Monitoring Hyperproliferative Disorders in Human Skin: Flow Cytometry of Changing Cytokeratin Expression

Abstract

Background: Monitoring dynamics of different cell populations in solid tissues using flow cytometry has several limitations. The interaction and changes in epidermal subpopulations in hyperproliferative skin disorders such as psoriasis, a very common chronic inflammatory skin disease, may, however, elucidate the role of different cell populations in the pathogenesis and the effect of therapy in these disorders. We describe a new, simple method for identifying and quantifying different epidermal subpopulations in hyperproliferative skin disorders and in vivo model for epidermal hyperproliferation by using six-parameter assessment and three-color flow cytometry. Methods: Epidermal single-cell suspensions were derived from normal human skin before and after standardized injury and from untreated and treated psoriatic lesions. Samples were stained with anti-cytokeratins 6 (K6) and 10 (K10), anti-vimentin, and 4′,6-diamidino-2-phenylindole. With three-color flow cytometry, different epidermal subpopulations were further defined by six different parameters. Results: Correlations were found for mild psoriasis and K1O+K6- cells and for moderate psoriasis and K1O -K6+ cells. Treatment of mild psoriasis resulted in a 70% increase of the K10+K6- cells and an 18% decrease of the K10-K6- cells, whereas treatment of more severe psoriasis resulted in a 77% increase of the K10+K6- cells and a 33% decrease of the K10-K6+ cells. The tape-stripping model showed changes in suprabasal keratin expression before proliferative activity. Conclusions: The present flow cytometric assay permits simultaneous quantification of epidermal differentiation, inflammation, proliferafion, and hyperproliferation-associated keratinization and provides information on pathogenesis and therapy of hyperproliferative skin disorders. © 2003 Wiley-Liss, Inc.