MMP9 and arthritic joint disease: Interestingly, Syk (see below) has been shown to regulate the expression of differentially expressed MMPs such as Mmp3[17] and Mmp9[18], further suggesting a potential central role for Syk in arthritis and a Syk-regulatory effect of Cia5a. Components of the extracellular matrix (ECM; Cthrc1, Col12a1, Emilin1) also had reduced expression in congenics, and together with the levels of proteases suggested that there was reduced matrix turnover and reduced degradation, compared with arthritic DA rats (Table 3).