TAPE STRIPPING INDUCES MARKED EPIDERMAL PROLIFERATION AND ALTERED TGF-ALPHA EXPRESSION IN NON-LESIONAL PSORIATIC SKIN

Psoriasis is a chronic inflammatory disorder characterized by epiderma l hyperproliferation. Although recent evidence suggests that T cell ac tivation is a primary trigger for psoriasis lesions, there may be alte rations in the keratinocyte growth regulatory pathways which induce ep idermal hyperproliferation in psoriatic patients. To test this hypothe sis, we investigated the proliferative activity of epidermal keratinoc ytes 48 h after tape stripping, one of the standard mechanical ways to stimulate the epidermis, in 20 psoriasis patients and in 18 controls. Epidermal cell kinetics were assessed with DNA flow cytometry, the mi totic index, bromodeoxyuridine incorporation, Ki-67 antigen expression and DNA polymerase cc expression. The expression of TGF-alpha and EGF receptors, critical mediators of keratinocyte proliferation, were als o investigated immunohistochemically. The results of multiparameter as says showed that the baseline proliferative activity in uninvolved ski n was the same in psoriasis patients and normal controls. After tape s tripping, although both psoriasis patients and the normal controls sho wed significant increases in epidermal cell proliferation, the values of all the parameters investigated were significantly greater in the p soriasis patients than in the normal controls. EGF receptors were over expressed in basal and suprabasal keratinocytes after tape stripping i n both the psoriasis patients and the normal controls. In contrast, ov erexpression of TGF-alpha was only observed in the patients with psori asis, which may explain their increased proliferative response to trau ma. Copyright (C) 1997 Elsevier Science Ireland Ltd.