Consistent delayed unilateral neuronal death after modified transient focal cerebral ischemia in mice that mimics neuronal injury after transient global cerebral ischemia.
OBJECTIVE
Numerous studies have attempted to reveal the pathophysiology of ischemic neuronal injury using a representative transient global cerebral ischemia (tGCI) model in rodents; however, most of them have used gerbil or rat models. Recent advances in transgene and gene-knockout technology have enabled the precise molecular mechanisms of ischemic brain injury to be investigated. Because the predominant species for the study of genetic mutations is the mouse, a representative mouse model of tGCI is of particular importance. However, simple mouse models of tGCI are less reproducible; therefore, a more complex process or longer duration of ischemia, which causes a high mortality rate, has been used in previous tGCI models in mice. In this study, the authors aimed to overcome these problems and attempted to produce consistent unilateral delayed hippocampal CA1 neuronal death in mice.


METHODS
C57BL/6 mice were subjected to short-term unilateral cerebral ischemia using a 4-mm silicone-coated intraluminal suture to obstruct the origin of the posterior cerebral artery (PCA), and regional cerebral blood flow (rCBF) of the PCA territory was measured using laser speckle flowmetry. The mice were randomly assigned to groups of different ischemic durations and histologically evaluated at different time points after ischemia. The survival rate and neurological score of the group that experienced 15 minutes of ischemia were also evaluated.


RESULTS
Consistent neuronal death was observed in the medial CA1 subregion 4 days after 15 minutes of ischemia in the group of mice with a reduction in rCBF of < 65% in the PCA territory during ischemia. Morphologically degenerated cells were mostly positive for terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and cleaved caspase 3 staining 4 days after ischemia. The survival rates of the mice 24 hours (n = 24), 4 days (n = 15), and 7 days (n = 7) after being subjected to 15 minutes of ischemia were 95.8%, 100%, and 100%, respectively, and the mice had slight motor deficits.


CONCLUSIONS
The authors established a model of delayed unilateral hippocampal neuronal death in C57BL/6 mice by inducing ischemia in the PCA territory using an intraluminal suture method and established inclusion criteria for PCAterritory rCBF monitored by laser speckle flowmetry. This model may be useful for investigating the precise molecular mechanisms of ischemic brain injury.
Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Yasuo
Y
Nishijima
Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Kuniyasu
K
Niizuma
Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Miki
M
Fujimura
Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Yosuke
Y
Akamatsu
Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Hiroaki
H
Shimizu
Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
Teiji
T
Tominaga
D000818:Animals; D056547:CA1 Region, Hippocampal / Q000473:pathology*; D016923:Cell Death; D002560:Cerebrovascular Circulation; D004195:Disease Models, Animal; D002546:Ischemic Attack, Transient / Q000209:etiology / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000473:pathology*; D019635:Neurosurgical Procedures; D013537:Sutures / Q000009:adverse effects; D013997:Time Factors
BCCAO = bilateral CCA occlusion; CBF = cerebral blood flow; CCA = common carotid artery; DAB = diaminobenzidine; ECA = external carotid artery; ICA = internal carotid artery; LSF = laser speckle flowmetry; MCA = middle cerebral artery; MCAO = MCA occlusion; PBS = phosphate-buffered saline; PCA = posterior cerebral artery; PCoA = posterior communicating artery; ROI = region of interest; TTC = 2,3,5-triphenyltetrazolium chloride; TUNEL = terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling; apoptosis; delayed neuronal death; hippocampus; laser speckle flowmetry; mice; rCBF = regional CBF; tGCI = transient global cerebral ischemia; unilateral