Augmentation of Hemostasis in Pediatric Cardiopulmonary Bypass

描述（由申请方提供）：体外循环（CPB）后出血是心脏手术的严重并发症，与大量发病率和死亡率相关;新生儿尤其容易发生CPB后出血。在这些患者中，CPB后输血是必要的。输注的血液制品主要由从成人血液制备的血小板和纤维蛋白原（以冷沉淀物的形式）组成。尽管常规向儿科患者输注成人血液制品以控制失血，但已证明减少输血制品的使用与更好的患者结局相关。不幸的是，几乎没有替代品，这突出了对更好的控制出血方法的需求。止血包括形成包埋在纤维蛋白网内的血小板栓。然而，新生儿的血凝块形成受损，部分原因是缺乏 出生时的几种凝血因子和血小板低反应性。CPB进一步损害这些已经受损的血小板。因此，本项目的总体设计目标是创建一种生物材料，其重现血小板的关键止血功能，以增强新生儿CPB患者的凝血。为了实现这一目标，我们利用我们实验室最近设计的血小板样颗粒（PLPs），通过与纤维蛋白高亲和力相互作用，更重要的是，在损伤部位的特异性，来模拟天然血小板的许多特征，以增强血小板的功能。 从接受CPB的新生儿获得的血浆样品中的凝血。为了实现这一目标，该提案分为两个具体目标：1.在a）不存在PLP和B）存在PLP的情况下新生儿CPB血浆样品中血小板功能和凝血的表征，以及2.在血小板低反应性啮齿动物模型中体内凝血增强的表征。在目标1中，我们将通过血栓弹力图/血小板图谱分析和动态凝血分析，利用我们实验室开发的新型内皮化微流体装置，分析CPB前（基线）、CPB后和接受择期心脏手术的新生儿输血后采集的血液样本中的新生儿血小板功能。然后，我们将对存在PLP的CPB后样本进行相同的分析。由于已知新生儿患者具有低反应性血小板，因此在目标2中，我们将对这种情况进行建模，并通过监测出血时间在小动物血小板缺乏模型中评价PLP的体内疗效。此外，还将评价PLP的生物分布和循环半衰期。拟议的研究是创新的，因为它结合了独特的微凝胶与纤维蛋白特异性结合基序，以创建与纤维蛋白网络广泛相互作用的PLPs。这些特征导致能够重现天然血小板的更多特征的颗粒，而不是先前通过其他血小板模拟材料实现的。拟议研究的意义在于，这项工作将为新生儿体外循环患者的凝血障碍提供更好的治疗选择。

DESCRIPTION (provided by applicant): Bleeding after cardiopulmonary bypass (CPB) is a serious complication of cardiac surgery and is associated with substantial morbidity and mortality; neonates in particular are vulnerable to post-CPB bleeding. In these patients, transfusion post-CPB is a necessity. Transfused blood products consist primarily of platelets and fibrinogen (in the form of cryoprecipitate) prepared from adult blood. Although the transfusion of adult blood products to pediatric patients is performed routinely to control blood loss, reduction in the usage of transfused blood products has been shown to correlate with better patient outcomes. Unfortunately, few alternatives exist, highlighting the need for better methods to control bleeding. Hemostasis involves the formation of a platelet plug embedded within a fibrin mesh. However, clot formation is impaired in neonates, in part, due to deficiencies in several coagulation factors at birth and platelet hyporeactivity. CPB further impairs these already compromised platelets. Thus, the overarching design goal of this project is to create a biomaterial that recapitulates key hemostatic functions of platelets to augment clotting in neonatal CPB patients. To achieve this objective, we utilize platelet-like particles (PLPs), recently designed in our lab, that mimic numerous features of natural platelets by interacting with fibrin with high affinity and, more importantly, specificity at the sites of injury to augment clotting in plasma samples obtained from neonates undergoing CPB. To achieve this objective, the proposal is divided into two specific aims: 1. Characterization of platelet function and clottig in neonatal CPB plasma samples in the a) absence and b) presence of PLPs and 2. Characterization of augmentation of clotting in vivo in a rodent model of platelet hyporeactivity. In Aim 1, we will analyze neonatal platelet function in blood samples collected prior to CPB (baseline), post-CPB and post-transfusion from neonates undergoing elective cardiac surgery, through thromboelastography/platelet mapping assays and dynamic clotting assays utilizing a novel endothelialized microfluidic device developed in our labs. We will then perform identical analyses with post-CPB samples in the presences of PLPs. Because neonatal patients are known to have hyporeactive platelets, in Aim 2, we will model this condition and evaluate the efficacy of PLPs in vivo in a small animal platelet deficiency model by monitoring bleeding times. Furthermore, the biodistribution and circulation half-life of PLPs will be evaluated. The proposed research is innovative because it combines unique microgels with fibrin specific binding motifs to create PLPs that interact extensively with fibrin networks. These features result in particles that are capable of recapitulating more features of nature platelets than previously achieved by other platelet-mimicking materials. The significance of the proposed research is that this work will enable better treatment options for coagulopathy in neonatal CPB patients.