Influence of vitamin D(3) analogues in combination with budesonid R on proliferation of nasal polyp fibroblasts

Vitamin D (VD) and its different analogues, besides their classic role as regulators of calcium and phosphor homeostasis, have emerged as a large family of antiproliferative agents. Such properties suggested VD potential as a therapy for chronic inflammatory diseases, including nasal polyposis (NP). NP growth involves both an inflammatory process and the proliferation of fibroblast as an important factor inducing aberrations in the phenotype of the epithelium. The aim of this study was to investigate the possible influence of 1alpha,25-dihydroxyvitamin D(3) (calcitriol) and 1alpha,24(R)-dihydroxyvitamin D(3) (tacalcitol) in monotherapy and in combination with budesonid R (BR) on NP fibroblast proliferation.

The study involved 26 samples of NP. NP cells were cultured on 96-well plates beginning with a concentration of 5 x 10(3) cells per well with RPMI 1640 medium supplemented with antibiotics and 10% foetal bovine serum. After the fourth to sixth passage the medium was replaced with a nutrient medium with calcitriol or tacalcitol in a defined concentration (from 10(-9) M to 10(-3) M) alone or in combination with BR in 1:1, 1:3 or 3:1 ratios, each at concentrations from 10(-5) M to 10(-3) M.

Growth inhibition of nasal fibroblasts exposed to calcitriol or tacalcitol was noted. Significant antiproliferating activity was observed at calcitriol concentrations of 10(-4) M and 10(-3) M after 48 h, and at a concentration of 10(-3) M after 72 h with the percentage of proliferating cells reduced to 30% compared to the control samples (P < 0.05). In cells treated with tacalcitol the maximal effect was seen at 10(-4) M after 48 h and at 10(-3)M after 72 h with a 60% inhibition with respect to the control (P < 0.05). The inhibition of fibroblast proliferation reached the maximal level when they were exposed to calcitriol: BR (1 : 1) or tacalcitol: BR (1 : 1), each at a concentration of 10(-4) M, after 72 h (82% and 69%, respectively).

The antiproliferative activity of calcitriol and tacalcitol in NP cultures was confirmed. Because of its lower toxicity and higher activity tacalcitol seems to be the more promising agent in NP therapy, both as a single medication and in treatment protocols with BR.