Becker T, Anliker B, Becker C G, Taylor J, Schachner M, Meyer R L, Bartsch U
Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Germany.
Glia. 2000 Feb 15;29(4):330-46. doi: 10.1002/(sici)1098-1136(20000215)29:4<330::aid-glia4>3.0.co;2-l.
Tenascin-R, an extracellular matrix constituent expressed by oligodendrocytes and some neuronal cell types, may contribute to the inhibition of axonal regeneration in the adult central nervous system. Here we show that outgrowth of embryonic and adult retinal ganglion cell axons from mouse retinal explants is significantly reduced on homogeneous substrates of tenascin-R or a bacterially expressed tenascin-R fragment comprising the epidermal growth factor-like repeats (EGF-L). When both molecules are presented as a sharp substrate border, regrowing adult axons do not cross into the tenascin-R or EGF-L containing territory. All in vitro experiments were done in the presence of laminin, which strongly promotes growth of embryonic and adult retinal axons, suggesting that tenascin-R and EGF-L actively inhibit axonal growth. Contrary to the disappearance of tenascin-R from the regenerating optic nerve of salamanders (Becker et al., J Neurosci 19:813-827, 1999), the molecule remains present in the lesioned optic nerve of adult mice at levels similar to those in unlesioned control nerves for at least 63 days post-lesion (the latest time point investigated), as shown by immunoblot analysis and immunohistochemistry. In situ hybridization analysis revealed an increase in the number of cells expressing tenascin-R mRNA in the lesioned nerve. We conclude that, regardless of the developmental stage, growth of retinal ganglion cell axons is inhibited by tenascin-R and we suggest that the continued expression of the protein after an optic nerve crush may contribute to the failure of adult retinal ganglion cells to regenerate their axons in vivo.
腱生蛋白-R是一种由少突胶质细胞和某些神经元细胞类型表达的细胞外基质成分，可能在成年中枢神经系统中对轴突再生产生抑制作用。在此我们表明，在腱生蛋白-R或包含表皮生长因子样重复序列（EGF-L）的细菌表达的腱生蛋白-R片段的均匀底物上，小鼠视网膜外植体中胚胎和成年视网膜神经节细胞轴突的生长显著减少。当这两种分子呈现为清晰的底物边界时，再生的成年轴突不会进入含有腱生蛋白-R或EGF-L的区域。所有体外实验均在层粘连蛋白存在的情况下进行，层粘连蛋白能强烈促进胚胎和成年视网膜轴突的生长，这表明腱生蛋白-R和EGF-L能积极抑制轴突生长。与蝾螈再生视神经中腱生蛋白-R消失的情况相反（Becker等人，《神经科学杂志》19:813 - 827，1999年），通过免疫印迹分析和免疫组织化学显示，在成年小鼠受损视神经中，该分子在损伤后至少63天（研究的最晚时间点）仍以与未损伤对照神经相似的水平存在。原位杂交分析显示，受损神经中表达腱生蛋白-R mRNA的细胞数量增加。我们得出结论，无论发育阶段如何，腱生蛋白-R都会抑制视网膜神经节细胞轴突的生长，并且我们认为视神经挤压后该蛋白的持续表达可能导致成年视网膜神经节细胞在体内无法再生其轴突。
