Name: measurement of mitochondrial mass and membrane potential in hematopoietic stem cells and t-cells by flow cytometry
Uploaded: 2019-12-26T14:00:00
Description: Watch this Scientific Journal Video about Measurement of Mitochondrial Mass and Membrane Potential in Hematopoietic Stem Cells and T-cells by Flow Cytometry at JoVE.com

We thank the UNIL Flow Cytometry Core Facility for their support especially Dr. Romain Bedel. This work was supported by the Kristian Gerhard Jebsen foundation grant to N.V and O.N.

All experiments described in the manuscript follow the guidelines of our institution and were carried out in accordance with Swiss law for animal experimentation (Authorization: VD3194) and for research involving human samples (Protocol: 235/14; CER-VD 2017-00490)
1. Hematopoietic Stem Cell Extraction
<ol>
	<li>Purchase wild type C57BL6/J mice and keep them in the animal house for at least a week to reduce transport-associated stress.</li>
	<li>On the day of the experiment, euthanize the mou...

<ol>
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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=T+cell+exhaustion.">T cell exhaustion.</a> Nature Immunology. 12 (6), 492-499 (2011).</li><li>Ho, P. C., 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=Phosphoenolpyruvate+Is+a+Metabolic+Checkpoint+of+Anti-tumor+T+Cell+Responses.">Phosphoenolpyruvate Is a Metabolic Checkpoint of Anti-tumor T Cell Responses.</a> Cell. 162 (6), 1217-1228 (2015).</li><li>Chang, C. 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=Metabolic+Competition+in+the+Tumor+Microenvironment+Is+a+Driver+of+Cancer+Progression.">Metabolic Competition in the Tumor Microenvironment Is a Driver of Cancer Progression.</a> Cell. 162 (6), 1229-1241 (2015).</li><li>van der Waart, A. B., 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=Inhibition+of+Akt+signaling+promotes+the+generation+of+superior+tumor-reactive+T+cells+for+adoptive+immunotherapy.">Inhibition of Akt signaling promotes the generation of superior tumor-reactive T cells for adoptive immunotherapy.</a> Blood. 124 (23), 3490-3500 (2014).</li><li>Crompton, J. G., 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=Akt+inhibition+enhances+expansion+of+potent+tumor-specific+lymphocytes+with+memory+cell+characteristics.">Akt inhibition enhances expansion of potent tumor-specific lymphocytes with memory cell characteristics.</a> Cancer Research. 75 (2), 296-305 (2015).</li><li>de Almeida, M. J., Luchsinger, L. L., Corrigan, D. J., Williams, L. J., Snoeck, H. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dye-Independent+Methods+Reveal+Elevated+Mitochondrial+Mass+in+Hematopoietic+Stem+Cells.">Dye-Independent Methods Reveal Elevated Mitochondrial Mass in Hematopoietic Stem Cells.</a> Cell Stem Cell. 21 (6), 725-729 (2017).</li><li>Abe, T., 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=Establishment+of+Conditional+Reporter+Mouse+Lines+at+ROSA26+Locus+For+Live+Cell+Imaging.">Establishment of Conditional Reporter Mouse Lines at ROSA26 Locus For Live Cell Imaging.</a> Genesis. 49 (7), 579-590 (2011).</li><li>Sukumar, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+Membrane+Potential+Identifies+Cells+with+Enhanced+Stemness+for+Cellular+Therapy.">Mitochondrial Membrane Potential Identifies Cells with Enhanced Stemness for Cellular Therapy.</a> Cell Metabolism. 23 (1), 63-76 (2016).</li><li>Sukumar, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibiting+glycolytic+metabolism+enhances+CD8++T+cell+memory+and+antitumor+function.">Inhibiting glycolytic metabolism enhances CD8+ T cell memory and antitumor function.</a> Journal of Clinical Investigation. 123 (10), 4479-4488 (2013).</li></ol>

A tight regulation of HSC function is important to maintain stable hematopoiesis during an organism&#39;s lifetime. Like various other cell types in the body, a key component that contributes to the regulation of HSC function is cellular metabolism. Previous studies from our lab9 and others2,3 have implicated the importance of mitochondria in maintaining a distinct metabolic state in HSCs. Due to the extremely low number of HSCs isolated f...

