapping the blade, place the sharp edge first into the slot of the blade tool. Then, fit the blade into the h...

<ol>
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R., 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=Revisiting+Cardiac+Cellular+Composition.">Revisiting Cardiac Cellular Composition.</a> Circulation Research. 118 (3), 400-409 (2016).</li><li>Kanisicak, O., 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=Genetic+lineage+tracing+defines+myofibroblast+origin+and+function+in+the+injured+heart.">Genetic lineage tracing defines myofibroblast origin and function in the injured heart.</a> Nature Communications. 7, 12260 (2016).</li><li>Fu, X., 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=Specialized+fibroblast+differentiated+states+underlie+scar+formation+in+the+infarcted+mouse+heart.">Specialized fibroblast differentiated states underlie scar formation in the infarcted mouse heart.</a> Journal of Clinical Investigations. 128 (5), 2127-2143 (2018).</li><li>Kretzschmar, K., 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=Profiling+proliferative+cells+and+their+progeny+in+damaged+murine+hearts.">Profiling proliferative cells and their progeny in damaged murine hearts.</a> Proceedings of the National Academy of Sciences of the United States of America. 115 (52), E12245-E12254 (2018).</li><li>Perbellini, 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=Investigation+of+cardiac+fibroblasts+using+myocardial+slices.">Investigation of cardiac fibroblasts using myocardial slices.</a> Cardiovascular Research. 114 (1), 77-89 (2018).</li><li>Watson, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+viable+adult+ventricular+myocardial+slices+from+large+and+small+mammals.">Preparation of viable adult ventricular myocardial slices from large and small mammals.</a> Nature Protocols. 12 (12), 2623-2639 (2017).</li><li>Kang, C., 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=Human+Organotypic+Cultured+Cardiac+Slices:+New+Platform+For+High+Throughput+Preclinical+Human+Trials.">Human Organotypic Cultured Cardiac Slices: New Platform For High Throughput Preclinical Human Trials.</a> Scientific Reports. 6, 28798 (2016).</li><li>Ou, Q., 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=Physiological+Biomimetic+Culture+System+for+Pig+and+Human+Heart+Slices.">Physiological Biomimetic Culture System for Pig and Human Heart Slices.</a> Circulation Research. 125 (6), 628-642 (2019).</li><li>Jones, S. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+NHLBI-sponsored+Consortium+for+preclinicAl+assESsment+of+cARdioprotective+therapies+(CAESAR):+a+new+paradigm+for+rigorous,+accurate,+and+reproducible+evaluation+of+putative+infarct-sparing+interventions+in+mice,+rabbits,+and+pigs.">The NHLBI-sponsored Consortium for preclinicAl assESsment of cARdioprotective therapies (CAESAR): a new paradigm for rigorous, accurate, and reproducible evaluation of putative infarct-sparing interventions in mice, rabbits, and pigs.</a> Circulation Research. 116 (4), 572-586 (2015).</li><li>Crick, S. J., Sheppard, M. N., Ho, S. Y., Gebstein, L., Anderson, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+of+the+pig+heart:+comparisons+with+normal+human+cardiac+structure.">Anatomy of the pig heart: comparisons with normal human cardiac structure.</a> Journal of Anatomy. 193 (Pt 1), 105-119 (1998).</li><li>Fischer, C., 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=Long-term+functional+and+structural+preservation+of+precision-cut+human+myocardium+under+continuous+electromechanical+stimulation+in+vitro.">Long-term functional and structural preservation of precision-cut human myocardium under continuous electromechanical stimulation in vitro.</a> Nature Communications. 10 (1), 117 (2019).</li><li>Franke, J., Abs, V., Zizzadoro, C., Abraham, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+study+of+the+effects+of+fetal+bovine+serum+versus+horse+serum+on+growth+and+differentiation+of+primary+equine+bronchial+fibroblasts.">Comparative study of the effects of fetal bovine serum versus horse serum on growth and differentiation of primary equine bronchial fibroblasts.</a> BMC Veterinary Research. 10, 119 (2014).</li><li>Vuorenpaa, H., 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=Novel+in+vitro+cardiovascular+constructs+composed+of+vascular-like+networks+and+cardiomyocytes.">Novel in vitro cardiovascular constructs composed of vascular-like networks and cardiomyocytes.</a> In Vitro Cellular &amp; Developmental Biology - Animal. 50 (4), 275-286 (2014).</li><li>Qiao, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiparametric+slice+culture+platform+for+the+investigation+of+human+cardiac+tissue+physiology.">Multiparametric slice culture platform for the investigation of human cardiac tissue physiology.</a> Progress in Biophysics and Molecular Biology. 144, 139-150 (2018).</li><li>Watson, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomimetic+electromechanical+stimulation+to+maintain+adult+myocardial+slices+in+vitro.">Biomimetic electromechanical stimulation to maintain adult myocardial slices in vitro.</a> Nature Communications. 10 (1), 2168 (2019).</li></ol>

