The Effects of Topical Alpha-hydroxyacids on the Normal Skin Barrier of Hairless Mice

Background: alpha-hydroxyacids (AHA), such as glycolic acid and lactic acid, have recently been used in cosmetic and dermatological formulations. However, the mechanisms of action of these substances have not been well documented.

Objectives: This study was done to investigate the effects of AHA on the skin barrier of hairless mice and to clarify the contribution of AHA to the formation and secretion of the lamellar bodies (LB), which are known to be the critical structure for barrier function in the epidermis.

Methods: 5% Lactic acid and 5% glycolic acid were applied to normal skin of the mice daily for 14 days.

Results: Changes in transepidermal water loss (TEWL), capacitance and electron microscopic findings of the epidermis of hairless mice were compared with those in which only the vehicle was applied.

Conclusions: There were no significant differences in TEWL, capacitance or epidermal thickness between the epidermis of the mice to which AHA or vehicle only had been applied. On electron micrographs, the normal epidermis to which AHA had been applied showed an increase in the number and secretion of LB and a decrease in the number of stratum corneum (SC) layers in comparison with the epidermis to which the vehicle only had been applied. The lipid layers of the SC intercellular spaces and calcium gradient in both the epidermis with application of AHA and that with vehicle only were normal. These results suggest that AHA, in low concentration (5%), may improve the skin barrier in hairless mice by inducing enhanced desquamation, and by increasing the number and secretion of LB without increasing TEWL.