Name: a simple and effective method to consistently isolate mouse cardiomyocytes
Uploaded: 2022-11-11T12:30:00
Description: Watch this Scientific Journal Video about A Simple and Effective Method to Consistently Isolate Mouse Cardiomyocytes at JoVE.com

This work was supported by National Institutes of Health Grants R01 HL114940 (Biesiadecki), R01 AG060542 (Ziolo), and T32 HL134616 (Sturgill and Salyer).

All procedures performed in this study were approved by the Institutional Animal Care and Use Committee at the Ohio State University in accordance with NIH guidelines.
1. Solution preparation
NOTE: Please see Table 2 for buffer concentrations.
<ol>
	<li>Pre-isolation (up to 2 weeks in advance of myocyte isolation)
	<ol>
		<li>Perfusion buffer base: Prepare 1 L of perfusion buffer base (NaCl, KCl, NaH2PO4, HEP...

<ol>
	<li>Ziolo, M. T., Dollinger, S. J., Wahler, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myocytes+isolated+from+rejecting+transplanted+rat+hearts+exhibit+reduced+basal+shortening+which+is+reversible+by+aminoguanidine.">Myocytes isolated from rejecting transplanted rat hearts exhibit reduced basal shortening which is reversible by aminoguanidine.</a> Journal of Molecular and Cellular Cardiology. 30 (5), 1009-1017 (1998).</li><li>Ziolo, M. T., 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=Myocytes+isolated+from+rejecting+transplanted+rat+hearts+exhibit+a+nitric+oxide-mediated+reduction+in+the+calcium+current.">Myocytes isolated from rejecting transplanted rat hearts exhibit a nitric oxide-mediated reduction in the calcium current.</a> Journal of Molecular and Cellular Cardiology. 33 (9), 1691-1699 (2001).</li><li>Traynham, C. J., 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=Diesterified+nitrone+rescues+nitroso-redox+levels+and+increases+myocyte+contraction+via+increased+SR+Ca(2+)+handling.">Diesterified nitrone rescues nitroso-redox levels and increases myocyte contraction via increased SR Ca(2+) handling.</a> PLoS One. 7 (12), 52005 (2012).</li><li>Nixon, B. 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=Combined+troponin+I+Ser-150+and+Ser-23/24+phosphorylation+sustains+thin+filament+Ca(2+)+sensitivity+and+accelerates+deactivation+in+an+acidic+environment.">Combined troponin I Ser-150 and Ser-23/24 phosphorylation sustains thin filament Ca(2+) sensitivity and accelerates deactivation in an acidic environment.</a> Journal of Molecular and Cellular Cardiology. 72, 177-185 (2014).</li><li>Swager, 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=Claudin-5+levels+are+reduced+from+multiple+cell+types+in+human+failing+hearts+and+are+associated+with+mislocalization+of+ephrin-B1.">Claudin-5 levels are reduced from multiple cell types in human failing hearts and are associated with mislocalization of ephrin-B1.</a> Cardiovascular Pathology. 24 (3), 160-167 (2015).</li><li>Pinckard, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+endocrine+role+for+the+BAT-released+lipokine+12,13-diHOME+to+mediate+cardiac+function.">A novel endocrine role for the BAT-released lipokine 12,13-diHOME to mediate cardiac function.</a> Circulation. 143 (2), 145-159 (2021).</li><li>Roof, S. R., Shannon, T. R., Janssen, P. M., Ziolo, M. 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E., 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=Exercise-induced+3'-sialyllactose+in+breast+milk+is+a+critical+mediator+to+improve+metabolic+health+and+cardiac+function+in+mouse+offspring.">Exercise-induced 3'-sialyllactose in breast milk is a critical mediator to improve metabolic health and cardiac function in mouse offspring.</a> Nature Metabolism. 2 (8), 678-687 (2020).</li><li>Roof, S. 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=CXL-1020,+a+novel+nitroxyl+(HNO)+prodrug,+is+more+effective+than+milrinone+in+models+of+diastolic+dysfunction-a+cardiovascular+therapeutic:+an+efficacy+and+safety+study+in+the+rat.">CXL-1020, a novel nitroxyl (HNO) prodrug, is more effective than milrinone in models of diastolic dysfunction-a cardiovascular therapeutic: an efficacy and safety study in the rat.</a> Frontiers in Physiology. 8, 894 (2017).</li><li>Milani-Nejad, N. 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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+apparatus+for+mammalian+heart+perfusion.">An improved apparatus for mammalian heart perfusion.</a> The Journal of Physiology. 