Augmentation of Hemostasis in Pediatric Cardiopulmonary Bypass

描述(由申请人提供)：体外循环(CPB)后出血是心脏手术的严重并发症，与相当高的发病率和死亡率有关；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。输血产品主要由成人血液中制备的血小板和纤维蛋白原(以冷沉淀的形式)组成。虽然给儿童患者输注成人血液制品是控制失血的常规做法，但减少输血制品的使用已被证明与更好的患者预后相关。不幸的是，几乎没有其他选择，这突显了需要更好的方法来控制出血。止血包括形成嵌入在纤维蛋白网中的血小板塞子。然而，新生儿的血栓形成受到损害，部分原因是缺乏症。 出生时的几种凝血因子和血小板的低反应性。体外循环进一步损害了这些已经受损的血小板。因此，该项目的总体设计目标是创造一种生物材料，它概括了血小板的关键止血功能，以增强新生儿体外循环患者的凝血功能。为了实现这一目标，我们利用了我们实验室最近设计的类血小板颗粒(Plp)，它通过与高亲和力的纤维蛋白相互作用来模拟天然血小板的许多特征，更重要的是，它在损伤部位具有增强的特异性。 体外循环新生儿血浆标本中的凝血现象。为了实现这一目标，该建议分为两个特定的目标：1.在a)缺乏和b)存在PLPs的情况下，表征新生儿体外循环血浆样本中的血小板功能和凝血酶；2.在血小板低反应性啮齿动物模型中表征体内凝血增强的特征。在目标1中，我们将利用我们实验室开发的新型内皮化微流控装置，通过血栓弹性图/血小板图谱分析和动态凝血分析，分析体外循环前(基线)、体外循环后和输血后新生儿的血小板功能。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存在低反应性血小板，在目标2中，我们将模拟这种情况，并通过监测出血时间来评估PLPs在体内的小动物血小板缺乏模型中的疗效。此外，还将对PLP的生物分布和循环半衰期进行评估。这项拟议的研究具有创新性，因为它将独特的微凝胶与纤维蛋白特定的结合基序相结合，创建了与纤维蛋白网络广泛相互作用的PLP。这些特征使颗粒能够重现天然血小板的更多特征，而不是以前由其他模拟血小板的材料实现的。这项拟议研究的意义在于，这项工作将使新生儿CPB患者的凝血障碍有更好的治疗选择。

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.