Identification of biomechanical pathways that promote hematopoiesis

描述（由申请人提供）：在妊娠中期胚胎中，血流在心跳开始后开始，并使血管壁受到粘性摩擦、压力和拉伸。这些生物力学力不仅在内皮细胞中而且在背主动脉的造血细胞中诱导形态变化和分化程序的激活。第一个真正的造血干细胞（HSC）出现在这个区域，称为腹主动脉旁内脏胸膜（PSp），负责所有血液谱系的终身造血。我们已经发现，当施加到PSp细胞时，流体摩擦力刺激对确定性造血至关重要的遗传途径，并促进成年受体小鼠中的长期植入（Nature 2009，459：1131-1135和未公开的数据）。内皮细胞中的流体流动激活了许多特征明确的通路，但对决定造血命运的信号通路知之甚少。本文提出的研究旨在鉴定对造血特化和扩增重要的机械敏感性遗传信号。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。这些研究旨在确定生物力学应力在造血潜能调节中的作用，并有望激发培养可移植HSC扩增的创新方法。 三个目标将测试造血干细胞的出现和扩增是由生物力学响应途径触发的假设，这些途径可以被生化和药理化合物刺激。目标1。确定对PSp内的生物力学力作出反应的细胞的细胞表面表型，PSp是第一个永久性HSC产生的胚胎区域。目标二。定义和询问由PSp造血前体生物力学刺激激活的遗传途径。目标3。识别通过模拟生物力学力促进HSC特化或扩增的药理学化合物和形态发生素。 波士顿儿童医院（CHB）的博士后研究员Pamela Wenzel博士概述了一项5年职业计划，该计划将增强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和响应生物力学力量的遗传机制。Wenzel博士将由造血、生物力学工程和血液动力学领域的国际领导人组成的咨询委员会指导，其中包括伦纳德Zon博士、Donald Ingber博士和Guillermo Garcma-Cardeqa博士。最后，拟议的研究将在波士顿儿童医院的血液学/肿瘤学部门进行，该部门是世界上最大的儿科医学中心研究所，也是哈佛医学院的主要儿科教学附属机构。

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and promotes long-term engraftment in adult recipient mice when applied to PSp cells (Nature 2009, 459:1131-1135 and unpublished data).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.