We thank Dr. Amanda Chase for her helpful feedback on the manuscript. Funding support was provided by the Tobacco-Related Disease Research Program (TRDRP) of the University of California, T29FT0380 (D.T.) and 27IR-0012 (J.C.W.); American Heart Association 20POST35210896 (H.K.) and 17MERIT33610009 (J.C.W.); and National Institutes of Health (NIH) R01 HL126527, R01 HL123968, R01 HL150693, R01 HL141851, and NIH UH3 TR002588 (J.C.W).

<ol>
	<li>Neofytou, E., O'Brien, C. G., Couture, L. A., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hurdles+to+clinical+translation+of+human+induced+pluripotent+stem+cells.">Hurdles to clinical translation of human induced pluripotent stem cells.</a> Journal of Clinical Investigation. 125 (7), 2551-2557 (2015).</li><li>Lancaster, M. A., Knoblich, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organogenesis+in+a+dish:+Modeling+development+and+disease+using+organoid+technologies.">Organogenesis in a dish: Modeling development and disease using organoid technologies.</a> Science. 345 (6194), 1247125 (2014).</li><li>Liu, C., Oikonomopoulos, A., Sayed, N., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+human+diseases+with+induced+pluripotent+stem+cells:+from+2D+to+3D+and+beyond.">Modeling human diseases with induced pluripotent stem cells: from 2D to 3D and beyond.</a> Development. 145 (5), 156166 (2018).</li><li>Yin, X., Mead, B. E., Safaee, H., Langer, R., Karp, J. M., Levy, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+stem+cell+organoids.">Engineering stem cell organoids.</a> Cell Stem Cell. 18 (1), 25-38 (2016).</li><li>Giacomelli, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+cardiac+microtissues+composed+of+cardiomyocytes+and+endothelial+cells+co-differentiated+from+human+pluripotent+stem+cells.">Three-dimensional cardiac microtissues composed of cardiomyocytes and endothelial cells co-differentiated from human pluripotent stem cells.</a> Development. 144 (6), 1008-1017 (2017).</li><li>Kurokawa, Y. K., George, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue+engineering+the+cardiac+microenvironment:+Multicellular+microphysiological+systems+for+drug+screening.">Tissue engineering the cardiac microenvironment: Multicellular microphysiological systems for drug screening.</a> Advances in Drug Delivery Reviews. 96, 225-233 (2016).</li><li>Cartledge, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+crosstalk+between+cardiac+fibroblasts+and+adult+cardiomyocytes+by+soluble+mediators.">Functional crosstalk between cardiac fibroblasts and adult cardiomyocytes by soluble mediators.</a> Cardiovascular Research. 105 (3), 260-270 (2015).</li><li>Ravenscroft, S. M., Pointon, A., Williams, A. W., Cross, M. J., Sidaway, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+non-myocyte+cells+show+enhanced+pharmacological+function+suggestive+of+contractile+maturity+in+stem+cell+derived+cardiomyocyte+microtissues.">Cardiac non-myocyte cells show enhanced pharmacological function suggestive of contractile maturity in stem cell derived cardiomyocyte microtissues.</a> Toxicology Science. 152 (1), 99-112 (2016).</li><li>Ieda, 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=Cardiac+fibroblasts+regulate+myocardial+proliferation+through+beta1+integrin+signaling.">Cardiac fibroblasts regulate myocardial proliferation through beta1 integrin signaling.</a> Developmental Cell. 16 (2), 233-244 (2009).</li><li>Brutsaert, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+endothelial-myocardial+signaling:+its+role+in+cardiac+growth,+contractile+performance,+and+rhythmicity.">Cardiac endothelial-myocardial signaling: its role in cardiac growth, contractile performance, and rhythmicity.</a> Physiological Reviews. 83 (1), 59-115 (2003).</li><li>Huebsch, 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=Automated+video-based+analysis+of+contractility+and+calcium+flux+in+human-induced+pluripotent+stem+cell-derived+cardiomyocytes+cultured+over+different+spatial+scales.">Automated video-based analysis of contractility and calcium flux in human-induced pluripotent stem cell-derived cardiomyocytes cultured over different spatial scales.</a> Tissue Engineering Part C Methods. 21 (5), 467-479 (2015).</li><li>Burridge, P. W., 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=Chemically+defined+generation+of+human+cardiomyocytes.">Chemically defined generation of human cardiomyocytes.</a> Nature Methods. 11 (8), 855-860 (2014).