Therapeutic assessment of synthetic heparin sulfates in transplantation models

尽管猪到灵长类器官异种移植取得了重大进展，但移植物的长期存活率是 目前受到血栓性微血管病和血小板隔离的发展的限制 移植器官和/或受者出现消耗性凝血障碍。目前的建议是测试同质性 利用计算模型和酶/化学工具合成的硫酸肝素(HSS)概述 在项目I(PL-I)。巴拉古鲁纳坦博士)和II(Pl-11.德赛博士)。我们假设化学合成的 优先抑制凝血因子Xa(FXA)和/或凝血酶的HSS将改善血栓形成 猪到灵长类异种移植中可见的微血管病变和/或消耗性凝血障碍 抑制凝血酶形成和血小板活化。此外，HSS优化为结合趋化因子(来自 项目三)可充当趋化因子诱骗因子，协同防止细胞隔离 抗凝剂。这些HSS将在各种异种移植模型的背景下进行评估 来自猪的细胞和器官经过基因改造，以防止抗体/补体介导的攻击， 炎症和凝血排斥机制。这些以HS为基础的疗法将由。-(I)在 体外试验以确定进一步研究的最佳HS候选药物：(Ii)体外猪肺血液灌流 使用人血，(Iii)在狒狒中的猪动脉Tx，和(Iv)在狒狒中的猪肾Tx。模式(II)构成了 短期模型(移植物功能以小时为单位)，允许快速筛查HSS 模型(三)和(四)构成了持续时间较长的模型(天或周)。此外， HS的效果将被监测(Iii)在没有免疫抑制治疗的低抗原负荷模型中，或(Iv) 在高抗原负荷模型中，移植物接受者将接受旨在 抑制适应性T细胞反应。研究的主要目标是确定一个(或多个)HS，即 更特异和更有效地抑制血栓性微血管病的发展和 消耗性凝血障碍是目前临床上使用的肝素，而且，这与 肝素的副作用，例如出血，限制了可以使用的剂量。第二 目的是研究被确定为最优的HS与遗传操作之间的协同作用 在器官来源的猪中，例如，表达人血栓调节蛋白以抑制血栓形成 微血管病和消耗性凝血障碍。 相关性(请参阅说明)： 从基因工程猪身上移植器官将提供一种替代来源 用于临床移植的人体器官，但目前并发凝血障碍，可能 是致命的。将于年设计和研究的特定合成肝素硫酸盐的给药 这一建议可能会防止这些凝血障碍，从而使异种移植能够 进入临床试验阶段。

Despite significant advances in pig-to-primate organ xenotransplantation, long-term graft survival is currently limited by the development of a thrombotic microangiopathy and platelet sequestration in the grafted organ and/or a consumptive coagulopathy in the recipient. The present proposal tests homogeneous heparin sulfates (HSs) synthesized using computational modeling and enzymatic/chemical tools as outlined in Projects I (PL-I. Dr. Balagurunathan) and II (Pl-ll. Dr. Desai). We hypothesize that chemically-synthesized HSs designed to preferentially inhibit Factor Xa (FXa) and/or thrombin will ameliorate the thrombotic microangiopathy and/or consumptive coagulopathy seen in the context of pig-to-primate xenografts by inhibiting thrombin formation and platelet activation. In addition, HSs optimized to bind chemokines (from Project III) may act as chemokine decoy factors to prevent cell sequestration synergistically with anticoagulation. These HSs will be evaluated in the context of various xenotransplantation models using cells and organs from pigs genetically modified to protect against antibody/complement-mediated, inflammatory, and coagulation rejection mechanisms. These HS-based therapies will be tested by. - (i) in vitro assays to determine the best HS candidate drugs for further studies, (ii) ex vivo pig lung hemoperfusion using human blood, (iii) pig artery Tx in baboons, and (iv) pig kidney Tx in baboons. Model (ii) constitutes a short-duration model (with graft function measured in hours) allowing rapid screening of the HSs being tested, whereas models (iii) and (iv) constitute longer-duration models (days or weeks). Furthermore, the effect of the HS will be monitored (iii) in a low-antigen load model without immunosuppressive therapy, or (iv) in a high-antigen load model in which graft recipients will receive immunosuppressive therapy aimed at inhibiting the adaptive T cell response. The prime aim of the study is to identify one (or more) HS that is more specific and more efficient at inhibiting the development of thrombotic microangiopathy and consumptive coagulopathy than is the current clinically-used heparin, and that, furthermore, is not associated with the side-effects of heparin, e.g., bleeding, that limit the dosage that can be administered. The second aim is to investigate the synergy between the HS identified as being optimal with the genetic manipulations in the organ-source pig, e.g., expression of human thrombomodulin directed towards inhibiting thrombotic microangiopathy and consumptive coagulopathy. RELEVANCE (See instructions): The transplantation of organs from genetically-engineered pigs would provide an alternative source to human organs for clinical transplantation, but is currently complicated by coagulation disturbances that can be fatal. The administration of specific synthetic heparan sulfates that will be designed and investigated in this proposal are likely to prevent these coagulation disturbances, thus enabling xenotransplantation to advance to clinical trials.