Mouse cuprizone model of demyelination

Key takeaway

In disease models, using less susceptible animals, providing an appropriate environment and applying technology to assess disease progression can reduce severity while maintaining a robust experimental outcome.

Background

Animals are used to study demyelinating diseases of the nervous system, in which the myelin sheath that insulates neurons (nerve cells) is damaged. These include multiple sclerosis, Charcot-Marie-Tooth disease and central nervous system neuropathies. In a commonly used model, mice are fed cuprizone, which causes neurons to degenerate throughout the nervous system, including the brain. Potential drugs and therapies can then be evaluated for the disease under study.

Six weeks of 0.2% cuprizone in the diet causes a significant level of reversible demyelination in mice, which becomes irreversible if exposure to cuprizone is continuous for up to 12 weeks. Mice treated with cuprizone invariably exhibit spontaneous seizures (fits), and mortality can be up to 50% in males. Treatment with cuprizone can therefore be severe.

A pharmaceutical company wanted to refine the use of cuprizone and, after evaluating the literature, they set up this protocol.

Mouse cuprizone model.

Refinements

  • Using female mice – according to the literature, female mice are less susceptible to cuprizone.
  • Incorporating 0.2% cuprizone into chow pellets, which mice prefer to powdered diet and find easier to handle.
  • Housing animals in a ‘quiet’ area of the animal facilities with low traffic.
  • Reducing the number of interventions by combining various activities within a single handling session, e.g. by weighing and checking the animals during cage clean.
  • Using MRI techniques to assess demyelination more accurately and refine humane endpoints, with scanning sessions lasting 15 minutes, under isoflurane anaesthesia.

Implications

As a result, the actual severity was ‘mild’ for all animals and the animal model was robust. MRI was also used to implement reduction, as longitudinal data were obtained from a single animal.