We are grateful to the Boettcher Foundation and the Amyotrophic Lateral Sclerosis Association (#17-II-344) for their support of this research.

All procedures involving mice were approved by the University of Colorado-Anschutz Medical Campus Institutional Animal Care and Use Committee (91813(05)1D).
1. Day 1: Primary (1&#176;) Immunostaining with Bovine Serum Albumin (BSA) Blocking
<ol>
	<li>Air-dry frozen sections of mouse hindlimb muscle (e.g., tibialis anterior, soleus) mounted on charged slides for ~ 30 min11. Draw a border around the sections using a hydrophobic barrier PAP pen.</li>
	<li>Place ~ 250 &#181;L of 5% BSA/phosphate buffered saline (BSA/PBS) on each slide to block non-specific antibody binding. Incubate slides at room temperature for 1 h.</li>
	<li>While blocking, prepare 1:50 dilutions of the 1&#176; antibody supernatant in 5% BSA/PBS (all are mouse monoclonal antibodies; see Table 16,12); prepare 250 &#181;L of solution per slide. Keep 1&#176; antibody stocks and dilutions on ice.</li>
</ol>
<img alt="Table 1" src="/files/ftp_upload/56024/56024table1.jpg" /> 
Table 1: Primary Antibodies used to Distinguish MyHCs.
<ol start="4">
	<li>Following aspiration of the 5% BSA/PBS blocking solution, add 250 &#181;L of 1&#176; antibody dilution to the appropriate slides. Add 250 &#181;L of 5% BSA/PBS to secondary (2&#176;) antibody-only negative control slides.</li>
	<li>Incubate at 4 &#176;C for 24 - 48 h in a humid environment. 
	NOTE: A Petri dish covered in aluminum foil with dampened filter paper may serve as a suitable incubation chamber.</li>
</ol>
2. Day 2: 2&#176; Immunostaining with Fluorescent Antibodies
<ol>
	<li>Aspirate 1&#176; antibody solution or control 5% BSA/PBS solution. Wash all slides three times, 10 min with 5% BSA.</li>
	<li>While washing, prepare 1:200 dilutions of the purified, fluorophore-conjugated 2&#176; antibodies in 5% BSA/PBS (see Table 2, all are goat anti-mouse). Prepare 250 &#181;L of solution per slide. Keep 2&#176; fluorophore-conjugated antibodies in the dark on ice.</li>
</ol>
<img alt="Table 2" src="/files/ftp_upload/56024/56024table2.jpg" /> 
Table 2: Fluorophore-conjugated Secondary Antibodies used to Visualize Primary Antibody Recognition of MyHCs.
<ol start="3">
	<li>Following aspiration of the third application of 5% BSA/PBS blocking solution, add 250 &#181;L of 2&#176; antibody dilution to all slides. Incubate for 90 min at room temperature in a dark, humid environment.</li>
	<li>Aspirate 2&#176; antibody solution. Wash all slides three times, 10 min with 5% BSA/PBS.</li>
	<li>Rinse with PBS. Dry for 10 min.</li>
	<li>Mount the coverglass with a non-permanent, low-viscosity aqueous mounting medium.</li>
	<li>When dry, seal the slide edges with nail polish. Dry and store in a dark slidebox.</li>
</ol>
3. Imaging Slides with Epifluorescence Microscopy
<ol>
	<li>Clean the slides with a small, 70% ethanol-soaked lab-wipe.</li>
	<li>Obtain digital images of immunostained muscle sections using an epifluorescence microscope equipped with a photographic apparatus (see the Table of Materials).
	<ol>
		<li>Select an area of approximately 1 mm2 (10X objective, 1.4 NA).</li>
		<li>View Alexa 488-conjugated 2&#176; antibody fluorescence via a 505 nm long-pass filter. View the fluorescence generated by excitation of Alexa 594-conjugated 2&#176; antibodies via a 595 nm long-pass filter. Digitize images with a PC computer equipped with a compatible imaging software. Include the scale bar from imaging software for later analysis.</li>
	</ol>
	</li>
</ol>
4. Analysis of Images with Fiji
Note: Before proceeding with analysis, Fiji (available freely from the National Institutes of Health, Bethesda, MD) must be installed via https://imagej.net/Fiji/Downloads. Also, the macro used in this process is provided in the Supplemental File. Place the macro file in an easily accessible directory.
<ol>
	<li>Load a brightfield image of a selected section in Fiji. Navigate to Plugins &#8594; Segmentation&#160;&#8594; Trainable Weka Segmentation.</li>
	<li>In order to stipulate the cellular areas of the section, draw a line on a fiber, and click &#34;Add to class 1&#34;. Then, draw a line on the space between fibers, and click &#34;Add to class 2&#34; to mark the extracellular domains. Repeat until there are 5-10 labels in each class.
	<ol>
		<li>Click Train Classifier. On the resulting red and green overlay, add more labels manually (see step 4.2) to incorrectly segmented pieces of the image, if necessary. Repeat until fibers (red) are appropriately separated from the space between fibers (green).</li>
	</ol>
	</li>
	<li>Click &#34;Get Probability&#34; and save the image in a newly labeled folder.</li>
	<li>Repeat the above procedure (steps 4.2 - 4.3) with the fluorescent image taken from the same field. Label immunostained fibers as &#34;class 1&#34; and all non-fluorescent regions as &#34;class 2&#34;. Save the resulting probability map to the same folder where the processed brightfield image is stored.</li>
	<li>Open one of the previously saved probability maps in Fiji. Draw a straight line on the scale bar provided by the imaging software. Go to Analyze&#160;&#8594; Set Scale. Change the parameters (i.e., known distance, unit of length) to their appropriate values as given by the scale bar, then check the &#34;Global&#34; box to standardize the scale for each image.</li>
	<li>Navigate to Plugins&#160;&#8594; Macros&#160;&#8594; Run&#160;&#8594; Tyagi et al. fiber quantification macro.ijm (see the Supplemental File). Immediately, a navigation pane will appear. Open the image&#39;s host folder; a dialog box will appear. For each dialog box, change the &#34;Background&#34; dropdown value to &#34;Light.&#34; 
	NOTE: The folder will now be populated with images of the fiber outlines and spreadsheet software files of the results (CSA and Feret diameter are most pertinent to quantifying fiber morphology; measured parameters can be adjusted in Analyze Set Measurements). Fiber morphology data generated by the pore-analysis function of Fiji will be automatically transferred to spreadsheet software files for both fluorescent and bright field images.</li>
	<li>Calculate the fraction of fibers expressing a given MyHC in a field by dividing the number of fluorescent fibers in the field by the number of total fibers in the corresponding bright field image.</li>
</ol>

