This work was supported by funding from American Heart Association 12BGIA12040477, NC State University Chancellor&#8217;s Faculty Excellence Program, and National Natural Science Foundation of China H020381370216.

The following protocol is designed for the isolation of cardiomyocytes from one litter of neonatal rat pups (10-14 pups). If litter size is significantly different, the procedure may have to be scaled to compensate. The pups should be around 48&#177;6 hr old. All procedures herein have been approved by the North Carolina State University Institutional Animal Care and Usage Committee (IACUC).
1. Cell Isolation Preparation
NOTE: Perform the following steps the day before isolation.
<ol>
	<li>Autoclave the following: large scissors, small scissors, small sharp forceps, large forceps. Use a gravity cycle for 60 min at a minimum of 121 &#176;C and a drying time of 30 min.</li>
	<li>Place 40 ml of 0.1% trypsin solution in refrigerator to thaw O/N. Refrigerate Hank&#8217;s Balanced Salts Solution (HBSS) if not already cold. Prepare a 20% fetal bovine serum (FBS) stock media solution.
	<ol>
		<li>In 400 ml of Iscove&#39;s Modified Dulbecco&#39;s media (IMDM) add 100 ml FBS, 5 ml L-glutamine (200 mM), 2.5 ml gentamicin (10 mg ml-1), and 0.9 ml 2-mercaptoethanol. Sterilize using vacuum filter. Store media at 4&#176;C for up to 3 weeks and this is scalable for smaller or larger volumes. Dilute 20% FBS stock media 1:1 with IMDM to produce 10% FBS NRCM media. Only make in small batches to prevent repeated heating and cooling of media.</li>
	</ol>
	</li>
</ol>
2. Cell Isolation Day 1
<ol>
	<li>Perform the following work in a culture hood to prevent contamination of the samples. For best timing start this work in the afternoon since there is an O/N incubation.</li>
	<li>Prepare workspace inside a sterile culture hood. Place bench pad in culture hood. Fill two 250 ml beakers with 70% ethanol and place surgical tools in them. Place small bucket of ice in hood. Ensure that it is large enough to hold several tubes and a 150 mm dish. UV sterilize the hood for 10 min. Place 40 ml 0.1% trypsin on ice.</li>
	<li>Retrieve neonatal rat pups from the mother. To keep the animals warm until use, place them in an insulated container such as an ice bucket wrapped in a bench pad to keep them warm.</li>
	<li>Fill a 150 mm culture dish with 25 ml HBSS and place on ice. Unwrap 2-3 gauze pads and place in work area. Holding pup by the skin on the back of the neck, spray it with 70% ethanol and place in hood. NOTE: To best maintain sterility, this is can be done by another person who then places the cleaned pup in the hood.</li>
	<li>Hold the pup by the skin on the back of the neck. Then using the large scissors, in one quick, strong cut euthanize by decapitation. Blot the blood with gauze. NOTE: Due to variances in IACUC requirements, it may be more appropriate to clean the pup with an ethanol wipe rather than spraying it. Be sure to check with the university IACUC as to their guidelines for this step.</li>
	<li>Continue cutting down anterior side of chest through the ribcage. Squeeze the skin on the neck to help open the ribcage until the heart is visible. Using the small scissors, remove the heart and place in the HBSS culture dish on ice. Repeat for the other pups.</li>
	<li>Remove any non-heart tissue from the samples and swirl the HBSS gently to wash the hearts. Transfer the heart tissue to another culture dish containing fresh HBSS and further wash the tissue. Cut the tissue further until the pieces are 1-3 mm3, and then transfer to the trypsin solution. Place trypsin solution on rocker in 4&#176;C refrigerator O/N.</li>
</ol>
Cell Isolation Day 2
NOTE: While aspirating in the following steps, use a pipette rather than a vacuum line. The tissue moves easily, and a vacuum line will clog or remove tissue still containing cells. It is best to use a pipette for aspiration instead. If tissue enters the pipette, pipette back out to remove it.
<ol>
	<li>Make three aliquots of 10% NRCM Media: one with 25 ml and two with 15 ml. Place one 25 ml tube of media in 37 &#176;C water bath. Add 4 ml HBSS to 5 different 15 ml conical tubes and place all on ice. Label each 15 ml tube #1-5.</li>
	<li>Add 40 ml HBSS to a 50 ml conical tube. Add 10 ml of HBSS to collagenase, pipette to suspend, and combine the solutions to create 50 ml of 1 mg ml-1 collagenase solution. Sterilize using 0.22 &#181;m vacuum filter, and store at RT.</li>
	<li>Retrieve heart tissue/trypsin tube. Ensure that trypsin is clear, and the tissue appears fluffy. Allow the tissue to settle to corner of tube and aspirate as much liquid as possible.</li>
