C57BL6 mouse substrains demonstrate differences in susceptibility to the demyelinating effects of Cuprizone toxin

Advances in our understanding of cellular functions and phenotypes in the brain rely on technically robust experimental in vivo models with face validity towards human disease. The cuprizone toxin-induced demyelination model is widely used to investigate pathophysiological mechanisms of demyelinating and remyelinating phases of multiple sclerosis. The C57BL6 mouse is a common inbred strain used as the genetic background for genetically engineered and congenic mice. Substrains of C57BL6 mice sourced from distinct vendors are often treated as equivalent in research studies. Here, we demonstrated that an alternative dosing approach via oral gavage with a well-tolerated, lower dose of cuprizone resulted in significant differences in C57BL/6NTac (Taconic) over C57BL/6J (Jax) mice. With consistent dosing of cuprizone for 5 weeks, body weights were significantly affected in C57BL/6NTac versus C57BL/6J mice. DT-MRI showed significant demyelination in white matter regions in the C57BL/6NTac mice. Concomitantly, histology analysis illustrated increased microgliosis and proliferation in C57BL/6NTac compared with C57BL/6J mice. These observations suggest that the C57BL/6NTac substrain of C57BL6 mice is more vulnerable to cuprizone challenge. Genetic factors along with breeder source appear to influence susceptibility to cuprizone toxin. Thus, the awareness of the limitations of in vivo models in addition to informed decision making on the appropriate background substrain can greatly improve sensitivity and reproducibility of results and use for evaluating investigational therapeutics.