Modulation of elastin exon 26A mRNA and protein expression in human skin in vivo.

Photoaged skin contains elastotic materials in the upper reticular dermis, a result of a commonly known as solar elastosis. It is known that the primary transcript of elastin undergoes extensive alternative splicing and that this results in the translation of multiple heterogeneous protein isoforms. In this study, we found that UV irradiation and heat treatment increased the levels of elastin transcript containing exon 26A and its encoded elastin isoform in the epidermis of human skin in vivo and in cultured human keratinocytes in vitro. We also found that the elastin transcript containing exon 26A was upregulated in photoaged forearm skin compared with intrinsically aged buttock skin in the same elderly individuals. We observed that topical retinoic acid treatment to human skin did not increase the expression of exon 26A mRNA, but that tropoelastin mRNA expression was increased by this treatment. These findings suggest that the production of the elastin isoform containing exon 26A peptide is increased by UV exposure and heat treatment in human skin in vivo and that it may play an important role in the development of solar elastosis in photoaged human skin.