Hematopoietic stem cells (HSCs) are a small population of cells residing in the bone marrow ensuring blood production and homeostasis throughout an organism&#39;s lifetime. HSCs mediate this process by giving rise to progenitors that in turn produce terminally differentiated mature blood cell lineages via several rounds of cell division and well-orchestrated differentiation steps1. Importantly, HSCs produce their energy via anaerobic glycolysis. In contrast, more committed and active hematopoietic progenitors switch their metabolism toward mitochondrial metabolism2,3,4. This distinct metabolic state is believed to protect the HSCs from cellular damage inflicted by reactive oxygen species (ROS) produced by active mitochondria, thereby maintaining their long-term in vivo function5,6,7,8. Direct measurement of the HSC metabolic state is challenging and often low throughput due to their limited numbers. Here, we describe a flow cytometry-based assay for robust measurement of mitochondrial membrane potential (&#916;&#936;m) using tetramethylrhodamine methyl ester (TMRM) fluorescence, and mitochondrial mass using a green fluorescent mitochondrial stain (Mitotracker Green) in HSCs. We have previously demonstrated that low &#916;&#936;m is a bona-fide functional marker of highly purified HSCs9 and metabolic modulators capable of lowering &#916;&#936;m enhance HSCs function9,10. Here we propose use of our method on HSCs mitochondrial profiling as strategy to identify novel molecules capable of improving the HSCs&#39; long-term blood reconstitution potential.
As an example, we demonstrate that this assay reliably measures the lowering of HSC &#916;&#936;m upon exposure to vitamin B3 analog nicotinamide riboside (NR). Accordingly, in our recently published study we demonstrate that NR strongly ameliorates blood recovery posttransplant in both mouse and humanized mouse systems by directly improving hematopoietic stem and progenitor functions10. The capacity of such metabolic modulators is of great clinical value considering that a 25% death rate is linked to delay in blood and immune recovery in posttransplanted patients11,12.
Moreover, we provide evidence that this methodology can be applied for the characterization of the metabolic profile and function of human T cells. In recent years, the development of adoptive cell therapy (ACT) using autologous tumor infiltrating lymphocytes (TILs) has become the most effective approach for certain types of advanced cancer with extremely unfavorable prognosis (e.g., metastatic melanoma, where &#62;50% of patients respond to treatment and up to 24% of patients have complete regression)13. However, TILs harboring sufficient antitumor activity are difficult to generate14. The extensive proliferation and stimulation that TILs undergo during ex vivo expansion cause T cell exhaustion and senescence that dramatically impair T cell antitumor response15. Importantly, the TILs&#39; antitumoral capacity is tightly linked to their metabolism16,17 and approaches aimed to modulate metabolism through the inhibition of the PI3K/Akt pathway have produced encouraging results18,19. For this reason, we compare the &#916;&#936;m of T cells derived from peripheral blood mononuclear cells (PBMCs) and patient-derived TILs, and show that less differentiated PBMC-derived T cells have lower &#916;&#936;m and mitochondrial mass as compared to terminally differentiated TILs.
We envision that this assay can be used to identify novel metabolic modulators that improve HSC and T cell function via the modulation of &#916;&#936;m.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>5 mL FACS tubes</td>
			<td>Falcon</td>
			<td>352235</td>
			<td>Sample preparation</td>
		</tr>
		<tr>
			<td>96-U bottom plate</td>
