Various experimental approaches have been used in mouse to induce muscle injury with the aim to study muscle regeneration, including
myotoxin injections (
bupivacaine,
cardiotoxin or
notexin), muscle
transplantations (
denervation-devascularization induced regeneration), intensive exercise, but also murine
muscular dystrophy models such as the mdx mouse (for a review of these approaches see). In zebrafish, genetic approaches include mutants that exhibit
muscular dystrophy phenotypes (such as runzel or sapje) and
antisense oligonucleotide morpholinos that block the expression of dystrophy-associated genes. Besides, chemical approaches are also possible, e.g. with
Galanthamine, a chemical compound inhibiting
acetylcholinesterase, thereby resulting in hypercontraction, which eventually leads to
muscular dystrophy. However, genetic and pharmacological approaches generally affect all muscles within an individual, whereas the extent of physically inflicted
injuries are more easily controlled spatially and temporally. Localized physical injury allows the assessment of contralateral muscle as an internal control. Indeed, we recently used
laser-mediated cell ablation to study skeletal muscle regeneration in the zebrafish embryo, while another group recently reported the use of a two-photon
laser (822 nm) to damage very locally the plasma membrane of individual embryonic zebrafish muscle cells. Here, we report a method for using the micropoint
laser (Andor Technology) for skeletal muscle cell injury in the zebrafish embryo. The micropoint
laser is a high energy
laser which is suitable for targeted cell ablation at a wavelength of 435 nm. The
laser is connected to a microscope (in our setup, an optical microscope from Zeiss) in such a way that the microscope can be used at the same time for focusing the
laser light onto the sample and for visualizing the effects of the wounding (brightfield or fluorescence). The parameters for controlling
laser pulses include wavelength, intensity, and number of pulses. Due to its transparency and external embryonic development, the zebrafish embryo is highly amenable for both
laser-induced injury and for studying the subsequent recovery. Between 1 and 2 days post-fertilization, somitic skeletal muscle cells progressively undergo maturation from anterior to posterior due to the progression of somitogenesis from the trunk to the tail. At these stages, embryos spontaneously twitch and initiate swimming. The zebrafish has recently been recognized as an important vertebrate model organism for the study of tissue regeneration, as many types of tissues (cardiac, neuronal, vascular etc.) can be regenerated after injury in the adult zebrafish.