Increased amount of type III pN-collagen in human abdominal aortic aneurysms: evidence for impaired type III collagen fibrillogenesis.
OBJECTIVE
This study aimed to characterize the distribution of structural domains of type I and III collagens in the wall of abdominal aortic aneurysms (AAAs), by the use of undilated atherosclerotic aortas (aortoiliac occlusive disease [AOD]) and healthy abdominal aortas as controls.


METHODS
Immunohistochemical staining was applied with antibodies for the aminoterminal propeptides of type I (PINP) and type III (PIIINP) procollagens, which represent newly synthesized type I and III pN-collagens. In addition, an antibody against the aminoterminal telopeptide of type III collagen (IIINTP) was used as a means of detecting maturely cross-linked type III collagen fibrils.


RESULTS
The newly synthesized type III procollagen detected by means of PIIINP staining was concentrated in the media in aneurysmal aortas, whereas type I pN-collagen was localized in the intima in both AAAs and AODs. The healthy aortas showed no immunoreactivity for either PIIINP or PINP. The cross-linked type III collagen, detected by means of IIINTP staining, stained transmurally in all study groups, but appeared more abundant in the media in AAAs.


CONCLUSIONS
Our results strongly suggest that the metabolism of type III collagen is enhanced in AAAs. Intensive type III pN-collagen staining was present mainly in the media layer in AAAs, suggesting a role of type III collagen in aneurysm formation, whereas type I pN-collagen was present in the intima in both AAAs and AODs, suggesting that type I collagen synthesis is a fibroproliferative response related to the atherosclerotic process. The increased type III pN-collagen in AAAs may result in impaired fibril formation and, thus, in decreased tensile strength of aneurysmal tissue.
Bode
M K
MK
Departments of Clinical Chemistry, University of Oulu, Finland.
Soini
Y
Y
Melkko
J
J
Satta
J
J
Risteli
L
L
Risteli
J
J
D000368:Aged; D017542:Aneurysm, Ruptured / Q000209:etiology; D001012:Aorta, Abdominal / Q000378:metabolism / Q000473:pathology; D017544:Aortic Aneurysm, Abdominal / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D001018:Aortic Diseases / Q000378:metabolism / Q000473:pathology; D001157:Arterial Occlusive Diseases / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D010455:Peptides / Q000276:immunology / Q000378:metabolism; D011347:Procollagen / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D013194:Staining and Labeling; D013718:Tensile Strength; D017539:Tunica Intima / Q000378:metabolism / Q000473:pathology
D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C098143:pN-collagen type III