Medline ® Abstracts for References 9,18

BACKGROUND: Abdominal aortic aneurysm (AAA) is a relatively common disease, with 1% to 2% of the population harboring aneurysms. Genetic risk factors are likely to contribute to the development of AAAs, although no such risk factors have been identified.

METHODS AND RESULTS: We performed a whole-genome scan of AAA using affected-relative-pair (ARP) linkage analysis that includes covariates to allow for genetic heterogeneity. We found strong evidence of linkage (logarithm of odds [LOD]score=4.64) to a region near marker D19S433 at 51.88 centimorgans (cM) on chromosome 19 with 36 families (75 ARPs) when including sex and the number of affected first-degree relatives of the proband (N(aff)) as covariates. We then genotyped 83 additional families for the same markers and typed additional markers for all families and obtained a LOD score of 4.75 (P=0.00014) with sex, N(aff), and their interaction as covariates near marker D19S416 (58.69 cM). We also identified a region on chromosome 4 with a LOD score of 3.73 (P=0.0012) near marker D4S1644 using the same covariate model as for chromosome 19.

CONCLUSIONS: Our results provide evidence for genetic heterogeneity and the presence of susceptibility loci for AAA on chromosomes 19q13 and 4q31.

BACKGROUND: Abdominal aortic aneurysm (AAA) expansion is characterized by extracellular matrix degradation and widespread inflammation. In contrast, the processes that characterize AAA rupture are not well understood. The aim of this study was to investigate the proteolytic and cellular activity of ruptured AAA, focusing on matrix metalloproteinases (MMPs) and their inhibitors (TIMPs).

METHODS AND RESULTS: Anterior aneurysm wall biopsies were taken from 55 nonruptured and 21 ruptured AAAs. A further biopsy from the site of rupture was taken from 12 of the ruptured AAAs. MMP-1, -2, -3, -8, -9, and -13, as well as TIMP-1 and -2, were quantified in each biopsy with ELISA. A comparison of anterior aneurysm biopsies showed no difference in MMP or TIMP concentrations between nonruptured and ruptured AAA. In a comparison of ruptured AAA biopsies, MMP-8 and -9 levels were significantly elevated in the 12 rupture site biopsies compared with their 12 paired anterior wall biopsies, whereas other MMPs and TIMPs showed no difference (MMP-8, P<0.001; MMP-9, P=0.01). MMP-8 and -9 expression was mediated by native mesenchymal cells and was independent of the inflammatory infiltrate.

CONCLUSIONS: A localized increase in MMP-8 and -9, mediated by native mesenchymal cells, presents a potential pathway for collagen breakdown and AAA rupture.