Examining Muscle Regeneration in Zebrafish Models of Muscle Disease
Summary
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.
Abstract
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.
Introduction
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 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-α2 (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.
Protocol
Representative Results
Discussion
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…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
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).
Materials
| 24 well plates | Thermo Fischer | 142475 | |
| 30 gauge needles | Terumo | NN-3013R | |
| 90 mm Petri Dishes | Pacific Laboratory Products PT | S9014S20 | |
| DNA extraction chips | wFluidx | ZEG chips | |
| Embryo genotyping platform | wFluidx | ZEG base unit | Zebrafish Embryo Genotyper |
| Glass pipette | Hirschmann | 9260101 | |
| Glass plate dish | WPI | FD35-100 | Commonly referred to as FluoroDish |
| Incubator | Thermoline Scientific | TEI-43L | |
| Plastic pipette | Livingstone | PTP03-01 | |
| Polarizing microscope | Abrio | N/A |
Riferimenti
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