<ol>
	<li>Engel, W. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+essentiality+of+histo-+and+cytochemical+studies+of+skeletal+muscle+in+the+investigation+of+neuromuscular+disease.">The essentiality of histo- and cytochemical studies of skeletal muscle in the investigation of neuromuscular disease.</a> Neurol. 12, 778-784 (1962).</li><li>Dobrowolny, 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=Skeletal+muscle+is+a+primary+target+of+SOD1G93A-mediated+toxicity.">Skeletal muscle is a primary target of SOD1G93A-mediated toxicity.</a> Cell Metab. 8, 425-436 (2008).</li><li>Sultana, N., 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=Restricting+calcium+currents+is+required+for+correct+fiber+type+specification+in+skeletal+muscle.">Restricting calcium currents is required for correct fiber type specification in skeletal muscle.</a> Development. 143 (9), 1547-1559 (2016).</li><li>Guth, L., Samaha, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Procedure+for+the+histochemical+demonstration+of+actomyosin+ATPase.">Procedure for the histochemical demonstration of actomyosin ATPase.</a> Exp Neurol. 28 (2), 365-367 (1970).</li><li>Bloemberg, D., Quadrilatero, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+determination+of+myosin+heavy+chain+expression+in+rat,+mouse,+and+human+skeletal+muscle+using+multicolor+immunofluorescence+analysis.">Rapid determination of myosin heavy chain expression in rat, mouse, and human skeletal muscle using multicolor immunofluorescence analysis.</a> PLoS One. 7 (4), (2012).</li><li>Lucas, C. A., Kang, L. H., Hoh, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monospecific+antibodies+against+the+three+mammalian+fast+limb+myosin+heavy+chains.">Monospecific antibodies against the three mammalian fast limb myosin heavy chains.</a> Biochem Biophys Res Commun. 272 (1), 303-308 (2000).</li><li>Lee, C. S., 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=Ca2++permeation+and/or+binding+to+Cav1.1+fine-tunes+skeletal+muscle+Ca2++signaling+to+sustain+muscle+function.">Ca2+ permeation and/or binding to Cav1.1 fine-tunes skeletal muscle Ca2+ signaling to sustain muscle function.</a> Skelet Muscle. 5 (4), (2015).</li><li>Sawano, S., 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=A+one-step+immunostaining+method+to+visualize+rodent+muscle+fiber+type+within+a+single+specimen.">A one-step immunostaining method to visualize rodent muscle fiber type within a single specimen.</a> PLoS One. 11 (11), (2016).</li><li>Meunier, B., Picard, B., Astruc, T., Labas, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+image+analysis+tool+for+the+classification+of+muscle+fibre+type+using+immunohistochemical+staining.">Development of image analysis tool for the classification of muscle fibre type using immunohistochemical staining.</a> Histochem Cell Biol. 134 (3), 307-317 (2010).</li><li>Kammoun, M., Casser-Malek, I., Meunier, B., Picard, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simplified+immunohistochemical+classification+of+skeletal+muscle+fibres+in+mouse.">A simplified immunohistochemical classification of skeletal muscle fibres in mouse.</a> Eur J Histochem. 58 (2), 2254 (2014).</li><li>Kumar, A., Accorsi, A., Rhee, Y., Girgenrath, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do's+and+don'ts+in+the+preparation+of+muscle+cryosections+for+histological+analysis.">Do's and don'ts in the preparation of muscle cryosections for histological analysis.</a> J Vis Exp. (99), (2015).</li><li>Schiaffino, S., 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=Three+myosin+heavy+chain+isoforms+in+type+2+skeletal+muscle+fibres.">Three myosin heavy chain isoforms in type 2 skeletal muscle fibres.</a> J Muscle Res Cell Motil. 10 (197), (1989).</li><li>Augusto, V., Padovani, C. R., Campos, G. E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Skeletal+muscle+fiber+types+in+C57Bl6j+mice.">Skeletal muscle fiber types in C57Bl6j mice.</a> Braz J Morphol Sci. 21 (2), 89-94 (2004).</li><li>Schiaffino, S., Reggiani, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fiber+types+in+mammalian+skeletal+muscles.">Fiber types in mammalian skeletal muscles.</a> Physiol Rev. 91 (4), 1447-1531 (2011).</li><li>Allen, D. L., Harrison, B. C., Maass, A., Bell, M. L., Byrnes, W. C., Leinwand, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+and+skeletal+muscle+adaptations+to+voluntary+wheel+running+in+the+mouse.">Cardiac and skeletal muscle adaptations to voluntary wheel running in the mouse.</a> J Appl Physiol. 90 (5), 1900-1908 (2001).</li></ol>

