Changes in keratin 6 and keratin 10 (co-)expression in lesional and symptomless skin of spreading psoriasis

Background: Keratin 6 (K6) and keratin 10(K10)are markers for epidermal hyp erproliferation and differentiation, respectively, and are both expressed i n the suprabasal layers of the epidermis. They may be co-expressed in diffe rent stages of the spreading psoriatic lesion, but single expression can al so occur. Objective: To investigate to what extent keratinocytes express K6 and K10, and to what extent they co-express K6 and K10 in different stages of the psoriatic lesion. We studied this in spreading psoriatic plaques. M ethods: Three 3-mm punch biopsies were obtained from the inner involved mar gin of a spreading lesion, from the uninvolved skin immediately adjacent to the spreading plaque, and from the distant uninvolved skin of 8 patients w ith incipient psoriasis. From 9 healthy volunteers, 3-mm punch biopsies wer e obtained as controls. After preparation of single cell suspensions of the se biopsies, a triple staining protocol was performed with markers for K6 ( monoclonal antibody LHK6B), K10 (monoclonal antibody RKSE60) and DNA conten t (TO-PRO-3 iodide). Subsequently, cells were measured with a flow cytomete r and the proportion of the markers was calculated using specific software. Results: We observed a population of K6/K10-co-expressing cells, but also populations expressing only K6. These subpopulations varied with the involv ement of the lesion. There was a statistically significant difference betwe en the inner margin and the outer margin with respect to the proportion of K6- and K10-expressing cells, whereas more K6-positive and K10-negative cel ls were detected in the inner margin of the lesions. The proportion of K6/K 10-co-expressing cells in the inner margin was significantly different from the distant uninvolved skin. Conclusion: We confirmed that individual kera tinocytes in psoriasis can express K6 or K10 depending on their localizatio n in involved or uninvolved skin. There is a unique subpopulation of cells in the psoriatic plaques which co-express K6 and K10. More studies are requ ired to fully understand the pathogenic relevance of coexpression and singl e expression of K6 and K10. Copyright (C) 2000 S. Karger AG, Basel.