Immunolocalization of FGF-2 and VEGF in rat periodontal ligament during experimental tooth movement

Abstract

Objective: This article aimed at identifying the expression of fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF) in the tension and pressure areas of rat periodontal ligament, in different periods of experimental orthodontic tooth movement.

Methods: An orthodontic force of 0.5 N was applied to the upper right first molar of 18 male Wistar rats for periods of 3 (group I), 7 (group II) and 14 days (group III). The counter-side first molar was used as a control. The animals were euthanized at the aforementioned time periods, and their maxillary bone was removed and fixed. After demineralization, the specimens were histologically processed and embedded in paraffin. FGF-2 and VEGF expressions were studied through immunohistochemistry and morphological analysis.

Results: The experimental side showed a higher expression of both FGF-2 and VEGF in all groups, when compared with the control side (P < 0.05). Statistically significant differences were also found between the tension and pressure areas in the experimental side.

Conclusion: Both FGF-2 and VEGF are expressed in rat periodontal tissue. Additionally, these growth factors are upregulated when orthodontic forces are applied, thereby suggesting that they play an important role in changes that occur in periodontal tissue during orthodontic movement.

Keywords: Fibroblast growth factor 1; Orthodontics; Periodontal ligament; Vascular endothelial growth factor A.

Figure 1

Occlusal view of orthodontic appliance placed on rat upper right first molar. The closed-coil spring (S) is attached to the molar (M) and incisor.

Figure 2

Diagrammatic representation of the areas chosen for morphological and immunohistochemical analyses. A and C correspond to pressure areas; B and D correspond to tension areas; arrow indicates direction of experimental orthodontic tooth movement.

Figure 3

Histological findings in the control (A) and experimental groups (B-D) after 3 days of orthodontic tooth movement, stained with H&E. (A) PDL without signs of alteration (100x). (B) Disrupted fibers (arrow) observed on the tension side (100x). (C) Hyalinized areas (h) seen on the pressure side (40x). (D) Resorption lacunae with osteoclasts (arrows) observed on the pressure side (200x). AB indicates alveolar bone; PDL, periodontal ligament; R, root; T, tension side; P, pressure side.

Figure 4

FGF-2 immunohistochemistry staining of the control (A,B) and experimental groups (C-H) after 3, 7 and 14 days of orthodontic tooth movement. (A) magnification of 40x; (B, C, H) 200x; (D, E, F) 100x; (G) 400x. AB indicates alveolar bone; PDL, periodontal ligament; R, root; Ob, osteoblasts; E, endothelial cells; h, hialinized area; F, fibroblasts.

Figure 5

VEGF immunohistochemistry staining of the control (A,B) and experimental groups (C-H) after 3, 7 and 14 days of orthodontic tooth movement. (A, E, F) magnification of 100x; (B, C, D, G, H) 200x. AB indicates alveolar bone; PDL, periodontal ligament; R, root; E, endothelial cells; Oc, osteoclasts; h, hialinized area.

Figure 6

Percentage of FGF-2 and VEGF stained area (%) in the experimental and control groups, after 3, 7 and 14 days of orthodontic tooth movement; * and ** indicate statistically significant differences between experimental and control groups (P < 0.05). T indicates tension side; P, pressure side. FGF-2 control values: group I (0.68 ± 0.26); group II (0.80 ± 0.20); group III (0.50 ± 0.19). VEGF control values: group I (0.50 ± 0.21); group II (0.72 ± 0.10); group III (0.56 ± 0.22).