The authors thank Chad MacArthur for helpful discussions.

1.Solution and Medium Preparation
<ol>
	<li>Basement Membrane Matrix (Purified from Engelbreth-Holm-Swarm Tumor)
	<ol>
		<li>Slowly thaw the basement membrane matrix (5 ml) on ice at 4 &#176;C overnight.</li>
		<li>Dilute the stock solution 1:1 with 5 ml of ice cold, sterile DMEM/F-12 medium in a sterile, pre-chilled 15 ml conical tube. Dispense aliquots into pre-chilled, 1.5 ml sterile micro centrifuge tubes and immediately store at -20 &#176;C.</li>
		<li>Prior to usage, thaw the frozen 1:1 basement ...

<ol>
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All of the authors [RHQ, JSTA, KS, and UL] are employees of Thermo Fisher Scientific, which produces some of the reagents and instruments used in this article.

This study provides strategies for monitoring and tracking of the reprogramming process using flow cytometry and real-time imaging-based analysis. The critical steps in the protocol are initiating reprogramming, measuring reprogramming progression based on marker expression and real-time monitoring of reprogramming. Any reprogramming method of choice can be used but here we focus on Sendai based reprogramming of human fibroblasts. The advantage of this method is the ease of use and consistent high efficiency of reprogram...

Patient-derived induced pluripotent stem cells (iPSCs) are promising tools for cell therapy and drug screening. They provide an autologous source of cells for therapy. In addition, they encompass a very broad set of genetic backgrounds, enabling a detailed in vitro analysis of genetic diseases beyond what current embryonic stem cell (ESC) lines would allow. Recent advances have led to the development of several methods for generating iPSCs, including reprogramming with Sendai virus, episomal plasmids or mRNAs 1,2. Notably, different reprogramming methods are associated with varying levels of efficiency and safety, and are likely to differ in other ways that influence their appropriateness for various applications. With the availability of a variety of reprogramming technologies, it has become important to develop methods for assessing the reprogramming process. Most existing methods rely on the qualitative inspection of morphology or staining with stem cell-specific dyes and antibodies. One recently developed method makes use of lentiviral fluorescence reporters that are sensitive to PSC-specific miRNAs or differentiated cell-specific mRNAs 3. Such monitoring methods facilitate the selection and optimization of reprogramming techniques for different situations. For example, CDy1 has been used as a fluorescent probe for early iPSCs in order to screen for reprogramming modulators 4. The ability to observe and compare different reprogramming experiments is also critical for gaining a better understanding of the process itself. For instance, it is now known that some somatic cell types are easier to reprogram than others 5, and that cells go through intermediate states during reprogramming 6-8. Unfortunately, the mechanisms underlying the reprogramming process are still not completely understood and consequently, the exact differences between reprogramming methods also remain to be defined. Thus, methods for monitoring, assessing, and comparing reprogramming events continue to be critical for the stem cell field.
The methods described in this protocol permit the monitoring and assessing of the reprogramming process and illustrate how these techniques can be used to compare different sets of reprogramming reagents. The first approach involves flow cytometry analyses using combinations of antibodies against positive and negative pluripotent stem cell (PSC) markers. The second approach couples real-time imaging and the measurement of total confluence (the percent surface area covered by the cells) and confluence of marker signals (the percent surface area covered by the fluorescent signals).

