Biomedicum Helsinki, Institute of Biomedicine/Physiology, PO Box 63, University of Helsinki, FIN-00014 Helsinki, Finland.
Neuroscience. 2012 Nov 8;224:223-34. doi: 10.1016/j.neuroscience.2012.08.038. Epub 2012 Aug 23.
Neurotrophins like brain-derived neurotrophic factor (BDNF) promote the migration of subsets of neural progenitor cells. The mechanism by which motility is increased and the functional properties of BDNF-responsive cells are not very well known. We have used the neurosphere model, combining time-lapse microscopy, immunocytochemistry, and Ca(2+) imaging, to study the effect of BDNF on parameters such as motility and neurotransmitter responsiveness of migrating neural progenitors. At the initiation of differentiation thick glial glutamate-aspartate transporter (GLAST)-positive radial processes emerged from the neurosphere, followed by the exit of neuron-like cells. The neuron-like cells moved outside the radial processes in a phasic manner with intermittent surges of motility and stationary periods. BDNF increased the number and promoted the progress of the neuron-like cells by prolonging surges and decreasing the length of stationary phases. The average rate of cellular movement during surges was unaffected by BDNF. BDNF also caused a several fold increase in positive staining for tropomyosin-related kinase B (TrkB) receptors and neuronal markers such as Calbindin, microtubule-associated protein-2 (MAP-2), and neuron-specific nuclear protein (NeuN) in cells outside the radial network. Calcium imaging allowed for further characterization of the BDNF-responsive cell population. Kainate-responsive cells, denoting the expression of AMPA/kainate receptors, dominated in the outer migration layers while cells responding to (S)-3,5-dihydroxyphenylglycine (DHPG) via metabotropic glutamate receptor 5 (mGluR5) dominated in the inner migration layers. BDNF did not appreciably affect the distribution of these cells but promoted the redistribution of a small subpopulation (about 20%) of N-methyl-D-aspartate (NMDA)- and GABA-responsive cells to the outermost layers of migration. The results demonstrate that BDNF does not affect cell motility per se but alters the phasic behavior of cell movement by promoting periods of high motility in a defined subpopulation of cells which give a robust Ca(2+) response to NMDA and GABA.
神经递因子，如脑源性神经营养因子（BDNF），可促进神经祖细胞亚群的迁移。但运动增加的机制以及 BDNF 反应细胞的功能特性还不是很清楚。我们使用神经球模型，结合延时显微镜、免疫细胞化学和 Ca（2+）成像，研究了 BDNF 对迁移神经祖细胞的运动参数和神经递质反应性的影响。在分化开始时，从神经球中出现了厚的胶质谷氨酸-天冬氨酸转运蛋白（GLAST）阳性的放射状突起，随后神经元样细胞从神经球中移出。神经元样细胞以阶段性方式移出放射状突起，其间有运动的间歇性激增和静止期。BDNF 通过延长激增和减少静止期的长度，增加了神经元样细胞的数量并促进了其迁移。在激增过程中细胞运动的平均速度不受 BDNF 的影响。BDNF 还使细胞外的放射状网络外的细胞中 tropomyosin-related kinase B (TrkB) 受体和神经元标志物（如 Calbindin、微管相关蛋白-2 (MAP-2) 和神经元特异性核蛋白 (NeuN)）的阳性染色增加了几倍。钙成像允许进一步描述 BDNF 反应细胞群体。在外部迁移层中，AMPA/kainate 受体的表达表示 kainate 反应细胞占主导地位，而在内部迁移层中，通过代谢型谷氨酸受体 5 (mGluR5) 对 (S)-3,5-二羟苯甘氨酸 (DHPG) 做出反应的细胞占主导地位。BDNF 没有明显影响这些细胞的分布，但促进了一小部分（约 20%）N-甲基-D-天冬氨酸（NMDA）和 GABA 反应细胞向迁移的最外层的重新分布。结果表明，BDNF 本身并不影响细胞运动，但通过促进对 NMDA 和 GABA 具有强 Ca（2+）反应的特定细胞亚群的高运动期，改变了细胞运动的阶段性行为。
