Name: performing human skeletal muscle xenografts in immunodeficient mice
Uploaded: 2019-09-16T14:30:00
Description: Watch this Scientific Journal Video about Performing Human Skeletal Muscle Xenografts in Immunodeficient Mice at JoVE.com

This work was supported by The Myositis Association and the Peter Buck Foundation. We would like to thank Dr. Yuanfan Zhang for sharing her expertise and training in the xenograft surgical technique.

All use of research specimens from human subjects was approved by the Johns Hopkins Institutional Review Board (IRB) to protect the rights and welfare of the participants. All animal experiments were approved by the Johns Hopkins University Institutional Animal Care and Use Committee (IACUC) in accordance with the National Institutes of Health (NIH) Guide for the Care and Use of Laboratory Animals. Male NOD-Rag1null IL2r&#947;null (NRG) host mice (8-12 weeks old) ...

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Patient-derived xenografts are an innovative way to model muscle disease and carry out preclinical studies. The method described here to create skeletal muscle xenografts is rapid, straightforward, and reproducible. Unilateral surgeries can be performed in 15 to 25 minutes, or bilaterally in 30 to 40 minutes. Bilateral xenografts can provide additional experimental flexibility. For instance, researchers can perform localized treatment of one xenograft, with the other left as a control. The NRG mice are resistant to surgi...

It has been reported that only 13.8% of all drug development programs undergoing clinical trials are successful and lead to approved therapies1. While this success rate is higher than the 10.4% previously reported2, there is still significant room for improvement. One approach to increase the success rate of clinical trials is to improve laboratory models used in preclinical research. The Food and Drug Administration (FDA) requires animal studies to show treatment efficacy and assess toxicity prior to Phase 1 clinical trials. However, there is often limited concordance in treatment outcomes between animal studies and clinical trials3. In addition, the need for preclinical animal studies can be an insurmountable barrier for therapeutic development in diseases that lack an accepted animal model, which is often the case for rare or sporadic diseases.
One way to model human disease is by transplanting human tissue into immunodeficient mice to generate xenografts. There are three key advantages to xenograft models: First, they can recapitulate the complex genetic and epigenetic abnormalities that exist in human disease that may never be reproducible in other animal models. Second, xenografts can be used to model rare or sporadic diseases if patient samples are available. Third, xenografts model the disease within a complete in vivo system. For these reasons, we hypothesize that treatment efficacy results in xenograft models are more likely to translate to trials in patients. Human tumor xenografts have already been successfully utilized to develop treatments for common cancers, including multiple myeloma, as well as personalized therapies for individual patients4,5,6,7.
Recently, xenografts have been used to develop a model of human muscle disease8. In this model, human muscle biopsy specimens are transplanted into the hindlimbs of immunodeficient NRG mice to form xenografts. The transplanted human myofibers die, but human muscle stem cells present in the xenograft subsequently expand and differentiate into new human myofibers which repopulate the engrafted human basal lamina. Therefore, the regenerated myofibers in these xenografts are entirely human and are spontaneously revascularized and innervated by the mouse host. Importantly, fascioscapulohumeral muscular dystrophy (FSHD) patient muscle tissue transplanted into mice recapitulates key features of the human disease, namely expression of the DUX4 transcription factor8. FSHD is caused by overexpression of DUX4, which is epigenetically silenced in normal muscle tissue9,10. In the FSHD xenograft model, treatment with a DUX4-specific morpholino has been shown to successfully repress DUX4 expression and function, and may be a potential therapeutic option for FSHD patients11. These results demonstrate that human muscle xenografts are a new approach to model human muscle disease and test potential therapies in mice. Here, we describe in detail the surgical method for creating human skeletal muscle xenografts in immunodeficient mice.

