Synaptic pathology, altered gene expression, and degeneration in photoreceptors impacted by drusen
Synaptic pathology, altered gene expression, and degeneration in photoreceptors impacted by drusen
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DOI：
10.1167/iovs.05-0767
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发表时间：
2005-12-01
影响因子：
4.4
通讯作者：
Johnson, LV
中科院分区：
文献类型：
--
作者：
Johnson, PT;Brown, MN;Johnson, LV
目的。玻璃体是老年性黄斑变性的危险因素，已被证明对RPE和视网膜的细胞有负面影响。在这项研究中，研究了玻璃体对视网膜光感受器突触机制的影响。方法：对含有视网膜、RPE和脉络膜的人供体眼组织进行共聚焦免疫荧光显微镜、激光捕获显微解剖以及光学和电子显微镜观察。组织切片用一组突触相关蛋白的抗体进行免疫染色。从新鲜冰冻组织中显微解剖玻璃膜上的光感受器群体和正常群体的光感受器，提取RNA，用定量聚合酶链式反应比较基因表达的相对水平。结果：在玻璃膜上的外丛状层区域，光感受器突触终末的数量减少，突触蛋白在光感受器细胞中定位错误，突触终末常出现在外核层内。玻璃体上的光感受器也增加了应激反应蛋白载脂蛋白E和αB-晶体蛋白的表达。异常的免疫标记模式不仅局限于直接位于玻璃膜上的光感受器，而且在玻璃膜两侧的细胞中也可以观察到。基因表达分析证实突触相关蛋白和信号转导蛋白编码基因的表达减少，载脂蛋白E和αB-晶体蛋白基因转录本的表达增加。光感受器突触末梢的超微结构分析显示玻璃膜上有明显的异常，细胞计数显示各种大小的玻璃膜上和侧面的光感受器密度降低。结论：覆盖在玻璃膜上和两侧的光感受器表现出退行性的形态和生化迹象。在光感受器突触终末，突触相关蛋白的表达减少，而应激反应蛋白的表达增加。光感受器细胞密度的减少，以及侧翼的玻璃体，表明这些退化效应最终导致光感受器的死亡。
PURPOSE. Drusen are risk factors for age-related macular degeneration and have been shown to negatively impact cells of the RPE and retina. In this study, the effects of drusen on the synaptic machinery of retinal photoreceptors are investigated.METHODS. Human donor eye tissue containing retina, RPE, and choroid was processed for confocal immunofluorescence microscopy, laser capture microdissection, and light and electron microscopy. Tissue sections were immunostained with a panel of antibodies to synapse-associated proteins. Populations of photoreceptors over drusen and normal populations of photoreceptors were microdissected from fresh frozen tissue, RNA was purified, and quantitative PCR was performed to compare relative levels of gene expression.RESULTS. The number of photoreceptor synaptic terminals is reduced in regions of the outer plexiform layer over drusen, synaptic proteins are mislocalized in photoreceptor cells, and synaptic terminals are often observed within the outer nuclear layer. Photoreceptors over drusen also increase expression of the stress response proteins apolipoprotein E and alpha B-crystallin. Abnormal immunolabeling patterns are not restricted to photoreceptors directly over drusen but are also observed in cells flanking drusen. Gene expression analysis confirms reductions in the expression of genes coding for synapse-associated proteins and signal transduction proteins and increases in the expression of apolipoprotein E and alpha B-crystallin gene transcripts. Ultrastructural analysis of photoreceptor synaptic terminals over drusen reveals significant abnormalities, and cell counts show a reduction in photoreceptor density directly over, and lateral to, drusen of all sizes.CONCLUSIONS. Photoreceptors overlying and flanking drusen exhibit morphologic and biochemical signs of degeneration. The expression of synapse-associated proteins decreases in photoreceptor synaptic terminals, whereas the expression of stress-response proteins increases. Reductions in photoreceptor cell densities over, and flanking, drusen suggest that these degenerative effects eventually result in the death of photoreceptors.