The authors have no conflicting interests to disclose.

Here, we have provided useful direction for the identification of skeletal muscle fiber types. In doing so, we describe a novel algorithm for analysis of the data.
Since our results largely confirm those of previous reports5,8,10 and reflect our own manual measurements, the algorithm appears to be accurate. Still, we encountered some infrequent experimental pitfalls including unclear fiber borders res...

It has been known for some time that skeletal muscle is composed of single fibers of many types1. Initially, two groups of fibers were characterized based on their contractile properties and named, appropriately, slow-twitch (type I) and fast-twitch (type II). These categories were further distinguished on the basis of fiber metabolism. Since type I fibers are rich in mitochondria and reliant on oxidative metabolism, they were elucidated by robustly positive nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR) diaphorase2 or succinate dehydrogenase (SDH)3 staining. By contrast, type II fibers exhibited lesser and variable degrees of NADH-TR diaphorase or SDH staining and were divided into two fast-twitch subgroups (type IIA and type IIB) somewhat crudely based on their relative oxidative capacities. These distinctions between fibers have been visualized more effectively by myosin-ATPase staining where type I fibers stain dark after a pre-incubation at pH 4.0 and type IIB fibers absorb precipitate following pre-incubation at pH 10.0 with type IIA fibers staining intermediately4.
More recently, immunohistochemical staining of myosin heavy chain (MyHC) isoforms has emerged as a finer discriminator of fiber-type5. Type I, type IIA and type IIB fibers can be all identified with precision based on their MyHC profile. In addition, another fast-twitch metabolically-intermediate fiber type, type IIX, has been identified6. Hybrid fibers expressing more than one MyHC have also been confirmed5,7,8. Some species such as the cat and the baboon are known not to express Type IIB MyHCs6. Though MyHC immunostaining is currently the state-of-the-art assessment of muscle composition, the analysis of the data obtained via this technique is cumbersome and time-consuming without automated assistance. To this end, a handful of semi-automated methods to analyze these data have been developed5,9,10. Here, we present a relatively standard protocol for immunohistochemical identification of muscle fiber-type5,7,8,10, along with a novel semi-automated algorithm that accelerates analysis of fiber-type and fiber morphology with accuracy.

