Department of Morphology, Cellular Biology, Faculty of Health Sciences, University of Las Palmas de Gran Canaria, 35016 Las Palmas, Canary Islands, Spain.
J Comp Neurol. 2010 Oct 1;518(19):4067-87. doi: 10.1002/cne.22444.
Spontaneous regrowth of retinal ganglion cell (RGC) axons occurs after optic nerve (ON) transection in the lizard Gallotia galloti. To gain more insight into this event we performed an immunohistochemical study on selected neuron and glial markers, which proved useful for analyzing the axonal regrowth process in different regeneration models. In the control lizards, RGCs were beta-III tubulin- (Tuj1) and HuCD-positive. The vesicular glutamate transporter-1 (VGLUT1) preferentially stained RGCs and glial somata rather than synaptic layers. In contrast, SV2 and vesicular GABA/glycine transporter (VGAT) labeling was restricted to both plexiform layers. Strikingly, the strong expression of glutamine synthetase (GS) in both Müller glia processes and macroglial somata revealed a high glutamate metabolism along the visual system. Upregulation of Tuj1 and HuCD in the surviving RGCs was observed at all the timepoints studied (1, 3, 6, 9, and 12 months postlesion). The significant rise of Tuj1 in the optic nerve head and optic tract (OTr) by 1 and 6 months postlesion, respectively, suggests an increase of the beta-III tubulin transport and incorporation into newly formed axons. Persistent Tuj1(+) and SV2(+) puncta and swellings were abnormally observed in putative degenerating/dystrophic fibers. Unexpectedly, neuron-like cells of obscure significance were identified in the control and regenerating ON-OTr. We conclude that: 1) the persistent upregulation of Tuj1 and HuCD favors the long-lasting axonal regrowth process; 2) the latter succeeded despite the ectopia and dystrophy of some regrowing fibers; and 3) maintenance of the glutamate-glutamine cycle contributes to the homeostasis and plasticity of the system.
蜥蜴 Gallotia galloti 的视神经（ON）切断后，视网膜神经节细胞（RGC）轴突会自发再生。为了更深入地了解这一事件，我们对选定的神经元和神经胶质标志物进行了免疫组织化学研究，这对于分析不同再生模型中的轴突再生过程非常有用。在对照蜥蜴中，RGC 呈β-III 微管蛋白（Tuj1）和 HuCD 阳性。囊泡谷氨酸转运体-1（VGLUT1）优先染色 RGC 及其神经胶质体，而不是突触层。相比之下，SV2 和囊泡 GABA/甘氨酸转运体（VGAT）的标记仅限于两个神经丛层。值得注意的是，谷氨酰胺合成酶（GS）在 Müller 胶质细胞突起和大胶质细胞体中的强表达表明沿视觉系统存在高谷氨酸代谢。在所有研究的时间点（损伤后 1、3、6、9 和 12 个月），存活的 RGC 中 Tuj1 和 HuCD 的上调均观察到。损伤后 1 个月和 6 个月，视神经头部和视束（OTr）中的 Tuj1 显著增加，表明β-III 微管蛋白的运输和掺入新形成的轴突增加。在推测的变性/营养不良纤维中异常观察到持续的 Tuj1（+）和 SV2（+）点状肿胀。出乎意料的是，在对照和再生的 ON-OTr 中鉴定出具有模糊意义的神经元样细胞。我们得出结论：1）Tuj1 和 HuCD 的持续上调有利于长期的轴突再生过程；2）尽管一些再生纤维异位和营养不良，但后者仍然成功；3）维持谷氨酸-谷氨酰胺循环有助于系统的内稳态和可塑性。
