Comparing Functional Consequences of Human <scp>iPSC</scp> ‐Microglia and Neural Stem Cell‐Derived Extracellular Vesicles in Mitigating Cognitive Decline in Alzheimer's Disease

Stem cell-derived extracellular vesicles (EVs) show promise as a therapeutic approach for neurodegenerative diseases, particularly Alzheimer's Disease (AD), where traditional regenerative interventions have achieved limited success. Our previous research demonstrated the neuroprotective benefits of human neural stem cell (hNSC)-derived EVs in 2- and 6-month-old AD mice (5xFAD) that exibited improved cognitive function and reduced AD-related neuropathology. This study aimed to compare the neuroprotective efficacy of EVs derived from two human cell lines: hNSCs from H9 embryonic stem cells and human iPSC-derived microglia (iMGLs). Additionally, we investigated the efficacy of an expanded EV treatment paradigm at subsequently longer time points. Three-month-old 5xFAD mice received weekly retro-orbital vein injections of either hNSC- or iMGL-derived EVs for 4 weeks. Cognitive function testing revealed comparable cognitive improvements in both EV treatment groups compared to vehicle-injected AD mice. Both iMGL- and hNSC-derived EVs significantly reduced amyloid beta plaques, astrogliosis, and microglial activation, while restoring synaptophysin and postsynaptic density protein PSD-95 to control levels in AD brains. Gene expression analysis revealed significantly reduced neuroinflammation and elevated neuroprotective signatures following both EV treatments. MicroRNA analysis of the EV-derived cargo revealed unique and shared miRNA signatures associated with differentially expressed genes in both cell lines. These findings demonstrate the feasibility and neuroprotective benefits of recurrent systemic injections of EVs derived from human NSCs and differentiated human microglia lines in alleviating cognitive dysfunction and neuropathology in Alzheimer's disease.