Abstract

Purpose

Despite being a major treatment modality for brain cancer due to its efficiency in achieving cancer control, radiotherapy has long been known to cause long-term side effects, including radiation-induced cognitive impairment (RICI). Neurogenesis inhibition due to radiation-induced damage in neural stem cells (NSCs) has been demonstrated to be an important mechanism underlying RICI. Radiation-induced bystander effects (RIBEs) denote the biological responses in non-targeted cells after their neighboring cells are irradiated. We have previously demonstrated that RIBEs could play an important role in the skin wound healing process. Therefore, we aimed to investigate whether RIBEs contribute to RICI in this study.

Materials and methods

The transwell co-culture method was used to investigate bystander effects in mouse NSCs induced by irradiated GL261 mouse glioma cells in vitro. The proliferation, neurosphere-forming capacity and differentiation potential of NSCs were determined as the bystander endpoints. The exosomes were extracted from the media used to culture GL261 cells and were injected into the hippocampus of C57BL/6 mice. Two months later, the neurogenesis of mice was assessed using BrdU incorporation and immunofluorescence microscopy, and cognitive function was evaluated by the Morris Water Maze.

Results

After co-culture with GL261 glioma cells, mouse NSCs displayed inhibited proliferation and reduced neurosphere-forming capacity and differentiation potential. The irradiated GL261 cells caused greater inhibition and reduction in NSCs than unirradiated GL261 cells. Moreover, adding the exosomes secreted by GL261 cells into the culture of NSCs inhibited NSC proliferation, suggesting that the cancer cell-derived exosomes may be critical intercellular signals. Furthermore, injection of the exosomes from GL261 cells into the hippocampus of mice caused significant neurogenesis inhibition and cognitive impairment two month later, and the exosomes from irradiated GL261 cells induced greater inhibitory effects.

Conclusion

RIBEs mediated by the exosomes from irradiated cancer cells could contribute to RICI and, therefore, could be a novel mechanism underlying RICI.

中文翻译：

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辐射引起的旁观者效应可能导致辐射引起的认知障碍

摘要

目的

尽管由于其在实现癌症控制方面的效率而成为脑癌的主要治疗方式，但人们早就知道放疗会引起长期副作用，包括辐射诱发的认知障碍 (RICI)。由于辐射诱导的神经干细胞 (NSCs) 损伤引起的神经发生抑制已被证明是 RICI 的重要机制。辐射诱导的旁观者效应 (RIBE) 表示非靶向细胞在其相邻细胞受到照射后的生物学反应。我们之前已经证明 RIBE 可以在皮肤伤口愈合过程中发挥重要作用。因此，我们旨在调查 RIBE 是否有助于本研究中的 RICI。

材料和方法

Transwell 共培养方法用于研究体外受照射的 GL261 小鼠神经胶质瘤细胞诱导的小鼠神经干细胞的旁观者效应。NSCs 的增殖、神经球形成能力和分化潜能被确定为旁观者终点。从用于培养 GL261 细胞的培养基中提取外泌体，并注射到 C57BL/6 小鼠的海马中。两个月后，使用 BrdU 掺入和免疫荧光显微镜评估小鼠的神经发生，并通过莫里斯水迷宫评估认知功能。

结果

与 GL261 神经胶质瘤细胞共培养后，小鼠神经干细胞表现出抑制增殖和降低神经球形成能力和分化潜能。经辐照的 GL261 细胞比未经辐照的 GL261 细胞对神经干细胞产生更大的抑制和减少。此外，将 GL261 细胞分泌的外泌体加入到 NSC 培养物中可抑制 NSC 增殖，表明癌细胞来源的外泌体可能是关键的细胞间信号。此外，两个月后将GL261细胞的外泌体注射到小鼠海马中会导致显着的神经发生抑制和认知障碍，而受照射的GL261细胞的外泌体则产生更大的抑制作用。

结论

由受照射癌细胞的外泌体介导的 RIBE 可能导致 RICI，因此可能是 RICI 的一种新机制。