An animal model for assessing the effects of chemical peels on photoaged skin

Abstract

The treatment of photoaged human skin by chemical peeling has become increasingly popular in recent decades. Controlled studies with facial biopsies to assess histologic effects are understandably limited. Animal studies have been on normal rather than ultraviolet-exposed skin. The aim of this study, with the extensively studied photoaged hairless mouse model, was to examine commonly used peeling agents at concentrations used by dermatologists. Mice (six per group) were UVB-irradiated for 10 weeks to mildly photodam-age the skin. A central dorsal strip of skin was then treated at 0, 2, 4, 6 and 8 weeks after irradiation with one of the following: glycolic acid (50% and 70% in water, alcohol and propylene glycol); salicylic acid (20% and 30% in ethanol and water); trichloracetic acid (25% in water). A sixth group of mice was topically untreated. The peeled area was excised at week 10 after irradiation, processed for light microscopy and stained as follows: hematoxylin and eosin for general morphology, Luna's aldehyde fuchsin for elastic fibers and Masson's tri-chrome for collagen. Salicylic acid at both concentrations produced mild to moderate inflammation, uniform epidermal hyperplasia, focal deposits of new subepidermal collagen and no increase in elastic fibers. Glycolic acid at 50% was slightly more irritating, epidermal hyperplasia was more variable and subepidermal deposits of new collagen were less obvious due to the frequent presence of dense mats of fine elastic fibers. Glycolic acid at 70% and 25% trichloracetic acid thickened the skin with severe fibrosis within which was entrapped elastosis.

Key Words:

• Chemical peels
• Photoaging
• Animal model