This research was supported by NIH 4R00HL094708-03, MCW Research Affairs Committee New Faculty Award, and the Kern foundation (startup funds) at the Medical College of Wisconsin (RLG); Research Grants Council of Hong Kong Theme-based Research Scheme T13-706/11 (KRB); U01 HL099776, CIRM TR3-05556, CIRM DR2A-05394, and AHA Established Investigator Award (JCW); AHA Postdoctoral Fellowship 12POST12050254 (PWB). We thank Hope Campbell at the Flow Cytometry Core of the Blood Research Institute of Wisconsin for assistance with data collection and careful review of the manuscript.

1. Solution and Media Preparation
<ol>
	<li>hESC Qualified Matrix Coating Stock Solution
	<ol>
		<li>Slowly thaw hESC qualified matrix (5 ml) on ice at 4 &#186;C overnight. Dispense aliquots into pre-chilled, 1.5 ml sterile microcentrifuge tubes and immediately store at -20 &#186;C. 
		NOTE: The volume of the aliquot will vary based on lot and typically ranges 270-350 &#181;l. Manufacturer provides details regarding volume of aliquot required to achieve a 1x concentration upon dilution into 25 ml as described in step 2.1.</li>
	</ol>
	</li>
	<li>hPSC Media Stock Solutions
	<ol>
		<li>Use ultrapure water as a diluent unless otherwise indicated. Sterilize all components using a 0.22 &#181;m filter. Store the following as bulk solutions at 4 &#186;C: sodium bicarbonate (75 mg/ml); citric acid (10 mM, pH = 3).</li>
		<li>Sterilize all components using 0.2 &#181;m syringe filter and store each as aliquots at -20 &#186;C: Rho kinase (ROCK) inhibitor Y-27632 (10 mM in DPBS, 100 &#181;l aliquot); L-ascorbic acid 2-phosphate (64 mg/ml, 500 &#181;l aliquot); sodium selenite (70 &#181;g/ml, 100 &#181;l aliquot); transferrin (50 mg/ml, 107 &#181;l aliquot); fibroblast growth factor 2 (FGF2; 200 ng/&#181;l in DPBS, 250 &#181;l aliquot); transforming growth factor beta 1 (TGF&#946;1, 100 ng/&#181;l in cold 10 mM citric acid,10 &#181;l aliquot).</li>
	</ol>
	</li>
	<li>hPSC Media E8 Solution Composition
	<ol>
		<li>Prepare media using aliquots prepared in Step 1.2: DMEM/F12 (with L-Glutamine and HEPES; 500 ml), sodium bicarbonate (3.62 ml; final: 543 &#181;g/ml), L-ascorbic acid 2-phosphate (500 &#181;l; final: 64 &#181;g/ml), sodium selenite (100 &#181;l; final: 140 ng/ml), transferrin (107 &#181;l; final: 10.7 &#181;g/ml), insulin (1 ml; final: 20 &#181;g/ml), FGF2 (250 &#181;l; final: 100 ng/ml), TGF&#946;1 (10 &#181;l; final: 2 ng/ml).</li>
		<li>Combine all components, filter sterilize and store at 4 &#186;C for up to 2 weeks.</li>
	</ol>
	</li>
	<li>hPSC Media E8 with ROCK Inhibitor
	<ol>
		<li>Add 15 &#181;l ROCK inhibitor to 12 ml of E8 media prepared as above and mix well. Ensure that the final concentration is 10 &#181;M after addition of cells/media in step 3.7.</li>
	</ol>
	</li>
	<li>Stock Solutions of Wnt Modulators
	<ol>
		<li>Store the following aliquots at -20 &#186;C. CHIR 99021 (6-[[2-[[4-(2,4-Dichlorophenyl)-5-(5&#8203;-methyl-1H-imidazol-2-yl)-2-pyrimidinyl]amino]ethy&#8203;l]amino]-3-pyridinecarbonitrile; 10 mM in DMSO, 15 &#181;l aliquot). IWR-1 (4-(1,3,3a,4,7,7a-Hexahydro-1,3-dioxo-4,7-methano-2H-isoindol-2-yl)-N-8-quinolinyl-Benzamide; 10 mM in DMSO, 6 &#181;l aliquot).</li>
	</ol>
	</li>
	<li>Differentiation Media
	<ol>
		<li>Prepare differentiation media #1 with RPMI 1640 (with L-glutamine) with 2% B27 minus insulin supplement.</li>
		<li>Prepare differentiation media #2 with RPMI 1640 (with L-glutamine) with 2% B27 plus insulin supplement and 2% FBS.</li>
	</ol>
	</li>
	<li>Cell Wash Solution for Cell Culture
	<ol>
		<li>Use Dulbecco&#8217;s phosphate buffered saline (DPBS), without calcium or magnesium.</li>
	</ol>
	</li>
	<li>Cell Wash Solution for Flow Cytometry
	<ol>
		<li>Use phosphate buffered saline (PBS, without calcium or magnesium) with 1% FBS. Store at 4 &#186;C.</li>
	</ol>
	</li>
	<li>Cell Maintenance Solution for Flow Cytometry
	<ol>
		<li>Use Hank&#8217;s Balanced Salt Solution (HBSS; without calcium or magnesium) with 5% FBS. Store at 4 &#186;C.</li>
	</ol>
	</li>
	<li>Fixation Solutions for Flow Cytometry
	<ol>
		<li>Use Cytofix buffer as fixation solution for TNNI3 and IRX4 antibodies.</li>
		<li>Use 4% paraformaldehyde in 1x PBS (make fresh) as fixation solution for TNNT2 and MLC2a antibodies.</li>
		<li>Use 70% methanol/30% acetone as fixation solution for MLC2v antibody.</li>
		<li>Store all solutions at 4 &#186;C.</li>
	</ol>
	</li>
	<li>Permeabilization Solutions for Flow Cytometry
	<ol>
		<li>Use Phosflow Perm Buffer III as permeabilization solution for TNNI3 and IRX4 antibodies. Store at room temperature (25 &#176;C).</li>
		<li>Use 0.2% Triton X-100 in 1x PBS as permeabilization solution for TNNT2, MLC2v, and MLC2a antibodies. Store at 4 &#186;C.</li>
	</ol>
	</li>
	<li>Blocking Solution
	<ol>
		<li>Use 10% goat serum in 1x&#160;PBS. Make fresh and store at 4 &#186;C until use.</li>
	</ol>
	</li>
</ol>
2. Plate Coating
<ol>
	<li>Slowly thaw 1 aliquot of hESC qualified matrix at 4 &#186;C for 30 min, add to 25 ml of chilled DMEM/F12 and mix well in sterilized tissue culture hood immediately before coating 6-well plates.</li>
	<li>Add 1 ml per well of a 6-well plate under sterilized tissue culture hood (1 aliquot of the hESC qualified matrix is sufficient to coat four 6-well plates).</li>
	<li>Allow hESC qualified matrix to set for 30 min at room temperature under the hood. Aspirate the excess hESC qualified matrix and add 2 ml of E8 media with ROCK inhibitor to each well. Use plates immediately, or if desired, store at 4 &#176;C immediately after plating for up to 1 week and equilibrate to room temperature for 30 min prior to use.</li>
</ol>
3. Passaging and Maintenance of Undifferentiated hPSCs in Monolayer Culture
<ol>
	<li>Maintain hPSCs in monolayer culture in 6-well plates and perform all steps under a sterile tissue culture hood.</li>
	<li>Use hPSC lines that are well established (&#62;p20) and exhibit a homogeneous morphology without the presence of cells with a neural, epithelial- or fibroblast-like morphology. Ensure cells proliferate robustly, and on average, passage every three days at 75% confluence when seeded at 0.75 x&#160;106 per well.</li>
