b-FGF Amplifies Effects of Dexamethasone on the PDL Cell Mineralization

Objectives: Growth factors alone or in combination have been demonstrated to promote periodontal ligament (PDL) cell migration, proliferation and differentiation. The purpose of this study was to determine the effects of basic-Fibroblast Growth Factor (b-FGF) and/or Dexamethasone (Dex) on mitotic activity, collagen type I (COL I) mRNA expression and, mineralization of PDL cells in vitro in order to understand the mechanisms for these effects and long-term, the predictability of regenerative therapies. Methods: PDL cells were obtained from premolar teeth extracted for orthodontic reasons. PDL cells were cultured with DMEM media containing, 5% FBS, 5% FBS+ ascorbic acid (AA, 50 ƒÝg/ml), and 5% FBS+Dex (10-7 M)+AA and/or b-FGF (1 or 10 ng/ml). The mitogenic effect of b-FGF and/or Dex was assessed by measuring 3H-thymidine incorporation. Cells within each group were evaluated on day 3 and 7 for gene expression profile using Northern analysis for COL I and on day 8, 16 and 24 for biomineralization by von Kossa stain in vitro. Results: Dex+FGF(1 ng/ml) significantly induced mitotic activity of PDL cells when compared to other groups. Although there was no significant difference between 1, 10, 100 ng/ml concentration of b-FGF, increased mitotic activity was noted at 1 ng/ml b-FGF group. Cells exposed to b-FGF (1 and 10 ng/ml) alone, demonstrated a more prominent decrease in COL I mRNA expression in comparison with combination groups on days 3 and 7. Whilst, b-FGF totally blocked mineralization of PDL cells on day 24, interestingly b-FGF(1 and 10 ng/ml) and Dex combination induced mineralization of PDL cells when compared to 5% FBS+Mineralization Media (MM) and MM+ Dex group. Conclusions: These results indicate that b-FGF, Dex and combination of DEX+b-FGF, each influence PDL cell activity differently suggesting that a combination of these two factors may enhance the biological activity of cells required for promoting periodontal regeneration.