nVista HD from Inscopix
Efforts to monitor neural activity as animals move about freely can be challenging due to the lack of appropriately sized equipment. Microscopes are often too big to mount on the head of a rodent and current electrophysiological techniques don’t allow for simultaneous monitoring of large networks of active neurons at the resolution of a single cell.
nVista HD, a new mini-microscope developed by Inscopix, provides a novel solution. This allows researchers to image thousands of neurons at the cellular level while the animal freely navigates an established behavioural task. Weighing just 2 grams, the microscope attaches to a magnetic platform that frames a window in the skull. It can be plugged in during behavioural tasks, or removed to share among a number of animals, and can be used over a period of several days or months.
Dr Holmes commented: “This approach gives users the opportunity to image in real time the same neurones in the same mouse longitudinally over days and potentially months. Traditionally this would require multiple mice to be sacrificed at different timepoints across a study so that tissue could be analysed. This type of technology has the potential to increase the amount and quality of data from each animal, greatly reducing the number of animals needed per study and the variability in the data obtained.
“Further 3Rs benefits of this technology could be realised if the nVista device was wireless and able to be used in automated behavioural tasks in the home-cage environment, as is being explored in the NC3Rs CRACK IT Cognition Challenge.”
Humanised Bacterial Luciferase from 490 BioTech
Molecular biologists insert bioluminescent genes into cells to report back on any number of measures, such as the toxicity or efficacy of a drug. Firefly luciferases are popular reporter proteins, but exogenous reagents must be added to target cells to switch on their glow, which kills cells and halts the experiment. This means that toxicity, for instance, can’t be measured continuously over the course of a drug’s dose, but only at discrete time points.
To combat this, 490 BioTech has developed a bioluminescent reporter system using bacterial luciferase which needs no additional substrate to switch the glow on. Although not as strong as those of other luciferases, it has been found to work especially well for 3D drug screens, where assays can be monitored continuously in real time.
Dr Holmes said: “Monitoring the same animal in real time over a prolonged period can greatly reduce the total number of animals needed in a study. The development of reporter systems that can self-activate without affecting the animal host provides a tool to enable continuous imaging in cell and animal models of disease, maximising the amount of information from each animal. Being able to track toxicity or efficacy in this way also gives an objective measure of the burden on each animal, so appropriate action can be taken to stop an experiment if the animals’ welfare is found to be compromised.”
SynVivo from CFD Research Corporation
SynVivo is a synthetic in vivo vascular environment on a microfluidic chip, similar in principle to the 3Rs Prize winning lung-on-a-chip from the Wyss Institute. This mimics the microenvironment of a real animal on a tiny, fluid-filled device to replace the use of an animal.
CRD Research Corporation have developed a platform of around 20 SynVivo chips to mimic the different vascular geometries of a hamster, rat, and mouse. Several chips also contain specialised cavities for seeding cells of a particular tissue type, such as neurons, hepatocytes, or tumour cells, which scientists can use to study interactions with drugs or other circulating compounds.
To construct a synthetic in vivo environment similar to that found in a animal, researchers simply coat the channels of the microchip with an appropriate substrate, such as fibronectin, and then seed it with cells. Fluid then moves through the system to mimic natural blood flow.
Dr Holmes said: “The development and application of ‘lab-on-a-chip’ devices offer substantial 3Rs benefits across many applications and sectors. Recreating structures from simple tissues through to more complicated 3D multi-cellular organ sections, and incorporating biologically important stimuli such as flow and mechanical stretch give researchers physiologically relevant in vitro tools amenable to high-throughput screening. When applied early in drug development these devices may better predict whether new drugs are likely to be safe in humans, so reduce the number of drugs being tested in animals which are destined to fail in man.”