MMP9 and chronic obstructive pulmonary disease: We next used a semiquantitative RT‐PCR method to profile the expression of MMP‐2/MMP‐9/MMP‐12, NGAL and IL‐6 transcripts in PBMCs isolated from blood samples of 19 COPD‐S patients and 12 healthy‐S participants (for the patients’ characteristics, see the Table S3).