Novel Assays Predicting Phenotypic Heterogeneity in Severe Hemophilia

项目总结（见说明）： 重度血友病患者的临床表型差异很大，尽管因子水平相似（<正常活动的1%）。即使在具有相同致病基因突变和因子水平的个体中，关节出血频率、关节出血发作年龄和对因子VIII（fVIII）的需求也存在显著差异。导致这些不同出血模式的生物学决定因素， 严重的血友病在很大程度上是未知的。这种知识的缺乏极大地阻碍了临床医生对重度血友病患者进行个体化治疗决策的能力。开发一种区分重度血友病患者轻度和重度临床表型的方法将具有多种临床益处。示例包括根据患者的具体情况调整预防性治疗的开始或停止的可能性。 对出血风险进行个体化评估，并确定最有可能从实验性治疗中获益的患者亚组。提出了新的概念和检测方法，可以根据出血风险对重度血友病A患者进行分层。中心假设是血小板表型有助于血友病A患者的出血表型， 将允许对重度血友病A患者出血表型进行前瞻性测定。提出了两种互补的研究途径;第一种侧重于血小板促凝活性和血小板-FVIII相互作用的调节，第二种侧重于评估 在动态流体环境中形成止血栓。目的1将检验血小板促凝活性的个体差异导致重度血友病A患者出血表型变异的假设，并研究促凝蛋白与活化血小板结合的调节机制。目的2将检验出血表型的差异可能是 通过评估新型内皮化微流体模型中的止血潜力进行前瞻性鉴定。 一系列系统的实验研究了血小板表型和凝血因子浓度的变化对这种新型系统中PRP和全血中止血栓形成的影响。

PROJECT SUMMARY (See instructions): The clinical phenotype of patients with severe hemophilia varies widely despite similarly low factor levels (<1% of normal activity). Even in individuals with the same causative genetic mutation and factor levels, there are significant differences in joint bleed frequencies, age of onset of joint bleeding, and requirements for factor Vlll (fVIII). The biological determinants that drive these different bleeding patterns in patients with severe hemophilia are largely unknown. This lack of knowledge considerably hampers the clinician's ability to individualize treatment decisions In patients with severe hemophilia. Development of a method that distinguished severe hemophilia patients with mild and severe clinical phenotypes would have multiple clinical benefits. Examples Include the potential to adjust the start or cessation of prophylactic therapy based on an individualized assessment of bleeding risk, and the identification of patient subgroups that would be most likely to benefit from experimental therapies. Novel concepts and assays are proposed that will allow the stratification of severe hemophilia A patients according to bleeding risk. The central hypothesis is that platelet phenotype contributes to bleeding phenotype in patients with hemophilia A, and hemostatic assays that incorporate platelet function will allow prospective determination of bleeding phenotype in patients with severe hemophilia A. Two complementary pathways of investigation are proposed; the first focused on platelet procoagulant activity and the regulation of platelet-fVIII interactions, the second on the assessment of hemostatic plug formation in a dynamic fluid environment. Aim 1 will test the hypothesis that individual differences in platelet procoagulant activity contribute to the variability in bleeding phenotype observed in patients with severe hemophilia A and investigate the mechanisms regulating the binding of procoagulant proteins to activated platelets. Aim 2 will test the hypothesis that differences in bleeding phenotype can be prospectively identified by assessment of hemostatic potential in a novel endothelialized microfluidics model. A systematic series of experiments examine the impact of variations in platelet phenotype and coagulation factor concentrations on hemostatic plug formation In PRP and whole blood in this novel system.