Yasuda T, Sobue G, Ito T, Mitsuma T, Takahashi A
Fourth Department of Internal Medicine, Aichi Medical University, Japan.
Brain Res. 1990 Jul 30;524(1):54-63. doi: 10.1016/0006-8993(90)90491-s.
Nerve growth factor (NGF) is a well-established trophic factor of sympathetic and sensory neurons during development. NGF is, however, little known to be required for the maintenance or regulation of differentiated phenotypes of matured peripheral neurons. Since trophic factors, including NGF, are currently known to be secreted by non-neuronal cells, like Schwann cells and fibroblasts, a highly pure-neuron culture is required to assess the direct action of trophic factors on neurons. We have developed a single-neuron culture from neonatal and adult rat dorsal root ganglia in serum-free conditions, and estimated the primary effect of NGF on the morphological geometry of sensory neurons. We found that NGF promoted the neurite length of neonatal sensory neurons, rather than promoting arborization (branching of neurites), while in adult matured neurons NGF significantly enhanced neurite arborizations, rather than the maximal neurite extension, distance from the cell soma to the maximum margin of the territory of neurite extension. Total neurite length, the summed length of all neurites per neuron was significantly increased by NGF in both neonatal and adult neurons. NGF also increased the size of neuronal soma independent of neuronal maturation. Neonatal sensory neurons tended to die in 1 week despite the presence of NGF. In contrast, some adult sensory neurons were alive for more than 2 weeks in the absence of NGF. These results indicate that NGF more than simply accelerates a pre-existing developmental program in the matured stage, and that the promotion of neurite arborization by NGF in adult sensory neurons suggests that NGF may have some role in peripheral nerve regeneration via promotion of axonal sprouting.
神经生长因子（NGF）是发育过程中交感神经元和感觉神经元公认的营养因子。然而，对于成熟外周神经元分化表型的维持或调节，NGF的作用却鲜为人知。由于目前已知包括NGF在内的营养因子由雪旺细胞和成纤维细胞等非神经元细胞分泌，因此需要高度纯化的神经元培养物来评估营养因子对神经元的直接作用。我们在无血清条件下从新生大鼠和成年大鼠背根神经节中培养出了单神经元，并评估了NGF对感觉神经元形态几何学的主要影响。我们发现，NGF促进新生感觉神经元的神经突长度，而非促进其分支（神经突的分支），而在成年成熟神经元中，NGF显著增强神经突分支，而非最大神经突延伸，即从细胞体到神经突延伸区域最大边缘的距离。NGF使新生神经元和成年神经元中每个神经元所有神经突的总长度显著增加。NGF还能增加神经元胞体的大小，且与神经元成熟无关。尽管存在NGF，新生感觉神经元仍倾向于在1周内死亡。相比之下，一些成年感觉神经元在没有NGF的情况下能存活超过2周。这些结果表明，NGF不仅仅是简单地加速成熟阶段预先存在的发育程序，而且NGF在成年感觉神经元中促进神经突分支表明，NGF可能通过促进轴突发芽在周围神经再生中发挥一定作用。
