The plasma level of matrix metalloproteinase 9 may predict the natural history of small abdominal aortic aneurysms. A preliminary study.

Objective: increased levels of various proteinases have been detected in abdominal aortic aneurysms (AAA) and are assumed to cause the degradation of the aortic wall. To determine whether systemic measurement of these proteinases and their inhibitors may predict the natural cause of AAA.

Methods: serum (S) and plasma (P) samples were obtained from 121 men following the diagnosis of a small AAA (3-5 cm) at population screening. Annual control scans were performed to check for expansion. Circulating levels of elastase-alpha 1 antitrypsin-complexes, alpha 1 antitrypsin, matrix metalloproteinase (MMP) 2 & 9, tissue-inhibitor-matrixproteinase 1 & 2, procollagen III-N-terminal-propeptide, and elastin-peptides were measured in a random group of 36 men.

Results: alpha 1 antitrypsin was significantly and positively associated with expansion. Similarly, P-MMP9 levels were significantly associated with size and expansion. There was a difference between median serum and plasma values, probably because of secretion from platelets.

Conclusions: P-MMP9 and P-alpha 1 antitrypsin may predict the natural history of AAA.