			<td>Corning</td>
			<td>3799</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>AutoMACS pro separator</td>
			<td>Miltenyi Biotec</td>
			<td></td>
			<td>Automatic Cell separation</td>
		</tr>
		<tr>
			<td>BD FACS AriaIII</td>
			<td>Becton and Dickinson</td>
			<td></td>
			<td>Cell sorting</td>
		</tr>
		<tr>
			<td>BD IMag mouse hematopoietic progenitor cell enrichment kit</td>
			<td>BD</td>
			<td>558451</td>
			<td>Lineage depletion</td>
		</tr>
		<tr>
			<td>BD LSRII</td>
			<td>Becton and Dickinson</td>
			<td></td>
			<td>FACS acquisition machine</td>
		</tr>
		<tr>
			<td>BD-DIVA</td>
			<td>Becton and Dickinson</td>
			<td></td>
			<td>Acquisition software</td>
		</tr>
		<tr>
			<td>CD150 PE</td>
			<td>Biolegend</td>
			<td>115904</td>
			<td>Antibody staining mix</td>
		</tr>
		<tr>
			<td>CD150 PE-Cy5</td>
			<td>Biolegend</td>
			<td>115912</td>
			<td>Antibody staining mix</td>
		</tr>
		<tr>
			<td>CD48 PB</td>
			<td>Biolegend</td>
			<td>103418</td>
			<td>Antibody staining mix</td>
		</tr>
		<tr>
			<td>Centrifuge- 5810R</td>
			<td>Eppendorf</td>
			<td></td>
			<td>Centrifugation</td>
		</tr>
		<tr>
			<td>Ckit PeCy7</td>
			<td>Biolegend</td>
			<td>105814</td>
			<td>Antibody staining mix</td>
		</tr>
		<tr>
			<td>Flow jo</td>
			<td>FlowJo LLC</td>
			<td></td>
			<td>FACS Analysis software</td>
		</tr>
		<tr>
			<td>GraphPad-Prism</td>
			<td>GraphPad</td>
			<td></td>
			<td>Plotting data into graphs</td>
		</tr>
		<tr>
			<td>Mitotracker Green</td>
			<td>Invitrogen</td>
			<td>M7514</td>
			<td>Green-fluorescent mitocondrial stain to measure mitochondrial mass; working concentration = 100 nM; stock concentration = 1 mM</td>
		</tr>
		<tr>
			<td>Nicotinamide Riboside (NR)</td>
			<td>Custom synthesized in house</td>
			<td></td>
			<td>Metabolic modulator; working concentration = 500 &#181;M; stock concentration = 50 mM</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>CHUV</td>
			<td>1000324</td>
			<td>Buffer preparation; working concentration = 1x; stock concentration = 1x</td>
		</tr>
		<tr>
			<td>Pen-Strep (P/S)</td>
			<td>Life technologies</td>
			<td>15140122</td>
			<td>Ex vivo culture; working concentration = 1x; stock concentration = 1x</td>
		</tr>
		<tr>
			<td>RBC Lysis buffer</td>
			<td>Biolegend</td>
			<td>420301</td>
			<td>Lysing Red blood cells; working concentration = 1x; stock concentration = 10x</td>
		</tr>
		<tr>
			<td>Recombinant Mouse Flt-3 Ligand (FLT3)</td>
			<td>RnD</td>
			<td>427-FL-005/CF</td>
			<td>Ex vivo culture; working concentration = 2 ng/mL; stock concentration = 10 &#181;g/mL</td>
		</tr>
		<tr>
			<td>Recombinant mouse stem cell factor (SCF)</td>
			<td>RnD</td>
			<td>455-MC-010/CF</td>
			<td>Ex vivo culture; working concentration = 100 ng/mL; stock concentration = 50 &#181;g/mL</td>
		</tr>
		<tr>
			<td>Sca1 APC</td>
			<td>Thermo Fisher Scientific</td>
			<td>17-5981-82</td>
			<td>Antibody staining mix</td>
		</tr>
		<tr>
			<td>StemlineII Hematopoietic Stem Cell Expansion Medium</td>
			<td>SIGMA</td>
			<td>S0192</td>
			<td>Ex vivo culture</td>
		</tr>
		<tr>
			<td>Streptavidin Pac orange</td>
			<td>Life Technologies</td>
			<td>S32365</td>
			<td>Antibody staining mix</td>
		</tr>
		<tr>
			<td>Streptavidin Tx red</td>
			<td>Life Technologies</td>
			<td>S872</td>
			<td>Antibody staining mix</td>
		</tr>
		<tr>
			<td>TMRM</td>
			<td>Invitrogen</td>
			<td>T668</td>
			<td>Staining mitochondrial membrane potential; working concentration = 200 nM; stock concentration = 10 mM</td>
		</tr>
		<tr>
			<td>Ultra pure EDTA</td>
			<td>Invitrogen</td>
			<td>15575-038</td>
			<td>Buffer preparation; working concentration = 0.5 M; stock concentration = 1 mM</td>
		</tr>
	</tbody>
</table>