Here we describe the detailed video protocol for our recently published method for simplified medium throughput (processes up to 48 slices/device) method that enables culture of pig heart slices for a period sufficiently long to test acute cardiotoxicity13. The proposed conditions mimic the environment of the heart, including frequency of electrical stimulation, nutrient availability, and intermittent oxygenation. We attribute the prolonged viability of heart slices in our biomimetic stimulated cu...

Drug induced cardiotoxicity is a major cause of market withdrawal1. In the last decade of the 20th century, eight non-cardiovascular drugs were withdrawn from the market as they resulted in sudden death due to ventricular arrhythmias2. In addition, several anti-cancer therapies (while in many cases effective) can lead to several cardiotoxic effects including cardiomyopathy and arrhythmias. For example, both traditional (e.g., anthracyclines and radiation) and targeted (e.g., trastuzumab) breast cancer therapies can result in cardiovascular complications in a subset of patients3. A close collaboration between cardiologists and oncologists (via the emerging field of &#34;cardio-oncology&#34;) has helped make these complications manageable ensuring that patients can be treated effectively2. Less clear are the cardiovascular effects of newer agents, including Her2 and PI3K inhibitors, especially when therapies are used in combination. Therefore, there is a growing need for reliable preclinical screening strategies for cardiovascular toxicities associated with emerging anti-cancer therapies prior to human clinical trials. The lack of availability of culture systems for human heart tissue that is functionally and structurally viable for more than 24 h is a limiting factor for reliable cardiotoxicity testing. Therefore, there is an urgent need to develop a reliable system for culturing human heart tissue under physiologic conditions for testing drug toxicity.
The recent move towards the use of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in cardiotoxicity testing has provided a partial solution to address this issue; however, the immature nature of the hiPSC-CMs and the loss of tissue integrity compared to multicellular nature of the heart tissue are major limitations of this technology4. A recent study has partially overcome this limitation through fabrication of cardiac tissues from hiPSC-CMs on hydrogels and subjecting them to gradual increase in electrical stimulation over time5. However, their electromechanical properties did not achieve the maturity seen in the adult human myocardium. Moreover, the heart tissue is structurally more complicated, being composed of various cell types including endothelial cells, neurons and various types of stromal fibroblasts linked together with a very specific mixture of extracellular matrix proteins6. This heterogeneity of the non-cardiomyocyte cell population7,8,9 in the adult mammalian heart is a major obstacle in modeling heart tissue using individual cell types. These major limitations highlight the importance of developing methods to enable culture of intact cardiac tissue for optimal studies involving physiological and pathological conditions of the heart5.
Culturing human heart slices is a promising model of intact human myocardium. This technology provides access to a complete 3D multicellular system that is similar to the human heart tissue which could reliably reflect the physiological or pathological conditions of the human myocardium. However, its use has been severely limited by the short period of viability in culture, which does not extend beyond 24 h using the most robust protocols reported until 201810,11,12. This limitation was due to multiple factors including the use of air-liquid interface to culture the slices, and the use of a simple culture medium that does not support the high energetic demands of the cardiac tissue. We have recently developed a submerged culture system which is able to provide continuous electrical stimulation and optimized the culture media components to keep cardiac tissue slices viable for up to 6 days13. This culture system has the potential to become a powerful predictive human in situ model for acute cardiotoxicity testing to close the gap between preclinical and clinical testing results. In the current article, we are detailing the protocol for slicing and culturing the heart slices using a pig heart as an example. The same process is applied to human, dog, sheep, or cat hearts. With this protocol, we are hoping to spread the technology to other laboratories in the scientific community.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1000ml, 0.22&#181;m, Vacuum Filter/Storage Systems</td>
			<td>VWR</td>
			<td>28199-812</td>
