Name: construction of defined human engineered cardiac tissues to study mechanisms of cardiac cell therapy
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This work was supported by NIH (1F30HL118923-01A1) to T.J.C., NIH/NHLBI PEN contract HHSN268201000045C to K.D.C., the research grant council of Hong Kong TRS T13-706/11(K.D.C), NIH (R01 HL113499) to B.D.G., the American Heart Association (12PRE12060254) to R.J., and Research Grant Council of HKSAR (TBRS, T13-706/11) to R.L. Additional funding was provided to T.J.C. by NIH DRB 5T32GM008553-18 and as a traineeship on NIDCR-Interdisciplinary Training in Systems and Developmental Biology and Birth Defects T32HD075735. The authors also wish to gratefully acknowledge Arthur Autz at The Zahn Center of The City College of New York for assistance with machining the bioreactor and Mamdouh Eldaly for technical assistance. We also thank Dr. Kenneth Boheler for advice on cardiac differentiation, and Dr. Joshua Hare for generously providing human mesenchymal stem cells.

Note: Perform all cell manipulations in aseptic conditions using a HEPA-filtered class II biological safety cabinet and sterilize all solutions by filtering them through a 0.2 &#181;m filter. Perform tissue construction and function testing in either the same aseptic conditions or a laminar flow hood.
1. Seeding of H7 hESCs in Preparation for Cardiac Differentiation
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	<li>(Day 1) Preparing the Basement Membrane Matrix
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		<li>Thaw 150 &#181;l aliquot of hESC qualified basement membra...

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Part A. 17 (23-24), 2973-2980 (2011).</li><li>Lesman, 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=Transplantation+of+a+tissue-engineered+human+vascularized+cardiac+muscle.">Transplantation of a tissue-engineered human vascularized cardiac muscle.</a> Tissue Eng. Part A. 16 (1), 115-125 (2010).</li><li>Turnbull, I. 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=Advancing+functional+engineered+cardiac+tissues+toward+a+preclinical+model+of+human+myocardium.">Advancing functional engineered cardiac tissues toward a preclinical model of human myocardium.</a> FASEB J. 28 (2), 644-654 (2014).</li><li>Thavandiran, N., Dubois, N., 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=Design+and+formulation+of+functional+pluripotent+stem+cell-derived+cardiac+microtissues.">Design and formulation of functional pluripotent stem cell-derived cardiac microtissues.</a> Proc. Natl. Acad. Sci. U. S. 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Res. 111 (3), 344-358 (2012).</li><li>Kim, 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=Non-cardiomyocytes+influence+the+electrophysiological+maturation+of+human+embryonic+stem+cell-derived+cardiomyocytes+during+differentiation.">Non-cardiomyocytes influence the electrophysiological maturation of human embryonic stem cell-derived cardiomyocytes during differentiation.</a> Stem Cells Dev. 19 (6), 783-795 (2010).</li><li>Dubois, N. 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=SIRPA+is+a+specific+cell-surface+marker+for+isolating+cardiomyocytes+derived+from+human+pluripotent+stem+cells.">SIRPA is a specific cell-surface marker for isolating cardiomyocytes derived from human pluripotent stem cells.</a> Nature Biotechnol. 29 (11), 1011-1018 (2011).</li><li>Hudon-David, F., Bouzeghrane, F., Couture, P., Thibault, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thy-1+expression+by+cardiac+fibroblasts:+lack+of+association+with+myofibroblast+contractile+markers.">Thy-1 expression by cardiac fibroblasts: lack of association with myofibroblast contractile markers.</a> J. Mol. Cell. Cardiol. 42 (5), 991-1000 (2007).</li><li>Gago-Lopez, N., 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=THY-1+receptor+expression+differentiates+cardiosphere-derived+cells+with+divergent+cardiogenic+differentiation+potential.">THY-1 receptor expression differentiates cardiosphere-derived cells with divergent cardiogenic differentiation potential.</a> Stem Cell Reports. 2 (5), 576-591 (2014).</li><li>Hare, J. M., Traverse, J. 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Cardiol. 54 (24), 2277-2286 (2009).</li><li>Bolli, 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=Cardiac+stem+cells+in+patients+with+ischaemic+cardiomyopathy+(SCIPIO):+initial+results+of+a+randomised+phase+1+trial.">Cardiac stem cells in patients with ischaemic cardiomyopathy (SCIPIO): initial results of a randomised phase 1 trial.</a> Lancet. 378 (9806), 1847-1857 (2011).</li><li>Wollert, K. 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Construction of defined human engineered cardiac tissues (hECT) can provide a more consistent and reliable model of human cardiac myocyte function. Critically, all cellular and extracellular components in the system are known and can be manipulated as desired, thus removing the confounding influence of other unknown cell types resulting from the differentiation process. To balance rapid cell growth and high yield, it is preferable that the differentiation starts at 75% confluence of the hESCs, ideally four days after pla...