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.

In Figure 1 we show the gating strategy for the isolation of hematopoietic stem cells from the mouse bone marrow and the layout of the plate for their ex vivo culture. Figure 1A shows the identification of the lymphocyte fraction in the SSC-A/FSC-A plot. Doublets were removed in the singlet gate followed by identification of live cells by the absence of DAPI signal. The LKS population, defined by lineage- Sca1+cKit+, was id...

Watch this Scientific Journal Video about Measurement of Mitochondrial Mass and Membrane Potential in Hematopoietic Stem Cells and T-cells by Flow Cytometry at JoVE.com

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

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 ...

This protocol is a simple flow cytometry-based assay allowing measurement of mitochondrial membrane potential and mitochondrial mass in living cells. Standard metabolic assays fail when working with rare populations such as the hematopoietic stem cells. This method enables users mitochondrial membrane profiling when working with low number of cells and to determine novel metabolic modulators of cells such as the HSCs.Moreover, you can combine it with downstream functional assays such as bone marrow transplantation or colony-forming assays to determine the functionality of your cells post-culture. Our technique can be exploited for the identification of novel molecules capable to improve HSC function in the context of bone marrow transplantation and hematopoietic immune recovery after ablative therapies. As described in our protocol, our method can be used to evaluate metabolic fitness of immune T cells.It is very important that the cells have minimal exposure to light after staining. Moreover, the use of pump inhibitor verapamil has to be included in order to evaluate the contribution of pump efflux. However, users have to be aware that verapamil profoundly perturbs ionic equilibrium and cannot be used in order to evaluate the effect of a metabolic modulator on mitochondrial membrane potential.Visual demonstration of this method is extremely important because there are some critical steps that one needs to keep in mind when working with low number of cells, and these steps are very often missing in the regular papers that users read on PubMed. For FAC sorting, the LKS population, defined by lineage negative, Sca1 positive, cKit positive is identified. Hematopoietic stem cells from around five to 10%of the cells in the LKS population are identified by gating for CD150 positive, CD48 negative population, labeled as HSCs.After hematopoietic stem cell sorting, Centrifuge the tubes at 300 times g for five minutes at four degrees Celsius. Gently remove most of the supernatant without dislodging the pellet, and leave 50 to 80 microliters on top of the cell pellet. Resuspend the cell pellet in stem cell expansion medium to a final volume of 200 microliters.Prepare a sterile tissue culture treated 96 U-bottom well plate, and identify the wells where the cells will be cultured. Transfer 100 microliters of 2x basal medium previously prepared in these wells. In the NR marked well, add two microliters of a 100x nicotinamide riboside solution.Transfer 100 microliters of 2x basal medium into wells for staining control. Seed 100 microliters of prepared hematopoietic stem cells on top of the wells containing 2x basal medium. Seed 100 microliters of whole bone marrow cells on wells marked as staining controls.Add 200 microliters of autoclaved water in all surrounding wells to reduce evaporation from wells containing cells. Place the plate undisturbed in an incubator at 37 degrees Celsius in 5%carbon dioxide for 72 hours. Take out the plate to replenish nicotinamide riboside every 24 hours, and put it back into the incubator.At the end of the culture period, add two microliters of 100x TMRM solution and two microliters of 100x green fluorescent stain solution in each of the test wells. Add two microliters of 100x TMRM in the TMRM staining control well. Add two microliters of 100x green fluorescent stain in the MitoTracker staining control well.Cover the top of the plate with aluminum foil. and place the plate back in an incubator at 37 degrees Celsius in 5%carbon dioxide for 45 minutes. Remove the plate from the incubator, and centrifuge it at 300 times g for five minutes.Invert the plate to remove the supernatant, and add 200 microliters of standard FACS buffer to resuspend. Cover the plate with foil. Centrifuge the plate at 300 times g for five minutes.Repeat this washing step three times. Resuspend the cells in 200 microliters of FACS buffer, and transfer to FACS tubes. To run the samples on the flow cytometer, first load the single color controls into the machine, and record at least 5, 000 events in each one by one.In the software, press Acquire and then Record on the dashboard to acquire and record single color controls. Press Compensation Setup, and click Calculate Compensation to calculate the compensation. Once the compensation has been applied, acquire the hematopoietic stem cell sample, and record as many events as possible.Export the FACS files from the cytometer, and open the file on the analysis software. On FlowJo, use forward scatter and side scatter gating to identify the cell population. Identify singlets in the next gates, and then plot the DAPI negative fraction representing live cells.In the live cell gate, make a contour plot in the TMRM and green fluorescent stain channel to measure mitochondrial membrane potential and mass, respectively. Export the mean fluorescence intensity of these two channels in the live cell gate. Then, export the proportion of cells in the TMRM low gate in all samples.The nicotinamide riboside treatment showed a clear increase in the TMRM low population. It also significantly increased the proportion of cells in the TMRM low gate and showed a significant lowering of TMRM fluorescence intensity. Mitochondrial mass did not change upon nicotinamide riboside supplementation.Additionally, stem cell marker staining was combined with mitochondrial staining post-culture. With the gating strategy to identify hematopoietic stem cells, exposure to nicotinamide riboside showed a significant increase in the TMRM low population and a significant decrease in the TMRM fluorescence intensity in gated HSCs. The green fluorescent mitochondrial stain green signal remained unchanged in the two conditions.It is important to cover the staining plate with aluminum foil in order to minimize the exposure of light to stained samples. This method can be combined with downstream assays such as bone marrow transplantation and colony-forming assays to determine the functionality of your stem cells. So this technique allows a simple screening method for the identification of novel metabolic modulators of HSCs.

