Thanks to Tim Doyle, PhD and the Stanford Center for In Vivo Imaging for assistance with bioluminescence imaging. Also thanks to Ngan Huang, PhD for sharing her technique on stem cell co-injection with matrix solution. Lastly, thanks to Steve Felt, Ph.D. for assistance with veterinary animal care.

<ol>
<li>Construction of Double Fusion Reporter Gene<ol>
<li>In order to perform bioluminescence imaging of human embryonic stem cells, you first need to obtain cells that stably express a luciferase reporter gene such as firefly luciferase driven by a constitutive promoter like Ubiquitin or EF1a.</li>
<li>The focus of this protocol is on reporter gene applications, so detailed procedures are not provided here. However, our lab's general strategy is to use a double fusion construct vector that contains firefly luciferase (fluc) and enhanced green fluorescent protein (egfp) separated by a spacer within pCDNA 3.1+.</li>
<li>Briefly, our double fusion gene was originally located downstream of the cytomegalovirus promoter in pCDNA 3.1(+), so the 3.3 kbp fragment was excised using NdeI and NotI digestion and blunt-end ligated into the multiple cloning site of a self-inactivating (SIN) lentiviral vector, under control of a Ubiquitin promoter. </li>
</ol></li>
<li>Lentiviral Transduction<ol>
<li>hESCs can be transduced 3-5 days after passage at a multiplicity of infection (MOI) of 10 (viral titer of approximately 107 incubated with 106 cells).</li>
<li>The thawed viral stock can be added directly to fresh hESC media.</li>
<li>Refresh the media 12 and 24 hours later.</li>
<li>After 48 h, transduction efficiency can by qualitatively assessed using fluorescence microscopy. Subsequently, FACS can be used to isolate infected cells. </li>
</ol></li>
<li>Culturing hESCs and Introduction to Imaging Set-up<ol>
<li>Culture your luciferase positive hESCs in feeder-free conditions. We typically follow the standard WiCell protocol and use 6-well plates coated in growth factor reduced Matrigel, using either conditioned media or commercial, feeder-free media.</li>
<li>To detect the luciferase positive cells, you will need to have the reporter probe D-luciferin already prepared. To do this, aliquot luciferin in 1-1.5 mL preparations at a final concentration of 45 mg/mL. Keep the aliquots at -20&deg;C when not in use and avoid exposure to light by covering with paper towel when not in storage.</li>
<li>In order to visualize the luciferase positive cells, we use IVIS 50 and IVIS 200 Imaging Systems (Xenogen Corporation, Alameda, CA). This latter system includes an integrated isoflourane apparatus and induction chamber for temporary anesthesia of small animals. </li>
</ol></li>
<li>In vitro bioluminescence imaging of hESCs<ol>
<li>For in vitro bioluminescence imaging, it is important to maintain sterile conditions. Therefore, the imaging system should be sterile, preferably in a cell culture room.</li>
<li>Before imaging, remove the cell media and add just enough PBS to cover the cells. For example, add 1mL PBS to each well of a 6-well plate containing your hESC cultures.</li>
<li>The ratio of D-Luciferin to PBS should be 1:100, so add 10 &micro;L of thawed D-Luciferin to each well of the 6-well plate.</li>
<li>Wait one minute, then take an image using an exposure time of 1 second. If signal is weak, increase the exposure interval and try again.</li>
<li>The bioluminescent signal reflects cell number, so quantitation assays can be performed that correlate signal with different cell numbers. </li>
</ol></li>
<li>Preparation of mouse and injecting cells for in vivo imaging<ol>
<li>Reporter gene imaging provides a high-throughput, inexpensive and sensitive method for tracking cells after transplantation over days, weeks, and even months. This is especially important since transplanted stem cells frequently form teratomas, are rejected by the host's immune system, or simply die.</li>
<li>The simplest method for imaging teratoma formation in vivo is to inject hESCs that express the firefly luciferase reporter gene into the backs of SCID mice and acquire bioluminescent images with the IVIS system.</li>
