TNF and rheumatoid arthritis: One of the earliest changes evident in the cartilage matrix structure is the loss of proteoglycans and glycosaminoglycans which is thought to facilitate the attachment and invasion of the pannus.67,68 Chondrocytes, which play an essential role in replenishing matrix components and maintaining cartilage structural integrity, are targeted by several cytokines (TNF-α and IL-1) in the RA microenvironment.