In Vitro Non-Genomic Effects of Calcifediol on Human Preosteoblastic Cells.

Several recent studies have demonstrated that the direct precursor of vitamin D, the calcifediol [25(OH)D], 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 by binding the VDR could have a vitamin's D 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 mobilization in response to 25(OH)D. Our result reveals the ability of 25(OH)D to activate rapid, non-genomic pathways, such as an increase of intracellular Ca levels, similar to what observed with the biologically active form of vitamin D. hADMSCs loaded with Fluo-4 AM exhibited a rapid and sustained increase in intracellular Ca concentration as a result of exposure to 10 M of 25(OH)D. In this work, we show for the first time the in vitro ability of 25(OH)D to induce a rapid increase of intracellular Ca levels in hADMSCs. These findings represent an important step to better understand the non-genomic effects of vitamin D and its role in endocrine system.