Woodhall E, West A K, Chuah M I
Department of Anatomy and Physiology, University of Tasmania, P.O. Box 252-24, Hobart, Tasmania 7001, Australia.
Brain Res Mol Brain Res. 2001 Mar 31;88(1-2):203-13. doi: 10.1016/s0169-328x(01)00044-4.
In the primary olfactory pathway axons of olfactory neurons (ONs) are accompanied by ensheathing cells (ECs) as the fibres course towards the olfactory bulb. Ensheathing cells are thought to play an important role in promoting and guiding olfactory axons to their appropriate target. In recent years, studies have shown that transplants of ECs into lesions in the central nervous system (CNS) are able to stimulate the growth of axons and in some cases restore functional connections. In an attempt to identify a possible mechanism underlying EC support for olfactory nerve growth and CNS axonal regeneration, this study investigated the production of growth factors and expression of corresponding receptors by these cells. Three techniques immunohistochemistry, enzyme linked immunosorbent assay (ELISA) and reverse transcriptase-polymerase chain reaction (RT-PCR) were used to assess growth factor expression in cultured ECs. Immunohistochemistry showed that ECs expressed nerve growth factor (NGF), brain derived neurotrophic factor (BDNF) and glial cell-line derived neurotrophic factor (GDNF). ELISA confirmed the intracellular presence of NGF and BDNF and showed that, compared to BDNF, about seven times as much NGF was secreted by ECs. RT-PCR analysis demonstrated expression of mRNA for NGF, BDNF, GDNF and neurturin (NTN). In addition, ECs also expressed the receptors trkB, GFRalpha-1 and GFRalpha-2. The results of the experiments show that ECs express a number of growth factors and that BDNF in particular could act both in a paracrine and autocrine manner.
在初级嗅觉通路中，嗅觉神经元（ONs）的轴突在向嗅球行进时伴有被囊细胞（ECs）。被囊细胞被认为在促进和引导嗅觉轴突到达其合适靶点方面发挥着重要作用。近年来，研究表明将被囊细胞移植到中枢神经系统（CNS）损伤部位能够刺激轴突生长，并且在某些情况下恢复功能连接。为了确定被囊细胞支持嗅觉神经生长和中枢神经系统轴突再生的潜在机制，本研究调查了这些细胞生长因子的产生及相应受体的表达。采用免疫组织化学、酶联免疫吸附测定（ELISA）和逆转录聚合酶链反应（RT-PCR）三种技术评估培养的被囊细胞中生长因子的表达。免疫组织化学显示被囊细胞表达神经生长因子（NGF）、脑源性神经营养因子（BDNF）和胶质细胞源性神经营养因子（GDNF）。ELISA证实了细胞内存在NGF和BDNF，并表明与BDNF相比，被囊细胞分泌的NGF约为其七倍。RT-PCR分析证明了NGF、BDNF、GDNF和神经营养素（NTN）的mRNA表达。此外，被囊细胞还表达trkB、GFRalpha-1和GFRalpha-2受体。实验结果表明，被囊细胞表达多种生长因子，特别是BDNF可以以旁分泌和自分泌方式发挥作用。
