In addition, the elevated expression of proteases, such as matrix metallopeptidase 9 (MMP-9), which may destroy the lung structure, was independently associated with COPD exacerbations [10]. Subsequently, elevated inflammation may result in secondary goblet cell hyperplasia and mucus hypersecretion, which can lead to airway obstruction, impairment of the pathogen and respiratory hazard clearance [11], airway inflammation, and deterioration of lung function [12]. Here, MMP9 is linked to chronic obstructive pulmonary disease.