</li><li>Gu, 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=Pravastatin+reverses+obesity-induced+dysfunction+of+induced+pluripotent+stem+cell-derived+endothelial+cells+via+a+nitric+oxide-dependent+mechanism.">Pravastatin reverses obesity-induced dysfunction of induced pluripotent stem cell-derived endothelial cells via a nitric oxide-dependent mechanism.</a> European Heart Journal. 36 (13), 806-816 (2015).</li><li>Williams, I. M., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+endothelial+cells+from+human+pluripotent+stem+cells.">Generation of endothelial cells from human pluripotent stem cells.</a> Arteriosclerosis, Thrombosis and Vascular Biology. 39 (7), 1317-1329 (2019).</li><li>Zhang, H., Shen, M., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+quiescent+cardiac+fibroblasts+derived+from+human+induced+pluripotent+stem+cells.">Generation of quiescent cardiac fibroblasts derived from human induced pluripotent stem cells.</a> Methods in Molecular Biology. , 1-7 (2020).</li><li>Zhang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+quiescent+cardiac+fibroblasts+from+human+induced+pluripotent+stem+cells+for+in+vitro+modeling+of+cardiac+fibrosis.">Generation of quiescent cardiac fibroblasts from human induced pluripotent stem cells for in vitro modeling of cardiac fibrosis.</a> Circulation Research. 125 (5), 552-566 (2019).</li><li>Zhang, 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=Functional+cardiac+fibroblasts+derived+from+human+pluripotent+stem+cells+via+second+heart+field+progenitors.">Functional cardiac fibroblasts derived from human pluripotent stem cells via second heart field progenitors.</a> Nature Communications. 10 (1), 2238-2315 (2019).</li><li>Giacomelli, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human-iPSC-derived+cardiac+stromal+cells+enhance+maturation+in+3d+cardiac+microtissues+and+reveal+non-cardiomyocyte+contributions+to+heart+disease.">Human-iPSC-derived cardiac stromal cells enhance maturation in 3d cardiac microtissues and reveal non-cardiomyocyte contributions to heart disease.</a> Cell Stem Cell. 26 (6), 862-879 (2020).</li><li>Burridge, P. W., Holmstr&#246;m, A., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemically+defined+culture+and+cardiomyocyte+differentiation+of+human+pluripotent+stem+cells.">Chemically defined culture and cardiomyocyte differentiation of human pluripotent stem cells.</a> Current Protocols in Human Genetics. 87 (1), 1-15 (2015).</li><li>Lian, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+cardiomyocyte+differentiation+from+human+pluripotent+stem+cells+by+modulating+Wnt/&#946;-catenin+signaling+under+fully+defined+conditions.">Directed cardiomyocyte differentiation from human pluripotent stem cells by modulating Wnt/&#946;-catenin signaling under fully defined conditions.</a> Nature Protocols. 8 (1), 162-175 (2013).</li><li>Buikema, J. W., 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=Wnt+activation+and+reduced+cell-cell+contact+synergistically+induce+massive+expansion+of+functional+human+iPSC-derived+cardiomyocytes.">Wnt activation and reduced cell-cell contact synergistically induce massive expansion of functional human iPSC-derived cardiomyocytes.</a> Cell Stem Cell. 27 (1), 50-63 (2020).</li><li>Feyen, D. A. 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=Metabolic+maturation+media+improve+physiological+function+of+human+iPSC-derived+cardiomyocytes.">Metabolic maturation media improve physiological function of human iPSC-derived cardiomyocytes.</a> Cell Reports. 32 (3), 107925 (2020).</li><li>Karbassi, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiomyocyte+maturation:+Advances+in+knowledge+and+implications+for+regenerative+medicine.">Cardiomyocyte maturation: Advances in knowledge and implications for regenerative medicine.</a> Nature Reviews Cardiology. 17 (6), 341-359 (2020).</li><li>Li, Z., Hu, S., Ghosh, Z., Han, Z., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+characterization+and+expression+profiling+of+human+induced+pluripotent+stem+cell-+and+embryonic+stem+cell-derived+endothelial+cells.">Functional characterization and expression profiling of human induced pluripotent stem cell- and embryonic stem cell-derived endothelial cells.</a> Stem Cells Development. 20 (10), 1701-1710 (2011).</li><li>Lian, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+differentiation+of+human+pluripotent+stem+cells+to+endothelial+progenitors+via+small-molecule+activation+of+WNT+signaling.">Efficient differentiation of human pluripotent stem cells to endothelial progenitors via small-molecule activation of WNT signaling.</a> Stem Cell Report. 3 (5), 804-816 (2014).