University Clinic of NeurosurgeryLaboratory of Neuropathology, Copenhagen University Hospital, RigshopitaletDepartment of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Neuropathol Appl Neurobiol. 2013 Feb;39(2):179-91. doi: 10.1111/j.1365-2990.2012.01275.x.
Aquaporin-4 (AQP4) is the most abundant cellular water channel in brain and could be a molecular basis for a cerebrospinal fluid absorption route additional to the arachnoid villi. In the search for 'alternative' cerebrospinal fluid absorption pathways it is important to compare experimental findings with human pathophysiology. This study compares expression of AQP4 in hydrocephalic human brain with human controls and hydrocephalic rat brain.
Cortical biopsies from patients with chronic hydrocephalus (n = 29) were sampled secondary to planned surgical intervention. AQP4 in human hydrocephalic cortex relative to controls was quantified by Western blotting (n = 28). A second biopsy (n = 13) was processed for immunohistochemistry [glial fibrillary acidic protein (GFAP), CD68, CD34 and AQP4] and double immunofluorescence (AQP4 + GFAP and AQP4 + CD34). Brain tissue from human controls and kaolin-induced hydrocephalic rats was processed in parallel. Immunohistochemistry and immunofluorescence were assessed qualitatively.
Western blotting showed that AQP4 abundance was significantly increased (P < 0.05) in hydrocephalic human brain compared with controls. AQP4 immunoreactivity was present in both white and grey matter. In human brain (hydrocephalic and controls) AQP4 immunoreactivity was found on the entire astrocyte membrane, unlike hydrocephalic rat brain where pronounced endfeet polarization was present. Endothelial AQP4 immunoreactivity was not observed.
This study shows a significant increase in astrocytic AQP4 in human hydrocephalic cortex compared with control. Cell type specific expression in astrocytes is conserved between rat and human, although differences of expression in specific membrane domains are seen. This study addresses direct translational aspects from rat to human, hereby emphasizing the relevance and use of models in hydrocephalus research.
水通道蛋白 4（AQP4）是脑内最丰富的细胞水通道，可能是蛛网膜绒毛以外的另一种脑脊液吸收途径的分子基础。在寻找“替代”脑脊液吸收途径时，将实验结果与人体病理生理学进行比较非常重要。本研究比较了脑积水患者大脑与正常对照组和脑积水大鼠大脑中 AQP4 的表达。
对因计划手术干预而接受皮质活检的慢性脑积水患者（n=29）进行皮质活检。通过 Western 印迹（n=28）定量比较人类脑积水皮质中 AQP4 与对照组的差异。对第二次活检（n=13）进行免疫组化（胶质纤维酸性蛋白（GFAP）、CD68、CD34 和 AQP4）和双免疫荧光（AQP4+GFAP 和 AQP4+CD34）处理。同时处理人类对照和高岭土诱导的脑积水大鼠的脑组织。对免疫组化和免疫荧光进行定性评估。
Western 印迹显示，与对照组相比，脑积水患者大脑中的 AQP4 丰度显著增加（P<0.05）。AQP4 免疫反应性存在于白质和灰质中。在人类大脑（脑积水和对照组）中，AQP4 免疫反应性存在于整个星形胶质细胞膜上，而在脑积水大鼠大脑中，存在明显的足突极化。未观察到内皮细胞 AQP4 免疫反应性。
本研究表明，与对照组相比，人类脑积水皮质中星形胶质细胞 AQP4 显著增加。在大鼠和人类之间，星形胶质细胞中 AQP4 的表达具有细胞类型特异性，但在特定膜结构域的表达存在差异。本研究从大鼠到人类进行了直接的转化研究，强调了在脑积水研究中使用模型的相关性和重要性。
