Cerebellar nuclei remain vulnerable to cuprizone-induced demyelination in adult and aged mice: A longitudinal multimodal MRI-histology study

Abstract

Age is a major determinant of demyelination and remyelination capacity. Here, we investigated age-dependent brain responses to acute cuprizone exposure in female C57BL/6 mice using longitudinal multimodal Magnetic resonance imaging (MRI) and histological analyses. Our aim was to determine whether any brain region in very old animals remains susceptible to cuprizone-induced pathology. Adult (6-month-old) and aged (18-month-old) mice received 0.2% cuprizone in the diet for 5 weeks, followed by 4 weeks of recovery on normal chow, with in vivo MRI performed at baseline, during intoxication, and throughout recovery. Magnetization transfer ratio (MTR) and T₂-weighted signal were used as MRI surrogates of myelin integrity and neuroinflammation, respectively, whereas T₁-weighted signal was assessed as a potential marker sensitive to oxidative stress. In adult mice, cuprizone induced robust and region-specific pathology, including reduced MTR and increased T₂-weighted signal in the corpus callosum, accompanied by microgliosis, astrocytosis, and increased APP-positive dystrophic neurites. These abnormalities showed only partial recovery following cuprizone withdrawal. In contrast, cuprizone elicited little or no detectable change in these forebrain white-matter regions and in other brain areas in aged mice. However, the cerebellar nuclei remained susceptible at both ages, exhibiting persistent MTR decreases and T₂-weighted signal increases, corroborated by histological evidence of demyelination and gliosis. T₁-weighted signal increased broadly in adult, but not in aged, mice during intoxication, consistent with cuprizone-associated oxidative stress. Together, these findings demonstrate pronounced age- and region-dependent effects of cuprizone and identify the cerebellar nuclei as a sensitive target of demyelination across the lifespan. Moreover, the non-invasive nature of MRI enables efficient assessment of regional differences over time.