Regulatory Cell Signals in the Bone Marrow

骨髓中的调节细胞信号

• 批准号: 7730038
• 负责人: Laura M Calvi
• 金额: $ 36.96万
• 依托单位: UNIVERSITY OF ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7730038
• 关键词: Blood Cells; Bone Marrow; Bone Marrow Cells; Bone Marrow Purging; Cell Communication; Cell Count; Cell Survival; Cells; Clinical; Collagen; Complex; Data; Elements; Event; Genetic; Genetic Models; Hematopoietic; Hematopoietic stem cells; Injury; Ligand Binding; Ligands; Mediating; Mediator of activation protein; Modeling; Molecular; Morbidity - disease rate; Mus; Osteoblasts; Osteocalcin; Osteocytes; Parathyroid Hormone Receptor; Parathyroid Hormone Receptors; Parathyroid Hormones; Population; Radiation Injuries; Regulation; Signal Pathway; Signal Transduction; Stromal Cells; Testing; Transplantation; base; cell injury; dentin matrix protein 1; human PTH protein; improved; in vivo; in vivo Model; mortality; new therapeutic target; notch protein; novel strategies; novel therapeutic intervention; overexpression; presenilin-1; promoter; public health relevance; receptor; secretase; stem cell niche

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to define the cellular and molecular mediators crucial for osteoblastic control of HSCs. We previously established that parathyroid hormone (PTH) activates osteoblastic cells to increase hematopoietic stem cell (HSC) numbers and that PTH improves HSC survival after radiation injury. These results give us a model to define a novel therapeutic approach to increase HSCs following iatrogenic or toxic injury to the bone marrow by stimulating osteoblastic cells. However, the specific osteoblastic cell subsets and the key osteoblastic-dependent molecular events regulating HSCs are unknown. Using pharmacologic and genetic models, we have identified Notch signaling as a potential mediator of PTH-dependent HSC regulation. Notch activation requires direct interaction of cell-bound ligands with receptors on neighboring cells. We demonstrated that 1) PTH or activation of its receptor stimulate the Notch ligand Jagged1 (Jag1) in osteoblastic cells; 2) in mice with constitutively active PTH receptors in osteoblastic cells, HSCs have increased Notch activation; 3) the PTH-dependent HSC increase is blocked by inhibition of ?-secretase activity, which is required for Notch activation. Our preliminary studies now demonstrate that expression of Jag1 in osteoblastic cells is required for the PTH-dependent HSC expansion. Together, these data suggest that PTH expands HSC through osteoblastic expression of Jag1, which then activates Notch signaling in neighboring bone marrow cells. Based on our data, we hypothesize that HSC expansion by osteoblasts requires Jag1-initiated Notch activation in the bone marrow microenvironment. To test this hypothesis, in Aim1 we will define the osteoblastic cell subset in which Jag1 is necessary and sufficient to mediate HSC expansion. In Aim2, we will identify the cell population (HSC, osteoblastic cells and/or other components of the bone marrow) in which Notch activation is required to achieve osteoblastic-dependent HSC expansion. Finally in Aim3 we will determine the contribution of Notch signaling to the myeloprotective effects of PTH, a clinical scenario in which HSC niche manipulation could be a novel strategy to reduce morbidity and mortality. We have already established and fully characterized in vivo models in which microenvironmental signals increase HSCs. Now that osteoblastic Jag1 has been identified as a key element of PTH-dependent HSC expansion, we have the unprecedented opportunity of defining the cellular and molecular components of the HSC niche using the in vivo strategies proposed here. Completion of our experimental aims will thus define novel therapeutic targets for HSC manipulation in the bone marrow microenvironment, which can be exploited to improve survival after bone marrow injury. PUBLIC HEALTH RELEVANCE: In this proposal, we study the regulation of hematopoietic stem cells (HSC) by their bone marrow microenvironment. Since HSC give rise to all blood cells, these regulatory mechanisms could be therapeutically exploited to increase HSC in specific situations of blood cell injury or deficiency.

描述（由申请人提供）：该提案的长期目标是定义细胞和分子介质对于HSC的成骨细胞控制至关重要。我们先前确定甲状旁腺激素（PTH）激活成骨细胞以增加造血干细胞（HSC）的数量，并且PTH改善了辐射损伤后的HSC存活率。这些结果为我们提供了一个模型，以定义一种新型的治疗方法，可通过刺激成骨细胞对骨髓的医源性或毒性损伤增加HSC。然而，调节HSC的特定成骨细胞亚群和关键成骨细胞依赖性分子事件是未知的。使用药理学和遗传模型，我们将Notch信号定义为PTH依赖性HSC调节的潜在介体。 Notch激活需要将细胞结合的配体与相邻细胞上的受体进行直接相互作用。我们证明了1）其受体的激活刺激成骨细胞中的Notch配体Jagged1（Jag1）； 2）在成骨细胞中具有组成症活性PTH受体的小鼠中，HSC的凹口激活增加； 3）依赖于PTH的HSC的增加被抑制？分泌酶活性阻止，这是Notch激活所必需的。我们的初步研究现在表明，依赖PTH依赖性HSC膨胀需要JAG1在成骨细胞中的表达。总之，这些数据表明PTH通过JAG1的成骨细胞表达扩展了HSC，然后激活相邻骨髓细胞中的Notch信号传导。根据我们的数据，我们假设成骨细胞的HSC扩展需要在骨髓微环境中JAG1引起的Notch激活。为了检验这一假设，在AIM1中，我们将定义成骨细胞细胞子集，其中JAG1是必要且足以介导HSC膨胀的。在AIM2中，我们将确定需要Notch激活的细胞群（HSC，成骨细胞和/或骨髓的其他成分）才能实现成骨细胞依赖性HSC膨胀。最后，在AIM3中，我们将确定Notch信号传导对PTH的骨髓保护作用的贡献，PTH是一种临床情况，其中HSC利基操纵可能是降低发病率和死亡率的新策略。我们已经建立并完全表征了体内模型，其中微环境信号会增加HSC。现在，成骨细胞JAG1已被确定为依赖PTH的HSC扩展的关键要素，我们有前所未有的机会，可以使用此处提出的体内策略来定义HSC利基的细胞和分子成分。因此，我们的实验目标的完成将定义骨髓微环境中HSC操纵的新型治疗靶标，可以利用该靶标在骨髓损伤后提高生存率。 公共卫生相关性：在此提案中，我们通过其骨髓微环境研究造血干细胞（HSC）的调节。由于HSC引起了所有血细胞，因此可以利用这些调控机制在血细胞损伤或缺乏的特定情况下进行治疗以增加HSC。