</li><li>Gu, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+differentiation+of+human+pluripotent+stem+cells+to+endothelial+cells.">Efficient differentiation of human pluripotent stem cells to endothelial cells.</a> Current Protocols in Human Genetics. 98 (1), 64 (2018).</li><li>Acharya, 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=The+bHLH+transcription+factor+Tcf21+is+required+for+lineage-specific+EMT+of+cardiac+fibroblast+progenitors.">The bHLH transcription factor Tcf21 is required for lineage-specific EMT of cardiac fibroblast progenitors.</a> Development. 139 (12), 2139-2149 (2012).</li><li>Wessels, 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=Epicardially+derived+fibroblasts+preferentially+contribute+to+the+parietal+leaflets+of+the+atrioventricular+valves+in+the+murine+heart.">Epicardially derived fibroblasts preferentially contribute to the parietal leaflets of the atrioventricular valves in the murine heart.</a> Development Biology. 366 (2), 111-124 (2012).</li><li>Ali, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developmental+heterogeneity+of+cardiac+fibroblasts+does+not+predict+pathological+proliferation+and+activation.">Developmental heterogeneity of cardiac fibroblasts does not predict pathological proliferation and activation.</a> Circulation Research. 115 (7), 625-635 (2014).</li><li>McMurtrey, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytic+and+numerical+models+of+oxygen+and+nutrient+diffusion,+metabolism+dynamics,+and+architecture+optimization+in+three-dimensional+tissue+constructs+with+applications+and+insights+in+cerebral+organoids.">Analytic and numerical models of oxygen and nutrient diffusion, metabolism dynamics, and architecture optimization in three-dimensional tissue constructs with applications and insights in cerebral organoids.</a> Tissue Engineering Part C Methods. (3), 221-249 (2015).</li><li>Thomas, D., O'Brien, T., Pandit, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+customized+extracellular+niche+engineering:+progress+in+cell-entrapment+technologies.">Toward customized extracellular niche engineering: progress in cell-entrapment technologies.</a> Advanced Materials. 30 (1), 1703948 (2018).</li><li>Thomas, D., Shenoy, S., Sayed, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Building+Multi-dimensional+induced+pluripotent+stem+cells-based+model+platforms+to+assess+cardiotoxicity+in+cancer+therapies.">Building Multi-dimensional induced pluripotent stem cells-based model platforms to assess cardiotoxicity in cancer therapies.</a> Front Pharmacol. 12, 39 (2021).</li><li>Rhee, J. -. W., 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=Modeling+secondary+iron+overload+cardiomyopathy+with+human+induced+pluripotent+stem+cell-derived+cardiomyocytes.">Modeling secondary iron overload cardiomyopathy with human induced pluripotent stem cell-derived cardiomyocytes.</a> Cell Reports. 32 (2), 107886 (2020).</li><li>Paik, D. T., Cho, S., Tian, L., Chang, H. Y., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+RNA+sequencing+in+cardiovascular+development,+disease,+and+medicine.">Single-cell RNA sequencing in cardiovascular development, disease, and medicine.</a> Nature Reviews Cardiology. 17 (8), 457-473 (2020).</li><li>Nguyen, Q. H., Pervolarakis, N., Nee, K., Kessenbrock, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+considerations+for+single-cell+RNA+sequencing+approaches.">Experimental considerations for single-cell RNA sequencing approaches.</a> Frontiers in Cell and Developmental Biology. 6, 108 (2018).</li><li>Lau, E., Paik, D. T., Wu, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systems-wide+approaches+in+induced+pluripotent+stem+cell+models.">Systems-wide approaches in induced pluripotent stem cell models.</a> Annual Reviews in Pathology. 14 (1), 395-419 (2019).</li><li>Maddah, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+non-invasive+platform+for+functional+characterization+of+stem-cell-derived+cardiomyocytes+with+applications+in+cardiotoxicity+testing.">A non-invasive platform for functional characterization of stem-cell-derived cardiomyocytes with applications in cardiotoxicity testing.</a> Stem Cell Report. 4 (4), 621-631 (2015).</li><li>Sala, L., 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=Musclemotion:+A+versatile+open+software+tool+to+quantify+cardiomyocyte+and+cardiac+muscle+contraction+in+vitro+and+in+vivo.">Musclemotion: A versatile open software tool to quantify cardiomyocyte and cardiac muscle contraction in vitro and in vivo.</a> Circulation Research. 122 (3), 5-16 (2018).</li></ol>

