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. 2021 Aug 2:13:697621.
doi: 10.3389/fnagi.2021.697621. eCollection 2021.

Functional Aging in Male C57BL/6J Mice Across the Life-Span: A Systematic Behavioral Analysis of Motor, Emotional, and Memory Function to Define an Aging Phenotype

Shuichi Yanai  1 , Shogo Endo  1
Affiliations

Functional Aging in Male C57BL/6J Mice Across the Life-Span: A Systematic Behavioral Analysis of Motor, Emotional, and Memory Function to Define an Aging Phenotype

Shuichi Yanai et al. Front Aging Neurosci. .

Abstract

Aging is characterized generally by progressive and overall physiological decline of functions and is observed in all animals. A long line of evidence has established the laboratory mouse as the prime model of human aging. However, relatively little is known about the detailed behavioral and functional changes that occur across their lifespan, and how this maps onto the phenotype of human aging. To better understand age-related changes across the life-span, we characterized functional aging in male C57BL/6J mice of five different ages (3, 6, 12, 18, and 22 months of age) using a multi-domain behavioral test battery. Spatial memory and physical activities, including locomotor activity, gait velocity, and grip strength progressively declined with increasing age, although at different rates; anxiety-like behaviors increased with aging. Estimated age-related patterns showed that these functional alterations across ages are non-linear, and the patterns are unique for each behavioral trait. Physical function progressively declines, starting as early as 6 months of age in mice, while cognitive function begins to decline later, with considerable impairment present at 22 months of age. Importantly, functional aging of male C57BL/6J mouse starts at younger relative ages compared to when it starts in humans. Our study suggests that human-equivalent ages of mouse might be better determined on the basis of its functional capabilities.

