Bone Abstracts

Mesenchymal stromal cells (MSC) have a potential to differentiate to osteoblasts and adipocytes. Differentiation can be stimulated or inhibited by different growth factors, including fibroblast growth factors (FGFs). In this study we evaluated the effect of FGF2 on the osteoblastic and adipocytic differentiation of MSCs in vitro.

Mouse MSC-derived cells were cultured in differentiation medium that led to differentiation to osteoblasts in 14 days and to adipocytes in 7 days. The cells were treated during the differentiation with FGF2 (25 ng/ml) for 24 h before sample collection (short-term treatment) or continuously through the whole culture period (long-term treatment). Samples were collected for qRT-PCR and western blot analysis.

Both short- and long-term treatment with FGF2 had an inhibitory effect on MSC differentiation. FGF2 decreased osteoblastic differentiation, as evaluated by a decrease in the expression of osteoblast marker genes (collagen I, osteocalcin, alkaline phosphatase, and RUNX2). We also observed changes in the expression of FGF-receptors as the mRNA levels of FGFR2, FGFR3, and FGFR5 were downregulated. Interestingly, the mRNA level of FGFR1 was increased by both treatments. FGF2 treatment also decreased adipocytic differentiation evaluated by the expression of the adipocyte markers (fatty acid binding protein 4 and PPARγ). During adipocyte differentiation FGF2 induced FGFR1 expression in undifferentiated cells but decreased it in later stages of differentiation. The mRNA levels of FGFR2, FGFR3, and FGFR5 were downregulated by short- and long-term treatment of FGF2.

We conclude that FGF2 treatment inhibits osteoblastic and adipocytic differentiation of MSCs in vitro. FGF2 inhibition of MSC differentiation was associated with differential alterations of the expression of the FGFRs.