The gingival crevicular fluid levels of growth factors in patients with amlodipine-induced gingival overgrowth: A pilot study.

BACKGROUND: Amlodipine, calcium channel blocker (CCB), is used in the management of cardiovascular diseases which causes gingival overgrowth (GO). The growth factors may have a role in the pathogenesis of amlodipine-induced GO. OBJECTIVES: This pilot study aimed to investigate the growth factors including transforming growth factor-b1 (TGF-b1), platelet-derived growth factor-BB (PDGF-BB), and basic fibroblast growth factor (bFGF) in gingival crevicular fluid (GCF) of patients with amlodipine-induced GO and compare with of healthy subjects. METHODS: GCF samples were collected from 56 sites presenting GO (GO + group) and from 38 sites not presenting GO (GO- group) of 5 patients using amlodipine for more than one year, and from 45 sites (control group) of 5 healthy subjects. The levels of TGF-b1, PDGF-BB, and bFGF were determined by using ELISA kits. RESULTS: The mean concentration of TGF-b1 in GCF samples of GO + group (9.50 ± 7.30 ng/ml) was higher than both GO- group (2.07 ± 0.50 ng/ml) and control group (2.74 ± 1.01 ng/ml) (P = 0.014). No significant difference was found among the groups in the GCF levels of PDGF-BB (P = 0.767). bFGF was detected in only 33% of the sites from patients. CONCLUSION: These preliminary results suggest that TGF-b1 may play a crucial role in the pathogenesis of amlodipine-induced GO.

Expression of growth factors in the gingival crevice fluid of patients with phenytoin-induced gingival enlargement.

The mechanism underlying phenytoin (PHT)-induced gingival enlargement (GE) is not yet known. The aim of the present study was to investigate transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor-BB (PDGF-BB) and basic fibroblast growth factor (bFGF) profiles in the gingival crevice fluid (GCF) of patients with PHT-induced GE and to compare the results with healthy controls. Five PHT-treated patients and five healthy subjects with normal periodontal tissue were included in this study. GCF samples were collected from (i) enlarged gingival sites in patients receiving PHT (GE+); (ii) non-enlarged gingival sites in the same patients (GE-); (iii) normal gingival sites of healthy subjects (control). The levels of TGF-beta1, PDGF-BB and bFGF in the GCF samples were analysed by ELISA. The results showed that the total amounts of TGF-beta1 and PDGF-BB in the GE+ group were higher than in the GE- group and significantly higher than in the control group (P < 0.05). However, no significant differences were found between the groups when the concentrations of these growth factors were compared. bFGF levels were not compared as this growth factor could be detected in only 33, 41 and 44% of the GE+, GE- and control GCF samples, respectively. These results show that TGF-beta1 and PDGF-BB are readily detectable in GCF obtained from enlarged and non-enlarged sites of PHT recipients and suggest that since the amounts were markedly higher at the GE+ than the GE- sites, the systemic administration of PHT has a pronounced localised effect on the levels of these growth factors. Moreover, our findings provide evidence that both TGF-beta1 and PDGF-BB are closely associated with the clinical manifestation of PHT-induced GE.

Pro-inflammatory cytokines downregulate platelet derived growth factor-alpha receptor gene expression in human osteoblastic cells.

Platelet derived growth factor (PDGF) is thought to play a significant role in bone repair and regeneration. We previously demonstrated that PDGF-AA binding can be modulated by interleukin-1 (IL-1). We now report that TNF-alpha significantly reduces PDGF-AA binding by decreasing the number of PDGF-alpha receptor subunits on the surface of normal human osteoblastic cells. This inhibition is likely due to a decrease in synthesis of PDGF-alpha receptors since TNF-alpha causes a relatively rapid decrease in PDGF-alpha receptor mRNA levels as determined by Northern blot analysis. The physiologic importance of this inhibition is demonstrated by a TNF-alpha induced decrease in PDGF-AA stimulated tyrosine kinase activity. When saturating concentrations of TNF-alpha were used, the addition of IL-1 further inhibited PDGF-AA binding and further decreased surface expression of PDGF-alpha receptors. In contrast, other mediators such as IL-6, PTH, 1,25(OH)2 vit D3, hydrocortisone, PGE2, bFGF, and IGF-1 had no effect. These results suggest that binding to the PDGF-alpha receptor is decreased by the strong pro-inflammatory cytokines such as IL-1 beta and TNF-alpha rather than as a general response to mediators important in bone resorption or bone formation. TNF-alpha and IL-1 are often co-expressed during destructive inflammatory processes. Thus, TNF-alpha and IL-1 may work in concert to limit the response of osteoblastic cells to PDGF-AA during periods of osseous inflammation.

Receptor binding of PDGF-AA and PDGF-BB, and the modulation of PDGF receptors by TGF-beta, in human periodontal ligament cells.

The growth factors PDGF-AA and PDGF-BB have previously been shown to be potent mitogens for human periodontal ligament (hPDL) cells in vitro. Additionally, the mitogenic response to PDGF-AA has been shown to be specifically inhibited by TGF-beta. The purpose of the present investigation was to examine the binding of PDGF-AA and PDGF-BB, and the modulation of PDGF binding by TGF-beta, in hPDL cells. Scatchard analysis identified an average of 32,000 PDGF-AA high-affinity binding sites per cell with a dissociation constant (Kd) of 0.66 nM and an average of 36,000 PDGF-BB binding sites per cell with a dissociation constant (kd) of 0.44 nM. After treatment with TGF-beta, the receptor number for PDGF-AA was found to specifically decrease by approximately 50%, with no change in binding affinity. This reduced number of binding sites was shown to correlate with both a decrease in levels of receptor tyrosine phosphorylation and a decreased number of alpha receptor subunits. Northern blot analysis identified the TGF-beta-mediated decrease in PDGF alpha receptor subunit mRNA levels. PDGF-BB showed little change in the number of binding sites or in the binding affinity with TGF-beta treatment, and the data were consistent with an increase in the number of beta receptor subunits. These results demonstrate nearly equivalent numbers of receptors for both PDGF-AA and PDGF-BB in hPDL cells. Also, modulation of PDGF binding, by TGF-beta, was shown to result in a reduced number of alpha receptor subunits with an increase in the number of beta receptor subunits.

Growth factors in periodontal regeneration.

Periodontal tissue repair and regeneration are regulated by the local production of growth factors. However, naturally produced growth factors may not be sufficient to optimally stimulate periodontal regeneration. Exogenous growth factors can be used to supplement natural growth factors in wound healing. The authors focus on describing the mechanisms of five growth factors in periodontal regeneration: platelet-derived growth factor; fibroblast growth factor; transforming growth factor-beta; insulinlike growth factor; and bone morphogenetic protein. The objective is to encourage strategies to exploit growth factors in the stimulation of cells in periodontal regeneration, which should result from continued in vivo animal studies.