Reduction of epidermal abnormalities and inflammatory changes in psoriatic plaques during treatment with vitamin D3 analogs.

Vitamin D3 analogs interfere with various aspects of epidermal growth, inflammation, and cellular differentiation. Most data are derived from in vitro studies. In the present review, the in vivo effects of vitamin D3 analogues on the psoriatic plaque are discussed. Calcipotriol, tacalcitol, and calcitriol in ointment modulate aspects of epidermal growth, differentiation, and inflammation. Immunohistochemical studies suggest that the inflammatory changes might be more expressed after treatment with calcitriol and tacalcitol. Flow cytometric quantification of the percentage of cells in SG2M phase and of keratin 10-positive cells revealed that calcipotriol reduced both indices significantly during treatment of psoriatic plaques. Flow cytometric analysis of epidermal cell suspensions using triple labeling for epidermal proliferation, expression of keratin 10, and vimentin permits a quantitative assessment of DNA synthesis selectively in the basal cells of the epidermis, an estimation of the distribution of the basal and suprabasal compartments, and a quantification of the distribution of mesenchymal and nonmesenchymal cells. Using this approach, the interference of tacalcitol with growth control of basal cells was demonstrated. Remarkably, recompartmentalization of basal and suprabasal cells and mesenchymal and nonmesenchymal cells proved to be inconspicuous during this treatment.