We thank the NIAMS Light Imaging Section for providing the microscopes and technical help. The MF20 and Pax7 antibodies were obtained from the Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by the Department of Biological Sciences, The University of Iowa, Iowa City. This work was supported by the Intramural Research Program of NIAMS of the National Institutes of Health.

In this protocol, the anterior hind limb muscles of adult mice (2-6 months), tibialis anterior (TA) and extensor digitorum longus (EDL), were employed as an example to perform the immunofluorescence staining on their SCs. All the steps handling mice and muscle tissue dissections have been approved by the Animal Care and Use Committee (ACUC) of NIAMS/NIH.
1. Dissect the TA/EDL Muscle from the Mouse Hind Limb
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	<li>Euthanize the mouse in a CO2 filled euthanasia chamber under the...

<ol>
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C., Chevalier, F. P., Rudnicki, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Satellite+Cells+in+Muscular+Dystrophy+-+Lost+in+Polarity.">Satellite Cells in Muscular Dystrophy - Lost in Polarity.</a> Trends Mol Med. 22 (6), 479-496 (2016).</li><li>Mauro, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Satellite+cell+of+skeletal+muscle+fibers.">Satellite cell of skeletal muscle fibers.</a> J Biophys Biochem Cytol. 9, 493-495 (1961).</li><li>Kuang, S., Rudnicki, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+emerging+biology+of+satellite+cells+and+their+therapeutic+potential.">The emerging biology of satellite cells and their therapeutic potential.</a> Trends Mol Med. 14 (2), 82-91 (2008).</li><li>Wang, Y. X., Rudnicki, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Satellite+cells,+the+engines+of+muscle+repair.">Satellite cells, the engines of muscle repair.</a> Nat Rev Mol Cell Biol. 13 (2), 127-133 (2011).</li><li>Rinaldi, F., Perlingeiro, R. 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The above protocol was based on a method of Pax7/MF20 staining on zebrafish skeletal muscle12. The solutions used and blocking steps are identical or similar. The antibodies used are identical. The adjusted steps were based on the features of mouse muscle tissue and SCs. First, Laminin antibody was added in the mix to help visualize and confirm the position of SCs. It was particularly helpful to count the number of SCs under the microscope when using the dual filter cube of 488/555; this greatly e...

Skeletal muscle is composed of multinucleated muscle cells, called myotubes, organized in myofibers, which generate force and movements through contraction. Most skeletal muscles, except for some craniofacial muscles, are derived from a temporary embryonic structure called a somite1. Myogenic precursor cells delaminate from the epithelial somite to become myoblasts. Myoblasts further differentiate into myocytes that fuse to become myotubes to form multi-nucleated myofibers. The above process is called myogenesis and is characterized by temporally-regulated control of gene expression. Myogenic precursors express Pax3 and Pax7, whereas myoblasts express MyoD and/or Myf5 and myocytes express myogenin and myosins2,3. Muscle growth is a process in which myofibers become larger by incorporating more myonuclei into existing fibers (hyperplasia) and by an increase in muscle fiber size (hypertrophy)4. During muscle growth, there is a sustainable source of myogenic cells that have stem cell properties in that they can differentiate and self-renew. These cells are termed satellite cells based on their physical location between the sarcolemma (cell membrane of the myofiber) and the basal lamina5. SCs vigorously contribute to muscle growth in the juvenile stage (the first 2-3 weeks of postnatal mice), but become quiescent in resting adult muscle6. Remarkably, they can be re-activated in response to muscle injures and differentiate into new muscle cells to repair the damaged muscle7.
The stem cell properties make the study of SCs relevant for both basic muscle biology and therapies of muscle diseases8. As a result, it has been an area of intense investigation in the past decades. A tremendous progress has been made in dissecting the genetics and epigenetics of SCs9,10. Techniques involved in isolating and identifying SCs in situ were developed and optimized along the way11. Immunofluorescent staining allows the identification of SCs through the use of specific antibodies, including that for Pax7. However, the scarcity and small size of the SCs combined with a strong auto-fluorescence of adult skeletal muscle tissue render the visualization challenging. Here, we describe an immunofluorescent staining protocol optimized for mouse muscle tissue for Pax7 and based on an existing method for zebrafish muscle12. In addition, a Laminin antibody labeled with a distinct fluorophore is employed to identify the basal lamina under which the SCs are located. This protocol consistently allows the visualization of Pax7-positive SCs and myogenic precursors under all tested physiological conditions and developmental stages.

