Non-invasive evaluation of skin cytokines secretion: an innovative complementary method for monitoring skin disorders.

In this review, a novel non-invasive approach based on skin surface wash sampling is described. Since the epidermis possesses a high metabolic activity, the secretion of various biomarkers can be exploited to develop non-invasive procedures for skin measurement to monitor disorders and to define a therapeutic strategy. Thus, we developed a method for the quantification of skin surface compounds. In this procedure, a well is placed on skin surface and is attached using an adhesive pad. Extraction buffer is introduced into the well for 30 min incubation period and the secretion of different biomarkers on skin surface can be measured: cytokines, antioxidants, peptides, RNA, DNA volatile organic compounds etc. Here, the focus is on cytokine measurement. After collecting skin samples cytokines can be quantified using ELISA assay. Since so far cytokine levels in skin have been evaluated mostly by invasive and prolonged procedures (punch biopsy, blister fluid and scrapping), employing this method has important implications, because it allows assessing cytokine amount with minimal invasion and high accuracy. We have already applied skin surface wash sampling for cytokine quantification in different clinical conditions: psoriasis, atopic dermatitis and chronic renal failure. A distinct pattern of cytokine secretion has been demonstrated for each disorder. Differences were also observed between lesional and non-lesional areas. The obtained results shed a new light on cutaneous cytokine expression in different clinical conditions. Moreover, the interplay between cytokines and other soluble compounds can give an added value in understanding the mechanism of skin pathologies.