Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America.
PLoS One. 2022 Jun 16;17(6):e0268541. doi: 10.1371/journal.pone.0268541. eCollection 2022.
Aquaporin 4 is absent from astrocytes in the rodent optic nerve head, despite high expression in the retina and myelinated optic nerve. The purpose of this study was to quantify regional aquaporin channel expression in astrocytes of the porcine and human mouse optic nerve (ON). Ocular tissue sections were immunolabeled for aquaporins 1(AQP1), 4(AQP4), and 9(AQP9), myelin basic protein (MBP), glial fibrillary acidic protein (GFAP) and alpha-dystroglycan (αDG) for their presence in retina, lamina, myelin transition zone (MTZ, region just posterior to lamina) and myelinated ON (MON). Semi- quantification of AQP4 labeling & real-time quantitative PCR (qPCR) data were analyzed in retina and ON tissue. Porcine and control human eyes had abundant AQP4 in Müller cells, retinal astrocytes, and myelinated ON (MON), but minimal expression in the lamina cribrosa. AQP1 and AQP9 were present in retina, but not in the lamina. Immunolabeling of GFAP and αDG was similar in lamina, myelin transition zone (MTZ) and MON regions. Semi-quantitative AQP4 labeling was at background level in lamina, increasing in the MTZ, and highest in the MON (lamina vs MTZ, MON; p≤0.05, p≤0.01, respectively). Expression of AQP4 mRNA was minimal in lamina and substantial in MTZ and MON, while GFAP mRNA expression was uniform among the lamina, MTZ, and MON regions. Western blot assay showed AQP4 protein expression in the MON samples, but none was detected in the lamina tissue. The minimal presence of AQP4 in the lamina is a specific regional phenotype of astrocytes in the mammalian optic nerve head.
水通道蛋白 4 不存在于啮齿动物视神经头部的星形胶质细胞中，尽管其在视网膜和有髓视神经中表达很高。本研究的目的是定量分析猪和人眼视神经（ON）星形胶质细胞中水通道蛋白的区域表达。眼部组织切片免疫标记水通道蛋白 1（AQP1）、4（AQP4）和 9（AQP9）、髓鞘碱性蛋白（MBP）、胶质纤维酸性蛋白（GFAP）和α- 肌营养不良糖蛋白（αDG），以确定它们在视网膜、神经节细胞层（lamina）、髓鞘过渡区（MTZ，位于 lamina 后）和有髓 ON（MON）中的存在情况。AQP4 标记的半定量和实时定量 PCR（qPCR）数据分析在视网膜和 ON 组织中进行。猪和对照人眼的 Müller 细胞、视网膜星形胶质细胞和有髓 ON（MON）中富含 AQP4，但在筛板中表达很少。AQP1 和 AQP9 存在于视网膜中，但不存在于 lamina 中。GFAP 和 αDG 的免疫标记在 lamina、髓鞘过渡区（MTZ）和 MON 区域相似。AQP4 标记的半定量在 lamina 中处于背景水平，在 MTZ 中增加，在 MON 中最高（lamina 与 MTZ、MON 相比；p≤0.05，p≤0.01）。AQP4 mRNA 的表达在 lamina 中最低，在 MTZ 和 MON 中较高，而 GFAP mRNA 的表达在 lamina、MTZ 和 MON 区域中均匀。Western blot 分析显示 MON 样本中存在 AQP4 蛋白表达，但在 lamina 组织中未检测到。AQP4 在 lamina 中的存在较少是哺乳动物视神经头部星形胶质细胞的特定区域表型。
