GTP cyclohydrolase I rescues microRNA‐34a impaired endothelial progenitor cell angiogenesis in aged mice

EPCs are regulated by eNOS for their angiogenesis, which is impaired in aging. MiR‐34a inhibits angiogenesis and is increased in aged mice, but its role on EPC angiogenesis related to eNOS essential cofactor BH4 is unknown. We hypothesized that miR‐34a impairs EPC angiogenesis in aging that is reversible by GTP cyclohydrolase I (GTPCH, BH4 rate‐limiting enzyme). Bone marrow‐derived EPCs from young (8 wk), endothelial‐specific GTPCH transgenic (Tg‐GTPCH), BH4 deficit hph‐1, aged and eNOS/GCH double‐transgenic mice (18‐20 mo, males) were used. EPC angiogenesis was reduced by 56% in aged mice with 46% reduction of Sirt1 protein, while miR‐34a was increased by ~1 fold. MiR‐34a inhibition in aged EPCs restored their angiogenesis with 33% decrease in EPC senescence, whereas miR‐34a overexpression in young EPCs impaired angiogenesis with 40% increase in EPC senescence. Sirt1 was reduced by 40% in young EPCs after miR‐34a overexpression, but increased by 127% in aged EPCs after miR‐34a inhibition. GTPCH protein was reduced by 37% in aged EPCs. However, miR‐34a was retarded with enhanced Sirt1 in EPCs from aged eNOS/GCH double‐transgenic mice vs. aged mice. Finally, miR‐34a was decreased in EPCs of Tg‐GTPCH mice with enhanced Sirt1, whereas it was increased in EPCs of hph‐1 mice with reduced Sirt1 and angiogenesis vs. young mice. Thus, miR‐34a impairs EPC angiogenesis by inhibiting Sirt1 in aging, which are retarded by GTPCH.