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Quantitative Measurement of GLUT4 Translocation to the Plasma Membrane by Flow Cytometry

Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces glucose uptake by insulin-sensitive tissues, most notably the brain, skeletal muscle, and adipocytes. Patients suffering from type-2 diabetes and/or obesity often develop insulin resistance and are unable to control their glucose homeostasis. New insights into the mechanisms of insulin resistance may provide new treatment strategies for type-2 diabetes.
The GLUT family of glucose transporters consists of thirteen members distributed on different tissues throughout the body1. Glucose transporter type 4 (GLUT4) is the major transporter that mediates glucose uptake by insulin sensitive tissues, such as the skeletal muscle. Upon binding of insulin to its receptor, vesicles containing GLUT4 translocate from the cytoplasm to the plasma membrane, inducing glucose uptake. Reduced GLUT4 translocation is one of the causes of insulin resistance in type-2 diabetes2,3.
The translocation of GLUT4 from the cytoplasm to the plasma membrane can be visualized by immunocytochemistry, using fluorophore-conjugated GLUT4-specific antibodies.
Here, we describe a technique to quantify total amounts of GLUT4 translocation to the plasma membrane of cells during a chosen duration, using flow cytometry. This protocol is rapid (less than 4 hours, including incubation with insulin) and allows the analysis of as few as 3,000 cells or as many as 1 million cells per condition in a single experiment. It relies on anti-GLUT4 antibodies directed to an external epitope of the transporter that bind to it as soon as it is exposed to the extracellular medium after translocation to the plasma membrane.

This protocol describes a rapid technique to quantify the translocation of GLUT4 from the cytoplasm to the plasma membrane of cells by flow cytometry.

Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces ...

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 ...

Phenotypic Analysis and Isolation of Murine Hematopoietic Stem Cells and Lineage-committed Progenitors