	<li>Passage hPSCs with dissociation to the single cell level at least 5x&#160;prior to start of differentiation to ensure maximum differentiation efficiency. To passage hPSCs, aspirate E8 media and wash cells twice with 4 ml of 1x DPBS (pre-warmed to room temperature). Add 1 ml of the cell detachment solution (pre-warmed to room temperature) to each well and leave the well undisturbed for 3-7 min, until cell boundaries begin to round-up.</li>
	<li>Use a cotton-plugged glass pipette with bulb to dislodge cells and transfer into a 15 ml conical tube containing 1 ml of DMEM/F12 media (to inactivate the cell detachment solution).</li>
	<li>Remove 10 &#181;l aliquot of cell solution and mix with 10 &#181;l of trypan blue in a microcentrifuge tube. Count cells (e.g. automated or manual hemocytometer) while remainder of cells are collected by centrifugation at 130 x g for 5 min at room temperature. Using this protocol, expect 70-80% viability using an automated hemocytometer and going forward, base all cell numbers on total cell counts.</li>
	<li>Aspirate media and resuspend the cell pellet in DMEM/F12 to a final concentration of 0.75 x 106 cells per 500 &#181;l.</li>
	<li>Add 500 &#181;l of the cell suspension to each well of a 6-well plate where each well contains 2 ml E8 media with ROCK inhibitor, prepared in step 2.3. Leaving plate on the worktop, gently move in a front-to-back and side-to-side motion to uniformly disperse cells across the well. Return cells to incubator at 5% CO2, 37 &#186;C.</li>
	<li>Beginning 24 hr after passaging, replace media daily using 2 ml/well E8 without ROCK inhibitor. Optimize seeding density to achieve 100% confluence prior to start of differentiation. Seed 0.75 x 106 cells/well four days prior to start of differentiation, but optimize for each cell line as needed.</li>
</ol>
4. Cardiomyocyte Induction of hPSCs by Selective Modulation of the Wnt Pathway
<ol>
	<li>Refresh media (2 ml/well) daily during days 0-7, and every other day after day 8.</li>
	<li>On day 0, begin differentiation process by replacing E8 media with differentiation media #1. Add 1.2 &#181;l CHIR (6 &#181;M final) to each well. Repeat on day 1.</li>
	<li>On days 2-3, replace with fresh differentiation media #1.</li>
	<li>On day 4, replace with fresh differentiation media #1. Add 1 &#181;l IWR-1 (5 &#181;M final) to each well. Repeat on day 5.</li>
	<li>On days 6-7, replace with fresh differentiation media #1.</li>
	<li>On day 8, replace with fresh differentiation media #2.</li>
	<li>Continue to replace with differentiation media #2 every other day for desired time of culture.</li>
	<li>If desired, passage cardiomyocytes using the cell detachment solution following steps outlined in 3.3-3.6, but substituting media with differentiation media #2. During passaging, dissociate cardiomyocytes into small clusters of ~3-10 cells. Seed at ~6 x 105 cells per well using hESC qualified matrix coated wells and differentiation media #2.</li>
</ol>
5. Collection of Cells for Flow Cytometry
<ol>
	<li>Perform all remaining aspects of steps 5-9 on the lab bench (i.e., not sterile).</li>
	<li>Aspirate growth media and wash cells twice with 1x PBS. Add 1 ml of the cell detachment solution (pre-warmed to room temp) to each well and leave undisturbed for 3-7 min, until cell boundaries begin to round-up. Use a cotton-plugged borosilicate glass disposable 9&#8221; pipette with bulb to dislodge cells and transfer into a 15 ml conical tube on ice.</li>
	<li>Throughout remainder of protocol, maintain cells on ice and perform centrifugations at 200 x g for 5 min at 4 &#186;C.</li>
	<li>Collect cells by centrifugation and aspirate solution. Resuspend cells in 10 ml cell wash solution using a 10 ml serological pipette with repeated trituration to ensure cell clumps are dispersed into single cells. Count cells as in step 3.5 while remainder of cells are collected by centrifugation.</li>
	<li>Resuspend cells in cell wash solution taking care to completely disaggregate cell pellet and aliquot 1 x 106 cells per round bottom tube. Collect cells by centrifugation and aspirate solution.</li>
</ol>
6. Fixation and Permeabilization of Cells for Intracellular Antigen Staining
<ol>
	<li>Add 100 &#181;l fixation solution to cell pellet. Add solution drop-wise with continuous gentle vortexing and then set on ice for 15 min.</li>
	<li>Add 3 ml cell wash solution. Collect cells by centrifugation and aspirate solution.</li>
	<li>Add 100 &#181;l permeabilization solution to cell pellet. Add solution drop-wise with continuous gentle vortexing then set on ice for 30 min. Use fixation and permeabilization conditions as outlined for each antibody in Table 1.</li>
	<li>Add 3 ml cell wash solution. Collect cells by centrifugation and aspirate solution. Repeat for a total of two washes after permeabilization.</li>
</ol>
<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td rowspan="2">Primary Antibody (Clone)</td>
			<td rowspan="2">Immunogen/Epitope Recognized</td>
			<td rowspan="2">Istotype Control</td>
			<td colspan="2">Amount of primary antibody per 1 x 106 cells in 100 &#181;l</td>
			<td rowspan="2">Fixation Solution</td>
			<td rowspan="2">Permeabilization Solution</td>
			<td rowspan="2">Secondary Antibody</td>
			<td rowspan="2">Amount of secondary antibody/1 x 106 cells in 100 &#181;l&#160;</td>
		</tr>
		<tr>
			<td>For percent positive measurements</td>
			<td>For Antigen Quantitation</td>
		</tr>
		<tr>
			<td>TNNI3 (284 (19C7)</td>
			<td>ISASRKLQL (human)</td>
			<td>Mouse IgG2b</td>
			<td>1.0&#160; &#181;g</td>
			<td>3.0 &#181;g</td>
			<td>BD Cytofix</td>
			<td>BD Phosflow perm III</td>
			<td>Goat anti-mouse IgG2b-Alexa488</td>
			<td>600 ng</td>
		</tr>
		<tr>
			<td>TNNT2 (1C11)</td>
			<td>Full length purified native human troponin T protein.</td>
			<td>Mouse IgG1</td>
			<td>1.0&#160; &#181;g</td>
			<td>2.0 &#181;g</td>
