For instance, TIMP-1 can bind the carboxyl terminal of catalytic center in MMP-9 to form an enzyme-inhibitor complex through noncovalent bonding, thereby specifically suppressing the activity of MMP-9.8 Thereby motivated, we herein studied the serum expressions of TIMP-1 and MMP-9 in COPD patients complicated with spontaneous pneumothorax, and their correlations with score of MRC breathlessness scale and score of St. Here, MMP9 is linked to pneumothorax.