Gene expression profiling of in vivo UVB-irradiated human epidermis

Background: Several recent studies have employed microarray profiling to study UVB‐regulated gene expression in human skin. These studies are all based on UV‐irradiated cultured cells that differ substantially from the intact tissues they are supposed to imitate. The purpose of the present study was to analyze the differential expression of UVB‐regulated genes in intact human epidermis following in vivo UV irradiation. Methods: The forearms of human volunteers were exposed to 4 MED of UVB in vivo, followed by removal of epidermal samples from exposed and non‐exposed areas after 24 h. RNA samples were analyzed using oligonucleotide microarray (Affymetrix) technology analyzing 12 500 genes simultaneously. Verification of selected genes was performed by semi‐quantitative reverse transcriptase polymerase chain reaction. Results: Gene expression patterns clearly distinguished UV‐exposed epidermis from unexposed skin. Classification of these genes into functional categories revealed that several biological processes are globally affected by UVB. Significant changes were seen in more than 800 genes. Conclusion: Human intact epidermis responds to a single low dose of in vivo UVB irradiation by differential regulation of numerous genes. Our results illustrate the power of global gene expression analysis of human epidermis to identify molecular pathways involved in UV‐induced photodamage.