			<td></td>
		</tr>
		<tr>
			<td>2,3-Butanedione monoxime (BDM)</td>
			<td>Fisher</td>
			<td>AC150375000</td>
			<td></td>
		</tr>
		<tr>
			<td>500ml, 0.22&#181;m, Vacuum Filter/Storage Systems</td>
			<td>VWR</td>
			<td>28199-788</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well C-Dish Cover (electrical-stimulation-plate-cover)</td>
			<td>Ion Optix</td>
			<td>CLD6WFC</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well plates</td>
			<td>Fisher</td>
			<td>08-772-1B</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Bioline USA</td>
			<td>BIO-41025</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic-Antimycotic</td>
			<td>Thermo</td>
			<td>15-240-062</td>
			<td></td>
		</tr>
		<tr>
			<td>C-Pace EM (cell-culture-electrical-stimulator)</td>
			<td>Ion Optix</td>
			<td>CEP100</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium Chloride (CaCl2)</td>
			<td>Fisher</td>
			<td>C79-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Ceramic Blades for Vibrating Microtome</td>
			<td>Campden Instruments</td>
			<td>7550-1-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Cooley Chest Retractor</td>
			<td>Millennium Surgical</td>
			<td>63-G5623</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Glucose</td>
			<td>Fisher</td>
			<td>D16-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable Scalpel #20</td>
			<td>Biologyproducts.com</td>
			<td>DS20X</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon Cell Strainers, Sterile, Corning</td>
			<td>VWR</td>
			<td>21008-952</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Thermo</td>
			<td>A3160502</td>
			<td></td>
		</tr>
		<tr>
			<td>Graefe Forceps</td>
			<td>Fisher</td>
			<td>NC9475675</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>H3149-50KU</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Fisher</td>
			<td>BP310-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Histoacryl BLUE Tissue glue</td>
			<td>Amazon</td>
			<td></td>
			<td><a href="https://www.amazon.com/HISTOACRYL-FLEXIBLE-1051260P-Aesculap-Adhesive/dp/B074WB5185/" target="_blank">https://www.amazon.com/HISTOACRYL-FLEXIBLE-1051260P-Aesculap-Adhesive/dp/B074WB5185/</a></td>
		</tr>
		<tr>
			<td>Iris Spring scissors</td>
			<td>Fisher</td>
			<td>NC9019530</td>
			<td></td>
		</tr>
		<tr>
			<td>Iris Straight Scissors</td>
			<td>Fisher</td>
			<td>731210</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane, USP</td>
			<td>Piramal</td>
			<td>NDC 66794-017-25</td>
			<td></td>
		</tr>
		<tr>
			<td>ITS Liquid Media Supplement</td>
			<td>Sigma-Aldrich</td>
			<td>I3146-5ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine HCl (500 mg/10 mL)</td>
			<td>West-Ward</td>
			<td>NDC 0143-9508</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium Chloride (MgCl2)</td>
			<td>Fisher</td>
			<td>M33-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Mayo SuperCut Surgical Scissors</td>
			<td>AROSurgical Instruments Corporation</td>
			<td>AROSuperCut&#8482; 07.164.17</td>
			<td></td>
		</tr>
		<tr>
			<td>Medium 199, Earle&#39;s Salts</td>
			<td>Thermo</td>
			<td>11-150-059</td>
			<td></td>
		</tr>
		<tr>
			<td>Oxygen regulator</td>
			<td>Praxair</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Oxygen tanks -</td>
			<td>Praxair</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic Pasteur pipettes</td>
			<td>Fisher</td>
			<td>13-711-48</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Chloride (KCl)</td>
			<td>Fisher</td>
			<td>AC193780010</td>
			<td></td>
		</tr>
		<tr>
			<td>Printer Timing Belt</td>
			<td>Amazon</td>
			<td></td>
			<td><a href="https://www.amazon.com/Uxcell-a14081200ux0042-PRINTER-Precision-Timing/dp/B00R1J3KDC/" target="_blank">https://www.amazon.com/Uxcell-a14081200ux0042-PRINTER-Precision-Timing/dp/B00R1J3KDC/</a></td>
		</tr>
		<tr>
			<td>Razor rectangle blades</td>
			<td>Fisher</td>
			<td>12-640</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Human FGF basic</td>
			<td>R&#38;D Systems</td>
			<td>233-FB-025/CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Human VEGF</td>
			<td>R&#38;D Systems</td>
			<td>293-VE-010/CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Retractable scalpels</td>
			<td>Fisher</td>
			<td>22-079-716</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate (NaHCO3)</td>
			<td>Fisher</td>
			<td>AC217125000</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride (NaCl)</td>
			<td>Fisher</td>
			<td>AC327300010</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibrating Microtome</td>
			<td>Campden Instruments</td>
			<td>7000 SMZ-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylazine HCl (100 mg/mL)</td>
			<td>Heartland Veterinary Supply</td>
			<td>NADA 139-236</td>
			<td></td>
		</tr>
	</tbody>
</table>

