Cell-dependent contributions of thrombospondin-1 to the rupture of abdominal aortic aneurysm in mice

Aims Abdominal aortic aneurysms (AAA) rupture is a life-threatening event with unclear molecular mechanisms. Our previous work demonstrated elevated levels of the matricellular protein thrombospondin-1 (TSP1, encoded by Thbs1) in human and mouse AAA tissues. Single-cell RNA sequencing analysis identified macrophages, endothelial cells, and smooth muscle cells as the major TSP1-expressing cells in aneurysmal tissues. Global Thbs1 deletion reduces aneurysm formation by inhibiting vascular inflammation. The aim of this study was to investigate how TSP1 deficiency in different cell types affects AAA rupture. Methods and results AAA and rupture were induced by angiotensin II infusion in hypercholesterolemic mice. In global Thbs1 deficient mice, hypercholesterolemia was achieved by crossing them with Apoe knockout mice. To generate cell type-specific TSP1 deficient mice, Thbs1 ^flox/flox mice were crossed with VE-cadherin-Cre, SMMHC-iCreER^T2, and Lyz2-Cre mice to target endothelial cells, smooth muscle cells, and myeloid cells, respectively. In these conditional knockout models, hypercholesterolemia was induced via AAV-PCSK9. We found that both global and myeloid-specific Thbs1 deletion increased rupture rate over two-fold, whereas endothelial- or smooth muscle cell-specific deletion had no significant effect. Endothelial-specific Thbs1 deletion reduced aneurysm size in the CaCl₂ model. Single-cell RNA sequencing and histology in myeloid-specific Thbs1 knockout aortas revealed broad suppression of inflammation and extracellular matrix production. Conclusion Myeloid-derived TSP1 plays a critical role in inhibiting aneurysm rupture in mice, likely by promoting matrix repair phenotypes in vascular smooth muscle cells, enhancing vascular wall integrity.