J.C.W. is a cofounder of Khloris Biosciences but has no competing interests, as the work presented here is completely independent. The other authors report no conflicts.

To generate cardiac microtissues from pre-differentiated iPSC-CMs, iPSC-ECs, and iPSC-CFs, it is essential to obtain a highly pure culture for better control of cell numbers after contact-inhibited cell compaction within the cardiac microtissues. Recently, Giacomelli et. al.18 have demonstrated the fabrication of cardiac microtissues using iPSC-CMs, iPSC-ECs, and iPSC-CFs. Cardiac microtissues generated using the described method consist of ~5,000 cells (70% iPSC-CMs, 15% iPSC-ECs, and 15% iPSC-CF...

Drug discovery and disease modeling in the field of cardiovascular research face several challenges due to a lack of clinically relevant samples and inadequate translational tools1. Highly complex pre-clinical models or oversimplified in vitro single-cell models do not exhibit pathophysiological conditions in a reproducible manner. Therefore, several miniaturized tissue-engineered platforms have evolved to help bridge the gap, with the goal of achieving a balance between ease of application in a high-throughput manner and faithful recapitulation of tissue function2,3. With the advent of induced pluripotent stem cell (iPSC) technology, tissue engineering tools can be applied to patient-specific cells with or without underlying cardiovascular disease state to answer research questions4,5,6. Such tissue engineered models with cellular composition similar to the heart tissue could be utilized in drug development efforts to test for cardiotoxicity and dysfunction induced by pathological changes in behavior of one or multiple cell types.
Self-assembled microtissues or organoids derived from human iPSCs are three-dimensional (3D) structures that are miniature tissue-like assemblies exhibiting functional similarities to their in vivo counterparts. There are several different approaches that allow formation of organoids in situ via directed differentiation of iPSCs or through the formation of embryoid bodies4. The resulting organoids are an indispensable tool to study morphogenetic processes that drive organogenesis. However, the presence of a variety of cell populations and differences in self-organization can lead to variability in outcomes between different organoids5. Alternatively, pre-differentiated cells that are self-assembled into microtissues with tissue-specific cell types to study local cell-cell interactions are excellent models, where it is feasible to isolate the self-assembled components. Particularly in human cardiac research, development of 3D cardiac microtissues with multicellular components has proven to be challenging when cells are derived from different patient lines or commercial sources.
To improve our mechanistic understanding of cell behaviors in a physiologically relevant, personalized, in vitro model, ideally all component cell types should be derived from the same patient line. In the context of a human heart, a truly representative cardiac in vitro model would capture the crosstalk among predominant cell types, namely, cardiomyocytes (CMs), endothelial cells (ECs), and cardiac fibroblasts (CFs)6,7. The faithful recapitulation of a myocardium not only requires biophysical stretch and electrophysiological stimulation, but also cell-cell signaling that arise from supporting cell types such as ECs and CFs8. CFs are involved in the synthesis of extracellular matrix and maintaining tissue structure; and in a pathological state, CFs can induce fibrosis and alter electrical conduction in the CMs9. Similarly, ECs can regulate contractile properties of CMs through paracrine signaling and supplying vital metabolic demands10. Hence, there is a need for human cardiac microtissues composed of all three major cell types to allow physiologically relevant high-throughput experiments to be conducted.
Here, we describe a bottom-up approach in fabrication of cardiac microtissues by derivation of human iPSC-derived cardiomyocytes (iPSC-CMs), iPSC-derived endothelial cells (iPSC-ECs), and iPSC-derived cardiac fibroblasts (iPSC-CFs) and their 3D culture in uniform cardiac microtissue arrays. This facile method of generating spontaneously beating cardiac microtissues can be utilized for disease modeling and rapid testing of drugs for functional and mechanistic understanding of heart physiology. Furthermore, such multicellular cardiac microtissue platforms could be exploited with genome editing techniques to emulate cardiac disease progression over time under chronic or acute culture conditions.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>12-well plates</td>
