Activated forms of MMP(2) and MMP(9) in abdominal aortic aneurysms

Purpose: The consistent observation of a reduction of the elastin concentration in abdominal aortic aneurysms (AAAs) has led us to investigate in AAA specimens two metalloproteinases that display elastase activity, MMP(2) (gelatinase A/72 kDa) and MMP(9) (gelatinase B/92 kDa). Methods: Samples of full-thickness aortic wall, adherent thrombus, and serum were collected in 10 patients with AAAs. Samples of normal aortic wall and serum were taken from 6 age-matched control patients. Quantitative gelatin-zymography and gelatinolytic soluble assays after acetyl-phenyl mercuric acid activation were performed on serum and tissue extracts, and the results were expressed in units on a comparative wet-weight basis. Histologic analysis was performed in parallel to score the inflammatory infiltrate. Results: The luminal and parietal parts of the thrombus contained, respectively, 20- and 10-fold more gelatinolytic activity than the serum. The predominate form was MMP(9). Although the total gelatinolytic activity was in the same range both in AAAs and in normal walls, a significantly higher proportion of MMP(9) was found in the aneurysmal aortic walls. furthermore, a significant proportion of MMP(9) was under its processed active form, which was never observed in normal samples. A significantly higher proportion of MMP(2) was also present as processed active form in AAA wall. This latter parameter positively correlated with the inflammatory score. Conclusions: The presence of activated MMP(9) and MMP(2) might contribute to the degradation of the extracellular matrix proteins that occurs during the development of aneurysms.