丰富环境促进缺氧缺血性脑损伤幼鼠髓鞘发育并改善神经功能

The role of environmental enrichment in promoting myelin formation and neural function in hypoxic-ischemic brain injury

摘要:

目的 探索丰富环境（environmental enrichment，EE）干预对缺氧缺血性脑损伤（hypoxic-ischemic brain damage，HIBD）幼鼠神经功能、脑室旁白质及海马髓鞘相关蛋白表达的影响。方法 取7 d SD大鼠随机分为假手术组（Sham组）、模型组+标准环境组（HIBD+SE组）及模型组+丰富环境组（HIBD+EE组），采用Rice-Vannucci法制备HIBD模型。Sham组及HIBD+SE组不予任何干预饲养于标准环境中，HIBD+EE组于术后8 d至术后18 d予以丰富环境干预处理。术后18 d采用Morris水迷宫定位航行实验测定平台区穿梭次数，采用Western blot检测脑室旁白质及海马区髓鞘生成相关蛋白尿苷二磷酸糖基转移酶8（recombinant UDP glycosyltransferase 8，UGT8）、少突胶质细胞转录因子2（oligodendrocyte transcription factor 2，OLIG2）的表达，采用RT-qPCR检测脑室旁白质及海马区UGT8、OLIG2、糖脂转运蛋白（glycolipid transfer protein，GLTP）、髓鞘转录因子（myelin regulatory factor Gene，MYRF）的表达水平，采用免疫组化法检测神经元核（neuronal nuclei antigen，NeuN）表达水平，采用免疫荧光检测胼胝体髓鞘标志（myelin basic protein，MBP）表达水平。结果 术后18 d，与HIBD+SE组比较，HIBD+EE组穿越平台次数增多（P<0.01），HIBD+EE组较HIBD+SE组脑室旁白质及海马区UGT8 mRNA及蛋白表达升高（P<0.05），脑室周围白质及海马区OLIG2、GLTP、MYRF mRNA表达升高（P<0.05），海马CA1区NeuN表达水平高于HIBD+SE组（P<0.05），胼胝体MBP平均荧光强度高于HIBD+SE组（P<0.05）。结论 丰富环境能促进缺氧缺血性脑损伤新生大鼠少突胶质细胞谱系分化、髓鞘发育，改善学习记忆能力，可能与上调脑室周围白质及海马区UGT8蛋白表达，增加神经元分化成熟细胞数量有关。

Abstract:

Objective To explore the effects of environmental enrichment（EE） on neural function，myelin-related protein expression of periventricular white matter and hippocampus in rats with hypoxic-ischemic brain injury（HIBD）.Method Seven-day-old SD rats were randomly divided into sham surgery group，model+standard environment group（HIBD+SE group） and model + environmental enrichment group（HIBD+EE group），and the HIBD model was established with the Rice-Vannucci method. The sham surgery group and the standard environment group were raised in the standard environment without any intervention，and the environmental enrichment group was treated with enriched environment from 8 to 18 days after surgery. At day18 after the surgery，Morris water maze was used to determine the escape latency of finding the hidden platform. Western blot was used to detect the expression of UGT8，a myelination-related protein，in periventricular white matter and hippocampus，and expression of oligodendrocyte differentiation gene OLIG2. RT-qPCR was used to detect the mRNA expression levels of OLIG2、GLTP、MYRF、UGT8 in periventricular white matter and hippocampus. Immunohistochemistry was used to detect the expression levels of NeuN，and immunofluorescence was used to detect the expression of myelin basic protein（MBP） in the corpus callosum.Result At 18 days after surgery，compared with HIBD+SE group，platform crossing times of the HIBD+EE group increased（P<0.01）. The HIBD+EE group showed higher expression of UGT8 mRNA and protein in the periventricular white matter and hippocampus compared to HIBD+SE group（P<0.05）. The expression of OLIG2，GLTP，MYRF mRNA in the periventricular white matter and hippocampus increased（P<0.05），and the expression of NeuN in CA1 region was higher than that of HIBD+SE group（P<0.01），the fluorescent intensity of MBP in corpus callosum region was higher than that in standard environment group（P<0.05）.Conclusion Environmental enrichment promotes the differentiation of oligodendrocyte lineages and myelin development in neonatal rats with HIBD，and improves learning and memory ability，which may be related to up-regulating UGT8 protein expression in periventricular white matter and hippocampus and increasing the number of neuronal mature cells.