Novel High-Throughput In Vitro Model for Identifying Hemodynamic-Induced Inflammatory Mediators of Cerebral Aneurysm Formation

Cerebral aneurysms are thought to develop at locations of hemodynamic shear stress, via an inflammatory process. The molecular mechanism that links shear stress to inflammation, however, is not completely understood. Progress in studying this disease is limited by a lack of a suitable in vitro model. To address this, we designed novel in vitro parallel-plate flow chamber models of a straight artery, a bifurcation, and a bifurcation aneurysm. We compared endothelial cell phenotypes across the 3 different models and among microenvironments within each flow model by cytokine array, ELISA, and relative immunofluorescence. Human aneurysms express interleukin-8 and chemokine (C-X-C motif) ligand 1 (CXCL1), whereas normal arteries do not. The bifurcation aneurysm model showed significantly higher interleukin-8 and CXCL1 levels than both the straight artery and bifurcation models. Within the bifurcation and bifurcation aneurysm models, endothelial cells near the bifurcation or within the aneurysm sac microenvironments have significantly higher expression of CXCL1, and interleukin-8 and CXCL1, respectively, than at the straight proximal segment or the limbs of the bifurcation. Murine aneurysms express CXCL1, and it is the primary ELR+ CXC chemokine expressed, whereas normal arteries do not. CXCL1 antibody blockade results in significantly fewer murine aneurysms (13.3 versus 66.7%; P=0.0078), decreased neutrophil infiltration, and vascular cell adhesion molecule 1 expression than an immunoglobulin G control. We successfully designed and validated a novel hemodynamic model of cerebral aneurysms in vitro. We also show that shear stress-induced CXCL1 plays a critical role in cerebral aneurysm formation.