Abstract

In field observation, cetaceans exhibit an extraordinary capacity to heal deep soft tissue injuries. However, little is known about the underlying mechanisms, and there is no histological study on full-thickness wound healing in cetaceans. The current study characterizes the macroscopic and histological features of full-thickness wound healing in Fraser’s dolphins (Lagenodelphis hosei). The skin samples were collected from normal skin and full-thickness cookiecutter shark (Isistius brasiliensis)-bite wounds of stranded carcasses. According to visual observation and histopathological examinations, we defined five stages of wound healing progress: stage 1, new wound; stage 2, initially healing wound without granulation tissue; stage 3, healing wound with granulation; stage 4, healed wound with cellular and vascular blubber; stage 5, healed wound with less cellular and vascular blubber. Wounds in stages 1 and 2 were characterized by intercellular and intracellular edema in the epidermal cells near the wound edge, mixed inflammatory cell infiltration, and degradation of collagen fibers. In stage 3 wounds, functional melanocytes, melanin granules, rete, and dermal ridges were noticed in the neo-epidermis, and the adipose tissue in adjacent blubber was replaced by cells and fibers. Wounds in stages 4 and 5 were characterized by gradual restoration of the normal skin architecture including rete and dermal ridges, collagen bundles, and adipose tissue. Moreover, the melanocyte number and skin pigmentation and pattern in healed wounds recovered to a condition similar to adjacent unwounded skin. The current study showed that Fraser’s dolphins can successfully restore skin architecture and pigmentation after full-thickness wounding. It indicates that the full-thickness wounds in cetaceans heal in a regenerative manner rather than repair. Further studies to elucidate the mechanisms of full-thickness wound healing in cetaceans may shed light on veterinary and human regenerative medicine, leading to novel therapies.

Acknowledgements

We would like to thank the Marine Biology and Cetacean Research Center in National Cheng Kung University and Taiwan Cetacean Society for assistance with sample collection. All animal procedures were conducted with the approval of the Ocean Conservation Administration, Taiwan (Permit #1090002352).

*Presenting author
+Student presenter

Literature Cited

1.  Su CY, Hughes MW, Liu TY, Chuong CM, Wang HV, Yang WC. Defining wound healing progression in cetacean skin: characteristics of full-thickness wound healing in Fraser’s dolphins (Lagenodelphis hosei). Animals. 2022;12.5:537.

2.  Su CY, Wang HV, Hughes MW, Liu TY, Chuong CM, Yang WC. Successful repigmentation of full-thickness wound healing in Fraser’s dolphins (Lagenodelphis hosei). Animals. 2022;12.12:1482.