In contrast, serum levels of MMP‐3 and MMP‐12 (but not MMP‐7) were significantly higher in COPD smokers than in healthy smokers (MMP‐3: 2.45 versus 1.44 ng/ml, respectively, P = 0.01; MMP‐12: 341.55 versus 171.65 ng/ml, respectively, P = 0.03; Table 3). Here, MMP3 is linked to chronic obstructive pulmonary disease.