RECRUITMENT OF CYCLING EPIDERMAL-CELLS AND EXPRESSION OF FILAGGRIN, INVOLUCRIN AND TENASCIN IN THE MARGIN OF THE ACTIVE PSORIATIC PLAQUE, IN THE UNINVOLVED SKIN OF PSORIATIC PATIENTS AND IN THE NORMAL HEALTHY SKIN

The peripheral changes in the uninvolved skin adjacent to the extendin g psoriatic lesions may represent early events. The sequence of these events remains controversial. In the present study we evaluated epider mal and dermal aspects of the margin of the progressive psoriatic plaq ue, the distant uninvolved skin and normal healthy skin, using immunoh istochemistry with markers for keratinization, proliferation and conne ctive tissue: filaggrin, involucrin, Ki-67 and tenascin. The results s howed that: (i) processes in distant uninvolved skin were comparable w ith the observations in normal skin; (ii) in the margin zone of the sp reading psoriatic lesion, following the increased appearance of tenasc in, the transition into parakeratosis, abnormal expression of filaggri n, involucrin and recruitment of cycling epidermal cells, happened sim ultaneously. The simultaneous normalization of these epidermal process es might be a consequence of a signal which is simultaneously transduc ed to the basal and suprabasal cell layers of the epidermis. Based on the present results and earlier findings, we would like to propose a t riple stage model for the development of the psoriatic lesion: Stage 1 , involvement of the stroma; stage II, inflammatory infiltrate formati on and penetration into the upper layers of the epidermis, with suprab asal expression of keratin 16; stage III, recruitment of cycling epide rmal cells and abnormal terminal differentiation. Further studies are required on the regulation of tenascin expression, focusing on factors derived from the stroma affecting both recruitment of cycling epiderm al cells, involucrin and filaggrin expression. An intermediate step in the dermo-epithelial interrelation is the inflammatory infiltrate, pe netrating into the most superficial zone of the epidermis, and the sup rabasal expression of keratin 16. (C) 1997 Elsevier Science Ireland Lt d.