			<td>4% PFA in 1% PBS</td>
			<td>0.2% Triton X-100 in 1% PBS</td>
			<td>Goat anti-mouse IgG1 - Alexa 488</td>
			<td>600 ng</td>
		</tr>
		<tr>
			<td>MLC2v&#160; (330G5)</td>
			<td>FDPEGKG</td>
			<td>Mouse IgG2a</td>
			<td>2.0&#160; &#181;g</td>
			<td>3.0 &#181;g</td>
			<td>70% methanol/30% acetone</td>
			<td>0.2% Triton X-100 in 1% PBS</td>
			<td>Goat anti-mouse IgG2a - Alexa 647</td>
			<td>600 ng</td>
		</tr>
		<tr>
			<td>MLC2a&#160; (4E7)</td>
			<td>full length human recombinant protein of human MYL7 produced in E. coli</td>
			<td>Mouse IgG1</td>
			<td>0.5 &#181;g</td>
			<td>3.0 &#181;g</td>
			<td>4% PFA in 1% PBS</td>
			<td>0.2% Triton X-100 in 1% PBS</td>
			<td>Goat anti-mouse IgG1 - Alexa 488</td>
			<td>600 ng</td>
		</tr>
		<tr>
			<td>IRX4</td>
			<td>LQEHRKNP 
			YPTKGEKI 
			MLAIITKM 
			TLTQVST</td>
			<td>Rabbit IgG</td>
			<td>0.5 &#181;g</td>
			<td>0.5 &#181;g</td>
			<td>BD Cytofix</td>
			<td>BD Phosflow perm III</td>
			<td>Goat anti-rabbit IgG-PE</td>
			<td>600 ng</td>
		</tr>
	</tbody>
</table>
Table 1. Antibody Concentrations. Listed are the primary antibody, clone (if monoclonal), optimized concentrations and fixation and permeabilization conditions for each primary and secondary antibody used for flow cytometry analyses. As antibody stock concentrations can vary among vendors of the same clone, final concentrations of each antibody per 1 x 106 cells in a fixed assay volume, rather than dilutions, are provided. The immunogen used to generate the antibody, or epitope recognized by antibody, as provided by manufacturer, is listed but was not experimentally verified here.
7. Antibody Staining
<ol>
	<li>For every experiment, include one unstained control per fixation/permeabilization condition and the appropriate isotype control for each primary antibody used. Include non-cardiomyocyte cell types as negative controls (e.g., pluripotent stem cells or fibroblasts). Use isotype controls at the same concentration as corresponding primary antibody (see Table 1).</li>
	<li>Resuspend cells in 100 &#181;l blocking solution using a P200 pipette to disaggregate cells. Set samples on ice for 25 min with gentle rocking.</li>
	<li>Without removing blocking solution, add primary antibody or isotype control per guidelines in Table 1. Incubate 45 min on ice with gentle rocking.</li>
	<li>Add 3 ml cell wash solution. Collect cells by centrifugation and aspirate solution. Repeat for a total of two washes after primary antibody labeling.</li>
	<li>If a fluorophore-conjugated primary antibody is used, proceed to 8.1. When an unconjugated primary antibody is used (such as for all markers described here), perform labeling with secondary antibody that is conjugated to a fluorophore as follows.</li>
	<li>Resuspend cells in 100 &#181;l blocking solution using a P200 pipette to disaggregate cells.</li>
	<li>Add secondary antibody per guidelines in Table 1. Incubate 30 min on ice with gentle rocking.</li>
	<li>Add 3 ml cell wash solution. Collect cells by centrifugation and aspirate solution. Repeat for a total of two washes after secondary antibody labeling.</li>
</ol>
8. Preparation of Cells for Flow Cytometry
<ol>
	<li>Resuspend cells in 400 &#181;l cell maintenance solution using a P1000 pipette to disaggregate cells.</li>
	<li>Prepare a cell strainer cap on a round bottom tube by pre-wetting with 50 &#181;l cell maintenance solution. Set tube on ice. Use the cell strainer cap to prevent cell aggregates from clogging the flow cytometer.</li>
	<li>Transfer cell solution to cell strainer cap and allow cell suspension to drain by gravity. Tap bottom of tube gently on bench top as necessary so that cells are collected into tube and set back on ice as quickly as possible. Rinse strainer with 250 &#181;l cell maintenance solution to ensure maximal recovery of cells.</li>
	<li>Maintain cells on ice and protect from light until analyzed by flow cytometry.</li>
</ol>
9. Flow Cytometry Analysis
Detailed acquisition settings will vary among instruments. Fundamental parameters to consider for optimal data collection are described below.
<ol>
	<li>For optimal stream stability, ensure that the nozzle size exceeds 5-6x&#160;the diameter of the cell being analyzed. 
	NOTE: This may vary among instruments but is an important consideration both for analyzers and selecting appropriate nozzle size for cell sorting. The average diameter of day 10 cardiomyocytes is 11 &#181;m (ranging 8-14 &#181;m); thus, a standard 150 &#181;m sample injection tube on an analyzer works well.</li>
	<li>Immediately prior to data analysis, vortex each tube briefly to disperse cell aggregates.</li>
	<li>Optimize forward and side scatter voltage settings for each cell type based on unstained control for each fixation/permeabilization condition used in the experiment such that the populations of interest are on scale and centered (Figure 2A).
	<ol>
		<li>Maintain these settings throughout a single experiment and be consistent from experiment to experiment on the same instrument, as significant shifts may indicate potential problems with the flow cytometer or sample preparation.</li>
	</ol>
	</li>
	<li>For each fluorophore, analyze the isotype control and adjust appropriate laser voltage to determine the minimum intensity required to obtain a fluorescence histogram that displays both left and right edges of the peak. Maintain the laser settings for each isotype control when acquiring data on corresponding antibody-stained samples. 
	NOTE: Signal drift often occurs over time on the same instrument. It is critical to adjust laser settings at the beginning of each experiment based on the appropriate isotype control.</li>
	<li>Collect a minimum of 10,000 events. 50,000 events are preferred.</li>
	<li>For statistical analyses, gate the live cell population to exclude debris (Figure 2A). Determine percent positive cells within the gated population based on marker placement that allows &#8804;2% contribution from isotype control, as shown in Figure 2B,C.</li>
</ol>

