Eliasieh Kasra, Liets Lauren C, Chalupa Leo M
Section of Neurobiology, Physiology and Behavior, College of Biological Science, University of California, CA 95616, USA.
Invest Ophthalmol Vis Sci. 2007 Jun;48(6):2824-30. doi: 10.1167/iovs.06-1228.
To characterize the nature and extent of neuronal reorganization in the human retina during normal aging.
Retinas of young (18-34 years old) and aged (68-77 years old) human donors were examined. Immunocytochemical methods and antibodies directed against Go-alpha, protein kinase C, parvalbumin, calbindin, calretinin, and choline acetyltransferase were used to stain different retinal cell types. Confocal images of retinal sections from the optic disc to the peripheral edge were taken at three eccentricities, and the density and length of cellular processes were quantified with neuroanatomical analysis software.
Dendritic fibers of rod and On-cone bipolar cells were found to extend well beyond the normal boundary of the outer plexiform layer (OPL) into the outer nuclear layer (ONL) in aged retinas. Length and density of these elongated fibers were significantly greater in aged than in young retinas. This phenomenon demonstrated a clear spatial gradient that was most prevalent in the periphery and was infrequent in the central region of the retina. Horizontal cells, which normally make triad synaptic connections with photoreceptors and bipolar cells, also had dendrites that extended into the ONL in aged retinas, and these were spatially juxtaposed with the elongated dendrites of bipolar cells.
Rod and On-cone bipolar cells, as well as horizontal cells of the human retina, undergo extensive dendritic reorganization during normal aging. Although literature on aging has tended to emphasize degenerative and regressive changes, the present findings provide evidence for a remarkable degree of cellular plasticity in the aged human retina.
描述正常衰老过程中人类视网膜神经元重组的性质和程度。
检查年轻（18 - 34岁）和老年（68 - 77岁）人类供体的视网膜。使用免疫细胞化学方法和针对Go-α、蛋白激酶C、小白蛋白、钙结合蛋白、钙视网膜蛋白和胆碱乙酰转移酶的抗体来标记不同的视网膜细胞类型。从视盘到周边边缘的视网膜切片的共聚焦图像在三个离心率下拍摄，并用神经解剖学分析软件对细胞突起的密度和长度进行量化。
在老年视网膜中，发现视杆细胞和视锥ON型双极细胞的树突纤维延伸到外网状层（OPL）的正常边界之外，进入外核层（ONL）。这些伸长纤维的长度和密度在老年视网膜中明显大于年轻视网膜。这种现象表现出明显的空间梯度，在周边最为普遍，在视网膜中央区域则很少见。通常与光感受器和双极细胞形成三联突触连接的水平细胞，在老年视网膜中其树突也延伸到ONL，并且这些树突在空间上与双极细胞的伸长树突并列。
人类视网膜的视杆细胞和视锥ON型双极细胞以及水平细胞在正常衰老过程中经历广泛的树突重组。尽管关于衰老的文献倾向于强调退行性和衰退性变化，但目前的研究结果为老年人类视网膜中显著程度的细胞可塑性提供了证据。
