OBJECTIVETo explore the feasibility of using a virus-free system in the induction of umbilical cord derived mesenchymal stem cells (UC-MSCs) into insulin-secreting cells.

METHODSMSCs were isolated from human umbilical cord and induced into insulin-secreting cells with a three-stage method. The mRNA expression levels of foxa2, sox17, pdx1, ngn3, pax4, insulin, and glut-2 were compared between induced and non-induced groups by RT-PCR in each stage. The distribution pattern of insulin and c-peptide were detected by immunofluorescence staining and observed by fluorescence microscopy. Insulin and c-peptide secretion and glucose responsiveness were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTSTranscription factors foxa2, sox17, pdx1, ngn3, pax4, insulin, and glut-2 were expressed in the induced cells. The mRNA expression levels of foxa2 and sox17 were significantly higher in the induced group than those in non-induced group in the first stage (all P < 0.05), pdx1, ngn3, and pax4 were significantly higher in the induced cells than those in non-induced cells in the second stage (all P < 0.05), and insulin and glut-2 expressions were significantly up-regulated in the induced group at last stage (all P < 0.05). Immunofluorescence staining showed that insulin and c-peptide were located in the cytoplasm of more than 90% of induced cells. ELISA showed that total intracellular insulin content of the induced cells contained up to (346.3 739 +/- 32.5 149) microU/ml, which was significantly higher than insulin in non-induced cells (17.69 +/- 1.46) microU/ml (P < 0.01). C-peptide content of the induced cells measured up to (195.10 +/- 8.88) pmol/L/h (P < 0.01), when exposed to 5.5 mmol/L glucose (P < 0.01). When stimulated with 22 mmol/L glucose, the c-peptide content of the induced cells increased to (340.99 +/- 7.91) pmol/L/h (P < 0.01 ).

CONCLUSIONThe umbilical cord derived MSCs can be efficiently induced into insulin-secreting cells via a virus-free system.