The authors have nothing to disclose.

Critical to the success of the differentiation protocol is the use of high quality cultures of hPSCs that have been passaged at the single cell level for at least five passages prior to the start of differentiation. Similar differentiation efficiencies are routinely observed among various hPSC lines if they are 100% confluent at the start of differentiation, independent of cell line. Suboptimal efficiency is observed if the confluence of cells at the start of differentiation is &#8804;95% or &#62;100%. Therefore, seeding...

The generation of cardiomyocytes from hPSCs, including hESC and hiPSC, can function as an in vitro model of very early human cardiac developmental processes, providing insight into stages not otherwise accessible for mechanistic studies. This model system provides unique opportunities to study the molecular pathways that control cardiac lineage commitment and cell fate specification. In recent years, the ability to efficiently generate cardiomyogenic cells from hPSCs has greatly improved1-15. However, among protocols there is cell line variation with respect to the efficiency in generating cardiomyogenic cells and timing at which the cells express chamber-specific markers (e.g., ventricle and atria). Ideally, for future applications of this model system, more homogeneous populations of functionally defined cells are desired. In contrast to previous methods, the cardiomyocyte differentiation protocol described here does not require cell aggregation or the addition of Activin A or Bone morphogenetic protein 4(BMP4) and robustly generates cultures highly positive for TNNI3, TNNT2, IRX4, MLC2v, and MLC2a by day 10 cells across all hESC and hiPSC lines tested to date. The strategy is technically simple to implement, especially compared to three-dimensional cultures, mass culture, or embryoid body based strategies4-9, and was recently defined in a study that describes a small molecule with selective toxicity to hPSCs (Boheler et al.)65. Features of this protocol include differentiation of hPSCs in monolayer culture using a single layer of a hESC qualified matrix (Matrigel), fully defined media using small molecules to modulate Wnt signaling (similar, yet distinct from1,2,7,13), and optimized flow cytometry staining methods for evaluation of differentiation efficiency and cell identity. In summary, advantages of this protocol compared to previous reports include its cost-effectiveness, reproducibility, and its high efficiency for generating cardiomyocytes among multiple hPSC lines, including hESC and hiPSC lines.
Flow cytometry is a powerful analytical tool for assessing the quality of cells in culture and determining subpopulation homogeneity, and with proper experimental design, can provide quantitative measurements. As with all antibody-based strategies, accurate interpretation of experimental results requires that elements of the assay design including antibody concentration and fixation and permeabilization conditions (when targeting intracellular antigens) are carefully tested for each antibody as sub-optimal conditions significantly affect efficiency of antibody binding, and therefore, interpretation of results. Importantly, if quantitation is required, monoclonal antibodies are essential, as polyclonal antibodies can recognize multiple epitopes and are prone to batch-to-batch variation. Currently, a variety of antibodies (polyclonal and monoclonal) and staining protocols have been described for the assessment of in vitro differentiation, making it difficult to compare efficiency of cardiomyogenesis among protocols1,2,9,11. For that reason, monoclonal antibodies are used when available for all flow cytometry analyses. Going forward, it is expected that standardization of these staining protocols, especially with regards to quantitation, should better permit comparison among differentiation strategies.
The choice of markers, and their corresponding antibodies, used to assess purity of in vitro cardiomyogenesis varies among reports. TNNT2 has been considered an indicator of cells committed to the cardiomyogenic fate and is routinely used to assess efficiency of cardiac differentiation protocols. However, TNNT2 is also expressed in skeletal muscle during early chick and rat development16,17 and it is present in human smooth muscle18. Thus, TNNT2 is not necessarily a specific marker of human cardiomyogenesis in vitro. MLC2v and MLC2a are routinely used as surrogate markers of ventricular and atrial subtypes, respectively. However, challenges with relying on MLC2v and MLC2a to determine cardiomyocyte subtype in the context of in vitro differentiation arise from the fact that these gene products may not be restricted to a specific chamber throughout cardiac development, from heart tube through adult. In the rodent looped heart, MLC2a mRNA is predominant in the atrial/inflow tract area and MLC2v mRNA is predominant in the ventricular/outflow tract regions. In the looped heart, co-expression of MLC2a and MLC2v mRNAs are observed in the inflow tract, atrioventricular canal, and the outflow tract19,20. By 3 days after birth, MLC2v mRNA is restricted to the ventricle and by 10 days after birth, MLC2a is restricted to the atria in the neonatal rat heart19. Therefore, interpretation of data regarding cardiomyogenesis efficiency and subtype identity must not only consider the presence and quantity of reference marker levels, but must consider the developmental stage(s) to which the timepoints of differentiation that are analyzed correspond. This is especially important considering that the maturation stage of cardiomyogenic cells generated by in vitro differentiation of hPSCs resembles most closely those of embryonic/fetal development21-25. Thus, relying on a marker&#8217;s spatial expression in the postnatal heart may not be appropriate for the assessment of hPSC-derived cells, at least in some cases.
In an effort to facilitate the development of more specific criteria for defining cardiomyocyte identity in vitro, TNNI3 is considered to be a valuable marker for evaluating cardiomyogenesis in vitro as it is restricted to cardiac muscle throughout embryogenesis in chick and zebrafish15,20 and is absent in human fetal skeletal muscle26. While TNNI1 is present in human fetal heart, TNNI3 is the only TNNI isoform present in normal adult heart27,28. Regarding cardiomyocyte subtype identity, IRX429-31 is an informative marker of cells with a ventricular fate. At the protein level, IRX4 has recently been shown to be restricted to the ventricle from linear heart tube through neonatal stages in the mouse32. Accordingly, optimized staining protocols for the analysis of TNNI3 and IRX4 by flow cytometry are described. To our knowledge, this is the first description of a method for efficient antibody-based staining and analysis of IRX4 levels in human cardiomyocytes by flow cytometry.

