This work was supported by a grant-in-aid from the Heart and Stroke Foundation of Canada (G-14-0006265), operating grants from the Canadian Institutes of Health Research (137352 and 143066), and a J.P. Bickell foundation grant (1013821) to SSN.

1. Master Design and Fabrication
NOTE: Use soft lithography for device fabrication. Make a two-layer SU-8 master for polydimethylsiloxane (PDMS) molding.
<ol>
	<li>Design the device using a design and drafting software (Figure 1A, left). Draw each layer of the master separately. Print the device design on two photomasks at 20,000 dpi, corresponding to the two layers of the master15. Set the device pattern as transparent and the surrounding area as dar...

<ol>
	<li>Sun, X., Nunes, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Overview+of+hydrogel-based+strategies+for+application+in+cardiac+tissue+regeneration.">Overview of hydrogel-based strategies for application in cardiac tissue regeneration.</a> Biomed Mater. 10 (3), 034005 (2015).</li><li>Sun, X., Altalhi, W., Nunes, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascularization+strategies+of+engineered+tissues+and+their+application+in+cardiac+regeneration.">Vascularization strategies of engineered tissues and their application in cardiac regeneration.</a> Adv Drug Deliv Rev. 96, 183-194 (2016).</li><li>Hastings, C. 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=Drug+and+cell+delivery+for+cardiac+regeneration.">Drug and cell delivery for cardiac regeneration.</a> Advanced Drug Delivery Reviews. 84, 85-106 (2015).</li><li>Yang, 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=Human+cardiovascular+progenitor+cells+develop+from+a+KDR++embryonic-stem-cell-derived+population.">Human cardiovascular progenitor cells develop from a KDR+ embryonic-stem-cell-derived population.</a> Nature. 453 (7194), 524-528 (2008).</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=Extracellular+matrix+promotes+highly+efficient+cardiac+differentiation+of+human+pluripotent+stem+cells:+the+matrix+sandwich+method.">Extracellular matrix promotes highly efficient cardiac differentiation of human pluripotent stem cells: the matrix sandwich method.</a> Circ Res. 111 (9), 1125-1136 (2012).</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=Robust+cardiomyocyte+differentiation+from+human+pluripotent+stem+cells+via+temporal+modulation+of+canonical+Wnt+signaling.">Robust cardiomyocyte differentiation from human pluripotent stem cells via temporal modulation of canonical Wnt signaling.</a> Proc Natl Acad Sci U S A. 109 (27), E1848-E1857 (2012).</li><li>Snir, 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=Assessment+of+the+ultrastructural+and+proliferative+properties+of+human+embryonic+stem+cell-derived+cardiomyocytes.">Assessment of the ultrastructural and proliferative properties of human embryonic stem cell-derived cardiomyocytes.</a> Am J Physiol Heart Circ Physiol. 285 (6), H2355-H2363 (2003).</li><li>Dolnikov, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+properties+of+human+embryonic+stem+cell-derived+cardiomyocytes:+intracellular+Ca2++handling+and+the+role+of+sarcoplasmic+reticulum+in+the+contraction.">Functional properties of human embryonic stem cell-derived cardiomyocytes: intracellular Ca2+ handling and the role of sarcoplasmic reticulum in the contraction.</a> Stem Cells. 24 (2), 236-245 (2006).</li><li>Yang, X., Pabon, L., Murry, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+adolescence:+maturation+of+human+pluripotent+stem+cell-derived+cardiomyocytes.">Engineering adolescence: maturation of human pluripotent stem cell-derived cardiomyocytes.</a> Circ Res. 114 (3), 511-523 (2014).</li><li>Zimmermann, W. 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=Tissue+engineering+of+a+differentiated+cardiac+muscle+construct.">Tissue engineering of a differentiated cardiac muscle construct.</a> Circ Res. 90 (2), 223-230 (2002).</li><li>Radisic, 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=Functional+assembly+of+engineered+myocardium+by+electrical+stimulation+of+cardiac+myocytes+cultured+on+scaffolds.">Functional assembly of engineered myocardium by electrical stimulation of cardiac myocytes cultured on scaffolds.</a> Proc Natl Acad Sci U S A. 101 (52), 18129-18134 (2004).</li><li>Schaaf, S., 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+engineered+heart+tissue+as+a+versatile+tool+in+basic+research+and+preclinical+toxicology.">Human engineered heart tissue as a versatile tool in basic research and preclinical toxicology.</a> PLoS One. 6 (10), e26397 (2011).</li><li>Tulloch, N. 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=Growth+of+engineered+human+myocardium+with+mechanical+loading+and+vascular+coculture.">Growth of engineered human myocardium with mechanical loading and vascular coculture.</a> Circ Res. 109 (1), 47-59 (2011).</li><li>Nunes, S. S., 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=Biowire:+a+platform+for+maturation+of+human+pluripotent+stem+cell-derived+cardiomyocytes.">Biowire: a platform for maturation of human pluripotent stem cell-derived cardiomyocytes.</a> Nat Methods. 10 (8), 781-787 (2013).</li><li>Lake, 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=Microfluidic+device+design,+fabrication,+and+testing+protocols.">Microfluidic device design, fabrication, and testing protocols.</a> Protocol Exchange. , (2015).</li><li>Shiba, Y., Hauch, K. D., Laflamme, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+applications+for+human+pluripotent+stem+cells.">Cardiac applications for human pluripotent stem cells.</a> Curr Pharm Des. 15 (24), 2791-2806 (2009).</li><li>Yang, 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=Tri-iodo-l-thyronine+promotes+the+maturation+of+human+cardiomyocytes-derived+from+induced+pluripotent+stem+cells.">Tri-iodo-l-thyronine promotes the maturation of human cardiomyocytes-derived from induced pluripotent stem cells.</a> J Mol Cell Cardiol. 72, 296-304 (2014).</li><li>Zhang, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue-engineered+cardiac+patch+for+advanced+functional+maturation+of+human+ESC-derived+cardiomyocytes.">Tissue-engineered cardiac patch for advanced functional maturation of human ESC-derived cardiomyocytes.</a> Biomaterials. 34 (23), 5813-5820 (2013).</li><li>Radisic, 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=Oxygen+gradients+correlate+with+cell+density+and+cell+viability+in+engineered+cardiac+tissue.">Oxygen gradients correlate with cell density and cell viability in engineered cardiac tissue.</a> Biotechnol Bioeng. 93 (2), 332-343 (2006).</li><li>Reubinoff, B. E., Pera, M. F., Fong, C. Y., Trounson, A., Bongso, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryonic+stem+cell+lines+from+human+blastocysts:+somatic+differentiation+in+vitro.">Embryonic stem cell lines from human blastocysts: somatic differentiation in vitro.</a> Nat Biotechnol. 18 (4), 399-404 (2000).</li></ol>

