Identification of biomechanical pathways that promote hematopoiesis

描述(申请人提供)：在中期胚胎中，血流在心跳开始后开始，使血管壁受到粘性摩擦、压力和拉伸。这些生物力学力量不仅诱导内皮细胞的形态改变和分化程序的激活，而且还诱导背主动脉造血细胞的形态改变和分化程序的激活。最早出现在该区域的真正的造血干细胞(HSCs)被称为腹主动脉旁内脏胸膜(PSP)，负责所有血系的终生造血。我们已经发现，当应用于PSP细胞时，流体摩擦力刺激对最终造血至关重要的遗传途径，并促进成年受体小鼠的长期植入(自然，2009,459：1131-1135和未发表的数据)。内皮细胞中的液体流动激活了许多具有良好特性的通路，但对决定造血命运的信号通路知之甚少。在此提出的研究旨在识别对造血规范和扩增重要的机械敏感遗传信号。此外，我将测试可溶性分子模拟机械力的促造血作用的能力。这些研究旨在明确生物机械应力在调节造血潜能中的作用，并有望激励创新的方法在培养中扩大可移植的HSCs。三个目标将检验这一假设，即造血干细胞的出现和扩张是由生物力学反应途径触发的，这些途径可以被生化和药物化合物刺激。目的1.确定PSP内对生物力学作用力反应的细胞表面表型(S)，PSP是第一个明确的HSC产生的胚胎区。目的2.定义和询问PSP中由生物力学刺激激活的造血祖细胞的遗传通路。目的3.通过模拟生物力学的作用，鉴定促进造血干细胞分化或扩增的药理化合物和形态因子。波士顿儿童医院(CHB)博士后研究员帕梅拉·温泽尔(Pamela Wenzel)博士概述了一项为期5年的职业计划，该计划将充实和加强她在发育造血和生物力学方面的背景。在干细胞生物学领域的先驱乔治·戴利博士的指导下，她试图确定在最终造血的最早阶段感知生物力学力量并对其做出反应的遗传机制。温泽尔博士将接受一个由造血、生物机械工程和血液动力学领域国际领袖组成的咨询委员会的指导，其中包括伦纳德·宗博士、唐纳德·英格伯博士和吉列尔莫·加尔马-卡德卡博士。最后，这项拟议的研究将在波士顿儿童医院的血液/肿瘤科进行，这是世界上最大的儿科医学中心研究机构，也是哈佛医学院的主要儿科教学附属机构。 公共卫生相关性：几十年来，造血干细胞(HSC)移植的临床成功一直受到供者匹配的骨髓、动员的外周血和脐带血来源的可用性和质量的限制。这导致了对可移植的患者特异性或普遍相容的造血细胞的扩展的迫切需要，然而，到目前为止，扩大HSC体外供应的努力基本上没有成功，导致自我更新能力差，多系潜力扭曲，植入效率低。识别促进造血细胞规范和扩增的生物机械激活途径将扩大我们对各种类型的信号的理解，这些信号包括可溶的和机械的，这些信号定义了造血细胞的生态位，此外，还将推动该领域朝着建立可用于治疗血液病、贫血和骨髓衰竭综合征的替代的、高质量的造血细胞来源的方向发展。

DESCRIPTION (provided by applicant): In the midgestation embryo, blood flow begins after initiation of the heartbeat and subjects vessel walls to viscous friction, pressure, and stretching. These biomechanical forces induce morphological change and activation of differentiation programs not only in endothelial cells but also in hematopoietic cells of the dorsal aorta. The first true hematopoietic stem cells (HSCs) that arise in this region, referred to as the para-aortic splanchnopleura (PSp), are responsible for life-long hematopoiesis of all blood lineages. We have found that fluid frictional force stimulates genetic pathways critical for definitive hematopoiesis and promotes long-term engraftment in adult recipient mice when applied to PSp cells (Nature 2009, 459:1131-1135 and unpublished data). A number of well-characterized pathways are activated by fluid flow in endothelial cells, yet little is known about the signaling pathways that determine hematopoietic fate. The studies proposed herein aim to identify the mechanosensitive genetic signals that are important for hematopoietic specification and expansion. Further, I will test the ability of soluble molecules to mimic the pro-hematopoietic effects of mechanical force. These studies are designed to define the role of biomechanical stress in regulation of hematopoietic potential and promise to inspire innovative approaches for the expansion of transplantable HSCs in culture. Three aims will test the hypothesis that hematopoietic stem cell emergence and expansion is triggered by biomechanically-responsive pathways that can be stimulated by biochemical and pharmacological compounds. Aim 1. Determine the cell surface phenotype(s) of cells that respond to biomechanical forces within the PSp, the embryonic region from which the first definitive HSCs arise. Aim 2. Define and interrogate genetic pathways activated by biomechanical stimulation in hematopoietic precursors from the PSp. Aim 3. Identify pharmacologic compounds and morphogens that promote specification or expansion of HSCs by mimicry of biomechanical forces. Dr. Pamela Wenzel, a postdoctoral research fellow at Children's Hospital Boston (CHB) has outlined a 5- year career plan that will augment and strengthen her background in developmental hematopoiesis and biomechanics. Under the mentorship of Dr. George Daley, a pioneer in the field of stem cell biology, she seeks to identify the genetic mechanisms that sense and respond to biomechanical forces at the earliest stages of definitive hematopoiesis. Dr. Wenzel will be mentored by an Advisory Committee of international leaders in hematopoiesis, biomechanical engineering, and hemodynamics, including Drs. Leonard Zon, Donald Ingber, and Guillermo Garcma-Cardeqa. Finally, the proposed research will be carried out in the Division of Hematology/Oncology at Children's Hospital Boston, the world's largest research institute at a pediatric medical center and the primary pediatric teaching affiliate of Harvard Medical School. PUBLIC HEALTH RELEVANCE: For several decades, the clinical success of hematopoietic stem cell (HSC) transplantation has been limited by the availability and quality of donor-matched sources of marrow, mobilized peripheral blood, and cord blood. This has led to an urgent need for expansion of transplantable patient-specific or universally compatible hematopoietic cells, and yet efforts to expand the HSC supply ex vivo have been largely unsuccessful to date, resulting in poor self-renewal, skewed multi-lineage potential, and low engraftment efficiencies. The identification of biomechanically activated pathways that promote specification and expansion of hematopoietic cells will broaden our understanding of the various types of signals, soluble and mechanical, that define the hematopoietic niche and, moreover, will advance the field toward establishing alternative, high quality sources of hematopoietic cells that can be used for the treatment of hematologic cancers, anemias, and bone marrow failure syndromes.