The structural characteristics of photoageing in mice caused by the effects of ultraviolet A radiation

Abstract

Background: Due to its deep penetration into the dermis, ultraviolet A (UVA) radiation is considered a primary factor in skin photoageing. The aim of this study is to use a qualitative and quantitative analysis to determine the structural parameters of skin photoageing in mice exposed to UVA radiation, with or without the application of a photoprotective cream. Materials and methods: The experiment consisted of the radiation of female BALBc mice in a solarium by UVA rays, up to total dosages of 7800 J/cm 2 and 12500 J/cm 2 . A total of 78 animals were divided into four experimental and two control groups. All animals were shaved and the animals in two experimental groups were treated with a photoprotective cream half an hour before exposure. The samples of the treated skin were stained with haematoxylin-eosin and Van-Gieson staining methods. All measurements, except for the presence of dyskeratosis, were taken using ImageJ 150i software. Results: In the study, the signs of skin photoageing were more evident in untreated groups of animals. Dyskeratosis was more frequent in both of the untreated groups of animals (p = 0.004 and p = 0.003). The lowest values of epidermal thickness (13.8 ± 2.6 μm and 12.7 ± 2.3 μm) were present in both of the untreated groups of animals (p < 0.001 and p < 0.001). The highest values of stratum corneum thickness (34.3 ± 8.5 μm) were observed in the untreated, shorter radiated group of animals (p < 0.001) which was irradiated for the shortest period of time. Beside the control groups, the highest length of dermo-epidermal junction was recorded in the group of treated, longer radiated animals (1467.6 ± 94.6 μm; p = 0.373). The lowest values of dermal thickness (115.9 ± 10.5 μm and 134.8 ± 21.8 μm) and volumetric density of the collagen fibres (31.92 ± 3.19% and 29.40 ± 4.54%) were present in both untreated groups of animals (p < 0.001, p < 0.001, p = 0.035). Conclusions: Skin photoageing was most pronounced in the groups of animals irradiated without the application of photoprotective cream.

The dark side of daylight: photoaging and the tumor microenvironment in melanoma progression

“…The integrity of this structural network decreases during both chronological aging and photoaging, as evidenced by the increased occurrence of skin wrinkling in both cases. Intrinsic aging and photoaging induce collagen fragmentation (98-100) and reductions in collagen density (101)(102)(103), as well as reduction of turnover of the collagen cross-linking proteins fibulin, fibrillin, elastin (104)(105)(106)(107)(108)(109)(110), and HA (111)(112)(113)(114). Although similarities exist in the types of alterations that occur with intrinsic and UVR-mediated extrinsic aging, there are visible differences between chronologically aged and photoaged skin.…”