Name: examining muscle regeneration in zebrafish models of muscle disease
Uploaded: 2021-01-18T15:00:00
Description: Watch this Scientific Journal Video about Examining Muscle Regeneration in Zebrafish Models of Muscle Disease at JoVE.com

We would like to thank Dr. Alex Fulcher, and Monash Micro Imaging for assistance with microscope maintenance and setup. The Australian Regenerative Medicine Institute is supported by grants from the State Government of Victoria and the Australian Government. This work was funded by a Muscular Dystrophy Association (USA) project grant to P.D.C (628882).

Zebrafish maintenance was carried out as per the standard operating procedures approved by the Monash University Animal Ethics Committee under breeding colony license ERM14481.
1. Determination of the genotype of live embryos using an embryo genotyping platform.
<ol>
	<li>Anesthetize 3 days post fertilization (dpf) zebrafish embryos by adding tricaine methanesulfonate to a final concentration of 0.016% (v/v) in embryo medium (5 mM NaCl, 0.17mM KCl, 0.33 mM CaCl2, 0.33 mM MgSO...

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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three+muscular+dystrophies:+loss+of+cytoskeleton-extracellular+matrix+linkage.">Three muscular dystrophies: loss of cytoskeleton-extracellular matrix linkage.</a> Cell. 80 (5), 675-679 (1995).</li><li>Cerletti, 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=Highly+efficient,+functional+engraftment+of+skeletal+muscle+stem+cells+in+dystrophic+muscles.">Highly efficient, functional engraftment of skeletal muscle stem cells in dystrophic muscles.</a> Cell. 134 (1), 37-47 (2008).</li><li>Dumont, N. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dystrophin+expression+in+muscle+stem+cells+regulates+their+polarity+and+asymmetric+division.">Dystrophin expression in muscle stem cells regulates their polarity and asymmetric division.</a> Nature Medicine. 21 (12), 1455-1463 (2015).</li><li>Lieschke, G. J., Currie, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+human+disease:+zebrafish+swim+into+view.">Animal models of human disease: zebrafish swim into view.</a> Nature Reviews. Genetics. 8 (5), 353-367 (2007).</li><li>Gurevich, D. 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=Asymmetric+division+of+clonal+muscle+stem+cells+coordinates+muscle+regeneration+in+vivo.">Asymmetric division of clonal muscle stem cells coordinates muscle regeneration in vivo.</a> Science. 353 (6295), (2016).</li><li>Lambert, C. J., 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=An+automated+system+for+rapid+cellular+extraction+from+live+zebrafish+embryos+and+larvae:+Development+and+application+to+genotyping.">An automated system for rapid cellular extraction from live zebrafish embryos and larvae: Development and application to genotyping.</a> PloS One. 13 (3), 0193180 (2018).</li><li>Berger, J., Sztal, T., Currie, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+birefringence+readily+measures+the+level+of+muscle+damage+in+zebrafish.">Quantification of birefringence readily measures the level of muscle damage in zebrafish.</a> Biochemical and Biophysical Research Communications. 423 (4), 785-788 (2012).</li><li>Hall, T. E., 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=The+zebrafish+candyfloss+mutant+implicates+extracellular+matrix+adhesion+failure+in+laminin+alpha2-deficient+congenital+muscular+dystrophy.">The zebrafish candyfloss mutant implicates extracellular matrix adhesion failure in laminin alpha2-deficient congenital muscular dystrophy.</a> Proceedings of the National Academy of Sciences of the United States of America. 104 (17), 7092-7097 (2007).</li><li>Otten, 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=Xirp+Proteins+Mark+Injured+Skeletal+Muscle+in+Zebrafish.">Xirp Proteins Mark Injured Skeletal Muscle in Zebrafish.</a> PLOS ONE. 7 (2), 31041 (2012).</li><li>Otten, C., Abdelilah-Seyfried, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser-inflicted+Injury+of+Zebrafish+Embryonic+Skeletal+Muscle.">Laser-inflicted Injury of Zebrafish Embryonic Skeletal Muscle.</a> Journal of Visualized Experiments JoVE. (71), e4351 (2013).</li><li>Nguyen, P. D., 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=Muscle+Stem+Cells+Undergo+Extensive+Clonal+Drift+during+Tissue+Growth+via+Meox1-Mediated+Induction+of+G2+Cell-Cycle+Arrest.">Muscle Stem Cells Undergo Extensive Clonal Drift during Tissue Growth via Meox1-Mediated Induction of G2 Cell-Cycle Arrest.</a> Cell Stem Cell. 21 (1), 107-119 (2017).</li><li>Ruparelia, A. A., Ratnayake, D., Currie, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stem+cells+in+skeletal+muscle+growth+and+regeneration+in+amniotes+and+teleosts:+Emerging+themes.">Stem cells in skeletal muscle growth and regeneration in amniotes and teleosts: Emerging themes.</a> Wiley Interdisciplinary Reviews. Developmental Biology. 9 (2), 365 (2020).</li></ol>

