Dexamethasone and basic-fibroblast growth factor regulate markers of mineralization in cementoblasts in vitro

Background: The aim of this study was to determine the effects of basic-fibroblast growth factor (b-FGF) and/or dexamethasone (Dex) on cementoblasts in vitro. Methods: Murine cementoblasts were treated as follows: 1) 5% FBS (fetal bovine serum) + ascorbic acid (AA, 50 mu g/ml, control); 2) 5% FBS+Dex (10(-7)M)+AA; 3) 5% FBS+b-FGF (50 ng/ml)+AA; or 4) 5% FBS+Dex (10(-7) M)+b-FGF (50 ng/ml)+AA and then evaluated by Northern analysis for changes in specific genes and by von Kossa stain for changes in mineral nodule formation. Results: Mitotic activity: b-FGF stimulated DNA synthesis significantly versus negative control. Gene expression: osteocalcin (OCN): Dex or b-FGF or the combination resulted in a decrease in expression versus control. Bone sialoprotein (BSP): Dex increased expression of BSP mRNA levels, b-FGF decreased transcript for BSP at 6 and 24 hours. Long-term (8 days) Dex, b-FGF, or Dex plus b-FGF caused a decrease in BSP expression versus control; osteopontin (OPN): both Dex and b-FGF increased transcripts for OPN seen by 6 hours, with a greater increase noted with b-FGF versus Dex. No apparent additive effect of Dex with b-FGF was noted; matrix gamma-carboxyglutamic acid protein (MGP): b-FGF induced transcripts for MGP and addition of Dex increased this effect, while Dex alone had no effect on expression. Biomineralization: Dex increased cementoblast-mediated biornineralization, while b-FGF blocked this activity, and addition of Dex to b-FGF did not alter FGF associated inhibition. Conclusion: Dex and FGF alone and in combination alter cementoblast behavior, but additional studies are required to determine whether these factors have beneficial effects at the clinical level.