Heterogenic Ascending Aortic Wall Tissue: A Translational Approach

Background: Successful surgery of the ascending aorta requires knowledge on tissue demeanor. Ascending aortic dilatation, tissue degeneration and inflammation may predispose to aortic events such as aortic dissection. We investigated the presence of complement C4d, Carbonic anhydrase 9 (CAIX), Immunoglobulin G4 (IgG4) and endothelial CD31 of the ascending aortic wall, and sought the interrelation of ascending aortic dilatation and ascending aortic wall histology.

Material and methods: After institutional review board approval and patient consent, ascending aortic tissue samples were procured from patients undergoing surgery for ascending aorta at Tampere University Hospital, Tays Heart Hospital. The samples were stained with Hematoxylin and Eosin (H&E), Verhoeff-van Gieson (VVG), underwent immunohistochemistry, and were processed for systematic semi- quantification.

Results: Intimal inflammation, thickness, cellularity, and a number of plasma cells were decreased in C4d-positive as compared with C4d-negative aortas (I). IgG4- positivity revealed concealed aortitis (II). Adventitial inflammation consisting of macrophages, B-cells and cellular proliferation, together with intimal macrophages and media elastin degradation, was increased in CA IX-positive as compared with CAIX negative aortas (III). CD31 positivity of the ascending aortic wall reflected neovascularization associated with aortic dissection (IV).

Conclusions: The lack of aortic wall C4d, increased IgG4- and CD31-positivity suggest increased risk of dissection, while CAIX-positivity suggests aortic wall stability. The aortic tissue immunohistochemistry reveals the heterogenic nature of the ascending aorta.