The Elevated Level of Circulating Matrix Metalloproteinase-9 in Patients with Abdominal Aortic Aneurysms Decreased to Levels Equal to Those of Healthy Controls after an Aortic Repair

Matrix metalloproteinase-9 (MMP-9) is abundantly expressed in abdominal aortic aneurysms (AAAs), and it is considered to play a pivotal role in aneurysmal formation. Elevated circulating concentrations of MMP-9 have been reported in patients with AAA, but the influence of an operation on circulating MMP-9 is unclear. Therefore, to clarify the influence of an operation on circulating MMP-9 levels and to determine the role of MMP-9 in the progression of AAA, we measured serum MMP-9 levels in patients before and after AAA repair. Blood samples were obtained from 53 patients with AAA; 22 patients underwent AAA operations, including 17 patients with arterial occlusive disease (AOD), and nine normal control subjects. Serum MMP-9 levels were determined by an enzyme-linked immunosorbent assay. The serum MMP-9 concentration was significantly higher in AAA patients (622.0 ± 400.2 ng/mL) than in either AOD patients (284.3 ± 151.4 ng/mL) or healthy controls (280.8 ± 165.5 ng/mL) (p < 0.001). The mean serum MMP-9 levels in patients undergoing surgery for AAA (268.1 ± 215.9 ng/mL) was significantly lower than that in AAA patients (p < 0.01). Among the 10 patients whose sera were obtained preoperatively and postoperatively, the serum MMP-9 concentration fell significantly after the patients underwent the operation (p = 0.004). No significant difference was identified in serum MMP-9 concentrations among AOD patients, controls, and postoperative patients. These studies suggest that MMP-9 plays a pivotal role in aneurysm formation, and the circulating MMP-9 level is thus considered to reflect the biological behavior of the aneurysm.