Skeletal muscle regeneration is driven by obligate tissue resident muscle stem cells, whose function is altered in many muscle diseases such as muscular dystrophy, subsequently impeding the process of muscle regeneration. Here, we describe a high throughput protocol to examine muscle regeneration in live zebrafish models of muscle disease. The first step of the pipeline utilizes a embryo genotyping platform14, which is a user-friendly and accurate method to determine the genotype of live larvae, b...

Skeletal muscle accounts for 30-50% of human body mass, and is not only indispensable for locomotion, but it also serves as a critical metabolic and storage organ1. Despite being postmitotic, skeletal muscle is highly dynamic and retains a tremendous regenerative capacity following injury. This is attributed to the presence of tissue resident stem cells (also called satellite cells), located under the basal lamina of myofibers and marked by the transcription factors paired box protein 7 (pax7) and/or paired box protein 3 (pax3), among others2,3. Following injury, the satellite cell is activated and undergoes cell proliferation to generate a pool of myoblasts, which subsequently differentiate to form new muscle fibers. The highly conserved cascade of pro-regenerative signals regulating satellite cell activation and robust muscle repair is&#160;affected in various conditions such as myopathies and homeostatic ageing4,5.
One such diverse group of myopathies is muscular dystrophy, characterized by progressive muscle wasting and degeneration6. These diseases are the consequence of genetic mutations in key proteins, including dystrophin and laminin-&#945;2 (LAMA2), responsible for the attachment of muscle fibers to the extracellular matrix7,8. Given that proteins implicated in muscular dystrophy play such a central role in maintaining muscle structure, for many years it was believed that a failure in this process was the mechanism responsible for disease pathogenesis9. However, recent studies have identified defects in the regulation of muscle stem cells and subsequent impairment in muscle regeneration as a second possible basis for the muscle pathology observed in muscular dystrophy10,11. As such, further studies are needed to investigate how an impairment in muscle stem cell function and associated niche elements contributes to muscular dystrophy.
Over the past decade, zebrafish (Danio rerio) has emerged as an important vertebrate model for disease modeling12. This is attributed to the rapid external development of the zebrafish embryo, coupled with its optical clarity, which allows the direct visualization of muscle formation, growth, and function. Additionally, not only is the development and structure of muscle highly conserved in zebrafish, they also display a highly conserved process of muscle regeneration13. Consequently, zebrafish represent an excellent system to study the pathobiology of muscle diseases, and explore how muscle regeneration is affected in it. To this end, we have developed a method that enables the timely study of skeletal muscle regeneration in zebrafish models of muscle disease. This high throughput pipeline involves a method to genotype live embryos14, following which a needle-stab injury is performed and the extent of muscle regeneration is imaged using polarizing light microscopy. The utilization of this technique will therefore reveal the regenerative capacity of muscle in zebrafish models of muscle disease.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>24 well plates</td>
			<td>Thermo Fischer</td>
			<td>142475</td>
			<td></td>
		</tr>
		<tr>
			<td>30 gauge needles</td>
			<td>Terumo</td>
			<td>NN-3013R</td>
			<td></td>
		</tr>
		<tr>
			<td>90 mm Petri Dishes</td>
			<td>Pacific Laboratory Products PT</td>
			<td>S9014S20</td>
			<td></td>
		</tr>
		<tr>
			<td>DNA extraction chips</td>
			<td>wFluidx</td>
			<td>ZEG chips</td>
			<td></td>
		</tr>
		<tr>
			<td>Embryo genotyping platform</td>
			<td>wFluidx</td>
			<td>ZEG base unit</td>
			<td>Zebrafish Embryo Genotyper</td>
		</tr>
		<tr>
			<td>Glass pipette</td>
			<td>Hirschmann</td>
			<td>9260101</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass plate dish</td>
			<td>WPI</td>
			<td>FD35-100</td>
			<td>Commonly referred to as FluoroDish</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Thermoline Scientific</td>
			<td>TEI-43L</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic pipette</td>
			<td>Livingstone</td>
			<td>PTP03-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Polarizing microscope</td>
			<td>Abrio</td>
			<td>N/A</td>
			<td></td>
		</tr>
	</tbody>
</table>