<table border="0" cellpadding="0" cellspacing="0" width="922">
	<tbody>
		<tr height="34">
			<td height="34" style="height:34px;width:431px;">Name of Reagent / Equipment</td>
			<td style="width:152px;">Company</td>
			<td style="width:111px;">Catalog Number</td>
			<td style="width:231px;">Comments/Description</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;"></td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:431px;">Cell Culture</td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">BD Matrigel, hESC-qualified matrix</td>
			<td style="width:152px;">BD Biosciences</td>
			<td style="width:111px;">354277</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Accutase cell detachment solution</td>
			<td style="width:152px;">Stem Cell Technologies</td>
			<td style="width:111px;">7920</td>
			<td></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:431px;">Dubelcco&#39;s phosphate buffered saline (DPBS), no calcium, no magnesium</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">14190-136</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Dimethyl sulfoxide (DMSO, Hybri-Max, sterile-filtered)</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">D2650</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Sodium bicarbonate</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">53817</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Citric acid</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">C2404-100G</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Y-27632 dihydrochloride selective p160ROCK inhibitor</td>
			<td style="width:152px;">R&#38;D Systems</td>
			<td style="width:111px;">1254</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">L-ascorbic acid-2-phosphate sesquimagnesium salt hydrate</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">A8960-5G</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Sodium selenite</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">S5261-10G</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Transferrin (Optiferrin &#8211; Defined, Animal-free, Recombinant Human)</td>
			<td style="width:152px;">Invitria</td>
			<td style="width:111px;">777TRF029</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Fibroblast growth factor 2 (FGF2)</td>
			<td style="width:152px;">R&#38;D Systems</td>
			<td style="width:111px;">4144-TC-01M</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Transforming growth factor beta 1 (TGF&#946;1)</td>
			<td style="width:152px;">Peprotech</td>
			<td style="width:111px;">100-21</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">DMEM/F12 with L-Glutamine and 15 mM HEPES</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">11330-032</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Insulin</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">I9278-5ML</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">CHIR-99021 HCl</td>
			<td style="width:152px;">Sellekchem</td>
			<td style="width:111px;">S2924</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">IWR-1</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">I0161</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">RPMI 1640 with L-Glutamine</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">11875-093</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">B-27 Supplement Minus Insulin</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">A1895601</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">B-27 Supplement (with Insulin)</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">17504-044</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Fetal bovine serum</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">10437</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;"></td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:431px;">Flow cytometry reagents</td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Phosphate buffered saline (10X)</td>
			<td style="width:152px;">Quality Biological Inc.</td>
			<td style="width:111px;">119-069-151</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:431px;">Hank&#39;s balanced salt solution without Ca2+ and Mg2+</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">14175-095</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">BD Cytofix</td>
			<td style="width:152px;">BD Biosciences</td>
			<td style="width:111px;">554655</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">BD Phosflow perm buffer III</td>
			<td style="width:152px;">BD Biosciences</td>
			<td style="width:111px;">558050</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">16% Paraformaldehyde</td>
			<td style="width:152px;">Thermo Scientific</td>
			<td style="width:111px;">28906</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Methanol</td>
			<td style="width:152px;">Sigma Aldrich</td>
			<td style="width:111px;">179957-4L</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Acetone</td>
			<td style="width:152px;">Mallenckrodt Chemicals&#160;</td>
			<td style="width:111px;">2440-16</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Triton X-100</td>
			<td style="width:152px;">Amresco</td>
			<td style="width:111px;">M236-10ML</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Goat serum</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">16210-064</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Trypan blue solution, 0.4%</td>
			<td style="width:152px;">Life Technologies</td>
			<td style="width:111px;">15250-061</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:431px;">Materials</td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">5 ml round bottom polystyrene tube (without cap)</td>
			<td style="width:152px;">Corning</td>
			<td style="width:111px;">352008</td>
			<td>for preparation of cells for flow cytometry</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">5 ml round bottom polystyrene tube (with 35 &#181;M cell strainer snap cap)</td>
			<td style="width:152px;">Corning</td>
			<td style="width:111px;">352235</td>
			<td>for preparation of cells for flow cytometry</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">2 ml rubber bulbs</td>
			<td style="width:152px;">Fischer Scientific</td>
			<td style="width:111px;">03-448-24</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">9&#34; borosilicate unplugged glass Pasteur pipets</td>
			<td style="width:152px;">BioExpress</td>
			<td style="width:111px;">P-2904-2</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">0.65 mL microcentrifuge tubes, graduated, green</td>
			<td style="width:152px;">GeneMate</td>
			<td style="width:111px;">C-3259-G</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">1.5 mL microcentrifuge tubes, graduated, red</td>
			<td style="width:152px;">GeneMate</td>
			<td style="width:111px;">C-3260-R</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">TC20 automated cell counter</td>
			<td style="width:152px;">BioRad</td>
			<td>145-0102</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Counting slides for TC20</td>
			<td style="width:152px;">BioRad</td>
			<td style="width:111px;">145-0011</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">6 well flat bottom tissue-culture treated plate</td>
			<td style="width:152px;">Corning</td>
			<td style="width:111px;">353046</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">20 mL syringes</td>
			<td style="width:152px;">BD Plastipak</td>
			<td style="width:111px;">300613</td>
			<td>For filter sterilization of aliquots</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Sterile syringe filters, 0.2 &#181;m polyethersulfone</td>
			<td style="width:152px;">VWR</td>
			<td style="width:111px;">28145-501</td>
			<td>For filter sterilization of aliquots</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">250 mL filter system, 0.22 &#181;m polyethersulfone, sterilizing, low binding&#160;</td>
			<td style="width:152px;">Corning</td>
			<td style="width:111px;">431096</td>
			<td>For filter sterilization of bulk media&#160;</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">500 mL filter system, 0.22 &#181;m polyethersulfone, sterilizing, low binding&#160;</td>
			<td style="width:152px;">Corning</td>
			<td style="width:111px;">431097</td>
			<td>For filter sterilization of bulk media&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:431px;">Antibodies and Isotype Controls</td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Anti-TNNI3 (clone: 284 (19C7))</td>
			<td style="width:152px;">Abcam</td>
			<td>ab19615</td>
			<td>Primary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Anti-TNNT2 (clone: 1C11)</td>
			<td>Thermo Scientific</td>
			<td>MA1-16687</td>
			<td>Primary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Anti-MYL2 (MLC2v, clone: 330G5)</td>
			<td>Synaptic Systems</td>
			<td>310111</td>
			<td>Primary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Anti-MYL7 (MLC2a, clone: 4E7)</td>
			<td>Abcam</td>
			<td>AB131661</td>
			<td>Primary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Anti-IRX4&#160;&#160;</td>
			<td>Bioss</td>
			<td>BS-9464R</td>
			<td>Primary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Alexa Fluor 488 Goat anti-mouse IgG1&#160;</td>
			<td style="width:152px;">Life Technologies</td>
			<td>A21121</td>
			<td>Secondary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Alexa Fluor 647 Goat anti-mouse IgG2a</td>
			<td style="width:152px;">Life Technologies</td>
			<td>A21241</td>
			<td>Secondary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Alexa Fluor 488 Goat anti-mouse IgG2b</td>
			<td style="width:152px;">Life Technologies</td>
			<td>A21141</td>
			<td>Secondary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">Phycoerythrin(PE) Goat anti-rabbit IgG</td>
			<td style="width:152px;">R&#38;D Systems</td>
			<td style="width:111px;">F0110</td>
			<td>Secondary antibody</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Mouse IgG1</td>
			<td>BD Biosciences</td>
			<td>557273</td>
			<td>Isotype Control</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Mouse IgG2a</td>
			<td>eBiosciences</td>
			<td>16-4724-81</td>
			<td>Isotype Control</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Rabbit IgG-PE</td>
			<td>R&#38;D Systems</td>
			<td>IC105P</td>
			<td>Isotype Control</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;"></td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:431px;">TaqMan Probesets for qRT-PCR</td>
			<td style="width:152px;"></td>
			<td style="width:111px;"></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">ACTB</td>
			<td>Life Technologies</td>
			<td>Hs01060665</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Brachyury T</td>
			<td>Life Technologies</td>
			<td>Hs00610080</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">CASQ2</td>
			<td>Life Technologies</td>
			<td>Hs00154286</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">IRX4</td>
			<td>Life Technologies</td>
			<td>Hs01100809</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">ISL1</td>
			<td>Life Technologies</td>
			<td>Hs00158126</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">MESP1</td>
			<td>Life Technologies</td>
			<td>Hs01001283</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">MYH11 (SMMHC)</td>
			<td>Life Technologies</td>
			<td>Hs00224610</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:431px;">MYH6</td>
			<td>Life Technologies</td>
			<td>Hs01101425</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">MYL2 (MLC2v)</td>
			<td>Life Technologies</td>
			<td>Hs00166405</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">MYL7 (MLC2a)</td>
			<td>Life Technologies</td>
			<td>Hs01085598</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">MYOG</td>
			<td>Life Technologies</td>
			<td>Hs01072232</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">NKX2.5</td>
			<td>Life Technologies</td>
			<td>Hs00231763</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">NPPA</td>
			<td>Life Technologies</td>
			<td>Hs01081097</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">POU5F1</td>
			<td>Life Technologies</td>
			<td>Hs04260367</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">SOX17</td>
			<td>Life Technologies</td>
			<td>HS00751752</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">TNNI1</td>
			<td>Life Technologies</td>
			<td>Hs00913333</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">TNNI2</td>
			<td>Life Technologies</td>
			<td>Hs00268536</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">TNNI3</td>
			<td>Life Technologies</td>
			<td>HS00165957</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">TNNT2</td>
			<td>Life Technologies</td>
			<td>Hs00165960</td>
			<td></td>
		</tr>
	</tbody>
</table>

