MicroRNA-221 inhibits the transition of endothelial progenitor cells to mesenchymal cells via the PTEN/FoxO3a signaling pathway

Background: Coronary heart disease is one of the most common cardiovascular diseases worldwide and is often associated with vascular endothelial injury. Endothelial-mesenchymal transition (EndMT) is an important process in vascular endothelial injury.

Objectives: This study investigated the function of miR-221 in the EndMT process of endothelial progenitor cells (EPCs).

Material and methods: Transforming growth factor beta (TGF-β1) was used to induce EndMT in EPCs, and SM22α expression was detected using immunocytochemistry. Western blot was used to detect alpha smooth muscle actin (αSMA) expression, and miR-221 function was evaluated using inhibitors or mimics of the miR-221 sequences that were transfected into EPCs. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the expression of miR-221 and western blot was used to detect the expression of αSMA, myocardin, phosphatase and tensin homolog (PTEN), p-FoxO3a, and FoxO3a in EPCs. Finally, the expression of the miR-221 target genes was determined using RT-PCR.

Results: The expression of SM22α and αSMA increased in EPCs treated with TGF-β1, while the expression of miR-221 was decreased in EPCs on the 5th day, when compared with the control. The expression of SM22α increased after inhibiting miR-221 in EPCs treated with TGF-β1 and this was reversed by the overexpression of miR-221. The expression of αSMA and myocardin was significantly increased after inhibiting miR-221 in EPCs treated with TGF-β1 and decreased in EPCs overexpressing miR-221. Conversely, PTEN was increased in TGF-β1-treated EPCs and decreased following the overexpression of miR-221. The decrease in phosphorylated-FoxO3a expression in EPCs was accompanied by an increase in αSMA expression, which was reversed in the presence of miR-221 mimics. This effect was nearly abolished following the addition of PTEN cDNA.

Conclusions: The overexpression of miR-221 inhibits EndMT in EPCs, possibly by interacting with PTEN to regulate FoxO3a signaling, to facilitate the repair of the endothelium by EPCs.