examining muscle regeneration in zebrafish models of muscle disease

Skeletal muscle has a remarkable ability to regenerate following injury, which is driven by obligate tissue resident muscle stem cells. Following injury, the muscle stem cell is activated and undergoes cell proliferation to generate a pool of myoblasts, which subsequently differentiate to form new muscle fibers. In many muscle wasting conditions, including muscular dystrophy and ageing, this process is impaired resulting in the inability of muscle to regenerate. The process of muscle regeneration in zebrafish is highly conserved with mammalian systems providing an excellent system to study muscle stem cell function and regeneration, in muscle wasting conditions such as muscular dystrophy. Here, we present a method to examine muscle regeneration in zebrafish models of muscle disease. The first step involves the use of a genotyping platform that allows the determination of the genotype of the larvae prior to eliciting an injury. Having determined the genotype, the muscle is injured using a needle stab, following which polarizing light microscopy is used to determine the extent of muscle regeneration. We therefore provide a high throughput pipeline which allows the examination of muscle regeneration in zebrafish models of muscle disease.

The ability to quantify birefringence of skeletal muscle provides a non-invasive but highly reproducible method to examine and compare levels of muscle damage, and examine muscle regeneration in vivo. Birefringence results from the diffraction of polarised light through the pseudo-crystalline array of the muscle sarcomeres15, and following injury or damage to the muscle, a reduction in birefringence is evident. Likewise, the activation and differentiation ...

Watch this Scientific Journal Video about Examining Muscle Regeneration in Zebrafish Models of Muscle Disease at JoVE.com

Examining Muscle Regeneration in Zebrafish Models of Muscle Disease

Skeletal muscle regeneration is driven by tissue resident muscle stem cells, which are impaired in many muscle diseases such as muscular dystrophy, and this results in the inability of muscle to regenerate. Here, we describe a protocol that allows the examination of muscle regeneration in zebrafish models of muscle disease.

Skeletal muscle has a remarkable ability to regenerate following injury, which is driven by obligate tissue resident muscle stem cells. Following injury, ...

