Defining Wound Healing Progression in Cetacean Skin: Characteristics of Full-Thickness Wound Healing in Fraser’s Dolphins (Lagenodelphis hosei)

Abstract

Cetaceans are tight-skinned mammals that exhibit an extraordinary capacity to heal deep soft tissue injuries. However, essential information of large full-thickness wound healing in cetaceans is still lacking. Here, the stages of full-thickness wound healing were characterized 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. We defined five stages of wound healing according to macroscopic and histopathological examinations. Wounds in Stage 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, 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 Stage 4 and 5 were characterized by gradual restoration of the normal skin architecture including rete and dermal ridges, collagen bundles, and adipose tissue. These phenomena were quite different from previous studies in terrestrial tight-skinned mammals, and therefore, further in-depth research into the mechanisms of dolphin wound healing would be needed to gain new insights into veterinary and human regenerative medicine.

Blubber biopsy in common bottlenose dolphins using a novel biopsy puncher: Evaluation of the impact on living individuals and possibility of applications in cetacean research

“…According to (Weller et al, 1997), field studies and necropsy reports of bottlenose dolphins in Texas coastal waters show that wounds caused by cookie cutters and other sharks heal in most instances without consequences. A histological study of cookie‐cutter shark bite wound healing in wild Fraser dolphins ( Lagenodelphis hosei ) also shows that the full‐thickness wounds in dolphins heal completely in a regenerative manner rather than repair (Su et al, 2022). As mentioned above, the impact of the biopsy puncher used in the present study on the individuals was negligible since the wounds caused on the individuals were considerably smaller than those inflicted on wild dolphins, and wound recovery was swift with little physiological disruption.…”

Successful Repigmentation of Full-Thickness Wound Healing in Fraser’s Dolphins (Lagenodelphis hosei)

“…The samples included normal skin and full-thickness wounds caused by cookiecutter shark ( Isistius brasiliensis ) bites. Full-thickness wounds were classified into stage 1 to stage 5, according to a previous study [ 35 ]. The sampling locations in the current study are shown in Figure 1 .…”

“…The traditional wound-healing animal models, such as mice and rats, are loose-skinned mammals, whereas humans, pigs and cetaceans are tight-skinned mammals (reviewed in [ 33 , 34 ]). Our previous study showed that Fraser’s dolphins ( Lagenodelphis hosei ) exhibit incredible healing ability to restore skin architecture and pigmentation after full-thickness wounding [ 35 ]. We suppose that cetaceans may be a novel approach to study wound healing and repigmentation in tight-skinned mammals.…”

“…To date, only one study has described repigmentation during skin wound healing in cetaceans [ 35 ]. The study showed that melanin and melanocytes were present in the migrating epithelial tongue of full-thickness wounds in Fraser’s dolphins, and the healed wounds restored pigmentation similar to surrounding unwounded skin.…”

Cetacean epidermal specialization: A review

“…By day 7, elevated mitotic activity of basal cells restored full epidermal thickness. A unique feature was the absence of a solid fibrin clot or typical scab formation (essential for healing wounds in dry environment); its purpose being served by a transformed barrier layer of epidermal cells (Su et al, 2022). A good histological description of the process of wound healing is provided by Su et al (2022).…”