Abstract：
The choroid plexus (CP) is a structure in the brain ventricles that produces the main part of the cerebrospinal fluid (CSF). It is covered with specialized cells which show epithelial characteristics and are the site of the blood-CSF barrier. These cells form a contiguous cell sheet with ventricle-lining ependymal cells which are known to express aquaporin-4 (AQP4). In contrast, CP epithelial cells express aquaporin-1 (AQP1) apically. We investigated the expression patterns of aquaporins in the CP-ependyma transition from human body donors using immunofluorescence and electron microscopy. Ependymal cells and subependymal astrocytes at the base of the CP showed a particularly high AQP4 immunoreactivity. Astrocytic processes formed a dense meshwork or glial plate around the blood vessels entering the CP. Interestingly, some of these astrocytic processes were in direct contact with the CP stroma, which contains fenestrated blood vessels, separated only by a basal lamina. Electron microscopy confirmed the continuity of the subastrocytic basal lamina with the CP epithelium. We also probed for components of the AQP4 anchoring dystrophin-dystroglycan complex. Immunolabeling for dystrophin and AQP4 showed an overlapping staining pattern in the glial plate but not in previously reported AQP4-positive CP epithelial cells. In contrast, dystroglycan expression was associated with laminin staining in the glial plate and the CP epithelium. This suggests different mechanisms for AQP4 anchoring in the cell membrane. The high AQP4 density in the connecting glial plate might facilitate the transport of water in and out of the CP stroma and could possibly serve as a drainage and clearing pathway for metabolites.
摘要：
脉络丛（CP）是脑室中产生脑脊液（CSF）的主要部分的结构。它覆盖有显示上皮特征的特化细胞,并且是血液-CSF屏障的位点。这些细胞与已知表达水通道蛋白4（AQP4）的心室衬里室管膜细胞形成连续的细胞片。相比之下,CP上皮细胞顶端表达水通道蛋白-1(AQP1)。我们使用免疫荧光和电子显微镜研究了人体供体CP-室管膜转变中水通道蛋白的表达模式。CP底部的室管膜细胞和室管膜下星形胶质细胞显示出特别高的AQP4免疫反应性。星形细胞过程在进入CP的血管周围形成致密的网状结构或神经胶质板。有趣的是,这些星形细胞过程中的一些与CP基质直接接触，包含有孔的血管，只被基底层隔开。电子显微镜证实星形细胞下基底层与CP上皮的连续性。我们还探讨了AQP4锚定肌营养不良蛋白-肌聚糖复合物的成分。肌养蛋白和AQP4的免疫标记在神经胶质板中显示重叠的染色模式，但在先前报道的AQP4阳性CP上皮细胞中没有。相比之下,神经胶质板和CP上皮中的营养不良聚糖表达与层粘连蛋白染色有关。这表明AQP4锚定在细胞膜中的不同机制。连接的神经胶质板中的高AQP4密度可能促进水进出CP基质的运输，并可能充当代谢物的排水和清除途径。