slicing and culturing pig hearts under physiological conditions

Many novel drugs fail in clinical studies due to cardiotoxic side effects as the currently available in vitro assays and in vivo animal models poorly predict human cardiac liabilities, posing a multi-billion-dollar burden on the pharmaceutical industry. Hence, there is a worldwide unmet medical need for better approaches to identify drug cardiotoxicity before undertaking costly and time consuming &#39;first in man&#39; trials. Currently, only immature cardiac cells (human induced pluripotent stem cell-derived cardiomyocytes [hiPSC-CMs]) are used to test therapeutic efficiency and drug toxicity as they are the only human cardiac cells that can be cultured for prolonged periods required to test drug efficacy and toxicity. However, a single cell type cannot replicate the phenotype of the complex 3D heart tissue which is formed of multiple cell types. Importantly, the effect of drugs needs to be tested on adult cardiomyocytes, which have different characteristics and toxicity responses compared to immature hiPSC-CMs. Culturing human heart slices is a promising model of intact human myocardium. This technology provides access to a complete multicellular system that mimics the human heart tissue and reflects the physiological or pathological conditions of the human myocardium. Recently, through optimization of the culture media components and the culture conditions to include continuous electrical stimulation at 1.2 Hz and intermittent oxygenation of the culture medium, we developed a new culture system setup that preserves viability and functionality of human and pig heart slices for 6 days in culture. In the current protocol, we are detailing the method for slicing and culturing pig heart as an example. The same protocol is used to culture slices from human, dog, sheep, or cat hearts. This culture system has the potential to become a powerful predictive human in situ model for acute cardiotoxicity testing that closes the gap between preclinical and clinical testing results.

Using a commercially available cell culture electrical stimulator that can accommodate eight 6 well plates at once, we emulated the adult cardiac milieu by inducing electrical stimulation at the physiological frequency (1.2 Hz), and screened for the fundamental medium components to prolong the duration of functional pig heart slices in culture13. Since pig and human hearts are similar in size and anatomy15, we developed a biomimetic heart sl...

Watch this Scientific Journal Video about Slicing and Culturing Pig Hearts under Physiological Conditions at JoVE.com

Slicing and Culturing Pig Hearts under Physiological Conditions

This protocol describes how to slice and culture heart tissue under physiological conditions for 6 days. This culture system could be used as a platform for testing the efficacy of novel heart failure therapeutics as well as reliable testing of acute cardiotoxicity in a 3D heart model.

Many novel drugs fail in clinical studies due to cardiotoxic side effects as the currently available in vitro assays and in vivo animal models poorly ...

