Comparative inhibitory effects of vitamin D₃ and an analogue on normal and psoriatic epidermis in organ culture

Abstract Recently, there have been many vitamin D₃ analogues synthesized and tried in the treatment of psoriasis. In the experiments reported here we observed and compared their effects on normal and psoriatic epidermis in organ culture in vitro. We employed a new vitamin D₃ analogue, 22-oxa-calcitriol (OCT), the effect of which was compared with that of calcitriol (1,25-D₃). Both caused suppression of proliferation of normal and psoriatic epidermis, dependent upon concentration and culture time. Histologically, in the presence of the agents, degeneration started from the top of the epidermis downwards. This is the first report of cell degeneration as a direct effect of vitamin D. The nature of the degeneration was evaluated by electron microscopy (EM) and by the in situ nick end labeling technique (TUNEL), and these studies revealed that the degeneration involved necrosis rather than apoptosis. This in vitro method may be useful to assess the effectiveness of newly synthesized vitamin D₃ analogues in the treatment of psoriasis

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