All research model systems have unique strengths and challenges regarding the generalizability of data to other systems. Pre-clinical researchers attempt to describe and interact with human clinical phenotypes using animal models. These models allow manipulation and testing of scientific hypotheses within the context of a complex system, providing insights that may be impossible using in vivo methods or within the constraints of clinical interventions. Well-characterized strains in popular animal models such as mice and rats facilitate important discoveries such as our understanding of normal or disease development. There are, however, well known translational difficulties when moving from in vitro to pre-clinical animal models and then to humans. These effects can be particularly challenging while developing drugs or vaccines, as noted by Khoury et al. in their recent review comparing SARS-CoV-2 intervention efficacies across models.1
Before any experimental interventions, subject housing and care considerations can have important effects on an animal’s physiology. For example, aspects as simple as the temperature mice are housed at can have important impacts on stress-related catecholamine regulation, which in turn alter tumour growth and response to therapeutic interventions.2 Variable significance of differing weaning age or housing density regimes is also reported.3, 4, 5, 6 Even the use of simple enrichment tools to reduce anxiety is linked to changes in animal behaviour, learning and physiology.7 One important and easily modified care factor is how an animal is handled, whether during routine health checks or more invasive processes.
Many institutions have recently adopted new guidelines for mouse handling. Use of either a short, plastic/cardboard tunnel or open-palmed “cupping” rather than the traditional tail grasp handling protocol appears to improve both animal and caretaker welfare. 8, 9
Henderson et al. recently test the initial findings found in the Hurst lab to test the reputed positive effect of using tunnel handling.10 In their tests, BALB/c mice in either tunnel or tail handling regimens experience repeated scuffing, IP injections or anesthesia. Willingness to approach the handler’s hand, as well as exploratory behaviour, is assessed. The mice retain a higher willingness to interact with the handler and show reduced anxiety when provided with an opportunity to explore in an open-armed behavioural setting when as opposed to their tail-handled counterparts (Figure 1). These findings are consistent with the aforementioned positive reports of tunnel handling. As the switch from tail to tunnel handling is simple and does not introduce any significant loss of time or handler expertise, positive impacts of improved handling are seen within only a few weeks of switching to tunnel methods, Henderson et al. support adoption of the tunnel handling method.8, 9, 10
Figure 1. Effect of handling method upon voluntary interaction (A) or spent exploring when tested using an elevated plus maze (EPM) following either IP injection or anesthesia application. Data collected from three tests done immediately post-intervention or with one day following the intervention. From Henderson et al. 2020
Based upon these and many other studies, the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) recommends the adoption of either tunnel or cupping techniques in laboratories using murine research models.11 SCIREQ stands with the ethical use of animals to advance research, including reducing the total number of animals through the use of highly precise and reproducible data collection, as well as improving the conditions of subjects. The impact of stress on animals and the resulting data should be a consideration for all researchers.9, 10, 12, 13 The NC3Rs provides many resources, including FAQs, videos and tutorials for any researchers/handlers interested in switching to this technique on their website.
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