Downregulation of microRNA‑221‑3p promotes angiogenesis of lipoprotein(a)‑injured endothelial progenitor cells by targeting silent information regulator 1 to activate the RAF/MEK/ERK signaling pathway.

The present study aimed to investigate the role of microRNA (miR)‑221‑3p in endothelial progenitor cells (EPCs) treated with lipoprotein(a) [LP(a)]. EPCs were identified using immunofluorescence assays and miR‑221‑3p levels were measured using reverse transcription‑quantitative PCR. EPC migration was detected using Transwell assays, proliferation was measured by staining with 5‑ethynyl‑2'‑deoxyuridine and adhesion was assessed by microscopy. Flow cytometry was used to measure apoptosis and protein expression was detected using western blotting. A dual‑luciferase reporter assay was used to confirm the target interactions. The proliferation, migration, adhesion and angiogenesis of EPCs were decreased, and apoptosis was increased after treatment with LP(a). These effects were weakened by transfection with miR‑221‑3p inhibitor. The negative effects of LP(a) on EPCs were also weakened by overexpression of silent information regulator 1 (SIRT1). Inhibition of the RAF/MEK/ERK signaling pathway blocked the effects of SIRT1 overexpression. In conclusion, miR‑221‑3p inhibitor transfection activated the RAF/MEK/ERK signaling pathway through SIRT1, promoted the proliferation, migration, adhesion and angiogenesis of EPCs, and reduced apoptosis.