Mechanisms of vaso-occlusion in sickle cell disease

血管闭塞，包括中风，是镰状细胞病（SS-C）发病和死亡的主要原因。目前尚不清楚SS-D中观察到的促凝剂或血小板活性的增强是否直接导致了血管阻塞的发病机制，还是仅仅反映了镰状红细胞引起的血管损伤。此外，尽管中枢神经系统外SS-D的血管闭塞主要涉及微血管，中枢神经系统血管阻塞或临床中风，但涉及大脑中大动脉，这是血小板诱导病理的可能部位。我们假设在SS-C中，凝血蛋白活性的增加对微血管阻塞起重要作用，而血小板优先促进中枢神经系统血管病理。因此，本项目的具体目标是：1)利用遗传学和药理学方法研究凝血途径对微血管闭塞发展的贡献；2)研究血小板对镰状细胞诱导的中枢神经系统血管病理演变的贡献。我们将使用完全表达人镰状血红蛋白的转基因小鼠，以及一种密切模仿人类严重SS-D病理生物学的表型，来确定慢性和急性微血管疾病部位的凝血酶激活和纤维蛋白积累水平。我们将测试抑制特定凝血途径的效果，同时使用基因操作和药物治疗。最后，我们将研究血小板在镰状细胞诱导的血管病理演变中的作用。最后，我们将研究血小板在镰状细胞诱导的脑循环血管病理演变中的作用，使用手术放置的颅窗检测单个细胞事件和激光多普勒血流仪（LDF）监测转基因镰状小鼠的脑血流。我们预计这些研究将阐明凝血蛋白在微血管闭塞中的作用以及血小板在中枢神经系统血管疾病中的作用。此外，这些研究将为抗凝血和抗血小板治疗和预防血管闭塞的价值提供见解。

Vaso-occlusion, including stroke, is the major cause of morbidity and mortality in sickle cell disease (SS-C). It is unclear whether the enhanced pro-coagulant or platelet activity observed in SS-D directly contributes to the pathogenesis of vascular obstruction or merely reflects vascular injury caused by the sickle erythrocyte. Furthermore, while vaso-occlusion in SS-D outside the central nervous system (CNS) primarily involves microvessels, CNS vascular obstruction, or clinical stroke, involves the middle to large cerebral arteries, a likely site for platelet-induced pathology. We hypothesize that in SS-C, increased activity of coagulant proteins contributes importantly to microvascular vaso-occlusion, while platelets preferentially contribute to CNS vascular pathology. Therefore, the Specific Aims for this project are to: 1) Examine the contribution of the coagulation pathway to the development of microvascular vaso- occlusion using both genetic and pharmacologic approaches and 2) Investigate the contribution of platelets towards the evolution of sickle cell-induced CNS vascular pathology. We will use transgenic mice that exclusively express human sickle hemoglobin, together with a phenotype that closely mimics the pathobiology of severe SS-D in man, to determine the level of thrombin activation and fibrin accumulation that occurs at sites of chronic and acute microvascular disease. We will test the effect of inhibition of specific coagulation pathways using both genetic manipulation and pharmacologic therapy. Finally, we will study the role of platelets in the evolution of sickle cell-induced vascular pathology. Finally, we will study the role of platelets in the evolution of sickle cell- induced vascular pathology of the cerebral circulation using both surgically placed cranial windows to detect individual cellular events and laser Doppler flowmetry (LDF) to monitor cerebral blood flow in transgenic sickle mice. We anticipate that these studies will clarify the role of coagulant proteins in microvascular vaso-occlusion as well as the role of platelets in CNS vascular disease. Additionally, these studies will provide insights into the value of anti-coagulant and anti-platelet therapies for the treatment and prevention of vaso-occlusion.