These diseases include osteoporosis, rheumatoid arthritis and periodontitis.2, 3 Two of the most important regulating factors during OC differentiation are receptor activator of nuclear factor κB ligand (RANKL) and macrophage-colony-stimulating factor (M-CSF).4, 5 Binding of RANKL to RANK results in the initiation of the TNF receptor-associated factor 6 signaling, which activates nuclear factor-κB, Akt and MAP kinase (ERk, JNK and p-38), and eventually leads to the proliferation, differentiation and maturation of OCs.6, 7. This evidence concerns the gene TNFSF11 and rheumatoid arthritis.