			<td>Fisher Scientific</td>
			<td>08-772-29</td>
			<td></td>
		</tr>
		<tr>
			<td>3D micro-molds</td>
			<td>Microtissues</td>
			<td>12-81 format</td>
			<td></td>
		</tr>
		<tr>
			<td>6-well plates</td>
			<td>Fisher Scientific</td>
			<td>08-772-1B</td>
			<td></td>
		</tr>
		<tr>
			<td>AutoMACS Rinsing Solution</td>
			<td>Thermo Fisher Scientific</td>
			<td>NC9104697</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 Supplement minus Insulin</td>
			<td>Life Technologies</td>
			<td>A1895601</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 Supplement plus Insulin</td>
			<td>Life Technologies</td>
			<td>17504-044</td>
			<td></td>
		</tr>
		<tr>
			<td>BD Cytofix</td>
			<td>BD Biosciences</td>
			<td>554655</td>
			<td></td>
		</tr>
		<tr>
			<td>BD Matrigel, hESC-qualified matrix</td>
			<td>BD Biosciences</td>
			<td>354277</td>
			<td></td>
		</tr>
		<tr>
			<td>Cardiac Troponin T Antibody</td>
			<td>Miltenyi</td>
			<td>130-120-403</td>
			<td></td>
		</tr>
		<tr>
			<td>CD144 (VE-Cadherin) MicroBeads</td>
			<td>Miltenyi</td>
			<td>130-097-857</td>
			<td></td>
		</tr>
		<tr>
			<td>CD31 Antibody</td>
			<td>Miltenyi</td>
			<td>130-110-670</td>
			<td></td>
		</tr>
		<tr>
			<td>CD31 Microbeads</td>
			<td>Miltenyi</td>
			<td>130-091-935</td>
			<td></td>
		</tr>
		<tr>
			<td>CHIR-99021</td>
			<td>Selleckchem</td>
			<td>S2924</td>
			<td></td>
		</tr>
		<tr>
			<td>DDR2</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-81707</td>
			<td></td>
		</tr>
		<tr>
			<td>Dead Cell Apoptosis Kit with Annexin V FITC and PI</td>
			<td>Thermo Fisher Scientific</td>
			<td>V13242</td>
			<td></td>
		</tr>
		<tr>
			<td>Dispase I</td>
			<td>Millipore Sigma</td>
			<td>4942086001</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM, high glucose (4.5g/L) no glutamine medium</td>
			<td></td>
			<td>11960044</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/F-12 basal medium</td>
			<td>Gibco</td>
			<td>11320033</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate buffered saline (DPBS), no calcium, no magnesium</td>
			<td>Life Technologies</td>
			<td>14190-136</td>
			<td></td>
		</tr>
		<tr>
			<td>EGM2 BulletKit</td>
			<td>Lonza</td>
			<td>CC-3124</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Life Technologies</td>
			<td>10437</td>
			<td></td>
		</tr>
		<tr>
			<td>FibroLife Serum-Free Fibroblast LifeFactors Kit</td>
			<td>LifeLIne Cell Technology</td>
			<td>LS-1010</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose free RPMI medium</td>
			<td>Life Technologies</td>
			<td>11879-020</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat serum</td>
			<td>Life Technologies</td>
			<td>16210-064</td>
			<td></td>
		</tr>
		<tr>
			<td>Human FGF-basic</td>
			<td>Thermo Fisher Scientific</td>
			<td>13256029</td>
			<td></td>
		</tr>
		<tr>
			<td>Human VEGF-165</td>
			<td>PeproTech</td>
			<td>100-20</td>
			<td></td>
		</tr>
		<tr>
			<td>IWR-1-endo</td>
			<td>Selleckchem</td>
			<td>S7086</td>
			<td></td>
		</tr>
		<tr>
			<td>Liberase TL</td>
			<td>Millipore Sigma</td>
			<td>5401020001</td>
			<td></td>
		</tr>
		<tr>
			<td>LS Sorting Columns</td>
			<td>Miltenyi</td>
			<td>130-042-401</td>
			<td></td>
		</tr>
		<tr>
			<td>MACS BSA Stock solution</td>
			<td>Miltenyi</td>
			<td>130-091-376</td>
			<td></td>
		</tr>
		<tr>
			<td>MACS Rinsing Buffer</td>
			<td>Miltenyi</td>
			<td>130-091-222</td>
			<td></td>
		</tr>
		<tr>
			<td>MidiMACS Separator</td>
			<td>Miltenyi</td>
			<td>130-042-302</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI medium</td>
			<td>Life Technologies</td>
			<td>11835055</td>
			<td></td>
		</tr>
		<tr>
			<td>SB431542</td>
			<td>Selleckchem</td>
			<td>S1067</td>
			<td></td>
		</tr>
		<tr>
			<td>TO-PRO 3</td>
			<td>Thermo Fisher Scientific</td>
			<td>R37170</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Millipore Sigma</td>
			<td>X100-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>TrypLE Select 10X</td>
			<td>Thermo Fisher Scientific</td>
			<td>red</td>
			<td></td>
		</tr>
		<tr>
			<td>Vimentin Alexa Fluor&#174; 488-conjugated Antibody</td>
			<td>R&#38;D Systems</td>
			<td>IC2105G</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

