Synergistic effect of recombinant human bone morphogenic protein-7 and osteogenic differentiation medium on human bone-marrow-derived mesenchymal stem cells in vitro

The purpose of this study was to investigate the effect of recombinant human bone morphogenetic protein-7 (rhBMP-7) with or without osteogenic differentiation medium (ODM) on osteogenic differentiation of primary human bone-marrow-derived mesenchymal stem cells (hBMSCs) in vitro. The hBMSCs were isolated from medullary reaming tissue. At 80% confluence, hBMSCs were treated with different concentrations of rhBMP-7 with and without ODM. Alkaline phosphatase (ALP) activity, calcium deposition and messenger RNA (mRNA) expression of osteocalcin (OC) and osteopontin (OPN) were examined. ALP activity and calcium deposits in hBMSC culture were significantly increased by rhBMP-7 at 0.1 mu g/ml (0.23 +/- 0.07 IU and 28.9 +/- 4.2 mg/dl) and 1.0 mu g/ml (0.32 +/- 0.03 IU and 38.7 +/- 3.0 mg/dl), respectively, in the presence of ODM, showing a clearly dose-dependent osteoblastic differentiation. However, the same dose of 0.1 mu g/ml rhBMP-7 without ODM and ODM alone induced low level of ALP and calcium deposits, indicating a synergistic effect of rhBMP-7 and ODM on committed osteogenic differentiation. Quantitative real-time reverse-transcriptase polymerase chain reaction (RT-PCR) analysis showed up-regulated OC and OPN mRNA levels, corroborating the synergistic effect of rhBMP-7 and ODM. Our study showed that rhBMP-7 with ODM created a synergistic effect on up-regulation of osteogenic genes as well as osteogenic differentiation of primary hBMSCs in vitro. In the presence of ODM, the lowest concentration of rhBMP-7 needed to induce significant osteogenic differentiation of hBMSCs was 0.1 mu g/ml.