Cardiac tissue engineering has advanced greatly in the last decade, with multiple groups publishing results of fully functional, beating tissues made from both murine cardiomyocytes1-6 and, more recently, human stem cell-derived cardiac myocytes7-12. The cardiac tissue engineering field is driven by two primary and essentially independent goals: 1) to develop exogenous grafts that can be transplanted into failing hearts to improve function4-6; and 2) to develop in vitro models for studying physiology and disease, or as screening tools for therapeutic development2,7.
Three-dimensional (3-D) cell culture is considered essential for developing next generation screening tools, as the 3-D matrix reflects a more natural cardiac microenvironment than traditional 2-D monolayer cell culture; indeed some aspects of cell biology are fundamentally different in 2-D vs. 3-D cultures13,14. Additionally, engineered cardiac tissues are constructed from completely defined components: an extracellular matrix, and a cell population. For traditional engineered human cardiac tissues, while the extracellular matrix composition (usually fibrin9 or collagen7,8,10) is strictly controlled, the input cell composition is less well defined, with the entire mixture of cells from a directed cardiac differentiation of either embryonic stem cells (ESC7,9) or induced pluripotent stem cells (iPSC10,12) being added to the tissues. Depending on the specific cell line and the efficiency of the differentiation protocol used, the resulting percentage of cardiomyocytes can range from less than 25% to over 90%, the specific cardiomyocyte phenotype (i.e., ventricular-, atrial-, or pacemaker-like) can also vary, even the non-cardiomyocyte fraction can be highly heterogeneous15,16 and alter the maturity of the differentiated cardiac myocytes17.
Recent cardiac tissue engineering work has attempted to control the input population of cells, with either a cardiac reporter human embryonic stem cell line8 or cell surface markers18 being used to isolate the cardiac myocyte component of the differentiation. While initially a tissue composed of only cardiac myocytes would seem to be the ideal, this is in fact not the case; hECTs composed solely of cardiac myocytes fail to compact into functional tissues, with some groups finding a 3:1 ratio of cardiac myocytes:fibroblasts producing the highest twitch force8. By using various cell selection methods, including surface markers for live cell sorting, it is possible to create hECTs with defined cell populations. While markers of non-cardiac stromal cells have been available for some time, such as the putative fibroblast marker CD9019,20, surface markers of cardiac myocytes have been more difficult to identify. SIRP&#945; was among the first cardiac surface markers identified for human cardiac myocytes18 and has been shown to be highly selective for the cardiac lineage. Recently, we have found that double-sorting for SIRP&#945;+ and CD90- cells yields nearly pure cardiomyocytes, with the CD90+ population exhibiting a fibroblast-like phenotype (Josowitz, unpublished observations). Based on these collected findings, herein we describe creating hECTs using a 3:1 combination of SIRP&#945;+/CD90- cardiomyocytes and CD90+ fibroblasts.
The ability to engineer a completely defined human cardiac tissue is essential not only for creating robust screening tools, but also for developing model systems to investigate emerging cell- and gene-based cardiac therapies. In particular, numerous cell therapies for heart failure, utilizing cell types including mesenchymal stem cells (MSC)21, cardiac stem cells22 and bone marrow mononuclear cells23-25, have been tested in clinical trials. While many of the initial results have been promising21,23,25, the initial benefit often diminishes over time26-29. A similar trend has been reported in murine engineered cardiac tissues, which display a significant functional benefit due to MSC supplementation, but the benefit is not sustained during long-term culture1. Underlying the sub-optimal performance is our limited knowledge of the mechanisms governing cell therapies. A deeper understanding of how therapeutic cells exert their beneficial influence, as well as potential negative consequences of myocyte-nonmyocyte interactions, would enable the development of improved therapies yielding clinically significant and sustained benefits, with minimal side effects, for patients with heart failure.
Here, we describe the use of defined hECTs to interrogate mechanisms of cell-based therapy. The controlled tissue composition is essential to identify specific factors impacting cardiomyocyte performance. Directly supplementing hECTs with the therapeutic cell type of interest (e.g., MSCs), can reveal the effects on cardiac myocyte performance, as we have demonstrated in rat ECTs1.
The following multi-step protocol begins with directed cardiac stem cell differentiation, followed by fabrication of the multi-tissue bioreactor, and concluding with a description of tissue construction and functional analysis. Our experiments are performed using the NIH-approved H7 human embryonic stem cell (hESC) line. However, the following protocols have also been tested using an additional hESC line and three induced pluripotent stem cell (hiPSC) lines with similar results. We have found that efficiency in cardiomyocyte differentiation and success in hECT fabrication can be cell line dependent, particularly for hiPSC lines derived from individual patients. By following this protocol, two 6-well dishes are plated with a total of 1.68 million hESCs (140,000 cells per well), which yields approximately 2.5 million myocytes after differentiating for 20 days and sorting, enough to make six defined tissues.

