25-Hydroxyvitamin D(3) induces osteogenic differentiation of human mesenchymal stem cells

25-Hydroxyvitamin D(3) [25(OH)D(3)] has recently been found to be an active hormone. Its biological actions are demonstrated in various cell types. 25(OH)D(3) deficiency results in failure in bone formation and skeletal deformation. Here, we investigated the effect of 25(OH)D(3) on osteogenic differentiation of human mesenchymal stem cells (hMSCs). We also studied the effect of 1α,25-dihydroxyvitamin D(3) [1α,25-(OH)(2)D(3)], a metabolite of 25(OH)D(3). One of the vitamin D responsive genes, 25(OH)D(3)-24-hydroxylase (cytochrome P450 family 24 subfamily A member 1) mRNA expression is up-regulated by 25(OH)D(3) at 250–500 nM and by 1α,25-(OH)(2)D(3) at 1–10 nM. 25(OH)D(3) and 1α,25-(OH)(2)D(3) at a time-dependent manner alter cell morphology towards osteoblast-associated characteristics. The osteogenic markers, alkaline phosphatase, secreted phosphoprotein 1 (osteopontin), and bone gamma-carboxyglutamate protein (osteocalcin) are increased by 25(OH)D(3) and 1α,25-(OH)(2)D(3) in a dose-dependent manner. Finally, mineralisation is significantly increased by 25(OH)D(3) but not by 1α,25-(OH)(2)D(3). Moreover, we found that hMSCs express very low level of 25(OH)D(3)-1α-hydroxylase (cytochrome P450 family 27 subfamily B member 1), and there is no detectable 1α,25-(OH)(2)D(3) product. Taken together, our findings provide evidence that 25(OH)D(3) at 250–500 nM can induce osteogenic differentiation and that 25(OH)D(3) has great potential for cell-based bone tissue engineering.