Role Of Glymphatic System Damage In Cognitive Impairment After Subarachnoid Hemorrhage

Objective: This study established subarachnoid hemorrhage（SAH）by model C57BL/6 mice,and the bilateral lateral ventricle/striatum injected amyloid β-protein 1-40（Aβ1-40）to establish SAH-（V）or SAH-（S）model.The neurological deficit symptoms,cognitive function status,brain histopathological changes and the change of glymphatic system related proteins aquaporin-4（AQP-4）and Aβ1-40 were detected at different time points after SAH in each group.To explore the role of glymphatic system damage in cognitive impairment after SAH.Methods : Healthy male C57BL/6 mice were used,a total of 120 rats,about 8-12 weeks old,weighing 20-25 g.Randomly divided into 12 groups（n =10）:（1）sham group;（2）SAH-7d group;（3）SAH-28 d group;（4）SAH-3m group;（5）sham（V）group;（6）SAH-7d（V）group;（7）SAH-28d（V）group;（8）SAH-3m（V）group;（9）sham（S）group;（10）SAH-7d（S）group;（11）SAH-28d（S）group;（12）SAH-3m（S）group.The SAH model was established by reference to the double-injection blood to the cisterna magna.Neurological deficits in mice were assessed using the Garcia scoring criteria.The open field test was used to observe the spontaneous exploration and anxiety behavior of mice to assess the cognitive status of the mice.Pathological changes were observed by HE and Nissl staining in the mice hippocampus.The polarity and expression of AQP-4and the expression of Aβ1-40 in brain tissue were detected by immunofluorescence staining and Western bolt.The protein content of Aβ1-40 in cerebrospinal fluid was measured by ELISA.Results:（1）Neurological deficit: The nerve defect was most significant 7days after SAH,and the symptoms gradually improved afterwards.Compared with the SAH group,the 28 d and 3m groups（SAH-（V）or SAH-（S））were significantly aggravated.The exclusion may be related to the multiple injections of the micro-sampler in the process of injecting protein to aggravate brain tissue damage.（2）The results of open field test: With the passage of time after SAH,the mean speed slowed down,the immobile time gradually prolonged,and the O zone time gradually decreased,suggesting that the cognitive function of the mice gradually deteriorated.Compared with the SAH group,the SAH-（V）or SAH-（S）group showed more significant differences in the 28 d and 3m groups,indicating that the cognitive impairment was more severe.（3）Pathological changes: After SAH,the hippocampus tissue gradually showed neuronal structural disorder,interstitial edema,narrowing of the cell body,deep stenosis of the nucleus,thick staining of cytoplasmic eosin,increased necrosis,and reduction of Nissl bodies.Compared with the SAH group at the same time,the nerve cells in the SAH-（V）or SAH-（S）group were more severely damaged,with fewer Nissl bodies and more necrosis.（4）AQP-4 and Aβ1-40 protein detection: After SAH,the polarity and expression of AQP-4 in brain tissue decreased gradually,and Aβ1-40 expression in brain tissue and cerebrospinal fluid gradually increased.Compared with the SAH group at the same time,the trend of protein expression were consistent in SAH-（V）or SAH-（S）group.But the difference was even greater,especially in the 28 d and 3m groups.Conclusions: The decrease in expression and polarity of AQP-4 after SAH in mice makes the AQP-4-dependent glymphatic system damage,resulting in decreased Aβ clearance,excessive aggregation and cognitive dysfunction in the long-term.