<li>When you're ready to transplant the cells, use dispase or collagenase to loosen the cells, wash several times, and suspend them in a 1:1 mixture of growth factor reduced-matrigel and DMEM. Typically we first mix the cells with chilled DMEM and then add in the matrigel. For each subcutaneous injection site, we inject 200,000 cells suspended in a 50-100 ul volume of the matrigel/DMEM mixture. The cell number can be adjusted depending on your application. Remember to keep everything on ice prior to injection.</li>
<li>Once the cells are ready, anesthetize the mouse by placing it in the induction box with isoflurane flow turned on. After 1-5 minutes, the mouse is asleep and can be placed on the operating table with continuous isoflurane.</li>
<li>Because fur naturally auto-fluoresces and may obscure the bioluminescent image, we will need to remove the hair from the back side of the mouse. The easiest way to do this is to use an electric shaver, but you can also use hair-removal gels. Wipe with alcohol to sterilize the skin afterwards</li>
<li>Next, draw up your cell suspension in a syringe. 23 to 27 gauge needles work best since they will not clog up with cells. If the needle is too large (&lt;23 gauge) the needle tract may leave a large hole through which cells can leak back out.</li>
<li>Inject the cells under the skin into the mouse's back. Because the skin is quite loose, use your thumb and forefinger to pinch and stretch out the area you want to inject. Inject just under the skin, taking care not to puncture too deeply. Also, try to keep the needle from sliding out of the injection site while depressing the plunger: this will prevent creating a hole in the skin through which the cells can leak if you try to inject again.</li>
<li>After the cells are injected, wait a few hours to allow the mouse to wake up and run around before re-anesthetizing for bioluminescence imaging. Doing so avoids isoflurane toxicity. </li>
</ol></li>
<li>In vivo bioluminescence imaging of transplanted cells<ol>
<li>For whole animal bioluminescence imaging, we do an intraperitoneal injection of D-luciferin at 375 mg/kg body weight. Weigh the animal to calculate the dosage prior to injection.</li>
<li>Inject the D-luciferin in the peritoneum, just off the midline. Be careful to not go too deep or you can damage internal organs. If the mouse begins to wake up, place it back in the knockout box and wait a minute or two. For mice, the maximum bioluminescence usually occurs 15-40 mins after injection.</li>
<li>Remember to place matte black paper in the imaging box to help absorb any light not emitted by the hESCs. Place the mouse (backside up) in the imaging chamber with isoflurane, on top of the black paper. Start with an exposure time of 10 seconds. If the signal is saturated, try decreasing the exposure time; if too weak, increase the exposure.</li>
<li>Once the signal exposure time has been optimized for your mouse, begin taking images every minute until the signal reaches a maximum. This is best done by using the imaging software to select "regions of interest (ROI)" that cover your injection sites. By monitoring the signal intensity at each ROI you can easily determine when the signal begins to decrease, indicating that the maximum signal intensity has been reached. The maximum signal should be used as your final data.</li>
<li>When you are satisfied with your images, remove the mouse from isoflurane and allow it to wake up in its cage. Usually, the mouse should wake up within 15 minutes.</li>
<li>Bioluminescence reporter gene imaging can be repeated daily, weekly and monthly for as long as the hESCs survive in the animal. Signal from a developing teratoma will increase exponentially over time, typically on the order of weeks, as the hESCs begin to proliferate.</li>
<li>After the desired time course of bioluminescence images is acquired, the animal may be sacrificed and tissue sections used for histology.</li>
</ol></li>
</ol>

