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美国研究人员指出，脊髓损伤后，如果脊髓中的干细胞被诱导分化成更多的愈合细胞和较少的疤痕细胞，将有望开发出一种脊髓损伤非手术治疗新法。

发表在《公共科学图书馆·生物学》（PLoS Biology）杂志7月号上的这项研究成果，是由美国麻省理工学院皮考尔研究所的康斯坦丁诺斯·麦勒提斯和瑞典卡罗林斯卡研究所的同事合作完成的。该成果将可能导致开发出新药，使世界各地每年3万名因脊髓受伤而造成行动不便的患者因此得以部分康复。

研究人员指出，在一个正在发育的胚胎中，干细胞分化为人体的各种特殊组织。在成年人身上，干细胞扮演着修复系统的作用，不仅能补充特殊细胞，还能维持再生器官（如血液、皮肤或肠组织）的正常运转。但成人脊髓中的少数干细胞增殖缓慢或很少增殖，从而不能促使自身再生。幸运的是，最近的实验表明，在实验室培养后返回受伤处的相同细胞，可以恢复瘫痪的啮齿动物和灵长类动物的部分功能。

研究人员发现，成人脊髓中的神经干细胞受限于一层呈立方形或柱形、覆有纤毛的细胞——室管膜细胞。这些细胞能形成衬于内脑脑室和连接脊髓中心柱的薄膜。

在对这种细胞的数量进行基因标记并跟踪其行为之后，研究人员发现，室管膜细胞拥有根据损伤转变成数个不同细胞类型的能力。脊髓受损后，室管膜细胞会增殖并迁移至受损区域，同时产生大量形成瘢痕的细胞，外加少量少突胶质细胞。该少突胶质细胞可恢复神经细胞长而纤细、能传达电脉冲的突出物（称为轴突）上的髓鞘质或外层。髓鞘质就像是电线外面的塑料绝缘层，没有髓鞘质，神经细胞就不能正常运作。

研究人员表示，中央神经系统受损后，相关的功能恢复通常是非常有限的，部分原因在于已脱离的轴突不能再生和重新连接至周围神经系统的目标细胞，而周围神经系统一直延伸至人体的四肢。如果科学家能够在脊髓受损后，通过基因操纵室管膜细胞以产生更多的髓鞘组织和更少的疤痕组织，就有可能避免或扭转此类损伤所产生的许多破坏性影响。

该研究揭示了已在啮齿动物和灵长类动物身上取得的诱人成果背后的分子机制，并向前又迈进了一步：通过首次确定这些细胞群被发现的位置，为对其实施药物操控、提高其修复受损神经细胞的先天能力铺平了道路。

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Spinal cord injury often results in permanent functional impairment. Neural stem cells present in the adult spinal cord can be expanded in vitro and improve recovery when transplanted to the injured spinal cord, demonstrating the presence of cells that can promote regeneration but that normally fail to do so efficiently. Using genetic fate mapping, we show that close to all in vitro neural stem cell potential in the adult spinal cord resides within the population of ependymal cells lining the central canal. These cells are recruited by spinal cord injury and produce not only scar-forming glial cells, but also, to a lesser degree, oligodendrocytes. Modulating the fate of ependymal progeny after spinal cord injury may offer an alternative to cell transplantation for cell replacement therapies in spinal cord injury.

http://biology.plosjournals.org/ ... pbio.0060182#equal1

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Author Summary
Spinal cord injuries occur in more than 30.000 individuals each year worldwide and result in significant morbidity, with patients requiring long physical and medical care. The recent identification of resident stem cells in the adult spinal cord has opened up for the possibility of pharmacological manipulation of these cells to produce cell types promoting recovery after injury. We have employed genetic tools to specifically address the identity and reaction to injury of a spinal cord subpopulation of cells known as ependymal cell. Genetic labeling of this putative stem cell population allows for the evaluation of stem cell activity in vitro and in vivo. We found that ependymal cells lining the central canal act as neural stem cells in vitro and contribute extensively to the glial scar in vivo. Interestingly, injury induces proliferation of ependymal cells and migration of ependyma-derived progeny towards the site of injury. Moreover, ependymal cell progeny differentiate and give rise to astrocytes as well as myelinating oligodendrocytes. In summary, our results point to ependymal cells as an attractive candidate population for non-invasive manipulation after injury.