Neural Stem Cell-derived EVs for Improving Aged Brain Function

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Project Summary This project's primary goal is to develop a non-invasive, extracellular vesicle (EV) therapy for maintaining better cognitive and memory function in old age. The project proposes to examine the effectiveness of intranasal (IN) administration of EVs generated from human induced pluripotent stem cell (hiPSC)-derived neural stem cells (hNSCs) for improving cognitive and memory function in a mouse model of aging. RNA-seq and proteomic studies have confirmed the presence of miRNAs and proteins having neuroprotective, antiinflammatory, and neurogenic properties in hNSC-EVs. Preliminary studies have suggested that IN administration of hNSC-EVs results in their uptake by microglia and neurons in all brain regions and leads to improved cognitive function in middle-aged mice, in association with diminished neuroinflammation, adenosine monophosphate-activated protein kinase (AMPK) activation, mammalian target of rapamycin (mTOR) inhibition, enhanced autophagy, and improved neurogenesis. Therefore, the rationale for the proposed approach is that the miRNA and protein cargo of hNSC-EVs would activate beneficial signaling pathways in target cells such as microglia, neurons, and neural stem cells in the aged brain, which, in turn, would reduce neuroinflammation, enhance neuronal function and neurogenesis, and thereby improve cognitive and memory function. The project will test the hypothesis that IN administration of hNSC-EVs in early or late middle age will maintain better cognitive function in old age, and hNSC-EV administration in old age will reverse cognitive dysfunction. Furthermore, it is envisaged that functional improvements with hNSC- EV treatment in the aged brain will involve modulation of activated microglia with inhibition of NLRP3 inflammasomes, AMPK activation, improved mitochondrial function, mTOR inhibition, enhanced autophagy, improved neurogenesis, and reduced synapse loss. Using a mouse model of aging, this project will first investigate the effectiveness of EVs administered in the early or late middle age to prevent cognitive and memory dysfunction in old age (Specific Aim 1). In Specific Aim 2, the effect of EVs administered in old age for reversing cognitive and memory dysfunction will be measured. Then, to understand the role of microglial modulation in hNSC-EV-mediated improved cognitive function, the effects of microglia depletion at the time of EV administration will be examined in both middle-aged and aged mice (Specific Aim 3). Since microglia depletion in the aged mice improves cognitive function, any additive effects of hNSC-EV treatment over the effects of microglia depletion would suggest that hNSC-EVs also act on other neural cell types or pathways to mediate therapeutic benefits. Two regions of the brain, the hippocampus, and the medial prefrontal cortex (mPFC), will be analyzed in male and female aged mice. The proposed studies are highly relevant for preventing and treating age-related cognitive and memory impairments in old age.