	<li>Add 25 ml warm 10% FBS NRCM media to the tube and swirl by hand. Cap and rotate in 37 &#176;C water bath for 2 min. Aspirate liquid again. The tissue should float at this step; if so, aspirate from the bottom of the tube.</li>
	<li>Add 10 ml collagenase. Rotate in water bath for 2 min or until the solution is cloudy. Quickly aspirate the liquid. Add 10 ml fresh collagenase to tube containing the tissue and rotate in water bath for 2 min. Pipette to mix, transfer solution to tube #1, and place on ice. It may not be possible to remove all of the liquid. Repeat steps 3.2-3.6 for the other three 15 ml conical tubes. Transfer any remaining liquid to tube # 5.</li>
	<li>Centrifuge 15 ml tubes at 410 rcf for 8 min. While centrifuging, place 15 ml 10% FBS NRCM media tube in water bath. Place 40 &#181;m cell strainer on top of a 50 ml conical tube and wet with 2 ml cold HBSS.</li>
	<li>Aspirate supernatant from spun down cells. Add 6 ml cold HBSS to each tube and resuspend. Pipette cell suspensions through the strainer into 50 ml conical to remove any tissue. Rinse sides of each 15 ml tube with 3 ml cold HBSS and add to strainer. Centrifuge cells at 410 rcf for 10 min. Aspirate supernatant. Resuspend cell pellet in 10 ml 10% FBS NRCM media and transfer to T-75 flask. Rinse conical with 5ml media and add to flask.</li>
	<li>Incubate for 1 h at 37 &#176;C and 5% CO2. Place last 15 ml 10% FBS NRCM media tube into water bath. Transfer contents of T-75 to a new T-175 flask, rinse T-75 with 15 ml media and add to T-175. Incubate for 1 hr.</li>
</ol>
4. Cryopreservation
<ol>
	<li>Place freezing media on ice. Transfer cell media from T-175 to 50 ml conical tube, and collect 10 &#181;l&#160;of cell suspension for cell counting using Trypan blue. Centrifuge at 410 rcf for 5 min. While centrifuging, count cells using a cell counter.</li>
	<li>Aspirate culture media, and resuspend cells in freezing media at a concentration of 2-4 million cells per ml. Place 1 ml of cell suspension in cryogenic vial, then place vials a controlled cooling rate freezing container, and place in -80 &#176;C freezer O/N. Within 1-2 days, transfer vials in liquid nitrogen.</li>
</ol>
5. Thawing Cells
<ol>
	<li>Coat dish in fibronectin by dissolving 250 &#181;l&#160;of fibronectin (stock concentration 1 mg ml-1) into 9.75 ml water (final concentration 0.025 mg ml-1). Add enough solution to cover culture plate and incubate at 37oC for at least 30 min.
	<ol>
		<li>In four 15 ml&#160;conical tubes, make the DMSO/media mixtures as follows by adding DMSO to 20% Media. Add (5%) 9.5 ml media with 500 &#181;l&#160;DMSO. Add (2.5%) 9.75 ml media with 250 &#181;l&#160;DMSO. Add 10 ml&#160;media (make two of these).</li>
	</ol>
	</li>
	<li>Heat the aforementioned media mixtures in 37 &#176;C water bath. Remove cells from liquid nitrogen and place on dry ice. When media mixtures are warm, thaw cells in 37 &#176;C water bath until just thawed. Do not leave cells in water bath for too long as this may cause damage to the cells.</li>
	<li>Transfer contents of cryogenic vial to 5% DMSO/media tube. Centrifuge at 410 rcf for 8 min. Aspirate supernatant leaving cell pellet. Add contents of 2.5% DMSO/media tube to cell pellet and resuspend. Centrifuge at 410 rcf for 8 min. Aspirate supernatant leaving cell pellet.</li>
	<li>Add contents of one 0% DMSO/media tube to cell pellet and resuspend. Centrifuge at 410 rcf for 8 min. Aspirate supernatant leaving cell pellet.</li>
	<li>Add contents of second 0% DMSO/media to cell pellet and resuspend. Take small sample for cell counting. Centrifuge at 410 rcf for 8 min. While centrifuging count cells in a haemocytometer using Trypan Blue to label dead cells. Record cell amount, as well as viability.</li>
	<li>Aspirate supernatant leaving cell pellet. Resuspend in 10% NRCM media (optional: add 100 &#181;M bromodeoxyuridine (BrdU)) and plate cells on fibronectin-coated dishes.</li>
</ol>
6. Cell Culture
<ol>
	<li>Plate cells at about 100k cells per cm2. Adjust the plating density based on the intended use of the culture. Prepare 2% NRCM media by diluting 20% Media in IMDM in a 1:10 ratio. The following is an outline of a typical culture.</li>
	<li>On day 1, rinse dead cells away with warm IMDM, add 10% NRCM (optional 100 &#181;M BrdU). On day 2, rinse dead cells away with warm IMDM, add 10% NRCM. Day 3&#8212;add 2% NRCM. On day 4 add 2% NRCM. On day 5 ensure that the cells are confluent and beating. Maintain cells in culture for around one week. At that point fibroblasts may begin to significantly outgrow the NRCMs.</li>
</ol>

