Mechanisms of GalTKO Lung Xenograft Injury

产品说明：针对各种靶标（尤其是Gal al、3Gal）和补体的抗体是心脏、肺和其它器官的超急性排斥的关键介质。然而，在猪-人和猪-非人灵长类动物模型中，我们一致发现，有效的补体调节加上抗猪抗体的有效去除与肺异种移植物的快速功能障碍相关。因此，超急性肺排斥反应（HALR）是介导的机制，除了那些引起其他器官的超急性排斥反应。 该范例通过初步研究得到加强，其中离体灌注的三个GalT-KO猪肺平均保留其功能2小时（60、134和170分钟），远长于对照（<10分钟）。失败是由于肺血管阻力突然快速增加。尽管在灌注10分钟和30分钟时获得的活检在组织学上不显著，但在移植物衰竭时观察到血管内血栓和毛细血管充血，尽管使用了高剂量肝素抗凝。凝血途径活化（F1 +2）被延迟但未被阻止，血小板活化（血小板反应蛋白释放）未减弱，并且灌注液中超过70%的血小板在开始灌注的几分钟内被隔离在肺中。肺中的补体激活和沉积虽然减少，但没有被阻止。基于这些观察结果和我们先前的工作证明凝血酶、血小板、补体和肺血管内巨噬细胞在Gal+肺的超急性排斥反应中的关键作用，我们假设血管内凝血失调和残余补体激活是GalT KO猪肺异种移植物急性损伤的主要原因。 为了检验这一假设，将在已建立的离体灌注模型中使用遗传（表达人组织因子途径抑制剂或衰变加速因子的GalTKO肺）和药理学方法（特异性血小板受体、凝血酶或补体抑制剂）的组合。然后将在维持生命的猪-狒狒肺异种移植模型中对离体产生最佳肺功能的方法进行体内验证。由于提出的研究，我们预计，超急性肺排斥反应将首次成功地预防，主要使用供体导向的，基于机制的策略，以持续实现狒狒猪肺的生命支持功能，允许随后的免疫屏障在这个器官系统中得到解决。

DESCRIPTION: Antibodies directed at various targets (especially Gal al,3Gal) and complement are pivotal mediators of hyperacute rejection of the heart, lung, and other organs. However in pig-to-human and pig-to-non-human primate models, we have consistently found that potent complement regulation coupled with efficient removal of anti-pig antibody is associated with rapid dysfunction of lung xenografts. Thus hyperacute lung rejection (HALR) is mediated by mechanisms in addition to those that cause hyperacute rejection of other organs. This paradigm is reinforced by the preliminary studies, where three GalT-KO swine lungs perfused ex vivo retained their function for an average of 2 hours (60, 134, and 170 minutes), far longer than controls (<10 minutes). Failure was due to sudden, rapid increase in pulmonary vascular resistance. Although biopsies obtained at 10 and 30 minutes of perfusion were histologically unremarkable, intravascular thrombi and capillary congestion were observed at graft failure, despite anticoagulation with high-dose heparin. Coagulation pathway activation (Fl+2) was delayed but not prevented, platelet activation (thrombospondin release) was not attenuated, and over 70% of platelets in the perfusate were sequestered in the lung within minutes of initiating perfusion. Complement activation and deposition in the lung, while reduced, were not prevented. Based on these observations and our previous work demonstrating pivotal roles for thrombin, platelets, complement, and pulmonary intravascular macrophages in hyperacute rejection of Gal+ lungs, we hypothesize that dysregulated intravascular coagulation and residual complement activation are the principle cause of acute injury of GalT KO pig lung xenograft. To test this hypothesis, a combination of genetic (GalTKO lungs expressing human tissue factor pathway inhibitor or decay accelerating factor) and pharmacologic approaches (specific platelet receptor, thrombin, or complement inhibitors) will be used in an established ex vivo perfusion model. Approaches that yield optimal lung function ex vivo will then be validated in vivo in a life-supporting pig-to-baboon lung xenograft model. As a result of the studies proposed, we anticipate that hyperacute lung rejection will be successfully prevented for the first time using primarily donor-directed, mechanism-based strategies to consistently achieve life-supporting function of a pig lung in a baboon, allowing subsequent immunologic barriers to be addressed in this organ system.