Pluripotent human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) can be directed to differentiate into a variety of different cell lineages, including insulin producing beta cells. Because of this, pluripotent stem cells have been advanced as a platform for novel cell based therapies for the treatment of conditions where beta cells are missing or compromised, such as type 1 diabetes. To help understand the process by which insulin producing beta cells are generated, we genetically modified human embryonic stem cells such that their differentiated derivatives express GFP when the insulin gene is activated. We used these reporter stem cell lines to monitor the genesis of beta cells in the laboratory and to enable the isolation of insulin-producing cells using flow cytometry.
Insulin expressing cell isolated by flow cytometry have been characterised using gene expression profiling, immunofluorescence and functional and ultrastructural studies. Flow cytometric sorting and re-culture experiments indicated that insulin marks a population of cells that can give rise to mono-hormonal cells representing the three major hormone producing cell types found in the adult pancreatic islet, insulin, glucagon and somatostatin. However, mono-hormonal insulin producing cells generated during this process fail to release insulin following glucose stimulation, suggesting other factors are involved in regulating the functional maturation of beta cells. The generation of insulin producing cells and the possible identity of maturation factors will be discussed in the context of beta cell developmental biology and islet function.