In RA, it has been reported that components of the non-collagenous matrix of the joints can be degraded by elevated MMP2,3, and 9 (Burrage et al., 2006), and degradation of aggrecan and cartilage oligomeric matrix protein (COMP) requires participation of MMP19 (Stracke et al., 2000). Here, ACAN is linked to rheumatoid arthritis.