The overall goal of this protocol is to examine and quantify muscle regeneration in a zebrafish model of muscle disease. This method provides a high-throughput pipeline that is not only cost-effective, but also highly reproducible in scoring the regenerative potential of a diseased muscle in an in vivo setting. Demonstrating the procedure with me will be Avnika Ruparelia, a research fellow at the Australian Regenerative Medicine Institute.For live embryo genotyping, peel the clear protective film from the top surface of a 24-chamber DNA extraction chip and use a 20 microliter filter tip with a cut tip to transfer a single anesthetized embryo in 13 microliters of embryo medium into each chamber of the chip. When all of the embryos have been loaded, gently mount the chip onto the zebrafish embryo genotyping platform by placing one side in first, followed by the rest of the chip. Affix the magnetic platform lid over the chip to prevent the evaporation of embryo medium during the DNA extraction protocol and close the lid.Set the base unit to 2.4 volts, 0.051 amps, and 0.12 watts and start the DNA extraction protocol. The platform should start vibrating, which can be assessed by gently touching the lid. While the program is running, prepare a 24-well plate by adding one milliliter of embryo medium to each well and label eight-well strip tubes to be used for the collection of DNA material from each embryo.After eight minutes of extraction, press the on/off button to stop the vibration of the platform, gently remove the magnetic lid and lift the chip from the platform. Transfer 10 microliters of embryo medium from one chamber into the appropriate well of the eight-well strip tube and immediately add two drops of fresh embryo medium to the chambers. Transfer the embryo from the chamber to an appropriate well of the previously prepared 24-well plate.When all of the embryos have been transferred, place the plate in a 28 degree Celsius incubator. Perform the appropriate downstream genotyping assays on the genetic material collected in the eight-well strip tubes to determine the genotype of each embryo. Once the genotype of each embryo has been identified, transfer the embryos to 90 millimeter Petri dishes containing 25 milliliters of medium water and incubate the plates at 28 degrees Celsius until muscle injury.At four days post-fertilization, use a pipette to transfer one anesthetized larva into a new Petri dish and carefully remove any excess medium from the dish under a dissecting microscope. Orient the fish such that the head is on the left, the tail is on the right, the dorsal region is up, and the ventral region is down, and use a 30 gauge needle to make a quick precise stab into one to two somites in the epaxial muscle above the anal pore and horizontal to the myoseptum. Apply a drop of embryo medium to the injured zebrafish and carefully transfer the larva into one well of a 24-well plate containing one milliliter of fresh embryo medium per well.When all of the larvae have been injured, place the plate in the 28 degree Celsius incubator until the zebrafish are imaged. To quantify the muscle regeneration, open a one-day post-injury image in an appropriate image analysis software program and use the polygon tool to draw a shape around the wound site. Use the software to measure the area and mean birefringence intensity of the region and copy these values to cells D3 and E3 of the provided template.Draw two additional regions each spanning one to two uninjured somites and measure the area and mean birefringence intensities of each of these regions. Copy these values to cells D4 and D5 and E4 and E5 in the template. Then repeat the measurement for same regions in the three days post-injury image.When the birefringence has been measured in the same manner in all of the images, calculate the normalized birefringence for each region by dividing the mean birefringence intensity of each region by its area. For each time point, calculate the average normalized birefringence of the two uninjured regions to provide a reference point for the uninjured muscle. To determine the extent of muscle injury at day one post-injury, divide the normalized birefringence of the injury region by the average normalized birefringence of the uninjured regions.To determine the extent of muscle regeneration, divide the normalized birefringence of the injury region in the three days post-injury image by the average normalized intensity of the uninjured regions at this stage. Finally, calculate the regenerative index by dividing the value for the extent of the muscle regeneration at day three post-injury by the value for the extent of the muscle injury at day one post-injury. In this representative analysis, a clutch of embryos from a cross between two Lama2 heterozygous zebrafish was transferred to a DNA extraction chip and subsequently genotyped.While muscle injury results in a reduction in birefringence intensity at day one post-injury, the successful regeneration of muscle results in an increased birefringence within the same region. It is also noteworthy that while wild type larvae display a uniform birefringence intensity due to a normal muscle patterning, the birefringence intensity in the muscle of Lama2 knockout larvae is uneven and highly sporadic likely due to a reduced muscle integrity. As observed, both wild type and Lama2-deficient larvae demonstrate a significantly increased birefringence intensity in the wound site at three days post-injury compared to at one day post-injury, indicating that the muscle has regenerated.Determination of the regenerative index reveals that Lama2-deficient larvae display a striking increase in muscle regeneration compared to wild type animals. While this protocol will allow us to identify any alterations in the ability of muscle to regenerate in models of muscle disease, downstream cellular and molecular analysis need to be performed to identify the mechanisms that are responsible for the observed changes. This method has allowed us to identify how impaired muscle stem cell function and an impairment in associated niche elements contributes to muscle disease pathogenesis, therefore allowing us to identify novel disease mechanisms.

