Torigoe K, Tanaka H F, Takahashi A, Awaya A, Hashimoto K
Department of Anatomy, Fukui Medical School, Matsuika, Fukui 910-11, Japan.
Exp Neurol. 1996 Feb;137(2):301-8. doi: 10.1006/exnr.1996.0030.
In axonal regeneration after a peripheral nerve injury, Schwann cells migrate from the two nerve ends and at last form a continuous tissue cable across the gap which guides the axons toward the bands of Bungner. However, the behavior of migratory Schwann cells and their possible role are obscure. Using a film model in which the proximal stump of a transected nerve in mice was sandwiched between two thin plastic films, we analyzed neural regeneration in the early phase up to the 6th day after axotomy. Regenerating neurites emerged from the nodes of Ranvier adjacent to the axotomized nerve stump within 3 h after axotomy and extended along the parent nerve onto the film. All of the regenerating neurites on the surface of the film consisted of naked axons for at least 2 days after axotomy. Thereafter, Schwann cells from the proximal nerve migrated along a network of the regenerating axons and then closely attached to the axons, ensheathing them. Some of the Schwann cells advanced ahead of the axonal growth cones and were distributed over regions in which axonal extension was not yet present. As calculated from the time course of regenerating neurites, the velocity of axonal regeneration showed two phases: an initial slow phase (77 mu m/day) up to the 2nd post-operative day followed by a faster phase (283 mu m/day). The first observation of Schwann cells coincided with the onset of the second phase. In addition, the length of regenerating axons on the surface of the film containing many Schwann cells was significantly greater than that on the surface where Schwann cells were not yet present. It meant that migratory Schwann cells stimulated axons to elongate for a longer distance. Furthermore, Schwann cells from a distal stump showed a stronger ability to accelerate the axonal outgrowth than these from a proximal stump.
在周围神经损伤后的轴突再生过程中，雪旺细胞从神经两端迁移，最终形成跨越间隙的连续组织索，引导轴突朝向邦格内带生长。然而，迁移性雪旺细胞的行为及其可能的作用尚不清楚。我们使用一种薄膜模型，将小鼠横断神经的近端残端夹在两片薄塑料薄膜之间，分析了轴突切断后直至第6天的早期神经再生情况。轴突切断后3小时内，再生神经突从靠近轴突切断残端的郎飞结处伸出，并沿着母神经延伸到薄膜上。轴突切断后的至少2天内，薄膜表面所有的再生神经突都由裸露的轴突组成。此后，来自近端神经的雪旺细胞沿着再生轴突网络迁移，然后紧密附着在轴突上，将它们包裹起来。一些雪旺细胞在轴突生长锥之前前进，并分布在轴突尚未延伸的区域。根据再生神经突的时间进程计算，轴突再生速度呈现两个阶段：术后第2天之前为初始缓慢阶段（77μm/天），随后是较快阶段（283μm/天）。对雪旺细胞的首次观察与第二阶段的开始相吻合。此外，含有许多雪旺细胞的薄膜表面上再生轴突的长度明显大于雪旺细胞尚未出现的表面上再生轴突的长度。这意味着迁移性雪旺细胞刺激轴突伸长更长的距离。此外，来自远端残端的雪旺细胞比来自近端残端的雪旺细胞具有更强的加速轴突生长的能力。
