Discussion

Type I Diabetes is an autoimmune disease characterized by the loss of beta cell tissue and beta-cell function in the pancreas that results in insufficient production of insulin and subsequent build-up of glucose. This excess of glucose in the body leads to numerous complications, such as blindness, kidney failure, heart disease, stroke,neuropathy, and amputation. Current methods of treatment range from continuous administration of insulin-related drugs to islet cell or whole-organ pancreas transplantation, but are limited by the inability to manage insulin dosing appropriately and the reliance on organ donations, challenges with isolation of islet cells from the pancreas and life-long use of immunosuppressive drugs. Human induced pluripotent stem cell (hiPSC)-derived beta cells have tremendous potential to advance diabetes treatment as they provide a reliable and renewable source of functional beta cells for use in not only regenerative medicine applications, but also provide a predictive, human, in vitro
model system for the discovery of new therapeutics. We have developed a four-step in vitro differentiation protocol to generate insulin-producing beta-cells from hiPS cells. Using this protocol, beta cells have been generated from three different hiPS cell lines. The iPSC-derived beta cells
exhibited MAFA expression and other markers characteristic of mature beta cells and were functionally responsive when exposed to varying levels of glucose in culture as shown by Glucose Stimulated Insulin Secretion (GSIS) response and a 4.4 to 9.9-fold induction of C-peptide secretion. Immunohistochemistry staining of these cells showed equal levels of insulin-producing cells among the different iPS lines while glucagon expression varied among cell lines. The iPSC-derived beta cells retained functionality after cryopreservation, thereby demonstrating their suitability for in vitro assays. These results suggest that iPSC-derived beta cells are an almost inexhaustible source of functional human beta cells that could replace the use of primary pancreatic islet cells from deceased donors. By providing better access to human beta cells and reduced batch-to- batch variability compared to primary islet cells,iPSC-derived beta cells provide a flexible in vitro model system for diabetes research that can be used to study beta cell function and/or differentiation, mechanism of insulin secretion, autoimmune beta-cell destruction or as a predictive cellular assay for screening compounds that regulate insulin secretion.