Connective tissue changes due to long-term ultraviolet exposure : Structural and biochemical studies

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The difference in dermal connective tissue alteration between chronological aging and photoaging using human and animal skin has been disclosed.Materials and Methods. Human skin and animal skin was used. Human skin : sun or UV exposed and protected skin of healthy men(31 young and 32 old)and patients with psoriasis(2 young and one old, treated with PUVA). Animal skin : hairless rats skin(5 UVB(1 MED)exposed for 13 months and 5 control). Ultrasonic skin images were obtained from sun-exposed and protected areas of some healthy men.Skin biopsy specimens were obtained from all men and animals mentioned above, and were processed for light and electron microscopy, and for amino acid analysis for elastic fibers.Results. Ultrasonically, on the images, the dermis was clearly located between white line of the epidermis and underlying fatty tissue. The dermis was thinner in aged persons than young persons, and that of sun-exposed area wag thinner than that of protected area. - One can observe below the white line, a black zone showing a relatively homogeneous, non-echogenic structure in only sun-exposed area of aged persons.Histologically, in sun-exposed, PUVA-treated and UVB exposed skin, multiplication and down ward to the dermis of the basal lamina, irregularly arranged thickened collagen fibers, increased and thickened, various degrees of damaged elastic fibers, and amyloid deposits(in some healthy and PUVA-treated persons)were seen. In protected skin or control rat skin, a layer of basal lamina, regularly arranged, thin collagen fibers, thickened but not damaged elastic fibers, were seen. No amyloid deposits were seen.Analysis of amino acid in elastic fibers showed glutamic and asparatic acid, sreonine, serine, and lysine were higher in sun-exposed skin, while they were lower in protected skin when compared with that in young adults' skin.