Gatzinsky K P, Persson G H, Berthold C H
Department of Anatomy and Cell Biology, University of Göteborg, Sweden.
Glia. 1997 Jun;20(2):115-26. doi: 10.1002/(sici)1098-1136(199706)20:2<115::aid-glia3>3.0.co;2-8.
The aim of this study was to investigate the potential ability of Schwann cells to sequester axonally transported material via so called axon-Schwann cell networks (ASNs). These are entities consisting of sheets of Schwann cell adaxonal plasma membrane that invade the axon and segregate portions of axoplasm in paranodes of large myelinated mammalian nerve fibres. Rat hindlimb alpha-motor axons were examined in the L4-S1 ventral roots using light/fluorescence, confocal laser, and electron microscopy for detection of retrogradely transported red-fluorescent latex nanospheres taken up at a sciatic nerve crush, and intramuscularly injected horseradish peroxidase endocytosed by intact synaptic terminals. Survival times after tracer administration ranged from 27 hours to 4 weeks. During their retrograde transport toward the motor neuron perikarya, organelles carrying nanospheres/peroxidase accumulated at nodes of Ranvier, where they often appeared in close association with the paranodal myelin sheath. Serial section electron microscopy showed that many of the tracer-containing bodies were situated within ASN complexes, thereby being segregated from the main axon. Four weeks after nanosphere administration, several node-paranode regions still showed ASN-associated aggregations of spheres, some of which were situated in the adaxonal Schwann cell cytoplasm. The data establish the ability of Schwann cells to segregate material from motor axons with intact myelin sheaths, using the ASN as mediator. Taken together with our earlier observations that ASNs in alpha-motor axons are also rich in lysosomes, this process would allow a local elimination and secluded degradation of retrogradely transported foreign substances and degenerate organelles before reaching the motor neuron perikarya. In addition, ASNs may serve as sites for disposal of indigestable material.
本研究的目的是探究雪旺细胞通过所谓的轴突 - 雪旺细胞网络（ASN）隔离轴突运输物质的潜在能力。这些网络由雪旺细胞近轴突质膜片组成，它们侵入轴突并在大型有髓哺乳动物神经纤维的结旁隔离部分轴质。使用光/荧光、共聚焦激光和电子显微镜检查大鼠后肢α运动轴突在L4 - S1腹根中的情况，以检测在坐骨神经挤压时摄取的逆行运输的红色荧光乳胶纳米球，以及完整突触终末内吞的肌肉注射辣根过氧化物酶。给予示踪剂后的存活时间为27小时至4周。在它们向运动神经元胞体逆行运输的过程中，携带纳米球/过氧化物酶的细胞器在郎飞结处聚集，它们经常与结旁髓鞘紧密相连。连续切片电子显微镜显示，许多含有示踪剂的小体位于ASN复合体中，从而与主轴突分离。给予纳米球4周后，几个结 - 结旁区域仍显示与ASN相关的球状体聚集，其中一些位于近轴突雪旺细胞胞质中。这些数据证实了雪旺细胞利用ASN作为介质从具有完整髓鞘的运动轴突中隔离物质的能力。结合我们早期的观察结果，即α运动轴突中的ASN也富含溶酶体，这一过程将允许在逆行运输的外来物质和退化细胞器到达运动神经元胞体之前进行局部清除和隔离降解。此外，ASN可能作为不可消化物质的处理场所。
