Role of Young Thrombocytes and Their Microparticles

描述(申请人提供)：血小板在止血和血栓形成中起重要作用。在哺乳动物中，有两种类型的血小板，即年轻的和成熟的，它们分别携带更多和更少数量的黏附受体。血小板产生微粒，并携带这些受体。尽管在止血和血栓形成方面做了几十年的工作，但年轻的血小板及其微粒在体内的功能尚不清楚。斑马鱼是一个很好的模型系统来描述年轻的血小板及其微粒的功能，因为他们拥有被称为血小板的等价物。在我们的初步研究中，我们发现在斑马鱼动脉损伤模型中，年轻的血小板细胞更活跃，携带更多的受体，并首先出现在损伤部位。同样，我们在循环中的血栓细胞微粒上也发现了类似的受体。由于年轻的血栓细胞更活跃，因此它们有可能随后产生更活跃的微粒。这些微粒可能是第一批参与粘连反应的微粒，因为在流动的血液中，更有可能在血管壁或附近发现较小尺寸的成分。此外，通过微泡脱落，年轻的血栓细胞可能会失去受体，成为不那么活跃的成熟血栓细胞。因此，我们的假设是年轻的血栓细胞以一种未知的机制产生微粒，失去其受体作为微泡而变成不那么活跃的成熟血栓细胞，这些微粒反过来可能与年轻的血栓细胞一起帮助血栓的启动。在这项资助申请中，我们建议建立斑马鱼中微粒和年轻的血栓细胞选择性地招募到损伤部位，并利用斑马鱼遗传学的力量来分离和鉴定具有微粒脱落缺陷的斑马鱼突变体。这样的研究应该有助于深入了解血小板微粒在止血中的作用，它们的产生机制和血小板的成熟。

DESCRIPTION (provided by applicant): Platelets are important players in hemostasis and thrombosis. In mammals, there are two types of platelets, namely young and mature, that carry greater and less numbers of adhesive receptors respectively. Platelets produce microparticles and also carry these receptors. Despite decades of work in hemostasis and thrombosis, the in vivo function of neither young platelets nor their microparticles, is known. Zebrafish is an excellent model system to delineate functions of young platelets and their microparticles since they possess platelet equivalents called thrombocytes. In our preliminary studies, we have shown young thrombocytes are more active, carry more receptors and appear at the wounding site first in the zebrafish arterial injury model. Likewise, we have identified similar receptors on circulating thrombocyte microparticles. Since young thrombocytes are more active, it is possible that they subsequently generate more active microparticles. These microparticles may be first ones to participate in the adhesive reaction because there is a greater likelihood of finding the smaller-sized components at or near the vessel wall in flowing blood. Furthermore, it is likely that by microvesicular shedding young thrombocytes may lose the receptors and become less active mature thrombocytes. Thus, our hypothesis is that young thrombocytes generate microparticles by an unknown mechanism, lose their receptors as micro vesicles to become less active mature thrombocytes, and these microparticles generated in turn may help in the initiation of the thrombus along with young thrombocytes. In this grant application, we propose to establish the selective recruitment of microparticles and young thrombocytes to the wounding site in zebrafish and use the power of zebrafish genetics to isolate and characterize zebrafish mutants with defects in microparticle shedding. Such studies should provide insight into the role of platelet microparticles in hemostasis, mechanisms of their production and platelet maturation.