Understanding the role of tanycytes in the mammalian brain

目的：本研究拟探讨下丘脑伸长细胞的作用。背景与理由：伸长细胞是一种特化的室管膜细胞，存在于缺乏完全血脑屏障（BBB）的少数受限下丘脑区域。在缺乏血脑屏障的区域，伸长细胞体形成脑室底，其突起深入脑实质，接触开窗血管，从而暴露于外周循环。人们对伸长细胞的功能了解甚少；然而，考虑到它们的战略位置，在循环系统和中枢神经系统之间架起桥梁，这些细胞可能在循环系统和大脑之间传递信号方面发挥重要作用。***我们最近的工作揭示了在终末板血管器官（OVLT）中存在大量的伸长细胞。OVLT是最重要的缺血脑屏障感觉区之一，为大脑提供来自外周的信息，并有助于中枢介导的生理反应的产生。我们的数据显示，OVLT伸长细胞形成密集的网络，紧密地嵌入局部神经元。尽管伸长细胞在这个重要的大脑区域中普遍存在，但它们的功能仍然难以捉摸。***目标与方法：***研究OVLT伸长细胞在检测血源性循环信号以改变神经元活性中的作用。为了选择性地靶向tanycytes，我们将使用遗传（他莫昔芬诱导的vimentin - cre小鼠系）和药理学工具来操纵vimentin （tanycytes的主要结构成分）的水平和活性，并将通过有条件的敲除和/或使用腺相关病毒过度表达来调节tanycytes中膜受体和转运蛋白的表达。这些方法将结合体外和体内使用电生理学和钙成像对伸长细胞活性的功能分析。* * * 2。OVLT细胞结构组织的研究。我们将利用超分辨率成像技术表征伸长细胞的形态和组织，以及它们与神经元和脉管系统的接触。OVLT细胞干细胞潜能的研究。我们将使用不同谱系的标记来评估OVLT伸长细胞的干细胞潜能，使用他莫昔芬诱导的Nestin-Cre小鼠在体内进行长期的伸长细胞谱系追踪，并通过检测OVLT伸长细胞的神经球性潜能和使用电生理学评估新生神经元的功能来研究神经发生。***结果：本研究将探索作为外周循环和中枢神经系统接口的重要脑区中先前描述的细胞群的功能。破译伸长细胞在这一领域的作用将为哺乳动物大脑中最不为人知的角落之一提供新的见解。

OBJECTIVES: The proposed research program will explore the role of hypothalamic tanycytes. ***BACKGROUND & RATIONALE: Tanycytes are specialized ependymal cells found in a few confined hypothalamic areas which lack a complete blood brain barrier (BBB). Tanycyte cell bodies form the ventricular floor in the BBB-lacking areas, and their processes extend deep into the brain parenchyma, contacting fenestrated vasculature, and thus are exposed to the peripheral circulation. The function of tanycytes is poorly understood; however, given their strategic location, bridging between the general circulation and the central nerve system, these cells might play an important role in transmitting signals between the circulation and the brain. ***Our recent work has revealed the presence of a large population of tanycytes in organum vasculosum of lamina terminalis (OVLT). OVLT is one of the most important BBB-lacking sensory areas providing the brain with the information from the periphery and contributing to the generation of centrally-mediated physiological responses. Our data show that OVLT tanycytes create a dense network tightly embedding local neurons. Although the tanycytes constitute a prevalent population in this vital brain region, their function remains elusive. ***AIMS & METHODS:***1. Studying the role of OVLT tanycytes in detecting blood-borne circulating signals to modify the activity of neurons. To selectively target tanycytes, we will manipulate the levels and activity of vimentin (a major structural component of tanycytes) with genetic (tamoxifen-inducible Vimentin-Cre mouse line) and pharmacological tools, and will modulate the expression of membrane receptors and transporters in tanycytes by conditional knockout and/or overexpression using adeno-associated virus. These approaches will be combined with functional analysis of tanycyte activity using electrophysiology and calcium imaging in vitro and in vivo. ***2. Investigating the structural organization of OVLT tanycytes. We will characterize tanycyte morphology and organization, and their contacts with neurons and vasculature using superresolution imaging.***3. Studying the stem cell potential of OVLT tanycytes. We will assess the stem cell potential of OVLT tanycytes using markers for different lineages, performing long-term tanycyte lineage tracing in vivo using tamoxifen-inducible Nestin-Cre mice, and studying the neurogenesis by examining neurospherogenic potential of OVLT tanycytes and evaluating the functionality of newborn neurons using electrophysiology. ***OUTCOME: The proposed work will explore the function of previously undescribed cell population in the vital brain area which serves as an interface between the peripheral circulation and the central nervous system. Deciphering the role of tanycytes in this area will provide new insights into one of the least-explored corners of the mammalian brain.