TNF and rheumatoid arthritis: The overexpression of TNF-α in RA also occurs on the osteogenic side of bone remodeling with the overexpression of Dickkopf-1 (DKK-1), one of the main negative regulators of the canonical Wnt-β-catenin pathway that is strongly implicated in the processes of proliferation, differentiation, and maturation of osteoblasts.