Collagen types and matrix protein content in human abdominal aortic aneurysms

Abstract

Deficiencies of total collagen, type III collagen, and elastin have been proposed to explain aneurysm formation. Infrarenal aortas were collected from 19 patients (age 70 +/- 7 years) undergoing operative repair of abdominal aortic aneurysms (diameter 7 +/- 2 cm) and from 13 autopsies (age 63 +/- 17 years) of patients without aneurysm disease (controls). Wall thickness and collagen and elastin concentration were determined in full-thickness aorta. Collagen types I and III were measured after digestion with cyanogen bromide, which solubilized nearly 90% of total collagen for typing. Cyanogen bromide peptides were separated by sequential carboxymethylcellulose and agarose chromatography and quantified by peak area measurement with computerized image analysis. Histologic examination revealed prominent inflammatory cell infiltration and deficient, fragmented elastin in the aneurysms. Aortic wall thickness was similar in aneurysms and in control specimens. In the aneurysms, collagen was increased (37% +/- 16% vs 24% +/- 5%; p less than 0.05) and elastin was decreased (1% +/- 1% vs 12% +/- 7%; p less than 0.001), expressed as a percentage of delipidized, decalcified dry weight. Collagen type I accounted for 74% +/- 4% of aneurysm and 73% +/- 4% of control collagen solubilized for typing, and collagen type III accounted for 26% +/- 4% of aneurysm and 27% +/- 4% of control collagen solubilized for typing. Neither patients with a family history of aneurysms nor those without a history of aneurysms had collagen type III deficiency. Atherosclerotic abdominal aortic aneurysms are associated with an inflammatory process and may result from elastin degradation and not a deficiency of type III collagen.

Elastin and collagen fibre microstructure of the human aorta in ageing and disease: a review

“…This trend also held true specifically looking at the medial layer [73] where elastin was virtually absent and completely disrupted with fewer cross-links. The elastin concentration in the wall of IRAA aneurysms was about 10 times less than the value in the wall of control IRAA [72]. This was further validated by two other studies that showed that the amount of total elastin in IRAA aneurysm was decreased compared with control [68,74].…”

“…The total collagen concentration was higher in the wall of IRAA aneurysms (37 + 16%) compared with control IRAA (24 + 5%), but no differences were seen in the concentrations of type I collagen (74 + 4% and 73 + 4%, respectively) or type III (26 + 4% and 27 + 4%, respectively). Rizzo et al [72] also reported a higher concentration of collagen in the wall of IRAA aneurysms compared with control IRAA. In another study, however, the collagen concentration was not statistically different between IRAA aneurysm and control IRAA [75].…”

“…Elastin content was also analysed specifically in the wall of IRAA aneurysms showing less and fragmented elastin [72]. This trend also held true specifically looking at the medial layer [73] where elastin was virtually absent and completely disrupted with fewer cross-links.…”

“…Total collagen concentration and concentration of collagen types I and III have also been evaluated specifically in the wall of IRAA aneurysm and in control IRAA [72]. The total collagen concentration was higher in the wall of IRAA aneurysms (37 + 16%) compared with control IRAA (24 + 5%), but no differences were seen in the concentrations of type I collagen (74 + 4% and 73 + 4%, respectively) or type III (26 + 4% and 27 + 4%, respectively).…”

Enhanced delineation of degradation in aortic walls through OCT

“…The aorta is a cardiovascular vessel which wall is structured in three different layers: intima, media and adventitia [2]. The media layer provides strength and elasticity to the wall due to an organized matrix of collagen and elastin fibers.…”