Structural and Functional Plasticity Surrounding Implanted Neuroprostheses

项目摘要 能够记录或刺激大脑电活动的可植入装置的开发已经 为治疗和研究神经系统疾病和损伤创造了前所未有的机会。然而，一个反应 组织反应通常发生在植入后， 性能炎症性小胶质细胞和星形胶质细胞包裹并隔离神经元的装置， 神经元信号源在电极表面的可记录半径内丢失。虽然这些观察 可能会导致信号不稳定和记录损失随着时间的推移，具体的机械联系， 炎症事件和信号质量的变化仍不清楚。我们的团队正在扩大 最近发表的一项研究表明， 围绕植入电极阵列的突触传递的亚型特异性标记。我们的数据表明 兴奋性传递标志物（囊泡谷氨酸转运蛋白1，VGLUT 1）的早期升高3天 植入后，随后转变为抑制性标记的表达增加， 神经传递（囊泡GABA转运蛋白，VGAT）。我们假设结构和功能可塑性 设备周围的突触输入可能会导致记录信号的丢失。我们进一步假设， 谷氨酸和GABA释放的定时升高可能作为“开始”和“停止”的线索， 组织反应在本提案中，我们将在初步观察的基础上，进一步研究潜在的 突触可塑性对设备性能的机制和功能后果。在具体目标1中， 将定义在记录的电极界面处的突触能突触重构的功能影响。 信号质量和反应性神经胶质增生。我们将把转运蛋白的表达与信号质量联系起来，并评估 VGLUT 1敲低对信号质量和组织反应的影响。在具体目标2中，我们同样将定义 电极界面GABA能突触重构对记录信号质量的功能影响 和反应性神经胶质增生我们假设，虽然早期谷氨酸释放可能会引起神经毒性和反应性， 神经胶质增生，随后的GABA释放发挥抗炎作用，以保持神经元的活力， 进一步降低神经胶质反应性。在具体目标3中，我们将揭示结构可塑性的树枝状乔木， 神经元在电极界面。为此，我们将使用双光子成像来评估树突状细胞的变化， 在离体脑组织切片中捕获的装置周围的棘密度和形态。为了所有的目标，我们将 测试硅基和聚酰亚胺基阵列，以比较 领域我们将检查阻抗测量和死后扫描电子显微镜图像的迹象 来加强对我们结果的解释。通过探索突触的新机制， 可塑性周围植入电极阵列，我们希望打开新的机会，既了解， 改善长期装置功能和生物相容性。

PROJECT SUMMARY The development of implantable devices capable of recording or stimulating electrical activity in the brain has created unprecedented opportunities to treat and study neurological diseases and injuries. However, a reactive tissue response typically occurs following implantation which is widely believed to interfere with long-term device performance. Inflammatory microglia and astrocytes encapsulate and isolate devices from neurons, while neuronal signal sources are lost within the recordable radius of the electrode surface. While these observations may contribute to signal instability and recording loss over time, the mechanistic link between specific inflammatory events and changes in signal quality remains unclear. Our group is expanding upon the current basic science understanding of device-tissue integration and recently published a study which showed shifts in subtype-specific markers of synaptic transmission surrounding implanted electrode arrays. Our data indicated an early elevation of markers of excitatory transmission (vesicular glutamate transporter-1, VGLUT1) three days post-implantation that was followed by a subsequent shift to increased expression of labeling for inhibitory neurotransmission (vesicular GABA transporter, VGAT). We hypothesize that structural and functional plasticity of synaptic inputs surrounding devices could contribute to loss of recorded signals. We further hypothesize that the timed elevation of glutamate and GABA release may act as “go” and “stop” cues which mediate the reactive tissue response. In this proposal, we will build upon our initial observations, further investigating the underlying mechanisms and functional consequences of synaptic plasticity on device performance. In Specific Aim 1, we will define the functional impacts of glutamatergic synaptic remodeling at the electrode interface on recorded signal quality and reactive gliosis. We will correlate transporter expression with signal quality and assess the effects of VGLUT1 knockdown on signal quality and tissue response. In Specific Aim 2, we similarly will define the functional impacts of GABAergic synaptic remodeling at the electrode interface on recorded signal quality and reactive gliosis. We hypothesize that while early glutamate release may incite neurotoxicity and reactive gliosis, subsequent GABA release acts in an anti-inflammatory capacity to preserve neuronal viability and mitigate further glial reactivity. In Specific Aim 3, we will reveal structural plasticity in the dendritic arbors of neurons at the electrode interface. For this aim, we will use two photon imaging to assess changes in dendritic spine density and morphology surrounding devices captured in ex vivo brain tissue slices. For all aims, we will test both silicon and polyimide-based arrays to compare results between device designs commonly used in the field. We will inspect impedance measurements and post-mortem scanning electron microscopy images for signs of device failure to strengthen the interpretation of our results. By exploring novel mechanisms of synaptic plasticity surrounding implanted electrode arrays, we expect to open new opportunities to both understand, and improve upon, long-term device function and biocompatibility.