TGF-β1 is expressed by cells of the synovial lining layer and macrophages as well as in the vascular endothelium of synovial tissues of RA patients compared to osteoarthritis (OA) and healthy controls [41], and synovial fluid of RA patients contains TGF-β1, which indicates that TGF-β1 may be involved in the destruction of the affected joints [16, 42]. The gene discussed is TGFB1; the disease is osteoarthritis.