Quantitative approaches to decipher neuronal network function in situ

长期以来，细胞外基质（extracellular matrix， ECM）被认为是一种专门用于维持神经元组织结构的支持结构。然而，现在很清楚的是，ECM与几个参与者合作调节许多细胞过程。其中，胶质细胞可以调节组织结构，膜受体可以调节细胞内外空间之间的离子和水的运动，从而改变细胞体积、ECM尺寸并最终改变它们各自的功能。然而，关于细胞外基质在活组织纳米水平上的功能和组织之间的相互作用知之甚少。******缺乏对这一学科的理解是由于缺乏对完整样本进行精确检查的工具。然而，我们最近开发了一种基于纳米探针跟踪的近红外显微镜方法。我们强调，细胞外空间（ECS）粘弹性特性在空间中变化，这些变化取决于ECM的组成。反过来，ECM的组织和功能依赖于离子稳态和神经元活动。为了了解这些相互作用，必须同时监测ECS （ECM的组成、离子浓度和受体分布）。为此，我们建立了一种在完整组织中监测活性和受体分布的方法。总之，这些方法允许监测网络的结构演变。我的研究项目将研究脑结构和脑外基质对细胞外流动性的作用。我将其分为3个目标：******1：研究细胞外空间组织与神经元活动的相互作用***2：研究细胞外基质对细胞外尺寸、自由离子浓度和离子稳态的作用***3：研究细胞外基质对组织神经递质/离子清除能力的作用。******该计划将解决与急性或慢性ECM组织改变相关的重要问题。这加强了ECS组织与离子稳态变化有关的概念。ECS生物物理特性的研究为探索完整的神经系统提供了新的途径。监测ECM组织的变化及其如何影响细胞稳态将为完整组织提供新的研究，我的研究计划将有助于研究重要但由于缺乏工具而被忽视的机制。长期计划将把细胞外组织与细胞稳态联系起来，同时将改变映射到ECM和细胞内机制（例如，受体分布、活动和运输）。通过研究完整活脑中的水运动，我预测，在纳米水平上更好地理解细胞外基质的扩散特性，将为阐述组织中水运输的新模型打开大门。

For a long time, the extracellular matrix (ECM) was considered a supportive structure solely dedicated to maintaining neuronal tissue architecture. Yet, it is now clear that the ECM regulates many cellular processes in partnership with several actors. Among those, glia cells can modulate tissue organization and membrane receptors can regulate ions and water movements between the intracellular and extracellular spaces thus modifying cell volume, the ECM dimensions and ultimately their respective functioning. Still, little is known about the interplay between function and organization of the extracellular matrix at the nanoscale level in living tissue. ******The lack of understanding of this discipline has been due to the absence of tools allowing precise examination in intact samples. However, we recently developed an approach using near-infrared microscopy based on nanoprobes tracking. We highlighted that the extracellular space (ECS) viscoelastic properties vary in space and that these changes are dependent on the ECM composition. In turn, the ECM organization and function rely on the ion homeostasis and neuronal activity. To understand these interplays, it is imperative to monitor the ECS concurrently (composition of the ECM, ion concentrations and receptors distributions). For this, we established an approach to monitor activity and receptor distribution in intact tissue. Together these approaches allow the monitoring of the structural evolution of the network. My research program will investigate the role of the brain structure and the ECM on the extracellular fluidity. I divided it into 3 aims: ******1: Study the interrelated roles of the extracellular space organization and neuronal activity***2: Investigate the role of the extracellular matrix on extracellular dimensions, free-ion concentrations and ion homeostasis***3: Investigate the role of the extracellular matrix in neurotransmitter/ion clearance capacity of tissue. ******This program will address important inquiries associated with acute or chronic alterations of the ECM organization. This reinforces the notion that the ECS organization is associated with changes in the ion homeostasis. The study of the biophysical properties of the ECS paves a new way of probing intact nervous system. Monitoring changes in the ECM organization and how it influences cellular homeostasis will offer new investigations of intact tissue and my research program will contribute to study important but still neglected mechanisms due to lack of tools. The long-term plan will link the extracellular organization to cellular homeostasis while mapping alterations to the ECM and intracellular mechanisms (e.g., receptor distribution, activity and trafficking). By studying water movements in the intact live brain, I predict that a better understanding of the diffusive properties of the extracellular matrix at the nanoscale level will open the door to the elaboration of new models of water transport in tissue.