high efficiency differentiation of human pluripotent stem cells to cardiomyocytes and characterization by flow cytometry

There is an urgent need to develop approaches for repairing the damaged heart, discovering new therapeutic drugs that do not have toxic effects on the heart, and improving strategies to accurately model heart disease. The potential of exploiting human induced pluripotent stem cell (hiPSC) technology to generate cardiac muscle &#8220;in a dish&#8221; for these applications continues to generate high enthusiasm. In recent years, the ability to efficiently generate cardiomyogenic cells from human pluripotent stem cells (hPSCs) has greatly improved, offering us new opportunities to model very early stages of human cardiac development not otherwise accessible. In contrast to many previous methods, the cardiomyocyte differentiation protocol described here does not require cell aggregation or the addition of Activin A or BMP4 and robustly generates cultures of cells that are highly positive for cardiac troponin I and T (TNNI3, TNNT2), iroquois-class homeodomain protein IRX-4 (IRX4), myosin regulatory light chain 2, ventricular/cardiac muscle isoform (MLC2v) and myosin regulatory light chain 2, atrial isoform (MLC2a) by day 10 across all human embryonic stem cell (hESC) and hiPSC lines tested to date. Cells can be passaged and maintained for more than 90 days in culture. The strategy is technically simple to implement and cost-effective. Characterization of cardiomyocytes derived from pluripotent cells often includes the analysis of reference markers, both at the mRNA and protein level. For protein analysis, flow cytometry is a powerful analytical tool for assessing quality of cells in culture and determining subpopulation homogeneity. However, technical variation in sample preparation can significantly affect quality of flow cytometry data. Thus, standardization of staining protocols should facilitate comparisons among various differentiation strategies. Accordingly, optimized staining protocols for the analysis of IRX4, MLC2v, MLC2a, TNNI3, and TNNT2 by flow cytometry are described.

On day 0, cells are 100% confluent with compact morphology and minimal cell debris. On days 1-2, it is common to observe significant cell death (40-50%), but attached cells will retain compact morphology (Figure 1A). During this time, media is orange and turbid. Pink media indicates excessive cell death, and in this case, confirm with trypan blue and discontinue if cell death exceeds 70%. Cells will recover during days 3-4 and density will increase. During days 5-6, minimal cell death occurs and dense pa...

Watch this Scientific Journal Video about High Efficiency Differentiation of Human Pluripotent Stem Cells to Cardiomyocytes and Characterization by Flow Cytometry at JoVE.com

High Efficiency Differentiation of Human Pluripotent Stem Cells to Cardiomyocytes and Characterization by Flow Cytometry

The article describes the detailed methodology to efficiently differentiate human pluripotent stem cells into cardiomyocytes by selectively modulating the Wnt pathway, followed by flow cytometry analysis of reference markers to assess homogeneity and identity of the population.

There is an urgent need to develop approaches for repairing the damaged heart, discovering new therapeutic drugs that do not have toxic effects on the ...

high-efficiency-differentiation-human-pluripotent-stem-cells-to

Research

JoVE Journal

Biology

30.0K Views.  Medical College of Wisconsin. The article describes the detailed methodology to efficiently differentiate human pluripotent stem cells into cardiomyocytes by selectively modulating the Wnt pathway, followed by flow cytometry analysis of reference markers to assess homogeneity and identity of the population. 

