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

SIMPLE SUMMARY: Scarring with abnormal pigmentation is an undesirable consequence of cutaneous wound healing in humans, which may lead to physiological effects as well as psychological distress. Despite extensive research into cutaneous wound healing and repigmentation, the underlying mechanisms remain largely unknown and there is no reliable and effective treatment to date. Our previous study showed that Fraser’s dolphins (Lagenodelphis hosei) have remarkable healing ability to restore skin architecture and pigmentation after full-thickness wounding. In the current study, the association among melanocytes, melanin and skin pigmentation during wound healing in Fraser’s dolphins was investigated. The results showed that the melanocyte density in Fraser’s dolphins was more related to the skin pigmentation than anatomical location and UV exposure, and the timing of melanocyte migration during wound healing in Fraser’s dolphins was different from humans. A better understanding of the mechanisms of successful repigmentation in Fraser’s dolphins will shed light on the development of novel therapies for abnormal pigmentation. ABSTRACT: Fraser’s dolphins (Lagenodelphis hosei) exhibit the capability to restore nearly normal pigmentation after full-thickness wounding. However, the association among melanocytes, melanin and skin pigmentation during wound healing in cetaceans has yet to be addressed. Here, the number of melanocytes and the distribution of melanocytes and melanin in different-colored skin and different wound-healing stages in Fraser’s dolphins were analyzed by using Fontana–Masson staining, immunofluorescence staining and immunohistochemical staining. It was noticed that there was the highest number of melanocytes in dark skin and the lowest number of melanocytes in white skin. The appearance of functional melanocytes and full-melanized neoepidermis was observed in the early stage of wound healing in Fraser’s dolphins. Furthermore, the melanocyte number and skin pigmentation and pattern in healed wounds recovered to a similar condition of unwounded skin. This study provides fundamental knowledge of skin repigmentation in cetaceans for further research, and it will be warranted to elucidate the mechanisms of the replenishment of melanocytes and the regulation of melanocyte activity that contribute to the successful repigmentation in cetacean skin wounds.