examining-muscle-regeneration-in-zebrafish-models-of-muscle-disease

Research

JoVE Journal

Developmental Biology

Kidney Regeneration in Adult Zebrafish by Gentamicin Induced Injury

The kidney is essential for fluid homeostasis, blood pressure regulation and filtration of waste from the body. The fundamental unit of kidney function is the nephron. Mammals are able to repair existing nephrons after injury, but lose the ability to form new nephrons soon after birth. In contrast to mammals, adult fish produce new nephrons (neonephrogenesis) throughout their lives in response to growth requirements or injury. Recently, lhx1a has been shown to mark nephron progenitor cells in the adult zebrafish kidney, however mechanisms controlling the formation of new nephrons after injury remain unknown. Here we show our method for robust and reproducible injury in the adult zebrafish kidney by intraperitoneal (i.p.) injection of gentamicin, which uses a noninvasive visual screening process to select for fish with strong but nonlethal injury. Using this method, we can determine optimal gentamicin dosages for injury and go on to demonstrate the effect of higher temperatures on kidney regeneration in zebrafish.

Here we present a reliable method to study adult kidney regeneration by inducing acute kidney injury by gentamicin injection. We show that injury is dependent on gentamicin dosage and environmental temperature using in situ hybridization to label lhx1a+ developing new nephrons.

The kidney is essential for fluid homeostasis, blood pressure regulation and filtration of waste from the body. The fundamental unit of kidney function is ...

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

Using Touch-evoked Response and Locomotion Assays to Assess Muscle Performance and Function in Zebrafish

Zebrafish muscle development is highly conserved with mammalian systems making them an excellent model to study muscle function and disease. Many myopathies affecting skeletal muscle function can be quickly and easily assessed in zebrafish over the first few days of embryogenesis. By 24 hr post-fertilization (hpf), wildtype zebrafish spontaneously contract their tail muscles and by 48 hpf, zebrafish exhibit controlled swimming behaviors. Reduction in the frequency of, or other alterations in, these movements may indicate a skeletal muscle dysfunction. To analyze swimming behavior and assess muscle performance in early zebrafish development, we utilize both touch-evoked escape response and locomotion assays.
Touch-evoked escape response assays can be used to assess muscle performance during short burst movements resulting from contraction of fast-twitch muscle fibers. In response to an external stimulus, which in this case is a tap on the head, wildtype zebrafish at 2 days post-fertilization (dpf) typically exhibit a powerful burst swim, accompanied by sharp turns. Our method quantifies skeletal muscle function by measuring the maximum acceleration during a burst swimming motion, the acceleration being directly proportional to the force produced by muscle contraction.
In contrast, locomotion assays during early zebrafish larval development are used to assess muscle performance during sustained periods of muscle activity. Using a tracking system to monitor swimming behavior, we obtain an automated calculation of the frequency of activity and distance in 6-day old zebrafish, reflective of their skeletal muscle function. Measurements of swimming performance are valuable for phenotypic assessment of disease models and high-throughput screening of mutations or chemical treatments affecting skeletal muscle function.

Zebrafish are an excellent model to study muscle function and disease. During early embryogenesis zebrafish begin regular muscle contractions producing rhythmic swimming behavior, which is altered when the muscle is disrupted. Here we describe a touch-evoked response and locomotion assay to examine swimming performance as a measure of muscle function.

Zebrafish muscle development is highly conserved with mammalian systems making them an excellent model to study muscle function and disease. Many ...

Induction of Acute Skeletal Muscle Regeneration by Cardiotoxin Injection

Skeletal muscle regeneration is a physiological process that occurs in adult skeletal muscles in response to injury or disease. Acute injury-induced skeletal muscle regeneration is a widely used, powerful model system to study the events involved in muscle regeneration as well as the mechanisms and different players. Indeed, a detailed knowledge of this process is essential for a better understanding of the pathological conditions that lead to skeletal muscle degeneration, and it aids in identifying new targeted therapeutic strategies. The present work describes a detailed and reproducible protocol to induce acute skeletal muscle regeneration in mice through a single intramuscular injection of cardiotoxin (CTX). CTX belongs to the family of snake venom toxins and causes myolysis of myofibers, which eventually triggers the regeneration events. The dynamics of skeletal muscle regeneration is evaluated by histological analysis of muscle sections. The protocol also illustrates the experimental procedures for dissecting, freezing, and cutting the Tibialis Anterior muscle, as well as the routine Hematoxylin &#38; Eosin staining that is widely used for subsequent morphological and morphometric analysis.