<ol>
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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiomyocytes+derived+from+human+embryonic+stem+cells+in+pro-survival+factors+enhance+function+of+infarcted+rat+hearts.">Cardiomyocytes derived from human embryonic stem cells in pro-survival factors enhance function of infarcted rat hearts.</a> Nature biotechnology. 25, 1015-1024 (2007).</li><li>Baharvand, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+differentiation+from+human+embryonic+stem+cells+in+a+defined+adherent+culture+conditi.">Neural differentiation from human embryonic stem cells in a defined adherent culture conditi.</a> Int J Dev Biol. 51, 371-378 (2007).</li><li>Schulz, T. 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Compared to other modalities such as PET and MRI, bioluminescence has limited spatial resolution and reduced tissue penetration due to the relatively weak energy of emitted photons (2-3 eV); for these reasons it has thus far not been applicable in large animals. However, bioluminescence has the advantage of being low-cost, high-throughput, and non-invasive, making it highly desirable for in vivo stem cell tracking in small animals. Non-bioluminescence reporter genes such as PET and fluorescence constructs may be used in ...

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		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Dulbecco's Modified Eagle's Medium (DMEM)</td>
<td>&nbsp;</td>
<td>HyClone</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>BD Matrigel&#x2122; Basement Membrane Matrix</td>
<td>Growth factor reduced (optional: phenol-red free)</td>
<td>BD Biosciences</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>mTeSR1 Maintenance Medium for Human Embryonic Stem Cells</td>
<td>&nbsp;</td>
<td>StemCell Technologies</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Phosphate Buffered Saline (PBS)</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>D-Luciferin Firefly, potassium salt</td>
<td>&nbsp;</td>
<td>Biosynth AG</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Collagenase IV solution</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Dissolve 30 mg Collagenase Type IV in 30 mL DMEM-F12 media. Sterile filter and store at 4 degrees (Celsius).</td>
</tr>
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<td>Baked Pasteur pipets</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
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<td>6-well tissue culture-treated plates</td>
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<td>TPP</td>
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in vitro and in vivo bioluminescence reporter gene imaging of human embryonic stem cells

The discovery of human embryonic stem cells (hESCs) has dramatically increased the tools available to medical scientists interested in regenerative medicine. However, direct injection of hESCs, and cells differentiated from hESCs, into living organisms has thus far been hampered by significant cell death, teratoma formation, and host immune rejection. Understanding the in vivo hESC behavior after transplantation requires novel imaging techniques to longitudinally monitor hESC localization, proliferation, and viability. Molecular imaging has given investigators a high-throughput, inexpensive, and sensitive means for tracking in vivo cell proliferation over days, weeks, and even months. This advancement has significantly increased the understanding of the spatio-temporal kinetics of hESC engraftment, proliferation, and teratoma-formation in living subjects.

A major advance in molecular imaging has been the extension of noninvasive reporter gene assays from molecular and cellular biology into in vivo multi-modality imaging platforms. These reporter genes, under control of engineered promoters and enhancers that take advantage of the host cell s transcriptional machinery, are introduced into cells using a variety of vector and non-vector methods. Once in the cell, reporter genes can be transcribed either constitutively or only under specific biological or cellular conditions, depending on the type of promoter used. Transcription and translation of reporter genes into bioactive proteins is then detected with sensitive, noninvasive instrumentation (e.g., CCD cameras) using signal-generating probes such as D-luciferin.

To avoid the need for excitatory light to track stem cells in vivo as is required for fluorescence imaging, bioluminescence reporter gene imaging systems require only an exogenously administered probe to induce light emission. Firefly luciferase, derived from the firefly Photinus pyralis, encodes an enzyme that catalyzes D-luciferin to the optically active metabolite, oxyluciferin. Optical activity can then be monitored with an external CCD camera. Stably transduced cells that carry the reporter construct within their chromosomal DNA will pass the reporter construct DNA to daughter cells, allowing for longitudinal monitoring of hESC survival and proliferation in vivo. Furthermore, because expression of the reporter gene product is required for signal generation, only viable parent and daughter cells will create bioluminescence signal; apoptotic or dead cells will not. 

In this video, the specific materials and methods needed for tracking stem cell proliferation and teratoma formation with bioluminescence imaging will be described.

Watch this Scientific Journal Video about In vitro and in vivo Bioluminescence Reporter Gene Imaging of Human Embryonic Stem Cells at JoVE.com

In vitro and in vivo Bioluminescence Reporter Gene Imaging of Human Embryonic Stem Cells

With the growing interest in stem cell therapies, molecular imaging techniques are ideal for monitoring stem cell behavior after transplantation. Luciferase reporter genes have enabled non-invasive, repetitive assessment of cell survival, location, and proliferation in vivo. This video will demonstrate how to track hESC proliferation in a living mouse.

