Osteo-Angio Coupling During Bone Repair - Resubmission - 1

项目概要/摘要 骨折愈合中最关键的事件之一是功能性血管网络的重建。 血管生成，即从现有血管生长出新血管，取决于生物学和机械学两个方面。 线索，越来越多的证据将重建血管网络的过程与骨骼的程序联系起来， 阵最近的研究表明，内皮细胞（EC）也接受来自相邻EC的信号线索 如来自多能基质细胞，包括骨祖细胞（OPCs），其存在于“血管周围 利基”。OPCs和ECs之间的这种紧密的空间关系表明通过细胞间的相互作用， 细胞接触和/或旁分泌信号传导。在这里，我们建议阐明细胞和分子基础，这 使用骨修复、基因敲除和高分辨率的新型体内机械生物学模型的效果 三维（3D）成像模式。趋化因子CXCL 12（SDF-1）是一种可溶性趋化因子， 在骨骼干细胞、成骨细胞和骨细胞中表达， 上调响应骨骼损伤和机械负荷。血管表达CXCR 4， 内皮细胞与表达CXCL 12的细胞共定位于损伤部位，表明CXCL 12可能 在骨修复过程中的血管生成中起关键作用。本项目的总体目标是阐明 CXCL 12/CXCR 4信号在骨血管偶联中的作用。我们的中心假设是， 通过CXCL 12信号调节H型血管，并且机械应变环境是 通过调节CXCL 12表达将其传递至局部脉管系统。我们的目标是（1） 证明骨修复过程中OPCs和H型血管之间的功能相互依赖性，（2） 确定CXCL 12/CXCR 4信号传导对OPC-EC偶联的影响。(3)执行无偏 在有和没有机械刺激的骨修复过程中CXCL 12+细胞的概况分析。从这些 这些研究将促进我们对骨生成-血管生成调节机制的基本理解 偶联在骨修复过程中，并可能揭示一个关键的信号通路调节骨血管生成。我们 研究结果将直接影响促血管生成生物制剂和自体干细胞的当前适应症 注射以治疗减少的血管生成、延迟愈合和骨不连。

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.