Effects of the combination of dexamethasone and fibroblast growth factor-2 on differentiation of osteoprecursor cells

Dexamethasone is a potent modulator of osteogenic differentiation and previous studies have shown that dexamethasone increases the bone formation capacity of osteoprogenitor cells in vitro. Fibroblast growth factor-2 (FGF-2) is reported to have numerous biological activities, including stimulation of cell growth, migration, angiogenesis, wound healing, tissue repair, differentiation and morphogenesis. In the present study, the dose-dependent effect of dexamethasone and FGF-2 on the differentiation of osteoprecursor cells was evaluated. The alkaline phosphatase (ALP) activity test was performed to assess differentiation and protein expression associated with bone formation was measured by western blot analysis. The results showed that the protein content of the cultures grown with the osteogenic differentiation media in the presence of 2 ng/ml FGF-2 was increased compared with that of the untreated control. ALP activity was increased when cells were treated with dexamethasone, with the highest value at 100 nM. The addition of 20 ng/ml FGF-2 to 100 nM dexamethasone showed an increase in ALP activity, however, this was not statistically significant. The combination of 100 nM dexamethasone and 20 ng/ml FGF-2 produced the highest expression of bone morphogenetic protein receptor-IA and bone morphogenetic protein receptor-II, leading to the highest value of pSmad1/5/8 expression. Within the limits of this study, dexamethasone significantly enhanced osteoblast differentiation, however, the combined delivery of dexamethasone and FGF-2 did not produce synergistic effects on osteoblast differentiation under the current experimental conditions.