<table border="0">
	<tbody>
		<tr>
			<td>Cell Culture</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Amphotericin B</td>
			<td>Sigma-Aldrich</td>
			<td>A2411</td>
			<td>Prepare a 2.5 mg/ml stock in DMSO and filter-sterilize</td>
		</tr>
		<tr>
			<td>B27 with Insulin</td>
			<td>Life Technologies</td>
			<td>17505055</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 without Insulin</td>
			<td>Life Technologies</td>
			<td>A1895601</td>
			<td></td>
		</tr>
		<tr>
			<td>CHIR99021</td>
			<td>Stemgent</td>
			<td>04-0004</td>
			<td>Create 6 &#956;M stock, then aliquot and store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>Essential 8 Media</td>
			<td>Life Technologies</td>
			<td>A1517001</td>
			<td></td>
		</tr>
		<tr>
			<td>H7 Human Embryonic Stem Cells</td>
			<td>WiCell</td>
			<td>WA07</td>
			<td></td>
		</tr>
		<tr>
			<td>hESC Qualified Matrix, Corning Matrigel</td>
			<td>Corning</td>
			<td>354277</td>
			<td>Thaw on ice at 4 &#176;C overnight then aliquot 150 &#956;l into separate tubes and store at -20 &#176;C.</td>
		</tr>
		<tr>
			<td>IWR-1</td>
			<td>Sigma-Aldrich</td>
			<td>I0161</td>
			<td>Create 10 mM stock and aliquot. Store at -20 &#176;C</td>
		</tr>
		<tr>
			<td>Neonatal Calf Serum</td>
			<td>Life Technologies</td>
			<td>16010159</td>
			<td></td>
		</tr>
		<tr>
			<td>Non-enzymatic Dissociation Reagent: Gentle Cell Dissociation Reagent</td>
			<td>Stem Cell Technologies</td>
			<td>7174</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Corning</td>
			<td>30-002-CI</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>Life Technologies</td>
			<td>11875-093</td>
			<td>Keep refrigerated</td>
		</tr>
		<tr>
			<td>Y-27632 (ROCK Inhibitor)</td>
			<td>Stemgent</td>
			<td>04-0012</td>
			<td>Resuspend to a 10 mM stock concentration, aliquot and store at -20 &#176;C.&#160; Avoid freeze thaw cycles.</td>
		</tr>
		<tr>
			<td>Cell Sorting</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>4&#8217;,6-Diamidino-2-Phenylindole, Dihydrochloride (DAPI)</td>
			<td>Life Technologies</td>
			<td>D1306</td>
			<td></td>
		</tr>
		<tr>
			<td>CD90-FITC</td>
			<td>BioLegend</td>
			<td>328107</td>
			<td></td>
		</tr>
		<tr>
			<td>Enzymatic Dissociation Reagent: Cell Detach Kit I (0.04 % Trypsin/ 0.03% EDTA, Trypsin neutralization solution and Hanks Buffered Salt Solution)&#160;</td>
			<td>PromoCell</td>
			<td>C-41200</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Atlanta Biologics</td>
			<td>S11250</td>
			<td></td>
		</tr>
		<tr>
			<td>SIRP&#945;-PE/Cy7</td>
			<td>BioLegend</td>
			<td>323807</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue Construction</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>0.25% Trypsin/0.1% EDTA</td>
			<td>Fisher Scientific</td>
			<td>25-053-CI</td>
			<td>Optional: For collection of supplemental cells of interest</td>
		</tr>
		<tr>
			<td>10x MEM</td>
			<td>Sigma-Aldrich</td>
			<td>M0275-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>10X PBS Packets</td>
			<td>Sigma-Aldrich</td>
			<td>P3813</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagen, Bovine Type I</td>
			<td>Life Technologies</td>
			<td>A10644-01</td>
			<td>Keep on ice</td>
		</tr>
		<tr>
			<td>DMEM/F12</td>
			<td>Life Technologies</td>
			<td>11330057</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s Modified Eagles Medium (DMEM), High Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>D5648</td>
			<td></td>
		</tr>
		<tr>
			<td>Polydimethylsiloxane (PDMS)</td>
			<td>Dow Corning</td>
			<td>Sylgard 184</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium HEPES</td>
			<td>Sigma-Aldrich</td>
			<td>H3784</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Hydroxide</td>
			<td>Sigma-Aldrich</td>
			<td>221465</td>
			<td></td>
		</tr>
		<tr>
			<td>Materials</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>1.5 ml microcentrifuge tubes</td>
			<td>Fisher Scientific</td>
			<td>NC0536757</td>
			<td></td>
		</tr>
		<tr>
			<td>15 ml polyproylene centrifuge tube</td>
			<td>Corning</td>
			<td>352096</td>
			<td></td>
		</tr>
		<tr>
			<td>5 ml Polystyrene Round-Bottom Tube</td>
			<td>Corning</td>
			<td>352235</td>
			<td>With integrated 35 &#956;m cell strainer</td>
		</tr>
		<tr>
			<td>50 ml polyproylene centrifuge tube</td>
			<td>Corning</td>
			<td>352070</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well flat bottom tissue-culture treated plate</td>
			<td>Corning</td>
			<td>353046</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Scraper, Disposable</td>
			<td>Biologix</td>
			<td>70-2180</td>
			<td></td>
		</tr>
		<tr>
			<td>Polysulfone</td>
			<td>McMaster-Carr</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polytetrafluoroethylene (Teflon)</td>
			<td>McMaster-Carr</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Dissecting Microscope</td>
			<td>Olympus</td>
			<td>SZ-61</td>
			<td>Or similar, must have a mount for the high speed camera to attach</td>
		</tr>
		<tr>
			<td>Electrical Pacing System</td>
			<td>Astro-Med, Inc</td>
			<td>Grass S88X Stimulator</td>
			<td></td>
		</tr>
		<tr>
			<td>High Speed Camera</td>
			<td>Pixelink</td>
			<td>PL-B741U</td>
			<td>Or similar, but must be capable of 100 frames per second for accurate data acquisition</td>
		</tr>
		<tr>
			<td>Plate Temperature Control</td>
			<td></td>
			<td></td>
			<td>Used to maintain media temperature during data acqusition.</td>
		</tr>
		<tr>
			<td>Custom Materials</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>LabView Post-tracking Program</td>
			<td></td>
			<td></td>
			<td>available upon request from the authors</td>
		</tr>
	</tbody>
</table>

construction of defined human engineered cardiac tissues to study mechanisms of cardiac cell therapy

