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The various beneficial effects of moisturizer have been well established. However, it remains still unknown whether daily-used moisturizer can affect the photoaging process over a long period or not. To investigate the effect of long-term use of moisturizer on the skin changes induced by long-term repeated exposure to suberythemal UV radiation, particularly focusing on the skin barrier properties and dermal components. Hairless mice were divided into 4 groups according to the application time of moisturizer and UV exposure status: untreated control, UV exposure only (UV only), application of moisturizer 2 hour before UV irradiation (Before), and application 1 hour after UV radiation (After) group. Each group was irradiated with 30mJ of UVB and 3J of UVA three times weekly for 18 weeks. Transepidermal water loss (TEWL) and stratum corneum(SC) hydration were measured every 6 weeks for evaluation of barrier properties. After 18 weeks of UV irradiation, Epidermal and dermal thickness, density of dermal fibrous components (collagen and elastic fiber) was measured from skin biopsy samples. Also, mRNA expression of matrix metalloprotease-13 and procollagen was quantified by real time reverse transcriptase-polymerase chain reaction. After 18 weeks of experimental period, all UV exposed groups showed increased epidermal thickness and TEWL. The Before group had a lower margin of increase in epidermal thickness and TEWL compared to the UV only and the After group. Dermis thickness and density of the dermal fibrous components in the Before group was similar to the control group, whereas that of the UV only group was most reduced. Also, UV induced reduction of type 1 procollagen and rise of MMP13 expression were alleviated in the Before group. Long-term application of moisturizer before UV exposure may have another beneficial role in the prevention against photo-aging, aside from its protective effect on the skin barrier function.
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