Analysis of Circadian Clock Gene Expression in Human Skin Explants.

Many aspects of skin biochemistry and physiology are known to vary over the course of the 24-hour day. Traditional approaches to study circadian rhythms in the skin have employed rodents or human subjects, which limit the experimental variables that can be studied. Although explants derived from discarded surgical skin are a commonly used model in the skin biology field, circadian rhythms have yet to be examined ex vivo. In this study, using human panniculectomy skin, we used RT-qPCR to monitor the epidermal expression of 4 core circadian clock genes over the course of 1 day ex vivo. Although significant interindividual variability in overall gene expression profiles was observed, robust circadian oscillations were observed in many of the genes and individual explants. Comparison of our gene expression data with microarray data from 2 previous human-subject studies involving primarily young adult White males revealed both similarities and differences, including greater distribution in the time of day of peak expression in the skin explants. This increased variability appears to be due in part to the increased age and altered sex distribution of the donated skin. Nonetheless, our results indicate that skin explants offer an additional experimental system for studying circadian skin biology.