Identification of A Novel Root Resorptive Function of Osteopontin Gene

Objective: Osteopontin (OPN) has been proposed to play a role in bone resorption. With regard to bone and cementum/dentin structural and histological similarities, it was hy-pothesized that expression of this gene might be increased in resorptive lacunae during orthodontic tooth movement.Materials and Methods: Fixed Nickel-Titanium closed coil springs (Dentaurum®) capa-ble of delivering approximately 60 gf were applied for mesial movement of maxillary left first molars in 26 male 8-week-old Wistar rats. The right maxillary molar served as inter-nal control for each subject. After 21 days, the rats were sacrificed. Tissues from 13 rats were examined by histomorphometric analysis and the scratched material from resorptive lacunae on mesial sides of the roots was used for extracting messenger ribonucleic acid (mRNA) in RT-PCR reactions. T-test and Wilcoxon signed-rank test served for statistical analyses.Results: Histomorphometric analysis of histologic sections revealed an increased resorbed area in test group compared to control animals (P<0.001). The integrity of mRNA con-firmed by RT-PCR for housekeeping gene glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Densitometric analysis of OPN mRNA on electrophoresis gel showed an in-crease in background levels of OPN in resorptive lacunae of test group (P<0.001).Conclusion: Data indicates that in the controlled environment of this study, an increase in OPN expression is associated with root resorption induced by orthodontic tooth move-ment