Fig. 5: Evidence of loss of structural integrity in the aging fiber tracts.

A Immunofluorescence microscopy of MBP (green) and AIF1 (red) -positive microglia in mouse hemisphere sections with nuclear staining with DAPI (blue). Scale bars are 500 µm. B Immunofluorescence microscopy of LGALS3 (green) and CNPase (red) proteins in the mouse brain. Scale bars are 500 µm. C Confocal images of MBP (green) and AIF1 (red) in the corpus callosum area. Scale bars are 50 µm. D Bar plot showing quantification of mean fluorescence intensity mean of MBP from five fields in the corpus callosum and corticospinal tract areas per mouse (n = 3 mice per group; average age, young = 14.67 weeks, old = 85.67 weeks). E Confocal images of LGALS3 (green) and CNPase (red) in the corpus callosum area. Scale bars are 50 µm. F Same as (D) except quantification from CNPase signal. For (D, F), data were summarized as mean ± standard error of the mean fluorescence intensity from 15 fields of three mice. p values are reported from an unpaired two-tailed t-test with Welch’s correction comparing old vs young mice. G Clipped 3D images of MBP (green) and AIF1 (red) -positive microglia in the corpus callosum area. The merged images show co-localization of AIF-positive microglia and MBP-labeled myelin at different angles. Scale bars are 15 µm. H Clipped 3D images of LGALS3 (green) and CNPase (red) in the corpus callosum area. The merged images show the co-localization of LGALS3+ microglia and CNPase-labeled myelin in the old sections at different angles. Scale bars are 15 µm. I Propagator anisotropy (PA), non-Gaussianity (NG), return-to-axis probability (RTAP), return-to-origin probability (RTOP), and return-to-plane probability (RTPP) maps in a representative young sample. J Percent change maps of dMRI metrics between group average young and old mice. K Box plot showing quantification of white matter PA, NG, RTAP, RTOP, and RTPP in young and old mice. The boxes are bounded by the 25th and 75th percentile values, with the median represented as the bar in the middle. For (J, K) n = 2 biological replicates per group. Source data are provided as a Source Data file.