Role of Young Thrombocytes and Their Microparticles

描述（由申请人提供）：血小板在止血和血栓形成中起着重要作用。在哺乳动物中，有两种类型的血小板，即年轻血小板和成熟血小板，它们分别携带较多和较少数量的粘附受体。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进行了数十年的研究，但年轻血小板及其微粒的体内功能都不为人所知。斑马鱼是描述年轻血小板及其微粒功能的一个很好的模型系统，因为它们具有血小板等同物，称为血小板。在我们的初步研究中，我们已经证明在斑马鱼动脉损伤模型中，年轻的血小板更活跃，携带更多的受体，并且首先出现在损伤部位。同样，我们已经在循环血栓细胞微粒上发现了类似的受体。由于年轻的血小板更活跃，它们随后可能产生更活跃的微粒。这些微粒可能首先参与黏附反应，因为在流动的血液中，更有可能在血管壁或血管壁附近发现较小尺寸的成分。此外，通过微泡脱落，年轻的血小板可能失去受体，成为活性较低的成熟血小板。因此，我们的假设是，年轻的血小板通过一种未知的机制产生微颗粒，失去它们作为微泡的受体，成为活性较低的成熟血小板，而这些微颗粒的产生反过来可能有助于年轻的血小板形成血栓。在这项拨款申请中，我们建议在斑马鱼的损伤部位建立微粒和年轻血栓细胞的选择性募集，并利用斑马鱼遗传学的力量分离和表征斑马鱼微粒脱落缺陷突变体。这些研究将有助于深入了解血小板微粒在止血中的作用、它们的产生和血小板成熟的机制。

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.