Aquatic Animal Models for Studies in Regenerative Medicine

Regeneration is an interesting and fascinating biological process that can restore organs, tissues, and cells damaged by diseases or traumatic events^1,2,3. After these events, transplantation of the damaged organ is the only salvation for the patients^4,5. Nevertheless, due to the short life of organ donations and the different effects (e.g., pain, infection, bleeding, and blood clots), the regenerative approach could represent a potential alternative to save the lives of these patients. Moreover, over the past decade, several model organisms (e.g., aquatic animals^{6,7,8,9,10,11,12} such as zebrafish, medaka, and xenopus) have been used to study the process of regeneration after an event of traumatic injury. The goal of this collection is to show standardized protocols for organ or tissue injury in aquatic animals, and thus demonstrate the enormous benefits that can be gained by using these model animals in regenerative medicine.

To study brain regeneration, Shimizu et al.¹³ propose an interesting model of brain injury, comparing medaka and zebrafish. The authors described a method using a needle to induce injury in the brain of adult fish for the investigation of the cell fate in the neurogenic stem cell niche. In detail, the authors manually inserted a needle in a specific region of the brain (the optic tectum), and the fish brain was removed and fixed. The brains were sectioned (using cryostat) and these sections were used to detect specific markers (proliferative or differentiative). The approach described by the authors produced the results in two different teleost fishes: medaka and zebrafish.

For spinal cord regeneration, Burris et al.¹⁴ describe an original protocol to evaluate the behavior of zebrafish, both uninjured and after an event of lesion in the spinal cord. The authors observed a significant decrease of swim capacity in fish with a spinal injury. Interestingly, this fish gradually restored swim capacity function at least 2 weeks after the lesion. Contributing to the studies of spinal cord regeneration using the zebrafish model, a protocol from El-Daher et al.¹⁵ made it possible to perform a spinal injury with greater precision. The authors used a laser to induce a specific lesion. This method differed from a manual approach as it allowed an increase in the number of animals and experiments.

As teleost fishes and other aquatic animals can regenerate after a spinal cord injury, Slater et al.¹⁶ describe in detail a protocol to transect the spinal cord in a frog animal model (xenopus). The authors also include steps on how to manage this animal model during surgery, how to provide post-surgery care, and how to perform functional tests. Continuing efforts to dissect the molecular mechanisms governing tissue regeneration, particularly the brain and the spinal cord, in these non-mammalian animal models can help to develop novel strategies for the treatment of several diseases.

The authors have nothing to disclose.

The authors have no acknowledgments.