How long have you worked on in vivo evaluations in animals?
It is a fairly new area for me. I’ve been doing it for about 3 years. The first requests were from Genethon research groups that carried out many in vitro evaluations at the time and a few evaluations of general motor skills in the mouse. At their request, we have developed a non-invasive evaluation system of the flexion and extension strength in the mouse ankle to monitor animals.

 

What is the significance of this type of evaluation?
It is very powerful from a methodological point of view to follow the same animal during treatment, with non-invasive methods that are the least traumatic as possible. Since we cannot ask the animal to make voluntary contractions, we anaesthetize it and mechanically stimulate the nerve to trigger a muscle contraction in which we want to measure the force. This type of longitudinal follow-up preserves animals and increases the methodological robustness of the studies: each mouse is its own control. However, we also keep in mind that for a given function, there is not necessarily a direct link between the measured force and the activity of the animal: force is an interesting but insufficient indicator.
Moreover, from an experimental viewpoint, we encounter the same problems as in any other context of force measurement: feasibility, repeatability (there is little difference in measurements with identical evaluator, device and location), reproducibility (there is little difference in measurements with varying evaluator, device and location), sensitivity to change (or when changes in the observed force is due to the treatment rather than variability, either individual or in a given group of mice). As for acceptability, it does not pose a problem in animals.

 

Can you explain your major ongoing projects?
At the Institute, for example, Yves Fromes is working on a hamster model of delta-sarcoglycanopathy. Valérie Decostre is developing the device: she is working on the operating instructions and will begin a study of reproducibility in a dozen animals.
We also have a research project in the mouse on myotonic dystrophy with a team from Quebec and Geneviève Gourdon’s team. We will develop an evaluation method for a mouse model of myotonic dystrophy. The idea, for research but also for industry, is to have a tool that is as simple as possible and foremost, non-invasive. 

Will you adjust your device to work on more advanced models?
We can consider force measurements in the cat, the dog; we were recently contacted to work in monkeys. For now, we are developing force measurements in the GRMD dog because it is a good model of Duchenne muscular dystrophy. We must consider the size of the animals tested, the function to be tested (for example, forelimb or hind limb), and their possible retractions. Furthermore, each species has its specificities. We have just published an article* in the dog on the measure of the animal’s activity via locomotion. In collaboration with Ines Barthélémy and Stéphane Blot at the Veterinary School of Maisons-Alfort, we have transferred to the animal, a method used in humans based on accelerometry. Dogs equipped with an accelerometer are regularly made to trot for about ten seconds in a corridor (see photo). Certain accelerometric variables are perfectly discriminating between populations of healthy and sick adult dogs. This device can also monitor a GRMD dog during its growth (between 2 and 9 months). We are currently transferring this technology and methodology to Boisbonne (Veterinary School of Nantes).
We are also using this device in the SMA cat model, in collaboration with Beatrice Joussemet (INSERM, Nantes). Even if we manage to test adult cats, it is still difficult for kittens!

 

What other tests can one envisage?
One has to strive towards more behavioural tests. For example, we put food on a shelf at a height that requires the dog to stand on its hind limbs, either the dog manages to reach it or he does not. It's simple, very robust but not at all sensitive to changes due to the threshold effect. If we begin with the idea that the more a dog moves, the more autonomous it is, to follow its activity is very interesting: for example, we can measure this activity using thermal cameras or accelerometric methods. Whatever the test, to go beyond the measurement of ‘raw’ force towards the measurement of motor activity or locomotion, for each animal species, even for each race, one must determine the behavioural constraints of the animals. This is the first step; we can then define the methodology. Each animal has its own system.