Bone and the Hematopoietic System

骨髓腔的发育是一个协调的过程，在这个过程中，造血干细胞（HSC）迁移并定居在胚胎骨和软骨雕刻出来的空间中。因此，骨细胞（成骨细胞或OBs）和造血干细胞之间的密切物理联系是在生命早期建立的。这些研究的重点是骨骼和血液之间的这种空间关系是否也反映了两种组织之间的功能相互依赖。我们假设成骨和造血是相互关联和相互依赖的发育过程，由直接的细胞间相互作用调节。本提案的总体目标是确定造血干细胞- ob相互作用在正常和异常造血中的具体机制和后果。根据我们的初步数据，我们将描述HSC衍生的细胞因子是否与OB中间体建立了旁分泌环，从而释放HSC生存所必需的细胞因子（Aim 1A）。我们将确定造血干细胞本身是否会改变ob产生的细胞因子，以应对造血应激（Aim 1B）。这种扰动可能是对影响OB细胞因子产生或影响OB成熟的功能需求的响应。此外，我们还了解到唾液化的n -连接糖蛋白介导hsc与OBs的初始捆绑，hsc上的LFA-1和VLA-4受体提供坚固的细胞-细胞接触，从而确保hsc在OBs上的存活。在第二个目标中，将制备候选受体蛋白的单克隆抗体，以进一步表征负责将hsc粘附到OBs的唾液化n -连接糖蛋白（aim 2A）。在本研究的第二部分，我们将通过改变粘附分子的表达来确定OBs对HSC的反应，以及是否可溶性重组受体配体可以替代HSC和OBs之间的直接接触，以确保HSC在体外存活（aim 2A）。在最终目标中，我们将使用转基因小鼠来确定活体动物骨髓内HSC的存活是否需要OBs，这使我们能够诱导成熟OBs死亡（aim 3A），以及不同成熟阶段的OBs是否支持HSC的存活（aim 3B）。这些研究的结果将为血液和骨骼在健康和疾病中的相互作用生物学的本质提供重要的新见解。这些研究将最终导致治疗造血和骨骼疾病的新策略。

The development of the bone marrow cavity is an coordinated process in which hematopoietic stem cell (HSC) migrate and colonize spaces carved out of embryonic bone and cartilage. Thus, an intimate physical association between bone cells (osteoblasts or OBs) and HSCs is established early in life. The focus of these studies relate to whether this spatial relationship between bone and blood also mirrors a functional interdependence between the two tissues. We hypothesize that osteogenesis and hematopoiesis are interrelated and interdependent developmental processes regulated by direct cell- to-cell interaction. The overall goal of this proposal is to define the specific mechanisms and consequences of HSC-OB interactions in normal as well as in abnormal hematopoiesis. Based upon our preliminary data we will delineate if HSC-derived cytokines establish a paracrine loop with OB intermediaries, which in turn release cytokines necessary for HSC survival (Aim 1A). We will determine whether HSCs themselves alter the cytokines produced by OBs in response to hematopoietic stresses (Aim 1B). Such perturbations may arise in response to functional demands that affect OB cytokine production or that influence OB maturation. Furthermore, we have also learned that sialated-N-linked glycoproteins mediate the initial tethering of HSCs to OBs and LFA-1 and VLA-4 receptors on HSCs provide firm cell-cell contact thereby assuring the survival of HSCs on OBs. In the second aim monoclonal antibodies to candidate receptor proteins will be made to further characterize the sialated N-linked glycoproteins responsible for the initial tethering of HSCs to OBs (Aim 2A). In the second part of this aim, we will determine of OBs respond to HSCs by altering the expression of their adhesion molecules, and if soluble recombinant receptor ligands to VLA-4 and LFA-1 will substitute for direct contact between HSCs and OBs to ensure HSC survival in vitro (Aim 2A). In the final aim, we will determine if OBs are required for survival of HSCs within the bone marrow of living animals using transgenic mice which allow us to induce the death of mature OBs (Aim 3A), and if OBs at different stages of maturation support HSC survival (Aim 3B). The results of these investigations will provide important new insights into the nature of the interactive biology of blood and bone in health and disease. These investigations will ultimately lead to new strategies for the treatment of hematopoietic and osseous disorders.