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. 2022 Jun 8;12(12):1482.
doi: 10.3390/ani12121482.

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

Chen-Yi Su  1 , Hao-Ven Wang  2   3 , Michael W Hughes  4   5 , Tzu-Yu Liu  2   4 , Cheng-Ming Chuong  6 , Wei-Cheng Yang  1
Affiliations

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

Chen-Yi Su et al. Animals (Basel). .

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.

Keywords: dolphins; full-thickness wound; melanin; melanocytes; repigmentation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The sampling locations in the current study. ★: normal skin; ○: wounded skin. Blue marks: animal ID TP20190115; green: IL20191105; red: ML20200807; purple: PT20201109.
Figure 2
Figure 2
The distribution of melanin in different skin color samples in Fraser’s dolphins. Fontana–Masson staining. All the images were captured from uninjured skin (yellow frame). Melanin granules were present throughout the epidermis, even in the stratum externum of white skin. Apical accumulation of melanin granules above the keratinocyte nucleus was observed in all skin samples. The last row shows the magnified images from the area of the white dotted frame.
Figure 3
Figure 3
The distribution of melanocytes and melanin in a stage 3 wound collected from dark skin region. (A,B): Immunohistochemical staining with cocktail antibody. Numerous melanocytes were observed in the basal layer of neoepidermis, including leading edge of migrating epithelial tongue. (C,D): Fontana–Masson staining. Abundant melanin granules were distributed throughout the neoepidermis, including the stratum externum of leading edge of migrating epithelial tongue.
Figure 4
Figure 4
The distribution of melanocytes and melanin in a stage 3 wound collected from white skin region. (A,B): Immunohistochemical staining with cocktail antibody. Few melanocytes (arrow) were present in the basal layer of neoepidermis, including leading edge of migrating epithelial tongue. (C,D): Fontana–Masson staining. Scarce melanin granules were distributed throughout the neoepidermis, including the stratum externum of leading edge of migrating epithelial tongue.
Figure 5
Figure 5
Immunofluorescence staining with anti-S100 antibody and cocktail antibody in normal white/gray/dark skin of Fraser’s dolphins. Signals color: red, S100; yellow, cocktail; blue, Hoechst. Scale bars = 20 μm. (A–C): IF staining with anti-S100 antibody. (D–F): IF staining with cocktail antibody. (G–I): Dual staining with anti-S100 and cocktail antibodies.
Figure 6
Figure 6
Fontana–Masson staining and immunohistochemical staining with anti-S100 antibody and cocktail antibody in normal white/gray/dark skin of Fraser’s dolphins. Scale bars = 20 μm. (A–C): Fontana–Masson staining. (D–F): IHC staining with anti-S100 antibody. (G–I): IHC staining with cocktail antibody. Some immunoreactive cells had a round to oval nucleus with clear cytoplasm (arrowhead), while some immunoreactive cells exhibited fusiform or dendritic morphology with long cytoplasmic processes (arrow).
Figure 7
Figure 7
Gross appearance of two full-thickness healed wounds in a Fraser’s dolphin. Site 1 and 5: light-gray unwounded skin; site 2 and 6: gray wounded skin; site 3 and 7: white wounded skin; site 4 and 8: white unwounded skin.
See this image and copyright information in PMC

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