TOPICAL TREATMENT BY UREA REDUCES EPIDERMAL HYPERPROLIFERATION AND INDUCES DIFFERENTIATION IN PSORIASIS

The mechanisms of action of urea-containing ointments in the treatment of eczema, ichthyosis and psoriasis are only partly known and related to proteolysis and keratinolysis, In this study, we have examined the effects of topical urea on epidermal proliferation and differentiatio n in 10 patients with psoriasis, Plaque type lesions were treated for 2 weeks with an ointment containing 10% urea with the vehicle alone, o r left untreated, Clinical score, hydration of the stratum corneum, tr ansepidermal water loss (TEWL), and immunohistochemical studies were p erformed, Epidermal proliferation was assessed using the Ki-S3 prolife ration-associated nuclear antigen. For epidermal differentiation antib odies against involucrin and against keratins CK 5, 6, 17 and CK 1, 5, 10, 14 were used. The patients showed a reduction of the clinical sco re (>50%), a 2-fold increase in stratum corneum hydration (p<0.01), an d a small decrease in TEWL (N.S.) on the urea- treated compared to the untreated site, Light microscopy studies revealed a 29% reduction in epidermal thickness (p<0.01); epidermal proliferation was decreased by 51% (p<0.005), The altered expression of involucrin and of cytokerati ns (reduction of CK 5, 1 and 10 and induction of CK 6 and 17) was part ially reversed, The ointment base also improved psoriasis, but urea wa s significantly better than the vehicle (urea: 40% reduction in epider mal proliferation vs, vehicle), In summary, these studies show that ur ea influences epidermal proliferation and differentiation in psoriasis .