title: 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 an 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 K10(+)K6(-) cells and for moderate psoriasis and K10(-)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, proliferation, and hyperproliferation-associated keratinization and provides information on pathogenesis and therapy of hyperproliferative skin disorders.
authors.affiliation: Department of Dermatology, University Medical Center Nijmegen, The Netherlands. m.frassen@derma.umcn.nl
authors.forename: M E J
authors.initials: ME
authors.lastname: Franssen
authors.forename: J B M
authors.initials: JB
authors.lastname: Boezeman
authors.forename: P C M
authors.initials: PC
authors.lastname: Van De Kerkhof
authors.forename: P E J
authors.initials: PE
authors.lastname: Van Erp
mesh_terms: D000906:Antibodies; D001706:Biopsy; D002455:Cell Division; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D007633:Keratins / Q000378:metabolism*; D011565:Psoriasis / Q000473:pathology*; D012016:Reference Values; D012044:Regression Analysis; D012867:Skin / Q000473:pathology*
chemical_list: D000906:Antibodies; D007633:Keratins