Fig. 3

Disrupted myelin, abnormal alterations of SCs, and loss of axons are identified in AAV-A53T-injected rats. A–F Representative TEM images of the ultrastructure of the left vagus nerve among three groups at 3 months post-injection; Low magnification (A, C, E), scale bar = 5 μm; High magnification of the boxed regions in the top row (B, D, F), scale bar = 2 μm. A–D The structure of vagus nerves was not significantly different between the control and AAV-EV groups; Large myelinated A-fibers, medium diameter myelinated B-fibers, and small unmyelinated C-fibers were distributed uniformly, with round or oval SCs located at the periphery of the myelin sheath or wrapped around several unmyelinated axons and exhibited normal cellular morphology and structural integrity. E, F Abnormal alterations in myelin structure and the loss of B- and C-fibers. G–N Representative TEM images of the ultrastructure of myelin sheaths of left vagus nerves. G Normal myelin sheath structure in the control group (red arrow), axon (green arrow), and SC (yellow arrow), scale bar = 1 μm. H–N Left vagus nerve samples from AAV-A53T-injected rats. H Atrophic collapsed myelin sheath (red arrow) and sparse myelin sheath (yellow arrow), scale bar = 500 nm. I Lipid vacuoles in the delaminated myelin sheath (red arrow), squeezed axon (green arrow), and electron-dense areas of interest perhaps associated with the presumed α-synucleinopathy (yellow arrow), scale bar = 1 μm. J Fractured myelin sheath (red arrow), scale bar = 500 nm. K Abnormal protein aggregates deposited in the myelin gap (red arrow), scale bar = 100 nm. L Lipid vacuoles in swollen SCs (red arrow), scale bar = 1 μm. M Degenerated SCs (red arrow), scale bar = 500 nm. N Electron-dense areas of interest perhaps associated with the presumed α-synucleinopathy (red arrow), scale bar = 500 nm. Classification and counting numbers of non-myelinated axons (O), myelinated axons (P), and anomalous-altered myelin (Q) in left vagus nerve fibers. n = 6 per group. Data were presented as mean ± SEM. Statistical significance was analyzed using one-way ANOVA followed by Bonferroni’s multiple comparison test. *P < 0.05, **P < 0.01, ****P < 0.0001. MA, myelinated axons; NMA, non-myelinated axons; MAA, Myelin anomalous alteration