MicroRNA-32 silences WWP2 expression to maintain the pluripotency of human amniotic epithelial stem cells and β islet-like cell differentiation

Human amniotic epithelial stem cells (HuAECs) exhibit pluripotent characteristics, which are similar to those of embryonic stem cells, and can differentiate into various adult tissues and cells through directed induction. However, in culture, HuAECs tend to lose their pluripotency, and their directed differentiation capability declines with increasing passage number. The stem cell pluripotency factor octamer‑binding protein 4 (Oct4) is an important transcription factor that promotes stem cell self‑proliferation and maintains their pluripotency. Previous studies have demonstrated that WW domain containing E3 ubiquitin protein ligase 2 (WWP2) negatively regulates Oct4 expression and stem cell pluripotency. Therefore, the present study aimed to investigate the regulation of WWP2 by microRNAs (miRs), and to evaluate the expression of the downstream factor Oct4 and the maintenance of HuAEC pluripotency. Bioinformatics analysis identified a complementary binding site for miR‑32 in the 3'untranslated region of the WWP2 gene, thus suggesting that it may be a target gene of miR‑32. Post‑infection of HuAECs with a vector overexpressing miR‑32, the endogenous expression of WWP2 was significantly decreased, whereas Oct4 expression was significantly increased. Furthermore, miR‑32‑infected cells differentiated into β islet‑like cells by directed induction. The results indicated that after induction, HuAECs overexpressing miR‑32 also overexpressed the biomarkers of β islet‑like cells. In addition, the ability to secrete insulin was markedly enhanced in response to glucose stimulation, in cells overexpressing miR‑32. In conclusion, the present study suggested that miR‑32 may effectively inhibit WWP2 expression in HuAECs and promote Oct4 overexpression to maintain their pluripotency.