Why do aortas cleave or dilate? Clues from an electronic scanning microscopy study in human ascending aortas

• Grant number: 13/23162-6
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: February 01, 2014
• End date: July 31, 2014
• Field of knowledge: Health Sciences - Medicine - Pathological Anatomy and Clinical Pathology
• Principal Investigator: Paulo Sampaio Gutierrez
• Grantee: Paulo Sampaio Gutierrez
• Host Institution: Instituto do Coração Professor Euryclides de Jesus Zerbini (INCOR). Hospital das Clínicas da Faculdade de Medicina da USP (HCFMUSP). Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil

Abstract

In ascending aorta aneurysms (AscAA) the whole vessel wall dilates. In aortic dissections (AD) the wall cleaves into two sheets. Both may present fine elastic fragmentation and decrease in collagen. We analyzed if alterations in the three-dimensional structure of these fibers could be involved in the pathogenesis of AscAA/AD. Specimens obtained at surgery for these diseases (n=4 for each) and on coronary artery bypass surgery (controls, n=4) were submitted to treatments which either preserves collagen or the elastic structure. These samples were examined by scanning electron microscopy. In all groups most of collagen fibers are packed forming laminar structures very similar to the elastic lamellae. In AscAA/ASD, the fibers show signs of degradation and/or fragmentation. Elastic tissue is distributed in large sheets with fenestrations, with smaller branches between them. Elastic sheet fragmentation, that at light microscopy seems to be located at random, in one case with dissection and 2 with aneurysm had a pattern of clefts, irregular but approximately transversal to the main axis of the wall. The recognition of this pattern and the degradation/fragmentation of collagen and elastic fibrils facilitate to understand why the wall is weak as to be affected by the aneurysms and mostly the dissections. (AU)