The Metabolic Regulation of Hematopoietic Stem Cell Function

项目概要/摘要 一个基本的问题是体内代谢水平的生理变化是否会影响干细胞功能 或组织再生。我们对体干细胞代谢的理解仍然有限， 与研究体内稀有细胞代谢相关的挑战。为了解决这个问题，我们优化了 代谢组学方法的灵敏度，使稀有细胞群体的分析。我们使用这种方法， 比较造血干细胞（HSC）和各种限制性 从小鼠骨髓分离的造血祖细胞。我们发现每个造血干细胞和 祖细胞群体具有独特的代谢特征。人和小鼠HSC与 大多数其他造血细胞异常高水平的抗坏血酸（维生素C）。小鼠抗坏血酸消耗， 在5%的美国人中观察到的水平，增加了HSC的频率和功能，部分是通过减少 Tet 2，一种抑制白血病发展的胞嘧啶脱甲基酶。抗坏血酸耗竭，如Tet 2缺失， 与Flt 3 ITD协同促进骨髓生成和白血病发生。抗坏血酸通过细胞自主作用， 主要通过Tet 2依赖性机制负性调节HSC功能和骨髓生成。这些 观察结果可能与公共健康有关，因为血浆抗坏血酸水平在美国人中变化很大， 主要是由于饮食差异。在任何时候，13%的美国人被认为是抗坏血酸缺乏。在Aim中 1，我们建议测试抗坏血酸水平是否影响稳态造血或再生后， 造血应激在目标2中，我们建议测试抗坏血酸消耗是否促进克隆形成， 在稳态条件下或响应于造血应激的造血。克隆性造血 最近发现，不确定的电位在健康的老年人和患者中很常见 再生障碍性贫血，实体癌，以及接受造血移植的患者。的存在 克隆造血与包括心血管疾病在内的不良健康结果有关。克隆 造血通常由Tet 2的一个等位基因的丢失或由Dnmt 3a的功能缺失突变引起。我们 假设抗坏血酸消耗可以通过以下方式促进克隆造血的发生和进展： 降低Tet 2功能。在目标3中，我们将评估抗坏血酸消耗的分子机制， Tet 2缺乏调节HSC功能和骨髓生成。我们希望这些研究能扩大我们的理解 代谢如何调节HSC表观基因组、HSC功能、正常造血和克隆 造血

PROJECT SUMMARY/ABSTRACT A fundamental question is whether physiological variations in metabolite levels in vivo influence stem cell function or tissue regeneration. Our understanding of somatic stem cell metabolism remains limited due to the technical challenges associated with studying metabolism in rare cells in vivo. To address this issue we optimized the sensitivity of metabolomics methods to enable the analysis of rare cell populations. We used this approach to compare metabolite levels between hematopoietic stem cells (HSCs) and a wide range of restricted hematopoietic progenitors isolated from mouse bone marrow. We found that each hematopoietic stem and progenitor cell population has a distinct metabolic signature. Human and mouse HSCs are distinguished from most other hematopoietic cells by unusually high levels of ascorbate (vitamin C). Ascorbate depletion in mice, to a level observed in 5% of Americans, increases HSC frequency and function, partly by reducing the activity of Tet2, a cytosine demethylase that suppresses leukemia development. Ascorbate depletion, like Tet2 deletion, cooperates with Flt3ITD to promote myelopoiesis and leukemogenesis. Ascorbate acts cell-autonomously to negatively regulate HSC function and myelopoiesis mainly through Tet2-dependent mechanisms. These observations are likely relevant to public health as plasma ascorbate levels vary widely among Americans, largely due to dietary differences. At any one time, 13% of Americans are considered ascorbate deficient. In Aim 1, we propose to test whether ascorbate levels influence steady-state hematopoiesis or regeneration after hematopoietic stresses. In Aim 2, we propose to test whether ascorbate depletion promotes clonal hematopoiesis under steady state conditions or in response to hematopoietic stresses. Clonal hematopoiesis of indeterminate potential has recently been shown to be common in healthy older people as well as in patients with aplastic anemia, solid cancers, and patients who have received hematopoietic transplants. The presence of clonal hematopoiesis is associated with adverse health outcomes including cardiovascular disease. Clonal hematopoiesis is usually caused by the loss of one allele of Tet2 or by loss-of-function mutations in Dnmt3a. We hypothesize that ascorbate depletion can promote the development and progression of clonal hematopoiesis by reducing Tet2 function. In Aim 3 we will assess the molecular mechanisms by which ascorbate depletion and Tet2 deficiency regulate HSC function and myelopoiesis. We expect these studies to expand our understanding of how metabolism regulates the HSC epigenome, HSC function, normal hematopoiesis, and clonal hematopoiesis.