Plasma and tissue levels of collagen types I and III markers in patients with abdominal aortic aneurysms

Background. To study the levels of the aminoterminal propeptide of type ZU (PIIINP) and carboxyterminal propeptide of type I procollagen (PICP) in pla sma and in the wall of abdominal aortic aneurysms in relation to their size and symptomatology. PIIINP serves as a marker of turnover and PICP as a ma rker of the synthesis of the corresponding collagens. Methods. Experimental design: A prospective non-randomised study. Setting: University Hospital, Plzen, Czech Republic. Patients: Eighty-six patients w ho underwent resection of abdominal aortic aneurysms, average age 70.1 year s (range 45 to 91 years), men to women ratio 5:1. The indication for resect ion was its symptomatology without relation to its diameter, and diameter o ver 5 cm in asymptomatic patients. Twenty patients (with similar age and ge nder distribution) scheduled for hernia repair or laparoscopic cholecystect omy were examined as a control group. Main outcome measures: The plasma and tissue PICP and PIIINP concentrations were evaluated using radioimmunoassa y methods. The plasma samples were taken from the cubital vein without the use of a tourniquet. Full-thickness sections of the anterior abdominal aort ic aneurysm wall at the site of the largest aneurysm diameter were taken at the time of operation. Results. A significant difference between plasma PIIINP levels in patients with abdominal aortic aneurysms and the control group was observed (p<0.01) . No correlation of PICP, PIIINP plasma levels with diameter and symptomato logy of abdominal aortic aneurysms was found. The increase in PIIINP tissue concentration was significant in patients with increasing diameter and pos itive symptomatology (p<0.01). No statistically significant correlation bet ween plasma and tissue PICP and PIIINP concentrations was observed. Conclusions. The metabolism of type III collagen is increased in patients w ith abdominal aortic aneurysm, in contrast to type I collagen. The result i s a degradation of collagen in the aneurysmal wall. The turnover of type 11 1 collagen increases with the enlargement of the aneurysm diameter and with the positive symptomatology. Degradation of type III collagen in the aneur ysmal wall has therefore a fundamental significance for abdominal aortic an eurysm rupture. Because no correlation between plasma and tissue levels of PIIINP was found, the plasma levels of PIIINP cannot be used as the plasma markers of this process.