Functional Analysis of the Hematopoietic Niche during Ontogeny

据认为，在骨髓中至少有两种解剖学和生理学上不同的 造血小生境;成骨细胞和血管。在这些壁龛中，大量的分子和分泌 这些因子与造血的严格调控过程有关。然而，A 深入了解与每个生态位相互作用的HSC亚群及其生理作用 在调节干细胞层次和功能的每一个小生境类型仍然缺失。在这里，我们将识别 在表型、功能和转录水平上的每个小生境内发生的细胞相互作用 水平，使用作为一个独特的范式的发展过程，其中骨髓获得的能力， 支持造血。待进行的实验将使用生理学相关的大型动物 模型，高分辨率成像/捕获技术，灵敏的转录组测序，和功能 研究，结合为我们提供了独特的能力，研究和操纵人类的相互作用， HSC和特定的小生境细胞在体内的作用，从而阐明了每个离散的微环境在 人体造血系统的建立和维持。这些研究的总体假设是， 胎儿骨髓获得支持造血的能力的发育过程可用于 作为理解HSC和包含HSC的细胞之间发生的相互作用的模型， 骨髓生态位，以及这些生态位元素在造血的启动/维持中的作用。我们 进一步假设，这些知识将提供必要的工具，操纵这些利基， 促进造血干细胞移植后的植入和造血恢复。我们建议 以下具体目的：1）定义胎儿BM出现的步骤和关键细胞参与者 造血生态位和骨髓造血的开始，作为一种工具，以了解细胞相互作用 当它们出现时，它们发生在血管和成骨细胞龛内和之间，并表征 造血细胞的性质，每个支持，从而描绘的作用，每个发挥在维护和 扩增干细胞库以驱动终身造血;2）确定血管/血管周围是否 新生骨髓中的小生境不仅作为HSC的支持位点， 胎儿肝脏，但也含有具有促进造血建立潜力的细胞;以及 3)研究骨和血管龛的组成是否可以通过特定的 供体来源的细胞群，以增加植入水平和/或加速移植物的重建。 同种异体移植后供体来源的HSC。如果拟议的研究取得成功， 在原始HSC的分离和扩增以及对HSC起源的理解中具有重要意义。 可显著提高临床HSC的安全性和成功率 移植，并潜在地允许其应用于影响人类患者的更广泛的疾病。

It is thought that within the marrow there are at least two anatomically and physiologically distinct hematopoietic niches; the osteoblastic and the vascular. Within these niches, numerous molecules and secreted factors have been implicated in the strictly regulated process of hematopoiesis. Nevertheless, a thorough understanding of the subpopulations of HSC that interact with each niche and the physiological role of each niche type in the regulation of stem cell hierarchy and function is still missing. Here, we will identify the cellular interactions that occur within each of the niches at the phenotypic, functional, and transcriptional levels, using as a distinct paradigm the developmental process whereby the marrow acquires the ability to support hematopoiesis. Experiments to be performed will employ a physiologically relevant large animal model, high resolution imaging/capture technology, sensitive transcriptome sequencing, and functional studies, which combined provide us with the unique ability to study and manipulate the interactions of human HSC and specific niche cells in vivo, thereby unraveling the role played by each discrete microenvironment in the establishment and maintenance of human hematopoiesis. The overall hypothesis of these studies is that the developmental process whereby the fetal marrow acquires the ability to support hematopoiesis can be used as a model for understanding both the interactions that occur between HSC and the cells comprising the marrow niches, and the role of these niche elements in the initiation/maintenance of hematopoiesis. We further hypothesize that this knowledge will provide the necessary tools for manipulating these niches to facilitate the engraftment and accelerate hematopoietic recover of donor HSC after HSCTx. We propose the following Specific Aims:1)Define the steps and key cellular players in the emergence of the fetal BM hematopoietic niche and in the onset of marrow hematopoiesis, as a tool to understand the cellular interactions that occur both within and amongst the vascular and the osteoblastic niches as they arise, and characterize the nature of the hematopoietic cells each supports, thus delineating the role each plays in the maintenance and expansion of the stem cell pool to drive lifelong hematopoiesis;2) Determine whether the vascular/perivascular niches present within the nascent marrow not only serve as a supportive site for lodging of HSC arriving from the fetal liver, but also harbor cells with the potential to contribute to the establishment of hematopoiesis; and 3) Investigate whether the composition of the bone and vascular niches can be manipulated by specific populations of donor-derived cells to increase the levels of engraftment and/or accelerate reconstitution of donor derived HSC following allogeneic transplantation. Success of the proposed studies would have significant implications in the isolation and expansion of primitive HSC and the understanding of the origin of hematologic malignancies, and could significantly improve the safety and success of clinical HSC transplantation and potentially allow its application to a wider range of diseases affecting human patients.