Differentiation-dependent up-regulation of BMP-2, TGF-β1, and VEGF expression by FGF-2 in human bone marrow stromal cells

Background: Bone tissue formation by bone marrow stromal cells I nay be supported and enhanced by multiple growth factors, particularly in cases of a compromised local microenvironment. In this study, the authors hypothesized that fibroblast growth factor (FGF)-2 can stimulate the production by human bone marrow stromal cells of osteogenic [i.e., bone morphogenetic protein (BMP)-2 and transforming growth factor (TGF)-beta 1] and angiogenic [i.e., vascular endothelial growth factor (VEGF)] factors. Methods: Human bone marrow stromal cells from six donors were expanded for two passages (expansion phase) and subsequently cultivated in osteogenic medium containing ascorbic acid,)beta-glycerophosphate, and dexamcthasonc (differentiation phase). After each phase, cells were transferred into serum-free medium with or without FGF-2 at different concentrations and for different times, and die expression of BMP-2, TGF-beta 1, and VEGF was quantified at the mRNA level by real-time quantitative reversetranscriptase polymerase chain reaction. The amounts of TGF-beta 1 and VEGF released in the culture medium were assessed using enzyme-linked immunosorbent assay kits and normalized to the DNA content. Results: In response to 5 ng/ml FGF-2 for24 hours, the mRNA expression of VEGF increased at both culture phases (up to 6.1fold), whereas that of BMP-2 and TGF-P1 significantly increased only after the expansion (3.1-fold) or differentiation phase (2.1-fold), respectively. Similar trends were observed in the amounts of proteins measured in the culture medium. Conclusions: The authors' results indicate that FGF-2 up-regulates the expression of BMP-2, TGF-beta 1, and VEGF in human bone marrow stromal cells, in a pattern dependent on the cell-differentiation stage. These findings prompt for in vivo investigations on the delivery of FGF-2 for the temporally/ functionally regulated enhancement of bone marrow stromal cell-based bone induction.