<ol>
	<li>Louch, W. E., Sheehan, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+in+cardiomyocyte+isolation,+culture,+and+gene+transfer.">Methods in cardiomyocyte isolation, culture, and gene transfer.</a> Journal of Molecular and Cellular Cardiology. 51 (3), 288-298 (2011).</li><li>Miragoli, M., Salvarani, N., Rohr, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myofibroblasts+Induce+Ectopic+Activity+in+Cardiac+Tissue.">Myofibroblasts Induce Ectopic Activity in Cardiac Tissue.</a> Circulation Research. 101, 755-758 (2007).</li><li>Simpson, P., Savion, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+rat+myocytes+in+single+cell+cultures+with+and+without+proliferating+nonmyocardial+cells.+Cross-striations,+ultrastructure,+and+chronotropic+response+to+isoproterenol.">Differentiation of rat myocytes in single cell cultures with and without proliferating nonmyocardial cells. Cross-striations, ultrastructure, and chronotropic response to isoproterenol.</a> Circulation Research. 50 (1), 101-116 (1982).</li><li>Simpson, P., McGrath, a., Savion, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myocyte+hypertrophy+in+neonatal+rat+heart+cultures+and+its+regulation+by+serum+and+by+catecholamines.">Myocyte hypertrophy in neonatal rat heart cultures and its regulation by serum and by catecholamines.</a> Circulation Research. 51 (6), 787-801 (1982).</li><li>Rohr, S., Fl&#252;ckiger-Labrada, R., Kucera, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photolithographically+defined+deposition+of+attachment+factors+as+a+versatile+method+for+patterning+the+growth+of+different+cell+types+in+culture.">Photolithographically defined deposition of attachment factors as a versatile method for patterning the growth of different cell types in culture.</a> Pfl&#252;gers Archive : European Journal of Physiology. 446 (1), 125-132 (2003).</li><li>Zhang, B., Green, J. V., Murthy, S. K., Radisic, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Label-free+enrichment+of+functional+cardiomyocytes+using+microfluidic+deterministic+lateral+flow+displacement.">Label-free enrichment of functional cardiomyocytes using microfluidic deterministic lateral flow displacement.</a> PloS One. 7 (5), e37619 (2012).</li><li>Boateng, S. Y., Hartman, T. J., Ahluwalia, N., Vidula, H., Desai, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+fibroblast+proliferation+in+cardiac+myocyte+cultures+by+surface+microtopography.">Inhibition of fibroblast proliferation in cardiac myocyte cultures by surface microtopography.</a> American Journal of Physiology. Cell Physiology. 285 (1), C171-C182 (2003).</li><li>Fu, J. -. D., Li, 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=Crucial+role+of+the+sarcoplasmic+reticulum+in+the+developmental+regulation+of+Ca2++transients+and+contraction+in+cardiomyocytes+derived+from+embryonic+stem+cells.">Crucial role of the sarcoplasmic reticulum in the developmental regulation of Ca2+ transients and contraction in cardiomyocytes derived from embryonic stem cells.</a> FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology. 20 (1), 181-183 (2006).</li><li>Liu, J., Fu, J. D., Siu, C. W., Li, 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+Functional+sarcoplasmic+reticulum+for+calcium+handling+of+human+embryonic+stem+cell-derived+cardiomyocytes:+insights+for+driven+maturation.">a Functional sarcoplasmic reticulum for calcium handling of human embryonic stem cell-derived cardiomyocytes: insights for driven maturation.</a> Stem Cells. 25 (12), 3038-3044 (2007).</li><li>Knollmann, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induced+pluripotent+stem+cell-derived+cardiomyocytes:+boutique+science+or+valuable+arrhythmia+model.">Induced pluripotent stem cell-derived cardiomyocytes: boutique science or valuable arrhythmia model.</a> Circulation Research. 112 (6), 969-976 (2013).</li><li>Uchida, T., Nagayama, M., Taira, T., Shimizu, K., Sakai, M., Gohara, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimal+temperature+range+for+low-temperature+preservation+of+dissociated+neonatal+rat+cardiomyocytes.">Optimal temperature range for low-temperature preservation of dissociated neonatal rat cardiomyocytes.</a> Cryobiology. 63 (3), 279-284 (2011).</li><li>Miyamura, K., Nagayama, 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=Evaluation+of+viability+of+cryopreserved+rat+cardiac+myocytes+and+effects+of+dimethyl+sulfoxide+concentration+on+cryopreservation.">Evaluation of viability of cryopreserved rat cardiac myocytes and effects of dimethyl sulfoxide concentration on cryopreservation.</a> Cryobiology. 59 (3), 375 (2010).</li><li>Rana, P., Anson, B., Engle, S., Will, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+human-induced+pluripotent+stem+cell-derived+cardiomyocytes:+bioenergetics+and+utilization+in+safety+screening.">Characterization of human-induced pluripotent stem cell-derived cardiomyocytes: bioenergetics and utilization in safety screening.</a> Toxicological Sciences: An Official Journal of the Society of Toxicology. 130 (1), 117-131 (2012).</li><li>Yokomuro, H., Mickle, D. a. G., Weisel, R. D., Li, R. -. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimal+conditions+for+heart+cell+cryopreservation+for+transplantation.">Optimal conditions for heart cell cryopreservation for transplantation.</a> Molecular and Cellular Biochemistry. 242 (1-2), 109-114 (2003).</li><li>Simpson, P., McGrath, a., Savion, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myocyte+hypertrophy+in+neonatal+rat+heart+cultures+and+its+regulation+by+serum+and+by+catecholamines.">Myocyte hypertrophy in neonatal rat heart cultures and its regulation by serum and by catecholamines.</a> Circulation Research. 51 (6), 787-801 (1982).</li><li>Evans, H. J., Western Goodwin, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=array+analysis+of+cell+cycle+protein+changes+during+the+hyperplastic+to+hypertrophic+transition+in+heart+development.">array analysis of cell cycle protein changes during the hyperplastic to hypertrophic transition in heart development.</a> Molecular and Cellular Biochemistry. 303 (1-2), 189-199 (2007).</li><li>Golden, H. B., Gollapudi, D., 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=Methods+in+Molecular+Biology.">Methods in Molecular Biology.</a> , 205-214 (2012).</li><li>Zlochiver, S., Mu&#241;oz, V., Vikstrom, K. L., Taffet, S. M., Berenfeld, O., Jalife, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrotonic+myofibroblast-to-myocyte+coupling+increases+propensity+to+reentrant+arrhythmias+in+two-dimensional+cardiac+monolayers.">Electrotonic myofibroblast-to-myocyte coupling increases propensity to reentrant arrhythmias in two-dimensional cardiac monolayers.</a> Biophysical Journal. 95 (9), 4469-4480 (2008).</li><li>Chang, M. G., Zhang, 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=Spiral+waves+and+reentry+dynamics+in+an+in+vitro+model+of+the+healed+infarct+border+zone.">Spiral waves and reentry dynamics in an in vitro model of the healed infarct border zone.</a> Circulation Research. 105 (11), 1062-1071 (2009).</li></ol>

