Abstract 17640: An in vitro Approach to Studying Shear Stress - Induced Inflammation in Cerebral Aneurysm Progression
OBJECTIVE: The development of cerebral aneurysms is thought to be an inflammatory process and related to shear stress, but how shear stress causes inflammatory progression of aneurysms is not fully known. We studied how shear stress induces inflammatory pathways in bio-reactor flow chamber models of an arterial bifurcation and a bifurcation aneurysm.
METHODS: We used computational fluid dynamics (CFD) using Ansys FLUENT to validate the designs mimicking an arterial bifurcation and a bifurcation aneurysm. The flow chambers consisted of a layer of human umbilical vein endothelial cells subjected to peristaltic flow at 60 bpm over 24-hrs. We analyzed PGE2 and PGI2 in the perfusate to ascertain the inflammatory conditions. Expression of COX-1, COX-2 and MCP-1 in vitro was measured by qRT-PCR and relative fluorescence immunohistochemistry (IHC). Next, we induced cerebral aneurysms in C57BL/6 mice by ligating the right renal and left common carotid arteries, and an intracranial injection of 8% elastase. Intracranial vessels were collected 1-wk post surgery and analyzed via IHC for COX-2 and MCP-1. Finally, a cytokine array was used to screen the in vitro perfusate.
RESULTS: Significantly more PGE2 was secreted in the aneurysm bioreactor (27.11 pg/mL, p<0.05) than the bifurcation (13.78 pg/mL) or straight segment flow chamber (11.33 pg/mL) systems. COX-2 and MCP-1 mRNA were significantly upregulated by qRT-PCR (5.84- vs 2.85 -fold for COX-2, p<0.05, and -2.65- vs -4.40 -fold for MCP-1, p<0.05) and by IHC (199 vs 171 RFU for COX-2, p<0.05) at the bifurcation and aneurysm pocket as compared to parent or limb segments of the chamber in vitro. Sections from mouse aneurysmal vessels showed increased expression of COX-2 and MCP-1 via IHC. Cytokine panel showed increased pro-inflammatory mediators in the bifurcation aneurysm chamber such as IL-3, IL-8, MCP-2, and RANTES.
CONCLUSIONS: Shear stress at bifurcation aneurysms induces endothelial COX-2, which results in increased production of pro-inflammatory prostaglandin E2, and MCP-1, a cytokine critical to vascular inflammatory pathways and aneurysm formation. Our novel in vitro model recreates these key features of aneurysm pathophysiology and suggests new molecular targets for modulation in aneurysm progression.
- © 2012 by American Heart Association, Inc.