E. T. was supported by The Magic That Matters and AHA. C. K. was supported by grants from NICHD/NIH (R01HD086026), AHA, and MSCRF.&#160;

NOTE: In vitro generation of heart field-specific mouse cardiac progenitor cells (Figure 1).
1. Maintenance of Mouse ESCs
<ol>
	<li>Grow mESCs (mESCsTbx1-Cre; Rosa-RFP; HCN4-GFP, mESCIsl1-RFP)25 on 0.1% (w/v) gelatin coated T25 flasks in 2i medium (870 mL of glascow minimum essential medium (GMEM), 100 mL of fetal bovine serum (FBS), 10 mL of GlutaMAX, 10 mL of non-essential amino acids, 10 mL of sodium pyruvate, 3 &#956;L of beta-mercaptoethanol, 20 &#956;L of Lif (200 U/mL), 0.3 &#956;M CHIR99021 and 0.1 &#956;M PD0325901).</li>
	<li>When the cells reach 70-80% confluence, rinse the cells once with phosphate buffer solution (PBS) and then dissociate into single cells by adding 1 mL of Trypsin and incubating at 37 &#176;C for 3 min.</li>
	<li>Neutralize Trypsin by adding 4 mL of 10% FBS in Dulbecco&#8217;s Modified Eagle Medium (DMEM). Count the cells using an automated cell counter.</li>
	<li>Centrifuge ~3 x 105 cells for 3 min at 270 x g and room temperature.</li>
	<li>Aspirate the supernatant, resuspend the cells in 5 mL of 2i medium and replate on 0.1% (w/v) gelatin coated T25 flasks for maintenance.</li>
</ol>
2. Generation of Cardiac Progenitor Cells Using Cardiac Spheroids
<ol>
	<li>Centrifuge 2.5 x 106 cells from step 1.3 for 3 min at 270 x g and room temperature.</li>
	<li>Aspirate the supernatant and resuspend the cells in 25 mL of SFD medium (105 cells/mL). Depending on the scale of the experiment, mESC number can be adjusted accordingly. 
	NOTE: SFD medium contains 715 mL of Iscove&#8217;s Modified Dulbecco&#8217;s Medium (IMDM), 250 mL of Ham&#8217;s F12, 5 mL of N2-supplement, 10 mL of B27 minus Vitamin A, 5 mL of 10% (w/v) BSA (in PBS), 7.5 mL of GlutaMAX and 7.5 mL of Penicillin-Streptomycin. Add ascorbic acid (50 &#956;g/mL) and 3.9 x 10-3% (v/v) of monothioglycerol prior to using.</li>
	<li>Plate the cell suspension into one 150 mm x 25 mm sterile plate and incubate at 37 &#176;C in the 5% CO2 incubator for 48 h. Cardiac spheroids should be formed within 24 h.</li>
	<li>Collect all the formed cardiac spheroids and centrifuge for 3 min at 145 x g and room temperature to selectively isolate spheroids and avoid single cells.</li>
	<li>Aspirate the supernatant and resuspend the spheroids in 25 mL of SFD medium with 1 ng/mL of Activin A and 1.5 ng/mL of BMP4 for differentiation induction. Plate the spheroids in the same 150 mm x 25mm sterile plate and incubate them at 37 &#176;C in the 5% CO2 incubator for 40 h. 
	NOTE: Different concentrations of Activin A (0-3 ng/mL) and BMP4 (0.5-2 ng/mL) can be used for differentiation optimization depending on the mESC line.</li>
	<li>Collect all the cardiac spheroids and centrifuge for 3 min at 145 x g and room temperature.</li>
	<li>Aspirate the supernatant and resuspend the spheroids in 25 mL of SFD medium. Transfer the resuspended EBs in an ultra-low attachment 75 cm2 flask and incubate them at 37 &#176;C in the 5% CO2 incubator for 48 h.&#160;</li>
</ol>
3. Isolation of Heart Field Specific Cardiac Progenitor Cells Using Fluorescent Reporters
<ol>
	<li>Centrifuge cardiac spheroids at 145 x g and room temperature for 3min and aspirate the supernatant. Add 1 mL of Trypsin and incubate at 37 &#176;C for 3 min. Mix well by pipetting to dissociate the cells.</li>
	<li>Add 4 mL of 10% FBS in DMEM to inactivate Trypsin and mix well by pipetting. To remove the non-dissociated EBs, filter the mix using a 70 &#956;m strainer and centrifuge the filtrated cells for 3 min at 270 x g and room temperature.</li>
