Impaired gait pattern as a sensitive tool to assess hypoxic brain damage in a novel mouse model of atherosclerotic plaque rupture

Abstract

Apolipoprotein E deficient (ApoE−/−) mice with a heterozygous mutation in the fibrillin-1 gene (Fbn1C1039G+/−) show spontaneous atherosclerotic plaque ruptures, disturbances in cerebral flow and sudden death when fed a Western-type diet (WD). The present study focused on motor coordination and spatial learning of ApoE−/− Fbn1C1039G+/− mice on WD for 20weeks (n=21). ApoE−/− mice on WD (n=24) and ApoE−/− Fbn1C1039G+/− mice on normal diet (ND, n=21) served as controls. Starting from 10weeks of diet, coordination was assessed every two weeks by the following tests: gait analysis, stationary beam, wire suspension and accelerating rotarod. The Morris water maze test was performed after 13weeks of diet to study spatial learning. At the end of the experiment (20weeks of WD), the mice were sacrificed and the brachiocephalic artery and brain were isolated. From 12weeks onward, gait analysis of ApoE−/− Fbn1C1039G+/− mice on WD revealed a progressive increase in track width as compared to ApoE−/− mice on WD and ApoE−/− Fbn1C1039G+/− mice on ND (at 20weeks: 29.8±0.6mm vs. 25.8±0.4mm and 26.0±0.5mm). Moreover, the stationary beam test showed a decrease in motor coordination of ApoE−/− Fbn1C1039G+/− mice on WD at 18 and 20weeks. The wire suspension test and accelerating rotarod could not detect signs of motor impairment. Spatial learning was also not affected. Histological analysis of the brachiocephalic artery showed larger and more stenotic plaques in ApoE−/− Fbn1C1039G+/− mice on WD. Furthermore, the parietal cortex of ApoE−/− Fbn1C1039G+/− mice on WD showed pyknotic nuclei as a sign of hypoxia and the percentage of pyknosis correlated with track width. In conclusion, gait analysis may be an efficient method for analyzing hypoxic brain damage in the ApoE−/− Fbn1C1039G+/− mouse model. This test could be of value to assess the effect of potential anti-atherosclerotic therapies in mice.