<table>
	<tbody>
		<tr>
			<td>100 mm x 15 mm Petri dish</td>
			<td>Fisher Scientific</td>
			<td>FB0875712</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Methylbutane</td>
			<td>Fisher</td>
			<td>O3551-4</td>
			<td></td>
		</tr>
		<tr>
			<td>20 x 30 mm micro cover glass</td>
			<td>VWR</td>
			<td>48393-151</td>
			<td></td>
		</tr>
		<tr>
			<td>Animal Weighing Scale</td>
			<td>Kent Scientific</td>
			<td>SCL- 1015</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic-Antimycotic Solution</td>
			<td>Corning, Cellgro</td>
			<td>30-004-CI</td>
			<td></td>
		</tr>
		<tr>
			<td>AutoClip System</td>
			<td>F.S.T</td>
			<td>12020-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Castroviejo Needle Holder</td>
			<td>F.S.T</td>
			<td>12565-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Chick embryo extract</td>
			<td>Accurate</td>
			<td>CE650TL</td>
			<td></td>
		</tr>
		<tr>
			<td>CM1860 UV cryostat</td>
			<td>Leica Biosystems</td>
			<td>CM1860UV</td>
			<td></td>
		</tr>
		<tr>
			<td>Coplin staining jar</td>
			<td>Thermo Scientific</td>
			<td>19-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissection Pins</td>
			<td>Fisher Scientific</td>
			<td>S13976</td>
			<td></td>
		</tr>
		<tr>
			<td>Dry Ice - pellet</td>
			<td>Fisher Scientific</td>
			<td>NC9584462</td>
			<td></td>
		</tr>
		<tr>
			<td>Embryonic Myosin antibody</td>
			<td>DSHB</td>
			<td>F1.652</td>
			<td>recommended concentration 1:10</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Fisher Scientific</td>
			<td>459836</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>GE Healthcare Life Sciences</td>
			<td>SH30071.01</td>
			<td></td>
		</tr>
		<tr>
			<td>Fiber-Lite MI-150</td>
			<td>Dolan-Jenner</td>
			<td>Mi-150</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>F.S.T</td>
			<td>11295-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-mouse IgG1, Alexa Fluor 488</td>
			<td>Invitrogen</td>
			<td>A-21121</td>
			<td>recommended concentration 1:500</td>
		</tr>
		<tr>
			<td>Goat anti-mouse IgG2b, AlexaFluor 594</td>
			<td>Invitrogen</td>
			<td>A-21145</td>
			<td>recommended concentration 1:500</td>
		</tr>
		<tr>
			<td>Gum tragacanth</td>
			<td>Sigma</td>
			<td>G1128</td>
			<td></td>
		</tr>
		<tr>
			<td>Hams F-10 Medium</td>
			<td>Corning</td>
			<td>10-070-CV</td>
			<td></td>
		</tr>
		<tr>
			<td>Histoacryl Blue Topical Skin Adhesive</td>
			<td>Tissue seal</td>
			<td>TS1050044FP</td>
			<td></td>
		</tr>
		<tr>
			<td>Human specific lamin A/C antibody</td>
			<td>Abcam</td>
			<td>ab40567</td>
			<td>recommended concentration 1:50-1:100</td>
		</tr>
		<tr>
			<td>Human specific spectrin antibody</td>
			<td>Leica Biosystems</td>
			<td>NCLSPEC1</td>
			<td>recommended concentration 1:20-1:100</td>
		</tr>
		<tr>
			<td>Induction Chamber</td>
			<td>VetEquip</td>
			<td>941444</td>
			<td></td>
		</tr>
		<tr>
			<td>Iris Forceps</td>
			<td>F.S.T</td>
			<td>11066-07</td>
			<td></td>
		</tr>
		<tr>
			<td>Irradiated Global 2018 (Uniprim 4100 ppm)</td>
			<td>Envigo</td>
			<td>TD.06596</td>
