基于Glymphatic系统阻塞探讨脑室出血后继发性脑损伤的机制及tPA的干预研究

Intraventricular hemorrhage (IVH) is proven to be the independent negative prognostic factor for patients with spontaneous intracerebral hemorrhage. The mechanism of secondary brain injury in IVH remains unclear, which causes the current managements being ineffective in improving the neurological functional outcome of these patients. Therefore, further investigation on secondary brain injury of IVH and exploration of effective treatment are of great importance. According to our preliminary study on IVH rat model, amount of fibrinogen was observed accumulating in whole-brain subarachnoid space and paravascular space, and the patency of paravascular pathway of cerebrospinal fluid recirculation was blocked. In the meantime, a significant aggregation of β-Amyloid, a large molecular toxic material, was observed in IVH model. In the next step, we are going to testify the hypothesis that blockage of cerebrospinal fluid recirculation caused by accumulation of blood clot in paravascular space may responsible for the Glymphatic dysfunction. And after Glymphatic dysfunction, β-Amyloid aggregation may occur and contribute to the severe secondary brain injury in IVH. Moreover, we are trying to investigate the potential role of tissue-type plasminogen activator (tPA) in relieving severe secondary brain injury in IVH via fibrinolysis of blood clot in paravascular space and improving the function of Glymphatic system.

脑室出血（IVH）是自发性脑出血中最严重的类型，现有治疗措施均难以显著改善IVH患者的神经功能预后。因此，深入研究IVH继发性脑损伤、探索有效的治疗方式具有重要的临床意义。本研究组通过预实验发现大鼠IVH后出现纤维蛋白可在血管周围间隙堆积，并伴随脑脊液无法经“血管周围间隙-Glymphatic系统”再循环进入脑组织的现象，同时IVH后脑组织β-Amyloid等大分子物质大量表达。本课题拟在此基础上，通过脑脊液示踪、溶质大分子示踪的方法，证明IVH后纤维蛋白堵塞血管周围间隙可导致脑脊液经Glymphatic系统对β-Amyloid等溶质大分子的清除功能障碍。再基于Glymphatic系统阻塞，分析β-Amyloid异常堆积与IVH继发性脑损伤的关系；最后进一步以tPA溶解血管周围间隙内纤维蛋白、改善Glymphatic系统的清除功能作为干预方式，探索tPA对IVH继发性脑损伤的治疗作用。

Glymphatic系统是脑内β-Amyloid等溶质大分子主要清除途径，研究表明，Glymphatic系统出现功能障碍后，β-Amyloid堆积可导致炎性反应加重、神经元及白质损伤，在一系列疾病的继发性脑损伤中扮演着重要的作用。本课题使用大鼠构建脑室出血动物模型，通过组织病理研究发现，脑室出血后脑组织血管周围间隙可见大量纤维蛋白表达，双光子显微镜实时观察到荧光示踪剂无法顺利进入血管周围间隙，脑脊液的Glymphatic循环受阻，ELISA定量检测发现脑组织内β-Amyloid含量明显增加。同时，脑室出血后大鼠脑组织继发性脑损伤相关指标包括炎性因子表达升高、神经元标志物和白质纤维标志物表达明显下降，MRI-DTI显示大鼠皮层下白质区FA值下降，透射电镜检查发现大鼠白质髓鞘变薄。大鼠认知功能表现出明显障碍。而采用tPA蛛网膜下腔注射的方法溶解血管周围间隙内纤维蛋白后，可以发现血管周围间隙的脑脊液Glymphatic系统发生堵塞的时间明显延后且堵塞程度明显减轻。同时大鼠脑组织炎性因子表达较实验组下降，而神经元标志物及白质纤维标志物表达升高。MRI-DTI显示皮层下白质FA值升高，透射电镜结果显示髓鞘厚度增加，大鼠表现出认知功能改善。上述研究结果表明，纤维蛋白阻塞脑脊液经Glymphatic系统对β-Amyloid的清除作用，致使脑组织炎性反应加重、白质纤维继发性损伤可能是脑室出血继发性脑损伤的重要机制。同时还表明通过tPA溶解血管周围间隙内纤维蛋白，从而改善Glymphatic系统对β-Amyloid的清除在改善脑室出血后继发性脑损伤的治疗中可能有一定的应用价值。