HEMOSTASIS IN SICKLE CELL ANEMIA--INFANCY TO ADULTHOOD

对镰状细胞病（SCD）止血的研究表明， 凝血酶和纤维蛋白的生成在稳态期间增加， 血管闭塞危象中是否发生进一步激活的相互矛盾的数据 （VOC）。VOC期间的血小板活化发生在 稳态止血途径的选择性评价，即 内源性或外源性活化、纤维蛋白溶解和血小板-内皮 尚未报告激活。也没有纵向评估， 在HbF水平从80%下降到80%的独特过渡期间， <10%。我们建议测试这一假设，即HbF水平升高， 婴儿防止凝血激活见于年龄较大的儿童， 成年人了研究设计将使我们能够确定保护是否是由于 抗干扰抑制红细胞内HbS聚合 体内镰状-去镰状，因此缺乏循环红细胞 膜促凝血囊泡，因此没有止血激活的迹象。 对年龄较大的儿童的研究将评估内在激活是否 （与疼痛和急性炎症的起源有关）仅发生在 VOC，以及单核细胞TF表达在外源性。研究将 包括内在标记物[高分子量（HK）和低分子量 激肽原（LK）、裂解、蛋白质印迹和激肽释放酶-α/2 巨球蛋白];外源性标志物[单核细胞TF测定、TFPI和因子 VIIa];其他活化和纤溶标志物[凝血酶原F1.2，FPA， TAT、tPA、PAI-1、D-二聚体和PAP]尿激酶型纤溶酶原激活剂 受体（uPAR）和可溶性uPAR;血小板内皮标志物[的 活化依赖性表位，体内血小板微粒， 循环可溶性粘附分子和尿类花生酸。 红细胞评价包括定量HbF、F细胞、粘附性， 表面粘附分子和红细胞促凝血活性。 神经功能评价包括定量HbF、F细胞、粘附、表面 粘附分子和红细胞促凝活性。中性粒 将通过Mac-1和血浆弹性蛋白酶-α 1蛋白酶监测活化 配合物我们使用HbF水平下降时的独特过渡期 从新生儿到成人的水平应该阐明的贡献， 体内红细胞促凝活性的凝血激活。这 信息具有相关性，因为治疗旨在逆转Hb 开关已经获得了优势。单核细胞TF的作用的描述， 纤维蛋白溶解和细胞活化在VOC的发生将提供 对SCD病理生理学的深刻见解。明确的接触证明 VOC期间的激活将提供VOC与其 伴随疼痛和炎症的现象。这可以便于 治疗策略的设计（即使用蛋白酶抑制剂，mAb 到FXII等）。最后，我们的研究应该提供一个独特的视角， 在SCD过程中出现的止血变化的连续性， 以及在成人中发展为血管并发症的那些。

Investigations into hemostasis in Sickle Cell Disease (SCD) suggests that thrombin and fibrin generation are increased during steady state, with conflicting data whether further activation occurs in vasocclusive crisis (VOC). Platelet activation during VOC occurs with variable findings during steady state. A selective, evaluation of hemostatic pathways i.e. intrinsic or extrinsic activation, fibrinolysis, and platelet-endothelial activation has not been reported. Neither has a longitudinal evaluation in infants during the unique transition when HbF levels fail from 80% to <10%. We propose to test the hypothesis that elevated HbF levels in the infant protects against coagulation activation seen in the older child and adult. Study design will allow us to ascertain if protection is due to inhibition of intraerythrocyte HbS polymerization with protection from in vivo sickling-desickling, the absence consequently of circulating red cell membrane pro-coagulant vesicle and thus no signs of hemostatic activation. Studies in older children will assess whether intrinsic activation (relevant to the origin of pain and acute inflammation) occurs only during VOC, and the role of monocyte TF expression in extrinsic. Studies will include intrinsic markers [high molecular (HK) and low molecular weight kininogen (LK), cleavages, western blotting, and kallikrein-alpha/2 macroglobulin]; extrinsic markers [TF assays on monocytes, TFPI and factor VIIa]; other activation and fibrinolytic markers [prothrombin F1.2, FPA, TAT, tPA, PAI-I, D-dimer and PAP] urokinase-type plasminogen activator receptor (uPAR) and soluble uPAR; platelet-endothelial markers [of activation dependent epitopes, in vivo platelet microparticles, circulating soluble adhesion molecules and urinary eicosanoids. Erythrocyte evaluation include quantitative HbF, F cells, adhesion, surface adhesion molecules, and erythrocyte procoagulant activity. Neutrophil evaluation include quantitative HbF, F cells, adhesion, surface adhesion molecule, and erythrocyte procoagulant activity. Neutrophil activation will be monitored via Mac-1 and plasma elastase-alpha1 protease complexes. Our use of the unique transition period when HbF levels fall from neonatal to adult levels should elucidate the contribution to coagulation activation of red cell procoagulent activity in vivo. This information is of pertinence since therapy targeted to reverse the Hb switch has gained ascendancy. A delineation of the roles of monocyte TF, fibrinolytic and cellular activation in the genesis of VOC will provide insights into SCD pathophysiology. Unequivocal demonstration of contact activation during VOC would provide a link between VOC and its accompanying phenomenon of pain, and inflammation. This could facilitate the design of treatment strategies (i.e. use of protease inhibitors, mab to FXII, etc). Finally our studies should provide a unique perspective on the continuum of hemostatic changes that unfold during the course of SCD, and those that develop as vascular insufficiencies supervene in the adult.