Fan W, Lin N, Sheedlo H J, Turner J E
Department of Anatomy and Cell Biology, University of North Texas Health Science Center, Fort Worth 76107, USA.
Exp Eye Res. 1996 Jul;63(1):9-18. doi: 10.1006/exer.1996.0086.
With increasing age, retinas of male Fischer rats gradually lose photoreceptor cells beginning at the ora serrata and extending to the central retina resulting in a pronounced peripheral retinopathy. In this study, we used immunocytochemical methods for glial fibrillary acidic protein (GFAP) and carbonic anhydrase II (CA II) to study the Müller cell response to age-related photoreceptor cell degeneration in the superior retina. Retinas of Fischer rats were also examined by electron microscopy to investigate retinal pigment epithelial (RPE) cell and Bruch's membrane structural changes with advancing age. Our study showed extensive photoreceptor cell loss in the region of the ora serrata beginning by 16 months, while few photoreceptor cells were found at 23 months. Neovascularization also occurred in the area of the peripheral retinopathy at the level of the RPE cells as determined by electron microscopy, as well as a thickening of Bruch's membrane with initial signs of small breaks. Dense areas of GFAP-immunostaining of Müller cell processes were found in the superior peripheral retina of 16-30 month-old rats where photoreceptor cells were degenerating. After 21 months, Müller cell processes extended into the subretinal space. However, in the central retina, where the photoreceptor cell population was more stable, GFAP-immunolabelled Můller cells were not detected. Immunoblots of retinal homogenates confirmed elevated GFAP levels at 18-30 months when compared to homogenates from retinas of 6-month-old Fischer rats. During photoreceptor cell degeneration, Müller cell processes were also prominently immunostained for CA II, which were seen to occupy the subretinal space at 18-30 months. Our results suggest that Müller cells respond to the age-related peripheral retinopathy in Fischer rats by increasing GFAP content and growth of their processes into the subretinal space to form a glial scar, but only in the area of severe photoreceptor cell loss. In addition, RPE and Bruch's membrane of aged retinas exhibit typical early age-related changes as also reported for aged human eyes.
随着年龄的增长，雄性Fischer大鼠的视网膜从锯齿缘开始逐渐失去光感受器细胞，并延伸至中央视网膜，导致明显的周边视网膜病变。在本研究中，我们使用免疫细胞化学方法检测胶质纤维酸性蛋白（GFAP）和碳酸酐酶II（CA II），以研究Müller细胞对视网膜上部与年龄相关的光感受器细胞变性的反应。还通过电子显微镜检查Fischer大鼠的视网膜，以研究随着年龄增长视网膜色素上皮（RPE）细胞和布鲁赫膜的结构变化。我们的研究表明，锯齿缘区域在16个月时开始出现广泛的光感受器细胞丢失，而在23个月时几乎找不到光感受器细胞。电子显微镜检查确定，在周边视网膜病变区域的RPE细胞水平也发生了新生血管形成，同时布鲁赫膜增厚，并出现小破裂的初步迹象。在16 - 30月龄大鼠视网膜上部周边区域，即光感受器细胞正在退化的区域，发现Müller细胞过程有密集的GFAP免疫染色区域。21个月后，Müller细胞过程延伸至视网膜下间隙。然而，在光感受器细胞群体更稳定的中央视网膜中，未检测到GFAP免疫标记的Müller细胞。视网膜匀浆的免疫印迹证实，与6月龄Fischer大鼠视网膜的匀浆相比，18 - 30个月时GFAP水平升高。在光感受器细胞变性期间，Müller细胞过程对CA II也有明显的免疫染色，在18 - 30个月时可见其占据视网膜下间隙。我们的结果表明，Müller细胞通过增加GFAP含量并使其过程生长到视网膜下间隙以形成胶质瘢痕来应对Fischer大鼠与年龄相关的周边视网膜病变，但仅在严重光感受器细胞丢失的区域。此外，老年视网膜的RPE和布鲁赫膜表现出典型的早期年龄相关变化，这在老年人类眼睛中也有报道。
