REGULATION OF OSTEOCLASTIC BONE RESORPTION BY RHO

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At the time when a mechanical force is applied onto the tooth, mechanical stress is loaded on the periodontal tissues. A number of osteocytes are located in the bone matrix, communicating each other, as well as with the osteoblasts on the bone surface, via cytoplasmatic processes and gap junctions. Such a cellular network is speculated to have certain important functions for the adaptation to a mechanical loaded environment by the detection of mechanical stress.In the present study, in order to investigate the role of osteocytes in bone resorption, we examined the effects of purified chick osteocyte-derived protein (ODP) and Rho-GTP-dissociation inhibitor (Rho-GDI) on bone resorption. Recently, we established a culture system which provided with human mature osteoclasts from peripheral mononuclear blood cells (PMBC) by using M-CSF and human soluble RANKL (sRANKL) in the absence of osteoblasts and stromal cells. FITC-labelled alpha-actinin pre-microinjected into human osteoclasts was in … More corporated into podosomes which lined the periphery of the cells. Although the podosomes were still observed after the injection of buffer, microinjection of ODP and Rho-GDI caused disruption of podosomes within 30 min of injection. Furthermore, both proteins markedly inhibited pit formation, whereas the conditioned medium of osteocytes had no effect.This study has also focused on a novel cysteine proteinase, cathepsin K, which is through to be specifically expressed in osteoclasts and plays an important part in osteoclastic bone resorption. We have investigated the mechanism of alveolar bone remodelling during orthodontic tooth movement based on an examination of changes in cathepsin K mRNA expression in parallel with the histological changes in alveolar bone.Therefore, further insights into osteoclasts differentiation and function mechanisms may provide stronger bases that will help to understand with more detail the fundaments of orthodontic tooth movement and the reaction of mechanically stressed periodontal tissues. Less