The bone marrow is the principal site where HSCs and more mature blood cells lineage progenitors reside and differentiate in an adult organism. HSCs constitute a minute cell population of pluripotent cells capable of generating all blood cell lineages for a life-time1. The molecular dissection of HSCs homeostasis in the bone marrow has important implications in hematopoiesis, oncology and regenerative medicine. We describe the labeling protocol with fluorescent antibodies and the electronic gating procedure in flow cytometry to score hematopoietic progenitor subsets and HSCs distribution in individual mice (Fig. 1). In addition, we describe a method to extensively enrich hematopoietic progenitors as well as long-term (LT) and short term (ST) reconstituting HSCs from pooled bone marrow cell suspensions by magnetic enrichment of cells expressing c-Kit. The resulting cell preparation can be used to sort selected subsets for in vitro and in vivo functional studies (Fig. 2).
Both trabecular osteoblasts2,3 and sinusoidal endothelium4 constitute functional niches supporting HSCs in the bone marrow. Several mechanisms in the osteoblastic niche, including a subset of N-cadherin+ osteoblasts3 and interaction of the receptor tyrosine kinase Tie2 expressed in HSCs with its ligand angiopoietin-15 concur in determining HSCs quiescence. "Hibernation" in the bone marrow is crucial to protect HSCs from replication and eventual exhaustion upon excessive cycling activity6. Exogenous stimuli acting on cells of the innate immune system such as Toll-like receptor ligands7 and interferon-&alpha;6 can also induce proliferation and differentiation of HSCs into lineage committed progenitors. Recently, a population of dormant mouse HSCs within the lin- c-Kit+ Sca-1+ CD150+ CD48- CD34- population has been described8. Sorting of cells based on CD34 expression from the hematopoietic progenitors-enriched cell suspension as described here allows the isolation of both quiescent self-renewing LT-HSCs and ST-HSCs9. A similar procedure based on depletion of lineage positive cells and sorting of LT-HSC with CD48 and Flk2 antibodies has been previously described10. In the present report we provide a protocol for the phenotypic characterization and ex vivo cell cycle analysis of hematopoietic progenitors, which can be useful for monitoring hematopoiesis in different physiological and pathological conditions. Moreover, we describe a FACS sorting procedure for HSCs, which can be used to define factors and mechanisms regulating their self-renewal, expansion and differentiation in cell biology and signal transduction assays as well as for transplantation.

A method to analyse the distribution of bone marrow hematopoietic progenitors in flow cytometry as well as to efficiently isolate highly purified hematopoietic stem cells (HSCs) is described. The isolation procedure is essentially based on magnetic enrichment of c-Kit+ cells and cell sorting to purify HSCs for cellular and molecular studies.

The bone marrow is the principal site where HSCs and more mature blood cells lineage progenitors reside and differentiate in an adult organism. HSCs ...

Optimized Staining and Proliferation Modeling Methods for Cell Division Monitoring using Cell Tracking Dyes

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of different cell types in vitro and in vivo.1-5 Although there are literally thousands of publications using such dyes, some of the most commonly encountered cell tracking applications include monitoring of:
<ol>
	<li>stem and progenitor cell quiescence, proliferation and/or differentiation6-8</li>
	<li>antigen-driven membrane transfer9 and/or precursor cell proliferation3,4,10-18 and</li>
	<li>immune regulatory and effector cell function1,18-21.</li>
</ol>
Commercially available cell tracking dyes vary widely in their chemistries and fluorescence properties but the great majority fall into one of two classes based on their mechanism of cell labeling. "Membrane dyes", typified by PKH26, are highly lipophilic dyes that partition stably but non-covalently into cell membranes1,2,11. "Protein dyes", typified by CFSE, are amino-reactive dyes that form stable covalent bonds with cell proteins4,16,18. Each class has its own advantages and limitations. The key to their successful use, particularly in multicolor studies where multiple dyes are used to track different cell types, is therefore to understand the critical issues enabling optimal use of each class2-4,16,18,24.
The protocols included here highlight three common causes of poor or variable results when using cell-tracking dyes. These are:
<ol>
	<li>Failure to achieve bright, uniform, reproducible labeling. This is a necessary starting point for any cell tracking study but requires attention to different variables when using membrane dyes than when using protein dyes or equilibrium binding reagents such as antibodies.</li>
	<li>Suboptimal fluorochrome combinations and/or failure to include critical compensation controls. Tracking dye fluorescence is typically 102 - 103 times brighter than antibody fluorescence. It is therefore essential to verify that the presence of tracking dye does not compromise the ability to detect other probes being used.</li>
	<li>Failure to obtain a good fit with peak modeling software. Such software allows quantitative comparison of proliferative responses across different populations or stimuli based on precursor frequency or other metrics. Obtaining a good fit, however, requires exclusion of dead/dying cells that can distort dye dilution profiles and matching of the assumptions underlying the model with characteristics of the observed dye dilution profile.</li>
</ol>
Examples given here illustrate how these variables can affect results when using membrane and/or protein dyes to monitor cell proliferation.