Immunostaining and flow cytometry characterization of iPSC-derived CMs, ECs, and CFs 
To generate cardiac microtissues composed of iPSC-CMs, iPSC-ECs, and iPSC-CFs, all three cell types are differentiated and characterized individually. In vitro differentiation of iPSCs to iPSC-CMs has improved over the past several years. However, the yield and purity of iPSC-CMs differ from line to line. The current protocol yields over 75% pure iPSC-CMs that spontaneously start beating around day 9 (<str...

Watch this Scientific Journal Video about Fabrication of 3D Cardiac Microtissue Arrays using Human iPSC-Derived Cardiomyocytes, Cardiac Fibroblasts, and Endothelial Cells at JoVE.com

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

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 ...

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Bioengineering

6.2K Views.  Stanford University School of Medicine. 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.

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

Encapsulation of Cardiomyocytes in a Fibrin Hydrogel for Cardiac Tissue Engineering

Culturing cells in a three dimensional hydrogel environment is an important technique for developing constructs for tissue engineering as well as studying cellular responses under various culture conditions in vitro. The three dimensional environment more closely mimics what the cells observe in vivo due to the application of mechanical and chemical stimuli in all dimensions 1. Three-dimensional hydrogels can either be made from synthetic polymers such as PEG-DA 2 and PLGA 3 or a number of naturally occurring proteins such as collagen 4, hyaluronic acid 5 or fibrin 6,7. Hydrogels created from fibrin, a naturally occurring blood clotting protein, can polymerize to form a mesh that is part of the body's natural wound healing processes 8. Fibrin is cell-degradable and potentially autologous 9, making it an ideal temporary scaffold for tissue engineering.
Here we describe in detail the isolation of neonatal cardiomyocytes from three day old rat pups and the preparation of the cells for encapsulation in fibrin hydrogel constructs for tissue engineering. Neonatal myocytes are a common cell source used for in vitro studies in cardiac tissue formation and engineering 4. Fibrin gel is created by mixing fibrinogen with the enzyme thrombin. Thrombin cleaves fibrinopeptides FpA and FpB from fibrinogen, revealing binding sites that interact with other monomers 10. These interactions cause the monomers to self-assemble into fibers that form the hydrogel mesh. Because the timing of this enzymatic reaction can be adjusted by altering the ratio of thrombin to fibrinogen, or the ratio of calcium to thrombin, one can injection mold constructs with a number of different geometries 11,12. Further we can generate alignment of the resulting tissue by how we constrain the gel during culture 13.
After culturing the engineered cardiac tissue constructs for two weeks under static conditions, the cardiac cells have begun to remodel the construct and can generate a contraction force under electrical pacing conditions 6. As part of this protocol, we also describe methods for analyzing the tissue engineered myocardium after the culture period including functional analysis of the active force generated by the cardiac muscle construct upon electrical stimulation, as well as methods for determining final cell viability (Live-Dead assay) and immunohistological staining to examine the expression and morphology of typical proteins important for contraction (Myosin Heavy Chain or MHC) and cellular coupling (Connexin 43 or Cx43) between myocytes.

