The effect of circadian rhythm on gene expression in human skin III

Skin is the largest organ in the body and serves important barrier, regulatory, and sensory functions. Like other tissues, skin is subject to temporal fluctuations in physiological responses under both homeostatic and stressed states. To gain insight into these fluctuations, we investigated the role of the circadian clock in the transcriptional regulation of skin The purpose of this study was to gain insight into the evolutionarily-conserved rhythmic patterns of the circadian transcriptome in human skin and how it relates to published transcriptomes from other human tissues. Twenty healthy male subjects aged 21-49 years (median age = 24.5 years) were enrolled in an overnight, time-ordered study. Four 2mm punch biopsies from the forearm were collected from each subject over the course of 24 hours (12pm, 6pm, 12am, and 6am the following day). In a separate unordered study, punch biopsies were taken from the face (cheek), forearm, and buttocks from approximately 150 females between 20-80 years old to 1) determine circadian phase, and 2) compare circadian phase across body sites. All samples were processed for RNA extraction and hybridized on the Affymetrix U219 GeneTitan array. Laser capure microdissection was performed to isolate the epidermal compartments for subsequent gene expression profiling.