Background The classical view of cerebrospinal fluid (CSF) production posits the choroid plexus as its major source. Although previous studies indicate that part of CSF production occurs in the subarachnoid space (SAS), the mechanisms underlying extra-choroidal CSF production remain elusive. We here investigated the distributions of aquaporin 1 (AQP1) and Na+/K+/2Cl− cotransporter 1 (NKCC1), key proteins for choroidal CSF production, in the adult rodent brain and spinal cord. Methods We have accessed AQP1 distribution in the intact brain using uDISCO tissue clearing technique and by Western blot. AQP1 and NKCC1 cellular localization were accessed by immunohistochemistry in brain and spinal cord obtained from adult rodents. Imaging was performed using light-sheet, confocal and bright field light microscopy. Results We determined that AQP1 is widely distributed in the leptomeningeal vasculature of the intact brain and that its glycosylated isoform is the most prominent in different brain regions. Moreover, AQP1 and NKCC1 show specific distributions in the smooth muscle cell layer of penetrating arterioles and veins in the brain and spinal cord, and in the endothelia of capillaries and venules, restricted to the SAS vasculature. Conclusions Our results shed light on the molecular framework that may underlie extra-choroidal CSF production and we propose that AQP1 and NKCC1 within the leptomeningeal vasculature, specifically at the capillary level, are poised to play a role in CSF production throughout the central nervous system.

中文翻译：

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水通道蛋白 1 和 Na+/K+/2Cl− 协同转运蛋白 1 存在于成年啮齿动物中枢神经系统的软脑膜血管系统中

背景 脑脊液 (CSF) 产生的经典观点认为脉络丛是其主要来源。尽管以前的研究表明部分脑脊液产生发生在蛛网膜下腔 (SAS)，但脉络膜外脑脊液产生的机制仍然难以捉摸。我们在这里研究了水通道蛋白 1 (AQP1) 和 Na+/K+/2Cl− 协同转运蛋白 1 (NKCC1)（脉络膜 CSF 产生的关键蛋白质）在成年啮齿动物大脑和脊髓中的分布。方法 我们使用 uDISCO 组织清除技术和蛋白质印迹获得了完整大脑中的 AQP1 分布。AQP1 和 NKCC1 细胞定位通过从成年啮齿动物获得的脑和脊髓中的免疫组织化学进行访问。使用光片、共焦和明场光学显微镜进行成像。结果我们确定AQP1广泛分布在完整大脑的软脑膜血管系统中，并且其糖基化异构体在不同大脑区域中最为突出。此外，AQP1 和 NKCC1 在大脑和脊髓的穿透性小动脉和静脉的平滑肌细胞层中以及毛细血管和小静脉的内皮中显示出特定分布，仅限于 SAS 脉管系统。结论我们的研究结果阐明了可能是脉络膜外 CSF 产生的分子框架，我们提出，软脑膜血管系统中的 AQP1 和 NKCC1，特别是在毛细血管水平，准备在整个中枢神经系统的 CSF 产生中发挥作用。