Heat Shock-Induced Extracellular Vesicles Derived from Neural Stem Cells Confer Marked Neuroprotection Against Oxidative Stress and Amyloid-β-Caused Neurotoxicity

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease and a leading cause of dementia. Although the amyloid-β (Aβ) peptide is deemed a crucial driver of AD, there are no effective therapeutics available to treat Aβ-caused neurotoxicity. Extracellular vesicles (EVs) are membrane-bound small particles mediating intercellular traffic of nucleic acids, lipids, proteins, and metabolites. Exosomes are a subtype of EVs with a size range of 30-150 nm in diameter. Stem cell-derived EVs are a potential therapeutic for AD, while EVs isolated from normal stem cell cultures generally have a low yield. Here, we studied the EVs secreted by the rat neural stem cells in the presence of heat shock (HS) stimulus. Nanoparticle tracking analysis confirmed that HS-derived EVs exhibit significantly higher concentration and larger diameter in comparison to the non-heat shock (NHS)-derived EVs. Mass spectrometric studies of EV proteins revealed that HS-derived EVs contained fewer diverse proteins than NHS-derived exosomes. GO enrichment analysis of the proteins suggested that the top two biological functions of the proteins in HS-derived EVs are involved in the negative regulation of apoptotic process and positive modulation of DNA repair. Importantly, the therapeutic efficacy of the NHS- and HS-derived EVs were tested in a cell culture model of AD: HS-derived EVs exhibited greater neuroprotection against not only oxidative stress but also amyloid-β (Aβ) induced neurotoxicity compared to NHS-derived EVs. Moreover, HS-derived EVs were also able to dramatically attenuate Aβ-induced apoptosis and oxidative stress. These data indicate that in response to HS, neural stem cells increase EV production and alter EV morphology and cargo to confer better neuroprotection against oxidative stress and Aβ-caused neurotoxicity, suggesting that HS-induced EVs from neural stem cells can be a therapeutic agent for AD and possibly other neurological disorders.