<table width="974">
	<colgroup>
		<col style="width:226pt" width="301" />
		<col style="width:140pt" width="187" />
		<col style="width:172pt" width="229" />
		<col style="width:193pt" width="257" />
	</colgroup>
	<tbody>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Bovine Serum Albumin</td>
			<td class="xl65" style="width:140pt" width="187">Sigma Aldrich</td>
			<td class="xl65" style="width:172pt" width="229">A9418-100G</td>
			<td class="xl66" style="width:193pt" width="257">5% in PBS</td>
		</tr>
		<tr height="41" style="height:30.75pt">
			<td class="xl65" height="41" style="width:226pt;height:30.75pt" width="301">Hydrophobic Barrier Pap Pen</td>
			<td class="xl65" style="width:140pt" width="187">Scientific Device Laboratory</td>
			<td class="xl65" style="width:172pt" width="229">9804-02</td>
			<td class="xl66"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Microscope Slides</td>
			<td class="xl65" style="width:140pt" width="187">Globe Scientific</td>
			<td class="xl65" style="width:172pt" width="229">1358W</td>
			<td class="xl66"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Coverglass</td>
			<td class="xl65" style="width:140pt" width="187">Fisher Scientific</td>
			<td class="xl65" style="width:172pt" width="229">12-544-E</td>
			<td class="xl66"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Immumount</td>
			<td class="xl65" style="width:140pt" width="187">Thermo Scientific</td>
			<td class="xl68" style="width:172pt" width="229">9990402</td>
			<td class="xl66"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Nail Polish</td>
			<td class="xl65" style="width:140pt" width="187">L&#39;Oreal</td>
			<td class="xl65" style="width:172pt" width="229"></td>
			<td class="xl66"></td>
		</tr>
		<tr height="41" style="height:30.75pt">
			<td class="xl65" height="41" style="width:226pt;height:30.75pt" width="301">Nikon Eclipse TE-200 Inverted Fluorescence and Brightfield Microscope</td>
			<td class="xl65" style="width:140pt" width="187"></td>
			<td class="xl65" style="width:172pt" width="229">Discontinued</td>
			<td class="xl66"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">SPOT RT/KE</td>
			<td class="xl65" style="width:140pt" width="187">SPOT Imaging Solutions</td>
			<td class="xl65" style="width:172pt" width="229">RT940</td>
			<td class="xl66"></td>
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		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Dell Optiplex</td>
			<td class="xl65" style="width:140pt" width="187"></td>
			<td class="xl65" style="width:172pt" width="229"></td>
			<td class="xl66"></td>
		</tr>
		<tr height="61" style="height:45.75pt">
			<td class="xl65" height="61" style="width:226pt;height:45.75pt" width="301">BA-F8 Primary Antibody</td>
			<td class="xl65" style="width:140pt" width="187">Developmental Studies Hybridoma Bank at the University of Iowa</td>
			<td class="xl65" style="width:172pt" width="229"></td>
			<td class="xl70">monoclonal mouse IgG2b; 1:50</td>
		</tr>
		<tr height="61" style="height:45.75pt">
			<td class="xl65" height="61" style="width:226pt;height:45.75pt" width="301">SC-71 Primary Antibody</td>
			<td class="xl65" style="width:140pt" width="187">Developmental Studies Hybridoma Bank at the University of Iowa</td>
			<td class="xl65" style="width:172pt" width="229"></td>
			<td class="xl70">monclonal mouse IgG1; 1:50</td>
		</tr>
		<tr height="61" style="height:45.75pt">
			<td class="xl65" height="61" style="width:226pt;height:45.75pt" width="301">BF-F3 Primary Antibody</td>
			<td class="xl65" style="width:140pt" width="187">Developmental Studies Hybridoma Bank at the University of Iowa</td>
			<td class="xl65" style="width:172pt" width="229"></td>
			<td class="xl70">monoclonal mouse IgGM; 1:50</td>
		</tr>
		<tr height="61" style="height:45.75pt">
			<td class="xl65" height="61" style="width:226pt;height:45.75pt" width="301">6H1 Primary Antibody</td>
			<td class="xl65" style="width:140pt" width="187">Developmental Studies Hybridoma Bank at the University of Iowa</td>
			<td class="xl65" style="width:172pt" width="229"></td>
			<td class="xl70">monoclonal mouse IgGM; 1:50</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Alexa Fluor 594 anti-IgG2b</td>
			<td class="xl65" style="width:140pt" width="187">Invitrogen</td>
			<td class="xl65" style="width:172pt" width="229">A21145</td>
			<td class="xl66">goat anti-mouse; 1:200</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Alexa Fluor 488 anti-IgG1</td>
			<td class="xl65" style="width:140pt" width="187">Invitrogen</td>
			<td class="xl65" style="width:172pt" width="229">A21121</td>
			<td class="xl66">goat anti-mouse;1:200</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Alexa Fluor 594 anti-IgGM</td>
			<td class="xl65" style="width:140pt" width="187">Invitrogen</td>
			<td class="xl65" style="width:172pt" width="229">A21044</td>
			<td class="xl66">goat anti-mouse;1:200</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">OCT</td>
			<td class="xl65" style="width:140pt" width="187">Sakura Finetek</td>
			<td class="xl68" style="width:172pt" width="229">4583</td>
			<td class="xl66"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">isopentane</td>
			<td class="xl65" style="width:140pt" width="187">Fisher Scientific</td>
			<td class="xl65" style="width:172pt" width="229">O3551-4</td>
			<td class="xl66">cool with liguid nitrogen</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">PBS</td>
			<td class="xl65" style="width:140pt" width="187">Fisher Bioreagents</td>
			<td class="xl65" style="width:172pt" width="229">BP665-1</td>
			<td class="xl66">10X, dilute to 1X</td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:226pt;height:15.75pt" width="301">Kim wipes</td>
			<td class="xl66">Kimberly-Clark</td>
			<td class="xl65" style="width:172pt" width="229">06-666A</td>
			<td class="xl66"></td>
		</tr>
	</tbody>
</table>

semi-automated analysis of mouse skeletal muscle morphology and fiber-type composition

