Analysis of RNA recovery and gene expression in the epidermis using non-invasive tape stripping.

BACKGROUND The recovery of RNA from the upper epidermis by tape stripping yields variable RNA mass but has not been evaluated for its dependence on anatomical location. Gene expression at different body locations and the origin of RNA recovered by tape stripping have not been investigated. OBJECTIVES To characterize the recovery of RNA from different anatomical locations by tape stripping; to correlate the recovery of RNA and removal of barrier by tape stripping, as assayed by transepidermal water loss; and to investigate gene expression in the upper epidermis at different body locations. METHODS Twelve subjects were tape stripped at 15 body locations. RNA mass was evaluated and gene expression assayed. Subjects were tape stripped 4, 8 and 12 times on the upper back and transepidermal water loss and RNA recovery assayed. RESULTS Ranked by median RNA recovery, the following order was observed: mastoid>forehead>chest>upper back>mid back>cheek>lower back>deltoid>forearm>abdomen>ventral thigh>inner arm>shin>dorsal thigh>lower leg. Expression of the housekeeping gene mRNAs is found to be uniform and reproducible while IL-8 and TNFalpha mRNAs are expressed in different quantities both at different body sites within an individual and between individuals at a specific anatomical site. Data show a significant and high correlation between the number of tapes used to strip a site and transepidermal water loss but no strong correlation between transepidermal water loss and RNA recovery or number of tapes used to strip a site and RNA recovery. CONCLUSIONS Subjects and anatomical location are shown to be significantly different for the ability to recover RNA by tape stripping. We hypothesize that RNA recovered by tape strip is not derived from corneocytes but from cells associated with the stratum corneum.