Home-cage monitoring of activity patterns of laboratory mice

The mouse, deriving from the house mouse, is the most common species used in biomedical research, and offers great advantages for researchers to study gene functions in a complex living organism. However, using animals as research models comes with a moral obligation to follow the 3Rs, (Refine, Reduce, Replace) and proved the best possible husbandry and welfare in order to secure scientific rigor. The problem with poor reproducibility, and contradicting results, has been discussed for many years and efforts have been made to reduce variability and to standardize experimental protocols. One approach has been to automate behavioral testing of mice, to move the test to the home cage, a familiar environment, instead of moving the mouse to the test arena. This has lead forward to the development of scalable systems with the possibility to monitor the animals 24/7 to ensure the welfare of the animals, and to collect unbiased data for research. We have used a scalable home-cage monitoring system based on capacitive-sensing technology, to characterize un-disturbed activity patterns of C57BL/6 female and male mice, and to monitor changes in activity patterns due to aging as well as in adaptation to a modest (30%) caloric restriction. In two studies using multi-center design, we conclude that the circadian rhythm of activity displays a very robust pattern across sites but despite efforts to harmonize protocols there are still un-elucidated differences between laboratories. In long-term recordings of un-disturbed activity from cages of female or male mice (400-600 days of recording), we describe an overall decline in activity with age and on top of this decline, there are slow oscillations in activity levels, varying 1-2 standard deviations from the overall mean activity and a period of 2-4 months. The oscillations does not synchronize with seasons, or between cages, and has an unknown origin. Mice on a modest caloric restriction spend more time in long periods of rest, have a lower body weight and lower body temperature during rest, than ad libitum fed controls. Our data support that mice on DR shift their metabolism to synthesize and burn fatty acids to produce energy. Daily energy expenditure is lowered and matches the extended time in long rest bouts with lowered body temperature and their smaller body size. In addition, when the mice are fed their daily food ration during the light phase, the food-entrained oscillator (FEO) will partially override the circadian rhythm of activity (which entrains to light) and the food anticipatory activity (FAA) will drive the pattern of activity and rest during daytime. These adaptations were present both in the short-term adjustment (2-3 months), after one year and after almost 2 years observations. Thus, the response to DR is remarkably stable over time and similar between sexes

Home-cage monitoring of mouse behaviours across life-span

Background and aim: The academic research involving animal testing is struggling with problems of reproducibility and a few of the specific reasons pointed out are for example insufficient reporting of animal strains and protocol details. It is everyone’s responsibility to follow the 3R’s (Replace, Reduce, Refine) and to ensure that the model used is well characterized. In this work we investigated how activity data collected from automated home-cage monitoring can be used to characterize behavior patterns and how well the results could be reproduced in a multi-center setup. We also studied if we can detect changes in behavior patterns through aging, using the same system. Finally, the impact of dietary restriction on behavior patterns and activity levels. Material and Methods: We used C57BL/6J male and female mice from young age and kept them in the study for as long as up to 70 weeks. Groups of both male and female mice were subjected to modest dietary restriction from the age of 3 months and throughout the study. The DVC TM system uses standard IVC cages and has an external board of sensor electrodes in each cage slot that can detect activity on the cage floor in cages of group-held mice. Results and conclusion: By analyzing activity data from the DVC system we could identify daily activity patterns with increased activity during lights off and also around the time for lights on in the holding room. We could also document the impact of husbandry procedures such as cage change. In addition, we identified additional behavioral rhythms with weekly variations and, importantly, a seasonal-like oscillation in activity with highs and lows and a periodicity of about 40 days. We hypothesized that activity levels would decrease with increasing age, and there is a small but highly significant decrease in overall activity between young adulthood and middle age. Monitoring mice on dietary restriction, we show that the diet regime is able to completely change the activity patterns, but we were not able to detect clear differences in activity levels between dietary restricted and ad libitum fed mice

Towards large scale automated cage monitoring - Diurnal rhythm and impact of interventions on in-cage activity of C57BL/6J mice recorded 24/7 with a non-disrupting capacitive-based technique.

