LAUSR

Background: Abdominal aortic aneurysm (AAA) is a deadly irreversible weakening and distension of the abdominal aortic wall. The pathogenesis of AAA remains poorly understood. Investigation into the physical and molecular characteristics of perivascular adipose tissue (PVAT) adjacent to AAA has not been done before and is the purpose of this study. Methods and Results: Human aortae, periaortic PVAT, and fat surrounding peripheral arteries were collected from patients undergoing elective surgical repair of AAA. Control aortas were obtained from recently deceased healthy organ donors with no known arterial disease. Aorta and PVAT was found in AAA to larger extent compared with control aortas. Immunohistochemistry revealed neutrophils, macrophages, mast cells, and T‐cells surrounding necrotic adipocytes. Gene expression analysis showed that neutrophils, mast cells, and T‐cells were found to be increased in PVAT compared with AAA as well as cathepsin K and S. The concentration of ceramides in PVAT was determined using mass spectrometry and correlated with content of T‐cells in the PVAT. Conclusions: Our results suggest a role for abnormal necrotic, inflamed, proteolytic adipose tissue to the adjacent aneurysmal aortic wall in ongoing vascular damage. Clinical Relevance: Abdominal aortic aneurysm is an inflammatory disease. This study shows that adipocytes surrounding the aorta may be a great source of inflammatory leukocytes that are attracted by adipocytes undergoing necrosis and by proinflammatory ceramides. Future strategies preventing the formation of perivascular adipose tissue and targeting inflammation from the adventitial side must be taken into consideration.