The Origin and Function of Lung Megakaryocytes

摘要 血小板母细胞是巨核细胞(MK)。历史上的研究一直集中在MK来源的血小板上 骨髓产生(BM)(1)。最近，产生血小板的巨噬细胞集落刺激因子被证明存在。 在肺中，我们的实验室和其他人描述了一种肺MKS的免疫调节表型(2-4)。这个 最近发现了一个低倍体、免疫分化的骨髓Mk亚群(5)，突出了两者之间的关系 较低的Mk倍体可能与免疫分化程度较高的Mk相关。我们指的是MK的发展 免疫调节亚群表现为MK免疫分化。肺MKS的起源及发病机制 它们的免疫分化仍不清楚。 在没有实验证据的情况下，假设肺间充质干细胞是从未成熟的循环中的骨髓“播种”出来的。 MKS。Lefrancais等人。显示mTmG肺的肺血管内存在GFP+MKS 移植到pF4-Cre-mTmG受体。作者认为，GFP+血管内肺的存在 MKS显示肺外来源。然而，血管内和血管外肺MKS有 形态和功能上的差异，血管外肺巨噬细胞约占所有肺的70%。 MKS。因此，大多数循环中的巨噬细胞必须离开血液和组织迁移成肺。 常住居民。在没有直接证据证明这种贩运的情况下，血管外肺MKS的确切来源仍然是 未知，但可能对它们的免疫分化有重大影响。我假设血管外肺 巨核细胞来源于一个独立于骨髓巨核细胞的局部造血祖细胞库。我要测试一下这个 假说使用互补的方法，包括辐射和转移实验，血统追踪， 体外集落形成单位实验。 MK免疫分化对血小板池的影响尚不清楚。肺巨噬细胞制造血小板，尽管 肺源性血小板的相对比例仍然存在争议(4，6)。研究中出现的新证据 血小板的异质性开始表明，血小板亚群可能具有功能意义。我 假设肺内MK对免疫分化的血小板亚群有贡献。为了测试这一点 假设，我将使用一种新的策略来识别肺来源的血小板，通过口咽CFSE给药 在生理和血小板减少的条件下，如PF4-Cre-iDTR小鼠和非致死性小鼠疟疾。 我提议的研究结果将有助于更好地理解免疫分化 巨核生成及其在协调免疫反应和血小板免疫表型中的作用 应用于多种血管炎症性疾病。

Abstract Platelet parent cells are megakaryocytes (Mks). Studies have historically focused on Mk derived platelet production in the bone marrow (BM) (1). More recently, platelet-producing Mks have been shown to be present in the lung, and our lab and others have described an immune modulatory phenotype of lung Mks (2-4). The recent identification of a low ploidy, immune differentiated BM Mk sub-population (5) highlights the relationship that lower Mk ploidy may correlate with a more immune differentiated Mk. We refer to the development of a Mk immune modulatory sub-population as Mk immune differentiation. The origin of lung Mks and mechanisms of their immune differentiation remain unknown. It is assumed, without experimental evidence, that lung Mks are ‘seeded’ from immature circulating BM Mks. Lefrancais et al. showed the presence of GFP+ Mks in the lung vasculature when a mTmG lung was transplanted to a PF4-Cre-mTmG recipient. The authors argued that the presence of GFP+ intravascular lung Mks demonstrated an extra-pulmonary source. However, intravascular and extravascular lung Mks have morphological and perhaps functional differences, and extravascular lung Mks make up about 70% of all lung Mks. Thus, the majority of circulating Mks would have to leave the blood and tissue migrate to become lung resident. Without direct evidence for this trafficking, the definitive origin of extravascular lung Mks remains unknown, but may have a major impact on their immune differentiation. I hypothesize that extravascular lung Mks derive from a local hematopoietic progenitor pool independent of BM megakaryopoiesis. I will test this hypothesis by using complementary methods, including irradiation and transfer experiments, lineage tracing, and in vitro colony forming unit assays. The impact of Mk immune differentiation on the platelet pool is still not clear. Lung Mks make platelets, although the relative proportion of lung derived platelets remains controversial (4, 6). Emerging evidence from studies of platelet heterogeneity are beginning to suggest that platelet subsets may have functional significance. I hypothesize that lung resident Mks contribute to an immune-differentiated platelet sub-population. To test this hypothesis, I will use a novel strategy to identify lung derived platelets using oropharyngeal CFSE administration in physiologic and thrombocytopenic conditions such as PF4-Cre-iDTR mice and nonlethal murine malaria. Results from my proposed studies will contribute to an improved understanding of immune differentiated megakaryopoiesis, and its role in coordinated immune responses and platelet immune phenotypes, with direct applications to many vascular inflammatory diseases.