Miniature pig as an animal model to study photoaging.

Seven miniature pigs were irradiated thrice weekly over a 14 months period with suberythematogenic doses of UVB and UVA. Another seven were not exposed, to record innate aging changes. Chronic irradiation induced the following changes: 1. Increased scaling, with thickening of the stratum corneum and decreased reactivity to acetic acid. 2. Increased minimum erythema dose, corresponding to decreased transmission of UV-radiation through isolated epidermis. 3. Increased elastic fibers, accompanied by strong deposition of glycosaminoglycans in the upper dermis. 4. Increased laxity with greater extensibility to a deforming torque. 5. Increased density of vessels. 6. More disorderly arrangement of collagen bundles with minor alterations in collagen biochemistry. These changes mimic those in photoaged human skin but are milder in degree, attributable to the low total dosage of ultraviolet radiation.