For years, distinctions between skeletal muscle fiber types were best visualized by myosin-ATPase staining. More recently, immunohistochemical staining of myosin heavy chain (MyHC) isoforms has emerged as a finer discriminator of fiber-type. Type I, type IIA, type IIX and type IIB fibers can now be identified with precision based on their MyHC profile; however, manual analysis of these data can be slow and down-right tedious. In this regard, rapid, accurate assessment of fiber-type composition and morphology is a very desirable tool. Here, we present a protocol for state-of-the-art immunohistochemical staining of MyHCs in frozen sections obtained from mouse hindlimb muscle in concert with a novel semi-automated algorithm that accelerates analysis of fiber-type and fiber morphology. As expected, the soleus muscle displayed staining for type I and type IIA fibers, but not for type IIX or type IIB fibers. On the other hand, the tibialis anterior muscle was composed predominantly of type IIX and type IIB fibers, a small fraction of type IIA fibers and little or no type I fibers. Several image transformations were used to generate probability maps for the purpose of measuring different aspects of fiber morphology (i.e., cross-sectional area (CSA), maximal and minimal Feret diameter). The values obtained for these parameters were then compared with manually-obtained values. No significant differences were observed between either mode of analysis with regards to CSA, maximal or minimal Feret diameter (all p &#62; 0.05), indicating the accuracy of our method. Thus, our immunostaining analysis protocol may be applied to the investigation of effects on muscle composition in many models of aging and myopathy.

Hindlimb muscles (i.e., tibialis anterior, soleus) dissected from a male C57BL/6 mouse of unknown age were flash frozen by sinking a plastic mold containing the muscle in OCT compound in liquid nitrogen-cooled isopentane. Then, using a cryotome, 8-10 &#181;m serial sections were cut at -20 &#176;C and transferred to different positively-charged glass slides12.
We chose tibialis anterior and soleu...

Watch this Scientific Journal Video about Semi-automated Analysis of Mouse Skeletal Muscle Morphology and Fiber-type Composition at JoVE.com

Semi-automated Analysis of Mouse Skeletal Muscle Morphology and Fiber-type Composition

Immunohistochemical staining of myosin heavy chain isoforms has emerged as the state-of-the-art discriminator of skeletal muscle fiber-type (i.e., type I, type IIA, type IIX, type IIB). Here, we present a staining protocol along with a novel semi-automated algorithm that facilitates rapid assessment of fiber-type and fiber morphology.

For years, distinctions between skeletal muscle fiber types were best visualized by myosin-ATPase staining. More recently, immunohistochemical staining of ...

semi-automated-analysis-mouse-skeletal-muscle-morphology-fiber-type

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10.3K Views.  University of Colorado School of Medicine. Immunohistochemical staining of myosin heavy chain isoforms has emerged as the state-of-the-art discriminator of skeletal muscle fiber-type (i.e., type I, type IIA, type IIX, type IIB). Here, we present a staining protocol along with a novel semi-automated algorithm that facilitates rapid assessment of fiber-type and fiber morphology.

Video: Semi-automated Analysis of Mouse Skeletal Muscle Morphology and Fiber-type Composition

Myo-mechanical Analysis of Isolated Skeletal Muscle

To assess the in vivo effects of therapeutic interventions for the treatment of muscle disease 1,2,3, quantitative methods are needed that measure force generation and fatigability in treated muscle. We describe a detailed approach to evaluating myo-mechanical properties in freshly explanted hindlimb muscle from the mouse. We describe the atraumatic harvest of mouse extensor digitorum longus muscle, mounting the muscle in a muscle strip myograph (Model 820MS; Danish Myo Technology), and the measurement of maximal twitch and tetanic tension, contraction time, and half-relaxation time, using a square pulse stimulator (Model S48; Grass Technologies). Using these measurements, we demonstrate the calculation of specific twitch and tetanic tension normalized to muscle cross-sectional area, the twitch-to-tetanic tension ratio, the force-frequency relationship curve and the low frequency fatigue curve 4. This analysis provides a method for quantitative comparison between therapeutic interventions in mouse models of muscle disease 1,2,3,5, as well as comparison of the effects of genetic modification on muscle function 6,7,8,9.

