Abstract 20212: MicroRNA-34a Impairs Endothelial Progenitor Cell-Mediated Angiogenesis through Silent Information Regulator 1 Inhibition during Aging
Background: Aging impairs angiogenesis and accelerates vascular disease with reduced eNOS function. EPCs are critically regulated by eNOS for angiogenesis, but have reduced proliferation and survival in aging. MiR-34a, a tumor suppressor, has been found to target silent information regulator 1 (Sirt1), leading to cell cycle arrest and apoptosis. However, whether miR-34a regulates EPC angiogenesis related to eNOS essential cofactor BH4 in aging is unknown. We tested the hypothesis that miR-34a impairs EPC angiogenesis through Sirt1 inhibition in aging.
Methods and Results: Bone marrow-derived EPCs from young (8 weeks), aged C57BL/6 and eNOS/GTP cyclohydrolase I (endothelial-specific GTPCH, the rate-limiting enzyme for BH4) double-transgenic mice (18 months, all males) were used. In vitro EPC angiogenesis was impaired by 56% in aged vs. young mice (Matrigel tube formation, n=4, p<0.01). MiR-34a level in EPCs was increased by ∼1 fold in aged vs. young mice (real time PCR, n=4, p<0.01), paralleled with 46% reduction of Sirt1 expression (Western blot, n=4, p<0.01). Overexpression of miR-34a in young EPCs by its mimic transfection impaired in vitro angiogenesis by 39.2% (n=5, p<0.05) and increased EPC senescence by 40% (senescence-associated β-galactosidase staining, n=3, p<0.01), while suppression of miR-34a in aged EPCs by its inhibitor transfection rescued impaired angiogenesis (by 159%, n=3, p<0.05) and decreased EPC senescence (by 33.1%, n=3, p<0.01). Furthermore, Sirt1 protein was reduced by 42% in young EPCs when transfected with miR-34a mimic (n=3, p<0.01), but increased by 125% in aged EPCs with miR-34a inhibitor transfection (n=3, p<0.05). Sirt1 knockdown by its siRNA in young EPCs resulted in diminished angiogenesis (by 43%, n=5, p<0.05) and augmented senescence (by 48%, n=3, p<0.01). Lastly, miR-34a level was attenuated in EPCs from aged eNOS/GTPCH double-transgenic mice vs. aged C57BL/6 mice (n=3, p<0.01), with a concomitant augmentation of Sirt1 level (n=3, p<0.01).
Conclusions: These data demonstrate that miR-34a impairs EPC angiogenesis through Sirt1 inhibition in aging, which is rescued in aged eNOS/GTPCH double-transgenic mice. They may provide a mechanistic basis for targeting miR-34a to rejuvenate EPC angiogenesis in aging.
- © 2010 by American Heart Association, Inc.