SMAD3 and rheumatoid arthritis: SMAD family member 3 (SMAD3) and transforming growth factor alpha (TGFA)-coded molecules are the factors of TGF signaling pathways, which, being overactivated both in OA and RA, are involved in ECM neogenesis as well as in other pathological processes (neoangiogenesis, apoptosis, and osteoblast differentiation; Figure 2).