BACKGROUND AND AIMS: Automated recording of laboratory animal\u27s home cage behavior is receiving increasing attention since such non-intruding surveillance will aid in the unbiased understanding of animal cage behavior potentially improving animal experimental reproducibility. MATERIAL AND METHODS: Here we investigate activity of group held female C57BL/6J mice (mus musculus) housed in standard Individually Ventilated Cages across three test-sites: Consiglio Nazionale delle Ricerche (CNR, Rome, Italy), The Jackson Laboratory (JAX, Bar Harbor, USA) and Karolinska Insititutet (KI, Stockholm, Sweden). Additionally, comparison of female and male C57BL/6J mice was done at KI. Activity was recorded using a capacitive-based sensor placed non-intrusively on the cage rack under the home cage collecting activity data every 250 msec, 24/7. The data collection was analyzed using non-parametric analysis of variance for longitudinal data comparing sites, weekdays and sex. RESULTS: The system detected an increase in activity preceding and peaking around lights-on followed by a decrease to a rest pattern. At lights off, activity increased substantially displaying a distinct temporal variation across this period. We also documented impact on mouse activity that standard animal handling procedures have, e.g. cage-changes, and show that such procedures are stressors impacting in-cage activity. These key observations replicated across the three test-sites, however, it is also clear that, apparently minor local environmental differences generate significant behavioral variances between the sites and within sites across weeks. Comparison of gender revealed differences in activity in the response to cage-change lasting for days in male but not female mice; and apparently also impacting the response to other events such as lights-on in males. Females but not males showed a larger tendency for week-to-week variance in activity possibly reflecting estrous cycling. CONCLUSIONS: These data demonstrate that home cage monitoring is scalable and run in real time, providing complementary information for animal welfare measures, experimental design and phenotype characterization

Towards large scale automated cage monitoring - Diurnal rhythm and impact of interventions on in-cage activity of C57BL/6J mice recorded 24/7 with a non-disrupting capacitive-based technique.

BACKGROUND AND AIMS:Automated recording of laboratory animal's home cage behavior is receiving increasing attention since such non-intruding surveillance will aid in the unbiased understanding of animal cage behavior potentially improving animal experimental reproducibility. MATERIAL AND METHODS:Here we investigate activity of group held female C57BL/6J mice (mus musculus) housed in standard Individually Ventilated Cages across three test-sites: Consiglio Nazionale delle Ricerche (CNR, Rome, Italy), The Jackson Laboratory (JAX, Bar Harbor, USA) and Karolinska Insititutet (KI, Stockholm, Sweden). Additionally, comparison of female and male C57BL/6J mice was done at KI. Activity was recorded using a capacitive-based sensor placed non-intrusively on the cage rack under the home cage collecting activity data every 250 msec, 24/7. The data collection was analyzed using non-parametric analysis of variance for longitudinal data comparing sites, weekdays and sex. RESULTS:The system detected an increase in activity preceding and peaking around lights-on followed by a decrease to a rest pattern. At lights off, activity increased substantially displaying a distinct temporal variation across this period. We also documented impact on mouse activity that standard animal handling procedures have, e.g. cage-changes, and show that such procedures are stressors impacting in-cage activity. These key observations replicated across the three test-sites, however, it is also clear that, apparently minor local environmental differences generate significant behavioral variances between the sites and within sites across weeks. Comparison of gender revealed differences in activity in the response to cage-change lasting for days in male but not female mice; and apparently also impacting the response to other events such as lights-on in males. Females but not males showed a larger tendency for week-to-week variance in activity possibly reflecting estrous cycling. CONCLUSIONS:These data demonstrate that home cage monitoring is scalable and run in real time, providing complementary information for animal welfare measures, experimental design and phenotype characterization

Expression of progerin in aging mouse brains reveals structural nuclear abnormalities without detectible significant alterations in gene expression, hippocampal stem cells or behavior

Hutchinson–Gilford progeria syndrome (HGPS) is a segmental progeroid syndrome with multiple features suggestive of premature accelerated aging. Accumulation of progerin is thought to underlie the pathophysiology of HGPS. However, despite ubiquitous expression of lamin A in all differentiated cells, the HGPS mutation results in organ-specific defects. For example, bone and skin are strongly affected by HGPS, while the brain appears to be unaffected. There are no definite explanations as to the variable sensitivity to progeria disease among different organs. In addition, low levels of progerin have also been found in several tissues from normal individuals, but it is not clear if low levels of progerin contribute to the aging of the brain. In an attempt to clarify the origin of this phenomenon, we have developed an inducible transgenic mouse model with expression of the most common HGPS mutation in brain, skin, bone and heart to investigate how the mutation affects these organs. Ultrastructural analysis of neuronal nuclei after 70 weeks of expression of the LMNA c.1824C>T mutation showed severe distortion with multiple lobulations and irregular extensions. Despite severe distortions in the nuclei of hippocampal neurons of HGPS animals, there were only negligible changes in gene expression after 63 weeks of transgenic expression. Behavioral analysis and neurogenesis assays, following long-term expression of the HGPS mutation, did not reveal significant pathology. Our results suggest that certain tissues are protected from functional deleterious effects of progerin