This manuscript describes the setup and implementation of the engineered platform, biowire, to improve the maturation of hPSC-CMs. The device can be made in standard microfabrication facilities, and biowires can be produced with common cell culture techniques and an electrical stimulator.
To our knowledge, there is no reported method similar to biowires. This strategy reveals that improved maturation properties were dependent on the electrical stimulation regimen, as evidenced by the greater m...

Cell-based therapy is one of the most promising and investigated strategies to achieve cardiac repair/regeneration. It has been aided by cardiac tissue engineering and the co-delivery of biomaterials1,2. Most available cell sources have been studied in animal models for their potentially beneficial effects on damaged, diseased, or aged hearts3. In particular, significant efforts have been made to use human pluripotent stem cell (hPSC)-derived cardiomyocytes (hPSC-CM), a potentially unlimited autologous cell source for cardiac tissue engineering. hPSC-CMs can be produced using several established protocols4,5,6. However, the obtained cells display fetal-like phenotypes, with a range of immature characteristics compared to adult ventricular cardiomyocytes7,8. This can be an obstacle to the application of hPSC-CMs as models of adult heart tissue in drug discovery research and in the development of adult cardiac disease models9.
In order to overcome this limitation of phenotypic immaturity, new approaches have been actively investigated to promote cardiomyocyte maturation. Early studies revealed effective pro-maturation properties in neonatal rat cardiomyocytes via cyclic mechanical10 or electrical stimulation11. Gel compaction and cyclic mechanical stimulation were also shown to improve some aspects of hPSC-CM maturation12,13, with minimal enhancement of the electrophysiological and calcium handling properties. Therefore, a platform system called &#34;biological wire&#34; (biowire) was devised by providing both structural cues and electrical field stimulation to enhance the maturation of hPSC-CMs14. This system uses a microfabricated platform to create aligned cardiac tissue that is amenable to electrical field stimulation. This can be used to improve the structural and electrophysiological maturity of hPSC-CMs. Here, we describe the details of making such biowires.

