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 < 0·001; 19 vs. 2·6, 19 vs. 3, and 12 vs. 1, respectively; P < 0·0005); cytoplasmic positivity to cyclin B was slightly higher before therapy (score 3 vs. 2–3). Cyclin D1 was negative or expressed in a low percentage of nuclei in psoriasis before therapy (0·78), whereas it was always negative after therapy. MI was 0·15 before therapy, whereas mitoses were almost absent afterwards. Apoptoses were undetectable before therapy, whereas a few apoptoses were observed after treatment (AI = 0·4).
Conclusions Overexpression of cyclins B and A, rather than D1 seems to characterize psoriasis. Their evaluation could provide further insights in understanding the development of this disorder and could be used to verify the efficacy of currently used therapies as well as future ones.