We describe the isolation of neonatal cardiomyocytes and the preparation of the cells for encapsulation in fibrin hydrogel constructs for tissue engineering. We describe methods for analyzing the tissue engineered myocardium after the culture period including active force generated upon electrical stimulation and cell viability and immunohistological staining.

Culturing cells in a three dimensional hydrogel environment is an important technique for developing constructs for tissue engineering as well as studying ...

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.

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 ...

Creation of Cardiac Tissue Exhibiting Mechanical Integration of Spheroids Using 3D Bioprinting

This protocol describes 3D bioprinting of cardiac tissue without the use of biomaterials, using only cells. Cardiomyocytes, endothelial cells and fibroblasts are first isolated, counted and mixed at desired cell ratios. They are co-cultured in individual wells in ultra-low attachment 96-well plates. Within 3 days, beating spheroids form. These spheroids are then picked up by a nozzle using vacuum suction and assembled on a needle array using a 3D bioprinter. The spheroids are then allowed to fuse on the needle array. Three days after 3D bioprinting, the spheroids are removed as an intact patch, which is already spontaneously beating. 3D bioprinted cardiac patches exhibit mechanical integration of component spheroids and are highly promising in cardiac tissue regeneration and as 3D models of heart disease.

This protocol describes 3D bioprinting of cardiac tissue without the use of biomaterials. 3D bioprinted cardiac patches exhibit mechanical integration of component spheroids and are highly promising in cardiac tissue regeneration and as 3D models of heart disease.

This protocol describes 3D bioprinting of cardiac tissue without the use of biomaterials, using only cells. Cardiomyocytes, endothelial cells and ...

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. ...

Intra-cardiac Side-Firing Light Catheter for Monitoring Cellular Metabolism using Transmural Absorbance Spectroscopy of Perfused Mammalian Hearts

Absorbance spectroscopy of cardiac muscle provides non-destructive assessment of cytosolic and mitochondrial oxygenation via myoglobin and cytochrome absorbance respectively. In addition, numerous aspects of the mitochondrial metabolic status such as membrane potential and substrate entry can also be estimated. To perform cardiac wall transmission optical spectroscopy, a commercially available side-firing optical fiber catheter is placed in the left ventricle of the isolated perfused heart as a light source. Light passing through the heart wall is collected with an external optical fiber to perform optical spectroscopy of the heart in near real- time. The transmission approach avoids numerous surface scattering interference occurring in widely used reflection approaches. Changes in transmural absorbance spectra were deconvolved using a library of chromophore reference spectra, providing quantitative measures of all the known cardiac chromophores simultaneously. This spectral deconvolution approach eliminated intrinsic errors that may result from using common dual wavelength methods applied to overlapping absorbance spectra, as well as provided a quantitative evaluation of the goodness of fit. A custom program was designed for data acquisition and analysis, which permitted the investigator to monitor the metabolic state of the preparation during the experiment. These relatively simple additions to the standard heart perfusion system provide a unique insight into the metabolic state of the heart wall in addition to conventional measures of contraction, perfusion, and substrate/oxygen extraction.