<table border="0" cellpadding="0" cellspacing="0" width="582">
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">L-Ascorbic acid</td>
			<td style="width:80px;">Sigma</td>
			<td style="width:119px;">A-4544</td>
			<td style="width:167px;">hPSC-CM culture media componet</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">AutoCAD</td>
			<td style="width:80px;">Autodesk, Inc</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Software to design device</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Carbon rods, &#216; 3 mm</td>
			<td style="width:80px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Electrical stimulator chamber component</td>
		</tr>
		<tr height="206">
			<td height="206" style="height:206px;width:216px;">Collagen, type 1, rat tail</td>
			<td style="width:80px;">BD Biosciences</td>
			<td style="width:119px;">354249</td>
			<td style="width:167px;">Collagen gel: 2.1 mg/ml of rat tail collagen type I in 24.9 mM glucose, 23.8 mM NaHCO3, 14.3 mM NaOH, 10 mM HEPES, in 1xM199 media with 10 % of growth factor-reduced Matrigel.</td>
		</tr>
		<tr height="164">
			<td height="164" style="height:164px;width:216px;">Collagenase type I&#160;</td>
			<td style="width:80px;">Sigma</td>
			<td style="width:119px;">C0130</td>
			<td style="width:167px;">0.2% collagenase type I (w/v) and 20% FBS (v/v) in PBS with Ca2+ and Mg2+. Sterilize with 0.22 &#956;m filter and make 12 ml aliquots. Store at -20 &#176;C.</td>
		</tr>
		<tr height="100">
			<td height="100" style="height:100px;width:216px;">Deoxyribonuclease I (DNase I)</td>
			<td style="width:80px;">EMD Millipore</td>
			<td style="width:119px;">260913-25MU</td>
			<td style="width:167px;">Make 1 mg/ml DNase I stock solution in water. Filter sterile and store 0.5 ml aliquots at &#8722;20 &#176;C</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Drill &#38; drill bits (&#216; 1mm and 2 mm)</td>
			<td style="width:80px;">Dremel</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Drill holes in polycarbonate frames</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Electrical stimulator</td>
			<td style="width:80px;">Grass</td>
			<td style="width:119px;">s88x</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Fetal bovine serum (FBS)</td>
			<td style="width:80px;">WISENT Inc.</td>
			<td style="width:119px;">080-450</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">D-(+)-Glucose&#160;</td>
			<td style="width:80px;">Sigma</td>
			<td style="width:119px;">G5767</td>
			<td style="width:167px;">Collagen gel component</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">L-Glutamine</td>
			<td style="width:80px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">25030081</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:216px;">H2O</td>
			<td style="width:80px;">MilliQ</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">18.2 M&#937;&#183;cm at 25 &#176;C, ultrapure, to make all solutions</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">HEPES</td>
			<td style="width:80px;">Sigma</td>
			<td style="width:119px;">H4034</td>
			<td style="width:167px;">Collagen gel component</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Hot plate</td>
			<td style="width:80px;">Torrey Pines</td>
			<td style="width:119px;">HS40</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Iscove&#39;s Modified Dulbecco&#39;s Medium(IMDM)</td>
			<td style="width:80px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">12440053</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Mask aligner</td>
			<td style="width:80px;">EVG&#160;</td>
			<td style="width:119px;">EVG 620</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Matrigel, growth factor reduced&#160;</td>
			<td style="width:80px;">Corning</td>
			<td style="width:119px;">354230</td>
			<td style="width:167px;">Collagen gel component</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Medium 199 (M199)</td>
			<td style="width:80px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">11150059</td>
			<td style="width:167px;">Collagen gel component</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Monothioglycerol (MTG)</td>
			<td style="width:80px;">Sigma</td>
			<td style="width:119px;">M-6145</td>
