Abstract <p>The biological activity of exosomes secreted by neural (NSC) and mesenchymal stem cells (MSC) isolated from a SC conditioned medium using differential ultracentrifugation, depth filtration, and sedimentation with polyethylene glycol is characterized and compared. The obtained preparations are characterized by size, presence of specific exosomal markers, and protein concentration. The biological activity of exosomes is assessed by their ability to increase the survival and clonogenic activity of irradiated NSCs. The ability of mouse SC exosomes isolated with all these methods to increase the survival and clonogenic activity of irradiated NSCs is shown, but NSC exosomes obtained by ultracentrifugation exhibited the highest efficiency. Any of these methods can be used to obtain biologically active exosomes.</p>