115 (1), 30-32 (1951).</li><li>Powell, T., Twist, V. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+technique+for+the+isolation+and+purification+of+adult+cardiac+muscle+cells+having+respiratory+control+and+a+tolerance+to+calcium.">A rapid technique for the isolation and purification of adult cardiac muscle cells having respiratory control and a tolerance to calcium.</a> Biochemical and Biophysical Research Communications. 72 (1), 327-333 (1976).</li><li>Motayagheni, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modified+Langendorff+technique+for+mouse+heart+cannulation:+Improved+heart+quality+and+decreased+risk+of+ischemia.">Modified Langendorff technique for mouse heart cannulation: Improved heart quality and decreased risk of ischemia.</a> MethodsX. 4, 508-512 (2017).</li><li>Zhang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+procedure+for+isolating+adult+mouse+cardiomyocytes+for+epicardial+activation+mapping.">An improved procedure for isolating adult mouse cardiomyocytes for epicardial activation mapping.</a> Journal of Cellular and Molecular Medicine. 25 (24), 11257-11263 (2021).</li><li>Jian, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+cannulation+methods+for+cardiomyocytes+isolation+from+heart+disease+models.">In vivo cannulation methods for cardiomyocytes isolation from heart disease models.</a> PLoS One. 11 (8), 0160605 (2016).</li><li>Ackers-Johnson, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simplified,+Langendorff-free+method+for+concomitant+isolation+of+viable+cardiac+myocytes+and+nonmyocytes+from+the+adult+mouse+heart.">A simplified, Langendorff-free method for concomitant isolation of viable cardiac myocytes and nonmyocytes from the adult mouse heart.</a> Circulation Research. 119 (8), 909-920 (2016).</li><li>Weldrick, J. J., Abdul-Ghani, M., Megeney, L. A., Burgon, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+and+efficient+method+for+the+isolation+of+postnatal+murine+cardiac+myocyte+and+fibroblast+cells.">A rapid and efficient method for the isolation of postnatal murine cardiac myocyte and fibroblast cells.</a> Canadian Journal of Physiology and Pharmacology. 96 (5), 535-539 (2018).</li><li>Myachina, T. A., Butova, X. A., Khohlova, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modified+Langendorff-free+method+for+isolation+of+cadiomyocytes+from+adult+rat+heart.">A modified Langendorff-free method for isolation of cadiomyocytes from adult rat heart.</a> AIP Conference Proceedings. 2174 (1), 020140 (2019).</li><li>Omatsu-Kanbe, M., Yoshioka, K., Fukunaga, R., Sagawa, H., Matsuura, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+antegrade+perfusion+method+for+isolating+viable+single+cardiomyocytes+from+neonatal+to+aged+mice.">A simple antegrade perfusion method for isolating viable single cardiomyocytes from neonatal to aged mice.</a> Physiological Reports. 6 (9), 13688 (2018).</li><li>Omatsu-Kanbe, M., Fukunaga, R., Mi, X., Matsuura, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+antegrade+perfusion+method+for+cardiomyocyte+isolation+from+mice.">An antegrade perfusion method for cardiomyocyte isolation from mice.</a> Journal of Visualized Experiments. (171), e61866 (2021).</li><li>Bers, D. M., Patton, C. W., Nuccitelli, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+to+the+preparation+of+Ca2++buffers.">A practical guide to the preparation of Ca2+ buffers.</a> Methods in Cell Biology. 99, 126 (1994).</li><li>Grosso, D. S., Frangakis, C. J., Carlson, E. C., Bressler, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+myocytes+from+the+adult+rat+heart.">Isolation and characterization of myocytes from the adult rat heart.</a> Preparative Biochemistry. 7 (5), 383-401 (1977).</li><li>Thum, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Butadione+Monoxime+increases+the+viability+and+yield+of+adult+cardiomyocytes+in+primary+cultures.">Butadione Monoxime increases the viability and yield of adult cardiomyocytes in primary cultures.</a> Cardiovascular Toxicology. 1 (1), 61-72 (2001).</li><li>Wolska, B. M., Solaro, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+for+isolation+of+adult+mouse+cardiac+myocytes+for+studies+of+contraction+and+microfluorimetry.">Method for isolation of adult mouse cardiac myocytes for studies of contraction and microfluorimetry.</a> American Journal of Physiology. 271 (3), 1250-1255 (1996).</li></ol>