<table border="0" cellpadding="0" cellspacing="0" width="795">
	<tbody>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">DMEM, high glucose, GlutaMAXSupplement, pyruvate</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">10569-010</td>
			<td style="width:88px;"></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Fetal Bovine Serum, embryonic stem cell-qualified, US origin</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">16141-061</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">MEM Non-Essential Amino Acids Solution (100X)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">11140-050</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Trypsin-EDTA (0.05%), phenol red&#160;</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">25300-054</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Mouse (ICR) Inactivated Embryonic Fibroblasts</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A24903</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Attachment Factor Protein (1X)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">S-006-100</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">DMEM/F-12, GlutaMAX supplement</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">10565-018</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">KnockOut Serum Replacement</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td align="right" style="width:147px;">10828010</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">2-Mercaptoethanol (55 mM)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">21985-023</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Collagenase, Type IV, powder</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">17104-019</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">TrypLE Select Enzyme (1X), no phenol red&#160;</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">12563-011</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">DPBS, no calcium, no magnesium&#160;</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">14190-144</td>
			<td></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:297px;">Geltrex LDEV-Free, hESC-Qualified, Reduced Growth Factor Basement Membrane Matrix</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A1413302</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Essential 8 Medium</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A1517001</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">FGF-Basic (AA 1-155) Recombinant Human Protein</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">PHG0264</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">UltraPure 0.5M EDTA, pH 8.0</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">15575-020</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Bovine Albumin Fraction V (7.5% solution)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">15260-037</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">HEPES (1 M)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">15630-080</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Penicillin-Streptomycin (10,000 U/mL)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">15140-122</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">InSolution Y-27632</td>
			<td style="width:263px;">EMD Millipore</td>
			<td align="right" style="width:147px;">688001</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">CytoTune-iPS Sendai Reprogramming Kit</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A1378001</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">CytoTune-iPS 2.0 Sendai Reprogramming Kit</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A16517</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Countess II Automated Cell Counter</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">AMQAX1000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Countess Cell Counting Chamber Slides</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">C10228</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">BJ ATCC Human Foreskin Fibroblasts, Neonatal</td>
			<td style="width:263px;">ATCC</td>
			<td style="width:147px;">CRL-2522</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">DF1 Adult Human Dermal Fibroblast</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">N/A</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">BG01V/hOG Cells Variant hESC hOct4-GFP Reporter Cells</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">R7799-105</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">IncuCyte ZOOM</td>
			<td style="width:263px;">Essen BioScience</td>
			<td style="width:147px;"></td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">SSEA-4 Antibody, Alexa Fluor 647 conjugate (MC813-70)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">SSEA421</td>
			<td></td>
		</tr>
		<tr height="61">
			<td height="61" style="height:61px;width:297px;">SSEA-4 Antibody, Alexa Fluor 488 conjugate (eBioMC-813-70 (MC-813-70))</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A14810</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">SSEA-4 Antibody (MC813-70)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">41-4000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">TRA-1-60 Antibody (cl.A)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">&#160;41-1000</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">CD44 Rat Anti-Human/Mouse mAb (clone IM7), PE-Cy5 conjugate</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A27094</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">CD44 Alexa Fluor 488 Conjugate Kit for Live Cell Imaging</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A25528</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">CD44 Rat Anti-Human/Mouse mAb (Clone IM7)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">RM-5700 (no longer available)</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Goat anti-Mouse IgG (H+L) Secondary Antibody, Alexa Fluor 488 conjugate</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">&#160;A-11029</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Goat anti-Rat IgG (H+L) Secondary Antibody, Alexa Fluor 594 conjugate</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">&#160;A-11007</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Alkaline Phosphatase Live Stain</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A14353</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">TRA-1-60 Alexa Fluor 488 Conjugate Kit for Live Cell Imaging</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A25618</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">CD24 Mouse Anti-Human mAb (clone SN3), FITC conjugate</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">MHCD2401</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">beta-2 Microglobulin Antibody, FITC conjugate (B2M-01)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A15737</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">EpCAM / CD326 Antibody, FITC conjugate (VU-1D9)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">A15755</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">CD73 / NT5E Antibody (7G2)</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">41-0200</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">VECTOR Red Alkaline Phosphatase (AP) Substrate Kit</td>
			<td style="width:263px;">Vector Laboratories</td>
			<td style="width:147px;">SK-5100</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Zeiss Axio Observer.Z1 microscope&#160;</td>
			<td style="width:263px;">Carl Zeiss</td>
			<td style="width:147px;">491912-0003-000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">FlowJo Data Analysis Software</td>
			<td style="width:263px;">FLOJO, LLC</td>
			<td style="width:147px;">N/A</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Attune Accoustic Focusing Cytometer, Blue/Red Laser</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td style="width:147px;">Use Attune NXT&#160;</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">S3e\ Cell Sorter (488/561 nm)</td>
			<td style="width:263px;">BIO-RAD</td>
			<td align="right" style="width:147px;">1451006</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Falcon 12 x 75 mm Tube with Cell Strainer Cap</td>
			<td style="width:263px;">Corning</td>
			<td align="right" style="width:147px;">352235</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Falcon 15 mL, high-clarity, dome-seal screw cap</td>
			<td style="width:263px;">Corning</td>
			<td align="right" style="width:147px;">352097</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Falcon T-75 Flask</td>
			<td style="width:263px;">Corning</td>
			<td align="right" style="width:147px;">353136</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Falcon T-175 Flask</td>
			<td style="width:263px;">Corning</td>
			<td align="right" style="width:147px;">353112</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:297px;">Falcon 6-well dish</td>
			<td style="width:263px;">Corning</td>
			<td align="right" style="width:147px;">353046</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">HERAEUS HERACELL CO2 ROLLING INCUBATOR</td>
			<td style="width:263px;">Thermo Fisher Scientific</td>
			<td align="right" style="width:147px;">51013669</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:297px;">Nonstick, RNase-free Microfuge Tubes, 1.5 mL</td>
			<td style="width:263px;"></td>
			<td style="width:147px;">AM12450</td>
			<td></td>
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		<tr height="22">
			<td height="22" style="height:22px;width:297px;">HulaMixer Sample Mixer</td>
			<td style="width:263px;"></td>
			<td style="width:147px;">15920D</td>
			<td></td>
		</tr>
	</tbody>
</table>