			<td>Antibiotic rodent diet to protect again respiratory infections</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>MWI Veterinary Supply</td>
			<td>502017</td>
			<td></td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>Kimberly-Clark</td>
			<td>34155</td>
			<td>surgical wipes</td>
		</tr>
		<tr>
			<td>Mapleson E Breathing Circuit</td>
			<td>VetEquip</td>
			<td>921412</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Fisher Scientific</td>
			<td>A412</td>
			<td></td>
		</tr>
		<tr>
			<td>Mobile Anesthesia Machine</td>
			<td>VetEquip</td>
			<td>901805</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse on Mouse Basic Kit</td>
			<td>Vector Laboratories</td>
			<td>BMK-2202</td>
			<td>mouse IgG blocking reagent</td>
		</tr>
		<tr>
			<td>Nail Polish</td>
			<td>Electron Microscopy Sciences</td>
			<td>72180</td>
			<td></td>
		</tr>
		<tr>
			<td>NAIR Hair remover lotion/oil</td>
			<td>Fisher Scientific</td>
			<td>NC0132811</td>
			<td></td>
		</tr>
		<tr>
			<td>NOD-Rag1null IL2rg null (NRG) mice</td>
			<td>The Jackson Laboratory</td>
			<td>007799</td>
			<td>2 to 3 months old</td>
		</tr>
		<tr>
			<td>O.C.T. Compound</td>
			<td>Fisher Scientific</td>
			<td>23-730-571</td>
			<td></td>
		</tr>
		<tr>
			<td>Oxygen</td>
			<td>Airgas</td>
			<td>OX USPEA</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS (phosphate buffered saline) buffer</td>
			<td>Fisher Scientific</td>
			<td>4870500</td>
			<td></td>
		</tr>
		<tr>
			<td>Povidone Iodine Prep Solution</td>
			<td>Dynarex</td>
			<td>1415</td>
			<td></td>
		</tr>
		<tr>
			<td>ProLong&#8482; Gold Antifade Mountant</td>
			<td>Fisher Scientific</td>
			<td>P10144 (no DAPI); P36935 (with DAPI)</td>
			<td></td>
		</tr>
		<tr>
			<td>Puralube Ophthalmic Ointment</td>
			<td>Dechra</td>
			<td>17033-211-38</td>
			<td></td>
		</tr>
		<tr>
			<td>Rimadyl (carprofen) injectable</td>
			<td>Patterson Veterinary</td>
			<td>10000319</td>
			<td>surgical analgesic, administered subcutaneously at a dose of 5mg/kg</td>
		</tr>
		<tr>
			<td>Scalpel Blades - #11</td>
			<td>F.S.T</td>
			<td>10011-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel Handle - #3</td>
			<td>F.S.T</td>
			<td>10003-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereo Microscope</td>
			<td>Accu-scope</td>
			<td>3075</td>
			<td></td>
		</tr>
		<tr>
			<td>Superfrost Plus Microscope Slides</td>
			<td>Fisher Scientific</td>
			<td>12-550-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Suture, Synthetic, Non-Absorbable, 30 inches long, CV-11 needle</td>
			<td>Covidien</td>
			<td>VP-706-X</td>
			<td></td>
		</tr>
		<tr>
			<td>1ml Syringe (26 gauge, 3/8 inch needle)</td>
			<td>BD Biosciences</td>
			<td>329412</td>
			<td></td>
		</tr>
		<tr>
			<td>Trimmer</td>
			<td>Kent Scientific</td>
			<td>CL9990-KIT</td>
			<td></td>
		</tr>
		<tr>
			<td>Vannas Spring Scissors, 8.0 mm cutting edge</td>
			<td>F.S.T</td>
			<td>15009-08</td>
			<td></td>
		</tr>
		<tr>
			<td>VaporGaurd Activated Charcoal Filter</td>
			<td>VetEquip</td>
			<td>931401</td>
			<td></td>
		</tr>
		<tr>
			<td>Wound clips, 9 mm</td>
			<td>F.S.T</td>
			<td>12022-09</td>
			<td></td>
		</tr>
	</tbody>
</table>

