Increased turnover of collagen in abdominal aortic aneurysms, demonstrated by measuring the concentration of the aminoterminal propeptide of type III procollagen in peripheral and aortal blood samples

Abstract

The pathogenesis of abdominal aortic aneurysm (AAA) involves many factors; elastin degradation is believed to lead to initial dilation, whereas changes in the collagen structure predispose the aneurysm to rupture. The major collagens in the aortic wall are types I and III. We set out here to determine whether changes in serum propeptide of type III procollagen (PIIINP), a biologically relevant marker of type III collagen turnover, could be associated with the characteristics of AAA. The aminoterminal PIIINP and the carboxyterminal propeptide of type I collagen were measured by radioimmunoassay in 87 patients with AAA and 90 control subjects with aortodistal arteriosclerosis. The samples were taken from the peripheral blood and from the abdominal aorta at the levels of the diaphragm and the common iliac artery. Mean PIIINP concentrations were higher in patients with AAA than in control subjects (3.47 micrograms/L vs 2.73 micrograms/L, p < 0.0001), correlating positively with aneurysm diameter in the former (r = 0.27, p = 0.04) and with the maximum thickness of the intraluminal thrombus (r = 0.39, p = 0.003). The gradient in PIIINP between the upper and lower end of the abdominal aorta was significant in the AAA group (-0.30 microgram/L, range -0.20 to -0.50 vs -0.10 micrograms/L, range -0.20 to 0.30, p = 0.002). These studies indicate that the turnover of type III collagen is increased in patients with AAA.