kinetic measurement and real time visualization of somatic reprogramming

Somatic reprogramming has enabled the conversion of adult cells to induced pluripotent stem cells (iPSC) from diverse genetic backgrounds and disease phenotypes. Recent advances have identified more efficient and safe methods for introduction of reprogramming factors. However, there are few tools to monitor and track the progression of reprogramming. Current methods for monitoring reprogramming rely on the qualitative inspection of morphology or staining with stem cell-specific dyes and antibodies. Tools to dissect the progression of iPSC generation can help better understand the process under different conditions from diverse cell sources. 
This study presents key approaches for kinetic measurement of reprogramming progression using flow cytometry as well as real-time monitoring via imaging. To measure the kinetics of reprogramming, flow analysis was performed at discrete time points using antibodies against positive and negative pluripotent stem cell markers. The combination of real-time visualization and flow analysis enables the quantitative study of reprogramming at different stages and provides a more accurate comparison of different systems and methods. Real-time, image-based analysis was used for the continuous monitoring of fibroblasts as they are reprogrammed in a feeder-free medium system. The kinetics of colony formation was measured based on confluence in the phase contrast or fluorescence channels after staining with live alkaline phosphatase dye or antibodies against SSEA4 or TRA-1-60. The results indicated that measurement of confluence provides semi-quantitative metrics to monitor the progression of reprogramming.

Monitoring Reprogramming Kinetics Using Flow Cytometry
CD44 is a fibroblast marker while SSEA4 is a PSC marker 6,10. As expected from this expression pattern, flow cytometry of BJ fibroblasts shows an SSEA4- CD44+ population that facilitates the creation of quadrant gates in combination with the unstained sample. During reprogramming of DF1 fibroblasts with the Sendai viruses, CD44 is gr...

Watch this Scientific Journal Video about Kinetic Measurement and Real Time Visualization of Somatic Reprogramming at JoVE.com

Kinetic Measurement and Real Time Visualization of Somatic Reprogramming

The protocol presented in this study describes methods for the real-time monitoring of reprogramming progression via the kinetic measurement of positive and negative pluripotent stem cell markers using flow cytometry analysis. The protocol also includes the imaging-based assessment of morphology, and marker or reporter expression during iPSC generation.

Somatic reprogramming has enabled the conversion of adult cells to induced pluripotent stem cells (iPSC) from diverse genetic backgrounds and disease ...