			<td style="width:167px;">hPSC-CM culture media componet</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Orbital shaker</td>
			<td style="width:80px;">VWR</td>
			<td style="width:119px;">89032-088</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Penicillin/Streptomycin (P/S)</td>
			<td style="width:80px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">15070063</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Phosphate-buffered saline (PBS) with Ca2+ and Mg2+&#160;</td>
			<td style="width:80px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">14040133</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Plate (6-well)</td>
			<td style="width:80px;">Corning</td>
			<td style="width:119px;">353046</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Plate (6-well), low attachment</td>
			<td style="width:80px;">Corning</td>
			<td style="width:119px;">3471</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Platinum wires, 0.2 mm</td>
			<td style="width:80px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Electrical stimulator chamber component</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Polydimethylsiloxane (PDMS)</td>
			<td style="width:80px;">Dow Corning</td>
			<td style="width:119px;">Sylgard 184</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Propylene glycol monomethyl ether acetate (PGMEA)</td>
			<td style="width:80px;">Doe &#38; Ingalls Inc.</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">To develop the wafer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Pouch, peel-open</td>
			<td style="width:80px;">Convertors</td>
			<td style="width:119px;">92308</td>
			<td style="width:167px;">For steam sterilization</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Silicon wafer, 4-inch</td>
			<td style="width:80px;">UniversityWafer Inc.</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="46">
			<td height="46" style="height:46px;width:216px;">Sodium bicarbonate (NaHCO3)</td>
			<td style="width:80px;">Sigma</td>
			<td style="width:119px;">S5761</td>
			<td style="width:167px;">Collagen gel component</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Sodium hydroxide</td>
			<td style="width:80px;">Sigma</td>
			<td style="width:119px;">S8045</td>
			<td style="width:167px;">Collagen gel component</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Sprin coater</td>
			<td style="width:80px;">Specialty Coating Systems</td>
			<td style="width:119px;">G3P-8</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="280">
			<td height="280" style="height:280px;width:216px;">StemPro-34 culture medium</td>
			<td style="width:80px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">10639011</td>
			<td style="width:167px;">hPSC-CM culture medium. To make 50 ml, add 1.3 ml supplement, 500 &#956;l of 100&#215; L-Glutamine, 250 &#956;l of 30 mg/ml transferrin, 500 &#956;l of 5 mg/ml ascorbic acid, 150 &#956;l of 26 &#956;l /2 ml monothioglycerol (MTG), and 500 &#956;l (1 %) penicillin/streptomycin.</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Stop media</td>
			<td style="width:80px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">&#160;Wash medium:FBS (1:1)</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">SU-8 50&#160;</td>
			<td style="width:80px;">MicroChem Corp.</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">photoresist, master component</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">SU-8 2050&#160;</td>
			<td style="width:80px;">MicroChem Corp.</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">photoresist, master component</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Transferrin</td>
			<td style="width:80px;">Roche</td>
			<td style="width:119px;">10-652-202</td>
			<td style="width:167px;">hPSC-CM culture media componet</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Trypsin/EDTA, 0.25%</td>
			<td style="width:80px;">Thermo Fisher Scientific</td>
			<td style="width:119px;">25200056</td>
			<td style="width:167px;">hPSC-CM culture media componet</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Wash medium</td>
			<td style="width:80px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">IMDM containing 1% Penicillin/Streptomycin</td>
		</tr>
	</tbody>
</table>

