Degenerative processes of elastic fibers in sun-protected and sun-exposed skin: immunoelectron microscopic observation of elastin, fibrillin-1, amyloid P component, lysozyme and alpha1-antitrypsin.

Degenerative processes of elastic fibers in sun-protected and sun-exposed skin were analyzed by light and electron microscopic (post-embedding) immunocytochemistry using antisera to elastin, fibrillin-1, amyloid P component, lysozyme and alpha1-antitrypsin. To assess the effect of aging and sun exposure, biopsy specimens of sun-protected skin (back) and severely and moderately sun-exposed skin (face and forearms) were obtained from a young age group (1-27 years), an adult group (31-56 years) and an old aged group (61-100 years). Elastin and fibrillin-1 were the essential components of elastic fibers; elastin being localized in the electron-lucent matrix and fibrillin-1 in the dense microfibrillar strands. Aging and sun exposure provoked degenerative condensed spots, which represented widened dense microfibrillar strands, in the matrix of altered elastic fibers in the reticular dermis. Amyloid P component was first deposited on the peripheral microfibrils, and then in the intermediate density zone of the spots. Lysozyme was observed in both the electron-dense core and in the intermediate density zone of the spots. Deposition of lysozyme correlated with basophilic degeneration of the elastic fibers. In the severely photodamaged facial skin of the aged, which showed solar elastosis in the upper reticular dermis, fibrillin-1 immunoreactivity was lost from the thickened and vacuolated elastic fibers that lacked condensed spots, and amyloid P component, lysozyme and alpha1-antitrypsin were diffusely deposited in the elastin-positive matrix. It seemed that amyloid P component deposition on the elastic fibers was closely associated with aging, while immunoreactive lysozyme was related to sun exposure. Vertically oriented, thin, elastic (oxytalan) fibers in the papillary dermis tended to decrease with age, with frequent deposition of amyloid P component but no lysozyme. In the facial skin of the aged, dermal papillae disappeared, with the formation of degenerative elastic globules beneath the dermal-epidermal junction. The present study demonstrated an intimate relationship between ultrastructural alterations and deposition of exogenous substances on the degenerative elastic fibers in sun-exposed and/or aged skin.