FGF2 Accelerates Recruitment Of Early Progenitors Into Odontoblast Lineage

Dentin matrix contains growth factors capable of stimulating regeneration of the dental-pulp complex. Although the mechanisms underlying the reparative dentinogenesis are not fully understood, many signaling networks including Fibroblast Growth Factor (FGF) signaling have been implicated in this process. However, most of the previous studies showed the inhibitory effects of FGFs on odontoblast differentiation. Objectives: To gain a better understanding of the effects of FGFs on in vitro mineralization of dental pulp and to identify population(s) of pulp cells responsive to FGF. Methods: Primary cultures derived from the coronal portion of dental pulp from various green fluorescent protein (GFP) reporter transgenic mice were treated with 20 ng/ml of FGF2 and vehicle (controls) during the proliferation phase and prior to induction of mineralization. Cultures were analyzed at various time points by FACS, qPCR, imaging and immunocytochemistry to determine the extent of mineralization and odontoblast differentiation in treated and control cultures. Results: FGF2 treatment significantly increased the level of Dspp expression and the number of cells expressing high levels of DSPP-GFP as compared to controls at all time points. FGF2 did not affect the extent of mineralization or the expression of other markers of mineralization. FACS analysis at day 7 showed significant increases in the percentage of DMP1-GFP⁺ cells (functional odontoblasts) in treated cultures. There were no significant differences in the percentage of the pOBCol3.6GFP⁺ and pOBCol2.3GFP⁺ cells (early progenitors). Cell cycle analysis demonstrated that FGF2 did not affect proliferation. Time-lapse imaging showed rapid appearance and increases in the number of DMP1-GFP⁺ cells in treated cultures. Conclusion: Short and early FGF2 treatment of dental pulp cultures resulted in accelerated recruitment of progenitor population into odontoblast lineage. These observations provide evidence for new ways to promote repair and regeneration of dentin from dental pulp progenitors. Supported by grant #DE016689.