This manuscript describes a detailed protocol to induce acute skeletal muscle regeneration in adult mice and subsequent manipulations of the muscles, such as dissection, freezing, cutting, routine staining, and myofiber cross-sectional area analysis.

Skeletal muscle regeneration is a physiological process that occurs in adult skeletal muscles in response to injury or disease. Acute injury-induced ...

Preparation and Culture of Myogenic Precursor Cells/Primary Myoblasts from Skeletal Muscle of Adult and Aged Humans

Skeletal muscle homeostasis depends on muscle growth (hypertrophy), atrophy and regeneration. During ageing and in several diseases, muscle wasting occurs. Loss of muscle mass and function is associated with muscle fiber type atrophy, fiber type switching, defective muscle regeneration associated with dysfunction of satellite cells, muscle stem cells, and other pathophysiological processes. These changes are associated with changes in intracellular as well as local and systemic niches. In addition to most commonly used rodent models of muscle ageing, there is a need to study muscle homeostasis and wasting using human models, which due to ethical implications, consist predominantly of in vitro cultures. Despite the wide use of human Myogenic Progenitor Cells (MPCs) and primary myoblasts in myogenesis, there is limited data on using human primary myoblast and myotube cultures to study molecular mechanisms regulating different aspects of age-associated muscle wasting, aiding in the validation of mechanisms of ageing proposed in rodent muscle. The use of human MPCs, primary myoblasts and myotubes isolated from adult and aged people, provides a physiologically relevant model of molecular mechanisms of processes associated with muscle growth, atrophy and regeneration. Here we describe in detail a robust, inexpensive, reproducible and efficient protocol for the isolation and maintenance of human MPCs&#160;and their progeny&#160;&#8212; myoblasts and myotubes from human muscle samples using enzymatic digestion. Furthermore, we have determined the passage number at which primary myoblasts from adult and aged people undergo senescence in an in vitro culture. Finally, we show the ability to transfect these myoblasts and the ability to characterize their proliferative and differentiation capacity and propose their suitability for performing functional studies of molecular mechanisms of myogenesis and muscle wasting in vitro.

This protocol describes a robust, reproducible and simple method of isolation and culture of myoblast progenitor cells from the skeletal muscle of adult and aged people. The muscles used here include foot and leg muscles. This approach enables the isolation of an enriched population of primary myoblasts for functional studies.

Skeletal muscle homeostasis depends on muscle growth (hypertrophy), atrophy and regeneration. During ageing and in several diseases, muscle wasting ...

Evaluation of Injury-induced Senescence and In Vivo Reprogramming in the Skeletal Muscle

Cellular senescence is a stress response that is characterized by a stable cellular growth arrest, which is important for many physiological and pathological processes, such as cancer and ageing. Recently, senescence has also been implicated in tissue repair and regeneration. Therefore, it has become increasingly critical to identify senescent cells in vivo. Senescence-associated &#946;-galactosidase (SA-&#946;-Gal) assay is the most widely used assay to detect senescent cells both in culture and in vivo. This assay is based on the increased lysosomal contents in the senescent cells, which allows the histochemical detection of lysosomal &#946;-galactosidase activity at suboptimum pH (6 or 5.5). In comparison with other assays, such as flow cytometry, this allows the identification of senescent cells in their resident environment, which offers valuable information such as the location relating to the tissue architecture, the morphology, and the possibility of coupling with other markers via immunohistochemistry&#160;(IHC). The major limitation of the SA-&#946;-Gal assay is the requirement of fresh or frozen samples.
Here, we present a detailed protocol to understand how cellular senescence promotes cellular plasticity and tissue regeneration in vivo. We use SA-&#946;-Gal to detect senescent cells in the skeletal muscle upon injury, which is a well-established system to study tissue regeneration. Moreover, we use&#160;IHC to detect Nanog, a marker of pluripotent stem cells, in a transgenic mouse model. This protocol enables us to examine and quantify cellular senescence in the context of induced cellular plasticity and in vivo reprogramming.