Human cardiac tissue engineering can fundamentally impact therapeutic discovery through the development of new species-specific screening systems that replicate the biofidelity of three-dimensional native human myocardium, while also enabling a controlled level of biological complexity, and allowing non-destructive longitudinal monitoring of tissue contractile function. Initially, human engineered cardiac tissues (hECT) were created using the entire cell population obtained from directed differentiation of human pluripotent stem cells, which typically yielded less than 50% cardiomyocytes. However, to create reliable predictive models of human myocardium, and to elucidate mechanisms of heterocellular interaction, it is essential to accurately control the biological composition in engineered tissues. 
To address this limitation, we utilize live cell sorting for the cardiac surface marker SIRP&#945; and the fibroblast marker CD90 to create tissues containing a 3:1 ratio of these cell types, respectively, that are then mixed together and added to a collagen-based matrix solution. Resulting hECTs are, thus, completely defined in both their cellular and extracellular matrix composition.
Here we describe the construction of defined hECTs as a model system to understand mechanisms of cell-cell interactions in cell therapies, using an example of human bone marrow-derived mesenchymal stem cells (hMSC) that are currently being used in human clinical trials. The defined tissue composition is imperative to understand how the hMSCs may be interacting with the endogenous cardiac cell types to enhance tissue function. A bioreactor system is also described that simultaneously cultures six hECTs in parallel, permitting more efficient use of the cells after sorting.

To obtain cardiac myocytes, a slightly modified version of the Boheler and Lian differentiation methods is used30,31. It is imperative that the differentiation starts during the log-phase of cell growth, but also that the starting population is sufficiently confluent to obtain a useable number of cells after sorting (approximately 75% is optimal). Typically, for H7 hESCs, plating at a density of 140,000 hESCs per well of a 6-well dish in essential 8 media and 5% CO2 incubator maintained at 37 &#176;...

Watch this Scientific Journal Video about Construction of Defined Human Engineered Cardiac Tissues to Study Mechanisms of Cardiac Cell Therapy at JoVE.com

Construction of Defined Human Engineered Cardiac Tissues to Study Mechanisms of Cardiac Cell Therapy

This manuscript describes the creation of defined engineered cardiac tissues using surface marker expression and cell sorting. The defined tissues can then be used in a multi-tissue bioreactor to investigate mechanisms of cardiac cell therapy in order to provide a functional, yet controlled, model system of the human heart.

Human cardiac tissue engineering can fundamentally impact therapeutic discovery through the development of new species-specific screening systems that ...

