Receptor activator of nuclear factor-kappa ligand,OPG, and IGF-I expression during orthodontically induced inflammatory root resorption in the recombinant human growth hormone–treated rats

Objective:To investigate the effects of growth hormone (GH) on local receptor activator of nuclear factor-kappa ligand (RANKL), OPG, and IGF-I expression during orthodontically induced inflammatory root resorption in rats.Materials and Methods:Forty Wistar rats (gender: male; age: 7 weeks) were randomly divided into control and experimental groups. A force of 50 g was applied to move the right upper first molars mesially. The experimental and control groups received daily subcutaneous injections of recombinant human growth hormone (GH; 2 mg/kg) and equivalent volumes of saline, respectively. The rats were sacrificed on days 1, 3, 7, and 14. Micro–computed tomography–reconstructed images of the upper right first molars were used to survey root resorption and tooth movement. Horizontal sections of the maxillae were prepared for hematoxylin and eosin, tartrate-resistant acid phosphatase, and immunohistochemical staining.Results:Resorption lacunae appeared on the compressed side of the distal buccal root of the right first molar on days 7 and 14. Compared with the control groups, GH-treated groups showed more RANKL-positive cells and osteoclasts on day 3 and more OPG- and IGF-I–positive cells and fewer odontoclasts on days 7 and 14. Indexes of root resorption were lower and tooth movement was faster in the GH-treated groups than in the control groups on days 7 and 14.Conclusions:The inhibitory effect of GH on root resorption by heavy force might be mediated by RANKL/OPG and IGF-I. Short-term GH administration may be a method with which to reduce root resorption and shorten treatment time, especially in patients who are susceptible to root resorption.