Abstract
Several recent studies have demonstrated that the direct precursor of vitamin D(3), the calcifediol [25(OH)D(3)], through the binding to the nuclear vitamin D receptor (VDR), is able to regulate the expression of many genes involved in several cellular processes. Considering that itself may function as a VDR ligand, although with a lower affinity, respect than the active form of vitamin D, we have assumed that 25(OH)D(3) by binding the VDR could have a vitamin's D(3) activity such as activating non-genomic pathways, and in particular we selected mesenchymal stem cells derived from human adipose tissue (hADMSCs) for the in vitro assessment of the intracellular Ca(2+) mobilization in response to 25(OH)D(3). Our result reveals the ability of 25(OH)D(3) to activate rapid, non-genomic pathways, such as an increase of intracellular Ca(2+) levels, similar to what observed with the biologically active form of vitamin D(3). hADMSCs loaded with Fluo-4 AM exhibited a rapid and sustained increase in intracellular Ca(2+) concentration as a result of exposure to 10(-5) M of 25(OH)D(3). In this work, we show for the first time the in vitro ability of 25(OH)D(3) to induce a rapid increase of intracellular Ca(2+) levels in hADMSCs. These findings represent an important step to better understand the non-genomic effects of vitamin D(3) and its role in endocrine system.