Abstract 17288: GTP Cyclohydrolase I Rescues microRNA-34a Impairment of Endothelial Progenitor Cell Angiogenesis in Aging
Introduction: Endothelial progenitor cells (EPCs) are critically regulated by eNOS for their angiogenic functions. eNOS and its essential cofactor tetrahydrobiopterin (BH4) are reduced during aging, and aged EPCs exhibit decreased proliferation, migration and survival. We recently reported that microRNA 34a (miR-34a) induces EPC senescence and inhibits its angiogenesis by targeting silent information regulator 1 (SIRT1). However, whether miR-34a regulation of EPC angiogenesis involves eNOS and BH4 in aging is unknown. We hypothesized that miR-34a promotes impairment of EPC angiogenesis in aging, which could be rescued by GTP cyclohydrolase I (GTPCH I, the rate-limiting enzyme for BH4 biosynthesis).
Methods: Bone marrow-derived EPCs from young (8-10 weeks) C57BL/6 (wild type, WT), GTPCH I transgenic (Tg-GCH, endothelial-specific GTPCH I overexpression), hph-1 (BH4-deficient), aged (18-20 months) C57BL/6 (WT) and eNOS/GCH double-transgenic (Tg-eNOS/GCH) mice (all males) were used.
Results: Aged WT mice showed significantly impaired recovery of hindlimb ischemia, compared with young WT mice (0.40±0.13 vs. 0.68±0.12, n=3, p<0.05). Consistently, EPCs from aged WT mice showed impaired Matrigel angiogenesis (0.46±0.03 vs. 1.00±0.04, n=4, p<0.01). Reactive oxygen species (ROS) level was significantly elevated in EPCs from aged WT mice (~1.6 folds vs. young WT mice, n=3, p<0.05), accompanied by reduced GTPCH I expression (0.63±0.07 vs. 1.00±0.08, n=3, p<0.05). Suppression of miR-34a in EPCs from aged WT mice rescued their impaired angiogenesis, while overexpression of miR-34a in EPCs from young WT mice impaired their angiogenesis in vitro. Moreover, miR-34a expression was decreased in EPCs from aged Tg-eNOS/GCH double-transgenic mice vs. aged WT mice (0.83±0.07 vs. 1.91±0.07, n=3, p<0.01), with a concomitant augmentation of SIRT1 level (1.14±0.02 vs. 0.54±0.06, n=3, p<0.01). Finally, miR-34a expression was down-regulated in EPCs from Tg-GCH mice with an increase in SIRT1 level, and was up-regulated in EPCs from BH4-deficient hph-1 mice with a decrease in SIRT1 level vs. WT mice.
Conclusion: These findings demonstrate, for the first time, that miR-34a promotes impairment of EPC angiogenesis in aging, which could be rescued by GTPCH I/BH4.
- © 2011 by American Heart Association, Inc.