To assess the in vivo effects of therapeutic interventions for muscle disease, methods are needed to quantitate force generation and fatigability in treated muscle. We detail an approach to evaluating myo-mechanical properties in explanted mouse hindlimb muscle. This analysis provides a robust approach to quantitating the effects of genetic modification on muscle function, as well as comparison of therapies in mouse models of muscle disease.

To assess the in vivo effects of therapeutic interventions for the treatment of muscle disease 1,2,3, quantitative methods are needed that measure force ...

Skeletal Muscle Gender Dimorphism from Proteomics

Gross contraction in skeletal muscle is primarily determined by a relatively small number of contractile proteins, however this tissue is also remarkably adaptable to environmental factors1 such as hypertrophy by resistance exercise and atrophy by disuse. It thereby exhibits remodeling and adaptations to stressors (heat, ischemia, heavy metals, etc.)2,3. Damage can occur to muscle by a muscle exerting force while lengthening, the so-called eccentric contraction4. The contractile proteins can be damaged in such exertions and need to be repaired, degraded and/or resynthesized; these functions are not part of the contractile proteins, but of other much less abundant proteins in the cell. To determine what subset of proteins is involved in the amelioration of this type of damage, a global proteome must be established prior to exercise5 and then followed subsequent to the exercise to determine the differential protein expression and thereby highlight candidate proteins in the adaptations to damage and its repair. Furthermore, most studies of skeletal muscle have been conducted on the male of the species and hence may not be representative of female muscle. 
In this article we present a method for extracting proteins reproducibly from male and female muscles, and separating them by two-dimensional gel electrophoresis followed by high resolution digital imaging6. This provides a protocol for spots (and subsequently identified proteins) that show a statistically significant (p &lt; 0.05) two-fold increase or decrease, appear or disappear from the control state. These are then excised, digested with trypsin and separated by high-pressure liquid chromatography coupled to a mass spectrometer (LC/MS) for protein identification (LC/MS/MS)5. This methodology (Figure 1) can be used on many tissues with little to no modification (liver, brain, heart etc.).

A straight-forward set of methods to isolate and determine the identity of the most abundant proteins expressed in skeletal muscle. About 800 spots are discerned on a two-dimensional gel from 10 mg muscle; this allows for the determination of gender-specific protein expression. These methods will give equivalent results in most tissues.

Gross contraction in skeletal muscle is primarily determined by a relatively small number of contractile proteins, however this tissue is also remarkably ...

Assessment of Right Ventricular Structure and Function in Mouse Model of Pulmonary Artery Constriction by Transthoracic Echocardiography

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, the RV is significantly affected in pulmonary diseases such as pulmonary artery hypertension (PAH). In addition, the RV is remarkably sensitive to cardiac pathologies, including left ventricular (LV) dysfunction, valvular disease or RV infarction4. To understand the role of RV in the pathogenesis of cardiac diseases, a reliable and noninvasive method to access the RV structurally and functionally is essential.
A noninvasive trans-thoracic echocardiography (TTE) based methodology was established and validated for monitoring dynamic changes in RV structure and function in adult mice. To impose RV stress, we employed a surgical model of pulmonary artery constriction (PAC) and measured the RV response over a 7-day period using a high-frequency ultrasound microimaging system. Sham operated mice were used as controls. Images were acquired in lightly anesthetized mice at baseline (before surgery), day 0 (immediately post-surgery), day 3, and day 7 (post-surgery). Data was analyzed offline using software.
Several acoustic windows (B, M, and Color Doppler modes), which can be consistently obtained in mice, allowed for reliable and reproducible measurement of RV structure (including RV wall thickness, end-diastolic&#160;and end-systolic dimensions), and function (fractional area change, fractional shortening, PA peak velocity, and peak pressure gradient) in normal mice and following PAC.
Using this method, the pressure-gradient resulting from PAC was accurately measured in real-time using Color Doppler mode and was comparable to direct pressure measurements performed with a Millar high-fidelity microtip catheter. Taken together, these data demonstrate that RV measurements obtained from various complimentary views using echocardiography are reliable, reproducible and can provide insights regarding RV structure and function. This method will enable a better understanding of the role of RV cardiac dysfunction.

Right ventricle (RV) dysfunction is critical to the pathogenesis of cardiovascular disease, yet limited methodologies are available for its evaluation. Recent advances in ultrasound imaging provide a noninvasive and accurate option for longitudinal RV study. Herein, we detail a step-by-step echocardiographic method using a murine model of RV pressure overload.

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, ...

