Torigoe K, Lundborg G
Department of Anatomy, Fukui Medical School, Matsuoka, Fukui, 910-1193, Japan.
Exp Neurol. 1998 Apr;150(2):254-62. doi: 10.1006/exnr.1997.6775.
When the distal stump of a transected peripheral nerve is brought into the vicinity of the proximal nerve stump, the regenerating axons advance toward it across the gap. Similar results are obtained when a predegenerated nerve segment is used. However, when a nerve segment subjected to proximal axotomy 7 days earlier (7-day nerve segment) was placed close to the proximal end of a freshly cut nerve at a distance of less than 1.5 mm, there were neither regenerating axons nor sprouts. The same inhibition of axonal regeneration was also exhibited when a nerve segment subjected to axotomy 9 to 14 days earlier was used. To examine the inhibitory effect of the nerve segments on established regenerating axons, we positioned a 7-day nerve segment in close apposition to a proximal nerve end at 2 or 3 days after transection. The growth of the 3-day-old regenerating axons, already ensheathed by Schwann cells, was not disturbed, but the 2-day-old regenerating axons, consisting of naked axons, were eliminated by the 7-day nerve segment. It is assumed that the findings reflect a mechanism serving to eliminate abundant sprouts and immature axons, probably conferring optimum regeneration and maturation of outgrowing pioneer axons. The inhibitory effect on abundant sprouts and immature axons was completely blocked by local application of antibodies to myelin-associated glycoprotein (MAG). The MAG-containing cells appeared at 6 to 12 days after axotomy.
当横断的周围神经远侧断端靠近近侧神经断端时，再生轴突会跨越间隙向其生长。使用预先变性的神经节段也能得到类似结果。然而，当将7天前进行近端轴突切断术的神经节段（7天神经节段）放置在新切断神经的近端附近，距离小于1.5毫米时，既没有再生轴突也没有芽生。使用9至14天前进行轴突切断术的神经节段时，也表现出对轴突再生的相同抑制作用。为了研究神经节段对已建立的再生轴突的抑制作用，我们在横断后2或3天将一个7天神经节段紧邻近端神经末端放置。已经被施万细胞包裹的3日龄再生轴突的生长未受干扰，但由裸露轴突组成的2日龄再生轴突被7天神经节段清除。据推测，这些发现反映了一种机制，用于清除大量的芽生和未成熟轴突，这可能赋予生长中的先驱轴突最佳的再生和成熟。对大量芽生和未成熟轴突的抑制作用可通过局部应用抗髓磷脂相关糖蛋白（MAG）抗体完全阻断。含MAG的细胞在轴突切断术后6至12天出现。
