BACKGROUND Few studies have explored the glial response to a standard environment and how the response may be associated with age-related cognitive decline in learning and memory. Here we investigated aging and environmental influences on hippocampal-dependent tasks and on the morphology of an unbiased selected population of astrocytes from the molecular layer of dentate gyrus, which is the main target of perforant pathway. RESULTS Six and twenty-month-old female, albino Swiss mice were housed, from weaning, in a standard or enriched environment, including running wheels for exercise and tested for object recognition and contextual memories. Young adult and aged subjects, independent of environment, were able to distinguish familiar from novel objects. All experimental groups, except aged mice from standard environment, distinguish stationary from displaced objects. Young adult but not aged mice, independent of environment, were able to distinguish older from recent objects. Only young mice from an enriched environment were able to distinguish novel from familiar contexts. Unbiased selected astrocytes from the molecular layer of the dentate gyrus were reconstructed in three-dimensions and classified using hierarchical cluster analysis of bimodal or multimodal morphological features. We found two morphological phenotypes of astrocytes and we designated type I the astrocytes that exhibited significantly higher values of morphological complexity as compared with type II. Complexity = [Sum of the terminal orders + Number of terminals] × [Total branch length/Number of primary branches]. On average, type I morphological complexity seems to be much more sensitive to age and environmental influences than that of type II. Indeed, aging and environmental impoverishment interact and reduce the morphological complexity of type I astrocytes at a point that they could not be distinguished anymore from type II. CONCLUSIONS We suggest these two types of astrocytes may have different physiological roles and that the detrimental effects of aging on memory in mice from a standard environment may be associated with a reduction of astrocytes morphological diversity.

中文翻译：

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GFAP免疫标记星形胶质细胞的年龄，环境，物体识别和形态多样性。

背景技术很少有研究探索神经胶质对标准环境的反应以及该反应如何与年龄相关的学习和记忆认知下降相关。在这里，我们研究了老化和环境影响对海马依赖性任务以及齿状回的分子层中无偏向的特定星形胶质细胞群形态的影响，齿状回是分子通路的主要靶标。结果六只和二十个月大的雌性白化病瑞士小鼠断奶后被饲养在标准或丰富的环境中，包括用于运动的跑步轮，并测试了对象识别和上下文记忆。不受环境影响的年轻人和成年受试者能够将熟悉的事物与新颖的事物区分开。除标准环境中的老年小鼠外，所有实验组 区分静止物体和位移物体。不受环境影响的年轻成年小鼠，但不是老年小鼠，能够区分较新物体和较旧物体。只有来自丰富环境的年幼小鼠才能够将小说与熟悉的情境区分开。从齿状回的分子层中无偏选择的星形胶质细胞三维重建，并使用双峰或多峰形态特征的层次聚类分析进行分类。我们发现了星形胶质细胞的两种形态学表型，我们将I型星形胶质细胞的形态复杂性值显着高于II型。复杂度= [终端订单总和+终端数量]×[总分支长度/主要分支数量]。一般，I型的形态复杂性似乎比II型对年龄和环境影响更为敏感。确实，衰老和环境贫困相互作用并降低了I型星形胶质细胞的形态复杂性，以至于它们无法再与II型星形胶质区分开。结论我们建议这两种类型的星形胶质细胞可能具有不同的生理作用，并且衰老对标准环境小鼠的记忆的有害影响可能与星形胶质细胞形态多样性的降低有关。