Age, environment, object recognition and morphological diversity of GFAP-immunolabeled astrocytes

Abstract

BackgroundFew 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.ResultsSix 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.ConclusionsWe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12993-016-0111-2) contains supplementary material, which is available to authorized users.

Astrocytes and Aging

“…Environmental factors can also induce epigenetic changes. In a recent study that assessed how environment impacted young vs. old astrocytes, it was reported that aged mice from a standard environment could not distinguish between stationary and displaced objects (Diniz et al, 2016 ). Upon further examination of the astrocytes in these animals, the authors found two distinct morphological phenotypes and speculated that aging and environment reduce the complexity of astrocytes (Diniz et al, 2016 ).…”

“…In a recent study that assessed how environment impacted young vs. old astrocytes, it was reported that aged mice from a standard environment could not distinguish between stationary and displaced objects (Diniz et al, 2016 ). Upon further examination of the astrocytes in these animals, the authors found two distinct morphological phenotypes and speculated that aging and environment reduce the complexity of astrocytes (Diniz et al, 2016 ). This agrees with previous literature showing morphological changes between young and old astrocytes (Kanaan et al, 2010 ; Cerbai et al, 2012 ; Jyothi et al, 2015 ).…”

Long-term multi-species Lactobacillus and Bifidobacterium dietary supplement enhances memory and changes regional brain metabolites in middle-aged rats

“…Furthermore, this integrated representation of object information relies on a well-characterised integrated neural network involving the perirhinal cortex (processing object identity familiarity and novelty), the hippocampus (processing the spatial location of objects) and the medial frontal cortex, which contributes to memory for the temporal order of objects (see Warburton & Brown, 2015). Consistent with age-related changes in this neural network, recognition memory involving object-place information and temporal order is sensitive to ageing (Diniz et al, 2016;Hernandez et al, 2015) and perturbation of this memory network is associated with increased risk of dementia (Hirni et al, 2016).…”

Environmental enrichment improves cognitive symptoms and pathological features in a focal model of cortical damage of multiple sclerosis

“…EE was demonstrated to be a useful tool to improve cognitive function and reduce anxiety-like behaviour in many models of neurodegenerative diseases (Sampedro-Piquero and Begega, 2017). Many authors described that EE animals performed better in the NOR test compared to those animals that were housed in SC (Diniz et al, 2016;Sampedro-Piquero and Begega, 2017). .…”