Expression of elastin-related proteins and matrix metalloproteinases in actinic elastosis of sun-damaged skin

Actinic elastosis is characterized by an accumulation of elastotic material in the upper dermis and is considered to be a manifestation of ultraviolet-induced skin aging. To compare the structural components of the elastotic material in actinic elastosis with those in normal skin, skin specimens were stained with antibodies raised against various elastin-related proteins. Elastotic materials exhibited a strong reaction to the antibodies for elastin, microfibril-associated glycoprotein-1 (MAGP-1), MAGP-4, matrix metalloproteinase 1 (MMP-1), MMP-2 and MMP-3, but a diminished reaction to anti-MMP-9 antibody. Fibroblast cell lines from the upper dermis of affected and unaffected skin were established, and the mRNA levels of MMPs were determined. MMP-1 and -2 mRNA levels were found to be elevated approximately twofold in the fibroblasts from actinic elastosis. Since MMP-1 and -2 are considered to be major enzymes involved in the degradation of matrix components, the accumulation of elastotic materials in actinic elastosis may be related to the degradation process.