Abdominal aortic aneurysm: characteristics of extracellular matrix abnormalities caused by disorders of collagen types I and III and elastin.

Abdominal aortic aneurysm (AAA) is a degenerative disorder of the infrarenal aorta leading to pathological dilatation and an increased risk of rupture. Despite significant progress in understanding AAA pathogenesis, the molecular and structural alterations within the aortic wall remain incompletely elucidated. Collagen and elastin, the principal components of the extracellular matrix (ECM), are crucial for maintaining vascular integrity. This study aimed to analyze the histological and molecular characteristics of AAA wall fragments to identify structural and compositional changes in ECM organization. Aneurysmal wall specimens were divided into three distinct layers: inner, middle, and external. Histological analysis focused on the morphology and spatial arrangement of collagen and elastin fibers. The molecular evaluation involved quantifying the expression of COL1A1, COL1A2, COL3A1, and ELN genes together with measurement of the corresponding protein levels of collagen type I and III α-chains and elastin. Collagen and elastin fibers exhibited marked heterogeneity in structure and distribution across the aortic wall layers, showing loss of regularity and linear alignment. These alterations correlated with a reduced number of smooth muscle cells. Expression of collagen-related genes and the relative abundance of collagen I and III α-chains varied between the analyzed layers, suggesting region-specific remodeling of the aneurysmal wall. Distinct structural and molecular changes within the extracellular matrix contribute to loss of aortic wall integrity and may underlie the progressive nature of AAA. Understanding these layer-dependent remodeling processes could provide new perspectives for targeted prevention and therapeutic strategies.