Endothelial to mesenchymal transition in the interleukin-1 pathway during aortic aneurysm formation

OBJECTIVE: Endothelial to mesenchymal transition may represent a key link between inflammatory stress and endothelial dysfunction seen in aortic aneurysm disease. Endothelial to mesenchymal transition is regulated by interleukin-1β, and previous work has demonstrated an essential role of interleukin-1 signaling in experimental aortic aneurysm models. We hypothesize that endothelial to mesenchymal transition is present in murine aortic aneurysms, and loss of interleukin-1 signaling attenuates this process.

METHODS: Murine aortic aneurysms were created in novel CDH5-Cre lineage tracking mice by treating the intact aorta with peri-adventitial elastase. Endothelial to mesenchymal transition transcription factors as well as endothelial and mesenchymal cell markers were analyzed via immunohistochemistry and immunofluorescence (n = 10/group). To determine the role of interleukin-1 signaling, endothelial-specific interleukin-1 receptor 1 knockout and wild-type mice (n = 10/group) were treated with elastase. Additionally, C57/BL6 mice were treated with the interleukin-1 receptor 1 antagonist Anakinra (n = 7) or vehicle (n = 8).

RESULTS: Elastase treatment yielded greater aortic dilation compared with controls (elastase 97.0% ± 34.0%; control 5.3% ± 4.8%; P < .001). Genetic deletion of interleukin-1 receptor 1 attenuated aortic dilation (control 126.7% ± 38.7%; interleukin-1 receptor 1 knockout 35.2% ± 14.7%; P < .001), as did pharmacologic inhibition of interleukin-1 receptor 1 with Anakinra (vehicle 146.3% ± 30.1%; Anakinra 63.5% ± 23.3%; P < .001). Elastase treatment resulted in upregulation of endothelial to mesenchymal transition transcription factors (Snail, Slug, Twist, ZNF) and mesenchymal cell markers (S100, alpha smooth muscle actin) and loss of endothelial cell markers (vascular endothelial cadherin, endothelial nitric oxide synthase, von Willebrand factor). These changes were attenuated by interleukin-1 receptor 1 knockout and Anakinra treatment.

CONCLUSIONS: Endothelial to mesenchymal transition occurs in aortic aneurysm disease and is attenuated by loss of interleukin-1 signaling. Endothelial dysfunction through endothelial to mesenchymal transition represents a new and novel pathway in understanding aortic aneurysm disease and may be a potential target for future treatment.