Apoptosis in established and healing psoriasis

Background: Previous studies have described apoptosis in the stratum granul osum and in the stratum corneum, but not in the germinative compartment in normal skin. In psoriasis, an increased epidermal apoptosis has been observ ed in the differentiated compartment, suggesting that apoptosis has a key r ole in the pathogenesis of psoriasis, as a counteracting factor to the over production of cells. Little is known on apoptosis in the germinative compar tment. Methods: Apoptosis was studied on biopsies of normal skin, established lesi ons of psoriasis and PUVA-treated psoriasis using the transferase-mediated uridine nick end labelling method, which detects fragmented DNA, and electr on microscopy. Counting of apoptotic cells was restricted to the germinativ e compartment as defined by Mib1 staining to evaluate the impact of cell lo ss on cell production and tissue architecture, Results: The apoptotic index was 0.12% in normal epidermis, 0.035% in estab lished psoriasis and 0.31% in regressive psoriasis. Conclusion: These results have three implications: (1) they show the physio logical presence of apoptosis in the germinative compartment in normal epid ermis; (2) they suggest that induction of apoptosis is involved in the regr ession of psoriatic hyperplasia after PUVA therapy; (3) the decrease of phy siological apoptosis in the psoriatic lesion suggests that this phenomenon could play a role in the induction of psoriatic hyperplasia. Copyright (C) 2000 S. Karger AG. Basel.