嗅鞘细胞移植在大鼠脊髓损伤处能够迁移和促进神经轴突生长吗?

目的：探讨嗅鞘细胞（olfactory ensheathing cells,OEC）移植在大鼠损伤脊髓后是否有独特的迁移和轴突生长导向特性。方法：将表达绿色荧光蛋白基因的OEC注入到C4脊髓损伤大鼠距离损伤部位头端1mm及尾端1mm背柱白质处,注射后1、3、12、24h及3、7、28d灌注固定取材,冰冻切片和免疫组化分析。用骨髓基质细胞和成纤维细胞移植到同样的损伤部位做为对照进行同样的分析。另将OEC注射到距离损伤部位头尾侧1mm处脊髓灰质内、小剂量注射在白质内、在损伤前3d或损伤后9d注射、注射到未损伤脊髓白质中,观察细胞迁移情况。结果：OEC在细胞注射后1h内即形成由注射压力造成的从注射部位向损伤处的被动性延伸带,并且不断地从注射部位向损伤处延伸扩散,在形态学方面好象起到＂桥接＂损伤处的作用。对照组骨髓基质细胞和成纤维细胞注射后也迅速形成细胞＂桥接＂带,并扩散至损伤空腔。将OEC注射到脊髓灰质内或小剂量注射或注射到未损伤的脊髓白质内、在脊髓损伤3d前或9d后注射细胞均没有见到细胞带延伸进入损伤部位。OEC在注射部位、细胞带以及损伤部位有增殖现象。28d后,共焦免疫酶标法证实细胞带取代了脊髓原有星形胶质细胞,但是下行或上行长束轴突没有优先延伸至该细胞带,也没能起到维持皮层脊髓轴突的桥接作用。结论：OEC在植入大鼠损伤脊髓后没有独特的迁移特性,与骨髓基质细胞或成纤维细胞相比没有明显促进轴突生长的作用,也没有支持皮层脊髓轴突在脊髓损伤处形成桥接的作用。

Do olfactory ensheathing cells exhibit unique migratory or axonal growth-promoting properties after spinal cord injury in rats?

Objective:To investigate whether olfactory ensheathing cells(OEC) have unique properties of migration and axonal guidance after spinal cord injury(SCI) in rats.Method:Green fluorescent protein transduced lamina propria OECs were injected into dorsal colum white matter 1mm rostral and caudal to C4 SCI sites in rats.The subjects were perfused 1,3,12hr and 3,7,28 days after SCI and the spinal cords were sectioned and immunohistochemically analyzed.Bone marrow stromal cells and fibroblasts were also injected in similar area and were analyzed in the same way as controls.In addition, OEC were injected either into spinal cord gray matter,or at low volumes,or three days before or nine days after SCI,or into intact spinal cord to monitor their migration.Result:A cell tract formed from injection site to SCI site even within one hour of OEC injection,probably due to cells passively spread from the pressure injection site rather than actively migrating.Later,OECs continued to spread into SCI site,physically bridging the lesion.Control injections of bone marrow stromal cells or fibroblasts 1mm from the lesion site also rapidly dispersed into the lesion cavity.Cell tracts extending into the lesion site were not seen when cells were injected either into spinal cord gray matter,or at low volumes,or three days before or nine days after SCI,or into intact spinal cord.Besides formation of cell tract by pressure injection,there was no apparent active OEC migration after SCI.OECs proliferated in injection sites,cell tracts,and lesion sites.28 days later,confocal immunolabeling demonstrated that whereas this cell tract displaced host astrocytes,descending or ascending long tract axons did not preferentially extend into the cell tract and OECs failed to support bridging of corticospinal axons.long tract axons did not preferentially extend into the cell tract and OECs failed to support bridging of corticospinal axons.OECs proliferated in injection sites,cell tracts,and lesion sites,indicating that OECs could also accumulate through cell proliferation.Conclusion:OECs do not to exhibit significant migratory properties when grafted to the spinal cord,exhibit no detectable difference in promoting axon growth into a SCI site compared to MSCs or fibroblasts,and do not support bridging of corticospinal axons beyond a dorsal column lesion.