Identification of odontoprogenitors responsive to FGF2

Previous studies have demonstrated that fibroblast growth factor (FGF) family of signaling molecules inhibited odontoblast differentiation in explanted dental papilla and cultured dental pulp cells. However, the underlying mechanisms regulating the negative effects of FGF2 on odontoblast differentiation are not well understood. Objectives: To gain a better understanding of the mechanism and specific population of cells affected by FGFs in dental pulp. Methods: Primary pulp culture was established from molars isolated from 5-7-day-old hemizygous pOBCol2.3GFP and non-transgenic mice. Mineralization was induced at day 7 and cultures were treated with vehicle (control) or 20 ng/ml of FGF2 between days 3-21 and processed for various analyses including cell proliferation, FACS analysis, qPCR and various staining assays. Results: FGF2 inhibited the mineralization, expression of 2.3-GFP transgene and markers of mineralization in primary pulp cultures. Upon removal of FGF2, mineralization in these cultures was partially recovered (35% decrease). CyQuant assay indicated increases in the DNA content of treated cells at 24 and 48 hrs as compared to controls. FACS analysis at day 7 showed increases in the intensity and percentage of cells expressing 2.3-GFP in treated cultures as compared to control. qPCR analysis showed increases in the levels of expression of Type I collagen, Dmp1 and Dspp genes in treated cultures as compared to controls at day 7. Conclusion: Despite its negative effects on mineralization, FGF2 increased the number of odontoblasts expressing 2.3-GFP transgene suggesting that FGFs may increase the pool of undifferentiated odontoprogenitors. Supported by grant # DE016689