TNF and rheumatoid arthritis: A wealth of investigators has established that TNF-α is mostly correlated with osteocytic-induced bone loss, either directly via RANKL expression in diseases of inflammatory bone loss, such as rheumatoid arthritis and periodontitis [23,179,180], or indirectly, via inducing osteocyte apoptosis, which releases osteoclast formation promoting factors RANKL, IL-6 and endothelial intercellular adhesion molecule-1 [181,182,183].