高切应力促进血管新生介导易损斑块形成的力生物学机制

Destabilization of atherosclerotic rupture-prone plaque is the main cause of acute coronary events leading to morbidity and mortality. It's traditionally thought that atherosclerotic lesions are predisposed to develop in arterial region with low shear stress, while clinical data show that plaque destabilization commonly occurs within proximal end of plaque, which experiences high shear stress. Despite that he proximal end of plaque contains abundant inflammatory cells and the distal end is enriched with smooth muscle cells, through which biomechanical and biological factors localize individual plaque on proximal end of plaque remains unknown. Considering that new-born microvessels, regulated by endothelium-derived pro-angiogenic factors under high shear stress, are the major entry points for inflammatory cells to intrude into plaque, we hypothesize that high shear stress stimulates endothelium to produce pro-angiogenic factors and induces intrapalque neovascularization, which in turn aggravates inflammation and promotes formation and destabilization of rupture-prone plaque. By establishing atherosclerosis animal model, we attempt to investigate in vivo how high shear stress regulates intraplaque neovascularization and rupture-prone plaque formation. In addition, we will elucidate the mechanism in which Id1 (inhibitor of DNA-binding) protein is involved in high shear stress-mediated angogenesis in vitro. Furthermore, secretome methodology will be applied to identify the high shear stress-induced Id1-mediated angiogenic factors involved in angiogenesis. By interpreting the biomechanical and biological mechanism underlying rupture-prone plaque localization on high shear stress region, this study will potentially offer accurate therapeutic target for clinical treatment of atherosclerotic rupture-prone plaques.

动脉粥样硬化（AS）易损斑块的破裂是急性心脑血管疾病致残致死的主要原因。传统观点认为AS好发于低切应力区域，而临床显示斑块破裂常发生在斑块近心端高切应力区域；已形成的斑块的近心端富含炎症细胞，远心端富含平滑肌细胞，单个斑块破裂发生在近心端的力生物学机制还远没有被阐明。基于斑块内的新生血管是炎症细胞进入斑块的通道和高切应力促进内皮层分泌血管新生因子，本项目提出如下科学假设：斑块近心端高切应力通过促进血管内皮层分泌促血管新生因子诱导斑块内血管新生，而新生血管加剧炎症反应来加速易损斑块的形成。项目拟通过动物模型研究高切应力如何调控斑块内血管新生和易损斑块的形成，通过体外实验研究分化抑制因子(Id1)参与高切应力介导血管新生的机理，并用蛋白质组学手段筛选切应力作用下Id1调控血管新生的蛋白。本研究不仅有助于阐明易损斑块发生在高切应力区域的力生物学机制，而且将为易损斑块的临床治疗提供精细的靶点。

急性心脑血管疾病发生的主要原因是动脉粥样硬化（AS）斑块破裂和血栓形成，易损斑块是AS斑块破裂和血栓形成的直接原因。因此，深入研究易损斑块发生机制对降低AS疾病的致残致死率有至关重要的意义。有研究报道斑块破裂主要发生在斑块近心端的高切应力区域，但是其机理一直没能阐明。本研究在新西兰大白兔和ApoE-/-小鼠中成功构建套环模型和颈总动脉部分结扎手术模型以模拟高，低和震荡切应力，通过小动物超声检测其血流状态后进行高脂饲料喂养以构建动脉硬化形成和易损斑块模型。模型构建成功后，结果显示低切应力促进动脉粥样硬化形成，而高切应力促进有大量新生血管浸润的易损斑块形成。使用血管新生抑制剂（TNP-470）对斑块进行治疗，显著抑制动脉粥样硬化易损斑块形成。颈总动脉部分结扎手术模型发现震荡流通过增强脂质吸收促进动脉硬化发生发展。通过在体及体外实验证实Id1蛋白是震荡切应力促进的脂质吸收的重要蛋白。基于切应力调控动脉硬化发生发展，我们提出了力学对血管平滑肌细胞调控机制以及三维基质中平滑肌细胞的迁移模型。在细胞和分子水平上阐述了切应力对力学响应蛋白Id1的调控和Id1调控VEGF和MT-MMPs等分泌蛋白在血管新生中的力学生物学机制及VEGF过表达细胞促进内皮化机制。也证明了切应力通过VEGF-VEGFR2 FAK/paxillin及VEGF-AAMP-RhoA/ROCK信号通路调控内皮细胞迁移和管腔形成的机制。此外，本研究还通过蛋白组学方法检测了不同力学条件下差异蛋白表达情况并进行了相关信号通路分析。综上所述，本研究的所有结果阐明了血管新生是动脉粥样硬化易损斑块发生在高切应力区域的关键机制，以及Id1参与高切应力介导动脉硬化发生发展以及易损斑块形成的相关分子机制，这将会为深入了解 AS 易损斑块的发生机制提供一定的理论依据，为动脉粥样硬化疾病治疗提供新的靶点。