Cyclin D1, B and A expression and cell turnover in psoriatic skin lesions before and after cyclosporin treatment

Background Cyclosporin induces a dramatic reversal to normality in psoriatic lesions, with a reduction of inflammatory infiltrate and epidermal proliferation. It is known that the cell cycle and cell proliferation are regulated by the sequential activation of cyclin‐dependent kinase/cyclin complexes. Aim We evaluated epidermal cell turnover and thickness, as well as the expression of cyclins D1, B and A in psoriatic skin before and after therapy with cyclosporin. Methods Epidermal thickness, mitotic and apoptotic indices (MI, AI), as well as the percentages of epidermal cell nuclei positive for Ki‐67 and cyclins D1, B and A were calculated. Cytoplasmic positivity to cyclin B was also evaluated. Results After 6 weeks of therapy, we observed a clinical improvement of the disease and normalization of the epidermis. Epidermal thickness and Ki‐67‐, cyclins B‐ and A‐positive nuclei percentage were significantly higher before therapy than after (0·52 ± 0·05 mm vs. 0·21 ± 0·03 mm, P