THE EFFECT OF LONG-TERM TREATMENT WITH TACALCITOL OIL THE PSORIATIC EPIDERMIS - A FLOW CYTOMETRIC ANALYSIS

During the last decade, novel analogues of 1 alpha,25-dihydroxy vitami n D-3 have been developed for the treatment of psoriasis. Recently, th e efficacy of short-term treatment with the novel derivative tacalcito l (1 alpha,24-dihydroxy vitamin D-3) has been documented. However data on the long-term effect of tacalcitol on psoriatic skin are sparse, I n this study, we assessed the cell characteristics of the psoriatic ep idermis after treatment with tacalcitol for up to 24 weeks. We in inve stigated how long-term treatment with tacalcitol modulates the percent ages of differentiated keratinocytes, inflammation cells and basal ker atinocytes, and the percentage of cells in the SG(2)M phase in the bas al cell population, From 11 patients who were treated with tacalcitol for up to IX months, we obtained single-cell suspensions of a represen tative psoriatic lesion after 0, 8, 12, 18 and 24 weeks of treatment. A Psoriasis Area and Severity Index was performed at each visit as wel l. Cell suspensions were stained with markers for inflammation (Vim3B4 ), differentiation (RKSE60) and proliferation (TO-PRO-3 iodide) and an alysed flow cytometrically Clinically patients improved significantly after 8 weeks of treatment. This clinical effect was: preserved for th e rest of the period of treatment with no further significant improvem ent. Proliferative activity also decreased significantly after 8 weeks of treatment. Proliferation did not show further significant decrease s or habituation after 12, 18 and 24 weeks. For inflammation, no stati stically reliable trends could be seen, Differentiation improved signi ficantly after 8 weeks of treatment, but decreased again significantly after 12 weeks, In the period from 12 to 24 weeks, no further signifi cant change was observed. We conclude that tacalcitol is an effective antipsoriatic drug. Prolonged treatment with tacalcitol will generally maintain improvement at the level reached after 8 weeks. Owing to the beneficial effect on both clinical state and proliferation. tacalcito l is likely to be an adequate maintenance therapy.