Abstract WP078: Stem Cell-Derived Exosomal miRNAs from Older Adults Induce Cerebrovascular Endothelial Dysfunction

Aging is associated with vascular cognitive impairment (VCI). CD34 + stem cells maintain endothelial health and regeneration via paracrine mechanisms largely mediated by exosomes. This study tested the hypothesis that exosomal cargo derived from the stem cells induce brain microvascular endothelial dysfunction thereby increases risk for VCI. CD34 + cells were isolated from peripheral blood mononuclear cells derived from subjects, 18-35 (Young) or > 60 (Old) years of age. Exosomes (Ex) were collected from the cell-supernatants by ultracentrifugation. Size distribution was analyzed by Nanosight and imaged by Atomic Force microscope. Cultured human brain microvascular endothelial cells (hBMECs) were exposed to Young- or Old-Ex and the Agilent Seahorse bioanalyzer was used to determine OxPhos and glycolysis. BODIPY staining of Ex was used to confirm the cellular internalization of Ex by confocal microscopy. Affymetrix GeneChip miRNA-array was used to profile miRNAs in Ex-treated hBMECs and the data was analyzed by using TAC v4.0.3. miRNA- target gene alignment was confirmed by miRWalk and TargetScan. OxPhos was impaired by Old-Ex with decreased basal and maximal respiration and ATP generation ( P < 0.05, n=6) while Young-Ex showed no effect. Basal glycolysis, proton efflux rate and compensatory glycolysis were decreased by Old-Ex ( P < 0.05, n=10) compared to the untreated. miRNA profiling revealed that 146 and 126 miRNAs were differentially altered by Young- and Old-Ex. miRNAs with higher fold-change by Old-Ex, hsa-miR-206, hsa-miR-6797, hsa-miR-4698 and mmu-miR-29b-1-5p appear to target the mitochondrial enzyme ARG2, which was confirmed in vitro by using the synthetic forms in vitro in hBMECs. The study infers that Old CD34-Ex impair endothelial bioenergetics via miRNA dysregulation of ARG2, which likely induce neurovascular uncoupling thereby increases risk for vascular cognitive decline in aging.