Successful use of cell tracking dyes to monitor immune cell function and proliferation involves several critical steps. We describe methods for: 1) obtaining bright, uniform, reproducible label-ing with membrane dyes; 2) selecting fluorochromes and data acquisition conditions; and 3) choosing a model to quantify cell proliferation based on dye dilution.

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Cytosolic Calcium Measurements in Renal Epithelial Cells by Flow Cytometry

A variety of cellular processes, both physiological and pathophysiological, require or are governed by calcium, including exocytosis, mitochondrial function, cell death, cell metabolism and cell migration to name but a few. Cytosolic calcium is normally maintained at low nanomolar concentrations; rather it is found in high micromolar to millimolar concentrations in the endoplasmic reticulum, mitochondrial matrix and the extracellular compartment. Upon stimulation, a transient increase in cytosolic calcium serves to signal downstream events. Detecting changes in cytosolic calcium is normally performed using a live cell imaging set up with calcium binding dyes that exhibit either an increase in fluorescence intensity or a shift in the emission wavelength upon calcium binding. However, a live cell imaging set up is not freely accessible to all researchers. Alternative detection methods have been optimized for immunological cells with flow cytometry and for non-immunological adherent cells with a fluorescence microplate reader. Here, we describe an optimized, simple method for detecting changes in epithelial cells with flow cytometry using a single wavelength calcium binding dye. Adherent renal proximal tubule epithelial cells, which are normally difficult to load with dyes, were loaded with a fluorescent cell permeable calcium binding dye in the presence of probenecid, brought into suspension and calcium signals were monitored before and after addition of thapsigargin, tunicamycin and ionomycin.

Calcium is involved in numerous physiological and pathophysiological signaling pathways. Live cell imaging requires specialized equipment and can be time consuming. A quick, simple method using a flow cytometer to determine relative changes in cytosolic calcium in adherent epithelial cells brought into suspension was optimized.

A variety of cellular processes, both physiological and pathophysiological, require or are governed by calcium, including exocytosis, mitochondrial ...

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.

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 ...

Simultaneous Measurement of Mitochondrial Calcium and Mitochondrial Membrane Potential in Live Cells by Fluorescent Microscopy

Apart from their essential role in generating ATP, mitochondria also act as local calcium (Ca2+) buffers to tightly regulate intracellular Ca2+ concentration. To do this, mitochondria utilize the electrochemical potential across their inner membrane (&#916;&#936;m) to sequester Ca2+. The influx of Ca2+ into the mitochondria stimulates three rate-limiting dehydrogenases of the citric acid cycle, increasing electron transfer through the oxidative phosphorylation (OXPHOS) complexes. This stimulation maintains &#916;&#936;m, which is temporarily dissipated as the positive calcium ions cross the mitochondrial inner membrane into the mitochondrial matrix.
We describe here a method for simultaneously measuring mitochondria Ca2+ uptake and &#916;&#936;m in live cells using confocal microscopy. By permeabilizing the cells, mitochondrial Ca2+ can be measured using the fluorescent Ca2+ indicator Fluo-4, AM, with measurement of &#916;&#936;m using the fluorescent dye tetramethylrhodamine, methyl ester, perchlorate (TMRM). The benefit of this system is that there is very little spectral overlap between the fluorescent dyes, allowing accurate measurement of mitochondrial Ca2+ and &#916;&#936;m simultaneously. Using the sequential addition of Ca2+ aliquots, mitochondrial Ca2+ uptake can be monitored, and the concentration at which Ca2+ induces mitochondrial membrane permeability transition and the loss of &#916;&#936;m determined.

Mitochondria can utilize the electrochemical potential across their inner membrane (&#916;&#936;m) to sequester calcium (Ca2+), allowing them to shape cytosolic Ca2+ signaling within the cell. We describe a method for simultaneously measuring mitochondria Ca2+ uptake and &#916;&#936;m in live cells using fluorescent dyes and confocal microscopy.

Apart from their essential role in generating ATP, mitochondria also act as local calcium (Ca2+) buffers to tightly regulate intracellular Ca2+ ...

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 ...