The authors have nothing to disclose.

This protocol allows for the NRCMs to be isolated, cryopreserved, and thawed. Thawing the cells is a crucial portion of the procedure. A series of DMSO dilutions is used to slowly remove DMSO from the cells14. It is important that the extraction of DMSO be performed quickly as the cells are particularly sensitive to dying immediately after thawing. If more or less cells are required for thawing, the volumes of the DMSO solutions can be scaled as needed.
One challenge to NRCM isolati...

Cell culture of cardiomyocytes is a critical tool in modern cardiac research. Neonatal rat cardiomyocytes (NRCMs) are commonly used since the isolation and culture is easier than that of adult rat cardiomyocytes1. The NRCM method still has several limitations including a long isolation procedure and limited cell proliferation in the dish. There are numerous protocols for the isolation of NRCMs with most generally requiring 4-48 hr of work2&#8211;6. In addition, the cells are frequently isolated from 1 to 2-day old rat pups2,4&#8211;7; the timing of the birth can be unpredictable and conflict with other work in the lab. The isolations can be inefficient and wasteful if only a small amount of cells are needed for experiments. Most efforts on improving the workflow focus on reducing the isolation time, yet this does not solve the problems of timing the birth of the pups.
As alternatives, many labs utilize cardiomyocytes derived from embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs). However, the reprogramming and/or differentiation process can be very time consuming and costly as well. There can be other problems when using these cells as in vitro myocyte models. Both ESC- and iPSC- derived cardiomyocytes have been shown to exhibit differences in electrophysiology from primary cardiomyocytes8&#8211;10.
Dissociated NRCMs are capable of being stored for several days using refrigeration11, yet this does allow for long term storage. Liquid nitrogen is typically used to preserve cells for a greater period of time, but requires a cryoprotectant such as dimethyl sulfoxide (DMSO). Previous research has shown that the ideal concentration between 5-10% DMSO in the freezing media allows for cryopreservation of NRCMs, yet even then the viability remains low12. Although DMSO helps protect the cells during freezing, it can be toxic to cells at concentrations above 1.5%13. Previous studies have shown that slowly removing DMSO from the cells, may improve cell viability14.
We sought to improve the efficiency of NRCM cell-based assays by cryopreserving the cells following isolation. This allows for the cells to be thawed and used when necessary, reducing the frequency of isolations and consumption of animals. Using this method, we show that it is possible to cryopreserve NRCMs and thaw them for use at a later time. After thawing the cells maintain an acceptable viability and produce NRCM cultures that are positive for &#945;-sarcomeric actinin (&#945;-SA) and contract spontaneously.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>IMDM (+25mM HEPES +L-glutamine)</td>
			<td>Gibco</td>
			<td>12440-046</td>
			<td>With added 25mM HEPES and L-glutamine</td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Gibco</td>
			<td>25030-081</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Hyclone</td>
			<td>SH30070.03</td>
			<td></td>
		</tr>
		<tr>
			<td>Gentamicin</td>
			<td>Gibco</td>
			<td>15710-064</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol</td>
			<td>Gibco</td>
			<td>21985-023</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS (+Ca +Mg)</td>
			<td>Corning</td>
			<td>21-020-CV</td>
			<td>With added calcium and magnesium, pH 7.1-7.4</td>
		</tr>
		<tr>
			<td>Trypsin 0.25%</td>
			<td>Gibco</td>
			<td>25300-056</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin 0.05%</td>
			<td>Gibco</td>
			<td>25300-054</td>
			<td></td>
		</tr>
		<tr>
			<td>Cryostor CS5</td>
			<td>BioLife Solutions</td>
			<td>205102</td>
			<td>Freezing media</td>
		</tr>
		<tr>
			<td>Cryogenic Vial</td>
			<td>Corning</td>
			<td>430659</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase</td>
			<td>Sigma</td>
			<td>C1889-50MG</td>
			<td></td>
		</tr>
		<tr>
			<td>40&#956;m Cell Strainer</td>
			<td>Greiner Bio-One</td>
			<td>542040</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilizing Vacuum Filter (0.22&#956;m)</td>
			<td>Corning</td>
			<td>431118</td>
			<td></td>
		</tr>
		<tr>
			<td>50mL Conical</td>
			<td>Corning</td>
			<td>430828</td>
			<td></td>
		</tr>
		<tr>
			<td>15mL Conical</td>
			<td>Corning</td>
			<td>430790</td>
			<td></td>
		</tr>
		<tr>
			<td>trypan blue</td>
			<td>Cellgro</td>
			<td>25-900-CI</td>
			<td></td>
		</tr>
		<tr>
			<td>Mr Frosty Freezing Container</td>
			<td>ThermoScientific</td>
			<td>5100-0001</td>
			<td></td>
		</tr>
		<tr>
			<td>Millicell EZ&#160;SLIDES</td>
			<td>Millipore</td>
			<td>PEZGS0416</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;-sarcomeric actinin antibody</td>
			<td>Sigma</td>
			<td>A7811</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibronectin</td>
			<td>Corning</td>
			<td>356008</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromodeoxyuridine</td>
			<td>BD Biosciences</td>
			<td>51-7581KZ</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation and cryopreservation of neonatal rat cardiomyocytes

