NGF-TrkA Signaling in Load-Induced Bone Formation

项目摘要/摘要 几乎所有支配骨骼的感觉神经都表达神经营养酪氨酸激酶受体1型(TrkA)， 神经生长因子的高亲和力受体。在成熟的骨骼中，这些特殊的感觉神经覆盖着 骨膜呈致密的网状网络，占据了生物力学信号传递的有利位置。 然而，NGF在成骨细胞中的调节机制以及通过 感觉神经仍然未知。我们在这个项目中的主要目标是确定上游调解人和 应变适应性骨重建中NGF-TrkA信号的下游效应因子。我们的中心假设是 成熟成骨细胞中的NF-κB信号的激活是神经生长因子表达所必需的 机械负荷，进而激活TrkA感觉神经，提供成骨信号，支持负荷- 诱导骨形成。在特定的目标1中，我们将确定成骨细胞中NGF的表达调控 使用体外脉动流体流动和体内条件基因敲除小鼠的前肢轴向压缩。具体而言 目的2，我们将通过分析m RNA和m RNA来识别促进负荷诱导骨形成的神经源性信号。 在NGF-TrkA信号减弱的小鼠模型中，来自负载肢体的蛋白质，并使用体外验证 微流控平台。在特定的目标3中，我们将评估该信号通路的潜在治疗应用。 在无痛觉过敏的情况下，增加成骨机械负荷后的骨积累。总体而言，结果来自 这项研究将确定NGF-TrkA信号的上游介体和下游效应因子 适应性骨重建，为利用该系统改善骨骼提供了一种潜在的治疗工具 健康。此外，拟议的研究与NIAMS长期计划高度一致，我们的 跨学科团队在推进这些具体目标方面具有独特的地位。

Project Summary/Abstract Nearly all of the sensory nerves that innervate bone express neurotrophic tyrosine kinase receptor type 1 (TrkA), the high affinity receptor for nerve growth factor (NGF). In mature bone, these specialized sensory nerves blanket the periosteum in a dense mesh-like network, occupying a preferential location for biomechanical signaling. However, the mechanism by which NGF is regulated in the osteoblast and the signals transmitted to bone by sensory nerves remain unknown. Our main objective in this project is to determine the upstream mediators and downstream effectors of NGF-TrkA signaling during strain adaptive bone remodeling. Our central hypothesis is that activation of NF-κB signaling in mature osteoblasts is required for the expression of NGF in response to mechanical load, which in turn activates TrKA sensory nerves to provide osteogenic cues that support load- induced bone formation. In Specific Aim 1, we will determine the regulation of NGF expression in osteoblasts using in vitro pulsatile fluid flow and in vivo forelimb axial compression of conditional knockout mice. In Specific Aim 2, we will identify nerve-derived signals that promote load-induced bone formation by analyzing mRNA and protein from loaded limbs in mouse models of diminished NGF-TrkA signaling, with validation using an in vitro microfluidic platform. In Specific Aim 3, we will assess a potential therapeutic application of this signaling pathway to increase bone accrual following osteogenic mechanical loading without hyperalgesia. In total, the results from this study will define the upstream mediators and downstream effectors of NGF-TrkA signaling during strain adaptive bone remodeling and provide a potential therapeutic tool for leveraging this system to improve skeletal health. Moreover, the proposed studies are highly aligned with the NIAMS Long-Range Plan, and our interdisciplinary team is uniquely positioned to advance these specific aims.