Noninvasive detection of cuprizone induced axonal damage and demyelination in the mouse corpus callosum

Previously, we tested the prediction that axonal damage results in decreased axial diffusivity (gimel(parallel to)) while demyelination leads to increased radial diffusivity (gimel(perpendicular to)). Cuprizone treatment of C57BL/6 mice was a highly reproducible model of CNS white matter demyelination and remyelination affecting the corpus callosum (CC). In the present study, six C57BL/6 male mice were fed 0.2% cuprizone for 12 weeks followed by 12 weeks of recovery on normal chow. The control mice were fed normal chow and imaged in parallel. Biweekly in vivo DTI examinations showed transient decrease of gimel(parallel to) in CC at 2-6 weeks of cuprizone treatment. Immunostaining for nonphosphorylated neurofilaments demonstrated corresponding axonal damage at 4 weeks of treatment. Significant demyelination was evident from loss of Luxol fast blue staining at 6-12 weeks of cuprizone ingestion and was paralleled by increased gimel(perpendicular to) values, followed by partial normalization during the remyelination phase. The sensitivity of gimel(perpendicular to) to detect demyelination may be modulated in the presence of axonal damage during the early stage of demyelination at 4 weeks of cuprizone treatment. Our results suggest that gimel(parallel to) and gimel(perpendicular to) may be useful in vivo surrogate markers of axonal and myelin damage in mouse CNS white matter.