Tajima K, Tohyama K, Ide C, Abe M
Department of Orthopaedic Surgery School of Medicine, Iwate Medical University, Morioka, Japan.
J Bone Joint Surg Am. 1991 Feb;73(2):172-85.
With the use of ulnar nerves of cynomolgus monkeys, the present study examined whether basal laminae of Schwann cells can serve as conduits for regenerating axons in nerve allografts from non-human primates. A segment of ulnar nerve was transected distal to the elbow joint one week before grafting. In Group A, a distal segment of the transected nerve was transplanted, after freezing and thawing, into the ulnar nerve of another monkey, at a level that corresponded to that from which the graft was taken. In Group B (the control group), the segment of nerve was grafted in the same manner but without cryotreatment. Two weeks, five weeks, eight weeks, and five months after grafting, the graft and the host nerve were examined with light and electron microscopy. Within two weeks after grafting in Group A, after degradation of the cellular components of the Schwann cells, the basal laminae of the Schwann cells were intact in the form of tubes. Within five weeks, many regenerating axons grew out into these basal lamina tubes in the three-centimeter-long grafts and extended into the host nerve. As seen at the wrist (seven centimeters from the distal suture) five months after grafting, the axons exhibited fully mature myelination both in the graft and in the host nerve. In contrast, in Group B, in which the Schwann cells had not been disrupted by cryotreatment, cellular components and connective-tissue matrices, including basal laminae, had been degraded and had been replaced by invading cells, which filled the endoneurial spaces of the graft. Five months after grafting, axonal growth had been arrested in the graft one centimeter distal to the proximal suture. The beneficial effect in Group A appears to have been the result of the retention and preservation of intact basal laminae of Schwann cells after rapid removal of killed Schwann cells and myelin debris. Killing of Schwann cells by freezing before grafting may abolish the immune response to the Schwann cells in allografts and lead to fragmentation and disruption of myelin, which facilitates the rapid removal of myelin by macrophages.
本研究利用食蟹猴的尺神经，探讨雪旺细胞的基膜是否可作为非人灵长类动物神经同种异体移植中轴突再生的管道。移植前一周，在肘关节远端切断一段尺神经。A组将切断神经的远端部分经冻融后移植到另一只猴子的尺神经中，移植部位与取材部位相对应。B组（对照组）以相同方式移植神经段，但未进行冷冻处理。移植后2周、5周、8周和5个月，用光镜和电镜检查移植体和宿主神经。A组移植后2周内，雪旺细胞的细胞成分降解后，雪旺细胞的基膜呈完整的管状。5周内，许多再生轴突长入3厘米长移植体中的这些基膜管，并延伸至宿主神经。移植后5个月在腕部（距远端缝合处7厘米）观察到，移植体和宿主神经中的轴突均呈现完全成熟的髓鞘形成。相比之下，B组中雪旺细胞未因冷冻处理而破坏，细胞成分和结缔组织基质（包括基膜）已降解，并被侵入细胞取代，这些细胞充满了移植体的神经内膜间隙。移植后5个月，移植体中近端缝合处远端1厘米处的轴突生长停滞。A组的有益效果似乎是由于在快速清除死亡的雪旺细胞和髓鞘碎片后，雪旺细胞完整的基膜得以保留。移植前通过冷冻杀死雪旺细胞可能消除对同种异体移植中雪旺细胞的免疫反应，并导致髓鞘碎片化和破坏，这有利于巨噬细胞快速清除髓鞘。