The overall goal of this procedure is to create human engineered cardiac tissues of a defined cellular composition. This method can address key challenges in the cardiac tissue engineering field, including controlling for variability and cardiac differentiation efficiencies and understanding how specific cell types impact cardiac contractile function. The main advantage of this technique is that the end result is human engineered cardiac tissue of a controlled and defined composition.Replications of this technique extend toward therapy for heart disease because defined tissues can provide a novel, biologically relevant and biomedic screening platform capable of evaluating therapeutic interventions. Though this method can provide insight into novel cardiac therapeutics, the human engineered cardiac tissue system can also be used to understand mechanisms of cardiac cell therapy. Beginning with human embryonic stem cell-derived cardiomyocyte cultures, wash the cells one time with PBS and add one milliliter of 0.04%trypsin-EDTA.Incubate the cells for 10 minutes at 37 degrees Celsius and 5%CO2. When the cells are incubating, add 12 microliters of ROCK inhibitor to six milliliters of trypsin neutralization solution. Remove the plates from the incubator and add one milliliter of the neutralization solution to each well of the six-well plate.Transfer all of the cells from each well into a single 15-milliliter centrifuge tube. Wash all six wells with one three-milliliter volume of PBS and combine this wash with the cells in the tube. Centrifuge the tube at 300 times G for five minutes at four degrees Celsius to pellet the cells.To prepare the cells for live cell sorting by FACS, prepare the staining buffer by adding five milliliters of FBS and 50 microliters of ROCK inhibitor to 45 milliliters of PBS on ice. Remove the supernatant from the pelleted cells and resuspend them in 1.2 milliliters of staining buffer. Transfer 200 microliters of the suspended cells to a new prechilled 50-milliliter centrifuge tube on ice.Next, transfer the remaining one milliliter of the cell suspension to a new prechilled 50-milliliter centrifuge tube on ice and add two microliters of SIRP alpha-PE/Cy7 and four microliters of CD90-FITC antibodies. Gently mix the cell suspension with a transfer pipette and place the tube on ice. Incubate the two 50-milliliter tubes containing the negative control and the sample on a rocker shaker on ice at four degrees Celsius for one hour.While the cells are incubating, transfer three milliliters of differentiation medium two to each of two 15-milliliter centrifuge tubes. Then add three microliters of ROCK inhibitor, and store these FACS collection tubes on ice prior to use. Next, pellet the stained cells at 300 times G for five minutes at four degrees Celsius.And wash them twice with 10 milliliters of ice-cold PBS. Gently resuspend the sample pellet with one to three milliliters of staining buffer containing DAPI. Add 500 microliters of staining buffer without DAPI to the negative control pellet.Filter both of the cell suspensions through a 40-micron cell strainer to remove cell clumps, and then transfer them to polystyrene FACS tubes on ice. Immediately bring the samples to the cell sorter. Beginning with the negative staining control sample, establish the gating parameters.Then, while running the sample cells, select for the DAPI negative live cell population. Collect both the FITC positive and PE/Cy7 positive cell populations independently at 20 PSI. After culturing and reaggregating cells, as indicated in the text protocol, remove the cell culture plates from the incubator and transfer the medium to a 50-milliliter centrifuge tube.Wash the plates with three milliliters of PBS and transfer the wash to the same 50-milliliter centrifuge tube. Then add three milliliters of 0.04%trypsin-EDTA to the plates and incubate at 37 degrees Celsius and 5%CO2. After five minutes, examine the plates for cell detachment using a microscope.Once all of the cells have detached, add three milliliters of trypsin neutralization solution to the plates. Gently mix and transfer the cells to the original 50-milliliter centrifuge tube. Wash the plates with five milliliters of PBS and add this wash to the tube as well.Pellet the cells by centrifugation at 300 times G for five minutes at room temperature. Remove the supernatant and resuspend the pellet in one milliliter of neonatal bovine serum, or NBS medium. Next, transfer the cells to a 1.5-milliliter microcentrifuge tube.Pellet the cells at 300 times G for five minutes at room temperature and remove the supernatant. To begin generating the six engineered cardiac tissues, dilute 60.0 microliters of the five milligrams per milliliter collagen stock to 3.125 milligrams per milliliter with 1.5 microliters of one molar sodium hydroxide, 9.6 microliters of 10X PBS, and 24.9 microliters of sterile ultra pure water. Here, it is critical to avoid the introduction of air bubbles into the collagen mix as the air bubbles are slow to release from the viscous solution and can interfere with tissue formation during tissue compaction.Pipette down the side of the 15-milliliter tube to add 12.0 microliters each of 10X MEM and 0.2 normal heaps at pH 9 to dilute the collagen mixture. Then add the basement membrane matrix to the collagen mixture to a final concentration of 0.9 milligrams per milliliter and mix gently. Store this final tissue mix on ice.Next, transfer the entire tissue mix to the cell pellet and add supplemental cells as indicated in the text protocol. Fill the tube to a final volume of 150 microliters with cell-free NBS media and mix gently. Carefully pipette 25 microliters of the cell suspension into each one of the six wells in the bioreactor base plate.Repeat the mixing procedure between each well to resuspend any cells that may have settled. Pipette only one tissue per well at a time to ensure a consistent volume and cell number per tissue. Separately, push two rows of polydimethylsiloxane, or PDMS, force sensors onto either side of the polysulfone frame to form six pairs of opposing posts.Invert the frame on top of the base plate so that one pair of posts enters each well containing the cell suspension. Then place the bioreactor into a 60-millimeter dish and place that dish without its cover inside of a 10-centimeter dish. Place the lid on the 10-centimeter dish and move the entire bioreactor assembly into the tissue culture incubator.After two hours of incubation, remove the bioreactor assembly and add 14 milliliters of NBS medium to cover the base plate. Return the bioreactor to the cell culture incubator and change half of the medium every day. After 48 hours, remove the base plate gently a few millimeters at a time.Then return the bioreactor with the tissue facing down to the medium. If a tissue falls off of a post when removing the base plate, gently reattach the tissue onto the post. Differentiation of human embryonic stem cells results in a mixed culture of primarily cardiomyocytes and fibroblasts that self-organize into clusters and form robustly beating webs throughout the dish.FACS sorting of these cultures revealed that this differentiation method results in a population that contains at least 65%SIRP alpha positive cells and 10%CD90 positive cells. After removing the base plate, the human engineered cardiac tissues, or HECTs, are allowed to self-assemble within the bioreactor. Mature and compacted HECTs visibly deflect the integrated force sensing posts with an average of five to 15 micronewtons of force.Twitch force measurements reveal how isolated variables alter the contractile force in these defined engineered tissues. Here, when the tissues are supplemented with 10%human mesenchymal stem cells, a substantial enhancement of the contractile force is observed at both the one-hertz and two-hertz pacing frequencies. Once mastered, the differentiation will take approximately 20 days, the cell sorting about five hours, and the tissue construction about three hours.Another seven days will be required for proper tissue formation after construction. Following this procedure, other methods, including cell labeling and supplementation of the tissue mix, can be performed in order to answer additional questions regarding the effects of specific cell-cell interactions or to determine the mechanisms of cell therapy. After watching this video, you should have a good understanding of how to create human engineered cardiac tissues with a known and controlled cellular composition.

construction-defined-human-engineered-cardiac-tissues-to-study

Research

JoVE Journal

Bioengineering

Shock Wave Application to Cell Cultures

Shock waves nowadays are well known for their regenerative effects. Basic research findings showed that shock waves do cause a biological stimulus to target cells or tissue without any subsequent damage. Therefore, in vitro experiments are of increasing interest. Various methods of applying shock waves onto cell cultures have been described. In general, all existing models focus on how to best apply shock waves onto cells.
However, this question remains: What happens to the waves after passing the cell culture? The difference of the acoustic impedance of the cell culture medium and the ambient air is that high, that more than 99% of shock waves get reflected! We therefore developed a model that mainly consists of a Plexiglas built container that allows the waves to propagate in water after passing the cell culture. This avoids cavitation effects as well as reflection of the waves that would otherwise disturb upcoming ones. With this model we are able to mimic in vivo conditions and thereby gain more and more knowledge about how the physical stimulus of shock waves gets translated into a biological cell signal (&#8220;mechanotransduction&#34;).

Shock waves nowadays are well known for their regenerative effects. Therefore in vitro experiments are of increasing interest. We therefore developed a model for in vitro shock wave trials (IVSWT) that enables us to mimic in vivo conditions thereby avoiding distracting physical effects.

