CD40/CD40L信号通路在犬大脑中动脉栓塞后微血管血栓形成中的作用及机制研究

Thrombolytic therapy is the only proven effective treatment for superacute ischemic stroke. However, part of the patients could not recover ideally, even the occluded vessel had been recanalized. Microvascular thrombosis followed after cerebral artery occlusion was deemed to be responsible for the unsatisfactory clinical outcome. Recent years, several studies indicated the CD40/CD40L signal pathway might result in the microvascular thrombosis. However, previous related studies have several problems. Firstly, the ischemic models were established using thread embolization or photochemical method. However, the human ischemic events were mostly due to the autogenous clot embolization. Secondly, most of the previous studies used the rats as the experiment animals. However, there were significant difference between the rats and human regarding the neurophysiology. Thirdly, previous studies did not clarify the potential exact mechanism regarding that how the CD40/CD40L signal pathway regulated the formation of the microvascular thrombosis. Therefore, base on our previous beagle dogs cerebral ischemic model established using intervention technique and autogenous clot , we try to evaluate the time course regarding the formation of microvascular thrombosis, clarify the potential mechanism regarding that how the CD40/CD40L signal pathway regulated the formation of the microvascular thrombosis via monitoring the temporal change of downstream cytokine and the multimodal MR methods. Meanwhile, we would use the signal pathway inhibitor to furnish counterevidence regarding CD40/CD40L signal pathway regulated the formation of the microvascular thrombosis. Finally, this study would provide theoretical basis for using the CD40/CD40L signal pathway related drugs to reduce the formation of the microvascular thrombosis and improve the clinical outcome of ischemic events after thrombolytic therapy.

超急性期溶栓治疗被认为是治疗急性脑梗死的有效方法。但部分患者溶栓治疗后，即使栓塞部位血流恢复，其近远期临床转归仍不理想。究其机制，可能与血管栓塞后微血管血栓形成有关。目前，部分研究提出颅内大血管栓塞后微血管血栓形成可能与CD40-CD40L信号通路有关。但仍存在一些问题：1）模型建立采用线栓法或光化学法，而人脑梗死是自体血栓栓塞，两者在发病机制上存在差别。2）既往研究多选用大鼠作实验对象，大鼠与人在神经体液调节方面差别较大。3）既往研究未能阐述CD40-CD40L信号通路在颅内微血管血栓形成过程中的具体机制。因此，本实验在成功建立犬脑梗死模型的基础上，拟研究：1）颅内大血管栓塞后微血管血栓形成量的时间变化规律。2）观察CD40-CD40L信号通路下游细胞因子的变化，并联合多模态MRI，阐述其调控微血管血栓形成的可能机制。同时采用通道抑制剂反证该信号通道的调控作用，具有重要的理论意义。

脑梗死是世界范围内最常见的致残和致死疾病之一。静脉溶栓和动脉取栓技术的发展使得血管再通率明显提高，但部分患者血管再通后恢复情况仍不理想。文献报道可能与脑血管栓塞后微血管血栓形成有关。本课题的研究内容摘要包括以下3个方面： 1）与国内外科研团队合作，优化了犬脑梗死多模式MR扫描参数。 2）研究体素内不相干运动MR成像（IVIM-MRI）的定量参数（D，D*和f）对急性脑梗死的诊断价值。同时将IVIM-MRI定量参数与sCD40L（sCD40L是脑梗死后梗死组织释放的重要炎症因子，是评估脑梗死后血管通透性的重要指标）的演变进行相关性分析，明确IVIM-MRI定量参数潜在的病理生理学意义。3）基于大鼠脑缺血模型，研究CD40与脑梗死后微血管内血栓形成、微血管渗透性，和脑梗死的发生及发展之间的关联。并阐述CD40发挥作用的潜在机制。通过研究，我们发现：1）采用临床用的3T MR扫描仪及膝关节线圈，可以完成大型模式动物（犬）脑缺血模型的MR评估。本研究中优化的犬脑梗死多模式MR扫描参数，可以为其他科研团队进行类似研究提供参考。2）IVIM-MRI定量参数弥散值（D）及灌注分数（f）可以在急性期发现脑梗死组织的弥散及灌注异常。同时f与sCD40L相关性良好，f值可能成为活体评估脑缺血后血管通透性改变的影像标志物。3）基于大鼠脑缺血模型，发现了CD40可以通过调节微血管内血栓形成、微血管渗透性，进而影响脑梗死的发生及发展。并且CD40可能是通过mTOR/S6K信号通道发挥调节作用。综上、本课题发现了CD40-CD40L信号轴能通过mTOR/S6K信号通道调节颅内大血管栓塞后微血管血栓形成。并且发现了IVIM成像中的灌注分数值与sCD40L的表达明显相关，可能是预测微血管血栓形成状态的有效影像标志物。研究结果为临床采用CD40拮抗剂抑制超急性期脑梗死微血管血栓形成并采用MRI技术进行活体评估奠定了理论基础。