Gao Junling, Grill Raymond J, Dunn Tiffany J, Bedi Supinder, Labastida Javier Allende, Hetz Robert A, Xue Hasen, Thonhoff Jason R, DeWitt Douglas S, Prough Donald S, Cox Charles S, Wu Ping
Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston, Galveston, TX, USA.
Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, USA.
Cell Transplant. 2016 Oct;25(10):1863-1877. doi: 10.3727/096368916X691150.
Neural stem cells (NSCs) promote recovery from brain trauma, but neuronal replacement is unlikely the sole underlying mechanism. We hypothesize that grafted NSCs enhance neural repair at least partially through modulating the host immune response after traumatic brain injury (TBI). C57BL/6 mice were intracerebrally injected with primed human NSCs (hNSCs) or vehicle 24 h after a severe controlled cortical impact injury. Six days after transplantation, brain tissues were collected for Western blot and immunohistochemical analyses. Observations included indicators of microglia/macrophage activation, M1 and M2 phenotypes, axonal injury detected by amyloid precursor protein (APP), lesion size, and the fate of grafted hNSCs. Animals receiving hNSC transplantation did not show significant decreases of brain lesion volumes compared to transplantation procedures with vehicle alone, but did show significantly reduced injury-dependent accumulation of APP. Furthermore, intracerebral transplantation of hNSCs reduced microglial activation as shown by a diminished intensity of Iba1 immunostaining and a transition of microglia/macrophages toward the M2 anti-inflammatory phenotype. The latter was represented by an increase in the brain M2/M1 ratio and increases of M2 microglial proteins. These phenotypic switches were accompanied by the increased expression of anti-inflammatory interleukin-4 receptor α and decreased proinflammatory interferon-γ receptor β. Finally, grafted hNSCs mainly differentiated into neurons and were phagocytized by either M1 or M2 microglia/macrophages. Thus, intracerebral transplantation of primed hNSCs efficiently leads host microglia/macrophages toward an anti-inflammatory phenotype that presumably contributes to stem cell-mediated neuroprotective effects after severe TBI in mice.
神经干细胞（NSCs）可促进脑损伤后的恢复，但神经元替代不太可能是唯一的潜在机制。我们推测，移植的神经干细胞至少部分是通过调节创伤性脑损伤（TBI）后的宿主免疫反应来增强神经修复的。在严重的控制性皮质撞击损伤24小时后，向C57BL/6小鼠脑内注射预处理的人神经干细胞（hNSCs）或赋形剂。移植后6天，收集脑组织进行蛋白质免疫印迹和免疫组织化学分析。观察指标包括小胶质细胞/巨噬细胞激活指标、M1和M2表型、淀粉样前体蛋白（APP）检测的轴突损伤、损伤大小以及移植的hNSCs的命运。与仅使用赋形剂的移植程序相比，接受hNSC移植的动物脑损伤体积没有显著减小，但损伤依赖性APP的积累显著减少。此外，hNSCs的脑内移植减少了小胶质细胞的激活，表现为Iba1免疫染色强度降低以及小胶质细胞/巨噬细胞向M2抗炎表型的转变。后者表现为脑内M2/M1比值增加以及M2小胶质细胞蛋白增加。这些表型转换伴随着抗炎性白细胞介素-4受体α表达增加和促炎性干扰素-γ受体β表达降低。最后，移植的hNSCs主要分化为神经元，并被M1或M2小胶质细胞/巨噬细胞吞噬。因此，预处理的hNSCs的脑内移植有效地使宿主小胶质细胞/巨噬细胞向抗炎表型转变，这可能有助于小鼠严重TBI后干细胞介导的神经保护作用。
