Poster abstracts
Poster number 12 submitted by Blain Jones
Abdominal aortic aneurysms and abnormal collagen fibril ultrastructure
Blain Jones (Department of Biomedical Engineering, The Ohio State University), Anna Debski (Department of Material Science and Engineering, The Ohio State University), Jeff R. Tonniges (Biophysics Graduate Program, The Ohio State University), David Yeung (Department of Biomedical Engineering, The Ohio State University), Michael Go (Department of Vascular Surgery, The Ohio State University)
Abstract:
Abdominal aortic aneurysms (AAA) represent a persistent abnormal dilatation of the aorta that is accompanied by significant, atypical remodeling of the extracellular matrix (ECM). Understanding the alterations in organization and structure of the elastin and collagen fibers in the ECM can provide novel insights into the functional characteristics of the aneurysm. While ultrastructural features of elastin remodeling are well characterized in AAA, little is understood about the quality of the collagen fibrils in the remodeled vessel wall in AAA.
The goal of this study was to determine if AAA contains collagen fibrils with ultrastructural abnormalities. Studies were conducted on clinical AAA tissue extracted during surgery. In addition, aortic tissue obtained from mouse models of ApoE -/- angiotension-II induced AAA were used in conjunction with saline-infused controls. Trichrome and immunohistochemistry were used to characterize the presence of collagen in AAA tissue sections. Collagen fibrils were imaged in situ using transmission electron microscopy (TEM). Additionally, atomic force microscopy (AFM) was used to map the topographic height as well as lateral features of a sample surface at the nanoscale level.
Our results show how abnormal collagen fibrils were present in both human and murine AAA. In particular TEM imaging revealed regions in AAA where the collagen fibrils were ‘wavy’ as compared to normal tissue and exhibited a reduced contrast in D-periodicity. Using AFM we could unequivocally characterize how the D-period depth (but not the width) is altered in the abnormal fibrils observed in AAA. To identify possible causes of this abnormal collagen structure, the mouse AAA sections were immunostained with antibodies against the collagen receptors (DDR1 and DDR2). Identifying the occurrence and possible causes of collagen fibril abnormalities may help identify new biomarkers associated with ECM remodeling accompanying the pathogenesis of AAA.
Keywords: collagen, atomic force microscopy, aneurysm