移植嗅鞘细胞可通过减弱纤维性瘢痕的产生而促进大鼠脊髓损伤后神经纤维的再生

背景：多项研究已证实嗅鞘细胞移植能促进脊髓损伤大鼠神经再生和功能的恢复，但嗅鞘细胞移植促进再生的分子机制还未完全阐明。 目的：观察嗅鞘细胞移植是否可以消除纤维性瘢痕的产生。 设计、时间及地点：对照随机动物实验，于2007年4月至2009年5月在日本东京都神经科学研究所发生形态部门和中国医科大学基础医学院解剖教研室完成。 材料：动物由日本东京都神经科学研究所动物管理及使用委员会提供 方法：选取体重为300-350克的SD大鼠23只，行胸椎9-10脊髓全横断，分为假手术对照组（n=3）、手术组（n=9）和嗅鞘细胞移植组（n=11）。嗅鞘细胞来源于未成熟的嗅球，并经过培养2-3周。 主要观察指标：分别应用GFAP和胶原IV蛋白免疫组化染色观察损伤部位胶质瘢痕和纤维性瘢痕的形成。脊髓内下行和上行的神经纤维束分别应用5-羟色胺和降钙素基因相关肽组化染色来观察。血管可用RECA-1染色来标识。同一切片上用RECA-1和胶原IV染色来比较血管的着色和胶原沉着的部位。 结果：在单纯的脊髓损伤组，损伤后一周的下行的5-羟色胺阳性纤维和上行的降钙素基因相关肽神经纤维均停止在纤维性瘢痕两端，在损伤部位周边有大量胶质细胞增生，损伤中心部位有大量胶原IV蛋白沉积而形成纤维性瘢痕。在损伤后同时移植嗅鞘细胞一周，5-羟色胺和降钙素基因相关肽阳性纤维均可见通过损伤部位。在损伤的脊髓节段，嗅鞘细胞移植组的阳性纤维均高于单纯损伤组。虽然移植组的损伤周边仍有大量的胶质细胞存在，但纤维性瘢痕却被显著的抑制。 结论：脊髓损伤过程中切断的神经纤维停止在纤维性瘢痕之前，移植嗅鞘细胞可以减弱纤维性瘢痕的产生而促进5-羟色胺阳性纤维越过脊髓损伤部位。

Transplantation of olfactory ensheathing cells suppresses the fibrotic scar formation in the lesion site and promotes axonal regeneration in the injured rat spinal cord

BACKGROUD: Although transplantation of olfactory ensheathing cells (OECs) into the injured spinal cord promotes axonal regeneration and functional recovery, the mechanism underlying the effects of OEC transplantation remains to be elucidated. OBJECTIVE: to determine whether cell transplantation into the damaged spinal cord reduces the fibrotic scar formation in the lesion site. DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed at Department of Developmental Morphology, Tokyo Metropolitan Institute for Neuroscience, Fuchu, Japan and Department of Human Anatomy, College of Basic Medical Sciences, China Medical University, Shenyang 110001, China between April 2007 and May 2009. MATERIALS: The experimental protocols were approved by the Animal Care and Use Committee of the Tokyo Metropolitan Institute for Neuroscience. METHODS Twenty three rats of Sprague Dawley strain weighing 300-350 g were used to prepare a spinal cord transection at the T9-10 level that were divided into three groups: first intact conrol (n = 3), second transected only (n = 9)and the third transplanted with OECs into the lesion site (n = 11). OECs were taken from the immature rat olfactory bulb and cultured for 2-3 weeks. MAIN OUTCOME MEASURES: The formation of glial and fibrotic scars was examined using immunohistochemistry for glial fibrillary acidic protein (GFAP) and type IV collagen (Col IV), respectively. Regeneration of spinal descending and ascending axons were detected by using immunohistochemistry for serotonin and calcitonin gene-related peptide (CGRP), respectively. Blood vessels were identified by using immunohistochemistry for RECA-1. Double immunofluoresence for ColIV and RECA-1 in single sections was also performed to compare the distribution of Col IV deposition and blood vessels. RESULTS: In the rats with transection only, most of descending serotonin- or ascending CGRP-immunoreactive axons stopped at the fibrotic scar formed in the lesion site at 1 weeks after the transection. Reactive astrocytes increased around the lesion and a fibrotic scar containing Col IV deposits developed in the lesion center. One week after transection and simultaneous OEC transplantation, serotonergic and CGRP-containing axons regenerated across the transplanted tissues. The number of serotonergic fibers in the lesion site and lumber spinal cord after OEC transplantion was significantly higher than after transected only (p < 0.05). Reactive astrocytes increased around the transplants, while the deposition of Col IV and the fibrotic scar formation were remarkably suppressed in the lesion site. CONCLUSION: Transected axons stop at the fibrotic scar which is formed in the lesion center of injured rat spinal cord. OEC transplantation into the lesion site suppresses the formation of inhibitory fibrotic scar and promotes serotonergic axons beyond the lesion site.