DiR hotspots in DiR-MSC<sup>exos</sup> infused animals co-localize with CD63 exosome marker.

<p>A-E: Representative region of a contused spinal cord 24 hours after DiR MSC<sup>exos</sup> (cyan) infusion stained with antibodies directed against OX42 (green) and the tetraspanin CD63 (red), and counterstained with DAPI (blue) (A) or DiR fluorescence only (cyan). Images show all wavelengths (A), OX42 & CD63 (B), OX42 & DiR (C), CD63 & DiR (D), DiR only (E). A<sup>1</sup>-E<sup>1</sup>: enlarged and rotated sections of boxed regions shown in A-E. Images below B<sup>1</sup>, C<sup>1</sup>, and D<sup>1</sup> respectively show full 90 degree rotations of boxed regions showing CD63, DiR, and CD63 & DiR fluorescence. Note the strong co-localization between DiR fluorescence and CD63 staining. Scale bar in E = 20 μm E<sup>1</sup> = 10 μm.</p>