<table>
	<tbody>
		<tr>
			<td>methylbutane</td>
			<td>Sigma-Aldrich</td>
			<td>M32631</td>
			<td></td>
		</tr>
		<tr>
			<td>Optimal Cutting Temperature (O.C.T.) compound</td>
			<td>Electron Microscopy Sciences</td>
			<td>62550-01</td>
			<td></td>
		</tr>
		<tr>
			<td>10x PBS</td>
			<td>Gibco, Themo Fisher</td>
			<td>70011-044</td>
			<td></td>
		</tr>
		<tr>
			<td>16% PFA</td>
			<td>TED PELLA</td>
			<td>50-00-0</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton-100</td>
			<td>Sigma-Aldrich</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr>
			<td>Normal Goat Serum</td>
			<td>Thermo Fisher</td>
			<td>0 1-6201</td>
			<td></td>
		</tr>
		<tr>
			<td>AffiniPure Fab Fragment Goat Anti-Mouse IgG (H+L)</td>
			<td>Jackson ImmunoResearch Laboratories Inc.</td>
			<td>115-007-003</td>
			<td></td>
		</tr>
		<tr>
			<td>20x Citrate Buffer</td>
			<td>Thermo Fisher</td>
			<td>00 500</td>
			<td></td>
		</tr>
		<tr>
			<td>Pax7 mono-clonal mouse antibody (IgG1) (supernatant)</td>
			<td>Developmental Study Hybridoma Bank</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminin polyclonal rabbit antibody</td>
			<td>Sigma-Aldrich</td>
			<td>L9393</td>
			<td></td>
		</tr>
		<tr>
			<td>MF20 mono-clonal mouse antibody (IgG2b) (supernatant)</td>
			<td>Developmental Study Hybridoma Bank</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG1 cross-absorbed secondary antibody, Alexa Fluor 488</td>
			<td>Thermo Fisher</td>
			<td>A-21121</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG2b cross-absorbed secondary antibody, Alexa Fluor 647</td>
			<td>Thermo Fisher</td>
			<td>A-21242</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG (H+L) Highly Cross-Adsorbed Secondary Antibody, Alexa Fluor Plus 555</td>
			<td>Thermo Fisher</td>
			<td>A32732</td>
			<td></td>
		</tr>
		<tr>
			<td>Leica CM1860 cryostat</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Leica DM6000 wide-field fluorescent microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Leica DMR wide-field fluorescent microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Zeiss LSM510 confocal microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Zeiss LSM780 confocal microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cuisinart electronic pressure cooker</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

identification of skeletal muscle satellite cells by immunofluorescence with pax7 and laminin antibodies

Immunofluorescence is an effective method that helps to identify different cell types on tissue sections. In order to study the desired cell population, antibodies for specific cell markers are applied on tissue sections. In adult skeletal muscle, satellite cells (SCs) are stem cells that contribute to muscle repair and regeneration. Therefore, it is important to visualize and trace the satellite cell population under different physiological conditions. In resting skeletal muscle, SCs reside between the basal lamina and myofiber plasma membrane. A commonly used marker for identifying SCs on the myofibers or in cell culture is the paired box protein Pax7. In this article, an optimized Pax7 immunofluorescence protocol on skeletal muscle sections is presented that minimizes non-specific staining and background. Another antibody that recognizes a protein (laminin) of the basal lamina was also added to help identify SCs. Similar protocols can also be used to perform double or triple labeling with Pax7 and antibodies for additional proteins of interest.

Following the above steps, SCs can be successfully visualized in adult resting muscle sections under a fluorescent microscope (Figure 1). Although the adult muscle tissue has strong auto-fluorescence in certain type of fibers, the bright Alexa series dyes can overcome the background noise and the signal stands out (Figure 1A, B; arrow heads). The two-photon confocal microscopy captures a relatively cleaner image ...

Watch this Scientific Journal Video about Identification of Skeletal Muscle Satellite Cells by Immunofluorescence with Pax7 and Laminin Antibodies at JoVE.com

Identification of Skeletal Muscle Satellite Cells by Immunofluorescence with Pax7 and Laminin Antibodies

The precise identification of satellite cells is essential for studying their functions under various physiological and pathological conditions. This article presents a protocol to identify satellite cells on adult skeletal muscle sections by immunofluorescence-based staining.

Immunofluorescence is an effective method that helps to identify different cell types on tissue sections. In order to study the desired cell population, ...

