Mature and Juvenile Tissue Models of Regeneration in Small Fish Species

TLDR: An overview of adult and juvenile tissue regeneration models in small fish species, such as zebrafish and medaka, are given, and recent advances at the molecular level are highlighted.

Abstract: The multitude of cells constituting organisms are fragile and easily damaged day by day. Therefore, maintenance of tissue morphology and function is funda- mental for multicellular organisms to attain long life. For proper maintenance of tissue integrity, organisms must have mechanisms that detect the loss of tissue mass, activate the de novo production of cells, and organize those cells into functional tissues. However, these processes are only poorly understood. Here we give an overview of adult and juvenile tissue regeneration models in small fish species, such as zebrafish and medaka, and highlight recent advances at the molecular level. From these advances, we have come to realize that the epidermal and mesenchymal parts of the regenerating fish fin—that is, the wound epidermis and blastema, respectively—comprise heterogeneous popula- tions of cells with different molecular identities that can be termed "compartments." These compartments and their mu- tual interactions are thought to play important roles in promoting the proper progression of tissue regeneration. We further describe the current understanding of these compart- ments and discuss the possible approaches to affording a better understanding of their roles and interactions during regeneration.