Vascular 03

Abstract

Matrix metalloproteinases (MMPs) play an important part in the expansion of abdominal aortic aneurysms (AAA). It has been suggested that MMPs appear to be present in differing concentrations during the progression of aneurysm development. Our aim was to determine the MMP profiles in tissue from aneurysms of differing sizes, to define whether rupture results from gradual widespread increases in proteolytic capacity, or is confined to a localized area of the aortic wall. Samples of anterior aortic wall were obtained from 81 patients undergoing elective AAA repair (n = 59, median age 72 years, diameter 6 cm), or emergency repair of ruptured AAA (rAAA) (n = 22, age 72). The elective group was divided by aneurysm size into 2 groups; medium sized (5–6.5 cm, n = 31, age 70) and large (>6.5 cm, n = 11, age 73). Paired samples of aortic sac were obtained from the sac and the site of aortic rupture from nine patients with rAAA (age 70). MMPs‐1, ‐2, ‐3, ‐9, and ‐13, and TIMPs‐1 and ‐2 were extracted from the tissue specimens and quantified using ELISA. There were no significant differences in MMP and TIMP levels in AAA sac of medium and large sized aneurysms, or ruptured and nonruptured AAA sac. In paired specimens taken from rAAA, MMP‐9 was seven times higher at the site of rupture than in the anterior sac (98.57 ng mg−1[IQR 56.02–134.5]versus 13.89 ng mg−1[7.80–46.81], P = 0.012). These data demonstrate that MMP profiles vary little with expansion of the aneurysm in medium‐ and large‐sized aneurysms. Rupture is likely to be a result of localized elevations in MMP‐9 and this would be an appropriate target for pharmacotherapy.