Shock waves nowadays are well known for their regenerative effects. Basic research findings showed that shock waves do cause a biological stimulus to ...

Automated Contraction Analysis of Human Engineered Heart Tissue for Cardiac Drug Safety Screening

Cardiac tissue engineering describes techniques to constitute three dimensional force-generating engineered tissues. For the implementation of these procedures in basic research and preclinical drug development, it is important to develop protocols for automated generation and analysis under standardized conditions. Here, we present a technique to generate engineered heart tissue (EHT) from cardiomyocytes of different species (rat, mouse, human). The technique relies on the assembly of a fibrin-gel containing dissociated cardiomyocytes between elastic polydimethylsiloxane (PDMS) posts in a 24-well format. Three-dimensional, force-generating EHTs constitute within two weeks after casting. This procedure allows for the generation of several hundred EHTs per week and is technically limited only by the availability of cardiomyocytes (0.4-1.0 x 106/EHT). Evaluation of auxotonic muscle contractions is performed in a modified incubation chamber with a mechanical interlock for 24-well plates and a camera placed on top of this chamber. A software controls a camera moved on an XYZ axis system to each EHT. EHT contractions are detected by an automated figure recognition algorithm, and force is calculated based on shortening of the EHT and the elastic propensity and geometry of the PDMS posts. This procedure allows for automated analysis of high numbers of EHT under standardized and sterile conditions. The reliable detection of drug effects on cardiomyocyte contraction is crucial for cardiac drug development and safety pharmacology. We demonstrate, with the example of the hERG channel inhibitor E-4031, that the human EHT system replicates drug responses on contraction kinetics of the human heart, indicating it to be a promising tool for cardiac drug safety screening.

Here, we show the generation of human engineered heart tissue from induced pluripotent stem cells (hiPSC)-derived cardiomyocytes. We present a method to analyze contraction force and exemplary alteration of contraction pattern by the hERG channel inhibitor E-4031. This method shows high level of robustness and suitability for cardiac drug screening.

Cardiac tissue engineering describes techniques to constitute three dimensional force-generating engineered tissues. For the implementation of these ...

Using Extraordinary Optical Transmission to Quantify Cardiac Biomarkers in Human Serum

For a biosensing platform to have clinical relevance in point-of-care (POC) settings, assay sensitivity, reproducibility, and ability to reliably monitor analytes against the background of human serum are crucial.
Nanoimprinting lithography (NIL) was used to fabricate, at a low cost, sensing areas as large as 1.5 mm x 1.5 mm. The sensing surface was made of high-fidelity arrays of nanoholes, each with an area of about 140 nm2. The great reproducibility of NIL made it possible to employ a one-chip, one-measurement strategy on 12 individually manufactured surfaces, with minimal chip-to-chip variation. These nanoimprinted localized surface plasmon resonance (LSPR) chips were extensively tested on their ability to reliably measure a bioanalyte at concentrations varying from 2.5 to 75 ng/mL amidst the background of a complex biofluid-in this case, human serum. The high fidelity of NIL enables the generation of large sensing areas, which in turn eliminates the need for a microscope, as this biosensor can be easily interfaced with a commonly available laboratory light source. These biosensors can detect cardiac troponin in serum with a high sensitivity, at a limit of detection (LOD) of 0.55 ng/mL, which is clinically relevant. They also show low chip-to-chip variance (due to the high quality of the fabrication process). The results are commensurable with widely used enzyme-linked immunosorbent assay (ELISA)-based assays, but the technique retains the advantages of an LSPR-based sensing platform (i.e., amenability to miniaturization and multiplexing, making it more feasible for POC applications).

This work describes a nanoimprinting lithography method to fabricate high-quality sensing arrays that work on the principle of extraordinary optical transmission. The biosensor is low-cost, robust, easy to use, and can detect cardiac troponin I in serum at clinically relevant concentrations (99th percentile cutoff &#8764;10-400 pg/mL, depending on the assay).

For a biosensing platform to have clinical relevance in point-of-care (POC) settings, assay sensitivity, reproducibility, and ability to reliably monitor ...

Protocol for MicroRNA Transfer into Adult Bone Marrow-derived Hematopoietic Stem Cells to Enable Cell Engineering Combined with Magnetic Targeting

While CD133+ hematopoietic stem cells (SCs) have been proven to provide high potential in the field of regenerative medicine, their low retention rates after injection into injured tissues as well as the observed massive cell death rates lead to very restricted therapeutic effects. To overcome these limitations, we sought to establish a non-viral based protocol for suitable cell engineering prior to their administration. The modification of human CD133+ expressing SCs using microRNA (miR) loaded magnetic polyplexes was addressed with respect to uptake efficiency and safety as well as the targeting potential of the cells. Relying on our protocol, we can achieve high miR uptake rates of 80&#8211;90% while the CD133+ stem cell properties remain unaffected. Moreover, these modified cells offer the option of magnetic targeting. We describe here a safe and highly efficient procedure for the modification of CD133+ SCs. We expect this approach to provide a standard technology for optimization of therapeutic stem cell effects and for monitoring of the administered cell product via magnetic resonance imaging (MRI).

This protocol illustrates a safe and efficient procedure to modify CD133+ hematopoietic stem cells. The presented non-viral, magnetic polyplex-based approach may provide a basis for the optimization of therapeutic stem cell effects as well as for monitoring the administered cell product via magnetic resonance imaging.

While CD133+ hematopoietic stem cells (SCs) have been proven to provide high potential in the field of regenerative medicine, their low retention rates ...

