Histological examination of abdominal aortic aneurysm (AAA) tissues demonstrates extracellular matrix destruction and infiltration of inflammatory cells. Previous work with mouse models of AAA has shown that anti-inflammatory strategies can effectively attenuate aneurysm formation. Thrombospondin-1 is a matricellular protein involved in the maintenance of vascular structure and homeostasis through the regulation of biological functions, such as cell proliferation, apoptosis, and adhesion. Expression levels of thrombospondin-1 correlate with vascular disease conditions.

To use thrombospondin-1–deficient (Thbs1^−/−) mice to test the hypothesis that thrombospondin-1 contributes to pathogenesis of AAAs.

Mouse experimental AAA was induced through perivascular treatment with calcium phosphate, intraluminal perfusion with porcine elastase, or systemic administration of angiotensin II. Induction of AAA increased thrombospondin-1 expression in aortas of C57BL/6 or apoE−/− mice. Compared with Thbs1^+/+ mice, Thbs1^−/− mice developed significantly smaller aortic expansion when subjected to AAA inductions, which was associated with diminished infiltration of macrophages. Thbs1^−/− monocytic cells had reduced adhesion and migratory capacity in vitro compared with wild-type counterparts. Adoptive transfer of Thbs1^+/+ monocytic cells or bone marrow reconstitution rescued aneurysm development in Thbs1^−/− mice.

Thrombospondin-1 expression plays a significant role in regulation of migration and adhesion of mononuclear cells, contributing to vascular inflammation during AAA development.