BACKGROUND: Cutaneous microdialysis in vivo in human skin is demonstrably of use in the study of skin metabolism, percutaneous absorption and skin inflammation. A promising area for cutaneous microdialysis is the measurement of cytokines. This requires catheters equipped with membranes permeable to molecules of high molecular weight. OBJECTIVES: To address technical problems of poor sample volume retrieval and analysis sensitivity in the simplest model of provocation, namely the insertion of the catheter itself in vivo into human dermis. METHODS: Use of a polyethylenesulphone membrane, with a cut-off value of 100,000 Da, allowed measurement of target molecules of large molecular weight. Using an adaptation of a commercially available high sensitivity enzyme-linked immunosorbent assay, the ubiquitous proinflammatory cytokine interleukin (IL)-6 was measured in the normal skin of six healthy volunteers after insertion of the microdialysis catheter. RESULTS: Reliable sample volumes and high analyte recovery were achieved either by push-pull pumping or by standard pumping using a perfusate consisting of Ringers Dextran 60 Braun. No IL-6 was detected in 25 of 26 samples taken during the first 100 min after catheter insertion. The IL-6 concentration then increased and remained elevated for the duration of the experiments. CONCLUSIONS: Technical and analytical modifications in the microdialysis technique have allowed the measurement of IL-6 in vivo in human dermis. It is suggested that the cytokine production is the result of the dermal trauma caused by catheter insertion, but the cellular source of the IL-6 is at present unknown.
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Sjögren et al. (2002) studied this question.