The principal advantage of our Langendorff-free cardiomyocyte isolation technique is that it limits hypoxia and ischemic time by not requiring cannulation to a Langendorff apparatus. Alternatively to classical Langendorff techniques that take several minutes to remove, clean, and hang the heart, often resulting in ischemic damage to the myocyte, our method includes an in vivo clearing of blood via an ice-cold clearing solution. The ice-cold clearing buffer contains ethylenediaminetetraacetic acid (EDTA)...

For decades, an essential idea in cardiac biology literature is the molecular mechanism of action. The mechanism of action must be established in order to publish reliable studies. A well-established strategy to determine molecular mechanism is isolated cardiomyocyte studies, which require high-quality cardiomyocytes for attaining trustable data. Cellular and molecular experiments performed on cardiomyocytes to determine mechanism of action are the gold standard for investigating contraction1, electrophysiology2, calcium (Ca2+) cycling3, myofilament Ca2+ sensitivity4, cytoskeleton5, metabolism6, effects of hormones7, signaling molecules8, drug studies9, etc. The mouse has become the species of choice for most cardiac biology experiments due to the ease of genetic manipulation, its small size, its relatively short lifespan, low cost, etc10. However, the reliable isolation of high-quality mouse cardiomyocytes is not trivial with current techniques.
Labs have been isolating cardiomyocytes for almost 70 years11. Virtually all techniques to isolate cardiomyocytes rely on digestion of the heart via various enzymes (collagenase, protease, trypsin, etc.). In the early periods (1950s-1960s), the chunk method was employed, which involved removing the heart, cutting into much smaller pieces and incubating in solution with collagenase/protease/trypsin12. In the 1970s labs implemented the ameliorated &#8220;Langendorff&#8221; method13, which isolated cardiomyocytes using a coronary artery perfusion-based isolation technique (retrograde perfusion with enzyme via the Langendorff apparatus); this technique remains the dominant method of myocyte isolation in the field today, ~50 years later14,15,16. Recent work has shifted to cannulating the heart in vivo to limit hypoxia time and ischemic damage resulting in superior cardiomyocyte isolations (better yields and higher quality)17. Recently, this has evolved into performing in vivo, Langendorff-free heart perfusions18,19,20,21,22. We have evolved the Langendorff-free cardiomyocyte isolation technique based on the Ackers-Johnson et al.18 technique and adapted various components from the many previous isolation techniques. These key adaptations include the injection of an ice-cold clearing buffer and the incorporation of a supporting platform to stabilize the needle, allowing for decreased manipulation of the heart. Also detailed in this technique is&#160; temperature control of injected buffers (37 &#176;C), which decreased the time between in vivo injection and digestion due to less EDTA perfusion as previously published18. By decreasing manipulation of the heart and therefore minimizing puncture site size, thorough and constant perfusion of the coronary arteries is obtained. We also refined the technique with a secondary chunk method digestion,&#160;the amount of EDTA in the injected clearing buffer, and changed the pH. Our described technique is more reliable, more efficient, and does not require the extensive training/practice compared to the using the Langendorff apparatus (Table 1).