	<li>To sort CPCs carrying fluorescent reporters (CPCs derived from mESCsTbx1-Cre; Rosa-RFP; HCN4-GFP), aspirate the supernatant and add 500 &#956;L of FACS sorting solution (1% (v/v) FBS, 200 mM HEPES and 10 mM of EDTA in PBS) to resuspend.</li>
	<li>To remove all cell clusters prior to sorting, filter the cells again using a 5 mL polystyrene round-bottom tube with a 40 &#956;m cell strainer. Keep the cells on ice until sorting.</li>
	<li>Sort the cells to isolate Tbx1-Cre; Rosa-RFP and HCN4-GFP positive CPCs using a fluorescent activated cell sorter (FACS). Collect the sorted cells in 1 mL of FBS. Keep the cell sample and sorted cells at 4 &#176;C.</li>
</ol>
4. Isolation of Heart Field Specific Cardiac Progenitor Cells Using Cxcr4 as a Cell Surface Protein Marker
<ol>
	<li>To isolate first vs second heart field CPCs based on the expression of the surface protein receptor Cxcr4, use the mESCIsl1-RFP line. Aspirate the supernatant from step 3.3 and resuspend the single CPCs in 300 &#956;L of 10% FBS in PBS containing 1:200 (vol/vol) PerCP-efluor 710 conjugated anti-Cxcr4 antibody.</li>
	<li>Incubate at room temperature for 5min and wash by adding 1-2 mL of cold PBS. Centrifuge the single CPCs for 3 min at 270 x g and room temperature and wash two more times followed by centrifugation.</li>
	<li>Aspirate the supernatant and add 500 &#956;L of FACS sorting solution to resuspend the single CPCs and filter as in step 3.4.</li>
	<li>Isolate Cxcr4+ and Cxcr4- cells using FACS. Collect the sorted cells in 1 mL of FBS. Keep the cell sample and sorted cells at 4 &#176;C.</li>
</ol>
5. Analysis of Isolated Heart Field Specific Cardiac Progenitor Cells
<ol>
	<li>Centrifuge sorted CPCs for 3 min at 270 x g and room temperature. Sorted cells can be used for gene and protein expression analyses or they can be recultured for analyses at later time points.&#160;</li>
	<li>To re-culture isolated CPCs, aspirate the supernatant, resuspend the cells in SFD medium and replate ~3 x 104 cells per well of a 384-well plate coated with 0.1% (w/v) gelatin.&#160; If increased cell death is noted after sorting, add 10 &#956;M of Y-27632 (ROCK inhibitor) to the sample. Two days after reculture, spontaneous beating should be noted.</li>
	<li>To analyze the ability of plated CPCs to differentiate to cardiomyocytes, collect the cells at day 12 of differentiation. Use Trypsin as described in steps 1.2-1.5 to isolate single CMs. Resuspend the cells in 4% (w/v) paraformaldehyde (PFA) and incubate for 30 min at room temperature to fix the cells.</li>
	<li>Centrifuge the cells for 3 min at 895 x g, and room temperature. Aspirate the supernatant and resuspend the cells in PBS to wash the PFA. Repeat this step once more.</li>
	<li>Aspirate the supernatant and resuspend the cells in 10% FBS in PBS. Incubate half of the cell sample with mouse anti-Troponin T antibody (1:500) and use the rest of the sample as a negative control. Incubate for 30 min at room temperature.</li>
	<li>Wash the cells twice as described in step 5.4 using PBS. Aspirate the supernatant and resuspend both cell samples in 10% FBS in PBS with 1:500 donkey anti-mouse IgG (H+L) secondary antibody, Alexa Fluor 647 conjugate. Incubate for 30 min at room temperature.</li>
	<li>Wash twice with PBS as in step 5.6. Aspirate the supernatant and resuspend the cells in 200 &#956;L of PBS. Use a flow cytometer to analyze the cells.</li>
</ol>

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The authors have nothing for disclosures.

