TNF and rheumatoid arthritis: Preclinical evidence comes from studies in a human TNFα transgenic mouse model where inhibition of the wnt signaling antagonist DKK1 resulted in a switch from RA-like erosive phenotype to bone formation phenotype with progressive ankylosis of both limb and sacroiliac joints, suggesting that Wnts may promote bone formation associated with pathological development of AS [128, 223].