The aging process can be divided into two components: intrinsic aging and photoaging. Intrinsic aging refers to those skin changes that occur as a result of largely unknown endogenous factors and genetically programmed senescence. Photoaging refers to those skin changes superimposed on intrinsic aging by chronic sun exposure. Most human studies have focused on photodamaged skin. Little information is available on the effects of tretinoin on intrinsically aged human skin. Our purpose was to know the differences of structural changes and collagen gene expression between exposed and non exposed human skin. So, we did skin biopsy on exposed skin and non exposed skin of 4 elderly peoples from 40 to 83 years of age. And then, we did light microscopic examination on H&E, Masson’s trichrome and elastic stain, and electron microscope examination for ultrastructural changes. After starting fibroblast culture with DMEM under several concentrations of all-trans retinoic acid, we cultured fibroblasts again under 10^(-5)M of all-trans retinoic acid for 8, 12, 24, and 48 hours. After isolation of total RNA from the cultured fibroblasts, northern blotting with collagen type α2(Ⅰ), collagen α1(Ⅲ) probe was performed.
The results were as follows;
1. On histologic findings of exposed skins, we could see thin epidermis, flattened dermoepidermal interface, well developed papillary grenz zone and increased dermal elastotic material and mucin deposition.
2. On histologic findings of non exposed skins, we could see relatively thick epidermis, and dermal rete, but could not see subepidermal grenz zone, elastotic material and mucin deposition.
3. Electron microscopic findings of exposed skins showed heterogeneity of epidermal cells and large bundles of collagen in papillary dermis.
4. The collagen gene expressions from exposed skin fibroblasts were slightly increased from 10^(-5)M concentration of all-trans retinoic acid but the collagen gene expression from nonexposed skin fibroblasts were increased from 10^(-7)M concentration of all-trans retinoic acid.
5. In the time course observation, collagen gene expressions of exposed skin fibroblasts were peak at 12 hours. On the contrary, they were increased at 12 hours and peak at 24hours in nonexposed skin fibroblsats. And collagen gene expressions of exposed skin fibroblasts were stronger than those one of nonexposed.
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