Expression of Matrix Metalloproteinases and TIMPs in Human Abdominal Aortic Aneurysms

n

= 3; donor, 4.5 ± 2.2, n= 6; AAA, 4.0 ± 0.95, n= 15). There was a significant increase in the level of MMP-9 mRNA in AAA specimens (occlusive, 16.8 ± 3, n= 3; donor, 5.7 ± 1.2, n= 6; AAA, 56.7 ± 11, n= 15, p= 0.0069). The levels of mRNA coding for TIMP-1 were not significantly different. There was a small but statistically significant increase in TIMP-2 mRNA in AAA tissue. These data support the hypothesis that increased activity of MMP-9, but not MMP-2, is an important factor in the etiology of AAAs. This enhanced MMP-9 activity could then result in degradation of the ECM, leading to aneurysmal dilatation.