Enhanced expression of matrix metalloproteinase-9 in abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are characterized by structural alteratio ns of the aortic wall resulting from degradation of collagen and elastin. M atrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, show strong elastinolytic activity. We examined the levels of mRNA for MMP-2, MMP-9, me mbrane type (MT)-MMP-1, tissue inhibitor of metalloproteinase-1 (TIMP-1), a nd TIMP-2 in AAAs (n = 8), atherosclerotic occlusive diseases (AOD) (n = 8) , and normal subjects (n = 8) using the reverse transcription-polymerase ch ain reaction (RT-PCR). We also analyzed the gelatinolytic activity of these metalloproteinases using gelatin zymography. The levels of MMP-2 and MMP-9 mRNA were increased in the AAA group compared with those in the AOD group and normal subjects. The levels for TIMP-1 and TIMP-2 mRNA in the AAA group were also higher than those in the AOD and normal groups. Only in the case of MT-MMP-1 was the difference between AAA and AOD not statistically signi ficant. By gelatin zymography with the same samples used for RT-PCR, gelati nolytic activity of MMP-9 was elevated in all AAA tissues. The 62-kDa form of MMP-2 was elevated in both the ABA and AOD groups and did not differ sig nificantly between them. Linear regression analysis demonstrated a signific ant positive correlation between mRNA levels of MMPs and those of TIMPs. Th ese observations suggest that aneurysm formation in patients with atheroscl erosis is related to the degree of MMP-9 expression.