This protocol is for slicing and culturing heart tissue sections for six days under physiological conditions which can be used for acute cardiac toxicity testing as well as testing efficacy of heart failure therapies. This culture system has the potential to become a powerful predictive human in situ model for acute cardiac toxicity testing that closes the gap between pre-clinical and clinical testing results. Demonstrating the procedures will be Qinghui Qu, a lab manager from our laboratory.To obtain pig heart tissue slices, first add ice to the tissue bath cooling jacket of a vibratome and add Tyrode solution to the bath. Use a one liter plastic jar to collect the melted ice runoff from the tissue bath cooling jacket and transfer the pig heart to a tray containing one liter of fresh cold cardioplegic solution in a biosafety cabinet. Use retractible sterile scalpels to dissect the heart to isolate the left ventricle and use rectangular razor blades to cut the left ventricle into one to two cube centimeter blocks.Set aside one tissue block for slicing and place the remaining tissue block pieces into a 50 milliliter tube of cold Tyrode solution on ice. Gently massage the reserved tissue block and add one to two drops of tissue glue to the metal sample holder of the vibratome. Stick a piece of 4%agar block with a surface area of approximately one square centimeter to the glue and add one to two drops of tissue glue to the agar.Attach the heart block to the agar cardiac epicardium side down with the tissue as flat against the holder as possible and place the tissue holder with the heart block into the slicing bath of the vibratome. It is crucial to stick the heart block to the agar with the cardiac epicardium side facing down on the tissue glue and to make sure the tissue is as flat as possible. Then attach the oxygen tube to the slicing bath and the metal tray filled with Tyrode solution and place 40 micrometer cell strainers onto the metal tray to collect the heart tissue sections as they're sliced.Use the vibratome operating software to adjust the height of the blade and sample so that the blade is close to the top of the tissue but below the papillary muscles and liquid is covering the tissue and the blade. Select advance to adjust where to begin slicing the tissue. Press slice to increase the speed and use the knob to move the blade toward the edge of the tissue.Press slice again to stop and advance to inactivate the process. Then adjust the cutting parameters as indicated and press slice to begin slicing the tissue. When the blade reaches the end of the tissue but before it hits the end of the specimen holder, press slice again to stop and press return to go back to the start position.When the slices reach full length and appear to be of good quality, use a plastic Pasteur pipette filled with cold Tyrode solution to gently collect the tissue from the bath using forceps and spring scissors to dislocate the slice from the heart as necessary. Place each collected slice in a single cell strainer in the oxygenated Tyrode bath and use the solution in the pipette to press the tissue on the cell strainer surface. Then place a metal washer onto the top of the tissue to hold it down.After at least one hour in oxygenated Tyrode solution, trim the outside of each slice to remove any uneven edges and glue the end of each slice onto a six millimeter wide piece of sterilized polyurethane printer timing belt with embedded metal wires. Place the supported heart slices into six-well plates containing six milliliters of culture medium per well and use sterile forceps to make sure that the tissue is in the center of the well. Take care that the plate cover will not touch the tissue and place the plate onto the culture plate so that the curved side of the plate cover matches up with the angled side of the plate and that the square corners line up.Place the slices into a 37 degree Celsius and 5%carbon dioxide incubator. Replace the culture supernatants with six milliliters of fresh oxygenated culture medium three times per day. Connect the cover to the cell culture electrical stimulator and adjust the stimulator to continuously deliver 10 volts of electricity and a 1.2 hertz frequency to the heart slices.After plugging in the stimulation, the heart slices will begin to beat. Everyday during the midday media change, replace the stimulation plate cover from the culture dish to prevent the release of toxic graphite particles into the culture medium. Insert the white foam plug where the used cover connects to the cable for the cell culture electrical stimulator to prevent water damage to the electric circuit and place the plate cover into a bath of autoclaved water supplemented with 2X antibiotic/antimycotic.The next day, decontaminate the plate cover in a 70%ethanol bath for five to 15 minutes before transferring the cover into a fresh autoclaved water bath supplemented with 2X antibiotic/antimycotic for three minutes. After rinsing the plate cover, use an ethanol-sprayed clean lint-free wipe to remove any residual water from the plastic parts and remove the white foam plug. The cover is then ready to be placed back into the culture plate.Using this new biomimetic culture setup as demonstrated, pig heart slices viability was maintained for six days as assessed by MTT assay. In the first six days, similar to the responses observed for fresh heart slices, there are no spontaneous calcium transients within the pig heart slice cardiomyocytes. The cardiomyocytes did respond to external electrical and beta-adrenergic stimulation.In addition, the contractile force and responses to isoproterenol were maintained in heart slice culture for up to six days similar to that observed in fresh heart slices. Several structural and functional assessments can be performed on the heart slices including MTT viability assays, immunostaining, electron microscopy, calcium transient measurements, contractile function assessments, metabolic assessments, and analysis. We are currently using this culture system to test the acute cardiac toxicity and efficacy of drugs and gene therapies of interest in pig and human heart slices.

slicing-and-culturing-pig-hearts-under-physiological-conditions

Research

JoVE Journal

Medicine

Assessment of Cardiac Function and Energetics in Isolated Mouse Hearts Using 31P NMR Spectroscopy

Bioengineered mouse models have become powerful research tools in determining causal relationships between molecular alterations and models of cardiovascular disease. Although molecular biology is necessary in identifying key changes in the signaling pathway, it is not a surrogate for functional significance. While physiology can provide answers to the question of function, combining physiology with biochemical assessment of metabolites in the intact, beating heart allows for a complete picture of cardiac function and energetics. For years, our laboratory has utilized isolated heart perfusions combined with nuclear magnetic resonance (NMR) spectroscopy to accomplish this task. Left ventricular function is assessed by Langendorff-mode isolated heart perfusions while cardiac energetics is measured by performing 31P magnetic resonance spectroscopy of the perfused hearts. With these techniques, indices of cardiac function in combination with levels of phosphocreatine and ATP can be measured simultaneously in beating hearts. Furthermore, these parameters can be monitored while physiologic or pathologic stressors are instituted. For example, ischemia/reperfusion or high workload challenge protocols can be adopted. The use of aortic banding or other models of cardiac pathology are apt as well. Regardless of the variants within the protocol, the functional and energetic significance of molecular modifications of transgenic mouse models can be adequately described, leading to new insights into the associated enzymatic and metabolic pathways. Therefore, 31P NMR spectroscopy in the isolated perfused heart is a valuable research technique in animal models of cardiovascular disease.