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			<td>10 cc Bd Luer-Lok Syringe</td>
			<td>Fisher Sci</td>
			<td>14-827-52</td>
			<td></td>
		</tr>
		<tr>
			<td>10 mL Pyrex Low-Form Beaker</td>
			<td>Cole-Palmer</td>
			<td>UX-34502-01</td>
			<td></td>
		</tr>
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			<td>100 mL polypropylene cap glass media storage bottle</td>
			<td>DWK Life Sciences</td>
			<td>UX-34523-00</td>
			<td></td>
		</tr>
		<tr>
			<td>14 mL Round-Bottom Polypropylene Test Tubes With Cap</td>
			<td>Fisher Sci</td>
			<td>14-959-11B</td>
			<td></td>
		</tr>
		<tr>
			<td>2,3-Butanedione Monoxime</td>
			<td>Sigma</td>
			<td>B0753</td>
			<td>&#62;98%</td>
		</tr>
		<tr>
			<td>3 cc BD Luer-Lok Syringe</td>
			<td>Fisher Sci</td>
			<td>14-823-435</td>
			<td></td>
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		<tr>
			<td>35 mm glass bottom dishes</td>
			<td>MatTek Corporation</td>
			<td>P35G-1.0-20-C</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL BD Syringe without Needle</td>
			<td>Fisher Sci</td>
			<td>13-689-8</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL Conical Centrifuge Tubes</td>
			<td>Cole-Palmer</td>
			<td>EW-22999-84</td>
			<td></td>
		</tr>
		<tr>
			<td>95% O2 5% CO2</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>AIMS Space Gel Heating Pad</td>
			<td>Fisher Sci</td>
			<td>14-370-223</td>
			<td></td>
		</tr>
		<tr>
			<td>BD PrecisionGlide 27 G X 1/2&#34; Hypodermic Needles</td>
			<td>Becton Dickinson</td>
			<td>305109</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Sigma</td>
			<td>A3803</td>
			<td>Heat shock fraction, lyophilized powder, essentially fatty acid free, &#62;98%</td>
		</tr>
		<tr>
			<td>Calcium Chloride dihydrate</td>
			<td>Sigma</td>
			<td>C7902</td>
			<td>&#62;99%</td>
		</tr>
		<tr>
			<td>D-(+)-Glucose</td>
			<td>Sigma</td>
			<td>G7021</td>
			<td>Suitable for cell culture, &#62;99.5%</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Fisher Sci</td>
			<td>11965092</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Fisher Sci</td>
			<td>AAA1071336</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon 100 mm TC-treated Cell Culture Dish</td>
			<td>Corning</td>
			<td>353003</td>
			<td></td>
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		<tr>
			<td>FBS</td>
			<td>R&#38;D Systems (Bio-techne)</td>
			<td>S11195</td>
			<td></td>
		</tr>
		<tr>
			<td>Fisherbrand Isotemp Heated Immersion Circulators</td>
			<td>Fisher Sci</td>
			<td>13-874-432</td>
			<td></td>
		</tr>
		<tr>
			<td>Hartman Mosquito Hemostatic Forceps</td>
			<td>World Precision Instruments</td>
			<td>15921</td>
			<td></td>
		</tr>
		<tr>
			<td>Hausser Scientific Hy-Lite Counting Chamber Set</td>
			<td>Fisher Sci</td>
			<td>02-671-11</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>H4034</td>
			<td>&#62;99.5%</td>
		</tr>
		<tr>
			<td>Labeling Tape</td>
			<td>Fisher Sci</td>
			<td>15-901-10R</td>
			<td></td>
		</tr>
		<tr>
			<td>Legato 100 Syringe Pump</td>
			<td>kdScientific</td>
			<td>788100</td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutathione</td>
			<td>Fisher Sci</td>
			<td>ICN19467980</td>
			<td></td>
		</tr>
		<tr>
			<td>Liberase TH Research Grade</td>
			<td>Sigma</td>
			<td>5401135001</td>
			<td>High thermolysin concentration</td>
		</tr>
		<tr>
			<td>M199</td>
			<td>Fisher Sci</td>
			<td>MT10060CV</td>
			<td></td>
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		<tr>
			<td>Magnesium Chloride</td>
			<td>Invitrogen</td>
			<td>AM9530G</td>
			<td></td>
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			<td>Mouse Laminin</td>
			<td>Corning</td>
			<td>354232</td>
			<td></td>
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		<tr>
			<td>Pen/Strep</td>
			<td>Fisher Sci</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Sigma</td>
			<td>P5405</td>
			<td>&#62;99%</td>
		</tr>
		<tr>
			<td>Precision Digital Reciprocating Water Bath</td>
			<td>ThermoFisher Scientific</td>
			<td>TSCIR19</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate</td>
			<td>Sigma</td>
			<td>S5761</td>
			<td>Suitable for cell culture</td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Sigma</td>
			<td>S5886</td>
			<td>&#62;99%</td>
		</tr>
		<tr>
			<td>Sodium phosphate monobasic</td>
			<td>Sigma</td>
			<td>S5011</td>
			<td>&#62;99%</td>
		</tr>
		<tr>
			<td>Sterile Cell Strainer 70 &#181;m</td>
			<td>Fisher Sci</td>
			<td>22-363-548</td>
			<td></td>
		</tr>
		<tr>
			<td>Student Fine Scissors</td>
			<td>Fine Science Tools</td>
			<td>91460-11</td>
			<td></td>
		</tr>
		<tr>
			<td>VWR Absorbent Underpads</td>
			<td>Fisher Sci</td>
			<td>NC9481815</td>
			<td></td>
		</tr>
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</table>

