Immunomodulation by splenic megakaryocytes and platelets in sepsis

项目摘要 脓毒症是一种失调的宿主对感染的反应，最终导致器官衰竭，导致数百万人死亡 随着人口老龄化，发病率不断增加。从根本上说， 了解脓毒症中复杂的宿主免疫反应限制了靶向免疫治疗的发展， 除了抗生素和支持性护理措施外，没有其他治疗方法。在其核心， 脓毒症中的大量免疫病理学，其贡献来自过度旺盛的免疫应答， 病原体清除无效。我们和其他人已经研究了血小板在免疫反应中的关键作用 在急性感染期间，包括肺在髓外血小板生物合成中的作用。在本申请中， 我们将探讨脾脏，一个中枢免疫器官，在髓外巨核细胞生成和血小板中的作用。 脓毒症的生产。基于初步的数据，我们假设脾脏在 脓毒症期间的血小板生物发生，并且从脾产生的血小板是免疫调节性的， 对宿主防御很重要在目标1中，我们将利用腹膜炎和多微生物败血症的小鼠模型， 在血小板减少症，以了解机制'强调'血小板生物合成在这种情况下。我们将研究 肾上腺素能依赖性造血祖细胞在脓毒症中从骨髓动员的作用， 调节这一过程的生态位促进因素。在目标2中，我们将询问循环的植入。 脾中的造血祖细胞，它们成熟为巨核细胞，以及介体（SCF， CXCL12，IL-3）调节这一过程。使用最先进的技术，如活体成像和谱系 通过脾脏移植实现追踪，我们将检验脾脏对以下假设有显着贡献： 脓毒症期间血小板的生物合成。在目标3中，我们将使用血小板单细胞RNA测序的新方法 以测试小鼠和人类体内稳态和脓毒症期间的血小板异质性。在这个目标下，我们会 通过将免疫偏斜的血小板植入脓毒症小鼠体内，并测试 治疗益处。总而言之，这些研究将产生关于 脾脏在髓外巨核细胞生成和血小板生成中的作用及血小板驱动的重要性 免疫，这将是设计治疗脓毒症的新治疗方法的基础。

Project Summary Sepsis is a dysregulated host response to infection that culminates in organ failure leading to millions of deaths worldwide each year with an increasing incidence as the population ages. There is a fundamental lack of understanding of the complex host immune response in sepsis that has limited the development of targeted therapeutics for which there are none beyond antibiotics and supportive care measures. At its core, there is substantial immunopathology in sepsis with contributions from an overly exuberant immune response and ineffective pathogen clearance. We and others have studied the critical role of platelets in immune responses during acute infections, including the role of the lung in extramedullary platelet biogenesis. In this application, we will explore the role of the spleen, a central immune organ, in extramedullary megakaryopoiesis and platelet production in sepsis. Based on preliminary data, we hypothesize that the spleen co-opts a significant role in platelet biogenesis during sepsis and that the platelets produced from the spleen are immunomodulatory and important in host defense. In Aim 1, we will utilize a mouse model of peritonitis and polymicrobial sepsis resulting in thrombocytopenia to understand the mechanics of ‘stressed’ platelet biogenesis in this setting. We will study the role of adrenergic-dependent hematopoietic progenitor mobilization from the bone marrow during sepsis and the niche-promoting factors that regulate this process. In Aim 2, we will interrogate the engraftment of circulating hematopoietic progenitors in the spleen, their maturation into megakaryocytes, and the mediators (SCF, CXCL12, IL-3) regulating this process. Using state-of-the-art techniques such as intravital imaging and lineage tracing enabled by splenic transplantation, we will test the hypothesis that the spleen significantly contributes to platelet biogenesis during sepsis. In Aim 3, we will use novel methods of single-cell RNA sequencing of platelets to test for platelet heterogeneity during homeostasis and sepsis in mice and humans. Within this aim, we will test a novel cellular therapy for sepsis by transfusing immune-skewed platelets into septic mice and testing for therapeutic benefit. In summary, these studies will produce paradigm-shifting knowledge on the role of the spleen in extramedullary megakaryopoiesis and platelet production and the importance of platelet driven immunity, which will be foundational in the design of new therapeutic approaches to treat sepsis.