Early effects of orthodontic forces on osteoblast differentiation in a novel mouse organ culture model

Abstract

To develop a mouse orthodontic organ culture model and examine early-induced changes in osteoblast differentiation markers within the periodontal ligament (PDL) and alveolar bone. Mandibles from 4- to 12-week-old transgenic mice were dissected and hemisected. A conventional superelastic orthodontic spring (25 grams) was bonded to the incisor and first molar on one side of the mandible; the other side served as a control. Dissected mandibles were cultured for 6 hours and then were histologically analyzed for proliferation (BrdU immunostaining) and fluorescent protein expression. Additionally, an in vivo model using the same methods was applied to 3.6 Col1-GFP transgenic mice. In vitro, after 6 hours of orthodontic loading, a significant increase was noted in 3.6Col1-GFP- and BSP-GFP-positive cells within the tension side of the PDL compared with unloaded controls. On the compression side, a significant decrease in positive cells in 3.6Col1-GFP mice was observed in the PDL compared with unloaded controls. In vivo, the same tendencies were found. This novel in vitro mandibular tooth movement organ culture model coupled with transgenic mouse technology provides a powerful tool for delineating initial cellular and molecular events of orthodontic tooth movement.