The overall goal of this protocol is to identify adult skeletal muscle satellite cells via immunofluorescence. This method can answer key questions related to the number and distribution of muscle stem cells in both physiological as well as pathological conditions. The main advantage of the technique is that one can identify muscle stem cells in their physiological environment with only limited manipulation.Demonstrating the procedure will be Faiza Naz, a postdoc from my laboratory. To begin, prepare a liquid nitrogen bath by pouring liquid nitrogen into a Dewar flask. Next, pour 10 milliliters of methylbutane into a 20-milliliter plastic beaker and transfer the beaker to the liquid nitrogen bath.Lay the dissected tibialis anterior muscle onto the flat surface of a small plastic syringe plunger. Next, cover the dissected muscle with a few drops of Optimal Cutting Temperature compound or O.C.T.Remove the beaker of methylbutane from the liquid nitrogen bath, then thaw the surface using the handles of a pair of scissors. Quickly dip the O.C.T.covered tissue into the melted methylbutane to snapfreeze it.Next, use forceps to detach the embedded tissue from the plunger and transfer it to a 1.5-milliliter microcentrifuge tube. Then, store the microcentrifuge tube in the liquid nitrogen. To start cryostat sectioning, add a drop of O.C.T.compound onto the center of the specimen holder of a cryostat and allow it to partially solidify.Then, stick the embedded tissue into the O.C.T.compound with the ankle side down and knee side up. Next, mount the specimen holder onto the cryostat and cut the tissue in 10-micrometer intervals. Collect four to eight cryosections on each frost-coated slide.Dry the sections at room temperature for three hours, then collect the slides in a slide box and store them at minus 80 degrees Celsius. Next, remove a slide from the slide box and warm it to room temperature. Then, use a liquid blocker pen to mark an area around the cryosections to prevent liquids from flowing off the side.In a fume hood, add 300 to 500 microliters of 4%paraformaldehyde to the marked area. Incubate the slide at room temperature for 10 minutes to fix the sections. Next, rinse the paraformaldehyde from the slide with PBS in a slide container.To begin antigen retrieval, fill a slide container with 200 milliliters of citrate buffer and transfer the slide to the container. Then, transfer the slide container to a pressure cooker at high pressure for 10 minutes. The antigen retrieval step is optional if the sections are dried at room temperature for 30 minutes and proceed immediately.Then the antigen retrieval step is not necessary. But if the sections are dried at room temperature for more than three hours then stored at minus 80 degrees Celsius, the antigen retrieval step is required. Next, cool the slide container under running water for 10 minutes.Then transfer the slide to a new container with 200 milliliters of PBST and rinse with PBST. Add water-soaked lab wipes to the tray, then remark the rinsed slide with a PAP pen and place it in the tray. Add 200 microliters of blocking solution to the slide.Then cover the tray and incubate at room temperature for 30 minutes. The blocking step is very important because the Pax7 antibody being used is a mouse mono-clonal antibody. The mouse-on-mouse blocking step reduces the unspecific bindings.Then, rinse the slide with PBST in the slide container and return it to the tray. Add 200 microliters of Primary Antibody mix to the slide and incubate at room temperature for one hour. Next, rinse the slide with PBST, then add 200 microliters of Secondary Antibody mix and incubate in the dark at room temperature for one hour.After the incubation period, rinse the slide with PBST. Dilute DAPI in a slide container and incubate the slide in the container for three minutes. Then, rinse the DAPI with PBST for five minutes.Finally, mount the slide with mounting media and apply a coverslip. In this study, satellite cells are successfully visualized in adult resting muscle sections under a fluorescent microscope. The background noise usually seen with adult muscle tissue and certain types of fibers is reduced by using mouse-on-mouse blocking.The specific immunostain signals are enhanced by using secondary antibodies conjugated with bright Alexa dyes. A two-photon confocal microscope captures a sharper image compared to the wide-field fluorescent microscope. The same protocol can also be applied to muscle tissue from juvenile mice, mouse embryos, and injured adult muscle tissues.Both juvenile and embryonic muscle tissues depict more activated satellite cells or Pax7 myogenic precursors with relatively larger nuclei. Thus it becomes easier to visualize the satellite cells of younger mice than of adult mice. In the injured muscle tissue, more activated Pax7-positive cells are visible.Once mastered, this technique can be done in five hours if it is performed properly. While attempting this procedure, it is important to remember that noise coming from autofluorescence and unspecific mouse-on-mouse immuno-binding cannot be totally eliminated, but with this protocol the noise can be largely reduced. After watching this video, you should have a good understanding of how to identify satellite cells in muscle cryosections.

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20.3K visualizações.  National Institutes of Health. The overall goal of this protocol is to identify adult skeletal muscle satellite cells via immunofluorescence. This method can answer key questions related to the number and distribution of muscle stem cells in both physiological as well as pathological conditions. The main advantage of the technique is that one can identify muscle stem cells in their physiological environment with only limited manipulation.Demonstrating the procedure will be Faiza Naz, a postdoc from my laboratory. To...