Human Skeletal Muscle Biopsy Procedures Using the Modified Bergstr&#246;m Technique

The percutaneous biopsy technique enables researchers and clinicians to collect skeletal muscle tissue samples. The technique is safe and highly effective. This video describes the percutaneous biopsy technique using a modified Bergstr&#246;m needle to obtain skeletal muscle tissue samples from the vastus lateralis of human subjects. The Bergstr&#246;m needle consists of an outer cannula with a small opening (&#8216;window&#8217;) at the side of the tip and an inner trocar with a cutting blade at the distal end. Under local anesthesia and aseptic conditions, the needle is advanced into the skeletal muscle through an incision in the skin, subcutaneous tissue, and fascia. Next, suction is applied to the inner trocar, the outer trocar is pulled back, skeletal muscle tissue is drawn into the window of the outer cannula by the suction, and the inner trocar is rapidly closed, thus cutting or clipping the skeletal muscle tissue sample. The needle is rotated 90&#176;&#160;and another cut is made. This process may be repeated three more times. This multiple cutting technique typically produces a sample of 100-200 mg or more in healthy subjects and can be done immediately before, during, and after a bout of exercise or other intervention. Following post-biopsy dressing of the incision site, subjects typically resume their activities of daily living right away and can fully participate in vigorous physical activity within 48-72 hr. Subjects should avoid heavy resistance exercise for 48 hr to reduce the risk of herniation of the muscle through the incision in the fascia.

The purpose of this video is to present the modified Bergstr&#246;m skeletal muscle biopsy technique on human subjects.

The percutaneous biopsy technique enables researchers and clinicians to collect skeletal muscle tissue samples. The technique is safe and highly ...

Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of living systems. Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using qMRI methods. The MRI acquisition protocol begins with localizer images (used to locate the position of the body and tissue of interest within the MRI system), quality control measurements of relevant magnetic field distributions, and structural imaging for general anatomical characterization. The qMRI portion of the protocol includes measurements of the longitudinal and transverse relaxation time constants (T1 and T2, respectively). Also acquired are diffusion-tensor MRI data, in which water diffusivity is measured and used to infer pathological processes such as edema. Quantitative magnetization transfer imaging is used to characterize the relative tissue content of macromolecular and free water protons. Lastly, fat-water MRI methods are used to characterize fibro-adipose tissue replacement of muscle. In addition to describing the data acquisition and analysis procedures, this paper also discusses the potential problems associated with these methods, the analysis and interpretation of the data, MRI safety, and strategies for artifact reduction and protocol optimization.

Neuromuscular diseases often exhibit a temporally varying, spatially heterogeneous, and multi-faceted pathology. The goal of this protocol is to characterize this pathology using non-invasive magnetic resonance imaging methods.

Quantitative magnetic resonance imaging (qMRI) describes the development and use of MRI to quantify physical, chemical, and/or biological properties of ...

Human Vastus Lateralis Skeletal Muscle Biopsy Using the Weil-Blakesley Conchotome

Percutaneous muscle biopsy using the Weil-Blakesley conchotome is well established in both clinical and research practice. It is a safe, effective and well tolerated technique. The Weil-Blakesley conchotome has a sharp biting tip with a 4 - 6 mm wide hollow. It is inserted through a 5 - 10 mm skin incision and can be maneuvered for controlled tissue penetration. The tip is opened and closed within the tissue and then rotated through 90 -180&#176; to cut the muscle. The amount of muscle obtained following repeated sampling can vary from 20 mg to 290 mg which can be processed for both histology and molecular studies. The wound needs to be kept dry and vigorous physical activity kept to a minimum for approximately 72 hr although normal levels of activity can restart immediately following the procedure. This procedure is safe and effective when close attention is paid to the selection of subjects, full asepsis and post procedure care. &#160;Both right and left vastus lateralis are suitable for biopsy dependent on participant preference.

Human Vastus Lateralis Skeletal Muscle Biopsy Using the Weil-Blakesley Conchotome

This video demonstrates the technique of percutaneous muscle biopsy of the human vastus lateralis using the Weil-Blakesley conchotome.

Percutaneous muscle biopsy using the Weil-Blakesley conchotome is well established in both clinical and research practice. It is a safe, effective and ...

Induction and Assessment of Exertional Skeletal Muscle Damage in Humans

Contraction-induced muscle damage via voluntary eccentric (lengthening) contractions offers an excellent model for studying muscle adaptation and recovery in humans. Herein we discuss the design of an eccentric exercise protocol to induce damage in the quadriceps muscles, marked by changes in strength, soreness, and plasma creatine kinase levels. This method is simple, ethical, and widely applicable since it is performed in human participants and eliminates the interspecies translation of the results. Subjects perform 300 maximal eccentric contractions of the knee extensor muscles at a speed of 120&#176;/sec on an isokinetic dynamometer. The extent of the damage is measurable using relatively non-invasive isokinetic and isometric measures of strength loss, soreness, and plasma creatine kinase levels over several days following the exercise. Therefore, its application can be directed to specific populations in an attempt to identify mechanisms for muscle adaptation and regeneration.