Assessment of Cardiac Function and Energetics in Isolated Mouse Hearts Using 31P NMR Spectroscopy

Langendorff-mode isolated heart perfusion, in conjunction with 31P NMR spectroscopy, combines the fields of biochemistry and physiology into one experiment. The protocol allows for the dynamic measurement of high energy phosphate content and turnover in the heart while concurrently monitoring physiologic function. When performed correctly, this is a valuable technique in the assessment of cardiac energetics.

Bioengineered mouse models have become powerful research tools in determining causal relationships between molecular alterations and models of ...

NADH Fluorescence Imaging of Isolated Biventricular Working Rabbit Hearts

Since its inception by Langendorff1, the isolated perfused heart remains a prominent tool for studying cardiac physiology2. However, it is not well-suited for studies of cardiac metabolism, which require the heart to perform work within the context of physiologic preload and afterload pressures. Neely introduced modifications to the Langendorff technique to establish appropriate left ventricular (LV) preload and afterload pressures3. The model is known as the isolated LV working heart model and has been used extensively to study LV performance and metabolism4-6. This model, however, does not provide a properly loaded right ventricle (RV). Demmy et al. first reported a biventricular model as a modification of the LV working heart model7, 8. They found that stroke volume, cardiac output, and pressure development improved in hearts converted from working LV mode to biventricular working mode8. A properly loaded RV also diminishes abnormal pressure gradients across the septum to improve septal function. Biventricular working hearts have been shown to maintain aortic output, pulmonary flow, mean aortic pressure, heart rate, and myocardial ATP levels for up to 3 hours8.
When studying the metabolic effects of myocardial injury, such as ischemia, it is often necessary to identify the location of the affected tissue. This can be done by imaging the fluorescence of NADH (the reduced form of nicotinamide adenine dinucleotide)9-11, a coenzyme found in large quantities in the mitochondria. NADH fluorescence (fNADH) displays a near linearly inverse relationship with local oxygen concentration12 and provides a measure of mitochondrial redox state13. fNADH imaging during hypoxic and ischemic conditions has been used as a dye-free method to identify hypoxic regions14, 15 and to monitor the progression of hypoxic conditions over time10.
The objective of the method is to monitor the mitochondrial redox state of biventricular working hearts during protocols that alter the rate of myocyte metabolism or induce hypoxia or create a combination of the two. Hearts from New Zealand white rabbits were connected to a biventricular working heart system (Hugo Sachs Elektronik) and perfused with modified Krebs-Henseleit solution16 at 37 &deg;C. Aortic, LV, pulmonary artery, and left &amp; right atrial pressures were recorded. Electrical activity was measured using a monophasic action potential electrode. To image fNADH, light from a mercury lamp was filtered (350&plusmn;25 nm) and used to illuminate the epicardium. Emitted light was filtered (460&plusmn;20 nm) and imaged using a CCD camera. Changes in the epicardial fNADH of biventricular working hearts during different pacing rates are presented. The combination of the heart model and fNADH imaging provides a new and valuable experimental tool for studying acute cardiac pathologies within the context of realistic physiological conditions.

The objective is to monitor the mitochondrial redox state of isolated hearts within the context of physiologic preload and afterload pressures. A biventricular working rabbit heart model is presented. High spatiotemporal resolution fluorescence imaging of NADH is used to monitor the mitochondrial redox state of epicardial tissue.

Since its inception by Langendorff1, the isolated perfused heart remains a prominent tool for studying cardiac physiology2. However, it is not well-suited ...

