Human induced pluripotent stem (hiPS) cells have potential uses for drug discovery and cell therapy, including generation of pancreatic β-cells for diabetes research and treatment. In this study, we developed a simple protocol for generating insulin-producing cells from hiPS cells. Treatment with activin A and a GSK3β inhibitor enhanced efficient endodermal differentiation, and then combined treatment with retinoic acid, a bone morphogenic protein inhibitor, and a transforming growth factor-β (TGF-β) inhibitor induced efficient differentiation of pancreatic progenitor cells from definitive endoderm. Expression of the pancreatic progenitor markers PDX1 and NGN3 was significantly increased at this step and most cells were positive for anti-PDX1 antibody. Moreover, several compounds, including forskolin, dexamethasone, and a TGF-β inhibitor, were found to induce the differentiation of insulin-producing cells from pancreatic progenitor cells. By combined treatment with these compounds, more than 10% of the cells became insulin positive. The differentiated cells secreted human c-peptide in response to various insulin secretagogues. In addition, all five hiPS cell lines that we examined showed efficient differentiation into insulin-producing cells with this protocol.

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Low molecular weight compounds have been shown to be useful for controlling stem cells, and various high-throughput screening systems have been developed for identifying compounds that regulate the differentiation of stem cells. However, the effects of such compounds on stem cell differentiation are usually evaluated by assessing a single parameter, which is insufficient for proper monitoring of the cellular status. In this study, to classify a number of compounds, the authors established a gene expression-based screening system using mouse embryonic stem (ES) cells that monitored multiple parameters. ES cells were differentiated into three germ layers by embryoid body formation and then treated with the test compounds. Next, cellular changes were assessed by analyzing the expression of multiple genes with the multiplex quantitative reverse transcriptase polymerase chain reaction. By screening a library of pharmacologically active compounds with this system, the authors were able to classify 52 compounds that influenced the gene expression profile of ES cells. They also found that some compounds identified by screening could enhance osteogenic or adipogenic differentiation of human mesenchymal stem cells. These results indicate that the screening system is effective for identifying compounds involved in regulating the differentiation of both ES cells and adult stem cells.