Cell culture has become increasingly important in cardiac research, but due to the limited proliferation of cardiomyocytes, culturing cardiomyocytes is difficult and time consuming. The most commonly used cells are neonatal rat cardiomyocytes (NRCMs), which require isolation every time cells are needed. The birth of the rats can be unpredictable. Cryopreservation is proposed to allow for cells to be stored until needed, yet freezing/thawing methods for primary cardiomyocytes are challenging due to the sensitivity of the cells. Using the proper cryoprotectant, dimethyl sulfoxide (DMSO), cryopreservation was achieved. By slowly extracting the DMSO while thawing the cells, cultures were obtained with viable NRCMs. NRCM phenotype was verified using immunocytochemistry staining for &#945;-sarcomeric actinin. In addition, cells also showed spontaneous contraction after several days in culture. Cell viability after thawing was acceptable at 40-60%. In spite of this, the methods outlined allow one to easily cryopreserve and thaw NRCMs. This gives researchers a greater amount of flexibility in planning experiments as well as reducing the use of animals.

Following the isolation of the neonatal rat cardiomyocytes, the cells are frozen down to liquid nitrogen, and can be stored for at least several months. Typically upon thawing, the viability determined by Trypan Blue analysis will be between 40-60%. Though this is lower than other cell types, with proper seeding and culture the cells will proliferate (Figure 1). In order to verify contractility, the cells can be imaged using a phase contrast microscopy. The cells should begin to spontaneously contract wi...

Watch this Scientific Journal Video about Isolation and Cryopreservation of Neonatal Rat Cardiomyocytes at JoVE.com

Isolation and Cryopreservation of Neonatal Rat Cardiomyocytes

The isolation of neonatal rat cardiomyocytes is a time consuming and unpredictable procedure. This study describes methods for cryopreservation and thawing of neonatal rat cardiomyocytes that allows for more efficient use of cells. The thawed NRCMs can be used for various experiments without the need for performing isolations each time.

Cell culture has become increasingly important in cardiac research, but due to the limited proliferation of cardiomyocytes, culturing cardiomyocytes is ...

isolation-and-cryopreservation-of-neonatal-rat-cardiomyocytes

Research

JoVE Journal

Developmental Biology

12.4K visualizações.  College of Veterinary Medicine, North Carolina State University. The isolation of neonatal rat cardiomyocytes is a time consuming and unpredictable procedure. This study describes methods for cryopreservation and thawing of neonatal rat cardiomyocytes that allows for more efficient use of cells. The thawed NRCMs can be used for various experiments without the need for performing isolations each time.

