MMP3 and rheumatoid arthritis: The percentage of lining MMP3+ cells was significantly higher in RA patients with high grade synovitis than that in RA patients with low grade synovitis (median 51%, IQR 47%~56% versus median 42%, IQR 36%~49%, P < 0.001), and synovial MMP-3 expression was also higher in high grade group of hyperplasia of lining layer, inflammatory infiltration, and activation of synovial stroma (Figure 2(a)).