Assessment of some of the factors involved in collagen metabolism in the abdominal aortic aneurysm wall

Abstract

Background. Extracellular matrix remodelling of the aortic wall plays an important role in abdominal aortic aneurysm (AAA) pathogenesis. With progress of the disease, elastin content decreases and the contents of collagen precursor forms increase in the AAA wall; however, total collagen content does not show any significant changes. The aim of the study was to evaluate the following factors involved in collagen metabolism: insulin-like growth factor I (IGF-I) and its binding proteins (IGFBP-1 and IGFBP-3), as well as metalloproteinases (MMP-1, MMP-2 and MMP-9) in the AAA wall when compared to the wall of normal aorta.
Material and methods. The studied material consisted of AAA walls that were collected during elective surgical treatment of 30 patients in the age range 65 ± 10 years. The AAA diameter was 80 ± 20 mm. Normal abdominal aortas from 10 organ donors in the age range 34 ± 5 years were the control material. Contents of IGF-I, IGFBP-1 and IGFBP-3 were evaluated according to radioimmunometric methods. Expression of MMP-1, MMP-2 and MMP-9 was also assessed.
Results. It was demonstrated that IGF-I content was decreased, whereas content of IGFBP-1 and IGFBP-3 were increased in the AAA wall when compared to the wall of normal aorta. Furthermore, increased intensity of MMP-1, MMP-2 and MMP-9 expression was found in the AAA wall in comparison with the wall of normal aorta.
Conclusions. Insulin-like growth factor 1 content and its bioavailability are decreased in the AAA wall when compared to the wall of normal aorta in young subjects. This may impede regeneration of collagen degraded by metalloproteinases (collagenase, gelatinases), increased expression of which is present in the AAA wall.