Vídeo: Isolation and Cryopreservation of Neonatal Rat Cardiomyocytes

Isolation of Neural Stem/Progenitor Cells from the Periventricular Region of the Adult Rat and Human Spinal Cord

Adult rat and human spinal cord neural stem/progenitor cells (NSPCs) cultured in growth factor-enriched medium allows for the proliferation of multipotent, self-renewing, and expandable neural stem cells. In serum conditions, these multipotent NSPCs will differentiate, generating neurons, astrocytes, and oligodendrocytes. The harvested tissue is enzymatically dissociated in a papain-EDTA solution and then mechanically dissociated and separated through a discontinuous density gradient to yield a single cell suspension which is plated in neurobasal medium supplemented with epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and heparin. Adult rat spinal cord NSPCs are cultured as free-floating neurospheres and adult human spinal cord NSPCs are grown as adherent cultures. Under these conditions, adult spinal cord NSPCs proliferate, express markers of precursor cells, and can be continuously expanded upon passage. These cells can be studied in vitro in response to various stimuli, and exogenous factors may be used to promote lineage restriction to examine neural stem cell differentiation. Multipotent NSPCs or their progeny can also be transplanted into various animal models to assess regenerative repair.

The adult mammalian spinal cord contains neural stem/progenitor cells (NSPCs) that can be isolated and expanded in culture. This protocol describes the harvesting, isolation, culture, and passaging of NSPCs generated from the periventricular region of the adult spinal cord from the rat and from human organ transplant donors.

Adult rat and human spinal cord neural stem/progenitor cells (NSPCs) cultured in growth factor-enriched medium allows for the proliferation of ...

Isolation and Characterization of Satellite Cells from Rat Head Branchiomeric Muscles

Fibrosis and defective muscle regeneration can hamper the functional recovery of the soft palate muscles after cleft palate repair. This causes persistent problems in speech, swallowing, and sucking. In vitro culture systems that allow the study of satellite cells (myogenic stem cells) from head muscles are crucial to develop new therapies based on tissue engineering to promote muscle regeneration after surgery. These systems will offer new perspectives for the treatment of cleft palate patients. A protocol for the isolation, culture and differentiation of satellite cells from head muscles is presented. The isolation is based on enzymatic digestion and trituration to release the satellite cells. In addition, this protocol comprises an innovative method using extracellular matrix gel coatings of millimeter size, which requires only low numbers of satellite cells for differentiation assays.

This protocol describes the isolation of satellite cells from branchiomeric head muscles of a 9 week-old rat. The muscles originate from different branchial arches. Subsequently, the satellite cells are cultured on a spot coating of millimeter size to study their differentiation. This approach avoids the expansion and passaging of satellite cells.

Fibrosis and defective muscle regeneration can hamper the functional recovery of the soft palate muscles after cleft palate repair. This causes persistent ...

Improved Generation of Induced Cardiomyocytes Using a Polycistronic Construct Expressing Optimal Ratio of Gata4, Mef2c and Tbx5

Direct conversion of cardiac fibroblasts (CFs) into induced cardiomyocytes (iCMs) holds great potential for regenerative medicine by offering alternative strategies for treatment of heart disease. This conversion has been achieved by forced expression of defined factors such as Gata4 (G), Mef2c (M) and Tbx5 (T). Traditionally, iCMs are generated by a cocktail of viruses expressing these individual factors. However, reprogramming efficiency is relatively low and most of the in vitro G,M,T-transduced fibroblasts do not become fully reprogrammed, making it difficult to study the reprogramming mechanisms. We recently have shown that the stoichiometry of G,M,T is crucial for efficient iCM reprogramming. An optimal stoichiometry of G,M,T with relative high level of M and low levels of G and T achieved by using our polycistronic MGT vector (hereafter referred to as MGT) significantly increased reprogramming efficiency and improved iCM quality in vitro. Here we provide a detailed description of the methodology used to generate iCMs with MGT construct from cardiac fibroblasts. Isolation of cardiac fibroblasts, generation of virus for reprogramming and evaluation of the reprogramming process are also included to provide a platform for efficient and reproducible generation of iCMs.

We describe here a protocol for the generation of iCMs using retrovirus-mediated delivery of Gata4, Tbx5 and Mef2c in a polycistronic construct. This protocol yields a relatively homogeneous population of reprogrammed cells with improved efficiency and quality and is valuable for future studies of iCM reprogramming.

Direct conversion of cardiac fibroblasts (CFs) into induced cardiomyocytes (iCMs) holds great potential for regenerative medicine by offering alternative ...

Isolation of Murine Embryonic Hemogenic Endothelial Cells

The specification of hemogenic endothelial cells from embryonic vascular endothelium occurs during brief developmental periods within distinct tissues, and is necessary for the emergence of definitive HSPC from the murine extra embryonic yolk sac, placenta, umbilical vessels, and the embryonic aorta-gonad-mesonephros (AGM) region. The transient nature and small size of this cell population renders its reproducible isolation for careful quantification and experimental applications technically difficult. We have established a fluorescence-activated cell sorting (FACS)-based protocol for simultaneous isolation of hemogenic endothelial cells and HSPC during their peak generation times in the yolk sac and AGM. We demonstrate methods for dissection of yolk sac and AGM tissues from mouse embryos, and we present optimized tissue digestion and antibody conjugation conditions for maximal cell survival prior to identification and retrieval via FACS. Representative FACS analysis plots are shown that identify the hemogenic endothelial cell and HSPC phenotypes, and describe a methylcellulose-based assay for evaluating their blood forming potential on a clonal level.