Here we introduce a method for using an intra-ventricle optical catheter in perfused hearts to perform absorbance spectroscopy across the heart wall. The data obtained provides robust information on tissue oxygen tension as well as substrate utilization and membrane potential simultaneously with cardiac performance measures in this ubiquitous preparation.

Absorbance spectroscopy of cardiac muscle provides non-destructive assessment of cytosolic and mitochondrial oxygenation via myoglobin and cytochrome ...

Standardized and Scalable Assay to Study Perfused 3D Angiogenic Sprouting of iPSC-derived Endothelial Cells In Vitro

Pre-clinical drug research of vascular diseases requires in vitro models of vasculature that are amendable to high-throughput screening. However, current in vitro screening models that have sufficient throughput only have limited physiological relevance, which hinders the translation of findings from in vitro to in vivo. On the other hand, microfluidic cell culture platforms have shown unparalleled physiological relevancy in vitro, but often lack the required throughput, scalability and standardization. We demonstrate a robust platform to study angiogenesis of endothelial cells derived from human induced pluripotent stem cells (iPSC-ECs) in a physiological relevant cellular microenvironment, including perfusion and gradients. The iPSC-ECs are cultured as 40 perfused 3D microvessels against a patterned collagen-1 scaffold. Upon the application of a gradient of angiogenic factors, important hallmarks of angiogenesis can be studied, including the differentiation into tip- and stalk cell and the formation of perfusable lumen. Perfusion with fluorescent tracer dyes enables the study of permeability during and after anastomosis of the angiogenic sprouts. In conclusion, this method shows the feasibility of iPSC-derived ECs in a standardized and scalable 3D angiogenic assay that combines physiological relevant culture conditions in a platform that has the required robustness and scalability to be integrated within the drug screening infrastructure.

This method describes the culture of iPSC-derived endothelial cells as 40 perfused 3D microvessels in a standardized microfluidic platform. This platform enables the study of gradient-driven angiogenic sprouting in 3D, including anastomosis and stabilization of the angiogenic sprouts in a scalable and high-throughput manner.

Pre-clinical drug research of vascular diseases requires in vitro models of vasculature that are amendable to high-throughput screening. However, current ...

Human iPSC-Derived Cardiomyocyte Networks on Multiwell Micro-electrode Arrays for Recurrent Action Potential Recordings

Cardiac safety screening is of paramount importance for drug discovery and therapeutics. Therefore, the development of novel high-throughput electrophysiological approaches for hiPSC-derived cardiomyocyte (hiPSC-CM) preparations is much needed for efficient drug testing. Although multielectrode arrays (MEAs) are frequently employed for field potential measurements of excitable cells, a recent publication by Joshi-Mukherjee and colleagues described and validated its application for recurrent action potential (AP) recordings from the same hiPSC-CM preparation over days. The aim here is to provide detailed step-by-step methods for seeding CMs and for measuring AP waveforms via electroporation with high precision and a temporal resolution of 1 &#181;s. This approach addresses the lack of easy-to-use methodology to gain intracellular access for high-throughput AP measurements for reliable electrophysiological investigations. A detailed work flow and methods for plating of hiPSC-CMs on multiwell MEA plates are discussed emphasizing critical steps wherever relevant. In addition, a custom-built MATLAB script for rapid data handling, extraction and analysis is reported for comprehensive investigation of the waveform analysis to quantify subtle differences in morphology for various AP duration parameters implicated in arrhythmia and cardiotoxicity.

This article contains a set of protocols for the development of human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) networks cultured on multiwell MEA plates to reversibly electroporate the cell membrane for action potential measurements. High-throughput recordings are obtained from the same cell sites repeatedly over days.

Cardiac safety screening is of paramount importance for drug discovery and therapeutics. Therefore, the development of novel high-throughput ...

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 ...