DKK1 and rheumatoid arthritis: In addition, genes in both the overexpressed Dkk1 and Bmi1 groups, compared with those in the control group, were significantly enriched in important subclasses, including ‘cytokine‐cytokine receptor interaction’ (Il23a, Cxcl13, Il15, and Acvrl1), ‘rheumatoid arthritis’ (Ctsk, Angpt1, Il23a, and Il15), ‘renin secretion’ (Clca2, Pde1c, and Ptger4), and ‘nitrogen metabolism’ (Car2 and Ca14).