A Net Mold-based Method of Scaffold-free Three-Dimensional Cardiac Tissue Creation

This protocol describes a novel and easy net mold-based method to create three-dimensional (3-D) cardiac tissues without additional scaffold material. Human-induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs), human cardiac fibroblasts (HCFs), and human umbilical vein endothelial cells (HUVECs) are isolated and used to generate a cell suspension with 70% iPSC-CMs, 15% HCFs, and 15% HUVECs. They are co-cultured in an ultra-low attachment "hanging drop" system, which contains micropores for condensing hundreds of spheroids at one time. The cells aggregate and spontaneously form beating spheroids after 3 days of co-culture. The spheroids are harvested, seeded into a novel mold cavity, and cultured on a shaker in the incubator. The spheroids become a mature functional tissue approximately 7 days after seeding. The resultant multilayered tissues consist of fused spheroids with satisfactory structural integrity and synchronous beating behavior. This new method has promising potential as a reproducible and cost-effective method to create engineered tissues for the treatment of heart failure in the future.

This protocol describes a net mold-based method to create three-dimensional scaffold-free cardiac tissues with satisfactory structural integrity and synchronous beating behavior.

This protocol describes a novel and easy net mold-based method to create three-dimensional (3-D) cardiac tissues without additional scaffold material. ...

Preclinical Cardiac Electrophysiology Assessment by Dual Voltage and Calcium Optical Mapping of Human Organotypic Cardiac Slices

Human cardiac slice preparations have recently been developed as a platform for human physiology studies and therapy testing to bridge the gap between animal and clinical trials. Numerous animal and cell models have been used to examine the effects of drugs, yet these responses often differ in humans. Human cardiac slices offer an advantage for drug testing in that they are directly derived from viable human hearts. In addition to having preserved multicellular structures, cell-cell coupling, and extracellular matrix environments, human cardiac tissue slices can be used to directly test the effect of innumerable drugs on adult human cardiac physiology. What distinguishes this model from other heart preparations, such as whole hearts or wedges, is that slices can be subjected to longer-term culture. As such, cardiac slices allow for studying the acute as well as chronic effects of drugs. Furthermore, the ability to collect several hundred to a thousand slices from a single heart makes this a high-throughput model to test several drugs at varying concentrations and combinations with other drugs at the same time. Slices can be prepared from any given region of the heart. In this protocol, we describe the preparation of left ventricular slices by isolating tissue cubes from the left ventricular free wall and sectioning them into slices using a high precision vibrating microtome. These slices can then either be subjected to acute experiments to measure baseline cardiac electrophysiological function or cultured for chronic drug studies. This protocol also describes dual optical mapping of cardiac slices for simultaneous recordings of transmembrane potentials and intracellular calcium dynamics to determine the effects of the drugs being investigated.

This protocol describes the procedure for sectioning and culturing human cardiac slices for preclinical drug testing and details the use of optical mapping for recording transmembrane voltage and intracellular calcium signals simultaneously from these slices.

Human cardiac slice preparations have recently been developed as a platform for human physiology studies and therapy testing to bridge the gap between ...

Preparation of Mesh-Shaped Engineered Cardiac Tissues Derived from Human iPS Cells for In Vivo Myocardial Repair

The current protocol describes methods to generate scalable, mesh-shaped engineered cardiac tissues (ECTs) composed of cardiovascular cells derived from human induced pluripotent stem cells (hiPSCs), which are developed towards the goal of clinical use. HiPSC-derived cardiomyocytes, endothelial cells, and vascular mural cells are mixed with gel matrix and then poured into a polydimethylsiloxane (PDMS) tissue mold with rectangular internal staggered posts. By culture day 14 ECTs mature into a 1.5 cm x 1.5 cm mesh structure with 0.5 mm diameter myofiber bundles. Cardiomyocytes align to the long-axis of each bundle and spontaneously beat synchronously. This approach can be scaled up to a larger (3.0 cm x 3.0 cm) mesh ECT while preserving construct maturation and function. Thus, mesh-shaped ECTs generated from hiPSC-derived cardiac cells may be feasible for cardiac regeneration paradigms.

The present protocol generates mesh-shaped engineered cardiac tissues containing cardiovascular cells derived from human induced pluripotent stem cells to allow the investigation of cell implantation therapy for heart diseases.

The current protocol describes methods to generate scalable, mesh-shaped engineered cardiac tissues (ECTs) composed of cardiovascular cells derived from ...

Fabrication of 3D Cardiac Microtissue Arrays using Human iPSC-Derived Cardiomyocytes, Cardiac Fibroblasts, and Endothelial Cells

Generation of human cardiomyocytes (CMs), cardiac fibroblasts (CFs), and endothelial cells (ECs) from induced pluripotent stem cells (iPSCs) has provided a unique opportunity to study the complex interplay among different cardiovascular cell types that drives tissue development and disease. In the area of cardiac tissue models, several sophisticated three-dimensional (3D) approaches use induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) to mimic physiological relevance and native tissue environment with a combination of extracellular matrices and crosslinkers. However, these systems are complex to fabricate without microfabrication expertise and require several weeks to self-assemble. Most importantly, many of these systems lack vascular cells and cardiac fibroblasts that make up over 60% of the nonmyocytes in the human heart. Here we describe the derivation of all three cardiac cell types from iPSCs to fabricate cardiac microtissues. This facile replica molding technique allows cardiac microtissue culture in standard multi-well cell culture plates for several weeks. The platform allows user-defined control over microtissue sizes based on initial seeding density and requires less than 3 days for self-assembly to achieve observable cardiac microtissue contractions. Furthermore, the cardiac microtissues can be easily digested while maintaining high cell viability for single-cell interrogation with the use of flow cytometry and single-cell RNA sequencing (scRNA-seq). We envision that this in vitro model of cardiac microtissues will help accelerate validation studies in drug discovery and disease modeling.

