ADAM17 constitutively expressed by several cell types, including T cells, monocytes, endothelial cells, and fibroblasts (10) , and increased expression of ADAM17 was observed in synovial tissue, as compared with patients with osteoarthritis, and was mainly seen in macrophage- and fibroblast-like synovial cells (18, 19) . Here, ADAM17 is linked to osteoarthritis.