a simple and effective method to consistently isolate mouse cardiomyocytes

The need for reproducible yet technically simple methods yielding high-quality cardiomyocytes is essential for research in cardiac biology. Cellular and molecular functional experiments (e.g., contraction, electrophysiology, calcium cycling, etc.) on cardiomyocytes are the gold standard for establishing mechanism(s) of disease. The mouse is the species of choice for functional experiments and the described technique is specifically for the isolation of mouse cardiomyocytes. Previous methods requiring a Langendorff apparatus require high levels of training and precision for aortic cannulation, often resulting in ischemia. The field is shifting toward Langendorff-free isolation methods that are simple, are reproducible, and yield viable myocytes for physiological data acquisition and culture. These methods greatly diminish ischemia time compared to aortic cannulation and result in reliably obtained cardiomyocytes. Our adaptation to the Langendorff-free method includes an initial perfusion with ice-cold clearing solution, use of a stabilizing platform that ensures a steady needle during perfusion, and additional digestion steps to ensure reliably obtained cardiomyocytes for use in functional measurements and culture. This method is simple and quick to perform and requires little technical skill.

There are a few elements to examine when determining the success of an isolation. First, the cardiomyocytes must be rod-shaped with no membrane blebs, such as the cells isolated in Figure 1. A typical isolation will yield ~80% of the myocytes being rod-shaped. If the isolation yields anything less than 50% rod-shaped cells, then it is considered an unsuccessful isolation and cardiomyocytes are not used. Lastly, the cardiomyocytes should be quiescent. Spontaneously contraction myocytes demons...

Watch this Scientific Journal Video about A Simple and Effective Method to Consistently Isolate Mouse Cardiomyocytes at JoVE.com

A Simple and Effective Method to Consistently Isolate Mouse Cardiomyocytes

The gold standard in cardiology for cellular and molecular functional experiments are cardiomyocytes. This article describes adaptations to the non-Langendorff technique to isolate mouse cardiomyocytes.

