Functional role of satellite glial cells in axon regeneration

摘要 确定提高轴突再生速度和程度的策略对中枢神经系统的恢复非常重要。 系统损伤，轴突再生通常失败。与此相反，外周感觉神经元与细胞体 在轴突损伤后，背根神经节可以转换到再生状态，以促进再生， 功能恢复神经损伤对感觉神经元影响的研究表明， 促进轴突再生的内在信号机制。然而，事实上， 在神经修复过程中包裹神经元索马的卫星胶质细胞（SGC）的贡献。更好的 理解SGC的作用是重要的，意义重大。在这份提案中，我们概述了实验 揭示神经损伤后引起的SGC转录变化，并建立其机制 SGC是通过什么来促进感觉神经元的再生能力的。 SGC形成完全包围感觉神经元的鞘，导致每个神经元与 其卫星细胞鞘构成一个独立的功能单位。我们知道SGCs在结构上发生了改变， 在与慢性疼痛和感觉之间的交流相关的病理条件下， 神经元和SGC在伤害感受中起关键作用。根据我们的初步研究，我们现在有理由 相信SGC在周围神经再生中发挥了以前未被认识的作用。我们将揭晓 使用单细胞测序方法， 确定是否存在SGC子类型。我们将使用人DRG来确定人DRG的转录谱， 使用共培养方法研究SGC及其在轴突生长中的作用。这些实验将使我们能够揭示， 在小鼠模型系统中得到的发现预测了人类神经元的生理学。我们还 建立了一个神经元-SGC共培养系统，使我们能够可视化和量化SGC如何包裹 感觉神经元索马并决定SGC在感觉轴突生长和再生中的作用。最后我们将 基于我们的发现，即SGC在损伤后上调与脂质代谢相关的基因， SGC中酸合成影响神经损伤后基因表达和轴突再生。我们将专注于 脂肪酸合成酶（Fatty acid synthase，Fasn）是脂肪酸从头合成中的关键酶，我们发现， 神经损伤后的SGC。Fasn合成棕榈酸，棕榈酸是合成更多 复合脂肪酸，如醚连接磷脂（包括缩醛磷脂）。缩醛磷脂富集 在大脑中，在细胞信号传导和分化中发挥重要作用，并与神经系统有关。 紊乱我们将使用遗传学和脂质组学方法来确定SGC中脂质代谢如何 有助于轴突再生过程。通过这些实验，我们将揭示 SGC和缩醛磷脂对神经损伤的影响及其在轴突再生中的作用。

ABSTRACT Identifying strategies to increase the speed and extent of axon regeneration is important for central nervous system injuries, where axon regeneration usually fails. In contrast, peripheral sensory neurons with cell body in dorsal root ganglia can switch to a regenerative state after axon injury to promote regeneration and functional recovery. Studies on the effect of nerve injury on sensory neurons have revealed multiple neuronal intrinsic signaling mechanisms that promote axon regeneration. However, virtually nothing is known about the contribution of satellite glial cells (SGC) that envelop the neuronal soma in the nerve repair process. A better understanding of the role of SGC is important and highly significant. In this proposal, we outline experiments to uncover the transcriptional changes elicited in SGC following nerve injury and establish the mechanisms by which SGC contribute to sensory neurons' regenerative abilities. SGC form a sheath that completely surround sensory neurons, resulting in each neuron together with its satellite cell sheath constituting a discrete functional unit. We know that SGCs are altered structurally and functionally under pathological conditions associated with chronic pain and communication between sensory neurons and SGC plays a critical role in nociception. Based on our preliminary studies, we have now reason to believe that SGC play a previously unrecognized role in peripheral nerve regeneration. We will reveal the transcriptional profile of SGC in response to nerve injury using single cell sequencing approaches and determine if SGC subtypes exist. We will use human DRG to determine the transcriptional profile of human SGC and their role in axon growth using co-culture approaches. These experiments will allow us to reveal if findings made in the mouse model system are predictive of the physiology of human neurons. We have also established a neuron-SGC co-culture system that allows us to visualize and quantify how SGC envelop sensory neuron soma and determine SGC's role in sensory axon growth and regeneration. Finally, we will build on our findings that SGC upregulate genes related to lipid metabolism after injury to test if de novo fatty acid synthesis in SGC affect gene expression and axon regeneration following nerve injury. We will focus on Fatty acid synthase (Fasn), the key enzyme in de novo fatty acid synthesis, which we found is upregulated in SGC after nerve injury. Fasn synthesizes palmitic acid, which is the substrate for the synthesis of more complex fatty acids, such as ether linked phospholipids (including plasmalogens). Plasmalogens are enriched in the brain and play important roles in cell signaling and differentiation and are implicated in neurological disorders. We will use genetic and lipidomics approaches to determine how lipid metabolism in SGC contribute to the axon regeneration process. Through these experiments, we will uncover the contribution of SGC and plasmalogens to nerve injury and their functional role in axon regeneration.