Intramyocardial Cell Delivery: Observations in Murine Hearts

Previous studies showed that cell delivery promotes cardiac function amelioration by release of cytokines and factors that increase cardiac tissue revascularization and cell survival. In addition, further observations revealed that specific stem cells, such as cardiac stem cells, mesenchymal stem cells and cardiospheres have the ability to integrate within the surrounding myocardium by differentiating into cardiomyocytes, smooth muscle cells and endothelial cells.
Here, we present the materials and methods to reliably deliver noncontractile cells into the left ventricular wall of immunodepleted mice. The salient steps of this microsurgical procedure involve anesthesia and analgesia injection, intratracheal intubation, incision to open the chest and expose the heart and delivery of cells by a sterile 30-gauge needle and a precision microliter syringe.
Tissue processing consisting of heart harvesting, embedding, sectioning and histological staining showed that intramyocardial cell injection produced a small damage in the epicardial area, as well as in the ventricular wall. Noncontractile cells were retained into the myocardial wall of immunocompromised mice and were surrounded by a layer of fibrotic tissue, likely to protect from cardiac pressure and mechanical load.

Intramyocardial cell delivery in murine models of cardiovascular diseases, such as hypertension or myocardial infarction, is widely used to test the therapeutic potential of different cell types in regenerative studies. Therefore, a detailed description and a clear visualization of this surgical procedure will help to define the limits and advantages of cardiovascular cell therapeutic analyses in small rodents.

Previous studies showed that cell delivery promotes cardiac function amelioration by release of cytokines and factors that increase cardiac tissue ...

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 ...

Primary Outcome Assessment in a Pig Model of Acute Myocardial Infarction

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are therefore required to confine cardiac damage, promote survival and reduce the disease burden of heart failure. Large animal experiments are an essential part in the translational process from experimental to clinical therapies. To optimize clinical translation, robust and representative outcome measures are mandatory. The present manuscript aims to address this need by describing the assessment of three clinically relevant outcome modalities in a pig acute myocardial infarction (AMI) model: infarct size in relation to area at risk (IS/AAR) staining, 3-dimensional transesophageal echocardiography (TEE) and admittance-based pressure-volume (PV) loops. Infarct size is the main determinant driving the transition from AMI to heart failure and can be quantified by IS/AAR staining. Echocardiography is a reliable and robust tool in the assessment of global and regional cardiac function in clinical cardiology. Here, a method for three-dimensional transesophageal echocardiography (3D-TEE) in pigs is provided. Extensive insight into cardiac performance can be obtained by admittance-based pressure-volume (PV) loops, including intrinsic parameters of myocardial function that are pre- and afterload independent. Combined with a clinically feasible experimental study protocol, these outcome measures provide researchers with essential information to determine whether novel therapeutic strategies could yield promising targets for future testing in clinical studies.

Reliable and accurate outcome assessment is the key for translation of preclinical therapies into clinical treatment. The current paper describes how to assess three clinically relevant primary outcome parameters of cardiac performance and damage in a pig acute myocardial infarction model.

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are ...

A Detailed Protocol for Physiological Parameters Acquisition and Analysis in Neurosurgical Critical Patients

Intracranial pressure (ICP) monitoring is now widely used in neurosurgical critical patients. Besides mean ICP value, the ICP derived parameters such as ICP waveform, amplitude of pulse (AMP), the correlation of ICP amplitude and ICP mean (RAP), pressure reactivity index (PRx), ICP and arterial blood pressure (ABP) wave amplitude correlation (IAAC), and so on, can reflect intracranial status, predict prognosis, and can also be used as guidance of proper treatment. However, most of the clinicians focus only on the mean ICP value while ignoring these parameters because of the limitations of the current devices. We have recently developed a multimodality monitoring system to address these drawbacks. This portable, user-friendly system will use a data collecting and storing device to continuously acquire patients&#39; physiological parameters first, i.e., ABP, ICP, and oxygen saturation, and then analyze these physiological parameters. We hope that the multimodality monitoring system will be accepted as a key measure to monitor physiological parameters, to analyze the current clinical status, and to predict the prognosis of the neurosurgical critical patients.

Recently, we have developed a portable multimodality monitoring system for the monitoring of various physiological parameters in neurosurgical critical patients. Detailed protocols on how to use this multimodality monitoring system are presented here.

Intracranial pressure (ICP) monitoring is now widely used in neurosurgical critical patients. Besides mean ICP value, the ICP derived parameters such as ...