Keywords: aging; animal models; anxiety; behavior rating scale; handgrip strength; inbred C57BL mice; locomotion; spatial memory.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Schematic diagram of the experimental design for the behavioral test battery group. Mice were handled for 3 days, then they were subjected to a series of tests: wire hanging test, open field test, marble burying test, rotor rod test, Barnes maze, Morris water maze, Pavlovian fear conditioning task, hotplate test, electrical footshock sensitivity test, and home-cage activity assessment. Approximately 2 months were required to complete the whole test battery. Therefore, 3- and 22-month-old mice at the beginning of the experiment were about 5 and 24 months old, respectively, when they completed the experiment.
FIGURE 2
FIGURE 2
Body weight increases with increasing age despite similar food and water consumption. (A) Mean body weights measured at the beginning of the behavioral test battery for each age cohort are significantly greater with increasing ages. Mean daily individual consumption of (B) food and (C) water showed no significant effect of age. ∗p < 0.05, ∗∗∗p < 0.001. Error bars indicate ± SEM in this figure and subsequent figures.
FIGURE 3
FIGURE 3
Locomotor activity decreases with increasing age in novel and familiar environments. Mean distance traveled and number of rearings of the different age cohorts in novel (open field) environment under low (dark) and high (bright) illumination and familiar (home cage) environment. In the open field test, (A) distance traveled and (B) number of rearings decreased significantly with increasing age and under both illumination conditions. (C) In the familiar environment of the home cage (sixth day), distance traveled decreased significantly with increasing age. ∗∗∗p < 0.001.
FIGURE 4
FIGURE 4
Gait velocity and grip strength decreases with increasing age. (A) Mean maximum gait velocity on the last training day (day 5) of the rotor rod test. (B) Grip strength as assessed by the wire hanging test. Mean latencies to fall from the wire grid are shown. Performance on these behavioral tests dramatically decreased with increasing age. ∗∗p < 0.01, ∗∗∗p < 0.001.
FIGURE 5
FIGURE 5
Trait anxiety increases with increasing age. Anxiety-like behaviors were evaluated with two types of tests: open field and marble burying. In the open field test, time spent in the periphery of the field was measured, and percentage of immobility time was calculated. Plotted are (A) mean time spent in the periphery, and (B) mean percentage of immobility time. In the marble burying test, percentage immobility time was measured, and total number of marbles buried was calculated. Plotted are (C) mean percentage of immobility time, and (D) mean total number marbles buried. Immobility times in both tests (B,C) generally increased significantly with increasing older age cohort. Contrary to expectations, number of marbles buried decreased with age. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001.
FIGURE 6
FIGURE 6
Impaired spatial memory in the Barnes maze. (A) Mean escape latency (s) and (B) mean escape distance (cm) to find the hidden escape box during 4 days of consecutive training (3 trials per day). Latencies and distance traveled were significantly longer for 22-month-old mice compared to 3-month-old mice. (C) In the probe test, 22-month-old mice spent significantly less time in the quadrant where the escape box was located previously. (D) Number of nose pokes in the target hole also indicated that memory for location of the training escape hole was impaired in 12-month-old mice and all older age cohorts compared to 3-month-old mice. ∗p < 0.05, ∗∗∗p < 0.001.
FIGURE 7
FIGURE 7
Impaired spatial memory in the Morris water maze. (A) Mean escape latencies and (B) mean swim distances to the submerged platform over 10 days of training. Performance of each cohort gradually improved over 10 days, eventually becoming asymptotic by day 10. (C) Swim speeds of older mice were significantly slower and swim distances significantly longer, suggesting that the appropriate index to evaluate spatial learning ability is swim distance. (D) Mean number of platform crossings during the probe test, which was carried out 1 day after the completion of training. (E) Mean time spent in the training quadrant during the probe test. In 22-month-old mice, platform crossings were significantly fewer than in younger mice, suggesting that 22-month-old mice were significantly impaired. (F) Mean escape latencies and (G) mean swim distances to the visible platform during cued training. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001.
FIGURE 8
FIGURE 8
Enhanced freezing of aged mice in Pavlovian fear conditioning. (A) Schematic diagram of the fear conditioning task, illustrating the elements of training, short-term and long-term memories for the cue, and long-term contextual memory. After conditioning with the tone (CS) and electrical footshock (US), conditioned freezing was tested at 1 and 24 h after the conditioning (cue-dependent fear memory). Context-dependent fear memory was then tested 48 h after the conditioning. (B) Mean percentage of conditioned freezing in the fear conditioning task. Age-dependent increase in conditioned freezing was observed before tone presentation (pre-tone phase) in short- and long-term cue-dependent fear memory test, and context-dependent fear memory test. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001.
FIGURE 9
FIGURE 9
Analgesia tests. Pain sensitivity to electrical and thermal stimuli was assessed. (A) A subtle but significant age-related increase was observed for paw flick and vocalization to electrical footshock. (B) In the hotplate test, sensitivity to thermal stimuli was indistinguishable across the different age cohorts. ∗p < 0.05.
FIGURE 10
FIGURE 10
Decay of acquired spatial memory in the Morris water maze. (A) Experimental scheme for how retention interval affects the Morris water maze probe test. For each age cohorts (3, 6, 12, 18, and 22 months), three different interval subgroups were arranged. After 10 days of spatial acquisition training, a 60-s probe test was conducted after 1-, 10-, or 30-day intervals. Green line indicates the spatial acquisition training, and orange line indicates the retention interval. Retention data on day 1 were obtained from the behavioral test battery experiment. (B) Mean escape latency and (C) mean swim distance to the submerged platform during spatial acquisition training. (D) Mean number of platform crossings during the probe test, and (E) mean time spent in the trained quadrant during the probe test. Acquired spatial memory was retained for at least 10 days, but decayed at 10 and 30 days. This forgetting process was nearly equivalent in all five age cohorts. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001.
FIGURE 11
FIGURE 11
Pattern of functional aging differs depending on behavioral trait. Estimated age-related patterns of representative performance for each trait plotted as a function of age. Least squares method was used to determine age-related patterns from representative data of behavioral test battery (Table 2). With the exception of body weight and trait anxiety, behavioral traits across age cohorts had different rates and patterns of decline. Survival rate of the mouse is adapted and modified from Goto (2015).
FIGURE 12
FIGURE 12
Assessment of functional aging in humans and mice. Age-related patterns were determined based on representative data (Table 2), and then superimposed onto survival rate. (A) Body weight, (B) locomotor activity, (C) gait velocity, (D) grip strength, (E) trait anxiety, (F) memory requiring low attention level, and (G) memory requiring high attention level. Survival rate is adapted and modified from Goto (2015). Original drawing is provided here courtesy of Goto (2015).
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References

    1. Bach M. E., Barad M., Son H., Zhuo M., Lu Y. F., Shih R., et al. (1999). Age-related defects in spatial memory are correlated with defects in the late phase of hippocampal long-term potentiation in vitro and are attenuated by drugs that enhance the cAMP signaling pathway. Proc. Natl. Acad. Sci. U. S. A. 96 5280–5285. 10.1371/10.1073/pnas.96.9.5280 - DOI - PMC - PubMed
    1. Barnes C. A. (1979). Memory deficits associated with senescence: a neuro physiological and behavioral study in the rat. J. Comp. Physiol. Psychol. 93 74–104. 10.1037/h0077579 - DOI - PubMed
    1. Bellantuono I., De Cabo R., Ehninger D., Di Germanio C., Lawrie A., Miller J., et al. (2020). A toolbox for the longitudinal assessment of healthspan in aging mice. Nat. Protoc. 15 540–574. 10.1038/s41596-019-0256-1 - DOI - PMC - PubMed
    1. Benice T. S., Rizk A., Kohama S., Pfankuch T., Raber J. (2006). Sex-differences in age-related cognitive decline in C57BL/6J mice associated with increased brain microtubule-associated protein 2 and synaptophysin immunoreactivity. Neuroscience 137 413–423. 10.1016/j.neuroscience.2005.08.029 - DOI - PubMed
    1. Berthelot G., Bar-Hen A., Marck A., Foulonneau V., Douady S., Noirez P., et al. (2019). An integrative modeling approach to the age-performance relationship in mammals at the cellular scale. Sci. Rep. 9:418. - PMC - PubMed

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