Neuronal Regulation of Skeletal Development and Repair

骨骼发育和修复的神经元调节

• 批准号: 10785405
• 负责人: Thomas L Clemens
• 金额: $ 47.94万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-20 至 2026-08-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10785405
• 关键词: Neuronal; Regulation; Skeletal; Development; Repair

This is a renewal application of a program investigating the role of sensory nerves in bone. Our studies during the first funding period demonstrate that NGF-dependent TrkA signaling by sensory nerves is the primary driver of angiogenesis and osteogenesis in the developing femur and skull. In these avascular settings, acute up-regulation of NGF in mesenchymal lineage cell domains is followed by nociceptive fiber ingrowth, which subsequently home to locations of proliferating mesenchymal cells. Blockade of sensory nerve ingrowth, either by inhibition of TrkA signaling or disruption of NGF, retards vascularization and disrupts femoral and calvarial bone formation. Histological data in the calvaria model revealed that loss of sensory nerve fibers is associated with reduced numbers of proliferating osteogenic precursors in the sutures and premature suture closure. These observations suggest a paradigm in which sensory nerves function in developing bone to maintain mesenchymal stem cell plasticity, a concept well established in models of limb regeneration and supported by recent studies in developing mouse femur. Our preliminary findings directly examining the interaction of sensory nerve axons with MSCs in microfluidic chambers suggest that infiltrating DRG nerve fibers induce MSC proliferation, but limit differentiation in a non-contact dependent fashion. These effects are accompanied by upregulation of osteoprogenitor mitogens (e.g. TGF) and inhibitors of MSC differentiation (e.g. follistatin-like 1). Together, this data support the premise that TrkA+ sensory nerves function in developing bone to maintain stem cells in a proliferative, undifferentiated state by delivering soluble factors that activate mitogenic and anti-differentiation signaling pathways. This conceptual model will be explored in studies divided into three Specific Aims. Specific Aim 1 will define the spatiotemporal patterning of TrkA+ skeletal sensory nerves in the developing cranium, and determine their influence on osteoprogenitor proliferation and cellular fate. Specific Aim 2 will identify key target genes in MSCs impacted by sensory nerve signals using previously validated co-culture methods. Specific Aim 3 will identify sensory axon-derived factors that regulate MSC proliferation and cell fate decisions. Our results should provide new insights into the fundamental roles sensory nerves play in skeletal morphogenesis, homeostasis and repair, and provide critical insight into the neuropathological manifestations associated with bone disorders in humans.

这是研究感觉神经在骨骼中的作用的程序的更新应用。我们的学习期间 第一个资助期证明感觉神经的 NGF 依赖性 TrkA 信号传导是主要的 股骨和颅骨发育中血管生成和骨生成的驱动因素。在这些无血管的环境中， 间充质谱系细胞域中 NGF 的急性上调随后是伤害性纤维向内生长， 随后成为增殖间充质细胞的所在地。感觉神经阻断 通过抑制 TrkA 信号传导或破坏 NGF 来向内生长，延缓血管形成并破坏 股骨和颅骨骨形成。颅骨模型中的组织学数据显示，感觉丧失 神经纤维与缝线中增殖的成骨前体细胞数量减少有关 缝线过早闭合。这些观察结果表明感觉神经在其中发挥作用的范例 发育骨骼以维持间充质干细胞可塑性，这是肢体模型中已确立的概念 再生并得到最近小鼠股骨发育研究的支持。我们的初步调查结果直接 检查微流体室中感觉神经轴突与 MSC 的相互作用表明 浸润的 DRG 神经纤维诱导 MSC 增殖，但以非接触依赖性方式限制分化。 这些效应伴随着骨祖细胞有丝分裂原（例如 TGF）和 MSC 抑制剂的上调 分化（例如卵泡抑素样 1）。总之，这些数据支持 TrkA+ 感觉神经的前提 在骨骼发育中发挥作用，通过传递维持干细胞处于增殖、未分化状态 激活有丝分裂和抗分化信号通路的可溶性因子。 该概念模型将在分为三个具体目标的研究中进行探索。具体目标 1 将定义 发育中的颅骨中 TrkA+ 骨骼感觉神经的时空模式，并确定它们的 对骨祖细胞增殖和细胞命运的影响。具体目标 2 将确定 MSC 中的关键靶基因 使用先前验证的共培养方法受到感觉神经信号的影响。具体目标 3 将确定 调节 MSC 增殖和细胞命运决定的感觉轴突衍生因子。我们的结果应该提供 对感觉神经在骨骼形态发生、稳态和修复中发挥的基本作用的新见解， 并提供对与人类骨骼疾病相关的神经病理学表现的重要见解。