In our protocol, we describe a methodology to generate cardiac spheroids and isolated heart field-specific CPCs. Those can be used to study mechanisms of CPC specification and their properties, as well as for cardiac chamber-specific disease modelling. One previously published work used a mESC line with two fluorescent reporters (Mef2c/Nkx2.5) to study cardiogenesis in vitro, however, both those markers are expressed at embryonic day 9.5-10 when cardiomyocytes are already formed26. To our knowledg...

The use of pluripotent stem cells (PSCs) has revolutionized the field of cardiac regeneration and personalized medicine with patient-specific myocytes for disease modeling and drug therapies1,2,3,4. More recently, in vitro protocols for the generation of atrial vs ventricular as well as pacemaker-like PSC-derived cardiomyocytes have been developed5,6. However, whether cardiogenesis can be recreated in vitro to study cardiac development and subsequently generate ventricular chamber-specific cardiac cells is still unclear.
During early embryonic development, mesodermal cells under the influence of secreted morphogens such as BMP4, Wnts and Activin A form the primitive streak7. Cardiac mesodermal cells marked by the expression of Mesp1, migrate anteriorly and latterly to form the cardiac crescent and then the primitive heart tube7,8. This migratory group of cells includes two very distinct populations of cardiac progenitor cells (CPCs), namely the first and the second heart field (FHF and SHF)9,10. Cells from the SHF are highly proliferative and migratory and are primarily responsible for the elongation and looping of the heart tube. Additionally, SHF cells differentiate to cardiomyocytes, fibroblasts, smooth muscle and endothelial cells as they enter the heart tube to form the right ventricle, right ventricular outflow tract and large part of both atria7,10. In contrast, FHF cells are less proliferative and migratory and differentiate mainly to cardiomyocytes as they give rise to the left ventricle and a smaller part of the atria11. Moreover, SHF progenitors are marked by the expression of Tbx1, FGF8, FGF10 and Six2 while FHF cells express Hcn4 and Tbx511,12,13,14,15.
PSCs can differentiate to all three germ layers and subsequently to any cell type in the body4,16. Therefore, they offer tremendous potential for understanding heart development and for modelling specific developmental defects resulting in congenital heart disease, the most frequent cause of birth defects17. A large subgroup of congenital heart disease includes chamber-specific cardiac abnormalities18,19. However, it still unclear whether these originate from anomalous heart field development. In addition, given the inability of cardiomyocytes to proliferate after birth, there have been extensive efforts to create cardiac tissue for heart regeneration1,7,20. Considering the physiological and morphological differences between cardiac chambers, generation of chamber-specific cardiac tissue using PSCs is of significant importance. While recent advances in developmental cardiology have led to robust generation of cardiac cells from PSCs, it is still unclear if the two heart fields can be induced in PSC systems.
To recapitulate cardiogenesis in vitro and study the specification and properties of CPCs, we previously used a system based on differentiating PSC-derived cardiac spheroids21,22,23,24. Recently, we generated mouse embryonic stem cells (mESCs) with GFP and RFP reporters under the control of the FHF gene Hcn4 and the SHF gene Tbx1, respectively (mESCsTbx1-Cre; Rosa-RFP; HCN4-GFP) 25. In vitro differentiated mESCs formed cardiac spheroids in which GFP+ and RFP+ cells appeared from two distinct areas of mesodermal cells and patterned in a complementary manner. The resulting GFP+ and RFP+ cells exhibited FHF and SHF characteristics, respectively, determined by RNA-sequencing and clonal analyses. Importantly, using mESCs carrying the Isl1-RFP reporter (mESCIsl1-RFP), we discovered that SHF cells were faithfully marked by the cell-surface protein CXCR4, and this can enable isolation of heart field-specific cells without transgenes. The present protocol will describe the generation and isolation of heart field-specific CPCs from mESCs, which may serve as a valuable tool for studying chamber-specific heart disease.

