IGF-I, IGF-IR and IRS1 expression as an early reaction of PDL cells to experimental tooth movement in the rat

Abstract

Objective: To characterize in vivo the role of IGF-I and its signalling, as an early reaction in the mechanotransduction process and to analyse changes of the local expression related to the magnitude of the applied force.

Materials and methods: Forces of 0.1N, 0.25 N and 0.5 N were applied to move the right upper first molars of 12 anaesthetized rats mesially. These forces were kept constant for 4h. The untreated contralateral side served as a control. Paraffin-embedded sections of the resected jaws were prepared for immunohistochemistry to localize insulin-like growth factor-I (IGF-I), its receptor (IGF-IR), and insulin receptor substrate 1 (IRS1). Histomorphometric analysis was performed to count the percentage of immunoreactive cells in different parts of the periodontal ligament.

Results: IGF-I, IGF-IR and IRS1 positive cells were observed in the periodontal tissues of the control and loaded teeth. In the experimental group, the number of IGF-I-, IGF-IR- and IRS1-positive cells increased significantly on the tension side and decreased on the compression side.

Conclusions: These data indicate a close relationship between mechanical loading of the PDL and the autocrine/paracrine expression of IGF components as an early step in the mechanotransduction process leading in the long term to an organized remodelling of the alveolar bone.