Cochlear Implantation in the Guinea Pig

Cochlear implants are highly efficient devices that can restore hearing in subjects with profound hearing loss. Due to improved speech perception outcomes, candidacy criteria have been expanded over the last few decades. This includes patients with substantial residual hearing that benefit from electrical and acoustical stimulation of the same ear, which makes hearing preservation during cochlear implantation an important issue. Electrode impedances and the related issue of energy consumption is another major research field, as progress in this area could pave the way for fully implantable auditory prostheses. To address these issues in a systematic way, adequate animal models are essential. Therefore, the goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address various research questions. Due to its large tympanic bulla, which allows easy surgical access to the inner ear, as well as its hearing range which is relatively similar to the hearing range of humans, the guinea pig is a commonly used species in auditory research. Cochlear implantation in the guinea pig is performed via a retroauricular approach. Through the bullostomy a cochleostomy is drilled and the cochlear implant electrode is inserted into the scala tympani. This electrode can then be used for electrical stimulation, determination of electrode impedances and the measurement of compound action potentials of the auditory nerve. In addition to these applications, cochlear implant electrodes can also be used as drug delivery devices, if a topical delivery of pharmaceutical agents to the cells or fluids of the inner ear is intended.

The goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address a multitude of research questions. Potential applications include the evaluation of pharmaceutical interventions or electrical stimulation for beneficial effects on hearing thresholds or electrode impedances.

Cochlear implants are highly efficient devices that can restore hearing in subjects with profound hearing loss. Due to improved speech perception ...

A Minimally Invasive Model to Analyze Endochondral Fracture Healing in Mice Under Standardized Biomechanical Conditions

Bone healing models are necessary to analyze the complex mechanisms of fracture healing to improve clinical fracture treatment. During the last decade, an increased use of mouse models in orthopedic research was noted, most probably because mouse models offer a large number of genetically-modified strains and special antibodies for the analysis of molecular mechanisms of fracture healing. To control the biomechanical conditions, well-characterized osteosynthesis techniques are mandatory, also in mice. Here, we report on the design and use of a closed bone healing model to stabilize femur fractures in mice. The intramedullary screw, made of medical-grade stainless steel, provides through fracture compression an axial and rotational stability compared to the mostly used simple intramedullary pins, which show a complete lack of axial and rotational stability. The stability achieved by the intramedullary screw allows the analysis of endochondral healing. A large amount of callus tissue, received after stabilization with the screw, offers ideal conditions to harvest tissue for biochemical and molecular analyses. A further advantage of the use of the screw is the fact that the screw can be inserted into the femur with a minimally invasive technique without inducing damage to the soft tissue. In conclusion, the screw is a unique implant that can ideally be used in closed fracture healing models offering standardized biomechanical conditions.

This protocol describes a minimally invasive osteosynthesis technique using an intramedullary screw for standardized stabilization of femur fractures, which can be used to analyze endochondral bone healing in mice.

Bone healing models are necessary to analyze the complex mechanisms of fracture healing to improve clinical fracture treatment. During the last decade, an ...

Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat

The main goal of this investigation is to show how to create and repair different types of median nerve (MN) lesions in the rat. Moreover, different methods of simulating postoperative physiotherapy are presented. Multiple standardized strategies are used to assess motor and sensory recovery using an MN model of peripheral nerve lesion and repair, thus permitting easy comparison of the results. Several options are included for providing a postoperative physiotherapy-like environment to rats that have undergone MN injuries. Finally, the paper provides a method to evaluate the recovery of the MN using several noninvasive tests (i.e., grasping test, pin prick test, ladder rung walking test, rope climbing test, and walking track analysis), and physiological measurements (infrared thermography, electroneuromyography, flexion strength evaluation, and flexor carpi radialis muscle weight determination). Hence, this model seems particularly appropriate to replicate a clinical scenario, facilitating extrapolation of results to the human species.
Although the sciatic nerve is the most studied nerve in peripheral nerve research, analysis of the rat MN presents various advantages. For example, there is a reduced incidence of joint contractures and automutilation of the affected limb in MN lesion studies. Furthermore, the MN is not covered by muscle masses, making its dissection easier than that of the sciatic nerve. In addition, MN recovery is observed sooner, because the MN is shorter than the sciatic nerve. Also, the MN has a parallel path to the ulnar nerve in the arm. Hence, the ulnar nerve can be easily used as the nerve graft for repairing MN injuries. Finally, the MN in rats is located in the forelimb, akin to the human upper limb; in humans, the upper limb is the site of most peripheral nerve lesions.

Presented is a protocol to produce different types of median nerve (MN) lesions and repair in the rat. Additionally, the protocol shows how to evaluate the functional recovery of the nerve using several noninvasive behavioral tests and physiological measurements.

The main goal of this investigation is to show how to create and repair different types of median nerve (MN) lesions in the rat. Moreover, different ...

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.

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 ...