RA SF had significantly higher levels of the bone destruction–related factors matrix metalloproteinase 3 (MMP3) and tissue inhibitor of metalloproteinases 1(TIMP1) than RA serum (Figure 1F, P < 0.001), suggesting that excessive immune response mediates the severe bone destruction and lesions in RA. The gene discussed is MMP3; the disease is rheumatoid arthritis.