COL18A1 and rheumatoid arthritis: Additionally, in contrast to the in vitro setting where only TNFα was added, in RA patients, other pro-inflammatory cytokines are elevated locally in the joints and systemically in the serum (e.g., IL-1β, IL-6, and IL-17, and their effects on the proteases, CD147, and endostatin are not represented in the in vitro system.