We studied the effect of bone morphogenetic protein-2 (BMP-2) and vitamin D-3 on the osteogenic differentiation of adipose stem cells (ASCs). ASCs were treated with 10, 50, and 100 ng/ml of BMP-2, and 10(-8), 10(-7), 10(-6) M vitamin D-3. Then, to investigate the effects of combined treatment, ASCs were treated with BMP-2 and vitamin D-3 dose-dependently and time-dependently. The osteogenic differentiation was assessed by alkaline phosphatase (ALP) activities/staining and the mineralization was evaluated by Alizarin red S staining. ALP activity and mineralization dose-dependently increased in early stages (ALP on 7th day and mineralization on the 14th day) while all three doses of BMP-2 or vitamin D-3 showed comparable effects in late stages (ALP on the 14th day and mineralization on the 21st day) in ASCs. BMP-2 and vitamin D-3 had synergistic effect on the osteogenic differentiation of ASCs. While all three doses of BMP-2 acted similarly in reinforcing the effect of vitamin D-3, vitamin D-3 dose-dependently augmented the osteogenic effect of BMP-2. When BMP-2 was constantly treated, vitamin D-3 effect did not differ depending on the period of vitamin D-3 treatment. However, when vitamin D-3 was constantly treated, the BMP was more effective when treated for the last 7 days than when treated for the first 7 days. In conclusion, BMP-2 and vitamin D-3 promote osteogenic differentiation of ASCs, and can work synergistically. These results can be used to induce effective and economical osteogenic induction of ASCs for bone tissue engineering. (C) 2011 Elsevier Inc. All rights reserved.