The role of RANKL and MMP-9 in the bone resorption caused by ameloblastoma

J Oral Pathol Med (2010) 39: 592–598 Background: Ameloblastoma, a common odontogenic tumor located in jaws, generally leads to severe damage to patient's complexion and masticatory function. To expand in jaws, ameloblastoma must have a mechanism of resorbing the surrounding bone. Our objective was to explore the bone-resorption mechanism of ameloblastoma by observing the role of Receptor activator of nuclear factor kappa B ligand (RANKL) and matrix metalloproteinase-9 (MMP-9) in the bone-resorption process. Methods: In the study, the expression of RANKL and MMP-9 in ameloblastoma was detected using immunohistochemistry (IHC) and RT-PCR. Then, co-culture system of ameloblastoma cells and bone marrow cells from neonatal rabbit was erected to observe the potential of ameloblastoma cells to induce osteoclastogenesis. Finally, the induced osteoclasts were used for in vitro bone-resorption assay. In the co-culture system and the bone-resorption assay, the selective inhibitor of RANKL and MMP-9, osteoprotegerin (OPG) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were, respectively, used for observing the role of RANKL and MMP-9. Results: The expression of RANKL and MMP-9 in ameloblastoma was confirmed. Ameloblastoma cells were found to induce bone marrow cells from neonatal rabbit differentiate into osteoclasts with bone-resorption activity. In addition, OPG was found to, respectively, have markedly inhibitory effect on osteoclastogenesis (P < 0.01), and slightly inhibitory action on bone resorption (P < 0.05). Conclusions: Ameloblastoma cells had the potential to induce osteoclastogenesis. Moreover, RANKL played an essential role in the in vitro osteoclast formation and bone resorption induced by ameloblastoma cells.