MiR-23a-5p was essential in promoting white matter structural remodeling and function repair afforded by M2-EVs after tMCAO. (A) Representative images and quantitative data of demyelinated axon (SMI32+) relative to myelin (MBP+) in the corpus callosum, striatum and cortex at 28 days after tMCAO (n = 5). Scale bar =100 µm. (B) Representative low and high magnification TEM images of myelinated axons in the striatum after 28 days of tMCAO. Scale bar = 0.5 µm. (C-D) Quantification of g-ratio of myelinated axons (C) and scatter plots of g-ratio (D) with respect to different axon diameter in each group (n = 3, 200-400 axons per mouse). (E-F) The N1 (left panel) and N2 (right panel) amplitude of the corpus callosum CAPs in 350-µm-thick coronal brain sections at bregma +0.51 mm (E) and bregma -1.59 mm (F) in each group, respectively (n = 6). Data are presented as mean ± SD, */#/$, p < 0.05. **/##/$$, p < 0.01, ***/###, p < 0.005; *, cn-EVs group vs. PBS group; #, kd-EVs group vs. PBS group; $, cn-EVs group vs. kd-EVs group.