Abstract
Background: With advancing age the regenerative properties of somatic stem cells deteriorate in part due to cellular senescence, eventually leading to the diminished repair capability. Endothelial progenitor cells (EPCs) play an important role in angiogenesis. Several miRNAs have been reported to be critical modulators for EPC plasticity. The aim of this study was to determine whether miRNAs regulated age-related senescence in lineage negative bone marrow cells (lin - BMCs) enriched for EPCs. Methods: Lin - BMCs were isolated from young (3-week-old) wild type (WT) and apoE -/- C57BL/6 mice and aged WT (29-month-old) and apoE -/- (12 month-old) mice. Global miRNA and gene expression profiling were analyzed. Results: Using genome-wide miRNA analysis, we found that miR-146a was increased 6.3-fold and 3.4-fold in aged WT and apoE -/- lin - BM cells, respectively, relative to their young counterparts. Microarray analysis showed that the Polo-like kinase 2 (Plk2), a member of the ‘polo’ family of serine/threonine protein kinases that are critical regulators of cell cycle progression or apoptosis, was decreased 18-fold in aged lin - BMC as compared to young cells. Luciferase assay showed miR-146a substantially inhibited WT Plk2-3’-UTR-luciferase activity in 293T cells, but not mutant Plk2-3’-UTR-luciferase reporter. Overexpression of lentiviral-derived miR-146a resulted in reduction of Plk2 expression, increased senescence-associated (SA) β-gal expression and decreased vascular tube formation in young EPCs, whereas miR-146a antagomir rejuvenated aged EPCs, causing increased Plk2 expression, decreased SA β-gal expression and enhanced vascular tube formation. Furthermore, knockdown of Plk2 by its siRNA resulted in increased senescence and diminished vascular tube formation. Conclusions: Using genomic and functional studies, we have discovered miR-146a controls age-associated EPC senescence via regulating Plk2 expression, thus negatively affecting their vascular repair capacity, which may impact atherogenesis. These findings advance our understanding of EPC aging and provide molecular targets for genetic modification to increase the therapeutic efficacy of EPCs in preventing and repairing vascular damage in atherosclerosis.
Published Version
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