<table><tbody><tr><td>&amp;beta;-mercaptoethanol</td><td>Sigma</td><td>M6250</td><td></td></tr><tr><td>0.1% (w/v) Gelatin</td><td>EMD Millipore</td><td>ES-006-B</td><td></td></tr><tr><td>100 mM Sodium Pyruvate</td><td>Gibco</td><td>11360</td><td></td></tr><tr><td>100x Pen/Strep</td><td>Gibco</td><td>15070-063</td><td></td></tr><tr><td>1x PBS w/o Calcium and Magnesium</td><td>Thermo Fisher Scientific</td><td>21-040-CV</td><td></td></tr><tr><td>20% Paraformaldehyde</td><td>Thermo Fisher Scientific</td><td>50-980-493</td><td></td></tr><tr><td>5 mL Polystyrene round-bottom tube with a 40&amp;mu;m cell strainer</td><td>BD Falcon</td><td>35223</td><td></td></tr><tr><td>Activin A</td><td>R &amp;amp; D Systems</td><td>338-AC-010</td><td></td></tr><tr><td>Ascorbic Acid</td><td>Sigma</td><td>A-4544</td><td></td></tr><tr><td>B27 minus vitamin A (50x)</td><td>Thermo Fisher Scientific</td><td>12587010</td><td></td></tr><tr><td>BMP4</td><td>R &amp;amp; D Systems</td><td>314-BP</td><td></td></tr><tr><td>Bovine Serum Albumin</td><td>Sigma</td><td>A2153</td><td></td></tr><tr><td>Cell sorter</td><td>Sony</td><td>SH800</td><td>Sony or any other fluorescence-activated cell sorter</td></tr><tr><td>Cell strainer 70&amp;mu;m</td><td>Thermo Fisher Scientific</td><td>08-771-2</td><td></td></tr><tr><td>Centrifuge Sorvall Legend XT</td><td>Thermo Fisher Scientific</td><td>75004508</td><td></td></tr><tr><td>CHIR99021</td><td>Selleck chemicals</td><td>S2924</td><td></td></tr><tr><td>CO&lt;sub&gt;2&lt;/sub&gt; Incubator</td><td>Thermo Fisher Scientific</td><td>51030285</td><td></td></tr><tr><td>Corning Ultra Low Attachment T75 flask</td><td>Corning</td><td>07-200-875</td><td></td></tr><tr><td>Countless II FL automated cell counter</td><td>Thermo Fisher Scientific</td><td></td><td></td></tr><tr><td>Donkey anti-mouse IgG secondary antibody, Alexa Fluor 647 conjugate</td><td>Thermo Fisher Scientific</td><td>A-31571, Lot #1757130</td><td></td></tr><tr><td>Dulbecco&#039;s Modified Eagle&#039;s Medium high glucose (DMEM)</td><td>Gibco</td><td>11965-092</td><td></td></tr><tr><td>EDTA</td><td>Sigma</td><td>E6758</td><td></td></tr><tr><td>ESGRO (LIF)</td><td>Millipore</td><td>ESG1106</td><td></td></tr><tr><td>EVOS FL microscope</td><td>Thermo Fisher Scientific</td><td>AMF4300</td><td></td></tr><tr><td>Fetal Bovine Serum</td><td>Invitrogen</td><td>SH30071.03</td><td></td></tr><tr><td>Glasgow&amp;rsquo;s MEM (GMEM)</td><td>Gibco</td><td>11710035</td><td></td></tr><tr><td>GlutaMAX (100x)</td><td>Gibco</td><td>35050-061</td><td></td></tr><tr><td>Ham&amp;rsquo;s F12</td><td>Gibco</td><td>10-080-CV</td><td></td></tr><tr><td>HEPES</td><td>Sigma</td><td>H3375</td><td></td></tr><tr><td>IMDM</td><td>Gibco</td><td>12440053</td><td></td></tr><tr><td>Monothioglycero (MTG)</td><td>Sigma</td><td>M-6145</td><td></td></tr><tr><td>Mouse anti-Troponin T antibody</td><td>Thermo Fisher Scientific</td><td>MS-295-P1</td><td></td></tr><tr><td>N2-SUPPLEMENT</td><td>Gibco</td><td>17502-048</td><td></td></tr><tr><td>Non-essential amino acid solution (NEAA</td><td>Invitrogen</td><td>11140-050</td><td></td></tr><tr><td>PD0325901</td><td>Selleckchem</td><td>S1036</td><td></td></tr><tr><td>PerCP-efluor 710 conjugated anti-Cxcr4 antibody</td><td>Thermo Fisher Scientific</td><td>46-9991-82</td><td></td></tr><tr><td>Suspension culture dish 150 mm x 25 mm</td><td>Corning</td><td>430597</td><td></td></tr><tr><td>T25 flasks</td><td>Corning</td><td>353109</td><td></td></tr><tr><td>TrypLE (Trypsin)</td><td>Gibco</td><td>12604</td><td></td></tr><tr><td>Y-27632 (ROCK inhibitor)</td><td>Stem cell technologies</td><td>72304</td><td></td></tr></tbody></table>