performing human skeletal muscle xenografts in immunodeficient mice

Treatment effects observed in animal studies often fail to be recapitulated in clinical trials. While this problem is multifaceted, one reason for this failure is the use of inadequate laboratory models. It is challenging to model complex human diseases in traditional laboratory organisms, but this issue can be circumvented through the study of human xenografts. The surgical method we describe here allows for the creation of human skeletal muscle xenografts, which can be used to model muscle disease and to carry out preclinical therapeutic testing. Under an Institutional Review Board (IRB)-approved protocol, skeletal muscle specimens are acquired from patients and then transplanted into NOD-Rag1null IL2r&gamma;null (NRG) host mice. These mice are ideal hosts for transplantation studies due to their inability to make mature lymphocytes and are thus unable to develop cell-mediated and humoral adaptive immune responses. Host mice are anaesthetized with isoflurane, and the mouse tibialis anterior and extensor digitorum longus muscles are removed. A piece of human muscle is then placed in the empty tibial compartment and sutured to the proximal and distal tendons of the peroneus longus muscle. The xenografted muscle is spontaneously vascularized and innervated by the mouse host, resulting in robustly regenerated human muscle that can serve as a model for preclinical studies.

As demonstrated by Yuanfan Zhang et al., this surgical protocol is a straightforward method to produce human skeletal muscle xenografts8. Regenerated xenografts become spontaneously innervated and display functional contractility. In addition, muscle xenografted from FSHD patients recapitulates changes in gene expression observed in FSHD patients8.
In our experience, approximately 7 out of 8 xenografts performed from control patient specimens wil...

Watch this Scientific Journal Video about Performing Human Skeletal Muscle Xenografts in Immunodeficient Mice at JoVE.com

Performing Human Skeletal Muscle Xenografts in Immunodeficient Mice

Complex human diseases can be challenging to model in traditional laboratory model systems. Here, we describe a surgical approach to model human muscle disease through the transplantation of human skeletal muscle biopsies into immunodeficient mice.

Treatment effects observed in animal studies often fail to be recapitulated in clinical trials. While this problem is multifaceted, one reason for this ...

This protocol is significant because it can be used to create human skeletal muscle xenografts, which can be used to model muscle disease and to carry out preclinical therapeutic testing. This xenograft model allows researchers to study human muscle in vivo to better understand human muscle cell biology and to develop novel models for rare or acquired muscle diseases. After obtaining a human muscle biopsy, place the specimen in a 100-by-15-millimeter Petri dish containing muscle medium, and use a stereo microscope and surgical scissors to remove any remaining fascia or fatty tissue.Dissect the muscle biopsy into approximately seven-by-three-by-three-millimeter pieces, taking care that the fibers are arranged longitudinally within the specimen. Next, transfer the Petri dish containing the dissected muscle on ice, and place synthetic, non-absorbable sutures in a 100-by-15-millimeter Petri dish of 70%ethanol. After confirming a lack of response to toe pinch in an eight-to 12-week-old, anesthetized NOD-Rag-gamma mouse, apply ointment to the immunodeficient animal's eyes, and use a trimmer to remove the hair overlying the tibialis anterior from the ankle to the knee.Then, apply depilatory cream to the exposed skin for one minute before disinfecting the surgical site with povidone-iodine solution and 70%ethanol. To graft the human tissue, first tape down the mouse leg, and make a straight incision over the tibialis anterior originating at the distal tendons and terminating below the knee. Use blunt dissection to separate the skin from the muscle tissue, and use scissors to make a less-than-0.5-millimeter incision through the epimysium of the tibialis anterior muscle, starting at the tendon and ending at the knee.After cutting the distal tendon of the tibialis anterior, grasp the tendon with iris forceps, and pull the muscle up toward the knee. Next, cut the distal tendon of the extensor digitorum longus, and pull the extensor digitorum longus up toward the knee. Once the proximal tendon of the peroneus longus muscle is visible, remove the extensor digitorum longus and the tibialis anterior with the scissors.Use a surgical wipe wet with PBS to apply slight pressure until hemostasis is achieved, and thread a suture through the proximal peroneus longus tendon, leaving an approximately 1.5-inch piece of thread on either side of the tendon. Make the first half of a two-hand surgical square knot without tightening to form a circle, and place a xenograft into the circle, tightening the loop to secure the graft tissue. Complete the other half of the square knot to suture the xenograft to the proximal tendon of the peroneus longus, and thread the suture through the distal peroneus longus tendon to repeat the square knot technique at the distal tendon.When both ends of the graft have been secured, pull the skin over the xenografted muscle, seal the incision with surgical glue, and place two to three surgical staples over the glue. Then, place the mouse in a clean cage on a heated pad with monitoring until full recumbency. Four to six months after the surgery, place a covered beaker containing 200 milliliters of 2-methylbutane in a box of dry ice for at least 30 minutes before the xenograft harvest.When the 2-methylbutane has cooled, confirm a lack of response to toe pinch, and remove the hair overlying the tibialis anterior from the ankle to the knee with a trimmer and depilatory cream. The sutures holding the xenograft in place should be observed through the skin. Secure the leg with tape, and use scissors and iris forceps to open the skin over the xenograft until both sutures are uncovered.Use a scalpel to cut between the xenograft and the tibia to free one side of the xenograft before cutting between the peroneus longus muscle and the gastrocnemius muscle. Cut below the distal suture and through the distal tendon of the peroneus longus, and use the iris forceps to grasp and deflect the suture toward the knee while using scissors to cut the xenograft away from the underlying muscle tissue. Then, use scissors to cut above the proximal suture to remove the xenograft and peroneus longus, and place the harvested specimen on a small piece of cardboard.Pin the tissue as close to the sutures as possible while gently stretching the muscle to ensure that the fiber orientation will be maintained during the snap-freezing process. When the pins are securely in place, slide the muscle up the pins so the tissue rests just above the cardboard, and snap freeze the xenograft in the pre-cooled 2-methylbutane for minus 80-degree Celsius storage. A successful xenograft demonstrates a robust regeneration of human myofibers as identified with human-specific antibodies.Positive embryonic myosin staining within a proportion of myofibers indicates that the regeneration process is still ongoing. In contrast, poor surgical technique or an inadequate specimen may lead to a poor regeneration of the muscle fibers. Xenografts performed from a patient diagnosed with an idiopathic inflammatory myopathy exhibit moderate numbers of regenerated human myofibers at four-and six-month collections, and embryonic myosin staining persists at six months.Inflammatory cells are also present within the xenograft, as observed by H and E staining. Individual myofiber sizes are similar between four and six months in idiopathic inflammatory myopathy xenografts. Rare fibers showing a cross-sectional area greater than 3, 500 micrometers squared are observed within the xenografts but not in the idiopathic inflammatory myopathy biopsies, indicating that some of the myofibers in the xenografts can regenerate to a cross-sectional area similar in size to healthy myofibers.The most important parts of this procedure are identifying all of the tendons in the ankle after the initial incision is made and successfully cutting through the epimysium. The functional competency of the xenografts can be assessed by enzymatically isolating single myofibers and testing calcium transients or by performing evoked forced measurements following electrical stimulation.