The need for reproducible yet technically simple methods yielding high-quality cardiomyocytes is essential for research in cardiac biology. Cellular and ...

This technique is more reliable and efficient and does not require extensive practice or training compared to the most commonly used Langendorff apparatus techniques. The main advantage of this technique is that it limits the ischemic time since the initial perfusion occurs in vivo. While performing this technique, it is essential to avoid bubbles in the manifold and to avoid excessive movement of the heart during digestion, these can decrease the yield.Demonstrating this technique will be Sarah Sturgill, a graduate student in Dr.Mark Ziolo's laboratory. Begin with clearing the temperature controlled manifold using freshly prepared perfusion buffer. To do so, screw in a 27 gauge needle and clear the bubbles using a luer lock connector.Ensure no bubbles remain. To isolate the cardiomyocyte, expose the sternum of the fully anesthetized mouse, and lateral to the midline, cut proximally through the ribs and to the axilla. Then cut through the diaphragm, ensuring shallow cuts to avoid the heart.Clamp the sternum with a hemostat and fold the ribs backward to expose the thoracic cavity. Remove the pericardium from the heart gently before cutting through the inferior vena cava immediately distal to the heart. Inject three milliliters of ice cold clearing buffer into the heart's right ventricle over one minute using a 27 gauge needle.Next, hold the heart using tweezers. Pull it away from the body and expose as much of the aorta as possible. Then clamp the ascending aorta using a hemostat and excise the heart.Quickly transfer the clamped heart to the lid of a polypropylene Petri dish containing 10 milliliters of warm perfusion buffer. Place the clamped heart into the supporting platform and inject 10 milliliters of temperature-controlled perfusion buffer at 37 degrees Celsius into the left ventricle over five minutes using a stabilized 27 gauge needle attached to the manifold. Next, transfer the clamped heart and supporting platform to a Petri dish with approximately five milliliters of digestion buffer.Exchange input syringes for a 50 milliliter syringe containing 25 milliliters of digestion Buffer. Clear the manifold of any bubbles and the remaining perfusion buffer before injection. Carefully replace the needle into the same needle position in the left ventricular apex.With the help of a perfusion pump, inject 37 degrees Celsius digestion buffer into the left ventricle for 15 minutes using a 50 milliliter syringe. Control the temperature of the solution with a water jacket calibrated to eject 37 degrees Celsius solution. Remove the ventricles from the atria before transferring them to a 10 milliliter beaker.Add three milliliters of digestion buffer to the beaker and cut the ventricles into large chunks using sharp scissors. Cover the beaker with aluminum foil and place it in a shaking water bath preheated to 37 degrees Celsius for five minutes. After discarding the supernatant, resuspend the tissue chunks in three milliliters of digestion buffer and triturate it for approximately four minutes or until a homogenous mixture is achieved.Once done, filter the cells into a 50 milliliter polypropylene tube using a 70 micrometer nylon cell strainer. Wash nylon cell strainer with three milliliters of digestion buffer. Return the filtrate to a 14 milliliter round bottom polypropylene tube and centrifuge it.Discard the supernatant before resuspending the pellet in three milliliters of stop buffer. To the cell suspension, add 54 microliters of 100 millimolar calcium chloride stock to make the final calcium chloride concentration 1.8 millimolar. Let the live cells settle for 10 minutes and remove the supernatant containing dead cells.After resuspending the pellet in a storage solution, the cells can be used for functional experiments and cultures. Brightfield microscope images of isolated cells showed that the isolation of mouse cardiomyocytes produced rod-shaped quiescent cells with no membrane blebs or rounded edges. The cells showed approximately 80%yield and high survival rates determining the success of the isolation technique.For successful isolation, it's most important to remove the bubbles from the manifold and insert the needle into the same hole in the heart. Once isolated, the cardiomyocytes can be used for cellular and molecular functional experiments.

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