in vitro generation of heart field-specific cardiac progenitor cells

Pluripotent stem cells offer great potential for understanding heart development and disease and for regenerative medicine. While recent advances in developmental cardiology have led to generating cardiac cells from pluripotent stem cells, it is unclear if the two cardiac fields - the first and second heart fields (FHF and SHF) &#8212; are induced in pluripotent stem cells systems. To address this, we generated a protocol for in vitro specification and isolation of heart field-specific cardiac progenitor cells. We used embryonic stem cells lines carrying Hcn4-GFP and Tbx1-Cre; Rosa-RFP reporters of the FHF and the SHF, respectively, and live cell immunostaining of the cell membrane protein Cxcr4, a SHF marker. With this approach, we generated progenitor cells which recapitulate the functional properties and transcriptome of their in vivo counterparts. Our protocol can be utilized to study early specification and segregation of the two heart fields and to generate chamber-specific cardiac cells for heart disease modelling. Since this is an in vitro organoid system, it may not provide precise anatomical information. However, this system overcomes the poor accessibility of gastrulation-stage embryos and can be upscaled for high-throughput screens.

After approximately 132 h of differentiation, Tbx1-RFP and Hcn4-GFP CPCs can be detected using a fluorescent microscope (Figure 2). Generally, GFP and RFP cells appear approximately around the same time. The two populations of CPCs continue to expand in close proximity and commonly in a complementary pattern. Adjusting the concentrations of Activin A and BMP4 will alter the percentages of FHF vs SHF CPCs (Figure 3). CPC specification in vitro was primarily deter...

Watch this Scientific Journal Video about In Vitro Generation of Heart Field-specific Cardiac Progenitor Cells at JoVE.com

In Vitro Generation of Heart Field-specific Cardiac Progenitor Cells

The purpose of this method is to generate heart field-specific cardiac progenitor cells in vitro in order to study the progenitor cell specification and functional properties, and to generate chamber specific cardiac cells for heart disease modelling.

Pluripotent stem cells offer great potential for understanding heart development and disease and for regenerative medicine. While recent advances in ...

in-vitro-generation-of-heart-field-specific-cardiac-progenitor-cells

Universidad de Cartagena UDEC

Research

JoVE Journal

Developmental Biology

6.2K Views.  Johns Hopkins School of Medicine. The purpose of this method is to generate heart field-specific cardiac progenitor cells in vitro in order to study the progenitor cell specification and functional properties, and to generate chamber specific cardiac cells for heart disease modelling.

Video: In Vitro Generation of Heart Field-specific Cardiac Progenitor Cells

Derivation of Cardiac Progenitor Cells from Embryonic Stem Cells

Cardiac progenitor cells (CPCs) have the capacity to differentiate into cardiomyocytes, smooth muscle cells (SMC), and endothelial cells and hold great promise in cell therapy against heart disease. Among various methods to isolate CPCs, differentiation of embryonic stem cell (ESC) into CPCs attracts great attention in the field since ESCs can provide unlimited cell source. As a result, numerous strategies have been developed to derive CPCs from ESCs. In this protocol, differentiation and purification of embryonic CPCs from both mouse and human ESCs is described. Due to the difficulty of using cell surface markers to isolate embryonic CPCs, ESCs are engineered with fluorescent reporters activated by CPC-specific cre recombinase expression. Thus, CPCs can be enriched by fluorescence-activated cell sorting (FACS). This protocol illustrates procedures to form embryoid bodies (EBs) from ESCs for CPC specification and enrichment. The isolated CPCs can be subsequently cultured for cardiac lineage differentiation and other biological assays. This protocol is optimized for robust and efficient derivation of CPCs from both mouse and human ESCs.

In this protocol, derivation of cardiac progenitor cells from both mouse and human embryonic stem cells will be illustrated. A major strategy in this protocol is to enrich cardiac progenitor cells with flow cytometry using fluorescent reporters engineered into the embryonic stem cell lines.

