['Islet transplantation is an effective way of reversing type I diabetes. However, islet transplantation is hampered by issues such as immune rejection and shortage of donor islets. Mesenchymal stem cells can differentiate into insulin-producing cells. However, the potential of human umbilical cord mesenchymal stem cells (huMSCs) to become insulin-producing cells remains undetermined.', 'We isolated and induced cultured huMSCs under islet cell culture conditions. The response of huMSCs were monitored under an inverted phase contrast microscope. Immunocytochemical and immunofluorescence staining methods were used to measure insulin and glucagon protein levels. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect gene expression of human insulin and PDX-1. Dithizone-staining was employed to determine the zinc contents in huMSCs. Insulin secretion was also evaluated through radioimmunoassay.', 'HuMSCs induced by nicotinamide and β-mercaptoethanol or by neurogenic differentiation 1 gene (NeuroD1) transfection gradually changed morphology from typically elongated fibroblast-shaped cells to round cells. They had a tendency to form clusters. Immunocytochemical studies showed positive expression of human insulin and glucagon in these cells in response to induction. RT-PCR experiments found that huMSCs expressed insulin and PDX-1 genes following induction and dithizone stained the cytoplasm of huMSCs a brownish red color after induction. Insulin secretion in induced huMSCs was significantly elevated compared with the control group (t = 6.183, P < 0.05).'] Do human umbilical cord mesenchymal stem cells derived from Wharton 's jelly differentiate into insulin-producing cells in vitro?