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Developmental Biology

Isolation and Quantitative Immunocytochemical Characterization of Primary Myogenic Cells and Fibroblasts from Human Skeletal Muscle

The repair and regeneration of skeletal muscle requires the action of satellite cells, which are the resident muscle stem cells. These can be isolated from human muscle biopsy samples using enzymatic digestion and their myogenic properties studied in culture. Quantitatively, the two main adherent cell types obtained from enzymatic digestion are: (i) the satellite cells (termed myogenic cells or muscle precursor cells), identified initially as CD56+ and later as CD56+/desmin+ cells and (ii) muscle-derived fibroblasts, identified as CD56&#8211; and TE-7+. Fibroblasts proliferate very efficiently in culture and in mixed cell populations these cells may overrun myogenic cells to dominate the culture. The isolation and purification of different cell types from human muscle is thus an important methodological consideration when trying to investigate the innate behavior of either cell type in culture. Here we describe a system of sorting based on the gentle enzymatic digestion of cells using collagenase and dispase followed by magnetic activated cell sorting (MACS) which gives both a high purity (&#62;95% myogenic cells) and good yield (~2.8 x 106 &#177; 8.87 x 105 cells/g tissue after 7 days in vitro) for experiments in culture. This approach is based on incubating the mixed muscle-derived cell population with magnetic microbeads beads conjugated to an antibody against CD56 and then passing cells though a magnetic field. CD56+ cells bound to microbeads are retained by the field whereas CD56&#8211; cells pass unimpeded through the column. Cell suspensions from any stage of the sorting process can be plated and cultured. Following a given intervention, cell morphology, and the expression and localization of proteins including nuclear transcription factors can be quantified using immunofluorescent labeling with specific antibodies and an image processing and analysis package.