Cardiac progenitor cells (CPCs) have the capacity to differentiate into cardiomyocytes, smooth muscle cells (SMC), and endothelial cells and hold great ...

Generation of Murine Cardiac Pacemaker Cell Aggregates Based on ES-Cell-Programming in Combination with Myh6-Promoter-Selection

Treatment of the &#8220;sick sinus syndrome&#8221; is based on artificial pacemakers. These bear hazards such as battery failure and infections. Moreover, they lack hormone responsiveness and the overall procedure is cost-intensive. &#8220;Biological pacemakers&#8221; generated from PSCs may become an alternative, yet the typical content of pacemaker cells in Embryoid Bodies (EBs) is extremely low. The described protocol combines &#8220;forward programming&#8221; of murine PSCs via the sinus node inducer TBX3 with Myh6-promoter based antibiotic selection. This yields cardiomyocyte aggregates consistent of &#62;80% physiologically functional pacemaker cells. These &#8220;induced-sinoatrial-bodies&#8221; (&#8220;iSABs&#8221;) are spontaneously contracting at yet unreached frequencies (400-500 bpm) corresponding to nodal cells isolated from mouse hearts and are able to pace murine myocardium ex vivo. Using the described protocol highly pure sinus nodal single cells can be generated which e.g. can be used for in vitro drug testing. Furthermore, the iSABs generated according to this protocol may become a crucial step towards heart tissue engineering.

This protocol describes how to produce functional sinus nodal tissue from murine pluripotent stem cells (PSC). T-Box3 (TBX3) overexpression plus cardiac Myosin-heavy-chain (Myh6) promoter antibiotic selection leads to highly pure pacemaker cell aggregates. These &#8220;Induced-sinoatrial-bodies&#8221; (&#8220;iSABs&#8221;) contain over 80% pacemaker cells, show highly increased beating rates and are able to pace myocardium ex vivo.

Treatment of the &#8220;sick sinus syndrome&#8221; is based on artificial pacemakers. These bear hazards such as battery failure and infections. Moreover, ...

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

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

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

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

Generation of Aligned Functional Myocardial Tissue Through Microcontact Printing

Advanced heart failure represents a major unmet clinical challenge, arising from the loss of viable and/or fully functional cardiac muscle cells. Despite optimum drug therapy, heart failure represents a leading cause of mortality and morbidity in the developed world. A major challenge in drug development is the identification of cellular assays that accurately recapitulate normal and diseased human myocardial physiology in vitro. Likewise, the major challenges in regenerative cardiac biology revolve around the identification and isolation of patient-specific cardiac progenitors in clinically relevant quantities. These cells have to then be assembled into functional tissue that resembles the native heart tissue architecture. Microcontact printing allows for the creation of precise micropatterned protein shapes that resemble structural organization of the heart, thus providing geometric cues to control cell adhesion spatially. Herein we describe our approach for the isolation of highly purified myocardial cells from pluripotent stem cells differentiating in vitro, the generation of cell growth surfaces micropatterned with extracellular matrix proteins, and the assembly of the stem cell-derived cardiac muscle cells into anisotropic myocardial tissue.

The generation of aligned myocardial tissue is a key requirement for adapting the recent advances in stem cell biology to clinically useful purposes. Herein we describe a microcontact printing approach for the precise control of cell shape and function. Using highly purified populations of embryonic stem cell derived cardiac progenitors, we then generate anisotropic functional myocardial tissue.

Advanced heart failure represents a major unmet clinical challenge,  arising from the loss of viable and/or fully functional cardiac muscle  cells. ...

Bioengineering

Generation of First Heart Field-like Cardiac Progenitors and Ventricular-like Cardiomyocytes from Human Pluripotent Stem Cells

The generation of large amounts of functional human pluripotent stem cells-derived cardiac progenitors and cardiomyocytes of defined heart field origin is a pre-requisite for cell-based cardiac therapies and disease modeling. We have recently shown that Id genes are both necessary and sufficient to specify first heart field progenitors during vertebrate development. This differentiation protocol leverages these findings and uses Id1 overexpression in combination with Activin A as potent specifying cues to produce first heart field-like (FHF-L) progenitors. Importantly, resulting progenitors efficiently differentiate (~70&#8211;90%) into ventricular-like cardiomyocytes. Here we describe a detailed method to 1) generate Id1-overexpressing hPSCs and 2) differentiate scalable quantities of cryopreservable FHF-L progenitors and ventricular-like cardiomyocytes.

