Survey
In the autumn of 2024, the National SBEA Network (RN-SBEA) launched a survey on the isolation of animals used for scientific purposes with a view to formulating recommendations.
Marco Valdebenito works at CERMEP, where he is in charge of a functional ultrasound imaging system (fUS). He is also in charge of the center's Animal Welfare Structure (SBEA). We interviewed him to find out more about the protective cover he has developed to allow rats with brain implants to be housed together in the same cage, avoiding their systematic isolation.
What 3Rs issues have you encountered?
As part of our research for drug candidates for Parkinson's disease, we use ultrasonic imaging on wakeful rodents, an innovative approach that enables us to gather detailed data on brain structure or function in real time. Respecting the 3Rs principle, this approach enables us to acquire knowledge about the brain without sacrificing animals, and to carry out longitudinal studies, thus Reducing the number of animals used. For a specific project, we designed a device enabling the precise and repeatable positioning of an ultrasound probe on the head of an awake rat. Unfortunately, in order to prevent the devices from being damaged by their fellow animals, the implanted animals are isolated, which is in contradiction with the standard practice of keeping laboratory rats in groups. The isolation of social animals such as rats has an undeniable impact on their behavior, and most certainly on their brain activity, which can influence the measurements made and affect the quality and robustness of scientific results. Once implanted, the rats were nevertheless kept together in pairs, under supervision, for one hour a day (30 minutes in the morning and 30 minutes in the afternoon) to avoid biases linked to isolation. In these animals, we observed lower stress levels and more sociable behavior towards the operators. However, this daily grouping required a human presence to prevent damage to the support covers, and did not fully meet the animals' social needs.
What have you done about it?
We therefore sought to address the problem of group housing of implanted rodents, by developing a protective 3D-printed plastic "cover".
We worked with Sébastien Daligault, an engineer at CERMEP, who helped us design and print the devices we had imagined. Several covers were tested to obtain the best compromise between protection of the support and the ability to be easily removed on a conscious animal. The first support cover was equipped with tabs, and allowed us to switch to pair housing of the rats. However, the tabs (measuring 1 cm on the implant), designed to dissociate the two parts, proved too cumbersome for the animals. A new version with shorter tabs (4 mm on the implant) was created to offer the animals greater comfort when moving around the cage. However, it was still necessary to perform a short anaesthetic before each imaging session, in order to remove the cover and attach the ultrasound probe.
We then designed a new implant with a support cover that does not protrude beyond the implant, and notches that allow a screwdriver to be inserted for removal, thus simplifying the procedure and improving animal welfare. The new support cover has been reduced in size and weight (1.6g), giving the animals greater comfort in their movements while protecting the implant used for ultrasound acquisitions.
What results did you achieve?
Thirty-two animals were implanted with these devices and housed in pairs or groups of four. Post-operative group housing of these animals improved their well-being and, consequently, the quality of the scientific data acquired. Despite possible degradation of the support cover by the conspecifics, the probe supports remained intact, enabling us to carry out ultrasound acquisitions of the wakeful animals without constraint for the duration of the experiment (one week). The results are very encouraging, robust and reproducible: we have already been able to carry out 53 imaging sessions for a total of 43 hours of exploitable acquisitions without artifacts. Focusing on animal welfare by involving the whole team in this multi-skilled project has also helped to create a more ethical and respectful working atmosphere, improving staff morale and satisfaction.
We are happy to share our 3D printing file on request, or to exchange or collaborate with interested colleagues. We also hope that our approach will inspire other colleagues, working on rats or other species or in other fields of research, to innovate to address their own 3Rs issues. The use of 3D printing is a simple and cheap way of developing innovative systems that are robust, lightweight and perfectly adaptable. It is also possible to divide costs by sharing the 3D printer between several teams, as is the case for us.
With the democratization of 3D printing, this type of implant combined with protection could be envisaged for any type of device implanted in rats - or other species. This would avoid the almost systematic isolation required today, and would have a positive effect on the quality of the data collected, contributing to more robust and ethical research.