The discovery of human embryonic stem cells (hESCs) has dramatically increased the tools available to medical scientists interested in regenerative ...

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21.7K 次观看.  Stanford University School of Medicine. 分子成像技术在干细胞疗法的兴趣与日俱增，是理想的监测干细胞移植后的行为。荧光素酶基因已启用非侵入性，重复评估细胞的存活，位置，并在体内扩散。本视频将演示如何跟踪生活在一个小鼠胚胎干细胞增殖。

视频: In vitro and in vivo Bioluminescence Reporter Gene Imaging of Human Embryonic Stem Cells

Derivation of Human Embryonic Stem Cells by Immunosurgery

The ability of human embryonic stem cells to self-renew and differentiate into all cell types of 
the body suggests that they hold great promise for both medical applications and as a research 
tool for addressing fundamental questions in development and disease. Here, we provide a 
concise, step-by-step protocol for the derivation of human embryonic stem cells from embryos 
by immunosurgical isolation of the inner cell mass. 


The ability of human embryonic stem cells to self-renew and differentiate into all cell types of 
the body suggests that they hold great promise for both medical applications and as a research 
tool for addressing fundamental questions in development and disease. Here, we provide a 
concise, step-by-step protocol for the derivation of human embryonic stem cells from embryos 
by immunosurgical isolation of the inner cell mass.

The ability of human embryonic stem cells to self-renew and differentiate into all cell types of 
the body suggests that they hold great promise for both ...

Probing for Mitochondrial Complex Activity in Human Embryonic Stem Cells

Mitochondria are cytoplasmic organelles that have a primary role in cellular metabolism and homeostasis, regulation of the cell signaling network, and programmed cell death. Mitochondria produce ATP, regulate the cytoplasmic redox state and Ca2+ balance, catabolize fatty acids, synthesize heme, nucleotides, steroid hormones, amino acids, and help assemble iron-sulfur clusters in proteins. Mitochondria also have an essential role in heat production. Mutations of the mitochondrial genome cause several types of human disorder. The accumulation of mtDNA mutations correlates with aging and is suspected to have an important role in the development of cancer. Due to their vitally important role in all cell types, the function of mitochondria must also be critical for stem cells. Key advances have been made in our understanding of stem cell viability, proliferation, and differentiation capacity. But the functional activity of stem cells, in particular their energy status, was not yet been studied in detail. Almost nothing is known about the mitochondrial properties of human embryonic stem cells (hESCs) and their differentiated precursor progeny. One way to understand and evaluate the role of mitochondria in hESC function and developmental potential is to directly measure the activity of mitochondrial respiratory complexes. Here, we describe high resolution clear native gel electrophoresis and subsequent in gel activity visualization as a method for analyzing the five respiratory chain complexes of hESCs.

In this video, we will show you how the mitochondrial respiratory chain complexes of human embryonic stem cells can be analyzed using in gel activity assays.

Mitochondria are cytoplasmic organelles that have a primary role in cellular metabolism and homeostasis, regulation of the cell signaling network, and ...

In vitro Labeling of Human Embryonic Stem Cells for Magnetic Resonance Imaging

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of the predominant imaging modalities to assess the restoration of the injured myocardium. Furthermore, ex-vivo labeling agents, such as iron-oxide nanoparticles, have been employed to track and localize the transplanted stem cells. However, this method does not monitor a fundamental cellular biology property regarding the viability of transplanted cells. It has been known that manganese chloride (MnCl2) enters the cells via voltage-gated calcium (Ca2+) channels when the cells are biologically active, and accumulates intracellularly to generate T1 shortening effect. Therefore, we suggest that manganese-guided MRI can be useful to monitor cell viability after the transplantation of hESC into the myocardium.
In this video, we will show how to label hESC with MnCl2 and how those cells can be clearly seen by using MRI in vitro. At the same time, biological activity of Ca2+-channels will be modulated utilizing both Ca2+-channel agonist and antagonist to evaluate concomitant signal changes.