Here we describe a scalable method, using a simple combination of Activin A and lentivirus-mediated Id1-overexpression, to generate first heart field-like cardiac progenitors and ventricular-like cardiomyocytes from human pluripotent stem cells.

The generation of large amounts of functional human pluripotent stem cells-derived cardiac progenitors and cardiomyocytes of defined heart field origin is ...

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 ...

Generating Self-Assembling Human Heart Organoids Derived from Pluripotent Stem Cells

The ability to study human cardiac development in health and disease is highly limited by the capacity to model the complexity of the human heart in vitro. Developing more efficient organ-like platforms that can model complex in vivo phenotypes, such as organoids and organs-on-a-chip, will enhance the ability to study human heart development and disease. This paper describes a protocol to generate highly complex human heart organoids (hHOs) by self-organization using human pluripotent stem cells and stepwise developmental pathway activation using small molecule inhibitors. Embryoid bodies (EBs) are generated in a 96-well plate with round-bottom, ultra-low attachment wells, facilitating suspension culture of individualized constructs.
The EBs undergo differentiation into hHOs by a three-step Wnt signaling modulation strategy, which involves an initial Wnt pathway activation to induce cardiac mesoderm fate, a second step of Wnt inhibition to create definitive cardiac lineages, and a third Wnt activation step to induce proepicardial organ tissues. These steps, carried out in a 96-well format, are highly efficient, reproducible, and produce large amounts of organoids per run. Analysis by immunofluorescence imaging from day 3 to day 11 of differentiation reveals first and second heart field specifications and highly complex tissues inside hHOs at day 15, including myocardial tissue with regions of atrial and ventricular cardiomyocytes, as well as internal chambers lined with endocardial tissue. The organoids also exhibit an intricate vascular network throughout the structure and an external lining of epicardial tissue. From a functional standpoint, hHOs beat robustly and present normal calcium activity as determined by Fluo-4 live imaging. Overall, this protocol constitutes a solid platform for in vitro studies in human organ-like cardiac tissues.

Here, we describe a protocol to create developmentally relevant human heart organoids (hHOs) efficiently using human pluripotent stem cells by self-organization. The protocol relies on the sequential activation of developmental cues and produces highly complex, functionally relevant human heart tissues.

The ability to study human cardiac development in health and disease is highly limited by the capacity to model the complexity of the human heart in ...

Biochemistry

Generation and Expansion of Human Cardiomyocytes from Patient Peripheral Blood Mononuclear Cells

Generating patient-specific cardiomyocytes from a single blood draw has attracted tremendous interest in precision medicine on cardiovascular disease. Cardiac differentiation from human induced pluripotent stem cells (iPSCs) is modulated by defined signaling pathways that are essential for embryonic heart development. Numerous cardiac differentiation methods on 2-D and 3-D platforms have been developed with various efficiencies and cardiomyocyte yield. This has puzzled investigators outside the field as the variety of these methods can be difficult to follow. Here we present a comprehensive protocol that elaborates robust generation and expansion of patient-specific cardiomyocytes from peripheral blood mononuclear cells (PBMCs). We first describe a high-efficiency iPSC reprogramming protocol from a patient&#39;s blood sample using non-integration Sendai virus vectors. We then detail a small molecule-mediated monolayer differentiation method that can robustly produce beating cardiomyocytes from most human iPSC lines. In addition, a scalable cardiomyocyte expansion protocol is introduced using a small molecule (CHIR99021) that could rapidly expand patient-derived cardiomyocytes for industrial- and clinical-grade applications. At the end, detailed protocols for molecular identification and electrophysiological characterization of these iPSC-CMs are depicted. We expect this protocol to be pragmatic for beginners with limited knowledge on cardiovascular development and stem cell biology.

Here, we present a protocol to robustly generate and expand human cardiomyocytes from patient peripheral blood mononuclear cells.

Generating patient-specific cardiomyocytes from a single blood draw has attracted tremendous interest in precision medicine on cardiovascular disease. ...