The main adherent cell types derived from human muscle are myogenic cells and fibroblasts. Here, cell populations are enriched using magnetic-activated cell sorting based on the CD56 antigen. Subsequent immunolabelling with specific antibodies and use of image analysis techniques allows quantification of cytoplasmic and nuclear characteristics in individual cells.

The repair and regeneration of skeletal muscle requires the action of satellite cells, which are the resident muscle stem cells. These can be isolated ...

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 Isolated Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High throughput Microplate Respiratory Measurements

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of mitochondrial function in this tissue has become more prevalent. Although many technologies and assays exist that measure mitochondrial respiratory pathways in a variety of cells, tissue and species, there is currently a void in the literature in regards to the compilation of these assays using isolated mitochondria from mouse skeletal muscle for use in microplate based technologies. Importantly, the use of microplate based respirometric assays is growing among mitochondrial biologists as it allows for high throughput measurements using minimal quantities of isolated mitochondria. Therefore, a collection of microplate based respirometric assays were developed that are able to assess mechanistic changes/adaptations in oxygen consumption in a commonly used animal model. The methods presented herein provide step-by-step instructions to perform these assays with an optimal amount of mitochondrial protein and reagents, and high precision as evidenced by the minimal variance across the dynamic range of each assay.

The methods presented provide step-by-step instructions for the performance of a collection of microplate based respirometric assays using isolated mitochondria from minimal quantities of mouse skeletal muscle. These assays are able to measure mechanistic changes/adaptations in mitochondrial oxygen consumption in a commonly used animal model.

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of ...

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 ...

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 ...

Isolation, Culture, Characterization, and Differentiation of Human Muscle Progenitor Cells from the Skeletal Muscle Biopsy Procedure

The use of primary human tissue and cells is ideal for the investigation of biological and physiological processes such as the skeletal muscle regenerative process. There are recognized challenges to working with human primary adult stem cells, particularly human muscle progenitor cells (hMPCs) derived from skeletal muscle biopsies, including low cell yield from collected tissue and a large degree of donor heterogeneity of growth and death parameters among cultures. While incorporating heterogeneity into experimental design requires a larger sample size to detect significant effects, it also allows us to identify mechanisms that underlie variability in hMPC&#160;expansion capacity, and thus allows us to better understand heterogeneity in skeletal muscle regeneration. Novel mechanisms that distinguish the expansion capacity of cultures have the potential to lead to the development of therapies to improve skeletal muscle regeneration.

We present techniques for isolating, culturing, characterizing, and differentiating human primary muscle progenitor cells (hMPCs) obtained from skeletal muscle biopsy tissue. hMPCs obtained and characterized through these methods can be used to subsequently address research questions related to human myogenesis and skeletal muscle regeneration.

The use of primary human tissue and cells is ideal for the investigation of biological and physiological processes such as the skeletal muscle ...

Isolation and Differentiation of Primary Myoblasts from Mouse Skeletal Muscle Explants

Primary myoblasts are undifferentiated proliferating precursors of skeletal muscle. They can be cultured and studied as muscle precursors or induced to differentiate into later stages of muscle development. The protocol provided here describes a robust method for the isolation and culture of a highly proliferative population of myoblast cells from young adult mouse skeletal muscle explants. These cells are useful for the study of the metabolic properties of skeletal muscle of different mouse models, as well as in other downstream applications such as transfection with exogenous DNA or transduction with viral expression vectors. The level of differentiation and metabolic profile of these cells depends on the length of exposure, and composition of the media used to induce myoblast differentiation. These methods provide a robust system for the study of mouse muscle cell metabolism ex vivo. Importantly, unlike in vivo models, the methods described here provide a cell population that can be expanded and studied with high levels of reproducibility.

Myoblasts are proliferating precursor cells that differentiate to form polynucleated myotubes and eventually skeletal muscle myofibers. Here, we present a protocol for efficient isolation and culture of primary myoblasts from young adult mouse skeletal muscles. The method enables molecular, genetic, and metabolic studies of muscle cells in culture.

Primary myoblasts are undifferentiated proliferating precursors of skeletal muscle. They can be cultured and studied as muscle precursors or induced to ...