Department of Cellular Neuroscience, Max Delbrück Center for Molecular Medicine (MDC), Robert Rössle Str. 10, 13125 Berlin, Germany.
Acta Neuropathol. 2013 Apr;125(4):609-20. doi: 10.1007/s00401-013-1079-8. Epub 2013 Jan 24.
High-grade gliomas are the most common primary brain tumors. Their malignancy is promoted by the complex crosstalk between different cell types in the central nervous system. Microglia/brain macrophages infiltrate high-grade gliomas and contribute to their progression. To identify factors that mediate the attraction of microglia/macrophages to malignant brain tumors, we established a glioma cell encapsulation model that was applied in vivo. Mouse GL261 glioma cell line and human high-grade glioma cells were seeded into hollow fibers (HF) that allow the passage of soluble molecules but not cells. The glioma cell containing HF were implanted into one brain hemisphere and simultaneously HF with non-transformed fibroblasts (controls) were introduced into the contralateral hemisphere. Implanted mouse and human glioma- but not fibroblast-containing HF attracted microglia and up-regulated immunoreactivity for GFAP, which is a marker of astrogliosis. In this study, we identified GDNF as an important factor for microglial attraction: (1) GL261 and human glioma cells secret GDNF, (2) reduced GDNF production by siRNA in GL261 in mouse glioma cells diminished attraction of microglia, (3) over-expression of GDNF in fibroblasts promoted microglia attraction in our HF assay. In vitro migration assays also showed that GDNF is a strong chemoattractant for microglia. While GDNF release from human or mouse glioma had a profound effect on microglial attraction, the glioma-induced astrogliosis was not affected. Finally, we could show that injection of GL261 mouse glioma cells with GDNF knockdown by shRNA into mouse brains resulted in reduced tumor expansion and improved survival as compared to injection of control cells.
高级别神经胶质瘤是最常见的原发性脑肿瘤。其恶性程度是由中枢神经系统中不同细胞类型之间的复杂串扰所促进的。小胶质细胞/脑巨噬细胞浸润高级别神经胶质瘤并促进其进展。为了鉴定介导小胶质细胞/巨噬细胞向恶性脑肿瘤趋化的因素，我们建立了一种神经胶质瘤细胞包封模型，并将其应用于体内。将小鼠 GL261 神经胶质瘤细胞系和人高级别神经胶质瘤细胞接种到允许可溶性分子但不允许细胞通过的中空纤维（HF）中。含有神经胶质瘤细胞的 HF 被植入一个大脑半球，同时将含有未转化成纤维细胞（对照）的 HF 引入对侧半球。植入的小鼠和人神经胶质瘤-HF 但不是成纤维细胞-HF 吸引了小胶质细胞，并上调了 GFAP 的免疫反应性，GFAP 是星形胶质细胞增生的标志物。在这项研究中，我们鉴定了 GDNF 是小胶质细胞趋化的一个重要因素：（1）GL261 和人神经胶质瘤细胞分泌 GDNF，（2）用 siRNA 降低 GL261 中的 GDNF 产生减少了小胶质细胞的趋化作用，（3）在我们的 HF 测定中，过表达 GDNF 促进了成纤维细胞中小胶质细胞的趋化作用。体外迁移测定也表明 GDNF 是小胶质细胞的强烈趋化因子。虽然人或鼠神经胶质瘤释放的 GDNF 对小胶质细胞的趋化作用有深远的影响，但神经胶质瘤诱导的星形胶质细胞增生没有受到影响。最后，我们可以证明，与注射对照细胞相比，向小鼠大脑中注射 GDNF 敲低的 GL261 小鼠神经胶质瘤细胞可减少肿瘤的扩张并提高存活率。