In this video, we are showing how to label human embryonic stem cells (hESC) with manganese chloride (MnCl2) which can enter cells via voltage-gated calcium channels when the cells are biologically active. Additionally, we show the use of MnCl2 as cellular MRI contrast agent to determine the in vitro viability of hESC.

Human embryonic stem cells (hESC) have demonstrated the ability to restore the injured myocardium. Magnetic resonance imaging (MRI) has emerged as one of ...

Culture and Maintenance of Human Embryonic Stem Cells  

Human embryonic stem (hES) cells must be monitored and cared for in order to maintain healthy, undifferentiated cultures. At minimum, the cultures must be  fed  every day by performing a complete medium change to replenish lost nutrients and to keep the cultures free of unwanted differentiation factors. Although a small amount of differentiation is normal and expected in stem cell cultures, the culture should be routinely cleaned up by manually removing, or "picking" differentiated areas. Identifying and removing excess differentiation from hES cell cultures are essential techniques in the maintenance of a healthy population of cells.

Culture and Maintenance of Human Embryonic Stem Cells

This protocol demonstrates how to maintain healthy, undifferentiated human embryonic stem (ES) cells.

Human embryonic stem (hES) cells must be monitored and cared for in order to maintain healthy, undifferentiated cultures. At minimum, the cultures must be ...

Freezing and Thawing Human Embryonic Stem Cells

Since James Thomson et al developed a technique in 1998 to isolate and grow hES in culture, freezing cells for later use and thawing and expanding cells from a frozen stock have become important procedures performed in routine hES cell culture. Since hES cells are very sensitive to the stresses of freezing and thawing, special care must taken. Here we demonstrate the proper technique for rapidly thawing hES cells from liquid nitrogen stocks, plating them on mouse embryonic feeder cells, and slowly freezing them for long-term storage.

Since James Thomson et al developed a technique in 1998 to isolate and grow hES in culture, freezing cells for later use and thawing and expanding cells from a frozen stock have become important procedures performed in routine hES cell culture. Since hES cells are very sensitive to the stresses of freezing and thawing, special care must taken. Here we demonstrate the proper technique for rapidly thawing hES cells from liquid nitrogen stocks, plating them on mouse embryonic feeder cells, and slowly freezing them for long-term storage.

Since James Thomson et al developed a technique in 1998 to isolate and grow hES in culture, freezing cells for later use and thawing and expanding cells ...

Video Bioinformatics Analysis of Human Embryonic Stem Cell Colony Growth

Because video data are complex and are comprised of many images, mining information from video material is difficult to do without the aid of computer software.  Video bioinformatics is a powerful quantitative approach for extracting spatio-temporal data from video images using computer software to perform dating mining and analysis. In this article, we introduce a video bioinformatics method for quantifying the growth of human embryonic stem cells (hESC) by analyzing time-lapse videos collected in a Nikon BioStation CT incubator equipped with a camera for video imaging. In our experiments, hESC colonies that were attached to Matrigel were filmed for 48 hours in the BioStation CT.  To determine the rate of growth of these colonies, recipes were developed using CL-Quant software which enables users to extract various types of data from video images.  To accurately evaluate colony growth, three recipes were created. The first segmented the image into the colony and background, the second enhanced the image to define colonies throughout the video sequence accurately, and the third measured the number of pixels in the colony over time.  The three recipes were run in sequence on video data collected in a BioStation CT to analyze the rate of growth of individual hESC colonies over 48 hours. To verify the truthfulness of the CL-Quant recipes, the same data were analyzed manually using Adobe Photoshop software. When the data obtained using the CL-Quant recipes and Photoshop were compared, results were virtually identical, indicating the CL-Quant recipes were truthful. The method described here could be applied to any video data to measure growth rates of hESC or other cells that grow in colonies. In addition, other video bioinformatics recipes can be developed in the future for other cell processes such as migration, apoptosis, and cell adhesion.  

