Fibroblasts isolated from a keratocystic odontogenic tumor promote osteoclastogenesis in vitro via interaction with epithelial cells.

ABSTRACT

OBJECTIVES: Investigate the role of the epithelial-mesenchymal interaction of keratocystic odontogenic tumor (KCOT) in influencing osteoclastogenesis. MATERIALS AND METHODS: Fibroblasts isolated from KCOT fibrous capsule and normal gingival mucosa were, respectively, co-cultured with human immortalized oral epithelial cells (HIOECs), and the supernatant was collected to make conditioned medium, in which the osteoclastogenesis of osteoclast precursor cell line Raw 264.7 was observed. Genes related to bone resorption (RANKL, OPG, COX-2, and M-CSF) were analyzed by real-time PCR. Antibodies against human sRANKL and inhibitor of COX-2 NS398 were added to conditioned medium to investigate the inhibitory effect on osteoclastogenesis. RESULTS: Compared with co-cultured gingival fibroblasts and HIOECs (GE-CM), the conditioned medium from co-cultured KCOT fibroblasts and HIOECs (KE-CM) induced more osteoclast-like cell formation and increased NFATC1 mRNA in Raw264.7 cells (P < 0.05). Co-cultured KCOT fibroblasts (KF) and HIOECs, respectively, expressed more COX-2 mRNA than the co-cultured gingival fibroblasts (GF) and HIOECs (P < 0.05). While the ratio of RANKL/OPG in HIOECs co-cultured with KF was also significantly higher than that co-cultured with GF (P < 0.05). The anti-human sRANKL antibody in KE-CM inhibited osteoclastogenesis of Raw264.7 cells; however, NS398 displayed little inhibition. CONCLUSION: An interesting phenomenon of osteoclastogenic effect of KE-CM in vitro was investigated, which suggested an indispensable role of epithelial-mesenchymal interaction of KCOT in its bone destruction. It could be at least partly attributed to the up-regulated ratio of RANKL/OPG in epithelium induced by KCOT fibroblasts, the aggressiveness of tumor as result of epithelial-mesenchymal interaction deserves exploration further.