Evaluation of murine models of permanent focal cerebral ischemia.

Background: To date murine models of permanent focal cerebral ischemia have not been well characterized. The purposes of this paper were to compare three different permanent middle cerebral artery occlusion (MCAo) models with or without craniectomy, and to identify an ideal mouse model of permanent focal cerebral ischemia.

Methods: Experiments were performed on 45 healthy adult male Kunming mice, weighing 28 to 42 g. The animals were randomly assigned to three groups (n = 15 in every group) based on surgical procedure: MCAo via the external carotid artery (ECA), MCAo via the common carotid artery (CCA), and direct ligation of the middle cerebral artery (MCA). Each day post-ischemia, the animals were scored using an eight-grade neurological function scale, and mortality was also recorded. Seven days post-ischemia, the brains were removed for lesion size determination using triphenyltetrazolium chloride staining. Correlation analysis of lesion volume and neurological score was carried out.

Results: Mortality in the group receiving direct MCA ligation was lowest among the three groups, and there was a significant difference between the direct MCA ligation group and the two intraluminal occlusion groups (P < 0.05). In all groups, neurological scores gradually increased with prolongation of ischemic duration, peaking after two days, then gradually decreasing. In the direct MCA ligation group, however, neurological scores were relatively stable. There was a significant correlation between infarct volume and neurological score 7 days after MCAo in every group (all r > 0.7, P < 0.05), suggesting good reproducibility of lesion volume in the three groups, but the infarct volume was more constant in the direct MCA ligation group.

Conclusion: The direct ligation model of MCAo provides an optimal means of studying permanent focal cerebral ischemia, and is preferable to the models using intraluminal sutures.