Fig. 3

Genetic ablation of Sarm1 attenuates loss of myelin staining in the cerebral cortex and corpus callosum as well as mitigates corpus callosum atrophy at 1 month after rTBI. Representative myelin staining (MBP) from the (A) cerebral cortex and the (D) corpus callosum at 1 month after rTBI with corresponding quantified signal from (B) one region of interest (ROI) in the cerebral cortex (square in inset) and (C) two ROIs in the corpus callosum (dots in inset). Sarm1^−/− mice had significantly greater MBP staining signal within the ipsilateral cortex when compared to Sarm1^+/+ and Sarm1^+/− (p < 0.001 for side effects, p = 0.032 for group effects, p = 0.513 for group x side interaction, arrows indicate region with attenuation of the MBP staining signal indicating axonal rarefaction). Similarly, genetic ablation of Sarm1 significantly attenuated myelin loss within the ipsilateral corpus callosum beneath the impact (ROI i1) and lateral to the impact (i2) (p = 0.023 for group effects, p < 0.001 for ROI effects, p = 0.079 for group x ROI interaction). There was no difference in myelin staining between groups in the corresponding contralateral ROIs (c1 and c2). (E) Sarm1^−/− mice had less corpus callosum atrophy (measured in the mid-sagittal plane, pink line) when compared to Sarm1^+/+ mice (One-way ANOVA with post hoc Holm-Šidák test). All data are mean ± sem; n = 9 per group. Scale bars = 200 μm