CD44-/- ANIMALS DISPLAY DECREASED ORTHODONTIC TOOTH MOVEMENT USING A MURINE MODEL

Abstract

Future improvements in orthodontic treatment require a comprehensive understanding of the reaction of paradental structures to an applied force, at the cellular and molecular level. Recent advances in molecular biology techniques have established transgenic and knock-out mice as robust tools in studying various physiological and pathological processes. To successfully utilize this tool in orthodontic research, a good model for orthodontic tooth movement (OTM) in mice is needed. The aim of this study was to characterize a model of OTM that can be used in effectively and efficiently in mice. As opposed to prior models, which apply mesializing forces to molars using NiTi coil springs, we fabricated orthodontic springs from 0.010" stainless steel wires designed to move maxillary molars in the palatal direction. The use of radiographs to measure tooth movement in our method, allows for multiple and frequent measurement to be made from individual animals over the entire experimental period, with good reliability and accuracy. We tested this method in mice lacking the CD44 gene and compared them to control mice. CD44 is a cell surface receptor present on osteoclasts and believed to be important in cell adhesion, migration and function. Our data indicate that CD44-/- animals have reduced overall tooth movement when compared to controls and also have a larger lag phase before tooth movement is observed. These data support existing evidence that CD44 may be important in osteoclast function and bone resorption.