The overall goal of these procedures is to visualize and track the progression of somatic cell reprogramming into induced pluripotent stem cells or iPSC. This method can be used to answer key questions in the iPSC field, such as how reprogramming kinetics and reprogramming efficiencies are altered by the somatic tissues used, the reprogramming technologies applied, and the matrix and media combinations used with it. The main advantage of this method is that it utilizes cell surface markers to look at the transitions of somatic cells into iPSCs such that you can use this technology to be able to monitor in real time the reprogramming events.On day seven post transduction, wash the fibroblasts with two milliliters of DPBS per well and add 0.5 milliliters of 37 degree celsius 05%EDTA to each well for a three to five minute incubation at 37 degrees celsius. When the cells have rounded, stop the reaction with two milliliters of 37 degree celsius fibroblast medium per well and gently pipette the medium across the bottom of each well to dislodge the cells. Transfer the fibroblasts from each well into individual 15 milliliter conical tubes and collect them by centrifugation.Resuspend the pellets in two milliliters of fresh 37 degree celsius fibroblast medium and count the cells from each culture condition. Next, seed one times 10 to the fifth cells into pre-prepared feeder-independent conditioned wells in a six-well tissue culture plate and incubate the transduced cells in the cell culture incubator overnight. The next day, replace the medium in each well with the appropriate medium for the cell application.Then place the plate in the imager and set the software to capture continuous whole-well phase contrast and fluorescent images for each well every six to eight hours for the next 14 days. At the end of the reprogramming experiment, wash the wells one time with two milliliters of 37 degree celsius DMEM/F12 medium. Discard the wash and label the cells with one milliliter per well of the appropriate primary antibodies in fresh DMEM/F12 medium for 45 minutes at 37 degree celsius in the incubator.At the end of the incubation, wash the cells two times with 37 degree celsius DMEM/F12 medium. Then discard the wash and label the cells with one milliliter of the appropriate secondary antibodies in 37 degree celsius DMEM/F12 medium for 30 minutes at 37 degree celsius. At the end of the incubation, wash the cells two more times with DMEM/F12 medium.Then replace the wash in each well with two milliliters of fresh 37 degree celsius DMEM/F12 medium. Place the dish into the imager and open the imaging software. To set up scans on the imaging system software, first select the position of the tray to be used and select the type of dish to be scanned.Next, select Whole Well Imaging, the pattern for scanning the desired wells, and the appropriate fluorescent channels for the real-time identification of the surface markers of interest. Then label the experiment to be scanned and set the time points and intervals for the samples to be scanned each day. To analyze a set of scanned experiments, select the experiment of interest and select Launch New Analysis Job.Then select the appropriate processing definition for the type of analysis according to the channels used for the imaging, for example, PSC Phase Colony Count. Name the analysis job. And select the time range for the analysis and the wells to be analyzed.Then launch the analysis job. To measure the desired reprogramming time points from individual wells, wash the well of interest one time with two milliliters of DPBS. Then replace the wash with one milliliter of pre-warmed 37 degree celsius 05%trypsin-EDTA solution.After five minutes of 37 degree celsius, flush the trypsin against the bottom of the well to dissociate the cells into a single-cell suspension and transfer the cells into a 15 milliliter conical tube. Using three milliliters of DPBS, wash any of the remaining cells from the well and pull them in the 15 milliliter tube. Add an additional 10 milliliters of DPBS to the cells and spin them down by centrifugation.Resuspend the pellet in one milliliter of DMEM/F12 medium for counting. Then dilute the cell suspension to a one times tenth of the six cells per milliliter concentration and aliquot one milliliter of cells per tube for the appropriate number of samples. Next, label the cells with the primary antibodies of interest in one milliliter of DMEM/F12 medium for 30 to 45 minutes at room temperature with mixing.At the end of the incubation, wash the cells two times in 37 degree celsius DMEM/F12 medium. Resuspend the pellets in one milliliter of DPBS and transfer the samples into individual FACS tubes. Acquire the flow cytometry profiles of the reprogrammed plates.Then transfer the FCS files to a computer and import the files into the appropriate analysis software. Open the first control file in a forward by side scatter plot and set the y-axis to a logarithmic scale. Then create a polygonal gate around the live population.Next, create a side scatter area by scatter height plot with the live cells and set a rectangular gate to exclude the doublets. Then use these gates to analyze the experimental sample files under the appropriate fluorescent channels to identify the populations of interest in their respective quadrants. Reprogramming BJ fibroblasts with Sendai reprogramming viruses generates SSEA4+CD44-cells at a different rate than reprogramming DF1 fibroblasts, demonstrating that an early comparison of the percentage of pluripotent stem cell-like SSEA4+CD44-cells can be used to track the reprogramming progression.In a flow cytometry time course, CD24-CD44+and EpCAM negative CD44+fibroblasts form double negative populations that later transition into CD24+CD44-and EpCAM positive CD44-pluripotent stem cell-like cells respectively, further outlining the reprogramming progression. Real-time imaging of the reprogramming cultures after reseeding demonstrates a gradual colony formation corresponding to a logarithmic increase in their confluence and demonstrating the final pluripotent positive and fibroblast negative marker expression at the completion of the reprogramming. Further, using a reporter gene allows the confluence to be measured under phase contrast with a more gradual increase of the GFP confluence observed compared to the total confluence.Indeed, in this representative experiment, the GFP confluence at day 19 was less than half of the total confluence corresponding to the complete reprogramming. Once mastered, this technique could be used to elucidate information about reprogramming events and track the kinetics of human fibroblast reprogramming. This technique could also be used to look at different starting somatic cell tissues, the reprogramming technologies used, and the medium matrix combinations to elucidate reprogramming events.After watching this video, you should have a good understanding on how to utilize real-time monitoring and cell surface marker expression, to be able to track the reprogramming of human fibroblasts into iPSCs.

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Research

JoVE Journal

Developmental Biology

6.6K visualizações.  Thermo Fisher Scientific. The overall goal of these procedures is to visualize and track the progression of somatic cell reprogramming into induced pluripotent stem cells or iPSC. This method can be used to answer key questions in the iPSC field, such as how reprogramming kinetics and reprogramming efficiencies are altered by the somatic tissues used, the reprogramming technologies applied, and the matrix and media combinations used with it. The main advantage of this method is that it utilizes cell surface markers to...