MMP9 and chronic obstructive pulmonary disease: Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease that is characterized by airway obstruction and progressive lung inflammation that is associated with the influx of inflammatory cells such as neutrophils, macrophages, lymphocytes and epithelial cells [1], [2], as well as increases in the levels of a complex cascade of inflammatory mediators including chemokines such as IL-8 and pro-inflammatory cytokines such as TNF-α, IL-1β, IL-6 and MMP-9 [3], [4].