Rothermel A, Layer P G
Darmstadt University of Technology, Developmental Biology & Neurogenetics, Schnittspahnstrasse 3, D-64287 Darmstadt, Germany.
Eur J Neurosci. 2001 Mar;13(5):949-58. doi: 10.1046/j.1460-9568.2001.01469.x.
Plasticity of photoreceptors and their integration into epithelial structures homologous to an outer nuclear layer (ONL), was investigated in embryonic chick retinal cell reaggregates by immunohistochemistry using an antibody specific for red plus green cones (RG-cones) and an antibody for rods. If reaggregates are raised in the presence of pigmented epithelium (RPE), completely reconstructed, stratified retinal spheres are produced, where all rods and cones are integrated into an outer laminar ONL, similar to a normal retina. In the absence of RPE, 'rosetted' spheres form which contain internal rosettes homologous to an ONL. Only a minor fraction of cones and rods of 'rosetted' spheres are located within rosettes, while a larger fraction is diffusely displaced in nonorganized areas, thus, not contributing to an ONL-like epithelium. In both types of spheres, the total percentage of RG-cones was similar to the in vivo retina, indicating that expression of cones is autonomous. Following cones, after about one day, rods developed only within already existing RG-cone clusters. Thereby, the ratio of rods to RG-cones increases as the tissue organization decreases: for stratified spheres this ratio is, 0.50 (1 rod/2 cones; similar to mature retina); for rosettes, 0.74 (3 rods/4 cones) and for nonorganized areas, 1.09 (1 rod/1 cone) -- a higher ratio under our conditions has never been detected. Thus, rod expression depends strictly on the presence of nearby cones; their relative numbers are distinctively adjusted according to the cytoarchitecture of the tissue environment. The biomedical implications of these findings are briefly discussed.
利用针对红+绿锥体细胞（RG-锥体细胞）的特异性抗体和视杆细胞抗体，通过免疫组织化学方法，在胚胎鸡视网膜细胞团聚体中研究了光感受器的可塑性及其整合到与外核层（ONL）同源的上皮结构中的情况。如果团聚体在色素上皮（RPE）存在的情况下培养，会产生完全重建的分层视网膜球体，其中所有视杆细胞和视锥细胞都整合到一个外层状ONL中，类似于正常视网膜。在没有RPE的情况下，会形成“玫瑰花结状”球体，其中包含与ONL同源的内部玫瑰花结。“玫瑰花结状”球体中只有一小部分视锥细胞和视杆细胞位于玫瑰花结内，而较大一部分则分散在无组织区域，因此，不会形成类似ONL的上皮。在这两种类型的球体中，RG-锥体细胞的总百分比与体内视网膜相似，表明锥体细胞的表达是自主的。在锥体细胞之后，大约一天后，视杆细胞仅在已经存在的RG-锥体细胞簇内发育。因此，随着组织组织性降低，视杆细胞与RG-锥体细胞的比例增加：对于分层球体，该比例为0.50（1个视杆细胞/2个锥体细胞；类似于成熟视网膜）；对于玫瑰花结，为0.74（3个视杆细胞/4个锥体细胞），对于无组织区域，为1.09（1个视杆细胞/1个锥体细胞）——在我们的条件下从未检测到更高的比例。因此，视杆细胞的表达严格依赖于附近锥体细胞的存在；它们的相对数量根据组织环境的细胞结构进行了独特的调整。简要讨论了这些发现的生物医学意义。
