Detection of type III collagen fragments in specimens of abdominal aortic aneurysms

The purpose of this study was to analyze the collagens in aortic aneurysm walls and to investigate the mechanism of the formation of calcified abdominal aortic aneurysms (AAAs). Collagens were extracted from human aneurysmal aortic walls obtained during surgery, and from human nonaneurysmal aortic walls obtained at autopsy, using pepsin-acetic acid digestion. Electrophoresis and immunoblotting were performed. Type III collagen was found to be reduced in the arteriosclerotic aneurysmal aortic walls. The alpha1 chain of type II collagen/alpha1 chain of type I collagen ratio was 0.35+/-0.11 in the aortic aneurysms and 0.68+/-0.11 in the nonaneurysmal aortic walls (P=0.0111). All the calcified aneurysms were associated with type III collagen fragments having molecular mass of approximately 70 kDa and 30 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Thus, we concluded that AAAs with calcification may be caused by an abnormal degradation of type III collagen.