25-Hydroxyvitamin D3 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.