This article describes a safe and reliable method to induce and quantify exertional skeletal muscle damage in human subjects.

Contraction-induced muscle damage via voluntary eccentric (lengthening) contractions offers an excellent model for studying muscle adaptation and recovery ...

Echocardiographic and Histological Examination of Cardiac Morphology in the Mouse

An increasing number of genetically modified mouse models has become available in recent years. Moreover, the number of pharmacological studies performed in mice is high. Phenotypic characterization of these mouse models also requires the examination of cardiac function and morphology. Echocardiography and magnetic resonance imaging (MRI) are commonly used approaches to characterize cardiac function and morphology in mice. Echocardiographic and MRI equipment specialized for use in small rodents is&#160;expensive and requires a dedicated space. This protocol describes cardiac measurements in mice using a clinical echocardiographic system with a 15 MHz human vascular probe. Measurements are performed on anesthetized adult mice. At least three image sequences are recorded and analyzed for each animal in M-mode in the parasternal short-axis view. Afterwards, cardiac histological examination is performed, and cardiomyocyte diameters are determined on hematoxylin-eosin- or wheat germ agglutinin (WGA)-stained paraffin sections. Vessel density is determined morphometrically after Pecam-1 immunostaining. The protocol has been applied successfully to pharmacological studies and different genetic animal models under baseline conditions, as well as after experimental myocardial infarction by the permanent ligation of the left anterior descending coronary artery (LAD). In our experience, echocardiographic investigation is limited to anesthetized animals and is feasible in adult mice weighing at least 25 g.

Echocardiographic examination is frequently used in mice. Expensive high-resolution ultrasound devices have been developed for this purpose. This protocol describes an affordable echocardiographic procedure combined with histological morphometric analyses to determine cardiac morphology.

An increasing number of genetically modified mouse models has become available in recent years. Moreover, the number of pharmacological studies performed ...

Body Composition and Metabolic Caging Analysis in High Fat Fed Mice

Alterations to body composition (fat or lean mass), metabolic parameters such as whole-body oxygen consumption, energy expenditure, and substrate utilization, and behaviors such as food intake and physical activity can provide important information regarding the underlying mechanisms of disease. Given the importance of body composition and metabolism to the development of obesity and its subsequent sequelae, it is necessary to make accurate measures of these parameters in the pre-clinical research setting. Advances in technology over the past few decades have made it possible to derive these measures in rodent models in a non-invasive and longitudinal fashion. Consequently, these metabolic measures have proven useful when assessing the response of genetic manipulations (for example knockout or transgenic mice, viral knock-down or overexpression of genes), experimental drug/compound screening and dietary, behavioral or physical activity interventions. Herein, we describe the protocols used to measure body composition and metabolic parameters using an animal monitoring system in chow-fed and high fat diet-fed mice.

This protocol describes the use of a body composition analyzer and metabolic animal monitoring system to characterize body composition and metabolic parameters in mice. An obesity model induced by high-fat feeding is used as an example for the application of these techniques.

Alterations to body composition (fat or lean mass), metabolic parameters such as whole-body oxygen consumption, energy expenditure, and substrate ...

Quantitative Analysis of Cellular Composition in Advanced Atherosclerotic Lesions of Smooth Muscle Cell Lineage-Tracing Mice

Atherosclerosis remains the leading cause of death worldwide and, despite countless preclinical studies describing promising therapeutic targets, novel interventions have remained elusive. This is likely due, in part, to a reliance on preclinical prevention models investigating the effects of genetic manipulations or pharmacological treatments on atherosclerosis development rather than the established disease. Also, results of these studies are often confounding because of the use of superficial lesion analyses and a lack of characterization of lesion cell populations. To help overcome these translational hurdles, we propose an increased reliance on intervention models that employ investigation of changes in cellular composition at a single cell level by immunofluorescent staining and confocal microscopy. To this end, we describe a protocol for testing a putative therapeutic agent in a murine intervention model including a systematic approach for animal dissection, embedding, sectioning, staining, and quantification of brachiocephalic artery lesions. In addition, due to the phenotypic diversity of cells within late-stage atherosclerotic lesions, we describe the importance of using cell-specific, inducible lineage tracing mouse systems and how this can be leveraged for unbiased characterization of atherosclerotic lesion cell populations. Together, these strategies may assist vascular biologists to more accurately model therapeutic interventions and analyze atherosclerotic disease and will hopefully translate into a higher rate of success in clinical trials.

We propose a standardized protocol to characterize the cellular composition of late-stage murine atherosclerotic lesions including systematic methods of animal dissection, tissue embedding, sectioning, staining, and analysis of brachiocephalic arteries from atheroprone smooth muscle cell lineage tracing mice.

Atherosclerosis remains the leading cause of death worldwide and, despite countless preclinical studies describing promising therapeutic targets, novel ...