Comparison of two porcine (Sus scrofa domestica) skin models for in vivo near-infrared laser exposure

Abstract

Background and purpose: The current safety standards for lasers operating in the 1,400- to 2,000-nanometer (nm) wavelength region are based on only a few observations at specific wavelengths. On the basis of experimental results conducted with Yorkshire pigs (Sus scrofa domestica), these standards may not accurately reflect the potential for laser injury when humans are exposed to these wavelengths. It is our belief that one of the damage mechanisms involved in these laser injuries results from energy absorption by skin pigmentation (melanin), and a more highly pigmented animal model, the Yucatan hairless minipig, may be a more suitable subject for laser exposure studies.

Methods: Skin specimens were collected from Yorkshire pigs and Yucatan minipigs for histologic examination, and the thickness of the epidermis was measured. Epidermal thickness of human skin also was determined, and a qualitative assessment of the melanin content in the epidermal layers was conducted.

Results: Mean +/- SD thicknesses of the Yucatan minipig flank and dorsal neck epidermis were 68 +/- 34 and 68 +/- 25 microm, respectively. Thicknesses of the Yucatan minipig skin were closely comparable to the thicknesses of human epidermis from the face (68 +/- 26 microm), neck (65 +/- 24 microm) and arms (68 +/- 21 microm). The Yorkshire pig lacks substantial melanin in the epidermis, whereas the skin of the Yucatan minipig is more similar to that of humans.

Conclusion: On the basis of epidermal skin thickness measurements and melanin assessment, the flank and dorsal neck of the Yucatan minipig are better suited to laser injury studies than are the Yorkshire pig models of human skin.