DKK1 and psoriatic arthritis: The IHC reactivity for TGF-β1 in the synovial tissue (Fig. 4) was higher in patients with psoriatic arthritis (p 0.010) and was positively correlated with IL-17 A (r = 0.389, p = 0.012) and Dkk1 (r = 0.388, p = 0.012), (Fig. 5).