Here, we describe an easy-to-use methodology to generate 3D self-assembled cardiac microtissue arrays composed of pre-differentiated human-induced pluripotent stem cell-derived cardiomyocytes, cardiac fibroblasts, and endothelial cells. This user-friendly and low cell requiring technique to generate cardiac microtissues can be implemented for disease modeling and early stages of drug development.

Generation of human cardiomyocytes (CMs), cardiac fibroblasts (CFs), and endothelial cells (ECs) from induced pluripotent stem cells (iPSCs) has provided ...

Cardiac Spheroids as in vitro Bioengineered Heart Tissues to Study Human Heart Pathophysiology

Despite several advances in cardiac tissue engineering, one of the major challenges to overcome remains the generation of a fully functional vascular network comprising several levels of complexity to provide oxygen and nutrients within bioengineered heart tissues. Our laboratory has developed a three-dimensional in vitro model of the human heart, known as the "cardiac spheroid" or "CS". This presents biochemical, physiological, and pharmacological features typical of the human heart and is generated by co-culturing its three major cell types, such as cardiac myocytes, endothelial cells, and fibroblasts. Human induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs or iCMs) are co-cultured at ratios approximating the ones found in vivo with human cardiac fibroblasts (HCFs) and human coronary artery endothelial cells (HCAECs) in hanging drop culture plates for three to four days. The confocal analysis of CSs stained with antibodies against cardiac Troponin T, CD31 and vimentin (markers for cardiac myocytes, endothelial cells and fibroblasts, respectively) shows that CSs present a complex endothelial cell network, resembling the native one found in the human heart. This is confirmed by the 3D rendering analysis of these confocal images. CSs also present extracellular matrix (ECM) proteins typical of the human heart, such as collagen type IV, laminin and fibronectin. Finally, CSs present a contractile activity measured as syncytial contractility closer to the one typical of the human heart compared to CSs that contain iCMs only. When treated with a cardiotoxic anti-cancer agent, such as doxorubicin (DOX, used to treat leukemia, lymphoma and breast cancer), the viability of DOX-treated CSs is significantly reduced at 10 &#181;M genetic and chemical inhibition of endothelial nitric oxide synthase, a downstream target of DOX in HCFs and HCAECs, reduced its toxicity in CSs. Given these unique features, CSs are currently used as in vitro models to study heart biochemistry, pathophysiology, and pharmacology.

This protocol aims to fabricate 3D cardiac spheroids (CSs) by co-culturing cells in hanging drops.&#160;Collagen-embedded CSs are treated with doxorubicin (DOX, a cardiotoxic agent) at physiological concentrations to model heart failure. In vitro testing using DOX-treated CSs may be used to identify novel therapies for heart failure patients.

Despite several advances in cardiac tissue engineering, one of the major challenges to overcome remains the generation of a fully functional vascular ...

Developing 3D Organized Human Cardiac Tissue within a Microfluidic Platform

The leading cause of death worldwide persists as cardiovascular disease (CVD). However, modeling the physiological and biological complexity of the heart muscle, the myocardium, is notoriously difficult to accomplish in vitro. Mainly, obstacles lie in the need for human cardiomyocytes (CMs) that are either adult or exhibit adult-like phenotypes and can successfully replicate the myocardium&#39;s cellular complexity and intricate 3D architecture. Unfortunately, due to ethical concerns and lack of available primary patient-derived human cardiac tissue, combined with the minimal proliferation of CMs, the sourcing of viable human CMs has been a limiting step for cardiac tissue engineering. To this end, most research has transitioned toward cardiac differentiation of human induced pluripotent stem cells (hiPSCs) as the primary source of human CMs, resulting in the wide incorporation of hiPSC-CMs within in vitro assays for cardiac tissue modeling.
Here in this work, we demonstrate a protocol for developing a 3D mature stem cell-derived human cardiac tissue within a microfluidic device. We specifically explain and visually demonstrate the production of a 3D in vitro anisotropic cardiac tissue-on-a-chip model from hiPSC-derived CMs. We primarily describe a purification protocol to select for CMs, the co-culture of cells with a defined ratio via mixing CMs with human CFs (hCFs), and suspension of this co-culture within the collagen-based hydrogel. We further demonstrate the injection of the cell-laden hydrogel within our well-defined microfluidic device, embedded with staggered elliptical microposts that serve as surface topography to induce a high degree of alignment of the surrounding cells and the hydrogel matrix, mimicking the architecture of the native myocardium. We envision that the proposed 3D anisotropic cardiac tissue-on-chip model is suitable for fundamental biology studies, disease modeling, and, through its use as a screening tool, pharmaceutical testing.

The goal of this protocol is to explain and demonstrate the development of a three-dimensional (3D) microfluidic model of highly aligned human cardiac tissue, composed of stem cell-derived cardiomyocytes co-cultured with cardiac fibroblasts (CFs) within a biomimetic, collagen-based hydrogel, for applications in cardiac tissue engineering, drug screening, and disease modeling.

The leading cause of death worldwide persists as cardiovascular disease (CVD). However, modeling the physiological and biological complexity of the heart ...