Video bioinformatics is the automated processing, analysis, understanding, and data mining of biological spatio-temporal data extracted from microscopic videos. The purpose of this article is to demonstrate a method for measuring human embryonic stem cell colony growth using a video bioinformatics method.

Because video data are complex and are comprised of many images, mining information from video material is difficult to do without the aid of computer ...

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 ...

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 ...

Reprogramming Human Somatic Cells into Induced Pluripotent Stem Cells (iPSCs) Using Retroviral Vector with GFP

Human embryonic stem cells (hESCs) are pluripotent and an invaluable cellular sources for in vitro disease modeling and regenerative medicine1. It has been previously shown that human somatic cells can be reprogrammed to pluripotency by ectopic expression of four transcription factors (Oct4, Sox2, Klf4 and Myc) and become induced pluripotent stem cells (iPSCs)2-4 . Like hESCs, human iPSCs are pluripotent and a potential source for autologous cells. Here we describe the protocol to reprogram human fibroblast cells with the four reprogramming factors cloned into GFP-containing retroviral backbone4. Using the following protocol, we generate human iPSCs in 3-4 weeks under human ESC culture condition. Human iPSC colonies closely resemble hESCs in morphology and display the loss of GFP fluorescence as a result of retroviral transgene silencing. iPSC colonies isolated mechanically under a fluorescence microscope behave in a similar fashion as hESCs. In these cells, we detect the expression of multiple pluripotency genes and surface markers.

Reprogramming Human Somatic Cells into Induced Pluripotent Stem Cells iPSCs Using Retroviral Vector with GFP

A method to generate human induced pluripotent stem cells (iPSCs) via retrovirus-mediated ectopic expression of OCT4, SOX2, KLF4 and MYC is described. A practical way to identify human iPSC colonies based on GFP expression is also discussed.

Human embryonic stem cells (hESCs) are pluripotent and an invaluable cellular sources for in vitro disease modeling and regenerative medicine1. It has ...

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the messagefor review see 1. However, it's now widely accepted that synonymous codon usage is the primary cause of non-uniform translational elongation rates1. Synonymous codons are not used with identical frequency. A bias exists in the use of synonymous codons with some codons used more frequently than others2. Codon bias is organism as well as tissue specific2,3. Moreover, frequency of codon usage is directly proportional to the concentrations of cognate tRNAs4. Thus, a frequently used codon will have higher multitude of corresponding tRNAs, which further implies that a frequent codon will be translated faster than an infrequent one. Thus, regions on mRNA enriched in rare codons (potential pause sites) will as a rule slow down ribosome movement on the message and cause accumulation of nascent peptides of the respective sizes5-8. These pause sites can have functional impact on the protein expression, mRNA stability and protein foldingfor review see 9. Indeed, it was shown that alleviation of such pause sites can alter ribosome movement on mRNA and subsequently may affect the efficiency of co-translational (in vivo) protein folding1,7,10,11. To understand the process of protein folding in vivo, in the cell, that is ultimately coupled to the process of protein synthesis it is essential to gain comprehensive insights into the impact of codon usage/tRNA content on the movement of ribosomes along mRNA during translational elongation.
Here we describe a simple technique that can be used to locate major translation pause sites for a given mRNA translated in various cell-free systems6-8. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA. The rationale is that at low-frequency codons, the increase in the residence time of the ribosomes results in increased amounts of nascent peptides of the corresponding sizes. In vitro transcribed mRNA is used for in vitro translational reactions in the presence of radioactively labeled amino acids to allow the detection of the nascent chains. In order to isolate ribosome bound nascent polypeptide complexes the translation reaction is layered on top of 30% glycerol solution followed by centrifugation. Nascent polypeptides in polysomal pellet are further treated with ribonuclease A and resolved by SDS PAGE. This technique can be potentially used for any protein and allows analysis of ribosome movement along mRNA and the detection of the major pause sites. Additionally, this protocol can be adapted to study factors and conditions that can alter ribosome movement and thus potentially can also alter the function/conformation of the protein.

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

A technique to identify translational pause sites on mRNA is described. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA, followed by the size analysis of the nascent chains using a denaturing gel electrophoresis.

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the ...