Hematopoietic stem and progenitor cells (HSPC) derive from specialized (hemogenic) endothelial cells during development, yet little is known about the process by which some endothelial cells specify to become blood forming. We demonstrate a flow-cytometry based method allowing simultaneous isolation of hemogenic endothelial cells and HSPC from murine embryonic tissues.

The specification of hemogenic endothelial cells from embryonic vascular endothelium occurs during brief developmental periods within distinct tissues, ...

Effective Isolation of Functional Islets from Neonatal Mouse Pancreas

Perfusion-based islet-isolation protocols from large mammalian pancreata are well established. Such protocols are readily conducted in many laboratories due to the large size of the pancreatic duct that allows for ready collagenase injection and subsequent tissue perfusion. In contrast, islet isolation from small pancreata, like that of neonatal mice, is challenging because perfusion is not readily achievable in the small pancreata. Here we describe a detailed simple procedure that recovers substantial numbers of islets from newly born mice with visual assistance. Freshly dissected whole pancreata were digested with 0.5 mg/mL collagenase IV dissolved in Hanks&#39; Balanced Salt Solution (HBSS) at 37 &#176;C, in microcentrifuge tubes. Tubes were tapped regularly to aid tissue dispersal. When most of the tissue was dispersed to small clusters around 1 mm, lysates were washed three to four times with culture media with 10% fetal bovine serum (FBS). Islet clusters, devoid of recognizable acinar tissues, can then be recovered under dissecting stereoscope. This method recovers 20 - 80 small- to large-sized islets per pancreas of newly born mouse. These islets are suitable for most conceivable downstream assays, including insulin secretion, gene expression, and culture. An example of insulin secretion assay is presented to validate the isolation process. The genetic background and degree of digestion are the largest factors determining the yield. Freshly made collagenase solution with high activity is preferred, as it aids in endocrine-exocrine isolation. The presence of cations [calcium (Ca2+) and magnesium (Mg2+)] in all solutions and fetal bovine serum in the wash/picking media are necessary for good yield of islets with proper integrity. A dissecting scope with good contrast and magnification will also help.

We describe a protocol herein for isolating intact islets from neonatal mice. Pancreata were partially digested with collagenase, followed by washing and hand picking. 20 - 80 islet clusters can be obtained per pancreas from newly born mice, which are suitable for several islet studies.

Perfusion-based islet-isolation protocols from large mammalian pancreata are well established. Such protocols are readily conducted in many laboratories ...

Visualization of Cell Cycle Variations and Determination of Nucleation in Postnatal Cardiomyocytes

Cardiomyocytes are prone to variations of the cell cycle, such as endoreduplication (continuing rounds of DNA synthesis without karyokinesis and cytokinesis) and acytokinetic mitosis (karyokinesis but no cytokinesis). Such atypical cell cycle variations result in polyploid and multinucleated cells rather than in cell division. Therefore, to determine cardiac turnover and regeneration, it is of crucial importance to correctly identify cardiomyocyte nuclei, the number of nuclei per cell, and their cell cycle status. This is especially true for the use of nuclear markers for identifying cell cycle activity, such as thymidine analogues Ki-67, PCNA, or pHH3. Here, we present methods for recognizing cardiomyocytes and their nuclearity and for determining their cell cycle activity. We use two published transgenic systems: the Myh6-H2B-mCh transgenic mouse line, for the unequivocal identification of cardiomyocyte nuclei, and the CAG-eGFP-anillin mouse line, for distinguishing cell division from cell cycle variations. Combined together, these two systems ease the study of cardiac regeneration and plasticity.

To distinguish cell division from cell cycle variations in cardiomyocytes, we present protocols using two transgenic mouse lines: Myh6-H2B-mCh transgenic mice, for the unequivocal identification of cardiomyocyte nuclei, and CAG-eGFP-anillin mice, for distinguishing cell division from cell cycle variations.

Cardiomyocytes are prone to variations of the cell cycle, such as endoreduplication (continuing rounds of DNA synthesis without karyokinesis and ...

Bottlenose Dolphin (Tursiops truncatus) Spermatozoa: Collection, Cryopreservation, and Heterologous In Vitro Fertilization

The use of cryopreserved dolphin spermatozoa facilitates the exchange of genetic material between aquatic parks and makes spermatozoa accessible to laboratories for studies to further our understanding of marine mammal reproduction. Heterologous IVF, a replacement for homologous IVF, could provide a means to test the sperm fertility potential; to study gamete physiology and early embryo development; and to avoid the use of valuable dolphin oocytes, which are difficult to obtain. Here, we present protocols that have been successfully used to collect and cryopreserve dolphin spermatozoa. The collection of semen is performed by manual stimulation on trained dolphins. Cryopreservation is accomplished using a TRIS egg-yolk based extender with glycerol. In addition, we present a protocol that describes heterologous IVF using dolphin spermatozoa and bovine oocytes and that verifies the hybrid nature of the resulting embryo using PCR. Heterologous fertilization raises questions on fertilization and can be used as a tool to study gamete physiology and early embryo development. In addition, the success of heterologous IVF demonstrates the potential of this technique to test dolphin sperm fertilizing capacity, which is worth further examination.

