Among the MMPs, MMP-9 and MMP-2 are most involved in emphysema.56 MMP-12 plays an influential role in severity of COPD.57 MMPs also play a role in vascular remodelling by modulating the migration and proliferation of smooth muscle cells and endothelial cells and mediating the release of the smooth muscle cell mitogens and growth factors, increasing the risk of COPD pulmonary hypertension.58–61 The endogenous inhibitors of MMPs are tissue inhibitors of metalloproteinases (TIMPs). The gene discussed is MMP9; the disease is chronic obstructive pulmonary disease.