Osteo-Angio Coupling During Bone Repair - Resubmission - 1

项目摘要/摘要 骨折愈合过程中最关键的事件之一是重建有功能的血管网络。 血管生成，即从现有血管生长出新的血管，取决于生物和机械两方面。 线索，越来越多的证据将重建血管网络的过程与骨骼程序联系起来 队形。最近的数据显示，内皮细胞(ECs)也从相邻的ECs接收信号信号 来自多能基质细胞，包括驻留在血管周围的骨祖细胞(OPC) 利基市场“。OPC和EC之间的这种密切的空间关系表明，通过细胞- 细胞接触和/或旁分泌信号。在这里，我们建议阐明这一现象的细胞和分子基础。 使用一种新的体内骨修复、基因敲除和高分辨率机械生物学模型的效果 三维(3D)成像方式。CXCL12(SDF-1)是一种参与干细胞的可溶性趋化因子 募集和分化，在骨骼干细胞、成骨细胞和骨细胞中表达，并且 因骨骼损伤和机械负荷而上调。血管表达CXCR4和 内皮细胞与表达CXCL12的细胞在损伤部位共定位，提示CXCL12可能 在骨修复过程中发挥着重要的血管生成作用。这个项目的总体目标是阐明 CXCL12/CXCR4信号通路在骨-血管偶联中的作用。我们的中心假设是当地的OPC 通过CXCL12信号调节H型血管，机械应变环境是 通过调节CXCL12的表达而传递到局部血管系统。我们的目标是(1) 演示OPC和H型血管在骨修复过程中的功能相关性，(2) 确定CXCL12/CXCR4信号对OPC-EC耦合的影响。(三)不偏不倚 在有和无机械刺激的情况下骨修复过程中CXCL12细胞的特征。来自这些的结果 研究将促进我们对骨生成-血管生成调控机制的基本理解 在骨修复过程中的偶联，并可能揭示调控骨中血管生成的关键信号通路。我们的 这些发现将直接影响促血管生成的生物制品和目前自体干细胞的适应症。 注射治疗血管生成减少、愈合延迟和骨不连。

PROJECT SUMMARY/ABSTRACT One of the most critical events in fracture healing is reestablishment of a functional vascular network. Angiogenesis, the growth of new vessels from existing vessels, depends on both biological and mechanical cues, and growing evidence links the process of rebuilding a vascular network with the program of bone formation. Recent data show that endothelial cells (ECs) receive signaling cues from adjacent ECs as well as from multipotent stromal cells, including osteoprogenitor cells (OPCs), which reside in the “perivascular niche”. This close spatial relationship between OPCs and ECs suggests functional codependency via cell– cell contact and/or paracrine signaling. Here we propose to elucidate the cellular and molecular basis of this effect using a novel in vivo mechanobiological model of bone repair, gene knockout, and high-resolution three-dimensional (3D) imaging modalities. CXCL12 (SDF-1) is a soluble chemokine involved in stem cell recruitment and differentiation, is expressed in skeletal stem cells, osteoblasts, and osteocytes, and is upregulated in response to skeletal injury and mechanical loading. Blood vessels express CXCR4 and endothelial cells co-localize with CXCL12-expressing cells at the injury site, suggesting that CXCL12 may play a critical role in angiogenesis during bone repair. The overall goal of this project is to elucidate the role of CXCL12/CXCR4 signaling in osteo-angio coupling in bone. Our central hypothesis is that OPCs locally regulate Type H vessels through CXCL12 signaling, and that the mechanical strain environment is communicated to the local vasculature through modulation of CXCL12 expression. Our Aims are (1) To demonstrate functional codependency between OPCs and Type H vessels during bone repair, (2) To determine the influence of CXCL12/CXCR4 signaling on OPC-EC coupling. (3) To perform unbiased profiling of CXCL12+ cells during bone repair with and without mechanical stimulation. Results from these studies will advance our fundamental understanding of mechanisms regulating osteogenesis-angiogenesis coupling during bone repair and may reveal a key signaling pathway regulating angiogenesis in bone. Our findings would directly impact pro-angiogenic biologics and current indications for autologous stem cell injections to treat diminished angiogenesis, delayed healing, and nonunion.