Joly Sandrine, Jordi Noémie, Schwab Martin E, Pernet Vincent
Brain Research Institute, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland; Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland.
Eur J Neurosci. 2014 Oct;40(7):3021-31. doi: 10.1111/ejn.12677. Epub 2014 Jul 12.
The lack of axonal regeneration in the adult central nervous system is in part attributable to the presence of inhibitory molecules present in the environment of injured axons such as the myelin-associated proteins Nogo-A and MAG and the repulsive guidance molecules Ephrins, Netrins and Semaphorins. In the present study, we hypothesized that EphA4 and one of its potential binding partners EphrinA3 may participate in the inhibition of adult axon regeneration in the model of adult mouse optic nerve injury. Axonal regeneration was analysed in three dimensions after tissue clearing of EphA4 knockout (KO), EphrinA3 KO and wild-type (WT) optic nerves. By immunohistochemistry, EphA4 was highly expressed in Müller glia endfeet in the retina and in astrocytes in the retina and the optic nerve, while EphrinA3 was present in retinal ganglion cells and oligodendrocytes. Optic nerve crush did not cause expression changes. Significantly more axons grew in the crushed optic nerve of EphA4 KO mice than in WT or EphrinA3 KO animals. Single axon analysis revealed that EphA4 KO axons were less prone to form aberrant branching than axons in the other mouse groups. The expression of growth-associated proteins Sprr1a and Gap-43 did not vary between EphA4 KO and WT retinae. However, glial fibrillary acidic protein-expressing astrocytes were withdrawn from the perilesional area in EphA4 KO, suggesting that gliosis down-regulation may locally contribute to improve axonal growth at the injury site. In summary, our three-dimensional analysis of injured mouse optic nerves reveals beneficial effects of EphA4 ablation on the intensity and the pattern of optic nerve axon regeneration.
成体中枢神经系统中轴突再生的缺乏部分归因于损伤轴突周围环境中存在的抑制性分子，如髓磷脂相关蛋白Nogo - A和MAG，以及排斥性导向分子Ephrins、Netrins和Semaphorins。在本研究中，我们假设EphA4及其潜在结合伴侣之一EphrinA3可能参与成年小鼠视神经损伤模型中成年轴突再生的抑制。在对EphA4基因敲除（KO）、EphrinA3基因敲除和野生型（WT）视神经进行组织透明化处理后，从三维角度分析轴突再生情况。通过免疫组织化学方法发现，EphA4在视网膜的Müller胶质细胞终足以及视网膜和视神经的星形胶质细胞中高表达，而EphrinA3存在于视网膜神经节细胞和少突胶质细胞中。视神经挤压并未引起表达变化。与野生型或EphrinA3基因敲除动物相比，EphA4基因敲除小鼠的挤压视神经中生长的轴突明显更多。单轴突分析显示，与其他小鼠组的轴突相比，EphA4基因敲除的轴突形成异常分支的倾向较小。生长相关蛋白Sprr1a和Gap - 43在EphA4基因敲除和野生型视网膜之间的表达没有差异。然而，在EphA4基因敲除小鼠中，表达胶质纤维酸性蛋白的星形胶质细胞从损伤周围区域撤离，这表明胶质增生下调可能在局部有助于改善损伤部位的轴突生长。总之，我们对损伤小鼠视神经的三维分析揭示了EphA4缺失对视神经轴突再生强度和模式的有益影响。
