Mechanisms of myelopoiesis after myocardial infarction

项目概要/摘要： 急性损伤，如心肌梗死（MI），诱导骨髓细胞的过度产生， 骨髓这些新生成的髓样细胞是炎症性的，在疾病中至关重要。 发病机制，加剧潜在的过程，如动脉粥样硬化。然而，长期以来， 距离信号和分子机制，触发骨髓造血后，缺血 在远处器官（例如心脏）发生的事件知之甚少。我们的初步数据显示， 心肌梗死后，骨髓造血干细胞和祖细胞（HSPC）重新定位到血管中， 壁龛血管龛赋予不同的微环境，促进HSPC增殖和分化。 在研究心肌梗死后产生的长距离信号时，我们发现血小板源性的 细胞外囊泡（pEV）在MI后患者和小鼠血液中的浓度。这些pEV增加了表达 PU.1是一种髓系转录因子，白细胞介素-3受体（IL-3R）增加 骨髓HSPC中的髓样细胞生成。此外，从MI小鼠中分离的pEV含有较高的 miR-499水平，其在体外增加骨髓HSPC增殖和分化。从这些 根据观察，我们假设MI后pEV中miR-499的增加使HSPC重新活化， 骨髓中的血管龛，在那里它们增殖并分化成髓样细胞。我们将测试 这一假设有两个具体的目的：（1）我们将确定pEV在HSPC重新定位到 骨髓中的血管龛(2)我们将研究pEV中miR-499表达的增加是否会影响pEV中miR-499的表达。 增加心肌梗死后的骨髓生成和动脉粥样硬化。为了验证这一假设，我们将KikGR+ HSPC使用缺乏miR-499的小鼠和两种不同的动脉粥样硬化小鼠模型。我们将 使用流式细胞术、ImageStream和NanoSight表征MI患者和小鼠中的pEV 技术.此外，我们将确定暴露于从miR-249分离的pEV的HSPC的增殖。 499+/+和miR-499-/-小鼠在体外和体内的MI后。拟议的拨款申请将进一步促进我们的 了解MI诱导骨髓细胞生成的机制，并探索新的治疗途径， 减轻心肌梗死后炎症和动脉粥样硬化。

Project Summary/ Abstract: An acute injury, such as myocardial infarction (MI), induces exaggerated production of myeloid cells in the bone marrow. These newly generated myeloid cells are inflammatory and are crucial in disease pathogenesis, exacerbating underlying processes such as atherosclerosis. However, the systemic long distance signals and molecular mechanisms that trigger myelopoiesis in the bone marrow after an ischemic event at a distant organ, such as the heart, are poorly understood. Our preliminary data revealed that, following an MI, bone marrow hematopoietic stem and progenitor cells (HSPC) relocated into the vascular niches. Vascular niches confer distinct microenvironments promoting HSPC proliferation and differentiation. In investigating the long-distance signals produced after MI, we found increased levels of platelet-derived extracellular vesicles (pEV) in the blood of patients and mice after MI. These pEV increased the expression of PU.1, which is a myeloid transcription factor, and the receptor for interleukin-3 (IL-3R), which increases myeloid cell generation, in bone marrow HSPC. Additionally, pEV isolated from mice with MI contained high levels of miR-499, which increased bone marrow HSPC proliferation and differentiation in vitro. From these observations, we hypothesize that increased miR-499 in pEV following MI relocates HSPC to active vascular niches in the bone marrow, where they proliferate and differentiate into myeloid cells. We will test this hypothesis in two specific aims: (1) We will determine the role of pEV in relocation of HSPC to the vascular niches in the bone marrow. (2) We will investigate if increased miR-499 expression in pEV augments myelopoiesis and atherosclerosis after MI. To test the hypothesis, we will photoconvert KikGR+ HSPC, use mice deficient of miR-499 and two different mouse models of atherosclerosis. We will characterize pEV in patients and mice with MI using flow cytometry, ImageStream and NanoSight technologies. Additionally, we will determine the proliferation of HSPC exposed to pEV isolated from miR- 499+/+ and miR-499-/- mice after MI in vitro and in vivo. The proposed grant application will further our understanding of the mechanisms of MI-induced myelopoiesis, and explore new therapeutic avenues to diminish inflammation and atherosclerosis after MI.