Electron-microscopic findings of elastic fibers in zebrafish skin

Background: The zebrafish, Danio rerio, is a small bony fish that has genetic information and organ systems similar to those seen in human beings. The zebrafish has many advantages as an experimental animal model. There have been studies of zebrafish skin, especially epidermis, but there have been no studies about the elastic fibers in zebrafish skin. Objective: The purpose of this study was to investigate the age-related, ultrastructural changes seen in the elastic fibers in zebrafish skin using electron microscopy. Methods: We examined zebrafish skin using elastic tissue stains, the results of which were confirmed with polymerase chain reaction. We observed the ultrastructural features and age-related degenerative changes using transmission electron microscopy. Results: Elastic fibers existed as a band-like layer beneath the epidermal basement membrane in zebrafish skin, which consisted of electron-dense homogeneous core material and microfibrils surrounding it and scattered inside. Elastic fibers were prominent and compact at 30 days post-fertilization. However, with aging, they started to develop small cysts and lacunae, and finally became fragmented and cracked. Conclusion: In zebrafish skin, elastic fibers exist beneath the epidermal basement membrane and, similar to human elastic fibers, show morphologic changes with age. Therefore, this study suggests that zebrafish skin may be useful in elastic tissue research.