Li Ying, Field Pauline M, Raisman Geoffrey
Spinal Repair Unit, Institute of Neurology, University College London, London, United Kingdom.
Glia. 2005 Nov 15;52(3):245-51. doi: 10.1002/glia.20241.
The ensheathing cells of the olfactory nerves are arranged end-to-end to form a continuous channel enclosing the olfactory axons from their origin in the olfactory mucosa to their termination in the olfactory bulb. On their outer surface, the olfactory ensheathing cell channels have a basal lamina and an outer encirclement of olfactory nerve fibroblasts. We present an anatomical model of the ensheathing arrangements for the entire transit of the olfactory axons from the horizontal basal cells of the mucosa through the nerves to the superficial astrocytes of the bulb. We used intracranial section of the olfactory nerves to induce a rapid retrograde loss of olfactory neurons and degeneration of their axons, followed by replacement of the neurons from stem cells in the mucosa and growth of the newly formed axons along the olfactory nerves. The olfactory ensheathing cells survive and play a vital role in this process. Unlike Schwann cells in damaged peripheral nerve, the olfactory ensheathing cells neither divide nor migrate. They are actively phagocytic for removal of the degenerating axons, and provide continuous stable open channels along which adventitious cells such as erythrocytes and macrophages can travel, and along which the newly formed axons can regenerate. We suggest that the persistence of these open channels is an important element in the effectiveness of the regeneration. These properties, which the olfactory ensheathing cells exert in collaboration with olfactory nerve fibroblasts, may also be involved in the reparative effects of these cells when transplanted into lesions of the spinal cord.
嗅神经的被膜细胞首尾相连排列，形成一个连续的通道，将嗅轴突从其在嗅黏膜的起源处包裹至其在嗅球的终止处。在其外表面，嗅被膜细胞通道有一层基膜和一层嗅神经成纤维细胞的外周包绕。我们提出了一个解剖模型，用于描述嗅轴突从黏膜的水平基底细胞经神经至嗅球浅层星形胶质细胞的整个行程中的被膜排列情况。我们采用嗅神经颅内横断术诱导嗅神经元快速逆行性丧失及其轴突退变，随后黏膜中的干细胞替代神经元，新形成的轴突沿嗅神经生长。嗅被膜细胞存活并在此过程中发挥重要作用。与受损周围神经中的施万细胞不同，嗅被膜细胞既不分裂也不迁移。它们积极吞噬以清除退变的轴突，并提供连续稳定的开放通道，诸如红细胞和巨噬细胞等外来细胞可沿此通道通行，新形成的轴突也可沿此通道再生。我们认为这些开放通道的持续存在是再生有效性的一个重要因素。嗅被膜细胞与嗅神经成纤维细胞协同发挥的这些特性可能也参与了这些细胞移植到脊髓损伤部位时的修复作用。
