TNF and rheumatoid arthritis: In RA patients, the levels of pro-inflammatory cytokines, such as TNF-α and IL-6, are significantly elevated, inducing an increase in the expression of RANKL in peripheral blood mononuclear cells (PBMC) (16), and the high expression of RANKL drives the generation of a large number of highly activated OC, which increases bone resorption, and is the core driver of the imbalance of bone metabolism and bone destruction in RA patients (17).