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

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.