Bottlenose Dolphin Tursiops truncatus Spermatozoa: Collection, Cryopreservation, and Heterologous In Vitro Fertilization

Here, we present protocols that have been successfully used for dolphin spermatozoa collection, cryopreservation, and heterologous IVF performance using bovine oocytes.

The use of cryopreserved dolphin spermatozoa facilitates the exchange of genetic material between aquatic parks and makes spermatozoa accessible to ...

Maturation of Human Stem Cell-derived Cardiomyocytes in Biowires Using Electrical Stimulation

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have been a promising cell source and have thus encouraged the investigation of their potential applications in cardiac research, including drug discovery, disease modeling, tissue engineering, and regenerative medicine. However, cells produced by existing protocols display a range of immaturity compared with native adult ventricular cardiomyocytes. Many efforts have been made to mature hPSC-CMs, with only moderate maturation attained thus far. Therefore, an engineered system, called biowire, has been devised by providing both physical and electrical cues to lead hPSC-CMs to a more mature state in vitro. The system uses a microfabricated platform to seed hPSC-CMs in collagen type I gel along a rigid template suture to assemble into aligned cardiac tissue (biowire), which is subjected to electrical field stimulation with a progressively increasing frequency. Compared to nonstimulated controls, stimulated biowired cardiomyocytes exhibit an enhanced degree of structural and electrophysiological maturation. Such changes are dependent upon the stimulation rate. This manuscript describes in detail the design and creation of biowires.

The cardiac biowire platform is an in vitro method used to mature human embryonic and induced pluripotent stem cell-derived cardiomyocytes (hPSC-CM) by combining three-dimensional cell cultivation with electrical stimulation. This manuscript presents the detailed setup of the cardiac biowire platform.

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have been a promising cell source and have thus encouraged the investigation of their ...

Isolation and Characterization of Primary Rat Valve Interstitial Cells: A New Model to Study Aortic Valve Calcification

Calcific aortic valve disease (CAVD) is characterized by the progressive thickening of the aortic valve leaflets. It is a condition frequently found in the elderly and end-stage renal disease (ESRD) patients, who commonly suffer from hyperphosphatemia and hypercalcemia. At present, there are no medication therapies that can stop its progression. The mechanisms that underlie this pathological process remain unclear. The aortic valve leaflet is composed of a thin layer of valve endothelial cells (VECs) on the outer surfaces of the aortic cusps, with valve interstitial cells (VICs) sandwiched between the VECs. The use of a rat model enables the in vitro study of ectopic calcification based on the in vivo physiopathological serum phosphate (Pi) and calcium (Ca) levels of patients who suffer from hyperphosphatemia and hypercalcemia. The described protocol details the isolation of a pure rat VIC population as shown by the expression of VIC markers: alpha-smooth muscle actin (&#945;-SMA) vimentin and tissue growth factor beta (TGF&#946;) 1 and 2, and the absence of cluster of differentiation (CD) 31, a VEC marker. By expanding these VICs, biochemical, genetic, and imaging studies can be performed to study and unravel the key mediators underpinning CAVD.

This protocol describes the isolation, culture, and calcification of rat-derived valve interstitial cells, a highly physiological in vitro model of calcific aortic valve disease (CAVD). Exploitation of this rat model facilitates CAVD research in exploring the cell and molecular mechanisms that underlie this complex pathological process.

Calcific aortic valve disease (CAVD) is characterized by the progressive thickening of the aortic valve leaflets. It is a condition frequently found in ...

Handling and Treatment of Male European Eels (Anguilla anguilla) for Hormonal Maturation and Sperm Cryopreservation

During the last years, several research groups have been working on the development and improvement of new protocols for the European eel handling and maturation. As of yet, weekly injections of human chorionic gonadotropin (hCG) have proved to maturate males after just 5-6 weeks of treatment, producing high volumes of high-quality sperm during several weeks. In addition, sperm cryopreservation protocols using different extenders, cryoprotectants and cooling and thawing times have been previously described for European eel. Here, we show that Tanaka&#180;s extender solution can be directly used for fertilization or for cryopreservation, making unnecessary the usage of different types of solutions and dilutions. Furthermore, the use of methanol as a cryoprotectant makes this protocol easy to use as methanol has low toxicity and does not activate the sperm. The sperm does not need to be cryopreserved immediately after the addition of the cryoprotectant, and it can be used long after being thawed. Moreover, sperm motility is still high after thawing although it is lower than that of fresh sperm. The aim of this work is to show the best available protocol for European eel handling, maturation, and sperm cryopreservation.

Handling and Treatment of Male European Eels Anguilla anguilla for Hormonal Maturation and Sperm Cryopreservation

Protocols for European eel maturation and sperm cryopreservation have been improved over the last years. This article describes the best protocol available using human chorionic gonadotropin (hCG) for inducing maturation and methanol as cryoprotectant.

During the last years, several research groups have been working on the development and improvement of new protocols for the European eel handling and ...