摘要目的:揭示电子束常规剂量率照射与电子束超高剂量率放疗(Flash)照射后小鼠脑的转录图谱差异，从多角度诠释Flash生物学效应与机制。方法:36只雌性C57BL/6J小鼠按体质量相近原则分为对照组、常规照射(CONV)组和Flash照射(Flash)组，每组12只。CONV组和Flash组均给予9 MeV电子束全脑单次15 Gy照射。照后3 d，取全脑组织标本，HE染色观察病理改变。分别在照射后第1、3和10周通过行为学评估小鼠的运动、认知能力、抑郁水平和空间记忆能力。在行为学实验结束后1和10周，取小鼠脑组织样本液氮速冻后进行有参转录组测序，进而分析CONV和Flash照射对小鼠放射性脑损伤的转录图谱差异。结果:HE病理结果显示，与CONV组相比，Flash组减少了小鼠脑组织中胶质细胞增生和炎性细胞的浸润。第1周行为学结果显示，与对照组和Flash组相比，CONV组总路程显著减少( t＝5.51、2.38， P<0.05)，与对照组相比，CONV组静止时间显著增加( t＝3.60， P<0.05)。第3周行为学结果显示，与CONV组相比，Flash组显著减轻小鼠认知功能损伤( t＝3.35， P<0.05)与抑郁程度( t＝2.39， P<0.05)。第10周行为学结果显示，CONV组小鼠的认知能力最差，与对照组之间差异有统计学意义( t＝4.53， P<0.05)。转录组学测序结果显示，与CONV组相比，Flash组除免疫相关通路外，多条代谢通路和成纤维细胞生长因子相关通路也在照射后上调。 结论:相比常规照射，Flash照射可有效减轻小鼠放射性脑损伤。这不仅与免疫途径相关，还与包括氨基酸代谢在内的多种代谢途径及成纤维细胞生长因子相关。

abstractsObjective:To reveal the differences in the transcriptome maps of brain tissues in mice subjected to Flash irradiation and conventional dose rate irradiation with electron beams and to explain the biological effect and mechanisms of Flash irradiation from multiple perspectives.Methods:Following the principle of grouping based on approximate body weights, 36 female C57BL/6J mice were divided into three groups, i. e., the control, conventional dose rate irradiation (CONV), and Flash irradiation (Flash) groups, with 12 mice in each group. Both the CONV and Flash groups received a single 15 Gy whole-brain irradiation with 9 MeV electron beams. At 3 d post-irradiation, the whole-brain tissue specimens were collected for hematoxylin-eosin (HE) staining to observe pathological changes. At 1, 3, and 10 weeks post-irradiation, the motion function, cognitive ability, depression level, and spatial memory capacity of the mice were assessed using ethology. At 1 and 10 weeks after behavioral experiments, brain tissue samples were collected and snap-frozen in liquid nitrogen for reference-based transcriptome sequencing. Accordingly, the differences in the transcriptome maps of radiation-induced brain injury between CONV and Flash groups were analyzed.Results:The HE staining-based pathological result revealed that compared to the CONV group, the Flash group exhibited reduced glial cell hyperplasia and inflammatory cell infiltration in brain tissues. Ethological research result at 1 week post-irradiation showed that the CONV group manifested a significantly decreased total traveled distance compared to the control and Flash groups ( t = 5.51, 2.38, P < 0.05) and a significantly increased immobility time compared to the control group ( t = 3.60, P < 0.05). Ethological research result at 3 weeks post-irradiation indicated that compared to the CONV group, the Flash group displayed significantly alleviated cognitive impairment ( t = 3.35, P < 0.05) and reduced depression levels ( t = 2.39, P < 0.05). Ethological research result at 10 weeks post-irradiation demonstrated that the CONV group showed the worst cognitive performance, significantly differing from the control group ( t = 4.53, P < 0.05). Transcriptome sequencing result revealed that besides immune-related pathways, the Flash group also exhibited multiple upregulated metabolic pathways and fibroblast growth factor (FGF)-related pathways compared to the CONV group. Conclusions:Compared to conventional dose rate irradiation, Flash irradiation can effectively alleviate radiation-induced brain injury in mice. This effect is associated with various metabolic pathways (including amino acid metabolism) and FGF-related pathways besides immune pathways.