EPCs were transfected with miR-138 mimics or miR-138 inhibitor, respectively. (A) RT-qPCR was performed to determine the expression of miR-138 in EPCs in each group. (B) RT-qPCR and (C) western blotting were performed to examine the levels of HIF-1α mRNA and protein, respectively, in EPCs in each group. GAPDH was used as an internal reference. Non-transfected EPCs were used as a control. **P<0.01 vs. control. RT-qPCR, reverse transcription-quantitative polymerase chain reaction; EPC, endothelial progenitor cells; miR-NC, scramble miR mimics; HIF-1α, hypoxia-inducible factor 1α.