A left/right comparison of twice-daily calcipotriol ointment and calcitriol ointment in patients with psoriasis: the effect on keratinocyte subpopulations.

Vitamin D3 analogues are a first-line treatment of chronic plaque psoriasis, but so far, comparative clinical studies on calcipotriol and calcitriol ointment are sparse, and in particular no comparative studies are available on cell biological effects of these compounds in vivo. Using flow cytometric assessment, we investigated whether these compounds had different effects on the composition and DNA synthesis of epidermal cell populations responsible for the psoriatic phenotype. For 8 weeks, 20 patients with psoriasis vulgaris were treated twice daily with calcipotriol and calcitriol ointment in a left/right comparative study. Before and after treatment, clinical assessment of target lesions was performed, together with flow cytometric analysis of epidermal subpopulations with respect to keratin (K) 10, K6, vimentin and DNA distribution. Treatment with each compound resulted in a substantial clinical improvement, a reduction of the K10-K6- population and an increase of the K10+K6- population. A correlation was found between the clinical response of calcipotriol and the K10+K6- population, and the clinical response of calcitriol and the K10+K6- population, as well as the percentage of cells in the S, G2 and M phase of the cell cycle within the K10-K6- population, suggesting that the analogues have a different preference for affecting the K10+K6- pool (committed differentiated cells) or affecting the K10-K6- pool (basal cells).