Scientific progress depends on constant innovation and the development and application of novel tools to push the research forward. Leonard (Leo) Khiroug, PhD is certainly one such researcher. As the CSO of award-winning life science company Neurotar, Leo develops tools for in vivo neurophysiology in unanesthetized, awake rodents.
Recently we had the opportunity to talk to Leo about current trends in Neuroscience, research using head-fixed rodents and the Mobile HomeCage, an air-lifted homecage that enables high precision neurophysiological tests in unanesthetized and behaving rodents.
What led to the development of the Mobile HomeCage?
Leo: Neurotar started 10 years ago as a service provider, and since then we have been doing two-photon imaging in live mice. For the first 10 years of our existence this was been done in anesthetized animals. However, there are limitations of this approach and our clients as well as academic scientists have been sort of waking up to realize the fact that anesthetics does affect brain function.
When we were asked by our clients whether we can do the same work in non-anesthetized awake animals, we looked at the range of existing devices and we were not happy with them. The first reason was that we couldn’t fit it in under our two-photon microscope because of the lack of vertical space. A second reason was that animals are not very happy on the brown surface of the styrofoam airlifted ball, and it’s not a very natural posture for them. Besides, they were stressed because it was an open space with a lack off walls, et cetera. To cut the long story short, we had to come up with our own design, which at the time we called the “Flat Ball with a Wall” and basically, it’s an airlifted homecage made of a very lightweight material. This is how the Mobile HomeCage line of products was born about five years ago.
The need that it was addressing was the need to precisely do the high precision microscopic analyses or electrophysiological recordings in the brain of an awake mouse that is not too stressed by the head fixation. It worked pretty well for us and we realized that this could also be useful for other researchers, so we decided to productize the invention, which was patented, and since then we’ve been developing it further. It’s now with the fifth generation.
It turned out that our design had some additional advantages, for instance, the wall around the cage allowed the mouse to be more relaxed. It can always come to the wall and whisker it and feel more protected. It also shields the animal from the flow of air, which is not the case in the air-lifted ball and it also creates a more cozy acoustic environment. Later on we also added the roof to make it even cozier, something that the mice are very familiar with – small enclosed spaces. They feel quite at home in this Mobile HomeCage.
Later on, we introduced locomotion tracking, which turned out to be very useful not only because it immediately shows you what the animal is doing in terms of locomotion, but also because the motion is analyzed on the fly and the information can be fed back into the experiments. For instance, the mouse could be rewarded automatically with a liquid reward for being in the right place in the cage or for moving at a certain speed. The dynamics of this device is that it is becoming more than more of an automated behavior analysis device that at the same time immobilizes the head of the animal, so that we can have access to it with fine electrodes or high-resolution microscopes, such as two-photon microscopes.
How many labs use the Mobile HomeCage and how are they using it?
Leo: We introduced the first Mobile HomeCage in 2014, and since then more than 100 labs have adopted this technology. I think the count right now is 110 or so. Most of these labs are in central Europe and North America, but some also are in Asia; China, Japan, Hong Kong, Korea, Taiwan. There’s plenty of these devices around the world.
We get tremendous feedback, not only in terms of the user satisfaction, because this device makes their life easier and, “happy mice, better data”, but also in terms of the the broad spectrum of research questions that they’re addressing. I’d say the most interesting trend lately has been the social interaction and social stress paradigms. Of course, it’s very difficult to do on the treadmill or on the ball, but in the Mobile HomeCage, the second mouse can walk around the cage while the ‘driver mouse’ drives the merry-go-round and round. If it’s a head-fixed male, we can record vocalizations as it sings love songs to the female running around.
Of course, there’s also criticism and wish lists that we get from our clients, and this is what feeds our product development pipeline. Most of the things that we’ve introduced recently, including the locomotion tracking, the roof above the Mobile HomeCage, the automatic liquid dispensary or air puff, the rotation of the clamp, the inclination of the clamp – all of this is based on user feedback. In fact, in some cases, we even name our products after the lab head who invented it. The magnetic clamp was developed in Christiaan Levelt’s lab in Amsterdam; we call it Levelt’s clamp.
The important thing for us is to stay active in research as well, and we do this both through collaboration with academia, but also as a service provider to Pharma. We use our devices on daily basis, we do two-photon imaging in awake mice still as a service and as internal validation, which, I’d say sets us apart from the majority of the manufacturers and developers of research equipment.
What are the trends in Neuroscience research now, and what is on the horizon?
Leo: In my opinion, neuroscience is heading very quickly and actively towards more holistic research in awake and behaving mice. The two main approaches there are the head-mounted devices and head fixation of the mice. Of course, we’re in one part of that, but the other part, head-mounted devices, is also very well developed, and there are companies and research groups who provide the DIY solution. And these techniques are complementary. They both have their pros and cons.
For instance, head-mounted devices allow maximal three-dimensional freedom of movement for the mice, so it’s a more natural behavior. But on the other hand, this comes at the expense of miniaturizing devices, whether it’s the electrodes that are implanted and attached to the skull—there’s a limit on how much weight you can put on a mouse’s head—or if it’s a miniaturized cameras, mini endoscopes, they also have to compromise in size and therefore the quality of the optical signal as well as the field of view have to be very small.
The other approach, head fixation, is a more limited range of behavior for the mice, but that the same time allows us to use these devices with much better quality microscopes or many more electrodes in the brain of the mice. These two approaches are complementary. The best labs who can afford it financially use both, and they they can investigate the differences in terms of mouse behavior when it comes to head-fixed versus head-mounted, but it clearly is the general trend in neuroscience.
Is there anything else you’d like them to know?
At the end, I’d like to say that it has been a privilege and a real joy to work with the research community, both on the industrial side and the academic side in the role of not just a scientific collaborator or advisor, but also as a developer of equipment that helps people do better science, and we are very open to conversations, proposals of collaboration or new ideas of the product.
Please contact us through neurotar.com. We have a chat window there – if you’re in the right time zone maybe you’ll catch us there, hopefully, but also [email protected] is the email that we reply to within 24 hours. We’re really looking forward to hearing from you.
Scientists present data on 2-photon imaging of hippocampal place cells and on stress monitoring in head-fixed awake behaving mice.
Scientists present methodology and research findings from neurophysiological studies in head-fixed, behaving mice.
Making Optical and Electrophysiological Measurements in the Brain of Head-Fixed, Freely-Moving Rodents
A must-watch webinar for researchers interested in optical and electrophysiological recordings from the brain of head-fixed but otherwise freely moving rodents.