Efficient Derivation of Human Cardiac Precursors and Cardiomyocytes from Pluripotent Human Embryonic Stem Cells with Small Molecule Induction

To date, the lack of a suitable human cardiac cell source has been the major setback in regenerating the human myocardium, either by cell-based transplantation or by cardiac tissue engineering1-3. Cardiomyocytes become terminally-differentiated soon after birth and lose their ability to proliferate. There is no evidence that stem/progenitor cells derived from other sources, such as the bone marrow or the cord blood, are able to give rise to the contractile heart muscle cells following transplantation into the heart1-3. The need to regenerate or repair the damaged heart muscle has not been met by adult stem cell therapy, either endogenous or via cell delivery1-3. The genetically stable human embryonic stem cells (hESCs) have unlimited expansion ability and unrestricted plasticity, proffering a pluripotent reservoir for in vitro derivation of large supplies of human somatic cells that are restricted to the lineage in need of repair and regeneration4,5. Due to the prevalence of cardiovascular disease worldwide and acute shortage of donor organs, there is intense interest in developing hESC-based therapies as an alternative approach. However, how to channel the wide differentiation potential of pluripotent hESCs efficiently and predictably to a desired phenotype has been a major challenge for both developmental study and clinical translation. Conventional approaches rely on multi-lineage inclination of pluripotent cells through spontaneous germ layer differentiation, resulting in inefficient and uncontrollable lineage-commitment that is often followed by phenotypic heterogeneity and instability, hence, a high risk of tumorigenicity6-8 (see a schematic in Fig. 1A). In addition, undefined foreign/animal biological supplements and/or feeders that have typically been used for the isolation, expansion, and differentiation of hESCs may make direct use of such cell-specialized grafts in patients problematic9-11. To overcome these obstacles, we have resolved the elements of a defined culture system necessary and sufficient for sustaining the epiblast pluripotence of hESCs, serving as a platform for de novo derivation of clinically-suitable hESCs and effectively directing such hESCs uniformly towards clinically-relevant lineages by small molecules12 (see a schematic in Fig. 1B). After screening a variety of small molecules and growth factors, we found that such defined conditions rendered nicotinamide (NAM) sufficient to induce the specification of cardiomesoderm direct from pluripotent hESCs that further progressed to cardioblasts that generated human beating cardiomyocytes with high efficiency (Fig. 2). We defined conditions for induction of cardioblasts direct from pluripotent hESCs without an intervening multi-lineage embryoid body stage, enabling well-controlled efficient derivation of a large supply of human cardiac cells across the spectrum of developmental stages for cell-based therapeutics.

We have established a protocol for induction of cardioblasts direct from pluripotent human embryonic stem cells maintained under defined conditions with small molecules, which enables derivation of a large supply of human cardiac progenitors and functional cardiomyocytes for cardiovascular repair.

To date, the lack of a suitable human cardiac cell source has been the major setback in regenerating the human myocardium, either by cell-based ...

Biology

Generation of Human Cardiomyocytes: A Differentiation Protocol from Feeder-free Human Induced Pluripotent Stem Cells

In order to investigate the events driving heart development and to determine the molecular mechanisms leading to myocardial diseases in humans, it is essential first to generate functional human cardiomyocytes (CMs). The use of these cells in drug discovery and toxicology studies would also be highly beneficial, allowing new pharmacological molecules for the treatment of cardiac disorders to be validated pre-clinically on cells of human origin. Of the possible sources of CMs, induced pluripotent stem (iPS) cells are among the most promising, as they can be derived directly from readily accessible patient tissue and possess an intrinsic capacity to give rise to all cell types of the body 1. Several methods have been proposed for differentiating iPS cells into CMs, ranging from the classical embryoid bodies (EBs) aggregation approach to chemically defined protocols 2,3. In this article we propose an EBs-based protocol and show how this method can be employed to efficiently generate functional CM-like cells from feeder-free iPS cells.

Pluripotent stem cells, either embryonic or induced pluripotent stem (iPS) cells, constitute a valuable source of human differentiated cells, including cardiomyocytes. Here, we will focus on cardiac induction of iPS cells, showing how to use them to obtain functional human cardiomyocytes through an embryoid bodies-based protocol.

In order to investigate the events driving heart development and to determine the molecular mechanisms leading to myocardial diseases in humans, it is ...