Gender differences in experimental aortic aneurysm formation

Objective - It is hypothesized that a male predominance, similar to that in humans, persists in a rodent model of experimental abdominal aortic aneurysm (AAA) via alterations in matrix metalloproteinases (MMPs). Methods and Results - Group I experiments were as follows: elastase perfusion of the infrarenal aorta was performed in male (M) and female (F) rats. At 14 days, aortas were harvested for immunohistochemistry, real-time polymerase chain reaction (PCR), and zymography. Group II experiments were the following: abdominal aorta was transplanted from F or M donors into F or M recipients. At 14 days, rodents that had undergone transplantation underwent elastase perfusion. In group III, male rats were given estradiol or sham 5 days before elastase perfusion. In group I, M rats had larger AAAs with higher frequency than did F rats. M rat aortas had more significant macrophage infiltrates and increased matrix metalloproteinase (MMP)-9 production and activity. In group II, M-to-M aortic transplants uniformly developed aneurysms after elastase perfusion, whereas F-to-F aortic transplants remained resistant to aneurysm formation. F aortas transplanted into M recipients, however, lost aneurysm resistance. In group III, estradiol-treated rats demonstrated smaller aneurysms and less macrophage infiltrate and MMP-9 compared with M controls after elastase. Conclusions - These data provide evidence of gender-related differences in AAA development, which may reflect an estrogen-mediated reduction in macrophage MMP-9 production.