MMP9 and thoracic aortic aneurysm: Additionally, no relationship was found via meta-analysis of MMP1 and MMP9 polymorphism studies with thoracic aortic aneurysmal diseases [33] and in a small preliminary study, researchers found no relationship between MMP1 and MMP9 levels and the elastic modulus of the aortic wall in patients with thoracic aortic aneurysm [34].