maturation of human stem cell-derived cardiomyocytes in biowires using electrical stimulation

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

The rational for the use of a suture in the biowires is to serve as a template for the formation of 3D constructs that align in one axis and mimic the shape of cardiac fibers. We show that after seven days of culture in the biowire, cells remodeled the gel around the suture (Figure 3A). The cells assembled along the axis of the suture to form aligned cardiac tissue (Figure 3). After 7 days of preculture, the biowires were subjected to 7 days of electrical...

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

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

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

The overall goal of this procedure is to utilize controlled three dimensional cell cultivation methods in electrical stimulation to promote the maturation of human embryonic and induced pluripotent stem cells derived cardiomyocytes. This method can help answer key questions in the cardiac tissue engineering field including how different electrical stimulation parameters or length of time affect cardiac cell function and maturation state. The end results are engineered human cardiac tissues of improved maturity.The implications of this technique extend toward diagnosis applications such as testing the safety and efficacy of new drugs because cardiomyocyte with mature characteristics such as electrical progress are most likely to serve as more accurate models of human cardiac cells in drug screening studies. Combine the PDMS monomer and curing agent at a 10:1 ratio and mix well. Let it set for five minutes to degas.Then load a Petri dish containing the master for the biowire template with the PDMS mixture. Try to minimize air bubble formation. Next cure the PDMS at 70 degree Celsius for two hours.Then recover the solidified mold by first using a sharp blade around the edges and then peeling it away. Then trim the excess PDMS and collect all the templates in a sterilization pouch. Steam auto clave the templates at 121 degree Celsius for 20 minutes.And then load each template into a sterile Petri dish under the ventilation of a biosafety cabinet. Now for each template use tweezers to mount a piece of sterile 6.0 silk suture into the groove spanning the entire channel. The templates are then ready for cell seeding.The suture will serve as a template for the formation of 3D constructs that align along the suture axis mimicking the shape of cardiac fibers. For each chamber, make a pair of rectangular polycarbonate pieces to serve as the frame for the electrical stimulation chamber. Along the center line of each piece, drill two three millimeter wide holes, two centimeters apart.For each chamber prepare two 1.5 centimeter long carbon rods. About 3 millimeters from the end of each rod drill a one millimeter wide hole. Then thread each hole with a platinum wire and wrap one end of the wire around the rod.Next, for each chamber insert two rods between two polycarbonate pieces making a frame. Then pour about two milliliters of PDMS into a well of a six well plate and place the frame into the well with PDMS, submerging the bottom of the frames. Cure the PDMS at 70 degree Celsius for two hours so the PDMS secures the frame.Then remove the completed chamber from the plate with the PDMS attached. To test the function of an assembled chamber connect the platinum wires to a battery and use a voltmeter to check that electricity is being passed through the rods. Now transfer the functional chambers into a sterilization pouch and use 20 minutes of steam sterilization at 121 degree celsius to prepare them for cell culture.To prepare the gel, precool all the gel components on ice before mixing them in a sterile tube. Make sure to add the collagen and extra cellular matrix last and mix the components using pipetting. For the cells have cardiomyocytes differentiated from human pluripotent stem cells.Collect the cells and for each biowire preparation plant prepare 3.5 microliters of collagen gel containing half a million cells. Now use a P10 pipette tip to load approximately four milliliters of suspension into the 0.5 centimeter long channel template in each dish. Adjust the position of the suture using sterile forceps as needed so it is fully stretched.Once seeding the cells, make sure to always resuspend the gel cell mixture before taking autoclave in order to have consistent results. After loading the channels, cover the bottom of the dish with sterile PBS making sure not to touch the gel. This will ensure that the biowires do not dehydrate during polymerization.After incubating the biowires at 37 degree celsius for 30 minutes, replace the PBS with enough culture medium to cover the cells. 12 milliliters is usually enough. Then culture the dish for a week replacing the medium every other day.In a bio safety cabinet add two milliliters of PBS to each well of a six well plate that will house an electrical stimulator chamber. Then use sterile tweezers to gently place the autoclave devices into the wells. Once in position, discard the PBS and replace it with five milliliters of warm medium which should completely cover the carbon rods.Before culturing the cells for 24 hours, observe the cardiomyocytes contractility in response to electrical stimulation to ensure that the cells are capturing the electrical stimulus and responding with contractions. Next, place the biowires into the electrical stimulator chamber and orient the channels perpendicularly to the carbon rods. Extend the platinum wires away from the plate and then cover the plates.Connect the wires to an electrical stimulator. Set the stimulator to deliver biphasic one millisecond pulses at one hertz and at three volts per centimeter. Then transfer the preparations in the electrical stimulator to an incubator at 37 degree celsius.Increase stimulation rate incrementally every 24 hours from one hertz at day zero to six hertz at day six. During this week of culture, change the medium every other day. And observe the cardiomyocytes contractility on a daily basis.After seven days of preculture in the biowire cells remolded the gel around the suture. The cells assembled along the axis of the suture to form aligned cardiac tissue. The cells expressed cardiac contractile proteins showed sarcomeric banding in the contractile apparatus and their myofibrils were aligned along the axis of the suture.Cells in the biowire exhibited lower proliferation rates than cells in embryoid bodies. Calcium handling was significantly improved in the cardiomyocytes cultivated in biowires. Treatment with caffeine induced an abrupt release of calcium from the sacroplasmic reticulum.Such transients were found only in stimulated cells. There were also significantly higher stimulation frequency depending calcium release amplitudes. In addition, cardiomyocytes cultured in biowires showed improved hERG and inward rectifier current densities compared to cultivation in embryoid bodies which was further enhanced by electrical stimulation.The improved inward rectifier current was consistent with increased expression of the potassium inwardly rectifying channel jean, KCN J2.Automaticity the ability to beat spontaneously was significantly higher in embryoid body derived cardiomyocytes compared to controlled biowires. Control showed automaticity comparable to biowire preparation subjected to the six hertz regimen. Once mastered the setup of the biowires can be done in half a day.The setup of electrical stimulation will take a couple of hours and the final results can be reached in two weeks. While attempting this procedure, it is important to remember that cardiomyocytes differentiated from different cell lines or by different protocols can vary slightly in their maturity and purity. Therefore optimizing the experimental parameters such as the stimulation rate to your cells might be required.Following this procedure, other conditions including variation of the cellular composition and the utilization of mutant cardiomyocytes can be optimized to answer a bevy of additional questions.

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9.0K vistas.  University Health Network. The overall goal of this procedure is to utilize controlled three dimensional cell cultivation methods in electrical stimulation to promote the maturation of human embryonic and induced pluripotent stem cells derived cardiomyocytes. This method can help answer key questions in the cardiac tissue engineering field including how different electrical stimulation parameters or length of time affect cardiac cell function and maturation state. The end results are engineered human cardiac tissues of...