The dynamics of cerebrospinal fluid (CSF) are essential for maintaining homeostasis in the central nerve system. Despite insufficiently detailed descriptions of their structural and molecular properties for a century, cranial arachnoid granulations (CAGs) on meninges have been thought to participate in draining CSF from the subarachnoid space into the dural sinuses. However, recent studies have demonstrated the existence of other types of CSF drainage systems, such as lymphatic vessels adjacent to dural sinus and paravascular space in the brain so-called glymphatic system. Therefore, the role of CAGs in CSF drainage has become dubious. To better understand CAG function, we analyzed the ultrastructure and molecular identity of CAG-like structure on meninges adjacent to the superior sagittal sinus of pigs. Transmission electron microscopy analysis revealed that this structure has a reticular conglomerate consisting of endothelial cells that resembles lymphatic linings. Furthermore, immunohistochemistry and immunoelectron microscopy showed that they express molecules specific to lymphatic endothelial cell. We coined a name "CAG-like dural gap (CAG-LDG)" to this structure and discussed the physiological relevance in terms of CSF drainage.

中文翻译：

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颅内蛛网膜肉芽样硬脑膜间隙淋巴内皮的鉴定

脑脊液 (CSF) 的动力学对于维持中枢神经系统的稳态至关重要。尽管一个世纪以来对其结构和分子特性的描述不够详细，但脑膜上的颅内蛛网膜颗粒 (CAG) 被认为参与了脑脊液从蛛网膜下腔排入硬脑膜窦的过程。然而，最近的研究表明存在其他类型的 CSF 引流系统，例如与硬脑膜窦相邻的淋巴管和大脑中所谓的淋巴系统。因此，CAGs 在脑脊液引流中的作用变得可疑。为了更好地了解 CAG 功能，我们分析了猪上矢状窦附近脑膜上 CAG 样结构的超微结构和分子特征。透射电子显微镜分析显示，该结构具有由内皮细胞组成的网状聚集体，类似于淋巴衬里。此外，免疫组织化学和免疫电子显微镜显示它们表达特定于淋巴管内皮细胞的分子。我们为这种结构创造了一个名称“CAG 样硬脑膜间隙 (CAG-LDG)”，并讨论了脑脊液引流方面的生理相关性。