Background: In animal models, flow-loading is a necessary and sufficient hemodynamic
factor to express the Cerebral Aneurysm (CA) phenotype. Using a rat model, this study
characterizes the molecular events that comprise the cerebral arterial response to flow-loading and
reveals their significance relating to the CA phenotype.
Objective: To characterize the molecular events that underlie expansive remodeling of cerebral arteries
in two genetically distinct inbred rat strains with differential susceptibility to flow-dependent
Methods: Thirty-two rats underwent bilateral common carotid artery ligation (BCL) (n=16) or
Sham Surgery (SS) (n=16). Nineteen days later, vertebrobasilar arteries were harvested, histologically
examined and analyzed for mRNA and protein expression. Flow-induced changes in histology,
mRNA and protein expression were compared between BCL and SS rats. Differences between
aneurysm-prone (Long Evans, LE) and resistant (Brown Norway, BN) strains were evaluated.
Results: Basilar Artery (BA) medial thickness/luminal diameter ratio was significantly reduced in
BCL rats, without significant differences between LE (2.02 fold) and BN (1.94 fold) rats. BCL
significantly altered BA expression of mRNA and protein but did not affect blood pressure. Eight
genes showed similarly large flow-induced expression changes in LE and BN rats. Twenty-six
flow responsive genes showed differences in flow-induced expression between LE and BN rats.
The Cthrc1, Gsta3, Tgfb3, Ldha, Myo1d, Ermn, PTHrp, Rgs16 and TRCCP genes showed the
strongest flow responsive expression, with the largest difference between LE and BN rats.
Conclusions: Our study reveals specific molecular biological responses involved in flow-induced
expansive remodeling of cerebral arteries that may influence differential expression of flowdependent