Video: High Efficiency Differentiation of Human Pluripotent Stem Cells to Cardiomyocytes and Characterization by Flow Cytometry

Differentiation of Embryonic Stem Cells into Oligodendrocyte Precursors

Oligodendrocytes are the myelinating cells of the central nervous system. For regenerative cell therapy in demyelinating diseases, there is significant interest in deriving a pure population of lineage-committed oligodendrocyte precursor cells (OPCs) for transplantation. OPCs are characterized by the activity of the transcription factor Olig2 and surface expression of a proteoglycan NG2. Using the GFP-Olig2 (G-Olig2) mouse embryonic stem cell (mESC) reporter line, we optimized conditions for the differentiation of mESCs into GFP+Olig2+NG2+ OPCs. In our protocol, we first describe the generation of embryoid bodies (EBs) from mESCs. Second, we describe treatment of mESC-derived EBs with small molecules: (1) retinoic acid (RA) and (2) a sonic hedgehog (Shh) agonist purmorphamine (Pur) under defined culture conditions to direct EB differentiation into the oligodendroglial lineage. By this approach, OPCs can be obtained with high efficiency (&gt;80%) in a time period of 30 days. Cells derived from mESCs in this protocol are phenotypically similar to OPCs derived from primary tissue culture. The mESC-derived OPCs do not show the spiking property described for a subpopulation of brain OPCs in situ. To study this electrophysiological property, we describe the generation of spiking mESC-derived OPCs by ectopically expressing NaV1.2 subunit. The spiking and nonspiking cells obtained from this protocol will help advance functional studies on the two subpopulations of OPCs.

We describe a small molecule-based protocol for differentiation of mouse embryonic stem cells into oligodendrocyte precursor cells (OPCs). This protocol generates Olig2+NG2+ OPCs with high efficiency by 30 days of differentiation. We also describe a method to generate "spiking" OPCs that can fire action potentials.

Oligodendrocytes are the myelinating cells of the central nervous system. For regenerative cell therapy in demyelinating diseases, there is significant ...

Flow Cytometry Purification of Mouse Meiotic Cells

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the unique differentiation programs that are manifest during meiosis. Two principal methods have been developed to purify, to varying degrees, various meiotic fractions from both adult and immature animals: elutriation or Staput (sedimentation) using BSA and/or percoll gradients. Both of these methods rely on cell size and density to separate meiotic cells1-5. Overall, except for few cell populations6, these protocols fail to yield sufficient purity of the numerous meiotic cell populations that are necessary for detailed molecular analyses. Moreover, with such methods usually one type of meiotic cells can be purified at a given time, which adds an extra level of complexity regarding the reproducibility and homogeneity when comparing meiotic cell samples.
Here, we describe a refined method that allows one to easily visualize, identify, and purify meiotic cells, from germ cells to round spermatids, using FACS combined with Hoechst 33342 staining7,8. This method provides an overall snapshot of the entire meiotic process and allows one to highly purify viable cells from most stage of meiosis. These purified cells can then be analyzed in detail for molecular changes that accompany progression through meiosis, for example changes in gene expression9,10and the dynamics of nucleosome occupancy at hotspots of meiotic recombination11.

An efficient method to obtain highly purified viable meiotic fractions from mouse testis is described, which combines a refined cell dissociation protocol with fluorescent activated cell sorting (FACS). This method takes advantage of differences in the DNA content and nuclear density of discrete meiotic fractions.

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the ...

Transfecting and Nucleofecting Human Induced Pluripotent Stem Cells

Genetic modification is continuing to be an essential tool in studying stem cell biology and in setting forth potential clinical applications of human embryonic stem cells (HESCs)1. While improvements in several gene delivery methods have been described2-9, transfection remains a capricious process for HESCs, and has not yet been reported in human induced pluripotent stem cells (iPSCs). In this video, we demonstrate how our lab routinely transfects and nucleofects human iPSCs using plasmid with an enhanced green fluorescence protein (eGFP) reporter. Human iPSCs are adapted and maintained as feeder-free cultures to eliminate the possibility of feeder cell transfection and to allow efficient selection of stable transgenic iPSC clones following transfection. For nucleofection, human iPSCs are pre-treated with ROCK inhibitor11, trypsinized into small clumps of cells, nucleofected and replated on feeders in feeder cell-conditioned medium to enhance cell recovery. Transgene-expressing human iPSCs can be obtained after 6 hours. Antibiotic selection is applied after 24 hours and stable transgenic lines appear within 1 week. Our protocol is robust and reproducible for human iPSC lines without altering pluripotency of these cells.

Despite recent advancements in genetic modification, transfection of human embryonic stem cells (HESCs) remains a capricious process. To our knowledge, systematic and efficient methods to transfect human induced pluripotent stem cells (iPSCs) have not been reported. Here, we describe robust protocols to efficiently transfect and nucleofect human iPSCs.

Genetic modification is continuing to be an essential tool in studying stem cell biology and in setting forth potential clinical applications of human ...

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 ...

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 ...

Analysis of Cell Suspensions Isolated from Solid Tissues by Spectral Flow Cytometry

Flow cytometry has been used for the past 40 years to define and analyze the phenotype of lymphoid and other hematopoietic cells. Initially restricted to the analysis of a few fluorochromes, currently there are dozens of different fluorescent dyes, and up to 14-18 different dyes can be combined at a time. However, several limitations still impair the analytical capabilities. Because of the multiplicity of fluorescent probes, data analysis has become increasingly complex due to the need of large, multi-parametric compensation matrices. Moreover, mutant mouse models carrying fluorescent proteins to detect and trace specific cell types in different tissues have become available, so the analysis (by flow cytometry) of auto-fluorescent cell suspensions obtained from solid organs is required. Spectral flow cytometry, which distinguishes the shapes of emission spectra along a wide range of continuous wavelengths, addresses some of these problems. The data is analyzed with an algorithm that replaces compensation matrices and treats auto-fluorescence as an independent parameter. Thus, spectral flow cytometry should be capable of discriminating fluorochromes with similar emission peaks and can provide a multi-parametric analysis without compensation requirements.
This protocol describes the spectral flow cytometry analysis, allowing for a 21-parameter (19 fluorescent probes) characterization and the management of an auto-fluorescent signal, providing high resolution in minor population detection. The results presented here show that spectral flow cytometry presents advantages in the analysis of cell populations from tissues difficult to characterize in conventional flow cytometry, such as the heart and the intestine. Spectral flow cytometry thus demonstrates the multi-parametric analytical capacity of high-performing conventional flow cytometry without the requirement for compensation and enables auto-fluorescence management.

This article describes spectral cytometry, a new approach in flow cytometry that uses the shapes of emission spectra to distinguish fluorochromes. An algorithm replaces compensations and can treat auto-fluorescence as an independent parameter. This new approach allows for the proper analysis of cells isolated from solid organs.