Evaluation of Injury-induced Senescence and In Vivo Reprogramming in the Skeletal Muscle

Here we present a detailed protocol to detect both senescent and pluripotent stem cells in the skeletal muscle upon injury while inducing in vivo reprogramming. This method is suitable for evaluating the role of cellular senescence during tissue regeneration and reprogramming in vivo.

Cellular senescence is a stress response that is characterized by a stable cellular growth arrest, which is important for many physiological and ...

Application of Chronic Stimulation to Study Contractile Activity-induced Rat Skeletal Muscle Phenotypic Adaptations

Skeletal muscle is a highly adaptable tissue, as its biochemical and physiological properties are greatly altered in response to chronic exercise. To investigate the underlying mechanisms that bring about various muscle adaptations, a number of exercise protocols such as treadmill, wheel running, and swimming exercise have been used in the animal studies. However, these exercise models require a long period of time to achieve muscle adaptations, which may be also regulated by humoral or neurological factors, thus limiting their applications in studying the muscle-specific contraction-induced adaptations. Indirect low frequency stimulation (10 Hz) to induce chronic contractile activity (CCA) has been used as an alternative model for exercise training, as it can successfully lead to muscle mitochondrial adaptations within 7 days, independent of systemic factors. This paper details the surgical techniques required to apply the treatment of CCA to the skeletal muscle of rats, for widespread application in future studies.

This protocol describes the use of the chronic contractile activity model of exercise to observe stimulation-induced skeletal muscle adaptations in the rat hindlimb.

Skeletal muscle is a highly adaptable tissue, as its biochemical and physiological properties are greatly altered in response to chronic exercise. To ...

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.

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, ...

In Vivo Imaging of Muscle-tendon Morphogenesis in Drosophila Pupae

Muscles together with tendons and the skeleton enable animals including humans to move their body parts. Muscle morphogenesis is highly conserved from animals to humans. Therefore, the powerful Drosophila model system can be used to study concepts of muscle-tendon development that can also be applied to human muscle biology. Here, we describe in detail how morphogenesis of the adult muscle-tendon system can be easily imaged in living, developing Drosophila pupae. Hence, the method allows investigating proteins, cells and tissues in their physiological environment. In addition to a step-by-step protocol with helpful tips, we provide a comprehensive overview of fluorescently tagged marker proteins that are suitable for studying the muscle-tendon system. To highlight the versatile applications of the protocol, we show example movies ranging from visualization of long-term morphogenetic events &#8211; occurring on the time scale of hours and days &#8211; to visualization of short-term dynamic processes like muscle twitching occurring on time scale of seconds. Taken together, this protocol should enable the reader to design and perform live-imaging experiments for investigating muscle-tendon morphogenesis in the intact organism.

In Vivo Imaging of Muscle-tendon Morphogenesis in Drosophila Pupae

Here, we present an easy-to-use and versatile method to perform live imaging of developmental processes in general and muscle-tendon morphogenesis in particular in living Drosophila pupae.

Muscles together with tendons and the skeleton enable animals including humans to move their body parts. Muscle morphogenesis is highly conserved from ...

X-ray Diffraction of Intact Murine Skeletal Muscle as a Tool for Studying the Structural Basis of Muscle Disease

Transgenic mouse models have been important tools for studying the relationship of genotype to phenotype for human diseases including those of skeletal muscle. Mouse skeletal muscle has been shown to produce high quality X-ray diffraction patterns on third generation synchrotron beamlines providing an opportunity to link changes at the level of the genotype to functional phenotypes in health and disease by determining the structural consequences of genetic changes. We present detailed protocols for preparation of specimens, collecting the X-ray patterns and extracting relevant structural parameters from the X-ray patterns that may help guide experimenters wishing to perform such experiments for themselves.

We present detailed protocols for performing small-angle X-ray diffraction experiments using intact mouse skeletal muscles. With the wide availability of transgenic mouse models for human diseases, this experimental platform can form a useful test bed for elucidating the structural basis of genetic muscle diseases

Transgenic mouse models have been important tools for studying the relationship of genotype to phenotype for human diseases including those of skeletal ...