Fig. 2

Correlation between varicosity formation and axon orientation to impact direction. A Axons (red arrows) from L6 to EC containing no varicosity (left, sham), varicosities in the EC portion (middle, CHIMERA) or varicosities in both sections (right, CHIMERA). YFP signals are inverted in gray scale. B Orientations parallel (blue) or perpendicular to (red) the impact direction in rcTBI (left) and CHIMERA (right). The brain regions above the gray line were the focus of our analysis. C YFP + dendrites of layer V pyramidal neurons and YFP + axons in cortical layers 1–5 (L1–L5). YFP signals are inverted. D High magnification confocal images showing that axons (L1-L5) perpendicular to the impact direction had more varicosities in CHIMERA. E YFP + axons (green) partially colocalizing with NF (red) in cortical layer 3 in sham (top) and axons containing varicosities with NF staining in CHIMERA (bottom). F Summary of percentage of YFP + axons (perpendicular (red) or parallel (blue) to the impact direction in the same image) with varicosities in L1-L5 in mouse brains of sham, rcTBI and CHIMERA. Image numbers are provided above the bars. Mouse numbers: 8 sham, 5 rcTBI and 6 CHIMERA. G Axons of YFP + layer 5 pyramidal neurons near external capsule (EC). YFP signals are inverted. In the L6-EC region of CHIMERA mice, different levels of varicosities in axons parallel (H) or perpendicular (I) to the impact direction. J YFP + axons (green) partially colocalizing with NF (red) in EC in sham (top) and axons containing varicosities with NF staining in CHIMERA (bottom). K Summary of percentage of YFP + axons (perpendicular (red) or parallel (blue) to the impact direction in the same image) with varicosities in L6 in mouse brains of sham, rcTBI and CHIMERA. Image numbers are provided above the bars. Mouse numbers: 8 sham, 5 rcTBI and 6 CHIMERA. Unpaired t-test: *, p < 0.05. Scale bars, 25 μm in A and 10 μm in D, E, H-J