Flow cytometry has been used for the past 40 years to define and analyze the phenotype of lymphoid and other hematopoietic cells. Initially restricted to ...

Measurement of Mitochondrial Mass and Membrane Potential in Hematopoietic Stem Cells and T-cells by Flow Cytometry

A fine balance of quiescence, self-renewal, and differentiation is key to preserve the hematopoietic stem cell (HSC) pool and maintain lifelong production of all mature blood cells. In recent years cellular metabolism has emerged as a crucial regulator of HSC function and fate. We have previously demonstrated that modulation of mitochondrial metabolism influences HSC fate. Specifically, by chemically uncoupling the electron transport chain we were able to maintain HSC function in culture conditions that normally induce rapid differentiation. However, limiting HSC numbers often precludes the use of standard assays to measure HSC metabolism and therefore predict their function. Here, we report a simple flow cytometry assay that allows reliable measurement of mitochondrial membrane potential and mitochondrial mass in scarce cells such as HSCs. We discuss the isolation of HSCs from mouse bone marrow and measurement of mitochondrial mass and membrane potential post ex vivo culture. As an example, we show the modulation of these parameters in HSCs via treatment with a metabolic modulator. Moreover, we extend the application of this methodology on human peripheral blood-derived T cells and human tumor infiltrating lymphocytes (TILs), showing dramatic differences in their mitochondrial profiles, possibly reflecting different T cell functionality. We believe this assay can be employed in screenings to identify modulators of mitochondrial metabolism in various cell types in different contexts.

Here we describe a reliable method to measure mitochondrial mass and membrane potential in ex vivo cultured hematopoietic stem cells and T cells.

A fine balance of quiescence, self-renewal, and differentiation is key to preserve the hematopoietic stem cell (HSC) pool and maintain lifelong production ...

Single Extracellular Vesicle Transmembrane Protein Characterization by Nano-Flow Cytometry

Single particle characterization has become increasingly relevant for research into extracellular vesicles, progressing from bulk analysis techniques and first-generation particle analysis to comprehensive multi-parameter measurements such as nano-flow cytometry (nFCM). nFCM is a form of flow cytometry that utilizes instrumentation specifically designed for nano-particle analysis, allowing for thousands of EVs to be characterized per minute both with and without the use of staining techniques. High resolution side scatter (SS) detection allows for size and concentration to be determined for all biological particles larger than 45 nm, while simultaneous fluorescence (FL) detection identifies the presence of labeled markers and targets of interest. Labeled subpopulations can then be described in quantitative units of particles/mL or as a percentage of the total particles identified by side scatter.
Here, EVs derived from conditioned cell culture media (CCM) are labeled with both a lipid dye, to identify particles with a membrane, and antibodies specific for CD9, CD63, and CD81 as common EV markers. Measurements of comparison material, a concentration standard and a size standard of silica nanospheres, as well as labeled sample material are analyzed in a 1-minute analysis. The software is then used to measure the concentration and size distribution profile of all particles, independent of labeling, before determining the particles that are positive for each of the labels.
Simultaneous SS and FL detection can be utilized flexibly with many different EV sources and labeling targets, both external and internal, describing EV samples in a comprehensive and quantitative manner.

The latest generation of EV characterization tools are capable of single EV analysis across multiple parameters simultaneously. Nano-flow cytometry measures all biological particles larger than 45 nm without labeling and identifies specific characteristics of subpopulations by a variety of fluorescent labeling techniques.

Single particle characterization has become increasingly relevant for research into extracellular vesicles, progressing from bulk analysis techniques and ...

Real-Time Measurements of Calcium and Contractility Parameters in hiPSC-CMs

Real-Time Measurements of Calcium and Contractility Parameters in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) represent a powerful tool for studying mutation-mediated changes in cardiomyocyte function and defining the effects of stressors and drug interventions. In this study, it is demonstrated that this optics-based system is a powerful tool to assess the functional parameters of hiPSC-CMs in 2D. By using this platform, it is possible to perform paired measurements in a well-preserved temperature environment on different plate layouts. Moreover, this system provides researchers with instant data analysis.
This paper describes a method for measuring the contractility of unmodified hiPSC-CMs. Contraction kinetics are measured at 37 &#176;C based on pixel correlation changes relative to a reference frame taken at relaxation at a 250 Hz sampling frequency. Additionally, simultaneous measurements of intracellular calcium transients can be acquired by loading the cell with a calcium-sensitive fluorophore, such as Fura-2. Using a hyperswitch, ratiometric calcium measurements can be performed on a 50 &#181;m diameter illumination spot, corresponding to the area of the contractility measurements.

Author Spotlight: Real-Time Measurements of Calcium and Contractility Parameters in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes  

Here, an established method is described to perform contractility and calcium measurements in human induced pluripotent stem cell-derived cardiomyocytes using an optics-based platform. This platform enables researchers to study the effect of mutations and the response to various stimuli in a rapid and reproducible manner.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) represent a powerful tool for studying mutation-mediated changes in cardiomyocyte ...

Characterizing Surface Antigens and Proliferation Ability in hiPSC-Driving MSCs

Comparison of Two Representative Methods for Differentiation of Human Induced Pluripotent Stem Cells into Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) are adult pluripotent stem cells which have been widely used in regenerative medicine. As somatic tissue-derived MSCs are restricted by limited donation, quality variations, and biosafety, the past 10 years have seen a great rise in efforts to generate MSCs from human induced pluripotent stem cells (hiPSCs). Past and recent efforts in the differentiation of hiPSCs into MSCs have been centered around two culture methodologies: (1) the formation of embryoid bodies (EBs) and (2) the use of monolayer culture. This protocol describes these two representative methods in deriving MSC from hiPSCs. Each method presents its advantages and disadvantages, including time, cost, cell proliferation ability, the expression of MSC markers, and their capability of differentiation in vitro. This protocol demonstrates that both methods can derive mature and functional MSCs from hiPSCs. The monolayer method is characterized by lower cost, simpler operation, and easier osteogenic differentiation, while the EB method is characterized by lower time consumption.

Author Spotlight: Advancements in iPSCs and Genetic Disease Research 

This protocol describes and compares two representative methods for differentiating hiPSCs into mesenchymal stromal cells (MSCs). The monolayer method is characterized by lower cost, simpler operation, and easier osteogenic differentiation. The embryoid bodies (EBs) method is characterized by lower time consumption.

Mesenchymal stromal cells (MSCs) are adult pluripotent stem cells which have been widely used in regenerative medicine. As somatic tissue-derived MSCs are ...